Exhaled breath condensate pH in patients with cystic fibrosis

Biomarkers of nitrosative stress in exhaled breath condensate and serum among patients with cystic fibrosis

PURPOSE

The measurement of biomarkers in exhaled breath condensate (EBC) offers a non-invasive way to assess airway disease and can be easily done in a clinical setting among patients with cystic fibrosis (CF). The role of oxidative and nitrosative stress in the complex pathophysiology of CF is widely accepted and biomarkers of oxidative and nitrosative stress can be measured in the serum and EBC. To our knowledge, this is the first study to assess markers of nitrosative stress in EBC and serum, collected simultaneously from the CF patients.

PATIENTS AND METHODS

Paired EBC and serum samples were collected from 36 stable patients with CF and 14 healthy controls. Markers of nitrosative stress ‒ 3-nitrotyrosine and nitrate/nitrite were measured in the EBC and serum using an enzyme-linked immunosorbent assay.

RESULTS

We found no differences in 3-nitrotyrosine and nitrate/nitrite in the EBC of patients with CF as compared to healthy controls (125.37 ​± ​3.29 vs. 126.24 ​± ​2.21 ​nmol/L, p ​= ​0.218; 12.66 ​± ​7.23 vs. 8.79 ​± ​4.83 ​μmol/L, p ​= ​0.133, respectively). Furthermore, 3-nitrotyrosine and nitrate/nitrite were significantly higher in the serum of patients with CF as compared to the healthy controls (0.13 ​± ​0.02 vs. 0.11 ​± ​0.01 ​nmol/mg protein, p ​= ​0.003; 70.78 ​± ​22.55 vs. 53.08 ​± ​8.5 ​μmol/L, p ​= ​0.009, respectively). No correlations were found between the markers determined in the EBC and serum.

CONCLUSIONS

The results of the EBC nitrosative stress biomarkers should be interpreted with caution, especially in patients with stable disease, as the EBC values may be independent on levels of circulating markers that are elevated in the serum of patients with stable CF.

Comparative proteomic analysis of exhaled breath condensate between lung adenocarcinoma and CT-detected benign pulmonary nodule patients

BACKGROUND

Lung cancer is the leading cause of cancer mortality worldwide. The collection of exhaled breath condensate (EBC) is a non-invasive method that may have enormous potential as a biomarker for the early detection of lung cancer.

OBJECTIVE

To investigate the proteomic differences of EBC between lung cancer and CT-detected benign nodule patients, and determine whether these proteins could be potential biomarkers.

METHODS

Proteomic analysis was performed on individual samples from 10 lung cancer patients and 10 CT-detected benign nodule patients using data-independent acquisition (DIA) mass spectrometry.

RESULTS

A total of 1,254 proteins were identified, and 21 proteins were differentially expressed in the lung adenocarcinoma group compared to the benign nodule group (p< 0.05). The GO analysis showed that most of these proteins were involved in neutrophil-related biological processes, and the KEGG analysis showed these proteins were mostly annotated to pyruvate and propanoate metabolism. Through protein-protein interactions (PPIs) analysis, ME1 and LDHB contributed most to the interaction-network of these proteins.

CONCLUSION

Significantly differentially expressed proteins were detected between lung cancer and the CT-detected benign nodule group from EBC samples, and these proteins might serve as potential novel biomarkers of EBC for early lung cancer detection.

cfDNA in exhaled breath condensate (EBC) and contamination by ambient air: toward volatile biopsies

Exhaled breath is a source of volatile and nonvolatile biomarkers in the body that can be accessed non-invasively and used for monitoring. The collection of lung secretions by conventional methods such as bronchoalveolar lavage, induced sputum collection, and core biopsies is limited by the invasive nature of these methods. Non-invasive collection of exhaled breath condensate (EBC) provides fluid samples that are representative of airway lining fluids. Various volatile and nonvolatile biomarkers can be detected in volatile condensates, such as H₂O₂, nitric oxide, lipid mediators, cytokines, chemokines, DNA, and microRNAs. Studies have examined cell-free DNA (cfDNA) in plasma samples from non-small-cell lung cancer patients, offering to new insights and fostering development of the liquid biopsy. However, few studies have examined cfDNA in EBC samples. This study examined whether EBC is an appropriate source of cfDNA using housekeeping-gene-specific primer probes and quantitative real-time polymerase chain reaction in healthy subjects. Ambient (room) air is contaminated with DNA, so caution is needed. Preliminary studies indicated that volatile biopsies are becoming an important diagnostic tool in lung cancer.

Elimination of bacterial DNA during RNA isolation from sputum: Bashing bead vortexing is preferable over prolonged DNase treatment

Sputum often contains large amounts of contaminating bacterial DNA that, if not eliminated during RNA isolation, may interfere with gene expression studies. During RNA isolation only repeated DNase treatment can effectively remove contaminating bacterial DNA from samples, but this compromises RNA quality. In this study we tested alternative methods to facilitate the removal of DNA and improve the quality of RNA obtained. Sputum samples obtained from patients with chronic obstructive pulmonary disease were processed with dithiothreitol and subjected to various RNA isolation methods, yet with modified protocols. Modifications included prolonged DNase treatment or vortexing of sputum cells in the presence of beads prior to RNA isolation. Bacterial DNA contamination was tested by PCR using universal bacterial primers, while RNA quality was assessed by real-time PCR using GAPDH primers for amplicons of different length. We found that the RNeasy Plus Mini kit equipped with the gDNA eliminator spin column was able to completely eliminate bacterial DNA, if sputum cells were lysed in the presence of bashing beads. Notably, compared with the standard protocol, the modified procedure yielded better quality RNA as well, as indicated by improved threshold profiles of qPCR. Bead vortexing of cells was less effective when combined with other RNA isolation methods, and the repeated DNase treatment needed to completely remove contaminating DNA from the samples reduced the quality of RNA markedly. Bead vortexing in combination with certain RNA extraction methods greatly facilitates the isolation of sputum RNA that is free of contaminating bacterial DNA, and is suitable for downstream applications.

Monitoring Antioxidant Enzyme Activity during Exacerbations of Chronic Obstructive Pulmonary Disease

Superoxide dismutases (SODs) and catalase (CAT) have been implicated as major antioxidant enzymes of the human lungs. In this study, we investigated whether activities of these enzymes are altered in the airways of patients hospitalized with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). SOD and CAT activities were measured in the sputum, exhaled breath condensate, and serum of 36 COPD patients experiencing a severe exacerbation. Measurements were performed using colorimetric assays in samples collected at the time of hospital admission and at the time of hospital discharge following treatment of AECOPD. For comparison, antioxidants were also assessed in 24 stable COPD patients and 23 healthy control subjects. SOD and CAT activities in sputum were significantly increased in patients with AECOPD compared to those with stable disease (SOD: 0.142 [0.053-0.81] vs. 0.038 [0.002-0.146] U/mL, p < 0.01; CAT: 48.7 [18.7-72.6] vs. 10.2 [2.9-40.6] nmol/min/mL, p < 0.05), while treatment of exacerbation led to a decrease in enzyme activities (SOD: 0.094 [0.046-0.45] U/mL, p < 0.05; CAT: 28.0 [7.3-60.4] nmol/min/mL, p < 0.005). No changes were observed in the serum (p > 0.05). Both SOD and CAT activities significantly correlated with sputum neutrophil and lymphocyte cell counts in patients with AECOPD. Moreover, SOD and CAT values correlated with each other and also with sputum malondialdehyde, an established marker for oxidative stress. Our data demonstrate that sputum antioxidant activity is elevated during COPD exacerbation and suggest that activation of SODs and CAT is an integral part of the human defense mechanism against the increased oxidant production associated with AECOPD.

Variability of breath condensate pH may contribute to the better understanding of non-allergic seasonal respiratory diseases

The seasonal variability of certain non-allergic respiratory diseases is not clearly understood. Analysis of the breath condensate, the liquid that can be collected by breathing into a cold tube, has been proposed to bring closer to the understanding of airway pathologies. It has been assumed, that (1) airway lining fluid was a stable body liquid and (2) the breath condensate samples were representative of the airway lining fluid. Research was focussed on the identification of biomarkers indicative of respiratory pathologies. Despite 30 years of extended investigations breath condensate analysis has not gained any clinical implementation so far. The pH of the condensate is the characteristic that can be determined with the highest reproducibility. The present paper shows, that contrary to the initial assumptions, breath condensate is not a representative of the airway lining fluid, and the airway lining fluid is not a stable body liquid. Condensate pH shows baseline variability and it is influenced by drinking and by the ambient temperature. The changes in condensate pH are linked to changes in airway lining fluid pH. The variability of airway lining fluid pH may explain seasonal incidence of certain non-allergic respiratory diseases such as the catching of a common cold and the increased incidence of COPD exacerbations and exercise-induced bronchoconstriction in cold periods.

Exhaled Breath Condensate: Technical and Diagnostic Aspects

Purpose. The aim of this study was to evaluate the 30-year progress of research on exhaled breath condensate in a disease-based approach. Methods. We searched PubMed/Medline, ScienceDirect, and Google Scholar using the following keywords: exhaled breath condensate (EBC), biomarkers, pH, asthma, gastroesophageal reflux (GERD), smoking, COPD, lung cancer, NSCLC, mechanical ventilation, cystic fibrosis, pulmonary arterial hypertension (PAH), idiopathic pulmonary fibrosis, interstitial lung diseases, obstructive sleep apnea (OSA), and drugs. Results. We found 12600 related articles in total in Google Scholar, 1807 in ScienceDirect, and 1081 in PubMed/Medline, published from 1980 to October 2014. 228 original investigation and review articles were eligible. Conclusions. There is rapidly increasing number of innovative articles, covering all the areas of modern respiratory medicine and expanding EBC potential clinical applications to other fields of internal medicine. However, the majority of published papers represent the results of small-scale studies and thus current knowledge must be further evaluated in large cohorts. In regard to the potential clinical use of EBC-analysis, several limitations must be pointed out, including poor reproducibility of biomarkers and absence of large surveys towards determination of reference-normal values. In conclusion, contemporary EBC-analysis is an intriguing achievement, but still in early stage when it comes to its application in clinical practice.

Predicting sputum eosinophilia in exacerbations of COPD using exhaled nitric oxide

Fractional exhaled nitric oxide (FENO) may be a pulmonary biomarker in chronic obstructive pulmonary disease (COPD). In this prospective study, the relationship between FENO and airway inflammation was assessed in COPD exacerbations. FENO and lung function were measured, and sputum was collected from 49 ex-smoking COPD patients, first at the time of hospital admission and again at discharge following treatment. There was a significant positive correlation between the percentage of sputum eosinophils and FENO concentrations, both at exacerbation (r = 0.593, p < 0.001) and discharge (r = 0.337, p = 0.044). The increase in forced expiratory volume in one second (FEV(1)) after treatment was greater in patients with sputum eosinophilia (ΔFEV(1) 0.35 ± 0.12 vs. 0.13 ± 0.04 L, p = 0.046), and FENO was a strong predictor of sputum eosinophilia (area under the receiver operating characteristic curve, 0.89). The optimum cut point was 19 parts per billion (sensitivity: 90 %; specificity: 74 %). Our data suggest that FENO is a good surrogate marker of eosinophilic inflammation in COPD patients with exacerbations.

Sputum eicosanoid profiling in exacerbations of chronic obstructive pulmonary disease

BACKGROUND

Eicosanoids are small lipid molecules with diverse biological functions in the airways.

OBJECTIVES

The aim of this study was to investigate changes in leukotriene B4 (LTB4), 8-isoprostane, prostaglandin E2 (PGE2) and cysteinyl-leukotriene (cys-LT) levels in the sputum of patients with chronic obstructive pulmonary disease (COPD) at the onset of a severe exacerbation and during the course of recovery.

METHODS

Thirty-seven ex-smoker COPD patients suffering an episode of acute exacerbation were enrolled. Samples were taken (i) on hospital admission and (ii) after regular treatment. Twenty-five stable ex-smoker COPD patients served as controls. Eicosanoids were determined by enzyme immunoassay.

RESULTS

Sputum PGE2 [39.8 (13.3-103.3) vs. 5.05 (2.3-12.1) pg/ml, p < 0.001], 8-isoprostane [89.5 (36.9-184.7) vs. 29.7 (13.8-68.8) pg/ml, p < 0.01] and LTB4 [587.7 (252.9-774.8) vs. 276.1 (105.4-594.7) pg/ml, p < 0.05] levels were increased in patients with exacerbation compared to stable subjects. After treatment only PGE2 levels decreased significantly [at discharge: 19.6 (4.6-52.5) pg/ml, p < 0.01], the levels of other eicosanoids remained elevated (p = NS). Sputum cys-LT levels were similar in stable patients and in those with exacerbation and treatment did not influence cys-LTs either. There was a significant correlation between PGE2 and sputum neutrophil and lymphocyte cell counts in patients with exacerbation.

CONCLUSIONS

Our results suggest that 8-isoprostane, LTB4 and PGE2 but not cys-LTs may be involved in exacerbation-associated inflammatory processes in the airways of patients with COPD. Validation of PGE2 for use as a biomarker of recovery from an exacerbation requires further studies.

Neonates with cystic fibrosis have a reduced nasal liquid pH; a small pilot study

BACKGROUND

Disrupted HCO3(-) transport and reduced airway surface liquid (ASL) pH in cystic fibrosis (CF) may initiate airway disease. We hypothesized that ASL pH is reduced in neonates with CF.

METHODS

In neonates with and without CF, we measured pH of nasal ASL. We also measured nasal pH in older children and adults.

RESULTS

In neonates with CF, nasal ASL (pH5.2 ± 0.3) was more acidic than in non-CF neonates (pH6.4 ± 0.2). In contrast, nasal pH of CF children and adults was similar to values measured in people without CF.

CONCLUSIONS

At an age when infection, inflammation and airway wall remodeling are minimal, neonates with CF had an acidic nasal ASL compared to babies without CF. The CF:non-CF pH difference disappeared in older individuals, perhaps because secondary manifestations of disease increase ASL pH. These results aid understanding of CF pathogenesis and suggest opportunities for therapeutic intervention and monitoring of disease.

Exhaled breath condensate--from an analytical point of view

Over the past three decades, the goal of many researchers is analysis of exhaled breath condensate (EBC) as noninvasively obtained sample. A total quality in laboratory diagnostic processes in EBC analysis was investigated: pre-analytical (formation, collection, storage of EBC), analytical (sensitivity of applied methods, standardization) and post-analytical (interpretation of results) phases. EBC analysis is still used as a research tool. Limitations referred to pre-analytical, analytical, and post-analytical phases of EBC analysis are numerous, e.g. low concentrations of EBC constituents, single-analyte methods lack in sensitivity, and multi-analyte has not been fully explored, and reference values are not established. When all, pre-analytical, analytical and post-analytical requirements are met, EBC biomarkers as well as biomarker patterns can be selected and EBC analysis can hopefully be used in clinical practice, in both, the diagnosis and in the longitudinal follow-up of patients, resulting in better outcome of disease.

[Clinical application of induced and spontaneous sputum in asthma and chronic obstructive pulmonary disease]

In recent years induced sputum analysis has become a non-invasive method for the assessment of airway inflammation in obstructive airway diseases. Sputum induction is safe and well tolerated by the patients. The method has been standardized, and this has markedly improved the quality and reproducibility of sputum samples. Identification of sputum eosinophilia has the greatest clinical relevance as it predicts a favorable response to corticosteroids. Treatment strategy aiming normalisation of sputum eosinophil cell count may reduce the rate of exacerbations in asthma. Profiling inflammatory mediators in sputum supernatant provides new insights into the pathogenesis of asthma and chronic obstructive pulmonary disease. Cell type analysis in spontaneous sputum may also provide much information about inflammatory processes in the airways. Based on the results of clinical studies sputum analysis should be more often used in clinical settings in the future.