Progress in chronic obstructive pulmonary disease genetics

COPD Patients Exhibit Distinct Gene Expression, Accelerated Cellular Aging, and Bias to M2 Macrophages

COPD, one of world's leading contributors to morbidity and mortality, is characterized by airflow limitation and heterogeneous clinical features. Three main phenotypes are proposed: overlapping asthma/COPD (ACO), exacerbator, and emphysema. Disease severity can be classified as mild, moderate, severe, and very severe. The molecular basis of inflammatory amplification, cellular aging, and immune response are critical to COPD pathogenesis. Our aim was to investigate EP300 (histone acetylase, HAT), HDAC 2 (histone deacetylase), HDAC3, and HDAC4 gene expression, telomere length, and differentiation ability to M1/M2 macrophages. For this investigation, 105 COPD patients, 42 smokers, and 73 non-smoker controls were evaluated. We identified a reduced HDAC2 expression in patients with mild, moderate, and severe severity; a reduced HDAC3 expression in patients with moderate and severe severity; an increased HDAC4 expression in patients with mild severity; and a reduced EP300 expression in patients with severe severity. Additionally, HDAC2 expression was reduced in patients with emphysema and exacerbator, along with a reduced HDAC3 expression in patients with emphysema. Surprisingly, smokers and all COPD patients showed telomere shortening. COPD patients showed a higher tendency toward M2 markers. Our data implicate genetic changes in COPD phenotypes and severity, in addition to M2 prevalence, that might influence future treatments and personalized therapies.

Integration of transcriptome analysis with pathophysiological endpoints to evaluate cigarette smoke toxicity in an in vitro human airway tissue model

Exposure to cigarette smoke (CS) is a known risk factor in the pathogenesis of smoking-caused diseases, such as chronic obstructive pulmonary diseases (COPD) and lung cancer. To assess the effects of CS on the function and phenotype of airway epithelial cells, we developed a novel repeated treatment protocol and comprehensively evaluated the progression of key molecular, functional, and structural abnormalities induced by CS in a human in vitro air-liquid-interface (ALI) airway tissue model. Cultures were exposed to CS (diluted with 0.5 L/min, 1.0 L/min, and 4.0 L/min clean air) generated from smoking five 3R4F University of Kentucky reference cigarettes under the International Organization for Standardization (ISO) machine smoking regimen, every other day for 4 weeks (3 days per week, 40 min/day). By integrating the transcriptomics-based approach with the in vitro pathophysiological measurements, we demonstrated CS-mediated effects on oxidative stress, pro-inflammatory cytokines and matrix metalloproteinases (MMPs), ciliary function, expression and secretion of mucins, and squamous cell differentiation that are highly consistent with abnormalities observed in airways of smokers. Enrichment analysis on the transcriptomic profiles of the ALI cultures revealed key molecular pathways, such as xenobiotic metabolism, oxidative stress, and inflammatory responses that were perturbed in response to CS exposure. These responses, in turn, may trigger aberrant tissue remodeling, eventually leading to the onset of respiratory diseases. Furthermore, changes of a panel of genes known to be disturbed in smokers with COPD were successfully reproduced in the ALI cultures exposed to CS. In summary, findings from this study suggest that such an integrative approach may be a useful tool for identifying genes and adverse cellular events caused by inhaled toxicants, like CS.

Comparative proteomics analysis of patients with quick development and slow development Chronic Obstructive Pulmonary Disease (COPD)

BACKGROUND

The development of Chronic Obstructive Pulmonary Disease (COPD) has been assessed and divided into slow development (SD), normal development (ND) and quick development (QD). Little is known about the plasma proteome characters among these three phenotypes.

METHODS

We performed a comparative proteomic analysis in the plasma of normal control (NC), SD, ND and QD phenotype COPD patients using isobaric tags for relative and absolute quantitation (iTRAQ) technique.

RESULTS

A total of 683 proteins were successfully identified in the plasma samples, of which 394 were considered as high-quality proteins (95% confidential peptides ≥ 2). Further, a total of 25, 19 and 27 different abundant proteins (DAPs) were identified in SD, ND and QD groups, respectively. Gene ontology (GO) classification analysis of all DAPs showed that immune system process (GO:0002376) were the most significant. The pathway enrichment analysis showed that innate immune response (GO:0045087), receptor-mediated endocytosis (GO:0006898) and proteolysis (GO:0006508) were the branch-end terms. Notably, the 15 QD special DAPs were considered as potential markers for identify patient might have quick development COPD, and thus provided more aggressive treatment strategy for these patients.

CONCLUSION

This work provides an insight into global plasma proteome profiles among the SD, ND and QD phenotypes of COPD patients. The most significant GO terms that the DAPs enriched in were immune system related terms. In addition, the 15 QD specific DPAs provided candidates of potential markers to predict the development types of COPD patients.

Animal Models Reflecting Chronic Obstructive Pulmonary Disease and Related Respiratory Disorders: Translating Pre-Clinical Data into Clinical Relevance

Chronic obstructive pulmonary disease (COPD) affects the lives of an ever-growing number of people worldwide. The lack of understanding surrounding the pathophysiology of the disease and its progression has led to COPD becoming the third leading cause of death worldwide. COPD is incurable, with current treatments only addressing associated symptoms and sometimes slowing its progression, thus highlighting the need to develop novel treatments. However, this has been limited by the lack of experimental standardization within the respiratory disease research area. A lack of coherent animal models that accurately represent all aspects of COPD clinical presentation makes the translation of promising in vitrodata to human clinical trials exceptionally challenging. Here, we review current knowledge within the COPD research field, with a focus on current COPD animal models. Moreover, we include a set of advantages and disadvantages for the selection of pre-clinical models for the identification of novel COPD treatments.

Altered regulation and expression of genes by BET family of proteins in COPD patients

BACKGROUND

BET proteins (BRD2, BRD3, BRDT and BRD4) belong to the family of bromodomain containing proteins, which form a class of transcriptional co-regulators. BET proteins bind to acetylated lysine residues in the histones of nucleosomal chromatin and function either as co-activators or co-repressors of gene expression. An imbalance between HAT and HDAC activities resulting in hyperacetylation of histones has been identified in COPD. We hypothesized that pan-BET inhibitor (JQ1) treatment of BET protein interactions with hyperacetylated sites in the chromatin will regulate excessive activation of pro-inflammatory genes in key inflammatory drivers of alveolar macrophages (AM) in COPD.

METHODS AND FINDINGS

Transcriptome analysis of AM from COPD patients indicated up-regulation of macrophage M1 type genes upon LPS stimulation. Pan-BET inhibitor JQ1 treatment attenuated expression of multiple genes, including pro-inflammatory cytokines and regulators of innate and adaptive immune cells. We demonstrated for the first time that JQ1 differentially modulated LPS-induced cytokine release from AM or peripheral blood mononuclear cells (PBMC) of COPD patients compared to PBMC of healthy controls. Using the BET regulated gene signature, we identified a subset of COPD patients, which we propose to benefit from BET inhibition.

CONCLUSIONS

This work demonstrates that the effects of pan-BET inhibition through JQ1 treatment of inflammatory cells differs between COPD patients and healthy controls, and the expression of BET protein regulated genes is altered in COPD. These findings provide evidence of histone hyperacetylation as a mechanism driving chronic inflammatory changes in COPD.

Passive smoking and chronic obstructive pulmonary disease mortality: findings from the Japan collaborative cohort study

OBJECTIVES

To elucidate the association between passive smoking at home and chronic obstructive pulmonary disease (COPD) mortality via a large-scale nationwide cohort study in Japan.

METHODS

Never smokers (n = 34,604) aged 40-79 years at baseline (1988-1990; 4884 men, 29,720 women) were included in the analysis. Passive smoking at home was measured based on self-reported frequency of weekly exposure to passive smoking at home. An inverse probability of treatment-weighted competing risk model was used to calculate the hazard ratio (HR) and 95% confidence interval (CI) for COPD mortality.

RESULTS

During a median follow-up of 16.4 years, 33 participants (10 men, 23 women) died of COPD. The HR for participants exposed to passive smoking at home ≤4 days per week or those who had almost daily exposure to passive smoking at home had a significantly increased risk of COPD mortality (HR 2.40, 95% CI 1.39-4.15, HR 2.88, 95% CI 1.68-4.93, respectively).

CONCLUSIONS

The present findings suggest that avoiding passive smoking at home may be beneficial for preventing death due to COPD among never smokers.

Gene-environment interaction between the MMP9 C-1562T promoter variant and cigarette smoke in the pathogenesis of chronic obstructive pulmonary disease

The aetiology of chronic obstructive pulmonary disease (COPD) is complex. While cigarette smoking is a well-established cause of COPD, a myriad of assessed genetic factors has given conflicting data. Since gene-environment interactions are thought to be implicated in aetiopathogenesis of COPD, we aimed to examine the matrix metalloproteinase (MMP) 9 C-1562T (rs3918242) functional variant and cigarette smoke in the pathogenesis of this disease. The distribution of the MMP9 C-1562T variant was analyzed in COPD patients and controls with normal pulmonary function from Serbia. Interaction between the C-1562T genetic variant and cigarette smoking was assessed using a case-control model. The response of the C-1562T promoter variant to cigarette smoke condensate (CSC) exposure was examined using a dual luciferase reporter assay. The frequency of T allele carriers was higher in the COPD group than in smoker controls (38.4% vs. 20%; OR = 2.7, P = 0.027). Interaction between the T allele and cigarette smoking was identified in COPD occurrence (OR = 4.38, P = 0.005) and severity (P = 0.001). A functional analysis of the C-1562T variant demonstrated a dose-dependent and allele-specific response (P < 0.01) to CSC. Significantly higher MMP9 promoter activity following CSC exposure was found for the promoter harboring the T allele compared to the promoter harboring the C allele (P < 0.05). Our study is the first to reveal an interaction between the MMP9-1562T allele and cigarette smoke in COPD, emphasising gene-environment interactions as a possible cause of lung damage in the pathogenesis of COPD. Environ. Mol. Mutagen. 57:447-454, 2016. © 2016 Wiley Periodicals, Inc.

Whole exome sequencing identifies novel candidate genes that modify chronic obstructive pulmonary disease susceptibility

Background

Chronic obstructive pulmonary disease (COPD) is characterized by an irreversible airflow limitation in response to inhalation of noxious stimuli, such as cigarette smoke. However, only 15–20 % smokers manifest COPD, suggesting a role for genetic predisposition. Although genome-wide association studies have identified common genetic variants that are associated with susceptibility to COPD, effect sizes of the identified variants are modest, as is the total heritability accounted for by these variants. In this study, an extreme phenotype exome sequencing study was combined with in vitro modeling to identify COPD candidate genes.

Results

We performed whole exome sequencing of 62 highly susceptible smokers and 30 exceptionally resistant smokers to identify rare variants that may contribute to disease risk or resistance to COPD. This was a cross-sectional case-control study without therapeutic intervention or longitudinal follow-up information. We identified candidate genes based on rare variant analyses and evaluated exonic variants to pinpoint individual genes whose function was computationally established to be significantly different between susceptible and resistant smokers. Top scoring candidate genes from these analyses were further filtered by requiring that each gene be expressed in human bronchial epithelial cells (HBECs). A total of 81 candidate genes were thus selected for in vitro functional testing in cigarette smoke extract (CSE)-exposed HBECs. Using small interfering RNA (siRNA)-mediated gene silencing experiments, we showed that silencing of several candidate genes augmented CSE-induced cytotoxicity in vitro.

Conclusions

Our integrative analysis through both genetic and functional approaches identified two candidate genes (TACC2 and MYO1E) that augment cigarette smoke (CS)-induced cytotoxicity and, potentially, COPD susceptibility.

Electronic supplementary material

The online version of this article (doi:10.1186/s40246-015-0058-7) contains supplementary material, which is available to authorized users.

A predictive model for the development of chronic obstructive pulmonary disease

The screening of a person at risk for chronic obstructive pulmonary disease (COPD) and timely treatment may provide opportunities to delay the progressive destruction of lung function. Therefore, a model to predict the disease is required. We hypothesized that demographic and clinical information in combination with genetic markers would aid in the prediction of COPD development, prior to its onset. The aim of the present study was to create a predictive model for COPD development. Demographic, clinical presentation and genetic polymorphisms were recorded in COPD patients and control subjects. Nighty-six single-nucleotide polymorphisms of 46 genes were selected for genotyping in the case-control study. A predictive model was produced using logistic regression with a stepwise model-building approach and was validated. A total of 331 patients and 351 control subjects were included. The logistic regression identified the following predictors: Gender, respiratory infection in early life, low birth weight, smoking history and genotype polymorphisms (rs2070600, rs10947233, rs1800629, rs2241712 and rs1205). The model was established using the following formula: COPD = 1/[1 + exp (-2.4933-1.2197 gender + 1.1842 respiratory infection in early life + 2.4350 low birth weight + 1.8524 smoking - 1.1978 rs2070600 + 2.0270 rs10947233 + 1.1913 rs10947233 + 0.6468 rs1800629 + 0.5272 rs2241712 + 0.4024 rs1205)] (when the value is >0.5). The Hosmer-Lemeshow test showed no significant deviations between the observed and predicted events. Validation of the model in 50 patients showed a modest sensitivity and specificity. Therefore, a predictive model based on demographic, clinical and genetic information may identify COPD prior to its onset.

Association of Functional Variants of Phase I and II Genes with Chronic Obstructive Pulmonary Disease in a Serbian Population

Background

Chronic obstructive pulmonary disease (COPD) is a complex disorder characterized by increased oxidative stress. Functional genetic variants of phase I and II genes are implicated in oxidants–antioxidants imbalance and may be involved in COPD development. In this study, we aimed to investigate the role of cytochrome P450 (CYP), glutathione S-transferase (GST) and microsomal epoxide hydrolase (mEH) functional variants in the pathogenesis of COPD in a Serbian population.

Methods

The genotypes of 122 COPD patients and 100 controls with normal lung function were determined for CYP1A1 *1A/*2A, CYP2E1 *1A/*5B, GSTM1 null, GSTT1 null GSTP1 Ile105Val, mEH Tyr113His and mEH His139Arg gene variants.

Results

Results obtained showed that GSTM1 null variant was significantly more represented in COPD patients than in controls (61.5% vs. 47.0%; OR=1.80; p=0.042). Also, a significant difference was observed for combinations of GSTM1 null and GSTP1 105Val/(Val) (38.5% vs. 24.0%; OR=1.98; p=0.029), as well as for CYP1A1 *1A/*2A, GSTM1 null and mEH 113His/(His) genotypes (7.4% vs. 1.0%; OR=7.88; p=0.025).

Conclusions

These are the first data concerning the analysis of the variants of phase I and II genes in the pathogenesis of COPD in a Serbian population. Results obtained in this study open up the possibility for thorough analyses of the role of genetic factors in COPD on larger cohorts. Also, they implicate the importance of previously described genetic associations with COPD in our population, as well as reveal a new one, not reported so far.

Common genetic determinants of lung function, subclinical atherosclerosis and risk of coronary artery disease

Chronic obstructive pulmonary disease (COPD) independently associates with an increased risk of coronary artery disease (CAD), but it has not been fully investigated whether this co-morbidity involves shared pathophysiological mechanisms. To identify potential common pathways across the two diseases, we tested all recently published single nucleotide polymorphisms (SNPs) associated with human lung function (spirometry) for association with carotid intima-media thickness (cIMT) in 3,378 subjects with multiple CAD risk factors, and for association with CAD in a case-control study of 5,775 CAD cases and 7,265 controls. SNPs rs2865531, located in the CFDP1 gene, and rs9978142, located in the KCNE2 gene, were significantly associated with CAD. In addition, SNP rs9978142 and SNP rs3995090 located in the HTR4 gene, were associated with average and maximal cIMT measures. Genetic risk scores combining the most robustly spirometry–associated SNPs from the literature were modestly associated with CAD, (odds ratio (OR) (95% confidence interval (CI₉₅) = 1.06 (1.03, 1.09); P-value = 1.5×10⁻⁴, per allele). In conclusion, our study suggests that some genetic loci implicated in determining human lung function also influence cIMT and susceptibility to CAD. The present results should help elucidate the molecular underpinnings of the co-morbidity observed across COPD and CAD.

Transposable elements and their potential role in complex lung disorder

Transposable elements (TEs) are a class of mobile genetic elements (MGEs) that were long regarded as junk DNA, which make up approximately 45% of the genome. Although most of these elements are rendered inactive by mutations and other gene silencing mechanisms, TEs such as long interspersed nuclear elements (LINEs) are still active and translocate within the genome. During transposition, they may create lesions in the genome, thereby acting as epigenetic modifiers. Approximately 65 disease-causing LINE insertion events have been reported thus far; however, any possible role of TEs in complex disorders is not well established. Chronic obstructive pulmonary disease (COPD) is one such complex disease that is primarily caused by cigarette smoking. Although the exact molecular mechanism underlying COPD remains unclear, oxidative stress is thought to be the main factor in the pathogenesis of COPD. In this review, we explore the potential role of oxidative stress in epigenetic activation of TEs such as LINEs and the subsequent cascade of molecular damage. Recent advancements in sequencing and computation have eased the identification of mobile elements. Therefore, a comparative study on the activity of these elements and markers for genome instability would give more insight on the relationship between MGEs and complex disorder such as COPD.

Second hand smoke and COPD: lessons from animal studies

Exposure to second hand smoke is a major cause of chronic obstructive pulmonary disease (COPD) in the non-smoker. In this review we explore the use of animal smoke exposure models and their insight into disease pathogenesis. The methods of smoke exposure, including exposure delivery systems, are described. Key findings from the acute and chronic smoke exposure models are outlined, including descriptions of the inflammation processes, proteases involved, oxidative stress, and apoptosis. Finally, alternatives to rodent models of lung disease are presented.

Is intrinsic aerobic exercise capacity a determinant of COPD susceptibility?

Chronic obstructive pulmonary disease is a leading cause of morbidity and mortality, which is most commonly associated with smoking or exposure to environmental pollutants. Unfortunately, there is an inadequate understanding of the molecular and physiological determinants governing one's susceptibility for developing COPD. Here, we describe a novel hypothesis: Individuals with intrinsically low aerobic exercise capacity are more likely to develop COPD after exposure to key risk factors. The hypothesis is based on observations that aerobic exercise capacity is tightly associated with mortality across many complex diseases. The premise is supported by recent studies demonstrating that smokers who exercise regularly are less likely to develop or be hospitalized for COPD. Herein, we describe the evolutionary and molecular basis for this hypothesis and how it is a natural extension of previous theories explaining COPD susceptibility.

Association of genetic polymorphisms with chronic obstructive pulmonary disease in the Chinese Han population: a case-control study

Background

Chronic obstructive pulmonary disease (COPD) is influenced by both environmental and genetic factors. Few gene studies of the Chinese population have focused on COPD. We investigated candidate genes associated with susceptibility to COPD in the Chinese Han population.

Methods

A total of 331 COPD patients and 213 control subjects were recruited for this study. Nighty-seven single-nucleotide polymorphisms (SNPs) of 46 genes were selected for genotyping. Genotypes were determined using multiplex polymerase chain reaction (PCR).

Results

Significant differences between patients and healthy controls were observed in the allele frequencies of seven SNPs: rs1205 C, rs2353397 C, rs20541 T, rs2070600 G, rs10947233 G, rs1800629 G, and rs2241712 A. After Bonferroni correction, rs2353397 C was most strongly associated with susceptibility to COPD. Haplotype analysis showed that the frequencies of the GC, GT haplotypes of rs2241718 (TGF-β1 gene), and rs6957 (CDC97 gene) were significantly higher in the control group than in the COPD case group (p=1.88×10^-9); the frequencies of the TT haplotype of rs1205 and rs2808630 (CRP gene) were significantly higher in the control group (p=0.0377).

Conclusion

Our study suggests some genetic variants associated with the susceptibility of COPD in the Chinese Han population.

Emerging genetics of COPD

Since the discovery of alpha-1 antitrypsin in the early 1960s, several new genes have been suggested to play a role in chronic obstructive pulmonary disease (COPD) pathogenesis. Yet, in spite of those advances, much about the genetic basis of COPD still remains to be discovered. Unbiased approaches, such as genome-wide association (GWA) studies, are critical to identify genes and pathways and to verify suggested genetic variants. Indeed, most of our current understanding about COPD candidate genes originates from GWA studies. Experiments in form of cross-study replications and advanced meta-analyses have propelled the field towards unravelling details about COPD's pathogenesis. Here, we review the discovery of genetic variants in association with COPD phenotypes by discussing the available approaches and current findings. Limitations of current studies are considered and future directions provided.

CFTR regulates early pathogenesis of chronic obstructive lung disease in βENaC-overexpressing mice

Background

Factors determining the onset and severity of chronic obstructive pulmonary disease remain poorly understood. Previous studies demonstrated that airway surface dehydration in βENaC-overexpressing (βENaC-Tg) mice on a mixed genetic background caused either neonatal mortality or chronic obstructive lung disease suggesting that the onset of lung disease was modulated by the genetic background.

Methods

To test this hypothesis, we backcrossed βENaC-Tg mice onto two inbred strains (C57BL/6 and BALB/c) and studied effects of the genetic background on neonatal mortality, airway ion transport and airway morphology. Further, we crossed βENaC-Tg mice with CFTR-deficient mice to validate the role of CFTR in early lung disease.

Results

We demonstrate that the C57BL/6 background conferred increased CFTR-mediated Cl⁻ secretion, which was associated with decreased mucus plugging and mortality in neonatal βENaC-Tg C57BL/6 compared to βENaC-Tg BALB/c mice. Conversely, genetic deletion of CFTR increased early mucus obstruction and mortality in βENaC-Tg mice.

Conclusions

We conclude that a decrease or absence of CFTR function in airway epithelia aggravates the severity of early airway mucus obstruction and related mortality in βENaC-Tg mice. These results suggest that genetic or environmental factors that reduce CFTR activity may contribute to the onset and severity of chronic obstructive pulmonary disease and that CFTR may serve as a novel therapeutic target.

Role of GSTM1 in resistance to lung inflammation

Lung inflammation resulting from oxidant/antioxidant imbalance is a common feature of many lung diseases. In particular, the role of enzymes regulated by the NF-E2-related factor 2 transcription factor has recently received increased attention. Among these antioxidant genes, glutathione S-transferase Mu 1 (GSTM1) has been most extensively characterized because it has a null polymorphism that is highly prevalent in the population and associated with increased risk of inflammatory lung diseases. Present evidence suggests that GSTM1 acts through interactions with other genes and environmental factors, especially air pollutants. Here, we review GSTM1 gene expression and regulation and summarize the findings from epidemiological, clinical, animal, and in vitro studies on the role played by GSTM1 in lung inflammation. We discuss limitations in the existing knowledge base and future perspectives and evaluate the potential of pharmacologic and genetic manipulation of the GSTM1 gene to modulate pulmonary inflammatory responses.

Role of mtDNA haplogroups in COPD susceptibility in a southwestern Han Chinese population

The interplay of a complex genetic basis with the environmental factors of chronic obstructive pulmonary disease (COPD) may account for the differences in individual susceptibility to COPD. Mitochondrial DNA (mtDNA) contributes to an individual's ability to resist oxidation, an important determinant that affects COPD susceptibility. To investigate whether mtDNA haplogroups play important roles in COPD susceptibility, the frequencies of mtDNA haplogroups and an 822-bp mtDNA deletion in 671 COPD patients and 724 control individuals from southwestern China were compared. Multivariate logistic regression analysis revealed that, whereas mtDNA haplogroups A and M7 might be associated with an increased risk for COPD (OR=1.996, 95% CI=1.149-2.831, p=0.006, and OR=1.754, 95% CI=1.931-2.552, p=0.021, respectively), haplogroups F, D, and M9 might be associated with a decreased risk for COPD in this population (OR=0.554, 95% CI=0.390-0.787, p=0.001; OR=0.758, 95% CI=0.407-0.965, p=0.002; and OR=0.186, 95% CI=0.039-0.881, p=0.034, respectively). Additionally, the increased frequency of the 822-bp mtDNA deletion in male cigarette-smoking subjects among COPD patients and controls of haplogroup D indicated that haplogroup D might increase an individual's susceptibility to DNA damage from external reactive oxygen species derived from heavy cigarette smoking. We conclude that haplogroups A and M7 might be risk factors for COPD, whereas haplogroups D, F, and M9 might decrease the COPD risk in this Han Chinese population.

Single-nucleotide polymorphisms in the TSPYL-4 and NT5DC1 genes are associated with susceptibility to chronic obstructive pulmonary disease

The risk of developing chronic obstructive pulmonary disease (COPD) is partially determined by genetic and environmental factors. Many published candidate gene studies show conflicting results due to ethnic differences and sample sizes. The number of these studies carried out in Chinese populations is small. To investigate candidate genes and haplotypes for susceptibility to COPD in a southern Han Chinese population, we performed genotyping of DNA samples in 200 COPD patients and 250 control subjects by analyzing 54 single-nucleotide polymorphisms (SNPs) in 23 genes associated with the development of COPD and/or pulmonary function identified by genome-wide association studies (GWAS). We also performed linkage disequilibrium (LD) and haplotype analysis according to the results of genotyping. The frequencies of the SNP [rs3749893 of testis‑specific protein Y-encoded-like 4 (TSPYL-4) gene] G allele and SNP [rs1052443 of 5'-nucleotidase domain containing 1 (NT5DC1) gene] A allele were significantly higher in the cases studied compared to the control subjects (P=0.032, P<0.05, OR=0.692, 95% CI 0.495‑0.970; P=0.0205, P<0.05, OR=0.670, 95% CI 0.477-0.941, respectively). Results showed that two blocks of SNPs (rs1052443 and rs3749893; rs11155242 and rs6937121) had sufficient precision to allow construction of a haplotype block. We constructed the TSPYL-4 and NT5DC1 haplotypes of the cases and controls, but no significant difference between the two groups was found. rs3749893 A allele of TSPYL-4 and rs1052443 C allele of NT5DC1 were associated with a protective effect against the deterioration of pulmonary function. In conclusion, TSPYL-4 and NT5DC1 gene polymorphisms are associated with susceptibility to COPD and pulmonary function.

Association of TNF-α -308G/A, SP-B 1580 C/T, IL-13 -1055 C/T gene polymorphisms and latent adenoviral infection with chronic obstructive pulmonary disease in an Egyptian population

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a leading cause of disability and death. The most common cause of COPD is smoking. There is evidence suggesting that genetic factors influence COPD susceptibility and variants in several candidate genes have been significantly associated with COPD. In this study, we aimed to investigate the possible association of the TNF-α -308, SPB+1580, IL-13 -1055 gene polymorphisms and latent adenovirus C infection with COPD in an Egyptian population.

MATERIAL AND METHODS

Our study included 115 subjects (75 smokers with COPD, 25 resistant smokers and 15 non-smokers) who were subjected to spirometric measurements, identification of adenovirus C and genotyping of TNF-α -308G/A, SP-B+1580 C/T and IL-13 -1055 C/T polymorphisms by real-time PCR.

RESULTS

The adenovirus C gene was identified in all subjects. The distribution of TNF-α genotypes showed no significant differences between different groups. However, homozygous A genotype was associated with a significant decrease in FEV(1), FEV(1)/FVC and FEF25/75% of predicted in COPD (p < 0.05). As regards SP-B genotypes, resistant smokers had a significantly higher homozygous T genotype frequency compared to COPD and non smokers (p = 0.005). Interleukin 13 genotypes showed no significant difference between different groups. There was a significant decrease in FEF25/75% of predicted in T allele carriers in COPD patients (p = 0.001).

CONCLUSIONS

The COPD is a disease caused by the interaction of combined genes and environmental influences, in the presence of smoking and latent adenovirus C infection, TNF-α -308A, SPB +1580 T and IL-13 -1055 T polymorphisms predispose to the development of COPD.

Gene-environment interaction testing in family-based association studies with phenotypically ascertained samples: a causal inference approach

We propose a method for testing gene-environment (G × E) interactions on a complex trait in family-based studies in which a phenotypic ascertainment criterion has been imposed. This novel approach employs G-estimation, a semiparametric estimation technique from the causal inference literature, to avoid modeling of the association between the environmental exposure and the phenotype, to gain robustness against unmeasured confounding due to population substructure, and to acknowledge the ascertainment conditions. The proposed test allows for incomplete parental genotypes. It is compared by simulation studies to an analogous conditional likelihood-based approach and to the QBAT-I test, which also invokes the G-estimation principle but ignores ascertainment. We apply our approach to a study of chronic obstructive pulmonary disorder.

Effect of heme oxygenase-1 polymorphisms on lung function and gene expression

Background

Oxidative stress induced by smoking is considered to be important in the pathogenesis of Chronic Obstructive Pulmonary Disease (COPD). Heme oxygenase-1 (HMOX1) is an essential enzyme in heme catabolism that is induced by oxidative stress and may play a protective role as an antioxidant in the lung. We determined whether HMOX1 polymorphisms were associated with lung function in COPD patients and whether the variants had functional effects.

Methods

We genotyped five single nucleotide polymorphisms (SNPs) in the HMOX1 gene in Caucasians who had the fastest (n = 278) and the slowest (n = 304) decline of FEV₁ % predicted, selected from smokers in the NHLBI Lung Health Study. These SNPs were also studied in Caucasians with the lowest (n = 535) or the highest (n = 533) baseline lung function. Reporter genes were constructed containing three HMOX1 promoter polymorphisms and the effect of these polymorphisms on H₂O₂ and hemin-stimulated gene expression was determined. The effect of the HMOX1 rs2071749 SNP on gene expression in alveolar macrophages was investigated.

Results

We found a nominal association (p = 0.015) between one intronic HMOX1 SNP (rs2071749) and lung function decline but this did not survive correction for multiple comparisons. This SNP was in perfect linkage disequilibrium with rs3761439, located in the promoter of HMOX1. We tested rs3761439 and two other putatively functional polymorphisms (rs2071746 and the (GT)_n polymorphism) in reporter gene assays but no significant effects on gene expression were found. There was also no effect of rs2071749 on HMOX1 gene expression in alveolar macrophages.

Conclusions

We found no association of the five HMOX1 tag SNPs with lung function decline and no evidence that the three promoter polymorphisms affected the regulation of the HMOX1 gene.

Improving the differential diagnosis of chronic obstructive pulmonary disease in primary care

Chronic obstructive pulmonary disease (COPD) and asthma represent a substantial portion of primary care practice. In adults, differentiating asthma from COPD can be difficult but is important because of the marked differences in treatment, disease progression, and outcomes between the 2 conditions. Currently, clinical COPD is often misdiagnosed or undiagnosed until late in the disease. Earlier diagnosis could markedly reduce morbidity and improve quality of life. Establishing a diagnosis of COPD requires spirometry testing, interpreted in the context of the patient's symptoms, smoking status, age, and comorbidities. Additional tests and tools may be helpful in the differential diagnosis, including questionnaires specifically developed to discriminate between COPD and asthma and, in special cases, imaging studies. Follow-up and monitoring of asthma and COPD are always necessary and provide additional benefit in patients in whom only continued care and reassessment can confirm the final diagnosis, such as younger individuals with fixed airway obstruction, smokers with asthma, and patients with both disorders. Key areas for improvement include enhanced case identification, improved quality and interpretation of findings on spirometry, and increased use of tools such as differential diagnosis questionnaires and algorithms to guide the diagnostic and monitoring process. To achieve optimal outcomes, the primary care team should make every effort to establish a firm diagnosis. For this review, we conducted a PubMed search with no time limits using the Medical Subject Headings chronic obstructive pulmonary disease or COPD and asthma, in association with the following search terms: diagnosis, differential diagnosis, mixed or comorbid disease, diagnostic techniques, spirometry, questionnaires, and primary care.

An official American Thoracic Society public policy statement: Novel risk factors and the global burden of chronic obstructive pulmonary disease

RATIONALE

Although cigarette smoking is the most important cause of chronic obstructive pulmonary disease (COPD), a substantial proportion of COPD cases cannot be explained by smoking alone.

OBJECTIVES

To evaluate the risk factors for COPD besides personal cigarette smoking.

METHODS

We constituted an ad hoc subcommittee of the American Thoracic Society Environmental and Occupational Health Assembly. An international group of members was invited, based on their scientific expertise in a specific risk factor for COPD. For each risk factor area, the committee reviewed the literature, summarized the evidence, and developed conclusions about the likelihood of it causing COPD. All conclusions were based on unanimous consensus.

MEASUREMENTS AND MAIN RESULTS

The population-attributable fraction for smoking as a cause of COPD ranged from 9.7 to 97.9%, but was less than 80% in most studies, indicating a substantial burden of disease attributable to nonsmoking risk factors. On the basis of our review, we concluded that specific genetic syndromes and occupational exposures were causally related to the development of COPD. Traffic and other outdoor pollution, secondhand smoke, biomass smoke, and dietary factors are associated with COPD, but sufficient criteria for causation were not met. Chronic asthma and tuberculosis are associated with irreversible loss of lung function, but there remains uncertainty about whether there are important phenotypic differences compared with COPD as it is typically encountered in clinical settings.

CONCLUSIONS

In public health terms, a substantive burden of COPD is attributable to risk factors other than smoking. To prevent COPD-related disability and mortality, efforts must focus on prevention and cessation of exposure to smoking and these other, less well-recognized risk factors.

Genetics of chronic obstructive pulmonary disease: a case-control study in Bergen, Norway

AIMS

Chronic obstructive pulmonary disease (COPD) is a complex disease influenced by multiple genetic and environmental factors. This short communication gives a description of the preliminary genetic results from a case-control study in Bergen, Norway.

METHODS

A large case-control study in Bergen in 2003-2005 with 6365 invited subjects generated 1954 cases or controls. The overall attendance of invited subjects was 60%, but causes of non-attendance varied considerably among different sources of recruitment.

RESULTS

In this case-control study, the candidate gene SERPINE2 on chromosome 2q has demonstrated significant association to COPD. However, only weak or lacking associations have so far been observed for the other candidate genes examined.

CONCLUSION

These findings provide support for SERPINE2 as a COPD susceptibility gene in the Norwegian population.

COPD and the risk of tuberculosis--a population-based cohort study

Background

Both chronic obstructive pulmonary disease (COPD) and tuberculosis (TB) primarily affect the lungs and are major causes of morbidity and mortality worldwide. COPD and TB have common risk factors such as smoking, low socioeconomic status and dysregulation of host defence functions. COPD is a prevalent co-morbid condition, especially in elderly with TB but in contrast to other diseases known to increase the risk of TB, relatively little is known about the specific relationship and impact from COPD on TB-incidence and mortality.

Methods and Findings

All individuals ≥40 years of age, discharged with a diagnosis of COPD from Swedish hospitals 1987–2003 were identified in the Swedish Inpatient Register (n = 115,867). Records were linked to the Swedish Tuberculosis Register 1989–2007 and the relative risk of active TB in patients with COPD compared to control subjects randomly selected from the general population (matched for sex, year of birth and county of residence) was estimated using Cox regression. The analyses were stratified by year of birth, sex and county of residence and adjusted for immigration status, socioeconomic status (SES) and inpatient co-morbidities previously known to increase the risk of TB. COPD patients had a three-fold increased hazard ratio (HR) of developing active TB (HR 3.0 (95% confidence interval 2.4 to 4.0)) that was mainly dependent on an increased risk of pulmonary TB. In addition, logistic regression estimates showed that COPD patients who developed active TB had a two-fold increased risk of death from all causes within first year after the TB diagnosis compared to the general population control subjects with TB (OR 2.2, 95% confidence interval 1.2 to 4.1).

Conclusions

This population-based study comprised of a large number of COPD patients shows that these patients have an increased risk of developing active TB compared to the general population. The results raise concerns that the increasing global burden of COPD will increase the incidence of active TB. The underlying contributory factors need to be disentangled in further studies.

Cluster analysis in severe emphysema subjects using phenotype and genotype data: an exploratory investigation

Background

Numerous studies have demonstrated associations between genetic markers and COPD, but results have been inconsistent. One reason may be heterogeneity in disease definition. Unsupervised learning approaches may assist in understanding disease heterogeneity.

Methods

We selected 31 phenotypic variables and 12 SNPs from five candidate genes in 308 subjects in the National Emphysema Treatment Trial (NETT) Genetics Ancillary Study cohort. We used factor analysis to select a subset of phenotypic variables, and then used cluster analysis to identify subtypes of severe emphysema. We examined the phenotypic and genotypic characteristics of each cluster.

Results

We identified six factors accounting for 75% of the shared variability among our initial phenotypic variables. We selected four phenotypic variables from these factors for cluster analysis: 1) post-bronchodilator FEV₁ percent predicted, 2) percent bronchodilator responsiveness, and quantitative CT measurements of 3) apical emphysema and 4) airway wall thickness. K-means cluster analysis revealed four clusters, though separation between clusters was modest: 1) emphysema predominant, 2) bronchodilator responsive, with higher FEV₁; 3) discordant, with a lower FEV₁ despite less severe emphysema and lower airway wall thickness, and 4) airway predominant. Of the genotypes examined, membership in cluster 1 (emphysema-predominant) was associated with TGFB1 SNP rs1800470.

Conclusions

Cluster analysis may identify meaningful disease subtypes and/or groups of related phenotypic variables even in a highly selected group of severe emphysema subjects, and may be useful for genetic association studies.

Variants in FAM13A are associated with chronic obstructive pulmonary disease

Substantial evidence suggests that there is genetic susceptibility to chronic obstructive pulmonary disease (COPD). To identify common genetic risk variants, we performed a genome-wide association study in 2940 cases and 1380 smoking controls with normal lung function. We demonstrate a novel susceptibility locus at 4q22.1 in FAM13A (rs7671167, OR=0.76, P=8.6×10⁻⁸) and provide evidence of replication in one case-control and two family-based cohorts (for all studies, combined P=1.2×10⁻¹¹).

Level and course of FEV1 in relation to polymorphisms in NFE2L2 and KEAP1 in the general population

Background

The metabolism of xenobiotics plays an essential role in smoking related lung function loss and development of Chronic Obstructive Pulmonary Disease. Nuclear Factor Erythroid 2-Like 2 (NFE2L2 or NRF2) and its cytosolic repressor Kelch-like ECH-associated protein-1 (KEAP1) regulate transcription of enzymes involved in cellular detoxification processes and Nfe2l2-deficient mice develop tobacco-induced emphysema. We assessed the impact of Single Nucleotide Polymorphisms (SNPs) in both genes on the level and longitudinal course of Forced Expiratory Volume in 1 second (FEV₁) in the general population.

Methods

Five NFE2L2 and three KEAP1 tagging SNPs were genotyped in the population-based Doetinchem cohort (n = 1,152) and the independent Vlagtwedde-Vlaardingen cohort (n = 1,390). On average 3 FEV₁ measurements during 3 surveys, respectively 7 FEV₁ measurements during 8 surveys were present. Linear Mixed Effect models were used to test cross-sectional and longitudinal genetic effects on repeated FEV₁ measurements.

Results

In the Vlagtwedde-Vlaardingen cohort SNP rs11085735 in KEAP1 was associated with a higher FEV₁ level (p = 0.02 for an additive effect), and SNP rs2364723 in NFE2L2 was associated with a lower FEV₁ level (p = 0.06). The associations were even more significant in the pooled cohort analysis. No significant association of KEAP1 or NFE2L2 SNPs with FEV₁ decline was observed.

Conclusion

This is the first genetic study on variations in key antioxidant transcriptional regulators KEAP1 and NFE2L2 and lung function in a general population. It identified 2 SNPs in NFE2L2 and KEAP1 which affect the level of FEV₁ in the general population. It additionally shows that NFE2L2 and KEAP1 variations are unlikely to play a role in the longitudinal course of FEV₁ in the general population.

Markers of early disease and prognosis in COPD

COPD is a complex disease with multiple pathological components, which we unfortunately tend to ignore when spirometry is used as the only method to evaluate the disorder. Additional measures are needed to allow a more complete and clinically relevant assessment of COPD. The earliest potential risk factors of disease in COPD are variations in the genetic background. Genetic variations are present from conception and can determine lifelong changes in enzyme activities and protein concentrations. In contrast, measurements in blood, sputum, exhaled breath, broncho-alveolar lavage, and lung biopsies may vary substantially over time. This review explores potential markers of early disease and prognosis in COPD by examining genetic markers in the α₁-antitrypsin, cystic fibrosis transmembrane conductance regulator (CFTR), and MBL-2 genes, and by examining the biochemical markers fibrinogen and C-reactive protein (CRP), which correlate with degree of pulmonary inflammation during stable conditions of COPD. Chronic lung inflammation appears to contribute to the pathogenesis of COPD, and markers of this process have promising predictive value in COPD. To implement markers for COPD in clinical practice, besides those already established for the α₁-antitrypsin gene, further research and validation studies are needed.

[Phenotypic heterogeneity of chronic obstructive pulmonary disease]

A functional definition of chronic obstructive pulmonary disease (COPD) based on airflow limitation has largely dominated the field. However, a view has emerged that COPD involves a complex array of cellular, organic, functional, and clinical events, with a growing interest in disentangling the phenotypic heterogeneity of COPD. The present review is based on the opinion of the authors, who have extensive research experience in several aspects of COPD. The starting assumption of the review is that current knowledge on the pathophysiology and clinical features of COPD allows us to classify phenotypic information in terms of the following dimensions: respiratory symptoms and health status, acute exacerbations, lung function, structural changes, local and systemic inflammation, and systemic effects. Twenty-six phenotypic traits were identified and assigned to one of the 6 dimensions. For each dimension, a summary is provided of the best evidence on the relationships among phenotypic traits, in particular among those corresponding to different dimensions, and on the relationship between these traits and relevant events in the natural history of COPD. The information has been organized graphically into a phenotypic matrix where each cell representing a pair of phenotypic traits is linked to relevant references. The information provided has the potential to increase our understanding of the heterogeneity of COPD phenotypes and help us plan future studies on aspects that are as yet unexplored.

Natural histories of chronic obstructive pulmonary disease

Concepts relating to the natural history of chronic obstructive pulmonary disease (COPD) arise most importantly from the classic study of Fletcher and colleagues (The Natural History of Chronic Bronchitis and Emphysema, Oxford University Press, New York, 1976). This study, which evaluated working English men over 8 years, was used to construct a proposed life-long natural history. Although this is a classic study that has greatly advanced understanding of COPD, it has a number of limitations. Its duration is relatively short compared with the duration of COPD, so it is more cross-sectional than longitudinal. It was unable to distinguish among varied "natural histories." It assessed primarily the FEV(1), and the natural history of other features of COPD is largely undescribed. With advances in understanding the clinical features of COPD and with the development of evaluating new tools to assess patients with COPD, longitudinal studies evaluating COPD in novel ways and for longer durations are needed.

Gene-environment interactions in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death throughout the world and is largely associated with cigarette smoking. Despite the appreciation of the central role of smoking in the development of COPD, only a relatively small number of smokers (15%–20%) develop COPD. Recent studies depicting familial aggregation suggest that some subjects may have a genetic predisposition to developing COPD. In this respect, a number of single nucleotide polymorphisms have been reported in association with different COPD features (subphenotypes), although much of this data remains controversial. Classical genetic studies (including twin and family studies) assume an “equal-environment” scenario, but as gene-environment interactions occur in COPD, this assumption needs revision. Thus, new integrated models are needed to examine the major environmental factors associated with COPD which include smoking as well as air pollution, and respiratory infections, and not only genetic predisposition. Revisiting this area, may help answer the question of what has more bearing in the pathogenesis of COPD—the environment or the genomic sequence of the affected subjects. It is anticipated that an improved understanding of this interaction will both enable improved identification of individuals susceptible to developing this disease, as well as improved future treatments for this disease.

C-reactive protein levels, haplotypes, and the risk of incident chronic obstructive pulmonary disease

RATIONALE

Chronic obstructive pulmonary disease (COPD) is characterized by substantial chronic inflammation in the pulmonary compartment as well as in the systemic circulation.

OBJECTIVES

To investigate potentially causal association, we examined whether serum levels of high-sensitivity C-reactive protein (hsCRP) and variations in the CRP gene are associated with the risk of developing COPD.

METHODS

This study is part of the Rotterdam Study, a prospective population-based cohort study among subjects aged 55 years or older. At baseline, 6,836 subjects without COPD had a blood sample available for assessment of hsCRP serum levels and haplotypes of the CRP gene. We analyzed the association between hsCRP levels, CRP gene haplotypes, and incident COPD with Cox proportional hazard models, adjusted for age, sex, and other confounders.

MEASUREMENTS AND MAIN RESULTS

High levels of hsCRP (>3 mg/L) were associated with a significantly increased risk of incident COPD (hazard ratio [HR], 1.7; 95% confidence interval [CI], 1.16-2.49) compared with persons with low levels (<1 mg/L). The risk remained increased after adjusting for potential confounders and introducing a latency period of 3 years. The risk was most pronounced in former smokers (HR, 2.2; 95% CI, 1.12-3.74). hsCRP was not a risk factor in never smokers. No CRP single nucleotide polymorphism or haplotype was associated with a significantly increased or decreased COPD risk.

CONCLUSIONS

Increased hsCRP levels are predictive for the occurrence of COPD in smokers. However, haplotypes of the CRP gene, which influence hsCRP levels, are not associated with an altered risk of developing COPD.

Analysis of exonic elastin variants in severe, early-onset chronic obstructive pulmonary disease

The destruction of elastic fibers has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Emphysema has been described in autosomal dominant cutis laxa, which can be caused by mutations in the elastin gene. Previously, a rare functional mutation in the terminal exon of elastin was found in a case of severe, early-onset COPD. To test the hypothesis that other similar elastin mutations may predispose to COPD, we screened 90 probands from the Boston Early-Onset COPD Study and 90 smoking control subjects from the Normative Aging Study for mutations in elastin exons using high-resolution DNA melt analysis followed by resequencing. Rare nonsynonymous single-nucleotide polymorphisms (SNPs) seen only in cases were examined for segregation with airflow obstruction within pedigrees. Common nonsynonymous SNPs were tested for association with COPD in a family-based analysis of 949 subjects from the Boston Early-Onset COPD Study, and in a case-control analysis in 389 COPD cases from the National Emphysema Treatment Trial and 472 control subjects from the Normative Aging Study. Of 28 elastin variants found, 3 were nonsynonymous SNPs found only in cases. The previously described Gly773Asp mutation was found in another proband. The other two SNPs did not clearly segregate with COPD within families. Two common nonsynonymous SNPs did not demonstrate significant associations in either a family-based or case-control analysis. Exonic SNPs in the elastin gene do not appear to be common risk factors for severe COPD.

Genetic associations with hypoxemia and pulmonary arterial pressure in COPD

BACKGROUND

Hypoxemia, hypercarbia, and pulmonary arterial hypertension are known complications of advanced COPD. We sought to identify genetic polymorphisms associated with these traits in a population of patients with severe COPD from the National Emphysema Treatment Trial (NETT).

METHODS

In 389 participants from the NETT Genetics Ancillary Study, single-nucleotide polymorphisms (SNPs) were genotyped in five candidate genes previously associated with COPD susceptibility (EPHX1, SERPINE2, SFTPB, TGFB1, and GSTP1). Linear regression models were used to test for associations among these SNPs and three quantitative COPD-related traits (Pao(2), Paco(2), and pulmonary artery systolic pressure). Genes associated with hypoxemia were tested for replication in probands from the Boston Early-Onset COPD Study.

RESULTS

In the NETT Genetics Ancillary Study population, SNPs in microsomal epoxide hydrolase (EPHX1) [p = 0.01 to 0.04] and serpin peptidase inhibitor, clade E, member 2 (SERPINE2) [p = 0.04 to 0.008] were associated with hypoxemia. One SNP within surfactant protein B (SFTPB) was associated with pulmonary artery systolic pressure (p = 0.01). In probands from the Boston Early-Onset COPD Study, SNPs in EPHX1 and in SERPINE2 were associated with the requirement for supplemental oxygen.

CONCLUSIONS

In participants with severe COPD, SNPs in EPHX1 and SERPINE2 were associated with hypoxemia in two separate study populations, and SNPs from SFTPB were associated with pulmonary artery pressure in the NETT participants.

Molecular biomarkers for quantitative and discrete COPD phenotypes

Chronic obstructive pulmonary disease (COPD) is an inflammatory lung disorder with complex pathological features and largely unknown etiology. The identification of biomarkers for this disease could aid the development of methods to facilitate earlier diagnosis, the classification of disease subtypes, and provide a means to define therapeutic response. To identify gene expression biomarkers, we completed expression profiling of RNA derived from the lung tissue of 56 subjects with varying degrees of airflow obstruction using the Affymetrix U133 Plus 2.0 array. We applied multiple, independent analytical methods to define biomarkers for either discrete or quantitative disease phenotypes. Analysis of differential expression between cases (n = 15) and controls (n = 18) identified a set of 65 discrete biomarkers. Correlation of gene expression with quantitative measures of airflow obstruction (FEV(1)%predicted or FEV(1)/FVC) identified a set of 220 biomarkers. Biomarker genes were enriched in functions related to DNA binding and regulation of transcription. We used this group of biomarkers to predict disease in an unrelated data set, generated from patients with severe emphysema, with 97% accuracy. Our data contribute to the understanding of gene expression changes occurring in the lung tissue of patients with obstructive lung disease and provide additional insight into potential mechanisms involved in the disease process. Furthermore, we present the first gene expression biomarker for COPD validated in an independent data set.

Glutathione S-transferase and microsomal epoxide hydrolase gene polymorphisms and risk of chronic obstructive pulmonary disease in Slovak population

AIM

To determine the risk of chronic obstructive pulmonary disease (COPD) associated with polymorphisms in the glutathione S-transferase (GST) M1, GST T1, and microsomal epoxide hydrolase (EPHX1) genes in a cohort of Slovak population.

METHODS

Two hundred and seventeen patients with the diagnosis of COPD and 160 control subjects were enrolled in the study. Blood samples were collected from all subjects and the DNA from peripheral blood lymphocytes was used for subsequent genotyping assays, using polymerase chain reaction and restriction fragment-length polymorphism methods.

RESULTS

In an unadjusted model, an increased risk for COPD was observed in subjects with EPHX1 His113-His113 genotype (odds ratio [OR], 2.32; 95% confidence interval [CI], 1.20-4.69; P=0.008), compared with the carriers of the Tyr113 allele. However, after the adjustments for age, sex, and smoking status, the risk was not significant (adjusted OR, 1.79; 95% CI, 0.91-3.53; P=0.093). In a combined analysis of gene polymorphisms, the genotype combination EPHX1 His113-His113/GSTM1 null significantly increased the risk of COPD in both, unadjusted (OR, 5.08; 95% CI, 1.70-20.43; P=0.001) and adjusted model (OR, 4.87; 95% CI, 1.57-15.13; P=0.006).

CONCLUSION

Although none of the tested gene polymorphisms was significantly related to an increased risk of COPD alone, our results suggest that the homozygous exon 3 mutant variant of EPHX1 gene in the combination with GSTM1 null genotype is a significant predictor of increased susceptibility to COPD in the Slovak population. The findings of the present study emphasize the importance of detoxifying and antioxidant pathways in the pathogenesis of COPD.

Variability in small airway epithelial gene expression among normal smokers

BACKGROUND

Despite overwhelming data that cigarette smoking causes COPD, only a minority of long-term smokers are affected, strongly suggesting that genetic factors modify susceptibility to this disease. We hypothesized that individual variations exist in the response to cigarette smoking, with variability among smokers in expression levels of protective/susceptibility genes.

METHODS

Affymetrix arrays and quantitative polymerase chain reaction were used to assess the variability of gene expression in the small airway epithelium obtained by fiberoptic bronchoscopy of 18 normal nonsmokers, 18 normal smokers, and 18 smokers with COPD.

RESULTS

We identified 201 probe sets representing 152 smoking-responsive genes that were significantly up-regulated or down-regulated, and assessed the coefficient of variation in expression levels among the study population. Variation was a reproducible property of each gene as assessed by different microarray probe sets and real-time polymerase chain reaction, and was observed in both normal smokers and smokers with COPD. Greater individual variability was found in smokers with COPD than in normal smokers. The majority of these highly variable smoking-responsive genes were in the functional categories of signal transduction, xenobiotic degradation, metabolism, transport, oxidant related, and transcription. A similar pattern of the same highly variable genes was observed in an independent data set.

CONCLUSIONS

We propose that genetic diversity is likely within this subset of genes, with highly variable individual-to-individual responses of the small airway epithelium to smoking, and that this subset of genes represents putative candidates for assessment of susceptibility/protection from disease in future gene-based epidemiologic studies of smokers' risk for COPD.

Increased risk of both ulcerative colitis and Crohn's disease in a population suffering from COPD

Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation of the airways. In the majority of cases, the inflammation is triggered by tobacco smoke. Smoking also affects the pathogenesis of inflammatory bowel disease (IBD), protecting against ulcerative colitis (UC) and promoting development of Crohn's disease (CD). The present study was undertaken to investigate occurrence of IBD among COPD patients, indicating common inflammatory pathways and shared vulnerability on a genetic basis. The study was designed as a population-based cohort study. All individuals discharged with a diagnosis of COPD from 1987 to 2002 were identified in the Swedish Inpatient Register (n=180,239). Controls and first-degree relatives of both cases and controls were identified using the Multi-Generation Register. Finally, all individuals (n=1,174,557) were compared with the Inpatient Register, identifying discharges with a diagnosis of UC or CD. Hazard ratios (HR) for IBD were determined by Cox proportional hazards regression analysis. COPD patients had a significantly higher risk of both UC (HR 1.83; 95% CI 1.61-2.09) and CD (HR 2.72; 95% CI 2.33-3.18). Among first-degree relatives of COPD patients, there was also an overall increased risk of CD (HR 1.25; 95% CI 1.09-1.43) but not of UC (HR 1.09; 95% CI 0.96-1.23). The kinship of first-degree relatives displayed an increased risk of both UC and CD among siblings (HR 1.49; 95% CI 1.15-1.91 and HR 1.46; 95% CI 1.12-1.89, respectively). The results suggest that COPD and IBD may have inflammatory pathways in common, including genetic variants of genes predisposing for disease.