15-Deoxy- Delta super(1) super(2) super(,) super(1) super(4)-prostaglandin J2 (15d-PGJ2) mediates repression of TNF- alpha by decreasing levels of acetylated histone H3 and H4 at its promoter

Prostaglandin metabolite 15-Deoxy- Delta super(1) super(2) super(,) super(1) super(4)-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 PPAR gamma -independent 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- alpha 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 immunoprecipitations (ChIP) were performed. ChIP assays demonstrated that LPS stimulation induced an increase in histone 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- alpha promoter and demonstrate that an additional important mechanism whereby 15d-PGJ2 mediates TNF- alpha transcriptional repression by altering levels of acetylated histone H3 and H4 at its promoter.