Prevention of VEGF-induced growth and tube formation in human retinal endothelial cells by aldose reductase inhibition

Objective: Since diabetes-induced vascular endothelial growth factor (VEGF) is implicated in retinal angiogenesis, we aimed to examine the role of aldose reductase (AR) in VEGF-induced human retinal endothelial cells (HREC) growth and tube formation. Materials and Methods: HRECs were stimulated with VEGF and cell-growth was determined by MTT assay. AR inhibitor, fidarestat, to block the enzyme activity and AR siRNA to ablate AR gene expression in HREC were used to investigate the role of AR in neovascularization using cell-migration and tube formation assays. Various signaling intermediates and angiogenesis markers were assessed by Western blot analysis. Immuno-histochemical analysis of diabetic rat eyes was performed to examine VEGF expression in the retinal layer. Results: Stimulation of primary HREC with VEGF caused increased cell growth and migration, and AR inhibition with fidarestat or ablation with siRNA significantly prevented it. VEGF-induced tube formation in HREC was also significantly prevented by fidarestat. Treatment of HREC with VEGF also increased the expression of VCAM, AR, and phosphorylation and activation of Akt and p38-MAP kinase, which were prevented by fidarestat. VEGF-induced expression of VEGFRII in HREC was also prevented by AR inhibition or ablation. Conclusions: Our results indicate that inhibition of AR in HREC prevents tube formation by inhibiting the VEGF-induced activation of the Akt and p38-MAPK pathway and suggest a mediatory role of AR in ocular neovascularization generally implicated in retinopathy and AMD.