Induced Sputum 8-Isoprostane Concentrations in Inflammatory Airway Diseases

Diversity of protein carbonylation in allergic airway inflammation

Oxidative stress is involved in asthma. This study assessed the carbonylation of sputum proteins in 23 uncontrolled adult asthmatic patients and 23 healthy controls. Carbonylated proteins (68 kDa and 53 kDa) were elevated in asthmatics when compared to controls and the 68-kDa carbonylated protein was significantly correlated with sputum eosinophilia. The kinetics of protein carbonylation in bronchoalveolar lavage fluid (BALF) were then examined in a mouse ovalbumin-induced allergic inflammation model. It was found that the carbonylation of various BALF proteins did not uniformly occur after challenge. The appearance of the 53-kDa carbonylated protein was limited within 24 h, while carbonylation of 68-kDa protein peaked at 48 h and was associated with BALF eosinophilia. Thus, it was demonstrated that the 68-kDa and 53-kDa proteins, corresponding to albumin and alpha1-antitrypsin, respectively, were specifically carbonylated in allergic inflammation in humans and in mice and that eosinophils may play a role in mediating carbonylation of albumin.

Urinary 8-isoprostane and 8-OHdG concentrations in boilermakers with welding exposure

OBJECTIVE

To investigate the association of exposure to fine particulate matter (PM2.5) with DNA damage and oxidative stress in boilermakers exposed to welding fumes.

METHODS

Forty-one workers were monitored over 24 hours during which baseline, postshift, bedtime, and next morning measurements were collected. Twenty-two workers participated as controls.

RESULTS

Linear regression was used to model pairwise change in u-8-isoprostane and u-8-OHdG: pre- to postshift, preshift to bedtime, postshift to bedtime, and postshift to next morning. In the models, pre- to postshift change in 8-OHdG was statistically significant, whereas postshift to bedtime change in 8-isoprostane showed an unexpected inverse relationship with PM2.5.

CONCLUSIONS

Acute welding exposure is associated with a postshift blunting of systemic inflammation in chronically exposed boilermakers, as measured by 8-isoprostane. The level of oxidative DNA damage as measured by 8-OHdG is less clear.

Steroid-resistant neutrophilic inflammation in a mouse model of an acute exacerbation of asthma

Neutrophilic inflammation in acute exacerbations of asthma tends to be resistant to treatment with glucocorticoids. This may be related to decreased activity and expression of histone deacetylase-2 (HDAC2), which down-regulates expression of proinflammatory genes via recruitment to the glucocorticoid receptor complex. We assessed airway inflammation and response to steroid treatment in a novel mouse model of an acute exacerbation of chronic asthma. Systemically sensitized mice received low-level challenge with aerosolized ovalbumin for 4 weeks, followed by a single moderate-level challenge to induce enhanced inflammation in distal airways. We assessed the effects of pre-treatment with dexamethasone on the accumulation of inflammatory cells in the airways, airway responsiveness to methacholine, expression and enzymatic activity of nuclear proteins including histone acetyl transferase (HAT) and HDAC2, and levels of transcripts for neutrophil chemoattractant and survival cytokines. Dexamethasone suppressed inflammation associated with eosinophil and T-lymphocyte recruitment, but did not prevent neutrophil accumulation or development of airway hyperresponsiveness. Increased activity of HAT was suppressed by steroid treatment, but the marked diminution of HDAC2 activity and increased activity of nuclear factor-kappaB were not reversed. Correspondingly, elevated expression of mRNA for TNF-alpha, granulocyte-macrophage colony-stimulating factor, IL-8, and p21(waf) were also not suppressed by dexamethasone. Levels of lipid peroxidation and protein nitration products were elevated in the acute exacerbation model. We conclude that impaired nuclear recruitment of HDAC2 could be an important mechanism of steroid resistance of the neutrophilic inflammation in exacerbations of asthma. Oxidative stress may contribute to decreased HDAC2 activity.

The value of sputum 8-isoprostane in detecting oxidative stress in mild asthma

BACKGROUND

Exhaled nitric oxide and induced sputum eosinophils are well established as direct markers of inflammation/oxidative stress in asthma. Recently, it has been proposed that sputum 8-isoprostane concentrations may present a reliable index for measuring oxidative stress in asthmatic patients. We assessed the value of sputum 8-isoprostane in mild asthma in children and adolescents.

METHODS

Patients with newly diagnosed asthma (children, n = 23; adults, n = 14) and age-matched healthy controls (children, n = 13; adults, n = 15) were studied. Lung function was measured by spirometry, sputum was induced by hypertonic saline, and fractional exhaled nitric oxide (FeNO) was measured with standard methods. Cell differential counts were obtained from sputum slides and the concentration of 8-isoprostane was measured with an enzyme immunoassay from sputum supernatants.

RESULTS

High-quality sputum specimens could be obtained from 10 children and 10 adults, and the sputum analyses were conducted only for the representative specimens. Asthmatics had increased FeNO (children 35.5 vs. 11.9 ppb; adults 81.1 vs. 16.6 ppb; p < 0.001) and sputum eosinophils (children 2.4% vs. 1.4%; adults 10.4% vs. 0.2%; p = 0.005) compared to healthy controls. There was a significant correlation between FeNO and eosinophils (R = 0.65; p < 0.0001). Sputum 8-isoprostane was not elevated in asthmatics compared to healthy subjects (children 81.1 vs. 89.9 and adults 76.9 vs. 73.4 pg/mL) and did not correlate with lung function or other measurements of airway inflammation. However, increased 8-isoprostane levels were detected in patients with chronic obstructive pulmonary disease (n = 11, 184.7 pg/mL, used as controls for assays).

CONCLUSIONS

In agreement with earlier studies, FeNo is sensitive in detecting oxidative/nitrosative stress in asthmatic airways. However, our results suggest that 8-isoprostane may not be sensitive in reflecting oxidant burden in mild asthma.

Oxidized vitamin E and glutathione as markers of clinical status in asthma

BACKGROUND & AIMS

Antioxidant status is disturbed in asthma. Measurement of both oxidized and reduced forms of antioxidants provides important information regarding the oxidant/antioxidant balance. The aim of this study was to investigate the clinical relevance of key antioxidants (alpha-tocopherol and glutathione) in asthma, by measuring the oxidized and reduced forms, in the airways (induced sputum) and systemically (peripheral blood).

METHODS

This cross-sectional study examines stable asthmatics (n=44) and healthy controls (n=31) recruited through John Hunter Hospital, NSW, Australia. We collected peripheral blood and induced sputum during hypertonic saline challenge. Alpha-tocopherol and alpha-tocopherol quinone were measured by HPLC. Total glutathione and glutathione disulfide were determined by a colorimetric assay.

RESULTS

Plasma alpha-tocopherol was low in asthma versus controls. Subjects with asthma had higher levels of whole blood alpha-tocopherol quinone and %alpha-tocopherol quinone than controls and %alpha-tocopherol quinone correlated with asthma control (p=0.009). Sputum supernatant levels of total, reduced and oxidized glutathione were elevated in asthma versus controls. Oxidized glutathione in sputum supernatant negatively correlated with FEV(1)/FVC% (p=0.029).

CONCLUSIONS

In asthma, both systemic and airway antioxidant defences are disturbed. Oxidized forms of alpha-tocopherol and glutathione are associated with clinical asthma outcomes, and should be further investigated as a tool for monitoring asthma.

Airway biomarkers of the oxidant burden in asthma and chronic obstructive pulmonary disease: current and future perspectives

The pathogenesis of asthma and chronic obstructive pulmonary disease (COPD) has been claimed to be attributable to increased systemic and local oxidative stress. Detection of the oxidant burden and evaluation of their progression and phenotypes by oxidant biomarkers have proved challenging and difficult. A large number of asthmatics are cigarette smokers and smoke itself contains oxidants complicating further the use of oxidant biomarkers. One of the most widely used oxidant markers in asthma is exhaled nitric oxide (NO), which plays an important role in the pathogenesis of asthma and disease monitoring. Another oxidant marker that has been widely investigated in COPD is 8-isoprostane, but it is probably not capable of differentiating asthma from COPD, or even sensitive in the early assessment of these diseases. None of the current biomarkers have been shown to be better than exhaled NO in asthma. There is a need to identify new biomarkers for obstructive airway diseases, especially their differential diagnosis. A comprehensive evaluation of oxidant markers and their combinations will be presented in this review. In brief, it seems that additional analyses utilizing powerful tools such as genomics, metabolomics, lipidomics, and proteomics will be required to improve the specificity and sensitivity of the next generation of biomarkers.

Changes in urinary dinor dihydro F(2)-isoprostane metabolite concentrations, a marker of oxidative stress, during and following asthma exacerbations

To investigate changes in oxidant stress during and following acute asthma exacerbations, this study measured 2,3-dinor-5,6-dihydro-15-F(2t)-IsoP (F(2)-IsoP-M), the major urinary metabolite of 15-F(2t)-IsoP, in eight asthmatic adults, during and following an asthma hospitalization. F(2)-IsoP-M concentrations at admission and follow-up were significantly higher than discharge (admission median: 4.12 ng/Cr mg, range 1.89-7.8; follow-up: 2.47 ng/Cr mg (1.56-6.86); discharge: 1.42 ng/Cr mg (0.7-4.44); both p<0.01), but not significantly different between admission and follow-up. F(2)-IsoP-M concentrations at follow-up were higher than a control group with stable asthma (0.68 ng/Cr mg (0.31-1.5), p=0.0008). In conclusion, asthma exacerbations requiring hospitalization are associated with 6-fold higher urinary F(2)-IsoP-M concentrations compared to stable asthmatics. F(2)-IsoP-M concentrations decreased significantly during hospitalization, but significant elevations 3 months following hospitalization suggest ongoing oxidative stress despite clinical improvement. Urinary F(2)-IsoP-M may be a clinically useful, simple non-invasive systemic measure of oxidative stress in asthmatics, providing information not captured by spirometry or symptoms.

Exhaled breath condensate 8-isoprostane, clinical parameters, radiological indices and airway inflammation in COPD

BACKGROUND

Exhaled breath condensate (EBC) 8-isoprostane levels were found increased in chronic obstructive pulmonary disease. However, the relation between EBC 8-isoprostane and parameters which have a known predictive value in COPD, remains vastly unknown, and so does subsequently its clinical value.

OBJECTIVES

To investigate the relationship between 8-isoprostane level in EBC and clinical parameters, radiological indices and airway inflammation in COPD patients.

MATERIALS AND METHODS

We studied 18 COPD patients (all ex-smokers) and 12 healthy controls (5 ex-smokers and 7 never-smokers). All patients underwent clinical evaluation, sputum induction, high-resolution computed tomography (HRCT) of the thorax and EBC 8-isoprostane measurement. 8-Isoprostane levels were correlated with markers that reflect disease severity, such as dyspnea severity, FEV(1) (%pred), emphysema changes and bronchiectasis in HRCT. Emphysema was quantified as the percentage of lung area with attenuation values < -950 Hounsfield units.

RESULTS

8-Isoprostane levels were significantly elevated in EBC of patients with COPD [mean (SE) 18.1 (2) vs. 5.6 (0.7) pg/ml, p = 0.0001], irrespective of lung function impairment. 8-Isoprostane levels were correlated with emphysema score in HRCT (r(2) = 0.43, p = 0.001) as well as with Medical Research Council dyspnea scale score (rho = 0.61, p = 0.005).

CONCLUSION

Our findings suggest that EBC 8-isoprostane levels may reflect the extension of lung emphysema in COPD patients. In this respect, further investigation is required in order to evaluate the possible role of EBC 8-isoprostane in assessing disease progress in COPD patients.

Oxidative stress and lipid-derived inflammatory mediators during acute exacerbations of cystic fibrosis

BACKGROUND AND OBJECTIVE

In cystic fibrosis (CF) very few studies have assessed sputum 8-iso-PGF2alpha levels during pulmonary exacerbations as a direct measure of airway oxidative stress. The role of other lipid-derived inflammatory mediators, such as the cysteinyl leukotrienes (cys-LTs) and prostaglandin (PG)-E2, during exacerbations is also poorly defined and the effect of conventional antibiotic therapy on these components of the inflammatory process is unclear.

METHODS

Sputum 8-iso-PGF2alpha, total cys-LT and PGE2 levels were measured in 17 CF patients experiencing a pulmonary exacerbation and repeated analysis were performed in 15 of these patients after antibiotic treatment. Eight stable CF and nine healthy subjects provided control data.

RESULTS

Sputum 8-iso-PGF2alpha was significantly elevated in acute, but not stable CF patients versus healthy controls (P < 0.001). Similarly, sputum cys-LT and PGE2 levels were increased in acute compared with stable CF patients and healthy controls (P <or= 0.001). Although substantially lower than in acute patients, sputum cys-LT levels in stable patients were also significantly higher than in normal controls (P = 0.01). There were strong associations between cys-LT levels and sputum total cell counts, and blood neutrophils in acute patients (r2 = 0.53, P = 0.001 and r2 = 0.33, P < 0.05, respectively). Overall in the CF patients, FEV1% predicted was strongly and negatively correlated with sputum 8-iso-PGF2alpha (r2 = 0.34, P = 0.006), cys-LT (r2 = 0.40, P = 0.002) and PGE2 (r2 = 0.52, P < 0.001) levels. Antibiotic treatment reduced sputum total cell count (P = 0.03), but did not affect 8-iso-PGF2alpha, cys-LT or PGE2 levels.

CONCLUSIONS

CF exacerbations are characterized by increased oxidative stress and sputum concentrations of bioactive lipid mediators. Treatment does not modulate these aspects of inflammation and more targeted therapy needs further study.

Asthma exacerbations . 3: Pathogenesis

Asthma exacerbations are an exaggerated lower airway response to an environmental exposure. Respiratory virus infection is the most common environmental exposure to cause a severe asthma exacerbation. Airway inflammation is a key part of the lower airway response in asthma exacerbation, and occurs together with airflow obstruction and increased airway responsiveness. The patterns of airway inflammation differ according to the trigger factor responsible for the exacerbation. The reasons for the exaggerated response of asthmatic airways are not completely understood, but recent studies have identified a deficient epithelial type 1 interferon response as an important susceptibility mechanism for viral infection.

Serum levels of oxidative stress as a marker of disease severity in idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a fatal illness characterized by progressive fibrosis resulting in severe dyspnea and impairment of lung function. Although the mechanisms by which lung fibrosis develops are not fully ascertained, recent findings suggest that oxidative stress may play an important role in the pathogenesis of tissue fibrosis.

AIM

To evaluate the oxidative stress in the serum of patients with IPF and to explore the relationship between oxidative stress levels, dyspnea and impairment of lung function.

MATERIAL AND METHODS

Blood samples from 21 untreated patients with IPF, sequentially recruited over a period of 2 years, and 12 controls were analyzed. The level of oxidative stress in the blood was determined through a spectrophotometric procedure (D-ROMs test). FVC and DLCO were measured in all patients. The level of dyspnea was assessed by the Medical Research Council (MRC) chronic dyspnea scale.

RESULTS

Serum levels of oxidative stress were significantly increased in patients with IPF compared to controls (mean+/-SEM: 356.8+/-14 and 201+/-10 Carratelli units respectively, p<0.001). Oxidative stress was negatively associated with FVC (p<0.01, r=-0.79) and with DLCO (p<0.01, r=-0.75). Furthermore, oxidative stress was significantly correlated with MRC dyspnea score (p<0.01, r=0.87). Oxidative stress measurements were highly reproducible on two consecutive measurements in the same patients.

CONCLUSION

The levels of systemic oxidative stress are enhanced in patients with IPF and could provide useful information about the classification of IPF severity. Strategies to reduce the oxidant burden in IPF may be beneficial in reducing the progressive deterioration of these patients.

A critical appraisal of methods used in early clinical development of novel drugs for the treatment of asthma

Asthma is a heterogeneous disorder characterized by chronic airway inflammation, hyperresponsiveness and remodeling. Being the hallmark of asthma, airway inflammation has become the most important target for therapeutic agents. Consequently, during the past decade various semi-and non-invasive methods have been explored to sample the airway inflammation in asthma. In this review, we provide a practical overview of the current status of various sampling techniques including sputum induction, exhaled breath analysis, and bronchoprovocation tests (BPTs). We focus on their applicability for monitoring in clinical practice and in intervention trials in asthma.

Airway inflammation in subjects with gastro-oesophageal reflux and gastro-oesophageal reflux-related asthma

STUDY OBJECTIVES

Asthma and gastro-oesophageal reflux (GER) are both characterized by airway inflammation.

DESIGN

The purposes of this work were (i) to study airway inflammation in patients troubled by gastro-oesophageal reflux (GER) and GER associated with asthma, (ii) to ascertain whether GER can aggravate asthma by exacerbating the pre-existing airway inflammation and oxidative stress and (iii) to establish the validity of analysing breath condensate and induced sputum when studying the airways of subjects affected by GER. PATIENT S AND METHODS: We enrolled 14 patients affected by mild asthma associated with GER (40 +/-12 years), nine with mild but persistent asthma (39 +/- 13 years), eight with GER (35 +/- 11 years) and 17 healthy subjects (37 +/- 9 years). Sputum cell counts and concentrations of interleukin-4 (IL-4), IL-6 and 8-isoprostane were measured in breath condensate and supernatant.

MEASUREMENTS AND RESULTS

GER-related asthma is characterized by an eosinophilic inflammation, as determined by elevated concentrations of IL-4 in breath condensate and sputum supernatant, and by sputum cell analysis. GER alone presents a neutrophilic pattern of inflammation when determined by elevated concentrations of IL-6 in sputum cell analysis. A concomitant increase has been found in 8-isoprostane in GER associated (or not associated) with asthma.

CONCLUSIONS

We conclude that GER is characterized by a neutrophilic airway inflammation and by increased oxidative stress. GER does not however aggravate pre-existing airway inflammation in asthma patients. Determinations of inflammatory and oxidant markers in the breath condensate of subjects with GER reflect these measured in the induced sputum.

HLA-C and Killer Cell Immunoglobulin-like Receptor Genes in Idiopathic Bronchiectasis

RATIONALE

In idiopathic bronchiectasis, lung inflammation and chronic bacterial infection lead to progressive lung damage. A possible role for natural killer (NK) cells is suggested by the observation that familial bronchiectasis occurs in a rare group of individuals with impaired HLA class I expression and consequent NK cell dysfunction.

OBJECTIVE

Because the HLA-C locus and killer cell immunoglobulin-like receptors (KIRs) are of key importance for NK cell recognition, we analyzed HLA-C/KIR combinations by genotyping patients with idiopathic bronchiectasis.

METHODS

Genomic DNA from 96 individuals with idiopathic bronchiectasis and 101 control subjects was analyzed by polymerase chain reaction with sequence-specific primers. High-resolution HLA-C genotyping was performed in addition to KIR analysis.

RESULTS

HLA-Cw*03 alleles and, in particular, HLA-C group 1 homozygosity are associated with the presence of bronchiectasis. Analysis of the relationship between HLA-C and KIR genes suggests a shift to activatory NK cell function.

CONCLUSION

This is the first demonstration of genetic susceptibility in idiopathic bronchiectasis. The association with HLA-C group 1 homozygosity, and the interplay between HLA-C and KIR genes, argue for a role for NK cells in the progressive lung damage seen in this disease. This will require further investigation using functional studies.

Inflammatory mediators in exhaled breath, induced sputum and saliva

BACKGROUND AND OBJECTIVE

Airway inflammation is assessed to monitor progression, control and treatment of asthma. The collection of exhaled breath condensate (EBC) provides a non-invasive alternative to induced sputum samples for the monitoring of airway inflammation. Both samples can be confounded by salivary contamination. The aim of this study was to compare the levels of inflammatory mediators in samples of EBC, induced sputum and saliva samples from subjects with asthma.

METHOD

EBC, saliva and induced sputum samples were collected from subjects with asthma (n=10). Total protein, IL-8, 8-isoprostane and surfactant protein A (SPA) were assessed in each sample.

RESULTS

Total protein, IL-8, 8-isoprostane and SPA were detected in all sputum samples. Only total protein and SPA were consistently measured in EBC, with levels at least 100-fold lower than those measured in induced sputum. In saliva, total protein, SPA and 8-isoprostane were detected in all samples, with IL-8 detected in 60% of samples.

CONCLUSIONS

Induced sputum is a reliable technique that can be used to assess markers of airway inflammation. While EBC is a simple and inexpensive technique to collect lower airway secretions, the detection of inflammatory mediators is variable, and further work is required to validate this technique to assess inflammatory mediators.

Airway and Circulating Levels of Carotenoids in Asthma and Healthy Controls

BACKGROUND

Elevated oxidative stress and impaired antioxidant defences are increasingly recognised features of asthma. Carotenoids are potent dietary antioxidants that may protect against asthma by reducing oxidative damage.

OBJECTIVES

This study aimed firstly, to characterise circulating and airway levels of carotenoids in asthma compared to healthy controls, in relation to dietary intake. Secondly, the study aimed to test whether airway lycopene defences can be improved using oral supplements.

METHODS

Induced sputum and peripheral blood samples were collected from subjects with asthma (n = 15) and healthy controls (n = 16). Dietary carotenoid intakes were estimated using the 24-hour recall method and analysed using a modified version of the Foodworks 210 Nutrient Calculation Software. Another group of healthy controls (n = 9) were supplemented with 20 mg/day lycopene for 4 weeks. Carotenoids (beta-carotene, lycopene, alpha-carotene, beta-cryptoxanthin, lutein/zeaxanthin) were measured by HPLC.

RESULTS

Despite similar dietary intake, whole blood levels of total carotenoids, lycopene, lutein, beta-cryptoxanthin, alpha-carotene and beta-carotene were significantly lower in asthma than controls. However, there were no differences in plasma or sputum carotenoid levels. Induced sputum carotenoid levels were significantly lower than plasma and whole blood levels, but correlated strongly with plasma levels (r = 0.798, p < 0.001). Although there were no overall increases in either plasma or sputum lycopene levels following supplementation, changes in airway lycopene levels correlated with changes in plasma levels (r = 0.908, p < 0.002).

CONCLUSIONS

Whole blood, but not plasma or sputum, carotenoid levels are deficient in asthma. Plasma carotenoid levels reflect airway carotenoid levels and when plasma levels are improved using oral supplements this is reflected in the airways.