Inhibitory effects of resveratrol on foam cell formation are mediated through monocyte chemotactic protein-1 and lipid metabolism-related proteins

Abstract

Resveratrol has been shown to exert anti-atherosclerotic effects. 5' AMP-activated protein kinase (AMPK) and monocyte chemotactic protein-1 (MCP-1) play key roles in foam cell formation, which is considered as the initiation of atherosclerosis. Thus, in this study, we investigated whether resveratrol inhibits foam cell formation by regulating lipid accumulation and inflammation. For this purpose, THP-1 cells were treated with 100 nM phorbol 12-myristate 13-acetate (PMA) to induce their differentiation into macrophages. The macrophages were then pre-treated with 2.5 µM resveratrol and subsequently with serum-free (SF) medium alone or SF medium containing lipopolysaccharide (LPS; 100 ng/ml) and oxidized low-density lipoprotein (ox-LDL; 50 µg/ml) for 24 h to detect foam cell formation. To detect the expression of lipid accumulation-related proteins, the macrophages were treated with resveratrol. For the detection MCP-1 expression, the macrophages were treated with LPS and resveratrol, or with resveratrol alone. We incubated the THP-1-derived macrophages in resveratrol (2.5 µM) for 6 h in the presence or absence of 30 µM compound C for 4 h to detect the influence of compound C on the effects of resveratrol. The foam cells were examined using Red O staining. Gene expression levels were determined by qRT-PCR, western blot analysis and ELISA; lipid analysis was carried out by high-performance liquid chromatography (HPLC). The results revealed that resveratrol effectively suppressed foam cell formation induced by LPS. Resveratrol also suppressed lipid accumulation and downregulated the mRNA expression of peroxisome proliferator-activated receptor (PPAR)γ and PPARα, but had no effect on the expression of PPARβ/δ. Resveratrol also upregulated the expression of AMPK and Silent information regulator T1 (SIRT1). However, the effects of resveratrol on SIRT1, PPARγ and PPARα expression and lipid accumulation were reversed when the cells were pre-treated with compound C. Resveratrol downregulated the mRNA expression of MCP-1 in a dose-dependent manner and LPS upregulate its expression in a time-dependent manner. MCP-1 expression induced by LPS was inhibited by resveratrol at both the transcriptional and translational level. These data suggest that resveratrol inhibits foam cell formation by regulating the expression of MCP-1 and activating the AMPK-SIRT1-PPAR signaling pathway; thus, resveratrol may be a novel therapeutic agent for atherosclerosis.