Polymorphisms in the beta2 adrenergic receptor and bronchodilator response, bronchial hyperresponsiveness, and rate of decline in lung function in smokers

Maternal-fetal vitamin D receptor polymorphisms significantly associated with preterm birth

PURPOSE

Preterm birth (PTB) is a complex trait with strong genetic background, whose etiology is not fully understood. It was recently suggested that pregnancy duration is affected by fetal genetic variation even more than by the maternal genome. Vitamin D receptor (VDR) is involved in embryonic implantation and fertility. We studied the association between both maternal and neonatal vitamin D receptor (VDR) genetic variation and PTB.

METHODS

Maternal and fetal (umbilical cord) DNA was isolated from Jewish Israeli idiopathic preterm newborns (24-36 weeks, n = 146) and control term newborns (>37 weeks, n = 229). Maternal and fetal VDR polymorphisms (FokI, ApaI, BsmI, TaqI) were analyzed by restriction fragment length polymorphism analysis. Using SPSS analysis to correlate VDR genotypes with phenotypic variation: pregnancy duration, preterm birth and spontaneous miscarriages, adjusted for gravidity, parity and gender of newborn.

RESULTS

Women homozygous to VDR ApaI (AA) genotype had significant twofold increase risk for PTB [OR 1.973, (CI) 1.183-3.289, p = 0.009] compared to heterozygous women. Male newborns had significant (p < 0.05) 1.73-fold increase of PTB. Women with history of previous (≥1) spontaneous miscarriage had a significant increased risk for PTB if their newborn carried either of the VDR BsmI homozygous (BB or bb) genotypes compared to the heterozygous (Bb) genotype [OR 6.857, (CI) 1.273-36.934, p = 0.018 and OR 9.231, (CI) 1.753-48.618, p = 0.008, respectively], or VDR ApaI homozygous (AA or aa) genotype compared to heterozygous (Aa) genotype [OR 4.33, (CI) 1.029-18.257, p = 0.046 and OR 7.2, (CI) 1.34-38.917, p = 0.021, respectively].

CONCLUSIONS

We show association between maternal and fetal VDR genotype variants with PTB.

Beta2-adrenergic receptor gene haplotypes and bronchodilator response in Egyptian patients with chronic obstructive pulmonary disease

PURPOSE

Chronic obstructive pulmonary disease (COPD) is a multi-factorial disorder caused by environmental determinants and genetic risk factors. Understanding the genetic predisposition of COPD is essential to develop personalized treatment regimens. Beta₂-adrenergic receptor (ADRB2) gene polymorphisms have been implicated in the pathogenesis of obstructive pulmonary diseases. This study was conducted to assess the genetic association between Arg16Gly and Gln27Glu polymorphisms and COPD in the Egyptian patients, and to analyze their impact on the clinical outcome and therapeutic response.

PATIENTS/METHODS

The study population included 115 participants (61 COPD patients and 54 healthy controls) were genotyped for the Arg16Gly (rs1042713) and Gln27Glu (rs1042714) polymorphisms. Pulmonary function test was done and repeated in patients after salbutamol inhalation.

RESULTS

The Gly₁₆ and Gln₂₇ alleles represented 57% and 70% of the whole study population, and only 3 haplotypes were detected; Arg₁₆/Gln₂₇, Gly₁₆/Gln₂₇, and Gly₁₆/Glu₂₇. Genotypes and haplotypes homozygous for Arg₁₆ and Gln₂₇ were more likely to develop COPD (p<0.05). However, individuals carrying Glu₂₇ allele conferred protection against COPD development (p=0.002). Furthermore, Arg₁₆ genotypes and haplotypes were significantly associated with higher grades of dyspnea, more COPD symptoms and frequent exacerbations. In contrast, patients carrying Glu₂₇ allele had better bronchial airway responsiveness to β₂-agonists.

CONCLUSIONS

Our findings suggested that the ADRB2 gene polymorphisms may have vital role in COPD risk, severity, and bronchodilator response among Egyptian population. Larger epidemiological studies are needed for results validation.

Preliminary evidence for a role of the adrenergic nervous system in generalized anxiety disorder

Generalized anxiety disorder (GAD) is a common chronic condition that is understudied compared to other psychiatric disorders. An altered adrenergic function has been reported in GAD, however direct evidence for genetic susceptibility is missing. This study evaluated the associations of gene variants in adrenergic receptors (ADRs) with GAD, with the involvement of stressful events. Data were obtained from 844 French community-dwelling elderly aged 65 or over. Anxiety disorders were assessed using the Mini-International Neuropsychiatry Interview, according to DSM-IV criteria. Eight single-nucleotide polymorphisms (SNPs) involved with adrenergic function were genotyped; adrenergic receptors alpha(1A) (ADRA1A), alpha(2A) (ADRA2A), and beta2 (ADRB2) and transcription factor TCF7L2. Questionnaires evaluated recent stressful life events as well as early environment during childhood and adolescence. Using multivariate logistic regression analyses four SNPs were significantly associated with GAD. A 4-fold modified risk was found with ADRA1A rs17426222 and rs573514, and ADRB2 rs1042713 which remained significant after Bonferroni correction. Certain variants may moderate the effect of adverse life events on the risk of GAD. Replication in larger samples is needed due to the small case number. This is the first study showing that ADR variants are susceptibility factors for GAD, further highlighting the critical role of the adrenergic nervous system in this disorder.

Analysis of ADRB2 (Arg16Gly) Gene Variant with Susceptibility, Pharmacogenetic Response and Disease Severity in South Indian Asthmatics

β2-Adrenergic receptor (β2-AR) plays a crucial role in asthma pathophysiology by regulating, processes of the lung function, and clinical response to bronchodilators. The +46G>A- Gly16Arg polymorphism in the gene encoding β2 adrenergic receptor (ADRB2) has been associated with receptor non-responsiveness after β2-agonist exposure. In the present study, we sought to evaluate the possible association of Gly16Arg polymorphism with asthma susceptibility, pharmacogenetic response to Salbutamol, and varying degrees of disease severity. Three hundred ninety-eight clinically diagnosed patients and 456 healthy controls were enrolled for the study. Patients were classified into severity classes according to Global Initiative for Asthma guidelines. To assess bronchodilator response, spirometry was performed before and 15 min after Salbutamol (200 μg) delivery. Responders to Salbutamol were categorized if percentage reversibility was greater than or equal to 12% in them, while those showing reversibility less than 12% were classified as non-responders. Genotyping was carried out by ARMS-PCR technique. Statistical methods were applied to test for the significance of the results. In the present study, there was lack of significant association of polymorphism with disease susceptibility as well as with bronchodilator response. The polymorphism was not associated with mild and moderate asthma subtypes; however, there was a notable association with severe asthma subtype. In addition, the polymorphism was associated with severe asthma compared to subtypes of mild and moderate asthma combined. In a South Indian population, the ADRB2 Arg/Gly may not form a susceptible variant to develop asthma nor can be a standard predictive marker to bronchodilator response; nevertheless, the patterns in asthma severity can be predicted by analyzing this variant.

Polymorphisms of beta2-adrenergic receptor gene in serbian asthmatic adults: effects on response to Beta-agonists

BACKGROUND AND OBJECTIVES

Polymorphisms of beta2-adrenergic receptor gene (ADRB2) are clinically relevant for several reasons, including as a risk factor for asthma development/severity and predicting the effectiveness of treatment with beta2-agonists in reducing asthma symptoms. The aim of this study was to examine the association between ADRB2 gene polymorphisms and asthma in the Serbian population, and to evaluate the therapeutic response in relation to the ADRB2 genotype.

METHODS

The study included 171 patients with asthma and 101 healthy subjects as the control group. Genotyping of Arg16Gly and Gln27Glu polymorphisms was performed by direct sequencing of polymerase chain reaction (PCR) products.

RESULTS

In Serbian adults, carriers of the 27Gln allele and 27Gln/Gln genotype were at higher risk of asthma [odds ratio (OR) 2.5, 95% confidence interval (CI) 1.6-3.8, and OR 3.00, 95% CI 1.7-5.3, respectively], while the presence of the 27Glu allele and 27Gln/Glu genotype were found to be protective of asthma (OR 0.4, 95% CI 0.3-0.6, and OR 0.3, 95% CI 0.1-0.7, respectively). Furthermore, we found that the presence of the 27Gln allele in asthmatics younger than 50 years leads to a better response to therapy with long-acting beta2-agonists (LABA) in combination with prevailing low and moderate doses of inhaled corticosteroids (ICS), while carriers of the 27Glu allele over 50 years old are more likely to respond to LABA + ICS therapy.

CONCLUSION

We identified that in Serbian adults the 27Gln allele and 27Gln homozygosity are risk factors for asthma, which may be of clinical interest in disease prevention. The finding that younger carriers of the 27Gln allele respond better to LABA + ICS therapy may be utilized in personalized asthma treatment.

Molecular Characterization and Expression Analysis of Adrenergic Receptor Beta 2 (ADRB2) Gene before and after Exercise in the Horse

The adrenergic receptor beta 2 (ADRB2) plays a role in various physiological responses of the muscle to exercise, such as contraction and relaxation. Given its important role in muscle function, we investigated the structure of the horse ADRB2 gene and its expression pattern after exercise to determine if it can serve as a putative biomarker for recovery. Evolutionary analyses using synonymous and non-synonymous mutation ratios, were compared with other species (human, chimpanzee, mouse, rat, cow, pig, chicken, dog, and cat), and revealed the occurrence of positive selection in the horse ADRB2 gene. In addition, expression analyses by quantitative polymerase chain reaction exhibited ubiquitous distribution of horse ADRB2 in various tissues including lung, skeletal muscle, kidney, thyroid, appendix, colon, spinal cord and heart, with the highest expression observed in the lung. The expression of ADRB2 in skeletal muscle was significantly up-regulated about four folds 30 minutes post-exercise compared to pre-exercise. The expression level of ADRB2 in leukocytes, which could be collected with convenience compared with other tissues in horse, increased until 60 min after exercise but decreased afterward until 120 min, suggesting the ADRB2 expression levels in leukocytes could be a useful biomarker to check the early recovery status of horse after exercise. In conclusion, we identified horse ADRB2 gene and analyzed expression profiles in various tissues. Additionally, analysis of ADBR2 gene expression in leukocytes could be a useful biomarker useful for evaluation of early recovery status after exercise in racing horses.

Modest genetic influence on bronchodilator response: a study in healthy twins

Aim

To determine the reasons for large standard deviation of bronchodilator response (BDR) and establish whether there is a potential heritable component in healthy subjects.

Methods

67 monozygotic and 42 dizygotic adult twin pairs were assessed for bronchodilator response (%change in FEV₁ after inhaling 400 µg salbutamol). Univariate quantitative genetic modeling was performed.

Results

Multiple regression modeling showed a significant association between BDR and sex and baseline FEV1 (P < 0.05), while no association was found with smoking habits, body mass index, or age. Within pair correlation in monozygotic twins was modest (0.332), but higher than in dizygotic twins (0.258). Age-, sex-, and baseline FEV1-adjusted genetic effect accounted for 14.9% (95% confidence interval, CI 0%-53.1%) of the variance of BDR, shared environmental effect for 18.4% (95% CI 0%-46.8%), and unshared environmental effect for 66.8% (95% CI 46.8%-88.7%).

Conclusion

Our twin study showed that individual differences in BDR can be mostly explained by unshared environmental effects. In addition, it is the first study to show low, insignificant hereditary influences, independently from sex, age, and baseline FEV1.

Genetic polymorphisms and asthma: findings from a case-control study in the Madeira island population

BACKGROUND

Asthma is a complex disease influenced by multiple genetic and environmental factors. While Madeira has the highest prevalence of asthma in Portugal (14.6%), the effect of both genetic and environmental factors in this population has never been assessed. We categorized 98 asthma patients according to the Global Initiative for Asthma (GINA) guidelines, established their sensitization profile, and measured their forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) indexes. Selected single nucleotide polymorphisms (SNPs) were analysed as potential markers for asthma susceptibility and severity in the interleukin 4 (IL4), interleukin 13 (IL13), beta-2-adrenergic receptor (ADRB2), a disintegrin and metalloprotease 33 (ADAM33), gasdermin-like (GSDML) and the signal transducer and activator of transcription 6 (STAT6) genes comparatively to a population reference set.

RESULTS

Although mites are the major source of allergic sensitization, no significant difference was found amongst asthma severity categories. IL4-590*CT/TT and IL4-RP2*253183/183183 were found to predict the risk (2-fold) and severity (3 to 4-fold) of asthma and were associated with a lower FEV1 index. ADRB2-c.16*AG is a risk factor (3.5-fold), while genotype GSDML-236*TT was protective (4-fold) for moderate-severe asthma. ADAM33-V4*C was associated to asthma and mild asthma by the transmission disequilibrium test (TDT). Finally, ADAM33-V4*CC and STAT6-21*TT were associated with higher sensitization (mean wheal size ≥10 mm) to house dust (1.4-fold) and storage mite (7.8-fold).

CONCLUSION

In Madeira, IL4-590C/T, IL4-RP2 253/183, GSDML-236C/T and ADAM33-V4C/G SNPs are important risk factors for asthma susceptibility and severity, with implications for asthma healthcare management.

Pharmacogenetics of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a complex genetic disease that develops as a result of the interaction of multiple susceptibility genes and environmental factors. Major therapeutic approaches include smoking cessation, treatment with bronchodilators and corticosteroid therapy. The goal of understanding the genetic defects in patients with COPD will be not only to redefine the disease phenotypes based on the genetic information, but also to alternatively approach patients based on the understanding of COPD pathogenesis, which will lead to improved clinical outcomes. Although there is no single ideal phenotype for COPD pharmacogenetic studies, thus far, most pharmacogenetics studies have focused on the role of variants in the β2-adrenergic receptor gene on bronchodilator response. The inconclusive results yielded by these studies highlight many of the difficulties researchers face in assessing the influence of genetic variants and in translating this to clinically relevant outcomes.

Methacholine PC20 in African Americans and whites with asthma with homozygous genotypes at ADRB2 codon 16

BACKGROUND

African Americans have worse asthma outcomes compared to whites. Adrenoceptor beta 2, surface gene (ADRB2) Gly16Arg genotypes have been associated with β2-agonist bronchodilator response, asthma exacerbation rate, response to methacholine, and lung function decline but not specifically in African Americans.

OBJECTIVE

We sought to compare the provocative concentration of methacholine that causes a 20% fall in FEV1 (PC20) in African Americans and whites with asthma who were ADRB2 homozygous at codon 16 (Arg16Arg or Gly16Gly).

METHODS

African Americans and whites whose parents and grandparents were of the same race, aged ≥10 years, with baseline FEV1 of ≥60% predicted, and no upper or lower respiratory tract infection within the previous 2 weeks meeting genotype criteria were enrolled. PC20 was measured after withholding short-acting and long-acting β2-agonists for 8 and 12 h respectively, montelukast for 24 h, ipratropium bromide and inhaled corticosteroids for 12 h, and antihistamines for 72 h.

RESULTS

423 participants were screened and 88 had a positive challenge. Participants were 32 yrs ± 19 yrs (mean ± SD), 70% female, 51% White (vs. African American), 6% Hispanic. Similar numbers of participants were using inhaled corticosteroids by race and genotype. There were significant differences in log PC20 between race/genotype groups (p = 0.012). African American Arg16Arg participants had a lower log PC20 than White Gly16Gly (p = 0.009) and African American Gly16Gly (p = 0.041) participants. Both race and genotype contributed significantly to the model (p = 0.037 and p = 0.014, respectively) but there was no interaction between race and genotype on log PC20.

CONCLUSIONS AND CLINICAL RELEVANCE

Airway hyperresponsiveness is influenced by race and the ADRB2 codon 16 polymorphism. African Americans with the Arg16Arg genotype have increased airway reactivity and may be at risk for worse asthma outcomes. Inclusion of genetic information as an additional clinical tool may aid in the personalization of asthma management decisions. [ClinicalTrials.gov Identifier: NCT00708227].

Updates on the COPD gene list

A genetic contribution to develop chronic obstructive pulmonary disease (COPD) is well established. However, the specific genes responsible for enhanced risk or host differences in susceptibility to smoke exposure remain poorly understood. The goal of this review is to provide a comprehensive literature overview on the genetics of COPD, highlight the most promising findings during the last few years, and ultimately provide an updated COPD gene list. Candidate gene studies on COPD and related phenotypes indexed in PubMed before January 5, 2012 are tabulated. An exhaustive list of publications for any given gene was looked for. This well-documented COPD candidate-gene list is expected to serve many purposes for future replication studies and meta-analyses as well as for reanalyzing collected genomic data in the field. In addition, this review summarizes recent genetic loci identified by genome-wide association studies on COPD, lung function, and related complications. Assembling resources, integrative genomic approaches, and large sample sizes of well-phenotyped subjects is part of the path forward to elucidate the genetic basis of this debilitating disease.

Genetics of COPD

Previous family studies suggested that genetic variation contributes to COPD susceptibility. The only gene proven to influence COPD susceptibility is SERPINA1, encoding α1-antitrypsin. Most studies on COPD candidate genes except SERPINA1, have not been consistently replicated. However, longitudinal studies of decline in lung function, meta-analyses of candidate gene studies, and family-based linkage analyses suggested that variants in EPHX1, GST, MMP12, TGFB1, and SERPINE2 were associated with susceptibility to COPD. A genome-wide association (GWA) study has recently demonstrated that CHRNA3/5 in 15q25 was associated with COPD compared with control smokers. It was of interest that the CHRNA3/5 locus was associated with nicotine dependence and lung cancer as well. The associations of HHIP on 4q31 and FAM13A on 4q22 with COPD were also suggested in GWA studies. Another GWA study has shown that BICD1 in 12p11 was associated with the presence or absence of emphysema. Although every genetic study on COPD has some limitations including heterogeneity in smoking behaviors and comorbidities, it has contributed to the progress in elucidating the pathogenesis of COPD. Future studies will make us understand the mechanisms underlying the polygenic disease, leading to the development of a specific treatment for each phenotype.

Evaluation of spirometry values in relation to beta-2-adrenergic receptor gene polymorphism

Introduction

The vagus nerve plays a special role in the control of respiratory system activity which represents the parasympathetic part of the autonomic nervous system. A small bronchial innervation by the sympathetic system also is observed, and there is a significant expression of adrenergic receptors, in particular β₂ receptors, in the airways. The development of genetics and molecular biology allows for a detailed study which can clarify the essential elements in the pathogenesis of many types of lung disease, as well as the physiological phenomena - bronchial smooth muscle tone and their contractile mechanism.

Materials and methods

The study involved 148 healthy male volunteers aged 20-26. In all subjects, gene polymorphism at nucleotide position 46 and 79 of β₂-adrenergic receptor (β₂-ADR) was assessed. According to the gene polymorphism data, we divided the whole examined population of males into 6 groups for further studies. Moreover, in all the subjects, we performed spirometry testing to verify their pulmonary functions.

Results

The basic values of spirometry tests in all subjects were in the range of normal values. The frequency of different genotypes in the gene polymorphism of the β₂-adrenergic receptor at nucleotide positions 46 and 79 were typical for the Caucasian population. Analysis of the output values of spirometry, conducted in the particular groups based on their genotype, showed significant inter-group differences in the selected spirometry tests.

Conclusions

Our results may be useful in explaining the differences in the measured values of spirometric indices in healthy subjects in relation to the polymorphism of β₂-ADR, and may also contribute to the verification of standards for spirometric indices for this selected group of young males in the Polish population.

Association between beta-adrenoceptor gene polymorphisms and relative response to beta 2-agonists and anticholinergic drugs in Japanese asthmatic patients

BACKGROUND AND OBJECTIVE

Whether beta(2)-adrenoceptor gene (ADRB2) polymorphisms are associated with airway responsiveness to beta(2)-agonist medications remains controversial, partly due to factors that may confound pharmacogenetic associations, including age, cigarette smoking and airway remodelling. To overcome these problems, we performed an analysis using parameters that reflected the specific bronchodilator response to beta(2)-agonists.

METHODS

The increases in FEV(1) after inhalation of procaterol hydrochloride (Delta FEV(1) procaterol) or oxitropium bromide (Delta FEV(1) oxitropium), and after sequential inhalation of procaterol and oxitropium (total airway reversibility), were measured in 81 Japanese patients with moderate to severe asthma. Approximately 3 kb of the DNA sequence of the coding and 5'-flanking regions of ADRB2 were genotyped by direct sequencing and PCR-restriction fragment length polymorphism assay.

RESULTS

The mean age of the participants was 54 years, and 38 (47%) were smokers. Although Delta FEV(1) procaterol and Delta FEV(1) oxitropium adjusted for predicted FEV(1) were not associated with ADRB2 polymorphisms, the ratio of Delta FEV(1) procaterol to total airway reversibility was significantly associated with the ADRB2 A46G genotype (P < 0.05). Patients who were homozygous for the A46 allele (arginine at amino acid 16) were more responsive than carriers of the G46 (glycine 16) allele (P = 0.008). Multivariate linear regression analysis showed that Delta FEV(1) procaterol was correlated with the number of A46 alleles (P = 0.014), and also with total airway reversibility (P < 0.001) and smoking index in current smokers (P = 0.009).

CONCLUSIONS

The ADRB2 A46G polymorphism was associated with a relatively greater bronchodilator responsiveness to beta(2)-agonists even in elderly asthmatic patients and smokers.

Pharmacogenetics of chronic obstructive pulmonary disease: challenges and opportunities

Similar to other common chronic diseases, chronic obstructive pulmonary disease (COPD) is a heterogeneous disorder with multiple disease subtypes. Candidate gene studies have found genetic associations for COPD-related phenotypes that may be relevant for pharmacogenetics studies, including lung function decline and COPD exacerbations. However, few COPD pharmacogenetics studies have been completed. Most studies have focused on the role of variants in the beta(2)-adrenergic receptor gene on bronchodilator response, but the findings have been inconclusive. Candidate gene studies highlight the concept that genes for COPD susceptibility may also be relevant in COPD pharmacogenetics. Currently, there are no clinical applications of pharmacogenetics to COPD therapy, but the use of pharmacogenetics to determine initial smoking cessation therapy may be closer to clinical application.

Traffic-related air pollution, oxidative stress genes, and asthma (ECHRS)

BACKGROUND

Traffic-related air pollution is related with asthma, and this association may be modified by genetic factors.

OBJECTIVES

We investigated the role of genetic polymorphisms potentially modifying the association between home outdoor levels of modeled nitrogen dioxide and asthma.

METHODS

Adults from 13 cities of the second European Community Respiratory Health Survey (ECRHS II) were included (n = 2,920), for whom both DNA and outdoor NO(2) estimates were available. Home addresses were geocoded and linked to modeled outdoor NO(2) estimates, as a marker of local traffic-related pollution. We examined asthma prevalence and evaluated polymorphisms in genes involved in oxidative stress pathways [gluthatione S-transferases M1 (GSTM1), T1 (GSTT1), and P1 (GSTP1) and NAD(P)H:quinine oxidoreductase (NQO1)], inflammatory response [tumor necrosis factor alpha (TNFA)], immunologic response [Toll-like receptor 4 (TLR4)], and airway reactivity [adrenergic receptor beta2 (ADRB2)].

RESULTS

The association between modeled NO(2) and asthma prevalence was significant for carriers of the most common genotypes of NQO1 rs2917666 [odds ratio (OR) = 1.54; 95% confidence interval (CI), 1.10-2.24], TNFA rs2844484 (OR = 2.02; 95% CI, 1.30-3.27). For new-onset asthma, the effect of NO(2) was significant for the most common genotype of NQO1 rs2917666 (OR = 1.52; 95% CI, 1.09-2.16). A significant interaction was found between NQO1 rs2917666 and NO(2) for asthma prevalence (p = 0.02) and new-onset asthma (p = 0.04).

CONCLUSIONS

Genetic polymorphisms in the NQO1 gene are related to asthma susceptibility among persons exposed to local traffic-related air pollution. This points to the importance of antioxidant pathways in the protection against the effects of air pollution on asthma.

Polymorphisms of the beta2 adrenoreceptor gene in chronic obstructive pulmonary disease

BACKGROUND

The beta2-adrenergic receptors are cell surface receptors playing a central role in the pharmacological targeting asthma and chronic obstructive pulmonary disease [COPD]. Recent studies suggest that patients who are homozygous for one of the two important polymorphisms of the beta2-adrenergic receptor [ADRB2] gene at codon 16 (arginine to glycine) and 27 (glutamine to glutamate) may have a reduced response to ss2-agonists. Since smoking patients who are Gly16 homozygotes have an increased risk of airway obstruction we hypothesized that beta2-adrenoreceptor gene polymorphisms may be also a cofounder for COPD development and disease severity.

METHODS

We investigated 190 COPD patients and 172 healthy volunteers in a case-control study. DNA was isolated from whole blood and beta2-AR gene polymorphisms Arg/Gly16 and Gln/Glu27 were determined using allele-specific polymerase chain reaction [PCR].

RESULTS

In COPD patients with Gly/Gly16 was found more frequently than in healthy smokers [29.47% COPD versus 18.18% controls, p = 0.026]. All other gene polymorphisms of the ADRB2 gene at codon 16 were equally distributed between groups. ss2-adrenoreceptor gene polymorphisms were neither a cofounder for COPD exacerbations [>or= 3 hospitalizations within the last 3 years] nor for disease severity [FEV1 <or= 30% predicted].

CONCLUSION

Our study suggests that the Gly16 allele of the beta2-AR gene predisposes to COPD development but not for exacerbation rates and disease severity. In contrast, Gln/Glu27 polymorphism was irrelevant in our COPD cohort.

National Emphysema Treatment Trial state of the art: genetics of emphysema

Although a hereditary contribution to emphysema has been long suspected, severe alpha1-antitrypsin deficiency remains the only conclusively proven genetic risk factor for chronic obstructive pulmonary disease (COPD). Recently, genome-wide linkage analysis has led to the identification of two promising candidate genes for COPD: TGFB1 and SERPINE2. Like multiple other COPD candidate gene associations, even these positionally identified genes have not been universally replicated across all studies. Differences in phenotype definition may contribute to nonreplication in genetic studies of heterogeneous disorders such as COPD. The use of precisely measured phenotypes, including emphysema quantification on high-resolution chest computed tomography scans, has aided in the discovery of additional genes for clinically relevant COPD-related traits. The use of computed tomography scans to assess emphysema and airway disease as well as newer genetic technologies, including gene expression microarrays and genome-wide association studies, has great potential to detect novel genes affecting COPD susceptibility, severity, and response to treatment.

Pharmacogenetics of the response to beta 2 agonist drugs: a systematic overview of the field

The response to beta2-agonist treatment shows large repeatability within individuals and may thus be determined by genetic influences. Here we present a systematic overview of the available genetic association and linkage data for beta2-agonist treatment response. Systematic searches identified 66 eligible articles, as of March 2007, pertaining either to B2AR gene polymorphisms and short-acting or long-acting beta2-agonists or to another 29 different genes. We systematize these study results according to gene, agent and type of outcomes addressed. The systematic review highlights major challenges in the field, including extreme multiplicity of analyses; lack of consensus for main phenotypes of interest; typically small sample sizes; and poor replicability of the proposed genetic variants. Future studies will benefit from standardization of analyses and outcomes, hypothesis-free genome-wide association testing platforms, potentially additional fine mapping around new discovered variants, and large-scale collaborative studies with prospective plans for replication among several teams, with transparent public recording of all data.

Phenotypes of chronic obstructive pulmonary disease

The current clinical classification of smoking-related lung disease fails to take into account the heterogeneity of chronic obstructive pulmonary disease (COPD). With an increased understanding of pathophysiologic variation, COPD now clearly represents a spectrum of overlapping diseases with important extrapulmonary consequences. A "phenotype" describes the outward physical manifestations of a particular disease, and compromises anything that is part of the observable structure, function or behavior of an individual. Such phenotypic distinctions in COPD include: frequent exacerbator, pulmonary cachectic, rapid decliner, airways hyperresponsiveness, impaired exercise tolerance, and emphysema versus airways disease. These variable manifestations, each with unique prognostic, clinical and physiologic ramifications, represent distinct phenotypes within COPD. While all of these phenotypes have smoking as a common risk factor, the other risk factors that determine these phenotypes remain poorly understood. An individual smoker has variable expression of each phenotype and there is mounting evidence that COPD phenotypes have different clinical outcomes. These phenotypes can be broadly classified into one of three groups: clinical, physiologic and radiographic. This review presents the evidence for the spectrum of COPD phenotypes with a focused discussion on the pathophysiologic, epidemiologic and clinical significance of each subtype.

Genetic predisposition to accelerated decline of lung function in COPD

Environmental exposures and genetic susceptibility can contribute to lung function decline in chronic obstructive pulmonary disease (COPD). The environmental factors are better known than the genetic factors. One of the commonest reasons of accelerated forced expiratory volume in one second (FEV1) decline in COPD is the continuation of the smoking habit. In addition, COPD patients have frequent acute respiratory infections which can also accelerate the decline of FEV1. All of the gene variants that have been reported in association with accelerated decline of lung function in COPD represent advancement because the findings generate plausible hypotheses about the possible mechanisms by which gene products could accelerate or avert FEV1 decline. Unfortunately, the results have not been consistently replicated and, animal models required to functionally assess the genetic findings, have not yet yielded sufficient data. Genome-wide association studies should provide more definitive results in COPD and other multigenic conditions. Until these studies are reported, the data to date suggest that products encoded by the alpha-1 antitrypsin, some matrix metalloproteinases, and a number of antioxidant genes are associated with accelerated FEV1 decline in COPD. Data on gene variants associated with acute exacerbations of COPD are now emerging.

Risk factors and myocardial infarction in patients with obstructive sleep apnea: impact of beta2-adrenergic receptor polymorphisms

BACKGROUND

The increased sympathetic nervous activity in patients with obstructive sleep apnea (OSA) is largely responsible for the high prevalence of arterial hypertension, and it is suggested to adversely affect triglyceride and high-density lipoprotein (HDL) cholesterol levels in these patients. The functionally relevant polymorphisms of the beta2-adrenergic receptor (Arg-47Cys/Arg16Gly and Gln27Glu) have been shown to exert modifying effects on these risk factors in previous studies, but results are inconsistent.

METHODS

We investigated a group of 429 patients (55 +/- 10.7 years; 361 men, 68 women) with moderate to severe obstructive sleep apnea (apnea/hypopnea index (AHI) 29.1 +/- 23.1/h) and, on average, a high cardiovascular risk profile (body mass index 31.1 +/- 5.6, with hypertension in 60.1%, dyslipidemia in 49.2%, and diabetes in 17.2% of patients). We typed the beta2-adrenergic receptor polymorphisms and investigated the five most frequent haplotypes for their modifying effects on OSA-induced changes in blood pressure, heart rate, and lipid levels. The prevalence of cardiovascular risk factors and coronary heart disease (n = 55, 12.8%) and survived myocardial infarction (n = 27, 6.3%) were compared between the genotypes and haplotypes.

RESULTS

Multivariate linear/logistic regressions revealed a significant and independent (from BMI, age, sex, presence of diabetes, use of antidiabetic, lipid-lowering, and antihypertensive medication) influence of AHI on daytime systolic and diastolic blood pressure, heart rate, prevalence of hypertension, and triglyceride and HDL levels. The beta2-adrenergic receptor genotypes and haplotypes showed no modifying effects on these relationships or on the prevalence of dyslipidemia, diabetes, and coronary heart disease, yet, for all three polymorphisms, heterozygous carriers had a significantly lower relative risk for myocardial infarction (Arg-47Cys: n = 195, odds ratio (OR) = 0.32, P = 0.012; Arg16Gly: n = 197, OR = 0.39, P = 0.031; Gln27Glu: OR = 0.37, P = 0.023). Carriers of the most frequent haplotype (n = 113) (haplotype 1; heterozygous for all three polymorphisms) showed a five-fold lower prevalence of survived myocardial infarction (OR = 0.21, P = 0.023).

CONCLUSION

Our study showed no significant modifying effect of the functionally relevant beta2-adrenergic receptor polymorphisms on OSA-induced blood pressure, heart rate, or lipid changes. Nevertheless, heterozygosity of these polymorphisms is associated with a lower prevalence of survived myocardial infarction in this group with, on average, a high cardiovascular risk profile.

Beta2-adrenergic receptor polymorphisms are associated with asthma and COPD in adults

The beta(2)-adrenergic receptor (beta(2)AR) is a transmembrane protein expressed by airway smooth muscle cells. In vitro studies have shown that polymorphisms at amino acid positions 16 and 27 alter receptor function. The aim of this study was to examine the associations between the beta ( 2 ) AR polymorphisms and risks of asthma, chronic obstructive pulmonary disease (COPD) and respiratory symptoms in a sample of adults. Participants were part of a cross-sectional population-based study of risk factors for respiratory disease. A total of 1,090 Caucasian participants completed a detailed respiratory questionnaire, spirometry, methacholine challenge and measurement of gas transfer. Genotyping for beta ( 2 ) AR polymorphisms at positions 16 and 27 was performed using the tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) method. Haplotype frequencies for the two polymorphisms were estimated using the E-M algorithm. We found the Arg16 homozygotes had an increased risk of COPD (OR 5.13; 95% CI 1.40,18.8), asthma (2.44; 1.12,5.31) and symptoms of wheeze (1.84; 1.02,3.35). The Gln27 homozygotes had an increased risk of asthma (2.08; 1.05,4.13) and bronchial hyperreactivity (BHR) (1.92; 1.07,3.46). The Arg16/Gln27 haplotype was associated with asthma (1.63; 1.12,2.38) and COPD (2.91; 1.42,5.94). The Arg16/Gln27 beta(2)AR haplotype is important in COPD, asthma and BHR, and may be associated with more severe respiratory symptoms in middle-aged and older adults.

Gene therapy for chronic obstructive pulmonary disease: twilight or triumph?

Chronic obstructive pulmonary disease (COPD) is a clinical syndrome presenting as progressive airflow limitation that is poorly reversible as a result of bronchitis and emphysema. The prevalence of COPD is alarming and even more so its current and projected impact on morbidity and mortality. To date, there are no effective treatments for emphysema, nor are there efficient clinical management strategies. Existing and prospective therapies, although promising, have yet to demonstrate their efficacy to slow, halt or reverse the disease. Novel approaches using gene therapy and stem cell technologies may offer new opportunities. However, this will remain almost entirely dependent on a more thorough understanding of the pathogenesis of COPD. This review is not aimed at highlighting the vast effort of studying COPD, but rather describing the state of the field in an abstract fashion to expose the focus of research efforts to date, which has primarily been limited to predisposing factors and inflammation. We would like to draw attention to other elements of the disease, such as the alveolar remodelling that characterises emphysema. Although the main cause may prove to be elusive, carefully designed clinical treatment and management may deliver the required therapeutic outcome.

Asthma pharmacogenomics

It is expected that future treatments will be preceded by genetic tests to prescribe the most effect asthma medication while lowering the risk of adverse side effects. However, it will not be necessary to describe all the genetic determinants affecting drug response to apply pharmacogenomics to asthma therapy. Whether pharmacogenomics becomes common practice may not depend on the availability of tests, but on factors such as affordability, ease of application, and ease of interpreting the results.

Beta-adrenoceptor responses of the airways: for better or worse?

Beta2-adrenoceptor agonists are the first-line treatment of asthma and chronic obstructive pulmonary disease (COPD), in which a short-acting beta2-adrenoceptor agonist is used as required for relief of bronchoconstriction. A long-acting beta2-adrenoceptor agonist may be added to an inhaled corticosteroid as step 3 in the management of chronic asthma. Long-acting beta2-adrenoceptor agonists may also be added in treatment of COPD. This review examines the beneficial and detrimental effects of beta2-adrenoceptor agonists. The beneficial effects of beta2-adrenoceptor agonists are mainly derived from their bronchodilator activity which relieves the bronchiolar narrowing and improves air flow. The potential anti-inflammatory actions of stabilizing mast cell degranulation and release of inflammatory and bronchoconstrictor mediators, is considered. Other potential beneficial responses include improvements in mucociliary clearance and inhibition of extravasation of plasma proteins that is involved in oedema formation in asthma. The side effects of beta2-adrenoceptor agonists are primarily related to beta2-adrenoceptor-mediated responses at sites outside the airways. Of major concern has been the development of tolerance and this is discussed in relation to incidence of increased morbidity and mortality to asthma over the past three decades. A clinical aspect of beta2-adrenoceptor pharmacology in recent years has been the recognition of genetic polymorphism of the receptor and how this affects responses to and tolerance to beta2-adrenoceptor agonists. A controversial feature of beta2-adrenoceptor agonists is their stereoisomerism and whether the inactive (S)-isomer of salbutamol had detrimental actions in the commercially used racemate. The consensus is that despite these adverse properties, beta2-adrenoceptor agonist remains the most useful pharmacological agents in the management of asthma and COPD.

Laboratory markers for COPD in “susceptible” smokers

Smoking is the major risk factor for the development of chronic obstructive pulmonary disease. Apart from the important preventive steps of smoking cessation, there are no other specific treatments for COPD that are as effective in reversing the condition. However, only a relatively small proportion of smokers-about 15%-will develop clinically relevant COPD. Allergy, airway hyper-responsiveness (AHR) to methacholine, and gender differences have been proposed to identify individuals susceptible to the development of COPD. However, variable response to cigarette smoke clearly suggests genetic susceptibility. Among the COPD candidate genes are those (a) that effect the production of proteases and antiproteases, (b) modulate the metabolism of toxic substances in cigarette smoke, (c) are involved with mucocilliary clearance, and (d) that influence inflammatory mediators. Recently, sputum cells from smokers with and without COPD were tested for Microsatellite DNA Instability (MSI) with positive results. This finding suggests that MSI can be a useful marker of genetic susceptibility and thereby indicate destabilization of the genome in the "susceptible" smoker. Nevertheless, COPD lacks established viable biomarkers to predict and monitor disease progression and outcome variables. Such monitoring tools may be induced sputum, exhaled air condensate, peripheral blood, urine, bronchial biopsies, and bronchoalveolar lavage fluid (BALF). This review summarizes recent research on potential laboratory markers in smokers and subsequent COPD development.

Genetics and the Dutch Hypothesis

BACKGROUND

Increasingly, molecular genetic techniques are being used to improve our understanding of a number of common late onset complex disorders, such as hypertension, Alzheimer's disease and noninsulin dependent diabetes mellitus. Molecular genetic approaches have the potential to yield new information about disease pathogenesis that may be of great importance for the development of future treatments.

AIMS

This review discusses the evidence for a genetic contribution to the development of chronic obstructive pulmonary disease (COPD) and specifically focuses on the hypothesis that asthma and COPD share some pathogenic mechanisms as originally proposed in 1960 in a theory that has since become known as the Dutch Hypothesis. In particular we will review the evidence from molecular genetics, both in support of and against the theory.

Tachyphylaxis to beta2-agonists in Spanish asthmatic patients could be modulated by beta2-adrenoceptor gene polymorphisms

BACKGROUND

The study of determinants of asthma is a subject of much interest currently, especially the pharmacogenetic aspects of asthma management. Genetic polymorphisms affecting amino-acids at positions 16 and 27 within beta(2)-adrenoceptor (beta(2)AR) gene have been implicated in the asthma phenotypes and influence on the variability observed in response to use of bronchodilator agents used in the treatment of asthma. Whether these polymorphisms alter the bronchoprotection response to beta(2)-agonist treatment in Spanish asthmatic population is unknown. The aim of this study was to investigate whether genetic polymorphisms within beta(2)AR gene modulate the clinical outcomes of the individual response to beta(2)-agonist therapy and the development of desensitization in Spanish asthmatic patients.

METHODS

In a prospective, case-control study were included 80 asthmatic patients. Based on the standard criteria, patients were classified into two groups: patients with tachyphylaxis and good responders to beta(2)-agonist therapy. DNA samples were genotyped for the Arg(16)Gly and Glu(27)Gln alleles within the beta(2)AR gene as well as in 64 control samples from blood donors.

RESULTS

Arg(16) allele was slightly more frequent within the group with tachyphylaxis (P=0.039), whereas Gly(16) allele carriers were overrepresented within the group of good responders (59.7%, P=0.028). On the other hand, the allele frequency of Gln(27) and the proportion of Gln(27) carriers was higher within the group with tachyphylaxis (P=0.010 and 0.049, respectively) and Glu(27) allele carriers were overrepresented within the group of good responders (P=0.026). The Arg(16) and Gln(27) alleles were in strong linkage disequilibrium across this locus, resulting in the occurrence of disease haplotype.

CONCLUSIONS

The predisposition to develop tachyphylaxis in our population seems to be linked to the Arg(16) and Gln(27) alleles and to the Arg(16)/Gln(27) risk haplotype (positive association between the presence of the Arg(16) and Gln(27) alleles and tachyphylaxis). The Arg(16) allele is perhaps overrepresented due to the strong linkage disequilibrium between both polymorphisms. The presence of the Glu(27) allele seems to be a protective factor against tachyphylaxis in this cohort study.

Bronchodilator response in relation to beta2-adrenoceptor haplotype in patients with asthma

RATIONALE

Genetic variation of the beta2-adrenoceptor (ADRB2) influences receptor function in vitro. There are reports that, in vivo, bronchodilator response is related to ADRB2 genotype, and that clinical outcomes during chronic therapy with beta2-agonist drugs are also influenced by genotype. Whether these features are related to single nucleotide polymorphisms or to combinations (haplotypes) is unclear.

OBJECTIVES

Our aim was to measure bronchodilator response in patients with asthma stratified by ADRB2 haplotype. This was done after eliminating the confounding effect of prior drug treatment with inhaled beta2-agonists and corticosteroids.

METHODS

ADRB2 haplotype was determined in 176 patients with asthma, of whom 161 harbored the six most common combinations. Treatment with inhaled beta2-agonists and inhaled corticosteroids was withheld for appropriate intervals. Spirometric changes 20 minutes after a single dose of albuterol (2.5 mg by nebulizer) were then recorded.

RESULTS

There were no significant differences in bronchodilator response (% improvement in FEV(1)) with respect to any of the major ADRB2 haplotypes or genotypes.

CONCLUSIONS

Genetic variation of the ADRB2 does not influence the immediate response to inhaled beta2-agonist. The confounding effect of tolerance resulting from regular beta2-agonist use must be controlled when assessing the pharmacogenetic influences on clinical outcomes with beta2-agonists.

The role of environmental tobacco smoke in genetic susceptibility to asthma

PURPOSE OF REVIEW

The increase in asthma prevalence over the past 50 years suggests that exposures to environmental risk factors have also increased during this time. Environmental tobacco smoke is one of the most common indoor air pollutants and has been associated in epidemiologic studies with airway and allergic phenotypes in exposed individuals. However, symptoms occur in only some individuals, suggesting that individual genotypes determine sensitivity to environmental tobacco smoke exposure. In this review, we summarize studies evaluating the relationship between genotype, environmental tobacco smoke exposure and risk for asthma and related phenotypes.

RECENT FINDINGS

Using either candidate gene or genome-wide approaches, a number of studies have examined interactions between genotypes at specific loci or genome regions and environmental tobacco smoke exposure and risk for asthma or asthma-associated phenotypes. These studies implicate variation in the genes encoding the alpha(2)-adrenergic receptor, interleukin-10, glutathione S-transferase M1, interleukin-1 beta and interleukin-1 receptor antagonist, matrix metalloproteinases 1 and 12, interleukin-4 receptor alpha-chain, alpha(1)-antitrypsin, and microsomal epoxide hydrolase, as well as unknown genes on chromosomes 1p, 5q and 17p as contributing toward susceptibility in smoking exposed individuals.

SUMMARY

Considering environmental tobacco smoke exposure in genetic studies may help to identify more homogeneous subsets of patients that share a common disease etiology. By stratifying samples by environmental tobacco smoke exposure, associations or linkages with specific polymorphisms or chromosomal region may be revealed, as illustrated in the studies discussed in this review.

Polymorphisms of IL4, IL13, and ADRB2 genes in COPD

STUDY OBJECTIVES

Interleukin (IL)-4, IL-13, and beta(2)-adrenoceptor (ADRB2) are involved in airway hyperresponsiveness (AHR), and their coding genes are located on chromosome 5q31-q33. AHR is one of the risk factors for COPD. Investigating polymorphisms within these genes may help to pinpoint the genetic susceptibility to COPD.

SUBJECTS AND MEASUREMENTS

A case-control association study was conducted on two different ethnic groups: Japanese subjects (88 patients with COPD and 61 control subjects) and Egyptian subjects (106 patients with COPD and 72 control subjects). The following polymorphisms were genotyped: - 589 C/T, - 33 C/T, and variable number of tandem repeat (VNTR) in IL4, - 1111 C/T and + 2044 G/A in IL13, and + 46 A/G and + 79 C/G in ADRB2. Pairwise haplotype frequencies as well as genotype and allele frequencies were analyzed.

RESULTS

The distribution of the genotype frequencies of ADRB2 + 79 C/G was significantly different between the COPD and the control groups in the Egyptians (p = 0.002). The distributions of the haplotypes in the Japanese (IL4 - 589 C/T: IL4 VNTR; IL4 - 33 C/T: IL4 VNTR) [corrected p values < 0.001 and 0.022, respectively], and those in the Egyptians (IL4 - 589 C/T: ADRB2 + 79 C/G; IL4 VNTR: ADRB2 + 79 C/G) [corrected p values, 0.033 and 0.001, respectively] showed significant differences between the COPD and the control groups.

CONCLUSIONS

The ADRB2 + 79 C/G polymorphism and the haplotypes shown in this study may be involved in the pathogenesis of COPD.

Genetics of COPD

COPD is a complex mix of signs and symptoms in patients with chronic bronchitis and emphysema, diseases that largely result from cigarette smoking. Not all smokers, however, acquire COPD, and COPD can develop in nonsmokers. In the United States, COPD is currently the fourth leading cause of death. Surprisingly, there are no effective drug therapies for COPD that are able to significantly alter disease progression, and little is known of the underlying molecular mechanisms that are responsible for its occurrence. Candidate gene-association studies and linkage analyses have been reported for COPD patients. This review describes the genetic predisposition of healthy subjects or relatives of COPD patients to acquire COPD. In addition, the genetic bases of COPD with rapid decline of FEV1 are described, and the current genetic data that have been distilled from studies of COPD patients with a predominant emphysema phenotype, with chronic bronchitis phenotype, and with a response to bronchodilators are discussed.