Polymorphisms in the beta2-adrenoreceptor gene are associated with decreased airway responsiveness

β2 Agonists

History suggests β agonists, the cognate ligand of the β₂ adrenoceptor, have been used as bronchodilators for around 5,000 years, and β agonists remain today the frontline treatment for asthma and chronic obstructive pulmonary disease (COPD). The β agonists used clinically today are the products of significant expenditure and over 100 year's intensive research aimed at minimizing side effects and enhancing therapeutic usefulness. The respiratory physician now has a therapeutic toolbox of long acting β agonists to prophylactically manage bronchoconstriction, and short acting β agonists to relieve acute exacerbations. Despite constituting the cornerstone of asthma and COPD therapy, these drugs are not perfect; significant safety issues have led to a black box warning advising that long acting β agonists should not be used alone in patients with asthma. In addition there are a significant proportion of patients whose asthma remains uncontrolled. In this chapter we discuss the evolution of β agonist use and how the understanding of β agonist actions on their principal target tissue, airway smooth muscle, has led to greater understanding of how these drugs can be further modified and improved in the future. Research into the genetics of the β₂ adrenoceptor will also be discussed, as will the implications of individual DNA profiles on the clinical outcomes of β agonist use (pharmacogenetics). Finally we comment on what the future may hold for the use of β agonists in respiratory disease.

Frequencies of the Arg16Gly, Gln27Glu and Thr164Ile Adrenoceptor β2 Polymorphisms among Omanis

OBJECTIVES

This study aimed to assess the distribution of missense mutations in the adrenoceptor β2 (ADRB2) gene in an Omani cohort.

METHODS

This study was carried out between May 2014 and March 2015 at the Sultan Qaboos University, Muscat, Oman. Blood samples were taken from 316 unrelated Omani subjects. Genotyping for rs1042713 (c.46A>G, p.Arg16Gly), rs1042714 (c.79C>G, p.Gln27Glu) and rs1800888 (c.491C>T, p.Thr164Ile) polymorphisms was performed by real-time polymerase chain reaction using single nucleotide polymorphism (SNP) genotyping assays. The allelic frequencies of these polymorphisms were estimated on the basis of the observed numbers of specific alleles from the genotype data for male and female subjects. The genotype frequencies for each polymorphism were tested for deviation from the Hardy-Weinberg equilibrium.

RESULTS

Gly16 and Glu27 were the most frequent variants found among the cohort (63% and 75%, respectively). The Ile164 variant was not detected in the study population. There was a significant linkage disequilibrium between the rs1042713 and rs1042714 SNPs (r(2) = 0.209; P ≤0.001). The most observed haplotypes were Gly16-Gln27 and Arg16-Gln27 (0.37 and 0.38, respectively). The frequency of Gly16-Glu27 was 0.25, comprising all Glu27 carriers.

CONCLUSION

The allelic distribution of variants in this Omani cohort was similar to distributions reported among Caucasian populations.

Longitudinal assessment of airway responsiveness from 1 month to 18 years in the PIAF birth cohort

The Perth Infant Asthma Follow-up (PIAF) study involves a birth cohort of unselected subjects who have undergone longitudinal assessments of airway responsiveness at 1, 6 and 12 months and 6, 11 and 18 years of age. The aim of this study was to determine the relationship between increased airway responsiveness throughout childhood and asthma in early adult life.Airway responsiveness to histamine, assessed as a dose-response slope (DRS), and a respiratory questionnaire were completed at 1, 6 and 12 months and 6, 11 and 18 years of age.253 children were initially recruited and studied. Airway responsiveness was assessed in 203, 174, 147, 103, 176 and 137 children at the above-mentioned time points, respectively (39 participants being assessed on all test occasions). Asthma at 18 years was associated with increased airway responsiveness at 6, 12 and 18 years, but not during infancy (slope 0.24, 95% CI 0.06-0.42; p=0.01; slope 0.25, 95% CI 0.08-0.49; p=0.006; and slope 0.56, 95% CI 0.29-0.83; p<0.001, respectively).Increased airway responsiveness and its association with asthma at age 18 years is established between infancy and 6 years. We propose that airway responsiveness in early life reflects the initial airway geometry and airway responsiveness later in childhood increasingly reflects immunological responses to environmental influences.

Association of β(2)-adrenergic receptor polymorphisms with asthma in a North Indian population

BACKGROUND

β(2)-Adrenergic receptor (β(2)AR), a G-protein coupled receptor, is present on the bronchial smooth muscle cells and results in bronchodilation upon activation. The genetic factors determining β(2)AR expression and function may not only alter the response of an individual to the therapy but also may serve as predictive markers for response to the agonists used in the therapy. The present study aimed at evaluating the role of β(2)AR-16 and β(2)AR-27 gene polymorphisms in asthma.

METHODS

A case-control study was performed with a total of 824 adult subjects, including 410 asthmatics and 414 healthy controls from regions of North India. The β(2)AR-16 and β(2)AR-27 polymorphisms were genotyped by PCR-RFLP.

RESULTS

Statistical analysis for the β(2)AR-16 polymorphism revealed that the mutant Gly16 allele was significantly associated with asthma, with OR = 0.80, 95 % CI = 0.65-0.99, and P = 0.032. The Gly16/Gly16 mutant genotype also confers decreased risk toward asthma, with OR = 0.65, 95 % CI = 0.41-1.02, and P = 0.049. However, the β(2)AR-27 polymorphism was not associated with asthma as it did not reach statistical significance, with OR = 0.86, 95 % CI = 0.69-1.07, and P = 0.163.

CONCLUSION

The β(2)AR-16 polymorphism confers a decreased risk toward asthma while the β(2)AR-27 polymorphism is not associated with asthma in the studied North Indian population.

Evidence for genetic susceptibility to developing early childhood diarrhea among shantytown children living in northeastern Brazil

To explore the genetic components of susceptibility to early childhood diarrhea (ECD), we used a quantitative genetic approach to estimate the heritability of ECD among children from two Brazilian favelas. Shared environment was used to model common exposure to environmental factors. Genetic relatedness was determined from pedigree information collected by screening household participants (n = 3,267) from two geographically related favelas located in Fortaleza, Brazil. There were 277 children within these pedigrees for whom diarrheal episodes in the first two years of life were recorded. Data on environmental exposure and pedigree relationship were combined to quantitatively partition phenotypic variance in ECD into environmental and genetic components by using a variance components approach as implemented in Sequential Oligogenic Linkage Analysis Routines program. Heritability accounted for 54% of variance in ECD and proximity of residence effect accounted for 21% (P < 0.0001). These findings suggest a substantial genetic component to ECD susceptibility and the potential importance of future genetics studies.

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.

beta(2)-adrenergic receptor promoter haplotype influences spirometric response during an acute asthma exacerbation

Genetic variants in the beta(2)-adrenergic receptor (ADRB2) coding block have been associated with different parameters of asthma severity, but there is no consensus on which variants are most important. Our objective was to determine whether the genetic variants in the 5'- or 3'-flanking regions of ADRB2 impact the response to therapy. DNA was obtained initially from 72 adults hospitalized for an asthma exacerbation. We sequenced a 5,000 bp region of the ADRB2 gene that spanned the flanking regions and identified 31 single nucleotide polymorphisms (SNPs). Nonresponders to asthma therapy were defined as patients whose forced expiratory volume in 1 second (FEV(1)) worsened by >10% at 24 hours after admission. We then evaluated the relationship between the 19 common SNPs and response to asthma-specific therapy during acute disease exacerbations. Our results showed a significant association between nonresponders and a haplotype of five promoter SNPs in a nearly complete linkage disequilibrium. An analysis of the promoter and coding block polymorphisms in an extended cohort of 99 patients confirmed that promoter haplotype was the genetic component most strongly associated with asthmatic nonresponders, which was statistically significant among whites (p < 0.05). An identification of this promoter haplotype may provide an alternate explanation for the variation in the asthma responses observed with ADRB2 coding block polymorphisms.

Associations of beta2-adrenergic receptor genotypes and haplotypes with wheezing illness in Taiwanese schoolchildren

BACKGROUND

Increasing attention was focused on the beta2-adrenergic receptor gene (ADRB2), whose genetic variability has been implicated as a risk factor for asthma-related phenotypes. However, only a few studies reported the associations by utilizing haplotypic approaches. We therefore examined the relationship of childhood wheezing illness with polymorphisms at codons 16 and 27, and evaluated the influence of polymorphisms individually and in combination as haplotypes.

METHODS

We conducted a genetic case-control study comprising 215 wheezing children and 183 nonwheezing controls, all of whom were selected from 2524 fourth- to ninth-grade schoolchildren in southern Taiwan.

RESULTS

All participants were homozygous at the ADRB2 Thr164 locus. After controlling for possible confounders, ADRB2 Glu27 allele was significantly associated with wheezing illness in all genetic models, but the risks on Arg16Gly genotypes were inconclusive. Estimated frequencies for the three main hyplotypes were Arg16/Gln27 57.2%, Gly16/Gln27 35.3%, Gly16/Glu27 7.4% in wheezing children, and Arg16/Gln27 56.3%, Gly16/Gln27 32.2%, Gly16/Glu27 10.4% in controls. The protective effect of Gly16/Glu27 haplotype remained relative to all other ADRB2 haplotypes [adjusted relative risk (aRR) = 0.58; 95% confidence interval (CI) 0.35-0.97]. As compared with children without Gly16/Glu27 haplotype, those with Gly16/Glu27 haplotype had a significantly lower risk for wheezing illness (aRR = 0.56; 95% CI 0.33-0.99). The copy numbers of Gly16/Glu27 haplotype also showed a clear dose-response relationship on the decreased risks. No significant association was found with the prevalence of wheezing illness for other haplotypes.

CONCLUSION

We concluded that ADRB2 Glu27 allele and Gly16/Glu27 haplotype were significantly protective factors for wheezing illness in Taiwanese schoolchildren.

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.

Beta2-adrenoceptor polymorphisms predict response to beta2-agonists in children with acute asthma

The aim of this study was to determine the influence of single nucleotide polymorphisms in the beta(2)-adrenoceptor gene, on the response to inhaled beta(2)-agonists in children with acute asthma. We hypothesised that children with polymorphisms that generate enhanced receptor downregulation in vitro, Gly16 and Gln27, would have a slower response to beta(2)-agonist therapy during acute asthma. One hundred and forty-eight children with acute asthma were recruited and genotyped for beta(2)Arg16Gly and beta(2)Gln27Glu. For Gln27Glu, individuals Gln27Gln took longest to stretch out to 1, 2 and 4 hourly beta(2)-agonists, followed by heterozygotes who were intermediate and Glu27Glu who responded most rapidly (1 hourly: 2.6 hr vs. 2.0 vs. 1.4, p = 0.02; 2 hourly: 10.6 hr vs. 10.7 vs. 6.8, p = 0.07; 4 hourly: 29.8 hr vs. 28.5 vs. 24.3, p = 0.30). The ability to prospectively identify children who respond less effectively to beta (2)-agonists during an acute asthma attack has the potential to allow the generation of genotype-specific treatment pathways.

Effects of in utero and childhood tobacco smoke exposure and beta2-adrenergic receptor genotype on childhood asthma and wheezing

OBJECTIVE

Associations between single-nucleotide polymorphisms in the beta2-adrenergic receptor gene and asthma and wheeze have been inconsistent. Recent studies indicated that tobacco smoke affects beta2-adrenergic receptor gene expression and associations of beta2-adrenergic receptor gene variants with asthma in adults. We aimed to investigate the joint effects of in utero and childhood secondhand tobacco smoke exposure and 2 well-characterized functional single-nucleotide polymorphisms (Arg16Gly and Glu27Gln) of beta2-adrenergic receptor gene on asthma and wheezing in 3128 non-Hispanic and Hispanic white children of the Children's Health Study.

METHODS

We fitted logistic regression models to estimate odds ratios and 95% confidence intervals for the independent and joint effects of these single-nucleotide polymorphisms and in utero and secondhand tobacco smoke exposure on asthma and wheeze outcomes.

RESULTS

Exposures to in utero maternal smoking and secondhand tobacco smoke were associated with wheezing. Children who were homozygous for the Arg16 allele and were exposed to maternal smoking in utero were at a threefold increased risk for lifetime wheeze compared with children who were unexposed and had at least 1 Gly16 allele. We found similar joint effects of secondhand tobacco smoke and Arg16Gly with wheezing. The risk for lifetime, current, and nocturnal wheeze increased with the number of smokers at home among Arg16 homozygous children. The results were consistent in 2 cohorts of children recruited in 1993 and 1996. Diplotype-based analyses were consistent with the single-nucleotide polymorphism-specific results. No associations were found for Glu27Gln.

CONCLUSIONS

Both in utero and childhood exposure to tobacco smoke were associated with an increased risk for wheeze in children, and the risks were greater for children with the Arg16Arg genotype or 2 copies of the Arg16-Gln27 diplotype. Exposures to smoking need to be taken into account when evaluating the effects of beta2-adrenergic receptor gene variants on respiratory health outcomes.

Enteric infections, diarrhea, and their impact on function and development

Enteric infections, with or without overt diarrhea, have profound effects on intestinal absorption, nutrition, and childhood development as well as on global mortality. Oral rehydration therapy has reduced the number of deaths from dehydration caused by infection with an enteric pathogen, but it has not changed the morbidity caused by such infections. This Review focuses on the interactions between enteric pathogens and human genetic determinants that alter intestinal function and inflammation and profoundly impair human health and development. We also discuss specific implications for novel approaches to interventions that are now opened by our rapidly growing molecular understanding.

Clinical consequences of ADRbeta2 polymorphisms

The most prescribed medication for controlling bronchoconstriction associated with asthma and chronic obstructive pulmonary disease are beta-agonists. The gene ADRbeta2 encodes the beta-2-adrenergic receptor and contains several common genetic variations that affect gene expression and receptor function in vitro. The ADRbeta2 variations Gly(16)Arg and Gln(27)Glu and, more recently, haplotypic variations, have been the focus of numerous pharmacogenetic studies looking at responses to short-acting (SABA) and long-acting beta-agonists (LABA) in subjects with asthma. Thus far, a consensus on the effects of ADRbeta2 genetic variations has not been reached, although there does appear to be a reproducible adverse effect in subjects homozygous for Arg(16) that are regularly treated with SABAs. The complexity of the genotype by response effects observed makes clinical application of ADRbeta2 genetic variations limited, and may require the use of detailed haplotypic variation to fully understand the role ADRbeta2 plays in regulating beta-agonist response.

Pharmacogenetics of the beta 2-adrenergic receptor gene

Asthma is a complex genetic disease with multiple genetic and environmental determinants contributing to the observed variability in response to common antiasthma therapies. One focus of asthma pharmacogenetic research has been the beta2-adrenergic receptor gene (ADR beta 2) and its effect on individual responses to beta agonist therapy. Knowledge about the effects of ADR beta 2 variation on therapeutic responses is evolving and should not alter current Asthma Guideline approaches, which consist of the use of short-acting beta agonists (SABAs) for as-needed symptom-based therapy and the use of a regular long-acting beta agonist (LABA) in combination with inhaled corticosteroid therapy for those asthmatics whose symptoms are not controlled by inhaled corticosteroid alone. These approaches are based upon studies showing a consistent pharmacogenetic response to regular use of SABAs and less consistent findings in studies evaluating LABAs. The emerging pharmacogenetic studies are provocative and should lead to functional studies. Meanwhile, the conflicting data concerning LABAs may be caused by such factors as small sample sizes of study populations and differences in experimental design.

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.

Adrenergic Receptor Genotype but Not Perioperative Bisoprolol Therapy May Determine Cardiovascular Outcome in At-risk Patients Undergoing Surgery with Spinal Block

Background:

Neuraxial blockade is used as primary anesthetic technique in one third of surgical procedures. The authors tested whether bisoprolol would protect patients at risk for cardiovascular complications undergoing surgery with spinal block.

Methods:

The authors performed a double-blinded, placebo-controlled, multicenter trial to compare the effect of bisoprolol with that of placebo on 1-yr composite outcome including cardiovascular mortality, nonfatal myocardial infarction, unstable angina, congestive heart failure, and cerebrovascular insult. Bisoprolol was given orally before and after surgery for a maximum of 10 days. Adrenergic receptor polymorphisms and safety outcome measures of bisoprolol therapy were also determined.

Results:

A total of 224 patients were enrolled. Spinal block could not be established in 5 patients. One hundred ten patients were assigned to the bisoprolol group, and 109 patients were assigned to the placebo group. The mean duration of treatment was 4.9 days in the bisoprolol group and 5.1 days in the placebo group. Bisoprolol therapy reduced mean heart rate by 10 beats/min. The primary outcome was identical between treatment groups and occurred in 25 patients (22.7%) in the bisoprolol group and 24 patients (22.0%) in the placebo group during the 1-yr follow-up (hazard ratio, 0.97; 95% confidence interval, 0.55–1.69; P = 0.90). However, carriers of at least one Gly allele of the β1-adrenergic receptor polymorphism Arg389Gly showed a higher number of adverse events than Arg homozygous (32.4% vs. 18.7%; hazard ratio, 1.87; 95% confidence interval, 1.04–3.35; P = 0.04).

Conclusions:

Perioperative bisoprolol therapy did not affect cardiovascular outcome in these elderly at-risk patients undergoing surgery with spinal block.

ADRB2 Arg16Gly polymorphism, lung function, and mortality: results from the Atherosclerosis Risk in Communities study

BACKGROUND

Growing evidence suggests that the Arg16Arg genotype of the beta-2 adrenergic receptor gene may be associated with adverse effects of beta-agonist therapy. We sought to examine the association of beta-agonist use and the Arg16Gly polymorphism with lung function and mortality among participants in the Atherosclerosis Risk in Communities study.

METHODOLOGY AND PRINCIPAL FINDINGS

We genotyped study participants and analyzed the association of the Arg16Gly polymorphism and beta-agonist use with lung function at baseline and clinical examination three years later and with all-cause mortality during 10 years of follow-up. Lung function was characterized by percent-predicted forced expiratory volume in 1 second. Associations were examined separately for blacks and whites. Black beta-agonist users with the Arg/Arg genotype had better lung function at baseline and at the second clinical visit than those with Arg/Gly and Gly/Gly genotypes. Adjusted mean percent-predicted FEV(1) was 21% higher in Arg/Arg subjects compared to Gly/Gly at baseline (p = 0.01) and 20% higher than Gly/Gly at visit 2 (p = 0.01). Arg/Gly subjects had adjusted percent-predicted FEV(1) 17% lower than Arg/Arg at baseline but were similar to Arg/Arg subjects at visit 2. Although black beta-agonist users with the Arg/Arg genotype appeared to have better crude survival rates, the association between genotype and all-cause mortality was inconclusive. We found no difference in lung function or mortality by genotype among blacks who did not use beta-agonists or among whites, regardless of beta-agonist use.

CONCLUSIONS

Black beta-agonist users with the ADRB2 Arg16Arg genotype had better lung function, and, possibly, better overall survival compared to black beta-agonist users with the Gly16Gly genotype. Our findings highlight the need for additional studies of sufficient size and statistical power to allow examination of outcomes among beta-agonist users of different races and genotypes.

Nocturnal asthma

PURPOSE OF REVIEW

To examine recent advancements of the epidemiology, pathophysiology, and treatment of nocturnal asthma.

RECENT FINDINGS

In a large cross-sectional survey, the prevalence of nocturnal symptoms was 60%. Forty-two percent of patients who completed the study did not declare nocturnal symptoms that were detected by physicians. A recent study including 47 individuals with nocturnal and nonnocturnal asthma showed that allele genotype Gly16 was significantly higher in the nocturnal asthma group (72%) compared with the nonnocturnal asthma group (54%). A randomized double-blind study of nocturnal asthma with esomeprazole improved the peak expiratory flow rate in individuals with both nocturnal asthma and gastroesophageal reflux disease. Of patients with nocturnal asthma and snoring, 48% had obstructive sleep apnea. After continuous positive airway pressure treatment, there was significant improvement of asthma nighttime symptom scores; however, no significant difference in lung functions was observed.

SUMMARY

Nocturnal symptoms in asthma are frequently underdiagnosed. Obstructive sleep apnea may be prevalent in nocturnal asthma. The Gly16 polymorphism of the beta2-receptor is common in nocturnal asthma. Gastric suppression treatment in patients with both gastroesophageal reflux disease and nocturnal asthma improved the peak expiratory flow rate. Continuous positive airway pressure improves nocturnal symptoms but not lung function tests.

Microarray profiling of lymphocytes in internal diseases with an altered immune response: potential and methodology

Recently it has become possible to investigate expression of all human genes with microarray technique. The authors provide arguments to consider peripheral white blood cells and in particular lymphocytes as a model for the investigation of pathophysiology of asthma, RA, and SLE diseases in which inflammation is a major component. Lymphocytes are an alternative to tissue biopsies that are most often difficult to collect systematically. Lymphocytes express more than 75% of the human genome, and, being an important part of the immune system, they play a central role in the pathogenesis of asthma, RA, and SLE. Here we review alterations of gene expression in lymphocytes and methodological aspects of the microarray technique in these diseases. Lymphocytic genes may become activated because of a general nonspecific versus disease-specific mechanism. The authors suppose that in these diseases microarray profiles of gene expression in lymphocytes can be disease specific, rather than inflammation specific. Some potentials and pitfalls of the array technologies are discussed. Optimal clinical designs aimed to identify disease-specific genes are proposed. Lymphocytes can be explored for research, diagnostic, and possible treatment purposes in these diseases, but their precise value should be clarified in future investigation.

Association of haplotypes of beta2-adrenoceptor polymorphisms with lung function and airway responsiveness in a pediatric cohort

We evaluated the influence of haplotypes of beta(2)-adrenergic receptor (ADRB2) polymorphisms on lung function and airway responsiveness (AR) in a pediatric cohort recruited before birth and followed up to 11 years of age. The subjects (180) were the participants in a prospective study of lung function and AR. They have been assessed five times (at 1 month, 6 months, 12 months, 6 and 11 years of age) for lung function and AR. The two ADRB2 single nucleotide polymorphisms (SNPs): Arg16Gly and Gln27Glu were genotyped by PCR-RLFP and their haplotypes inferred using the program PHASE. An association between the haplotype arg16gln27 and the prevalence of positive AR was found at age 6 years (P = 0.009). The gly16gln27 haplotype was associated with higher FEV1 (P = 0.015) at age 6 and both higher FEV1 and FVC (P = 0.018 and P = 0.001, respectively) at age 11. In contrast, arg16gln27 was associated with both lower FEV1 and FVC (P = 0.028 and P = 0.011, respectively) at age 11. Children with the gly16gln27 haplotype were less likely to have asthma-ever or doctor-diagnosed asthma at age 11 (OR: 0.38; P = 0.019 and OR: 0.31; P = 0.041, respectively). In conclusion, haplotypes of beta(2)-adrenoceptor polymorphisms are associated with lung function, AR, and asthma susceptibility in childhood.

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.

Association between beta2-adrenergic receptor genetic polymorphisms and total serum IgE in asthmatic patients of Chinese Han nationality

BACKGROUND

beta(2)-Adrenergic receptor (beta(2)-AR) polymorphisms occurring at amino acid position 16 (Arg-Gly) and 27 (Gln-Glu) are known to be functionally relevant and also disease-modifying in subjects with asthma. It has been found in Caucasoid asthmatic patients that the Gln27 genotype beta(2)-AR was associated with an increase in total serum IgE levels. The association between beta(2)-AR genetic polymorphisms and total serum IgE in asthmatic patients of Chinese Han nationality remains to be established.

OBJECTIVES

It was the aim of this study to investigate the association between beta(2)-AR genetic polymorphisms and total serum IgE in asthmatic patients of Chinese Han nationality.

METHODS

All 59 asthmatic patients investigated (27 males and 32 females, aged between 16 and 60 years) were people of Chinese Han nationality. They were tested for their total serum IgE levels with the enzyme-linked immunosorbent assay test, and beta(2)-AR genetic polymorphisms were tested with the polymerase chain reaction allele-specific oligonucleotide hybridization assay.

RESULTS

There was a significant difference of serum IgE levels among three beta(2)-AR 27 loci groups (p < 0.0001), with the highest IgE level [(1.24 +/- 0.25) x 10(6) IU/l] in the Gln/Gln group and the lowest IgE level [(0.48 +/- 0.06) x 10(6) IU/l] in the Glu/Glu group. No polymorphism of beta(2)-AR 16 loci was found to be associated with total serum IgE (p > 0.05).

CONCLUSIONS

Our research suggested that in asthmatic patients of Chinese Han nationality, the beta(2)-AR genetic polymorphism at 27 loci could be associated with serum IgE levels and it might therefore play an important role in the determination of phenotypes of bronchial asthma.

The C523A beta2 adrenergic receptor polymorphism associates with markers of asthma severity in African Americans

Our goal was to explore associations between ss2 adrenergic receptor polymorphisms and markers of asthma severity in African American and Caucasian patients with asthma. Polymorphisms at loci -1023, -654, -47, 46, 79, 491, and 523 were genotyped and haplotypes were imputed in 143 African Americans and 336 Caucasians. C523A genotype associated with percentage of African Americans (but not of Caucasians) having an asthma exacerbation: AA, AC, and CC genotypes were 17, 29, and 40%, respectively (p = 0.018). Symptom scores, pulmonary function, and rescue inhaler use paralleled exacerbation prevalence. We conclude the 523 A allele modifies asthma severity in African Americans.

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.

The effect of beta2-adrenoceptor haplotypes on bronchial hyper-responsiveness in patients with asthma

BACKGROUND

The beta2-adrenoceptor exhibits genetic polymorphism which may be clinically relevant in terms of treatment response or bronchial hyper-responsiveness (BHR). The combined effect of these genotypes, or the haplotype, has not been fully characterized in terms of BHR.

METHODS

We performed a retrospective analysis of the effects of haplotypes of amino acid substitution at position 16 (Gly/Arg) and position 27 (Gln/Glu) on spirometry and BHR to methacholine and adenosine monophosphate (AMP) in 594 asthmatic patients.

RESULTS

There was a significant (P < 0.05) overall effect for forced expiratory volume (FEV(1)) but not after correction for steroid dose and atopic status. There were no significant differences for BHR to methacholine or AMP between the different haplotypes and no difference between the numbers of patients with or without clinically relevant BHR. Methacholine PD20 geometric mean-fold difference was 1.63 (95% CI: 0.95-2.80) between Arg-Arg/Gln-Gln and Gly-Gly/Gln-Gln and 1.26 (95% CI: 0.75-2.11) between Gly-Gly/Gln-Gln and Gly-Gly/Glu-Glu.

CONCLUSIONS

The degree of BHR to indirect and direct stimuli does not differ between beta2-adrenoceptor haplotypes, and haplotypes cannot be used to predict BHR in patients presenting with asthma. Although beta2-adrenoceptor haplotypes do not predict BHR they may be important in predicting response to bronchodilator therapy.

Familial aggregation of airway responsiveness: a community-based study

PURPOSE

We investigated the familial aggregation of airway hyper-responsiveness (AHR) to methacoline among randomly chosen families in a rural community in Anqing, China.

METHODS

Airway responsiveness (AR) to methacoline and related risk factors were assessed in each subject. We first modeled the within family correlation in AR and demonstrated the familial aggregation of this trait. Furthermore, we examined the effect size (e.g., odds ratio, OR) of this correlation in a "subsequent offspring model."

RESULTS

The correlation coefficient is significantly positive for parent-offspring and offspring-offspring pairs, but not significant in father-mother pairs, suggesting a genetic component. The strength of the relationships is in the order of father-offspring < mother-offspring < offspring-offspring. The OR of a positive AHR test for subsequent offspring who had mothers and an eldest sibling with positive AHR is 4.12 (95% CI, 1.72-9.87), compared with subsequent offspring whose mother and eldest sibling were negative in the test.

CONCLUSION

Our study supports a familial clustering of AHR in a Chinese population, which points to a role for genetic factors.

Systematic review and meta-analysis of the association between {beta}2-adrenoceptor polymorphisms and asthma: a HuGE review

A number of studies have investigated two common polymorphisms in the beta(2)-adrenoceptor gene, Arg/Gly16 and Gln/Glu27, in relation to asthma susceptibility. The authors performed a meta-analysis of each polymorphism, as well as haplotype analysis, for adult and pediatric populations separately, using published data, supplemented by additional data requested from the original authors. Individual analysis detected no effect of Arg/Gly16 in adults but did suggest a recessive protective effect of Gly16 for children, with an odds ratio of 0.71 (95% confidence interval (CI): 0.53, 0.96) compared with the other genotypes. Results for Gln/Glu27 in adults seem to indicate that heterozygotes are at decreased risk of asthma than either homozygote (odds ratio = 0.73, 95% CI: 0.62, 0.87), although the studies are heterogeneous; in children, the Glu/Glu genotype has a decreased risk of asthma (odds ratio = 0.60, 95% CI: 0.35, 0.99) compared with the other genotypes. Despite the proximity of these two polymorphic sites, the linkage disequilibrium coefficient of 0.41 was not high (p < 0.001). Haplotype analysis suggests that there may be an interaction between the two sites, with a lower risk of asthma associated with the Glu27 allele (compared with Gln27), and that this risk is modified by the allele at position 16.

Past, present and future--beta2-adrenoceptor agonists in asthma management

The beta-adrenoceptor agonists (beta-agonists) have been used to relieve bronchoconstriction for at least 5000 years. beta-agonists are based on adrenaline and early forms, such as isoprenaline, Lacked bronchial selectivity and had unpleasant side effects. Modern beta-agonists are more selective for the beta2-adrenoceptors (beta2-receptors) located in bronchial smooth muscle and have less cardiotoxicity. Traditional beta2-adrenoceptor agonists (beta2-agonists), such as salbutamol, terbutaline and fenoterol, were characterised by a rapid onset but relatively short duration of action. While valuable as reliever medication, their short duration gave inadequate night-time relief and limited protection from exercise-induced bronchoconstriction. beta2-agonists with longer durations of action, formoterol and salmeterol, were subsequently discovered or developed. When combined with inhaled corticosteroids they improved lung function, and reduced symptoms and exacerbations more than an increased dose of corticosteroids. However, tolerance to the bronchprotective effects of long-acting beta2-agonists and cross-tolerance to the bronchodilator effects of short-acting beta2-agonists is apparent despite use of inhaled corticosteroids. The role of beta2-receptor polymorphisms in the development of tolerance has yet to be fully determined. Formoterol is unique in having both a long-lasting bronchodilator effect (> 12 h) and a fast onset of action (1-3min from inhalation), making it effective both as maintenance and reliever medication. The recent change in classification from short- and long-acting beta2-agonists to rapid-acting and/or long-acting agents reflects the ongoing evolution of beta2-agonist therapy.

Modifier genes in cystic fibrosis

Although over 1,000 disease-causing mutations in the CFTR gene have been described, the highly variable disease phenotype in cystic fibrosis (CF) cannot be explained on the basis of this gene alone. Both the environment and other non-CFTR genes are likely to be important. The increased understanding of pathophysiological processes in the CF lung has led to several studies on genes in these pathways, including those involved in host defense, mucin production, and airway responsiveness. Additionally, candidate modifiers of the gastrointestinal manifestations of CF have been explored. One of the major aims of such studies is to produce targets for novel drug developments. This review will summarize the field to date and discuss some of the methodological issues important in the design and interpretation of such studies.

Airway reactivity is a determinant of bronchodilator responsiveness after methacholine-induced bronchoconstriction

Airway hyperresponsiveness (AHR) is one of the characteristics of asthma and a risk factor for persistent airflow limitation. Poor response to bronchodilator may be a cause of persistent airflow limitation. Multiple factors may determine bronchodilator responsiveness, including airway reactivity to nonspecific bronchoconstrictive agents. If patients with AHR have poor bronchodilator responsiveness, then it could be a potential mechanism for asthma and persistent airflow limitation in these patients. The objective of this study is to assess the relationship between airway reactivity to methacholine and responsiveness to beta-agonist and beta-agonist/anticholinergic combination in a large subject population. A retrospective data analysis was undertaken of 764 consecutive subjects with > or = 20% reduction in forced expiratory volume during the first second of exhalation from total lung capacity (FEV1) after < or = 189 cumulative units of methacholine. The first 382 subjects received 3 inhalations of metaproterenol and the second 382 subjects received 3 inhalations of albuterol and ipratropium combination after > or = 20% reduction in FEV1. Bronchodilator responsiveness was measured as the percent increase in FEV1 after the treatment. Airway reactivity was assessed as the log10 of methacholine dose response slope. In a simple linear regression model, airway reactivity was significantly related to bronchodilator responsiveness. The coefficient of determination (r2) was 0.15 for the whole groups; 0.14 for metaproterenol group and 0.18 for albuterol/ipratropium combination group (all p<0.0001). The regression coefficient (beta) was 14.0 for the whole group; 14.8 and 13.2, respectively, for the two bronchodilator groups. Airway reactivity to methacholine is a determinant of airway responsiveness to both beta-agonist and beta-agonist/anticholinergic combination. Subjects with higher airway reactivity have higher bronchodilator responsiveness.

beta2 adrenoceptor Arg16Gly polymorphism, airway responsiveness, lung function and asthma in infants and children

BACKGROUND

We have previously reported a relationship between increased airway responsiveness (AR) in infancy and reduced childhood lung function.

OBJECTIVE

The current study aimed to determine whether the Arg16Gly polymorphism of the beta2 adrenoceptor (beta2AR) gene was important to this relationship.

METHODS

A cohort that initially numbered 253 individuals underwent assessments of AR and lung function aged 1 month, 6 and 11 years; genotyping for polymorphisms of the beta(2)AR was performed.

RESULTS

At 1 month of age, the genotype homozygous Arg16 (n=24) was associated with a mean increase in log dose-response slope (AR) of 0.27 [95% confidence interval (CI) 0.07, 0.49] compared with the genotype homozygous Gly16 (n=58), P=0.01. At 11 years of age, the genotype homozygous Arg16 (n=35) was associated with a mean reduction in the percentage of forced expiratory volume in 1 s of 5.3% [95% CI 0.3, 10.2] compared with the genotype homozygous Gly16 (n=65), P=0.03. There was no association between the Arg16Gly polymorphism and atopy or diagnosed asthma. However, nine of 69 individuals with the genotype homozygous Gly16 were admitted to hospital with asthma compared with five out of 111 individuals with the remaining genotypes (P<0.05).

CONCLUSION

The Arg16Gly polymorphism may be important to the association between increased AR in infancy and reduced lung function in childhood and may also be a determinant of asthma severity in children but not asthma per se.

Therapeutic response to asthma medications: genotype predictors

Asthma is a major social and economic burden. Studies have shown that genetic polymorphisms can influence drug efficacy and/or toxicity. The understanding of the pharmacogenetics of asthma will allow therapeutic regimens to be tailored on an individual basis. It is hoped that linkage and association studies will define new therapeutic targets for asthma but until then, studies have focused on improving response to beta(2)-adrenoceptor agonist and leukotriene modifier therapy. Genetic polymorphism may account for interindividual differences in toxicity and efficacy of asthma medications. To date, single nucleotide polymorphism and limited haplotype analysis have provided inconclusive evidence as to how genotype predictors can be used to optimize current asthma therapies based on each patient's genetic profile.

Beta 2-adrenergic receptor polymorphisms and haplotypes are associated with airways hyperresponsiveness among nonsmoking men

STUDY OBJECTIVE

To investigate the relationship of common single nucleotide polymorphisms (SNPs) of the beta(2)-adrenergic receptor (AR) gene at codons 16 and 27, and the intermediate phenotype of airways hyperresponsiveness.

DESIGN

A case-control study in 543 white men (152 case patients and 391 control subjects), who were nested in an ongoing longitudinal cohort.

SETTING

Subjects were selected from the Normative Aging Study, an ongoing longitudinal cohort of healthy aging.

PARTICIPANTS

Case patients were defined as those having a positive response to methacholine challenge testing. Control subjects were selected among those who did not have a diagnosis of asthma and who had no response to methacholine.

RESULTS

There was a trend for an association of the Arg16 SNP genotype with airways hyperresponsiveness (odds ratio, 1.25; 95% confidence interval, 0.96 to 1.64 [in an additive model]). In stratified analyses, the effect of the Arg16 variant was seen mainly among nonsmokers. Smokers had increased risks for airway hyperresponsiveness regardless of genotype at either SNP. Using a program to estimate haplotype frequencies, three common haplotypes were identified. Adjusting for age, baseline FEV(1), serum IgE level, and smoking status, the Gly16/Gln27 haplotype was negatively associated with airways hyperresponsiveness in the full complement of case patients and control subjects (score statistic, - 2.43; p = 0.02). The effect of the beta(2)-AR haplotypes was much stronger among lifelong nonsmokers, among whom the Gly16/Gln27 haplotype remained negatively associated with airways hyperresponsiveness (score statistic, - 3.114; p = 0.002), whereas the Arg16/Gln27 haplotype was positively associated with airways hyperresponsiveness (score statistic, 3.142; p = 0.002). No effects were seen among ever-smokers.

CONCLUSIONS

In this cohort of middle-aged to older white men, beta(2)-AR polymorphisms were associated with airways hyperresponsiveness, particularly among lifelong nonsmokers. Our results illustrate an instance in which greater power is obtained by performing haplotype analyses as opposed to single SNP analysis.

Symptoms, lung function, and beta2-adrenoceptor polymorphisms in a birth cohort followed for 10 years

As little is known about the natural history of bronchial responsiveness and the development of wheezing symptoms in early childhood, a cohort of children at risk of allergy, whose lung function and bronchial responsiveness had been measured in the neonatal period, was followed prospectively for 10 (SD, 0.8) years in order to determine the role of neonatal measurements on wheezing history and later lung function. A potential role for beta-2 adrenoceptor (beta2AR) polymorphisms in these relationships was also sought as a secondary objective. Of the original 73 children, wheezing history was available in 65 (89%), and 49 (67%) attended the laboratory for physiological measurements and genotyping of beta2AR. Wheezing was categorized as occurring 1) only before the fourth birthday, 2) after the fourth birthday, or 3) never. No relation was seen between neonatal and later lung function. However, neonatal bronchial responsiveness predicted subsequent FEV1 (P = 0.03). Increased neonatal bronchial responsiveness was associated with transient wheeze <4 years but not with later wheeze. Neonatal V'maxFRC was reduced in those possessing Gln27 or Arg16 alleles, but there was no effect of beta2AR polymorphisms on FEV1 at 10 years. Wheeze after 4 years of age was typical of classical asthma, as it was strongly related to atopy and bronchial responsiveness at age 10. In conclusion, we confirmed the association of neonatal bronchial responsiveness with both early wheezing and later lung function. We also showed an influence of polymorphisms at both aa16 and aa27 on neonatal lung function. Wheezing beyond 4 years, typical of classical asthma, was unrelated to early measurements of lung function or bronchial responsiveness.

Association between beta2-adrenoceptor polymorphisms and asthma diagnosis among Mexican adults

BACKGROUND

Recent studies demonstrate that genetic variations in the human beta(2)-adrenergic receptor (beta(2)AR) structure at codons 16 and 27 alter receptor function in vitro and are associated with asthma severity and airway hyperresponsiveness but have not been linked to asthma diagnosis. The nature of the relation in a more homogeneous population is uncertain.

OBJECTIVE

We determined frequencies of these polymorphisms to explore the association between beta(2)AR haplotypes and asthma diagnosis and phenotype.

METHODS

This is a population-based, case-control study that involves a total sample of 907 unrelated Mexican Mestizos. Genotyping at beta(2)AR was identified by polymerase chain reaction-restriction fragment length polymorphism analysis. Multivariate logistic regression analysis was used to estimate the odds ratio (OR) of the association between beta(2)AR haplotype status and asthma diagnosis.

RESULTS

A significant inverse association was found between subjects with Glu27 allele (OR, 0.5; 95% CI, 0.4 to 0.7) and Gly16-Glu27 alleles (OR, 0.5; 95% CI, 0.3 to 0.8) and asthma. Sex differences in this association were explored, given the complex relation between sex and asthma. Among men, a positive association was present between the "Gly16 allele without Glu27" (OR, 2.9; 95% CI, 1.26 to 6.8) and asthma. In contrast, a lower risk of asthma was found among women Gly16-Glu27 alleles (OR, 0.3; 95% CI, 0.2 to 0.6). Nocturnal asthma was associated with the Gly16 allele (OR, 1.8; 95% CI, 1.3 to 2.6).

CONCLUSIONS

Variation in the beta(2)AR gene is associated in the pathogenesis of asthma and acts as a disease modifier in nocturnal asthma.

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

BACKGROUND

Non-specific bronchial hyperresponsiveness (NSBH) is a known predictor of accelerated rate of decline in lung function in smokers. Polymorphisms of the beta(2) adrenergic receptor (ADRB2) have previously been associated with NSBH and bronchodilator response (BDR) in asthmatics. Based on these associations, we hypothesised that ADRB2 polymorphisms would be associated with NSBH and BDR as well as an accelerated rate of decline in lung function among smokers.

METHODS

The prevalence of two ADRB2 polymorphisms, Arg16-->Gly and Gln27-->Glu, was examined in 587 smokers chosen from the NHLBI Lung Health Study for having the fastest (n=282) and slowest (n=305) 5 year rate of decline in forced expiratory volume in 1 second (FEV(1); mean DeltaFEV(1) -4.14 and +1.08% predicted/year, respectively).

RESULTS

Contrary to our hypothesis, no ADRB2 allele or haplotype was associated with NSBH, BDR, or rate of decline in lung function. However, there was a significant negative association between heterozygosity at position 27 and a fast decline in lung function (adjusted odds ratio 0.56, 95% CI 0.40 to 0.78, p=0.0007).

CONCLUSIONS

Heterozygosity at position 27 may be protective against an accelerated rate of decline in lung function. The polymorphism at position 16 does not contribute to the rate of decline in lung function, measures of NSBH, or BDR in smokers.

Roles of genotypes of beta2-adrenergic receptor in the relationship between eosinophil counts and lung function in Taiwanese adolescents

To examine the roles of genetic polymorphism of the beta2-adrenergic receptor (beta2AR) in the relationship between eosinophil (EOS) counts and eosinophil cationic protein (ECP) counts and lung function, we recruited a random sample from the 1996 nationwide survey of asthma prevalence in middle school children. A total of 149 subjects--42 asthmatic children, 38 asthmatics in remission (no reported attack for more than 12 months), and 69 nonasthmatics--completed a physical evaluation, pulmonary function test, and determination of EOS, ECP, and beta2AR genotypes at amino acids 16 and 27. Asthmatic children had higher EOS and ECP than did nonasthmatics. No association was found between asthma and beta2AR genotypes. Lung function was significantly and inversely correlated with EOS but not with ECP in asthmatic children. By genotype, an inverse correlation between lung function and EOS was found in asthmatic children with Arg16Arg or Gln27Glu. A nonsignificant but similar inverse correlation was found in asthmatic children with Arg16Gly or Gln27Gln. However, a nonsignificant but positive correlation was found in asthmatic children with Gly16Gly. In conclusion, we suggest that EOS is a better clinical indicator of airway inflammation than ECP when children are not having an asthma attack. The association between an increase of EOS and lower lung function can be differentiated by beta2AR genotypes at amino acid 16.

Nocturnal asthma

Lung function in a healthy individual varies in a circadian rhythm, with peak lung function occurring near 4:00 PM (1600 hours) and minimal lung function occurring near 4:00 AM (0400 hours). An episode of nocturnal asthma is characterized by an exaggeration in this normal variation in lung function from daytime to nighttime, with diurnal changes in pulmonary function generally of > 15%. The occurrence of nocturnal asthma is associated with increased morbidity and inadequate asthma control, and has an important negative impact on quality of life (QOL). Newer data have shed light on physiologic and immunologic mechanisms that underlie the nocturnal development of airway obstruction. It remains controversial whether nocturnal asthma is a distinct entity or is a manifestation of more severe asthma. The current data do not resolve these two alternatives, as well-controlled studies have reached opposite conclusions. However, the clinical associations of gastroesophageal reflux disease and obesity appear to be strong. The treatment of asthma with effective controller agents can reduce nighttime symptoms, improve psychometric outcomes, and improve QOL.

Bronchoscopic findings in children with non-cystic fibrosis chronic suppurative lung disease

BACKGROUND

Published data on the frequency and types of flexible bronchoscopic airway appearances in children with non-cystic fibrosis bronchiectasis and chronic suppurative lung disease are unavailable. The aims of this study were to describe airway appearances and frequency of airway abnormalities and to relate these airway abnormalities to chest high resolution computed tomography (cHRCT) findings in a cohort of children with non-cystic fibrosis chronic suppurative lung disease (CSLD).

METHODS

Indigenous children with non-cystic fibrosis CSLD (>4 months moist and/or productive cough) were prospectively identified and collected over a 2.5 year period at two paediatric centres. Their medical charts and bronchoscopic notes were retrospectively reviewed.

RESULTS

In all but one child the aetiology of the bronchiectasis was presumed to be following a respiratory infection. Thirty three of the 65 children with CSLD underwent bronchoscopy and five major types of airway findings were identified (mucosal abnormality/inflammation only, bronchomalacia, obliterative-like lesion, malacia/obliterative-like combination, and no macroscopic abnormality). The obliterative-like lesion, previously undescribed, was present in 16.7% of bronchiectatic lobes. Structural airway lesions (bronchomalacia and/or obliterative-like lesion) were present in 39.7% of children. These lesions, when present, corresponded to the site of abnormality on the cHRCT scan.

CONCLUSIONS

Structural airway abnormality is commonly found in children with post-infectious bronchiectasis and a new bronchoscopic finding has been described. Airway abnormalities, when present, related to the same lobe abnormality on the cHRCT scan. How these airway abnormalities relate to aetiology, management strategy, and prognosis is unknown.

Genetic variation of the beta(2)-adrenoceptor: its functional and clinical importance in bronchial asthma

Asthma is a polygenic disease for which no clear genotype-phenotype relationships have emerged. In contrast, although not associated with the diagnosis of asthma per se, variant forms of the beta(2)-adrenoceptor (beta2-AR) gene (ADRB2) display functional effects that may be clinically relevant. Single nucleotide polymorphisms (SNPs) of ADBR2 are common and result in amino acid substitutions at positions 16, 27, and 164 of the receptor as well as position 19 of its 5' upstream peptide. These SNPs influence receptor function in vitro, although evidence regarding exact relationships is conflicting. This has raised the possibility that phenotypes such as bronchial hyper-responsiveness (BHR) and responses to (beta2)-agonist drugs may be genetically determined. To date, no unequivocal relationships between SNPs and phenotype have been identified. In some studies the Gly(16) allele has been associated with increased BHR and asthma severity. In others, the Arg(16) allele has been shown to determine acute bronchodilator response and adverse events during long term beta(2)-agonist therapy. The latter may provide the basis for clinical application of this new knowledge. More recently, a small number of frequently occurring, functionally relevant ADRB2 haplotype pairs have been confirmed. These combinations of alleles may be more important in determining genotype/phenotype relationships than individual SNPs, and may explain why earlier investigations have yielded contrasting results. Future studies will be required to clarify the pharmacodynamic effects of ADRB2haplotypes both in vitro and in vivo.