RESUMO
BACKGROUND: Recent studies have shown that exogenous administration of vascular endothelial growth factor (VEGF) is protective against cyclosporine A (CsA) renal toxicity. No data are available, however, on the possible role of endogenous VEGF. Our objective was to examine whether endogenous VEGF has a significant role in the renal response against CsA toxicity. METHODS: In vivo, we used high-dose (50-150 mg/kg/day) CsA +/- specific goat anti-mouse VEGF blocking monoclonal antibody (alpha-VEGF) in mice. In vitro, we exposed mouse tubular cells (MCT) to CsA +/- alpha-VEGF. RESULTS: alpha-VEGF markedly enhanced CsA renal toxicity, inducing severe tubular damage and increased blood urea nitrogen. In animals treated with CsA + alpha-VEGF, damage progressed to generalized tubular injury (histology) and apoptosis (terminal deoxynucleotide transferase-mediated dUTP nick-end labeling) with associated anemia and reticulocytosis (18 days of treatment). CsA + alpha-VEGF treatments strikingly increased tubular VEGF and Bcl-xL proteins. In vitro, autocrine production of VEGF by MCT was identified by Western blot. Of specific interest, CsA toxicity in MCT increased significantly in the presence of alpha-VEGF. CONCLUSIONS: Endogenous VEGF has a relevant role in the renal tubular defense against CsA toxicity. Blockade of the VEGF effect by alpha-VEGF results in clear-cut intensification of the tubular injury and appearance of regenerative anemia in the CsA + alpha-VEGF-treated animals. The occurrence of both in vivo and in vitro effects of VEGF blockade provides evidence of a direct protective effect of VEGF on the tubular cell.