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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.

Background. Age-related macular degeneration (AMD) mainly affects the central region of retina and has many late-stage manifestations.Objectives. Age-related macular degeneration is a leading cause of irreversible blindness in older people. The main feature of AMD is retinal pigment epithelium (RPE) degeneration. In this study, we aimed to explore the influence of HTRA1 expression on the proliferation and migration of RPE cells. Materials and methods.Human ARPE-19 cells were transfected with an HTRA1 overexpression lentivirus or HTRA1 siRNA to silence HtrA1 expression. Quantitave reverse-transcription polymerase chain reaction (qRT-PCR) and western blotting were used to verify the relative level of HTRA1 mRNA and expression of HTRA1 protein of transfected human ARPE-19 cells. The MTT clone formation and transwell assays were used to confirm the effect of HTRA1 expression on the proliferation, colony forming ability and migration of ARPE-19 cells.Results. The proliferation capacity (shown as optical density value) of ARPE-19 cells in the HTRA1-overexpressing group at culture times of 24 h and 48 h were 0.595 ±0.032 and 0.867 ±0.037 respectively, which were much higher than in the mock group. However, the proliferative capacity of cells in the HTRA1-silenced group decreased with increasing time of culture, compared with the mock group. The number of cloned and migrating cells in the HTRA1-overexpressing group were much higher than in the mock group, whereas the numbers in the HTRA1-silenced group were significantly lower.Conclusions. Overexpression of HTRA1 promotes proliferation and migration of RPE cells, which can help maintain the function of sensory neurons in the retina. Therefore, HTRA1 may be a suitable target for AMD treatments.

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