Recent studies on the pathogenesis of
diabetic retinopathy have focused on correcting adverse biochemical alterations, but there have been fewer efforts to enhance prosurvival pathways. Bcl-2 is the archetypal member of a group of antiapoptotic
proteins. In this study, we investigated the ability of overexpressing Bcl-2 in vascular endothelium to protect against early stages of
diabetic retinopathy. Transgenic mice overexpressing Bcl-2 regulated by the pre-proendothelin promoter were generated, resulting in increased endothelial Bcl-2. Diabetes was induced with
streptozotocin, and mice were sacrificed at 2 months of study to measure
superoxide generation,
leukostasis, and immunohistochemistry, and at 7 months to assess
retinal histopathology. Diabetes of 2 months duration caused a significant decrease in expression of Bcl-2 in retina, upregulation of Bax in whole retina and isolated
retinal microvessels, and increased generation of
retinal superoxide and
leukostasis. Seven months of diabetes caused a significant increase in the number of degenerate (acellular) capillaries in diabetic animals. Furthermore, overexpression of Bcl-2 in the vascular endothelium inhibited the diabetes-induced degeneration of
retinal capillaries and aberrant
superoxide generation, but had no effect on Bax expression or
leukostasis. Therefore, overexpression of Bcl-2 in endothelial cells inhibits the capillary degeneration that is characteristic of the early stages of
diabetic retinopathy, and this effect seems likely to involve inhibition of oxidative stress.