Abstract
Tissue factor (TF) has been shown to be up-regulated in endothelial cells by the inflammatory cytokine tumor necrosis factor alpha (TNF-alpha) as well as by the main angiogenic factor VEGF. Since both stimuli induce the transcription factor EGR-1, which is critically involved in TF gene regulation, we used EGR-1-dependent TF induction as a model to identify potential cross-talks between the various signal transduction cascades initiated by VEGF and TNF-alpha. The data show that at the MAP kinase level, VEGF mainly activates ERK1/2 and p38 MAP kinases in human endothelial cells. TNF-alpha is able to activate all three MAP kinase cascades as well as the classical inflammatory IkappaB/NFkappaB pathway. Furthermore, the MEK/ERK module of MAP kinases appears to act as the convergence point of VEGF- and TNF-alpha-initiated signaling cascades, which lead to the activation of EGR-1 and subsequent TF expression, whereas the upstream signals are distinct. We found that induction of TF by VEGF via EGR-1 is strongly PKC dependent. The TNF-alpha-initiated MEK/ERK cascade connected to EGR-1 and TF expression is clearly less sensitive to PKC inhibition. TNF-alpha-mediated activation of MEK/ERK and EGR-1 can be blocked by adenoviral expression of a dominant negative mutant of IKK2, whereas the VEGF signaling pathway is unaffected. Thus, our data demonstrate a new link between the classical inflammatory IKK/IkappaB and the MEK/ERK cascades triggered by TNF-alpha. The additional finding that EGF induces ERK and EGR-1 in a PKC-independent manner and that this signal is not sufficient to up-regulate TF emphasizes the importance of a VEGF-specific signaling pattern for the induction of TF.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Cells, Cultured
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DNA-Binding Proteins / metabolism*
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Early Growth Response Protein 1
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Endothelial Growth Factors / pharmacology*
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Endothelium, Vascular / cytology
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Endothelium, Vascular / drug effects*
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Endothelium, Vascular / metabolism
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Enzyme Activation / drug effects
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Epidermal Growth Factor / pharmacology
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Flavonoids / pharmacology
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Genes, Dominant
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Humans
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I-kappa B Kinase
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Immediate-Early Proteins*
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Lymphokines / pharmacology*
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MAP Kinase Signaling System / drug effects*
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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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Mutation / genetics
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Protein Kinase C / antagonists & inhibitors
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Protein Kinase C / metabolism
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Receptor Cross-Talk / drug effects*
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Receptor Protein-Tyrosine Kinases / metabolism
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Receptors, Growth Factor / metabolism
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Receptors, Vascular Endothelial Growth Factor
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Substrate Specificity
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Tetradecanoylphorbol Acetate / pharmacology
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Thromboplastin / metabolism*
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Transcription Factors / metabolism*
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Tumor Necrosis Factor-alpha / pharmacology*
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Umbilical Veins
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Up-Regulation / drug effects
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Vascular Endothelial Growth Factor A
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Vascular Endothelial Growth Factors
Substances
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DNA-Binding Proteins
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EGR1 protein, human
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Early Growth Response Protein 1
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Endothelial Growth Factors
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Flavonoids
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Immediate-Early Proteins
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Lymphokines
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Receptors, Growth Factor
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Transcription Factors
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Tumor Necrosis Factor-alpha
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Vascular Endothelial Growth Factor A
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Vascular Endothelial Growth Factors
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Epidermal Growth Factor
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Thromboplastin
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Receptor Protein-Tyrosine Kinases
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Receptors, Vascular Endothelial Growth Factor
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Protein Serine-Threonine Kinases
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CHUK protein, human
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I-kappa B Kinase
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IKBKB protein, human
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IKBKE protein, human
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Protein Kinase C
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Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinase Kinases
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Tetradecanoylphorbol Acetate
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2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one