The anti-atherogenic effects of berberine on foam cell formation are mediated through the upregulation of sirtuin 1.

Abstract

Berberine (BBR) is a botanical alkaloid that has been reported to have effects in cardiovascular diseases; however, the mechanisms involved are not yet fully understood. In the present study, the protective effects of BBR were evaluated, and the underlying molecular mechanisms were investigated. The effects of a combination of atorvastatin and BBR on foam cell formation were also investigated. THP-1-derived macrophages were pre-treated with BBR (5, 10 and 20 mg/l) for 2 h prior to the addition of oxidized low density lipoprotein (ox-LDL; 50 mg/l). Small interfering RNA (siRNA) targeting sirtuin 1 (SIRT1) and the adenosine 5'-monophosphate-activated protein kinase (AMPK) inhibitor, compound C, were used to investigate the mechanisms through which BBR exerts its effects. To determine the effect of a combination of atorvastatin and BBR, the macrophages were treated with atorvastatin and BBR separately or jointly for 2 h, and then treated with ox-LDL (50 mg/l) or lipopolysaccharide (LPS; 10 µM) for 12 h. Oil Red O staining was used to detect foam cell formation. Lipid amounts were assessed by high-performance liquid chromatography (HPLC). Gene and protein expression was evaluated by RT-qPCR, western blot analysis and enzyme-linked immunosorbent assay (ELISA) carried out separately or jointly. The results from Oil Red O staining and HPLC revealed that BBR effectively suppressed foam cell formation and lipid and cholesterol accumulation. Furthermore, BBR upregulated the expression of SIRT1 and AMPK and downregulated the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ). Pre-treatment of the cells with SIRT1-siRNA or compound C attenuated the anti-atherosclerotic effects of BBR. The results obtained in the present study demonstrate that the combination of atorvastatin and BBR is more effective in inhibiting foam cell formation than using atorvastatin alone. These data suggest that BBR suppresses foam cell formation by activating the AMPK-SIRT1-PPAR-γ pathway and diminishing the uptake of ox-LDL. Combination therapy with BBR and atorvastatin was more effective in preventing atherosclerotic processes than atorvastatin alone.