VEGF-mediated endothelial P-selectin translocation: role of VEGF receptors and endogenous PAF synthesis

The acute increase in vascular permeability produced by vascular endothelial growth factor (VEGF-A(165)) requires activation of endothelial Flk-1 receptors (VEGFR-2) and stimulation of platelet-activating factor (PAF) synthesis. Like PAF, VEGF-A(165) promotes translocation of P-selectin to the endothelial cell (EC) surface. However, the mechanisms involved remain unknown. By treating human umbilical vein endothelial cells (HUVECs) with VEGF analogs, we show that activation of VEGFR-1 or VEGFR-2 or both induced a rapid and transient translocation of endothelial P-selectin and neutrophil adhesion to activated ECs. The effects mediated by VEGF-A(165) and VEGF-A(121) (VEGFR-1/VEGFR-2 agonists) were blocked by a selective VEGFR-2 inhibitor, SU1498. VEGF-A(165) was twice as potent as VEGF-A(121), which can be explained by the binding capacity of VEGF-A(165) to its coreceptor neuropilin-1 (NRP-1). Indeed, treatment with NRP-1 antagonist (GST-Ex7) reduced the effect of VEGF-A(165) to the levels observed upon stimulation with VEGF-A(121). Finally, the use of selective PAF receptor antagonists reduced VEGF-A(165)-mediated P-selectin translocation. Together, these data show that maximal P-selectin translocation and subsequent neutrophil adhesion was mediated by VEGF-A(165) on the activation of VEGFR-2/NRP-1 complex and required PAF synthesis.