Combination immunotherapy with soluble tumor necrosis factor receptors plus interleukin 1 receptor antagonist decreases sepsis mortality

The protective effect of the mitochondrial-derived peptide MOTS-c on LPS-induced septic cardiomyopathy

<p indent="0mm">Septic cardiomyopathy is associated with mechanisms such as excessive inflammation, oxidative stress, regulation of calcium homeostasis, endothelial dysfunction, mitochondrial dysfunction, and cardiomyocyte death, and there is no effective treatment at present. MOTS-c is a mitochondria-derived peptide (MDP) encoded by mitochondrial DNA (mtDNA) that protects cells from stresses in an AMPK-dependent manner. In the present study, we aim to explore the protective effect of MOTS-c on lipopolysaccharide (LPS)-induced septic cardiomyopathy. LPS is used to establish a model of septic cardiomyopathy. Our results demonstrate that MOTS-c treatment reduces the mRNA levels of inflammatory cytokines ( <italic>IL-1β</italic>, <italic>IL-4</italic>, <italic>IL-6</italic>, and <italic>TNFα</italic>) in cardiomyocytes and the levels of circulating myocardial injury markers, such as CK-MB and TnT, alleviates cardiomyocyte mitochondrial dysfunction and oxidative stress, reduces cardiomyocyte apoptosis, activates cardioprotection-related signaling pathways, including AMPK, AKT, and ERK, and inhibits the inflammation-related signaling pathways JNK and STAT3. However, treatment with the AMPK pathway inhibitor compound C (CC) abolishes the positive effect of MOTS-c on LPS stress. Collectively, our research suggests that MOTS-c may attenuate myocardial injury in septic cardiomyopathy by activating AMPK and provides a new idea for therapeutic strategies in septic cardiomyopathy. </p>.

Effect of Celecoxib and Infliximab against Multiple Organ Damage Induced by Sepsis in Rats: A Comparative Study

In cases of sepsis, the immune system responds with an uncontrolled release of proinflammatory cytokines and reactive oxygen species. The lungs, kidneys, and liver are among the early impacted organs during sepsis and are a direct cause of mortality. The aim of this study was to compare the effects of infliximab (IFX) and celecoxib (CLX) on septic rats that went through a cecal ligation and puncture (CLP) surgery to induce sepsis. This study included four groups: sham, CLP (untreated), and CLP-treated with CLX or IFX. The administration of “low dose” CLX or IFX was performed after 2 h following the induction of sepsis. Twenty-four hours following the induction of sepsis, the rats were sacrificed and blood samples were collected to evaluate kidney, liver, and lung injuries. MDA and NOx content, in addition to SOD activity and GSH levels, were evaluated in the tissue homogenates of each group. Tissue samples were also investigated histopathologically. In a separate experiment, the same groups were employed to evaluate the survival of septic rats in a 7-day observation period. The results of this study showed that treatment with either CLX or IFX ameliorated the three organs’ damage compared to septic-untreated rats, decreased oxidative stress, enhanced the antioxidant defense, and reduced serum cytokines. As a result, a higher survival rate resulted: 62.5% and 37.5% after the administration of CLX and IFX, respectively, compared to 0% in the CLP group after 7 days. No significant differences were observed between the two agents in all measured parameters. Histopathological examination confirmed the observed results. In conclusion, CLX and IFX ameliorated lung, kidney, and liver injuries associated with sepsis through anti-inflammatory and antioxidant actions, which correlated to the increase in survival observed with both of them.

The role of influenza A virus-induced hypercytokinemia

Influenza viruses are one of the leading causes of respiratory tract infections in humans and their newly emerging and re-emerging virus strains are responsible for seasonal epidemics and occasional pandemics, leading to a serious threat to global public health systems. The poor clinical outcome and pathogenesis during influenza virus infection in humans and animal models are often associated with elevated proinflammatory cytokines and chemokines production, which is also known as hypercytokinemia or "cytokine storm", that precedes acute respiratory distress syndrome (ARDS) and often leads to death. Although we still do not fully understand the complex nature of cytokine storms, the use of immunomodulatory drugs is a promising approach for treating hypercytokinemia induced by an acute viral infection, including highly pathogenic avian influenza virus infection and Coronavirus Disease 2019 (COVID-19). This review aims to discuss the immune responses and cytokine storm pathology induced by influenza virus infection and also summarize alternative experimental strategies for treating hypercytokinemia caused by influenza virus.

Temperature Trajectory Subphenotypes Correlate With Immune Responses in Patients With Sepsis

OBJECTIVES

We recently found that distinct body temperature trajectories of infected patients correlated with survival. Understanding the relationship between the temperature trajectories and the host immune response to infection could allow us to immunophenotype patients at the bedside using temperature. The objective was to identify whether temperature trajectories have consistent associations with specific cytokine responses in two distinct cohorts of infected patients.

DESIGN

Prospective observational study.

SETTING

Large academic medical center between 2013 and 2019.

SUBJECTS

Two cohorts of infected patients: 1) patients in the ICU with septic shock and 2) hospitalized patients with Staphylococcus aureus bacteremia.

INTERVENTIONS

Clinical data (including body temperature) and plasma cytokine concentrations were measured. Patients were classified into four temperature trajectory subphenotypes using their temperature measurements in the first 72 hours from the onset of infection. Log-transformed cytokine levels were standardized to the mean and compared with the subphenotypes in both cohorts.

MEASUREMENTS AND MAIN RESULTS

The cohorts consisted of 120 patients with septic shock (cohort 1) and 88 patients with S. aureus bacteremia (cohort 2). Patients from both cohorts were classified into one of four previously validated temperature subphenotypes: "hyperthermic, slow resolvers" (n = 19 cohort 1; n = 13 cohort 2), "hyperthermic, fast resolvers" (n = 18 C1; n = 24 C2), "normothermic" (n = 54 C1; n = 31 C2), and "hypothermic" (n = 29 C1; n = 20 C2). Both "hyperthermic, slow resolvers" and "hyperthermic, fast resolvers" had high levels of G-CSF, CCL2, and interleukin-10 compared with the "hypothermic" group when controlling for cohort and timing of cytokine measurement (p < 0.05). In contrast to the "hyperthermic, slow resolvers," the "hyperthermic, fast resolvers" showed significant decreases in the levels of several cytokines over a 24-hour period, including interleukin-1RA, interleukin-6, interleukin-8, G-CSF, and M-CSF (p < 0.001).

CONCLUSIONS

Temperature trajectory subphenotypes are associated with consistent cytokine profiles in two distinct cohorts of infected patients. These subphenotypes could play a role in the bedside identification of cytokine profiles in patients with sepsis.

Glatiramer acetate treatment inhibits inflammatory responses and improves survival in a mice model of cecal ligation and puncture-induced sepsis

OBJECTIVES

Sepsis is a clinical crisis which has been considered as one of the important causes of mortality across the world. We hypothesized that modulation of hyper-inflammatory phase of sepsis pathophysiology can lead to protective effects on survival outcome. Glatiramer acetate (GA) is a neuroprotective drug commonly used in multiple sclerosis (MS). GA is characterized by immunom activity via regulation of innate and adaptive immunity. This study was designed to evaluate the acute treatment with GA on initial inflammatory response-induced mortality in septic mice.

METHODS

Cecal ligation and puncture (CLP) model was operated on male mice as a model of Polymicrobial sepsis. GA was administrated intraperitoneally after the sepsis induction at doses of 0.5, 1, and 2 mg/kg in three treatment groups. To investigate the effect of GA on short-term survival, septic mice were observed during 72 h after CLP. Serum levels of TNF-α, IL-1β, and IL-6 as pro-inflammatory cytokines and also IL-10 as a critical anti-inflammatory cytokine were analysed. To consider sepsis-induced acute kidney injury, renal functional biomarkers and histopathological changes was assessed.

RESULTS

GA treatment significantly improved survival rate at doses of 1, and 2 mg/kg. Survival improvement was accompanied by remarkable reduction in the pro-inflammatory cytokines and enhanced production of IL-10. GA showed to have protective effects on renal function as well.

CONCLUSIONS

Immunomodulatory and anti-inflammatory properties of GA resulted in increase in survival rate and decrease in inflammatory markers in mice model of cecal ligation and puncture-induced sepsis.

Prompt Administration of Antibiotics and Fluids in the Treatment of Sepsis: A Murine Trial

OBJECTIVES

Sepsis, the acute organ dysfunction caused by a dysregulated host response to infection, poses a serious public health burden. Current management includes early detection, initiation of antibiotics and fluids, and source control as necessary. Although observational data suggest that delays of even a few hours in the initiation of antibiotics or IV fluids is associated with survival, these findings are controversial. There are no randomized data in humans, and prior animal studies studied time from experimental manipulation, not from the onset of clinical features of sepsis. Using a recently developed murine cecal ligation and puncture model that precisely monitors physiologic deterioration, we hypothesize that incremental hourly delays in the first dose of antibiotics, in the first bolus of fluid resuscitation, or a combination of the two at a clinically relevant point of physiologic deterioration during polymicrobial sepsis will shorten survival.

DESIGN

Randomized laboratory animal experimental trial.

SETTING

University basic science laboratory.

SUBJECTS

Male C57BL/6J, female C57BL/6J, aged (40-50 wk old) male C57BL/6J, and BALB/C mice.

INTERVENTIONS

Mice (n = 200) underwent biotelemetry-enhanced cecal ligation and puncture and were randomized after meeting validated criteria for acute physiologic deterioration. Treatment groups consisted of a single dose of imipenem/cilastatin, a single bolus of 30 mL/kg fluid resuscitation, or a combination of the two. Mice were allocated to receive treatment at the time of meeting deterioration criteria, after a 2-hour delay or after a 4-hour delay.

MEASUREMENTS AND MAIN RESULTS

Hourly delays in the initiation of antibiotic therapy led to progressively shortened survival in our model (p < 0.001). The addition of fluid resuscitation was unable to rescue animals, which received treatment 4 hours after meeting enrollment criteria. Systemic inflammation was increased, and host physiology was increasingly deranged with hourly delays to antibiotics.

CONCLUSIONS

We conclude that antibiotic therapy is highly time sensitive, and efforts should be made to deliver this critical therapy as early as possible in sepsis, perhaps extending into the first point of medical contact outside the hospital.

Cutting Edge: IL-1α and Not IL-1β Drives IL-1R1-Dependent Neonatal Murine Sepsis Lethality

Sepsis disproportionately affects the very old and the very young. IL-1 signaling is important in innate host defense but may also play a deleterious role in acute inflammatory conditions (including sepsis) by promulgating life-threatening inflammation. IL-1 signaling is mediated by two distinct ligands: IL-1α and IL-1β, both acting on a common receptor (IL-1R1). IL-1R1 targeting has not reduced adult human sepsis mortality despite biologic plausibility. Because the specific role of IL-1α or IL-1β in sepsis survival is unknown in any age group and the role of IL-1 signaling remains unknown in neonates, we studied the role of IL-1 signaling, including the impact of IL-1α and IL-1β, on neonatal murine sepsis survival. IL-1 signaling augments the late plasma inflammatory response to sepsis. IL-1α and not IL-1β is the critical mediator of sepsis mortality, likely because of paracrine actions within the tissue. These data do not support targeting IL-1 signaling in neonates.

Translational Sepsis Research: Spanning the Divide

OBJECTIVE

Our knowledge of the molecular mechanisms of sepsis has attained exponential growth. Yet, the pillars of its care remain antibiotics, fluid resuscitation, and physiologic support of failing organ systems. The inability to bring biologic breakthroughs to the bedside is not for lack of effort. Over 60 clinical trials of novel therapies, each heavily supported by the momentum of biologic data suggesting clinical utility, have been conducted and have failed to identify benefit. This mass of "negative" clinical data abut an equally towering mound of knowledge of sepsis biology, which collectively have led investigators to ask, "what happened?"

DATA SOURCES

Review of published scientific literature via MEDLINE searches using key terms related to the article topics.

STUDY SELECTION

Original articles, review articles, and systematic reviews were considered.

DATA EXTRACTION

Articles were selected for inclusion based upon author consensus.

DATA SYNTHESIS

Here, we present a synthetic review of some of the challenges in translating experimental animal models of sepsis to the bedside. We commence with the concept that the heterogeneity in the kinetics of the sepsis response serves as an important, often underappreciated but surmountable, source of translational impedance. Upon this groundwork, we discuss distinctions between animal experimentation and clinical trial design in the elements for hypothesis testing: cohort selection, power and sample size, randomization and blinding, and timing of intervention. From this concept, we develop a contextual framework for advancing the paradigm of animal-based investigations to facilitate science that transitions from molecule to medicine.

CONCLUSIONS

A persistent divide exists between the laboratory and clinical research arenas, which may be addressable via systematic targeting of identified translational gaps.

A New Venue of TNF Targeting

The first Food and Drug Administration-(FDA)-approved drugs were small, chemically-manufactured and highly active molecules with possible off-target effects, followed by protein-based medicines such as antibodies. Conventional antibodies bind a specific protein and are becoming increasingly important in the therapeutic landscape. A very prominent class of biologicals are the anti-tumor necrosis factor (TNF) drugs that are applied in several inflammatory diseases that are characterized by dysregulated TNF levels. Marketing of TNF inhibitors revolutionized the treatment of diseases such as Crohn’s disease. However, these inhibitors also have undesired effects, some of them directly associated with the inherent nature of this drug class, whereas others are linked with their mechanism of action, being pan-TNF inhibition. The effects of TNF can diverge at the level of TNF format or receptor, and we discuss the consequences of this in sepsis, autoimmunity and neurodegeneration. Recently, researchers tried to design drugs with reduced side effects. These include molecules with more specificity targeting one specific TNF format or receptor, or that neutralize TNF in specific cells. Alternatively, TNF-directed biologicals without the typical antibody structure are manufactured. Here, we review the complications related to the use of conventional TNF inhibitors, together with the anti-TNF alternatives and the benefits of selective approaches in different diseases.

Simultaneous Inhibition of Tumor Necrosis Factor Receptor 1 and Matrix Metalloproteinase 8 Completely Protects Against Acute Inflammation and Sepsis

OBJECTIVES

Sepsis causes very high mortality and morbidity rates and remains one of the biggest medical challenges. This study investigates whether plasma levels of both matrix metalloproteinase 8 and tumor necrosis factor receptor 1 are associated with sepsis severity and also investigates the therapeutic applicability of simultaneous inhibition of the two molecules in sepsis.

DESIGN

Observational human pilot study-prospective controlled animal study.

SETTING

University hospital and research laboratory.

SUBJECTS

Sepsis patients and C57BL/6 mice deficient for matrix metalloproteinase 8 and/or tumor necrosis factor receptor 1.

INTERVENTION

Plasma and whole blood RNA were collected from 13 sepsis patients for 7 consecutive days and within 24 hours of admission to ICU. Matrix metalloproteinase 8 and tumor necrosis factor receptor 1 plasma and expression levels were determined in these patients. Mice deficient for both matrix metalloproteinase 8 and tumor necrosis factor receptor 1 were generated and subjected to endotoxemia and cecal ligation and puncture. Additionally, a bispecific Nanobody that simultaneously blocks matrix metalloproteinase 8 and tumor necrosis factor receptor 1 was created.

MEASUREMENTS AND MAIN RESULTS

Plasma levels of matrix metalloproteinase 8 and tumor necrosis factor receptor 1 were positively correlated with the Sequential Organ Failure Assessment score (r, 0.51 and 0.58) and interleukin 6 levels (r, 0.59 and 0.52) in 13 sepsis patients. Combined elimination of tumor necrosis factor receptor 1 and matrix metalloproteinase 8 in double knockout mice resulted in superior survival in endotoxemia and CLP compared with single knockouts and wild-type mice. Cotreatment with our bispecific Nanobody in CLP resulted in improved survival rates (28% vs 19%) compared with untreated mice.

CONCLUSIONS

Inhibition of matrix metalloproteinase 8 and tumor necrosis factor receptor 1 might have therapeutic potential to treat sepsis and proof-of-principle was provided as therapeutics that inhibit both tumor necrosis factor receptor 1 and matrix metalloproteinase 8 are effective in CLP.

Use of Biotelemetry to Define Physiology-Based Deterioration Thresholds in a Murine Cecal Ligation and Puncture Model of Sepsis

OBJECTIVES

Murine models of critical illness are commonly used to test new therapeutic interventions. However, these interventions are often administered at fixed time intervals after the insult, perhaps ignoring the inherent variability in magnitude and temporality of the host response. We propose to use wireless biotelemetry monitoring to define and validate criteria for acute deterioration and generate a physiology-based murine cecal ligation and puncture model that is more similar to the conduct of human trials of sepsis.

DESIGN

Laboratory and animal research.

SETTING

University basic science laboratory.

SUBJECTS

Male C57BL/6 mice.

INTERVENTIONS

Mice underwent cecal ligation and puncture, and an HD-X11 wireless telemetry monitor (Data Sciences International) was implanted that enabled continuous, real-time measurement of heart rate, core temperature, and mobility. We performed a population-based analysis to determine threshold criteria that met face validity for acute physiologic deterioration. We assessed construct validity by temporally matching mice that met these acute physiologic deterioration thresholds with mice that had not yet met deterioration threshold. We analyzed matched blood samples for blood gas, inflammatory cytokine concentration, cystatin C, and alanine aminotransferase.

MEASUREMENTS AND MAIN RESULTS

We observed that a 10% reduction in both heart rate and temperature sustained for greater than or equal to 10 minutes defined acute physiologic deterioration. There was significant variability in the time to reach acute deterioration threshold across mice, ranging from 339 to 529 minutes after cecal ligation and puncture. We found adequate construct validity, as mice that met criteria for acute deterioration had significantly worse shock, systemic inflammation (elevated tumor necrosis factor-α, p = 0.003; interleukin-6, p = 0.01; interleukin-10, p = 0.005), and acute kidney injury when compared with mice that had not yet met acute deterioration criteria.

CONCLUSIONS

We defined a murine threshold for acute physiologic deterioration after cecal ligation and puncture that has adequate face and construct validity. This model may enable a more physiology-based model for evaluation of novel therapeutics in critical illness.

Comparison of the Functional microRNA Expression in Immune Cell Subsets of Neonates and Adults

Diversity of biological molecules in newborn and adult immune cells contributes to differences in cell function and atopic properties. Micro RNAs (miRNAs) are reported to involve in the regulation of immune system. Therefore, determining the miRNA expression profile of leukocyte subpopulations is important for understanding immune system regulation. In order to explore the unique miRNA profiling that contribute to altered immune in neonates, we comprehensively analyzed the functional miRNA signatures of eight leukocyte subsets (polymorphonuclear cells, monocytes, CD4⁺ T cells, CD8⁺ T cells, natural killer cells, B cells, plasmacytoid dendritic cells, and myeloid dendritic cells) from both neonatal and adult umbilical cord and peripheral blood samples, respectively. We observed distinct miRNA profiles between adult and neonatal blood leukocyte subsets, including unique miRNA signatures for each cell lineage. Leukocyte miRNA signatures were altered after stimulation. Adult peripheral leukocytes had higher let-7b-5p expression levels compared to neonatal cord leukocytes across multiple subsets, irrespective of stimulation. Transfecting neonatal monocytes with a let-7b-5p mimic resulted in a reduction of LPS-induced interleukin (IL)-6 and TNF-α production, while transfection of a let-7b-5p inhibitor into adult monocytes enhanced IL-6 and TNF-α production. With this functional approach, we provide intact differential miRNA expression profiling of specific immune cell subsets between neonates and adults. These studies serve as a basis to further understand the altered immune response observed in neonates and advance the development of therapeutic strategies.

Pathophysiology of sepsis-related cardiac dysfunction: driven by inflammation, energy mismanagement, or both?

Sepsis is a systemic inflammatory response that follows bacterial infection. Cardiac dysfunction is an important consequence of sepsis that affects mortality and has been attributed to either elevated inflammation or suppression of both fatty acid and glucose oxidation and eventual ATP depletion. Moreover, cardiac adrenergic signaling is compromised in septic patients and this aggravates further heart function. While anti-inflammatory therapies are important for the treatment of the disease, administration of anti-inflammatory drugs did not improve survival in septic patients. This review article summarizes findings on inflammatory and other mechanisms that are triggered in sepsis and affect cardiac function and mortality. Particularly, it focuses on the effects of the disease in metabolic pathways, as well as in adrenergic signaling and the potential interplay of the latter with inflammation. It is suggested that therapeutic approaches should include combination of anti-inflammatory treatments, stimulation of energy production, and restoration of adrenergic signaling in the heart.

Ly6Chigh Monocytes Protect against Kidney Damage during Sepsis via a CX3CR1-Dependent Adhesion Mechanism

Monocytes have a crucial role in both proinflammatory and anti-inflammatory phenomena occurring during sepsis. Monocyte recruitment and activation are orchestrated by the chemokine receptors CX3CR1 and CCR2 and their cognate ligands. However, little is known about the roles of these cells and chemokines during the acute phase of inflammation in sepsis. Using intravital microscopy in a murine model of polymicrobial sepsis, we showed that inflammatory Ly6C(high) monocytes infiltrated kidneys, exhibited altered motility, and adhered strongly to the renal vascular wall in a chemokine receptor CX3CR1-dependent manner. Adoptive transfer of Cx3cr1-proficient monocyte-enriched bone marrow cells into septic Cx3cr1-depleted mice prevented kidney damage and promoted mouse survival. Modulation of CX3CR1 activation in septic mice controlled monocyte adhesion, regulated proinflammatory and anti-inflammatory cytokine expression, and was associated with the extent of kidney lesions such that the number of lesions decreased when CX3CR1 activity increased. Consistent with these results, the pro-adhesive I249 CX3CR1 allele in humans was associated with a lower incidence of AKI in patients with sepsis. These data show that inflammatory monocytes have a protective effect during sepsis via a CX3CR1-dependent adhesion mechanism. This receptor might be a new therapeutic target for kidney injury during sepsis.

Determination of the safety and efficacy of therapeutic neutralization of tumor necrosis factor-α (TNF-α) using AZD9773, an anti-TNF-α immune Fab, in murine CLP sepsis

OBJECTIVE AND DESIGN

TNF-α neutralization is associated with increased mortality in mouse cecal ligation puncture (CLP) models. AZD9773 is an ovine polyclonal human TNF-α immune Fab, with pharmacological properties that differ from previously studied anti-TNF-α agents. We explored the safety and efficacy of therapeutically administered AZD9773 in mouse CLP sepsis.

METHODS

A moderate/severe-grade CLP model resulting in 20-30 % 5-day survival and a mild-grade CLP model resulting in ~70 % 5-day survival were established in human TNF-α transgene/murine TNF null (Tg1278/-/-) mice.

TREATMENT

Mice received saline resuscitation and imipenem administration every 12 h (0-72 h post-CLP). AZD9773 (or DigiFab control) was dosed 24, 36, 48 and 60 h post-CLP.

RESULTS

Therapeutic dosing of AZD9773 in moderate/severe-grade CLP resulted in significantly increased survival (>70 %) compared with DigiFab (27 %, P < 0.05). Therapeutic dosing of AZD9773 in mild-grade CLP did not significantly affect survival outcome compared with DigiFab or imipenem alone (~60-70 % survival).

CONCLUSIONS

These data demonstrate that TNF-α neutralization can improve survival in moderate/severe CLP sepsis. TNF-α suppression in mild-grade models was not associated with survival benefit and did not increase 5-day mortality. These findings suggest that therapeutic benefit following TNF-α attenuation in models of sepsis may depend on model severity.

Genetic deletion of the HIF-1α isoform I.1 in T cells enhances antibacterial immunity and improves survival in a murine peritonitis model

Hypoxia-adenosinergic suppression and redirection of the immune response has been implicated in the regulation of antipathogen and antitumor immunity, with hypoxia-inducible factor 1α (HIF-1α) playing a major role. In this study, we investigated the role of isoform I.1, a quantitatively minor alternative isoform of HIF-1α, in antibacterial immunity and sepsis survival. By using the cecal ligation and puncture model of bacterial peritonitis, we studied the function of I.1 isoform in T cells using mice with total I.1 isoform deficiency and mice with T-cell-targeted I.1 knockdown. We found that genetic deletion of the I.1 isoform resulted in enhanced resistance to septic lethality, significantly reduced bacterial load in peripheral blood, increased M1 macrophage polarization, augmented levels of proinflammatory cytokines in serum, and significantly decreased levels of the anti-inflammatory cytokine IL-10. Our data suggest a previously unrecognized immunosuppressive role for the I.1 isoform in T cells during bacterial sepsis. We interpret these data as indicative that the activation-inducible isoform I.1 hinders the contribution of T cells to the antibacterial response by affecting M1/M2 macrophage polarization and microbicidal function.

Myeloid-derived suppressor cells evolve during sepsis and can enhance or attenuate the systemic inflammatory response

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous Gr1(+) CD11b(+) population of immature cells containing granulocytic and monocytic progenitors, which expand under nearly all inflammatory conditions and are potent repressors of T-cell responses. Studies of MDSCs during inflammatory responses, including sepsis, suggest they can protect or injure. Here, we investigated MDSCs during early and late sepsis. To do this, we used our published murine model of cecal ligation and puncture (CLP)-induced polymicrobial sepsis, which transitions from an early proinflammatory phase to a late anti-inflammatory and immunosuppressive phase. We confirmed that Gr1(+) CD11b(+) MDSCs gradually increase after CLP, reaching ∼88% of the bone marrow myeloid series in late sepsis. Adoptive transfer of early (day 3) MDSCs from septic mice into naive mice after CLP increased proinflammatory cytokine production, decreased peritoneal bacterial growth, and increased early mortality. Conversely, transfer of late (day 12) MDSCs from septic mice had the opposite effects. Early and late MDSCs studied ex vivo also differed in their inflammatory phenotypes. Early MDSCs expressed nitric oxide and proinflammatory cytokines, whereas late MDSCs expressed arginase activity and anti-inflammatory interleukin 10 (IL-10) and transforming growth factor β (TGF-β). Late MDSCs had more immature CD31(+) myeloid progenitors and, when treated ex vivo with granulocyte-macrophage colony-stimulating factor (GM-CSF), generated fewer macrophages and dendritic cells than early MDSCs. We conclude that as the sepsis inflammatory process progresses, the heterogeneous MDSCs shift to a more immature state and from being proinflammatory to anti-inflammatory.

Effect of Traumeel S on cytokine profile in a cecal ligation and puncture (CLP) sepsis model in rats

BACKGROUND

Sepsis results in significant morbidity and mortality, with current treatment options limited with respect to efficacy as well as safety. The complex homeopathic remedy Traumeel S has been shown to have both anti-inflammatory and immunostimulatory effects in the in vitro setting.

OBJECTIVES

The objective was to explore the effects of Traumeel S in an in vivo setting, using a cecal ligation and puncture (CLP) sepsis model in rats, evaluating the effects of the medication on cytokine activity.

DESIGN

Sepsis was induced in 30 rats using accepted CLP methodology. Following the procedure, rats were randomly allocated to receive an intraperitoneal injection of either Traumeel S (n=15) or normal saline (n=15). At 6 hours post-CLP, serum cytokines (interleukin [IL]-1β, tumor necrosis factor-α, IL-6, and IL-10) were evaluated.

RESULTS

IL-1β levels were significantly higher in the treatment group (p=0.03) with no significant differences found between the groups with respect to the other cytokines tested.

CONCLUSIONS

In contrast to in vitro studies, Traumeel significantly increased IL-1β levels in an in vivo model, without influencing other cytokines. IL-1β is a proinflammatory cytokine that has been shown to have a protective effect in the CLP rat model. Further research is warranted to examine this finding, as well as its clinical implications.

Selective inhibition of TNF-alpha or IL-1 beta does not affect E. coli-induced inflammation in human whole blood

Inhibition of the inappropriate and excessive inflammatory response has been a main issue in sepsis-related research. Historically, TNF-alpha and IL-1 beta have been postulated as key mediators in sepsis, but selective inhibition of these cytokines has failed in clinical trials. Recently it was found that inhibition of upstream recognition by complement and CD14 could efficiently reduce Escherichia coli (E. coli)-induced inflammation. An ex vivo model with lepirudin-anticoagulated human whole blood was used to explore the significance of selective inhibition of TNF-alpha and IL-1 beta in E. coli-induced inflammation. The effect of TNF-alpha, IL-1 beta, complement and CD14 on the inflammatory response was assessed by adding highly specific neutralizing agents to these mediators. Proinflammatory cytokines, expression of CD11b and oxidative burst were measured. The controls included relevant isotype-matched immunoglobulins and peptides. Selective inhibition of TNF-alpha or IL-1 beta had no impact on E. coli-induced release of proinflammatory cytokines, CD11b-upregulation or oxidative burst. In contrast, the combined inhibition of complement and CD14 virtually abolished these responses. These data suggest that both TNF-alpha and IL-1 beta are downstream mediators and as single mediators play a limited role within the complex inflammatory reactions induced by E. coli.

Differential role for CD80 and CD86 in the regulation of the innate immune response in murine polymicrobial sepsis

BACKGROUND

Inflammation in the early stages of sepsis is governed by the innate immune response. Costimulatory molecules are a receptor/ligand class of molecules capable of regulation of inflammation in innate immunity via macrophage/neutrophil contact. We recently described that CD80/86 ligation is required for maximal macrophage activation and CD80/86(-/-) mice display reduced mortality and inflammatory cytokine production after cecal ligation and puncture (CLP). However, these data also demonstrate differential regulation of CD80 and CD86 expression in sepsis, suggesting a divergent role for these receptors. Therefore, the goal of this study was to determine the individual contribution of CD80/86 family members in regulating inflammation in sepsis.

METHODOLOGY/PRINCIPAL FINDINGS

CD80(-/-) mice had improved survival after CLP when compared to WT or CD86(-/-) mice. This was associated with preferential attenuation of inflammatory cytokine production in CD80(-/-) mice. Results were confirmed with pharmacologic blockade, with anti-CD80 mAb rescuing mice when administered before or after CLP. In vitro, activation of macrophages with neutrophil lipid rafts caused selective disassociation of IRAK-M, a negative regulator of NF-kappaB signaling from CD80; providing a mechanism for preferential regulation of cytokine production by CD80. Finally, in humans, upregulation of CD80 and loss of constitutive CD86 expression on monocytes was associated with higher severity of illness and inflammation confirming the findings in our mouse model.

CONCLUSIONS

In conclusion, our data describe a differential role for CD80 and CD86 in regulation of inflammation in the innate immune response to sepsis. Future therapeutic strategies for blockade of the CD80/86 system in sepsis should focus on direct inhibition of CD80.

Mast cells are necessary for the hypothermic response to LPS-induced sepsis

As central nervous system residents, mast cells contain many cytokines and are localized primarily near large blood vessels in the diencephalon and within the leptomeninges, making them candidates for immune to neural "cross talk." Using mast cell-deficient Kit(W-sh/W-sh) mice, we assessed the role of these cells in the thermoregulatory component of the immune response to lipopolysaccharide (LPS). Kit(W-sh/W-sh) and wild-type (WT) mice differed in several respects in response to injection of a high dose of LPS (1 mg/kg ip). Core temperature (T(c)) of WT mice decreased by approximately 3 degrees C, whereas Kit(W-sh/W-sh) mice did not become hypothermic but instead exhibited pronounced low-frequency T(c) oscillations around their baseline temperature. In addition, Kit(W-sh/W-sh) mice had lower levels of whole brain TNF-alpha but no differences in IL-1beta, IL-6, IFN-gamma, or histamine compared with WT mice following injection of the high dose of LPS, consistent with the role of TNF-alpha in sepsis. Kit(W-sh/W-sh) mice had increased resistance to LPS, and some survived a dose of LPS that was lethal in littermate controls. In contrast, Kit(W-sh/W-sh) and WT mice were similar in other aspects, namely, in the hyperthermia following injection of TNF-alpha (1.5 microg icv), reduced nighttime T(c) and locomotor activity (to 1 mg/kg LPS), response to a low dose of LPS (10 microg/kg ip), and response to subcutaneous turpentine injection. These results indicate that mast cells play a role in the regulation of thermoregulatory responses and survival following sepsis induction and suggest a brain site of action.

Comparison of the susceptibilities of C57BL/6 and A/J mouse strains to Streptococcus suis serotype 2 infection

Streptococcus suis is an important swine and human pathogen. Assessment of susceptibility to S. suis using animal models has been limited to monitoring mortality rates. We recently developed a hematogenous model of S. suis infection in adult CD1 outbred mice to study the in vivo development of an early septic shock-like syndrome that leads to death and a late phase that clearly induces central nervous system damage, including meningitis. In the present study, we compared the severities of septic shock-like syndrome caused by S. suis between adult C57BL/6J (B6) and A/J inbred mice. Clinical parameters, proinflammatory mediators, and bacterial clearance were measured to dissect potential immune factors associated with genetic susceptibility to S. suis infection. Results showed that A/J mice were significantly more susceptible than B6 mice to S. suis infection, especially during the acute septic phase of infection (100% of A/J and 16% of B6 mice died before 24 h postinfection). The greater susceptibility of A/J mice was associated with an exaggerated inflammatory response, as indicated by their higher production of tumor necrosis factor alpha, interleukin-12p40/p70 (IL-12p40/p70), gamma interferon, and IL-1beta, but not with different bacterial loads in the blood. In addition, IL-10 was shown to be responsible, at least in part, for the higher survival in B6 mice. Our findings demonstrate that A/J mice are very susceptible to S. suis infection and provide evidence that the balance between pro- and anti-inflammatory mediators is crucial for host survival during the septic phase.

Mechanisms of mortality in early and late sepsis

A recent hypothesis postulates that sepsis moves through different phases, with periods of enhanced inflammation alternating with periods of immune suppression. In this study we determined the levels of inflammation present during early and late septic deaths to examine whether death was due to hyperinflammation or immunosuppression. The murine model of sepsis induced by cecal ligation and puncture (CLP) was used. Complete blood counts, plasma interleukin-6 (IL-6) levels, and body weights were determined. Mice that died within the first 4 days had increased plasma levels of IL-6, indicating that there was activation of the immune system. Cecal resection on day 4 after CLP resulted in decreased abscess size, lower circulating neutrophil counts, decreased anemia, and improved survival compared to the results for mice that received only antibiotic and fluid therapy. All of the mice that died in the chronic phase of infection (after day 4) had positive peritoneal cultures containing significantly more bacteria than the cultures for surviving mice. After day 4, none of the surviving mice exhibited increases in the plasma levels of IL-6. Dying mice exhibited mixed IL-6 responses; for 41% of the mice there was never an increase in the IL-6 levels in the chronic phase, while for other mice the levels of IL-6 transiently increased prior to death. Peritoneal macrophages were obtained in the late phase of sepsis from moribund and healthy mice and were stimulated ex vivo. The cells from the moribund mice produced significantly less IL-6 than the cells obtained from healthy mice produced. These results indicate that in mice that die in the early phase there is uniformly increased inflammation. However, during the chronic phase of sepsis, some mice die with evidence of immunosuppression (increased bacterial growth and low IL-6 levels), while other mice die with immunostimulation (high IL-6 levels and bacterial growth). Determining the inflammatory status of individual patients may help guide appropriate, targeted therapy.

Circulating cytokine/inhibitor profiles reshape the understanding of the SIRS/CARS continuum in sepsis and predict mortality

Mortality in sepsis remains unacceptably high and attempts to modulate the inflammatory response failed to improve survival. Previous reports postulated that the sepsis-triggered immunological cascade is multimodal: initial systemic inflammatory response syndrome (SIRS; excessive pro-, but no/low anti-inflammatory plasma mediators), intermediate homeostasis with a mixed anti-inflammatory response syndrome (MARS; both pro- and anti-inflammatory mediators) and final compensatory anti-inflammatory response syndrome (CARS; excessive anti-, but no/low proinflammatory mediators). To verify this, we examined the evolution of the inflammatory response during the early phase of murine sepsis by repetitive blood sampling of septic animals. Increased plasma concentrations of proinflammatory (IL-6, TNF, IL-1beta, KC, MIP-2, MCP-1, and eotaxin) and anti-inflammatory (TNF soluble receptors, IL-10, IL-1 receptor antagonist) cytokines were observed in early deaths (days 1-5). These elevations occurred simultaneously for both the pro- and anti-inflammatory mediators. Plasma levels of IL-6 (26 ng/ml), TNF-alpha (12 ng/ml), KC (33 ng/ml), MIP-2 (14 ng/ml), IL-1 receptor antagonist (65 ng/ml), TNF soluble receptor I (3 ng/ml), and TNF soluble receptor II (14 ng/ml) accurately predicted mortality within 24 h. In contrast, these parameters were not elevated in either the late-deaths (day 6-28) or survivors. Surprisingly, either pro- or anti-inflammatory cytokines were also reliable in predicting mortality up to 48 h before outcome. These data demonstrate that the initial inflammatory response directly correlates to early but not late sepsis mortality. This multifaceted response questions the use of a simple proinflammatory cytokine measurement for classifying the inflammatory status during sepsis.

Use of cytokines in infection

Infectious disease remains an ever-growing health concern worldwide due to increasing antibiotic-resistant microbial strains, immune-compromised populations, international traffic and globalisation, and bioterrorism. There exists an urgent need to develop novel prophylactic and therapeutic strategies. In addition to classic antibiotic therapeutics, immune-modulatory molecules such as cytokines or their inhibitors represent a promising form of antimicrobial therapeutics or immune adjuvant used for the purpose of vaccination. These molecules, in the form of either recombinant protein or transgene, exert their antimicrobial effect by enhancing infectious agent-specific immune activation or memory development, or by dampening undesired inflammatory and immune responses resulting from infection and host defence mechanisms. In the last two decades, a number of cytokine therapy-based experimental and clinical trials have been conducted, and some of these efforts have led to the routine clinical use of cytokines. For instance, although IFNs have been used to treat hepatitis C with great success, many other cytokines are yet to be fully evaluated for their antimicrobial potential. This review discusses the biology and therapeutic potential of selected immune modulatory cytokines and their inhibitors, including granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, IFN-gamma, IL-12 and TNF.

Cytokine-related genotypic differences in peak interleukin-6 blood levels of patients with SIRS and septic complications

BACKGROUND

The aim of the present study was to investigate whether tumor necrosis factor (TNF), interleukin (IL)-1, and IL-6-related genotypic differences affect IL-6 blood levels in patients with systemic inflammatory response syndrome (SIRS) in an intensive care unit (ICU).

METHODS

Seven polymorphisms of TNF, IL-1, and IL-6-related polymorphisms were studied with an allele-specific polymerase chain reaction. One hundred and thirteen patients diagnosed with SIRS whose sequential organ failure assessment scores were > or =5 at the time when their daily measured IL-6 blood level peaked during the ICU stay (IL-6 max) were examined. IL-6 max, survival, and septic complications were compared between carriers and non-carriers of less frequent alleles, indicated as allele*2, in each polymorphism.

RESULTS

In single nucleotide polymorphism (SNP) at position -238 site of TNF-alpha (TNF-alpha-238*G/A), IL-6-596*G/A, and IL-6-174*C/T, allele*2 frequencies were much lower in the Japanese than in the Caucasian population. IL-6 max was significantly higher in allele*2 carriers of IL-1beta-511*C/T. Associations were found between susceptibility to septic shock and allele*2 carriage for both IL-1beta-511*C/T and TNF-alpha-308*G/A, and also between poor prognosis and allele*2 carriage in both IL-1 receptor antagonist second intron various number of tandem repeats polymorphism (IL-1raRN*1-5) and TNF-alpha-308*G/A. IL-1beta-511*C/T and IL-1raRN*1-5 were in linkage disequilibrium in this study population.

CONCLUSIONS

Carriers of less frequent alleles in IL-1-related polymorphisms appear to have significant vulnerability to production of excessive IL-6 blood levels and to deterioration in septic shock.

Opposing effects of tumor necrosis factor receptor 1 and 2 in sepsis due to cecal ligation and puncture

Tumor necrosis factor (TNF)-alpha, a cardinal molecule in the cascade of sepsis-induced host injury, binds to two distinct receptors: tumor necrosis factor receptor (TNFR) 1 and TNFR2. We used the cecal ligation and puncture model of polymicrobial sepsis to elucidate the role of these receptors in sepsis pathogenesis. Mice lacking TNFR1 had prolonged survival with less hypothermia, whereas mice lacking TNFR2-/- had shortened survival and more profound hypothermia than wild-type mice. TNFR1-/- and TNFR2-/- mice had increased serum concentrations of interleukin (IL) 1beta and total TNF-alpha (free plus receptor bound) compared with wild-type mice, but there were no differences in IL6 or IL10 concentrations. Furthermore, free TNF-alpha was markedly elevated in the serum and peritoneal fluid of mice lacking TNFR2, supporting a role for this receptor in regulating the concentration of TNF-alpha. Lastly, apoptosis of ileal crypt epithelial cells was increased in mice lacking TNFR1, but there were no differences in lymphocyte apoptosis. These data suggest that in sepsis, TNFR1 mediates much of the TNF-alpha-induced pathology, whereas TNFR2 mediates protective effects.

Role of interleukin-6 in mortality from and physiologic response to sepsis

Previous studies have suggested that interleukin-6 (IL-6) serves as both a marker and a mediator for the severity of sepsis. We tested whether interleukin 6 knockout (IL-6KO) mice were more susceptible to sepsis mortality induced by cecal ligation and puncture. IL-6KO and wild-type (WT) mice were subjected to increasing degrees of sepsis severity. Physiologic support was given with fluids and appropriate antibiotics. Plasma IL-6 levels were determined 6 h after the onset of sepsis, and a complete hematologic profile was performed on day 2. As expected, increasing sepsis severity resulted in greater and more rapid mortality. However, the mortality was nearly identical in the IL-6KO and WT mice. All WT septic mice had high plasma levels of IL-6 6 h after the onset of sepsis, while IL-6KO were near or below the lower limit of detection. Among the WT mice, mortality was significantly higher in mice with plasma IL-6 >3,000 pg/ml. Both IL-6KO and WT mice destined to die in the early stages of sepsis had substantial and nearly identical weight gain in the first 24 h. However, at later stages the WT mice had significantly greater weight loss than the KO mice. The KO mice failed to develop the characteristic hypothermia within the first 24 h of severe sepsis routinely observed in the WT mice. These data demonstrate that IL-6 serves as a marker of disease severity in sepsis and does modulate some physiologic responses, but complete lack of IL-6 does not does not alter mortality due to sepsis.

Extremely high interleukin-6 blood levels and outcome in the critically ill are associated with tumor necrosis factor- and interleukin-1-related gene polymorphisms

OBJECTIVE

To determine the allelic frequencies of interleukin (IL)-6-, IL-1-, and tumor necrosis factor-alpha (TNF)-related gene polymorphisms in critically ill patients with extremely high IL-6 blood level and to examine the genetic effects on their clinical courses.

DESIGN

Population-based association study.

SETTING

A general intensive care unit in a university teaching hospital.

PATIENTS

A total of 150 consecutive critically ill patients recruited at admission to the intensive care unit, regardless of diagnosis, and 150 healthy volunteers.

MEASUREMENTS AND MAIN RESULTS

IL-6 blood levels were measured daily with chemiluminescence immunoassay. The IL-6 peak levels were significantly correlated with simultaneously measured TNF (r = .659, p < .0001) and IL-1beta levels (r = .518, p < .0001), respectively. Single nucleotide polymorphism at position -174 and -596 sites of the IL-6 (IL6-174*G/C and IL6-596*G/A), -308 site of the TNF (TNF-308*G/A), and -511 site of the IL-1beta (IL1B-511*C/T) were identified with real-time polymerase chain reaction assay using specific fluorescence-labeled probe. Within the IL-1 receptor antagonist intron 2, a various number of tandem repeat polymorphisms (IL1RN*1-5) were identified after polymerase chain reaction with gel electrophoresis. Allelic frequencies of patients with IL-6 peak levels of > or =10,000 pg/mL (group A) were compared with those of patients with IL-6 peak levels of <10,000 pg/mL (group B). Neither IL6-174*C nor IL6-596*A were recognized in all the subjects; however, group A showed a higher frequency of TNF-308*A (p = .054), IL1B-511*T (p = .013), and non-IL1RN*1 (p = .008) allele compared with group B. TNF-308*A, IL1RN*2 or IL1RN*3 allele carriers of group A showed sustained high IL-6 levels, despite countermeasures against hypercytokinemia, and their survival rate was lower than that of the noncarriers of those high-risk alleles (p = .025).

CONCLUSIONS

TNF-308*A, IL1RN*2, and IL1RN*3 alleles were associated with the prevalence of the extremely high IL-6 blood level in the critically ill, their uncontrollable blood IL-6 kinetics, and outcome.

Anti-inflammatory response is associated with mortality and severity of infection in sepsis

Using a murine model of sepsis, we found that the balance of tissue pro- to anti-inflammatory cytokines directly correlated with severity of infection and mortality. Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). Liver tissue was analyzed for levels of IL-1beta, IL-1 receptor antagonist (IL-1ra), tumor necrosis factor (TNF)-alpha, and soluble TNF receptor 1 by ELISA. Bacterial DNA was measured using quantitative real-time PCR. After CLP, early predominance of proinflammatory cytokines (6 h) transitioned to anti-inflammatory predominance at 24 h. The elevated anti-inflammatory cytokines were mirrored by increased tissue bacterial levels. The degree of anti-inflammatory response compared with proinflammatory response correlated with the bacterial concentration. To modulate the timing of the anti-inflammatory response, mice were treated with IL-1ra before CLP. This resulted in decreased proinflammatory cytokines, earlier bacterial load, and increased mortality. These studies show that the initial tissue proinflammatory response to sepsis is followed by an anti-inflammatory response. The anti-inflammatory phase is associated with increased bacterial load and mortality. These data suggest that it is the timing and magnitude of the anti-inflammatory response that predicts severity of infection in a murine model of sepsis.

The Lung in Sepsis: Fueling the Fire

Advances in our understanding of the molecular mechanisms underlying the pathophysiology of sepsis have generated considerable efforts in manipulating the host response during this frequently lethal condition. While existing trials of immune modulation have been largely unsuccessful, an appreciation for the roles of individual organ systems in sepsis is important to enable clinicians to discern how each functions as both a target for injury and a contributor to the derangement in homeostasis seen in sepsis. Such awareness will encourage treatment decisions aimed at optimizing conventional therapy while minimizing the adverse effects of supportive care, and it may also guide the incorporation of newer immunomodulatory therapeutics into our existing modalities. This article discusses the lung's response to sepsis, from the standpoint of organ dysfunction related to sepsis as well as its participation in the generation and maintenance of the systemic inflammatory state.

In silico experiments of existing and hypothetical cytokine-directed clinical trials using agent-based modeling*

OBJECTIVES

To introduce a form of mathematical modeling, agent-based modeling (ABM), and demonstrate its potential uses in the evaluation of the dynamics of the innate immune response (IIR) and the development of possible treatments for systemic inflammatory response syndrome (SIRS)/multiple organ failure (MOF).

RATIONALE

The IIR can be categorized as a complex system that responds to interventions in a nonintuitive fashion, leading to difficulty in translating basic science knowledge into effective treatments for SIRS/MOF. It is proposed that ABM is particularly well suited to examining the complex interactions of the IIR and its disordered states of SIRS/MOF.

STUDY DESIGN

Computer simulation and mathematical modeling.

DATA SOURCE

Review articles on components and mechanisms involved in the IIR. Published results from phase III anticytokine/mediator trials. Published results from smaller clinical trials and animal studies.

MAIN RESULTS

An abstract ABM of the IIR was created. The model reproduces the general behavior of the IIR with respect to outcome and cause of system "death." Patterns of levels of individual cytokines matched patterns of measured cytokines reported in the existing literature. Clinical trials of anticytokine therapy were simulated and produced outcomes qualitatively similar to those reported in the literature. A series of hypothetical treatment regimes (variation of dose and length of treatment [anti-tumor necrosis factor and anti-interleukin-1], anti-CD-18, and multiple-drug regimes [combination of anti-tumor necrosis factor, anti-interleukin-1, and anti-CD-18]) were formulated and implemented in the ABM. None of the simulated therapies showed a statistically significant improvement in system mortality.

CONCLUSIONS

Presented herein is an abstracted ABM of the IIR. This model is intended primarily as an introduction to and demonstration of this technique. However, even this relatively simple model demonstrates counterintuitive system responses and the difficulty of effectively manipulating a complex system like the IIR. ABM may provide a synthetic, analytical platform to integrate basic science data on the IIR, thus eventually aiding in formulating and testing future mediator-directed therapies for SIRS/MOF before clinical trials, and it may provide insights into directions of future research.

Modulation of adhesion molecule expression on endothelial cells after induction by lipopolysaccharide-stimulated whole blood

The relative contribution of the pro-inflammatory cytokines tumour necrosis factor (TNF)-alpha and interleukin (IL)-1 beta and the lipopolysaccharide (LPS)-induced pathways that result in endothelial activation during sepsis are not fully understood. We have examined the effects of plasma obtained from LPS-treated human whole blood on the expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1) on human endothelial cells. Stimulation of blood with 10 pg/ml of LPS is sufficient to produce plasma that induces E-selectin and ICAM-1 expression, while direct induction by LPS alone requires a 100-fold higher concentration. Characteristics for the plasma-induced adhesion molecule expression were similar to the LPS-induced production of TNF-alpha and IL-1 beta in blood. A complete inhibition of E-selectin and ICAM-1 expression was observed when antibodies against TNF-alpha and IL-1 beta were added to plasma prior to the incubation to endothelial cultures. Significant inhibition was even observed if antibodies were added to the cultures up until 3 h after LPS-conditioned plasma. The plasma-induced adhesion molecule response could also be prevented with inhibitors of nuclear factor (NF)-kappaB, such as pyrollidine dithiocarbamate. These findings emphasize the central role of TNF-alpha and IL-1 beta in LPS-induced endothelial activation and suggest that simultaneous neutralization of these cytokines or their common pathways may, even after the initial stimulus, prevent endothelial response during sepsis.

Treatment of Multiple Organ Failure through Sepsis by Surgery and Blood Purification

For the treatment of multiple organ failure (MOF) through sepsis, we have commonly applied various blood purification modalities during the perioperative period. From January 1996 to December 2000, 33 patients with MOF through sepsis were admitted and operated on in the First Department of Surgery, Akita University School of Medicine, and 21 of these 33 patients were treated using various blood purification modalities during the perioperative period: endotoxin-adsorbing therapy using polymyxin B (PMX) in 17 patients, continuous hemofiltration (CHF)/continuous hemodiafiltration (CHDF) in 15 patients, and plasma exchange (PE) and CHDF in 3 patients. Of the outcome of these 33 patients with MOF through sepsis, 17 survived and 16 died (48% mortality). Of the 21 patients with MOF through sepsis treated by surgery and blood purification, 12 survived and 9 died (43% mortality). We evaluated APACHE II and the number of failed organs before operation. Amongst the group with 12 survivors and 9 deaths, Acute Physiology and Chronic Health Evaluation II (APACHE II) was 15 +/- 5, 23 +/- 2 and the number of failed organs was 2.7 +/- 0.7, 3.9 +/- 0.8, respectively. An increased APACHE II score and number of failed organs were significantly associated with mortality. As to the treatment of MOF through sepsis due to acute peritonitis, patients with APACHE II scores ranging from 15 to 20, and those with 2-3 failed organs seem to be the candidates for the application of blood purification during the perioperative period.

Cardiac Myocytes Activated by Septic Plasma Promote Neutrophil Transendothelial Migration

Cardiac myocytes isolated from rats with peritonitis (cecal ligation and perforation; CLP) promote PMN transendothelial migration. Herein, we assessed (1) the mechanisms involved in cardiac myocyte activation during peritonitis and (2) the means by which these activated myocytes promote PMN transendothelial migration. Plasma obtained from mice subjected to CLP (septic plasma) activated isolated cardiac myocytes as evidenced by (1) increased nuclear levels of nuclear factor-κB (NF-κB) and (2) their ability to promote PMN migration across endothelial cell monolayers. Pretreatment of septic plasma with an antibody against tumor necrosis factor-α (TNF-α), but not interleukin-1β (IL-1β), blunted the ability of septic plasma to activate the myocytes. However, septic plasma obtained from TNF-α–deficient mice could still activate the myocytes; an effect attenuated by an antibody against IL-1β. If the myocytes were pretreated with a proteasome inhibitor (MG 132) to prevent NF-κB activation, the myocyte-induced PMN transendothelial migration was compromised. The activated myocytes released platelet-activating factor (PAF), and myocyte-induced PMN migration was abrogated by a PAF receptor antagonist (WEB 2086). These myocytes also released the CXC chemokines LIX and KC; an event prevented by MG 132. Antibodies against LIX and KC abrogated the myocyte-induced PMN migration. However, LIX and KC, but not PAF, could promote PMN migration when used at concentrations produced by activated myocytes. These observations indicate that TNF-α and IL-1β are, in part, responsible for the ability of septic plasma to activate cardiac myocytes. The activated myocytes promote PMN transendothelial migration, an effect attributable to LIX and KC, and possibly, PAF.

Roles for early response cytokines during Escherichia coli pneumonia revealed by mice with combined deficiencies of all signaling receptors for TNF and IL-1

During infection, inflammation is essential for host defense, but it can injure tissues and compromise organ function. TNF-alpha and IL-1 (alpha and beta) are early response cytokines that facilitate inflammation. To determine the roles of these cytokines with overlapping functions, we generated mice deficient in all of the three receptors mediating their effects (TNFR1, TNFR2, and IL-1RI). During Escherichia coli pneumonia, receptor deficiency decreased neutrophil recruitment and edema accumulation to half of the levels observed in wild-type mice. Thus these receptors contributed to maximal responses, but substantial inflammation progressed independently of them. Receptor deficiency compromised antibacterial efficacy for some infectious doses. Decreased ventilation during E. coli pneumonia was not affected by receptor deficiency. However, the loss of lung compliance during pneumonia was substantially attenuated by receptor deficiency. Thus during E. coli pneumonia in mice, the lack of signaling from TNF-alpha and IL-1 decreases inflammation and preserves lung compliance.

Therapeutic effects of lysophosphatidylcholine in experimental sepsis

Sepsis represents a major cause of death in intensive care units. Here we show that administration of lysophosphatidylcholine (LPC), an endogenous lysophospholipid, protected mice against lethality after cecal ligation and puncture (CLP) or intraperitoneal injection of Escherichia coli. In vivo treatment with LPC markedly enhanced clearance of intraperitoneal bacteria and blocked CLP-induced deactivation of neutrophils. In vitro, LPC increased bactericidal activity of neutrophils, but not macrophages, by enhancing H(2)O(2) production in neutrophils that ingested E. coli. Incubation with an antibody to the LPC receptor, G2A, inhibited LPC-induced protection from CLP lethality and inhibited the effects of LPC in neutrophils. G2A-specific antibody also blocked the inhibitory effects of LPC on certain actions of lipopolysaccharides (LPS), including lethality and the release of tumor necrosis factor-alpha (TNF-alpha) from neutrophils. These results suggest that LPC can effectively prevent and treat sepsis and microbial infections.

Hemodynamic and Cardiac Contractile Function During Sepsis Caused by Cecal Ligation and Puncture in Mice

Sepsis is among the leading causes of death in the critically ill, yet the pathophysiology of sepsis is incompletely understood. Genetically engineered mice offer a unique opportunity to explore the cellular and molecular pathogenesis of sepsis. However, the hemodynamic responses of mice during sepsis are not completely understood because of the difficulty in performing cardiovascular measurements in mice. We used a 1.4-F pressure and conductance catheter to measure hemodynamics in wild-type C57BL/6J mice during sepsis caused by cecal ligation and puncture. Septic mice exhibited significant hypothermia compared with the sham group. In addition, there was a progressive decrease in mean arterial blood pressure and systemic vascular resistance in septic mice as well as an increase in stroke volume and cardiac output. Sepsis also caused a significant time-dependent impairment of left ventricular function as indicated by decreased dp/dtmax and dp/dtmin. The slope of end systolic pressure volume relationship also decreased over time, as did the time varying maximum elastance and preload-recruitable stroke work of the left ventricle. In conclusion, septic mice exhibit hemodynamic alterations during sepsis that are similar to those observed in humans. The miniaturized conductance catheter allows for effective measurements of hemodynamic function in septic mice and provides measurements that cannot be obtained using other cardiovascular monitoring techniques.

Computational design of variant TNF molecules: a novel methodology for inhibition of proinflammatory cascades

Site-directed mutagenesis of tumor necrosis factor (TNF) based on prediction of the interaction of specific residues with TNF receptors generated dominant-negative constructs, in which single- or double-amino acid changes result in decreased receptor binding and cellular activation. These dominant-negatives not only provide a novel manner to block the proinflammatory effects of TNF, but also can be used as a tool to examine ligand-receptor interactions and their importance in signaling. Because these TNF mutant molecules are smaller than those used for conventional anti-TNF therapies, such as etanercept or infliximab, they are likely to achieve greater tissue concentrations and may provide enhanced therapeutic effect. However, the immunogenicity, as well as efficacy, of the dominant-negative TNF constructs must be more completely examined.

Lipopolysaccharide and proinflammatory cytokines stimulate interleukin-6 expression in C2C12 myoblasts: role of the Jun NH2-terminal kinase

IL-6 is a major inflammatory cytokine that plays a central role in coordinating the acute-phase response to trauma, injury, and infection in vivo. Although IL-6 is synthesized predominantly by macrophages and lymphocytes, skeletal muscle is a newly recognized source of this cytokine. IL-6 from muscle spills into the circulation, and blood-borne IL-6 can be elevated >100-fold due to exercise and injury. The purpose of the present study was to determine whether inflammatory stimuli, such as LPS, TNF-alpha, and IL-1beta, could increase IL-6 expression in skeletal muscle and C2C12 myoblasts. Second, we investigated the role of mitogen-activated protein (MAP) kinases, and the Jun NH2-terminal kinase (JNK) in particular, as a mediator of this response. Intraperitoneal injection of LPS in mice increased the circulating concentration of IL-6 from undetectable levels to 4 ng/ml. LPS also increased IL-6 mRNA 100-fold in mouse fast-twitch skeletal muscle. Addition of LPS, IL-1beta, or TNF-alpha directly to C2C12 myoblasts increased IL-6 protein (6- to 8-fold) and IL-6 mRNA (5- to 10-fold). The response to all three stimuli was completely blocked by the JNK inhibitor SP-600125 but not as effectively by other MAP kinase inhibitors. SP-600125 blocked LPS-stimulated IL-6 synthesis dose dependently at both the RNA and protein level. SP-600125 was as effective as the synthetic glucocorticoid dexamethasone at inhibiting IL-6 expression. SP-600125 inhibited IL-6 synthesis when added to cells up to 60 min after LPS stimulation, but its inhibitory effect waned with time. LPS stimulated IL-6 mRNA in both myoblasts and myotubes, but myoblasts showed a proportionally greater LPS-induced increase in IL-6 protein expression compared with myotubes. SP-600125 and the proteasomal inhibitor MG-132 blocked LPS-induced degradation of IkappaB-alpha/epsilon and LPS-stimulated expression of IkappaB-alpha mRNA. Yet, only SP-600125 and not MG-132 blocked LPS-induced IL-6 mRNA expression. This suggests that IL-6 gene expression is a downstream target of JNK in C2C12 myoblasts.

Nuclear factor-kappaB p50 limits inflammation and prevents lung injury during Escherichia coli pneumonia

Inflammatory responses to infection must be precisely regulated to facilitate microbial killing while limiting host tissue damage. Many inflammatory genes are regulated by kappaB sites, and the p50 subunit of nuclear factor-kappaB suppresses the expression of kappaB-associated genes in vitro. We hypothesized that p50 is essential to prevent excessive inflammation and injury during infection. During pulmonary infection with Escherichia coli, the gene-targeted deficiency of p50 did not affect bacterial clearance from mouse lungs, but it resulted in increased expression of proinflammatory cytokines 6 to 24 hours after infection. This dysregulation exacerbated inflammation (neutrophil recruitment), respiratory distress (pulmonary edema and blood gas exchange impairment), and decompartmentalization (transit of protein and bacteria from the air spaces to the blood). We interpret these studies to indicate that endogenous p50 protects the host by curbing inflammatory responses to prevent injury, essential to survive pneumonia.

Inflammatory status in sepsis alters efficacy of interleukin-18 binding protein therapy

OBJECTIVE

Sepsis remains a serious clinical problem, and multiple attempts at blocking inflammation have failed to decrease mortality rate. Interleukin-18 has been demonstrated to be an important component of the innate immune response to bacterial infections.

DESIGN

Previous work demonstrated that elevated plasma concentrations of interleukin-6 obtained in the first 6 hrs of sepsis predict a worse outcome. Mice were subjected to cecal ligation and puncture and, on the basis of the plasma concentration of interleukin-6, were randomized to receive either interleukin-18 binding protein or vehicle approximately 8 hrs after the onset of sepsis.

SETTING

University research laboratory.

SUBJECTS

Adult, female BALB/c mice.

INTERVENTIONS

We sought to determine the role of interleukin-18 in sepsis by blocking its biological activity with the interleukin-18 binding protein in the murine model of sepsis induced by cecal ligation and puncture.

MEASUREMENTS AND MAIN RESULTS

In this study, elevated plasma concentrations of interleukin-6 were associated with a worse outcome. Treatment with interleukin-18 binding protein decreased inflammation as determined by lower concentrations of plasma interleukin-6 obtained 48 hrs after the onset of sepsis. In mice with increased risk of dying, interleukin-18 binding protein slightly decreased mortality rate. However, in those mice with a predicted low mortality rate, interleukin-18 binding protein significantly increased mortality rate.

CONCLUSIONS

In this study, mice at low risk of death due to sepsis had decreased survival when treated with interleukin-18 binding protein. These results have potential implications for the use of interleukin-18 binding protein for treatment of chronic inflammatory conditions since it may place the host at increased risk of infectious complications.

Troponin as a risk factor for mortality in critically ill patients without acute coronary syndromes

OBJECTIVES

We sought to assess the mechanism and prognostic value of elevated troponins in patients without acute coronary syndromes (ACS).

BACKGROUND

Cardiac troponins are used as specific markers for the diagnosis of ACS. Recent studies reported a considerable number of critically ill patients without ACS as being troponin-positive, especially patients with sepsis, pulmonary embolism, renal failure, and stroke.

METHODS

We analyzed 58 consecutive, critically ill patients admitted for reasons other than ACS, according to their troponin status. Thirty-day mortality, left ventricular ejection fraction (LVEF), and a panel of inflammatory cytokines were compared between troponin-positive and troponin-negative patients. Relevant coronary artery disease was excluded either by stress echocardiography or autopsy.

RESULTS

Of the 58 critically ill patients, 32 (55%) without evidence of ACS were troponin-positive. Positive troponin levels were associated with higher mortality (22.4% vs. 5.2%, p < 0.018) and a lower LVEF (p = 0.0006). Troponin-positive patients had significantly higher median levels of tumor necrosis factor (TNF)-alpha, its soluble receptor, and interleukin (IL)-6. A subgroup of 10 aplastic patients was troponin-negative at study entry. Three became troponin-positive during leukocyte recovery and subsequently died, whereas all the others stayed troponin-negative and survived. Flow-limiting coronary artery disease was not demonstrable at autopsy or stress echocardiography in 72% of troponin-positive patients.

CONCLUSIONS

Elevated troponin is a mortality risk factor for medical intensive care patients admitted for reasons other than ACS. It is associated with decreased left ventricular function and higher levels of TNF-alpha and IL-6.

Late immunoneutralization of procalcitonin arrests the progression of lethal porcine sepsis

BACKGROUND

Procalcitonin (ProCT) is becoming increasingly recognized as a mediator as well as a marker of sepsis. Serum ProCT concentrations rise soon after induction of sepsis and remain elevated over a prolonged period of time. In contrast, many pro-inflammatory cytokines, e.g., tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1beta), rise and decline early in the course of sepsis. Researchers have improved survival in animal models of sepsis by prophylactically blocking IL-1beta and TNF-alpha with immunotherapy, but therapeutic treatment has been less successful in clinical trials. We hypothesized that the sustained elevation of ProCT in the serum would allow for effective therapeutic immunoneutralization of this peptide late in the course of sepsis.

METHODS

Lethal polymicrobial sepsis was induced in 10 castrated, male Yorkshire pigs by intraabdominal spillage of cecal contents (1 gm/kg) and intraabdominal instillation of 2 x 10(11) cfu of a toxigenic strain of E. coli (O18:K1:H7). The treated group (n = 5) received an intravenous infusion of purified rabbit antiserum to the aminoterminus of porcine ProCT. The control group (n = 5) received nonreactive, purified rabbit IgG. The purified antiserum was infused to all animals 3 h after the induction of sepsis, at which time very severe physiologic dysfunction was manifest, and many of the animals appeared to be preterminal. Physiologic and metabolic parameters were measured until death or for 15 h after induction of sepsis, at which time all surviving animals were euthanized.

RESULTS

Therapeutic immunoneutralization of serum ProCT improved most measured physiologic and metabolic parameters in septic pigs. Specifically, there was a significant increase in mean arterial pressure, urine output and cardiac index in all animals treated with ProCT antibody. Serum creatinine was significantly lower in treated animals. Although acidosis was not as severe in treated animals, as indicated by higher pH values and lower lactate concentrations, these results did not achieve statistical significance. Significantly, 11 h after the induction of sepsis there was 100% mortality in the control group while only one animal in the treated group expired.

CONCLUSION

The prolonged elevation of ProCT concentrations in sepsis allows neutralization of this peptide to be effective during the course of this disorder. These findings suggest that immunoneutralization of ProCT may be a useful treatment in clinical situations where sepsis is already fully established.

Inhibition of muscle insulin-like growth factor I expression by tumor necrosis factor-alpha

The role of TNF-alpha in muscle catabolism is well established, but little is known about the mechanisms of its catabolic action. One possibility could be that TNF-alpha impairs the production of local growth factors like IGF-I. The aim of this study was to investigate whether TNF-alpha can directly inhibit IGF-I gene and protein expression in muscle. First, we investigated whether the acute inflammation induced by endotoxin injection changes IGF-I and TNF-alpha mRNA in rat tibialis anterior muscle. Endotoxin rapidly increased TNF-alpha mRNA (7-fold at 1 h, P < 0.001) and later decreased IGF-I mRNA (-73% at 12 h, P < 0.001). Furthermore, in a model of C2C12 myotubes, TNF-alpha strongly inhibited IGF-I mRNA and protein (-73 and -47% after 72 h, P < 0.001 and P < 0.01, respectively). Other proinflammatory cytokines failed to inhibit IGF-I mRNA. The effect of TNF-alpha on IGF-I mRNA was not mediated by nitric oxide, and the activation of NF-kappaB was insufficient to inhibit IGF-I expression. Taken together, our data suggest that TNF-alpha induced in muscle after LPS injection can locally inhibit IGF-I expression. The inhibition of muscle IGF-I production could contribute to the catabolic effect of TNF-alpha.

Mechanisms of the beneficial effect of adrenomedullin and adrenomedullin-binding protein-1 in sepsis: down-regulation of proinflammatory cytokines

OBJECTIVE

Our recent study indicates that administration of adrenomedullin (AM) in combination with AM-binding protein-1 (AMBP-1) before sepsis (i.e., pretreatment) maintains cardiovascular stability and reduces the mortality rate. The aim of the present study was to determine whether administration of AM/AMBP-1 after the onset of sepsis (posttreatment) has any salutary effects on the septic host, and if so, whether AM/AMBP-1 down-regulates proinflammatory cytokines, such as tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6.

DESIGN

Prospective, controlled, randomized animal study.

SETTING

A university research laboratory.

SUBJECTS

Male adult Sprague-Dawley rats.

INTERVENTIONS

Rats were subjected either to polymicrobial sepsis by cecal ligation and puncture or to sham operation followed by the administration of normal saline solution (i.e., fluid resuscitation).

MEASUREMENTS AND MAIN RESULTS

At 5 hrs after cecal ligation and puncture, AM (12 microg/kg body weight) and AMBP-1 (40 microg/kg body weight) were administered intravenously over 1 hr. At 20 hrs after cecal ligation and puncture (i.e., the late, hypodynamic stage of sepsis), cardiac output, stroke volume, total peripheral resistance, systemic oxygen delivery, and organ blood flow were determined by radioactive microspheres, and circulating concentrations of proinflammatory cytokines were measured using enzyme-linked immunosorbent assay kits. Moreover, plasma concentrations of transaminases and lactate were measured. The results indicated that administration of AM/AMBP-1 at 5 hrs after cecal ligation and puncture prevented the decrease in measured systemic and regional hemodynamic variables and reduced plasma concentrations of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 at 20 hrs after the onset of sepsis. Moreover, administration of AM/AMBP-1 attenuated hepatic damage and the increase in plasma lactate and prevented hemoconcentration.

CONCLUSION

Administration of AM/AMBP-1 may provide a novel approach to the treatment of sepsis. Moreover, because AM/AMBP-1 significantly reduced circulating concentrations of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6, down-regulation of those proinflammatory cytokines by AM/AMBP-1 appears to play an important role for the beneficial effects of these agents in polymicrobial sepsis.