1
|
Salin P, Melon C, Chassain C, Gubellini P, Pages G, Pereira B, Le Fur Y, Durif F, Kerkerian-Le Goff L. Interhemispheric reactivity of the subthalamic nucleus sustains progressive dopamine neuron loss in asymmetrical parkinsonism. Neurobiol Dis 2024; 191:106398. [PMID: 38182075 DOI: 10.1016/j.nbd.2023.106398] [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: 10/30/2023] [Revised: 12/21/2023] [Accepted: 12/30/2023] [Indexed: 01/07/2024] Open
Abstract
Parkinson's disease (PD) is characterized by the progressive and asymmetrical degeneration of the nigrostriatal dopamine neurons and the unilateral presentation of the motor symptoms at onset, contralateral to the most impaired hemisphere. We previously developed a rat PD model that mimics these typical features, based on unilateral injection of a substrate inhibitor of excitatory amino acid transporters, L-trans-pyrrolidine-2,4-dicarboxylate (PDC), in the substantia nigra (SN). Here, we used this progressive model in a multilevel study (behavioral testing, in vivo 1H-magnetic resonance spectroscopy, slice electrophysiology, immunocytochemistry and in situ hybridization) to characterize the functional changes occurring in the cortico-basal ganglia-cortical network in an evolving asymmetrical neurodegeneration context and their possible contribution to the cell death progression. We focused on the corticostriatal input and the subthalamic nucleus (STN), two glutamate components with major implications in PD pathophysiology. In the striatum, glutamate and glutamine levels increased from presymptomatic stages in the PDC-injected hemisphere only, which also showed enhanced glutamatergic transmission and loss of plasticity at corticostriatal synapses assessed at symptomatic stage. Surprisingly, the contralateral STN showed earlier and stronger reactivity than the ipsilateral side (increased intraneuronal cytochrome oxidase subunit I mRNA levels; enhanced glutamate and glutamine concentrations). Moreover, its lesion at early presymptomatic stage halted the ongoing neurodegeneration in the PDC-injected SN and prevented the expression of motor asymmetry. These findings reveal the existence of endogenous interhemispheric processes linking the primary injured SN and the contralateral STN that could sustain progressive dopamine neuron loss, opening new perspectives for disease-modifying treatment of PD.
Collapse
Affiliation(s)
- Pascal Salin
- Aix-Marseille Univ, CNRS, IBDM, Marseille, France
| | | | - Carine Chassain
- University of Clermont Auvergne, CHU, CNRS, Clermont Auvergne INP, Institut Pascal, F-63000 Clermont-Ferrand, France; INRAE, AgroResonance Facility, F-63122 Saint-Genès-Champanelle, France
| | | | - Guilhem Pages
- INRAE, AgroResonance Facility, F-63122 Saint-Genès-Champanelle, France; INRAE, UR QuaPA, F-63122 Saint-Genès-Champanelle, France
| | - Bruno Pereira
- University Hospital Clermont-Ferrand, Biostatisticis Unit (DRCI), Clermont-Ferrand, France
| | - Yann Le Fur
- Aix-Marseille Univ, CNRS, CRMBM, Marseille, France
| | - Franck Durif
- University of Clermont Auvergne, CHU, CNRS, Clermont Auvergne INP, Institut Pascal, F-63000 Clermont-Ferrand, France.
| | | |
Collapse
|
2
|
Krishna G, Pillai VS, Gopi P, Nair AS, Veettil MV. Epstein-Barr virus infection controls the concentration of the intracellular antioxidant glutathione by upregulation of the glutamate transporter EAAT3 in tumor cells. Virus Genes 2023; 59:55-66. [PMID: 36344769 DOI: 10.1007/s11262-022-01951-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 10/04/2022] [Indexed: 11/09/2022]
Abstract
Epstein-Barr virus or human herpesvirus 4 (EBV/HHV-4) is an omnipresent oncovirus etiologically associated with various B-cell lymphomas and epithelial cancers. The malignant transformation associated with the persistent expression of viral proteins often deregulates the host cellular machinery and EBV infection is coupled to elevated levels of reactive oxygen species. Here, we investigated the role that the glutamate transporter EAAT3 plays in regulating the antioxidant system as a protective mechanism of EBV-infected cells against the virus-induced oxidative stress. Our study demonstrated that the expression of EAAT3 was upregulated and localized to the plasma membrane in EBV latently infected and de novo EBV-infected cells. EAAT3 was regulated by the transcription factor NFAT5 in the infected cells. Membrane localized EAAT3 was found to be involved in the transportation of glutamate from the extracellular space into the cell, as EAAT3 and NFAT5 inhibitors markedly reduced the levels of intracellular glutamate levels in EBV latently infected cells. Additionally, our data demonstrated a notable decrease in the intracellular glutathione levels following treatment with an EAAT3 inhibitor. Collectively, our results suggest that upregulation of the glutamate transporter EAAT3 is an adaptation of EBV-infected cells to maintain cellular redox homeostasis against the virus-induced oxidative stress, and that this cellular balance could be therapeutically destroyed by targeting EAAT3 to impede EBV-associated cancers.
Collapse
Affiliation(s)
- Gayathri Krishna
- Department of Biotechnology, Cochin University of Science and Technology, Cochin, Kerala, 682022, India
| | - Vinod Soman Pillai
- Department of Biotechnology, Cochin University of Science and Technology, Cochin, Kerala, 682022, India
- Institute of Advanced Virology (IAV), Thonnakkal, Thiruvananthapuram, Kerala, 695317, India
| | - Poornima Gopi
- Department of Biotechnology, Cochin University of Science and Technology, Cochin, Kerala, 682022, India
| | - Anuja S Nair
- Institute of Advanced Virology (IAV), Thonnakkal, Thiruvananthapuram, Kerala, 695317, India
| | - Mohanan Valiya Veettil
- Department of Biotechnology, Cochin University of Science and Technology, Cochin, Kerala, 682022, India.
- Institute of Advanced Virology (IAV), Thonnakkal, Thiruvananthapuram, Kerala, 695317, India.
| |
Collapse
|
3
|
Hann Yih T, Abd Ghapor AA, Agarwal R, Razali N, Iezhitsa I, Mohd Ismail N. Effect of trans-resveratrol on glutamate clearance and visual behaviour in rats with glutamate induced retinal injury. Exp Eye Res 2022; 220:109104. [DOI: 10.1016/j.exer.2022.109104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 04/20/2022] [Accepted: 04/27/2022] [Indexed: 11/04/2022]
|
4
|
Beckers P, Lara O, Belo do Nascimento I, Desmet N, Massie A, Hermans E. Validation of a System xc– Functional Assay in Cultured Astrocytes and Nervous Tissue Samples. Front Cell Neurosci 2022; 15:815771. [PMID: 35095428 PMCID: PMC8793334 DOI: 10.3389/fncel.2021.815771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 12/24/2021] [Indexed: 11/13/2022] Open
Abstract
Disruption of the glutamatergic homeostasis is commonly observed in neurological diseases and has been frequently correlated with the altered expression and/or function of astrocytic high-affinity glutamate transporters. There is, however, a growing interest for the role of the cystine-glutamate exchanger system xc– in controlling glutamate transmission. This exchanger is predominantly expressed in glial cells, especially in microglia and astrocytes, and its dysregulation has been documented in diverse neurological conditions. While most studies have focused on measuring the expression of its specific subunit xCT by RT-qPCR or by Western blotting, the activity of this exchanger in tissue samples remains poorly examined. Indeed, the reported use of sulfur- and carbon-radiolabeled cystine in uptake assays shows several drawbacks related to its short radioactive half-life and its relatively high cost. We here report on the elaborate validation of a method using tritiated glutamate as a substrate for the reversed transport mediated by system xc–. The uptake assay was validated in primary cultured astrocytes, in transfected cells as well as in crude synaptosomes obtained from fresh nervous tissue samples. Working in buffers containing defined concentrations of Na+, allowed us to differentiate the glutamate uptake supported by system xc– or by high-affinity glutamate transporters, as confirmed by using selective pharmacological inhibitors. The specificity was further demonstrated in primary astrocyte cultures from transgenic mice lacking xCT or in cell lines where xCT expression was genetically induced or reduced. As such, this assay appears to be a robust and cost-efficient solution to investigate the activity of this exchanger in physiological and pathological conditions. It also provides a reliable tool for the screening and characterization of new system xc– inhibitors which have been frequently cited as valuable drugs for nervous disorders and cancer.
Collapse
Affiliation(s)
- Pauline Beckers
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Olaya Lara
- Neuro-Aging & Viro-Immunotherapy, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Ines Belo do Nascimento
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Nathalie Desmet
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Ann Massie
- Neuro-Aging & Viro-Immunotherapy, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Emmanuel Hermans
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
- *Correspondence: Emmanuel Hermans,
| |
Collapse
|
5
|
Cocaine use disorder: A look at metabotropic glutamate receptors and glutamate transporters. Pharmacol Ther 2021; 221:107797. [DOI: 10.1016/j.pharmthera.2020.107797] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 11/04/2020] [Indexed: 01/08/2023]
|
6
|
Martinez D, Kline DD. The role of astrocytes in the nucleus tractus solitarii in maintaining central control of autonomic function. Am J Physiol Regul Integr Comp Physiol 2021; 320:R418-R424. [PMID: 33439770 PMCID: PMC8238142 DOI: 10.1152/ajpregu.00254.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 12/16/2020] [Accepted: 01/07/2021] [Indexed: 12/24/2022]
Abstract
The nucleus tractus solitarii (nTS) is the first central site for the termination and integration of autonomic and respiratory sensory information. Sensory afferents terminating in the nTS as well as the embedded nTS neurocircuitry release and utilize glutamate that is critical for maintenance of baseline cardiorespiratory parameters and initiating cardiorespiratory reflexes, including those activated by bouts of hypoxia. nTS astrocytes contribute to synaptic and neuronal activity through a variety of mechanisms, including gliotransmission and regulation of glutamate in the extracellular space via membrane-bound transporters. Here, we aim to highlight recent evidence for the role of astrocytes within the nTS and their regulation of autonomic and cardiorespiratory processes under normal and hypoxic conditions.
Collapse
Affiliation(s)
- Diana Martinez
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - David D Kline
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| |
Collapse
|
7
|
Gagliardi M, Saverio V, Monzani R, Ferrari E, Piacentini M, Corazzari M. Ferroptosis: a new unexpected chance to treat metastatic melanoma? Cell Cycle 2020; 19:2411-2425. [PMID: 32816618 PMCID: PMC7553499 DOI: 10.1080/15384101.2020.1806426] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 07/14/2020] [Accepted: 07/28/2020] [Indexed: 01/14/2023] Open
Abstract
Human skin melanoma is one of the most aggressive and difficult to treat human malignancies, with an increasing incidence over the years. While the resection of the early diagnosed primary tumor remains the best clinical approach, advanced/metastatic melanoma still remains with a poor prognosis. Indeed, although enormous progress in the therapeutic treatment of human tumors has been made in recent years, patients affected by metastatic melanoma are still poorly affected by these clinical advances. Therefore, new valuable therapeutic approaches are urgently needed, to design and define effective treatments to consistently increase the overall survival rate of patients affected by this malignancy. In this review we summarize the main signaling pathways studied to kill human skin melanoma, and introduce the ferroptotic cell death as a new pathway to be explored to eradicate this tumor.
Collapse
Affiliation(s)
- Mara Gagliardi
- Department of Health Science, University of Piemonte Orientale, Novara, Italy
- Center for Translational Research on Autoimmune and Allergic Disease (CAAD), University of Piemonte Orientale, Novara, Italy
| | - Valentina Saverio
- Department of Health Science, University of Piemonte Orientale, Novara, Italy
- Center for Translational Research on Autoimmune and Allergic Disease (CAAD), University of Piemonte Orientale, Novara, Italy
| | - Romina Monzani
- Department of Health Science, University of Piemonte Orientale, Novara, Italy
- Center for Translational Research on Autoimmune and Allergic Disease (CAAD), University of Piemonte Orientale, Novara, Italy
| | - Eleonora Ferrari
- Department of Health Science, University of Piemonte Orientale, Novara, Italy
- Center for Translational Research on Autoimmune and Allergic Disease (CAAD), University of Piemonte Orientale, Novara, Italy
| | - Mauro Piacentini
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
- Institute of Cytology of the Russian Academy of Sciences, Saint Petersburg, Russia
| | - Marco Corazzari
- Department of Health Science, University of Piemonte Orientale, Novara, Italy
- Center for Translational Research on Autoimmune and Allergic Disease (CAAD), University of Piemonte Orientale, Novara, Italy
- Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), University of Piemonte Orientale, Novara, Italy
| |
Collapse
|
8
|
Martinez D, Rogers RC, Hasser EM, Hermann GE, Kline DD. Loss of excitatory amino acid transporter restraint following chronic intermittent hypoxia contributes to synaptic alterations in nucleus tractus solitarii. J Neurophysiol 2020; 123:2122-2135. [PMID: 32347148 PMCID: PMC7311725 DOI: 10.1152/jn.00766.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Peripheral viscerosensory afferent signals are transmitted to the nucleus tractus solitarii (nTS) via release of glutamate. Following release, glutamate is removed from the extrasynaptic and synaptic cleft via excitatory amino acid transporters (EAATs), thus limiting glutamate receptor activation or over activation, and maintaining its working range. We have shown that EAAT block with the antagonist threo-β-benzyloxyaspartic acid (TBOA) depolarized nTS neurons and increased spontaneous excitatory postsynaptic current (sEPSC) frequency yet reduced the amplitude of afferent (TS)-evoked EPSCs (TS-EPSCs). Interestingly, chronic intermittent hypoxia (CIH), a model of obstructive sleep apnea (OSA), produces similar synaptic responses as EAAT block. We hypothesized EAAT expression or function are downregulated after CIH, and this reduction in glutamate removal contributes to the observed neurophysiological responses. To test this hypothesis, we used brain slice electrophysiology and imaging of glutamate release and TS-afferent Ca2+ to compare nTS properties of rats exposed to 10 days of normoxia (Norm; 21%O2) or CIH. Results show that EAAT blockade with (3S)-3-[[3-[[4-(trifluoromethyl)benzoyl]-amino]phenyl]methoxy]-l-aspartic acid (TFB-TBOA) in Norm caused neuronal depolarization, generation of an inward current, and increased spontaneous synaptic activity. The latter augmentation was eliminated by inclusion of tetrodotoxin in the perfusate. TS stimulation during TFB-TBOA also elevated extracellular glutamate and decreased presynaptic Ca2+ and TS-EPSC amplitude. In CIH, the effects of EAAT block are eliminated or attenuated. CIH reduced EAAT expression in nTS, which may contribute to the attenuated function seen in this condition. Therefore, CIH reduces EAAT influence on synaptic and neuronal activity, which may lead to the physiological consequences seen in OSA and CIH.NEW & NOTEWORTHY Removal of excitatory amino acid transporter (EAAT) restraint increases spontaneous synaptic activity yet decreases afferent [tractus solitarius (TS)]-driven excitatory postsynaptic current (EPSC) amplitude. In the chronic intermittent hypoxia model of obstructive sleep apnea, this restraint is lost due to reduction in EAAT expression and function. Thus EAATs are important in controlling elevated glutamatergic signaling, and loss of such control results in maladaptive synaptic signaling.
Collapse
Affiliation(s)
- Diana Martinez
- 1Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | | | - Eileen M. Hasser
- 1Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri,2Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri
| | | | - David D. Kline
- 1Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| |
Collapse
|
9
|
Piccirillo S, Magi S, Castaldo P, Preziuso A, Lariccia V, Amoroso S. NCX and EAAT transporters in ischemia: At the crossroad between glutamate metabolism and cell survival. Cell Calcium 2020; 86:102160. [PMID: 31962228 DOI: 10.1016/j.ceca.2020.102160] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 01/10/2020] [Accepted: 01/10/2020] [Indexed: 01/29/2023]
Abstract
Energy metabolism impairment is a central event in the pathophysiology of ischemia. The limited availability of glucose and oxygen strongly affects mitochondrial activity, thus leading to ATP depletion. In this setting, the switch to alternative energy sources could ameliorate cells survival by enhancing ATP production, thus representing an attractive strategy for ischemic treatment. In this regard, some studies have recently re-evaluated the metabolic role of glutamate and its potential to promote cell survival under pathological conditions. In the present review, we discuss the ability of glutamate to exert an "energizing role" in cardiac and neuronal models of hypoxia/reoxygenation (H/R) injury, focusing on the Na+/Ca2+ exchanger (NCX) and the Na+-dependent excitatory amino acid transporters (EAATs) as key players in this metabolic pathway.
Collapse
Affiliation(s)
- Silvia Piccirillo
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126, Ancona, Italy
| | - Simona Magi
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126, Ancona, Italy.
| | - Pasqualina Castaldo
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126, Ancona, Italy
| | - Alessandra Preziuso
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126, Ancona, Italy
| | - Vincenzo Lariccia
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126, Ancona, Italy
| | - Salvatore Amoroso
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche", Via Tronto 10/A, 60126, Ancona, Italy
| |
Collapse
|
10
|
Magi S, Piccirillo S, Amoroso S, Lariccia V. Excitatory Amino Acid Transporters (EAATs): Glutamate Transport and Beyond. Int J Mol Sci 2019; 20:ijms20225674. [PMID: 31766111 PMCID: PMC6888595 DOI: 10.3390/ijms20225674] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 11/08/2019] [Accepted: 11/10/2019] [Indexed: 01/02/2023] Open
Abstract
Na+-dependent excitatory amino acid transporters (EAATs) are the major transport mechanisms for extracellular glutamate removal in the central nervous system (CNS). The primary function assigned to EAATs is the maintenance of low extracellular glutamate levels, thus allowing glutamate to be used as a signaling molecule in the brain and to avoid excitotoxicity. However, glutamate has other recognized functions. For instance, it is a key anaplerotic substrate for the tricarboxylic acid (TCA) cycle, as it can be converted to α-ketoglutarate by transaminases or glutamate dehydrogenase. Furthermore, glutamate is a precursor of the main antioxidant glutathione, which plays a pivotal role in preventing oxidative cell death. Therefore, glutamate signaling/use is at the crossroad of multiple metabolic pathways and accordingly, it can influence a plethora of cell functions, both in health and disease. Here, we provide an overview of the main functions of glutamate and its transport systems, analyzing its role as a neurotransmitter and at the same time, the possible metabolic fates it can undergo in the intracellular milieu. Specifically, the metabolic role of glutamate and the molecular machinery proposed to metabolically support its transport will be further analyzed.
Collapse
|
11
|
Fern R, Matute C. Glutamate receptors and white matter stroke. Neurosci Lett 2018; 694:86-92. [PMID: 30476568 DOI: 10.1016/j.neulet.2018.11.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 11/19/2018] [Accepted: 11/21/2018] [Indexed: 12/23/2022]
Abstract
White matter (WM) damage during ischemia occurs at multiple sites including myelin, oligodendrocytes, astrocytes and axons. A major driver of WM demise is excitoxicity as a consequence of excessive glutamate release by vesicular and non-vesicular mechanisms from axons and glial cells. This results in over-activation of ionotropic glutamate receptors (GluRs) profusely expressed by all cell compartments in WM. Thus, blocking excitotoxicity in WM with selective antagonists of those receptors has a potential therapeutic value. The significance of WM GluR expression for WM stroke injury is the focus of this review, and we will examine the role of GluRs in injury to myelin, oligodendrocytes, astrocytes and the axon cylinder.
Collapse
Affiliation(s)
- Robert Fern
- Faculty of Medicine and Dentistry, University of Plymouth, Plymouth, United Kingdom
| | - Carlos Matute
- Achucarro Basque Center for Neuroscience, CIBERNED and Department of Neuroscience, University of the Basque Country, Leioa, Spain.
| |
Collapse
|
12
|
Tambasco N, Romoli M, Calabresi P. Selective basal ganglia vulnerability to energy deprivation: Experimental and clinical evidences. Prog Neurobiol 2018; 169:55-75. [DOI: 10.1016/j.pneurobio.2018.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 07/24/2018] [Accepted: 07/27/2018] [Indexed: 02/07/2023]
|
13
|
Mn Inhibits GSH Synthesis via Downregulation of Neuronal EAAC1 and Astrocytic xCT to Cause Oxidative Damage in the Striatum of Mice. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:4235695. [PMID: 30228854 PMCID: PMC6136513 DOI: 10.1155/2018/4235695] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 06/24/2018] [Accepted: 07/12/2018] [Indexed: 11/17/2022]
Abstract
Excessive manganese (Mn) can accumulate in the striatum of the brain following overexposure. Oxidative stress is a well-recognized mechanism in Mn-induced neurotoxicity. It has been proven that glutathione (GSH) depletion is a key factor in oxidative damage during Mn exposure. However, no study has focused on the dysfunction of GSH synthesis-induced oxidative stress in the brain during Mn exposure. The objective of the present study was to explore the mechanism of Mn disruption of GSH synthesis via EAAC1 and xCT in vitro and in vivo. Primary neurons and astrocytes were cultured and treated with different doses of Mn to observe the state of cells and levels of GSH and reactive oxygen species (ROS) and measure mRNA and protein expression of EAAC1 and xCT. Mice were randomly divided into seven groups, which received saline, 12.5, 25, and 50 mg/kg MnCl2, 500 mg/kg AAH (EAAC1 inhibitor) + 50 mg/kg MnCl2, 75 mg/kg SSZ (xCT inhibitor) + 50 mg/kg MnCl2, and 100 mg/kg NAC (GSH rescuer) + 50 mg/kg MnCl2 once daily for two weeks. Then, levels of EAAC1, xCT, ROS, GSH, malondialdehyde (MDA), protein sulfhydryl, carbonyl, 8-hydroxy-2-deoxyguanosine (8-OHdG), and morphological and ultrastructural features in the striatum of mice were measured. Mn reduced protein levels, mRNA expression, and immunofluorescence intensity of EAAC1 and xCT. Mn also decreased the level of GSH, sulfhydryl, and increased ROS, MDA, 8-OHdG, and carbonyl in a dose-dependent manner. Injury-related pathological and ultrastructure changes in the striatum of mice were significantly present. In conclusion, excessive exposure to Mn disrupts GSH synthesis through inhibition of EAAC1 and xCT to trigger oxidative damage in the striatum.
Collapse
|
14
|
Doll S, Conrad M. Iron and ferroptosis: A still ill-defined liaison. IUBMB Life 2017; 69:423-434. [PMID: 28276141 DOI: 10.1002/iub.1616] [Citation(s) in RCA: 299] [Impact Index Per Article: 42.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 02/13/2017] [Indexed: 12/16/2022]
Abstract
Ferroptosis is a recently described form of regulated necrotic cell death, which appears to contribute to a number of diseases, such as tissue ischemia/reperfusion injury, acute renal failure, and neurodegeneration. A hallmark of ferroptosis is iron-dependent lipid peroxidation, which can be inhibited by the key ferroptosis regulator glutathione peroxidase 4(Gpx4), radical trapping antioxidants and ferroptosis-specific inhibitors, such as ferrostatins and liproxstatins, as well as iron chelation. Although great strides have been made towards a better understanding of the proximate signals of distinctive lipid peroxides in ferroptosis, still little is known about the mechanistic implication of iron in the ferroptotic process. Hence, this review aims at summarizing recent advances in our understanding to what is known about enzymatic and nonenzymatic routes of lipid peroxidation, the involvement of iron in this process and the identification of novel players in ferroptotic cell death. Additionally, we review early works carried out long time before the term "ferroptosis" was actually introduced but which were instrumental in a better understanding of the role of ferroptosis in physiological and pathophysiological contexts. © 2017 IUBMB Life, 69(6):423-434, 2017.
Collapse
Affiliation(s)
- Sebastian Doll
- Helmholtz Zentrum München, Institute of Developmental Genetics, Neuherberg, Germany
| | - Marcus Conrad
- Helmholtz Zentrum München, Institute of Developmental Genetics, Neuherberg, Germany
| |
Collapse
|
15
|
Mancic B, Stevanovic I, Ilic TV, Djuric A, Stojanovic I, Milanovic S, Ninkovic M. Transcranial theta-burst stimulation alters GLT-1 and vGluT1 expression in rat cerebellar cortex. Neurochem Int 2016; 100:120-127. [DOI: 10.1016/j.neuint.2016.09.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 08/31/2016] [Accepted: 09/09/2016] [Indexed: 12/13/2022]
|
16
|
Acaz-Fonseca E, Avila-Rodriguez M, Garcia-Segura LM, Barreto GE. Regulation of astroglia by gonadal steroid hormones under physiological and pathological conditions. Prog Neurobiol 2016; 144:5-26. [DOI: 10.1016/j.pneurobio.2016.06.002] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 06/05/2016] [Indexed: 01/07/2023]
|
17
|
Abstract
Astrocytes are the most explored non-neuronal cells in the brain under neurophysiological and neurodegenerative conditions. Extensive research has been done to understand their specific role during neuropathological conditions but still the existing findings could not conclude their mechanism of action and their specific role in neurodegenerative conditions. This review discusses their physiological and pathological roles, their activation, morphological alterations and their probable use in search of new therapeutic targets for the treatment of neurodegenerative diseases.
Collapse
Affiliation(s)
- Sarika Singh
- a 1 Toxicology Division, CSIR-CDRI , Lucknow , India.,b 2 Department of Biochemistry and Biophysics , University of California , San Francisco, San Francisco , CA , USA
| | - Neeraj Joshi
- a 1 Toxicology Division, CSIR-CDRI , Lucknow , India.,b 2 Department of Biochemistry and Biophysics , University of California , San Francisco, San Francisco , CA , USA
| |
Collapse
|
18
|
Martinez-Lozada Z, Guillem AM, Robinson MB. Transcriptional Regulation of Glutamate Transporters: From Extracellular Signals to Transcription Factors. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 76:103-45. [PMID: 27288076 DOI: 10.1016/bs.apha.2016.01.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Glutamate is the predominant excitatory neurotransmitter in the mammalian CNS. It mediates essentially all rapid excitatory signaling. Dysfunction of glutamatergic signaling contributes to developmental, neurologic, and psychiatric diseases. Extracellular glutamate is cleared by a family of five Na(+)-dependent glutamate transporters. Two of these transporters (GLAST and GLT-1) are relatively selectively expressed in astrocytes. Other of these transporters (EAAC1) is expressed by neurons throughout the nervous system. Expression of the last two members of this family (EAAT4 and EAAT5) is almost exclusively restricted to specific populations of neurons in cerebellum and retina, respectively. In this review, we will discuss our current understanding of the mechanisms that control transcriptional regulation of the different members of this family. Over the last two decades, our understanding of the mechanisms that regulate expression of GLT-1 and GLAST has advanced considerably; several specific transcription factors, cis-elements, and epigenetic mechanisms have been identified. For the other members of the family, little or nothing is known about the mechanisms that control their transcription. It is assumed that by defining the mechanisms involved, we will advance our understanding of the events that result in cell-specific expression of these transporters and perhaps begin to define the mechanisms by which neurologic diseases are changing the biology of the cells that express these transporters. This approach might provide a pathway for developing new therapies for a wide range of essentially untreatable and devastating diseases that kill neurons by an excitotoxic mechanism.
Collapse
Affiliation(s)
- Z Martinez-Lozada
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, United States
| | - A M Guillem
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, United States
| | - M B Robinson
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, United States.
| |
Collapse
|
19
|
Homeostasis of the astrocytic glutamate transporter GLT-1 is altered in mouse models of Lafora disease. Biochim Biophys Acta Mol Basis Dis 2016; 1862:1074-83. [PMID: 26976331 DOI: 10.1016/j.bbadis.2016.03.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 02/04/2016] [Accepted: 03/10/2016] [Indexed: 11/20/2022]
Abstract
Lafora disease (LD, OMIM 254780) is a fatal rare disorder characterized by epilepsy and neurodegeneration. Although in recent years a lot of information has been gained on the molecular basis of the neurodegeneration that accompanies LD, the molecular basis of epilepsy is poorly understood. Here, we present evidence indicating that the homeostasis of glutamate transporter GLT-1 (EAAT2) is compromised in mouse models of LD. Our results indicate that primary astrocytes from LD mice have reduced capacity of glutamate transport, probably because they present a reduction in the levels of the glutamate transporter at the plasma membrane. On the other hand, the overexpression in cellular models of laforin and malin, the two proteins related to LD, results in an accumulation of GLT-1 (EAAT2) at the plasma membrane and in a severe reduction of the ubiquitination of the transporter. All these results suggest that the laforin/malin complex slows down the endocytic recycling of the GLT-1 (EAAT2) transporter. Since, defects in the function of this transporter lead to excitotoxicity and epilepsy, we suggest that the epilepsy that accompanies LD could be due, at least in part, to deficiencies in the function of the GLT-1 (EAAT2) transporter.
Collapse
|
20
|
Tardito S, Oudin A, Ahmed SU, Fack F, Keunen O, Zheng L, Miletic H, Sakariassen PØ, Weinstock A, Wagner A, Lindsay SL, Hock AK, Barnett SC, Ruppin E, Mørkve SH, Lund-Johansen M, Chalmers AJ, Bjerkvig R, Niclou SP, Gottlieb E. Glutamine synthetase activity fuels nucleotide biosynthesis and supports growth of glutamine-restricted glioblastoma. Nat Cell Biol 2015; 17:1556-68. [PMID: 26595383 PMCID: PMC4663685 DOI: 10.1038/ncb3272] [Citation(s) in RCA: 382] [Impact Index Per Article: 42.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 10/19/2015] [Indexed: 12/27/2022]
Abstract
L-Glutamine (Gln) functions physiologically to balance the carbon and nitrogen requirements of tissues. It has been proposed that in cancer cells undergoing aerobic glycolysis, accelerated anabolism is sustained by Gln-derived carbons, which replenish the tricarboxylic acid (TCA) cycle (anaplerosis). However, it is shown here that in glioblastoma (GBM) cells, almost half of the Gln-derived glutamate (Glu) is secreted and does not enter the TCA cycle, and that inhibiting glutaminolysis does not affect cell proliferation. Moreover, Gln-starved cells are not rescued by TCA cycle replenishment. Instead, the conversion of Glu to Gln by glutamine synthetase (GS; cataplerosis) confers Gln prototrophy, and fuels de novo purine biosynthesis. In both orthotopic GBM models and in patients, (13)C-glucose tracing showed that GS produces Gln from TCA-cycle-derived carbons. Finally, the Gln required for the growth of GBM tumours is contributed only marginally by the circulation, and is mainly either autonomously synthesized by GS-positive glioma cells, or supplied by astrocytes.
Collapse
Affiliation(s)
- Saverio Tardito
- Cancer Metabolism Research Unit, Cancer Research UK, Beatson Institute, Switchback Road, Glasgow, G61 1BD, Scotland, UK
| | - Anaïs Oudin
- NorLux Neuro-Oncology Laboratory, Department of Oncology, Luxembourg Institute of Health, L-1526, Luxembourg
| | - Shafiq U. Ahmed
- Institute of Cancer Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Fred Fack
- NorLux Neuro-Oncology Laboratory, Department of Oncology, Luxembourg Institute of Health, L-1526, Luxembourg
| | - Olivier Keunen
- NorLux Neuro-Oncology Laboratory, Department of Oncology, Luxembourg Institute of Health, L-1526, Luxembourg
| | - Liang Zheng
- Cancer Metabolism Research Unit, Cancer Research UK, Beatson Institute, Switchback Road, Glasgow, G61 1BD, Scotland, UK
| | - Hrvoje Miletic
- Kristian Gerhard Jebsen Brain Tumour Research Center, Department of Biomedicine, University of Bergen, Bergen, N-5009, Norway
| | - Per Øystein Sakariassen
- Kristian Gerhard Jebsen Brain Tumour Research Center, Department of Biomedicine, University of Bergen, Bergen, N-5009, Norway
| | - Adam Weinstock
- The Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Allon Wagner
- The Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Susan L. Lindsay
- Institute of Infection, Immunity and inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, Scotland, UK
| | - Andreas K. Hock
- Cancer Metabolism Research Unit, Cancer Research UK, Beatson Institute, Switchback Road, Glasgow, G61 1BD, Scotland, UK
| | - Susan C. Barnett
- Institute of Infection, Immunity and inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, Scotland, UK
| | - Eytan Ruppin
- The Blavatnik School of Computer Science, Tel Aviv University, Tel Aviv, 69978, Israel
- The Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | | | - Morten Lund-Johansen
- Department of Neurosurgery, Haukeland University Hospital, N-5021, Norway
- Department of Clinical Medicine, University of Bergen, N-5020, Norway
| | | | - Rolf Bjerkvig
- NorLux Neuro-Oncology Laboratory, Department of Oncology, Luxembourg Institute of Health, L-1526, Luxembourg
- Kristian Gerhard Jebsen Brain Tumour Research Center, Department of Biomedicine, University of Bergen, Bergen, N-5009, Norway
| | - Simone P. Niclou
- NorLux Neuro-Oncology Laboratory, Department of Oncology, Luxembourg Institute of Health, L-1526, Luxembourg
- Kristian Gerhard Jebsen Brain Tumour Research Center, Department of Biomedicine, University of Bergen, Bergen, N-5009, Norway
| | - Eyal Gottlieb
- Cancer Metabolism Research Unit, Cancer Research UK, Beatson Institute, Switchback Road, Glasgow, G61 1BD, Scotland, UK
| |
Collapse
|
21
|
The in ovo administration of L-trans pyrrolidine-2,4-dicarboxylic acid regulates small intestinal growth in chicks. Animal 2015; 8:1677-83. [PMID: 25231282 DOI: 10.1017/s1751731114001645] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Glutamate, which is one of the most important contributors to oxidative metabolism in the intestinal mucosa, is mainly transported by the excitatory amino acids transporters (EAATs) that are expressed in enterocytes. The objective of this study was to evaluate the effects of in ovo administration of l-trans pyrrolidine-2,4-dicarboxylic acid (l-trans-PDC), a potent competitive inhibitor of glutamate uptake by EAATs, on the growth of the small intestine in chicks. Two series of experiments were conducted with hatching eggs; 100 μl of various l-trans-PDC solutions (0, 0.075 or 0.225 mg/egg for the Control group, low-dose l-trans pyrrolidine 2,4-dicarboxylic acid group (L-PDC) or high-dose l-trans pyrrolidine 2,4-dicarboxylic acid group (H-PDC), respectively) was injected into the albumen sac of these hatching eggs before incubation. Hatchlings were sacrificed by cervical dislocation to determine the embryonic development in Experiment I, whereas the birds in Experiment II were raised or sampled at hatching, days 7 and 14 (D7 and D14) for further study. Gene expression in the small intestines was determined by real-time RT-PCR; and serum concentration of free amino acids was determined by an amino acid analyzer. The results showed that the hatchability was decreased by in ovo administration of l-trans-PDC. The small intestinal weights of the H-PDC group were decreased (P<0.05) at hatching and increased (P<0.05) on D7 and D14 compared with those in the Control group. In addition, the gene expression of EAAT2 in the completed or segmental small intestines was not changed (P>0.05); EAAT3 gene expression in the duodenum (P<0.05), jejunum (P=0.084) and ileum (P=0.060) on D14 was lower in the H-PDC group than in the Control group. Furthermore, the serum concentrations of free proline, threonine and phenylalanine but not glutamate or aspartate were increased (P<0.06) in H-PDC group. In conclusion, this paper is the first to report that in ovo administration of l-trans-PDC induces small intestinal growth retardation during the embryonic period and catch-up growth after hatching.
Collapse
|
22
|
Puttachary S, Sharma S, Stark S, Thippeswamy T. Seizure-induced oxidative stress in temporal lobe epilepsy. BIOMED RESEARCH INTERNATIONAL 2015; 2015:745613. [PMID: 25650148 PMCID: PMC4306378 DOI: 10.1155/2015/745613] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/11/2014] [Accepted: 09/11/2014] [Indexed: 01/08/2023]
Abstract
An insult to the brain (such as the first seizure) causes excitotoxicity, neuroinflammation, and production of reactive oxygen/nitrogen species (ROS/RNS). ROS and RNS produced during status epilepticus (SE) overwhelm the mitochondrial natural antioxidant defense mechanism. This leads to mitochondrial dysfunction and damage to the mitochondrial DNA. This in turn affects synthesis of various enzyme complexes that are involved in electron transport chain. Resultant effects that occur during epileptogenesis include lipid peroxidation, reactive gliosis, hippocampal neurodegeneration, reorganization of neural networks, and hypersynchronicity. These factors predispose the brain to spontaneous recurrent seizures (SRS), which ultimately establish into temporal lobe epilepsy (TLE). This review discusses some of these issues. Though antiepileptic drugs (AEDs) are beneficial to control/suppress seizures, their long term usage has been shown to increase ROS/RNS in animal models and human patients. In established TLE, ROS/RNS are shown to be harmful as they can increase the susceptibility to SRS. Further, in this paper, we review briefly the data from animal models and human TLE patients on the adverse effects of antiepileptic medications and the plausible ameliorating effects of antioxidants as an adjunct therapy.
Collapse
Affiliation(s)
- Sreekanth Puttachary
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA
| | - Shaunik Sharma
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA
| | - Sara Stark
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA
| | - Thimmasettappa Thippeswamy
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA
| |
Collapse
|
23
|
Glutathione-Dependent Detoxification Processes in Astrocytes. Neurochem Res 2014; 40:2570-82. [PMID: 25428182 DOI: 10.1007/s11064-014-1481-1] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 11/10/2014] [Accepted: 11/15/2014] [Indexed: 01/17/2023]
Abstract
Astrocytes have a pivotal role in brain as partners of neurons in homeostatic and metabolic processes. Astrocytes also protect other types of brain cells against the toxicity of reactive oxygen species and are considered as first line of defence against the toxic potential of xenobiotics. A key component in many of the astrocytic detoxification processes is the tripeptide glutathione (GSH) which serves as electron donor in the GSH peroxidase-catalyzed reduction of peroxides. In addition, GSH is substrate in the detoxification of xenobiotics and endogenous compounds by GSH-S-transferases which generate GSH conjugates that are efficiently exported from the cells by multidrug resistance proteins. Moreover, GSH reacts with the reactive endogenous carbonyls methylglyoxal and formaldehyde to intermediates which are substrates of detoxifying enzymes. In this article we will review the current knowledge on the GSH metabolism of astrocytes with a special emphasis on GSH-dependent detoxification processes.
Collapse
|
24
|
Zhang Y, Zhang X, Qu S. Ceftriaxone Protects Astrocytes from MPP(+) via Suppression of NF-κB/JNK/c-Jun Signaling. Mol Neurobiol 2014; 52:78-92. [PMID: 25112679 DOI: 10.1007/s12035-014-8845-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 07/31/2014] [Indexed: 12/23/2022]
Abstract
Ceftriaxone has been shown to attenuate the dopaminergic neuron death and alleviate behavioral disorders in Parkinson's disease models via upregulation of glutamate transporter-1 (GLT-1) and decreases in extracellular glutamate. However, details of how this neuroprotection occurs are uncertain. We hypothesized that cytoprotection by ceftriaxone in astrocytes exposed to 1-methyl-4-phenylpyridinium (MPP(+)) involves suppression of the NF-κB/JNK/c-Jun signaling pathway. Here, we observed a protective effect of ceftriaxone in primary astrocytes exposed to MPP(+). Ceftriaxone enhanced glutamate uptake and promoted primary astrocyte viability after MPP(+) exposure. Ceftriaxone enhances glutamate uptake via upregulation of GLT-1 in the plasma membrane, and alleviates MPP(+)-induced neurotoxicity via suppression of NF-κB/JNK/c-Jun signaling. Collectively, our data offer evidence that increased expression and function of GLT-1 are involved in the protective mechanism of ceftriaxone in astrocytes exposed to MPP(+) in vitro, and we offer insight into the potential therapeutic role of ceftriaxone in treatment of Parkinson's disease.
Collapse
Affiliation(s)
- Yunlong Zhang
- Department of Immunology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong, 510515, China
| | | | | |
Collapse
|
25
|
Butt AM, Fern RF, Matute C. Neurotransmitter signaling in white matter. Glia 2014; 62:1762-79. [PMID: 24753049 DOI: 10.1002/glia.22674] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 03/04/2014] [Accepted: 03/31/2014] [Indexed: 12/16/2022]
Abstract
White matter (WM) tracts are bundles of myelinated axons that provide for rapid communication throughout the CNS and integration in grey matter (GM). The main cells in myelinated tracts are oligodendrocytes and astrocytes, with small populations of microglia and oligodendrocyte precursor cells. The prominence of neurotransmitter signaling in WM, which largely exclude neuronal cell bodies, indicates it must have physiological functions other than neuron-to-neuron communication. A surprising aspect is the diversity of neurotransmitter signaling in WM, with evidence for glutamatergic, purinergic (ATP and adenosine), GABAergic, glycinergic, adrenergic, cholinergic, dopaminergic and serotonergic signaling, acting via a wide range of ionotropic and metabotropic receptors. Both axons and glia are potential sources of neurotransmitters and may express the respective receptors. The physiological functions of neurotransmitter signaling in WM are subject to debate, but glutamate and ATP-mediated signaling have been shown to evoke Ca(2+) signals in glia and modulate axonal conduction. Experimental findings support a model of neurotransmitters being released from axons during action potential propagation acting on glial receptors to regulate the homeostatic functions of astrocytes and myelination by oligodendrocytes. Astrocytes also release neurotransmitters, which act on axonal receptors to strengthen action potential propagation, maintaining signaling along potentially long axon tracts. The co-existence of multiple neurotransmitters in WM tracts suggests they may have diverse functions that are important for information processing. Furthermore, the neurotransmitter signaling phenomena described in WM most likely apply to myelinated axons of the cerebral cortex and GM areas, where they are doubtless important for higher cognitive function.
Collapse
Affiliation(s)
- Arthur M Butt
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, United Kingdom
| | | | | |
Collapse
|
26
|
Zhang Y, Zhang X, Qu S. Cysteine mutagenesis reveals alternate proximity between transmembrane domain 2 and hairpin loop 1 of the glutamate transporter EAAT1. Amino Acids 2014; 46:1697-705. [PMID: 24692063 DOI: 10.1007/s00726-014-1731-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2013] [Accepted: 03/18/2014] [Indexed: 12/26/2022]
Abstract
Excitatory amino acid transporter 1 (EAAT1) plays an important role in restricting the neurotoxicity of glutamate. Previous structure-function studies have provided evidence that reentrant helical hairpin loop (HP) 1 has predominant function during the transport cycle. The proposed internal gate HP1 is packed against transmembrane domain (TM) 2 and TM5 in its closed state, and two residues located in TM2 and HP2 of EAAT1 are in close proximity. However, the spatial relationship between TM2 and HP1 during the transport cycle remains unknown. In this study, we used chemical cross-linking of introduced cysteine pair (V96C and S366C) in a cysteine-less version of EAAT1 to assess the proximity of TM2 and HP1. Here, we show that inhibition of transport by copper(II)(1,10-phenanthroline)3 (CuPh) and cadmium ion (Cd(2+)) were observed in the V96C/S366C mutant. Glutamate or potassium significantly protected against the inhibition of transport activity of V96C/S366C by CuPh, while TBOA potentiated the inhibition of transport activity of V96C/S366C by CuPh. We also checked the kinetic parameters of V96C/S366C treated with or without CuPh in the presence of NaCl, NaCl + L-glutamate, NaCl + TBOA, and KCl, respectively. The sensitivity of V96C and S366C to membrane-impermeable sulfhydryl reagent MTSET [(2-trimethylammonium) methanethiosulfonate] was attenuated by glutamate or potassium. TBOA had no effect on the sensitivity of V96C and S366C to MTSET. These data suggest that the spatial relationship between Val-96 of TM2 and Ser-366 of HP1 is altered in the transport cycle.
Collapse
Affiliation(s)
- Yunlong Zhang
- Department of Immunology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | | | | |
Collapse
|
27
|
The potential therapeutic effect of guanosine after cortical focal ischemia in rats. PLoS One 2014; 9:e90693. [PMID: 24587409 PMCID: PMC3938812 DOI: 10.1371/journal.pone.0090693] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 02/04/2014] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE Stroke is a devastating disease. Both excitotoxicity and oxidative stress play important roles in ischemic brain injury, along with harmful impacts on ischemic cerebral tissue. As guanosine plays an important neuroprotective role in the central nervous system, the purpose of this study was to evaluate the neuroprotective effects of guanosine and putative cerebral events following the onset of permanent focal cerebral ischemia. METHODS Permanent focal cerebral ischemia was induced in rats by thermocoagulation. Guanosine was administered immediately, 1 h, 3 h and 6 h after surgery. Behavioral performance was evaluated by cylinder testing for a period of 15 days after surgery. Brain oxidative stress parameters, including levels of ROS/RNS, lipid peroxidation, antioxidant non-enzymatic levels (GSH, vitamin C) and enzymatic parameters (SOD expression and activity and CAT activity), as well as glutamatergic parameters (EAAC1, GLAST and GLT1, glutamine synthetase) were analyzed. RESULTS After 24 h, ischemic injury resulted in impaired function of the forelimb, caused brain infarct and increased lipid peroxidation. Treatment with guanosine restored these parameters. Oxidative stress markers were affected by ischemic insult, demonstrated by increased ROS/RNS levels, increased SOD expression with reduced SOD activity and decreased non-enzymatic (GSH and vitamin C) antioxidant defenses. Guanosine prevented increased ROS/RNS levels, decreased SOD activity, further increased SOD expression, increased CAT activity and restored vitamin C levels. Ischemia also affected glutamatergic parameters, illustrated by increased EAAC1 levels and decreased GLT1 levels; guanosine reversed the decreased GLT1 levels and did not affect the EAAC1 levels. CONCLUSION The effects of brain ischemia were strongly attenuated by guanosine administration. The cellular mechanisms involved in redox and glutamatergic homeostasis, which were both affected by the ischemic insult, were also modulated by guanosine. These observations reveal that guanosine may represent a potential therapeutic agent in cerebral ischemia by preventing oxidative stress and excitotoxicity.
Collapse
|
28
|
Exploring cross-talk between oxidative damage and excitotoxicity and the effects of riluzole in the rat cortex after exposure to methylmercury. Neurotox Res 2014; 26:40-51. [PMID: 24519665 DOI: 10.1007/s12640-013-9448-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 11/07/2013] [Accepted: 12/05/2013] [Indexed: 12/22/2022]
Abstract
Methylmercury (MeHg) is a ubiquitous environmental toxin that causes neurologic and developmental diseases. Oxidative damage and excitotoxicity are putative mechanisms, which underlie MeHg-induced neurotoxicity. In this study, the cross-talk between the oxidative damage and excitotoxicity pathways and the protective effects of riluzole in the rat cortex were explored. Rats were injected with MeHg and/or riluzole, and cold vapor atomic fluorescence spectrometry, hematoxylin and eosin staining, flow cytometry, fluorescence assays, spectrophotometry, real-time PCR, and Western blotting were used to evaluate neurotoxicity. The present study showed that (1) MeHg accumulated in the cerebral cortex and caused pathology. (2) MeHg caused oxidative damage by inducing glutathione (GSH) depletion, reactive oxygen species (ROS) production, inhibition of antioxidant enzyme activity, and alteration of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. (3) MeHg disrupted the glutamate transporters (GluTs), glutamate-glutamine cycle, and N-methyl-D-aspartate receptor expression and induced excitotoxicity. (4) Excitotoxicity resulted in disruption of GSH synthesis, calcium overloading, oxidative damage, and excessive ROS production. (5) Pretreatment with riluzole antagonized MeHg neurotoxicity by down regulating cross-talk between the oxidative damage and excitotoxicity pathways. In conclusion, the cross-talk between the oxidative damage and excitotoxicity pathways caused by MeHg exposure was linked by GluTs and calcium and inhibited by riluzole treatment.
Collapse
|
29
|
Assous M, Had-Aissouni L, Gubellini P, Melon C, Nafia I, Salin P, Kerkerian-Le-Goff L, Kachidian P. Progressive Parkinsonism by acute dysfunction of excitatory amino acid transporters in the rat substantia nigra. Neurobiol Dis 2014; 65:69-81. [PMID: 24480091 DOI: 10.1016/j.nbd.2014.01.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 01/10/2014] [Accepted: 01/14/2014] [Indexed: 10/25/2022] Open
Abstract
Parkinson's disease (PD) is characterized by the progressive degeneration of substantia nigra (SN) dopamine neurons, involving a multifactorial cascade of pathogenic events. Here we explored the hypothesis that dysfunction of excitatory amino acid transporters (EAATs) might be involved. Acutely-induced dysfunction of EAATs in the rat SN, by single unilateral injection of their substrate inhibitor l-trans-pyrrolidine-2,4-dicarboxylate (PDC), triggers a neurodegenerative process mimicking several PD features. Dopamine neurons are selectively affected, consistent with their sustained excitation by PDC measured by slice electrophysiology. The anti-oxidant N-acetylcysteine and the NMDA receptor antagonists ifenprodil and memantine provide neuroprotection. Besides oxidative stress and NMDA receptor-mediated excitotoxicity, glutathione depletion and neuroinflammation characterize the primary insult. Most interestingly, the degeneration progresses overtime with unilateral to bilateral and caudo-rostral evolution. Transient adaptive changes in dopamine function markers in SN and striatum accompany cell loss and axonal dystrophy, respectively. Motor deficits appear when neuron loss exceeds 50% in the most affected SN and striatal dopamine tone is dramatically reduced. These findings outline a functional link between EAAT dysfunction and several PD pathogenic mechanisms/pathological hallmarks, and provide a novel acutely-triggered model of progressive Parkinsonism.
Collapse
Affiliation(s)
- Maxime Assous
- Aix-Marseille Université, CNRS, IBDML, UMR7288, 13009, Case 907, Parc Scientifique de Luminy, 13009 Marseille, France
| | - Laurence Had-Aissouni
- Aix-Marseille Université, CNRS, IBDML, UMR7288, 13009, Case 907, Parc Scientifique de Luminy, 13009 Marseille, France
| | - Paolo Gubellini
- Aix-Marseille Université, CNRS, IBDML, UMR7288, 13009, Case 907, Parc Scientifique de Luminy, 13009 Marseille, France
| | - Christophe Melon
- Aix-Marseille Université, CNRS, IBDML, UMR7288, 13009, Case 907, Parc Scientifique de Luminy, 13009 Marseille, France
| | - Imane Nafia
- Fluofarma, 2 Rue Robert Escarpit, 33607, Pessac, France
| | - Pascal Salin
- Aix-Marseille Université, CNRS, IBDML, UMR7288, 13009, Case 907, Parc Scientifique de Luminy, 13009 Marseille, France
| | - Lydia Kerkerian-Le-Goff
- Aix-Marseille Université, CNRS, IBDML, UMR7288, 13009, Case 907, Parc Scientifique de Luminy, 13009 Marseille, France.
| | - Philippe Kachidian
- Aix-Marseille Université, CNRS, IBDML, UMR7288, 13009, Case 907, Parc Scientifique de Luminy, 13009 Marseille, France.
| |
Collapse
|
30
|
Aoyama K, Nakaki T. Impaired glutathione synthesis in neurodegeneration. Int J Mol Sci 2013; 14:21021-44. [PMID: 24145751 PMCID: PMC3821656 DOI: 10.3390/ijms141021021] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 09/30/2013] [Accepted: 10/01/2013] [Indexed: 12/20/2022] Open
Abstract
Glutathione (GSH) was discovered in yeast cells in 1888. Studies of GSH in mammalian cells before the 1980s focused exclusively on its function for the detoxication of xenobiotics or for drug metabolism in the liver, in which GSH is present at its highest concentration in the body. Increasing evidence has demonstrated other important roles of GSH in the brain, not only for the detoxication of xenobiotics but also for antioxidant defense and the regulation of intracellular redox homeostasis. GSH also regulates cell signaling, protein function, gene expression, and cell differentiation/proliferation in the brain. Clinically, inborn errors in GSH-related enzymes are very rare, but disorders of GSH metabolism are common in major neurodegenerative diseases showing GSH depletion and increased levels of oxidative stress in the brain. GSH depletion would precipitate oxidative damage in the brain, leading to neurodegenerative diseases. This review focuses on the significance of GSH function, the synthesis of GSH and its metabolism, and clinical disorders of GSH metabolism. A potential approach to increase brain GSH levels against neurodegeneration is also discussed.
Collapse
Affiliation(s)
- Koji Aoyama
- Department of Pharmacology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi, Tokyo 173-8605, Japan.
| | | |
Collapse
|
31
|
Cho CH. New mechanism for glutamate hypothesis in epilepsy. Front Cell Neurosci 2013; 7:127. [PMID: 23964202 PMCID: PMC3741557 DOI: 10.3389/fncel.2013.00127] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 07/25/2013] [Indexed: 11/22/2022] Open
Affiliation(s)
- Chang-Hoon Cho
- Epilepsy Research Laboratory, Department of Pediatrics, Abramson Research Center, Children's Hospital of Philadelphia Philadelphia, PA, USA
| |
Collapse
|
32
|
Neuroprotective properties of the excitatory amino acid carrier 1 (EAAC1). Amino Acids 2013; 45:133-42. [PMID: 23462929 DOI: 10.1007/s00726-013-1481-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 02/23/2013] [Indexed: 01/09/2023]
Abstract
Extracellular glutamate should be maintained at low levels to conserve optimal neurotransmission and prevent glutamate neurotoxicity in the brain. Excitatory amino acid transporters (EAATs) play a pivotal role in removing extracellular glutamate in the central nervous system (CNS). Excitatory amino acid carrier 1 (EAAC1) is a high-affinity Na⁺-dependent neuronal EAAT that is ubiquitously expressed in the brain. However, most glutamate released in the synapses is cleared by glial EAATs, but not by EAAC1 in vivo. In the CNS, EAAC1 is widely distributed in somata and dendrites but not in synaptic terminals. The contribution of EAAC1 to the control of extracellular glutamate levels seems to be negligible in the brain. However, EAAC1 can transport not only extracellular glutamate but also cysteine into the neurons. Cysteine is an important substrate for glutathione (GSH) synthesis in the brain. GSH has a variety of neuroprotective functions, while its depletion induces neurodegeneration. Therefore, EAAC1 might exert a critical role for neuroprotection in neuronal GSH metabolism rather than glutamatergic neurotransmission, while EAAC1 dysfunction would cause neurodegeneration. Despite the potential importance of EAAC1 in the brain, previous studies have mainly focused on the glutamate neurotoxicity induced by glial EAAT dysfunction. In recent years, however, several studies have revealed regulatory mechanisms of EAAC1 functions in the brain. This review will summarize the latest information on the EAAC1-regulated neuroprotective functions in the CNS.
Collapse
|
33
|
Ishikawa M. Abnormalities in glutamate metabolism and excitotoxicity in the retinal diseases. SCIENTIFICA 2013; 2013:528940. [PMID: 24386591 PMCID: PMC3872404 DOI: 10.1155/2013/528940] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 11/17/2013] [Indexed: 05/14/2023]
Abstract
In the physiological condition, glutamate acts as an excitatory neurotransmitter in the retina. However, excessive glutamate can be toxic to retinal neurons by overstimulation of the glutamate receptors. Glutamate excess is primarily attributed to perturbation in the homeostasis of the glutamate metabolism. Major pathway of glutamate metabolism consists of glutamate uptake by glutamate transporters followed by enzymatic conversion of glutamate to nontoxic glutamine by glutamine synthetase. Glutamate metabolism requires energy supply, and the energy loss inhibits the functions of both glutamate transporters and glutamine synthetase. In this review, we describe the present knowledge concerning the retinal glutamate metabolism under the physiological and pathological conditions.
Collapse
Affiliation(s)
- Makoto Ishikawa
- Department of Ophthalmology, Akita Graduate University Faculty of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan
- *Makoto Ishikawa:
| |
Collapse
|
34
|
Riluzole-triggered GSH synthesis via activation of glutamate transporters to antagonize methylmercury-induced oxidative stress in rat cerebral cortex. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2012; 2012:534705. [PMID: 22966415 PMCID: PMC3432391 DOI: 10.1155/2012/534705] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 06/25/2012] [Accepted: 07/08/2012] [Indexed: 11/18/2022]
Abstract
OBJECTIVE This study was to evaluate the effect of riluzole on methylmercury- (MeHg-) induced oxidative stress, through promotion of glutathione (GSH) synthesis by activating of glutamate transporters (GluTs) in rat cerebral cortex. METHODS Eighty rats were randomly assigned to four groups, control group, riluzole alone group, MeHg alone group, and riluzole + MeHg group. The neurotoxicity of MeHg was observed by measuring mercury (Hg) absorption, pathological changes, and cell apoptosis of cortex. Oxidative stress was evaluated via determining reactive oxygen species (ROS), 8-hydroxy-2-deoxyguanosine (8-OHdG), malondialdehyde (MDAs), carbonyl, sulfydryl, and GSH in cortex. Glutamate (Glu) transport was studied by measuring Glu, glutamine (Gln), mRNA, and protein of glutamate/aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1). RESULT (1) MeHg induced Hg accumulation, pathological injury, and apoptosis of cortex; (2) MeHg increased ROS, 8-OHdG, MDA, and carbonyl, and inhibited sulfydryl and GSH; (3) MeHg elevated Glu, decreased Gln, and downregulated GLAST and GLT-1 mRNA expression and protein levels; (4) riluzole antagonized MeHg-induced downregulation of GLAST and GLT-1 function and expression, GSH depletion, oxidative stress, pathological injury, and apoptosis obviously. CONCLUSION Data indicate that MeHg administration induced oxidative stress in cortex and that riluzole could antagonize this situation through elevation of GSH synthesis by activating of GluTs.
Collapse
|
35
|
Abstract
The phylogenetic enlargement of cerebral cortex culminating in the human brain imposed greater communication needs that have been met by the massive expansion of WM (white matter). Damage to WM alters brain function, and numerous neurological diseases feature WM involvement. In the current review, we discuss the major features of WM, the contributions of WM compromise to brain pathophysiology, and some of the mechanisms mediating WM injury. We will emphasize the newly appreciated importance of neurotransmitter signalling in WM, particularly glutamate and ATP signalling, to understanding both normal and abnormal brain functions. A deeper understanding of the mechanisms leading to WM damage will generate much-needed insights for developing therapies for acute and chronic diseases with WM involvement.
Collapse
|
36
|
Bethea CL, Reddy AP. Ovarian steroids increase glutamatergic related gene expression in serotonin neurons of macaques. Mol Cell Neurosci 2011; 49:251-62. [PMID: 22154832 DOI: 10.1016/j.mcn.2011.11.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 11/11/2011] [Accepted: 11/22/2011] [Indexed: 11/29/2022] Open
Abstract
Dendritic spines are the elementary structural units of neuronal plasticity and their proliferation and stabilization involve components of glutamate neurotransmission. In a model of hormone replacement therapy (HT), we sought the effect of estradiol (E) and progesterone (P) on gene expression related to glutamate neurotransmission in a laser captured preparation enriched for serotonin neurons from rhesus macaques. Microarray analysis was conducted (n=2 animals/treatment) and then confirmed for pivotal genes with qRT-PCR on additional laser captured material (n=3 animals/treatment). Ovariectomized rhesus macaques were treated with either placebo, E or E+P via Silastic implants for 1month prior to euthanasia. The midbrain was obtained, sectioned and immunostained for TPH. TPH-positive neurons were laser captured using an Arcturus Laser Dissection Microscope (Pixel II). RNA from laser captured serotonin neurons (n=2 animals/treatment) was hybridized to Rhesus Affymetrix GeneChips for screening purposes. There was a 2-fold or greater change in the expression of 28 probe sets related to glutamate processes in E and E+P treated animals. Quantitative (q) RT-PCR was conducted for 11 genes with a custom Taqman PCR array containing monkey specific primers and analyzed with ANOVA followed by Bonferroni's test. The log of the relative expression values indicated that in general, the responses to E and E+P were similar. Comparison of the relative expression or log relative expression in Ovx-controls to combined E and E+P treated groups with t-tests showed a significant increase in AMPA1 (GRIA1), AMPA2 (GRIA2), AMPA4 (GRIA4), NMDA2a (GRIN2A), metabotrophic glutamate receptor (GRM1), glutamine synthetase (GLUL), glutamate dehydrogenase (GLUD), glutamate cysteine ligase modifier subunit (GCLM), the glutamate transporter 2 (SLC1A2) and the glutamate transporter 3 (SLC1A3) with steroid treatment. There was no effect of steroid treatment on gene expression of the glutamate cysteine ligase catalytic subunit (GCLC). These data suggest that ovarian steroids target gene expression of ionotrophic and metabotrophic glutamate receptors in serotonin neurons. These receptors are present on dendritic spines and are necessary for spine maturation. The mRNAs coding for glutamate-related enzymes and transporters are likely derived from astrocytes or glutamate-containing terminals. Their induction by ovarian steroids indicates a complex upregulation of multiple components in the glutamate cycle and antioxidation, in addition to spine proliferation.
Collapse
Affiliation(s)
- Cynthia L Bethea
- Division of Reproductive Sciences, Oregon National Primate Research Center, Beaverton, OR 97006, USA.
| | | |
Collapse
|
37
|
Had-Aissouni L. Maintenance of antioxidant defenses of brain cells: plasma membrane glutamate transporters and beyond. Amino Acids 2011; 42:159-61. [DOI: 10.1007/s00726-011-0860-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/17/2011] [Indexed: 01/17/2023]
|
38
|
Persson M, Rönnbäck L. Microglial self-defence mediated through GLT-1 and glutathione. Amino Acids 2011; 42:207-19. [PMID: 21373770 DOI: 10.1007/s00726-011-0865-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/17/2011] [Indexed: 11/27/2022]
Abstract
Glutamate is stored in synaptic vesicles in presynaptic neurons. It is released into the synaptic cleft to provide signalling to postsynaptic neurons. Normally, the astroglial glutamate transporters GLT-1 and GLAST take up glutamate to mediate a high signal-to-noise ratio in the synaptic signalling, and also to prevent excitotoxic effects by glutamate. In astrocytes, glutamate is transformed into glutamine, which is safely transported back to neurons. However, in pathological conditions, such as an ischemia or virus infection, astroglial transporters are down-regulated which could lead to excitotoxicity. Lately, it was shown that even microglia can express glutamate transporters during pathological events. Microglia have two systems for glutamate transport: GLT-1 for transport into the cells and the x (c) (-) system for transport out of the cells. We here review results from our work and others, which demonstrate that microglia in culture express GLT-1, but not GLAST, and transport glutamate from the extracellular space. We also show that TNF-α can induce increased microglial GLT-1 expression, possibly associating the expression with inflammatory systems. Furthermore, glutamate taken up through GLT-1 may be used for direct incorporation into glutathione and to fuel the intracellular glutamate pool to allow cystine uptake through the x (c) (-) system. This can lead to a defence against oxidative stress and have an antiviral function.
Collapse
Affiliation(s)
- Mikael Persson
- Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Per Dubbsgatan 14, 1tr, 41345, Gothenburg, Sweden
| | | |
Collapse
|
39
|
Aoyama K, Watabe M, Nakaki T. Modulation of neuronal glutathione synthesis by EAAC1 and its interacting protein GTRAP3-18. Amino Acids 2011; 42:163-9. [PMID: 21373771 DOI: 10.1007/s00726-011-0861-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/17/2011] [Indexed: 01/17/2023]
Abstract
Glutathione (GSH) plays essential roles in different processes such as antioxidant defenses, cell signaling, cell proliferation, and apoptosis in the central nervous system. GSH is a tripeptide composed of glutamate, cysteine, and glycine. The concentration of cysteine in neurons is much lower than that of glutamate or glycine, so that cysteine is the rate-limiting substrate for neuronal GSH synthesis. Most neuronal cysteine uptake is mediated through the neuronal sodium-dependent glutamate transporter, known as excitatory amino acid carrier 1 (EAAC1). Glutamate transporters are vulnerable to oxidative stress and EAAC1 dysfunction impairs neuronal GSH synthesis by reducing cysteine uptake. This may start a vicious circle leading to neurodegeneration. Intracellular signaling molecules functionally regulate EAAC1. Glutamate transporter-associated protein 3-18 (GTRAP3-18) activation down-regulates EAAC1 function. Here, we focused on the interaction between EAAC1 and GTRAP3-18 at the plasma membrane to investigate their effects on neuronal GSH synthesis. Increased level of GTRAP3-18 protein induced a decrease in GSH level and, thereby, increased the vulnerability to oxidative stress, while decreased level of GTRAP3-18 protein induced an increase in GSH level in vitro. We also confirmed these results in vivo. Our studies demonstrate that GTRAP3-18 regulates neuronal GSH level by controlling the EAAC1-mediated uptake of cysteine.
Collapse
Affiliation(s)
- Koji Aoyama
- Department of Pharmacology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi, Tokyo, 173-8605, Japan
| | | | | |
Collapse
|
40
|
Gras G, Samah B, Hubert A, Léone C, Porcheray F, Rimaniol AC. EAAT expression by macrophages and microglia: still more questions than answers. Amino Acids 2011; 42:221-9. [PMID: 21373769 DOI: 10.1007/s00726-011-0866-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/17/2011] [Indexed: 01/07/2023]
Abstract
Glutamate is the main excitatory amino acid, but its presence in the extracellular milieu has deleterious consequences. It may induce excitotoxicity and also compete with cystine for the use of the cystine-glutamate exchanger, blocking glutathione neosynthesis and inducing an oxidative stress-induced cell death. Both mechanisms are critical in the brain where up to 20% of total body oxygen consumption occurs. In normal conditions, the astrocytes ensure that extracellular concentration of glutamate is kept in the micromolar range, thanks to their coexpression of high-affinity glutamate transporters (EAATs) and glutamine synthetase (GS). Their protective function is nevertheless sensitive to situations such as oxidative stress or inflammatory processes. On the other hand, macrophages and microglia do not express EAATs and GS in physiological conditions and are the principal effector cells of brain inflammation. Since the late 1990s, a number of studies have now shown that both microglia and macrophages display inducible EAAT and GS expression, but the precise significance of this still remains poorly understood. Brain macrophages and microglia are sister cells but yet display differences. Both are highly sensitive to their microenvironment and can perform a variety of functions that may oppose each other. However, in the very particular environment of the healthy brain, they are maintained in a repressed state. The aim of this review is to present the current state of knowledge on brain macrophages and microglial cells activation, in order to help clarify their role in the regulation of glutamate under pathological conditions as well as its outcome.
Collapse
Affiliation(s)
- Gabriel Gras
- Division of Immuno-Virology, Institute of Emerging Diseases and Innovative Therapies, UMR E1 CEA DSV/IMETI/SIV and University Paris South-Paris 11, 18, route du Panorama, 92265, Fontenay-aux Roses, France.
| | | | | | | | | | | |
Collapse
|
41
|
Lewerenz J, Maher P, Methner A. Regulation of xCT expression and system x (c) (-) function in neuronal cells. Amino Acids 2011; 42:171-9. [PMID: 21369940 DOI: 10.1007/s00726-011-0862-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/17/2011] [Indexed: 12/14/2022]
Abstract
The glutamate/cystine antiporter system x(c)(-) transports cystine into cells in exchange for glutamate at a ratio of 1:1. It is composed of a specific light chain, xCT, and a heavy chain, 4F2, linked by a disulfide bridge. Intracellularly, cystine is reduced into cysteine, the rate-limiting precursor of glutathione (GSH), an important small molecule antioxidant. Several lines of evidence suggest that the expression of xCT and thereby the presence system x(c)(-) activity plays an important role in the brain. First, it regulates extracellular glutamate concentrations. Second, as brain is prone to oxidative stress due to its high oxygen consumption and lipid content, system x(c)(-) by favoring GSH synthesis, may prevent oxidative damage. Thus, to understand how xCT expression and system x(c)(-) activity are regulated in the central nervous system is of utmost importance. In this review, we will summarize the current knowledge about the molecular basis by which xCT expression and system x(c)(-) activity are regulated in neuronal cell lines, especially the hippocampal cell line, HT22. In addition, we will relate these pathways to findings in other cell types, especially those found in the central nervous system. We will focus on the signaling pathways that modulate the transcription of the xCT gene. Furthermore, we describe possible pathways that modify system x(c)(-) activity beyond the level of xCT transcription, including regulation on the level of membrane trafficking and substrate availability, especially the regulation by glutamate transport through excitatory amino acid transporters.
Collapse
Affiliation(s)
- Jan Lewerenz
- Department of Neurology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20241, Hamburg, Germany.
| | | | | |
Collapse
|