Objective: This study aimed at investigating whether notoginsenoside R1(R1), a unique saponin found in Panax notoginseng could promote angiogenic activity on human umbilical vein endothelial cells(HUVECs) and elucidate their potential molecular mechanisms. In addition, vascular restorative activities of R1 was assessed in a chemically-induced blood vessel loss model in zebrafish. Methods: The in vitro angiogenic effect of R1 was compared with other previously reported angiogenic saponins Rg1 and Re. The HUVECs proliferation in the presence of R1 was determined by cell proliferation kit Ⅱ(XTT) assay. R1, Rg1 and Re-induced HUVECs invasion across polycarbonate membrane was stained with Hoechst-33342 and quantified microscopically. Tube formation assay using matrigelcoated wells was performed to evaluate the pro-angiogenic actions of R1. In order to understand the mechanism underlying the pro-angiogenic effect, various pathway inhibitors such as SU5416, wortmannin(wort) or L-Nω-nitroL-arginine methyl ester hydrochloride(L-NAME), SH-6 were used to probe the possible involvement of signaling pathway in the R1 mediated HUVECs proliferation. In in vivo assays, zebrafish embryos at 21 hpf were pre-treated with vascular endothelial growth factor(VEGF) receptor kinase inhibitor Ⅱ(VRI) for 3 h only and subsequently post-treated with R1 for 48 h, respectively. The intersegmental vessels(ISVs) in zebrafish were assessed for the restorative effect of R1 on defective blood vessels. Results: R1 could stimulate the proliferation of HUVECs. In the chemoinvasion assay, R1 significantly increased the number of cross-membrane HUVECs. In addition, R1 markedly enhanced the tube formation ability of HUVECs. The proliferative effects of these saponins on HUVECs were effectively blocked by the addition of SU5416(a VEGF-KDR/Flk-1 inhibitor). Similarly, pre-treatment with wort [a phosphatidylinositol 3-kinase(PI3K)-kinase inhibitor], L-NAME [an endothelial nitric oxide synthase(eN OS) inhibitor] or SH-6(an Akt pathway inhibitor) signif
