1
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Sinclair P, Kabbani N. Ionotropic and metabotropic responses by alpha 7 nicotinic acetylcholine receptors. Pharmacol Res 2023; 197:106975. [PMID: 38032294 DOI: 10.1016/j.phrs.2023.106975] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 10/12/2023] [Accepted: 10/26/2023] [Indexed: 12/01/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) belong to a superfamily of cys-loop receptors characterized by the assembly of five subunits into a multi-protein channel complex. Ligand binding to nAChRs activates rapid allosteric transitions of the receptor leading to channel opening and ion flux in neuronal and non-neuronal cell. Thus, while ionotropic properties of nAChRs are well recognized, less is known about ligand-mediated intracellular metabotropic signaling responses. Studies in neural and non-neural cells confirm ionotropic and metabotropic channel responses following ligand binding. In this review we summarize evidence on the existence of ionotropic and metabotropic signaling responses by homopentameric α7 nAChRs in various cell types. We explore how coordinated calcium entry through the ion channel and calcium release from nearby stores gives rise to signaling important for the modulation of cytoskeletal motility and cell growth. Amino acid residues for intracellular protein binding within the α7 nAChR support engagement in metabotropic responses including signaling through heterotrimeric G proteins in neural and immune cells. Understanding the dual properties of ionotropic and metabotropic nAChR responses is essential in advancing drug development for the treatment of various human disease.
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Affiliation(s)
| | - Nadine Kabbani
- Interdisciplinary Program in Neuroscience, Fairfax, VA, USA; School of Systems Biology, George Mason University, Fairfax, VA, USA.
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2
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Kyi CW, Garcia VB, Garcia ML, Schulz DJ. Spinal cord injury is associated with changes in synaptic properties of the mouse major pelvic ganglion. J Neurophysiol 2022; 128:892-909. [PMID: 36069457 DOI: 10.1152/jn.00477.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spinal cord injury (SCI) has substantial impacts on autonomic function. In part, SCI results in loss of normal autonomic activity that contributes to injury-associated pathology such as neurogenic bladder, bowel, and sexual dysfunction. Yet little is known of the impacts of SCI on peripheral autonomic neurons that directly innervate these target organs. In this study, we measured changes in synaptic properties of neurons of the mouse major pelvic ganglion (MPG) associated with acute and chronic SCI. Our data show that functional and physiological properties of synapses onto MPG neurons are altered after SCI, and differ between acute and chronic injury. After acute injury, excitatory post-synaptic potentials (EPSPs) show increased rise and decay time constants leading to overall broader and longer EPSPs, while in chronic injured animals EPSPs are reduced in amplitude and show faster rise and decay leading to shorter EPSPs. Synaptic depression and low pass filtering are also altered in injured animals. Lastly, cholinergic currents are smaller in acute injured animals, but larger in chronic injured animals relative to controls. These changes in synaptic properties are associated with differences in nicotinic receptor subunit expression as well. MPG CHRNA3 mRNA levels decreased after injury, while CHRNA4 mRNAs increased. Further, changes in the correlations of alpha- and beta-subunit mRNAs suggests that nicotinic receptor subtype composition is altered after injury. Taken together, our data demonstrate that peripheral autonomic neurons are fundamentally altered after SCI, suggesting that longer-term therapeutic approaches could target these neurons directly to potentially help ameliorate neurogenic target organ dysfunction.
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Affiliation(s)
- Cindy W Kyi
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - Virginia B Garcia
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - Michael L Garcia
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - David J Schulz
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
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3
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Bernardo A, Lee P, Marcotte M, Mian MY, Rezvanian S, Sharmin D, Kovačević A, Savić MM, Cook JM, Sibille E, Prevot TD. Symptomatic and neurotrophic effects of GABAA receptor positive allosteric modulation in a mouse model of chronic stress. Neuropsychopharmacology 2022; 47:1608-1619. [PMID: 35701547 PMCID: PMC9283409 DOI: 10.1038/s41386-022-01360-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 05/17/2022] [Accepted: 05/31/2022] [Indexed: 12/27/2022]
Abstract
Chronic stress is a risk factor for Major Depressive Disorder (MDD), and in rodents, it recapitulates human behavioral, cellular and molecular changes. In MDD and after chronic stress, neuronal dysfunctions and deficits in GABAergic signaling are observed and responsible for symptom severity. GABA signals predominantly through GABAA receptors (GABAA-R) composed of various subunit types that relate to downstream outcomes. Activity at α2-GABAA-Rs contributes to anxiolytic properties, α5-GABAA-Rs to cognitive functions, and α1-GABAA-Rs to sedation. Therefore, a therapy aiming at increasing α2- and α5-GABAA-Rs activity, but devoid of α1-GABAA-R activity, has potential to address several symptomologies of depression while avoiding side-effects. This study investigated the activity profiles and behavioral efficacy of two enantiomers of each other (GL-II-73 and GL-I-54), separately and as a racemic mixture (GL-RM), and potential disease-modifying effects on neuronal morphology. Results confirm GL-I-54 and GL-II-73 exert positive allosteric modulation at the α2-, α3-, α5-GABAA-Rs and α5-containing GABAA-Rs, respectively, and separately reduces immobility in the forced swim test and improves stress-induced spatial working memory deficits. Using unpredictable chronic mild stress (UCMS), we show that acute and chronic administration of GL-RM provide pro-cognitive effects, with mild efficacy on mood symptoms, although at lower doses avoiding sedation. Morphology studies showed reversal of spine density loss caused by UCMS after chronic GL-RM treatment at apical and basal dendrites of the PFC and CA1. Together, these results support using a racemic mixture with combined α2-, α3-, α5-GABAA-R profile to reverse chronic stress-induced mood symptoms, cognitive deficits, and with anti-stress neurotrophic effects.
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Affiliation(s)
- Ashley Bernardo
- grid.155956.b0000 0000 8793 5925Campbell Family Mental Health Research Institute of CAMH, Toronto, Canada
| | - Philip Lee
- grid.17063.330000 0001 2157 2938Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Michael Marcotte
- grid.155956.b0000 0000 8793 5925Campbell Family Mental Health Research Institute of CAMH, Toronto, Canada
| | - Md Yeunus Mian
- grid.267468.90000 0001 0695 7223Department of Chemistry and Biochemistry, University of Wisconsin–Milwaukee, Milwaukee, USA
| | - Sepideh Rezvanian
- grid.267468.90000 0001 0695 7223Department of Chemistry and Biochemistry, University of Wisconsin–Milwaukee, Milwaukee, USA
| | - Dishary Sharmin
- grid.267468.90000 0001 0695 7223Department of Chemistry and Biochemistry, University of Wisconsin–Milwaukee, Milwaukee, USA
| | - Aleksandra Kovačević
- grid.7149.b0000 0001 2166 9385Department of Pharmacology, Faculty of Pharmacy, University of Belgrade, Belgrade, Serbia
| | - Miroslav M. Savić
- grid.7149.b0000 0001 2166 9385Department of Pharmacology, Faculty of Pharmacy, University of Belgrade, Belgrade, Serbia
| | - James M. Cook
- grid.267468.90000 0001 0695 7223Department of Chemistry and Biochemistry, University of Wisconsin–Milwaukee, Milwaukee, USA
| | - Etienne Sibille
- Campbell Family Mental Health Research Institute of CAMH, Toronto, Canada. .,Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada. .,Department of Psychiatry, University of Toronto, Toronto, Canada.
| | - Thomas D. Prevot
- grid.155956.b0000 0000 8793 5925Campbell Family Mental Health Research Institute of CAMH, Toronto, Canada ,grid.17063.330000 0001 2157 2938Department of Psychiatry, University of Toronto, Toronto, Canada
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4
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Alijevic O, Jaka O, Alzualde A, Maradze D, Xia W, Frentzel S, Gifford AN, Peitsch MC, Hoeng J, Koshibu K. Differentiating the Neuropharmacological Properties of Nicotinic Acetylcholine Receptor-Activating Alkaloids. Front Pharmacol 2022; 13:668065. [PMID: 35392565 PMCID: PMC8980233 DOI: 10.3389/fphar.2022.668065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 02/21/2022] [Indexed: 11/13/2022] Open
Abstract
Alkaloids that target nicotinic acetylcholine receptors (nAChR) are of great interest because of the critical role they play in mood and anxiety. However, understanding of the neuropharmacological effects of nicotinic alkaloids, such as cotinine and anatabine, is very limited. In this study, we investigated the neuropharmacological effects of three naturally occurring alkaloids-nicotine, cotinine, and anatabine-in vitro and in vivo. A single injection of nicotine induced anxiolytic-like behavioral features in mice by using the SmartCube® behavioral profiling system, while cotinine and anatabine had no detectable effect. The results were corroborated by using the zebrafish novel tank test (NTT), which showed a profound anxiolytic-like effect induced by multiple doses of nicotine after a single 20-min treatment. When the regulation of dopamine and norepinephrine release-the neurotransmitter systems relevant for anxiety-were examined in vitro, we found that nicotine stimulated the release of both norepinephrine and dopamine, while cotinine and anatabine mainly stimulated the dopamine release. The molecular targets of nicotine were confirmed to be nAChRs with its most potent activities against α4β2 and α6/3β2β3 subtypes in vitro. Anatabine was a weaker agonist for these receptors than nicotine. Cotinine was the least potent nAChR compound, only being able to activate α4β2 and α6/3β2β3 subtypes at high doses and no detectable activities against α3β4 and α7 subtypes at the concentrations tested. The observed effects were unlikely due to the off-target effect, because these alkaloids did not bind or regulate >160 other molecular targets in vitro. Thus, the present results suggest that natural nicotinic alkaloids can induce an anxiolytic-like behavior in nonclinical animal models, potency of which may depend on the activation of various nAChRs and regulation of various neurotransmitter systems. Further investigations would help understand their effects on humans, because non-clinical studies should not be taken as a direct indication for human behavior and nicotine is not risk free.
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Affiliation(s)
- Omar Alijevic
- PMI R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
| | | | | | - Diana Maradze
- Gifford Bioscience Ltd., The BioHub Birmingham, Birmingham, United Kingdom
| | - Wenhao Xia
- PMI R&D, Philip Morris International Research Laboratories Pte. Ltd., Singapore, Singapore
| | - Stefan Frentzel
- PMI R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
| | - Andrew N Gifford
- Gifford Bioscience Ltd., The BioHub Birmingham, Birmingham, United Kingdom
| | | | - Julia Hoeng
- PMI R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
| | - Kyoko Koshibu
- PMI R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
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5
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Kassner M, Eaton JB, Tang N, Petit JL, Meurice N, Yin HH, Whiteaker P. High-throughput cell-based assays for identifying antagonists of multiple smoking-associated human nicotinic acetylcholine receptor subtypes. SLAS DISCOVERY : ADVANCING LIFE SCIENCES R & D 2022; 27:68-76. [PMID: 35058178 PMCID: PMC8816891 DOI: 10.1016/j.slasd.2021.10.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
There is substantial evidence that in addition to nicotine, other compounds found in tobacco smoke significantly influence smoking behavior. Further, recent years have seen an explosion in the availability of non-combusted products that deliver nicotine, such as e-cigarettes and “home-brew” vaping devices that are essentially unregulated. There are many thousands of compounds in tobacco smoke alone, and new products are constantly introducing new compounds. Uncovering which of these compounds are active, across multiple smoking-relevant subtypes of the nicotinic acetylcholine receptor (nAChR) that influence tobacco/nicotine addiction, requires a high-throughput screening (HTS) approach. Accordingly, we developed a panel of HTS-friendly cell-based assays, all performed in the same cellular background and using the same membrane potential dye readout, to measure the function of the α3β4-, α4β2-, and α6β2-nAChR subtypes. These subtypes have each been prominently and consistently associated with human smoking behavior. We validated our assays by performing pilot screening of an expanded set of the Prestwick FDA-approved drug library. The screens displayed excellent performance parameters, and moderate hit rates (mean of 1.2% across all three assays) were achieved when identifying antagonists (chosen since effects of endogenous antagonists on consumption of nicotine/tobacco products are under-studied). Validation rates using an orthogonal assay (86Rb+ efflux) averaged 73% across the three assays. The resulting panel of assays represents a valuable new platform with which to screen and identify nAChR subtype-selective compounds. This provides a resource for identifying smoking-related compounds in both combusted and non-combusted tobacco products, with potential relevance in the search for additional smoking-cessation therapies.
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Affiliation(s)
- Michelle Kassner
- Cancer and Cell Biology Division, Translational Genomics Research Institute, Phoenix, AZ 85004, United States
| | - J Brek Eaton
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, United States
| | - Nanyun Tang
- Cancer and Cell Biology Division, Translational Genomics Research Institute, Phoenix, AZ 85004, United States
| | - Joachim L Petit
- Department of Hematology/Oncology, Mayo Clinic, Scottsdale, AZ 85259, United States
| | - Nathalie Meurice
- Department of Hematology/Oncology, Mayo Clinic, Scottsdale, AZ 85259, United States
| | - Hongwei Holly Yin
- Cancer and Cell Biology Division, Translational Genomics Research Institute, Phoenix, AZ 85004, United States.
| | - Paul Whiteaker
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, United States.
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6
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Thomson K, Kelly T, Karouta C, Morgan I, Ashby R. Insights into the mechanism of atropine's anti-myopia effects: evidence against cholinergic hyperactivity and modulation of dopamine release. Br J Pharmacol 2021; 178:4501-4517. [PMID: 34302355 PMCID: PMC9293064 DOI: 10.1111/bph.15629] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 04/29/2021] [Accepted: 06/25/2021] [Indexed: 11/27/2022] Open
Abstract
Background and Purpose The ability of the muscarinic cholinergic antagonist atropine to inhibit myopia development in humans and animal models would suggest that cholinergic hyperactivity may underlie myopic growth. To test this, we investigated whether cholinergic agonists accelerate ocular growth rates in chickens. Furthermore, we investigated whether atropine alters ocular growth by downstream modulation of dopamine levels, a mechanism postulated to underlie its antimyopic effects. Experimental Approach Muscarinic (muscarine and pilocarpine), nicotinic (nicotine) and non‐specific (oxotremorine and carbachol) cholinergic agonists were administered to chicks developing form‐deprivation myopia (FDM) or chicks that were otherwise untreated. Vitreal levels of dopamine and its primary metabolite 3,4‐dihydroxyphenylacetic acid (DOPAC) were examined using mass spectrometry MS in form‐deprived chicks treated with atropine (360, 15 or 0.15 nmol). Further, we investigated whether dopamine antagonists block atropine's antimyopic effects. Key Results Unexpectedly, administration of each cholinergic agonist inhibited FDM but did not affect normal ocular development. Atropine only affected dopamine and DOPAC levels at its highest dose. Dopamine antagonists did not alter the antimyopia effects of atropine. Conclusion and Implications Muscarinic, nicotinic and non‐specific cholinergic agonists inhibited FDM development. This indicates that cholinergic hyperactivity does not underlie myopic growth and questions whether atropine inhibits myopia via cholinergic antagonism. This study also demonstrates that changes in retinal dopamine release are not required for atropine's antimyopic effects. Finally, nicotinic agonists may represent a novel and more targeted approach for the cholinergic control of myopia as they are unlikely to cause the anterior segment side effects associated with muscarinic treatment.
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Affiliation(s)
- Kate Thomson
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Australia
| | - Tamsin Kelly
- National Centre for Forensic Studies, Faculty of Science and Technology, University of Canberra, Australia
| | - Cindy Karouta
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Australia
| | - Ian Morgan
- Research School of Biology, Australian National University, Australia
| | - Regan Ashby
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Australia.,Research School of Biology, Australian National University, Australia
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7
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Sakkiah S, Leggett C, Pan B, Guo W, Valerio LG, Hong H. Development of a Nicotinic Acetylcholine Receptor nAChR α7 Binding Activity Prediction Model. J Chem Inf Model 2020; 60:2396-2404. [PMID: 32159345 DOI: 10.1021/acs.jcim.0c00139] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Despite the well-known adverse health effects associated with tobacco use, addiction to nicotine found in tobacco products causes difficulty in quitting among users. Nicotinic acetylcholine receptors (nAChRs) are the physiological targets of nicotine and facilitate addiction to tobacco products. The nAChR-α7 subtype plays an important role in addiction; therefore, predicting the binding activity of tobacco constituents to nAChR-α7 is an important component for assessing addictive potential of tobacco constituents. We developed an α7 binding activity prediction model based on a large training data set of 843 chemicals with human α7 binding activity data extracted from PubChem and ChEMBL. The model was tested using 1215 chemicals with rat α7 binding activity data from the same databases. Based on the competitive docking results, the docking scores were partitioned to the key residues that play important roles in the receptor-ligand binding. A decision forest was used to train the human α7 binding activity prediction model based on the partition of docking scores. Five-fold cross validations were conducted to estimate the performance of the decision forest models. The developed model was used to predict the potential human α7 binding activity for 5275 tobacco constituents. The human α7 binding activity data for 84 of the 5275 tobacco constituents were experimentally measured to confirm and empirically validate the prediction results. The prediction accuracy, sensitivity, and specificity were 64.3, 40.0, and 81.6%, respectively. The developed prediction model of human α7 may be a useful tool for high-throughput screening of potential addictive tobacco constituents.
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Affiliation(s)
- Sugunadevi Sakkiah
- Division of Bioinformatics and Biostatistics, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Road, Jefferson, Arkansas 72079, United States
| | - Carmine Leggett
- Division of Nonclinical Science, Office of Science, Center for Tobacco Products, U.S. Food and Drug Administration, 11785 Beltsville Drive, Calverton, Maryland 20705, United States
| | - Bohu Pan
- Division of Bioinformatics and Biostatistics, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Road, Jefferson, Arkansas 72079, United States
| | - Wenjing Guo
- Division of Bioinformatics and Biostatistics, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Road, Jefferson, Arkansas 72079, United States
| | - Luis G Valerio
- Division of Nonclinical Science, Office of Science, Center for Tobacco Products, U.S. Food and Drug Administration, 11785 Beltsville Drive, Calverton, Maryland 20705, United States
| | - Huixiao Hong
- Division of Bioinformatics and Biostatistics, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Road, Jefferson, Arkansas 72079, United States
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8
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Alijevic O, McHugh D, Rufener L, Mazurov A, Hoeng J, Peitsch M. An electrophysiological characterization of naturally occurring tobacco alkaloids and their action on human α4β2 and α7 nicotinic acetylcholine receptors. PHYTOCHEMISTRY 2020; 170:112187. [PMID: 31865001 DOI: 10.1016/j.phytochem.2019.112187] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 10/21/2019] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
Nicotinic acetylcholine receptor (nAChR) subtype-selective pharmacological profiles of tobacco alkaloids are essential for understanding the physiological effects of tobacco products. In this study, automated electrophysiology was used to functionally characterize the effects of distinct groups of tobacco alkaloids on human α4β2 and α7 nAChRs. We found that, in tobacco alkaloids, pyridine as a hydrogen bond acceptor and a basic nitrogen atom at a distance of 4-7 Å are pharmacophoric elements necessary for molecular recognition by α4β2 and α7 nAChRs with various degrees of selectivity, potency, and efficacy. While four alkaloids-nicotine, nornicotine, anabasine and R-anatabine-potently activated α4β2, they were also weak agonists of α7 nAChRs. Nicotine was the most potent agonist of α4β2, while anabasine elicited the highest activation of α7. None of the tobacco alkaloids enhanced nAChR activity elicited by the endogenous ligand acetylcholine; therefore, none was considered to be a positive allosteric modulator (PAM) of either α4β2 or α7 nAChRs. In contrast, we identified tobacco alkaloids, such as the tryptophan metabolite 6-hydroxykynurenic acid, that decreased the activity of both α4β2 and α7 nAChRs. Our study identified a class of alkaloids with positive and negative effects against human α4β2 and α7 nAChRs. It also revealed human α4β2 to be the principal receptor for sensing the most abundant alkaloids in tobacco leaves.
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Affiliation(s)
- Omar Alijevic
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, CH-2000, Neuchâtel, Switzerland
| | - Damian McHugh
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, CH-2000, Neuchâtel, Switzerland.
| | | | - Anatoly Mazurov
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, CH-2000, Neuchâtel, Switzerland
| | - Julia Hoeng
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, CH-2000, Neuchâtel, Switzerland
| | - Manuel Peitsch
- PMI R&D, Philip Morris Products S.A., Quai Jeanrenaud 5, CH-2000, Neuchâtel, Switzerland
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9
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Designing selective modulators for the nicotinic receptor subtypes: challenges and opportunities. Future Med Chem 2018; 10:433-459. [PMID: 29451400 DOI: 10.4155/fmc-2017-0169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nicotinic receptors are membrane proteins involved in several physiological processes. They are considered suitable drug targets for various CNS disorders or conditions, as shown by the large number of compounds which have entered clinical trials. In recent years, nonconventional agonists have been discovered: positive allosteric modulators, allosteric agonists, site-specific agonists and silent desensitizers are compounds able to modulate the receptor interacting at sites different from the orthodox one, or to desensitize the receptor without prior opening. While these new findings can further complicate the pharmacology of these proteins and the design and optimization of ligands, they undoubtedly offer new opportunities to find drugs for the many therapeutic indications involving nicotinic receptors.
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10
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Szabo M, Svensson Akusjärvi S, Saxena A, Liu J, Chandrasekar G, Kitambi SS. Cell and small animal models for phenotypic drug discovery. DRUG DESIGN DEVELOPMENT AND THERAPY 2017; 11:1957-1967. [PMID: 28721015 PMCID: PMC5500539 DOI: 10.2147/dddt.s129447] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The phenotype-based drug discovery (PDD) approach is re-emerging as an alternative platform for drug discovery. This review provides an overview of the various model systems and technical advances in imaging and image analyses that strengthen the PDD platform. In PDD screens, compounds of therapeutic value are identified based on the phenotypic perturbations produced irrespective of target(s) or mechanism of action. In this article, examples of phenotypic changes that can be detected and quantified with relative ease in a cell-based setup are discussed. In addition, a higher order of PDD screening setup using small animal models is also explored. As PDD screens integrate physiology and multiple signaling mechanisms during the screening process, the identified hits have higher biomedical applicability. Taken together, this review highlights the advantages gained by adopting a PDD approach in drug discovery. Such a PDD platform can complement target-based systems that are currently in practice to accelerate drug discovery.
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Affiliation(s)
- Mihaly Szabo
- Department of Microbiology Tumor, and Cell Biology
| | | | - Ankur Saxena
- Department of Microbiology Tumor, and Cell Biology
| | - Jianping Liu
- Department of Biochemistry and Biophysics, Karolinska Institutet, Solna, Sweden
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11
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Ekins S, Mathews P, Saito EK, Diaz N, Naylor D, Chung J, McMurtray AM. α7-Nicotinic acetylcholine receptor inhibition by indinavir: implications for cognitive dysfunction in treated HIV disease. AIDS 2017; 31:1083-1089. [PMID: 28358738 DOI: 10.1097/qad.0000000000001488] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE The study set out to determine if the HIV protease inhibitor, indinavir, alters responsiveness of α7-nicotinic acetylcholine receptors to acetylcholine. DESIGN Treatment with HAART has dramatically reduced development of HIV-associated dementia and more severe forms of cognitive impairment. However, many individuals continue to experience cognitive decline of uncertain cause. Previous studies have failed to demonstrate significant alterations of functional brain connectivity, structural brain changes, or changes in cerebral blood flow sufficient to explain cognitive decline in virally suppressed individuals. This suggests that the mechanisms underlying development and progression of cognitive problems likely occurs at a micro rather than macro level, such as disruptions in neurotransmitter system signaling. MATERIALS AND METHODS Indinavir's effects on α7-nicotinic acetylcholine receptor activity was tested using a ScreenPatch IonWorks Barracuda-based assay in a mammalian cell model. RESULTS At low concentrations (0.0003-10 μmol/l) indinavir acts as a positive allosteric modulator (EC50 = 0.021 μmol/l), whereas at concentrations greater than 10 μmol/l (30-100 μmol/l) indinavir acts as an inhibitor of the α7-nicotinic acetylcholine receptor. CONCLUSION At concentrations greater than 10 μmol/l indinavir reduces synaptic transmission in the acetylcholine neurotransmitter system, which could possibly contribute to cognitive dysfunction. These results suggest that further experiments should be considered to assess whether patients might benefit from treatment with cholinesterase inhibitors that counteract the effects of indinavir.
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12
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Armstrong LC, Kirsch GE, Fedorov NB, Wu C, Kuryshev YA, Sewell AL, Liu Z, Motter AL, Leggett CS, Orr MS. High-Throughput Patch Clamp Screening in Human α6-Containing Nicotinic Acetylcholine Receptors. SLAS DISCOVERY 2017; 22:686-695. [PMID: 28298165 PMCID: PMC5480602 DOI: 10.1177/2472555217696794] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Nicotine, the addictive component of tobacco products, is an agonist at nicotinic acetylcholine receptors (nAChRs) in the brain. The subtypes of nAChR are defined by their α- and β-subunit composition. The α6β2β3 nAChR subtype is expressed in terminals of dopaminergic neurons that project to the nucleus accumbens and striatum and modulate dopamine release in brain regions involved in nicotine addiction. Although subtype-dependent selectivity of nicotine is well documented, subtype-selective profiles of other tobacco product constituents are largely unknown and could be essential for understanding the addiction-related neurological effects of tobacco products. We describe the development and validation of a recombinant cell line expressing human α6/3β2β3V273S nAChR for screening and profiling assays in an automated patch clamp platform (IonWorks Barracuda). The cell line was pharmacologically characterized by subtype-selective and nonselective reference agonists, pore blockers, and competitive antagonists. Agonist and antagonist effects detected by the automated patch clamp approach were comparable to those obtained by conventional electrophysiological assays. A pilot screen of a library of Food and Drug Administration–approved drugs identified compounds, previously not known to modulate nAChRs, which selectively inhibited the α6/3β2β3V273S subtype. These assays provide new tools for screening and subtype-selective profiling of compounds that act at α6β2β3 nicotinic receptors.
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Affiliation(s)
| | | | | | - Caiyun Wu
- 1 Charles River Discovery, Cleveland, OH, USA
| | | | | | - Zhiqi Liu
- 1 Charles River Discovery, Cleveland, OH, USA
| | - Arianne L Motter
- 2 U.S. Food and Drug Administration/Center for Tobacco Products, Silver Spring, MD, USA
| | - Carmine S Leggett
- 2 U.S. Food and Drug Administration/Center for Tobacco Products, Silver Spring, MD, USA
| | - Michael S Orr
- 2 U.S. Food and Drug Administration/Center for Tobacco Products, Silver Spring, MD, USA.,PAREXEL International, Bethesda, MD, USA
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