Ethanolic Extract of Propolis Promotes Reverse Cholesterol Transport and the Expression of ATP-Binding Cassette Transporter A1 and G1 in Mice

The ethanolic extract of propolis (EEP) is beneficial in increasing high density lipoprotein (HDL) cholesterol (HDL-C) and diminishing risks of atheroscle- rosis. In this study, we examined the effects of EEP on reverse cholesterol transport in mice. 3 H -cholesterol laden macrophage was injected intraperitoneally into mice fed by gastric gavage with EEP. Plasma lipid level was deter- mined and 3 H-cholesterol was traced in plasma, liver and feces. The effects of EEP on ATP-binding cassette trans- porter A1 and G1 (ABCA1 and ABCG1) and scavenger receptor BI (SR-BI) in mice liver and in cultured cells were also investigated. EEP administration led to a significant increase in HDL-C and peritoneal macrophage-original 3 H- cholesterol in plasma, liver and feces. Liver protein expressions of ABCA1 and ABCG1 were increased but SR-B1 was not. In vitro experiments with HepG2 and Raw264.7 cell lines confirmed the above results. The finding of these studies shows that EEP-enhanced reverse cholesterol transport may have resulted from EEP stimu- lated plasma HDL level and hepatic ABCA1 and ABCG1 expression.