title: IGF-1 signaling via the PI3K/Akt pathway confers neuroprotection in human retinal pigment epithelial cells exposed to sodium nitroprusside insult.
abstract: The pathological increase in the levels of the second messenger nitric oxide (NO) in the vitreous cavity and retina leads to injury and cell death of the retinal pigment epithelium (RPE) cells and eventually may contribute to the occurrence and development of diabetic retinopathy. In this study, we developed a cellular model of retinopathy using D407 cells (a human RPE cell line) exposed to sodium nitroprusside (SNP) and investigated the protective effect of the insulin-like growth factor-1 (IGF-1) towards this insult. Cell death and apoptosis were examined by the methyl thiazolyl tetrazolium assay and Hoechst staining, respectively. Specific inhibitors were used and phosphorylation of relevant signaling proteins was determined by Western blotting. SNP, in a concentration-dependent fashion, increased the production of reactive oxygen species (ROS) and lipid peroxidation process causing cell death by apoptosis of D407 cells. IGF-1, in a time- and dose-dependent manner, conferred protection towards SNP-mediated insult. Both phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) and mitogen-activated protein kinase (MAPK) were activated by IGF-1 in relation to the protective effect. Blockade of the PI3K/Akt pathway abolished the protective effect of IGF-1 whereas inhibition of the MAPK pathway was ineffective. SNP decreased the phosphorylation of Akt in the cells while IGF-1 reversed this inhibitory effect. These results indicate that the protective effect of IGF-1 on D407 exposed to SNP insult is mediated by the PI3K/Akt pathway. This proposal may be exploited in the clinic to improve the viability of insulted retinal cells for maintaining physiological vision.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, 510060, China.
authors.forename: Haitao
authors.initials: H
authors.lastname: Wang
authors.forename: Sufen
authors.initials: S
authors.lastname: Liao
authors.forename: Ruojun
authors.initials: R
authors.lastname: Geng
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Zheng
authors.forename: Rifang
authors.initials: R
authors.lastname: Liao
authors.forename: Fengxia
authors.initials: F
authors.lastname: Yan
authors.forename: Thilini
authors.initials: T
authors.lastname: Thrimawithana
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Little
authors.forename: Zhong-Ping
authors.initials: ZP
authors.lastname: Feng
authors.forename: Philip
authors.initials: P
authors.lastname: Lazarovici
authors.forename: Wenhua
authors.initials: W
authors.lastname: Zheng
mesh_terms: D017209:Apoptosis; D002460:Cell Line; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D015227:Lipid Peroxidation; D020935:MAP Kinase Signaling System; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009599:Nitroprusside / Q000633:toxicity; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D017382:Reactive Oxygen Species; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: D018696:Neuroprotective Agents; D017382:Reactive Oxygen Species; D009599:Nitroprusside; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt