Abstract
BackgroundChronic obstructive pulmonary disease (COPD) is associated with increased oxidative and nitrosative stress. The aim of our study was to assess the importance of these factors in the airways of healthy smokers and symptomatic smokers without airway obstruction, i.e. individuals with GOLD stage 0 COPD.MethodsExhaled NO (FENO) and induced sputum samples were collected from 22 current smokers (13 healthy smokers without any respiratory symptoms and 9 with symptoms i.e. stage 0 COPD) and 22 healthy age-matched non-smokers (11 never smokers and 11 ex-smokers). Sputum cell differential counts, and expressions of inducible nitric oxide synthase (iNOS), myeloperoxidase (MPO), nitrotyrosine and 4-hydroxy-2-nonenal (4-HNE) were analysed from cytospins by immunocytochemistry. Eosinophil cationic protein (ECP) and lactoferrin were measured from sputum supernatants by ELISA.ResultsFENO was significantly decreased in smokers, mean (SD) 11.0 (6.7) ppb, compared to non-smokers, 22.9 (10.0), p < 0.0001. Induced sputum showed increased levels of neutrophils (p = 0.01) and elevated numbers of iNOS (p = 0.004), MPO (p = 0.003), nitrotyrosine (p = 0.003), and 4-HNE (p = 0.03) positive cells in smokers when compared to non-smokers. Sputum lactoferrin levels were also higher in smokers than in non-smokers (p = 0.02). Furthermore, we noted four negative correlations between FENO and 1) total neutrophils (r = -0.367, p = 0.02), 2) positive cells for iNOS (r = -0.503, p = 0.005), 3) MPO (r = -0.547, p = 0.008), and 4) nitrotyrosine (r = -0.424, p = 0.03). However, no major differences were found between never smokers and ex-smokers or between healthy smokers and stage 0 COPD patients.ConclusionOur results clearly indicate that several markers of oxidative/nitrosative stress are increased in current cigarette smokers compared to non-smokers and no major differences can be observed in these biomarkers between non-symptomatic smokers and subjects with GOLD stage 0 COPD.
Highlights
The most important factor causing chronic obstructive pulmonary disease (COPD) is cigarette smoking which causes increased oxidative and nitrosative stress in this disease [1,2,3]
FEV1/FVC was in all subjects over 70%, but healthy smokers had better lung function i.e. post bronchodilator FEV1/FVC 81 (4.1) % than stage 0 Chronic obstructive pulmonary disease (COPD) 76 (3.4) % (p = 0.04)
fractional exhaled NO (FENO) was significantly lower in smokers 11 (6.7) ppb compared to non-smokers 23 (10.0) (p < 0.0001) (Fig. 1.)
Summary
The most important factor causing chronic obstructive pulmonary disease (COPD) is cigarette smoking which causes increased oxidative and nitrosative stress in this disease [1,2,3]. One of the most widely investigated non-invasive markers of nitrosative stress and airway inflammation is fractional exhaled NO (FENO). It is a sensitive and specific marker for eosinophilic inflammation in non-smokers [9], but its significance in smokers and its association with other markers of oxidative/nitrosative stress in the lung are poorly understood. Chronic obstructive pulmonary disease (COPD) is associated with increased oxidative and nitrosative stress. The aim of our study was to assess the importance of these factors in the airways of healthy smokers and symptomatic smokers without airway obstruction, i.e. individuals with GOLD stage 0 COPD
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