ABSTRACT
BACKGROUND: Apart from inducing apoptosis in tumor cells, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) influences inflammatory reactions. Murine colon ascendens stent peritonitis (CASP) represents a model of diffuse peritonitis. Recently, it has been demonstrated that administration of exogenous TRAIL not only induces apoptosis in neutrophils but also enhances survival in this model. The aim of this study was to examine the impact of genetic TRAIL deficiency on the course of CASP. METHODS: Peritonitis was induced in 6- to 8-week-old female TRAIL (-/-) mice as well as in wild-type mice. The sepsis severity score and survival of mice were monitored. Bacterial loads in blood as well as in the lymphoid organs were examined. Additionally, the number of apoptotic cells within the lymphoid organs was determined. RESULTS: As early as 8 hours postinduction of CASP, TRAIL (-/-) mice were significantly more affected by sepsis than wild-type mice, as measured by the sepsis severity score. However, during the further course of sepsis, TRAIL deficiency led to significantly decreased sepsis severity scores, resulting in an enhanced overall survival in TRAIL (-/-) mice. The better survival of TRAIL (-/-) mice was accompanied by a decreased bacterial load within the blood. In marked contrast, the number of apoptotic cells within the lymphoid organs was highly increased in TRAIL (-/-) mice 20 hours after induction of CASP. CONCLUSION: Hence, exogenous and endogenous TRAIL is protective during the early phase of sepsis, while endogenous TRAIL appears to be detrimental in the later course of this disease.
ABSTRACT
TNF-related apoptosis inducing ligand (TRAIL) influences several inflammatory reactions by partially still unknown mechanisms. TRAIL is produced and expressed by several cells of the immune system. Murine Colon Ascendens Stent Peritonitis (CASP) represents a hyperinflammatory model of diffuse peritonitis. As we have shown previously, TRAIL strongly improves survival in murine CASP. This is accompanied by a significantly reduced infiltration of neutrophils in the associated lymphoid tissue. Additionally, it is known that TRAIL induces apoptosis in neutrophils and acceleration of neutrophil apoptosis enhances resolution of inflammatory reactions. In this study, we investigated the correlation of the protective effect of TRAIL in sepsis and its influence on neutrophils. We found that neutrophils infiltrating the lymphoid organs express the TRAIL-receptor DR5 at high density. Furthermore, we demonstrated that TRAIL-treatment enhances apoptosis of neutrophils in the spleen, lung and liver and decreases organ injury during sepsis. To further examine a role for neutrophils in TRAIL-mediated protection in CASP, we have depleted neutrophils 24 hours prior to CASP. In these depleted mice, administration of TRAIL was ineffective. We conclude that TRAIL induces apoptosis in tissue-infiltrating neutrophils thereby protecting organs from sepsis-induced injury.
Subject(s)
Apoptosis/drug effects , Colon/pathology , Neutrophils/pathology , Organ Specificity/drug effects , Peritonitis/pathology , Sepsis/pathology , TNF-Related Apoptosis-Inducing Ligand/pharmacology , Alanine Transaminase/metabolism , Animals , Aspartate Aminotransferases/metabolism , Cell Membrane/drug effects , Cell Membrane/metabolism , Cell Survival/drug effects , Colon/drug effects , Disease Models, Animal , Female , Lipopolysaccharides , Mice, Inbred C57BL , Neutrophils/drug effects , Neutrophils/metabolism , Peritonitis/complications , Receptors, TNF-Related Apoptosis-Inducing Ligand/metabolism , Sepsis/complications , Spleen/pathology , Stents/adverse effects , Survival AnalysisABSTRACT
PURPOSE: Major surgery can modulate the immune system and by this the clinical course of following complications. Effects of minor surgical treatments on the immune system and septic complications are poorly understood. MATERIALS AND METHODS: We investigated the effect of a minor surgical procedure--the implantation of an osmotic pump--on the outcome of experimental polymicrobial sepsis (colon ascendens stent-induced peritonitis, CASP) in mice. RESULTS: Animals with pumps implanted 3 days prior to CASP showed an attenuated clinical course of sepsis and increased survival. While measured serum cytokine levels were not affected by the minor surgical stress of pump implantation, splenocyte secretion of IFN-gamma in response to lipopolysaccharide was increased. CONCLUSION: The early implantation of alloplastic material modulates the immune system and leads to an increased survival of a polymicrobial sepsis. Identifying the molecular nature of this effect might point the way to a new therapeutic approach to reduce sepsis mortality.
