Vascular endothelial growth factor signals endothelial cell production of nitric oxide and prostacyclin through Flk-1/KDR activation of c-Src

Vascular endothelial growth factor (VEGF) is a potent endothelial cell-spec ific mitogen that promotes angiogenesis, vascular hyperpermeability, and va sodilation by autocrine mechanisms involving nitric oxide (NO) and prostacy clin (PGI(2)) production, These experiments used immunoprecipitation and im munoassay procedures to characterize the signaling pathways by which VEGF i nduces NO and PGI(2) formation in cultured endothelial cells. The data show ed that VEGF stimulates complex formation of the flk-1/kinase-insert domain -containing receptor (KDR) VEGF receptor with c-Src and that Src activation is required for VEGF induction of phospholipase C gamma 1 activation and i nositol 1,4,5-trisphosphate formation. Reporter cell assays showed that VEG F promotes a similar to 50-fold increase in NO formation, which peaks at 5- 20 min. This effect is mediated by a signaling cascade initiated by flk-1/K DR activation of c-Src, leading to phospholipase C gamma 1 activation, inos itol 1,4,5-trisphosphate formation, release of [Ca2+](i) and nitric oxide s ynthase activation. Immunoassays of VEGF-induced 6-keto prostaglandin F-1 a lpha formation as an indicator of PGI(2) production revealed a 3-4-fold inc rease that peaked at 45-60 min. The PGI(2) signaling pathway follows the NO pathway through release of [Ca2+](i), but diverges prior to NOS activation and also requires activation of mitogen-activated protein kinase, These re sults suggest that NO and PGI(2) function in parallel in mediating the effe cts of VEGF.