title: Regulation of lipopolysaccharide sensitivity by IFN regulatory factor-2.
abstract: IFN regulatory factors (IRFs) are a family of transcription factors and include several members that regulate expression of pro- and anti-inflammatory genes. Mice with a targeted mutation in IRF-2 (IRF-2(-/-)) were studied after injection of LPS to evaluate the importance of IRF-2 in the regulation of endotoxicity. IRF-2(-/-) mice were highly refractory to LPS-induced lethality. Although hepatic TNF-alpha mRNA and circulating TNF-alpha were significantly elevated in LPS-challenged IRF-2(-/-) mice, levels of IL-1, IL-12, and IFN-gamma mRNA and protein, as well as IL-6 protein, were significantly lower than levels seen in LPS-challenged IRF-2(+/+) mice. IRF-2(-/-) mice were also more refractory to TNF-alpha challenge than were control mice, which was consistent with their diminished sensitivity to LPS, yet no significant difference in the mRNA expression of TNFRs was observed. IL-12R beta 2 mRNA levels from LPS-challenged IRF-2(-/-) mice were significantly different after 1, 6, and 8 h, suggesting that both diminished IL-12 and altered IL-12R expression contribute to the paucity of IFN-gamma produced. IRF-2 knockout mice also failed to sustain LPS-inducible levels of IRF-1 and IFN consensus sequence binding protein mRNA expression, two transacting factors required for IL-12 transcription, perhaps as a result of diminished IL-1 beta, IL-6, and IFN-gamma levels. Liver sections from IRF-2(+/+) and IRF-2(-/-) mice were analyzed 6 h after a typically lethal injection of LPS. IRF-2(-/-) mice exhibited greater numbers of apoptotic Kupffer cells than did wild-type mice, suggesting a novel anti-apoptotic role for IRF-2. Collectively, these findings reveal a critical role for IRF-2 in endotoxicity, and point to a previously unappreciated role for IRF-2 in the regulation of apoptosis.
authors.affiliation: Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201, USA.
authors.forename: Natalia
authors.initials: N
authors.lastname: Cuesta
authors.forename: Cindy A
authors.initials: CA
authors.lastname: Salkowski
authors.forename: Karen E
authors.initials: KE
authors.lastname: Thomas
authors.forename: Stefanie N
authors.initials: SN
authors.lastname: Vogel
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics; D017209:Apoptosis / Q000276:immunology; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D019446:Endotoxemia / Q000235:genetics / Q000276:immunology / Q000401:mortality; D005786:Gene Expression Regulation / Q000276:immunology; D007113:Immunity, Innate / Q000235:genetics; D007274:Injections, Intraperitoneal; D050836:Interferon Regulatory Factor-2; D050835:Interferon Regulatory Factors; D007371:Interferon-gamma / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D007375:Interleukin-1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D016753:Interleukin-10 / Q000096:biosynthesis / Q000235:genetics; D018664:Interleukin-12 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism; D015850:Interleukin-6 / Q000096:biosynthesis; D007728:Kupffer Cells / Q000166:cytology / Q000276:immunology; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000633:toxicity*; D008099:Liver / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000096:biosynthesis; D018123:Receptors, Interleukin / Q000096:biosynthesis / Q000235:genetics; D053707:Receptors, Interleukin-12; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis / Q000235:genetics; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000633:toxicity; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage / Q000633:toxicity; D000099185:Interferon Regulatory Factor-8; D000093242:Interleukin-6 Inhibitors
chemical_list: D015703:Antigens, CD; D004268:DNA-Binding Proteins; D050836:Interferon Regulatory Factor-2; D050835:Interferon Regulatory Factors; D007371:Interferon-gamma; D007375:Interleukin-1; D016753:Interleukin-10; D018664:Interleukin-12; D015850:Interleukin-6; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D000099185:Interferon Regulatory Factor-8; D000093242:Interleukin-6 Inhibitors; C494230:Irf2 protein, mouse