The diagnosis of acute lung injury (ALI) is based on a consensus clinical definition. Despite the simplicity of this definition, ALI remains underdiagnosed and undertreated. Severe trauma is a well-described cause of ALI that represents a relatively homogeneous subset of ALI patients. The goals of this study were to develop a panel of plasma biomarkers to facilitate diagnosis of trauma-induced ALI and to enhance our understanding of the pathogenesis of human ALI.
A retrospective nested case control of 192 patients admitted to the trauma intensive care unit (ICU) at a university hospital between 2002 and 2006. We compared 107 patients with ALI to 85 patients without ALI. Plasma was collected within 72 h of ICU admission. Twenty-one plasma biomarkers were measured in duplicate in each plasma sample.
Patients with ALI had higher severity of illness scores, more days of mechanical ventilation, longer hospital stays and higher mortality versus controls. Seven biomarkers (RAGE, PCPIII, BNP, ANG2, IL10, TNF-α, and IL8) had a high diagnostic accuracy as reflected by the area under the receiver operating characteristic curve of 0.86 (95% CI 0.82 – 0.92) in differentiating ALI from controls.
A model utilizing seven plasma biomarkers had a high diagnostic accuracy in differentiating patients with trauma-induced ALI from trauma patients without ALI. In addition, use of a panel of biomarkers provides insight into the likely importance of alveolar epithelial injury in the pathogenesis of early acute lung injury.
Acute respiratory distress syndrome; acute pulmonary edema; pulmonary contusion; alveolar epithelium
Rationale: Acute lung injury (ALI) acts as a complex genetic trait, yet its genetic risk factors remain incompletely understood. Large-scale genotyping has not previously been reported for ALI.
Objectives: To identify ALI risk variants after major trauma using a large-scale candidate gene approach.
Methods: We performed a two-stage genetic association study. We derived findings in an African American cohort (n = 222) using a cardiopulmonary disease–centric 50K single nucleotide polymorphism (SNP) array. Genotype and haplotype distributions were compared between subjects with ALI and without ALI, with adjustment for clinical factors. Top performing SNPs (P < 10−4) were tested in a multicenter European American trauma-associated ALI case-control population (n = 600 ALI; n = 2,266 population-based control subjects) for replication. The ALI-associated genomic region was sequenced, analyzed for in silico prediction of function, and plasma was assayed by ELISA and immunoblot.
Measurements and Main Results: Five SNPs demonstrated a significant association with ALI after adjustment for covariates in Stage I. Two SNPs in ANGPT2 (rs1868554 and rs2442598) replicated their significant association with ALI in Stage II. rs1868554 was robust to multiple comparison correction: odds ratio 1.22 (1.06–1.40), P = 0.0047. Resequencing identified predicted novel splice sites in linkage disequilibrium with rs1868554, and immunoblots showed higher proportion of variant angiopoietin-2 (ANG2) isoform associated with rs1868554T (0.81 vs. 0.48; P = 0.038).
Conclusions: An ANGPT2 region is associated with both ALI and variation in plasma angiopoietin-2 isoforms. Characterization of the variant isoform and its genetic regulation may yield important insights about ALI pathogenesis and susceptibility.
acute lung injury; acute respiratory distress syndrome; functional genetic polymorphism; genetic association study
Rationale: Oxygen supplementation (e.g., hyperoxia) is used to support critically ill patients with noninfectious and infectious acute lung injury (ALI); however, hyperoxia exposure can potentially further contribute to and/or perpetuate preexisting ALI. Thus, developing novel therapeutic agents to minimize the side effects of hyperoxia is essential to improve the health of patients with severe ALI and respiratory dysfunction. We have previously shown that mice with a genetic disruption of the Nrf2 transcription factor, which squelches cellular stress by up-regulating the induction of several antioxidant enzymes and proteins, have greater susceptibility to hyperoxic lung injury. Moreover, we have recently demonstrated that Nrf2-deficiency impairs the resolution of lung injury and inflammation after nonlethal hyperoxia exposure.
Objectives: To test the hypothesis that amplification of endogenous Nrf2 activity would prevent or dampen ALI induced by hyperoxia.
Methods: Here, we tested our hypothesis using a synthetic triterpenoid compound CDDO-imidazole (CDDO-Im) (1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl] imidazole) in Nrf2-sufficient and Nrf2-deficient mice subjected to hyperoxia-induced ALI.
Measurements and Main Results: We demonstrate that oral administration of CDDO-Im at a dose of 30 μmol/kg body weight during the hyperoxic exposure is sufficient to markedly attenuate hyperoxia-induced ALI in Nrf2-sufficient but not Nrf2-deficient mice. This protection by the CDDO-Im against hyperoxic insult was accompanied by increased levels of Nrf2-regulated cytoprotective gene expression and reduced levels of DNA damage in the lung.
Conclusions: These results suggest that up-regulation of Nrf2 signaling by CDDO-Im or its analogs may provide a novel therapeutic strategy to minimize the adverse effects of hyperoxia.
Nrf2; Keap1; antioxidants; stress response
Endocan is a proteoglycan expressed by endothelial cells in the lung which may inhibit leukocyte recruitment and thus prevent the development of acute lung injury (ALI). We tested the association of serum endocan levels with subsequent development of ALI after major trauma.
Materials and Methods
Single-center nested case control study within a prospective cohort study of major trauma patients. Using an ELISA test, we measured endocan levels from admission serum in 24 controls (no ALI) and 24 cases (ALI within 5 days of trauma). Multivariable logistic regression was used to test the association of admission serum endocan levels with subsequent ALI.
Patients who developed ALI had lower levels of endocan on admission (mean 3.5 ± 1.4 ng/mL vs. 4.9 ± 2.6 ng/mL in controls, p=0.02). For each 1-unit increase in serum endocan level, the odds ratio for ALI development decreased (0.69, 95% confidence interval (CI): 0.49, 0.97, p=0.03). Lower endocan levels remained associated with a higher incidence of ALI after adjustment for age and illness severity.
Lower levels of serum endocan on admission are associated with subsequent development of ALI in trauma patients. These observations may be explained by endocan-mediated blockade of leukocyte recruitment in the lung.
Trauma; acute respiratory distress syndrome; acute lung injury; biomarkers; endothelium
Acute lung injury (ALI) is a syndrome with significant morbidity and mortality, but its genetic susceptibility is not clearly understood. In the present study, we characterized functional promoter single nucleotide polymorphisms (SNPs) in the phase II antioxidant gene NQO1 (NAD(P)H:quinone oxidoreductase1) to evaluate its role in susceptibility to ALI.
Three previously uncharacterized SNPs in the NQO1 promoter were selected for investigation. Luciferase assays were performed using constructs of each promoter polymorphism to evaluate function. Functional SNPs were genotyped in prospective cohort of major trauma patients (N = 264) and assessed for association with development of ALI.
The A/C SNP at -1221decreased in vitro transcription of NQO1 at baseline and after exposure to hyperoxia and other oxidant stressors. Patients heterozygous for the -1221 C allele were at significantly lesser risk of ALI after major trauma compared with patients with wild type alleles, even after adjustment for APACHE III score, and mechanism of trauma [OR, 0.46 (95% CI, 0.23, 0.90); p = 0.024].
This study demonstrated that the AC genotype at position -1221 in the NQO1 gene caused decreased transcription and was associated with a lower incidence of ALI following major trauma. These novel findings may have important implications in diseases with oxidant stress etiologies.
gene; susceptibility; ARDS; acute respiratory distress syndrome; hyperoxia; endotoxin; hydrogen peroxide; oxidant stress; SNP; single nucleotide polymorphism; lung disease
Rationale: Microvascular injury, inflammation, and coagulation play critical roles in the pathogenesis of acute lung injury (ALI). Plasma protein C levels are decreased in patients with acute lung injury and are associated with higher mortality and fewer ventilator-free days.
Objectives: To test the efficacy of activated protein C (APC) as a therapy for patients with ALI.
Methods: Eligible subjects were critically ill patients who met the American/European consensus criteria for ALI. Patients with severe sepsis and an APACHE II score of 25 or more were excluded. Participants were randomized to receive APC (24 μg/kg/h for 96 h) or placebo in a double-blind fashion within 72 hours of the onset of ALI. The primary endpoint was ventilator-free days.
Measurements and Main Results: APC increased plasma protein C levels (P = 0.002) and decreased pulmonary dead space fraction (P = 0.02). However, there was no statistically significant difference between patients receiving placebo (n = 38) or APC (n = 37) in the number of ventilator-free days (median [25–75% interquartile range]: 19 [0–24] vs. 19 [14–22], respectively; P = 0.78) or in 60-day mortality (5/38 vs. 5/37 patients, respectively; P = 1.0). There were no differences in the number of bleeding events between the two groups.
Conclusions: APC did not improve outcomes from ALI. The results of this trial do not support a large clinical trial of APC for ALI in the absence of severe sepsis and high disease severity.
Clinical trial registered with www.clinicaltrials.gov (NCT 00112164).
acute respiratory distress syndrome; acute lung injury; activated protein C; ventilator-free days; mortality
Acute lung injury (ALI) is a common and frequently devastating illness characterized by acute hypoxemic respiratory failure, profound inflammation, and flooding of the alveoli. Despite recent advances in ALI care, the morbidity and mortality of ALI continues to be unacceptably high. ALI-inciting events (e.g., sepsis, trauma, aspiration, pneumonia) are quite common, yet only a fraction of patients develop the syndrome. This heterogeneity of patients presenting with ALI has sparked interest in identifying the role of genetic factors that contribute to ALI susceptibility and prognosis. Recent advances in high-throughput sequencing and expression technologies now provide the tools to perform large-scale genomic analyses in complex disorders such as ALI; gene expression profiling and pathway analysis provide further insight into previously described molecular pathways involved in the syndrome. In this article, we describe the use of genomewide association studies, ortholog in silico techniques, utility of consomic rat methods, and candidate gene approaches using expression profiling and pathway analyses. These methods have confirmed suspected ALI candidate genes (e.g., IL-6 and MIF), but more impressively have identified novel genes (e.g., GADD45α and PBEF) not previously suspected in ALI. The analysis of the molecular pathways (e.g., the cytoskeleton in vascular barrier regulation) has identified additional genes contributing to the development and severity of ALI (e.g., MLCK), thereby providing therapeutic targets in this devastating illness.
acute lung injury; genetics; ventilator-induced lung injury
Rationale: Indirect acute lung injury (ALI) is associated with high morbidity and mortality. No specific therapies have been developed, because the underlying pathophysiological processes remain elusive.
Objectives: To investigate the contribution of Fas-induced apoptotic and nonapoptotic/inflammatory signaling to the pathology of indirect ALI.
Methods: A mouse model of indirect ALI, induced by successive exposure to hemorrhagic shock and cecal ligation and puncture, was used. Quantification of active caspase-3 and the short splice variant of FLICE-inhibitory protein, (FLIP)short, was performed by Western blotting and immunohistochemistry, and cytokines/chemokines were assessed by cytometric bead array or ELISA. M30 immunostaining was done to evaluate epithelial cell apoptosis. Lung injury was assessed on the basis of myeloperoxidase activity, bronchoalveolar lavage protein, and lung histology.
Measurements and Main Results: Twelve hours after insult, lung monocyte chemoattractant protein-1, keratinocyte-derived chemokine, macrophage inflammatory protein-2, IL-6, tumor necrosis factor-α, and caspase-3 were increased and FLIPshort was decreased. Fas- and Fas ligand–deficient mice showed marked protection from lung inflammation and apoptosis and decreased ALI. This was associated with a 10-day survival benefit. Similarly, 4 hours after pulmonary instillation of Fas-activating antibody in vivo, lung chemokines were markedly elevated in background mice and, interestingly, to a similar degree in macrophage-deficient animals. Fas activation on lung epithelial cells in vitro led to chemokine production that was dependent on extracellular signal–regulated kinase.
Conclusions: Activation of apoptotic and nonapoptotic/inflammatory Fas signaling is an early important pathophysiological event in the development of indirect ALI after hemorrhagic shock and sepsis, in which lung epithelial cells appear to play a central role.
hemorrhagic shock; sepsis; epithelial cell; cell death; death receptors
Activation of adenosine A2A receptor aggravates lung damage in a neurogenic mouse model of acute lung injury (ALI) but protects against nonneurogenic ALI.
The bone marrow–derived cell (BMDC)–associated inflammatory response plays a key role in the development of acute lung injury (ALI). Activation of adenosine A2A receptor (A2AR) is generally considered to be antiinflammatory, inhibiting BMDC activities to protect against ALI. However, in the present study, we found that in a mouse model of neurogenic ALI induced by severe traumatic brain injury (TBI), BMDC A2AR exerted a proinflammatory effect, aggravating lung damage. This is in contrast to the antiinflammatory effect observed in the mouse oleic acid–induced ALI model (a nonneurogenic ALI model.) Moreover, the A2AR agonist CGS21680 aggravated, whereas the antagonist ZM241385 attenuated, the severe TBI-induced lung inflammatory damage in mice. Further investigation of white blood cells isolated from patients or mouse TBI models and of cultured human or mouse neutrophils demonstrated that elevated plasma glutamate after severe TBI induced interaction between A2AR and the metabotropic glutamate receptor 5 (mGluR5) to increase phospholipase C–protein kinase C signaling, which mediated the proinflammatory effect of A2AR. These results are in striking contrast to the well-known antiinflammatory and protective role of A2AR in nonneurogenic ALI and indicate different therapeutic strategies should be used for nonneurogenic and neurogenic ALI treatment when targeting A2AR.
Packed Red Blood Cell (PRBC) transfusion is associated with Acute Lung Injury (ALI) development after trauma, but this risk may not be constant through time after trauma. We hypothesized the relationship between PRBC delivery and ALI risk varies through time after injury.
Data were collected prospectively from 1999–2006. Inclusion criteria: age > 13 years, SICU admission, and injury severity score (ISS) ≥ 16. Exclusion criteria included discharge/death within 24 hours of admission. Patients were followed prospectively for ALI development for 5 days after trauma. Discrete time models were fit to test the association of timing of PRBC delivery with development of ALI while controlling for patient demographics, resuscitation variables, ISS, and APACHE III scores.
At total of 602 patients were included. Median age was 33 years, 77% were male, and 50% were African American. Using a discrete time-survival model, the relation between transfusion and ALI development was found to vary by transfusion time-window (p<0.0001). The major effect of PRBC delivery on ALI risk occurred in the first 24 hours after trauma; this finding persisted in multivariable modeling (adjusted OR = 1.07 per unit; 95%CI 1.02–1.11, p<0.001). Cumulative incidence of ALI approached 50% in patients receiving ≥ 6u PRBC in the first 24 hours.
The association between PRBC transfusion and ALI development in trauma patients is time-dependent, with PRBC delivery in the first 24 hours after injury driving the overall relation. Each PRBC unit during this time period increases odds of subsequent ALI development by 7%.
Rationale: Accurate, early identification of patients at risk for developing acute lung injury (ALI) provides the opportunity to test and implement secondary prevention strategies.
Objectives: To determine the frequency and outcome of ALI development in patients at risk and validate a lung injury prediction score (LIPS).
Methods: In this prospective multicenter observational cohort study, predisposing conditions and risk modifiers predictive of ALI development were identified from routine clinical data available during initial evaluation. The discrimination of the model was assessed with area under receiver operating curve (AUC). The risk of death from ALI was determined after adjustment for severity of illness and predisposing conditions.
Measurements and Main Results: Twenty-two hospitals enrolled 5,584 patients at risk. ALI developed a median of 2 (interquartile range 1–4) days after initial evaluation in 377 (6.8%; 148 ALI-only, 229 adult respiratory distress syndrome) patients. The frequency of ALI varied according to predisposing conditions (from 3% in pancreatitis to 26% after smoke inhalation). LIPS discriminated patients who developed ALI from those who did not with an AUC of 0.80 (95% confidence interval, 0.78–0.82). When adjusted for severity of illness and predisposing conditions, development of ALI increased the risk of in-hospital death (odds ratio, 4.1; 95% confidence interval, 2.9–5.7).
Conclusions: ALI occurrence varies according to predisposing conditions and carries an independently poor prognosis. Using routinely available clinical data, LIPS identifies patients at high risk for ALI early in the course of their illness. This model will alert clinicians about the risk of ALI and facilitate testing and implementation of ALI prevention strategies.
Clinical trial registered with www.clinicaltrials.gov (NCT00889772).
respiratory distress syndrome, adult; prevention; prediction model; acute respiratory failure
Rationale: Acute lung injury (ALI) that develops 6 hours after transfusion (TRALI) is the leading cause of transfusion-related mortality. Several transfusion characteristics have been postulated as risk factors for TRALI, but the evidence is limited to retrospective studies.
Objectives: To compare patient and transfusion risk factors between patients who do and do not develop ALI.
Methods: In this prospective cohort study, consecutive transfused critically ill patients were closely observed for development of ALI. Donor samples were collected from the transfusion bags. Risk factors were compared between patients who developed ALI after transfusion and transfused control patients, matched by age, sex, and admission diagnosis.
Measurements and Main Results: Seventy-four of 901 transfused patients developed ALI within 6 hours of transfusion (8%). Compared with transfused control subjects, patients with ALI were more likely to have sepsis (37 vs. 22%, P = 0.016) and a history of chronic alcohol abuse (37 vs. 18%, P = 0.006). When adjusted for patient characteristics, transfusion of plasma from female donors (odds ratio [OR], 5.09; 95% confidence interval [95% CI], 1.37–18.85) rather than male donors (OR, 1.60; 95% CI, 0.76 to 3.37), number of pregnancies among the donors (OR, 1.19; 95% CI, 1.05 to 1.34), number of donor units positive for anti-granulocyte antibodies (OR, 4.85; 95% CI, 1.32–17.86) and anti–HLA class II antibodies (OR, 3.08; 95% CI, 1.15–8.25), and concentration of lysophosphatidylcholine in the donor product (OR, 1.69; 95% CI, 1.10 to 2.59) were associated with the development of ALI.
Conclusions: Both patient and transfusion risk factors determine the probability of ALI after transfusion. Transfusion factors represent attractive targets for the prevention of ALI.
fresh-frozen plasma; platelet transfusion; pulmonary edema; female; blood donors
Neutrophil elastase plays a crucial role in the development of acute lung injury (ALI) in patients with systemic inflammatory response syndrome (SIRS). The clinical efficacy of the neutrophil elastase inhibitor, sivelestat, for patients with ALI associated with SIRS has not been convincingly demonstrated. The aim of this study was to determine if there are clinical features of patients with this condition that affect the efficacy of sivelestat.
This was a retrospective study of 110 ALI patients with SIRS. Clinical information, including the etiology of ALI, the number of organs failing, scoring systems for assessing the severity of illness, and laboratory data, was collected at the time of diagnosis. Information on the number of ventilator-free days (VFDs) and changes in PaO2/FIO2 (ΔP/F) before and 7 days after the time of ALI diagnosis was also collected. The effect of sivelestat on ALI patients was also examined based on whether they had sepsis and whether their initial serum procalcitonin level was ≥0.5 ng/mL.
There were 70 patients who were treated with sivelestat and 40 control patients. VFDs and ΔP/F were significantly higher in the treated patients than in the control patients. However, there was no significant difference in the patient survival rate between the two groups. Sivelestat was more effective in ALI patients with a PaO2/FIO2 ratio ≥ 140 mmHg or sepsis. Sivelestat significantly prolonged survival and led to higher VFDs and increased ΔP/F in septic patients and patients with initial serum procalcitonin levels ≥ 0.5 ng/mL.
The results may facilitate a future randomized controlled trial to determine whether sivelestat is beneficial for ALI patients with sepsis.
systemic inflammatory response syndrome; procalcitonin; ventilator-free days; neutrophil elastase
Neutral endopeptidase (NEP), an enzyme that cleaves inflammatory bioactive peptides, may play a protective role in the pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). However, its low extracellular activity hinders the precise measurement of changes that take place during ALI/ARDS. The main objective of this study was to clarify the regulation of NEP activity and its expression during ALI/ARDS.
In a clinical study, we measured plasma NEP activity in patients who developed postoperative ALI/ARDS, using a HPLC fluorometric system. In an experimental study, we induced ALI by intratracheal instillation of hydrochloric acid (HCl) or lipopolysaccharide (LPS) in mice, and similarly measured NEP activity in plasma, lung tissue, and broncho-alveolar lavage fluid (BALF). We also studied the distribution and measured the amounts of NEP protein, using immuno-histochemical and immunoblot analyses, and measured the levels of NEP mRNA, using real-time reverse transcription-polymerase chain reaction, in the lungs of mice with ALI.
The plasma NEP activity was significantly lower in patients presenting with ALI/ARDS than in controls. Similarly, the NEP activity in plasma and lung tissue was markedly lower, and lung injuries more severe in LPS- than in HCl-treated mice. In contrast, the activity of NEP in the BALF of LPS-treated mice was increased. The intratracheal instillation of LPS decreased the gene expression of NEP in the lung. Immuno-histochemical and Western immunoblot studies in mice confirmed a) the presence of NEP in the alveolar wall, a critical target in ALI/ARDS, and b) a decrease in its expression in HCl- and LPS-induced ALI.
In this experimental and clinical study of ALI/ARDS, the activity of NEP was significantly decreased in plasma and increased in the alveolar air space.
Deposition of fibrin in the alveolar space is a hallmark of acute lung injury (ALI). Plasminogen activator inhibitor-1 (PAI-1) is an antifibrinolytic agent that is activated during inflammation. Increased plasma and pulmonary edema fluid levels of PAI-1 are associated with increased mortality in adults with ALI. This relationship has not been examined in children. The objective of this study was to test whether increased plasma PAI-1 levels are associated with worse clinical outcomes in pediatric patients with ALI.
We measured plasma PAI-1 levels on the first day of ALI among 94 pediatric patients enrolled in two separate prospective, multicenter investigations and followed them for clinical outcomes. All patients met American European Consensus Conference criteria for ALI.
A total of 94 patients were included. The median age was 3.2 years (range 16 days–18 years), the PaO2/FiO2 was 141 ± 72 (mean ± SD), and overall mortality was 14/94 (15%). PAI-1 levels were significantly higher in nonsurvivors compared to survivors (P < 0.01). The adjusted odds of mortality doubled for every log increase in the level of plasma PAI-1 after adjustment for age and severity of illness.
Higher PAI-1 levels are associated with increased mortality and fewer ventilator-free days among pediatric patients with ALI. These findings suggest that impaired fibrinolysis may play a role in the pathogenesis of ALI in pediatric patients and suggest that PAI-1 may serve as a useful biomarker of prognosis in patients with ALI.
Accurate respiratory distress syndrome; Acute lung injury; Clinical studies; Pediatrics; Plasminogen activator inhibitor-1 (PAI-1)
Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine central to the response to endotoxemia, is a putative biomarker in acute lung injury (ALI). To explore MIF as a molecular target and candidate gene in ALI, we examined MIF gene and protein expression in murine and canine models of ALI (high tidal volume mechanical ventilation, endotoxin exposure) and in patients with either sepsis or sepsis-induced ALI. MIF gene expression and protein levels were significantly increased in each ALI model, with serum MIF levels significantly higher in patients with either sepsis or ALI compared to healthy controls (African- and European- descent). We next studied the association of 8 MIF gene polymorphisms (SNPs) (within a 9.7 kb interval on chromosome 22q11.23) with the development of sepsis and ALI in European- and African- descent populations. Genotyping in 506 DNA samples (sepsis patients, sepsis-associated ALI patients, and healthy controls) revealed haplotypes located in the 3′ end of the MIF gene, but not individual SNPs, associated with sepsis and ALI in both populations. These data, generated via functional genomic and genetic approaches, suggest that MIF is a relevant molecular target in ALI.
mechanical ventilation; MIF; gene expression profiling; polymorphism
An integral membrane protein, Claudin 5 (CLDN5), is a critical component of endothelial tight junctions that control pericellular permeability. Breaching of endothelial barriers is a key event in the development of pulmonary edema during acute lung injury (ALI). A major irritant in smoke, acrolein can induce ALI possibly by altering CLDN5 expression. This study sought to determine the cell signaling mechanism controlling endothelial CLDN5 expression during ALI. To assess susceptibility, 12 mouse strains were exposed to acrolein (10 ppm, 24 h), and survival monitored. Histology, lavage protein, and CLDN5 transcripts were measured in the lung of the most sensitive and resistant strains. CLDN5 transcripts and phosphorylation status of forkhead box O1 (FOXO1) and catenin (cadherin-associated protein) beta 1 (CTNNB1) proteins were determined in control and acrolein-treated human endothelial cells. Mean survival time (MST) varied more than 2-fold among strains with the susceptible (BALB/cByJ) and resistant (129X1/SvJ) strains (MST, 17.3 ± 1.9 h vs. 41.4 ± 5.1 h, respectively). Histological analysis revealed earlier perivascular enlargement in the BALB/cByJ than in 129X1/SvJ mouse lung. Lung CLDN5 transcript and protein increased more in the resistant strain than in the susceptible strain. In human endothelial cells, 30 nM acrolein increased CLDN5 transcripts and increased p-FOXO1 protein levels. The phosphatidylinositol 3-kinase inhibitor LY294002 diminished the acrolein-induced increased CLDN5 transcript. Acrolein (300 nM) decreased CLDN5 transcripts, which were accompanied by increased FOXO1 and CTNNB1. The phosphorylation status of these transcription factors was consistent with the observed CLDN5 alteration. Preservation of endothelial CLDN5 may be a novel clinical approach for ALI therapy.
ARDS; perivascular edema; vascular permeability; smoke inhalation; carboxyl stress
4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol plus its glucuronides (total NNAL), metabolites of the lung carcinogen NNK, and total cotinine, metabolites of nicotine, are biomarkers of active and passive cigarette smoking. We calculated the total NNAL: total cotinine (× 103) ratio in 408 passive (infants, children, adults) and 1088 active smokers. The weighted averages were 0.73 (95% CI 0.71, 0.76) for passive smokers and 0.07 (0.06, 0.08) for active smokers (p<0.0001). These results demonstrate that cotinine measurements may underestimate exposure of passive smokers to the lung carcinogen NNK in secondhand cigarette smoke. The total NNAL:total cotinine (× 103) ratio may provide an improved biomarker for evaluating the health effects of passive smoking.
cotinine; NNAL; passive smoking
Several biological markers of lung injury are predictors of morbidity and mortality in patients with acute lung injury (ALI). The low tidal volume lung-protective ventilation strategy is associated with a significant decrease in plasma biomarker levels compared to the high tidal volume ventilation strategy. The primary objective of this study was to test whether the institution of lung-protective positive pressure ventilation in spontaneously ventilating patients with ALI exacerbates pre-existing lung injury by using measurements of biomarkers of lung injury before and after intubation.
Materials and methods
A prospective observational cohort study was conducted in the intensive care unit of a tertiary care university hospital. Twenty-five intubated, mechanically ventilated patients with ALI were enrolled. Physiologic data and serum samples were collected within 6 hours before intubation and at two different time points within the first 24 hours after intubation to measure the concentration of interleukin (IL)-6, IL-8, intercellular adhesion molecule 1 (ICAM-1), and von Willebrand factor (vWF). The differences in biomarker levels before and after intubation were analysed using repeated measures analysis of variance and a paired t test with correction for multiple comparisons.
Before endotracheal intubation, all of the biological markers (IL-8, IL-6, ICAM-1, and vWF) were elevated in the spontaneously breathing patients with ALI. After intubation and the institution of positive pressure ventilation (tidal volume 7 to 8 ml/kg per ideal body weight), none of the biological markers was significantly increased at either an early (3 ± 2 hours) or later (21 ± 5 hours) time point. However, the levels of IL-8 were significantly decreased at the later time point (21 ± 5 hours) after intubation. During the 24-hour period after intubation, the PaO2/FiO2 (partial pressure of arterial oxygen/fraction of the inspired oxygen) ratio significantly increased and the plateau airway pressure significantly decreased.
Levels of IL-8, IL-6, vWF, and ICAM-1 are elevated in spontaneously ventilating patients with ALI prior to endotracheal intubation. The institution of a lung-protective ventilation strategy with positive pressure ventilation does not further increase the levels of biological markers of lung injury. The results suggest that the institution of a lung-protective positive pressure ventilation strategy does not worsen the pre-existing lung injury in most patients with ALI.
To determine risk factors for development of recurrent acute lung injury (ALI).
A population-based case-control study.
The study was conducted in Olmsted County, Minnesota from 1999 to 2008.
Using a validated electronic screening protocol, investigators identified intensive care patients with acute hypoxemia and bilateral pulmonary infiltrates.
The presence of ALI was independently confirmed according to American-European Consensus Conference (AECC) criteria. Recurrent ALI cases were subsequently matched (1:1:1) with two controls (single ALI and no ALI) on age, gender, duration of follow-up, and predisposing conditions. Risk factors evaluated included gastroesophageal reflux disease (GERD), alcohol consumption, smoking, chronic opioid use, and transfusions.
We identified 917 patients with ALI, of which 19 developed a second episode, yielding an incidence of 2.02 (95%CI 1.10–2.93) per 100,000 person years. The median time to development of the second episode was 264 days (IQR 80 – 460) days, with a mortality of 47% during the episode. The history of GERD was highly prevalent in patients who developed recurrent ALI: 15/19 patients (79%), compared to 5/19 (26%) matches with single episode of ALI (p=0.006) and 8/19 (42%) matches without ALI (p=0.016). Other exposures were similar between the cases and the two matched controls.
Recurrent ALI is not a rare phenomenon in the ICU, and may continue to increase with improvements in survival following ALI. GERD was identified as an important risk factor for recurrent ALI and may suggest an important role of gastric aspiration in the development of this syndrome.
epidemiology; incidence; recurrent acute lung injury; acute lung injury; acute respiratory distress syndrome; gastroesophageal reflux disease
Rationale: Acute lung injury (ALI) causes high mortality, but its molecular mechanisms and therapeutic options remain ill-defined. Gram-negative bacterial infections are the main cause of ALI, leading to lung neutrophil infiltration, permeability increases, deterioration of gas exchange, and lung damage. Platelets are activated during ALI, but insights into their mechanistic contribution to neutrophil accumulation in the lung are elusive.
Objectives: To determine mechanisms of platelet-mediated neutrophil recruitment in ALI.
Methods: Interference with platelet–neutrophil interactions using antagonists to P-selectin and glycoprotein IIb/IIIa or a small peptide antagonist disrupting platelet chemokine heteromer formation in mouse models of ALI.
Measurements and Main Results: In a murine model of LPS-induced ALI, we uncover important roles for neutrophils and platelets in permeability changes and subsequent lung damage. Furthermore, platelet depletion abrogated lung neutrophil infiltration, suggesting a sequential participation of platelets and neutrophils. Whereas antagonists to P-selectin and glycoprotein IIb/IIIa had no effects on LPS-mediated ALI, antibodies to the platelet-derived chemokines CCL5 and CXCL4 strongly diminished neutrophil eflux and permeability changes. The two chemokines were found to form heteromers in human and murine ALI samples, positively correlating with leukocyte influx into the lung. Disruption of CCL5-CXCL4 heteromers in LPS-, acid-, and sepsis-induced ALI abolished lung edema, neutrophil infiltration, and tissue damage, thereby revealing a causal contribution.
Conclusions: Taken together, our data identify a novel function of platelet-derived chemokine heteromers during ALI and demonstrate means for therapeutic interference.
neutrophil; platelet; chemokine; recruitment; acute lung injury
Seven non-smokers were exposed to tobacco smoke under natural conditions for two hours in a public house. Measures of nicotine and cotinine in plasma, saliva, and urine and expired air carbon monoxide all showed reliable increases. The concentrations of carbon monoxide and nicotine after exposure averaged 15.7% and 7.5% respectively of the values found in heavy smokers. Although the increase in expired air carbon monoxide of 5.9 ppm was similar to increases in smokers after a single cigarette, the amount of nicotine absorbed was between a tenth and a third of the amount taken in from one cigarette. Since this represented a relatively extreme acute natural exposure, any health risks of passive smoking probably depend less on quantitative factors than on qualitative differences between sidestream and mainstream smoke.
ALI (acute lung injury) and its more severe form ARDS (acute respiratory distress syndrome) are inflammatory diseases of the lung characterized by hypoxaemia and diffuse bilateral infiltrates. Disruption of epithelial integrity and injury to endothelium are contributing factors of the development of ALI/ARDS, and alveolar damage is the most pronounced feature of ALI/ARDS. The resulting increase in lung microvascular permeability promotes influx of inflammatory cells to the alveolar spaces. Oedema fluid contains pro-nflammatory mediators and plasma proteins, including Igs (immunoglobulins). Moreover, several reports describe the presence of autoantibodies and immune complexes [anti-IL-8 (interleukin-8) autoantibody/IL-8 complexes] in lung fluids (oedema and bronchoalveolar lavage fluids) from patients with ALI/ARDS. These immune complexes associate with FcγRIIa (Fcγ IIa receptor) in lungs of patients with ARDS. Furthermore, the expression of FcγRIIa is substantially elevated in lungs of these patients. FcγRIIa appears on virtually all myeloid cells, platelets and endothelial cells. It is a low-affinity receptor for IgG that preferentially binds aggregated immunoglobulins and immune complexes. FcγRs regulate phagocytosis and cell-mediated cytotoxicity, and initiate the release of inflammatory mediators. It should be noted that immune complexes formed between either anti-neutrophil autoantibodies and their specific antigens or anti-HLA (human leucocyte antigen) antibodies and target antigens are implicated in the pathogenesis of TRALI (transfusion-related acute lung injury), and importantly, animal studies indicate that FcγRs are essential for these complexes to cause damage to the lungs. Therefore, we hypothesize that FcγRs such as FcγRIIa could contribute to the pathogenesis of ALI/ARDS.
acute lung injury; FcγRIIa; IgG receptor; lung; signal transduction; ALI, acute lung injury; ARDS, acute respiratory distress syndrome; FcγR, Fcγ receptor; IL, interleukin; ITAM, immunoreceptor tyrosine-based activation motif; ITIM, immunoreceptor tyrosine-based inhibitory motif; KC, keratinocyte-derived chemokine; LIX, lipopolysaccharide-induced CXC chemokine; LPS, lipopolysaccharide; MIP-2, macrophage inflammatory protein 2; TLR4, Toll-like receptor 4; TRALI, transfusion-related acute lung injury
Cotinine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are widely used biomarkers for tobacco-derived nicotine and the lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), respectively. The discrepancy between cotinine levels in relation to disease risk comparing active vs. passive smoking suggests a non-linear tobacco smoke dose-response and/or that cotinine is not providing an accurate measure of exposure to tobacco smoke toxic constituents from secondhand smoke.
Cotinine and NNAL were measured in urine of 373 active smokers and 228 passive smokers.
Average cotinine levels were 1,155 (IQR 703-2,715) for active smokers and 1.82 (0.45-7.33) ng/mg creatinine for passive smokers. Average NNAL levels were 183 (103-393) and 5.19 (2.04-11.6) pg/mg creatinine, respectively. NNAL/cotinine ratio in urine was significantly higher for passive smokers when compared to active smokers (2.85×103 vs. 0.16×103, p<0.0001).
Passive smoking is associated with a much higher ratio of NNAL/cotinine in the urine compared to active smoking.
Cotinine measurement leads to an underestimation of exposure to the carcinogen NNK from second-hand smoke when compared with active smoking.
cotinine; NNAL; smokers; tobacco smoke; exposure
To evaluate intensive care-related factors as predictors of depressive symptoms 6 months after acute lung injury (ALI)
Prospective cohort study
Thirteen intensive care units (ICUs) in 4 hospitals in Baltimore, MD
Consecutive ALI survivors (n = 160; 71% from medical ICUs) screened for depressive symptoms at six months post-ALI
Measurements and Main Results
We prospectively measured 12 features of critical illness and ICU care and used multivariable regression to evaluate associations with depressive symptoms as measured by the Hospital Anxiety and Depression (HAD) depression score. The prevalence of a positive screening for depression (score ≥8) at 6 months post-ALI was 26%. Depressive symptoms were significantly associated with surgical (versus medical or trauma) ICU admission (relative risk [RR] 2.2, 95% confidence interval [CI] 1.1 – 4.2), maximum daily Sequential Organ Failure Assessment score of >10 (RR 2.1, 95% CI 1.1 – 3.5), and mean daily ICU benzodiazepine dose of ≥75mg of midazolam-equivalent (RR 2.1, 95% CI 1.1 – 3.5).
Depressive symptoms at 6 months post-ALI are common and potentially associated with ICU-related factors. Mechanisms by which critical illness and intensive care management associate with depressive symptoms merit further investigation.
depression; intensive care units; respiratory distress syndrome; adult; critical care; outcome assessment (health care)