Association between beta 2-adrenoceptor polymorphism and susceptibility to bronchodilator desensitisation in moderately severe stable asthmatics

Pharmacogenomic associations of adverse drug reactions in asthma: systematic review and research prioritisation

A systematic review of pharmacogenomic studies capturing adverse drug reactions (ADRs) related to asthma medications was undertaken, and a survey of Pharmacogenomics in Childhood Asthma (PiCA) consortia members was conducted. Studies were eligible if genetic polymorphisms were compared with suspected ADR(s) in a patient with asthma, as either a primary or secondary outcome. Five studies met the inclusion criteria. The ADRs and polymorphisms identified were change in lung function tests (rs1042713), adrenal suppression (rs591118), and decreased bone mineral density (rs6461639) and accretion (rs9896933, rs2074439). Two of these polymorphisms were replicated within the paper, but none had external replication. Priorities from PiCA consortia members (representing 15 institution in eight countries) for future studies were tachycardia (SABA/LABA), adrenal suppression/crisis and growth suppression (corticosteroids), sleep/behaviour disturbances (leukotriene receptor antagonists), and nausea and vomiting (theophylline). Future pharmacogenomic studies in asthma should collect relevant ADR data as well as markers of efficacy.

Role of THRB, ARG1, and ADRB2 Genetic Variants on Bronchodilators Response in Asthmatic Children

Background: An interindividual variability in response to short-acting bronchodilator drugs (short-acting inhaled β2-agonists, SABA) exists and this is linked in part to genetic factors. The aim of this study was to verify the influence of single nucleotide polymorphisms (SNPs) of a previously studied gene (ADRB2) and of new candidate genes (THRB and ARG1) on the acute response to SABA in children with asthma. Methods: One hundred asthmatic children (mean age 9.6 ± 3.0 years, 77 boys) underwent allergological and lung function evaluations. Spirometry was performed before and after bronchodilation test (BD test). The ADRB2 region containing the Arg16Gly (rs1042713) and Gln27Glu (rs1042714) variants were amplified by polymerase chain reaction, whereas ARG1 rs2781659 (A>G) and THRB rs892940 (G>A) SNPs were genotyped by high-resolution melting (HRM) analysis. Results: Seventy-seven percent of children developed asthma in the first 6 years of life. Allergic sensitization was observed in 92% (total immunoglobulin G: 529.8 ± 477. kU/L). All patients exhibited respiratory allergy: 43% has multiple respiratory, 22% to single respiratory, and 27% multiple respiratory and food allergies. Fifty four percent children showed positive BD response (forced expiratory volume in 1 second [FEV1] > 12%). Presence of Arg/Gly or Gly/Gly genotypes in position 16 of ADRB2 was significantly associated to a worse BD response (post-BD FEV1: 108.68% ± 15.62% in Arg/Arg vs. 101.86% ± 14.03% in Arg/Gly or Gly/Gly patients, p = 0.02). No significant association was found between spirometric parameters before and after BD for the other three examined SNPs. Conclusion: The influence of genetic variability on responsiveness to drugs could become a key parameter to optimize a tailored therapy for young patients with asthma, especially if drug-resistance occurs.

β2‑adrenergic receptor functionality and genotype in two different models of chronic inflammatory disease: Liver cirrhosis and osteoarthritis

The present study was designed to investigate the functional status of β2 adrenoceptors (β2AR) in two models of chronic inflammatory disease: liver cirrhosis (LC) and osteoarthritis (OA). The β2AR gene contains three single nucleotide polymorphisms at amino acid positions 16, 27 and 164. The aim of the present study was to investigate the potential influence of lymphocyte β2AR receptor functionality and genotype in LC and OA patients. Blood samples from cirrhotic patients (n=52, hepatic venous pressure gradient 13±4 mmHg, CHILD 7±2 and MELD 11±4 scores), OA patients (n=30, 84% Kellgren‑Lawrence severity 4 grade, 14% knee replacement joint) and healthy volunteers as control group (n=26) were analyzed. Peripheral blood mononuclear cells (PBMC) were isolated from whole blood and basal and isoproterenol induced adenylate cyclase activity (isoproterenol stimulus from 10‑9 to 10‑4 mM), and β2AR allelic variants (rs1042713, rs1042714, rs1800888) were determined. β2AR functionality was decreased in the two different models of chronic inflammatory disease studied, OA (50% vs. control) and LC (85% vs. control). In these patients, the strength of the β2AR response to adrenergic stimulation was very limited. Adrenergic modulation of PBMC function through the β2AR stimulus is decreased in chronic inflammatory processes including LC and OA, suggesting that the adrenergic system may be important in the development of these processes.

Oxidative stress and cellular pathways of asthma and inflammation: Therapeutic strategies and pharmacological targets

Asthma is a complex inflammatory disease characterized by airway inflammation and hyperresponsiveness. The mechanisms associated with the development and progression of asthma have been widely studied in multiple populations and animal models, and these have revealed involvement of various cell types and activation of intracellular signaling pathways that result in activation of inflammatory genes. Significant contributions of Toll-like-receptors (TLRs) and transcription factors such as NF-кB, have been reported as major contributors to inflammatory pathways. These have also recently been associated with mechanisms of oxidative biology. This is of important clinical significance as the observed inefficacy of current available treatments for severe asthma is widely attributed to oxidative stress. Therefore, targeting oxidizing molecules in conjunction with inflammatory mediators and transcription factors may present a novel therapeutic strategy for asthma. In this review, we summarize TLRs and NF-кB pathways in the context of exacerbation of asthma pathogenesis and oxidative biology, and we discuss the potential use of polyphenolic flavonoid compounds, known to target these pathways and possess antioxidant activity, as potential therapeutic agents for asthma.

Heat Shock-Related Protein 20 Peptide Decreases Human Airway Constriction Downstream of β2-Adrenergic Receptor

Severe bronchospasm refractory to β-agonists is a challenging aspect of asthma therapy, and novel therapeutics are needed. β-agonist-induced airway smooth muscle (ASM) relaxation is associated with increases in the phosphorylation of the small heat shock-related protein (HSP) 20. We hypothesized that a transducible phosphopeptide mimetic of HSP20 (P20 peptide) causes relaxation of human ASM (HASM) by interacting with target(s) downstream of the β2-adrenergic receptor (β2AR) pathway. The effect of the P20 peptide on ASM contractility was determined in human and porcine ASM using a muscle bath. The effect of the P20 peptide on filamentous actin dynamics and migration was examined in intact porcine ASM and cultured primary HASM cells. The efficacy of the P20 peptide in vivo on airway hyperresponsiveness (AHR) was determined in an ovalbumin (OVA) sensitization and challenge murine model of allergic airway inflammation. P20 peptide caused dose-dependent relaxation of carbachol-precontracted ASM and blocked carbachol-induced contraction. The β2AR inhibitor, (±)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride (ICI 118,551), abrogated isoproterenol but not P20 peptide-mediated relaxation. The P20 peptide decreased filamentous actin levels in intact ASM, disrupted stress fibers, and inhibited platelet-derived growth factor-induced migration of HASM cells. The P20 peptide treatment reduced methacholine-induced AHR in OVA mice without affecting the inflammatory response. These results suggest that the P20 peptide decreased airway constriction and disrupted stress fibers through regulation of the actin cytoskeleton downstream of β2AR. Thus, the P20 peptide may be a potential therapeutic for asthma refractory to β-agonists.

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.

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.

The Relationship Between Glutathione S-Transferase-P1 and Beta-2 Adrenoreceptor Genotypes with Asthmatic Patients in the Turkish Population

BACKGROUND

Individual differences in the activity of enzymes that metabolize xenobiotics can impact health and disease. Beta-2 adrenoreceptor (ADRB2) is a functional G-coupled protein expressed in the vascular endothelium of lungs, alveolar walls, and the ganglions of cholinergic nerves which induces bronchodilation in response to catecholamines. Glutathione S-Transferase-P1 (GSTP1) is a candidate pi class GST gene, which controls pi class glutathione S-transferase activity.

AIMS

In this study we determined the relationship between the ADRB2 Arg16Gly polymorphism and GSTP1 polymorphisms, involved in bronchodilator response and oxidative stress, respectively, with susceptibility to asthma.

METHODS

In this study, 129 asthmatic patients and 127 healthy control cases were recruited to determine ADRB2 and GSTP1 genotypes by allele-specific polymerase chain reaction and restriction fragment length polymorphism assays, respectively.

RESULTS

The ADRB2 genotype frequencies of the patients and control cases were found to be 10.9% (Arg16Arg), 48.8% (Arg16Gly), and 40.3% (Gly16Gly) and 24.4% (Arg16Arg), 36.2% (Arg16Gly), and 39.4% (Gly16Gly), respectively. GSTP1 genotype frequencies of patients and control cases were found to be 55% (Ile105Ile), 43.4% (Ile105Val), and 1.6% (Val105Val) and 75.6% (Ile105Ile), 22% (Ile105Val), and 2.4% (Val105Val), respectively. In the case of the GSTP1 gene, we found statistically significant differences in the genotype frequency of Ile105Val and the allele frequency of Val105 in the asthmatic group compared with the controls. Moreover, we observed a relationship between allele frequencies and clinical phenotypes including atopia nocturnal dyspnea, and steroid dependency in the asthmatic patients.

CONCLUSION

Our results suggest that the GSTP1 Ile105Val polymorphism may be linked to the severeness of airway dysfunction.

Association between Polymorphisms in Bitter Taste Receptor Genes and Clinical Features in Korean Asthmatics

BACKGROUND

Bitter taste receptors (TAS2R) in human airway smooth muscle have recently been shown to have an important role in bronchodilation, together with β2-adrenergic receptors.

OBJECT

To evaluate the association between genetic variations in TAS2R and clinical features, including bronchodilator response and asthma control.

METHOD

We analyzed the association between single nucleotide polymorphisms (SNPs) of TAS2R10 and TAS2R14 and variables such as demographic data, atopy, duration of disease, and asthma control status, including variables such as asthma control test (ACT) score, percent predicted value of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio, as well as bronchodilator response (BDR), in 721 asthma patients in Korea.

RESULT

Three novel SNPs of 633G>A, 645C>A, and -79G>A in TAS2R10 and 3 known SNPs of -815T>C, -1267G>A, and -1897T>C in TAS2R14 were analyzed. Increased BDR was significantly associated with SNPs of -815T>C [OR (95% CI) = 1.88 (1.01-3.49), p = 0.04 ] [J Gen Physiol 2005;125:535-553; Am J Respir Cell Mol Biol 2010;42:373-3812], -1267A>G [OR (95% CI) = 2.07 (1.03-4.15), p = 0.04] and -1897T>C [OR (95% CI) = 3.05 (1.01-9.23), p = 0.04, in a dominant model, and OR = 1.91 (1.08-3.36), p = 0.02, in a codominant model] of the TAS2R14 gene. There was a significant association between -815T>C and a low mean ACT score [OR (95% CI) = 5.84 (1.94-17.61), p = 0.001]. In haplotype analysis, TAC, CAT, and TGT, or TG and CA haplotypes on TAS2R14 were significantly associated with increased BDR; CAT and CA haplotypes were significantly associated with a low ACT score.

CONCLUSION

Genetic variations in TAS2Rs may be valuable genetic markers to predict therapeutic response and outcomes in asthma. Further research in an independent cohort is needed.

Pharmacogenomics of long-acting β2-agonists

INTRODUCTION

Long-acting β2-agonists are an effective class of drugs, when combined with inhaled corticosteroids, for reducing symptoms and exacerbations in patients with asthma that is not adequately controlled by inhaled corticosteroids alone. However, because this class of drugs has been associated with severe adverse events, including hospitalization and death in small numbers of patients, efforts to identify a pharmacogenetic profile for patients at risk has been diligently investigated.

AREAS COVERED

The PubMed search engine of the National Library of Medicine was used to identify English-language and non-English language articles published from 1947 to March 2015 pertinent to asthma, pharmacogenomics, and long-acting β2-agonists. Keywords and topics included: asthma, asthma control, long-acting β2-agonists, salmeterol, formoterol, pharmacogenetics, and pharmacogenomics. This strategy was also used for the Cochrane Library Database and CINAHL. Reference types were randomized controlled trials, reviews, and editorials. Additional publications were culled from reference lists. The publications were reviewed by the authors and those most relevant were used to support the topics covered in this review.

EXPERT OPINION

Children, who carry the ADRB2 Arg16Arg genotype, may be at greater risk than adults for severe adverse events. Rare ADRB2 variants appear to provide better clues for identifying the at-risk population of asthmatics.

Role of single nucleotide polymorphisms in pharmacogenomics and their association with human diseases

Global statistical data shed light on an alarming trend that every year thousands of people die due to adverse drug reactions as each individual responds in a different way to the same drug. Pharmacogenomics has come up as a promising field in drug development and clinical medication in the past few decades. It has emerged as a ray of hope in preventing patients from developing potentially fatal complications due to adverse drug reactions. Pharmacogenomics also minimizes the exposure to drugs that are less/non-effective and sometimes even found toxic for patients. It is well reported that drugs elicit different responses in different individuals due to variations in the nucleotide sequences of genes encoding for biologically important molecules (drug-metabolizing enzymes, drug targets and drug transporters). Single nucleotide polymorphisms (SNPs), the most common type of polymorphism found in the human genome is believed to be the main reason behind 90% of all types of genetic variations among the individuals. Therefore, pharmacogenomics may be helpful in answering the question as to how inherited differences in a single gene have a profound effect on the mobilization and biological action of a drug. In the present review, we have discussed clinically relevant examples of SNP in associated diseases that can be utilized as markers for "better management of complex diseases" and attempted to correlate the drug response with genetic variations. Attention is also given towards the therapeutic consequences of inherited differences at the chromosomal level and how associated drug disposition and/or drug targets differ in various diseases as well as among the individuals.

Beta2 adrenergic receptor (ADRβ2) haplotype pair (2/4) is associated with severe asthma

Background

β2 adrenergic receptor (ADRβ2) polymorphisms including ADRβ2+46G>A have been reported to cause adverse outcomes in mild asthmatics. The extent to which ADRβ2 polymorphisms and in particular their haplotypes contribute to severe asthma is unknown.

Objective

To determine the association of ADRβ2 polymorphisms and haplotypes with asthma severity.

Methods

Caucasians (n = 2979) were genotyped for 11 ADRβ2 polymorphisms. The cohort (mean age 39.6, 60% female) included 2296 non-asthmatics, 386 mild asthmatics, 172 moderate asthmatics and 125 severe asthmatics. Haplotype frequency and haplotype pair for each subject was determined using the PHASE algorithm.

Results

The three asthmatic cohorts were comparable in age and gender but were distinguishable from each other in terms of symptoms, spirometry, medication use and health care utilisation (p <0.001). None of the polymorphisms showed a genotypic or allelic association with asthma diagnosis or severity. Nine haplotypes were identified and no association was found with asthma diagnosis or severity per se. Haplotype pair 2/4 was associated with asthma severity (Trend Test, OR 1.42, p = 0.0008) but not with asthma per se. Prevalence of haplotype pair 2/2 appeared to decrease with asthma severity (Trend Test, OR 0.78, p = 0.067). Two new haplotypes were identified, occurring exclusively in asthmatics at a frequency of ≥ 1%. In addition, a positive association between carriage of ADRβ2 +523*C and increased risk of atopy was discovered.

Conclusions

ADRβ2 haplotype pair 2/4 is associated with severe asthma and is consistent with findings of poor bronchodilator response in mild asthmatics who are also haplotype 2/4.

Asthma: Gln27Glu and Arg16Gly polymorphisms of the beta2-adrenergic receptor gene as risk factors

Background

Asthma is caused by both environmental and genetic factors. The ADRB2 gene, which encodes the beta 2-adrenergic receptor, is one of the most extensively studied genes with respect to asthma prevalence and severity. The Arg16Gly (+46A > G) and Gln27Glu (+79C > G) polymorphisms in the ADRB2 gene cause changes in the amino acids flanking the receptor ligand site, altering the response to bronchodilators and the risk of asthma through complex pathways. The ADRB2 polymorphisms affect beta-adrenergic bronchodilator action and are a tool to identify at-risk populations.

Objective

To determine the frequency of these two polymorphisms in allergic asthma patients and healthy subjects and to correlate these data with the occurrence and severity of asthma.

Methods

Eighty-eight allergic asthma patients and 141 healthy subjects were included in this study. The ADRB2 polymorphisms were analyzed using the amplification-refractory mutation system – polymerase chain reaction (ARMS-PCR) technique. The statistical analysis was performed with the SPSS 21.0 software using the Fisher’s Exact and χ² tests.

Results

The ADRB2 polymorphisms were associated with asthma occurrence. The Arg16Arg, Gln27Gln and Gln27Glu genotypes were risk factors; the odds ratios were 6.782 (CI = 3.07 to 16.03), 2.120 (CI = 1.22 to 3.71) and 8.096 (CI = 3.90 to 17.77), respectively. For the Gly16Gly and Glu27Glu genotypes, the odds ratios were 0.312 (CI = 0.17 to 0.56) and 0.084 (CI = 0.04 to 0.17), respectively. The haplotype analysis showed that there were associations between the following groups: Arg16Arg-Gln27Gln (OR = 5.108, CI = 1.82 to 16.37), Gly16Gly-Glu27Glu (OR = 2.816, CI = 1.25 to 6.54), Arg16Gly-Gln27Glu (OR = 0.048, CI = 0.01 to 0.14) and Gly16Gly-Gln27Glu (OR = 0.1036, CI = 0.02 to 0.39). The polymorphism Gln27Glu was associated with asthma severity, as the Gln27Gln genotype was a risk factor for severe asthma (OR = 2.798, CI = 1.099 to 6.674) and the Gln27Glu genotype was a protective factor for mild (OR = 3.063, CI = 1.037 to 9.041) and severe (OR = 0.182, CI = 0.048 to 0.691) asthma.

Conclusions

The Arg16Gly and Gln27Glu polymorphisms in the ADRB2 gene are associated with asthma presence and severity.

Obesity and asthma

Asthma is a chronic disorder affecting millions of people worldwide. The prevalence of asthma is around 300 million and is expected to increase another 100 million by 2025. Obesity, on the other hand, also affects a large number of individuals. Overweight in adults is defined when body mass index (BMI) is between 25 to 30 kg/m(2) and obesity when the BMI >30 kg/m(2). It has been a matter of interest for researchers to find a relation between these two conditions. This knowledge will provide a new insight into the management of both conditions. At present, obese asthma patients may be considered a special category and it is important to assess the impact of management of obesity on asthma symptoms.

Association of the ADRB2 Gly16Arg and Glu27Gln polymorphisms with athlete status

The β-adrenergic receptors (β-ARs) have known functional roles in cardiovascular and pulmonary responses as well as the appropriate substrate metabolism required for athletic ability. Thus, the β-AR genes are plausible candidates for the variations observed in strength/power and endurance performance levels. The aims of the present study were to compare the frequency distribution of the ADRB2 Gly16Arg and ADRB2 Glu27Gln polymorphisms among athletes of sports with different metabolic and cardiopulmonary demands (endurance vs. strength/power) and to test the association between the Gly16Arg and Glu27Gln genotypes and athlete status. The study was performed in a group of 223 Polish athletes of the highest nationally competitive standard (123 endurance-oriented athletes and 100 strength/power athletes). Control samples were prepared from 354 unrelated, sedentary volunteers. The χ² test of independence revealed that the frequencies of the Gly16 and Glu27 alleles were significantly higher in the strength/power athletes than in the controls (69.0% vs. 59.7%; df = 1, P = 0.017 and 51% vs. 41.5%; df = 1 P = 0.017, respectively). The study showed that ADRB2 Gly16Arg and Glu27Gln markers are associated with athlete status in Polish athletes. An excess of Gly16 and Glu27 alleles and the Gly16:Glu27 haplotype observed in the strength/power athlete subgroup suggests that the Gly16 and Glu27 alleles might increase the probability of becoming a strength/power athlete rather than an endurance-oriented athlete.

Personalised medicine and asthma diagnostics/management

Human beings come in all shapes and sizes. Heterogeneity makes life interesting, but leads to inter-individual variation in disease susceptibility and response to therapy. One major health challenge is to develop "personalised medicine"; therapeutic interventions tailored to an individual to ensure optimal treatment of disease. Asthma is a heterogeneous disease with several different phenotypes triggered by multiple gene-environment interactions. Inhaled corticosteroids and β2-agonists have been the mainstay asthma therapies for 30 years, but they are not effective in all patients, while high costs and side-effects also drive the need for better targeted treatment of asthma. Pharmacogenetics is the study of variations in the genetic code for proteins in signaling pathways targeted by pharmacological therapies. Biomarkers are biological markers obtained from patients that can aid in asthma diagnosis, prediction of treatment response, and monitoring of disease control. This review presents a broad discussion of the use of genetic profiling and biomarkers to better diagnose, monitor, and tailor the treatment of asthmatics. We also discuss possible future developments in personalised medicine, including the construction of artificially engineered airway tissues containing a patient's own cells for use as personalised drug-testing tools.

Pharmacogenetics of β2-agonists

Short-acting β2-agonists (SABAs) and long-acting β2-agonists (LABAs) are both important for treatment of asthma and chronic obstructive pulmonary disease (COPD) because of their bronchodilator and bronchoprotective effects. However, the use of these agonists, at least for asthma, has generated some controversy because of their association with increased mortality. Pharmacogenetics is the study of genetically determined variation in response to medications, which might prove useful for target therapies in highly responsive patients, especially for more expensive therapies or those with increased risk of side effects. Variation in response to both SABAs and LABAs has been observed in patients with polymorphisms in the β2 adrenoceptor gene (ADRB2). This review summarizes results from various studies on the possible relationship between ADRB2 polymorphisms and the bronchodilator or bronchoprotective effects of inhaled β2-agonists. By assessing the ADRB2 genotype, the hope is that it will be possible to predict the responsiveness to chronic administration of β2-agonists. Genetic testing, however, is of limited usefulness at this stage for ADRB2 because the common variants identified thus far account for only a small proportion of the variation observed for given responses. Carefully performed and adequately powered clinical trials continue to be important for achieving the goal of pharmacogenetic approaches to therapy.

Pharmacogenetics of β2 adrenergic receptor gene polymorphisms, long-acting β-agonists and asthma

Adrenergic β2 receptor (ADRβ2) agonists are widely used in asthma. Approximately 10% of patients have severe, poorly controlled disease despite extensive use of ADRβ2 agonists. Variations in responses to ADRβ2 agonists can, in part, be attributed to genetic variation, with 49 different polymorphisms having been identified for the ADRβ2 gene. Although clear associations exist between ADRβ2 gene polymorphisms, such as +46G>A, and patient response, the importance of these polymorphisms remains controversial. Patient selection, the number of polymorphisms analysed, differences in the type/dose of ADRβ2 agonist, use of inhaled corticosteroids and population sizes have all varied. Most studies were limited to mild or moderate asthmatics using ADRβ2 agonists sparingly. It is difficult to extrapolate from these studies to individual patients who have severe asthma, use a variety of ADRβ2 agonists and do so frequently. The extent to which ADRβ2 gene polymorphisms are relevant to asthma management needs further review, both clinically and at the molecular level. In vitro studies have helped to define the functional changes induced by specific ADRβ2 gene polymorphisms, including 3'-untranslated region poly-C repeat. The resulting ADRβ2 gene haplotypes (rather than genotypes), the interactions among ADRβ2 gene haplotypes and variations in the chemistry of different agonists deserve more detailed assessment. Responses to ADRβ2 agonists depend on effective downstream signalling following ADRβ2 activation and also on receptor regulation. Studies on other regulators of ADRβ2 receptor signalling and trafficking may be equally important in understanding the functional role of ADRβ2 gene polymorphisms. The role of ADRβ2 gene polymorphisms in the pathogenesis and management of severe asthma cannot be clearly defined until more specific and targeted research studies are performed.

Genetic polymorphisms of the beta2-adrenergic receptor relate to guanosine protein-coupled stimulator receptor dysfunction in fibromyalgia syndrome

OBJECTIVE

To determine the genotype frequencies of ß(2)-adrenergic receptor (ß(2)AR) gene polymorphisms (Gly16Arg, Glu27Gln) in patients with fibromyalgia syndrome (FM) by comparison with unrelated healthy controls. We sought any clinical association with these polymorphisms and determined whether the polymorphisms would associate with a biologic guanosine protein-coupled stimulator receptor (Gs) dysfunction in FM.

METHODS

Study subjects included 97 clinically characterized patients with FM and 59 controls. The ß(2)AR polymorphisms at codons 16 and 27 were determined using polymerase chain reaction-restriction fragment length polymorphism. The Gs functions of peripheral blood mononuclear cells (PBMC) were tested using isoproterenol (ISO) as the adrenergic Gs ligand and measuring intracellular cyclic adenosine monophosphate (cAMP) levels.

RESULTS

The frequency of the ß(2)AR gene polymorphism Gly16Arg in FM (43.5%) was significantly lower than in controls (63.2%), suggesting that this genotype might have some effect on the risk of developing FM. The only clinical association in FM was with sleep dysfunction. Patients with FM who carried the ß(2)AR polymorphism Arg16Arg also exhibited significantly lower PBMC basal cAMP levels (p < 0.05) and lower ISO-stimulated cAMP levels (p < 0.05) than FM carrying Gly16Gly or Gly16Arg.

CONCLUSION

This confirms a relationship between ß(2)AR polymorphism and FM. It is the first study to demonstrate ß(2)AR polymorphism-related differences in intracellular cAMP responses of FM PBMC after ß(2)AR stimulation in vitro. These findings may explain some of the differences in responsiveness of FM subgroups to the adrenergic agonist medications currently approved for FM treatment.

Polymorphisms of the β2-adrenergic receptor correlated to nocturnal asthma and the response of terbutaline nebulizer

BACKGROUND

Inhaled β(2)-adrenergic receptor (β(2)-AR) agonists are the mainstay of treatment of acute asthma. Polymorphisms of the β(2)-AR, especially codons 16, 27, and 164, may affect the functions of the receptor. This study was conducted to investigate whether different polymorphisms of the β(2)-AR are related to the treatment responses of an inhaled β(2)-AR agonist in children with nocturnal and nonnocturnal asthma in Taiwan.

METHODS

The nocturnal asthma group consisted of 27 children (mean age of 10.3±2.4 years), and the nonnocturnal asthma group consisted of 24 patients (mean age of 9.9±3.0 years). Allele-specific polymerase chain reaction was performed to determine 16, 27, and 164 loci alleles of β(2)-AR genetic polymorphisms, and peak expiratory flow (PEF) was measured before and 1 hour after inhalation of 0.2mg/kg/dose of terbutaline to determine the treatment response in these patients.

RESULTS

The polymorphisms of β(2)-AR 27 but not 16 or 164 were significantly associated with the response to terbutaline nebulizer (p<0.05). The polymorphism of β(2)-AR 16 was associated with nocturnal asthma (p=0.027). The Gly16 allele was more prevalent in the nocturnal asthma group (9/27; 33.3%) than in the nonnocturnal asthma group (3/24; 12.5%). Arg16 allele was less prevalent in the nocturnal asthma (3/27; 11.1%) than in the nonnocturnal asthma group (10/24; 41.7%). There was also a linkage disequilibrium found between β(2)-AR 16 (Arg/Arg) and β(2)-AR 27 (Gln/Gln).

CONCLUSION

These findings suggest that polymorphisms of β(2)-AR 16 are related to nocturnal asthma and polymorphisms of β(2)-AR 27 are associated with the variable responses to the inhaled terbutaline in children with nocturnal and nonnocturnal asthma.

Relationship between the benefits of suplatast tosilate, a Th2 cytokine inhibitor, and gene polymorphisms in children with bronchial asthma

Although currently available antiasthmatic drugs are effective for many patients with bronchial asthma, some patients do not respond well to medications or exhibit more frequent adverse effects compared to other patients. Antiasthmatic treatment should be tailored individually according to the predispositions and pathophysiological conditions of patients. No reports have been made concerning the relationships between the effects of Th2 cytokine inhibitors and gene polymorphisms. The present study was therefore performed to investigate the relationships between gene polymorphisms known to be involved in allergy and cytokine production in peripheral blood mononuclear cells and the clinical efficacy of suplatast tosilate, a Th2 cytokine inhibitor, to clarify factors determining responses to treatment. A total of 20 children were enrolled in the study. The children were enrolled in a run-in period of 2 weeks and then received suplatast tosilate orally for 8 weeks. The children or their parents were instructed to keep an asthma diary to record changes in signs/symptoms of bronchial asthma before and after treatment. Concentrations of interferon (IFN)-γ and interleukin (IL)-4 in the supernatant were determined using ELISA methods. Using the invader assay method, the genotypes of polymorphisms of the genes were determined. Treatment with suplatast tosilate was more effective in children without the -444 A/C polymorphism of the LTC4 synthase gene and in children without the IL-13 variant R110Q. In children who responded well, production of IFN-γ was significantly increased after treatment. In this study, responses to suplatast tosilate were associated with SNPs of the LTC4 synthase and IL-13 gene as well as change in the production of IFN-γ before and after drug administration.

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.

Addition of long-acting beta2-agonists to inhaled corticosteroids versus same dose inhaled corticosteroids for chronic asthma in adults and children

BACKGROUND

Long-acting inhaled ss(2)-adrenergic agonists (LABAs) are recommended as 'add-on' medication to inhaled corticosteroids (ICS) in the maintenance therapy of asthmatic adults and children aged two years and above.

OBJECTIVES

To quantify in asthmatic patients the safety and efficacy of the addition of LABAs to ICS in patients insufficiently controlled on ICS alone.

SEARCH STRATEGY

We identified randomised controlled trials (RCTs) through electronic database searches (the Cochrane Airways Group Specialised Register, MEDLINE, EMBASE and CINAHL), bibliographies of RCTs and correspondence with manufacturers until May 2008.

SELECTION CRITERIA

We included RCTs if they compared the addition of inhaled LABAs versus placebo to the same dose of ICS in children aged two years and above and in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for methodological quality and extracted data. We obtained confirmation from the trialists when possible. The primary endpoint was the relative risk (RR) of asthma exacerbations requiring rescue oral corticosteroids. Secondary endpoints included pulmonary function tests (PFTs), rescue beta2-agonist use, symptoms, withdrawals and adverse events.

MAIN RESULTS

Seventy-seven studies met the entry criteria and randomised 21,248 participants (4625 children and 16,623 adults). Participants were generally symptomatic at baseline with moderate airway obstruction despite their current ICS regimen. Formoterol or salmeterol were most frequently added to low-dose ICS (200 to 400 microg/day of beclomethasone (BDP) or equivalent) in 49% of the studies. The addition of a daily LABA to ICS reduced the risk of exacerbations requiring oral steroids by 23% from 15% to 11% (RR 0.77, 95% CI 0.68 to 0.87, 28 studies, 6808 participants). The number needed to treat with the addition of LABA to prevent one use of rescue oral corticosteroids is 41 (29, 72), although the event rates in the ICS groups varied between 0% and 38%. Studies recruiting adults dominated the analysis (6203 adult participants versus 605 children). The subgroup estimate for paediatric studies was not statistically significant (RR 0.89, 95% CI 0.58 to 1.39) and includes the possibility of the superiority of ICS alone in children.Higher than usual dose of LABA was associated with significantly less benefit. The difference in the relative risk of serious adverse events with LABA was not statistically significant from that of ICS alone (RR 1.06, 95% CI 0.87 to 1.30). The addition of LABA led to a significantly greater improvement in FEV(1) (0.11 litres, 95% 0.09 to 0.13) and in the proportion of symptom-free days (11.88%, 95% CI 8.25 to 15.50) compared to ICS monotherapy. It was also associated with a reduction in the use of rescue short-acting ss(2)-agonists (-0.58 puffs/day, 95% CI -0.80 to -0.35), fewer withdrawals due to poor asthma control (RR 0.50, 95% CI 0.41 to 0.61), and fewer withdrawals due to any reason (RR 0.80, 95% CI 0.75 to 0.87). There was no statistically significant group difference in the risk of overall adverse effects (RR 1.00, 95% 0.97 to 1.04), withdrawals due to adverse health events (RR 1.04, 95% CI 0.86 to 1.26) or any of the specific adverse health events.

AUTHORS' CONCLUSIONS

In adults who are symptomatic on low to high doses of ICS monotherapy, the addition of a LABA at licensed doses reduces the rate of exacerbations requiring oral steroids, improves lung function and symptoms and modestly decreases use of rescue short-acting ss(2)-agonists. In children, the effects of this treatment option are much more uncertain. The absence of group difference in serious adverse health events and withdrawal rates in both groups provides some indirect evidence of the safety of LABAs at usual doses as add-on therapy to ICS in adults, although the width of the confidence interval precludes total reassurance.

Addition of long-acting beta2-agonists to inhaled steroids versus higher dose inhaled steroids in adults and children with persistent asthma

BACKGROUND

In asthmatic patients inadequately controlled on inhaled corticosteroids and/or those with moderate persistent asthma, two main options are recommended: the combination of a long-acting inhaled ss2 agonist (LABA) with inhaled corticosteroids (ICS) or use of a higher dose of inhaled corticosteroids.

OBJECTIVES

To determine the effect of the combination of long-acting ss(2) agonists and inhaled corticosteroids compared to a higher dose of inhaled corticosteroids on the risk of asthma exacerbations, pulmonary function and on other measures of asthma control, and to look for characteristics associated with greater benefit for either treatment option.

SEARCH STRATEGY

We identified randomised controlled trials (RCTs) through electronic database searches (MEDLINE, EMBASE and CINAHL), bibliographies of RCTs, clinical trial registries and correspondence with manufacturers until May 2008.

SELECTION CRITERIA

RCTs that compared the combination of inhaled LABA and ICS to a higher dose of inhaled corticosteroids, in children and adults with asthma.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed methodological quality and extracted data. We obtained confirmation from the trialists when possible. The primary endpoint was the number of patients experiencing one or more asthma exacerbations requiring oral corticosteroids.

MAIN RESULTS

This review included 48 studies (15,155 participants including 1155 children and 14,000 adults). Participants were inadequately controlled on their current ICS regimen, experiencing ongoing symptoms and with generally moderate (FEV1 60% to 79% of predicted) airway obstruction. The studies tested the combination of salmeterol or formoterol with a median dose of 400 mcg/day of beclomethasone or equivalent (BDP-eq) compared to a median of 1000 mcg/day of BDP-eq, usually for 24 weeks or less. There was a statistically significantly lower risk of exacerbations requiring systemic corticosteroids in patients treated with LABA and ICS (RR 0.88, 95% CI 0.78 to 0.98, 27 studies, N = 10,578) from 11.45% to 10%, with a number needed to treat of 73 (median study duration: 12 weeks). The study results were dominated by adult studies; trial data from three paediatric studies showed a trend towards increased risk of rescue oral steroids (RR 1.24, 95% CI 0.58 to 2.66) and hospital admission (RR 2.21, 95% CI 0.74 to 6.64) associated with combination therapy. Overall, there was no statistically significant difference in the risk ratios for either hospital admission (RR 1.02, 95% CI 0.67 to 1.56) or serious adverse events (RR 1.12, 95% CI 0.91 to 1.37). The combination of LABA and ICS resulted in significantly greater but modest improvement from baseline in lung function, symptoms and rescue medication use than with higher ICS dose. Despite no significant group difference in the risk of overall adverse events (RR 0.99, 95% CI 0.95 to 1.03), there was an increase in the risk of tremor (RR 1.84, 95% CI 1.20 to 2.82) and a lower risk of oral thrush (RR 0.58, 95% CI 0.40 to 0.86)) in the LABA and ICS compared to the higher ICS group. There was no significant difference in hoarseness or headache between the treatment groups. The rate of withdrawals due to poor asthma control favoured the combination of LABA and ICS (RR 0.65, 95% CI 0.51 to 0.83).

AUTHORS' CONCLUSIONS

In adolescents and adults with sub-optimal control on low dose ICS monotherapy, the combination of LABA and ICS is modestly more effective in reducing the risk of exacerbations requiring oral corticosteroids than a higher dose of ICS. Combination therapy also led to modestly greater improvement in lung function, symptoms and use of rescue ss(2) agonists and to fewer withdrawals due to poor asthma control than with a higher dose of inhaled corticosteroids. Apart from an increased rate of tremor and less oral candidiasis with combination therapy, the two options appear relatively safe in adults although adverse effects associated with long-term ICS treatment were seldom monitored. In children, combination therapy did not lead to a significant reduction, but rather a trend towards an increased risk, of oral steroid-treated exacerbations and hospital admissions. These trends raised concern about the safety of combination therapy in view of modest improvement in children under the age of 12 years.

An empirical evaluation of multifarious outcomes in pharmacogenetics: beta-2 adrenoceptor gene polymorphisms in asthma treatment

OBJECTIVE

Pharmacogenetics promises to individualize therapeutics. Concerns, however, exist about the lack of replication of discoveries. Selective use of different endpoints, times of assessment, types of interventions and genetic groups across studies may lead to spurious results. Here, we examined the variability of definitions of endpoints and analyses reported across studies addressing the association of the Arg16Gly and/or Gln27Glu polymorphisms of the beta2-adrenergic receptor gene with clinical response to beta2-agonist therapy in asthma.

METHODS

We systematically calculated the number and type of endpoints and analyses reported across studies and recorded the appraisal of their statistical significance.

RESULTS

Across 21 studies, the total number of probed and reported associations was 487 when the multiple endpoints and types of comparisons presented by multiple comparisons were considered (337 for Arg16Gly, 98 for Gln27Glu and 52 for their haplotypes): 465 (95%) were probed only once; only six associations were probed twice and two associations were probed five times, for the same endpoint, time of assessment, type of interventions and genetic group. Most studies (17/21) claimed at least one significant association. Overall, however, 243/487 (49.9%) probed and reported associations were not statistically significant, 120 (24.6%) were of unspecified statistical significance, 86 (17.7%) were statistically significant only for specific selected genetic contrasts and only 38 (7.8%) were genuinely statistically significant for the comparison between all available genetic groups.

CONCLUSIONS

The multifarious outcomes in this literature are inconsistent across studies and susceptible to selective reporting. The lack of standardization hinders the evaluation of replication validity for reported discoveries.

Beta2-receptor polymorphisms in patients receiving salmeterol with or without fluticasone propionate

RATIONALE

Retrospective pharmacogenetic studies have questioned whether patients with asthma who are arginine homozygous at the beta(2-)adrenergic receptor (position 16) should use long-acting beta-agonists.

OBJECTIVES

To examine whether the response to salmeterol alone or in combination with an inhaled corticosteroid is influenced by beta- receptor polymorphisms.

METHODS

Subjects using only as-needed albuterol were screened and completed two sequential open-label run-in periods (8 wk on as-needed albuterol; 8 wk on as-needed ipratropium). Five hundred forty-four subjects were randomized by Arg16Gly genotype to salmeterol alone or with fluticasone propionate for 16 weeks. Change from baseline in morning peak expiratory flow was the primary endpoint.

MEASUREMENTS AND MAIN RESULTS

Lung function responses were sustained over treatment and no statistically significant changes from baseline between genotypes within treatments were observed. Overall mean changes in morning peak flow for salmeterol with fluticasone propionate were 32.6 L/min (Arg/Arg vs. Gly/Gly, 95% confidence interval [CI], -6.3, 22.1), 25.9 L/min (Arg/Arg vs. Arg/Gly, 95% CI, -7.1, 21.3), and 24.9 L/min (Arg/Gly vs. Gly/Gly, 95% CI, -13.0, 14.6), and for salmeterol alone were 19.4 L/min (Arg/Arg vs. Gly/Gly, 95% CI, -1.7, 21.4), 24.6 L/min (Arg/Arg vs. Arg/Gly, 95% CI, -13.0, 10.6), and 12.4 L/min (Arg/Gly vs. Gly/Gly, 95% CI, -0.2, 22.3) for Arg/Arg, Arg/Gly, and Gly/Gly genotypes, respectively. Other measures of asthma control showed similar responses.

CONCLUSIONS

The results showed no evidence of a pharmacogenetic effect of beta-receptor variation on salmeterol response. Clinical trial registered with www.clinicaltrials.gov (NCT 00102882).

Role of ADRB2 gene polymorphism in asthma and response to beta(2)-agonists in Polish children

The aims of this study were: (1) to find associations of asthma with single-nucleotide polymorphisms (SNPs) within the ADRB2 gene: Arg16Gly, Gln27Glu, -1023 G/A, -367 T/C, -47 C/T ; (2) to define linkage disequilibrium in the gene region, basing on the analyzed SNPs; and (3) to analyze the importance of ADRB2 polymorphism for response to bronchodilator drugs in children diagnosed with bronchial asthma. We compared 113 asthmatic children and 123 healthy subjects from the Polish population. Genotyping was performed by PCR-RFLP. We found an association of the A allele of -1023A/G ADRB2 polymorphism with asthma (P = 0.024). No significant associations with other SNPs were detected. Moderate linkage was found between Gln27Glu and -47C/T polymorphisms in linkage disequilibrium analysis (D' = 0.85, r(2) = 0.429, LOD = 31.97). No significant differences were found in haplotype frequencies in comparison to the control group, implicating that they are not associated with susceptibility to asthma in the analyzed population. There was no significant correlation between the analyzed SNPs of the ADRB2 gene and the response to beta(2)-agonists. This is the first report providing suggestive evidence for association of -1023A/G ADRB2 polymorphism with an increased risk of asthma. The analyzed SNPs may not play a major role in response to beta(2)-agonists in asthmatic children.

Addition of inhaled long-acting beta2-agonists to inhaled steroids as first line therapy for persistent asthma in steroid-naive adults and children

BACKGROUND

Consensus statements recommend the addition of long-acting inhaled ss2-agonists (LABA) only in asthmatic patients who are inadequately controlled on inhaled corticosteroids (ICS). It is not uncommon for some patients to be commenced on ICS and LABA together as initial therapy.

OBJECTIVES

To compare the efficacy of combining inhaled corticosteroids with long-acting ss2-agonists (ICS+LABA) with inhaled corticosteroids alone (ICS alone) in steroid-naive children and adults with persistent asthma. We assessed two protocols: (1) LABA + ICS versus a similar dose of ICS (comparison 1) and (2) LABA + ICS versus a higher dose of ICS (comparison 2).

SEARCH STRATEGY

We identified randomised controlled trials through electronic database searches (May 2008).

SELECTION CRITERIA

Randomised trials comparing ICS + LABA with ICS alone in children and adults with asthma who had no inhaled corticosteroids in the preceding 28 days prior to enrolment.

DATA COLLECTION AND ANALYSIS

Each author assessed studies independently for risk of bias and extracted data. We obtained confirmation from the trialists when possible. The primary endpoint was rate of patients with one or more asthma exacerbations requiring rescue systemic corticosteroids. Results are expressed as relative risks (RR) for dichotomous data and as mean differences (MD) or standardised mean differences (SMD) for continuous data.

MAIN RESULTS

Twenty-eight study comparisons drawn from 27 trials (22 adult; five paediatric) met the review entry criteria (8050 participants). Baseline data from the studies indicated that trial populations had moderate or mild airway obstruction (FEV1>/=65% predicted), and that they were symptomatic prior to randomisation. In comparison 1, the combination of ICS and LABA was not associated with a significantly lower risk of patients with exacerbations requiring oral corticosteroids (RR 1.04; 95% confidence interval (CI) 0.73 to 1.47) or requiring hospital admissions (RR 0.38; 95% CI 0.09 to 1.65) compared to a similar dose of ICS alone. The combination of LABA and ICS led to a significantly greater improvement from baseline in FEV1 (0.12 L/sec; 95% CI 0.07 to 0.17), in symptoms (SMD -0.26; 95% CI -0.37 to -0.14) and in rescue ss2-agonist use (-0.41 puffs/day; 95% CI -0.73 to -0.09) compared with a similar dose of ICS alone. There was no significant group difference in the risk of serious adverse events (RR 1.15; 95% CI 0.64 to 2.09), any adverse events (RR 1.02; 95% CI 0.96 to 1.09), study withdrawals (RR 0.95; 95% CI 0.82 to 1.11), or withdrawals due to poor asthma control (RR 0.94; 95% CI 0.63 to 1.41).In comparison 2, the combination of LABA and ICS was associated with a higher risk of patients requiring oral corticosteroids (RR 1.24; 95% CI 1 to 1.53) and study withdrawal (RR 1.31; 95% CI 1.07 to 1.59) than a higher dose of ICS alone. For every 100 patients treated over 43 weeks, nine patients using a higher dose ICS compared to 11 (95% CI 9 to 14) on LABA and ICS suffered one or more exacerbations requiring rescue oral corticosteroids. There was a high level of statistical heterogeneity for FEV1 and morning peak flow. There was no statistically significant group difference in the risk of serious adverse events. Due to insufficient data we could not aggregate results for hospital admission, symptoms and other outcomes.

AUTHORS' CONCLUSIONS

In steroid-naive patients with mild to moderate airway obstruction, the combination of ICS and LABA does not significantly reduce the risk of patients with exacerbations requiring rescue oral corticosteroids over that achieved with a similar dose of ICS alone. However, it significantly improves lung function, reduces symptoms and marginally decreases rescue ss2-agonist use. Initiation of a higher dose of ICS is more effective at reducing the risk of exacerbations requiring rescue systemic corticosteroids, and of withdrawals, than combination therapy. Although children appeared to respond similarly to adults, no firm conclusions can be drawn regarding combination therapy in steroid-naive children, given the small number of children contributing data.

Harvesting candidate genes responsible for serious adverse drug reactions from a chemical-protein interactome

Identifying genetic factors responsible for serious adverse drug reaction (SADR) is of critical importance to personalized medicine. However, genome-wide association studies are hampered due to the lack of case-control samples, and the selection of candidate genes is limited by the lack of understanding of the underlying mechanisms of SADRs. We hypothesize that drugs causing the same type of SADR might share a common mechanism by targeting unexpectedly the same SADR-mediating protein. Hence we propose an approach of identifying the common SADR-targets through constructing and mining an in silico chemical-protein interactome (CPI), a matrix of binding strengths among 162 drug molecules known to cause at least one type of SADR and 845 proteins. Drugs sharing the same SADR outcome were also found to possess similarities in their CPI profiles towards this 845 protein set. This methodology identified the candidate gene of sulfonamide-induced toxic epidermal necrolysis (TEN): all nine sulfonamides that cause TEN were found to bind strongly to MHC I (Cw*4), whereas none of the 17 control drugs that do not cause TEN were found to bind to it. Through an insight into the CPI, we found the Y116S substitution of MHC I (B*5703) enhances the unexpected binding of abacavir to its antigen presentation groove, which explains why B*5701, not B*5703, is the risk allele of abacavir-induced hypersensitivity. In conclusion, SADR targets and the patient-specific off-targets could be identified through a systematic investigation of the CPI, generating important hypotheses for prospective experimental validation of the candidate genes.

Why do tragedies caused by Vioxx or Avandia only happen to certain individuals? The unexpected bindings among drugs and human proteins might play important roles in such serious adverse drug reactions (SADRs). To mine these unexpected chemical-protein interactions, 162 drug molecules known to cause SADRs are ‘hybridized’ onto 845 proteins to construct a chemical-protein interaction matrix, from which two aspects of the information, the binding strength and the binding conformation, are disclosed. Followed by the data-mining strategies, the unexpected bindings that mediate SADRs are identified. For example, abacavir is found to bind to the antigen presentation groove of MHC I molecule in patients carrying the B*5701 allele but not B*5703, which explains why HLA-B*5701, not B*5703, is the risk allele of abacavir hypersensitivity. This research could explain to the public that SADR happens when some of the innocent proteins are attacked by drugs unexpectedly, and variances in certain people's genome make their proteins more sensitive to the drug. By pre-therapy screening, the susceptible people could be protected. Furthermore, new drugs or modified drugs will be designed to avoid these patient-specific unintended bindings, in a step toward realizing personalized medicine.

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.

Beta 2-adrenergic polymorphisms and total serum IgE levels in children with asthma from Argentina

BACKGROUND

Beta 2-Adrenergic receptor polymorphisms occurring at amino acid positions 16 (arginine/glycine) and 27 (glutamine/glutamic acid) are known to be functionally relevant. Associations with several asthma-related phenotypes, such as total serum IgE, have been investigated with different results.

OBJECTIVE

To determine the contribution of polymorphisms and haplotypes of beta 2-adrenergic receptor with serum IgE levels in children from Argentina with mild, moderate, and severe asthma.

METHODS

Beta 2-Adrenergic receptor polymorphisms were analyzed in 124 white asthmatic children using polymerase chain reaction during a 3-year period (January 1, 2005, through December 31, 2007). Total serum IgE level was measured by standard methods in all study participants, and age-adjusted values were determined for each individual.

RESULTS

Serum levels of IgE were 4.3-fold higher than age-adjusted normal values in the study population. No association was found in regard to asthma severity. A significant difference of IgE serum levels was observed among polymorphisms at position 16, with the highest IgE level in the arginine/arginine group (P = .04). At position 27, even though median levels of IgE in homozygous glutamine were 2.2 times higher than homozygous glutamic acid, this increase did not reach statistical significance. When the population was stratified according to the most common homozygous haplotypes (arginine-arginine 16/glutamine-glutamine 27, glycine-glycine 16/glutamine-glutamine 27, and glycine-glycine 16/glutamic acid-glutamic acid 27), no association was found in relation to the serum levels of IgE.

CONCLUSIONS

Beta 2-Adrenergic receptor polymorphisms, especially homozygous arginine 16, were associated with higher serum IgE levels in children with asthma. These genetic variants appear to contribute to the IgE level in asthmatic children from Argentina.

Acute and chronic lung function responses to salmeterol and salmeterol plus fluticasone propionate in relation to Arg16Gly beta(2)-adrenergic polymorphisms

OBJECTIVE

There is conflicting clinical evidence describing the response to long-acting beta-agonist (LABA) bronchodilators for patients with Arg16Gly beta(2)-adrenergic receptor (ADRB2 ) genotype differences. Furthermore, the role of inhaled corticosteroids (ICS) in modulating Arg16Gly clinical responses is not well understood. The objective of this study was to investigate the effects of Arg16Gly polymorphism on the 12 hour post-dose bronchodilator response to the LABA salmeterol (SAL) or SAL plus fluticasone propionate (FSC) on first administration and following 12 weeks of treatment.

RESEARCH DESIGN AND METHODS

Genotyping was retrospectively performed in patients with persistent asthma randomized to SAL or FSC who were participating in three similar double-blind clinical trials of 12 week duration. The primary outcome was area under the curve (AUC) for 12 hour serial FEV(1) by treatment and Arg16Gly genotype, recorded on Day 1 and Week 12. In addition, other single nucleotide polymorphisms (SNPs) associated with asthma outcomes we assessed at positions -47, +79 and +491 as well as common ADRB2 haplotypes.

RESULTS

No statistically significant associations between Arg16Gly genotypes and serial FEV(1) clinical responses to SAL and FSC were observed following acute assessment. In addition, the FEV(1) response was preserved following 12 weeks of treatment with SAL and FSC and was not altered by Arg16Gly genotypes analyzed. These results may not be generalizable to other ethnic groups since they are derived predominantly from Caucasians.

CONCLUSIONS

In subjects with persistent asthma, the ADRB2 Arg16Gly polymorphism does not alter lung function responses to SAL or FSC over the 12 hour dosing interval following acute and chronic dosing.

Pharmacogenetic response to albuterol among asthmatics

Pharmacogenetics offers to individualize asthma treatment by identifying genetic variants associated with drug efficacy or adverse events. Several studies have focused on pharmacogenetic associations with albuterol, the most commonly prescribed medication for asthma worldwide. However, pharmacogenetic associations have varied within and between studies and across populations. Herein, we focus on pharmacogenetic associations between genetic variants in the beta(2)-adrenergic receptor gene and bronchodilator response to albuterol among subjects with asthma.

Pathways to the Best Fit of Triptans for Migraine Patients

Variability in drug response is a major barrier to the successful treatment of migraine, and most treatments are only optimal in a subset of patients. Although triptans provide the best therapeutic option for the treatment of acute migraine, it has not previously been possible to predict how well patients will respond to a specific triptan or whether they will experience unpleasant adverse events. Hence, it has been difficult for physicians to match individual patients with the most suitable agent to treat their migraine pain. Intrapatient variability has been associated with polymorphisms in genes encoding drug-metabolizing enzymes, drug transporters and drug targets. Pharmacogenetics provides the possibility of tailoring the therapeutic approach to individual patients, in order to maximize treatment efficacy while minimizing the potential for unwanted side-effects. This review demonstrates how almotriptan may overcome genetically determined responses by utilizing diverse metabolic pathways to provide therapeutic benefit to many migraineurs.

Potential adverse effects of bronchodilators in the treatment of airways obstruction in older people: recommendations for prescribing

Asthma and chronic obstructive pulmonary disease (COPD) are common disorders that are associated with increasing morbidity and mortality in older people. Bronchodilators are used widely in patients with these conditions, but even when used in inhaled form can have systemic as well as local effects. Older people experience more adverse drug effects because of pharmacodynamic and pharmacokinetic changes and particularly drug-drug and drug-disease interactions. Cardiovascular disease is common in older people and beta-adrenoceptor agonists (beta-agonists) have inotropic and chronotropic effects that can increase arrhythmias and cardiomyopathy. They can also worsen or induce myocardial ischaemia and cause electrolyte disturbances that contribute to arrhythmias. Tremor is a well known distressing adverse effect of beta-agonist administration. Long-term beta-agonist use can be associated with tolerance, poor disease control, sudden life-threatening exacerbations and asthma-related deaths. Functional beta2-adrenoceptors are present in osteoblasts, and chronic use of beta-agonists has been implicated in osteoporosis. Inhaled anticholinergics are usually well tolerated but may cause dry mouth, which can be troublesome in older people. Pupillary dilatation, blurred vision and acute glaucoma can occur from escape of droplets from loosely fitting nebulizer masks. Although ECG changes have not been seen in randomized controlled trials of long-acting inhaled anticholinergics, supraventricular tachycardias have been observed in a 5-year randomized controlled trial of ipratropium bromide. Paradoxical bronchoconstriction can occur with inhaled anticholinergics as well as with beta-agonists, but tolerance has not been reported with anticholinergics. Anticholinergic drugs also cause central effects, most notably impairment of cognitive function, and these effects have been noted with inhaled agents. Use of theophylline is limited by its adverse effects, which range from commonly occurring gastrointestinal symptoms to palpitations, arrhythmias and reports of myocardial infarction. Seizures have been reported, but are rare. Theophylline is metabolized primarily by the liver, and commonly interacts with other medications. Its concentration in plasma should be monitored closely, especially in older people. Although many clinical trials have been conducted on bronchodilators in obstructive airways disease, the results of these clinical trials need to be interpreted with caution as older people are often under-represented and subjects with co-morbidities actively excluded from these trials.

A simple and rapid genotyping assay for simultaneous detection of two ADRB2 allelic variants using fluorescence resonance energy transfer probes and melting curve analysis

Allelic variants at codons 16 and 27 of the beta(2)-adrenergic receptor gene (ADRB2) have shown clinical and pharmacological implications in asthma, hypertension, ischemic heart failure, diabetes, obesity, and cystic fibrosis. We have developed a simultaneous genotyping assay for the c.46A>G and c.79C>G allelic variants using hybridization probes and melting curve analysis. The assay was optimized on a panel of 30 DNA samples of known ADRB2 genotype as determined by sequencing with 100% concordance between the two techniques. Melting temperature (Tm) ranges for the different genotypes were obtained using data from three independent experiments. Single peaks for p.Arg16Arg (Tm = 57.76 degrees C +/- 0.10 degrees C) and p.Gly16Gly (Tm = 66.73 degrees C +/- 0.18 degrees C) and two melting peaks for p.Arg16Gly were obtained. Similarly, single peaks for p.Gln27Gln (Tm = 53.98 degrees C +/- 0.19 degrees C) and p.Glu27Glu (Tm = 64.93 degrees C +/- 0.16 degrees C) and two peaks for p.Gln27Glu were detected. Independent operators easily assigned genotypes in a sample set of 385 asthmatic patients. Haplotype and allele frequencies were in concordance with previously published data: Arg allele frequencies in children/adults were 0.34/0.30 in Caucasians and 0.45/0.52 in African Americans, and Gln allele frequencies were 0.58/0.52 in Caucasians and 0.82/0.84 in African Americans. Thus, the ADRB2 genotyping assay represents a highly reliable and rapid technique for routine clinical use in the simultaneous detection of ADRB2 variants.

Slow-responders to IV beta2-adrenergic agonist therapy: defining a novel phenotype in pediatric asthma

OBJECTIVES

While aerosolized administration of beta(2)-adrenergic receptor (beta(2)-AR) agonists is the mainstay of treatment for pediatric asthma exacerbations, the efficacy of intravenous (IV) delivery is controversial. Failure to demonstrate improved outcomes with IV beta(2)-AR agonists may be due to phenotypic differences within this patient population. Our hypothesis is that children who respond more slowly to IV beta(2)-AR agonist therapy comprise a distinct phenotype.

METHODS

Retrospective chart review of all children admitted to the ICU for status asthmaticus who were treated with IV terbutaline between December 2002 and September 2006.

RESULTS

Seventy-eight children were treated with IV terbutaline according to guidelines that adjusted the dose by clinical asthma score. After examining the histogram of duration of terbutaline infusions, a 48-hr cutoff was chosen to define responsiveness. Thirty-eight (49%) children were slow-responders by this definition. There were no significant differences in baseline asthma severity or severity on admission between the slow-responders and responders. Slow-responders required significantly higher total doses of IV terbutaline, higher maximum administration rates, and had longer ICU and hospital length of stay.

CONCLUSION

There were significant differences in outcomes between the responders and slow-responders without differences in acute or chronic illness severity. Other factors may have lead to slower response to IV beta(2)-agonist therapy.

Pharmacogenetics of asthma

Asthma is a common disease characterized by airway inflammation and bronchorestriction. There are several common categories of medications for treating asthma; however, not all asthmatics have the same response to these medications, some of which are adverse responses that are potentially life threatening. Because interindividual responses to asthma medications can vary considerably, the potential for genetic contributions to variable drug responses is significant. This chapter reviews the most common biological pathways targeted by asthma therapy and briefly discusses the genetic contribution to varied responses to asthma therapy for four common types of asthma medications: beta-agonists, anticholinergics, leukotriene modifiers, and corticosteroids.

Influence of beta2-adrenoceptor polymorphisms on the response to chronic use of albuterol in asthmatic children

BACKGROUND

Several studies have suggested that after regular use of short acting beta2-agonists the bronchodilator effect of the drug may decline and this condition would be related to polymorphisms of the beta2-adrenergic receptor (beta2-AR).

OBJECTIVE

To assess the frequency of beta2-AR polymorphisms in asthmatic children from Argentina, and to evaluate their influence on bronchodilator desensitization to albuterol over a 4-week treatment.

METHODS

beta2-AR genotypes were determined in 117 children with asthma and 101 of them were under 4 weeks treatment with albuterol. Spirometric changes in FEV(1) were recorded at the beginning (day 1) and at the end of the study (day 30) and compared to genotypes at position 16 and 27 of the receptor. The frequency of the polymorphisms was calculated in all population.

RESULTS

The presence of glutamine at position 27 (Gln27) was significantly more frequent in this Argentinean study population than in other Caucasian populations. The homozygosity for Gln27 polymorphism was associated to a desensitization of the receptor with a decline in the bronchodilator response to albuterol after chronic use.

CONCLUSION

Gln27 polymorphism might be a marker for adverse clinical outcomes with chronic beta2-agonist exposure in children with asthma from Argentina.

Confirmed beta16 Arg/Arg polymorphism in a patient with uncontrolled asthma

OBJECTIVE

To report a case of confirmed beta(16) Arg/Arg polymorphism (Arg/Arg) in a patient with uncontrolled asthma.

CASE SUMMARY

A 49-year-old black female presented to the emergency department with acute shortness of breath with subsequent intubation. After extubation, she reported multiple hospitalizations for asthma with one prior intubation, adherence to asthma medications, and very frequent use of her short-acting beta(2)-agonist (SABA). Because of her asthma history, self-reported adherence, and race, she was tested for beta(2)-adrenoreceptor genotype, which revealed Arg/Arg. Based on these findings, beta(2)-agonists were discontinued and tiotropium (maintenance) and ipratropium (primary rescue) were initiated as part of her asthma regimen. Application of the Naranjo probability scale revealed probable causality between uncontrolled asthma in our patient and SABA use. The patient is followed in our outpatient pulmonary clinic and, at time of writing, had not been admitted to our hospital for asthma-related events.

DISCUSSION

Approximately 15% of Americans with asthma are Arg/Arg, with an increased prevalence in black and Asian populations. It is hypothesized that changes in the degree of sensitivity or desensitization to the bronchodilator effect of beta(2)-agonists may occur in these individuals. Data exist, although they are conflicting, suggesting that inhaled beta(2)-agonists may worsen clinical outcomes. Trials have reported declines in peak expiratory flow rates plus increases in asthma symptoms and exacerbations when SABAs have been used regularly in patients with Arg/Arg. Studies evaluating long-acting beta(2)-agonists (LABAs) have inconsistent results. Preliminary data suggest that anticholinergics may serve as a beneficial primary rescue medication instead of beta(2)-agonists in patients with Arg/Arg.

CONCLUSIONS

Clinicians should be aware of factors (eg, race and polymorphisms) that may predict unfavorable outcomes with regular SABA and possibly LABA use. Patients with poor asthma control despite adherence to asthma therapy may benefit from beta(2)-adrenoreceptor genotyping and, possibly, from anticholinergics.

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.

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.