Objective: There is limited knowledge about potential therapeutic targets in Hepatocyte growth factor/scatter factor (HGF)-induced pathophysiological angiogenesis. Recent candidates have included phosphatidylinositol-3-kinase, which is an upstream activator for endothelial nitric oxide (NO) synthase (NOS III). The current study is the first to evaluate the possible involvement of NOS-NO cascade in HGF-induced angiogenesis.
Methods and results: NOS III inhibitors blocked the HGF-induced functional neovascularization in vivo, as quantified using vessel counts, 133Xe-clearance, and immunohistology. This was reversed by L-arginine. Western blot analysis of HGF-treated cells also revealed a temporal increase in HGF-induced phosphorylation. In a deconstructional approach, HGF induced the proliferation and chemokinesis of human endothelial cells. These phenotypic effects were inhibited by NOS inhibitors, L-NAME and L-NIO, and the NO scavenger, carboxy PTIO, but unaltered by 1400W, a NOS II inhibitor. This inhibition was reversed by spermine NONOate, a NO donor, which independently exerted a biphasic effect on endothelial cell proliferation. The modulation of NO did not alter HGF-induced chemoinvasion of endothelial cells, while spermine-NONOate destabilized HGF-induced tubulogenesis, suggesting that a single assay is not sufficient for predicting the final phenotypic outcome on angiogenesis.
Conclusions: The study is the first to demonstrate that the NOS III nitric oxide is a key signal cascade in HGF-induced angiogenesis, and represents a promising target for the clinical management of pathological conditions characterized by overt HGF signaling.