title: Astaxanthin protects ARPE-19 cells from oxidative stress via upregulation of Nrf2-regulated phase II enzymes through activation of PI3K/Akt.
abstract: OBJECTIVE
  Oxidative stress on retinal pigment epithelial (RPE) cells is thought to play a crucial role in the development and progression of age-related macular degeneration. Astaxanthin (AST) is a carotenoid that shows significant antioxidant properties. This study was designed to investigate the protective effect of AST on ARPE-19 cells against oxidative stress and the possible underlying mechanism.
  
  
  METHODS
  ARPE-19 cells exposed to different doses of H2O2 were incubated with various concentrations of AST and cell viability subsequently detected with the (4-[3-[4-iodophenyl]-2-4(4-nitrophenyl)-2H-5- tetrazolio-1,3-benzene disulfonate]; WST-1) assay. The apoptosis rate and intracellular levels of reactive oxygen species (ROS) were measured with flow cytometry. NAD(P)H quinine oxidoreductase 1 (NQO1), hemeoxygenase-1 (HO-1), glutamate-cysteine ligase modiﬁer subunit (GCLM), and glutamate-cysteine ligase catalytic subunit (GCLC) expression were examined with real-time PCR and western blotting. The nuclear localization of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) protein and the expression levels of cleaved caspase-3 and protein kinase B proteins were evaluated with western blotting.
  
  
  RESULTS
  AST clearly reduced H2O2-induced cell viability loss, cell apoptosis, and intracellular generation of ROS. Furthermore, treatment with AST activated the Nrf2-ARE pathway by inducing Nrf2 nuclear localization. Consequently, Phase II enzymes NQO1, HO-1, GCLM, and GCLC mRNA and proteins were increased. AST inhibited expression of H2O2-induced cleaved caspase-3 protein. Activation of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway was involved in the protective effect of AST on the ARPE-19 cells.
  
  
  CONCLUSIONS
  AST protected ARPE-19 cells against H2O2-induced oxidative stress via Nrf2-mediated upregulation of the expression of Phase II enzymes involving the PI3K/Akt pathway.
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province, P.R. China.
authors.forename: Zhongrui
authors.initials: Z
authors.lastname: Li
authors.forename: Xin
authors.initials: X
authors.lastname: Dong
authors.forename: Hongling
authors.initials: H
authors.lastname: Liu
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.forename: Huanqi
authors.initials: H
authors.lastname: Shi
authors.forename: Yan
authors.initials: Y
authors.lastname: Fan
authors.forename: Dingshan
authors.initials: D
authors.lastname: Hou
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Zhang
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D005786:Gene Expression Regulation / Q000187:drug effects; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D050217:Metabolic Detoxication, Phase II; D016660:NAD(P)H Dehydrogenase (Quinone); D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D020011:Protective Agents / Q000737:chemistry / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology*; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects*; D024341:Xanthophylls / Q000737:chemistry / Q000494:pharmacology
chemical_list: D053148:Caspase 3; D005721:Glutamate-Cysteine Ligase; D051547:Heme Oxygenase-1; D006861:Hydrogen Peroxide; D016660:NAD(P)H Dehydrogenase (Quinone); D051267:NF-E2-Related Factor 2; D019869:Phosphatidylinositol 3-Kinases; D020011:Protective Agents; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D024341:Xanthophylls; C005948:astaxanthine; C447479:NQO1 protein, human; C546365:GCLM protein, human
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