Interleukin-17 enhances bFGF-, HGF- and VEGF-induced growth of vascular endothelial cells

Interleukin-17 (IL-17) is a CD4 T cell-derived proinflammatry and proangiogenic cytokine. In this study, we investigated the effects of this cytokine on vascular endothelial cell growth induced by a well-known direct angiogenic factor bFGF, HGF, VEGF, CXCL5/ENA-78 or CXCL8/IL-8. While a wide range of doses of IL-17 alone did not show the ability to stimulate the growth of human dermal microvascular endothelial cells (HMVECs), bFGF, HGF, VEGF, CXCL5 or CXCL8 significantly induced the growth of HMVECs in vitro. When bFGF and IL-17 were used in combination, 10 or 100 ng/ml IL-17 enhanced 10 ng/ml bFGF-induced growth of HMVECs. Similarly, when HGF and IL-17 were combined together, 10 or 100 ng/ml IL-17 potentiated 10 ng/ml HGF-induced growth of HMVECs. When VEGF and IL-17 were used together, 10 ng/ml IL-17 did not significantly enhance 10 ng/ml VEGF-induced growth, whereas 100 ng/ml IL-17 clearly promoted 10 ng/ml VEGF-mediated proliferation of HMVECs. On the contrary, IL-17 did not augment CXCL5- and CXCL8-mediated growth. These results indicate that IL-17 itself does not have the capability to stimulate the growth of vascular endothelial cells, whereas IL-17 is able to selectively enhance the mitogenic activity of bFGF, HGF, and VEGF for vascular endothelial cells. Our findings also suggest that IL-17 may promote bFGF-, HGF- and VEGF-meadiated angiogenesis through enhancing bFGF-, HGF- and VEGF-induced growth of vascular endothelial cells.