Vasorelaxation Effect and Mechanism of Action of Vascular Endothelial Growth Factor-165 in Isolated Perfused Human Skin Flaps

BackgroundExperimental evidence is accumulating to indicate that local acute vascular endothelial growth factor-165 (VEGF165) therapy is effective in attenuation of skin ischemia and increase in skin viability in rat skin flap surgery and the mechanism involves vasodilation induced by VEGF165. So far, the vasodilator effect and mechanism of action of VEGF165 have not been studied in human skin. The objective of this project is to test the hypothesis that VEGF165 is also a potent vasodilator in human skin vasculature.Materials and MethodsWe used an established isolated perfused human skin flap model and pharmacologic probes to demonstrate that VEGF165 is a potent vasodilator in human skin vasculature and the mechanism involves activation of receptors and postreceptor signaling pathway, which in turn stimulates local synthesis/release of endothelial vasodilators.ResultsWe observed that VEGF165 induced a concentration-dependent vasorelaxation in human skin flaps preconstricted with norephinephrine (8 × 10−7M; n = 7) or endothelin-1 (3 × 10−9M; n = 6). The vasorelaxation potency of VEGF165 (pD2 = 12.02 ± 0.25; n = 7) was higher (P < 0.05) than that of acetylcholine (pD2 = 6.76 ± 0.06; n = 5) in human skin flaps preconstricted with 8 x 10−7M of norepinephrine. Using pharmacologic probes, we also detected that the vasorelaxation effect of VEGF165 in the isolated perfused human skin flaps (n = 4) was triggered by activation of VEGF receptor-2. Furthermore, the postreceptor signaling pathway involved activation of Src family tyrosine kinase, phospholipase C, protein kinase C, an increase in inositol 1,4,5-triphosphate activity, a release of the intracellular Ca2+ store, and finally synthesis/release of the endothelial nitric oxide (eNO) and prostacyclin and eNO predominantly mediated the vasodilator effect of VEGF165 in the effector mechanism.ConclusionThese findings support our hypothesis that VEGF165 is a potent vasodilator in human skin vasculature and also provide important insights into the clinical study of local acute VEGF165 therapy for prevention/treatment of skin ischemia in skin flap surgery.