Adrenoceptor Gene Research Articles

Cardiac PDGFRα+ interstitial cells generate spontaneous inward currents that contribute to excitability in the heart.

The cell types and conductance that contribute to normal cardiac functions remain under investigation. We used mice that express an enhanced green fluorescent protein (eGFP)-histone 2B fusion protein driven off the cell-specific endogenous promoter for Pdgfra to investigate the distribution and functional role of PDGFRα+ cells in the heart. Cardiac PDGFRα+ cells were widely distributed within the endomysium of atria, ventricle, and sino-atrial node (SAN) tissues. PDGFRα+ cells formed a discrete network of cells, lying in close apposition to neighboring cardiac myocytes in mouse and Cynomolgus monkey (Macaca fascicularis) hearts. Expression of eGFP in nuclei allowed unequivocal identification of these cells following enzymatic dispersion of muscle tissues. FACS purification of PDGFRα+ cells from the SAN and analysis of gene transcripts by qPCR revealed that they were a distinct population of cells that expressed gap junction transcripts, Gja1 and Gjc1. Cardiac PDGFRα+ cells generated spontaneous transient inward currents (STICs) and spontaneous transient depolarizations (STDs) that reversed at 0 mV. Reversal potential was maintained when ECl = -40 mV. [Na+ ]o replacement and FTY720 abolished STICs, suggesting they were due to a non-selective cation conductance (NSCC) carried by TRPM7. PDGFRα+ cells also express β2 -adrenoceptor gene transcripts, Adrb2. Zinterol, a selective β2 -receptor agonist, increased the amplitude and frequency of STICs, suggesting these cells could contribute to adrenergic regulation of cardiac excitability. PDGFRα+ cells in cardiac muscles generate inward currents via an NSCC. STICs generated by these cells may contribute to the integrated membrane potentials of cardiac muscles, possibly affecting the frequency of pacemaker activity.

Genetic Variants of Adrenoceptors.

Adrenoceptors are class A G-protein-coupled receptors grouped into three families (α1-, α2-, and β-adrenoceptors), each one including three members. All nine corresponding adrenoceptor genes display genetic variation in their coding and adjacent non-coding genomic region. Coding variants, i.e., nucleotide exchanges within the transcribed and translated receptor sequence, may result in a difference in amino acid sequence thus altering receptor function and signaling. Such variants have been intensely studied in vitro in overexpression systems and addressed in candidate-gene studies for distinct clinical parameters. In recent years, large cohorts were analyzed in genome-wide association studies (GWAS), where variants are detected as significant in context with specific traits. These studies identified two of the in-depth characterized 18 coding variants in adrenoceptors as repeatedly statistically significant genetic risk factors - p.Arg389Gly in the β1- and p.Thr164Ile in the β2-adrenoceptor, along with 56 variants in the non-coding regions adjacent to the adrenoceptor gene loci, the functional role of which is largely unknown at present. This chapter summarizes current knowledge on the two coding variants in adrenoceptors that have been consistently validated in GWAS and provides a prospective overview on the numerous non-coding variants more recently attributed to adrenoceptor gene loci.

Correlation between Adrenoceptor Expression and Clinical Parameters in Degenerated Lumbar Intervertebral Discs

Despite advanced knowledge of the cellular and biomechanical processes of intervertebral disc degeneration (IVDD), the trigger and underlying mechanisms remain unclear. Since the sympathetic nervous system (SNS) has been shown to exhibit catabolic effects in osteoarthritis pathogenesis, it is attractive to speculate that it also influences IVDD. Therefore, we explored the adrenoceptor (AR) expression profile in human IVDs and correlated it with clinical parameters of patients. IVD samples were collected from n = 43 patients undergoing lumbar spinal fusion surgery. AR gene expression was analyzed by semi-quantitative polymerase chain reaction. Clinical parameters as well as radiological Pfirrmann and Modic classification were collected and correlated with AR expression levels. In total human IVD homogenates α1A-, α1B-, α2A-, α2B-, α2C-, β1- and β2-AR genes were expressed. Expression of α1A- (r = 0.439), α2A- (r = 0.346) and β2-AR (r = 0.409) showed a positive and significant correlation with Pfirrmann grade. α1A-AR expression was significantly decreased in IVD tissue of patients with adjacent segment disease (p = 0.041). The results of this study indicate that a relationship between IVDD and AR expression exists. Thus, the SNS and its neurotransmitters might play a role in IVDD pathogenesis. The knowledge of differential AR expression in different etiologies could contribute to the development of new therapeutic approaches for IVDD.

Are β3 -adrenoceptor gene polymorphisms relevant for urology?

β3 -adrenoceptors (ARs) are an important drug target for the treatment of overactive bladder syndrome (OAB) and are under investigation for other indications. The human β3 -AR gene is polymorphic; an exchange of amino acid tryptophan (Trp) for arginine (Arg) in position 64 of the receptor protein is the most frequent and best-studied polymorphism. A narrative review on the impact of β3 -AR polymorphisms on urological disease and its treatment is presented. Two out of four studies have reported that the 64Arg allele was found more frequently in subjects with OAB thanin healthy controls. A large study in a highly selective population (men undergoing prostatectomy for cancer treatment) did not confirm this. On the other hand, studies examining symptom severity typically found little difference between 64Arg and 64Trp carriers. In vitro studies with endogenously expressed β3 -AR reported a decreased lipolytic response in human adipose tissue. Studies with heterologously expressed receptors sometimes found a decreased responsiveness to agonists including β3 -AR agonists, but others did not confirm that. The overall evidence points to carriers of the 64Arg genotype expressing fewer and/or hypofunctional β3 -ARs and being associated with the presence of OAB but such findings were only detected inconsistently. If this hypofunctionality exists, the consequences may be of insufficient magnitude to allow a robust detection. Only adequately powered studies comparing responses with a β3 -AR agonist in 64Arg carriers versus wild-type patients can address this.

Heteromerization between α2A adrenoceptors and different polymorphic variants of the dopamine D4 receptor determines pharmacological and functional differences. Implications for impulsive-control disorders

Polymorphic alleles of the human dopamine D4 receptor gene (DRD4) have been consistently associated with individual differences in personality traits and neuropsychiatric disorders, particularly between the gene encoding dopamine D4.7 receptor variant and attention deficit hyperactivity disorder (ADHD). The α2A adrenoceptor gene has also been associated with ADHD. In fact, drugs targeting the α2A adrenoceptor (α2AR), such as guanfacine, are commonly used in ADHD treatment. In view of the involvement of dopamine D4 receptor (D4R) and α2AR in ADHD and impulsivity, their concurrent localization in cortical pyramidal neurons and the demonstrated ability of D4R to form functional heteromers with other G protein-coupled receptors, in this study we evaluate whether the α2AR forms functional heteromers with D4R and weather these heteromers show different properties depending on the D4R variant involved. Using cortical brain slices from hD4.7R knock-in and wild-type mice, here, we demonstrate that α2AR and D4R heteromerize and constitute a significant functional population of cortical α2AR and D4R. Moreover, in cortical slices from wild-type mice and in cells transfected with α2AR and D4.4R, we detect a negative crosstalk within the heteromer. This negative crosstalk is lost in cortex from hD4.7R knock-in mice and in cells expressing the D4.7R polymorphic variant. We also show a lack of efficacy of D4R ligands to promote G protein activation and signaling only within the α2AR-D4.7R heteromer. Taken together, our results suggest that α2AR-D4R heteromers play a pivotal role in catecholaminergic signaling in the brain cortex and are likely targets for ADHD pharmacotherapy.

ARG16GLY POLYMORPHISM IN THE Β2-ADRENOCEPTOR GENE IN PATIENTS WITH BRONCHIAL ASTHMA

The aim: The objective of the study was to analyze the frequency of Arg16Gly polymorphism in the β2 -adrenoceptor (β2 -АR) gene in patients with bronchial asthma (BA) and to assess the association of the polymorphism with BA risk. Materials and methods: We examined 553 BA patients and 95 apparently healthy individuals. Arg16Gly polymorphism in the β2 -АR gene (rs1042713) was determined using polymerase chain reaction-restriction fragment length polymorphism analysis. Statistical analysis of obtained results was performed using SPSS-17 program. Results: It was established that distribution of Arg/Arg, Arg/Gly, and Gly/Gly genotypes for Arg16Gly polymorphism in the β2 -АR gene was 44.2%, 40.0%, 15.8% in the control group vs. 31.3%; 45.7% and 23.0 among BA patients, respectively (χ2 = 6.59; р = 0.037). No significant difference was observed with regards to the distribution of genotypes for Arg16Gly polymorphism in the β2 -АR gene in men and women controls (χ2 = 4.05; р = 0.13) and BA patients (χ2 = 4.34; р = 0.11). BA risk was 1.74 times higher in the minor allele carriers (Arg/Gly + Gly/Gly genotypes) for Arg16Gly polymorphism in the β2 -АR gene. Conclusions: Analysis of Arg16Gly polymorphic variants in the β2-AR gene showed a statistically significant difference in the distribution of Arg/Arg, Arg/Gly, and Gly/Gly genotypes in patients with BA and apparently healthy individuals due to the higher frequency of Arg/Arg genotype in controls and higher frequency of Gly/Gly genotype in patients with asthma. No difference with regard to gender was found in the distribution of genotypes.

The role of Beta-1 receptor gene polymorphism in Beta-Blocker therapy for vasovagal syncope.

Vasovagal syncope (VVS) is a common clinical condition involving genetic background. The role of beta-blockers in the treatment is controversial. The aim of this study was to investigate the effect of beta-1 gene polymorphism on beta-blocker therapy in patients with VVS. We included 123 patients who were diagnosed with VVS after the tilttable test. We searched for the polymorphism Arg389Gly (rs1801253) in the beta-1 adrenoceptor gene. Overall, 64 patients (52%) had Arg389Arg with Arg389Arg genotype were more frequent compared with patients having Arg389Gly genotype (total syncopal episodes [TSE], 7.9 ± 3.7 vs. 6.4 ± 3.0; p = 0.012). TSE in patients with Arg389Arg genotype decreased significantly after 18 months of beta-blocker treatment (7.9 ± 3.7 vs. 3.0 ± 1.4, p < 0.001). After 18 months of beta-blocker treatment, patients with Arg389Arg genotype had significantly fewer syncopal episodes than patients with Arg389Gly genotype (3.0 ± 1.4 vs. 6.8 ± 3.2, p < 0.001). Results of beta-blocker therapy in patients with Arg389Arg genotype suggest that VVS pathophysiology is a multifactorial condition, with genetic, psychological, and environmental components, and therefore, treatment selection can be based on gene polymorphism.

Adrenoceptor Expression during Intervertebral Disc Degeneration.

Healthy and degenerating intervertebral discs (IVDs) are innervated by sympathetic nerves, however, adrenoceptor (AR) expression and functionality have never been investigated systematically. Therefore, AR gene expression was analyzed in both tissue and isolated cells from degenerated human IVDs. Furthermore, human IVD samples and spine sections of wildtype mice (WT) and of a mouse line that develops spontaneous IVD degeneration (IVDD, in SM/J mice) were stained for ARs and extracellular matrix (ECM) components. In IVD homogenates and cells α1a-, α1b-, α2a-, α2b-, α2c-, β1-, and β2-AR genes were expressed. In human sections, β2-AR was detectable, and its localization parallels with ECM alterations. Similarly, in IVDs of WT mice, only β2-AR was expressed, and in IVDs of SM/J mice, β2AR expression was stronger accompanied by increased collagen II, collagen XII, decorin as well as decreased cartilage oligomeric matrix protein expression. In addition, norepinephrine stimulation of isolated human IVD cells induced intracellular signaling via ERK1/2 and PKA. For the first time, the existence and functionality of ARs were demonstrated in IVD tissue samples, suggesting that the sympathicus might play a role in IVDD. Further studies will address relevant cellular mechanisms and thereby help to develop novel therapeutic options for IVDD.

β2-Adrenergic Signalling Promotes Cell Migration by Upregulating Expression of the Metastasis-Associated Molecule LYPD3.

Metastasis is associated with poor prognosis in breast cancer. Although some studies suggest beta-blockers increase survival by delaying metastasis, others have been discordant. This study provides both insights into the anomalous findings and identifies potential biomarkers that may be treatment targets. Cell line models of basal-type and oestrogen receptor-positive breast cancer were profiled for basal levels of adrenoceptor gene/protein expression, and β2-adrenoceptor mediated cell behaviour including migration, invasion, adhesion, and survival in response to adrenoceptor agonist/antagonist treatment. Protein profiling and histology identified biomarkers and drug targets. Baseline levels of adrenoceptor gene expression are higher in basal-type rather than oestrogen receptor-positive cancer cells. Norepinephrine (NE) treatment increased invasive capacity in all cell lines but did not increase proliferation/survival. Protein profiling revealed the upregulation of the pro-metastatic gene Ly6/PLAUR Domain-Containing Protein 3 (LYPD3) in norepinephrine-treated MDA-MB-468 cells. Histology confirmed selective LYPD3 expression in primary and metastatic breast tumour samples. These findings demonstrate that basal-type cancer cells show a more aggressive adrenoceptor-β2-activated phenotype in the resting and stimulated state, which is attenuated by adrenoceptor-β2 inhibition. This study also highlights the first association between ADRβ2 signalling and LYPD3; its knockdown significantly reduced the basal and norepinephrine-induced activity of MCF-7 cells in vitro. The regulation of ADRβ2 signalling by LYPD3 and its metastasis promoting activities, reveal LYPD3 as a promising therapeutic target in the treatment of breast and other cancers.

016 Single Nucleotide Polymorphism in Beta2 Adrenoceptor Gene and Risk of Acute Myocardial Infarction

Increased adrenergic activity resulting from emotional and physical stressors may trigger cases of Acute Myocardial Infarction (AMI). This study aimed to determine whether there were differences in the distribution of single nucleotide polymorphisms (SNPs) in the beta2 adrenoceptor gene in patients with AMI compared to a control population. Study participants (n=623) were recruited between 2006-2012 after they presented with an AMI to a tertiary referral centre. Blood samples were stored until gene extraction was performed. Genotyping was performed for three beta2 adrenoceptor SNPs, rs1800888 (Thr164Ile) (also known as Ile164), rs1042713 (Arg16Gly), and rs1042714 (Gln27Glu) using a TruSeq custom amplicon kit and MiSeq. ANNOVAR was used for data analysis. Genotype frequencies were compared to the global populations in Genome Aggregation Database (GnomAd version 3) which uses the allele frequency from an amalgamation of multiple databases. Statistical analysis was performed with SPSS version 26.0 software using Goodness of fitness χ2 tests. For rs1800888 (Thr164Ile) polymorphism, the T Allele frequency in the AMI patients was greater than the GnomAd database population [0.0209 vs 0.0089 (p<0.001)]. No significant differences were found for the rs1042713 (Arg16Gly) and rs1042714 (Gln27Glu) polymorphisms. A cohort of patients with AMI had a higher T allele frequency for SNP rs1800888 compared to the general population. This SNP in the beta 2 adrenergic receptor gene, which has previously been associated with increased cardiovascular risk, requires further investigation.

Systolic Blood Pressure Response to Orthostasis after Concussion is Related to ADRA2A Gene Receptor Subtypes

Orthostasis causes a gravity-dependent redistribution of blood volume to the lower extremities. The baroreflex coordinates effector organs of the cardiovascular autonomic nervous system (CV-ANS) to produce a proportional response to mitigate an aberrant change in systolic blood pressure (SBP). In autonomic dysfunction (AD), there may be a lag or impaired accommodation leading to dramatic changes in SBP. Growing evidence indicates that AD is a part of the post-injury period after concussion. The impact of genetic variability of CV-ANS receptors including that of alpha-2 adrenoceptor (ADRA2A) gene polymorphisms remains undefined. PURPOSE: To evaluate the effect of ADRA2A gene variants on SBP responses to orthostasis in recently concussed athletes. METHODS: A prospective study was performed in 13 concussed college athletes (gender: 10 female, 3 male; age: 20±1 yrs; height: 1.70±0.11 m; weight: 74±17 kg). Beat-to-beat SBP was assessed digitally at rest for 10 minutes in the supine (SUP) position and then for 3 minutes in the standing (STND) position within 48 hours (48H) of concussion; SBP was averaged and a change score computed (ΔSBP = STND SBP - SUP SBP). Fast-Fourier transform was performed and power calculated for the low frequency (LF) spectra in each position (e.g., SUP LF-SBP, STND LF-SBP); the variables were log10 transformed for parametric analyses. A saliva sample was obtained from each participant and a commercial laboratory identified the ADRA2A single nucleotide polymorphism (rs1800544) using PMR-array. RESULTS: Data are presented as group mean (±SD). There were no ADRA2A [C/C: n=5; C/G: n=5, G/G: n=3) group differences for demographics, SUP and STND SBP or LF-SBP. A significant group main effect (p<0.05) was observed for ΔSBP and post-hoc tests revealed that the G/G [-21(±3)] response was significantly (p<0.05) lower than the C/G [7(±18)] group. A 3 X 2 RMANOVA for LF-SBP was performed. A significant group, position and interaction effect (p<0.05) was observed; post-hoc tests were not significant, but trending for an effect in the G/G group. CONCLUSION: The ADRA2A receptor, whose activation is known to inhibit the release of norepinephrine and reduce peripheral vasoconstriction, contributed to a blunted SBP response to orthostasis in G/G homozygotes compared to other variants within 48H of concussion.

What makes the α1A -adrenoceptor gene product assume an α1L -adrenoceptor phenotype?

The α1A -adrenoceptor is abundantly expressed in the lower urinary tract and is the principal therapeutic target for the symptomatic treatment of lower urinary tract symptoms in men. Prazosin has a lower affinity for the lower urinary tract α1A -adrenoceptor than α1A -adrenoceptors found in other parts of the body. This has led to the lower urinary tract α1A -adrenoceptor being subclassified as an α1L -adrenoceptor. It was demonstrated that this pharmacologically distinct α1L -adrenoceptor is a product of the α1A -adrenoceptor gene, but the mechanism by which this altered phenotype is achieved remains a mystery. Hypotheses for this altered pharmacology include the presence of an interacting protein such as cysteine-rich with EGF-like domain (CRELD) 1 or other GPCRs such as the CXCR2 chemokine or 5-HT1B receptor. Alternatively, the influence of breast cancer resistance protein (BCRP) efflux transporters on the pharmacology of α1A -adrenoceptors has also been investigated. These and other hypotheses will be described and discussed in this review. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.

Synergistical action of the β2 adrenoceptor and fatty acid binding protein 2 polymorphisms on the loss of glomerular filtration rate in Chinese patients with type 2 diabetic nephropathy.

Since altered sympathetic nerve activity and insulin resistance are implicated in the pathogenesis of type 2 diabetic nephropathy, we investigated the effect of polymorphic Arg16Gly and Gln27Glu in the β2 adrenoceptor gene and Ala54Thr in the fatty acid binding protein 2 gene on the estimated glomerular filtration rate (eGFR) in Chinese patients with the above disease. A total of 552 diabetic subjects recruited from annual health examinations were studied. The eGFR was calculated from the Modification of Diet in Renal Disease equation for the Chinese. Plasma norepinephrine level and genotype were determined by high-performance liquid chromatography-tandem mass spectrometry and TaqMan method, respectively. Holter-derived heart rate viability (HRV) and the MRI-generated renal apparent diffusion coefficient (ADC) were evaluated. The Gly16Gly and Thr54Thr homozygotes had significantly higher microalbuminuria and lower eGFR against other genotypes in their individual polymorphism. Besides, the Gly16Gly variant exhibited markedly elevated norepinephrine level, whereas indicative of insulin resistance was increased in the Thr54Thr one. Multiple linear regression analysis further confirmed the independent genetic effect on the eGFR. Moreover, multifactor dimensionality reduction method detected a gene-gene synergistic action that subjects with the Gly16Gly/Thr54Thr genotype were exposed to higher risk of eGFR loss. Finally, these findings were accompanied by lower HRV and ADC, indicating sympathetically mediated hemodynamic changes. By uncovering the genetic component of the coherent interplay between the elevated sympathetic nerve activity and metabolic disorders, our observations might promote the development of novel personalized prevention and management strategies against the diabetic nephropathy, especially in the genetically susceptible individuals.

0257 : Cardiac function under stress conditions in heart failure with preserved ejection fraction rat model

Heart failure (HF) with preserved ejection fraction (pEF) is a growing health burden affecting the elderly. Patients express slight diastolic impairment at rest, this alteration is potentiated with exercice leading to an acute decompensated HF and ultimately to death. The aim of our study was to determine the cardiac consequences of an increased afterload in a relevant rat model of HFpEF, which presented at 45 weeks a diastolic dysfunction and a myocardial fibrosis. Our model is a transgenic rat (Tgβ 3 ) which overexpressed in endothelium the human β 3 -adrenoceptor gene upon ICAM2 promoter. Cardiac function was investigated using isolated working heart. After 7 min under physiological conditions (afterload 80 mmHg, preload 12.5 mmHg), cardiac parameters were recorded during afterload increase to 140 mmHg, by 10 mmHg increments. Under physiological conditions, Tgβ 3 hearts showed a reduced relaxation rate (WT: –5171±195 mmHg/s; Tgβ 3 : –4433±220 mmHg/s; p<0.05), associated with an increased minimal pressure (WT: –9.9±2.1 mmHg; Tgβ 3 : –0.8±1.1 mmHg; p<0.01), characteristics of a diastolic dysfunction. During the protocol of stress (afterload 140 mmHg), Tgβ 3 hearts presented a significantly lower developed pressure (WT: 217.2±7.8 mmHg; Tgβ 3 : 179.4±3.9 mmHg; p<0.001) and contractility (WT: 9167±510 mmHg/s; Tgβ 3 : 7234±263 mmHg/s; p<0.001), suggesting an inability of the hearts to correctly adapt to stress condition. Cardiac output, aortic and coronary flows were similar between WT and Tgβ 3 hearts, in agreement with the pEF. Our results confirmed the diastolic dysfunction of Tgβ 3 hearts in physiological condition, previously described in vivo. Moreover, the afterload increase worsened cardiac function, as it occurs in human patients under stress condition. The study of the effect of an increase in preload is in progress. This HFpEF model could allow to better characterize pathological mechanisms involved in this disease in order to identify molecular targets. The author hereby declares no conflict of interest

Insertion and deletion polymorphism in the alpha-2B adrenoceptor gene in pregnant women ripens gestational diabetes mellitus

There are no earlier studies that reported the association of the 12Glu9 polymorphism in the alpha-2B adrenoceptor (ADRA2B) gene with gestational diabetes mellitus (GDM). We examined the potential association between the ADRA2B gene insertion/deletion (I/D) polymorphism in the Saudi population with GDM. Pregnant women with GDM have been reported to exhibit the same susceptibility as that observed in type 2 diabetes mellitus (T2DM). We have selected I/D polymorphism of the ADRA2B gene located in chromosome 2q11.1 that has been extensively related to T2DM and cardiovascular diseases. This case–control study was conducted with 200 GDM and 300 non-GDM pregnant women. Genotyping of I/D polymorphism was performed by conventional PCR method. Biochemical analyses were found to be significantly different between GDM and non-GDM subjects (p<0.05). Genotype (ID+DD vs II, p=0.0002) and allele (D vs I, p=0.0002) frequencies of the 12Glu9 polymorphism were found to be statistically significant. However, a significant difference was found between allele and genotypes of I/D polymorphism of the ADRA2B gene or the clinical characteristics of the subjects. Our results obtained in this study indicate the ADRA2B gene in the Saudi women was associated with the development of GDM.

Additive effect of polymorphisms in the β2 -adrenoceptor and NADPH oxidase p22 phox genes contributes to the loss of estimated glomerular filtration rate in Chinese.

Because increased oxidative stress may mediate the detrimental actions of enhanced sympathetic nervous activity on renal function and vice versa, we investigated the effect of the polymorphic Arg16Gly in the β2 -adrenoceptor (ADRB2) gene, Trp64Arg in the β3 -adrenoceptor (ADRB3) gene and C242T in the NADPH oxidase p22phox (CYBA) gene on estimated glomerular filtration rate (eGFR) in a Chinese population. Initially recruited from different outpatient services of HeBei General Hospital in northern China, 668 individuals were finally included in the study, with complete demographic information. Laboratory tests were performed and estimated glomerular filtration rate (eGFR) was derived from the Modification of Diet in Renal Disease (MDRD) equation for the Chinese population. Plasma noradrenaline levels and genotype were determined by HPLC and the TaqMan method, respectively. Only across the Arg16Gly polymorphism did eGFR show significant difference: it was lower in individuals with the Gly16Gly variation, who also had the highest plasma noradrenaline levels. This polymorphism remained a significant determinant of eGFR after multivariate analysis. Of importance, the multifactor dimensionality reduction method further detected a significant synergism between the Arg16Gly and C242T polymorphisms in reducing eGFR. These observations clarify the effects of the studied polymorphisms on eGFR and exemplify gene-gene interactions influencing renal function.

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.

Rasgrf2 controls noradrenergic involvement in the acute and subchronic effects of alcohol in the brain.

Alcohol addiction is a major psychiatric disease, and yet, the underlying molecular adaptations in the brain remain unclear. Recent evidence suggests a functional role for the ras-specific guanine-nucleotide releasing factor 2 (Rasgrf2) in alcoholism. Rasgrf2(-/-) mice consume less alcohol and show entirely absent dopamine responses to an alcohol challenge compared to wild types (WT). In order to further investigate how Rasgrf2 modifies the acute and subchronic effects of alcohol in the brain, we investigated its effects on the noradrenergic and serotonergic systems. We measured noradrenaline and serotonin activity in the brain by in vivo microdialysis and RNA expression by chip analysis and RT-PCR after acute and sub-chronic alcohol exposure in Rasgrf2(-/-) and WT mice. In vivo microdialysis showed a significantly reduced noradrenergic response and an absent serotonergic response in the nucleus accumbens (NAcc) and caudate putamen (CPu) after an alcohol challenge in Rasgrf2(-/-) mice. A co-expression analysis showed that there is a high correlation between Rasgrf2 and α2 adrenoceptor RNA expression in the ventral striatum in naïve animals. Accordingly, we further assessed the role of Rasgrf2 in the response of the noradrenergic system to subchronic alcohol exposure. A decrease in β1 adrenoceptor gene expression was seen in Rasgrf2(+/+), but not Rasgrf2(-/-) mice following alcohol exposure. Conversely, alcohol resulted in a decrease in both β2 and α2 adrenoceptor gene expression in knockout but not WT Rasgrf2 mice. These findings suggest that adaptations in the noradrenergic system contribute to the Rasgrf2 enhanced risk of alcoholism.

Association of beta 2 adrenoceptor gene polymorphisms in Malaysian hypertensive subjects.

The sympathetic nervous system plays a major role in blood pressure regulation. Beta 2 (β2) adrenoceptor gene polymorphisms have been associated with hypertension in different populations with conflicting results. We examined the association of three common polymorphisms, Arg16Gly, Gln27Glu, and Thr164Ile, of the β2 adrenoceptor gene in Malaysian hypertensive subjects. A total of 160 hypertensive and control subjects were recruited. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and anthropometric measurements were obtained from each subject. Biochemical analyses of lipid profiles were conducted with an autoanalyzer. DNA samples were extracted from blood and buccal cells. Genotyping was accomplished with polymerase chain reaction-restriction fragment length polymorphism. SBP, DBP, body mass index, and biochemical factors all differed significantly between case and control subjects (P < 0.05). The genotype frequencies of Arg16Arg, Arg16Gly, and Gly16Gly were 22.5, 70, and 7.5% among cases and 33.1, 63.1, and 3.8% among controls, respectively. The genotype frequencies of Gln27Gln, Gln27Glu, and Glu27Glu among cases were 41.1, 50, and 1.9% compared to 77.5, 20.6, and 1.9% among controls, respectively. In this study, the Gln27Glu polymorphism was significantly associated with Malaysian hypertensive subjects (P < 0.05). Therefore, the Gln27Glu polymorphism of the β2 adrenoceptor could be a risk factor associated with hypertension among Malaysians.

Agonist pharmacology at recombinant α1A- and α1L-adrenoceptors and in lower urinary tract α1-adrenoceptors

Two distinct α1 -adrenoceptor phenotypes (α1A and α1L ) have recently been demonstrated to originate from a single α1A -adrenoceptor gene. Here, we examined the agonist profiles of recombinant α1A and α1L phenotypes and of lower urinary tract (LUT) α1 -adrenoceptors. A series of drugs (A61603, Ro 115-1240, NS-49 , MK017 and ESR1150) originally developed for stress urinary incontinence (SUI) therapy were used to stimulate recombinant α1A - and α1L -adrenoceptor phenotypes, and their potencies and intrinsic activity estimated from Ca(2+) responses. Agonist-induced contractions were also examined in LUT tissues of rats and humans and in human mesenteric artery and rat tail artery. All the drugs were potent agonists of the α1A -adrenoceptor compared with the α1L -adrenoceptor phenotype. Among them, Ro 115-1240 was shown to be an α1A -specific partial agonist that produced partial contractions through α1A -adrenoceptors in rat prostate and tail artery, but not in the other LUT tissues and human mesenteric artery. In contrast, P-come 102 showed full agonist activity at α1A - and α1L -adrenoceptors, but was less selective than noradrenaline for α1A -adrenoceptors. Like noradrenaline, P-come 102 was highly potent at inducing contractions in all of the LUT tissues tested. However, the potency and intrinsic activity of P-come 102 were significantly lower than those of noradrenaline in human mesenteric artery. The α1A - and α1L -adrenoceptor phenotypes and LUT α1 -adrenoceptors were demonstrated to have distinct agonist profiles. As adrenergic contractions in LUT are predominantly mediated through α1L -adrenoceptors, the development of α1L -selective agonists may provide clinically useful drugs for SUI therapy.