Histone deacetylase inhibitor KBH-A42 inhibits cytokine production in RAW 264.7 macrophage cells and in vivo endotoxemia model

In light of the anti-inflammatory properties of histone deacetylase (HDAC) inhibitors, such as suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA), we examined a new HDAC inhibitor KBH-A42 for its anti-inflammatory activities. KBH-A42 showed noteworthy anti-inflammatory properties in vitro via suppression of the production of TNF-α, a proinflammatory cytokine, and nitric oxide (NO), a proinflammatory effector molecule, in LPS-stimulated RAW264.7 cells and peritoneal macrophages. It also inhibited TNF-α production in vivo as demonstrated in a LPS-induced mouse endotoxemia model. The levels of TNF-α, IL-1β, IL-6 and iNOS mRNAs determined by RT-PCR propose that the inhibition of these pro-inflammatory mediators by KBH-A42 resulted from inhibiting expression of these genes. However, the EMSA study to see the effect of KBH-A42 on the binding of NF-κB, a transcription factor, to a specific DNA sequence showed that the binding of NF-κB to DNA was not changed regardless of increasing the concentration of KBH-A42 in the presence and absence of LPS stimulation. Interestingly, DNA binding of another transcription factor AP-1 dose-dependently increased by KBH-A42. KBH-A42 differentially regulated the phosphorylation of MAP kinases. While the phosphprylation of ERK1/2 and SAPK/JNK was not affected by KBH-A42, the phosphorylation of p38 decreased by KBH-A42. These results showed that KBH-A42 inhibits production of proinflammatory cytokines in macrophages by decreasing their mRNA levels, and p38 kinase is involved in the KBH-A42-mediated inhibition.