1
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Braidy N, Liu Y. NAD+ therapy in age-related degenerative disorders: A benefit/risk analysis. Exp Gerontol 2020; 132:110831. [PMID: 31917996 DOI: 10.1016/j.exger.2020.110831] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/23/2019] [Accepted: 01/02/2020] [Indexed: 02/06/2023]
Abstract
Nicotinamide adenine dinucleotide (NAD+) is an essential pyridine nucleotide that is present in all living cells. NAD+ acts as an important cofactor and substrate for a multitude of biological processes including energy production, DNA repair, gene expression, calcium-dependent secondary messenger signalling and immunoregulatory roles. The de novo synthesis of NAD+ is primarily dependent on the kynurenine pathway (KP), although NAD+ can also be recycled from nicotinic acid (NA), nicotinamide (NAM) and nicotinamide riboside (NR). NAD+ levels have been reported to decline during ageing and age-related diseases. Recent studies have shown that raising intracellular NAD+ levels represents a promising therapeutic strategy for age-associated degenerative diseases in general and to extend lifespan in small animal models. A systematic review of the literature available on Medline, Embase and Pubmed was undertaken to evaluate the potential health and/or longevity benefits due to increasing NAD+ levels. A total of 1545 articles were identified and 147 articles (113 preclinical and 34 clinical) met criteria for inclusion. Most studies indicated that the NAD+ precursors NAM, NR, nicotinamide mononucleotide (NMN), and to a lesser extent NAD+ and NADH had a favourable outcome on several age-related disorders associated with the accumulation of chronic oxidative stress, inflammation and impaired mitochondrial function. While these compounds presented with a limited acute toxicity profile, evidence is still quite limited and long-term human clinical trials are still nascent in the current literature. Potential risks in raising NAD+ levels in various clinical disorders using NAD+ precursors include the accumulation of putative toxic metabolites, tumorigenesis and promotion of cellular senescence. Therefore, NAD+ metabolism represents a promising target and further studies are needed to recapitulate the preclinical benefits in human clinical trials.
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Affiliation(s)
- Nady Braidy
- Centre for Healthy Brain Ageing, School of Psychiatry, University of New South Wales, Sydney, Australia.
| | - Yue Liu
- Centre for Healthy Brain Ageing, School of Psychiatry, University of New South Wales, Sydney, Australia
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2
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Garrison AM, Parrott JM, Tuñon A, Delgado J, Redus L, O'Connor JC. Kynurenine pathway metabolic balance influences microglia activity: Targeting kynurenine monooxygenase to dampen neuroinflammation. Psychoneuroendocrinology 2018; 94:1-10. [PMID: 29734055 PMCID: PMC5995655 DOI: 10.1016/j.psyneuen.2018.04.019] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 04/12/2018] [Accepted: 04/20/2018] [Indexed: 10/17/2022]
Abstract
Chronic stress or inflammation increases tryptophan metabolism along the kynurenine pathway (KP), and the generation of neuroactive kynurenine metabolites contributes to subsequent depressive-like behaviors. Microglia regulate KP balance by preferentially producing oxidative metabolites, including quinolinic acid. Research has focused on the interplay between cytokines and HPA axis-derived corticosteroids in regulating microglial activity and effects of KP metabolites directly on neurons; however, the potential role that KP metabolites have directly on microglial activity is unknown. Here, murine microglia were stimulated with lipopolysaccharide(LPS). After 6 h, mRNA expression of interleukin(IL)-1β, IL-6, tumor necrosis factor(TNF)-α and inducible nitric oxide synthase(iNOS) was dose-dependently increased along with the rate-limiting enzymes for oxidative KP metabolism, indoleamine-2,3-dioxygenase(IDO)-1 and kynurenine 3-monooxygenase(KMO). By 24 h post-LPS, kynurenine and quinolinic acid in the media was elevated. Inhibiting KMO with Ro 61-8048 during LPS challenge attenuated extracellular nitrite accumulation and expression of KMO and TNF-α in response to LPS. Similarly, primary microglia isolated from KMO-/- mice exhibited a significantly reduced pro-inflammatory response to LPS compared to WT controls. To determine whether the substrate (kynurenine) or end product (quinolinic acid) of KMO-dependent metabolism modulates the LPS response, microglia were treated with increasing concentrations of L-kynurenine or quinolinic acid in combination with LPS or saline. Interestingly, quinolinic acid did not impact the microglial LPS response. However, L-kynurenine had dose-dependent inhibitory effect on the LPS response. These data are the first to show an anti-inflammatory effect of KMO inhibition on microglia during immune challenge and suggest that KP metabolic balance may play a direct role in regulating microglia activity.
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Affiliation(s)
- Allison M. Garrison
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio
| | - Jennifer M. Parrott
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio
| | - Arnulfo Tuñon
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio
| | - Jennifer Delgado
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio
| | - Laney Redus
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio
| | - Jason C. O'Connor
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio,The Center for Biomedical Neuroscience, School of Medicine, The University of Texas Health Science Center at San Antonio,Audie L. Murphy VA Hospital, South Texas Veterans Health System, San Antonio, Texas
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3
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Lanz TV, Becker S, Mohapatra SR, Opitz CA, Wick W, Platten M. Suppression of Th1 differentiation by tryptophan supplementation in vivo. Amino Acids 2017; 49:1169-1175. [PMID: 28421297 DOI: 10.1007/s00726-017-2415-4] [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: 03/26/2017] [Accepted: 03/31/2017] [Indexed: 12/30/2022]
Abstract
Metabolism of the essential amino acid tryptophan (trp) is a key endogenous immunosuppressive pathway restricting inflammatory responses. Tryptophan metabolites promote regulatory T cell (Treg) differentiation and suppress proinflammatory T helper cell (Th)1 and Th17 phenotypes. It has been shown that treatment with natural and synthetic tryptophan metabolites can suppress autoimmune neuroinflammation in preclinical animal models. Here, we tested if oral intake of tryptophan would increase immunosuppressive tryptophan metabolites and ameliorate autoimmune neuroinflammation as a safe approach to treat autoimmune disorders like multiple sclerosis (MS). Without oral supplementation, systemic kynurenine levels decrease during the initiation phase of experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, indicating systemic activation of tryptophan metabolism. Daily oral gavage of up to 10 mg/mouse/day was safe and increased serum kynurenine levels by more than 20-fold for more than 3 h after the gavage. While this treatment resulted in suppression of myelin-specific Th1 responses, there was no relevant impact on clinical disease activity. These data show that oral trp supplementation at subtoxic concentrations suppresses antigen-specific Th1 responses, but suggest that the increase in trp metabolites is not sustained enough to impact neuroinflammation.
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Affiliation(s)
- Tobias V Lanz
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany. .,Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. .,Division of Immunology and Rheumatology, Department of Medicine, Stanford University School of Medicine, CCSR, 269 Campus Dr., Stanford, CA, 94305, USA.
| | - Simon Becker
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Soumya R Mohapatra
- Brain Cancer Metabolism, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Christiane A Opitz
- Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany.,Brain Cancer Metabolism, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Wolfgang Wick
- Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany.,DKTK Clinical Cooperation Unit Neurooncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Michael Platten
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany.,Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany.,Department of Neurology, University Medical Center Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim, Germany
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4
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Lanz TV, Williams SK, Stojic A, Iwantscheff S, Sonner JK, Grabitz C, Becker S, Böhler LI, Mohapatra SR, Sahm F, Küblbeck G, Nakamura T, Funakoshi H, Opitz CA, Wick W, Diem R, Platten M. Tryptophan-2,3-Dioxygenase (TDO) deficiency is associated with subclinical neuroprotection in a mouse model of multiple sclerosis. Sci Rep 2017; 7:41271. [PMID: 28117398 PMCID: PMC5259766 DOI: 10.1038/srep41271] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 12/19/2016] [Indexed: 11/15/2022] Open
Abstract
The catabolism of tryptophan to immunosuppressive and neuroactive kynurenines is a key metabolic pathway regulating immune responses and neurotoxicity. The rate-limiting step is controlled by indoleamine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO). IDO is expressed in antigen presenting cells during immune reactions, hepatic TDO regulates blood homeostasis of tryptophan and neuronal TDO influences neurogenesis. While the role of IDO has been described in multiple immunological settings, little is known about TDO’s effects on the immune system. TDO-deficiency is neuroprotective in C. elegans and Drosophila by increasing tryptophan and specific kynurenines. Here we have determined the role of TDO in autoimmunity and neurodegeneration in experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis. We created reporter-TDO mice for in vivo imaging to show that hepatic but not CNS TDO expression is activated during EAE. TDO deficiency did not influence myelin-specific T cells, leukocyte infiltration into the CNS, demyelination and disease activity. TDO-deficiency protected from neuronal loss in the spinal cord but not in the optic nerves. While this protection did not translate to an improved overt clinical outcome, our data suggest that spatially distinct neuroprotection is conserved in mammals and support TDO as a potential target for treatment of diseases associated with neurodegeneration.
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Affiliation(s)
- Tobias V Lanz
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany.,Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany
| | - Sarah K Williams
- AG Neuroinflammation, Department of Neurology, University Hospital Heidelberg, Otto-Meyerhof Zentrum, Im Neuenheimer Feld 350, 69120 Heidelberg, Germany
| | - Aleksandar Stojic
- AG Neuroinflammation, Department of Neurology, University Hospital Heidelberg, Otto-Meyerhof Zentrum, Im Neuenheimer Feld 350, 69120 Heidelberg, Germany
| | - Simeon Iwantscheff
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Jana K Sonner
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Carl Grabitz
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Simon Becker
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Laura-Inés Böhler
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Soumya R Mohapatra
- AG Brain Tumor Metabolism, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Felix Sahm
- Department of Neuropathology, University Hospital Heidelberg, and Clinical Cooperation Unit Neuropathology, German Cancer Consortium (DKTK), German cancer Research Center (DKFZ), Im Neuenheimer Feld 224, 69120 Heidelberg, Germany
| | - Günter Küblbeck
- Department of Molecular Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | | | - Hiroshi Funakoshi
- Center for Advanced Research and Education (CARE), Asahikawa Medical University, 2-1-1-1 Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan
| | - Christiane A Opitz
- Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.,AG Brain Tumor Metabolism, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Wolfgang Wick
- Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.,DKTK Clinical Cooperation Unit Neurooncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - Ricarda Diem
- Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.,AG Neuroinflammation, Department of Neurology, University Hospital Heidelberg, Otto-Meyerhof Zentrum, Im Neuenheimer Feld 350, 69120 Heidelberg, Germany
| | - Michael Platten
- DKTK Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany.,Department of Neurology and National Center for Tumor Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.,Department of Neurology, University Medical Center Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim, Germany
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5
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Lee JM, Tan V, Lovejoy D, Braidy N, Rowe DB, Brew BJ, Guillemin GJ. Involvement of quinolinic acid in the neuropathogenesis of amyotrophic lateral sclerosis. Neuropharmacology 2017; 112:346-364. [DOI: 10.1016/j.neuropharm.2016.05.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 05/13/2016] [Accepted: 05/17/2016] [Indexed: 10/21/2022]
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6
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Bay-Richter C, Linderholm KR, Lim CK, Samuelsson M, Träskman-Bendz L, Guillemin GJ, Erhardt S, Brundin L. A role for inflammatory metabolites as modulators of the glutamate N-methyl-D-aspartate receptor in depression and suicidality. Brain Behav Immun 2015; 43:110-7. [PMID: 25124710 DOI: 10.1016/j.bbi.2014.07.012] [Citation(s) in RCA: 203] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 07/16/2014] [Accepted: 07/25/2014] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Patients with depression and suicidality suffer from low-grade neuroinflammation. Pro-inflammatory cytokines activate indoleamine 2,3-dioxygenase, an initial enzyme of the kynurenine pathway. This pathway produces neuroactive metabolites, including quinolinic- and kynurenic acid, binding to the glutamate N-methyl-d-aspartate-receptor, which is hypothesized to be part of the neural mechanisms underlying symptoms of depression. We therefore hypothesized that symptoms of depression and suicidality would fluctuate over time in patients prone to suicidal behavior, depending on the degree of inflammation and kynurenine metabolite levels in the cerebrospinal fluid (CSF). METHODS We measured cytokines and kynurenine metabolites in CSF, collected from suicide attempters at repeated occasions over 2 years (total patient samples n=143, individuals n=30) and healthy controls (n=36). The association between the markers and psychiatric symptoms was assessed using the Montgomery Asberg Depression Rating Scale and the Suicide Assessment Scale. RESULTS Quinolinic acid was increased and kynurenic acid decreased over time in suicidal patients versus healthy controls. Furthermore, we found a significant association between low kynurenic acid and severe depressive symptoms, as well as between high interleukin-6 levels and more severe suicidal symptoms. CONCLUSIONS We demonstrate a long-term dysregulation of the kynurenine pathway in the central nervous system of suicide attempters. An increased load of inflammatory cytokines was coupled to more severe symptoms. We therefore suggest that patients with a dysregulated kynurenine pathway are vulnerable to develop depressive symptoms upon inflammatory conditions, as a result the excess production of the NMDA-receptor agonist quinolinic acid. This study provides a neurobiological framework supporting the use of NMDA-receptor antagonists in the treatment of suicidality and depression.
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Affiliation(s)
- Cecilie Bay-Richter
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Risskov, Denmark.
| | - Klas R Linderholm
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Chai K Lim
- Neuroinflammation Group, Australian School of Advanced Medicine, Macquarie University, NSW, Australia
| | - Martin Samuelsson
- Faculty of Health Sciences, Department of Clinical and Experimental Medicine, Division of Psychiatry, Linköping University, Linköping, Sweden
| | - Lil Träskman-Bendz
- Department of Clinical Sciences, Section of Psychiatry, Lund University, Lund, Sweden
| | - Gilles J Guillemin
- Neuroinflammation Group, Australian School of Advanced Medicine, Macquarie University, NSW, Australia
| | - Sophie Erhardt
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Lena Brundin
- Division of Psychiatry and Behavioral Medicine, Michigan State University, Grand Rapids, MI, USA; Laboratory of Behavioral Medicine, Van Andel Research Institute, Grand Rapids, MI, USA
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7
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Inhibition of the kynurenine-NAD+ pathway leads to energy failure and exacerbates apoptosis in pneumococcal meningitis. J Neuropathol Exp Neurol 2010; 69:1096-104. [PMID: 20940631 DOI: 10.1097/nen.0b013e3181f7e7e9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Pneumococcal meningitis causes neurological sequelae, including learning and memory deficits in up to half of the survivors. In both humans and in animal models of the disease, there is apoptotic cell death in the hippocampus, a brain region involved in learning and memory function. We previously demonstrated that in an infant rat model of pneumococcal meningitis, there is activation of the kynurenine (KYN) pathway in the hippocampus, and that there was a positive correlation between the concentration of 3-hydroxykynurenine and the extent of hippocampal apoptosis. To clarify the role of the KYN pathway in the pathogenesis of hippocampal apoptosis in pneumococcal meningitis, we specifically inhibited 2 key enzymes of the KYN pathway and assessed hippocampal apoptosis, KYN pathway metabolites, and nicotinamide adenine dinucleotide (NAD) concentrations by high-performance liquid chromatography. Pharmacological inhibition of kynurenine 3-hydroxylase and kynureninase led to decreased cellular NAD levels and increased apoptosis in the hippocampus. The cerebrospinal fluid levels of tumor necrosis factor and interleukin-1α and -β were not affected. Our data suggest that activation of the KYN pathway in pneumococcal meningitis is neuroprotective by compensating for an increased NAD demand caused by infection and inflammation;this mechanism may prevent energy failure and apoptosis in the hippocampus.
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8
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Induction of indolamine 2,3-dioxygenase and kynurenine 3-monooxygenase in rat brain following a systemic inflammatory challenge: a role for IFN-gamma? Neurosci Lett 2008; 441:29-34. [PMID: 18584961 DOI: 10.1016/j.neulet.2008.06.007] [Citation(s) in RCA: 152] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 05/10/2008] [Accepted: 06/04/2008] [Indexed: 12/31/2022]
Abstract
Inflammation-mediated dysregulation of the kynurenine pathway has been implicated as a contributor to a number of major brain disorders. Consequently, we examined the impact of a systemic inflammatory challenge on kynurenine pathway enzyme expression in rat brain. Indoleamine 2,3-dioxygenase (IDO) expression was induced in cortex and hippocampus following systemic lipopolysaccharide (LPS) administration. Whilst IDO expression was paralleled by increased circulating interferon (IFN)-gamma concentrations, IFN-gamma expression in the brain was only modestly altered following LPS administration. In contrast, induction of IDO was associated with increased central tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 expression. Similarly, in cultured glial cells LPS-induced IDO expression was accompanied by increased TNF-alpha and IL-6 expression, whereas IFN-gamma was not detectable. These findings indicate that IFN-gamma is not required for LPS-induced IDO expression in brain. A robust increase in kynurenine-3-monooxygenase (KMO) expression was observed in rat brain 24h post LPS, without any change in kynurenine aminotransferase II (KAT II) expression. In addition, we report that constitutive expression of KAT II is approximately 8-fold higher than KMO in cortex and 20-fold higher in hippocampus. Similarly, in glial cells constitutive expression of KAT II was approximately 16-fold higher than KMO, and expression of KMO but not KAT II was induced by LPS. These data are the first to demonstrate that a systemic inflammatory challenge stimulates KMO expression in brain; a situation that is likely to favour kynurenine metabolism in a neurotoxic direction. However, our observation that expression of KAT II is much higher than KMO in rat brain is likely to counteract potential neurotoxicity that could arise from KMO induction following an acute inflammation.
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9
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Poeggeler B, Rassoulpour A, Wu HQ, Guidetti P, Roberts RC, Schwarcz R. Dopamine receptor activation reveals a novel, kynurenate-sensitive component of striatal N-methyl-D-aspartate neurotoxicity. Neuroscience 2007; 148:188-97. [PMID: 17629627 PMCID: PMC2034343 DOI: 10.1016/j.neuroscience.2007.05.033] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 05/04/2007] [Accepted: 05/07/2007] [Indexed: 11/24/2022]
Abstract
The N-methyl-d-aspartate (NMDA) subtype of glutamate receptors plays an important role in brain physiology, but excessive receptor stimulation results in seizures and excitotoxic nerve cell death. NMDA receptor-mediated neuronal excitation and injury can be prevented by high, non-physiological concentrations of the neuroinhibitory tryptophan metabolite kynurenic acid (KYNA). Here we report that endogenous KYNA, which is formed in and released from astrocytes, controls NMDA receptors in vivo. This was revealed with the aid of the dopaminergic drugs d-amphetamine and apomorphine, which cause rapid, transient decreases in striatal KYNA levels in rats. Intrastriatal injections of the excitotoxins NMDA or quinolinate (but not the non-NMDA receptor agonist kainate) at the time of maximal KYNA reduction resulted in two- to threefold increases in excitotoxic lesion size. Pre-treatment with a kynurenine 3-hydroxylase inhibitor or with dopamine receptor antagonists, i.e., two classes of pharmacological agents that prevented the reduction in brain KYNA caused by dopaminergic stimulation, abolished the potentiation of neurotoxicity. Thus, the present study identifies a previously unappreciated role of KYNA as a functional link between dopamine receptor stimulation and NMDA neurotoxicity in the striatum.
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Affiliation(s)
- B Poeggeler
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, P.O. Box 21247, Baltimore, MD 21228, USA
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10
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Bellac CL, Coimbra RS, Christen S, Leib SL. Pneumococcal meningitis causes accumulation of neurotoxic kynurenine metabolites in brain regions prone to injury. Neurobiol Dis 2006; 24:395-402. [PMID: 16956766 DOI: 10.1016/j.nbd.2006.07.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 07/20/2006] [Accepted: 07/25/2006] [Indexed: 10/24/2022] Open
Abstract
Pneumococcal meningitis (PM) is characterized by an intense inflammatory host reaction that contributes to the development of cortical necrosis and hippocampal apoptosis. Inflammatory conditions in the brain are known to induce tryptophan degradation along the kynurenine pathway, resulting in accumulation of neurotoxic metabolites. In the present study, we investigated the contribution of the kynurenine pathway to brain injury in experimental PM by measuring the concentration of its metabolites and the enzymatic activities and mRNA levels of its major enzymes in the vulnerable brain regions. In the late phase of acute PM, we found a significant transcriptional upregulation of kynurenine-3-hydroxylase and an accumulation of the neurotoxic metabolites 3-hydroxykynurenine (3-HKYN) and 3-hydroxyanthranilic acid in cortex and hippocampus. The positive correlation between the concentration of 3-HKYN and the extent of hippocampal apoptosis adds support to the concept that 3-HKYN contributes to brain injury in PM.
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Affiliation(s)
- Caroline L Bellac
- Institute for Infectious Diseases, University of Bern, Friedbuehlstrasse 51, PO Box 61, CH-3010 Bern, Switzerland
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11
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Rae C, Moussa CEH, Griffin JL, Parekh SB, Bubb WA, Hunt NH, Balcar VJ. A metabolomic approach to ionotropic glutamate receptor subtype function: a nuclear magnetic resonance in vitro investigation. J Cereb Blood Flow Metab 2006; 26:1005-17. [PMID: 16395280 DOI: 10.1038/sj.jcbfm.9600257] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A range of behaviours are elucidated via ionotropic glutamate receptors (iGluR). In this work, we examined the acute activation of iGluRs by a range of receptor ligands and effectors to see whether distinguishable metabolic sequelae were elucidated by the activity. We used a guinea-pig brain cortical tissue slice model using targeted receptor ligands ((RS)-(tetrazol-5-yl)glycine (TZG), (5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801, dizocilpine), cis-4-[phosphomethyl]-piperidine-2-carboxylic acid (CGS 19755), (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, (2S, 3S, 4S)-2-carboxy-4-(1-methylethenyl)-3-pyrrolidineacetic acid (kainate) and D-serine (D-Ser), as well as compounds (quinolinic acid and kynurenic acid (KynA)) involved in some neuroinflammatory responses. The data were derived using 13C and 1H NMR spectroscopy, and analysed by metabolomic approaches and multivariate statistics. The metabolic effects of agonists at the three major classes of iGluR were easily separated from each other using this method. The classical N-methyl-D-aspartate receptor agonist TZG and the antagonist CGS 19755 produced excitatory and inhibitory metabolic responses, respectively, while the blocker MK-801 resulted in a significant decrease in net metabolism and produced the largest decrease in all metabolite pool sizes seen by any glutamatergic ligand we have studied. Quinolinic acid and KynA produced similar acute metabolic responses, which were unlike those to TZG or CGS 19755, but similar to that of D-Ser. D-Ser was highly stimulatory of net flux into the Krebs cycle. These data show that the metabolic response to iGluR perturbation in vitro is a sensitive discriminator of function.
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Affiliation(s)
- Caroline Rae
- School of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, Australia.
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12
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Rzeski W, Kocki T, Dybel A, Wejksza K, Zdzisińska B, Kandefer-Szerszeń M, Turski WA, Okuno E, Albrecht J. Demonstration of kynurenine aminotransferases I and II and characterization of kynurenic acid synthesis in cultured cerebral cortical neurons. J Neurosci Res 2005; 80:677-82. [PMID: 15880762 DOI: 10.1002/jnr.20505] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The present study characterizes the synthesis of kynurenic acid (KYNA) from exogenously added kynurenine and its regulation by extrinsic factors, in cultured cerebral cortical neurons and, for comparison, in astrocytes incubated under identical conditions. The neuronal culture showed positive immunostaining for both kynurenic acid aminotransferase (KAT) isoforms I and II. Neurons synthesized KYNA at a rate about 2.3 times higher than astrocytes. Neuronal, but not astrocytic, KYNA synthesis was lowered approximately 30% by ionotropic glutamate receptor agonists [(R,S)-3-hydroxy-5-methoxyloxasole-4-propionic acid (AMPA; 100 microM) and N-methyl-D-aspartic acid (NMDA; 100 microM)] and depolarizing agents [KCl (50 mM) and 4-aminopyridine (4-AP; 10 microM)]. Neuronal and astrocytic synthesis alike were vulnerable to inhibition exerted by the aminotransferase inhibitor aminooxyacetic acid (AOAA), glutamate (IC50: 31 and 85 microM, respectively), substrates of the L-amino transport system [leucine (Leu); IC50: 19 and 42 microM, respectively] and 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH; IC50: 19 and 28 microM, respectively). Glutamine (Gln), which is a metabolic precursor of glutamate in astrocytes and L-system substrate in both cell types, inhibited KYNA synthesis both in neurons and in astrocytes (IC50: 268 and 318 microM, respectively). alpha-Ketoisocaproic acid (KIC), a Leu transamination product that is produced mainly in astrocytes and shuttled to neurons to modulate intraneuronal concentration of glutamate, stimulated KYNA synthesis in neurons but did not affect the synthesis in astrocytes. In conclusion, this study is the first to demonstrate active, regulation-prone KYNA synthesis in neurons.
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Affiliation(s)
- Wojciech Rzeski
- Department of Virology and Immunology, Institute of Microbiology and Biotechnology, Maria Curie-Skodowska University, Lublin, Poland
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