Compound 9a, a novel synthetic histone deacetylase inhibitor, protects against septic injury in mice by suppressing MAPK signalling

Background and Purpose Sepsis is a life-threatening clinical condition characterized by uncontrolled inflammatory responses and is a major cause of death in intensive care units. Histone deacetylase (HDAC) inhibitors have recently exhibited anti-inflammatory properties. MAPK phosphatase (MKP) suppresses MAPK signalling, which plays an important role in inflammatory responses. The purpose of this study was to investigate the protective mechanisms of Compound 9a, a newly synthetized HDAC inhibitor, against septic injury. Experimental Approach The anti-inflammatory properties of Compound 9a were assayed in LPS-stimulated RAW264.7 cells. In vivo, polymicrobial sepsis was induced in C57BL/6 mice by caecal ligation and puncture (CLP). The mice were treated with Compound 9a (i.p., 10 mgkg^-1) 2 h before and immediately after CLP. Key Results Compound 9a inhibited the increased production of TNF-α, IL-6 and NO in LPS-stimulated RAW264.7 cells. In mice with CLP, Compound 9a improved survival rate, attenuated organ injuries and decreased serum TNF-α and IL-6 levels. CLP increased expression of toll-like receptor 4, phosphorylated (p)-p38, p-JNK and p-ERK proteins, which was attenuated by Compound 9a. Compound 9a decreased MKP-1 association with HDAC1 and enhanced MKP-1 acetylation and enhanced MKP-1 association with p-p38 and p-ERK. Moreover, the inhibitory effects of Compound 9a on serum cytokine levels and phosphorylation of MAPK were abolished by MKP-1 siRNA. Conclusions and Implications Our findings suggest that Compound 9a protected against septic injury by suppressing MAPK-mediated inflammatory signalling.