VEGF increases retinal vascular ICAM-1 expression in vivo

PURPOSE. Intraocular injections of vascular endothelial growth factor (VEGF ), a peptide implicated in the pathogenesis of diabetic retinopathy, can in duce retinal ischemia. Diabetic retinal ischemia may be caused, in part, by the adhesion of leukocytes to the retinal vasculature. In this study, the ability of VEGF to increase the expression of intercellular adhesion molecu le-1 (ICAM-1) and other adhesion molecules in capillary endothelium and the retinal vasculature was examined. METHODS. The expression of ICAM-1, vascular cell adhesion molecule-1 (VCAM- 1), E-selectin, and P-selectin on human brain capillary endothelial cell mo nolayers exposed to VEGF was quantitated by immunoassay. The effect of VEGF on retinal vascular ICAM-1 expression was determined in ICAM-1 immunofluor escence studies of retinal flat-mounts and in RNase protection assays. RESULTS. VEGF increased capillary endothelial cell ICAM-1 levels in a dose- and time-dependent manner (6-24 hours, plateau after 6 hours; EC50, 25 ng/ ml). VEGF failed to alter E-selectin, P-selectin, or VCAM-1 levels under th e conditions tested. Intravitreal injections of pathophysiologically releva nt concentrations of VEGF increased ICAM-1 protein and mRNA levels in the r etinal vasculature. CONCLUSIONS. VEGF increases retinal vascular ICAM-1 expression. VEGF-induce d increases in ICAM-1 may promote retinal leukostasis in diabetic eyes.