Baicalein inhibits angiogenesis induced by lipopolysaccharide through TRAF6 mediated toll-like receptor 4 pathway

Angiogenesis is a pivotal step occurred both in inflammation and cancer development. In the recent years, relationships between inflammation and cancer have received more and more attention. Baicalein, which was isolated from Radix Scutellariae Georgi, has been widely used in inflammation and cancer therapy. Here, we focus on influence of baicalein on angiogenesis induced by inflammatory factor and its mechanism of action. In our present study, we assessed its potential as an anti-angiogenic agent in vivo employing chicken chorioallantoic membrane (CAM) assay and in vitro cell migration assay of human umbilical vein endothelial cells (HUVECs), tube formation assay and rat aortic ring assay which were induced by lipopolysaccharide (LPS). Baicalein inhibited LPS-induced proliferation, migration and tube formation of human umbilical vein endothelial cell (HUVECs) as well as microvessel sprouting from rat aortic rings in vitro and CAM in vivo. Moreover, western blot analysis showed that baicalein affected the level of cell membrane receptor toll-like receptor 4 (TLR4) of HUVECs and resulted in a significant decrease in LPS-triggered TNF receptor associated factor 6 (TRAF6), and phosphorylated forms of extracellular regulated protein kinases (ERK), AKT and p38. These results of our study provide evidences that baicalein possesses anti-angiogenic potential induced by LPS both in vitro and in vivo through TRAF6 mediated TLR4 pathway.