The role of the interferon regulatory factors, IRF-1 and IRF-2, in LPS-induced cyclooxygenase-2 (COX-2) expression in vivo and in vitro.
Cyclooxygenase (COX) exists as two isoforms: COX-1, which is constitutively expressed in most cell types; and COX-2, which is inducible by lipopolysaccharide (LPS) and cytokines in a variety of cell types. Although previous studies have implicated two DNA binding proteins, interferon regulatory factor (IRF)-1 and IRF-2, in the regulation of LPS- and IFN-gamma-induced COX-2, their effects in vivo and in vitro are not well-defined. Using real-time PCR, COX-2 gene expression in the livers and lungs of mice challenged in vivo and in macrophages stimulated with LPS in vitro was investigated in wild-type and in IRF-1 and IRF-2 knockout mice. In response to 35 mg/kg LPS, IRF-1-, but not IRF-2-deficient mice, exhibited much poorer induction of COX-2 gene expression in both the livers and lungs. In vitro, COX-2 mRNA levels were also poorly induced in IRF-1-deficient macrophages, while IRF-2- deficient macrophages exhibited higher levels than in normal macrophages. IRF-1 and IRF-2 were confirmed to activate and repress expression of the COX-2 promoter, respectively, in a transient transfection system and the role of specific DNA binding sites confirmed by site-specific mutagenesis. Collectively, these data provide evidence for an important role for IRF-1 in vivo and in vitro and for IRF-2 in vitro in the regulation of COX-2 expression by LPS.
Zhang
Shuling
S
Department of Microbiology and Immunology, University of Maryland, Baltimore, Maryland 21201, USA.
Thomas
Karen
K
Blanco
Jorge C G
JC
Salkowski
Cindy A
CA
Vogel
Stefanie N
SN
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D051546:Cyclooxygenase 2; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000276:immunology*; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008099:Liver / Q000276:immunology; D008168:Lung / Q000276:immunology; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051818:Replication Protein C; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; C494258:Irf1 protein, mouse; C494230:Irf2 protein, mouse; D008070:Lipopolysaccharides; D010750:Phosphoproteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C095385:Rfc1 protein, mouse; D014157:Transcription Factors; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D051818:Replication Protein C