Inhibition of vascular endothelial growth factor-induced angiogenesis by scopoletin through interrupting the autophosphorylation of VEGF receptor 2 and its downstream signaling pathways.

Our previous studies revealed that scopoletin, the main bioactive constituent of Erycibe obtusifolia Benth stems, exerted anti-arthritic activity in vivo partly by preventing synovial angiogenesis. Herein we further investigated the anti-angiogenic potential and related mechanisms of this coumarin compound in vivo and in vitro. On chick chorioallantoic membrane (CAM) model, scopoletin (10, 30, 100 nmol/egg) dose-dependently reduced the blood vessels that were quantified by counting the number of blood vessel branch points. In vitro, scopoletin at concentrations above 30 microM obviously inhibited the VEGF-induced tube formation, proliferation and migration of human umbilical vein endothelial cells (HUVECs). Furthermore, scopoletin was shown to block VEGF-induced autophosphorylation of VEGFR2 but not VEGFR1, and down-regulate the following activation of ERK1/2, p38 MAPK and endothelial nitric oxide synthase (eNOS) as well as the production of nitric oxide (NO) in HUVECs. In sum, our findings further support that scopoletin is a candidate of angiogenesis inhibitors, and it functions by interrupting the autophosphorylation of VEGF receptor 2 (VEGFR2) and the downstream signaling pathways.