Quercetin upregulates ABCA1 expression through liver X receptor alpha signaling pathway in THP-1 macrophages

Quercetin has been reported to have the activities of antioxidant, anti-inflammatory, anti-virus, anti-cancer and so on. Many studies showed that quercetin could lower blood pressure and improve blood capillary elasticity, and it can also reduce LDL oxidation and prevent atherosclerosis. Although quercetin has been recognized to have the function of preventing atherosclerosis, little is known about its underlying mechanism. In this study, we try to explore whether quercetin up-regulates LXRa-mediated ABCA1 expression.

THP-1 cells were cultured. The expression of ABCA1 and LXRa were detected by real-time PCR and western blot. Cellular cholesterol efflux from THP-1 macrophages was analyzed using liquid scintillation counting assays.

Real-time PCR and Western blot showed quercetin increased the expression of ABCA1 and LXRα at both the mRNA and protein levels in a concentration-dependent and time-dependent manner in THP-1 macrophages. Liquid scintillation counting assays indicated quercetin increased the cholesterol efflux and decreased the cellular cholesterol content. Furthermore, the expression of LXRa was decreased after THP-1 macrophage transfected with LXRα siRNA. Meanwhile, the expression of ABCA1 was also recovered after incubated with the combination of LXRa siRNA and quercetin compared with quercetin alone.

Quercetin could increase ABCA1 expression and cholesterol efflux through LXRα pathway to eventually promote RCT in the THP-1 macrophage.