Abstract
Nitric oxide (NO.) produced by inducible nitric oxide synthase (iNOS) mediates a number of important physiological and pathophysiological processes. The objective of this investigation was to examine the role of mitogen-activated protein kinases (MAPKs) in the regulation of iNOS and NO. by interferon-gamma (IFN-gamma) + lipopolysaccharide (LPS) in macrophages using specific inhibitors and dominant inhibitory mutant proteins of the MAPK pathways. The signaling pathway utilized by IFN-gamma in iNOS induction is well elucidated. To study signaling pathways that are restricted to the LPS-signaling arm, we used a subclone of the parental RAW 264.7 cell line that is unresponsive to IFN-gamma alone with respect to iNOS induction. In this RAW 264.7gammaNO(-) subclone, IFN-gamma and LPS are nevertheless required for synergistic activation of the iNOS promoter. We found that extracellular signal-regulated kinase (ERK) augmented and p38(mapk) inhibited IFN-gamma + LPS induction of iNOS. Dominant-negative MAPK kinase-4 inhibited iNOS promoter activation by IFN-gamma + LPS, also implicating the c-Jun NH(2)-terminal kinase (JNK) pathway in mediating iNOS induction. Inhibition of the ERK pathway markedly reduced IFN-gamma + LPS-induced tumor necrosis factor-alpha protein expression, providing a possible mechanism by which ERK augments iNOS expression. The inhibitory effect of p38(mapk) appears more complex and may be due to the ability of p38(mapk) to inhibit LPS-induced JNK activation. These results indicate that the MAPKs are important regulators of iNOS-NO. expression by IFN-gamma + LPS.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Cell Line
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DNA-Binding Proteins
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Drug Synergism
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Enzyme Induction / physiology
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Enzyme Inhibitors / pharmacology
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Genes, Dominant
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Imidazoles / pharmacology
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Interferon-gamma / pharmacology*
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Interleukin-1 / physiology
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JNK Mitogen-Activated Protein Kinases
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Lipopolysaccharides / pharmacology*
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MAP Kinase Kinase 1
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MAP Kinase Kinase 4*
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Macrophages / metabolism*
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Mice
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Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinase Kinases / genetics
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Mitogen-Activated Protein Kinase Kinases / pharmacology
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Mitogen-Activated Protein Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinases / physiology*
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Nitric Oxide Synthase / genetics
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Nitric Oxide Synthase / metabolism*
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Nitric Oxide Synthase Type II
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Nitrites / metabolism
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Nuclear Proteins / antagonists & inhibitors
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Nuclear Proteins / physiology*
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Phosphorylation / drug effects
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Promoter Regions, Genetic / drug effects
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Pyridines / pharmacology
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RNA-Binding Proteins
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Tumor Necrosis Factor-alpha / antagonists & inhibitors
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Tumor Necrosis Factor-alpha / metabolism
Substances
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DNA-Binding Proteins
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Enzyme Inhibitors
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Imidazoles
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Interleukin-1
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Lipopolysaccharides
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Nitrites
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Nuclear Proteins
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Pa2g4 protein, mouse
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Pyridines
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RNA-Binding Proteins
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Tumor Necrosis Factor-alpha
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Interferon-gamma
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Nitric Oxide Synthase
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Nitric Oxide Synthase Type II
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Nos2 protein, mouse
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Protein Serine-Threonine Kinases
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JNK Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 1
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MAP Kinase Kinase 4
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Map2k1 protein, mouse
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Map2k4 protein, mouse
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Mitogen-Activated Protein Kinase Kinases
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SB 203580