Redox imbalance provokes deactivation of macrophages in sepsis

Abstract

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 H(2) O(2) -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 H(2) O(2) -treated macrophages demonstrated decreased cytokine release, whereas TLR4 expression was up-regulated. Western blot analysis showed decreased levels of phosphorylation of MAP kinases and IκB. Electrophoretic mobility shift assay analysis demonstrated attenuated DNA-binding activities of AP-1 and NF-κB, 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.