PPARgamma agonists inhibit angiogenesis by suppressing PKCalpha- and CREB-mediated COX-2 expression in the human endothelium.
OBJECTIVE
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.


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.


CONCLUSIONS
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.
Scoditti
Egeria
E
CNR Institute of Clinical Physiology, Lecce, Italy.
Massaro
Marika
M
Carluccio
Maria Annunziata
MA
Distante
Alessandro
A
Storelli
Carlo
C
De Caterina
Raffaele
R
D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000813:Anilides / Q000494:pharmacology; D001559:Benzhydryl Compounds; D001577:Benzophenones / Q000494:pharmacology*; D001665:Binding Sites; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015536:Down-Regulation; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology; D004852:Epoxy Compounds / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D009578:Nitrobenzenes / Q000494:pharmacology; D047495:PPAR gamma / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D021381:Protein Transport; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D000077154:Rosiglitazone; D013449:Sulfonamides / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D045162:Thiazolidinediones / Q000494:pharmacology*; D014162:Transfection; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D000098826:Bisphenol A Compounds
D020533:Angiogenesis Inhibitors; D000813:Anilides; D001559:Benzhydryl Compounds; D001577:Benzophenones; D017362:Cyclic AMP Response Element-Binding Protein; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D004852:Epoxy Compounds; D009578:Nitrobenzenes; D047495:PPAR gamma; D051571:Protein Kinase C-alpha; D012333:RNA, Messenger; D000077154:Rosiglitazone; D013449:Sulfonamides; D013755:Tetradecanoylphorbol Acetate; D045162:Thiazolidinediones; D014443:Tyrosine; D042461:Vascular Endothelial Growth Factor A; C457499:2-chloro-5-nitrobenzanilide; C115163:CREB1 protein, human; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; C496540:PTGS2 protein, human; C496628:PRKCA protein, human; C019273:bisphenol A diglycidyl ether; D000098826:Bisphenol A Compounds; C120099:GW 1929