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Mitochondrial Metabolism behind Region-Specific Resistance to Ischemia-Reperfusion Injury in Gerbil Hippocampus. Role of PKCβII and Phosphate-Activated Glutaminase. Int J Mol Sci 2021; 22:ijms22168504. [PMID: 34445210 PMCID: PMC8395184 DOI: 10.3390/ijms22168504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/03/2021] [Accepted: 08/03/2021] [Indexed: 11/17/2022] Open
Abstract
Ischemic episodes are a leading cause of death worldwide with limited therapeutic interventions. The current study explored mitochondrial phosphate-activated glutaminase (GLS1) activity modulation by PKCβII through GC-MS untargeted metabolomics approach. Mitochondria were used to elucidate the endogenous resistance of hippocampal CA2-4 and dentate gyrus (DG) to transient ischemia and reperfusion in a model of ischemic episode in gerbils. In the present investigation, male gerbils were subjected to bilateral carotids occlusion for 5 min followed by reperfusion (IR). Gerbils were randomly divided into three groups as vehicle-treated sham control, vehicle-treated IR and PKCβII specific inhibitor peptide βIIV5-3-treated IR. Vehicle or βIIV5-3 (3 mg/kg, i.v.) were administered at the moment of reperfusion. The gerbils hippocampal tissue were isolated at various time of reperfusion and cell lysates or mitochondria were isolated from CA1 and CA2-4,DG hippocampal regions. Recombinant proteins PKCβII and GLS1 were used in in vitro phosphorylation reaction and organotypic hippocampal cultures (OHC) transiently exposed to NMDA (25 μM) to evaluate the inhibition of GLS1 on neuronal viability. PKCβII co-precipitates with GAC (GLS1 isoform) in CA2-4,DG mitochondria and phosphorylates GLS1 in vitro. Cell death was dose dependently increased when GLS1 was inhibited by BPTA while inhibition of mitochondrial pyruvate carrier (MPC) attenuated cell death in NMDA-challenged OHC. Fumarate and malate were increased after IR 1h in CA2-4,DG and this was reversed by βIIV5-3 what correlated with GLS1 activity increases and earlier showed elevation of neuronal death (Krupska et al., 2017). The present study illustrates that CA2-4,DG resistance to ischemic episode at least partially rely on glutamine and glutamate utilization in mitochondria as a source of carbon to tricarboxylic acid cycle. This phenomenon depends on modulation of GLS1 activity by PKCβII and remodeling of MPC: all these do not occur in ischemia-vulnerable CA1.
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Endocytosis and lysosomal degradation of GluA2/3 AMPARs in response to oxygen/glucose deprivation in hippocampal but not cortical neurons. Sci Rep 2017; 7:12318. [PMID: 28951554 PMCID: PMC5614987 DOI: 10.1038/s41598-017-12534-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 09/06/2017] [Indexed: 02/04/2023] Open
Abstract
Global cerebral ischemia results in oxygen and glucose deprivation (OGD) and consequent delayed cell death of vulnerable neurons, with hippocampal CA1 neurons more vulnerable than cortical neurons. Most AMPA receptors (AMPARs) are heteromeric complexes of subunits GluA1/GluA2 or GluA2/GluA3, and the presence of GluA2 renders AMPARs Ca2+-impermeable. In hippocampal CA1 neurons, OGD causes the synaptic expression of GluA2-lacking Ca2+-permeable AMPARs, contributing to toxic Ca2+ influx. The loss of synaptic GluA2 is caused by rapid trafficking of GluA2-containing AMPARs from the cell surface, followed by a delayed reduction in GluA2 mRNA expression. We show here that OGD causes endocytosis, lysosomal targeting and consequent degradation of GluA2- and GluA3-containing AMPARs, and that PICK1 is required for both OGD-induced GluA2 endocytosis and lysosomal sorting. Our results further suggest that GluA1-containing AMPARs resist OGD-induced endocytosis. OGD does not cause GluA2 endocytosis in cortical neurons, and we show that PICK1 binding to the endocytic adaptor AP2 is enhanced by OGD in hippocampal, but not cortical neurons. We propose that endocytosis of GluA2/3, caused by a hippocampal-specific increase in PICK1-AP2 interactions, followed by PICK1-dependent lysosomal targeting, are critical events in determining changes in AMPAR subunit composition in the response to ischaemia.
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Masuch A, Shieh CH, van Rooijen N, van Calker D, Biber K. Mechanism of microglia neuroprotection: Involvement of P2X7, TNFα, and valproic acid. Glia 2015; 64:76-89. [PMID: 26295445 DOI: 10.1002/glia.22904] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 08/03/2015] [Accepted: 08/05/2015] [Indexed: 11/05/2022]
Abstract
Recently, we have demonstrated that ramified microglia are neuroprotective in N-methyl-D-aspartate (NMDA)-induced excitotoxicity in organotypic hippocampal slice cultures (OHSCs). The present study aimed to elucidate the underlying neuron-glia communication mechanism. It is shown here that pretreatment of OHSC with high concentrations of adenosine 5'-triphosphate (ATP) reduced NMDA-induced neuronal death only in presence of microglia. Specific agonists and antagonists identified the P2X7 receptor as neuroprotective receptor which was confirmed by absence of ATP-dependent neuroprotection in P2X7-deficient OHSC. Microglia replenished chimeric OHSC consisting of wild-type tissue replenished with P2X7-deficient microglia confirmed the involvement of microglial P2X7 receptor in neuroprotection. Stimulation of P2X7 in primary microglia induced tumor necrosis factor α (TNFα) release and blocking TNFα by a neutralizing antibody in OHSC abolished neuroprotection by ATP. OHSC from TNFα-deficient mice show increased exicitoxicity and activation of P2X7 did not rescue neuronal survival in the absence of TNFα. The neuroprotective effect of valproic acid (VPA) was strictly dependent on the presence of microglia and was mediated by upregulation of P2X7 in the cells. The present study demonstrates that microglia-mediated neuroprotection depends on ATP-activated purine receptor P2X7 and induction of TNFα release. This neuroprotective pathway was strengthened by VPA elucidating a novel mechanism for the neuroprotective function of VPA.
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Affiliation(s)
- Annette Masuch
- Department of Psychiatry and Psychotherapy, University Hospital Freiburg, Freiburg, Germany
| | - Chu-Hsin Shieh
- Department of Psychiatry and Psychotherapy, University Hospital Freiburg, Freiburg, Germany
| | - Nico van Rooijen
- Department of Molecular Cell Biology, Free University Medical Center (VUMC), Amsterdam, the Netherlands
| | - Dietrich van Calker
- Department of Psychiatry and Psychotherapy, University Hospital Freiburg, Freiburg, Germany
| | - Knut Biber
- Department of Psychiatry and Psychotherapy, University Hospital Freiburg, Freiburg, Germany.,Department of Neuroscience, University Medical Center Groningen (UMCG), University of Groningen, the Netherlands
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The effects of black garlic ethanol extract on the spatial memory and estimated total number of pyramidal cells of the hippocampus of monosodium glutamate-exposed adolescent male Wistar rats. Anat Sci Int 2014; 90:275-86. [DOI: 10.1007/s12565-014-0262-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 11/06/2014] [Indexed: 10/24/2022]
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Allard J, Paci P, Vander Elst L, Ris L. Regional and time-dependent neuroprotective effect of hypothermia following oxygen-glucose deprivation. Hippocampus 2014; 25:197-207. [DOI: 10.1002/hipo.22364] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/05/2014] [Indexed: 11/08/2022]
Affiliation(s)
- Justine Allard
- Department of Neurosciences; Research Institute for Health Sciences and Technology, University of Mons; Mons Belgium
| | - Paula Paci
- Department of Neurosciences; Research Institute for Health Sciences and Technology, University of Mons; Mons Belgium
| | - Luce Vander Elst
- Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory; Research Institute for Health Sciences and Technology, University of Mons; Mons Belgium
| | - Laurence Ris
- Department of Neurosciences; Research Institute for Health Sciences and Technology, University of Mons; Mons Belgium
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Blanco-Suarez E, Hanley JG. Distinct subunit-specific α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor trafficking mechanisms in cultured cortical and hippocampal neurons in response to oxygen and glucose deprivation. J Biol Chem 2014; 289:4644-51. [PMID: 24403083 DOI: 10.1074/jbc.m113.533182] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Brain ischemia occurs when the blood supply to the brain is interrupted, leading to oxygen and glucose deprivation (OGD). This triggers a cascade of events causing a synaptic accumulation of glutamate. Excessive activation of glutamate receptors results in excitotoxicity and delayed cell death in vulnerable neurons. Following global cerebral ischemia, hippocampal CA1 pyramidal neurons are more vulnerable to injury than their cortical counterparts. The mechanisms that underlie this difference are unclear. Cultured hippocampal neurons respond to OGD with a rapid internalization of AMPA receptor (AMPAR) subunit GluA2, resulting in a switch from GluA2-containing Ca(2+)-impermeable receptors to GluA2-lacking Ca(2+)-permeable subtypes (CP-AMPARs). GluA2 internalization is a critical component of OGD-induced cell death in hippocampal neurons. It is unknown how AMPAR trafficking is affected in cortical neurons following OGD. Here, we show that cultured cortical neurons are resistant to an OGD insult that causes cell death in hippocampal neurons. GluA1 is inserted at the plasma membrane in both cortical and hippocampal neurons in response to OGD. In contrast, OGD causes a rapid endocytosis of GluA2 in hippocampal neurons, which is absent in cortical neurons. These data demonstrate that populations of neurons with different vulnerabilities to OGD recruit distinct cell biological mechanisms in response to insult, and that a crucial aspect of the mechanism leading to OGD-induced cell death is absent in cortical neurons. This strongly suggests that the absence of OGD-induced GluA2 trafficking contributes to the relatively low vulnerability of cortical neurons to ischemia.
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Affiliation(s)
- Elena Blanco-Suarez
- From the School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
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Sevoflurane preconditioning attenuates the fall in adenosine triphosphate levels, but does not alter the changes in sodium and potassium levels during hypoxia in rat hippocampal slices. Anesthesiology 2013; 119:119-28. [PMID: 23459218 DOI: 10.1097/aln.0b013e31828ce844] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Sevoflurane preconditioning improves recovery after hypoxia. Sevoflurane administered before and during hypoxia improved recovery and attenuated the changes in intracellular sodium, potassium, and adenosine triphosphate (ATP) levels during hypoxia. In this study, the authors examine the effects of sevoflurane applied only before hypoxia on sodium, potassium, and ATP. METHODS Hippocampal slices from adult male Sprague-Dawley rats were pretreated with 4% sevoflurane, washed, and then subjected to hypoxia (n≥8 animals/group). The cornus ammonis 1 regions of the hippocampal slices were micro-dissected and sodium, potassium, and ATP concentrations measured. RESULTS Pretreatment with sevoflurane for 15 or 60 min did not attenuate the increase in intracellular sodium or the decrease in intracellular potassium during hypoxia. After 60 min of preconditioning and 5 min of hypoxia, sodium increased 57% (vs. nonpreconditioned hypoxia 54% increase) and potassium decreased 31% (vs. 26%). These changes were not statistically significant versus untreated hypoxia. The 60-min sevoflurane preconditioning group had statistically significant higher ATP levels at 5 min of hypoxia (3.8 nmol/mg dry wt.) when compared to untreated hypoxic tissue (2.1 nmol/mg). There was no significant difference in ATP levels between the sevoflurane preconditioned and the untreated tissue before hypoxia (8.9 vs. 8.5 nmoles/mg, respectively). CONCLUSION Preconditioning with sevoflurane for 60 min before hypoxia does not alter changes in intracellular sodium and potassium during hypoxia but does attenuate the fall in intracellular ATP levels during hypoxia. Thus, there are differences between anesthetic preconditioning and when anesthetics are present before and during hypoxia.
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Pirchl M, Marksteiner J, Humpel C. Effects of acidosis on brain capillary endothelial cells and cholinergic neurons: relevance to vascular dementia and Alzheimer's disease. Neurol Res 2013; 28:657-64. [PMID: 16945219 DOI: 10.1179/016164106x130371] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Alzheimer's disease is a progressive brain disorder which is neuropathologically characterized by an increased number of beta-amyloid plaques, tau pathology and synapse loss. Recent research suggests that vascular pathology may be also important for the development and progression of Alzheimer's disease. It is still unknown whether there is a relation between damage of brain capillary endothelial cells (BCEC) and subsequent cholinergic cell death. The aim of this study was to examine the effects of acidosis on cell death of BCEC and cholinergic neurons in an organotypic brain slice model. We show that BCEC were heavily damaged in medium at pH<6.6. Cholinergic neurons incubated in medium pH 6.0 degenerated within 2-3 days and were not rescued by nerve growth factor (NGF). Lactate did not affect the survival of BCEC or cholinergic neurons. Both BCEC and cholinergic cells were not affected at pH 7.4, 7.0 or 6.6. It is concluded that both endothelial cells and cholinergic neurons have a high capacity to compensate for pH changes. At a certain pH, however, the vascular and neuronal cells show the same vulnerability, indicating that a low pH is deleterious for the cerebral microenvironment. Future studies are necessary to explore whether temporary pH changes could be responsible for cerebrovascular damage and cholinergic cell death. Acidosis may play an important role in the development of vascular dementia and Alzheimer's disease.
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Affiliation(s)
- Michael Pirchl
- Laboratory of Experimental Alzheimer's Research, Department of General Psychiatry, Innsbruck Medical University, Austria
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Hellwig S, Heinrich A, Biber K. The brain's best friend: microglial neurotoxicity revisited. Front Cell Neurosci 2013; 7:71. [PMID: 23734099 PMCID: PMC3655268 DOI: 10.3389/fncel.2013.00071] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 04/26/2013] [Indexed: 01/13/2023] Open
Abstract
One long standing aspect of microglia biology was never questioned; their involvement in brain disease. Based on morphological changes (retracted processes and amoeboid shape) that inevitably occur in these cells in case of damage in the central nervous system, microglia in the diseased brain were called “activated.” Because “activated” microglia were always found in direct neighborhood to dead or dying neuron, and since it is known now for more than 20 years that cultured microglia release numerous factors that are able to kill neurons, microglia “activation” was often seen as a neurotoxic process. From an evolutionary point of view, however, it is difficult to understand why an important, mostly post-mitotic and highly vulnerable organ like the brain would host numerous potential killers. This review is aimed to critically reconsider the term microglia neurotoxicity and to discuss experimental problems around microglia biology, that often have led to the conclusion that microglia are neurotoxic cells.
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Affiliation(s)
- Sabine Hellwig
- Department of Psychiatry and Psychotherapy, University Hospital Freiburg Freiburg, Germany
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Vinet J, Weering HRJV, Heinrich A, Kälin RE, Wegner A, Brouwer N, Heppner FL, Rooijen NV, Boddeke HWGM, Biber K. Neuroprotective function for ramified microglia in hippocampal excitotoxicity. J Neuroinflammation 2012; 9:27. [PMID: 22293457 PMCID: PMC3292937 DOI: 10.1186/1742-2094-9-27] [Citation(s) in RCA: 200] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 01/31/2012] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Most of the known functions of microglia, including neurotoxic and neuroprotective properties, are attributed to morphologically-activated microglia. Resting, ramified microglia are suggested to primarily monitor their environment including synapses. Here, we show an active protective role of ramified microglia in excitotoxicity-induced neurodegeneration. METHODS Mouse organotypic hippocampal slice cultures were treated with N-methyl-D-aspartic acid (NMDA) to induce excitotoxic neuronal cell death. This procedure was performed in slices containing resting microglia or slices that were chemically or genetically depleted of their endogenous microglia. RESULTS Treatment of mouse organotypic hippocampal slice cultures with 10-50 μM N-methyl-D-aspartic acid (NMDA) induced region-specific excitotoxic neuronal cell death with CA1 neurons being most vulnerable, whereas CA3 and DG neurons were affected less. Ablation of ramified microglia severely enhanced NMDA-induced neuronal cell death in the CA3 and DG region rendering them almost as sensitive as CA1 neurons. Replenishment of microglia-free slices with microglia restored the original resistance of CA3 and DG neurons towards NMDA. CONCLUSIONS Our data strongly suggest that ramified microglia not only screen their microenvironment but additionally protect hippocampal neurons under pathological conditions. Morphological activation of ramified microglia is thus not required to influence neuronal survival.
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Affiliation(s)
- Jonathan Vinet
- Department of Neuroscience, Section Medical Physiology, University Medical Center Groningen (UMCG), Rijksuniversiteit Groningen (RUG), Groningen, The Netherlands
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Oxygen/glucose deprivation induces a reduction in synaptic AMPA receptors on hippocampal CA3 neurons mediated by mGluR1 and adenosine A3 receptors. J Neurosci 2011; 31:11941-52. [PMID: 21849555 DOI: 10.1523/jneurosci.1183-11.2011] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Hippocampal CA1 pyramidal neurons are highly sensitive to ischemic damage, whereas neighboring CA3 pyramidal neurons are less susceptible. It is proposed that switching of AMPA receptor (AMPAR) subunits on CA1 neurons during an in vitro model of ischemia, oxygen/glucose deprivation (OGD), leads to an enhanced permeability of AMPARs to Ca(2+), resulting in delayed cell death. However, it is unclear whether the same mechanisms exist in CA3 neurons and whether this underlies the differential sensitivity to ischemia. Here, we investigated the consequences of OGD for AMPAR function in CA3 neurons using electrophysiological recordings in rat hippocampal slices. Following a 15 min OGD protocol, a substantial depression of AMPAR-mediated synaptic transmission was observed at CA3 associational/commissural and mossy fiber synapses but not CA1 Schaffer collateral synapses. The depression of synaptic transmission following OGD was prevented by metabotropic glutamate receptor 1 (mGluR1) or A(3) receptor antagonists, indicating a role for both glutamate and adenosine release. Inhibition of PLC, PKC, or chelation of intracellular Ca(2+) also prevented the depression of synaptic transmission. Inclusion of peptides to interrupt the interaction between GluA2 and PICK1 or dynamin and amphiphysin prevented the depression of transmission, suggesting a dynamin and PICK1-dependent internalization of AMPARs after OGD. We also show that a reduction in surface and total AMPAR protein levels after OGD was prevented by mGluR1 or A(3) receptor antagonists, indicating that AMPARs are degraded following internalization. Thus, we describe a novel mechanism for the removal of AMPARs in CA3 pyramidal neurons following OGD that has the potential to reduce excitotoxicity and promote neuroprotection.
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Ginet V, Puyal J, Clarke PGH, Truttmann AC. Enhancement of autophagic flux after neonatal cerebral hypoxia-ischemia and its region-specific relationship to apoptotic mechanisms. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 175:1962-74. [PMID: 19815706 PMCID: PMC2774060 DOI: 10.2353/ajpath.2009.090463] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/30/2009] [Indexed: 12/19/2022]
Abstract
The multiplicity of cell death mechanisms induced by neonatal hypoxia-ischemia makes neuroprotective treatment against neonatal asphyxia more difficult to achieve. Whereas the roles of apoptosis and necrosis in such conditions have been studied intensively, the implication of autophagic cell death has only recently been considered. Here, we used the most clinically relevant rodent model of perinatal asphyxia to investigate the involvement of autophagy in hypoxic-ischemic brain injury. Seven-day-old rats underwent permanent ligation of the right common carotid artery, followed by 2 hours of hypoxia. This condition not only increased autophagosomal abundance (increase in microtubule-associated protein 1 light chain 3-11 level and punctuate labeling) but also lysosomal activities (cathepsin D, acid phosphatase, and beta-N-acetylhexosaminidase) in cortical and hippocampal CA3-damaged neurons at 6 and 24 hours, demonstrating an increase in the autophagic flux. In the cortex, this enhanced autophagy may be related to apoptosis since some neurons presenting a high level of autophagy also expressed apoptotic features, including cleaved caspase-3. On the other hand, enhanced autophagy in CA3 was associated with a more purely autophagic cell death phenotype. In striking contrast to CA3 neurons, those in CA1 presented only a minimal increase in autophagy but strong apoptotic characteristics. These results suggest a role of enhanced autophagy in delayed neuronal death after severe hypoxia-ischemia that is differentially linked to apoptosis according to the cerebral region.
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Affiliation(s)
- Vanessa Ginet
- Department of Pediatrics and Pediatric Surgery, University Hospital Center, Switzerland
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Reduction of β-amyloid-induced neurotoxicity on hippocampal cell cultures by moderate acidosis is mediated by transforming growth factor β. Neuroscience 2009; 158:1338-47. [DOI: 10.1016/j.neuroscience.2008.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Revised: 10/13/2008] [Accepted: 11/03/2008] [Indexed: 11/17/2022]
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Ryan SD, Harris CS, Mo F, Lee H, Hou ST, Bazan NG, Haddad PS, Arnason JT, Bennett SAL. Platelet activating factor-induced neuronal apoptosis is initiated independently of its G-protein coupled PAF receptor and is inhibited by the benzoate orsellinic acid. J Neurochem 2007; 103:88-97. [PMID: 17877634 DOI: 10.1111/j.1471-4159.2007.04740.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The bioactive lipid mediator platelet activating factor (PAF) is recognized as a key effecter of neuronal apoptosis, yet it is not clear whether its G-protein coupled receptor (PAFR) initiates or prevents PAF neurotoxicity. Using PAFR-/- and congenic wild-type mice, we show that PAF triggers caspase-3/7 activity and neuronal death in PAFR-/- but not PAFR+/+ cerebellar granule neurons. Restoring receptor expression by recombinant adenoviral infection protected cells from PAF challenge. Neuronal death was not mediated by nitric oxide or N-methyl-d-aspartate receptor signaling given that N-nitro-l-arginine methyl ester and MK-801 did not inhibit PAF-induced neuronal loss in PAFR-/- neurons. To intervene in PAFR-independent neurotoxicity, the anti-apoptotic actions of three structurally distinct PAF antagonists were compared to a panel of plant and fungal benzoic acid derivatives. We found that the PAF antagonist BN 52021 but not FR 49175 or CV 3988 inhibited PAFR-independent neurotoxicity. Orsellinic acid, a fungal-derived benzoic acid, blocked PAF-mediated neuronal apoptosis without affecting PAFR-mediated neuroprotection. These findings demonstrate that PAF can transduce apoptotic death in primary neurons independently of its G-protein coupled receptor, that PAFR activation is neuroprotective, and that orsellinic acid effectively attenuates PAFR-independent neuronal apoptosis.
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Affiliation(s)
- Scott D Ryan
- Department of Biochemistry, Microbiology, and Immunology, Neural Regeneration Laboratory and Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada
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Tai KK, Truong DD. NMDA receptor-mediated excitotoxicity contributes to the cerebral hypoxic injury of a rat model of posthypoxic myoclonus. Brain Res 2006; 1133:209-15. [PMID: 17196560 DOI: 10.1016/j.brainres.2006.11.076] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Revised: 11/16/2006] [Accepted: 11/17/2006] [Indexed: 11/16/2022]
Abstract
Cardiac arrest-induced cerebral hypoxic injury could induce posthypoxic movement disorders. Here we investigated the effects of memantine, an NMDA receptor channel blocker, on the neurodegeneration occurred in an established rat model of posthypoxic myoclonus. We found that administration of memantine for 7 days significantly reduced cerebral hypoxia-induced neurodegeneration in the CA1 of the hippocampus, the reticular thalamic nucleus (RTN) and the primary fissure of the cerebellum of the posthypoxic animals. The results suggest that the neurodegeneration observed in specific areas of the brain of the posthypoxic rats is contributed by NMDA receptor-mediated excitotoxicity.
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Affiliation(s)
- Kwok-Keung Tai
- The Parkinson's and Movement Disorder Research Laboratory, Long Beach Memorial Medical Center, Long Beach, CA 90806, USA.
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16
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Gee CE, Benquet P, Raineteau O, Rietschin L, Kirbach SW, Gerber U. NMDA receptors and the differential ischemic vulnerability of hippocampal neurons. Eur J Neurosci 2006; 23:2595-603. [PMID: 16817862 DOI: 10.1111/j.1460-9568.2006.04786.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transient cerebral ischemia causes an inhomogeneous pattern of cell death in the brain. We investigated mechanisms, which may underlie the greater susceptibility of hippocampal CA1 vs. CA3 pyramidal cells to ischemic insult. Using an in vitro oxygen-glucose deprivation (OGD) model of ischemia, we found that N-methyl-D-aspartate (NMDA) responses were enhanced in the more susceptible CA1 pyramidal cells and transiently depressed in the resistant CA3 pyramidal cells. The long-lasting potentiation of NMDA responses in CA1 cells was associated with delayed cell death and was prevented by blocking tyrosine kinase-dependent up-regulation of NMDA receptor function. In CA3 cells, the energy deprivation-induced transient depression of NMDA responses was converted to potentiation by blocking protein phosphatase signalling. These results suggest that energy deprivation differentially shifts the intracellular equilibrium between the tyrosine kinase and phosphatase activities that modulate NMDA responses in CA1 and CA3 pyramidal cells. Therapeutic modulation of tyrosine phosphorylation may thus prove beneficial in mitigating ischemia-induced neuronal death in vulnerable brain areas.
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Affiliation(s)
- Christine E Gee
- Brain Research Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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Rytter A, Cardoso CMP, Johansson P, Cronberg T, Hansson MJ, Mattiasson G, Elmér E, Wieloch T. The temperature dependence and involvement of mitochondria permeability transition and caspase activation in damage to organotypic hippocampal slices following in vitro ischemia. J Neurochem 2005; 95:1108-17. [PMID: 16144540 DOI: 10.1111/j.1471-4159.2005.03420.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The aggravating effect of hyperglycemia on ischemic brain injury can be mimicked in a model of in vitro ischemia (IVI) using murine hippocampal slice cultures. Using this model, we found that the damage in the CA1 region following IVI in the absence or presence of 40 mm glucose (hyperglycemia) is highly temperature dependent. Decreasing the temperature from 35 to 31 degrees C during IVI prevented cell death, whereas increasing the temperature by 2 degrees C markedly aggravated damage. As blockade of the mitochondrial permeability transition (MPT) is equally effective as hypothermia in preventing ischemic cell death in vivo, we investigated whether inhibition of MPT or of caspases was protective following IVI. In the absence of glucose, the MPT blockers cyclosporin A and MeIle4-CsA but not the immunosuppressive compound FK506 diminished cell death. In contrast, following hyperglycemic IVI, MPT blockade was ineffective. Also, the pan-caspase inhibitor Boc-Asp(OMe)fluoromethyl ketone did not decrease cell death in the CA1 region following IVI or hyperglycemic IVI. We conclude that cell death in the CA1 region of organotypic murine hippocampal slices following IVI is highly temperature dependent and involves MPT. In contrast, cell death following hyperglycemic IVI, although completely prevented by hypothermia, is not mediated by mechanisms that involve MPT or caspase activation.
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Affiliation(s)
- Anna Rytter
- Laboratory for Experimental Brain Research, Lund University, Sweden
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