Exendin-4 Protects Human Retinal Pigment Epithelial Cells from H₂O₂-Induced Oxidative Damage via Activation of NRF2 Signaling

Aims: Oxidative damage plays a vital role in the pathogenesis of age-related macular degeneration (AMD). Exendin-4 (EX4), a glucagon-like peptide-1 receptor agonist, possesses several pharmacological functions, such as anti-inflammatory and antioxidative properties. However, the effects and mechanism of EX4 on oxidative stress in retinal pigment epithelial (RPE) cells induced by hydrogen peroxide (H₂O₂) remain unclear. The present study aimed to investigate the protective mechanism of EX4 on human RPE cells subjected to oxidative stress. Methods: Human RPE ARPE-19 cells were treated with H₂O₂ to induce oxidative damage. Cell viability was determined by Cell Counting Kit-8 and lactate dehydrogenase assay. Levels of intracellular reactive oxygen species (ROS), malonyldialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH) were measured using commercial kits. The expression of nuclear factor erythroid 2-related factor-2 (NRF2), heme oxygenase-1 (HO-1), and NAD(P)H:quinone oxidoreductase-1 (NQO-1) was measured using reverse transcription quantitative polymerase chain reaction assay and western blot, respectively. Results: H₂O₂ significantly induced oxidative stress to reduce viability of RPE cells and increased intracellular ROS generation. EX4 significantly ameliorated H₂O₂-induced oxidative damage by reducing intracellular ROS generation, decreasing MDA concentration, and increasing antioxidant enzymes activities (SOD and GSH). In addition, EX4 markedly increased expression of NRF2, HO-1, and NQO-1 and significantly improved protein expression of NRF2 and HO-1 in H₂O₂-treated ARPE-19 cells, caused by increased nuclear NRF2 protein expression. NRF2 knockdown by targeted siRNA alleviated EX4-mediated HO-1 expression and significantly nullified EX4-mediated RPE cell protection against H₂O₂. Conclusions: EX4 attenuated oxidative damage induced by H₂O₂ in ARPE-19 cells through the activation of the NRF2 signaling pathway. The findings suggested that EX4 may be a potential therapeutic agent for the treatment of AMD.