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Harders AR, Spellerberg P, Dringen R. Exogenous Substrates Prevent the Decline in the Cellular ATP Content of Primary Rat Astrocytes During Glucose Deprivation. Neurochem Res 2024; 49:1188-1199. [PMID: 38341839 PMCID: PMC10991069 DOI: 10.1007/s11064-024-04104-0] [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: 11/29/2023] [Revised: 01/04/2024] [Accepted: 01/05/2024] [Indexed: 02/13/2024]
Abstract
Brain astrocytes are well known for their broad metabolic potential. After glucose deprivation, cultured primary astrocytes maintain a high cellular ATP content for many hours by mobilizing endogenous substrates, but within 24 h the specific cellular ATP content was lowered to around 30% of the initial ATP content. This experimental setting was used to test for the potential of various exogenous substrates to prevent a loss in cellular ATP in glucose deprived astrocytes. The presence of various extracellular monocarboxylates, purine nucleosides or fatty acids prevented the loss of ATP from glucose-deprived astrocytes. Of the 20 proteinogenic amino acids, only alanine, aspartate, glutamate, glutamine, lysine or proline maintained high ATP levels in starved astrocytes. Among these amino acids, proline was found to be the most potent one to prevent the ATP loss. The astrocytic consumption of proline as well as the ability of proline to maintain a high cellular ATP content was prevented in a concentration-dependent manner by the proline dehydrogenase inhibitor tetrahydro-2-furoic acid. Analysis of the concentration-dependencies obtained by considering the different carbon content of the applied substrates revealed that fatty acids and proline are more potent than glucose and monocarboxylates as exogenous substrates to prevent ATP depletion in glucose-deprived astrocytes. These data demonstrate that cultured astrocytes can utilise a wide range of extracellular substrates as fuels to support mitochondrial ATP regeneration and identify proline as potent exogenous substrate for the energy metabolism of starved astrocytes.
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Affiliation(s)
- Antonia Regina Harders
- Centre for Biomolecular Interactions Bremen, Faculty 2 (Biology/Chemistry), University of Bremen, P.O. Box 330440, 28334, Bremen, Germany
- Centre for Environmental Research and Sustainable Technologies, University of Bremen, Bremen, Germany
| | - Paul Spellerberg
- Centre for Biomolecular Interactions Bremen, Faculty 2 (Biology/Chemistry), University of Bremen, P.O. Box 330440, 28334, Bremen, Germany
| | - Ralf Dringen
- Centre for Biomolecular Interactions Bremen, Faculty 2 (Biology/Chemistry), University of Bremen, P.O. Box 330440, 28334, Bremen, Germany.
- Centre for Environmental Research and Sustainable Technologies, University of Bremen, Bremen, Germany.
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2
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Orr TJ, Lesha E, Kramer AH, Cecia A, Dugan JE, Schwartz B, Einhaus SL. Traumatic Brain Injury: A Comprehensive Review of Biomechanics and Molecular Pathophysiology. World Neurosurg 2024; 185:74-88. [PMID: 38272305 DOI: 10.1016/j.wneu.2024.01.084] [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: 09/25/2023] [Revised: 01/14/2024] [Accepted: 01/16/2024] [Indexed: 01/27/2024]
Abstract
Traumatic brain injury (TBI) is a critical public health concern with profound consequences for affected individuals. This comprehensive literature review delves into TBI intricacies, encompassing primary injury biomechanics and the molecular pathophysiology of the secondary injury cascade. Primary TBI involves a complex interplay of forces, including impact loading, blast overpressure, and impulsive loading, leading to diverse injury patterns. These forces can be categorized into inertial (e.g., rotational acceleration causing focal and diffuse injuries) and contact forces (primarily causing focal injuries like skull fractures). Understanding their interactions is crucial for effective injury management. The secondary injury cascade in TBI comprises multifaceted molecular and cellular responses, including altered ion concentrations, dysfunctional neurotransmitter networks, oxidative stress, and cellular energy disturbances. These disruptions impair synaptic function, neurotransmission, and neuroplasticity, resulting in cognitive and behavioral deficits. Moreover, neuroinflammatory responses play a pivotal role in exacerbating damage. As we endeavor to bridge the knowledge gap between biomechanics and molecular pathophysiology, further research is imperative to unravel the nuanced interplay between mechanical forces and their consequences at the molecular and cellular levels, ultimately guiding the development of targeted therapeutic strategies to mitigate the debilitating effects of TBI. In this study, we aim to provide a concise review of the bridge between biomechanical processes causing primary injury and the ensuing molecular pathophysiology of secondary injury, while detailing the subsequent clinical course for this patient population. This knowledge is crucial for advancing our understanding of TBI and developing effective interventions to improve outcomes for those affected.
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Affiliation(s)
- Taylor J Orr
- College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee.
| | - Emal Lesha
- Department of Neurological Surgery, University of Tennessee Health Science Center, Memphis, Tennessee; Semmes Murphey Clinic, Memphis, Tennessee
| | - Alexandra H Kramer
- College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Arba Cecia
- School of Medicine, Loyola University Chicago, Chicago, Illinois
| | - John E Dugan
- College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Barrett Schwartz
- Department of Neurological Surgery, University of Tennessee Health Science Center, Memphis, Tennessee; Semmes Murphey Clinic, Memphis, Tennessee
| | - Stephanie L Einhaus
- Department of Neurological Surgery, University of Tennessee Health Science Center, Memphis, Tennessee; Semmes Murphey Clinic, Memphis, Tennessee
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3
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Understanding ayahuasca effects in major depressive disorder treatment through in vitro metabolomics and bioinformatics. Anal Bioanal Chem 2023:10.1007/s00216-023-04556-3. [PMID: 36717401 DOI: 10.1007/s00216-023-04556-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/27/2022] [Accepted: 01/19/2023] [Indexed: 02/01/2023]
Abstract
Emerging insights from metabolomic-based studies of major depression disorder (MDD) are mainly related to biochemical processes such as energy or oxidative stress, in addition to neurotransmission linked to specific metabolite intermediates. Hub metabolites represent nodes in the biochemical network playing a critical role in integrating the information flow in cells between metabolism and signaling pathways. Limited technical-scientific studies have been conducted to understand the effects of ayahuasca (Aya) administration in the metabolism considering MDD molecular context. Therefore, this work aims to investigate an in vitro primary astrocyte model by untargeted metabolomics of two cellular subfractions: secretome and intracellular content after pre-defined Aya treatments, based on DMT concentration. Mass spectrometry (MS)-based metabolomics data revealed significant hub metabolites, which were used to predict biochemical pathway alterations. Branched-chain amino acid (BCAA) metabolism, and vitamin B6 and B3 metabolism were associated to Aya treatment, as "housekeeping" pathways. Dopamine synthesis was overrepresented in the network results when considering the lowest tested DMT concentration (1 µmol L-1). Building reaction networks containing significant and differential metabolites, such as nicotinamide, L-DOPA, and L-leucine, is a useful approach to guide on dose decision and pathway selection in further analytical and molecular studies.
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Fisher ES, Chen Y, Sifuentes MM, Stubblefield JJ, Lozano D, Holstein DM, Ren J, Davenport M, DeRosa N, Chen TP, Nickel G, Liston TE, Lechleiter JD. Adenosine A1R/A3R agonist AST-004 reduces brain infarction in mouse and rat models of acute ischemic stroke. FRONTIERS IN STROKE 2022; 1:1010928. [PMID: 38348128 PMCID: PMC10861240 DOI: 10.3389/fstro.2022.1010928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/15/2024]
Abstract
Acute ischemic stroke (AIS) is the second leading cause of death globally. No Food and Drug Administration (FDA) approved therapies exist that target cerebroprotection following stroke. Our group recently reported significant cerebroprotection with the adenosine A1/A3 receptor agonist, AST-004, in a transient stroke model in non-human primates (NHP) and in a preclinical mouse model of traumatic brain injury (TBI). However, the specific receptor pathway activated was only inferred based on in vitro binding studies. The current study investigated the underlying mechanism of AST-004 cerebroprotection in two independent models of AIS: permanent photothrombotic stroke in mice and transient middle cerebral artery occlusion (MCAO) in rats. AST-004 treatments across a range of doses were cerebroprotective and efficacy could be blocked by A3R antagonism, indicating a mechanism of action that does not require A1R agonism. The high affinity A3R agonist MRS5698 was also cerebroprotective following stroke, but not the A3R agonist Cl-IB-MECA under our experimental conditions. AST-004 efficacy was blocked by the astrocyte specific mitochondrial toxin fluoroacetate, confirming an underlying mechanism of cerebroprotection that was dependent on astrocyte mitochondrial metabolism. An increase in A3R mRNA levels following stroke suggested an intrinsic cerebroprotective response that was mediated by A3R signaling. Together, these studies confirm that certain A3R agonists, such as AST-004, may be exciting new therapeutic avenues to develop for AIS.
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Affiliation(s)
- Elizabeth S. Fisher
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | - Yanan Chen
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | - Mikaela M. Sifuentes
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | - Jeremy J. Stubblefield
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | - Damian Lozano
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | - Deborah M. Holstein
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | - JingMei Ren
- NeuroVasc Preclinical Services, Inc., Lexington, MA, United States
| | | | - Nicholas DeRosa
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | - Tsung-pei Chen
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | - Gerard Nickel
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
| | | | - James D. Lechleiter
- Department of Cell Systems and Anatomy, University of Texas Health at San Antonio, San Antonio, TX, United States
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5
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Ma H, Dong Y, Chu Y, Guo Y, Li L. The mechanisms of ferroptosis and its role in alzheimer’s disease. Front Mol Biosci 2022; 9:965064. [PMID: 36090039 PMCID: PMC9459389 DOI: 10.3389/fmolb.2022.965064] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 07/25/2022] [Indexed: 12/06/2022] Open
Abstract
Alzheimer’s disease (AD) accounts for two-thirds of all dementia cases, affecting 50 million people worldwide. Only four of the more than 100 AD drugs developed thus far have successfully improved AD symptoms. Furthermore, these improvements are only temporary, as no treatment can stop or reverse AD progression. A growing number of recent studies have demonstrated that iron-dependent programmed cell death, known as ferroptosis, contributes to AD-mediated nerve cell death. The ferroptosis pathways within nerve cells include iron homeostasis regulation, cystine/glutamate (Glu) reverse transporter (system xc−), glutathione (GSH)/glutathione peroxidase 4 (GPX4), and lipid peroxidation. In the regulation pathway of AD iron homeostasis, abnormal iron uptake, excretion and storage in nerve cells lead to increased intracellular free iron and Fenton reactions. Furthermore, decreased Glu transporter expression leads to Glu accumulation outside nerve cells, resulting in the inhibition of the system xc− pathway. GSH depletion causes abnormalities in GPX4, leading to excessive accumulation of lipid peroxides. Alterations in these specific pathways and amino acid metabolism eventually lead to ferroptosis. This review explores the connection between AD and the ferroptosis signaling pathways and amino acid metabolism, potentially informing future AD diagnosis and treatment methodologies.
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Affiliation(s)
- Hongyue Ma
- Department of Neurology, Hongqi Hospital of Mudanjiang Medical University, Mudanjiang, China
| | - Yan Dong
- Department of Neurology, Hongqi Hospital of Mudanjiang Medical University, Mudanjiang, China
| | - Yanhui Chu
- College of Life Sciences, Mudanjiang Medical University, Mudanjiang, China
- Heilongjiang Key Laboratory of Tissue Damage and Repair, Mudanjiang Medical University, Mudanjiang, China
| | - Yanqin Guo
- Department of Neurology, Hongqi Hospital of Mudanjiang Medical University, Mudanjiang, China
- Heilongjiang Key Laboratory of Tissue Damage and Repair, Mudanjiang Medical University, Mudanjiang, China
- *Correspondence: Yanqin Guo, ; Luxin Li,
| | - Luxin Li
- College of Life Sciences, Mudanjiang Medical University, Mudanjiang, China
- Heilongjiang Key Laboratory of Tissue Damage and Repair, Mudanjiang Medical University, Mudanjiang, China
- *Correspondence: Yanqin Guo, ; Luxin Li,
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6
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Andersen JV, Schousboe A, Verkhratsky A. Astrocyte energy and neurotransmitter metabolism in Alzheimer's disease: integration of the glutamate/GABA-glutamine cycle. Prog Neurobiol 2022; 217:102331. [PMID: 35872221 DOI: 10.1016/j.pneurobio.2022.102331] [Citation(s) in RCA: 64] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 07/14/2022] [Accepted: 07/19/2022] [Indexed: 02/06/2023]
Abstract
Astrocytes contribute to the complex cellular pathology of Alzheimer's disease (AD). Neurons and astrocytes function in close collaboration through neurotransmitter recycling, collectively known as the glutamate/GABA-glutamine cycle, which is essential to sustain neurotransmission. Neurotransmitter recycling is intimately linked to astrocyte energy metabolism. In the course of AD, astrocytes undergo extensive metabolic remodeling, which may profoundly affect the glutamate/GABA-glutamine cycle. The consequences of altered astrocyte function and metabolism in relation to neurotransmitter recycling are yet to be comprehended. Metabolic alterations of astrocytes in AD deprive neurons of metabolic support, thereby contributing to synaptic dysfunction and neurodegeneration. In addition, several astrocyte-specific components of the glutamate/GABA-glutamine cycle, including glutamine synthesis and synaptic neurotransmitter uptake, are perturbed in AD. Integration of the complex astrocyte biology within the context of AD is essential for understanding the fundamental mechanisms of the disease, while restoring astrocyte metabolism may serve as an approach to arrest or even revert clinical progression of AD.
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Affiliation(s)
- Jens V Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK; Achucarro Center for Neuroscience, IKERBASQUE, 48011 Bilbao, Spain; Department of Stem Cell Biology, State Research Institute Centre for Innovative Medicine, LT-01102 Vilnius, Lithuania.
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7
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Dyakin VV, Uversky VN. Arrow of Time, Entropy, and Protein Folding: Holistic View on Biochirality. Int J Mol Sci 2022; 23:ijms23073687. [PMID: 35409047 PMCID: PMC8998916 DOI: 10.3390/ijms23073687] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 03/23/2022] [Accepted: 03/25/2022] [Indexed: 02/06/2023] Open
Abstract
Chirality is a universal phenomenon, embracing the space–time domains of non-organic and organic nature. The biological time arrow, evident in the aging of proteins and organisms, should be linked to the prevalent biomolecular chirality. This hypothesis drives our exploration of protein aging, in relation to the biological aging of an organism. Recent advances in the chirality discrimination methods and theoretical considerations of the non-equilibrium thermodynamics clarify the fundamental issues, concerning the biphasic, alternative, and stepwise changes in the conformational entropy associated with protein folding. Living cells represent open, non-equilibrium, self-organizing, and dissipative systems. The non-equilibrium thermodynamics of cell biology are determined by utilizing the energy stored, transferred, and released, via adenosine triphosphate (ATP). At the protein level, the synthesis of a homochiral polypeptide chain of L-amino acids (L-AAs) represents the first state in the evolution of the dynamic non-equilibrium state of the system. At the next step the non-equilibrium state of a protein-centric system is supported and amended by a broad set of posttranslational modifications (PTMs). The enzymatic phosphorylation, being the most abundant and ATP-driven form of PTMs, illustrates the principal significance of the energy-coupling, in maintaining and reshaping the system. However, the physiological functions of phosphorylation are under the permanent risk of being compromised by spontaneous racemization. Therefore, the major distinct steps in protein-centric aging include the biosynthesis of a polypeptide chain, protein folding assisted by the system of PTMs, and age-dependent spontaneous protein racemization and degradation. To the best of our knowledge, we are the first to pay attention to the biphasic, alternative, and stepwise changes in the conformational entropy of protein folding. The broader view on protein folding, including the impact of spontaneous racemization, will help in the goal-oriented experimental design in the field of chiral proteomics.
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Affiliation(s)
- Victor V. Dyakin
- Virtual Reality Perception Lab (VRPL), The Nathan S. Kline Institute for Psychiatric Research (NKI), 140 Old Orangeburg Road, Bldg, 35, Orangeburg, NY 10962, USA
- Correspondence:
| | - Vladimir N. Uversky
- Department of Molecular Medicine, Byrd Alzheimer’s Research Institute, Morsani College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., MDC07, Tampa, FL 33612, USA;
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Song J, Yang X, Zhang M, Wang C, Chen L. Glutamate Metabolism in Mitochondria is Closely Related to Alzheimer's Disease. J Alzheimers Dis 2021; 84:557-578. [PMID: 34602474 DOI: 10.3233/jad-210595] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Glutamate is the main excitatory neurotransmitter in the brain, and its excitatory neurotoxicity is closely related to the occurrence and development of Alzheimer's disease. However, increasing evidence shows that in the process of Alzheimer's disease, glutamate is not only limited to its excitotoxicity as a neurotransmitter but also related to the disorder of its metabolic balance. The balance of glutamate metabolism in the brain is an important determinant of central nervous system health, and the maintenance of this balance is closely related to glutamate uptake, glutamate circulation, intracellular mitochondrial transport, and mitochondrial metabolism. In this paper, we intend to elaborate the key role of mitochondrial glutamate metabolism in the pathogenesis of Alzheimer's disease and review glutamate metabolism in mitochondria as a potential target in the treatment of Alzheimer's disease.
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Affiliation(s)
- Jiayi Song
- Department of Pharmacology, Basic College of Medicine, Jilin University, Changchun, People's Republic of China.,Cadre's Ward, The First Hospital of Jilin University, Changchun, People's Republic of China
| | - Xuehan Yang
- Department of Pharmacology, Basic College of Medicine, Jilin University, Changchun, People's Republic of China
| | - Ming Zhang
- Department of Pharmacology, Basic College of Medicine, Jilin University, Changchun, People's Republic of China
| | - Chunyan Wang
- Cadre's Ward, The First Hospital of Jilin University, Changchun, People's Republic of China
| | - Li Chen
- Department of Pharmacology, Basic College of Medicine, Jilin University, Changchun, People's Republic of China
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9
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Bozdemir E, Vigil FA, Chun SH, Espinoza L, Bugay V, Khoury SM, Holstein DM, Stoja A, Lozano D, Tunca C, Sprague SM, Cavazos JE, Brenner R, Liston TE, Shapiro MS, Lechleiter JD. Neuroprotective Roles of the Adenosine A 3 Receptor Agonist AST-004 in Mouse Model of Traumatic Brain Injury. Neurotherapeutics 2021; 18:2707-2721. [PMID: 34608616 PMCID: PMC8804149 DOI: 10.1007/s13311-021-01113-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2021] [Indexed: 10/20/2022] Open
Abstract
Traumatic brain injury (TBI) remains one of the greatest public health concerns with increasing morbidity and mortality rates worldwide. Our group reported that stimulation of astrocyte mitochondrial metabolism by P2Y1 receptor agonists significantly reduced cerebral edema and reactive gliosis in a TBI model. Subsequent data on the pharmacokinetics (PK) and rapid metabolism of these compounds suggested that neuroprotection was likely mediated by a metabolite, AST-004, which binding data indicated was an adenosine A3 receptor (A3R) agonist. The neuroprotective efficacy of AST-004 was tested in a control closed cortical injury (CCCI) model of TBI in mice. Twenty-four (24) hours post-injury, mice subjected to CCCI and treated with AST-004 (0.22 mg/kg, injected 30 min post-trauma) exhibited significantly less secondary brain injury. These effects were quantified with less cell death (PSVue794 fluorescence) and loss of blood brain barrier breakdown (Evans blue extravasation assay), compared to vehicle-treated TBI mice. TBI-treated mice also exhibited significantly reduced neuroinflammatory markers, glial-fibrillary acidic protein (GFAP, astrogliosis) and ionized Ca2+-binding adaptor molecule 1 (Iba1, microgliosis), both at the mRNA (qRT-PCR) and protein (Western blot and immunofluorescence) levels, respectively. Four (4) weeks post-injury, both male and female TBI mice presented a significant reduction in freezing behavior during contextual fear conditioning (after foot shock). AST-004 treatment prevented this TBI-induced impairment in male mice, but did not significantly affect impairment in female mice. Impairment of spatial memory, assessed 24 and 48 h after the initial fear conditioning, was also reduced in AST-004-treated TBI-male mice. Female TBI mice did not exhibit memory impairment 24 and 48 h after contextual fear conditioning and similarly, AST-004-treated female TBI mice were comparable to sham mice. Finally, AST-004 treatments were found to increase in vivo ATP production in astrocytes (GFAP-targeted luciferase activity), consistent with the proposed mechanism of action. These data reveal AST-004 as a novel A3R agonist that increases astrocyte energy production and enhances their neuroprotective efficacy after brain injury.
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Affiliation(s)
- Eda Bozdemir
- Department of Cell Systems and Anatomy, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Fabio A. Vigil
- Department of Cellular and Integrative Physiology, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Sang H. Chun
- Department of Cell Systems and Anatomy, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Liliana Espinoza
- Department of Cellular and Integrative Physiology, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Vladislav Bugay
- Department of Cellular and Integrative Physiology, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Sarah M. Khoury
- Department of Cell Systems and Anatomy, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Deborah M. Holstein
- Department of Cell Systems and Anatomy, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Aiola Stoja
- Department of Cellular and Integrative Physiology, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Damian Lozano
- Department of Cell Systems and Anatomy, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Ceyda Tunca
- Department of Cell Systems and Anatomy, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Shane M. Sprague
- Department of Neurosurgery, UT Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Jose E. Cavazos
- Department of Neurology, UT Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Robert Brenner
- Department of Cellular and Integrative Physiology, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - Theodore E. Liston
- Astrocyte Pharmaceuticals Inc, 245 First Street, Suite 1800, Cambridge, MA 02142 USA
| | - Mark S. Shapiro
- Department of Cellular and Integrative Physiology, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
| | - James D. Lechleiter
- Department of Cell Systems and Anatomy, UT Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229-3904 USA
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10
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Kim KJ, Diaz JR, Presa JL, Muller PR, Brands MW, Khan MB, Hess DC, Althammer F, Stern JE, Filosa JA. Decreased parenchymal arteriolar tone uncouples vessel-to-neuronal communication in a mouse model of vascular cognitive impairment. GeroScience 2021; 43:1405-1422. [PMID: 33410092 PMCID: PMC8190257 DOI: 10.1007/s11357-020-00305-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 11/22/2020] [Indexed: 01/18/2023] Open
Abstract
Chronic hypoperfusion is a key contributor to cognitive decline and neurodegenerative conditions, but the cellular mechanisms remain ill-defined. Using a multidisciplinary approach, we sought to elucidate chronic hypoperfusion-evoked functional changes at the neurovascular unit. We used bilateral common carotid artery stenosis (BCAS), a well-established model of vascular cognitive impairment, combined with an ex vivo preparation that allows pressurization of parenchymal arterioles in a brain slice. Our results demonstrate that mild (~ 30%), chronic hypoperfusion significantly altered the functional integrity of the cortical neurovascular unit. Although pial cerebral perfusion recovered over time, parenchymal arterioles progressively lost tone, exhibiting significant reductions by day 28 post-surgery. We provide supportive evidence for reduced adenosine 1 receptor-mediated vasoconstriction as a potential mechanism in the adaptive response underlying the reduced baseline tone in parenchymal arterioles. In addition, we show that in response to the neuromodulator adenosine, the action potential frequency of cortical pyramidal neurons was significantly reduced in all groups. However, a significant decrease in adenosine-induced hyperpolarization was observed in BCAS 14 days. At the microvascular level, constriction-induced inhibition of pyramidal neurons was significantly compromised in BCAS mice. Collectively, these results suggest that BCAS uncouples vessel-to-neuron communication-vasculo-neuronal coupling-a potential early event in cognitive decline.
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Affiliation(s)
- Ki Jung Kim
- Department of Physiology, Augusta University, Augusta, GA, 30912, USA
| | - Juan Ramiro Diaz
- Department of Physiology, Augusta University, Augusta, GA, 30912, USA
| | - Jessica L Presa
- Department of Physiology, Augusta University, Augusta, GA, 30912, USA
| | - P Robinson Muller
- Department of Physiology, Augusta University, Augusta, GA, 30912, USA
| | - Michael W Brands
- Department of Physiology, Augusta University, Augusta, GA, 30912, USA
| | - Mohammad B Khan
- Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - David C Hess
- Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | | | - Javier E Stern
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - Jessica A Filosa
- Department of Physiology, Augusta University, Augusta, GA, 30912, USA.
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11
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Seo JH, Dalal MS, Contreras JE. Pannexin-1 Channels as Mediators of Neuroinflammation. Int J Mol Sci 2021; 22:ijms22105189. [PMID: 34068881 PMCID: PMC8156193 DOI: 10.3390/ijms22105189] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 05/04/2021] [Accepted: 05/06/2021] [Indexed: 02/06/2023] Open
Abstract
Neuroinflammation is a major component of central nervous system (CNS) injuries and neurological diseases, including Alzheimer’s disease, multiple sclerosis, neuropathic pain, and brain trauma. The activation of innate immune cells at the damage site causes the release of pro-inflammatory cytokines and chemokines, which alter the functionality of nearby tissues and might mediate the recruitment of leukocytes to the injury site. If this process persists or is exacerbated, it prevents the adequate resolution of the inflammation, and ultimately enhances secondary damage. Adenosine 5′ triphosphate (ATP) is among the molecules released that trigger an inflammatory response, and it serves as a chemotactic and endogenous danger signal. Extracellular ATP activates multiple purinergic receptors (P2X and P2Y) that have been shown to promote neuroinflammation in a variety of CNS diseases. Recent studies have shown that Pannexin-1 (Panx1) channels are the principal conduits of ATP release from dying cells and innate immune cells in the brain. Herein, we review the emerging evidence that directly implicates Panx-1 channels in the neuroinflammatory response in the CNS.
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Affiliation(s)
- Joon Ho Seo
- Department of Neurology and Nash Family, Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine, Mount Sinai, New York, NY 10029, USA;
| | - Miloni S. Dalal
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA;
| | - Jorge E. Contreras
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA;
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA 95616, USA
- Correspondence: ; Tel.: +1-530-754-2770
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12
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Nguyen H, Zerimech S, Baltan S. Astrocyte Mitochondria in White-Matter Injury. Neurochem Res 2021; 46:2696-2714. [PMID: 33527218 DOI: 10.1007/s11064-021-03239-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 01/05/2021] [Accepted: 01/06/2021] [Indexed: 12/11/2022]
Abstract
This review summarizes the diverse structure and function of astrocytes to describe the bioenergetic versatility required of astrocytes that are situated at different locations. The intercellular domain of astrocyte mitochondria defines their roles in supporting and regulating astrocyte-neuron coupling and survival against ischemia. The heterogeneity of astrocyte mitochondria, and how subpopulations of astrocyte mitochondria adapt to interact with other glia and regulate axon function, require further investigation. It has become clear that mitochondrial permeability transition pores play a key role in a wide variety of human diseases, whose common pathology may be based on mitochondrial dysfunction triggered by Ca2+ and potentiated by oxidative stress. Reactive oxygen species cause axonal degeneration and a reduction in axonal transport, leading to axonal dystrophies and neurodegeneration including Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and Huntington's disease. Developing new tools to allow better investigation of mitochondrial structure and function in astrocytes, and techniques to specifically target astrocyte mitochondria, can help to unravel the role of mitochondrial health and dysfunction in a more inclusive context outside of neuronal cells. Overall, this review will assess the value of astrocyte mitochondria as a therapeutic target to mitigate acute and chronic injury in the CNS.
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Affiliation(s)
- Hung Nguyen
- Anesthesiology and Peri-Operative Medicine (APOM), Oregon Health and Science University, Portland, OR, 97239, USA
| | - Sarah Zerimech
- Anesthesiology and Peri-Operative Medicine (APOM), Oregon Health and Science University, Portland, OR, 97239, USA
| | - Selva Baltan
- Anesthesiology and Peri-Operative Medicine (APOM), Oregon Health and Science University, Portland, OR, 97239, USA.
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13
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Gonçalves MCB, Corrêa-Velloso J, Naaldijk Y, Cheffer A, Ulrich H. Purinergic modulation of pathways associated to suicidal behavior. Mol Psychiatry 2020; 25:514-516. [PMID: 29892056 DOI: 10.1038/s41380-018-0088-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 04/09/2018] [Indexed: 12/14/2022]
Affiliation(s)
| | - Juliana Corrêa-Velloso
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Yahaira Naaldijk
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Arquimedes Cheffer
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Henning Ulrich
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil.
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14
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Voss CM, Andersen JV, Jakobsen E, Siamka O, Karaca M, Maechler P, Waagepetersen HS. AMP-activated protein kinase (AMPK) regulates astrocyte oxidative metabolism by balancing TCA cycle dynamics. Glia 2020; 68:1824-1839. [PMID: 32092215 DOI: 10.1002/glia.23808] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 02/12/2020] [Accepted: 02/12/2020] [Indexed: 12/14/2022]
Abstract
AMP-activated protein kinase (AMPK) is an important energy sensor located in cells throughout the human body. From the periphery, AMPK is known to be a metabolic master switch controlling the use of energy fuels. The energy sensor is activated when the energy status of the cell is low, initiating energy-producing pathways and deactivating energy-consuming pathways. All brain cells are crucially dependent on energy production for survival, and the availability of energy substrates must be closely regulated. Intriguingly, the role of AMPK in the regulation of brain cell metabolism has been sparsely investigated, particularly in astrocytes. By investigating metabolism of 13 C-labeled energy substrates in acutely isolated hippocampal slices and cultured astrocytes, with subsequent mass spectrometry analysis, we here show that activation of AMPK increases glycolysis as well as the capacity of the TCA cycle, that is, anaplerosis, through the activity of pyruvate carboxylase (PC) in astrocytes. In addition, we demonstrate that AMPK activation leads to augmented astrocytic glutamate oxidation via pyruvate recycling (i.e., cataplerosis). This regulatory mechanism induced by AMPK activation is mediated via glutamate dehydrogenase (GDH) shown in a CNS-specific GDH knockout mouse. Collectively, these findings demonstrate that AMPK regulates TCA cycle dynamics in astrocytes via PC and GDH activity. AMPK functionality has been shown to be hampered in Alzheimer's and Parkinson's disease and our findings may therefore add to the toolbox for discovery of new metabolic drug targets.
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Affiliation(s)
- Caroline M Voss
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Emil Jakobsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Olga Siamka
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Melis Karaca
- Department of Cell Physiology and Metabolism, CMU, University of Geneva, Geneva, Switzerland
| | - Pierre Maechler
- Department of Cell Physiology and Metabolism, CMU, University of Geneva, Geneva, Switzerland
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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15
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Tóth A, Antal Z, Bereczki D, Sperlágh B. Purinergic Signalling in Parkinson's Disease: A Multi-target System to Combat Neurodegeneration. Neurochem Res 2019; 44:2413-2422. [PMID: 31054067 PMCID: PMC6776560 DOI: 10.1007/s11064-019-02798-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 04/04/2019] [Accepted: 04/10/2019] [Indexed: 12/13/2022]
Abstract
Parkinson's disease (PD) is the second most common neurodegenerative disorder, characterized by progressive loss of dopaminergic neurons that results in characteristic motor and non-motor symptoms. L-3,4 dihydroxyphenylalanine (L-DOPA) is the gold standard therapy for the treatment of PD. However, long-term use of L-DOPA leads to side effects such as dyskinesias and motor fluctuation. Since purines have neurotransmitter and co-transmitter properties, the function of the purinergic system has been thoroughly studied in the nervous system. Adenosine and adenosine 5'-triphosphate (ATP) are modulators of dopaminergic neurotransmission, neuroinflammatory processes, oxidative stress, excitotoxicity and cell death via purinergic receptor subtypes. Aberrant purinergic receptor signalling can be either the cause or the result of numerous pathological conditions, including neurodegenerative disorders. Many data confirm the involvement of purinergic signalling pathways in PD. Modulation of purinergic receptor subtypes, the activity of ectonucleotidases and ATP transporters could be beneficial in the treatment of PD. We give a brief summary of the background of purinergic signalling focusing on its roles in PD. Possible targets for pharmacological treatment are highlighted.
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Affiliation(s)
- Adrián Tóth
- Department of Neurology, Faculty of Medicine, Semmelweis University, Balassa u. 6., Budapest, 1083, Hungary
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony u. 43., Budapest, 1083, Hungary
- János Szentágothai School of Neurosciences, Semmelweis University School of PhD Studies, Üllői út 26., Budapest, 1085, Hungary
| | - Zsófia Antal
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony u. 43., Budapest, 1083, Hungary
| | - Dániel Bereczki
- Department of Neurology, Faculty of Medicine, Semmelweis University, Balassa u. 6., Budapest, 1083, Hungary
| | - Beáta Sperlágh
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony u. 43., Budapest, 1083, Hungary.
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16
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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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17
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Juaristi I, Llorente-Folch I, Satrústegui J, Del Arco A. Extracellular ATP and glutamate drive pyruvate production and energy demand to regulate mitochondrial respiration in astrocytes. Glia 2019; 67:759-774. [PMID: 30623988 DOI: 10.1002/glia.23574] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 11/08/2018] [Accepted: 11/13/2018] [Indexed: 12/26/2022]
Abstract
Astrocytes respond to energetic demands by upregulating glycolysis, lactate production, and respiration. This study addresses the role of respiration and calcium regulation of respiration as part of the astrocyte response to the workloads caused by extracellular ATP and glutamate. Extracellular ATP (100 μM to 1 mM) causes a Ca2+ -dependent workload and fall of the cytosolic ATP/ADP ratio which acutely increases astrocytes respiration. Part of this increase is related to a Ca2+ -dependent upregulation of cytosolic pyruvate production. Conversely, glutamate (200 μM) causes a Na+ , but not Ca2+ , dependent workload even though glutamate-induced Ca2+ signals readily reach mitochondria. The glutamate workload triggers a rapid fall in the cytosolic ATP/ADP ratio and stimulation of respiration. These effects are mimicked by D-aspartate a nonmetabolized agonist of the glutamate transporter, but not by a metabotropic glutamate receptor agonist, indicating a major role of Na+ -dependent workload in stimulated respiration. Glutamate-induced increase in respiration is linked to a rapid increase in glycolytic pyruvate production, suggesting that both glutamate and extracellular ATP cause an increase in astrocyte respiration fueled by workload-induced increase in pyruvate production. However, glutamate-induced pyruvate production is partly resistant to glycolysis blockers (iodoacetate), indicating that oxidative consumption of glutamate also contributes to stimulated respiration. As stimulation of respiration by ATP and glutamate are similar and pyruvate production smaller in the first case, the results suggest that the response to extracellular ATP is a Ca2+ -dependent upregulation of respiration added to glycolysis upregulation. The global contribution of astrocyte respiratory responses to brain oxygen consumption is an open question.
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Affiliation(s)
- Inés Juaristi
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz (IIS-FJD), Madrid, Spain
| | - Irene Llorente-Folch
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland.,Center for Systems Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Jorgina Satrústegui
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz (IIS-FJD), Madrid, Spain
| | - Araceli Del Arco
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz (IIS-FJD), Madrid, Spain.,Facultad de Ciencias Ambientales y Bioquímica, Centro Regional de Investigaciones Biomédicas, Universidad de Castilla la Mancha, Toledo, Spain
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18
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Liu T, Zhou J, Cui H, Li P, Li H, Wang Y, Tang T. Quantitative proteomic analysis of intracerebral hemorrhage in rats with a focus on brain energy metabolism. Brain Behav 2018; 8:e01130. [PMID: 30307711 PMCID: PMC6236229 DOI: 10.1002/brb3.1130] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 08/31/2018] [Accepted: 09/05/2018] [Indexed: 12/19/2022] Open
Abstract
INTRODUCTION Intracerebral hemorrhage (ICH) is a lethal cerebrovascular disorder with a high mortality and morbidity. The pathophysiological mechanisms underlying ICH-induced secondary injury remain unclear. METHODS To examine one of the gaps in the knowledge about ICH pathological mechanisms, isobaric tag for relative and absolute quantification (iTRAQ)-based liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used in collagenase-induced ICH rats on the 2nd day. RESULTS A total of 6,456 proteins were identified with a 1% false discovery rate (FDR). Of these proteins, 126 and 75 differentially expressed proteins (DEPs) were substantially increased and decreased, respectively. Based on Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and STRING analyses, the protein changes in cerebral hemorrhage were comprehensively evaluated, and the energy metabolism in ICH was anchored. The core position of the nitrogen metabolism pathway in brain metabolism in ICH was found for the first time. Carbonic anhydrase 1 (Ca1), carbonic anhydrase 2 (Ca2), and glutamine synthetase (Glul) participated in this pathway. We constructed the protein-protein interaction (PPI) networks for the energy metabolism of ICH, including the Atp6v1a-Atp6v0c-Atp6v0d1-Ppa2-Atp6ap2 network. CONCLUSIONS It seems that dysregulation of energy metabolism, especially nitrogen metabolism, may be a major cause in secondary ICH injury. This information provides novel insights into secondary events following ICH.
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Affiliation(s)
- Tao Liu
- Institute of Integrative MedicineXiangya Hospital, Central South UniversityChangshaChina
- Department of GerontologyTraditional Chinese Medicine Hospital Affiliated to Xinjiang Medical UniversityUrumqiChina
| | - Jing Zhou
- Institute of Integrative MedicineXiangya Hospital, Central South UniversityChangshaChina
| | - Hanjin Cui
- Institute of Integrative MedicineXiangya Hospital, Central South UniversityChangshaChina
| | - Pengfei Li
- Institute of Integrative MedicineXiangya Hospital, Central South UniversityChangshaChina
| | - Haigang Li
- Department of PharmacyChangsha Medical UniversityChangshaChina
| | - Yang Wang
- Institute of Integrative MedicineXiangya Hospital, Central South UniversityChangshaChina
| | - Tao Tang
- Institute of Integrative MedicineXiangya Hospital, Central South UniversityChangshaChina
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19
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Köhler S, Winkler U, Sicker M, Hirrlinger J. NBCe1 mediates the regulation of the NADH/NAD + redox state in cortical astrocytes by neuronal signals. Glia 2018; 66:2233-2245. [PMID: 30208253 DOI: 10.1002/glia.23504] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 06/19/2018] [Accepted: 06/25/2018] [Indexed: 12/20/2022]
Abstract
Astrocytes are a glial cell type, which is indispensable for brain energy metabolism. Within cells, the NADH/NAD+ redox state is a crucial node in metabolism connecting catabolic pathways to oxidative phosphorylation and ATP production in mitochondria. To characterize the dynamics of the intracellular NADH/NAD+ redox state in cortical astrocytes Peredox, a genetically encoded sensor for the NADH/NAD+ redox state, was expressed in cultured cortical astrocytes as well as in cortical astrocytes in acutely isolated brain slices. Calibration of the sensor in cultured astrocytes revealed a mean basal cytosolic NADH/NAD+ redox ratio of about 0.01; however, with a broad distribution and heterogeneity in the cell population, which was mirrored by a heterogeneous basal cellular concentration of lactate. Inhibition of glucose uptake decreased the NADH/NAD+ redox state while inhibition of lactate dehydrogenase or of lactate release resulted in an increase in the NADH/NAD+ redox ratio. Furthermore, the NADH/NAD+ redox state was regulated by the extracellular concentration of K+ , and application of the neurotransmitters ATP or glutamate increased the NADH/NAD+ redox state dependent on purinergic receptors and glutamate uptake, respectively. This regulation by K+ , ATP, and glutamate involved NBCe1 mediated sodium-bicarbonate transport. These results demonstrate that the NADH/NAD+ redox state in astrocytes is a metabolic node regulated by neuronal signals reflecting physiological activity, most likely contributing to adjust astrocytic metabolism to energy demand of the brain.
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Affiliation(s)
- Susanne Köhler
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Ulrike Winkler
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Marit Sicker
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Johannes Hirrlinger
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
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20
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Ferrari F, Gorini A, Hoyer S, Villa RF. Glutamate metabolism in cerebral mitochondria after ischemia and post-ischemic recovery during aging: relationships with brain energy metabolism. J Neurochem 2018; 146:416-428. [PMID: 29779216 DOI: 10.1111/jnc.14464] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Revised: 05/11/2018] [Accepted: 05/14/2018] [Indexed: 12/17/2022]
Abstract
Glutamate is involved in cerebral ischemic injury, but its role has not been completely clarified and studies are required to understand how to minimize its detrimental effects, contemporarily boosting the positive ones. In fact, glutamate is not only a neurotransmitter, but primarily a key metabolite for brain bioenergetics. Thus, we investigated the relationships between glutamate and brain energy metabolism in an in vivo model of complete cerebral ischemia of 15 min and during post-ischemic recovery after 1, 24, 48, 72, and 96 h in 1-year-old adult and 2-year-old aged rats. The maximum rates (Vmax ) of glutamate dehydrogenase (GlDH), glutamate-oxaloacetate transaminase, and glutamate-pyruvate transaminase were assayed in somatic mitochondria (FM) and in intra-synaptic 'Light' mitochondria and intra-synaptic 'Heavy' mitochondria ones purified from cerebral cortex, distinguishing post- and pre-synaptic compartments. During ischemia, none of the enzymes were modified in adult animals. In aged ones, glutamate-oxaloacetate transaminase was increased in FM and GlDH in intra-synaptic 'Heavy' mitochondria, stimulating glutamate catabolism. During post-ischemic recovery, FM did not show modifications at both ages while, in intra-synaptic mitochondria of adult animals, glutamate catabolism was increased after 1 h of recirculation and decreased after 48 and 72 h, whereas it remained decreased up to 96 h in aged rats. These results, with those previously published about Krebs' cycle and Electron Transport Chain (Villa et al., [2013] Neurochem. Int. 63, 765-781), demonstrate that: (i) Vmax of energy-linked enzymes are different in the various cerebral mitochondria, which (ii) respond differently to ischemia and post-ischemic recovery, also (iii) with respect to aging.
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Affiliation(s)
- Federica Ferrari
- Laboratory of Pharmacology and Molecular Medicine of Central Nervous System, Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
| | - Antonella Gorini
- Laboratory of Pharmacology and Molecular Medicine of Central Nervous System, Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
| | - Siegfried Hoyer
- Laboratory of Pharmacology and Molecular Medicine of Central Nervous System, Department of Biology and Biotechnology, University of Pavia, Pavia, Italy.,Department of Pathology, University Clinic, University of Heidelberg, Heidelberg, Germany
| | - Roberto Federico Villa
- Laboratory of Pharmacology and Molecular Medicine of Central Nervous System, Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
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21
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Wang YF, Parpura V. Astroglial Modulation of Hydromineral Balance and Cerebral Edema. Front Mol Neurosci 2018; 11:204. [PMID: 29946238 PMCID: PMC6007284 DOI: 10.3389/fnmol.2018.00204] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 05/22/2018] [Indexed: 12/11/2022] Open
Abstract
Maintenance of hydromineral balance (HB) is an essential condition for life activity at cellular, tissue, organ and system levels. This activity has been considered as a function of the osmotic regulatory system that focuses on hypothalamic vasopressin (VP) neurons, which can reflexively release VP into the brain and blood to meet the demand of HB. Recently, astrocytes have emerged as an essential component of the osmotic regulatory system in addition to functioning as a regulator of the HB at cellular and tissue levels. Astrocytes express all the components of osmoreceptors, including aquaporins, molecules of the extracellular matrix, integrins and transient receptor potential channels, with an operational dynamic range allowing them to detect and respond to osmotic changes, perhaps more efficiently than neurons. The resultant responses, i.e., astroglial morphological and functional plasticity in the supraoptic and paraventricular nuclei, can be conveyed, physically and chemically, to adjacent VP neurons, thereby influencing HB at the system level. In addition, astrocytes, particularly those in the circumventricular organs, are involved not only in VP-mediated osmotic regulation, but also in regulation of other osmolality-modulating hormones, including natriuretic peptides and angiotensin. Thus, astrocytes play a role in local/brain and systemic HB. The adaptive astrocytic reactions to osmotic challenges are associated with signaling events related to the expression of glial fibrillary acidic protein and aquaporin 4 to promote cell survival and repair. However, prolonged osmotic stress can initiate inflammatory and apoptotic signaling processes, leading to glial dysfunction and a variety of brain diseases. Among many diseases of brain injury and hydromineral disorders, cytotoxic and osmotic cerebral edemas are the most common pathological manifestation. Hyponatremia is the most common cause of osmotic cerebral edema. Overly fast correction of hyponatremia could lead to central pontine myelinolysis. Ischemic stroke exemplifies cytotoxic cerebral edema. In this review, we summarize and analyze the osmosensory functions of astrocytes and their implications in cerebral edema.
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Affiliation(s)
- Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, United States
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22
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Cooper JM, Halter KA, Prosser RA. Circadian rhythm and sleep-wake systems share the dynamic extracellular synaptic milieu. Neurobiol Sleep Circadian Rhythms 2018; 5:15-36. [PMID: 31236509 PMCID: PMC6584685 DOI: 10.1016/j.nbscr.2018.04.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 03/06/2018] [Accepted: 04/10/2018] [Indexed: 01/23/2023] Open
Abstract
The mammalian circadian and sleep-wake systems are closely aligned through their coordinated regulation of daily activity patterns. Although they differ in their anatomical organization and physiological processes, they utilize overlapping regulatory mechanisms that include an assortment of proteins and molecules interacting within the extracellular space. These extracellular factors include proteases that interact with soluble proteins, membrane-attached receptors and the extracellular matrix; and cell adhesion molecules that can form complex scaffolds connecting adjacent neurons, astrocytes and their respective intracellular cytoskeletal elements. Astrocytes also participate in the dynamic regulation of both systems through modulating neuronal appositions, the extracellular space and/or through release of gliotransmitters that can further contribute to the extracellular signaling processes. Together, these extracellular elements create a system that integrates rapid neurotransmitter signaling across longer time scales and thereby adjust neuronal signaling to reflect the daily fluctuations fundamental to both systems. Here we review what is known about these extracellular processes, focusing specifically on areas of overlap between the two systems. We also highlight questions that still need to be addressed. Although we know many of the extracellular players, far more research is needed to understand the mechanisms through which they modulate the circadian and sleep-wake systems.
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Key Words
- ADAM, A disintegrin and metalloproteinase
- AMPAR, AMPA receptor
- Astrocytes
- BDNF, brain-derived neurotrophic factor
- BMAL1, Brain and muscle Arnt-like-1 protein
- Bmal1, Brain and muscle Arnt-like-1 gene
- CAM, cell adhesion molecules
- CRY, cryptochrome protein
- Cell adhesion molecules
- Circadian rhythms
- Cry, cryptochrome gene
- DD, dark-dark
- ECM, extracellular matrix
- ECS, extracellular space
- EEG, electroencephalogram
- Endo N, endoneuraminidase N
- Extracellular proteases
- GFAP, glial fibrillary acidic protein
- IL, interleukin
- Ig, immunoglobulin
- LC, locus coeruleus
- LD, light-dark
- LH, lateral hypothalamus
- LRP-1, low density lipoprotein receptor-related protein 1
- LTP, long-term potentiation
- MMP, matrix metalloproteinases
- NCAM, neural cell adhesion molecule protein
- NMDAR, NMDA receptor
- NO, nitric oxide
- NST, nucleus of the solitary tract
- Ncam, neural cell adhesion molecule gene
- Nrl, neuroligin gene
- Nrx, neurexin gene
- P2, purine type 2 receptor
- PAI-1, plasminogen activator inhibitor-1
- PER, period protein
- PPT, peduculopontine tegmental nucleus
- PSA, polysialic acid
- Per, period gene
- REMS, rapid eye movement sleep
- RSD, REM sleep disruption
- SCN, suprachiasmatic nucleus
- SWS, slow wave sleep
- Sleep-wake system
- Suprachiasmatic nucleus
- TNF, tumor necrosis factor
- TTFL, transcriptional-translational negative feedback loop
- VIP, vasoactive intestinal polypeptide
- VLPO, ventrolateral preoptic
- VP, vasopressin
- VTA, ventral tegmental area
- dNlg4, drosophila neuroligin-4 gene
- nNOS, neuronal nitric oxide synthase gene
- nNOS, neuronal nitric oxide synthase protein
- tPA, tissue-type plasminogen activator
- uPA, urokinase-type plasminogen activator
- uPAR, uPA receptor
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23
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Oliveira-Giacomelli Á, Naaldijk Y, Sardá-Arroyo L, Gonçalves MCB, Corrêa-Velloso J, Pillat MM, de Souza HDN, Ulrich H. Purinergic Receptors in Neurological Diseases With Motor Symptoms: Targets for Therapy. Front Pharmacol 2018; 9:325. [PMID: 29692728 PMCID: PMC5902708 DOI: 10.3389/fphar.2018.00325] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Accepted: 03/21/2018] [Indexed: 12/13/2022] Open
Abstract
Since proving adenosine triphosphate (ATP) functions as a neurotransmitter in neuron/glia interactions, the purinergic system has been more intensely studied within the scope of the central nervous system. In neurological disorders with associated motor symptoms, including Parkinson's disease (PD), motor neuron diseases (MND), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Huntington's Disease (HD), restless leg syndrome (RLS), and ataxias, alterations in purinergic receptor expression and activity have been noted, indicating a potential role for this system in disease etiology and progression. In neurodegenerative conditions, neural cell death provokes extensive ATP release and alters calcium signaling through purinergic receptor modulation. Consequently, neuroinflammatory responses, excitotoxicity and apoptosis are directly or indirectly induced. This review analyzes currently available data, which suggests involvement of the purinergic system in neuro-associated motor dysfunctions and underlying mechanisms. Possible targets for pharmacological interventions are also discussed.
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Affiliation(s)
| | - Yahaira Naaldijk
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Laura Sardá-Arroyo
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Maria C. B. Gonçalves
- Department of Neurology and Neuroscience, Medical School, Federal University of São Paulo, São Paulo, Brazil
| | - Juliana Corrêa-Velloso
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Micheli M. Pillat
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Héllio D. N. de Souza
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Henning Ulrich
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
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Andersen JV, McNair LF, Schousboe A, Waagepetersen HS. Specificity of exogenous acetate and glutamate as astrocyte substrates examined in acute brain slices from female mice using methionine sulfoximine (MSO) to inhibit glutamine synthesis. J Neurosci Res 2017; 95:2207-2216. [DOI: 10.1002/jnr.24038] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 01/05/2017] [Accepted: 01/26/2017] [Indexed: 12/13/2022]
Affiliation(s)
- Jens Velde Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences; University of Copenhagen; DK-2100 Copenhagen Denmark
| | - Laura Frendrup McNair
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences; University of Copenhagen; DK-2100 Copenhagen Denmark
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences; University of Copenhagen; DK-2100 Copenhagen Denmark
| | - Helle Sønderby Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences; University of Copenhagen; DK-2100 Copenhagen Denmark
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Martín-Jiménez CA, Salazar-Barreto D, Barreto GE, González J. Genome-Scale Reconstruction of the Human Astrocyte Metabolic Network. Front Aging Neurosci 2017; 9:23. [PMID: 28243200 PMCID: PMC5303712 DOI: 10.3389/fnagi.2017.00023] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 01/27/2017] [Indexed: 12/22/2022] Open
Abstract
Astrocytes are the most abundant cells of the central nervous system; they have a predominant role in maintaining brain metabolism. In this sense, abnormal metabolic states have been found in different neuropathological diseases. Determination of metabolic states of astrocytes is difficult to model using current experimental approaches given the high number of reactions and metabolites present. Thus, genome-scale metabolic networks derived from transcriptomic data can be used as a framework to elucidate how astrocytes modulate human brain metabolic states during normal conditions and in neurodegenerative diseases. We performed a Genome-Scale Reconstruction of the Human Astrocyte Metabolic Network with the purpose of elucidating a significant portion of the metabolic map of the astrocyte. This is the first global high-quality, manually curated metabolic reconstruction network of a human astrocyte. It includes 5,007 metabolites and 5,659 reactions distributed among 8 cell compartments, (extracellular, cytoplasm, mitochondria, endoplasmic reticle, Golgi apparatus, lysosome, peroxisome and nucleus). Using the reconstructed network, the metabolic capabilities of human astrocytes were calculated and compared both in normal and ischemic conditions. We identified reactions activated in these two states, which can be useful for understanding the astrocytic pathways that are affected during brain disease. Additionally, we also showed that the obtained flux distributions in the model, are in accordance with literature-based findings. Up to date, this is the most complete representation of the human astrocyte in terms of inclusion of genes, proteins, reactions and metabolic pathways, being a useful guide for in-silico analysis of several metabolic behaviors of the astrocyte during normal and pathologic states.
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Affiliation(s)
- Cynthia A Martín-Jiménez
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana Bogotá, Colombia
| | - Diego Salazar-Barreto
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana Bogotá, Colombia
| | - George E Barreto
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad JaverianaBogotá, Colombia; Instituto de Ciencias Biomédicas, Universidad Autónoma de ChileSantiago, Chile
| | - Janneth González
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana Bogotá, Colombia
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McNair LF, Kornfelt R, Walls AB, Andersen JV, Aldana BI, Nissen JD, Schousboe A, Waagepetersen HS. Metabolic Characterization of Acutely Isolated Hippocampal and Cerebral Cortical Slices Using [U-13C]Glucose and [1,2-13C]Acetate as Substrates. Neurochem Res 2016; 42:810-826. [DOI: 10.1007/s11064-016-2116-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 11/11/2016] [Accepted: 11/16/2016] [Indexed: 12/21/2022]
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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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Age-Related Changes in Axonal and Mitochondrial Ultrastructure and Function in White Matter. J Neurosci 2016; 36:9990-10001. [PMID: 27683897 DOI: 10.1523/jneurosci.1316-16.2016] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/02/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED The impact of aging on CNS white matter (WM) is of general interest because the global effects of aging on myelinated nerve fibers are more complex and profound than those in cortical gray matter. It is important to distinguish between axonal changes created by normal aging and those caused by neurodegenerative diseases, including multiple sclerosis, stroke, glaucoma, Alzheimer's disease, and traumatic brain injury. Using three-dimensional electron microscopy, we show that in mouse optic nerve, which is a pure and fully myelinated WM tract, aging axons are larger, have thicker myelin, and are characterized by longer and thicker mitochondria, which are associated with altered levels of mitochondrial shaping proteins. These structural alterations in aging mitochondria correlate with lower ATP levels and increased generation of nitric oxide, protein nitration, and lipid peroxidation. Moreover, mitochondria-smooth endoplasmic reticulum interactions are compromised due to decreased associations and decreased levels of calnexin and calreticulin, suggesting a disruption in Ca(2+) homeostasis and defective unfolded protein responses in aging axons. Despite these age-related modifications, axon function is sustained in aging WM, which suggests that age-dependent changes do not lead to irreversible functional decline under normal conditions, as is observed in neurodegenerative diseases. SIGNIFICANCE STATEMENT Aging is a common risk factor for a number of neurodegenerative diseases, including stroke. Mitochondrial dysfunction and oxidative damage with age are hypothesized to increase risk for stroke. We compared axon-myelin-node-mitochondrion-smooth endoplasmic reticulum (SER) interactions in white matter obtained at 1 and 12 months. We show that aging axons have enlarged volume, thicker myelin, and elongated and thicker mitochondria. Furthermore, there are reduced SER connections to mitochondria that correlate with lower calnexin and calreticulin levels. Despite a prominent decrease in number, elongated aging mitochondria produce excessive stress markers with reduced ATP production. Because axons maintain function under these conditions, our study suggests that it is important to understand the process of normal brain aging to identify neurodegenerative changes.
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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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