R A Stockley

COPD exacerbations · 2: Aetiology

Exacerbations of COPD are thought to be caused by complex interactions between the host, bacteria, viruses, and environmental pollution. These factors increase the inflammatory burden in the lower airways, overwhelming the protective anti-inflammatory defences leading to tissue damage. Frequent exacerbations are associated with increased morbidity and mortality, a faster decline in lung function, and poorer health status, so prevention or optimal treatment of exacerbations is a global priority. In order to evolve new treatment strategies there has been great interest in the aetiology and pathophysiology of exacerbations, but progress has been hindered by the heterogeneous nature of these episodes, vague definitions of an exacerbation, and poor stratification of known confounding factors when interpreting results. We review how an exacerbation should be defined, its inflammatory basis, and the importance of exacerbations on disease progression. Important aetiologies, with their potential underlying mechanisms, are discussed and the significance of each aetiology is considered.

Relationship between airway inflammation and the frequency of exacerbations in patients with smoking related COPD

BACKGROUND Patients with more frequent exacerbations of chronic obstructive pulmonary disease (COPD) may have increased bronchial inflammation. Airway inflammation was measured in patients who had been thoroughly investigated with full pulmonary function testing, thoracic HRCT scanning, and sputum microbiology to examine further the relationship between exacerbation frequency and bronchial inflammation. METHODS Airway inflammation (spontaneous sputum sol phase myeloperoxidase (MPO), elastase, leukotriene (LT)B4, interleukin (IL)-8, secretory leukoprotenase inhibitor (SLPI), protein leakage) and serum levels of C reactive protein (CRP) were compared in 40 patients with stable, smoking related COPD, divided into those with frequent (⩾3/year) or infrequent (⩽2/year) exacerbations according to the number of primary care consultations during the preceding year. The comparisons were repeated after excluding eight otherwise clinically indistinguishable patients who had tubular bronchiectasis on the HRCT scan. RESULTS Patients with frequent (n=12) and infrequent (n=28) exacerbations were indistinguishable in terms of their clinical, pulmonary function, and sputum characteristics, CRP concentrations, and all of their bronchial inflammatory parameters (p>0.05). The patients without evidence of tubular bronchiectasis (n=32) were equally well matched but the sputum concentrations of SLPI were significantly lower in the frequent exacerbators (n=8) in this subset analysis (p<0.05). CONCLUSIONS There are several clinical features that directly influence bronchial inflammation in COPD. When these were carefully controlled for, patients with more frequent reported exacerbations had lower sputum concentrations of SLPI. This important antiproteinase is also known to possess antibacterial and antiviral activity. Further studies are required into the nature of recurrent exacerbations and, in particular, the regulation and role of SLPI in affected individuals.

Wnt signalling in lung development and diseases

There are several signalling pathways involved in lung organogenesis including Notch, TGFβ /BMP, Sonic hedgehog (Shh), FGF, EGF, and Wnt. Despite the widely acknowledged significance of Wnt signalling in embryonic lung development, the role of different Wnt pathways in lung pathologies has been slow to emerge.In this review, we will present a synopsis of current Wnt research with particular attention paid to the role of Wnt signals in lung development and in pulmonary diseases.

Sputum chemotactic activity in chronic obstructive pulmonary disease: effect of α1–antitrypsin deficiency and the role of leukotriene B4 and interleukin 8

Background: Neutrophil recruitment to the airway is thought to be an important component of continuing inflammation and progression of chronic obstructive pulmonary disease (COPD), particularly in the presence of severe α1–antitrypsin (α1–AT) deficiency. However, the chemoattractant nature of secretions from these patients has yet to be clarified. Methods: The chemotactic activity of spontaneous sputum from patients with stable COPD, with (n=11) and without (n=11) α1–AT deficiency (PiZ), was assessed using the under-agarose assay. The contribution of leukotriene B4 (LTB4) and interleukin 8 (IL-8) to the chemotactic activity was examined using an LTB4 receptor antagonist (BIIL 315 ZW) and an IL-8 monoclonal antibody, respectively. Results: Sputum neutrophil chemotactic activity (expressed as % n-formylmethionyl leucylphenylalanine (fMLP) control) was significantly higher in patients with α1–AT deficiency (mean (SE) 63.4 (8.9)% v 36.7 (5.5)%; mean difference 26.7% (95% CI 4.9 to 48.4), p<0.05). The mean (SE) contribution of both LTB4 and IL-8 (expressed as % fMLP control) was also significantly higher in α1–AT deficient patients than in patients with COPD with normal levels of α1–AT (LTB4: 31.9 (6.3)% v 18.0 (3.7)%; mean difference 13.9% (95% CI –1.4 to 29.1), p<0.05; IL-8: 24.1 (5.2)% v 8.1 (1.2)%; mean difference 15.9% (95% CI 4.7 to 27.2), p<0.05). When all the subjects were considered together the mean (SE) contribution of LTB4 (expressed as % total chemotactic activity) was significantly higher than IL-8 (46.8 (3.5)% v 30.8 (4.6)%; mean difference 16.0% (95% CI 2.9 to 29.2), p<0.05). This difference was not significantly influenced by α1–AT phenotype (p=0.606). Conclusions: These results suggest that the bronchial secretions of COPD patients with α1–AT deficiency have increased neutrophil chemotactic activity. This relates to the increased levels of IL-8 and, in particular LTB4, which accounted most of the sputum chemotactic activity in the patients with COPD as a whole. Increased chemotactic activity, together with inhibitor deficiency, may contribute to the more rapid disease progression seen in α1–AT deficiency via increased neutrophil recruitment and release of neutrophil elastase.

Assessment of airway neutrophils by sputum colour: correlation with airways inflammation

BACKGROUND Airway inflammation, with recruitment of neutrophils to the airway lumen, results in purulent secretions and a variety of potential adverse consequences for patients with chronic bronchitis and bronchiectasis. We hypothesised that gradations of sputum colour would correlate directly with the myeloperoxidase content of sputum and with various other indicators of the activity and consequences of bronchial diseases. METHODS To test this hypothesis, we quantified sputum colour by reference to a sensitive nine point colour chart and correlated this assessment with indices of a number of inflammatory mediators in sputum. RESULTS The results indicate that standardised visual measurements of sputum colour correlated strongly with myeloperoxidase, interleukin 8, leucocyte elastase (both activity and total quantity), sputum volume, protein leak, and secretory leucocyte proteinase inhibitor (p<0.001 for all). In addition, there was a strong direct correlation between leucocyte elastase and both myeloperoxidase (p<0.003) and sputum volume (p<0.001), but a strong negative correlation with secretory leucocyte proteinase inhibitor (p<0.001). CONCLUSIONS These results indicate that sputum colour graded visually relates to the activity of the underlying markers of bronchial inflammation. The results of this simple visual analysis of sputum provides guidance concerning underlying inflammation and its damaging potential. It also provides a useful scientific tool for improving the monitoring of chronic airways diseases and response to treatment.

Phosphoinositide 3-kinase inhibition restores neutrophil accuracy in the elderly: toward targeted treatments for immunosenescence

Immunosenescence is the functional deterioration of the immune system during natural aging. Despite increased susceptibility to bacterial infections in older adults, age-associated changes to neutrophil responses are only partially understood, and neutrophil migration has not been characterized in detail. Here we describe reduced chemotaxis but preserved chemokinesis toward a range of inflammatory stimuli in migrating neutrophils isolated from healthy older subjects. Cross-sectional data indicate that migratory behavior changes in the sixth decade of life. Crucially, aberrant migration may increase bystander tissue damage and heighten inflammation as a result of excess proteinase release during inaccurate chemotaxis, as well as reducing pathogen clearance. We show evidence of increased neutrophil proteinase activity in older adults, namely, raised levels of neutrophil proteinase substrate-derived peptides and evidence of primary granule release, associated with increased systemic inflammation. Inaccurate migration was causally associated with increased constitutive phosphoinositide 3-kinase (PI3K) signaling; untreated neutrophils from old donors demonstrated significant PI3K activation compared with cells from young donors. PI3K-blocking strategies, specifically inhibition of PI3Kγ or PI3Kδ, restored neutrophil migratory accuracy, whereas SHIP1 inhibition worsened migratory flaws. Targeting PI3K signaling may therefore offer a new strategy in improving neutrophil functions during infections and reduce inappropriate inflammation in older patients.

Effect of sputum processing with dithiothreitol on the detection of inflammatory mediators in chronic bronchitis and bronchiectasis

Background: Sputum analysis is used increasingly to assess airway inflammation in patients with chronic obstructive pulmonary disease, including those with chronic bronchitis and bronchiectasis. However, it is not known whether dithiothreitol (DTT), a reducing mucolytic agent regularly used to homogenise sputum, affects the detection of inflammatory mediators in the sputum soluble phase from such patients. Methods: Thirty two spontaneous sputum samples were collected from 13 patients with chronic bronchitis and 17 with bronchiectasis. An aliquot from each sample was treated with either freshly prepared 0.1% DTT plus normal saline (NaCl) or NaCl alone, then ultracentrifuged to obtain the sputum sol phase. Interleukin (IL)-1β, IL-6, IL-8, leukotriene B4 (LTB4), secretory leukoprotease inhibitor (SLPI), alpha-1-antitrypsin (α1-AT), and tumour necrosis factor alpha (TNFα) were measured by ELISA, and neutrophil elastase (NE) and myeloperoxidase (MPO) by chromogenic substrate assay. The effect of DTT on the detection of assay standards was also determined. Results: Median levels of IL-1β, IL-6, IL-8, SLPI, and NE were similar in the DTT and NaCl treated samples. There was a significant reduction in median (IQR) levels of detectable TNFα (0.07 (0.00–0.47) pM v 0.90 (0.06–6.98) pM, p<0.001), LTB4 (1.67 (1.31–2.64) nM v 2.29 (0.95–4.22) nM, p<0.05) and MPO (0.00 (0.00–0.00) mg/l v 4.48 (0.00–33.66) mg/l, p<0.001) and a small increase in the median α1-AT concentration (0.05 (0.03–0.08) nM v 0.03 (0.02–0.08) nM, p<0.01) in the DTT treated samples. DTT had no effect on the assay standards for IL-1β, IL-8 or TNFα, but at higher concentrations it did affect IL-6, SLPI, NE, and LTB4 standards (43%, 70%, 76% and 643% of control value for top standard, respectively) and at all concentrations DTT completely abolished MPO activity. Conclusions: Sputum processing with DTT significantly reduces the detectable concentration of TNFα, LTB4 and MPO, and produces a small but significant increase in median α1-AT levels. To avoid this problem we recommend that an untreated aliquot of sputum be retained for cytokine analysis, unless the assay has been specifically validated.

High-resolution computed tomography scanning in α1-antitrypsin deficiency: relationship to lung function and health status

The development of computed tomography (CT) has enabled emphysema to be assessed noninvasively. Objective quantification of lung density correlates well with lung function in patients with chronic obstructive pulmonary disease and has been shown to be a sensitive tool for monitoring disease progression. In order to determine the clinical impact of changes seen on high-resolution computed tomography (HRCT), the relationship between the objective quantification of emphysema on HRCT, lung function and health status in 111 patients with α 1 -antitrypsin deficiency was examined (PiZ). The degree of HRCT scan abnormality correlated well (p e.g. physical functioning: r=−0.39–0.54). In summary, other workers have shown high-resolution computed tomography to be a sensitive indicator of disease progression. This study confirms the relationship between high-resolution computed tomography and lung physiology, and suggests the relationship is even stronger in patients with predominantly lower zone pan-lobular emphysema than in usual chronic obstructive pulmonary disease. High-resolution computed tomography also relates to patients disability and impairment as defined by health status questionnaires and, therefore, should be considered as an alternative outcome measure particularly in a 1 -antitrypsin deficiency.

Short term response of patients with bronchiectasis to treatment with amoxycillin given in standard or high doses orally or by inhalation.

The effect of three amoxycillin treatment regimens on purulent secretions of patients with bronchiectasis has been studied. On the basis of information recorded on a diary card the patients were divided into three groups, according to the usual nature of their secretions: seven who produced mucoid sputum, which occasionally became purulent; seven whose secretions were usually mucopurulent but occasionally purulent; and 19 whose secretions were persistently purulent. Treatment with capsules of amoxycillin in a dosage of 250 mg three times a day resulted in clearance of purulent secretions in patients of the mucoid group when they were treated for a clinical exacerbation. The sputum remained clear in these patients for long periods before a further exacerbation (median 6 1/2, range 1-11 months). The mucopurulent-purulent group also responded to this dosage but sputum purulence returned more rapidly (median 9, range 4-31 days). Only three of the 19 (17%) patients with persistently purulent secretions showed a macroscopic response to this dosage, whereas seven (60%) of 12 patients who received the higher dosage (3 g sachets twice a day) responded. Among the failures, some responded to nebulised amoxycillin, suggesting that higher levels of amoxycillin in secretions are required in these patients. Macroscopic clearance of purulent secretions was finally achieved in most of the patients studied. The response was not always predictable from the results of sputum culture. Clearance of secretions by antibiotics was also identified by the patients, using a diary card score. Improvements in well being and in symptoms were noticed even in the group who usually produced mucopurulent and purulent secretions even though they appeared to be clinically stable before treatment.

Predictors of mortality in alpha1-antitrypsin deficiency.

Background: Lung density measurements by computed tomography have previously been found to be a more sensitive indicator of disease progression in emphysema of α1-antitrypsin deficiency than lung function measurements. The aim of this study was to investigate the predictive potential of several parameters, including CT scanning, for mortality in patients with severe α1-antitrypsin deficiency. Methods: Over a 5 year period, 256 patients with α1-antitrypsin deficiency (PiZ phenotype) were assessed, of whom 254 underwent lung function testing and 197 had thoracic CT scans. Lung function, CT scans, health status (St George’s Respiratory Questionnaire, SGRQ), and other clinical data of survivors and non-survivors were compared and these parameters were applied to survival analyses. Results: There were 22 deaths in this patient cohort, 10 of which were classified as “respiratory” deaths. Baseline lung function parameters (forced expiratory volume in 1 second (FEV1), carbon monoxide transfer coefficient (Kco)), and CT scores were significantly lower in the non-survivors than in the survivors. 170 of the 256 patients had complete data for entry into multiple regression analyses (Cox proportional hazards model). In the univariate analysis, upper zone expiratory scan had the best association with all cause (pu200a=u200a0.001) and respiratory mortality (p<0.001), whereas FEV1 (pu200a=u200a0.158 all cause, 0.015 respiratory) and Kco (pu200a=u200a0.002 all cause, 0.012 respiratory) had poorer associations with mortality. Only age gave further independent predictive information regarding all cause or respiratory mortality when the CT scan was entered into the survival analyses. Conclusions: CT scanning predicts respiratory and all cause mortality in α1-antitrypsin deficiency and appears to be superior to lung function parameters, especially FEV1.