18-glycyrrhetinic acid extracted from Glycyrrhiza radix inhibits proliferation and promotes apoptosis of the hepatic stellate cell line

Objective To evaluate the effect of 18-glycyrrhetinic acid (18-GA) on the proliferation and apoptosis of hepatic stellate cells (HSCs) and its underlying mechanisms. Methods HSCs (both human and rat HSCs) were pretreated with or without selective peroxisome proliferator-activated receptor- (PPAR-) antagonist, GW9662, before 18a-GA treatment. Cell cycle and apoptosis of HSCs were analyzed by flow cytometry, and changes in cell cycle and apoptosis-related proteins were analyzed by Western blot. The effect of 18-GA on nuclear factor kappa-light-chain-enhancer of activated B cells (NF-B) DNA-binding activity was measured by ArrayStar transcription factor activity assay. Results 18-GA markedly reduced LX-2 cell numbers by 14.8% and 31.2% after 48h and 72h of treatment, respectively (P<0.05). 18-GA also significantly increased the percentage of LX-2 cells in phase G0/G1 and decreased it in phase S after treated for 48h and 72h compared with the control group. 18-GA increased apoptosis to 6.8% at 48h, compared with control (2.5%), and at 72h the percentages of apoptotic cells in control and the treatment groups were 3.1% and 15.6%, respectively, in LX-2 cells (P<0.01). Similar changes occurred in CCl4-cirrhotic fat-storing cells. Furthermore, 18-GA induced expression of PPAR- and altered some cell cycle and apoptosis-related proteins. 18-GA also inhibited NF-B DNA-binding activity. All these effects were abolished by GW9662. Conclusions 18-GA inhibits the proliferation of activated HSCs and induces apoptosis in culture. It also increases PPAR- expression and decreases NF-B DNA-binding activity, which may be involved in these effects.