Impaired IFN-gamma production in IFN regulatory factor-1 knockout mice during endotoxemia is secondary to a loss of both IL-12 and IL-12 receptor expression.
Mice with a targeted mutation in the gene that encodes the transcription factor IFN regulatory factor-1 (IRF-1) were used to assess the contribution of IRF-1 to IL-12-dependent and IL-12-independent pathways of IFN-gamma production. In response to LPS, IRF. 1-/- mice produced less IL-12 p40, IL-12 p35, and IFN-gamma mRNA in the liver than IRF-1+/+ mice. While pulmonary IFN-gamma mRNA levels were also mitigated in IRF-1-/- mice, pulmonary IL-12 p40 and IL-12 p35 mRNA were not dysregulated. Circulating IL-12 p70 and IFN-gamma levels were profoundly attenuated in LPS-challenged IRF-1-/- mice. Further analysis revealed a major deficiency in hepatic IL-12Rbeta1 and IL-12Rbeta2 mRNA expression as well as pulmonary IL-12Rbeta1 mRNA expression in LPS-challenged IRF-1-/- mice. In vitro, IFN-gamma up-regulated IL-12Rbeta1 mRNA in macrophages from IRF-1+/+, but not IRF-1-/-, mice. IFN-gamma-induced IL-12Rbeta2 mRNA expression was also diminished in macrophages from IRF-1-/- mice. In contrast to IRF-1+/+ mice, administration of exogenous IL-12 to IRF-1-/- mice resulted in reduced serum IFN-gamma and hepatic and pulmonary IFN-gamma mRNA, demonstrating that loss of IL-12R results in diminished IL-12 responsiveness. While LPS-challenged IRF-1-/- mice also had reduced IL-15 mRNA levels, serum IL-18 responses were intact. Finally, induction of IRF-1 mRNA by LPS in livers of IFN-gamma knockout mice were markedly attenuated, suggesting a feedback amplification loop. These studies indicate that IRF-1 deficiency disrupts both IL-12-dependent and -independent pathways of IFN-gamma production and that IRF-1 is a critical transcription factor involved in the regulation of not only IL-12, but also IL-12R.
Salkowski
C A
CA
Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Thomas
K E
KE
Cody
M J
MJ
Vogel
S N
SN
D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D019446:Endotoxemia / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D007153:Immunologic Deficiency Syndromes / Q000235:genetics* / Q000276:immunology; D007274:Injections, Intraperitoneal; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000502:physiology; D018664:Interleukin-12 / Q000008:administration & dosage / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D019409:Interleukin-15 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000008:administration & dosage; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010750:Phosphoproteins / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D018123:Receptors, Interleukin / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D053707:Receptors, Interleukin-12; D014157:Transcription Factors / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology
D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D019409:Interleukin-15; C494258:Irf1 protein, mouse; D008070:Lipopolysaccharides; D010750:Phosphoproteins; D012333:RNA, Messenger; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D014157:Transcription Factors; D018664:Interleukin-12; D007371:Interferon-gamma