Characterization of endocrine gland-derived vascular endothelial growth factor signaling in adrenal cortex capillary endothelial cells

Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) has been recently identified as a mitogen specific for the endothelium of steroidogenic glands. Here we report a characterization of the signal transduction of EG-VEGF in a responsive cell type, bovine adrenal cortex-derived endothelial (ACE) cells. EG-VEGF led to a time- and dose-dependent phosphorylation of p44/42 MAPK. This effect was blocked by pretreatment with pertussis toxin, suggesting that Galpha(i) plays an important role in mediating EG-VEGF-induced activation of MAPK signaling. The inhibitor of p44/42 MAPK phosphorylation PD 98059 resulted in suppression of both proliferation and migration in response to EG-VEGF. EG-VEGF also increased the phosphorylation of Akt in a phosphatidylinositol 3-kinase-dependent manner. Consistent with such an effect, EG-VEGF was a potent survival factor for ACE cells. We also identified endothelial nitric-oxide synthase as one of the downstream targets of Akt activation. Phosphorylation of endothelial nitric-oxide synthase in ACE cells was stimulated by EG-VEGF with a time course correlated to the Akt phosphorylation. Our data demonstrate that EG-VEGF, possibly through binding to a G-protein coupled receptor, results in the activation of MA-PK p44/42 and phosphatidylinositol 3-kinase signaling pathways, leading to proliferation, migration, and survival of responsive endothelial cells.