Abstract
Glutamate excitotoxicity and oxidative stress represent two major pathological mechanisms implicated in retinal disorders. In Diabetic Retinopathy (DR), oxidative stress is correlated to NADPH oxidase (NOX), a major source of Reactive Oxygen Species (ROS), and glutamate metabolism impairments. This study investigated the role of NOX2 and the novel NOX2 inhibitor, GLX7013170, in two models of a) retinal AMPA excitotoxicity [AMPA+GLX7013170 (10-4 M, intravitreally)] and b) early-stage DR paradigm (ESDR), GLX7013170: 14-day therapeutic treatment (topically, 20 μL/eye, 10 mg/mL (300 × 10-4 M), once daily) post-streptozotocin (STZ)-induced DR. Immunohistochemical studies for neuronal markers, nitrotyrosine, micro/macroglia, and real-time PCR, Western blot, and glutamate colorimetric assays were conducted. Diabetes increased NOX2 expression in the retina. NOX2 inhibition limited the loss of NOS-positive amacrine cells and the overactivation of micro/macroglia in both models. In the diabetic retina, GLX7013170 had no effect on retinal ganglion cell axons, but reduced oxidative damage, increased Bcl-2, reduced glutamate levels, and partially restored excitatory amino acid transporter (EAAT1) expression. These results suggest that NOX2 in diabetes is part of the triad, oxidative stress, NOX, and glutamate excitotoxicity, key players in the induction of DR. GLX7013170 is efficacious as a neuroprotective/anti-inflammatory agent and a potential therapeutic in retinal diseases, including ESDR.