Ryo Hayakawa, Takeshi Ishii, Taiki Fushimi, Yuki Kamei, Ai Yamaguchi, Kenji Sugimoto, Hitoshi Ashida and Mitsugu Akagawa : Luteolin protects human ARPE-19 retinal pigment epithelium cells from blue light-induced phototoxicity through activation of Nrf2/Keap1 signaling, Free Radical Research, 59, 4, 356-368, 2025.
(Summary)
Age-related macular degeneration (AMD), a serious physical and mental health problem worldwide, is the leading cause of irreversible, severe vision impairment and loss in older people. AMD is associated with multiple risk factors, many of which are closely linked to increased oxidative stress. Some studies have suggested that long-term and excessive exposure to blue light may be a potential risk factor for the development or progression of AMD. Recently, we demonstrated that blue light irradiation caused oxidative stress in all-trans-retinal (atRAL)-exposed human ARPE-19 retinal pigment epithelium cells by generating singlet oxygen (1O2), leading to apoptotic cell death. Luteolin, a flavonoid found in various edible plants, has been reported to possess divergent health-promoting properties including anti-oxidative and chemopreventive effects by up-regulating anti-oxidative and phase II detoxifying enzymes through activation of Keap1/Nrf2 signaling. Herein, we verified the cytoprotective action of luteolin against blue light irradiation using atRAL-exposed ARPE-19 cells. Our results established that luteolin effectively prevented blue light-induced apoptosis of ARPE-19 cells by mitigating oxidative stress. We also confirmed that luteolin suppressed intracellular accumulation of 1O2 and formation of atRAL-derived lipofuscin by increased expression of heme oxygenase-1 and aldehyde dehydrogenase 1A1 through activation of Keap1/Nrf2 signaling. Furthermore, our data implied that the luteolin-provoked activation of Keap1/Nrf2 signaling might be due to covalent binding of luteolin o-quinone to the critical cysteinyl thiol in Keap1. The present results suggest that luteolin could be helpful in the prevention and amelioration of blue light-induced retinal degeneration, including AMD.
(Keyword)
age-related macular degeneration / blue light / Luteolin / retinal pigment epithelium cells / singlet oxygen
Yuki Nagara, Kentaro Tsuji, Yuki Kamei and Mitsugu Akagawa : Bergenin promotes mitochondrial biogenesis via the AMPK/SIRT1 axis in hepatocytes, The Journal of Medical Investigation : JMI, 72, 1.2, 66-75, 2025.
(Summary)
Aging and obesity trigger liver mitochondrial decline, impairing liver function and energy metabolism. Effective hepatic mitochondrial biogenesis helps maintain and restore hepatocyte function. The effects of bergenin, a polyphenol with various pharmacological effects, on hepatic mitochondrial biogenesis remain unclear. Therefore, we aimed to determine its effects on mitochondrial biogenesis in hepatocytes. We measured mitochondrial content in human HepG2 hepatocytes using MitoTracker Green FM ; intracellular ATP content using an ATP assay kit ; and mitochondrial DNA (mtDNA) using the ratio of mtDNA to nuclear DNA by qPCR. Protein levels were analyzed using immunoblotting. Nuclear translocation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) was assessed by immunofluorescence staining and immunoblotting. In human HepG2 hepatocytes, bergenin increased mitochondrial content, elevated mitochondrial DNA and constituent proteins, and enhanced intracellular ATP levels and PGC-1α nuclear translocation, possibly promoting mitochondrial biosynthesis. SIRT1 expression was induced in bergenin-treated cells and may be responsible for bergenin-inducible mitochondrial biogenesis, which was abolished by the SIRT1 inhibitor EX-527. Furthermore, bergenin activated AMP-activated protein kinase (AMPK). Compound C, an AMPK inhibitor, abolished bergenin-induced SIRT1 expression and mitochondrial biogenesis. Overall, bergenin activates hepatic mitochondrial biogenesis through the AMPK / SIRT1 axis, which could help to prevent and ameliorate serious aging- and obesity-related liver diseases. J. Med. Invest. 72 : 66-75, February, 2025.
Ryosuke Kamikubo, Hiroki Yoshida, Taiki Fushimi, Yuki Kamei and Mitsugu Akagawa : β-Caryophyllene, a dietary phytocannabinoid, alleviates high-fat diet-induced hepatic steatosis in mice via AMPK activation, Bioscience, Biotechnology, and Biochemistry, 88, 12, 1465-1471, 2024.
(Summary)
β-Caryophyllene (BCP), a dietary phytocannabinoid, significantly suppresses palmitate-induced lipid accumulation in human HepG2 hepatocytes via activation of AMP-activated protein kinase (AMPK) signaling. The objective of the preset research was to assess whether oral administration of BCP alleviates obesity-induced hepatic steatosis in mice through AMPK activation. We examined the protective action of supplementation of 0.3% BCP (w/w) in a high-fat diet (HFD) on C57BL/6J mice for 12 weeks. BCP supplementation evidently ameliorated histological hepatic steatosis features, and significantly reduced triglycerides and cholesterol levels in the liver, and serum levels of aspartate aminotransferase and alanine aminotransferase as compared with non-supplemented HFD-fed mice. Immunoblotting revealed that BCP supplementation in HFD-fed mice also caused hepatic AMPK activation. Furthermore, treatment with BCP in HFD-fed mice significantly suppressed body weight gain and attenuated obesity-related phenotypes relative to the HFD mice. Our results suggest the usefulness of BCP in the prevention of obesity-related liver steatosis and liver injury.
Yuki Mori, Masashi Masuda, Risa Yoshida-Shimizu, Saki Aoyagi, Yuichiro Adachi, The Anh Nguyen, Yusuke Maruyama, Yosuke Okumura, Yuki Kamei, Maiko Sakai, Kohta Ohnishi, Hirokazu Ohminami and Yutaka Taketani : All-trans retinoic acid induces lipophagy through the activation of the AMPK-Beclin1 signaling pathway and reduces Rubicon expression in adipocytes., The Journal of Nutritional Biochemistry, 126, 2024.
(Summary)
Lipophagy is defined as a lipolysis pathway that degrades lipid droplet (LD) via autophagy. All-trans retinoic acid (atRA), a metabolite of vitamin A, stimulates lipolysis through hormone-sensitive lipase and β-oxidation. However, the regulation of lipolysis by atRA-induced autophagy in adipocytes remains unclear. In this study, we investigated the effect of atRA on autophagy in epididymal fat of mice and the molecular mechanisms of autophagy in 3T3-L1 adipocytes. Western blotting showed that atRA decreased the expression of p62, a cargo receptor for autophagic degradation, and increased the expression of the lipidated LC3B (LC3B-II), an autophagy marker, in epididymal fat. Next, we confirmed that atRA increased autophagic flux in differentiated 3T3-L1 cells using the GFP-LC3-RFP-LC3ΔG probe. Immunofluorescent staining revealed that the colocalization of LC3B with perilipin increased in differentiated 3T3-L1 cells treated with atRA. The knockdown of Atg5, an essential gene in autophagy induction, partly suppressed the atRA-induced release of non-esterified fatty acid (NEFA) from LDs in differentiated 3T3-L1 cells. atRA time-dependently elicited the phosphorylation of AMPK and Beclin1, autophagy-inducing factors, in mature 3T3-L1 adipocytes. Inversely, atRA decreased the protein expression of Rubicon, an autophagy repressor, in differentiated 3T3-L1 cells and epididymal fat. Interestingly, the expression of ALDH1A1, atRA-synthesizing enzymes, increased in epididymal fat with decreased protein expression of Rubicon in aged mice. These results suggest that atRA may partially induce lipolysis through lipophagy by activating the AMPK-Beclin1 signaling pathway in the adipocytes and increased atRA levels may contribute to decreased Rubicon expression in the epididymal fat of aged mice. (248/250 words).
Mana Kitao, Ai Yamaguchi, Takuma Tomioka, Kenji Kai, Yuki Kamei, Kenji Sugimoto and Mitsugu Akagawa : Astaxanthin protects human ARPE-19 retinal pigment epithelium cells from blue light-induced phototoxicity by scavenging singlet oxygen., Free Radical Research, 57, 6-12, 430-443, 2023.
(Summary)
directly. Our results suggest the potential value of astaxanthin as a dietary strategy to prevent blue light-induced retinal degeneration including AMD.
(Keyword)
Humans / Aged / Singlet Oxygen / Reactive Oxygen Species / Blue Light / Retinal Pigment Epithelium / Oxidative Stress / Apoptosis / Xanthophylls / Macular Degeneration
Yuki Kamei, Yosuke Okumura, Yuichiro Adachi, Yuki Mori, Maiko Sakai, Kohta Ohnishi, Hirokazu Ohminami, Masashi Masuda, Hisami Yamanaka-Okumura and Yutaka Taketani : Humoral and cellular factors inhibit phosphate-induced vascular calcification during the growth period., Journal of Clinical Biochemistry and Nutrition, 73, 3, 198-204, 2023.
(Summary)
, obvious calcification was observed in the adult aorta but not in the young aorta. Furthermore, culture in high Pi medium increased the mRNA level of tissue-nonspecific alkaline phosphatase (TNAP), which degrades pyrophosphate, only in the adult aorta. Collectively, our findings indicate that the aorta in growing mouse may be resistant to Pi-induced vascular calcification via a mechanism in which high serum fetuin-A levels and suppressed TNAP expression.
Vascular calcification is an important pathogenesis related to cardiovascular disease and high mortality rate in chronic kidney disease (CKD) patients. It has been well-known that hyper-phosphatemia induces osteochondrogenic transition of vascular smooth muscle cells (VSMCs) resulting ectopic calcification in aortic media, cardiac valve, and kidney. However, the detailed mechanism of the ectopic calcification has been not clarified yet. Here, we found that the co-localization of CYP27B1 with the calcified lesions of aorta and arteries in kidney of klotho mutant () mice, and then investigated the role of CYP27B1 in the mineralization of the VSMCs. Under high phosphate condition, overexpression of CYP27B1 induced calcification and osteocalcin mRNA expression in the VSMCs. Inversely, siRNA- inhibited high phosphate-induced calcification of the VSMCs. We also found that the accumulated CYP27B1 protein was glycosylated in the kidney of mice. Therefore, overexpression of CYP27B1-N310A and CYP27B1-T439A, which are a mutation for -linked glycosylation site (N310A) and a mutation for -linked glycosylation site (T439A) in CYP27B1, decreased calcium deposition and expression of RUNX2 induced by high phosphate medium in VSMCs compared with wild-type CYP27B1. These results suggest that extra-renal expression of glycosylated CYP27B1 would be required for ectopic calcification of VSMCs under hyperphosphatemia.
Yuichiro Adachi, Masashi Masuda, Iori Sakakibara, Takayuki Uchida, Yuki Niida, Yuki Mori, Yuki Kamei, Yosuke Okumura, Hirokazu Ohminami, Kohta Ohnishi, Hisami Okumura, Takeshi Nikawa and Yutaka Taketani : All-trans retinoic acid changes muscle fiber type via increasing GADD34 dependent on MAPK signal., Life Science Alliance, 5, 7, 2022.
(Summary)
All-trans retinoic acid (ATRA) increases the sensitivity to unfolded protein response in differentiating leukemic blasts. The downstream transcriptional factor of PERK, a major arm of unfolded protein response, regulates muscle differentiation. However, the role of growth arrest and DNA damage-inducible protein 34 (GADD34), one of the downstream factors of PERK, and the effects of ATRA on GADD34 expression in muscle remain unclear. In this study, we identified ATRA increased the GADD34 expression independent of the PERK signal in the gastrocnemius muscle of mice. ATRA up-regulated GADD34 expression through the transcriptional activation of gene via inhibiting the interaction of homeobox Six1 and transcription co-repressor TLE3 with the MEF3-binding site on the gene promoter in skeletal muscle. ATRA also inhibited the interaction of TTP, which induces mRNA degradation, with AU-rich element on mRNA via p-38 MAPK, resulting in the instability of mRNA. Overexpressed GADD34 in C2C12 cells changes the type of myosin heavy chain in myotubes. These results suggest ATRA increases GADD34 expression via transcriptional and post-transcriptional regulation, which changes muscle fiber type.
Yuki Kamei, Okumura Yosuke, Adachi Yuichiro, mori Yuki, Hirokazu Ohminami, Masashi Masuda and Yutaka Taketani : Inhibitory Mechanism of Ectopic Calcification during Growth Period, The American Society for Bone and Mineral Research 2022 Annual Meeting, Online, Sep. 2022.
Proceeding of Domestic Conference:
1.
MATSUMOTO Hina, Taiki Fushimi, Yuki Kamei, OSAKABE Naomi and Mitsugu Akagawa : 緑茶ポリフェノールによる神経および免疫細胞への作用機構の解析, 第80回日本栄養・食糧学会大会, May 2026.
2.
MATSUMOTO Hina, Taiki Fushimi, Yuki Kamei, 越阪部 奈緒美 and Mitsugu Akagawa : 緑茶カテキンによる神経および免疫細胞への作用機構の解析, 日本農芸化学会2026年度大会, Mar. 2026.