Oxidative stress and inflammation are implicated in the pathogenesis of retinopathy in diabetes. The aim of this study is to examine the effect of curcumin, a polyphenol with antioxidant and anti-inflammatory properties, on diabetes-induced oxidative stress and inflammation in the retina of rats.
A group of streptozotocin-induced diabetic rats received powdered diet supplemented with 0.05% curcumin (w/w), and another group received diet without curcumin. The diets were initiated soon after induction of diabetes, and the rats were sacrificed 6 weeks after induction of diabetes. The retina was used to quantify oxidative stress and pro-inflammatory markers.
Antioxidant capacity and the levels of intracellular antioxidant, GSH (reduced form of glutathione) levels were decreased by about 30–35%, and oxidatively modified DNA (8-OHdG) and nitrotyrosine were increased by 60–70% in the retina of diabetic rats. The levels of interleukin-1β (IL-1β) and vascular endothelial growth factor (VEGF) were elevated by 30% and 110% respectively, and the nuclear transcription factor (NF- kB) was activated by 2 fold. Curcumin administration prevented diabetes-induced decrease in the antioxidant capacity, and increase in 8-OHdG and nitrotyrosine; however, it had only partial beneficial effect on retinal GSH. Curcumin also inhibited diabetes-induced elevation in the levels of IL-1β, VEGF and NF- kB. The effects of curcumin were achieved without amelioration of the severity of hyperglycemia.