Resveratrol induces AMPK-dependent MDR1 inhibition in colorectal cancer HCT116/L-OHP cells by preventing activation of NF-κB signaling and suppressing cAMP-responsive element transcriptional activity

Resveratrol, a natural polyphenolic compound found in foods and beverages, has attracted increasing attention in recent years because of its potent chemopreventive and anti-tumor effects. In this study, the effects of resveratrol on the expression of P-glycoprotein/multi-drug resistance protein 1 (P-gp/MDR1), and the underlying molecular mechanisms, were investigated in oxaliplatin (L-OHP)-resistant colorectal cancer cells (HCT116/L-OHP). Resveratrol downregulated MDR1 protein and mRNA expression levels and reduced MDR1 promoter activity. It also enhanced the intracellular accumulation of rhodamine 123, suggesting that resveratrol can reverse multi-drug resistance by downregulating MDR1 expression and reducing drug efflux. Resveratrol treatment also reduced nuclear factor-κB (NF-κB) activity, reduced phosphorylation levels of IκBα, and reduced nuclear translocation of the NF-κB subunit p65. Moreover, downregulation of MDR1 expression and promoter activity was mediated by resveratrol-induced AMP-activated protein kinase (AMPK) phosphorylation. The inhibitory effects of resveratrol on MDR1 expression and cAMP-responsive element-binding protein (CREB) phosphorylation were reversed by AMPKα siRNA transfection. We found that the transcriptional activity of cAMP-responsive element (CRE) was inhibited by resveratrol. These results demonstrated that the inhibitory effects of resveratrol on MDR1 expression in HCT116/L-OHP cells were closely associated with the inhibition of NF-κB signaling and CREB activation in an AMPK-dependent manner.