Vascular endothelial growth factor regulation of Weibel-Palade-body exocytosis.

Vascular endothelial growth factor (VEGF) not only regulates angiogenesis, vascular permeability, and vasodilation but also promotes vascular inflammation. However, the molecular basis for the proinflammatory effects of VEGF is not understood. We now show that VEGF activates endothelial cell exocytosis of Weibel-Palade bodies, releasing vasoactive substances capable of causing vascular thrombosis and inflammation. VEGF triggers endothelial exocytosis in part through calcium and phospholipase C-gamma (PLC-gamma) signal transduction. However, VEGF also modulates endothelial cell exocytosis by activating endothelial nitric oxide synthase (eNOS) production of nitric oxide (NO), which nitrosylates N-ethylmaleimide sensitive factor (NSF) and inhibits exocytosis. Thus, VEGF plays a dual role in regulating endothelial exocytosis, triggering pathways that both promote and inhibit endothelial exocytosis. Regulation of endothelial exocytosis may explain part of the proinflammatory effects of VEGF.