Prostaglandin metabolite 15-Deoxy-Delta (12.14)-prostaglandin J2 (15d-PGJ2) is known to inhibit a number of pro-inflammatory cytokines as well as being a ligand for nuclear receptor PPAR gamma. We investigated the ability of 15d-PGJ2 to inhibit TNF-alpha gene expression through mechanisms that involve histone modification. Pretreatment with 15d-PGJ2 (10 mu M) inhibited LPS-stimulated TNF-alpha mRNA in THP-1 monocytes or PMA-differentiated cells to nearly basal levels. A specific PPAR gamma ligand, GW1929, failed to inhibit LPS-induced TNF-alpha mRNA expression nor did a PPAR gamma antagonist, GW9662, alter the repression of TNF-alpha mRNA in LPS-stimulated cells pretreated with 15d-PGJ2 suggesting a PPA R gamma-indepen dent inhibition of TNF-alpha mRNA in THP-1 cells. Transfection studies with a reporter construct and subsequent treatment with 15d-PGJ2 demonstrated a dose-dependent inhibition of the TNF-alpha promoter. Additional studies demonstrated that inhibition of histone deacetylases with trichostatin A (TSA) or overexpression of histone acetyltransferase CBP could overcome 15d-PGJ2-mediated repression of the TNF-a promoter, suggesting that an important mechanism whereby 15d-PGJ2 suppresses a cytokine is through factors that regulate histone modifications. To examine the endogenous TNF-alpha promoter, chromatin imm u no precipitations (ChIP) were performed. ChIP assays demonstrated that LPS stimulation induced an increase in historic H3 and H4 acetylation at the TNF-alpha promoter, which was reduced in cells pretreated with 15d-PGJ2. These results highlight the ability of acetylation and deacetylation factors to affect the TNF-a promoter and demonstrate that an additional important mechanism whereby 15d-PGJ2 mediates TNF-alpha transcriptional repression by altering levels of acetylated historic H3 and H4 at its promoter. (C) 2007 Elsevier Inc. All rights reserved.