Updates on the COPD gene list

Cytokine inhibition in the treatment of COPD

Cytokines play an important part in many pathobiological processes of chronic obstructive pulmonary disease (COPD), including the chronic inflammatory process, emphysema, and altered innate immune response. Proinflammatory cytokines of potential importance include tumor necrosis factor (TNF)-α, interferon-γ, interleukin (IL)-1β, IL-6, IL-17, IL-18, IL-32, and thymic stromal lymphopoietin (TSLP), and growth factors such as transforming growth factor-β. The current objectives of COPD treatment are to reduce symptoms, and to prevent and reduce the number of exacerbations. While current treatments achieve these goals to a certain extent, preventing the decline in lung function is not currently achievable. In addition, reversal of corticosteroid insensitivity and control of the fibrotic process while reducing the emphysematous process could also be controlled by specific cytokines. The abnormal pathobiological process of COPD may contribute to these fundamental characteristics of COPD, and therefore targeting cytokines involved may be a fruitful endeavor. Although there has been much work that has implicated various cytokines as potentially playing an important role in COPD, there have been very few studies that have examined the effect of specific cytokine blockade in COPD. The two largest studies that have been reported in the literature involve the use of blocking antibody to TNFα and CXCL8 (IL-8), and neither has provided benefit. Blocking the actions of CXCL8 through its CXCR2 receptor blockade was not successful either. Studies of antibodies against IL-17, IL-18, IL-1β, and TSLP are currently either being undertaken or planned. There is a need to carefully phenotype COPD and discover good biomarkers of drug efficacy for each specific target. Specific groups of COPD patients should be targeted with specific anticytokine therapy if there is evidence of high expression of that cytokine and there are features of the clinical expression of COPD that will respond.

Longer telomere length in COPD patients with α1-antitrypsin deficiency independent of lung function

Oxidative stress is involved in the pathogenesis of airway obstruction in α₁-antitrypsin deficient patients. This may result in a shortening of telomere length, resulting in cellular senescence. To test whether telomere length differs in α₁-antitrypsin deficient patients compared with controls, we measured telomere length in DNA from peripheral blood cells of 217 α₁-antitrypsin deficient patients and 217 control COPD patients. We also tested for differences in telomere length between DNA from blood and DNA from lung tissue in a subset of 51 controls. We found that telomere length in the blood was significantly longer in α₁-antitrypsin deficient COPD patients compared with control COPD patients (p = 1×10⁻²⁹). Telomere length was not related to lung function in α₁-antitrypsin deficient patients (p = 0.3122) or in COPD controls (p = 0.1430). Although mean telomere length was significantly shorter in the blood when compared with the lungs (p = 0.0078), telomere length was correlated between the two tissue types (p = 0.0122). Our results indicate that telomere length is better preserved in α₁-antitrypsin deficient COPD patients than in non-deficient patients. In addition, measurement of telomere length in the blood may be a suitable surrogate for measurement in the lung.

Regulation of IL-4 receptor signaling by STUB1 in lung inflammation

RATIONALE

IL-4Rα, the common receptor component for IL-4 and IL-13, plays a critical role in IL-4- and IL-13-mediated signaling pathways that regulate airway inflammation and remodeling. However, the regulatory mechanisms underlying IL-4Rα turnover and its signal termination remain elusive.

OBJECTIVES

To evaluate the role of STUB1 (STIP1 homology and U-Box containing protein 1) in regulating IL-4R signaling in airway inflammation.

METHODS

The roles of STUB1 in IL-4Rα degradation and its signaling were investigated by immunoblot, immunoprecipitation, and flow cytometry. The involvement of STUB1 in airway inflammation was determined in vivo by measuring lung inflammatory cells infiltration, mucus production, serum lgE levels, and alveolar macrophage M2 activation in STUB1(-/-) mice. STUB1 expression was evaluated in airway epithelium of patients with asthma and lung tissues of subjects with chronic obstructive pulmonary disease.

MEASUREMENTS AND MAIN RESULTS

STUB1 interacted with IL-4Rα and targeted it for ubiquitination-mediated proteasomal degradation, terminating IL-4 or IL-13 signaling. STUB1 knockout cells showed increased levels of IL-4Rα and sustained STAT6 activation, whereas STUB1 overexpression reduced IL-4Rα levels. Mice deficient in STUB1 had spontaneous airway inflammation, alternative M2 activation of alveolar macrophage, and increased serum IgE. STUB1 levels were increased in airways of subjects with asthma or chronic obstructive pulmonary disease, suggesting that up-regulation of STUB1 might be an important feedback mechanism to dampen IL-4R signaling in airway inflammation.

CONCLUSIONS

Our study identified a previously uncharacterized role for STUB1 in regulating IL-4R signaling, which might provide a new strategy for attenuating airway inflammation.

Oxidants in Acute and Chronic Lung Disease

Oxidants play an important role in homeostatic function, but excessive oxidant generation has an adverse effect on health. The manipulation of Reactive Oxygen Species (ROS) can have a beneficial effect on various lung pathologies. However indiscriminate uses of anti-oxidant strategies have not demonstrated any consistent benefit and may be harmful. Here we propose that nuanced strategies are needed to modulate the oxidant system to obtain a beneficial result in the lung diseases such as Acute Lung Injury (ALI) and Chronic Obstructive Pulmonary Disease (COPD). We identify novel areas of lung oxidant responses that may yield fruitful therapies in the future.

Asthma and chronic obstructive pulmonary disease: similarities and differences

Asthma and COPD are both heterogeneous lung diseases including many different phenotypes. The classical asthma and COPD phenotypes are easy to discern because they reflect extremes of a phenotypical spectrum. Thus asthma in childhood and COPD in smokers have their own phenotypic expression with underlying pathophysiological mechanisms that differ importantly. In older adults, asthma and COPD are more difficult to differentiate and there exists a bronchodilator response in most but not all patients with asthma and persistent airway obstruction in most but not all patients with COPD where even up to 50% have been reported to have some bronchodilator response as assessed with FEV1. Airway obstruction is generated in the large and small airways both in asthma and COPD, and this small airway obstruction is located more proximally in asthma, yet is found more distally in severe and older individuals with asthma, comparable to COPD. Though the underlying inflammation and remodelling processes in asthma and COPD are different in their extreme phenotypes, there are overlap phenotypes with eosinophilic inflammation even in stable COPD and neutrophilic inflammation in longstanding and severe asthma.

Pooled subpopulation analyses of the effects of roflumilast on exacerbations and lung function in COPD

BACKGROUND

This post-hoc analysis examined the impact of roflumilast on chronic obstructive pulmonary disease (COPD) exacerbations and lung function in patients with COPD who received concomitant long-acting β2-agonists (LABA) with or without prior inhaled corticosteroid (ICS) and the influence of various demographic and clinical characteristics on these outcomes.

METHODS

Data were pooled from 2 double-blind, placebo-controlled, 52-week studies of once-daily roflumilast 500 μg in patients with COPD. Endpoints were mean rate of exacerbations and change from baseline in pre- and postbronchodilator FEV1.

RESULTS

In this pooled analysis (N = 3091), addition of roflumilast to LABAs for 1 year in patients who discontinued ICS prior to study entry (n = 945) significantly reduced the risk of COPD exacerbations vs. placebo by 19.2% (p < 0.05) and significantly improved pre- and postbronchodilator FEV1 by 40 mL and 34 mL, respectively (both, p < 0.01). Similar improvements were observed in patients who received concomitant LABAs but were not taking ICS prior to study entry (n = 597). A significant reduction in COPD exacerbation risk with roflumilast vs. placebo was observed regardless of age or smoking status, and in patients who had severe or very severe COPD. Significantly improved lung function was observed with roflumilast in all the subgroups (p < 0.05), with the exception of patients with moderate COPD.

CONCLUSIONS

Roflumilast reduced exacerbation rates and improved lung function in patients with COPD who received concomitant LABA, regardless of prior ICS use, and across various patient subgroups regardless of age and smoking status.

CLINICALTRIALSGOV REGISTRATION NUMBERS

NCT00297102 (M2-124) and NCT00297115 (M2-125).

Refining susceptibility loci of chronic obstructive pulmonary disease with lung eqtls

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of mortality worldwide. Recent genome-wide association studies (GWAS) have identified robust susceptibility loci associated with COPD. However, the mechanisms mediating the risk conferred by these loci remain to be found. The goal of this study was to identify causal genes/variants within susceptibility loci associated with COPD. In the discovery cohort, genome-wide gene expression profiles of 500 non-tumor lung specimens were obtained from patients undergoing lung surgery. Blood-DNA from the same patients were genotyped for 1,2 million SNPs. Following genotyping and gene expression quality control filters, 409 samples were analyzed. Lung expression quantitative trait loci (eQTLs) were identified and overlaid onto three COPD susceptibility loci derived from GWAS; 4q31 (HHIP), 4q22 (FAM13A), and 19q13 (RAB4B, EGLN2, MIA, CYP2A6). Significant eQTLs were replicated in two independent datasets (n = 363 and 339). SNPs previously associated with COPD and lung function on 4q31 (rs1828591, rs13118928) were associated with the mRNA expression of HHIP. An association between mRNA expression level of FAM13A and SNP rs2045517 was detected at 4q22, but did not reach statistical significance. At 19q13, significant eQTLs were detected with EGLN2. In summary, this study supports HHIP, FAM13A, and EGLN2 as the most likely causal COPD genes on 4q31, 4q22, and 19q13, respectively. Strong lung eQTL SNPs identified in this study will need to be tested for association with COPD in case-control studies. Further functional studies will also be needed to understand the role of genes regulated by disease-related variants in COPD.

Chronic obstructive pulmonary disease

The global prevalence of physiologically defined chronic obstructive pulmonary disease (COPD) in adults aged >40 yr is approximately 9-10 per cent. Recently, the Indian Study on Epidemiology of Asthma, Respiratory Symptoms and Chronic Bronchitis in Adults had shown that the overall prevalence of chronic bronchitis in adults >35 yr is 3.49 per cent. The development of COPD is multifactorial and the risk factors of COPD include genetic and environmental factors. Pathological changes in COPD are observed in central airways, small airways and alveolar space. The proposed pathogenesis of COPD includes proteinase-antiproteinase hypothesis, immunological mechanisms, oxidant-antioxidant balance, systemic inflammation, apoptosis and ineffective repair. Airflow limitation in COPD is defined as a postbronchodilator FEV1 (forced expiratory volume in 1 sec) to FVC (forced vital capacity) ratio <0.70. COPD is characterized by an accelerated decline in FEV1. Co morbidities associated with COPD are cardiovascular disorders (coronary artery disease and chronic heart failure), hypertension, metabolic diseases (diabetes mellitus, metabolic syndrome and obesity), bone disease (osteoporosis and osteopenia), stroke, lung cancer, cachexia, skeletal muscle weakness, anaemia, depression and cognitive decline. The assessment of COPD is required to determine the severity of the disease, its impact on the health status and the risk of future events (e.g., exacerbations, hospital admissions or death) and this is essential to guide therapy. COPD is treated with inhaled bronchodilators, inhaled corticosteroids, oral theophylline and oral phosphodiesterase-4 inhibitor. Non pharmacological treatment of COPD includes smoking cessation, pulmonary rehabilitation and nutritional support. Lung volume reduction surgery and lung transplantation are advised in selected severe patients. Global strategy for the diagnosis, management and prevention of Chronic Obstructive Pulmonary Disease guidelines recommend influenza and pneumococcal vaccinations.