Chrysin inhibits lipopolysaccharide-induced angiogenesis via down-regulation of VEGF/VEGFR-2(KDR) and IL-6/IL-6R pathways

The relationship between chrysin and inflammation-induced angiogenesis remains unclear. The aim of this study was to evaluate the suppressive effects of chrysin on lipopolysaccharide (LPS)-induced angiogenesis in chicken chorioallantoic membrane (CAM) as well as in human umbilical endothelial cells (HUVEC). The in vivo CAM model was applied to evaluate the percentage of new vessels formation, followed by measuring endothelial migration and tube formation in HUVEC cultures. The mechanisms of the suppressive effect of chrysin on LPS-induced angiogenesis, in terms of VEGF, VEGF receptors (VEGFR), interleukin 6 (IL-6) and IL-6 receptor gene expressions, were analyzed by Western blot, ELISA cytokine assay, and quantitative real time PCR. The results showed that chrysin (10^-8-10^-5M) inhibited LPS-induced CAM neovascular density. There was a significant down-regulation of VEGF and VEGFR-2 (KDR) but not VEGFR-1 (Flt-1) gene expression by chrysin in LPS-treated HUVEC cultures. Besides, chrysin concentration-dependently inhibited the auto-regulation loop of IL-6/IL-6R in LPS-treated HUVEC cells. We conclude that chrysin suppresses both in vitro and in vivo LPS-induced angiogenesis.