Ketamine inhibits LPS-induced HGMB1 release in vitro and in vivo

High mobility group box 1 (HMGB1) has been identified to be a critical mediator of severe sepsis. Ketamine has been shown to reduce sepsis-induced pathological complications. These effects are because of the reduced expression and release of several inflammatory mediators. However, whether ketamine affects the expression and release of HMGB1 is not known. We investigated the effect of ketamine on HMGB1 release in lipopolysaccharide (LPS)-induced macrophages in vitro and in cecal ligation and puncture (CLP)-induced septic rats in vivo, and determined its molecular mechanism of action. RAW264.7 cells or primary macrophages were incubated with or without LPS (500 ng/mL) in the presence or absence of ketamine, a p38 mitogen-activated protein kinase (p38 MAPK) inhibitor (SB203580), a nuclear factor-kappa B (NF-κB) inhibitor (pyrimidine dithiocarbamate), or small interfering RNA. The protein and expression levels of inflammatory mediators, such as HMGB1, tumor necrosis factor-α, and interleukin-1β were measured using enzyme-linked immunosorbent assays and real-time polymerase chain reaction. The effect of ketamine on NF-κB and p38 MAPK activation was evaluated using enzyme-linked immunosorbent assays, Western blot analysis, and electrophoretic mobility shift assay. Western blotting was used to observe changes in translocation of HMGB1 from the nucleus to cytoplasm. In addition, CLP-induced septic rats were treated with ketamine (0.5, 5, 10 mg/kg) or saline (10 mL/kg) 3h after sepsis, and the levels of HMGB1 and functional parameters of multiple organs were determined using several detection kits. Seven-day survival was also assessed. Ketamine inhibited HMGB1 release in LPS-activated RAW264.7 cells and CLP-induced septic rats. Translocation of HMGB1 from the nucleus to cytosol and expression of HMGB1 mRNA were inhibited significantly by ketamine. Ketamine inhibited the translocation of NF-κB from the cytoplasm to the nucleus and phosphorylation of p38 MAPK in LPS-activated RAW264.7 cells. Rats treated with ketamine improved survival in rats and significantly reduced CLP-induced dysfunction/injury of organs. Ketamine suppresses LPS-induced HMGB1 release in LPS-activated RAW264.7 cells and a CLP-induced model of sepsis in rats by partially inhibiting NF-κB/p38 MAPK pathways. Ketamine increased survival time induced by CLP and reduced organ dysfunction in septic peritonitis.