Nrf2 Activation Is a Potential Therapeutic Approach to Attenuate Diabetic Retinopathy

PURPOSE. Oxidative stress is a causal factor in the development of diabetic retinopathy; however, clinically relevant strategies to treat the disease by augmenting antioxidant defense mechanisms have not been fully explored. We hypothesized that boosting nuclear factor erythroid-2-related factor 2 (Nrf2) antioxidant capacity with the novel Nrf2 activator dh404, would protect the retina in diabetes including vision-threatening breakdown of the blood-retinal barrier (BRB) and associated damage to macroglial Muller cells. METHODS. Sprague-Dawley rats were randomized to become diabetic or nondiabetic and administered dh404 by gavage for 10 weeks. Complementary in vitro studies were performed in cultured Muller cells exposed to hyperglycemia. RESULTS. In diabetes, dh404 prevented vascular leakage into the retina and vitreous cavity as well as upregulation of the vascular permeability and angiogenic factors, VEGF, and angiopoietin-2, and inflammatory mediators, including TNF-alpha and IL-6. Muller cells, which maintain BRB integrity and become gliotic in diabetes with increased immunolabeling for glial fibrillary acidic protein, were protected by dh404. In diabetes, dh404 bolstered the antioxidant capacity of the retina with an increase in hemeoxygenase-1, nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) quinine oxido-reductase-1, and Nrf2. Further, dh404 attenuated the diabetes-induced increase in oxidative stress as measured by dihydroethidium and 8-oxo-2'-deoxyguanosine (8-OHdG) immunolabeling as well as NADPH oxidase isoform expression. Studies in Muller cells supported these findings with dh404 attenuating the hyperglycemia-induced increase in vascular permeability, angiogenic and inflammatory mediators, and oxidative stress. CONCLUSIONS. Our data demonstrate the ability of dh404 to protect the retina against diabetes-induced damage and potentially prevent vision loss.