Polymorphisms in human muscarinic receptor subtype genes

Associations of genetic variations in the M3 receptor with salt sensitivity, longitudinal changes in blood pressure and the incidence of hypertension in Chinese adults

Recent studies have reported the role of the M3 muscarinic acetylcholine receptor (M3R), a member of the G-protein coupled receptor superfamily, encoded by the CHRM3 gene, in cardiac function and the regulation of blood pressure (BP). The aim of this study was to investigate the associations of CHRM3 genetic variants with salt sensitivity, longitudinal BP changes, and the development of hypertension in a Chinese population. We conducted a chronic dietary salt intervention experiment in a previously established Chinese cohort to analyze salt sensitivity of BP. Additionally, a 14-year follow-up was conducted on all participants in the cohort to evaluate the associations of CHRM3 polymorphisms with longitudinal BP changes, as well as the incidence of hypertension. The single nucleotide polymorphism (SNP) rs10802811 within the CHRM3 gene displayed significant associations with low salt-induced changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP), while rs373288072, rs114677844, and rs663148 exhibited significant associations with SBP and MAP responses to a high-salt diet. Furthermore, the SNP rs58359377 was associated with changes in SBP and pulse pressure (PP) over the course of 14 years. Additionally, the 14-year follow-up revealed a significant association between the rs619288 polymorphism and an increased risk of hypertension (OR = 1.74, 95% CI: 1.06-2.87, p = .029). This study provides evidence that CHRM3 may have a role in salt sensitivity, BP progression, and the development of hypertension.

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.

Drug-Drug Interactions in Vestibular Diseases, Clinical Problems, and Medico-Legal Implications

Peripheral vestibular disease can be treated with several approaches (e.g., maneuvers, surgery, or medical approach). Comorbidity is common in elderly patients, so polytherapy is used, but it can generate the development of drug-drug interactions (DDIs) that play a role in both adverse drug reactions and reduced adherence. For this reason, they need a complex kind of approach, considering all their individual characteristics. Physicians must be able to prescribe and deprescribe drugs based on a solid knowledge of pharmacokinetics, pharmacodynamics, and clinical indications. Moreover, full information is required to reach a real therapeutic alliance, to improve the safety of care and reduce possible malpractice claims related to drug-drug interactions. In this review, using PubMed, Embase, and Cochrane library, we searched articles published until 30 August 2021, and described both pharmacokinetic and pharmacodynamic DDIs in patients with vestibular disorders, focusing the interest on their clinical implications and on risk management strategies.

Muscarinic Acetylcholine Receptors in the Retina-Therapeutic Implications

Muscarinic acetylcholine receptors (mAChRs) belong to the superfamily of G-protein-coupled receptors (GPCRs). The family of mAChRs is composed of five subtypes, M1, M2, M3, M4 and M5, which have distinct expression patterns and functions. In the eye and its adnexa, mAChRs are widely expressed and exert multiple functions, such as modulation of tear secretion, regulation of pupil size, modulation of intraocular pressure, participation in cell-to-cell signaling and modula-tion of vascular diameter in the retina. Due to this variety of functions, it is reasonable to assume that abnormalities in mAChR signaling may contribute to the development of various ocular diseases. On the other hand, mAChRs may offer an attractive therapeutic target to treat ocular diseases. Thus far, non-subtype-selective mAChR ligands have been used in ophthalmology to treat dry eye disease, myopia and glaucoma. However, these drugs were shown to cause various side-effects. Thus, the use of subtype-selective ligands would be useful to circumvent this problem. In this review, we give an overview on the localization and on the functional role of mAChR subtypes in the eye and its adnexa with a special focus on the retina. Moreover, we describe the pathophysiological role of mAChRs in retinal diseases and discuss potential therapeutic approaches.

A Novel Genotyping Method for Detection of the Muscarinic Receptor M1 Gene rs2067477 Polymorphism and Its Genotype/Allele Frequencies in a Turkish Population

Objectives

Gene variation in the cholinergic muscarinic receptor 1 (CHRM1) has potential to become a candidate biomarker in the development of several disorders as well as drug response. In this study, a novel polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was developed to determine the C to A single nucleotide polymorphism at position 267 in the CHRM1 gene.

Materials and Methods

A new reverse primer and a mismatched forward primer were designed to obtain 125 bp PCR products. The PCR products were then digested with the Hae III restriction enzyme to detect the rs2067477 polymorphism that comprises a C to A base change. The novel assay developed was tested in 51 Turkish schizophrenia patients.

Results

The genotyping assay was successfully performed in patients with schizophrenia in order to confirm the accuracy and validity of this method. The frequency of CC, CA, and AA genotypes was 72.5%, 25.5%, and 2%, respectively. On the basis of these findings, the allele frequency of C was 0.85 and the allele frequency of A was 0.15.

Conclusion

This genotyping assay is practical for screening the CHRM1 C267A polymorphism in pharmacogenetic studies. The present polymorphism may be used as a candidate biomarker to determine genetic susceptibility to related diseases and may contribute to the implementation of individualized drug therapy for M1-related diseases.

Association of Cholinergic Muscarinic M4 Receptor Gene Polymorphism with Schizophrenia

Background

Previous studies have linked muscarinic M4 receptors (CHRM4) to schizophrenia. Specifically, the rs2067482 polymorphism was found to be highly associated with this disease.

Purpose

To test whether rs2067482 and rs72910092 are potential risk factors for schizophrenia and/or pharmacogenetic markers for antipsychotic-induced tardive dyskinesia.

Patients and Methods

We genotyped DNA of 449 patients with schizophrenia and 134 healthy controls for rs2067482 and rs72910092 polymorphisms of the CHRM4 gene with the use of the MassARRAY^® System by Agena Bioscience. Mann–Whitney test was used to compare qualitative traits and χ² test was used for categorical traits.

Results

The frequency of genotypes and alleles of rs72910092 did not differ between patients with schizophrenia and control subjects. We did not reveal any statistical differences for both rs2067482 and rs72910092 between schizophrenia patients with and without tardive dyskinesia. The frequency of the C allele of the polymorphic variant rs2067482 was significantly higher in healthy persons compared to patients with schizophrenia (OR=0.51, 95% CI [0.33–0.80]; p=0.003). Accordingly, the CC genotype was found significantly more often in healthy persons compared to patients with schizophrenia (OR=0.49, 95% CI [0.31–0.80]; p=0.010).

Conclusion

Our study found the presence of the minor allele (T) of rs2067482 variant being associated with schizophrenia. We argue that the association of rs2067482 with schizophrenia may be via its regulatory effect on some other gene with protein kinase C and casein Kknase substrate in neurons 3 (PACSIN3) as a possible candidate. Neither rs2067482 nor rs72910092 is associated with tardive dyskinesia.

Pharmacogenetics of tardive dyskinesia in schizophrenia: The role of CHRM1 and CHRM2 muscarinic receptors

Objectives: Acetylcholine M (muscarinic) receptors are possibly involved in tardive dyskinesia (TD). The authors tried to verify this hypothesis by testing for possible associations between two muscarinic receptor genes (CHRM1 and CHRM2) polymorphisms and TD in patients with schizophrenia.Methods: A total of 472 patients with schizophrenia were recruited. TD was assessed cross-sectionally using the Abnormal Involuntary Movement Scale. Fourteen allelic variants of CHRM1 and CHRM2 were genotyped using Applied Biosystems amplifiers (USA) and the MassARRAY System by Agena Bioscience.Results: The prevalence of the rs1824024*GG genotype of the CHRM2 gene was lower in TD patients compared to the group without it (χ2 = 6.035, p = 0.049). This suggested that this genotype has a protective effect for the development of TD (OR = 0.4, 95% CI: 0.19-0.88). When age, gender, duration of schizophrenia and dosage of antipsychotic treatment were added as covariates in regression analysis, the results did not reach statistical significance.Conclusions: This study did identify associations between CHRM2 variations and TD; the results of logistic regression analysis with covariates suggest that the association is, however, likely to be secondary to other concomitant factors.

Scientific opinion on the risks for animal and human health related to the presence of quinolizidine alkaloids in feed and food, in particular in lupins and lupin-derived products

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of quinolizidine alkaloids (QAs) in feed and food. This risk assessment is limited to QAs occurring in Lupinus species/varieties relevant for animal and human consumption in Europe (i.e. Lupinus albus L., Lupinus angustifolius L., Lupinus luteus L. and Lupinus mutabilis Sweet). Information on the toxicity of QAs in animals and humans is limited. Following acute exposure to sparteine (reference compound), anticholinergic effects and changes in cardiac electric conductivity are considered to be critical for human hazard characterisation. The CONTAM Panel used a margin of exposure (MOE) approach identifying a lowest single oral effective dose of 0.16 mg sparteine/kg body weight as reference point to characterise the risk following acute exposure. No reference point could be identified to characterise the risk of chronic exposure. Because of similar modes of action for QAs, the CONTAM Panel used a group approach assuming dose additivity. For food, the highest mean concentration of Total QAs (TotQAs) (i.e. the 6 most abundant QAs) was found in lupin seed samples classified as 'Lupins (dry) and similar-'. Due to the limited data on occurrence and consumption, dietary exposure was calculated for some specific scenarios and no full human health risk characterisation was possible. The calculated margin of exposures (MOEs) may indicate a risk for some consumers. For example, when lupin seeds are consumed without a debittering step, or as debittered lupin seeds high in QA content and when 'lupin-based meat imitates' are consumed. For horses, companion and farm animals, other than salmonids, the available database on adverse effects was too limited to identify no-observed-adverse-effect levels and/or lowest-observed-adverse-effect levels and no risk characterisation was possible. For salmonids, the CONTAM Panel considers the risk for adverse effects to be low.

Proteomics screen to reveal molecular changes mediated by C722G missense mutation in CHRM2 gene

Previously, we reported a missense mutation (C722G) in the M2-muscarinic acetylcholine receptor (CHRM2) gene associated with familial dilated cardiomyopathy. However, the exact molecular mechanisms by the related protein changes of CHRM2-C722G mutation induced are still unclear. CHRM2 and CHRM2-C722G lentiviral vector was infected to CHO cells. Proteomic analysis by label-free shotgun strategy and the STRING 9.0 software were performed. A total of 102 proteins with at least 2-fold change in the CHRM2-C722G group were identified, 42 proteins were up-regulated, whereas 57 were down-regulated. These altered proteins belong to three broad functional categories: (i) metabolic (e.g. Cytosolic acyl coenzyme A thioester hydrolase, Malate dehydrogenase); (ii) cytoskeletal (e.g. Actin-related protein, Myosin light polypeptide 6 and Alpha-actinin-1) and (iii) stress response (e.g. heat shock protein 70, Ras-related protein Rab-10). Interestingly, the marked differences in the expression of selected eight proteins (change >4.0-fold), were connected with many proteins related to apoptosis and immune/inflammatory response such as: FOS, BAX, MYC, TP53 and IL6. This novel study demonstrated for the first time a full-scale screening of the proteomics research by CHRM2-C722G mutation and profiled 102 changed proteins, of which, eight might be critical in cardiac dysfunction for future mapping.

SIGNIFICANCE

It was a full-scale screening of the proteomics research by CHRM2-C722G mutation. These proteins might serve as valuable biomarkers that could predict the presence of a precursor field. These proteins might serve to further explore the pathophysiological mechanisms in familial DCM patients with C176W mutation.