Phenotypic and functional translation of IL33 genetics in asthma.

BACKGROUND: Asthma is a complex disease with multiple phenotypes that may differ in disease pathobiology and treatment response. IL33 single nucleotide polymorphisms (SNPs) have been reproducibly associated with asthma. IL33 levels are elevated in sputum and bronchial biopsies of patients with asthma. The functional consequences of IL33 asthma SNPs remain unknown. OBJECTIVE: This study sought to determine whether IL33 SNPs associate with asthma-related phenotypes and with IL33 expression in lung or bronchial epithelium. This study investigated the effect of increased IL33 expression on human bronchial epithelial cell (HBEC) function. METHODS: Association between IL33 SNPs (Chr9: 5,815,786-6,657,983) and asthma phenotypes (Lifelines/DAG [Dutch Asthma GWAS]/GASP [Genetics of Asthma Severity & Phenotypes] cohorts) and between SNPs and expression (lung tissue, bronchial brushes, HBECs) was done using regression modeling. Lentiviral overexpression was used to study IL33 effects on HBECs. RESULTS: We found that 161 SNPs spanning the IL33 region associated with 1 or more asthma phenotypes after correction for multiple testing. We report a main independent signal tagged by rs992969 associating with blood eosinophil levels, asthma, and eosinophilic asthma. A second, independent signal tagged by rs4008366 presented modest association with eosinophilic asthma. Neither signal associated with FEV1, FEV1/forced vital capacity, atopy, and age of asthma onset. The 2 IL33 signals are expression quantitative loci in bronchial brushes and cultured HBECs, but not in lung tissue. IL33 overexpression in vitro resulted in reduced viability and reactive oxygen species-capturing of HBECs, without influencing epithelial cell count, metabolic activity, or barrier function. CONCLUSIONS: We identify IL33 as an epithelial susceptibility gene for eosinophilia and asthma, provide mechanistic insight, and implicate targeting of the IL33 pathway specifically in eosinophilic asthma.

Asthma and smoking-induced airway disease without spirometric COPD.

Due to the high prevalence rates of cigarette smoking and asthma, current and ex-smokers frequently develop chronic airway disease without spirometric evidence of chronic obstructive pulmonary disease (COPD), either alone or associated with asthma. This review considers the classification, clinical outcomes, inflammatory and imaging variables, phenotypes, and management of current and ex-smokers with airway disease without COPD, focusing on overlaps in those with and without asthma. These individuals have more respiratory symptoms, worse quality of life, increased exacerbation rates, reduced lung function and more comorbidities than never-smokers with asthma or healthy never-smokers. As well as clinical features, airway inflammatory and structural changes in smoking-induced airway disease without COPD overlap with those found in smokers with asthma. Cigarette smoking is associated with worse clinical outcomes in some phenotypes of asthma. Management involves public health measures to control exposure to tobacco smoke, personal advice on smoking cessation and the use of appropriate targeted therapies, although evidence is limited on their effectiveness. Understanding the mechanisms, natural history and management of current and ex-smokers with asthma and smoking-induced airway disease without COPD is a priority for future research.

The cost of treating severe refractory asthma in the UK: an economic analysis from the British Thoracic Society Difficult Asthma Registry.

Severe refractory asthma poses a substantial burden in terms of healthcare costs but relatively little is known about the factors which drive these costs. This study uses data from the British Thoracic Society Difficult Asthma Registry (n=596) to estimate direct healthcare treatment costs from an National Health Service perspective and examines factors that explain variations in costs. Annual mean treatment costs among severe refractory asthma patients were £2912 (SD £2212) to £4217 (SD £2449). Significant predictors of costs were FEV1% predicted, location of care, maintenance oral corticosteroid treatment and body mass index. Treating individuals with severe refractory asthma presents a substantial cost to the health service.

Atorvastatin in combination with inhaled beclometasone modulates inflammatory sputum mediators in smokers with asthma.

BACKGROUND: Statins have pleiotropic immunomodulatory effects that may be beneficial in the treatment of asthma. We previously reported that treatment with atorvastatin improved asthma symptoms in smokers with asthma in the absence of a change in the concentration of a selection of sputum inflammatory mediators. OBJECTIVE: To determine the effects of atorvastatin alone and in combination with inhaled corticosteroid on a range of sputum cytokines, chemokines and growth factors implicated in the pathogenesis of asthma, and their association with asthma control questionnaire (ACQ) and/or asthma quality of life questionnaire (AQLQ) scores. METHODS: Sputum samples were analysed from a sub-group of 39 smokers with mild to moderate asthma recruited to a randomised controlled trial comparing atorvastatin (40 mg/day) versus placebo for four weeks, followed by inhaled beclometasone (400 µg/day) for a further four weeks. Induced sputum supernatant fluid was analysed (Luminex or biochemical analyses) for concentrations of 35 mediators. RESULTS: Sputum mediator concentrations were not reduced by inhaled beclometasone alone. Atorvastatin significantly reduced sputum concentrations of CCL7, IL-12p70, sCD40L, FGF-2, CCL4, TGF-α and MMP-8 compared with placebo and, when combined with inhaled beclometasone, reduced sputum concentrations of MMP-8, IL-1ß, IL-10, MMP-9, sCD40L, FGF-2, IL-7, G-CSF and CCL7 compared to ICS alone. Improvements in ACQ and/or AQLQ scores with atorvastatin and ICS were associated with decreases in G-CSF, IL-7, CCL2 and CXCL8. CONCLUSION: Short-term treatment with atorvastatin alone or in combination with inhaled beclometasone reduces several sputum cytokines, chemokines and growth factors concentrations unresponsive to inhaled corticosteroids alone, in smokers with asthma.

The effect of inhaled IFN-ß on worsening of asthma symptoms caused by viral infections. A randomized trial.

RATIONALE: Ex vivo, bronchial epithelial cells from people with asthma are more susceptible to rhinovirus infection caused by deficient induction of the antiviral protein, IFN-ß. Exogenous IFN-ß restores antiviral activity. OBJECTIVES: To compare the efficacy and safety of inhaled IFN-ß with placebo administered to people with asthma after onset of cold symptoms to prevent or attenuate asthma symptoms caused by respiratory viruses. METHODS: A total of 147 people with asthma on inhaled corticosteroids (British Thoracic Society Steps 2-5), with a history of virus-associated exacerbations, were randomized to 14-day treatment with inhaled IFN-ß (n = 72) or placebo (n = 75) within 24 hours of developing cold symptoms and were assessed clinically, with relevant samples collected to assess virus infection and antiviral responses. MEASUREMENTS AND MAIN RESULTS: A total of 91% of randomized patients developed a defined cold. In this modified intention-to-treat population, asthma symptoms did not get clinically significantly worse (mean change in six-item Asthma Control Questionnaire <0.5) and IFN-ß treatment had no significant effect on this primary endpoint, although it enhanced morning peak expiratory flow recovery (P = 0.033), reduced the need for additional treatment, and boosted innate immunity as assessed by blood and sputum biomarkers. In an exploratory analysis of the subset of more difficult-to-treat, Step 4-5 people with asthma (n = 27 IFN-ß; n = 31 placebo), Asthma Control Questionnaire-6 increased significantly on placebo; this was prevented by IFN-ß (P = 0.004). CONCLUSIONS: Although the trial did not meet its primary endpoint, it suggests that inhaled IFN-ß is a potential treatment for virus-induced deteriorations of asthma in difficult-to-treat people with asthma and supports the need for further, adequately powered, trials in this population. Clinical trial registered with www.clinicaltrials.gov (NCT 01126177).

Details of development of the resource for adults with asthma in the RAISIN (randomized trial of an asthma internet self-management intervention) study.

BACKGROUND: Around 300 million people worldwide have asthma and prevalence is increasing. Self-management can be effective in improving a range of outcomes and is cost effective, but is underutilised as a treatment strategy. Supporting optimum self-management using digital technology shows promise, but how best to do this is not clear. We aimed to develop an evidence based, theory informed, online resource to support self-management in adults with asthma, called 'Living well with Asthma', as part of the RAISIN (Randomized Trial of an Asthma Internet Self-Management Intervention) study. METHODS: We developed Living well with Asthma in two phases. Phase 1: A low fidelity prototype (paper-based) version of the website was developed iteratively through input from a multidisciplinary expert panel, empirical evidence from the literature, and potential end users via focus groups (adults with asthma and practice nurses). Implementation and behaviour change theories informed this process. Phase 2: The paper-based designs were converted to a website through an iterative user centred process. Adults with asthma (n = 10) took part in think aloud studies, discussing the paper based version, then the web-based version. Participants considered contents, layout, and navigation. Development was agile using feedback from the think aloud sessions immediately to inform design and subsequent think aloud sessions. Think aloud transcripts were also thematically analysed, further informing resource development. RESULTS: The website asked users to aim to be symptom free. Key behaviours targeted to achieve this include: optimising medication use (including inhaler technique); attending primary care asthma reviews; using asthma action plans; increasing physical activity levels; and stopping smoking. The website had 11 sections, plus email reminders, which promoted these behaviours. Feedback on the contents of the resource was mainly positive with most changes focussing on clarification of language, order of pages and usability issues mainly relating to navigation difficulties. CONCLUSIONS: Our multifaceted approach to online intervention development underpinned by theory, using evidence from the literature, co-designed with end users and a multidisciplinary panel has resulted in a resource which end users find relevant to their needs and easy to use. Living well with Asthma is undergoing evaluation within a randomized controlled trial.

Increased sputum endotoxin levels are associated with an impaired lung function response to oral steroids in asthmatic patients.

BACKGROUND: Airway endotoxin might contribute to corticosteroid insensitivity in asthmatic patients. OBJECTIVE: Because cigarette smoke contains endotoxin, we tested the hypothesis that sputum endotoxin concentrations are increased in cigarette smokers and that endotoxin concentrations are associated with corticosteroid insensitivity in asthmatic patients. METHODS: Sixty-nine asthmatic patients (never smokers, smokers, and exsmokers) and 20 healthy subjects (never smokers and smokers) were recruited. Fifty-three asthmatic patients received a 2-week course of oral dexamethasone. Serum and induced sputum endotoxin and cytokine concentrations were quantified by using an enzyme immunoassay. RESULTS: Median (interquartile range [IQR]) sputum endotoxin concentration were not significantly different between asthmatic never smokers (184 endotoxin units [EU]/mL; IQR, 91-310 EU/mL), exsmokers (123 EU/mL; IQR, 39-207 EU/mL), and smokers (177 EU/mL; IQR, 41-772 EU/mL; P = .703) and healthy subjects (164 EU/mL; IQR, 106-373 EU/mL). The lung function response to oral corticosteroids decreased with increasing sputum endotoxin concentrations in the never smokers (linear regression α = .05, Spearman r = -0.503, P = .009) but not in smokers (α = .587, r = -0.282, P = .257), as confirmed by using multiple regression analysis. Asthmatic smokers had higher concentrations of serum endotoxin than asthmatic nonsmokers (0.25 EU/mL [IQR, 0.09-0.39 EU/mL] vs 0.08 EU/mL [IQR, 0.05-0.19 EU/mL], P = .042) unrelated to steroid insensitivity or serum cytokine concentrations. In the asthmatic group sputum endotoxin concentrations correlated with sputum IL-1 receptor antagonist concentrations (r = 0.510, P < .001), and serum endotoxin concentrations significantly correlated with sputum IL-6, IL-8, and chemokine motif ligand 2 concentrations. CONCLUSION: Asthmatic smokers have similar sputum endotoxin concentrations compared with those of asthmatic never smokers. The association between higher sputum endotoxin levels and an impaired lung function response to oral corticosteroids, particularly in asthmatic never smokers, suggests that airway endotoxin might contribute to corticosteroid insensitivity in asthmatic patients.

Low sputum MMP-9/TIMP ratio is associated with airway narrowing in smokers with asthma.

Asthmatic smokers have poor symptom control and accelerated decline in lung function. A reduced ratio of matrix metalloproteinase (MMP)-9/tissue inhibitors of metalloproteinases (TIMPs) in nonsmokers with asthma has been implicated in airway remodelling. We tested the hypothesis that sputum MMP-9 activity/TIMPs ratios are reduced in smokers compared with never-smokers with asthma and are associated with reduced lung function and altered computed tomography (CT) measures of airway wall dimensions. Lung function, airway dimensions by CT, and induced sputum concentrations (and activity) of MMP-9 and TIMP-1 and -2 were measured in 81 asthmatics and 43 healthy subjects (smokers and never-smokers). Respiratory epithelial MMP9 and TIMP mRNA was quantified in 31 severe asthmatics and 32 healthy controls. Sputum MMP-9 activity/TIMP-1 and TIMP-2 ratios, and nasal epithelial MMP9/TIMP1 and MMP9/TIMP2 expression ratios were reduced in smokers with asthma compared with never-smokers with asthma. Low sputum ratios in asthmatic smokers were associated with reduced post-bronchodilator forced expiratory volume in 1 s (FEV1), FEV1/forced vital capacity ratio and segmental airway lumen area. The association of a low sputum MMP-9 activity/TIMP-1 ratio with persistent airflow obstruction and reduced CT airway lumen area in smokers with asthma may indicate that an imbalance of MMP-9 and TIMPs contributes to structural changes to the airways in this group.

Digital asthma self-management interventions: a systematic review.

BACKGROUND: Many people with asthma tolerate symptoms and lifestyle limitations unnecessarily by not utilizing proven therapies. Better support for self-management is known to improve asthma control, and increasingly the Internet and other digital media are being used to deliver that support. OBJECTIVE: Our goal was to summarize current knowledge, evidenced through existing systematic reviews, of the effectiveness and implementation of digital self-management support for adults and children with asthma and to examine what features help or hinder the use of these programs. METHODS: A comprehensive search strategy combined 3 facets of search terms: (1) online technology, (2) asthma, and (3) self-management/behavior change/patient experience. We undertook searches of 14 databases, and reference and citation searching. We included qualitative and quantitative systematic reviews about online or computerized interventions facilitating self-management. Title, abstract, full paper screening, and quality appraisal were performed by two researchers independently. Data extraction was undertaken using standardized forms. RESULTS: A total of 3810 unique papers were identified. Twenty-nine systematic reviews met inclusion criteria: the majority were from the United States (n=12), the rest from United Kingdom (n=6), Canada (n=3), Portugal (n=2), and Australia, France, Spain, Norway, Taiwan, and Greece (1 each). Only 10 systematic reviews fulfilled pre-determined quality standards, describing 19 clinical trials. Interventions were heterogeneous: duration of interventions ranging from single use, to 24-hour access for 12 months, and incorporating varying degrees of health professional involvement. Dropout rates ranged from 5-23%. Four RCTs were aimed at adults (overall range 3-65 years). Participants were inadequately described: socioeconomic status 0/19, ethnicity 6/19, and gender 15/19. No qualitative systematic reviews were included. Meta-analysis was not attempted due to heterogeneity and inadequate information provision within reviews. There was no evidence of harm from digital interventions. All RCTs that examined knowledge (n=2) and activity limitation (n=2) showed improvement in the intervention group. Digital interventions improved markers of self care (5/6), quality of life (4/7), and medication use (2/3). Effects on symptoms (6/12) and school absences (2/4) were equivocal, with no evidence of overall benefits on lung function (2/6), or health service use (2/15). No specific data on economic analyses were provided. Intervention descriptions were generally brief making it impossible to identify which specific "ingredients" of interventions contribute most to improving outcomes. CONCLUSIONS: Digital self-management interventions show promise, with evidence of beneficial effects on some outcomes. There is no evidence about utility in those over 65 years and no information about socioeconomic status of participants, making understanding the "reach" of such interventions difficult. Digital interventions are poorly described within reviews, with insufficient information about barriers and facilitators to their uptake and utilization. To address these gaps, a detailed quantitative systematic review of digital asthma interventions and an examination of the primary qualitative literature are warranted, as well as greater emphasis on economic analysis within trials.

Clinical outcomes and inflammatory biomarkers in current smokers and exsmokers with severe asthma.

BACKGROUND: Clinical outcomes are worse in current smokers and exsmokers with mild-to-moderate asthma compared with never smokers, but little is known about the influence of smoking status in patients with severe asthma. OBJECTIVES: We sought to examine the association of current or previous cigarette smoking with clinical and inflammatory variables in patients with severe asthma. METHODS: We compared patients' demographics, disease characteristics, and biomarkers of inflammation in current smokers (n=69 [9%]), exsmokers (n=210 [28%]), and never smokers (n=461 [62%]) with severe asthma (n=760) recruited to the British Thoracic Society Severe Asthma Registry. RESULTS: Current smokers had poorer asthma control, more unscheduled health care visits, more rescue courses of oral steroids, and higher anxiety and depression scale scores than exsmokers or never smokers. Current smokers had a reduced proportion of sputum eosinophils compared with never smokers (1% and 4%, respectively) and lower fraction of expired nitric oxide (50 mL/s; 14 ppb and 35 ppb, respectively). Exsmokers compared with never smokers had an increased proportion of sputum neutrophils (59% and 43%, respectively) but a similar proportion of sputum eosinophils (3%) and fraction of expired nitric oxide (50 mL/s; 35 ppb). Both current smokers and exsmokers had reduced serum specific IgE levels to several common environmental allergens. CONCLUSION: Current smokers with severe asthma exhibit worse clinical and health care outcomes compared with exsmokers and never smokers with severe asthma. Their inflammatory profiles in sputum and blood differ.

Bronchial thermoplasty: Long-term safety and effectiveness in patients with severe persistent asthma.

BACKGROUND: Bronchial thermoplasty (BT) has previously been shown to improve asthma control out to 2 years in patients with severe persistent asthma. OBJECTIVE: We sought to assess the effectiveness and safety of BT in asthmatic patients 5 years after therapy. METHODS: BT-treated subjects from the Asthma Intervention Research 2 trial (ClinicalTrials.govNCT01350414) were evaluated annually for 5 years to assess the long-term safety of BT and the durability of its treatment effect. Outcomes assessed after BT included severe exacerbations, adverse events, health care use, spirometric data, and high-resolution computed tomographic scans. RESULTS: One hundred sixty-two (85.3%) of 190 BT-treated subjects from the Asthma Intervention Research 2 trial completed 5 years of follow-up. The proportion of subjects experiencing severe exacerbations and emergency department (ED) visits and the rates of events in each of years 1 to 5 remained low and were less than those observed in the 12 months before BT treatment (average 5-year reduction in proportions: 44% for exacerbations and 78% for ED visits). Respiratory adverse events and respiratory-related hospitalizations remained unchanged in years 2 through 5 compared with the first year after BT. Prebronchodilator FEV1 values remained stable between years 1 and 5 after BT, despite a 18% reduction in average daily inhaled corticosteroid dose. High-resolution computed tomographic scans from baseline to 5 years after BT showed no structural abnormalities that could be attributed to BT. CONCLUSIONS: These data demonstrate the 5-year durability of the benefits of BT with regard to both asthma control (based on maintained reduction in severe exacerbations and ED visits for respiratory symptoms) and safety. BT has become an important addition to our treatment armamentarium and should be considered for patients with severe persistent asthma who remain symptomatic despite taking inhaled corticosteroids and long-acting ß2-agonists.

Accelerated elastin degradation by age-disease interaction: a common feature in age-related diseases.

Aging is a major driving force for many diseases but the relationship between chronological age, the aging process and age-related diseases is not fully understood. Fragmentation and loss of ultra-long-lived elastin are key features in aging and several age-related diseases leading to increased mortality. By comparing the relationship between age and elastin turnover with healthy volunteers, we show that accelerated elastin turnover by age-disease interaction is a common feature of age-related diseases.

Smoking and asthma: dangerous liaisons.

Cigarette smoking and asthma interact to induce important adverse effects on clinical, prognostic and therapeutic outcomes. This review examines recent evidence on the harmful effects of smoking in asthma, possible underlying inflammatory mechanisms for this altered response, management options for these patients and potential future therapeutic directions. Active smokers, particularly females, are at risk of developing asthma. Prevalence rates for smoking in asthma are relatively close to those found in the general population. Smokers with asthma experience worse asthma control than nonsmokers with asthma. Mechanisms for the adverse effects of smoking in asthma include altered airway inflammation and corticosteroid insensitivity. Quitting smoking can improve symptoms and lung function, but the low rates of smoking cessation highlights the need for improved strategies for managing these patients. Clinical trials assessing new therapies for asthma need to enroll smokers to identify treatments that are effective in the asthma smoking phenotype.

Safety of bronchial thermoplasty in patients with severe refractory asthma.

BACKGROUND: Patients with severe refractory asthma treated with bronchial thermoplasty (BT), a bronchoscopic procedure that improves asthma control by reducing excess airway smooth muscle, were followed up for 5 years to evaluate long-term safety of this procedure. OBJECTIVES: To assess long-term safety of BT for 5 years. METHODS: Patients with asthma aged 18 to 65 years requiring high-dose inhaled corticosteroids (ICSs) (>750 µg/d of fluticasone propionate or equivalent) and long-acting ß2-agonists (LABAs) (at least 100 µg/d of salmeterol or equivalent), with or without oral prednisone (≤30 mg/d), leukotriene modifiers, theophylline, or other asthma controller medications were enrolled in the Research in Severe Asthma (RISA) Trial. Patients had a prebronchodilator forced expiratory volume in 1 second of 50% or more of predicted, demonstrated methacholine airway hyperresponsiveness, had uncontrolled symptoms despite taking maintenance medication, abstained from smoking for 1 year or greater, and had a smoking history of less than 10 pack-years. RESULTS: Fourteen patients (of the 15 who received active treatment in the RISA Trial) participated in the long-term follow-up study for 5 years. The rate of respiratory adverse events (AEs per patient per year) was 1.4, 2.4, 1.7, and 2.4, respectively, in years 2 to 5 after BT. There was a decrease in hospitalizations and emergency department visits for respiratory symptoms in each of years 1, 2, 3, 4, and 5 compared with the year before BT treatment. Measures of lung function showed no deterioration for 5 years. CONCLUSION: Our findings suggest that BT is safe for 5 years after BT in patients with severe refractory asthma. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00401986.

IL-33 induces innate lymphoid cell-mediated airway inflammation by activating mammalian target of rapamycin.

BACKGROUND: The IL-1 family cytokine IL-33 is involved in the induction of airway inflammation in allergic patients and after viral infection. Several cell types, including CD4(+) T(H)2 cells and the recently described type 2 innate lymphoid cells (ILCs), are targets for IL-33, yet the mechanisms by which this cytokine modulates their activation are not clear. OBJECTIVES: Our goal was to investigate a role for mammalian target of rapamycin (mTOR) signaling in the activation of T(H)2 and ILC responses and the induction of airway inflammation by IL-33. METHODS: We biochemically determined the effect of IL-33 on mTOR activation in T(H)2 cells and ILCs and examined the effect of this signaling pathway in vivo using a murine model of IL-33-induced lung inflammation. RESULTS: We found that IL-33 induces mTOR activation through p110δ phosphoinositide 3-kinase and that blockade of the mTOR pathway inhibited IL-33-induced IL-5 and IL-13 production by T(H)2 cells and ILCs. Furthermore, use of a ribosomal protein S6 kinase 1 inhibitor implicated a role for ribosomal protein S6 kinase 1 in IL-33-induced mTOR-dependent cytokine production. Intranasal administration of IL-33 to wild-type mice induced airway inflammation, whereas adoptive transfer of wild-type ILCs to IL-33 receptor-deficient (St2(-/-)) mice recapitulated this response. Importantly, coadministration of the mTOR inhibitor rapamycin reduced IL-33-dependent ILC, macrophage, and eosinophil accumulation; cytokine secretion; and mucus deposition in the airways. CONCLUSION: These data reveal a hitherto unrecognized role of mTOR signaling in IL-33-driven, ILC-dependent inflammation in vivo and suggest that manipulation of this pathway might represent a target for therapeutic intervention for airway inflammation.

Sputum matrix metalloproteinase-12 in patients with chronic obstructive pulmonary disease and asthma: relationship to disease severity.

BACKGROUND: Matrix metalloproteinase (MMP)-12 has been implicated in the pathogenesis of both chronic obstructive pulmonary disease (COPD) and asthma. The influence of disease severity on sputum MMP-12 concentrations and activity is not known. OBJECTIVES: We sought to examine the relationship between disease severity assessed by means of lung function and computed tomography (CT) and induced sputum MMP-12 concentrations and activity in patients with asthma and COPD. METHODS: In 208 subjects (109 asthmatic patients, smokers and never smokers, mild, moderate, and severe; 53 patients with COPD, smokers and exsmokers, mild, moderate, and severe; and 46 healthy control subjects, smokers and never smokers), we measured induced sputum MMP-12 concentrations (ELISA) and enzyme activity (fluorescence resonance energy transfer), sputum cell MMP12 mRNA expression (quantitative PCR [qPCR]), diffusing capacity for carbon monoxide (Dlco), and CT assessment of emphysema (percentage of low-attenuation areas at less -950 Hounsfield units). RESULTS: Sputum MMP-12 concentrations are greater in patients with COPD and smokers with asthma than in healthy nonsmokers (P = .003 and P = .035, respectively) but similar to those seen in healthy smokers. In patients with COPD, disease severity, when measured by means of CT-assessed emphysema, but not by means of spirometry or Dlco values, is directly associated with sputum MMP-12 concentrations and activity. In the asthma groups there is no significant association between disease severity and sputum MMP-12 concentrations or activity. CONCLUSIONS: Sputum MMP-12 concentrations and activity in patients with COPD are directly associated with the extent of emphysema measured by means of CT. This finding supports a role for MMP-12 in the pathogenesis of COPD and might suggest that blocking MMP-12 activity in patients with COPD could prevent the further development of emphysema.