Artemisinin protects mice against burn sepsis through inhibiting NLRP3 inflammasome activation.

BACKGROUND: NLRP3 inflammasome activation is recently reported to be linked to the pathogenesis of sepsis. Artemisinin is shown to play beneficial effects in sepsis. However, the impacts of artemisinin on burn sepsis have not been investigated. This study is designed to investigate the role of artemisinin in burn sepsis and the involvement of NLRP3 inflammasome activation. METHODS: Male BALB/c mice were randomly divided into sham burn, burn, burn sepsis, and artemisinin treated groups. Inflammatory cytokines were measured by enzyme-linked immunosorbent assay. Adhesion molecules and neutrophil infiltration in lung and heart were detected by real-time polymerase chain reaction. Mortality rates were monitored. Artemisinin was added to Raw 264.7 cells that were stimulated with burn sepsis serum in the presence/absence of an inhibitor of NLRP3 inflammasome, 3, 4-methylenedioxy-ß-nitrostyrene. Interleukin (IL) 1ß and IL-18 messenger RNA expression as well as NLRP3 and caspase 1 protein were measured. RESULTS: Production of inflammatory cytokines in serum, levels of adhesion molecules and neutrophil infiltration in lung and heart, and mortality rate of burn septic mice were significantly higher than those of control. These effects were attenuated by artemisinin. Artemisinin down-regulated protein levels of NLRP3 and caspase 1 and inhibited the increases of IL-1ß and IL-18 messenger RNA expression from Raw 264.7 cells that were stimulated with burn sepsis serum. These effects of artemisinin were not further strengthened in the presence of 4-methylenedioxy-ß-nitrostyrene. CONCLUSION: Artemisinin protects mice from burn sepsis by attenuating the inflammatory response and alleviating inflammatory infiltration in vital organs, likely through inhibiting the activation of NLRP3 inflammasome.

Metallothionein ameliorates burn sepsis partly via activation of Akt signaling pathway in mice: a randomized animal study.

INTRODUCTION: Metallothioneins (MTs) are a family of cysteine-rich and low molecular-weight proteins that can regulate metal metabolism and act as antioxidants. Recent studies showed that MTs played a protective role in excessive inflammation and sepsis. However, the role of MTs in burn sepsis remains unclear. This study is designed to investigate the role of MTs in burn sepsis in an experimental mouse model. METHODS: MT-I/II knockout (-/-) mice on a C57BL/6 background and their wild-type (WT) littermates were randomly divided into sham burn, burn, burn sepsis, Zn treated and Zn-MT-2 treated groups. Levels of inflammatory cytokines were measured by enzyme-linked immunosorbent assay (ELISA). Myeloperoxidase (MPO) activity was detected by spectrophotometry. In in vitro study, exogenous MT was added to macrophages that stimulated with serum from burn sepsis mice with or without Akt inhibitor LY294002. The IL-1 ß and IL-6 mRNA expression were detected by quantitative real-time polymerase chain reaction. The levels of Akt expression were determined by western blot. RESULTS: Burn sepsis induced significantly elevated levels of inflammatory cytokines in serum and increased inflammatory infiltration in the liver and lung. These effects were more prominent in MT (-/-) mice than in WT mice. Furthermore, exogenous MT-2 inhibited these elevated inflammatory response in both WT and MT (-/-) mice. MT-2 up-regulated Akt phosphorylation and abrogated the increase of IL-1ß and IL-6 mRNA expression from macrophages that stimulated with burn sepsis serum. These effects of MT-2 were abolished in the presence of LY294002. CONCLUSION: MT-2 ameliorates burn sepsis by attenuating inflammatory response and diminishing inflammatory organ damage, which is at least partly mediated by activation of Akt signaling pathway.

Apelin attenuates postburn sepsis via a phosphatidylinositol 3-kinase/protein kinase B dependent mechanism: A randomized animal study.

INTRODUCTION: This study aims to investigate whether apelin would regulate inflammatory response and promote survival in an experimental burn sepsis model through a phosphatidylinositol 3-kinase/protein kinase B dependent pathway. METHODS: Male BALB/c mice were divided into the following groups: sham, burn, burn sepsis, burn sepsis treated with apelin, burn sepsis treated with apelin plus LY294002, and burn sepsis treated with LY294002 alone. Apelin level and inflammatory cytokines in serum were detected by enzyme-linked immuno sorbent assay. Apelin/APJ (apelin receptor, gene symbol APLNR) mRNA expression in spleen and adhesion molecules levels in lung was detected by real-time polymerase chain reaction. Neutrophil infiltration in lung was determined by myeloperoxidase assay. Phosphorylation of protein kinase B in lung was determined by western blot. Mortality rate was monitored. RESULTS: Burn sepsis induced decreased apelin/APJ mRNA expression in spleen and reduced apelin level in plasma, which were both restored by exogenous apelin treatment. Burn sepsis treated with apelin resulted in decreased interleukin-6, tumor-necrosis factor-alpha, interleukin -1ß and monocyte chemotactic protein-1 levels in plasma. Mice with apelin treatment also showed decreased neutrophil infiltration and adhesion molecules expression, accompanied by a remarkable increased protein kinase B phosphorylation in lung tissue. The mortality rate in apelin treated animals was also significantly reduced. Importantly, the above effects of apelin were abolished by LY294002 treatment. CONCLUSION: Apelin regulates inflammatory response, diminishes inflammatory remote organ damage and improves survival in an experimental model of burn sepsis, which is at least partly mediated by a phosphatidylinositol 3-kinase/protein kinase B dependent pathway.