Cytokine-induced hepatic apoptosis is dependent on FGL2/fibroleukin: the role of Sp1/Sp3 and STAT1/PU.1 composite cis elements.
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.
Liu
Mingfeng
M
Multi-Organ Transplant Program, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada.
Mendicino
Michael
M
Ning
Qin
Q
Ghanekar
Anand
A
He
Wei
W
McGilvray
Ian
I
Shalev
Itay
I
Pivato
David
D
Clark
David A
DA
Phillips
M James
MJ
Levy
Gary A
GA
D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D002460:Cell Line; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D005340:Fibrinogen / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D022781:Hepatocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D007371:Interferon-gamma / Q000008:administration & dosage / Q000502:physiology*; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D050794:STAT1 Transcription Factor / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D016329:Sp1 Transcription Factor / Q000502:physiology*; D051705:Sp3 Transcription Factor / Q000502:physiology*; D013552:Swine; D015534:Trans-Activators / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D000099232:Proto-Oncogene Protein Spi-1
D005340:Fibrinogen; D007371:Interferon-gamma; D011518:Proto-Oncogene Proteins; D050794:STAT1 Transcription Factor; D016329:Sp1 Transcription Factor; D051705:Sp3 Transcription Factor; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; D000099232:Proto-Oncogene Protein Spi-1; C490637:Fgl2 protein, mouse