Granulocyte colony-stimulating factor and antibiotics in the prophylaxis of a murine model of polymicrobial peritonitis and sepsis

Systemic inflammation and protease profile of Afro-Caribbean patients with sepsis

Objectives:

Sepsis is one of the leading causes of morbidity and mortality within the healthcare system and remains a diagnostic and therapeutic challenge. A major issue in the diagnosis of sepsis is understanding the pathophysiologic mechanism, which revolves around host immune system activation and dysregulated responses. African Americans are more likely to experience severe sepsis with higher mortality rates compared to the general population. This pilot study characterized multiple inflammatory markers and proteases in plasma of primarily African American and Afro-Caribbean patients with mild sepsis.

Methods:

Plasma was collected from 16 healthy controls and 15 subjects presenting with sepsis, on admission, and again upon resolution of the signs of sepsis, defined as a resolution of sepsis criteria. Plasma samples were analyzed for cytokines, chemokines, and proteases using multiplex bead assays.

Results:

Elevated levels of granulocyte colony-stimulating factor, interleukin-10, interleukin-15, interleukin-1 receptor antagonist, interleukin-8, interferon gamma-induced protein 10, monocyte chemoattractant protein-1, matrix metallopeptidase 12, and cathepsin S were identified in plasma from sepsis patients on admission compared to control subjects. Interleukin-6, interleukin-8, granulocyte colony-stimulating factor, and cathepsin S were reduced in sepsis patients upon clinical resolution of sepsis.

Conclusion:

These findings profile the circulating inflammatory cytokines, chemokines, and proteases in African Americans and Afro-Caribbean patients during sepsis. The role of these targets in sepsis needs addressing in this patient population.

Modulation of Innate Immunity by G-CSF and Inflammatory Response by LBPK95A Improves the Outcome of Sepsis in a Rat Model

Introduction

Sepsis is the primary cause of death from infection. We wanted to improve the outcome of sepsis by stimulating innate immunity in combination with modulating the severity of inflammatory responses in rats.

Method

Sepsis was induced by the injection of feces suspension (control). A 5-day course of G-CSF treatment was given before the septic insult (G-CSF). The inflammatory response was decreased using various doses of the LPS-blocking peptide LBPK95A (5 mg/kg = 100% Combi group, 0.5 mg/kg = 10% Combi group, and 0.05 mg/kg = 1% Combi group). Survival rates were observed. Bacterial clearance, neutrophil infiltration, tissue damage, and the induction of hepatic and systemic inflammatory responses were determined 2 h and 12 h after the septic insult.

Results

High-dose LBPK95A (100% Combi) reduced the survival rate to 10%, whereas low-dose LBPK95A (10% and 1% Combi) increased the survival rates to 50% and 80%, respectively. The survival rates inversely correlated with multiorgan damage as indicated by the serum levels of ALT and urea. G-CSF treatment increased the white blood cell counts, hepatic neutrophil infiltration, and bacterial clearance in the liver, lung, and blood. The blockade of the LPS-LBP interaction decreased neutrophil infiltration, led to increased white blood cell count, and decreased hepatic neutrophil infiltration, irrespective of dose. However, bacterial clearance improved in the 1% and 10% Combi groups but worsened in the 100% Combi group. G-CSF increased TNF-α and IL-6 levels. Irrespective of dose, the blockade of the LPS-LBP interaction was associated with low systemic cytokine levels and delayed increases in hepatic TNF-α and IL-6 mRNA expression. The delayed increase in cytokines was associated with the phosphorylation of STAT3 and AKT.

Conclusion

Our results revealed that increasing innate immunity by G-CSF pretreatment and decreasing inflammatory responses using LBPK95A improved the survival rates in a rat sepsis model and could be a novel strategy to treat sepsis.

Balancing Innate Immunity and Inflammatory State via Modulation of Neutrophil Function: A Novel Strategy to Fight Sepsis

Sepsis and SIRS (systemic inflammatory response syndrome) belong to a severe disease complex characterized by infection and/or a whole-body inflammatory state. There is a growing body of evidence that neutrophils are actively involved in sepsis and are responsible for both release of cytokines and phagocytosis of pathogens. The neutrophil level is mainly regulated by G-CSF, a cytokine and drug, which is widely used in the septic patient with neutropenia. This review will briefly summarize the role of neutrophils and the therapeutic effect of G-CSF in sepsis. We further suggest that targeting neutrophil function to modulate the balance between innate immunity and inflammatory injury could be a worthwhile therapeutic strategy for sepsis.

Inflammatory mediators in intra-abdominal sepsis or injury - a scoping review

Introduction

Inflammatory and protein mediators (cytokine, chemokine, acute phase proteins) play an important, but still not completely understood, role in the morbidity and mortality of intra-abdominal sepsis/injury. We therefore systematically reviewed preclinical and clinical studies of mediators in intra-abdominal sepsis/injury in order to evaluate their ability to: (1) function as diagnostic/prognostic biomarkers; (2) serve as therapeutic targets; and (3) illuminate the pathogenesis mechanisms of sepsis or injury-related organ dysfunction.

Methods

We searched MEDLINE, PubMed, EMBASE and the Cochrane Library. Two investigators independently reviewed all identified abstracts and selected articles for full-text review. We included original studies assessing mediators in intra-abdominal sepsis/injury.

Results

Among 2437 citations, we selected 182 studies in the scoping review, including 79 preclinical and 103 clinical studies. Serum procalcitonin and C-reactive protein appear to be useful to rule out infection or monitor therapy; however, the diagnostic and prognostic value of mediators for complications/outcomes of sepsis or injury remains to be established. Peritoneal mediator levels are substantially higher than systemic levels after intra-abdominal infection/trauma. Common limitations of current studies included small sample sizes and lack of uniformity in study design and outcome measures. To date, targeted therapies against mediators remain experimental.

Conclusions

Whereas preclinical data suggests mediators play a critical role in intra-abdominal sepsis or injury, there is no consensus on the clinical use of mediators in diagnosing or managing intra-abdominal sepsis or injury. Measurement of peritoneal mediators should be further investigated as a more sensitive determinant of intra-abdominal inflammatory response. High-quality clinical trials are needed to better understand the role of inflammatory mediators.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1093-4) contains supplementary material, which is available to authorized users.

Strategies to improve drug development for sepsis

Sepsis, a common and potentially fatal systemic illness, is triggered by microbial infection and often leads to impaired function of the lungs, kidneys or other vital organs. Since the early 1980s, a large number of therapeutic agents for the treatment of sepsis have been evaluated in randomized controlled clinical trials. With few exceptions, the results from these trials have been disappointing, and no specific therapeutic agent is currently approved for the treatment of sepsis. To improve upon this dismal record, investigators will need to identify more suitable therapeutic targets, improve their approaches for selecting candidate compounds for clinical development and adopt better designs for clinical trials.

Depletion of neutrophil extracellular traps in vivo results in hypersusceptibility to polymicrobial sepsis in mice

Introduction

Although the formation of neutrophil (PMN) extracellular traps (NETs) has been detected during infection and sepsis, their role in vivo is still unclear. This study was performed in order to evaluate the influence of NETs depletion by administration of recombinant human (rh)DNase on bacterial spreading, PMN tissue infiltration and inflammatory response in a mouse model of polymicrobial sepsis.

Methods

In a prospective controlled double-armed animal trial, polymicrobial sepsis was induced by cecal ligation and puncture (CLP). After CLP, mice were treated with rhDNase or phosphate buffered saline, respectively. Survival, colony forming unit (CFU) counts in the peritoneal cavity, lung, liver and blood were determined. PMN and platelet counts, IL-6 and circulating free (cf)-DNA/NETs levels were monitored. PMN infiltration, as well as organ damage, was analyzed histologically in the lungs and liver. Capability and capacity of PMN to form NETs were determined over time.

Results

cf-DNA/NETs were found to be significantly increased 6, 24, and 48 hours after CLP when compared to the levels determined in sham and naïve mice. Peak levels after 24 hours were correlated to enhanced capacity of bone marrow-derived PMN to form NETs after ex vivo stimulation with phorbol-12-myristate-13-acetate at the same time. rhDNase treatment of mice resulted in a significant reduction of cf-DNA/NETs levels 24 hours after CLP (P < 0.001). Although overall survival was not affected by rhDNase treatment, median survival after 24 hours was significantly lower when compared with the CLP group (P < 0.01). In mice receiving rhDNase treatment, CFU counts in the lung (P < 0.001) and peritoneal cavity (P < 0.05), as well as serum IL-6 levels (P < 0.001), were found to be already increased six hours after CLP. Additionally, enhanced PMN infiltration and tissue damage in the lungs and liver were found after 24 hours. In contrast, CFU counts in mice without rhDNase treatment increased later but more strongly 24 hours after CLP (P < 0.001). Similarly, serum IL-6 levels peaked after 24 hours (P < 0.01).

Conclusions

This study shows, for the first time, that depletion of NETs by rhDNase administration impedes the early immune response and aggravates the pathology that follows polymicrobial sepsis in vivo.

Prophylactic uses of integrin CD18-βA peptide in a murine polymicrobial peritonitis model

AIM: To evaluate the prophylactic properties of integrin CD18-βA peptide in a murine model of abdominal polymicrobial peritonitis and sepsis.

METHODS: Bacterial sepsis was induced in Institute of Cancer Research (ICR) mice by cecal ligation and puncture (CLP) surgery. Inflicted mice were then injected with either sterile saline or CD18-βA peptide intraperitoneally at 2 h after surgery, and were sacrificed at 12 and 24 h after surgery. Blood samples were immediately collected, and analyzed for endotoxin activity and tumor necrosis factor (TNF)-α and interleukin (IL)-6. Lungs and liver were studied for CD45+ leukocyte and CD3 mRNA content. Pulmonary expression of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM) and E-selectin was also determined.

RESULTS: Intraperitoneal injection of CD18-βA peptide significantly suppressed circulating endotoxin activity (P < 0.01) at 24 h, as well as serum levels of TNF-α (P < 0.05 at 12 and 24 h) and IL-6 (P < 0.01 at 12 h, P < 0.05 at 24 h) in CLP-inflicted mice. CD18-βA peptide also abrogated leukocyte infiltration into liver and lungs as unveiled by reduced CD45+ leukocyte and CD3 mRNA contents. Furthermore, the peptide significantly reduced pulmonary expression of VCAM (P < 0.01 at 12 h, P < 0.001 at 24 h), E-selectin (P < 0.01 at 12 and 24 h), and ICAM-1 (P < 0.01 at 12 h, P < 0.001 at 24 h). These actions of CD18-βA peptide collectively protected septic mice against lethality (P < 0.01).

CONCLUSION: CD18-βA peptide is a potent endotoxin antagonist that can protect surgical patients against sepsis-associated lethality.

G-CSF induction early in uropathogenic Escherichia coli infection of the urinary tract modulates host immunity

Uropathogenic Escherichia coli (UPEC), the causative agent of approximately 85% of urinary tract infections (UTI), is a major health concern primarily affecting women. During infection, neutrophils infiltrate the bladder, but the mechanism of recruitment is not well understood. Here, we investigated the role of UPEC-induced cytokine production in neutrophil recruitment and UTI progression. We first examined the kinetics of cytokine expression during UPEC infection of the bladder, and their contribution to neutrophil recruitment. We found that UPEC infection induces expression of several pro-inflammatory cytokines including granulocyte colony-stimulating factor (G-CSF, CSF-3), not previously known to be involved in the host response to UTI. G-CSF induces neutrophil emigration from the bone marrow; these cells are thought to be critical for bacterial clearance during infection. Upon neutralization of G-CSF during UPEC infection, we found fewer circulating neutrophils, decreased neutrophil infiltration into the bladder and, paradoxically, a decreased bacterial burden in the bladder. However, depletion of G-CSF resulted in a corresponding increase in macrophage-activating cytokines, such as monocyte chemotactic protein-1 (MCP-1, CCL-2) and Il-1beta, which may be key in host response to UPEC infection, potentially resolving the paradoxical decreased bacterial burden. Thus, G-CSF acts in a previously unrecognized role to modulate the host inflammatory response during UPEC infection.

The innate immune response to secondary peritonitis

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

Effects of granulocyte-colony stimulating factor on the polymorphonuclear leukocyte activity and the course of sepsis in rats with experimental peritonitis

PURPOSE

Polymorphonuclear leucocytes (PML) play an essential role in the host immune response to severe infections. The effects of granulocyte-colony stimulating factor (G-CSF) on the PML immune functions during serious abdominal infection and course of sepsis, and on the survival in rats with peritonitis are the main subjects of this study.

METHODS

The first phase of the study was carried out on 30 Wistar-albino rats equally divided into three groups; Group 1 (control) sham laparotomy; Group 2 (peritonitis); and Group 3 (peritonitis+G-CSF) with fecal peritonitis created by a cecal puncture. At postoperative hours 3, 12, and 24, 0.5 ml normal saline was injected subcutaneously in groups 1 and 2, and 0.5 ml solution containing 50 microg/kg of G-CSF in group 3. The phagocytic and chemotactic activities of neutrophils and monocytes were evaluated by a flow cytometry analysis. The plasma lactate concentrations were assessed as a marker of tissue perfusion during sepsis. The second phase was a survival analysis, which was observed during 10 days on 20 rats equally divided into two groups; group 1 (peritonitis) and group 2 (peritonitis+G-CSF). 0.5 ml normal saline in group 1 and 50 microg/kg of G-CSF in group 2 was injected subcutaneously at the 3rd hour and twice daily.

RESULTS

Both the neutrophil- (1.636 vs 2.236) and monocyte-related (1.789 vs 2.465) phagocytic activities significantly (P < 0.001) improved after the G-CSF administration in the rats with peritonitis. In addition, the G-CSF treatment significantly (P < 0.0014) improved the chemotactic activity (1.18 vs 2.75) of neutrophils, and partly supported (P < 0.0952) the chemotactic activity (1.69 vs 2.37) of monocytes. The plasma lactate level (1.86 vs 4.9 mmol/l) was significantly (P < 0.0001) increased after septic changes due to experimental peritonitis. On the other hand, the lactate concentration was significantly (P < 0.001) decreased (4.9 vs 2.63 mmol/l) after the G-CSF administration. The survival was 20% at the 4th day and 0 at the 6th day in peritonitis, and 90% at the 4th day (P = 0.0055) and 80% at the 6th day (P = 0.0007) days in the peritonitis+G-CSF groups.

CONCLUSION

G-CSF enhances the immune functions of neutrophils and monocytes. The increased activities of these cells have a beneficial effect on the enhancement of the host immune response during severe infections. The improved immune function of PML due to the G-CSF treatment thus ameliorates the survival and the courses of sepsis, which is also defined by tissue perfusion and the cellular oxygen balance, which is affected by septic changes.

Effect of granulocyte colony-stimulating factor on IL-12 p40 production during chemotherapy for B-cell lineage non-Hodgkin's lymphoma patients

Interleukin (IL)-12 is a 70-kDa cytokine comprised of two disulfide-linked proteins (p35 and p40) and is essential for the initiation of effective immune response. Granulocyte-colony stimulating factor (G-CSF) affects the balance in the production of anti-inflammatory cytokines. We investigated the serum IL-12 p40 and IL-12 Mix (p40 and p70) production in 28 patients with B-cell lineage non-Hodgkin's lymphoma (NHL) treated with chemotherapy (e.g., CHOP regimen) with or without G-CSF administration and eight healthy volunteers. We found that serum levels of IL-12 p40 (191.2 +/- 150.0 pg/mL) and IL-12 Mix (277.4 +/- 274.5 pg/mL) in the patients before chemotherapy were higher than those in the healthy volunteers (IL-12 p40: 76.4 +/- 25.3 pg/mL, IL-12 Mix: 48.5 +/- 33.4 pg/mL) (P = 0.04 and 0.02, respectively). Next, we examined the serum IL-12 p40 and IL-12 Mix levels in nine patients receiving chemotherapy with administration of G-CSF (CG group, n = 9) and without G-CSF (C group, n = 9). Serum IL-12 p40 and IL-12 Mix levels were decreased on 10 d after chemotherapy in both groups, and those in CG groups were significantly lower than those in C group. These results indicated that administration of G-CSF decreased serum IL-12 p40 and IL-12 Mix levels. Overall survival (OS) at 24 months was not significantly different in the two groups (58.3% in group C vs. 80.0% in group CG, P = 0.67). However, the survival rate of patients at clinical stages III and IV in CG group (n = 6, 66.0%) was significantly better than that of patients in C group (n = 4, 25.0%) (P = 0.02). Long-term administration of G-CSF appears to influence the survival rate by reducing immunosuppressive IL-12 p40 production.

THE EFFECTS OF GRANULOCYTE COLONY-STIMULATING FACTOR IN PRECLINICAL MODELS OF INFECTION AND ACUTE INFLAMMATION

The cytokine granulocyte colony-stimulating factor (G-CSF) is a potent endogenous trigger for the release of neutrophils from bone marrow stores and for their activation for enhanced antimicrobial activity. G-CSF has been widely evaluated in preclinical models of acute illness, with generally promising though divergent results. A recombinant G-CSF molecule has recently undergone clinical trials to assess its efficacy as an adjuvant therapy in community-acquired and nosocomial pneumonia, however, these studies failed to provide convincing evidence of benefit. We undertook a systematic review of the published literature reporting the effects of modulation of G-CSF in preclinical in vivo models to determine whether evidence of differential efficacy might explain the disappointing results of human studies and point to disease states that might be more likely to benefit from G-CSF therapy. G-CSF has been evaluated in 86 such studies involving a variety of different models. The strongest evidence of benefit was seen in studies involving intraperitoneal challenge with live organisms; benefit was evident whether the agent was given before or after challenge. G-CSF demonstrates anti-inflammatory activity in models of systemic challenge with viable organisms or endotoxin, but only when the agent is given before challenge; evidence of benefit after challenge was minimal. Preclinical models of intrapulmonary challenge only show efficacy when the cytokine is administered before the infectious challenge, and suggested harm in gram-negative pneumonia resulting from challenge with Escherichia coli or Klebsiella. There is little evidence for therapeutic efficacy in noninfectious models of acute illness. We conclude that the most promising populations for evaluation of G-CSF are neutropenic patients with invasive infection and patients with intra-abdominal infection, particularly those with the syndrome of tertiary, or recurrent, peritonitis. Significant variability in the design and reporting of studies of preclinical models of acute illness precludes more sophisticated data synthesis.

Effect of recombinant murine granulocyte colony-stimulating factor with or without fluoroquinolone therapy on mixed-infection abscesses in mice

The aim of the study was to determine if immunomodulation of host defense with recombinant murine granulocyte colony-stimulating factor (G-CSF) improves the efficacy of trovafloxacin or moxifloxacin in abscesses containing Bacillus fragilis ATCC 23745 and different Escherichia coli strains varying in virulence. Treatment of mice inoculated with 10(7) CFU B. fragilis and 10(5) CFU low-virulence E. coli with either trovafloxacin (150 mg/kg/day every 24 hours, days 3 to 7) or moxifloxacin (96 mg/kg/day every 12 hours, days 3 to 7), significantly reduced the number of B. fragilis to 6.9 +/- 0.35 and 5.8 +/- 0.10 and that of E. coli to 4.9 +/- 0.09 and 4.2 +/- 0.07 log CFU/abscess for trovafloxacin and moxifloxacin, respectively, compared to controls (B. fragilis 8.7 and E. coli 7.4 log CFU/abscess) on day 8. Also, moxifloxacin was more potent than trovafloxacin. Addition of G-CSF prophylaxis (1 mug once on day -1) or therapy (1 mug/day on days 3 to 7) to fluoroquinolone treatment did not improve the efficacy of fluoroquinolone therapy alone. The effect of moxifloxacin with or without G-CSF prophylaxis on abscesses with a virulent hemolytic E. coli strain was also studied. In moxifloxacin-treated mice, 75% survived infection compared to 10% of controls. Combining moxifloxacin with G-CSF prophylaxis significantly decreased survival (30%) compared to moxifloxacin alone. In addition, G-CSF prophylaxis resulted in a threefold (E. coli) to 100-fold (B. fragilis) increased outgrowth in the abscesses of surviving mice. In conclusion, the addition of G-CSF to a fluoroquinolone is not advisable since, depending on the virulence of the E. coli strains, this might detrimentally influence the outcome of therapy.

Bovine intestinal alkaline phosphatase attenuates the inflammatory response in secondary peritonitis in mice

Lipopolysaccharide (LPS) contributes importantly to morbidity and mortality in sepsis. Bovine intestinal alkaline phosphatase (BIAP) was demonstrated to detoxify LPS through dephosphorylation. LPS injection combined with BIAP reduced inflammation and improved survival in various experimental settings. In this study, single-dose intravenous administration of BIAP (0.15 IU/g) was applied in a murine cecal ligation and puncture (CLP) model of polymicrobial sepsis. Saline was given as control (S group). Treatment with BIAP prior to CLP (prophylaxis; BIAP-P group) or shortly after (early treatment; BIAP-ET group) reduced cytokine concentrations in plasma and peritoneal lavage fluid (PLF). Tumor necrosis factor-alpha peak levels decreased from 170 pg/ml (S) to 57.5 (BIAP-P) and 82.5 (BIAP-ET) in plasma and in PLF from 57.5 pg/ml (S) to 35.3 (BIAP-P) and 16.8 (BIAP-ET) (all, P < 0.05). Peak interleukin-6 levels in plasma decreased from 19.3 ng/ml (S) to 3.4 (BIAP-P) and 11.5 (BIAP-ET) and in PLF from 32.6 ng/ml (S) to 13.4 (BIAP-P) and 10.9 (BIAP-ET) (all, P < 0.05). Macrophage chemoattractant protein 1 peak levels in plasma decreased from 2.0 ng/ml (S) to 1.0 (BIAP-P) and 0.7 (BIAP-ET) and in PLF from 6.4 (S) to 2.3 (BIAP-P) and 1.3 ng/ml (BIAP-ET) (all, P < 0.05). BIAP-treated groups showed decreased transaminase activity in plasma and decreased myeloperoxidase activity in the lung, indicating reduced associated hepatocellular and pulmonary damage. Survival was not significantly altered by BIAP in this single-dose regimen. In polymicrobial secondary peritonitis, both prophylactic and early BIAP treatment attenuates the inflammatory response both locally and systemically and reduces associated liver and lung damage.

Developing animal models for polymicrobial diseases

Although polymicrobial diseases are not a new concept for microbiologists, they are experiencing a resurgence of interest owing to the development of suitable animal models and new molecular techniques that allow these diseases to be studied effectively. This broad review provides an excellent introduction to this fascinating topic.

Examples are included of each type of polymicrobial disease and the animal models that are used to study these diseases are discussed. In many instances, schematics for the animal model are presented.

Viral co-infections including bovine viral diarrhoeal viruses, porcine reproductive and respiratory syndrome, mixed hepatitis virus infections and HIV co-infection with hepatitis virus are discussed, together with attempts to model these diseases in animals.

Viral and bacterial co-infections are reviewed with a special focus on otitis media and the rodent models that have been used to probe this important childhood illness.

Of the polybacterial diseases, periodontitis is one of the best understood and a clinically relevant rodent model is now available. This model, and the role of biofilm formation in periodontitis are examined.

Fungal infections of humans are often referred to as 'opportunistic' but in fact these infections are often fungal co-infections with viruses such as HIV and fungal mixed co-infections. The roles of these infections in disease and the rodent models used to study them are discussed.

Parasite co-infections are thought to have a role in the severity of malaria and the severity of Lyme arthritis. These diseases and attempts to model them are evaluated.

Finally, co-infections that are associated with virus-induced immunosuppression are discussed, together with their animal models.

Polymicrobial diseases involve two or more microorganisms that act synergistically, or in succession, to mediate complex disease processes. Although polymicrobial diseases in animals and humans can be caused by similar organisms, these diseases are often also caused by organisms from different kingdoms, genera, species, strains, substrains and even by phenotypic variants of a single species. Animal models are often required to understand the mechanisms of pathogenesis, and to develop therapies and prevention regimes. However, reproducing polymicrobial diseases of humans in animal hosts presents significant challenges.

Pretreatment with granulocyte-colony stimulating factor decreases lipopolysaccharide-induced interferon-γ production in mice in association with the production of interleukin-18

We studied the effects of pretreatment with granulocyte-colony stimulating factor (G-CSF) on the production of pro- and anti-inflammatory cytokines induced by lipopolysaccharide (LPS). Mice received G-CSF or control saline once a day for 7 days or once at 1 h before the injection of LPS. Cytokines were measured by enzyme-linked immunosorbent assay or antibody-based electrochemiluminescence assay and cytokine mRNA was measured by RNAse protection assay. Mice pretreated with G-CSF for 7 days before LPS had lower serum levels of LPS-induced interferon-gamma (IFN-gamma) and higher levels of interleukin (IL)-6 and IL-10 than controls. G-CSF-pretreated mice also had lower mRNA levels of IFN-gamma and higher mRNA levels of IL-6 and IL-10 in the spleen and/or liver than controls. G-CSF-pretreated mice had serum levels of tumor necrosis factor, IL-12 p70 and IL-12 p40 similar to controls. G-CSF-pretreated mice had lower levels of spleen IL-18 than controls-serum IL-18 being undetectable in mice after LPS-and lower levels of IL-18 mRNA in the spleen. Mice pretreated with G-CSF 1 h before LPS had lower levels of serum IFN-gamma and spleen IL-18 than controls. G-CSF pretreatment alters the expression of LPS-induced cytokines with a decrease in pro-inflammatory IFN-gamma and an increase in anti-inflammatory IL-6 and IL-10. G-CSF decrease of IL-18 production may be a major mechanism explaining the effects of G-CSF on the production of IFN-gamma.

Induction and regulation of endogenous granulocyte colony-stimulating factor formation

Granulocyte colony-stimulating factor (G-CSF) is one of the most prominent endogenous proteins in broad clinical use. While its biological and clinical effects are relatively well studied, little is known about its endogenous formation in health and disease. However, such knowledge is crucial to decide in which situations G-CSF should be applied efficiently in the clinic, ie. when endogenous production does not suffice. The dramatic changes induced by G-CSF in the differential blood cell count are directly immunomodulatory, strengthening the innate defence by multiplying neutrophilic granulocytes. A multitude of further immunomodulatory effects contribute to the regulation of the concerted host defence. In this review, following a short introduction into the biology of G-CSF, the available data on endogenous formation in a number of animal models and human diseases is compiled. The cellular sources and inducers of G-CSF formation are reviewed and the regulation of G-CSF expression on both the transcriptional and translational level are discussed. The emerging understanding of the role and regulation of endogenous G-CSF formation opens up possibilities to define therapeutic windows as well as targets for diagnostics or drug development. Lastly, the modulation of G-CSF formation by various pharmacological agents alerts to putative side effects of these drug treatments.

Cytokine modulation in sepsis and septic shock

Sepsis and septic shock are a major cause of morbidity and mortality in patients admitted to the intensive care unit. Since the introduction of antibiotic therapy, the mortality associated with sepsis has remained within the 30- 50% range. Sepsis constitutes the systemic response to infection. This response encompasses both pro-inflammatory and anti-inflammatory phases that are marked by the sequential generation of pro- and anti-inflammatory cytokines. Among the most important pro-inflammatory cytokines are TNF-alpha and IL-1beta. The pro-inflammatory effects of such cytokines are inhibited by soluble receptors/receptor antagonists and anti-inflammatory cytokines including IL-10 and transforming growth factor-beta. Modulation of the activity of both pro- and anti-inflammatory cytokines to improve outcome in patients with sepsis has been subject of multiple clinical studies. This review will examine clinical trials evaluating several strategies for blocking or attenuating TNF-alpha and IL-1beta activity. This review will also survey the current state of experimental therapies involving IL-10, transforming growth factor-beta, granulocyte colony-stimulating factor and IFN-phi. Finally, newer developments related to less known cytokines such as macrophage migration inhibitory factor and high mobility group 1 protein will be evaluated.

Six at six: interleukin-6 measured 6 h after the initiation of sepsis predicts mortality over 3 days

Virtually of the all recent therapeutic interventions for treating sepsis have failed to improve survival. One potential explanation is that the heterogeneity of the immune response to the septic challenge is such that only a portion of the patients die as a result of excessive inflammation. The clinical trials lacked power because traditional measurements do not accurately identify these patients. Previous work has shown that higher levels of interleukin (IL)-6 are found in those mice that die from septic peritonitis; therefore, we sought to determine whether IL-6 measured 6 h after surgery could predict outcome. Adult, female BALB/c mice (n = 79) were subjected to cecal ligation and puncture with a 21-gauge needle and treated with imipenem in D5W every 12 h for 5 days, resulting in a homogenous population at the outset. Six hours after surgery, 20 microL of blood was obtained from the tail vein to measure IL-6. Mortality was followed for 21 days. Overall 3-day survival was 77%, and 21-day mortality was 56%. Plasma IL-6 levels >2,000 pg/mL were determined to predict mortality within the first 3 days with a sensitivity of 58% and specificity of 97%. To further refine the mortality prediction, body weight and a complete blood count were performed 24 hours after cecal ligation and puncture. Discriminate analysis indicated that a weighted formula combining body mass, lymphocyte, and platelet count would predict death with sensitivity of 83% and a specificity of 79%. We tested the value of the IL-6 prediction by surgically resecting the cecum in those animals with IL-6 > 2000 pg/mL, which resulted in a significant improvement in survival. These data demonstrate that IL-6 measured 6 h after injury accurately predicts mortality resulting from experimental sepsis. This measurement may be determined quickly so that therapy may be targeted only to those individuals at significant risk of dying and initiated within sufficient time to be effective.

Acute G-CSF therapy is not protective during lethal E. coli sepsis

We investigated whether decreases in circulating polymorphonuclear neutrophils (PMN) during lethal Escherichia coli (E. coli) sepsis in canines are related to insufficient host granulocyte colony-stimulating factor (G-CSF). Two-year-old purpose-bred beagles had intraperitoneal E. coli-infected or -noninfected fibrin clots surgically placed. By 10 to 12 h following clot, both infected survivors and nonsurvivors had marked increases (P = 0.001) in serum G-CSF levels (mean peak G-CSF ng/ml +/- SE, 1,931 +/- 364 and 2,779 +/- 681, respectively) compared with noninfected controls (134 +/- 79), which decreased at 24 to 48 h. Despite increases in G-CSF, infected clot placement caused delayed (P = 0.06) increases in PMN (mean +/- SE change from baseline in cells x 10(3)/mm(3) at 24 and 48 h) in survivors (+3.9 +/- 3.9 and +13.8 +/- 3.6) compared with noninfected controls (+13.1 +/- 2.8 and +9.1 +/- 2.5). Furthermore, infected nonsurvivors had decreases in PMN (-1.4 +/- 1.0 and -1.1 +/- 2.3, P = 0.006 compared with the other groups). We next investigated whether administration of G-CSF immediately after clot placement and continued for 96 h to produce more rapid and prolonged high levels of G-CSF after infection would alter PMN levels. Although G-CSF caused large increases in PMN compared with control protein from 2 to 48 h following clot in noninfected controls, it caused much smaller increases in infected survivors and decreases in infected nonsurvivors (P = 0.03 for the ordered effect of G-CSF comparing the three groups). Thus insufficient host G-CSF is unlikely the cause of decreased circulating PMN in this canine model of sepsis. Other factors associated with sepsis either alone or in combination with G-CSF itself may reduce increases or cause decreases in circulating PMN.

Propofol depressed neutrophil hydrogen peroxide production more than midazolam, whereas adhesion molecule expression was minimally affected by both anesthetics in rats with abdominal sepsis

The treatment of sepsis may require mechanical ventilation of the lungs and sedation. Because neutrophils are the most important effector cells for protecting against sepsis, and propofol and midazolam are the most widely used anesthetics for sedation, we studied the effects of these two anesthetics on the neutrophil function during sepsis. Sepsis was induced in rats by cecal ligation and puncture. At either 4 h or 24 h after cecal ligation and puncture, blood and peritoneal neutrophils were obtained, incubated with the test anesthetics, and the hydrogen peroxide (H(2)O(2)) production and CD11b/c expression were determined by flow cytometry. In both early (at 4 h) and late (at 24 h) sepsis, propofol and midazolam depressed H(2)O(2) production by blood and peritoneal neutrophils at clinical concentrations. Propofol caused more depression than midazolam (P < 0.005). In both early and late sepsis, the effect of the anesthetics on the up-regulation of the stimulation-induced CD11b/c expression on blood neutrophils was minimal at clinical concentrations. If these results ultimately become clinically relevant, midazolam may be preferable to propofol for sedation during sepsis.

Diagnosis and management of peritonitis

Peritonitis is a clinical syndrome rather than a definitive diagnosis and, as such, the underlying cause must be identified. Many potential causes exist, and peritonitis may be classified as primary or secondary, local or diffuse, acute or chronic, or according to the causative agent. Peritonitis is one of the most common initiators of the systemic inflammatory response syndrome faced by the small animal practitioner. Because systemic inflammatory response syndrome is such a devastating disease process, aggressive stabilization, rapid definitive diagnosis, and prompt surgical and medical treatment are vital for optimizing outcome.

Granulocyte colony-stimulating factor (G-CSF) induces the production of cytokines in vivo

Granulocyte colony-stimulating factor (G-CSF) is a haematopoietic growth factor required for the proliferation and differentiation of haematopoietic precursors of neutrophil granulocytes and is now used to overcome congenital and acquired neutropenia. In addition to increasing the numbers of neutrophils in vivo and modulating neutrophil functions, G-CSF may induce the production of cytokines such as tumour necrosis factor alpha (TNF-alpha). In the present study, the plasma levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) in six healthy volunteers given G-CSF at 10 microgram/kg once daily for 6 d were measured and found to be elevated. The elevated levels (P < 0.05) were detected on day 2, peaked on days 6-7 and returned to baseline on day 12. In vitro, G-CSF did not enhance the secretion of TNF-alpha and GM-CSF from mononuclear cells, whole blood or endothelial cells. However, in the co-presence of whole blood and endothelial cells, the secretion of TNF-alpha was significantly enhanced by G-CSF at low concentrations. The GM-CSF secretion, however, was unaltered. G-CSF pretreatment of whole blood suppressed lipopolysaccharide (LPS)-induced secretion of TNF-alpha and GM-CSF in a dose-dependent manner. These results together with our previous findings suggest that G-CSF induces the production of TNF-alpha and GM-CSF in vivo, and that this production may be due to the co-effects of endothelial cells and whole blood under the influence of G-CSF through an as yet unknown network of cells and cytokines. Treatment of whole blood with G-CSF suppresses LPS-induced secretion of TNF-alpha and GM-CSF.