Persistent elevation of inflammatory cytokines predicts a poor outcome in ARDS. Plasma IL-1 beta and IL-6 levels are consistent and efficient predictors of outcome over time

Inflammation and immune-related candidate gene associations with acute lung injury susceptibility and severity: a validation study

Introduction

Common variants in genes related to inflammation, innate immunity, epithelial cell function, and angiogenesis have been reported to be associated with risks for Acute Lung Injury (ALI) and related outcomes. We tested whether previously-reported associations can be validated in an independent cohort at risk for ALI.

Methods

We identified 37 genetic variants in 27 genes previously associated with ALI and related outcomes. We prepared allelic discrimination assays for 12 SNPs from 11 genes with MAF>0.05 and genotyped these SNPs in Caucasian subjects from a cohort of critically ill patients meeting criteria for the systemic inflammatory response syndrome (SIRS) followed for development of ALI, duration of mechanical ventilation, and in-hospital death. We tested for associations using additive and recessive genetic models.

Results

Among Caucasian subjects with SIRS (n = 750), we identified a nominal association between rs2069832 in IL6 and ALI susceptibility (OR_adj 1.61; 95% confidence interval [CI], 1.04–2.48, P = 0.03). In a sensitivity analysis limiting ALI cases to those who qualified for the Acute Respiratory Distress Syndrome (ARDS), rs61330082 in NAMPT was nominally associated with risk for ARDS. In terms of ALI outcomes, SNPs in MBL2 (rs1800450) and IL8 (rs4073) were nominally associated with fewer ventilator-free days (VFDs), and SNPs in NFE2L2 (rs6721961) and NAMPT (rs61330082) were nominally associated with 28-day mortality. The directions of effect for these nominal associations were in the same direction as previously reported but none of the associations survived correction for multiple hypothesis testing.

Conclusion

Although our primary analyses failed to statistically validate prior associations, our results provide some support for associations between SNPs in IL6 and NAMPT and risk for development of lung injury and for SNPs in IL8, MBL2, NFE2L2 and NAMPT with severity in ALI outcomes. These associations provide further evidence that genetic factors in genes related to immunity and inflammation contribute to ALI pathogenesis.

Expression of Angiotensin II and Aldosterone in Radiation-induced Lung Injury

OBJECTIVE

Radiation-induced lung injury (RILI) is the most common, dose-limiting complication in thoracic malignancy radiotherapy. Considering its negative impact on patients and restrictions to efficacy, the mechanism of RILI was studied.

METHODS

Wistar rats were locally irradiated with a single dose of 0, 16, and 20 Gy to the right half of the lung to establish a lung injury model. Two and six months after irradiation, the right half of the rat lung tissue was removed, and the concentrations of TGF-β1, angiotensin II, and aldosterone were determined via enzyme-linked immunosorbent assay.

RESULTS

Statistical differences were observed in the expression levels of angiotensin II and aldosterone between the non-irradiation and irradiation groups. Moreover, the expression level of the angiotensin II-aldosterone system increased with increasing doses, and the difference was still observed as time progressed.

CONCLUSIONS

Angiotensin II-aldosterone system has an important pathophysiological function in the progression of RILI.

Anti-inflammatory activity of a novel family of aryl ureas compounds in an endotoxin-induced airway epithelial cell injury model

Background

Despite our increased understanding of the mechanisms involved in acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS), there is no specific pharmacological treatment of proven benefit. We used a novel screening methodology to examine potential anti-inflammatory effects of a small structure-focused library of synthetic carbamate and urea derivatives in a well established cell model of lipopolysaccharide (LPS)-induced ALI/ARDS.

Methodology/Principal Findings

After a pilot study to develop an in vitro LPS-induced airway epithelial cell injury model, a library of synthetic carbamate and urea derivates was screened against representative panels of human solid tumor cell lines and bacterial and fungal strains. Molecules that were non-cytotoxic and were inactive in terms of antiproliferative and antimicrobial activities were selected to study the effects on LPS-induced inflammatory response in an in vitro cell culture model using A549 human alveolar and BEAS-2B human bronchial cells. These cells were exposed for 18 h to LPS obtained from Escherichia coli, either alone or in combination with the test compounds. The LPS antagonists rhein and emodin were used as reference compounds. The most active compound (CKT0103) was selected as the lead compound and the impact of CKT0103 on pro-inflammatory IL-6 and IL-8 cytokine levels, expression of toll-like receptor-4 (TLR4) and nuclear factor kappa B inhibitor alpha (IκBα) was measured. CKT0103 significantly inhibited the synthesis and release of IL-6 and IL-8 induced by LPS. This suppression was associated with inhibition of TLR4 up-regulation and IκBα down-regulation. Immunocytochemical staining for TLR4 and IκBα supported these findings.

Conclusions/Significance

Using a novel screening methodology, we identified a compound – CKT0103 – with potent anti-inflammatory effects. These findings suggest that CKT0103 is a potential target for the treatment of the acute phase of sepsis and sepsis-induced ALI/ARDS.

Effects of a "two-hit" model of organ damage on the systemic inflammatory response and development of laminitis in horses

The role of endotoxemia in the development of laminitis remains unclear. Although systemic inflammation is a risk factor for laminitis in hospitalized horses, experimental endotoxin administration fails to induce the disease. While not sufficient to cause laminitis by itself, endotoxemia might predispose laminar tissue to damage from other mediators during systemic inflammation. In "two-hit" models of organ damage, sequential exposure to inflammatory stimuli primes the immune system and causes exaggerated inflammatory responses during sepsis. Acute laminitis shares many characteristics with sepsis-associated organ failure, therefore an equine "two-hit" sepsis model was employed to test the hypothesis that laminitis develops with increased frequency and severity when repeated inflammatory events exacerbate systemic inflammation and organ damage. Twenty-four light breed mares (10) and geldings (14) with chronic disease conditions or behavioral abnormalities unrelated to laminitis that warranted euthanasia were obtained for the study. Horses were randomly assigned to receive an 8-h intravenous infusion of either lipopolysaccharide (5 ng/kg/h) or saline beginning at -24h, followed by oligofructose (OF; 5 g/kg) via nasogastric tube at 0 h. Euthanasia and tissue collection occurred at Obel grade 2 laminitis, or at 48 h if laminitis had not developed. Liver biopsies were performed at 24h in laminitis non-responders. Blood cytokine gene expression was measured throughout the study period. Lipopolysaccharide and OF administration independently increased mean rectal temperature (P<0.001), heart rate (P=0.003), respiratory rate (P<0.001), and blood interleukin (IL)-1β gene expression (P<0.0016), but responses to OF were not exaggerated in endotoxin-pretreated horses. The laminitis induction rate did not differ between treatment groups and was 63% overall. When horses were classified as laminitis responders and non-responders, area under the blood IL-1β expression curve (P=0.010) and liver and lung gene expression of IL-1β, IL-6, IL-8, IL-10, and tumor necrosis factor-α (P<0.05) were higher in responders following OF administration. The results indicate that endotoxin pretreatment did not enhance responses to OF. However, systemic inflammation was more pronounced in laminitis responders compared to non-responders, and tissue-generated inflammatory mediators could pose a greater risk than those produced by circulating leukocytes.

BLT1-dependent alveolar recruitment of CD4(+)CD25(+) Foxp3(+) regulatory T cells is important for resolution of acute lung injury

RATIONALE

Recent study has demonstrated that CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) present in bronchoalveolar lavage fluid (BALF) contribute to the resolution of an experimental acute lung injury (ALI). However, the molecular mechanism underlying the alveolar recruitment of Treg remains unclear.

OBJECTIVES

To determine the role of BLT1, a chemotactic receptor for leukotriene B4 (LTB4), in Treg recruitment to BALF of LPS-induced ALI.

METHODS

We examined BLT1 expression in mouse and human Tregs and evaluated its role in mediating Treg migration in vitro and in vivo.

MEASUREMENTS AND MAIN RESULTS

We found that BLT1 expression was strongly up-regulated in Tregs on activation, and that BLT1 mediated the migration of activated, but not resting, Tregs toward LTB4 in vitro. LTB4 levels were persistently elevated in BALF of LPS-induced ALI. Blockade of LTB4-BLT1 pathway by administrating antagonists 1 day after LPS exposure significantly decreased BALF Treg numbers and impaired resolution of ALI characterized by persistent BALF protein, neutrophilic infiltrates, and elevated proinflammatory cytokines. Furthermore, there were significantly less BLT1(-/-) Tregs than wild-type Tregs migrating to BALF of LPS-exposed recipient Rag-1(-/-) mice after adoptive transfer (point estimate 299.73; 95% confidence interval, 255.77-343.69; P < 0.00001), and the impaired alveolar recruitment of BLT1(-/-) Tregs caused the inability to restore the resolution of ALI.

CONCLUSIONS

Our findings reveal a novel antiinflammatory role of BLT1 in the resolution of ALI by mediating the alveolar recruitment of Tregs, and indicate that therapies aimed at interrupting the LTB4-BLT1 pathway after ALI onset could be harmful to the resolution of ALI.

The 5-lipoxygenase pathway is required for acute lung injury following hemorrhagic shock

The cellular and biochemical mechanisms leading to acute lung injury (ALI) and subsequent multiple organ failure are only partially understood. To study the potential role of eicosanoids, particularly leukotrienes, as possible mediators of ALI, we used a murine experimental model of ALI induced by hemorrhagic shock after blood removal via cardiac puncture. Neutrophil sequestration, as shown by immunofluorescence and protein leakage into the alveolar space were measured as markers of injury. We used liquid chromatography coupled to tandem mass spectrometry to unequivocally identify several eicosanoids in the bronchoalveolar lavage fluid of experimental animals. MK886, a specific inhibitor of the 5-lipoxygenase (5-LO) pathway, and transgenic mice deficient in 5-LO were used to determine the role of this enzymatic pathway in this model. Leukotriene B4 and leukotriene C4 were consistently elevated in shock-treated mice compared with sham-treated mice. MK886 attenuated neutrophil infiltration and protein extravasation induced by hemorrhagic shock. 5-Lipoxygenase-deficient mice showed reduced neutrophil infiltration and protein extravasation after shock treatment, indicating greatly reduced lung injury. These results support the hypothesis that 5-LO, most likely through the generation of leukotrienes, plays an important role in the pathogenesis of ALI induced by hemorrhagic shock in mice. This pathway could represent a new target for pharmacological intervention to reduce lung damage following severe primary injury.

[Corticosteroid administration for acute respiratory distress syndrome : therapeutic option?]

Despite a number of clinical trials there is still controversy about the role of corticosteroid therapy in acute respiratory distress syndrome (ARDS). In addition recent meta-analyses differed markedly in the conclusions. This review is intended to provide a short practical guide for the clinician. Based on the available literature, high-dose and pre-emptive administration of corticosteroids is hazardous and not indicated. A low-dose corticosteroid regime given for 4 weeks may potentially be helpful and can be considered in acute or unresolved ARDS in less than 14 days after onset of ARDS, if a close infection surveillance program is available, if neuromuscular blockade can be avoided and if a stepwise dose reduction of corticosteroids is performed. The total daily dose at the beginning of treatment should not exceed 2 mg/kg body weight (BW) methylprednisolone.

Circulating IL-6 mediates lung injury via CXCL1 production after acute kidney injury in mice

Serum IL-6 is increased in patients with acute kidney injury (AKI) and is associated with prolonged mechanical ventilation and increased mortality. Inhibition of IL-6 in mice with AKI reduces lung injury associated with a reduction in the chemokine CXCL1 and lung neutrophils. Whether circulating IL-6 or locally produced lung IL-6 mediates lung injury after AKI is unknown. We hypothesized that circulating IL-6 mediates lung injury after AKI by increasing lung endothelial CXCL1 production and subsequent neutrophil infiltration. To test the role of circulating IL-6 in AKI-mediated lung injury, recombinant murine IL-6 was administered to IL-6-deficient mice. To test the role of CXCL1 in AKI-mediated lung injury, CXCL1 was inhibited by use of CXCR2-deficient mice and anti-CXCL1 antibodies in mice with ischemic AKI or bilateral nephrectomy. Injection of recombinant IL-6 to IL-6-deficient mice with AKI increased lung CXCL1 and lung neutrophils. Lung endothelial CXCL1 was increased after AKI. CXCR2-deficient and CXCL1 antibody-treated mice with ischemic AKI or bilateral nephrectomy had reduced lung neutrophil content. In summary, we demonstrate for the first time that circulating IL-6 is a mediator of lung inflammation and injury after AKI. Since serum IL-6 is increased in patients with either AKI or acute lung injury and predicts prolonged mechanical ventilation and increased mortality in both conditions, our data suggest that serum IL-6 is not simply a biomarker of poor outcomes but a pathogenic mediator of lung injury.

Cytochrome b5 and cytokeratin 17 are biomarkers in bronchoalveolar fluid signifying onset of acute lung injury

Acute lung injury (ALI) is characterized by pulmonary edema and acute inflammation leading to pulmonary dysfunction and potentially death. Early medical intervention may ameliorate the severity of ALI, but unfortunately, there are no reliable biomarkers for early diagnosis. We screened for biomarkers in a mouse model of ALI. In this model, inhalation of S. aureus enterotoxin A causes increased capillary permeability, cell damage, and increase protein and cytokine concentration in the lungs. We set out to find predictive biomarkers of ALI in bronchoalveolar lavage (BAL) fluid before the onset of clinical manifestations. A cutting edge proteomic approach was used to compare BAL fluid harvested 16 h post S. aureus enterotoxin A inhalation versus BAL fluid from vehicle alone treated mice. The proteomic PF 2D platform permitted comparative analysis of proteomic maps and mass spectrometry identified cytochrome b5 and cytokeratin 17 in BAL fluid of mice challenged with S. aureus enterotoxin A. Validation of cytochrome b5 showed tropic expression in epithelial cells of the bronchioles. Importantly, S. aureus enterotoxin A inhalation significantly decreased cytochrome b5 during the onset of lung injury. Validation of cytokeratin 17 showed ubiquitous expression in lung tissue and increased presence in BAL fluid after S. aureus enterotoxin A inhalation. Therefore, these new biomarkers may be predictive of ALI onset in patients and could provide insight regarding the basis of lung injury and inflammation.

Effect on extrapulmonary sepsis-induced acute lung injury by hemoperfusion with neutral microporous resin column

The aim of this study was to investigate the effect of neutral microporous resin hemoperfusion on oxygenation improvement, removal of inflammatory cytokines in plasma and bronchoalveolar lavage, and mortality in acute lung injury induced by extrapulmonary sepsis. Forty-six patients with acute lung injury induced by extrapulmonary sepsis were randomized to HA type hemoperfusion treatment (N=25) or standard therapy (N=21). Those undergoing hemoperfusion treatment received HA330 hemoperfusion. We measured the plasma and bronchoalveolar lavage concentrations of TNF-α and IL-1, and the following parameters were compared between the control group and the hemoperfusion group on days 0, 3 and 7: lung injury measurements (arterial oxygen tension/fractional inspired oxygen ratio, lung injury score, chest X-ray score); interstitial edema of lung (extravascular lung water). Duration of mechanical ventilation, hospital, 28-day, and intensive care unit mortality were also observed. Patients treated with HA hemoperfusion showed a significant removal of plasma and bronchoalveolar lavage TNF-α and IL-1 over time while in the study. Patients in the HA group also demonstrated not only significant improvement of PaO2 /FiO2 , but also decreased Lung Injury Score and chest X-ray score at days 3 and 7. Furthermore, the measurements of the arterial oxygen tension/fractional inspired oxygen ratio, lung injury score and extravascular lung water (EVLWI) significantly correlated with and the concentration of cytokines in the plasma (all P<0.05). The HA hemoperfusion treatment group had a significant reduction in duration of mechanical ventilation, length of intensive care unit stay, and intensive care unit mortality. Significant removal of inflammatory cytokines from circulation and lung by hemoperfusion treatment using the HA type cartridge may contribute to the improvement of lung injury and intensive care unit outcome in extrapulmonary septic patients.

Regional pulmonary inflammation in an endotoxemic ovine acute lung injury model

The regional distribution of inflammation during acute lung injury (ALI) is not well known. In an ovine ALI model we studied regional alveolar inflammation, surfactant composition, and CT-derived regional specific volume change (sVol) and specific compliance (sC). 18 ventilated adult sheep received IV lipopolysaccharide (LPS) until severe ALI was achieved. Blood and bronchoalveolar lavage (BAL) samples from apical and basal lung regions were obtained at baseline and injury time points, for analysis of cytokines (IL-6, IL-1β), BAL protein and surfactant composition. Whole lung CT images were obtained in 4 additional sheep. BAL protein and IL-1β were significantly higher in injured apical vs. basal regions. No significant regional surfactant composition changes were observed. Baseline sVol and sC were lower in apex vs. base; ALI enhanced this cranio-caudal difference, reaching statistical significance only for sC. This study suggests that apical lung regions show greater inflammation than basal ones during IV LPS-induced ALI which may relate to differences in regional mechanical events.

Several Cytokines and Protein C Levels with the Apache II Scoring System for Evaluation of Patients with Sepsis

OBJECTIVE

We investigated whether determination IL-6, IL-8, IL-1beta and TNF-alpha at baseline, total protein C (PC) levels at time of admission and 48 hours after initiation could complement the Acute Physiology and Chronic Health Evaluation (APACHE) II scoring system to identify patients with sepsis, severe sepsis or septic shock for clinical outcome.

MATERIAL AND METHODS

The study was carried out prospectively. 60 consecutive patients with sepsis, severe sepsis or septic shock were included. Blood samples were obtained at baseline and 48 hours after initiation. Cytokines and PC levels in plasma were measured with an enzyme-linked immunoabsorbent assay (ELISA). APACHE II score was calculated on admission.

RESULTS

Baseline IL-6 levels and PC levels 48 hours after initiation were predictive of increased mortality (p=0.016, p=0.044 respectively). Baseline IL-6, IL-8 and TNF-alpha baseline levels correlate with the severity of physiologic insult, as determined by the APACHE II score. However, our multiple logistic regression analysis of these did not reveal any predictive value in combination with the APACHE II score.

CONCLUSION

Determination of baseline IL-6 and PC 48 hours after initiation were of predictive value for prognostic evaluation of septic patients, but did not significantly increase predictive power of the APACHE scoring system to identify patients with sepsis for fatal clinical outcome.

Biomarkers in acute lung injury

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) result in high permeability pulmonary edema causing hypoxic respiratory failure with high morbidity and mortality. As the population ages, the incidence of ALI is expected to rise. Over the last decade, several studies have identified biomarkers in plasma and bronchoalveolar lavage fluid providing important insights into the mechanisms involved in the pathophysiology of ALI. Several biomarkers have been validated in subjects from the large, multicenter ARDS clinical trials network. Despite these studies, no single or group of biomarkers has made it into routine clinical practice. New high throughput "omics" techniques promise improved understanding of the biologic processes in the pathogenesis in ALI and possibly new biomarkers that predict disease and outcomes. In this article, we review the current knowledge on biomarkers in ALI.

Obesity is associated with neutrophil dysfunction and attenuation of murine acute lung injury

Although obesity is implicated in numerous health complications leading to increased mortality, the relationship between obesity and outcomes for critically ill patients appears paradoxical. Recent studies have reported better outcomes and lower levels of inflammatory cytokines in obese patients with acute lung injury (ALI)/acute respiratory distress syndrome, suggesting that obesity may ameliorate the effects of this disease. We investigated the effects of obesity in leptin-resistant db/db obese and diet-induced obese mice using an inhaled LPS model of ALI. Obesity-associated effects on neutrophil chemoattractant response were examined in bone marrow neutrophils using chemotaxis and adoptive transfer; neutrophil surface levels of chemokine receptor CXCR2 were determined by flow cytometry. Airspace neutrophilia, capillary leak, and plasma IL-6 were all decreased in obese relative to lean mice in established lung injury (24 h). No difference in airspace inflammatory cytokine levels was found between obese and lean mice in both obesity models during the early phase of neutrophil recruitment (2-6 h), but early airspace neutrophilia was reduced in db/db obese mice. Neutrophils from uninjured obese mice demonstrated diminished chemotaxis to the chemokine keratinocyte cytokine compared with lean control mice, and adoptive transfer of obese mouse neutrophils into injured lean mice revealed a defect in airspace migration of these cells. Possibly contributing to this defect, neutrophil CXCR2 expression was significantly lower in obese db/db mice, and a similar but nonsignificant decrease was seen in diet-induced obese mice. ALI is attenuated in obese mice, and this blunted response is in part attributable to an obesity-associated abnormal neutrophil chemoattractant response.

Mechanical stress induces lung fibrosis by epithelial-mesenchymal transition

OBJECTIVES

Many mechanically ventilated patients with acute respiratory distress syndrome develop pulmonary fibrosis. Stresses induced by mechanical ventilation may explain the development of fibrosis by a number of mechanisms (e.g., damage the alveolar epithelium, biotrauma). The objective of this study was t test the hypothesis that mechanical ventilation plays an important role in the pathogenesis of lung fibrosis.

METHODS

C57BL/6 mice were randomized into four groups: healthy controls; hydrochloric acid aspiration alone; vehicle control solution followed 24 hrs later by mechanical ventilation (peak inspiratory pressure 22 cm H(2)O and positive end-expiratory pressure 2 cm H(2)O for 2 hrs); and acid aspiration followed 24 hrs later by mechanical ventilation. The animals were monitored for up to 15 days after acid aspiration. To explore the direct effects of mechanical stress on lung fibrotic formation, human lung epithelial cells (BEAS-2B) were exposed to mechanical stretch for up to 48 hrs.

MEASUREMENT AND MAIN RESULTS

Impaired lung mechanics after mechanical ventilation was associated with increased lung hydroxyproline content, and increased expression of transforming growth factor-β, β-catenin, and mesenchymal markers (α-smooth muscle actin and vimentin) at both the gene and protein levels. Expression of epithelial markers including cytokeratin-8, E-cadherin, and prosurfactant protein B decreased. Lung histology demonstrated fibrosis formation and potential epithelia-mesenchymal transition. In vitro direct mechanical stretch of BEAS-2B cells resulted in similar fibrotic and epithelia-mesenchymal transition formation.

CONCLUSIONS

Mechanical stress induces lung fibrosis, and epithelia-mesenchymal transition may play an important role in mediating the ventilator-induced lung fibrosis.

Markers of inflammation and coagulation may be modulated by enteral feeding strategy

BACKGROUND

Although enteral nutrition (EN) is provided to most mechanically ventilated patients, the effect of specific feeding strategies on circulating markers of coagulation and inflammation is unknown.

METHODS

Markers of inflammation (tumor necrosis factor [TNF]-α, interleukin [IL]-1β, interferon [IFN]-γ, IL-6, IL-8, IL-10, IL-12) and coagulation (tissue factor [TF], plasminogen activator inhibitor-1) were measured at baseline (n = 185) and 6 days (n = 103) in mechanically ventilated intensive care unit patients enrolled in a randomized controlled study of trophic vs full-energy feeds to test the hypothesis that trophic enteral feeds would be associated with decreases in markers of inflammation and coagulation compared to full-energy feeds.

RESULTS

There were no differences in any of the biomarkers measured at day 6 between patients who were randomized to receive trophic feeds compared to full-energy feeds. However, TF levels decreased modestly in patients from baseline to day 6 in the trophic feeding group (343.3 vs 247.8 pg/mL, P = .061) but increased slightly in the full-calorie group (314.3 vs 331.8 pg/mL). Lower levels of TF at day 6 were associated with a lower mortality, and patients who died had increasing TF levels between days 0 and 6 (median increase of 39.7) compared to decreasing TF levels in patients who lived (median decrease of 95.0, P = .033).

CONCLUSIONS

EN strategy in critically ill patients with acute respiratory failure does not significantly modify inflammation and coagulation by day 6, but trophic feeds may have some modest effects in attenuating inflammation and coagulation.

Complement takes its Toll: an inflammatory crosstalk between Toll-like receptors and the receptors for the complement anaphylatoxin C5a

The innate immune system is responsible for a rapid inflammatory response to pathogens that is essential for the clearance of infections. Although this response is vital, it is nonetheless potentially harmful, and dysregulated inflammation is a feature of many disease states. Thus, the mechanisms that regulate the release of soluble mediators of inflammation are an active focus of investigation. The activation by infections of two key components of the innate immune system, the Toll-like receptors (TLRs) and complement, leading to the release of soluble mediators of inflammation, is critical to microbial killing and clearance. Both TLRs and complement are independently capable of triggering pro-inflammatory responses, but their synergistic interaction resulting from a substantial crosstalk markedly amplifies those responses and may contribute to the pathophysiology of diseases such as sepsis.

Lung Injury Prevention with Aspirin (LIPS-A): a protocol for a multicentre randomised clinical trial in medical patients at high risk of acute lung injury

INTRODUCTION

Acute lung injury (ALI) is a devastating condition that places a heavy burden on public health resources. Although the need for effective ALI prevention strategies is increasingly recognised, no effective preventative strategies exist. The Lung Injury Prevention Study with Aspirin (LIPS-A) aims to test whether aspirin (ASA) could prevent and/or mitigate the development of ALI.

METHODS AND ANALYSIS

LIPS-A is a multicentre, double-blind, randomised clinical trial testing the hypothesis that the early administration of ASA will result in a reduced incidence of ALI in adult patients at high risk. This investigation will enrol 400 study participants from 14 hospitals across the USA. Conditional logistic regression will be used to test the primary hypothesis that early ASA administration will decrease the incidence of ALI.

ETHICS AND DISSEMINATION

Safety oversight will be under the direction of an independent Data and Safety Monitoring Board (DSMB). Approval of the protocol was obtained from the DSMB prior to enrolling the first study participant. Approval of both the protocol and informed consent documents were also obtained from the institutional review board of each participating institution prior to enrolling study participants at the respective site. In addition to providing important clinical and mechanistic information, this investigation will inform the scientific merit and feasibility of a phase III trial on ASA as an ALI prevention agent. The findings of this investigation, as well as associated ancillary studies, will be disseminated in the form of oral and abstract presentations at major national and international medical specialty meetings. The primary objective and other significant findings will also be presented in manuscript form. All final, published manuscripts resulting from this protocol will be submitted to Pub Med Central in accordance with the National Institute of Health Public Access Policy.

Glucocorticoid treatment in acute lung injury and acute respiratory distress syndrome

Experimental and clinical evidence show a strong association between dysregulated systemic inflammation and progression of acute respiratory distress syndrome (ARDS). This article reviews eight controlled studies evaluating corticosteroid treatment initiated before day 14 of ARDS. Available data provide a consistent strong level of evidence for improving outcomes. Treatment was also associated with a markedly reduced risk of death. This low-cost highly effective therapy is well-known, and has a low-risk profile when secondary prevention measures are implemented. The authors recommend prolonged methylprednisolone at 1 mg/kg/d initially in early ARDS, increasing to 2 mg/kg/d after 7 to 9 days of no improvement.

Biomarkers in acute lung injury--marking forward progress

This article reviews the state of the art regarding biomarkers for prediction, diagnosis, and prognosis in acute lung injury. Biomarkers and the goals of biomarker research are defined. Progress along 4 general routes is examined. First, the results of wide-ranging existing protein biomarkers are reported. Second, newer biomarkers awaiting or with strong potential for validation are described. Third, progress in the fields of genomics and proteomics is reported. Finally, given the complexity and number of potential biomarkers, the results of combining clinical predictors with protein and other biomarkers to produce better prognostic and diagnostic indices are examined.

Pathophysiology of acute respiratory distress syndrome. Glucocorticoid receptor-mediated regulation of inflammation and response to prolonged glucocorticoid treatment

Based on molecular mechanisms and physiologic data, a strong association has been established between dysregulated systemic inflammation and progression of ARDS. In ARDS patients, glucocorticoid receptor-mediated down-regulation of systemic inflammation is essential to restore homeostasis, decrease morbidity and improve survival and can be significantly enhanced with prolonged low-to-moderate dose glucocorticoid treatment. A large body of evidence supports a strong association between prolonged glucocorticoid treatment-induced down-regulation of the inflammatory response and improvement in pulmonary and extrapulmonary physiology. The balance of the available data from controlled trials provides consistent strong level of evidence (grade 1B) for improving patient-centered outcomes. The sizable increase in mechanical ventilation-free days (weighted mean difference, 6.58 days; 95% CI, 2.93 -10.23; P<0.001) and ICU-free days (weighted mean difference, 7.02 days; 95% CI, 3.20-10.85; P<0.001) by day 28 is superior to any investigated intervention in ARDS. The largest meta-analysis on the subject concluded that treatment was associated with a significant risk reduction (RR=0.62, 95% CI: 0.43-0.91; P=0.01) in mortality and that the in-hospital number needed to treat to save one life was 4 (95% CI 2.4-10). The balance of the available data, however, originates from small controlled trials with a moderate degree of heterogeneity and provides weak evidence (grade 2B) for a survival benefit. Treatment decisions involve a tradeoff between benefits and risks, as well as costs. This low cost highly effective therapy is familiar to every physician and has a low risk profile when secondary prevention measures are implemented.

Surfactant administration prior to one lung ventilation: physiological and inflammatory correlates in a piglet model

OBJECTIVES

To test the hypothesis that surfactant, when given prophylactically during one lung ventilation (OLV), improves physiological stability and reduces inflammation.

METHODS

Prospective controlled animal study. After 30 min of mechanical ventilation, surfactant was administered to the left lung of the treatment group. Right lung mechanical ventilation continued for 3 hr, after which the left lung was unblocked. Bilateral mechanical ventilation was continued for 30 min thereafter. Physiological parameters and biomarkers of inflammation in plasma, lung tissue homogenates, and bronchoalveolar lavage (BAL) were measured.

MEASUREMENTS AND MAIN RESULTS

Oxygenation improved in the surfactant group, reaching statistical significance at 3 hr of OLV and again after 30 min of bilateral mechanical ventilation following the OLV. Plasma levels of interleukin (IL)-1 β, IL-6, and tumor necrosis factor (TNF)-α showed a trend for reduction. The lung homogenates from the ventilated lungs had significantly lower levels of IL-1 β (P < 0.01) and IL-6 (P < 0.01). The BAL specimen showed an overall reduction in the cytokine levels; IL-1 β was significantly lower in the ventilated lungs (P < 0.01).

CONCLUSIONS

Surfactant administration improves oxygenation and decreases inflammation, as evidenced by a decrease in several inflammatory cytokines both in the plasma and lungs of a piglet model of OLV.

Regulation and function of the two-pore-domain (K2P) potassium channel Trek-1 in alveolar epithelial cells

Hyperoxia can lead to a myriad of deleterious effects in the lung including epithelial damage and diffuse inflammation. The specific mechanisms by which hyperoxia promotes these pathological changes are not completely understood. Activation of ion channels has been proposed as one of the mechanisms required for cell activation and mediator secretion. The two-pore-domain K(+) channel (K2P) Trek-1 has recently been described in lung epithelial cells, but its function remains elusive. In this study we hypothesized that hyperoxia affects expression of Trek-1 in alveolar epithelial cells and that Trek-1 is involved in regulation of cell proliferation and cytokine secretion. We found gene expression of several K2P channels in mouse alveolar epithelial cells (MLE-12), and expression of Trek-1 was significantly downregulated in cultured cells and lungs of mice exposed to hyperoxia. Similarly, proliferation cell nuclear antigen (PCNA) and Cyclin D1 expression were downregulated by exposure to hyperoxia. We developed an MLE-12 cell line deficient in Trek-1 expression using shRNA and found that Trek-1 deficiency resulted in increased cell proliferation and upregulation of PCNA but not Cyclin D1. Furthermore, IL-6 and regulated on activation normal T-expressed and presumably secreted (RANTES) secretion was decreased in Trek-1-deficient cells, whereas release of monocyte chemoattractant protein-1 was increased. Release of KC/IL-8 was not affected by Trek-1 deficiency. Overall, deficiency of Trek-1 had a more pronounced effect on mediator secretion than exposure to hyperoxia. This is the first report suggesting that the K(+) channel Trek-1 could be involved in regulation of alveolar epithelial cell proliferation and cytokine secretion, but a direct association with hyperoxia-induced changes in Trek-1 levels remains elusive.

Nicotine exerts an anti-inflammatory effect in a murine model of acute lung injury

Activation of the cholinergic anti-inflammatory pathway through direct activation of nicotinic acetylcholine receptors on immune cells can inhibit pro-inflammatory chemokine and cytokine release and thereby protect in a variety of inflammatory diseases. The aim of this study was to investigate whether nicotine treatment protected against acute lung inflammation. Mice challenged with intratracheal lipopolysaccharide (LPS, 50 μg) were treated with nicotine (0.2 or 0.4 mg/kg, sc). After 24 h, bronchoalveolar lavage fluid (BALF) was obtained to measure leukocyte infiltration, lung edema, and pro-inflammatory chemokine (MIP-1α, MIP-2, and eotaxin) and cytokine (IL-1, IL-6, and TNF-α) levels. Nicotine treatment reduced the LPS-mediated infiltration of leukocytes and edema as evidenced by decreased BALF inflammatory cells, myeloperoxidase, and protein. Nicotine also downregulated lung production of pro-inflammatory chemokines and cytokines. These data support the proposal that activation of the cholinergic anti-inflammatory pathway may represent a useful addition to the therapy of acute respiratory distress syndrome.

Role of human recombinant activated protein C and low dose corticosteroid therapy in sepsis

Despite advances in modern medicine, sepsis remains a complex syndrome that has been associated with significant morbidity and mortality. Multiple organ failure associated with sepsis leads to high mortality and morbidity. About 28 - 50% deaths have been reported in patients with sepsis. The number of sepsis patients is increasing, with considerable burden on healthcare facilities. Various factors leading to a rise in the incidence of sepsis are (1) Improvement of diagnostic procedures (2) Increase in the number of immunocompromised patients taking treatment for various autoimmune disease, carcinomas, organ transplantation (3) Advances in intensive procedures (4) Nosocomial infections (5) Extensive use of antibiotics. With the better understanding of sepsis various modalities to modify pathophysiological response of septic patients have developed. Activated protein C and low-dose corticosteroid therapy have been tried in patients, with variable results.

Coagulation, fibrinolysis and cytokine responses to intramedullary nailing of the femur: an experimental study in pigs comparing traditional reaming and reaming with a one-step reamer-irrigator-aspirator system

INTRODUCTION

Operations in trauma patients represent a second insult and the extent of the surgical procedures influences the magnitude of the inflammatory response. Our hypothesis was that a reamer-irrigator-aspirator (RIA) system would cause a lesser inflammatory response than traditional reaming (TR).

MATERIALS AND METHODS

Coagulation, fibrinolysis and cytokine responses were studied in Norwegian landrace pigs during and after intramedullary nailing (IMN) with two different reaming systems using ELISA and chromogenic peptide substrate assays. The TR (n=8) and the RIA (n=7) reaming systems were compared to a control group (n=7). The animals were followed for 72 h. Arterial, mixed venous and femoral vein blood were withdrawn simultaneously peroperatively and until 2 h after the nail was inserted for demonstration of local, pulmonary and systemic activation of the cascade systems. At 6 h, 24 h, 48 h and 72 h postoperatively arterial blood samples were withdrawn.

RESULTS

Significantly procedure-related increased levels were found for thrombin-antithrombin (TAT) and tissue plasminogen activator (t-PA) in the TR group and TAT in the RIA group. The local and the pulmonary activation of coagulation and fibrinolysis were more pronounced in the TR than in the RIA group, the difference reached significance for plasminogen activator inhibitor-1 (PAI-1) (arterial blood). The cytokine response, mainly represented by IL-6 increase, was more pronounced in the TR than the RIA group, and was significant for IL-6 in femoral vein blood. The arterial levels of IL-6 exceeded the mixed venous levels indicating an additional pulmonary activation of IL-6. Two animals in the TR group, who died of pulmonary embolism (PE) prior to planned study end point, had a more pronounced response compared to the rest of the TR group.

CONCLUSION

A procedure-related coagulation and fibrinolytic response was demonstrated in both reaming groups, with more pronounced response in the TR than in the RIA group. Elevated levels of cytokines were demonstrated related to reaming and nailing, with significantly higher IL-6 levels in the TR than in the RIA group.

Biomarkers in acute lung injury: insights into the pathogenesis of acute lung injury

Studies of potential biomarkers of acute lung injury (ALI) have provided information relating to the pathophysiology of the mechanisms of lung injury and repair. The utility of biomarkers remains solely among research tools to investigate lung injury and repair mechanisms. Because of lack of sensitivity and specificity, they cannot be used in decision making in patients with ALI or acute respiratory distress syndrome. The authors reviewed known biomarkers in context of their major biologic activity. The continued interest in identifying and studying biomarkers is relevant, as it provides information regarding the mechanisms involved in lung injury and repair and how this may be helpful in identifying and designing future therapeutic targets and strategies and possibly identifying a sensitive and specific biomarker.

Does Vitamin E and C Supplementation Improve the Recovery From Anterior Cruciate Ligament Surgery?

Muscular (quadriceps) weakness is a predominant impairment that follows anterior cruciate ligament injury and surgery. This continued weakness impairs activities of daily living and could predispose patients to adverse conditions later in life, such as knee osteoarthritis. Vitamins E and C have potent antioxidant and anti-inflammatory activity. Herein, the authors summarize the state-of-the science and suggest directions for future research endeavors regarding the therapeutic influence of vitamins E and C, or other antioxidants, on the recovery from anterior cruciate ligament injury and surgery.

Characterization of TNF receptor subtype expression and signaling on pulmonary endothelial cells in mice

TNF plays a crucial role in the pathogenesis of acute lung injury. However, the expression profile of its two receptors, p55 and p75, on pulmonary endothelium and their influence on TNF signaling during lung microvascular inflammation remain uncertain. Using flow cytometry, we characterized the expression profile of TNF receptors on the surface of freshly harvested pulmonary endothelial cells (PECs) from mice and found expression of both receptors with dominance of p55. To investigate the impact of stimulating individual TNF receptors, we treated wild-type and TNF receptor knockout mice with intravenous TNF and determined surface expression of adhesion molecules (E-selectin, VCAM-1, ICAM-1) on PECs by flow cytometry. TNF-induced upregulation of all adhesion molecules was substantially attenuated by absence of p55, whereas lack of p75 had a similar but smaller effect that varied between adhesion molecules. Selective blockade of individual TNF receptors by specific antibodies in wild-type primary PEC culture confirmed that the in vivo findings were due to direct effects of TNF receptor inhibition on endothelium and not other cells (e.g., circulating leukocytes). Finally, we found that PEC surface expression of p55 dramatically decreased in the early stages of endotoxemia following intravenous LPS, while no change in p75 expression was detected. These data demonstrate a crucial in vivo role of p55 and an auxiliary role of p75 in TNF-mediated adhesion molecule upregulation on PECs. It is possible that the importance of the individual receptors varies at different stages of pulmonary microvascular inflammation following changes in their relative expression.

Glyburide is anti-inflammatory and associated with reduced mortality in melioidosis

Patients with diabetes have better survival from septic melioidosis than patients who without diabetes. This difference was seen only in patients taking glyburide prior to presentation and was associated with an anti-inflammatory effect of glyburide.

Background. Patients with diabetes mellitus are more prone to bacterial sepsis, but there are conflicting data on whether outcomes are worse in diabetics after presentation with sepsis. Glyburide is an oral hypoglycemic agent used to treat diabetes mellitus. This K_ATP-channel blocker and broad-spectrum ATP-binding cassette (ABC) transporter inhibitor has broad-ranging effects on the immune system, including inhibition of inflammasome assembly and would be predicted to influence the host response to infection.

Methods. We studied a cohort of 1160 patients with gram-negative sepsis caused by a single pathogen (Burkholderia pseudomallei), 410 (35%) of whom were known to have diabetes. We subsequently studied prospectively diabetics with B. pseudomallei infection (n = 20) to compare the gene expression profile of peripheral whole blood leukocytes in patients who were taking glyburide against those not taking any sulfonylurea.

Results. Survival was greater in diabetics than in nondiabetics (38% vs 45%, respectively, P = .04), but the survival benefit was confined to the patient group taking glyburide (adjusted odds ratio .47, 95% confidence interval .28–.74, P = .005). We identified differential expression of 63 immune-related genes (P = .001) in patients taking glyburide, the sum effect of which we predict to be antiinflammatory in the glyburide group.

Conclusions. We present observational evidence for a glyburide-associated benefit during human melioidosis and correlate this with an anti-inflammatory effect of glyburide on the immune system.

Genomics of Acute Lung Injury and Vascular Barrier Dysfunction

Acute lung injury (ALI) is a devastating ­syndrome of diffuse alveolar damage that develops via a variety of local and systemic insults such as sepsis, trauma, ­pneumonia, and aspiration. It is interestingly to note that only a subset of individuals exposed to potential ALI-inciting insults develop the disorder and the severity of the disease varies from complete resolution to death. In addition, ALI susceptibility and severity are also affected by ethnicity as evidenced by the higher mortality rates observed in African-American ALI patients compared with other ethnic groups in the USA. Moreover, marked differences in strain-specific ALI responses to inflammatory and injurious agents are observed in preclinical animal models. Together, these observations strongly indicate genetic components to be involved in the pathogenesis of ALI. The identification of genes contributing to ALI would potentially provide a better understanding of ALI pathobiology, yield novel biomarkers, identify individuals or populations at risk, and prove useful for the development of novel and individualized therapies. Genome-wide searches in animal models have identified a number of quantitative trait loci that associate with ALI susceptibility. In this chapter, we utilize a systems biology approach combining cellular signaling pathway analysis with population- based association studies to review established and suspected candidate genes that contribute to dysfunction of endothelial cell barrier integrity and ALI susceptibility.

Using Complementary and Alternative Medicines to Target the Host Response during Severe Influenza

It is now accepted that an overwhelming inflammatory response is the cause of human deaths from avian H5N1 influenza infection. With this in mind we sought to examine the literature for examples of complementary and alternative medicines that reduce inflammation, and to place the results of this search in the context of our own work in a mouse model of influenza disease, using a pharmaceutical agent with anti-inflammatory properties. Two Chinese herbs, Angelica sinensis (Dang Gui) and Salvia miltiorrhiza (Danshen), have been recently shown to protect mice during lethal experimental sepsis via inhibition of the novel inflammatory cytokine High Mobility Group Box 1 protein (HMGB1). Biochanin A, a ligand of the peroxisome proliferator activated receptors (PPAR) alpha and gamma and the active isoflavone in Trifolium pratense (red clover), has anti-inflammatory properties, and thus could be used as an influenza treatment. This is of great interest since we have recently shown that gemfibrozil, a drug used to treat hyperlipidemia in humans and a synthetic ligand of PPAR alpha, significantly reduces the mortality associated with influenza infections in mice. The inflammation-modulating abilities of these natural agents should be considered in light of what is now known about the mechanisms of fatal influenza, and tested as potential candidates for influenza treatments in their own right, or as adjunct treatments to antivirals.

The neuronal guidance protein netrin-1 reduces alveolar inflammation in a porcine model of acute lung injury

Introduction

Acute lung injury (ALI) is an inflammatory disorder of pulmonary or extrapulmonary origin. We have previously demonstrated that netrin-1 dampens murine ALI, and in an attempt to advance this finding into future clinical practice we evaluated whether netrin-1 would reduce alveolar inflammation during porcine ALI.

Methods

This was a controlled in vivo experimental study in pigs. We induced ALI through lipoploysaccharide (LPS) infusion (50 μg/kg) for 2 hours. Following this, we exposed animals to either vehicle, intravenous netrin-1 (netrin-1 i.v.) or inhaled netrin-1 (netrin-1 inh.). Serum samples and bronchoalveolar lavage (BAL) were obtained to determine levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, interleukin-6 and interleukin-8 at baseline and 6 hours following treatment. Myeloperoxidase activity (MPO) and protein levels were determined in the BAL, and tissue samples were obtained for histological evaluation. Finally, animals were scanned with spiral CT.

Results

Following LPS infusion, animals developed acute pulmonary injury. Serum levels of TNF-α and IL-6 were significantly reduced in the netrin-1 i.v. group. BAL demonstrated significantly reduced cytokine levels 6 hours post-netrin-1 treatment (TNF-α: vehicle 633 ± 172 pg/ml, netrin-1 i.v. 84 ± 5 pg/ml, netrin-1 inh. 168 ± 74 pg/ml; both P < 0.05). MPO activity and protein content were significantly reduced in BAL samples from netrin-1-treated animals. Histological sections confirmed reduced inflammatory changes in the netrin-1-treated animals. Computed tomography corroborated reduced pulmonary damage in both netrin-1-treated groups.

Conclusions

We conclude that treatment with the endogenous anti-inflammatory protein netrin-1 reduces pulmonary inflammation during the initial stages of ALI and should be pursued as a future therapeutic option.

Urine interleukin-6 is an early biomarker of acute kidney injury in children undergoing cardiac surgery

Introduction

Interleukin-6 (IL-6) is a proinflammatory cytokine that increases early in the serum of patients with acute kidney injury (AKI). The aim of this study was to determine whether urine IL-6 is an early biomarker of AKI and determine the source of urine IL-6. Numerous proteins, including cytokines, are filtered by the glomerulus and then endocytosed and metabolized by the proximal tubule. Since proximal tubule injury is a hallmark of AKI, we hypothesized that urine IL-6 would increase in AKI due to impaired proximal tubule metabolism of filtered IL-6.

Methods

Urine was collected in 25 consecutive pediatric patients undergoing cardiac bypass surgery (CPB). AKI was defined as a 50% increase in serum creatinine at 24 hours (RIFLE (Risk, Injury, Failure, Loss, End stage), R). Mouse models of AKI and freshly isolated proximal tubules were also studied.

Results

Urine IL-6 increased at six hours in patients with AKI versus no AKI (X² = 8.1750; P < 0.0042). Urine IL-6 > 75 pg/mg identified AKI with a sensitivity of 88%. To assess whether increased urine IL-6 occurs in functional versus structural renal failure, mouse models of pre-renal azotemia after furosemide injection (no tubular injury), ischemic AKI (tubular injury) and cisplatin AKI (tubular injury) were studied. Urine IL-6 did not significantly increase in pre-renal azotemia but did increase in ischemic and cisplatin AKI. To determine if circulating IL-6 appears in the urine in AKI, recombinant human (h)IL-6 was injected intravenously and urine collected for one hour; urine hIL-6 increased in ischemic AKI, but not pre-renal azotemia. To determine the effect of AKI on circulating IL-6, serum hIL-6 was determined one hour post-intravenous injection and was increased in ischemic AKI, but not pre-renal azotemia. To directly examine IL-6 metabolism, hIL-6 was added to the media of normal and hypoxic isolated proximal tubules; hIL-6 was reduced in the media of normal versus injured hypoxic proximal tubules.

Conclusions

Urine IL-6 increases early in patients with AKI. Animal studies demonstrate that failure of proximal tubule metabolism of IL-6 results in increased serum and urine IL-6. Impaired IL-6 metabolism leading to increased serum IL-6 may contribute to the deleterious systemic effects and increased mortality associated with AKI.

The association between BMI and plasma cytokine levels in patients with acute lung injury

BACKGROUND

Obesity is associated with poor outcomes in many diseases, although recent data suggest that acute lung injury (ALI) is an exception. This is particularly interesting because obesity is marked by increased levels of proinflammatory mediators associated with increased morbidity and mortality in ALI. We hypothesized that cytokine response might be attenuated in patients who are obese and critically ill or that obesity might modify the relationship between plasma cytokines and clinical outcomes in ALI.

METHODS

We analyzed plasma biomarker levels (interleukin [IL]-6, IL-8, tumor necrosis factor-alpha receptor 1, surfactant protein D [SP-D], soluble intracellular adhesion molecule, von Willebrand factor (vWF), protein C, and plasminogen activator inhibitor-1) collected at baseline and day 3 in 1,409 participants in prior National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome Network (ARDSNet) trials. BMI was calculated for each patient, and associations with cytokine levels and ventilator-free days (VFDs), organ failure-free days (OFDs), and mortality were investigated in regression models adjusting for confounders.

RESULTS

In adjusted analyses, plasma IL-6 (P = .052), IL-8 (P = .001), and SP-D (P < .001) were inversely related to BMI, whereas vWF (P = .001) and WBC count (P = .042) increased proportionally with BMI. BMI was not associated with increased morbidity or mortality and did not modify the association between baseline biomarker levels and mortality, VFDs, or OFDs.

CONCLUSIONS

Patients who are obese and have ALI have lower levels of several proinflammatory cytokines, suggesting that the inflammatory response may be altered in patients with ALI and a high BMI. Lower SP-D but higher vWF suggests decreased epithelial and increased endothelial injury in the lung of patients who are obese. Mechanisms by which obesity may modulate innate immunity in critical illness are unclear, and future studies should elucidate such mechanisms.

Prolonged glucocorticoid treatment and secondary prevention in acute respiratory distress syndrome

Experimental and clinical evidence has demonstrated a strong association between dysregulated systemic inflammation and progression of acute respiratory distress syndrome (ARDS). In ARDS, glucocorticoid receptor-mediated downregulation of inflammation is essential to restore homeostasis and decrease morbidity and mortality. We review the findings of eight controlled studies (n = 569) evaluating treatment initiated before day 14 of ARDS. These trials consistently reported that treatment-induced reduction in systemic inflammation was associated with a significant improvement in ratio of partial arterial oxygen tension to fraction of inspired oxygen, and reductions in multiple organ dysfunction score, duration of mechanical ventilation and intensive care unit length of stay. Treatment was also associated with a marked reduction in the risk of death (relative risk: 0.68; 95% CI: 0.56-0.81; p < 0.001) and a sizable increase in mechanical ventilation-free days (weighted mean difference: 6.58 days; 95% CI: 2.93-10.23; p < 0.001); and intensive care unit-free days (weighted mean difference: 7.02 days; 95% CI: 3.20-10.85; p < 0.001). We recommend that prolonged methylprednisolone treatment, at an initial dose of 1 mg/kg/day in early ARDS and 2 mg/kg/day in unresolving ARDS, be delivered as an infusion to avoid glycemic variability, and that infection surveillance be strictly implemented to identify infections in the absence of fever.

Gram-negative versus Gram-positive bacteremia: what is more alarmin(g)?

Gram-negative bacteremia has been associated with severe sepsis, although the exact mechanism and pathophysiological differences among bacterial species are not well understood. In the previous issue of Critical Care, Abe and colleagues report results of a retrospective study that show a significantly higher incidence of Gram-negative bacteremia among adult intensive care unit patients with septic shock than in those with sepsis or severe sepsis. In this study, C-reactive protein and IL-6 levels were significantly higher in Gram-negative bacteremia than in Gram-positive bacteremia. These observations suggest a distinct immunopathophysiologic behavior of sepsis in patients with Gram-negative bacteremia that may influence clinical outcomes. Future research exploring new biomarkers and danger signals and further characterizing differences in the virulence mechanisms between Gram-negative and Gram-positive bacteria appears promising and could lead to new therapeutics and to improved clinical outcomes.

Protective mechanism of ultrafiltration against cardiopulmonary bypass-induced lung injury

BACKGROUND

We previously demonstrated a negative effect of cardiopulmonary bypass (CPB) in a canine model of single-lung graft function and an improved effect with ultrafiltration during CPB.

OBJECTIVE

To investigate the mechanism of these effects, focusing on cytokines and pulmonary surfactants using real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR).

MATERIALS AND METHODS

Fifteen left-sided single-lung transplant procedures were performed in pairs of dogs. The animals were divided into 3 groups. In one group, transplantation was performed without CPB (non-CPB group); in a second group, transplantation was performed with CPB and CPB flow was decreased slowly and pulmonary artery pressure was controlled (CPB group; and in the third group, transplantation was performed with CPB and ultrafiltration (CPB+UF group). Grafted lung specimens were harvested for RT-PCR of cytokines (IL-6, IL-8, and IL-10) and surfactant proteins (SP-A, SP-B, and SP-C).

RESULTS

Real-time quantitative RT-PCR demonstrated increased IL-6 expression in the CPB group compared with the non-CPB group. IL-6 gene expression was suppressed and pulmonary surfactant restored using ultrafiltration. Gene expression of surfactant protein (SP)-A, SP-B, and SP-C was decreased in the CPB group compared with normal lung and ultrafiltration groups, which demonstrated sustained gene expression of SP-A and SP-B.

CONCLUSION

Cardiopulmonary bypass has negative effects on grafts; however, ultrafiltration attenuates acute lung dysfunction by decreasing the inflammatory response and increasing pulmonary surfactant.

Prolonged inflammation following critical illness may impair long-term survival: a hypothesis with potential therapeutic implications

Despite successful intensive care a substantial portion of critically ill patients dies after discharge from the intensive care unit or hospital. Observational studies investigating long-term survival of critically ill patients reported that most deaths occur during the first months or year after discharge. Only limited data on the causes of impaired quality of life and post-intensive care unit deaths exist in the current literature. In this manuscript we hypothesize that the acute inflammatory response which characteristically accompanies critical illness is ensued by a prolonged imbalance or activation of the immune system. Such a chronic low-grade inflammatory response to critical illness may be sub-clinical and persist for a variable period of time after discharge from the intensive care unit and hospital. Chronic inflammation is a well-recognized risk factor for long-term morbidity and mortality, particularly from cardiovascular causes, and may thus partly contribute to the impaired quality of life as well as increased morbidity and mortality following intensive care unit and hospital discharge of critically ill patients. Assuming that critical illness is indeed followed by a prolonged inflammatory response, important implications for treatment would arise. An interesting and potentially beneficial therapy could be the administration of immune-modulating drugs during the time after intensive care unit or hospital discharge until chronic inflammation has subsided. Statins are well-investigated and effective drugs to attenuate chronic inflammation and could potentially also improve long-term outcome of critically ill patients after intensive care unit or hospital discharge. Future studies evaluating the course of inflammation during and after critical illness as well as its response to statin therapy are required.

Genetic polymorphisms associated with acute lung injury

Acute lung injury and acute respiratory distress syndrome are the result of intense inflammation in the lungs leading to respiratory failure. The causes of acute lung injury/acute respiratory distress syndrome are numerous (e.g., pneumonia, sepsis and trauma) but the reasons why certain individuals develop lung injury in response to these stimuli and others do not are not well understood. There is ample evidence in the literature that gene-host and gene-environment interactions may play a large role in the morbidity and mortality associated with this syndrome. In this review, we initially discuss methods for identification of candidate acute lung injury/acute respiratory distress syndrome susceptibility genes using a number of model systems including in vitro cell systems and inbred mice. We then describe examples of polymorphisms in genes that have been associated with the pathogenesis of acute lung injury/acute respiratory distress syndrome in human case-control studies. Systematic bench to bedside approaches to understand the genetic contribution to acute lung injury/acute respiratory distress syndrome have provided important insight to this complex disease and continuation of these investigations could lead to the development of novel prevention or intervention strategies.

Matrilysin (Matrix Metalloproteinase-7) regulates anti-inflammatory and antifibrotic pulmonary dendritic cells that express CD103 (alpha(E)beta(7)-integrin)

The E-cadherin receptor CD103 (alpha(E)beta(7)-integrin) is expressed on specific populations of pulmonary dendritic cells (DC) and T cells. However, CD103 function in the lung is not well understood. Matrilysin (MMP-7) expression is increased in lung injury and cleaves E-cadherin from injured lung epithelium. Thus, to assess matrilysin effects on CD103-E-cadherin interactions in lung injury, wild-type, CD103(-/-), and Mmp7(-/-) mice, in which E-cadherin isn't cleaved in the lung, were treated with bleomycin or bleomycin with nFMLP to reverse the defect in acute neutrophil influx seen in Mmp7(-/-) mice. Pulmonary CD103(+) DC were significantly increased in injured wild-type compared with Mmp7(-/-) mice, and CD103(+) leukocytes showed significantly enhanced interaction with E-cadherin on injured wild-type epithelium than with Mmp7(-/-) epithelium in vitro and in vivo. Bleomycin-treated CD103(-/-) mice had persistent neutrophilic inflammation, increased fibrosis, and increased mortality compared with wild-type mice, a phenotype that was partially recapitulated in bleomycin/nFMLP-treated Mmp7(-/-) mice. Soluble E-cadherin increased IL-12 and IL-10 and reduced IL-6 mRNA expression in wild-type bone marrow-derived DC but not in CD103(-/-) bone marrow-derived DC. Similar mRNA patterns were seen in lungs of bleomycin-injured wild-type, but not CD103(-/-) or Mmp7(-/-), mice. In conclusion, matrilysin regulates pulmonary localization of DC that express CD103, and E-cadherin cleavage may activate CD103(+) DC to limit inflammation and inhibit fibrosis.

Corticosteroid therapy for acute lung injury, acute respiratory distress syndrome, and severe pneumonia: a meta-analysis of randomized controlled trials

BACKGROUND

Randomized trials investigating the effect of corticosteroids in the treatment of acute lung injury, acute respiratory distress syndrome, and severe pneumonia have had mixed results. We sought to determine whether systemic corticosteroids reduce hospital mortality from these illnesses.

METHODS

We conducted a systematic review of published and unpublished randomized trials. We searched MEDLINE, EMBASE, CENTRAL, and CINAHL and reviewed proceedings from relevant society meetings. Two reviewers screened the literature and extracted data independently. For each outcome, we used Grading of Recommendations Assessments, Development and Evaluation (GRADE) criteria to evaluate the quality of the underlying evidence.

RESULTS

We included 12 trials enrolling 966 patients. Pooling across all trials, corticosteroids did not significantly reduce hospital mortality (relative risk, 0.84; 95% confidence interval, 0.66-1.06). In a subgroup analysis by dose of corticosteroid, trials using the equivalent of 2 mg kg(-1) d(-1) or less of methylprednisolone (9 trials) found lower hospital mortality with corticosteroid therapy (relative risk 0.68; 95% confidence interval, 0.49-0.96). The quality of the evidence underlying the pooled estimate of effect on hospital mortality was low, downgraded for inconsistency and imprecision.

CONCLUSIONS

Low-dose corticosteroids administered within 14 days of disease onset may reduce all-cause mortality in patients with acute lung injury, acute respiratory distress syndrome, and severe pneumonia. However, the overall quality of the evidence precludes definitive conclusions regarding the use of corticosteroids in this population.