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Plaitakis A, Sidiropoulou K, Kotzamani D, Litso I, Zaganas I, Spanaki C. Evolution of Glutamate Metabolism via GLUD2 Enhances Lactate-Dependent Synaptic Plasticity and Complex Cognition. Int J Mol Sci 2024; 25:5297. [PMID: 38791334 PMCID: PMC11120665 DOI: 10.3390/ijms25105297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/07/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
Human evolution is characterized by rapid brain enlargement and the emergence of unique cognitive abilities. Besides its distinctive cytoarchitectural organization and extensive inter-neuronal connectivity, the human brain is also defined by high rates of synaptic, mainly glutamatergic, transmission, and energy utilization. While these adaptations' origins remain elusive, evolutionary changes occurred in synaptic glutamate metabolism in the common ancestor of humans and apes via the emergence of GLUD2, a gene encoding the human glutamate dehydrogenase 2 (hGDH2) isoenzyme. Driven by positive selection, hGDH2 became adapted to function upon intense excitatory firing, a process central to the long-term strengthening of synaptic connections. It also gained expression in brain astrocytes and cortical pyramidal neurons, including the CA1-CA3 hippocampal cells, neurons crucial to cognition. In mice transgenic for GLUD2, theta-burst-evoked long-term potentiation (LTP) is markedly enhanced in hippocampal CA3-CA1 synapses, with patch-clamp recordings from CA1 pyramidal neurons revealing increased sNMDA receptor currents. D-lactate blocked LTP enhancement, implying that glutamate metabolism via hGDH2 potentiates L-lactate-dependent glia-neuron interaction, a process essential to memory consolidation. The transgenic (Tg) mice exhibited increased dendritic spine density/synaptogenesis in the hippocampus and improved complex cognitive functions. Hence, enhancement of neuron-glia communication, via GLUD2 evolution, likely contributed to human cognitive advancement by potentiating synaptic plasticity and inter-neuronal connectivity.
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Affiliation(s)
- Andreas Plaitakis
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
| | - Kyriaki Sidiropoulou
- Department of Biology, University of Crete, Voutes, 71003 Heraklion, Crete, Greece;
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas (IMBB-FORTH), 70013 Heraklion, Crete, Greece
| | - Dimitra Kotzamani
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
| | - Ionela Litso
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
| | - Ioannis Zaganas
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
- Neurology Department, PaGNI University General Hospital of Heraklion, 71500 Heraklion, Crete, Greece
| | - Cleanthe Spanaki
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
- Neurology Department, PaGNI University General Hospital of Heraklion, 71500 Heraklion, Crete, Greece
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2
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Rae CD, Baur JA, Borges K, Dienel G, Díaz-García CM, Douglass SR, Drew K, Duarte JMN, Duran J, Kann O, Kristian T, Lee-Liu D, Lindquist BE, McNay EC, Robinson MB, Rothman DL, Rowlands BD, Ryan TA, Scafidi J, Scafidi S, Shuttleworth CW, Swanson RA, Uruk G, Vardjan N, Zorec R, McKenna MC. Brain energy metabolism: A roadmap for future research. J Neurochem 2024; 168:910-954. [PMID: 38183680 PMCID: PMC11102343 DOI: 10.1111/jnc.16032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 11/29/2023] [Accepted: 12/05/2023] [Indexed: 01/08/2024]
Abstract
Although we have learned much about how the brain fuels its functions over the last decades, there remains much still to discover in an organ that is so complex. This article lays out major gaps in our knowledge of interrelationships between brain metabolism and brain function, including biochemical, cellular, and subcellular aspects of functional metabolism and its imaging in adult brain, as well as during development, aging, and disease. The focus is on unknowns in metabolism of major brain substrates and associated transporters, the roles of insulin and of lipid droplets, the emerging role of metabolism in microglia, mysteries about the major brain cofactor and signaling molecule NAD+, as well as unsolved problems underlying brain metabolism in pathologies such as traumatic brain injury, epilepsy, and metabolic downregulation during hibernation. It describes our current level of understanding of these facets of brain energy metabolism as well as a roadmap for future research.
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Affiliation(s)
- Caroline D. Rae
- School of Psychology, The University of New South Wales, NSW 2052 & Neuroscience Research Australia, Randwick, New South Wales, Australia
| | - Joseph A. Baur
- Department of Physiology and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Karin Borges
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
| | - Gerald Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
- Department of Cell Biology and Physiology, University of New Mexico School of Medicine, Albuquerque, New Mexico, USA
| | - Carlos Manlio Díaz-García
- Department of Biochemistry and Molecular Biology, Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | | | - Kelly Drew
- Center for Transformative Research in Metabolism, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - João M. N. Duarte
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, Lund, & Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Jordi Duran
- Institut Químic de Sarrià (IQS), Universitat Ramon Llull (URL), Barcelona, Spain
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Oliver Kann
- Institute of Physiology and Pathophysiology, University of Heidelberg, D-69120; Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, Heidelberg, Germany
| | - Tibor Kristian
- Veterans Affairs Maryland Health Center System, Baltimore, Maryland, USA
- Department of Anesthesiology and the Center for Shock, Trauma, and Anesthesiology Research (S.T.A.R.), University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Dasfne Lee-Liu
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Región Metropolitana, Chile
| | - Britta E. Lindquist
- Department of Neurology, Division of Neurocritical Care, Gladstone Institute of Neurological Disease, University of California at San Francisco, San Francisco, California, USA
| | - Ewan C. McNay
- Behavioral Neuroscience, University at Albany, Albany, New York, USA
| | - Michael B. Robinson
- Departments of Pediatrics and System Pharmacology & Translational Therapeutics, Children’s Hospital of Philadelphia, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Douglas L. Rothman
- Magnetic Resonance Research Center and Departments of Radiology and Biomedical Engineering, Yale University, New Haven, Connecticut, USA
| | - Benjamin D. Rowlands
- School of Chemistry, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Timothy A. Ryan
- Department of Biochemistry, Weill Cornell Medicine, New York, New York, USA
| | - Joseph Scafidi
- Department of Neurology, Kennedy Krieger Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Susanna Scafidi
- Anesthesiology & Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - C. William Shuttleworth
- Department of Neurosciences, University of New Mexico School of Medicine Albuquerque, Albuquerque, New Mexico, USA
| | - Raymond A. Swanson
- Department of Neurology, University of California, San Francisco, and San Francisco Veterans Affairs Medical Center, San Francisco, California, USA
| | - Gökhan Uruk
- Department of Neurology, University of California, San Francisco, and San Francisco Veterans Affairs Medical Center, San Francisco, California, USA
| | - Nina Vardjan
- Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology—Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology—Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Mary C. McKenna
- Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, USA
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3
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Dienel GA, Schousboe A, McKenna MC, Rothman DL. A tribute to Leif Hertz: The historical context of his pioneering studies of the roles of astrocytes in brain energy metabolism, neurotransmission, cognitive functions, and pharmacology identifies important, unresolved topics for future studies. J Neurochem 2024; 168:461-495. [PMID: 36928655 DOI: 10.1111/jnc.15812] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 03/10/2023] [Accepted: 03/13/2023] [Indexed: 03/18/2023]
Abstract
Leif Hertz, M.D., D.Sc. (honōris causā) (1930-2018), was one of the original and noteworthy participants in the International Conference on Brain Energy Metabolism (ICBEM) series since its inception in 1993. The biennial ICBEM conferences are organized by neuroscientists interested in energetics and metabolism underlying neural functions; they have had a high impact on conceptual and experimental advances in these fields and on promoting collaborative interactions among neuroscientists. Leif made major contributions to ICBEM discussions and understanding of metabolic and signaling characteristics of astrocytes and their roles in brain function. His studies ranged from uptake of K+ from extracellular fluid and its stimulation of astrocytic respiration, identification, and regulation of enzymes specifically or preferentially expressed in astrocytes in the glutamate-glutamine cycle of excitatory neurotransmission, a requirement for astrocytic glycogenolysis for fueling K+ uptake, involvement of glycogen in memory consolidation in the chick, and pharmacology of astrocytes. This tribute to Leif Hertz highlights his major discoveries, the high impact of his work on astrocyte-neuron interactions, and his unparalleled influence on understanding the cellular basis of brain energy metabolism. His work over six decades has helped integrate the roles of astrocytes into neurotransmission where oxidative and glycogenolytic metabolism during neurotransmitter glutamate turnover are key aspects of astrocytic energetics. Leif recognized that brain astrocytic metabolism is greatly underestimated unless the volume fraction of astrocytes is taken into account. Adjustment for pathway rates expressed per gram tissue for volume fraction indicates that astrocytes have much higher oxidative rates than neurons and astrocytic glycogen concentrations and glycogenolytic rates during sensory stimulation in vivo are similar to those in resting and exercising muscle, respectively. These novel insights are typical of Leif's astute contributions to the energy metabolism field, and his publications have identified unresolved topics that provide the neuroscience community with challenges and opportunities for future research.
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Affiliation(s)
- Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, 72205, USA
- Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, New Mexico, 87131, USA
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, 2100, Denmark
| | - Mary C McKenna
- Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA
| | - Douglas L Rothman
- Department of Radiology, Magnetic Resonance Research Center (MRRC), Yale University, New Haven, Connecticut, 06520, USA
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4
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Satrustegui J, Larrubia PL, Rodrigues TB, Choi IY, McKenna MC. A tribute to Sebastián Cerdán and his key contributions to brain metabolism. J Neurochem 2024; 168:455-460. [PMID: 37169729 DOI: 10.1111/jnc.15828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 04/06/2023] [Indexed: 05/13/2023]
Abstract
This is a tribute to Sebastián Cerdán, a brilliant and innovative NMR spectroscopist whose studies contributed greatly to the fundamental information to the understanding of brain metabolism, particularly in regard to multinuclear magnetic resonance spectroscopy (MRS) techniques. Sebastián Cerdán sadly passed away in May 2022. He was a wonderful mentor and colleague who will be greatly missed.
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Affiliation(s)
- Jorgina Satrustegui
- Departamento de Biologia Molecular & Centro de Biología Molecular Severo Ochoa CSIC-UAM, Madrid, Spain
| | | | - Tiago B Rodrigues
- Member of the Parliament and President of the Parliamentary Committee of Environment and Energy Portuguese Parliament, Lisbon, Portugal
| | - In-Young Choi
- Department of Neurology, Department of Radiology, Hoglund Biomedical Imaging Center, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Mary C McKenna
- Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, USA
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5
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Cao P, Kang Y, Liu J, Liu X, Jin Y, Zhang Z. Urinary metabolomics study of vancomycin-associated nephrotoxicity based on ultra-performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry. Hum Exp Toxicol 2022; 41:9603271221119178. [PMID: 35984423 DOI: 10.1177/09603271221119178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Drug-induced nephrotoxicity is widespread and seriously affects human health. Vancomycin is a classical glycopeptide antibiotic. Vancomycin is widely used for severe infections caused by Gram-positive bacteria, especially methicillin-resistant Staphylococcus aureus but its obvious nephrotoxicity affects the safety of its clinical application. However, the etiology of vancomycin induced kidney injury is not well understood. This study aimed to explore the potential mechanism of vancomycin-induced nephrotoxicity in rats. Vancomycin (400 mgkg-1) was used to establish kidney injury models in rats. A metabonomic approach was employed using ultra-performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) to delineate metabolic alterations. As a result, 15, 22, and 37 biomarkers were identified in urine samples from the treatment group compared to the control model on D2, D4, and D7, respectively. Changes in the levels of these metabolites indicated that amino acid metabolism and energy metabolism were disturbed in rats with vancomycin-associated nephrotoxicity. This study revealed the kidney effect of vancomycin, which may provide novel and promising research approaches to vancomycin-induced renal toxicity.
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Affiliation(s)
- Pei Cao
- Department of Pharmacy, 71213The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Yu Kang
- Department of Pharmacy, 71213The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Jian Liu
- Department of Pharmacy, 71213The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Xiuju Liu
- Department of Pharmacy, 71213The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Yiran Jin
- Department of Pharmacy, 71213The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Zhiqing Zhang
- Department of Pharmacy, 71213The Second Hospital of Hebei Medical University, Shijiazhuang, China
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6
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Dietary Supplement Enriched in Antioxidants and Omega-3 Promotes Glutamine Synthesis in Müller Cells: A Key Process against Oxidative Stress in Retina. Nutrients 2021; 13:nu13093216. [PMID: 34579093 PMCID: PMC8468588 DOI: 10.3390/nu13093216] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/26/2021] [Accepted: 09/11/2021] [Indexed: 12/16/2022] Open
Abstract
To prevent ocular pathologies, new generation of dietary supplements have been commercially available. They consist of nutritional supplement mixing components known to provide antioxidative properties, such as unsaturated fatty acid, resveratrol or flavonoids. However, to date, only one preclinical study has evaluated the impact of a mixture mainly composed of those components (Nutrof Total®) on the retina and demonstrated that in vivo supplementation prevents the retina from structural and functional injuries induced by light. Considering the crucial role played by the glial Müller cells in the retina, particularly to regulate the glutamate cycle to prevent damage in oxidative stress conditions, we questioned the impact of this ocular supplement on the glutamate metabolic cycle. To this end, various molecular aspects associated with the glutamate/glutamine metabolism cycle in Müller cells were investigated on primary Müller cells cultures incubated, or not, with the commercially mix supplement before being subjected, or not, to oxidative conditions. Our results demonstrated that in vitro supplementation provides guidance of the glutamate/glutamine cycle in favor of glutamine synthesis. These results suggest that glutamine synthesis is a crucial cellular process of retinal protection against oxidative damages and could be a key step in the previous in vivo beneficial results provided by the dietary supplementation.
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Rose J, Brian C, Pappa A, Panayiotidis MI, Franco R. Mitochondrial Metabolism in Astrocytes Regulates Brain Bioenergetics, Neurotransmission and Redox Balance. Front Neurosci 2020; 14:536682. [PMID: 33224019 PMCID: PMC7674659 DOI: 10.3389/fnins.2020.536682] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 10/14/2020] [Indexed: 01/17/2023] Open
Abstract
In the brain, mitochondrial metabolism has been largely associated with energy production, and its dysfunction is linked to neuronal cell loss. However, the functional role of mitochondria in glial cells has been poorly studied. Recent reports have demonstrated unequivocally that astrocytes do not require mitochondria to meet their bioenergetics demands. Then, the question remaining is, what is the functional role of mitochondria in astrocytes? In this work, we review current evidence demonstrating that mitochondrial central carbon metabolism in astrocytes regulates overall brain bioenergetics, neurotransmitter homeostasis and redox balance. Emphasis is placed in detailing carbon source utilization (glucose and fatty acids), anaplerotic inputs and cataplerotic outputs, as well as carbon shuttles to neurons, which highlight the metabolic specialization of astrocytic mitochondria and its relevance to brain function.
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Affiliation(s)
- Jordan Rose
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Christian Brian
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Aglaia Pappa
- Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece
| | - Mihalis I Panayiotidis
- Department of Electron Microscopy & Molecular Pathology, Cyprus Institute of Neurology & Genetics, Nicosia, Cyprus
| | - Rodrigo Franco
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
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8
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McIntyre KR, Hayward CE, Sibley CP, Greenwood SL, Dilworth MR. Evidence of adaptation of maternofetal transport of glutamine relative to placental size in normal mice, and in those with fetal growth restriction. J Physiol 2019; 597:4975-4990. [PMID: 31400764 PMCID: PMC6790568 DOI: 10.1113/jp278226] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 08/09/2019] [Indexed: 12/18/2022] Open
Abstract
Key points Fetal growth restriction (FGR) is a major risk factor for stillbirth and has significant impact upon lifelong health. A small, poorly functioning placenta, as evidenced by reduced transport of nutrients to the baby, underpins FGR. It remains unclear how a small but normal placenta differs from the small FGR placenta in terms of ability to transfer nutrients to the fetus. Placental transport of glutamine and glutamate, key amino acids for fetal growth, was assessed in normal mice and those with FGR. Glutamine and glutamate transport was greater in the lightest versus heaviest placenta in a litter of normally grown mice. Placentas of mice with FGR had increased transport capacity in mid‐pregnancy, but this adaptation was insufficient in late pregnancy. Placental adaptations, in terms of increased nutrient transport (per gram) to compensate for small size, appear to achieve appropriate fetal growth in normal pregnancy. Failure of this adaptation might contribute to FGR.
Abstract Fetal growth restriction (FGR), a major risk factor for stillbirth, and neonatal and adulthood morbidity, is associated with reduced placental size and decreased placental nutrient transport. In mice, a small, normal placenta increases its nutrient transport, thus compensating for its reduced size and maintaining normal fetal growth. Whether this adaptation occurs for glutamine and glutamate, two key amino acids for placental metabolism and fetal growth, is unknown. Additionally, an assessment of placental transport of glutamine and glutamate between FGR and normal pregnancy is currently lacking. We thus tested the hypothesis that the transport of glutamine and glutamate would be increased (per gram of tissue) in a small normal placenta [C57BL6/J (wild‐type, WT) mice], but that this adaptation fails in the small dysfunctional placenta in FGR [insulin‐like growth factor 2 knockout (P0) mouse model of FGR]. In WT mice, comparing the lightest versus heaviest placenta in a litter, unidirectional maternofetal clearance (Kmf) of 14C‐glutamine and 14C‐glutamate (glutamineKmf and glutamateKmf) was significantly higher at embryonic day (E) 18.5, in line with increased expression of LAT1, a glutamine transporter protein. In P0 mice, glutamineKmf and glutamateKmf were higher (P0 versus wild‐type littermates, WTL) at E15.5. At E18.5, glutamineKmf remained elevated whereas glutamateKmf was similar between groups. In summary, we provide evidence that glutamineKmf and glutamateKmf adapt according to placental size in WT mice. The placenta of the growth‐restricted P0 fetus also elevates transport capacity to compensate for size at E15.5, but this adaptation is insufficient at E18.5; this may contribute to decreased fetal growth. Fetal growth restriction (FGR) is a major risk factor for stillbirth and has significant impact upon lifelong health. A small, poorly functioning placenta, as evidenced by reduced transport of nutrients to the baby, underpins FGR. It remains unclear how a small but normal placenta differs from the small FGR placenta in terms of ability to transfer nutrients to the fetus. Placental transport of glutamine and glutamate, key amino acids for fetal growth, was assessed in normal mice and those with FGR. Glutamine and glutamate transport was greater in the lightest versus heaviest placenta in a litter of normally grown mice. Placentas of mice with FGR had increased transport capacity in mid‐pregnancy, but this adaptation was insufficient in late pregnancy. Placental adaptations, in terms of increased nutrient transport (per gram) to compensate for small size, appear to achieve appropriate fetal growth in normal pregnancy. Failure of this adaptation might contribute to FGR.
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Affiliation(s)
- Kirsty R McIntyre
- Maternal and Fetal Health Research Centre, Division of Developmental Biology and Medicine, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Manchester Academic Health Science Centre, St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK.,School of Medicine, Dentistry and Nursing, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Christina E Hayward
- Maternal and Fetal Health Research Centre, Division of Developmental Biology and Medicine, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Manchester Academic Health Science Centre, St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
| | - Colin P Sibley
- Maternal and Fetal Health Research Centre, Division of Developmental Biology and Medicine, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Manchester Academic Health Science Centre, St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
| | - Susan L Greenwood
- Maternal and Fetal Health Research Centre, Division of Developmental Biology and Medicine, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Manchester Academic Health Science Centre, St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
| | - Mark R Dilworth
- Maternal and Fetal Health Research Centre, Division of Developmental Biology and Medicine, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Manchester Academic Health Science Centre, St. Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
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9
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Astrocytic pyruvate carboxylation: Status after 35 years. J Neurosci Res 2019; 97:890-896. [DOI: 10.1002/jnr.24402] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/11/2019] [Accepted: 02/05/2019] [Indexed: 12/24/2022]
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10
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Mahan VL. Neurointegrity and neurophysiology: astrocyte, glutamate, and carbon monoxide interactions. Med Gas Res 2019; 9:24-45. [PMID: 30950417 PMCID: PMC6463446 DOI: 10.4103/2045-9912.254639] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 02/15/2019] [Indexed: 12/27/2022] Open
Abstract
Astrocyte contributions to brain function and prevention of neuropathologies are as extensive as that of neurons. Astroglial regulation of glutamate, a primary neurotransmitter, is through uptake, release through vesicular and non-vesicular pathways, and catabolism to intermediates. Homeostasis by astrocytes is considered to be of primary importance in determining normal central nervous system health and central nervous system physiology - glutamate is central to dynamic physiologic changes and central nervous system stability. Gasotransmitters may affect diverse glutamate interactions positively or negatively. The effect of carbon monoxide, an intrinsic central nervous system gasotransmitter, in the complex astrocyte homeostasis of glutamate may offer insights to normal brain development, protection, and its use as a neuromodulator and neurotherapeutic. In this article, we will review the effects of carbon monoxide on astrocyte homeostasis of glutamate.
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Affiliation(s)
- Vicki L. Mahan
- Division of Pediatric Cardiothoracic Surgery in the Department of Surgery, St. Christopher's Hospital for Children/Drexel University College of Medicine, Philadelphia, PA, USA
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11
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Pyruvate cycle increases aminoglycoside efficacy and provides respiratory energy in bacteria. Proc Natl Acad Sci U S A 2018; 115:E1578-E1587. [PMID: 29382755 DOI: 10.1073/pnas.1714645115] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The emergence and ongoing spread of multidrug-resistant bacteria puts humans and other species at risk for potentially lethal infections. Thus, novel antibiotics or alternative approaches are needed to target drug-resistant bacteria, and metabolic modulation has been documented to improve antibiotic efficacy, but the relevant metabolic mechanisms require more studies. Here, we show that glutamate potentiates aminoglycoside antibiotics, resulting in improved elimination of antibiotic-resistant pathogens. When exploring the metabolic flux of glutamate, it was found that the enzymes that link the phosphoenolpyruvate (PEP)-pyruvate-AcCoA pathway to the TCA cycle were key players in this increased efficacy. Together, the PEP-pyruvate-AcCoA pathway and TCA cycle can be considered the pyruvate cycle (P cycle). Our results show that inhibition or gene depletion of the enzymes in the P cycle shut down the TCA cycle even in the presence of excess carbon sources, and that the P cycle operates routinely as a general mechanism for energy production and regulation in Escherichia coli and Edwardsiella tarda These findings address metabolic mechanisms of metabolite-induced potentiation and fundamental questions about bacterial biochemistry and energy metabolism.
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12
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Jackson JG, Robinson MB. Regulation of mitochondrial dynamics in astrocytes: Mechanisms, consequences, and unknowns. Glia 2017; 66:1213-1234. [PMID: 29098734 DOI: 10.1002/glia.23252] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 09/20/2017] [Accepted: 10/09/2017] [Indexed: 12/15/2022]
Abstract
Astrocytes are the major glial cell in the central nervous system. These polarized cells possess numerous processes that ensheath the vasculature and contact synapses. Astrocytes play important roles in synaptic signaling, neurotransmitter synthesis and recycling, control of nutrient uptake, and control of local blood flow. Many of these processes depend on local metabolism and/or energy utilization. While astrocytes respond to increases in neuronal activity and metabolic demand by upregulating glycolysis and glycogenolysis, astrocytes also possess significant capacity for oxidative (mitochondrial) metabolism. Mitochondria mediate energy supply and metabolism, cellular survival, ionic homeostasis, and proliferation. These organelles are dynamic structures undergoing extensive fission and fusion, directed movement along cytoskeletal tracts, and degradation. While many of the mechanisms underlying the dynamics of these organelles and their physiologic roles have been characterized in neurons and other cells, the roles that mitochondrial dynamics play in glial physiology is less well understood. Recent work from several laboratories has demonstrated that mitochondria are present within the fine processes of astrocytes, that their movement is regulated, and that they contribute to local Ca2+ signaling within the astrocyte. They likely play a role in local ATP production and metabolism, particularly that of glutamate. Here we will review these and other findings describing the mechanism by which mitochondrial dynamics are regulated in astrocytes, how mitochondrial dynamics might influence astrocyte and brain metabolism, and draw parallels to mitochondrial dynamics in neurons. Additionally, we present new analyses of the size, distribution, and dynamics of mitochondria in astrocytes performed using in vivo using 2-photon microscopy.
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Affiliation(s)
- Joshua G Jackson
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, 19104.,Departments of Pediatrics, University of Pennsylvania, Philadelphia, PA, 19104
| | - Michael B Robinson
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, 19104.,Departments of Pediatrics, University of Pennsylvania, Philadelphia, PA, 19104.,Department of Pharmacology, University of Pennsylvania, Philadelphia, PA, 19104
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13
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Liu B, Teschemacher AG, Kasparov S. Neuroprotective potential of astroglia. J Neurosci Res 2017; 95:2126-2139. [PMID: 28836687 DOI: 10.1002/jnr.24140] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 07/14/2017] [Accepted: 07/24/2017] [Indexed: 12/13/2022]
Abstract
Astroglia are the homoeostatic cells of the central nervous system, which participate in all essential functions of the brain. Astrocytes support neuronal networks by handling water and ion fluxes, transmitter clearance, provision of antioxidants, and metabolic precursors and growth factors. The critical dependence of neurons on constant support from the astrocytes confers astrocytes with intrinsic neuroprotective properties. On the other hand, loss of astrocytic support or their pathological transformation compromises neuronal functionality and viability. Manipulating neuroprotective functions of astrocytes is thus an important strategy to enhance neuronal survival and improve outcomes in disease states. © 2017 The Authors Journal of Neuroscience Research Published by Wiley Periodicals, Inc.
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Affiliation(s)
- Beihui Liu
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, United Kingdom
| | - A G Teschemacher
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, United Kingdom
| | - Sergey Kasparov
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, United Kingdom.,Institute of Living Systems, School of Life Sciences, Immanuel Kant Baltic Federal University, Kaliningrad, Russian Federation
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14
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Abstract
Epilepsy is a common and devastating neurological disorder characterized by recurrent and unprovoked spontaneous seizures. One leading hypothesis for the development and progression of epilepsy is that large-scale changes in gene transcription and protein expression contribute to aberrant network restructuring and hyperexcitability, resulting in the genesis of repeated seizures. Current research shows that epigenetic mechanisms, including posttranslational alterations to the proteins around which DNA is coiled, chemical modifications to DNA, and the activity of various noncoding RNA molecules exert important influences on these gene networks in experimental epilepsy. Key findings from animal models have been replicated in humans using brain tissue obtained from living patients at the time of neurosurgical resection for pharmacoresistant epilepsy. These findings have spurred efforts to target epigenetic processes to disrupt or modify epilepsy in experimental models with varying degrees of success. In this review, we will (1) summarize the epigenetic mechanisms implicated in epileptogenesis and epilepsy, (2) explore the influence of metabolic factors on epigenetic mechanisms, and (3) assess the potential of using epigenetic markers to support diagnosis and prognosis. Translation of these findings may guide the development of molecular biomarkers and novel therapeutics for prevention or modification of epileptic disorders.
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Affiliation(s)
- Rebecca M. Hauser
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - David C. Henshall
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Farah D. Lubin
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
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15
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Dar NJ, Satti NK, Dutt P, Hamid A, Ahmad M. Attenuation of Glutamate-Induced Excitotoxicity by Withanolide-A in Neuron-Like Cells: Role for PI3K/Akt/MAPK Signaling Pathway. Mol Neurobiol 2017; 55:2725-2739. [DOI: 10.1007/s12035-017-0515-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 04/04/2017] [Indexed: 12/30/2022]
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16
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Świątkiewicz M, Fiedorowicz M, Orzeł J, Wełniak-Kamińska M, Bogorodzki P, Langfort J, Grieb P. Increases in Brain 1H-MR Glutamine and Glutamate Signals Following Acute Exhaustive Endurance Exercise in the Rat. Front Physiol 2017; 8:19. [PMID: 28197103 PMCID: PMC5281557 DOI: 10.3389/fphys.2017.00019] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 01/10/2017] [Indexed: 11/15/2022] Open
Abstract
Objective: Proton magnetic resonance spectroscopy (1H-MRS) in ultra-high magnetic field can be used for non-invasive quantitative assessment of brain glutamate (Glu) and glutamine (Gln) in vivo. Glu, the main excitatory neurotransmitter in the central nervous system, is efficiently recycled between synapses and presynaptic terminals through Glu-Gln cycle which involves glutamine synthase confined to astrocytes, and uses 60–80% of energy in the resting human and rat brain. During voluntary or involuntary exercise many brain areas are significantly activated, which certainly intensifies Glu-Gln cycle. However, studies on the effects of exercise on 1H-MRS Glu and/or Gln signals from the brain provided divergent results. The present study on rats was performed to determine changes in 1H-MRS signals from three brain regions engaged in motor activity consequential to forced acute exercise to exhaustion. Method: After habituation to treadmill running, rats were subjected to acute treadmill exercise continued to exhaustion. Each animal participating in the study was subject to two identical imaging sessions performed under light isoflurane anesthesia, prior to, and following the exercise bout. In control experiments, two imaging sessions separated by the period of rest instead of exercise were performed. 1H-NMR spectra were recorded from the cerebellum, striatum, and hippocampus using a 7T small animal MR scanner. Results: Following exhaustive exercise statistically significant increases in the Gln and Glx signals were found in all three locations, whereas increases in the Glu signal were found in the cerebellum and hippocampus. In control experiments, no changes in 1H-MRS signals were found. Conclusion: Increase in glutamine signals from the brain areas engaged in motor activity may reflect a disequilibrium caused by increased turnover in the glutamate-glutamine cycle and a delay in the return of glutamine from astrocytes to neurons. Increased turnover of Glu-Gln cycle may be a result of functional activation caused by forced endurance exercise; the increased rate of ammonia detoxification may also contribute. Increases in glutamate in the cerebellum and hippocampus are suggestive of an anaplerotic increase in glutamate synthesis due to exercise-related stimulation of brain glucose uptake. The disequilibrium in the glutamate-glutamine cycle in brain areas activated during exercise may be a significant contributor to the central fatigue phenomenon.
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Affiliation(s)
- Maciej Świątkiewicz
- Department of Experimental Pharmacology and Laboratory of Nuclear Magnetic Resonance Imaging, Mossakowski Medical Research Centre, Polish Academy of Sciences Warsaw, Poland
| | - Michał Fiedorowicz
- Department of Experimental Pharmacology and Laboratory of Nuclear Magnetic Resonance Imaging, Mossakowski Medical Research Centre, Polish Academy of Sciences Warsaw, Poland
| | - Jarosław Orzeł
- Department of Experimental Pharmacology and Laboratory of Nuclear Magnetic Resonance Imaging, Mossakowski Medical Research Centre, Polish Academy of SciencesWarsaw, Poland; Faculty of Electronics, Warsaw University of TechnologyWarsaw, Poland
| | - Marlena Wełniak-Kamińska
- Department of Experimental Pharmacology and Laboratory of Nuclear Magnetic Resonance Imaging, Mossakowski Medical Research Centre, Polish Academy of Sciences Warsaw, Poland
| | - Piotr Bogorodzki
- Department of Experimental Pharmacology and Laboratory of Nuclear Magnetic Resonance Imaging, Mossakowski Medical Research Centre, Polish Academy of SciencesWarsaw, Poland; Faculty of Electronics, Warsaw University of TechnologyWarsaw, Poland
| | - Józef Langfort
- Department of Experimental Pharmacology and Laboratory of Nuclear Magnetic Resonance Imaging, Mossakowski Medical Research Centre, Polish Academy of Sciences Warsaw, Poland
| | - Paweł Grieb
- Department of Experimental Pharmacology and Laboratory of Nuclear Magnetic Resonance Imaging, Mossakowski Medical Research Centre, Polish Academy of Sciences Warsaw, Poland
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17
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18
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Hohnholt MC, Blumrich EM, Waagepetersen HS, Dringen R. The tricarboxylic acid cycle activity in cultured primary astrocytes is strongly accelerated by the protein tyrosine kinase inhibitor tyrphostin 23. Neurochem Int 2016; 102:13-21. [PMID: 27894844 DOI: 10.1016/j.neuint.2016.11.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Revised: 11/09/2016] [Accepted: 11/14/2016] [Indexed: 11/28/2022]
Abstract
Tyrphostin 23 (T23) is a well-known inhibitor of protein tyrosine kinases and has been considered as potential anti-cancer drug. T23 was recently reported to acutely stimulate the glycolytic flux in primary cultured astrocytes. To investigate whether T23 also affects the tricarboxylic acid (TCA) cycle, we incubated primary rat astrocyte cultures with [U-13C]glucose in the absence or the presence of 100 μM T23 for 2 h and analyzed the 13C metabolite pattern. These incubation conditions did not compromise cell viability and confirmed that the presence of T23 doubled glycolytic lactate production. In addition, T23-treatment strongly increased the molecular carbon labeling of the TCA cycle intermediates citrate, succinate, fumarate and malate, and significantly increased the incorporation of 13C-labelling into the amino acids glutamate, glutamine and aspartate. These results clearly demonstrate that, in addition to glycolysis, also the mitochondrial TCA cycle is strongly accelerated after exposure of astrocytes to T23, suggesting that a protein tyrosine kinase may be involved in the regulation of the TCA cycle in astrocytes.
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Affiliation(s)
- Michaela C Hohnholt
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Science, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark.
| | - Eva-Maria Blumrich
- Centre for Biomolecular Interactions Bremen, Faculty 2 (Biology/Chemistry), University of Bremen, PO. Box 330440, D-28334 Bremen, Germany; Centre for Environmental Research and Sustainable Technology, Leobener Strasse, D-28359 Bremen, Germany
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Science, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Ralf Dringen
- Centre for Biomolecular Interactions Bremen, Faculty 2 (Biology/Chemistry), University of Bremen, PO. Box 330440, D-28334 Bremen, Germany; Centre for Environmental Research and Sustainable Technology, Leobener Strasse, D-28359 Bremen, Germany
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19
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Amorini AM, Lazzarino G, Di Pietro V, Signoretti S, Lazzarino G, Belli A, Tavazzi B. Severity of experimental traumatic brain injury modulates changes in concentrations of cerebral free amino acids. J Cell Mol Med 2016; 21:530-542. [PMID: 27696676 PMCID: PMC5323875 DOI: 10.1111/jcmm.12998] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 08/26/2016] [Indexed: 12/29/2022] Open
Abstract
In this study, concentrations of free amino acids (FAA) and amino group containing compounds (AGCC) following graded diffuse traumatic brain injury (mild TBI, mTBI; severe TBI, sTBI) were evaluated. After 6, 12, 24, 48 and 120 hr aspartate (Asp), glutamate (Glu), asparagine (Asn), serine (Ser), glutamine (Gln), histidine (His), glycine (Gly), threonine (Thr), citrulline (Cit), arginine (Arg), alanine (Ala), taurine (Tau), γ‐aminobutyrate (GABA), tyrosine (Tyr), S‐adenosylhomocysteine (SAH), l‐cystathionine (l‐Cystat), valine (Val), methionine (Met), tryptophane (Trp), phenylalanine (Phe), isoleucine (Ile), leucine (Leu), ornithine (Orn), lysine (Lys), plus N‐acetylaspartate (NAA) were determined in whole brain extracts (n = 6 rats at each time for both TBI levels). Sham‐operated animals (n = 6) were used as controls. Results demonstrated that mTBI caused modest, transient changes in NAA, Asp, GABA, Gly, Arg. Following sTBI, animals showed profound, long‐lasting modifications of Glu, Gln, NAA, Asp, GABA, Ser, Gly, Ala, Arg, Citr, Tau, Met, SAH, l‐Cystat, Tyr and Phe. Increase in Glu and Gln, depletion of NAA and Asp increase, suggested a link between NAA hydrolysis and excitotoxicity after sTBI. Additionally, sTBI rats showed net imbalances of the Glu‐Gln/GABA cycle between neurons and astrocytes, and of the methyl‐cycle (demonstrated by decrease in Met, and increase in SAH and l‐Cystat), throughout the post‐injury period. Besides evidencing new potential targets for novel pharmacological treatments, these results suggest that the force acting on the brain tissue at the time of the impact is the main determinant of the reactions ignited and involving amino acid metabolism.
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Affiliation(s)
- Angela Maria Amorini
- Institute of Biochemistry and Clinical Biochemistry, Catholic University of Rome, Rome, Italy
| | - Giacomo Lazzarino
- Institute of Biochemistry and Clinical Biochemistry, Catholic University of Rome, Rome, Italy
| | - Valentina Di Pietro
- Neuroscience and Ophthalmology group, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Stefano Signoretti
- Division of Neurosurgery, Department of Neurosciences Head and Neck Surgery, S. Camillo Hospital, Rome, Italy
| | - Giuseppe Lazzarino
- Division of Medical Biochemistry, Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Antonio Belli
- Neuroscience and Ophthalmology group, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.,National Institute for Health Research Surgical Reconstruction and Microbiology Research Centre, Queen Elizabeth Hospital, Birmingham, UK
| | - Barbara Tavazzi
- Institute of Biochemistry and Clinical Biochemistry, Catholic University of Rome, Rome, Italy
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20
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McKenna MC, Stridh MH, McNair LF, Sonnewald U, Waagepetersen HS, Schousboe A. Glutamate oxidation in astrocytes: Roles of glutamate dehydrogenase and aminotransferases. J Neurosci Res 2016; 94:1561-1571. [PMID: 27629247 DOI: 10.1002/jnr.23908] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 07/22/2016] [Accepted: 08/05/2016] [Indexed: 12/11/2022]
Abstract
The cellular distribution of transporters and enzymes related to glutamate metabolism led to the concept of the glutamate-glutamine cycle. Glutamate is released as a neurotransmitter and taken up primarily by astrocytes ensheathing the synapses. The glutamate carbon skeleton is transferred back to the presynaptic neurons as the nonexcitatory amino acid glutamine. The cycle was initially thought to function with a 1:1 ratio between glutamate released and glutamine taken up by neurons. However, studies of glutamate metabolism in astrocytes have shown that a considerable proportion of glutamate undergoes oxidative degradation; thus, quantitative formation of glutamine from the glutamate taken up is not possible. Oxidation of glutamate is initiated by transamination catalyzed by an aminotransferase, or oxidative deamination catalyzed by glutamate dehydrogenase (GDH). We discuss methods available to elucidate the enzymes that mediate this conversion. Methods include pharmacological tools such as the transaminase inhibitor aminooxyacetic acid, studies using GDH knockout mice, and siRNA-mediated knockdown of GDH in astrocytes. Studies in brain slices incubated with [15 N]glutamate demonstrated activity of GDH in astrocytes in situ. These results, in conjunction with reports in the literature, support the conclusion that GDH is active in astrocytes both in culture and in vivo and that this enzyme plays a significant role in glutamate oxidation. Oxidative metabolism of glutamate, primarily mediated by GDH, but also by transamination by aspartate aminotransferase, provides considerably more energy than is required to maintain the activity of the high-affinity glutamate transporters needed for efficient removal of glutamate from the synaptic cleft. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Mary C McKenna
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland. .,Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland.
| | - Malin H Stridh
- Department of Drug Design and Pharmacology, Faculty of Health and Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Laura F McNair
- Department of Drug Design and Pharmacology, Faculty of Health and Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Ursula Sonnewald
- Department of Drug Design and Pharmacology, Faculty of Health and Medicine, University of Copenhagen, Copenhagen, Denmark.,Department of Neuroscience, Faculty of Medicine, University of Science and Technology, Trondheim, Norway
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, Faculty of Health and Medicine, University of Copenhagen, Copenhagen, Denmark
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21
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Neuroprotection against glutamate-induced excitotoxicity and induction of neurite outgrowth by T-006, a novel multifunctional derivative of tetramethylpyrazine in neuronal cell models. Neurochem Int 2016; 99:194-205. [PMID: 27445088 DOI: 10.1016/j.neuint.2016.07.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 07/05/2016] [Accepted: 07/13/2016] [Indexed: 01/04/2023]
Abstract
Alzheimer's disease is a progressive neurodegenerative disorder, characterized by irreversible impairment of memory and cognitive function. The exact causes of Alzheimer's disease still remain unclear and current single target drugs could only offer limited therapeutic effect to the patients. We have previously reported that T-006, a promising anti-Alzheimer's compound derived from Chinese medicinal component tetramethylpyrazine, might protect neurons through inhibiting the overproduction of intracellular reactive oxygen species (ROS) and reactive nitrogen species (RNS). In this study, we further investigated the neuroprotective effects, as well as the molecular pathways involved, of T-006 against glutamate-induced excitotoxicity in rat cerebellar granule neurons (CGNs). T-006 was also found to promote neuronal differentiation in both PC12 cells and primary cultured rat cortical neurons. The results showed that the pretreatment of T-006 (0.01-1 μM) might prevent glutamate-induced neuronal loss in a concentration-dependent manner. T-006 is found to inhibit the over-activation of NMDAR and ensued calcium overload caused by glutamate. The following activation of phosphorylated extracellular signal-regulated kinase (ERK) were also abolished. Moreover, T-006 concurrently prevented the suppression of phosphorylated protein kinase B (Akt) and glycogen synthase kinase 3β (GSK3β). T-006 was also found to promote neurite outgrowth in PC12 cells and primary cortical neurons. In our study, T-006 (0.1-3 μM) dose-dependently stimulated neurite outgrowth in PC12 cells and the efficacy was comparable to nerve growth factor (NGF). Moreover, co-treatment of T-006 and NGF revealed that T-006 could robustly potentiate the NGF-induced neuritogenesis. Further signal transduction studies indicated that T-006 rapidly up-regulated phosphorylation of ERK but did not activate tyrosine kinase receptor A (Trk A). These findings offer deeper understanding of the anti-neurodegenerative activity of T-006 and provide insight into its possible therapeutic potential for AD treatment in light of the multipotent nature of T-006.
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