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Knippenberg N, Lowdon JW, Frigoli M, Cleij TJ, Eersels K, van Grinsven B, Diliën H. Development towards a novel screening method for nipecotic acid bioisosteres using molecular imprinted polymers (MIPs) as alternative to in vitro cellular uptake assays. Talanta 2024; 278:126500. [PMID: 38991407 DOI: 10.1016/j.talanta.2024.126500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 06/12/2024] [Accepted: 06/29/2024] [Indexed: 07/13/2024]
Abstract
Impaired expression of GABA transporters (GATs) is closely related to the pathogenesis of among others Parkinson's disease and epilepsy. As such, lipophilic nipecotic acid analogs have been extensively studied as GAT1-addressing drugs and radioligands but suffer from limited brain uptake due to the zwitterionic properties of the nipecotic acid moiety. Bioisosteric replacement of the carboxylic acid group is a promising strategy to improve the brain uptake, though it requires knowledge on the binding of these isosteres to GAT1. To screen nipecotic acid isosteres for their affinity to GAT1 in a time- and cost-effective manner, this research aims to develop a molecular imprinted polymer (MIP) that mimics the natural binding site of GAT1 and can act as an alternative screening tool to the current radiometric and mass spectrometry cellular-based assays. To this end, a nipecotic acid MIP was created using the electropolymerization of ortho-phenylenediamine (oPD) by cyclic voltammetry (CV). The optimization of the generated receptor layer was achieved by varying the scan rate (50-250 mV/s) and number of CV cycles (5-12), yielding an optimized MIP with an average imprinting factor of 2.6, a linear range of 1-1000 nm, and a theoretical LOD of 0.05 nm, as analyzed by electrical impedance spectroscopy (EIS). Selectivity studies facilitated the investigation of major binding interactions between the MIP and the substrate, building an experimental model that compares characteristics of various analogs. Results from this model indicate that the substrate carboxylic acid group plays a more important role in binding than an amine group, after comparing the binding of cyclohexanecarboxylic acid (average IF of 1.7) and piperidine (average IF of 0.46). The research culminates in a discussion regarding the feasibility of the in vitro model, comparing the synthetic system against the biological performance of GAT1. Thus, evaluating if it is possible to generate a synthetic GAT1 mimic, and if so, provide directions for follow-up research.
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Affiliation(s)
- Niels Knippenberg
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, the Netherlands.
| | - Joseph W Lowdon
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, the Netherlands
| | - Margaux Frigoli
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, the Netherlands
| | - Thomas J Cleij
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, the Netherlands
| | - Kasper Eersels
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, the Netherlands
| | - Bart van Grinsven
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, the Netherlands
| | - Hanne Diliën
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, the Netherlands
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2
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Knippenberg N, Bauwens M, Schijns O, Hoogland G, Florea A, Rijkers K, Cleij TJ, Eersels K, van Grinsven B, Diliën H. Visualizing GABA transporters in vivo: an overview of reported radioligands and future directions. EJNMMI Res 2023; 13:42. [PMID: 37171631 PMCID: PMC10182260 DOI: 10.1186/s13550-023-00992-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 05/02/2023] [Indexed: 05/13/2023] Open
Abstract
By clearing GABA from the synaptic cleft, GABA transporters (GATs) play an essential role in inhibitory neurotransmission. Consequently, in vivo visualization of GATs can be a valuable diagnostic tool and biomarker for various psychiatric and neurological disorders. Not surprisingly, in recent years several research attempts to develop a radioligand have been conducted, but so far none have led to suitable radioligands that allow imaging of GATs. Here, we provide an overview of the radioligands that were developed with a focus on GAT1, since this is the most abundant transporter and most of the research concerns this GAT subtype. Initially, we focus on the field of GAT1 inhibitors, after which we discuss the development of GAT1 radioligands based on these inhibitors. We hypothesize that the radioligands developed so far have been unsuccessful due to the zwitterionic nature of their nipecotic acid moiety. To overcome this problem, the use of non-classical GAT inhibitors as basis for GAT1 radioligands or the use of carboxylic acid bioisosteres may be considered. As the latter structural modification has already been used in the field of GAT1 inhibitors, this option seems particularly viable and could lead to the development of more successful GAT1 radioligands in the future.
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Affiliation(s)
- Niels Knippenberg
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, The Netherlands.
| | - Matthias Bauwens
- Department of Nuclear Medicine, University Hospital Aachen, RWTH Aachen University, 52074, Aachen, Germany
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Centre+ (MUMC+), 6229 HX, Maastricht, The Netherlands
| | - Olaf Schijns
- Department of Neurosurgery, Maastricht University Medical Centre+ (MUMC+), 6229 HX, Maastricht, The Netherlands
- School for Mental Health and Neuroscience (MHeNS), Maastricht University, 6200 MD, Maastricht, The Netherlands
- Academic Center for Epileptology (ACE), Maastricht University Medical Centre+ (MUMC+), 6229 HX, Maastricht, The Netherlands
| | - Govert Hoogland
- Department of Neurosurgery, Maastricht University Medical Centre+ (MUMC+), 6229 HX, Maastricht, The Netherlands
- School for Mental Health and Neuroscience (MHeNS), Maastricht University, 6200 MD, Maastricht, The Netherlands
| | - Alexandru Florea
- Department of Nuclear Medicine, University Hospital Aachen, RWTH Aachen University, 52074, Aachen, Germany
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Centre+ (MUMC+), 6229 HX, Maastricht, The Netherlands
- School for Cardiovascular Diseases (CARIM), Maastricht University Medical Centre+ (MUMC+), 6229 HX, Maastricht, The Netherlands
| | - Kim Rijkers
- Department of Neurosurgery, Maastricht University Medical Centre+ (MUMC+), 6229 HX, Maastricht, The Netherlands
- School for Mental Health and Neuroscience (MHeNS), Maastricht University, 6200 MD, Maastricht, The Netherlands
- Academic Center for Epileptology (ACE), Maastricht University Medical Centre+ (MUMC+), 6229 HX, Maastricht, The Netherlands
| | - Thomas J Cleij
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, The Netherlands
| | - Kasper Eersels
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, The Netherlands
| | - Bart van Grinsven
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, The Netherlands
| | - Hanne Diliën
- Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, 6200 MD, Maastricht, The Netherlands
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3
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Bhatt M, Gauthier-Manuel L, Lazzarin E, Zerlotti R, Ziegler C, Bazzone A, Stockner T, Bossi E. A comparative review on the well-studied GAT1 and the understudied BGT-1 in the brain. Front Physiol 2023; 14:1145973. [PMID: 37123280 PMCID: PMC10137170 DOI: 10.3389/fphys.2023.1145973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/30/2023] [Indexed: 05/02/2023] Open
Abstract
γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system (CNS). Its homeostasis is maintained by neuronal and glial GABA transporters (GATs). The four GATs identified in humans are GAT1 (SLC6A1), GAT2 (SLC6A13), GAT3 (SLC6A11), and betaine/GABA transporter-1 BGT-1 (SLC6A12) which are all members of the solute carrier 6 (SLC6) family of sodium-dependent transporters. While GAT1 has been investigated extensively, the other GABA transporters are less studied and their role in CNS is not clearly defined. Altered GABAergic neurotransmission is involved in different diseases, but the importance of the different transporters remained understudied and limits drug targeting. In this review, the well-studied GABA transporter GAT1 is compared with the less-studied BGT-1 with the aim to leverage the knowledge on GAT1 to shed new light on the open questions concerning BGT-1. The most recent knowledge on transporter structure, functions, expression, and localization is discussed along with their specific role as drug targets for neurological and neurodegenerative disorders. We review and discuss data on the binding sites for Na+, Cl-, substrates, and inhibitors by building on the recent cryo-EM structure of GAT1 to highlight specific molecular determinants of transporter functions. The role of the two proteins in GABA homeostasis is investigated by looking at the transport coupling mechanism, as well as structural and kinetic transport models. Furthermore, we review information on selective inhibitors together with the pharmacophore hypothesis of transporter substrates.
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Affiliation(s)
- Manan Bhatt
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
- Centre for Neuroscience—University of Insubria, Varese, Italy
| | - Laure Gauthier-Manuel
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | - Erika Lazzarin
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstr, Vienna
| | - Rocco Zerlotti
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
- Nanion Technologies GmbH, Munich, Germany
| | - Christine Ziegler
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | | | - Thomas Stockner
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstr, Vienna
- *Correspondence: Thomas Stockner, ; Elena Bossi,
| | - Elena Bossi
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
- Centre for Neuroscience—University of Insubria, Varese, Italy
- *Correspondence: Thomas Stockner, ; Elena Bossi,
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Synthesis and biological evaluation of novel N-substituted nipecotic acid derivatives with tricyclic cage structures in the lipophilic domain as GABA uptake inhibitors. Med Chem Res 2020. [DOI: 10.1007/s00044-020-02647-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
AbstractA new class of GABA reuptake inhibitors with sterically demanding, highly rigid tricyclic cage structures as the lipophilic domain was synthesized and investigated in regard to their biological activity at the murine GABA transporters (mGAT1–mGAT4). The construction of these compounds, consisting of nipecotic acid, a symmetric tricyclic amine, and a plain hydrocarbon linker connecting the two subunits via their amino nitrogens, was accomplished via reductive amination of a nipecotic acid derivative with an N-alkyl substituent displaying a terminal aldehyde function with tricyclic secondary amines. The target compounds varied with regard to spacer length, the bridge size of one of the bridges, and the substituents of the tricyclic skeleton to study the impact of these changes on their potency. Among the tested compounds nipecotic acid ethyl ester derivates with phenyl residues attached to the cage subunit showed reasonable inhibitory potency and subtype selectivity in favor of mGAT3 and mGAT4, respectively.
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5
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Andreß JC, Böck MC, Höfner G, Wanner KT. Synthesis and biological evaluation of α- and β-hydroxy substituted amino acid derivatives as potential mGAT1–4 inhibitors. Med Chem Res 2020. [DOI: 10.1007/s00044-020-02548-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AbstractIn this study, we report the synthesis and biological evaluation of a variety of α- and β-hydroxy substituted amino acid derivatives as potential amino acid subunits in inhibitors of GABA uptake transporters (GATs). In order to ensure that the test compounds adopt a binding pose similar to that presumed for related larger GAT inhibitors, lipophilic residues were introduced either at the amino nitrogen atom or at the alcohol function. Several of the synthesized compounds were found to exhibit similar inhibitory activity at the GAT subtypes mGAT2, mGAT3, and mGAT4, respectively, as compared with the reference N-butylnipecotic acid. Hence, these compounds might serve as starting point for future developments of more complex GAT inhibitors.
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Fu J, Wurzer N, Lehner V, Reiser O, Davies HML. Rh(II)-Catalyzed Monocyclopropanation of Pyrroles and Its Application to the Synthesis Pharmaceutically Relevant Compounds. Org Lett 2019; 21:6102-6106. [DOI: 10.1021/acs.orglett.9b02250] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Jiantao Fu
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
| | - Nikolai Wurzer
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
- Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany
| | - Verena Lehner
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
- Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany
| | - Oliver Reiser
- Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany
| | - Huw M. L. Davies
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States
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Application of the concept of oxime library screening by mass spectrometry (MS) binding assays to pyrrolidine-3-carboxylic acid derivatives as potential inhibitors of γ-aminobutyric acid transporter 1 (GAT1). Bioorg Med Chem 2019; 27:2753-2763. [PMID: 31097402 DOI: 10.1016/j.bmc.2019.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 04/15/2019] [Accepted: 05/01/2019] [Indexed: 11/20/2022]
Abstract
In the present study, the concept of oxime library screening by MS Binding Assays was successfully extended to N-substituted lipophilic pyrrolidine-3-carboxylic acid derivatives in the pursuit of varying the amino acid motif in order to identify new inhibitors for GAT1 and to broaden structure-activity-relationships for this target, the most abundant GABA transporter in the central nervous system. For the screening, 28 different oxime sub-libraries were employed that were generated by simple condensation reaction of an excess of pyrrolidine-3-carboxylic acid derivatives carrying a hydroxylamine functionality with various sub-libraries each assembled of eight aldehydes with broadly varying chemical structures and functionalities. The compounds responsible for the activity of an oxime sub-library were identified by deconvolution experiments performed by employing single oximes. Binding affinities of the oxime hits were confirmed in full-scale competitive MS Binding Assays. Thereby, oxime derivatives with a 1,1'-biphenyl moiety were found as the first inhibitors of mGAT1 comprising a pyrrolidine-3-carboxylic acid motif with affinities in the submicromolar range.
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8
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Kickinger S, Hellsberg E, Frølund B, Schousboe A, Ecker GF, Wellendorph P. Structural and molecular aspects of betaine-GABA transporter 1 (BGT1) and its relation to brain function. Neuropharmacology 2019; 161:107644. [PMID: 31108110 DOI: 10.1016/j.neuropharm.2019.05.021] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 04/14/2019] [Accepted: 05/16/2019] [Indexed: 01/09/2023]
Abstract
ɣ-aminobutyric-acid (GABA) functions as the principal inhibitory neurotransmitter in the central nervous system. Imbalances in GABAergic neurotransmission are involved in the pathophysiology of various neurological diseases such as epilepsy, Alzheimer's disease and stroke. GABA transporters (GATs) facilitate the termination of GABAergic signaling by transporting GABA together with sodium and chloride from the synaptic cleft into presynaptic neurons and surrounding glial cells. Four different GATs have been identified that all belong to the solute carrier 6 (SLC6) transporter family: GAT1-3 (SLC6A1, SLC6A13, SLC6A11) and betaine/GABA transporter 1 (BGT1, SLC6A12). BGT1 has emerged as an interesting target for treating epilepsy due to animal studies that reported anticonvulsant effects for the GAT1/BGT1 selective inhibitor EF1502 and the BGT1 selective inhibitor RPC-425. However, the precise involvement of BGT1 in epilepsy remains elusive because of its controversial expression levels in the brain and the lack of highly selective and potent tool compounds. This review gathers the current structural and functional knowledge on BGT1 with emphasis on brain relevance, discusses all available compounds, and tries to shed light on the molecular determinants driving BGT1 selectivity. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- Stefanie Kickinger
- University of Vienna, Department of Pharmaceutical Chemistry, Althanstrasse 14, 1090, Vienna, Austria
| | - Eva Hellsberg
- University of Vienna, Department of Pharmaceutical Chemistry, Althanstrasse 14, 1090, Vienna, Austria
| | - Bente Frølund
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, 2 Universitetsparken, 2100, Copenhagen, Denmark
| | - Arne Schousboe
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, 2 Universitetsparken, 2100, Copenhagen, Denmark
| | - Gerhard F Ecker
- University of Vienna, Department of Pharmaceutical Chemistry, Althanstrasse 14, 1090, Vienna, Austria
| | - Petrine Wellendorph
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, 2 Universitetsparken, 2100, Copenhagen, Denmark.
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Schaarschmidt M, Höfner G, Wanner KT. Synthesis and Biological Evaluation of Nipecotic Acid and Guvacine Derived 1,3-Disubstituted Allenes as Inhibitors of Murine GABA Transporter mGAT1. ChemMedChem 2019; 14:1135-1151. [PMID: 30957949 DOI: 10.1002/cmdc.201900170] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Indexed: 12/18/2022]
Abstract
A new class of nipecotic acid and guvacine derivatives has been synthesized and characterized for their inhibitory potency at mGAT1-4 and binding affinity for mGAT1. Compounds of the described class are defined by a four-carbon-atom allenyl spacer connecting the nitrogen atom of the nipecotic acid or guvacine head with an aromatic residue. Among the compounds investigated, the mixture of nipecotic acid derivatives rac-{(Ra )-1-[4-([1,1':2',1''-terphenyl]-2-yl)buta-2,3-dien-1-yl](3R)-piperidine-3-carboxylic acid} and rac-{(Sa )-1-[4-([1,1':2',1''-terphenyl]-2-yl)buta-2,3-dien-1-yl](3R)-piperidine-3-carboxylic acid} (21 p), possessing an o-terphenyl residue, was identified as highly selective and the most potent mGAT1 inhibitor in this study. For the (R)-nipecotic acid derived form of 21 p, the inhibitory potency in [3 H]GABA uptake assays was determined as pIC50 =6.78±0.08, and the binding affinity in MS Binding Assays as pKi =7.10±0.12. The synthesis of the designed compounds was carried out by a two-step procedure, generating the allene moiety via allenylation of terminal alkynes which allows broad variation of the terminal phenyl and biphenyl subunit.
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Affiliation(s)
- Maren Schaarschmidt
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 7-13, 81377, Munich, Germany
| | - Georg Höfner
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 7-13, 81377, Munich, Germany
| | - Klaus T Wanner
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 7-13, 81377, Munich, Germany
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10
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Hauke TJ, Höfner G, Wanner KT. MS-Based Screening of 5-Substituted Nipecotic Acid Derived Hydrazone Libraries as Ligands of the GABA Transporter 1. ChemMedChem 2019; 14:583-593. [PMID: 30663849 DOI: 10.1002/cmdc.201800729] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 01/09/2019] [Indexed: 11/09/2022]
Abstract
A screening of compound libraries based on nipecotic acid derivatives with lipophilic residues attached to the scarcely explored 5-position of the core structure was used for the search of new inhibitors of the γ-aminobutyric acid (GABA) transporter 1 (mGAT1). The generated compound libraries, which were based on hydrazone chemistry commonly used in dynamic combinatorial chemistry but rendered pseudostatic, were screened for their binding affinities toward mGAT1 by means of MS Binding Assays. With nipecotic acid derived hydrazone rac-16 h [rac-(3R,5S)-{5-[(E)-2-{[5-(2-phenylethynyl)thiophen-2-yl]methylidene}hydrazin-1-yl]piperidine-3-carboxylic acid}-sodium chloride (1/2)], one hit was found and evaluated displaying sub-micromolar potency (pKi =6.62±0.04) and a noncompetitive interaction mode at mGAT1. By bearing a 5-(2-phenylethynyl)thiophen-2-yl residue attached to the 5-position of nipecotic acid via a three-atom spacer, compound rac-16 h contains a structural moiety so far unprecedented for these kinds of bioactive molecules, and complements novel 5-substituted nipecotic acid derived ligands of mGAT1 revealed in a recently published screening campaign. This new class of ligands, with an inhibition mode distinct from that of benchmark mGAT1 inhibitors, could serve as research tools for investigations of mGAT1-mediated GABA transport.
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Affiliation(s)
- Tobias J Hauke
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
| | - Georg Höfner
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
| | - Klaus T Wanner
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
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11
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Nowaczyk A, Fijałkowski Ł, Kowalska M, Podkowa A, Sałat K. Studies on the Activity of Selected Highly Lipophilic Compounds toward hGAT1 Inhibition. Part II. ACS Chem Neurosci 2019; 10:337-347. [PMID: 30222312 DOI: 10.1021/acschemneuro.8b00282] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In this paper, we describe the latest results involving molecular modeling and pharmacodynamic studies of the selected highly lipophilic compounds acting by human GABA transporter 1 (hGAT1) inhibition. The chemical interaction of 17 GABA analogues with a model of hGAT1 is described using the molecular docking method. The biological role of GAT1 is related to the regulation of GABA level in the central nervous system and GAT1 inhibition plays an important role in the control of seizure threshold. To confirm that GAT1 can be also a molecular target for drugs used to treat other neurological and psychiatric diseases (e.g., pain and anxiety), in the in vivo part of this study, potential antinociceptive and anxiolytic-like properties of tiagabine, a selective GAT1 inhibitor, are described.
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Affiliation(s)
- Alicja Nowaczyk
- Department of Organic Chemistry, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, 2 dr. A. Jurasza St., 85-094 Bydgoszcz, Poland
| | - Łukasz Fijałkowski
- Department of Organic Chemistry, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, 2 dr. A. Jurasza St., 85-094 Bydgoszcz, Poland
| | - Magdalena Kowalska
- Department of Organic Chemistry, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, 2 dr. A. Jurasza St., 85-094 Bydgoszcz, Poland
| | - Adrian Podkowa
- Chair of Inorganic and Analytical Chemistry, Jagiellonian University Medical College, 9 Medyczna St., 30-688 Kraków, Poland
| | - Kinga Sałat
- Department of Pharmacodynamics, Chair of Pharmacodynamics, Jagiellonian University Medical College, 9 Medyczna St., 30-688 Krakow, Poland
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12
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Huber SK, Höfner G, Wanner KT. Identification of Pyrrolidine‐3‐acetic Acid Derived Oximes as Potent Inhibitors of γ‐Aminobutyric Acid Transporter 1 through Library Screening with MS Binding Assays. ChemMedChem 2018; 13:2488-2503. [DOI: 10.1002/cmdc.201800556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Simone K. Huber
- Department of Pharmacy, Center of Drug ResearchLudwig Maximilians University of Munich Butenandtstr. 7 81377 Munich Germany
| | - Georg Höfner
- Department of Pharmacy, Center of Drug ResearchLudwig Maximilians University of Munich Butenandtstr. 7 81377 Munich Germany
| | - Klaus T. Wanner
- Department of Pharmacy, Center of Drug ResearchLudwig Maximilians University of Munich Butenandtstr. 7 81377 Munich Germany
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13
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Hauke TJ, Wein T, Höfner G, Wanner KT. Novel Allosteric Ligands of γ-Aminobutyric Acid Transporter 1 (GAT1) by MS Based Screening of Pseudostatic Hydrazone Libraries. J Med Chem 2018; 61:10310-10332. [DOI: 10.1021/acs.jmedchem.8b01602] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Tobias J. Hauke
- Department of Pharmacy—Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany
| | - Thomas Wein
- Department of Pharmacy—Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany
| | - Georg Höfner
- Department of Pharmacy—Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany
| | - Klaus T. Wanner
- Department of Pharmacy—Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany
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14
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Zafar S, Jabeen I. Structure, Function, and Modulation of γ-Aminobutyric Acid Transporter 1 (GAT1) in Neurological Disorders: A Pharmacoinformatic Prospective. Front Chem 2018; 6:397. [PMID: 30255012 PMCID: PMC6141625 DOI: 10.3389/fchem.2018.00397] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 08/20/2018] [Indexed: 02/03/2023] Open
Abstract
γ-Aminobutyric acid (GABA) Transporters (GATs) belong to sodium and chloride dependent-transporter family and are widely expressed throughout the brain. Notably, GAT1 is accountable for sustaining 75% of the synaptic GABA concentration and entails its transport to the GABAA receptors to initiate the receptor-mediated inhibition of post-synaptic neurons. Imbalance in ion homeostasis has been associated with several neurological disorders related to the GABAergic system. However, inhibition of the GABA uptake by these transporters has been accepted as an effective approach to enhance GABAergic inhibitory neurotransmission in the treatment of seizures in epileptic and other neurological disorders. Here, we reviewed computational methodologies including molecular modeling, docking, and molecular dynamic simulations studies to underscore the structure and function of GAT1 in the GABAergic system. Additionally, various SAR and QSAR methodologies have been reviewed to probe the 3D structural features of inhibitors required to modulate GATs activity. Overall, present review provides an overview of crucial role of GAT1 in GABAergic system and its modulation to evade neurological disorders.
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Affiliation(s)
| | - Ishrat Jabeen
- Research Center for Modeling and Simulation, National University of Sciences and Technology, Islamabad, Pakistan
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15
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Nowaczyk A, Fijałkowski Ł, Zaręba P, Sałat K. Docking and pharmacodynamic studies on hGAT1 inhibition activity in the presence of selected neuronal and astrocytic inhibitors. Part I. J Mol Graph Model 2018; 85:171-181. [PMID: 30219588 DOI: 10.1016/j.jmgm.2018.09.003] [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: 06/04/2018] [Revised: 08/11/2018] [Accepted: 09/02/2018] [Indexed: 12/30/2022]
Abstract
Inhibition of 4-aminobutanoic acid (GABA) uptake is a strategy for enhancing GABA transmission. The utility of this approach is demonstrated by the successful development of such agents for the treatment of epilepsy and pain. Existing reports on acute brain slice preparations indicate the intersecting of complementary channels and receptors sets between astrocytes and neurons cells. Thorough analysis of astroglial cells by means of molecular and functional studies demonstrated their active modulatory role in intercellular communication. The chemical interactions between sixteen GABA analogues and isoform of hGAT1 is outlined in the light of molecular docking results. In the in vivo part antinociceptive properties of racemic nipecotic acid, its R and S enantiomers and isonipecotic acid, each administered intraperitoneally at 3 fixed doses (10, 30 and 100 mg/kg), were assessed in a thermally-induced acute pain model i.e. the mouse hot plate test. Docking analyses provided complex binding energies, specific h-bond components, and h-bond properties, such as energies, distances and angles. In vivo tests revealed statistically significant antinociceptive properties of isonipecotic acid (10 and 30 mg/kg), R-nipecotic acid (30 and 100 mg/kg) and S-nipecotic acid (100 mg/kg) in mice. The docking data endorse the hypothesis of correlation between the strength of their chemical interactions with hGAT1 and analgesic action of studied compounds.
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Affiliation(s)
- Alicja Nowaczyk
- Department of Organic Chemistry, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, 2 dr. A. Jurasza St., 85-094, Bydgoszcz, Poland.
| | - Łukasz Fijałkowski
- Department of Organic Chemistry, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, 2 dr. A. Jurasza St., 85-094, Bydgoszcz, Poland.
| | - Paula Zaręba
- Department of Physicochemical Drug Analysis, Chair of Pharmaceutical Chemistry, Jagiellonian University Medical College, 9 Medyczna St., 30 - 688, Krakow, Poland.
| | - Kinga Sałat
- Department of Pharmacodynamics, Chair of Pharmacodynamics, Jagiellonian University Medical College, 9 Medyczna St., 30 - 688, Krakow, Poland.
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Lutz T, Wein T, Höfner G, Pabel J, Eder M, Dine J, Wanner KT. Development of New Photoswitchable Azobenzene Based γ-Aminobutyric Acid (GABA) Uptake Inhibitors with Distinctly Enhanced Potency upon Photoactivation. J Med Chem 2018; 61:6211-6235. [DOI: 10.1021/acs.jmedchem.8b00629] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Toni Lutz
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-University Munich, Butenandtstrasse 5-13, D-81377 Munich, Germany
| | - Thomas Wein
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-University Munich, Butenandtstrasse 5-13, D-81377 Munich, Germany
| | - Georg Höfner
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-University Munich, Butenandtstrasse 5-13, D-81377 Munich, Germany
| | - Jörg Pabel
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-University Munich, Butenandtstrasse 5-13, D-81377 Munich, Germany
| | - Matthias Eder
- Scientific Core Unit Electrophysiology, Max-Planck-Institut für Psychiatrie, Kraepelinstrasse 2-10, 80804 Munich, Germany
| | - Julien Dine
- Scientific Core Unit Electrophysiology, Department of Stress Neurobiology and Neurogenetics, Max-Planck-Institut für Psychiatrie, Kraepelinstrasse 2-10, 80804 Munich, Germany
| | - Klaus T. Wanner
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-University Munich, Butenandtstrasse 5-13, D-81377 Munich, Germany
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Yan T, Feringa BL, Barta K. Direct N-alkylation of unprotected amino acids with alcohols. SCIENCE ADVANCES 2017; 3:eaao6494. [PMID: 29226249 PMCID: PMC5722651 DOI: 10.1126/sciadv.aao6494] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 11/08/2017] [Indexed: 05/20/2023]
Abstract
N-alkyl amino acids find widespread application as highly valuable, renewable building blocks. However, traditional synthesis methodologies to obtain these suffer from serious limitations, providing a major challenge to develop sustainable alternatives. We report the first powerful catalytic strategy for the direct N-alkylation of unprotected α-amino acids with alcohols. This method is highly selective, produces water as the only side product leading to a simple purification procedure, and a variety of α-amino acids are mono- or di-N-alkylated, in most cases with excellent retention of optical purity. The hydrophobicity of the products is tunable, and even simple peptides are selectively alkylated. An iron-catalyzed route to mono-N-alkyl amino acids using renewable fatty alcohols is also described that represents an ideal green transformation for obtaining fully bio-based surfactants.
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Jørgensen L, Al-Khawaja A, Kickinger S, Vogensen SB, Skovgaard-Petersen J, Rosenthal E, Borkar N, Löffler R, Madsen KK, Bräuner-Osborne H, Schousboe A, Ecker GF, Wellendorph P, Clausen RP. Structure–Activity Relationship, Pharmacological Characterization, and Molecular Modeling of Noncompetitive Inhibitors of the Betaine/γ-Aminobutyric Acid Transporter 1 (BGT1). J Med Chem 2017; 60:8834-8846. [DOI: 10.1021/acs.jmedchem.7b00924] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Lars Jørgensen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Anas Al-Khawaja
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Stefanie Kickinger
- Department of Pharmaceutical Chemistry, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Stine B. Vogensen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Jonas Skovgaard-Petersen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Emil Rosenthal
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Nrupa Borkar
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Rebekka Löffler
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Karsten K. Madsen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Arne Schousboe
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Gerhard F. Ecker
- Department of Pharmaceutical Chemistry, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Petrine Wellendorph
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Rasmus P. Clausen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
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Pilsl LKA, Ertl T, Reiser O. Enantioselective Three-Step Synthesis of Homo-β-proline: A Donor–Acceptor Cyclopropane as Key Intermediate. Org Lett 2017; 19:2754-2757. [DOI: 10.1021/acs.orglett.7b01111] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ludwig K. A. Pilsl
- Institut für Organische
Chemie, Universität Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany
| | - Thomas Ertl
- Institut für Organische
Chemie, Universität Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany
| | - Oliver Reiser
- Institut für Organische
Chemie, Universität Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany
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Lutz T, Wein T, Höfner G, Wanner KT. Development of Highly Potent GAT1 Inhibitors: Synthesis of Nipecotic Acid Derivatives withN-Arylalkynyl Substituents. ChemMedChem 2017; 12:362-371. [DOI: 10.1002/cmdc.201600599] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 01/20/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Toni Lutz
- Department for Pharmacy, Center for Drug Research; Ludwig-Maximilians-Universität München; Butenandtstr. 7-13 81377 Munich Germany
| | - Thomas Wein
- Department for Pharmacy, Center for Drug Research; Ludwig-Maximilians-Universität München; Butenandtstr. 7-13 81377 Munich Germany
| | - Georg Höfner
- Department for Pharmacy, Center for Drug Research; Ludwig-Maximilians-Universität München; Butenandtstr. 7-13 81377 Munich Germany
| | - Klaus T. Wanner
- Department for Pharmacy, Center for Drug Research; Ludwig-Maximilians-Universität München; Butenandtstr. 7-13 81377 Munich Germany
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Damgaard M, Haugaard AS, Kickinger S, Al-Khawaja A, Lie MEK, Ecker GF, Clausen RP, Frølund B. Development of Non-GAT1-Selective Inhibitors: Challenges and Achievements. ADVANCES IN NEUROBIOLOGY 2017; 16:315-332. [DOI: 10.1007/978-3-319-55769-4_16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
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22
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Schmidt SK, Höfner G, Wanner KT. Determination of enantiomeric excess of nipecotic acid as 1-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl) derivatives. Chirality 2016; 29:48-56. [DOI: 10.1002/chir.22670] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 11/04/2016] [Accepted: 11/07/2016] [Indexed: 11/09/2022]
Affiliation(s)
- Simone K. Schmidt
- Department of Pharmacy - Center of Drug Research; Ludwig-Maximilians-Universität München; Munich Germany
| | - Georg Höfner
- Department of Pharmacy - Center of Drug Research; Ludwig-Maximilians-Universität München; Munich Germany
| | - Klaus T. Wanner
- Department of Pharmacy - Center of Drug Research; Ludwig-Maximilians-Universität München; Munich Germany
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Fijałkowski Ł, Sałat K, Podkowa A, Zaręba P, Nowaczyk A. Potential role of selected antiepileptics used in neuropathic pain as human GABA transporter isoform 1 (GAT1) inhibitors-Molecular docking and pharmacodynamic studies. Eur J Pharm Sci 2016; 96:362-372. [PMID: 27721044 DOI: 10.1016/j.ejps.2016.10.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 09/30/2016] [Accepted: 10/03/2016] [Indexed: 01/31/2023]
Abstract
The chemical interaction of nine antiepileptic drugs (tiagabine, gabapentin, pregabalin, lamotrigine, zonisamide, valproic acid, valpromide, vigabatrin, progabide) and two endogenous metabolites (4-aminobutanoic acid, 4-hydroxybutanoic acid) with a model of human GABA transporter 1 (hGAT1) is described using the molecular docking method. To establish the role of hGAT1 in chronic pain, tiagabine, a selective hGAT1 inhibitor, was assessed in the in vivo experiments for its antiallodynic properties in two mouse models of neuropathic pain. Docking analyses performed in this study provided the complex binding energies, specific hydrogen bond components, and hydrogen bond properties such as energies, distances and angles. The data of the docking studies strongly support the assumption that the antiepileptic and analgesic actions of the studied drugs can be at least in part related to the strength of their chemical interactions with hGAT1. In vivo experiments with tiagabine confirmed the involvement of hGAT1 in the regulation of the mechanical nociceptive threshold in neuropathic pain.
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Affiliation(s)
- Łukasz Fijałkowski
- Department of Organic Chemistry, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, 2 dr. A. Jurasza St., 85-094 Bydgoszcz, Poland
| | - Kinga Sałat
- Department of Pharmacodynamics, Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St., 30-688 Cracow, Poland
| | - Adrian Podkowa
- Department of Pharmacodynamics, Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St., 30-688 Cracow, Poland
| | - Paula Zaręba
- Department of Physicochemical Drug Analysis, Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St., 30-688 Cracow, Poland
| | - Alicja Nowaczyk
- Department of Organic Chemistry, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, 2 dr. A. Jurasza St., 85-094 Bydgoszcz, Poland.
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Hellenbrand T, Höfner G, Wein T, Wanner KT. Synthesis of 4-substituted nipecotic acid derivatives and their evaluation as potential GABA uptake inhibitors. Bioorg Med Chem 2016; 24:2072-96. [PMID: 27039250 DOI: 10.1016/j.bmc.2016.03.038] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 03/16/2016] [Accepted: 03/21/2016] [Indexed: 02/01/2023]
Abstract
In this study, we disclose the design and synthesis of novel 4-susbtituted nipecotic acid derivatives as inhibitors of the GABA transporter mGAT1. Based on molecular modeling studies the compounds are assumed to adopt a binding pose similar to that of the potent mGAT1 inhibitor nipecotic acid. As substitution in 4-position should not cause an energetically unfavorable orientation of nipecotic acid as it is the case for N-substituted derivatives this is expected to lead to highly potent binders. For the synthesis of novel 4-substituted nipecotic acid derivatives a linear synthetic strategy was employed. As a key step, palladium catalyzed cross coupling reactions were used to attach the required biaryl moieties to the ω-position of the alkenyl- or alkynyl spacers of varying length in the 4-position of the nipecotic acid scaffold. The resulting amino acids were characterized with respect to their binding affinities and inhibitory potencies at mGAT1. Though the biological activities found were generally insignificant to poor, two compounds, one of which possesses a reasonable binding affinity for mGAT1, rac-57, the other a notable inhibitory potency at mGAT4, rac-84, both displaying a slight subtype selectivity for the individual transporters, could be identified.
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Affiliation(s)
- Tim Hellenbrand
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 Munich, Germany
| | - Georg Höfner
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 Munich, Germany
| | - Thomas Wein
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 Munich, Germany
| | - Klaus T Wanner
- Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 Munich, Germany.
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