Good glycemic control can inhibit the development of diabetic retinopathy, but such metabolic control is difficult to achieve and maintain. Thus, supplemental therapies need to be identified by which the retinopathy can be prevented. Hyperglycemia has been found experimentally to be sufficient to initiate the development of diabetic retinopathy, but the mechanism by which hyperglycemia causes the retinal disease remains unclear. Cells of the retina and its microvasculature die at an accelerated rate in diabetes by process consistent with apoptosis, and the accelerated cell death is believed to contribute to the development of diabetic retinopathy. Glyceraldehyde-3-phosphate dehydrogenase is a key enzyme in glycolysis catalyzing the conversion of D-glyceraldehyde-3-phosphate to 1,3-diphosphoglycerate, and is commonly considered a housekeeping gene. However, in recent years more non-glycolytic functions of the enzymes have been emerging, among them its role in the induction of apoptosis. During apoptosis GAPDH accumulates in the nucleus, an effect that seems to be correlated with the induction of oxidative stress. We have found that hyperglycemia causes GAPDH translocation to the nucleus in retinal cells prior to the onset of apoptosis. We propose to assess (1) the role of GAPDH nuclear translocation in diabetes-induced apoptosis of retinal cells, and the contribution of oxidative stress to the induction GAPDH nuclear translocation, (2) the effect of GAPDH nuclear translocation on glycolytic flux and energy levels, and (3) the effect of inhibiting GAPDH nuclear translocation on hyperglycemia-induced apoptosis in the retina. The experiments are to be conducted in vivo and in vitro using diabetic mice, cultured retinal Muller and endothelial cells. These studies will determine the role of GAPDH in the development of diabetes-induced apoptosis in the retina, will help to clarify the relation of glycolytic activity to apoptosis in elevated glucose, and will clarify the suitability of inhibiting GAPDH nuclear translocation as potential therapeutic strategy, at which the diabetic retinopathy might be inhibited.
