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.

Determination of Region-Specific Roles of the M3 Muscarinic Acetylcholine Receptor in Gastrointestinal Motility

BACKGROUND

The specific role of the M₃ muscarinic acetylcholine receptor in gastrointestinal motility under physiological conditions is unclear, due to a lack of subtype-selective compounds.

AIMS

The objective of this study was to determine the region-specific role of the M₃ receptor in gastrointestinal motility.

METHODS

We developed a novel positive allosteric modulator (PAM) for the M₃ receptor, PAM-369. The effects of PAM-369 on the carbachol-induced contractile response of porcine esophageal smooth muscle and mouse colonic smooth muscle (ex vivo) and on the transit in mouse small intestine and rat colon (in vivo) were examined.

RESULTS

PAM-369 selectively potentiated the M₃ receptor under the stimulation of its orthosteric ligands without agonistic or antagonistic activity. Half-maximal effective concentrations of PAM activity for human, mouse, and rat M₃ receptors were 0.253, 0.345, and 0.127 μM, respectively. PAM-369 enhanced carbachol-induced contraction in porcine esophageal smooth muscle and mouse colonic smooth muscle without causing any contractile responses by itself. The oral administration of 30 mg/kg PAM-369 increased the small intestinal transit in both normal motility and loperamide-induced intestinal dysmotility mice but had no effects on the colonic transit, although the M₃ receptor mRNA expression is higher in the colon than in the small intestine.

CONCLUSIONS

This study provided the first direct evidence that the M₃ receptor has different region-specific roles in the motility function between the small intestine and colon in physiological and pathophysiological contexts. Selective PAMs designed for targeted subtypes of muscarinic receptors are useful for elucidating the subtype-specific function.

Chronic exposure to the anti-m3 muscarinic acetylcholine receptor autoantibody in pemphigus vulgaris contributes to disease pathophysiology

Pemphigus vulgaris (PV) is a potentially lethal autoimmune mucocutaneous blistering disease characterized by binding of IgG autoantibodies (AuAbs) to keratinocytes (KCs). In addition to AuAbs against adhesion molecules desmogleins 1 and 3, PV patients also produce an AuAb against the M3 muscarinic acetylcholine (ACh) receptor (M3AR) that plays an important role in regulation of vital functions of KCs upon binding endogenous ACh. This anti-M3AR AuAb is pathogenic because its adsorption eliminates the acantholytic activity of PV IgG; however, the molecular mechanism of its action is unclear. In the present study, we sought to elucidate the mode of immunopharmacologic action of the anti-M3AR AuAb in PV. Short-term exposures of cultured KCs to PV IgG or the muscarinic agonist muscarine both induced changes in the expression of keratins 5 and 10, consistent with the inhibition of proliferation and upregulated differentiation and in keeping with the biological function of M3AR. In contrast, long-term incubations induced a keratin expression pattern consistent with upregulated proliferation and decreased differentiation, in keeping with the hyperproliferative state of KCs in PV. This change could result from desensitization of the M3AR, representing the net antagonist-like effect of the AuAb. Therefore, chronic exposure of KCs to the anti-M3AR AuAb interrupts the physiological regulation of KCs by endogenous ACh, contributing to the onset of acantholysis. Since cholinergic agents have already demonstrated antiacantholytic activity in a mouse model of PV and in PV patients, our results have translational significance and can guide future development of therapies for PV patients employing cholinergic drugs.

Ecklonia cava Extract and Its Derivative Dieckol Promote Vasodilation by Modulating Calcium Signaling and PI3K/AKT/eNOS Pathway in In Vitro and In Vivo Models

Nitric oxide (NO), an endothelial-derived relaxing factor synthesized by endothelial nitric oxide synthase (eNOS) in endothelial cells, enhances vasodilation by modulating vascular tone. The calcium concentration critically influences eNOS activation in endothelial cells. Thus, modulation of calcium-dependent signaling pathways may be a potential therapeutic strategy to enhance vasodilation. Marine algae reportedly possess protective effects against cardiovascular disorders, including hypertension and vascular dysfunction; however, the underlying molecular signaling pathways remain elusive. In the present study, we extracted and isolated dieckol from Ecklonia cava and investigated calcium transit-enhanced vasodilation. Calcium modulation via the well-known M3 muscarinic acetylcholine receptor (AchM3R), which is linked to NO formation, was investigated and the vasodilatory effect of dieckol was verified. Our results indicated that dieckol effectively promoted NO generation via the PI3K/Akt/eNOS axis and calcium transients influenced by AchM3R. We also treated Tg(flk: EGFP) transgenic zebrafish with dieckol to assess its vasodilatory effect. Dieckol promoted vasodilation by enlarging the dorsal aorta diameter, thus regulating blood flow velocity. In conclusion, our findings suggest that dieckol modulates calcium transit through AchM3R, increases endothelial-dependent NO production, and efficiently enhances vasodilation. Thus, E. cava and its derivative, dieckol, can be considered as potential natural vasodilators.

Design, Synthesis, and Structure-Activity Relationships Study of N-Pyrimidyl/Pyridyl-2-thiazolamine Analogues as Novel Positive Allosteric Modulators of M3 Muscarinic Acetylcholine Receptor

The M₃ muscarinic acetylcholine receptor (mAChR) plays an essential pharmacological role in mediating a broad range of actions of acetylcholine (ACh) released throughout the periphery and central nerve system (CNS). Nevertheless, its agonistic functions remain unclear due to the lack of available subtype-selective agonists or positive allosteric modulators (PAMs). In the course of our extended structure-activity relationships (SARs) study on 2-acylaminothiazole derivative 1, a previously reported PAM of the M₃ mAChR, we successfully identified N-pyrimidyl/pyridyl-2-thiazolamine analogues as new scaffolds. The SARs study was rationalized using conformational analyses based on intramolecular interactions. A comprehensive study of a series of analogues described in this paper suggests that a unique sulfur-nitrogen nonbonding interaction in the N-pyrimidyl/pyridyl-2-thiazolamine moiety enable conformations that are essential for activity. Further, a SARs study around the N-pyrimidyl/pyridyl-2-thiazolamine core culminated in the discovery of compound 3g, which showed potent in vitro PAM activity for the M₃ mAChR with excellent subtype selectivity. Compound 3g also showed a distinct pharmacological effect on isolated smooth muscle tissue from rat bladder and favorable pharmacokinetics profiles, suggesting its potential as a chemical tool for probing the M₃ mAChR in further research.

R2-8018 reduces the proliferation and migration of non-small cell lung cancer cells by disturbing transactivation between M3R and EGFR

AIMS

The M3 muscarinic acetylcholine receptor (M3R) is a G protein-coupled receptor that is expressed in cases of non-small cell lung cancer (NSCLC). Previous studies demonstrated that M3R antagonists reduce the proliferation of NSCLC. However, how antagonists inhibit the NSCLC proliferation and migration is still little known. This study aims to investigate the mechanism of M3R involved in the growth of NSCLC.

MAIN METHODS

The CRISPR/Cas9 was used to knock out (KO) the M3R gene. A real-time cell analyzer (RTCA) was used to record the proliferation of NSCLC cells. The migration and cell cycle of NSCLC cells were evaluated with scratch test and flow cytometry (FCM), respectively. Antibody microarray analysis was performed to detect the expression of proteins after antagonizing M3R and knocking out of M3R, subsequently some of these important proteins were verified by western blot.

KEY FINDINGS

The proliferation and migration of NSCLC cells were inhibited by M3R antagonist R2-8018 and knocking out of M3R. Antagonism or knocking out of M3R reduced the phosphorylation of EGFR. Moreover, c-Src and β-arrestin-1 are involved in the mechanism of how the inhibition of M3R affects EGFR in NSCLC. Further study demonstrated that PI3K/AKT and MEK/ERK signal pathways are involved in M3R-induced EGFR transactivation in NSCLC, and the molecules involved in the cell cycle progression and migration of NSCLC cells were identified.

SIGNIFICANCE

This further understanding of the relationship between M3R and NSCLC facilitates the design of therapeutic strategy with M3R antagonist as an adjuvant drug for NSCLC treatment.

Transgenic rice seeds expressing altered peptide ligands against the M3 muscarinic acetylcholine receptor suppress experimental sialadenitis-like Sjögren's syndrome

Objective: We previously reported that Rag1^-/- mice inoculated with splenocytes from M3 muscarinic acetylcholine receptor (M3R) knockout mice immunized with an M3R peptide mixture developed sialadenitis-like Sjögren's syndrome (M3R-induced sialadenitis [MIS]). We also found that intravenous administration of altered peptide ligand (APL) of N-terminal 1 (N1), which is one of the T-cell epitopes of M3R, suppressed MIS. In this study, we aimed to evaluate the suppressive ability and its mechanisms of rice seeds expressing N1-APL7 against MIS.Methods: Rice seeds expressing N1 and N1-APL7 were orally administered to MIS mice for 2 weeks. The changes in saliva flow and sialadenitis (salivary gland inflammation) were analyzed. The M3R-specific T-cell response in the spleen and the expression of regulatory molecules in the cervical lymph nodes and mesenteric lymph nodes were also analyzed.Results: Oral administration of N1-APL7-expressing rice seeds significantly recovered reduction in saliva flow and suppressed sialadenitis when compared with treatment with nontransgenic rice seeds and N1 rice seeds. IFNγ production from M3R-reactive T cells tended to decline in the N1-APL7 rice-treated group as compared with those in the other groups. In the N1-APL7 rice-treated group, the mRNA expression levels of Foxp3 in the cervical-lymph-node CD4⁺ T cells were higher than those in the other groups.Conclusion: Oral administration of N1-APL7-expressing rice suppressed MIS via suppression of M3R-specific IFNγ and IL-17 production and via enhancement of regulatory molecule expression.Key messagesWe generated N1-peptide- or N1-APL7-expressing rice seeds. Oral administration of N1-APL7-expressing rice seeds significantly recovered the reduction of saliva flow and suppressed sialadenitis via the suppression of M3R specific IFNγ and IL-17 production and via enhancement of regulatory T (Treg) cells.

MicroRNA-30e inhibits adhesion, migration, invasion and cell cycle progression of prostate cancer cells via inhibition of the activation of the MAPK signaling pathway by downregulating CHRM3

Prostate cancer (PCa) testing is currently based on measurement of serum prostate‑specific antigen levels and digital rectal examination, which are limited by a low predictive value and the adverse effects associated with overdiagnosis and overtreatment. Recent studies have reported that the abnormal expression of microRNAs (miRNAs) is associated with the mechanism underlying the development of PCa. Thus, the aim of the present study was to investigate the effects of miR‑30e and its target gene, M3 muscarinic acetylcholine receptor (CHRM3), on the adhesion, migration, invasion and cell cycle distribution of PCa cells via the mitogen‑activated protein kinase (MAPK) signaling pathway. The differentially expressed genes were screened in the Gene Expression Omnibus database from a gene expression microarray (GSE55945) of PCa. PCa tissues and adjacent tissues were collected from patients with PCa. The PC‑3 and DU145 human PCa cell lines were treated with activator, inhibitor and siRNAs. The effects of miR‑30e on cell adhesion, migration, invasion and cell cycle distribution with the involvement of CHRM3 and the MAPK signaling pathway were investigated. The bioinformatics results demonstrated that the CHRM3 gene and the MAKP signaling pathway were involved in the progression of PCa, and has‑miR‑30e was selected for further study. The levels of miR‑30e were significantly downregulated, while the levels of CHRM3 were obviously upregulated in PCa. CHRM3 was verified as a target gene of miR‑30e. Upregulation of miR‑30e and downregulation of CHRM3 decreased the levels of p‑P38, p‑extracellular signal‑regulated kinase, p‑c‑Jun N‑terminal kinase, p‑c‑fos and p‑c‑JUN, cell adhesion, migration and invasion ability, and the number of cells in the S phase, while they increased the number of cells in the G0 and G1 phases. The findings of the present study suggest that miR‑30e inhibited the adhesion, migration, invasion and cell cycle entry of PCa cells by suppressing the activation of the MAPK signaling pathway and inhibiting CHRM3 expression. Thus, miR‑30e may serve as a candidate target for the treatment of PCa.

Activation of M3 Muscarinic Acetylcholine Receptors Delayed Cardiac Aging by Inhibiting the Caspase-1/IL-1β Signaling Pathway

BACKGROUND/AIMS

Because the prevalence of age-related cardiac impairment increases as the human lifespan increases, it is important to combat the effects of aging. Recently, the cardiac M3 muscarinic acetylcholine receptor (M3-mAChR) has been demonstrated to play important roles in cardiac development and in the pathogenesis of cardiac diseases. However, the role of M3-mAChR in aging remains largely unknown. Therefore, the aim of this study was to investigate the involvement of M3-mAChR in the progression of cardiac aging.

METHODS

We established a cardiac aging model in mice through subcutaneous injection with D-galactose at a dose of 100 mg/kg/day for 6 weeks. D-galactose was also used to induce aging in primary cultured neonatal mouse cardiomyocytes. The myocardium from mice was stained with hematoxylin and eosin for histological analysis. The protein expression levels of p53 and p21 were determined using western blotting. The mRNA and protein expression levels of M3-mAChR, caspase-1, and interleukin (IL)-1β were determined using real-time PCR, immunohistochemical staining, and western blotting.

RESULTS

The expression of M3-mAChR was down-regulated in the myocardium from aged mice and D-galactose-treated mice, while the expression levels of caspase-1 and its downstream molecule IL-1β were significantly increased. The M3-mAChR agonist choline reduced the increase in caspase-1 in cardiomyocytes induced by D-galactose, which was reversed by the M3-mAChR antagonist 4-DAMP. Moreover, 4-DAMP promoted D-galactose-induced cardiomyocyte aging, which was attenuated by a caspase-1 inhibitor.

CONCLUSION

Activation of M3-mAChR delayed cardiac aging by inhibiting the caspase-1/IL-1β signaling pathway.

RORγt antagonist suppresses M3 muscarinic acetylcholine receptor-induced Sjögren's syndrome-like sialadenitis

We showed recently that M3 muscarinic acetylcholine receptor (M3R)-reactive CD3⁺ T cells play a pathogenic role in the development of murine autoimmune sialadenitis (MIS), which mimics Sjögren's syndrome (SS). The aim of this study was to determine the effectiveness and mechanism of action of retinoic acid-related orphan receptor-gamma t (RORγt) antagonist (A213) in MIS. Splenocytes from M3R knockout (M3R^-/- ) mice immunized with murine M3R peptide mixture were inoculated into recombination-activating gene 1 knockout (Rag-1^-/- ) mice (M3R^-/- →Rag-1^-/- ) with MIS. Immunized M3R^-/- mice (pretransfer treatment) and M3R^-/- →Rag-1^-/- mice (post-transfer treatment) were treated with A213 every 3 days. Salivary volume, severity of sialadenitis and cytokine production from M3R peptide-stimulated splenocytes and lymph node cells were examined. Effects of A213 on cytokine production were analysed by enzyme-linked immunosorbent assay (ELISA) and on T helper type 1 (Th1), Th17 and Th2 differentiation from CD4⁺ T cells by flow cytometry. Pretransfer A213 treatment maintained salivary volume, improved MIS and reduced interferon (IFN)-γ and interleukin (IL)-17 production significantly compared with phosphate-buffered saline (PBS) (P < 0·05). These suppressive effects involved CD4⁺ T cells rather than CD11c⁺ cells. Post-transfer treatment with A213 increased salivary volume (P < 0·05), suppressed MIS (P < 0·005) and reduced IFN-γ and IL-17 production (P < 0·05). In vitro, A213 suppressed IFN-γ and IL-17 production from M3R-stimulated splenocytes and CD4⁺ T cells of immunized M3R^-/- mice (P < 0·05). In contrast with M3R specific responses, A213 suppressed only IL-17 production from Th17 differentiated CD4⁺ T cells without any effect on Th1 and Th2 differentiation in vitro. Our findings suggested that RORγt antagonism is potentially suitable treatment strategy for SS-like sialadenitis through suppression of IL-17 and IFN-γ production by M3R-specific T cells.

Selective expression of muscarinic acetylcholine receptor subtype M3 by mouse type III taste bud cells

Each taste bud cell (TBC) type responds to a different taste. Previously, we showed that an unidentified cell type(s) functionally expresses a muscarinic acetylcholine (ACh) receptor subtype, M3, and we suggested the ACh-dependent modification of its taste responsiveness. In this study, we found that M3 is expressed by type III TBCs, which is the only cell type that possesses synaptic contacts with taste nerve fibers in taste buds. The application of ACh to the basolateral membrane of mouse fungiform TBCs in situ increased the intracellular Ca²⁺ concentration in 2.4 ± 1.4 cells per taste bud (mean ± SD, n = 14). After Ca²⁺ imaging, we supravitally labeled type II cells (phospholipase C β2 [PLCβ2]-immunoreactive cells) with Lucifer yellow CH (LY), a fluorescent dye and investigated the positional relationship between ACh-responding cells and LY-labeled cells. After fixation, the TBCs were immunohistostained to investigate the positional relationships between immunohistochemically classified cells and LY-labeled cells. The overlay of the two positional relationships obtained by superimposing the LY-labeled cells showed that all of the ACh-responding cells were type III cells (synaptosomal-associated protein 25 [SNAP-25]-immunoreactive cells). The ACh responses required no added Ca²⁺ in the bathing solution. The addition of 1 μM U73122, a phospholipase C inhibitor, decreased the magnitude of the ACh response, whereas that of 1 μM U73343, a negative control, had no effect. These results suggest that type III cells respond to ACh and release Ca²⁺ from intracellular stores. We also discuss the underlying mechanism of the Ca²⁺ response and the role of M3 in type III cells.

Signal transduction by M3 muscarinic acetylcholine receptor in prostate cancer

The present study aimed to investigate the potential mechanisms used during signal transduction by M3 muscarinic acetylcholine receptor (CHRM3) in prostate cancer. The microarray datasets of GSE3325, including 5 clinically localized primary prostate cancers and 4 benign prostate tissues, were downloaded from the Gene Expression Omnibus database. The differentially-expressed genes (DEGs) in primary prostate cancer tissues compared with benign controls were screened using the Limma package. Gene Ontology and pathway enrichment analyses were performed using the Database for Annotation Visualization and Integrated Discovery. Next, a protein-protein interaction (PPI) network was constructed. Additionally, microRNAs (miRNAs) associated with DEGs were predicted and miRNA-target DEG analysis was performed using a Web-based Gene Set Analysis Toolkit. Finally, the PPI network and the miRNA-target DEG network were integrated using Cytoscape. In total, 224 DEGs were screened in the prostate cancer tissues, including 113 upregulated and 111 downregulated genes. CHRM3 and epidermal growth factor (EGF) were enriched in the regulation of the actin cytoskeleton. EGF and v-myc avian myelocytomatosis viral oncogene homolog (Myc) were enriched in the mitogen-activated protein kinase (MAPK) signaling pathway. EGF with the highest degree of connectivity was the hub node in the PPI network, and miR-34b could interact with Myc directly in the miRNA-target DEG network. EGF and Myc may exhibit significant roles in the progression of prostate cancer via regulation of the actin cytoskeleton and the MAPK signaling pathway. CHRM3 may activate these two pathways in prostate cancer progression. Thus, these two key factors and pathways may be crucial mechanisms during signal transduction by CHRM3 in prostate cancer.

Anti-M3 muscarinic acetylcholine receptor antibodies in patients with primary biliary cirrhosis

AIM

M3 muscarinic acetylcholine receptor (M3R) is expressed in biliary tracts as well as in exocrine glands. It is reported that some patients with primary biliary cirrhosis (PBC) carry autoantibodies against M3R. The aim of this study is to clarify the presence, potential use as diagnostic marker and clinical roles of anti-M3R antibodies in PBC.

METHODS

We synthesized peptides encoding the extracellular domains of human-M3R, including the N-terminal region, the first, second and third extracellular loops. Antibodies against these regions were examined by peptide-based enzyme-linked immunoassay in sera of 90 patients with PBC and 40 with chronic hepatitis C (CHC), 21 with non-alcoholic steatohepatitis (NASH), 10 with primary sclerosing cholangitis (PSC), 14 with obstructive jaundice, 10 with drug-induced liver injury and 42 healthy controls.

RESULTS

Antibodies to the N-terminal, first, second and third loop were detected in 90.0% (81/90), 73.3% (66/90), 76.7% (69/90) and 66.7% (60/90) of PBC, in 67.5% (27/40), 10.0% (4/40), 67.5% (27/40) and 27.5% (11/40) of CHC, in 85.7% (18/21), 9.5% (2/21), 4.8% (1/21) and 57.1% (12/21) of NASH, in 60.0% (6/10), 20.0% (2/10), 60.0% (6/10) and 60.0% (6/10) of PSC, in 100.0% (14/14), 0% (0/14), 64.3% (9/14) and 78.6% (11/14) of obstructive jaundice, in 100.0% (10/10), 0% (0/10), 30.0% (3/10) and 10.0% (1/10) of drug-induced liver injury, and in 4.8% (2/42), 7.1% (3/42), 2.4% (1/42) and 2.4% (1/42) of the controls, respectively.

CONCLUSION

A high frequency of PBC carried anti-M3R antibodies. Anti-M3R antibodies against the first loop of M3R are a potentially useful diagnostic marker for PBC.