t-PA stimulates VEGF expression in endothelial cells via ERK2/p38 signaling pathways

Vascular endothelial growth factor (VEGF) plays an essential role in the initiation and regulation of angiogenesis, which is a crucial component of wound healing and vessel growth. Tissue-type plasminogen activator (t-PA) could stimulate angiogenesis but the precise mechanisms of their proangiogenic actions remain unclear. We investigated whether t-PA can induce VEGF expression in ECV304 and further explored the underlying signaling pathway(s) involved. Through adenovirus mediated overexpression of t-PA in ECV304 cells, we demonstrated that t-PA significantly increased both VEGF mRNA and protein expression. A further mechanistic study showed that both ERK and p38 MAPK activation were involved in this process. Incubation of RVEC with PD 98059 (MEK kinase inhibitor) significantly reduced t-PA-induced ERK2 activity, VEGF mRNA and protein expression. Furthermore, PD 98059 treatment almost completely abolished p38 activation. Our data suggest that t-PA-stimulates VEGF expression in RVEC via transactivation of p38 by ERK. One potential implication of this finding is that increased t-PA levels in thomb could facilitate vessel growth by stimulating VEGF synthesis and angiogenesis.