Effect of delayed treatment with recombinant human granulocyte colony-stimulating factor on survival and plasma cytokine levels in a non-neutropenic porcine model of Pseudomonas aeruginosa sepsis

The phosphoinositide-3 kinase survival signaling mechanism in sepsis

Phosphoinositide-3 kinases (PI3Ks) are critical regulatory proteins in the immunologic defense system against sepsis. The PI3K mechanism helps modulate cellular survival, innate and adaptive immunities, inflammation, nuclear factor-κB transcription, and may, in turn, play a protective role in sepsis. Animal studies confirm its role in the prevention of organ dysfunction and improvement of survival outcomes. Further advances in the understanding of this key immunomodulatory pathway may provide valuable insights into the manipulation of cellular function for therapeutic treatment of sepsis and other inflammatory diseases.

Effect of anti-OprF-OprI immunoglobulin on APACHE II score in a porcine two-hit model of hemorrhagic shock/resuscitation and pseudomonas aeruginosa sepsis

BACKGROUND

Up to now, randomized clinical trials of treatment of bacterial sepsis with immunoglobulins show conflicting results. This paper investigates the effect of prophylactic immunization with anti-OprF-OprI antiserum on the APACHE II score in a clinically relevant two-hit model of hemorrhagic shock/resuscitation followed by Pseudomonas aeruginosa sepsis in pigs.

METHODS

Twenty-three German Landrace-Hybrid pigs underwent chronic implantation of vascular catheters (internal and external jugular vein, carotic and pulmonary artery), hemorrhagic shock (mean blood loss 40% of estimated blood volume) for 45 min, followed by resuscitation with crystalloid, colloid, and shed blood. Randomization was to a control group (no immunization, n=6), an F-I group (50 mg/kg i.p. anti-OprF-OprI immunoglobulin, n=6), an S group (50 mg/kg i.p. unspecific porcine immunoglobulins, n=6), and a PS group (50 mg/kg i.p. immunoglobulin against the antigens of heat-killed P. aeruginosa, n=5). After at least 18 h for recovery from anesthesia, the pigs underwent a continuous intravenous infusion of P. aeruginosa for 48 h. Thereafter, the animals were monitored for another 48 h and then dissected.

RESULTS

The APACHE II score significantly increased from baseline value in all groups during bacterial challenge. However, there were no between-group differences in APACHE II score. In contrast, pigs of the F-I and PS groups showed significant lower lung concentrations of P. aeruginosa (p<0.05 vs. control group) at autopsy.

CONCLUSION

These experimental data suggest that under comparable clinical conditions, a prophylactic immunization with anti-OprF-OprI immunoglobulin would not have an overall benefit to patients with P. aeruginosa sepsis.

The effect of G-CSF in an experimental MRSA graft infection in mice

Wound infection after prosthetic material implantation is a troublesome complication with an incidence of 2% to 10%. The effect of granulocyte colony-stimulating factor (G-CSF) was studied in an experimental methicillin-resistant Staphylococcus aureus (MRSA) graft infection model. Eighty adult mice were used. Under general anesthesia an abdominal incision of 2 cm in length was performed. A subcutaneous cavity of 2 x 2 cm in size was created. Polypropylene mesh pieces of 2 x 1 cm and MRSA solution of 0.1ml of 10(8) CFU/mL were used. G-CSF was applied systemically or locally in a dosage of 0.02 MU/30 g body weight. There were 8 groups: group I, wound + MRSA; group II, wound + mesh + MRSA; group III, wound + mesh + MRSA + G-CSF (ip, 48 h before operation); group IV, wound + mesh + MRSA + G-CSF (ip, 24 h before operation); group V, wound + mesh + MRSA + G-CSF (locally, into the cavity); group VI, wound + mesh (incubated in G-CSF solution for 4 h) + MRSA; group VII, wound + mesh + MRSA + G-CSF, ip, 24 h from operation; and group VIII (positive control group), wound + mesh + MRSA + Teicoplanin (0.03 mg/30 g body weight, ip, 1/2 h before operation). Three days after, animals were killed and incisions were examined for possible infection or abscess formation and wound failure. Meshes were removed; after vortexing and dilution, samples were incubated with 5% agar media. Results of bacterial incubation were evaluated 24 h and 48 h later. There were symptoms of wound infection and abscess formation in all groups except group VIII. In group VIII, MRSA was isolated in 7 events with a colony count below 10(3). Bacterial counts were above 10(6) (10(6)-10(8)) in all other groups. Thus, it was observed that wound infection could be created with this model, but G-CSF could not prevent the development of wound infection, whether it was administered systemically or locally. Teicoplanin decreased the number of colony-forming units of MRSA, and prevents wound infection in this MRSA wound infection model.

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.

Granulocyte colony-stimulating factor has differing effects comparing intravascular versus extravascular models of sepsis

BACKGROUND

Previously, neutrophil stimulation with granulocyte colony-stimulating factor (G-CSF) pretreatment increased survival rates in canines challenged with intraperitoneal or intrabronchial Escherichia coli and in rats challenged with intrabronchial Staphylococcus aureus. We investigated whether G-CSF pretreatment would be beneficial with intravascular challenge in these models.

METHODS

Animals were randomized to G-CSF or placebo pretreatment followed by intravenous E. coli challenge in canines (n = 24) or intravenous or intrabronchial S. aureus challenge in rats (n = 273). All animals were treated with antibiotics.

RESULTS

In canines, G-CSF before intravenous E. coli did not decrease mortality rates (7 of 12 [58%] G-CSF vs. 5 of 12 [42%] controls), which contrasted with prior reductions during extravascular infection (10 of 35 [29%] G-CSF vs. 37 of 65 [57%] controls). Consistent with the present and previously published studies in canines, in rats, G-CSF decreased mortality rates with intrabronchial S. aureus (22 of 90 [24%] G-CSF vs. 26 of 51 [51%] controls, p = 0.009) but did not decrease them with intravenous infection (34 of 67 [50%] G-CSF vs. 27 of 65 [42%] controls, p = 0.2) in patterns that were very different (p = 0.005 for the effects of G-CSF with intravascular vs. intrabronchial S. aureus).

CONCLUSION

In contrast to extravascular infection, sepsis with intravascular E. coli in canines and S. aureus in rats may not provide a compartmentalized nidus of bacteria on which G-CSF-stimulated neutrophils can exert a beneficial antimicrobial effect. Extrapolated clinically, a proinflammatory agent like G-CSF may be most beneficial with sepsis related primarily to a compartmentalized extravascular site of infection.

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.

The effects of granulocyte colony-stimulating factor and neutrophil recruitment on the pulmonary chemokine response to intratracheal endotoxin

Although G-CSF has been shown to increase neutrophil (polymorphonuclear leukocyte, PMN) recruitment into the lung during pulmonary infection, relatively little is known about the local chemokine profiles associated with this enhanced PMN delivery. We investigated the effects of G-CSF and PMN recruitment on the pulmonary chemokine response to intratracheal LPS. Rats pretreated twice daily for 2 days with an s.c. injection of G-CSF (50 microg/kg) were sacrificed at either 90 min or 4 h after intratracheal LPS (100 microg) challenge. Pulmonary recruitment of PMNs was not observed at 90 min post LPS challenge. Macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant (CINC) concentrations in bronchoalveolar lavage (BAL) fluid were similar in animals pretreated with or without G-CSF at this time. G-CSF pretreatment enhanced pulmonary recruitment of PMNs (5-fold) and greatly reduced MIP-2 and CINC levels in BAL fluid at 4 h after LPS challenge. In vitro, the presence of MIP-2 and CINC after LPS stimulation of alveolar macrophages was decreased by coculturing with circulating PMNs but not G-CSF. G-CSF had no direct effect on LPS-induced MIP-2 and CINC mRNA expression by alveolar macrophages. Pulmonary recruited PMNs showed a significant increase in cell-associated MIP-2 and CINC. Cell-associated MIP-2 and CINC of circulating PMNs were markedly increased after exposure of these cells to the BAL fluid of LPS-challenged lungs. These data suggest that recruited PMNs are important cells in modulating the local chemokine response. G-CSF augments PMN recruitment and, thereby, lowers local chemokine levels, which may be one mechanism resulting in the subsidence of the host proinflammatory response.

Colony-Stimulating Factors in the Therapeutic Approach to Sepsis

Sepsis and its complications continue to be a leading cause of death in the United States despite availability of potent broad-spectrum antimicrobial agents. Current in vitro, ex vivo, animal, and human data are reviewed. Present data shows that colony-stimulating factors (CSFs), granulocyte CSFs, and granulocyte-macrophage CSFs are very effective in raising the leukocyte count and shortening the number of neutropenic days. CSFs in some studies improved outcome of neutropenic septic patients especially when given very early. However, there are studies that do not show any benefit. CSFs appear to be safe and should be limited to septic, neutropenic patients whose duration of neutropenia is anticipated to be prolonged, or to patients who are seriously ill.