Activation of peroxisome proliferator-activated receptor gamma inhibits interleukin-1beta-induced membrane-associated prostaglandin E2 synthase-1 expression in human synovial fibroblasts by interfering with Egr-1.
Membrane-associated prostaglandin (PG) E(2) synthase-1 (mPGES-1) catalyzes the conversion of PGH(2) to PGE(2), which contributes to many biological processes. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor and plays an important role in growth, differentiation, and inflammation in different tissues. Here, we examined the effect of PPARgamma ligands on interleukin-1beta (IL-1beta)-induced mPGES-1 expression in human synovial fibroblasts. PPARgamma ligands 15-deoxy-Delta(12,14) prostaglandin J(2) (15d-PGJ(2)) and the thiazolidinedione troglitazone (TRO), but not PPARalpha ligand Wy14643, dose-dependently suppressed IL-1beta-induced PGE(2) production, as well as mPGES-1 protein and mRNA expression. 15d-PGJ(2) and TRO suppressed IL-1beta-induced activation of the mPGES-1 promoter. Overexpression of wild-type PPARgamma further enhanced, whereas overexpression of a dominant negative PPARgamma alleviated, the suppressive effect of both PPARgamma ligands. Furthermore, pretreatment with an antagonist of PPARgamma, GW9662, relieves the suppressive effect of PPARgamma ligands on mPGES-1 protein expression, suggesting that the inhibition of mPGES-1 expression is mediated by PPARgamma. We demonstrated that PPARgamma ligands suppressed Egr-1-mediated induction of the activities of the mPGES-1 promoter and of a synthetic reporter construct containing three tandem repeats of an Egr-1 binding site. The suppressive effect of PPARgamma ligands was enhanced in the presence of a PPARgamma expression plasmid. Electrophoretic mobility shift and supershift assays for Egr-1 binding sites in the mPGES-1 promoter showed that both 15d-PGJ(2) and TRO suppressed IL-1beta-induced DNA-binding activity of Egr-1. These data define mPGES-1 and Egr-1 as novel targets of PPARgamma and suggest that inhibition of mPGES-1 gene transcription may be one of the mechanisms by which PPARgamma regulates inflammatory responses.
Cheng
Saranette
S
Osteoarthritis Research Unit, Centre Hospitalier de l'Université de Montréal, Hôpital Notre-Dame, Canada.
Afif
Hassan
H
Martel-Pelletier
Johanne
J
Pelletier
Jean-Pierre
JP
Li
Xinfang
X
Farrajota
Katherine
K
Lavigne
Martin
M
Fahmi
Hassan
H
D020816:Amino Acid Motifs; D000813:Anilides / Q000494:pharmacology; D001665:Binding Sites; D015153:Blotting, Western; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D002839:Chromans / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D051766:Early Growth Response Protein 1; D005347:Fibroblasts / Q000378:metabolism*; D005799:Genes, Dominant; D017930:Genes, Reporter; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D007155:Immunologic Factors / Q000494:pharmacology; D007249:Inflammation; D007375:Interleukin-1 / Q000378:metabolism*; D019746:Intramolecular Oxidoreductases / Q000096:biosynthesis*; D008024:Ligands; D020025:Peroxisome Proliferators / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D015230:Prostaglandin D2 / Q000031:analogs & derivatives / Q000378:metabolism; D000071876:Prostaglandin-E Synthases; D011485:Protein Binding; D011743:Pyrimidines / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013583:Synovial Membrane / Q000166:cytology*; D045162:Thiazolidinediones / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D000077288:Troglitazone
C097240:15-deoxy-delta(12,14)-prostaglandin J2; C457499:2-chloro-5-nitrobenzanilide; D000813:Anilides; D002839:Chromans; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D007155:Immunologic Factors; D007375:Interleukin-1; D008024:Ligands; D020025:Peroxisome Proliferators; D011743:Pyrimidines; D018160:Receptors, Cytoplasmic and Nuclear; D045162:Thiazolidinediones; D014157:Transcription Factors; D012313:RNA; C006253:pirinixic acid; D019746:Intramolecular Oxidoreductases; C000605862:PTGES protein, human; D000071876:Prostaglandin-E Synthases; D000077288:Troglitazone; D015230:Prostaglandin D2