Curcumin regulates peroxisome proliferator-activated receptor-γ coactivator-1α expression by AMPK pathway in hepatic stellate cells in vitro

Abstract

Curcumin exerts an inhibitory effect on hepatic stellate cell (HSC) activation, a key step for liver fibrogenesis, and on liver fibrosis by up-regulation of peroxisome proliferator-activated receptor-γ (PPARγ) expression. PPARγ plays a crucial role in suppression of HSC activation. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) functions as a co-activator for PPARγ. Therefore, researches on the effect of curcumin on PGC-1α might contribute to understanding of the mechanisms underlying curcumin inhibition of HSC activation and liver fibrosis through PPARγ. The present study aimed to investigate the effect of curcumin on PGC-1α expression in HSCs in vitro and examine the underlying molecular mechanisms by western blot, reat-time PCR, and transfection. Our results showed that curcumin stimulation increased PGC-1α expression and the effects of curcumin on PGC-1α expression were correlated with the activation of adenosine monophosphate-activated protein kinase (AMPK). Curcumin increased superoxide dimutase-2 (SOD2) transcription and activity by AMPK/PGC-1α axis. Moreover, PGC-1α was demonstrated to inhibit α1(I) collagen (a marker for liver fibrosis) transcription in cultured HSCs. These results demonstrated the promotion effect of curcumin on PGC-1α expression through AMPK pathway, which led to the increases in PPARγ activity and in SOD-2 transcription and activity. These data might suggest a possible new explanation for the inhibitory effect of curcumin on HSC activation and on liver fibrogenesis.