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Bourque M, Grégoire L, Patel W, Dickens D, Snodgrass R, Di Paolo T. AV-101, a Pro-Drug Antagonist at the NMDA Receptor Glycine Site, Reduces L-Dopa Induced Dyskinesias in MPTP Monkeys. Cells 2022; 11:cells11223530. [PMID: 36428960 PMCID: PMC9688762 DOI: 10.3390/cells11223530] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 10/24/2022] [Accepted: 11/02/2022] [Indexed: 11/10/2022] Open
Abstract
N-methyl-D-aspartate (NMDA) receptors have been implicated in L-Dopa-induced dyskinesias (LID) in Parkinson's disease patients, but the use of antagonists that directly inhibit this receptor is associated with severe side effects. L-4-chlorokynurenine (4-Cl-KYN or AV-101) is a pro-drug of 7-chlorokynurenic acid (7-Cl-KYNA), a potent and specific antagonist of the glycine (GlyB) co-agonist site of NMDA receptors. The 7-Cl-KYNA has limited ability to cross the blood-brain barrier, whereas AV-101 readily accesses the brain. We investigated if AV-101 reduces LID in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys while maintaining the antiparkinsonian activity of L-Dopa. A first pilot study using three dyskinetic MPTP monkeys showed that acute AV-101 treatment (250 and 450 mg/kg) reduced LID and maintained the antiparkinsonian activity of L-Dopa. The main study using six additional dyskinetic MPTP monkeys showed that repeated AV-101 treatment (250 mg/kg, b.i.d. for 4 consecutive days) maintained their L-Dopa antiparkinsonian response. We measured significantly less LID when AV-101 was combined with L-Dopa treatment. AV-101 alone or with L-Dopa had no non-motor adverse effects in MPTP monkeys. Our study showed antidyskinetic activity of AV-101 in MPTP monkeys was comparable to amantadine tested previously in our laboratory in this model. We observed no adverse effects with AV-101, which is an improvement over amantadine, with its known side effects.
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Affiliation(s)
- Mélanie Bourque
- Centre de Recherche du CHU de Québec, Axe Neurosciences, Québec, QC G1V4G2, Canada
| | - Laurent Grégoire
- Centre de Recherche du CHU de Québec, Axe Neurosciences, Québec, QC G1V4G2, Canada
| | - Waseema Patel
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool L69 3GL, UK
| | - David Dickens
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool L69 3GL, UK
| | - Ralph Snodgrass
- Vistagen Therapeutics, Inc., South San Francisco, CA 94080, USA
| | - Thérèse Di Paolo
- Centre de Recherche du CHU de Québec, Axe Neurosciences, Québec, QC G1V4G2, Canada
- Faculté de Pharmacie, Université Laval, Québec, QC G1V0A6, Canada
- Correspondence:
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Majerova P, Olesova D, Golisova G, Buralova M, Michalicova A, Vegh J, Piestansky J, Bhide M, Hanes J, Kovac A. Analog of kynurenic acid decreases tau pathology by modulating astrogliosis in rat model for tauopathy. Biomed Pharmacother 2022; 152:113257. [PMID: 35714514 DOI: 10.1016/j.biopha.2022.113257] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 05/30/2022] [Accepted: 06/06/2022] [Indexed: 11/17/2022] Open
Abstract
Kynurenines have immunomodulatory and neuroactive properties and can influence the central nervous system. Previous studies showed the involvement of the kynurenines in the pathogenesis and progression of neurodegenerative disease. In neurodegenerative disorders, including tauopathies, the tryptophan metabolism is shifted toward neurotoxic agents and the reduction of neuroprotectant products. Astrocyte-derived kynurenic acid serves as a neuroprotectant. However, systemic administration of kynurenic acid is not effective because of low permeability across the blood-brain barrier (BBB). We used a kynurenic acid analog with similar biological activity but higher brain permeability to overcome BBB limitations. In the present study, we used amide derivate of kynurenic acid N-(2-N, N-dimethylaminoethyl)- 4-oxo-1 H-quinoline-2-carboxamid (KYNA-1). We administered KYNA-1 for three months to tau transgenic rats SHR-24 and analyzed the effect on tau pathology and activation of glial cells. Primary glial cell cultures were applied to identify the mechanism of the KYNA-1 effect. KYNA-1 was not toxic to rats after chronic three-month administration. When chronically administered, KYNA-1 reduced hyperphosphorylation of insoluble tau in the brain of transgenic rats. Noteworthily, the plasma total tau was also reduced. We determined that the effect of KYNA-1 on tau pathology was induced through the modulation of glial activation. KYNA-1 inhibited LPS induced activation of astrocytes and induced transformation of microglia to M2 phenotype. We identified that the administration of KYNA-1 reduced tau hyperphosphorylation and neuroinflammation. KYNA-1 may serve as a promising treatment for tauopathies.
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Affiliation(s)
- Petra Majerova
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia.
| | - Dominika Olesova
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia; Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Kosice, Kosice, Slovakia.
| | - Greta Golisova
- Faculty of Natural Sciences, Department of Biochemistry, Comenius University in Bratislava, Mlynska dolina, Ilkovicova 6, 842 15 Bratislava, Slovakia.
| | - Martina Buralova
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia.
| | - Alena Michalicova
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia.
| | - Jozef Vegh
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia.
| | - Juraj Piestansky
- Department of Pharmaceutical Analysis and Nuclear Pharmacy, Faculty of Pharmacy, Comenius University in Bratislava, Odbojarov 10, SK-832 32 Bratislava, Slovakia.
| | - Mangesh Bhide
- Laboratory of Biomedical Microbiology and Immunology, The University of Veterinary Medicine and Pharmacy in Kosice, Kosice, Slovakia.
| | - Jozef Hanes
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia.
| | - Andrej Kovac
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia.
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Mithaiwala MN, Santana-Coelho D, Porter GA, O’Connor JC. Neuroinflammation and the Kynurenine Pathway in CNS Disease: Molecular Mechanisms and Therapeutic Implications. Cells 2021; 10:1548. [PMID: 34205235 PMCID: PMC8235708 DOI: 10.3390/cells10061548] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Revised: 06/13/2021] [Accepted: 06/15/2021] [Indexed: 12/16/2022] Open
Abstract
Diseases of the central nervous system (CNS) remain a significant health, social and economic problem around the globe. The development of therapeutic strategies for CNS conditions has suffered due to a poor understanding of the underlying pathologies that manifest them. Understanding common etiological origins at the cellular and molecular level is essential to enhance the development of efficacious and targeted treatment options. Over the years, neuroinflammation has been posited as a common link between multiple neurological, neurodegenerative and neuropsychiatric disorders. Processes that precipitate neuroinflammatory conditions including genetics, infections, physical injury and psychosocial factors, like stress and trauma, closely link dysregulation in kynurenine pathway (KP) of tryptophan metabolism as a possible pathophysiological factor that 'fuel the fire' in CNS diseases. In this study, we aim to review emerging evidence that provide mechanistic insights between different CNS disorders, neuroinflammation and the KP. We provide a thorough overview of the different branches of the KP pertinent to CNS disease pathology that have therapeutic implications for the development of selected and efficacious treatment strategies.
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Affiliation(s)
- Mustafa N. Mithaiwala
- Integrated Biomedical Sciences Program, Graduate School of Biomedical Sciences, UT Health San Antonio, San Antonio, TX 78229, USA; (M.N.M.); (D.S.-C.); (G.A.P.)
- Department of Pharmacology, Long School of Medicine, UT Health San Antonio, Mail Code 8864, San Antonio, TX 78229, USA
| | - Danielle Santana-Coelho
- Integrated Biomedical Sciences Program, Graduate School of Biomedical Sciences, UT Health San Antonio, San Antonio, TX 78229, USA; (M.N.M.); (D.S.-C.); (G.A.P.)
- Department of Pharmacology, Long School of Medicine, UT Health San Antonio, Mail Code 8864, San Antonio, TX 78229, USA
| | - Grace A. Porter
- Integrated Biomedical Sciences Program, Graduate School of Biomedical Sciences, UT Health San Antonio, San Antonio, TX 78229, USA; (M.N.M.); (D.S.-C.); (G.A.P.)
- Department of Pharmacology, Long School of Medicine, UT Health San Antonio, Mail Code 8864, San Antonio, TX 78229, USA
| | - Jason C. O’Connor
- Integrated Biomedical Sciences Program, Graduate School of Biomedical Sciences, UT Health San Antonio, San Antonio, TX 78229, USA; (M.N.M.); (D.S.-C.); (G.A.P.)
- Department of Pharmacology, Long School of Medicine, UT Health San Antonio, Mail Code 8864, San Antonio, TX 78229, USA
- Department of Research, Audie L. Murphy VA Hospital, South Texas Veterans Heath System, San Antonio, TX 78229, USA
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A randomized cross-over trial to define neurophysiological correlates of AV-101 N-methyl-D-aspartate receptor blockade in healthy veterans. Neuropsychopharmacology 2021; 46:820-827. [PMID: 33318635 PMCID: PMC8027791 DOI: 10.1038/s41386-020-00917-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 10/22/2020] [Accepted: 11/13/2020] [Indexed: 12/03/2022]
Abstract
The kynurenine pathway (KP) is a strategic metabolic system that combines regulation of neuronal excitability via glutamate receptor function and neuroinflammation via other KP metabolites. This pathway has great promise in treatment of depression and suicidality. The KP modulator AV-101 (4-chlorokynurenine, 4-Cl-KYN), an oral prodrug of 7-chlorokynurenic acid (7-Cl-KYNA), an N-methyl-D-aspartate receptor (NMDAR) glycine site antagonist, and of 4-chloro-3-hydroxyanthranilic acid (4-Cl-3-HAA), a suppressor of NMDAR agonist quinolinic acid (QUIN), is a promising potential antidepressant that targets glutamate functioning via the KP. However, a recent placebo-controlled clinical trial of AV-101 in depression found negative results. This raises the question of whether AV-101 can penetrate the brain and engage the NMDAR and KP effectively. To address this problem, ten healthy US military veterans (mean age = 32.6 years ± 6.11; 1 female) completed a phase-1 randomized, double-blind, placebo-controlled, crossover study to examine dose-related effects of AV-101 (720 and 1440 mg) on NMDAR engagement measured by γ-frequency band auditory steady-state response (40 Hz ASSR) and resting EEG. Linear mixed models revealed that 1440 mg AV-101, but not 720 mg, increased 40 Hz ASSR and 40 Hz ASSR γ-inter-trial phase coherence relative to placebo. AV-101 also increased 4-Cl-KYN, 7-Cl-KYNA, 4-Cl-3-HAA, 3-HAA, and KYNA in a dose-dependent manner, without affecting KYN and QUIN. AV-101 was safe and well tolerated. These results corroborate brain target engagement of 1440 mg AV-101 in humans, consistent with blockade of interneuronal NMDAR blockade. Future studies should test higher doses of AV-101 in depression. Suicidal behavior, which has been associated with high QUIN and low KYNA, is also a potential target for AV-101.
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Venkatesan D, Iyer M, Narayanasamy A, Siva K, Vellingiri B. Kynurenine pathway in Parkinson's disease-An update. eNeurologicalSci 2020; 21:100270. [PMID: 33134567 PMCID: PMC7585940 DOI: 10.1016/j.ensci.2020.100270] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 08/05/2020] [Accepted: 08/26/2020] [Indexed: 12/24/2022] Open
Abstract
Parkinson's disease (PD) is a complex multi-factorial neurodegenerative disorder where various altered metabolic pathways contribute to the progression of the disease. Tryptophan (TRP) is a major precursor in kynurenine pathway (KP) and it has been discussed in various in vitro studies that the metabolites quinolinic acid (QUIN) causes neurotoxicity and kynurenic acid (KYNA) acts as neuroprotectant respectively. More studies are also focused on the effects of other KP metabolites and its enzymes as it has an association with ageing and PD pathogenesis. Until now, very few studies have targeted the role of genetic mutations in abnormal KP metabolism in adverse conditions of PD. Therefore, the present review gives an updated research studies on KP in connection with PD. Moreover, the review emphasizes on the urge for the development of biomarkers and also this would be an initiative in generating an alternative therapeutic approach for PD.
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Key Words
- 3-HAA, 3-hydroxyanthranilic acid
- 3-HK, 3-hydroxykynurenine
- 6-OHDA, 6-hydroxydopamine
- AA, anthranilic acid
- ACMSD, amino-carboxymuconatesemialdehyde decarboxylase
- AD, Alzheimer's disease
- ATP, adenosine triphosphate
- Ageing
- AhR, aryl hydrocarbon receptor
- Biomarkers
- CNS, central nervous system
- CSF, cerebrospinal fluid
- DA, dopaminergic
- FAM, formamidase
- IDO-1, indoleamine-2,3-dioxygenases
- IFN-γ, interferon-γ
- KATs, kynurenine aminotransferases
- KMO, kynurenine −3-monooxygenase
- KP, Kynurenine pathway
- KYN, kynurenine
- KYNA, kynurenic acid
- Kynurenine pathway (KP)
- L-DOPA, L-dopamine
- LID, L-DOPA-induced dyskinesia
- MPTP, 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine
- NAD+, nicotinamide adenine dinucleotide
- NADPH, nicotinamide adenine dinucleotide phosphate
- NFK, N′-formylkynurenine
- NMDA, N-methyl-d-aspartate
- PA, picolinic acid
- PD, Parkinson's disease
- Parkinson's disease (PD)
- QUIN, quinolinic acid
- RBCs, red blood cells
- SNpc, substantianigra pars compacta
- TDO, tryptophan 2,3-dioxygenase
- TRP, tryptophan
- Therapeutics
- XA, xanthurenic acid
- ZNS, zonisamide
- α-synuclein, αSyn
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Affiliation(s)
- Dhivya Venkatesan
- Human Molecular Cytogenetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India
| | - Mahalaxmi Iyer
- Department of Zoology, Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore 641 043, Tamil Nadu, India
| | - Arul Narayanasamy
- Disease Proteomics Laboratory, Department of Zoology, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India
| | - Kamalakannan Siva
- National Centre for Disease Control, Ministry of Health and Family Welfare, Government of India, New Delhi 110054, India
| | - Balachandar Vellingiri
- Human Molecular Cytogenetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India
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Zádori D, Veres G, Szalárdy L, Klivényi P, Vécsei L. Alzheimer's Disease: Recent Concepts on the Relation of Mitochondrial Disturbances, Excitotoxicity, Neuroinflammation, and Kynurenines. J Alzheimers Dis 2019; 62:523-547. [PMID: 29480191 DOI: 10.3233/jad-170929] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The pathomechanism of Alzheimer's disease (AD) certainly involves mitochondrial disturbances, glutamate excitotoxicity, and neuroinflammation. The three main aspects of mitochondrial dysfunction in AD, i.e., the defects in dynamics, altered bioenergetics, and the deficient transport, act synergistically. In addition, glutamatergic neurotransmission is affected in several ways. The balance between synaptic and extrasynaptic glutamatergic transmission is shifted toward the extrasynaptic site contributing to glutamate excitotoxicity, a phenomenon augmented by increased glutamate release and decreased glutamate uptake. Neuroinflammation in AD is predominantly linked to central players of the innate immune system, with central nervous system (CNS)-resident microglia, astroglia, and perivascular macrophages having been implicated at the cellular level. Several abnormalities have been described regarding the activation of certain steps of the kynurenine (KYN) pathway of tryptophan metabolism in AD. First of all, the activation of indolamine 2,3-dioxygenase, the first and rate-limiting step of the pathway, is well-demonstrated. 3-Hydroxy-L-KYN and its metabolite, 3-hydroxy-anthranilic acid have pro-oxidant, antioxidant, and potent immunomodulatory features, giving relevance to their alterations in AD. Another metabolite, quinolinic acid, has been demonstrated to be neurotoxic, promoting glutamate excitotoxicity, reactive oxygen species production, lipid peroxidation, and microglial neuroinflammation, and its abundant presence in AD pathologies has been demonstrated. Finally, the neuroprotective metabolite, kynurenic acid, has been associated with antagonistic effects at glutamate receptors, free radical scavenging, and immunomodulation, giving rise to potential therapeutic implications. This review presents the multiple connections of KYN pathway-related alterations to three main domains of AD pathomechanism, such as mitochondrial dysfunction, excitotoxicity, and neuroinflammation, implicating possible therapeutic options.
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Affiliation(s)
- Dénes Zádori
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, Szeged, Hungary
| | - Gábor Veres
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, Szeged, Hungary
| | - Levente Szalárdy
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, Szeged, Hungary
| | - Péter Klivényi
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, Szeged, Hungary
| | - László Vécsei
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, Szeged, Hungary.,MTA-SZTE Neuroscience Research Group, Szeged, Hungary
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Fakan B, Szalardy L, Vecsei L. Exploiting the Therapeutic Potential of Endogenous Immunomodulatory Systems in Multiple Sclerosis-Special Focus on the Peroxisome Proliferator-Activated Receptors (PPARs) and the Kynurenines. Int J Mol Sci 2019; 20:ijms20020426. [PMID: 30669473 PMCID: PMC6358998 DOI: 10.3390/ijms20020426] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 01/13/2019] [Accepted: 01/15/2019] [Indexed: 01/20/2023] Open
Abstract
Multiple sclerosis (MS) is a progressive neurodegenerative disease, characterized by autoimmune central nervous system (CNS) demyelination attributable to a disturbed balance between encephalitic T helper 1 (Th1) and T helper 17 (Th17) and immunomodulatory regulatory T cell (Treg) and T helper 2 (Th2) cells, and an alternatively activated macrophage (M2) excess. Endogenous molecular systems regulating these inflammatory processes have recently been investigated to identify molecules that can potentially influence the course of the disease. These include the peroxisome proliferator-activated receptors (PPARs), PPARγ coactivator-1alpha (PGC-1α), and kynurenine pathway metabolites. Although all PPARs ameliorate experimental autoimmune encephalomyelitis (EAE), recent evidence suggests that PPARα, PPARβ/δ agonists have less pronounced immunomodulatory effects and, along with PGC-1α, are not biomarkers of neuroinflammation in contrast to PPARγ. Small clinical trials with PPARγ agonists have been published with positive results. Proposed as immunomodulatory and neuroprotective, the therapeutic use of PGC-1α activation needs to be assessed in EAE/MS. The activation of indolamine 2,3-dioxygenase (IDO), the rate-limiting step of the kynurenine pathway of tryptophan (Trp) metabolism, plays crucial immunomodulatory roles. Indeed, Trp metabolites have therapeutic relevance in EAE and drugs with structural analogy to kynurenines, such as teriflunomide, are already approved for MS. Further studies are required to gain deeper knowledge of such endogenous immunomodulatory pathways with potential therapeutic implications in MS.
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Affiliation(s)
- Bernadett Fakan
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, H-6725 Szeged, Semmelweis u. 6, Hungary.
| | - Levente Szalardy
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, H-6725 Szeged, Semmelweis u. 6, Hungary.
| | - Laszlo Vecsei
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, H-6725 Szeged, Semmelweis u. 6, Hungary.
- MTA-SZTE Neuroscience Research Group, H-6725 Szeged, Semmelweis u. 6, Hungary.
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Boros FA, Klivényi P, Toldi J, Vécsei L. Indoleamine 2,3-dioxygenase as a novel therapeutic target for Huntington’s disease. Expert Opin Ther Targets 2018; 23:39-51. [DOI: 10.1080/14728222.2019.1549231] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Fanni A. Boros
- Department of Neurology, Albert Szent-Györgyi Clinical Center, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Péter Klivényi
- Department of Neurology, Albert Szent-Györgyi Clinical Center, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - József Toldi
- Department of Physiology, Anatomy and Neuroscience, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
- MTA-SZTE Neuroscience Research Group of the Hungarian Academy of Sciences and the University of Szeged, Szeged, Hungary
| | - László Vécsei
- Department of Neurology, Albert Szent-Györgyi Clinical Center, Faculty of Medicine, University of Szeged, Szeged, Hungary
- MTA-SZTE Neuroscience Research Group of the Hungarian Academy of Sciences and the University of Szeged, Szeged, Hungary
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9
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Rojewska E, Ciapała K, Piotrowska A, Makuch W, Mika J. Pharmacological Inhibition of Indoleamine 2,3-Dioxygenase-2 and Kynurenine 3-Monooxygenase, Enzymes of the Kynurenine Pathway, Significantly Diminishes Neuropathic Pain in a Rat Model. Front Pharmacol 2018; 9:724. [PMID: 30050435 PMCID: PMC6050382 DOI: 10.3389/fphar.2018.00724] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 06/15/2018] [Indexed: 01/02/2023] Open
Abstract
Neuropathic pain caused by a primary injury or dysfunction in the peripheral or central nervous system is a tremendous therapeutic challenge. Here, we have collected the first evidence from a single study on the potential contributions to neuropathic pain development by enzymes in the kynurenine pathway [tryptophan 2,3-dioxygenase (TDO), indoleamine 2,3-dioxygenase (IDO1/2), kynurenine 3-monooxygenase (KMO); kynureninase, 3-hydroxyanthranilate-3,4-dioxygenase (HAOO)] at the spinal cord and dorsal root ganglia (DRG) levels. At the spinal cord, mRNA levels of IDO2, KMO, and HAOO were elevated as measured on day 7 after chronic constriction injury in a rat model, parallel to the C1q-positive cell activation. According to our data obtained from primary microglial cell cultures, all enzymes of the kynurenine pathway except TDO were derived from these cells; however, the activation of microglia induced stronger changes in IDO2 and KMO. Our pharmacological studies gave evidence that the repeated intraperitoneal administration of minocycline, a microglia/macrophage inhibitor, not only attenuated tactile and thermal hypersensitivity but also diminished the levels of IDO2 and KMO mRNA. Our further pharmacological studies confirmed that IDO2 and KMO enzymes take part in the development of neuropathic pain, since we observed that the repeated administration of IDO2 (1-methyl-D-tryptophan) and KMO [UPF 648 – (1S,2S)-2-(3,4-dichlorobenzoyl)cyclopropanecarboxylic acid] inhibitors diminished hypersensitivity development as measured on days 2 and 7. The results of our studies show that the kynurenine pathway is an important mediator of neuropathic pain pathology in rats and indicate that IDO2 and KMO represent novel pharmacological targets for treating neuropathy.
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Affiliation(s)
- Ewelina Rojewska
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Katarzyna Ciapała
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Anna Piotrowska
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Wioletta Makuch
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Joanna Mika
- Department of Pain Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
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Randomized, double-blind, placebo-controlled, dose-escalation study: Investigation of the safety, pharmacokinetics, and antihyperalgesic activity of l-4-chlorokynurenine in healthy volunteers. Scand J Pain 2017; 17:243-251. [PMID: 29229209 DOI: 10.1016/j.sjpain.2017.05.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 05/16/2017] [Accepted: 05/17/2017] [Indexed: 12/17/2022]
Abstract
BACKGROUND AND AIMS Neuropathic pain is a significant medical problem needing more effective treatments with fewer side effects. Overactive glutamatergic transmission via N-methyl-d-aspartate receptors (NMDARs) are known to play a role in central sensitization and neuropathic pain. Although ketamine, a NMDAR channel-blocking antagonist, is often used for neuropathic pain, its side-effect profile and abusive potential has prompted the search for a safer effective oral analgesic. A novel oral prodrug, AV-101 (l-4 chlorokynurenine), which, in the brain, is converted into one of the most potent and selective GlyB site antagonists of the NMDAR, has been demonstrated to be active in animal models of neuropathic pain. The two Phase 1 studies reported herein were designed to assess the safety and pharmacokinetics of AV-101, over a wide dose range, after daily dosing for 14-days. As secondary endpoints, AV-101 was evaluated in the capsaicin-induced pain model. METHODS The Phase 1A study was a single-site, randomized, double-blind, placebo-controlled, single oral ascending dose (30-1800mg) study involving 36 normal healthy volunteers. The Phase 1B study was a single-site randomized, double-blind, placebo-controlled, study of multiple ascending doses (360, 1080, and 1440mg/day) of AV-101 involving 50 normal healthy volunteers, to whom AV-101 or placebo were administered orally daily for 14 consecutive days. Subjects underwent PK blood analyses, laboratory assessments, physical examination, 12-lead ECG, ophthalmological examination, and various neurocognitive assessments. The effect of AV-101 was evaluated in the intradermally capsaicin-induced pain model (ClinicalTrials.gov Identifier: NCT01483846). RESULTS Two Phase 1, with an aggregate of 86 subjects, demonstrated that up to 14 days of oral AV-101, up to 1440mg per day, was safe and very well tolerated with AEs quantitively and qualitatively like those observed with placebo. Mean half-life values of AV-101 were consistent across doses, ranging with an average of 1.73h, with the highest Cmax (64.4μg/mL) and AUC0-t (196μgh/mL) values for AV-101 occurring in the 1440-mg dose group. In the capsaicin induce-pain model, there was no significant change in the area under the pain time curve (AUPC) for the spontaneous pain assessment between the treatment and the placebo groups on Day 1 or 14 (the primary endpoint). In contrast, there were consistent reductions at 60-180min on Day 1 after dosing for allodynia, mechanical hyperalgesia, heat hyperalgesia, and spontaneous pain, and on Day 14 after dosing for heat hyperalgesia. CONCLUSIONS Although, AV-101 did not reach statistical significance in reducing pain, there were consistent reductions, for allodynia pain and mechanical and heat hyperalgesia. Given the excellent safety profile and PK characteristics demonstrated by this study, future clinical trials of AV-101 in neuropathic pain are justified. IMPLICATIONS This article presents the safety and PK of AV-101, a novel oral prodrug producing a potent and selective GlyB site antagonist of the NMDA receptor. These data indicate that AV-101 has excellent safety and PK characteristics providing support for advancing AV-101 into Phase 2 studies in neuropathic pain, and even provides data suggesting that AV-101 may have a role in treating depression.
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Yaksh TL, Schwarcz R, Snodgrass HR. Characterization of the Effects of L-4-Chlorokynurenine on Nociception in Rodents. THE JOURNAL OF PAIN 2017; 18:1184-1196. [PMID: 28428091 DOI: 10.1016/j.jpain.2017.03.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 03/16/2017] [Accepted: 03/30/2017] [Indexed: 10/19/2022]
Abstract
Upon systemic administration in rats, the prodrug L-4-chlorokynurenine (4-Cl-KYN; AV-101; VistaGen Therapeutics, Inc, South San Francisco, CA) is rapidly absorbed, actively transported across the blood-brain barrier, and converted in astrocytes to 7-chlorokynurenic acid (7-Cl-KYNA), a potent and specific antagonist of the glycine B coagonist site of the N-methyl-D-aspartate (NMDA) receptor. We examined the effects of 4-Cl-KYN in several rat models of hyperalgesia and allodynia and determined the concentrations of 4-Cl-KYN and newly produced 7-Cl-KYNA in serum, brain, and spinal cord. Adult male rats were given 4-Cl-KYN (56, 167, 500 mg/kg), the NMDA receptor antagonist MK-801 (.1, .3, 1.0 mg/kg), or gabapentin (33, 100, 300 mg/kg) intraperitoneally, and were then examined on rotarod, intraplantar formalin-evoked flinching, thermal escape in the normal and carrageenan-inflamed paw, and allodynia after sciatic nerve ligation. Our conclusions show that after systemic delivery, the highest 2 doses (167 and 500 mg/kg) of 4-Cl-KYN yielded brain concentrations of 7-Cl-KYNA exceeding its half maximal inhibitory concentration (IC50) at the glycine B site and resulted in dose-dependent antihyperalgesia in the 4 models of facilitated processing associated with tissue inflammation and nerve injury. On the basis of the relative dose requirements for analgesic actions and side effect profiles from these experiments, 4-Cl-KYN is predicted to have antihyperalgesic efficacy and a therapeutic ratio equal to gabapentin and superior to MK-801. PERSPECTIVE These studies show that systemic administration of the prodrug 4-Cl-KYN produces high central nervous system levels of 7-Cl-KYNA, a potent and highly selective antagonist of the NMDA receptor. Compared with other drugs tested, 4-Cl-KYN has robust antinociceptive effects with a better side effect profile, highlighting its potential for treating hyperpathic pain states.
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Affiliation(s)
- Tony L Yaksh
- Department of Anesthesiology, University of California, San Diego, La Jolla, California.
| | - Robert Schwarcz
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, Maryland
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Zádori D, Veres G, Szalárdy L, Klivényi P, Fülöp F, Toldi J, Vécsei L. Inhibitors of the kynurenine pathway as neurotherapeutics: a patent review (2012–2015). Expert Opin Ther Pat 2016; 26:815-32. [DOI: 10.1080/13543776.2016.1189531] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Abstract
Various pathologies of the central nervous system (CNS) are accompanied by alterations in tryptophan metabolism. The main metabolic route of tryptophan degradation is the kynurenine pathway; its metabolites are responsible for a broad spectrum of effects, including the endogenous regulation of neuronal excitability and the initiation of immune tolerance. This Review highlights the involvement of the kynurenine system in the pathology of neurodegenerative disorders, pain syndromes and autoimmune diseases through a detailed discussion of its potential implications in Huntington's disease, migraine and multiple sclerosis. The most effective preclinical drug candidates are discussed and attention is paid to currently under-investigated roles of the kynurenine pathway in the CNS, where modulation of kynurenine metabolism might be of therapeutic value.
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Vecsei L, Plangar I, Szalardy L. Manipulation with kynurenines: a possible tool for treating neurodegenerative diseases? Expert Rev Clin Pharmacol 2012; 5:351-3. [PMID: 22943114 DOI: 10.1586/ecp.12.36] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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Zádori D, Klivényi P, Szalárdy L, Fülöp F, Toldi J, Vécsei L. Mitochondrial disturbances, excitotoxicity, neuroinflammation and kynurenines: novel therapeutic strategies for neurodegenerative disorders. J Neurol Sci 2012; 322:187-91. [PMID: 22749004 DOI: 10.1016/j.jns.2012.06.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 06/08/2012] [Indexed: 12/25/2022]
Abstract
A mitochondrial dysfunction causes an abatement in ATP production, the induction of oxidative damage and the propagation of cell death pathways. It is additionally closely related to both glutamate excitotoxicity and neuroinflammation. All of these interconnected aspects of a cellular dysfunction are involved in the pathogenesis of numerous neurological disorders, including those with an acute (e.g. ischemic stroke) or a chronic (e.g. Huntington's disease) onset. Both acute and chronic neurodegenerative disorders have been demonstrated to involve multiple imbalances of the kynurenine pathway metabolism in the pathogenesis of the disease. As regards neuroactive compounds featuring in the pathway, quinolinic acid is a specific agonist of N-methyl-d-aspartate receptors, and a potent neurotoxin with additional and marked free radical-producing and lipid peroxidation-inducing properties. The toxic effects of 3-hydroxy-L-kynurenine are mediated by free radicals. Besides the possibility of increasing brain kynurenic acid concentrations, L-kynurenine may have vasoactive properties, too. Kynurenic acid has proven to be neuroprotective in several experimental settings, but in consequence of its pharmacokinetic properties it is not applicable as systemic administration in human cases. The aim of this short review is to emphasize the common features of cerebral ischemia and Huntington's disease and to highlight therapeutic strategies targeting the kynurenine pathway.
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Affiliation(s)
- Dénes Zádori
- Department of Neurology, Faculty of Medicine, Albert Szent-Györgyi Clinical Center, University of Szeged, Semmelweis u. 6, H-6725 Szeged, Hungary.
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Zádori D, Klivényi P, Plangár I, Toldi J, Vécsei L. Endogenous neuroprotection in chronic neurodegenerative disorders: with particular regard to the kynurenines. J Cell Mol Med 2011; 15:701-17. [PMID: 21155972 PMCID: PMC3922661 DOI: 10.1111/j.1582-4934.2010.01237.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Parkinson's disease (PD) and Huntington's disease (HD) are progressive chronic neurodegenerative disorders that are accompanied by a considerable impairment of the motor functions. PD may develop for familial or sporadic reasons, whereas HD is based on a definite genetic mutation. Nevertheless, the pathological processes involve oxidative stress and glutamate excitotoxicity in both cases. A number of metabolic routes are affected in these disorders. The decrease in antioxidant capacity and alterations in the kynurenine pathway, the main pathway of the tryptophan metabolism, are features that deserve particular interest, because the changes in levels of neuroactive kynurenine pathway compounds appear to be strongly related to the oxidative stress and glutamate excitotoxicity involved in the disease pathogenesis. Increase of the antioxidant capacity and pharmacological manipulation of the kynurenine pathway are therefore promising therapeutic targets in these devastating disorders.
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Affiliation(s)
- Dénes Zádori
- Department of Neurology, Albert Szent-Györgyi Clinical Centre, University of Szeged, Szeged, Hungary
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17
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Zádori D, Klivényi P, Toldi J, Fülöp F, Vécsei L. Kynurenines in Parkinson's disease: therapeutic perspectives. J Neural Transm (Vienna) 2011; 119:275-83. [PMID: 21858430 DOI: 10.1007/s00702-011-0697-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 07/29/2011] [Indexed: 12/21/2022]
Abstract
Parkinson's disease (PD) is a chronic progressive neurodegenerative disorder the pathomechanism of which is not yet fully known. With regard to the molecular mechanism of development of the disease, oxidative stress/mitochondrial impairment, glutamate excitotoxicity and neuroinflammation are certainly involved. Alterations in the kynurenine pathway, the main pathway of the tryptophan metabolism, can contribute to the complex pathomechanism. There are several possibilities for therapeutic intervention involving targeting of this altered metabolic route. The development of synthetic molecules that would shift the altered balance towards the achievement of neuroprotective effects would be of great promise for future clinical studies on PD.
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Affiliation(s)
- Dénes Zádori
- Department of Neurology, Albert Szent-Györgyi Clinical Centre, University of Szeged, Semmelweis u. 6, Szeged, 6725, Hungary
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Abstract
Alzheimer’s disease (AD) is one of the major causes of dementia. The pathogenesis of the disease is not entirely understood, but the amyloid β peptide (Aβ) and the formation of senile plaques seem to play pivotal roles. Oligomerization of the Aβ is thought to trigger a cascade of events, including oxidative stress, glutamate excitotoxicity and inflammation. The kynurenine (KYN) pathway is the major route for the metabolism of the essential amino acid tryptophan. Some of the metabolites of this pathway, such as 3-hydroxykynurenine and quinolinic acid, are known to have neurotoxic properties, whereas others, such as kynurenic acid, are putative neuroprotectants. Among other routes, the KYN pathway has been shown to be involved in AD pathogenesis, and connections to other known mechanisms have also been demonstrated. Oxidative stress, glutamate excitotoxicity and the neuroinflammation involved in AD pathogenesis have been revealed to be connected to the KYN pathway. Intervention at these key steps may serve as the aim of potential therapy.
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Affiliation(s)
- Zsigmond Tamas Kincses
- Department of Neurology, Albert Szent-Györgyi Clinical Center, University of Szeged, Hungary
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Kynurenines in chronic neurodegenerative disorders: future therapeutic strategies. J Neural Transm (Vienna) 2009; 116:1403-9. [PMID: 19618107 DOI: 10.1007/s00702-009-0263-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Accepted: 06/11/2009] [Indexed: 10/20/2022]
Abstract
Parkinson's, Alzheimer's and Huntington's diseases are chronic neurodegenerative disorders of a progressive nature which lead to a considerable deterioration of the quality of life. Their pathomechanisms display some common features, including an imbalance of the tryptophan metabolism. Alterations in the concentrations of neuroactive kynurenines can be accompanied by devastating excitotoxic injuries and metabolic disturbances. From therapeutic considerations, possibilities that come into account include increasing the neuroprotective effect of kynurenic acid, or decreasing the levels of neurotoxic 3-hydroxy-L-kynurenine and quinolinic acid. The experimental data indicate that neuroprotection can be achieved by both alternatives, suggesting opportunities for further drug development in this field.
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Klivényi P, Toldi J, Vécsei L. Kynurenines in neurodegenerative disorders: therapeutic consideration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 541:169-83. [PMID: 14977214 DOI: 10.1007/978-1-4419-8969-7_10] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Affiliation(s)
- Péter Klivényi
- Department of Neurology, University of Szeged POB 427, H-6701, Szeged, Hungary
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Schwarcz R, Pellicciari R. Manipulation of brain kynurenines: glial targets, neuronal effects, and clinical opportunities. J Pharmacol Exp Ther 2002; 303:1-10. [PMID: 12235226 DOI: 10.1124/jpet.102.034439] [Citation(s) in RCA: 418] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Degradation of the essential amino acid tryptophan along the kynurenine pathway (KP) yields several neuroactive intermediates, including the free radical generator 3-hydroxykynurenine, the excitotoxic N-methyl-D-aspartate (NMDA) receptor agonist quinolinic acid, and the NMDA and alpha7 nicotinic acetylcholine receptor antagonist kynurenic acid. The ambient levels of these compounds are determined by several KP enzymes, which in the brain are preferentially localized in astrocytes and microglial cells. Normal fluctuations in the brain levels of neuroactive KP intermediates might modulate several neurotransmitter systems. Impairment of KP metabolism is functionally significant and occurs in a variety of diseases that affect the brain. Pharmacological agents targeting specific KP enzymes are now available to manipulate the concentration of neuroactive KP intermediates in the brain. These compounds can be used to normalize KP defects, show remarkable efficacy in animal models of central nervous system disorders, and offer novel therapeutic opportunities.
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Affiliation(s)
- Robert Schwarcz
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, USA.
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22
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Stone TW, Darlington LG. Endogenous kynurenines as targets for drug discovery and development. Nat Rev Drug Discov 2002; 1:609-20. [PMID: 12402501 DOI: 10.1038/nrd870] [Citation(s) in RCA: 573] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The kynurenine pathway is the main pathway for tryptophan metabolism. It generates compounds that can modulate activity at glutamate receptors and possibly nicotinic receptors, in addition to some as-yet-unidentified sites. The pathway is in a unique position to regulate other aspects of the metabolism of tryptophan to neuroactive compounds, and also seems to be a key factor in the communication between the nervous and immune systems. It also has potentially important roles in the regulation of cell proliferation and tissue function in the periphery. As a result, the pathway presents a multitude of potential sites for drug discovery in neuroscience, oncology and visceral pathology.
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Affiliation(s)
- Trevor W Stone
- Institute of Biomedical and Life Sciences, West Medical Building, University of Glasgow, Glasgow G12 8QQ, UK.
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Lee SC, Schwarcz R. Excitotoxic injury stimulates pro-drug-induced 7-chlorokynurenate formation in the rat striatum in vivo. Neurosci Lett 2001; 304:185-8. [PMID: 11343833 DOI: 10.1016/s0304-3940(01)01791-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Peripheral administration of L-4-chlorokynurenine (4-Cl-KYN), which is enzymatically converted in astrocytes to form the glycine(B) receptor antagonist 7-chlorokynurenic acid (7-Cl-KYNA), has been shown to provide neuroprotection against excitotoxic damage. The present study was designed to examine the metabolic fate of 4-Cl-KYN after systemic injection, and to study its brain uptake and subsequent transamination during the acute phase following an excitotoxic insult. To this end, adult rats received intrastriatal injections of vehicle (1 microl) or quinolinic acid (QUIN) (240 nmol/1 microl), and were administered 50 mg/kg 4-Cl-KYN (intraperitoneally) immediately after surgery. After 90 and 180 min, 7-Cl-KYNA concentrations in the vehicle-injected striatum were 54+/-13 and 16+/-2 nM, respectively. The contralateral, QUIN-injected striatum contained 212+/-39 and 97+/-27 nM 7-Cl-KYNA, respectively. This injury-induced increase was accompanied by slightly higher 4-Cl-KYN levels in the QUIN-treated striatum, indicating that better pro-drug availability in part accounts for the enhanced 7-Cl-KYNA formation. These data demonstrate that systemic 4-Cl-KYN application, by targeting reactive glial cells during the early, reversible stage of excitotoxic neurodegeneration, produces disproportionately large amounts of the neuroprotectant 7-Cl-KYNA at the site of the emerging lesion.
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Affiliation(s)
- S C Lee
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, MD 21228, USA
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Abstract
The kynurenine pathway accounts for the metabolism of around 80% of non-protein tryptophan metabolism. It includes both an agonist (quinolinic acid) at NMDA receptors and an antagonist (kynurenic acid). Since their discovery, there has been a major development of kynurenic acid analogues as neuroprotectants for the treatment of stroke and neurodegenerative disease. Several prodrugs of kynurenic acid or its analogues that can be hydrolysed within the CNS are also available. More recently, the pathway itself has proved to be a valuable drug target, affected by agents which reduce the synthesis of quinolinic acid and increase the formation of kynurenic acid. The change in the balance of these, away from the excitotoxin and towards the neuroprotectant, has anticonvulsant and neuroprotective properties.
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Affiliation(s)
- T W Stone
- Institute of Biomedical & Life Sciences, West Medical Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
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