Polymorphisms of the 5' leader cistron of the human beta2-adrenergic receptor regulate receptor expression

Update on the Role of β2AR and TRPV1 in Respiratory Diseases

Respiratory diseases (RDs) constitute a common public health problem both in industrialized and developing countries. The comprehension of the pathophysiological mechanisms underlying these conditions and the development of new therapeutic strategies are critical for improving the quality of life of affected patients. β2-adrenergic receptor (β2AR) and transient receptor potential vanilloid 1 (TRPV1) are both involved in physiological responses in the airways. β2AR is implicated in bronchodilation, mucociliary clearance, and anti-inflammatory effects, while TRPV1 is involved in the mediation of pain and cough reflexes. In RDs, such as respiratory infections, asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis, the concentration and expression of these receptors can be altered, leading to significant consequences. In this review, we provided an update on the literature about the role of β2AR and TRPV1 in these conditions. We reported how the diminished or defective expression of β2AR during viral infections or prolonged therapy with β2-agonists can increase the severity of these pathologies and impact the prognosis. Conversely, the role of TRPV1 was pivotal in neuroinflammation, and its modulation could lead to innovative treatment strategies in specific patients. We indicate future perspectives and potential personalized treatments in RDs through a comprehensive analysis of the roles of these receptors in the physiological and pathological mechanisms of these pathologies.

β-Adrenoceptors in Cancer: Old Players and New Perspectives

Distress, or negative stress, is known to considerably increase the incidence of several diseases, including cancer. There is indeed evidence from pre-clinical models that distress causes a catecholaminergic overdrive that, mainly through the activation of β-adrenoceptors (β-ARs), results in cancer cell growth and cancer progression. In addition, clinical studies have evidenced a role of negative stress in cancer progression. Moreover, plenty of data demonstrates that β-blockers have positive effects in reducing the pro-tumorigenic activity of catecholamines, correlating with better outcomes in some type of cancers as evidenced by several clinical trials. Among β-ARs, β2-AR seems to be the main β-AR subtype involved in tumor development and progression. However, there are data indicating that also β1-AR and β3-AR may be involved in certain tumors. In this chapter, we will review current knowledge on the role of the three β-AR isoforms in carcinogenesis as well as in cancer growth and progression, with particular emphasis on recent studies that are opening new avenues in the use of β-ARs as therapeutic targets in treating tumors.

The impact of genomic variants on patient response to inhaled bronchodilators: a comprehensive update

INTRODUCTION

The bronchodilator response (BDR) depends on many factors, including genetic ones. Numerous single nucleotide polymorphisms (SNPs) influencing BDR have been identified. However, despite several studies in this field, genetic variations are not currently being utilized to support the use of bronchodilators.

AREAS COVERED

In this narrative review, the possible impact of genetic variants on BDR is discussed.

EXPERT OPINION

Pharmacogenetic studies of β₂-agonists have mainly focused on ADRB2 gene. Three SNPs, A46G, C79G, and C491T, have functional significance. However, other uncommon variants may contribute to individual variability in salbutamol response. SNPs haplotypes in ADRB2 may have a role. Many variants in genes coding for muscarinic ACh receptor (mAChR) have been reported, particularly in the M₂ and, to a lesser degree, M₃ mAChRs, but no consistent evidence for a pharmacological relevance of these SNPs has been reported. Moreover, there is a link between SNPs and ethnic and/or age profiles regarding BDR. Nevertheless, replication of pharmacogenetic results is limited and often, BDR is dissociated from what is expected based on SNP identification. Pharmacogenetic studies on bronchodilators must continue. However, they must integrate data derived from a multi-omics approach with epigenetic factors that may modify BDR.

Association between the Ile164 β2 Adrenergic Receptor Polymorphism and Fatigue in Patients with Rheumatoid Arthritis

INTRODUCTION

In the present work, the frequency of inherited polymorphisms of the beta 2 adrenergic receptor (β2AR) gene and their association with fatigue in patients with rheumatoid arthritis (RA) was examined.

METHODS

An allele-specific polymerase chain reaction was used to determine the common variants of the β2AR at position 16, 27, and 164 in 92 German RA outpatients. Health Assessment Questionnaire (HAQ-DI), Beck Depression Inventory (BDI), Perceived Stress Questionnaire (PSQ-30), Multidimensional Fatigue Inventory (MFI-20) were utilized.

RESULTS

34.7% of German RA patients were diagnosed with associated fatigue. Fatigued patients were more likely to carry the Ile allele at position 164 (OR 7.33, 95% CI 1.09-59.8, p = 0.049). Comparing these risk factors' contribution to different fatigue dimensions revealed that Ile164 carriers only had significantly higher MFI-20 mean values for general fatigue (p = 0.014) while the clinical difference among other MFI subscales was the largest for mental fatigue (carrier: 8.23, SD: 4.22, noncarrier: 5.67, SD: 1.56, p = 0.089, Cohen's d = 0.629). Disease activity, perceived stress, and depression were also associated with fatigue with higher mean values for DAS28CRP (p = 0.038), PSQ (p < 0.001), and BDI-II (p < 0.001) in fatigued patients. Physical fatigue was correlated with disease activity (p = 0.009) and depression (p = 0.001) while mental fatigue showed associations with depression (p = 0.001) and perceived stress (p = 0.028).

CONCLUSION

The discovery study indicates that the Ile164 polymorphism might in contrast to other β2AR polymorphisms affect fatigue levels in RA patients. This association was observed especially with mental fatigue. Further replication studies are warranted to determine further role of β2AR polymorphisms in RA patients.

The impact of ADRB2 polymorphisms on immune responses and norepinephrine-induced immunosuppression

RATIONALE

To evaluate whether common nonsynonymous variants [single-nucleotide polymorphisms (SNPs) or SNP haplotypes] in the β2-adrenergic receptor render subjects more susceptible to norepinephrine-induced immunosuppression and whether they are associated with dysregulated ex vivo and in vivo inflammatory responses.

METHODS

Peripheral blood mononuclear cells from healthy volunteers (main cohort: n = 106, secondary cohort: n = 408) were ex vivo stimulated with various stimuli and production of cytokines was assessed. Additionally, ex vivo modulation of cytokine production by norepinephrine was evaluated in the main cohort. Volunteers from the main cohort also underwent experimental endotoxemia (administration of 1 ng/kg lipopolysaccharide), during which in vivo plasma cytokine concentrations and clinical inflammatory parameters were measured. Subjects were genotyped, common SNPs in the ADRB2 gene were extracted (rs1042711, rs1042713, and rs1042714), and the presence of haplotypes was identified (CysGlyGln, CysArgGln, and ArgGlyGlu).

RESULTS

In both cohorts, presence of ADRB2 SNPs or haplotypes was not associated with altered ex vivo cytokine responses. Norepinephrine attenuated production of the proinflammatory cytokines TNF and IL-6 [-26% (-22% to -30%) and -14% (-9% to -18%), respectively, both P < 0.0001] and enhanced release of the anti-inflammatory IL-10 [+9% (+3% to +15%), P = 0.003]. These effects were not modulated by the presence of ADRB2 SNPs or haplotypes (all P values >0.37). In addition, no influence of SNPs or haplotypes on in vivo cytokine concentrations or clinical inflammatory parameters was observed (P values >0.14).

CONCLUSIONS

Common nonsynonymous variants in the ADRB2 gene influence neither ex vivo cytokine production or norepinephrine-mediated immunosuppression nor the systemic in vivo inflammatory response induced by lipopolysaccharide administration in healthy volunteers.

ADRB2 expression predicts the clinical outcomes and is associated with immune cells infiltration in lung adenocarcinoma

The gene encoding beta2-adrenergic receptor (β2-AR), adrenoceptor beta 2 (ADRB2), has been reported to closely associated with various cancers. However, its role in lung adenocarcinoma (LUAD) remains controversial. This research shed light on the prognostic value of ADRB2 in LUAD and further explored its association with immune cell infiltration. ADRB2 was significantly decreased in LUAD. ADRB2 expression in LUAD was significantly correlated with gender, smoking status, T classification, and pathologic stage. Patients in the low ADRB2 expression group presented with significantly poorer overall survival (OS) and disease-specific survival (DSS). Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Set Enrichment Analysis (GSEA) results showed that ADRB2 participates in immune response. The expression of ADRB2 was positively correlated with the infiltration level of most immune cells. Notably, ADRB2 is involved in LUAD progression partly by regulating the immune microenvironment, which may potentially serve as a significant prognostic biomarker as well as a potential drug target.

Association between beta-2 adrenergic receptor variants and clinical outcomes in children and adolescents with acute asthma

Objective

To investigate whether different genotypes of p.Arg16Gly, p.Gln27Glu, p.Arg19Cys and p.Thr164Ile variants interfere in response to treatment in children and adolescents with moderate to severe acute asthma.

Methods

This sample comprised patients aged 2 to 17 years with a history of at least two wheezing episodes and current moderate to severe asthma exacerbation. All patients received multiple doses of albuterol and ipratropium bromide delivered via pressurized metered-dose inhaler with holding chamber and systemic corticosteroids. Hospital admission was defined as the primary outcome. Secondary outcomes were changes in forced expiratory volume in the first second after 1 hour of treatment, and for outpatients, length of stay in the emergency room. Variants were genotyped by sequencing.

Results

A total of 60 patients were evaluated. Hospital admission rates were significantly higher in carriers of the genotype AA relative to those with genotype AG or GG, within the p.Arg16Gly variant (p=0.03, test χ², alpha=0.05). Secondary outcomes did not differ between genotypes.

Conclusion

Hospital admission rates were significantly higher among carriers of the genotype AA within the p.Arg16Gly variant. Trial registration: ClinicalTrials.gov: NCT01323010

The role of ADRB2 gene polymorphisms in malignancies

Beta-2-adrenergic receptor is a member of the G protein-coupled receptor superfamily, which is highly expressed in most malignancies. There is increasing evidence showing that beta-2-adrenergic receptors are associated with carcinogenesis, proliferation, immune regulation, invasion, angiogenesis, clinical prognosis and treatment resistance in malignancies. Polymorphisms of the ADRB2 gene have been confirmed to be associated with transcriptional activity, mRNA translation, and beta-2-adrenergic receptor expression and sensitivity. This review discusses clinically relevant examples of single nucleotide polymorphisms of ADRB2 in malignancies and the effects of these polymorphisms on cancer susceptibility, prognosis and treatment response of cancer patients.

CRISPR/Cas9-mediated generation and analysis of N terminus polymorphic models of β2AR in isogenic hPSC-derived cardiomyocytes

During normal- and patho-physiological situations, the behavior of the beta2-adrenoreceptor (β₂AR) is influenced by polymorphic variants. The functional impact of such polymorphisms has been suggested from data derived from genetic association studies, in vitro experiments with primary cells, and transgenic overexpression models. However, heterogeneous genetic background and non-physiological transgene expression levels confound interpretation, leading to conflicting mechanistic conclusions. To overcome these limitations, we used CRISPR/Cas9 gene editing technology in human pluripotent stem cells (hPSCs) to create a unique suite of four isogenic homozygous variants at amino acid positions 16(G/R) and 27(G/Q), which reside in the N terminus of the β₂AR. By producing cardiomyocytes from these hPSC lines, we determined that at a functional level β₂AR signaling dominated over β₁AR . Examining changes in beat rates and responses to isoprenaline, Gi coupling, cyclic AMP (cAMP) production, downregulation, and desensitization indicated that responses were often heightened for the GE variant, implying differential dominance of both polymorphic location and amino acid substitution. This finding was corroborated, since GE showed hypersensitivity to doxorubicin-induced cardiotoxicity relative to GQ and RQ variants. Thus, understanding the effect of β₂AR polymorphisms on cardiac response to anticancer therapy may provide a route for personalized medicine and facilitate immediate clinical impact.

Quantification of neural and hormonal receptors at the prostate of long-term sexual behaving male rats after lesion of pelvic and hypogastric nerves

Prostate function is regulated by androgens and a neural control via the pelvic and hypogastric nerves. As such, this sexual gland contains receptors for acetylcholine and noradrenaline, although it is unknown whether the expression of these receptors is affected by sexual behavior and even less by denervation of the gland. Thus, the purpose of this work was to evaluate the effect of repeated sexual behavior on the expression of noradrenaline, acetylcholine, and androgen receptors at the prostate, and how they are affected by denervation. To achieve this, we used sexually experienced males denervated at the pelvic or hypogastric nerves, or both. The messenger (mRNA) and protein for androgen, noradrenergic, and cholinergic receptors were evaluated. The weight of the gland and the levels of serum testosterone were also measured. We found that: (1) sexual behavior was not affected by denervation; (2) blood testosterone levels increased due to sexual behavior but such increase is prevented by denervation; (3) the weight of the ventral prostate increased with sexual behavior but was not affected by denervation; (4) AR messenger levels increased with sexual behavior but were not altered by denervation; (5) the messenger for noradrenergic and cholinergic receptors decreased after denervation, and those for muscarinic receptors increased, and (6) only AR protein decreased after denervation of both nerves, while those for other receptors remained unchanged. In summary, we show that the three receptors have different regulatory mechanisms, and that only androgen receptors are regulated by both autonomic systems.

Association of β2-adrenergic receptor gene polymorphisms (rs1042713, rs1042714, rs1042711) with asthma risk: a systematic review and updated meta-analysis

Background

The published data on the association between β2-adrenergic receptor gene polymorphisms and asthma susceptibility are inconclusive. To derive a more precise estimation of this association, a meta-analysis was performed.

Methods

A literature search was conducted in PubMed, Web of Science, EMBASE, Wanfang, and the China National Knowledge Infrastructure (CNKI) databases to identify eligible studies. The pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to calculate the strength of the association. A sensitivity analysis was performed to evaluate the influence of individual studies on the overall effect estimates, and funnel plots and Egger’s tests were used for indications of publication bias.

Results

Seventy three studies with three single nucleotide polymorphisms (SNP) (rs1042713, c.G46A, p.Gly16Arg; rs1042714, c.G79C, p.Gln27Glu; rs1042711, c.T-47C, p.Cys19Arg) were finally identified. For the rs1042713 polymorphism, no significant association with asthma risk was found in the overall population. However, a significant protective association was found in the Indian population in the dominant model comparison (OR = 0.72, 95% CI = 0.59–0.87, I² = 25%, studies = 5, cases = 1190, controls = 1241). A significant risk association was found in the Arab population in the dominant model comparison (OR = 1.75, 95% CI = 1.14–2.70, I² = 0%, studies = 2, cases = 307, controls = 361) and the homozygote model comparison (OR = 1.88, 95% CI = 1.17–3.02, I² = 0%, studies = 2, cases = 307, controls = 361), and in the Hispanic-Latino population in the dominant model comparison (OR = 1.68, 95% CI = 1.10–2.55, I² = 77%, studies = 5, cases = 1026, controls = 1412). For the rs1042714 polymorphism, we found a significant association in the recessive model comparison (OR = 0.83, 95% CI = 0.70–0.98, I² = 44%, studies = 52, cases = 8242, controls = 16,832), the homozygote genotype comparison (OR = 0.84, 95% CI = 0.72–0.98, I² = 25%, studies = 52, cases = 8242, controls = 16,832) and the allelic genetic model (OR = 0.91, 95% CI = 0.83–0.99, I² = 59%, studies = 52, cases = 8242, controls = 16,832) in the overall population. When stratified by age, a significant association was also found in children in the recessive model comparison (OR = 0.59, 95% CI = 0.39–0.88, I² = 58%, studies = 18, cases = 2498, controls = 2510) and the homozygote genotype comparison (OR = 0.63, 95% CI = 0.43–0.92, I² = 46%, studies = 18, cases = 2498, controls = 2510), but not in adult. For the rs1042711 polymorphism, no significant associations were found in the any genetic model.

Conclusion

The meta-analysis suggests that the ADRB2 rs1042714 polymorphism has a protective association with asthma in the overall population and the pediatric subgroup.

A functional SNP upstream of the ADRB2 gene is associated with COPD

Background

Previous studies have suggested that β2-adrenergic receptor (ADRB2) is associated with COPD. However, the role of genetic polymorphisms in ADRB2 on COPD has not been evaluated yet.

Methods

In this study, SNaPshot genotyping, luciferase assay, chromatin immunoprecipitation and real-time polymerase chain reaction were adopted to investigate the association between ADRB2 genetic polymorphisms and COPD, comprehensively.

Results

One single nucleotide polymorphism (rs12654778), located upstream of ADRB2, showed a significant association with COPD by the logistic regression analysis after adjusting for age, sex and smoking history (p=0.04) in 200 COPD patients and 222 controls from southwest Chinese population. Furthermore, the luciferase assay indicated that rs12654778-A allele reduced the relative promoter activity by ~26% compared with rs12654778-G allele (p=0.0034). The chromatin immunoprecipitation analysis demonstrated that rs12654778 modulated the binding affinity of transcription factor neurofibromin 1. In addition, a significantly reduced expression of ADRB2 in COPD patients was observed, compared with normal controls (p=0.017).

Conclusion

Our findings suggest a previously unknown mechanism linking allele-specific effects of rs12654778 on ADRB2 expression to COPD onset, for the first time.

ADRB2 polymorphisms and dyslipidemia risk in Chinese hypertensive patients

Single nucleotide polymorphisms (SNPs) within a β-adrenergic receptor (ADRB2) were shown to be related to lipid traits or hyperlipidemia in different ethnicities, but not in a Chinese population. We performed the present study to investigate the possible relationship between them in a Chinese hypertensive population. Seven hundred and eighty-three hypertensive subjects were enrolled in the hospital-based retrospective research. Using the TaqMan PCR method, three polymorphisms (C-47T, A46G, and C79G) of ADRB2 were detected. For the whole population, no significant statistical difference was found for all serum lipids. Similar findings were seen in men and women subgroups. Subsequently, in the case-control study, we observed that the A46G polymorphism was significantly associated with the elevated risk of hypertriglyceridemia in the dominant model (OR: 1.47, 95%CI: 1.05-2.06, P = 0.025). There are no significant differences in the other four models. With regard to C79G and C-47T, no significant association was seen in this population. In addition, haplotype analysis showed that the TAC haplotype carrying frequent alleles of the three SNPs played a reduced role in hypertriglyceridemia risk and the TGC haplotype carrying rare allele of A46G expressed a significant risk effect. In conclusion, these findings indicated that the ADRB2 SNPs might be a genetic risk factor for dyslipidemia in the Chinese hypertensive patients.

A 5'-upstream short open reading frame encoded peptide regulates angiotensin type 1a receptor production and signalling via the β-arrestin pathway

AUG sequences and short open reading frames are commonly present in the 5'-leader sequence of G protein-coupled receptor mRNAs. The presence of these upstream AUG sequences has been demonstrated to inhibit downstream receptor translation efficiency and, most recently, receptor signal transduction. A seven amino acid peptide encoded by a short open reading frame in exon 2 of the angiotensin type 1a receptor has been shown to inhibit non-G protein-coupled signalling of angiotensin II, without altering the classical G protein-coupled pathway activated by the ligand. This finding may lead to the development of a new class of angiotensin receptor antagonists with activities biased for one, but not all, of the signalling cascades activated by angiotensin II, which could have therapeutic implications for the myriad hormones and neurotransmitters that signal through G protein-coupled receptors.

β2-Adrenergic receptor promoter haplotype influences the severity of acute viral respiratory tract infection during infancy: a prospective cohort study

BACKGROUND

Despite the significant interest in β2-Adrenergic receptor (ADRB2) polymorphisms related to asthma, whether ADRB2 genetic variants are similarly associated with acute respiratory tract infections have not been studied. We hypothesized that genetic variants in ADRB2 associated with a response to asthma therapy during an asthma exacerbation were also associated with severity of acute respiratory tract infections.

METHODS

To test this hypothesis, we genotyped 5 common polymorphisms in the promoter region and coding block of the ADRB2 gene (loci -2387, -2274, -1343, +46, and +79) from 374 Caucasian and African American term infants who were enrolled at the time of acute respiratory illness over four respiratory viral seasons. Severity of respiratory tract infections was measured using a bronchiolitis severity score (BSS; range = 0-12, clinically significant difference = 0.5) with a higher score indicating more severe disease. We assigned the promoter, coding and combined promoter and coding haplotypes to the unphased genotype data. The associations between each of these five single-nucleotide polymorphisms (SNPs) as well as the haplotypes and infant BSS were analyzed using nonparametric univariate analysis and multivariable proportional odds model separately in Caucasians and African Americans.

RESULTS

There was no significant association between infant BSS and each of the SNPs in both Caucasians and African Americans. However, promoter haplotype CCA was associated with a decreased BSS in African Americans in a dose dependent manner. The median (interquartile range) BSS of infants with no copies of the CCA haplotype, one copy, and two copies of the CCA haplotype were 5.5 (2.0, 8.0), 4.0 (1.0, 7.5), and 3.0 (1.0, 4.0), respectively. This dose dependent relationship persisted after adjusting for infant age, gender, daycare exposure, secondhand smoke exposure, prior history of breastfeeding, siblings at home, and enrollment season (adjusted odds ratio: 0.59, 95% confidence interval: 0.36, 0.98). There was no similar protective relationship of haplotype CCA on severity of respiratory tract infections identified in Caucasians.

CONCLUSIONS

ADRB2 genotype may be predictive of severity of acute respiratory tract infections in African Americans, and potentially identify a subset of infants who may respond to beta-agonist therapy.

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.

Effect of ADRB2 (adrenergic receptor β2) gene polymorphisms on the occurrence of asthma and on the response to nebulized salbutamol in South Indian patients with bronchial asthma

INTRODUCTION

Genetic mutations in the β2 receptor could alter its functioning and the response to β2 agonists. The study was done to find out the effect of two commonly occurring polymorphisms-Arg16Gly and Gln27Glu, on cause of asthma and on response to nebulized salbutamol in South Indian subjects of asthma.

METHODS

After baseline measurements of Forced Expiratory Volume in 1st second (FEV1), Forced Vital Capacity (FVC) and Peak Expiratory Flow Rate (PEFR), five mg of nebulized salbutamol was administered and spirometry was repeated. The increase in these parameters was calculated and patients were included for genotyping if the percentage increase in FEV1 was ≥12%. The frequencies of these polymorphisms in patients were compared with those of healthy volunteers.

RESULTS

112 patients and 127 healthy volunteers were genotyped. The frequencies of the polymorphisms were found to be similar to previously published Dravidian population frequencies. The frequencies of genotypes in asthmatics were similar to healthy volunteers. The increase in FEV1, FVC and PEFR was similar across various genotypes and haplotypes in both the polymorphisms. The GG-CG haplotype was associated with 3.1 times increased occurrence of asthma (p value = 0.02). The G allele of the Arg16Gly polymorphism was associated with lower baseline FEV1, FVC and PEFR values, but these were not statistically significant.

CONCLUSION

The Arg16Gly and Gln27Glu polymorphisms do not determine the occurrence of asthma individually, but the GG-CG haplotype is associated with an increased risk of asthma. There is no effect of the genotypes on the response to nebulized salbutamol.

Beta2-Adrenergic Receptor Gene Polymorphisms in Egyptian Patients with Acute Myocardial Infarction

Background. Beta2-adrenergic receptor (ADRB2) gene polymorphisms, Arg16Gly and Gln27Glu, have been implicated in the pathogenesis of cardiovascular diseases. The aim of this study was to determine the association of these two polymorphisms with the risk of myocardial infarction (MI) in the Egyptian population. Methods. Blood samples were collected from 68 MI patients and 75 healthy controls. They were assessed for the presence of cardiovascular risk factors and genotyped for the Arg16Gly (rs1042713) and Gln27Glu (rs1042714) polymorphisms using allelic-discrimination polymerase chain reaction. Results. There is no significant difference in genotype and allele frequencies at codon 16 between MI patients and controls (P=0.919). However, at codon 27, MI risk was higher in Gln27 homozygous participants than in Glu27 carriers (P=0.045). The haplotype frequency distribution showed significant difference among cases and controls (P=0.002); homozygotes for Gly16/Gln27 haplotype were more susceptible to MI than Gly16/Glu27 carriers. Patients with Arg16/Gln27 haplotype had higher serum total cholesterol levels (P<0.05) and lower frequency of diabetes in MI patients (P<0.01). However, both Glu27 genotypes and haplotype showed lower frequency of hypertension (P<0.001). Conclusions. Our findings suggested that the ADRB2 gene polymorphisms may play an important role in susceptibility of MI among Egyptian population.

The β2-adrenoreceptor gene promoter polymorphisms may modulate β2-agonist- and glucocorticoid-induced IgE synthesis

BACKGROUND

β2-adrenoreceptor (β2-AR) agonists and glucocorticoids (GCS) were shown to induce IgE synthesis in human PBMCs. Serum total IgE levels are associated with single nucleotide polymorphisms (SNPs) of the β2-AR gene. We aimed to assess the association of the effect of fenoterol (β2-AR agonist) on IL-4-driven and budesonide-induced IgE synthesis with genetic variants of β2-AR.

METHODS

The study included 25 individuals: 13 with allergic asthma and/or allergic rhinitis and 12 healthy volunteers. PBMCs were cultured with IL-4, fenoterol and/or budesonide, and IgE concentrations in supernatants were assessed. Five SNPs in positions: -47, -20, 46, 79 and 252 of β2-AR were determined by direct DNA sequencing.

RESULTS

In -47 T/T and -20 T/T patients, incubation with fenoterol resulted in decreased IgE production, whereas in -47 C/T and -47 C/C as well as in -20 C/T and -20 C/C individuals, it was enhanced. In contrast to fenoterol, budesonide-induced IgE synthesis was significantly increased in -47 T/T and -20 T/T patients as compared to -47 C/T, -47 C/C, -20 C/T and -47 C/C individuals. Polymorphisms in positions 46, 79 and 252 were not associated with fenoterol- or budesonide-modulated IgE synthesis. No differences in the distribution of IgE synthesis was seen between atopic and non-atopic individuals carrying the same alleles.

CONCLUSIONS

The differential effect of β2-agonists and GCS on IgE synthesis may be associated with genetic variants of promoter region of the β2-AR gene.

What the Genetic Background of Individuals with Asthma and Obesity Can Reveal: Is β2-Adrenergic Receptor Gene Polymorphism Important?

The goal of this review was to evaluate the association of β2-adrenergic receptor (ADRB2) gene polymorphisms with asthma and obesity. Asthma is the most common pediatric inflammatory disorder. The prevalence, severity, and hospitalization index for asthma have increased markedly in the last several decades. Interestingly, asthma is often diagnosed along with obesity. Genetic factors are essential for both conditions, and some of the candidate pleiotropic genes thought to be involved in the development of these diseases are ADRB2, vitamin D receptor (VDR), leptin (LEP), protein kinase C alpha (PRKCA), and tumor necrosis factor alpha (TNFα). The ADRB2 has been studied in multiple populations and more than 80 polymorphisms, mainly single-nucleotide polymorphisms, have been identified. For nonsynonymous Arg16Gly, Gln27Glu, and Thr164Ile, functional effects have been shown. In vivo, these polymorphisms have been evaluated to determine their association with both obesity and asthma, but the results are inconsistent and depend on the population studied or how the disease was defined. Currently, there are only few reports describing the genetic background for the comorbidity of asthma and obesity.

Polymorphic variants of adrenoceptors: pharmacology, physiology, and role in disease

The human genome encodes nine different adrenoceptor genes. These are grouped into three families, namely, the α1-, α2-, and β-adrenoceptors, with three family members each. Adrenoceptors are expressed by most cell types of the human body and are primary targets of the catecholamines epinephrine and norepinephrine that are released from the sympathetic nervous system during its activation. Upon catecholamine binding, adrenoceptors change conformation, couple to and activate G proteins, and thereby initiate various intracellular signaling cascades. As the primary receivers and transducers of sympathetic activation, adrenoceptors have a central role in human physiology and disease and are important targets for widely used drugs. All nine adrenoceptor subtypes display substantial genetic variation, both in their coding sequence as well as in adjacent regions. Despite the fact that some of the adrenoceptor variants range among the most frequently studied genetic variants assessed in pharmacogenetics to date, their functional relevance remains ill defined in many cases. A substantial fraction of the associations reported from early candidate gene approaches have not subsequently been confirmed in different cohorts or in genome-wide association studies, which have increasingly been conducted in recent years. This review aims to provide a comprehensive overview of all adrenoceptor variants that have reproducibly been detected in the larger genome sequencing efforts. We evaluate these variants with respect to the modulation of receptor function and expression and discuss their role in physiology and disease.

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.

Pharmacogenetics of chronic obstructive pulmonary disease

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

Selective inhibition of angiotensin receptor signaling through Erk1/2 pathway by a novel peptide

A seven-amino acid peptide (PEP7) is encoded within a short open reading frame within exon 2 (E2) in the 5'-leader sequence (5'LS) upstream of the rat ANG 1a-receptor (rAT1aR) mRNA. A chemically synthesized PEP7 markedly inhibited ANG II-induced Erk1/2 activation in cell culture by 62% compared with a scrambled PEP7 (sPEP7) [pErk1/2/Erk1/2 (AU): ANG II, 1.000 ± 0.0, ANG II+PEP7, 0.3812 ± 0.086, ANG II+sPEP7, 1.069 ± 0.18; n = 3]. Under these same conditions, PEP7 had no effect on ANG II-stimulated inositol-trisphosphate production. PEP7 also had no effect on epidermal growth factor- and phorbol methyl ester-induced Erk1/2 activation, suggesting PEP7 selectively inhibits AT1aR-mediated Erk1/2 signaling. PEP7 intracerebroventricularly inhibited ANG II-induced saline intake but had no effect on water intake in male and female rats, indicating PEP7 also selectively inhibits the ANG II-Erk1/2 pathway in vivo since saline drinking is Erk1/2-mediated, while water drinking is not. PEP7 inhibition of ANG II-induced saline ingestion was rapidly reversed by a subsequent intracerebroventricular injection of an oxytocin antagonist, suggesting when PEP7 blocks ANG II-stimulated Erk1/2 activation, animals no longer ingest saline to balance the continued water intake, due to the release of oxytocin and its subsequent inhibitory effects on saline drinking. PEP7 also attenuated ANG II-induced increases in arterial pressure by 35% compared with sPEP7 at the same dose. Thus, we have identified a novel peptide encoded within the rAT1aR E2 that selectively inhibits Erk1/2 activation, resulting in physiological consequences for sodium ingestion and arterial pressure that may have implications for treating sodium-sensitive diseases like hypertension and chronic kidney disease.

Childhood lung function and the association with β2-adrenergic receptor haplotypes

AIM

To determine associations between ADRB2 polymorphisms and lung function through childhood, and possible modification by gender, pet keeping or tobacco smoke.

METHODS

Four ADRB2 single nucleotide polymorphisms (rs1042711, rs1042713, rs1042714 and rs1800888) were genotyped in 953 children from the prospective birth cohort 'Environment and Childhood Asthma' study and analysed for association with flow-volume parameters at birth (tidal breathing) and at 10 years of age (maximally forced), stratified by environmental exposures.

RESULTS

The risk of reduced lung function was reduced in 10-year-old children carrying the most common ADRB2 haplotype (CGGC) (OR 0.45 (95% CI 0.25, 0.82)), whereas there was no association between lung function at birth and ADRB2 haplotypes. Tobacco smoke exposure, gender and pet keeping did not significantly interact with the haplotypes in influencing lung function.

CONCLUSION

This study demonstrates a possible protective effect by the ADRB2 haplotype I (CGGC) on reduced FEV1 in 10-year-old children, whereas no ADRB2 geno-/haplotypes were significantly associated with neonatal lung function. The ADRB2 gene thus appears to contribute to lung function development in childhood, independently of smoking, pets and gender.

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.

Association between β2-adrenoceptor (ADRB2) haplotypes and insulin resistance in PCOS

OBJECTIVE

The aim of this study was to explore β2-adrenoceptor (ADRB2) haplotype associations with phenotypes and quantitative traits related to insulin resistance (IR) and the metabolic syndrome (MS) in a polycystic ovary syndrome (PCOS) population. A secondary purpose was to assess the association between ADRB2 haplotype and PCOS.

DESIGN

Genetic polymorphism analysis. Cross-sectional case-control association study.

SETTING

Medical University Hospital and research laboratory.

PATIENTS

One hundred and sixty-five unrelated women with PCOS and 116 unrelated women without PCOS (control sample).

MEASUREMENTS

Clinical and biochemical measurements, and ADRB2 genotyping in PCOS patients and control subjects.

METHODS

ADRB2 haplotypes (comprising rs1042711, rs1801704, rs1042713 and rs1042714 in that order), genotyping and statistical analysis to evaluate associations with continuous variables and traits related to IR and MS in a PCOS population. Associations between ADRB2 haplotypes and PCOS were also assessed.

RESULTS

We observed an age-adjusted association between ADRB2 haplotype CCGG and lower insulin (P = 0·018) and HOMA (P = 0·008) in the PCOS sample. Interestingly, the expected differences in surrogate measures of IR between cases and controls were not significant in CCGG/CCGG carriers. In the case-control study, genotype CCGG/CCGG was associated with a 14% decrease in PCOS risk (P = 0·043), taking into account confounding variables.

CONCLUSIONS

Haplotype I (CCGG) has a protective role for IR and MS in PCOS.

β2-adrenergic receptor haplotype may be associated with susceptibility to desensitization to long-acting β2-agonists in COPD patients

PURPOSE

Τhat β2-adrenergic receptor (β2AR) haplotypes may play a key role in clinical response to β2-agonists and haplotype Cys-19Gly16Gln27 (CysGlyGln) is reported to be associated with desensitization of β2AR to β-agonists in lymphocytes isolated from patients with asthma and septic shock. We sought to determine whether haplotypic variation of the β2AR affects the functional outcomes of long-acting β2-agonist (LABA) treatment for chronic obstructive pulmonary disease (COPD) when used as monotherapy.

METHODS

Treatment-naïve patients with COPD (n = 36) were prospectively treated with two kinds of LABA--inhaled salmeterol and transdermal tulobuterol patch--for 12 weeks in crossover study, and changes in pulmonary function data and 6-minute walk distance (6 MWD) were compared between groups stratified by the CysGlyGln.

RESULTS

Frequencies of haplotype and diplotype for the CysGlyGln were 0.51 and 0.36, respectively. The individuals homozygous for CysGlyGln showed less improvement in FEV(1), %FEF(25-75 %), and IC/TLC than those with 0 or 1 copy of CysGlyGln after treatment with both LABAs despite initial bronchodilator responses to albuterol being similar in these groups. The response in these parameters was not significantly different between two types of LABA. Overall changes in 6 MWD in individuals with 2 copies of CysGlyGln versus 0 or 1 copy for salmeterol were 2.8 and 11 m, and for tulobuterol were -1.3 and 16 m, respectively.

CONCLUSIONS

Homozygous haplotype for the CysGlyGln of β2AR may be associated with susceptibility to desensitization to LABA in patients with COPD.

Association of adrenergic receptor gene polymorphisms with adolescent obesity in Taiwan

BACKGROUND

Polymorphisms of β2-adrenergic receptor (ADRB2) and β3-adrenergic receptor (ADRB3) have been reported to be associated with obesity in adults and adolescents, although study results have been controversial. The aim of the present study was to investigate the association of polymorphisms of ADRB2 (Arg16Gly, Gln27Glu) and ADRB3 (Trp64Arg) with adolescent obesity in Taiwan.

METHODS

A total of 559 adolescent volunteers with equal numbers female and male were enrolled. Participants were divided into two groups: obese (body mass index [BMI]≥ 95th percentile) and normal weight (BMI 15th-85th percentile). Genomic DNA was extracted from buccal mucosa cells and genotyped in TaqMan assays. Genotype results and clinical subject characteristics were analyzed.

RESULTS

Among the three ADRB polymorphisms, only Arg16Gly polymorphism was found to be significantly correlated with adolescent obesity, especially in girls. Girls with genotype Gly/Gly had a lower probability of obesity than those with genotypes Arg/Gly or Arg/Arg (P= 0.006; Arg/Gly: odds ratio [OR], 2.57, 95% confidence interval [95%CI]: 1.22-5.41; Arg/Arg: OR, 3.03, 95%CI: 1.50-6.12). Girls with genotype Gly/Gly had lower BMI than those with genotype Arg/Arg (P= 0.049). Obese adolescents with genotype Gly/Gly had a lower probability of hypertension than those with genotype Arg/Gly or Arg/Arg (P= 0.005).

CONCLUSIONS

Arg16Gly polymorphism of ADRB2 was significantly associated with obesity in female adolescents, and those with the Gly/Gly genotype were associated with a lower possibility of obesity and lower BMI. This polymorphism was also associated with a lower probability of hypertension in obese adolescents. The other two polymorphisms of ADRB (Gln27Glu and Trp64Arg) were not associated with adolescent obesity in Taiwan.

Relationship between polymorphisms in the 5' leader cistron, positions 16 and 27 of the adrenergic β2 receptor gene and asthma in a Han population from southwest China

BACKGROUND AND OBJECTIVE

Adrenergic β2 receptors (ADRB2) play an important role in regulating pulmonary function. Many previous studies have investigated possible associations between polymorphisms in the ADRB2 gene and asthma, but have yielded conflicting results. Furthermore, little is known regarding the possible role of the Arg19Cys polymorphism in susceptibility to asthma among Chinese.

METHODS

This case-control association study involved 238 patients with asthma and 265 healthy subjects from a Han population in southwest China. For all subjects, the 5' leader cistron Arg19Cys, Arg16Gly and Gln27Glu polymorphisms in the ADRB2 gene were characterized by direct sequencing. Genotype, allele and haplotype frequencies were determined. In addition, to evaluate the association between the ADRB2 polymorphisms and lung function, bronchodilator response to inhaled β2 agonists (400 µg of albuterol) was assessed in the asthmatic patients.

RESULTS

There were no significant differences in genotype or allele frequencies for the three ADRB2 polymorphisms between the two cohorts. The Arg19/Arg16/Gln27 haplotype was more frequent among asthmatic patients than control subjects (odds ratio 2.24, 95% confidence interval (CI): 1.05-4.73, P=0.04). Moreover, the Arg19/Cys19 genotype was associated with a lower FEV₁% (mean difference -4.5, 95% CI: -12.5 to 3.6, P=0.02) and FEV₁/FVC (mean difference 8.9, 95% CI: 8.5-9.4, P=0.01). The bronchodilator response to albuterol was also marginally lower in individuals who were homozygous for the Arg19 genotype (mean difference 4.2, 95% CI: 3.7-4.8, P=0.03).

CONCLUSIONS

The Arg19/Cys19 genotype was an independent risk factor for lower FEV₁% and FEV₁/FVC. Asthmatic patients with the Arg19/Arg19 genotype showed decreased responsiveness to albuterol. Furthermore, the Arg19/Arg16/Gln27 haplotype may contribute to increased susceptibility to asthma in the Chinese population.

Differential expression of the β2-adrenoreceptor and M3-cholinoreceptor genes in bronchial mucosa of patients with asthma and chronic obstructive pulmonary disease

BACKGROUND

Bronchodilators are drugs of choice in the combined therapy of bronchial asthma and chronic obstructive pulmonary disease (COPD). However, the therapeutic sensitivity is variable between patients, probably because of structural features of regulating molecules or variation in key genes' expression.

OBJECTIVES

The aim of this study was to evaluate the β2-adrenoceptor (ADRB2) and M3-cholinoreceptor (CHRM3) gene expression in bronchial mucosa in patients with COPD and different severity of asthma.

METHODS

Biopsy specimens of right middle lobar bronchus were obtained from 59 asthma patients (10 patients with severe brittle phenotype, 14 patients with severe asthma with persistent airflow limitation, 27 patients with moderate asthma, and 8 patients with mild asthma) and 10 COPD patients with or without bronchial hyperresponsiveness (BHR). The messenger RNA (mRNA) levels for the ADRB2 and CHRM3 genes in bronchial mucosa were revealed using quantitative reverse transcription polymerase chain reaction (RT-PCR) and compared between groups.

RESULTS

An increase of the ADRB2 genes expression was demonstrated in patients with severe asthma and COPD as compared with patients with mild and moderate disease. Significantly higher levels of ADRB2 mRNA were observed in patients with severe asthma with persistent airflow limitation. Significantly lower levels of the CHRM3 mRNA were observed in patients with COPD as compared with asthma patients. Also, CHRM3 gene expression was significantly elevated in COPD patients with BHR as compared with patients without BHR.

CONCLUSIONS

The results of the study suggest that the differential expression of the ADRB2 and CHRM3 genes is associated with asthma and COPD clinical subtypes.

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.

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.

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.

Association of WNK1 exon 1 polymorphisms with essential hypertension in Hani and Yi minorities of China

The association of polymorphisms in exon 1 of the WNK1 gene with essential hypertension in the minority groups of Hani and Yi of China was investigated in the case-control study. The sequence of 1257bp containing the WNK1 gene exon 1 was determined in 1307 individuals (649 essential hypertension subjects and 658 controls) to identify SNPs in Hani and Yi minority groups. Four of eleven previously known SNPs (rs3168640, rs11885, rs11554421 and rs34880640) were identified. The SNP analysis indicated that SNPs rs11885 and rs11554421 were significantly associated with hypertension in both Hani and Yi populations, and rs34880640 was significantly associated with hypertension in Hani but not in Yi population, adjusted for covariates. Haplotype analysis indicated that the haplotype H1 significantly decreased the risk of hypertension in both populations. These results suggested that WNK1 polymorphisms were involved in the predisposition of essential hypertension in Hani and Yi populations and its effects showed a clear population specificity. This finding supported the importance of population specificity in determining the genetic factors associated with diseases and thus disease treatment.

Association study of the β2-adrenergic receptor gene polymorphisms and hypertension in the Northern Han Chinese

Background

The β2-adrenergic receptor (ADRB2) gene has been widely researched as a candidate gene for essential hypertension (EH), but no consensus has been reached in different ethnicities. The aim of the present study was to evaluate the possible association between the ADRB2 gene polymorphisms and the EH risk in the Northern Han Chinese population.

Methodology/Principal Findings

This study included 747 hypertensive subjects and 390 healthy volunteers as control subjects in the Northern Han Chinese. Genotyping was performed to identify the C-47T, A46G and C79G polymorphisms of the ADRB2 gene. G allelic frequency of A46G polymorphism was significantly higher in hypertensive subjects (P = 0.011, OR = 1.287, 95%CI [1.059–1.565]) than that in controls. Significant association could also be found in dominant genetic model (GG+AG vs. AA, P = 0.006, OR = 1.497, 95%CI [1.121–1.998]), in homozygote comparison (GG vs. AA, P = 0.025, OR = 1.568, 95%CI [1.059–2.322]), and in additive genetic model (GG vs. AG vs. AA, P = 0.012, OR = 1.282, 95%CI [1.056–1.555]). Subgroup analyses performed by gender suggested that this association could be found in male, but not in female. Stratification analyses by obesity showed that A46G polymorphism was related to the prevalence of hypertension in the obese population (GG vs. AG vs. AA, P<0.001, OR = 1.645, 95%CI [1.258–2.151]). Significant interaction was found between A46G genotypes and body mass index on EH risk. No significant association could be found between C-47T or C79G polymorphism and EH risk. Linkage disequilibrium was detected between the C-47T, A46G and C79G polymorphisms. Haplotype analyses observed that the T-47-A46-C79 haplotype was a protective haplotype for EH, while the T-47-G46-C79 haplotype increased the risk.

Conclusions/Significances

We revealed that the ADRB2 A46G polymorphism might increase the risk for EH in the Northern Han Chinese population.

Cardiovascular pharmacogenomics of adrenergic receptor signaling: clinical implications and future directions

G-protein-coupled receptors (GPCRs) are the targets for many drugs, and genetic variation in coding and noncoding regions is apparent in many such receptors. In this superfamily, adrenergic receptors (ARs) were among the first in which single-nucleotide polymorphisms (SNPs) were discovered, and studies including in vitro mutagenesis, genetically modified mouse models, human ex vivo and in vitro studies and pharmacogenetic association studies were conducted. The signal transduction in these receptors includes amplification steps, desensitization, crosstalk, and redundancies, enabling potential mitigation of the size of the clinical effect for a single variant in a single gene. Nevertheless, convincing evidence has emerged that several variants have an impact on therapy, with certain caveats as to how the results are to be interpreted. Here we review these results for selected ARs and associated regulatory kinases relative to the pharmacogenomics of β-blocker treatment for hypertension and heart failure. We emphasize the linking of clinical results to molecular mechanisms, discuss study design limitations, and offer some recommendations for future directions.

Genetic covariance between gamma-glutamyl transpeptidase and fatty liver risk factors: role of beta2-adrenergic receptor genetic variation in twins

BACKGROUND & AIMS

Plasma levels of gamma-glutamyl transpeptidase (GGT) are associated with risk factors for nonalcoholic fatty liver disease (NAFLD), such as dyslipidemia, insulin resistance (IR), and hypertension. Limited data exist on whether there is genetic covariance between plasma levels of GGT and NAFLD risk factors. Variants of beta2-adrenergic receptor gene (ADRB2) have been associated with dyslipidemia, IR, and hypertension, but its effect on GGT secretion is not known. We estimated the heritability of GGT using a twin-study design and examined the genetic covariance between GGT levels, IR, hypertension, levels of low-density lipoproteins and triglycerides, and ADRB2 variants.

METHODS

We studied phenotypes of 362 twins; the heritabilities of increased GGT activity and genetic covariance with NAFLD risk factors were estimated by variance-component methodology. ADRB2 genotype associations with plasma GGT activity were examined using generalized estimating equations to account for intra-twinship correlations.

RESULTS

GGT activity was heritable at 49% +/- 8% of the twin cohort and had significant covariance with IR; insulin, triglyceride, and uric acid levels; and diastolic blood pressure. In generalized estimating equation models, the most common haplotype of ADRB2 was significantly associated with plasma GGT activity. Five single nucleotide polymorphisms in ADRB2 were associated with levels of GGT; ADRB2 haplotypes displayed pleiotropic effects on GGT and triglyceride levels.

CONCLUSIONS

In a twin study, GGT shared genetic codetermination with traits of metabolic syndrome. The ADRB2 gene had pleiotropic effects on plasma levels of GGT and triglycerides, indicating linked pathways (eg, adrenergic) between genetic susceptibility to NAFLD and metabolic syndrome.

A46G and C79G polymorphisms in the β2-adrenergic receptor gene (ADRB2) and essential hypertension risk: a meta-analysis

No consensus has been reached on the association between the β2-adrenergic receptor polymorphisms A46G and C79G and essential hypertension risk. We performed a meta-analysis to confirm the possible association. After reviewing 303 reports in PubMed and 359 reports in Embase, we included in our meta-analysis 18 articles (20 studies) that met our inclusion criteria. The fixed-effects model and the random-effects model were applied for dichotomous outcomes to combine the results of the individual studies. There was no statistical association between A46G and hypertension risk in all subjects, Asians or Caucasians. However, an association was observed in the dominant genetic model (AA vs. (AG+GG)) (P=0.04, odds ratio (OR)=1.38, 95% confidence interval (CI) 1.01-1.87, P(heterogeneity)=0.98, fixed-effects model) in the subgroup of mixed Africans. No overall statistical association could be found between C79G and hypertension risk or any ethnic subgroup. In the research conducted on severe hypertension (systolic blood pressure ≥160 mm Hg and/or diastolic blood pressure ≥95 mm Hg hypertensive population), significant association was found in the dominant genetic model (CC vs. (CG+GG)) (P=0.04, OR=1.38, 95% CI 1.02-1.86, P(heterogeneity)=0.03, random-effects model), and there was also a borderline significance between the C79 allele and severe hypertension (P=0.05, OR=1.26, 95% CI 1.00-1.57, P(heterogeneity)=0.04, random-effects model). No association could be found in this study between the two polymorphisms and stage 2 hypertension. More studies stratified for different ethnicities and different stages of hypertension should be performed in the future.

Adrenergic signaling polymorphisms and their impact on cardiovascular disease

This review examines the impact of recent discoveries defining personal genetics of adrenergic signaling polymorphisms on scientific discovery and medical practice related to cardiovascular diseases. The adrenergic system is the major regulator of minute-by-minute cardiovascular function. Inhibition of adrenergic signaling with pharmacological beta-adrenergic receptor antagonists (beta-blockers) is first-line therapy for heart failure and hypertension. Advances in pharmacology, molecular biology, and genetics of adrenergic signaling pathways have brought us to the point where personal genetic differences in adrenergic signaling factors are being assessed as determinants of risk or progression of cardiovascular disease. For a few polymorphisms, functional data generated in cell-based systems, genetic mouse models, and pharmacological provocation of human subjects are concordant with population studies that suggest altered risk of cardiovascular disease or therapeutic response to beta-blockers. For the majority of adrenergic pathway polymorphisms however, published data conflict, and the clinical relevance of individual genotyping remains uncertain. Here, the current state of laboratory and clinical evidence that adrenergic pathway polymorphisms can affect cardiovascular pathophysiology is comprehensively reviewed and compared, with a goal of placing these data in the broad context of potential clinical applicability.

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.

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

BACKGROUND AND OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Synopsis and data synthesis of genetic association studies in hypertension for the adrenergic receptor family genes: the CUMAGAS-HYPERT database

BACKGROUND

The adrenergic receptor (adrenoceptor) family genes have been extensively studied as candidate genes in hypertension but the results of individual genetic association studies (GAS) are controversial and inconclusive. To clarify these data, a systematic assessment of GAS for adrenoceptor family genes in hypertension was conducted.

METHODS

Data from 163 GAS involving 7 genes and 37 distinct genetic variants were analyzed and cataloged in CUMAGAS-HYPERT (Cumulative Meta-analysis of Genetic Association Studies-HYPERTension; a web-based information system, which allows the retrieval and synthesis of data from GAS in hypertension, available at http://biomath.med.uth.gr). Data from genome-wide association studies involving the adrenoceptor family genes were also systematically searched.

RESULTS

Individual GAS reported inconsistent associations and had limited power to detect modest genetic effects, with only 1.2% having power >80%. Thirteen variants were investigated by three or more studies and their results were subject to meta-analysis. In the main meta-analyses, significant results were shown for five variants (ADRB1 p.Arg389Gly, ADRB1 p.Ser49Gly, ADRB2 g.9368308A>G, ADRB3 p.Trp64Arg, and ADRA1A p.Cys347Arg) under the allelic contrast and/or the dominant model. Subgroup analyses by ethnicity and gender detected significant associations for three variants (ADRB1 p.Arg389Gly in east Asians, ADRB2 p.Gln27Glu in whites, and ADRB3 p.Trp64Arg in whites and in males). Heterogeneity ranged from none to high. No significant associations were recorded from genome-wide studies.

CONCLUSIONS

There is evidence to implicate adrenoceptor genes in hypertension, although future studies designed to investigate epistatic and gene-environment interactions would allow more solid conclusions to be drawn about the role of these genes in hypertension.

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.

Influence of beta2-adrenoceptor gene polymorphisms on beta2-adrenoceptor expression in human lung

BACKGROUND

The aim of the present study was to establish whether polymorphisms, especially those within the promoter region, of the beta(2)-adrenoceptor gene (ADRB2) influence beta(2)-adrenoceptor expression in human lung.

METHODS

The density of beta-adrenoceptors in human lung tissue (n=88) was determined by saturation binding using the radioligand, iodinated cyanopindolol. Discrimination of beta(1)- and beta(2)-adrenoceptors was determined using the highly selective beta(1)-adrenoceptor antagonist, CGP20712A. Genotype was determined at 5 positions of ADRB2 previously reported as polymorphic. Potential influences of single nucleotide polymorphisms (SNPs) within the promoter region (-367, -47) and coding block (46, 79, 491) of ADRB2 on beta(2)-adrenoceptor expression were investigated.

RESULTS

The density of beta(2)-adrenoceptors was variable among the 88 lung preparations studied ranging from 17 to 177fmol/mg protein (mean+/-S.E.M., 72+/-4fmol/mg protein). There was no influence of genotype on beta(2)-adrenoceptor expression for any of the polymorphisms studied except at position 491. The polymorphism at position 491C>T, leading to a change from thr to ile at amino acid 164, is uncommon. Preparations genotyped as heterozygous (126+/-15fmol/mg protein; n=5) expressed significantly (P=0.0005) higher levels of beta(2)-adrenoceptor than those that were homozygous (69+/-4fmol/mg protein; n=83).

CONCLUSION

With the exception of position 491, these data indicate that polymorphisms of ADRB2 do not influence beta(2)-adrenoceptor expression in human lung.