牛磺酸通过调控细胞周期蛋白抑制肝星状细胞增殖

目的进一步研究牛磺酸对肝星状细胞(HSC)增殖抑制作用的机制。方法用四甲基偶氮唑盐法检测细胞增殖;流式细胞仪测定细胞周期;免疫细胞化学和实时荧光定量PCR测定细胞周期调控蛋白Cyclin D1和P21waf1表达。结果牛磺酸对HSC增殖具有抑制作用,在浓度为5、10、20,30、40、50 mmol/L 作用48h时的抑制率分别为6.7%、14.4%、23.3%、32.2%、36.7%和45.6%,t值为2.939～6.369,P<0.05～0.01。流式细胞仪检测发现牛磺酸可阻滞HSC由G0/G1期向S期转换,使G0/G1期细胞增多,S期细胞减少。G0/G1期、S期细胞,牛磺酸浓度为40 mmol/L时,分别为(68.2±1.4)%和(26.2±1.3)%,与对照组分别为(56.2±1.7)%和(38.5±0.8)%,差异有统计学意义,t≥5.422,P<0.01。牛磺酸可抑制Cyclin D1表达、促进P21waf1表达,用免疫细胞化学染色结合数码图像分析系统软件分析发现牛磺酸浓度在40 mmol/L时HSC的Cyclin D1表达的平均吸光度为0.13±0.02,P21waf1为0.19±0.02,对照组分别为0.18±0.02和0.14±0.01,差异有统计学意义,t=6.689和t=6.528,P<0.01。实时荧光定量PCR检测也发现经40 mmol/L牛磺酸处理的HSC的Cyclin D1 mRNA表达量(拷贝数与106磷酸甘油醛脱氢酶比值)降低为5776.7±3345.0,对照组为18 400.6±1374.8,而P21waf1 mRNA表达量(拷贝/106磷酸甘油醛脱氢酶)增多为44 866.7±3910.7,对照组为16 933.3±960.9。结论牛磺酸通过抑制Cyclin D1表达、促进P21waf1表达,使HSC阻滞于G0/G1期,而抑制HSC增殖。

Inhibition of proliferation of hepatic stellate cells by taurine is mediated via regulating cell cycle proteins

OBJECTIVE: To explore the possible mechanism(s) of taurine-inhibiting the proliferation of hepatic stellate cells (HSC), this study investigated the effect of taurine on the HSC cell cycle and its regulatory protein expression. METHODS: Cell proliferation was assessed by MTT assay. Cell cycle was analyzed by flow cytometry. Cell cycle regulatory protein Cyclin D1 and P21waf1 expression were determined by immunocytochemistry and image-analysis system, and real-time quantitative PCR. RESULTS: HSC proliferation was markedly inhibited when HSC were treated with taurine at concentrations of 5, 10, 20, 30, 40 and 50 mmol/L for 48 hours, and the inhibition rates were 6.7%, 14.4%, 23.3%, 32.2%, 36.7% and 45.6% respectively (P < 0.05-0.01). In the flow cytometry analysis, it was found that taurine could block HSC in the G0/G1 phase from entering the S phase, resulting in more cells in the G0/G1 phase and fewer in the S phase. The percentage of the cells in the G0/G1 phase and the S phase at the dosage of 40 mmol/L were 68.2%+/-1.4% and 26.2+/-1.3% respectively, which was significantly different in comparison to the controls (56.2%+/-1.7% and 38.5%+/-0.8% respectively, P < 0.01). HSC expressed cyclin D1 and P21waf1. Taurine inhibited cyclin D1 expression and induced P21waf1 expression. The cyclin D1 protein and mRNA in the HSC treated with 40 mmol/L taurine were significantly reduced compared with the controls protein (optical density value): 0.13+/-0.02 versus 0.18+/-0.02, P < 0.01; mRNA: 5776.7+/-3345.0 versus 18,400.6+/-1374.8 copies/10(6) GAPDH, P < 0.01]; and the P21waf1 protein and mRNA were markedly increased compared with the controls protein (optical density value): 0.19+/-0.02 versus 0.14+/-0.01, P < 0.01; mRNA: 44,866.7+/-3910.7 versus 16,933.3+/-960.9 copies/10(6) GAPDH, P less than 0.05]. CONCLUSIONS: Cyclin D1 and P21waf1 were cell cycle regulatory proteins in HSC, and taurine can inhibit the HSC cyclin D1 expression and stimulate P21waf1 expression, facilitate arresting cells in G0/G1 phase, and suppress cell proliferation.