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Behl T, Kaur I, Sehgal A, Singh S, Bhatia S, Al-Harrasi A, Zengin G, Bumbu AG, Andronie-Cioara FL, Nechifor AC, Gitea D, Bungau AF, Toma MM, Bungau SG. The Footprint of Kynurenine Pathway in Neurodegeneration: Janus-Faced Role in Parkinson's Disorder and Therapeutic Implications. Int J Mol Sci 2021; 22:6737. [PMID: 34201647 PMCID: PMC8268239 DOI: 10.3390/ijms22136737] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/17/2021] [Accepted: 06/21/2021] [Indexed: 02/06/2023] Open
Abstract
Progressive degeneration of neurons and aggravation of dopaminergic neurons in the substantia nigra pars compacta results in the loss of dopamine in the brain of Parkinson's disease (PD) patients. Numerous therapies, exhibiting transient efficacy have been developed; however, they are mostly accompanied by side effects and limited reliability, therefore instigating the need to develop novel optimistic treatment targets. Significant therapeutic targets have been identified, namely: chaperones, protein Abelson, glucocerebrosidase-1, calcium, neuromelanin, ubiquitin-proteasome system, neuroinflammation, mitochondrial dysfunction, and the kynurenine pathway (KP). The role of KP and its metabolites and enzymes in PD, namely quinolinic acid (QUIN), kynurenic acid (KYNA), 3-hydroxykynurenine (3-HK), 3-hydroxyanthranillic acid (3-HAA), kunurenine-3-monooxygenase (KMO), etc. has been reported. The neurotoxic QUIN, N-methyl-D-aspartate (NMDA) receptor agonist, and neuroprotective KYNA-which antagonizes QUIN actions-primarily justify the Janus-faced role of KP in PD. Moreover, KP has been reported to play a biomarker role in PD detection. Therefore, the authors detail the neurotoxic, neuroprotective, and immunomodulatory neuroactive components, alongside the upstream and downstream metabolic pathways of KP, forming a basis for a therapeutic paradigm of the disease while recognizing KP as a potential biomarker in PD, thus facilitating the development of a suitable target in PD management.
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Affiliation(s)
- Tapan Behl
- Department of Pharmacology, Chitkara College of Pharmacy, Chitkara University, Punjab 140401, India; (I.K.); (A.S.); (S.S.)
| | - Ishnoor Kaur
- Department of Pharmacology, Chitkara College of Pharmacy, Chitkara University, Punjab 140401, India; (I.K.); (A.S.); (S.S.)
| | - Aayush Sehgal
- Department of Pharmacology, Chitkara College of Pharmacy, Chitkara University, Punjab 140401, India; (I.K.); (A.S.); (S.S.)
| | - Sukhbir Singh
- Department of Pharmacology, Chitkara College of Pharmacy, Chitkara University, Punjab 140401, India; (I.K.); (A.S.); (S.S.)
| | - Saurabh Bhatia
- Amity Institute of Pharmacy, Amity University, Gurugram, Haryana 122412, India;
- Natural and Medical Sciences Research Centre, University of Nizwa, P.O. Box 33, PC 616 Birkat Al Mouz, Nizwa 611, Oman;
| | - Ahmed Al-Harrasi
- Natural and Medical Sciences Research Centre, University of Nizwa, P.O. Box 33, PC 616 Birkat Al Mouz, Nizwa 611, Oman;
| | - Gokhan Zengin
- Department of Biology, Faculty of Science, Selcuk University Campus, Konya 42130, Turkey;
| | - Adrian Gheorghe Bumbu
- Department of Surgical Disciplines, Faculty of Medicine and Pharmacy, University of Oradea, 410073 Oradea, Romania;
| | - Felicia Liana Andronie-Cioara
- Department of Psycho-Neuroscience and Recovery, Faculty of Medicine and Pharmacy, University of Oradea, 410073 Oradea, Romania;
| | - Aurelia Cristina Nechifor
- Analytical Chemistry and Environmental Engineering Department, Polytechnic University of Bucharest, 011061 Bucharest, Romania;
| | - Daniela Gitea
- Department of Pharmacy, Faculty of Medicine and Pharmacy, University of Oradea, 410028 Oradea, Romania; (D.G.); (M.M.T.)
| | | | - Mirela Marioara Toma
- Department of Pharmacy, Faculty of Medicine and Pharmacy, University of Oradea, 410028 Oradea, Romania; (D.G.); (M.M.T.)
- Doctoral School of Biomedical Sciences, University of Oradea, 410087 Oradea, Romania
| | - Simona Gabriela Bungau
- Department of Pharmacy, Faculty of Medicine and Pharmacy, University of Oradea, 410028 Oradea, Romania; (D.G.); (M.M.T.)
- Doctoral School of Biomedical Sciences, University of Oradea, 410087 Oradea, Romania
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Mor A, Kalaska B, Pawlak D. Kynurenine Pathway in Chronic Kidney Disease: What’s Old, What’s New, and What’s Next? Int J Tryptophan Res 2020; 13:1178646920954882. [PMID: 35210786 PMCID: PMC8862190 DOI: 10.1177/1178646920954882] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 08/06/2020] [Indexed: 11/25/2022] Open
Abstract
Impaired kidney function and increased inflammatory process occurring in the course of Chronic Kidney Disease (CKD) contribute to the development of complex amino-acid alterations. The essential amino-acid tryptophan (TRP) undergoes extensive metabolism along several pathways, resulting in the production of many biologically active compounds. The results of many studies have shown that its metabolism via the kynurenine pathway is potently increased in the course of CKD. Metabolites of this pathway exhibit differential, sometimes opposite, roles in several biological processes. Their accumulation in the course of CKD may induce oxidative cell damage which stimulates inflammatory processes. They can also modulate the activity of numerous cellular signaling pathways through activation of the aryl hydrocarbon receptor, leading to the disruption of homeostasis of various organs. As a result, they can contribute to the development of the systemic disorders accompanying the course of chronic renal failure. This review gathers and systematizes reports concerning the knowledge connecting the kynurenine pathway metabolites to systemic disorders accompanying the development of CKD.
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Affiliation(s)
- Adrian Mor
- Department of Pharmacodynamics, Medical University of Bialystok, Bialystok, Poland
| | - Bartlomiej Kalaska
- Department of Pharmacodynamics, Medical University of Bialystok, Bialystok, Poland
| | - Dariusz Pawlak
- Department of Pharmacodynamics, Medical University of Bialystok, Bialystok, Poland
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Laumet G, Zhou W, Dantzer R, Edralin JD, Huo X, Budac DP, O’Connor JC, Lee AW, Heijnen CJ, Kavelaars A. Upregulation of neuronal kynurenine 3-monooxygenase mediates depression-like behavior in a mouse model of neuropathic pain. Brain Behav Immun 2017; 66:94-102. [PMID: 28709913 PMCID: PMC5650931 DOI: 10.1016/j.bbi.2017.07.008] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 07/10/2017] [Accepted: 07/10/2017] [Indexed: 12/18/2022] Open
Abstract
Pain and depression often co-occur, but the underlying mechanisms have not been elucidated. Here, we used the spared nerve injury (SNI) model in mice to induce both neuropathic pain and depression-like behavior. We investigated whether brain interleukin (IL)-1 signaling and activity of kynurenine 3-monoxygenase (KMO), a key enzyme for metabolism of kynurenine into the neurotoxic NMDA receptor agonist quinolinic acid, are necessary for comorbid neuropathic pain and depression-like behavior. SNI mice showed increased expression levels of Il1b and Kmo mRNA in the contralateral side of the brain. The SNI-induced increase of Kmo mRNA was associated with increased KMO protein and elevated quinolinic acid and reduced kynurenic acid in the contralateral hippocampus. The increase in KMO-protein in response to SNI mostly took place in hippocampal NeuN-positive neurons rather than microglia. Inhibition of brain IL-1 signaling by intracerebroventricular administration of IL-1 receptor antagonist after SNI prevented the increase in Kmo mRNA and depression-like behavior measured by forced swim test. However, inhibition of brain IL-1 signaling has no effect on mechanical allodynia. In addition, intracerebroventricular administration of the KMO inhibitor Ro 61-8048 abrogated depression-like behavior without affecting mechanical allodynia after SNI. We show for the first time that the development of depression-like behavior in the SNI model requires brain IL-1 signaling and activation of neuronal KMO, while pain is independent of this pathway. Inhibition of KMO may represent a promising target for treating depression.
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Affiliation(s)
- Geoffroy Laumet
- Laboratory of Neuroimmunology, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
| | - Wenjun Zhou
- Laboratory of Neuroimmunology, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
| | - Robert Dantzer
- Laboratory of Neuroimmunology, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
| | - Jules D. Edralin
- Laboratory of Neuroimmunology, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - XiaoJiao Huo
- Laboratory of Neuroimmunology, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
| | - David P. Budac
- Bioanalysis and Physiology, Lundbeck Research, Paramus, NJ, USA
| | - Jason C. O’Connor
- Department of Pharmacology, The University of Texas Health Science Center and Audie L. Murphy VA Hospital, South Texas Veteran’s Heath Care System, San Antonio, TX, USA
| | - Anna W. Lee
- Neuroinflammation Disease Biology Unit, Lundbeck Research USA, Paramus, NJ, USA at the time the analysis of kynurenine metabolites was carried out
| | - Cobi J. Heijnen
- Laboratory of Neuroimmunology, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Annemieke Kavelaars
- Laboratory of Neuroimmunology, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
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Involvement of the kynurenine pathway in the pathogenesis of Parkinson’s disease. Prog Neurobiol 2017; 155:76-95. [DOI: 10.1016/j.pneurobio.2015.12.009] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 12/18/2015] [Accepted: 12/30/2015] [Indexed: 12/14/2022]
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Abstract
Tryptophan-2, 3-dioxygenase (TDO) is a heme-containing protein catalyzing the first reaction in the kynurenine pathway, which incorporates oxygen into the indole moiety of tryptophan and catalyzes it into kynurenine (KYN). The activation of TDO results in the depletion of tryptophan and the accumulation of kynurenine and its metabolites. These metabolites can affect the function of neurons and inhibit the proliferation of T cells. Increasing evidence demonstrates that TDO is a potential therapeutic target in the treatment of brain diseases as well as in the antitumor and transplant fields. Despite its growing popularity, there are few reviews only focusing on TDO. Hence, we herein review TDO by providing a comprehensive overview of TDO, including its biological functions as well as the evolution, structure and catalytic process of TDO. Additionally, this review will focus on the role of TDO in the pathology of three groups of brain diseases: Schizophrenia, Alzheimer's disease (AD) and Glioma. Finally, we will also provide an opinion regarding the future developmental directions of TDO in brain diseases, especially whether TDO has a potential role in other brain diseases as well as the development and applications of TDO inhibitors as treatments.
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Affiliation(s)
- Cheng-Peng Yu
- The Second Clinic Medical College, School of Medicine, Nanchang University, Nanchang, China
| | - Ze-Zheng Pan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Nanchang University, Nanchang, China
| | - Da-Ya Luo
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Nanchang University, Nanchang, China.
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Hüske C, Sander SE, Hamann M, Kershaw O, Richter F, Richter A. Towards optimized anesthesia protocols for stereotactic surgery in rats: Analgesic, stress and general health effects of injectable anesthetics. A comparison of a recommended complete reversal anesthesia with traditional chloral hydrate monoanesthesia. Brain Res 2016; 1642:364-375. [DOI: 10.1016/j.brainres.2016.04.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 03/17/2016] [Accepted: 04/07/2016] [Indexed: 11/29/2022]
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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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Fan HC, Chi CS, Cheng SN, Lee HF, Tsai JD, Lin SZ, Harn HJ. Targeting New Candidate Genes by Small Molecules Approaching Neurodegenerative Diseases. Int J Mol Sci 2015; 17:E26. [PMID: 26712747 PMCID: PMC4730273 DOI: 10.3390/ijms17010026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 12/10/2015] [Accepted: 12/21/2015] [Indexed: 02/08/2023] Open
Abstract
Neurodegenerative diseases (NDs) are among the most feared of the disorders that afflict humankind for the lack of specific diagnostic tests and effective treatments. Understanding the molecular, cellular, biochemical changes of NDs may hold therapeutic promise against debilitating central nerve system (CNS) disorders. In the present review, we summarized the clinical presentations and biology backgrounds of NDs, including Parkinson's disease (PD), Huntington's disease (HD), and Alzheimer's disease (AD) and explored the role of molecular mechanisms, including dys-regulation of epigenetic control mechanisms, Ataxia-telangiectasia-mutated protein kinase (ATM), and neuroinflammation in the pathogenesis of NDs. Targeting these mechanisms may hold therapeutic promise against these devastating diseases.
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Affiliation(s)
- Hueng-Chuen Fan
- Department of Pediatrics, Tung's Taichung Metroharbor Hospital, Wuchi, Taichung 435, Taiwan.
- Department of Nursing, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli 356, Taiwan.
| | - Ching-Shiang Chi
- Department of Pediatrics, Tung's Taichung Metroharbor Hospital, Wuchi, Taichung 435, Taiwan.
- Department of Nursing, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli 356, Taiwan.
| | - Shin-Nan Cheng
- Department of Pediatrics, Tung's Taichung Metroharbor Hospital, Wuchi, Taichung 435, Taiwan.
- Department of Nursing, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli 356, Taiwan.
| | - Hsiu-Fen Lee
- Department of Pediatrics, Taichung Veterans General Hospital, Taichung 407, Taiwan.
| | - Jeng-Dau Tsai
- School of Medicine, Chung Shan Medical University, Taichung 402, Taiwan.
- Department of Pediatrics, Chung Shan Medical University Hospital, Taichung 402, Taiwan.
| | - Shinn-Zong Lin
- Graduate Institute of Immunology, China Medical University, Taichung 404, Taiwan.
- Center for Neuropsychiatry, China Medical University and Hospital, Taichung 404, Taiwan.
- Department of Neurosurgery, China Medical University Beigang Hospital, Yunlin 651, Taiwan.
| | - Horng-Jyh Harn
- Department of Pathology, China Medical University and Hospital, Taichung 404, Taiwan.
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Campbell BM, Charych E, Lee AW, Möller T. Kynurenines in CNS disease: regulation by inflammatory cytokines. Front Neurosci 2014; 8:12. [PMID: 24567701 PMCID: PMC3915289 DOI: 10.3389/fnins.2014.00012] [Citation(s) in RCA: 250] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 01/20/2014] [Indexed: 12/27/2022] Open
Abstract
The kynurenine pathway (KP) metabolizes the essential amino acid tryptophan and generates a number of neuroactive metabolites collectively called the kynurenines. Segregated into at least two distinct branches, often termed the “neurotoxic” and “neuroprotective” arms of the KP, they are regulated by the two enzymes kynurenine 3-monooxygenase and kynurenine aminotransferase, respectively. Interestingly, several enzymes in the pathway are under tight control of inflammatory mediators. Recent years have seen a tremendous increase in our understanding of neuroinflammation in CNS disease. This review will focus on the regulation of the KP by inflammatory mediators as it pertains to neurodegenerative and psychiatric disorders.
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Affiliation(s)
- Brian M Campbell
- Neuroinflammation Disease Biology Unit, Lundbeck Research USA Paramus, NJ, USA
| | - Erik Charych
- Neuroinflammation Disease Biology Unit, Lundbeck Research USA Paramus, NJ, USA
| | - Anna W Lee
- Neuroinflammation Disease Biology Unit, Lundbeck Research USA Paramus, NJ, USA
| | - Thomas Möller
- Neuroinflammation Disease Biology Unit, Lundbeck Research USA Paramus, NJ, USA
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Avchalumov Y, Volkmann C, Rückborn K, Hamann M, Kirschstein T, Richter A, Köhling R. Persistent changes of corticostriatal plasticity in dtsz mutant hamsters after age-dependent remission of dystonia. Neuroscience 2013; 250:60-9. [DOI: 10.1016/j.neuroscience.2013.06.048] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2013] [Revised: 06/01/2013] [Accepted: 06/21/2013] [Indexed: 10/26/2022]
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Zinger A, Barcia C, Herrero MT, Guillemin GJ. The involvement of neuroinflammation and kynurenine pathway in Parkinson's disease. PARKINSON'S DISEASE 2011; 2011:716859. [PMID: 21687761 PMCID: PMC3109408 DOI: 10.4061/2011/716859] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 01/31/2011] [Indexed: 12/15/2022]
Abstract
Parkinson's disease (PD) is a common neurodegenerative disorder characterised by loss of dopaminergic neurons and localized neuroinflammation occurring in the midbrain several years before the actual onset of symptoms. Activated microglia themselves release a large number of inflammatory mediators thus perpetuating neuroinflammation and neurotoxicity. The Kynurenine pathway (KP), the main catabolic pathway for tryptophan, is one of the major regulators of the immune response and may also be implicated in the inflammatory response in parkinsonism. The KP generates several neuroactive compounds and therefore has either a neurotoxic or neuroprotective effect. Several of these molecules produced by microglia can activate the N-methyl-D-aspartate (NMDA) receptor-signalling pathway, leading to an excitotoxic response. Previous studies have shown that NMDA antagonists can ease symptoms and exert a neuroprotective effect in PD both in vivo and in vitro. There are to date several lines of evidence linking some of the KP intermediates and the neuropathogenesis of PD. Moreover, it is likely that pharmacological modulation of the KP will represent a new therapeutic strategy for PD.
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Affiliation(s)
- Anna Zinger
- Department of Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Carlos Barcia
- Experimental and Clinical Neuroscience (NiCE-CIBERNED), Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia, Murcia, Spain
| | - Maria Trinidad Herrero
- Experimental and Clinical Neuroscience (NiCE-CIBERNED), Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia, Murcia, Spain
| | - Gilles J. Guillemin
- Department of Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
- Experimental and Clinical Neuroscience (NiCE-CIBERNED), Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia, Murcia, Spain
- St Vincent's Centre for Applied Medical Research, Darlinghurst, NSW 2010, Australia
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Schwarcz R, Guidetti P, Sathyasaikumar KV, Muchowski PJ. Of mice, rats and men: Revisiting the quinolinic acid hypothesis of Huntington's disease. Prog Neurobiol 2010; 90:230-45. [PMID: 19394403 PMCID: PMC2829333 DOI: 10.1016/j.pneurobio.2009.04.005] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Accepted: 04/17/2009] [Indexed: 12/31/2022]
Abstract
The neurodegenerative disease Huntington's disease (HD) is caused by an expanded polyglutamine (polyQ) tract in the protein huntingtin (htt). Although the gene encoding htt was identified and cloned more than 15 years ago, and in spite of impressive efforts to unravel the mechanism(s) by which mutant htt induces nerve cell death, these studies have so far not led to a good understanding of pathophysiology or an effective therapy. Set against a historical background, we review data supporting the idea that metabolites of the kynurenine pathway (KP) of tryptophan degradation provide a critical link between mutant htt and the pathophysiology of HD. New studies in HD brain and genetic model organisms suggest that the disease may in fact be causally related to early abnormalities in KP metabolism, favoring the formation of two neurotoxic metabolites, 3-hydroxykynurenine and quinolinic acid, over the related neuroprotective agent kynurenic acid. These findings not only link the excitotoxic hypothesis of HD pathology to an impairment of the KP but also define new drug targets and therefore have direct therapeutic implications. Thus, pharmacological normalization of the imbalance in brain KP metabolism may provide clinical benefits, which could be especially effective in early stages of the disease.
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Affiliation(s)
- Robert Schwarcz
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, MD, USA.
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Hamann M, Sohr R, Morgenstern R, Richter A. Extracellular amino acid levels in the striatum of the dt(sz) mutant, a model of paroxysmal dystonia. Neuroscience 2008; 157:188-95. [PMID: 18824218 DOI: 10.1016/j.neuroscience.2008.08.059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 08/27/2008] [Accepted: 08/31/2008] [Indexed: 10/21/2022]
Abstract
The pathophysiology of idiopathic dystonia is still unknown, but it is regarded as a basal ganglia disorder. Previous studies indicated an involvement of a striatal GABAergic disinhibition and a cortico-striatal glutamatergic overactivity in the manifestation of stress-inducible dystonic episodes in the dt(sz) hamster, a model of idiopathic paroxysmal dystonia. These investigations were carried out postmortem or in anesthetized animals. In the present study, in vivo microdialysis in conscious, freely-moving dt(sz) and non-dystonic control hamsters was used to examine the levels of GABA, aspartate, glutamate, glutamine, glycine and taurine in each animal during following conditions: (1) at baseline in the absence of dystonia, (2) during an episode of paroxysmal dystonia precipitated by stressful stimuli, (3) during a recovery period and (4) at baseline after complete recovery. In comparison to non-dystonic controls, which were treated in the same manner as the dystonic animals, no differences could be detected under basal conditions. The induction of a dystonic episode in mutant hamsters led to higher contents of glycine in these animals in comparison to stressed but non-dystonic controls. Significant changes of glycine levels within the animal groups were not detected. The levels of the excitatory amino acids glutamate, glutamine and aspartate as well as the levels of the inhibitory amino acids GABA and taurine did not differ between the animal groups or between the periods of measurement. The higher levels of glycine might contribute to the manifestation of paroxysmal dystonia in dt(sz) hamsters, although unaltered glutamate, glutamine and aspartate levels do not support the hypothesis of a critical involvement of a cortico-striatal overactivity. It seems that a deficiency of GABAergic interneurons, found by previous immunohistochemical examinations, does not lead to reduced extracellular GABA levels in the striatum.
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Affiliation(s)
- M Hamann
- Institute of Pharmacology and Toxicology, Department of Veterinary Medicine, Freie Universität Berlin, Koserstr. 20, 14195 Berlin, Germany.
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