Tumor necrosis factor-dependent adhesions as a major protective mechanism early in septic peritonitis in mice

Electrical stimulation of the dorsal motor nucleus of the vagus in male mice can regulate inflammation without affecting the heart rate

BACKGROUND

The vagus nerve plays an important role in neuroimmune interactions and in the regulation of inflammation. A major source of efferent vagus nerve fibers that contribute to the regulation of inflammation is the brainstem dorsal motor nucleus of the vagus (DMN), as recently shown using optogenetics. In contrast to optogenetics, electrical neuromodulation has broad therapeutic implications. However, the anti-inflammatory effectiveness of electrical stimulation of the DMN (eDMNS) and the possible heart rate (HR) alterations associated with this approach have not been investigated. Here, we examined the effects of eDMNS on HR and cytokine levels in mice administered with lipopolysaccharide (LPS, endotoxin) and in mice subjected to cecal ligation and puncture (CLP) sepsis.

METHODS

Anesthetized male 8-10-week-old C57BL/6 mice on a stereotaxic frame were subjected to eDMNS using a concentric bipolar electrode inserted into the left or right DMN or sham stimulation. eDMNS (500, 250 or 50 μA at 30 Hz, for 1 min) was performed and HR recorded. In endotoxemia experiments, sham or eDMNS utilizing 250 μA or 50 μA was performed for 5 mins and was followed by LPS (0.5 mg/kg) i.p. administration. eDMNS was also applied in mice with cervical unilateral vagotomy or sham operation. In CLP experiments sham or left eDMNS was performed immediately post CLP. Cytokines and corticosterone were analyzed 90 mins after LPS administration or 24 h after CLP. CLP survival was monitored for 14 days.

RESULTS

Either left or right eDMNS at 500 μA and 250 μA decreased HR, compared with baseline pre-stimulation. This effect was not observed at 50 μA. Left side eDMNS at 50 μA, compared with sham stimulation, significantly decreased serum and splenic levels of the pro-inflammatory cytokine TNF and increased serum levels of the anti-inflammatory cytokine IL-10 during endotoxemia. The anti-inflammatory effect of eDMNS was abrogated in mice with unilateral vagotomy and was not associated with serum corticosterone alterations. Right side eDMNS in endotoxemic mice suppressed serum TNF and increased serum IL-10 levels but had no effects on splenic cytokines. In mice with CLP, left side eDMNS suppressed serum IL-6, as well as splenic IL-6 and increased splenic IL-10 and significantly improved the survival rate of CLP mice.

CONCLUSIONS

For the first time we show that a regimen of eDMNS which does not cause bradycardia alleviates LPS-induced inflammation. These eDMNS anti-inflammatory effects require an intact vagus nerve and are not associated with corticosteroid alterations. eDMNS also decreases inflammation and improves survival in a model of polymicrobial sepsis. These findings are of interest for further studies exploring bioelectronic anti-inflammatory approaches targeting the brainstem DMN.

Can serum tumor necrosis factor-alpha predict peritoneal adhesions prior to secondary laparoscopic procedures?

AIM OF THE STUDY

This study aimed to investigate the incidence and degree of postoperative intra-abdominal adhesions(POAs) in secondary laparoscopic procedures and assess the power of the preoperative levels of tumor necrosis factor-alpha(TNF-α) and interleukin-1 beta(IL-1β) and selected peripheral inflammatory biomarkers(PIBs) in the prediction of the development and extent of POA.

PATIENTS AND METHODS

This prospective study enrolled 103 patients who had previously undergone at least one or more laparoscopic abdominal or gynecological operations. We examined TNF-α, IL-1β, and PIBs, namely C-reactive protein, white blood cell count, neutrophil-to-lymphocyte ratio(NLR), platelet-to-lymphocyte ratio, and systemic immune-inflammation index(SII) according to the presence, location, and score of adhesions determined during secondary laparoscopic procedures.

RESULTS

Only age, postoperative adhesion index(PAI) score, NLR, SII, TNF-α, and IL-1β resulted in a significant difference in the existence of adhesion(P<0.05). The correlation analysis of TNF-α with variables showed that the PAI score and IL 1β levels had a significantly positive correlation.

CONCLUSION

The presence and extent of POA could be predicted by examining the preoperative TNF-α level in patients who had laparoscopic abdominal surgery previously. We could overcome adverse events during secondary laparoscopic procedures by assessing high-risk patients and integrating a personalized surgical approach to managing selected patients.

Endothelial Activation and Microcirculatory Disorders in Sepsis

The vascular endothelium is crucial for the maintenance of vascular homeostasis. Moreover, in sepsis, endothelial cells can acquire new properties and actively participate in the host's response. If endothelial activation is mostly necessary and efficient in eliminating a pathogen, an exaggerated and maladaptive reaction leads to severe microcirculatory damage. The microcirculatory disorders in sepsis are well known to be associated with poor outcome. Better recognition of microcirculatory alteration is therefore essential to identify patients with the worse outcomes and to guide therapeutic interventions. In this review, we will discuss the main features of endothelial activation and dysfunction in sepsis, its assessment at the bedside, and the main advances in microcirculatory resuscitation.

Intraperitoneal microbial contamination drives post-surgical peritoneal adhesions by mesothelial EGFR-signaling

Abdominal surgeries are lifesaving procedures but can be complicated by the formation of peritoneal adhesions, intra-abdominal scars that cause intestinal obstruction, pain, infertility, and significant health costs. Despite this burden, the mechanisms underlying adhesion formation remain unclear and no cure exists. Here, we show that contamination of gut microbes increases post-surgical adhesion formation. Using genetic lineage tracing we show that adhesion myofibroblasts arise from the mesothelium. This transformation is driven by epidermal growth factor receptor (EGFR) signaling. The EGFR ligands amphiregulin and heparin-binding epidermal growth factor, are sufficient to induce these changes. Correspondingly, EGFR inhibition leads to a significant reduction of adhesion formation in mice. Adhesions isolated from human patients are enriched in EGFR positive cells of mesothelial origin and human mesothelium shows an increase of mesothelial EGFR expression during bacterial peritonitis. In conclusion, bacterial contamination drives adhesion formation through mesothelial EGFR signaling. This mechanism may represent a therapeutic target for the prevention of adhesions after intra-abdominal surgery.

The Role of Fibrin(ogen) in Wound Healing and Infection Control

Fibrinogen, one of the most abundant plasma proteins playing a key role in hemostasis, is an important modulator of wound healing and host defense against microbes. In the current review, we address the role of fibrin(ogen) throughout the process of wound healing and subsequent tissue repair. Initially fibrin(ogen) acts as a provisional matrix supporting incoming leukocytes and acting as reservoir for growth factors. It later goes on to support re-epithelialization, angiogenesis, and fibroplasia. Importantly, removal of fibrin(ogen) from the wound is essential for wound healing to progress. We also discuss how fibrin(ogen) functions through several mechanisms to protect the host against bacterial infection by providing a physical barrier, entrapment of bacteria in fibrin(ogen) networks, and by directing immune cell function. The central role of fibrin(ogen) in defense against bacterial infection has made it a target of bacterial proteins, evolved to interact with fibrin(ogen) to manipulate clot formation and degradation for the purpose of promoting microbial virulence and survival. Further understanding of the dual roles of fibrin(ogen) in wound healing and infection could provide novel means of therapy to improve recovery from surgical or chronic wounds and help to prevent infection from highly virulent bacterial strains, including those resistant to antibiotics.

Sepsis: Inflammation Is a Necessary Evil

Sepsis is one of the leading causes of deaths world-wide and yet there are no therapies available other than ICU treatment. The patient outcome is determined by a complex interplay between the pro and anti-inflammatory responses of the body i.e., a homeostatic balance between these two competing events to be achieved for the patient’s recovery. The initial attempts on drug development mainly focused on controlling inflammation, however, without any tangible outcome. This was despite most deaths occurring during the immune paralysis stage of this biphasic disease. Recently, the focus has been shifting to understand immune paralysis (caused by apoptosis and by anti-inflammatory cytokines) to develop therapeutic drugs. In this review we put forth an argument for a proper understanding of the molecular basis of inflammation as well as apoptosis for developing an effective therapy.

Expression of factor V by resident macrophages boosts host defense in the peritoneal cavity

Macrophages resident in different organs express distinct genes, but understanding how this diversity fits into tissue-specific features is limited. Here, we show that selective expression of coagulation factor V (FV) by resident peritoneal macrophages in mice promotes bacterial clearance in the peritoneal cavity and serves to facilitate the well-known but poorly understood "macrophage disappearance reaction." Intravital imaging revealed that resident macrophages were nonadherent in peritoneal fluid during homeostasis. Bacterial entry into the peritoneum acutely induced macrophage adherence and associated bacterial phagocytosis. However, optimal control of bacterial expansion in the peritoneum also required expression of FV by the macrophages to form local clots that effectively brought macrophages and bacteria in proximity and out of the fluid phase. Thus, acute cellular adhesion and resident macrophage-induced coagulation operate independently and cooperatively to meet the challenges of a unique, open tissue environment. These events collectively account for the macrophage disappearance reaction in the peritoneal cavity.

Basophil-derived tumor necrosis factor can enhance survival in a sepsis model in mice

Basophils are evolutionarily conserved in vertebrates, despite their small numbers and short lifespan, suggesting that basophils have beneficial roles in maintaining health. However, these roles are not fully defined. Here, we demonstrate that basophil-deficient mice exhibited reduced bacterial clearance, and increased morbidity and mortality, in the cecal ligation and puncture (CLP) model of sepsis. Among the several pro-inflammatory mediators we measured, tumor necrosis factor (TNF) was the only cytokine that was significantly reduced in basophil-deficient mice after CLP. In accordance with that observation, we found that mice with genetic ablation of Tnf in basophils exhibited reduced systemic TNF concentrations during endotoxemia. Moreover, during CLP, mice whose basophils could not produce TNF exhibited reduced neutrophil and macrophage TNF production and effector functions, reduced bacterial clearance, and increased mortality. Taken together, our studies show that basophils can enhance the innate immune response against bacterial infection and help prevent sepsis.

Targeting ADAM17 in leukocytes increases neutrophil recruitment and reduces bacterial spread during polymicrobial sepsis

A rapid and robust recruitment of circulating neutrophils at sites of infection is critical for preventing bacterial spread. The efficiency of this process, however, is greatly diminished during sepsis, a severe systemic inflammatory response to infection. The proteolytic activity of a disintegrin and metalloprotease-17 is induced in the cell membrane of leukocytes upon their activation, resulting in the conversion of membrane to soluble TNF-α and the release of assorted receptors from the surface of neutrophils important for their effector functions. We show that conditional knockout mice lacking a disintegrin and metalloprotease-17 in all leukocytes had a survival advantage when subjected to polymicrobial sepsis. Bacteremia and the levels of circulating proinflammatory cytokines, key determinants of sepsis severity, were significantly reduced in conditional a disintegrin and metalloprotease-17 knockout mice during sepsis. Although cecal bacterial microbiota and load were similar in unmanipulated conditional a disintegrin and metalloprotease-17 knockout and control mice, peritoneal spread of bacteria was significantly reduced in conditional a disintegrin and metalloprotease-17 knockout mice following sepsis induction, which was associated with an amplified recruitment of neutrophils. Taken together, our findings suggest that extensive a disintegrin and metalloprotease-17 induction during sepsis may tip the balance between efficient and impaired neutrophil recruitment.

Endothelial and Microcirculatory Function and Dysfunction in Sepsis

The microcirculation is a series of arterioles, capillaries, and venules that performs essential functions of oxygen and nutrient delivery, customized to the unique physiologic needs of the supplied organ. The homeostatic microcirculatory response to infection can become harmful if overactive and/or dysregulated. Pathologic microcirculatory dysfunction can be directly visualized by intravital microscopy or indirectly measured via detection of circulating biomarkers. Although several treatments have been shown to protect the microcirculation during sepsis, they have not improved patient outcomes when applied indiscriminately. Future outcomes-oriented studies are needed to test sepsis therapeutics when personalized to a patient's microcirculatory dysfunction.

Antimicrobial cathelicidin peptide LL-37 inhibits the pyroptosis of macrophages and improves the survival of polybacterial septic mice

LL-37 is the only known member of the cathelicidin family of antimicrobial peptides in humans. In addition to its broad spectrum of antimicrobial activities, LL-37 can modulate various inflammatory reactions. We previously revealed that LL-37 suppresses the LPS/ATP-induced pyroptosis of macrophages in vitro by both neutralizing the action of LPS and inhibiting the response of P2X7 (a nucleotide receptor) to ATP. Thus, in this study, we further evaluated the effect of LL-37 on pyroptosis in vivo using a cecal ligation and puncture (CLP) sepsis model. As a result, the intravenous administration of LL-37 improved the survival of the CLP septic mice. Interestingly, LL-37 inhibited the CLP-induced caspase-1 activation and pyroptosis of peritoneal macrophages. Moreover, LL-37 modulated the levels of inflammatory cytokines (IL-1β, IL-6 and TNF-α) in both peritoneal fluids and sera, and suppressed the activation of peritoneal macrophages (as evidenced by the increase in the intracellular levels of IL-1β, IL-6 and TNF-α). Finally, LL-37 reduced the bacterial burdens in both peritoneal fluids and blood samples. Together, these observations suggest that LL-37 improves the survival of CLP septic mice by possibly suppressing the pyroptosis of macrophages, and inflammatory cytokine production by activated macrophages and bacterial growth. Thus, the present findings imply that LL-37 can be a promising candidate for sepsis because of its many functions, such as the inhibition of pyroptosis, modulation of inflammatory cytokine production and antimicrobial activity.

Vascular endothelial cell Toll-like receptor pathways in sepsis

The endothelium forms a vast network that dynamically regulates vascular barrier function, coagulation pathways and vasomotor tone. Microvascular endothelial cells are uniquely situated to play key roles during infection and injury, owing to their widespread distribution throughout the body and their constant interaction with circulating blood. While not viewed as classical immune cells, endothelial cells express innate immune receptors, including the Toll-like receptors (TLRs), which activate intracellular inflammatory pathways mediated through NF-κB and the MAP kinases. TLR agonists, including LPS and bacterial lipopeptides, directly upregulate microvascular endothelial cell expression of inflammatory mediators. Intriguingly, TLR activation also modulates microvascular endothelial cell permeability and the expression of coagulation pathway intermediaries. Microvascular thrombi have been hypothesized to trap microorganisms thereby limiting the spread of infection. However, dysregulated activation of endothelial inflammatory pathways is also believed to lead to coagulopathy and increased vascular permeability, which together promote sepsis-induced organ failure. This article reviews vascular endothelial cell innate immune pathways mediated through the TLRs as they pertain to sepsis, highlighting links between TLRs and coagulation and permeability pathways, and their role in healthy and pathologic responses to infection and sepsis.

Systemic inhibition and liver-specific over-expression of PAI-1 failed to improve survival in all-inclusive populations or homogenous cohorts of CLP mice

BACKGROUND

The role of plasminogen activator inhibitor type-1 (PAI-1) in abdominal sepsis remains elusive.

OBJECTIVES

To study the influence of inhibition and over-expression of PAI-1 upon survival in cecal ligation and puncture (CLP) sepsis.

METHODS

(i) Mice underwent moderate CLP and received 10 mg kg(-1) of either monoclonal anti-PAI-1 (MA-MP6H6) or control (MA-Control) antibody intravenously at 0, 18 or 30 h post-CLP. The 30-h treatment group was additionally stratified into mice predicted to survive (P-SUR) or die (P-DIE) based on IL 6 measured at 24 h post-CLP. (ii) PAI-1 expression was induced with pLIVE.PAI-1 plasmid administered 72 h pre-CLP. Blood was sampled for 5 days and survival was monitored for 28 days.

RESULTS

MA-MP6H6 effectively neutralized active PAI-1 and fully restored fibrinolysis while PAI-1 over-expression was liver-specific and correlated with PAI-1 increase in the blood. Without stratification, MA-MP6H6 co-/post-treatment conferred no survival benefit. Prospective stratification (IL-6 cut-off: 14 ng mL(-1) ) suggested increased mortality by MA-MP6H6 treatment in P-SUR that reached 30% difference (vs. MA-Control; P < 0.05) after a retrospective cut-off readjustment to 3.3 ng mL(-1) for better P-SUR homogeneity. Subsequent prospective anti-PAI-1 treatment in P-SUR mice with 3.3 ng mL(-1) cut-off demonstrated a negative but statistically insignificant effect: mortality was higher by 17% after MA-MP6H6 vs. MA-Control. Over-expression of PAI 1 did not alter post-CLP survival. Neither PAI-1 inhibition nor over-expression meaningfully modified inflammatory response and/or organ function.

CONCLUSIONS

Restoration of fibrinolysis in early abdominal sepsis was not beneficial and it may prove detrimental in subjects with the lowest risk of death, while preemptive PAI-1 up-regulation at the current magnitude was not protective.

Anti-TNF-α therapy for patients with sepsis: a systematic meta-analysis

OBJECTIVE

In humans, the role of anti-tumour necrosis factor (TNF)-α therapy in severe sepsis and septic shock is debatable. The aim of this meta-analysis was to determine the efficacy of anti-TNF-α therapies against placebo in patients with severe sepsis or septic shock.

METHODS

A structured literature search was undertaken to identify randomised controlled trials (RCTs) conducted in patients with severe sepsis or septic shock receiving anti-TNF-α therapy or placebo. A meta-analysis on relative risk (OR) with a 95% confidence interval (95% CI) was performed.

RESULTS

Seventeen studies with a total of 8971 patients were included. When all forms of anti-TNF-α therapy were pooled together, there was a significant reduction of 28-day all-cause mortality with respect to placebo (OR = 0.91, 95% CI: 0.83-0.99; p = 0.04). Subgroup analysis showed that anti-TNF-α antibodies (monoclonal and polyclonal) reduced mortality (OR = 0.90, 95% CI: 0.81-0.99; p = 0.04). Monoclonal antibodies enhanced survival (OR = 0.91, 95% CI: 0.82-1.00; p = 0.05), while polyclonal antibodies or receptor blockers did not enhance survival (OR = 0.71, 95% CI: 0.39-1.28, p = 0.25; OR = 0.95, 95% CI: 0.78-1.17, p = 0.65). There was a trend towards better survival in patients with high levels of IL-6 (> 1000 pg/ml) and patients with shock if they were treated with anti-TNF-α therapy (OR = 0.85, 95% CI: 0.72-1.00; OR = 0.80, 95% CI: 0.62-1.04). Publication bias and statistical heterogeneity (I(2)  < 50% and p > 0.1) were absent. Sensitivity analysis suggests that these results are highly stable.

CONCLUSIONS

This meta-analysis suggests that in patients with severe sepsis (before shock), immunotherapy with anti-TNF-α monoclonal antibodies reduces overall mortality. In patients with shock or high levels of IL-6 (> 1000 pg/ml), anti-TNF-α therapy may improve survival.

Effect of chronic ethanol consumption in female rats subjected to experimental sepsis

The objective of this research was to evaluate the interference of ethanol consumption by female rats with cytokines involved in the sepsis process and its correlation with mortality, the main outcome of sepsis. Female Wistar rats in estrus phase were evaluated in three experiments. Experiment 1 (n=40) was performed to determine survival rates. Experiment 2 (n=69) was designed for biochemical analysis, measurement of cytokine and estrogen levels before and after sepsis, and experiment 3 (n=10) was performed to evaluate bacterial growth by colony counts of peritoneal fluid. In all experiments, treated animals were exposed to a 10% ethanol/water solution (v/v) as the single drinking source, while untreated animals were given tap water. After 4 weeks, sepsis was induced in the rats by ip injection of feces. In experiment 1, mortality in ethanol-exposed animals was delayed compared with those that drank water (48 h; P=0.0001). Experiment 2 showed increased tumor necrosis factor alpha (TNF-α) and decreased interleukin-6 (IL-6) and macrophage migration inhibitory factor in septic animals exposed to ethanol compared to septic animals not exposed. Sepsis also increased TNF-α and IL-6 levels in both ethanol- and water-exposed groups. Biochemical analysis showed higher creatinine, alanine aminotransferase and aspartate aminotransferase and decreased glucose levels in septic animals that were exposed to ethanol. In experiment 3, septic animals exposed to ethanol showed decreased numbers of colony-forming units than septic animals exposed to water. These results suggest that ethanol consumption delays the mortality of female rats in estrus phase after sepsis induction. Female characteristics, most probably sex hormones, may be involved in cytokine expression.

Tumour necrosis factor in infectious disease

TNF signals through two distinct receptors, designated TNFR1 and TNFR2, which initiate diverse cellular effects that include cell survival, activation, differentiation, and proliferation and cell death. These cellular responses can promote immunological and inflammatory responses that eradicate infectious agents, but can also lead to local tissue injury at sites of infection and harmful systemic effects. Defining the molecular mechanisms involved in TNF responses, the effects of natural and experimental genetic diversity in TNF signalling and the effects of therapeutic blockade of TNF has increased our understanding of the key role that TNF plays in infectious disease.

Fibrin facilitates both innate and T cell-mediated defense against Yersinia pestis

The Gram-negative bacterium Yersinia pestis causes plague, a rapidly progressing and often fatal disease. The formation of fibrin at sites of Y. pestis infection supports innate host defense against plague, perhaps by providing a nondiffusible spatial cue that promotes the accumulation of inflammatory cells expressing fibrin-binding integrins. This report demonstrates that fibrin is an essential component of T cell-mediated defense against plague but can be dispensable for Ab-mediated defense. Genetic or pharmacologic depletion of fibrin abrogated innate and T cell-mediated defense in mice challenged intranasally with Y. pestis. The fibrin-deficient mice displayed reduced survival, increased bacterial burden, and exacerbated hemorrhagic pathology. They also showed fewer neutrophils within infected lung tissue and reduced neutrophil viability at sites of liver infection. Depletion of neutrophils from wild-type mice weakened T cell-mediated defense against plague. The data suggest that T cells combat plague in conjunction with neutrophils, which require help from fibrin to withstand Y. pestis encounters and effectively clear bacteria.

Mechanisms and functional consequences of liver failure substantially differ between endotoxaemia and faecal peritonitis in rats

BACKGROUND

Many of the concepts describing molecular mechanisms of sepsis-induced liver failure are derived from endotoxin models. However, the biological significance of such models is questionable as the complexity of clinical sepsis and associated organ failure is only partially replicated.

AIMS

Comparison of cytokine response, leucocyte recruitment, oxidative stress and markers of hepatic organ dysfunction in rat models of endotoxaemia or peritoneal contamination and infection (PCI).

METHODS

Endotoxemia and polymicrobial sepsis were induced in rats by intraperitoneal injection of lipopolysaccharide (LPS) or stool suspension, respectively.

RESULTS

Both insults produced clinical and laboratory signs of multiple organ dysfunction, including hepatic excretory dysfunction. However, TNF alpha, oxidative stress responses and the degree of cell death were significantly higher in endotoxaemia compared to PCI (e.g. serum TNF levels (pg/ml) at 1.5 h post-insult: sham 5 ± 1.4, LPS 1 mg/kg bw 2176.92 ± 373.78, sepsis below detection limit; P P < 0.05). Cholestasis was significantly more pronounced in polymicrobial sepsis whereas serum bilirubin in endotoxaemic animals did not differ from sham-operated controls (plasma levels of bilirubin (μmol/L) at 15 h after the insult: sham 7.1 ± 0.6, LPS 30 mg/kg 9.1 ± 0.6, sepsis 15.2 ± 1.3).

CONCLUSIONS

Polymicrobial sepsis produces profound hepatocellular dysfunction in the absence of traditional cytokine-mediated mechanisms of cellular injury. This questions the central role of cytokines and the ensuing oxidative stress as key molecular events in mediating liver dysfunction.

The evolving experience with therapeutic TNF inhibition in sepsis: considering the potential influence of risk of death

INTRODUCTION

Septic shock is highly lethal and its incidence is increasing. Although TNF-α plays a key role in sepsis pathogenesis, past efforts to therapeutically inhibit it had limited success. However, there is continued interest in such therapies and there are now ongoing Phase II sepsis trials testing the effects of AZD9773, a TNF-directed polyclonal antibody fragment preparation. Experience with anti-inflammatory agents suggested that their efficacy may relate to sepsis-associated risk of death.

AREAS COVERED

An overview of the biology of TNF and experimental data implicating TNF as a key mediator in sepsis pathogenesis; a review of the earlier clinical experience with anti-TNF therapies demonstrating that when examined across 12 trials, these agents had a highly consistent overall effect which although not reaching significance, was on the side of benefit; a review of data showing that sepsis-associated risk of death may influence the efficacy of anti-inflammatory agents like anti-TNF ones and a review of the rational and clinical experience to date with AZD9773 and its precursor, CytoFab.

EXPERT OPINION

Discusses variables that may need to be accounted for to maximize the success of clinical trials in sepsis testing agents that modulate host inflammation.

The effect of heparin administration in animal models of sepsis: a prospective study in Escherichia coli-challenged mice and a systematic review and metaregression analysis of published studies

INTRODUCTION

If thrombosis contributes to sepsis, heparin titrated using activated partial thromboplastin times may be efficacious. We investigated heparin in preclinical models.

METHODS AND MAIN RESULTS

In unchallenged mice (n = 107), heparin at 100, 500, or 2500 units/kg produced activated partial thromboplastin time levels less than, within, or greater than a prespecified therapeutic range (1.5-2.5 times control), respectively. In animals (n = 142) administered intratracheal Escherichia coli challenge, compared to placebo treatment, heparin at 100, 500, or 2500 units/kg were associated with dose dependent increases in the hazard ratios of death (hazard ratio [95% confidence interval]: 1.08 [0.66, 1.76]; 1.34 [0.80, 2.24]; 3.02 [1.49, 6.10], respectively) (p = .001 for the dose effect). Compared to normal saline challenge, E. coli without heparin (i.e., with placebo) increased the activated partial thromboplastin time (p = .002) close to the therapeutic range. While heparin at 100 and 500 units/kg with E. coli further increased activated partial thromboplastin time (p < .0001 vs. placebo) within or above the therapeutic range, respectively, these did not decrease inflammatory cytokines or lung injury. In metaregression analysis of published preclinical studies, heparin improved survival with lipopolysaccharide (n = 23, p < .0001) or surgically induced infection (n = 14, p < .0001) but not monobacterial (n = 7, p = .29) challenges.

CONCLUSION

Coagulopathy with sepsis or other variables, such as type of infectious source, may influence the efficacy of heparin therapy for sepsis.

Protective roles for fibrin, tissue factor, plasminogen activator inhibitor-1, and thrombin activatable fibrinolysis inhibitor, but not factor XI, during defense against the gram-negative bacterium Yersinia enterocolitica

Septic infections dysregulate hemostatic pathways, prompting coagulopathy. Nevertheless, anticoagulant therapies typically fail to protect humans from septic pathology. The data reported in this work may help to explain this discrepancy by demonstrating critical protective roles for coagulation leading to fibrin deposition during host defense against the Gram-negative bacterium Yersinia enterocolitica. After i.p. inoculation with Y. enterocolitica, fibrinogen-deficient mice display impaired cytokine and chemokine production in the peritoneal cavity and suppressed neutrophil recruitment. Moreover, both gene-targeted fibrinogen-deficient mice and wild-type mice treated with the anticoagulant coumadin display increased hepatic bacterial burden and mortality following either i.p. or i.v. inoculation with Y. enterocolitica. Mice with low tissue factor activity succumb to yersiniosis with a phenotype similar to fibrin(ogen)-deficient mice, whereas factor XI-deficient mice show wild-type levels of resistance. Mice deficient in plasminogen activator inhibitor-1 or thrombin-activatable fibrinolysis inhibitor display modest phenotypes, but mice deficient in both plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor succumb to yersiniosis with a phenotype resembling fibrin(ogen)-deficient mice. These findings demonstrate critical protective roles for the tissue factor-dependent extrinsic coagulation pathway during host defense against bacteria and caution that therapeutics targeting major thrombin-generating or antifibrinolytic pathways may disrupt fibrin-mediated host defense during Gram-negative sepsis.

Age and pro-inflammatory cytokine production: wound-healing implications for scar-formation and the timing of genital surgery in boys

PURPOSE

Fewer complications occur when hypospadias is repaired early in childhood. We hypothesize that the production of pro-inflammatory cytokines by fibroblasts from neonatal foreskin is decreased compared with fibroblasts from older boys. We believe that these age-related differences may explain the greater risk of complications following repair in older boys.

MATERIALS AND METHODS

With IRB approval, we collected 15 samples of foreskin from boys undergoing elective circumcision. They were divided into one of three groups: a neonatal group (under 28 days), an intermediate age group (6 months-1 year), and an older age group (7-17-years-olds). Fibroblasts were cultured then incubated for 16 h with serum-free medium containing 0, 0.1, 1 or 10 ng/mL of PDGF. Supernatants were analyzed for production of IL-6 and IL-8 with quantitative ELISA. Fibroblasts had RT-PCR performed for IL-6, IL-8, IL-10, TGF-β1, TGF-β3 and TNF-α.

RESULTS

Fibroblasts from neonatal foreskin produced significantly less IL-6 and IL-8 at baseline and following stimulation with PDGF compared to the intermediate and older age groups (P < 0.01). Real-time PCR revealed greater expression of IL-6, IL-8, TNF-α and TGF-β1 mRNA in the older age groups (P < 0.05).

CONCLUSIONS

There is a clear association between age and production of pro-inflammatory cytokines by genitourinary fibroblasts. This relationship exists at baseline and following stimulation with PDGF. The dramatic difference in levels of pro-inflammatory factors may explain the observed age-associated differences in wound scarring and stricture formation following hypospadias repair. Further clinical studies are needed, however, to validate this finding.

Improved host defense against septic peritonitis in mice lacking MyD88 and TRIF is linked to a normal interferon response

The signaling adapters MyD88 and TRIF are engaged by TLRs and/or receptors of the IL-1 family and are considered important for innate immune responses that combat bacterial infections. Here, the consequences of a combined MyD88 and TRIF deficiency for the innate immune response against severe septic peritonitis was examined. We demonstrate that Myd88(-/-);Trif(Lps2/Lps2) mice had markedly reduced bacterial numbers in the peritoneal cavity and peripheral blood, indicating that bacterial clearance in this model is improved in the absence of MyD88/TRIF signals. Survival of Myd88(-/-); Trif(Lps2/Lps2) mice was improved significantly. The lack of MyD88/TRIF signaling prevented the excessive production of inflammatory cytokines and of IL-10. In contrast, Ifng mRNA was expressed at WT levels, and induction of Ifnb mRNA was reduced only by one-half. Consistent with these findings, numerous IFN-regulated genes, including p47 and p65 GTPases, as well as CXCL10, were expressed in a MyD88/TRIF-independent manner. In support of the in vivo data, Myd88(-/-); Trif(Lps2/Lps2) macrophages stimulated with live intestinal bacteria produced normal amounts of CXCL10. The production of p47 GTPases and CXCL10 in septic peritonitis was found to be dependent on the presence of IFNAR1, but not IFN-γ, indicating a normal induction of the type I IFN response in Myd88(-/-);Trif(Lps2/Lps2) mice, despite attenuated IFN-β production. Together, these results provide evidence that in severe septic peritonitis, the absence of MyD88 and TRIF balances the innate immune response in a favorable manner by attenuating deleterious responses such as excessive cytokine release, while leaving intact protective IFN responses.

Increased inflammation and lethality of Dusp1-/- mice in polymicrobial peritonitis models

The mitogen-activated protein kinase phosphatase Dusp1 (also known as MKP-1) is essential for control of the inflammatory response to systemic challenge with the lipopolysaccharide of Gram-negative bacteria. Here, we have investigated the consequences of Dusp1-deficiency in colon ascendens stent peritonitis (CASP) and caecal ligation and puncture (CLP), two mouse models of septic peritonitis. Following CASP, Dusp1(-/-) mice had increased serum levels of CCL4, interleukin-10 (IL-10) and IL-6, with differences from wild-type mice being dependent on severity of sepsis. These cytokines, along with inducible nitric oxide synthase messenger RNA, were also expressed at higher levels in spleen and liver. Similar over-production of these cytokines was detected in the CLP model, with even larger differences from wild-type mice. Despite the increased inflammatory response, bacterial clearance was impaired in Dusp1(-/-) mice subjected to CASP and CLP. Dusp1(-/-) mice suffered increased lethality in both peritonitis models. Together our data indicate that exaggerated inflammatory responses to gut bacteria introduced into the peritoneum in the absence of Dusp1 do not help to control bacterial replication but are detrimental for the host.

Activation of mannan-binding lectin-associated serine proteases leads to generation of a fibrin clot

The lectin pathway of complement is activated upon binding of mannan-binding lectin (MBL) or ficolins (FCNs) to their targets. Upon recognition of targets, the MBL-and FCN-associated serine proteases (MASPs) are activated, allowing them to generate the C3 convertase C4b2a. Recent findings indicate that the MASPs also activate components of the coagulation system. We have previously shown that MASP-1 has thrombin-like activity whereby it cleaves and activates fibrinogen and factor XIII. MASP-2 has factor Xa-like activity and activates prothrombin through cleavage to form thrombin. We now report that purified L-FCN-MASPs complexes, bound from serum to N-acetylcysteine-Sepharose, or MBL-MASPs complexes, bound to mannan-agarose, generate clots when incubated with calcified plasma or purified fibrinogen and factor XIII. Plasmin digestion of the clot and analysis using anti-D-dimer antibodies revealed that the clot was made up of fibrin and was similar to that generated by thrombin in normal human plasma. Fibrinopeptides A and B (FPA and FPB, respectively) were released after fibrinogen cleavage by L-FCN-MASPs complexes captured on N-acetylcysteine-Sepharose. Studies of inhibition of fibrinopeptide release indicated that the dominant pathway for clotting catalysed by the MASPs is via MASP-2 and prothrombin activation, as hirudin, a thrombin inhibitor that does not inhibit MASP-1 and MASP-2, substantially inhibits fibrinopeptide release. In the light of their potent chemoattractant effects on neutrophil and fibroblast recruitment, the MASP-mediated release of FPA and FPB may play a role in early immune activation. Additionally, MASP-catalysed deposition and polymerization of fibrin on the surface of micro-organisms may be protective by limiting the dissemination of infection.

Cytokine orchestration in post-operative peritoneal adhesion formation

Peritoneal adhesions are a near inevitable occurrence after laparotomy and a major cause of both patient and physician misery. To date, clinical attempts at their amelioration have concentrated on manipulating the physical factors that affect their development despite a wealth of experimental data elucidating the molecular mechanisms that underlie their initiation, development and maturation. However, the advent of targeted, specific anti-cytokine agents as directed therapy for inflammatory and neoplastic conditions raises the prospect of a new era for anti-adhesion strategies. To harness this potential will require considerable cross-disciplinary collaboration and that surgeon-scientists propel themselves to the forefront of this emerging field.

[Surgical trauma and postoperative immunosuppression]

Abdominal surgery is regularly followed by immune dysfunction that can last for several days. In case of septic complications during this period, there is imminent danger of mortality due to reduced immune function. This fact leads to classification of sepsis in regard to its genesis: spontaneously acquired sepsis type A is distinguishable from sepsis type B, which is acquired postoperatively. The main difference between these types is the immunologic condition at the time point of sepsis development. Postoperative immune dysfunction can be described by several parameters, i.e. reduction of HLA-DR expression on monocytes and increased apoptosis of T lymphocytes. A direct correlation exists between magnitude of immune dysfunction and complexity of the previous surgical trauma. For the first time it is now possible to study this phenomenon of postoperative immune dysfunction by use of an adequate animal model. Intestinal manipulation in mice fulfils the necessary criteria to serve as a model of surgically induced immune dysfunction.

Properdin deficiency in murine models of nonseptic shock

Hereditary properdin deficiency is linked to susceptibility to meningococcal disease (Neisseria meningitidis serotypes Y and W-135) with high mortality. Its relative contribution toward the outcome of nonseptic shock has not been investigated. Using properdin-deficient C57BL/6 mice and their littermates, this study examines their survival of zymosan-induced and LPS-induced shock. Properdin-deficient mice were more resistant to zymosan shock compared with wild-type mice, which showed greater impairment of end-organ function 24 h after zymosan injection, higher TNF-alpha production by alveolar and peritoneal macrophages, higher TNF-alpha, and, inversely, lower IL-10 levels in peritoneal lavage and circulation and higher plasma C5a levels. Properdin-deficient mice showed significantly higher mortality in LPS shock, elevated TNF-alpha, and, inversely, reduced IL-10 production by peritoneal macrophages as well as lower plasma C5a levels compared with wild-type littermates. NO production by peritoneal macrophages and plasma alpha1-antitrypsin levels at 24 h after the injection of LPS or zymosan were decreased in properdin-deficient mice in both models, and fewer histopathologic changes in liver were observed in properdin-deficient animals. This study provides evidence that properdin deficiency attenuates zymosan-induced shock and exacerbates LPS-induced shock.

The innate immune response to secondary peritonitis

Secondary peritonitis continues to cause high morbidity and mortality despite improvements in medical and surgical therapy. This review combines data from published literature, focusing on molecular patterns of inflammation in pathophysiology and prognosis during peritonitis. Orchestration of the innate immune response is essential. To clear the microbial infection, activation and attraction of leukocytes are essential and beneficial, just like the expression of inflammatory cytokines. Exaggeration of these inflammatory systems leads to tissue damage and organ failure. Nonsurvivors have increased proinflammation, complement activation, coagulation, and chemotaxis. In these patients, anti-inflammatory systems are decreased in blood and lungs, whereas the abdominal compartment shows decreased neutrophil activation and decreased or stationary chemokine and cytokine levels. A later down-regulation of proinflammatory mediators with concomitant overexpression of anti-inflammatory mediators leads to immunoparalysis and failure to clear residual bacterial load, resulting in the occurrence of superimposed infections. Thus, in patients with adverse outcome, the inflammatory reaction is no longer contained within the abdomen, and the inflammatory response has shifted to other compartments. For the understanding of the host response to secondary peritonitis, it is essential to realize that the defense systems presumably are expressed differently and, in part, autonomously in different compartments.

Role of LPS in the hepatic microvascular dysfunction elicited by cecal ligation and puncture in mice

BACKGROUND/AIMS

Sepsis remains a leading cause of death in critically ill patients. Because endotoxemia is viewed as a key mediator of sepsis-induced inflammation, administration of bacterial endotoxin (LPS) is often used to simulate sepsis in experimental animals. This study tests the hypothesis that LPS is a critical determinant of the hepatic microvascular dysfunction in mice made septic by cecal ligation and puncture (CLP).

METHODS

Intravital videomicroscopy was used to quantify sinusoidal perfusion, and platelet and leukocyte adhesion in terminal hepatic venules (THV) and sinusoids in LPS-sensitive and LPS-insensitive mice subjected to CLP or LPS (i.p.). mRNA expression of TLR-2, TLR-4, MyD-88, and Ly-96 was also assessed.

RESULTS

While LPS-sensitive mice responded to both CLP and LPS challenges with elevated leukocyte and platelet adhesion in THV and sinusoids, and a reduced sinusoidal perfusion density, LPS-insensitive mice exhibited comparable blood cell adhesion and sinusoidal malperfusion following CLP, but not LPS. Hepatic mRNA of MyD-88 and TLR-2 was elevated in the CLP and LPS groups. Endotoxin was not detectable in the blood of LPS-sensitive mice after CLP, but was elevated after LPS administration.

CONCLUSIONS

These findings do not support a major role for LPS in the hepatic microvascular disturbances associated with polymicrobial sepsis.

Mast cells in the promotion and limitation of chronic inflammation

Observations of increased numbers of mast cells at sites of chronic inflammation have been reported for over a hundred years. Light and electron microscopic evidence of mast cell activation at such sites, taken together with the known functions of the diverse mediators, cytokines, and growth factors that can be secreted by appropriately activated mast cells, have suggested a wide range of possible functions for mast cells in promoting (or suppressing) many features of chronic inflammation. Similarly, these and other lines of evidence have implicated mast cells in a variety of adaptive or pathological responses that are associated with persistent inflammation at the affected sites. Definitively characterizing the importance of mast cells in chronic inflammation in humans is difficult. However, mice that genetically lack mast cells, especially those which can undergo engraftment with wildtype or genetically altered mast cells, provide a means to investigate the importance of mast cells and specific mast cell functions or products in diverse models of chronic inflammation. Such work has confirmed that mast cells can significantly influence multiple features of chronic inflammatory responses, through diverse effects that can either promote or, perhaps more surprisingly, suppress aspects of these responses.

TREM-1 promotes survival during septic shock in mice

Triggering receptor expressed on myeloid (TREM)-1 is integral to the inflammatory response occurring during septic shock, although its precise function has yet to be determined. Here we show that in vivo silencing of TREM-1 using siRNA duplexes in a fecal peritonitis mouse model resulted in a blunted inflammatory response and increased mortality. This was associated with impaired bacterial clearance related to marked inhibition of the neutrophil oxidative burst. By contrast, TREM-1-silenced mice were highly resistant to a lethal endotoxin challenge, while partial silencing of TREM-1 in the bacterial peritonitis model produced a significant survival benefit. These data highlight the crucial role of the TREM-1 pathway in mounting an adequate inflammatory and cytotoxic response to polymicrobial sepsis, and both the therapeutic promise and potential risks of its modulation.

Emerging drugs for the treatment of sepsis

Septic shock still places a major burden on the healthcare system, although recent years have been marked by the demonstration that corticosteroids and activated protein C may substantially improve survival in selected populations. This review discusses the current management of septic shock and the potential development of new therapeutics following impressive advances in the pathomechanisms of septic shock.

Hyperbaric oxygen protects from sepsis mortality via an interleukin-10-dependent mechanism

OBJECTIVE

This study was performed to determine whether hyperbaric oxygen (HBO2) therapy is protective in cecal ligation and puncture (CLP)-induced sepsis and if protection is dependent on oxygen dosing. We also wished to determine whether HBO2 affected bacterial clearance or altered macrophage production of interleukin-10 (IL-10)s in the setting of CLP sepsis. Finally, we wished to determine whether the mechanism of HBO2 protection in sepsis was dependent on IL-10 production.

DESIGN

Prospective, experimental study.

SETTING

University experimental research laboratory.

SUBJECTS

C57BL/6 and C57BL/6 IL-10 mice.

INTERVENTIONS

Sepsis was induced by CLP. Mice were randomized to receive a 1.5-hr HBO2 treatment at either 1, 2.5, or 3 atmospheres absolute every 12 hrs or HBO2 at 2.5 atmospheres absolute every 24 hrs. Mice were also harvested at 24 hrs for determination of bacterial load and isolation and study of CD11b peritoneal macrophages.

MEASUREMENTS AND MAIN RESULTS

Survival was monitored for 100 hrs after CLP +/- HBO2 treatment. HBO2 significantly improved survival when administered at 2.5 atmospheres absolute every 12 hrs. Other treatment schedules were not protective, and treatment at 3.0 atmospheres absolute significantly worsened survival outcome. Bacterial load was significantly reduced in splenic homogenates but not peritoneal fluid at 24 hrs. Macrophages isolated from HBO2-treated mice demonstrated enhanced IL-10 secretion in response to lipopolysaccharide as compared with CLP controls. Mice genetically deficient in IL-10 expression treated with HBO2 at 2.5 atmospheres absolute every 12 hrs were not protected from CLP-induced mortality.

CONCLUSION

HBO2 may be protective in CLP sepsis within a window of oxygen dosing. The mechanism of HBO2 protection may be potentially linked in part to expression of IL-10, as peritoneal macrophages demonstrated enhanced IL-10 expression and IL-10 mice were not protected by HBO2 treatment.

In situ assays demonstrate that interferon-gamma suppresses infection-stimulated hepatic fibrin deposition by promoting fibrinolysis

BACKGROUND

Inflammatory cytokines potently impact hemostatic pathways during infection, but the tissue-specific regulation of coagulation and fibrinolysis complicates studies of the underlying mechanisms.

METHODS AND RESULTS

Here, we describe assays that quantitatively measuring prothrombinase (PTase), protein C-ase (PCase) and plasminogen activator (PA) activities in situ, thereby facilitating studies of tissue-specific hemostasis. Using these assays, we investigate the mechanisms regulating hepatic fibrin deposition during murine toxoplasmosis and the means by which interferon-gamma (IFN-gamma) suppresses infection-stimulated fibrin deposition. We demonstrate that Toxoplasma infection upregulates hepatic PTase, PCase, and PA activity. Wild type and gene-targeted IFN-gamma-deficient mice exhibit similar levels of infection-stimulated PTase activity. By contrast, IFN-gamma-deficiency is associated with increased PCase activity and reduced PA activity during infection. Parallel analyses of hepatic gene expression reveal that IFN-gamma-deficiency is associated with increased expression of thrombomodulin (TM), a key component of the PCase, increased expression of thrombin-activatable fibrinolysis inhibitor (TAFI), a PC substrate, and reduced expression of urokinase PA (u-PA).

CONCLUSIONS

These findings suggest that IFN-gamma suppresses infection-stimulated hepatic fibrin deposition by suppressing TM-mediated activation of TAFI, thereby destabilizing fibrin deposits, and concomitantly increasing hepatic u-PA activity, thereby promoting fibrinolysis. We anticipate that further application of these in situ assays will improve our understanding of tissue-specific hemostasis, its regulation by cytokines, and its dysregulation during coagulopathy.

Simvastatin improves sepsis-induced mortality and acute kidney injury via renal vascular effects

Acute kidney injury (AKI) occurs in about half of patients in septic shock and the mortality of AKI with sepsis is extremely high. An effective therapeutic intervention is urgently required. Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors that also have pleiotropic actions. They have been reported to increase the survival of septic or infectious patients. But the effect of simvastatin, a widely used statin, on sepsis-induced AKI is unknown. The effects of simvastatin and tumor necrosis factor (TNF)-alpha neutralizing antibody were studied in a clinically relevant model of sepsis-induced AKI using cecal ligation and puncture (CLP) in elderly mice. Simvastatin significantly improved CLP-induced mortality and AKI. Simvastatin attenuated CLP-induced tubular damage and reversed CLP-induced reduction of intrarenal microvascular perfusion and renal tubular hypoxia at 24 h. Simvastatin also restored towards normal CLP-induced renal vascular protein leak and serum TNF-alpha. Neither delayed simvastatin therapy nor TNF-alpha neutralizing antibody improved CLP-induced AKI. Simvastatin improved sepsis-induced AKI by direct effects on the renal vasculature, reversal of tubular hypoxia, and had a systemic anti-inflammatory effect.

Modulation of the triggering receptor expressed on the myeloid cell type 1 pathway in murine septic shock

The triggering receptor expressed on myeloid cell type 1 (TREM-1) is a cell surface molecule that has been identified on both human and murine polymorphonuclear neutrophils and mature monocytes. The activation of TREM-1 in the presence of microbial components amplifies the inflammatory response and may be responsible for the hyperresponsiveness observed during the initial stage of sepsis. To investigate the effect of the modulation of the TREM-1 pathway during experimental murine sepsis, we used analogue synthetic peptides derived from the extracellular moiety of TREM-1. The TREM-1 ligand was expressed on both peritoneal and peripheral neutrophils during experimental peritonitis in mice. The TREM-1 peptides inhibited the recognition by TREM-1 of its ligand and protected endotoxinic mice from death. In septic rats, the TREM-1 peptides improved the hemodynamic status, attenuated the development of lactic acidosis, modulated the production of such proinflammatory cytokines as tumor necrosis factor alpha and interleukin-1beta, and improved survival. The protective effect of these peptides on arterial pressure could partly be explained by a decreased production of nitric oxide. These data suggest that in vivo modulation of TREM-1 might be a suitable therapeutic tool for the treatment of sepsis.

Secretory phospholipase A2 of group IIA: Is it an offensive or a defensive player during atherosclerosis and other inflammatory diseases?

Since its discovery in the serum of patients with severe inflammation and in rheumatoid arthritic fluids, the secretory phospholipase A2 of group IIA (sPLA2-IIA) has been chiefly considered as a proinflammatory enzyme, the result of which has been very intense interest in selective inhibitors of sPLA2-IIA in the hope of developing new and efficient therapies for inflammatory diseases. The recent discovery of the antibacterial properties of sPLA2-IIA, however, has raised the question of whether the upregulation of sPLA2-IIA during inflammation is to be considered uniformly negative and the hindrance of sPLA2-IIA in every instance beneficial. The aim of this review is for this reason, along with the results of various investigations which argue for the proinflammatory and proatherogenic effects of an upregulation of sPLA2-IIA, also to array data alongside which point to a protective function of sPLA2-IIA during inflammation. Thus, it could be shown that sPLA2-IIA, apart from the bactericidal effects, possesses also antithrombotic properties and indeed plays a possible role in the resolution of inflammation and the accelerated clearance of oxidatively modified lipoproteins during inflammation via the liver and adrenals. Based on these multipotent properties the knowledge of the function of sPLA2-IIA during inflammation is a fundamental prerequisite for the development and establishment of new therapeutic strategies to prevent and treat severe inflammatory diseases up to and including sepsis.

Tumor necrosis factor alpha and gamma interferon, but not hemorrhage or pathogen burden, dictate levels of protective fibrin deposition during infection

While coagulation often causes pathology during infectious disease, we recently demonstrated that fibrin, a product of the coagulation pathway, performs a critical protective function during acute toxoplasmosis (L. L. Johnson, K. N. Berggren, F. M. Szaba, W. Chen, and S. T. Smiley, J. Exp. Med. 197:801-806, 2003). Here, we investigate the mechanisms regulating the formation of this protective fibrin. Through comparisons of Toxoplasma-infected wild-type and cytokine-deficient mice we dissociate, for the first time, the relative fibrin-regulating capacities of pathogen products, host cytokines, and infection-stimulated hemorrhage. Remarkably, neither the pathogen burden nor hemorrhage is a primary regulator of fibrin levels. Rather, two type 1 cytokines exert dominant and counterregulatory roles: tumor necrosis factor alpha (TNF-alpha), acting via the type 1 TNF-alpha receptor, promotes fibrin deposition, while gamma interferon (IFN-gamma), acting via STAT1 and IFN-gamma receptors expressed on radioresistant cells, suppresses fibrin deposition. These findings have important clinical implications, as they establish that cytokines known to regulate pathological coagulation also dictate levels of protective fibrin deposition. We present a novel model depicting mechanisms by which the immune system can destroy infected tissue while independently restraining hemorrhage and promoting tissue repair through the deliberate deposition of protective fibrin.

Seprafilm Does Not Aggravate Intraperitoneal Septic Conditions or Evoke Systemic Inflammatory Response

PURPOSE

To determine whether Seprafilm aggravates the systemic inflammatory response and adversely affects the outcome of postoperative intraperitoneal septic conditions.

METHODS

We retrospectively analyzed the relationship between the intraperitoneal placement of Seprafilm and the rate of intraperitoneal septic complications in 278 consecutive patients. Experimentally, 40 rats were subjected to laparotomy with or without the intraperitoneal placement of Seprafilm. Bacterial peritonitis was induced by cecal ligation and puncture (CLP) and the serum cytokine levels were measured.

RESULTS

Seprafilm did not increase the rate of septic complications or aggravate inflammatory responses in patients with or without postoperative intraperitoneal inflammatory complications. Experimentally, there was no significant difference between the serum inflammatory cytokine levels after CLP with or without Seprafilm.

CONCLUSIONS

Seprafilm did not adversely affect postoperative inflammatory response or clinical outcomes, even in patients with intraperitoneal septic complications.

NEUTRALIZATION OF TUMOR NECROSIS FACTOR IN PRECLINICAL MODELS OF SEPSIS

Tumor necrosis factor (TNFalpha), a cardinal early mediator of the innate host inflammatory response, has been an attractive target for therapeutic intervention in human sepsis. However, pooled data from 12 completed randomized controlled trials show only a very modest impact on mortality in a highly heterogeneous population of patients. To gain insight into the preclinical in vivo biology of TNFalpha that might aid in better identifying appropriate patient populations for therapeutic intervention, we undertook a systematic review of published reports of preclinical studies assessing the consequences of neutralization of TNFalpha in models of acute infection or inflammation. We identified 143 reports incorporating 484 unique experimental comparisons in seven different animal species. The effects of neutralization of TNFalpha in these were quite variable. Neutralization of TNFalpha was beneficial in endotoxemia, or after systemic challenge with gram-negative organisms, Staphylococcus aureus, or Group B streptococci. On the other hand, neutralization was detrimental in infections caused by Streptococcus pneumoniae, Candida spp., or intracellular pathogens such as Listeria and Mycobacterium tuberculosis, and in models of pneumonia. Treatment was more efficacious when delivered before infectious challenge, and the therapeutic signal increased as the baseline mortality in the placebo group increased. Evidence of neutralization of TNFalpha bioactivity, and of attenuation of inflammation, was typically accompanied by evidence of impairment of antimicrobial defenses. Multiple specific and nonspecific therapeutic strategies were identified. We conclude that the beneficial effects of TNF in systemic inflammation occur at the cost of impaired antimicrobial defenses, and that a better understanding of the consequences of neutralization of TNFalpha in vivo could aid in better defining optimal patient populations for therapeutic intervention.

Animal models of sepsis: setting the stage

Sepsis is a state of disrupted inflammatory homeostasis that is often initiated by infection. The development and progression of sepsis is multi-factorial, and affects the cardiovascular, immunological and endocrine systems of the body. The complexity of sepsis makes the clinical study of sepsis and sepsis therapeutics difficult. Animal models have been developed in an effort to create reproducible systems for studying sepsis pathogenesis and preliminary testing of potential therapeutic agents. However, demonstrated benefit from a therapeutic agent in animal models has rarely been translated into success in human clinical trials. This review summarizes the common animal sepsis models and highlights how results of recent human clinical trials might affect their use.

Besonderheiten der abdominellen Sepsis

Abdominal sepsis remains a major cause of perioperative morbidity and mortality in surgical intensive care units. It must be considered a life-threatening condition and requires multidisciplinary coordination of intensive care. Apart from the local abdominal infection (peritonitis), abdominal sepsis is defined by extraperitoneal systemic reactions potentially leading to septic shock and death in the further course. Early and radical focus sanitation as well as aggressive systemic antimicrobial therapy remain the causal therapy strategies of abdominal sepsis.

Divergence of protection induced by bacterial products and sepsis-induced immune suppression

Susceptibility to bacterial infections after a primary immune stimulation differs drastically depending on the presensitization of the innate immune system. To determine the conditions that either induce protection or enhanced susceptibility to infection with Salmonella enterica serovar Typhimurium, we pretreated mice either with tumor necrosis factor (TNF), whole killed bacteria, or sublethal cecal ligation and puncture (CLP) as a mouse model for septic peritonitis. Impaired production of the cytokines TNF, interleukin-6 (IL-6), and IL-10 was induced by these pretreatment schedules, with TNF-signaling not being essential for this effect. Injection of TNF or killed bacteria enhanced survival of mice infected subsequently with serovar Typhimurium. In contrast, sepsis such as that induced by CLP only protected from shock induced by d-galactosamine and lipopolysaccharide or by a high dose of bacteria but sensitized to a secondary bacterial infection. Such sepsis-induced enhanced susceptibility to infection was critically dependent on TNF function.