Madecassoside protects retinal pigment epithelial cells against hydrogen peroxide-induced oxidative stress and apoptosis through the activation of Nrf2/HO-1 pathway

Age-related macular degeneration (AMD) is a progressive and degenerative ocular disease associated with oxidative stress. Madecassoside (MADE) is a major bioactive triterpenoid saponin that possesses antioxidative activity. However, the role of MADE in AMD has never been investigated. In the current study, we aimed to evaluate the protective effect of MADE on retinal pigment epithelium (RPE) cells under oxidative stress condition. We used hydrogen peroxide (H2O2) to induce oxidative damage in human RPE cells (ARPE-19 cells). Our results showed that H2O2-caused significant decrease in cell viability and increase in lactate dehydrogenase (LDH) release were dose-dependently attenuated by MADE. MADE treatment also attenuated H2O2-induced reactive oxygen species (ROS) and malondialdehyde (MDA) production in RPE cells. The reduced glutathione (GSH) level and superoxide dismutase (SOD) activity in H2O2-induced ARPE-19 cells were elevated after MADE treatment. MADE also suppressed caspase-3 activity and bax expression, as well as increased bcl-2 expression. Furthermore, H2O2-induced increase in expression levels of HO-1 and nuclear Nrf2 were enhanced by MADE treatment. Finally, knockdown of Nrf2 reversed the protective effects of MADE on H2O2-induced ARPE-19 cells. In conclusion, these findings demonstrated that MADE protected ARPE-19 cells from H2O2-induced oxidative stress and apoptosis by inducing the activation of Nrf2/HO-1 signaling pathway.