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Hiranita T, Obeng S, Sharma A, Wilkerson JL, McCurdy CR, McMahon LR. In vitro and in vivo pharmacology of kratom. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2021; 93:35-76. [PMID: 35341571 DOI: 10.1016/bs.apha.2021.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Kratom products have been historically and anecdotally used in south Asian countries for centuries to manage pain and opioid withdrawal. The use of kratom products has dramatically increased in the United States. More than 45 kratom alkaloids have been isolated, yet the overall pharmacology of the individual alkaloids is still not well characterized. The purpose of this chapter is to summarize in vitro and in vivo opioid activities of the primary kratom alkaloid mitragynine and its more potent metabolite 7-hydroxymitragynine. Following are experimental procedures described to characterize opioid receptor activity; receptor binding and functional assays, antinociceptive assays, operant conditioning assays, and respiratory plethysmography. The capacity of kratom alkaloids to confer tolerance and physical dependence as well as their pharmacokinetic properties are also summarized. The data reviewed here suggest that kratom products and mitragynine possess low efficacy agonist activity at the mu-opioid receptor in vivo. In addition, kratom products and mitragynine have been demonstrated to antagonize the effects of high efficacy mu-opioid agonists. The data further suggest that 7-hydroxymitragynine formed in vivo by metabolism of mitragynine may be minimally involved in the overall behavioral profile of mitragynine and kratom, whereas 7-hydroxymitragynine itself, at sufficiently high doses administered exogenously, shares many of the same abuse- and dependence-related behavioral effects associated with traditional opioid agonists. The apparent low efficacy of kratom products and mitragynine at mu-opioid receptors supports the development of these ligands as effective and potentially safe medications for opioid use disorder.
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Affiliation(s)
- Takato Hiranita
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, United States
| | - Samuel Obeng
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, United States; Department of Medicinal Chemistry, College of Pharmacy, University of Florida, Gainesville, FL, United States
| | - Abhisheak Sharma
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, United States; Translational Drug Development Core, Clinical and Translational Sciences Institute, College of Pharmacy, University of Florida, Gainesville, FL, United States
| | - Jenny L Wilkerson
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, United States
| | - Christopher R McCurdy
- Department of Medicinal Chemistry, College of Pharmacy, University of Florida, Gainesville, FL, United States; Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, United States; Translational Drug Development Core, Clinical and Translational Sciences Institute, College of Pharmacy, University of Florida, Gainesville, FL, United States
| | - Lance R McMahon
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, United States.
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Casanovas M, Jiménez-Rosés M, Cordomí A, Lillo A, Vega-Quiroga I, Izquierdo J, Medrano M, Gysling K, Pardo L, Navarro G, Franco R. Discovery of a macromolecular complex mediating the hunger suppressive actions of cocaine: Structural and functional properties. Addict Biol 2021; 26:e13017. [PMID: 33559278 DOI: 10.1111/adb.13017] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 01/14/2021] [Accepted: 01/18/2021] [Indexed: 12/16/2022]
Abstract
Cocaine not only increases brain dopamine levels but also activates the sigma1 receptor (σ1 R) that in turn regulates orexigenic receptor function. Identification of interactions involving dopamine D1 (D1 R), ghrelin (GHS-R1a ), and σ1 receptors have been addressed by biophysical techniques and a complementation approach using interfering peptides. The effect of cocaine on receptor functionality was assayed by measuring second messenger, cAMP and Ca2+ , levels. The effect of acute or chronic cocaine administration on receptor complex expression was assayed by in situ proximity ligation assay. In silico procedures were used for molecular model building. σ1 R KO mice were used for confirming involvement of this receptor. Upon identification of protomer interaction and receptor functionality, a unique structural model for the macromolecular complex formed by σ1 R, D1 R, and GHS-R1a is proposed. The functionality of the complex, able to couple to both Gs and Gq proteins, is affected by cocaine binding to the σ1 R, as confirmed using samples from σ1 R-/- mice. The expression of the macromolecular complex was differentially affected upon acute and chronic cocaine administration to rats. The constructed 3D model is consistent with biochemical, biophysical, and available structural data. The σ1 R, D1 R, and GHS-R1a complex constitutes a functional unit that is altered upon cocaine binding to the σ1 R. Remarkably, the heteromer can simultaneously couple to two G proteins, thus allowing dopamine to signal via Ca2+ and ghrelin via cAMP. The anorexic action of cocaine is mediated by such complex whose expression is higher after acute than after chronic administration regimens.
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Affiliation(s)
- Mireia Casanovas
- Department of Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red, Enfermedades Neurodegenerativas, Instituto de Salud Carlos III, Madrid, Spain
| | - Mireia Jiménez-Rosés
- Laboratory of Computational Medicine, Biostatistics Unit, Faculty of Medicine, Autonomous University of Barcelona, Barcelona, Spain
| | - Arnau Cordomí
- Laboratory of Computational Medicine, Biostatistics Unit, Faculty of Medicine, Autonomous University of Barcelona, Barcelona, Spain
| | - Alejandro Lillo
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Barcelona, Spain
| | - Ignacio Vega-Quiroga
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontifical Catholic University of Chile, Santiago, Chile
| | - Joan Izquierdo
- Department of Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain
| | - Mireia Medrano
- Department of Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Katia Gysling
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontifical Catholic University of Chile, Santiago, Chile
| | - Leonardo Pardo
- Laboratory of Computational Medicine, Biostatistics Unit, Faculty of Medicine, Autonomous University of Barcelona, Barcelona, Spain
| | - Gemma Navarro
- Centro de Investigación Biomédica en Red, Enfermedades Neurodegenerativas, Instituto de Salud Carlos III, Madrid, Spain
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Barcelona, Spain
| | - Rafael Franco
- Department of Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red, Enfermedades Neurodegenerativas, Instituto de Salud Carlos III, Madrid, Spain
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3
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Casanovas M, Reyes-Resina I, Lillo A, Lillo J, López-Arnau R, Camarasa J, Escubedo E, Navarro G, Franco R. Methamphetamine Blocks Adenosine A 2A Receptor Activation via Sigma 1 and Cannabinoid CB 1 Receptors. Int J Mol Sci 2021; 22:2743. [PMID: 33803075 PMCID: PMC7963146 DOI: 10.3390/ijms22052743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 03/01/2021] [Indexed: 11/16/2022] Open
Abstract
Methamphetamine is, worldwide, one of the most consumed drugs of abuse. One important side effect is neurodegeneration leading to a decrease in life expectancy. The aim of this paper was to check whether the drug affects one of the receptors involved in neurodegeneration/neuroprotection events, namely the adenosine A2A receptor (A2AR). First, we noticed that methamphetamine does not affect A2A functionality if the receptor is expressed in a heterologous system. However, A2AR becomes sensitive to the drug upon complexes formation with the cannabinoid CB1 receptor (CB1R) and the sigma 1 receptor (σ1R). Signaling via both adenosine A2AR and cannabinoid CB1R was affected by methamphetamine in cells co-expressing the two receptors. In striatal primary cultures, the A2AR-CB1R heteromer complex was detected and methamphetamine not only altered its expression but completely blocked the A2AR- and the CB1R-mediated activation of the mitogen activated protein kinase (MAPK) pathway. In conclusion, methamphetamine, with the participation of σ1R, alters the expression and function of two interacting receptors, A2AR, which is a therapeutic target for neuroprotection, and CB1R, which is the most abundant G protein-coupled receptor (GPCR) in the brain.
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Affiliation(s)
- Mireia Casanovas
- Biology School, Department of Biochemistry and Molecular Biomedicine, University of Barcelona, 08028 Barcelona, Spain; (M.C.); (I.R.-R.); (J.L.)
- Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CiberNed), Instituto de Salud Carlos III, 28031 Madrid, Spain
| | - Irene Reyes-Resina
- Biology School, Department of Biochemistry and Molecular Biomedicine, University of Barcelona, 08028 Barcelona, Spain; (M.C.); (I.R.-R.); (J.L.)
| | - Alejandro Lillo
- Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028 Barcelona, Spain;
| | - Jaume Lillo
- Biology School, Department of Biochemistry and Molecular Biomedicine, University of Barcelona, 08028 Barcelona, Spain; (M.C.); (I.R.-R.); (J.L.)
- Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CiberNed), Instituto de Salud Carlos III, 28031 Madrid, Spain
| | - Raul López-Arnau
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, Institute of Biomedicine (IBUB), University of Barcelona, 08028 Barcelona, Spain; (R.L.-A.); (J.C.); (E.E.)
| | - Jorge Camarasa
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, Institute of Biomedicine (IBUB), University of Barcelona, 08028 Barcelona, Spain; (R.L.-A.); (J.C.); (E.E.)
| | - Elena Escubedo
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, Institute of Biomedicine (IBUB), University of Barcelona, 08028 Barcelona, Spain; (R.L.-A.); (J.C.); (E.E.)
| | - Gemma Navarro
- Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CiberNed), Instituto de Salud Carlos III, 28031 Madrid, Spain
- Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028 Barcelona, Spain;
| | - Rafael Franco
- Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CiberNed), Instituto de Salud Carlos III, 28031 Madrid, Spain
- Chemistry School, Department of Biochemistry and Molecular Biomedicine, University of Barcelona, 08028 Barcelona, Spain
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Agha H, McCurdy CR. In vitro and in vivo sigma 1 receptor imaging studies in different disease states. RSC Med Chem 2021; 12:154-177. [PMID: 34046607 PMCID: PMC8127618 DOI: 10.1039/d0md00186d] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/02/2020] [Indexed: 12/11/2022] Open
Abstract
The sigma receptor system has been classified into two distinct subtypes, sigma 1 (σ1R) and sigma 2 (σ2R). Sigma 1 receptors (σ1Rs) are involved in many neurodegenerative diseases and different central nervous system disorders such as Alzheimer's disease, Parkinson's disease, schizophrenia, and drug addiction, and pain. This makes them attractive targets for developing radioligands as tools to gain a better understanding of disease pathophysiology and clinical diagnosis. Over the years, several σ1R radioligands have been developed to image the changes in σ1R distribution and density providing insights into their role in disease development. Moreover, the involvement of both σ1Rs and σ2Rs with cancer make these ligands, especially those that are σ2R selective, great tools for imaging different types of tumors. This review will discuss the principles of molecular imaging using PET and SPECT, known σ1R radioligands and their applications for labelling σ1Rs under different disease conditions. Furthermore, this review will highlight σ1R radioligands that have demonstrated considerable potential as biomarkers, and an opportunity to fulfill the ultimate goal of better healthcare outcomes and improving human health.
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Affiliation(s)
- Hebaalla Agha
- Department of Medicinal Chemistry, College of Pharmacy, University of Florida Gainesville FL 32610 USA +(352) 273 7705 +1 (352) 294 8691
| | - Christopher R McCurdy
- Department of Medicinal Chemistry, College of Pharmacy, University of Florida Gainesville FL 32610 USA +(352) 273 7705 +1 (352) 294 8691
- UF Translational Drug Development Core, University of Florida Gainesville FL 32610 USA
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5
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Szczepańska K, Kuder KJ, Kieć-Kononowicz K. Dual-targeting Approach on Histamine H 3 and Sigma-1 Receptor Ligands as Promising Pharmacological Tools in the Treatment of CNS-linked Disorders. Curr Med Chem 2021; 28:2974-2995. [PMID: 32767910 DOI: 10.2174/0929867327666200806103144] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 07/16/2020] [Accepted: 07/16/2020] [Indexed: 11/22/2022]
Abstract
With the recent market approval of Pitolisant (Wakix®), the interest in clinical application for novel multifunctional histamine H3 receptor antagonists has clearly increased. Several combinations of different H3R pharmacophores with pharmacophoric elements of other G-protein coupled receptors, transporters, or enzymes have been synthesized by numerous pharmaceutical companies and academic institutions. Since central nervous system disorders are characterized by diverse physiological dysfunctions and deregulations of a complex network of signaling pathways, optimal multipotent drugs should simultaneously and peculiarly modulate selected groups of biological targets. Interestingly, very recent studies have shown that some clinically evaluated histamine H3 receptor antagonists possess a nanomolar affinity for sigma-1 receptor binding sites, suggesting that this property might play a role in their overall efficacy. The sigma-1 receptor, unusual and yet obscure protein, is supposed to be involved in numerous CNS pathologies through neuroprotection and neuroplasticity. These two different biological structures, histamine H3 and sigma-1 receptors, combined, can represent a potential fruitful target for therapeutic developments in tackling numerous human diseases.
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Affiliation(s)
- Katarzyna Szczepańska
- Department of Technology and Biotechnology of Drugs, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Krakow 30-688, Poland
| | - Kamil J Kuder
- Department of Technology and Biotechnology of Drugs, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Krakow 30-688, Poland
| | - Katarzyna Kieć-Kononowicz
- Department of Technology and Biotechnology of Drugs, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Krakow 30-688, Poland
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6
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Hong WC. Distinct Regulation of σ 1 Receptor Multimerization by Its Agonists and Antagonists in Transfected Cells and Rat Liver Membranes. J Pharmacol Exp Ther 2020; 373:290-301. [PMID: 32060048 DOI: 10.1124/jpet.119.262790] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 02/04/2020] [Indexed: 11/22/2022] Open
Abstract
Extensive studies have shown that the σ 1 receptor (σ 1R) interacts with and modulates the activity of multiple proteins with important biological functions. Recent crystal structures of σ 1R as a homotrimer differ from a dimer-tetramer model postulated earlier. It remains inconclusive whether ligand binding regulates σ 1R oligomerization. Here, novel nondenaturing gel methods and mutational analysis were used to examine σ 1R oligomerization. In transfected cells, σ 1R exhibited as multimers, dimers, and monomers. Overall, σ 1R agonists decreased, whereas σ 1R antagonists increased σ 1R multimers, suggesting that agonists and antagonists differentially affect the stability of σ 1R multimers. Endogenous σ 1R in rat liver membranes also showed similar regulation of oligomerization as in cells. Mutations at key residues lining the trimerization interface (Arg119, Asp195, Phe191, Trp136, and Gly91) abolished multimerization without disrupting dimerization. Intriguingly, truncation of the N terminus reduced σ 1R to apparent monomer. These results demonstrate that multiple domains play crucial roles in coordinating high-order quaternary organization of σ 1R. The E102Q σ 1R mutant implicated in juvenile amyotrophic lateral sclerosis formed dimers only, suggesting that dysregulation of σ 1R multimeric assembly may impair its function. Interestingly, oligomerization of σ 1R was pH-dependent and correlated with changes in [3H](+)-pentazocine binding affinity and Bmax Combined with mutational analysis, it is reasoned that σ 1R multimers possess high-affinity and high-capacity [3H](+)-pentazocine binding, whereas monomers likely lack binding. These results suggest that σ 1R may exist in interconvertible oligomeric states in a dynamic equilibrium. Further exploration of ligand-regulated σ 1R multimerization may provide novel approaches to modulate the function of σ 1R and its interacting proteins. SIGNIFICANCE STATEMENT: The σ 1 receptor (σ 1R) modulates the activities of various partner proteins. Recently, crystal structures of σ 1R were elucidated as homotrimers. This study used novel nondenaturing gel methods to examine σ1R oligomerization in transfected cells and rat liver membranes. Overall, agonist binding decreased, whereas antagonist binding increased σ 1R multimers, which comprised trimers and larger units. σ 1R multimers were shown to bind [3H](+)-pentazocine with high affinity and high capacity. Furthermore, mutational analysis revealed a crucial role of its N-terminal domain in σ 1R multimerization.
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Affiliation(s)
- Weimin Conrad Hong
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana
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7
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Yano H, Liu L, Naing S, Shi L. The Effects of Terminal Tagging on Homomeric Interactions of the Sigma 1 Receptor. Front Neurosci 2019; 13:1356. [PMID: 31920515 PMCID: PMC6930887 DOI: 10.3389/fnins.2019.01356] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 12/02/2019] [Indexed: 11/13/2022] Open
Abstract
The sigma 1 receptor (σ1R) has been implicated in cancers, neurological disorders, and substance use disorders. Yet, its molecular and cellular functions have not been well-understood. Recent crystal structures of σ1R reveal a single N-terminal transmembrane segment and C-terminal ligand-binding domain, and a trimeric organization. Nevertheless, outstanding issues surrounding the functional or pharmacological relevance of σ1R oligomerization remain, such as the minimal protomeric unit and the differentially altered oligomerization states by different classes of ligands. Western blot (WB) assays have been widely used to investigate protein oligomerizations. However, the unique topology of σ1R renders several intertwined challenges in WB. Here we describe a WB protocol without temperature denaturization to study the ligand binding effects on the oligomerization state of σ1R. Using this approach, we observed unexpected ladder-like incremental migration pattern of σ1R, demonstrating preserved homomeric interactions in the detergent environment. We compared the migration patterns of intact σ1R construct and the C-terminally tagged σ1R constructs, and found similar trends in response to drug treatments. In contrast, N-terminally tagged σ1R constructs show opposite trends to that of the intact construct, suggesting distorted elicitation of the ligand binding effects on oligomerization. Together, our findings indicate that the N-terminus plays an important role in eliciting the impacts of bound ligands, whereas the C-terminus is amenable for modifications for biochemical studies.
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Affiliation(s)
- Hideaki Yano
- Computational Chemistry and Molecular Biophysics Unit, National Institute on Drug Abuse - Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Leanne Liu
- Computational Chemistry and Molecular Biophysics Unit, National Institute on Drug Abuse - Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Sett Naing
- Computational Chemistry and Molecular Biophysics Unit, National Institute on Drug Abuse - Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Unit, National Institute on Drug Abuse - Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
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Job MO, Katz JL. A behavioral economic analysis of the effects of rimcazole on reinforcing effects of cocaine injection and food presentation in rats. Psychopharmacology (Berl) 2019; 236:3601-3612. [PMID: 31399853 PMCID: PMC6895418 DOI: 10.1007/s00213-019-05332-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 07/10/2019] [Indexed: 11/27/2022]
Abstract
RATIONALE AND OBJECTIVES Rimcazole, a σ-receptor antagonist with affinity for the dopamine transporter (DAT), decreases rates of cocaine self-administration at doses lower than those that affect food-reinforced responding. As response rates are multiply determined, behavioral-economic analyses were used to provide measures of the reinforcing effectiveness of cocaine and food after rimcazole treatment. Further, effects of combinations of the DAT inhibitor, methylphenidate, and σ-receptor antagonists (BD1008, BD1063) were compared to those of rimcazole to assess mechanism of rimcazole effects. METHODS Male Sprague-Dawley rats were trained to lever press with food reinforcement (one or three 20-mg sucrose pellets) or cocaine injection (0.1 or 0.32 mg/kg) under fixed-ratio (FR) 5-response schedules. Drugs or vehicle were administered (i.p.) 5-min before sessions in which FR value was increased from 5 to 80. Economic demand functions were generated from effects of FR value (price) on intake (consumption), with the parameters of demand, consumption at no cost (Q0) and sensitivity to price (essential value, EV), derived. RESULTS Rimcazole dose-dependently decreased Q0 and EV at both cocaine doses/injection. In contrast, rimcazole had no effect on these parameters at either food amount. Combinations of methylphenidate and the σ-receptor antagonists decreased Q0 at the lower cocaine dose/injection but had no effect on EV; these treatments were ineffective on both economic parameters at the higher cocaine dose/injection and at either food amount. CONCLUSIONS Though the drug combinations only replicated rimcazole's effects incompletely, the present results suggest a specific decrease in the reinforcing effects of cocaine due to dual DAT σ-receptor blockade.
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Affiliation(s)
- Martin O Job
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 251 Bayview Boulevard, Baltimore, MD, 21224, USA
| | - Jonathan L Katz
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 251 Bayview Boulevard, Baltimore, MD, 21224, USA.
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Oyer HM, Sanders CM, Kim FJ. Small-Molecule Modulators of Sigma1 and Sigma2/TMEM97 in the Context of Cancer: Foundational Concepts and Emerging Themes. Front Pharmacol 2019; 10:1141. [PMID: 31695608 PMCID: PMC6816035 DOI: 10.3389/fphar.2019.01141] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 09/04/2019] [Indexed: 12/17/2022] Open
Abstract
There are two known subtypes of the so-called sigma receptors, Sigma1 and Sigma2. Sigma1 (encoded by the SIGMAR1 gene and also known as Sigma-1 receptor, S1R) is a unique pharmacologically regulated integral membrane chaperone or scaffolding protein that allosterically modulates the activity of its associated proteins. Sigma2, recently identified as transmembrane protein 97 (TMEM97), is an integral membrane protein implicated in cellular cholesterol homeostasis. A number of publications over the past two decades have suggested a role for both sigma proteins in tumor biology. Although there is currently no clinically used anti-cancer drug that targets Sigma1 or Sigma2/TMEM97, a growing body of evidence supports the potential of small-molecule compounds with affinity for these proteins, putative sigma ligands, as therapeutic agents to treat cancer. In preclinical models, these compounds have been reported to inhibit cancer cell proliferation, survival, adhesion, and migration; furthermore, they have been demonstrated to suppress tumor growth, to alleviate cancer-associated pain, and to exert immunomodulatory properties. Here, we will address the known knowns and the known unknowns of Sigma1 and Sigma2/TMEM97 ligand actions in the context of cancer. This review will highlight key discoveries and published evidence in support of a role for sigma proteins in cancer and will discuss several fundamental questions regarding the physiological roles of sigma proteins in cancer and sigma ligand mechanism of action.
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Affiliation(s)
- Halley M Oyer
- Department of Cancer Biology, Sidney Kimmel Cancer Center at Thomas Jefferson University, Philadelphia, PA, United States
| | - Christina M Sanders
- Department of Cancer Biology, Sidney Kimmel Cancer Center at Thomas Jefferson University, Philadelphia, PA, United States
| | - Felix J Kim
- Department of Cancer Biology, Sidney Kimmel Cancer Center at Thomas Jefferson University, Philadelphia, PA, United States
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10
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Romero L, Portillo-Salido E. Trends in Sigma-1 Receptor Research: A 25-Year Bibliometric Analysis. Front Pharmacol 2019; 10:564. [PMID: 31178733 PMCID: PMC6543269 DOI: 10.3389/fphar.2019.00564] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 05/06/2019] [Indexed: 12/14/2022] Open
Abstract
Purpose: There are previous reviews focused on Sigma-1 receptor but no bibliometric studies examining this field as a whole. This article aims to present a global view of Sigma-1 receptor research and its intellectual structure. Methods: We used bibliometric indicators of a basic nature as well as techniques for the visualization and analysis of networks of scientific information extracted from Scopus database. Results: In total, 1,102 articles from 1992 to 2017 were identified. The growth in the production of articles is not constant over time, with periods of stagnation of approximately 5 years. Only 247 authors have five or more publications. The authors appear grouped in relatively independent clusters, thus suggesting a low level of collaborations between those dedicated to the Sigma-1 receptor. The United States was the country with the highest production followed by Japan and Germany. Spain, Japan, and Italy showed the highest per million inhabitants ratio. The highest citation/article ratio was reached in France, United States, and Canada. The leading institutions were the University of Münster, the National Institutes of Health, ESTEVE, and INSERM. The top authors in number of publications were Wünsch-B, Schepmann-D, and Maurice-T. Hayashi-T, Su-TP and Bowen-WD showed the highest citations per article. The article by Hayashi-T and Su-TP in Cell (2007) describing the Sigma-1 receptor as a chaperone protein is the top cited reference. Cluster labeling from author co-citation analysis shows that research has been focused on specific diseases such as addiction, neuroprotection and neurodegenerative diseases, psychiatric disorders, and pain. High-frequency terms in author keywords suggest that the research efforts in some areas such as neuroimaging, cocaine addiction or psychiatric disorders have declined over time, while others such as neurodegenerative diseases or pain are currently most popular. Perspective: A greater involvement of the scientific community, with an increase in the scientific production related to Sigma-1, is desirable. Additional boost needed to improve research performance is likely to come from combining data from different laboratories to overcome the limitations of individual approaches. The resulting maps are a useful and attractive tool for the Sigma-1 receptor research community, as they reveal the main lines of exploration at a glance.
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Affiliation(s)
- Luz Romero
- Drug Discovery and Preclinical Development, Esteve Pharmaceuticals, Parc Científic de Barcelona, Barcelona, Spain
| | - Enrique Portillo-Salido
- Drug Discovery and Preclinical Development, Esteve Pharmaceuticals, Parc Científic de Barcelona, Barcelona, Spain
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Tomlinson MJ, Krout D, Pramod AB, Lever JR, Newman AH, Henry LK, Vaughan RA. Identification of the benztropine analog [ 125I]GA II 34 binding site on the human dopamine transporter. Neurochem Int 2018; 123:34-45. [PMID: 30125594 DOI: 10.1016/j.neuint.2018.08.008] [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] [Received: 06/01/2018] [Revised: 08/10/2018] [Accepted: 08/14/2018] [Indexed: 12/21/2022]
Abstract
The dopamine transporter (DAT) is a neuronal membrane protein that is responsible for reuptake of dopamine (DA) from the synapse and functions as a major determinant in control of DA neurotransmission. Cocaine and many psychostimulant drugs bind to DAT and block reuptake, inducing DA overflow that forms the neurochemical basis for euphoria and addiction. Paradoxically, however, some ligands such as benztropine (BZT) bind to DAT and inhibit reuptake but do not produce these effects, and it has been hypothesized that differential mechanisms of binding may stabilize specific transporter conformations that affect downstream neurochemical or behavioral outcomes. To investigate the binding mechanisms of BZT on DAT we used the photoaffinity BZT analog [125I]N-[n-butyl-4-(4‴-azido-3‴-iodophenyl)]-4',4″-difluoro-3α-(diphenylmethoxy)tropane ([125I]GA II 34) to identify the site of cross-linking and predict the binding pose relative to that of previously-examined cocaine photoaffinity analogs. Biochemical findings show that adduction of [125I]GA II 34 occurs at residues Asp79 or Leu80 in TM1, with molecular modeling supporting adduction to Leu80 and a pharmacophore pose in the central S1 site similar to that of cocaine and cocaine analogs. Substituted cysteine accessibility method protection analyses verified these findings, but identified some differences in structural stabilization relative to cocaine that may relate to BZT neurochemical outcomes.
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Affiliation(s)
- Michael J Tomlinson
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, United States
| | - Danielle Krout
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, United States
| | - Akula Bala Pramod
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, United States
| | - John R Lever
- Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, 65201, United States; Department of Radiology and Radiopharmaceutical Sciences Institute, University of Missouri, Columbia, MO 65211, United States
| | - Amy Hauck Newman
- Medicinal Chemistry Section, National Institute on Drug Abuse - Intramural Research Program, Baltimore, MD 21224, United States
| | - L Keith Henry
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, United States.
| | - Roxanne A Vaughan
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, ND 58202, United States.
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Hong WC, Wasko MJ, Wilkinson DS, Hiranita T, Li L, Hayashi S, Snell DB, Madura JD, Surratt CK, Katz JL. Dopamine Transporter Dynamics of N-Substituted Benztropine Analogs with Atypical Behavioral Effects. J Pharmacol Exp Ther 2018; 366:527-540. [PMID: 29945932 DOI: 10.1124/jpet.118.250498] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 06/22/2018] [Indexed: 01/07/2023] Open
Abstract
Atypical dopamine transporter (DAT) inhibitors, despite high DAT affinity, do not produce the psychomotor stimulant and abuse profile of standard DAT inhibitors such as cocaine. Proposed contributing features for those differences include off-target actions, slow onsets of action, and ligand bias regarding DAT conformation. Several 3α-(4',4''-difluoro-diphenylmethoxy)tropanes were examined, including those with the following substitutions: N-(indole-3''-ethyl)- (GA1-69), N-(R)-2''-amino-3''-methyl-n-butyl- (GA2-50), N-2''aminoethyl- (GA2-99), and N-(cyclopropylmethyl)- (JHW013). These compounds were previously reported to have rapid onset of behavioral effects and were presently evaluated pharmacologically alone or in combination with cocaine. DAT conformational mode was assessed by substituted-cysteine accessibility and molecular dynamics (MD) simulations. As determined by substituted-cysteine alkylation, all BZT analogs except GA2-99 showed bias for a cytoplasmic-facing DAT conformation, whereas cocaine stabilized the extracellular-facing conformation. MD simulations suggested that several analog-DAT complexes formed stable R85-D476 "outer gate" bonds that close the DAT to extracellular space. GA2-99 diverged from this pattern, yet had effects similar to those of other atypical DAT inhibitors. Apparent DAT association rates of the BZT analogs in vivo were slower than that for cocaine. None of the compounds was self-administered or stimulated locomotion, and each blocked those effects of cocaine. The present findings provide more detail on ligand-induced DAT conformations and indicate that aspects of DAT conformation other than "open" versus "closed" may facilitate predictions of the actions of DAT inhibitors and may promote rational design of potential treatments for psychomotor-stimulant abuse.
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Affiliation(s)
- Weimin C Hong
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Michael J Wasko
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Derek S Wilkinson
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Takato Hiranita
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Libin Li
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Shuichiro Hayashi
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - David B Snell
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Jeffry D Madura
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Christopher K Surratt
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Jonathan L Katz
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
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13
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Yano H, Bonifazi A, Xu M, Guthrie DA, Schneck SN, Abramyan AM, Fant AD, Hong WC, Newman AH, Shi L. Pharmacological profiling of sigma 1 receptor ligands by novel receptor homomer assays. Neuropharmacology 2018; 133:264-275. [PMID: 29407216 PMCID: PMC5858991 DOI: 10.1016/j.neuropharm.2018.01.042] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 01/06/2018] [Accepted: 01/29/2018] [Indexed: 12/20/2022]
Abstract
The sigma 1 receptor (σ1R) is a structurally unique transmembrane protein that functions as a molecular chaperone in the endoplasmic reticulum (ER), and has been implicated in cancer, neuropathic pain, and psychostimulant abuse. Despite physiological and pharmacological significance, mechanistic underpinnings of structure-function relationships of σ1R are poorly understood, and molecular interactions of selective ligands with σ1R have not been elucidated. The recent crystallographic determination of σ1R as a homo-trimer provides the foundation for mechanistic elucidation at the molecular level. Here we report novel bioluminescence resonance energy transfer (BRET) assays that enable analyses of ligand-induced multimerization of σ1R and its interaction with BiP. Haloperidol, PD144418, and 4-PPBP enhanced σ1R homomer BRET signals in a dose dependent manner, suggesting their significant effects in stabilizing σ1R multimerization, whereas (+)-pentazocine and several other ligands do not. In non-denaturing gels, (+)-pentazocine significantly decreased whereas haloperidol increased the fraction of σ1R multimers, consistent with the results from the homomer BRET assay. Further, BRET assays examining heteromeric σ1R-BiP interaction revealed that (+)-pentazocine and haloperidol induced opposite trends of signals. From molecular modeling and simulations of σ1R in complex with the tested ligands, we identified initial clues that may lead to the differed responses of σ1R upon binding of structurally diverse ligands. By combining multiple in vitro pharmacological and in silico molecular biophysical methods, we propose a novel integrative approach to analyze σ1R-ligand binding and its impact on interaction of σ1R with client proteins.
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Affiliation(s)
- Hideaki Yano
- Computational Chemistry and Molecular Biophysics Unit, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institute of Health, 333 Cassell Drive, Baltimore, MD 21224, USA.
| | - Alessandro Bonifazi
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institute of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Min Xu
- Computational Chemistry and Molecular Biophysics Unit, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institute of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Daryl A Guthrie
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institute of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Stephanie N Schneck
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, IN 46208, USA
| | - Ara M Abramyan
- Computational Chemistry and Molecular Biophysics Unit, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institute of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Andrew D Fant
- Computational Chemistry and Molecular Biophysics Unit, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institute of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - W Conrad Hong
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, IN 46208, USA
| | - Amy H Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institute of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Unit, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institute of Health, 333 Cassell Drive, Baltimore, MD 21224, USA.
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14
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Hiranita T, Hong WC, Kopajtic T, Katz JL. σ Receptor Effects of N-Substituted Benztropine Analogs: Implications for Antagonism of Cocaine Self-Administration. J Pharmacol Exp Ther 2017; 362:2-13. [PMID: 28442581 PMCID: PMC5454590 DOI: 10.1124/jpet.117.241109] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 04/20/2017] [Indexed: 11/22/2022] Open
Abstract
Several N-substituted benztropine (BZT) analogs are atypical dopamine transport inhibitors as they have affinity for the dopamine transporter (DAT) but have minimal cocaine-like pharmacologic effects and can block numerous effects of cocaine, including its self-administration. Among these compounds, N-methyl (AHN1-055), N-allyl (AHN2-005), and N-butyl (JHW007) analogs of 3α-[bis(4'-fluorophenyl)methoxy]-tropane were more potent in antagonizing self-administration of cocaine and d-methamphetamine than in decreasing food-maintained responding. The antagonism of cocaine self-administration (0.03-1.0 mg/kg per injection) with the above BZT analogs was reproduced in the present study. Further, the stimulant-antagonist effects resembled previously reported effects of pretreatments with combinations of standard DAT inhibitors and σ1-receptor (σ1R) antagonists. Therefore, the present study examined binding of the BZT analogs to σRs, as well as their in vivo σR antagonist effects. Each of the BZT analogs displaced radiolabeled σR ligands with nanomolar affinity. Further, self-administration of the σR agonist DTG (0.1-3.2 mg/kg/injection) was dose dependently blocked by AHN2-005 and JHW007 but potentiated by AHN1-055. In contrast, none of the BZT analogs that were active against DTG self-administration was active against the self-administration of agonists at dopamine D1-like [R(+)-SKF 81297, (±)-SKF 82958 (0.00032-0.01 mg/kg per injection each)], D2-like [R(-)-NPA (0.0001-0.0032 mg/kg per injection), (-)-quinpirole (0.0032-0.1 mg/kg per injection)], or μ-opioid (remifentanil, 0.0001-0.0032 mg/kg per injection) receptors. The present results indicate that behavioral antagonist effects of the N-substituted BZT analogs are specific for abused drugs acting at the DAT and further suggest that σR antagonism contributes to those actions.
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Affiliation(s)
- Takato Hiranita
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health (T.H., T.K., J.L.K.), and Department of Pharmaceutical Sciences, Butler University (W.C.H.), Indianapolis, Indiana
| | - Weimin C Hong
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health (T.H., T.K., J.L.K.), and Department of Pharmaceutical Sciences, Butler University (W.C.H.), Indianapolis, Indiana
| | - Theresa Kopajtic
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health (T.H., T.K., J.L.K.), and Department of Pharmaceutical Sciences, Butler University (W.C.H.), Indianapolis, Indiana
| | - Jonathan L Katz
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health (T.H., T.K., J.L.K.), and Department of Pharmaceutical Sciences, Butler University (W.C.H.), Indianapolis, Indiana
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15
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Abstract
For over 40 years, scientists have endeavored to understand the so-called sigma receptors. During this time, the concept of sigma receptors has continuously and significantly evolved. With thousands of publications on the subject, these proteins have been implicated in various diseases, disorders, and physiological processes. Nevertheless, we are just beginning to understand what sigma proteins do and how they work. Two subtypes have been identified, Sigma1 and Sigma2. Whereas Sigma1 (also known as sigma-1 receptor, Sig1R, σ1 receptor, and several other names) was cloned over 20 years ago, Sigma2 (sigma-2 receptor, σ2 receptor) was cloned very recently and had remained a pharmacologically defined entity. In this volume, we will focus primarily on Sigma1. We will highlight several key subject areas in which Sigma1 has been well characterized as well as (re)emerging areas of interest. Despite the large number of publications regarding Sigma1, several fundamental questions remain unanswered or only partially answered. Most of what we know about Sigma1 comes from pharmacological studies; however, a clearly defined molecular mechanism of action remains elusive. One concept has become clear; Sigma1 is not a traditional receptor. Sigma1 is now considered a unique pharmacologically regulated integral membrane chaperone or scaffolding protein. A number of landmark discoveries over the past decade have begun to reshape the concept of sigma receptors. With the rapid emergence of new information, development of new tools, and changing conceptual frameworks, the field is poised for a period of accelerated progress.
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Affiliation(s)
- Felix J Kim
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, USA.
- Sidney Kimmel Cancer Center, Philadelphia, PA, USA.
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