Liu Mingfeng, Mendicino Michael, Ning Qin, Ghanekar Anand, He Wei, McGilvray Ian, Shalev Itay, Pivato David, Clark David A, Phillips M James, Levy Gary A
Multi-Organ Transplant Program, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada.
J Immunol. 2006 Jun 1;176(11):7028-38. doi: 10.4049/jimmunol.176.11.7028.
Previous studies from our laboratory have shown that fulminant hepatitis caused by the mouse hepatitis virus, MHV-3, is dependent on production of the novel immune coagulant fgl2/fibroleukin. In this study, we investigate the role of IFN-gamma and TNF-alpha in the induction of fgl2 expression and fgl2-dependent hepatic apoptosis. Infusion of IFN-gamma in combination with TNF-alpha through the portal vein of fgl2+/+ mice led to widespread hepatic apoptosis and fibrin deposition. Livers from fgl2-/- mice were normal, although strong expression of the fgl2 knockout reporter gene Lac Z was seen in both resident hepatic macrophages and endothelial cells. In vitro, IFN-gamma and TNF-alpha induced fgl2 expression in a macrophage and endothelial cell-specific manner. In macrophages (peritoneal and RAW 264.7 cells), IFN-gamma, but not IFN-alpha, LPS, TNF-alpha, or IL-1 induced fgl2 mRNA transcription and protein expression, while in endothelial cells TNF-alpha, but not IFN-gamma, induced fgl2 transcription. In addition, while TNF-alpha enhanced IFN-gamma-induced macrophage fgl2 transcription, IFN-gamma also enhanced TNF-alpha-induced endothelial cell fgl2 transcription. The induction of fgl2 by IFN-gamma in macrophages involved a STAT1-dependent pathway, involving the composite cis elements Sp1/Sp3 and GAS/PU.1. The latter interacted with IFN-gamma-dependent Sp1/Sp3, STAT1, and the ETS family of transcription factors member PU.1. The interaction of PU.1 with the IFN-gamma-activated sequence/ETS family of transcription factors site determined the macrophage-specific induction of fgl2 by IFN-gamma. Overall, this study demonstrates that IFN-gamma and TNF-alpha induce hepatocyte apoptosis in vivo, which is dependent on induction of fgl2, and defines the molecular basis of transcription of fgl2 in vitro.
我们实验室之前的研究表明，由小鼠肝炎病毒MHV-3引起的暴发性肝炎依赖于新型免疫凝血因子fgl2/纤维白细胞介素的产生。在本研究中，我们调查了干扰素-γ（IFN-γ）和肿瘤坏死因子-α（TNF-α）在诱导fgl2表达及fgl2依赖性肝凋亡中的作用。通过门静脉向fgl2+/+小鼠输注IFN-γ与TNF-α的组合，导致广泛的肝凋亡和纤维蛋白沉积。fgl2-/-小鼠的肝脏正常，尽管在驻留肝巨噬细胞和内皮细胞中均可见fgl2基因敲除报告基因Lac Z的强表达。在体外，IFN-γ和TNF-α以巨噬细胞和内皮细胞特异性方式诱导fgl2表达。在巨噬细胞（腹腔巨噬细胞和RAW 264.7细胞）中，IFN-γ而非IFN-α、脂多糖（LPS）、TNF-α或白细胞介素-1（IL-1）诱导fgl2 mRNA转录和蛋白表达，而在内皮细胞中，TNF-α而非IFN-γ诱导fgl2转录。此外，虽然TNF-α增强IFN-γ诱导的巨噬细胞fgl2转录，但IFN-γ也增强TNF-α诱导的内皮细胞fgl2转录。IFN-γ在巨噬细胞中诱导fgl2涉及一条依赖信号转导和转录激活因子1（STAT1）的途径，涉及复合顺式元件Sp1/Sp3以及γ干扰素激活位点（GAS）/PU.1。后者与IFN-γ依赖性Sp1/Sp3、STAT1以及转录因子家族ETS成员PU.1相互作用。PU.1与IFN-γ激活序列/ETS转录因子家族位点的相互作用决定了IFN-γ对巨噬细胞fgl2的特异性诱导。总体而言，本研究表明IFN-γ和TNF-α在体内诱导肝细胞凋亡，这依赖于fgl2的诱导，并确定了体外fgl2转录的分子基础。
