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  1. Article ; Online: Astroglial Connexins as a Therapeutic Target for Alzheimer's Disease.

    Yi, Chenju / Koulakoff, Annette / Giaume, Christian

    Current pharmaceutical design

    2017  Volume 23, Issue 33, Page(s) 4958–4968

    Abstract: Background: In Alzheimer's disease (AD), modification of astrocytic properties is a well-known and documented fact, but their involvement in pathophysiology has only been examined in recent years. One distinct hallmark of AD is reactive gliosis which ... ...

    Abstract Background: In Alzheimer's disease (AD), modification of astrocytic properties is a well-known and documented fact, but their involvement in pathophysiology has only been examined in recent years. One distinct hallmark of AD is reactive gliosis which are represented in microglial and astrocytic phenotype changes. This reactive gliosis has been associated with changes in the expression and function of connexins. Connexins are proteins that can form gap junction channels and hemichannels, and in a disease context, have shown increased expression in astrocytes that contact amyloid plaques in vivo. Amyloid plaques are aggregates of the amyloid-beta protein, which present in the AD brain in patients and in animal models.
    Methods: Murine AD models demonstrate changes in connexin channel activity which mirror in cell culture systems treated with amyloid-beta peptide. This has been closely studied in the familial AD mouse model APPSwe/ PS1dE9 where the implications of connexin channel functions have been examined.
    Results: These studies demonstrate that while gap junctional communication was unaffected, hemichannel activation could be detected in the astrocytes of hippocampal slices containing amyloid-beta plaques. Most critically, the activation of hemichannels is associated with the release of gliotransmitters (such as ATP and glutamate) which results in the maintenance of a high intracellular free Ca2+ concentration within astrocytes, which initiates the start of a vicious cycle. Strategies that target astroglial connexin hemichannels include the knocking out of the connexin 43 gene in astrocytes of the APPSwe/PS1dE9 mice, as well as using various pharmacological tools. This results in the decrease of gliotransmitter release and the alleviation of neuronal damage. This includes the reduction of oxidative stress and neuritic dystrophies in neurons that are typically associated with plaque formation in the hippocampus. Concusion: In this review, we summarize recent findings on astroglial connexin channels in the neurodegenerative process of Alzheimer's disease, and discuss how this can be a strategy in AD treatment to block the activity of hemichannels in astrocytes.
    MeSH term(s) Alzheimer Disease/drug therapy ; Alzheimer Disease/metabolism ; Animals ; Astrocytes/drug effects ; Astrocytes/metabolism ; Connexins/antagonists & inhibitors ; Connexins/metabolism ; Drug Delivery Systems/methods ; Drug Delivery Systems/trends ; Humans ; Neuroprotective Agents/administration & dosage
    Chemical Substances Connexins ; Neuroprotective Agents
    Language English
    Publishing date 2017-11-01
    Publishing country United Arab Emirates
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 1304236-1
    ISSN 1873-4286 ; 1381-6128
    ISSN (online) 1873-4286
    ISSN 1381-6128
    DOI 10.2174/1381612823666171004151215
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Monitoring gap junctional communication in astrocytes from acute adult mouse brain slices using the gap-FRAP technique.

    Yi, Chenju / Teillon, Jérémy / Koulakoff, Annette / Berry, Hugues / Giaume, Christian

    Journal of neuroscience methods

    2018  Volume 303, Page(s) 103–113

    Abstract: Intercellular communication through gap junction channels plays a key role in cellular homeostasis and in synchronizing physiological functions, a feature that is modified in number of pathological situations. In the brain, astrocytes are the cell ... ...

    Abstract Intercellular communication through gap junction channels plays a key role in cellular homeostasis and in synchronizing physiological functions, a feature that is modified in number of pathological situations. In the brain, astrocytes are the cell population that expresses the highest amount of gap junction proteins, named connexins. Several techniques have been used to assess the level of gap junctional communication in astrocytes, but so far they remain very difficult to apply in adult brain tissue. Here, using specific loading of astrocytes with sulforhodamine 101, we adapted the gap-FRAP (Fluorescence Recovery After Photobleaching) to acute hippocampal slices from 9 month-old adult mice. We show that gap junctional communication monitored in astrocytes with this technique was inhibited either by pharmacological treatment with a gap junctional blocker or in mice lacking the two main astroglial connexins, while a partial inhibition was measured when only one connexin was knocked-out. We validate this approach using a mathematical model of sulforhodamine 101 diffusion in an elementary astroglial network and a quantitative analysis of the exponential fits to the fluorescence recovery curves. Consequently, we consider that the adaptation of the gap-FRAP technique to acute brain slices from adult mice provides an easy going and valuable approach that allows overpassing this age-dependent obstacle and will facilitate the investigation of gap junctional communication in adult healthy or pathological brain.
    MeSH term(s) Animals ; Astrocytes/metabolism ; Connexins/metabolism ; Fluorescence Recovery After Photobleaching/methods ; Gap Junctions/physiology ; Hippocampus/metabolism ; Mice ; Signal Transduction/physiology
    Chemical Substances Connexins
    Language English
    Publishing date 2018-03-15
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 282721-9
    ISSN 1872-678X ; 0165-0270
    ISSN (online) 1872-678X
    ISSN 0165-0270
    DOI 10.1016/j.jneumeth.2018.03.005
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Hemichannels Are Required for Amyloid β-Peptide-Induced Degranulation and Are Activated in Brain Mast Cells of APPswe/PS1dE9 Mice.

    Harcha, Paloma A / Vargas, Aníbal / Yi, Chenju / Koulakoff, Annette A / Giaume, Christian / Sáez, Juan C

    The Journal of neuroscience : the official journal of the Society for Neuroscience

    2015  Volume 35, Issue 25, Page(s) 9526–9538

    Abstract: Mast cells (MCs) store an array of proinflammatory mediators in secretory granules that are rapidly released upon activation by diverse conditions including amyloid beta (Aβ) peptides. In the present work, we found a rapid degranulation of cultured MCs ... ...

    Abstract Mast cells (MCs) store an array of proinflammatory mediators in secretory granules that are rapidly released upon activation by diverse conditions including amyloid beta (Aβ) peptides. In the present work, we found a rapid degranulation of cultured MCs through a pannexin1 hemichannel (Panx1 HC)-dependent mechanism induced by Aβ25-35 peptide. Accordingly, Aβ25-35 peptide also increased membrane current and permeability, as well as intracellular Ca(2+) signal, mainly via Panx1 HCs because all of these responses were drastically inhibited by Panx1 HC blockers and absent in the MCs of Panx1(-/-) mice. Moreover, in acute coronal brain slices of control mice, Aβ25-35 peptide promoted both connexin 43 (Cx43)- and Panx1 HC-dependent MC dye uptake and histamine release, responses that were only Cx43 HC dependent in Panx1(-/-) mice. Because MCs have been found close to amyloid plaques of patients with Alzheimer's disease (AD), their distribution in brain slices of APPswe/PS1dE9 mice, a murine model of AD, was also investigated. The number of MCs in hippocampal and cortical areas increased drastically even before amyloid plaque deposits became evident. Therefore, MCs might act as early sensors of amyloid peptide and recruit other cells to the neuroinflammatory response, thus playing a critical role in the onset and progression of AD.
    MeSH term(s) Alzheimer Disease/pathology ; Amyloid beta-Peptides/metabolism ; Amyloid beta-Peptides/pharmacology ; Animals ; Blotting, Western ; Brain/pathology ; Cell Degranulation/physiology ; Disease Models, Animal ; Electrophysiology ; Fluorescent Antibody Technique ; HeLa Cells ; Humans ; Mast Cells/drug effects ; Mast Cells/metabolism ; Mice ; Mice, Knockout ; Peptide Fragments/metabolism ; Peptide Fragments/pharmacology ; Transfection
    Chemical Substances Amyloid beta-Peptides ; Peptide Fragments ; amyloid beta-protein (25-35)
    Language English
    Publishing date 2015-05-12
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 604637-x
    ISSN 1529-2401 ; 0270-6474
    ISSN (online) 1529-2401
    ISSN 0270-6474
    DOI 10.1523/JNEUROSCI.3686-14.2015
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Contribution of Astroglial Cx43 Hemichannels to the Modulation of Glutamatergic Currents by D-Serine in the Mouse Prefrontal Cortex.

    Meunier, Claire / Wang, Nan / Yi, Chenju / Dallerac, Glenn / Ezan, Pascal / Koulakoff, Annette / Leybaert, Luc / Giaume, Christian

    The Journal of neuroscience : the official journal of the Society for Neuroscience

    2017  Volume 37, Issue 37, Page(s) 9064–9075

    Abstract: Astrocytes interact dynamically with neurons by modifying synaptic activity and plasticity. This interplay occurs through a process named gliotransmission, meaning that neuroactive molecules are released by astrocytes. Acting as a gliotransmitter, D- ... ...

    Abstract Astrocytes interact dynamically with neurons by modifying synaptic activity and plasticity. This interplay occurs through a process named gliotransmission, meaning that neuroactive molecules are released by astrocytes. Acting as a gliotransmitter, D-serine, a co-agonist of the NMDA receptor at the glycine-binding site, can be released by astrocytes in a calcium [Ca
    MeSH term(s) Animals ; Astrocytes/physiology ; Calcium Signaling/physiology ; Cells, Cultured ; Connexin 43/metabolism ; Female ; Glutamic Acid/metabolism ; Male ; Mice ; Mice, Knockout ; Mice, Transgenic ; Neuronal Plasticity/physiology ; Neurotransmitter Agents/metabolism ; Prefrontal Cortex/physiology ; Serine/metabolism ; Synaptic Transmission/physiology
    Chemical Substances Connexin 43 ; GJA1 protein, mouse ; Neurotransmitter Agents ; Glutamic Acid (3KX376GY7L) ; Serine (452VLY9402)
    Language English
    Publishing date 2017-08-11
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 604637-x
    ISSN 1529-2401 ; 0270-6474
    ISSN (online) 1529-2401
    ISSN 0270-6474
    DOI 10.1523/JNEUROSCI.2204-16.2017
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Inhibition of glial hemichannels by boldine treatment reduces neuronal suffering in a murine model of Alzheimer's disease.

    Yi, Chenju / Ezan, Pascal / Fernández, Paola / Schmitt, Julien / Sáez, Juan C / Giaume, Christian / Koulakoff, Annette

    Glia

    2017  Volume 65, Issue 10, Page(s) 1607–1625

    Abstract: The contribution of reactive gliosis to the pathological phenotype of Alzheimer's disease (AD) opened the way for therapeutic strategies targeting glial cells instead of neurons. In such context, connexin hemichannels were proposed recently as potential ... ...

    Abstract The contribution of reactive gliosis to the pathological phenotype of Alzheimer's disease (AD) opened the way for therapeutic strategies targeting glial cells instead of neurons. In such context, connexin hemichannels were proposed recently as potential targets since neuronal suffering is alleviated when connexin expression is genetically suppressed in astrocytes of a murine model of AD. Here, we show that boldine, an alkaloid from the boldo tree, inhibited hemichannel activity in astrocytes and microglia without affecting gap junctional communication in culture and acute hippocampal slices. Long-term oral administration of boldine in AD mice prevented the increase in glial hemichannel activity, astrocytic Ca
    Language English
    Publishing date 2017-10
    Publishing country United States
    Document type Journal Article
    ZDB-ID 639414-0
    ISSN 1098-1136 ; 0894-1491
    ISSN (online) 1098-1136
    ISSN 0894-1491
    DOI 10.1002/glia.23182
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  6. Article ; Online: Connexin 43 deletion in astrocytes promotes CNS remyelination by modulating local inflammation.

    Li, Tao / Niu, Jianqin / Yu, Guangdan / Ezan, Pascal / Yi, Chenju / Wang, Xiaorui / Koulakoff, Annette / Gao, Xing / Chen, Xianjun / Sáez, Juan C / Giaume, Christian / Xiao, Lan

    Glia

    2019  Volume 68, Issue 6, Page(s) 1201–1212

    Abstract: As the most abundant gap junction protein in the central nervous system (CNS), astrocytic connexin 43 (Cx43) maintains astrocyte network homeostasis, affects oligodendroglial development and participates in CNS pathologies as well as injury progression. ... ...

    Abstract As the most abundant gap junction protein in the central nervous system (CNS), astrocytic connexin 43 (Cx43) maintains astrocyte network homeostasis, affects oligodendroglial development and participates in CNS pathologies as well as injury progression. However, its role in remyelination is not yet fully understood. To address this issue, we used astrocyte-specific Cx43 conditional knockout (Cx43 cKO) mice generated through the use of a hGFAP-cre promoter, in combination with mice carrying a floxed Cx43 allele that were subjected to lysolecithin so as to induce demyelination. We found no significant difference in the demyelination of the corpus callosum between Cx43 cKO mice and their non-cre littermate controls, while the remyelination process in Cx43 cKO mice was accelerated. Moreover, an increased number of mature oligodendrocytes and an unaltered number of oligodendroglial lineage cells were found in Cx43 cKO mouse lesions. This indicates that oligodendrocyte precursor cell (OPC) differentiation was facilitated by astroglial Cx43 depletion as remyelination progressed. Underlying the latter, there was a down-regulated glial activation and modulated local inflammation as well as a reduction of myelin debris in Cx43 cKO mice. Importantly, 2 weeks of orally administrating boldine, a natural alkaloid that blocks Cx hemichannel activity in astrocytes without affecting gap junctional communication, obviously modulated local inflammation and promoted remyelination. Together, the data suggest that the astrocytic Cx43 hemichannel is negatively involved in the remyelination process by favoring local inflammation. Consequently, inhibiting Cx43 hemichannel functionality may be a potential therapeutic approach for demyelinating diseases in the CNS.
    MeSH term(s) Animals ; Astrocytes/metabolism ; Cell Differentiation/physiology ; Central Nervous System/metabolism ; Connexin 43/metabolism ; Demyelinating Diseases/pathology ; Gap Junctions/metabolism ; Inflammation/metabolism ; Mice ; Myelin Sheath/metabolism ; Oligodendrocyte Precursor Cells/metabolism ; Oligodendroglia/metabolism ; Remyelination/physiology
    Chemical Substances Connexin 43 ; GJA1 protein, mouse
    Language English
    Publishing date 2019-12-23
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 639414-0
    ISSN 1098-1136 ; 0894-1491
    ISSN (online) 1098-1136
    ISSN 0894-1491
    DOI 10.1002/glia.23770
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  7. Article ; Online: Neurons control the expression of connexin 30 and connexin 43 in mouse cortical astrocytes.

    Koulakoff, Annette / Ezan, Pascal / Giaume, Christian

    Glia

    2008  Volume 56, Issue 12, Page(s) 1299–1311

    Abstract: A characteristic feature of astrocytes is their high level of intercellular communication mediated by gap junctions. The two main connexins, Cx30 and Cx43, that form these junctions in astrocytes of adult brain display different developmental and ... ...

    Abstract A characteristic feature of astrocytes is their high level of intercellular communication mediated by gap junctions. The two main connexins, Cx30 and Cx43, that form these junctions in astrocytes of adult brain display different developmental and regional expression, with a delayed onset of appearance for Cx30. In primary cultures of astrocytes from newborn cerebral cortex, while Cx43 is abundantly expressed, Cx30 is not detectable. In the present report, Western blot and confocal immunofluorescence analysis performed in astrocyte/neuron cocultures demonstrate that neurons upregulate the expression of Cx43 and induce that of Cx30 in subsets of astrocytes preferentially located in close proximity to neuronal soma. In Cx43 lacking astrocytes cocultured with neurons, the induction of Cx30 allows the restoration of dye coupling within islets of Cx30-positive astrocytes, indicating that intercellular channels formed by Cx30 are functional. The upregulating effect of neurons on the expression of connexins in cortical astrocytes is independent of their electrical activity and requires tight interactions between both cell types. This effect is reversed after neuronal death induced by neurotoxic treatments. Furthermore, excitotoxic treatments triggering neuronal death in vivo lead to a downregulation of both connexins in reactive astrocytes located within the area depleted in neurons. Altogether these observations indicate that the expression of the two main astrocyte connexins is tightly regulated by neurons.
    MeSH term(s) Animals ; Animals, Newborn ; Astrocytes/physiology ; Cells, Cultured ; Cerebral Cortex/embryology ; Cerebral Cortex/growth & development ; Cerebral Cortex/physiology ; Coculture Techniques ; Connexin 30 ; Connexin 43/biosynthesis ; Connexin 43/genetics ; Connexins/biosynthesis ; Connexins/genetics ; Gene Expression Regulation/physiology ; Mice ; Mice, Transgenic ; Neurons/physiology
    Chemical Substances Connexin 30 ; Connexin 43 ; Connexins ; Gjb6 protein, mouse
    Language English
    Publishing date 2008-09
    Publishing country United States
    Document type Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 639414-0
    ISSN 1098-1136 ; 0894-1491
    ISSN (online) 1098-1136
    ISSN 0894-1491
    DOI 10.1002/glia.20698
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  8. Article ; Online: Astroglial networks: a step further in neuroglial and gliovascular interactions.

    Giaume, Christian / Koulakoff, Annette / Roux, Lisa / Holcman, David / Rouach, Nathalie

    Nature reviews. Neuroscience

    2010  Volume 11, Issue 2, Page(s) 87–99

    Abstract: Dynamic aspects of interactions between astrocytes, neurons and the vasculature have recently been in the neuroscience spotlight. It has emerged that not only neurons but also astrocytes are organized into networks. Whereas neuronal networks exchange ... ...

    Abstract Dynamic aspects of interactions between astrocytes, neurons and the vasculature have recently been in the neuroscience spotlight. It has emerged that not only neurons but also astrocytes are organized into networks. Whereas neuronal networks exchange information through electrical and chemical synapses, astrocytes are interconnected through gap junction channels that are regulated by extra- and intracellular signals and allow exchange of information. This intercellular communication between glia has implications for neuroglial and gliovascular interactions and hence has added another level of complexity to our understanding of brain function.
    MeSH term(s) Animals ; Astrocytes/cytology ; Astrocytes/physiology ; Cell Communication/physiology ; Humans ; Intracellular Membranes/physiology ; Nerve Net/blood supply ; Nerve Net/cytology ; Nerve Net/physiology ; Neuroglia/cytology ; Neuroglia/physiology
    Language English
    Publishing date 2010-02
    Publishing country England
    Document type Journal Article ; Review
    ZDB-ID 2034150-7
    ISSN 1471-0048 ; 1471-0048 ; 1471-003X
    ISSN (online) 1471-0048
    ISSN 1471-0048 ; 1471-003X
    DOI 10.1038/nrn2757
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  9. Article ; Online: Glucocorticoid receptor in astrocytes regulates midbrain dopamine neurodegeneration through connexin hemichannel activity.

    Maatouk, Layal / Yi, Chenju / Carrillo-de Sauvage, Maria-Angeles / Compagnion, Anne-Claire / Hunot, Stéphane / Ezan, Pascal / Hirsch, Etienne C / Koulakoff, Annette / Pfrieger, Frank W / Tronche, François / Leybaert, Luc / Giaume, Christian / Vyas, Sheela

    Cell death and differentiation

    2018  Volume 26, Issue 3, Page(s) 580–596

    Abstract: The precise contribution of astrocytes in neuroinflammatory process occurring in Parkinson's disease (PD) is not well characterized. In this study, using ... ...

    Abstract The precise contribution of astrocytes in neuroinflammatory process occurring in Parkinson's disease (PD) is not well characterized. In this study, using GR
    MeSH term(s) Animals ; Astrocytes/metabolism ; Connexins/metabolism ; Dopaminergic Neurons/metabolism ; Humans ; Male ; Mice ; Parkinson Disease/genetics ; Parkinson Disease/pathology
    Chemical Substances Connexins ; GJE1 protein, human
    Language English
    Publishing date 2018-07-13
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1225672-9
    ISSN 1476-5403 ; 1350-9047
    ISSN (online) 1476-5403
    ISSN 1350-9047
    DOI 10.1038/s41418-018-0150-3
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  10. Article: Glial connexin expression and function in the context of Alzheimer's disease.

    Koulakoff, Annette / Mei, Xin / Orellana, Juan A / Sáez, Juan C / Giaume, Christian

    Biochimica et biophysica acta

    2012  Volume 1818, Issue 8, Page(s) 2048–2057

    Abstract: A hallmark of neurodegenerative diseases is the reactive gliosis characterized by a phenotypic change in astrocytes and microglia. This glial response is associated with modifications in the expression and function of connexins (Cxs), the proteins ... ...

    Abstract A hallmark of neurodegenerative diseases is the reactive gliosis characterized by a phenotypic change in astrocytes and microglia. This glial response is associated with modifications in the expression and function of connexins (Cxs), the proteins forming gap junction channels and hemichannels. Increased Cx expression is detected in most reactive astrocytes located at amyloid plaques, the histopathological lesions typically present in the brain of Alzheimer's patients and animal models of the disease. The activity of Cx channels analyzed in vivo as well as in vitro after treatment with the amyloid β peptide is also modified and, in particular, hemichannel activation may contribute to neuronal damage. In this review, we summarize and discuss recent data that suggest glial Cx channels participate in the neurodegenerative process of Alzheimer's disease. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
    MeSH term(s) Alzheimer Disease/metabolism ; Amyloid beta-Peptides/metabolism ; Animals ; Astrocytes/metabolism ; Brain/metabolism ; Connexins/metabolism ; Disease Models, Animal ; Gap Junctions/metabolism ; Gliosis/metabolism ; Humans ; Mice ; Microglia/metabolism ; Models, Biological ; Neuroglia/metabolism ; Neurons/metabolism ; Phenotype
    Chemical Substances Amyloid beta-Peptides ; Connexins
    Language English
    Publishing date 2012-08
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 60-7
    ISSN 1879-2596 ; 1879-260X ; 1872-8006 ; 1879-2642 ; 1879-2618 ; 1879-2650 ; 0006-3002 ; 0005-2728 ; 0005-2736 ; 0304-4165 ; 0167-4838 ; 1388-1981 ; 0167-4889 ; 0167-4781 ; 0304-419X ; 1570-9639 ; 0925-4439 ; 1874-9399
    ISSN (online) 1879-2596 ; 1879-260X ; 1872-8006 ; 1879-2642 ; 1879-2618 ; 1879-2650
    ISSN 0006-3002 ; 0005-2728 ; 0005-2736 ; 0304-4165 ; 0167-4838 ; 1388-1981 ; 0167-4889 ; 0167-4781 ; 0304-419X ; 1570-9639 ; 0925-4439 ; 1874-9399
    DOI 10.1016/j.bbamem.2011.10.001
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