Divergent efficacy of antibody to tumor necrosis factor-alpha in intravascular and peritonitis models of sepsis

Initial Immune Response in Escherichia coli, Staphylococcus aureus, and Candida albicans Bacteremia

Sepsis remains a leading cause of mortality worldwide and is characterized by sustained inflammatory responses, reflected as changes in the expression profile of cytokines with time. The aim of the present study was to investigate the dynamic changes in complete blood count, serum chemistry, procalcitonin (PCT), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in Escherichia coli, Staphylococcus aureus, and Candida albicans bacteremia. Study subjects were 32 healthy male Landrace-Large White pigs, aged 10-15 weeks and of average weight 19 ± 2 kg. Bacteremia was induced by continuous intravenous infusion of microbial suspensions during a period of 8 h. E. coli and S. aureus bacteremia were associated with a significant gradual decrease in white blood cells and platelets, respectively (p = 0.002 and p = 0.004), while candidemia was characterized by a significant gradual decrease in lymphocytes (p = 0.009). Serum PCT levels were either undetectable or very low, with no significant changes with time in all groups. E. coli bacteremia elicited a strong pro-inflammatory response, characterized by a significant increase in TNF-α expression from the onset of bacteremia (p = 0.042). C. albicans exhibited a different profile with an early, moderate increase in TNF-α followed by a subsequent marked increase in IL-6 levels (p = 0.03). The differential regulation of inflammatory and hematological responses depending on the pathogenic agent can reveal differences in the underlying inflammatory mechanisms, which may assist in the ongoing quest for the identification of a panel of circulating biomarkers during bacteremia.

Checkpoint inhibitor therapy in preclinical sepsis models: a systematic review and meta-analysis

BACKGROUND

Animal studies reporting immune checkpoint inhibitors (CPIs) improved host defense and survival during bacterial sepsis provided one basis for phase I CPI sepsis trials. We performed a systematic review and meta-analysis examining the benefit of CPI therapy in preclinical studies, and whether variables potentially altering this clinical benefit were investigated. Studies were analyzed that compared survival following bacteria or lipopolysaccharide challenge in animals treated with inhibitors to programmed death-1 (PD-1), PD-ligand1 (PD-L1), cytotoxic T lymphocyte-associated protein-4 (CTLA-4), or B- and T-lymphocyte attenuator (BTLA) versus control.

RESULTS

Nineteen experiments from 11 studies (n = 709) were included. All experiments were in mice, and 10 of the 19 were published from a single research group. Sample size calculations and randomization were not reported in any studies, and blinding procedures were reported in just 1. Across all 19 experiments, CPIs increased the odds ratio for survival (OR, 95% CI) [3.37(1. 55, 7.31)] but with heterogeneity (I² = 59%, p < 0.01). After stratification by checkpoint molecule targeted, challenge site or type, or concurrent antibacterial treatment, CPIs had consistent effects over most experiments in the 9 that included antibacterial treatment [OR = 2.82 (1.60, 4.98), I² = 6%, p = 0.39 with versus 4.01 (0.89, 18.05), I² = 74%, p < 0.01 without]. All 9 antibiotic experiments employed cecal-ligation and puncture (CLP) bacterial challenge while 6 also included a Candida albicans challenge 3-4 days after CLP. In these six experiments (n = 322), CPIs were directed at the fungal challenge when CLP lethality had resolved, and were consistently beneficial [2.91 (2.41, 3.50), I² = 0%, p = 0.99]. In the three experiments (n = 66) providing antibiotics without fungal challenge, CPIs were administered within 1 day of CLP and had variable and non-significant effects [0.05 (0.00, 1.03); 7.86 (0.28, 217.11); and 8.50 (0.90, 80.03)]. No experiment examined pneumonia.

CONCLUSIONS

Preclinical studies showing that CPIs add benefit to antibiotic therapy for the common bacterial infections causing sepsis clinically are needed to support this therapeutic approach. Studies should be reproducible across multiple laboratories and include procedures to reduce the risk of bias.

Fundamental differences during Gram-positive versus Gram-negative sepsis become apparent during bacterial challenge of D-galactosamine-treated mice

Gram-negative and Gram-positive bacteria have been compared with respect to lethal effects when each is administered to normal and D-galactosamine-sensitized mice, both with and without concomitant dexamethasone treatment. In the case of Escherichia coli, the extent of sensitization by D-galactosamine treatment (10,000-fold) and the relative magnitude of the corresponding protection with dexamethasone (150-fold) are both consistent with an expected significant role of LPS in production of TNFα that then mediates lethal toxicity. With Staphylococcus aureus, however, marginal sensitization by D-galactosamine (5-fold) and a corresponding lack of dexamethasone protection indicate a reduced role for TNFα as a lethal mediator. In vitro comparisons of TNFα release from E. coli and S. aureus stimulated peritoneal macrophages (100-fold difference) add further support to this conclusion. Endotoxin hypo-responsive mice (C3H/HeJ) infected with E. coli are not protected by dexamethasone. Each of these comparisons indicate that the contribution of TNFα to the pathophysiological manifestations of experimental sepsis may vary substantially even among extracellular bacteria and, correspondingly, that differential dexamethasone protection may serve a discriminatory function for the potential involvement of this cytokine.

Contribution of TNF and of LPS in endotoxemic shock in mice. A reappraisal

Species of mice have a different sensitivity to LPS. The mechanisms underlying these differences are not clear. We have investigated the contribution of TNF and of LPS in inducing lethality in endotoxemic models using LPSsensitive C57BI/6 and Balb/c mice, OF1 mice with an intermediate sensitivity, and LPS-resistant C3H/HeJ mice. Our observations showed that TNF largely contributed to lethality, since anti-TNF antibodies protected sensitive Balb/c mice from death over a large range of LPS concentrations. OF1 mice were relatively insensitive to LPS and this was associated with a lesser production of TNF. Similarly, OF1 mice had a reduced sensitivity to challenge with recombinant TNF than Balb/c mice. These observations, therefore, indicated that TNF production and sensitivity were determinant for outcome upon LPS challenge. LPS levels were similar in Balb/c, C57BI/6, and OF1 mice, suggesting that a difference in LPS clearance did not contribute to the differences in sensitivity to LPS. The contribution of the combination of both TNF and LPS in endotoxemic shock was investigated with the LPS-resistant C3H/HeJ mice. While these mice were resistant to challenge with either LPS or a low dose of TNF, combination of non lethal concentrations of LPS and TNF induced death. These data, thus, suggest that while TNF is critical for mediating LPS-induced death, the combination of both LPS and TNF act synergistically in contributing to death, particularly in animal species with reduced sensitivity to LPS.

Effects of anti-interleukin 6 on inflammatory responses during murine septic peritonitis

Interleukin (IL)-6 has a limited role in the pathogenesis of the acute systemic inflammatory response syndrome elicited by bolus administration of bacteria or bacterial products. We sought to determine the role of IL-6 in septic peritonitis induced by cecal ligation and puncture (CLP). CLP led to a rapid and sustained induction of IL-6 in plasma and organ homogenates. Pretreatment (-2 h) with an anti-IL-6 mAb (1 mg) resulted in higher plasma and hepatic levels of tumor necrosis factor (TNF), as well as higher plasma concentrations of soluble TNF receptors and IL-10, while attenuating the acute phase protein response. Administration of anti-IL-6 did not influence survival. These results suggest that IL-6 production during septic peritonitis serves to inhibit the appearance of both agonist and antagonist members of the cytokine network. The importance of IL-6 in mediating the cytokine response to infection may be underestimated in more acute sepsis models.

Effects of bactericidal/permeability-increasing protein on endotoxin-induced fever and Escherichia coli-induced shock in rabbits

Binding of bactericidal/permeability-increasing protein (BPI) to endotoxin inhibits endotoxin-triggered responses. We investigated the effects of BPI on endotoxin fever and E. coli-induced septic shock in rabbits. Pre-incubation of endotoxin with BPI blocked fever compared to control rabbits (n = 6). A marked reduction in fever was also observed when BPI was injected before endotoxin. E. coli-challenge resulted in 66% mortality (n = 6); pre-treatment with BPI resulted in survival of all animals (n = 3). Mean arterial blood pressure was higher in BPI-treated compared to control rabbits. Comparable leukopenia and thrombocytopenia was observed with either BPI or vehicle treatment. Tumor necrosis factor (TNF) and interleukin-1 receptor antagonist were similarly elevated in both BPI- and saline-treated rabbits. However, in BPI treated rabbits, peak TNF levels were 34 % lower compared to saline controls ( P < 0.05). Further studies are warranted to assess whether BPI may have therapeutic potential for the treatment of septic shock.

Cross-tolerance between bacterial endotoxin and group B Streptococcus in neonatal rats

Although endotoxin tolerance can be induced in newborns, potential cross-tolerance to group B Streptococcus (GBS), a common Gram-positive neonatal pathogen has not been investigated. In the present study we tested the hypothesis that endotoxin or recombinant tumor necrosis factor (rTNFα) can induce tolerance to lethal injection of heat-killed GBS in rat newborn pups and vice versa. The effect of such cross-tolerance on endogenous generation of plasma TNFα was subsequently evaluated. Rat pups (18-24 h old) were pretreated intracardially (i.c.) with either phosphate buffered saline (PBS), Salmonella enteritidis endotoxin (30 μg/kg) or rTNFα (35, 70 or 140 μg/kg). The pups were pretreated for either 4, 24, 48, 96 or 240 h prior to a lethal heat-killed GBS challenge. The susceptibility of the neonates to GBS-induced mortality was dependent on the duration of the pretreatment period. At 4 h of pretreatment with endotoxin or TNF, GBS-induced mortality was augmented relative to the PBS group. However, by 24-48 h the endotoxin and TNF pretreated neonates became more resistant to GBS-induced mortality. In a converse of the above experiment, neonates were pretreated with heat killed GBS (0.7 mg/kg) or rTNFα (70 μg/kg) and sensitivity to endotoxin was determined at 4-240 h after pretreatment. The data were qualitatively similar to endotoxin pretreatment. The 4 h GBS or TNF pretreatment rendered the neonates more susceptible to endotoxin-induced mortality. However, by 24-48 h the pretreatment groups were more resistant (P < 0.05) to endotoxin than the PBS controls. Plasma TNFα levels were increased (P < 0.05) 2 h after challenge i.c. with lethal heat-killed GBS or S. enteritidis endotoxin. In the 4 h pretreatment groups that received either GBS or endotoxin and then challenged with endotoxin or GBS, respectively, the plasma TNFα response was markedly augmented (P < 0.05). By 48 h of pretreatment, however, the plasma TNFα response in these groups to the stimuli was significantly reduced (P < 0.05) compared to the PBS pretreated groups. Therefore, plasma TNFα parallels lethality induced by GBS or endotoxin pretreatment. The ability of GBS and endotoxin to induce cross tolerance suggests that common pathophysiological pathways are involved in these syndromes.

Disparities in efficacies of anti-LPS agents in burned mouse models of LPS intoxication versus Gram-negative sepsis

Results of anti-LPS treatments in LPS-intoxicated animals have been promising, but use of anti-LPS agents in clinical trials of sepsis have been disappointing. The purpose of this study was to determine if treatment results in intoxicated animals would hold in animal models of sepsis. Burned (15% body surface) mice were injected immediately postburn with either LPS (= intoxication) or with bacteria, which lead to sepsis. When possible, bacteria used were of the same genus and species as bacteria from which LPS was extracted for intoxication studies. Polymyxin, monophosphoryl lipid A or monoclonal antibody E5 given 1 h postburn, each protected long term against death from endotoxin intoxication. However, in septic mice, monophosphoryl lipid A and monoclonal antibody E5 did not improve survival, and polymyxin showed only transient improvement. Hence, animal models of LPS intoxication may not be optimal for testing anti-sepsis agents; use of such models, rather than of models of sepsis, may account partly for the overly optimistic expectations for anti-sepsis agents which have recently been shown to be rather ineffective in clinical trials.

Recombinant human interleukin-11 prevents hypotension in LPS-treated anesthetized rabbits

Recombinant human interleukin-11 (rhlL-11) was evaluated in a New Zealand White rabbit model of endotoxemia. Animals received Escherichia coli LPS (150 μg/kg i.v.) via a femoral venous catheter. 30 min later, animals were treated with rhlL-11 (100 μg/kg i.v., n = 7), or rhlL-11 formulation buffer (n = 6). Arterial pressures were monitored for 6 h following rhlL-11. Approximately 5 h after LPS treatment, mean arterial pressure in vehicle-treated control animals was 46.7 mmHg, or 55% of group mean baseline, while that of rhlL-11-treated animals was 74.8 mmHg, or 94% of group mean baseline (P < 0.0005). Histologic evaluation of ileum, cecum and colon from rhlL-11-treated rabbits showed decreased hemorrhage, edema, and mucosal damage (P < 0.02), compared to the vehicle-treated controls. Intravenous LPS evokes hypotension mediated by the induction of inducible nitric oxide synthase (iNOS) and subsequent production of NO. Maintenance of blood pressure by rhIL-11 in LPS-treated rabbits in addition to the concurrent significant decrease in NO levels compared to vehicle-treated animals ( P < 0.04) suggests that rhlL-11 interferes with the production of NO by iNOS and or the physiologic effects of NO on vascular smooth muscle.

An N-terminal fragment of bactericidal/permeability-increasing protein protects against hemodynamic and metabolic derangements in rat Gram-negative sepsis

Recombinant N-terminal fragments of bactericidal/permeability-increasing protein (BPI) are protective in acute models of endotoxemia or bacteremia. However, their usefulness in models utilizing slow infusion of bacteria has not been reported. Anesthetized rats were infused with Escherichia coli 07:K1 bacteria (5 x 109 cfu/h) for 2 h. Hemodynamics, glucose and lactate levels, tumor necrosis factor-α (TNFα) and endotoxin levels were measured for 210 min. The rats were treated with a 2 h infusion of RBPI21 or thaumatin (10 mg/kg/h), a protein that does not bind endotoxin but is similar to rBPI21 in molecular weight and isoelectric point. Control rats received only saline and vehicle. In animals treated with thaumatin, blood pressure, cardiac index and stroke volume declined rapidly (within 30 min). After 90 min glucose levels were significantly depressed whereas lactate was elevated. Endotoxemia (764 ± 353 ng/ml) was observed within 30 min. rBPI 21 significantly reduced the cardiovascular depression observed after 30 min and abolished all hemodynamic responses by the end of the experiment. rBPI21 significantly reduced hypoglycemia, elevated lactate levels, and endotoxin levels after 90 min. These results indicate that reduction of endotoxin levels resulting from RBPI21 therapy leads to significant protection in this model of acute Gram-negative bacterial sepsis.

Evaluating the effects of protective ventilation on organ-specific cytokine production in porcine experimental postoperative sepsis

Background

Protective ventilation with lower tidal volume (V_T) and higher positive end-expiratory pressure (PEEP) reduces the negative additive effects of mechanical ventilation during systemic inflammatory response syndrome. We hypothesised that protective ventilation during surgery would affect the organ-specific immune response in an experimental animal model of endotoxin-induced sepsis-like syndrome.

Methods

30 pigs were laparotomised for 2 hours (h), after which a continuous endotoxin infusion was started at 0.25 micrograms × kg⁻¹ × h⁻¹ for 5 h. Catheters were placed in the carotid artery, hepatic vein, portal vein and jugular bulb. Animals were randomised to two protective ventilation groups (n = 10 each): one group was ventilated with V_T 6 mL × kg⁻¹ during the whole experiment while the other group was ventilated during the surgical phase with V_T of 10 mL × kg⁻¹. In both groups PEEP was 5 cmH₂O during surgery and increased to 10 cmH₂O at the start of endotoxin infusion. A control group (n = 10) was ventilated with V_T of 10 mL × kg⁻¹ and PEEP 5 cm H₂0 throughout the experiment. In four sample locations we a) simultaneously compared cytokine levels, b) studied the effect of protective ventilation initiated before and during endotoxemia and c) evaluated protective ventilation on organ-specific cytokine levels.

Results

TNF-alpha levels were highest in the hepatic vein, IL-6 levels highest in the artery and jugular bulb and IL-10 levels lowest in the artery. Protective ventilation initiated before and during endotoxemia did not differ in organ-specific cytokine levels. Protective ventilation led to lower levels of TNF-alpha in the hepatic vein compared with the control group, whereas no significant differences were seen in the artery, portal vein or jugular bulb.

Conclusions

Variation between organs in cytokine output was observed during experimental sepsis. We see no implication from cytokine levels for initiating protective ventilation before endotoxemia. However, during endotoxemia protective ventilation attenuates hepatic inflammatory cytokine output contributing to a reduced total inflammatory burden.

Acute lung injury and pulmonary vascular permeability: use of transgenic models

Acute lung injury is a general term that describes injurious conditions that can range from mild interstitial edema to massive inflammatory tissue destruction. This review will cover theoretical considerations and quantitative and semi-quantitative methods for assessing edema formation and increased vascular permeability during lung injury. Pulmonary edema can be quantitated directly using gravimetric methods, or indirectly by descriptive microscopy, quantitative morphometric microscopy, altered lung mechanics, high-resolution computed tomography, magnetic resonance imaging, positron emission tomography, or x-ray films. Lung vascular permeability to fluid can be evaluated by measuring the filtration coefficient (Kf) and permeability to solutes evaluated from their blood to lung clearances. Albumin clearances can then be used to calculate specific permeability-surface area products (PS) and reflection coefficients (σ). These methods as applied to a wide variety of transgenic mice subjected to acute lung injury by hyperoxic exposure, sepsis, ischemia-reperfusion, acid aspiration, oleic acid infusion, repeated lung lavage, and bleomycin are reviewed. These commonly used animal models simulate features of the acute respiratory distress syndrome, and the preparation of genetically modified mice and their use for defining specific pathways in these disease models are outlined. Although the initiating events differ widely, many of the subsequent inflammatory processes causing lung injury and increased vascular permeability are surprisingly similar for many etiologies.

Microencapsulated drug delivery: a new approach to pro-inflammatory cytokine inhibition

CONTEXT

This article reviews the use of albumin microcapsules 3-4 µm in size containing cytokine inhibiting drugs which include neutralizing antibodies to TNF and IL1, CNI-1493, antisense oligonucleotides to TNF and NF-kappaB, and the antioxidant catalase.

OBJECTIVE

Describe the effects, cellular uptake and distribution of microencapsulated drugs and the effect in both a peritonitis model of infection and a model of adjuvant-induced arthritis.

METHODS

The studies performed by our group are reviewed, the only such studies available.

RESULTS

Microencapsulation of these compounds produced high intracellular drug concentrations due to rapid uptake by phagocytic cells, including endothelial cells, without toxicity. All compounds produced excellent inhibition of TNF and IL1 resulting in improved animal survival in a peritonitis model of septic shock and inflammation in an arthritis model.

CONCLUSION

Albumin microencapsulated pro-inflammatory cytokine inhibiting compounds are superior to equivalent concentration of these compounds administered in solution form.

The individual survival benefits of tumor necrosis factor soluble receptor and fluid administration are not additive in a rat sepsis model

BACKGROUND

Tumor necrosis factor (TNF) antagonists [e.g., TNF soluble receptor (TNFsr)] improved survival in preclinical but not clinical sepsis trials. However fluid support-itself beneficial-is standard clinically but rarely employed in preclinical sepsis models. We hypothesized that these therapies may not have additive benefit.

METHODS AND RESULTS

Antibiotic-treated rats (n = 156) were randomized to intratracheal or intravenous Escherichia coli challenges (>LD50) and either placebo or TNFsr and 24 h fluid treatments alone or together. The survival effects of these therapies did not differ significantly comparing challenge routes. When averaged across route, while TNFsr or fluid alone decreased the hazard ratio of death significantly [ln ± standard error (SE): -0.65 ± 0.30 and -0.62 ± 0.30, respectively, p ≤ 0.05], together they did not (p = 0.16). Furthermore, the observed effect of TNFsr and fluid together on reducing the hazard ratio was significantly less than estimated (-0.37 ± 0.29 versus -1.27 ± 0.43, respectively, p = 0.027) based on TNFsr and fluid alone. While each treatment increased central venous pressure at 6 and 24 h, the observed effects of the combination were also less than estimated ones (p ≤ 0.0005).

CONCLUSIONS

The individual survival benefits of TNFsr and fluids were not additive in this rat sepsis model. Investigating new sepsis therapies together with conventional ones during preclinical testing may be informative.

Association of tumor necrosis factor β genetic polymorphism and sepsis susceptibility

The association of the tumor necrosis factor β (TNF-β) Nco1 genetic polymorphism with susceptibility to sepsis was evaluated in 60 consecutive patients diagnosed with sepsis and in 148 healthy blood donors. Genomic DNA was extracted from peripheral blood cells and a 782 base-pair fragment of the TNF-β gene was amplified by PCR. The PCR products were subjected to Nco1 restriction digestion and analysed by restriction fragment length polymorphism analysis. Tumor necrosis factor α (TNF-α) and the C-reactive protein (CRP) serum levels were also determined by ELISA and nephelometry, respectively. Among the septic patients, the allelic frequencies of TNFB1 and TNFB2 were 0.2833 and 0.7166, respectively, and they differed from those observed in the blood donors (p=0.0282). The TNFB2 allele frequency was higher in the septic patients than in the blood donors [odds ratio=1.65 (CI 95% 1.02-2.69), p=0.0315]. The TNF-α and CRP serum levels and the APACHE II and SOFA clinical scores did not differ in the patients with the TNFB1 or TNFB2 alleles (p>0.05). The results suggest that the TNFB2 allele is associated with susceptibility to sepsis, but it was not found to be associated with the immunological and clinical biomarkers of the disease.

Different bacteria species lipopolysaccharide co-exposure with Pseudomonas exotoxin A on multiple organ injury induction

The present study investigated the effect of different bacterial species lipopolysaccharide plus Pseudomonas exotoxin A (LPS/PEA) on the induction of multiple organ injury (MOI). Rats were injected with various LPS from Salmonella (SAE, SAT), E. coli (EB4, EB5), or P. aeruginosa (PAL) and PEA showed a greater mortality in the SAE/PEA and SAT/PEA groups. Histological alterations, serum enzymes, and cytokines changes were severer in the SAE/PEA group than the EB4/PEA or PAL/PEA group. EB4/PEA and PAL/PEA failed to induce MOI, even at the LPS doses increased up to 2-4- and 4-8-fold, respectively. Rats co-treated with Salmonella lipid A/PEA developed severer MOI than the E. coli lipid A/PEA. The results indicated the critical roles of MOI induction, which were related to LPS derived from appropriate bacterial species.

Pro-inflammatory cytokine inhibition in the primate using microencapsulated antisense oligomers to NF-kappaB

PRIMARY OBJECTIVE

Antisense oligomers to NF-kappaB (ASO) were incorporated into albumin microspheres to determine if microcapsules containing ASO inhibit pro-inflammatory cytokines to a greater extent than comparable doses of ASO in solution. Phagocytosis of microcapsules and intracellular release of ASO in macrophages was evaluated.

RESEARCH DESIGN

Comparable doses of microencapsulated ASO and ASO in solution were evaluated in non-human primates.

METHODS

Blood was sampled and stimulated with Escherichia coli endotoxin ex vivo. TNF, IL-1 and IL-6 concentrations were compared for 72 hrs. The intracellular concentration of ASO was measured in macrophages in vitro to evaluate the difference in intracellular penetration of microencapsulated ASO.

RESULTS

Microencapsulated ASO produced significantly greater cytokine inhibition at all time points compared to ASO in solution. There were no side effects to ASO in the baboons. Intracellular ASO concentration was 10 fold greater in macrophages using microencapsulation.

CONCLUSIONS

Microencapsulated ASO to NF-kappaB is more effective than ASO in solution in pro-inflammatory cytokine inhibition in non-human primates.

Large animal models: baboons for trauma, shock, and sepsis studies

A few limited examples of large animal models are outlined, with the main emphasis on baboon models. The baboon offers all the advantages of a large animal and is comparable with humans in nearly all physiological and immunological aspects. In addition, cross-reactivity with human therapeutic and diagnostic reagents allows testing of new species-specific therapies such as antihuman antibodies, on the one hand, and monitoring with available human analytical procedures, on the other.

Evaluation of endotoxin models for the study of sepsis

Many strategies have been proposed for the treatment of sepsis, and most of the proposed treatment modalities have failed in clinical trials. Many of the previous treatment protocols called for blocking the activity of a single, clearly defined mediator. The underlying hypothesis was that sepsis induced a specific mediator that then caused organ injury and death. This simple, linear reasoning was frequently based on cytokines that were defined using endotoxin models of sepsis. The endotoxin models were widely used to study the pathophysiology of sepsis and were felt to adequately reproduce the full spectrum of inflammatory changes observed in patients with sepsis. Based on mortality and hematologic changes, these assumptions appeared justified. As the models were examined more closely, and directly compared with focus of infection models that more accurately portray the changes in sepsis, it became apparent that the endotoxin models did not accurately mimic the patient with sepsis. In the endotoxin models, the explosive release of cytokines into the circulating blood volume was reproducibly found regardless of the species studied (human, primate, pig, rat, or mouse). This lead to a series of anticytokine sepsis trials, all of which failed. The cytokine response in focus of infection models, such as that induced by cecal ligation and puncture, was examined and found to be more similar to that observed in patients with sepsis. When cytokine inhibitor strategies were used in the cecal ligation and puncture model, they were also generally found to lack efficacy. Compounds that have been shown to be effective at reducing mortality in endotoxin models should be re-evaluated in more clinically relevant models of sepsis.

Apolipoprotein CI stimulates the response to lipopolysaccharide and reduces mortality in Gram‐negative sepsis

Gram-negative sepsis is a major death cause in intensive care units. Accumulating evidence indicates the protective role of plasma lipoproteins such as high-density lipoprotein (HDL) in sepsis. It has recently been shown that septic HDL is almost depleted from apolipoprotein CI (apoCI), suggesting that apoCI may be a protective factor in sepsis. Sequence analysis revealed that apoCI possesses a highly conserved consensus KVKEKLK binding motif for lipopolysaccharide (LPS), an outer-membrane component of gram-negative bacteria. Through avid binding to LPS involving this motif, apoCI improved the presentation of LPS to macrophages in vitro and in mice, thereby stimulating the inflammatory response to LPS. Moreover, apoCI dose-dependently increased the early inflammatory response to Klebsiella pneumoniae-induced pneumonia, reduced the number of circulating bacteria, and protected mice against fatal sepsis. Our data support the hypothesis that apoCI is a physiological protector against infection by enhancing the early inflammatory response to LPS and suggest that timely increase of apoCI levels could be used to efficiently prevent and treat early sepsis.

A. Deficiency of gammadelta T lymphocytes contributes to mortality and immunosuppression in sepsis

Studies have indicated that gammadelta T lymphocytes play an important role in the regulation of immune function and the clearance of intracellular pathogens. We have recently reported that intraepithelial lymphocytes (IEL), which are rich in gammadelta T cells, within the small intestine illustrated a significant increase in apoptosis and immune dysfunction in mice subjected to sepsis. However, the contribution of gammadelta T cells to the host response to polymicrobial sepsis remains unclear. In this study, we initially observed that after sepsis induced by cecal ligation and puncture (CLP), there was an increase in small intestinal IEL CD8+gammadelta+ T cells in control gammadelta+/+ mice. Importantly, we subsequently found an increased early mortality in mice lacking gammadelta T cells (gammadelta-/- mice) after sepsis. This was associated with decreases in plasma TNF-alpha, IL-6, and IL-12 levels in gammadelta-/- mice compared with gammadelta+/+ mice after sepsis. In addition, even though in vitro LPS-stimulated peritoneal macrophages showed a reduction in IL-6 and IL-12 release after CLP, these cytokines were less suppressed in macrophages isolated from gammadelta-/- mice. Alternatively, IL-10 release was not different between septic gammadelta+/+ and gammadelta-/- mice. Whereas T helper (Th)1 cytokine release by anti-CD3-stimulated splenocytes was significantly depressed in septic gammadelta+/+ mice, there was no such depression in gammadelta-/- mice. However, gammadelta T cell deficiency had no effect on Th2 cytokine release. These findings suggest that gammadelta T cells may play a critical role in regulating the host immune response and survival to sepsis, in part by alteration of the level of IEL CD8+gammadelta+ T cells and through the development of the Th1 response.

DTPA Fe(III) decreases cytokines and hypotension but worsens survival with Escherichia coli sepsis in rats

OBJECTIVE

Nonselective inhibition of nitric oxide (NO) with NO synthase antagonists decreases hypotension but worsens outcome clinically. We investigated whether iron (III) complex of diethylenetriaminepentaacetic acid [DTPA Fe(III)], a scavenger of NO as well as other oxidant mediators, has similar divergent effects in E. coli challenged rats.

METHODS

Animals with venous and arterial catheters and challenged with intrabronchial or intravenous E. coli were randomized to treatment with DTPA Fe(III) in doses from 3 to 800 mg/kg or placebo. Mean blood pressure (MBP) was measured in all animals and plasma NO, cytokines, and blood and lung leukocyte and bacteria counts in animals administered intrabronchial E. coli and DTPA Fe(III) 50 mg/kg or placebo. Animals received antibiotics and were observed 168 h.

RESULTS

Independent of drug regimen or infection site, compared to placebo, DTPA Fe(III) increased MBP although this was greater with high vs. lower doses. Despite increased MBP, DTPA Fe(III) worsened the hazards ratio of survival . At 6 and 24 h DTPA Fe(III) decreased NO but not significantly and decreased four cytokines (tumor necrosis factor-alpha, interleukins 1 and 10, and macrophage inflammatory protein 3alpha) and lung lavage neutrophils. From 6 to 24 h DTPA Fe(III) increased blood bacteria.

CONCLUSIONS

DTPA Fe(III) while increasing blood pressure has the potential to worsen outcome in sepsis. Further preclinical testing is required before this agent is applied clinically.

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.

TNF-alpha contributes to endothelial dysfunction in ischemia/reperfusion injury

BACKGROUND

Despite the importance of endothelial function for coronary regulation, there is little information and virtually no consensus about the causal mechanisms of endothelial dysfunction in myocardial ischemia/reperfusion (I/R) injury. Because tumor necrosis factor-alpha (TNF-alpha) is reportedly expressed during ischemia and can induce vascular inflammation leading to endothelial dysfunction, we hypothesized that this inflammatory cytokine may play a pivotal role in I/R injury-induced coronary endothelial dysfunction.

METHODS AND RESULTS

To test this hypothesis, we used a murine model of I/R (30 minutes/90 minutes) in conjunction with neutralizing antibodies to block the actions of TNF-alpha. TNF-alpha expression was increased >4-fold after I/R. To determine whether TNF-alpha abrogates endothelial function after I/R, we assessed endothelial-dependent (ACh) and endothelial-independent (SNP) vasodilation. In sham controls, ACh induced dose-dependent vasodilation that was blocked by the nitric oxide synthase (NOS) inhibitor L-NMMA (10 micromol/L), suggesting a key role for NO. In the I/R group, dilation to ACh was blunted, but SNP-induced dilation was preserved. Subsequent incubation of vessels with the superoxide (O2*-) scavenger (TEMPOL), or with the inhibitors of xanthine oxidase (allopurinol, oxypurinol), or previous administration of anti-TNF-alpha restored endothelium-dependent dilation in the I/R group and reduced I/R-stimulated O2*- production in arteriolar endothelial cells. Activation of xanthine oxidase with I/R was prevented by allopurinol or anti-TNF-alpha.

CONCLUSIONS

These results suggest that myocardial I/R initiates expression of TNF-alpha, which induces activation of xanthine oxidase and production of O2*-, leading to coronary endothelial dysfunction.

THE USE OF IMMUNOCOMPROMISED ANIMALS AS MODELS FOR HUMAN SEPTIC SHOCK

Although it is generally understood that no single animal model truly reflects human sepsis, the study of sepsis in immunocompromised animals is highly relevant to human sepsis research. The majority of patients with severe sepsis have significant underlying diseases that may alter innate immune defenses, disrupt microbial clearance mechanisms, and complicate the pathophysiology of human sepsis. Septic shock itself has significant effects upon the innate and adaptive host immune responses that may contribute to a state of sepsis-induced immune dysregulation. A number of animal models of sepsis displaying an array of immunocompromised states are now available. Most of these systems are small animal models with genetically defined defects of immune defenses or acquired defects from receipt of immunosuppressive or myeloablative agents. Greater emphasis should be placed on preclinical models of immunocompromised animals in the future to assess the potential clinical utility of novel drugs for human septic shock.

NEUTRALIZATION OF TUMOR NECROSIS FACTOR IN PRECLINICAL MODELS OF SEPSIS

Tumor necrosis factor (TNFalpha), a cardinal early mediator of the innate host inflammatory response, has been an attractive target for therapeutic intervention in human sepsis. However, pooled data from 12 completed randomized controlled trials show only a very modest impact on mortality in a highly heterogeneous population of patients. To gain insight into the preclinical in vivo biology of TNFalpha that might aid in better identifying appropriate patient populations for therapeutic intervention, we undertook a systematic review of published reports of preclinical studies assessing the consequences of neutralization of TNFalpha in models of acute infection or inflammation. We identified 143 reports incorporating 484 unique experimental comparisons in seven different animal species. The effects of neutralization of TNFalpha in these were quite variable. Neutralization of TNFalpha was beneficial in endotoxemia, or after systemic challenge with gram-negative organisms, Staphylococcus aureus, or Group B streptococci. On the other hand, neutralization was detrimental in infections caused by Streptococcus pneumoniae, Candida spp., or intracellular pathogens such as Listeria and Mycobacterium tuberculosis, and in models of pneumonia. Treatment was more efficacious when delivered before infectious challenge, and the therapeutic signal increased as the baseline mortality in the placebo group increased. Evidence of neutralization of TNFalpha bioactivity, and of attenuation of inflammation, was typically accompanied by evidence of impairment of antimicrobial defenses. Multiple specific and nonspecific therapeutic strategies were identified. We conclude that the beneficial effects of TNF in systemic inflammation occur at the cost of impaired antimicrobial defenses, and that a better understanding of the consequences of neutralization of TNFalpha in vivo could aid in better defining optimal patient populations for therapeutic intervention.

Treatment of Experimental Septic Shock with Microencapsulated Antisense Oligomers to NF-κB

NF-kappaB is an ideal target for inhibition of proinflammatory cytokines. The purpose of this study was to determine if microencapsulated antisense oligomer to NF-kappaB can inhibit proinflammatory cytokine release in response to Escherichia coli endotoxin and bacteria. Microencapsulation takes advantage of the phagocytic function of the macrophage to deliver the oligomer intracellularly and enhance the effect. Albumin microcapsules 1 microm in size were prepared by a nebulization method containing antisense oligomers to NF-kappaB. E. coli endotoxin was incubated in 1 ml aliquots of whole blood. Microencapsulated antisense to NF-kappaB was given, and the inhibition of tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6, and IL-8 was compared with similar amounts of oligomer in solution. Endotoxic shock was produced in rats using E. coli endotoxin (15 mg/kg). Peritonitis was induced by injecting 10(10) CFU E. coli. Cytokines were measured after simultaneous and delayed (4 h) administration of antisense to NF-kappaB in microcapsules and solution form. TNF was suppressed by 81% in whole blood, 56% in the endotoxic shock model, 89% in the peritonitis model (simultaneous treatment), and 56% in the delayed treatment group. Survival was 70% in the endotoxic shock group, 80% in the simultaneous peritonitis group, and 70% in the delayed treatment group. Microcapsule treatment using antisense to NF-kappaB suppressed TNF and IL-1 levels and mortality significantly better than all solution treatment groups in the whole blood model, endotoxic shock model, and peritonitis model.

Cecal ligation and puncture versus colon ascendens stent peritonitis: two distinct animal models for polymicrobial sepsis

Colon ascendens stent peritonitis (CASP) and cecal ligation and puncture (CLP), two animal models designed to closely mimic the clinical course of intra-abdominal sepsis, were compared. In the past, immunomodulatory therapies developed in animal studies failed to be successful in humans. As a consequence, the established animal sepsis models were criticized. It has been proposed that present models had to be reevaluated, and new, clinically more relevant models should be evolved. CLP procedure was performed puncturing once (CLP[1]) or twice (CLP[2]) the ligated cecum of C57BL/6 mice. In the CASP model, a stent with defined diameter was surgically inserted into the ascending colon. Survival, bacterial load, immunohistochemistry, and serum cytokine levels were analyzed in the groups. Survival after CASP procedure correlated strongly with the stent diameter, whereas the number of punctures in CLP did not significantly change survival rate. Bacterial loads of peritoneal lavage, liver, and lung, as well as serum cytokine levels (tumor necrosis factor, interleukin 1 beta, interleukin 10) steadily increased from 6 to 24 h after the CASP procedure. In contrast, continuously low amounts of bacteria and cytokines were found in CLP mice at any point of time. Twenty-four hours after CLP surgery, the ligated cecum was covered by adhesive small bowel loops, whereas in CASP mice, the intestinal leakage was then still present. The CASP model mimics closely the clinical course of diffuse peritonitis with early and steadily increasing systemic infection and inflammation (systemic inflammatory response syndrome). In contrast, CLP reveals a model of intra-abdominal abscess formation with sustained and minor signs of systemic inflammation.

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.

Research: advances in cell biology relevant to critical illness

During the past decade, enormous advances have been made in cell biology. Major advances included the publication of the human genome sequence, the development of proteomics, and DNA microarray technologies and techniques to selectively "silence" genes using short strands of double-stranded RNA. Some areas of great progress that are particularly relevant to critical care medicine include huge improvements in our understanding of the signal transduction pathways involved in the innate immune response and adaptation to hypoxia. Other areas of important progress include improvements in our understanding of how inflammation causes derangements in epithelial structure and function and impairs cellular utilization of oxygen.

Tumor necrosis factor-alpha from resident lung cells is a key initiating factor in pulmonary ischemia-reperfusion injury

OBJECTIVE

A central role of macrophages in initiating lung ischemia-reperfusion injury is emerging. Tumor necrosis factor-alpha is a proinflammatory cytokine secreted mainly by macrophages under various conditions. We hypothesized that tumor necrosis factor-alpha from resident lung cells is a key initiating factor in pulmonary ischemia-reperfusion injury.

METHODS

We used an isolated, buffer-perfused lung system to explore the role of tumor necrosis factor-alpha production by resident lung cells in pulmonary ischemia-reperfusion injury. Lungs from wild-type mice and tumor necrosis factor-alpha-deficient mice were subjected to 60 minutes of ischemia followed by 60 minutes of reperfusion. Histologic injury scores and measurements of lung compliance, airway resistance, mean pulmonary artery pressure, vascular reactivity, and wet lung weight index were obtained and compared using repeated-measures analysis of variance.

RESULTS

Lungs from tumor necrosis factor-alpha-deficient mice showed significantly less injury in all physiologic parameters throughout the entire 60 minutes of reperfusion compared with lungs from wild-type mice (P <.001). The most notable effects were observed in pulmonary artery pressure and airway resistance. Vascular reactivity (acute vasoconstrictive episodes per 60 minutes) was also blunted in the lungs from tumor necrosis factor-alpha-deficient mice compared with the lungs from wild-type mice (5.8 responses/hour vs 1.2 responses). Histologic injury scores and wet lung weight index were significantly reduced in lungs from tumor necrosis factor-alpha-deficient mice.

CONCLUSIONS

By using the advantages of a nonblood-perfused system, we have focused our investigation on resident lung cells. Our results demonstrate that resident cell-produced tumor necrosis factor-alpha is a key initiating factor in acute lung ischemia-reperfusion injury.

Tissue factor and tissue factor pathway inhibitor

The classical 'cascade/waterfall' hypothesis formulated to explain in vitro coagulation organised the amplification processes into the intrinsic and extrinsic pathways. Recent molecular biology and clinical data indicate that tissue factor/factor-VII interaction is the primary cellular initiator of coagulation in vivo. The process of blood coagulation is divided into an initiation phase followed by a propagation phase. The discovery of tissue factor pathway inhibitor further supports the revised theory of coagulation. Tissue factor is also a signalling receptor. Recent evidence has shown that blood-borne tissue factor has an important procoagulant function in sepsis, atherosclerosis and cancer, and other functions beyond haemostasis such as immune function and metastases.

Microencapsulation of tumor necrosis factor oligomers: a new approach to proinflammatory cytokine inhibition

Antisense oligonucleotides offer great therapeutic potential provided adequate intracellular penetration can be achieved. In this study, we evaluated the effectiveness of microencapsulating antisense oligonucleotides to tumor necrosis factor (TNF) in suppressing TNF release in vitro and in vivo. Microencapsulation of TNF oligomers was performed using albumin to produce microcapsules 0.6-1.0 mum in size that target phagocytic cells. Albumin microcapsules containing fluoresceinated TNF oligomers were incubated with U-937 cells to observe uptake. Microcapsules were added to whole blood and stimulated with Escherichia coli endotoxin. Endotoxin was given intravenously (i.v.) to rats along with 100 mug microencapsulated TNF oligomers to determine TNF inhibition and animal survival. E. coli was given intraperitoneally (i.p.) along with gentamicin and microencapsulated TNF oligomers to assess TNF inhibition and animal survival. The duration of microencapsulated antisense TNF oligomers was also determined in vivo. The results demonstrated rapid uptake of the microcapsules by macrophages after 2 h and 4 h incubation. There was improvement in TNF inhibition in vitro and improved animal survival by microencapsulated antisense in both endotoxin (100% survival) and peritonitis models (70% survival) compared with free antisense oligomers in solution. Microencapsulation extended the duration of action of the oligomers to 72 h. Intracellular targeting of macrophages with antisense oligomers to TNF by microencapsules as a delivery system improves TNF inhibition using the models of whole blood endotoxin stimulation and endotoxic shock and peritonitis in rats.

Spermine-induced maturation in wistar rat intestine: a cytokine-dependent mechanism

OBJECTIVES

Polyamines are of great importance in biologic processes such as cell proliferation and differentiation. The ingestion of spermidine or spermine by suckling rats induces the precocious maturation of the small intestine. In a previous article, the authors hypothesized that this phenomenon could be mediated by interleukins. This work was performed to examine the role of IL-1, IL-2, and tumor necrosis factor (TNF)- alpha in the spermine-induced maturation of the small intestine.

METHODS

Wistar suckling rats were treated with spermine, FR167653 (inhibitor of IL-1beta/TNF-alpha production), IL-1beta/TNF-alpha neutralizing antibodies, lipopolysaccharide, or IL-2. Intestinal disaccharidase-specific activities, polyamine content, and IL-2 plasma concentration were analyzed. Comparisons were made with untreated control animals.

RESULTS

Spermine-induced maturation of the small intestine was decreased by FR167653 but not by the neutralizing antibodies. Lipopolysaccharide injection induced an increase in disaccharidase-specific activity. IL-2 induced a decrease of the intestinal lactase-specific activity. Spermine administration led to a similar decrease of lactase activity and to an increase of IL-2 plasma concentration.

CONCLUSIONS

The authors conclude that IL-1beta and TNF-alpha are involved in the spermine effects on maltase- and sucrase-specific activities and suggest that IL-2 is involved in the spermine-induced decrease of lactase activity.

Interleukin-18 concentration in the peritoneal fluid correlates with the severity of peritonitis

BACKGROUND

Interleukin (IL)-18 is a novel cytokine that has recently been characterized as an inducer of interferon-gamma (IFN-gamma). The aim of this study was to investigate the clinical significance of peritoneal IL-18 concentrations in patients with peritonitis.

METHODS

We measured IL-18, IFN-gamma, and IL-10 concentrations in the peritoneal fluid of 28 patients undergoing laparotomy for peritonitis. Correlations between the peritoneal cytokine concentrations and the severity of illness determined by systemic inflammatory response syndrome (SIRS) criteria, Acute Physiological and Chronic Health Evaluation II (APACHE II) score, peritoneal fluid bacterial culture results, subsequent development of organ failure, and length of hospital stay were assessed.

RESULTS

Interleukin-18 concentration was significantly increased in patients who developed SIRS, in those with culture-positive peritonitis, and in those who developed organ failure, as compared with the other patients. Interleukin-10 concentration, which was also significantly increased in patients with culture-positive peritonitis, showed a close correlation with IL-18 concentration. Although a weak correlation was observed between IL-18 and IFN-gamma concentrations, IFN-gamma concentrations did not show any association with patients' clinical parameters. However, the IFN-gamma/IL-18 ratio was significantly lower in patients with an APACHE II >/=10, and in those with culture-positive peritonitis, as compared with the other patients.

BACKGROUND

Peritoneal IL-18 concentration increased in response to intraperitoneal bacterial infection and seemed to reflect the severity of peritonitis. However, the capacity of IL-18 to produce IFN-gamma may be altered depending on the severity of peritonitis.

Circulating endotoxin and antiendotoxin antibodies during severe sepsis and septic shock

The presence of circulating endotoxin is common during sepsis but its prognostic value is poor. We hypothesized that this lack of correlation with outcome could be related in part to the presence of circulating antiendotoxin antibodies. In a 14-bed medical intensive care unit, in an 821-bed tertiary teaching hospital, we prospectively assessed endotoxin and antiendotoxin antibodies in patients with severe sepsis or septic shock. Blood samples for the determination of circulating endotoxin and antiendotoxin antibodies were drawn when severe sepsis or septic shock were diagnosed (day 0) and then on day 1, day 2, and day 4. Daily measurements of antiendotoxin antibodies did not discriminate survivors from nonsurvivors. No antibody depletion was observed. However, during follow-up, the antiendotoxin immunoglobulin (Ig)M antibody level increased among survivors but decreased among nonsurvivors (51.2 vs -44.8 MU/mL, P=007). Circulating endotoxin was detectable among 9 of 17 patients on inclusion but neither the basal value nor sequential measurements correlated with outcome. These results suggest that during severe sepsis and septic shock, circulating endotoxin is a poor prognostic marker whereas the detection of an increase in IgM antiendotoxin antibody levels could identify survivors. This increase in IgM antibody levels could be attributed to a reactivation of the immune system.

Regional and systemic cytokine responses to acute inflammation of the vermiform appendix

OBJECTIVE

To measure local (peritoneal fluid) and systemic (plasma) cytokine profiles in patients with infection-inflammation of the vermiform appendix, a relatively mild, localized inflammatory process.

SUMMARY BACKGROUND DATA

The systemic host response to invading microorganisms, often termed the systemic inflammatory response syndrome (SIRS), includes changes in heart rate, respiratory rate, body temperature, and circulating white blood cell numbers. Although these changes can be induced experimentally by administering proinflammatory cytokines, the mediators that appear in the bloodstream during early, localized infection in humans have not been defined.

METHODS

The authors studied 56 patients with pathologically proven appendicitis. Blood was obtained before the induction of anesthesia, when 82% of the patients met the criteria for SIRS. Peritoneal fluid (PF) was obtained by intraoperative lavage. Cytokines were measured by immunoassay. To assess the net impact of the mediators within plasma, the authors studied the ability of patient plasma to augment or suppress bacterial lipopolysaccharide (LPS) stimulation of monocytes in vitro.

RESULTS

Of the proinflammatory cytokines, tumor necrosis factor-alpha was present in PF but not in plasma, interleukin (IL)-1beta and interferon-gamma were found in low concentrations in both PF and plasma, and IL-12 (p70) was detectable in plasma but not PF. In contrast, IL-6 and IL-1 receptor antagonist (IL-1ra) were the most abundant cytokines in the PF and plasma, and the concentrations of IL-4 and IL-10 were also elevated in both compartments. Patients with more severe appendicitis had higher plasma levels of IL-6 and IL-10 and lower plasma levels of IL-12 and interferon-gamma than did those with uncomplicated disease. Patient plasma inhibited LPS-induced stimulation of a monocyte cell line, and this inhibition was accentuated by complicated disease.

CONCLUSIONS

As judged from the pattern of soluble cytokines in plasma and the effect of the plasma on monocyte activation by LPS, mild, localized infection can induce a systemic response that is predominantly anti-inflammatory.

Increasing the efficacy of anti-inflammatory agents used in the treatment of sepsis

Excessive production of inflammatory mediators during invasive infection plays a key role in the pathogenesis of septic shock. In an attempt to improve survival of patients with this lethal syndrome, agents were developed to selectively inhibit mediators in this inflammatory response. Despite promising preclinical results, several different mediator-specific anti-inflammatory agents failed to demonstrate significant benefit in patients. There was, however, a significant difference in mortality between preclinical and clinical trials. The median control mortality in preclinical trials, performed almost uniformly in highly lethal sepsis models, was 88%. In clinical trials however, the median control mortality rate was much lower, at 41%. A recent meta-regression analysis of these preclinical and clinical trials in combination with prospective confirmatory studies demonstrated that risk of death as assessed by control group mortality rate significantly altered the treatment effect of these agents in both humans and animals. While anti-inflammatory agents were very beneficial in groups with high control mortality rates, they were ineffective or harmful in groups with low control mortality rates. Thus, variation in the risk of death due to sepsis provides a basis for the marked difference in the efficacy of these anti-inflammatory agents in preclinical and clinical trials over the last decade. In contrast to mediator-specific anti-inflammatory agents, glucocorticoids and activated protein C have recently demonstrated significant beneficial effects in individual clinical trials. However, glucocorticoids were studied only in patients with vasopressor-dependent septic shock, which is associated with a high control mortality rate (i.e. 61%) similar to the level at which mediator-specific agents would have been expected to be markedly beneficial. Furthermore, consistent with earlier findings for mediator-specific anti-inflammatory agents, analysis of the activated protein C study also demonstrated a relationship between risk of death and effect of treatment. Developing better methods to define high-risk septic populations for treatment with anti-inflammatory agents will increase the efficacy of this therapeutic approach and minimize its potential for harm.

Risk and the efficacy of antiinflammatory agents: retrospective and confirmatory studies of sepsis

We investigated whether a relationship between risk of death and treatment effect could explain the disparate results between the preclinical and clinical sepsis trials of antiinflammatory agents over the last decade. A metaregression analysis of cited preclinical studies showed that the treatment effects of these agents were highly dependent on risk of death (p = 0.0001) and that animals were studied at significantly higher control mortality rates than humans (median [25th-75th quartile], 88% [79-96%] versus 39% [32-42%], p = 0.0001). An analysis of the clinical trials showed that antiinflammatory agents were also significantly more efficacious in septic patients with higher risk of death (p = 0.002) and were harmful in those with low risk. To test this relationship prospectively, we studied antiinflammatory agents in models employing differing doses of bacterial challenge to produce the full range of risk of death. We found that the efficacy of these agents, although very beneficial at high control mortality rates, was much reduced (p = 0.0001) and similar to those in human trials at moderate control mortality rates (i.e., 30 to 40%). The efficacy of antiinflammatory agents during sepsis is dependent on the risk of death, an observation that explains the apparent contradiction between preclinical and clinical trial results. Accounting for this relationship may be necessary for the safe and effective development of antiinflammatory therapies for sepsis.

NF-kappaB activation has tissue-specific effects on immune cell apoptosis during polymicrobial sepsis

Studies indicate that critically ill patients who succumb to sequela of sepsis/multiorgan failure, as well as septic animals, exhibit an apparently pathological increase in apoptosis (Ao) in the immune system. However, the mechanisms regulating these changes are unclear. Studies also indicate that, dependent on the cell population and the nature and/or duration of the stimuli, activation of the nuclear factor (NF)-kappaB can either suppress or enhance Ao. Thus, the aim of this study was to determine the contribution of NF-kappaB activation to the onset of Ao seen in divergent immune cell populations during sepsis, as produced by cecal ligation and puncture (CLP). To assess this, C3H/HeN mice were pretreated (for 1 h) subcutaneously with either 100 mg/kg body weight of pyrrolidine dithiocarbamate (PDTC), an NF-kappaB inhibitor, or with saline vehicle, prior to subjecting them to CLP or Sham-CLP (Sham). Thymocytes, phagocytes, and Peyers Patch cells were harvested 24 h later, and the extent of Ao was determined by flow cytometry. The results indicate that PDTC pretreatment had no marked effect on the increase in thymocyte or phagocyte Ao seen following CLP, but there was a significant decline in the extent of Ao observed in septic mouse Peyer's patch B cells. To the extent that this was a result of NF-kappaB inhibition, we demonstrate by Western analysis, electrophoretic mobility shift assay (EMSA) and transfactor assay that the translocation of c-Rel to septic mouse Peyer's patch B cell nuclei is attenuated by PDTC. PDTC pretreatment also markedly reduced the number of Peyer's patch B cells that were producing IgA as well as attenuated the increase of proinflammatory cytokines in the blood. Interestingly, PDTC pretreatment did not restore peritoneal macrophage function or improve animal survival. Taken together, the inability of PDTC pretreatment to alter the Ao response of thymocytes or phagocytes, while inhibiting the increase in Peyer's patch B cell Ao in septic mice, implies not only that the activation of NF-kappaB has highly tissue/cell-specific effects that must be discerned when trying to clarify the pathophysiological role of NF-kappaB in sepsis, but that the activation of NF-kappaB may contribute to the early adaptive responses required by the host to fend off septic challenge.

Back to the future: antibody-based strategies for the treatment of infectious diseases

Before antibiotics, sera from immune animals and humans were used to treat a variety of infectious diseases, often with successful results. After the discovery of antimicrobial agents, serum therapy for bacterial infections was rapidly forsaken. In the last two decades, problems with treatment of newly emerged, re-emerged, or persistent infectious diseases necessitated researchers to develop new and/or improved antibody-based therapeutic approaches. This article reviews some information on the use of antibodies for the treatment of infectious diseases, with special reference to the most seminal discoveries and current advances as well as available treatment approaches in this field.

Inhibition of leukocyte rolling by nitric oxide during sepsis leads to reduced migration of active microbicidal neutrophils

We developed two models of sepsis with different degrees of severity, sublethal and lethal sepsis, induced by cecal ligation and puncture. Lethal sepsis induced by cecal ligation and puncture (L-CLP) resulted in failure of neutrophil migration to the infection site and high mortality. Treatment of septic animals with aminoguanidine (AG), a nitric oxide (NO) synthase inhibitor, precluded the failure of neutrophil migration and protected the animals from death. However, cytokine-induced NO synthase (iNOS)-deficient (iNOS(-/-)) mice subjected to L-CLP did not present neutrophil migration failure, but 100% lethality occurred. iNOS(-/-) mice subjected to sublethal sepsis induced by cecal ligation and puncture (SL-CLP) also suffered high mortality despite the occurrence of neutrophil migration. This apparent paradox could be explained by the lack of microbicidal activity in neutrophils of iNOS(-/-) mice present at the infection site due to their inability to produce NO. Notably, SL- and L-CLP iNOS(-/-) mice showed high bacterial numbers in exudates. The inhibition of neutrophil migration by NO is due to inhibition of a neutrophil/endothelium adhesion mechanism, since a reduction in leukocyte rolling, adhesion, and emigration was observed in L-CLP wild-type mice. These responses were prevented by AG treatment and were not observed in the iNOS(-/-) L-CLP group. There was no significant change in L-selectin expression in neutrophils from L-CLP mice. Thus, it seems that the decrease in leukocyte rolling is due to a defect in the expression of adhesion molecules on endothelial surfaces mediated by iNOS-derived NO. In conclusion, the results indicate that despite the importance of NO in neutrophil microbicidal activity, its generation in severe sepsis reduces neutrophil migration by inhibiting leukocyte rolling and their firm adhesion to the endothelium, in effect impairing the migration of leukocytes and consequently their fundamental role in host cell defense mechanisms.