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Baranovicova E, Kalenska D, Kovalska M, Lehotsky J. Hippocampal metabolic recovery as a manifestation of the protective effect of ischemic preconditioning in rats. Neurochem Int 2022; 160:105419. [PMID: 36113578 DOI: 10.1016/j.neuint.2022.105419] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 08/25/2022] [Accepted: 09/04/2022] [Indexed: 10/31/2022]
Abstract
The ever-present risk of brain ischemic events in humans and its full prevention make the detailed studies of an organism's response to ischemia at different levels essential to understanding the mechanism of the injury as well as protection. We used the four-vessel occlusion as an animal model of forebrain ischemia to investigate its impact on the metabolic alterations in both the hippocampus and the blood plasma to see changes on the systemic level. By inducing sublethal ischemic stimuli, we focused on the endogenous phenomena known as ischemic tolerance. NMR spectroscopy was used to analyze relative metabolite levels in tissue extracts from rats' hippocampus and blood plasma in three various ischemic/reperfusion times: 3 h, 24 h, and 72 h. Hippocampal tissues were characterized by postischemically decreased glutamate and GABA (4-aminobutyrate) tissue content balanced with increased glutamine level, with most pronounced changes at 3 h reperfusion time. Glutamate (as well as glutamine) levels recovered towards the control levels on the third day, as if the glutamate re-synthesis would be firstly preferred before GABA. These results are indicating the higher feasibility of re-establishing of glutamatergic transmission three days after an ischemic event, in contrast to GABA-ergic. Tissue levels of N-acetylaspartate (NAA), as well as choline, were decreased without the tendency to recover three days after the ischemic event. Metabolomic analysis of blood plasma revealed that ischemically preconditioned rats, contrary to the non-preconditioned animals, did not show hyperglycemic conditions. Ischemically induced semi-ketotic state, manifested in increased plasma ketone bodies 3-hydroxybutyrate and acetoacetate, seems to be programmed to support the brain tissue revitalization after the ischemic event. These and other metabolites changes found in blood plasma as well as in the hippocampus were observed to a lower extent or recovered faster in preconditioned animals. Some metabolomic changes in hippocampal tissue extract were so strong that even single metabolites were able to differentiate between ischemic, ischemically preconditioned, and control brain tissues.
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Affiliation(s)
- Eva Baranovicova
- Biomedical Center BioMed, Jessenius Faculty of Medicine, Comenius University in Bratislava, Mala Hora 4, 036 01, Martin, Slovakia
| | - Dagmar Kalenska
- Department of Anatomy, Jessenius Faculty of Medicine, Comenius University in Bratislava, Mala Hora 4, 036 01, Martin, Slovakia
| | - Maria Kovalska
- Department of Histology and Embryology, Jessenius Faculty of Medicine, Comenius University in Bratislava, Mala Hora 4, 036 01, Martin, Slovakia
| | - Jan Lehotsky
- Department of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University in Bratislava, Mala Hora 4, 036 01, Martin, Slovakia.
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Du Z, Song Y, Chen X, Zhang W, Zhang G, Li H, Chang L, Wu Y. Knockdown of astrocytic Grin2a aggravates β-amyloid-induced memory and cognitive deficits through regulating nerve growth factor. Aging Cell 2021; 20:e13437. [PMID: 34291567 PMCID: PMC8373273 DOI: 10.1111/acel.13437] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/14/2021] [Accepted: 07/03/2021] [Indexed: 12/14/2022] Open
Abstract
Synapse degeneration correlates strongly with cognitive impairments in Alzheimer's disease (AD) patients. Soluble Amyloid-beta (Aβ) oligomers are thought as the major trigger of synaptic malfunctions. Our earlier studies have demonstrated that Aβ oligomers interfere with synaptic function through N-methyl-D-aspartate receptors (NMDARs). Our recent in vitro study found the neuroprotective role of astrocytic GluN2A in the promotion of synapse survival and identified nerve growth factor (NGF) derived from astrocytes, as a likely mediator of astrocytic GluN2A buffering against Aβ synaptotoxicity. Our present in vivo study focused on exploring the precise mechanism of astrocytic GluN2A influencing Aβ synaptotoxicity through regulating NGF. We generated an adeno-associated virus (AAV) expressing an astrocytic promoter (GfaABC1D) shRNA targeted to Grin2a (the gene encoding GluN2A) to perform astrocyte-specific Grin2a knockdown in the hippocampal dentate gyrus, after 3 weeks of virus vector expression, Aβ were bilaterally injected into the intracerebral ventricle. Our results showed that astrocyte-specific knockdown of Grin2a and Aβ application both significantly impaired spatial memory and cognition, which associated with the reduced synaptic proteins PSD95, synaptophysin and compensatory increased NGF. The reduced astrocytic GluN2A can counteract Aβ-induced compensatory protective increase of NGF through regulating pNF-κB, Furin and VAMP3, which modulating the synthesis, mature and secretion of NGF respectively. Our present data reveal, for the first time, a novel mechanism of astrocytic GluN2A in exerting protective effects on synapses at the early stage of Aβ exposure, which may contribute to establish new targets for AD prevention and early therapy.
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Affiliation(s)
- Zunshu Du
- Beijing Key Laboratory of Neural Regeneration and Repair Department of Anatomy School of Basic Medical Sciences Beijing Institute of Brain Disorders Capital Medical University Beijing China
| | - Yizhi Song
- Beijing Key Laboratory of Neural Regeneration and Repair Department of Anatomy School of Basic Medical Sciences Beijing Institute of Brain Disorders Capital Medical University Beijing China
| | - Xinyue Chen
- Beijing Key Laboratory of Neural Regeneration and Repair Department of Anatomy School of Basic Medical Sciences Beijing Institute of Brain Disorders Capital Medical University Beijing China
| | - Wanning Zhang
- Beijing Key Laboratory of Neural Regeneration and Repair Department of Anatomy School of Basic Medical Sciences Beijing Institute of Brain Disorders Capital Medical University Beijing China
| | - Guitao Zhang
- Beijing Key Laboratory of Neural Regeneration and Repair Department of Anatomy School of Basic Medical Sciences Beijing Institute of Brain Disorders Capital Medical University Beijing China
| | - Hui Li
- Beijing Key Laboratory of Neural Regeneration and Repair Department of Anatomy School of Basic Medical Sciences Beijing Institute of Brain Disorders Capital Medical University Beijing China
| | - Lirong Chang
- Beijing Key Laboratory of Neural Regeneration and Repair Department of Anatomy School of Basic Medical Sciences Beijing Institute of Brain Disorders Capital Medical University Beijing China
| | - Yan Wu
- Beijing Key Laboratory of Neural Regeneration and Repair Department of Anatomy School of Basic Medical Sciences Beijing Institute of Brain Disorders Capital Medical University Beijing China
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Wang Z, Hou L, Wang D. Effects of exercise-induced fatigue on the morphology of asymmetric synapse and synaptic protein levels in rat striatum. Neurochem Int 2019; 129:104476. [PMID: 31145967 DOI: 10.1016/j.neuint.2019.104476] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 04/20/2019] [Accepted: 05/26/2019] [Indexed: 12/12/2022]
Abstract
Corticostriatal synaptic plasticity is considered to be a cellular basis for somatic motor regulation and motor skill learning. Changes in synaptic transmission efficiency underlie functional plasticity, while structural plasticity involves changes in the ultrastructure of the synapse and the levels of synaptic proteins. Exercise-induced fatigue may impair corticostriatal synaptic plasticity, and this impairment may be an important mechanism for exercise-induced fatigue. However, prior research focused mainly on functional plasticity such that the structural plasticity was not well understood. Because corticostriatal synapses are typical asymmetric synapses, here we have used transmission electron microscopy to examine the changes of asymmetry synaptic ultrastructure in rat striatum before and after repetitive exercise-induced fatigue; we have also used western blotting to detect the levels of synaptic active region protein Munc 13, RIM1 and synaptic vesicle protein Rab3A and postsynaptic density PSD-95 protein in rat striatum before and after exercise-induced fatigue. The results showed that the ultrastructure of asymmetry corticostriatal synapses and synaptic protein levels in the striatum of rats were abnormally changed after repetitive exercise-induced fatigue. These abnormal changes in synaptic ultrastructure and related protein levels may be the structural basis for the corticostriatal plasticity impairment after exercise-induced fatigue.
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Affiliation(s)
- Zhifeng Wang
- Department of Physical Education, Xi'an Polytechnic University, Xi'an, Shanxi, 710048, China
| | - Lijuan Hou
- Physical Education and Sports College, Beijing Normal University, Beijing, 100875, China
| | - Dongmei Wang
- College of Sports Medicine and Rehabilitation, Shandong First Medical University & Shandong Academy of Medical Sciences, Tai'an, Shandong, 271000, China.
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Li Y, Chang L, Song Y, Gao X, Roselli F, Liu J, Zhou W, Fang Y, Ling W, Li H, Almeida OFX, Wu Y. Astrocytic GluN2A and GluN2B Oppose the Synaptotoxic Effects of Amyloid-β1-40 in Hippocampal Cells. J Alzheimers Dis 2018; 54:135-48. [PMID: 27497478 DOI: 10.3233/jad-160297] [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] [Indexed: 01/25/2023]
Abstract
Early-stage Alzheimer's disease (AD) is characterized by synaptic dysfunction, a phenomenon in which soluble oligomers of amyloid-beta (Aβ) and N-methyl-D-aspartate receptor (NMDAR) are implicated. Here, we demonstrated that astrocytes express NMDARs and therefore have the potential to modulate the synaptotoxic actions of Aβ. We found that specific pharmacological antagonism of two of the major NMDAR subunits, GluN2A and GluN2B, exacerbates Aβ-induced synaptotoxicity suggesting, for the first time, that astrocytic GluN2A and GluN2B mediate synaptoprotection. From the perspective of the pathogenic mechanisms of Alzheimer's disease, in which Aβ and NMDAR play significant roles, these observations are striking since neuronal GluN2A and GluN2B are well known modulators of neurodegeneration. We did initial studies to understand the basis for the differential effects of astrocytic and neuronal GluN2A and GluN2B in the promotion of synapse survival, and identified a neurotrophin produced by astrocytes, nerve growth factor β (β-NGF), as a likely mediator of the synaptoprotective effects of astrocytic GluN2A and GluN2B activation. The results presented suggest that astrocytes may be suitable druggable targets for the prevention and/or delay of the synaptic loss that occurs during early stages of AD.
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Affiliation(s)
- Yan Li
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Lirong Chang
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Yizhi Song
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Xianghong Gao
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Francesco Roselli
- Departments of Neurology and Anatomy, University of Ulm School of Medicine, Germany.,Max Planck Institute of Psychiatry, Munich, Germany
| | - Jinping Liu
- School of Medicine, Tsinghua University, Beijing, China
| | - Wei Zhou
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Yuan Fang
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Wei Ling
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Hui Li
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | | | - Yan Wu
- Department of Anatomy, Ministry of Science and Technology Laboratory of Brain Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
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DOPAL derived alpha-synuclein oligomers impair synaptic vesicles physiological function. Sci Rep 2017; 7:40699. [PMID: 28084443 PMCID: PMC5233976 DOI: 10.1038/srep40699] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 12/06/2016] [Indexed: 12/15/2022] Open
Abstract
Parkinson’s disease is a neurodegenerative disorder characterized by the death of dopaminergic neurons and by accumulation of alpha-synuclein (aS) aggregates in the surviving neurons. The dopamine catabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) is a highly reactive and toxic molecule that leads to aS oligomerization by covalent modifications to lysine residues. Here we show that DOPAL-induced aS oligomer formation in neurons is associated with damage of synaptic vesicles, and with alterations in the synaptic vesicles pools. To investigate the molecular mechanism that leads to synaptic impairment, we first aimed to characterize the biochemical and biophysical properties of the aS-DOPAL oligomers; heterogeneous ensembles of macromolecules able to permeabilise cholesterol-containing lipid membranes. aS-DOPAL oligomers can induce dopamine leak in an in vitro model of synaptic vesicles and in cellular models. The dopamine released, after conversion to DOPAL in the cytoplasm, could trigger a noxious cycle that further fuels the formation of aS-DOPAL oligomers, inducing neurodegeneration.
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Guariglia SR, Stansfield KH, McGlothan J, Guilarte TR. Chronic early life lead (Pb 2+) exposure alters presynaptic vesicle pools in hippocampal synapses. BMC Pharmacol Toxicol 2016; 17:56. [PMID: 27802838 PMCID: PMC5090882 DOI: 10.1186/s40360-016-0098-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 10/14/2016] [Indexed: 12/23/2022] Open
Abstract
Background Lead (Pb2+) exposure has been shown to impair presynaptic neurotransmitter release in both in vivo and in vitro model systems. The mechanism by which Pb2+ impairs neurotransmitter release has not been fully elucidated. In previous work, we have shown that Pb2+ exposure inhibits vesicular release and reduces the number of fast-releasing sites in cultured hippocampal neurons. We have also shown that Pb2+ exposure inhibits vesicular release and alters the distribution of presynaptic vesicles in Shaffer Collateral – CA1 synapses of rodents chronically exposed to Pb2+ during development. Methods In the present study, we used transmission electron microscopy to examine presynaptic vesicle pools in Mossy Fiber-CA3 synapses and in Perforant Path-Dentate Gyrus synapses of rats to determine if in vivo Pb2+ exposure altered presynaptic vesicle distribution in these hippocampal regions. Data were analyzed using T-test for each experimental endpoint. Results We found that Pb2+ exposure significantly reduced the number of vesicles in the readily releasable pool and recycling pool in Mossy Fiber-CA3 terminals. In both Mossy Fiber-CA3 terminals and in Perforant Path-Dentate Gyrus terminals, Pb2+ exposure significantly increased vesicle nearest neighbor distance in all vesicular pools (Rapidly Releasable, Recycling and Resting). We also found a reduction in the size of the postsynaptic densities of CA3 dendrites in the Pb2+ exposed group. Conclusions In our previous work, we have demonstrated that Pb2+ exposure impairs vesicular release in Shaffer Collateral - CA1 terminals of the hippocampus and that the number of docked vesicles in the presynaptic active zone was reduced. Our current data shows that Pb2+ exposure reduces the number of vesicles that are in proximity to release sites in Mossy Fiber- CA3 terminals. Furthermore, Pb2+ exposure causes presynaptic vesicles to be further from one another, in both Mossy Fiber- CA3 terminals and in Perforant Pathway – Dentate Gyrus terminals, which may interfere with vesicle movement and release. Our findings provide a novel in vivo mechanism by which Pb2+ exposure impairs vesicle dynamics and release in the hippocampus.
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Affiliation(s)
- Sara Rose Guariglia
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th Street, New York, NY, 10032, USA
| | - Kirstie H Stansfield
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th Street, New York, NY, 10032, USA
| | - Jennifer McGlothan
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th Street, New York, NY, 10032, USA
| | - Tomas R Guilarte
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th Street, New York, NY, 10032, USA.
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Zhang XL, Guariglia SR, McGlothan JL, Stansfield KH, Stanton PK, Guilarte TR. Presynaptic mechanisms of lead neurotoxicity: effects on vesicular release, vesicle clustering and mitochondria number. PLoS One 2015; 10:e0127461. [PMID: 26011056 PMCID: PMC4444102 DOI: 10.1371/journal.pone.0127461] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 04/15/2015] [Indexed: 01/12/2023] Open
Abstract
Childhood lead (Pb2+) intoxication is a global public health problem and accounts for 0.6% of the global burden of disease associated with intellectual disabilities. Despite the recognition that childhood Pb2+ intoxication contributes significantly to intellectual disabilities, there is a fundamental lack of knowledge on presynaptic mechanisms by which Pb2+ disrupts synaptic function. In this study, using a well-characterized rodent model of developmental Pb2+ neurotoxicity, we show that Pb2+ exposure markedly inhibits presynaptic vesicular release in hippocampal Schaffer collateral-CA1 synapses in young adult rats. This effect was associated with ultrastructural changes which revealed a reduction in vesicle number in the readily releasable/docked vesicle pool, disperse vesicle clusters in the resting pool, and a reduced number of presynaptic terminals with multiple mitochondria with no change in presynaptic calcium influx. These studies provide fundamental knowledge on mechanisms by which Pb2+ produces profound inhibition of presynaptic vesicular release that contribute to deficits in synaptic plasticity and intellectual development.
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Affiliation(s)
- Xiao-lei Zhang
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, New York, United States of America
| | - Sara R. Guariglia
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - Jennifer L. McGlothan
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - Kirstie H. Stansfield
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - Patric K. Stanton
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, New York, United States of America
| | - Tomás R. Guilarte
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, United States of America
- * E-mail:
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Altered presynaptic ultrastructure in excitatory hippocampal synapses of mice lacking dystrophins Dp427 or Dp71. Neurobiol Dis 2011; 43:134-41. [DOI: 10.1016/j.nbd.2011.02.017] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 01/20/2011] [Accepted: 02/27/2011] [Indexed: 11/13/2022] Open
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LRRK2 controls synaptic vesicle storage and mobilization within the recycling pool. J Neurosci 2011; 31:2225-37. [PMID: 21307259 DOI: 10.1523/jneurosci.3730-10.2011] [Citation(s) in RCA: 220] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Mutations in leucine-rich repeat kinase 2 (LRRK2) are the single most common cause of inherited Parkinson's disease. Little is known about its involvement in the pathogenesis of Parkinson's disease mainly because of the lack of knowledge about the physiological role of LRRK2. To determine the function of LRRK2, we studied the impact of short hairpin RNA-mediated silencing of LRRK2 expression in cortical neurons. Paired recording indicated that LRRK2 silencing affects evoked postsynaptic currents. Furthermore, LRRK2 silencing induces at the presynaptic site a redistribution of vesicles within the bouton, altered recycling dynamics, and increased vesicle kinetics. Accordingly, LRRK2 protein is present in the synaptosomal compartment of cortical neurons in which it interacts with several proteins involved in vesicular recycling. Our results suggest that LRRK2 modulates synaptic vesicle trafficking and distribution in neurons and in consequence participates in regulating the dynamics between vesicle pools inside the presynaptic bouton.
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Abstract
Brain plasticity describes the potential of the organ for adaptive changes involved in various phenomena in health and disease. A substantial amount of experimental evidence, received in animal and cell models, shows that a cascade of plastic changes at the molecular, cellular, and tissue levels, is initiated in different regions of the postischemic brain. Underlying mechanisms include neurochemical alterations, functional changes in excitatory and inhibitory synapses, axonal and dendritic sprouting, and reorganization of sensory and motor central maps. Multiple lines of evidence indicate numerous points in which the process of postischemic recovery may be influenced with the aim to restore the full capacity of the brain tissue injured by an ischemic episode.
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Affiliation(s)
- Galyna G Skibo
- Department of Cytology, Bogomoletz Institute of Physiology, Kiev, Ukraine
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Nikonenko AG, Radenovic L, Andjus PR, Skibo GG. Structural Features of Ischemic Damage in the Hippocampus. Anat Rec (Hoboken) 2009; 292:1914-21. [DOI: 10.1002/ar.20969] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Different expression of caspase-3 in rat hippocampal subregions during postnatal development. Microsc Res Tech 2008; 71:633-8. [DOI: 10.1002/jemt.20600] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Store-operated Ca2+ entry in astrocytes: different spatial arrangement of endoplasmic reticulum explains functional diversity in vitro and in situ. Cell Calcium 2007; 43:591-601. [PMID: 18054077 DOI: 10.1016/j.ceca.2007.10.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2007] [Revised: 09/19/2007] [Accepted: 10/05/2007] [Indexed: 11/23/2022]
Abstract
Ca(2+) signaling is the astrocyte form of excitability and the endoplasmic reticulum (ER) plays an important role as an intracellular Ca(2+) store. Since the subcellular distribution of the ER influences Ca(2+) signaling, we compared the arrangement of ER in astrocytes of hippocampus tissue and astrocytes in cell culture by electron microscopy. While the ER was usually located in close apposition to the plasma membrane in astrocytes in situ, the ER in cultured astrocytes was close to the nuclear membrane. Activation of metabotropic receptors linked to release of Ca(2+) from ER stores triggered distinct responses in cultured and in situ astrocytes. In culture, Ca(2+) signals were commonly first recorded close to the nucleus and with a delay at peripheral regions of the cells. Store-operated Ca(2+) entry (SOC) as a route to refill the Ca(2+) stores could be easily identified in cultured astrocytes as the Zn(2+)-sensitive component of the Ca(2+) signal. In contrast, such a Zn(2+)-sensitive component was not recorded in astrocytes from hippocampal slices despite of evidence for SOC. Our data indicate that both, astrocytes in situ and in vitro express SOC necessary to refill stores, but that a SOC-related signal is not recorded in the cytoplasm of astrocytes in situ since the stores are close to the plasma membrane and the refill does not affect cytoplasmic Ca(2+) levels.
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Kovalenko T, Osadchenko I, Nikonenko A, Lushnikova I, Voronin K, Nikonenko I, Muller D, Skibo G. Ischemia-induced modifications in hippocampal CA1 stratum radiatum excitatory synapses. Hippocampus 2006; 16:814-25. [PMID: 16892187 DOI: 10.1002/hipo.20211] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Relatively mild ischemic episode can initiate a chain of events resulting in delayed cell death and significant lesions in the affected brain regions. We studied early synaptic modifications after brief ischemia modeled in rats by transient vessels' occlusion in vivo or oxygen-glucose deprivation in vitro and resulting in delayed death of hippocampal CA1 pyramidal cells. Electron microscopic analysis of excitatory spine synapses in CA1 stratum radiatum revealed a rapid increase of the postsynaptic density (PSD) thickness and length, as well as formation of concave synapses with perforated PSD during the first 24 h after ischemic episode, followed at the long term by degeneration of 80% of synaptic contacts. In presynaptic terminals, ischemia induced a depletion of synaptic vesicles and changes in their spatial arrangement: they became more distant from active zones and had larger intervesicle spacing compared to controls. These rapid structural synaptic changes could be implicated in the mechanisms of cell death or adaptive plasticity. Comparison of the in vivo and in vitro model systems used in the study demonstrated a general similarity of these early morphological changes, confirming the validity of the in vitro model for studying synaptic structural plasticity.
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Affiliation(s)
- Tatiana Kovalenko
- Department of Cytology, Bogomoletz Institute of Physiology, Kiev, Ukraine
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Nikonenko AG, Skibo GG. Age-related changes in synaptic vesicle pools of axo-dendritic synapses on hippocampal CA1 pyramidal neurons in mice. NEUROPHYSIOLOGY+ 2006. [DOI: 10.1007/s11062-006-0069-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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16
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Nikonenko AG, Skibo GG. Estimation of the number of synaptic vesicles in asymmetric synapses between hippocampal neurons. NEUROPHYSIOLOGY+ 2006. [DOI: 10.1007/s11062-006-0043-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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