Anti-angiogenic activity of Ipomoea obscura extract and Ipobscurine-A

Objective: Ipomoea obscura (L.) Ker-Gawl, is a medicinal herb with indole alkaloids as an active constituent. In this study, we investigated the anti-angiogenic activity of I. obscura extract and one of its major compounds Ipobscurine-A (IPO-A). Methods: In vivo angiogenesis was induced by injecting B16F10 melanoma cells intradermally on the shaven ventral skin of C57BL/6 mice. In vitro experiments were conducted using human umbilical vein endothelial cells. Results: I. obscura and IPO-A significantly inhibited endothelial cell proliferation, migration, invasion, and tube formation in vitro. Vascular endothelial growth factor (VEGF)-induced sprouting of endothelial cells from rat aorta ex vivo was also inhibited. A marked decrease in the production of matrix metalloproteinases (MMPs) and the expressions of VEGF, cyclooxygenase-2, and nitric oxide synthase by B16F10 cells were observed after the treatment with the extract or IPO-A. Intraperitoneal administration of the extract significantly inhibited B16F10 melanoma cell line-induced neo-vessel formation in C57BL/6 mice in vivo. Analysis of serum cytokine profile clearly showed that extract significantly reduced the elevated levels of pro-inflammatory cytokines such as interleukins (IL)-1 beta, IL-6, tumor necrosis factor-alpha, and granulocyte-monocyte colony stimulating factor and the most potent angiogenic factor VEGF in animals. Serum NO level was also found to be significantly lowered by the administration of the extract. Antiangiogenic factors such as TIMP-1 and IL-2 level were elevated in the extract-treated animals. Conclusion: These data clearly demonstrate that I. obscura extract and IPO-A inhibit the tumor-specific angiogenesis by downregulating pro-angiogenic factors such as MMP, VEGF, and pro-inflammatory mediators and upregulating anti-angiogenic factors such as IL-2 and TIMP-1.