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R.A. Kowluru; Mitochondrial Oxidative Stress and Retinal Capillary Cell Death in Diabetes . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3889.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: In the pathogenesis of diabetic retinopathy, capillary cells are lost before other histological lesions are detectable in the retina, and apoptosis is considered as one of the mechanisms underlying in their death. We have shown that in diabetes oxidative stress is increased in retina, and antioxidants inhibit activation of apoptosis executor enzyme, caspase-3, and the development of histopathology. The purpose of this study is to investigate the mechanism by which increased oxidative stress could result in capillary cell death. Methods: Retinal capillary endothelial cells and pericytes were incubated in 5mM or 20mM glucose medium for 7 days in the presence of superoxide dismutase (SOD, 0-20mU/ml). At the end of the incubation the cells were washed, and mitochondria and cytosol fractions were isolated by centrifugation. The release of cytochrome c from the mitochondria into the cytosol, and translocation of pro-apoptotic protein Bax into the mitochondria were determined by western blot technique. Oxidative stress was estimated by measuring GSH levels, and apoptosis by ELISA assay. Results: Incubation of capillary cells in high glucose medium resulted in increased oxidative stress, release of cytochrome c from mitochondria into the cytosol, and translocation of Bax into the mitochondria, as compared to the cells incubated in 5mM glucose (P<0.02). These glucose-induced abnormalities were accompanied by 75% increase in the apoptosis of capillary cells. Inclusion of SOD in the medium inhibited increased oxidative stress, release of cytochrome c, translocation of Bax, and apoptosis. Conclusions: These results demonstrate that in high glucose conditions mitochondrial function is impaired in retinal capillary cells, and antioxidants inhibit glucose-induced mitochondrial dysfunction. Identifying the mechanism by which retinal capillary cells undergo apoptosis may reveal novel therapies to inhibit the development of retinopathy in diabetes.
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