title: The novel triterpenoid RTA 408 protects human retinal pigment epithelial cells against H2O2-induced cell injury via NF-E2-related factor 2 (Nrf2) activation.
abstract: Oxidative stress-induced retinal pigment epithelial (RPE) cell damage is an important factor in the pathogenesis of age-related macular degeneration (AMD). Previous studies have shown that RTA 408, a synthetic triterpenoid compound, potently activates Nrf2. This study aimed to investigate the protective effects of RTA 408 in cultured RPE cells during oxidative stress and to determine the effects of RTA 408 on Nrf2 and its downstream target genes. Primary human RPE cells were pretreated with RTA 408 and then incubated in 200μM H2O2 for 6h. Cell viability was measured with the WST-8 assay. Apoptosis was quantitatively measured by annexin V/propidium iodide (PI) double staining and Hoechst 33342 fluorescent staining. Reduced (GSH) and oxidized glutathione (GSSG) were measured using colorimetric assays. Nrf2 activation and its downstream effects on phase II enzymes were examined by Western blot. Treatment of RPE cells with nanomolar ranges (10 and 100nM) of RTA 408 markedly attenuated H2O2-induced viability loss and apoptosis. RTA 408 pretreatment significantly protected cells from oxidative stress-induced GSH loss, GSSG formation and decreased ROS production. RTA 408 activated Nrf2 and increased the expression of its downstream genes, such as HO-1, NQO1, SOD2, catalase, Grx1, and Trx1. Consequently, the enzyme activities of NQO1, Grx1, and Trx1 were fully protected by RTA 408 pretreatment under oxidative stress. Moreover, knockdown of Nrf2 by siRNA significantly reduced the cytoprotective effects of RTA 408. In conclusion, our data suggest that RTA 408 protect primary human RPE cells from oxidative stress-induced damage by activating Nrf2 and its downstream genes.
authors.affiliation: Pharmaceutical Sciences, University of North Texas System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA.
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Liu
authors.affiliation: REATA Pharmaceuticals, Inc., Irving, TX, USA.
authors.forename: Keith
authors.initials: K
authors.lastname: Ward
authors.affiliation: Pharmaceutical Sciences, University of North Texas System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA.
authors.forename: Christy
authors.initials: C
authors.lastname: Xavier
authors.affiliation: Pharmaceutical Sciences, University of North Texas System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA.
authors.forename: Jamieson
authors.initials: J
authors.lastname: Jann
authors.affiliation: Department of Cell Biology & Immunology, UNTHSC, Ft. Worth, TX, USA; North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX, USA.
authors.forename: Abbot F
authors.initials: AF
authors.lastname: Clark
authors.affiliation: Pharmaceutical Sciences, University of North Texas System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA; North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX, USA.
authors.forename: Iok-Hou
authors.initials: IH
authors.lastname: Pang
authors.affiliation: Pharmaceutical Sciences, University of North Texas System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, TX, USA; North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX, USA; Institute for Cancer Research, University of North Texas Health Science Center, Fort Worth, TX, USA.
authors.forename: Hongli
authors.initials: H
authors.lastname: Wu
mesh_terms: D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D020011:Protective Agents / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism*; D014315:Triterpenes / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D051267:NF-E2-Related Factor 2; D020011:Protective Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014315:Triterpenes; D051028:bcl-2-Associated X Protein; D006861:Hydrogen Peroxide; D053148:Caspase 3; C000589490:omaveloxolone; D005978:Glutathione; D019803:Glutathione Disulfide
keywords: Nrf2; Oxidative stress; RTA 408; Retinal pigment epithelial cells