Inhibition of interleukin-1beta-induced cyclooxygenase 2 expression in human synovial fibroblasts by 15-deoxy-Delta12,14-prostaglandin J2 through a histone deacetylase-independent mechanism.
OBJECTIVE
The cyclooxygenase (COX) metabolite, 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), has been reported to inhibit the expression of a number of genes involved in the pathogenesis of arthritis. However, its effects on COX-2 remain controversial. We undertook this study to investigate the effects of 15d-PGJ(2) on interleukin-1beta (IL-1beta)-induced COX-2 expression in human synovial fibroblasts (HSFs).


METHODS
HSFs were cultured with IL-1beta in the absence or presence of 15d-PGJ(2), and the levels of COX-2 protein and messenger RNA (mRNA) expression were evaluated using Western blotting and real-time reverse transcriptase-polymerase chain reaction, respectively. COX-2 promoter activity was analyzed in transient transfection experiments. Chromatin immunoprecipitation assays were performed to evaluate the level of histone acetylation and the recruitment of histone deacetylases (HDACs) 1, 2, and 3 and histone acetylase (HAT) p300 to the COX-2 promoter.


RESULTS
IL-1beta-induced COX-2 protein and mRNA expression, as well as COX-2 promoter activation, were inhibited by 15d-PGJ(2). Troglitazone, a selective peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, enhanced COX-2 expression, while GW9662, a specific PPARgamma antagonist, relieved the suppressive effect of 15d-PGJ(2). IL-1beta-induced histone H3 acetylation was selectively blocked by 15d-PGJ(2). The reduction of histone H3 acetylation did not correlate with the recruitment of HDACs to the COX-2 promoter. Also, treatment with the specific HDAC inhibitor, trichostatin A, did not relieve the suppressive effect of 15d-PGJ(2), indicating that HDACs are not involved in the inhibitory effect of 15d-PGJ(2). Furthermore, 15d-PGJ(2) blocked IL-1beta-induced recruitment of p300 to the COX-2 promoter, which may be the mechanism for decreased histone H3 acetylation and COX-2 expression. In accordance with this, overexpression of p300, but not of a mutant p300 lacking HAT activity, relieved the inhibitory effect of 15d-PGJ(2) on COX-2 promoter activation.


CONCLUSIONS
These data suggest that 15d-PGJ(2) can inhibit IL-1beta-induced COX-2 expression by an HDAC-independent mechanism, probably by interfering with HAT p300.
Farrajota
Katherine
K
Osteoarthritis Research Unit, Centre Hospitalier de l'Université de Montréal, Hôpital Notre-Dame, 1560 Sherbrooke Street East, Montreal, Quebec H2L 4M1, Canada.
Cheng
Saranette
S
Martel-Pelletier
Johanne
J
Afif
Hassan
H
Pelletier
Jean-Pierre
JP
Li
Xinfang
X
Ranger
Pierre
P
Fahmi
Hassan
H
D000107:Acetylation / Q000187:drug effects; D000123:Acetyltransferases / Q000378:metabolism; D000368:Aged; D018797:Cell Cycle Proteins / Q000378:metabolism; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000201:enzymology*; D051548:Histone Acetyltransferases; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins; D008875:Middle Aged; D047495:PPAR gamma / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology; D015230:Prostaglandin D2 / Q000031:analogs & derivatives* / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D013583:Synovial Membrane / Q000166:cytology / Q000201:enzymology*; D014157:Transcription Factors; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor
D000123:Acetyltransferases; D018797:Cell Cycle Proteins; D051546:Cyclooxygenase 2; D004791:Enzyme Inhibitors; D051548:Histone Acetyltransferases; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases; D006657:Histones; D006877:Hydroxamic Acids; D007375:Interleukin-1; D007527:Isoenzymes; D008565:Membrane Proteins; D047495:PPAR gamma; D015230:Prostaglandin D2; D011451:Prostaglandin-Endoperoxide Synthases; D012319:RNA Polymerase II; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C477819:15-deoxyprostaglandin J2; C012589:trichostatin A; C496540:PTGS2 protein, human