Objective Plasminogen activator inhibitor-1 (PAI-1) regulates angiogenesis via effects on extracellular matrix proteolysis and cell adhesion. However, no previous study has implicated PAI-1 in controlling vascular endothelial growth factor (VEGF) signaling. We tested the hypothesis that PAI-1 down-regulates VEGF receptor-2 (VEGFR-2) activation by inhibiting a vitronectin (VN)-dependent cooperative binding interaction between VEGFR-2 and αVβ3. Approach and Results We studied PAI-1's effects on VEGF signaling in human umbilical vein endothelial cells (HUVECs). PAI-1 inhibited VEGF-induced phosphorylation of VEGFR-2 in HUVECs grown on VN, but not on fibronectin or collagen. PAI-1 inhibited binding of VEGFR-2 to β3 integrin, VEGFR-2 endocytosis, and intracellular signaling pathways downstream of VEGFR-2. The anti-VEGF effect of PAI-1 was mediated by 2 distinct pathways, one requiring binding to VN and another requiring binding to very-low-density-lipoprotein receptor (VLDLR). PAI-1 inhibited VEGF-induced angiogenesis in vitro and in vivo, and pharmacological inhibition of PAI-1 promoted collateral arteriole development and recovery of hindlimb perfusion after femoral artery interruption. Conclusions PAI-1 inhibits activation of VEGFR-2 by VEGF by disrupting a VN-dependent, pro-angiogenic binding interaction involving αVβ3 and VEGFR-2. These results broaden our understanding of the roles of PAI-1, VN, and endocytic receptors in regulating VEGFR-2 activation and suggest novel therapeutic strategies for regulating VEGF signaling.

No abstract

No abstract