Use of regularly scheduled albuterol treatment in asthma: genotype-stratified, randomised, placebo-controlled cross-over trial

Genomewide association between GLCCI1 and response to glucocorticoid therapy in asthma

BACKGROUND

The response to treatment for asthma is characterized by wide interindividual variability, with a significant number of patients who have no response. We hypothesized that a genomewide association study would reveal novel pharmacogenetic determinants of the response to inhaled glucocorticoids.

METHODS

We analyzed a small number of statistically powerful variants selected on the basis of a family-based screening algorithm from among 534,290 single-nucleotide polymorphisms (SNPs) to determine changes in lung function in response to inhaled glucocorticoids. A significant, replicated association was found, and we characterized its functional effects.

RESULTS

We identified a significant pharmacogenetic association at SNP rs37972, replicated in four independent populations totaling 935 persons (P=0.0007), which maps to the glucocorticoid-induced transcript 1 gene (GLCCI1) and is in complete linkage disequilibrium (i.e., perfectly correlated) with rs37973. Both rs37972 and rs37973 are associated with decrements in GLCCI1 expression. In isolated cell systems, the rs37973 variant is associated with significantly decreased luciferase reporter activity. Pooled data from treatment trials indicate reduced lung function in response to inhaled glucocorticoids in subjects with the variant allele (P=0.0007 for pooled data). Overall, the mean (±SE) increase in forced expiratory volume in 1 second in the treated subjects who were homozygous for the mutant rs37973 allele was only about one third of that seen in similarly treated subjects who were homozygous for the wild-type allele (3.2±1.6% vs. 9.4±1.1%), and their risk of a poor response was significantly higher (odds ratio, 2.36; 95% confidence interval, 1.27 to 4.41), with genotype accounting for about 6.6% of overall inhaled glucocorticoid response variability.

CONCLUSIONS

A functional GLCCI1 variant is associated with substantial decrements in the response to inhaled glucocorticoids in patients with asthma.

Pharmacogenomics of β-adrenergic receptor physiology and response to β-blockade

Myocardial β-adrenergic receptors (βARs) are important in altering heart rate, inotropic state, and myocardial relaxation (lusitropy). The β1AR and β2AR stimulation increases cyclic adenosine monophosphate concentration with the net result of myocyte contraction, whereas β3AR stimulation results in decreased inotropy. Downregulation of β1ARs in heart failure, as well as an increased β3AR activity and density, lead to decreased cyclic adenosine monophosphate production and reduced inotropy. The βAR antagonists are commonly used in patients with coronary artery disease and heart failure; however, perioperative use of βAR antagonists is controversial. Individual patient's response to beta-blocker therapy is an area of intensive research, and apart from pharmacokinetics, pharmacodynamics, and ethnic differences, genetic alterations have become more important in the last 20 years. The most common genetic variants in humans are single nucleotide polymorphisms (SNPs). There are 2 clinically relevant SNPs for the β1AR (Ser49Gly, Arg389Gly), 3 for the β2AR (Arg16Gly, Gln27Glu, Thr164Ile), and 1 for the β3AR (Trp64Arg). Although results are somewhat controversial, generally large datasets have the potential to show a relationship between βAR SNPs and outcomes such as development and progression of heart failure, coronary artery disease, vascular reactivity, hypertension, asthma, obesity, and diabetes. Although βAR SNPs may not directly cause disease, they appear to be risk factors for, and modifiers of, disease and the response to stress and drugs. In the perioperative setting, this has specifically been demonstrated for the Arg389Gly β1AR polymorphism with which patients with the Gly variant had a higher incidence of adverse perioperative events. Knowing that genetic variants play an important role, perioperative medicine will likely change from simple therapeutic intervention to a more personalized way of adrenergic receptor modulation.

Protective effects of glycyrrhizin against β₂-adrenergic receptor agonist-induced receptor internalization and cell apoptosis

It has been reported that treatment with β₂ adrenergic receptor (β₂AR) agonist bronchodilators may result in airway β₂ARs internalization and cardiac muscle cells apoptosis. This could lead to the loss of pharmacological effect of β₂AR agonists and increase adverse cardiovascular events in asthma patients receiving β₂AR agonist therapy. Glycyrrhizin, the major bioactive component of licorice root extract, has been reported to exhibit protective effect on respiratory system. Here, we investigate the effects of glycyrrhizin against β₂AR agonist salbutamol-induced receptor internalization and cell apoptosis. In our study, the live cell confocal imaging and fixed-cell enzyme-linked immunosorbent assay (ELISA) assay revealed that glycyrrhizin significantly inhibited salbutamol-induced surface β₂AR internalization. The underlying mechanisms were then identified to be that glycyrrhizin could reduce the association of β₂ARs with β-arrestins and clathrin heavy chain as well as the level of G protein-coupled receptor kinase (GRK) mediated phosphorylation of β₂ARs. The inhibition of receptor internalization by glycyrrhizin further lead to stabilization of the β₂AR mRNA and protein expression, thus amplified the transmembrane signaling via the β₂ARs. We also proved that glycyrrhizin could profoundly attenuate salbutamol-induced early cellular apoptosis by regulating the expressions of B-cell lymphoma 2 (Bcl-2) family genes. Taken together, our results suggest that glycyrrhizin exhibits protective effects against β₂AR agonist-induced receptor internalization and cell apoptosis. These findings might have practical implications for future strategies of combined application of glycyrrhizin with β₂AR receptor agonists to improve the efficacy of bronchodilators in patients with asthma and chronic obstructive pulmonary disease (COPD).

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.

Arg16Gly β2-adrenergic receptor gene polymorphism in Japanese patients with aspirin-exacerbated respiratory disease

BACKGROUND

There has been no report that investigated β(2)-adrenergic receptor (ADRB2) gene polymorphism in patients with aspirin-exacerbated respiratory disease (AERD).

METHODS

DNA in the specimens in three groups of study subjects classified patients with AERD, patients with aspirin-tolerant asthma (ATA) and normal controls was extracted, and the target DNA sequence of the ADRB2 was amplified using a set of primers to generate an amplicon of 219 bp in length. Allelic discrimination assay for single nucleotide polymorphisms relating to the ADRB2 gene expression was carried out by using a previously described single nucleotide polymorphism detective system, sequence-specific thermal-elution chromatography.

RESULTS

The frequency of the Gly variant allele in patients with AERD was significantly lower than that in patients with ATA (p = 0.007), and the odds ratio (OR) of AERD to ATA associated with wild-type ArgArg homozygote was 3.300. Frequencies of wild-type ArgArg homozygote are significantly higher than those of variant-type ArgGly/GlyGly genotype in patients with AERD compared with those with ATA (p < 0.001, OR = 3.153). In patients with AERD, frequencies of wild-type ArgArg homozygote in both female and male patients are significantly higher than those of variant-type ArgGly/GlyGly genotype in male patients compared with those with ATA (p < 0.001, OR = 5.128 and p = 0.007, OR = 4.367, respectively). Also, in patients with AERD, frequencies of wild-type ArgArg homozygote in female patients are significantly higher than those of variant-type ArgGly/GlyGly genotype in female patients compared with those with ATA (p = 0.002, OR = 2.825).

CONCLUSIONS

We were the first to analyze Arg16Gly ADRB2 gene polymorphism in Japanese patients with AERD, and showed that Arg16Gly ADRB2 gene polymorphism in Japanese patients with AERD is different from that in the patients with ATA.

The impact of tiotropium on mortality and exacerbations when added to inhaled corticosteroids and long-acting β-agonist therapy in COPD

BACKGROUND

Tiotropium has been shown to improve lung function, quality of life, and exacerbations and reduce mortality when compared with placebo in COPD. It remains unclear whether benefits are seen when tiotropium is used in conjunction with inhaled corticosteroids (ICSs) plus long-acting β-agonists (LABAs).

METHODS

We performed a retrospective cohort study using a National Health Service database of patients with COPD in Tayside, Scotland, between 2001 and 2010 that is linked with databases regarding hospital admissions, pharmacy prescriptions, and death registries. The impact of the addition of tiotropium (Tio) to ICS + LABA therapy on all-cause mortality, hospital admissions for respiratory disease, and emergency oral corticosteroid bursts was evaluated. Adjusted hazard ratios (HRs) were calculated by Cox regression after inclusion of the following covariates: cardiovascular and respiratory disease, diabetes, smoking, age, sex, and deprivation index.

RESULTS

A total of 1,857 patients were given ICS + LABA + Tio, and 996 were given ICS + LABA. Mean follow-up was 4.65 years. The adjusted HR for all-cause mortality for ICS + LABA + Tio vs ICS + LABA was 0.65 (95% CI, 0.57-0.75; P < .001). Adjusted HRs for hospital admissions and oral corticosteroid bursts were 0.85 (95% CI, 0.73-0.99; P = .04) and 0.71 (95% CI, 0.63-0.80; P < .001), respectively.

CONCLUSIONS

The study suggests that the addition of tiotropium to ICSs and LABA therapy may confer benefits in reducing all-cause mortality, hospital admissions, and oral corticosteroid bursts in patients with COPD. Triple therapy is widely used in the real-life management of COPD, with only limited scientific support. The study supports the use of triple therapy in COPD and provides a platform for randomized controlled trials specifically addressing this topic.

Biochemical basis of asthma therapy

Current therapy for asthma is highly effective. β(2)-Adrenergic receptor (β(2)AR) agonists are the most effective bronchodilators and relax airway smooth muscle cells through increased cAMP concentrations and directly opening large conductance Ca(2+) channels. β(2)AR may also activate alternative signaling pathways that may have detrimental effects in asthma. Glucocorticoids are the most effective anti-inflammatory treatments and switch off multiple activated inflammatory genes through recruitment of histone deacetylase-2, activating anti-inflammatory genes, and through increasing mRNA stability of inflammatory genes. There are beneficial molecular interactions between β(2)AR and glucocorticoid-activated pathways. Understanding these signaling pathways may lead to even more effective therapies in the future.

Pharmacogenomics of pediatric asthma

CONTEXT:

Asthma is a complex disease with multiple genetic and environmental factors contributing to it. A component of this complexity is a highly variable response to pharmacological therapy. Pharmacogenomics is the study of the role of genetic determinants in the variable response to therapy. A number of examples of possible pharmacogenomic approaches that may prove of value in the management of asthma are discussed below.

EVIDENCE ACQUISITION:

A search of PubMed, Google scholar, E-Medicine, BMJ and Mbase was done using the key words “pharmacogenomics of asthma”, “pharmacogenomics of β-agonist, glucocorticoids, leukotriene modifiers, theophylline, muscarinic antagonists in asthma”.

RESULTS:

Presently, there are limited examples of gene polymorphism that can influence response to asthma therapy. Polymorphisms that alter response to asthma therapy include Arg16Gly, Gln27Glu, Thr164Ile for β-agonist receptor, polymorphism of glucocorticoid receptor gene, CRHR1 variants and polymorphism of LTC4S, ALOX5. Polymorphic variants of muscarinic receptors, PDE4 and CYP450 gene variants.

CONCLUSION:

It was concluded that genetic variation can improve the response to asthma therapy. However, no gene polymorphism has been associated with consistent results in different populations. Therefore, asthma pharmacogenomic studies in different populations with a large number of subjects are required to make possible tailoring the asthma therapy according to the genetic characteristic of individual patient.

New approaches to managing asthma: a US perspective

Despite remarkable advances in diagnosis and long-term management, asthma remains a serious public health concern. Newly updated expert guidelines emphasize the intra- and inter-individual variability of asthma and highlight the importance of periodic assessment of asthma control. These guidelines update recommendations for step-wise asthma treatment, address the burgeoning field of asthma diagnostics, and stress the importance of a patient and health care professional partnership, including written action plans and self monitoring. The field of asthma therapeutics is expanding rapidly, with promising new treatment options available or in development that may address some of the existing barriers to successful asthma management. These approaches simplify treatment, use combinations of agents in one delivery device that have complementary actions, or target specific pathways involved in asthma patho-physiology. Considerable activity is taking place in asthma pharmacogenetics. This review provides an overview of these new approaches to managing asthma, including their present status and future potential.

Albuterol enantiomer levels, lung function and QTc interval in patients with acute severe asthma and COPD in the emergency department

Background

This observational study was designed to investigate plasma levels of albuterol enantiomers among patients with acute severe asthma or COPD presenting to the emergency department, and the relationship with extra-pulmonary cardiac effects (QTc interval) and lung function. Recent reviews have raised concerns about the safety of using large doses of β₂-agonists, especially in patients with underlying cardiovascular comorbidity. It has been demonstrated that significant extrapulmonary effects can be observed in subjects given nebulised (R/S)-albuterol at a dose of as little as 6.5 mg.

Methods

Blood samples were collected and plasma/serum levels of (R)- and (S)-albuterol enantiomers were determined by LC-MS and LC-MS/MS assay. Extra-pulmonary effects measured at presentation included ECG measurements, serum potassium level and blood sugar level, which were collected from the hospital medical records.

Results

High plasma levels of both enantiomers were observed in some individuals, with median (range) concentrations of 8.2 (0.6-24.8) and 20.6 (0.5-57.3) ng/mL for (R)- and (S)- albuterol respectively among acute asthma subjects, and 2.1 (0.0-16.7) to 4.1 (0.0-36.1) ng/mL for (R)- and (S)- albuterol respectively among COPD subjects. Levels were not associated with an improvement in lung function or adverse cardiac effects (prolonged QTc interval).

Conclusions

High plasma concentrations of albuterol were observed in both asthma and COPD patients presenting to the emergency department. Extra-pulmonary cardiac adverse effects (prolonged QTC interval) were not associated with the plasma level of (R)- or (S)-albuterol when administered by inhaler in the emergency department setting. Long-term effect(s) of continuous high circulating albuterol enantiomer concentrations remain unknown, and further investigations are required.

Current progress in pharmacogenetics

The study of genetic variation has the potential to aid understanding of the mechanisms underlying the observed inter-individual variation in drug response and by which idiosyncratic adverse effects occur. In this review, we outline current progress in pharmacogenetics using examples to highlight both mechanisms of influence of polymorphisms and research strategies for their detection. In the final sections we discuss contemporary challenges for both researchers and clinicians.

Association of β₂-adrenergic receptor polymorphism with work-related symptoms in workers exposed to wheat flour

PURPOSE

Our previous study indicated that the presence of wheat-specific IgG1 and IgG4 antibodies was associated with work-related symptoms in workers exposed to wheat flour. We performed this study to investigate the genetic polymorphisms of β₂-adrenergic receptors and wheat-specific antibodies in association with the clinical parameters of baker's asthma.

MATERIALS AND METHODS

In total, 379 subjects working in a single industrial bakery were enrolled in this study. The skin prick test was performed with common inhalant allergens and wheat flour extract. The presence of serum- specific IgE, IgG1, and IgG4 antibodies to wheat flour were determined by ELISA. Whole blood samples were obtained for genotype analysis. Subjects were genotyped with regard to five candidate single nucleotide polymorphisms (SNPs) of the β₂-adrenergic receptor gene (ADRB2; -47 T>C, 46 A>G, 79 C>G, 252 G>A, and 523 C>A) using a single-base extension method.

RESULTS

No significant associations were observed between the genotype/allele frequencies of any of the SNPs tested and any clinical parameters. The haplotype of ADRB2 (GAA composed of 46 A>G, 252 G>A, and 523 C>A) was significantly associated with work-related symptoms (p<0.05). Moreover, in subjects with the AG or GG genotype at 46 A>G and haplotype [GAA] of ADRB2, the prevalence rates of wheat-specific IgG1 antibodies and lower respiratory symptoms increased significantly with exposure intensity (both p<0.05).

CONCLUSION

The findings of the present study suggest that ADRB2 genetic polymorphism may contribute to the development of work-related symptoms in workers exposed to wheat flour, which can lead to baker's asthma.

Asthma in sickle cell disease: implications for treatment

Objective. To review issues related to asthma in sickle cell disease and management strategies. Data Source. A systematic review of pertinent original research publications, reviews, and editorials was undertaken using MEDLlNE, the Cochrane Library databases, and CINAHL from 1947 to November 2010. Search terms were [asthma] and [sickle cell disease]. Additional publications considered relevant to the sickle cell disease population of patients were identified; search terms included [sickle cell disease] combined with [acetaminophen], [pain medications], [vitamin D], [beta agonists], [exhaled nitric oxide], and [corticosteroids]. Results. The reported prevalence of asthma in children with sickle cell disease varies from 2% to approximately 50%. Having asthma increases the risk for developing acute chest syndrome , death, or painful episodes compared to having sickle cell disease without asthma. Asthma and sickle cell may be linked by impaired nitric oxide regulation, excessive production of leukotrienes, insufficient levels of Vitamin D, and exposure to acetaminophen in early life. Treatment of sickle cell patients includes using commonly prescribed asthma medications; specific considerations are suggested to ensure safety in the sickle cell population. Conclusion. Prospective controlled trials of drug treatment for asthma in patients who have both sickle cell disease and asthma are urgently needed.

Anticholinergics in Chronic Asthma: A Promising Future?

Anticholinergics have been used for the treatment of asthma as bronchodilators for centuries, yet they have not gained U.S. Food and Drug Administration approval for use in asthma. Previous studies with the short-acting inhaled anticholinergics, ipratropium bromide, oxitropium bromide, and atropine methonitrate, have failed to demonstrate improved outcomes in chronic persistent asthma. Ipratropium bromide is recommended by national and international guidelines for the adjunctive treatment of severe acute asthma exacebations in the emergency department to reduce hospitalizations. A recent trial reported that the long-acting anticholinergic, tiotropium bromide, in those adult patients not adequately controlled on inhaled corticosteroid monotherapy improved impairment outcomes of lung function and symptoms compared to doubling the dose of inhaled corticosteroid similar to the effect of the addition of a long-acting β₂ agonist. More studies are needed to determine whether tiotropium bromide can reduce the risk of asthma exacerbations, but the early results from the first study are promising.

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.

A novel small molecule target in human airway smooth muscle for potential treatment of obstructive lung diseases: a staged high-throughput biophysical screening

Background

A newly identified mechanism of smooth muscle relaxation is the interaction between the small heat shock protein 20 (HSP20) and 14-3-3 proteins. Focusing upon this class of interactions, we describe here a novel drug target screening approach for treating airflow obstruction in asthma.

Methods

Using a high-throughput fluorescence polarization (FP) assay, we screened a library of compounds that could act as small molecule modulators of HSP20 signals. We then applied two quantitative, cell-based biophysical methods to assess the functional efficacy of these molecules and rank-ordered their abilities to relax isolated human airway smooth muscle (ASM). Scaling up to the level of an intact tissue, we confirmed in a concentration-responsive manner the potency of the cell-based hit compounds.

Results

Among 58,019 compound tested, 268 compounds caused 20% or more reduction of the polarized emission in the FP assay. A small subset of these primary screen hits, belonging to two scaffolds, caused relaxation of isolated ASM cell in vitro and attenuated active force development of intact tissue ex vivo.

Conclusions

This staged biophysical screening paradigm provides proof-of-principle for high-throughput and cost-effective discovery of new small molecule therapeutic agents for obstructive lung diseases.

Acceptance of Asthma Pharmacogenetic Study by Children and Adults

BACKGROUND

Pharmacogenetic testing may change clinical medicine by allowing clinicians to tailor medications based on a patient's genetic makeup, however, these tests must first be validated in large, real-life populations of subjects that include children. A dearth of knowledge exists for whether pediatric populations are as willing as adult populations to provide samples for such studies.

OBJECTIVE

(1) To assess whether pediatric and adult patients with persistent asthma are willing to provide specimens for DNA extraction and genetic studies. (2) To assess whether patients' willingness to provide blood as compared to buccal smear specimens differ.

METHODS

Of 644 patients ages 4-38 years who had three or more prescription fills for inhaled corticosteroids in one year, 60% (385) were randomized to the blood specimen group and 40% (259) were randomized to the buccal smear group in order to study acceptance of different biospecimen collection methods. Research assistants contacted subjects to obtain consent, perform a phone survey, and request a specimen.

RESULTS

There were no baseline differences between subjects randomized to the blood specimen group versus buccal smear group with respect to age, gender, or number of dispensings of inhaled corticosteroids. Of 259 subjects in the buccal smear group, 30% (78) provided samples, and of 385 subjects in the blood specimen group, 16% (60) provided samples. Subjects randomized to the buccal smear group were more likely to provide specimens for genetic study compared to subjects randomized to the blood specimen group (RR 1.21; 95% CI 1.10 - 1.32), even after adjusting for age. Pediatric subjects were more likely to provide specimens for genetic study than adult subjects with 23% (113) of pediatric subjects providing samples and 15% (25) of adult subjects providing samples (p=0.03).

CONCLUSION

Children with asthma are as likely to participate in genetic studies as adults. Both children and adult subjects are more likely to provide buccal smear specimens rather than blood specimens for genetic study.

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.

Common ADRB2 haplotypes derived from 26 polymorphic sites direct beta2-adrenergic receptor expression and regulation phenotypes

Background

The β₂-adrenergic receptor (β₂AR) is expressed on numerous cell-types including airway smooth muscle cells and cardiomyocytes. Drugs (agonists or antagonists) acting at these receptors for treatment of asthma, chronic obstructive pulmonary disease, and heart failure show substantial interindividual variability in response. The ADRB2 gene is polymorphic in noncoding and coding regions, but virtually all ADRB2 association studies have utilized the two common nonsynonymous coding SNPs, often reaching discrepant conclusions.

Methodology/Principal Findings

We constructed the 8 common ADRB2 haplotypes derived from 26 polymorphisms in the promoter, 5′UTR, coding, and 3′UTR of the intronless ADRB2 gene. These were cloned into an expression construct lacking a vector-based promoter, so that β₂AR expression was driven by its promoter, and steady state expression could be modified by polymorphisms throughout ADRB2 within a haplotype. “Whole-gene” transfections were performed with COS-7 cells and revealed 4 haplotypes with increased cell surface β₂AR protein expression compared to the others. Agonist-promoted downregulation of β₂AR protein expression was also haplotype-dependent, and was found to be increased for 2 haplotypes. A phylogenetic tree of the haplotypes was derived and annotated by cellular phenotypes, revealing a pattern potentially driven by expression.

Conclusions/Significance

Thus for obstructive lung disease, the initial bronchodilator response from intermittent administration of β-agonist may be influenced by certain β₂AR haplotypes (expression phenotypes), while other haplotypes may influence tachyphylaxis during the response to chronic therapy (downregulation phenotypes). An ideal clinical outcome of high expression and less downregulation was found for two haplotypes. Haplotypes may also affect heart failure antagonist therapy, where β₂AR increase inotropy and are anti-apoptotic. The haplotype-specific expression and regulation phenotypes found in this transfection-based system suggest that the density of genetic information in the form of these haplotypes, or haplotype-clusters with similar phenotypes can potentially provide greater discrimination of phenotype in human disease and pharmacogenomic association studies.

Pharmacogenetics and human genetic polymorphisms

The term pharmacogenetics was first used in the late 1950s and can be defined as the study of genetic factors affecting drug response. Prior to formal use of this term, there was already clinical data available in relation to variable patient responses to the drugs isoniazid, primaquine and succinylcholine. The subject area developed rapidly, particularly with regard to genetic factors affecting drug disposition. There is now comprehensive understanding of the molecular basis for variable drug metabolism by the cytochromes P450 and also for variable glucuronidation, acetylation and methylation of certain drugs. Some of this knowledge has already been translated to the clinic. The molecular basis of variation in drug targets, such as receptors and enzymes, is generally less well understood, although there is consistent evidence that polymorphisms in the genes encoding the β-adrenergic receptors and the enzyme vitamin K epoxide reductase is of clinical importance. The genetic basis of rare idiosyncratic adverse drug reactions had also been examined. Susceptibility to reactions affecting skin and liver appears to be determined in part by the HLA (human leucocyte antigen) genotype, whereas reactions affecting the heart and muscle may be determined by polymorphisms in genes encoding ion channels and transporters respectively. Genome-wide association studies are increasingly being used to study drug response and susceptibility to adverse drug reactions, resulting in identification of some novel pharmacogenetic associations.

Recent advances in pediatric asthma treatment

Although wheezing illness is at its most prevalent in infancy and early childhood, its self-limiting nature in the majority poses considerable challenges in offering a long-term prognosis and in initiating long-term prophylaxis. Many of the established treatments in adults have not been adequately assessed in children. Evidence is also emerging for a number of different wheezing syndromes, several of which do not to respond well to currently available medicines. Much research interest is being directed to underlying changes within the airway that appear to be independent of allergic mechanisms and that may lead to novel therapeutic approaches. The aim of this review is to restate and update current best-practice based on evidence, to encourage effective and safe use of asthma medication in children and to point to areas of ongoing research that are likely to influence management decisions in the near future.

Treatment of persistent asthma with Symbicort (budesonide/formoterol inhalation aerosol): an inhaled corticosteroid and long-acting beta2-adrenergic agonist in one pressurized metered-dose inhaler

OBJECTIVE

Budesonide/formoterol inhalation aerosol (Symbicort AstraZeneca, Wilmington, Delaware) is an inhaled corticosteroid (ICS) and long-acting beta(2)-adrenergic agonist (LABA) combination administered twice daily via one hydrofluoroalkane pressurized metered-dose inhaler (pMDI) approved in the United States for the long-term maintenance treatment of persistent asthma in patients >or=12 years of age whose asthma cannot be controlled by an ICS alone. The objective was to review efficacy, safety, and pharmacogenetic data on budesonide/formoterol pMDI in the treatment of persistent asthma.

METHODS

The authors searched PubMed and respiratory meeting databases to identify asthma studies of budesonide/formoterol pMDI. Studies involving traditional and patient-reported outcomes, safety, tolerability, or pharmacogenetics were included.

RESULTS

In two 12-week pivotal trials in adolescents and adults, treatment with budesonide/formoterol pMDI 160/4.5 microg x 2 inhalations (320/9 microg) twice daily for moderate to severe persistent asthma or 80/4.5 microg x 2 inhalations (160/9 microg) twice daily for mild to moderate persistent asthma, demonstrated greater efficacy and similar tolerability compared with placebo and the same nominal dose of its monocomponents. Comparisons with formoterol dry powder inhaler (DPI) for predose forced expiratory volume in one second (FEV(1)) and with budesonide pMDI for 12-hour mean postdose FEV(1) demonstrated the anti-inflammatory and bronchodilatory contributions of budesonide and formoterol, respectively. Evaluations of patient-reported outcomes, including asthma-specific quality of life and treatment satisfaction, further supported the clinical benefits of budesonide/formoterol pMDI. In a 52-week tolerability study of patients aged >or=12 years, budesonide/formoterol pMDI was delivered at up to double the maximum dose (640/18 microg twice daily) and demonstrated a safety profile similar to that of budesonide (640 microg twice daily), with no unexpected pattern of abnormalities. Additional studies reported that budesonide/formoterol pMDI 320/9 microg twice daily and fluticasone propionate/salmeterol DPI 250/50 microg twice daily have similar efficacy and tolerability, with significantly more patients achieving >or=15% improvement in FEV(1) within 15 minutes with budesonide/formoterol pMDI compared with fluticasone/salmeterol DPI. Moreover, inheritance of the Gly16Arg polymorphism of the beta(2)-adrenergic receptor does not appear to affect clinical outcomes with budesonide/formoterol pMDI.

CONCLUSION

Budesonide/formoterol pMDI administered twice daily is effective and generally well tolerated in patients whose asthma is not well controlled on ICS alone.

Genetic factors in the treatment of bronchial asthma

Owing to the recent vast progress in analytical tools and procedures to elucidate the relationship between genes and diseases, many candidate genes leading to the development of bronchial asthma have been reported. However, the quantitative phenotypes of asthma, such as decrease in forced expiratory volume in the first second, serum hyper-IgE, bronchial hyperresponsiveness and blood hyper-eosinophilia, do not represent this disease completely. On the other hand, eosinophilic inflammation of the bronchial mucosa represents accurately the feature of bronchial asthma, although accurate quantification of its status is difficult. While the production of interleukin (IL)-5 in peripheral CD4(+) T cells probably correlates with eosinophilic inflammation of the airway, the effectiveness of anti-IL-5 antibody for the treatment of bronchial asthma is controversial. Since intervention with asthma-causing gene products may not be sufficient for the treatment of this disease, identification of therapy-responsive genes should become more important in the near future.

Effects of asthma treatment: the present and future

The increasing burden of asthma in both primary and secondary care has led to extensive research into its genetics, pathophysiology and treatment over the past few decades. Inhaled corticosteroids remain an integral component in all but the mildest disease, although despite a low-to-moderate dose, many individuals remain symptomatic. In patients with persistent symptoms despite inhaled corticosteroids, a variety of different nonsteroidal second-line therapies are available as add-on therapy. In this review, existing and potential future pharmacological strategies involved in the management of asthma will be highlighted.

Use and safety of long-acting β2-agonists for pediatric asthma

Asthma guidelines recommend the use of long-acting β2-agonists (LABAs) as the preferred add-on therapy for adults and children over 5 years of age when asthma is inadequately controlled by inhaled corticosteroids alone. It has been suggested that LABA use may be associated with an increased risk of morbidity and mortality; however, this view is controversial since study findings have been inconsistent. While the safety profile of LABA monotherapy has been questioned, the value of concomitant inhaled corticosteroids to eliminate possible risks remains unproven. There is a paucity of efficacy and safety data for LABA use in children, and existing evidence is not sufficiently convincing to demonstrate a clear position for LABAs in the management of childhood asthma. The main aims of this article are to place LABAs in context in the management of childhood asthma and evaluate the current evidence for safety and efficacy.

Paradoxical trough effects of triple therapy with budesonide/formoterol and tiotropium bromide on pulmonary function outcomes in COPD

BACKGROUND

Lowest receptor occupancy for a drug occurs at trough prior to the next dose. Previous studies have focused on the effects of triple therapy at peak dose intervals using forced expiratory maneuvers. Impulse oscillometry (IOS) and body plethysmography (PLETH) are more sensitive than spirometry to assess inhaled therapies in COPD.

METHODS

Nineteen patients with COPD (FEV(1)/FVC ratio < 0.7; FEV(1) < 60%) completed a double-blind randomized crossover trial of tiotropium 18 microg/d or placebo for 2 weeks each, with a 1-week washout. Prior to this procedure, there was a nonrandomized 4 week run-in of budesonide/formoterol 200/6 2 puffs bid, which continued throughout the study. Spirometry, IOS, and PLETH were performed both before pre- and post-budesonide/formoterol run-in and at trough following the first and last dose of tiotropium (ie, 24 h posttiotropium and 12 h post-budesonide/formoterol).

RESULTS

Mean +/- SEM for age and FEV(1) were 65 +/- 2 years and 42 +/- 2%, respectively. Following initial budesonide/formoterol, there were no significant changes in spirometry; however, all measures of IOS and PLETH deteriorated (P < .01 for all outcomes). Compared with placebo, tiotropium was additive to budesonide/formoterol after single and chronic dosing measured by FEV(1) (P < .001 and P = .014, respectively) and forced expiratory flow, midexpiratory phase (P = .001; P= .026), whereas specific airway resistance, reactance, resonant frequency, and area under the reactance curve showed additive benefits at a single dose only.

CONCLUSIONS

Budesonide/formoterol caused an unexpected worsening of IOS and PLETH outcomes compared with a washed-out baseline in the nonplacebo-controlled run-in. This finding was not observed with spirometry. Subsequent addition of tiotropium improved lung function with all techniques after a single dose and for spirometry after chronic dosing. These paradoxical findings may reflect beta2-adrenoceptor downregulation and muscarinic 3 receptor cross talk. Placebo-controlled studies are required to explore this result.

The role of pharmacogenomics in improving the management of asthma

There is a large amount of interindividual variability in both therapeutic and adverse responses to asthma therapies. Genetic variability can account for 50% to 60% of this variability. Pharmacogenomics holds out the promise of allowing clinicians to prospectively choose therapies that have the greatest likelihood to be effective for individual patients and to avoid those that might have a high likelihood of producing adverse effects. In this article we review the principles of pharmacogenomic investigation. We explore the data developed from the early pharmacogenomic studies with the most common asthma therapies. Furthermore, we explore the potential use of pharmacogenomics, as well as caveats in interpreting such information.

Gene--environment-wide association studies: emerging approaches

Despite the yield of recent genome-wide association (GWA) studies, the identified variants explain only a small proportion of the heritability of most complex diseases. This unexplained heritability could be partly due to gene--environment (G×E) interactions or more complex pathways involving multiple genes and exposures. This Review provides a tutorial on the available epidemiological designs and statistical analysis approaches for studying specific G×E interactions and choosing the most appropriate methods. I discuss the approaches that are being developed for studying entire pathways and available techniques for mining interactions in GWA data. I also explore methods for marrying hypothesis-driven pathway-based approaches with 'agnostic' GWA studies.

Beta-Adrenergic Agonists

Inhaled β₂-adrenoceptor (β₂-AR) agonists are considered essential bronchodilator drugs in the treatment of bronchial asthma, both as symptoms-relievers and, in combination with inhaled corticosteroids, as disease-controllers. In this article, we first review the basic mechanisms by which the β₂-adrenergic system contributes to the control of airway smooth muscle tone. Then, we go on describing the structural characteristics of β₂-AR and the molecular basis of G-protein-coupled receptor signaling and mechanisms of its desensitization/ dysfunction. In particular, phosphorylation mediated by protein kinase A and β-adrenergic receptor kinase are examined in detail. Finally, we discuss the pivotal role of inhaled β₂-AR agonists in the treatment of asthma and the concerns about their safety that have been recently raised.

Clinical implications of the intrinsic efficacy of beta-adrenoceptor drugs in asthma: full, partial and inverse agonism

PURPOSE OF REVIEW

beta2-Adrenoceptor (AR) agonists are the most effective bronchodilators known, and play important roles in every step of asthma therapy. Intrinsic efficacy is an important pharmacological property that differentiates the clinical effects and safety profile of beta2-AR agonists. We review the role of beta2-AR agonist intrinsic efficacy in asthma treatment focusing on recent literature.

RECENT FINDINGS

In acute asthma, a full agonist (high intrinsic efficacy) offers a clinical advantage over a partial agonist (low intrinsic efficacy) but with the potential of inducing dose-dependent adverse effects. The chronic use of beta2-AR agonists may be associated with several adverse outcomes including loss of asthma control and even increased mortality. Recently, the role of beta-AR inverse agonists (beta-blockers) which have a negative intrinsic efficacy was studied. Whereas contraindicated in acute asthma, preliminary data suggest that the chronic use of these agents may be associated with attenuation of airway hyper-responsiveness in patients with mild asthma. Studies in a murine model of asthma suggest that such effects may be related to decreased airway inflammation and mucous metaplasia.

SUMMARY

Rational choice among beta2-AR agonists in acute and chronic asthma should be influenced by differences in intrinsic efficacy among these agents. In acute severe asthma, a full agonist offers a clinical advantage over a partial agonist. Whereas the use of inverse agonists in the treatment of asthma is still experimental and needs further exploration in future trials, preliminary studies suggest that their chronic use is well tolerated and is associated with decreased airway hyper-responsiveness.

Heterogeneity of response to asthma controller therapy: clinical implications

PURPOSE OF REVIEW

Patients with asthma exhibit heterogeneous responses to all classes of asthma medication. This review examines clinical characteristics, biomarkers of inflammation, and genetic polymorphisms associated with treatment responsiveness in studies of adults and children with asthma, with an emphasis on inhaled corticosteroids and leukotriene modifiers.

RECENT FINDINGS

Recent clinical studies extended previous observations of associations between biomarkers of allergic inflammation and responsiveness to inhaled corticosteroids, and between cigarette smoke exposure and responsiveness to montelukast. Pharmacogenetic studies revealed associations between treatment response and genetic variations in CRHR1, as well as a number of genes encoding proteins involved in the absorption, production, and action of the cysteinyl leukotrienes. Very few studies have attempted to test the ability of these phenotypic and genotypic associations to predict treatment responsiveness.

SUMMARY

Additional prospective studies of sufficient size, quality, and ethnic diversity are needed to determine how best to incorporate information about genetic variations, clinical characteristics, and biomarkers into decisions about asthma therapy for individual patients.

Long-term maintenance of pediatric asthma: focus on budesonide/formoterol inhalation aerosol

Current national and international asthma guidelines recommend treatment of children with asthma towards achieving and maintaining asthma control. These guidelines provide more stringent recommendations to increase therapy for patients with uncontrolled asthma in order to reduce asthma-related morbidity and mortality. Newer combination agents such as budesonide and formoterol have been shown to be safe and effective in treatment of asthma in children. Use of long-term controller agents like this in combination with improved compliance and treatment of co-morbid conditions have been successful in this endeavor. This review discusses control of pediatric asthma with focus on the use of budesonide in combination with formoterol.

A retrospective characterization of African- and European American asthmatic children in a pediatric critical care unit

OBJECTIVE

To determine if African American and European American children with asthma admitted to an intensive care unit (ICU) had different characteristics, we conducted a retrospective chart review of asthma admissions to the region's only pediatric ICU.

PATIENTS AND METHODS

A chart review was performed on 125 patients with asthma admitted to the pediatric critical care unit at Vanderbilt Children's Hospital. Descriptive statistics, clinical characteristics, and disparities in care were compared using either Fisher's exact tests or Wilcoxon ranksum tests.

RESULTS

Most of the children reported previous admissions to a pediatric ICU (63%) or a hospital (82%) for asthma. Despite this, only 48% of the children were taking inhaled corticosteroids before admission. Only 28% of the children reported being followed by an asthma specialist, but, of these, 97% were taking corticosteroids. There were no racial/ethnic disparities in medication use, treatment, or outcomes.

CONCLUSION

We found no racial/ethnic disparities in inpatient/outpatient medication usage, treatment, or outcomes between African American and European American children in our cohort. Recurrent admissions to the ICU among children with severe asthma are common, and inhaled corticosteroids usage is relatively low. Asthmatic children with ICU admissions should be followed and treated aggressively by an asthma specialist.

The small heat shock protein, HSPB6, in muscle function and disease

The small heat shock protein, HSPB6, is a 17-kDa protein that belongs to the small heat shock protein family. HSPB6 was identified in the mid-1990s when it was recognized as a by-product of the purification of HSPB1 and HSPB5. HSPB6 is highly and constitutively expressed in smooth, cardiac, and skeletal muscle and plays a role in muscle function. This review will focus on the physiologic and biochemical properties of HSPB6 in smooth, cardiac, and skeletal muscle; the putative mechanisms of action; and therapeutic implications.

Pharmacogenetics of asthma in children

Allergic diseases such as bronchial asthma and atopic dermatitis develop by a combination of genetic and environmental factors. Several candidate causative genes of asthma and atopy have been reported as the genetic factors. The clinical features of patients and causes of diseases vary. Therefore, personalized medicine (tailor-made medicine) is necessary for the improvement of quality of life (QOL) and for asthma cure. Pharmacogenetics is very important for personalized medicine. Here, we present the genetics and pharmacogenetics of asthma in children. Finally, we show the guideline for personalized medicine for asthma, particularly in childhood, including the pharmacogenetics of anti-asthmatic drugs, preliminarily produced by the authors.

Polymorphism of the ADRB2 gene and response to inhaled beta- agonists in children with asthma: a meta-analysis

BACKGROUND

About 9% of children have asthma, corresponding to almost 6.8 million children in the USA and 1.1 million in the UK. Asthma exacerbations are the leading cause of pediatric emergency room visits and impose a large burden on the individual, family, and society. There is mounting evidence that therapeutic failure of inhaled beta-agonists is associated with polymorphisms of the beta(2)-adrenergic receptor gene (ADRB2); specifically, mutations leading to amino acid changes at positions 16 and 27, which alter down-regulation of the beta(2)-adrenergic receptor (beta(2)AR), induce resistance to the smooth-muscle relaxing effect of beta(2)-adrenergic agonists.

METHODS

We conducted a meta-analysis to examine the association between ADRB2 polymorphisms and the response to inhaled beta(2)-adrenergic agonists in children with asthma. We included all published studies until November 2008, in which asthmatic children underwent testing for acute bronchodilator response, defined as > or = 15% improvement in forced expiratory volume in 1 second (FEV(1)) and single nucleotide polymorphism (SNP) genotyping for positions 16 and/or 27 of the beta(2)AR. Individual and summary odds ratios were calculated using a random effects model.

RESULTS

We identified three case-control or family-based studies involving 960 asthmatic children (692 children with negative beta(2)-bronchodilator response, defined as < 15% improvement in FEV(1) and 268 children with positive bronchodilator response). We found a significant association between favorable therapeutic response to inhaled beta(2)-adrenergic agonists in asthmatic children and the Arg/Arg phenotype at position 16 of the beta(2)AR [OR = 1.77; 95% CI (1.01; 3.1); p = 0.029], compared with the Arg/Gly or Gly/Gly phenotypes. The beneficial effect of Arg at position 16 of the beta(2)AR was most pronounced in African-American asthmatic children [OR = 3.54; 95% CI (1.37, 9.13)]. There was no association between clinical response to beta(2)-agonists and polymorphism at amino acid position 27 of the beta(2)AR (OR = 1.04; 95% CI [0.76,1.42]).

CONCLUSIONS

Failure of bronchodilator response to inhaled beta-agonists in asthmatic children is associated with the Gly allele (Arg/Gly and Gly/Gly genotypes) at position 16 of the beta(2)-adrenergic receptor. Genetic typing for beta(2)AR polymorphism may help identify children with drug-resistant asthma.

Predicting response to short-acting bronchodilator medication using Bayesian networks

AIMS

Bronchodilator response tests measure the effect of beta(2)-agonists, the most commonly used short-acting reliever drugs for asthma. We sought to relate candidate gene SNP data with bronchodilator response and measure the predictive accuracy of a model constructed with genetic variants.

MATERIALS & METHODS

Bayesian networks, multivariate models that are able to account for simultaneous associations and interactions among variables, were used to create a predictive model of bronchodilator response using candidate gene SNP data from 308 Childhood Asthma Management Program Caucasian subjects.

RESULTS

The model found that 15 SNPs in 15 genes predict bronchodilator response with fair accuracy, as established by a fivefold cross-validation area under the receiver-operating characteristic curve of 0.75 (standard error: 0.03).

CONCLUSION

Bayesian networks are an attractive approach to analyze large-scale pharmacogenetic SNP data because of their ability to automatically learn complex models that can be used for the prediction and discovery of novel biological hypotheses.

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.