Acteoside inhibits high glucose-induced oxidative stress injury in RPE cells and the outer retina through the Keap1/Nrf2/ARE pathway

Diabetes retinopathy (DR) is one of the most common microvascular complications of diabetes. Retinal pigment epithelial (RPE) cells exposed to a high glucose environment experience a series of functional damages, which is an important factor in promoting the progression of DR. Acteoside (ACT) has strong antioxidant and anti-apoptotic properties, but the mechanism of ACT in DR is not completely clear. Therefore, the purpose of the present study was to explore whether ACT inhibits the damage to RPE cells in a high glucose environment through antioxidative effects to alleviate the DR process. The DR in vitro cell model was constructed by treating RPE cells with high glucose, and the DR in vivo animal model was constructed by injecting streptozotocin (STZ) into the peritoneal cavity of mice to induce diabetes. The proliferation and apoptosis of RPE cells were detected by CCK-8 and flow cytometry assays, respectively. The expression changes in Nrf2, Keap1, NQO1 and HO-1 were evaluated by qRT‒PCR, Western blot and immunohistochemistry analyses. The MDA, SOD, GSH-Px and T-AOC contents were detected by kits. The changes in ROS and nuclear translocation of Nrf2 were observed by immunofluorescence assays. HE staining was used to measure the thickness of the outer nuclear layer (ONL) of the retina, and TUNEL staining was used to detect the number of apoptotic cells in the retinas of mice. In the present study, ACT effectively ameliorated outer retina damage in diabetic mice. In high glucose (HG)-induced RPE cells, ACT treatment had the following effects: improved proliferation, decreased apoptosis, inhibited Keap1 expression, promoted the nuclear translocation and expression of Nrf2, upregulated NQO1 and HO-1 (the target genes of Nrf2) expression, decreased ROS concentration, and increased the levels of the SOD, GSH-Px and T-AOC antioxidant indicators. However, knockdown of Nrf2 reversed the above phenomena, which indicated that the protective function of ACT in HG-induced RPE cells are closely related to Nrf2. In summary, the present study demonstrated that HG-induced oxidative stress injury is inhibited by ACT in RPE cells and the outer retina through the Keap1/Nrf2/ARE pathway.