Mitogenic and Anti-Apoptotic Actions of Hepatocyte Growth Factor Through Erk, Stat3 and Akt in Human Aortic Endothelial Cells
Background: Hepatocyte growth factor (HGF), an angiogenic growth factor, may play a pivotal role in the regulation of endothelial cells (EC), since HGF demonstrated the mitogenic and anti-apoptotic actions in endothelial cells. However, it is still unclear how HGF demonstrated those actions. Therefore, in this study, we have focused on the signal transduction systems. Methods: Human aortic EC death was induced by serum-deprived condition. Cell growth was assessed by WST assay, and thymidine incorporation and cell death was measured by LDH release and caspase 3 activity. Phosphorylation of ERK, STAT and Akt was measured by western blotting as assessed by the specific phospho-specific antibody. Results: Treatment of EC with recombinant HGF (rHGF) resulted in a significant increase in cell growth (WST: control; 0.267±0.02, rHGF 100ng/ml; 0.385±0.003, p≤0.01) and also attenuated the cell death (LDH release: control; 0.94±0.04, rHGF 100ng/ml; 0.43±0.024, p≤0.01). ERK and STAT3 (Ser727) was phosphorylated by rHGF (100 ng/ml) as assessed by the specific phospho-specific antibody, while PD98059, the inhibitor of MEK, attenuated endothelial cell growth (HGF; 0.385±0.003, HGF+PD 30uM; 0.203±0.003, p≤0.01) and the phosphorylation of STAT3 (Ser727). On the other hand, STAT3 (Tyr705), which was usually stimulated by JAK, was not phosphorylated by rHGF. In addition, Akt on the down stream of PI3 kinase was also phosphorylated by rHGF, while the specific inhibitor of PI3kinase, wortomanin and LY294002, markedly attenuated endothelial cell death assessed by LDH release and caspase3 activity. Conclusions: Overall, this study demonstrated that HGF stimulated cell growth through ERK cascade including STAT3(Ser727) activation, not JAK-STAT3(Tyr705) pathway, and inhibited endothelial cell death through PI3 kinase-Akt pathway. HGF may stimulate angiogenesis through both mitogenic and anti-cell death function in endothelial cells.