1
|
Karin KN, Mustafa MA, Poklis JL, Buzzi B, Schlosburg JE, Parker L, Damaj MI, Lichtman AH. N-oleoyl alanine attenuates nicotine reward and spontaneous nicotine withdrawal in mice. Drug Alcohol Depend 2024; 259:111276. [PMID: 38676968 DOI: 10.1016/j.drugalcdep.2024.111276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 02/19/2024] [Accepted: 03/25/2024] [Indexed: 04/29/2024]
Abstract
BACKGROUND As nicotine dependence represents a longstanding major public health issue, new nicotine cessation pharmacotherapies are needed. Administration of N-oleoyl glycine (OlGly), an endogenous lipid signaling molecule, prevents nicotine-induced conditioned place preference (CPP) through a peroxisome proliferator-activated receptor-alpha (PPARα) dependent mechanism, and also ameliorated withdrawal signs in nicotine-dependent mice. Pharmacological evidence suggests that the methylated analog of OlGly, N-oleoyl alanine (OlAla), has an increased duration of action and may offer translational benefit. Accordingly, OlAla was assessed in nicotine CPP and dependence assays as well as its pharmacokinetics compared to OlGly. METHODS ICR female and male mice were tested in nicotine-induced CPP with and without the PPARα antagonist GW6471. OlAla was also assessed in nicotine-dependent mice following removal of nicotine minipumps: somatic withdrawal signs, thermal hyper-nociception and altered affective behavior (i.e., light/dark box). Finally, plasma and brain were collected after administration of OlGly or OlAla and analyzed by high-performance liquid chromatography tandem mass spectrometry. RESULTS OlAla prevented nicotine-induced CPP, but this effect was not blocked by GW6471. OlAla attenuated somatic and affective nicotine withdrawal signs, but not thermal hyper-nociception in nicotine-dependent mice undergoing withdrawal. OlAla and OlGly showed similar time-courses in plasma and brain. CONCLUSIONS The observation that both molecules showed similar pharmacokinetics argues against the notion that OlAla offers increased metabolic stability. Moreover, while these structurally similar lipids show efficacy in mouse models of reward and dependence, they reduce nicotine reward through distinct mechanisms.
Collapse
Affiliation(s)
- Kimberly N Karin
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Mohammed A Mustafa
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Justin L Poklis
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Belle Buzzi
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Joel E Schlosburg
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Linda Parker
- Department of Psychology, University of Guelph, Guelph, Ontario, Canada
| | - M Imad Damaj
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Aron H Lichtman
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA; Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, VA 23298, USA.
| |
Collapse
|
2
|
Chater RC, Quinn AS, Wilson K, Frangos ZJ, Sutton P, Jayakumar S, Cioffi CL, O'Mara ML, Vandenberg RJ. The efficacy of the analgesic GlyT2 inhibitor, ORG25543, is determined by two connected allosteric sites. J Neurochem 2023. [PMID: 38131125 DOI: 10.1111/jnc.16028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/23/2023] [Accepted: 11/28/2023] [Indexed: 12/23/2023]
Abstract
Glycine Transporter 2 (GlyT2) inhibitors have shown considerable potential as analgesics for the treatment of neuropathic pain but also display considerable side effects. One potential source of side effects is irreversible inhibition. In this study, we have characterized the mechanism of ORG25543 inhibition of GlyT2 by first considering three potential ligand binding sites on GlyT2-the substrate site, the vestibule allosteric site and the lipid allosteric site. The three sites were tested using a combination of molecular dynamics simulations and analysis of the inhibition of glycine transport of a series point mutated GlyT2 using electrophysiological methods. We demonstrate that the lipid allosteric site on GlyT2 is the most likely binding site for ORG25543. We also demonstrate that cholesterol derived from the cell membrane can form specific interactions with inhibitor-bound transporters to form an allosteric network of regulatory sites. These observations will guide the future design of GlyT2 inhibitors with the objective of minimising on-target side effects and improving the therapeutic window for the treatment of patients suffering from neuropathic pain.
Collapse
Affiliation(s)
- Ryan Cantwell Chater
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Ada S Quinn
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Katie Wilson
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Zachary J Frangos
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Patrick Sutton
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Srinivasan Jayakumar
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Christopher L Cioffi
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Megan L O'Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Robert J Vandenberg
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| |
Collapse
|
3
|
Gallagher CI, Frangos ZJ, Sheipouri D, Shimmon S, Duman MN, Jayakumar S, Cioffi CL, Rawling T, Vandenberg RJ. Novel Phenylene Lipids That Are Positive Allosteric Modulators of Glycine Receptors and Inhibitors of Glycine Transporter 2. ACS Chem Neurosci 2023; 14:2634-2647. [PMID: 37466545 DOI: 10.1021/acschemneuro.3c00167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023] Open
Abstract
Chronic pain is a complex condition that remains resistant to current therapeutics. We previously synthesized a series of N-acyl amino acids (NAAAs) that inhibit the glycine transporter, GlyT2, some of which are also positive allosteric modulators of glycine receptors (GlyRs). In this study, we have synthesized a library of NAAAs that contain a phenylene ring within the acyl tail with the objective of improving efficacy at both GlyT2 and GlyRs and also identifying compounds that are efficacious as dual-acting modulators to enhance glycine neurotransmission. The most efficacious positive allosteric modulator of GlyRs was 2-[8-(2-octylphenyl)octanoylamino]acetic acid (8-8 OPGly) which potentiates the EC5 for glycine activation of GlyRα1 by 1500% with an EC50 of 664 nM. Phenylene-containing NAAAs with a lysine headgroup were the most potent inhibitors of GlyT2 with (2S)-6-amino-2-[8-(3-octylphenyl)octanoylamino]hexanoic acid (8-8 MPLys) inhibiting GlyT2 with an IC50 of 32 nM. The optimal modulator across both proteins was (2S)-6-amino-2-[8-(2-octylphenyl)octanoylamino]hexanoic acid (8-8 OPLys), which inhibits GlyT2 with an IC50 of 192 nM and potentiates GlyRs by up to 335% at 1 μM. When tested in a dual GlyT2/GlyRα1 expression system, 8-8 OPLys caused the greatest reductions in the EC50 for glycine. This suggests that the synergistic effects of a dual-acting modulator cause greater enhancements in glycinergic activity compared to single-target modulators and may provide an alternate approach to the development of new non-opioid analgesics for the treatment of chronic pain.
Collapse
Affiliation(s)
- Casey I Gallagher
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Zachary J Frangos
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Diba Sheipouri
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Meryem-Nur Duman
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Srinivasan Jayakumar
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
| | - Christopher L Cioffi
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Robert J Vandenberg
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| |
Collapse
|
4
|
Frangos ZJ, Wilson KA, Aitken HM, Cantwell Chater R, Vandenberg RJ, O'Mara ML. Membrane cholesterol regulates inhibition and substrate transport by the glycine transporter, GlyT2. Life Sci Alliance 2023; 6:e202201708. [PMID: 36690444 PMCID: PMC9873984 DOI: 10.26508/lsa.202201708] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/25/2023] Open
Abstract
Membrane cholesterol binds to and modulates the function of various SLC6 neurotransmitter transporters, including stabilizing the outward-facing conformation of the dopamine and serotonin transporters. Here, we investigate how cholesterol binds to GlyT2 (SLC6A5), modulates glycine transport rate, and influences bioactive lipid inhibition of GlyT2. Bioactive lipid inhibitors are analgesics that bind to an allosteric site accessible from the extracellular solution when GlyT2 adopts an outward-facing conformation. Using molecular dynamics simulations, mutagenesis, and cholesterol depletion experiments, we show that bioactive lipid inhibition of glycine transport is modulated by the recruitment of membrane cholesterol to a binding site formed by transmembrane helices 1, 5, and 7. Recruitment involves cholesterol flipping from its membrane orientation, and insertion of the 3' hydroxyl group into the cholesterol binding cavity, close to the allosteric site. The synergy between cholesterol and allosteric inhibitors provides a novel mechanism of inhibition and a potential avenue for the development of potent GlyT2 inhibitors as alternative therapeutics for the treatment of neuropathic pain and therapeutics that target other SLC6 transporters.
Collapse
Affiliation(s)
- Zachary J Frangos
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Katie A Wilson
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada
| | - Heather M Aitken
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Australia
| | - Ryan Cantwell Chater
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Robert J Vandenberg
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Megan L O'Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Australia
| |
Collapse
|
5
|
Natale CA, Christie MJ, Aubrey KR. Spinal glycinergic currents are reduced in a rat model of neuropathic pain following partial nerve ligation but not chronic constriction injury. J Neurophysiol 2023; 129:333-341. [PMID: 36541621 DOI: 10.1152/jn.00451.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Animal models have consistently indicated that central sensitization and the development of chronic neuropathic pain are linked to changes to inhibitory signaling in the dorsal horn of the spinal cord. However, replication of data investigating the cellular mechanisms that underlie these changes remains a challenge and there is still a lack of understanding about what aspects of spinal inhibitory transmission most strongly contribute to the disease. Here, we compared the effect of two different sciatic nerve injuries commonly used to generate rodent models of neuropathic pain on spinal glycinergic signaling. Using whole cell patch-clamp electrophysiology in spinal slices, we recorded from neurons in the lamina II of the dorsal horn and evoked inhibitory postsynaptic currents with a stimulator in lamina III, where glycinergic cell bodies are concentrated. We found that glycine inputs onto radial neurons were reduced following partial nerve ligation (PNL) of the sciatic nerve, consistent with a previous report. However, this finding was not replicated in animals that underwent chronic constriction injury (CCI) to the same nerve region. To limit the between-experiment variability, we kept the rat species, sex, and age consistent and had a single investigator carry out the surgeries. These data show that PNL and CCI cause divergent spinal signaling outcomes in the cord and add to the body of evidence suggesting that treatments for neuropathic pain should be triaged according to nerve injury or cellular dysfunction rather than the symptoms of the disease.NEW & NOTEWORTHY Neuropathic pain models are used in preclinical research to investigate the mechanisms underlying allodynia, a common symptom of neuropathic pain, and to test, develop, and validate therapies for persistent pain. We demonstrate that a glycinergic dysfunction is consistently associated with partial nerve ligation but not the chronic constriction injury model. This suggests that the cellular effects produced by each injury are distinct and that data from different neuropathic pain models should be considered separately.
Collapse
Affiliation(s)
- Claudia A Natale
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, Australia
| | - Macdonald J Christie
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, Australia
| | - Karin R Aubrey
- Pain Management Research, Kolling Institute, Royal North Shore Hospital, St Leonards, New South Wales, Australia.,Northern Clinical School, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, Australia
| |
Collapse
|
6
|
Gallagher CI, Ha DA, Harvey RJ, Vandenberg RJ. Positive Allosteric Modulators of Glycine Receptors and Their Potential Use in Pain Therapies. Pharmacol Rev 2022; 74:933-961. [PMID: 36779343 PMCID: PMC9553105 DOI: 10.1124/pharmrev.122.000583] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 04/26/2022] [Accepted: 05/13/2022] [Indexed: 11/22/2022] Open
Abstract
Glycine receptors are ligand-gated ion channels that mediate synaptic inhibition throughout the mammalian spinal cord, brainstem, and higher brain regions. They have recently emerged as promising targets for novel pain therapies due to their ability to produce antinociception by inhibiting nociceptive signals within the dorsal horn of the spinal cord. This has greatly enhanced the interest in developing positive allosteric modulators of glycine receptors. Several pharmaceutical companies and research facilities have attempted to identify new therapeutic leads by conducting large-scale screens of compound libraries, screening new derivatives from natural sources, or synthesizing novel compounds that mimic endogenous compounds with antinociceptive activity. Advances in structural techniques have also led to the publication of multiple high-resolution structures of the receptor, highlighting novel allosteric binding sites and providing additional information for previously identified binding sites. This has greatly enhanced our understanding of the functional properties of glycine receptors and expanded the structure activity relationships of novel pharmacophores. Despite this, glycine receptors are yet to be used as drug targets due to the difficulties in obtaining potent, selective modulators with favorable pharmacokinetic profiles that are devoid of side effects. This review presents a summary of the structural basis for how current compounds cause positive allosteric modulation of glycine receptors and discusses their therapeutic potential as analgesics. SIGNIFICANCE STATEMENT: Chronic pain is a major cause of disability, and in Western societies, this will only increase as the population ages. Despite the high level of prevalence and enormous socioeconomic burden incurred, treatment of chronic pain remains limited as it is often refractory to current analgesics, such as opioids. The National Institute for Drug Abuse has set finding effective, safe, nonaddictive strategies to manage chronic pain as their top priority. Positive allosteric modulators of glycine receptors may provide a therapeutic option.
Collapse
Affiliation(s)
- Casey I Gallagher
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Damien A Ha
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Robert J Harvey
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Robert J Vandenberg
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| |
Collapse
|
7
|
Analysis of Binding Determinants for Different Classes of Competitive and Noncompetitive Inhibitors of Glycine Transporters. Int J Mol Sci 2022; 23:ijms23148050. [PMID: 35887394 PMCID: PMC9317360 DOI: 10.3390/ijms23148050] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/14/2022] [Accepted: 07/18/2022] [Indexed: 11/16/2022] Open
Abstract
Glycine transporters are interesting therapeutic targets as they play significant roles in glycinergic and glutamatergic systems. The search for new selective inhibitors of particular types of glycine transporters (GlyT-1 and GlyT-2) with beneficial kinetics is hampered by limited knowledge about the spatial structure of these proteins. In this study, a pool of homology models of GlyT-1 and GlyT-2 in different conformational states was constructed using the crystal structures of related transporters from the SLC6 family and the recently revealed structure of GlyT-1 in the inward-open state, in order to investigate their binding sites. The binding mode of the known GlyT-1 and GlyT-2 inhibitors was determined using molecular docking studies, molecular dynamics simulations, and MM-GBSA free energy calculations. The results of this study indicate that two amino acids, Gly373 and Leu476 in GlyT-1 and the corresponding Ser479 and Thr582 in GlyT-2, are mainly responsible for the selective binding of ligands within the S1 site. Apart from these, one pocket of the S2 site, which lies between TM3 and TM10, may also be important. Moreover, selective binding of noncompetitive GlyT-1 inhibitors in the intracellular release pathway is affected by hydrophobic interactions with Ile399, Met382, and Leu158. These results can be useful in the rational design of new glycine transporter inhibitors with desired selectivity and properties in the future.
Collapse
|
8
|
Wilson BS, Peiser-Oliver J, Gillis A, Evans S, Alamein C, Mostyn SN, Shimmon S, Rawling T, Christie MJ, Vandenberg RJ, Mohammadi SA. Peripheral administration of selective GlyT2 inhibitor, oleoyl-D-lysine, reverses chronic neuropathic pain but not acute or inflammatory pain in mice. J Pharmacol Exp Ther 2022; 382:246-255. [PMID: 35779948 DOI: 10.1124/jpet.122.001265] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 06/13/2022] [Indexed: 11/22/2022] Open
Abstract
Aberrations in spinal glycinergic signalling are a feature of pain chronification. Normalising these changes by inhibiting glycine transporter-2 (GlyT2) is a promising treatment strategy. However, existing GlyT2 inhibitors e.g. ORG25543 are limited by narrow therapeutic windows and severe dose-limiting side effects such as convulsions, and are therefore poor candidates for clinical development. Here, intraperitoneally administered oleoyl-D-lysine, a lipid-based GlyT2 inhibitor, was characterised in mouse models of acute (hotplate), inflammatory (CFA) and chronic neuropathic (CCI) pain. Side effects were also assessed on a numerical rating score, convulsions score, for motor incoordination (rotarod) and for respiratory depression (whole body plethysmography). Oleoyl-D-lysine produced near complete anti-allodynia for chronic neuropathic pain but no anti-allodynia/analgesia in inflammatory or acute pain. No side effects were seen at the peak analgesic dose, 30 mg/kg. Mild side effects were observed at the highest dose, 100 mg/kg, on the numerical rating score, but no convulsions. These results contrasted markedly with ORG25543, which reached less than 50% reduction in allodynia score only at the lethal/near-lethal dose of 50 mg/kg. At this dose, ORG25543 caused maximal side effects on the numerical rating score and severe convulsions. Oleoyl-D-lysine (30 mg/kg) did not cause any respiratory depression, a problematic side effect of opiates. These results show the safe and effective reversal of neuropathic pain in mice by oleoyl-D-lysine and provide evidence for a distinct role of glycine in chronic pain over acute or short-term pain conditions. Significance Statement Partially inhibiting GlyT2 can alleviate chronic pain by restoring lost glycinergic function. Novel lipid-based GlyT2 inhibitor, ol-D-lys, is safe and effective in alleviating neuropathic pain, but not inflammatory or acute pain. Clinical application of GlyT2 inhibitors may be better suited to chronic neuropathic pain over other pain aetiologies.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Sarasa A Mohammadi
- Discipline of Pharmacology, Sydney Pharmacy School, The University of Sydney, Australia
| |
Collapse
|
9
|
Peiser-Oliver JM, Evans S, Adams DJ, Christie MJ, Vandenberg RJ, Mohammadi SA. Glycinergic Modulation of Pain in Behavioral Animal Models. Front Pharmacol 2022; 13:860903. [PMID: 35694265 PMCID: PMC9174897 DOI: 10.3389/fphar.2022.860903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 04/19/2022] [Indexed: 11/16/2022] Open
Abstract
Animal models of human pain conditions allow for detailed interrogation of known and hypothesized mechanisms of pain physiology in awake, behaving organisms. The importance of the glycinergic system for pain modulation is well known; however, manipulation of this system to treat and alleviate pain has not yet reached the sophistication required for the clinic. Here, we review the current literature on what animal behavioral studies have allowed us to elucidate about glycinergic pain modulation, and the progress toward clinical treatments so far. First, we outline the animal pain models that have been used, such as nerve injury models for neuropathic pain, chemogenic pain models for acute and inflammatory pain, and other models that mimic painful human pathologies such as diabetic neuropathy. We then discuss the genetic approaches to animal models that have identified the crucial glycinergic machinery involved in neuropathic and inflammatory pain. Specifically, two glycine receptor (GlyR) subtypes, GlyRα1(β) and GlyRα3(β), and the two glycine transporters (GlyT), GlyT1 and GlyT2. Finally, we review the different pharmacological approaches to manipulating the glycinergic system for pain management in animal models, such as partial vs. full agonism, reversibility, and multi-target approaches. We discuss the benefits and pitfalls of using animal models in drug development broadly, as well as the progress of glycinergic treatments from preclinical to clinical trials.
Collapse
Affiliation(s)
| | - Sally Evans
- School of Medical Sciences, The University of Sydney, Sydney, NSW, Australia
| | - David J. Adams
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
| | | | | | - Sarasa A. Mohammadi
- School of Medical Sciences, The University of Sydney, Sydney, NSW, Australia
- *Correspondence: Sarasa A. Mohammadi,
| |
Collapse
|
10
|
Frangos ZJ, Cantwell Chater RP, Vandenberg RJ. Glycine Transporter 2: Mechanism and Allosteric Modulation. Front Mol Biosci 2021; 8:734427. [PMID: 34805268 PMCID: PMC8602798 DOI: 10.3389/fmolb.2021.734427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 10/25/2021] [Indexed: 01/19/2023] Open
Abstract
Neurotransmitter sodium symporters (NSS) are a subfamily of SLC6 transporters responsible for regulating neurotransmitter signalling. They are a major target for psychoactive substances including antidepressants and drugs of abuse, prompting substantial research into their modulation and structure-function dynamics. Recently, a series of allosteric transport inhibitors have been identified, which may reduce side effect profiles, compared to orthosteric inhibitors. Allosteric inhibitors are also likely to provide different clearance kinetics compared to competitive inhibitors and potentially better clinical outcomes. Crystal structures and homology models have identified several allosteric modulatory sites on NSS including the vestibule allosteric site (VAS), lipid allosteric site (LAS) and cholesterol binding site (CHOL1). Whilst the architecture of eukaryotic NSS is generally well conserved there are differences in regions that form the VAS, LAS, and CHOL1. Here, we describe ligand-protein interactions that stabilize binding in each allosteric site and explore how differences between transporters could be exploited to generate NSS specific compounds with an emphasis on GlyT2 modulation.
Collapse
Affiliation(s)
- Zachary J Frangos
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Ryan P Cantwell Chater
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Robert J Vandenberg
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| |
Collapse
|
11
|
Inhibition of Glycine Re-Uptake: A Potential Approach for Treating Pain by Augmenting Glycine-Mediated Spinal Neurotransmission and Blunting Central Nociceptive Signaling. Biomolecules 2021; 11:biom11060864. [PMID: 34200954 PMCID: PMC8230656 DOI: 10.3390/biom11060864] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 12/23/2022] Open
Abstract
Among the myriad of cellular and molecular processes identified as contributing to pathological pain, disinhibition of spinal cord nociceptive signaling to higher cortical centers plays a critical role. Importantly, evidence suggests that impaired glycinergic neurotransmission develops in the dorsal horn of the spinal cord in inflammatory and neuropathic pain models and is a key maladaptive mechanism causing mechanical hyperalgesia and allodynia. Thus, it has been hypothesized that pharmacological agents capable of augmenting glycinergic tone within the dorsal horn may be able to blunt or block aberrant nociceptor signaling to the brain and serve as a novel class of analgesics for various pathological pain states. Indeed, drugs that enhance dysfunctional glycinergic transmission, and in particular inhibitors of the glycine transporters (GlyT1 and GlyT2), are generating widespread interest as a potential class of novel analgesics. The GlyTs are Na+/Cl−-dependent transporters of the solute carrier 6 (SLC6) family and it has been proposed that the inhibition of them presents a possible mechanism by which to increase spinal extracellular glycine concentrations and enhance GlyR-mediated inhibitory neurotransmission in the dorsal horn. Various inhibitors of both GlyT1 and GlyT2 have demonstrated broad analgesic efficacy in several preclinical models of acute and chronic pain, providing promise for the approach to deliver a first-in-class non-opioid analgesic with a mechanism of action differentiated from current standard of care. This review will highlight the therapeutic potential of GlyT inhibitors as a novel class of analgesics, present recent advances reported for the field, and discuss the key challenges associated with the development of a GlyT inhibitor into a safe and effective agent to treat pain.
Collapse
|
12
|
Halloy F, Iyer PS, Ghidini A, Lysenko V, Barman-Aksözen J, Grubenmann CP, Jucker J, Wildner-Verhey van Wijk N, Ruepp MD, Minder EI, Minder AE, Schneider-Yin X, Theocharides APA, Schümperli D, Hall J. Repurposing of glycine transport inhibitors for the treatment of erythropoietic protoporphyria. Cell Chem Biol 2021; 28:1221-1234.e6. [PMID: 33756123 DOI: 10.1016/j.chembiol.2021.02.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 01/19/2021] [Accepted: 02/23/2021] [Indexed: 12/16/2022]
Abstract
Erythropoietic protoporphyria (EPP) is a rare disease in which patients experience severe light sensitivity. It is caused by a deficiency of ferrochelatase (FECH), the last enzyme in heme biosynthesis (HBS). The lack of FECH causes accumulation of its photoreactive substrate protoporphyrin IX (PPIX) in patients' erythrocytes. Here, we explored an approach for the treatment of EPP by decreasing PPIX synthesis using small-molecule inhibitors directed to factors in the HBS pathway. We generated a FECH-knockout clone from K562 erythroleukemia cells, which accumulates PPIX and undergoes oxidative stress upon light exposure. We used these matched cell lines to screen a set of publicly available inhibitors of factors in the HBS pathway. Inhibitors of the glycine transporters GlyT1 and GlyT2 lowered levels of PPIX and markers of oxidative stress selectively in K56211B4 cells, and in primary erythroid cultures from an EPP patient. Our findings open the door to investigation of glycine transport inhibitors for HBS disorders.
Collapse
Affiliation(s)
- François Halloy
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Pavithra S Iyer
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Alice Ghidini
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Veronika Lysenko
- Department of Medical Oncology and Hematology, University Hospital and University of Zurich, 8091 Zurich, Switzerland
| | - Jasmin Barman-Aksözen
- Institute of Laboratory Medicine, Municipal Hospital Waid and Triemli, 8063 Zurich, Switzerland
| | - Chia-Pei Grubenmann
- Institute of Laboratory Medicine, Municipal Hospital Waid and Triemli, 8063 Zurich, Switzerland
| | - Jessica Jucker
- Institute of Laboratory Medicine, Municipal Hospital Waid and Triemli, 8063 Zurich, Switzerland
| | | | - Marc-David Ruepp
- UK Dementia Research Institute at King's College London, SE5 9RT London, UK; Institute of Psychiatry, Psychology and Neuroscience, King's College London, SE5 8AF London, UK
| | - Elisabeth I Minder
- Department for Endocrinology, Diabetology, Porphyria, Municipal Hospital Waid and Triemli, 8063 Zurich, Switzerland
| | - Anna-Elisabeth Minder
- Department for Endocrinology, Diabetology, Porphyria, Municipal Hospital Waid and Triemli, 8063 Zurich, Switzerland
| | - Xiaoye Schneider-Yin
- Institute of Laboratory Medicine, Municipal Hospital Waid and Triemli, 8063 Zurich, Switzerland
| | - Alexandre P A Theocharides
- Department of Medical Oncology and Hematology, University Hospital and University of Zurich, 8091 Zurich, Switzerland
| | - Daniel Schümperli
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland.
| | - Jonathan Hall
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland.
| |
Collapse
|
13
|
Pharmacological Evidence on Augmented Antiallodynia Following Systemic Co-Treatment with GlyT-1 and GlyT-2 Inhibitors in Rat Neuropathic Pain Model. Int J Mol Sci 2021; 22:ijms22052479. [PMID: 33804568 PMCID: PMC7957511 DOI: 10.3390/ijms22052479] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/19/2021] [Accepted: 02/25/2021] [Indexed: 12/16/2022] Open
Abstract
The limited effect of current medications on neuropathic pain (NP) has initiated large efforts to develop effective treatments. Animal studies showed that glycine transporter (GlyT) inhibitors are promising analgesics in NP, though concerns regarding adverse effects were raised. We aimed to study NFPS and Org-25543, GlyT-1 and GlyT-2 inhibitors, respectively and their combination in rat mononeuropathic pain evoked by partial sciatic nerve ligation. Cerebrospinal fluid (CSF) glycine content was also determined by capillary electrophoresis. Subcutaneous (s.c.) 4 mg/kg NFPS or Org-25543 showed analgesia following acute administration (30-60 min). Small doses of each compound failed to produce antiallodynia up to 180 min after the acute administration. However, NFPS (1 mg/kg) produced antiallodynia after four days of treatment. Co-treatment with subanalgesic doses of NFPS (1 mg/kg) and Org-25543 (2 mg/kg) produced analgesia at 60 min and thereafter meanwhile increased significantly the CSF glycine content. This combination alleviated NP without affecting motor function. Test compounds failed to activate G-proteins in spinal cord. To the best of our knowledge for the first time we demonstrated augmented analgesia by combining GlyT-1 and 2 inhibitors. Increased CSF glycine content supports involvement of glycinergic system. Combining selective GlyT inhibitors or developing non-selective GlyT inhibitors might have therapeutic value in NP.
Collapse
|
14
|
Brill SE, Maraslioglu A, Kurz C, Kramer F, Fuhr MF, Singh A, Friauf E. Glycinergic Transmission in the Presence and Absence of Functional GlyT2: Lessons From the Auditory Brainstem. Front Synaptic Neurosci 2021; 12:560008. [PMID: 33633558 PMCID: PMC7900164 DOI: 10.3389/fnsyn.2020.560008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 12/01/2020] [Indexed: 12/20/2022] Open
Abstract
Synaptic transmission is controlled by re-uptake systems that reduce transmitter concentrations in the synaptic cleft and recycle the transmitter into presynaptic terminals. The re-uptake systems are thought to ensure cytosolic concentrations in the terminals that are sufficient for reloading empty synaptic vesicles (SVs). Genetic deletion of glycine transporter 2 (GlyT2) results in severely disrupted inhibitory neurotransmission and ultimately to death. Here we investigated the role of GlyT2 at inhibitory glycinergic synapses in the mammalian auditory brainstem. These synapses are tuned for resilience, reliability, and precision, even during sustained high-frequency stimulation when endocytosis and refilling of SVs probably contribute substantially to efficient replenishment of the readily releasable pool (RRP). Such robust synapses are formed between MNTB and LSO neurons (medial nucleus of the trapezoid body, lateral superior olive). By means of patch-clamp recordings, we assessed the synaptic performance in controls, in GlyT2 knockout mice (KOs), and upon acute pharmacological GlyT2 blockade. Via computational modeling, we calculated the reoccupation rate of empty release sites and RRP replenishment kinetics during 60-s challenge and 60-s recovery periods. Control MNTB-LSO inputs maintained high fidelity neurotransmission at 50 Hz for 60 s and recovered very efficiently from synaptic depression. During 'marathon-experiments' (30,600 stimuli in 20 min), RRP replenishment accumulated to 1,260-fold. In contrast, KO inputs featured severe impairments. For example, the input number was reduced to ~1 (vs. ~4 in controls), implying massive functional degeneration of the MNTB-LSO microcircuit and a role of GlyT2 during synapse maturation. Surprisingly, neurotransmission did not collapse completely in KOs as inputs still replenished their small RRP 80-fold upon 50 Hz | 60 s challenge. However, they totally failed to do so for extended periods. Upon acute pharmacological GlyT2 inactivation, synaptic performance remained robust, in stark contrast to KOs. RRP replenishment was 865-fold in marathon-experiments, only ~1/3 lower than in controls. Collectively, our empirical and modeling results demonstrate that GlyT2 re-uptake activity is not the dominant factor in the SV recycling pathway that imparts indefatigability to MNTB-LSO synapses. We postulate that additional glycine sources, possibly the antiporter Asc-1, contribute to RRP replenishment at these high-fidelity brainstem synapses.
Collapse
Affiliation(s)
- Sina E Brill
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Ayse Maraslioglu
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Catharina Kurz
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Florian Kramer
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Martin F Fuhr
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Abhyudai Singh
- Electrical & Computer Engineering, University of Delaware, Newark, DE, United States
| | - Eckhard Friauf
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| |
Collapse
|
15
|
Wilson KA, Mostyn SN, Frangos ZJ, Shimmon S, Rawling T, Vandenberg RJ, O'Mara ML. The allosteric inhibition of glycine transporter 2 by bioactive lipid analgesics is controlled by penetration into a deep lipid cavity. J Biol Chem 2021; 296:100282. [PMID: 33450225 PMCID: PMC7949037 DOI: 10.1016/j.jbc.2021.100282] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 01/06/2021] [Accepted: 01/08/2021] [Indexed: 01/07/2023] Open
Abstract
The role of lipids in modulating membrane protein function is an emerging and rapidly growing area of research. The rational design of lipids that target membrane proteins for the treatment of pathological conditions is a novel extension in this field and provides a step forward in our understanding of membrane transporters. Bioactive lipids show considerable promise as analgesics for the treatment of chronic pain and bind to a high-affinity allosteric-binding site on the human glycine transporter 2 (GlyT2 or SLC6A5). Here, we use a combination of medicinal chemistry, electrophysiology, and computational modeling to develop a rational structure-activity relationship for lipid inhibitors and demonstrate the key role of the lipid tail interactions for GlyT2 inhibition. Specifically, we examine how lipid inhibitor head group stereochemistry, tail length, and double-bond position promote enhanced inhibition. Overall, the l-stereoisomer is generally a better inhibitor than the d-stereoisomer, longer tail length correlates with greater potency, and the position of the double bond influences the activity of the inhibitor. We propose that the binding of the lipid inhibitor deep into the allosteric-binding pocket is critical for inhibition. Furthermore, this provides insight into the mechanism of inhibition of GlyT2 and highlights how lipids can modulate the activity of membrane proteins by binding to cavities between helices. The principles identified in this work have broader implications for the development of a larger class of compounds that could target SLC6 transporters for disease treatment.
Collapse
Affiliation(s)
- Katie A Wilson
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT, Australia
| | - Shannon N Mostyn
- Discipline of Pharmacology, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Zachary J Frangos
- Discipline of Pharmacology, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW, Australia
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW, Australia
| | - Robert J Vandenberg
- Discipline of Pharmacology, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Megan L O'Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT, Australia.
| |
Collapse
|
16
|
Ackermann TM, Allmendinger L, Höfner G, Wanner KT. MS Binding Assays for Glycine Transporter 2 (GlyT2) Employing Org25543 as Reporter Ligand. ChemMedChem 2021; 16:199-215. [PMID: 32734692 PMCID: PMC7821181 DOI: 10.1002/cmdc.202000342] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/29/2020] [Indexed: 12/13/2022]
Abstract
This study describes the first binding assay for glycine transporter 2 (GlyT2) following the concept of MS Binding Assays. The selective GlyT2 inhibitor Org25543 was employed as a reporter ligand and it was quantified with a highly sensitive and rapid LC-ESI-MS/MS method. Binding of Org25543 at GlyT2 was characterized in kinetic and saturation experiments with an off-rate of 7.07×10-3 s-1 , an on-rate of 1.01×106 M-1 s-1 , and an equilibrium dissociation constant of 7.45 nM. Furthermore, the inhibitory constants of 19 GlyT ligands were determined in competition experiments. The validity of the GlyT2 affinities determined with the binding assay was examined by a comparison with published inhibitory potencies from various functional assays. With the capability for affinity determination towards GlyT2 the developed MS Binding Assays provide the first tool for affinity profiling of potential ligands and it represents a valuable new alternative to functional assays addressing GlyT2.
Collapse
Affiliation(s)
- Thomas M. Ackermann
- Department of Pharmacy, Center for Drug ResearchLudwig-Maximilians-Universität MunichButenandtstraße 781377MunichGermany
| | - Lars Allmendinger
- Department of Pharmacy, Center for Drug ResearchLudwig-Maximilians-Universität MunichButenandtstraße 781377MunichGermany
| | - Georg Höfner
- Department of Pharmacy, Center for Drug ResearchLudwig-Maximilians-Universität MunichButenandtstraße 781377MunichGermany
| | - Klaus T. Wanner
- Department of Pharmacy, Center for Drug ResearchLudwig-Maximilians-Universität MunichButenandtstraße 781377MunichGermany
| |
Collapse
|
17
|
Sheipouri D, Gallagher CI, Shimmon S, Rawling T, Vandenberg RJ. A System for Assessing Dual Action Modulators of Glycine Transporters and Glycine Receptors. Biomolecules 2020; 10:biom10121618. [PMID: 33266066 PMCID: PMC7760315 DOI: 10.3390/biom10121618] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 11/23/2020] [Accepted: 11/25/2020] [Indexed: 12/13/2022] Open
Abstract
Reduced inhibitory glycinergic neurotransmission is implicated in a number of neurological conditions such as neuropathic pain, schizophrenia, epilepsy and hyperekplexia. Restoring glycinergic signalling may be an effective method of treating these pathologies. Glycine transporters (GlyTs) control synaptic and extra-synaptic glycine concentrations and slowing the reuptake of glycine using specific GlyT inhibitors will increase glycine extracellular concentrations and increase glycine receptor (GlyR) activation. Glycinergic neurotransmission can also be improved through positive allosteric modulation (PAM) of GlyRs. Despite efforts to manipulate this synapse, no therapeutics currently target it. We propose that dual action modulators of both GlyTs and GlyRs may show greater therapeutic potential than those targeting individual proteins. To show this, we have characterized a co-expression system in Xenopus laevis oocytes consisting of GlyT1 or GlyT2 co-expressed with GlyRα1. We use two electrode voltage clamp recording techniques to measure the impact of GlyTs on GlyRs and the effects of modulators of these proteins. We show that increases in GlyT density in close proximity to GlyRs diminish receptor currents. Reductions in GlyR mediated currents are not observed when non-transportable GlyR agonists are applied or when Na+ is not available. GlyTs reduce glycine concentrations across different concentration ranges, corresponding with their ion-coupling stoichiometry, and full receptor currents can be restored when GlyTs are blocked with selective inhibitors. We show that partial inhibition of GlyT2 and modest GlyRα1 potentiation using a dual action compound, is as useful in restoring GlyR currents as a full and potent single target GlyT2 inhibitor or single target GlyRα1 PAM. The co-expression system developed in this study will provide a robust means for assessing the likely impact of GlyR PAMs and GlyT inhibitors on glycine neurotransmission.
Collapse
Affiliation(s)
- Diba Sheipouri
- School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia; (D.S.); (C.I.G.)
| | - Casey I. Gallagher
- School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia; (D.S.); (C.I.G.)
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (S.S.); (T.R.)
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (S.S.); (T.R.)
| | - Robert J. Vandenberg
- School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia; (D.S.); (C.I.G.)
- Correspondence:
| |
Collapse
|
18
|
Seckler JM, Lewis SJ. Advances in D-Amino Acids in Neurological Research. Int J Mol Sci 2020; 21:ijms21197325. [PMID: 33023061 PMCID: PMC7582301 DOI: 10.3390/ijms21197325] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/29/2020] [Accepted: 09/29/2020] [Indexed: 12/16/2022] Open
Abstract
D-amino acids have been known to exist in the human brain for nearly 40 years, and they continue to be a field of active study to today. This review article aims to give a concise overview of the recent advances in D-amino acid research as they relate to the brain and neurological disorders. This work has largely been focused on modulation of the N-methyl-D-aspartate (NMDA) receptor and its relationship to Alzheimer’s disease and Schizophrenia, but there has been a wealth of novel research which has elucidated a novel role for several D-amino acids in altering brain chemistry in a neuroprotective manner. D-amino acids which have no currently known activity in the brain but which have active derivatives will also be reviewed.
Collapse
Affiliation(s)
- James M. Seckler
- Department Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
- Correspondence:
| | - Stephen J. Lewis
- Department Pediatrics, Case Western Reserve University, Cleveland, OH 44106, USA;
| |
Collapse
|
19
|
Imam MZ, Kuo A, Nicholson JR, Corradini L, Smith MT. Assessment of the anti-allodynic efficacy of a glycine transporter 2 inhibitor relative to pregabalin and duloxetine in a rat model of prostate cancer-induced bone pain. Pharmacol Rep 2020; 72:1418-1425. [PMID: 32715433 DOI: 10.1007/s43440-020-00145-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 07/16/2020] [Accepted: 07/18/2020] [Indexed: 12/12/2022]
Abstract
BACKGROUND The pathobiology of prostate cancer-induced bone pain (PCIBP) is underpinned by both inflammatory and neuropathic components. Here, we used a rat model of PCIBP to assess the analgesic efficacy of a glycine transporter 2 (GlyT2) inhibitor (N-(6-((1,3-dihydroxypropan-2-yl)amino)-2-(dimethylamino)pyridin-3-yl)-3,5-dimethoxy-4-(4-(trifluoromethyl)phenoxy) benzamide) relative to two clinically available adjuvant drugs that are recommended for the relief of neuropathic pain, viz, pregabalin and duloxetine. METHODS PCIBP was induced in male Wistar Han rats following intra-tibial injection (ITI) of rat prostate cancer (AT3B) cells into the left tibia. Sham-rats received an ITI of heat-killed AT3B cells. PCIBP rats with fully developed mechanical allodynia in the ipsilateral hindpaws as assessed using von Frey filaments, received single oral (p.o.) bolus doses of the GlyT2 inhibitor (3-30 mg/kg), pregabalin (3-100 mg/kg), duloxetine (3-100 mg/kg), or vehicle. Baseline paw withdrawal thresholds (PWTs) were determined in the ipsilateral (injured side) and contralateral hindpaws immediately prior to dosing and at scheduled times for 3 h post dosing in individual animals. RESULTS Single oral bolus doses of the GlyT2 inhibitor (3-30 mg/kg) evoked partial pain relief at the doses tested in the ipsilateral hindpaws of PCIBP rats without any discernible behavioural side effects. By contrast, single oral bolus doses of pregabalin at 10-100 mg/kg evoked dose-dependent and complete alleviation of mechanical allodynia. By comparison, single oral bolus doses of duloxetine at doses up to 100 mg/kg lacked efficacy. CONCLUSION Oral administration of this GlyT2 inhibitor evoked partial pain relief in PCIBP rats and did not evoke central nervous system side effects in contrast to GlyT2 inhibitors reported by others.
Collapse
Affiliation(s)
- Mohammad Zafar Imam
- Centre for Integrated Preclinical Drug Development, School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
| | - Andy Kuo
- Centre for Integrated Preclinical Drug Development, School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
| | | | - Laura Corradini
- Boehringer Ingelheim Pharma GmbH and Co. KG, Biberach, Germany
| | - Maree T Smith
- Centre for Integrated Preclinical Drug Development, School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia.
| |
Collapse
|
20
|
Niello M, Gradisch R, Loland CJ, Stockner T, Sitte HH. Allosteric Modulation of Neurotransmitter Transporters as a Therapeutic Strategy. Trends Pharmacol Sci 2020; 41:446-463. [PMID: 32471654 PMCID: PMC7610661 DOI: 10.1016/j.tips.2020.04.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 04/21/2020] [Accepted: 04/22/2020] [Indexed: 12/11/2022]
Abstract
Neurotransmitter transporters (NTTs) are involved in the fine-tuning of brain neurotransmitter homeostasis. As such, they are implicated in a plethora of complex behaviors, including reward, movement, and cognition. During recent decades, compounds that modulate NTT functions have been developed. Some of them are in clinical use for the management of different neuropsychiatric conditions. The majority of these compounds have been found to selectively interact with the orthosteric site of NTTs. Recently, diverse allosteric sites have been described in a number of NTTs, modulating their function. A more complex NTT pharmacology may be useful in the development of novel therapeutics. Here, we summarize current knowledge on such modulatory allosteric sites, with specific focus on their pharmacological and therapeutic potential.
Collapse
Affiliation(s)
- Marco Niello
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ralph Gradisch
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Claus Juul Loland
- Laboratory for Membrane Protein Dynamics. Department of Neuroscience. University of Copenhagen, Copenhagen, Denmark
| | - Thomas Stockner
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Harald H Sitte
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria; AddRess, Centre for Addiction Research and Science, Medical University of Vienna, Vienna, Austria.
| |
Collapse
|
21
|
Identification of N-acyl amino acids that are positive allosteric modulators of glycine receptors. Biochem Pharmacol 2020; 180:114117. [PMID: 32579961 DOI: 10.1016/j.bcp.2020.114117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/16/2020] [Accepted: 06/18/2020] [Indexed: 01/31/2023]
Abstract
Glycine receptors (GlyRs) mediate inhibitory neurotransmission within the spinal cord and play a crucial role in nociceptive signalling. This makes them primary targets for the development of novel chronic pain therapies. Endogenous lipids have previously been shown to modulate glycine receptors and produce analgesia in pain models, however little is known about what chemical features mediate these effects. In this study, we characterised lipid modulation of GlyRs by screening a library of N-acyl amino acids across all receptor subtypes and determined chemical features crucial for their activity. Acyl-glycine's with a C18 carbon tail were found to produce the greatest potentiation, and require a cis double bond within the central region of the carbon tail (ω6 - ω9) to be active. At 1 µM, C18 ω6,9 glycine potentiated glycine induced currents in α3 and α3β receptors by over 50%, and α1, α2, α1β and α2β receptors by over 100%. C18 ω9 glycine (N-oleoyl glycine) significantly enhance glycine induced peak currents and cause a dose-dependent shift in the glycine concentration response. In the presence of 3 µM C18 ω9 glycine, the EC5o of glycine at the α1 receptor was reduced from 17 µM to 10 µM. This study has identified several acyl-amino acids which are positive allosteric modulators of GlyRs and make promising lead compounds for the development of novel chronic pain therapies.
Collapse
|
22
|
Mostyn SN, Sarker S, Muthuraman P, Raja A, Shimmon S, Rawling T, Cioffi CL, Vandenberg RJ. Photoswitchable ORG25543 Congener Enables Optical Control of Glycine Transporter 2. ACS Chem Neurosci 2020; 11:1250-1258. [PMID: 32191428 PMCID: PMC7206614 DOI: 10.1021/acschemneuro.9b00655] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
![]()
Glycine
neurotransmission in the dorsal horn of the spinal cord
plays a key role in regulating nociceptive signaling, but in chronic
pain states reduced glycine neurotransmission is associated with the
development of allodynia and hypersensitivity to painful stimuli.
This suggests that restoration of glycine neurotransmission may be
therapeutic for the treatment of chronic pain. Glycine transporter
2 inhibitors have been demonstrated to enhance glycine neurotransmission
and provide relief from allodynia in rodent models of chronic pain.
In recent years, photoswitchable compounds have been developed to
provide the possibility of controlling the activity of target proteins
using light. In this study we have developed a photoswitchable noncompetitive
inhibitor of glycine transporter 2 that has different affinities for
the transporter at 365 nm compared to 470 nm light.
Collapse
Affiliation(s)
- Shannon N. Mostyn
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Subhodeep Sarker
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Parthasarathy Muthuraman
- Basic and Clinical Sciences and Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, United States
| | - Arun Raja
- Basic and Clinical Sciences and Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, United States
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Christopher L. Cioffi
- Basic and Clinical Sciences and Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, United States
| | - Robert J. Vandenberg
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia
| |
Collapse
|
23
|
Gupta S, Bera S, Mondal D. Nascent-HBr-Catalyzed Removal of Orthogonal Protecting Groups in Aqueous Surfactants. J Org Chem 2020; 85:2635-2645. [PMID: 31875403 DOI: 10.1021/acs.joc.9b02561] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Organic reactions in the aqueous environment have recently emerged as a promising research area. The generation of nascent-HBr from the slow hydrolysis of the dispersed catalyst, benzyl bromide, with the interior water present in the hydrophobic core of the confined micellar medium in aqueous surfactant is described for the first time. The sustained-release nascent-HBr enabled the chemoselective cleavages of acid-sensitive orthogonal functionalities present in carbohydrates, amino alcohols, and hydroxylated acyclic compounds in good to excellent yields.
Collapse
Affiliation(s)
- Shilpi Gupta
- School of Chemical Sciences , Central University of Gujarat , Gandhinagar - 382030 , India
| | - Smritilekha Bera
- School of Chemical Sciences , Central University of Gujarat , Gandhinagar - 382030 , India
| | - Dhananjoy Mondal
- School of Chemical Sciences , Central University of Gujarat , Gandhinagar - 382030 , India
| |
Collapse
|
24
|
Mostyn SN, Wilson KA, Schumann-Gillett A, Frangos ZJ, Shimmon S, Rawling T, Ryan RM, O'Mara ML, Vandenberg RJ. Identification of an allosteric binding site on the human glycine transporter, GlyT2, for bioactive lipid analgesics. eLife 2019; 8:e47150. [PMID: 31621581 PMCID: PMC6797481 DOI: 10.7554/elife.47150] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 09/30/2019] [Indexed: 01/01/2023] Open
Abstract
The treatment of chronic pain is poorly managed by current analgesics, and there is a need for new classes of drugs. We recently developed a series of bioactive lipids that inhibit the human glycine transporter GlyT2 (SLC6A5) and provide analgesia in animal models of pain. Here, we have used functional analysis of mutant transporters combined with molecular dynamics simulations of lipid-transporter interactions to understand how these bioactive lipids interact with GlyT2. This study identifies a novel extracellular allosteric modulator site formed by a crevice between transmembrane domains 5, 7, and 8, and extracellular loop 4 of GlyT2. Knowledge of this site could be exploited further in the development of drugs to treat pain, and to identify other allosteric modulators of the SLC6 family of transporters.
Collapse
Affiliation(s)
- Shannon N Mostyn
- School of Medical Sciences, Faculty of Medicine and HealthUniversity of SydneySydneyAustralia
| | - Katie A Wilson
- Research School of Chemistry, College of ScienceThe Australian National UniversityCanberraAustralia
| | | | - Zachary J Frangos
- School of Medical Sciences, Faculty of Medicine and HealthUniversity of SydneySydneyAustralia
| | - Susan Shimmon
- School of Mathematical and Physical SciencesUniversity of Technology SydneySydneyAustralia
| | - Tristan Rawling
- School of Mathematical and Physical SciencesUniversity of Technology SydneySydneyAustralia
| | - Renae M Ryan
- School of Medical Sciences, Faculty of Medicine and HealthUniversity of SydneySydneyAustralia
| | - Megan L O'Mara
- Research School of Chemistry, College of ScienceThe Australian National UniversityCanberraAustralia
| | - Robert J Vandenberg
- School of Medical Sciences, Faculty of Medicine and HealthUniversity of SydneySydneyAustralia
| |
Collapse
|
25
|
Al-Khrasani M, Mohammadzadeh A, Balogh M, Király K, Barsi S, Hajnal B, Köles L, Zádori ZS, Harsing LG. Glycine transporter inhibitors: A new avenue for managing neuropathic pain. Brain Res Bull 2019; 152:143-158. [PMID: 31302238 DOI: 10.1016/j.brainresbull.2019.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 06/27/2019] [Accepted: 07/08/2019] [Indexed: 12/12/2022]
Abstract
Interneurons operating with glycine neurotransmitter are involved in the regulation of pain transmission in the dorsal horn of the spinal cord. In addition to interneurons, glycine release also occurs from glial cells neighboring glutamatergic synapses in the spinal cord. Neuronal and glial release of glycine is controlled by glycine transporters (GlyTs). Inhibitors of the two isoforms of GlyTs, the astrocytic type-1 (GlyT-1) and the neuronal type-2 (GlyT-2), decrease pain sensation evoked by injuries of peripheral sensory neurons or inflammation. The function of dorsal horn glycinergic interneurons has been suggested to be reduced in neuropathic pain, which can be reversed by GlyT-2 inhibitors (Org-25543, ALX1393). Several lines of evidence also support that peripheral nerve damage or inflammation may shift glutamatergic neurochemical transmission from N-methyl-D aspartate (NMDA) NR1/NR2A receptor- to NR1/NR2B receptor-mediated events (subunit switch). This pathological overactivation of NR1/NR2B receptors can be reduced by GlyT-1 inhibitors (NFPS, Org-25935), which decrease excessive glycine release from astroglial cells or by selective antagonists of NR2B subunits (ifenprodil, Ro 25-6981). Although several experiments suggest that GlyT inhibitors may represent a novel strategy in the control of neuropathic pain, proving this concept in human beings is hampered by lack of clinically applicable GlyT inhibitors. We also suggest that drugs inhibiting both GlyT-1 and GlyT-2 non-selectively and reversibly, may favorably target neuropathic pain. In this paper we overview inhibitors of the two isoforms of GlyTs as well as the effects of these drugs in experimental models of neuropathic pain. In addition, the possible mechanisms of action of the GlyT inhibitors, i.e. how they affect the neurochemical and pain transmission in the spinal cord, are also discussed. The growing evidence for the possible therapeutic intervention of neuropathic pain by GlyT inhibitors further urges development of drugable compounds, which may beneficially restore impaired pain transmission in various neuropathic conditions.
Collapse
Affiliation(s)
- Mahmoud Al-Khrasani
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary.
| | - Amir Mohammadzadeh
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Mihály Balogh
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Kornél Király
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Szilvia Barsi
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Benjamin Hajnal
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - László Köles
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Zoltán S Zádori
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Laszlo G Harsing
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| |
Collapse
|