Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) improves the innate immune response and enhances survival in murine polymicrobial sepsis.

OBJECTIVE: To investigate the role of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) in postoperative polymicrobial abdominal sepsis.Sepsis is the leading cause of death among critically ill surgical patients. TRAIL is commonly known as an apoptosis-inducing agent in cancer cells. It also plays an important role in the regulation of inflammatory reactions. The role of TRAIL in polymicrobial sepsis is still unclear. DESIGN: Experimental animal model. SETTING: University laboratory. SUBJECTS: C57BL/6 mice. INTERVENTIONS: Colon ascendens stent peritonitis (CASP) was induced in female mice. One hour, 24 hrs, and 48 hrs after induction of CASP, murine recombinant TRAIL was given intravenously. MEASUREMENTS AND MAIN RESULTS: This study demonstrates a protective effect of TRAIL in CASP, an experimental model of murine polymicrobial sepsis. Intravenous administration of recombinant TRAIL to mice after CASP induction led to highly significantly prolonged survival. The migration of effector cells into the peritoneal cavity was strongly enhanced. Consequently, TRAIL-treated mice eliminated bacteria significantly better from the peritoneal cavity, the source of infection. Systemic spread of gut bacteria was also reduced by several orders of magnitude. As a result of the reduced systemic spread of bacteria, the accumulation of neutrophils within the spleen and mesenteric lymph nodes was strongly decreased. CONCLUSION: TRAIL-treated mice are highly protected from abdominal sepsis. Because diagnosis and therapy are frequently delayed in human sepsis, it is remarkable that TRAIL is effective when given via a therapeutic approach. Therefore, this study suggests a therapeutic potential for TRAIL in human sepsis. This should be addressed in future trials.

Colon ascendens stent peritonitis (CASP)--a standardized model for polymicrobial abdominal sepsis.

Sepsis remains a persistent problem on intensive care units all over the world. Understanding the complex mechanisms of sepsis is the precondition for establishing new therapeutic approaches in this field. Therefore, animal models are required that are able to closely mimic the human disease and also sufficiently deal with scientific questions. The Colon Ascendens Stent Peritonitis (CASP) is a highly standardized model for polymicrobial abdominal sepsis in rodents. In this model, a small stent is surgically inserted into the ascending colon of mice or rats leading to a continuous leakage of intestinal bacteria into the peritoneal cavity. The procedure results in peritonitis, systemic bacteraemia, organ infection by gut bacteria, and systemic but also local release of several pro- and anti-inflammatory cytokines. The lethality of CASP can be controlled by the diameter of the inserted stent. A variant of this model, the so-called CASP with intervention (CASPI), raises opportunity to remove the septic focus by a second operation according to common procedures in clinical practice. CASP is an easily learnable and highly reproducible model that closely mimics the clinical course of abdominal sepsis. It leads way to study on questions in several scientific fields e.g. immunology, infectiology, or surgery.

Implantation of alloplastic material increases survival of mice subsequently exposed to polymicrobial sepsis.

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.

Selective depletion of alveolar macrophages in polymicrobial sepsis increases lung injury, bacterial load and mortality but does not affect cytokine release.

BACKGROUND: Resident tissue macrophages exert important functions during severe systemic infection and contribute to changes in local as well as systemic immune responses. Alveolar macrophages (AM) play a crucial role in airway diseases and in the defense against microorganisms invading the body via the bronchopulmonary tract. It has been postulated that AM are involved in the development of acute local disorders as a consequence of extrapulmonary stimuli like pancreatitis, peritonitis, or trauma. OBJECTIVE: The aim of this study was to analyze the local and systemic role of AM during sepsis using selective AM depletion in the murine colon ascendens stent peritonitis (CASP) model of polymicrobial sepsis. METHODS: 48 h prior to CASP surgery, AM of female C57BL/6 mice were selectively depleted by intratracheal application of clodronate liposomes (Lipo-clod). For control purposes, phosphate-buffered saline (PBS) liposomes (Lipo-PBS) were used. RESULTS: CASP led to significantly elevated levels of local and systemic cytokines independent of the presence of AM. In contrast, levels of gut-derived bacteria in bronchoalveolar lavage and lung of septic mice were significantly higher in Lipo-clod-treated animals compared to Lipo-PBS-treated animals. After CASP-induced sepsis, local barrier dysfunction in the lung was detected; AM depletion resulted in severely enhanced development of acute lung injury. Consequently, Lipo-clod-treated animals showed strongly reduced survival rates after CASP. CONCLUSIONS: Contrarily to other macrophage populations, AM do not significantly contribute to local and systemic cytokine release during polymicrobial abdominal sepsis. AM have important protective functions for local clearance of gut-derived bacteria and attenuation of lung injury.

Detrimental role of CC chemokine receptor 4 in murine polymicrobial sepsis.

CC chemokine receptor 4 (CCR4) and its two ligands, CCL17 and CCL22, are critically involved in different immune processes. In models of lipopolysaccharide-induced shock, CCR4-deficient (CCR4(-/-)) mice showed improved survival rates associated with attenuated proinflammatory cytokine release. Using CCR4(-/-) mice with a C57BL/6 background, this study describes for the first time the role of CCR4 in a murine model of polymicrobial abdominal sepsis, the colon ascendens stent peritonitis (CASP). CASP-induced sepsis led to a massive downregulation of CCR4 in lymphoid and nonlymphoid tissues, whereas the expression of CCL17 and CCL22 was independent of the presence of CCR4. After CASP, CCR4(-/-) animals showed a strongly enhanced bacterial clearance in several organs but not in the peritoneal lavage fluid and the blood. In addition, significantly reduced levels of proinflammatory cytokines/chemokines were measured in organ supernatants as well as in the sera of CCR4(-/-) mice. CCR4 deficiency consequently resulted in an attenuated severity of systemic sepsis and a strongly improved survival rate after CASP or CASP with intervention. Thus, our data provide clear evidence that CCR4 plays a strictly detrimental role in the course of polymicrobial sepsis.

Seasonal variations in inflammatory responses to sepsis and stress in mice.

OBJECTIVE: In this study, we analyzed seasonal variations of immunoreactivity using a model of septic shock and a model of immunosuppression induced by chronic stress in mice. DESIGN: Retrospective comparative study using animals of experiments performed between 2001 and 2006 to identify seasonal variations in inflammatory responsiveness of mice. SETTING: University-based research laboratory. SUBJECTS: C57Bl/6 mice and BALB/c mice. INTERVENTIONS: For analyzing septic shock, we used the hyperinflammatory model of colon ascendens stent peritonitis. Immunosuppression was induced by 4.5 days of intermittent combined acoustic and restraint stress. MEASUREMENTS AND MAIN RESULTS: We show that mice kept with 12:12-hr light/dark rhythm had an enhanced risk to die of experimentally-induced hyperinflammatory peritonitis performed in summer or autumn compared with the other seasons. This finding was associated with an exaggerated proinflammatory response of C57Bl/6 mice in summer or autumn compared with moderate inflammatory reactivity in winter and spring. Consistent with these results, we report that the severity of a stress-induced immunosuppression is less pronounced in BALB/c mice that were exposed to chronic psychological stress in the summer compared with exposure in winter. Coping with chronic psychological stress of these animals was correlated with less pronounced corticosterone release, less severe lymphocytopenia, and a lower ex vivo inducibility of interleukin-10, thereby attenuating a stress-mediated immunosuppressive state. Mice subjected to chronic stress in the summer season showed increased coping compared with mice that were stressed in the winter season. CONCLUSIONS: Our results suggest that seasonal changes of the host's hypothalamus-pituitary-adrenal axis response influence the risk of infection and the susceptibility to stress, which interferes with the outcome after infection.

Evidence for histamine as a transmitter in rat carotid body sensor cells.

Carotid bodies harboring sensor cells for oxygen have a strategic location at the bifurcation of the carotid artery, which supplies the brain. Upon arterial hypoxia they transmit signals to the respiratory center, which increases the frequency of breathing. Dopamine is considered as the predominant transmitter of the rat carotid body sensor cells. Here we show that the rat carotid body sensor cells are the first cell type known to have the complete apparatus to synthesize, store and release both dopamine and histamine. The tyrosine hydroxylase positive dopaminergic sensor cells of juvenile rats express the histamine biosynthesis enzyme, histidine decarboxylase. Moreover, the sensor cells have not only vesicular monoamine transporter 1 (VMAT1) transporting catecholamines but also VMAT2, which is highly specific for histamine. Additionally, we found that these cells possess components of the neuroendocrine exocytosis apparatus, synaptosome-associated protein of 25 kDa (SNAP 25) and syntaxin1. The amount of histamine determined in the rat carotid body (164 pmol/carotid body) is more than 10-fold higher compared with that of dopamine. As a main effect, hypoxia significantly increased histamine release from isolated rat carotid bodies as it has been shown for dopamine. Finally, RT-PCR experiments indicate the presence of histamine receptors H1, H2 and H3 in the carotid body. Our data suggest that histamine is synthesized, stored and released upon hypoxia by dopaminergic sensor cells of the rat carotid body.