Diabetic retinopathy is the leading cause of blindness in working age Americans, affecting more than a third of the ~20 million individuals with diabetes. The pathogenesis of this disease is defined by a combination of hyperglycemia and a reduction in insulin mediated signaling, which impacts retinal neurons, glia, and vasculature. A unifying theory for the pathophysiology of diabetic complications suggests that the principle pathways responsible for hyperglycemia-induced tissue damage are all linked to the accumulation of reactive oxygen species (ROS). In diabetes, the retina exhibits an increase in the production of ROS and an impaired capacity to reduce free radicals. My central hypothesis is that diabetes-induced expression of the stress response protein regulated in development and DNA damage 1 (REDD1) inhibits the nuclear factor erythroid- 2-related factor 2 (Nrf2)-related antioxidant response in the retina, leading to increased oxidative stress and retinal pathology. In support of my hypothesis, I present compelling preliminary data demonstrating that diabetes-induced oxidative stress is attenuated in the retina of REDD1 knockout mice. In addition, expression of Nrf2-responsive mRNAs is increased in the retina of REDD1 knockout mice and nuclear Nrf2 protein expression and activity are enhanced in REDD1 knockout human MIO-M1 retinal cells in culture. I plan to test my central hypothesis by pursuing the following specific aims: 1. Establish the impact of REDD1 on Nrf2 synthesis in experimental models of diabetes. 2. Delineate the impact of REDD1 on Nrf2 degradation in experimental models of diabetes. To test my hypothesis, I will pursue an experimental protocol involving model systems ranging from cell culture to intact mice, as well as cutting-edge technologies for analyzing mRNA translation. This fellowship award will also provide two key training opportunities. First, I will train with Dr. Sui Wang (Stanford University) to develop skills necessary to manipulate gene expression in the retina in vivo. Subsequently, I will receive training from Dr. Alistair Barber (Penn State College of Medicine) to develop the technical expertise to assess the impact of diabetes on retinal pathophysiology using optical coherence tomography, electroretinograms, and virtual optomotry. With respect to outcomes, this project will not only expand my skills and systems of analysis, but will also identify novel mechanisms that link the molecular events caused by the diabetic metabolic environment to the development of retinal pathology. Identification of such mechanisms is significant because it will validate new targets for the development of preventive and/or therapeutic interventions aimed at addressing the molecular basis of diabetic retinopathy and promoting healthy vision.
PUBLIC HEALTH RELEVANCE: A deficit in our understanding of the molecular defects that underlie the development of diabetic retinopathy represents a critical barrier to the design and implementation of therapeutics that more fully address its molecular pathogenesis. The present application will identify a novel mechanism that regulates the endogenous antioxidant response of the retina. These findings are expected to provide new targets for intervention and lead to the development of innovative therapies that target a leading cause of blindness.
