S. R. Rutgers

Comparison of induced sputum with bronchial wash, bronchoalveolar lavage and bronchial biopsies in COPD

It is unclear how cellular and soluble inflammatory markers in induced sputum relate to markers in lavage fluid and biopsies in chronic obstructive pulmonary disease (COPD). This was investigated and also the possible differences between subjects with COPD and healthy controls assessed. Eighteen nonatopic subjects with COPD and 11 healthy controls were studied. Sputum was induced by inhalation of hypertonic saline. The airways were lavaged, using the first 50 mL for bronchial wash (BW) and the subsequent 150 mL for bronchoalveolar lavage (BAL), and biopsies were taken from subsegmental carinae. Neutrophils were the predominant cell type in sputum in COPD (median 77.3%) but not in BW (5.5%) and BAL fluid (1.7%). Differential cell counts in sputum did not correlate with the counts in BW or BAL fluid or biopsies, whereas sputum eosinophil cationic protein (ECP) levels correlated with BW fluid ECP levels (p=0.66, p=0.007) and sputum interleukin-8 (IL-8) concentration with BAL fluid IL-8 concentration (p= 0.52, p=0.026). Subjects with COPD had a higher percentage of sputum neutrophils and eosinophils and higher concentrations of ECP and IL-8 than healthy controls. The higher percentages of eosinophils and concentrations of ECP were also seen in BW and BAL fluid. Finally, higher numbers of macrophages and eosinophils were found in biopsies. In conclusion, induced sputum is derived from a different compartment from BW and BAL fluid and biopsies. Induced sputum may be useful for studying the contribution of luminal neutrophils and eosinophils in chronic obstructive pulmonary disease.

Markers of nitric oxide metabolism in sputum and exhaled air are not increased in chronic obstructive pulmonary disease

BACKGROUND Nitric oxide (NO) is involved in inflammation and host defence of the lung. It has been found in increased concentrations in the airways in asthmatic subjects but its levels in patients with chronic obstructive pulmonary disease (COPD) have not been investigated. A study was undertaken to determine whether markers of NO metabolism (NO in exhaled air, iNOS expression in sputum cells, and nitrite + nitrate (NO2 –/NO3 –) in sputum supernatant) are increased in subjects with COPD, and whether they correlate with inflammatory indices in induced sputum. The associations of these markers with smoking were also assessed. METHODS Sixteen subjects with COPD (median age 66 years, median forced expiratory volume in one second (FEV1) 63% predicted, eight current smokers) and 16 healthy subjects (median age 63 years, median FEV1 113% predicted, eight current smokers) participated in the study. NO was measured during tidal breathing and sputum was induced by inhalation of hypertonic saline. RESULTS No differences were observed between subjects with COPD and healthy controls in exhaled NO excretion rate (median 5.15 and 6.25 nmol/min), sputum macrophage iNOS expression (14% and 12%), and sputum supernatant NO2 –/NO3 – (46 and 73 μM). NO in exhaled air correlated with the percentage of sputum eosinophils in patients with COPD (rho = 0.65, p = 0.009) but not in healthy individuals. Exhaled NO and supernatant NO2 –/NO3 – levels were lower in healthy smokers than in healthy non/ex-smokers. CONCLUSIONS Our findings indicate that NO metabolism is not increased in patients with stable COPD. The close association between exhaled NO levels and sputum eosinophils suggests a role for NO in airway inflammation in COPD. Studies performed during exacerbations may clarify this role.

Reticular basement membrane in asthma and COPD: Similar thickness, yet different composition

Background Reticular basement membrane (RBM) thickening has been variably associated with asthma and chronic obstructive pulmonary disease (COPD). Even if RBM thickness is similar in both diseases, its composition might still differ. Objective To assess whether RBM thickness and composition differ between asthma and COPD. Methods We investigated 24 allergic asthmatics (forced expiratory volume in one second [FEV1] 92% predicted), and 17 nonallergic COPD patients (FEV1 60% predicted), and for each group a control group of similar age and smoking habits (12 and 10 persons, respectively). Snap-frozen sections of bronchial biopsies were stained with hematoxylin/eosin and for collagen I, III, IV, V, laminin and tenascin. RBM thickening was assessed by digital image analysis. Relative staining intensity of each matrix component was determined. Results Mean (SD) RBM thickness was not significantly different between asthma and COPD 5.5 (1.3) vs 6.0 (1.8) μm, but significantly larger than in their healthy counterparts, ie, 4.7 (0.9) and 4.8 (1.2) μm, respectively. Collagen I and laminin stained significantly stronger in asthma than in COPD. Tenascin stained stronger in asthma than in healthy controls of similar age, and stronger in COPD controls than in asthma controls (p < 0.05). Conclusion RBM thickening occurs both in asthma and COPD. We provide supportive evidence that its composition differs in asthma and COPD.

Nitric oxide measured with single-breath and tidal-breathing methods in asthma and COPD

Nitric oxide (NO) can be measured in exhaled air with the single-breath (SB) and tidal-breathing (TB) methods. To allow comparison between different laboratories, a European Respiratory Society task force recently reported guidelines for standardization of both methods. To facilitate comparison between laboratories further, this study investigated whether there is a difference between NO values measured with SB and TB methods in subjects with asthma or chronic obstructive pulmonary disease (COPD), and in healthy subjects. Moreover, the differences between groups were studied and the influence of smoking in asthma was assessed. Sixteen atopic nonsmoking asthmatics, 16 atopic currently smoking asthmatics, 16 nonatopic nonsmoking healthy controls, 16 nonatopic exsmokers with COPD and 16 nonatopic exsmoking healthy controls were studied. NO concentrations differed substantially between both methods. Mean NO concentrations were higher with the SB than with the TB method in nonsmoking and in smoking asthmatics and especially so with the higher NO values. Furthermore, NO values with both methods were higher in nonsmoking asthmatics than in nonsmoking healthy subjects. NO was not significantly different between exsmokers with COPD and healthy exsmokers. In conclusion nitric oxide values of the single-breath and tidal-breathing methods are not interchangeable. Both methods can be used to measure differences between groups.

Markers of active airway inflammation and remodelling in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is defined as a disorder characterized by reduced maximum expiratory flow and slow forced emptying of the lungs, features which do not change markedly over several months [1]. Most of the airflow limitation is slowly progressive and irreversible. COPD is a broad term and includes three clinical conditions: chronic bronchitis, small airways disease and emphysema. The airflow limitation is due to varying combinations of destruction and remodelling of the small airways and the lung parenchyma, which cause an increase in airway resistance mainly in the small airways [2]. Cigarette smoking has been shown to be the most important risk factor and accounts for 80±90% of the risk of developing COPD [3]. Airway hyperresponsiveness, a1-antitrypsin deficiency and certain occupational exposures are other established risk factors for the development of COPD [4]. The mechanism via which the presence of these risk factors results in airflow limitation has been investigated intensively in the last decades, but has not been clarified yet. It is probable that the development of airflow limitation in COPD is mainly caused by inflammatory changes in the airways and lung parenchyma. The introduction of fiberoptic bronchoscopy in the early seventies opened the way to perform airway wall biopsies, thereby facilitating invasive research of the airways and providing tissue samples to study inflammation. It has demonstrated directly, combined with results of analysis of induced sputum, and indirectly via investigation of exhaled air and hyperresponsiveness, the presence of airway inflammation. With regard to the development of airflow limitation, the emphasis until recently has been on tissue destruction caused by mediators of inflammatory cells. The parenchymal destruction as seen in emphysema was suggested to be caused by an inflammatory process due to a protease-antiprotease-imbalance and oxidant-antioxidant-imbalance [5]. The basis for this theory of parenchymal destruction was the association of emphysema with congenital a1-antitrypsin deficiency and the occurrence of emphysema-like pathological changes in hamsters after intratracheal instillation of elastase. The protease-antiprotease-imbalance suggests that proteases with elastin degrading capacity are insufficiently inhibited by antiproteases and thereby induce emphysema. The oxidantantioxidant-imbalance suggests that oxidants, which can injure lung tissue, interfere with repair of the extracellular matrix and inactivate antiproteases, are insufficiently inhibited by antioxidants and thereby induce emphysema. The theory about oxidant-antioxidant-imbalance was excellently reviewed by Rahman and McNee recently [6]. However, as the activity of proteases and oxidants can be expected to be quite similar in all smokers, the protease-antiproteaseimbalance and the oxidant-antioxidant-imbalance theories do not explain why only 10±20% of all smokers develop emphysema. Moreover, these theories explain the parenchymal destruction of emphysema but do not explain changes in the small airways. Therefore, the concept of airway remodelling caused by abnormal repair of the small airways and parenchyma has become more and more accepted [7].