Effects of tetrandrine on cell cycle of rat quiescent hepatic stellate cells

Objective To investigate the effect of tetrandrine on cell cycle of rat quiescent hepatic stellate cells(HSCs) and the involved mechanisms.Methods Primary-cultured rat HSCs which were cultivated 48 hours were subjected to tetrandrine(1.6 μmol/L) and/or TGF-β1(5 μg/L) for 3 days.Effects of tetrandrine on cell cycle progression of rat HSCs were determined by flow cytometry.The mRNA of Cyclin D1,Cyclin E,p21WAF1/CiP1 and p27Kip1 were analyzed by RT-PCR.Protein levels of Cyclin D1 and PPARγ were further determined by Western blot.Results Tetrandrine induced an increase in quiescent HSCs in the portion of cells in the G0/G1 and G2/M-phase as well as a decrease in the S-phase.The decreased number of cells in the G0/G1-phase and the increased number of cells in S-phase resulting from TGFβ1 treatment were also reversed by tetrandrine and a majority of HSCs in the G0/G1 and G2/M-phase was restored.Meanwhile,the expression of Cyclin D1 obviously decreased and in contrast,p21WAF1/CiP1 mRNA was slightly elevated and PPARγ was sustained.Conclusion These results suggest that a G0/G1-arrest and accelerated transition from the S-to G2/M-phase of the cell cycle are induced by tetrandrine in quiescent HSCs,and the effect results from the inhibition of Cyclin D1,up-regulation of p21WAF1/CiP1and a sustained PPARγ level.