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Takeda A. [Brain Function and Pathophysiology Focused on Zn 2+ Dynamics]. YAKUGAKU ZASSHI 2022; 142:855-866. [PMID: 35908946 DOI: 10.1248/yakushi.22-00074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The basal levels of intracellular Zn2+ and extracellular Zn2+ are in the range of ~100 pM and ~10 nM, respectively, in the brain. Extracellular Zn2+ dynamics is involved in both cognitive performance and neurodegeneration. The bidirectional actions are linked with extracellular glutamate and amyloid-β1-42 (Aβ1-42). Intracellular Zn2+ signaling via extracellular glutamate is required for learning and memory, while intracellular Zn2+ dysregulation induces cognitive decline. Furthermore, human Aβ1-42, a causative peptide in Alzheimer's disease pathogenesis captures extracellular Zn2+ and readily taken up into hippocampal neurons followed by intracellular Zn2+ dysregulation. Aβ1-42-mediated intracellular Zn2+ dysregulation is accelerated with aging, because extracellular Zn2+ is age-relatedly increased, resulting in Aβ1-42-induced cognitive decline and neurodegeneration with aging. On the other hand, metallothioneins, zinc-binding proteins can capture Zn2+ released from intracellular Zn-Aβ1-42 complexes and serve for intracellular Zn2+-buffering to maintain intracellular Zn2+ homeostasis. This review summarizes Zn2+ function and its neurotoxicity in the brain, and also the potential defense strategy via metallothioneins against Aβ1-42-induced pathogenesis.
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Affiliation(s)
- Atsushi Takeda
- School of Pharmaceutical Sciences, University of Shizuoka
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2
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Feijó GDS, Jantsch J, Correia LL, Eller S, Furtado-Filho OV, Giovenardi M, Porawski M, Braganhol E, Guedes RP. Neuroinflammatory responses following zinc or branched-chain amino acids supplementation in obese rats. Metab Brain Dis 2022; 37:1875-1886. [PMID: 35556196 DOI: 10.1007/s11011-022-00996-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 04/27/2022] [Indexed: 11/24/2022]
Abstract
The excessive production of pro-inflammatory mediators, characteristic of obesity, leads to neuroinflammation. Zinc (Zn) and the branched-chain amino acids (BCAA) are supplements known for their immunomodulatory properties. Our goal was to evaluate if Zn or BCAA supplementation can affect long-term recognition memory and neuroinflammatory parameters of obese rats after a high-fat diet (HFD). Three-month-old Wistar rats were divided into six groups: Standard diet (SD) + vehicle; SD + Zn; SD + BCAA; High-fat diet (HFD) + vehicle; HFD + Zn; and HFD + BCAA. Diets were administrated for 19 weeks, Zn (1,2 mg/kg/day) or BCAA (750 mg/kg/day) supplementation was conducted in the last 4 weeks. Long-term recognition memory was evaluated by the novel object recognition test. IL-1β immunoreactivity in the cortex and hippocampus, and IL-6 levels in the cortex tissue were assessed. Astrogliosis were evaluated through GFAP + cell count and morphological analysis (Sholl Method). Zn supplementation improved object recognition memory in HFD-fed rats, which was not observed following BCAA supplementation. The levels of IL-6 in the cerebral cortex were higher after HFD, which was not diminished after neither supplementation. Obesity also led to increased IL-1β immunoreactivity in the cerebral cortex and hippocampus, which was reduced by Zn. BCAA supplementation also diminished IL-1β immunoreactivity, but only in the hippocampus. We also showed that astrocyte reactivity caused by HFD is area-dependent, being the cerebral cortex more susceptible to the diet. Even though BCAA and Zn can affect IL-1β immunoreactivity and astrocyte morphology, only Zn improved memory. Future studies are needed to clarify the pathways by which Zn improves cognition in obesity.
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Affiliation(s)
- Grace Dos Santos Feijó
- Programa de Pós-Graduação Em Biociências, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Brazil
| | - Jeferson Jantsch
- Programa de Pós-Graduação Em Biociências, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Brazil
| | - Lidia Luz Correia
- Federal University of Health Sciences of Porto Alegre, Porto Alegre, RS, 90050-170, Brazil
| | - Sarah Eller
- Programa de Pós-Graduação Em Patologia, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Brazil
| | - Orlando Vieira Furtado-Filho
- Programa de Pós-Graduação Em Biociências, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Brazil
| | - Márcia Giovenardi
- Programa de Pós-Graduação Em Biociências, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Brazil
- Programa de Pós-Graduação Em Ciências da Saúde, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite 245, 308 C, Porto Alegre, RS, 90050-170, Brazil
| | - Marilene Porawski
- Programa de Pós-Graduação Em Biociências, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Brazil
| | - Elizandra Braganhol
- Programa de Pós-Graduação Em Biociências, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Brazil
- Programa de Pós-Graduação Em Ciências da Saúde, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite 245, 308 C, Porto Alegre, RS, 90050-170, Brazil
| | - Renata Padilha Guedes
- Programa de Pós-Graduação Em Biociências, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Brazil.
- Programa de Pós-Graduação Em Ciências da Saúde, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite 245, 308 C, Porto Alegre, RS, 90050-170, Brazil.
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3
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Kudryashova IV. The Reorganization of the Actin Matrix as a Factor of Presynaptic Plasticity. NEUROCHEM J+ 2021. [DOI: 10.1134/s1819712421030089] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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4
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Sato Y, Takiguchi M, Tamano H, Takeda A. Extracellular Zn 2+-Dependent Amyloid-β 1-42 Neurotoxicity in Alzheimer's Disease Pathogenesis. Biol Trace Elem Res 2021; 199:53-61. [PMID: 32281074 DOI: 10.1007/s12011-020-02131-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 03/23/2020] [Indexed: 02/07/2023]
Abstract
The basal level of extracellular Zn2+ is in the range of low nanomolar (~ 10 nM) in the hippocampus. However, extracellular Zn2+ dynamics plays a key role for not only cognitive activity but also cognitive decline. Extracellular Zn2+ dynamics is modified by glutamatergic synapse excitation and the presence of amyloid-β1-42 (Aβ1-42), a causative peptide in Alzheimer's disease (AD). When human Aβ1-42 reaches high picomolar (> 100 pM) in the extracellular compartment of the rat dentate gyrus, Zn-Aβ1-42 complexes are readily formed and taken up into dentate granule cells, followed by Aβ1-42-induced cognitive decline that is linked with Zn2+ released from intracellular Zn-Aβ1-42 complexes. Aβ1-42-induced intracellular Zn2+ toxicity is accelerated with aging because of age-related increase in extracellular Zn2+. The recent findings suggest that Aβ1-42 secreted continuously from neuron terminals causes age-related cognitive decline and neurodegeneration via intracellular Zn2+ dysregulation. On the other hand, metallothioneins (MTs), zinc-binding proteins, quickly serve for intracellular Zn2+-buffering under acute intracellular Zn2+ dysregulation. On the basis of the idea that the defense strategy against Aβ1-42-induced pathogenesis leads to preventing the AD development, this review deals with extracellular Zn2+-dependent Aβ1-42 neurotoxicity, which is accelerated with aging.
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Affiliation(s)
- Yuichi Sato
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Mako Takiguchi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan.
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5
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Wiqas A, LeSauter J, Taub A, Austin RN, Silver R. Elevated zinc transporter ZnT3 in the dentate gyrus of mast cell-deficient mice. Eur J Neurosci 2019; 51:1504-1513. [PMID: 31502721 DOI: 10.1111/ejn.14575] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 07/01/2019] [Accepted: 07/25/2019] [Indexed: 11/27/2022]
Abstract
Zinc is important in neurogenesis, but excessive levels can cause apoptosis and other pathologies leading to cognitive impairments. Mast cells are present in many brain regions including the hippocampus, an area rich in vesicular zinc. Mast cells contain zinc-rich granules and a well-developed mechanism for uptake of zinc ions; both features point to the potential for a role in zinc homeostasis. Prior work using the Timm stain supported this hypothesis, as increased labile zinc was detected in the hippocampus of mast cell-deficient mice compared to wild-type mice while no differences in total zinc were found between the two genotypes in the whole brain or other tissues. The current report further examines differences in zinc homeostasis between wild-type and mast cell-deficient mice by exploring the zinc transporter ZnT3, which transports labile zinc into synaptic vesicles. The first study used immunocytochemistry to localize ZnT3 within the mossy fibre layer of the hippocampus to determine whether there was differential expression of ZnT3 in wild-type versus mast cell-deficient mice. The second study used inductively coupled plasma mass spectrometry (ICP-MS) to determine total zinc content in the whole dentate gyrus of the two genotypes. The immunocytochemical results indicate that there are higher levels of ZnT3 localized to the mossy fibre layer of the dentate gyrus of mast cell-deficient mice than in wild-type mice. The ICP-MS data reveal no differences in total zinc in dentate gyrus as a whole. The results are consistent with the hypothesis that mast cells participate in zinc homeostasis at the level of synaptic vesicles.
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Affiliation(s)
- Amen Wiqas
- Department of Biology, Barnard College, Columbia University, New York, New York
| | - Joseph LeSauter
- Department of Neuroscience, Barnard College, Columbia University, New York, New York
| | - Alana Taub
- Department of Psychology, Columbia University, New York, New York
| | | | - Rae Silver
- Department of Neuroscience, Barnard College, Columbia University, New York, New York.,Department of Psychology, Columbia University, New York, New York
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6
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Kudryashova IV. The Molecular Basis of Destabilization of Synapses as a Factor of Structural Plasticity. NEUROCHEM J+ 2019. [DOI: 10.1134/s1819712419010136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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7
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Neely CLC, Lippi SLP, Lanzirotti A, Flinn JM. Localization of Free and Bound Metal Species through X-Ray Synchrotron Fluorescence Microscopy in the Rodent Brain and Their Relation to Behavior. Brain Sci 2019; 9:brainsci9040074. [PMID: 30925761 PMCID: PMC6523809 DOI: 10.3390/brainsci9040074] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 03/23/2019] [Accepted: 03/26/2019] [Indexed: 12/27/2022] Open
Abstract
Biometals in the brain, such as zinc, copper, and iron, are often discussed in cases of neurological disorders; however, these metals also have important regulatory functions and mediate cell signaling and plasticity. With the use of synchrotron X-ray fluorescence, our lab localized total, both bound and free, levels of zinc, copper, and iron in a cross section of one hemisphere of a rat brain, which also showed differing metal distributions in different regions within the hippocampus, the site in the brain known to be crucial for certain types of memory. This review discusses the several roles of these metals in brain regions with an emphasis on hippocampal cell signaling, based on spatial mapping obtained from X-ray fluorescence microscopy. We also discuss the localization of these metals and emphasize different cell types and receptors in regions with metal accumulation, as well as the potential relationship between this physiology and behavior.
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Affiliation(s)
- Caroline L C Neely
- Department of Psychology, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA.
| | - Stephen L P Lippi
- Department of Psychology & Sociology, Angelo State University, 2601 W. Avenue N, ASU Station #10907, San Angelo, TX 76909, USA.
| | - Antonio Lanzirotti
- Center for Advanced Radiation Sources, University of Chicago, 9700 South Cass Avenue, Argonne, IL 60439, USA.
| | - Jane M Flinn
- Department of Psychology, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA.
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8
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Amyloid β1–42-Induced Rapid Zn2+ Influx into Dentate Granule Cells Attenuates Maintained LTP Followed by Retrograde Amnesia. Mol Neurobiol 2018; 56:5041-5050. [DOI: 10.1007/s12035-018-1429-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 11/13/2018] [Indexed: 12/30/2022]
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9
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Takeda A, Tamano H. Is Vulnerability of the Dentate Gyrus to Aging and Amyloid-β 1-42 Neurotoxicity Linked with Modified Extracellular Zn 2+ Dynamics? Biol Pharm Bull 2018; 41:995-1000. [PMID: 29962410 DOI: 10.1248/bpb.b17-00871] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The basal levels of extracellular Zn2+ are in the range of low nanomolar concentrations in the hippocampus and perhaps increase age-dependently. Extracellular Zn2+ dynamics is critical for cognitive activity and excess influx of extracellular Zn2+ into hippocampal neurons is a known cause of cognitive decline. The dentate gyrus is vulnerable to aging in the hippocampus and affected in the early stage of Alzheimer's disease (AD). The reasons remain unclear. Neurogenesis-related apoptosis may induce non-specific neuronal depolarization by efflux of intracellular K+ in the dentate gyrus and be markedly increased along with aging. Extracellular Zn2+ influx into dentate granule cells via high K+-induced perforant pathway excitation leads to cognitive decline. Modified extracellular Zn2+ dynamics in the dentate gyrus of aged rats is linked with vulnerability to cognitive decline. Amyloid-β1-42 (Aβ1-42) is a causative candidate for AD pathogenesis. When Aβ1-42 concentration reaches picomolar in the extracellular compartment in the dentate gyrus, Zn-Aβ1-42 is formed in the extracellular compartment and rapidly taken up into dentate granule cells, followed by Aβ1-42-induced cognitive decline that is due to Zn2+ released from Aβ1-42, suggesting that dentate granule cells are sensitive to extracellular Zn2+-dependent Aβ1-42 toxicity. This paper deals with proposed vulnerability of the dentate gyrus to aging and Aβ1-42 neurotoxicity.
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Affiliation(s)
- Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka
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10
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Zinc Signal in Brain Diseases. Int J Mol Sci 2017; 18:ijms18122506. [PMID: 29168792 PMCID: PMC5751109 DOI: 10.3390/ijms18122506] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 11/15/2017] [Accepted: 11/16/2017] [Indexed: 12/14/2022] Open
Abstract
The divalent cation zinc is an integral requirement for optimal cellular processes, whereby it contributes to the function of over 300 enzymes, regulates intracellular signal transduction, and contributes to efficient synaptic transmission in the central nervous system. Given the critical role of zinc in a breadth of cellular processes, its cellular distribution and local tissue level concentrations remain tightly regulated via a series of proteins, primarily including zinc transporter and zinc import proteins. A loss of function of these regulatory pathways, or dietary alterations that result in a change in zinc homeostasis in the brain, can all lead to a myriad of pathological conditions with both acute and chronic effects on function. This review aims to highlight the role of zinc signaling in the central nervous system, where it may precipitate or potentiate diverse issues such as age-related cognitive decline, depression, Alzheimer's disease or negative outcomes following brain injury.
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11
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Takeda A, Tamano H. The Impact of Synaptic Zn 2+ Dynamics on Cognition and Its Decline. Int J Mol Sci 2017; 18:ijms18112411. [PMID: 29135924 PMCID: PMC5713379 DOI: 10.3390/ijms18112411] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 10/31/2017] [Accepted: 11/09/2017] [Indexed: 11/16/2022] Open
Abstract
The basal levels of extracellular Zn2+ are in the range of low nanomolar concentrations and less attention has been paid to Zn2+, compared to Ca2+, for synaptic activity. However, extracellular Zn2+ is necessary for synaptic activity. The basal levels of extracellular zinc are age-dependently increased in the rat hippocampus, implying that the basal levels of extracellular Zn2+ are also increased age-dependently and that extracellular Zn2+ dynamics are linked with age-related cognitive function and dysfunction. In the hippocampus, the influx of extracellular Zn2+ into postsynaptic neurons, which is often linked with Zn2+ release from neuron terminals, is critical for cognitive activity via long-term potentiation (LTP). In contrast, the excess influx of extracellular Zn2+ into postsynaptic neurons induces cognitive decline. Interestingly, the excess influx of extracellular Zn2+ more readily occurs in aged dentate granule cells and intracellular Zn2+-buffering, which is assessed with ZnAF-2DA, is weakened in the aged dentate granule cells. Characteristics (easiness) of extracellular Zn2+ influx seem to be linked with the weakened intracellular Zn2+-buffering in the aged dentate gyrus. This paper deals with the impact of synaptic Zn2+ signaling on cognition and its decline in comparison with synaptic Ca2+ signaling.
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Affiliation(s)
- Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
| | - Hanuna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
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Takeda A, Tamano H, Murakami T, Nakada H, Minamino T, Koike Y. Weakened Intracellular Zn 2+-Buffering in the Aged Dentate Gyrus and Its Involvement in Erasure of Maintained LTP. Mol Neurobiol 2017; 55:3856-3865. [PMID: 28547527 DOI: 10.1007/s12035-017-0615-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 05/11/2017] [Indexed: 11/24/2022]
Abstract
Memory is lost by the increased influx of extracellular Zn2+ into neurons. It is possible that intracellular Zn2+ dynamics is modified even at non-zincergic medial perforant pathway-dentate granule cell synapses along with aging and that vulnerability to the modification is linked to age-related cognitive decline. To examine these possibilities, vulnerability of long-term potentiation (LTP) maintenance, which underlies memory retention, to modification of synaptic Zn2+ dynamics was compared between young and aged rats. The influx of extracellular Zn2+ into dentate granule cells was increased in aged rats after injection of high K+ into the dentate gyrus, but not in young rats. This increase impaired maintained LTP in aged rats. However, the impairment was rescued by co-injection of CaEDTA, an extracellular Zn2+ chelator, or CNQX, an AMPA receptor antagonist, which suppressed the Zn2+ influx. Maintained LTP was also impaired in aged rats after injection of ZnAF-2DA into the dentate gyrus that chelates intracellular Zn2+, but not in young rats. Interestingly, the capacity of chelating intracellular Zn2+ with intracellular ZnAF-2 was almost lost in the aged dentate gyrus 2 h after injection of ZnAF-2DA into the dentate gyrus, suggesting that intracellular Zn2+-buffering is weakened in the aged dentate gyrus, compared to the young dentate gyrus. In the dentate gyrus of aged rats, maintained LTP is more vulnerable to modification of intracellular Zn2+ dynamics than in young rats, probably due to weakened intracellular Zn2+-buffering.
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Affiliation(s)
- Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan.
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Taku Murakami
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Hiroyuki Nakada
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Tatsuya Minamino
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Yuta Koike
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
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13
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Tamano H, Nishio R, Takeda A. Involvement of intracellular Zn 2+ signaling in LTP at perforant pathway-CA1 pyramidal cell synapse. Hippocampus 2017; 27:777-783. [PMID: 28380662 DOI: 10.1002/hipo.22730] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/28/2017] [Accepted: 03/29/2017] [Indexed: 11/06/2022]
Abstract
Physiological significance of synaptic Zn2+ signaling was examined at perforant pathway-CA1 pyramidal cell synapses. In vivo long-term potentiation (LTP) at perforant pathway-CA1 pyramidal cell synapses was induced using a recording electrode attached to a microdialysis probe and the recording region was locally perfused with artificial cerebrospinal fluid (ACSF) via the microdialysis probe. Perforant pathway LTP was not attenuated under perfusion with CaEDTA (10 mM), an extracellular Zn2+ chelator, but attenuated under perfusion with ZnAF-2DA (50 μM), an intracellular Zn2+ chelator, suggesting that intracellular Zn2+ signaling is required for perforant pathway LTP. Even in rat brain slices bathed in CaEDTA in ACSF, intracellular Zn2+ level, which was measured with intracellular ZnAF-2, was increased in the stratum lacunosum-moleculare where perforant pathway-CA1 pyramidal cell synapses were contained after tetanic stimulation. These results suggest that intracellular Zn2+ signaling, which originates in internal stores/proteins, is involved in LTP at perforant pathway-CA1 pyramidal cell synapses. Because the influx of extracellular Zn2+ , which originates in presynaptic Zn2+ release, is involved in LTP at Schaffer collateral-CA1 pyramidal cell synapses, synapse-dependent Zn2+ dynamics may be involved in plasticity of postsynaptic CA1 pyramidal cells.
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Affiliation(s)
- Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Ryusuke Nishio
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
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14
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Tamano H, Nishio R, Shakushi Y, Sasaki M, Koike Y, Osawa M, Takeda A. In vitro and in vivo physiology of low nanomolar concentrations of Zn 2+ in artificial cerebrospinal fluid. Sci Rep 2017; 7:42897. [PMID: 28211543 PMCID: PMC5314341 DOI: 10.1038/srep42897] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/18/2017] [Indexed: 11/15/2022] Open
Abstract
Artificial cerebrospinal fluid (ACSF), i.e., brain extracellular medium, which includes Ca2+ and Mg2+, but not other divalent cations such as Zn2+, has been used for in vitro and in vivo experiments. The present study deals with the physiological significance of extracellular Zn2+ in ACSF. Spontaneous presynaptic activity is suppressed in the stratum lucidum of brain slices from young rats bathed in ACSF containing 10 nM ZnCl2, indicating that extracellular Zn2+ modifies hippocampal presynaptic activity. To examine the in vivo action of 10 nM ZnCl2 on long-term potentiation (LTP), the recording region was perfused using a recording electrode attached to a microdialysis probe. The magnitude of LTP was not modified in young rats by perfusion with ACSF containing 10 nM ZnCl2, compared to perfusion with ACSF without Zn2+, but attenuated by perfusion with ACSF containing 100 nM ZnCl2. Interestingly, the magnitude of LTP was not modified in aged rats even by perfusion with ACSF containing 100 nM ZnCl2, but enhanced by perfusion with ACSF containing 10 mM CaEDTA, an extracellular Zn2+ chelator. The present study indicates that the basal levels of extracellular Zn2+, which are in the range of low nanomolar concentrations, are critical for synaptic activity and perhaps increased age-dependently.
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Affiliation(s)
- Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Ryusuke Nishio
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Yukina Shakushi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Miku Sasaki
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Yuta Koike
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Misa Osawa
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
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Maintained LTP and Memory Are Lost by Zn 2+ Influx into Dentate Granule Cells, but Not Ca 2+ Influx. Mol Neurobiol 2017; 55:1498-1508. [PMID: 28176276 DOI: 10.1007/s12035-017-0428-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Accepted: 01/26/2017] [Indexed: 12/21/2022]
Abstract
The idea that maintained LTP and memory are lost by either increase in intracellular Zn2+ in dentate granule cells or increase in intracellular Ca2+ was examined to clarify significance of the increases induced by excess synapse excitation. Both maintained LTP and space memory were impaired by injection of high K+ into the dentate gyrus, but rescued by co-injection of CaEDTA, which blocked high K+-induced increase in intracellular Zn2+ but not high K+-induced increase in intracellular Ca2+. High K+-induced disturbances of LTP and intracellular Zn2+ are rescued by co-injection of 6-cyano-7-nitroquinoxakine-2,3-dione, an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor antagonist, but not by co-injection of blockers of NMDA receptors, metabotropic glutamate receptors, and voltage-dependent calcium channels. Furthermore, AMPA impaired maintained LTP and the impairment was also rescued by co-injection of CaEDTA, which blocked increase in intracellular Zn2+, but not increase in intracellular Ca2+. NMDA and glucocorticoid, which induced Zn2+ release from the internal stores, did not impair maintained LTP. The present study indicates that increase in Zn2+ influx into dentate granule cells through AMPA receptors loses maintained LTP and memory. Regulation of Zn2+ influx into dentate granule cells is more critical for not only memory acquisition but also memory retention than that of Ca2+ influx.
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16
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Shetty MS, Sharma M, Sajikumar S. Chelation of hippocampal zinc enhances long-term potentiation and synaptic tagging/capture in CA1 pyramidal neurons of aged rats: implications to aging and memory. Aging Cell 2017; 16:136-148. [PMID: 27633878 PMCID: PMC5242293 DOI: 10.1111/acel.12537] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/18/2016] [Indexed: 01/08/2023] Open
Abstract
Aging is associated with decline in cognitive functions, prominently in the memory consolidation and association capabilities. Hippocampus plays a crucial role in the formation and maintenance of long‐term associative memories, and a significant body of evidence shows that impairments in hippocampal function correlate with aging‐related memory loss. A number of studies have implicated alterations in hippocampal synaptic plasticity, such as long‐term potentiation (LTP), in age‐related cognitive decline although exact mechanisms underlying are not completely clear. Zinc deficiency and the resultant adverse effects on cognition have been well studied. However, the role of excess of zinc in synaptic plasticity, especially in aging, is not addressed well. Here, we have investigated the hippocampal zinc levels and the impairments in synaptic plasticity, such as LTP and synaptic tagging and capture (STC), in the CA1 region of acute hippocampal slices from 82‐ to 84‐week‐old male Wistar rats. We report increased zinc levels in the hippocampus of aged rats and also deficits in the tetani‐induced and dopaminergic agonist‐induced late‐LTP and STC. The observed deficits in synaptic plasticity were restored upon chelation of zinc using a cell‐permeable chelator. These data suggest that functional plasticity and associativity can be successfully established in aged neural networks by chelating zinc with cell‐permeable chelating agents.
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Affiliation(s)
- Mahesh Shivarama Shetty
- Department of Physiology; Yong Loo Lin School of Medicine; National University of Singapore; Block MD9, 2 Medical Drive Singapore 117 597 Singapore
- Neurobiology/Aging Program; Life Sciences Institute (LSI); National University of Singapore; #04-44, 28 Medical Drive Singapore 117 456 Singapore
| | - Mahima Sharma
- Department of Physiology; Yong Loo Lin School of Medicine; National University of Singapore; Block MD9, 2 Medical Drive Singapore 117 597 Singapore
- Neurobiology/Aging Program; Life Sciences Institute (LSI); National University of Singapore; #04-44, 28 Medical Drive Singapore 117 456 Singapore
| | - Sreedharan Sajikumar
- Department of Physiology; Yong Loo Lin School of Medicine; National University of Singapore; Block MD9, 2 Medical Drive Singapore 117 597 Singapore
- Neurobiology/Aging Program; Life Sciences Institute (LSI); National University of Singapore; #04-44, 28 Medical Drive Singapore 117 456 Singapore
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17
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Takeda A, Tamano H. New Insight into Metallomics in Cognition. Metallomics 2017. [DOI: 10.1007/978-4-431-56463-8_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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18
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Takeda A, Tamano H. Innervation from the entorhinal cortex to the dentate gyrus and the vulnerability to Zn 2. J Trace Elem Med Biol 2016; 38:19-23. [PMID: 27267970 DOI: 10.1016/j.jtemb.2016.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 05/20/2016] [Accepted: 05/23/2016] [Indexed: 11/30/2022]
Abstract
Hippocampal Zn2+ homeostasis is critical for cognitive activity and hippocampus-dependent memory. Extracellular Zn2+ signaling is linked to extracellular glutamate signaling and leads to intracellular Zn2+ signaling, which is involved in cognitive activity. On the other hand, excess intracellular Zn2+ signaling that is induced by excess glutamate signaling is involved in cognitive decline. In the hippocampal formation, the dentate gyrus is the most vulnerable to aging and is thought to contribute to age-related cognitive decline. The layer II of the entorhinal cortex is the most vulnerable to neuronal death in Alzheimer's disease. The perforant pathway provides input from the layer II to the dentate gyrus and is one of the earliest affected pathways in Alzheimer's disease. Medial perforant pathway-dentate granule cell synapses are vulnerable to either excess intracellular Zn2+ or β-amyloid (Aβ)-bound zinc, which induce transient cognitive decline via attenuation of medial perforant pathway LTP. However, it is unknown whether the vulnerability to excess intracellular Zn2+ is involved in region-specific vulnerability to aging and Alzheimer's disease. To discover a strategy to prevent short-term cognitive decline in normal aging process and the pre-dementia stage of Alzheimer's disease, the present paper deals with vulnerability of medial perforant pathway-dentate granule cell synapses to intracellular Zn2+ dyshomeostasis and its possible involvement in differential vulnerability to aging and Alzheimer's disease in the hippocampal formation.
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Affiliation(s)
- Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
| | - Hanuna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
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19
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Tamano H, Koike Y, Nakada H, Shakushi Y, Takeda A. Significance of synaptic Zn 2+ signaling in zincergic and non-zincergic synapses in the hippocampus in cognition. J Trace Elem Med Biol 2016; 38:93-98. [PMID: 26995290 DOI: 10.1016/j.jtemb.2016.03.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/07/2016] [Accepted: 03/07/2016] [Indexed: 11/24/2022]
Abstract
A portion of zinc concentrates in the synaptic vesicles in the brain and is released from glutamatergic (zincergic) neuron terminals. It serves as a signaling factor (in a form of free Zn2+). Both extracellular Zn2+ signaling, which predominantly originates in Zn2+ release from zincergic neuron terminals, and intracellular Zn2+ signaling, which is often linked to extracellular Zn2+ signaling, are involved in hippocampus-dependent memory. At mossy fiber-CA3 pyramidal cell synapses and Schaffer collateral-CA1 pyramidal cell synapses, which are zincergic, extracellular Zn2+ signaling leads to intracellular Zn2+ signaling and is involved in learning and memory. At medial perforant pathway-dentate granule cell synapses, which are non-zincergic, intracellular Zn2+ signaling, which originates in the internal stores containing Zn2+, is involved in learning and memory. The blockade of Zn2+ signaling with Zn2+ chelators induces memory deficit, while the optimal amount range of Zn2+ signaling is unknown. It is possible that the degree and frequency of Zn2+ signaling, which determine the increased Zn2+ levels, modulates learning and memory as well as intracellular Ca2+ signaling. To understand the precise role of synaptic Zn2+ signaling in the hippocampus, the present paper summarizes the current knowledge on Zn2+ signaling at zincergic and non-zincergic synapses in the hippocampus in cognition and involvement of zinc transporters and zinc-binding proteins in synaptic Zn2+ signaling.
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Affiliation(s)
- Hanuna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Yuta Koike
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Hiroyuki Nakada
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Yukina Shakushi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
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20
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Choi BY, Kim IY, Kim JH, Lee BE, Lee SH, Kho AR, Sohn M, Suh SW. Zinc plus cyclo-(His-Pro) promotes hippocampal neurogenesis in rats. Neuroscience 2016; 339:634-643. [DOI: 10.1016/j.neuroscience.2016.10.035] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 09/23/2016] [Accepted: 10/12/2016] [Indexed: 10/20/2022]
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21
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Yang K, Broussard JI, Levine AT, Jenson D, Arenkiel BR, Dani JA. Dopamine receptor activity participates in hippocampal synaptic plasticity associated with novel object recognition. Eur J Neurosci 2016; 45:138-146. [PMID: 27646422 DOI: 10.1111/ejn.13406] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 09/14/2016] [Accepted: 09/16/2016] [Indexed: 01/24/2023]
Abstract
Physiological and behavioral evidence supports that dopamine (DA) receptor signaling influences hippocampal function. While several recent studies examined how DA influences CA1 plasticity and learning, there are fewer studies investigating the influence of DA signaling to the dentate gyrus. The dentate gyrus receives convergent cortical input through the perforant path fiber tracts and has been conceptualized to detect novelty in spatial memory tasks. To test whether DA-receptor activity influences novelty-detection, we used a novel object recognition (NOR) task where mice remember previously presented objects as an indication of learning. Although DA innervation arises from other sources and the main DA signaling may be from those sources, our molecular approaches verified that midbrain dopaminergic fibers also sparsely innervate the dentate gyrus. During the NOR task, wild-type mice spent significantly more time investigating novel objects rather than previously observed objects. Dentate granule cells in slices cut from those mice showed an increased AMPA/NMDA-receptor current ratio indicative of potentiated synaptic transmission. Post-training injection of a D1-like receptor antagonist not only effectively blocked the preference for the novel objects, but also prevented the increased AMPA/NMDA ratio. Consistent with that finding, neither NOR learning nor the increase in the AMPA/NMDA ratio were observed in DA-receptor KO mice under the same experimental conditions. The results indicate that DA-receptor signaling contributes to the successful completion of the NOR task and to the associated synaptic plasticity of the dentate gyrus that likely contributes to the learning.
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Affiliation(s)
- Kechun Yang
- Department of Neuroscience, Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - John I Broussard
- Department of Neuroscience, Center on Addiction, Learning, Memory, Baylor College of Medicine, Houston, TX, USA
| | - Amber T Levine
- Department of Neuroscience, Center on Addiction, Learning, Memory, Baylor College of Medicine, Houston, TX, USA
| | - Daniel Jenson
- Department of Neuroscience, Center on Addiction, Learning, Memory, Baylor College of Medicine, Houston, TX, USA
| | - Benjamin R Arenkiel
- Program in Developmental Biology, Jan and Dan Duncan Neurological Research Institute, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA
| | - John A Dani
- Department of Neuroscience, Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
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22
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Albayram Ö, Passlick S, Bilkei-Gorzo A, Zimmer A, Steinhäuser C. Physiological impact of CB1 receptor expression by hippocampal GABAergic interneurons. Pflugers Arch 2016; 468:727-37. [DOI: 10.1007/s00424-015-1782-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 12/20/2015] [Accepted: 12/22/2015] [Indexed: 10/22/2022]
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23
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Takeda A, Tamano H. Significance of the degree of synaptic Zn2+ signaling in cognition. Biometals 2015; 29:177-85. [DOI: 10.1007/s10534-015-9907-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 12/17/2015] [Indexed: 11/24/2022]
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24
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Takeda A, Suzuki M, Tempaku M, Ohashi K, Tamano H. Influx of extracellular Zn(2+) into the hippocampal CA1 neurons is required for cognitive performance via long-term potentiation. Neuroscience 2015. [PMID: 26204819 DOI: 10.1016/j.neuroscience.2015.07.042] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Physiological significance of synaptic Zn(2+) signaling was examined in the CA1 of young rats. In vivo CA1 long-term potentiation (LTP) was induced using a recording electrode attached to a microdialysis probe and the recording region was locally perfused with artificial cerebrospinal fluid (ACSF) via the microdialysis probe. In vivo CA1 LTP was inhibited under perfusion with CaEDTA and ZnAF-2DA, extracellular and intracellular Zn(2+) chelators, respectively, suggesting that the influx of extracellular Zn(2+) is required for in vivo CA1 LTP induction. The increase in intracellular Zn(2+) was chelated with intracellular ZnAF-2 in the CA1 1h after local injection of ZnAF-2DA into the CA1, suggesting that intracellular Zn(2+) signaling induced during learning is blocked with intracellular ZnAF-2 when the learning was performed 1h after ZnAF-2DA injection. Object recognition was affected when training of object recognition test was performed 1h after ZnAF-2DA injection. These data suggest that intracellular Zn(2+) signaling in the CA1 is required for object recognition memory via LTP. Surprisingly, in vivo CA1 LTP was affected under perfusion with 0.1-1μM ZnCl2, unlike the previous data that in vitro CA1 LTP was enhanced in the presence of 1-5μM ZnCl2. The influx of extracellular Zn(2+) into CA1 pyramidal cells has bidirectional action in CA1 LTP. The present study indicates that the degree of extracellular Zn(2+) influx into CA1 neurons is critical for LTP and cognitive performance.
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Affiliation(s)
- A Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
| | - M Suzuki
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - M Tempaku
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - K Ohashi
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - H Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
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25
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Suzuki M, Fujise Y, Tsuchiya Y, Tamano H, Takeda A. Excess influx of Zn(2+) into dentate granule cells affects object recognition memory via attenuated LTP. Neurochem Int 2015; 87:60-5. [PMID: 26044210 DOI: 10.1016/j.neuint.2015.05.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 04/21/2015] [Accepted: 05/26/2015] [Indexed: 10/23/2022]
Abstract
The influx of extracellular Zn(2+) into dentate granule cells is nonessential for dentate gyrus long-term potentiation (LTP) and the physiological significance of extracellular Zn(2+) dynamics is unknown in the dentate gyrus. Excess increase in extracellular Zn(2+) in the hippocampal CA1, which is induced with excitation of zincergic neurons, induces memory deficit via excess influx of Zn(2+) into CA1 pyramidal cells. In the present study, it was examined whether extracellular Zn(2+) induces object recognition memory deficit via excess influx of Zn(2+) into dentate granule cells. KCl (100 mM, 2 µl) was locally injected into the dentate gyrus. The increase in intracellular Zn(2+) in dentate granule cells induced with high K(+) was blocked by co-injection of CaEDTA and CNQX, an extracellular Zn(2+) chelator and an AMPA receptor antagonist, respectively, suggesting that high K(+) increases the influx of Zn(2+) into dentate granule cells via AMPA receptor activation. Dentate gyrus LTP induction was attenuated 1 h after KCl injection into the dentate gyrus and also attenuated when KCl was injected 5 min after the induction. Memory deficit was induced when training of object recognition test was performed 1 h after KCl injection into the dentate gyrus and also induced when KCl was injected 5 min after the training. High K(+)-induced impairments of LTP and memory were rescued by co-injection of CaEDTA. These results indicate that excess influx of Zn(2+) into dentate granule cells via AMPA receptor activation affects object recognition memory via attenuated LTP induction. Even in the dentate gyrus where is scarcely innervated by zincergic neurons, it is likely that extracellular Zn(2+) homeostasis is strictly regulated for cognition.
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Affiliation(s)
- Miki Suzuki
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Yuki Fujise
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Yuka Tsuchiya
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Haruna Tamano
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Atsushi Takeda
- Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
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