Histone deacetylase inhibitors suppress interleukin-1β-induced nitric oxide and prostaglandin E2 production in human chondrocytes

Objective: Overproduction of nitric oxide (NO) and prostaglandin E-2 (PGE(2)) plays an important role in the pathogenesis of osteoarthritis (OA). In the present study. we determined the effect of trichostatin A (TSA) and butyric acid (BA), two histone deacetylase (HDAC) inhibitors, on NO and PGE2 synthesis, inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 expression, and nuclear factor (NF)-kappa B DNA-binding activity, in interleukin-1 beta (IL-1)-stimulated human OA chondrocytes, and on IL-1-induced proteoglycan degradation in cartilage explants. Methods: Chondrocytes were stimulated with IL-1 in the absence or presence of increasing concentrations of TSA or BA. The production of NO and PGE2 was evaluated using Griess reagent and an enzyme immunoassay, respectively. The expression of iNOS and COX-2 proteins and mRNAs was evaluated using Western blotting and real-time reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. Proteoglycan degradation was measured with dimethymethylene blue assay. Electrophoretic mobility shift assay (EMSA) was utilized to analyze the DNA-binding activity of NF-kappa B. Results: HDAC inhibition with TSA or BA resulted in a dose-dependent inhibition of IL-1-induced NO and PGE2 production. IL-17- and tumor necrosis factor-alpha (TNF-alpha)-induced NO and PGE(2) production was also inhibited by TSA and BA. This inhibition correlated with the suppression of iNOS and COX-2 protein and mRNA expression. TSA and BA also prevented IL-1-induced proteoglycan release from cartilage explants. Finally, we demonstrate that the DNA-binding activity of NF-kappa B, was induced by IL-1, but was not affected by treatment with HDAC inhibitors. Conclusions: These data indicate that HDAC inhibitors suppressed IL-1-induced NO and PGE2 synthesis, iNOS and COX-2 expression, as well as proteoglycan degradation. The suppressive effect of HDAC inhibitors is not due to impaired DNA-binding activity of NF-kappa B. These findings also suggest that HDAC inhibitors may be of potential therapeutic value in the treatment of OA. (D 2008 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.