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Deba F, Ramos K, Vannoy M, Munoz K, Akinola LS, Damaj MI, Hamouda AK. Examining the Effects of (α4)3(β2)2 Nicotinic Acetylcholine Receptor-Selective Positive Allosteric Modulator on Acute Thermal Nociception in Rats. Molecules 2020; 25:molecules25122923. [PMID: 32630476 PMCID: PMC7355939 DOI: 10.3390/molecules25122923] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 06/19/2020] [Accepted: 06/22/2020] [Indexed: 12/14/2022] Open
Abstract
Neuronal nicotinic acetylcholine receptor (nAChR)-based therapeutics are sought as a potential alternative strategy to opioids for pain management. In this study, we examine the antinociceptive effects of 3-(2-chlorophenyl)-5-(5-methyl-1-(piperidin-4-yl)-1H-pyrazol-4-yl)isoxazole (CMPI), a novel positive allosteric modulator (PAM), with preferential selectivity to the low agonist sensitivity (α4)3(β2)2 nAChR and desformylflustrabromine (dFBr), a PAM for α4-containing nAChRs. We used hot plate and tail flick tests to measure the effect of dFBr and CMPI on the latency to acute thermal nociceptive responses in rats. Intraperitoneal injection of dFBr, but not CMPI, dose-dependently increased latency in the hot plate test. In the tail flick test, the effect achieved at the highest dFBr or CMPI dose tested was only <20% of the maximum possible effects reported for nicotine and other nicotinic agonists. Moreover, the coadministration of dFBr did not enhance the antinociceptive effect of a low dose of nicotine. Our results show that the direct acute effect of dFBr is superior to that for CMPI, indicating that selectivity to (α4)3(β2)2 nAChR is not advantageous in alleviating responses to acute thermal nociceptive stimulus. However, further studies are necessary to test the suitability of (α4)3(β2)2 nAChR-selective PAMs in chronic pain models.
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Affiliation(s)
- Farah Deba
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Texas at Tyler, Tyler, TX 75799, USA;
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
| | - Kara Ramos
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
| | - Matthew Vannoy
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
| | - Kemburli Munoz
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
| | - Lois S. Akinola
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Kontos Medical Science Building, 1217 E. Marshall St., P.O. Box 980613, Richmond, VA 23298, USA; (L.S.A.); (M.I.D.)
| | - M. Imad Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Kontos Medical Science Building, 1217 E. Marshall St., P.O. Box 980613, Richmond, VA 23298, USA; (L.S.A.); (M.I.D.)
| | - Ayman K. Hamouda
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Texas at Tyler, Tyler, TX 75799, USA;
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
- Correspondence: ; Tel.: +1-903-565-6578
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Mussina K, Toktarkhanova D, Filchakova O. Nicotinic Acetylcholine Receptors of PC12 Cells. Cell Mol Neurobiol 2020; 41:17-29. [PMID: 32335772 DOI: 10.1007/s10571-020-00846-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Accepted: 04/09/2020] [Indexed: 12/18/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) have gained much attention in the scientific community since they play a significant role in multiple physiological and pathophysiological processes. Multiple approaches to study the receptors exist, with characterization of the receptors' functionality at a single cellular level using cell culturing being one of them. Derived from an adrenal medulla tumor, PC12 cells express nicotinic receptor subunits and form functional nicotinic receptors. Thus, the cells offer a convenient environment to address questions related to the functionality of the receptors. The review summarizes the findings on nicotinic receptors' expression and functions which were conducted using PC12 cells. Specific focus is given to α3-containing receptors as well as α7 receptor. Critical evaluation of findings is provided alongside insights into what can still be learned about nAChRs, using PC12 cells.
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Affiliation(s)
- Kamilla Mussina
- Biology Department, School of Sciences and Humanities, Nazarbayev University, NurSultan, Republic of Kazakhstan
| | - Dana Toktarkhanova
- Biology Department, School of Sciences and Humanities, Nazarbayev University, NurSultan, Republic of Kazakhstan
| | - Olena Filchakova
- Biology Department, School of Sciences and Humanities, Nazarbayev University, NurSultan, Republic of Kazakhstan.
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Nikiforuk A, Litwa E, Krawczyk M, Popik P, Arias H. Desformylflustrabromine, a positive allosteric modulator of α4β2-containing nicotinic acetylcholine receptors, enhances cognition in rats. Pharmacol Rep 2020; 72:589-599. [PMID: 32207091 PMCID: PMC7329799 DOI: 10.1007/s43440-020-00092-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 02/04/2020] [Accepted: 02/05/2020] [Indexed: 11/30/2022]
Abstract
Rationale The α4β2 nicotinic acetylcholine receptors (α4β2-nAChRs) may represent useful targets for cognitive improvement. It has been recently proposed that a strategy based on positive allosteric modulation of α4β2-nAChRs reveals several advantages over the direct agonist approach. Nevertheless, the procognitive effects of α4β2-nAChR positive allosteric modulators (PAMs) have not been extensively characterized. Objectives The aim of the present study was to evaluate the procognitive efficacy of desformylflustrabromine (dFBr), a selective α4β2-nAChR PAM. Methods Cognitive effects were investigated in the novel object recognition task (NORT) and the attentional set-shifting task (ASST) in rats. Results The results demonstrate that dFBr attenuated the delay-induced impairment in NORT performance and facilitated cognitive flexibility in the ASST. The beneficial effects of dFBr were inhibited by dihydro-β-erythroidine, a relatively selective α4β2-nAChR antagonist, indicating the involvement of α4β2-nAChRs in cognitive processes. The tested α4β2-PAM was also effective against ketamine- and scopolamine-induced deficits of object recognition memory. Moreover, procognitive effects were also observed after combined treatment with inactive doses of dFBr and TC-2403, a selective α4β2-nAChR agonist. Conclusions These findings indicate that dFBr presents procognitive activity, supporting the strategy based on α4β2-nAChR potentiation as a plausible therapy for cognitive impairment. Electronic supplementary material The online version of this article (10.1007/s43440-020-00092-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Agnieszka Nikiforuk
- Department of Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology Polish Academy of Sciences, 12 Smetna Street, 31-343, Krakow, Poland.
| | - Ewa Litwa
- Department of Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology Polish Academy of Sciences, 12 Smetna Street, 31-343, Krakow, Poland
| | - Martyna Krawczyk
- Department of Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology Polish Academy of Sciences, 12 Smetna Street, 31-343, Krakow, Poland
| | - Piotr Popik
- Department of Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology Polish Academy of Sciences, 12 Smetna Street, 31-343, Krakow, Poland
| | - Hugo Arias
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, OK, USA
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Weggel LA, Pandya AA. Acute Administration of Desformylflustrabromine Relieves Chemically Induced Pain in CD-1 Mice. Molecules 2019; 24:molecules24050944. [PMID: 30866543 PMCID: PMC6432607 DOI: 10.3390/molecules24050944] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 02/27/2019] [Accepted: 03/04/2019] [Indexed: 01/28/2023] Open
Abstract
Neuronal nicotinic acetylcholine receptors are cell membrane-bound ion channels that are widely distributed in the central nervous system. The α4β2 subtype of neuronal nicotinic acetylcholine receptor plays an important role in modulating the signaling pathways for pain. Previous studies have shown that agonists, partial agonists, and positive allosteric modulators for the α4β2 receptors are effective in relieving pain. Desformylflustrabromine is a compound that acts as an allosteric modulator of α4β2 receptors. The aim of this study was to assess the effects of desformylflustrabromine on chemically induced pain. For this purpose, the formalin-induced pain test and the acetic acid-induced writhing response test were carried out in CD-1 mice. Both tests represent chemical assays for nociception. The results show that desformylflustrabromine is effective in producing an analgesic effect in both tests used for assessing nociception. These results suggest that desformylflustrabromine has the potential to become a clinically used drug for pain relief.
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Affiliation(s)
- Loni A Weggel
- Department of Biosciences, College of Rural and Community Development, 101D Harper Building, 810 Draanjik Drive, University of Alaska Fairbanks, Fairbanks, AK 99709-3419, USA.
| | - Anshul A Pandya
- Department of Biosciences, College of Rural and Community Development, 101D Harper Building, 810 Draanjik Drive, University of Alaska Fairbanks, Fairbanks, AK 99709-3419, USA.
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Liu W, Li MD. Insights Into Nicotinic Receptor Signaling in Nicotine Addiction: Implications for Prevention and Treatment. Curr Neuropharmacol 2018; 16:350-370. [PMID: 28762314 PMCID: PMC6018190 DOI: 10.2174/1570159x15666170801103009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 06/18/2017] [Accepted: 07/28/2017] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Nicotinic acetylcholine receptors (nAChRs) belong to the Cys-loop ligandgated ion-channel (LGIC) superfamily, which also includes the GABA, glycine, and serotonin receptors. Many nAChR subunits have been identified and shown to be involved in signal transduction on binding to them of either the neurotransmitter acetylcholine or exogenous ligands such as nicotine. The nAChRs are pentameric assemblies of homologous subunits surrounding a central pore that gates cation flux, and they are expressed at neuromuscular junctions throughout the nervous system. METHODS AND RESULTS Because different nAChR subunits assemble into a variety of pharmacologically distinct receptor subtypes, and different nAChRs are implicated in various physiological functions and pathophysiological conditions, nAChRs represent potential molecular targets for drug addiction and medical therapeutic research. This review intends to provide insights into recent advances in nAChR signaling, considering the subtypes and subunits of nAChRs and their roles in nicotinic cholinergic systems, including structure, diversity, functional allosteric modulation, targeted knockout mutations, and rare variations of specific subunits, and the potency and functional effects of mutations by focusing on their effects on nicotine addiction (NA) and smoking cessation (SC). Furthermore, we review the possible mechanisms of action of nAChRs in NA and SC based on our current knowledge. CONCLUSION Understanding these cellular and molecular mechanisms will lead to better translational and therapeutic operations and outcomes for the prevention and treatment of NA and other drug addictions, as well as chronic diseases, such as Alzheimer's and Parkinson's. Finally, we put forward some suggestions and recommendations for therapy and treatment of NA and other chronic diseases.
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Affiliation(s)
- Wuyi Liu
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, China.,School of Biological Sciences and Food Engineering, Fuyang Normal University, Fuyang, Anuhi 236041, China
| | - Ming D Li
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, China.,Research Center for Air Pollution and Health, Zhejiang University, Hangzhou, China.,Institute of NeuroImmune Pharmacology, Seton Hall University, South Orange, NJ, United States
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Pan Z, Zhao M, Peng Y, Wang J. Functional divergence analysis of vertebrate neuronal nicotinic acetylcholine receptor subunits. J Biomol Struct Dyn 2018; 37:2938-2948. [PMID: 30044167 DOI: 10.1080/07391102.2018.1500945] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are pentamers formed by subunits from a large multigene family and are highly variable in kinetic, electrophysiological and pharmacological properties. Due to the essential roles of nAChRs in many physiological procedures and diversity in function, identifying the function-related sites specific to each subunit is not only necessary to understand the properties of the receptors but also useful to design potential therapeutic compounds that target these macromolecules for treating a series of central neuronal disorders. By conducting a detailed function divergence analysis on nine neuronal nAChR subunits from representative vertebrate species, we revealed the existence of significant functional variation between most subunit pairs. Specifically, 44 unique residues were identified for the α7 subunit, while another 22 residues that were likely responsible for the specific features of other subunits were detected. By mapping these sites onto the 3 D structure of the human α7 subunit, a structure-function relationship profile was revealed. Our results suggested that the functional divergence related sites clustered in the ligand binding domain, the β2-β3 linker close to the N-terminal α-helix, the intracellular linkers between transmembrane domains, and the "transition zone" may have experienced altered evolutionary rates. The former two regions may be potential binding sites for the α7* subtype-specific allosteric modulators, while the latter region is likely to be subtype-specific allosteric modulations of the heteropentameric descendants such as the α4β2* nAChRs. Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Zhenhua Pan
- a School of Biomedical Engineering , Tianjin Medical University , Tianjin , China.,b Tianjin Key Laboratory of Lung Cancer Metastasis and Tumor Microenvironment , Tianjin Lung Cancer Institute, Tianjin Medical University General Hospital , Tianjin , China
| | - Mengwen Zhao
- a School of Biomedical Engineering , Tianjin Medical University , Tianjin , China
| | - Yonglin Peng
- a School of Biomedical Engineering , Tianjin Medical University , Tianjin , China
| | - Ju Wang
- a School of Biomedical Engineering , Tianjin Medical University , Tianjin , China
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Role of Exogenous Progesterone in the Treatment of Men and Women with Substance Use Disorders: A Narrative Review. CNS Drugs 2018; 32:421-435. [PMID: 29761343 PMCID: PMC6235727 DOI: 10.1007/s40263-018-0525-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Substance use disorders (SUDs) remain problematic as many individuals are untreated or do not benefit from the currently available interventions. Thus, there is an urgent need to develop novel pharmacological interventions to treat SUDs. Evidence suggests that the female sex hormone, progesterone, attenuates the craving for and the euphoric effects of drugs of abuse. Research to date has demonstrated that progesterone may modulate responses to drugs of abuse and may have utility as a novel treatment for SUDs. A literature search was conducted to identify and examine studies that administered exogenous progesterone. Sixteen publications were identified, exploring the utility of exogenous progesterone or its metabolite, allopregnanolone, among a range of substances, including amphetamines (one study), benzodiazepines (one study), cocaine (nine studies), and tobacco/nicotine (five studies). Results indicated that exogenous progesterone and, its metabolite allopregnanolone, demonstrated preliminary efficacy as a treatment for substance use in both men and women. Notably, progesterone appears to target negative affect and augment cognitive functioning, especially among female substance users. Additional research is needed to explore the potential use of exogenous progesterone and allopregnanolone in the treatment of SUDs, including that associated with alcohol and opioids, but considering the current promising findings, exogenous progesterone and allopregnanolone may have utility as novel pharmacological treatments for SUDs.
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Lewis JA, Yakel JL, Pandya AA. Levamisole: A Positive Allosteric Modulator for the α3β4 Nicotinic Acetylcholine Receptors Prevents Weight Gain in the CD-1 Mice on a High Fat Diet. Curr Pharm Des 2018; 23:1869-1872. [PMID: 27908269 DOI: 10.2174/1381612822666161201145648] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 09/01/2016] [Indexed: 11/22/2022]
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) regulate the function of multiple neurotransmitter pathways throughout the central nervous system. This includes nAChRs found on the proopiomelanocortin neurons in the hypothalamus. Activation of these nAChRs by nicotine causes a decrease in the consumption of food in rodents. This study tested the effect of subtype selective allosteric modulators for nAChRs on the body weight of CD-1 mice. Levamisole, an allosteric modulator for the α3β4 subtype of nAChRs, prevented weight gain in mice that were fed a high fat diet. PNU-120596 and desformylflustrabromine were observed to be selective PAMs for the α7 and α4β2 nAChR, respectively. Both of these compounds failed to prevent weight gain in the CD-1 mice. These results suggest that the modulation of hypothalamic α3β4 nAChRs is an important factor in regulating food intake, and the PAMs for these receptors need further investigation as potential therapeutic agents for controlling weight gain.
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Affiliation(s)
- Jeanne A Lewis
- Department of Bioscience, College of Rural and Community Development, Room 116, Harper Building, 4280, Geist Road, University of Alaska Fairbanks, Fairbanks, AK. 99709-3419. United States
| | - Jerrel L Yakel
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709. United States
| | - Anshul A Pandya
- Room 116, Harper Building, 4280, Geist Road, University of Alaska Fairbanks, Fairbanks, AK. 99709- 3419. United States
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Bagdas D, Ergun D, Jackson A, Toma W, Schulte M, Damaj M. Allosteric modulation of α4β2* nicotinic acetylcholine receptors: Desformylflustrabromine potentiates antiallodynic response of nicotine in a mouse model of neuropathic pain. Eur J Pain 2018; 22:84-93. [PMID: 28809075 PMCID: PMC9829446 DOI: 10.1002/ejp.1092] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/08/2017] [Indexed: 01/12/2023]
Abstract
BACKGROUND Neuronal nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels. The α4β2 subtype of nAChRs plays an important role in the mediation of pain and several nicotine-evoked responses. Agonists and partial agonists of α4β2 nAChRs show efficacy in animal pain models. In addition, the antinociceptive properties of nicotine, a non-selective nAChR agonist with a high affinity for α4β2 nAChRs, is well-known. There is a growing body of evidence pointing to allosteric modulation of nAChRs as an alternative treatment strategy in experimental pain. Desformylflustrabromine (dFBr) is a positive allosteric modulator (PAM) at α4β2 nAChRs that enhances agonist responses without activating receptors. We hypothesized that dFBr may enhance nicotine-induced antinociception. METHODS The present study investigated whether dFBr could attenuate mouse chronic constriction injury (CCI)-induced neuropathic pain by increasing endogenous cholinergic tone or potentiating the nicotine-evoked antiallodynic response. RESULTS We found that subcutaneous administration of dFBr failed to reduce pain behaviour on its own. However, the combination of dFBr with nicotine significantly reversed neuropathic pain behaviour dose- and time-dependently without motor impairment. Our data revealed that this effect was mediated by the α4β2 nAChRs by using competitive α4β2 antagonist dihydro-β-erythroidine. In addition, dFBr failed to potentiate the antiallodynic effect of morphine, which shows the effect of dFBr is unique to α4β2 nAChRs. CONCLUSIONS The present results suggest that allosteric modulation of α4β2 nAChR may provide new strategies in chronic neuropathic pain. SIGNIFICANCE α4β2 nAChRs are involved in pain modulation. dFBr, a PAM at α4β2 nAChRs, potentiates the nicotine response dose-dependently in neuropathic pain. Thus, the present results suggest that allosteric modulation of α4β2* nAChR may provide new strategies in chronic neuropathic pain.
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Affiliation(s)
- D. Bagdas
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0613 USA,Experimental Animals Breeding and Research Center, Faculty of Medicine, Uludag University, Bursa 16059, Turkey
| | - D. Ergun
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0613 USA
| | - A. Jackson
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0613 USA
| | - W. Toma
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0613 USA
| | - M.K. Schulte
- Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, PA, USA
| | - M.I. Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0613 USA
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Reyes-Parada M, Iturriaga-Vasquez P. The development of novel polypharmacological agents targeting the multiple binding sites of nicotinic acetylcholine receptors. Expert Opin Drug Discov 2016; 11:969-81. [DOI: 10.1080/17460441.2016.1227317] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Zoli M, Pistillo F, Gotti C. Diversity of native nicotinic receptor subtypes in mammalian brain. Neuropharmacology 2015; 96:302-11. [DOI: 10.1016/j.neuropharm.2014.11.003] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 10/11/2014] [Accepted: 11/08/2014] [Indexed: 01/01/2023]
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12
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Multiple binding sites in the nicotinic acetylcholine receptors: An opportunity for polypharmacolgy. Pharmacol Res 2015; 101:9-17. [PMID: 26318763 DOI: 10.1016/j.phrs.2015.08.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 08/20/2015] [Accepted: 08/20/2015] [Indexed: 12/21/2022]
Abstract
For decades, the development of selective compounds has been the main goal for chemists and biologists involved in drug discovery. However, diverse lines of evidence indicate that polypharmacological agents, i.e. those that act simultaneously at various protein targets, might show better profiles than selective ligands, regarding both efficacy and side effects. On the other hand, the availability of the crystal structure of different receptors allows a detailed analysis of the main interactions between drugs and receptors in a specific binding site. Neuronal nicotinic acetylcholine receptors (nAChRs) constitute a large and diverse family of ligand-gated ion channels (LGICs) that, as a product of its modulation, regulate neurotransmitter release, which in turns produce a global neuromodulation of the central nervous system. nAChRs are pentameric protein complexes in such a way that expression of compatible subunits can lead to various receptor assemblies or subtypes. The agonist binding site, located at the extracellular region, exhibits different properties depending on the subunits that conform the receptor. In the last years, it has been recognized that nAChRs could also contain one or more allosteric sites which could bind non-classical nicotinic ligands including several therapeutically useful drugs. The presence of multiple binding sites in nAChRs offers an interesting possibility for the development of novel polypharmacological agents with a wide spectrum of actions.
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Grupe M, Jensen AA, Ahring PK, Christensen JK, Grunnet M. Unravelling the mechanism of action of NS9283, a positive allosteric modulator of (α4)3(β2)2 nicotinic ACh receptors. Br J Pharmacol 2015; 168:2000-10. [PMID: 23278456 DOI: 10.1111/bph.12095] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 11/22/2012] [Accepted: 12/14/2012] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Strong implications in major neurological diseases make the neuronal α4β2 nicotinic ACh receptor (nAChR) a highly interesting drug target. In this study, we present a detailed electrophysiological characterization of NS9283, a potent positive allosteric modulator acting selectively at 3α:2β stoichiometry of α2* and α4* nAChRs. EXPERIMENTAL APPROACH The whole-cell patch-clamp technique equipped with an ultra-fast drug application system was used to perform electrophysiological characterization of NS9283 modulatory actions on human α4β2 nAChRs stably expressed in HEK293 cells (HEK293-hα4β2). KEY RESULTS NS9283 was demonstrated to increase the potency of ACh-evoked currents in HEK293-hα4β2 cells by left-shifting the concentration-response curve ~60-fold. Interestingly, this modulation did not significantly alter maximal efficacy levels of ACh. Further, NS9283 did not affect the rate of desensitization of ACh-evoked currents, was incapable of reactivating desensitized receptors and only moderately slowed recovery from desensitization. However, NS9283 strongly decreased the rate of deactivation kinetics and also modestly decreased the rate of activation. This resulted in a left-shift of the ACh window current of (α4)3(β2)2 nAChRs in the presence of NS9283. CONCLUSIONS AND IMPLICATIONS This study demonstrates that NS9283 increases responsiveness of human (α4)3(β2)2 nAChR to ACh with no change in maximum efficacy. We propose that this potentiation is due to a significant slowing of deactivation kinetics. In summary, the mechanism of action of NS9283 bears high resemblance to that of benzodiazepines at the GABAA receptor and to our knowledge, NS9283 constitutes the first nAChR compound of this class.
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Affiliation(s)
- M Grupe
- NeuroSearch A/S, Ballerup, Denmark.
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Ton HT, Smart AE, Aguilar BL, Olson TT, Kellar KJ, Ahern GP. Menthol Enhances the Desensitization of Human α3β4 Nicotinic Acetylcholine Receptors. Mol Pharmacol 2015; 88:256-64. [PMID: 25964258 DOI: 10.1124/mol.115.098285] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 05/11/2015] [Indexed: 11/22/2022] Open
Abstract
The α3β4 nicotinic acetylcholine receptor (nAChR) subtype is widely expressed in the peripheral and central nervous systems, including in airway sensory nerves. The nAChR subtype transduces the irritant effects of nicotine in tobacco smoke and, in certain brain areas, may be involved in nicotine addiction and/or withdrawal. Menthol, a widely used additive in cigarettes, is a potential analgesic and/or counterirritant at sensory nerves and may also influence nicotine's actions in the brain. We examined menthol's effects on recombinant human α3β4 nAChRs and native nAChRs in mouse sensory neurons. Menthol markedly decreased nAChR activity as assessed by Ca(2+) imaging, (86)Rb(+) efflux, and voltage-clamp measurements. Coapplication of menthol with acetylcholine or nicotine increased desensitization, demonstrated by an increase in the rate and magnitude of the current decay and a reduction of the current integral. These effects increased with agonist concentration. Pretreatment with menthol followed by its washout did not affect agonist-induced desensitization, suggesting that menthol must be present during the application of agonist to augment desensitization. Notably, menthol acted in a voltage-independent manner and reduced the mean open time of single channels without affecting their conductance, arguing against a simple channel-blocking effect. Further, menthol slowed or prevented the recovery of nAChRs from desensitization, indicating that it probably stabilizes a desensitized state. Moreover, menthol at concentrations up to 1 mM did not compete for the orthosteric nAChR binding site labeled by [(3)H]epibatidine. Taken together, these data indicate that menthol promotes desensitization of α3β4 nAChRs by an allosteric action.
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Affiliation(s)
- Hoai T Ton
- Department of Pharmacology and Physiology, Georgetown University, Washington, District of Columbia
| | - Amanda E Smart
- Department of Pharmacology and Physiology, Georgetown University, Washington, District of Columbia
| | - Brittany L Aguilar
- Department of Pharmacology and Physiology, Georgetown University, Washington, District of Columbia
| | - Thao T Olson
- Department of Pharmacology and Physiology, Georgetown University, Washington, District of Columbia
| | - Kenneth J Kellar
- Department of Pharmacology and Physiology, Georgetown University, Washington, District of Columbia
| | - Gerard P Ahern
- Department of Pharmacology and Physiology, Georgetown University, Washington, District of Columbia
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15
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Matsunaga S, Kishi T, Iwata N. Combination therapy with cholinesterase inhibitors and memantine for Alzheimer's disease: a systematic review and meta-analysis. Int J Neuropsychopharmacol 2015; 18:pyu115. [PMID: 25548104 PMCID: PMC4376554 DOI: 10.1093/ijnp/pyu115] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND We performed an updated meta-analysis of randomized controlled trials of combination therapy with cholinesterase inhibitors and memantine in patients with Alzheimer's disease. METHODS We reviewed cognitive function, activities of daily living, behavioral disturbance, global assessment, discontinuation rate, and individual side effects. RESULTS Seven studies (total n=2182) were identified. Combination therapy significantly affected behavioral disturbance scores (standardized mean difference=-0.13), activity of daily living scores (standardized mean difference=-0.10), and global assessment scores (standardized mean difference=-0.15). In addition, cognitive function scores (standardized mean difference=-0.13, P=.06) exhibited favorable trends with combination therapy. The effects of combination therapy were more significant in the moderate-to-severe Alzheimer's disease subgroup in terms of all efficacy outcome scores. The discontinuation rate was similar in both groups, and there were no significant differences in individual side effects. CONCLUSIONS Combination therapy was beneficial for the treatment of moderate-to-severe Alzheimer's disease in terms of cognition, behavioral disturbances, activities of daily living, and global assessment was well tolerated.
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Affiliation(s)
- Shinji Matsunaga
- Department of Psychiatry, Fujita Health University School of Medicine, Toyoake, Aichi, Japan.
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16
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Dineley KT, Pandya AA, Yakel JL. Nicotinic ACh receptors as therapeutic targets in CNS disorders. Trends Pharmacol Sci 2015; 36:96-108. [PMID: 25639674 PMCID: PMC4324614 DOI: 10.1016/j.tips.2014.12.002] [Citation(s) in RCA: 334] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 01/30/2023]
Abstract
The neurotransmitter acetylcholine (ACh) can regulate neuronal excitability by acting on the cys-loop cation-conducting ligand-gated nicotinic ACh receptor (nAChR) channels. These receptors are widely distributed throughout the central nervous system (CNS), being expressed on neurons and non-neuronal cells, where they participate in a variety of physiological responses such as anxiety, the central processing of pain, food intake, nicotine seeking behavior, and cognitive functions. In the mammalian brain, nine different subunits have been found thus far, which assemble into pentameric complexes with much subunit diversity; however, the α7 and α4β2 subtypes predominate in the CNS. Neuronal nAChR dysfunction is involved in the pathophysiology of many neurological disorders. Here we will briefly discuss the functional makeup and expression of the nAChRs in mammalian brain, and their role as targets in neurodegenerative diseases (in particular Alzheimer's disease, AD), neurodevelopmental disorders (in particular autism and schizophrenia), and neuropathic pain.
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Affiliation(s)
- Kelly T Dineley
- Department of Neurology, Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch at Galveston (UTMB), Galveston, TX, USA
| | - Anshul A Pandya
- Chukchi Campus, Department of Bioscience, College of Rural and Community Development, University of Alaska Fairbanks, P.O. Box 297, Kotzebue, AK 99752-0297, USA
| | - Jerrel L Yakel
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health (NIEHS/NIH), Department of Health and Human Services (DHHS), F2-08, P.O. Box 12233, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA.
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17
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Rowe AR, Mercer L, Casetti V, Sendt KV, Giaroli G, Shergill SS, Tracy DK. Dementia praecox redux: a systematic review of the nicotinic receptor as a target for cognitive symptoms of schizophrenia. J Psychopharmacol 2015; 29:197-211. [PMID: 25567553 DOI: 10.1177/0269881114564096] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Most individuals with schizophrenia suffer some cognitive dysfunction: such deficits are predictive of longer-term functioning; and current dopamine-blocking antipsychotics have made little impact on this domain. There is a pressing need to develop novel pharmacological agents to tackle this insidious but most disabling of problems. The acetylcholinergic system is involved in cognitive and attentional processing, and its metabotropic and nicotinic receptors are widespread throughout the brain. Deficits in acetylcholinergic functioning occur in schizophrenia, and high rates of tobacco smoking have been posited to represent a form of self-medication. The nicotinic acetylcholine receptor (nAChR) has emerged as a putative target to improve cognitive deficits in schizophrenia, and this study systematically reviewed the emerging data. Nineteen studies were identified, covering three compound classes: agonists at the α7 and α 4β2 nAChRs, and positive allosteric modulators. Overall data are underwhelming: some studies showed significant improvements in cognition but as many studies had negative findings. It remains unclear if this represents drug limitations or nascent study methodology problems. The literature is particularly hindered by variability in inclusion of smokers, generally small sample sizes, and a lack of consensus on cognitive test batteries. Future work should evaluate longer-term outcomes, and, particularly, the effects of concomitant cognitive training.
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Affiliation(s)
- Arann R Rowe
- The Institute of Psychiatry, King's College London, London, UK
| | - Louise Mercer
- The Institute of Psychiatry, King's College London, London, UK
| | - Valentina Casetti
- The Institute of Psychiatry, King's College London, London, UK Oxleas NHS Foundation Trust, London, UK
| | | | | | - Sukhwinder S Shergill
- The Institute of Psychiatry, King's College London, London, UK South London and Maudsley NHS Foundation Trust, London, UK
| | - Derek K Tracy
- The Institute of Psychiatry, King's College London, London, UK Oxleas NHS Foundation Trust, London, UK
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18
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Multiplexing Label-Free and Fluorescence-Based Methods for Pharmacological Characterization of GPCR Ligands. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2015. [DOI: 10.1007/978-1-4939-2617-6_12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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19
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: ligand-gated ion channels. Br J Pharmacol 2014; 170:1582-606. [PMID: 24528238 PMCID: PMC3892288 DOI: 10.1111/bph.12446] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Ligand-gated ion channels are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen P H Alexander
- School of Life Sciences, University of Nottingham Medical School, Nottingham, NG7 2UH, UK
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20
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Abstract
We have characterized the effect of triazine derivatives on neuronal nicotinic receptors expressed in Xenopus oocytes. All triazines investigated inhibit the current of α7 and α3β4 neuronal nicotinic receptors elicited by acetylcholine. The effect is concentration dependent, reversible, and noncompetitive. In contrast, some derivatives have a dual effect on α4β2 receptors, by potentiating the currents at intermediate concentration and causing inhibition at higher concentrations. Triazine derivatives also affect the macroscopic kinetics of the heteromeric receptors α3β4 and α4β2 accelerating the rise and decay time course of the currents, but have no significant effect on the kinetics of homomeric α7 receptors. Two simple kinetic models are presented. The first reproduces the effects of different concentrations of triazines both on the peak currents and on the macroscopic kinetics of α7 with a simple inhibitory result. The second model describes the behavior of α4β2 receptors involving a more complex dual action.
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21
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Olsen JA, Ahring PK, Kastrup JS, Gajhede M, Balle T. Structural and functional studies of the modulator NS9283 reveal agonist-like mechanism of action at α4β2 nicotinic acetylcholine receptors. J Biol Chem 2014; 289:24911-21. [PMID: 24982426 DOI: 10.1074/jbc.m114.568097] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Modulation of Cys loop receptor ion channels is a proven drug discovery strategy, but many underlying mechanisms of the mode of action are poorly understood. We report the x-ray structure of the acetylcholine-binding protein from Lymnaea stagnalis with NS9283, a stoichiometry selective positive modulator that targets the α4-α4 interface of α4β2 nicotinic acetylcholine receptors (nAChRs). Together with homology modeling, mutational data, quantum mechanical calculations, and pharmacological studies on α4β2 nAChRs, the structure reveals a modulator binding mode that overlaps the α4-α4 interface agonist (acetylcholine)-binding site. Analysis of contacts to residues known to govern agonist binding and function suggests that modulation occurs by an agonist-like mechanism. Selectivity for α4-α4 over α4-β2 interfaces is determined mainly by steric restrictions from Val-136 on the β2-subunit and favorable interactions between NS9283 and His-142 at the complementary side of α4. In the concentration ranges where modulation is observed, its selectivity prevents NS9283 from directly activating nAChRs because activation requires coordinated action from more than one interface. However, we demonstrate that in a mutant receptor with one natural and two engineered α4-α4 interfaces, NS9283 is an agonist. Modulation via extracellular binding sites is well known for benzodiazepines acting at γ-aminobutyric acid type A receptors. Like NS9283, benzodiazepines increase the apparent agonist potency with a minimal effect on efficacy. The shared modulatory profile along with a binding site located in an extracellular subunit interface suggest that modulation via an agonist-like mechanism may be a common mechanism of action that potentially could apply to Cys loop receptors beyond the α4β2 nAChRs.
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Affiliation(s)
- Jeppe A Olsen
- From NeuroSearch A/S, Pederstrupvej 93, 2750 Ballerup, Denmark, the Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark, the Faculty of Pharmacy, The University of Sydney, Sydney, New South Wales 2006, Australia, and
| | - Philip K Ahring
- the Faculty of Pharmacy, The University of Sydney, Sydney, New South Wales 2006, Australia, and Saniona AB, Baltorpvej 54, 2750 Ballerup, Denmark
| | - Jette S Kastrup
- the Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Michael Gajhede
- the Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Thomas Balle
- the Faculty of Pharmacy, The University of Sydney, Sydney, New South Wales 2006, Australia, and
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22
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Functional Distribution and Regulation of Neuronal Nicotinic ACh Receptors in the Mammalian Brain. NICOTINIC RECEPTORS 2014. [DOI: 10.1007/978-1-4939-1167-7_5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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23
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Intra-subunit flexibility underlies activation and allosteric modulation of neuronal nicotinic acetylcholine receptors. Neuropharmacology 2013; 79:420-31. [PMID: 24373904 DOI: 10.1016/j.neuropharm.2013.12.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 12/12/2013] [Accepted: 12/14/2013] [Indexed: 01/20/2023]
Abstract
Allosteric modulation is a general feature of nicotinic acetylcholine receptors, yet the structural components and movements important for conversions among functional states are not well understood. In this study, we examine the communication between the binding sites for agonist and the modulator morantel (Mor) of neuronal α3β2 receptors, measuring evoked currents of receptors expressed in Xenopus oocytes with the two-electrode voltage-clamp method. We hypothesized that movement along an interface of β sheets connecting the agonist and modulator sites is necessary for allosteric modulation. To address this, we created pairs of substituted cysteines that span the cleft formed where the outer β sheet meets the β sheet constituting the (-)-face of the α3 subunit; the three pairs were L158C-A179C, L158C-G181C and L158C-K183C. Employing a disulfide trapping approach in which bonds are formed between neighboring cysteines under oxidation conditions, we found that oxidation treatments decreased the amplitude of currents evoked by either the agonist (ACh) or co-applied agonist and modulator (ACh + Mor), by as much as 51%, consistent with the introduced bond decreasing channel efficacy. Reduction treatment increased evoked currents up to 89%. The magnitude of the oxidation effects depended on whether agonists were present during oxidation and on the cysteine pair. Additionally, the cysteine mutations themselves decreased Mor potentiation, implicating these residues in modulation. Our findings suggest that these β sheets in the α3 subunit move with respect to each other during activation and modulation, and the residues studied highlight the contribution of this intramolecular allosteric pathway to receptor function.
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24
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Burk JA. Roles of cholinergic receptors during attentional modulation of cue detection. World J Pharmacol 2013; 2:84-91. [DOI: 10.5497/wjp.v2.i4.84] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Revised: 08/17/2013] [Accepted: 09/13/2013] [Indexed: 02/06/2023] Open
Abstract
Basal forebrain corticopetal cholinergic neurons are known to be necessary for normal attentional processing. Alterations of cholinergic system functioning have been associated with several neuropsychiatric diseases, such as Alzheimer’s disease and schizophrenia, in which attentional dysfunction is thought to be a key contributing factor. Loss of cortical cholinergic inputs impairs performance in attention-demanding tasks. Moreover, measures of acetylcholine with microdialysis and, more recently, of choline with enzyme-coated microelectrodes have begun to elucidate the precise cognitive demands that activate the cholinergic system on distinct time scales. However, the receptor actions following acetylcholine release under attentionally-challenging conditions are only beginning to be understood. The present review is designed to summarize the evidence regarding the actions of acetylcholine at muscarinic and nicotinic receptors under cognitively challenging conditions in order to evaluate the functions mediated by these two different cholinergic receptor classes. Moreover, evidence that supports beneficial effects of muscarinic muscarinic-1 receptor agonists and selective nicotinic receptor subtype agonists for cognitive processing will be discussed. Finally, some challenges and limitations of targeting the cholinergic system for treating cognitive deficits along with future research directions will be mentioned. In conclusion, multiple aspects of cholinergic neurotransmission must be considered when attempting to restore function of this neuromodulatory system.
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25
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Olsen JA, Kastrup JS, Peters D, Gajhede M, Balle T, Ahring PK. Two distinct allosteric binding sites at α4β2 nicotinic acetylcholine receptors revealed by NS206 and NS9283 give unique insights to binding activity-associated linkage at Cys-loop receptors. J Biol Chem 2013; 288:35997-6006. [PMID: 24169695 DOI: 10.1074/jbc.m113.498618] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Positive allosteric modulators (PAMs) of α4β2 nicotinic acetylcholine receptors have the potential to improve cognitive function and alleviate pain. However, only a few selective PAMs of α4β2 receptors have been described limiting both pharmacological understanding and drug-discovery efforts. Here, we describe a novel selective PAM of α4β2 receptors, NS206, and compare with a previously reported PAM, NS9283. Using two-electrode voltage-clamp electrophysiology in Xenopus laevis oocytes, NS206 was observed to positively modulate acetylcholine (ACh)-evoked currents at both known α4β2 stoichiometries (2α:3β and 3α:2β). In the presence of NS206, peak current amplitudes surpassed those of maximal efficacious ACh stimulations (Emax(ACh)) with no or limited effects at potencies and current waveforms (as inspected visually). This pharmacological action contrasted with that of NS9283, which only modulated the 3α:2β receptor and acted by left shifting the ACh concentration-response relationship. Interestingly, the two modulators can act simultaneously in an additive manner at 3α:2β receptors, which results in current levels exceeding Emax(ACh) and a left-shifted ACh concentration-response relationship. Through use of chimeric and point-mutated receptors, the binding site of NS206 was linked to the α4-subunit transmembrane domain, whereas binding of NS9283 was shown to be associated with the αα-interface in 3α:2β receptors. Collectively, these data demonstrate the existence of two distinct modulatory sites in α4β2 receptors with unique pharmacological attributes that can act additively. Several allosteric sites have been identified within the family of Cys-loop receptors and with the present data, a detailed picture of allosteric modulatory mechanisms of these important receptors is emerging.
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Affiliation(s)
- Jeppe A Olsen
- From NeuroSearch A/S, Pederstrupvej 93, 2750 Ballerup, Denmark
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26
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Pandya AA, Yakel JL. Effects of neuronal nicotinic acetylcholine receptor allosteric modulators in animal behavior studies. Biochem Pharmacol 2013; 86:1054-62. [PMID: 23732296 PMCID: PMC3797251 DOI: 10.1016/j.bcp.2013.05.018] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 05/20/2013] [Accepted: 05/21/2013] [Indexed: 12/11/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are ligand-gated cation-conducting transmembrane channels from the cys-loop receptor superfamily. The neuronal subtypes of these receptors (e.g. the α7 and α4β2 subtypes) are involved in neurobehavioral processes such as anxiety, the central processing of pain, food intake, nicotine seeking behavior, and a number of cognitive functions like learning and memory. Neuronal nAChR dysfunction is involved in the pathophysiology of many neurological disorders, and behavioral studies in animals are useful models to assess the effects of compounds that act on these receptors. Allosteric modulators are ligands that bind to the receptors at sites other than the orthosteric site where acetylcholine, the endogenous agonist for the nAChRs, binds. While conventional ligands for the neuronal nAChRs have been studied for their behavioral effects in animals, allosteric modulators for these receptors have only recently gained attention, and research on their behavioral effects is growing rapidly. Here we will discuss the behavioral effects of allosteric modulators of the neuronal nAChRs.
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Affiliation(s)
- Anshul A Pandya
- Chukchi Campus, Department of Bio-science, College of Rural and Community Development, University of Alaska Fairbanks, P.O. Box 297, Kotzebue, AK 99752-0297, USA.
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27
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Pandya AA, Yakel JL. Activation of the α7 nicotinic ACh receptor induces anxiogenic effects in rats which is blocked by a 5-HT₁a receptor antagonist. Neuropharmacology 2013; 70:35-42. [PMID: 23321689 PMCID: PMC3640667 DOI: 10.1016/j.neuropharm.2013.01.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 12/19/2012] [Accepted: 01/06/2013] [Indexed: 12/13/2022]
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) is highly expressed in different regions of the brain and is associated with cognitive function as well as anxiety. Agonists and positive allosteric modulators (PAMs) of the α7 subtype of nAChRs have been shown to improve cognition. Previously nicotine, which activates both α7 and non-α7 subtypes of nAChRs, has been shown to have an anxiogenic effect in behavioral tests. In this study, we compared the effects of the α7-selective agonist (PNU-282987) and PAM (PNU-120596) in a variety of behavioral tests in Sprague Dawley rats to look at their effects on learning and memory as well as anxiety. We found that neither PNU-282987 nor PNU-120596 improved spatial-learning or episodic memory by themselves. However when cognitive impairment was induced in the rats with scopolamine (1 mg/kg), both PNU-120596 and PNU-282987 were able to reverse this memory impairment and restore it back to normal levels. While PNU-120596 reversed the scopolamine-induced cognitive impairment, it did not have any adverse effect on anxiety. PNU-282987 on the other hand displayed an increase in anxiety-like behavior at a higher dose (10 mg/kg) that was significantly reduced by the serotonin 5-HT₁a receptor antagonist WAY-100135. However the α7 receptor antagonist methyllycaconitine was unable to reverse these anxiety-like effects seen with PNU-282987. These results suggest that α7 nAChR PAMs are pharmacologically advantageous over agonists, and should be considered for further development as therapeutic drugs targeting the α7 receptors.
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Affiliation(s)
- Anshul A Pandya
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, MD F2-08, PO Box 12233, NC 27709, USA.
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Ashare RL, Falcone M, Lerman C. Cognitive function during nicotine withdrawal: Implications for nicotine dependence treatment. Neuropharmacology 2013; 76 Pt B:581-91. [PMID: 23639437 DOI: 10.1016/j.neuropharm.2013.04.034] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 04/04/2013] [Accepted: 04/16/2013] [Indexed: 11/25/2022]
Abstract
Nicotine withdrawal is associated with deficits in neurocognitive function including sustained attention, working memory, and response inhibition. Several convergent lines of evidence suggest that these deficits may represent a core dependence phenotype and a target for treatment development efforts. A better understanding of the mechanisms underlying withdrawal-related cognitive deficits may lead to improve nicotine dependence treatment. We begin with an overview of the neurocognitive effects of withdrawal in rodent and human models, followed by discussion of the neurobehavioral mechanisms that are thought to underlie these effects. We then review individual differences in withdrawal-related neurocognitive effects including genetics, gender, and psychiatric comorbidity. We conclude with a discussion of the implications of this research for developing improved therapies, both pharmacotherapy and behavioral treatments, that target cognitive symptoms of nicotine withdrawal. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.
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Affiliation(s)
- Rebecca L Ashare
- Center for Interdisciplinary Research on Nicotine Addiction, Department of Psychiatry, University of Pennsylvania, 3535 Market Street, Suite 4100, Philadelphia, PA 19104, USA.
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Ashare RL, Ray R, Lerman C, Strasser AA. Cognitive effects of the acetylcholinesterase inhibitor, donepezil, in healthy, non-treatment seeking smokers: a pilot feasibility study. Drug Alcohol Depend 2012; 126:263-7. [PMID: 22595038 PMCID: PMC3424358 DOI: 10.1016/j.drugalcdep.2012.04.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 04/18/2012] [Accepted: 04/21/2012] [Indexed: 01/29/2023]
Abstract
BACKGROUND There is a need to identify medications to aid in smoking cessation. Reducing withdrawal-related cognitive deficits represents a pharmacological target for new pharmacotherapies. Endogenous acetylcholine levels, which are modulated by acetylcholinesterase inhibitors (AChEIs), play an important role in smoking behavior and cognition. This pilot feasibility study tested whether an AChEI, donepezil, enhanced cognitive performance among healthy smokers. METHODS Eighteen non-treatment seeking daily smokers (6 female) received either donepezil (5 mg q.d) or placebo (double-blind; 2:1 allocation ratio) for 4 weeks. Smoking rate, side effects, and neurocognitive measures of working memory (Letter-N-back) and sustained attention (Penn Continuous Performance Task) were assessed weekly. RESULTS For the working memory task, there was a significant group×load×time interaction (p=0.03) indicating that the donepezil group demonstrated an increase in true positives from baseline to week 4 at the highest working memory load (3-back). The placebo group showed no change in accuracy. For the sustained attention task, there was a marginal effect in the same direction for discriminability, or d', p=0.08. There were no significant effects on reaction time during either task. There was also a reduction in cigarettes per day in the placebo group, but not the donepezil group. CONCLUSIONS AChEIs, such as donepezil, may have pro-cognitive effects among healthy smokers while they continue to smoke as usual. Given the association between cognitive deficits and relapse, AChEIs should be explored as potential therapeutics for smoking cessation.
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Affiliation(s)
- Rebecca L. Ashare
- University of Pennsylvania Perelman School of Medicine, Department of Psychiatry, Philadelphia, PA, 19104, USA
| | - Riju Ray
- University of Pennsylvania Perelman School of Medicine, Department of Psychiatry, Philadelphia, PA, 19104, USA
| | - Caryn Lerman
- University of Pennsylvania Perelman School of Medicine, Department of Psychiatry, Philadelphia, PA, 19104, USA,Abramson Cancer Center, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Andrew A. Strasser
- University of Pennsylvania Perelman School of Medicine, Department of Psychiatry, Philadelphia, PA, 19104, USA,Abramson Cancer Center, University of Pennsylvania, Philadelphia, PA, 19104, USA,Corresponding author: Andrew A. Strasser, University of Pennsylvania, Center for Interdisciplinary Research on Nicotine Addiction, 3535 Market St, Suite 4100, Philadelphia, PA 19104, Phone: (215) 746-5788,
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Corringer PJ, Poitevin F, Prevost MS, Sauguet L, Delarue M, Changeux JP. Structure and pharmacology of pentameric receptor channels: from bacteria to brain. Structure 2012; 20:941-56. [PMID: 22681900 DOI: 10.1016/j.str.2012.05.003] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Revised: 05/16/2012] [Accepted: 05/17/2012] [Indexed: 01/21/2023]
Abstract
Orthologs of the pentameric receptor channels that mediate fast synaptic transmission in the central and peripheral nervous systems have been found in several bacterial species and in a single archaea genus. Recent X-ray structures of bacterial and invertebrate pentameric receptors point to a striking conservation of the structural features within the whole family, even between distant prokaryotic and eukaryotic members. These structural data reveal general principles of molecular organization that allow allosteric membrane proteins to mediate chemoelectric transduction. Notably, several conformations have been solved, including open and closed channels with distinct global tertiary and quaternary structure. The data reveal features of the ion channel architecture and of diverse categories of binding sites, such as those that bind orthosteric ligands, including neurotransmitters, and those that bind allosteric modulators, such as general anesthetics, ivermectin, or lipids. In this review, we summarize the most recent data, discuss insights into the mechanism of action in these systems, and elaborate on newly opened avenues for drug design.
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NMR structures of the transmembrane domains of the α4β2 nAChR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1261-8. [PMID: 22361591 DOI: 10.1016/j.bbamem.2012.02.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 01/30/2012] [Accepted: 02/07/2012] [Indexed: 11/21/2022]
Abstract
The α4β2 nicotinic acetylcholine receptor (nAChR) is the predominant heteromeric subtype of nAChRs in the brain, which has been implicated in numerous neurological conditions. The structural information specifically for the α4β2 and other neuronal nAChRs is presently limited. In this study, we determined structures of the transmembrane (TM) domains of the α4 and β2 subunits in lauryldimethylamine-oxide (LDAO) micelles using solution NMR spectroscopy. NMR experiments and size exclusion chromatography-multi-angle light scattering (SEC-MALS) analysis demonstrated that the TM domains of α4 and β2 interacted with each other and spontaneously formed pentameric assemblies in the LDAO micelles. The Na(+) flux assay revealed that α4β2 formed Na(+) permeable channels in lipid vesicles. Efflux of Na(+) through the α4β2 channels reduced intra-vesicle Sodium Green™ fluorescence in a time-dependent manner that was not observed in vesicles without incorporating α4β2. The study provides structural insight into the TM domains of the α4β2 nAChR. It offers a valuable structural framework for rationalizing extensive biochemical data collected previously on the α4β2 nAChR and for designing new therapeutic modulators.
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Zhong H, Sánchez C, Caron MG. Consideration of allosterism and interacting proteins in the physiological functions of the serotonin transporter. Biochem Pharmacol 2011; 83:435-42. [PMID: 21983034 DOI: 10.1016/j.bcp.2011.09.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Accepted: 09/19/2011] [Indexed: 11/25/2022]
Abstract
The serotonin transporter (SERT) functions to transport serotonin (5-HT) from the extracellular space into neurons to maintain homeostatic control of 5-HT. It is the molecular target for selective serotonin reuptake inhibitor (SSRI) antidepressants. Preclinical research has shown that some SERT inhibitors can bind to two distinct binding sites on the SERT, a primary high affinity binding site and a low affinity allosteric binding site. Mutational studies of the SERT and computational modeling methods with escitalopram resulted in the identification of key amino acid residues important for the function of the allosteric binding site. While this allosteric binding site appears to influence the clinical efficacy of escitalopram under physiological conditions, the molecular mechanism of this effect is still poorly understood and may involve a large network of protein-protein interactions with the SERT. Dynamic interfaces between the SERT and the SERT interacting proteins (SIPs) potentially influence not only the SERT on its uptake function, its regulation, and trafficking, but also on known as well as yet to be identified non-canonical signaling pathways through SIPs. In this commentary, we outline approaches in the areas of selective small-molecule allosteric compound discovery, biochemistry, in vivo genetic knock-in mouse models, as well as computational and structural biology. These studies of the intra-molecular allosteric modulation of the SERT in the context of the myriad of potential inter-molecular signaling interactions with SIPs may help uncover unknown physiological functions of the SERT.
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Affiliation(s)
- Huailing Zhong
- U-Pharm Laboratories LLC, 239 New Road, Suite A-107, Parsippany, NJ 07054, USA.
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