Rationale: A genome-wide association study (GWAS) for circulating chronic obstructive pulmonary disease (COPD) biomarkers could identify genetic determinants of biomarker levels and COPD susceptibility.
Objectives: To identify genetic variants of circulating protein biomarkers and novel genetic determinants of COPD.
Methods: GWAS was performed for two pneumoproteins, Clara cell secretory protein (CC16) and surfactant protein D (SP-D), and five systemic inflammatory markers (C-reactive protein, fibrinogen, IL-6, IL-8, and tumor necrosis factor-α) in 1,951 subjects with COPD. For genome-wide significant single nucleotide polymorphisms (SNPs) (P < 1 × 10−8), association with COPD susceptibility was tested in 2,939 cases with COPD and 1,380 smoking control subjects. The association of candidate SNPs with mRNA expression in induced sputum was also elucidated.
Measurements and Main Results: Genome-wide significant susceptibility loci affecting biomarker levels were found only for the two pneumoproteins. Two discrete loci affecting CC16, one region near the CC16 coding gene (SCGB1A1) on chromosome 11 and another locus approximately 25 Mb away from SCGB1A1, were identified, whereas multiple SNPs on chromosomes 6 and 16, in addition to SNPs near SFTPD, had genome-wide significant associations with SP-D levels. Several SNPs affecting circulating CC16 levels were significantly associated with sputum mRNA expression of SCGB1A1 (P = 0.009–0.03). Several SNPs highly associated with CC16 or SP-D levels were nominally associated with COPD in a collaborative GWAS (P = 0.001–0.049), although these COPD associations were not replicated in two additional cohorts.
Conclusions: Distant genetic loci and biomarker-coding genes affect circulating levels of COPD-related pneumoproteins. A subset of these protein quantitative trait loci may influence their gene expression in the lung and/or COPD susceptibility.
Clinical trial registered with www.clinicaltrials.gov (NCT 00292552).
biomarker; chronic obstructive pulmonary disease; genome-wide association study
Rationale: Systemic glucocorticoids are used therapeutically to treat a variety of medical conditions. Epigenetic processes such as DNA methylation may reflect exposure to glucocorticoids and may be involved in mediating the responses and side effects associated with these medications.
Objectives: To test the hypothesis that differences in DNA methylation are associated with current systemic steroid use.
Methods: We obtained DNA methylation data at 27,578 CpG sites in 14,475 genes throughout the genome in two large, independent cohorts: the International COPD Genetics Network (ndiscovery = 1,085) and the Boston Early Onset COPD study (nreplication = 369). Sites were tested for association with current systemic steroid use using generalized linear mixed models.
Measurements and Main Results: A total of 511 sites demonstrated significant differential methylation by systemic corticosteroid use in all three of our primary models. Pyrosequencing validation confirmed robust differential methylation at CpG sites annotated to genes such as SLC22A18, LRP3, HIPK3, SCNN1A, FXYD1, IRF7, AZU1, SIT1, GPR97, ABHD16B, and RABGEF1. Functional annotation clustering demonstrated significant enrichment in intrinsic membrane components, hemostasis and coagulation, cellular ion homeostasis, leukocyte and lymphocyte activation and chemotaxis, protein transport, and responses to nutrients.
Conclusions: Our analyses suggest that systemic steroid use is associated with site-specific differential methylation throughout the genome. Differentially methylated CpG sites were found in biologically plausible and previously unsuspected pathways; these genes and pathways may be relevant in the development of novel targeted therapies.
DNA methylation; glucocorticoids; chronic obstructive pulmonary disease
In the current study, we investigated the effect of a long-acting β-agonist (salmeterol) and a phosphodiesterase 4 (PDE4) inhibitor (cilomilast) on human lung fibroblast-mediated collagen gel contraction. Higher concentrations of salmeterol (10−7 and 10−6 M) inhibited fibroblast-mediated collagen gel contraction. No effect was observed with cilomilast alone (up to 10−5 M). In the presence of 10−8 M salmeterol, however, cilomilast could significantly inhibit fibroblast-mediated collagen gel contraction in a concentration-dependent manner (10−7~10−5 M). Blockade of endogenous PGE2 by indomethacin further potentiated the inhibitory effect of salmeterol on fibroblast-mediated collagen gel contraction, but it did not affect cilomilast's effect. Pretreatment with PGE2 abolished the inhibitory effect of salmeterol, but it potentiated the inhibitory effect of cilomilast on fibroblast-mediated collagen gel contraction. Finally, indomethacin slightly inhibited PDE4C expression, while PGE2 stimulated the expression of PDE4A and -4C in human lung fibroblasts. These findings suggest that long-acting β-agonist and PDE4 inhibitor have a synergistic effect in regulating fibroblast tissue repair functions and that PGE2 can modulate the effect of β-agonist and PDE4 inhibitor at least in part through the mechanism of regulating PDE4 expression.
Objective and design
Reduced expression of histone deacetylase 2 (HDAC2) in alveolar macrophages and epithelial cells may account for reduced response of chronic obstructive pulmonary disease (COPD) patients to glucocorticoids. HDAC2 expression and its role in mediating glucocorticoid effects on fibroblast functions, however, has not been fully studied. This study was designed to investigate whether HDAC2 mediates glucocorticoid effects on release of inflammatory cytokines and matrix metalloproteinases (MMPs) from human lung fibroblasts.
Human lung fibroblasts (HFL-1 cells) were stimulated with interleukin (IL)-1 β plus tumor necrosis factor (TNF)-α in the presence or absence of the glucocorticoid budesonide. Cytokines (IL-6 and IL-8) were quantified by enzyme linked immunosorbent assay (ELISA) and MMPs (MMP-1 and MMP-3) by immunoblotting in culture medium. The role of HDAC2 was investigated using a pharmacologic inhibitor as well as a small interfering ribonucleic acid (siRNA) targeting HDAC2.
We have demonstrated that budesonide concentration-dependently (10−10–10−7 M) inhibited IL-6, IL-8, MMP-1, and MMP-3 release by HFL-1 cells in response to IL-1β plus TNF-α. While an HDAC inhibitor significantly blocked the inhibitory effect of budesonide on human bronchial epithelial cells (HBECs) and monocytes (THP-1 cells), it did not block the inhibitory effect of budesonide on release of cytokines and MMPs from HFL-1 cells. Similarly, an HDAC2-siRNA blocked budesonide inhibition of cytokine release in HBECs, but it did not block the inhibitory effect of budesonide on HFL-1 cytokine and MMP release. Furthermore, budesonide significantly blocked release of cytokines and MMPs to a similar degree in normal and COPD lung fibroblasts as well as in HFL-1 cells exposed or not exposed to cigarette smoke extract.
These findings suggest that, in contrast to airway epithelial cells and monocytes/macrophages, HDAC2 is not required for budesonide to inhibit MMP and cytokine release by lung fibroblasts and this inhibitory pathway appears to be intact in cultured fibroblasts from COPD patients. These results also suggest that budesonide has the potential to modulate fibroblast-mediated tissue remodeling following airway inflammation in COPD, which is mediated via an HDAC2 independent pathway.
budesonide; fibroblasts; HDAC2
The impact of cigarette smoking can persist for extended periods following smoking cessation and may involve epigenetic reprogramming. Changes in DNA methylation associated with smoking may help to identify molecular pathways that contribute to the latency between exposure and disease onset. Cross-sectional cohort data from subjects in the International COPD Genetics Network (n = 1085) and the Boston Early-Onset COPD study (n = 369) were analyzed as the discovery and replication cohorts, respectively. Genome-wide methylation data on 27 578 CpG sites in 14 475 genes were obtained on DNA from peripheral blood leukocytes using the Illumina HumanMethylation27K Beadchip in both cohorts. We identified 15 sites significantly associated with current smoking, 2 sites associated with cumulative smoke exposure, and, within the subset of former smokers, 3 sites associated with time since quitting cigarettes. Two loci, factor II receptor-like 3 (F2RL3) and G-protein-coupled receptor 15 (GPR15), were significantly associated in all three analyses and were validated by pyrosequencing. These findings (i) identify a novel locus (GPR15) associated with cigarette smoking and (ii) suggest the existence of dynamic, site-specific methylation changes in response to smoking which may contribute to the extended risks associated with cigarette smoking that persist after cessation.
Alpha-1 antitrypsin (AAT) deficiency and tobacco smoking are confirmed risk factors for Chronic Obstructive Pulmonary Disease. We hypothesized that variable DNA methylation would be associated with smoking and inflammation, as reflected by the level of C-Reactive Protein (CRP) in AAT-deficient subjects. Methylation levels of 1,411 autosomal CpG sites from the Illumina GoldenGate Methylation Cancer Panel I were analyzed in 316 subjects. Associations of five smoking behaviors and CRP levels with individual CpG sites and average methylation levels were assessed using non-parametric testing, linear regression and linear mixed effect models, with and without adjustment for age and gender. Univariate linear regression analysis revealed that methylation levels of 16 CpG sites significantly associated with ever-smoking status. A CpG site in the TGFBI gene was the only site associated with ever-smoking after adjustment for age and gender. No highly significant associations existed between age at smoking initiation, pack-years smoked, duration of smoking, and time since quitting smoking as predictors of individual CpG site methylation levels. However, ever-smoking and younger age at smoking initiation associated with lower methylation level averaged across all sites. DNA methylation at CpG sites in the RUNX3, JAK3 and KRT1 genes associated with CRP levels. The most significantly associated CpG sites with gender and age mapped to the CASP6 and FZD9 genes, respectively. In summary, this study identified multiple potential candidate CpG sites associated with ever-smoking and CRP level in AAT-deficient subjects. Phenotypic variability in Mendelian diseases may be due to epigenetic factors.
68kDa (TGFBI); C-Reactive Protein (CRP); Chronic Obstructive Pulmonary Disease (COPD); Illumina GoldenGate Methylation Cancer Panel I; alpha-1 antitrypsin (AAT) deficiency; beta-induced; methylation; smoking behaviors; transforming growth factor
The balance between production and degradation of extracellular matrix is crucial in maintaining normal tissue structure. This study was designed to investigate the effect of budesonide on fibroblast-mediated tissue repair and remodeling.
Using human fetal lung fibroblasts in a three-dimensional collagen gel culture system, we investigated the effect of budesonide (1-1000 nM) on collagen gel contraction and degradation in the presence or absence of Inflammatory cytokines (interleukin-1β and tumor necrosis factor α; 5 ng/mL each) and, in order to activate latent proteases, serine protease trypsin 0.25 μg/mL. The effects of budesonide on metalloproteinase production and activation were also investigated.
Inflammatory cytokines significantly inhibited collagen gel contraction mediated by lung fibroblasts. Budesonide counteracted the effect of cytokines in a concentration-dependent manner (to 50%, P< 0.01). Budesonide 100 nM almost completely inhibited the release and mRNA expression of metalloproteinase-1, metalloproteinase-3, and metalloproteinase-9 induced by the cytokines (P< 0.05). Exposure to the cytokines plus trypsin increased collagen degradation and conversion of the metalloproteinases to lower molecular weight forms corresponding to their active forms. Budesonide blocked both enhanced collagen degradation (P< 0.01) and suppressed trypsin-mediated conversion of cytokine-induced metalloproteinase-9 and metalloproteinase-3 to lower molecular weight forms. Similar effects were observed with dexamethasone 1 μM, suggesting a class effect.
These findings demonstrate that budesonide directly modulates contraction of collagen gels and can decrease collagen degradation under Inflammatory conditions. The mechanism of this effect is through suppressing gene expression, release, and activation of metalloproteinases. By modulating the release and activity of metalloproteinases, inhaled budesonide may be able to modify airway tissue repair and remodeling.
metalloproteinase; budesonide; tissue remodeling
Rationale: Chronic obstructive pulmonary disease (COPD) is associated with local (lung) and systemic (blood) inflammation and manifestations. DNA methylation is an important regulator of gene transcription, and global and specific gene methylation marks may vary with cigarette smoke exposure.
Objectives: To perform a comprehensive assessment of methylation marks in DNA from subjects well phenotyped for nonneoplastic lung disease.
Methods: We conducted array-based methylation screens, using a test-replication approach, in two family-based cohorts (n = 1,085 and 369 subjects).
Measurements and Main Results: We observed 349 CpG sites significantly associated with the presence and severity of COPD in both cohorts. Seventy percent of the associated CpG sites were outside of CpG islands, with the majority of CpG sites relatively hypomethylated. Gene ontology analysis based on these 349 CpGs (330 genes) suggested the involvement of a number of genes responsible for immune and inflammatory system pathways, responses to stress and external stimuli, as well as wound healing and coagulation cascades. Interestingly, our observations include significant, replicable associations between SERPINA1 hypomethylation and COPD and lower average lung function phenotypes (combined P values: COPD, 1.5 × 10−23; FEV1/FVC, 1.5 × 10−35; FEV1, 2.2 × 10−40).
Conclusions: Genetic and epigenetic pathways may both contribute to COPD. Many of the top associations between COPD and DNA methylation occur in biologically plausible pathways. This large-scale analysis suggests that DNA methylation may be a biomarker of COPD and may highlight new pathways of COPD pathogenesis.
chronic obstructive pulmonary disease; epigenetics; DNA methylation; smoking
The genetic risk factors for chronic obstructive pulmonary disease (COPD) are still largely unknown. To date, genome-wide association studies (GWASs) of limited size have identified several novel risk loci for COPD at CHRNA3/CHRNA5/IREB2, HHIP and FAM13A; additional loci may be identified through larger studies. We performed a GWAS using a total of 3499 cases and 1922 control subjects from four cohorts: the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE); the Normative Aging Study (NAS) and National Emphysema Treatment Trial (NETT); Bergen, Norway (GenKOLS); and the COPDGene study. Genotyping was performed on Illumina platforms with additional markers imputed using 1000 Genomes data; results were summarized using fixed-effect meta-analysis. We identified a new genome-wide significant locus on chromosome 19q13 (rs7937, OR = 0.74, P = 2.9 × 10−9). Genotyping this single nucleotide polymorphism (SNP) and another nearby SNP in linkage disequilibrium (rs2604894) in 2859 subjects from the family-based International COPD Genetics Network study (ICGN) demonstrated supportive evidence for association for COPD (P = 0.28 and 0.11 for rs7937 and rs2604894), pre-bronchodilator FEV1 (P = 0.08 and 0.04) and severe (GOLD 3&4) COPD (P = 0.09 and 0.017). This region includes RAB4B, EGLN2, MIA and CYP2A6, and has previously been identified in association with cigarette smoking behavior.
Fibroblasts are the major mesenchymal cells present within the interstitium of the lung and are a major source of vascular endothelial growth factor (VEGF), which modulates the maintenance of pulmonary microvasculature. Prostaglandin E2 (PGE2) acts on a set of E-prostanoid (EP) receptors that activate multiple signal transduction pathways leading to downstream responses. We investigated the modulation by PGE2 of VEGF release by human lung fibroblasts. Human lung fibroblasts were cultured until reaching 90% confluence in tissue culture plates, after which the culture media were changed to serum-free Dulbecco's modified Eagle's medium, with or without PGE2, and with specific agonists or antagonists for each EP receptor. After 2 days, culture media were assayed for VEGF by ELISA. The results demonstrated that PGE2 and the EP2 agonist ONO-AE1-259-01 significantly stimulated the release of VEGF in a concentration-dependent manner. Agonists for other EP receptors did not stimulate the release of VEGF. The stimulatory effect of PGE2 was blocked by the EP2 antagonist AH6809, but was not blocked by antagonists for other EP receptors. The protein kinase–A (PKA) inhibitor KT-5720 also blocked the stimulatory effect of PGE2. The increased release of VEGF induced by PGE2 was accompanied by a transient increase in the concentration of VEGF mRNA. These findings demonstrate that PGE2 can modulate the release of VEGF by human lung fibroblasts through its actions in the EP2 receptor/PKA pathway. This activity may contribute to the maintenance of pulmonary microvasculature in the alveolar wall.
prostaglandin E2; vascular endothelial growth factor; human lung fibroblasts; tissue repair
Nicotine replacement therapy to aid smoking reduction increases the probability of a future quit attempt among smokers not currently planning to quit smoking. We tested whether varenicline, a partial nicotine agonist, would also increase future quit attempts.
This randomized, placebo-controlled trial recruited 218 smokers who were interested in quitting but had no plans to quit in the next month. Participants used varenicline (2 mg/day) or placebo for 2–8 weeks plus received brief counseling on methods to reduce cigarettes/day. The primary measure was the incidence of a quit attempt within 6 months of study entry. Secondary measures were point prevalence abstinence, motivation to stop smoking, and reduction in cigarettes/day.
Varenicline increased the incidence of a quit attempt more than placebo at the Nebraska site (73% vs. 41%; p < .001) but not at the Vermont site (45% vs. 51%; p = .45). Varenicline increased most other measures of quit attempts, motivation and abstinence, independent of site. The beneficial effects of varenicline in quit attempts appeared to be mediated by greater reductions in cigarettes/day, dependence, craving, and cigarette satisfaction. Varenicline had a greater effect on quit attempts in less-dependent smokers, in minority smokers, and in those who had less prior cessation or reduction activity. Adverse events were minimal.
Varenicline increased quit attempts in smokers who are not currently trying to quit at one of the two study sites and improved most all secondary outcomes independent of site. This appeared to be due to decreasing cigarettes/day and level of dependence.
Cigarette smoking is a major risk factor for COPD and COPD severity. Previous genome-wide association studies (GWAS) have identified numerous single nucleotide polymorphisms (SNPs) associated with the number of cigarettes smoked per day (CPD) and a Dopamine Beta-Hydroxylase (DBH) locus associated with smoking cessation in multiple populations.
To identify SNPs associated with lifetime average and current CPD, age at smoking initiation, and smoking cessation in COPD subjects.
GWAS were conducted in 4 independent cohorts encompassing 3,441 ever-smoking COPD subjects (GOLD stage II or higher). Untyped SNPs were imputed using HapMap (phase II) panel. Results from all cohorts were meta-analyzed.
Several SNPs near the HLA region on chromosome 6p21 and in an intergenic region on chromosome 2q21 showed associations with age at smoking initiation, both with the lowest p=2×10−7. No SNPs were associated with lifetime average CPD, current CPD or smoking cessation with p<10−6. Nominally significant associations with candidate SNPs within alpha-nicotinic acetylcholine receptors 3/5 (CHRNA3/CHRNA5; e.g. p=0.00011 for SNP rs1051730) and Cytochrome P450 2A6 (CYP2A6; e.g. p=2.78×10−5 for a nonsynonymous SNP rs1801272) regions were observed for lifetime average CPD, however only CYP2A6 showed evidence of significant association with current CPD. A candidate SNP (rs3025343) in the DBH was significantly (p=0.015) associated with smoking cessation.
We identified two candidate regions associated with age at smoking initiation in COPD subjects. Associations of CHRNA3/CHRNA5 and CYP2A6 loci with CPD and DBH with smoking cessation are also likely of importance in the smoking behaviors of COPD patients.
Chronic Obstructive Pulmonary Disease (COPD); Genome Wide Association study (GWAS); smoking behaviors; Single Nucleotide Polymorphism (SNP)
Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation in the small airways. The effect of inhaled corticosteroids (ICS) on lung inflammation in COPD remains uncertain. We sought to determine the effects of ICS on inflammatory indices in bronchial biopsies and bronchoalveolar lavage fluid of patients with COPD.
We searched Medline, Embase, Cinahl, and the Cochrane database for randomized, controlled clinical trials that used bronchial biopsies and bronchoalveolar lavage to evaluate the effects of ICS in stable COPD. For each chosen study, we calculated the mean differences in the concentrations of inflammatory cells before and after treatment in both intervention and control groups. These values were then converted into standardized mean differences (SMD) to accommodate the differences in patient selection, clinical treatment, and biochemical procedures that were employed across the original studies. If significant heterogeneity was present (P < 0.1), then a random effects model was used to pool the original data; otherwise, a fixed effects model was used.
We identified eight original studies that met the inclusion criteria. Four studies used bronchial biopsies (n =102 participants) and showed that ICS were effective in reducing CD4 and CD8 cell counts (SMD, −0.52 units and −0.66 units, 95% confidence interval). The five studies used bronchoalveolar lavage fluid (n =309), which together showed that ICS reduced neutrophil and lymphocyte counts (SMD, −0.64 units and −0.64 units, 95% confidence interval). ICS on the other hand significantly increased macrophage counts (SMD, 0.68 units, 95% confidence interval) in bronchoalveolar lavage fluid.
ICS has important immunomodulatory effects in airways with COPD that may explain its beneficial effect on exacerbations and enhanced risk of pneumonia.
chronic obstructive pulmonary disease; bronchial biopsies; bronchoalveolar lavage; inhaled corticosteroids; inflammation; inflammatory markers; meta-analysis
Background: Combination therapy with a long-acting bronchodilator and an inhaled corticosteroid (ICS) is recommended in patients with chronic obstructive pulmonary disease (COPD) who have frequent exacerbations. The efficacy and tolerability of the combination of budesonide/formoterol have been demonstrated in patients with COPD when administered via the dry powder inhaler (DPI) in a 1-year study and when administered via the hydrofluoroalkane (HFA) pressurized metered-dose inhaler (pMDI) in a 6-month study.
Objective: This study assessed the long-term efficacy and tolerability of budesonide/formoterol HFA pMDI in patients with moderate to very severe COPD.
Methods: This was a 12-month, randomized, double-blind, double-dummy, parallel-group, active- and placebo-controlled, multicentre study (NCT00206167) of 1964 patients aged ≥40 years with moderate to very severe COPD conducted from 2005 to 2007 at 237 sites in the US, Europe and Mexico. After 2 weeks of treatment based on previous therapy (ICSs, short-acting bronchodilators allowed), patients received one of the following treatments twice daily: budesonide/formoterol pMDI 160/4.5 μg × two inhalations (320/9 μg); budesonide/formoterol pMDI 80/4.5 μg × two inhalations (160/9 μg); formoterol DPI 4.5 μg × two inhalations (9 μg); or placebo.
Main outcome measures: The co-primary efficacy variables were pre-dose forced expiratory volume in 1 second (FEV1) and 1-hour post-dose FEV1.
Results: Budesonide/formoterol 320/9 μg demonstrated greater improvements in pre-dose FEV1 versus formoterol (p = 0.008), and both budesonide/formoterol doses demonstrated greater improvements in 1-hour post-dose FEV1 versus placebo (p < 0.001). The rate of COPD exacerbations was lower in both budesonide/formoterol groups compared with formoterol and placebo (p ≤ 0.004). Both budesonide/formoterol doses were more effective than placebo (p ≤ 0.006) for controlling dyspnoea and improving health status (St George’s Respiratory Questionnaire). All treatments were generally well tolerated. The incidence of pneumonia was not different for active (3.4–4.0%) and placebo (5.0%) groups.
Conclusions: Budesonide/formoterol pMDI (320/9 μg and 160/9 μg) improved pulmonary function and reduced symptoms and exacerbations over 1 year in patients with moderate to very severe COPD. Only budesonide/formoterol pMDI 320/9 μg demonstrated greater efficacy for both co-primary variables compared with formoterol DPI 9 μg. Both budesonide/formoterol pMDI dosages were well tolerated relative to formoterol and placebo.
Electronic Supplementary Material
Supplementary material is available for this article at 10.2165/00003495-200969050-00004 and is accessible for authorized users.
Fatigue is a disruptive symptom that inhibits normal functional performance of COPD patients in daily activities. The availability of a short, simple, reliable and valid scale would improve assessment of the characteristics and influence of fatigue in COPD.
At baseline, 2107 COPD patients from the ECLIPSE cohort completed the Functional Assessment of Chronic Illness Therapy Fatigue (FACIT-F) scale. We used well-structured classic method, the principal components analysis (PCA) and Rasch analysis for structurally examining the 13-item FACIT-F.
Four items were less able to capture fatigue characteristics in COPD and were deleted. PCA was applied to the remaining 9 items of the modified FACIT-F and resulted in three interpretable dimensions: i) general (5 items); ii) functional ability (2 items); and iii) psychosocial fatigue (2 items). The modified FACIT-F had high internal consistency (Cronbach's α = 0.91) and it did not fit a uni-dimensional Rasch model, confirming the prior output from the PCA. The correlations between total score and each dimension were ≥ 0.64 and within dimensions ≥0.43 (p < 0.001 for all).
The original and modified FACIT-F had significant convergent validity; its scores were associated with SGRQ total score (0.69 and 0.7) and mMRC dyspnoea scores (0.48 and 0.47), (p = <0.001 for all). The scale had meaningful discriminating ability in identifying patients with poor exercise performance and more depressive symptoms.
The original and modified FACIT-F are valid and reliable scales in COPD. The modified version is shorter and measures not only total fatigue but also its sub-components in COPD.
Chronic obstructive pulmonary disease; Fatigue; Exercise capacity; Health status
Fibroblast heterogeneity is recognized and fibroblasts from diseased tissues, including asthma, have functional phenotypes that differ from normal. However, progenitor progeny relationships and the factors that control fibroblast differentiation are poorly defined.
To determine if interleukin-4 could alter the functional phenotype of fibroblasts during their differentiation from stem/progenitor cells.
Using a three-dimensional collagen gel system, we embryoid bodies derived from human embryonic stem cells and recovered spindle-shaped cells consistent with fibroblasts that had differentiated in the presence or absence of interleukin-4.
Interleukin-4 induced fibroblast-like cells were more active in contracting collagen gels, in migration and in producing fibronectin than control (without interleukin-4) cells. Interleukin-4 induced cells demonstrated less expression of miR-155 that modulated contraction, migration and fibronectin production. These differences persisted in culture without further addition of interleukin-4, suggesting the differentiated phenotype might be a permanent alteration.
The current study demonstrates that interleukin-4 induces differentiation of stem/precursor cells into fibroblast-like cells that demonstrate a more “fibrogenic” phenotype, which is due to reduced expression of miR-155. These findings provide a novel mechanism for the persistent abnormalities in IL-4 related diseases and a novel target to regulate tissue remodeling by fibroblasts.
embryonic stem cells; fibroblasts; IL-4; fibrosis; asthma; microRNA; miR-155; chemotaxis; collagen gel contraction; TGF-β
Because chronic obstructive pulmonary disease (COPD) is a heterogeneous condition, the identification of specific clinical phenotypes is key to developing more effective therapies. To explore if the persistence of systemic inflammation is associated with poor clinical outcomes in COPD we assessed patients recruited to the well-characterized ECLIPSE cohort (NCT00292552).
Methods and Findings
Six inflammatory biomarkers in peripheral blood (white blood cells (WBC) count and CRP, IL-6, IL-8, fibrinogen and TNF-α levels) were quantified in 1,755 COPD patients, 297 smokers with normal spirometry and 202 non-smoker controls that were followed-up for three years. We found that, at baseline, 30% of COPD patients did not show evidence of systemic inflammation whereas 16% had persistent systemic inflammation. Even though pulmonary abnormalities were similar in these two groups, persistently inflamed patients during follow-up had significantly increased all-cause mortality (13% vs. 2%, p<0.001) and exacerbation frequency (1.5 (1.5) vs. 0.9 (1.1) per year, p<0.001) compared to non-inflamed ones. As a descriptive study our results show associations but do not prove causality. Besides this, the inflammatory response is complex and we studied only a limited panel of biomarkers, albeit they are those investigated by the majority of previous studies and are often and easily measured in clinical practice.
Overall, these results identify a novel systemic inflammatory COPD phenotype that may be the target of specific research and treatment.
The identification of gene-by-environment interactions is important to understand the genetic basis of chronic obstructive pulmonary disease (COPD). Many COPD genetic association analyses assume a linear relationship between pack-years of smoking exposure and FEV1; however, this assumption has not been evaluated empirically in cohorts with a wide spectrum of COPD severity.
We examined the relationship between FEV1 and pack-years of smoking exposure in 4 large cohorts assembled for the purpose of identifying genetic associations with COPD. Using data from the Alpha-1 Antitrypsin Genetic Modifiers Study, we compared the accuracy and power of two different approaches to model smoking by performing a simulation study of a genetic variant with a range of gene-by-smoking interaction effects.
We identified nonlinear relationships between smoking and FEV1 in 4 large cohorts. We demonstrated that in most situations where the relationship between pack-years and FEV1 is nonlinear, a piecewise-linear approach to model smoking and gene-by-smoking interactions is preferable to the commonly used total pack-years approach. We applied the piecewise linear approach to a genetic association analysis of the PI*Z allele in the Norway case-control cohort and identified a potential PI*Z-by-smoking interaction (p=0.03 for FEV1 analysis, p= 0.01 for COPD susceptibility analysis).
In study samples with subjects having a wide range of COPD severity, a nonlinear relationship between pack-years of smoking and FEV1 is likely. In this setting, approaches that account for this nonlinearity can be more powerful and less-biased than the commonly-used approach of using total pack-years to model the smoking effect.
smoking; FEV1; gene-by-environment interaction; COPD; gene
The development of COPD in subjects with alpha-1 antitrypsin (AAT) deficiency is likely to be influenced by modifier genes. Genome-wide association studies and integrative genomics approaches in COPD have demonstrated significant associations with SNPs in the chromosome 15q region that includes CHRNA3 (cholinergic nicotine receptor alpha3) and IREB2 (iron regulatory binding protein 2).
We investigated whether SNPs in the chromosome 15q region would be modifiers for lung function and COPD in AAT deficiency.
The current analysis included 378 PIZZ subjects in the AAT Genetic Modifiers Study and a replication cohort of 458 subjects from the UK AAT Deficiency National Registry. Nine SNPs in LOC123688, CHRNA3 and IREB2 were selected for genotyping. FEV1 percent of predicted and FEV1/FVC ratio were analyzed as quantitative phenotypes. Family-based association analysis was performed in the AAT Genetic Modifiers Study. In the replication set, general linear models were used for quantitative phenotypes and logistic regression models were used for the presence/absence of emphysema or COPD.
Three SNPs (rs2568494 in IREB2, rs8034191 in LOC123688, and rs1051730 in CHRNA3) were associated with pre-bronchodilator FEV1 percent of predicted in the AAT Genetic Modifiers Study. Two SNPs (rs2568494 and rs1051730) were associated with the post-bronchodilator FEV1 percent of predicted and pre-bronchodilator FEV1/FVC ratio; SNP-by-gender interactions were observed. In the UK National Registry dataset, rs2568494 was significantly associated with emphysema in the male subgroup; significant SNP-by-smoking interactions were observed.
IREB2 and CHRNA3 are potential genetic modifiers of COPD phenotypes in individuals with severe AAT deficiency and may be sex-specific in their impact.
CHRNA3; Chronic obstructive pulmonary disease; Genetic association analysis; Genetic modifiers; IREB2
Chronic obstructive pulmonary disease (COPD) is characterized by progressive worsening of airflow limitation associated with abnormally inflamed airways in older smokers. Despite correlative evidence for a role for tumor necrosis factor-alpha in the pathogenesis of COPD, the anti-tumor necrosis factor-alpha, infliximab did not show clinical efficacy in a double-blind, placebo-controlled, phase II clinical trial. This study sought to evaluate the systemic inflammatory profile associated with COPD and to assess the impact of tumor necrosis factor neutralization on systemic inflammation.
Serum samples (n = 234) from the phase II trial were collected at baseline and after 24 weeks of placebo or infliximab. Additionally, baseline serum samples were obtained from an independent COPD cohort (n = 160) and 2 healthy control cohorts (n = 50; n = 109). Serum concentrations of a broad panel of inflammation-associated analytes were measured using a 92-analyte multiplex assay.
Twenty-five proteins were significantly elevated and 2 were decreased in COPD, including highly elevated CD40 ligand, brain-derived neurotrophic factor, epidermal growth factor, acute-phase proteins, and neutrophil-associated proteins. This profile was largely independent of smoking status, age, and clinical phenotype. The majority of these associations of serum analytes with COPD are novel findings. Increased serum creatine kinase-muscle/brain and myoglobin correlated modestly with decreased forced expiratory volume at 1 second, suggesting cardiac involvement. Infliximab did not affect this systemic inflammatory profile.
A robust systemic inflammatory profile was associated with COPD. This profile was generally independent of disease severity. Because anti-tumor necrosis factor-alpha did not influence systemic inflammation, how to control the underlying pathology beyond symptom suppression remains unclear.
ClinicalTrials.gov, No.: NCT00056264.
chronic obstructive pulmonary disease; inflammation; biological biomarkers; tumor necrosis factor-alpha; infliximab
Cell-cell interactions are particularly important for modulating the monocyte to macrophage transition in tissue compartments. Both cell membrane contacts and soluble signals from the environment might be involved in these interactions. The aim of our study was to characterize gene expression profiles of human mononuclear phagocytes induced by a co-culture with epithelial cells.
Human THP-1 macrophages were co-cultured with A549 epithelial cells either directly or separated by a filter insert. At different time points, THP-1 cells were aspirated and the mRNA expression was evaluated by multiplex Real-time RT-PCR, the release of selected cytokines was evaluated by Luminex technology or ELISA. The phenotype of both cultured cells was evaluated by flow cytometry.
Co-culture with epithelial cells induced a number of cytokine genes (IL-1 beta, IL-6, IL-10, TNF alpha, IL-19, GM-CSF, …etc) together with upregulation of genes associated with NFkappaB activation including REL, RELB, transcription co-activator BCL3, MALT gene, and NFKB1 subunit. Our recent study has confirmed the role of NFkB signalling by inhibition of IL-6 release from co-cultured cells by p65 siRNA transfection1. Phenotypic pattern of THP-1 cells co-cultured with epithelial monolayers showed maturation and activation associated changes such as CD14 upregulation associated with higher release of the soluble form (sCD14) from macrophage membrane.
Our data suggest that properties of human mononuclear phagocytes in tissues are highly influenced by their immediate interactions with other, e.g. epithelial cells. These factors might be of particular importance in final steps of differenciation of monocytes/macrophages into fully competent effector cells.
The migration of fibroblasts is believed to play a key role in both normal wound repair and abnormal tissue remodeling. Prostaglandin E (PGE)2, a mediator that can inhibit many fibroblast functions including chemotaxis, was reported to be mediated by the E-prostanoid (EP) receptor EP2. PGE2, however, can act on four receptors. This study was designed to determine if EP receptors, in addition to EP2, can modulate fibroblast chemotaxis. Using human fetal lung fibroblasts, the expression of all four EP receptors was demonstrated by Western blotting. EP2-selective and EP4-selective agonists inhibited both chemotaxis toward fibronectin in the blindwell assay and migration in a wound-closure assay. In contrast, EP1-selective and EP3-selective agonists stimulated cell migration in both assay systems. These results were confirmed using EP-selective antagonists. The role of both EP2 and EP4 receptors in mediating the PGE2 inhibition of chemotaxis was also confirmed by small interfering RNA suppression. Furthermore, the role of EP receptors was confirmed by blocking the expected signaling pathways. Taken together, these results demonstrate that PGE2 can act on multiple EP receptors in human lung fibroblasts, to exert disparate effects. Alterations in EP receptor expression may have the potential to alter PGE2 action. Targeting specific EP receptors may offer therapeutic opportunities in conditions characterized by abnormal tissue repair and remodeling.
human lung fibroblast; cell migration; EP receptors
Exposure to cigarette smoke is associated with airway epithelial mucus cell hyperplasia and a decrease in cilia and ciliated cells. Few models have addressed the long-term effects of chronic cigarette smoke exposure on ciliated epithelial cells. Our previous in vitro studies showed that cigarette smoke decreases ciliary beat frequency (CBF) via the activation of protein kinase C (PKC). We hypothesized that chronic cigarette smoke exposure in an in vivo model would decrease airway epithelial cell ciliary beating in a PKC-dependent manner. We exposed C57BL/6 mice to whole-body cigarette smoke 2 hours/day, 5 days/week for up to 1 year. Tracheal epithelial cell CBF and the number of motile cells were measured after necropsy in cut tracheal rings, using high-speed digital video microscopy. Tracheal epithelial PKC was assayed according to direct kinase activity. At 6 weeks and 3 months of smoke exposure, the baseline CBF was slightly elevated (∼ 1 Hz) versus control mice, with no change in β-agonist–stimulated CBF between control mice and cigarette smoke–exposed mice. By 6 months of smoke exposure, the baseline CBF was significantly decreased (2–3 Hz) versus control mice, and a β-agonist failed to stimulate increased CBF. The loss of β-agonist–increased CBF continued at 9 months and 12 months of smoke exposure, and the baseline CBF was significantly decreased to less than one third of the control rate. In addition to CBF, ciliated cell numbers significantly decreased in response to smoke over time, with a significant loss of tracheal ciliated cells occurring between 6 and 12 months. In parallel with the slowing of CBF, significant PKC activation from cytosol to the membrane of tracheal epithelial cells was detected in mice exposed to smoke for 6–12 months.
chronic cigarette smoke; cilia; PKC
Current smoking cessation guidelines recommend setting a quit date prior to starting pharmacotherapy. However, providing flexibility in the date of quitting may be more acceptable to some smokers. The objective of this study was to compare varenicline 1 mg twice daily (b.i.d.) with placebo in subjects using a flexible quit date paradigm after starting medication.
In this double-blind, randomized, placebo-controlled international study, smokers of ≥10 cigarettes/day, aged 18–75 years, and who were motivated to quit were randomized (3:1) to receive varenicline 1 mg b.i.d. or placebo for 12 weeks. Subjects were followed up through Week 24. Subjects were instructed to quit between Days 8 and 35 after starting medication. The primary endpoint was carbon monoxide–confirmed continuous abstinence during Weeks 9–12, and a key secondary endpoint was continuous abstinence during Weeks 9–24.
Overall, 493 subjects were randomized to varenicline and 166 to placebo. Continuous abstinence was higher for varenicline than for placebo subjects at the end of treatment (Weeks 9–12: 53.1% vs. 19.3%; odds ratio [OR] 5.9; 95% CI, 3.7–9.4; p < .0001) and through 24 weeks follow-up (Weeks 9–24: 34.7% vs. 12.7%; OR 4.4; 95% CI, 2.6–7.5; p < .0001). Serious adverse events occurred in 1.2% varenicline (none were psychiatric) and 0.6% placebo subjects. Fewer varenicline than placebo subjects reported depression-related adverse events (2.3% vs. 6.7%, respectively).
Varenicline 1 mg b.i.d. using a flexible quit date paradigm had similar efficacy and safety compared with previous fixed quit date studies.
Rationale: Persistent inflammation plays a major role in chronic obstructive pulmonary disease (COPD) pathogenesis, but its mechanisms are incompletely defined. Overproduction of the inflammatory mediator prostaglandin (PG) E2 by COPD fibroblasts contributes to reduced repair function.
Objectives: The present study determined if fibroblasts from subjects with COPD overproduce PGE2 after stimulation with the inflammatory cytokines IL-1β and tumor necrosis factor-α, and further defined the mechanism for overproduction.
Methods: Fibroblasts were isolated from parenchymal tissue obtained from smokers with and without COPD undergoing lung surgery. PGE2, cyclooxygenases (COX), and miR-146a in these cells were evaluated by in vitro studies.
Measurements and Main Results: After stimulation with inflammatory cytokines, COPD fibroblasts produced 2.7-fold more PGE2 compared with controls with similar smoking history. The increase in PGE2 depended on induction of COX-2, which increased to a greater degree in fibroblasts from subjects with COPD. Cytokines also induced microRNA miR-146a expression in both fibroblasts, but significantly less in COPD fibroblasts. miR-146a caused degradation of COX-2 mRNA; reduced expression prolonged COX-2 mRNA half-life in fibroblasts from subjects with COPD. Cytokine-stimulated PGE2 production and miR-146a expression in cultured fibroblasts correlated with clinical severity assessed by expiratory airflow and diffusion capacity.
Conclusions: miR-146a seems to play a pathogenetic role in the abnormal inflammatory response in COPD. Increased half-life of inflammatory mRNAs is a mechanism of abnormal inflammation in this disease.
chronic obstructive pulmonary disease; miR-146a; prostaglandin E2; cyclooxygenase-2; fibroblasts