Background. Nuclear factor-kappa B (NF-kB) and p38 mitogen-activated protein kinase (MAPK) are critical intracellular signal transduction pathways that mediate the systemic inflammatory response syndrome. Antibiotics induce bacterial lysis, which also contributes to cytokine production and the inflammatory response by activating NF-KB and p38 kinase. In this study, we set out to examine the effects of inhibition of p38 MAPK and NF-kB translation in in vivo models of sepsis.Materials and methods. Intraperitoneal lipopolysaccharide (30 mg/kg), tail vein injection of bacteria (Staphylococcus aureus + Salmonella Typhimurium, 5 x 10(7) colony forming units/kg) and cecal ligation and puncture (CLP) with or without antibiotics (Augmentin, 100 mg/kg) were the septic models used. Animals received control, SB-202190 (a p38 inhibitor), or SN-50 (an NF-kB inhibitor), and mortality was assessed by log-rank analysis. Blood was collected at different time points for cytokine analysis, and splenic tissue was used for cytoplasmic protein extraction to assess kinase activation.Results. SB-202190 and SN-50 resulted in significant survival benefit in the lipopolysaccharide model (P = 0.0006) but not bacterial or CLP models (P = 0.9 and 0.3, respectively). SB-202190 and SN-50, in combination with antibiotic, resulted in a significant survival benefit in the CLP model (P = 0.0001 and 0.006, respectively). Circulating levels of both tumor necrosis factor-alpha and interleukin-6 were significantly reduced at 2 h (P = 0.047 and 0.036, respectively) and Western blot demonstrated down-regulation of p38 kinase 2 h after CLP in animals treated with p38MAPK, and SN-50 inhibitors in combination with antibiotics.Conclusions. We have demonstrated that p-38 and NF-kB inhibition improve survival in endotoxin shock, whereas the survival benefit in polymicrobial sepsis requires coexistent antibiotic treatment. (c) 2009 Elsevier Inc. All rights reserved.