Increased H2O2, vascular endothelial growth factor and receptors in the retina of the BBZ/WOR diabetic rat

Hyperglycemia in diabetes induces increased levels of hydrogen peroxide (H2 O2), a reactive oxygen species generated by reduced nicotinamide adenine di nucleotide (NADH) oxidase, Nontoxic levels of H2O2 increase endothelial cel l permeability. Using a model of non-insulin-dependent diabetes, the BBZ/Wo r rat, we investigated retinal levels of H2O2, vascular endothelial growth factor (VEGF) and its receptors, VEGF-R1 and VEGF-R2 by transmission electr on microscopy at sites of the blood-retinal barrier (BRB). H2O2 localizatio n was done by the cerium NADH oxidase method, and extravasation of endogeno us serum albumin was used to document disruption of the BRB. Higher levels of H2O2 were detected in blood vessels of diabetic (78.7 +/- 4.84%) as comp ared with vessels from nondiabetic rats (39.0 +/- 4.47%). VEGF immunoreacti vity was statistically higher in the inner BRB (24.67 +/- 0.33 colloidal go ld particles/63 mu m(2) vs 21.52 +/- 0.43 colloidal gold particles/63 mu m( 2), p = .0001) and outer BRB (42.56 +/- 0.45 colloidal gold particles/63 mu m(2) vs. 15.51 +/- 0.51 colloidal gold particles/63 mu m(2), p = .0001) of diabetic rats as compared with age matched nondiabetic control rats. VEGF- R1 immunoreactivity was significantly higher in diabetic retinas in both th e inner BRB (21.66 +/- 0.75 colloidal gold particles/63 mu m(2) vs, 12.69 /- 0.61 colloidal gold particles/63 mu m(2), p = .0001) and outer BRB (22.7 6 +/- 2.36 colloidal gold particles/63 mu m(2) vs. 8.53 +/- 2.67 colloidal gold particles/63 mu m(2), p = .0013), VEGF-R2 was statistically higher in the inner BRB (5.97 +/- 0.57 colloidal gold particles/63 mu m(2) versus 7.0 3 +/- 0.65 colloidal gold particles/63 mu m(2), p = .0419) but not in the o uter BRB (29.42 +/- 1.25 colloidal gold particles/63 mu m(2) vs. 28.07 +/- 1.42 colloidal gold particles/63 mu m(2), p = .4889). H2O2 levels correlate d with increased VEGF (correlation coefficient = 0.82, p = .001) in this mo del of nonproliferative diabetic retinopathy. These results support that hy perglycemia is one factor that induces retinal endothelial cells in vivo to increase H2O2 via NADH oxidase and stimulates increases in VEGF resulting in disruption of the BRB. (C) 2000 Elsevier Science Inc.