Post-insult treatment with interleukin-1 receptor antagonist decreases oxidative lung injury in rats given intratracheal interleukin-1

Immunotherapy in sepsis - brake or accelerate?

Sepsis, a life threating syndrome characterized by organ failure after infection, is the most common cause of death in hospitalized patients. The treatment of sepsis is generally supportive in nature, involving the administration of intravenous fluids, vasoactive substances and oxygen plus antibiotics to eliminate the pathogen. No drugs have been approved specifically for the treatment of sepsis, and clinical trials of potential therapies have failed to reduce mortality - suggesting that new approaches are needed. Abnormalities in the immune response elicited by the pathogen, ranging from excessive inflammation to immunosuppression, contribute to disease pathogenesis. Although hundreds of immunomodulatory agents are potentially available, it remains unclear which patient benefits from which immune therapy at a given time point. Results indicate the importance of personalized therapy, specifically the need to identify the type of intervention required by each individual patient at a given point in the disease process. To address this issue will require using biomarkers to stratify patients based on their individual immune status. This article reviews recent and ongoing clinical investigations using immunostimulatory or immunosuppressive therapies against sepsis including non-pharmacological and novel preclinical approaches.

Cytokine-Ion Channel Interactions in Pulmonary Inflammation

The lungs conceptually represent a sponge that is interposed in series in the bodies’ systemic circulation to take up oxygen and eliminate carbon dioxide. As such, it matches the huge surface areas of the alveolar epithelium to the pulmonary blood capillaries. The lung’s constant exposure to the exterior necessitates a competent immune system, as evidenced by the association of clinical immunodeficiencies with pulmonary infections. From the in utero to the postnatal and adult situation, there is an inherent vital need to manage alveolar fluid reabsorption, be it postnatally, or in case of hydrostatic or permeability edema. Whereas a wealth of literature exists on the physiological basis of fluid and solute reabsorption by ion channels and water pores, only sparse knowledge is available so far on pathological situations, such as in microbial infection, acute lung injury or acute respiratory distress syndrome, and in the pulmonary reimplantation response in transplanted lungs. The aim of this review is to discuss alveolar liquid clearance in a selection of lung injury models, thereby especially focusing on cytokines and mediators that modulate ion channels. Inflammation is characterized by complex and probably time-dependent co-signaling, interactions between the involved cell types, as well as by cell demise and barrier dysfunction, which may not uniquely determine a clinical picture. This review, therefore, aims to give integrative thoughts and wants to foster the unraveling of unmet needs in future research.

Mortality Benefit of Recombinant Human Interleukin-1 Receptor Antagonist for Sepsis Varies by Initial Interleukin-1 Receptor Antagonist Plasma Concentration

OBJECTIVE

Plasma interleukin-1 beta may influence sepsis mortality, yet recombinant human interleukin-1 receptor antagonist did not reduce mortality in randomized trials. We tested for heterogeneity in the treatment effect of recombinant human interleukin-1 receptor antagonist by baseline plasma interleukin-1 beta or interleukin-1 receptor antagonist concentration.

DESIGN

Retrospective subgroup analysis of randomized controlled trial.

SETTING

Multicenter North American and European clinical trial.

PATIENTS

Five hundred twenty-nine subjects with sepsis and hypotension or hypoperfusion, representing 59% of the original trial population.

INTERVENTIONS

Random assignment of placebo or recombinant human interleukin-1 receptor antagonist × 72 hours.

MEASUREMENTS AND MAIN RESULTS

We measured prerandomization plasma interleukin-1 beta and interleukin-1 receptor antagonist and tested for statistical interaction between recombinant human interleukin-1 receptor antagonist treatment and baseline plasma interleukin-1 receptor antagonist or interleukin-1 beta concentration on 28-day mortality. There was significant heterogeneity in the effect of recombinant human interleukin-1 receptor antagonist treatment by plasma interleukin-1 receptor antagonist concentration whether plasma interleukin-1 receptor antagonist was divided into deciles (interaction p = 0.046) or dichotomized (interaction p = 0.028). Interaction remained present across different predicted mortality levels. Among subjects with baseline plasma interleukin-1 receptor antagonist above 2,071 pg/mL (n = 283), recombinant human interleukin-1 receptor antagonist therapy reduced adjusted mortality from 45.4% to 34.3% (adjusted risk difference, -0.12; 95% CI, -0.23 to -0.01), p = 0.044. Mortality in subjects with plasma interleukin-1 receptor antagonist below 2,071 pg/mL was not reduced by recombinant human interleukin-1 receptor antagonist (adjusted risk difference, +0.07; 95% CI, -0.04 to +0.17), p = 0.230. Interaction between plasma interleukin-1 beta concentration and recombinant human interleukin-1 receptor antagonist treatment was not statistically significant.

CONCLUSIONS

We report a heterogeneous effect of recombinant human interleukin-1 receptor antagonist on 28-day sepsis mortality that is potentially predictable by plasma interleukin-1 receptor antagonist in one trial. A precision clinical trial of recombinant human interleukin-1 receptor antagonist targeted to septic patients with high plasma interleukin-1 receptor antagonist may be worthy of consideration.

Regulation of Lung Epithelial Sodium Channels by Cytokines and Chemokines

Acute lung injury leading to acute respiratory distress (ARDS) is a global health concern. ARDS patients have significant pulmonary inflammation leading to flooding of the pulmonary alveoli. This prevents normal gas exchange with consequent hypoxemia and causes mortality. A thin fluid layer in the alveoli is normal. The maintenance of this thin layer results from fluid movement out of the pulmonary capillaries into the alveolar interstitium driven by vascular hydrostatic pressure and then through alveolar tight junctions. This is then balanced by fluid reabsorption from the alveolar space mediated by transepithelial salt and water transport through alveolar cells. Reabsorption is a two-step process: first, sodium enters via sodium-permeable channels in the apical membranes of alveolar type 1 and 2 cells followed by active extrusion of sodium into the interstitium by the basolateral Na⁺, K⁺-ATPase. Anions follow the cationic charge gradient and water follows the salt-induced osmotic gradient. The proximate cause of alveolar flooding is the result of a failure to reabsorb sufficient salt and water or a failure of the tight junctions to prevent excessive movement of fluid from the interstitium to alveolar lumen. Cytokine- and chemokine-induced inflammation can have a particularly profound effect on lung sodium transport since they can alter both ion channel and barrier function. Cytokines and chemokines affect alveolar amiloride-sensitive epithelial sodium channels (ENaCs), which play a crucial role in sodium transport and fluid reabsorption in the lung. This review discusses the regulation of ENaC via local and systemic cytokines during inflammatory disease and the effect on lung fluid balance.

Hypoxia and sterile inflammation in cystic fibrosis airways: mechanisms and potential therapies

Cystic fibrosis is one of the most common autosomal recessive genetic diseases in Caucasian populations. Diagnosisvianewborn screening and targeted nutritional and antibiotic therapy have improved outcomes, however respiratory failure remains the key cause of morbidity and mortality. Progressive respiratory disease in cystic fibrosis is characterised by chronic neutrophilic airway inflammation associated with structural airway damage leading to bronchiectasis and decreased lung function. Mucus obstruction is a characteristic early abnormality in the cystic fibrosis airway, associated with neutrophilic inflammation often in the absence of detectable infection. Recent studies have suggested a link between hypoxic cell death and sterile neutrophilic inflammation in cystic fibrosis and other diseasesviathe IL-1 signalling pathway. In this review, we consider recent evidence regarding the cellular responses to respiratory hypoxia as a potential driver of sterile neutrophilic inflammation in the lung, current knowledge on hypoxia as a pathogenic mechanism in cystic fibrosis and the potential for current and future therapies to alleviate hypoxia-driven sterile inflammation.

Opposing roles of LTB4 and PGE2 in regulating the inflammasome-dependent scorpion venom-induced mortality

Tityus serrulatus sting causes thousands of deaths annually worldwide. T. serrulatus-envenomed victims exhibit local or systemic reaction that culminates in pulmonary oedema, potentially leading to death. However, the molecular mechanisms underlying T. serrulatus venom (TsV) activity remain unknown. Here we show that TsV triggers NLRP3 inflammasome activation via K(+) efflux. Mechanistically, TsV triggers lung-resident cells to release PGE2, which induces IL-1β production via E prostanoid receptor 2/4-cAMP-PKA-NFκB-dependent mechanisms. IL-1β/IL-1R actions account for oedema and neutrophil recruitment to the lungs, leading to TsV-induced mortality. Inflammasome activation triggers LTB4 production and further PGE2 via IL-1β/IL-1R signalling. Activation of LTB4-BLT1/2 pathway decreases cAMP generation, controlling TsV-induced inflammation. Exogenous administration confirms LTB4 anti-inflammatory activity and abrogates TsV-induced mortality. These results suggest that the balance between LTB4 and PGE2 determines the amount of IL-1β inflammasome-dependent release and the outcome of envenomation. We suggest COX1/2 inhibition as an effective therapeutic intervention for scorpion envenomation.

Increased benefit of interleukin-1 inhibition on vascular function, myocardial deformation, and twisting in patients with coronary artery disease and coexisting rheumatoid arthritis

BACKGROUND

We investigated the effects of anakinra, an interleukin-1 receptor antagonist, on coronary and left ventricular function in coronary artery disease (CAD) patients with rheumatoid arthritis.

METHODS AND RESULTS

In a double-blind crossover trial, 80 patients with rheumatoid arthritis (60 with CAD and 20 without) were randomized to a single injection of anakinra or placebo and after 48 hours to the alternative treatment. At baseline and 3 hours after treatment, we assessed (1) flow-mediated dilation of brachial artery; (2) coronary flow reserve, ejection fraction, systemic arterial compliance, and resistance by echocardiography; (3) left ventricular global longitudinal and circumferential strain, peak twisting, untwisting velocity by speckle tracking; and (4) interleukin-1β, nitrotyrosine, malondialdehyde, protein carbonyl, and Fas/Fas ligand levels. At baseline, patients with CAD had 3-fold higher interleukin-1β, protein carbonyl, higher nitrotyrosine, malondialdehyde, and Fas/Fas ligand than non-CAD (P<0.05). After anakinra, there was a greater improvement of flow-mediated dilation (57±4% versus 47±5%), coronary flow reserve (37±4% versus 29±2%), arterial compliance (20±18% versus 2±17%), resistance (-11±19% versus 9±21%), longitudinal strain (33±5% versus 18±2%), circumferential strain (22±5% versus 13±5%), peak twisting (30±5% versus 12±5%), untwisting velocity (23±5% versus 13±5%), ejection fraction (12±5% versus 0.5±5%), apoptotic and oxidative markers, and, in particular, of protein carbonyl (35±20% versus 14±9%) in CAD than in non-CAD patients (P<0.01). No changes in the examined markers were observed after placebo.

CONCLUSIONS

Interleukin-1 inhibition causes a greater improvement in endothelial, coronary aortic function in addition to left ventricular myocardial deformation and twisting in rheumatoid arthritis patients with CAD than in those without.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01566201.

Lung-derived soluble mediators are pathogenic in ventilator-induced lung injury

Ventilator-induced lung injury (VILI) due to high tidal volume (V(T)) is associated with increased levels of circulating factors that may contribute to, or be markers of, injury. This study investigated if exclusively lung-derived circulating factors produced during high V(T) ventilation can cause or worsen VILI. In isolated perfused mouse lungs, recirculation of perfusate worsened injury (compliance impairment, microvascular permeability, edema) induced by high V(T). Perfusate collected from lungs ventilated with high V(T) and used to perfuse lungs ventilated with low V(T) caused similar compliance impairment and permeability and caused a dose-dependent decrease in transepithelial electrical resistance (TER) across rat distal lung epithelial monolayers. Circulating soluble factors derived from the isolated lung thus contributed to VILI and had deleterious effects on the lung epithelial barrier. These data demonstrate transferability of an injury initially caused exclusively by mechanical ventilation and provides novel evidence for the biotrauma hypothesis in VILI. Mediators of the TER decrease were heat-sensitive, transferable via Folch extraction, and (following ultrafiltration, 3 kDa) comprised both smaller and larger molecules. Although several classes of candidate mediators, including protein cytokines (e.g., tumor necrosis factor-α, interleukin-6, macrophage inflammation protein-1α) and lipids (e.g., eicosanoids, ceramides, sphingolipids), have been implicated in VILI, only prostanoids accumulated in the perfusate in a pattern consistent with a pathogenic role, yet cyclooxygenase inhibition did not protect against injury. Although no single class of factor appears solely responsible for the decrease in barrier function, the current data implicate lipid-soluble protein-bound molecules as not just markers but pathogenic mediators in VILI.

Anakinra (IL-1R antagonist) lowers pulmonary artery pressure in a neonatal surfactant depleted piglet model

In acute respiratory distress syndrome (ARDS) with pulmonary hypertension, interleukin-1 beta (IL-1 beta) and interleukin-8 (IL-8) are involved in the pulmonary inflammatory reaction. The purpose of this study was to determine whether systemic and aerosolized administered IL-1 receptor antagonist (IL-1Ra) Anakinra (Kineret) improves lung mechanics and pulmonary artery pressure in surfactant depleted newborn piglets. After induction of acute lung injury by lung lavage, neonatal piglets received repetitive treatment of either aerosolized IL-1Ra (IL-1Ra-Aerosol) or intravenous IL-1Ra (IL-1Ra-i.v.), or saline solution as control. IL-1Ra given as aerosol or intravenously significantly reduced mean pulmonary artery pressure (MPAP) but did not influence mean systemic arterial pressure (MAP) compared with the control group. IL-1 beta and IL-8 mRNA expressions normalized to beta-actin and hypoxanthine-guanine-phosphoribosyl transferase were significantly reduced in the IL-1Ra-Aerosol group but not in IL-1Ra-i.v. group compared to the control group. The lung injury score was not significantly different between IL-1Ra groups and the control group. Application of aerosolized IL-1Ra reduced MPAP without affecting MAP in a piglet model of surfactant depletion with pulmonary hypertension. Furthermore, there is evidence for reduction of early pro-inflammatory pulmonary reaction.

Inhibition of Interleukin-1 by Anakinra Improves Vascular and Left Ventricular Function in Patients With Rheumatoid Arthritis

Background— Interleukin-1 increases nitrooxidative stress. We investigated the effects of a human recombinant interleukin-1a receptor antagonist (anakinra) on nitrooxidative stress and vascular and left ventricular function.

Methods and Results— In an acute, double-blind trial, 23 patients with rheumatoid arthritis were randomized to receive a single injection of anakinra (150 mg SC) or placebo and, after 48 hours, the alternative treatment. At baseline and 3 hours after the injection, we assessed (1) coronary flow reserve, aortic distensibility, systolic and diastolic (Em) velocity of the mitral annulus, and E to Em ratio (E/Em) using echocardiography; (2) flow-mediated, endothelium-dependent dilation of the brachial artery; and (3) malondialdehyde, nitrotyrosine, interleukin-6, endothelin-1, and C-reactive protein. In a chronic, nonrandomized trial, 23 patients received anakinra and 19 received prednisolone for 30 days, after which all indices were reassessed. Compared with baseline, there was a greater reduction in malondialdehyde, nitrotyrosine, interleukin-6, and endothelin-1 and a greater increase in flow-mediated dilation, coronary flow reserve, aortic distensibility, systolic velocity of mitral annulus, and E/Em after anakinra than after placebo (malondialdehyde −25% versus 9%; nitrotyrosine −38% versus −11%; interleukin-6 −29% versus 0.9%; endothelin-1 −36% versus −11%; flow-mediated dilation 45% versus −9%; coronary flow reserve 29% versus 4%; and aortic distensibility 45% versus 2%; P <0.05 for all comparisons). After 30 days of treatment, the improvement in biomarkers and in vascular and left ventricular function was greater in the anakinra group than in the prednisolone group ( P <0.05).

Conclusions— Interleukin-1 inhibition improves vascular and left ventricular function and is associated with reduction of nitrooxidative stress and endothelin.

Effects of cyclic opening and closing at low- and high-volume ventilation on bronchoalveolar lavage cytokines

OBJECTIVE

To examine the mechanisms of ventilator-induced lung injury at low and high lung volumes.

DESIGN

Prospective, randomized, laboratory study.

SETTING

University research laboratory.

SUBJECTS

Eighty-eight adult male Sprague-Dawley rats.

INTERVENTIONS

Mechanical ventilation using low and high lung volumes.

MEASUREMENTS AND MAIN RESULTS

An ex vivo rat lung model was used. In study I (ventilation at low lung volumes), rat lungs (n = 40) were randomly assigned to various modes of ventilation: a) opening and closing with positive end-expiratory pressure (PEEP; control): tidal volume 7 mL/kg and PEEP 5 cm H2O; b) opening and closing from zero end-expiratory pressure (ZEEP): tidal volume 7 mL/kg and PEEP 0; or c) atelectasis. Peak inspiratory pressure was monitored at the beginning and end of 3 hrs of ventilation. At the end of 3 hrs of ventilation, the lungs were lavaged, and the concentrations of tumor necrosis factor-alpha, macrophage inflammatory protein-2, and interleukin-6 cytokines were measured in the lavage. In study II (ventilation at high volumes), rat lungs (n = 45) were randomly assigned to a) cyclic lung stretch: pressure-controlled ventilation, peak inspiratory pressure 50 cm H2O, and PEEP 8 cm H2O; b) continuous positive airway pressure at 50 cm H2O (CPAP50); or c) CPAP at the mean airway pressure of the cyclic stretch group (CPAP 31 cm H2O). Bronchoalveolar lavage cytokine concentrations (tumor necrosis factor-alpha, macrophage inflammatory protein-2, and interleukin-6) were measured at the end of 3 hrs of ventilation. In the low volume study, there was no difference in bronchoalveolar lavage cytokine concentrations between the PEEP group and the atelectatic group. All cytokines were significantly higher in the ZEEP group compared with the atelectasis group. Macrophage inflammatory protein-2 was significantly higher in the ZEEP group compared with the PEEP group. Lung compliance, as reflected by change in peak inspiratory pressure, was also significantly worse in the ZEEP compared with the PEEP group. In the high-volume study, tumor necrosis factor-alpha and interleukin-6 were significantly higher in the cyclic stretch group compared with the CPAP 31 group. There was no significant difference between the cytokine concentrations in the cyclic stretch group compared with the CPAP 50 group.

CONCLUSION

We conclude that at low lung volumes, cyclic opening and closing from ZEEP leads to greater increases in bronchoalveolar lavage cytokines than atelectasis. With high-volume ventilation, over time, the degree of overdistension is more associated with increases in bronchoalveolar lavage cytokines than cyclic opening and closing alone.

The balance between IL-1 and IL-1Ra in disease

IL-1 is an important mediator of inflammation and tissue damage in multiple organs, both in experimental animal models of disease and in human diseases. The IL-1 family consists of two agonists, IL-1alpha and IL-1beta, two receptors, biologically active IL-1RI and inert IL-1RII, and a specific receptor antagonist, IL-1Ra. The balance between IL-1 and IL-1Ra in local tissues plays an important role in the susceptibility to and severity of many diseases. An allelic polymorphism in the IL-1Ra gene has been associated with a variety of human diseases primarily of epithelial and endothelial cell origin. This association may be secondary to an imbalance in the IL-1 system with enhanced production of IL-1beta and reduced production of the major intracellular isoform of IL-1Ra. Treatment of RA with daily subcutaneous injections of recombinant IL-1Ra protein has been shown to be efficacious. Gene therapy approaches with IL-1Ra are being evaluated for the treatment of RA and other human diseases.

Effect of theophylline on induced sputum inflammatory indices and neutrophil chemotaxis in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by a neutrophilic airway inflammation that can be demonstrated by examination of induced sputum. Theophylline has antiinflammatory effects in asthma, and in the present study we investigated whether a similar effect occurs in COPD patients treated with low doses of theophylline. Twenty-five patients with COPD were treated with theophylline (plasma level of 9-11 mg/L) for 4 weeks in a placebo-controlled, randomized, double-blind crossover study. Theophylline was well tolerated. Induced sputum inflammatory cells, neutrophils, interleukin-8, myeloperoxidase, and lactoferrin were all significantly reduced by about 22% by theophylline. Neutrophils from subjects treated with theophylline showed reduced chemotaxis to N-formyl-met-leu-phe (approximately 28%) and interleukin-8 (approximately 60%). Neutrophils from a healthy donor showed reduced chemotaxis (approximately 30%) to induced sputum samples obtained during theophylline treatment. These results suggest that theophylline has antiinflammatory properties that may be useful in the long-term treatment of COPD.

A prospective study of inflammation markers in patients at risk of indirect acute lung injury

Systemic inflammation triggered by insults like sepsis and acute pancreatitis may play a role in development of indirect acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Because little is known about the course of systemic inflammation on the days preceding diagnosis of ARDS, we prospectively monitored immune inflammatory status in 52 patients at risk and we assessed the presence of ALI and ARDS on day 7 after admission to the intensive care unit. On admission, serum interleukin (IL) 8, IL-6, and soluble IL-2 receptor concentrations were significantly higher in patients with subsequent ALI (n = 18) than in patients without ALI (n = 30). During a 4-day follow-up, IL-8 and IL-6 levels of ALI patients remained high and those of non-ALI patients decreased. None of the markers discriminated ARDS patients (n = 9) from non-ARDS ALI patients (n = 9). Among 11 patients with acute pancreatitis, ALI patients had significantly higher IL-8, IL-6, and phagocyte CD11b expression levels than did non-ALI patients, whereas among 14 patients with massive transfusion, respective findings in ALI and non-ALI patients were comparable. Results give credence to the view that systemic inflammation plays a role in development of ALI triggered by pancreatitis, but not in that by massive transfusion. This finding, if confirmed in studies with sufficient statistical power, suggests that the patients with massive transfusion do not necessarily benefit from novel biotherapies aimed at altering the course of systemic inflammation.

Alveolar type II cell abnormalities and peroxide formation in lungs of rats given IL-1 intratracheally

Acute lung injury (ALI) is characterized by increased lung levels of proinflammatory cytokines, inflammation, oxidative stress, edema, and impaired gas exchange. Notably, ALI patients also exhibit pulmonary surfactant abnormalities, including increased levels of phospholipids in their lung lavages. In the present study, to assess early alterations of the lung surfactant system in ALI, we induced inflammation and acute lung injury in rats by administering interleukin-1alpha (IL-1) intratracheally. Five h after IL-1 instillation, we examined lung tissue ultrastructure by electron microscopy using both routine staining methods and cerium chloride staining to localize hydrogen peroxide (H2O2) histologically. We also measured lung lavage phospholipid levels, lung tissue gamma-glutamyl transpeptidase (GGT) activities (a marker of oxidative stress), and arterial blood oxygen tensions. We observed that lungs of rats given IL-1 intratracheally had increased neutrophil accumulation, increased H2O2 production, and increased alveolar type II (ATII) pneumocyte ultrastructural abnormalities compared to rats given saline intratracheally. Intratracheal instillation of IL-1 also increased phospholipid levels in the bronchoalveolar lavage (BAL), possibly as a consequence of the abnormal discharge of lamellar bodies into the alveolar lumen. In addition, IL-1-insuffated rats had increased lung GGT levels and impaired blood oxygenation compared to saline-insufflated rats. Treatment with mepacrine decreased lung neutrophil accumulation, ultrastructural lung abnormalities, lung lavage phospholipid levels, lung tissue GGT levels, and blood oxygenation impairment in rats given IL-1 intratracheally, suggesting a possible relationship between these events. Our results indicate that IL-1-induced acute lung injury in rats is marked by neutrophil-dependent oxidative stress, ATII cell defects, abnormal discharge of lamellar body phospholipids, and impaired blood oxygenation.

Generation of a transgenic mouse with lung-specific overexpression of the human interleukin-1 receptor antagonist protein

The purpose of the studies described here was to test the hypothesis that overexpression of the human interleukin-1 receptor antagonist (IL-1ra) in the distal airway epithelia of mice would result in amelioration of the inflammatory effects of IL-1alpha. The coding region of the human IL-1ra gene was placed under transcriptional control of the 5' flanking region of the human SP-C gene. Transgenic mice were generated by pronuclear injection of the transgene and identified by Southern blot analysis of genomic DNA. RNA expression of the transgene was confirmed by Northern blot analysis. In order to determine whether expression of the transgene conferred protection against inflammatory stimuli, control and transgenic mice were treated with IL-1alpha by intratracheal instillation. Six hours after treatment, bronchoalveolar lavage was performed, which revealed a statistically significant decrease in the degree of neutrophilia in the transgenic mice as compared with control mice. Furthermore, there was a significant reduction in the whole-lung myeloperoxidase concentration. Reverse transcription-polymerase chain reaction analysis of whole-lung RNA revealed a significant reduction in the messenger RNA/beta-actin ratio of macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-2 in the transgenic animals as compared with controls. The results of these studies indicate that distal airway epithelial cell expression of human IL-1ra results in partial protection from IL-1alpha-induced airway inflammation and injury.

Phagocytes and acute lung injury: dual roles for interleukin-1

Interleukin-1 (IL-1) and neutrophils are increased in lungs of patients with the acute respiratory distress syndrome (ARDS). We found that rats given IL-1 intratracheally rapidly developed lung neutrophil accumulation and a neutrophil-dependent acute edematous lung leak. Lung leak was associated with increased lung lavage cytokine-induced chemoattractant (CINC) levels and increased oxidative stress that was manifested by increased exhaled H2O2 levels and increased lung oxidized glutathione levels. IL-1-induced lung leak was decreased by treatment with superoxide dismutase (SOD), dimethylsulfoxide (DMSO), supercritical fluid-aerosolized vitamin E, interleukin-1-receptor antagonist (IL-1ra), or liposome-associated PGE1 (Lip-PGE1). Importantly, Lip-PGE1 treatment also reduced ventilator dependence in a small clinical study of ARDS patients. Another series of investigations revealed that IL-1 pretreatment could prevent lung leak in rats given IL-1 intratracheally. These findings point to the possible dual effects of IL-1 with respect to the development of acute lung injury.

Tumor necrosis factor induced acute lung leak in rats: less than with interleukin-1

Although local tumor necrosis factor-alpha (TNF) release by alveolar macrophages has been postulated to contribute to the development of acute respiratory distress syndrome (ARDS), the effects of instilling TNF intratracheally on the development of acute lung leak are not known. Our goal was to determine the effect of intratracheally administered TNF on the development of acute lung leak in rats. We found that rats given TNF (500 ng) 5 hours previously intratracheally had increased (p < 0.05) lung lavage cytokine induced neutrophil chemoattractant (CINC) concentrations, lung lavage neutrophils, lung myeloperoxidase (MPO) activity, and lung leak compared to saline-treated control rats. However, all of the responses following TNF instillation were much lower than the responses to interleukin-1 alpha (IL-1) instillation. For example, instilling 50 ng of IL-1 caused 6.4 times the increases in lung lavage CINC concentrations, 15.5 times the increase in lung lavage neutrophils, 3.6 times the increase in lung MPO activity and 3.8 times the increase in lung leak caused by giving 500 ng of TNF intratracheally. Co-treatment with TNF-binding protein decreased both lung MPO and lung leak increases in rats given TNF intratracheally. These observations suggest that locally elevated levels of TNF may induce lung neutrophil recruitment and acute lung leak but that IL-1 is a much more potent agent than TNF in causing lung neutrophil accumulation and lung leak.

Injurious ventilatory strategies increase cytokines and c-fos m-RNA expression in an isolated rat lung model

We examined the effect of ventilation strategy on lung inflammatory mediators in the presence and absence of a preexisting inflammatory stimulus. 55 Sprague-Dawley rats were randomized to either intravenous saline or lipopolysaccharide (LPS). After 50 min of spontaneous respiration, the lungs were excised and randomized to 2 h of ventilation with one of four strategies: (a) control (C), tidal volume (Vt) = 7 cc/kg, positive end expiratory pressure (PEEP) = 3 cm H2O; (b) moderate volume, high PEEP (MVHP), Vt = 15 cc/kg; PEEP = 10 cm H2O; (c) moderate volume, zero PEEP (MVZP), Vt = 15 cc/kg, PEEP = 0; or (d) high volume, zero PEEP (HVZP), Vt = 40 cc/kg, PEEP = 0. Ventilation with zero PEEP (MVZP, HVZP) resulted in significant reductions in lung compliance. Lung lavage levels of TNFalpha, IL-1beta, IL-6, IL-10, MIP-2, and IFNgamma were measured by ELISA. Zero PEEP in combination with high volume ventilation (HVZP) had a synergistic effect on cytokine levels (e.g., 56-fold increase of TNFalpha versus controls). Identical end inspiratory lung distention with PEEP (MVHP) resulted in only a three-fold increase in TNFalpha, whereas MVZP produced a six-fold increase in lavage TNFalpha. Northern blot analysis revealed a similar pattern (C, MVHP < MVZP < HVZP) for induction of c-fos mRNA. These data support the concept that mechanical ventilation can have a significant influence on the inflammatory/anti-inflammatory milieu of the lung, and thus may play a role in initiating or propagating a local, and possibly systemic inflammatory response.

Lisofylline prevents leak, but not neutrophil accumulation, in lungs of rats given IL-1 intratracheally

Interleukin-1 (IL-1) is increased in lung lavages from patients with the acute respiratory distress syndrome, and administering IL-1 intratracheally causes neutrophil accumulation and a neutrophil-dependent oxidative leak in lungs of rats. In the present study, we found that rats pretreated intraperitoneally with lisofylline [(R)-1-(5-hydroxyhexyl)-3, 7-dimethylxanthine (LSF)], an inhibitor of lysophosphatidic acid acyl transferase, which reduces the production of unsaturated phosphatidic acid species, did not develop the lung leak or the related ultrastructural abnormalities that occur after intratracheal administration of IL-1. However, rats pretreated with LSF and then given IL-1 intratracheally did develop the same elevations of lung lavage cytokine-induced neutrophil chemoattractant (CINC) levels and the same increased numbers of lung lavage neutrophils as rats given IL-1 intratracheally. Lungs of rats given IL-1 intratracheally also had increased unsaturated phosphatidic acid and free acyl (linoleate, linolenate) concentrations compared with untreated rats, and these lipid responses were prevented by pretreatment of LSF. Our results reveal that LSF decreases lung leak and lung lipid alterations without decreasing neutrophil accumulation or lung lavage CINC increases in rats given IL-1 intratracheally.

Interleukin-1 stimulates rapid release of cytokine-induced neutrophil chemoattractant (CINC) in rat lungs

We found that intratracheal insufflation of interleukin-1 alpha (IL-1) in rats rapidly increased lung lavage cytokine-induced neutrophil chemoattractant (CINC) concentrations, lung tissue myeloperoxidase (MPO) activity, and lung lavage neutrophil counts, and that CINC elevation preceded the migration of neutrophils into the lung. Further, we found that bolus CINC insufflation increased CINC concentrations in plasma, and we found that alveolar macrophages (AM) in lung tissue selections or AM recovered by lavage from rats given IL-1 intratracheally stained positively for CINC by immunohistochemistry. In addition, incubating rat AM with increasing doses of IL-1 in vitro progressively increased CINC concentrations in the culture medium. Our results suggest that the potent neutrophil chemoattractant CINC is rapidly produced and released by rat AM following challenge with IL-1 in vivo or in vitro, and support the hypothesis that CINC is an important mediator in the development of pulmonary inflammation in the rat.

Tumor necrosis factor induced acute lung leak in rats: less than with interleukin-1

Although local tumor necrosis factor-alpha (TNF) release by alveolar macrophages has been postulated to contribute to the development of acute respiratory distress syndrome (ARDS), the effects of instilling TNF intratracheally on the development of acute lung leak are not known. Our goal was to determine the effect of intratracheally administered TNF on the development of acute lung leak in rats. We found that rats given TNF (500 ng) 5 hours previously intratracheally had increased (p < 0.05) lung lavage cytokine induced neutrophil chemoattractant (CINC) concentrations, lung lavage neutrophils, lung myeloperoxidase (MPO) activity, and lung leak compared to saline-treated control rats. However, all of the responses following TNF instillation were much lower than the responses to interleukin-1 alpha (IL-1) instillation. For example, instilling 50 ng of IL-1 caused 6.4 times the increases in lung lavage CINC concentrations, 15.5 times the increase in lung lavage neutrophils, 3.6 times the increase in lung MPO activity and 3.8 times the increase in lung leak caused by giving 500 ng of TNF intratracheally. Co-treatment with TNF-binding protein decreased both lung MPO and lung leak increases in rats given TNF intratracheally. These observations suggest that locally elevated levels of TNF may induce lung neutrophil recruitment and acute lung leak but that IL-1 is a much more potent agent than TNF in causing lung neutrophil accumulation and lung leak.