Polymorphisms of adrenergic receptors: variations on a theme

Role of S1P/S1PR3 axis in release of CCL20 from human bronchial epithelial cells

Background

Sphingosine kinase phosphorylates sphingosine to generate sphingosine 1 phosphate (S1P) following stimulation of the five plasma membrane G-protein-coupled receptors. The objective of this study is to clarify the role of S1P and its receptors (S1PRs), especially S1PR3 in airway epithelial cells.

Methods

The effects of S1P on asthma-related genes expression were examined with the human bronchial epithelial cells BEAS-2B and Calu-3 using a transcriptome analysis and siRNA of S1PRs. To clarify the role of CCL20 in the airway inflammation, BALB/c mice were immunized with ovalbumin (OVA) and subsequently challenged with an OVA-containing aerosol to induce asthma with or without intraperitoneal administration of anti-CCL20. Finally, the anti-inflammatory effect of VPC 23019, S1PR1/3 antagonist, in the OVA-induced asthma was examined.

Results

S1P induced the expression of some asthma-related genes, such as ADRB2, PTGER4, and CCL20, in the bronchial epithelial cells. The knock-down of SIPR3 suppressed the expression of S1P-inducing CCL20. Anti-CCL20 antibody significantly attenuated the eosinophil numbers in the bronchoalveolar lavage fluid (P<0.01). Upon OVA challenge, VPC23019 exhibited substantially attenuated eosinophilic inflammation.

Conclusions

S1P/S1PR3 pathways have a role in release of proinflammatory cytokines from bronchial epithelial cells. Our results suggest that S1P/S1PR3 may be a possible candidate for the treatment of bronchial asthma.

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

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

Polymorphisms in human heat shock factor-1 and analysis of potential biological consequences

The stress-activated transcription factor, heat shock factor-1 (HSF1), regulates many genes including cytoprotective heat shock proteins (HSPs). We hypothesized that polymorphisms in HSF1 may alter the level or function of HSF1 protein accounting for interindividual viability in disease susceptibility or prognosis. We searched for exomic variants in HSF1 by querying human genome databases and directly sequencing DNA from 80 anonymous genomic DNA samples. Overall, HSF1 sequence was highly conserved, with no common variations. We found 31 validated deviations from a reference sequence in the dbSNP database and an additional 5 novel variants by sequencing, with allele frequencies that were 0.06 or less. Of these 36, 2 were in 5'-untranslated region (5'UTR), 10 in 3'UTR, and 24 in the coding region. The potential effects of 5'UTR on secondary structure, protein structure/function, and 3'UTR targets of microRNAs were analyzed using RNAFold, PolyPhen-2, SIFT, and MicroSNiper. One of the 5'UTR variants was predicted to strengthen secondary structure. Eight of 3'UTR variants were predicted to modify microRNA target sequences. Eight of the coding region variants were predicted to modify HSF1 structure/function. Reducing HSF1 levels in A549 cells using short hairpin RNA (shRNA) increased sensitivity to heat-induced killing demonstrating the impact that genetic variants that reduce HSF1 levels might have. Using the pmirGLO expression system, we found that the wild-type HSF1 3'UTR suppressed translation of a firefly luciferase reporter plasmid by 65 %. Introducing two of four 3'UTR single nucleotide polymorphisms (SNPs) increased HSF1 3'UTR translational suppression by 27-44 % compared with the wild-type HSF1 3'UTR sequence while a third SNP reduced suppression by 25 %. HSF1 variants may alter HSF1 protein levels or function with potential effects on cell functions, including sensitivity to stress.

Arg389Gly β1-adrenergic receptor polymorphism and susceptibility to syncope during tilt test

INTRODUCTION

Numerous hormones, neurotransmitters, and other stimuli exert their biological effect on cellular functioning through heptahelical receptors coupled to G proteins (GPCR - G protein-coupled receptors). Adrenergic receptors that belong to this superfamily of receptors are components of the sympathetic nervous system. They play a pivotal role in blood pressure regulation and myocardial contractility. Alterations of the adrenergic receptor pathway have been suggested to be involved in the pathophysiology of vasovagal syncope (VVS). The aim of the present study was to evaluate the distribution of Arg389Gly polymorphism within the ADRB1 gene among patients with recurrent syncope.

MATERIAL AND METHODS

Arg389Gly single nucleotide polymorphism was analyzed in 205 patients with recurrent syncope. Ninety-five patients (46%) had a positive head-up tilt test (HUT) result. The control group comprised 143 non-fainting subjects. Genotyping was performed by restriction fragment length polymorphism (RFLP) with BstNI enzyme.

RESULTS

Both analyzed groups had similar distribution of the 389Gly allele. Sixty percent of polymorphic 389Gly carriers belong to the group of syncopal patients, while 40% belong to the control group of healthy subjects.

CONCLUSIONS

An association between syncopal incidence and Arg389Gly polymorphism within the ADRB1 gene was not found. The analyzed polymorphism affecting sympathetic activity does not influence vasovagal syncope in Polish patients.

Association of single nucleotide polymorphisms of β2-adrenergic receptor gene with clinicopathological features of pancreatic carcinoma

β2-Adrenoceptor agonists induce pancreatic cancer occurrence and progression through β2-AR. Polymorphisms in β2-AR gene lead to modified sensitivity to agonists and variable tumorigenic potential. In this study, pancreatic carcinoma and non-neoplastic pancreatic tissues were genotyped at codons 16 and 27 by PCR-restriction fragment length polymorphism and DNA sequencing. Expressions of β2-AR, EGFR, VEGF and MMP-2 were detected by immunohistochemistry. The frequencies of genotypes and alleles at codon 16 between pancreatic carcinoma and non-neoplastic pancreatic tissues showed no difference. The genotype frequencies were associated with TNM grade, lymph node metastasis, and one-year survival rate. The allele G at codon 16 frequently appeared in tumors with high TNM grade, lymph node metastasis, poor prognosis, high expression levels of β2-AR, EGFR, VEGF and MMP-2. The genotype and allele frequencies of codon 27 were not associated with clinicopathological features and down-stream protein expressions. Collectively, SNPs of β2-AR gene at codon 16 were associated with the biological behavior of pancreatic carcinoma. The allele G at codon 16 could facilitate the progression and metastasis of pancreatic carcinoma through elevating vascularization and activating the EGFR pathway. SNPs at codon 16 of β2-AR are new useful biomarkers for predicting biological behavior and survival of pancreatic carcinoma and might be used as a new gene therapeutic target.

Genetic variation, β-blockers, and perioperative myocardial infarction

Perioperative myocardial infarction is a common and potentially fatal complication after noncardiac surgery, particular among patients with cardiovascular risk factors. β-blockers have been considered a mainstay in prevention and treatment of perioperative myocardial infarction, yet recent evidence suggests that β-blockers may have an unfavorable risk profile in this setting, and the use has become controversial. What seems conspicuously absent from the current discussion is the appreciation of how much interindividual genetic variation influences the clinical response to β-blocker therapy. Genetic variation in the adrenergic signaling pathway is common, and has a major impact on adrenergic receptor function and β-blocker efficacy in other cardiovascular diseases, such as heart failure and hypertension. Genetic variation in the cytochrome P450 2D6, or CYP2D6, enzyme, which is responsible for the metabolism of most β-blockers, is also important and can lead to poor metabolizing of β-blockers (potential toxicity) or their ultra-rapid degradation (decreased efficacy). Here, we review the molecular, cellular, and physiologic consequences of polymorphisms in the adrenergic signaling pathway and CYP2D6 gene, and show that these are likely relevant factors influencing efficacy, safety, and toxicity of β-blocker therapy in prevention and treatment of perioperative myocardial infarction.

The relationship between birthweight and longitudinal changes of blood pressure is modulated by beta-adrenergic receptor genes: the Bogalusa Heart Study

This study examines the genetic influence of beta-adrenergic receptor gene polymorphisms (beta(2)-AR Arg16Gly and beta(3)-AR Trp64Arg) on the relationship of birthweight to longitudinal changes of blood pressure (BP) from childhood to adulthood in 224 black and 515 white adults, aged 21-47 years, enrolled in the Bogalusa Heart Study. Blacks showed significantly lower birthweight and frequencies of beta(2)-AR Gly16 and beta(3)-AR Trp64 alleles and higher BP levels and age-related trends than whites. In multivariable regression analyses using race-adjusted BP and birthweight, low birthweight was associated with greater increase in age-related trend of systolic BP (standardized regression coefficient beta = -0.09, P = .002) and diastolic BP (beta = -0.07, P = .037) in the combined sample of blacks and whites, adjusting for the first BP measurement in childhood, sex, age, and gestational age. Adjustment for the current body mass index strengthened the birthweight-BP association. Importantly, the strength of the association, measured as regression coefficients, was modulated by the combination of beta(2)-AR and beta(3)-AR genotypes for systolic (P = .042 for interaction) and diastolic BP age-related trend (P = .039 for interaction), with blacks and whites showing a similar trend in the interaction. These findings indicate that the intrauterine programming of BP regulation later in life depends on beta-AR genotypes.

Asthma from a pharmacogenomic point of view

Pharmacogenomics, a fascinating, emerging area of biomedical research is strongly influenced by growing availability of genomic databases, high-throughput genomic technologies, bioinformatic tools and artificial computational modelling approaches. One main area of pharmacogenomics is the discovery of new drugs and drug targets with molecular genetic, genomic or even bioinformatic methods; the other is the study of how genomic differences influence the variability in patients' responses to drugs. From a genetic point of view, asthma is multifactorial, which means that the susceptibility to the disease is determined by interactions between multiple genes, and involves important non-genetic factors such as the environment for their expression. In this review, we summarize collective evidence from linkage and association studies that have consistently reported suggestive linkage or association of asthma or its associated phenotypes to polymorphic markers and single nucleotide polymorphisms in selected chromosomes. Genes that have been found implicated in the disease are potential new drug targets and several pharmacological investigations are underway to utilize these new discoveries. Next, we will focus on the inter-individual variability in anti-asthmatic drug responses and review the recent results in this topic.

Genome-wide linkage scan for submaximal exercise heart rate in the HERITAGE family study

The purpose of this study was to identify regions of the human genome linked to submaximal exercise heart rates in the sedentary state and in response to a standardized 20-wk endurance training program in blacks and whites of the HERITAGE Family Study. A total of 701 polymorphic markers covering the 22 autosomes were used in the genome-wide linkage scan, with 328 sibling pairs from 99 white nuclear families and 102 pairs from 115 black family units. Steady-state heart rates were measured at the relative intensity of 60% maximal oxygen uptake (HR60) and at the absolute intensity of 50 W (HR50). Baseline phenotypes were adjusted for age, sex, and baseline body mass index (BMI) and training responses (posttraining minus baseline, Δ) were adjusted for age, sex, baseline BMI, and baseline value of the phenotype. Two analytic strategies were used, a multipoint variance components and a regression-based multipoint linkage analysis. In whites, promising linkages (LOD > 1.75) were identified on 18q21-q22 for baseline HR50 (LOD = 2.64; P = 0.0002) and ΔHR60 (LOD = 2.10; P = 0.0009) and on chromosome 2q33.3 for ΔHR50 (LOD = 2.13; P = 0.0009). In blacks, evidence of promising linkage for baseline HR50 was detected with several markers within the chromosomal region 10q24-q25.3 (peak LOD = 2.43, P = 0.0004 with D10S597). The most promising regions for fine mapping in the HERITAGE Family Study were found on 2q33 for HR50 training response in whites, on 10q25-26 for baseline HR60 in blacks, and on 18q21–22 for both baseline HR50 and ΔHR60 in whites.

Sudden Cardiac Death: Epidemiology, Mechanisms, and Therapy

Sudden cardiac death is a major public health problem affecting 500,000 patients annually in the United States alone. The major risk factor for sudden cardiac death is the presence of coronary artery disease, usually in the setting of reduced ejection fraction. Globally, the incidence is expected to rise sharply as the prevalence of coronary artery disease and heart failure continue to increase. However, sudden cardiac death is a heterogeneous condition and may be caused by acute ischemia, structural defects, myocardial scar, and/or genetic mutations. Sudden death may occur even in a grossly normal heart. Beta-blockers can reduce the risk of sudden cardiac death, while implantable cardioverter defibrillators are effective at terminating malignant arrhythmias. Ejection fraction remains the major criterion to stratify patients for defibrillator implantation but this strategy alone is insensitive and nonspecific. Novel clinical, electrophysiologic, and genetic markers have been identified that may increase precision in patient selection for primary prevention therapy. This review discusses the epidemiology, mechanisms, etiologies, therapies, treatment guidelines, and future directions in the management of sudden cardiac death.

Gene-trapped mouse embryonic stem cell-derived cardiac myocytes and human genetics implicate AKAP10 in heart rhythm regulation

Sudden cardiac death due to abnormal heart rhythm kills 400,000-460,000 Americans each year. To identify genes that regulate heart rhythm, we are developing a screen that uses mouse embryonic stem cells (mESCs) with gene disruptions that can be differentiated into cardiac cells for phenotyping. Here, we show that the heterozygous disruption of the Akap10 (D-AKAP2) gene that disrupts the final 51 aa increases the contractile response of cultured cardiac cells to cholinergic signals. In both heterozygous and homozygous mutant mice derived from these mESCs, the same Akap10 disruption increases the cardiac response to cholinergic signals, suggesting a dominant interfering effect of the Akap10 mutant allele. The mutant mice have cardiac arrhythmias and die prematurely. We also found that a common variant of AKAP10 in humans (646V, 40% of alleles) was associated with increased basal heart rate and decreased heart rate variability (markers of low cholinergic/vagus nerve sensitivity). These markers predict an increased risk of sudden cardiac death. Although the molecular mechanism remains unknown, our findings in mutant mESCs, mice, and a common human AKAP10 SNP all suggest a role for AKAP10 in heart rhythm control. Our stem cell-based screen may provide a means of identifying other genes that control heart rhythm.

Allele-specific binding of airway nuclear extracts to polymorphic beta2-adrenergic receptor 5' sequence

Like other intronless G protein-coupled receptor genes, the beta(2)-adrenergic receptor (beta(2)AR) has minimal genetic space for population variability, and has attained such via multiple coding and noncoding polymorphisms. Yet most clinical studies use the two nonsynonymous polymorphisms of the coding region for association analysis despite low levels of linkage disequilibrium with some promoter and 5'UTR polymorphisms. To assess the potential for allele-specific transcription factor binding to beta(2)AR 5'-flanking sequence, 3'-biotin-labeled oligonucleotide duplexes were synthesized. Each was centered on variable sites representing major or minor alleles found in the human population with frequencies of 5% or greater (20 polymorphic sites). Electrophoretic mobility shift assays were performed using human airway smooth muscle or airway epithelial cell nuclear extracts. Many of these polymorphisms resulted in an alteration in binding, and both major allele and minor allele dominance were observed. For example, in airway smooth muscle nuclear extracts, 10 polymorphisms decreased and 2 increased binding, whereas 5 showed no differences. Concordance between airway smooth muscle and epithelial cell nuclear extract binding to polymorphic alleles was found in only approximately 50% of cases. There was no tendency for the rare variants to be more likely to have altered nuclear extract binding compared to the more common variants. Taken together, these results provide potential mechanisms by which beta(2)AR 5'-flanking polymorphisms affect obstructive lung phenotypes.

The Finnish Cardiovascular Study (FINCAVAS): characterising patients with high risk of cardiovascular morbidity and mortality

Background

The purpose of the Finnish Cardiovascular Study (FINCAVAS) is to construct a risk profile – using genetic, haemodynamic and electrocardiographic (ECG) markers – of individuals at high risk of cardiovascular diseases, events and deaths.

Methods and design

All patients scheduled for an exercise stress test at Tampere University Hospital and willing to participate have been and will be recruited between October 2001 and December 2007. The final number of participants is estimated to reach 5,000. Technically successful data on exercise tests using a bicycle ergometer have been collected of 2,212 patients (1,400 men and 812 women) by the end of 2004. In addition to repeated measurement of heart rate and blood pressure, digital high-resolution ECG at 500 Hz is recorded continuously during the entire exercise test, including the resting and recovery phases. About 20% of the patients are examined with coronary angiography. Genetic variations known or suspected to alter cardiovascular function or pathophysiology are analysed to elucidate the effects and interactions of these candidate genes, exercise and commonly used cardiovascular medications.

Discussion

FINCAVAS compiles an extensive set of data on patient history, genetic variation, cardiovascular parameters, ECG markers as well as follow-up data on clinical events, hospitalisations and deaths. The data enables the development of new diagnostic and prognostic tools as well as assessments of the importance of existing markers.

Effects of polymorphisms in β1-adrenoceptor and α-subunit of G protein on heart rate and blood pressure during exercise test. The Finnish Cardiovascular Study

We tested whether the Arg389Gly and Ser49Gly polymorphisms of the β1-adrenergic receptor gene ADRB1 and the T393C polymorphism of the G protein α-subunit gene GNAS1 modulate heart rate (HR) and blood pressure responses during an exercise stress test. The study population comprised 890 participants (563 men and 327 women, mean age 58.1 ± 12.6 yr) of the Finnish Cardiovascular Study. Their HR, systolic (SAP), and diastolic arterial pressures (DAP) at rest, during exercise, and 4 min after the test were measured and analyzed by repeated-measurement ANOVA (RANOVA). Genotypes were detected by TaqMan 5′ nuclease assay. In all subjects, and in men and women separately, the T393C of GNAS1 was the only polymorphism with genotype × time interaction in HR over the three study phases ( P = 0.04, RANOVA). None of the polymorphisms presented genotype × time interaction in SAP or DAP responses ( P > 0.10, RANOVA). In all subjects at rest, the Ser49Gly polymorphism of ADRB1 tended ( P = 0.06, ANOVA) to differentiate HR. Arg389Gly polymorphism of ADRB1 affected maximal SAP during exercise ( P = 0.04, ANOVA) and the change in SAP from rest to maximal ( P = 0.03, ANOVA). Arg389 homozygotes, particularly men, were less likely to have ventricular extrasystoles during the exercise (odds ratio = 0.68, 95% confidence interval = 0.51–0.91, P = 0.009, and odds ratio = 0.60, 95% confidence interval = 0.42–0.86, P = 0.006, respectively) than did Gly389 carriers. In conclusion, polymorphisms examined appear to have modulatory effects on hemodynamics in a clinical exercise test setting. However, the effects in absolute numbers were minor and clinically possibly insignificant.

Polymorphisms of genes CYP2D6, ADRB1 and GNAS1 in pharmacokinetics and systemic effects of ophthalmic timolol. A pilot study

OBJECTIVE

To test the hypotheses that (1) CYP2D6 genotype is associated with pharmacokinetics of ophthalmic timolol and (2) variation in genotypes of ADRB1 (beta(1)-adrenoceptor) and GNAS1 (alpha-subunit of G-protein) modulate heart rate (HR), and systolic (SAP) and diastolic (DAP) arterial pressure responses to timolol.

METHODS

Nineteen glaucoma patients and eighteen healthy volunteers were treated with 0.5% aqueous and 0.1% hydrogel formulations of ophthalmic timolol using a randomised cross-over design. The participants conducted head-up tilt and maximum exercise test at four visits. Plasma concentration of timolol was measured twice for glaucoma patients and ten times for healthy volunteers on each visit. Also, the genotypes for CYP2D6, ADRB1 and GNAS1 were determined.

RESULTS

Among healthy volunteers using aqueous timolol, poor metabolisers (PMs, n=2) of CYP2D6 had higher maximum plasma concentrations (C(max), values 2.63 and 2.94 ng/ml), longer elimination half-lives ( T(1/2), 5.49 and 6.75 h), and higher area-under-curve (AUC, 19.54 and 23.25 ng.h/ml) than intermediate [IMs, n=6, mean+/-SD 1.73+/-0.59 ng/ml (not significant), 3.30+/-0.48 h, 11.32+/-3.72 ng.h/ml], extensive (EMs, n=8, 1.60+/-0.72 ng/ml, 3.24+/-1.24 h, 8.52+/-6.12 ng.h/ml) and ultra-rapid (UMs, n=2, values 1.23 and 1.67 ng/ml, 2.22 and 2.52 h, 6.16 and 6.94 ng.h/ml) metabolisers. The IMs, EMs and UMs did not differ from each other for any of the kinetic variables. Also, the elevation of HR from rest to maximum level tended to differ between PMs and IMs, and between PMs and UMs. The pharmacokinetics and pharmacodynamics between the CYP2D6 groups did not differ with statistical significance when hydrogel timolol was used. Upon head-up tilt, the Ser49 homozygotes (n=26) had higher SAP (P=0.03) and DAP (P<0.01) than the Gly carriers (n=11). The change in DAP from rest to maximum during exercise was lower (P<0.01) in subjects with CC alleles of GNAS1 (n=13) than those with at least one T allele (n=24).

CONCLUSION

The CYP2D6 poor metabolisers may be more prone to systemic adverse events with aqueous timolol than extensive metabolisers. Since CYP2D6 genotyping is not routine clinical practice, using 0.1% timolol hydrogel instead of 0.5% aqueous preparation will increase patient safety.

Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced pulmonary adenocarcinomas in Syrian golden hamsters contain beta 2-adrenergic receptor single-nucleotide polymorphisms

Cigarette smoking contributes to the development of lung cancer throughout the world, with cases of pulmonary adenocarcinoma (PAC) the most numerous. Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which is formed from nicotine, has been demonstrated to cause mutations in genes that affect cell regulation and proliferation. Moreover, NNK has been shown to interact directly with and stimulate beta adrenergic receptor (ADRB) signal transduction pathways. Our goal was to determine whether single-nucleotide polymorphisms (SNPs) in the Adrb2 from PAC tumors were induced in golden hamsters by the injection of NNK. Here we report the cloning and sequencing of Adrb2 clones from either dissected lung tumors from NNK-injected animals or whole-lung tissue from water-injected controls. Both sets of animals contained SNPs; however, we found significantly more SNPs in the Adrb2 from NNK-injected animals than in the controls. The majority of these SNPs were novel, nonsynonymous mutations found in regions of the Adrb2 known to be involved in ligand binding, G-protein coupling, and desensitization/down-regulation. Our data verified the mutagenic effects of NNK as well as demonstrated that this animal model provides an outstanding way of identifying mutations not only in the Adrb2, but also in other genes that may play essential roles in the regulation and growth of pulmonary adenocarcinomas.