title: Signalling events involved in interferon-gamma-inducible macrophage nitric oxide generation.
abstract: Nitric oxide (NO) produced by macrophages (Mphi) in response to interferon-gamma (IFN-gamma) plays a pivotal role in the control of intracellular pathogens. Current knowledge of the specific biochemical cascades involved in this IFN-gamma-inducible Mphi function is still limited. In the present study, we evaluated the participation of various second messengers--Janus kinase 2 (JAK2), signal transducer and activator of transcription (STAT) 1alpha, MAP kinase kinase (MEK1/2), extracellular signal-regulated kinases 1 and 2 (Erk1/Erk2) and nuclear factor kappa B (NF-kappaB)--in the regulation of NO production by IFN-gamma-stimulated J774 murine Mphi. The use of specific signalling inhibitors permitted us to establish that JAK2/STAT1alpha- and Erk1/Erk2-dependent pathways are the main players in IFN-gamma-inducible Mphi NO generation. To determine whether the inhibitory effect was taking place at the pre- and/or post-transcriptional level, we evaluated the effect of each antagonist on inducible nitric oxide synthase (iNOS) gene and protein expression, and on the capacity of IFN-gamma to induce JAK2, Erk1/Erk2 and STAT1alpha phosphorylation. All downregulatory effects occurred at the pretranscriptional level, except for NF-kappaB, which seems to exert its role in NO production through an iNOS-independent event. In addition, electrophoretic mobility shift assay (EMSA) analysis revealed that STAT1alpha is essential for IFN-gamma-inducible iNOS expression and NO production, whereas the contribution of NF-kappaB to this cellular regulation seems to be minimal. Moreover, our data suggest that Erk1/Erk2 are responsible for STAT1alpha Ser727 residue phosphorylation in IFN-gamma-stimulated Mphi, thus contributing to the full activation of STAT1alpha. Taken together, our results indicate that JAK2, MEK1/2, Erk1/Erk2 and STAT1alpha are key players in the IFN-gamma-inducible generation of NO by Mphi.
authors.affiliation: Centre de Recherche en Infectiologie et Département de Biologie Médicale, Pavillon CHUL, Faculté de Médecine, Université Laval, Ste-Foy (Québec) Canada.
authors.forename: Julie
authors.initials: J
authors.lastname: Blanchette
authors.forename: Maritza
authors.initials: M
authors.lastname: Jaramillo
authors.forename: Martin
authors.initials: M
authors.lastname: Olivier
mesh_terms: D000818:Animals; D002460:Cell Line; D050832:Interferon-Stimulated Gene Factor 3; D007371:Interferon-gamma / Q000494:pharmacology*; D053614:Janus Kinase 2; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D008262:Macrophage Activation / Q000187:drug effects / Q000502:physiology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics; D014178:Translocation, Genetic
chemical_list: D050832:Interferon-Stimulated Gene Factor 3; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; C079868:gamma interferon activation factor; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases