J Donald Hanahan, Hiroshi Homma, J Sugatani, Akira Tokumura and E D. Ayer : Biochemical characteristics of the interaction of synthetic platelet-activating factor with platelets, 1986.
Tsutsumi Toshihiko, Taira Satoshi, Matsuda Risa, Kageyama Chieko, Wada Mamiko, Kitayama Tomoya, Morioka Norimitsu, Morita Katsuya, Tsuboi Kazuhito, Naoshi Yamazaki, Jun-ichi Kido, Toshihiko Nagata, Dohi Toshihiro and Akira Tokumura : Lysophospholipase D activity on oral mucosa cells in whole mixed human saliva involves in production of bioactive lysophosphatidic acid from lysophosphatidylcholine., Prostaglandins & Other Lipid Mediators, Vol.174, 106881, 2024.
2.
Toshihiko Tsutsumi, Kohei Kawabata, Naoshi Yamazaki, Kenji Tsukigawa, Hiroyuki Nishi and Akira Tokumura : Extracellular and intracellular productions of lysophosphatidic acids and cyclic phosphatidic acids by lysophospholipase D from exogenously added lysophosphatidylcholines to cultured NRK52E cells, Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1868, No.9, 159349, 2023.
(要約)
Lysophosphatidic acid (LPA) is a bioactive lysophospholipid that is a notable biomarker of kidney injury. However, it is not clear how LPA is produced in renal cells. In this study, we explored LPA generation and its enzymatic pathway in a rat kidney-derived cell, NRK52E cells. Culturing of NRK52E cells with acyl lysophosphatidylcholine (acyl LPC), or lyso-platelet activating factor (lysoPAF, alkyl LPC) was resulted in increased extracellular level of choline, co-product with LPA by lysophospholipase D (lysoPLD). Their activities were enhanced by addition of calcium ions to the cell culture medium, but failed to be inhibited by S32826, an autotaxin (ATX)-specific inhibitor. Liquid chromatography-tandem mass spectrometric analysis revealed the small, but significant extracellular production of acyl LPA/cyclic phosphatidic acid (cPA) and alkyl LPA/cPA. The mRNA expression of glycerophosphodiesterase (GDE) 7 with lysoPLD activity was elevated in confluent NRK52E cells cultured over 3 days. GDE7 plasmid-transfection of NRK52E cells augmented both extracellular and intracellular productions of LPAs (acyl and alkyl) as well as extracellular productions of cPAs (acyl and alkyl) from exogenous LPCs (acyl and alkyl). These results suggest that intact NRK52E cells are able to produce choline and LPA/cPA from exogenous LPCs through the enzymatic action of GDE7 that is located on the plasma membranes and intracellular membranes.
Midori Fukui, Toshihiko Tsutsumi, Aimi Yamamoto-Mikami, Katsuya Morito, Naoko Takahashi, Tamotsu Tanaka, Tekeshi Iwasa, Akira Kuwahara, Minoru Irahara and Akira Tokumura : Distinct contributions of two choline-producing enzymatic activities to lysophosphatidic acid production in human amniotic fluid from pregnant women in the second trimester and after parturition, Prostaglandins & Other Lipid Mediators, Vol.150, 106471, 2020.
Tohru Hashimura, Jun-ichi Kido, Risa Matsuda, Miho Yokota, Hirokazu Matsui, Manami Inoue-Fujiwara, Yuji Inagaki, Mayumi Hidaka, Tamotsu Tanaka, Toshihiko Tsutsumi, Toshihiko Nagata and Akira Tokumura : A low level of lysophosphatidic acid in human gingival crevicular fluid from patients with periodontitis due to high soluble lysophospholipase activity: Its potential protective role on alveolar bone loss by periodontitis., Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1865, No.7, 158698, 2020.
(要約)
We previously detected a submicromolar concentration of lysophosphatidic acid (LPA) in human saliva. Here, we compare LPA concentrations in human gingival crevicular fluid (GCF) from patients with periodontitis and healthy controls, and examine how the local LPA levels are regulated enzymatically. The concentrations of LPA and its precursor lysophospholipids in GCF was measured by liquid chromatography-tandem mass spectrometry. The LPA-producing and LPA-degrading enzymatic activities were measured by quantifying the liberated choline and free fatty acid, respectively. The concentration of LPA in GCF of periodontitis patients was lower than that of healthy controls, due to higher soluble lysophospholipase activity toward LPA. LPA was found to prevent survival of Sa3, a human gingival epithelium-derived tumor cell line, activate Sa3 through Ca mobilization, and release interleukin 6 from Sa3 in vitro. Furthermore, local injection of LPA into the gingiva attenuated ligature-induced experimental alveolar bone loss induced by oral bacteria inoculation in a rat model of periodontitis in vivo. A high concentration of LPA in human GCF is necessary to maintain normal gingival epithelial integrity and function, protecting the progression of periodontitis.
Sheuli Afroz, Ayano Yagi, Kouki Fujikawa, M. Motiur Rahman, Katsuya Morito, Tatsuya Fukuta, Shiro Watanabe, Kazunori Toida, Emi Kiyokage, Taro Shimizu, Tatsuhiro Ishida, Kentaro Kogure, Akira Tokumura and Tamotsu Tanaka : Lysophosphatidic acid in medicinal herbs enhances prostaglandin E2 and protects against indomethacin-induced gastric cell damage in vivo and in vitro, Prostaglandins & Other Lipid Mediators, Vol.135, 36-44, 2018.
(要約)
Lysophosphatidic acid (LPA) is a bioactive phospholipid that induces diverse biological responses. Recently, we found that LPA ameliorates NSAIDs-induced gastric ulcer in mice. Here, we quantified LPA in 21 medicinal herbs used for treatment of gastrointestinal (GI) disorders. We found that half of them contained LPA at relatively high levels (40-240 μg/g) compared to soybean seed powder (4.6 μg/g), which we previously identified as an LPA-rich food. The LPA in peony (Paeonia lactiflora) root powder is highly concentrated in the lipid fraction that ameliorates indomethacin-induced gastric ulcer in mice. Synthetic 18:1 LPA, peony root LPA and peony root lipid enhanced prostaglandin E production in a gastric cancer cell line, MKN74 cells that express LPA abundantly. These materials also prevented indomethacin-induced cell death and stimulated the proliferation of MKN74 cells. We found that LPA was present in stomach fluids at 2.4 μM, which is an effective LPA concentration for inducing a cellular response in vitro. These results indicated that LPA is one of the active components of medicinal herbs for the treatment of GI disorder and that orally administered LPA-rich herbs may augment the protective actions of endogenous LPA on gastric mucosa.
Manami Inoue, Kazuhito Tsuboi, Yoko Okamoto, Mayumi Hidaka, Toru Uyama, Toshihiko Tsutsumi, Tamotsu Tanaka, Natsuo Ueda and Akira Tokumura : Peripheral tissue levels and molecular species compositions of N-acyl-phosphatidylethanolamine and its metabolites in mice lacking N-acyl-phosphatidylethanolamine-specific phospholipase D., The Journal of Biochemistry, Vol.162, No.6, 449-458, 2017.
(要約)
N-acylethanolamines (NAEs), a class of lipid mediators, are produced from N-acyl-phosphatidylethanolamine (NAPE) by several pathways, including the direct release by NAPE-specific phospholipase D (NAPE-PLD) or the multistep pathway via sn-glycero-3-phospho-N-acylethanolamine (Gp-NAE). Using liquid chromatography-tandem mass spectrometry, we compared peripheral tissue levels of NAPE, Gp-NAE and NAE in NAPE-PLD-deficient (NAPE-PLD-/-) and wild type (WT) mice. NAPE-PLD was suggested to play a major role in the NAPE degradation in heart, kidney, and liver, but not in jejunum, because the NAPE levels except jejunum were significantly higher in NAPE-PLD-/- mice than in WT mice. The deletion of NAPE-PLD failed to alter the NAE levels of these tissues, suggesting its limited role in the NAE production. The enzyme assays with tissue homogenates confirmed the presence of NAPE-PLD-independent pathways in these peripheral tissues. Gp-NAE species having an acyl moiety with 22 carbons and 6 double bonds was enriched in these peripheral tissues. As for sn-2 acyl species of NAPE, 18:2-acyl-containing NAPE species were predominant over 18:1-containing species in heart, liver, and jejunum. Our results show that both molecular species composition of NAPE, NAE and Gp-NAE and their dependencies on Napepld are different among the peripheral tissues, suggesting that each tissue has distinct metabolic pathways and these NAE-containing lipids play tissue-specific roles.
Kida Takashi, Itoh Aoi, Kimura Akari, Matsuoka Hisatsugu, Imai Hiroyuki, Kentaro Kogure, Akira Tokumura and Tamotsu Tanaka : Distribution of glycosylinositol phosphoceramide-specific phospholipase D activity in plants, The Journal of Biochemistry, Vol.161, No.2, 187-195, 2017.
(要約)
Previously, we detected an unknown sphingophospholipid in cabbage leaves and identified it as phytoceramide-1-phosphate (PC1P). We also found an enzyme activity that produces PC1P by glycosylinositol phosphoceramide (GIPC)-specific hydrolysis in cabbage leaves. To characterize the GIPC-specific phospholipase D (GIPC-PLD) activity, we investigated distributions of GIPC-PLD activity in 25 tissues of 10 plants. In most plants, the GIPC-PLD activity was the highest in roots. Young leaves of cabbage and Welsh onion had higher activities than corresponding aged outer leaves. The GIPC-PLD activities in leaves, stems and roots of mung bean were higher in the sprouting stage than in more mature stages. We also examined the distribution of substrate GIPC and product PC1P and found that GIPC was ubiquitously distributed at 50-280 nmol/g (wet wt) in tissues of plants, whereas PC1P was detectable (3-60 nmol/g wet wt.) only in tissues showing considerable GIPC-PLD activity. These results suggest a possibility that GIPC-PLD activity is involved in plant growth.
S Afroz, Teru Ikoma, Ayano Yagi, Kentaro Kogure, Akira Tokumura and Tamotsu Tanaka : Concentrated phosphatidic acid in cereal brans as potential protective agents against indomethacin-induced stomach ulcer., Journal of Agricultural and Food Chemistry, Vol.64, No.37, 6950-6957, 2016.
(要約)
One of complications associated with long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) is peptic ulcer. Recently, we found that orally administered phosphatidic acid (PA) ameliorated aspirin-induced stomach lesions in mice. In this study, we identified PA-rich food sources and examined the effects of the food materials on indomethacin-induced stomach ulcer. Among examined, buckwheat (Fagopyrum esculentum) bran contained the highest level of PA (188 mg/100 g). PA was the richest phospholipid (25%) in the lipid fraction of the buckwheat bran. Administration of the lipid extracts of buckwheat bran significantly ameliorated indomethacin-induced stomach lesions in mice. In contrast, wheat (Triticum durum) bran lipids (PA, 4%) and soybean (Glycine max) lipids (PA, 3%) were not associated with ameliorative effects. These results indicated that PA-rich lipids can be used as an effective supplement for prevention of NSAID-induced stomach ulcer.
Junpei Yamamoto, Midori Omura, Koichiro Tuchiya, Mayumi Hidaka, Akira Kuwahara, Minoru Irahara, Tamotsu Tanaka and Akira Tokumura : Preferable existence of polyunsaturated lysophosphatidic acids in human follicular fluid from patients programmed with in vitro fertilization., Prostaglandins & Other Lipid Mediators, Vol.126, 16-23, 2016.
(要約)
Lysophosphatidic acid (LPA) exerts diverse physiological effects on various types of animal cells, including reproductive cells, through its binding to six LPA receptors. We previously found that LPA promoted maturation of the nucleus and cytoplasm of mouse and hamster oocytes surrounded by cumulus cells in vitro. Using gas-liquid chromatography, we previously reported detection of several species of LPA by analyzing the fatty acid methyl esters derived from thin layer chromatography-purified LPA in lipid extract from incubated follicular fluids programmed with in vitro fertilization. In this study using liquid chromatography- tandem mass spectrometry, we directly detected high levels of linoleoyl, arachidonoyl, and docosahexaenoyl LPAs in human follicular fluid. This unique molecular species composition of LPA was suggested to be due to a balance between the low LPA-degrading activity and high LPA-producing activity of autotaxin in human follicular fluid. Our results suggest that polyunsaturated LPAs produced by autotaxin in human follicular fluid exert unknown physiological effects on cumulus cells.
Toshihiko Tsutsumi, Yoko Okamoto, Syougo Yamakawa, Cheng Bingjun, Akira Ishihara, Tamotsu Tanaka and Akira Tokumura : Reduced rat plasma lysophosphatidylglycerol or lysophosphatidic acid level as a biomarker of aristolochic acid-induced renal and adipose dysfunctions., Life Sciences, Vol.157, 208-216, 2016.
(要約)
Food products and diet pills containing aristolochic acid (AA) are responsible for a rapid progression of nephropathy associated with reduced body weight in human beings. In this study, we investigated the relationship of dietary NaCl and lysophospholipid (LPL) plasma levels to body weight gain in AA-treated rats. Male rats receiving a salt-deficient chow, normal salt chow or high salt chow were injected intraperitoneally daily with AA for 15days. Body weight, visceral fat mass, food intake, levels of LPL in plasma and its synthesized enzyme were investigated. Body weight gain, visceral fat mass and daily food intake were smaller in AA-treated rats than those of control rats, regardless of dietary salt concentration. AA treatment decreased plasma levels of major lysophosphatidic acid (LPA) molecular species in rats fed the normal or high-salt chow but not the salt-deficient chow, whereas both the plasma lysophospholipase D activity and kidney mRNA level of autotaxin of AA-treated rats fed chow with defined salt concentrations were lower than those of control rats. Plasma levels of major molecular species of lysophosphatidylglycerol (LPG) in AA-treated rat groups fed chow with defined salt concentrations were lower than those of control rats. Plasma levels of LPG and LPA seem to be relevant to the reduced body weight gain and fat mass due to AA treatment.
Ryouhei Yamashita, Yumika Tabata, Erina Iga, Michiyasu Nakao, Shigeki Sano, Kentaro Kogure, Akira Tokumura and Tamotsu Tanaka : Analysis of molecular species profiles of ceramide-1-phosphate and sphingomyelin using MALDI-TOF mass spectrometry, Lipids, Vol.51, No.2, 263-270, 2016.
(要約)
Ceramide-1-phosphate (C1P) is a potential signaling molecule that modulates various cellular functions in animals. It has been known that C1P with different N-acyl lengths induce biological responses differently. However, molecular species profiles of the C1P in animal tissues have not been extensively examined yet. Here, we developed a method for determination of the molecular species of a C1P using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with Phos-tag, a phosphate capture molecule. The amounts of total C1P in skin, brain, liver, kidney and small intestine of mice were determined to be 344, 151, 198, 96 and 90 pmol/g wet weight, respectively. We found a C1P species having an α-hydroxypalmitoyl residue (h-C1P, 44 pmol/g wet weight) in mouse skin. The h-C1P was detected only in the skin, and not other tissues of mice. The same analysis was applied to sphingomyelin after conversion of sphingomyelin to C1P by Streptomyces chromofuscus phospholipase D. We found that molecular species profiles of sphingomyelin in skin, kidney and small intestine of mice were similar to those of C1P in corresponding tissues. In contrast, molecular species profiles of sphingomyelin in liver and brain were quite different from those of C1P in these tissues, indicating selective synthesis or degradation of C1P in these tissues. The method described here will be useful for detection of changes in molecular species profiles of C1P and sphingomyelin.
Toshihiko Tsutsumi, Syougo Yamakawa, Akira Ishihara, Aimi Yamamoto, Tamotsu Tanaka and Akira Tokumura : Reduced kidney levels of lysophosphatidic acids in rats after chronic administration of aristolochic acid: Its possible protective role in renal fibrosis, Toxicology Reports, Vol.2, 121-129, 2015.
Yoshibumi Shimizu, Yoshiyuki Morikawa, Shinichi Okudaira, Shigenobu Kimoto, Tamotsu Tanaka, Junken Aoki and Akira Tokumura : Potentials of the circulating pruritogenic mediator lysophosphatidic acid in development of allergic skin inflammation in mice: role of blood cell-associated lysophospholipase D activity of autotaxin., The American Journal of Pathology, Vol.184, No.5, 1593-1603, 2014.
(要約)
Itching and infiltration of immune cells are important hallmarks of atopic dermatitis (AD). Although various studies have focused on peripheral mediator-mediated mechanisms, systemic mediator-mediated mechanisms are also important in the pathogenesis and development of AD. Herein, we found that intradermal injection of lysophosphatidic acid (LPA), a bioactive phospholipid, induces scratching responses by Institute of Cancer Research mice through LPA1 receptor- and opioid μ receptor-mediating mechanisms, indicating its potential as a pruritogen. The circulating level of LPA in Naruto Research Institute Otsuka Atrichia mice, a systemic AD model, with severe scratching was found to be higher than that of control BALB/c mice, probably because of the increased lysophospholipase D activity of autotaxin (ATX) in the blood (mainly membrane associated) rather than in plasma (soluble). Heparan sulfate proteoglycan was shown to be involved in the association of ATX with blood cells. The sequestration of ATX protein on the blood cells by heparan sulfate proteoglycan may accelerate the transport of LPA to the local apical surface of vascular endothelium with LPA receptors, promoting the hyperpermeability of venules and the pathological uptake of immune cells, aggravating lesion progression and itching in Naruto Research Institute Otsuka Atrichia mice.
Tamotsu Tanaka, Sachika Uozumi, Katsuya Morito, Takashi Osumi and Akira Tokumura : Metabolic conversion of C20 polymethylene-interrupted polyunsaturated fatty acids to essential fatty acids., Lipids, Vol.49, No.5, 423-429, 2014.
(要約)
Polymethylene-interrupted (PMI)-polyunsaturated fatty acids (PUFA) are fatty acids present largely in gymnosperm. Sciadonic acid (SciA, 20:3 Δ-5,11,14) and juniperonic acid (JA, 20:4 Δ-5,11,14,17) are typical C20 PMI-PUFA with an isolated double bond at Δ5. Previously, we found that SciA and JA are converted to linoleic acid (LNA) and α-linolenic acid (ΑLA), respectively. The conversion process includes chain-shortening step by peroxisomal β-oxidation for elimination a double bond at Δ5, and subsequent chain-elongation step in microsomes. In this study, we examined the substrate specificity of this metabolism in rodent and human cells. Supplementation of SciA, eicosadienoic acid (EDA, 20:2 Δ-11,14) or JA to CHO-K1 cells (wild type) induced an accumulation of LNA, LNA or ALA, respectively, in cellular lipids. These changes were not observed in the peroxisomes-deficient CHO cells, indicating involvement of peroxisomes in the metabolism. Two types of human cells (MKN74 and HepG2) also converted the C20 PMI-PUFA and EDA to the respective essential fatty acids. In contrast, no chain-shortened metabolite of pinolenic acid (18:3 Δ-5,9,12) was detected in any cell lines tested. From these results, C20 PMI-PUFA and EDA, but not C18 PMI-PUFA, are suggested as being effectively converted to essential fatty acids by the fatty acid remodeling system in rodent and human cells.
Yoshibumi Shimizu, Kazutoshi Murao, Tamotsu Tanaka, Yoshiaki Kubo and Akira Tokumura : Increased lysophospholipase D activity of autotaxin in sera of patients with atopic dermatitis., Journal of Dermatological Science, Vol.74, No.2, 162-165, 2014.
Tamotsu Tanaka, T. Kida, H. Imai, J. Morishige, R. Yamashita, H. Matsuoka, S. Uozumi, K. Satouchi, M. Nagano and Akira Tokumura : Identification of a sphingolipid-specific phospholipase D activity associated with the generation of phytoceramide-1-phosphate in cabbage leaves, The FEBS Journal, Vol.280, No.16, 3797-3809, 2013.
(要約)
The structure and biosynthetic route for an unidentified lipid (lipid X) detected by TLC of cabbage (Brassica oleracea) lipids was determined. Lipid X is a phospholipid that is resistant to mild alkali and detectable by MALDI-TOF MS as an adduct with Phos-tag, a phosphate-capture zinc complex. Various α-hydroxy fatty acids (16:0, 22:0, 24:0 and 24:1) were detected by GC-MS of fatty acid methyl esters prepared from lipid X. The deacyl derivative of lipid X was determined to be 4-hydroxysphingenine (dehydrophytosphingosine)-1-phosphate by MALDI-TOF MS with Phos-tag. From these results, lipid X was determined to be phytoceramide-1-phosphate (PC1P) with an α-hydroxy fatty acid. When cabbage homogenates were incubated, PC1P was formed, with a concomitant decrease in the amount of glycosylinositol phosphoceramide (GIPC). The formation of PC1P from GIPC was confirmed by treatment of purified cabbage GIPC with a membrane fraction of cabbage homogenates. Using a partially purified enzyme fraction, we found that the enzyme hydrolyzes GIPC specifically, but not glycerophospholipids and sphingomyelin. Arabidopsis thaliana also had this enzyme activity. From these results, we conclude that a previously uncharacterized phospholipase D activity that specifically hydrolyzes GIPC produces PC1P in brassicaceous plants.
Mari Kotosai, Sachiko Shimada, Mai Kanda, Namiko Matsuda, Keiko Sekido, Yoshibumi Shimizu, Akira Tokumura, Toshiyuki Nakamura, Kaeko Murota, Yoshichika Kawai and Junji Terao : Plasma HDL reduces nonesterified fatty acid hydroperoxides originating from oxidized LDL., Lipids, Vol.48, No.6, 569-578, 2013.
(要約)
The antioxidant property of plasma high-density lipoprotein (HDL) is thought to be involved in potential anti-atherogenic effects but the exact mechanism is not known. We aimed to reveal the contribution of HDL on the elimination of lipid hydroperoxides (LOOH) derived from oxidized low-density lipoprotein (LDL). Oxidized LDL prepared by copper ion-induced oxidation contained nonesterified fatty acid hydroperoxides (FFA-OOH) and lysophosphatidylcholine (lysoPtdCho), in addition to cholesteryl ester hydroperoxides (CE-OOH) and phosphatidylcholine hydroperoxides (PtdCho-OOH). A platelet-activating factor-acetylhydrolase (PAF-AH) inhibitor suppressed formation of FFA-OOH and lysoPtdCho in oxidized LDL. Among LOOH species, FFA-OOH was preferentially reduced by incubating oxidized LDL with HDL. HDL exhibited selective FFA-OOH reducing ability if it was mixed with a liposomal solution containing FFA-OOH, CE-OOH and PtdCho-OOH. Two-electron reduction of the hydroperoxy group to the hydroxy group was confirmed by the formation of 13-hydroxyoctadecadienoic acid from 13-hydroperoxyoctadecadienoic acid in HPLC analyses. This reducing effect was also found in apolipoprotein A-1 (apoA-1). FFA-OOH released from PtdCho-OOH due to PAF-AH activity in oxidized LDL undergo two-electron reduction by the reducing ability of apoA1 in HDL. This preferential reduction of FFA-OOH may participate in the mechanism of the antioxidant property of HDL.
Junichi Morishige, Yoshihiro Uto, Hitoshi Hori, Kiyoshi Satouchi, Tanihiro Yoshiomoto and Akira Tokumura : Lysophosphatidic Acid Produced by Hen Egg White Lysophospholipase D Induces Vascular Development on Extraembryonic Membranes, Lipids, Vol.48, No.3, 251-262, 2013.
(要約)
Lysophosphatidic acid (lysoPtdOH), a lysophospholipid mediator, exerts diverse physiological effects, including angiogenesis, through its specific G-protein-coupled receptors. Previously, we showed that unfertilized hen egg white contains polyunsaturated fatty acid-rich lysoPtdOH and lysophospholipase D (lysoPLD). Here, we examined whether lysoPtdOH was produced by lysoPLD in the presence and absence of a hen fertilized ovum and what the physiological role of lysoPtdOH in hen egg white is. Mass spectrometry showed that fertilized hen egg white contained about 8 μM lysoPtdOH before incubation with an ovum, mainly comprised of 18:1- (12.6 %), 18:2- (37.8 %) and 20:4-molecular species (41.5 %). In an early gestation period, the lysoPtdOH was increased up to 9.6 μM, concomitant with a decrease in the level of polyunsaturated lysophosphatidylcholine (lysoPtdCho). Moreover, lysoPtdOH-degrading activities were found in egg white and the vitelline membrane, showing that these enzymes control lysoPtdOH levels in egg white. In an egg yolk angiogenesis assay, two lysoPtdOH receptor antagonists, Ki16425 and N-palmitoyl serine phosphoric acid (NASP), inhibited blood vessel formation induced by exogenously added 18:1-lysoPtdOH and its precursor lysoPtdCho on the hen yolk sac. Ki16425 and NASP also inhibited blood vessel formation in the chorioallantoic membrane (CAM). Furthermore, the relatively higher levels of LPA1, LPA2, LPA4 and LPA6 mRNA were present in the yolk sac and CAM. These results suggest that lysoPtdOH produced from lysoPtdCho by the action of lysoPLD in hen egg white is involved in the formation of blood vessel networks through several lysoPtdOH receptors on various extraembryonic membranes, including the yolk sac membrane and CAM.
Tamotsu Tanaka, K. Morito, M. Kinoshita, M. Ohmoto, M. Urikura, K. Satouchi and Akira Tokumura : Orally administered phosphatidic acids and lysophosphatidic acids ameliorate aspirin-induced stomach mucosal injury in mice, Digestive Diseases and Sciences, Vol.58, No.4, 950-958, 2013.
(要約)
Recent investigations revealed that lysophosphatidic acid (LPA), a phospholipid with a growth factor-like activity, plays an important role in the integrity of the gastrointestinal tract epithelium. This paper attempts to clarify the effect of orally administered phosphatidic acid (PA) and LPA on aspirin-induced gastric lesions in mice. Phospholipids, a free fatty acid, a diacylglycerol and a triglyceride at 1 mM (5.7 μmol/kg body weight) or 0.1 mM were orally administered to mice 0.5 h before oral administration of aspirin (1.7 mmol/kg). The total length of lesions formed on the stomach wall was measured as a lesion index. Formation of LPA from PA in the mouse stomach was examined by in vitro (in stomach lavage fluid), ex vivo (in an isolated stomach) and in vivo (in the stomach of a living mouse) examinations of phospholipase activity. Palmitic acid, dioleoyl-glycerol, olive oil and lysophosphatidylcholine did not affect the aspirin-induced lesions. In contrast, phosphatidylcholine (1 mM), LPA (1 mM) and PA (0.1, 1 mM) significantly reduced the lesion index. Evidence for formation of LPA from PA in the stomach by gastric phospholipase A2 was obtained by in vitro, ex vivo and in vivo experiments. An LPA-specific receptor, LPA2, was found to be localized on the gastric surface-lining cells of mice. Pretreatment with PA-rich diets may prevent nonsteroidal anti-inflammatory drug-induced stomach ulcers.
Tohru Uyama, Natsuki Ikematsu, Manami Inoue, Naoki Shinohara, X-H Jin, Kazuhito Tsuboi, Tekuharu Tonai, Akira Tokumura and Natsuo Ueda : Generation of N-acylphosphatidylethanolamine by members of the phospholipase A/acyltransferase (PLA/AT) family, The Journal of Biological Chemistry, Vol.287, No.38, 31905-31919, 2012.
(要約)
Bioactive N-acylethanolamines (NAEs), including N-palmitoylethanolamine, N-oleoylethanolamine, and N-arachidonoylethanolamine (anandamide), are formed from membrane glycerophospholipids in animal tissues. The pathway is initiated by N-acylation of phosphatidylethanolamine to form N-acylphosphatidylethanolamine (NAPE). Despite the physiological importance of this reaction, the enzyme responsible, N-acyltransferase, remains molecularly uncharacterized. We recently demonstrated that all five members of the HRAS-like suppressor tumor family are phospholipid-metabolizing enzymes with N-acyltransferase activity and are renamed HRASLS1-5 as phospholipase A/acyltransferase (PLA/AT)-1-5. However, it was poorly understood whether these proteins were involved in the formation of NAPE in living cells. In the present studies, we first show that COS-7 cells transiently expressing recombinant PLA/AT-1, -2, -4, or -5, and HEK293 cells stably expressing PLA/AT-2 generated significant amounts of [(14)C]NAPE and [(14)C]NAE when cells were metabolically labeled with [(14)C]ethanolamine. Second, as analyzed by liquid chromatography-tandem mass spectrometry, the stable expression of PLA/AT-2 in cells remarkably increased endogenous levels of NAPEs and NAEs with various N-acyl species. Third, when NAPE-hydrolyzing phospholipase D was additionally expressed in PLA/AT-2-expressing cells, accumulating NAPE was efficiently converted to NAE. We also found that PLA/AT-2 was partly responsible for NAPE formation in HeLa cells that endogenously express PLA/AT-2. These results suggest that PLA/AT family proteins may produce NAPEs serving as precursors of bioactive NAEs in vivo.
(キーワード)
Acyltransferases / Animals / Base Sequence / COS Cells / Cercopithecus aethiops / Gene Expression Regulation / HEK293 Cells / HeLa Cells / Humans / Molecular Sequence Data / Multigene Family / Peroxisomes / Phosphatidylethanolamines / Phospholipase D / Phospholipases A / Phospholipids / RNA Interference / Tandem Mass Spectrometry
Tamotsu Tanaka, Ayaka Kassai, Mayumi Ohmoto, Katsuya Morito, Yoshiki Kashiwada, Yoshihisa Takaishi, Mai Urikura, Jun-ichi Morishige, Kiyoshi Satouchi and Akira Tokumura : Quantification of phosphatidic acid in foodstuffs using TLC-imaging technique, Journal of Agricultural and Food Chemistry, Vol.60, No.16, 4156-4161, 2012.
(要約)
Apical application of lysophosphatidic acid (LPA), a growth-factor-like phospholipid, was shown to prevent or restore gastrointestinal (GI) disorders, such as diarrhea and stomach ulcer, in experimental animals. Because LPA is formed from phosphatidic acid (PA) by the activity of digestive phospholipase A(2), PA is a potential component for dietary treatment of such GI disorders. Here, we quantified PA contained in 38 foodstuffs and 3 herbs by a thin-layer-chromatography-imaging technique. Vegetables belonging to Brassicaceae, such as cabbage leaves (700 nmol/g of wet weight) and Japanese radish leaves (570 nmol/g), contained higher amounts of PA than other foodstuffs. Amounts of PA in fruits, cereals, and starchy root vegetables were below 300 nmol/g. Animal foodstuffs contained low amounts of PA (<60 nmol/g). Interestingly, leaves of Mallotus japonicas, a Japanese edible herb used for treatment of stomach ulcer, had the highest PA (1410 nmol/g) among those examined. The data shown here will be useful for the development of dietary treatment for a damaged GI tract.
Akira Tokumura, Satoshi Taira, Masaki Kikuchi, Toshihiko Tsutsumi, Yoshibumi Shimizu and Michell A Watsky : Lysophospholipids and lysophospholipase D in rabbit aqueous humor following corneal injury., Prostaglandins & Other Lipid Mediators, Vol.97, No.3-4, 83-89, 2012.
(要約)
We previously found that lysophosphatidic acid (LPA)-like activity eliciting Cl(-) currents in Xenopus oocytes is increased in rabbit aqueous humor (AH) following corneal freeze wounds. The purpose of this study was to examine whether actual levels of LPA in AH from wounded eyes are higher than those from control eyes, and to determine the sources and enzymatic pathways of AH LPA in control and wounded conditions. Lysophospholipase D (lysoPLD) activity was measured by the enzymatic determination of choline following incubation of AH samples with exogenous lysophosphatidylcholines (LPCs). The molecular species compositions of LPA and LPC in fresh and incubated AH were determined by liquid chromatography-tandem mass spectrometry. A high, but similar activity of lysoPLD in the samples from both control and freeze-wounded eyes was detected. Its enzymatic properties resemble those of plasma lysoPLD, identified as autotaxin. Levels of LPCs, predominant substrates of lysoPLD in AH, were several times higher in the AH samples from injured eyes than those from the control eyes. Our results suggest that lysoPLD is constitutively released from corneal tissues and/or ciliary body into the AH, with no injury-induced increase in release following freeze-wounding. They also suggest that wound-induced increases in LPA-like biological activity are due to linoleoyl species-rich molecular composition in AH from wounded eyes. A possible mechanism of the altered molecular composition is an increase in the AH concentrations of LPCs, linoleoyl species of which are preferentially converted to corresponding unsaturated LPA by the constitutively active lysoPLD.
(キーワード)
Animals / Aqueous Humor / Chromatography, Liquid / Eye Injuries / Lysophospholipase / Lysophospholipids / Rabbits / Tandem Mass Spectrometry
Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are growth factor-like bioactive lipids having a phosphate monoester residue. Phos-tag can bind to them and be used both for purification and quantification. In a two-phase solvent system consisting of chloroform/methanol/water, addition of Phos-tag move LPA and S1P from a hydrophilic phase to a hydrophobic phase in the form of their Phos-tag complexes. Using this property, we developed a method for purification of LPA and S1P in biological materials by the phase separation technique. Advantages of use of Phos-tag for detection of LPA and S1P in MALDI-TOF MS are an increase in ionization efficiency and detection as a single-ion form. Homologues of LPA and S1P in natural samples can be quantified by MALDI-TOF MS by using internal standards.<br>
Masaki Ino, Yoshibumi Shimizu, Tamotsu Tanaka and Akira Tokumura : Alterations of plasma levels of lysophosphatidic acid in response to fasting of rats, Biological & Pharmaceutical Bulletin, Vol.35, No.11, 2059-2063, 2012.
(要約)
The aim of this study was to investigate the effect of fasting on in vivo plasma levels of lysophosphatidic acid (LPA), a physiologically important lysophospholipid mediator. We assayed to measure activities of an LPA-producing enzyme (lysophospholipase D) and LPA-degrading enzyme activities (lysophspholipase A, lipid phosphate phosphatase) in rat plasma or blood, by measuring choline, fatty acid and inorganic phosphate, respectively. Both LPA and its precursor lysophosphatidylcholine (LPC) were quantified by liquid chromatography-tandem mass spectrometry. Fasting of rats for 24 h decreased plasma concentrations of oleoyl-, linoleoyl-, arachidonoyl- and docosahexaenoyl-LPAs, but not palmitoyl- and stearoyl-LPAs, possibly due to decreased levels of corresponding LPCs in the plasma and elevated lipid phosphate phosphatase activity for LPAs in the blood. Our results indicate that the in vivo circulating levels of LPAs in rats are affected by fasting.
Kazuhito Tsuboi, Yasuo Okamoto, Natsuki Ikematsu, Manami Inoue, Yoshinobu Shimizu, Toru Uyama, Jun Wang, G Dale Deutsch, P Mattew Burns, M Nadine Ulloa, Akira Tokumura and Natsuo Ueda : Enzymatic formation of N-acylethanolamine from N-acylethanlamine plasmalogen through N-acylphosphatidylethanolamine-hydrolyzing phospholipase D-dependent and -independent pathways., Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1811, No.10, 568-577, 2011.
(要約)
Bioactive N-acylethanolamines include anandamide (an endocannabinoid), N-palmitoylethanolamine (an anti-inflammatory), and N-oleoylethanolamine (an anorexic). In the brain, these molecules are formed from N-acylphosphatidylethanolamines (NAPEs) by a specific phospholipase D, called NAPE-PLD, or through NAPE-PLD-independent multi-step pathways, as illustrated in the current study employing NAPE-PLD-deficient mice. Although N-acylethanolamine plasmalogen (1-alkenyl-2-acyl-glycero-3-phospho(N-acyl)ethanolamine, pNAPE) is presumably a major class of N-acylethanolamine phospholipids in the brain, its enzymatic conversion to N-acylethanolamines is poorly understood. In the present study, we focused on the formation of N-acylethanolamines from pNAPEs. While recombinant NAPE-PLD catalyzed direct release of N-palmitoylethanolamine from N-palmitoylethanolamine plasmalogen, the same reaction occurred in the brain homogenate of NAPE-PLD-deficient mice, suggesting that this reaction occurs through both the NAPE-PLD-dependent and -independent pathways. Liquid chromatography-mass spectrometry revealed a remarkable accumulation of 1-alkenyl-2-hydroxy-glycero-3-phospho(N-acyl)ethanolamines (lyso pNAPEs) in the brain of NAPE-PLD-deficient mice. We also found that brain homogenate formed N-palmitoylethanolamine, N-oleoylethanolamine, and anandamide from their corresponding lyso pNAPEs by a Mg(2+)-dependent "lysophospholipase D". Moreover, the brain levels of alkenyl-type lysophosphatidic acids, the other products from lyso pNAPEs by lysophospholipase D, also increased in NAPE-PLD-deficient mice. Glycerophosphodiesterase GDE1 can hydrolyze glycerophospho-N-acylethanolamines to N-acylethanolamines in the brain. In addition, we discovered that recombinant GDE1 has a weak activity to generate N-palmitoylethanolamine from its corresponding lyso pNAPE, suggesting that this enzyme is at least in part responsible for the lysophospholipase D activity. These results strongly suggest that brain tissue N-acylethanolamines, including anandamide, can be formed from N-acylated plasmalogen through an NAPE-PLD-independent pathway as well as by their direct release via NAPE-PLD.
Manami Inoue, Mika Adachi, Yoshibumi Shimizu, Toshihiko Tsutsumi and Akira Tokumura : Compariosns of lysophospholipid levles in rat feces with those in a standard chow, Journal of Agricultural and Food Chemistry, Vol.59, No.13, 7062-7067, 2011.
(要約)
Although lysophospholipids have attracted much attention due to their diverse physiological activities through their specific receptors, little is known about their metabolic fates in mammalian digestive systems after their ingestion as a minor food component. In this study, we analyzed five lysophospholipids in lipid extracts of a standard rat chow and feces of rats fed the chow by two-dimensional thin layer chromatography and liquid chromatography-tandem mass spectrometry. The most abundant lysophospholipid in the rat chow was lysophosphatidylcholine followed by lysophosphatidylethanolamine, lysophosphatidic acid (LPA), lysophosphatidylinositol and lysophosphatidylserine (LPS) in an increasing order, but their concentrations were very low in rat feces. Among the molecular species of LPS in the chow, only saturated species were detected in the feces in significant amounts. In addition, several molecular species of LPA remained in the feces in variable portions (saturated > monounsaturated > polyunsaturated). These results suggest that a portion of ingested LPA and LPS reach the rat large intestine, affecting physiological colon functions.
Saki Yoshino, Aya Hara, Hiroyuki Sakakibara, Kyuichi Kawabata, Akira Tokumura, Akari Ishisaka, Yoshichika Kawai and Junji Terao : Effect of quercetin and glucuronide metabolites on the monoamine oxidase-A reaction in mouse brain mitochondria., Nutrition, 2011.
(要約)
OBJECTIVE: Quercetin is a flavonoid found in plant foods and herbal medicines. It possesses antidepressant-like effects in forced swimming test-loaded rodents. We wanted to clarify the mechanism of action of dietary quercetin for exerting antidepressant-like effects. The effect of quercetin and its antioxidative metabolite quercetin 3-glucuronide (Q3GA) on the activity of mouse brain mitochondrial monoamine oxidase-A (MAO-A) was evaluated by measuring the deamination product of serotonin, 5-hydroxyindole acetaldehyde (5-HIAL). METHODS: An ultraviolet high-performance liquid chromatographic analysis was applied to measure the 5-HIAL generated by the reaction of MAO-A with serotonin. The inhibitory effect of quercetin and Q3GA on mitochondrial MAO-A activity was estimated by the content of 5-HIAL and hydrogen peroxide accompanied by the MAO-A reaction. RESULTS: Quercetin (but not Q3GA) decreased the production of 5-HIAL by MAO-A activity. Q3GA inhibited the generation of hydrogen peroxide from the MAO-A reaction with serotonin. A periodic forced swimming test in mice increased brain mitochondrial MAO-A activity. Brain mitochondrial MAO-A activity was decreased in mice administered quercetin for 7 d, but its effect was much weaker than that of the selective MAO-A inhibitor clorgyline. CONCLUSION: Quercetin is effective in the modulation of serotonergic activity by attenuating mitochondrial MAO-A activity in the brain. Its antioxidative metabolite Q3GA attenuates oxidative stress by interrupting the generation of hydrogen peroxide accompanying the MAO-A reaction.
MIka Adachi, Gou Horiuchi, Natsuki Ikematsu, Tamotsu Tanaka, Shigeki Sano, Kenji Fukuzawa and Akira Tokumura : Intragastrically administrered lysophospatidic acid protect against gastric ulcer in rats under water-immersion restraint stress, Digestive Diseases and Sciences, Vol.56, No.8, 2252-2261, 2011.
(要約)
Lysophosphatidic acid exerts important physiological effects on many types of animal cells through its specific binding to several G protein-coupled receptors. In particular, its potent wound-healing effect has attracted much attention. To determine whether lysophosphatidic acids in a foodstuff and Chinese medicine are effective in protecting against gastric ulcer, we subjected rats to water-immersion restraint stress. Three direct administrations of a solution of lysophosphatidic acid with a C18 fatty acyl group to the rat stomach in a concentration range of 0.001-0.1 mM resulted in a significant reduction in the number of gastric ulcers induced during water-immersion restraint stress, and the potencies were as follows: linoleoyl species=α-linolenoyl species>oleoyl species. Intragastric administrations of a solution of highly purified lysophosphatidic acid from soybean lecithin significantly protected against the stress-induced gastric ulcers at lower concentrations than partially purified lysophosphatidic acid from soybean lecithin did. In addition, administration of a decocted solution of antyu-san, and lysophosphatidic acid-rich Chinese medicine, to the stomach was more effective in protecting against stress-induced ulcer than decoctations of antyu-san lacking the corydalis tuber component that is rich in lysophosphatidic acid. These results clearly show that lysophosphatidic acid is the effective component of soybean lecithin and antyu-san in protection against stress-induced gastric ulcer in the rat model, and suggest that daily intake of lysophosphatidic acid-rich foods or Chinese medicines may be beneficial for prevention of stress-induced gastric ulcer in human subjects.
Akira Tokumura : Physiological significance of lysophosphatidic acids that act on the lumen side of mammalian lower digestive tracts, Journal of Health Science, Vol.57, No.2, 115-128, 2011.
(要約)
The lysophospholipid mediator family is attracting increased attention for its role in the maintenance of human health and the prevention and treatment of human chronic diseases. This review focuses on recent findings about lysophosphatidic acid (LPA) and its potential precursor phospholipids present in the apical lumen of mammalian lower digestive tracts. In particular, information on the protective effect of LPA toward rat gastric mucosa allowed us to better understand the mechanisms of the gastric ulcer-protective effect of a Chinese medicine and the beneficial effects of intake of vegetables and/or soybean lecithin in foods. These findings may indicate that LPA-rich foodstuffs promote human health by regulating the integral and functional homeostasis of the gastrointestinal mucosa, although the safety of LPA supplementation should be intensively investigated further.
Kaori Ueda, Masanori Yoshihara, Michiyasu Nakao, Tamotsu Tanaka, Shigeki Sano, Kenji Fukuzawa and Akira Tokumura : Evaluation of inhibitory actions of flavonols and related substances on lysophospholipase d activity of serum autotaxin by a convenient assay using a chromogenic substrate., Journal of Agricultural and Food Chemistry, Vol.58, No.10, 6053-6063, 2010.
(要約)
Overproduction of lysophosphatidic acid (LPA) by lysophospholipase D/autotaxin (lysoPLD/ATX) is postulated to be involved in the promotion of cancer and atherosclerosis. A lysoPLD inhibitor may be utilized to ameliorate the LPA-related pathological conditions. In this study, a new assay was devised to quantify p-nitrophenol from hydrolysis of chromogenic substrate by serum lysoPLD without tedious lipid extraction procedures. Flavonols, phenolic acids, free fatty acids, and N-acyltyrosines inhibited lysoPLD activity in a micromolar range. They were classified into competitive, noncompetitive, or mixed type inhibitors. The results show that the low hydrophobicity of an inhibitor is a critical factor in its preference for the binding to a noncatalytic binding site over a catalytic binding site. Considering its reported bioavailability and the low dependency of its inhibitory activity on serum dilution, flavonol is likely to be a more effective lysoPLD inhibitor in human blood circulation in vivo than the other inhibitors including LPA.
Saori Oka, Shunsuke Arai, Keizo Waku, Akira Tokumura and Takayuki Sugiura : Depolarization-induced rapid generation of 2-arachidonoylglycerol, an endogenous cannabinoid receptor ligand, in rat brain synaptosomes, The Journal of Biochemistry, Vol.141, No.5, 687-697, 2007.
(要約)
2-arachidonoylglycerol (2-AG) is an endogenous ligand for the cannabinoid receptors with a variety of potent biological activities. In this study, we first examined the effects of potassium-induced depolarization on the level of 2-AG in rat brain synaptosomes. We found that a significant amount of 2-AG was generated in the synaptosomes following depolarization. Notably, depolarization did not affect the levels of other molecular species of monoacylglycerols. Furthermore, the level of anandamide was very low and did not change markedly following depolarization. It thus appeared that the depolarization-induced accelerated generation is a unique feature of 2-AG. We obtained evidence that phospholipase C is involved in the generation of 2-AG in depolarized synaptosomes: U73122, a phospholipase C inhibitor, markedly reduced the depolarization-induced generation of 2-AG, and the level of diacylglycerol was rapidly elevated following depolarization. A significant amount of 2-AG was released from synaptosomes upon depolarization. Interestingly, treatment of the synaptosomes with SR141716A, a CB1 receptor antagonist, augmented the release of glutamate from depolarized synaptosomes. These results strongly suggest that the endogenous ligand for the cannabinoid receptors, i.e. 2-AG, generated through increased phospholipid metabolism upon depolarization, plays an important role in attenuating glutamate release from the synaptic terminals by acting on the CB1 receptor.
Akira Tokumura, Tetsuya Kume, Kenji Fukuzawa, Masahiro Tahara, Keiichi Tasaka, Junken Aoki, Hiroyuki Arai, Katsuhiko Yasuda and Hideyo Kanzaki : Peritoneal fluids from patients with certain gynecologic tumor contain elevated levels of bioactive lysophospholipase D activity, Life Sciences, Vol.80, No.18, 1641-1649, 2007.
(要約)
Levels of lysophosphatidic acid (LPA), an important phospholipid mediator, in serum and ascitic fluid from ovarian cancer patients were shown to be higher than those from healthy women and from patients with other type of cancer, respectively. Although LPA in human serum seems mainly to be generated by lysophospholipase D (lysoPLD), the source and pathway for LPA in the ascitic fluid remain still obscure. In this study, we examined whether lysoPLD activity producing bioactive LPA in human peritoneal fluid was significantly elevated under pathological statuses. Lysophospholipase D activity in human peritoneal fluids was measured by quantifying choline released from exogenous lysophosphatidylcholine on their incubation at 37 degrees C. We also compared the activity of lysoPLD in sera from patients with different gynecologic diseases. We found relatively high lysoPLD activity in peritoneal fluids from patients with ovarian cancer, dermoid cyst or mucinous cystadenoma, whereas there were no significant differences in the serum lysoPLD activity among clinical groups and healthy subjects. The lysoPLD in the peritoneal fluid was found to have similar substrate specificity and metal ion requirement to those of serum lysoPLD, that has been identified as autotaxin, a tumor cell-motility stimulating protein. Our results suggest that increased lysoPLD activity in peritoneal fluid from patients with certain gynecologic tumors might be relevant to its potential of tumor progression.
Junichi Morishige, Kanako Touchika, Tamotsu Tanaka, Kiyoshi Satouchi, Kenji Fukuzawa and Akira Tokumura : Production of bioactive lysophosphatidic acid by lysophospholipase D in hen egg white, Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1771, No.4, 491-499, 2007.
(要約)
Lysophosphatidic acid (LPA), a lysophospholipid mediator, is produced extracellularly by lysophospholipase D (lysoPLD) secreted in several animal body fluids including blood plasma. Previously, we reported that hen egg white contains polyunsaturated fatty acid-rich LPA. In this study, we examined whether lysoPLD is involved in the production of LPA in hen egg white. LysoPLD activity was measured by determining LPA and choline by mass spectrometric and enzyme-linked fluorometric analyses, respectively. LysoPLD increased with increased dilution of egg white, indicating that one or more components of egg white strongly inhibit its lysoPLD activity. This dilution-dependent increase in the lysoPLD activity was masked by co-incubation of the egg white with lysozyme, a major protein in hen egg white. Furthermore, addition of Zn(2+), Mn(2+), Ni(2+), or Co(2+) to diluted egg white altered preference patterns of lysoPLD toward choline-containing substrates. In particular, the egg white lysoPLD activity was greatly increased when Co(2+) was added. The cation-requirement of lysoPLD activity in hen egg white resembled that of plasma autotaxin (ATX)/lysoPLD. Western blot analysis revealed that egg white contained a protein that was immunostained with anti-ATX antibody. These results suggested that LPA in hen egg white is produced from lysophospholipids, especially LPC, by the action of ATX/lysoPLD, possibly originating from hen oviduct fluid.
Toshihiko Tsutsumi, Junichi Morishige, Kenji Fukuzawa and Akira Tokumura : Movememt of monoglyceride derived from hydrolysis of fluorescence-labeled lyso platelet-activating factor by lysophospholipase C through plasma membranes of porcinr kidney epithelial cell line LLC-PK1, Prostaglandins & Other Lipid Mediators, Vol.83, No.1-2, 33-41, 2007.
(要約)
To investigate the mechanisms of the release of lyso platelet-activating factor (PAF), an alkyl ether-linked lysophosphatidylcholine, from the kidney epithelial cell line LLC-PK1, the cell monolayer was incubated with a fluorescence-labeled lysoPAF analog, Bodipy-lysoPAF, on either the basolateral or apical side. The fluorescent lipids in the culture media mixed with or without bovine serum albumin at a final concentration of 2% were analyzed by thin layer chromatography. In both cases, two major bands, assignable to Bodipy-lysoPAF and Bodipy-monoglyceride (MG), were detected in the culture medium to which Bodipy-lysoPAF had been added, whereas the culture medium at the opposite side exhibited only the major band of Bodipy-MG. Our results suggest that lysoPAF was degraded by high ecto-lysophospholipase C activity. The possible physiological significance of this metabolic pathway is discussed.
Kenji Fukuzawa, Aya Fujisaki, Kaori Akai, Akira Tokumura, Junji Terao and Jansuz M. Gebicki : Measurement of phosphatidylcholine hydroperoxides in solution and in intact membranes by the ferric-xylenol orange assay, Analytical Biochemistry: Methods in the Biological Sciences, Vol.359, No.1, 18-25, 2006.
(要約)
Formation of a colored complex between ferric iron and xylenol orange (XO) has been used for the determination of hydroperoxides (FOX method). Original or modified FOX methods were performed on aqueous or organic solutions consisting of a single phase. However, for lipid peroxides in heterogeneous samples, such as biological materials, much of the lipid is sequestered in a separate phase. Organic solvent extraction of these lipids is often incomplete and may result in additional peroxidation during the extraction procedure. In this study, we applied the FOX assay for measurement of the membrane phosphatidylcholine hydroperoxides (PC-OOH) in separated phases. The presence of membranous egg yolk phosphatidylcholine (EYPC) in 60% MeOH shifted the broad peak at 560 nm of Fe(3+)-XO complex to 610 nm with a sharp peak associated with the increased intensity of the absorbance. The shift of the peak is useful to measure the unknown amounts of Fe(3+) because the uncomplexed XO considerably contributed to the absorbance of the peak at 560 nm but did not affect the absorbance at 610 nm. EYPC was required to form the membranes to shift the peak because the shift occurred in 60% MeOH but did not by the treatment with detergents or in 90% MeOH in which EYPC did not form the membranes. The molar absorption coefficient (epsilon 610) was 32,700 M(-1) cm(-1), which was about twice the molar absorption co efficient (epsilon 560) reported. We applied this method to the assay of PC-OOH prepared from EYPC and obtained the molar absorption coefficients (epsilon 610), which were 79,100 and 115,700 M(-1) cm(-1) in the presence and absence of BHT, respectively. This finding allows the determination of PC-OOH concentration even in chemically complex systems.
Junko Komatsu, Shuji Yamano, Akira Kuwahara, Akira Tokumura and Minoru Irahara : The signalling pathways linking to lysophosphatidic acid-promoted meiotic maturation, Life Sciences, Vol.79, No.5, 506-511, 2006.
(要約)
The signaling pathways linking to lysophosphatidic acid-promoted meiotic maturation in mice were studied. When mouse oocyte-cumulus cells complexes were cultured with 10(-5) M lysophosphatidic acid (the LPA group), the rate of oocyte nuclear maturation was significantly increased. Additions of pertussis toxin, genistein, U73122, Ro320432, PD98059 or SB203580 significantly suppressed the increase in lysophosphatidic acid-stimulated nuclear maturation rate. These results suggested that Gi/o-coupled lysophosphatidic acid receptors activate phosphatidylinositol-specific phospholipase C, and result in ERK and MAP kinase activation, which is triggered by diacylglycerol-dependent protein kinase C. When intracellular cAMP concentrations of oocytes in the LPA and control groups were measured using the acetylation assay, the intracellular cAMP concentration of an oocyte in the LPA group was significantly lower than the control oocyte (0.117+/-0.04 fmol/oocyte vs. 0.176+/-0.036 fmol/oocyte, p<0.05). In conclusion, our results suggested that lysophosphatidic acid stimulates phospholipase C through a Gi-protein linked receptor on the surface of mouse cumulus cells and stimulates both extracellular signal-regulated kinase and p38 mitogen-activated kinase, resulting in the closure or loose of gap junctions between cumulus cells and the oocyte. The resultant early decrease of oocyte cAMP levels may promote nuclear maturation of mouse oocytes in vitro.
Kentaro Kogure, Sachie Manabe, Ichiro Suzuki, Akira Tokumura and Kenji Fukuzawa : Cytotoxicity of α-tocopheryl succinate, malonate and oxalate in normal and cancer cells in vitro and their anti-cancer effects on mouse melanoma in vivo, Journal of Nutritional Science and Vitaminology, Vol.51, No.6, 392-397, 2005.
(要約)
alpha-Tocopheryl succinate (TS), which is known to induce apoptosis selectively in cancer cells, has attracted attention as a chemotherapeutic agent. Recently, we found that alpha-tocopheryl malonate (TM) and alpha-tocopheryl oxalate (TO), among the alpha-tocopheryl esters tested, have high apoptogenic activity as well as TS. In this study, we investigated the characteristics of their cytotoxicity on normal cells and cancer cells in vitro, and their anti-cancer effects on mice inoculated with melanoma B16-F1 cells in vivo. The order of in vitro cytotoxicity was TO > or = TM > TS in all cell lines examined. Addition of exogenous superoxide dismutase (SOD) and the antioxidant N-acetyl cysteine (NAC) inhibited TS- and TM- but not TO-induced cell deaths. A selective cytotoxic effect on cancer cells was observed with TS but not with TM or TO. c-Jun N-terminal kinase (JNK) inhibitor II prevented cell death induced by TS but did not prevent cell deaths induced either by TM or TO. Intravenous administration of vesiculated TS and TM to mice inoculated with melanoma B16-F1 cells prevented tumor growth and enhanced the mean survival time, but TO administration killed the mice due to its acute high toxicity. From these results, we discussed the characteristics of their selective cytotoxicity toward tumor cells in vitro and anti-cancer effects in vivo.
Yuko Fujiwara, Vineet Sardar, Akira Tokumura, Daniel Baker, Kimiko Murakami-Murofushi, Abby Parrill and Gabor Tigyi : Identification of residues responsible for ligand recognition and regioisomeric selectivity of lysophosphatidic acid receptors expressed in mammalian cells., The Journal of Biological Chemistry, Vol.280, No.41, 35038-35050, 2005.
(要約)
The endothelial differentiation gene family encodes three highly homologous G protein-coupled receptors for lysophosphatidic acid (LPA). Based on baculoviral overexpression studies, differences have been proposed in the structure-activity relationship (SAR) of these receptors. We have compared the SAR of the individual receptors either overexpressed transiently at high or at lower levels following stable transfection in LPA-nonresponsive RH7777 cells. The SAR in transfected RH7777 cells was markedly different from that described in insect cells. The LPA(3) receptor has been proposed to be selectively activated by unsaturated LPA species and shows a strong preference for sn-2 versus the sn-1 acyl-LPA regioisomer. Because of the short half-life of sn-2 LPA due to acyl migration under some conditions, we have synthesized acyl migration-resistant analogs using an acetyl group in place of the free hydroxyl group in order to evaluate LPA receptor SAR. Only LPA(1) and LPA(2) showed regioisomeric preference and only for the 18:2 fatty acyl-stabilized LPA sn-1 regioisomer. To identify residues involved in ligand recognition of LPA(3), we developed and validated computational models of LPA(3) complexes with the analogs studied. The models revealed that Arg-3.28 and Gln-3.29 conserved within the LPA-selective endothelial differentiation gene receptors and the more variable Lys-7.35 and Arg-5.38 of LPA(3) form critical interactions with the polar headgroup of LPA. The models identified Leu-2.60 and Val-7.39 of LPA(3) underlying the regioisomer-selective interaction with the acetyl group of the stabilized regioisomers. Mutation of Leu-2.60 to alanine selectively increased the EC(50) of the sn-2 acetyl-LPA regioisomers, whereas alanine replacement of Val-7.39 profoundly affected both regioisomers.
Koichiro Tsuchiya, Kaori Akai, Akira Tokumura, Shinji Abe, Toshiaki Tamaki, Yoshiharu Takiguchi and Kenji Fukuzawa : Oxygen radical photo-induced by ferric nitrilotriacetate complex, Biochimica et Biophysica Acta (BBA) - General Subjects, Vol.1725, No.1, 111-119, 2005.
(要約)
This study examined the photo-induced generation of reactive oxygen species (ROS) by the carcinogenic iron(III)-NTA complex. Iron(III)-NTA complex (1:1) has three conformations (type (a) in acidic conditions of pH 1-6, type (n) in neutral conditions of pH 3-9, and type (b) in basic conditions of pH 7-10) with two pK(a) values (pK(a1) approximately 4, pK(a2) approximately 8). The iron(III)-NTA complex was reduced to iron(II) under cool-white fluorescent light without the presence of any reducing agent, and the reduction rates of the three conformations of iron(III)-NTA were in the order type (a)>type (n)>type (b) as reported previously (Akai K. et al., Free Radic. Res. 38, 951-962, 2004). ROS generation was investigated by electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique. Apparent EPR signals attributed to PBN/*(13)CH(3) and PBN/*OCH(3) spin adducts were observed after incubation of the iron(III)-NTA complex was mixed with alpha-phenyl-tert-butylnitrone (PBN) and (13)C-DMSO in an aerobic condition. The addition of catalase effectively attenuated the PBN adducts, but superoxide dismutase enhanced them. Taken together, these results indicate that the iron(III)-NTA complex is spontaneously reduced to the iron(II)-NTA complex by light under acidic to neutral pH, and in turn transfers an electron to molecular oxygen to form ROS.
Kenji Fukuzawa, Yasuaki Saitoh, Kaori Akai, Kentaro Kogure, Satoru Ueno, Akira Tokumura, Masaki Otagiri and Akira Shibata : Antioxidant effect of bovine serum albumin on membrane lipid peroxidation induced by iron chelate and superoxide, Biochimica et Biophysica Acta (BBA) - Biomembranes, Vol.1668, No.1, 145-155, 2005.
(要約)
Albumin is supposed to be the major antioxidant circulating in blood. This study examined the prevention of membrane lipid peroxidation by bovine serum albumin (BSA). Lipid peroxidation was induced by the exposing of enzymatically generated superoxide radicals to egg yolk phosphatidylcholine liposomes incorporating lipids with different charges in the presence of chelated iron catalysts. We used three kinds of Fe3+-chelates, which initiated reactions that were dependent on membrane charge: Fe3+-EDTA and Fe3+-EGTA catalyzed peroxidation in positively and negatively charged liposomes, respectively, and Fe3+-NTA, a renal carcinogen, catalyzed the reaction in liposomes of either charge. Fe3+-chelates initiated more lipid peroxidation in liposomes with increased zeta potentials, followed by an increase of their availability for the initiation of the reaction at the membrane surface. BSA inhibits lipid peroxidation by preventing the interaction of iron chelate with membranes, followed by a decrease of its availability in a charge-dependent manner depending on the iron-chelate concentration: one is accompanied and the other is unaccompanied by a change in the membrane charge. The inhibitory effect of BSA in the former at high concentrations of iron chelate would be attributed to its electrostatic binding with oppositely charged membranes. The inhibitory effect in the latter at low concentrations of iron chelate would be caused by BSA binding with iron chelates and keeping them away from membrane surface where lipid peroxidation is initiated. Although these results warrant further in vivo investigation, it was concluded that BSA inhibits membrane lipid peroxidation by decreasing the availability of iron for the initiation of membrane lipid peroxidation, in addition to trapping active oxygens and free radicals.
Kentaro Kogure, Aiko Yamauchi, Akira Tokumura, Kyoko Kondou, Naonobu Tanaka, Yoshihisa Takaishi and Kenji Fukuzawa : Novel antioxidants isolated from plants of the genera Ferula, Inula, Prangos and Rheum collected in Uzbekistan, Phytomedicine, Vol.11, No.7-8, 645-651, 2004.
(要約)
We examined the effects of 48 compounds isolated from Ferula pallida, F. penninervis, Inula macrophylla, Prangos pabularia, P. tschimganica and Rheum maximowiczii collected in Uzbekistan on ADP/Fe2+-induced lipid peroxidation of egg yolk phosphatidylcholine liposomes. Of those compounds, 23 inhibited ADP/Fe2+-induced lipid peroxidation and nine showed especially strong inhibition of lipid peroxidation. Most compounds that inhibited peroxidation scavenged the 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical, indicating that the inhibition was due to radical scavenging. However, some compounds did not scavenge DPPH but inhibited lipid peroxidation significantly, suggesting that their inhibitory effect was not due to radical scavenging but to some other mechanism, such as prevention of Fe2+ function. Thus, we found various new antioxidants, some of which had a unique mechanism of action, in Ferula, Inula, Prangos and Rheum plants collected in Uzbekistan as seeds used in medicine.
Tamotsu Tanaka, Hideki Tsutsui, Kaoru Hirano, Tohru Koike, Akira Tokumura and Kiyoshi Satouchi : Quantitative analysis of lysophosphatidic acid by time-of-flight mass spectrometry using a phosphate-capture molecule, Journal of Lipid Research, Vol.45, No.11, 2145-2150, 2004.
(要約)
Lysophosphatidic acid (LPA) is a lipid mediator that may play an important role in wound healing, embryonic development, and progression of cancer. Here, we report a procedure for the quantification of LPA by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The method is based on a characteristic mass shift with total charge change (from -2 to +1) of the phosphate species due to 1:1 complexation of LPA(2-) with a dinuclear zinc (II) complex [1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-olato dizinc(II) complex; Zn(2)L(3+)] at physiological pH. The monocationic complex [LPA(2-)-Zn(2)L(3+)](+) was detected in the positive mode, in which no other signal of cation adducts of LPA(2-) was observed. The detection limit of 18:1 LPA by this method was 0.1 pmol on a sample plate. The intensity ratio of [LPA(2-)-Zn(2)L(3+)](+) against an internal standard [17:0 LPA(2-)-Zn(2)L(3+)](+) increased linearly with their molar ratio. Based on the relative intensities of complex ions, we determined the amounts of LPA homologs in an egg white by this method; the results obtained were in good agreement with those by gas liquid chromatography. This sensitive and convenient procedure for LPA-specific detection is useful for the quantification of LPA homologs occurring in biological materials.
Koji Nakagawa, Shuji Yamano, Masaharu Kamada, Masahiko Maegawa, Akira Tokumura, Minoru Irahara and Hidekazu Saito : Sperm-immobilizing antibodies suppress an increase in the plasma membrane fluidity of human spermatozoa, Fertility and Sterility, Vol.82, No.Supplement 3, 1054-1058, 2004.
(要約)
To clarify the mechanism by which capacitation is blocked by sperm-immobilizing antibodies, changes in the plasma membrane fluidity of human spermatozoa exposed to sperm-immobilizing antibodies were evaluated. In vitro cell culture study using human spermatozoa. Department of Obstetrics and Gynecology, School of Medicine, The University of Tokushima. Semen samples were obtained from four healthy, fertile volunteers. The internalization of [3H]lyso-platelet activating factor (lyso-PAF) across the plasma membranes of human spermatozoa, which were exposed to sperm-immobilizing antibodies (antisperm group) or not exposed (control group), was measured at 20 and 60 minutes after the addition of a phospholipid probe using the modified albumin-back extraction method. The percentage of internalization of [3H]lyso-PAF across the plasma membrane of human spermatozoa. Although the percentages of internalization of [3H]lyso-PAF (mean +/- SE) in the antisperm and control groups 20 minutes after addition of [3H]lyso-PAF were not significantly different (6.6% +/- 1.5% and 9.2% +/- 2.1%, respectively), at 60 minutes after the addition, the percentage in the antisperm group (9.0% +/- 1.3%) was significantly lower than that in the control group (13.4% +/- 1.3%). This inhibitory effect was diminished when spermatozoa exposed to sperm-immobilizing antibodies were incubated in an antibody-free medium. Sperm-immobilizing antibodies suppress the increase in internalization of an alkyl ester lysophospholipid probe in plasma membranes of human spermatozoa, and this inhibitory effect is reversible. Therefore, sperm-immobilizing antibodies suppress the fluidity of the plasma membranes of human spermatozoa, thus blocking capacitation.
Kentaro Kogure, Susumu Hama, Mayumi Kisaki, Hideaki Takemasa, Akira Tokumura, Ichiro Suzuki and Kenji Fukuzawa : Structural characteristic of terminal dicarboxyric moiety required for apoptogenic activity of α-Tocopheryl esters., Biochimica et Biophysica Acta (BBA) - General Subjects, Vol.1672, No.2, 93-99, 2004.
(要約)
alpha-Tocopheryl succinate (TS) is known to induce apoptosis in various cells and has attracted attention as a chemotherapeutic agent. Recently, we reported the structural significance of the terminal dicarboxylic moiety for the action of TS [J. Nutr. Sci. Vitaminol. 49 (2003) 310-314]. In this study, to determine details of the relationship between the structure and the function of the terminal ester moiety of alpha-tocopherol (alpha-T), we synthesized four novel esters, alpha-tocopheryl oxalate (TO), alpha-tocopheryl malonate (TM), alpha-tocopheryl pimelate (TP) and alpha-tocopheryl succinate ethyl ester (TSE), and compared their apoptogenic activities with those of TS, alpha-T, gamma-tocopherol (gamma-T) and two commercially available alpha-T derivatives, alpha-tocopheryl nicotinate (TN) and alpha-tocopheryl acetate (TA), in vascular smooth muscle cells and a mouse breast cancer cell line C127I. TO and TM in addition to TS, but not the others, induced apoptosis in both cells. Particularly, TO was the most potent of all alpha-T derivatives used. The addition of exogenous superoxide dismutase (SOD) significantly prevented the apoptosis induced by TM as well as that by TS as reported previously, but did not affect TO-induced apoptosis. These results suggest that O(2)(-) generated exogenously participates in TM-induced apoptosis but not in TO-induced apoptosis. The difference in their apoptotic effects is attributed to structural properties of the terminal dicarboxylic moiety, which has an inflexible plane conformation in TO, while it is highly flexible in TM and TS.
Shuji Yamano, Jun Yamazaki, Minoru Irahara, Akira Tokumura, Koji Nakagawa and Hidekazu Saito : Human spermatozoa capacitated with progesterone or a long incubation show accelerated internalization by an alkyl ether lysophospholipid, Fertility and Sterility, Vol.81, No.3, 605-610, 2004.
(要約)
To evaluate changes that occur in sperm plasma membranes during capacitation, the internalization of [(3)H]lyso-platelet activating factor ([(3)H]lyso-PAF) across the plasma membrane of human spermatozoa was measured as a function of incubation time or exposure to progesterone (P). In vitro cell culture study using human spermatozoa. Department of Obstetrics and Gynecology, School of Medicine, the University of Tokushima, Japan. Semen were obtained from three fertile healthy volunteers. The internalization of [(3)H]lyso-PAF across the plasma membranes of human spermatozoa that were incubated for an extended period or exposed to P was measured at 5, 20, 60, and 120 minutes after the addition of the phospholipid probe using the modified albumin back-exchange method. The percentage of capacitated and acrosome-reacted sperm and the proportion of internalization of lyso-PAF across the plasma membrane. A 6-hour incubation period significantly increased the percentage of capacitated spermatozoa and the proportion of internalization of [(3)H]lyso-PAF across the plasma membrane of human spermatozoa compared with controls (capacitated spermatozoa, 20.3 +/- 10.6% vs. 8.5 +/- 1.8%; internalization 120 minutes after the addition of the phospholipid probe, 25.6 +/- 2.5% vs. 11.6 +/- 3.0%) (mean +/- SEM). Exposure to P significantly increased the percentage of capacitated spermatozoa compared with controls (19.6 +/- 6.8% vs. 11.0 +/- 2.4%) and also significantly accelerated the internalization of [(3)H]lyso-PAF compared with controls (internalization 120 minutes after the addition of the phospholipid probe, 26.2 +/- 1.8% vs. 21.4 +/- 1.1%). The administration of P or a long incubation increased the proportion of internalization and consequently induced capacitation in human spermatozoa.
Toshihiko Tsutsumi, Akira Tokumura, Masaya Yamaguchi, Shikifumi Kitazawa and Yusuke Tanigawara : Phorbol Myristate Acetate Stimulates Degradation of a Structural Analogue of Platelet-Activating Factor to a Neutral Lipid in Human Leukemic K562 Cells: Relevance to the Release of Lipids, Biological & Pharmaceutical Bulletin, Vol.27, No.1, 24-28, 2004.
(要約)
In our attempt to investigate the mechanism of the release of platelet-activating factor (PAF) from cells, the erythroleukemic cell line K562 was preloaded with a radiolabeled PAF analogue having an ethylcarbamyl residue, 1-O-octadecyl-2-O-ethylcarbamyl-sn-glycero-3-phosphocholine (ethylcarbamyl-PAF), that is resistant to the hydrolytic action of PAF acetylhydrolase. Its extracellular release was monitored using an albumin back-extraction method, and its metabolic degradation was analyzed by TLC. Phorbol myristate acetate (PMA) was found to stimulate the release of two radioactive lipids, ethylcarbamyl-PAF itself and its metabolite, 1-O-octadecyl-2-ethylcarbamyl-sn-glycerol, whereas only ethylcarbamyl-PAF was released from the resting cells. The increased release of radioactive lipids in PMA-stimulated cells was suggested to be due to stimulated degradation of intracellular ethylcarbamyl-PAF into the cell-permeable metabolite. Thus K562 cells have much less capacity to release intact PAF-like lipid in comparison with its high ability to uptake exogenously added PAF analogues previously described by us and others.
Kentaro Kogure, Sawa Nakashima, Akiko Tsuchie, Akira Tokumura and Kenji Fukuzawa : Temporary membrane distortion of vascular smooth muscle cells is responsible for their apoptosis induced by platelet-activating factor-like oxidized phospholipids and thair degradation product lysophosphatidylcholine., Chemistry and Physics of Lipids, Vol.126, No.1, 29-38, 2003.
(要約)
To obtain information about the mechanism of apoptosis induced by oxidized low density lipoproteins (oxLDL) in atherosclerotic plaques, we examined the effects of lysophosphatidylcholine (LPC) and platelet-activating factor (PAF)-like lipids (PAF-LL), which can be derived from oxLDL, on rat vascular smooth muscle cells (VSMC). All the lipids with different structures examined induced apoptosis of VSMC, so we studied the mechanism of induction of apoptosis by LPC. LPC-induced apoptosis was inhibited by alpha-tocopherol (alpha-T) and cholesterol (Chol), but not by other antioxidants such as palmitoyl ascorbic acid and PAF receptor antagonist. The cells temporarily became spherical and highly permeable before induction of apoptosis, and their change in shape was prevented by alpha-T and Chol. From these results, we suggest that the apoptosis induced by oxLDL-derived phospholipids in VSMC is caused by temporary membrane distortion, not through specific receptors.
Kentaro Kogure, Susumu Hama, Satoru GOTO, Tatsuo Munakata, Akira Tokumura and Kenji Fukuzawa : alpha-Tocopheryl succinate activates protein kinase C in cellular and cell-free systems, Journal of Nutritional Science and Vitaminology, Vol.49, No.5, 310-314, 2003.
(要約)
The effect of alpha-tocopheryl succinate (TS) on protein kinase C (PKC) activity was examined. TS increased the auto-phosphorylation of PKC in vascular smooth muscle cells. Furthermore TS activated isolated PKC-like phorbol 12-myristate 13-acetate (PMA), although it was required at a significantly higher concentration than PMA for PKC activation. Molecular superimposition of the TS on PMA by computation suggested that TS took an active binding conformation to the PKC-like PMA, but that the conformational population was about 1/1.000. Consequently, we conclude that TS interacts directly with PKC, and activates it by taking an active conformation like PMA.
Saori Oka, Akiko Tsuchie, Akira Tokumura, Mayumi Muramatsu, Yoshitomo Suhara, Hiroaki Takayama, Keizo Waku and Takayuki Sugiura : Ether-linked analog of 2-arachidonoylglycerol (noladin ether) was not detected in the brains of various mammalian species, Journal of Neurochemistry, Vol.85, No.6, 1374-1381, 2003.
(要約)
2-Eicosa-5',8',11',14'-tetraenylglycerol (2-AG ether, HU310, noladin ether) is a metabolically stable ether-linked analogue of 2-arachidonoylglycerol (2-AG), an endogenous cannabinoid receptor ligand. 2-AG ether has been used as a valuable experimental tool by a number of investigators. Recently, several groups reported that 2-AG ether is present in mammalian brains. We examined in detail whether 2-AG ether actually exists in the brains of various mammalian species. We found that 2-AG ether is not present, at least in an appreciable amount, in the rat brain by gas chromatography-mass spectrometry analysis and fluorometric high performance liquid chromatography analysis. The level of 2-AG ether in the rat brain was below 0.2 pmol/g brain, if at all present. Similar results were obtained for the mouse brain, hamster brain, guinea-pig brain and pig brain. The fact that 2-AG ether was not detected in the brains of various mammalian species is consistent with the fact that an ether bond is formed through enzymatic replacement of the fatty acyl moiety of 1-acyl dihydroxyacetone phosphate by a fatty alcohol, the resultant 1-O-alkyl dihydroxyacetone phosphate being a common intermediate of the biosynthesis of ether-linked lipids in mammalian tissues. It is rather questionable whether 2-AG ether is present in appreciable amounts in the brain and acts as an 'endogenous' cannabinoid receptor ligand.
Kentaro Kogure, Sachie Manabe, Susumu Hama, Akira Tokumura and Kenji Fukuzawa : Potentiation of anti-cancer effect by intravenous administration of vesiculated α-tocopheryl hemisuccinate on mouse melanoma in vivo., Cancer Letters, Vol.192, No.1, 19-24, 2003.
(要約)
We examined the effect of alpha-tocopheryl hemisuccinate (TS) on the growth of mouse melanoma cells B16-F1 inoculated on the back of hairless mice by two administration procedures of TS, i.p. administration of TS dissolved with dimethyl sulfoxide (TS i.p.) and i.v. administration of TS vesicles (TS-vesicle i.v.). TS i.p. significantly prevented the tumor growth of only half the mice in the group. However, TS-vesicle i.v. almost completely inhibited the tumor growth of all mice. Furthermore, the mean survival of the TS-vesicle i.v. group was 1.4-fold those of the control and TS i.p. groups.
Kentaro Kogure, Susumu Hama, Sachie Manabe, Akira Tokumura and Kenji Fukuzawa : High cytotoxicity of α-tocopheryl hemisuccinate to cancer cells is due to failure of their antioxidative defense systems., Cancer Letters, Vol.186, No.2, 151-156, 2002.
(要約)
Alpha-tocopheryl hemisuccinate (TS) has been reported to induce apoptosis in various cells, and to show higher toxicity to cancer cells than to normal cells. In this study, although TS induced apoptosis in both a mouse breast normal cell line NMuMG and a mouse breast cancer cell line C127I, the latter were more susceptible to TS. TS-induced apoptosis in C127I was inhibited by superoxide dismutase, alpha-tocopherol and butylated hydroxyanisol. From these results, superoxide (O(2)(-)) itself and reactive oxygen species derived from O(2)(-) and/or free radicals are assumed to be associated with TS toxicity, and the high toxicity of TS to cancer cells is suggested to be due to failure of their antioxidative defense systems.
Akira Tokumura, Yumi Kanaya, Maki Miyake, Shuji Yamano, Minoru Irahara and Kenji Fukuzawa : Increased Production of Bioactive Lysophosphatidic Acid by Serum Lysophospholipase D in Human Pregnancy, Biology of Reproduction, Vol.67, No.5, 1386-1392, 2002.
(要約)
Lysophosphatidic acid (LPA) is a prototype of the lysophospholipid mediator family and has multiple effects in the female reproductive system. Although several metabolic routes have been reported for intracellular formation of LPA, a unique route involving lysophospholipase D, an extracellular enzyme that produces LPA in blood and body fluids, is particularly intriguing for its agonistic role. In this study, using an assay with radioactive palmitoyl-lysophosphatidylcholine, we found that lysophospholipase D activity producing palmitoyl-LPA in human serum gradually increased during pregnancy. Elevated activity of lysophospholipase D was not caused by changes in levels of their precursors, lysophosphatidylcholines, in nonpregnant women or in pregnant women at different gestational periods. With increasing length of gestation, the elevated activity in pregnant women was found to produce increasing proportions of LPA with a palmitoyl group versus other LPAs. These results suggest that LPA formed by increased activity of lysophospholipase D in blood might participate in maintenance of pregnancy.
Akira Tokumura, Eiji Majima, Yuko Kariya, Kyoko Tominaga, Kentarou Kogure, KAtuhiko Yasuda and Kenji Fukuzawa : Identification of human plasma lysophospholipase D, a lysophosphatidic acid-producing enzyme, as autotaxin, a multifunctional phosphodiesterase, The Journal of Biological Chemistry, Vol.277, No.42, 39436-39442, 2002.
(要約)
We purified human plasma lysophospholipase D that produces physiologically active lysophosphatidic acid and showed that it is a soluble form of autotaxin, an ecto-nucleotide pyrophosphatase/phosphodiesterase, originally found as a tumor cell motility-stimulating factor. Its lower K(m) value for a lysophosphatidylcholine than that for a synthetic substrate of nucleotide suggests that lysophosphatidylcholine is a more likely physiological substrate for autotaxin and that its predicted physiological and pathophysiological functions could be mediated by its activity to produce lysophosphate acid, an intercellular mediator. Recombinant autotaxin was found to have lysophospholipase D activity; its substrate specificity and metal ion requirement were the same as those of the purified plasma enzyme. The activity of lysophospholipase D for exogenous lysophosphatidylcholine in human serum was found to increase in normal pregnant women at the third trimester of pregnancy and to a higher extent in patients in threatened preterm delivery, suggesting its roles in induction of parturition.
Takayuki Sugiura, Shinji Nakane, Seishi Kishimoto, keizo Waku, Yasuko Yoshioka and Akira Tokumura : Lysophosphatidic acid, a growth factor-like lipid, in the saliva, Journal of Lipid Research, Vol.43, No.12, 2049-2055, 2002.
(要約)
Lysophosphatidic acid is a multifunctional phospholipid mediator and elicits a variety of biological responses in vitro and in vivo. Evidence is accumulating that lysophosphatidic acid plays important physiological roles in diverse mammalian tissues and cells. In the present study, we first examined whether lysophosphatidic acid is present in human saliva. We found that a significant amount of lysophosphatidic acid is present in the saliva (0.785 nmol/ml). The predominant fatty acyl moiety of lysophosphatidic acid was 18:1n-9 + n-7 followed by 18:0 and 16:0. A small amount of lysoplasmanic acid, an alkyl ether-linked analog of lysophosphatidic acid, was also detected in the saliva (0.104 nmol/ml). We found that physiologically relevant concentrations of lysophosphatidic acid induced accelerated growth of cells of mouth, pharynx, and esophagus origin in vitro. Lysophosphatidic acid also induced rapid increases in the intracellular free Ca2+ concentrations in these cells. We obtained evidence that lysophosphatidic acid receptor mRNAs are actually present in these cells. These results strongly suggest that lysophosphatidic acid is involved in wound healing in the upper digestive organs such as the mouth, pharynx, and esophagus.
Akira Tokumura, Junya Shinomiya, Seishi Kishimoto, Tamotsu Tanaka, Kentaro Kogure, Takayuki Sugiura, Kiyoshi Satouchi, Keizo Waku and Kenji Fukuzawa : Human platelets respond differentially to lysophosphatidic acids having a highly unsaturated fatty acyl group and alkyl ether-linked lysophosphatidic acids, The Biochemical Journal, Vol.365, No.Pt 3, 617-628, 2002.
(要約)
Lysophosphatidic acid (LPA) is a physiological agonist that is produced by lysophospholipase D, phospholipase A(1) and phospholipase A(2) in the blood of animals. It exerts diverse biological actions on a broad range of animal cells. Specific receptors for this important agonist have been characterized. In this investigation, for the first time we prepared LPAs having a highly unsaturated fatty acyl group, such as the eicosapentaenoyl or docosahexaenoyl residue, and their acetylated derivatives. Human platelets aggregated more potently in response to the highly unsaturated acyl-LPAs than to LPAs with a C(18) fatty acyl group, such as an oleoyl group, while alkyl ether-linked LPAs (alkyl-LPA) had much stronger aggregating activity. Two positional isomers of LPAs with an arachidonoyl, eicosapentaenoyl or docosahexaenoyl group had equipotent aggregatory activity as well as the positional isomers of their acetylated analogues, indicating that putative LPA receptors could not distinguish the difference between the positional isomers. We found that platelet preparations from two individuals showed no aggregatory response to alkyl-LPAs, although they contained mRNAs for known LPA receptors in the following order of expression level: endothelial differentiation gene (Edg)-4>Edg-7>Edg-2. We also obtained evidence that 2-(p-amylcinnamoyl)amino-4-chlorobenzoic acid (ONO-RS-082), a phospholipase A(2) inhibitor, potentiated alkyl-LPA-induced platelet aggregation, but inhibited highly unsaturated acyl-LPA-induced platelet aggregation. These results indicated that human platelets express acyl-LPA-selective and alkyl-LPA-selective receptors on their plasma membrane.
Shinji Nakane, Saori Oka, Shunsuke Arai, Keizo Waku, Yoshio Ishima, Akira Tokumura and Takayuki Sugiura : 2-Arachidonoyl-sn-glycero-3-phosphate, an arachidonic acid-containing lysophosphatidic acid: occurrence and rapid enzymatic conversion to 2-arachidonoyl-sn-glycerol, a cannabinoid receptor ligand, in rat brain, Archives of Biochemistry and Biophysics, Vol.402, No.1, 51-58, 2002.
(要約)
A substantial amount of lysophosphatidic acid (LPA) (15.66 nmol/g tissue) was found to occur in the brain isolated from rats killed in liquid nitrogen. We found that a significant portion of brain LPA was accounted for by the arachidonic acid-containing species (5.4%). We obtained evidence that both 2-arachidonoyl species and 1-arachidonoyl species of LPA are present. The occurrence of 2-arachidonoyl LPA in the brain (0.53 nmol/g tissue) is a notable observation, because of its structural resemblance to 2-arachidonoyl-sn-glycerol (2-AG), an endogenous cannabinoid receptor ligand. We then examined the biological activity of 2-arachidonoyl LPA and compared it with that of 2-AG using neuroblastoma x glioma hybrid NG108-15 cells which express both the LPA receptor and cannabinoid CB1 receptor. We found that 2-arachidonoyl LPA interacts with the LPA receptor(s) to elicit the elevation of intracellular free Ca(2+) concentrations, whereas 2-AG interacts exclusively with the cannabinoid CB1 receptor. Next, we examined the possible metabolic relationship between 2-arachidonoyl LPA and 2-AG and obtained clear evidence that rapid enzymatic conversion of 2-arachidonoyl LPA to 2-AG took place in the brain homogenate. It is noteworthy that two types of endogenous ligands, that interact with different types of receptors, are closely related metabolically and rapidly interconvert.
Kentaro Kogure, Motoki Morita, Susumu Hama, Sawa Nakashima, Akira Tokumura and Kenji Fukuzawa : Enhancement by α-tocopheryl hemisuccinate of nitric oxide production induced by lypopolysaccharide and interferon-γ through up-regulation of protein kinase C in rat vascular smooth muscle cells., European Journal of Biochemistry, Vol.269, No.9, 2367-2372, 2002.
(要約)
The effect of alpha-tocopheryl hemisuccinate (TS) on lipopolysaccharide (LPS)/interferon-gamma (IFN)-induced nitric oxide production in rat vascular smooth muscle cells (VSMC) was examined. The LPS/IFN-induced NO production was enhanced by TS but not by the other alpha-tocopherol (alpha-T) derivatives alpha-tocopheryl acetate (TA) and alpha-tocopheryl nicotinate (TN), or alpha-T itself. alpha-T, TA and TN inhibited the enhancement by TS of LPS/IFN-induced NO production. The enhancing effect of TS was observed in the presence of LPS, but not IFN, suggesting that TS participates in the LPS-stimulated signal pathway leading to NO production. Protein kinase C (PKC) inhibitors, but not protein kinase A inhibitors, inhibited the enhancing effect of TS on LPS/IFN-induced NO production. Furthermore, TS enhanced the amount of PKCalpha in VSMC. From these results, we concluded that the enhancing effect of LPS/IFN-induced NO production was caused by upregulation of PKC in VSMC.
(キーワード)
Animals / Cyclic AMP-Dependent Protein Kinase Type II / Cyclic AMP-Dependent Protein Kinases / Interferon-gamma / Lipopolysaccharides / Muscle, Smooth, Vascular / 一酸化窒素 (nitric oxide) / Protein Kinase C / Rats / Tocopherols / Up-Regulation / ビタミンE (vitamin E)
Yumi Kanaya, Akira Tokumura, Masaki Kitahara, Maki Miyake, Yasuko Yoshioka and Kenji Fukuzawa : Increased formation of lysophosphatidic acids by lysophospholipase D in serum of hypercholesterolemic rabbits., Journal of Lipid Research, Vol.43, No.2, 307-315, 2002.
(要約)
Lysophosphatidic acid (LPA) is a biologically active phospholipid that has been identified as a vasoactive principle in incubated plasma and serum of mammals. Previously, we found that mammalian plasma and serum contain a lysophospholipase D, which hydrolyzes lysophosphatidylcholines (LPCs) with different fatty acyl groups to the corresponding LPAs during its incubation at 37 degree C. In this study, we examined whether lysophospholipase D activity and levels of LPCs in rabbit serum were modulated by feeding rabbits a high cholesterol diet. Results showed that the serum levels of LPCs increased gradually in animals fed a high cholesterol diet for 12 weeks. We found that the levels of individual LPAs formed on incubation of serum for 24 h increased with an increase in the period of feeding of rabbits a high cholesterol diet. LPA with a linoleate residue was the most abundant LPA, followed in order by 16:0-, 18:1- and 18:0-LPAs. LPA was found to increase attachment of the monocytic cell line THP-1 to vascular endothelial cells pre-stimulated with tumor necrosis factor-alpha. These results indicated that increases in the levels of LPAs generated by lysophospholipase D in the blood of hypercholesterolemic rabbits may be relevant to attachment of monocytes to vascular walls, a key phenomenon observed at an early stage of atherosclerosis.
Kenji Hinokio, Shuji Yamano, Koji Nakagawa, Minoru Irahara, Masaharu Kamada, Akira Tokumura and Toshihiro Aono : Lysophosphatidic acid stimulates nuclear and cytoplasmic maturation of golden hamster immature oocytes in vitro via cumulus cells, Life Sciences, Vol.70, No.7, 759-767, 2002.
(要約)
Lysophosphatidic acid (LPA), a member of the phospholipid autacoid family, is induced in incubated human follicular fluid by lysophospholipase D. It is well known that LPA functions as a growth factor and the hypothesis that LPA in human follicular fluid takes a part in meiosis of oocytes is quite plausible. We studied the effects of LPA on the maturation of golden hamster immature oocytes in vitro. Hamster oocytes with a germinal vesicle were cultured in Tyrode's albumin lactate pyruvate (TALP) medium with 10(-5) M LPA, 10 ng/ml epidermal growth factor (EGF), 30 ng/ml insulin-like growth factor-1, 1 ng/ml tumor growth factor-alpha or 1 ng/ml basic fibroblast growth factor. The nuclear maturation rates in the LPA and EGF groups were significantly higher than in the control group and the other growth factors did not show any stimulatory effect (LPA group; 74.3% [75/101], EGF group; 82.4% [89/108] vs. control group; 60.2% [59/98], p < 0.05, p < 0.01, respectively). When the cells of cumulus were removed, EGF and LPA did not increase the nuclear maturation rates. Cotreatment EGF and LPA did not significantly enhance the stimulatory effect observed with LPA alone on maturation in vitro. The penetration rate determined by the zona-free hamster oocyte test was significantly higher in the LPA group than in the control group (26.7% vs. 13.2%, p < 0.05) and was comparable with that of oocytes matured in vivo. In conclusion, LPA stimulates the nuclear and cytoplasmic maturation of hamster immature oocytes via cumulus cells.
Akira Tokumura, Kyoko Tominaga, Yasuda Katsuhiko, Hideharu Kanzaki, Kentaro Kogure and Kenji Fukuzawa : Lack of significant differences in the corrected activity of lysophospholipase D, producer of phospholipid mediator lysophosphatidic acid, in incubated serum from women with and without ovarian tumors, Cancer, Vol.94, No.1, 141-151, 2002.
(要約)
Several studies have shown that lysophosphatidic acid (LPA), a phospholipidic chemical mediator, is relevant to the pathogenesis of ovarian carcinoma. Higher plasma levels of LPA have been reported in patients with ovarian carcinoma than in healthy patients, and LPA is known to activate ovarian carcinoma cells. To determine the reason for the increased plasma LPA levels in ovarian carcinoma patients, we compared the activities of serum lysophospholipase D, a novel LPA-producing metallo-enzyme, in healthy volunteers, patients with benign ovarian tumor, and patients with ovarian carcinoma. Lysophospholipase D activity was assessed by measuring the percentage conversion of [14C]palmitoyl-lysophosphatidylcholine (LPC) added to human serum. The apparent enzyme activities were corrected based on the serum levels of palmitoyl-LPC determined by gas-liquid chromatography after its purification and conversion to fatty acid methyl esters. The apparent activity of lysophospholipase D in serum preparations from four patients with ovarian carcinoma at Stage IV was significantly higher than those from five healthy subjects, five patients with benign ovarian tumors, and fourteen patients with ovarian carcinoma at Stages I (n = 5), II (n = 4), and III (n = 5). The serum levels of LPC, an endogenous substrate of lysophospholipase D, in ovarian carcinoma patients were less than those in patients with benign ovarian tumors. There were no significant differences in the corrected lysophospholipase D activity for the LPC levels in healthy women, patients with benign ovarian tumors, and patients with ovarian carcinoma at various stages. The current results suggest that lysophospholipase D is not associated with the elevated plasma levels of LPA in ovarian carcinoma patients previously reported, although only a limited number of patients were analyzed.
Kentaro Kogure, Motoki Morita, Sawa Nakashima, Susumu Hama, Akira Tokumura and Kenji Fukuzawa : Superoxide is responsible for apoptosis in rat vascular smooth muscle cells induced by α-tocopheryl hemisuccinate., Biochimica et Biophysica Acta (BBA) - General Subjects, Vol.1528, No.1, 25-30, 2001.
(要約)
We investigated the mechanism of cell toxicity of alpha-tocopheryl hemisuccinate (TS). TS concentration- and time-dependently induced the lactate dehydrogenase release and DNA fragmentation of rat vascular smooth muscle cells (VSMC). Exogenous addition of superoxide dismutase, but not catalase, significantly inhibited the cell toxicity of TS. The NADPH-dependent oxidase activity of VSMC was stimulated by TS treatment. The cell toxicity of TS was inhibited by NADPH oxidase inhibitor 4-(2-aminoethyl)-benzenesulfonyl fluoride. Consequently, TS-induced apoptosis of VSMC was suggested to be caused by exogenous O(2)(-) generated via the oxidase system activated with TS.
(キーワード)
Animals / Apoptosis / Ascorbic Acid / Catalase / Cells, Cultured / Cytochrome c Group / DNA Fragmentation / Dose-Response Relationship, Drug / Enzyme Activation / L-Lactate Dehydrogenase / Muscle, Smooth, Vascular / NADPH Oxidase / Oxygen / Rats / Superoxide Dismutase / Superoxides / Tocopherols / Vitamin E
Kazuaki Yokoyama, Shigeaki Saitoh, Mayuko Ishida, Yoshio Yamakawa, Kazumi Nakamura, Keizo Inoue, Ryo Taguchi, Akira Tokumura, Masahiro Nishijima, Mitsuhiro Yanagida and Morio Setaka : Very-long-chain fatty acid-containing phospholipids accumulate in fatty acid synthase temperature-sensitive mutant strains of the fission yeast Schizosaccharomyces pombe fas2/lsd1, Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1532, No.3, 223-233, 2001.
(要約)
Fission yeast lsd1 strains show aberrant mitosis with a lsd phenotype, large and small daughter nuclei, and a very thick septum, the phenotypic expression being temperature-sensitive. The lsd1(+) gene is the homologue of the budding yeast FAS2 gene encoding the fatty acid synthase alpha-subunit as reported previously (S. Saitoh, K. Takahashi, K. Nabeshima, Y. Yamashita, Y. Nakaseko, A. Hirata, M. Yanagida, J. Cell Biol. 134 (1996) 949--961). In this paper, lsd1 is considered to represent fas2. Here, three fas2 strains were investigated and found to have missense point mutations at different sites in the gene encoding the alpha-subunit of fatty acid synthase. The mutation affected only slightly the enzymatic activities monitored in vitro. Unexpectedly, abnormal phospholipids, phosphatidylcholine and phosphatidylethanolamine, both of which contain a very-long-chain fatty acyl residue (1-melissoyl-2-oleolyl-sn-glycero-3-phosphocholine and 1-melissoyl-2-oleolyl-sn-glycero-3-phosphoethanolamine), accumulated in fas2 strains in a temperature-sensitive manner. Rescue of the fas2 strains by addition of palmitate to the medium at restrictive temperature was accompanied by disappearance of these abnormal phospholipids. Accumulation of these lipids in membranes may cause alteration of various cellular functions.
Shinji Nakane, Keizo Waku, Akira Tokumura and Takayuki Sugiura : Hen egg yolk and white contain high amounts of lysophosphatidic acids, growth factor-like lipids: distinct molecular species compositions, Lipids, Vol.36, No.4, 413-419, 2001.
(要約)
Hen egg yolk and white were found to contain high amounts of lysophosphatidic acid (acyl LPA) in addition to small amounts of lysoplasmanic acid (alkyl LPA). The levels of acyl LPA in hen egg yolk (44.23 nmol/g tissue) and white (8.81 nmol/g tissue) were on the same order as or higher than the levels of acyl LPA known to be required to elicit biological responses in various animal tissues. Noticeably, there is a marked difference between the fatty acid composition of egg yolk acyl LPA and of egg white acyl LPA; egg yolk acyl LPA predominantly contains saturated fatty acids as the acyl moiety, whereas egg white acyl LPA primarily contains polyunsaturated fatty acids. We found that the level of acyl LPA, especially polyunsaturated fatty acid-containing acyl LPA, in egg white was augmented markedly during the incubation at 37 degrees C, while there was no change in egg yolk. We confirmed that egg white contains both the substrate, i.e., polyunsaturated fatty acid-containing lysophosphatidylcholine (LPC), and the enzyme activity catalyzing the hydrolysis of polyunsaturated fatty acid-containing LPC to the corresponding acyl LPA. Egg yolk LPA and egg white LPA may play separate physiological roles in the development, differentiation, and growth of embryos.
(キーワード)
Animals / Chickens / Egg White / Egg Yolk / Fatty Acids, Unsaturated / Female / Growth Substances / Lipids / Lysophospholipids / Spectrometry, Mass, Fast Atom Bombardment
(文献検索サイトへのリンク)
● PubMed @ National Institutes of Health, US National Library of Medicine (PMID): 11383695
Kenji Fukuzawa, Akira Tokumura, Kentaro Kogure, Masahito Iemura, Naoto Gondoh, Masanobu Fujii, Satoru Ueno and Akira Shibata : A comparative study of the ability of ferric nitrilotriacetate and other iron chelators to assist membrane lipid peroxidation by superoxide radicals, Chemistry and Physics of Lipids, Vol.110, No.1, 69-84, 2001.
(要約)
This study examined some of the variables determining the efficiency of lipid peroxidation in egg yolk phosphatidylcholine liposomes and in microsomes exposed to enzymatically-generated superoxide radicals. The initiation of peroxidation required the presence of preformed lipid peroxides and a chelated metal catalyst. Comparison of the relative effectiveness of four iron chelating agents showed that the chelate must bind to the membrane by coulombic attraction between the charged membrane and a chelate carrying an opposite net charge. Of the chelates tested, only the carcinogenic ferric nitrilotriacetate [corrected] (Fe(3+)-NTA) was an effective catalyst of oxidation of all membranes, whether carrying a net charge, or not. We postulate that the unique catalytic capacity of the ferric nitrilotriacetate [corrected] (Fe(3+)-NTA) can be explained by its existence in two forms at neutral pH, each binding to oppositely charged membranes and initiating their peroxidation. This gives the complex the unique ability to bind to any membrane, which may be a factor in its carcinogenicity.
Akira Tokumura, T. Sumida, M. Toujima, Kentaro Kogure, Kenji Fukuzawa, Y. Takahashi and S. Yamamoto : Structural identification of phosphatidylcholines having an oxidatively shortened linoleate residue generated through its oxygenation with soybean or rabbit reticulocyte lipoxygenase., Journal of Lipid Research, Vol.41, No.6, 953-962, 2000.
(要約)
Phosphatidylcholines (PCs) with platelet-activating factor (PAF)-like biological activities are known to be generated by fragmentation of the sn-2-esterified polyunsaturated fatty acyl group. The reaction is free radical-mediated and triggered by oxidants such as metal ions, oxyhemoglobin, and organic hydroperoxides. In this study, we characterized the PAF-like phospholipids produced on reaction of PC having a linoleate group with lipoxygenase enzymes at low oxygen concentrations. When the oxidized PCs were analyzed by gas chromatography-mass spectrometry, two types of oxidatively fragmented PC were detected. One PC had an sn-2-short chain saturated or unsaturated acyl group (C(8)-C(13)) with an aldehydic terminal; the abundant species were PCs with C(9) and C(13). The other PC had a short chain saturated acyl group (C(6)-C(9)) with a methyl terminal, and the most predominant species was PC with C(8). When the extracts of oxidation products were subjected to catalytic hydrogenation, PCs having saturated acyl groups (C(6)-C(14)) were detected; the most abundant was C(12) species. The less regiospecific formation of PAF-like lipids suggests that they were generated by oxidative fragmentation of PC hydroperoxides formed by non-stereoselective oxygenation of the alkyl radical of esterified linoleate that escaped from the active centers of lipoxygenases. One of the PAF-like PC with an aldehydic terminal was found to be bioactive; it inhibited the production of nitric oxide induced by lipopolysaccharide and interferon-gamma in vascular smooth muscle cells from rat aorta.
Takayuki Sugiura, Shinji Nakane, Seishi Kishimoto, Keizo Waku, Yasuko Yoshioka, Akira Tokumura and Donald J Hanahan : Occurrence of lysophosphatidic acid and its alkyl ether-linked analog in rat brain and comparison of their biological activities toward cultured neural cells, Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1440, No.2-3, 194-204, 1999.
(要約)
Rat brain was found to contain substantial amounts of potent bioactive lipids lysophosphatidic acid (acyl LPA) (3.73 nmol/g tissue) and lysoplasmanic acid (alkyl LPA) (0.44 nmol/g tissue). The presence of alkyl LPA was confirmed by mild alkaline hydrolysis analysis and by gas chromatography/mass spectrometry analysis of the trimethylsilyl derivative. This is the first clear evidence of the occurrence of an alkyl LPA in nature. The predominant molecular species of acyl LPA are 18:1-, 18:0- and 16:0-containing species (46. 9, 22.5 and 18.8%, respectively). A significant amount of a 20:4-containing species (7.2%) was also detected in the acyl LPA fraction. We also confirmed that rat brain alkyl LPA consists of 16:0-, 18:0- and 18:1-containing species. Noticeably, either acyl or alkyl LPA is capable of stimulating neuroblastomaxglioma hybrid NG108-15 cells to elicit a Ca(2+) transient, the potencies being almost the same. Both acyl and alkyl LPAs also induce cell rounding upon addition to the cells. These results suggest that acyl and alkyl LPAs play important physiological roles as intercellular signaling molecules as well as the roles as metabolic intermediates in the nervous system.
kenji Kunikata, Shuji Yamano, Akira Tokumura and Toshihiro Aono : Effect of lysophosphatidic acid on the ovum transport in mouse oviducts, Life Sciences, Vol.65, No.8, 833-840, 1999.
(要約)
The effects of lysophosphatidic acid (LPA) on ovum transport in mouse oviducts were studied. When excised oviducts were incubated at 37 degrees C under 5% CO2 in humidified air for 24 hours, addition of LPA at 10 microM to the medium significantly accelerated the rate of ovum transport, and 1 microM LPA slightly increased the ovum transport rate. These increases were not inhibited by 10 microM indomethacin, a cyclooxygense inhibitor, but were suppressed by 260 ng/ml of pertussis toxin or 10 microM verapamil, a voltage-sensitive calcium channel blocker. These data suggested that LPA stimulates mouse ovum transport by contracting oviductual smooth muscle via a voltage-sensitive calcium channel mediated by a pertussis toxin-sensitive G-protein-linked receptor.
Akira Tokumura, Maki Miyake, Yuko Nishioka, Shuji Yamano, Toshihiro Aono and Kenji Fukuzawa : Production of Lysophosphatidic Acids by Lysophospholipase D in Human Follicular Fluids of In Vitro Fertilization Patients, Biology of Reproduction, Vol.61, No.1, 195-199, 1999.
(要約)
Lysophosphatidic acids (LPAs) are known to be normal constituents of mammalian serum, and they mimic some biological effects of the serum. We previously reported that lysophospholipase D (LPLD) was involved in the accumulation of LPAs in incubated rat plasma and serum. In this study we detected, by gas-liquid chromatography, various molecular species of LPA in follicular fluids collected from women programmed for in vitro fertilization. When the follicular fluid was incubated at 37 degrees C for 48 h, persistent increases in the amounts of LPAs were observed concomitant with decreases in the amounts of the corresponding lysophosphatidylcholines (LPCs), although the concentrations of saturated LPCs increased in the first 6 h of incubation. These results suggest that human follicular fluid has LPLD activity, and this was confirmed by experiments with follicular fluids mixed with an exogenous radioactive LPC. The LPLD showed preference for unsaturated over saturated LPCs, similar to plasma LPLD, indicating that it originated from the circulation.
Akira Tokumura, Hiroaki Fujimoto, Osamu Yoshimoto, Yuko Nishioka, Maki Miyake and Kenji Fukuzawa : Production of lysophosphatidic acid by lysophospholipase D in incubated plasma of spontaneously hypertensive rats and Wistar Kyoto rats, Life Sciences, Vol.65, No.3, 245-253, 1999.
(要約)
Lysophosphatidic acid has been identified as a vasopressor principle in incubated mammalian plasma and sera, and shown to be generated extracellulary by lysophospholipase D-like activity. In this study, we monitored the time course of changes in the major phospholipid fractions during incubation of plasma, and found that polyunsaturated lysophosphatidic acids accumulate more rapidly than saturated lysophosphatidic acids at expense of the corresponding lysophosphatidylcholines. We compared the phospholipase activities for producing bioactive LPA in age-matched spontaneously hypertensive rats and Wistar Kyoto rats. The lysophospholipase D activity in rat plasma was found to be independent of strain and age. We suggest that lysophospholipase D functions in rat for persistent production of bioactive LPA in the circulation throughout life. However, our finding that production of LPA in spontaneously hypertensive rats was not greater than that in Wistar Kyoto rats does not seem to support the idea that increased production of LPA is involved in the pathogenesis of hypertension.
(キーワード)
加齢 (aging) / Animals / Chromatography, Gas / Chromatography, Thin Layer / Fatty Acids / In Vitro Techniques / Lysophospholipids / Male / Phosphatidylcholines / Phosphoric Diester Hydrolases / Rats / Rats, Inbred SHR / Rats, Inbred WKY / Species Specificity / Time Factors
Takayo Sasagawa, Tatsuzo Oka, Akira Tokumura, Yuriko Nishimoto, Saturnino Munoz, Masashi Kuwahata, Misako Okita, Hideaki Tsuji and Yasuo Natori : Analysis of the fatty acid components in a perchloric acid-soluble protein, Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1437, No.3, 317-324, 1999.
(要約)
We had previously found that a perchloric acid-soluble protein (PSP1) occurs in rat liver, and that this novel protein inhibits protein synthesis in a rabbit reticulocyte lysate system (T. Oka, H. Tsuji, C. Noda, K. Sakai, Y.-H. Hong, I. Suzuki, S. Muñoz, Y. Natori, J. Biol. Chem. 270 (1995) 30060-30067). In the present study, we analyzed lipid components bound to PSP1. Native PSP1 was purified from rat liver using Sephadex G-75, DE-52 cellulose and IgGPSP-affinity chromatography, and the lipid components were extracted. The components obtained from the purified PSP1 were shown to be free fatty acids by thin-layer chromatography. By GC-MS, six major fatty acids were identified as 14:0, 16:0, 18:0, 18:1, 18:2 and 20:4. 1 mol of PSP1 contained 1.26 mol of total fatty acid components. The fatty acid-binding assay of PSP1 showed that the Bmax was 1.25 mol fatty acid/mol PSP1 and the Kd value for palmitic acid was 6.03 microM. The concentration of PSP1 mRNA in rat liver increased 2.3-fold by the administration of peroxisome proliferator, bezafibrate. These findings show that PSP1 is a fatty acid-binding protein-like protein, which is involved in the intracellular metabolism of fatty acid and is quite different from the known fatty acid-binding proteins.
Akira Tokumura, Yuko Nishioka, Osamu Yoshimoto, Junya Shinomiya and Kenji Fukuzawa : Substrate specificity of lysophospholipase D which produces bioactive lysophosphatidic acids in rat plasma, Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1437, No.2, 235-245, 1999.
(要約)
Previously we reported that lysophospholipase D in rat plasma hydrolyzes endogenous unsaturated lysophosphatidylcholines (LPCs) preferentially to saturated LPCs to lysophosphatidic acids with growth factor-like and hormone-like activities. In this study, we examined the possibility that association of LPCs with different proteins in rat plasma has an effect on the preference of lysophospholipase D for unsaturated LPCs. Large portions of various LPCs were found to be recovered in the lipoprotein-poor bottom fraction. Furthermore, the percentages of LPCs associated with albumin isolated from rat plasma were shown not to be consistent with their percentage conversions to lysophosphatidic acids by lysophospholipase D on incubation of rat plasma at 37 degrees C. These results indicate that distinct distributions of LPCs in the plasma protein fractions are not critical factors for the substrate specificity of lysophospholipase D. Experiments with Nagase analbuminemic rats suggested that albumin-LPC complexes are not necessarily required for the hydrolysis by lysophospholipase D; lipoprotein-associate LPCs appeared to be good substrates for the phospholipase. We found that both saturated and unsaturated LPCs are present mainly as 1-acyl isomers in rat plasma. This result indicates that the preference of lysophospholipase D for unsaturated LPCs is not attributable to a difference in position of the acyl group attached to the glycerol backbone of LPC. In addition, lysophospholipase D was also found to attack choline phospholipids with a long chain group and a short chain alkyl group, although their percentage hydrolyses were low. Taken altogether, these results suggest that lysophospholipase D shows higher affinities for free forms of unsaturated acyl type LPCs equilibrated with albumin-bound and lipoprotein-associated forms, than for free forms of saturated acyl type LPCs and analogs of platelet-activating factor.
Akira Tokumura, Maki Miyake, Osamu Yoshimoto, Mayumi Shimizu and Kenji Fukuzawa : Metal-ion stimulation and inhibition of lysophospholipase D which generates bioactive lysophosphatidic acid in rat plasma, Lipids, Vol.33, No.10, 1009-1015, 1998.
(要約)
We found that lysophospholipase D (LPLD) in rat plasma prefers unsaturated to saturated lysophosphatidylcholines as substrates, generating a biologically active lipid, lysophosphatidic acid, but it does not hydrolyze diacyl-phospholipids. In this study, this LPLD required a metal ion for activity, Co2+ being the most effective, followed in order by Zn2+, Mn2+, and Ni2+. This metal-ion-stimulated LPLD with unique substrate specificity, which has not been described previously, was susceptible to thiol-blocking reagents and serine esterase inhibitors, but not to a histidine-modifying reagent. Consistent with results using thiol-modifying agents, short-chain fatty aldehydes, secondary products of lipid peroxidation, were found to inhibit LPLD. Addition of dibutylhydroxytoluene or butylhydroxyanisole to the plasma increased the activity of this enzyme, probably in a manner independent of its antioxidant activity, since another antioxidant, propyl gallate, was rather inhibitory. These results suggest that rat plasma contains an active LPLD that differs in some properties from other members of the known phospholipase D family detected in animal tissues and body fluids.
Kenji Fukuzawa, Yasuki Inokami, Akira Tokumura, Junji Terao and Asahi Suzuki : Rate constants for quenching singlet oxygen and activities for inhibiting lipid peroxidation of carotenoids and alpha-tocopherol in liposomes, Lipids, Vol.33, No.8, 751-756, 1998.
(要約)
The (1)O2 quenching rate constants (kQ) of alpha-tocopherol (alpha-Toc) and carotenoids such as beta-carotene, astaxanthin, canthaxanthin, and lycopene in liposomes were determined in light of the localization of their active sites in membranes and the micropolarity of the membrane regions, and compared with those in ethanol solution. The activities of alpha-Toc and carotenoids in inhibiting (1)O2-dependent lipid peroxidation (reciprocal of the concentration required for 50% inhibition of lipid peroxidation: [IC50](-1)) were also measured in liposomes and ethanol solution and compared with their kQ values. The kQ and [IC50](-1) values were also compared in two photosensitizing systems containing Rose bengal (RB) and pyrenedodecanoic acid (PDA), respectively, which generate (1)O2 at different sites in membranes. The kQ values of alpha-Toc were 2.9 x 10(8) M(-1) s(-1) in ethanol solution and 1.4 x 10(7) M(-1) s(-1) (RB system) or 2.5 x 10(6) M(-1) s(-1) (PDA system) in liposomes. The relative [IC50](-1) value of alpha-Toc in liposomes was also five times higher in the RB system than in the PDA-system. In consideration of the local concentration of the OH-group of alpha-Toc in membranes, the kQ value of alpha-Toc in liposomes was recalculated as 3.3 x 10(6) M(-1) s(-1) in both the RB and PDA systems. The kQ values of all the carotenoids tested in two photosensitizing systems were almost the same. The kQ value of alpha-Toc in liposomes was 88 times less than in ethanol solution, but those of carotenoids in liposomes were 600-1200 times less than those in ethanol solution. The [IC50](-1) value of alpha-Toc in liposomes was 19 times less than that in ethanol solution, whereas those of carotenoids in liposomes were 60-170 times less those in ethanol solution. There were no great differences (less than twice) in the kQ and [IC50](-1) values of any carotenoids. The kQ values of all carotenoids were 40-80 times higher than that of alpha-Toc in ethanol solution but only six times higher that of alpha-Toc in liposomes. The [IC50](-1) values of carotenoid were also higher than that of alpha-Toc in ethanol solution than in liposomes, and these correlated well with the kQ values.
Sachiko Kondo, Takayuki Sugiura, Tomoko Kodaka, Naomi Kudo, Keizo Waku and Akira Tokumura : Accumulation of VariousN-Acylethanolamines IncludingN-Arachidonoylethanolamine (Anandamide) in Cadmium Chloride-Administered Rat Testis, Archives of Biochemistry and Biophysics, Vol.354, No.2, 303-310, 1998.
(要約)
Changes in the levels of various molecular species of N-acylethanolamine in CdCl2-administered rat testis were examined. We found that the levels of various N-acylethanolamines including anandamide (N-arachidonoylethanolamine), an endogenous cannabinoid receptor ligand, were dramatically increased in CdCl2-admin-istered rat testis. Such changes were particularlyprominent for saturated and monoenoic species such as N-palmitoyl species (39-fold at 9 h) and N-stearoyl species (21-fold at 9 h), compared with unsaturated fatty acid-containing species such as anandamide (5-fold at 9 h). Noticeably, increased levels were observed of not only N-acylethanolamines but also several species of N-acylphosphatidylethanolamine, potential precursors for N-acylethanolamines. We confirmed that the rat testis microsomal fraction contains phosphodiesterase activity catalyzing the release of N-acylethanolamine from N-acylphosphatidylethanolamine and transacylase activity catalyzing the formation of N-acylphosphatidylethanolamine from phosphatidylethanolamine and phosphatidylcholine. These enzyme activities were not dramatically different in the microsomal fraction obtained from CdCl2-administered rat testis compared with that in the case of control rat testis, at least when estimated in cell-free assay systems, suggesting that the accessibility of the substrates to the enzymes may be increased in CdCl2-administered rat testis to generate a large amount of N-acylethanolamine. Possible pathophysiological implications of the augmented generation of N-acylethanolamine including anandamide in CdCl2-administered rat testis were discussed.
Sachiko Kondo, Hironori Kondo, Shinji Nakane, Tomoko Kodaka, Akira Tokumura, Keizo Waku and Takayuki Sugiura : 2-Arachidonoylglycerol, an endogenous cannabinoid receptor agonist: identification as one of the major species of monoacylglycerols in various rat tissues, and evidence for its generation through Ca2+-dependent and -independent mechanisms, FEBS Letters, Vol.429, No.2, 152-156, 1998.
82.
Toshihiko Tsutsumi, Akira Tokumura and Shikifumi Kitazawa : Undifferentiated HL-60 cells internalize an antitumor alkyl ether phospholipid more rapidly than resistant K562 cells, Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol.1390, No.1, 73-84, 1998.
(要約)
In this study, we confirmed a previous finding that 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (methyl-PAF) expresses higher antineoplastic activity against the promyelocytic leukemia cell line HL-60, than against the erythroleukemic cell line K562, and intended to clarify the reason for this. Using an albumin back-exchange method, we measured the rates of binding and internalization of [3H]methyl-PAF by HL-60 and K562 cells. We found that methyl-PAF associated very rapidly and to similar extents with the two types of cells at low concentrations of extracellular bovine serum albumin, but that when bound to the cell surface, it was internalized into HL-60 cells faster than into K562 cells. The internalization of methyl-PAF by HL-60 cells was concentration-independent, intracellular ATP-independent and susceptible to thiol group-modifying reagents and cytochalasin B. Thus the inward transbilayer movement of methyl-PAF seems to occur by cytochalasin B-sensitive protein-mediated mechanism based on passive diffusion not requiring energy, in which SH-groups of protein play a critical role. We also found that the internalization of 1-hexadecanoyl-2-(4,4-difluoro-5,7- dimethyl-4-bora-3a, 4a-diaza-s-indacene-3-pentanoyl)-sn-glycero-3-phosphocholine (Bodipy-C5-PC), whose structure resembles that of methyl-PAF, into HL-60 cells was faster than that into K562 cells. Using a combination of an albumin back-exchange method and observation by confocal laser scanning microscopy, we next examined the intracellular distribution of this fluorescent phospholipid probe after its internalization. Intracellular membranes, especially those peripheral to nuclei, were fluorescence-labeled in both HL-60 and K562 cells, but fluorescence of the nuclear membranes was weak, suggesting that this probe seems mainly to accumulate in intracellular granules, and may interact directly with several key enzymes for phospholipid metabolism, leading to cell injury. Because the difference between the internalization rates of methyl-PAF in HL-60 and K562 cells was correlated with their different susceptibilities to the cytotoxic effect of methyl-PAF, we suggest that the capacities for uptake of methyl-PAF and its accumulation in intracellular membranes are critical factor for its induction of apoptosis. (c) 1998 Elsevier Science B.V.
Akira Tokumura, Masaaki Okuno, Kenji Fukuzawa, Hitoshi Houchi, Koichiro Tsuchiya and Motoo Oka : Positive and negative controls by protein kinases of sodium-dependent Ca2+ efflux from cultured bovine adrenal chromaffin cells stimulated by lysophosphatidic acid, Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol.1389, No.1, 67-75, 1998.
(要約)
We previously found that lysophosphatidic acid (LPA), a bioactive phospholipid, induced Na+-dependent Ca2+ efflux from cultured bovine adrenal chromaffin cells, possibly by activating a Na+/Ca2+ exchanger. The present study on the structure-activity relationship of its action revealed that 1-acyl type LPAs were stronger stimulants than the corresponding 1-O-alkyl type LPAs having a long alkyl moiety with the same chain length. Lysophosphatidylglycerol, suramin and N-palmitoyl-tyrosine phosphoric acid have all been reported to inhibit the action of LPA in some animal cells and platelets, but only lysophosphatidylglycerol was found to inhibit selectively LPA-induced Ca2+ efflux from chromaffin cells. LPA-induced Ca2+ extrusion was suggested to be involved in both acceleration of return of intracellular Ca2+ in Fura 2-loaded bovine chromaffin cells after addition of carbachol, and inhibition of carbachol-induced catecholamine release when the cells were co-incubated with LPA. The Ca2+ efflux from chromaffin cells stimulated by LPA was augmented by their pretreatment with staurosporine or calphostin C, inhibitors of protein kinase C, but reduced by their preincubation with phorbol 12-myristate 13-acetate. Furthermore, the response to LPA was potentiated by sodium vanadate, a protein tyrosine phosphatase inhibitor, but inhibited by genistein, an inhibitor of protein tyrosine kinase. These results suggest that protein kinase C and protein tyrosine kinase are involved negatively and positively, respectively, in the signal transduction triggered by LPA, leading to activation of the Na+/Ca2+ exchanger.
Kenji Fukuzawa, Yasuki Inokami, Akira Tokumura, Junji Terao and Asahi Suzuki : Singlet oxygen scavenging by lpha-tocopherol and eta-carotene: Kinetic studies in phospholipid membranes and ethanol solution, BioFactors, Vol.7, No.1-2, 31-40, 1998.
(要約)
The rate constants (ks) of 1O2 scavenging for alpha-tocopherol (alpha-Toc) and beta-carotene (beta-Car) were measured in liposome membranes, and compared with those in EtOH solution. 1O2 was site-specifically generated by photoirradiation using two photosensitizers, water-soluble Rose bengal (RB) and lipid-soluble 12-(1-pyrene)-dodecanoic acid (PDA). The ks value for beta-Car in EtOH solution was 1.3 x 10(10) M-1 s-1, which was 36 times that for alpha-Toc (3.6 x 10(8) M-1 s-1), but there was no difference between their ks values in liposomes (1.8 x 10(7) M-1 s-1 for beta-Car and 1.2 x 10(7) M-1 s-1 for alpha-Toc). In the liposomes, the ks value for alpha-Toc was affected by the membrane site where 1O2 was generated, which depended on the localization of the photosensitizer, being high at the membrane surface in the RB-system and low in the inner region of the membrane in the PDA-system. In contrast, the ks value for beta-Car was not affected by the 1O2-generating site. These differences were supposed to be caused by differences in the relative concentrations of 1O2 and active sites of alpha-Toc and beta-Car in the membranes. alpha-Toc and beta-Car inhibited 1O2-dependent peroxidation of egg yolk phosphatidylcholine (egg PC). The concentrations of alpha-Toc required for 50% inhibition of lipid peroxidation (IC50) were higher than those of beta-Car, being more than 6 times higher in EtOH solution and less than 2 times higher in liposomes. The ratio of the antioxidant activity of beta-Car to that of alpha-Toc was more in EtOH solution than in liposomes, and was well correlated with the ratio of their 1O2 scavenging rate constants.
Akira Tokumura, Toshihiko Tsutsumi, Yuko Nishioka and Hiroaki Tsukatani : Exogenously added alkylmethylglycerophosphocholine and alkylmethylcarbamylglycerophosphocholine accumulate in plasma membranes more than in intracellular membranes of rabbit platelets, Chemistry and Physics of Lipids, Vol.86, No.1, 75-83, 1997.
(要約)
We found that extracellular addition of 2% bovine serum albumin (BSA) to a suspension of rabbit platelets after stimulation with platelet-activating factor resulted in a biphasic extraction of [3H]1-O-alkyl-2-O-methyl (or 2-O-methylcarbamyl)-sn-glycero-3-phosphocholine. A fast phase of extraction of the phospholipid probe by BSA was found to be mainly due to removal of the probe remaining in an outer layer of platelet plasma membrane, whereas a second phase of extraction of the probe by BSA was mostly attributed to redistribution of the probe which had been flipped across the plasma membrane. On the basis of analysis of the biphasic extraction by BSA of 1-O-alkyl-2-O-methyl (or methylcarbamyl)-sn-glycero-3-phosphocholine at various times after its addition, we suggested that the radioactive phospholipid accumulated in plasma membrane more than in intracellular membranes of rabbit platelets. In similar experiments with guinea-pig polymorphonuclear leukocytes, we observed a monophasic extraction of 1-O-alkyl-2-O-methyl (or methylcarbamyl)-sn-glycero-3-phosphocholine by BSA, indicating its unidirectional movement across the plasma membrane.
Akira Tokumura, Tomoko Moriyama, Hiroshi Minamino, Takao Hayakawa and Hiroaki Tsukatani : Exogenous phosphatidic acid with saturated short-chain fatty acyl groups induces superoxide anion release from guinea pig peritoneal polymorphonuclear leukocytes by three different mechanisms, Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol.1344, No.1, 87-102, 1997.
(要約)
Treatment of suspensions of guinea pig peritoneal polymorphonuclear leukocytes (PMN) with four species of phosphatidate (PA) containing short-chain fatty acids induced sustained superoxide anion (O2-) production after a lag time. The rank order of efficiency of these PAs in triggering O2- production was PA8:0 [1,2-dioctanoyl-sn-glycerol-3-phosphate (GP)] > PA10:0 (1,2-didecanoyl-GP) > PA6:0 (1,2-dicaproyl-GP) > > PA12:0 (1,2-dilauroyl-GP). The O2- release from PMN stimulated with PA10:0 or PA12:0, but not with PA6:0 or PA8:0, was lowered by the addition of 1 mM extracellular Ca2+. Studies with various inhibitors showed that the mechanism of multiphasic O2- production induced by PA8:0 depended on its concentration: 1 and 3 microM PA8:0 induced O2- production constantly after a lag time through a protein kinase-dependent mechanism that was inhibited by 100 nM staurosporine. With concentrations of PA of 10 microM or more, an additional mechanism that was independent of protein kinase became operative and predominant over the protein kinase-dependent one. This protein kinase-independent mechanism was inhibited selectively by 80 microM TMB-8. Concentrations of 30, 60 and 100 microM PA first elicited transient O2- production via another protein kinase-dependent mechanism that was more sensitive to H-7 than to staurosporine, and then sustained O2- production, mainly driven by the protein kinase-independent mechanism. Metabolism of exogenously added [14C]PA8:0 in intact PMN was examined in the presence and absence of propranolol. Results suggest that PA itself is more important rather than its degradation products such as diacylglycerol, in inducing O2- production via three different mechanisms described above.
Kenji Fukuzawa, Kayo Matsuura, Akira Tokumura, Asahi Suzuki and Junji Terao : Kinetics and Dynamics of Singlet Oxygen Scavenging by -Tocopherol in Phospholipid Model Membranes, Free Radical Biology and Medicine, Vol.22, No.5, 923-930, 1997.
(要約)
Scavenging of singlet oxygen (1O2) by alpha-tocopherol (alpha-Toc) was investigated in liposomes. 1O2 was generated by photoirradiation in the presence of two photosensitizers, water-soluble methylene blue (MB) and lipid-soluble 12-(1-pyrene)dodecanoic acid (PDA). The rates of oxidation of alpha-Toc differed depending on the photosensitizing dye and the membrane charge: in the MB-system, alpha-Toc was oxidized fast in negatively charged dimyristoylphosphatidylcholine (DMPC) liposomes containing dicetylphosphate (DCP) and slowly in neutrally charged DMPC liposomes and positively charged DMPC liposomes containing stearylamine (SA), but in the PDA-system, the oxidation rate was independent of the membrane charge. The charge-dependent difference in the MB-system would be due to the site of 1O2 generation depending on the charge-dependent distribution of MB, because positively charged MB increased the zeta-potential of DCP-DMPC liposomes by its interaction with DCP at the membrane surface, but changed the zeta-potentials of DMPC and SA-DMPC liposomes less because of its location in the bulk water phase. The oxidation rate of alpha-Toc in liposomes was different from that in EtOH solution: in the MB system, the oxidation rate was faster in EtOH solution than in DMPC or SA-DMPC liposomes but the same as that in DCP-DMPC liposomes. However, in the PDA system, the oxidation rate was slower in EtOH solution than in DMPC liposomes with or without a charge. Membrane fluidity changed the rate of alpha-Toc oxidation in liposomes, the rate being higher in the liquid crystalline phase than the gel phase, as judged by the higher rate in DMPC liposomes than in dipalmitoylphosphatidylcholine (DPPC) liposomes at 30 degrees C. The rate constants of alpha-Toc for scavenging, the chemical reaction and physical quenching of 1O2 were determined in membranes using DCP-DMPC liposomes labeled with 1,3-diphenyl-isobenzofuran (DPBF), which traps 1O2. These constants differed in the two photosensitizing systems, being higher in the MB-system than in the PDA-system, and were lower than those in EtOH solution.
Akira Tokumura, M Toujima, Yasuko Yoshioka and Kenji Fukuzawa : Lipid peroxidation in low density lipoproteins from human plasma and egg yolk promotes accumulation of 1-acyl analogues of platelet-activating factor-like lipids, Lipids, Vol.31, No.12, 1251-1258, 1996.
(要約)
Oxidative modification of low density lipoprotein (LDL) is known to be a key event for induction of atherosclerosis. However, there has been little progress in structural elucidation of oxidized lipids, especially oxidatively fragmented phospholipids retaining a glycerol backbone. In this study, we found that LDL derived from egg yolk has no platelet-activating factor (PAF) acetylhydrolase activity, and that prolonged incubation of egg yolk LDL with Cu2+ resulted in the formation of various PAF-like lipids: 1-acyl type phosphatidylcholines with an sn-2-short-chain dicarboxylate or monocarboxylate group. Only a very small amount of the PAF-like lipid having an sn-2-short-chain monocarboxylate group was detected by gas chromatography-mass spectrometry in Cu(2+)-oxidized LDL from human plasma with high PAF-acetylhydrolase activity, which has been reported to hydrolyze PAF-like lipids to lysophosphatidyl-cholines. Preincubation of plasma LDL with diisopropyl fluorophosphate dose-dependently inhibited PAF-acetylhydrolase activity, resulting in accumulation of the PAF-like lipids when the LDL was oxidized with Cu2+. As well as PAF and lysophosphatidylcholines, several PAF-like lipids were found to inhibit [3H]thymidine incorporation into cultured vascular smooth muscle cells derived from rat aorta. The possible formation of PAF-like lipids by lipid peroxidation in LDL is discussed as well as its possible significance for induction of atherosclerosis.
Akira Tokumura, Masaaki Okuno, Kenji Fukuzawa, Hitoshi Houchi and Motoo Oka : Two effects of lysophosphatidic acid on Ca(2+)-movement in cultured bovine adrenal chromaffin cells, Journal of Lipid Mediators and Cell Signalling, Vol.14, No.1-3, 127-135, 1996.
(要約)
We found that lysophosphatidic acid (LPA) exerted two effects on Ca(2+)-movement in cultured bovine adrenal chromaffin cells. At concentrations of above 10(-5) M, it induced slight, but significant 45Ca2+ influx, resulting in release of a small portion of stored catecholamine. At high concentrations it also significantly increased the intracellular Ca2+ concentration in Fura-2-loaded cells. At concentrations as low as 10(-7) M, it stimulated extracellular Na(+)-dependent 45Ca2+ efflux, possibly by increasing Na+/Ca2+ exchange. The maximal efflux of Ca2+ attained with 10(-5) M LPA was inhibited by tyrosine kinase inhibitors, but augmented by a protein kinase C inhibitor. These results suggest that LPA-induced Ca2+ efflux is controlled positively and negatively by mechanisms involving tyrosine kinase and protein kinase C, respectively.
Kenji Fukuzawa, Masahito Iemura and Akira Tokumura : Lipid peroxidation in egg phosphatidylcholine liposomes: comparative studies on the induction systems Fe2+/ascorbate and Fe3+-chelates/xanthine-xanthine oxidase., Biological & Pharmaceutical Bulletin, Vol.19, No.5, 665-671, 1996.
(要約)
Two typical systems of lipid peroxidation in egg yolk phosphatidylcholine (egg PC) liposomes were compared: an enzymic system involving superoxide (O2) generated by xanthine (X), xanthine oxidase (XO) and Fe(3+)-chelates (Fe(3+)-ADP and Fe(3+)-EDTA), and a non-enzymic system involving ascorbic acid (ASA) and Fe2+. These two systems exhibited a different pH-dependence: the rate in the enzymic system was maximal at pH 8-8.5, whereas that in the non-enzymic system was high below pH 7.4 and low above pH 7.6. The rates of lipid peroxidation differed with the membrane charge, and this charge-dependent phenomenon differed in the two peroxidation systems: in the Fe(3+)-chelates/X-XO-system, the rate was slow in neutrally charged egg PC liposomes and rapid in egg PC liposomes containing negatively charged dicetylphosphate (DCP) or positively charged stearylamine (SA), whereas in the Fe2+/AsA-system, the rate was rapid in neutral egg PC liposomes but no lipid peroxidation occurred in egg PC liposomes charged with DCP or SA. The decomposition rate of the hydroperoxide of PC (PC-OOH) incorporated into dimyristoyl-phosphatidylcholine (DMPC) liposomes differed depending on the membrane charge in the two systems and this charge-dependence of the rates correlated well with that of the initiation rate of lipid peroxidation dependent on membrane charge. In the Fe2+/AsA-system, lipid peroxidation depended on the endogenous presence of PC-OOH, and the amounts of PC-OOH required for initiation of the reaction differed depending on the membrane charge. However, in the Fe(3+)-chelates/X-XO-system, lipid peroxidation occurred very slowly in the absence of PC-OOH, but rapidly in its presence.
Hitoshi Houchi, M. Okuno, Masayuki Shono, Akira Tokumura and M. Oka : Regulations by cyclic nucleotides and phorbol ester of calcium efflux from cultured bovine adrenal chromaffin cells., Life Sciences, Vol.57, No.15, 211-215, 1995.
(キーワード)
calcium efflux / chromaffin cells
92.
Akira Tokumura, T Yotsumoto, Y Masuda and S Tanaka : Vasopressor effect of lysophosphatidic acid on spontaneously hypertensive rats and Wistar Kyoto rats, Research Communications in Molecular Pathology and Pharmacology, Vol.90, No.1, 96-102, 1995.
(要約)
Intravenous injection of lysophosphatidic acid (LPA, 1-acyl-sn-glycerol-3-phosphate) into conscious, spontaneously hypertensive rats (SHR) promptly elicited hypertension in a dose-dependent manner, its effect being significantly higher than in conscious, age-matched Wistar Kyoto strain rats (WKY). There was, however, no difference between the potencies of LPA in raising the mean blood pressure of SHR and WKY anesthetized with pentobarbital. The releases of norepinephrine, angiotensin II, prostaglandin and leukotriene were found not to be involved in the vasopressor effect of LPA in SHR, although thromboxane seemed to be slightly related to the action of LPA.
Takayuki Sugiura, Atsushi Yamashita, Naomi Kudo, Teruo Fukuda, Tatsuya Miyamoto, Neng Neng Cheng, Seishi Kishimoto, Keizo Waku, Tamotsu Tanaka, Hiroaki Tsukatani and Akira Tokumura : Platelet-activating factor and its structural analogues in the earthworm Eisenia foetida, Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol.1258, No.1, 19-26, 1995.
(要約)
The earthworm Eisenia foetida was shown to contain large amounts of ether-containing phospholipids such as alkylacylglycerophosphocholine (61.3% of choline glycerophospholipids) and alkenylacylglycerophosphoethanolamine (66.0% of ethanolamine glycerophospholipids). We also found a substantial amount of ether-containing PAF-like lipid in this animal, its level being increased after the animal is injured. We showed evidence that this PAF-like lipid consists of PAF and PAF analogues containing short chain fatty acids other than acetic acid. Notably, a propionic acid-containing species but not PAF itself, is the most predominant species in this animal. We also confirmed that the earthworms contain enzyme activities involved in the synthesis of PAF and short chain fatty acid-containing PAF analogues. Interestingly, the acetyltransferase activity in earthworms is resistant to high concentrations of the substrate lysophospholipid. Thus, both the structure of the PAF-like lipid and the properties of the enzymes involved in the PAF-like lipid metabolism in the earthworms are somewhat different from those in mammalian tissues.
Tamotsu Tanaka, Akira Tokumura and H. Tsukatani : Platelet activating factor (PAF)-like phospholipids formed during peroxidation of phosphatidylcholines from different foodstuffs, Bioscience, Biotechnology, and Biochemistry, Vol.59, No.8, 1389-1393, 1995.
(要約)
Previously, we reported that induction of peroxidation of synthetic phosphatidylcholines (PCs) containing a polyunsaturated fatty acid by Fe(2+)-EDTA in the presence of ascorbate resulted in the formation of four types of PCs with an sn-2-oxidatively fragmented acyl group, which had platelet-aggregating activity due to interaction with platelet-activating factor (PAF) receptors. These PCs were compounds with a short-chain monocarboxylate, omega-hydroxymonocarboxylate, dicarboxylate, and dicarboxylate semialdehyde residue, respectively. In this study, we investigated the PAF-like lipids formed during peroxidation of PCs from hen egg yolk, salmon roe, sea urchin eggs, and krill in an FeSO4/EDTA/ascorbate system. The platelet-aggregating activities of these oxidized PCs were all inhibited by FR-900452, an antagonist of PAF. The activity of oxidized krill PC, which was equivalent of 89.8 +/- 8.8 pmol 16:0-PAF/mumol of starting PC, was about 5 times those of oxidized PCs from salmon roe and sea urchin eggs, and about 50 times that of oxidized hen egg yolk PC. The PAF-like phospholipids that had different combinations of long-chain alkyl or acyl groups with one of the above four types of short-chain acyl groups were identified by gas chromatography-mass spectrometry. The results indicated that foodstuffs that are rich in 1-O-alkyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine are potential sources of compounds with high PAF-like activity formed by deleterious lipid peroxidation.
Kazushi Minami, Yasushi Hirata, Akira Tokumura, Yutaka Nakaya and Kenji Fukuzawa : Protein kinase c-independent inhibition of the Ca2+-activated K+ channel by angiotensin II and endothelin-1, Biochemical Pharmacology, Vol.49, No.8, 1051-1056, 1995.
(要約)
We previously reported that the Ca(2+)-activated K+ channel (KCa-channel) in cultured smooth muscle cells from porcine coronary artery was inhibited by protein kinase C (C-kinase). In this study, inhibition of the KCa-channel by receptor-mediated vascular contractile agonists, such as angiotensin II (ANG II) and endothelin-1 (ET-1), was investigated by the patch-clamp technique. In cell-attached patches, addition of ANG II (500 nM) or ET-1 (50 nM) to the bath inhibited the KCa-channel activated by the calcium ionophore A23187 (10-20 microM). Phorbol 12-myristate 13-acetate (PMA, 1 microM), a C-kinase activator, also decreased the open probability of the KCa-channel. The PMA-induced decrease in the open probability was reversed by subsequent application of staurosporine (1 nM), a C-kinase inhibitor, but the ANG II- and ET-1-induced decreases were not reversed by subsequent application of staurosporine (> 30 nM). Pretreatment of smooth muscle cells with 30 nM staurosporine, a protein kinase inhibitor, or 1 mM neomycin, an inhibitor of phospholipase C, also did not abolish the inhibition of the KCa-channel by ANG II. Furthermore, ANG II inhibited the KCa-channel in cells in which C-kinase was down-regulated. These results indicate that, in porcine coronary artery smooth muscle cells, ANG II and ET-1 inhibit the KCa-channel by a C-kinase-independent mechanism.
Kenji Fukuzawa, Keiji Soumi, Masahito Iemura, Satoru GOTO and Akira Tokumura : Dynamics of xanthine oxidase- and Fe^{3+}-ADP-dependent lipid peroxidation in negatively charged phospholipid vesicles, Archives of Biochemistry and Biophysics, Vol.316, No.1, 83-91, 1995.
(要約)
Superoxide (O2-)-dependent lipid peroxidation on addition of xanthine oxidase (XO) and Fe(3+)-ADP was induced in egg phosphatidylcholine (PC) liposomes containing dicetylphosphate (DCP), which are negatively charged like biological membranes, but not in uncharged egg PC liposomes. Positively charged Fe(3+)-ADP interacted more with negatively charged egg PC-DCP liposomes than with uncharged egg PC liposomes. The activities of Fe(3+)-chelates for initiating O(2-)-dependent lipid peroxidation were in the order Fe(3+)-ADP > Fe(3+)-citrate > Fe(3+)-oxalate = Fe(3+)-malonate > Fe(3+)-EDTA = 0. This order was the same as that for the reduction rates of these Fe(3+)-chelates to Fe(2+)-chelates by O(2-)-generated by XO. Lineweaver-Burk plots showed that the chelators inhibited XO by different mechanisms: uncompetitively by ADP and adenosine and non-competitively by organic acid chelators (citrate and oxalate) and EDTA. These results suggest that ADP interacts with XO in a manner different from the other chelators. Lipid peroxidation by XO-xanthine and Fe(3+)-ADP was induced in egg PC liposomes containing a trace (0.31-0.35 mol%) of peroxidized egg PC (PC-OOH), but not in PC-OOH-free liposomes of egg PC obtained by their pretreatment with triphenylphosphine. PC-OOH incorporated into dimyristoyl phosphatidylcholine (DMPC) liposomes was degraded on addition of both XO-xanthine and Fe(3+)-chelate, but not of either one alone. alpha-Tocopherol in DMPC liposomes was oxidized on addition of XO-xanthine and Fe(3+)-chelates in the presence, but not in the absence of PC-OOH. Furthermore, PC-OOH was required for decrease of the ESR spectrum of the spin probe 12-(N-oxyl-4,4'-dimethyloxazolidin-2-yl)stearic acid, which labels the hydrophobic region of egg PC liposome membranes, on addition of XO-xanthine and Fe(3+)-chelates. These results indicate that the "induction message of lipid peroxidation," which is associated with reduction of Fe(3+)-ADP by O2- and concurrent degradation of PC-OOH, must be transferred from the membrane surface to the inner hydrophobic region of the membranes.
T. Sugiura, A. Yamashita, N. Kudo, Tamotsu Tanaka and Akira Tokumura : Platelet-activating factor and its structural analogues in the earthworm Eisenia foetida, Biochim. Biophys. Acta, Vol.1258, 19-26, 1995.
98.
Hitoshi Houchi, Masaaki Okuno, Akira Tokumura, M Yoshizumi, Kenji Fukuzawa and Motoo Oka : Stimulatory effect of lysophosphatidic acid on calcium efflux from cultured bovine adrenal chromaffin cells, Life Sciences, Vol.57, 205-210, 1995.
99.
Hitoshi Houchi, Masaaki Okuno, M Shono, Akira Tokumura and Motoo Oka : Regulation by cyclic nucleotides and phorbol ester of calcium efflux from cultured bovine Adrenal chromaffin ccells, Life Sciences, Vol.57, 211-215, 1995.
100.
Hitoshi Houchi, Masaaki Okuno, Katsuji Kitamura, Yasuko Ishimura, Takeshi Ohuchi, Akira Tokumura and Motoo Oka : Stimulatory effect of angiotensin II on calcium efflux from cultured bovine adrenal chromaffin cells, Life Sciences, Vol.56, No.5, 109-114, 1994.
(要約)
The effect of angiotensin II on Ca2+ mobilization in cultured bovine adrenal chromaffin cells was examined. Angiotensin II (10(-7)M) increased the intracellular free Ca2+ level ([Ca2+]i) to a peak in the presence or absence of extracellular Ca2+, followed by decrease with time. Angiotensin II (10(-9)-10(-6)M) also stimulated 45Ca2+ efflux from cultured bovine adrenal chromaffin cells in a concentration-dependent manner. Its stimulatory effect on 45Ca2+ efflux was inhibited by the angiotensin II antagonist [Sar1, Ile8]-angiotensin II or [Sar1, Val5, Ala8]-angiotensin II. The increase in angiotensin II-stimulated 45Ca2+ efflux was dependent on the extracellular Na+ concentration. Angiotensin II also increased 22Na+ influx into the cells. These results indicate that stimulation of the angiotensin II receptor induces extracellular Na(+)-dependent Ca2+ efflux from cultured bovine adrenal chromaffin cells, probably by acceleration of Na+/Ca2+ exchange.
(キーワード)
Adrenal Medulla / Angiotensin II / Animals / カルシウム (calcium) / Calcium Radioisotopes / Carrier Proteins / Cattle / Cells, Cultured / Chromaffin System / Extracellular Space / Sodium / Sodium Radioisotopes / Sodium-Calcium Exchanger / Stimulation, Chemical
Tsuzuki Kobayashi, Shuji Yamano, Shinji Murayama, Hiromi Ishikawa, Akira Tokumura and Toshihiro Aono : Effect of lysophosphatidic acid on the preimplantation development of mouse embryos, FEBS Letters, Vol.351, No.1, 38-40, 1994.
(要約)
The effect of lysophosphatidic acid (LPA) on the preimplantation development of mouse embryos was examined. The blastocyst rates from 2-cell and 4-cell stage embryos were significantly higher in the presence of LPA at the pronuclear stage. However, the blastocyst rate from 4-cell stage embryos was significantly lower when LPA was added to the medium at the 4-cell stage than when it was added at the pronuclear stage. Furthermore, pretreatment of pronuclear stage embryos with pertussis toxin suppressed LPA-induced embryo development, suggesting that it is probably mediated by a Gi-protein-linked receptor.
(キーワード)
Animals / Blastocyst / Culture Techniques / Embryonic Development / Embryonic and Fetal Development / Female / Lysophospholipids / Mice / Mice, Inbred ICR / Pregnancy
Akira Tokumura, Makoto Iimori, Yuko Nishioka, Maki Kitahara, Mitsuaki Sakashita and Sakuya Tanaka : Lysophosphatidic acids induce proliferation of cultured vascular smooth muscle cells from rat aorta, The American Journal of Physiology, Vol.267, No.1 Pt 1, 204-210, 1994.
(要約)
Lysophosphatidic acids (LPA) with a C18 fatty acyl group accelerated thymidine incorporation into cultured rat aortic vascular smooth muscle cells and stimulated their cell division. LPA acted synergistically with epidermal growth factor and fibroblast growth factor but additively with platelet-derived growth factor. The stimulatory actions of LPA were suggested to be rather specific from the following findings: 1) their stimulation of DNA synthesis increased with an increase in their acyl moiety; 2) lysophosphatidylcholine, a neutral lysophospholipid, had no mitogenic action but was cytotoxic at high concentrations; and 3) LPA induced a rapid external Ca(2+)-independent increase in intracellular Ca2+ concentration ([Ca2+]i) in single fura 2-loaded cells that resembled the receptor-mediated increases in [Ca2+]i triggered by different agonists, whereas lysophosphatidylcholine provoked a slow sustained increase in [Ca2+]i in an external Ca(2+)-dependent manner. These results are discussed in relation to the possible pathophysiological role of LPA.
Takayuki Sugiura, Akira Tokumura, L Gregory, Teri Nouchi, T S. Weintraub and J Donald Hanahan : Biochemical Characterization of the Interaction of Lipid Phosphoric Acids with Human Platelets: Comparison with Platelet Activating Factor, Archives of Biochemistry and Biophysics, Vol.311, No.2, 358-368, 1994.
(要約)
A series of lipid phosphoric acids, including 1-O-alkyl-2-lyso-glycerophosphoric acid, 1-O-acyl-2-lyso-glycerophosphoric acid, hexadecylpropanediolphosphoric acid, N-acyl-2-aminoethanolphosphoric acid, sphingosine phosphoric acid, and certain homologues and analogues, were synthesized and characterized by thin-layer chromatography, fast-atom bombardment mass spectrometry, and their ability to aggregate human platelets. The presence of a receptor for these lipid phosphoric acids that is distinct from the PAF receptor is strongly suggested from experiments involving a desensitization procedure, platelet-activating factor (PAF) receptor antagonists, and inhibitors of the lipid phosphoric acids. The unique features of the interaction of these lipid phosphoric acids with platelets include: (a) evidence for a separate receptor(s) for this diverse group of synthetic compounds, (b) no requirement for stereospecificity (i.e., no glycerol backbone), and (c) a structural requirement for a long-chain hydrocarbon residue covalently bound to a phosphoric acid residue. In the interaction of these compounds with the platelet, it is mandatory that extracellular Ca2+ and ADP be present for maximum biological activity. The potential involvement of a lipid phosphoric acid receptor, which could form a component of the activation pathway associated with various lysophospholipids and analogues, such as PAF, via a phospholipase D activation, is discussed.
Tamotsu Tanaka, M Iimori, Hiroaki Tsukatani and Akira Tokumura : Platelet-aggregating effects of platelet-activating factor-like phospholipids formed by oxidation of phosphatidylcholines containing an sn-2-polyunsaturated fatty acyl group, Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol.1210, No.2, 202-208, 1994.
(要約)
Previously, we reported the formation of four kinds of phosphatidylcholines (PC) with a short-chain monocarboxylate, dicarboxylate, dicarboxylate semialdehyde or omega-hydroxymonocarboxylate group by oxidation of PCs containing polyunsaturated fatty acid (PUFA) in an FeSO4/ascorbate/EDTA system. In this study, we identified these novel phospholipids by GC-MS as oxidation products of two alkyl ether-linked PCs, 1-O-hexadecyl-2-docosahexaenoyl and 1-O-hexadecyl-2-arachidonoyl-sn-glycero-3- phosphocholine (GPC). The sn-2-acyl moieties of oxidatively fragmented PCs derived from PCs containing docosahexaenoate were one methylene unit shorter than those detected as major oxidation products of PCs containing arachidonate. The platelet-aggregations induced by the oxidized PCs were all inhibited by FR-900452, an antagonist of platelet activating factor (PAF). The PAF-like activity of oxidized 1-O-hexadecyl-2-docosahexaenoyl-GPC, which was equivalent of 1372 +/- 262 pmol 16:0-PAF/mumol starting PC, was 5 times that of oxidized 1-O-hexadecyl-2-arachidonoyl-GPC and 150 times that of oxidized 1-palmitoyl-2-docosahexaenoyl-GPC, suggesting that both an sn-1-alkyl ether linkage and an sn-2-acyl group with a short chain length are important structural requirements for induction of platelet aggregation. These possibilities were confirmed by experiments on the platelet-aggregating activities of synthetic PAF-like compounds. Quantitative measurements by GC-MS of PAF-like phospholipids formed by lipid peroxidation and the activities of synthetic PAF-like phospholipids, suggested that the activities of most oxidized PCs containing PUFA were ascribable to those of PCs with an sn-2-short-chain monocarboxylate group.
Tamotsu Tanaka, H. Iimori, H. Tsukatani and Akira Tokumura : Platelet-aggregating effects of platelet-activating factor-like phospholipids formed by oxidation of phosphatidylcholines containing an sn-2 polyunsaturated fatty acyl group, Biochim. Biophys. Acta, Vol.1210, 202-208, 1994.
106.
Tamotsu Tanaka, H. Minamino, S. Unezaki, H. Tsukatani and Akira Tokumura : Formation of platelet-activating factor-like phospholipids by Fe2+/ascorbate/EDTA-induced lipid peroxidation, Biochim. Biophys. Acta, Vol.1210, 202-208, 1994.
107.
Marilena E Lekka, Akira Tokumura, Hideaki Tsuji and Donald J Hanahan : Isolation of a phospholipid inhibitor of platelet activating factor-induced activity from perfused rat liver: identification as phosphatidylglycerol, Archives of Biochemistry and Biophysics, Vol.302, No.2, 380-384, 1993.
(要約)
An endogenous inhibitor of platelet activating factor action was isolated from perfused rat liver. It was purified by thin-layer chromatography and high-performance liquid chromatography and subjected to chemical modifications in order to identify its structure. On the basis of its fast atom bombardment-mass spectrum it was characterized as phosphatidylglycerol composed mainly of 16:0/18:1 and 16:0/20:2 fatty acyl chains ([M+H]+ at m/z 749 and 775, respectively) and very minor levels of 18:0/18:1 and 18:0/20:2. The purified compound exhibited inhibition on rabbit platelet aggregation induced by 5 x 10(-10) M platelet activating factor (PAF) at an EC50 value near 2.5 x 10(-6) M and on the serotonin secretion at an EC50 7 x 10(-6) M. Other phospholipids isolated from the liver preparations, such as phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, cardiolipin (diphosphatidylglycerol), and phosphatidic acid, exhibited no inhibitory activity in the concentration range from 1 x 10(-4) to 1 x 10(-7) M nor did they induce any aggregation, or lysis, of the platelets. Of importance, phosphatidylglycerol could inhibit thrombin- and ADP-induced aggregation of rabbit platelets. These results suggested a possible site of inhibition common to the signal transduction pathway of these agonists. Preliminary binding experiments showed a noncompetitive type of inhibition on PAF binding to intact rabbit platelets.
Yasuhito Nakagawa, Masaki Sugai, Ken Karasawa, Akira Tokumura, Hiroaki Tsukatani, Morio Setaka and Shoshichi Nojima : Possible influence of lysophospholipase on the production of 1-acyl-2-acetylglycerophosphocholine in macrophages, Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol.1126, No.3, 277-285, 1992.
(要約)
The rate of production of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF) and 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (acylPAF) was measured in macrophages following the incorporation of [3H]acetate. Upon activation by A23187, guinea pig alveolar macrophages incorporated [3H]acetate into PAF, but a little radioactivity was found in acylPAF. However, labeling of acylPAF and PAF with [3H]acetate was greatly enhanced in A23187-stimulated alveolar macrophages that had been pretreated with phenylmethanesulphonyl fluoride (PMSF). [3H]PAF was predominantly converted to 1-[3H]alkyl-2-acyl glycerophosphocholine, but [14C]acylPAF rapidly hydrolyzed to 14C-labeled free fatty acid by the incubation with lysates prepared from macrophages. The deacetylation of [14C]acylPAF and [3H]PAF by acetylhydrolase and also the hydrolysis of [14C]lysoPC by lysophospholipase were strongly inhibited in macrophages that had been pretreated with PMSF, while PMSF failed to inhibit the activities of acetyltransferase and acyltransferase. The relative proportions of PAF and acylPAF were quite different in different types of cells. In contrast to alveolar macrophages, peritoneal macrophages, neutrophils and spleen cells from guinea pigs incorporated 2-4 times more [3H]acetate into acylPAF than into PAF. The presence of high levels of acylPAF in peritoneal macrophages was confirmed by GLC-MS analysis. The activities of lysophospholipase, acetylhydrolase and acetyltransferase were measured in alveolar and peritoneal macrophages to determine whether the preferential formation of acylPAF as compared to PAF in peritoneal macrophages was due to differences in these activities between alveolar and peritoneal macrophages. The activity of acetylhydrolase of peritoneal macrophages was almost the same as that in alveolar macrophages. The activity of acetyltransferase in peritoneal macrophages was about half of that in alveolar macrophages. However, the activity of lysophospholipase in peritoneal macrophages was one-sixth of that in alveolar macrophages. These results suggest that lysophospholipase is one of the primary factors involved in the control of the production of acylPAF in activated cells, and that it acts by modulating the availability of lysoPC for the synthesis of acylPAF. Furthermore, high levels of activity of lysophospholipase allow the preferential formation of PAF, via the rapid hydrolysis of lysoPC which would act as a competitive inhibitor of the incorporation of acetate into lysoPAF.
Akira Tokumura, Toshihiko Tsutsumi and Hiroaki Tsukatani : Transbilayer movement and metabolic fate of ether-linked phosphatidic acid (1-O-Octadecyl-2-acetyl-sn-glycerol 3-phosphate) in guinea pig peritoneal polymorphonuclear leukocytes, The Journal of Biological Chemistry, Vol.267, No.11, 7275-7283, 1992.
111.
Akira Tokumura, Takashi Yotsumoto, T. Hoshikawa, Tamotsu Tanaka and Hiroaki Tsukatani : Quantitative analysis of platelet-activating factor in rat brain, Life Sciences, Vol.51, 303-308, 1992.
112.
Masanobu Fujii, Akira Tokumura, Toshihiko Tsutsumi, Hiroaki Tsukatani, Mikiko Kano and Akira Tanaka : Residue analysis of oleic acid in cucumber fruits after spraying sodium oleate solution, Journal of Pesticide Science, Vol.17, No.3, 141-145, 1992.
Akira Tokumura, Takashi Yotsumoto, Takefumi Hoshikawa, Tamotsu Tanaka and Hiroaki Tsukatani : Quantitative analysis of platelet-activating factor in rat brain, Life Sciences, Vol.51, No.4, 303-308, 1992.
(要約)
Age-related decrease of the platelet-activating factor (PAF) content in rat brain was shown by a convenient method consisting of solid extraction of lipids with a Sep-Pak C-18 cartridge, lipid separation by HPLC and bioassay on rabbit platelets. This method was sufficiently sensitive to allow measurement of PAF in a single brain, and the recovery of PAF was quite high throughout the procedure.
Akira Tokumura, Nobuyuki Yube, Motonori Terao and Hiroaki Tsukatani : Antagonism of platelet-activating factor in isolated rat colon: possible mechanism, Lipids, Vol.26, No.12, 1344-1346, 1991.
(要約)
The contractions of three different regions of rat colon in response to platelet-activating factor (PAF) were compared. The ascending colon was found to be the most responsive. The slow contraction of the ascending colon induced by PAF was dependent on external Ca2+. CV-3988, a structural analog of PAF, slowly induced irreversible inhibition of PAF-induced contraction, whereas FR-900452, which is structurally unrelated to PAF, caused rapid reversible inhibition of PAF-induced contraction. No inhibitory effects of CV-3988 were observed when the strip was washed with Tyrode's solution containing 1% bovine serum albumin (BSA). The results suggest that PAF and CV-3988 penetrate slowly into the outer half of the lipid bilayer of plasma membranes of cells in isolated rat colon, and then rapidly diffuse laterally to associate firmly with specific binding sites.
Akira Tokumura, Nobuyuki Yube, Hiroaki Fujimoto and Hiroaki Tsukatani : Lysophosphatidic acids induce contraction of rat isolated colon by two different mechanisms, The Journal of Pharmacy and Pharmacology, Vol.43, No.11, 774-778, 1991.
(要約)
Lysophosphatidic acids (1-linoleoyl-, 1-linolenoyl, 1-arachidonoyl- and 1-O-hexadecyl-sn-glycero-3-phosphate) induced rapid contraction of rat isolated colon which was dependent on external Ca2+, 1-linolenoyl-lysophosphatidic acid having the greatest effect. The contraction induced by 1-linolenoyl-lysophosphatidic acid was reduced considerably by nifedipine and verapamil, but not by atropine or indomethacin. Phosphatidic acids with two short-chain acyl groups induced a small, atropine-sensitive contraction at 100 microM, but phosphatidic acids with two long-chain acyl groups were inactive. These results suggest that unlike phosphatidic acids, lysophosphatidic acids act directly on extracellular sites of the plasma membrane of smooth muscle cells in rat colon, mainly through activation of voltage-sensitive Ca2+ channels.
Akira Tokumura, Tamotsu Tanaka, Takashi Yotsumoto and Hiroaki Tsukatani : Identification of sn-2-ω-hydroxycarboxylate-containing phospholipids in a lipid extract from bovine brain, Biochemical and Biophysical Research Communications, Vol.177, No.1, 466-473, 1991.
(要約)
Phospholipids having both a long-chain acyl (palmitoyl or stearoyl) and a short-chain hydroxycarboxylyl (C3-C9) residue were identified by GC-MS in a fraction with PAF-like activity from a bovine brain lipid extract. The hydroxyl group in the hydroxycarboxylate residue was determined to be at the omega-position by comparison of the mass spectra of the tert-butyl-dimethylsilyl derivatives of these compounds with those of synthetic hydroxybutyrate-containing phosphatidylcholines. The co-existence of short-chain hydroxycarboxylate-, monocarboxylate- and dicarboxylate-containing phospholipids in the bovine brain lipid extract suggested that these compounds were formed by peroxidation of membrane phospholipids, especially phosphatidylcholines.
Akira Tokumura, Toshihiko Tsutsumi, Junichi Yoshida and Hiroaki Tsukatani : Translocation of exogenous platelet-activating factor and its lyso-compound through plasma membranes is a rate-limiting step for their metabolic conversions into alkylacylglycerophosphocholines in rabbit platelets and guinea-pig leukocytes, Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol.1044, No.1, 91-100, 1990.
(要約)
Platelets and leukocytes are known to degrade platelet-activating factor (PAF), a potential mediator of inflammation, to its lyso-derivative (lyso-PAF) and then convert this to 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholines. However, little is known about the mechanism of internalization of PAF and lyso-PAF, which is a prerequisite for their metabolism within the cells. In this work, the internalization of PAF and lyso-PAF by rabbit platelet and guinea-pig leukocyte plasma-membranes were examined by the washing method with bovine serum albumin. The rates of translocation of PAF and lyso-PAF across guinea-pig plasma membranes were significantly higher than those across rabbit platelets. In these cells, the translocation of PAF was found to be accelerated indirectly by activation of PAF receptors by a small portion of added PAF. Results suggest that a temperature-dependent diffusion process is involved in the internalization of these phospholipids. In both rabbit platelets and guinea-pig leukocytes, the translocation of PAF and lyso-PAF through the plasma membranes was shown to be rate-limiting for the metabolic conversion of these compounds to 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine.
Akira Tokumura, Kazuya Morisawa, Akihiko Hiroshima, Toshihiko Tsutsumi, Kenji Fukuzawa and Hiroaki Tsukatani : Calcium movements in rabbit platelets induced by platelet-activating factor and its regulation by an antagonist of platelet-activating factor,, platelet-activating factor and its regulation by an antagonist of platelet-activating factor,, Vol.9, 63-71, 1990.
119.
Kenji Fukuzawa, Y Kurotori, Akira Tokumura and Hiroaki Tsukatani : Vitamin E. deficiency increases the synthesis of platelet-activating factor (PAF) in rat polymorphonuclear leucocytes, Lipids, Vol.24, No.3, 236-239, 1989.
(要約)
Vitamin E deficiency was found to stimulate FMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine)-induced biosynthesis of PAF (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in polymorphonuclear leucocytes (PMN) from rat peritoneum. In three separate experiments each, the amounts of PAF synthesized during 6 min and 12 min incubation of PMN cells from control, vitamin E-supplemented, and vitamin E-deficient rats were 129-240, 131-227 and 248-354 pmol/10(6) cells, respectively. The activity of the acetyl-transferase, which transfers the acetyl moiety of [3H]acetyl-CoA to 2-lysoPAF (1-O-alkyl-sn-glycero-3-phosphocholine) to form [3H]PAF, was higher in PMN homogenates from vitamin E-deficient rats (2.28 +/- 0.07 nmol/min/mg protein) than in those from E-supplemented rats (1.06 +/- 0.10 nmol/min/mg protein). However, there was no difference between the two groups in the activity of acetylhydrolase (4.26 +/- 0.71 and 4.26 +/- 0.06 nmol/min/mg protein, respectively), measured as degradation of [3H]PAF to [3H]lysoPAF. In vitro addition of alpha-tocopherol did not inhibit the increased activity of acetyl-transferase in vitamin E-deficient rats, indicating that the enzyme in vitamin E-supplemented rats was not directly inhibited by alpha-tocopherol. The acetyl-transferases of the two groups showed similar Km values for acetyl-CoA, but different Vmax values (225 microM and 6.4 nmol/min/mg protein in vitamin E-deficient rats, and 216 microM and 3.6 nmol/min/mg protein in vitamin E-supplemented rats), suggesting that the enzyme was not activated but increased in amount in vitamin E deficiency.
(キーワード)
Acetyl Coenzyme A / Acetyltransferases / Animals / Enzyme Activation / Male / Neutrophils / Platelet Activating Factor / Rats / Rats, Inbred Strains / Time Factors / Vitamin E Deficiency
Akira Tokumura, Kenkichi Takauchi, Tsuyoshi Asai, Koumei Kamiyasu, Tadashi Ogawa and Hiroaki Tsukatani : Novel molecular analogues of phosphatidylcholines in a lipid extract from bovine brain: 1-long-chain acyl-2-short-chain acyl-sn-glycero-3- phosphocholines, Journal of Lipid Research, Vol.30, No.2, 219-224, 1989.
121.
Akira Tokumura, Tsuyoshi Asai, Keichnki Takauchi, Koumei Kamiyasu, Tadashi Ogawa and Hiroaki Tsukatani : Novel phospholipids with aliphatic dicarboxylic acid residues in a lipid extract from bovine brain, Biochemical and Biophysical Research Communications, Vol.155, No.2, 863-869, 1988.
(要約)
A vasodepressor phospholipid fraction purified from a lipid extract of bovine brain was found to contain novel phospholipids with both a long-chain acyl group and an aliphatic dicarboxylic acid residue. This was shown by analyzing the fraction as tert-butyldimethylsilyl derivatives of glyceride by capillary GC-MS after hydrolysis with phospholipase C. Six molecular species with a palmitoyl group and an aliphatic dicarboxylate (chain length C4-C9), and two species with both a stearoyl group and a succinate or glutarate residue were detected.
(キーワード)
Animals / Brain Chemistry / Cattle / Gas Chromatography-Mass Spectrometry / Phospholipids / Type C Phospholipases
Akira Tokumura, M Terao, M Okamoto, K Yoshida and Hiroaki Tsukatani : Study of platelet activating factor and its antagonists on rat colon strip with a new method avoiding tachyphylaxis, European Journal of Pharmacology, Vol.148, No.3, 353-360, 1988.
(要約)
Platelet activating factor induced slow, but sustained contraction of isolated rat colon in a dose-dependent manner. The contraction persisted even when the strips were washed several times with Tyrode solution. However, the addition of high concentrations of bovine serum albumin to the washing solution led to the rapid relaxation of the strips to the basal level, possibly by removing platelet activating factor tightly bound to rat colon. These strips then responded normally to a second addition of platelet activating factor. Neither the cholinergic nervous system nor release of histamine, serotonin, prostaglandins or leukotriene D4 were significantly involved in the contraction induced by platelet activating factor. FR-900452 and CV-3988, recently found to be antagonists of platelet activating factor, selectively blocked the contraction of rat colon induced by the active phospholipid, indicating that it induced contraction by a direct stimulatory effect on the smooth muscle of rat colon in a receptor-mediated manner.
Kenji Fukuzawa, Katsuya Kishikawa, Toyohiro Tadokoro, Akira Tokumura, Hiroaki Tsukatani and Janusz M Gebicki : The effect of a-tocopherol on site-specific lipid peroxidation induced by iron in charged micelles, Archives of Biochemistry and Biophysics, Vol.260, No.1, 153-160, 1988.
(要約)
alpha-Tocopherol inhibited H2O2-Fe2+-induced lipid peroxidation of linoleic acid (LA) by scavenging OH radicals in tetradecyltrimethylammonium bromide (TTAB) micelles. The inhibiting ability of alpha-tocopherol was much greater than that of OH-radical scavengers mannitol and t-butanol. In contrast, alpha-tocopherol enhanced linoleic acid hydroperoxide (LOOH)-Fe2+-induced lipid peroxidation through regeneration of Fe2+ in sodium dodecyl sulfate (SDS) micelles containing LA. alpha-Tocopherol was oxidized by Fenton's reagent (FeSO4 + H2O2) at a higher rate in SDS micelles than in TTAB micelles. The likely oxidants were OH radicals in the former and Fe3+ in the latter. Both reagents formed in the Fenton reaction. Ferrous ion catalyzed in a dose-dependent manner the decomposition of LOOH and conjugated diene compounds in SDS but not in TTAB micelles. alpha-Tocopherol and Fe3+ individually had no effect on the decomposition of LOOH, but together were quite effective. The rate of the decomposition was a function of the concentration of alpha-tocopherol. The mechanism of "site-specific" antioxidant action of alpha-tocopherol in charged micelles is discussed.
Hiroshi Homma, Akira Tokumura and J Donald Hanahan : Binding and internalization of platelet-activating factor 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine in washed rabbit platelets, The Journal of Biological Chemistry, Vol.262, No.22, 10582-10587, 1987.
(要約)
The binding profile of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC, platelet-activating factor) to washed rabbit platelets was investigated through the use of structural analogs of AGEPC, e.g. U66985, which specifically suppressed AGEPC biological activities on rabbit platelets. This interaction of AGEPC with platelets could be divided into three different components termed A, B, and C. Component A was considered as one of high affinity (Kd = 0.5 X 10(-9) M) and with a low capacity (about 400 sites/platelet). The binding of AGEPC to component A was reversible and was blocked by the inhibitory analogs of AGEPC. This was considered to be the AGEPC receptor site(s). Component B was irreversible in nature and was presumed to be associated with internalization of AGEPC. The latter process was sensitive to the structural inhibitors. Component C was not affected by the inhibitors and probably represented a nonspecific binding to the lipid layer of the membrane. The binding profile of 1-O-alkyl-2-(lyso)-sn-glycero-3-phosphocholine, a biologically inactive and noninhibitory analog of AGEPC, was observed to consist of a single component and was (also) unaffected by the inhibitors. Internalization of AGEPC into rabbit platelets was further examined by the bovine serum albumin extraction method, which was originally developed by Mohandas et al. (Mohandas, N., Wyatt, J., Mel, S. F., Rossi, M. E., and Shohet, S. B. (1982) J. Biol. Chem. 257, 6537-6543). AGEPC was instantly taken up by the cell and internalization into its membrane, where it remained and was not released into cytosol. The internalization of AGEPC was suppressed by pretreating the cells with AGEPC analogs. In platelets desensitized to AGEPC, no down-regulation of the receptor site(s) was observed. The internalization of AGEPC in the desensitized cells was clearly enhanced and this was obvious even in the presence of the AGEPC inhibitor(s). Even in the presence of the inhibitors, effective internalization of AGEPC was also evident in thrombin-treated cells. These results suggested that the internalization of AGEPC was irreversibly enhanced in the platelets which were activated by AGEPC itself as well as by thrombin.
Akira Tokumura, Koumei Kamiyasu, Kenkichi Takauchi and Hiroaki Tsukatani : Evidence for existence of various homologues and analogues of platelet activating factor in a lipid extract of bovine brain, Biochemical and Biophysical Research Communications, Vol.145, No.1, 415-425, 1987.
(要約)
Vasodepressor phospholipid with platelet-aggregating activity was highly purified from a lipid extract of bovine brain and subjected to field desorption-mass spectrometry. It was further analyzed by gas-liquid chromatography-mass spectrometry after hydrolysis with phospholipase C and conversion to tert-butyldimethylsilyl derivatives. Results indicated the presence of four species of platelet activating factor (1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) and ten acyl analogues of PAF. The acyl analogues of PAF included species having an sn-2-propionyl or sn-2-butyryl group, which have not been previously detected in natural sources. The total amount of acyl analogues of PAF was much higher than that of PAF.
Akira Tokumura, Junichi Yoshida, Takayuki Maruyama, Kenji Fukuzawa and Hiroaki Tsukatani : Platelet aggregation induced by ether-linked phospholipids. 1. Inhibitory actions of bovine serum albumin and structural analogues of platelet activating factor, Thrombosis Research, Vol.46, No.1, 51-63, 1987.
(要約)
Ether-linked lysophosphatidic acid was able to induce aggregation of platelets from various animals. Feline platelets were the most sensitive followed in decreasing order by human, bovine and rabbit platelets. ONO-6240 and CV-3988, which are antagonists of platelet activating factor, did not inhibit aggregation of feline platelets induced by ether-linked lysophosphatidic acid, indicating that the aggregation induced by the lysophosphatidic acid did not involve receptors for platelet activating factor. An addition of bovine serum albumin caused dose-dependent inhibitions on the aggregation of platelets by both ether-linked lysophosphatidic acid and platelet activating factor. Moreover, 0.5% bovine serum albumin reversed platelet aggregation by the active phospholipid before this aggregation reached a maximum. These results suggest that the lysophosphatidic acid exerts its stimulatory action extracellularly, probably by interacting with specific sites on the surface of platelet.
Akira Tokumura, Junichi Yoshida, Nobuko Okasaka, Kenji Fukuzawa and Hiroaki Tsukatani : Platelet aggregation induced by ether-linked phospholipids. 2. Mechanism of desensitization of rabbit platelets by platelet activating factor and reversibility of inhibitory actions of its antagonists, Thrombosis Research, Vol.46, No.1, 153-161, 1987.
(要約)
Rabbit platelets pretreated with CV-3988 had reduced responsiveness to platelet activating factor(PAF) even after the platelets had been washed with a buffer. This was due to its tight binding to receptor sites for PAF, but not conformational changes of the receptor, because the platelets that were pretreated with CV-3988 and then washed with buffer containing 0.5% bovine serum albumin showed full responsiveness to PAF. In contrast, the reduced responsiveness of PAF-pretreated rabbit platelets was not reversed by washing with buffer containing 0.5% BSA. The PAF-pretreated platelets showed significantly lower responsiveness to 1-O-hexadecyl-2-O-monomethylaminocarbonyl-sn-glycero-3-phosphochol ine (MC-PAF) than to PAF, although MC-PAF had the same potency as PAF on inducing aggregation of normal rabbit platelets by interacting with receptor sites for PAF. These results suggest that the desensitization is accompanied by a decreased affinity of receptor sites for PAF or reduced efficiency in coupling of activated receptor to regulatory protein in plasma membranes rather than loss of receptor sites.
Junichi Yoshida, Akira Tokumura, Kenji Fukuzawa, Motomori Terao, Kenkichi Takauchi and Hiroaki Tsukatani : A platelet-aggregating and hypotensive phospholipid isolated from bovine brain, The Journal of Pharmacy and Pharmacology, Vol.38, No.12, 878-882, 1986.
(要約)
A phospholipid that differs from known active lipids and causes potent platelet aggregation and weak hypotension has been isolated from bovine brain. Its platelet aggregating effect on heparinized platelet-rich plasma from rabbits, was at a threshold concentration of about 0.2 nmol ml-1 as phosphorus. The effect was inhibited by CV-3988. The phospholipid was converted by diazomethane treatment to another active lipid that caused short-term hypotension, but not platelet aggregation, rather it inhibited the aggregation of rabbit heparinized platelets induced by platelet-activating factor.
Akira Tokumura, William Kramp and Donald J Hanahan : Alkylacetylglycerophosphocholine effects on the metabolism of phospholipids in rabbit platelets: effects of extracellular Ca2+ and prostacyclin, Archives of Biochemistry and Biophysics, Vol.247, No.2, 403-413, 1986.
(要約)
Alkylacetylglycerophosphocholine (AGEPC) stimulation of 32P-labeled lysophosphatidic acid formation in washed rabbit platelets was dependent on extracellular Ca2+. Its accumulation was slower and required a higher concentration of AGEPC in comparison to the degradation of inositol phospholipids and production of phosphatidic acid induced by the same agonist. These results suggest that the formation of lysophosphatidic acid is not directly related to the primary activation of rabbit platelets by AGEPC. AGEPC elicited a preferential degradation of inositol phospholipids in the following order: phosphatidylinositol 4,5-bisphosphate greater than phosphatidylinositol 4-phosphate greater than phosphatidylinositol. The degradation of inositol phospholipids and subsequent production of phosphatidic acid were affected by pretreatment of platelets with prostacyclin or ethylene glycol bis (beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA). Synergistic inhibitions of these metabolic changes were observed in the platelets pretreated with both prostacyclin and EGTA. These results were compared with effects of prostacyclin and EGTA on serotonin release induced by AGEPC, and the possible roles of metabolic changes in phospholipids induced by AGEPC are discussed with respect to the mechanism of platelet activation.
Akira Tokumura, Yasuko Yoshioka, Hiroaki Tsukatani and Yasomi Handa : Gas chromatographic/mass spectrometric analyses of ether-linked lysophosphatidic acid and its analogues, Biomedical & Environmental Mass Spectrometry, Vol.13, No.4, 175-180, 1986.
Akira Tokumura, Kengo Harada, Kenji Fukuzawa and Hiroaki Tsukatani : Involvement of lysophospholipase D in the production of lysophosphatidic acid in rat plasma., Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol.875, No.1, 31-38, 1986.
Kenji Fukuzawa, K Kishikawa, Akira Tokumura, Hiroaki Tsukatani and M Shibuya : Fluorescent pigments by covalent binding of lipid peroxidation by-products to protein and amino acids, Lipids, Vol.20, No.12, 854-861, 1985.
(要約)
The fluorescent products formed on reaction of 12-oxo-cis-9-octadecenoic acid (12-keto-oleic acid) with about 20 different amino acids, polylysine and bovine serum albumin (BSA) were studied. Besides glycine, only the basic amino acids histidine, lysine and arginine gave products with strong fluorescence. N-Acetylation of amino acids greatly reduced the fluorescence of their reaction products. The formation of fluorescent products was inhibited strongly by SH-amino acids such as N-acetyl-cysteine and glutathione. Polyacrylamide gel electrophoresis showed that BSA treated with 12-keto-oleic acid was more acidic than untreated or ricinoleic acid-treated BSA, indicating that basic amino acid residues in BSA were modified by reaction with the keto fatty acid. None of the structural analogs of 12-keto-oleic acid tested--12-oxo-trans-10-octadecenoic acid, 12-oxo-octadecanoic acid, 12-hydroxy-cis-9-octadecenoic acid (ricinoleic acid), cis-9-octadecenoic acid (oleic acid) and linoleic acid--reacted with glycine to give a fluorescent product. The fluorescent products formed on reaction of 12-keto-oleic acid methyl ester with benzyl amine and glycine methyl ester were shown to be 8-(N-substituted-4,5-dihydro-4-oxo-5-hexyl-5-hydroxy-2-pyrrolyl) octanoic acid methyl esters. The fluorescence properties of these compounds were attributed to the chromophobic system NC = CC = O which contains 6 pi electrons. This investigation contributes to insight of the mechanism of formation of fluorescent pigments, probably by a similar reaction of other compounds of the beta, gamma-unsaturated carbonyl type.
J Donald Hanahan, T Susan Weintraub, J Samuel Friedberg, Akira Tokumura and E D. Ayer : A novel approach to structure proof of glyceryl ether-containing glycerophospholipids. Base-catalyzed methanolysis of platelet-activating factor (AGEPC) at 60 degrees C, Journal of Lipid Research, Vol.26, No.11, 1345-1355, 1985.
(要約)
A novel reaction was explored in which synthetic platelet-activating factor, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC), upon treatment with 1 N NaOH in methanol at 60 degrees C for 20 min, sequentially released the acetyl group, then the choline moiety with concomitant formation of the monomethyl ester of 1-O-alkyl-glycero-phosphoric acid. A mechanism is proposed in which a transient cyclic phosphate intermediate is formed and then attacked by a CH3O moiety to yield a mixture of the sn-2 and sn-3 methyl esters. Proof of structure of the monomethyl ester derivative was achieved through the use of thin-layer chromatography, aluminum oxide chromatography, and examination of the trimethylsilyl derivative of the monomethyl ester by gas-liquid chromatography-mass spectrometry. Replacement of the acyl group on the 2 position with an ethyl or methyl residue completely prevented any attack by 1 N NaOH in methanol at 60 degrees C. Sphingomyelin was not attacked and only acetate removal was noted with 1-O-alkyl-2-acetyl-sn-glycero-3-phosphoethanolamine under similar conditions. The significance of these findings as they relate to the influence of substituents on the chemical and biological reactivity of AGEPC is discussed.
Akira Tokumura, Hiroshi Homma and J Donald Hanahan : Structural analogs of alkylacetylglycerophosphocholine inhibitory behavior on platelet activation, The Journal of Biological Chemistry, Vol.260, No.23, 12710-12714, 1985.
(要約)
Several analogs of alkylacetylglycerophosphocholine (AGEPC; platelet-activating factor) were investigated as potential selective inhibitors of AGEPC-induced activation of washed rabbit platelets. Two particular compounds, CV-3988 (rac-3-(N-n-octadecylcarbamoyloxy)-2-methoxypropyl-2-thiazolioethyl++ + phosphate) and U66985 (1-O-octadecyl-2-acetyl-sn-glycero-3-phosphoric acid-6'-trimethylammonium-hexyl ester) emerged as particularly active and effective inhibitors. Aggregation and secretion profiles, as well as the degradation of inositol phospholipids and production of phosphatidic acid, were used as monitors of their inhibitory capabilities. U66985 was the most effective inhibitor, giving an IC50 value of 4.1 +/- 1.5 X 10(-8) M against a challenge of 1 X 10(-10) M AGEPC in the secretion assay. Phospholipid turnover was blocked completely at this inhibitor concentration. On the other hand, while CV-3988 was an effective inhibitor, a higher concentration was required and a more restricted range of activity was noted with an IC50 value of 5.9 +/- 1.3 X 10(-7) M against a challenge of 1 X 10(-10) M AGEPC in the secretion assay. While CV-3988 did indeed completely block the turnover of inositol phospholipids and phosphatidic acid formation, these effects were noted at a higher concentration than with U66985. On the basis of data obtained in desensitization experiments with AGEPC and U66985, it appears that each inhibitor occupies the same receptor site as the agonist, AGEPC. These results illustrate the usefulness of these AGEPC analogs in exploring the biochemical characteristics of the interaction of AGEPC with a cell.
Akira Tokumura, T Suzuki, Kenkichi Takauchi and Hiroaki Tsukatani : Gas chromatographic-mass spectrometric analysis of biologically active phospholipids having an sn-2-acetyl group., Journal of Chromatography. A., Vol.343, No.1, 138-142, 1985.
(キーワード)
Chemical Phenomena / 化学 (chemistry) / Gas Chromatography-Mass Spectrometry / Hydrolysis / Phospholipids / Platelet Activating Factor / Propionates
Kenkichi Takauchi, Akira Tokumura, Junichi Yoshida, T Iwama, Yasomi Handa, H Tatsumichi and Hiroaki Tsukatani : Identification of steroidal compounds as acetates in a lysate of "Depressor-I," an antihypertensive phospholipid occurring in acetone-soluble fraction of bovine brain, Chemical & Pharmaceutical Bulletin, Vol.33, No.4, 1334-1341, 1985.
(要約)
The alkaline hydrolysate of "Depressor-I", an antihypertensive phospholipid occurring in the acetone-soluble fraction of bovine brain, was [<SUP>3</SUP>H] acetylated and applied to an alumina column. Various [<SUP>3</SUP>H] acetylated compounds were eluted. Among the major fractions, the eluates with hexane and hexane-benzene (9 : 1, 7 : 3 and 5 : 5, v/v) mixtures contained labile compounds which decomposed on standing for one month. Gas chromatography-mass spectrometry was carried out with the corresponding sample obtained in a "cold"experiment, and diosgenin acetate, a sapogenin, was detected besides cholesteryl acetate. A new class of phospholipid containing steroidal components is proposed.
Hiroaki Tsukatani, Kenkichi Takauchi, Junichi Yoshida, Sadaji Yamada, Akira Tokumura and C Hamaguchi : Isolation of diosgenin[(25R)-spirost-5-en-3 beta-ol] from a lysate of a new hypotensive phospholipid occurring in bovine brain, Journal of Neurochemistry, Vol.44, No.2, 658-661, 1985.
(要約)
Diosgenin[(25R)-spirost-5-en-3 beta-ol] and cholesterol were detected as trimethylsilyl derivatives by gas chromatography-mass spectrometry in an alkaline lysate of a new hypotensive phospholipid from the lipid fraction of bovine brain. These steroids seemed to be present in the hypotensive phospholipid fraction in some bound forms.
Akira Tokumura, H M. Mostafa, R D. Nelson and J Donald Hanahan : Stimulation of (Ca2++Mg2+)-ATPase in human erythrocytes membranes by synthetic lysophosphatidic acids and lysophosphatidylcholines. Effects of chain length and degree of unsaturation, Biochimica et Biophysica Acta (BBA) - Biomembranes, Vol.812, No.2, 568-574, 1985.
(要約)
Synthetic lysophosphatidic acids and lysophosphatidylcholines were examined for their effects on the (Ca2+ + Mg2+)-ATPase of human erythrocyte membranes. Addition of these compounds to erythrocyte ghosts caused significant changes in ATPase activity. The degree of unsaturation and the length of the sn-1 long chain hydrocarbon moiety were both contributing factors. All lysophosphatidic acids tested stimulated (Ca2+ + Mg2+)-ATPase activity. Of the species having a saturated acyl group, the most active was the myristoyl derivative. Linoleoyllysophosphatidic acid was the most potent of the unsaturated species. Saturated lysophosphatidylcholines with a short chain fatty acyl group (C10 to C14) exhibited only a moderate stimulatory activity, whereas the longer chain homologues, i.e., C16 and C18 were inhibitory at high concentrations. On the other hand, unsaturated lysophosphatidylcholines had stimulatory activities comparable to the unsaturated lysophosphatidic acids. These results suggest that the acidic moiety of lysophosphatidic acid is not an important structural determinant for expressing ATPase stimulatory activity in ghosts. Rather the nature of the hydrocarbon chain as well as the lyso structure of these compounds appear most critical under these conditions. The stimulatory effects of lysophosphatidic acids or lysophosphatidylcholines were additive to that induced with calmodulin, suggesting that these lysophospholipids affect the (Ca2+ + Mg2+)-ATPase by a mechanism which is different from that seen with calmodulin.
Akira Tokumura, T Maruyama, Kenji Fukuzawa and Hiroaki Tsukatani : Effects of lysophosphatidic acids and their structural analogs on arterial blood pressure of cats, Arzneimittel-Forschung, Vol.35, No.3, 287-292, 1985.
(要約)
On intravenous injection into cats, lysophosphatidic acid elicited a biphasic change in arterial blood pressure: sharp hypotension followed immediately by hypertension. Respiration was greatly disturbed immediately after injection of lysophosphatidic acid, and remained stimulated for a long period, and the heart rate increased during the period of hypertension. Unsaturated lysophosphatidic acids were more potent in evoking hypertension than saturated ones. The hypotensive activity of 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphate was about half that of 1-palmitoyl-2-lyso-sn-glycero-3-phosphate (lysophosphatidic acid). Elongation of the acyl chain at the sn-2-position of the glycerol moiety resulted in progressive reduction in the hypotensive activity. Chemically modified analogs with a head group, such as phosphoryl-methanol, ethanol, propanol and choline, had little or no activity. However, sn-2-acetyl-analogs of lyso-phosphatidyl cholines had hypotensive activity. 1-0-Hexadecyl-2-lyso-sn-glycero-3-phosphate, an alkyl-lyso-phosphatidic acid, had much stronger hypotensive activity than the corresponding acyl-lysophosphatidic acid, like its sn-2-0-acetyl analog. These structure-activity relationships of lysophosphatidic acids indicate the existence of their specific binding sites on cardiovascular cells.
Hiroaki Tsukatani, Junichi Yoshida, Kenkichi Takauchi, Sadaji Yamada, Akira Tokumura, K Nakanishi and T Hayakawa : Comparison of antispasmodic effect of synthetic lysolecithins with various fatty acid moieties on guinea pig ileum, Journal of Pharmacobio-Dynamics, Vol.7, No.6, 400-406, 1984.
(要約)
Non-competitive antispasmodic effects of 8 kinds of synthetic L-alpha-lysolecithins (1-O-acyl-2-lyso-sn-glycero-3-phosphocholine, LPC) with various fatty acid moieties were examined upon the spasmodic actions of histamine and acetylcholine on guinea pig ileum. Five-min pretreatment of the gut with the synthetic LPC was required to be effective. With increase of the concentration of a synthetic LPC for pretreatment of the ileum, the slope of the dose-response curve of histamine or acetylcholine added cumulatively became more gentle, the maximal contraction was suppressed apparently, and which were associated with the shift of the curve to the higher concentration of the stimulants. Of LPCs with saturated fatty acid palmitoyl-LPC showed the strongest effect, followed by myristoyl-, stearoyl-, lauroyl- and decanoyl-LPCs in order. Incorporation of cis-double bond into the C18 fatty acid chain of LPC resulted in slight decrease of the antispasmodic effect. The relaxating effect of LPCs on perfused rabbit ear vessel preparations was similar in order.
Akira Tokumura, K Harada, Yasuko Yoshioka, Hiroaki Tsukatani and Yasomi Handa : Analyses of lysophosphatidic acids by gas chromatography mass spectrometry without hydrolytic pretreatment, Biomedical Mass Spectrometry, Vol.11, No.4, 167-171, 1984.
(要約)
Lysophosphatidic acids having different fatty acyl moieties were directly analysed by gas chromatography/mass spectrometry after silylation. Trimethylsilyl derivatives of various LPAs escaped thermal degradation, and electron impact and chemical ionization of these derivatives yielded many ions which were useful for the structural determination. It was found by this new method that five species of lysophosphatidic acids were formed in rat plasma during incubation at 37 degrees C.
Akira Tokumura, Kenji Fukuzawa and Hiroaki Tsukatani : Contractile action of 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine on strips of isolated rat intestine, The Journal of Pharmacy and Pharmacology, Vol.36, No.3, 210-212, 1984.
(要約)
The contractile effects of AGEPC were examined on various regions of rat isolated intestine. The duodenum, jejunum and ileum showed only the tonic component of contraction to AGEPC at the low dose (less than 10(-9) M) but at the high dose (10(-7) M) biphasic contractions were induced, consisting of a phasic followed by a tonic component. In the colon, however, the AGEPC-induced maximum contraction was comparable in magnitude to that produced by acetylcholine; also the contraction profile was different from that elicited from the other regions of the intestine. Low doses of AGEPC caused a slow, sustained contraction and at high doses phasic and tonic components were not dissociated.
Akira Tokumura, Yasomi Handa, Yasuko Yoshioka and Hiroaki Tsukatani : Mass spectrometric analyses of biologically active choline phospholipids and their lysoderivatives, Chemical & Pharmaceutical Bulletin, Vol.31, No.12, 4425-4435, 1983.
(要約)
The electron impact and chemical ionization mass spectra of 1-O-hexadecyl- and 1-palmitoyl-2-O-acetyl-sn-glycero-3-phosphocholines and their lyso derivatives were measured by insertion of the compounds into a direct inlet system. The lysophospholipids were decomposed by heating at over 300℃ into multiple compounds that volatilized together and gave several characteristic ion peaks when subjected to electron impact or interaction with an ion plasma of reactant gas. The mass spectral data indicated that the major pyrolysis products of these lysophospholipids were produced by elimination of methanol or N, N-dimethylethanolamine. When sn-2-acetyl phospholipids were introduced on the direct insertion probe and heated, several pyrolysis products volatilized together at above 350℃. The results suggested the major pyrolysis mechanism was loss of the phosphorylcholine moiety, together with some deacetylation and subsequent elimination of methanol and N, N-dimethylethanolamine from the sn-2-acetyl phospholipids.
(キーワード)
platelet-activating factor / lysophosphatidylcholine / phospholipid pyrolysis / electron impact mass spectrometry / chemical ionization mass spectrometry
Akira Tokumura, K Harada, Kenji Fukuzawa and Hiroaki Tsukatani : Biphasic action of platelet-activating factor on isolated guinea-pig ileum, Lipids, Vol.18, No.11, 848-850, 1983.
(要約)
1-0-Hexadecyl-2-0-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor) at 10(-10)-10(-9) M induced slow contraction of isolated guinea-pig ileal muscles and the contraction persisted for a long time. At a higher concentration of 10(-7) M, this phospholipid induced more rapid, but not greater, contraction. At higher concentrations (10(-6)-10(-5) M), this phospholipid induced a biphasic response: rapid contraction followed by relaxation. At high concentrations, this compound inhibited acetyl-choline-induced contractions. The stimulatory effect of this phospholipid was ca. 300 times that of 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine, while its inhibitory potency on induced contraction was similar to those of 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine and its lyso derivative. It was suggested that the differences in effects on contraction of different concentrations of 1-0-hexadecyl- and 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine were due to the effects of these compounds on the ileum: a strong stimulatory effect and a moderate inhibitory effect on contraction.
Akira Tokumura, Kenji Fukuzawa and Hiroaki Tsukatani : Contractile actions of lysophosphatidic acids with a chemically-defined fatty acyl group on longitudinal muscle from guinea-pig ileum., The Journal of Pharmacy and Pharmacology, Vol.34, No.8, 514-516, 1982.
(要約)
Various lysophosphatidic acids caused phasic contractions of longitudinal muscle from guinea-pig ileum, followed by rhythmical contractions of lower magnitude. Polyunsaturated lysophosphatidic acids were more potent than saturated lysophosphatidic acids. Among the lysophosphatidic acids tested, linolenoyl-lysophosphatidic acid was the most active, but its activity was about 3-5 times less than that of prostaglandin F2 alpha. Contractile responses to various lysophosphatidic acids, were partially suppressed by tetrodotoxin, atropine and chlorpheniramine. In addition, lysophosphatidic acid-induced contractions were considerably reduced by pretreatment of the muscle with indomethacin.
(キーワード)
Animals / Chemical Phenomena / 化学 (chemistry) / Drug Interactions / Fatty Acids / Guinea Pigs / Ileum / In Vitro Techniques / Indomethacin / Lysophospholipids / Male / Muscle Contraction / Muscle, Smooth / Phosphatidic Acids / Prostaglandins
(文献検索サイトへのリンク)
● PubMed @ National Institutes of Health, US National Library of Medicine (PMID): 6126563
Kenji Fukuzawa, Akira Tokumura, S Ouchi and Hiroaki Tsukatani : Antioxidant activities of tocopherols on Fe2+-ascorbate-induced lipid peroxidation in lecithin liposomes, Lipids, Vol.17, No.7, 511-513, 1982.
(要約)
The antioxidant activities of 4 tocopherols, tocol, and a water-soluble model analog of alpha-tocopherol were compared. Egg lecithin liposomes were used and oxidation was catalyzed by Fe2+-ascorbate. The activities decreased in the order alpha greater than beta greater than gamma greater than delta-tocopherol greater than tocol, in agreement with their potencies in vivo. The water-soluble analog was the least effective. Activity depended on the molar ratio of antioxidant to unsaturated lipid, with one molecule each of the alpha-, beta-, gamma-, delta-tocopherol and tocol capable of protecting, respectively, 220, 120, 100, 30 and 20 molecules of polyunsaturated fatty acid. The mechanism of possible antioxidant effect of the compounds used is discussed.
Akira Tokumura, Yasomi Handa, Yasuko Yoshioka, Minoru Higashimoto and Hiroaki Tsukatani : Mass Spectrometric analyses of lysophosphatidic acids and their dimethyl ester, Chemical & Pharmaceutical Bulletin, Vol.30, 2119-2126, 1982.
148.
Akira Tokumura, Tetsuya Kume, Kenji Fukuzawa and Hiroaki Tsukatani : Cardiovascular effects of lysophosphatidic acid and its structural analogs in rats, The Journal of Pharmacology and Experimental Therapeutics, Vol.219, No.1, 219-224, 1981.
(要約)
Injection of lysophosphatidic acid into anesthetized rats induced immediate hypertension, the effect depending on the structure of the sn-1-acyl moiety of the molecule. A hydroxyl group at the sn-2-position was not necessary, but a wedgeshaped structure was suitable for hypertensive activity. Most lysophospholipids with a chemical group attached to the phosphate portion had only weak hypotensive effects, but the sn-2-acetylated analogs of these depressor lysophospholipids elicited a hypotension at much lower doses. The durations of the hypotensions evoked by the sn-2-acetylated choline phospholipids were longer than those produced by 1-palmitoyl-2-acetoyl-sn-glycerol-3-phosphorylmethanol, ethanol and propanol.
Akira Tokumura, Kenji Fukuzawa, Junichi Isobe and Hiroaki Tsukatani : Lysophosphatidic acid-induced aggregation of human and feline platelets: Structure-activity relationship, Biochemical and Biophysical Research Communications, Vol.99, No.2, 391-398, 1981.
Akira Tokumura, Kenji Fukuzawa, S Yamada and Hiroaki Tsukatani : Stimulatory effect of lysophosphatidic acids on uterine smooth muscles of non-pregant rats, Archives internationales de Pharmacodymie et de Therapie, Vol.245, No.1, 74-83, 1980.
(要約)
Lysophosphatidic acids stimulated isolated uterine smooth muscle dose-dependently. The contractions were not reduced by pretreatment with atropine or an anti-5-hydroxytryptaminic agent. The potency depended on the nature of the acyl chain in the molecule. Of the compounds with a saturated fatty acyl group tested, the most effective were myristoyl- and lauroyl-lysophosphatidic acid. In a series of unsaturated lysophosphatidic acids, the potency increased with the number of cis double bonds in the acyl chain, and linolenoyl-lysophosphatidic acid was the most active. When injected intravenously, these compounds induced an immediate rise in blood pressure and intrauterine pressure, like prostaglandin F2 alpha: The order of potency of their effects on the intact uterus was consistent with that of their effects on isolated uterine smooth muscle, but not with that of their hypertensive effects in rats.
hiroaki Tsukatani, Sadaji Yamada, Akira Tokumura, Takafumi Itami and Kenkichi Takauchi : Occurrence of short-duration hypotensive phospholipid from dog peritoneal dialysate, Journal of Pharmaceutical Sciences, Vol.68, No.11, 1426-1429, 1979.
(要約)
From the total lipid fraction of dog peritoneal dialysate after freeze drying and extraction, a hypotensive phospholipid was isolated through silicic acid, cellulose, and Sephadex LH-20 column chromatography in a pure grade; it showed a single spot on TLC. The purified hypotensive factor, designated as Peritoneal Dialysate Depressor-I, elicited potent depressor responses in anesthetized rats, and its threshold dose was approximately 35 microgram/kg. The material resisted proteases and 15-hydroxyprostanoate oxidoreductase. In mobility on TLC, the hypotensive factor was distinuishable from water-soluble hypotensive substances and also from depressor lipids. Judging from its behavior on TLC and column chromatography during the purification procedure, the hypotensive factor seems to be a choline-containing phospholipid and shows the general characteristics of hysolecithin, except for its potent hypotensive activity, and 2',7'-dichlorofluorescein on TLC. The molar ratio of phosphorusurated ones such as stearic and palmitic acids.
Hiroaki Tsukatani, Sadaji Yamada, Akira Tokumura and T Itami : Action of depressor-I, a hypotensive phospholipid from bovine brain, on systemic and arterial blood pressures of various species, The Japanese Journal of Pharmacology, Vol.29, No.5, 695-705, 1979.
(要約)
Effects of "Depressor-I" (D-I), a new hypotensive phospholipid obtained from bovine brain lipid fraction, on systemic arterial blood pressure were investigated. The hypotensive activity of D-I in urethane anaesthetized rats was dose dependent and tachyphylaxis and/or sensitization were not observed. Increments of the respiration and the heart rate were observed with sharp falls in blood pressures following intravenous administration of D-I, in simultaneous recordings in anaesthetized rats. D-I elicited hypotension in all species of animals examined, and the sensitivities to D-I were much the same, however, there were two types in patterns of duration on responses and the durations were also dose dependent. D-I exhibited depressor-responses even in conscious rats, though responses were much smaller compared with those seen in anaesthetized rats. In a comparison of anaesthetic agents in rats, the highest hypotensive activity of D-I was observed with pentobarbital anaesthesia, a moderate response was seen with alpha-chloralose and the least response was seen with urethane. In spinal rats or those pretreated with reserpine or antagonists, such as atropine, diphenhydramine, propranolol and hexamethonium, D-I also elicited hypotension. These results suggest that "Depressor-I" does not elicit the depressor action via the stimulation of the central and the autonomic nervous systems but rather by a direct action on peripheral blood vessels.
Hiroaki Tsukatani, Sadaji Yamada, Akira Tokumura, Kenkichi Takauchi and T Itami : A hypotensive phospholipid from dog peritoneal dialysate, The Journal of Pharmacy and Pharmacology, Vol.31, No.8, 569-571, 1979.
(キーワード)
Animals / 血圧 (blood pressure) / Chemical Phenomena / 化学 (chemistry) / Depression, Chemical / Dogs / Dose-Response Relationship, Drug / Peptide Hydrolases / Peritoneal Dialysis / Phospholipids
(文献検索サイトへのリンク)
● PubMed @ National Institutes of Health, US National Library of Medicine (PMID): 40007
Kenji Fukuzawa, H Ikeno, Akira Tokumura and Hiroaki Tsukatani : Effect of α-tocopherol incorporation on glucose permeability and phase transition of lecithin liposomes, Chemistry and Physics of Lipids, Vol.23, No.1, 13-22, 1979.
(要約)
Liposomes were prepared from dipalmitoyllecithin, dimyristoyllecithin, dioleoyllecithin, egg lecithin, and soybean lecithin, and the effects of incorporation of various quantities of alpha-tocopherol or its analogs on permeability of the liposomes to glucose were studied at various temperatures (4--40 degrees C). Results showed that increase in the quantity of alpha-tocopherol incorporated into dipalmitoyllecithin and dimyristoyllecithin liposomes lowered the transition temperature for marked release of glucose and also decreased the maximum rate of temperature-dependent permeability, alpha-Tocopherol also had similar but less marked effects on the permeability of dioleoyllecithin and egg lecithin liposomes, but little effect on those of soybean lecithin, which has a higher degree of unsaturation. In dipalmitoyllecithin liposomes phytol showed a similar effect of permeability to that of alpha-tocopherol, but phytanic acid caused a different pattern of temperature-dependent permeability. With analogs of alpha-tocopherol, the regulatory effect on permeability decreased with shortening and disappearance of the isoprenoid side chain. The significance of these observations is discussed in relation to the physiological functions of tocopherols in natural membranes.
Hiroaki Tsukatani, Sadaji Yamada, Kenkichi Takauchi, Akira Tokumura, H Tatsumichi and K Kumegawa : Physico-chemical characteristics of D-I, a hypotensive factor occurred in acetone extract of the bovine brain, Chemical & Pharmaceutical Bulletin, Vol.26, No.11, 3281-3288, 1978.
Akira Tokumura, Kenji Fukuzawa and Hiroaki Tsukatani : Effects of synthetic and natural lysophosphatidic acids on the arterial blood pressure of different animal species, Lipids, Vol.13, No.8, 572-574, 1978.
(要約)
Intravenous injection of lysophosphatidic acid was found to cause hypertension in rats and guinea pigs, but hypotension in cats and rabbits. The potencies of the pressor and depressor effects of synthetic lysophosphatidic acids in rats and cats depended on their chain length and the degree of unsaturation of their fatty acyl moieties.
Akira Tokumura, Kenji Fukuzawa, Yasue Akamatsu, Sadaji Yamada, Tetsuya Suzuki and Hiroaki Tsukatani : Identification of vasopressor phospholipid in crude soybean lecithin, Lipids, Vol.13, No.7, 468-472, 1978.
(要約)
The vasopressor phospholipid in crude soybean lecithin was isolated by column chromatography on Sephadex LH-20. It represented 0.1% of crude soybean lecithin. The isolated phospholipid was identified to be lysophosphatidic acid by gas chromatography-mass spectrometry analysis of TMS-deacylated product and acetolysis product. Nuclear magnetic resonance analysis favored the 1-monoacyl isomer over the 2-isomer. By enzymic determination with L-3-glycerophosphate dehydrogenase, the isolated phospholipid was identified as 1-monoacyl-L-3-glycerophosphate. Gas chromatographic examination revealed that it was composed of a large percentage of unsaturated fatty acids, especially linoleic acid. The activity of isolated lysophosphatidic acid was slightly less than that of synthetic 1-linoleoyl-L-3-glycerophosphate.
Weanling male rats were bred with a drinking water containing sodium dodecyl sulfate (SDS) at concentrations of 0.25,0.05,or 0% for 5 months. Increase of organ weights was observed in the lung and kidney, though body weight was not affected at a higher concentration (0.25%). Histopathology of major organs indicated the characteristic symptom to be bronchopneumonia by the continued ingestion of a small amount of SDS. Activities of serum enzymes, such as GOT, GPT, alkaline phosphatase, and cholinesterase, were not affected at the dosages used. In rats taking 0.25% of SDS, triglyceride level increased in the liver but decreased in serum, while hepatic and serum levels of cholesterol, phospholipid, and free fatty acid were unchanged.
Akira Tokumura, Yasue AKAMATSU, Sadaji YAMADA and Hiroaki TSUKATANI : Chemical and pharmacological properties of vasopressor phospholipid in crude soybean lecithin, Agricultural and Biological Chemistry, Vol.42, No.3, 515-521, 1978.
(要約)
Commercial soybean lecithin has a potent hypertensive effect on anesthetized rats. Crude soybean lecithin was separated into two fractions with respect to solubility in cold acetone. The acetone-insoluble fraction containing most pressor activity was separated into two further active fractions by column chromatography on silicic acid. The active fraction eluted with chloroform-methanol mixture (4:6) was further purified by gel filtration on Sephadex LH-20. The purified pressor substance had phosphorus and was labile to alkali. Its chromatographic and partition behaviors indicate that it may be a polar acidic phospholipid. The short-lasting pressor response produced by the active lipid was not reduced by mechanical injury to the central nervous system or treatment with an a-adrenergic blocking agent or a ganglion-blocking agent.
Kenji Fukuzawa and Akira Tokumura : Glutathione peroxidase activity in tissues of vitamin E-deficient mice, Journal of Nutritional Science and Vitaminology, Vol.22, No.5, 405-407, 1976.
K Takeo, Akira Tokumura and T Kuge : Complexes of starch and its related materials with organic compounds. Part X, X-ray diffraction of amylose-fatty acid complexes, Starke, Vol.25, No.11, 357-362, 1973.
Kenji Fukuzawa, Kentaro Kogure, M Morita, S Hama, S Nakashima and Akira Tokumura : Enhancement by α-tocopherol hemisuccinate of nitric oxide production induced by lipopolysaccharide and interferon-γ through up-regulation of protein kinase C in rat vascular smooth muscle cells, Proc.Of the second China-Japan international Conference on Vitamins, 262-267, 2001.
13.
Takayuki Sugiura, Keizo Waku and Akira Tokumura : Acyl and alkyl ether-linked lysophosphatidic acids in the nervous system, Annals of the New York Academy of Sciences, Vol.905, 351-353, 2000.
Akira Tokumura, Shuji Yamano, Toshihiro Aono and Kenji Fukuzawa : Lysophosphatidic Acids Produced by Lysophospholipase D in Mammalian Serum and Body Fluid, Annals of the New York Academy of Sciences, Vol.905, 347-350, 2000.
Akira Tokumura, Tamotsu Tanaka and Hiroaki Tsukatani : Characterization of PAF-like phospholipids formed by lipid peroxidation, Journal of Lipid Mediators and Cell Signalling, Vol.10, 179-181, 1994.
28.
J Donald Hanahan, Takayuki Sugiura, L Gregory, Teri Nouchi and Akira Tokumura : Phosphoric acid analogs of PAF, Journal of Lipid Mediators and Cell Signalling, Vol.10, 169-170, 1994.
Kenji Fukuzawa, T Hiramoto, T Fujii, K Kishikawa and Akira Tokumura : Lipid peroxidation induced by hydroxyl-and lipid free-radicals and iron-oxygen complexes,and its inhibition by a-tocopherol, Medical,Biochemical and Chemical Aspects of Free Radicals, 275-278, 1989.
35.
Kenji Fukuzawa, Yasuhiro Kurotori, Akira Tokumura and Hiroaki Tsukatani : Increased platelet-activating factor (PAF) synthesis in polymorphonuclear leukocytes of vitamin E-deficient rats, Annals of the New York Academy of Sciences, Vol.570, 449-454, 1989.
Toshihiko Tsutsumi, Mika Adachi, Miki Nikawadori, Junichi Morishige and Akira Tokumura : Presence of bioactive lysophosphatidic acid in renal effluent of rtas with unilateral ureteral obstruction, Life Sciences, Vol.89, No.5-6, 195-203, 2011.
(要約)
Abnormal production of lysophosphatidic acid (LPA), an important lysophospholipid mediator, in the kidney was examined to participate in the pathogenesis of renal fibrosis in rats. The secretory lysophospholipase D activity of autotoxin was considered as a possible pathway for extracellular production of LPA in the pathological renal fluids. In this study of rats with unilateral ureteral obstruction for two weeks, we measured concentrations of LPA and its precursor, lysophosphatidylcholine stored in the urinary bladder and present in the swollen pelvis of the ligated kidney as well as the corresponding blood plasma by liquid chromatography-tandem mass spectrometry. We found that concentrations of LPA and lysophosphatidylcholine accumulated in the effluent in the swollen pelvis of the ligated kidney of unilateral ureteral obstruction rats were much higher than those in the urinary bladder. The molecular species composition of LPA in the former was considerably different from that in the blood plasma, indicating the involvement of an additional source other than the blood circulation supplying LPA to the effluent in the swollen kidney. A potential mechanism is increased release of LPA from activated renal cells in the ureter-ligated kidney. Both pathways for supply of extracellular LPA may participate in the induction and progression of renal tubulofibrosis.
Akira Tokumura : Metabolic pathways and physiological and pathophysiological significances of lysolipid phosphate mediators, Journal of Cellular Biochemistry, Vol.92, No.5, 869-881, Jun. 2004.
(要約)
Lysophosphatidic acid and sphingosine 1-phosphate are structurally simple and physiologically very important lysophospholipids. Because they possess distinct structural backbones (glycerol and sphingosine, respectively), there are different metabolic pathways for their intracellular production. Recently, several key enzymes that produce or degrade these lysolipid phosphate mediators extracellularly have been characterized. This review focuses on the physiological and pathophysiological significances of the extracellular metabolic pathways involving recently characterized exo-type lysophospholipase D, ecto-type phospholipase A, and ecto-type lipid phosphate phosphatase.
Kenji Fukuzawa, Kentaro Kogure, Motoki Morita, Susumu Hama and Akira Tokumura : Enhancement of Nitric Oxide and Superoxide Generations by α-Tocopheryl Succinate and Its Apoptotic and Anticancer Effects, Biochemistry (Moscow), Vol.69, No.1, 50-57, Jan. 2004.
(要約)
Tocopheryl succinate (TS), a succinyl ester of alpha-tocopherol (alpha-T), has been reported to have various biological activities. In this communication, we review the current findings about TS including our recent studies of its effects on nitric oxide (NO) and superoxide (O2-) generations implicated in cancer and atherosclerosis. First, we investigated the effect of TS on NO production in vascular smooth muscle cells (VSMC) under atherosclerosis-like conditions using lipopolysaccharide (LPS) and interferon-gamma (IFN). TS enhanced LPS/IFN-dependent NO production, but alpha-T itself did not. The enhancement by TS of NO production was inhibited by alpha-T but not by antioxidants such as ascorbic acid and 2[3]-t-butyl-4-hydroxyanisole (BHA). TS enhanced the amount of protein kinase Calpha (PKCalpha) in VSMC, and PKC inhibitors inhibited TS-enhanced NO production, suggesting that the enhancing effect of TS on NO production is caused by up-regulation of PKC. Second, we found that TS induced apoptosis in VSMC associated with increase in O2- generation via NADPH-dependent oxidase. We further observed that a mouse breast cancer cell line C127I was more susceptible for TS-induced apoptosis than a mouse breast normal cell line NmuMG, and that superoxide dismutase, alpha-T, and BHA inhibited TS-caused morphological cell damage in C127I. From these results, O2- itself and/or other reactive oxygen species are assumed to associate with TS-induced cell toxicity, and antioxidative defense systems are supposed to be lowered in cancer cells. Finally, we found that intravenous injection of TS vesicles completely inhibited the growth of melanoma cells B16-F1 inoculated on the back of hairless mice and enhanced their survival time.
Akira Tokumura, A. Tuchie, M. Imasaki and Kenji Fukuzawa : Generation of platelet-activating factor (PAF)-like phospholipids in blood circulation under elevated oxidative stress:its pathological significance on atherosclerosis, Journal of Clinical Biochemistry and Nutrition, Vol.34, No.1, 35-42, 2003.
德村 彰 : GC/MS によるリン脂質メディエーター産生機構の解析, Journal of the Mass Spectrometry Society of Japan, Vol.50, No.3, 100-107, 2002年6月.
(要約)
Structures of phosphatidylcholines having an oxidatively shortened fatty acyl group resemble that of the platelet-activating factor (PAF), a chemical mediator of inflammation, and therefore they are classified as PAF-like lipids. Gas chromatography-mass spectrometry has been utilized for analysis of the class, subclass and molecular species compositions of PAF-like lipids, providing usefel informations on mechanisms of their formation. Gas chromatography-mass spectrometry was also found to be useful for the determination of lysophosphatidic acid, a growth factor in animal plasma, and clarification of mechanisms of its formation.
(キーワード)
Gas chromatography-mass spectrometry / リゾホスファチジン酸 (lysophosphatidic acid) / Lysophospholipase D / Oxidized phosphatidylcholine / Platelet-activating factor
Akira Tokumura : Physiological and pathophysiological roles of lysophosphatidic acid produced by secretory lysophospholipase D in body fluids, Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, Vol.1582, No.1-3, 18-25, May 2002.
(要約)
Recently, a family of phospholipid mediators has received much attention because of its variety of biological activities. Lysophosphatidic acid (LPA) is a central member of the phospholipid autacoid family that exerts diverse effects through binding to and activation of several specific receptors coupled to G-proteins. In accordance with its function as a receptor agonist, there are pathways for extracellular generation of LPA in vivo. One pathway involves a novel lysophospholipase D activity that was originally found in rat plasma. LPA is also produced in significant amounts after incubation of various plasma-derived body fluids such as human follicular fluid at 25-37 degrees C. In animal models, LPA was shown to stimulate oocyte maturation, embryonic development and transport in the oviduct. An increase in serum lysophospholipase D activity was observed during pregnancy in human. These results suggest that LPA generated by lysophospholipase D is likely to play an important role in reproductive biology. LPA produced by lysophospholipase D activity in body fluids has also been observed under pathophysiological conditions: serum and ascitic fluid from ovarian cancer patients and serum from hypercholesterolemic rabbits. Hence, excess generation of LPA by lysophospholipase D activity in body fluids has been suggested to be relevant to the pathogenesis of cancer and atherosclerosis.
The singlet oxygen (^1O_2) deactivating rate constants (k_s) of α-tocopherol (α-Toc) and carotenoids such as β-carotene, astaxanthin and canthaxanthin and their inhibiting activities for ^1O_2-dependentlipid peroxidation (IC_50' that is, the concentration required for 50% inhibition of lipid peroxidation) were investigated in liposomes and compared to those in EtOH solution. Liposomes were prepared from dimyristoylphosphatidylcholine to measure the k_s and egg yolk phosphatidylcholine to measure the IC_50 values. ^1O_2 was generated by photoirradiation using three photosensitizers, Rose bengal and methylene blue, which generate ^1O_2 at the membrane surface or in bulk water, and 2-(1-pyrene) dodecanoic acid, which generates ^1O_2 in the membrane hydrophobic inner region. The k_s and IC_50 values were determined in membranes considering the following two points: (1) antioxidants exist in membranes and their active moieties are distributed in different regions of membranes at different concentrations; (2) dynamics of ^1O_2 in membranes (generation site of ^1O_2 depending on the localization of photosensitizer in membranes, and solubility of ^1O_2 which differs in the site of membranes). In conclusion, the following three factors are experimentally confirmed to be important for the consideration of ^1O_2 deactivating activities of α-Toc and carotenoids in membranes:(1) the concentration of antioxidants (EtOH solution < membrane), especially the local concentration of their active moieties in membranes (in the case of OH-group of α-Toc, 0%, 50-60%, and 40-50% at polar zone, hydrogen belt, and hydrophobic core, respectively, of the membranes); (2) the mobility of antioxidants (EtOH solution > membrane), the mobility of membrane phospholipid (liquid crystalline state > gel state), the mobility of antioxidants in membranes (antioxidants located at one half of the bilayer membrane such as α-tocopherol > antioxidants located across the bilayer such as β-carotene; antioxidants interactive with polar head group of lipid in membrane such as astaxanthin < antioxidants nointeractive with polar head group of lipid in membrane such as β-carotene), and the local mobility of their active moieties (in case of OH-group of α-Toc, membrane surface < membrane inner region); (3) the dielectric constant (micropolarity) at the domains in membranes, that is higher in membrane surface than in membrane inner region, where the active moieties of antioxidants deactivate ^1O_2 (in case of α-Toc, reactivity is high in the solution with high dielectric constant).
Akira Tokumura, Tuneki Sumida, Masaoki Toujima, Kentaro Kogure and Kenji Fukuzawa : Platelet-activating factor (PAF)- like oxidized phospholipids: relevance to atherosclerosis, BioFactors, Vol.13, No.1-4, 29-33, 2000.
(要約)
Lipid peroxidation is involved in the pathogenesis of chronic diseases including atherosclerosis. Oxidized lipoprotein has diverse biological activities and is believed to initiate atheroma formation and maturate fatty plaque. The active components of oxidized lipoproteins still remain to be clarified, but a likely candidate is the phosphatidylcholine (PC) having an sn-2-short-chain acyl group with a methyl, hydroxyl, aldehydic or carboxylic terminal. These unique PCs, formed by oxidative fragmentation of the polyunsaturated acyl group of the parent PC in liposomes, low density lipoproteins and blood plasma, induce platelet aggregation through the activation of the receptor for platelet-activating factor (PAF), due to their resemblance in structure with PAF. We have found that PAF-like lipids regulate DNA synthesis and production of nitric oxide independently of the activation of the PAF receptor in vascular smooth muscle cells. Regulation of vascular cell function through two distinct signaling pathways mediated by PAF-like lipids provides new insight into the mechanism of induction of atherosclerosis.
Akira Tokumura, Tamotsu Tanaka and Hiroaki Tsukatani : Characterization of PAF-like phospholipids formed by lipid peroxidation, Journal of Lipid Mediators and Cell Signalling, Vol.10, 179-181, 1994.
Akira Tokumura, Tamotsu Tanaka, Takashi Yotsumoto and Hiroaki Tsukatani : Formation of PAF-like compounds by peroxidation of phospholipids from bovine brain, Journal of Lipid Mediators, Vol.5, No.2, 127-130, 1992.
(要約)
This short review describes the identification by mass spectrometry of phospholipids having an sn-2-short-chain monocarboxylate, dicarboxylate or omega-hydroxycarboxylate group in a fraction with PAF-like activity from a bovine brain lipid extract. The similar molecular heterogeneities of these unique phospholipids suggest that they are formed via a common mechanism, possibly peroxidation of membrane phosphatidylcholines. This possibility is supported by the finding that these PAF-like compounds were actually formed during peroxidation of synthetic phosphatidylcholines induced by Fe2+/ascorbate/EDTA.
Tamotsu Tanaka, 盛重 純一, 近藤 宏樹, 木下 正文, 足立 美佳, 瓜倉 真衣, 里内 清 and Akira Tokumura : Formation of lysophosphatidic acid, a wound-healing lipid, during digestion of cabbage leaves, Keystone Symposia, Bioactive lipids: Biochemistry & Diseases, Abstract Book, 105, 京都, Jun. 2010.
2.
Mika Adachi, Jun-ichi Morishige, Tamotsu Tanaka, Junji Terao, Kiyoshi Satouchi and Akira Tokumura : Lysophosphatidic acid in foods and herbs protects gastric ulcer in rats under water-immersion stress, 4th international conference on phospholipase A2 and lipid mediators, Vol.Final program and abstracts book, 131, Tokyo, May 2009.
3.
Akira Tokumura, Emi Kuwahara, Junichi Morishige, Kenji Fukuzawa and Shuji Yamano : Physiological and pathophysiological roles of lysophosphatidic acid production by by lysophospholipase D in the reproductive system, 3rd International Conference on phospholipase A2 and lipid mediators, Sorrento, May 2007.
4.
Junichi Morishige, Kenji Fukuzawa, Hideko Nagasawa, Hitoshi Hori and Akira Tokumura : Lysophosphatidic acid produced by lysophospholipase D in hen egg white induces blood vessel formation on hen chorioallantoic membrane, 3rd International Conference on phospholipase A2 and lipid mediators, Sorrento, May 2007.
5.
Akira Tokumura, Satoshi Taira, Kenji Fukuzawa, Toshihiko Tsutsumi, Tomoya Kitayama, K Morita and Toshihiro Dohi : LC-MS analysis on productions of bioactive lysophosphatidic acids from lysophosphatidylcholines in human mixed saliva, 47th International Conference on theBioscience of Lipids, Pecos, Sep. 2006.
6.
Kenji Fukuzawa, A. Fujiwara, Akira Tokumura, Junji Terao and Jansuz M. Gebicki : Measurement of phosphatidylcholine hydroperoxides in membranes by the ferric-xylenol orange (FOX) assay, XIII the Biennial Meeting of the Society for Free Radical Research International, Davos, Aug. 2006.
7.
Kenji Fukuzawa, Akira Shibata, Koichiro Tsuchiya, Akira Tokumura, H. Ichikawa and Jansuz M. Gebicki : Colored complex of ferric-xylenol orange/phosphatidylcholine vesicle in the Fox assay, XIII the Biennial Meeting of the Society for Free Radical Research International, Davos, Aug. 2006.
8.
Kenji Fukuzawa, Kentaro Kogure, Sachie Manabe and Akira Tokumura : In vitro cytotoxicity of alpha-tocopherol succinate, malonate and oxalate on cancer cells and their in vivo anti-cancer effects on mouse melanoma, XIII the Biennial Meeting of the Society for Free Radical Research International, Davos, Aug. 2006.
9.
Akira Tokumura, Emi Kuwahara, Junichi Morishige, Kenji Fukuzawa and Shuji Yamano : Lysophosphatidic acid stimulates hyaluronic acid production in mouse oocyte-cumulus cells complex in vitro, 20thIUBMB International Congress of Biochemistry and Molecular Biology and 11th FAOBMB Congress, Kyoto, Jun. 2006.
10.
Tamotsu Tanaka, Goh Horiuti, Kaoru Hirano, Junichi Morishige, Akira Tokumura and Kiyoshi Satouchi : Pccurrence pf lysophosphatidic acids in herbs, 20thIUBMB International Congress of Biochemistry and Molecular Biology and 11th FAOBMB Congress, Kyoto, Jun. 2006.
11.
Kenji Fukuzawa, Kentaro Kogure, S. Manabe, Ichiro Suzuki and Akira Tokumura : Selective cytotoxicity to cancer cells of α-tocopheryl succinate analogues in vitro and their anti-cancer effects on mouse melanoma in vivo, International Interdisciplinary Conference on Vitamins, Coenzymes, and Biofactors 2005, Awaji, Hyogo, Nov. 2005.
K. Tsuchiya, K. Akai, Akira Tokumura, S. Abe, T. Tamaki, Y. Takiguchi and Kenji Fukuzawa : Oxygen radicals photo-induced by ferric nitrilotriacetate(Fe-NTA) complex, EPR 2005. The international Conference/Workshop on Electron Paramagnetic Resonance Spectroscopy and Imaging of Biological Systems, Ohio,U.S.A., Sep. 2005.
14.
Akira Tokumura, S. Taira, J. Morishige, T. Tsutsumi and Kenji Fukuzawa : Lysophospholipase C and D produce lysolipids that may intercellularly mediate signals from mammalian cell lines, 46th International Conference on the Bioscience of Lipids, Ajaccio-Corsica, Sep. 2005.
15.
M. Watsky, W. Hatsuyama, T. Tsutsumi, Kenji Fukuzawa and Akira Tokumura : Lysophospholipase D and elevates lysophosphatidylcholine as sources of elevated aqeous humor LPA following corneal injury, ARVO 2005 Annual Meeting, Fort Lauderdale, Florida,U.S.A., May 2005.
16.
Tamotsu Tanaka, K. Hirano, T. Koike, Akira Tokumura and K. Satouchi : Quantitative analysis of lysophosphatidic acid by matrix-assisted laser desorption time-of-flight mass spectrometry using a phosphate capture molecule, 2nd International Conference Phospholipase A2 and 8th International Congress Platelet-activating Factor and Related Lipid Mediators, 204, Berlin, Oct. 2004.
17.
Akira Tokumura, C. Kageyama, W. Hatuyama, S. Taira, K. Touchika and Kenji Fukuzawa : Lysophosphatidic acid production by secretory lysophosholipase D:Physiological implications, 2nd International Conference on Phospholipase A2 and 8th International congress on Platelet-Activating Factor and Related Lipid Mediators, Berlin, Oct. 2004.
18.
Kenji Fukuzawa, Kentaro Kogure, M. Morita, S. Hama and Akira Tokumura : Enhancement by alpha-tocopheryl succinate of superoxide and nitric oxide generations in cultured cells, International Symposium: Reactive Oxygen and Nitrogen Species: Diagnostic,Preventive and Therapeutic Values, St. Petersburg-Kizhi-St.Petersburg Russia, Jul. 2002.
19.
Akira Tokumura, A. Tsuchie, Kentaro Kogure and Kenji Fukuzawa : Cigarette smoking increases plasma level of phosphatidylcholine having an oxidatively shortened fatty acyl group with a carboxyl terminal, 11th Biennial Scientific Meeting of the International Society for Free Radical Research, Paris, Jul. 2002.
20.
Kentaro Kogure, S. Hama, S. Manabe, M. Kisaki, Akira Tokumura and Kenji Fukuzawa : High toxicity of α-tocopheryl succinate to cancer cells is due to their failed antioxidative deffence system, 11th Biennial Scientific Meeting of the International Society for Free Radical Research, Paris, Jul. 2002.
21.
Kenji Fukuzawa, Y. Saitoh, K. Arai, Kentaro Kogure, Akira Tokumura and A. Shibata : Antioxidant effect of bovine serum albumin on iron-chelate superoxide-dependent membrane lipid peroxidation, 11th Biennial Scientific Meeting of the International Society for Free Radical Research, Paris, Jul. 2002.
22.
Kentaro Kogure, S. Hama, S. Manabe, Ichiro Suzuki, M. Shibuya, Akira Tokumura and Kenji Fukuzawa : Role of terminal structure of a-tocopheryl esters in nitric oxide production and apoptosis, The 9th Korea-Japan joint symposium of drug design and development, Seoul, May 2002.
23.
S. Hama, Kentaro Kogure, S. Manabe, Akira Tokumura and Kenji Fukuzawa : Anti-cancer effect of a-tocopheryl succinate mediated by apoptosis, The 9th Korea-Japan joint symposium of drug design and development, Seoul, May 2002.
24.
K. Tominaga, 小暮 健太朗, 福澤 健治, 德村 彰 : Property of secretory phospholipase D which generates bioactive lysophosphatidic acid in guinea-pig peritoneal washing, The 1st Takeda Science Foundation Symposium on Pharma Sciences:Lipids in Signaling and Related Diseases, 東京, 2001年10月.
25.
Kentaro Kogure, M. Morita, S. Nakashima, S. Hama, Akira Tokumura and Kenji Fukuzawa : Superoxide is responsible for apoptosis in rat vascular smooth muscle cells induced by α-tocopheryl hemisuccinate, 2nd China-Japan International Conference on Vitamins, Shanghai, Oct. 2001.
26.
Kenji Fukuzawa, Kentaro Kogure, M. Morita, S. Hama, S. Nakashima and Akira Tokumura : Enhancement by α-tocopheryl hemisuccinate of nitric oxide production indeced by lipopolysaccharide and interferon-γthrough up-regulation of protein kinase C in rat vascular smooth muscle cells, 2nd China-Japan International Conference on Vitamins, Shanghai, Oct. 2001.
Afroz Sheuli, 生駒 照, 屋宜 彩乃, Akira Tokumura and Tamotsu Tanaka : Effect of phosphatidic acid on indomethacin-induced stomach ulcer and its content in plant sources, 第88回日本生化学会大会, Dec. 2015.
三木 敏史, 清水 嘉文, 井上 友希子, 田中 保, 德村 彰 : Mass spectrometric analysis of dicarboxylate semialdehyde-containing lysophosphatidylcholine produced during peroxidation of lysophosphatidylcholine by lipoxygenase, 第33回日本分子生物学会・第83会日本生化学会合同大会，プログラム, 317, 2010年12月.
68.
片山 貴大, 西本 真梨子, 清水 嘉文, 稲葉 真衣子, 田中 保, 德村 彰 : Exposure to the surface of cultured vascular smooth muscle cells of lysophospholipid and their extracellular release, 第33回日本分子生物学会・第83会日本生化学会合同大会，プログラム, 317, 2010年12月.
Akira Tokumura, Yamamoto Junpei, YAmazato Mssashi, Nikawadori Miki, Shimizu Yoshinobu and Tamotsu Tanaka : Preferable production of lysophosphatidic acids having a polyunsaturated fatty acyl group by lysophospholipase D activity of autotaxin in fresh follicular fluid from patients programmed with in vitro fertilization., Sep. 2010.
Toshihiko Tsutsumi, Mika Adachi and Akira Tokumura : Metabolism and internalization of lysophosphatidylcholine in kidney epithelial cells, 第80回日本生化学会, Dec. 2007.
Akira Tokumura, Toshihiko Tsutsumi, Satoshi Taira, Kenji Fukuzawa and Mitchel Watsky : Lysophospholipase D and elevates lysophosphatidylcholine as sources of elevated aqueous humor LPA following rabbit corneal injury, 第78回日本生化学会, Oct. 2005.
116.
Toshihiko Tsutsumi and Akira Tokumura : METABOLISM AND INTERNALIZATION OF LYSOPAF IN KIDNEY EPITHELIAL CELLS, 第78回日本生化学会, Oct. 2005.
117.
J. Morishige, T. Tanaka, K. Satouchi, Akira Tokumura and Kenji Fukuzawa : Production of lysophosphatidic acid by lysophospholipase D in hen egg white, 第78回日本生化学会, Oct. 2005.
118.
Akira Tokumura, Toshihiko Tsutsumi, Satoshi Taira, Kenji Fukuzawa and Michel Watsky : Lysophospholipase D and elevates lysophosphatidylcholine as sources of elevated aqueous humor LPA following rabbit corneal injury, 第78回日本生化学会, Oct. 2005.