Protective Effect of Metformin against Hydrogen Peroxide-Induced Oxidative Damage in Human Retinal Pigment Epithelial (RPE) Cells by Enhancing Autophagy through Activation of AMPK Pathway

Abstract

Age-related macular degeneration (AMD) is a leading cause of blindness with limited effective treatment. Although the pathogenesis of this disease is complex and not fully understood, the oxidative damage caused by excessive reactive oxygen species (ROS) in retinal pigment epithelium (RPE) has been considered as a major cause. Autophagy is essential for the degradation of cellular components damaged by ROS, and its dysregulation has been implicated in AMD pathogenesis. Therefore, strategies aiming to boost autophagy could be effective in protecting RPE cells from oxidative damage. Metformin is the first-line anti-type 2 diabetes drug and has been reported to stimulate autophagy in many tissues. We therefore hypothesized that metformin may be able to protect RPE cells against H2O2-induced oxidative damage by autophagy activation. In the present study, we found that metformin attenuated H2O2-induced cell viability loss, apoptosis, elevated ROS levels, and the collapse of the mitochondria membrane potential in D407 cells. Autophagy was stimulated by metformin, and inhibition of autophagy by 3-methyladenine (3-MA) and chloroquine (CQ) or knockdown of Beclin1 and LC3B blocked the protective effects of metformin. In addition, we showed that metformin could activate the AMPK pathway, whereas both pharmacological and genetic inhibitions of AMPK blocked the autophagy-stimulating and protective effects of metformin. Metformin conferred a similar protection against H2O2-induced oxidative damage in primary cultured human RPE cells. Taken together, these results demonstrate that metformin could protect RPE cells from H2O2-induced oxidative damage by stimulating autophagy via the activation of the AMPK pathway, supporting its potential use in the prevention and treatment of AMD.

Key Signaling Pathways in Aging and Potential Interventions for Healthy Aging

“…The AMPK signaling activation ameliorated autophagy and the level of coactivator-associated arginine methyltransferase 1 (CARM1), which involves several cellular processes, including autophagy in the aging heart [ 75 ]. Metformin can stimulate autophagy via activating AMPK signaling to protect human retinal pigment epithelial cells from hydrogen peroxide induced-oxidative stress [ 76 ]. In a d -galactose-induced renal aging model, hyperoxide attenuated a renal injury by augmenting autophagy through AMPK/ULK1 signaling [ 77 , 78 ].…”

Metformin prevents methylglyoxal-induced apoptosis by suppressing oxidative stress in vitro and in vivo

“…Metformin (MET) is an oral antidiabetic biguanide agent derived from Galega officinalis that not only reduces blood glucose levels and improves insulin sensitivity but also has benefits against cardiovascular diseases [21][22][23][24]. Several studies have shown that MET appears to reduce excessive ROS production and limit early apoptosis [25,26]. Whether MET can reduce MGOinduced EC apoptosis, what roles MET and MGO play, and how MET and MGO interact with each other in the context of the cardiovascular protective effects of MET remain to be determined.…”

Suppressor of Cytokine Signaling 2 Regulates Retinal Pigment Epithelium Metabolism by Enhancing Autophagy

“…The transcription factor EB (TFEB) inducer trehalose protects RPE against oxidative damage and cell death by upregulating autophagy ( Abokyi et al, 2020 ). Metformin defenses hydrogen peroxide-induced oxidative damage in RPE by enhancing autophagy through activation of the AMP-activated protein kinase (AMPK) pathway ( Zhao et al, 2020 ). Two recent studies described that SOCS2 is involved in autophagy in myocardial I/R and Huntington’s disease ( Li et al, 2019 ; Cho et al, 2021 ), but the underlying molecular mechanisms for SOCS2 regulating autophagy are unclear.…”