Activation of Human fms-Like Tyrosine Kinase-1 Receptor in Porcine Aortic Endothelial Cells Induces Angiogenesis Via Phosphatidylinositol 3-Kinase

Objective: Activation of the endothelial receptor fms-like tyrosine kinase-1 (Flt-1), also known as VEGFR-1, in human umbilical vein endothelial cells (HUVEC) induced endothelial nitric oxide synthase phosphorylation and nitric oxide (NO) release. This activation was dependent on phosphatidylinositol 3-kinase (PI3K). We sought to determine whether angiogenesis-mediated by the transfected human Flt-1 into endothelial cells derived from a large elastic artery can also be directed by PI3K. Design: Experimental cell lines study. Setting: School of Experimental Medicine, College of Medicine and Dentistry, University of Birmingham, Birming-ham, UK. Method: NO assay and in vitro angiogenesis were determined in porcine aortic endothelial cells stably expressing human Flt-1 (PAEC-Flt-1). Result: Using NO assay, we found that incubation of PAEC-Flt-1 with the growth factor VEGF-A caused a significant release of NO that was abrogated with LY294002, a PI3K inhibitor. In addition, using in vitro angiogenesis assay, PAEC-Flt-1 cells plated on growth-factor reduced Matrigel form a complete capillary-like tube network upon activation with VEGF-A which was significantly inhibited by preincubation of these cells with LY294002. Conclusion: This study provides evidence that upon activation of Flt-1, the enzyme PI3K directed the release of NO and in vitro angiogenesis in endothelial cells, PAEC, derived from the aorta.