Tormentic acid inhibits proliferation and promotes apoptosis of LX-2 human hepatic stellate cells via blocking NF-κB signaling pathway

Objective To investigate the regulating function of tormentic acid (TA) on the NF-κB signaling pathway and analyze its effect on proliferation and apoptosis of LX-2 human hepatic stellate cells and its mechanism. Methods The cultured LX-2 cells were randomized into normal control group, platelet-derived growth factor BB (PDGF-BB) stimulated group (20 ng/mL), PDTC group (20 ng/mL of PDGF-BB combined with 10 mmol/L of PDTC), and TA treated groups (20 ng/mL of PDGF-BB combined with 35, 25, 15 μmol/L of TA). The effects of TA on cell proliferation were detected by MTT assay. The activities of ASL, ALT, and TBIL were detected by using commercially available kits. Cell apoptosis was determined by flow cytometry. The mRNA of NF-κB p65 was detected by real-time quantitative PCR; and the protein expressions of NF-κB p65, phosphorylated NF-κB p65(p-NF-κB p65), IκBα, α-SMA, TGF-β, Bcl2, and Bax were detected by Western blot. Results Compared with PDGF-BB, TA significantly inhibited the activation and proliferation of LX-2 cells, and decreased the protein expressions of α-SMA and TGF-β. TA treatment reduced the levels of ASL, ALT, and TBIL in the cells and the cellular damage. TA significantly induced LX-2 cells apoptosis by down-regulating the expression of the anti-apoptotic protein Bcl2 and up-regulating the expression of the pro-apoptotic protein Bax. In addition, TA markedly inhibited the expressions of NF-κB p65 mRNA and protein, and the phosphorylation of NF-κB p65 and IκBα proteins. Conclusion TA inhibits proliferation and promotes apoptosis of LX-2 cells by blocking the NF-κB signaling pathway.