VEGF UP-REGULATES ECNOS MESSAGE, PROTEIN, AND NO PRODUCTION IN HUMAN ENDOTHELIAL-CELLS

Vascular endothelial growth factor (VEGF) is an endothelium-specific s ecreted protein that potently stimulates vasodilation, microvascular h yperpermeability, and angiogenesis. Nitric oxide (NO) is also reported to modulate vascular tone, permeability, and capillary growth. Theref ore, we hypothesized that VEGF might regulate endothelial production o f NO. The production of nitrogen oxides by human umbilical vein endoth elial cells (HUVECs) was measured after 1, 12, 24, and 48 h of incubat ion with VEGF. VEGF treatment resulted in both an acute (1 h) and chro nic (>24 h) stimulation of NO production. Furthermore, Western and Nor thern blotting revealed a VEGF-elicited, dose-dependent increase in th e cellular content of endothelial cell nitric oxide synthase (ecNOS) m essage and protein that may account for the chronic upregulation of NO production elicited by VEGF. Finally, endothelial cells pretreated wi th VEGF for 24 h and subsequently exposed to A-23187 for 1 h produced NO at approximately twice the rate of cells that were not pretreated w ith VEGF. We conclude that VEGF upregulates ecNOS enzyme and elicits a biphasic stimulation of endothelial NO production.