Abstract
Lipopolysaccharide (LPS) is a potent activator of tumor necrosis factor-alpha (TNF-alpha) production by macrophages. LPS stimulates the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and increases TNF-alpha mRNA and protein accumulation in RAW 264.7 murine macrophages. However, the role of ERK1/2 activation in mediating LPS-stimulated TNF-alpha production is not well understood. Inhibition of ERK1/2 activation with PD-98059 or overexpression of dominant negative ERK1/2 decreased LPS-induced TNF-alpha mRNA quantity. LPS rapidly increased early growth response factor (Egr)-1 binding to the TNF-alpha promoter; this response was blunted in cells treated with PD-98059 or transfected with dominant-negative ERK1/2. Using a chloramphenicol acetyltransferase reporter gene linked to the Egr-1 promoter, we show that LPS increased Egr-1 promoter activity via an ERK1/2-dependent mechanism. These results delineate the role of ERK1/2 activation of Egr-1 activity in mediating LPS-induced increases in TNF-alpha mRNA expression in macrophages.
Publication types
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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 / genetics
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DNA-Binding Proteins / metabolism*
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Early Growth Response Protein 1
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Enzyme Activation / drug effects
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Enzyme Inhibitors / pharmacology
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Flavonoids / pharmacology
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Gene Expression Regulation / drug effects
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Gene Expression Regulation / genetics
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Genes, Dominant
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Genes, Reporter
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Immediate-Early Proteins*
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Lipopolysaccharides / pharmacology*
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Macrophages / cytology
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Macrophages / drug effects
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Macrophages / metabolism*
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Mice
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Mitogen-Activated Protein Kinase 1 / antagonists & inhibitors
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Mitogen-Activated Protein Kinase 1 / genetics
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Mitogen-Activated Protein Kinase 1 / metabolism*
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinases / genetics
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Mitogen-Activated Protein Kinases / metabolism*
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Phosphorylation / drug effects
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Promoter Regions, Genetic / physiology
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RNA, Messenger / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transfection
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Tumor Necrosis Factor-alpha / genetics
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Tumor Necrosis Factor-alpha / metabolism*
Substances
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DNA-Binding Proteins
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Early Growth Response Protein 1
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Egr1 protein, mouse
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Enzyme Inhibitors
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Flavonoids
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Immediate-Early Proteins
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Lipopolysaccharides
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RNA, Messenger
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Transcription Factors
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Tumor Necrosis Factor-alpha
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one