Inhibition of LPS-induced C/EBPδ by trichostatin A has a positive effect on LPS-induced cyclooxygenase 2 expression in RAW264.7 cells

Cyclooxygenase 2 (COX-2) is an important inflammatory factor. Previous studies have indicated that COX-2 is induced with lipopolysaccharide (LPS) treatment. Here, we found that an inhibitor of histone deacetylase (HDAC), trichostatin A (TSA), cannot repress LPS-induced COX-2 but it increased the COX-2 level in RAW264.7 cells. We found no significant difference in NF-κB activation and ERK1/2 phosphorylation, but LPS-induced C/EBPδ expression was completely abolished after TSA treatment of LPS-treated cells. Interesting, reporter assay of C/EBPδ promoter revealed that Sp1-binding site is important. Although there was no alteration in c-Jun levels, but the phosphorylation of c-Jun at its C-terminus was increased dramatically. A DNA-associated protein assay (DAPA) and chromatin immuno-precipitation assay (ChIP) indicated that c-Jun was recruited via Sp1 to the promoter of C/EBPδ after LPS treatment; this recruitment of c-Jun was repressed by TSA. C/EBPδ inhibition by TSA resulted in increased binding of C/EBPα and C/EBPβ to the COX-2 promoter. Therefore, TSA has a positive effect on LPS-induced COX-2 since it decreases the C/EBPδ level by reducing c-Jun recruitment by Sp1 to the C/EBPδ promoter, resultinginincreased the recruitment of C/EBPα and C/EBPβ to the COX-2 promoter.