Non-invasive evaluation of pulmonary glutathione in the exhaled breath condensate of otherwise healthy alcoholics

Exhaled Breath Condensate: An Update

Exhaled breath condensate (EBC) is a promising source of biomarkers of lung disease. EBC research and utility has increased substantially over the past 2 decades. This review summarizes many of the factors regarding the composition of EBC, its collection, and analysis for the utility of both clinicians and researchers.

The Effect of Alcohol Consumption on the Risk of ARDS: A Systematic Review and Meta-Analysis

BACKGROUND

To conduct a systematic review and meta-analysis evaluating the association between alcohol consumption and the risk of ARDS in adults.

METHODS

Medline, EMBASE and Web of Science were searched to identify observational studies evaluating the association between prior alcohol intake and the occurrence of ARDS among adults, published between 1985 and 2015 and with no language restriction. Reference lists were also screened. Demographic baseline data were extracted independently by two reviewers and random-effects meta-analyses were used to estimate pooled effect sizes with 95% confidence intervals. Subgroup analyses were used to explore heterogeneity.

RESULTS

Seventeen observational studies (177,674 people) met the inclusion criteria. Meta-analysis of 13 studies showed that any measure of high relative to low alcohol consumption was associated with a significantly increased risk of ARDS (OR, 1.89; 95% CI, 1.45-2.48; I2 = 48%; 13 studies); no evidence of publication bias was seen (P = .150). Sensitivity analyses indicated that this association was attributable primarily to an effect of a history of alcohol abuse (OR, 1.90; 95% CI, 1.40-2.60; 10 studies). Also, subgroup analyses identified that heterogeneity was explained by predisposing condition (trauma, sepsis/septic shock, pneumonia; P = .003).

CONCLUSIONS

Chronic high alcohol consumption significantly increases the risk of ARDS. This finding suggests that patients admitted to hospital should be screened for chronic alcohol use.

CNT Foam-Embedded Micro Gas Preconcentrator for Low-Concentration Ethane Measurements

Breath analysis has become increasingly important as a noninvasive process for the clinical diagnosis of patients suffering from various diseases. Many commercial gas preconcentration instruments are already being used to overcome the detection limits of commercial gas sensors for gas concentrations which are as low as ~100 ppb in exhaled breath. However, commercial instruments are large and expensive, and they require high power consumption and intensive maintenance. In the proposed study, a micro gas preconcentrator (μ-PC) filled with a carbon nanotube (CNT) foam as an adsorbing material was designed and fabricated for the detection of low-concentration ethane, which is known to be one of the most important biomarkers related to chronic obstructive pulmonary disease (COPD) and asthma. A comparison of the performance of two gas-adsorbing materials, i.e., the proposed CNT foam and commercial adsorbing material, was performed using the developed μ-PC. The experimental results showed that the synthesized CNT foam performs better than a commercial adsorbing material owing to its lower pressure drop and greater preconcentration efficiency in the μ-PC. The present results show that the application of CNT foam-embedded μ-PC in portable breath analysis systems holds great promise.

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.

Air pollution, physical activity, and markers of acute airway oxidative stress and inflammation in adolescents

BACKGROUND

The airway inflammatory response is likely the mechanism for adverse health effects related to exposure to air pollution. Increased ventilation rates during physical activity in the presence of air pollution increases the inhaled dose of pollutants. However, physical activity may moderate the relationship between air pollution and the inflammatory response. The present study aimed to characterize, among healthy adolescents, the relationship between dose of inhaled air pollution, physical activity, and markers of lung function, oxidative stress, and airway inflammation.

METHODS

With a non-probability sample of adolescents, this observational study estimated the association between air pollution dose and outcome measures by use of general linear mixed models with an unstructured covariance structure and a random intercept for subjects to account for repeated measures within subjects.

RESULTS

A one interquartile range (IQR) (i.e., 345.64 μg) increase in ozone (O3) inhaled dose was associated with a 29.16% average decrease in the percentage of total oxidized compounds (%Oxidized). A one IQR (i.e., 2.368E+10 particle) increase in total particle number count in the inhaled dose (PNT) was associated with an average decrease in forced expiratory flow (FEF25-75) of 0.168 L/second. Increasing activity levels attenuated the relationship between PNT inhaled dose and exhaled nitric oxide (eNO). The relationship between O3 inhaled dose and percent oxidized exhaled breath condensate cystine (%CYSS) was attenuated by activity level, with increasing activity levels corresponding to smaller changes from baseline for a constant O3 inhaled dose.

CONCLUSIONS

The moderating effects of activity level suggest that peaks of high concentration doses of air pollution may overwhelm the endogenous redox balance of cells, resulting in increased airway inflammation. Further research that examines the relationships between dose peaks over time and inflammation could help to determine whether a high concentration dose over a short period of time has a different effect than a lower concentration dose over a longer period of time.

An acetone bio-sniffer (gas phase biosensor) enabling assessment of lipid metabolism from exhaled breath

Several volatile organic compounds (VOCs) are released from human breath or skin. Like chemical substances in blood or urine, some of these vapors can provide valuable information regarding the state of the human body. A highly sensitive acetone biochemical gas sensor (bio-sniffer) was developed and used to measure exhaled breath acetone concentration, and assess lipid metabolism based on breath acetone analysis. A fiber-optic biochemical gas sensing system was constructed by attaching a flow-cell with nicotinamide adenine dinucleotide (NADH)-dependent secondary alcohol dehydrogenase (S-ADH) immobilized membrane onto a fiber-optic NADH measurement system. The NADH measurement system utilizes an ultraviolet-light emitting diode with peak emission of 335 nm as an excitation light source. NADH is consumed by the enzymatic reaction of S-ADH, and the consumption is proportional to the concentration of acetone vapor. Phosphate buffer which contained NADH was circulated into the flow-cell to rinse products and the excessive substrates from the optode. The change of fluorescent emitted from NADH is analyzed by the PMT. Hence, fluorescence intensity decreased as the acetone concentration increased. The relationship between fluorescence intensity and acetone concentration was identified from 20 ppb to 5300 ppb. This interval included the concentration of acetone vapor in the breath of healthy people and those suffering from disorders of carbohydrate metabolism. Finally, the acetone bio-sniffer was used to measure breath acetone during an exercise stress test on an ergometer after a period of fasting. The concentration of acetone in breath was shown to significantly increase after exercise. This biosensor allows rapid, highly sensitive and selective measurement of lipid metabolism.

The Physiology and Genetics of Oxidative Stress in Mycobacteria

During infection, Mycobacterium tuberculosis is exposed to a diverse array of microenvironments in the human host, each with its own unique set of redox conditions. Imbalances in the redox environment of the bacillus or the host environment serve as stimuli, which could regulate virulence. The ability of M. tuberculosis to evade the host immune response and cause disease is largely owing to the capacity of the mycobacterium to sense changes in its environment, such as host-generated gases, carbon sources, and pathological conditions, and alter its metabolism and redox balance accordingly for survival. In this article we discuss the redox sensors that are, to date, known to be present in M. tuberculosis , such as the Dos dormancy regulon, WhiB family, anti-σ factors, and MosR, in addition to the strategies present in the bacillus to neutralize free radicals, such as superoxide dismutases, catalase-peroxidase, thioredoxins, and methionine sulfoxide reductases, among others. M. tuberculosis is peculiar in that it appears to have a hierarchy of redox buffers, namely, mycothiol and ergothioneine. We discuss the current knowledge of their biosynthesis, function, and regulation. Ergothioneine is still an enigma, although it appears to have distinct and overlapping functions with mycothiol, which enable it to protect against a wide range of toxic metabolites and free radicals generated by the host. Developing approaches to quantify the intracellular redox status of the mycobacterium will enable us to determine how the redox balance is altered in response to signals and environments that mimic those encountered in the host.

Alcohol induced mitochondrial oxidative stress and alveolar macrophage dysfunction

An alcohol use disorder increases the risk of invasive and antimicrobial resistant community-acquired pneumonia and tuberculosis. Since the alveolar macrophage (AM) orchestrates the immune response in the alveolar space, understanding the underlying mechanisms by which alcohol suppresses AM phagocytosis is critical to improving clinical outcomes. In the alveolar space, chronic alcohol ingestion causes severe oxidative stress and depletes antioxidants which are critical for AM function. The mitochondrion is important in maintaining cellular redox balance and providing the ATP critical for phagocytosis. The focus of this study was to understand how alcohol triggers mitochondrial reactive oxygen species (ROS), stimulates cellular oxidative stress, and induces AM dysfunction. The current study also investigated the capacity of the mitochondrial targeted antioxidant, mitoTEMPOL (mitoT), in modulating mitochondrial oxidative stress, and AM dysfunction. Using in vitro ethanol exposure and AMs from ethanol-fed mice, ethanol promoted mitochondrial dysfunction including increased mitochondrial ROS, decreased mitochondrial membrane potential, and decreased ATP. Treatment with mitoT reversed these effects. Ethanol-induced decreases in phagocytosis and cell viability were also attenuated with mitoT. Therefore, antioxidants targeted to the mitochondria have the potential to ameliorate ethanol-induced mitochondrial oxidative stress and subsequent decreases in AM phagocytosis and cell viability.

Exhaled breath condensate in intubated neonates--a window into the lung's glutathione status

BACKGROUND

Analysis of exhaled breath condensates (EBC) is a non-invasive technique to evaluate biomarkers such as antioxidants in the pediatric population, but limited data exists of its use in intubated patients, particularly newborns. Currently, tracheal aspirate (TA) serves as the gold standard collection modality in critically ill newborns, but this method remains invasive. We tested the hypothesis that glutathione status would positively correlate between EBC and TA collections in intubated newborns in the Newborn Intensive Care Unit (NICU). We also hypothesized that these measurements would be associated with alveolar macrophage (AM) glutathione status in the newborn lung.

METHODS

Reduced glutathione (rGSH), glutathione disulfide (GSSG), and total GSH (rGSH + (2 X GSSG)) were measured in sequential EBC and TA samples from 26 intubated newborns via high performance liquid chromatography (HPLC). Additionally, AM glutathione was evaluated via immunofluorescence. Pearson's correlation coefficient and associated 95% confidence intervals were used to quantify the associations between raw and urea-corrected concentrations in EBC and TA samples and AM staining. Statistical significance was defined as p ≤ 0.05 using two-tailed tests. The sample size was projected to allow for a correlation coefficient of 0.5, with 0.8 power and alpha of 0.05.

RESULTS

EBC was obtainable from intubated newborns without adverse clinical events. EBC samples demonstrated moderate to strong positive correlations with TA samples in terms of rGSH, GSSG and total GSH. Positive correlations between the two sampling sites were observed in both raw and urea-corrected concentrations of rGSH, GSSG and total GSH. AM glutathione staining moderately correlated with GSSG and total GSH status in both the TA and EBC.

CONCLUSIONS

GSH status in EBC samples of intubated newborns significantly correlated with the GSH status of the TA sample and was reflective of cellular GSH status in this cohort of neonatal patients. Non-invasive EBC sampling of intubated newborns holds promise for monitoring antioxidant status such as GSH in the premature lung. Further studies are necessary to evaluate the potential relationships between EBC biomarkers in the intubated premature newborn and respiratory morbidities.

PROTEINS, PEPTIDES AND AMINO ACIDS AS MARKERS OF BRONCHOPULMONARY DISEASES

The article is a review of current literature on a content of proteins, peptides and amino acids in human exhaled breath. The results of proteomics and metabolomics applying for selective detection of individual proteins, peptides and amino acids are described. The study of exhaled breath condensate and exhaled endogenous particles contained lung proteins are considered. The peculiarities of protein, peptide and amino acid content in exhaled breath at various respiratory diseases are described. It is shown that the detectable substances may be specific markers of individual diseases.

Chronic-alcohol-abuse-induced oxidative stress in the development of acute respiratory distress syndrome

Chronic alcohol ingestion increases the risk of developing acute respiratory distress syndrome (ARDS), a severe form of acute lung injury, characterized by alveolar epithelial and endothelial barrier disruption and intense inflammation. Alcohol abuse is also associated with a higher incidence of sepsis or pneumonia resulting in a higher rate of admittance to intensive care, longer inpatient stays, higher healthcare costs, and a 2-4 times greater mortality rate. Chronic alcohol ingestion induced severe oxidative stress associated with increased ROS generation, depletion of the critical antioxidant glutathione (GSH), and oxidation of the thiol/disulfide redox potential in the alveolar epithelial lining fluid and exhaled breath condensate. Across intracellular and extracellular GSH pools in alveolar type II cells and alveolar macrophages, chronic alcohol ingestion consistently induced a 40-60 mV oxidation of GSH/GSSG suggesting that the redox potentials of different alveolar GSH pools are in equilibrium. Alcohol-induced GSH depletion or oxidation was associated with impaired functions of alveolar type II cells and alveolar macrophages but could be reversed by restoring GSH pools in the alveolar lining fluid. The aims of this paper are to address the mechanisms for alcohol-induced GSH depletion and oxidation and the subsequent effects in alveolar barrier integrity, modulation of the immune response, and apoptosis.

Exhaled breath condensate: a promising source for biomarkers of lung disease

Exhaled breath condensate (EBC) has been increasingly studied as a noninvasive research method for sampling the alveolar and airway space and is recognized as a promising source of biomarkers of lung diseases. Substances measured in EBC include oxidative stress and inflammatory mediators, such as arachidonic acid derivatives, reactive oxygen/nitrogen species, reduced and oxidized glutathione, and inflammatory cytokines. Although EBC has great potential as a source of biomarkers in many lung diseases, the low concentrations of compounds within the EBC present challenges in sample collection and analysis. Although EBC is viewed as a noninvasive method for sampling airway lining fluid (ALF), validation is necessary to confirm that EBC truly represents the ALF. Likewise, a dilution factor for the EBC is needed in order to compare across subjects and determine changes in the ALF. The aims of this paper are to address the characteristics of EBC; strategies to standardize EBC sample collection and review available analytical techniques for EBC analysis.

Respiratory health and breath condensate acidity in sawmill workers

PURPOSE

The aim of the study was to evaluate exhaled breath condensate acidity (EBC pH) as a biomarker of airway response to occupational respiratory hazards present in sawmill.

METHODS

Sixty-one sawmill workers in total (26 from Sawmill 1 and 35 from Sawmill 2) provided EBC samples at the beginning and at the end of the working week. Respiratory symptoms, lung function, bronchodilator test and atopy status were assessed. Occupational environment was checked for the levels of respiratory hazards.

RESULTS

Airborne dust concentrations were below threshold limit value. Endotoxin in Sawmill 1 and Sawmill 2, and moulds in Sawmill 1 were at the levels able to induce inflammatory response in the airways. Mould levels were 2.5 times higher in Sawmill 1 than in Sawmill 2. Compared to Sawmill 2 workers, lower spirometry values, higher prevalence of dry cough and positive bronchodilator test were found in Sawmill 1 workers. Monday EBC pH values did not differ between sawmills, but declined after one working week in Sawmill 1 workers (from 7.88 to 7.49, P = 0.012) and not in Sawmill 2 workers. Similar results were obtained when only respiratory healthy non-smokers were analysed. Monday-to-Friday change of other respiratory parameters was not observed.

CONCLUSION

The results suggest EBC pH as a biomarker of acute respiratory effects related to occupational exposure to respiratory hazards in sawmills, presumably increased mould levels. The effect was present even at subclinical level, namely in respiratory healthy subjects. The long-term health implications remain unclear and should be evaluated in a follow-up study.

Exhaled breath condensate: an overview

Exhaled breath condensate (EBC) is a promising source of biomarkers of lung disease. EBC may be thought of either as a body fluid or as a condensate of exhaled gas. There are 3 principal contributors to EBC: variable-sized particles or droplets that are aerosolized from the airway lining fluid, distilled water that condenses from gas phase out of the nearly water-saturated exhalate, and water-soluble volatiles that are exhaled and absorbed into the condensing breath. The nonvolatile constituents and the water-soluble volatile constituents are of particular interest. Several key issues are discussed in this article.

Glutathione redox control of asthma: from molecular mechanisms to therapeutic opportunities

Asthma is a chronic inflammatory disorder of the airways associated with airway hyper-responsiveness and airflow limitation in response to specific triggers. Whereas inflammation is important for tissue regeneration and wound healing, the profound and sustained inflammatory response associated with asthma may result in airway remodeling that involves smooth muscle hypertrophy, epithelial goblet-cell hyperplasia, and permanent deposition of airway extracellular matrix proteins. Although the specific mechanisms responsible for asthma are still being unraveled, free radicals such as reactive oxygen species and reactive nitrogen species are important mediators of airway tissue damage that are increased in subjects with asthma. There is also a growing body of literature implicating disturbances in oxidation/reduction (redox) reactions and impaired antioxidant defenses as a risk factor for asthma development and asthma severity. Ultimately, these redox-related perturbations result in a vicious cycle of airway inflammation and injury that is not always amenable to current asthma therapy, particularly in cases of severe asthma. This review will discuss disruptions of redox signaling and control in asthma with a focus on the thiol, glutathione, and reduced (thiol) form (GSH). First, GSH synthesis, GSH distribution, and GSH function and homeostasis are discussed. We then review the literature related to GSH redox balance in health and asthma, with an emphasis on human studies. Finally, therapeutic opportunities to restore the GSH redox balance in subjects with asthma are discussed.

Downregulation of glutathione S-transferase pi in asthma contributes to enhanced oxidative stress

BACKGROUND

Glutathione S-transferase pi (GSTPi) is the predominant redox regulator in the lung. Although evidence implicates an important role for GSTPi in asthma, the mechanism for this has remained elusive.

OBJECTIVES

We sought to determine how GSTPi is regulated in asthma and to elucidate its role in maintaining redox homeostasis.

METHODS

We elucidated the regulation of GSTPi in children with asthma and used murine models of asthma to determine the role of GSTPi in redox homeostasis.

RESULTS

Our findings demonstrate that GSTPi transcript levels are markedly downregulated in allergen- and IL-13-treated murine models of asthma through signal transducer and activator of transcription 6-dependent and independent pathways. Nuclear factor erythroid 2-related factor 2 was also downregulated in these models. The decrease in GSTPi expression was associated with decreased total glutathione S-transferase activity in the lungs of mice. Examination of cystine intermediates uncovered a functional role for GSTPi in regulating cysteine oxidation, whereby GSTPi-deficient mice exhibited increased oxidative stress (increase in percentage cystine) compared with wild-type mice after allergen challenge. GSTPi expression was similarly downregulated in children with asthma.

CONCLUSIONS

These data collectively suggest that downregulation of GSTPi after allergen challenge might contribute to the asthma phenotype because of disruption of redox homeostasis and increased oxidative stress. Furthermore, GSTPi might be an important therapeutic target for asthma, and evaluation of GSTPi expression might prove beneficial in identifying patients who would benefit from therapy targeting this pathway.