Metformin inhibits oxidative stress in human retinal pigment epithelial cells
Qiao X, Li Y, Zhou T, Hsu A, Edwards PA, and Gao H. Metformin inhibits oxidative stress in human retinal pigment epithelial cells. Invest Ophthalmol Vis Sci 2019; 60(9).
Invest Ophthalmol Vis Sci
Purpose: Oxidative stress is a contributing factor to many retinal diseases including diabetic retinopathy (DR). We have previously reported significantly decreased severity of DR in metformin-treated type 2 diabetes patients, a remarkable anti-inflammatory effect of metformin in diabetic retinal vasculature, and an anti-oxidative effect of metformin in human retinal vascular endothelial cells. In this study, we investigated the possible role of metformin in oxidative stress responses of human retinal pigment epithelial cells (RPEs).
Methods: ARPE-19 (ATCC® CRL 2302™), a human RPE cell line, was pretreated with metformin (5 mM) then exposed to H2O2(1 mM). Intracellular reactive oxygen species (ROS) were measured using a cell permeant reagent 2',7'-Dichlorodihydrofluorescein diacetate (DCF). Expressions of Nrf2/HO-1 and mTOR effectors 4EBP-1/P70S6 were examined by immunoblots. The impact of metformin on ARPE-19 apoptosis was determined by TUNEL assay.
Results: H2O2exposure drastically enhanced intracellular ROS production by over three times (p < 0.01) in ARPE-19. Metformin pretreatment significantly reduced the surge of ROS level induced by H2O2(p < 0.05). Preliminary data also revealed that metformin pretreatment was associated with substantial reduction of HO-1 levels (p < 0.05), but had minimal effect on Nrf-2 levels in ARPE19 cells. In addition, reduced expressions of mTOR effectors 4EBP-1/P70S6 were observed in metformin treated ARPE19 cells. Metformin did not induce notable apoptosis in ARPE19 cells at the dose range of 1-20 mM used in this study.
Conclusions: Metformin attenuates oxidative stress in human RPEs potentially through targeting multiple signaling molecules/pathways including HO-1 and mTOR. In addition to our previous reports of metformin's anti-angiogenic, anti-inflammatory, and anti-oxidative effects on retinal vascular endothelial cells, this study further supports the notion that metformin has multiple protective effects on different retinal cells against pathogenesis of DR.