Redox imbalance provokes deactivation of macrophages in sepsis

Sepsis accounts for the majority of deaths in critically ill patients. Symptoms of septic disease are often associated with monocyte/macrophage desensitization. In the current study, impaired macrophage function was determined in a sepsis mouse model with decreased cytokine release and weak phagocytosis, coinciding with ectopic elevation of serum-ROS levels. Furthermore, in the experimental cell model, RAW264.7 macrophages displayed a deactivated phenotype, characterized by impaired inflammatory and phagocytosis function. Cellular anti-oxidative proteins were further investigated; lipopolysaccharide (LPS)- and H2O2-treated cells exhibited lower ratio of reductive-to-oxidized glutathione as compared with LPS-treated cells only, without inducing cell death. 2-DE and MALTI-TOF/TOF were employed to illustrate protein expression differentiation patterns. A total of 33 proteins were found to be differently expressed Among them, 33% of proteins were associated with oxidative stress. We further investigated the role of the ROS/LPS/Toll-like receptor 4 (TLR4) axis in modulating the immunosuppression during sepsis. LPS- and H2O2-treated macrophages demonstrated decreased cytokine release, whereas TLR4 expression was upregulated. Western blot analysis showed decreased levels of phosphorylation of MAP kinases and I kappa B. Electrophoretic mobility shift assay analysis demonstrated attenuated DNA-binding activities of AP-1 and NF-kappa B, as compared with those of their control. Collectively, these findings indicate that ROS mediates critical aspects of innate immunity that result in an immunocompromised state through an imbalance of cellular oxidation/reduction during sepsis.