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Kwon D, Zhang Z, Zeisler J, Kuo HT, Lin KS, Benard F. Reducing the Kidney Uptake of High Contrast CXCR4 PET Imaging Agents via Linker Modifications. Pharmaceutics 2022; 14:pharmaceutics14071502. [PMID: 35890397 PMCID: PMC9316317 DOI: 10.3390/pharmaceutics14071502] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 07/02/2022] [Accepted: 07/07/2022] [Indexed: 01/27/2023] Open
Abstract
Purpose: The C-X-C chemokine receptor 4 (CXCR4) is highly expressed in many subtypes of cancers, notably in several kidney-based malignancies. We synthesized, labeled, and assessed a series of radiotracers based on a previous high contrast PET imaging radiopharmaceutical [68Ga]Ga-BL02, with modifications to its linker and metal chelator, in order to improve its tumor-to-kidney contrast ratio. Methods: Based on the design of BL02, a piperidine-based cationic linker (BL06) and several anionic linkers (tri-Aad (BL17); tri-D-Glu (BL20); tri-Asp (BL25); and tri-cysteic acid (BL31)) were substituted for the triglutamate linker. Additionally, the DOTA chelator was swapped for a DOTAGA chelator (BL30). Each radiotracer was labeled with 68Ga and evaluated in CXCR4-expressing Daudi xenograft mice with biodistribution and/or PET imaging studies. Results: Of all the evaluated radiotracers, [68Ga]Ga-BL31 showed the most promising biodistribution profile, with a lower kidney uptake compared to [68Ga]Ga-BL02, while retaining the high imaging contrast capabilities of [68Ga]Ga-BL02. [68Ga]Ga-BL31 also compared favorably to [68Ga]Ga-Pentixafor, with superior imaging contrast in all non-target organs. The other anionic linker-based radiotracers showed either equivocal or worse contrast ratios compared to [68Ga]Ga-BL02; however, [68Ga]Ga-BL25 also showed lower kidney uptake, as compared to that of [68Ga]Ga-BL02. Meanwhile, [68Ga]Ga-BL06 had high non-target organ uptake and relatively lower tumor uptake, while [68Ga]Ga-BL30 showed significantly increased kidney uptake and similar tumor uptake values. Conclusions: [68Ga]Ga-BL31 is an optimized CXCR4-targeting radiopharmaceutical with lower kidney retention that has clinical potential for PET imaging and radioligand therapy.
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Affiliation(s)
- Daniel Kwon
- Department of Molecular Oncology, BC Cancer, Vancouver, BC V5Z 1L3, Canada; (D.K.); (Z.Z.); (J.Z.); (H.-T.K.); (K.-S.L.)
| | - Zhengxing Zhang
- Department of Molecular Oncology, BC Cancer, Vancouver, BC V5Z 1L3, Canada; (D.K.); (Z.Z.); (J.Z.); (H.-T.K.); (K.-S.L.)
| | - Jutta Zeisler
- Department of Molecular Oncology, BC Cancer, Vancouver, BC V5Z 1L3, Canada; (D.K.); (Z.Z.); (J.Z.); (H.-T.K.); (K.-S.L.)
| | - Hsiou-Ting Kuo
- Department of Molecular Oncology, BC Cancer, Vancouver, BC V5Z 1L3, Canada; (D.K.); (Z.Z.); (J.Z.); (H.-T.K.); (K.-S.L.)
| | - Kuo-Shyan Lin
- Department of Molecular Oncology, BC Cancer, Vancouver, BC V5Z 1L3, Canada; (D.K.); (Z.Z.); (J.Z.); (H.-T.K.); (K.-S.L.)
- Department of Radiology, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
| | - Francois Benard
- Department of Molecular Oncology, BC Cancer, Vancouver, BC V5Z 1L3, Canada; (D.K.); (Z.Z.); (J.Z.); (H.-T.K.); (K.-S.L.)
- Department of Radiology, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
- Correspondence: ; Tel.: +1-604-675-8206
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Fairweather SJ, Shah N, Brӧer S. Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 21:13-127. [PMID: 33052588 DOI: 10.1007/5584_2020_584] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H+ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b0,+AT-rBAT and the SLC6 family heteromer B0AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.
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Affiliation(s)
- Stephen J Fairweather
- Research School of Biology, Australian National University, Canberra, ACT, Australia. .,Resarch School of Chemistry, Australian National University, Canberra, ACT, Australia.
| | - Nishank Shah
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Stefan Brӧer
- Research School of Biology, Australian National University, Canberra, ACT, Australia.
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3
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Böhme I, Schönherr R, Eberle J, Bosserhoff AK. Membrane Transporters and Channels in Melanoma. Rev Physiol Biochem Pharmacol 2020; 181:269-374. [PMID: 32737752 DOI: 10.1007/112_2020_17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recent research has revealed that ion channels and transporters can be important players in tumor development, progression, and therapy resistance in melanoma. For example, members of the ABC family were shown to support cancer stemness-like features in melanoma cells, while several members of the TRP channel family were reported to act as tumor suppressors.Also, many transporter proteins support tumor cell viability and thus suppress apoptosis induction by anticancer therapy. Due to the high number of ion channels and transporters and the resulting high complexity of the field, progress in understanding is often focused on single molecules and is in total rather slow. In this review, we aim at giving an overview about a broad subset of ion transporters, also illustrating some aspects of the field, which have not been addressed in detail in melanoma. In context with the other chapters in this special issue on "Transportome Malfunctions in the Cancer Spectrum," a comparison between melanoma and these tumors will be possible.
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Affiliation(s)
- Ines Böhme
- Institute of Biochemistry, Emil Fischer Center, Friedrich-Alexander-University of Erlangen-Nürnberg, Erlangen, Germany
| | - Roland Schönherr
- Institute of Biochemistry and Biophysics, Friedrich Schiller University Jena and Jena University Hospital, Jena, Germany
| | - Jürgen Eberle
- Department of Dermatology, Venerology and Allergology, Skin Cancer Center Charité, University Medical Center Charité, Berlin, Germany
| | - Anja Katrin Bosserhoff
- Institute of Biochemistry, Emil Fischer Center, Friedrich-Alexander-University of Erlangen-Nürnberg, Erlangen, Germany. .,Comprehensive Cancer Center (CCC) Erlangen-EMN, Erlangen, Germany.
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4
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Thompson CM, Chao CK. VGLUT substrates and inhibitors: A computational viewpoint. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183175. [PMID: 31923412 DOI: 10.1016/j.bbamem.2020.183175] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/30/2019] [Accepted: 12/31/2019] [Indexed: 02/07/2023]
Abstract
The vesicular glutamate transporters (VGLUTs) bind and move glutamate (Glu) from the cytosol into the lumen of synaptic vesicles using a H+-electrochemical gradient (ΔpH and Δψ) generated by the vesicular H+-ATPase. VGLUTs show very low Glu binding and to date, no three-dimensional structure has been elucidated. Prior studies have attempted to identify the key residues involved in binding VGLUT substrates and inhibitors using homology models and docking experiments. Recently, the inward and outward oriented crystal structures of d-galactonate transporter (DgoT) emerged as possible structure templates for VGLUT. In this review, a new homology model for VGLUT2 based on DgoT has been developed and used to conduct docking experiments to identify and differentiate residues and binding orientations involved in ligand interactions. This review describes small molecule-ligand interactions including docking using a VGLUT2 homology model derived from DgoT.
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Affiliation(s)
- Charles M Thompson
- Center for Structural and Functional Neurosciences, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, United States.
| | - Chih-Kai Chao
- Center for Structural and Functional Neurosciences, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, United States
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5
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Amantadine Combines Astroglial System Xc - Activation with Glutamate/NMDA Receptor Inhibition. Biomolecules 2019; 9:biom9050191. [PMID: 31108896 PMCID: PMC6572554 DOI: 10.3390/biom9050191] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Revised: 05/11/2019] [Accepted: 05/15/2019] [Indexed: 01/06/2023] Open
Abstract
A glutamate/NMDA receptor (NMDA-R) antagonist, amantadine (AMA) exhibits a broad spectrum of clinically important properties, including antiviral, antiparkinsonian, neuroprotective, neuro-reparative and cognitive-enhancing effects. However, both clinical and pre-clinical studies have demonstrated that noncompetitive NMDA-R antagonists induce severe schizophrenia-like cognitive deficits. Therefore, this study aims to clarify the clinical discrepancy between AMA and noncompetitive NMDA-R antagonists by comparing the effects of AMA with those of a noncompetitive NMDA-R antagonist, MK801, on rat tripartite glutamatergic synaptic transmission using microdialysis and primary cultured astrocytes. Microdialysis study demonstrated that the stimulatory effects of AMA on L-glutamate release differed from those of MK801 in the globus pallidus, entorhinal cortex and entopeduncular nucleus. The stimulatory effect of AMA on L-glutamate release was modulated by activation of cystine/glutamate antiporter (Sxc). Primary cultured astrocytes study demonstrated that AMA also enhanced glutathione synthesis via Sxc activation. Furthermore, carbon-monoxide induced damage of the astroglial glutathione synthesis system was repaired by AMA but not MK801. Additionally, glutamate/AMPA receptor (AMPA-R) antagonist, perampanel enhanced the protective effects of AMA. The findings of microdialysis and cultured astrocyte studies suggest that a combination of Sxc activation with inhibitions of ionotropic glutamate receptors contributes to neuroprotective, neuro-reparative and cognitive-enhancing activities that can mitigate several neuropsychiatric disorders.
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6
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Thomas AG, Sattler R, Tendyke K, Loiacono KA, Hansen H, Sahni V, Hashizume Y, Rojas C, Slusher BS. High-Throughput Assay Development for Cystine-Glutamate Antiporter (xc-) Highlights Faster Cystine Uptake than Glutamate Release in Glioma Cells. PLoS One 2015; 10:e0127785. [PMID: 26252954 PMCID: PMC4529246 DOI: 10.1371/journal.pone.0127785] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 04/19/2015] [Indexed: 01/22/2023] Open
Abstract
The cystine-glutamate antiporter (system xc-) is a Na+-independent amino acid transporter that exchanges extracellular cystine for intracellular glutamate. It is thought to play a critical role in cellular redox processes through regulation of intracellular glutathione synthesis via cystine uptake. In gliomas, system xc- expression is universally up-regulated while that of glutamate transporters down-regulated, leading to a progressive accumulation of extracellular glutamate and excitotoxic cell death of the surrounding non-tumorous tissue. Additionally, up-regulation of system xc- in activated microglia has been implicated in the pathogenesis of several neurodegenerative disorders mediated by excess glutamate. Consequently, system xc- is a new drug target for brain cancer and neuroinflammatory diseases associated with excess extracellular glutamate. Unfortunately no potent and selective small molecule system xc- inhibitors exist and to our knowledge, no high throughput screening (HTS) assay has been developed to identify new scaffolds for inhibitor design. To develop such an assay, various neuronal and non-neuronal human cells were evaluated as sources of system xc-. Human glioma cells were chosen based on their high system xc- activity. Using these cells, [14C]-cystine uptake and cystine-induced glutamate release assays were characterized and optimized with respect to cystine and protein concentrations and time of incubation. A pilot screen of the LOPAC/NINDS libraries using glutamate release demonstrated that the logistics of the assay were in place but unfortunately, did not yield meaningful pharmacophores. A larger, HTS campaign using the 384-well cystine-induced glutamate release as primary assay and the 96-well 14C-cystine uptake as confirmatory assay is currently underway. Unexpectedly, we observed that the rate of cystine uptake was significantly faster than the rate of glutamate release in human glioma cells. This was in contrast to the same rates of cystine uptake and glutamate release previously reported in normal human fibroblast cells.
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Affiliation(s)
- Ajit G. Thomas
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
| | - Rita Sattler
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
| | - Karen Tendyke
- Next Generation Systems CFU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Kara A. Loiacono
- Next Generation Systems CFU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Hans Hansen
- Next Generation Systems CFU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Vishal Sahni
- Neuroscience and General Medicine PCU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Yutaka Hashizume
- Neuroscience and General Medicine PCU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Camilo Rojas
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Comparative Medicine and Molecular Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- * E-mail: (CR); (BSS)
| | - Barbara S. Slusher
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- * E-mail: (CR); (BSS)
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7
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Carrigan CN, Patel SA, Cox HD, Bolstad ES, Gerdes JM, Smith WE, Bridges RJ, Thompson CM. The development of benzo- and naphtho-fused quinoline-2,4-dicarboxylic acids as vesicular glutamate transporter (VGLUT) inhibitors reveals a possible role for neuroactive steroids. Bioorg Med Chem Lett 2013; 24:850-4. [PMID: 24424130 DOI: 10.1016/j.bmcl.2013.12.086] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2013] [Revised: 12/17/2013] [Accepted: 12/19/2013] [Indexed: 11/19/2022]
Abstract
Substituted quinoline-2,4-dicarboxylates (QDCs) are conformationally-restricted mimics of glutamate that were previously reported to selectively block the glutamate vesicular transporters (VGLUTs). We find that expanding the QDC scaffold to benzoquinoline dicarboxylic acids (BQDC) and naphthoquinoline dicarboxylic acids (NQDCs) improves inhibitory activity with the NQDCs showing IC50∼70 μM. Modeling overlay studies showed that the polycyclic QDCs resembled steroid structures and led to the identification and testing of estrone sulfate, pregnenolone sulfate and pregnanolone sulfate that blocked the uptake of l-Glu by 50%, 70% and 85% of control, respectively. Pregnanolone sulfate was further characterized by kinetic pharmacological determinations that demonstrated competitive inhibition and a Ki of ≈20 μM.
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Affiliation(s)
- Christina N Carrigan
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Sarjubhai A Patel
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Holly D Cox
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Erin S Bolstad
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
| | - John M Gerdes
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Wesley E Smith
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Richard J Bridges
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Charles M Thompson
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA.
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8
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Neale SA, Copeland CS, Salt TE. Effect of VGLUT inhibitors on glutamatergic synaptic transmission in the rodent hippocampus and prefrontal cortex. Neurochem Int 2013; 73:159-65. [PMID: 24121008 DOI: 10.1016/j.neuint.2013.10.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 09/30/2013] [Accepted: 10/02/2013] [Indexed: 01/23/2023]
Abstract
Vesicular glutamate transporters (VGLUTs) are known to be important in the uptake of glutamate into vesicles in the presynaptic terminal; thereby playing a role in synaptic function. VGLUT dysfunction has also been suggested in neurological and psychiatric disorders such as epilepsy and schizophrenia. A number of compounds have been identified as VGLUT inhibitors; however, little is known as to how these compounds affect synaptic transmission. We therefore investigated the effects of structurally unrelated VGLUT inhibitors on synaptic transmission in the rodent hippocampus and prefrontal cortex. In the CA1 and dentate gyrus regions of the in vitro slice preparation of mouse hippocampus, AMPA receptor-mediated field excitatory postsynaptic potentials (fEPSPs) were evoked in response to Schaffer collateral/commissural pathway stimulation. Application of the VGLUT inhibitors Rose Bengal (RB), Congo Red (CR) or Chicago Sky Blue 6B (CB) resulted in a concentration-related reduction of fEPSP amplitudes. RB (30μM) or CB (300μM) also depressed NMDA receptor-mediated responses in the CA1 region. The naturally occurring kynurenine Xanthurenic Acid (XA) is reported to be a VGLUT inhibitor. We found XA attenuated both AMPA and NMDA receptor-mediated synaptic transmission. The potency order of the VGLUT inhibitors was consistent with literature Ki values for VGLUT inhibition. Impaired glutamatergic neurotransmission is believed to contribute to schizophrenia, and VGLUTs have also been implicated in this disease. We therefore investigated the effect of VGLUT inhibition in the prefrontal cortex. Application of the VGLUT inhibitors RB or CB resulted in a concentration-dependent reduction in the amplitude of glutamate receptor-mediated fEPSPs recorded in layer V/VI in response to stimulation in the forceps minor. We conclude that VGLUT inhibitors can modulate glutamatergic synaptic transmission in the PFC and hippocampus. This could be important in the pathophysiology of nervous system disorders and might represent a target for developing novel pharmacological therapies.
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Affiliation(s)
- S A Neale
- Neurexpert Ltd., Kemp House, London EC1V 2NX, UK; UCL Institute of Ophthalmology, London EC1V 9EL, UK
| | - C S Copeland
- UCL Institute of Ophthalmology, London EC1V 9EL, UK
| | - T E Salt
- UCL Institute of Ophthalmology, London EC1V 9EL, UK.
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9
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Matti AA, Mirzaei J, Rudolph J, Smith SA, Newell JL, Patel SA, Braden MR, Bridges RJ, Natale NR. Microwave accelerated synthesis of isoxazole hydrazide inhibitors of the system xc- transporter: Initial homology model. Bioorg Med Chem Lett 2013; 23:5931-5. [PMID: 24042010 DOI: 10.1016/j.bmcl.2013.08.080] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Revised: 08/16/2013] [Accepted: 08/19/2013] [Indexed: 01/18/2023]
Abstract
Microwave accelerated reaction system (MARS) technology provided a good method to obtain selective and open isoxazole ligands that bind to and inhibit the Sxc- antiporter. The MARS provided numerous advantages, including: shorter time, better yield and higher purity of the product. Of the newly synthesized series of isoxazoles the salicyl hydrazide 6 exhibited the highest level of inhibitory activity in the transport assay. A homology model has been developed to summarize the SAR results to date, and provide a working hypothesis for future studies.
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Affiliation(s)
- Afnan A Matti
- Department of Biomedical & Pharmaceutical Sciences, Center for Structural & Functional Neuroscience, The University of Montana, Missoula, MT 59812, United States; Medicinal Chemistry Graduate Program, The University of Montana, Missoula, MT 59812, United States
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10
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Bridges RJ, Natale NR, Patel SA. System xc⁻ cystine/glutamate antiporter: an update on molecular pharmacology and roles within the CNS. Br J Pharmacol 2012; 165:20-34. [PMID: 21564084 DOI: 10.1111/j.1476-5381.2011.01480.x] [Citation(s) in RCA: 369] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
System x(c)(-) is an amino acid antiporter that typically mediates the exchange of extracellular l-cystine and intracellular L-glutamate across the cellular plasma membrane. Studied in a variety of cell types, the import of L-cystine through this transporter is critical to glutathione production and oxidative protection. The exchange-mediated export of L-glutamate takes on added significance within the CNS, as it represents a non-vesicular route of release through which this excitatory neurotransmitter can participate in either neuronal signalling or excitotoxic pathology. When both the import of L-cystine and the export of L-glutamate are taken into consideration, system x(c)(-) has now been linked to a wide range of CNS functions, including oxidative protection, the operation of the blood-brain barrier, neurotransmitter release, synaptic organization, viral pathology, drug addiction, chemosensitivity and chemoresistance, and brain tumour growth. The ability to selectively manipulate system x(c)(-), delineate its function, probe its structure and evaluate it as a therapeutic target is closely linked to understanding its pharmacology and the subsequent development of selective inhibitors and substrates. Towards that goal, this review will examine the current status of our understanding of system x(c)(-) pharmacology and the structure-activity relationships that have guided the development of an initial pharmacophore model, including the presence of lipophilic domains adjacent to the substrate binding site. A special emphasis is placed on the roles of system x(c)(-) within the CNS, as it is these actions that are among the most exciting as potential long-range therapeutic targets.
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Affiliation(s)
- Richard J Bridges
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, USA.
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Shukla K, Thomas AG, Ferraris DV, Hin N, Sattler R, Alt J, Rojas C, Slusher BS, Tsukamoto T. Inhibition of xc⁻ transporter-mediated cystine uptake by sulfasalazine analogs. Bioorg Med Chem Lett 2011; 21:6184-7. [PMID: 21889337 DOI: 10.1016/j.bmcl.2011.07.081] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 07/20/2011] [Accepted: 07/22/2011] [Indexed: 01/18/2023]
Abstract
A series of sulfasalazine analogs were synthesized and tested for their ability to block cystine-glutamate antiporter system xc⁻ using L-[(14)C]cystine as a substrate. Replacement of sulfasalazine's diazo group with an alkyne group led to an equally potent inhibitor, 2-hydroxy-5-((4-(N-pyridin-2-ylsulfamoyl)phenyl)ethynyl)benzoic acid 6. Our SAR studies also revealed that the carboxylate group of sulfasalazine is essential for its inhibitory activity while the phenolic hydroxyl group is dispensable. Truncated analogs lacking an N-pyridin-2-ylsulfamoyl moiety were less potent than sulfasalazine, but may serve as more tractable templates because of their low molecular weight by applying a variety of fragment growing approaches. Given that sulfasalazine is rapidly metabolized through cleavage of the diazo bond, these analogs may possess a more desirable pharmacological profile as system xc- blockers, in particular, for in vivo studies.
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Affiliation(s)
- Krupa Shukla
- Department of Neurology, Johns Hopkins University, Baltimore, MD 21205, USA
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12
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Ahmed SK, Etoga JLG, Patel SA, Bridges RJ, Thompson CM. Use of the hydantoin isostere to produce inhibitors showing selectivity toward the vesicular glutamate transporter versus the obligate exchange transporter system x(c)(-). Bioorg Med Chem Lett 2011; 21:4358-62. [PMID: 21669531 DOI: 10.1016/j.bmcl.2011.05.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 05/04/2011] [Accepted: 05/06/2011] [Indexed: 12/20/2022]
Abstract
Evidence was acquired prior to suggest that the vesicular glutamate transporter (VGLUT) but not other glutamate transporters were inhibited by structures containing a weakly basic α-amino group. To test this hypothesis, a series of analogs using a hydantoin (pK(a)∼9.1) isostere were synthesized and analyzed as inhibitors of VGLUT and the obligate cystine-glutamate transporter (system x(c)(-)). Of the hydantoin analogs tested, a thiophene-5-carboxaldehyde analog 2l and a bis-hydantoin 4b were relatively strong inhibitors of VGLUT reducing uptake to less than 6% of control at 5mM but few inhibited system x(c)(-) greater than 50% of control. The benzene-2,4-disulfonic acid analog 2b and p-diaminobenzene analog 2e were also good hydantoin-based inhibitors of VGLUT reducing uptake by 11% and 23% of control, respectively, but neither analog was effective as a system x(c)(-) inhibitor. In sum, a hydantoin isostere adds the requisite chemical properties needed to produce selective inhibitors of VGLUT.
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Affiliation(s)
- S Kaleem Ahmed
- Core Laboratory for Neuromolecular Production, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
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13
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Conformationally constrained histidines in the design of peptidomimetics: strategies for the χ-space control. Int J Mol Sci 2011; 12:2853-90. [PMID: 21686155 PMCID: PMC3116161 DOI: 10.3390/ijms12052853] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 04/18/2011] [Accepted: 04/20/2011] [Indexed: 11/20/2022] Open
Abstract
A successful design of peptidomimetics must come to terms with χ-space control. The incorporation of χ-space constrained amino acids into bioactive peptides renders the χ1 and χ2 torsional angles of pharmacophore amino acids critical for activity and selectivity as with other relevant structural features of the template. This review describes histidine analogues characterized by replacement of native α and/or β-hydrogen atoms with alkyl substituents as well as analogues with α, β-didehydro unsaturation or Cα-Cβ cyclopropane insertion (ACC derivatives). Attention is also dedicated to the relevant field of β-aminoacid chemistry by describing the synthesis of β2- and β3-models (β-hHis). Structural modifications leading to cyclic imino derivatives such as spinacine, aza-histidine and analogues with shortening or elongation of the native side chain (nor-histidine and homo-histidine, respectively) are also described. Examples of the use of the described analogues to replace native histidine in bioactive peptides are also given.
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Cheng XR, Yang Y, Zhou WX, Zhang YX. Expression of VGLUTs contributes to degeneration and acquisition of learning and memory. Neurobiol Learn Mem 2011; 95:361-75. [PMID: 21295146 DOI: 10.1016/j.nlm.2011.01.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Revised: 01/16/2011] [Accepted: 01/25/2011] [Indexed: 12/27/2022]
Abstract
Vesicular glutamate transporters (VGLUTs), which include VGLUT1, VGLUT2 and VGLUT3, are responsible for the uploading of L-glutamate into synaptic vesicles. The expression pattern of VGLUTs determines the level of synaptic vesicle filling (i.e., glutamate quantal size) and directly influences glutamate receptors and glutamatergic synaptic transmission; thus, VGLUTs may play a key role in learning and memory in the central nervous system. To determine whether VGLUTs contribute to the degeneration or acquisition of learning and memory, we used an animal model for the age-related impairment of learning and memory, senescence-accelerated mouse/prone 8 (SAMP8). KM mice were divided into groups based on their learning and memory performance in a shuttle-box test. The expression of VGLUTs and synaptophysin (Syp) mRNA and protein in the cerebral cortex and hippocampus were investigated with real-time fluorescence quantitative PCR and western blot, respectively. Our results demonstrate that, in the cerebral cortex, protein expression of VGLUT1, VGLUT2, VGLUT3 and Syp was decreased in SAMP8 with age and increased in KM mice, which displayed an enhanced capacity for learning and memory. The protein expression of VGLUT2 and Syp was decreased in the hippocampus of SAMP8 with aging. The expression level of VGLUT1 and VGLUT2 proteins were highest in KM mouse group with a 76-100% avoidance score in the shuttle-box test. These data demonstrate that protein expression of VGLUT1, VGLUT2 and Syp decreases age-dependently in SAMP8 and increases in a learning- and memory-dependent manner in KM mice. Correlation analysis indicated the protein expression of VGLUT1, VGLUT2 and Syp has a positive correlation with the capacity of learning and memory.
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Affiliation(s)
- Xiao-Rui Cheng
- Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
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