title: Carbon monoxide induces cyclooxygenase-2 expression through MAPKs and PKG in phagocytes.
abstract: Many biological functions of heme oxygenase (HO) have been attributed to its enzymatic byproduct carbon monoxide (CO). CO has been demonstrated to play an important role in down-regulation of pro-inflammatory cytokines, but few studies have investigated the effects of CO on the cyclooxygenase-2 (COX-2) expression in macrophage. Here, we assessed the induction of COX-2 by CO in macrophage with or without lipopolysaccharide (LPS) stimulation. Tricarbonyldichloro ruthenium (II) dimmer (CORM-2) is a well known CO-releasing molecule, and exhibits anti-inflammatory activity in several cell types. In this study, both CORM-2 and CO gas were used to investigate the induction of COX-2 and the underlying molecular mechanisms in macrophage. Western blot and RT-PCR analysis demonstrated that CORM-2 and CO gas (500 ppm) significantly inhibited the protein and mRNA expression of iNOS in LPS-activated macrophages. In contrast, CORM-2 and CO gas up-regulated COX-2 expression and prostaglandin E₂ (PGE₂) production in the macrophage with or without LPS. CORM-2 time-dependently induced the phosphorylation of Akt and MAPKs, and the induction of COX-2 could be blocked by Akt, PKG, and MAPKs inhibitors. Indomethacin was used to decrease CORM-2-induced PGE₂ production by inhibiting COX-2 enzyme activity. Indomethacin was unable to reverse the decrease of iNOS, but it could restore the IL-1β expression and decrease the IL-10 expression in CORM-2-treated cells. The results suggest that CO induced COX-2 expression and PGE₂ production through activating the Akt, PKG, and MAPK pathways, and CO-induced PGE₂ may modulate inflammation during macrophage activation by suppressing IL-1β expression and inducing IL-10 production.
authors.affiliation: Department of Radiation Oncology, Chi-Mei Foundation Medical Center, Taiwan.
authors.forename: Li-Ching
authors.initials: LC
authors.lastname: Lin
authors.forename: Feng-Ming
authors.initials: FM
authors.lastname: Ho
authors.forename: Shish-Jung
authors.initials: SJ
authors.lastname: Yen
authors.forename: Pei-Yi
authors.initials: PY
authors.lastname: Wu
authors.forename: Ling-Fang
authors.initials: LF
authors.lastname: Hung
authors.forename: Wei-Jan
authors.initials: WJ
authors.lastname: Huang
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Liang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002248:Carbon Monoxide / Q000494:pharmacology* / Q000502:physiology; D018929:Cell Culture Techniques; D002460:Cell Line; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D015232:Dinoprostone / Q000378:metabolism; D004790:Enzyme Induction; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D017628:Microglia / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors; D009942:Organometallic Compounds / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D008070:Lipopolysaccharides; D009942:Organometallic Compounds; C447082:tricarbonyldichlororuthenium (II) dimer; D002248:Carbon Monoxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051546:Cyclooxygenase 2; D017869:Cyclic GMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D015232:Dinoprostone