Stigmasterol improves diabetic retinopathy by inhibiting VAMP7-mediated autophagy/mitophagy

Diabetic retinopathy (DR) is a disease derived from diabetes, which brings great trouble to patients' lives. Stigmasterol has demonstrated beneficial effects in the management of diabetes; however, its influence on DR and the underlying mechanisms remain to be elucidated. Here, we cultured high-glucose (HG)-induced ARPE-19 cells and constructed a DR mice model, which were subsequently treated with stigmasterol. The function and mechanism of stigmasterol on HG-damaged cells were evaluated in vivo and in vitro models. The results showed that 10 μM stigmasterol effectively alleviated the HG-induced cell damage, as evidenced by the significant suppression of ROS levels and the protein expression of pro-apoptosis BAX, the enhancement of protein expression of anti-apoptosis BCL2. The increase in the pro-autophagy protein LC3B and the decrease in the anti-autophagy protein induced by HG were reversed by stigmasterol. Additionally, the co-localization of TOMM20 and LC3B enhanced by HG indicated the occurrence of mitophagy, while mitophagy was inhibited by stigmasterol. RNA-seq revealed that stigmasterol mediates differential gene enrichment in autophagy/mitophagy-related GO terms, while also resulting in a reduction of the autophagy/mitophagy-related gene VAMP7. The over-expression of VAMP7 diminished the effective benefits of stigmasterol in HG-induced cells. In vivo, Stigmasterol effectively reduced blood glucose levels and alleviated retinal damage in DR mice. The decreased expression of VAMP7 and LC3 in the retina of the DR mice with stigmasterol treatment were detected by immunohistochemistry. These results reveal that stigmasterol alleviates DR by inhibiting VAMP7-mediated autophagy/mitophagy. Our findings provide new insights into the treatment and drug development of DR.