Vascular Endothelial Growth Factor (VEGF) Enhances the Expression of Receptors and Activates Mitogen-Activated Protein (MAP) Kinase of Dog Retinal Capillary Endothelial Cells

ABSTRACT

Since the galactose-fed dog is an animal model that develops the advanced stage of proliferative retinopathy, the effects of vascular endothelial growth factor (VEGF) on cell growth, receptor expression and the activation of mitogen-activated protein (MAP) kinase pathway of dog retinal capillary endothelial cells were investigated. Dog retinal endothelial cells were cultured at 37°C under 5% carbon dioxide atmosphere in CS-C medium supplemented with endothelial cell growth factor (ECGF). VEGF receptor expression was examined by RT-PCR, and activation of MAP kinase was examined with antibody against phospho-E1k-1 (Ser383). When growth factors were removed from the culture medium, cell survival of dog endothelial cells was significantly reduced. Addition of VEGF protected these cells from cell death induced by growth factor starvation. VEGF also enhanced tube formation in dog endothelial cells and increased the expression of two VEGF receptors, F1t-1 and KDR/F1k-1. Cells treated with VEGF also displayed the phosphorylation of the transcription factor, E1k-1. Addition of the tyrosine kinase inhibitor, genistein, eliminated VEGFinduced cell growth and E1k-1 phosphorylation. These data confirm that cell growth and tube formation of dog retinal capillary endothelial cells are stimulated by VEGF. VEGF also increases the expression of the receptors, KDR and F1t-1, and activates the p44/42 MAP kinase pathway.