Role of pro- and anti-angiogenic factors in endothelial cell migration

Endothelial cell migration is a critical step in angiogenesis, a process of new vessel formation from existing blood vessels. Our study focuses on the mechanisms that promote or inhibit endothelial cell migration. Domain 5 (D5) of cleaved-high-molecular weight-kininogen (HKa) inhibits angiogenesis in vivo. We tested the hypothesis that HKa and D5 inhibit endothelial cell migration in response to vascular endothelial growth factor (VEGF) and Sphingosine 1-phosphate (S1P) through Akt. S1P or VEGF, activate the phosphotidyl-inositol-3 kinase (PI3-kinase)-Akt signaling pathway to promote endothelial cell migration. HKa and D5 inhibit migration and cell speed of bovine pulmonary artery endothelial cell (BPAEC) in response to VEGF or S1P. HKa's effect on BPAEC migration is reversed by antibodies to urokinase-type plasminogen activator receptor. Furthermore, HKa and D5 reduce the localization of paxillin to the focal adhesions and inhibit phosphorylation of Akt and GSK-3alpha induced by VEGF or S1P. Effect of HKa and D5 on paxillin localization and BPAEC migration was duplicated with inhibitors of Akt and PI3-kinase. Therefore we suggest that domain 5 of HKa inhibits endothelial cell migration via attenuation of PI3-kinase-Akt signaling leading to alterations in the focal adhesions.