title: Mitochondria contribute to LPS-induced MAPK activation via uncoupling protein UCP2 in macrophages.
abstract: The mitochondrion is a major organelle contributing to energy metabolism but also a main site of ROS (reactive oxygen species) production. LPS (lipopolysaccharide)-induced ROS signalling is a critical event in macrophage activation. In the present paper we report that part of LPS-mediated ROS signalling comes from mitochondria inside a signal amplification loop that enhances MAPK (mitogen-activated protein kinase) activation. More precisely, we have identified the inner mitochondrial membrane UCP2 (uncoupling protein 2) as a physiological brake on ROS signalling. Stimulation of murine bone marrow-derived macrophages by LPS quickly down-regulated UCP2 through the JNK (c-Jun N-terminal kinase) and p38 pathways. UCP2 down-regulation was shown to be necessary to increase mitochondrial ROS production in order to potentiate MAPK activation. Consistent with this, UCP2-deficient macrophages exhibit an enhanced inflammatory state characterized by increased nitric oxide production and elevated migration ability. Additionally, we found that the absence of UCP2 renders macrophages more resistant to nitric oxide-induced apoptosis.
authors.affiliation: CNRS UPR 9078, Faculté de Médecine Paris 5 Descartes-Necker, 156 rue de Vaugirard, 75730 Paris Cedex 15, France.
authors.forename: Yalin
authors.initials: Y
authors.lastname: Emre
authors.forename: Corinne
authors.initials: C
authors.lastname: Hurtaud
authors.forename: Tobias
authors.initials: T
authors.lastname: Nübel
authors.forename: François
authors.initials: F
authors.lastname: Criscuolo
authors.forename: Daniel
authors.initials: D
authors.lastname: Ricquier
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Cassard-Doulcier
mesh_terms: D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D015536:Down-Regulation; D004789:Enzyme Activation / Q000187:drug effects; D018836:Inflammation Mediators / Q000378:metabolism; D007473:Ion Channels / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D000071246:Uncoupling Protein 2
chemical_list: D018836:Inflammation Mediators; D007473:Ion Channels; D008070:Lipopolysaccharides; D024101:Mitochondrial Proteins; D016328:NF-kappa B; D017382:Reactive Oxygen Species; C000604390:Ucp2 protein, mouse; D000071246:Uncoupling Protein 2; D009569:Nitric Oxide; D020928:Mitogen-Activated Protein Kinases