Acid aspiration-induced lung injury in rabbits is mediated by interleukin-8-dependent mechanisms

Importance of interleukin-8 in the development of reexpansion lung injury in rabbits

Reexpansion of a collapsed lung induces increased microvascular permeability leading to reexpansion pulmonary edema (REPE). This study was designed to prove the hypothesis that local overproduction of interleukin-8 (IL-8) induces inflammatory cell accumulation which leads to the induction of REPE. Initially, we examined the detailed characteristics of a rabbit model of REPE in association with IL-8 production and its mRNA expression. The lung tissue to plasma ratio of radiolabeled albumin (T/P ratio), the lung wet to dry ratio, and bronchoalveolar lavage (BAL) neutrophil counts were significantly increased in the reexpanded lung. IL-8 concentrations and mRNA expression were significantly increased in the reexpanded lung homogenate. Immunohistochemically, alveolar macrophages (AMs) and epithelial cells in the reexpanded lung and AMs in the collapsed lung were positive for IL-8. Second, we examined the effect of pretreatment with a specific monoclonal anti-IL-8 antibody (Ab) or control IgG on the development of REPE. The T/P ratio and BAL neutrophil counts were conspicuously decreased by pretreatment with anti-IL-8 Ab, but not with control IgG. On a histopathological study, lung injury and leukocyte infiltration were attenuated by the pretreatment with anti-IL-8 Ab. In conclusion, IL-8 production is enhanced in the reexpanded lung, and contributes to the development of REPE. The pretreatment with anti-IL-8 antibody may be useful as a novel protective therapy for this disease.

Immunopathology of a two-hit murine model of acid aspiration lung injury

In a two-hit model of acid aspiration lung injury, mice were subjected to nonlethal cecal ligation and puncture (CLP). After 48 h, intratracheal (IT) acid was administered, and mice were killed at several time points. Recruitment of neutrophils in response to acid was documented by myeloperoxidase assay and neutrophil counts in bronchoalveolar lavage (BAL) fluid and peaked at 8 h post-IT injection. Albumin in BAL fluid, an indicator of lung injury, also peaked at 8 h. When the contributions of the two hits were compared, neutrophil recruitment and lung injury occurred in response to acid but were not greatly influenced by addition of another hit. Neutrophil sequestration was preceded by elevations in KC and macrophage inflammatory protein-2alpha in plasma and BAL fluid. KC levels in BAL fluid were higher and peaked earlier than macrophage inflammatory protein-2alpha levels. When KC was blocked with specific antiserum, neutrophil recruitment was significantly reduced, whereas albumin in BAL fluid was not affected. In conclusion, murine KC mediated neutrophil recruitment but not lung injury in a two-hit model of aspiration lung injury.

Systemic perfluorocarbons suppress the acute lung inflammation after gastric acid aspiration in rats

Perflurocarbons (PFCs) are used during liquid ventilation and as hemoglobin substitutes. PFCs reduce free radical generation and damage to the lung during liquid ventilation. Thus, we examined the effects of parenteral administration of PFCs on lung injury after acid aspiration. Rats were treated with intraperitoneal injection of either FC-77 or IV injection of Fluosol. Controls received intraperitoneal or IV normal saline (NS) before or at the time of injury and then were injured by instillation of NS + HCl (pH = 1.25) into their lungs via a tracheotomy. The animals were exposed to air or 98% oxygen, breathing spontaneously. The rats were injected with 0.05 microCi of (125)I-albumin (bovine serum albumin) before injury. The extent of lung injury was assessed 5 h postinjury by compliance and lung albumin permeability index measurement. Myeloperoxidase (MPO) activity and histologic examination were used to assess neutrophilic infiltration. Both FC-77 and Fluosol decreased the permeability index compared with controls (1.05 +/- 0.08; 1.08 +/- 0. 12, respectively, versus 1.34 +/- 0.21) and improved lung compliance after intratracheal instillation of 1.2 mL/kg of HCl/NS, pH = 1.25 + hyperoxia injury (P < 0.05). Lung MPO activity decreased in the FC-77 group and was associated with a concomitant decrease in neutrophil infiltration. MPO activity of the spleen increased after FC-77 treatment. The administration of FC-77 decreased the severity of lung permeability changes associated with acid in the presence or absence of hyperoxia exposure. These data suggest that attenuation of neutrophilic infiltration by PFCs decreases lung injury.

IMPLICATIONS

Intraperitoneally administered perfluorocarbons in rats attenuate the neutrophilic infiltration in the lung after acid aspiration, thereby decreasing the alveolar protein leakage and improving pulmonary compliance.

Hyperoxia synergistically increases TNF-alpha-induced interleukin-8 gene expression in A549 cells

Interleukin (IL)-8 is an important mediator of acute lung injury. Hyperoxia induces IL-8 production in some cell types, but its effect on IL-8 gene expression in respiratory epithelium is not well described. In addition, IL-8 gene expression resulting from the combined effects of hyperoxia and proinflammatory cytokines has not been well characterized. We treated cultured respiratory epithelial-like cells (A549 cells) with hyperoxia alone, tumor necrosis factor (TNF)-alpha alone, or the combination of TNF-alpha and hyperoxia and evaluated IL-8 gene expression. Hyperoxia alone had a minimal effect on IL-8 gene expression, and TNF-alpha alone increased IL-8 gene expression in a time-dependent manner. In contrast, the combination of TNF-alpha and hyperoxia synergistically increased IL-8 gene expression as measured by ELISA (TNF-alpha alone for 24 h = 769 +/- 89 pg/ml vs. hyperoxia + TNF-alpha for 24 h = 1, 189 +/- 89 pg/ml) and Northern blot analyses. Experiments involving IL-8 promoter-reporter assays, electromobility shift assays, and Western blot analyses demonstrated that hyperoxia augmented TNF-alpha-mediated activation of the IL-8 promoter by a nuclear factor (NF)-kappaB-dependent mechanism and increased the duration of NF-kappaB nuclear translocation after concomitant treatment with TNF-alpha. Additional reporter gene assays demonstrated, however, that increased activation of NF-kappaB does not fully account for the synergistic effect of hyperoxia and that the NF-IL-6 site in the IL-8 promoter is also required for the synergistic effect of hyperoxia. We conclude that hyperoxia alone has a minimal effect on IL-8 gene expression but synergistically increases IL-8 gene expression in the presence of TNF-alpha by a mechanism involving cooperative interaction between the transcription factors NF-kappaB and NF-IL-6.

Thrombin upregulates interleukin-8 in lung fibroblasts via cleavage of proteolytically activated receptor-I and protein kinase C-gamma activation

Acute and chronic interstitial lung diseases are accompanied by evidence of inflammation and vascular injury. Thrombin activity in bronchoalveolar lavage fluid from such conditions is often increased, as well as interleukin (IL)-8. We observed that conditioned medium from lung fibroblasts exposed to thrombin has chemotactic activity for polymorphonuclear cells, and that this activity can be abolished by antibody to IL-8. We report that thrombin stimulates expression of IL-8 in human lung fibroblasts on both the messenger RNA and protein levels in a time- and dose-dependent manner. Stimulation of IL-8 expression by thrombin is inhibited by specific thrombin inhibitors. Synthetic thrombin receptor agonist peptide-14 mimics thrombin's stimulation of IL-8 expression in a dose-dependent manner consistent with the idea that upregulation of IL-8 by thrombin in human lung fibroblasts requires cleavage of proteolytically activated receptor-I. We demonstrate further that thrombin-induced IL-8 synthesis is regulated by protein kinase (PK) C. PKC-gamma may be involved in the upregulation of lung fibroblast IL-8 by thrombin because stimulation of lung fibroblasts with thrombin caused significant upregulation of PKC-gamma and because PKC-gamma antisense oligonucleotides inhibited the accumulation of PKC-gamma protein and IL-8 protein. Our data suggest that the PKC-gamma isoform increase observed after thrombin stimulation is required for thrombin-induced IL-8 formation by human lung fibroblasts.

Upregulation of two death pathways of perforin/granzyme and FasL/Fas in septic acute respiratory distress syndrome

Accumulation and activation of inflammatory cells in the lung characterize the acute respiratory distress syndrome (ARDS). However, the precise mechanism for lung epithelial and endothelial cell damage remains unknown. Based on evidence that rapid apoptosis caused by CD8(+) cytolytic T cells can induce pathological cell death, we hypothesized that this mechanism may also participate in the acute lung injury, and attempted to evaluate apoptosis-related factors in bronchoalveolar lavage fluid (BALF) from ARDS patients. Quantitative polymerase chain reaction (PCR) analysis revealed that the messenger ribonucleic acids (mRNAs) for several apoptosis molecules, such as perforin, granzyme A, granzyme B, FasL, and Fas were highly upregulated in the acute phase of ARDS following sepsis. In contrast, low or negligible mRNA expression of these molecules was detected in patients with normal lung function, in septic patients without lung injury (septic non-ARDS), and in patients in the late phase of septic ARDS (late ARDS). While the genes of the classic proinflammatory cytokines interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), IL-6, and IL-8, and inducible nitric oxide synthase (iNOS) were upregulated in septic non-ARDS or late ARDS patients, expressions of these genes in the acute phase of septic ARDS were most distinct. The immunofluorescence flow cytometry showed that only the lymphocyte population in BALF from acute phase of septic ARDS patients expressed perforin and granzyme. The level of soluble FasL in the BALF increased only in the acute ARDS patients. These results thus suggested that the dual apoptosis pathway, perforin/granzyme and FasL/Fas system, is likely to be another participant for the pathogenesis of acute lung injury.

Consensus conference definitions for sepsis, septic shock, acute lung injury, and acute respiratory distress syndrome: time for a reevaluation

Definitions for sepsis, septic shock, acute lung injury (ALI), and acute respiratory distress syndrome (ARDS) were developed by consensus conferences with the goal of achieving standardization of terminology and improved homogeneity of patient populations in clinical studies. Although such definitions have been useful in epidemiologic investigations, the criteria specified by the consensus conferences are broad and insufficiently specific to address the problem of heterogeneous mechanisms leading to clinical syndromes. An important challenge is to progress from clinical syndromes, as presently defined, to more specific entities that are delineated by alterations in specific immunologic or biochemical pathways. Such mechanistic definitions will provide more homogeneous groups of patients who can be identified at early stages of their clinical course. This approach encourages focused investigation of pathways leading to organ system dysfunction and death and, also, provides an efficient framework for the development of new therapies useful in critically ill patients.

Intradermal anti-loxosceles Fab fragments attenuate dermonecrotic arachnidism

OBJECTIVE

Bites from the brown recluse spider and other arachnids from the genus Loxosceles frequently induce necrotic skin lesions that can be recalcitrant to treatment and disfiguring. The authors used a rabbit model of dermonecrotic arachnidism to address the therapeutic efficacy of intradermal (id) polyclonal anti-Loxosceles Fab fragments (alphaLoxd Fab) raised against Loxosceles deserta spider venom.

METHODS

Fab fragments were prepared by papain digestion and affinity chromatography from the IgG fraction of L. deserta antivenom raised in rabbits. Eighteen inbred New Zealand white rabbits were assigned to six groups of three. The rabbits received L. deserta venom (3 microg, id) injections into each flank. Cohorts of rabbits received single id injections (at one venom site/rabbit) of 30 microg alphaLoxd Fab at different times (T = 0, 1, 2, 4, 8, and 12 hours) after venom injection. In each rabbit the opposite flank was left untreated. As an additional control, one group of rabbits (T = 0) received nonspecific Fab (30 microg, id) in the opposite flank. Dermal lesions were quantified as a function of time through the use of a series of digital photographs and imaging software. In addition, myeloperoxidase (MPO) activity, a measure ofneutrophil accumulation, was determined in lesion biopsies. Lesion areas and MPO activities were analyzed by repeated-measures analysis of variance (ANOVA).

RESULTS

Lesion areas and MPO activity were markedly reduced when alphaLoxd Fab was administered very early after venom injections. As the interval between venom inoculation and antivenom treatment increased, the therapeutic benefit of alphaLoxd Fab decreased. The final time tested that demonstrated therapeutic efficacy of alphaLoxd Fab was T = 4 hours. Lesion attenuation was no longer apparent when alphaLoxd Fab was given 8 hours post inoculation.

CONCLUSIONS

Intradermal administration of alphaLoxd Fab attenuates Loxosceles-induced dermonecrotic lesion formation when given up to 4 hours after venom inoculation in this rabbit model.

Membrane attack complex of complement and neutrophils mediate the injury of acid aspiration

A significant role for the alternative complement pathway in acid aspiration has been demonstrated by the observation that C3 genetic knockout mice are protected from injury. Utilizing C5-deficient mice, we now test the role of the terminal complement components in mediating injury. Lung permeability in C5-deficient mice was 64% less than in wild-type animals and was similar to wild-type mice treated with soluble complement receptor type 1, which gave a 67% protection. Injury was fully restored in C5-deficient mice reconstituted with wild-type serum. The role of neutrophils was established in immunodepleted wild-type animals that showed a 58% protection. Injury was further reduced (90%) with the addition of soluble complement receptor type 1, indicating an additive effect of neutrophils and complement. Similarly, an additional protection was noted in C5-deficient neutropenic mice, indicating that neutrophil-mediated injury does not require C5a. Thus acid aspiration injury is mediated by the membrane attack complex and neutrophils. Neutrophil activity is independent of C5a.

Acid-induced lung injury. Protective effect of anti-interleukin-8 pretreatment on alveolar epithelial barrier function in rabbits

Although prior experimental work has demonstrated that anti-interleukin-8 (anti-IL-8) therapy reduces lung endothelial injury after acid instillation, there is no information regarding the effect of anti-IL-8 on the function of the alveolar epithelial barrier after acid-induced lung injury. Therefore, the primary objective of this study was to determine the effect of acid-induced lung injury on the function of the alveolar epithelium, and secondly to determine whether pretreatment with anti-IL-8 attenuates acid-induced injury to the lung epithelial barrier. Hydrochloric acid (pH = 1.5 in 1/3 normal saline) was instilled into the lungs of anesthetized, ventilated rabbits. Anti-IL-8 monoclonal antibody (2 mg/kg) or saline was given intravenously 5 min before acid instillation. Acid instillation into the distal airspaces caused an increase in the alveolar epithelial permeability to protein and an approximately 50% reduction in net alveolar fluid clearance. Because a decrease in net alveolar fluid clearance could be due to lung endothelial injury and increased fluid flux from the blood into the airspaces, additional experiments were carried out in which pulmonary blood flow was eliminated. In the absence of pulmonary blood flow, acid instillation led to a 50% decrease in net alveolar fluid clearance. Pretreatment with anti-IL-8 antibody significantly reduced the acid-mediated increase in bi-directional transport of protein across the alveolar epithelium and restored alveolar fluid clearance to normal. The results indicate that acid instillation causes injury to the alveolar epithelial barrier that can be distinguished from the injury to the lung endothelium. Furthermore, pretreatment with anti-IL-8 therapy prevents acid-induced alveolar epithelial injury, a finding of potential clinical importance.

Interleukin-8 mediates injury from smoke inhalation to both the lung endothelial and the alveolar epithelial barriers in rabbits

Although prior studies have shown that smoke inhalation causes lung endothelial injury and formation of pulmonary edema, there is no information about the effect of smoke inhalation on the function of the alveolar epithelial barrier. Therefore, the primary objective of this study was to determine the effect of smoke-induced lung injury on the alveolar epithelial barrier in a rabbit experimental model. The second objective was to investigate whether pretreatment with a monoclonal anti-interleukin (IL)-8 antibody prevented alveolar epithelial barrier injury after smoke inhalation. Anesthetized rabbits were tracheotomized and were insufflated with cooled smoke generated from burning cotton cloth (75 breaths). In some experiments, anti-IL-8 antibody or an irrelevant antibody (2 mg/¿g) was given intravenously 5 min before insufflation of cotton smoke. Smoke inhalation caused a significant increase in the alveolar epithelial permeability to protein and a 40% reduction in the fluid transport capacity of the alveolar epithelium. Pretreatment with anti-IL-8 antibody, but not with an irrelevant-isotype antibody, significantly reduced the smoke-mediated increase in bidirectional transport of protein across the alveolar epithelium, and restored alveolar liquid clearance to a normal level. The results of the study show that smoke inhalation causes injury to both the alveolar epithelial barrier and the lung endothelium, and that IL-8 is an important mediator of this injury.

Fluoride-induced interleukin-6 and interleukin-8 synthesis in human epithelial lung cells

Exposure to fluorides has been associated with asthmatic symptoms among workers in the aluminium industry. In a recent experimental study hydrogen fluoride (HF) was found to induce a weak inflammatory response in humans. In the present study the potential of sodium fluoride (NaF) and HF to induce cytokine response was examined and how these responses are modulated by Al3+ in a human epithelial lung cell line (A549). Dose-response experiments showed a maximal release of IL-6 and IL-8 at a concentration of 5 mM NaF 24 h after addition. The responses to HF were of a similar magnitude as for NaF. Time-course experiments showed a NaF-induced IL-6 response at 5 h, whereas an IL-8 response was observed after 10 h. Cycloheximide treatment completely abolished the NaF-induced cytokine responses. A marked increase in the mRNA level for IL-6 was observed already 2 h after exposure to 5 mM NaF, and presumably is a prerequisite for the subsequent increase of IL-6. The fluoride-induced effects on IL-6 and IL-8 release were strongly reduced by pretreatment with deferoxamine (an Al3+-chelator), and enhanced by addition of Al3+. This indicates that an AlF4-- complex, a known activator of GTP-binding proteins, is involved in fluoride-induced IL-6 and IL-8 responses in A549 cells.

Platelet-activating factor mediates acid-induced lung injury in genetically engineered mice

Adult respiratory distress syndrome (ARDS) is an acute lung injury of high mortality rate, and the molecular mechanisms underlying it are poorly understood. Acid aspiration-induced lung injury is one of the most common causes of ARDS, characterized by an increase in lung permeability, enhanced polymorphonuclear neutrophil (PMN) sequestration, and respiratory failure. Here, we investigated the role of platelet-activating factor (PAF) and the PAF receptor (PAFR) gene in a murine model of acid aspiration-induced lung injury. Overexpression of the PAFR gene in transgenic mice enhanced lung injury, pulmonary edema, and deterioration of gas exchange caused by HCl aspiration. Conversely, mice carrying a targeted disruption of the PAFR gene experienced significantly less acid-induced injury, edema, and respiratory failure. Nevertheless, the efficiency of PMN sequestration in response to acid aspiration was unaffected by differences in PAFR expression level. The current observations suggest that PAF is involved in the pathogenesis of acute lung injury caused by acid aspiration. Thus, inhibition of this pathway might provide a novel therapeutic approach to acute lung injury, for which no specific pharmaceutical agents are currently available.

High-dose nitric oxide inhalation increases lung injury after gastric aspiration

BACKGROUND

Inhaled nitric oxide is often used in patients with adult respiratory distress syndrome. However, nitric oxide also may be significantly toxic, especially if administered concurrently with hyperoxia. The authors evaluated the isolated effect of nitric oxide and the combined effects of nitric oxide and hyperoxia on lung injury in rats after acid aspiration.

METHODS

Animals were injured by instillation of 1.2 ml/kg hydrogen chloride in low-pH saline (the acid group) or acidified gastric particles (the casp group) into the lungs under halothane anesthesia via a tracheal catheter. Controls received no injury vehicle but rather underwent the surgical process. After recovery from anesthesia, the animals were exposed to 20% or 90% oxygen with or without 20, 40, or 80 ppm nitric oxide for 5 h. The permeability index, alveolar-arterial oxygen difference, the ratio of oxygen pressure to the inspired fraction of oxygen, and the ratio of wet to dry weight were assessed 5 h after injury as indices of lung injury. Data were assessed using analysis of variance.

RESULTS

Each group included 6-10 rats. Exposure to nitric oxide (80 ppm) in air increased protein permeability in the lungs to a permeability index of 1.42+/-0.12 after acid aspiration. The combination of nitric oxide (80 ppm) and hyperoxia further increased protein leakage to a permeability index of 2.1+/-0.25. Exposure to lower concentrations of nitric oxide (e.g., 20 and 40 ppm) increased the permeability index of the lungs (1.44+/-0.21, 1.75+/-0.29, respectively) in the presence of hyperoxia, although it did not affect the permeability index of the lungs during exposure to air. Pretreatment of animals with deferoxamine and methylene blue partially inhibited the adverse effect of hyperoxia and nitric oxide, which suggested a complex underlying mechanism involving both reactive-species generation and pulmonary vasomotor changes.

CONCLUSIONS

These results show that inhaled nitric oxide at 80 ppm for a short duration (5 h) increases the severity of the inflammatory microvascular lung injury after acid aspiration. The pulmonary damage is exacerbated further in the presence of high oxygen concentrations. Although lower concentrations of nitric oxide did not increase the extent of lung injury, longer exposure times need to be assessed.

Interfering with chemokine networks--the hope for new therapeutics

Chemokines are a large family of cytokines with a wide variety of biological actions. Originally, they were identified as controllers of the routine trafficking of immune cells, and directed migration of cells during inflammatory response - from which they get their name, a contraction of chemotactic cytokines. They are now also known to be active in angiogenesis, embryonic development and infection by viruses such as HIV-1. Studies with antibodies, modified chemokine and transgenic mice suggest that chemokine receptor antagonists may be selective anti-inflammatory, antiviral or immunomodulatory agents. Small-molecule antagonists of seven of the receptors have been reported, some with potency in the low nanomolar range. These compounds are shown to be active in cell biology assays; the next step will be to determine their efficacy in animal models of disease.

Intratracheal anti-tumor necrosis factor-alpha antibody attenuates ventilator-induced lung injury in rabbits

To evaluate the role of tumor necrosis factor (TNF)-alpha in the pathogenesis of ventilator-induced lung injury, we 1) measured TNF-alpha production in the lung caused by conventional mechanical ventilation (CMV) and 2) evaluated the protective effect of anti-TNF-alpha antibody (Ab) in saline-lavaged rabbit lungs. After they received saline lung lavage, rabbits were intratracheally instilled with 1 mg/kg of polyclonal anti-TNF-alpha Ab in the high-dose group (n = 6), 0.2 mg/kg of anti-TNF-alpha Ab in the low-dose group (n = 6), serum IgG fraction in the Ab control group (n = 6), and saline in the saline control group (n = 7). Animals then underwent CMV for 4 h. Levels of TNF-alpha in lung lavage fluid were significantly higher after CMV than before in both control groups. Pretreatment with intratracheal instillation of high and low doses of anti-TNF-alpha Ab improved oxygenation and respiratory compliance, reduced the infiltration of leukocytes, and ameliorated pathological findings. CMV led to TNF-alpha production in the lungs, and intratracheal instillation of anti-TNF-alpha Ab attenuated CMV-induced lung injury in this model.

Avoiding cardiopulmonary bypass in multivessel CABG reduces cytokine response and myocardial injury

BACKGROUND

Proinflammatory cytokines play a key role in the inflammatory cascade after cardiopulmonary bypass and may induce cardiac dysfunction. We compared the production of cytokines and the degree of postoperative myocardial injury in patients with multivessel coronary artery disease undergoing coronary artery bypass grafting through median sternotomy with or without cardiopulmonary bypass.

METHODS

Forty-four consecutive patients were studied. Patients were selected for off-pump coronary artery bypass grafting whenever complete revascularization was technically feasible. There were no differences between the two groups with respect to age, sex, symptoms, or functional class. Plasma levels of tumor necrosis factor-alpha, interleukin (IL)-6, IL-8, and IL-10 were measured before the operation, at the end of the procedure, and 2, 4, 8, 24, and 48 hours thereafter. Levels of the MB isoenzyme of creatine kinase and cardiac troponin-I were also measured after the operation.

RESULTS

The number of grafts was 2+/-0.7 in the off-pump group (n = 18) and 3+/-0.8 in the cardiopulmonary bypass group (n = 26). There were no deaths or major complications in either group. Levels of tumor necrosis factor-alpha were low in both groups. No significant intergroup differences were noted regarding serial IL-6 measurements. However, IL-8 and IL-10 levels after the operation were lower in the off-pump group (IL-8, 4+/-1 versus 38+/-12 pg/mL, p < 0.01; IL-10, 5+/-2 versus 191+/-33 pg/mL, p < 0.001). Whereas postoperative creatine kinase-MB values were similar in the two groups, cardiac troponin-I levels were significantly lower in the off-pump group (8 hours, p < 0.005; 24 hours, p < 0.02, respectively). Moreover, cardiac troponin-I values 24 hours after operation correlated strongly with IL-8 levels (r = 0.61, p < 0.005), indicating that the degree of myocardial injury may be related to IL-8 production.

CONCLUSIONS

Compared with conventional coronary artery bypass grafting, coronary revascularization without cardiopulmonary bypass is associated with reduced cytokine responses and less myocardial injury.

The effect of aprotinin on interleukin-8 concentration and leukocyte adhesion molecule expression in an isolated cardiopulmonary bypass system

We examined the effect of aprotinin on the production of interleukin-8 and the expression of leukocyte adhesion molecules in an isolated cardiopulmonary bypass circuit. Five healthy volunteers each donated 500 ml blood which was divided into equal portions (A) and (B). Portion A was treated with aprotinin 250000 kallikrein inactivator units and added to a circuit primed with a further 250000 kallikrein inactivator units. Portion B was simultaneously treated with 25 ml normal saline and added to an aprotinin-free circuit. Samples of blood were taken at donation, after addition of a drug and at 30-min intervals throughout isolated cardiopulmonary bypass. The interleukin-8 increase was smaller in the aprotinin group but the difference between groups was not statistically significant (p > 0.05). In contrast, aprotinin inhibited the cardiopulmonary bypass-induced increase in monocyte (p < 0.05) and granulocyte (p < 0.01) CD18 and the increase in granulocyte, but not monocyte, CD11b (p < 0.05). Cardiopulmonary bypass had little effect on expression of L-selectin. These results confirm that aprotinin attenuates leukocyte activation during isolated cardiopulmonary bypass.

Inhibition of beta-adrenergic-dependent alveolar epithelial clearance by oxidant mechanisms after hemorrhagic shock

Endogenous release of catecholamines is an important mechanism that can prevent alveolar flooding after brief but severe hemorrhagic shock. The objective of this study was to determine whether this catecholamine-dependent mechanism upregulates alveolar liquid clearance after prolonged hemorrhagic shock. Rats were hemorrhaged to a mean arterial pressure of 30-35 mmHg for 60 min and then resuscitated with a 4% albumin solution. Alveolar liquid clearance was measured 5 h later as the concentration of protein in the distal air spaces over 1 h after instillation of a 5% albumin solution into one lung. There was no upregulation of alveolar liquid clearance after prolonged hemorrhagic shock and fluid resuscitation despite a significant increase in plasma epinephrine levels. The intravenous or intra-alveolar administration of exogenous catecholamines did not upregulate alveolar liquid clearance. In contrast, catecholamine-mediated upregulation of alveolar liquid clearance was restored either by depletion of neutrophils with vinblastine, by the normalization of the concentration of reduced glutathione in the alveolar epithelial lining fluid by N-acetylcysteine, or by the inhibition of the conversion from xanthine dehydrogenase to xanthine oxidase. These experiments provide the first in vivo evidence that a neutrophil-dependent oxidant injury to the alveolar epithelium prevents the upregulation of alveolar fluid clearance by catecholamines in the absence of a major alteration in paracellular permeability to protein after prolonged hemorrhagic shock.

Adult respiratory distress syndrome - an update

In adults, acute lung injury or adult respiratory distress syndrome (ARDS) may complicate a wide range of serious medical and surgical conditions, only some of which involve direct pulmonary insult. The characteristic histological feature of ARDS is an intense inflammatory process in the lungs, which may progress to fibrosis. The earliest physiological characteristic is an increase in the protein permeability across the endothelial and epithelial barriers of the lungs. This clinical syndrome is characterized by arterial hypoxaemia and bilateral radiographic infiltrates, which represent protein-rich oedema fluid. In addition there is a neutrophilic and macrophage infiltrate. Pulmonary endothelium is actively involved in the development of ARDS. It alters cell-cell adhesion as the initial step in leucocyte migration which, in turn, changes the permeability that allows protein-rich fluid to move into the interstitium. The quantity of this interstitial oedema may be sufficient to cause bulk flow through the epithelial barrier. There is probably independent epithelial injury. Finally, the endothelium can release and metabolize vasoactive and inflammatory substances, such as endothelins, nitric oxide and cytokines, etc. No single substance is responsible for acute lung injury, but rather a complex interplay exists between diverse pro- and anti-inflammatory mediators.

Aspiration of activated charcoal elicits an increase in lung microvascular permeability

BACKGROUND

Gastric decontamination with orally administered activated charcoal is the recommended treatment for many poisonings. However, ingestion of central nervous system depressants resulting in loss of protective airway reflexes may result in pulmonary aspiration of activated charcoal. Although activated charcoal has been reported to be an inert substance, evidence suggests that pulmonary aspiration of charcoal is associated with lung edema formation and pulmonary compromise. This study tested the hypothesis that intratracheal instillation of activated charcoal disrupts the integrity of the lung microvascular barrier.

METHODS

The capillary filtration coefficient (Kf,c), a sensitive measure of lung microvascular permeability, was determined isogravimetrically prior to and after intratracheal instillation of activated charcoal 0.04 g/kg (12% weight/vol solution, pH 7.4) or an equal volume of sterile water in isolated, perfused rat lungs. Arterial blood gas analysis was determined prior to and after tracheal instillation of activated charcoal or sterile water in a separate group of animals.

RESULTS

Intratracheal instillation of activated charcoal resulted in a significant increase in pulmonary microvascular permeability compared to lungs treated with sterile water or control lungs (delta Kf,c = +0.21 +/- 0.076; -0.014 +/- 0.04; and -0.041 +/- 0.02 mL/min/cm H2O/100 g lung tissue, respectively, p < 0.05 ANOVA). There was no significant difference in baseline blood gases in the 3 experimental groups. There was a significant decrease in arterial Po2, bicarbonate, and pH in animals administered activated charcoal compared to time-matched controls and animals administered sterile water.

CONCLUSIONS

Intratracheal instillation of activated charcoal is associated with a significant increase in lung microvascular permeability and arterial blood gas derangements. The effects of activated charcoal on pulmonary microvascular barrier integrity may contribute to the lung edema formation and pulmonary compromise observed following clinical aspiration of activated charcoal.

Expression and Function of the Chemokine Receptors CXCR1 and CXCR2 in Sepsis

Neutrophils (polymorphonuclear neutrophils; PMN) and a redundant system of chemotactic cytokines (chemokines) have been implicated in the pathogenesis of the acute respiratory distress syndrome in patients with sepsis. PMN express two cell surface receptors for the CXC chemokines, CXCR1 and CXCR2. We investigated the expression and function of these receptors in patients with severe sepsis. Compared with normal donors, CXCR2 surface expression was down-regulated by 50% on PMN from septic patients (p &lt; 0.005), while CXCR1 expression persisted. In vitro migratory responses to the CXCR1 ligand, IL-8, were similar in PMN from septic patients and normal donors. By contrast, the migratory response to the CXCR2 ligands, epithelial cell-derived neutrophil activator (ENA-78) and the growth-related oncogene proteins, was markedly suppressed in PMN from septic patients (p &lt; 0.05). Ab specific for CXCR1 blocked in vitro migration of PMN from septic patients to IL-8 (p &lt; 0.05), but not to FMLP. Thus, functionally significant down-regulation of CXCR2 occurs on PMN in septic patients. We conclude that in a complex milieu of multiple CXC chemokines, CXCR1 functions as the single dominant CXC chemokine receptor in patients with sepsis. These observations offer a potential strategy for attenuating adverse inflammation in sepsis while preserving host defenses mediated by bacteria-derived peptides such as FMLP.

Ischemia-reperfusion lung injury in rabbits: mechanisms of injury and protection

To study the mechanisms responsible for ischemia-reperfusion lung injury, we developed an anesthetized rabbit model in which the effects of lung deflation, lung inflation, alveolar gas composition, hypothermia, and neutrophils on reperfusion pulmonary edema could be studied. Rabbits were anesthetized and ventilated, and the left pulmonary hilum was clamped for either 2 or 4 h. Next, the left lung was reperfused and ventilated with 100% oxygen. As indexes of lung injury, we measured arterial oxygenation, extravascular lung water, and the influx of a vascular protein (131I-labeled albumin) into the extravascular space of the lungs. The principal results were that 1) all rabbits with the deflation of the lung during ischemia for 4 h died of fulminant pulmonary edema within 1 h of reperfusion; 2) inflation of the ischemic lung with either 100% oxygen, air, or 100% nitrogen prevented the reperfusion lung injury; 3) hypothermia at 6-8 degreesC also prevented the reperfusion lung injury; 4) although circulating neutrophils declined during reperfusion lung injury, there was no increase in interleukin-8 levels in the plasma or the pulmonary edema fluid, and, furthermore, neutrophil depletion did not prevent the reperfusion injury; and 5) ultrastructural studies demonstrated injury to both the lung endothelium and the alveolar epithelium after reperfusion in deflated lungs, whereas the inflated lungs had no detectable injury. In summary, ischemia-reperfusion injury to the rabbit lung can be prevented by either hypothermia or lung inflation with either air, oxygen, or nitrogen.

The Role of Leukocyte Emigration and IL-8 on the Development of Lipopolysaccharide-Induced Lung Injury in Rabbits

Leukocyte emigration and alveolar macrophage-derived cytokines may contribute to lung microvascular injury associated with adult respiratory distress syndrome. We have used mAbs against cell adhesion molecules on leukocytes (anti-CD18 and anti-CD49d) or against IL-8 to investigate these contributions. Intratracheal (i.t.) instillation of LPS (50 μg/kg) caused a significant increase in bronchoalveolar lavage polymorphonuclear leukocytes (PMNs) without an increase in mononuclear cells (MNCs) or an increase in lung permeability. Injection of LPS (10 μ/kg) i.v. at 24 h after i.t. LPS caused significant increases in bronchoalveolar lavage PMNs, MNCs, IL-8, and monocyte chemotactic protein-1, as well as increases in lung permeability. Rabbits that were administered i.t. LPS followed by i.v. LPS and treated with anti-CD18 mAb had a significantly lower lung permeability index and emigration of fewer PMNs but no change in MNC emigration compared with saline treatment. Anti-IL-8 mAb treatment resulted in a significantly lower lung permeability index with no change in PMN emigration compared with no treatment. These results suggest that PMN emigration is necessary but not sufficient for the development of LPS-induced lung injury, and that IL-8 plays a significant role in PMN-dependent lung injury, independent of PMN emigration.

Upregulation of alveolar epithelial fluid transport after subacute lung injury in rats from bleomycin

Alveolar epithelial fluid transport was studied 10 days after subacute lung injury had been induced with intratracheal bleomycin (0.75 U). An isosmolar Ringer lactate solution with 5% bovine serum albumin and 125I-labeled albumin as the alveolar protein tracer was instilled into the right lung; the rats were then studied for either 1 or 4 h. Alveolar fluid clearance was increased in bleomycin-injured rats by 110% over 1 h and by 75% over 4 h compared with control rats (P < 0.05). The increase in alveolar fluid clearance was partially inhibited by amiloride (10(-3) M). Alveolar fluid clearance decreased toward normal levels in rats that were studied 60 days after bleomycin instillation. Remarkably, the measured increase in net alveolar fluid clearance occurred in the presence of a significant increase in alveolar epithelial permeability to protein. Moreover, the increase in alveolar epithelial fluid clearance occurred even though the mRNA for the alpha-subunit of the epithelial sodium channel was decreased in alveolar epithelial type II cells isolated from these rats. In addition, 22Na uptake by isolated alveolar epithelial type II cells from rats treated with bleomycin demonstrated a 52% decrease in uptake compared with type II cells from control rats. Morphological results demonstrated a significant hyperplasia of alveolar type II epithelial cells 10 days after bleomycin injury. Thus, these results provide evidence that proliferation of alveolar epithelial type II cells after acute lung injury may upregulate the transport capacity of the alveolar epithelium, even though the expression of epithelial sodium channels is reduced and the uptake of 22Na per cell is also reduced. These results may have clinical relevance for the resolution of alveolar edema in the subacute phase of lung injury.

Definition, function and pathophysiological significance of chemokine receptors

Chemokines and their receptors are at the core of many processes in biology, from routine immunosurveillance and the inflammatory process, through to the infection of cells by HIV. In the past two years, various bioinformatic and cloning strategies have led to an explosion in the number of chemokines and receptors that have been identified. Although the picture is far from complete, several themes are emerging. In particular, there are important differences between observations in vitro, where there appears to be much redundancy, and studies in vivo, where distinct roles are clearer. In this review, Timothy Wells, Christine Power and Amanda Proudfoot discuss the chemokines and their receptors and recent data from immunological and virology studies, and speculate on the potential of interfering with the chemokine network as a useful approach to ameliorating disease.

Inhibition of interleukin-8 blocks myocardial ischemia-reperfusion injury

INTRODUCTION

Interleukin-8 is thought to play a role in neutrophil activation and transcapillary migration into the interstitium. Because neutrophils are principal effector cells in acute myocardial ischemia-reperfusion injury, we postulated that the inhibition of interleukin-8 activity with a neutralizing monoclonal antibody directed against rabbit interleukin-8 (ARIL8.2) would attenuate the degree of myocardial injury encountered during reperfusion.

METHODS

In New Zealand White rabbits, the large branch of the marginal coronary artery supplying most of the left ventricle was occluded for 45 minutes, followed by 2 hours of reperfusion. Fifteen minutes before reperfusion, animals were given an intravenous bolus of either 2 mg/kg of ARIL8.2 or 2 mg/kg anti-glycoprotein-120, an isotype control antibody that does not recognize interleukin-8. At the completion of the 120-minute reperfusion period, infarct size was determined.

RESULTS

In the area at risk for infarction, 44.3% +/- 4% of the myocardium was infarcted in the anti-glycoprotein-120 group compared with 24.8% +/- 9% in the ARIL8.2 group (p < 0.005). In control animals, edema and diffuse infiltration of neutrophils were observed predominantly in the infarct zone and the surrounding area at risk. Tissue myeloperoxidase determinations did not differ significantly between groups, indicating that the cardioprotective effect of ARIL8.2 was independent of an effect on neutrophil infiltration.

CONCLUSIONS

A specific monoclonal antibody that neutralizes interleukin-8 significantly reduces the degree of necrosis in a rabbit model of myocardial ischemia-reperfusion injury.

Alveolar epithelial fluid clearance is mediated by endogenous catecholamines at birth in guinea pigs

Transition from placental to pulmonary oxygenation at birth depends on a rapid removal of fetal lung fluid from the developing alveoli. Alveolar fluid clearance was examined in ventilated, anesthetized developing guinea pigs of the ages newborn, 2-d-old, 5-d-old, 30-d-old, and 60-d-old (adult). An isosmolar 5% albumin solution was instilled into the lungs of the guinea pigs; the guinea pigs were then studied for 1 h. Alveolar fluid clearance was measured from the increase in alveolar protein concentration as water was reabsorbed. Newborn guinea pigs had a very high alveolar fluid clearance rate that declined rapidly within the first 5 postnatal days towards adult levels. The high alveolar fluid clearance at birth was apparently mediated by the beta-adrenergic system as demonstrated by the elevated plasma epinephrine levels and the increased sensitivity to inhibition by the beta-adrenergic antagonist propranolol immediately after birth. Surprisingly, exogenous addition of epinephrine was not able to stimulate alveolar fluid clearance in the newborn lung, but exogenous epinephrine stimulation increased over time to adult levels. The elevated alveolar fluid clearance at birth was associated with a significantly greater amiloride sensitivity in the newborn guinea pig lung. Northern blot analysis of distal lung tissue as well as isolated alveolar epithelial type II cells showed and confirmed higher levels of the alpha-subunit of the epithelial sodium channel mRNA in the newborn lung that rapidly tapered off toward adult levels. In conclusion, these data demonstrate the importance of the beta-adrenergic system and amiloride-sensitive sodium transporting pathways for clearance of fetal lung fluid at birth.

Interleukin-8 (IL-8) and monocyte chemotactic and activating factor (MCAF/MCP-1), chemokines essentially involved in inflammatory and immune reactions

Leukocyte infiltration is a hallmark of inflammation. Knowledge on molecular mechanisms of leukocyte infiltration has advanced rapidly due to the recent elucidation of structures and functions of adhesion molecules and chemokines. Since the discovery of interleukin-8 (IL-8), a prototype of CXC chemokines, in 1987 and monocyte chemotactic and activating factor/monocyte chemoattractant protein-1 (MCAF/MCP-1), a prototype of chemotactic cytokines (CC) chemokines, in 1989, more than 30 members of chemokines have been identified so far. Evidence is accumulating that these chemokines exert overlapping but distinct actions on specific types of leukocytes in vitro through interacting with their specific G-protein-coupled receptors with seven transmembrane domains. However, redundancy at receptor levels has frequently hindered the clarification on the precise physiological or pathophysiological roles of chemokines. Here, we describe the pathophysiological roles of IL-8 and MCAF/MCP-1 in several animal models of neutrophil- and macrophage-mediated inflammation, respectively, by focusing on our recent work using neutralizing antibodies to these chemokines. We discuss further potential roles of these chemokines in T-lymphocyte-mediated immune responses.

Aspiration-Induced Pulmonary Injury

Pulmonary aspiration of gastric contents can cause a spectrum of sequelae that spans from relatively minor to rapidly lethal disease. To emphasize the extent of this spectrum and to encompass both noninfectious complications and infection, we use the term “aspiration-induced pulmonary injury” rather than “aspiration pneumonia.” In this article we review the relevant literature, focusing on more recent insights into the pathogenesis of lung injury, the natural history of aspiration, risk factors, the relationship between aspiration and infection, and recommendations for management. The relevance to human disease of studies using intra-airway acid instillation in animals is questioned. We discuss the difficulties in predicting the clinical course after aspiration. We identify risk factors for aspiration-induced pulmonary injury that are commonly encountered in the intensive care unit, and discuss in detail factors of special interest to the intensivist, including the impact of tracheal intubation; the effects of enteric intubation, particularly the comparison between pre- and postpyloric routes of enteric feeding administration; and the relative risks associated with particular feeding protocols. We conclude with recommendations regarding treatment and prevention strategies.

Molecular cloning and functional characterization of a novel CC chemokine, stimulated T cell chemotactic protein (STCP-1) that specifically acts on activated T lymphocytes

A novel human chemokine STCP-1 (stimulated T cell chemotactic protein) was isolated from an activated macrophage cDNA library. The chemokine has four cysteines positioned in a manner that identifies STCP-1 as a member of the CC chemokine family. The amino acid sequence shows 34% identity with RANTES. The gene consists of 3 exons and 2 introns with the position of intron/exon boundaries similar to that of RANTES. The gene is expressed as a 3.4-kilobase transcript on lymph node, thymus, and Appendix. STCP-1 induces Ca2+ mobilization in a small percentage of primary activated T lymphocytes, but on repeated stimulation the percentage of T lymphocytes that respond to STCP-1 increases. The chemokine STCP-1 does not induce Ca2+ mobilization in monocytes, dendritic cells, neutrophils, eosinophils, lipopolysaccharide-activated B lymphocytes, and freshly isolated resting T lymphocytes. Similarly, STCP-1, while acting as a mild chemoattractant for primary activated T lymphocytes, is a potent chemoattractant for chronically activated T lymphocytes but has no chemoattractant activity for monocytes, neutrophils, eosinophils, and resting T lymphocytes. As STCP-1 acts specifically on activated T lymphocytes, it may play a role in the trafficking of activated/effector T lymphocytes to inflammatory sites and other aspects of activated T lymphocyte physiology.

Experimental murine acid aspiration injury is mediated by neutrophils and the alternative complement pathway

Acid aspiration may result in the development of the acute respiratory distress syndrome, an event associated with significant morbidity and mortality. Although once attributed to direct distal airway injury, the pulmonary failure after acid aspiration is more complex and involves an inflammatory injury mediated by complement (C) and polymorphonuclear leukocytes. This study examines the injurious inflammatory cascades that are activated after acid aspiration. The role of neutrophils was defined by immunodepletion before aspiration, which reduced injury by 59%. The injury was not modified in either P- or E-selectin-knockout mice, indicating that these adhesion molecules were not operative. C activation after aspiration was documented with immunochemistry by C3 deposition on injured alveolar pneumocytes. Animals in which C activation was inhibited with soluble C receptor type 1 (sCR1) had a 54% reduction in injury, similar to the level of protection seen in C3-knockout mice (58%). However C4-knockout mice were not protected from injury, indicating that C activation is mediated by the alternative pathway. Finally, an additive effect of neutrophils and C was demonstrated whereby neutropenic animals that were treated with sCR1 showed an 85% reduction in injury. Thus acid aspiration injury is mediated by neutrophils and the alternative C pathway.

Anti-interleukin-8 monoclonal antibody reduces free radical production and improves hemodynamics and survival rate in endotoxic shock in rabbits

BACKGROUND

Although high levels of interleukin-8 (IL-8) have been found in patients with sepsis and a monoclonal antibody (MoAb) against IL-8 has been successfully used in some animal models of inflammation, no specific therapeutic agent against IL-8 has been tested for the treatment of sepsis. We studied the effects of a MoAb against IL-8 in the treatment of endotoxic shock with a prospective randomized rabbit endotoxic shock model.

METHODS

Twenty New Zealand white rabbits were anesthetized and divided into four groups: normal, anti-IL-8, control-Ab, and lipopolysaccharide (LPS). Anti-IL-8 and control-Ab groups received a MoAb (immunoglobulin G, 3 mg/kg) 5 minutes before the LPS injection. All groups, except the normal group, received a continuous 20-minute infusion of LPS (500 micrograms/kg). The normal group received NaCl (0.9%) rather than LPS.

RESULTS

The 7-day survival rates were 100% for normal group, 80% for anti-IL-8 group, 40% for control-Ab group, and 0% for LPS group. Compared with the LPS group, anti-IL-8 rabbits had a smaller decrease in mean arterial blood pressure (p < 0.05) and increased urinary volume (p < 0.05). Anti-IL-8 rabbits had lower plasmatic levels of IL-1 beta, less free radical production (p < 0.05), and a higher survival rate (p < 0.01).

CONCLUSIONS

IL-8 plays a significant role in endotoxic shock, and IL-8 blockage results in attenuation of the hypotensive and tachypneic effects of LPS, reduced free radical production, and an increased survival rate after lethal endotoxic shock.

Inhibition of CD18 or CD11b attenuates acute lung injury after acid instillation in rabbits

Acid-induced lung injury is mediated primarily by activated neutrophils. Although a prior study demonstrated that acid-induced neutrophil influx into the air spaces was not CD18 dependent, we hypothesized that either a neutralizing anti-CD18 monoclonal antibody (MHM23) or a neutrophil inhibitory factor (NIF), NIF (CD11b,18), might attenuate acid-induced lung injury in rabbits by interfering with neutrophil activation. This hypothesis derived from in vitro stu ies that reported that anti-CD18 therapy prevented tumor necrosis factor-alpha-induced neutrophil activation. Hydrochloric acid (pH = 1.5 in one-third normal saline) or one-third normal saline (4 ml/kg) was instilled into the lungs of ventilated, anesthetized rabbits. The rabbits were studied for 6 h. In acid-instilled rabbits without the anti-CD18 monoclonal antibody or NIF (CD11b,18), severe lung injury developed. In acid-instilled rabbits, pretreatment (5 min before acid) with the anti-CD18 monoclonal antibody (2 mg/kg i.v.) or pretreatment with the NIF (anti-CD11b,18, 10 mg/kg i.v.) prevented 50-70% of acid-induced abnormalities in oxygenation, the increase in extravascular lung water, and extravascular protein accumulation. The anti-CD18 monoclonal antibody was associated with a significant increase in air space neutrophils by bronchoalveolar lavage, suggesting that the neutrophils respond normally to chemotactic stimuli but that the neutrophils did not injure the lung even though they accumulated in the air spaces. In summary, neutralization of CD18 attenuates the acute lung injury after acid instillation without reducing the number of neutrophils in the air spaces, suggesting that anti-CD18 therapy may be beneficial because of its capacity to reduce neutrophil activation.

Regulatory role for macrophage migration inhibitory factor in acute respiratory distress syndrome

Migration inhibitory factor (MIF) is known to exert significant pro-inflammatory effects and has the potential to override the anti-inflammatory action of glucocorticoids. In this study we have identified significant quantities of MIF in the alveolar airspaces of patients with acute respiratory distress syndrome (ARDS). We show in alveolar cells from patients with ARDS that MIF augments pro-inflammatory cytokine secretion (TNF alpha and IL-8), anti-MIF significantly attenuates TNF alpha and IL-8 secretion and MIF overrides, in a concentration-related fashion, the anti-inflammatory effects of glucocorticoids. These findings suggest that MIF may act as a mediator sustaining the pulmonary inflammatory response in ARDS and that an anti-MIF strategy may represent a novel therapeutic approach in inflammatory diseases such as ARDS.

Interleukin 8 as a novel target for intervention therapy in acute inflammatory diseases

Aberrant production of interleukin 8 (IL-8) has been shown in various human inflammatory diseases. Recent investigations in animal models using either blocking antibodies against IL-8 or disruption of the gene encoding the IL-8 receptor have revealed the involvement of IL-8 in the recruitment of neutrophils and in neutrophil-associated tissue injury in acute inflammation. These studies suggest that IL-8 is a novel target to alleviate acute inflammation. This review describes the properties of IL-8 and discusses different therapeutic approaches to target IL-8, particularly the use of humanized monoclonal antibodies against IL-8 and inhibition of IL-8 gene transcription.

Increased interleukin-8 concentrations in the pulmonary edema fluid of patients with acute respiratory distress syndrome from sepsis

OBJECTIVE

To test the hypothesis that significantly higher concentrations of interleukin-8 (IL-8) are found in the pulmonary edema fluid and plasma of patients with a septic vs. a nonseptic etiology of acute respiratory distress syndrome (ARDS).

DESIGN

Prospective measurement of IL-8 concentrations in previously collected edema fluid and plasma.

SETTING

Adult intensive care units at a university medical center.

PATIENTS

There were 27 patients with ARDS (16 patients with a septic etiology and nine patients with a nonseptic etiology) plus eight control patients with hydrostatic pulmonary edema.

MEASUREMENTS AND MAIN RESULTS

IL-8 was present in the pulmonary edema fluid of all patients with ARDS, but the median IL-8 concentration was higher in the edema fluid of patients with ARDS associated with sepsis (84.2 ng/mL, n = 16) compared with the ARDS patients without sepsis (14.8 ng/mL, n = 11) (p < .05). In patients with cardiogenic edema, IL-8 concentration (5.0 ng/mL,n = 8, p < .05) was significantly lower than those values in patients with ARDS. Median plasma concentration of IL-8 was increased in septic individuals (1.3 ng/mL), but these concentrations were not significantly higher than in patients with a nonseptic etiology of ARDS (0.35 ng/mL) (p = .14) or those patients with cardiac failure (0.21 ng/mL).

CONCLUSIONS

The high concentrations of IL-8 in pulmonary edema fluid, coupled with the relatively low concentrations of IL-8 in the plasma, suggest that the lung was the primary source of IL-8 in the patients with ARDS. The markedly increased concentrations of IL-8 in the pulmonary edema fluid of patients with ARDS from sepsis suggests that this group of patients may be particularly suitable for potential trials directed at inhibiting the activity of this important chemokine.

Peptide inhibitor of interleukin-8 (IL-8) reduces staphylococcal enterotoxin-A (SEA) induced neutrophil trafficking to the lung

Staphylococcal enterotoxin A (SEA) is a superantigen, produced by some strains of Staphylococcus aureus (S. aureus), which can cause a variety of clinical manifestations ranging from food poisoning to shock. SEA can also stimulate human alveolar macrophages to produce interleukin-8 (IL-8), a member of the alpha-chemokine subfamily that activates and is chemotactic for neutrophils. In these studies we showed that in rabbits, intravenous SEA significantly decreased the circulating white blood cell population from a baseline value of 6409 +/- 2027 x 10(3) cells/ml to 1943 +/- 862 x 10(3) cells/ml in 7 h. There was a concommitent increase in IL-8 in the circulating plasma (baseline: 60 +/- 34 pg/ml, 7 h post SEA: 109 +/- 64 pg/ml). The increase in circulating IL-8 was accompanied by a much greater increase in the IL-8 concentration of the epithelial lining fluid (ELF) where the IL-8 increased from 0.05 +/- 0.08 ng/ml (control) to 13.8 +/- 9.3 ng/ml (SEA treated). The increase in IL-8 concentration in the alveolar spaces was paralleled by an increase in both the percentage of neutrophils (1.4 +/- 0.9% (control) to 26.0 +/- 10.8% (SEA treated)) and total number of neutrophils (0.04 +/- 0.02 x 10(6)/ml (control) to 4.8 +/- 3.3 10(6)/ml (SEA treated) in the airspaces, and the numbers of neutrophils in the ELF correlated with the IL-8 concentration r = 0.62, p = 0.006). When antileukinate, a hexapeptide which inhibits the binding of IL-8 to neutrophils, was administered to animals receiving SEA, the IL-8 concentration in the ELF (14.8 +/- 10.7 ng/ml) was not significantly different from the concentration of IL-8 in those animals receiving SEA alone). However, both the percentage of neutrophils (9.5 +/- 3.2%), and the total number of neutrophils (1.3 +/- 1.0 x 10(6)/ml) in the ELF following SEA and antileukinate administration was significantly lower than in animals which only received SEA (p < 0.05). The findings suggest that SEA released into the circulation during a Staphylococcal infection can cause an inflammatory reaction in the lung. Since this reaction is at least partially mediated by IL-8, antileukinate may have pharmacologic potential in reducing the inflammatory reaction.