Panax notoginseng saponins decrease cholesterol ester via up-regulating ATP-binding cassette transporter A1 in foam cells

Abstract

Accumulating evidence has indicated that Panax notoginseng saponins (PNS), the major ingredients in Panax notoginseng (Burk.) F.H. Chen which could be found widely in Asia, can attenuate atherogenesis in vivo. This study was designed to examine the relationship of PNS with cholesterol ester in foam cells sourced from macrophages and the effect of PNS on the expression of ATP-binding cassette transporter A1 (ABCA1). Foam cells sourced from macrophages were cultured with PNS. The content of cholesterol ester in foam cells was analyzed and expressions of ABCA1 and liver X receptor α (LXRα) in foam cells were measured by real-time PCR and western blotting methods. The results showed that PNS could significantly decrease the level of cholesterol ester in foam cells at middle and high dosages. The real-time PCR and western blotting assays indicated that the expression of ABCA1 was up-regulated by PNS in a dose-dependent manner. Analysis based on these results showed that the cholesterol ester level was negatively correlated with ABCA1 expression. As a result, we conclude that by up-regulating the expression of ABCA1, PNS could lower the cholesterol ester level, which resulted in the attenuation of the foam cell formation. This bioactivity might be associated with the special chemical structures of PNS that are similar to the natural agonist of LXRα.