title: The anthocyanin cyanidin-3-O-β-glucoside, a flavonoid, increases hepatic glutathione synthesis and protects hepatocytes against reactive oxygen species during hyperglycemia: Involvement of a cAMP-PKA-dependent signaling pathway.
abstract: Enhanced oxidative stress due to high glucose contributes to pathological changes in diabetes-related liver complications. Reducing oxidative stress may alleviate these pathogenic processes. Anthocyanin, a natural antioxidant, has been reported to reduce intracellular reactive oxygen species (ROS) levels but the mechanism of this reduction is not fully understood. The glutathione (GSH) antioxidant system is critical for counteracting oxidative stress-induced intracellular injury. In this study, we evaluated the mechanism of the anthocyanin-mediated regulation of GSH synthesis and reduction in intracellular ROS levels. We observed that treatment of human HepG2 cells with the anthocyanin C3G significantly reduced ROS levels induced by high glucose. C3G incubation increased glutamate-cysteine ligase expression, which in turn mediated the reduction in ROS levels. However, the upregulation of glutamate-cysteine ligase catalytic subunit (Gclc) expression by C3G occurred independent of the Nrf1/2 transcription factors. Notably, the cAMP-response element binding protein (CREB) was identified as the target transcription factor involved in the C3G-mediated upregulation of Gclc expression. C3G increased phosphorylation of CREB through protein kinase A (PKA) activation, which induced a CREB-mediated upregulation of Gclc transcription. In vivo, treatment with C3G increased the GSH synthesis in the liver of diabetic db/db mice through PKA-CREB-dependent induction of Gclc expression. Finally, oxidative stress determined by lipid peroxidation, neutrophil infiltration, and hepatic steatosis was attenuated in C3G-treated db/db mice. Our results demonstrate that the anthocyanin C3G has an effect of activating GSH synthesis through a novel antioxidant defense mechanism against excessive ROS production, contributing to the prevention of hyperglycemia-induced hepatic oxidative damage.
authors.affiliation: Department of Toxicology, Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhu
authors.forename: Qianju
authors.initials: Q
authors.lastname: Jia
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Zhang
authors.forename: Min
authors.initials: M
authors.lastname: Xia
mesh_terms: D000818:Animals; D000872:Anthocyanins / Q000494:pharmacology* / Q000627:therapeutic use; D000975:Antioxidants / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D002470:Cell Survival / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D019610:Cytoprotection; D004789:Enzyme Activation / Q000187:drug effects; D005234:Fatty Liver / Q000517:prevention & control; D015870:Gene Expression; D005960:Glucosides / Q000494:pharmacology* / Q000627:therapeutic use; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000096:biosynthesis*; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000188:drug therapy* / Q000378:metabolism; D008099:Liver / Q000378:metabolism / Q000473:pathology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D008297:Male; D051379:Mice; D008820:Mice, Obese; D018384:Oxidative Stress; D011485:Protein Binding; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D015854:Up-Regulation; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D000975:Antioxidants; C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; C491901:FAS protein, human; D005960:Glucosides; D017382:Reactive Oxygen Species; D017392:Thiobarbituric Acid Reactive Substances; C462279:cyanidin-3-O-beta-glucopyranoside; D019014:fas Receptor; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione