A trial of antioxidants N-acetylcysteine and procysteine in ARDS. The Antioxidant in ARDS Study Group

Treating oxidative stress in heart failure: past, present and future

Advances in cardiovascular research have identified oxidative stress as an important pathophysiological pathway in the development and progression of heart failure. Oxidative stress is defined as the imbalance between the production of reactive oxygen species (ROS) and the endogenous antioxidant defence system. Under physiological conditions, small quantities of ROS are produced intracellularly, which function in cell signalling, and can be readily reduced by the antioxidant defence system. However, under pathophysiological conditions, the production of ROS exceeds the buffering capacity of the antioxidant defence system, resulting in cell damage and death. Over the last decades several studies have tried to target oxidative stress with the aim to improve outcome in patients with heart failure, with very limited success. The reasons as to why these studies failed to demonstrate any beneficial effects remain unclear. However, one plausible explanation might be that currently employed strategies, which target oxidative stress by exogenous inhibition of ROS production or supplementation of exogenous antioxidants, are not effective enough, while bolstering the endogenous antioxidant capacity might be a far more potent avenue for therapeutic intervention. In this review, we provide an overview of oxidative stress in the pathophysiology of heart failure and the strategies utilized to date to target this pathway. We provide novel insights into modulation of endogenous antioxidants, which may lead to novel therapeutic strategies to improve outcome in patients with heart failure.

Pretreatment of ferulic acid attenuates inflammation and oxidative stress in a rat model of lipopolysaccharide-induced acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a fatal clinical condition that can be caused by pulmonary and non-pulmonary diseases. Oxidative stress and inflammation play key roles in the development of ARDS. In this study, we investigated whether ferulic acid (FA), an anti-oxidant, was beneficial for prophylaxis of ARDS. We established an ARDS rat model using lipopolysaccharide (LPS) administration. Lung injury was assessed by lung wet/dry ratio and broncho-alveolar lavage fluid (BALF) analysis. Hematoxylin and eosin staining was performed to evaluate the histological changes of the lungs. Enzyme-linked immunosorbent assay (ELISA) and immunoblotting were performed to detect proteins in BALF and lung tissue, respectively. Pulmonary function was determined by testing the oxygen level in BALF. FA pretreatment significantly alleviated LPS-induced pulmonary histological changes. FA reversed LPS-induced changes of lung wet/dry ratio, total protein in BALF, P(A-a)O₂, and PaO₂/FiO₂. In addition, LPS dramatically up-regulated the secretion of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and IL-10 in BALF (P < 0.01). However, pretreatment of FA significantly improved LPS-induced inflammation. We found that FA indeed reduced oxidative stress in the lungs by testing malondialdehyde level, myeloperoxidase level, and total anti-oxidant capacity. We also proved that FA inactivated multiple mitogen-activated protein kinase signaling pathways in the lungs. In conclusion, FA alleviated LPS-induced ARDS through its anti-inflammatory and anti-oxidant activities.

Evaluating Muscle Mass in Survivors of Acute Respiratory Distress Syndrome: A 1-Year Multicenter Longitudinal Study

OBJECTIVES

Rapid muscle wasting occurs during acute respiratory failure, resulting in muscle weakness and functional impairments. This study examines survivors' body composition in the year after acute respiratory distress syndrome and tests associations of patient characteristics, hospital exposures, and survivors' strength and physical functioning with whole body percent lean mass.

DESIGN

Prospective cohort study with 6- and 12-month follow-up.

SETTING

National study enrolling patients from five study centers.

PATIENTS

Acute respiratory distress syndrome survivors (n = 120).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Lean and fat mass from dual energy x-ray absorptiometry. On average, survivors gained whole body total mass (+1.4 kg; 0.1-2.7) and fat mass (+1.2 kg; 0.2-2.2) and maintained lean mass (+0.2 kg; -0.4 to 0.8) between 6 and 12 months. Proportionally, percent fat mass increased and percent lean mass decreased for the whole body, trunk, and legs (p < 0.05). Greater whole body percent lean mass was associated with younger age, male sex, and lower baseline body mass index, but not other patient characteristics or ICU/hospital exposures. Greater percent lean mass was also significantly associated with gait speed and 6-minute walk distance, but not volitional strength or self-reported functional status.

CONCLUSIONS

In the first year after acute respiratory distress syndrome, patients gained fat mass and maintained lean mass. We found no association of whole body percent lean mass with commonly hypothesized hospital risk factors. Direct measurement of body composition and performance-based functional measures may be helpful for understanding functional recovery in ICU survivors.

Angiotensin II type 2 receptor agonist Compound 21 attenuates pulmonary inflammation in a model of acute lung injury

Purpose

Although the role of the angiotensin II type 2 (AT2) receptor in acute lung injury is not yet completely understood, a protective role of this receptor subtype has been suggested. We hypothesized that, in a rodent model of acute lung injury, stimulation of the AT2 receptor with the direct agonist Compound 21 (C21) might have a beneficial effect on pulmonary inflammation and might improve pulmonary gas exchange.

Materials and methods

Male adult rats were divided into a treatment group that received pulmonary lavage followed by mechanical ventilation (LAV, n=9), a group receiving pulmonary lavage, mechanical ventilation, and direct stimulation of the AT2 receptor with C21 (LAV+C21, n=9), and a control group that received mechanical ventilation only (control, n=9). Arterial blood gas analysis was performed every 30 min throughout the 240-min observation period. Lung tissue and plasma samples were obtained at 240 min after the start of mechanical ventilation. Protein content and surface activity of bronchoalveolar lavage fluid were assessed and the wet/dry-weight ratio of lungs was determined. Transcriptional and translational regulation of pro- and antiinflammatory cytokines IL-1β, tumor necrosis factor-alpha, IL-6, IL-10, and IL-4 was determined in lungs and in plasma.

Results

Pulmonary lavage led to a significant impairment of gas exchange, the formation of lung edema, and the induction of pulmonary inflammation. Protein content of lavage fluid was increased and contained washed-out surfactant. Direct AT2 receptor stimulation with C21 led to a significant inhibition of tumor necrosis factor-alpha and IL-6 expressions in the lungs, whereas the expressions of IL-1, IL-10, and IL-4 remained unchanged. During the 240-min observation period, AT2 receptor stimulation did not improve pulmonary gas exchange or lung edema.

Conclusion

In this rodent model of acute lung injury after repeated pulmonary lavage, AT2 receptor stimulation attenuates pulmonary inflammation but does not improve gas exchange.

Neutrophil-mediated vascular barrier injury: Role of neutrophil extracellular traps

Neutrophils play an essential role in host defense against infection or injury. While neutrophil activation is necessary for pathogen clearance and tissue repair, a hyperactive response can lead to tissue damage and microcirculatory disorders, a process involving complex neutrophil-endothelium cross talk. This review highlights recent research findings about neutrophil-mediated signaling and structural changes, including those induced by neutrophil extracellular traps, which ultimately lead to vascular barrier injury.

Mechanisms and consequences of oxidative stress in lung disease: therapeutic implications for an aging populace

The rapid expansion of the elderly population has led to the recent epidemic of age-related diseases, including increased incidence and mortality of chronic and acute lung diseases. Numerous studies have implicated aging and oxidative stress in the pathogenesis of various pulmonary diseases; however, despite recent advances in these fields, the specific contributions of aging and oxidative stress remain elusive. This review will discuss the consequences of aging on lung morphology and physiology, and how redox imbalance with aging contributes to lung disease susceptibility. Here, we focus on three lung diseases for which aging is a significant risk factor: acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). Preclinical and clinical development for redox- and senescence-altering therapeutic strategies are discussed, as well as scientific advancements that may direct current and future therapeutic development. A deeper understanding of how aging impacts normal lung function, redox balance, and injury-repair processes will inspire the development of new therapies to prevent and/or reverse age-associated pulmonary diseases, and ultimately increase health span and longevity. This review is intended to encourage basic, clinical, and translational research that will bridge knowledge gaps at the intersection of aging, oxidative stress, and lung disease to fuel the development of more effective therapeutic strategies for lung diseases that disproportionately afflict the elderly.

Alcohol abuse is associated with enhanced pulmonary and systemic xanthine oxidoreductase activity

Acute respiratory distress syndrome (ARDS) is a common and devastating disorder. Alcohol use disorders (AUDs) increase ARDS risk and worsen outcomes through mechanisms that may include enhancement of pulmonary oxidative stress. Alcohol consumption increases activity of the enzyme xanthine oxidoreductase (XOR) that contributes to production of both reactive oxygen species (ROS) and uric acid, a damage-associated molecular pattern. These by-products have the potential to modulate proinflammatory pathways, such as those involving cyclooxygenase (COX)-2, and to activate the nucleotide-binding domain, leucine-rich-containing family, pyrin-domain containing-3 (NLRP3) inflammasome. We sought to determine if pulmonary and systemic XOR activity was altered by AUDs. Bronchoscopy with bronchoalveolar lavage (BAL) and blood sampling was performed in otherwise healthy human subjects with AUDs and controls. Uric acid in epithelial-lining fluid, derived from BAL, was substantially higher among individuals with AUDs and did not normalize after 7 days of abstinence; serum uric acid did not differ across groups. XOR enzyme activity in fresh BAL cells and serum was significantly increased in subjects with AUDs. XOR protein in BAL cells from AUD subjects was increased in parallel with COX-2 expression, and furthermore, mRNA expression of NLRP3 inflammasome components was sustained in LPS-stimulated BAL cells from AUD subjects in conjunction with increased IL-1β. Our data suggest that AUDs augment pulmonary and systemic XOR activity that may contribute to ROS and uric acid generation, promoting inflammation. Further investigations will be necessary to determine if XOR inhibition can mitigate alcohol-associated pulmonary oxidative stress, diminish inflammation, and improve ARDS outcomes.

Bronchoalveolar Lavage Fluid Protein Expression in Acute Respiratory Distress Syndrome Provides Insights into Pathways Activated in Subjects with Different Outcomes

Acute respiratory distress syndrome (ARDS) is associated with high mortality. We sought to identify biological pathways in ARDS that differentiate survivors from non-survivors. We studied bronchoalveolar lavage fluid (BALF) from 36 patients with ARDS (20 survivors, 16 non-survivors). Each sample, obtained within seven days of ARDS onset, was depleted of high abundance proteins and labeled for iTRAQ LC-MS/MS separately. Protein identification and relative quantification was performed employing a target-decoy strategy. A variance weighted t-test was used to identify differential expression. Ingenuity Pathway Analysis was used to determine the canonical pathways that differentiated survivors from non-survivors. We identified 1115 high confidence proteins in the BALF out of which 142 were differentially expressed between survivors and non-survivors. These proteins mapped to multiple pathways distinguishing survivors from non-survivors, including several implicated in lung injury and repair such as coagulation/thrombosis, acute phase response signaling and complement activation. We also identified proteins assigned to fibrosis and ones involved in detoxification of lipid peroxide-mediated oxidative stress to be different in survivors and non-survivors. These results support our previous findings demonstrating early differences in the BALF protein expression in ARDS survivors vs. non-survivors, including proteins that counter oxidative stress and canonical pathways associated with fibrosis.

Effects of N-acetylcysteine treatment in acute respiratory distress syndrome: A meta-analysis

Acute respiratory distress syndrome (ARDS) is a serious complication of acute lung injury. Severe systemic inflammation is the main cause of multiple organ dysfunction and high mortality. Removal of reactive oxygen species by anti-oxidants has been applied in clinical practice. N-acetylcysteine (NAC) is the most commonly used anti-oxidant. However, the benefit of anti-oxidant therapy was not consistently demonstrated by previous studies. In the present study, a meta-analysis was performed to evaluate the effects of NAC for adult patients with ARDS. The PubMed, Cochrane and EMBASE databases were searched to retrieve all of the available randomized controlled trials (RCTs) published until October 2015. Quality evaluation of included studies was performed according to the modified Jadad scale score. The Cochrane Collaboration Review Manager 5.3 software was used to perform the meta-analysis. Five RCTs comprising 183 patients were found to be eligible for inclusion in the meta-analysis. Pooled analysis showed that NAC did not contribute to reduce short-term mortality [risk ratio (RR)=0.73; 95% confidence interval (CI): 0.50–1.07; P=0.10] or 30-day mortality (RR=0.72; 95% CI: 0.44–1.19; P=0.20) when compared with those in the control group. However, duration of intensive care unit (ICU) stay in the NAC group was shortened [weighted mean difference (WMD), −4.56; 95% CI: (−7.32 to −1.80); P=0.001]. There was no significant difference in the ratio of partial arterial oxygen pressure to the fraction of inspired oxygen between the two groups [WMD, 54.34; 95% CI: (−30.50 to 139.17); P=0.21]. No severe adverse reactions were observed in the patients included. Although the duration of ICU stay was shortened, the clinical benefits of NAC were limited for ARDS based on the present meta-analysis. As the number of included trials and patients was small, additional trials are required to provide sufficient evidence for the efficacy of NAC in ARDS.

The clinical practice guideline for the management of ARDS in Japan

BACKGROUND

The Japanese Society of Respiratory Care Medicine and the Japanese Society of Intensive Care Medicine provide here a clinical practice guideline for the management of adult patients with ARDS in the ICU.

METHOD

The guideline was developed applying the GRADE system for performing robust systematic reviews with plausible recommendations. The guideline consists of 13 clinical questions mainly regarding ventilator settings and drug therapies (the last question includes 11 medications that are not approved for clinical use in Japan).

RESULTS

The recommendations for adult patients with ARDS include: we suggest against early tracheostomy (GRADE 2C), we suggest using NPPV for early respiratory management (GRADE 2C), we recommend the use of low tidal volumes at 6-8 mL/kg (GRADE 1B), we suggest setting the plateau pressure at 30cmH20 or less (GRADE2B), we suggest using PEEP within the range of plateau pressures less than or equal to 30cmH2O, without compromising hemodynamics (Grade 2B), and using higher PEEP levels in patients with moderate to severe ARDS (Grade 2B), we suggest using protocolized methods for liberation from mechanical ventilation (Grade 2D), we suggest prone positioning especially in patients with moderate to severe respiratory dysfunction (GRADE 2C), we suggest against the use of high frequency oscillation (GRADE 2C), we suggest the use of neuromuscular blocking agents in patients requiring mechanical ventilation under certain circumstances (GRADE 2B), we suggest fluid restriction in the management of ARDS (GRADE 2A), we do not suggest the use of neutrophil elastase inhibitors (GRADE 2D), we suggest the administration of steroids, equivalent to methylprednisolone 1-2mg/kg/ day (GRADE 2A), and we do not recommend other medications for the treatment of adult patients with ARDS (GRADE1B; inhaled/intravenous β2 stimulants, prostaglandin E1, activated protein C, ketoconazole, and lisofylline, GRADE 1C; inhaled nitric oxide, GRADE 1D; surfactant, GRADE 2B; granulocyte macrophage colony-stimulating factor, N-acetylcysteine, GRADE 2C; Statin.).

CONCLUSIONS

This article was translated from the Japanese version originally published as the ARDS clinical practice guidelines 2016 by the committee of ARDS clinical practice guideline (Tokyo, 2016, 293p, available from http://www.jsicm.org/ARDSGL/ARDSGL2016.pdf). The original article, written for Japanese healthcare providers, provides points of view that are different from those in other countries.

Clinical trials in acute respiratory distress syndrome: challenges and opportunities

This year is the 50th anniversary of the first description of acute respiratory distress syndrome (ARDS). Since then, much has been learned about the pathogenesis of lung injury in ARDS, with an emphasis on the mechanisms of injury to the lung endothelium and the alveolar epithelium. In terms of treatment, major progress has been made in reducing mortality from ARDS with lung-protective ventilation, using a tidal volume of 6 mL per kg of predicted bodyweight and a plateau airway pressure of less than 30 cm H₂O. In more severely hypoxaemic patients with ARDS, neuromuscular blockade and prone positioning have further reduced mortality, probably by extending the therapeutic effects of lung protective ventilation. Fluid-conservative therapy has also increased ventilator-free days in patients with ARDS. The lack of success of pharmacological therapies for ARDS, however, presents a continued challenge in the field. In addition to presenting a brief summary of previous experience with clinical trials in ARDS, we focus in this Review on future opportunities to improve clinical trial design to maximise the likelihood of identifying beneficial pharmacological therapies. In view of the heterogeneity in ARDS, both prognostic and predictive enrichment strategies are needed that target therapies toward specific subgroups of patients with ARDS on the basis of both severity and biology. Approaches to reducing heterogeneity in ARDS clinical trials include using physiological, radiographic, and biological criteria to select patients for both phase 2 and 3 trials. Additionally, interest is growing in the design of preventive clinical trials in ARDS and to initiate early treatment of patients with acute lung injury before the need for endotracheal intubation. We also present promising new approaches to treating ARDS, including combination therapies, cell-based therapies, and generic pharmacological compounds with low-risk profiles that are already in routine clinical use for other clinical indications.

Fifty Years of Research in ARDS. Is Acute Respiratory Distress Syndrome a Preventable Disease?

Despite significant advances in our understanding and management of patients with acute respiratory distress syndrome (ARDS), the morbidity and mortality from ARDS remains high. Given the limited number of effective treatments for established ARDS, the strategic focus of ARDS research has shifted toward identifying patients with or at high risk of ARDS early in the course of the underlying illness, when strategies to reduce the development and progression of ARDS and associated organ failures can be systematically evaluated. In this review, we summarize the rationale, current evidence, and future directions in ARDS prevention.

Upregulation of nuclear factor-κB activity mediates CYP24 expression and reactive oxygen species production in indoxyl sulfate-induced chronic kidney disease

AIM

Chronic kidney disease (CKD) is associated with an inflammation-mediated process, and the vitamin D (3) catabolizing enzyme, CYP24, is frequently overexpressed in CKD, where it may play a crucial role in kidney disease.

METHODS

Herein, in this study, we investigated CYP24, reactive oxygen species (ROS), and inflammatory responses in an indoxyl sulfate (IS)-induced CKD model to elucidate the role of CYP24 in CKD.

RESULTS

Our results showed that IS upregulates proinflammatory cytokine, CYP24 and nuclear factor-κB (NF-κB) expression in human renal proximal tubule epithelial cells. In addition, IS treatment increased ROS production and simultaneously upregulated CYP24 expression and NF-κB translocation. Moreover, the IS-induced upregulation of CYP24 expression was alleviated by an inhibitor of NF-κB, as well as a siRNA specific to NF-κB p65. Furthermore, the renal cortex of DN (Dahl salt-resistant normotensive) + IS, DH (Dahl salt-sensitive hypertensive), and DH + IS rats showed increased expression of NF-κB p65, CYP24, 8-hydroxydeoxyguanosine (8-OHdG), a marker of ROS and macrophage infiltration compared with DN rats.

CONCLUSIONS

These results provide evidence that administration of IS in human renal tubular epithelial cells upregulates NF-κB, which leads to increase CYP24 expression and ROS production. They also suggest that suppressing NF-κB signalling is promising for the development into a strategy for CKD treatment.

ROS Signaling in the Pathogenesis of Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS)

The generation of reactive oxygen species (ROS) plays an important role for the maintenance of cellular processes and functions in the body. However, the excessive generation of oxygen radicals under pathological conditions such as acute lung injury (ALI) and its most severe form acute respiratory distress syndrome (ARDS) leads to increased endothelial permeability. Within this hallmark of ALI and ARDS, vascular microvessels lose their junctional integrity and show increased myosin contractions that promote the migration of polymorphonuclear leukocytes (PMNs) and the transition of solutes and fluids in the alveolar lumen. These processes all have a redox component, and this chapter focuses on the role played by ROS during the development of ALI/ARDS. We discuss the origins of ROS within the cell, cellular defense mechanisms against oxidative damage, the role of ROS in the development of endothelial permeability, and potential therapies targeted at oxidative stress.

Bioavailable estradiol concentrations are elevated and predict mortality in septic patients: a prospective cohort study

BACKGROUND

Experimental studies demonstrate beneficial immunological and hemodynamic effects of estradiol in animal models of sepsis. This raises the question whether estradiol contributes to sex differences in the incidence and outcomes of sepsis in humans. Yet, total estradiol levels are elevated in sepsis patients, particularly nonsurvivors. Bioavailable estradiol concentrations have not previously been reported in septic patients. The bioavailable estradiol concentration accounts for aberrations in estradiol carrier protein concentrations that could produce discrepancies between total and bioavailable estradiol levels. We hypothesized that bioavailable estradiol levels are low in septic patients and sepsis nonsurvivors.

METHODS

We conducted a combined case-control and prospective cohort study. Venous blood samples were obtained from 131 critically ill septic patients in the medical and surgical intensive care units at the University of Rochester Medical Center and 51 control subjects without acute illness. Serum bioavailable estradiol concentrations were calculated using measurements of total estradiol, sex hormone-binding globulin, and albumin. Comparisons were made between patients with severe sepsis and control subjects and between hospital survivors and nonsurvivors. Multivariable logistic regression analysis was also performed.

RESULTS

Bioavailable estradiol concentrations were significantly higher in sepsis patients than in control subjects (211 [78-675] pM vs. 100 [78-142] pM, p < 0.01) and in sepsis nonsurvivors than in survivors (312 [164-918] pM vs. 167 [70-566] pM, p = 0.04). After adjustment for age and comorbidities, patients with bioavailable estradiol levels above the median value had significantly higher risk of hospital mortality (OR 4.27, 95 % CI 1.65-11.06, p = 0.003). Bioavailable estradiol levels were directly correlated with severity of illness and did not differ between men and women.

CONCLUSIONS

Contrary to our hypothesis, bioavailable estradiol levels were elevated in sepsis patients, particularly nonsurvivors, and were independently associated with mortality. Whether estradiol's effects are harmful, beneficial, or neutral in septic patients remains unknown, but our findings raise caution about estradiol's therapeutic potential in this setting. Our findings do not provide an explanation for sex-based differences in sepsis incidence and outcomes.

The Relationship Between Airway Antioxidant Levels, Alcohol Use Disorders, and Cigarette Smoking

BACKGROUND

Alcohol use disorders (AUDs) and cigarette smoking are associated with pulmonary oxidative stress, likely related to antioxidant depletion. Pulmonary oxidative stress may adversely affect innate immunity, leading to increased pneumonia susceptibility and severity, including development of the acute respiratory distress syndrome. In people with AUDs, most of whom smoke, antioxidant therapy can potentially restore immune cell function and attenuate pneumonia development. Challenges to human investigations of antioxidant therapies include an inability to identify pulmonary oxidative stress noninvasively and the optimal route to deliver pulmonary antioxidants. We sought to determine whether bronchoalveolar lavage (BAL) measures of thiol antioxidants from a 50-ml upper airway aliquot approximated those in the alveolar space and to determine whether AUDs and/or smoking affected these relationships.

METHODS

Healthy human subjects with and without AUDs, including smokers and nonsmokers, underwent BAL. Samples obtained after the first 50-ml normal saline aliquot were analyzed as representing bronchial airways; subsequent 50-ml aliquots were analyzed as representative of the alveolar space. Reduced and oxidized (GSSG) glutathione, cysteine (Cys), and its oxidized species, cystine, along with mixed disulfides (MDs) were quantified using high-performance liquid chromatography. The percent of total thiols present in their oxidized forms, and thiol redox potentials, were calculated.

RESULTS

Positive correlations between upper and lower BAL fluid thiol species were observed that were most robust for GSSG (ρ = 0.85), Cys (ρ = 0.83), and MDs (ρ = 0.69), but poor for thiol redox potential measures. In contrast to nonsmokers (either with or without AUDs), in subjects with AUDs who smoked, upper BAL fluid %GSSG, Cys, and MD measures were relatively increased compared to lower.

CONCLUSIONS

A small volume BAL procedure may be suitable to assess intrapulmonary oxidative stress related to thiol depletion. Factors including AUDs and smoking may disproportionately increase upper airways oxidative stress that could be relevant for therapeutic interventions.

Alcohol and lung injury and immunity

Annually, excessive alcohol use accounts for more than $220 billion in economic costs and 80,000 deaths, making excessive alcohol use the third leading lifestyle-related cause of death in the US. Patients with an alcohol-use disorder (AUD) also have an increased susceptibility to respiratory pathogens and lung injury, including a 2-4-fold increased risk of acute respiratory distress syndrome (ARDS). This review investigates some of the potential mechanisms by which alcohol causes lung injury and impairs lung immunity. In intoxicated individuals with burn injuries, activation of the gut-liver axis drives pulmonary inflammation, thereby negatively impacting morbidity and mortality. In the lung, the upper airway is the first checkpoint to fail in microbe clearance during alcohol-induced lung immune dysfunction. Brief and prolonged alcohol exposure drive different post-translational modifications of novel proteins that control cilia function. Proteomic approaches are needed to identify novel alcohol targets and post-translational modifications in airway cilia that are involved in alcohol-dependent signal transduction pathways. When the upper airway fails to clear inhaled pathogens, they enter the alveolar space where they are primarily cleared by alveolar macrophages (AM). With chronic alcohol ingestion, oxidative stress pathways in the AMs are stimulated, thereby impairing AM immune capacity and pathogen clearance. The epidemiology of pneumococcal pneumonia and AUDs is well established, as both increased predisposition and illness severity have been reported. AUD subjects have increased susceptibility to pneumococcal pneumonia infections, which may be due to the pro-inflammatory response of AMs, leading to increased oxidative stress.

Timing of Intubation and Clinical Outcomes in Adults With Acute Respiratory Distress Syndrome

OBJECTIVE

The prevalence, clinical characteristics, and outcomes of critically ill, nonintubated patients with evidence of the acute respiratory distress syndrome remain inadequately characterized.

DESIGN

Secondary analysis of a prospective observational cohort study.

SETTING

Vanderbilt University Medical Center.

PATIENTS

Among adult patients enrolled in a large, multi-ICU prospective cohort study between the years of 2006 and 2011, we studied intubated and nonintubated patients with acute respiratory distress syndrome as defined by acute hypoxemia (PaO2/FIO2 ≤ 300 or SpO2/FIO2 ≤ 315) and bilateral radiographic opacities not explained by cardiac failure. We excluded patients not committed to full respiratory support.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 457 patients with acute respiratory distress syndrome, 106 (23%) were not intubated at the time of meeting all other acute respiratory distress syndrome criteria. Nonintubated patients had lower morbidity and severity of illness than intubated patients; however, mortality at 60 days was the same (36%) in both groups (p = 0.91). Of the 106 nonintubated patients, 36 (34%) required intubation within the subsequent 3 days of follow-up; this late-intubation subgroup had significantly higher 60-day mortality (56%) when compared with the both early intubation group (36%, P<0.03) and patients never requiring intubation (26%; p = 0.002). Increased mortality in the late intubation group persisted at 2-year follow-up. Adjustment for baseline clinical and demographic differences did not change the results.

CONCLUSIONS

A substantial proportion of critically ill adults with acute respiratory distress syndrome were not intubated in their initial days of intensive care, and many were never intubated. Late intubation was associated with increased mortality. Criteria defining the acute respiratory distress syndrome prior to need for positive pressure ventilation are required so that these patients can be enrolled in clinical studies and to facilitate early recognition and treatment of acute respiratory distress syndrome.

Isovitexin Exerts Anti-Inflammatory and Anti-Oxidant Activities on Lipopolysaccharide-Induced Acute Lung Injury by Inhibiting MAPK and NF-κB and Activating HO-1/Nrf2 Pathways

Oxidative damage and inflammation are closely associated with the pathogenesis of acute lung injury (ALI). Thus, we explored the protective effect of isovitexin (IV), a glycosylflavonoid, in the context of ALI. To accomplish this, we created in vitro and in vivo models by respectively exposing macrophages to lipopolysaccharide (LPS) and using LPS to induce ALI in mice. In vitro, our results showed that IV treatment reduced LPS-induced pro-inflammatory cytokine secretion, iNOS and COX-2 expression and decreased the generation of ROS. Consistent findings were obtained in vivo. Additionally, IV inhibited H₂O₂-induced cytotoxicity and apoptosis. However, these effects were partially reversed following the use of an HO-1 inhibitor in vitro. Further studies revealed that IV significantly inhibited MAPK phosphorylation, reduced NF-κB nuclear translocation, and upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) expression in RAW 264.7 cells. In vivo, pretreatment with IV attenuated histopathological changes, infiltration of polymorphonuclear granulocytes and endothelial activation, decreased the expression of ICAM-1 and VCAM-1, reduced the levels of MPO and MDA, and increased the content of GSH and SOD in ALI. Furthermore, IV treatment effectively increased Nrf2 and HO-1 expression in lung tissues. Therefore, IV may offer a protective role against LPS-induced ALI by inhibiting MAPK and NF-κB and activating HO-1/Nrf2 pathways.

Systemic inflammation and oxidative stress post-lung resection: Effect of pretreatment with N-acetylcysteine

BACKGROUND AND OBJECTIVE

N-acetylcysteine has been used to treat a variety of lung diseases, where is it thought to have an antioxidant effect. In a randomized placebo-controlled double-blind study, the effect of N-acetylcysteine on systemic inflammation and oxidative damage was examined in patients undergoing lung resection, a human model of acute lung injury.

METHODS

Eligible adults were randomized to receive preoperative infusion of N-acetylcysteine (240 mg/kg over 12 h) or placebo. Plasma thiols, interleukin-6, 8-isoprostane, ischaemia-modified albumin, red blood cell glutathione and exhaled breath condensate pH were measured pre- and post-operatively as markers of local and systemic inflammation and oxidative stress.

RESULTS

Patients undergoing lung resection and one-lung ventilation exhibited significant postoperative inflammation and oxidative damage. Postoperative plasma thiol concentration was significantly higher in the N-acetylcysteine-treated group. However, there was no significant difference in any of the measured biomarkers of inflammation or oxidative damage, or in clinical outcomes, between N-acetylcysteine and placebo groups.

CONCLUSION

Preoperative administration of N-acetylcysteine did not attenuate postoperative systemic or pulmonary inflammation or oxidative damage after lung resection.

CLINICAL TRIAL REGISTRATION

NCT00655928 at ClinicalTrials.gov.

Reciprocal regulation of TGF-β and reactive oxygen species: A perverse cycle for fibrosis

Transforming growth factor beta (TGF-β) is the most potent pro-fibrogenic cytokine and its expression is increased in almost all of fibrotic diseases. Although signaling through Smad pathway is believed to play a central role in TGF-β's fibrogenesis, emerging evidence indicates that reactive oxygen species (ROS) modulate TGF-β's signaling through different pathways including Smad pathway. TGF-β1 increases ROS production and suppresses antioxidant enzymes, leading to a redox imbalance. ROS, in turn, induce/activate TGF-β1 and mediate many of TGF-β's fibrogenic effects, forming a vicious cycle (see graphic flow chart on the right). Here, we review the current knowledge on the feed-forward mechanisms between TGF-β1 and ROS in the development of fibrosis. Therapeutics targeting TGF-β-induced and ROS-dependent cellular signaling represents a novel approach in the treatment of fibrotic disorders.

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TGF-β1 is the most potent ubiquitous profibrogenic cytokine.

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TGF- β 1 induces redox imbalance by ↑ ROS production and ↓ anti-oxidant defense system

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Redox imbalance, in turn, activates latent TGF-β1 and induces TGF-β1 expression.

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Redox imbalance also mediates many of TGF-β1’s profibrogenic effects

Non-ventilatory approaches to prevent postoperative pulmonary complications

This educational narrative review provides a summary of non-ventilatory strategies to prevent postoperative pulmonary complications (PPCs). It highlights patient- and procedure-related risk factors for PPCs that are non-modifiable, potentially modifiable, or well modifiable. Non-ventilatory strategies, mainly based on the modification of risk factors, play a key role in reducing PPCs. Non-modifiable risk factors, most importantly age, American Society of Anesthesiologists (ASA) class, and risk of the procedure, should be recognized and patients intensively screened for the potential to optimize other, potentially or well-modifiable, risk factors. Potentially modifiable risk factors, mainly comorbidities and the surgical approach, increase the risk of PPCs. Patient-related factors can be improved while procedure-related factors may be adapted in high-risk patients. Well-modifiable risk factors, mainly certain anesthesia techniques, for example, general anesthesia, intravenous opioids or liberal fluid management, and smoking or alcohol abuse, should be avoided as far as possible in order to prevent PPCs.

Stem cells for respiratory failure

PURPOSE OF REVIEW

The prognosis of patients with respiratory failure in the ICU remains poor, while current therapeutic approaches are aimed at minimizing ventilator-induced lung injury. Stem cell-based therapies have the potential to transform respiratory failure treatment by achieving lung repair. The purpose of this article is to critically review the large body of clinical and experimental work performed with respect to the use of stem/progenitor cells in respiratory failure, and to discuss current challenges and future directions.

RECENT FINDINGS

Since the initial report of cell therapy for lung injury in 2005, numerous preclinical and clinical studies have been performed that support the ability of various stem cell populations to improve physiologic lung function and reduce inflammation in both infective and sterile acute respiratory distress syndrome. Nevertheless, many important issues (e.g., mechanism of action, long-term engraftment, optimal cell type, dose, route of administration) remain to be resolved.

SUMMARY

Cell-based therapeutics hold promise, particularly for acute respiratory distress syndrome, and early preclinical testing has been encouraging. To advance clinical testing of cell therapies in respiratory failure, and to help ensure that this approach will facilitate bench-to-bedside and bedside-to-bench discoveries, parallel paths of basic and clinical research are needed, including measures of cell therapy effectiveness in vivo and in vitro.

Targeting normoxemia in acute respiratory distress syndrome may cause worse short-term outcomes because of oxygen toxicity

It was suggested that targeting normoxemia (PaO2 85-110 mm Hg) in patients with acute respiratory distress syndrome (ARDS) might prevent neurocognitive dysfunction in survivors. However, targeting normoxemia may cause detrimental effects to the lungs from oxygen toxicity. Some have suggested that oxygen is not harmful to the lungs at FiO2 (fraction of inspired oxygen) levels less than 0.6-0.7, but contrasting evidence in normal humans suggests that there can be untoward effects of moderate FiO2 levels. Furthermore, in experimental models of the acute respiratory distress syndrome, coexisting lung inflammation increases susceptibility to oxygen toxicity. Coexisting lung inflammation may lower the threshold for oxygen toxicity in patients with ARDS or in other acute illnesses in the lung. Moreover, physicians frequently prescribe higher FiO2 levels than are necessary to achieve their arterial oxygenation goal, further increasing the risk of oxygen toxicity. Targeting normoxemia in patients with ARDS may prevent some long-term neurocognitive deficits in survivors, but it may increase lung inflammation and cause worse short-term clinical outcomes. We advocate for a clinical trial in patients with ARDS to determine more appropriate goals for arterial oxygenation.

Identification of a nonsynonymous polymorphism in the SVEP1 gene associated with altered clinical outcomes in septic shock

OBJECTIVES

Mortality from septic shock is highly heritable. The identification of causal genetic factors is insufficient. To discover key contributors, we first identified nonsynonymous single-nucleotide polymorphisms in conserved genomic regions that are predicted to have significant effects on protein function. We then test the hypothesis that these nonsynonymous single-nucleotide polymorphisms across the genome alter clinical outcome of septic shock.

DESIGN

Genetic-association study plus in vitro experiment using primary cells plus in silico analysis using genomic DNA and protein database.

SETTING

Twenty-seven ICUs at academic teaching centers in Canada, Australia, and the United States.

PATIENTS

Patients with septic shock of European ancestry (n = 520).

INTERVENTIONS

Patients with septic shock were genotyped for 843 nonsynonymous single-nucleotide polymorphisms in conserved regions of the genome and are predicted to have damaging effects from the protein sequence.

MEASUREMENTS AND MAIN RESULTS

The primary outcome variable was 28-day mortality. Secondary outcome variables were organ dysfunction. Productions of adhesion molecules including interleukin-8, growth-regulated oncogene-α, monocyte chemoattractant protein-1, and monocyte chemoattractant protein-3 were measured in human umbilical vein endothelial cells after SVEP1 gene silencing by RNA interference. Patients with septic shock having the SVEP1 C allele of nonsynonymous single-nucleotide polymorphism, SVEP1 c.2080A>C (p. Gln581His, rs10817033), had a significant increase in the hazard of death over the 28 days (hazard ratio, 1.72; 95% CI, 1.31-2.26; p = 9.7 × 10-5) and increased organ dysfunction and needed more organ support (p < 0.05). Silencing SVEP1 significantly increased interleukin-8, growth-regulated oncogene-α, monocyte chemoattractant protein-1, monocyte chemoattractant protein-3 production in human umbilical vein endothelial cells under lipopolysaccharide stimulation (p < 0.01).

CONCLUSIONS

C allele of SVEP1 c.2080A>C (p. Gln581His) single-nucleotide polymorphism, a non-synonymous single-nucleotide polymorphism in conserved regions and predicted to have damaging effects on protein structure, was associated with increased 28-day mortality and organ dysfunction of septic shock. SVEP1 appears to regulate molecules of the leukocyte adhesion pathway.

Alcohol abuse: critical pathophysiological processes and contribution to disease burden

Alcohol abuse; the most common and costly form of drug abuse, is a major contributing factor to many disease categories. The alcohol-attributable disease burden is closely related to the average volume of alcohol consumption, with dose-dependent relationships between amount and duration of alcohol consumption and the incidence of diabetes mellitus, hypertension, cardiovascular disease, stroke, and pneumonia. The frequent occurrence of alcohol use disorders in the adult population and the significant and widespread detrimental organ system effects highlight the importance of recognizing and further investigating the pathophysiological mechanisms underlying alcohol-induced tissue and organ injury.

Preservation of renal blood flow by the antioxidant EUK-134 in LPS-treated pigs

Sepsis is associated with an increase in reactive oxygen species (ROS), however, the precise role of ROS in the septic process remains unknown. We hypothesized that treatment with EUK-134 (manganese-3-methoxy N,N'-bis(salicyclidene)ethylene-diamine chloride), a compound with superoxide dismutase and catalase activity, attenuates the vascular manifestations of sepsis in vivo. Pigs were instrumented to measure cardiac output and blood flow in renal, superior mesenteric and femoral arteries, and portal vein. Animals were treated with saline (control), lipopolysaccharide (LPS; 10 µg·kg-1·h-1), EUK-134, or EUK-134 plus LPS. Results show that an LPS-induced increase in pulmonary artery pressure (PAP) as well as a trend towards lower blood pressure (BP) were both attenuated by EUK-134. Renal blood flow decreased with LPS whereas superior mesenteric, portal and femoral flows did not change. Importantly, EUK-134 decreased the LPS-induced fall in renal blood flow and this was associated with a corresponding decrease in LPS-induced protein nitrotyrosinylation in the kidney. PO2, pH, base excess and systemic vascular resistance fell with LPS and were unaltered by EUK-134. EUK-134 also had no effect on LPS-associated increase in CO. Interestingly, EUK-134 alone resulted in higher CO, BP, PAP, mean circulatory filling pressure, and portal flow than controls. Taken together, these data support a protective role for EUK-134 in the renal circulation in sepsis.

Emerging drugs for acute lung injury

INTRODUCTION

Acute respiratory distress syndromes (ARDS) are devastating disorders of overwhelming pulmonary inflammation and hypoxemia, resulting in high morbidity and mortality.

AREAS COVERED

The main pharmacological treatment strategies have focused on the attempted inhibition of excessive inflammation or the manipulation of the resulting physiological derangement causing respiratory failure. Additionally, such interventions may allow reduced occurence mechanical ventilation injury. Despite promising preclinical and small clinical studies, almost all therapies have been shown to be unsuccessful in large-scale randomized controlled trials. The evidence for pharmacological treatment for ARDS is reviewed. Potential future treatments are also presented.

EXPERT OPINION

We suggest for future clinical trials addressing prevention and early intervention to attenuate lung injury and progression to respiratory failure.

Environmental risk factors for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) remains a major cause of morbidity and mortality in critically ill patients. Over the past several decades, alcohol abuse and cigarette smoke exposure have been identified as risk factors for the development of ARDS. The mechanisms underlying these relationships are complex and remain under investigation but are thought to involve pulmonary immune impairment and alveolar epithelial and endothelial dysfunction. This review summarizes the epidemiologic data supporting links between these exposures and ARDS susceptibility and outcomes and highlights key mechanistic investigations that provide insight into the pathways by which each exposure is linked to ARDS.

Krüppel-like factor 5 mediates proinflammatory cytokine expression in lipopolysaccharide-induced acute lung injury through upregulation of nuclear factor-κB phosphorylation in vitro and in vivo

Acute lung injury (ALI) is associated with an inflammation-mediated process, and the transcription factor, Krüppel-like factor 5 (KLF5), might play a crucial role in inflammatory lung disease. In this study, we evaluated KLF5, reactive oxygen species (ROS), and inflammatory responses in a lipopolysaccharide- (LPS-) induced ALI model to elucidate the role of KLF5 in ALI. Our data indicated that LPS upregulates proinflammatory cytokine expression in human bronchial epithelial cells in a dose-dependent manner. We observed upregulated KLF5 protein expression in human bronchial epithelial cells exposed to LPS, with peak expression 1 h after LPS treatment, and subsequent upregulation of p65 protein expression and p65 phosphorylation at Ser276. These results indicate that KLF5 mediates proinflammatory cytokine expression by upregulating nuclear factor-kappaB (NF-κB) phosphorylation at p65 in response to LPS. LPS treatment also increased ROS production and simultaneously upregulated KLF5 expression and NF-κB translocation. N-acetylcysteine significantly reduced ROS levels and KLF5 and NF-κB translocation in nuclear extracts. Therefore, N-acetylcysteine pretreatment before LPS exposure reduces ROS, downregulates KLF5 expression, and subsequently reduces inflammatory responses by scavenging ROS. Overall, our study results indicate that KLF5 mediates proinflammatory cytokine expression through upregulation of NF-κB phosphorylation at p65 in LPS-induced ALI.

Effect of procysteine on aging-associated changes in hepatic GSH and SMase: evidence for transcriptional regulation of smpd3

In hepatocytes, aging-associated decline in GSH has been linked to activation of neutral SMase (nSMase), accumulation of bioactive ceramide, and inflammation. In this study, we seek to test whether dietary supplementation with the cysteine precursor, L-2-oxothiazolidine-4-carboxylic acid (OTC), would correct the aging-associated differences in hepatic GSH, nSMase, and ceramide. Young and aged mice were placed on a diet that either lacked sulfur-containing amino acids (SAAs) or had 0.5% OTC for 4 weeks. Mice fed standard chow were used as an additional control. SAA-deficient mice exhibited significant aging-associated differences in hepatic GSH, GSH/GSSG, ceramide, and nSMase. C24:1 ceramide, the major ceramide species in liver, was affected the most by aging, followed by the less abundant C16:0 ceramide. OTC supplementation eliminated the aging-associated differences in hepatic GSH and GSH/GSSG ratio. Surprisingly, however, instead of decreasing, the nSMase activity and ceramide increased in the OTC-fed mice irrespective of their age. These effects were due to elevated nSMase-2 mRNA and protein and appeared to be direct. Similar increases were seen in HepG2 cells following treatment with OTC. The OTC-fed aged mice also exhibited hepatic steatosis and triacylglyceride accumulation. These results suggest that OTC is a potent stimulant of nSMase-2 expression and that there may be unanticipated complications of OTC supplementation.

Oxidative Stress and Therapeutic Development in Lung Diseases

Oxidative stress has many implications in the pathogenesis of lung diseases. In this review, we provide an overview of Reactive Oxygen Species (ROS) and nitrogen (RNS) species and antioxidants, how they relate to normal physiological function and the pathophysiology of different lung diseases, and therapeutic strategies. The production of ROS/RNS from endogenous and exogenous sources is first discussed, followed by antioxidant systems that restore oxidative balance and cellular homeostasis. The contribution of oxidant/antioxidant imbalance in lung disease pathogenesis is also discussed. An overview of therapeutic strategies is provided, such as augmenting NO bioactivity, blocking the production of ROS/RNS and replacement of deficient antioxidants. The limitations of current strategies and failures of clinical trials are then addressed, followed by discussion of novel experimental approaches for the development of improved antioxidant therapies.

The immunological benefit of higher dose N-acetyl cysteine following mechanical ventilation in critically ill patients

BACKGROUND

Sepsis complication is a major cause of death in multiple trauma critically ill patients. Defensin (cysteine rich anti-microbial peptides), as an important component of immune system, might play an important role in this process. There is also rising data on immunological effects of N-acetyl-cysteine (NAC), a commonly used anti-oxidant in oxidative stress conditions and glutathione (GSH) deficiencies. The aim of the present study was to evaluate the potential beneficial effects of NAC administration on multiple trauma patients with sepsis.

METHODS

In a prospective, randomized controlled study, 44 multiple trauma critically ill patients who were mechanically ventilated and met the criteria of sepsis and admitted to the intensive care unit (ICU) were randomized into two groups . Control group received all standard ICU therapies and NAC group received intravenous NAC 3 gr every 6 hours for 72 hours in addition to standard therapies. Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA) scores, length of ICU stay, ICU mortality were recorded. Levels of serum Immunoglobulin M (IgM), Human β-Defensin 2 (HβD2) and GSH were assessed at baseline and 24, 72, 120 hours after intervention.

RESULTS

During a period of 13-month screening, 44 patients underwent randomization but 5 patients had to be excluded. 21 patients in NAC group and 18 patients in control group completed the study. For both groups the length of ICU stay, SOFA score and systemic oxygenation were similar. Mortality rate (40% vs. 22% respectively, p = 0.209) and ventilator days (Mean ± SD 19.82 ± 19.55 days vs. 13.82 ± 11.89 days respectively, p = 0.266) were slightly higher for NAC group. IgM and GSH levels were similar between two groups (p = 0.325, 0.125 respectively), HβD2 levels were higher for NAC group (at day 3).

CONCLUSION

High dose of NAC administration not only did not improve patients' outcome, but also raised the risk of inflammation and was associated with increased serum creatinine.

Lung injury and its prognostic significance in acute liver failure

OBJECTIVE

Hypoxemia is a feared complication of acute liver failure, and high oxygen requirements will frequently lead to removal of patients from the transplant list. As data regarding the prevalence and outcome of acute respiratory distress syndrome in acute liver failure are scant and hypoxemia being a commonly encountered systemic complication, we analyzed radiological, gas exchange, and ventilator data in consecutive patients admitted with acute liver failure.

PATIENTS

Acute liver failure patients receiving mechanical ventilation admitted between January 2007 and February 2011 were included.

INTERVENTIONS

Patients were categorized according to the Berlin definition as: no acute respiratory distress syndrome, acute respiratory distress syndrome (PaO2/FIO2 < 300 mm Hg), and subdivisions of mild, moderate, and severe acute respiratory distress syndrome (200-300 mm Hg, 100-200 mm Hg, and < 100 mm Hg, respectively). Chest radiographs were independently assessed by two observers for the presence or absence of acute respiratory distress syndrome. Absence of left atrial pressure elevation was based on combined hemodynamic and echocardiographic assessment.

MEASUREMENTS AND MAIN RESULTS

Two hundred acute liver failure patients were admitted during the study period of whom 148, median age 39 years (16-74 yr), were included. Thirty-one (21%) had acute respiratory distress syndrome (17 mild acute respiratory distress syndrome [12%], 9 moderate acute respiratory distress syndrome [12%], and 5 severe acute respiratory distress syndrome) within the first 72 hours following admission. Acute respiratory distress syndrome patients required higher positive end-expiratory pressure (7 vs 6 vs 10 vs 15 cm H2O for no, mild, moderate, or severe acute respiratory distress syndrome, p = 0.014), had reduced respiratory system compliance (34 vs 29 vs 30 vs 23 L/cm H2O, p = 0.028), and an increased number of ventilator days (no acute respiratory distress syndrome, 10 d; mild acute respiratory distress syndrome acute lung injury, 12 d; moderate acute respiratory distress syndrome, 23 d; severe acute respiratory distress syndrome, 22 d; p = 0.097). Duration of liver intensive therapy unit stay (p = 0.175), survival (p = 0.877), inotrope requirements (p = 0.495), need for extracorporeal renal support (p = 0.565), and severity of organ failure scores were not affected. Extravascular lung water index had a moderate sensitivity of 65% and specificity of 77% for the prediction of acute respiratory distress syndrome.

CONCLUSION

The prevalence of lung injury is relatively low in acute liver failure, where 21% fulfilled acute respiratory distress syndrome criteria. Overall presence of acute respiratory distress syndrome appeared to have a limited impact on outcome.

Protein-based therapies for acute lung injury: targeting neutrophil extracellular traps

INTRODUCTION

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the acute onset of noncardiac respiratory insufficiency associated with bilateral lung infiltrations. During the past decade, mechanical ventilation strategies using low tidal volumes have reduced the mortality of ALI/ARDS to ∼ 20 - 40%. However, ALI/ARDS continues to be a major factor in global burden of diseases, with no pharmacological agents currently available.

AREAS COVERED

In this review, we discuss several inflammatory proteins involved in the molecular pathogenesis of ALI/ARDS. The complement cleavage product, C5a, is a peptide acting as a potent anaphylatoxin. C5a may trigger the formation of neutrophil extracellular traps (NETs) and release of histone proteins to the extracellular compartment during ALI/ARDS. NETs may activate platelets to release TGF-β, which is involved in tissue remodeling during the later phases of ALI/ARDS. Interception of C5a signaling or blockade of extracellular histones has recently shown promising beneficial effects in small animal models of ALI/ARDS.

EXPERT OPINION

Novel protein-based strategies for the treatment of ALI/ARDS may inspire the hopes of scientists, clinicians, and patients. Although neutralization of extracellular histones/NETs, C5a, and TGF-β is effective in experimental models of ALI/ARDS, controlled clinical trials will be necessary for further evaluation in future.

Rethinking antioxidants in the intensive care unit

Recently there was yet another clinical trial using antioxidants that failed in patients with critical illness. In this perspective, we suggest that antioxidants likely interfere with the normal immune response, thus contributing to the lack of efficacy in patients with critical illness.

One-year mortality and predictors of death among hospital survivors of acute respiratory distress syndrome

PURPOSE

Advances in supportive care and ventilator management for acute respiratory distress syndrome (ARDS) have resulted in declines in short-term mortality, but risks of death after survival to hospital discharge have not been well described. Our objective was to quantify the difference between short-term and long-term mortality in ARDS and to identify risk factors for death and causes of death at 1 year among hospital survivors.

METHODS

This multi-intensive care unit, prospective cohort included patients with ARDS enrolled between January 2006 and February 2010. We determined the clinical characteristics associated with in-hospital and 1-year mortality among hospital survivors and utilized death certificate data to identify causes of death.

RESULTS

Of 646 patients hospitalized with ARDS, mortality at 1 year was substantially higher (41 %, 95% CI 37-45%) than in-hospital mortality (24%, 95% CI 21-27%), P < 0.0001. Among 493 patients who survived to hospital discharge, the 110 (22%) who died in the subsequent year were older (P < 0.001) and more likely to have been discharged to a nursing home, other hospital, or hospice compared to patients alive at 1 year (P < 0.001). Important predictors of death among hospital survivors were comorbidities present at the time of ARDS, and not living at home prior to admission. ARDS-related measures of severity of illness did not emerge as independent predictors of mortality in hospital survivors.

CONCLUSIONS

Despite improvements in short-term ARDS outcomes, 1-year mortality is high, mostly because of the large burden of comorbidities, which are prevalent in patients with ARDS.

Endothelial targeting of liposomes encapsulating SOD/catalase mimetic EUK-134 alleviates acute pulmonary inflammation

Production of excessive levels of reactive oxygen species (ROS) in the vascular endothelium is a common pathogenic pathway in many dangerous conditions, including acute lung injury, ischemia-reperfusion, and inflammation. Ineffective delivery of antioxidants to the endothelium limits their utility for management of these conditions. In this study, we devised a novel translational antioxidant intervention targeted to the vascular endothelium using PEG-liposomes loaded with EUK-134 (EUK), a potent superoxide dismutase/catalase mimetic. EUK loaded into antibody-coated liposomes (size 197.8±4.5 nm diameter, PDI 0.179±0.066) exerted partial activity in the intact carrier, while full activity was recovered upon liposome disruption. For targeting we used antibodies (Abs) to platelet-endothelial cell adhesion molecule (PECAM-1). Both streptavidin-biotin and SATA/SMCC conjugation chemistries provided binding of 125-150 Ab molecules per liposome. Ab/EUK/liposomes, but not IgG/EUK/liposomes: i) bound to endothelial cells and inhibited cytokine-induced inflammatory activation in vitro; and, ii) accumulated in lungs after intravascular injection, providing >60% protection against pulmonary edema in endotoxin-challenged mice (vs <6% protection afforded by IgG/liposome/EUK counterpart). Since the design elements of this drug delivery system are already in clinical use (PEG-liposomes, antibodies, SATA/SMCC conjugation), it is an attractive candidate for translational interventions using antioxidant molecules such as EUK and other clinically acceptable drugs.

Oxidants and redox signaling in acute lung injury

Acute lung injury (ALI) and its more severe form of clinical manifestation, the acute respiratory distress syndrome is associated with significant dysfunction in air exchange due to inflammation of the lung parenchyma. Several factors contribute to the inflammatory process, including hypoxia (inadequate oxygen), hyperoxia (higher than normal partial pressure of oxygen), inflammatory mediators (such as cytokines), infections (viral and bacterial), and environmental conditions (such as cigarette smoke or noxious gases). However, studies over the past several decades suggest that oxidants formed in the various cells of the lung including endothelial, alveolar, and epithelial cells as well as lung macrophages and neutrophils in response to the factors mentioned above mediate the pathogenesis of ALI. Oxidants modify cellular proteins, lipids, carbohydrates, and DNA to cause their aberrant function. For example, oxidation of lipids changes membrane permeability. Interestingly, recent studies also suggest that spatially and temporally regulated production of oxidants plays an important role antimicrobial defense and immunomodulatory function (such as transcription factor activation). To counteract the oxidants an arsenal of antioxidants exists in the lung to maintain the redox status, but when overwhelmed tissue injury and exacerbation of inflammation occurs. We present below the current understanding of the pathogenesis of oxidant-mediated ALI.

The concentration of glutathione in human erythrocytes is a heritable trait

Glutathione (GSH) is a ubiquitous, redox-active, small molecule that is critical to cellular and organism health. In red blood cells (RBCs), the influence of the environment (e.g., diet and lifestyle) on GSH levels has been demonstrated in numerous studies. However, it remains unknown if levels of GSH are determined principally by environmental factors or if there is a genetic component, i.e., heritability. To investigate this we conducted a twin study. Twin studies are performed by comparing the similarity in phenotypes between mono- and dizygotic twin pairs. We determined the heritability of GSH, as well as its oxidation product glutathione disulfide (GSSG), the sum of GSH equivalents (tGSH), and the status of the GSSG/2GSH couple (marker of oxidation status, Ehc) in RBCs. In our study population we found that the estimated heritability for the intracellular concentration of GSH in RBCs was 57 %; for GSSG it was 51 %, tGSH 63 %, and Ehc 70 %. We conclude that a major portion of the phenotype of these traits is controlled genetically. We anticipate that these heritabilities will also be reflected in other cell types. The discovery that genetics plays a major role in the innate levels of redox-active species in RBCs is paradigm shifting and opens new avenues of research in the field of redox biology. Inherited RBC antioxidant levels may be important disease modifiers. By identifying the relative contributions of genes and the environment to antioxidant variation between individuals, new therapeutic strategies can be developed. Understanding the genetic determinants of these inherited traits may allow personalized approaches to relevant therapies.

Fluid flux and clearance in acute lung injury

Acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), were presciently described nearly two centuries ago by René Laennec, later to be described clinically in the 1950s and 1960s. Substantial advances have been made in understanding the pathogenesis of these forms of permeability pulmonary edema, including Starling forces and cellular transport mechanisms involved in the generation and resolution of this form of lung injury. Functional animal models and clinically applicable case definitions for ALI and ARDS were instrumental in gaining these new insights. Although no specific pharmacological therapies for ALI and ARDS yet exist, outcomes have improved with advancements in respiratory and fluid-based supportive therapies, and methods to prevent the development or exacerbation of lung injury. Newer targeted therapies continue to be tested for efficacy in this condition where mortality rates frequently exceed 30%. In this article, we review the history of the pathophysiology of lung fluid and solute movement and the seminal clinical observations that brought that history to clinical relevance. We review the relevant lung structure and function and the dynamics of edema formation and resolution, and we describe the related clinical syndromes and the current treatment modalities.

Reactive oxygen species in pulmonary vascular remodeling

The pathogenesis of pulmonary hypertension is a complex multifactorial process that involves the remodeling of pulmonary arteries. This remodeling process encompasses concentric medial thickening of small arterioles, neomuscularization of previously nonmuscular capillary-like vessels, and structural wall changes in larger pulmonary arteries. The pulmonary arterial muscularization is characterized by vascular smooth muscle cell hyperplasia and hypertrophy. In addition, in uncontrolled pulmonary hypertension, the clonal expansion of apoptosis-resistant endothelial cells leads to the formation of plexiform lesions. Based upon a large number of studies in animal models, the three major stimuli that drive the vascular remodeling process are inflammation, shear stress, and hypoxia. Although, the precise mechanisms by which these stimuli impair pulmonary vascular function and structure are unknown, reactive oxygen species (ROS)-mediated oxidative damage appears to play an important role. ROS are highly reactive due to their unpaired valence shell electron. Oxidative damage occurs when the production of ROS exceeds the quenching capacity of the antioxidant mechanisms of the cell. ROS can be produced from complexes in the cell membrane (nicotinamide adenine dinucleotide phosphate-oxidase), cellular organelles (peroxisomes and mitochondria), and in the cytoplasm (xanthine oxidase). Furthermore, low levels of tetrahydrobiopterin (BH4) and L-arginine the rate limiting cofactor and substrate for endothelial nitric oxide synthase (eNOS), can cause the uncoupling of eNOS, resulting in decreased NO production and increased ROS production. This review will focus on the ROS generation systems, scavenger antioxidants, and oxidative stress associated alterations in vascular remodeling in pulmonary hypertension.

Ionizing irradiation-induced radical stress stalls live meiotic chromosome movements by altering the actin cytoskeleton

Meiosis generates haploid cells or spores for sexual reproduction. As a prelude to haploidization, homologous chromosomes pair and recombine to undergo segregation during the first meiotic division. During the entire meiotic prophase of the yeast Saccharomyces cerevisiae, chromosomes perform rapid movements that are suspected to contribute to the regulation of recombination. Here, we investigated the impact of ionizing radiation (IR) on movements of GFP-tagged bivalents in live pachytene cells. We find that exposure of sporulating cultures with >40 Gy (4-krad) X-rays stalls pachytene chromosome movements. This identifies a previously undescribed acute radiation response in yeast meiosis, which contrasts with its reported radioresistance of up to 1,000 Gy in survival assays. A modified 3'-end labeling assay disclosed IR-induced dsDNA breaks (DSBs) in pachytene cells at a linear dose relationship of one IR-induced DSB per cell per 5 Gy. Dihydroethidium staining revealed formation of reactive oxygen species (ROS) in irradiated cells. Immobility of fuzzy-appearing irradiated bivalents was rescued by addition of radical scavengers. Hydrogen peroxide-induced ROS did reduce bivalent mobility similar to 40 Gy X IR, while they failed to induce DSBs. IR- and H2O2-induced ROS were found to decompose actin cables that are driving meiotic chromosome mobility, an effect that could be rescued by antioxidant treatment. Hence, it appears that the meiotic actin cytoskeleton is a radical-sensitive system that inhibits bivalent movements in response to IR- and oxidant-induced ROS. This may be important to prevent motility-driven unfavorable chromosome interactions when meiotic recombination has to proceed in genotoxic environments.

Alcohol and the Alveolar Epithelium

The distal airways are covered with a heterogeneous layer of cells known as the alveolar epithelium. Alveolar epithelial cells provide the major barrier between the airspace and fluid filled tissue compartments. As such, regulation of the alveolar epithelium is critical to maintain a healthy lung and for optimal gas exchange. In this chapter, we discuss functional roles for alveolar epithelial cells with particular emphasis on intercellular junctions and communication. As a thin layer of cells directly exposed to atmospheric oxygen, alveoli are particularly sensitive to oxidant insults. Alcohol significantly diminishes the normal antioxidant reserves of the alveolar epithelium, thereby rendering it sensitized for an exaggerated damage response to acute and chronic injuries. The effects of alcohol on alveolar epithelia are discussed along with open questions and potential therapeutic targets to prevent the pathophysiology of alcoholic lung disease.