Abstract
Aims:
The activation of peroxisome proliferator-activated receptor (PPAR)gamma is known to inhibit angiogenesis. As a potential mechanism for this, we aimed at examining the effects of PPARgamma agonists on the pro-angiogenic enzyme cyclooxygenase (COX)-2 in human endothelium.
Methods and results:
Cultured endothelial cells were pre-incubated with the PPARgamma agonists rosiglitazone (RSG) or GW1929 before stimulation with vascular endothelial growth factor (VEGF) or phorbol myristate acetate (PMA). RSG and GW1929 attenuated VEGF- and PMA-stimulated COX-2 activity, as well as protein and mRNA expression. This effect was abolished by the PPARgamma antagonists bisphenol A diglycidyl ether and GW9662 as well as by PPARgamma small-interfering RNAs (siRNAs). Transient transfection experiments revealed that the induction of COX-2 promoter was significantly inhibited by RSG through an interference with the cAMP response element (CRE) site. COX-2 downregulation after siRNA targeting CRE-binding protein (CREB) confirmed the role of CREB in mediating COX-2 transcription. Correspondingly, PPARgamma agonists attenuated CREB activation. As both protein kinase C (PKC)alpha and beta are involved in VEGF-induced COX-2 expression and CREB activation, we investigated which isoform(s) of PKC was affected by RSG. RSG only reduced VEGF- and PMA-stimulated PKCalpha membrane translocation.
Conclusion:
VEGF induces CREB-mediated COX-2 expression through a PKCalpha-dependent pathway in human endothelium. The anti-angiogenic effect of PPARgamma agonists is due, at least in part, to an interference with the VEGF-stimulated PKCalpha-mediated activation of CREB and the related expression of COX-2.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Angiogenesis Inhibitors / pharmacology*
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Anilides / pharmacology
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Benzhydryl Compounds
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Benzophenones / pharmacology*
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Binding Sites
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Cells, Cultured
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Cyclic AMP Response Element-Binding Protein / genetics
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Cyclic AMP Response Element-Binding Protein / metabolism*
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Cyclooxygenase 2 / genetics
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Cyclooxygenase 2 / metabolism*
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Cyclooxygenase 2 Inhibitors / pharmacology
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Down-Regulation
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Endothelial Cells / drug effects*
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Endothelial Cells / enzymology
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Epoxy Compounds / pharmacology
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Gene Expression Regulation, Enzymologic / drug effects
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Humans
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Neovascularization, Physiologic / drug effects*
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Nitrobenzenes / pharmacology
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PPAR gamma / agonists*
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PPAR gamma / antagonists & inhibitors
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PPAR gamma / genetics
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PPAR gamma / metabolism
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Promoter Regions, Genetic / drug effects
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Protein Kinase C-alpha / metabolism*
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Protein Transport
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RNA Interference
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RNA, Messenger / metabolism
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Rosiglitazone
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Sulfonamides / pharmacology
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Tetradecanoylphorbol Acetate / pharmacology
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Thiazolidinediones / pharmacology*
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Transfection
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Tyrosine / analogs & derivatives*
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Tyrosine / pharmacology
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Vascular Endothelial Growth Factor A / metabolism
Substances
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2-chloro-5-nitrobenzanilide
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Angiogenesis Inhibitors
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Anilides
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Benzhydryl Compounds
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Benzophenones
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CREB1 protein, human
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Cyclic AMP Response Element-Binding Protein
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Cyclooxygenase 2 Inhibitors
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Epoxy Compounds
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Nitrobenzenes
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PPAR gamma
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RNA, Messenger
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Sulfonamides
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Thiazolidinediones
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Vascular Endothelial Growth Factor A
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Rosiglitazone
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N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide
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Tyrosine
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Cyclooxygenase 2
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PTGS2 protein, human
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PRKCA protein, human
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Protein Kinase C-alpha
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2,2-bis(4-glycidyloxyphenyl)propane
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Tetradecanoylphorbol Acetate
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GW 1929