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Myslivecek J. Multitargeting nature of muscarinic orthosteric agonists and antagonists. Front Physiol 2022; 13:974160. [PMID: 36148314 PMCID: PMC9486310 DOI: 10.3389/fphys.2022.974160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 08/01/2022] [Indexed: 11/16/2022] Open
Abstract
Muscarinic receptors (mAChRs) are typical members of the G protein-coupled receptor (GPCR) family and exist in five subtypes from M1 to M5. Muscarinic receptor subtypes do not sufficiently differ in affinity to orthosteric antagonists or agonists; therefore, the analysis of receptor subtypes is complicated, and misinterpretations can occur. Usually, when researchers mainly specialized in CNS and peripheral functions aim to study mAChR involvement in behavior, learning, spinal locomotor networks, biological rhythms, cardiovascular physiology, bronchoconstriction, gastrointestinal tract functions, schizophrenia, and Parkinson’s disease, they use orthosteric ligands and they do not use allosteric ligands. Moreover, they usually rely on manufacturers’ claims that could be misleading. This review aimed to call the attention of researchers not deeply focused on mAChR pharmacology to this fact. Importantly, limited selective binding is not only a property of mAChRs but is a general attribute of most neurotransmitter receptors. In this review, we want to give an overview of the most common off-targets for established mAChR ligands. In this context, an important point is a mention the tremendous knowledge gap on off-targets for novel compounds compared to very well-established ligands. Therefore, we will summarize reported affinities and give an outline of strategies to investigate the subtype’s function, thereby avoiding ambiguous results. Despite that, the multitargeting nature of drugs acting also on mAChR could be an advantage when treating such diseases as schizophrenia. Antipsychotics are a perfect example of a multitargeting advantage in treatment. A promising strategy is the use of allosteric ligands, although some of these ligands have also been shown to exhibit limited selectivity. Another new direction in the development of muscarinic selective ligands is functionally selective and biased agonists. The possible selective ligands, usually allosteric, will also be listed. To overcome the limited selectivity of orthosteric ligands, the recommended process is to carefully examine the presence of respective subtypes in specific tissues via knockout studies, carefully apply “specific” agonists/antagonists at appropriate concentrations and then calculate the probability of a specific subtype involvement in specific functions. This could help interested researchers aiming to study the central nervous system functions mediated by the muscarinic receptor.
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Bhattarai Y, Williams BB, Battaglioli EJ, Whitaker WR, Till L, Grover M, Linden DR, Akiba Y, Kandimalla KK, Zachos NC, Kaunitz JD, Sonnenburg JL, Fischbach MA, Farrugia G, Kashyap PC. Gut Microbiota-Produced Tryptamine Activates an Epithelial G-Protein-Coupled Receptor to Increase Colonic Secretion. Cell Host Microbe 2019; 23:775-785.e5. [PMID: 29902441 DOI: 10.1016/j.chom.2018.05.004] [Citation(s) in RCA: 222] [Impact Index Per Article: 44.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 03/28/2018] [Accepted: 05/09/2018] [Indexed: 02/06/2023]
Abstract
Tryptamine, a tryptophan-derived monoamine similar to 5-hydroxytryptamine (5-HT), is produced by gut bacteria and is abundant in human and rodent feces. However, the physiologic effect of tryptamine in the gastrointestinal (GI) tract remains unknown. Here, we show that the biological effects of tryptamine are mediated through the 5-HT4 receptor (5-HT4R), a G-protein-coupled receptor (GPCR) uniquely expressed in the colonic epithelium. Tryptamine increases both ionic flux across the colonic epithelium and fluid secretion in colonoids from germ-free (GF) and humanized (ex-GF colonized with human stool) mice, consistent with increased intestinal secretion. The secretory effect of tryptamine is dependent on 5-HT4R activation and is blocked by 5-HT4R antagonist and absent in 5-HT4R-/- mice. GF mice colonized by Bacteroides thetaiotaomicron engineered to produce tryptamine exhibit accelerated GI transit. Our study demonstrates an aspect of host physiology under control of a bacterial metabolite that can be exploited as a therapeutic modality. VIDEO ABSTRACT.
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Affiliation(s)
- Yogesh Bhattarai
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA
| | - Brianna B Williams
- Department of Bioengineering and ChEM-H, Stanford University, Stanford, CA 94305, USA
| | - Eric J Battaglioli
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA
| | - Weston R Whitaker
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Lisa Till
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Madhusudan Grover
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - David R Linden
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Yasutada Akiba
- Department of Medicine, School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, CA 90073, USA; Brentwood Biomedical Research Institute, Los Angeles, CA 90073, USA
| | - Karunya K Kandimalla
- Department of Pharmaceutics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Nicholas C Zachos
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jonathan D Kaunitz
- Department of Medicine, School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, CA 90073, USA; Brentwood Biomedical Research Institute, Los Angeles, CA 90073, USA; Department of Surgery, School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Justin L Sonnenburg
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Michael A Fischbach
- Department of Bioengineering and ChEM-H, Stanford University, Stanford, CA 94305, USA
| | - Gianrico Farrugia
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA; Division of Gastroenterology and Hepatology, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Purna C Kashyap
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA.
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Armstrong S, Steinfeld T, Pulido-Rios MT, Hegde SS. In vivo pharmacodynamic assays for M2 and M3 muscarinic receptors. CURRENT PROTOCOLS IN PHARMACOLOGY 2010; Chapter 12:Unit 12.13. [PMID: 22294364 DOI: 10.1002/0471141755.ph1213s48] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
M(2) and M(3) muscarinic receptor subtypes are attractive drug targets for the treatment of pulmonary and urological disorders. Described in this unit is an in vivo pithed rat assay for estimating agonist and antagonist potency at M(2) and M(3) receptors. In the pithed rat, the muscarinic agonist methacholine induces reduction in heart rate (bradycardia) and blood pressure (depressor response) through interaction with M(2) and M(3) receptors, respectively. The dissociation of the peripheral and central nervous system in the pithed rat preparation permits the direct assessment of compound effects on the heart and vasculature in the absence of cardiovascular reflexes. Estimates of antagonist potency can be reliably established by quantifying the shift in the agonist dose-effect curve produced under appropriate equilibrium or non-equilibrium conditions.
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Kortezova NI, Shikova LI, Milusheva EA, Itzev DE, Bagaev VA, Mizhorkova ZN. Muscarinic modulation of nitrergic neurotransmission in guinea-pig gastric fundus. Neurogastroenterol Motil 2004; 16:155-65. [PMID: 15086869 DOI: 10.1111/j.1365-2982.2004.00514.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Muscarinic receptor activation by (4-Hydroxy-2-butynyl)-1-trimethylammonium-m-chlorocarbanilate chloride (McN-A-343) was investigated both on NADPH-d staining and on electrically induced responses in guinea-pig gastric fundus. McN-A-343 (10 micromol L(-1)) significantly increased the optical density of NADPH-d positive neurones, while blockade of nitric oxide synthase with N(omega)-nitro-L-arginine (L-NA) decreased it, suggesting facilitation of nitric oxide (NO) production. Electrical field stimulation (EFS; 2 Hz, 0.2 ms, supramaximal current intensity, 10 s train duration) elicited on-contraction followed by off-relaxation in the circular muscle strips. McN-A-343 (10 micromol L(-1)) transformed the EFS-evoked response from on-contraction into on-relaxation, which was neurogenic, tetrodotoxin-sensitive and hexamethonium-resistant. L-NA partly reduced the EFS-evoked relaxation, revealing two components: a nitrergic and a non-nitrergic one. The effect of McN-A-343 on the amplitude of the EFS-evoked relaxation was not changed by the M(3) receptor antagonist para-fluoro-hexahydro-sila-difenidol hydrochloride, but was significantly enhanced by M(1) receptor blockade with telenzepine. In the presence of telenzepine, the L-NA-dependent nitrergic component of the EFS-induced relaxation predominates. We suggest that cholinergic receptor activation has a dual effect on nitrergic neurotransmission: (i) stimulation of NOS by muscarinic receptor(s) different from M(1) and M(3) subtype, (ii) prejunctional inhibition of NO-mediated relaxation via M(1) receptors. In addition, M(1) receptors may facilitate the non-nitrergic relaxation.
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Affiliation(s)
- N I Kortezova
- Institute of Physiology, Bulgarian Academy of Sciences, Sofia, Bulgaria.
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