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Original Article |
dependent Cyclooxygenase 2 Expression
Correspondence to: Stefanie N. Vogel, Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, Maryland 20814. Tel:301-295-3446 Fax:301-295-1545 E-mail:vogel{at}bob.usuhs.mil.
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)-
alone or in synergy with lipopolysaccharide (LPS) or interleukin 1
induces Cox-2 expression in mouse peritoneal macrophages, which is paralleled by changes in Cox-2 protein levels and prostaglandin E2 (PGE2) 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-
stimulated PGE2 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-1/2dependent manner. Our data demonstrate conclusively the importance of IFN-
as a direct activator and coactivator of the Cox-2 gene, and the central role of IRF-1/2 family members in this process.
Key Words: inflammation, prostaglandin, macrophage, cytokine, septic shock
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