Artepillin C Suppresses Angiogenesis by Inhibiting Tube-Formation and Inducing Apoptosis of Endothelial Cells

Artepillin C (ARC) is a major active ingredient of Brazilian propolis which is a resinous mixed compound collected by honeybeesfrom various plant sources. Previously, we reported that the ethanol extract of Brazilian propolis possesses antiangiogenic activity both in vitro and in vivo. However, the mechanism of angiogenesis inhibitionby purified ARC has not been well-clarified. In this study, we investigated the effects of ARC on tube-forming human umbilical vein endothelial cells (HUVECs). We found that inhibition of tube formation by ARC was accompanied by partial fragmentation of endothelial cells, indicating that it induced cell death. Western blotting revealed that ARC induced the reduction of vascular endothelial cadherinand platelet endothelial cell adhesion molecule-1. ARC also induced chromatin condensation and cell nuclear fragmentation, morphological markers of apoptosis, in tube-forming HUVECs. Furthermore, ARC suppressed phosphorylation of extracellular signal-regulated kinase 1/2, but upregulated phosphorylation of p38. It was also shown that ARC induced apoptosis via activation of proapototic signaling, activation of caspase-3 and cleavage of poly ADP-ribose polymerase and lamin A/C. In conclusion, ARC exerts its antiangiogenic effects through induction of endothelial apoptosis.