Early antibiotic administration but not antibody therapy directed against IL-6 improves survival in septic mice predicted to die on basis of high IL-6 levels

GENETIC ABLATION OF THE C-TYPE LECTIN RECEPTOR CLEC2D INCREASES PERITONITIS MORTALITY, INFLAMMATION, AND PHYSIOLOGY WITHOUT DIMINISHING ORGAN INJURY

ABSTRACT

Background: Sepsis accounts for substantial morbidity and mortality motivating investigators to continue the search for pathways and molecules driving the pathogenesis of the disease. The current study examined if the novel C-type lectin receptor (CLR), Clec2d, plays a significant role in the pathogenesis of sepsis. Methods: Clec2d knockout (KO) mice were fully backcrossed onto the C57/BL6 background. Acute endotoxemia was induced with an intraperitoneal injection of lipopolysaccharide (LPS). Sepsis was induced in two different models, cecal ligation and puncture (CLP) and Pseudomonas aeruginosa pneumonia. Both models were treated with antibiotics and fluid resuscitation. In the sepsis models, physiologic and hematologic measurements were measured at 24 h by collecting a small sample of peripheral blood. Mortality was followed for 14 days. Results : A total of 197 mice were studied, 58 wild type (WT) and 54 knock-out (KO) in the LPS model; 27 wild type and 21 KO mice in the CLP model; and 22 WT and 15 KO mice in the pneumonia model. Clec2d KO mice had greater mortality in the LPS and CLP studies but not the pneumonia model. There were significant differences in multiple parameters determined 24 h post sepsis between mice who subsequently died and those lived. Consistent with previous reports in the CLP model, higher concentrations of IL-6, increased numbers of peripheral blood lymphocytes and greater renal injury were found in the dying mice. In contrast, in the pneumonia model, IL-6 was higher in the surviving mice; however, the IL-6 levels in the pneumonia model (0.6 ± 0.3 ng/mL mean ± SEM) were less than 2% of the IL-6 levels of mice that died in the CLP model (41 ± 9 ng/mL, mean ± SEM). There were no differences in the lymphocyte count or renal injury between living and dying mice in the pneumonia model. In both sepsis models, dying mice had lower heart rates, respiratory rates, and body temperatures. These values were also lower in the KO mice compared to the WT in CLP, but the breath rate and body temperature were increased in the KO pneumonia mice. Conclusion: The C-type lectin receptor Clec2d plays a complicated role in the pathogenesis of sepsis, which varies with source of infection as demonstrated in the models used to study the disease. These data highlight the heterogeneity of the responses to sepsis and provide further evidence that a single common pathway driving sepsis organ injury and death likely does not exist.

Potential therapeutic effect of Carica papaya leaves extract on immune response, biochemical and hematological mechanisms on cecal ligation and puncture model of sepsis in rats: an in vivo study

Antibiotics and immunotherapies possess unavoidable adverse effects that hinder sepsis management. Herbal drugs have demonstrated potential immunomodulatory properties vital for sepsis treatment. We hypothesized in the present study that the use of Carica papaya leaves extract had the potential to improve survival and modulate immune cytokine release during sepsis. Animals were subjected to cecal ligation and puncture (CLP) to induce sepsis. Septic rats divided into 10 groups received ethanol extract of C. papaya leaves (50 and 100 mg/kg), imipenem (120 mg/kg) and cyclophosphamide (CP, 10 mg/kg). To investigate the immunomodulatory potentials of EE, cytokine levels like interleukin (IL-6), tumor necrosis factor (TNF-α), and IL-10 along with hematological and biochemical parameters were analyzed. Our results exhibited improved survival rates concerning ethanol extract treatment alone and in combination with imipenem and CP (100%) as compared to the CLP group (33.3%) on day 7 post-surgery. The combination treatment of ethanol extract with imipenem and CP significantly (P < 0.001) ameliorated cytokine levels and hematological and biochemical parameters in septic rats. A histopathological examination suggested improved liver and kidney tissue condition after combination treatment as compared to the CLP group. Therefore, it was concluded that combination therapy of extract with imipenem and CP improved survival rates and marked immunomodulatory potential in septic rats compared to monotherapy. The findings suggested the use of a mixture of these drugs in clinical settings to treat sepsis.

Common Variables That Influence Sepsis Mortality in Mice

Introduction

Sepsis is characterized by a dysregulated host immune response to infection, leading to organ dysfunction and a high risk of death. The cecal ligation and puncture (CLP) mouse model is commonly used to study sepsis, but animal mortality rates vary between different studies. Technical factors and animal characteristics may affect this model in unanticipated ways, and if unaccounted for, may lead to serious biases in study findings. We sought to evaluate whether mouse sex, age, weight, surgeon, season of experiments, and timing of antibiotic administration influenced mortality in the CLP model.

Methods

We created a comprehensive dataset of C57BL/6J mice that had undergone CLP surgery within our lab during years 2015-2020 from published and unpublished studies. The primary outcome was defined as the time from sepsis induction to death or termination of study (14 days). The Log rank test and Cox regression models were used to analyze the dataset. The study included 119 mice, of which 43% were female, with an average age of 12.6 weeks, an average weight of 25.3 g. 38 (32%) of the animals died.

Results

In the unadjusted analyses, experiments performed in the summer and higher weight predicted a higher risk of mortality. In the stratified Cox model by sex, summer season (adjusted hazard ratio [aHR]=5.61, p=0.004) and delayed antibiotic administration (aHR=1.46, p=0.029) were associated with mortality in males, whereas higher weight (aHR=1.52, p=0.005) significantly affected mortality in females. In addition, delayed antibiotic administration (HR=1.42, p=0.025) was associated with mortality in the non-summer seasons, but not in the summer season.

Discussion

In conclusion, some factors specific to sex and season have a significant influence on sepsis mortality in the CLP model. Consideration of these factors along with appropriate group matching or adjusted analysis is critical to minimize variability beyond the experimental conditions within a study.

Corticosterone and Adrenocorticotrophic Hormone Secretion Is Recovered after Immune Challenge or Acute Restraint Stress in Sepsis Survivor Animals

BACKGROUND

Clinical and experimental studies report a dysregulation of hypothalamus-pituitary-adrenal (HPA) axis during sepsis that causes impairment in hormone secretion in the late phase contributing for the pathophysiology of the disease. However, it is unclear whether this alteration persists even after the disease remission.

METHODS

We evaluated the effect of an immune challenge or restraint stress on the hormone secretion of HPA axis in sepsis survivor rats. Sepsis was induced by cecal ligation-puncture (CLP) surgery. Naive or animals that survive 5 or 10 days after CLP were submitted to lipopolysaccharide (LPS) injection or restraint stress. After 60 min, blood was collected for plasma nitrate, cytokines, adrenocorticotropic hormone (ACTH), and corticosterone (CORT) and brain for synaptophysin and hypothalamic cytokines.

RESULTS

Five days survivor animals showed increased plasma nitrate (p < 0.001) and interleukin (IL)-1β levels (p < 0.05) that were abolished in the 10 days survivors. In the hypothalamus of both survivors, the reverse was seen with IL-6 increased (p < 0.01), while IL-1β did not show any alteration. Synaptophysin expression was reduced in both survivors and did not change after any stimuli. Only the LPS administration increased plasma and/or inflammatory mediators levels in both groups (survivors and naive) being apparently lower in the survivors. There was no difference in the increased secretion pattern of ACTH and CORT observed in the naive and sepsis survivor animals submitted to immune challenge or restraint stress.

CONCLUSION

We conclude that the HPA axis is already recovered soon after 5 days of sepsis induction responding with normal secretion of ACTH and CORT when required.

Macrophage-derived cytokines in pneumonia: Linking cellular immunology and genetics

Macrophages represent the first line of anti-pathogen defense - they encounter invading pathogens to perform the phagocytic activity, to deliver the plethora of pro- and anti-inflammatory cytokines, and to shape the tissue microenvironment. Throughout pneumonia course, alveolar macrophages and infiltrated blood monocytes produce increasing cytokine amounts, which activates the antiviral/antibacterial immunity but can also provoke the risk of the so-called cytokine "storm" and normal tissue damage. Subsequently, the question of how the cytokine spectrum is shaped and balanced in the pneumonia context remains a hot topic in medical immunology, particularly in the COVID19 pandemic era. The diversity in cytokine profiles, involved in pneumonia pathogenesis, is determined by the variations in cytokine-receptor interactions, which may lead to severe cytokine storm and functional decline of particular tissues and organs, for example, cardiovascular and respiratory systems. Cytokines and their receptors form unique profiles in individual patients, depending on the (a) microenvironmental context (comorbidities and associated treatment), (b) lung monocyte heterogeneity, and (c) genetic variations. These multidisciplinary strategies can be proactively considered beforehand and during the pneumonia course and potentially allow the new age of personalized immunotherapy.

Feeding-induced resistance to acute lethal sepsis is dependent on hepatic BMAL1 and FXR signalling

In mice, time of day strongly influences lethality in response to LPS, with survival greatest at the beginning compared to the end of the light cycle. Here we show that feeding, rather than light, controls time-of-day dependent LPS sensitivity. Mortality following LPS administration is independent of cytokine production and the clock regulator BMAL1 expressed in myeloid cells. In contrast, deletion of BMAL1 in hepatocytes globally disrupts the transcriptional response to the feeding cycle in the liver and results in constitutively high LPS sensitivity. Using RNAseq and functional validation studies we identify hepatic farnesoid X receptor (FXR) signalling as a BMAL1 and feeding-dependent regulator of LPS susceptibility. These results show that hepatocyte-intrinsic BMAL1 and FXR signalling integrate nutritional cues to regulate survival in response to innate immune stimuli. Understanding hepatic molecular programmes operational in response to these cues could identify novel pathways for targeting to enhance endotoxemia resistance.

Skeletal Muscle Interleukin-6 Contributes to the Innate Immune Response in Septic Mice

ABSTRACT

Interleukin-6 (IL-6) is a major cytokine released by skeletal muscle. Although IL-6 plays complex but well-known roles in host defense, the specific contribution of skeletal muscle IL-6 to innate immunity remains unknown. We tested its functional relevance by exposing inducible skeletal muscle IL-6 knockdown (skmIL-6KD) mice to a cecal slurry model of polymicrobial peritonitis and compared responses to strain-matched controls and skeletal muscle Cre-matched controls at 3, 6, and 12 h postinfection. In both sexes, skmIL-6KD mice at 6 h of infection exhibited marked changes to leukocyte trafficking in the peritoneum, characterized by ∼1.75-fold elevation in %neutrophils, a ∼3-fold reduction in %lymphocytes and a ∼2 to 3-fold reduction in %basophils. A similar pattern was seen at 12 h. No changes were observed in plasma leukocyte counts. Circulating cytokines in female skmIL-6KD mice at 6 h consistently showed modest reductions in IL-6, but marked reductions in a broad range of both pro- and anti-inflammatory cytokines, e.g., TNFα and IL-10. In both sexes at 12 h, a generalized suppression of plasma cytokines was also seen after the effects of Cre-induction with raloxifene were addressed. There were no significant effects of skmIL-6KD on mortality in either sex. Collectively, our results are consistent with skmIL-6 playing an important and previously unrecognized role in immune cell trafficking and cytokine regulation during septic shock.

Umbilical cord mesenchymal stem cells enhance the therapeutic effect of imipenem by regulating myeloid-derived suppressor cells in septic mice

Background

Umbilical cord mesenchymal stem cells (UC-MSCs), which possess potent immunomodulatory effects and low immunogenicity, are considered to be a promising stem cell-based therapy for sepsis. In the current study, we aimed to investigate whether the combined use of UC-MSCs and imipenem has a better effect than imipenem alone in treating Escherichia coli (E. coli)-induced sepsis and to explore the mechanism by which UC-MSCs exert their therapeutic effect in septic mice.

Methods

We randomly divided mice into five groups with 10 mice in each group: the normal control group (control group), the sepsis group (vehicle group), the MSCs treatment group (MSCs group), the imipenem treatment group (imipenem group), and the imipenem plus MSCs treatment group (imipenem + MSCs group). We monitored the survival rate in each group every 12 h for 3 days. After observing the survival rate, another 50 mice were also randomly divided into five groups, and the mice were sacrificed after 24 h. Bacterial colonies from the blood and peritoneal lavage fluid were counted in a blinded manner. Organ injury was analyzed by hematoxylin and eosin (HE) staining. Frequencies of myeloid-derived suppressor cells (MDSCs) in the blood, spleen, and bone marrow (BM) were determined by flow cytometry. Plasma levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-1β, and IL-10 were detected by enzyme-linked immunosorbent assay (ELISA).

Results

Compared with imipenem treatment, the co-administration of UC-MSCs and imipenem dramatically improved the survival rate, decreased the bacterial load, and ameliorated organ injury. Furthermore, UC-MSCs treatment, either alone or in combination with imipenem, significantly increased plasma levels of IL-10 and the percentage of MDSCs by inducing arginase-1 in septic mice.

Conclusions

Our results indicated that UC-MSCs protect mice against sepsis by acting on MDSCs. Combination therapy of UC-MSCs and imipenem may be a new approach for the future clinical treatment of sepsis.

Can the Cecal Ligation and Puncture Model Be Repurposed To Better Inform Therapy in Human Sepsis?

A recent report by the National Institutes of Health on sepsis research has implied there is a trend to move away from mouse models of sepsis. The most commonly used animal model to study the pathogenesis of human sepsis is cecal ligation and puncture (CLP) in mice. The model has been the mainstay of sepsis research for decades and continues to be considered the gold standard to inform novel pathways of sepsis physiology and its therapeutic direction. As there have been many criticisms of the model, particularly regarding its relevance to human disease, how this model might be repurposed to be more reflective of the human condition begs discussion. In this piece, we compare and contrast the mouse microbiome of the CLP model to the emerging science of the microbiome of human sepsis and discuss the relevance for mice to harbor the specific pathogens present in the human microbiome during sepsis, as well as an underlying disease process to mimic the characteristics of those patients with undesirable outcomes. How to repurpose this model to incorporate these "human factors" is discussed in detail and suggestions offered.

Premise for Standardized Sepsis Models

Sepsis morbidity and mortality exacts a toll on patients and contributes significantly to healthcare costs. Preclinical models of sepsis have been used to study disease pathogenesis and test new therapies, but divergent outcomes have been observed with the same treatment even when using the same sepsis model. Other disorders such as diabetes, cancer, malaria, obesity, and cardiovascular diseases have used standardized, preclinical models that allow laboratories to compare results. Standardized models accelerate the pace of research and such models have been used to test new therapies or changes in treatment guidelines. The National Institutes of Health mandated that investigators increase data reproducibility and the rigor of scientific experiments and has also issued research funding announcements about the development and refinement of standardized models. Our premise is that refinement and standardization of preclinical sepsis models may accelerate the development and testing of potential therapeutics for human sepsis, as has been the case with preclinical models for other disorders. As a first step toward creating standardized models, we suggest standardizing the technical standards of the widely used cecal ligation and puncture model and creating a list of appropriate organ injury and immune dysfunction parameters. Standardized sepsis models could enhance reproducibility and allow comparison of results between laboratories and may accelerate our understanding of the pathogenesis of sepsis.

Immune Response Resetting in Ongoing Sepsis

Cure of severe infections, sepsis, and septic shock with antimicrobial drugs is a challenge because morbidity and mortality in these conditions are essentially caused by improper immune response. We have tested the hypothesis that repeated reactivation of established memory to pathogens may reset unfavorable immune responses. We have chosen for this purpose a highly stringent mouse model of polymicrobial sepsis by cecum ligation and puncture. Five weeks after priming with a diverse Ag pool, high-grade sepsis was induced in C57BL/6j mice that was lethal in 24 h if left untreated. Antimicrobial drug (imipenem) alone rescued 9.7% of the animals from death, but >5-fold higher cure rate could be achieved by combining imipenem and two rechallenges with the Ag pool (p < 0.0001). Antigenic stimulation fine-tuned the immune response in sepsis by contracting the total CD3+ T cell compartment in the spleen and disengaging the hyperactivation state in the memory T subsets, most notably CD8+ T cells, while preserving the recovery of naive subsets. Quantitative proteomics/lipidomics analyses revealed that the combined treatment reverted the molecular signature of sepsis for cytokine storm, and deregulated inflammatory reaction and proapoptotic environment, as well as the lysophosphatidylcholine/phosphatidylcholine ratio. Our results showed the feasibility of resetting uncontrolled hyperinflammatory reactions into ordered hypoinflammatory responses by memory reactivation, thereby reducing morbidity and mortality in antibiotic-treated sepsis. This beneficial effect was not dependent on the generation of a pathogen-driven immune response itself but rather on the reactivation of memory to a diverse Ag pool that modulates the ongoing response.

Targeting the Blood-Brain Barrier to Prevent Sepsis-Associated Cognitive Impairment

Sepsis is a systemic inflammatory disease resulting from an infection. This disorder affects 750 000 people annually in the United States and has a 62% rehospitalization rate. Septic symptoms range from typical flu-like symptoms (eg, headache, fever) to a multifactorial syndrome known as sepsis-associated encephalopathy (SAE). Patients with SAE exhibit an acute altered mental status and often have higher mortality and morbidity. In addition, many sepsis survivors are also burdened with long-term cognitive impairment. The mechanisms through which sepsis initiates SAE and promotes long-term cognitive impairment in septic survivors are poorly understood. Due to its unique role as an interface between the brain and the periphery, numerous studies support a regulatory role for the blood-brain barrier (BBB) in the progression of acute and chronic brain dysfunction. In this review, we discuss the current body of literature which supports the BBB as a nexus which integrates signals from the brain and the periphery in sepsis. We highlight key insights on the mechanisms that contribute to the BBB's role in sepsis which include neuroinflammation, increased barrier permeability, immune cell infiltration, mitochondrial dysfunction, and a potential barrier role for tissue non-specific alkaline phosphatase (TNAP). Finally, we address current drug treatments (eg, antimicrobials and intravenous immunoglobulins) for sepsis and their potential outcomes on brain function. A comprehensive understanding of these mechanisms may enable clinicians to target specific aspects of BBB function as a therapeutic tool to limit long-term cognitive impairment in sepsis survivors.

Impairment of osmotic challenge-induced neurohypophyseal hormones secretion in sepsis survivor rats

BACKGROUND/PURPOSE

Recent studies have reported that sepsis survivors show impaired central nervous system functions. The osmoregulation in this post-sepsis condition has not been well investigated. In the present study, we evaluated the secretion of neurohypophyseal hormones, arginine vasopressin (AVP) and oxytocin (OT), and water intake induced by osmotic challenge in survivor rats.

METHODS

Wistar rats were submitted to sepsis by cecal ligation and puncture (CLP). Five days after CLP surgery, the survivor and naive animals were stimulated with an osmotic challenge consisting of hypertonic saline administration. Thirty minutes later, blood and brain were collected for determination of osmolality, nitrite, interleukin (IL)-1β, IL-6, AVP and OT levels and c-fos expression analysis of hypothalamic supraoptic nuclei (SON), respectively. In another set of sepsis survivor animals, water intake was measured for 240 min after the osmotic stimulus.

RESULTS

High levels of nitrite and IL-1β, but not IL-6, were found in the plasma of sepsis survivors and this long-term systemic inflammation was not altered by the osmotic challenge. Moreover, the AVP and OT secretion (but not the osmolality) and c-fos expression in SON were significantly attenuated in CLP survivor animals. Additionally, there was no alteration in the water intake response induced by osmotic challenge in the sepsis survivor group.

CONCLUSION

The results suggest that the inflammatory components mediated a persistent impairment in the component of the osmoregulatory reflex affecting the secretion of neurohypophyseal hormones in sepsis survivor animals.

Reducing Animal Use with a Biotelemetry-Enhanced Murine Model of Sepsis

Animal models of sepsis exhibit considerable variability in the temporal development of the physiologic response, which reduces the power of studies, particularly if interventions are tested at arbitrary time points. We developed a biotelemetry-based model of cecal ligation and puncture (CLP) that standardizes the testing of time-sensitive therapies to specific criteria of physiologic deterioration. In this study we seek to further define the variability in physiologic response to CLP sepsis and conduct a cost analysis detailing the potential for reducing animal usage. We have further characterized the variability in physiologic response after CLP in mice and determined peaks in the temporal distribution of points of physiologic decline. Testing therapies at physiologic thresholds reduces the variability found in historical fixed time-based models. Though initial cost is higher with biotelemetry, this is eventually offset by the significantly reduced number of mice needed to conduct physiologically relevant sepsis experiments.

Antagonism of the Neurokinin-1 Receptor Improves Survival in a Mouse Model of Sepsis by Decreasing Inflammation and Increasing Early Cardiovascular Function

OBJECTIVES

Sepsis remains a serious clinical problem despite intensive research efforts and numerous attempts to improve outcome by modifying the inflammatory response. Substance P, the principal ligand for the neurokinin-1 receptor, is a potent proinflammatory mediator that exacerbates inflammatory responses and cardiovascular variables in sepsis.

DESIGN

The current study examined whether inhibition of the neurokinin-1 receptor with a specific antagonist (CJ-12,255) would improve survival in the cecal ligation and puncture model of sepsis in adult female outbred mice.

SETTING

University basic science research laboratory.

MEASUREMENTS AND MAIN RESULTS

Neurokinin-1 receptor treatment at the initiation of sepsis improved survival in cecal ligation and puncture sepsis (neurokinin-1 receptor antagonist survival = 79% vs vehicle = 54%). Delaying therapy for as little as 8 hours postcecal ligation and puncture failed to provide a survival benefit. Neurokinin-1 receptor antagonist treatment did not prevent the sepsis-induced decrease in circulating WBCs, augment the early (6 hr postcecal ligation and puncture) recruitment of inflammatory cells to the peritoneum, or improve phagocytic cell killing of pathogens. However, the neurokinin-1 receptor antagonist significantly reduced both circulating and peritoneal cytokine concentrations. In addition, the cardiovascular variable, pulse distension (a surrogate for stroke volume) was improved in the neurokinin-1 receptor antagonist group during the first 6 hours of sepsis, and there was a significant reduction in loss of fluid into the intestine.

CONCLUSION

These data show that early activation of the neurokinin-1 receptor by substance P decreases sepsis survival through multiple mechanisms including depressing stroke volume, increasing fluid loss into the intestine, and increasing inflammatory cytokine production.

Shorter Duration of Post-Operative Antibiotics for Cecal Ligation and Puncture Does Not Increase Inflammation or Mortality

Antimicrobial therapy for sepsis has beneficial effects, but prolonged use fosters emergence of resistant microorganisms, increases cost, and secondary infections. We tested whether 3 days versus 5 days of antibiotics in the murine model of cecal ligation and puncture (CLP) negatively influences outcomes. Following CLP mice were randomized to receive the antibiotic imipenem-cilastatin (25mg/kg) in dextrose 5% in Lactated Ringer’s solution every 12 hours for either three or five days. Serial monitoring over 28 days included body weight, temperature, pulse oximetry, and facial vein sampling for hematological analysis and glucose. A separate group of mice were euthanized on post-CLP day 5 to measure cytokines and peritoneal bacterial counts. The first study examined no antimicrobial therapy and demonstrated that antibiotics significantly improved survival compared to fluids only (p = 0.004). We next tested imipenem-cilastatin therapy for 3 days versus 5 days. Body weight, temperature, glucose, and pulse oximetry measurements remained generally consistent between both groups as did the hematological profile. Pro-inflammatory plasma cytokines were comparable between both groups for IL-6, IL-1β, MIP-2 and anti-inflammatory cytokines IL-10, and TNF SRI. At 5 days post-CLP, i.e. 2 days after the termination of antibiotics in the 3 day group, there were no differences in the number of peritoneal bacteria. Importantly, shortening the course of antibiotics by 40% (from 5 days to 3 days) did not decrease survival. Our results indicate that reducing the duration of broad-spectrum antibiotics in murine sepsis did not increase inflammation or mortality.

Beneficial Effects of Anti-Interleukin-6 Antibodies on Impaired Gastrointestinal Motility, Inflammation and Increased Colonic Permeability in a Murine Model of Sepsis Are Most Pronounced When Administered in a Preventive Setup

BACKGROUND AND OBJECTIVES

During sepsis, gastrointestinal ileus, mucosal barrier dysfunction and bacterial translocation are accepted to be important triggers that can maintain or exacerbate the septic state. In the caecal ligation and puncture animal model of sepsis, we demonstrated that systemic and colonic interleukin-6 levels are significantly increased coinciding with an impaired colonic barrier function. We therefore aimed to study the effect of therapeutic or curative administration of anti-IL6 antibodies on overall GI motility, colonic permeability and translocation of intestinal bacteria in blood and mesenteric lymph nodes in the mouse caecal ligation and puncture model.

METHODS

OF-1 mice were randomized to either the preventive or curative protocol, in which they received 1 mg/kg of antibodies to interleukin-6, or its IgG isotype control solution. They subsequently underwent either the caecal ligation and puncture procedure, or sham-surgery. GI motility was assessed 48 h following the procedure, as well as colonic permeability, serum and colon cytokines, colonic tight junction proteins at the mRNA level; cultures of blood and mesenteric lymph nodes were performed.

RESULTS

Preventive administration of anti-interleukin-6 antibodies successfully counteracted the gastrointestinal motility disturbances and impaired colonic barrier function that could be observed in vehicle-treated septic animals. Serum and colonic levels of proinflammatory cytokines were significantly lower when animals were preventively treated with anti-interleukin-6 antibodies. A repetitive injection 24 h later resulted in the most pronounced effects. Curative treatment significantly lowered systemic and colonic inflammation markers while the effects on transit and permeability were unfortunately no longer significant.

CONCLUSIONS

Caecal ligation and puncture resulted in septic ileus with an increased colonic permeability. Antibodies to interleukin-6 were able to ameliorate gastro-intestinal motility, suppress inflammation and normalize the permeability of the colonic wall, with the preventive administration combined with a repeat injection being far more efficacious than the sole preventive or curative one.

Intraperitoneal adipose tissue is strongly related to survival rate in a mouse cecal ligation and puncture model

Cecal ligation and puncture (CLP) models exhibiting polymicrobial sepsis are considered as the gold standard in sepsis research. However, despite meticulous research being conducted in this field, only few treatment drugs are available, indicating that CLP sepsis models do not completely mimic human sepsis models. The greatest flaw in CLP models is abscess formation because the localization of inflammation caused by abscess formation increases the survival rate. Therefore, by resecting intraperitoneal adipose tissue, we developed a mouse CLP model wherein abscess formation was unlikely. Survival rates at 7 days postoperatively were compared using the Kaplan–Meier method for an intraperitoneal adipose tissue resection group (resection group, n=34), an intraperitoneal adipose tissue non-resection group (non-resection group, n=35) and a sham group (n=10). Results indicated that the survival rate was significantly higher in the non-resection group compared with the resection group. Intraperitoneal macroscopic findings in the non-resection group revealed the localization of inflammation caused by abscesses formation covered in adipose tissue. The survival rate for the sham group was 100%. Measurement of interleukin 6 (IL-6) indicated that during the 12 h after the creation of the CLP model, the median level of IL-6 was 1300 (552–3000) pg ml⁻¹ in the non-resection group (n=19) and 3000 (1224–8595) pg ml⁻¹ in the resection group (n=19). Meanwhile, for the sham group, IL-6 values were below measurement sensitivity in most cases (9/10 mice). Thus our results suggest that, in CLP models, intraperitoneal adipose tissue has an important role in abscess formation and is strongly related to the survival rate.

Atorvastatin along with imipenem attenuates acute lung injury in sepsis through decrease in inflammatory mediators and bacterial load

Lung is one of the vital organs which is affected during the sequential development of multi-organ dysfunction in sepsis. The purpose of the present study was to examine whether combined treatment with atorvastatin and imipenem could attenuate sepsis-induced lung injury in mice. Sepsis was induced by caecal ligation and puncture. Lung injury was assessed by the presence of lung edema, increased vascular permeability, increased inflammatory cell infiltration and cytokine levels in broncho-alveolar lavage fluid (BALF). Treatment with atorvastatin along with imipenem reduced the lung bacterial load and pro-inflammatory cytokines (IL-1β and TNFα) level in BALF. The markers of pulmonary edema such as microvascular leakage and wet-dry weight ratio were also attenuated. This was further confirmed by the reduced activity of MPO and ICAM-1 mRNA expression, indicating the lesser infiltration and adhesion of inflammatory cells to the lungs. Again, expression of mRNA and protein level of iNOS in lungs was also reduced in the combined treatment group. Based on the above findings it can be concluded that, combined treatment with atorvastatin and imipenem dampened the inflammatory response and reduced the bacterial load, thus seems to have promising therapeutic potential in sepsis-induced lung injury in mice.

Doxorubicin-Hyaluronan Conjugated Super-Paramagnetic Iron Oxide Nanoparticles (DOX-HA-SPION) Enhanced Cytoplasmic Uptake of Doxorubicin and Modulated Apoptosis, IL-6 Release and NF-kappaB Activity in Human MDA-MB-231 Breast Cancer Cells

Triple negative breast cancer exhibit increased IL-6 expression compared with matched healthy breast tissue and a strong link between inflammation and cancer progression and metastasis has been reported. We investigated whether doxorubicin-hyaluronan-super-paramagnetic iron oxide nanoparticles (DOX-HA-SPION) would show greater therapeutic efficacy in human triple negative breast cancer cells (TNBC) MDA-MB-231, as was recently shown in drug-sensitive and multi-drug-resistant ovarian cancer cells. Therefore, we measured cellular DOX uptake via confocal microscopy; observed morphologic changes: mitochondrial and nuclear changes with electron microscopy, and quantitated apoptosis using FACS analysis after Annexin V and PI staining in MDA-MB-231 cells treated with either DOX alone or DOX-HA-SPION. We also measured both proinflammatory and anti-inflammatory cytokines; IL-6, IL-10 respectively and also measured nitrate levels in the conditioned medium by ELISA. Inaddition, NF-κB activity was measured by luciferase assay. Confocal microscopy demonstrated greater cytoplasmic uptake of DOX-HA-SPION than free DOX. We also demonstrated reduction of Vimentin with DOX-HA-SPION which is significantly less than both control and DOX. DOX-HA-SPION enhanced apoptosis and significantly down regulated both pro-inflammatory mediators IL-6 and NF-κB in comparison to DOX alone. The secretion levels of anti-inflammatory mediators IL-10 and nitrate was not decreased in the DOX or DOX-HA-SPION treatment groups. Our data suggest that DOX-HA-SPION nanomedicine-based drug delivery could have promising potential in treating metastasized and chemoresistant breast cancer by enhancing the drug efficacy and minimizing off-target effects.

Combined treatment with atorvastatin and imipenem improves survival and vascular functions in mouse model of sepsis

We have recently reported that pre-treatment, but not the post-treatment with atorvastatin showed survival benefit and improved hemodynamic functions in cecal ligation and puncture (CLP) model of sepsis in mice. Here we examined whether combined treatment with atorvastatin and imipenem after onset of sepsis can prolong survival and improve vascular functions. At 6 and 18h after sepsis induction, treatment with atorvastatin plus imipenem, atorvastatin or imipenem alone or placebo was initiated. Ex vivo experiments were done on mouse aorta to examine the vascular reactivity to nor-adrenaline and acetylcholine and mRNA expressions of α1D AR, GRK2 and eNOS. Atorvastatin plus imipenem extended the survival time to 56.00±4.62h from 20.00±1.66h observed in CLP mice. The survival time with atorvastatin or imipenem alone was 20.50±1.89h and 27.00±4.09h, respectively. The combined treatment reversed the hyporeactivity to nor-adrenaline through preservation of α1D AR mRNA/protein expression and reversal of α1D AR desensitization mediated by GRK2/Gβγ pathway. The treatment also restored endothelium-dependent relaxation to ACh through restoration of aortic eNOS mRNA expression and NO availability. In conclusion, combined treatment with atorvastatin and imipenem exhibited survival benefit and improved vascular functions in septic mice.

The antinociceptive effect of dexmedetomidine modulates spleen cell immunity in mice

BACKGROUND

Pain plays roles in both the nervous system and immune system. Changes in the neuroendocrine pathway under pain conditions give rise to sympathetic outflow with increased plasma catecholamines and activate immune reactions. Dexmedetomidine exerts sedative, analgesic, and anesthetic-sparing effects and is known to diminish pro-inflammatory processes by central sympatholytic effects. To investigate the influence of the analgesic effect of dexmedetomidine on immunomodulation under pain conditions, splenic natural killer (NK) tumoricidal cytotoxic activity, proliferative ability of T lymphocytes, and cytokine changes were assessed.

METHODS

After evaluation of the analgesic efficacy of dexmedetomidine in C57BL mice that were subjected to formalin-induced pain, dexmedetomidine (30 µg/kg) or saline was injected intraperitoneally (ip) 30 min before formalin (20 µL of 2% formalin in 0.9% saline) injection. NK cell activity against NK-sensitive YAC-1 lymphoma cells was evaluated by the percentage of specific lactate dehydrogenase (LDH) release. Various numbers of effector cells (NK cells) were added to the wells of a microtiter plate containing 2 × 10(4) target YAC-1 cells in 100 μL, to achieve final effector-to-target cell ratios of 80:1, 40:1, and 20:1. The level of lymphocyte proliferation in response to phytohemagglutinin (PHA) was detected by bromodeoxyuridine (BrdU) incorporation assay. TNF-α, IL-1β, and IL-10 levels were determined in blood samples and supernatants of splenocyte preparations.

RESULTS

IP administration of dexmedetomidine significantly decreased the time of licking and biting during the first and second phases of the formalin test (p <0.001). Formalin-induced pain led to higher activity of NK cells than in sham-treated mice (p <0.05), but NK activity was not increased significantly by ip dexmedetomidine treatment. Formalin-induced pain significantly increased splenic lymphocyte proliferation (p <0.05), but dexmedetomidine did not alter this response. There was a significant increase in plasma TNF-α (p = 0.048) and IL-6 (p = 0.014) levels after formalin-induced pain. However, the differences between the responses after ip dexmedetomidine did not change significantly.

CONCLUSIONS

Dexmedetomidine showed antinociceptive effect on both of acute pain phase 1 and hyperalgesic phase 2 of formalin pain model. Formalin-induced pain alters cellular immunity of spleen in mice. Dexmedetomidine attenuates the activation of NK cells under pain condition, but neither the proliferative response of the splenic lymphocytes nor the cytokine production was affected by dexmedetomidine.

Sepsis: multiple abnormalities, heterogeneous responses, and evolving understanding

Sepsis represents the host's systemic inflammatory response to a severe infection. It causes substantial human morbidity resulting in hundreds of thousands of deaths each year. Despite decades of intense research, the basic mechanisms still remain elusive. In either experimental animal models of sepsis or human patients, there are substantial physiological changes, many of which may result in subsequent organ injury. Variations in age, gender, and medical comorbidities including diabetes and renal failure create additional complexity that influence the outcomes in septic patients. Specific system-based alterations, such as the coagulopathy observed in sepsis, offer both potential insight and possible therapeutic targets. Intracellular stress induces changes in the endoplasmic reticulum yielding misfolded proteins that contribute to the underlying pathophysiological changes. With these multiple changes it is difficult to precisely classify an individual's response in sepsis as proinflammatory or immunosuppressed. This heterogeneity also may explain why most therapeutic interventions have not improved survival. Given the complexity of sepsis, biomarkers and mathematical models offer potential guidance once they have been carefully validated. This review discusses each of these important factors to provide a framework for understanding the complex and current challenges of managing the septic patient. Clinical trial failures and the therapeutic interventions that have proven successful are also discussed.

Sepsis-induced morbidity in mice: effects on body temperature, body weight, cage activity, social behavior and cytokines in brain

Infection negatively impacts mental health, as evidenced by the lethargy, malaise, and cognitive deficits experienced during illness. These changes in central nervous system processes, collectively termed sickness behavior, have been shown in animal models to be mediated primarily by the actions of cytokines in brain. Most studies of sickness behavior to date have used bolus injection of bacterial lipopolysaccharide (LPS) or selective administration of the proinflammatory cytokines interleukin-1β (IL-1β) or IL-6 as the immune challenge. Such models, although useful for determining mechanisms responsible for acute changes in physiology and behavior, do not adequately represent the more complex effects on central nervous system (CNS) processes of a true infection with replicating pathogens. In the present study, we used the cecal ligation and puncture (CLP) model to quantify sepsis-induced alterations in several facets of physiology and behavior of mice. We determined the impact of sepsis on cage activity, body temperature, food and water consumption and body weights of mice. Because cytokines are critical mediators of changes in behavior and temperature regulation during immune challenge, we also quantified sepsis-induced alterations in cytokine mRNA and protein in brain during the acute period of sepsis onset. We now report that cage activity and temperature regulation in mice that survive are altered for up to 23 days after sepsis induction. Food and water consumption are transiently reduced, and body weight is lost during sepsis. Furthermore, sepsis decreases social interactions for 24-48 h. Finally, mRNA and protein for IL-1β, IL-6, and tumor necrosis factor-α (TNFα) are upregulated in the hypothalamus, hippocampus, and brain stem during sepsis onset, from 6h to 72 h post sepsis induction. Collectively, these data indicate that sepsis not only acutely alters physiology, behavior and cytokine profiles in brain, but that some brain functions are impaired for long periods in animals that survive.

Bai-hu-tang, ancient chinese medicine formula, may provide a new complementary treatment option for sepsis

Bai-Hu-Tang (BHT) has been broadly applied to treating the early stage of acute infection with systemic inflammation for two thousand years in Chinese medicine. We explore whether BHT is beneficial in treating sepsis and its effects on proinflammatory cytokine, interleukin-6, and anti-inflammatory cytokine interleukin-10, in which both play key roles in the progress of sepsis. Thirty-six male Sprague-Dawley rats were randomized into six groups, with cecal ligation and puncture (CLP) performed in all but the sham-control group. Rats in CLP + BHT-L6 and CLP + BHT-H6 groups, respectively, received a low (0.45 g/kg) and high doses (0.9 g/kg) of BHT, 6 hrs postoperatively. CLP + BHT-L12 and CLP + BHT-H12 groups, respectively, received low and high doses of BHT, 12 hrs postoperatively. Sham-control and sepsis-control groups received distilled water (1 mL) as vehicle, 6 hrs postoperatively. Serial blood samples were drawn before operation, as baseline, and at 4, 8, and 12 hrs postoperatively for IL-6 and IL-10 assay. All rats were monitored for 3 days for survival study. Rats in the CLP + BHT-H6 group had significantly higher survival rate (80%) and significantly lower levels of both IL-6 and IL-10 at 12 hrs postoperatively than those in the sepsis-control group. Results suggested that BHT may be a new complementary treatment option for sepsis.

Is there value in plasma cytokine measurements in patients with severe trauma and sepsis?

For the past thirty years, since IL-1β and TNFα were first cloned, there have been efforts to measure plasma cytokine concentrations in patients with severe sepsis and trauma, and to use these measurements to predict clinical outcome and response to therapies. The numbers of cytokines and chemokines that have been measured in the plasma have literally exploded with the development of multiplex immune approaches. Dozens of relatively small cohort studies have shown plasma cytokine concentrations correlating with outcome in sepsis and trauma. Despite what appears to be a consensus that plasma cytokine concentrations should be useful in the clinical setting, only two cytokines, IL-6 and procalcitonin, have approached routine clinical use. IL-6 has been used as a research tool for entry into sepsis-intervention trials, while procalcitonin is being used clinically at a large number of institutions to distinguish sepsis from other inflammatory processes. For most cytokines, the relative lack of sensitivity and specificity of individual or multiplex cytokine measurements has hindered their utility to predict clinical trajectory in individual patients. The problem rests with a general misunderstanding of cytokine biology, failing to appreciate the general paracrine nature of these mediators, the presence of binding proteins, chaperones and inhibitors in the plasma, and the rapid clearance of these proteins by binding to cell receptors and clearance predominantly by the kidney. The future of using plasma cytokine measurements as an indicator of sepsis/trauma severity or predicting outcome is generally behind us, although there is optimism that procalcitonin measurements may ultimately prove to have utility in the diagnosis of severe sepsis.

Cecal ligation and puncture-induced murine sepsis does not cause lung injury

OBJECTIVE

The cause of death in murine models of sepsis remains unclear. The primary purpose of this study was to determine if significant lung injury develops in mice predicted to die after cecal ligation and puncture-induced sepsis compared with those predicted to live.

DESIGN

Prospective, laboratory controlled experiments.

SETTING

University research laboratory.

SUBJECTS

Adult, female, outbred Institute of Cancer Research mice.

INTERVENTIONS

Mice underwent cecal ligation and puncture to induce sepsis. Two groups of mice were euthanized at 24 and 48 hrs postcecal ligation and puncture and samples were collected. These mice were further stratified into groups predicted to die (Die-P) and predicted to live (Live-P) based on plasma interleukin-6 levels obtained 24 hrs postcecal ligation and puncture. Multiple measures of lung inflammation and lung injury were quantified in these two groups. Results from a group of mice receiving intratracheal normal saline without surgical intervention were also included as a negative control. As a positive control, bacterial pneumonia was induced with Pseudomonas aeruginosa to cause definitive lung injury. Separate mice were followed for survival until Day 28 postcecal ligation and puncture. These mice were used to verify the interleukin-6 cutoffs for survival prediction.

MEASUREMENTS AND MAIN RESULTS

After sepsis, both the Die-P and Live-P mice had significantly suppressed measures of respiratory physiology but maintained normal levels of arterial oxygen saturation. Bronchoalveolar lavage levels of pro- and anti-inflammatory cytokines were not elevated in the Die-P mice compared with the Live-P. In addition, there was no increase in the recruitment of neutrophils to the lung, pulmonary vascular permeability, or histological evidence of damage. In contrast, all of these pulmonary injury and inflammatory parameters were increased in mice with Pseudomonas pneumonia.

CONCLUSIONS

These data demonstrate that mice predicted to die during sepsis have no significant lung injury. In murine intra-abdominal sepsis, pulmonary injury cannot be considered the etiology of death in the acute phase.

Bactericidal antibiotics temporarily increase inflammation and worsen acute kidney injury in experimental sepsis

OBJECTIVE

To explore the relationships among bactericidal antimicrobial treatment of sepsis, inflammatory response, severity of acute kidney injury, and outcomes.

DESIGN

Controlled laboratory experiment.

SETTING

University laboratory.

INTERVENTIONS

Sepsis was induced by cecal ligation and puncture in 52 rats and was treated with either bactericidal antibiotics (ampicillin/sulbactam) or placebo (saline). Serial blood specimens were obtained after cecal ligation and puncture for serum creatinine, interleukin-6, and neutrophil gelatinase-associated lipocalin concentrations. RIFLE (Risk, Injury, Failure, Loss, End-stage kidney disease) criteria were used to assess severity of acute kidney injury. All animals were observed for survival up to 1 wk. In a separate experiment, six healthy animals were given antibiotics and renal function was assessed. Another 12 animals were euthanized 2 days after laparotomy for kidney histology.

MEASUREMENTS AND MAIN RESULTS

Survival in the placebo group was 50% compared with 81.8% in the antibiotic group (p < .05). Most animals (93%) without antibiotics developed acute kidney injury, of which 39% exhibited greater than a threefold rise in serum creatinine (RIFLE-F). Furthermore, survival decreased as acute kidney injury severity increased. Surprisingly, all antibiotic-treated animals developed acute kidney injury, of which 68.6% reached RIFLE-F. However, renal dysfunction was less persistent in these animals. Patterns of plasma interleukin-6 were similar to creatinine with higher concentrations seen earlier in antibiotic-treated animals but with faster resolution. Interleukin-6 concentration at 24 hrs was independently associated with the development of RIFLE-F. Histologic findings were consistent with functional parameters showing that antibiotics worsened acute kidney injury.

CONCLUSION

In polymicrobial sepsis, bactericidal antibiotics resulted in more inflammation and more severe acute kidney injury. However, resolution of inflammation and acute kidney injury was faster with antibiotics and correlated best with survival. These results suggest that transient worsening of renal function may be an expected consequence of sepsis therapy. These findings also question the value of peak severity of acute kidney injury as a primary end point and suggest that resolution of acute kidney injury may be more appropriate.

Improved antimicrobial host defense in mice following poly-(1,6)-β-D-glucopyranosyl-(1,3)-β-D-glucopyranose glucan treatment by a gender-dependent immune mechanism

Clinical trials with biological modifiers targeting specific inflammatory mediators associated with severe sepsis have shown no or limited survival benefit. The approach taken in studies reported here was to limit the point source of intra-abdominal infection by potentiating innate immune function, thereby lessening the severity of sepsis and improving survival. Soluble beta-glucans, glucose polymers of the fungal cell wall, have been shown to stimulate innate immune host defense in animal and human studies when administered prior to an infectious challenge. We evaluated the effects of poly-(1,6)-β-d-glucopyranosyl-(1,3)-β-d-glucopyranose glucan (PGG glucan) on overall survival when administered intraperitoneally after the onset of polymicrobial infection by cecal ligation and puncture (CLP). Since gender-dependent differences in host immune response to infection have been reported, male and female mice were prospectively stratified for PGG glucan treatment. Outbred CD-1 mice were administered 10 mg/kg of body weight PGG glucan or the polysaccharide control, dextran, 1 h after CLP. Six hours after CLP, blood samples were obtained for cytokine measurements. Surprisingly, a gender-dependent effect on the response to PGG glucan was revealed. PGG glucan enhanced survival in female mice over a 10-day period, but survival in males was improved for only 24 h. In female mice, PGG glucan reduced interleukin-6 (IL-6) and IL-10 levels and reduced the bacterial burden in the liver. Ovariectomy abrogated the response to PGG glucan. Together, the translational potential of these findings is the indicated use of PGG glucan given locally, rather than intravenously, for improved source control during the management of sepsis. This therapy does not require prophylactic beta-glucan administration.

Cecal ligation and puncture: the gold standard model for polymicrobial sepsis?

Sepsis is a serious medical condition characterized by dysregulated systemic inflammatory responses followed by immunosuppression. To study the pathophysiology of sepsis, diverse animal models have been developed. Polymicrobial sepsis induced by cecal ligation and puncture (CLP) is the most frequently used model because it closely resembles the progression and characteristics of human sepsis. Here we summarize the role of several immune components in the pathogenesis of sepsis induced by CLP. However, several therapies proposed on the basis of promising results obtained by CLP could not be translated to the clinic. This demonstrates that experimental sepsis models do not completely mimic human sepsis. We propose several strategies to narrow the gap between experimental sepsis models and clinical sepsis, including targeting factors that contribute to the immunosuppressive phase of sepsis, and reproducing the heterogeneity of human patients.

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.

Repetitive low-volume blood sampling method as a feasible monitoring tool in a mouse model of sepsis

Blood-based monitoring of immunoinflammatory and organ function fluctuations is essential in models of critical illness. This is challenging in diseased mice as repetitive blood collection may be harmful and/or affect end points. We studied the influence of daily sampling in acutely septic (days 1-5) mice upon survival and selected hematologic and organ function parameters. In addition, we tested the reliabilty of complete blood cell (CBC) count using resuspended blood cells. Female OF-1 and CD-1 mice underwent cecal ligation and puncture (CLP) and were subdivided into Daily and Day 5 groups. Blood was collected daily for 5 days in the Daily group and only on day 5 post-CLP in the Day 5 group. We tested 20 μL (both strains) and 35 μL (OF-1 mice) sampling volumes. The 35-μL volume simultaneously served to test the CBC reliabilty in resuspended versus unprocessed blood. Daily sampling did not affect the 14-day CLP mortality. Compared with the Day 5 group, daily 35-μL sampling in OF-1 mice decreased the red blood cell count and hemoglobin concentration by 22% and 23% (P < 0.05). In neither strain did daily 20-μL sampling affect the red blood cell count, whereas there was a 9% hemoglobin decrease (P < 0.05) in OF-1 mice. Although alanine aminotransferase, lactate dehydrogenase, and glucose levels were comparable, urea significantly increased by 24% in the Daily group (20-μL volume, OF-1 mice). Interleukin 6, platelets, and white blood cell counts remained unaffected. There was an excellent correlation between regular and resuspended CBC for all cell types (r ≥ 0.9; slope, ≥0.9), except lymphocytes (r > 0.5; slope, >0.5). This method provides a feasible and safe translation of clinically relevant daily immunomonitoring to the mouse sepsis model.

Sedation improves early outcome in severely septic Sprague Dawley rats

INTRODUCTION

Sepsis, a systemic inflammatory response to infective etiologies, has a high mortality rate that is linked both to excess cytokine activity and apoptosis of critical immune cells. Dexmedetomidine has recently been shown to improve outcome in a septic cohort of patients when compared to patients randomized to a benzodiazepine-based sedative regimen. We sought to compare the effects of dexmedetomidine and midazolam, at equi-sedative doses, on inflammation and apoptosis in an animal model of severe sepsis.

METHODS

After central venous access, Sprague Dawley rats underwent cecal ligation and intestinal puncture (CLIP) with an 18 G needle without antibiotic cover and received either saline, or an infusion of comparable volume of saline containing midazolam (0.6 mg.kg-1.h-1) or dexmedetomidine (5 ug.kg-1.h-1) for 8 hours. Following baseline measurements and CLIP, blood was sampled for cytokine measurement (tumour necrosis factor (TNF)-alpha and interleukin (IL)-6; n = 4-6 per group) at 2, 4 and 5 hours, and animal mortality rate (MR) was monitored (n = 10 per group) every 2 hours until 2 hours had elapsed. In addition, spleens were harvested and apoptosis was assessed by immunoblotting (n = 4 per group).

RESULTS

The 24 hour MR in CLIP animals (90%) was significantly reduced by sedative doses of either dexmedetomidine (MR = 20%) or midazolam (MR = 30%). While both sedatives reduced systemic levels of the inflammatory cytokine TNF-alpha (P < 0.05); only dexmedetomidine reduced the IL-6 response to CLIP, though this narrowly missed achieving significance (P = 0.05). Dexmedetomidine reduced splenic caspase-3 expression (P < 0.05), a marker of apoptosis, when compared to either midazolam or saline.

CONCLUSIONS

Sedation with midazolam and dexmedetomidine both improve outcome in polymicrobial severely septic rats. Possible benefits conveyed by one sedative regimen over another may become evident over a more prolonged time-course as both IL-6 and apoptosis were reduced by dexmedetomidine but not midazolam. Further studies are required to evaluate this hypothesis.

Failed interleukin-6 signal transduction in murine sepsis: attenuation of hepatic glycoprotein 130 phosphorylation

OBJECTIVE

Sepsis impairs the activation of the interleukin (IL)-6 dependent transcription factor signal transducer and activator of transcription (STAT)-3. However, the molecular basis for depressed functionality has not been characterized. In this study, we test the hypothesis that altered signal transduction results from a change in the activation state of one or more of the components of the intracellular IL-6-linked pathway.

DESIGN

Randomized prospective experimental study.

SETTING

University medical laboratory.

SUBJECTS

Male, 6-8-week-old C57/Bl6 mice.

INTERVENTIONS

Cecal ligation and single puncture (CLP) or cecal ligation and double puncture (2CLP) was used to model mild and fulminant sepsis, respectively. Sham-operated and unoperated animals served as controls. All animals were fluid resuscitated at the time of surgery and every 24 hours thereafter. Surviving animals were euthanized at 3, 6, 16, 24, 48, and 72 hours; blood samples were obtained and liver tissue was harvested.

MEASUREMENTS AND MAIN RESULTS

Serum IL-6 levels were elevated in both CLP and 2CLP relative to controls. STAT-3 DNA binding activity and nuclear phosphorylated-STAT-3 levels were elevated in CLP but decreased abruptly 24 hours after 2CLP. This 2CLP-induced alteration was associated with attenuated phosphorylation of the key transcellular glycoprotein (gp) 130. Abundance and phosphorylation of the other key component of IL-6 signal transduction pathway, janus kinase-1, was unchanged following either CLP or 2CLP. 2CLP also did not cause disassociation of the gp130-janus kinase-1 complex.

CONCLUSIONS

Impaired gp130 phosphorylation may be responsible for IL-6 hyporesponsiveness during sepsis.

Lipopolysaccharide-induced interleukin-6 production is controlled by glycogen synthase kinase-3 and STAT3 in the brain

Background

Septic shock is a prevalent condition that, when not lethal, often causes disturbances in cognition, mood, and behavior, particularly due to central actions of the inflammatory cytokine interleukin-6 (IL-6). To identify potential targets to control brain IL-6, we tested if IL-6 produced by glia is regulated by signal transducer and activator of transcription-3 (STAT3) and glycogen synthase kinase-3 (GSK3).

Methods

Lipopolysaccharide (LPS) was used to induce inflammatory responses in mice or cultured primary glia. IL-6 was measured by ELISA and other inflammatory molecules were measured using an array.

Results

Mouse brain IL-6 levels increased after central, as well as peripheral, LPS administration, consistent with glia producing a portion of brain IL-6. STAT3 in the brain was activated after peripheral or central LPS administration, and in LPS-stimulated cultured primary glia. Inhibition of STAT3 expression, function, or activation reduced by ~80% IL-6 production by primary glia, demonstrating the dependence on active STAT3. GSK3 promotes STAT3 activation, and array analysis of inflammatory molecules produced by LPS-stimulated primary glia demonstrated that IL-6 was the cytokine most diminished (>90%) by GSK3 inhibition. Inhibition of GSK3, and knockdown of GSK3β, not GSK3α, greatly inhibited IL-6 production by LPS-stimulated primary glia. Conversely, expression of active STAT3 and active GSK3 promoted IL-6 production. In vivo inhibition of GSK3 reduced serum and brain IL-6 levels, brain STAT3 activation, and GFAP upregulation following LPS administration.

Conclusion

STAT3 and GSK3 cooperatively promote neuroinflammation, providing novel targets for anti-inflammatory intervention.

PACAP inhibit the release and cytokine activity of HMGB1 and improve the survival during lethal endotoxemia

The pathogenesis of sepsis is mediated in part by bacterial endotoxin (lipopolysaccharide; LPS), which stimulates macrophages/monocytes to sequentially release early (e.g., TNF-alpha, IL-1beta) and late [e.g., high mobility group box 1 (HMGB1) protein] pro-inflammatory cytokines. Specifically targeting early mediators has not been effective clinically, in part, because peak mediator activity often has passed before therapy can be initiated. Recent discovery of HMGB1 as a late mediator of lethal sepsis has provided a new target for the treatment of septic shock. Here, we demonstrate that pituitary adenylate cyclase-activating polypeptide (PACAP), an endogenous neuropeptide, significantly attenuated circulating HMGB1 levels and increased survival in animals with established endotoxemia, even if treatment began after acute cytokine response has occurred. In vitro, PACAP suppressed LPS-induced HMGB1 release from macrophages/monocytes, even when given 2-4 h after LPS stimulation. PACAP also suppressed HMGB1 release induced by TNF-alpha or IFN-gamma. Moreover, PACAP inhibits HMGB1-induced cytokine release in vitro and in vivo. These results indicate that PACAP inhibits the release and pro-inflammatory activity of HMGB1 and improves survival during lethal endotoxemia, which confirms this peptide as a candidate for therapy of septic shock.

CD4-expressing cells are early mediators of the innate immune system during sepsis

It is well established that the immune response to sepsis is mediated by leukocytes associated with the innate immune system. However, there is an emerging view that T lymphocytes can also mediate this response. Here, we observed a significant depletion of both CD4 and CD8 T cells in human patients after blunt trauma. To determine what effect the loss of these cells may have during a subsequent infection, we obtained CD4- and CD8-deficient mice and subjected them to cecal ligation and puncture (CLP). We observed that CD4 knockout (KO) mice showed increased CLP-induced mortality compared with CD8-deficient and wild-type (WT) mice especially within the first 30 h of injury. CD4 KO mice also exhibited significantly increased IL-6 concentrations after the CLP. The CD4 KO mice had an increased concentration of bacteremia as compared with WT mice. Antibiotic treatment decreased mortality in the CD4 KO mice as compared with no changes in the wild mice after CLP. Neutrophils isolated from septic CD4 KO mice showed decreased spontaneous oxidative burst compared with neutrophils taken from septic controls. We examined the role of IFN-gamma by using mice deficient in this cytokine and found these mice to have significantly higher mortality as compared with WT mice. Finally, we detected a 2-fold increase in CD11b+ cells that exhibited intracellular IFN-gamma staining in the peritoneum of WT mice after CLP. The data suggest that CD4+ cells may facilitate the early clearance of bacteria by regulating neutrophils function possibly through an IFN-gamma-dependent mechanism.

Intestine-specific overexpression of IL-10 improves survival in polymicrobial sepsis

Targeted IL-10 therapy improves survival in preclinical models of critical illness, and intestine-specific IL-10 decreases inflammation in models of chronic Inflammatory disease. We therefore sought to determine whether intestine-specific overexpression of IL-10 would improve survival in sepsis. Transgenic mice that overexpress IL-10 in their gut epithelium (Fabpi-IL-10 mice) and wild-type (WT) littermates (n = 127) were subjected to cecal ligation and puncture with a 27-gauge needle. The 7-day survival rate was 45% in transgenic animals and 30% in WT animals (P < or = 0.05). Systemic levels of IL-10 were undetectable in both groups of animals under basal conditions and were elevated to a similar degree in septic animals regardless of whether they expressed the transgene. Local parameter of injury, including gut epithelial apoptosis, intestinal permeability, peritoneal lavage cytokines, and stimulated cytokines from intraepithelial lymphocytes, were similar between transgenic and WT mice. However, in stimulated splenocytes, proinflammatory cytokines monocyte chemoattractant protein 1 (189 +/- 43 vs. 40 +/- 8 pg/mL) and IL-6 (116 +/- 28 vs. 34 +/- 9 pg/mL) were lower in Fabpi-IL-10 mice than WT littermates despite the intestine-specific nature of the transgene (P < 0.05). Cytokine levels were similar in blood and bronchoalveolar lavage fluid between the 2 groups, as were circulating LPS levels. Transgenic mice also had lower white blood cell counts associated with lower absolute neutrophil counts (0.5 +/- 0.1 vs. 1.0 +/- 0.2 10(3)/mm3; P < 0.05). These results indicate that gut-specific overexpression of IL-10 improves survival in a murine model of sepsis, and interactions between the intestinal epithelium and the systemic immune system may play a role in conferring this survival advantage.

Gammadelta T cells mitigate the organ injury and mortality of sepsis

Sepsis is a difficult condition to treat and is associated with a high mortality rate. Sepsis is known to cause a marked depletion of lymphocytes, although the function of different lymphocyte subsets in the response to sepsis is unclear. gammadelta T cells are found largely in epithelial-rich tissues, and previous studies of gammadelta T cells in models of sepsis have yielded divergent results. In the present study, we examined the function of gammadelta T cells during sepsis in mice using cecal ligation and puncture (CLP). Mice deficient in gammadelta T cells had decreased survival times and increased tissue damage after CLP compared with wild-type mice. Furthermore, bacterial load was increased in gammadelta T cell-deficient mice, yet antibiotic treatment did not change mortality. Additionally, we found that recruitment of neutrophils and myeloid suppressor cells to the site of infection was diminished in gammadelta T cell-deficient mice. Finally, we found that circulating levels of IFN-gamma were increased, and systemic levels of IL-10 were decreased in gammadelta T cell-deficient mice after CLP compared with wild-type mice. gammadelta T cell-deficient mice also had increased intestinal permeability after CLP compared with wild-type mice. Neutralization of IFN-gamma abrogated the increase in intestinal permeability in gammadelta T cell-deficient mice. The intestines taken from gammadelta T cell-deficient mice had decreased myeloperoxidase yet had increased tissue damage as compared with wild-type mice. Collectively, our data suggest that gammadelta T cells modulate the response to sepsis and may be a potential therapeutic target.

A major ingredient of green tea rescues mice from lethal sepsis partly by inhibiting HMGB1

Background

The pathogenesis of sepsis is mediated in part by bacterial endotoxin, which stimulates macrophages/monocytes to sequentially release early (e.g., TNF, IL-1, and IFN-γ) and late (e.g., HMGB1) pro-inflammatory cytokines. Our recent discovery of HMGB1 as a late mediator of lethal sepsis has prompted investigation for development of new experimental therapeutics. We previously reported that green tea brewed from the leaves of the plant Camellia sinensis is effective in inhibiting endotoxin-induced HMGB1 release.

Methods and Findings

Here we demonstrate that its major component, (-)-epigallocatechin-3-gallate (EGCG), but not catechin or ethyl gallate, dose-dependently abrogated HMGB1 release in macrophage/monocyte cultures, even when given 2–6 hours post LPS stimulation. Intraperitoneal administration of EGCG protected mice against lethal endotoxemia, and rescued mice from lethal sepsis even when the first dose was given 24 hours after cecal ligation and puncture. The therapeutic effects were partly attributable to: 1) attenuation of systemic accumulation of proinflammatory mediator (e.g., HMGB1) and surrogate marker (e.g., IL-6 and KC) of lethal sepsis; and 2) suppression of HMGB1-mediated inflammatory responses by preventing clustering of exogenous HMGB1 on macrophage cell surface.

Conclusions

Taken together, these data suggest a novel mechanism by which the major green tea component, EGCG, protects against lethal endotoxemia and sepsis.

Role of CD14 in responses to clinical isolates of Escherichia coli: effects of K1 capsule expression

Severe bacterial infections leading to sepsis or septic shock can be induced by bacteria that utilize different factors to drive pathogenicity and/or virulence, leading to disease in the host. One major factor expressed by all clinical isolates of gram-negative bacteria is lipopolysaccharide (LPS); a second factor expressed by some Escherichia coli strains is a K1 polysaccharide capsule. To determine the role of the CD14 LPS receptor in the pathogenic effects of naturally occurring E. coli, the responses of CD14-/- and CD14+/+ mice to three different isolates of E. coli obtained from sepsis patients were compared; two isolates express both smooth LPS and the K1 antigen, while the third isolate expresses only LPS and is negative for K1. An additional K1-positive isolate obtained from a newborn with meningitis and a K1-negative isogenic mutant of this strain were also used for these studies. CD14-/- mice were resistant to the lethal effects of the K1-negative isolates. This resistance was accompanied by significantly lower levels of systemic tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) in these mice than in CD14+/+ mice, enhanced clearance of the bacteria, and significantly fewer additional gross symptoms. In contrast, CD14-/- mice were as sensitive as CD14+/+ mice to the lethal effects of the K1-positive isolates, even though they had significantly lower levels of TNF-alpha and IL-6 than CD14+/+ mice. These studies show that different bacterial isolates can use distinctly different mechanisms to cause disease and suggest that new, nonantibiotic therapeutics need to be directed against multiple targets.

Glucose-6-phosphate dehydrogenase deficiency and the inflammatory response to endotoxin and polymicrobial sepsis*

OBJECTIVE

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common human genetic polymorphism. The deficiency protects against malaria but was shown to worsen the clinical course after severe trauma. This study tested whether the deficiency is associated with altered cytokine responses in vitro and in vivo and affects survival after endotoxemia or polymicrobial sepsis (cecal ligation and puncture).

DESIGN

Genotyping of animals was carried out using a novel and improved allele-specific polymerase chain reaction assay. Macrophage and splenocyte responses in vitro and ex vivo were compared using gene array analyses and enzyme-linked immunosorbent assays and flow cytometry under both baseline and lipopolysaccharide-stimulated conditions. Endotoxemia- or sepsis-induced mortality was compared under a variety of treatment and resuscitation protocols.

SETTINGS

Medical school research laboratories.

SUBJECTS

Litter mates of wild-type and G6PD-mutant mice that display a degree of G6PD deficiency similar to that observed in the African-type human deficiency (20% of normal).

MEASUREMENTS AND MAIN RESULTS

Lipopolysaccharide in vivo (lipopolysaccharide from Escherichia coli, 10-35 mg/kg body weight intraperitoneally) resulted in greater interleukin-1beta, interleukin-6, and interleukin-10 levels in serum and peritoneal lavage in G6PD-deficient mice compared with wild type. Prevailing doses of lipopolysaccharide in vivo increased mortality in G6PD-deficient animals (40-70%) as compared with wild type (5-40%). In contrast, mortality after cecal ligation and puncture-induced sepsis was similar in G6PD-deficient and wild-type animals either in saline-resuscitated or antibiotic-treated animals. Splenic and blood phagocytes from septic G6PD-deficient and wild-type animals displayed attenuated ex vivo lipopolysaccharide responsiveness.

CONCLUSIONS

This study demonstrates that G6PD deficiency augments cytokine responses after inflammatory challenges. The deficiency is disadvantageous as reflected in increased mortality after hyperinflammation caused by acute endotoxemia. However, the deficiency may not manifest worsened survival after the immunosuppressed condition associated with severe sepsis.

Sepsis-induced cholestasis, steatosis, hepatocellular injury, and impaired hepatocellular regeneration are enhanced in interleukin-6 -/- mice

OBJECTIVE

Hepatic dysfunction is an important but poorly understood component of sepsis. In severe sepsis, liver dysfunction is characterized by cholestasis, steatosis, hepatocellular injury, impaired regeneration, a decreased response to the cytokine interleukin-6, and high mortality. To determine whether loss of interleukin-6 activity caused hepatic dysfunction and mortality, we induced sepsis in wild-type (interleukin-6 +/+) and interleukin-6 knockout (interleukin-6 -/-) mice. We hypothesized that sepsis in interleukin-6 -/- mice would increase cholestasis, steatosis, hepatocellular injury, and mortality and impair hepatocyte regeneration.

DESIGN

Randomized prospective experimental study.

SETTING

University medical laboratory.

SUBJECTS

Male adolescent C57Bl6 interleukin-6 +/+ and interleukin-6 -/- mice.

INTERVENTIONS

Mild sepsis was induced using cecal ligation and single puncture (CLP). Severe, lethal sepsis was induced using cecal ligation and double puncture (2CLP). Some mice received recombinant human interleukin-6 at the time of CLP/2CLP. All animals were fluid resuscitated at the time of surgery and every 24 hrs thereafter. In survival cohorts, mortality at 16, 24, 48, and 72 hrs was recorded. In separate cohorts, surviving animals were killed at 24 and 48 hrs, and liver tissue was harvested. A separate cohort of mice received bromodeoxyuridine for detection of regeneration.

MEASUREMENTS AND MAIN RESULTS

2CLP was 100% fatal within the first 12 hrs in interleukin-6 -/- mice. Mortality from 2CLP in interleukin-6 +/+ mice before 24 hrs was nil but was 90% by 72 hrs. At 72 hrs, CLP was 40% fatal in interleukin-6 +/+ mice but 90% in interleukin-6 -/- mice. CLP induced cholestasis, steatosis, and hepatocellular injury in interleukin-6 -/-, but not interleukin-6 +/+, mice. Regeneration was absent following CLP in interleukin-6 -/- animals but occurred in interleukin-6 +/+ mice. Early administration of recombinant human interleukin-6 did not reverse abnormalities in interleukin-6 -/- mice.

CONCLUSIONS

The absence of interleukin-6 is an important determinant of hepatic dysfunction and mortality in sepsis.