Beneficial Dysregulation of the Time Course of Inflammatory Mediators in Lipopolysaccharide-Induced Tumor Necrosis Factor Alpha Factor-Deficient Mice

To begin to understand the surprising survival of macrophage-specific lipopolysaccharide-induced tumor necrosis factor alpha factor-deficient (macLITAF−/− ) animals after a lethal dose of lipopolysaccharide (LPS), as reported earlier, the present follow-up study focuses on the role of LITAF in the regulation of inflammatory cytokines secreted in response to lethal or sublethal doses of LPS administered to wild-type (WT) and macLITAF−/− mice. A time course study of kinase expression in peritoneal macrophages revealed increased phosphorylation of prosurvival kinases Akt, Erk1/2, and ribosomal S6 kinase (RSK) in macLITAF−/− mice compared to that in WT mice (n = 8), confirming their role in LPS-mediated diseases. macLITAF−/− mice (n = 8) survived a lethal dose of LPS plusd -galactosamine (d -GalN), expressing lower serum levels of pro- and anti-inflammatory cytokines than the WT levels. To extend our knowledge on LPS-induced inflammatory events, an effective sublethal dose of LPS was administered to the animals (n = 14). WT animals exhibited an acute inflammatory response that decreased after 4 h. Interestingly, macLITAF−/− mice exhibited an initial delay in the secretion of proinflammatory cytokines that peaked after 8 h and reached WT levels after 18 h. Anti-inflammatory cytokine secretions were initially delayed but increased after 4 h and remained elevated compared to WT levels, even after 18 h. Our results demonstrate that LITAF deficiencyin vivo affects cytokines other than TNF-α and influences the balance between the pro- and anti-inflammatory cytokines, which protects the animals from the deleterious effects of an LPS-induced inflammatory response, resulting in a beneficial host regulation of inflammatory cytokines and in enhanced survival. Therapeutic intervention aimed at reducing LITAF via kinase modulators may prove useful in preventing LPS-induced mortality.