NO-1886 up-regulates Niemann-Pick C1 protein (NPC1) expression through liver X receptor alpha signaling pathway in THP-1 macrophage-derived foam cells.

ABSTRACT

BACKGROUND: The Niemann-Pick C1 (NPC1) protein regulates the transport of cholesterol from late endosomes/lysosomes to other compartments responsible for maintaining intracellular cholesterol homeostasis. Liver X receptors (LXRs) operate as cholesterol sensors which may protect from cholesterol overload by increasing the amount of free cholesterol in the plasma membrane through inducing NPC1 expression. NO-1886 has been proven to be highly effective at increasing liver X receptor alpha expression and promoting cellular cholesterol efflux. In this study, the effects of NO-1886 on NPC1 expression were investigated in THP-1 macrophage-derived foam cells. METHODS AND RESULTS: Results showed that NO-1886 markedly increased expression of NPC1 at both mRNA level and protein level in a dose-dependent and time-dependent manner. Cellular cholesterol content was decreased while cholesterol efflux was increased by NO-1886 treatment. In addition, LXR alpha was also up-regulated by NO-1886 treatment. And LXR alpha small interfering RNA completely abolished the promotion effect which was induced by NO-1886. CONCLUSION: These results provide evidence that NO-1886 up-regulates expression of NPC1 through LXR alpha pathway in THP-1 macrophage- derived foam cells.