Resveratrol downregulates PCSK9 expression and attenuates steatosis through estrogen receptor α-mediated pathway in L02 cells

Proprotein convertase subtilisin kexin type 9 (PCSK9) is a promising target for treating dyslipidemia and atherosclerosis. Circulating PCSK9 levels are closely related to hepatic steatosis severity and endogenous estrogen levels. Resveratrol (RSV) is a phytoestrogens that protects against atherosclerosis and hepatic steatosis. Thus, we sought to determine whether RSV had the activities to inhibit PCSK9 expression and to attenuate lipid accumulation in free fatty acid (FFA)-induced L02 cells via ERa pathway. In this study, RSV (10, 20 mu M) were cultured with L02 cells in the presence of FFA (oleate:palmitate = 2:1). RSV significantly reduced the number of lipid droplets and intracellular TG in steatotic L02 cells, and Oil red O staining and Nile red staining had the same results. Western blot analysis showed that RSV significantly reduced apoB secretion and intracellular microsomal triglyceride transporter (MTP) expression under lipid-rich conditions. Treatment with RSV reduced expression of PCSK9 while maintaining LDL receptor (LDLR) expression and LDL uptake. RSV decreased SREBP-1c expression at both mRNA and protein levels. In addition, RSV significantly reduced the expression of liver X receptor alpha (LXR alpha) mRNA in L02 cells, but did not affect the expression of liver X receptor beta (LXR beta) mRNA. The luciferase reporter assays suggested that RSV inhibited SREBP-mediated transcription of PCSK9. Finally, these results could be partly reversed by Estrogen receptor alpha (ER alpha) gene silencing. These results suggest that RSV attenuates steatosis and PCSK9 expression through down-regulation of SREBP-1c expression, at least in part through ERa-mediated pathway.