Tricin attenuates diabetic retinopathy by inhibiting oxidative stress and angiogenesis through regulating Sestrin2/Nrf2 signaling

To explore the potential function of tricin in diabetic retinopathy (DR) and investigate whether Sestrin2 is closely involved in DR. A single intraperitoneal injection of streptozotocin-induced diabetes model in Sprague-Dawley rats and a high glucose-induced retinal epithelial cell model in ARPE-19 cells were established. The retinas were removed and examined by hematoxylin-eosin (HE) staining and dihydroethidium (DHE) staining. The proliferation ability and reactive oxygen species (ROS) level of ARPE-19 cells were detected by 5-ethynyl-2 '-deoxyuridine (EdU) and flow cytometry. Then, the content of superoxide dismutase (SOD), malonaldehyde (MDA), and glutathione peroxidase (GSH-Px) in serum or cell supernatant was tested using enzyme linked immunosorbent assay (ELISA). In addition, the expression of Sestrin2, nuclear factor erythroid-2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), platelet endothelial cell adhesion molecule-1 (CD31), and vascular endothelial growth factor receptor 2 (VEGFR2) in retina tissue or ARPE-19 cells were validated through western blot and immunofluorescence assays. With the increase of MDA and ROS concentration, Sestrin2 expression was downregulated significantly, and Nrf2 and HO-1 expression was also reduced in retina tissue or ARPE-19 cells of model group, whereas CD31 and VEGFR2 expression was upregulated. However, tricin ameliorated the oxidative stress and angiogenesis and rectified the abnormal expression of Sestrin2/Nrf2 in diabetic retinopathy. Further mechanistic studies showed that silence Sestrin2 reduced the protective effect of tricin on ARPE-19 cells, as well as abolished its regulating effect on the Nrf2 pathway. These results suggested that tricin inhibits oxidative stress and angiogenesis in retinal epithelial cells of DR rats via reinforcing Sestrin2/Nrf2 signaling.