Abstract
The molecular mechanisms that drive expression of the alarmin interleukin-33 (IL-33) in endothelial cells are unknown. Because nuclear IL-33 is a marker of endothelial cell quiescence (corroborated in this study by coexpression of cyclin-dependent kinase inhibitor p27(Kip1)), we hypothesized that Notch signaling might be involved in regulating IL-33 expression. Activation of Notch1 by immobilized Notch ligands was sufficient to induce nuclear IL-33 expression in cultured endothelial cells. Conversely, IL-33 expression was inhibited by the γ-secretase inhibitor DAPT or by inhibiting the function of Dll4, Jagged1, Notch1, or the canonical Notch transcription factor RBP-Jκ. Insensitivity to cycloheximide indicated that IL-33 was a direct target of Notch signaling, well in line with the identification of several conserved RBP-Jκ binding sites in the IL33 gene. The in vivo expression of Dll4 but not of Jagged1 was well correlated with expression of IL-33 in quiescent vessels, and subcutaneous injection of DAPT in healthy skin reduced IL-33 expression, indicating that Notch signaling was involved. On the other hand, loss of IL-33 during angiogenesis occurred despite sustained Dll4 and Notch1 expression, suggesting that other signals may override the IL-33-driving signal in this context. Taken together, our data demonstrate that endothelial nuclear IL-33 is induced by Notch and that Dll4 may be the dominant ligand responsible for this signaling in vivo.
Copyright © 2012 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing
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Amyloid Precursor Protein Secretases / antagonists & inhibitors
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Amyloid Precursor Protein Secretases / metabolism
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Animals
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Binding Sites
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Biomarkers / metabolism
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Calcium-Binding Proteins / metabolism
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Cell Nucleus / drug effects
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Cell Nucleus / metabolism
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Dipeptides / pharmacology
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Down-Regulation / drug effects
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Down-Regulation / genetics
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Endothelial Cells / cytology*
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Endothelial Cells / drug effects
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Endothelial Cells / enzymology
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Endothelial Cells / metabolism*
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Female
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Genetic Loci / genetics
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Genome, Human / genetics
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Human Umbilical Vein Endothelial Cells / metabolism
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Humans
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Immunoglobulin J Recombination Signal Sequence-Binding Protein / metabolism
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Intercellular Signaling Peptides and Proteins / metabolism
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Interleukin-33
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Interleukins / genetics
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Interleukins / metabolism*
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Jagged-1 Protein
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Male
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Membrane Proteins / metabolism
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Neovascularization, Physiologic / drug effects
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Neovascularization, Physiologic / genetics
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Protein Binding / drug effects
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Rats
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Rats, Wistar
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Receptor, Notch1 / antagonists & inhibitors
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Receptor, Notch1 / metabolism*
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Serrate-Jagged Proteins
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Signal Transduction / drug effects
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Signal Transduction / genetics
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Wound Healing / drug effects
Substances
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Adaptor Proteins, Signal Transducing
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Biomarkers
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Calcium-Binding Proteins
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DLL4 protein, human
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Dipeptides
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IL33 protein, human
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Immunoglobulin J Recombination Signal Sequence-Binding Protein
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Intercellular Signaling Peptides and Proteins
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Interleukin-33
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Interleukins
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JAG1 protein, human
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Jag1 protein, rat
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Jagged-1 Protein
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Membrane Proteins
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N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester
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Receptor, Notch1
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Serrate-Jagged Proteins
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Amyloid Precursor Protein Secretases