Interferon regulatory factor (IRF)-1 and IRF-2 regulate interferon gamma-dependent cyclooxygenase 2 expression.
Cyclooxygenases (Cox) are rate-limiting enzymes that initiate the conversion of arachidonic acid to prostanoids. Cox-2 is the inducible isoform that is upregulated by proinflammatory agents, initiating many prostanoid-mediated pathological aspects of inflammation. In this study, we demonstrate that interferon (IFN)-gamma alone or in synergy with lipopolysaccharide (LPS) or interleukin 1alpha induces Cox-2 expression in mouse peritoneal macrophages, which is paralleled by changes in Cox-2 protein levels and prostaglandin E(2) (PGE(2)) release. Induction of Cox-2 was abrogated in macrophages that lack IFN regulatory factor (IRF)-1, consistent with an attenuated hepatic mRNA response in IRF-1(-/-) mice injected with LPS. Conversely, the absence of IRF-2 in macrophages resulted in a significant increase in both basal and inducible Cox-2 gene and protein expression as well as IFN-gamma-stimulated PGE(2) release, identifying IRF-2 as negative regulator of this promoter. Two IFN stimulation response elements were identified in the mouse Cox-2 promoter that were highly conserved in the human Cox-2 gene. Both bind endogenous IRF-1 and IRF-2 and regulate transcription in an IRF-1/2-dependent manner. Our data demonstrate conclusively the importance of IFN-gamma as a direct activator and coactivator of the Cox-2 gene, and the central role of IRF-1/2 family members in this process.
Blanco
J C
JC
Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
Contursi
C
C
Salkowski
C A
CA
DeWitt
D L
DL
Ozato
K
K
Vogel
S N
SN
D000818:Animals; D001665:Binding Sites; D051546:Cyclooxygenase 2; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004357:Drug Synergism; D015971:Gene Expression Regulation, Enzymologic; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D007371:Interferon-gamma / Q000378:metabolism*; D007375:Interleukin-1 / Q000494:pharmacology; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000276:immunology; D051379:Mice; D008817:Mice, Mutant Strains; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D011485:Protein Binding; D012097:Repressor Proteins; D020218:Response Elements; D012772:Shock, Septic / Q000209:etiology / Q000276:immunology; D014157:Transcription Factors; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D007375:Interleukin-1; C494258:Irf1 protein, mouse; C494230:Irf2 protein, mouse; D007527:Isoenzymes; D008070:Lipopolysaccharides; D010750:Phosphoproteins; D012097:Repressor Proteins; D014157:Transcription Factors; D007371:Interferon-gamma; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases