The protective effect and mechanism of phycocyanin on diabetic retinopathy in rats.

Phycocyanin (PC), a bioactive pigment extracted from Spirulina, possesses multiple biological activities, including anti-inflammatory, antioxidant, and anticancer effects. The present study aimed to investigate the protective role of PC on the retina of diabetic rats and to elucidate its underlying mechanisms.Diabetes mellitus (DM) was induced in the model group (DM group) and the treatment group (PC group) by a single intraperitoneal injection of streptozotocin (STZ) at a dose of 55 mg/kg. After model establishment, the PC group received PC solution by daily oral gavage at a dose of 300 mg/kg for 12 consecutive weeks.Diabetic status was assessed by monitoring fasting blood glucose(FBG) levels, body weight, and general condition of the rats. Retinal histopathological changes were evaluated using hematoxylin and eosin H&E staining. Oxidative stress parameters, including catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH), were measured using commercial biochemical assay kits. Reactive oxygen species (ROS) levels were determined by enzyme-linked immunosorbent assay (ELISA). Additionally, the expression of NRF2 and HO-1 proteins in retinal tissue was assessed by immunohistochemistry and Western blot analysis, while NRF2 and HO-1 mRNA expression levels were quantified using Real-Time PCR.The results indicated that PC administration did not significantly improve FBG or body weight in diabetic rats. However, PC markedly enhanced the activities of CAT, SOD, and GSH, reduced ROS accumulation, upregulated NRF2 and HO-1 protein expression, and attenuated oxidative stress-induced retinal injury in diabetic rats.