Abstract
Lipopolysaccharide (LPS) induces human monocytes to express many proinflammatory mediators, including the procoagulant molecule tissue factor (TF) and the cytokine tumor necrosis factor alpha (TNF-alpha). The TF and TNF-alpha genes are regulated by various transcription factors, including nuclear factor (NF)-kappaB/Rel proteins and Egr-1. In this study, the role of the MEK-ERK1/2 mitogen-activated protein kinase (MAPK) pathway in LPS induction of TF and TNF-alpha gene expression in human monocytic cells was investigated. The MAPK kinase (MEK)1 inhibitor PD98059 reduced LPS induction of TF and TNF-alpha expression in a dose-dependent manner. PD98059 did not affect LPS-induced nuclear translocation of NF-kappaB/Rel proteins and minimally affected LPS induction of kappaB-dependent transcription. In contrast, PD98059 and dominant-negative mutants of the Ras-Raf1-MEK-ERK (extacellular signal-regulated kinase) pathway strongly inhibited LPS induction of Egr-1 expression. In kinetic experiments LPS induction of Egr-1 expression preceded induction of TF expression. In addition, mutation of the Egr-1 sites in the TF and TNF-alpha promoters reduced expression of these proinflammatory genes. It was demonstrated that LPS induction of the Egr-1 promoter was mediated by 3 SRE sites, which bound an LPS-inducible complex containing serum response factor and Elk-1. LPS stimulation transiently induced phosphorylation of Elk-1 and increased the functional activity of a GAL4-Elk-1TA chimeric protein via the MEK-ERK1/2 pathway. The data indicate that LPS induction of Egr-1 gene expression is required for maximal induction of the TNF-alpha and TF genes in human monocytic cells.
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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DNA-Binding Proteins / biosynthesis*
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DNA-Binding Proteins / genetics
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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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Humans
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Immediate-Early Proteins*
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Lipopolysaccharides / pharmacology*
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MAP Kinase Kinase 1
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MAP Kinase Kinase 2
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MAP Kinase Signaling System / drug effects*
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Mitogen-Activated Protein Kinase 1 / antagonists & inhibitors
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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 Kinase Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinase Kinases / metabolism
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Mitogen-Activated Protein Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinases / metabolism
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Monocytes / drug effects*
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Monocytes / enzymology
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NF-kappa B / metabolism
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Phosphorylation / drug effects
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Protein Processing, Post-Translational / drug effects
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Protein Serine-Threonine Kinases / metabolism
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Protein-Tyrosine Kinases / antagonists & inhibitors
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Protein-Tyrosine Kinases / metabolism
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Proto-Oncogene Proteins / metabolism*
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Recombinant Fusion Proteins / metabolism
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Thromboplastin / biosynthesis*
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Thromboplastin / genetics
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Transcription Factors / biosynthesis*
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Transcription Factors / genetics
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Tumor Cells, Cultured
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Tumor Necrosis Factor-alpha / biosynthesis*
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Tumor Necrosis Factor-alpha / genetics
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Tumor Necrosis Factor-alpha / pharmacology
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ets-Domain Protein Elk-1
Substances
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DNA-Binding Proteins
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EGR1 protein, human
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ELK1 protein, human
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Early Growth Response Protein 1
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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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NF-kappa B
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Proto-Oncogene Proteins
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Recombinant Fusion Proteins
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Transcription Factors
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Tumor Necrosis Factor-alpha
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ets-Domain Protein Elk-1
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Thromboplastin
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MAP2K2 protein, human
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Protein-Tyrosine Kinases
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Protein Serine-Threonine Kinases
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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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MAP Kinase Kinase 1
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MAP Kinase Kinase 2
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MAP2K1 protein, human
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Mitogen-Activated Protein Kinase Kinases
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2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one