Delayed neutralization of interferon-gamma prevents lethality in primate Gram-negative bacteremic shock

Kidney and Liver Injuries After Major Burns in Rats Are Prevented by Resolvin D2

OBJECTIVES

Innate immune dysfunction after major burn injuries increases the susceptibility to organ failure. Lipid mediators of inflammation resolution, e.g., resolvin D2, have been shown recently to restore neutrophil functionality and reduce mortality rate in a rat model of major burn injury. However, the physiological mechanisms responsible for the benefic activity of resolvin D2 are not well understood.

DESIGN

Prospective randomized animal investigation.

SETTING

Academic research setting.

SUBJECTS

Wistar male rats.

INTERVENTIONS

Animals were subjected to a full-thickness burn of 30% total body surface area. Two hours after burn, 25 ng/kg resolvin D2 was administered IV and repeated every day, for 8 days. At day 10 post burn, 2 mg/kg of lipopolysaccharide was administered IV, and the presence of renal and hepatic injuries was evaluated at day 11 post burn by histology, immunohistochemistry, and relevant blood chemistry.

MEASUREMENTS AND MAIN RESULTS

In untreated animals, we found significant tissue damage in the kidneys and liver, consistent with acute tubular necrosis and multifocal necrosis, and changes in blood chemistry, reflecting the deterioration of renal and hepatic functions. We detected less tissue damage and significantly lower values of blood urea nitrogen (26.4 ± 2.1 vs 36.0 ± 9.3 mg/dL; p ≤ 0.001), alanine aminotransferase (266.5 ± 295.2 vs 861.8 ± 813.7 U/L; p ≤ 0.01), and total bilirubin (0.13 ± 0.05 vs 0.30 ± 0.14 mg/dL; p ≤ 0.01) in resolvin D2-treated rats than in untreated animals. The mean blood pressure of all animals was above 65 mm Hg, indicating adequate tissue perfusion throughout the experiments. We measured significantly larger amounts of chromatin in the circulation of untreated than of resolvin D2-treated rats (575.1 ± 331.0 vs 264.1 ± 122.4 ng/mL; p ≤ 0.05) and identified neutrophil extracellular traps in kidney and liver tissues from untreated rats, consistent with the tissue damage.

CONCLUSIONS

Pathologic changes in kidney and liver tissues in a rat model of major burn and endotoxin insults are ameliorated by resolvin D2.

The immunologic profile of adoptively transferred lymphocytes influences stroke outcome of recipients

Animals that have myelin basic protein (MBP) specific lymphocytes with a Th1(+) phenotype have worse stroke outcome than those that do not. Whether these MBP specific cells contribute to worsened outcome or are merely a consequence of worse outcome is unclear. In these experiments, lymphocytes were obtained from donor animals one month after stroke and transferred to naïve recipient animals at the time of cerebral ischemia. The MBP specific phenotype of donor cells was determined prior to transfer. Animals that received either MBP specific Th1(+) or Th17(+) cells experienced worse neurological outcome, and the degree of impairment correlated with the robustness of MBP specific Th1(+) and Th17(+) responses. These data demonstrate that the immunologic phenotype of antigen specific lymphocytes influences stroke outcome.

Natural killer (NK) cells in antibacterial innate immunity: angels or devils?

Natural killer (NK) cells were first described as immune leukocytes that could kill tumor cells and soon after were reported to kill virus-infected cells. In the mid-1980s, 10 years after their discovery, NK cells were also demonstrated to contribute to the fight against bacterial infection, particularly because of crosstalk with other leukocytes. A wide variety of immune cells are now recognized to interact with NK cells through the production of cytokines such as interleukin (IL)-2, IL-12, IL-15 and IL-18, which boost NK cell activities. The recent demonstration that NK cells express pattern recognition receptors, namely Toll-like and nucleotide oligomerization domain (NOD)-like receptors, led to the understanding that these cells are not only under the control of accessory cells, but can be directly involved in the antibacterial response thanks to their capacity to recognize pathogen-associated molecular patterns. Interferon (IFN)-γ is the predominant cytokine produced by activated NK cells. IFN-γ is a key contributor to antibacterial immune defense. However, in synergy with other inflammatory cytokines, IFN-γ can also lead to deleterious effects similar to those observed during sepsis. Accordingly, as the main source of IFN-γ in the early phase of infection, NK cells display both beneficial and deleterious effects, depending on the circumstances.

Enhanced survival from CLP-induced sepsis following late administration of low doses of anti-IFNγ F(ab')2 antibody fragments

OBJECTIVE

To assess the impact of different doses of anti-interferon gamma (anti-IFNγ) F(ab')2 fragments, administered prophylactically, on survival and on serum concentration of cytokines in a murine model of sepsis induced by cecal ligation and puncture (CLP). We further explore the impact of therapeutic administration of the most protective dose on survival.

SUBJECTS AND TREATMENT

Balb/c mice were prophylactically treated by the intraperitoneal route with anti-IFNγ initiated 2 h before CLP and every 24 h for a total of five times in each of the following doses: 0.01, 0.1, or 1 mg/kg. Sham and control groups received sterile saline solution in a similar scheme.

METHODS

Serum tumor necrosis factor (TNF), interleukin (IL)-1β, IL-6, IL-10 and IFNγ were measured at 3, 24 and 48 h after CLP by ELISA. Survival curves were compared using a Mantel-Haenzel method.

RESULTS

Significant prophylactic protection was found only with 0.01 mg/kg, in association with regulation of IL-1β and IL-10 concentrations. As therapy, anti-IFNγ fragments were protective only when initiated 24 h after CLP.

CONCLUSIONS

Delicate modulation of IFNγ at the correct timing, even when the septic process has begun, is an exciting alternative to explore in the treatment of sepsis.

The role of interferon-γ in the pathogenesis of acute intra-abdominal sepsis

Several studies indicate that IFN-γ facilitates systemic inflammation during endotoxin-induced shock. However, the pathobiology of IFN-γ in clinically relevant models of septic shock, such as CLP, is not well understood. In this study, the role of IFN-γ in the pathogenesis of CLP-induced septic shock was evaluated by examining IFN-γ production at the tissue and cellular levels. The impact of IFN-γ neutralization on systemic inflammation, bacterial clearance, and survival was also determined. Following CLP, concentrations of IFN-γ in plasma and peritoneal lavage fluid were low in comparison with concentrations of IL-6 and MIP-2, as was IFN-γ mRNA expression in liver and spleen. The overall percentage of IFN-γ+ splenocytes was <5% after CLP and not statistically different from control mice. Intracellular IFN-γ was present in a large proportion of peritoneal exudate cells after CLP, primarily in infiltrating myeloid cells and NK cells. i.p. myeloid cell activation was decreased in IFN-γKO mice, and plasma concentrations of IL-6 and MIP-2 were significantly lower in IFN-γKO mice and in mice treated with anti-IFN-γ compared with controls, but bacterial clearance was not affected. IFN-γKO mice were resistant to CLP-induced mortality when treated with systemic antibiotics. However, neutralization of IFN-γ with blocking antibodies did not improve survival significantly. These studies show that IFN-γ facilitates the proinflammatory response during CLP-induced septic shock. However, neutralization of IFN-γ did not improve survival uniformly.

Neutralization of IFNgamma defeats haemophagocytosis in LCMV-infected perforin- and Rab27a-deficient mice

Hereditary haemophagocytic lymphohistiocytosis (HLH) is a fatal inflammatory disease and treatments currently may lead to serious side effects. There is a pressing need for effective, less toxic treatments for this disease. Previous reports have suggested that interferon γ (IFNγ) has a role in the pathogenesis of HLH. Here, we report that blocking IFNγ had a therapeutic effect in two different murine models of human hereditary HLH (perforin-deficient and Rab27a-deficient mice, both infected with lymphocytic choriomeningitis virus). Therapeutic administration of an anti-IFNγ antibody induced recovery from haemophagocytosis in both genetic models, as evidenced by increased survival in perforin-deficient mice and correction of blood cytopenia, moderation of body temperature changes, decreased cytokinaemia, restoration of splenic architecture and reduced haemophagocytosis in the liver of both murine models. Involvement of the central nervous system in Rab27a-deficient mice was prevented by anti-IFNγ therapy. Hepatic T-cell infiltrates and virus persisted, with no detectable harm during the time course of these studies. These data strongly suggest that neutralization of IFNγ could be used in humans to safely alleviate the clinical manifestations of haemophagocytosis.

Alveolar macrophage suppression in sepsis is associated with high mobility group box 1 transmigration

Macrophage dysfunction occurs late in sepsis and is implicated in increased mortality. Interferon gamma (IFN-gamma) stimulates transmigration of high mobility group box 1 (HMGB-1) from the nucleus into cytoplasm of macrophages and subsequent release. Because HMGB-1 release also occurs late, and because one of the actions of HMGB-1 in the nucleus is to enhance transcription factors, we investigated if HMGB-1 transmigration is involved in macrophage suppression in sepsis. Alveolar macrophages were isolated 12 and 24 h from sham controls, cecal ligation and puncture (CLP), and CLP rats given IFN-gamma antibody (1.2 mg/kg, i.v.). All injections were given immediately after surgery. At 12 h, 60% of cells from sham controls had HMGB-1 located primarily in the nucleus, whereas 35% of cells had diffuse staining in both cytoplasm and nucleus. In CLP rats, HMGB-1 was located predominantly in the cytoplasm of 37% of cells, and 48% had diffuse staining, whereas in IFN-gamma antibody (Ab)-treated rats, HMGB-1 was located predominantly in the nucleus of 56% of cells, whereas 32% had diffuse staining. At 24 h, most cells from CLP rats (82%) had HMGB-1 located in the cytoplasm, whereas in contrast, HMGB-1 was located in the nucleus of 80% and 82% of cells from sham control and IFN-gamma Ab-treated rats, respectively. Gene expression of TNF-alpha was not significantly changed 12 h after surgery, but at 24 h, alveolar macrophages from CLP rats had reduced gene expression of TNF-alpha. Interferon gamma Ab treatment prevented the reduction in TNF-alpha gene expression. TNF-alpha release was not altered at 12 h. At 24 h, LPS-stimulated release of TNF-alpha was decreased in macrophages from CLP rats compared with sham controls. Interferon gamma Ab treatment prevented the decrease in LPS-stimulated TNF-alpha release. The results suggest that alveolar macrophage suppression after CLP is associated with HMGB-1 transmigration out of the cell nucleus and provides evidence that intranuclear HMGB-1 may play an integral role in macrophage activation in sepsis.

Cytokines and Escherichia coli Sepsis

This review reviews the critical role played by cytokines in the pathogenesis of Escherichia coli sepsis. It focuses on prototypic pro-inflammatory and anti-inflammatory cytokines and their influence on mortality in experimental animal models of E. coli endotoxemia and of live E. coli sepsis. The review reviews the results of clinical trials on anticytokine therapy in patients with severe sepsis or septic shock. The recognition of the critical role played by tumor necrosis factor (TNF), a secreted 17kDa cytokine, in endotoxic and gram-negative shock has been a major step forward in our understanding of the pathogenesis of sepsis. The review describes the role of TNF, IL1, and IL6 in animal models of E. coli endotoxemia and sepsis. Given the pivotal role played by TNF in experimental sepsis and the fact that elevated concentrations of TNF were detected in the circulation of patients with sepsis, anti-TNF treatment strategies were investigated as adjunctive therapy for severe sepsis and septic shock. Several studies demonstrated that high levels of interleukin-6 (IL-6) are associated with an increased risk for fatal outcome. Gamma interferon (IFN-γ), IL-12, and IL-18 are functionally related cytokines. A recent study has indicated that transgenic mice overexpressing IL-15 are resistant to an otherwise lethal intraperitoneal E. coli challenge. IL4, IL10, and IL13are prototypic anti-inflammatory cytokines. Their classification as anti-inflammatory cytokines is based on the observation that these molecules inhibit the production of proinflammatory cytokines (primarily TNF and IL1) and toxic oxygen and reactive nitrogen species by myeloid cells.