title: NADH oxidase signaling induces cyclooxygenase-2 expression during lipopolysaccharide stimulation in cardiomyocytes.
abstract: Cyclooxygenase-2 (COX-2) is induced in response to lipopolysaccharide (LPS). However, the signaling mechanisms of LPS-induced COX-2 expression in cardiomyocytes are not well understood. The aim of this study was to investigate the role of gp91(phox)-containing NADH oxidase signaling pathway in LPS-induced COX-2 expression in cardiomyocytes. Cultured neonatal mouse cardiomyocytes showed basal COX-2 expression and PGE2 production. In response to LPS, COX-2 expression and PGE2 production increased by two- to four-fold, which were completely blocked by a selective COX-2 inhibitor NS398. LPS also increased NADH oxidase (gp91(phox) and p47(phox) subunits) expression and superoxide generation. Deficiency of gp91(phox) or suppression of p22(phox) expression decreased NADH oxidase activity and down-regulated COX-2 expression and PGE2 production stimulated by LPS. Pharmacological inhibitors of NADH oxidase prevented LPS-induced COX-2 expression and PGE2 production. The effect of NADH oxidase was mediated through MAPK activation, since inhibition of NADH-oxidase activity prevented phosphorylation of ERK1/2, p38, and JNK1/2, as well as selective inhibition of each subfamily of MAPK by siRNAs and a dominant negative mutant of JNK1 decreased COX-2 expression and completely abrogated PGE2 production in response to LPS. Furthermore, LPS-induced NF-kappaB activation was decreased by inhibition of NADH oxidase, ERK1/2 or JNK1/2 activation, suggesting that LPS increases NF-kappaB activity and COX-2 expression via NADH oxidase-dependent activation of ERK1/2 and JNK1/2. In conclusion, NADH oxidase signaling represents a novel pathway leading to COX-2 expression via MAPK/NF-kappaB-dependent mechanisms in cardiomyocytes during LPS stimulation. Our study suggests that gp91(phox)-containing NADH oxidase is a potential therapeutic target of sepsis.
authors.affiliation: Cardiology Research Laboratory, Lawson Health Research Institute, London Health Sciences Centre, Ontario, Canada.
authors.forename: Tianqing
authors.initials: T
authors.lastname: Peng
authors.forename: Xiangru
authors.initials: X
authors.lastname: Lu
authors.forename: Qingping
authors.initials: Q
authors.lastname: Feng
mesh_terms: D000256:Adenoviridae; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D008070:Lipopolysaccharides / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000502:physiology* / Q000821:virology; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D015398:Signal Transduction / Q000502:physiology*; D014161:Transduction, Genetic / Q000379:methods
chemical_list: D008070:Lipopolysaccharides; D009097:Multienzyme Complexes; D016328:NF-kappa B; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D020928:Mitogen-Activated Protein Kinases