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
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: 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
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: 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
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
Lung protective ventilation (LPV) has been shown to improve survival and the duration of mechanical ventilation in acute lung injury (ALI) patients. Mortality of ALI may vary by gender, which could result from treatment variability. Whether gender is associated with the use of LPV is not known.
A total of 421 severe sepsis-related ALI subjects in the Consortium to Evaluate Lung Edema Genetics from seven teaching hospitals between 2002 and 2008 were included in our study. We evaluated patients' tidal volume, plateau pressure and arterial pH to determine whether patients received LPV during the first two days after developing ALI. The odds ratio of receiving LPV was estimated by a logistic regression model with robust and cluster options.
Women had similar characteristics as men with the exception of lower height and higher illness severity, as measured by Acute Physiology and Chronic Health Evaluation (APACHE) II score. 225 (53%) of the subjects received LPV during the first two days after ALI onset; women received LPV less frequently than men (46% versus 59%, P < 0.001). However, after adjustment for height and severity of illness (APACHE II), there was no difference in exposure to LPV between men and women (P = 0.262).
Short people are less likely to receive LPV, which seems to explain the tendency of clinicians to adhere to LPV less strictly in women. Strategies to standardize application of LPV, independent of differences in height and severity of illness, are necessary.
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
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
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
Sepsis-induced acute lung injury (ALI) has been reported to have a higher case fatality rate than other causes of ALI. However, differences in the severity of illness in septic vs. non-septic ALI patients might explain this finding.
520 patients enrolled in the Improving Care of ALI Patients Study (ICAP) were prospectively characterized as having sepsis or non sepsis-induced ALI. Biologically plausible risk factors for in-hospital death were considered in multiple logistic regression models to evaluate the independent association of sepsis vs. non-sepsis ALI risk factors with mortality.
Patients with sepsis-induced ALI had greater illness severity and organ dysfunction (APACHE II and SOFA scores) at ALI diagnosis and higher crude in-hospital mortality rates compared with non-sepsis ALI patients. Patients with sepsis-induced ALI received similar tidal volumes, but higher levels of positive end expiratory pressure, and had a more positive net fluid balance in the first week after ALI diagnosis. In multivariable analysis, the following variables (odds ratio, 95% confidence interval) were significantly associated with hospital mortality: age (1.04, 1.02 to 1.05), admission to a medical intensive care unit (ICU) (2.76, 1.42 to 5.36), ICU length of stay prior to ALI diagnosis (1.15, 1.03 to 1.29), APACHE II (1.05, 1.02 to 1.08), SOFA at ALI diagnosis (1.17, 1.09 to 1.25), Lung Injury Score (2.33, 1.74 to 3.12) and net fluid balance in liters in the first week after ALI diagnosis (1.06, 1.03 to 1.09). Sepsis did not have a significant, independent association with mortality (1.02, 0.59 to 1.76).
Greater severity of illness contributes to the higher case fatality rate observed in sepsis-induced ALI. Sepsis was not independently associated with mortality in our study.
Acute lung injury (ALI) is an inflammatory disease with a high mortality rate. Although typically seen in individuals with sepsis, ALI is also a major complication in severe acute pancreatitis (SAP). The pathophysiology of SAP-associated ALI is poorly understood, but elevated serum levels of IL-6 is a reliable marker for disease severity. Here, we used a mouse model of acute pancreatitis–associated (AP-associated) ALI to determine the role of IL-6 in ALI lethality. Il6-deficient mice had a lower death rate compared with wild-type mice with AP, while mice injected with IL-6 were more likely to develop lethal ALI. We found that inflammation-associated NF-κB induced myeloid cell secretion of IL-6, and the effects of secreted IL-6 were mediated by complexation with soluble IL-6 receptor, a process known as trans-signaling. IL-6 trans-signaling stimulated phosphorylation of STAT3 and production of the neutrophil attractant CXCL1 in pancreatic acinar cells. Examination of human samples revealed expression of IL-6 in combination with soluble IL-6 receptor was a reliable predictor of ALI in SAP. These results demonstrate that IL-6 trans-signaling is an essential mediator of ALI in SAP across species and suggest that therapeutic inhibition of IL-6 may prevent SAP-associated ALI.
Acute lung injury (ALI) is associated with severe alterations in lung structure and function and is characterized by hypoxemia, pulmonary edema, low lung compliance and widespread capillary leakage. Asymmetric dimethylarginine (ADMA), a known cardiovascular risk factor, has been linked to endothelial dysfunction and the pathogenesis of a number of cardiovascular diseases. However, the role of ADMA in the pathogenesis of ALI is less clear. ADMA is metabolized via hydrolytic degradation to L-citrulline and dimethylamine by the enzyme, dimethylarginine dimethylaminohydrolase (DDAH). Recent studies suggest that lipopolysaccharide (LPS) markedly increases the level of ADMA and decreases DDAH activity in endothelial cells. Thus, the purpose of this study was to determine if alterations in the ADMA/DDAH pathway contribute to the development of ALI initiated by LPS-exposure in mice. Our data demonstrate that LPS exposure significantly increases ADMA levels and this correlates with a decrease in DDAH activity but not protein levels of either DDAH I or DDAH II isoforms. Further, we found that the increase in ADMA levels cause an early decrease in nitric oxide (NOx) and a significant increase in both NO synthase (NOS)-derived superoxide and total nitrated lung proteins. Finally, we found that decreasing peroxynitrite levels with either uric acid or Manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin (MnTymPyp) significantly attenuated the lung leak associated with LPS-exposure in mice suggesting a key role for protein nitration in the progression of ALI. In conclusion, this is the first study that suggests a role of the ADMA/DDAH pathway during the development of ALI in mice and that ADMA may be a novel therapeutic biomarker to ascertain the risk for development of ALI.
Nitration; Superoxide; Arginine metabolism
Quantitation of urinary cotinine, a major metabolite of nicotine, by an enzyme-linked immunosorbent assay (ELISA), was performed in parallel with questionnaires containing items on smoking status, such as active and/or passive smokers, the number of cigarettes smoked, and the presence or absence of active smokers in the surroundings in a department store (517 employees). The cotinine values corrected by creatinine (cotinine-creatinine ratios, CCRs) approximately conformed to the extent of self-recognition of their exposure status to tobacco-smoke, and were low in the order of active smokers, passive smokers and non-smokers who felt they were not exposed to tobacco-smoke. Occupational differences of the CCRs were not found in the employees.
In the active smokers, the CCRs were increasing according to the number of cigarettes per day they smoked, and the values were nearly proportional to nicotine contents of cigarette in the moderate smokers who smoked 11-20 cigarettes per day. The CCRs of males were higher than those of females in the active smokers, which also agreed well with the numbers of cigarettes they smoked per day. In the passive smokers, the CCRs were remarkably and significantly higher in subjects who felt they were exposed to tobacco-smoke both in their workplaces and homes.
Urinary CCRs measured by ELISA are thus found to be a reliable and excellent objective indicator of both active and passive exposure-status to tobacco-smoke.
Urinary cotinine; Exposure status to tobacco-smoke; Relationship between subjective recognition and cotinine values; ELISA; Department store employees
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are sequelae of severe trauma. It is unknown if certain races are at greater risk of developing ALI/ARDS, and once established, if there are racial differences in the severity of lung injury or mortality.
Retrospective cohort study of 4,397 trauma patients (1,831 Caucasians, 871 African-Americans, 886 Hispanics, and 809 Asian/Pacific Islanders) requiring ICU admission between 1996-2007 at an urban level I trauma center.
African-American patients were most likely to present in shock with penetrating trauma and receive a massive transfusion. The incidence of ALI/ARDS was similar by race (p=0.99). Among patients who developed ALI/ARDS, there was no evidence to support a difference in initial PaO2/FiO2 (p=0.33), lung injury score (p=0.67) or mortality (p=0.78) by race.
Despite differences in baseline characteristics, the incidence of ALI/ARDS, severity of lung injury, and mortality were similar by race.
acute respiratory distress syndrome; acute lung injury; trauma; race; epidemiology; adult
Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome, are complex illnesses involving the interplay of both environmental (such as mechanical ventilation) and genetic factors. To understand better the underlying mechanisms of pathogenesis associated with ALI, we recently identified several candidate genes by global expression profiling in preclinical models of ALI and relevant single-nucleotide polymorphisms. We summarize here several strategies successfully used to identify novel ALI candidate genes and detail the validation of variants in these genes as contributing factors to ALI pathobiology, conclusions based on functional analyses, and specific genetic association studies conducted in ALI cohorts. Continued insights into ALI pathogenesis and identification of genetic variants, which confer ALI risk and severity, promise to reveal novel molecular therapeutic targets that can be translated into personalized treatments to reduce the very high, unacceptable mortality of this disorder.
acute lung injury; SNP; microarray; PBEF; inflammation
A 61-year-old woman with lung cancer developed delayed transfusion-related acute lung injury (TRALI) syndrome after transfusion of plasma- and leukoreduced red blood cells (RBCs) for gastrointestinal bleeding due to intestinal metastasis. Acute lung injury (ALI) recurred 31 days after the first ALI episode. Both ALI episodes occurred 48 hours after transfusion. Laboratory examinations revealed the presence of various antileukocyte antibodies including antiplatelet antibody in the recipient’s serum but not in the donors’ serum. The authors speculate that antiplatelet antibodies can have an inhibitory effect in the recipient, which can modulate the bona fide procedure of ALI and lead to a delay in the onset of ALI. This case illustrates the crucial role of a recipient’s platelets in the development of TRALI.
delayed TRALI syndrome; recurrence; anti-platelet antibody
Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are characterized by rapid-onset respiratory failure following a variety of direct and indirect insults to the parenchyma or vasculature of the lungs. Mortality from ALI/ARDS is substantial, and current therapy primarily emphasizes mechanical ventilation and judicial fluid management plus standard treatment of the initiating insult and any known underlying disease. Current pharmacotherapy for ALI/ARDS is not optimal, and there is a significant need for more effective medicinal chemical agents for use in these severe and lethal lung injury syndromes. To facilitate future chemical-based drug discovery research on new agent development, this paper reviews present pharmacotherapy for ALI/ARDS in the context of biological and biochemical drug activities. The complex lung injury pathophysiology of ALI/ARDS offers an array of possible targets for drug therapy, including inflammation, cell and tissue injury, vascular dysfunction, surfactant dysfunction, and oxidant injury. Added targets for pharmacotherapy outside the lungs may also be present, since multiorgan or systemic pathology is common in ALI/ARDS. The biological and physiological complexity of ALI/ARDS requires the consideration of combined-agent treatments in addition to single-agent therapies. A number of pharmacologic agents have been studied individually in ALI/ARDS, with limited or minimal success in improving survival. However, many of these agents have complementary biological/biochemical activities with the potential for synergy or additivity in combination therapy as discussed in this article.
ARDS; ALI; inflammatory lung injury; lung injury therapy; anti-inflammatory therapy; surfactant therapy; INO therapy; anti-oxidants; pharmacotherapy
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.
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by acute respiratory failure and are associated with diverse disorders, such as pulmonary edema, pneumonia, sepsis, trauma, shock and lung contusion. Gene therapy is a potentially powerful approach to treat a variety of diseases related to ALI/ARDS. Numerous viral and non-viral methods for gene delivery to the lung have been developed, although pulmonary architecture and immune activation represent barriers to successful gene transfer. In this review, recent advances in the development of more efficient viral and non-viral gene transfer systems are discussed. In addition, the current status of gene therapy applied to ALI/ARDS-associated pulmonary diseases is reviewed. With the development of more efficient gene therapy vectors, gene therapy is a promising strategy for clinical application in the not too distant future.
Gene therapy; acute lung injury; viral vectors; non-viral vectors
Acute lung injury (ALI) and severe sepsis are common critical illnesses associated with the mobilization of bone marrow–derived cells into the circulation. By identifying and determining these cells' functional characteristics, unique prognostic biomarkers can be developed to help investigators understand the mechanisms underlying the pathophysiology of these disorders. We previously demonstrated an increased colony-forming unit (CFU) ability of circulating peripheral blood mononuclear cells (PBMCs) in patients with ALI, compared with healthy control subjects, that also correlated with improved survival. Here we hypothesized that the increased CFUs in ALI are associated with lung injury, and therefore ALI will result in an increased number of CFUs compared with patients exhibiting severe sepsis. To test this, blood was collected from 80 patients (63 with ALI, and 17 with severe sepsis) within 72 hours of diagnosis, and from 5 healthy control subjects. A CFU assay was performed on isolated PBMCs. Lung injury scores and the need for mechanical ventilation were greater in patients with ALI than in patients with severe sepsis (P < 0.0001 for each). CFU numbers were highest in patients with ALI compared with patients manifesting severe sepsis or control subjects (median CFU number [25–75% quartiles] of 61 [13–104] versus 17 [3–34] versus 5 [2–13], P < 0.0005). A trend toward improved survival was demonstrated in patients with high (≥ 48) CFUs (P = 0.06). No relationship between CFUs and mechanical ventilation was evident. Our findings suggest that increased colony-forming ability by PBMCs in ALI results from lung injury, independent of sepsis and mechanical ventilation. Factors contributing to colony formation by PBMCs in ALI, and the role PBMCs play in its pathogenesis remain to be fully established.
endothelium; critical illness; repair; prognosis; ARDS
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)
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