中文摘要：

目的：研究曲古抑菌素A（Trichostatin A,TSA）下调γ干扰素（interferon-gamma,IFN-γ）诱导的人肝癌细胞HepG2内吲哚胺2,3-双加氧酶（indoleamine 2,3-dioxygenase,IDO）表达的分子机制。方法：Western blot检测TSA在IFN-γ诱导的HepG2细胞中IDO的表达、信号转导及转录激活子1（STAT1）的磷酸化和干扰素调节因子1（IRF-1）的诱导表达情况。用免疫细胞化学法检测TSA处理HepG2细胞后对IDO表达的影响。流式细胞术分析TSA处理后IFN-γ受体2表达量的变化,进一步在激光共聚焦显微镜下观察TSA对STAT1核转位的影响,利用双荧光素酶报告基因系统检测TSA对IFN-γ激活位点（γ-activated sites,GAS）、干扰素刺激应答元件（interferonstimulated response elements,ISRE）和核因子-κB（NF-κB）的激活的影响。结果：TSA以剂量依赖方式下调HepG2细胞内IFN-γ诱导的IDO表达、能明显抑制STAT1第701位酪氨酸的磷酸化和STAT1的核转位,但是上调IFN-γ受体2受体的表达。双荧光素酶报告基因分析和Westernblot结果表明：TSA能显著抑制GAS和IRF-1的激活却不能抑制NF-κB和ISRE的激活。结论：TSA能下调IFN-γ诱导的HepG2细胞中IDO的表达,其机制可能是与其抑制STAT1的磷酸化和核转位,以及抑制STAT1与GAS的结合有关,而不是通过下调IFN-γ受体的表达来实现的。

英文摘要：

Objective： To study the molecular mechanism of TSA-induced indoleamine 2,3-dioxygenase（IDO） downregulation in human liver cancer cell line HepG2.Methods： The roles of TSA on the IFN-γ induced IDO expression in HepG2 cell,the phosphorylation of signal transducer and activator of transcription 1（STAT1） and the activation of interferon regulatory factor 1（IRF-1） were examined by western blotting.IDO expression in TSA-treated HepG2 cells was also detected by immunocytochemistry,and changes in the expression of IFN-γ receptor 2 was analyzed by Flow cytometry.Effect of TSA on STAT1 nuclear translocation was observed by a confocal laser-scanning microscope.The Luciferase activity of the activation of γ-interferon activated sites（GAS）,interferon stimulated response element（ISRE） and nuclear factor-κB（NF-κB） was measured by Dual Luciferase Reporter Assay System.Results： TSA dose-dependently reduced IFN-γ induced IDO expression,and inhibited STAT1 phosphorylation at Tyr-701 and nuclear translocation in HepG2 cell,but it upregulated the expression of IFN-γ receptor 2.Dual luciferase reporter assay and Western blotting results showed that TSA blocked IFN-γ-induced activation of GAS and IRF-1,but not NF-κB and ISRE.Conclusion： TSA can down-regulated IFN-γ induced IDO expression in HepG2 cell,which may be associated with the repression of phosphorylation and nuclear translocation of STAT1 and its binding to GAS,not due to reduced expression of the IFN-γ receptor.