CCAAT/enhancer-binding protein mediates carbon monoxide-induced suppression of cyclooxygenase-2.
Cyclooxygenase-2 (COX-2) is a key enzyme involved in the inflammatory process that is rapidly induced in macrophages in response to LPS. Carbon monoxide (CO), a byproduct of heme oxygnease-1, can suppress proinflammatory response in various in vitro and in vivo models of inflammation. This study was undertaken to examine whether CO can regulate (and if so, to delineate the mechanism by which CO regulates) LPS-induced COX-2 expression in macrophages. RAW 264.7 murine macrophages were stimulated with LPS (0-10 ng/ml) with or without CO (500 ppm). Northern and Western blot analysis was done. Progstaglandin E(2) and nitrite concentration was measured from cell culture supernatant. Electrophoretic mobility shift assay was performed to assess nuclear factor binding. CO downregulated LPS-induced COX-2 mRNA and protein expression. CO also inhibited LPS-induced prostaglandin E(2) secretion (P < 0.05). CO also decreased LPS-induced CCAAT/enhancer-binding protein (C/EBP) beta and delta protein expression in LPS-treated RAW 264.7 cells. Gel shift analysis revealed that CO treatment decreased LPS-induced activation of protein binding to C/EBP consensus oligonucleotides of murine cyclooxygenase-2 promoter. CO also decreased LPS-induced nitric oxide synthase-2 protein expression and nitrite production, and decreased LPS-induced activation of protein binding to C/EBP consensus oligonucleotides of murine nitric oxide synthase-2 promoter. CO may act as an important regulator of inflammation by virtue of its ability to regulate C/EBPs.
Suh
Gee Young
GY
Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, 3459 Fifth Avenue, MUH 628, PA 15213, USA.
Jin
Yang
Y
Yi
Ae-Kyung
AK
Wang
Xiao Mei
XM
Choi
Augustine M K
AM
D000818:Animals; D051743:CCAAT-Enhancer-Binding Protein-delta / Q000235:genetics / Q000378:metabolism; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002248:Carbon Monoxide / Q000494:pharmacology*; D018929:Cell Culture Techniques; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015232:Dinoprostone / Q000032:analysis / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D051547:Heme Oxygenase-1 / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism
D022762:CCAAT-Enhancer-Binding Proteins; D007527:Isoenzymes; D008070:Lipopolysaccharides; D009573:Nitrites; D012333:RNA, Messenger; D051743:CCAAT-Enhancer-Binding Protein-delta; D002248:Carbon Monoxide; D008156:Luciferases; D052247:Nitric Oxide Synthase Type II; D051547:Heme Oxygenase-1; D051546:Cyclooxygenase 2; D015232:Dinoprostone