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Abstract
Astrocytes have been found to play important roles in physiology being fundamental for ionic homeostasis and glutamate clearance from the synaptic cleft by their plasma membrane glutamate transporters. Astrocytes are electrically non-excitable, but they exhibit Ca(2+) signaling, which now has been demonstrated to serve as an indirect mediator of neuron-glia bidirectional interactions through gliotransmission via tripartite synapses and to modulate synaptic function and plasticity. Spontaneous astrocytic Ca(2+) signaling was observed in vivo. Intercellular Ca(2+) waves in astrocytes can be evoked by a variety of stimulations. Astrocytes are critically involved in many pathological conditions including ischemic stroke. For example, it is well known that astrocytes become reactive and form glial scar after stroke. In animal models of some brain disorders, astrocytes have been shown to exhibit enhanced Ca(2+) excitability featured as regenerative intercellular Ca(2+) waves. This chapter briefly summarizes astrocytic Ca(2+) signaling pathways under normal conditions and in experimental in vitro and in vivo ischemic models. It discusses the possible mechanisms and therapeutic implication underlying the enhanced astrocytic Ca(2+) excitability in stroke.
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Affiliation(s)
- Shinghua Ding
- Dalton Cardiovascular Research Center, Department of Bioengineering, University of Missouri-Columbia, 134 Research Park Drive, Columbia, MO, 65211, USA,
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102
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Sayre NL, Chen Y, Sifuentes M, Stoveken B, Lechleiter JD. Purinergic receptor stimulation decreases ischemic brain damage by energizing astrocyte mitochondria. ADVANCES IN NEUROBIOLOGY 2014; 11:121-50. [PMID: 25236727 DOI: 10.1007/978-3-319-08894-5_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
As a leading cause of death in the world, cerebral ischemic stroke has limited treatment options. The lack of glucose and oxygen after stroke is particularly harmful in the brain because neuronal metabolism accounts for significantly more energy consumption per gram of body weight compared to other organs. Our laboratory has identified mitochondrial metabolism of astrocytes to be a key target for pharmacologic intervention, not only because astrocytes play a central role in regulating brain metabolism, but also because they are essential for neuronal health and support. Here we review current literature pertaining to the pathobiology of stroke, along with the role of astrocytes and metabolism in stroke. We also discuss our research, which has revealed that pharmacologic stimulation of metabotropic P2Y1 receptor signaling in astrocytes can increase mitochondrial energy production and also reduce damage after stroke.
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Affiliation(s)
- Naomi L Sayre
- Department of Cellular and Structural Biology, University of Texas Health Science Center San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
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103
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Xiao Y, Wu X, Deng X, Huang L, Zhou Y, Yang X. Optimal electroacupuncture frequency for maintaining astrocyte structural integrity in cerebral ischemia. Neural Regen Res 2014; 8:1122-31. [PMID: 25206406 PMCID: PMC4145895 DOI: 10.3969/j.issn.1673-5374.2013.12.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 03/19/2013] [Indexed: 11/18/2022] Open
Abstract
The astrocyte is a critical regulator of neuronal survival after ischemic brain injury. Electroacupuncture may be an effective therapy for cerebral ischemia, as electroacupuncture frequency can affect the structural integrity of astrocytes. In this study, a rat model of middle cerebral artery occlusion established using the modified thread embolism method was treated with electroacupuncture of the bilateral Quchi (LI11) and Zusanli (ST36) at 15, 30, and 100 Hz frequencies. Behavioral testing, immunohistochemistry and electron microscopy were used to explore the effect of these electroacupuncture frequencies used on maintaining the structural integrity of ischemic brain tissue. Compared with the model and 100 Hz electroacupuncture groups, the 15 and 30 Hz electroacupuncture groups displayed decreased neurological deficit scores, as evaluated by the "Longa" method, significantly increased glial fibrillary acidic protein expression, and alleviated ultrastructural damage of astrocytes at the edge of the infarct. Our experimental findings indicate that 15 and 30 Hz electroacupuncture intervention can favorably maintain the structural integrity of astrocytes and play a protective role in cerebral ischemic injury. Astrocyte structural integrity may be the mechanism underlying acupuncture production of ischemic tolerance.
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Affiliation(s)
- Yicai Xiao
- Department of Traditional Chinese Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning 530021, Guangxi Zhuang Autonomous Region, China
| | - Xingui Wu
- Department of Traditional Chinese Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning 530021, Guangxi Zhuang Autonomous Region, China
| | - Xiangfa Deng
- Department of Anatomy, Faculty of Preclinical Medicine, Guangxi Medical University, Nanning 530021, Guangxi Zhuang Autonomous Region, China
| | - Liping Huang
- Department of Traditional Chinese Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning 530021, Guangxi Zhuang Autonomous Region, China
| | - Yuancheng Zhou
- Department of Traditional Chinese Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning 530021, Guangxi Zhuang Autonomous Region, China
| | - Xuejie Yang
- Department of Traditional Chinese Medicine, First Affiliated Hospital of Guangxi Medical University, Nanning 530021, Guangxi Zhuang Autonomous Region, China
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104
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Hong S, Son MR, Yun K, Lee WT, Park KA, Lee JE. Retroviral expression of human arginine decarboxylase reduces oxidative stress injury in mouse cortical astrocytes. BMC Neurosci 2014; 15:99. [PMID: 25156824 PMCID: PMC4150973 DOI: 10.1186/1471-2202-15-99] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 08/20/2014] [Indexed: 12/17/2022] Open
Abstract
Background In physiologic and pathologic conditions of the central nervous system (CNS), astrocytes are a double-edged sword. They not only support neuronal homeostasis but also contribute to increases in neuronal demise. A large body of experimental evidence has shown that impaired astrocytes play crucial roles in the pathologic process of cerebral ischemia; therefore, astrocytes may represent a breakthrough target for neuroprotective therapeutic strategies. Agmatine, an endogenous polyamine catalyzed from L-arginine by arginine decarboxylase (ADC), is a neuromodulator and it protects neurons/glia against various injuries. Results In this investigation, agmatine-producing mouse cortical astrocytes were developed through transduction of the human ADC gene. Cells were exposed to oxygen-glucose deprivation (OGD) and restored to a normoxic glucose-supplied condition. Intracellular levels of agmatine were measured by high performance liquid chromatography. Cell viability was evaluated by Hoechest/propidium iodide nuclear staining and lactate dehydrogenase assay. Expression of inducible nitric oxide synthase (iNOS) and matrix metalloproteinase s (MMPs) were assessed by a reverse transcription polymerase chain reaction, Western immunoblots, and immunofluorescence. We confirmed that ADC gene-expressed astrocytes produce a great amount of agmatine. These cells were highly resistant to not only OGD but also restoration, which mimicked ischemia-reperfusion injury in vivo. The neuroprotective effects of ADC seemed to be related to its ability to attenuate expression of iNOS and MMPs. Conclusion Our findings imply that astrocytes can be reinforced against oxidative stress by endogenous agmatine production through ADC gene transduction. The results of this study provide new insights that may lead to novel therapeutic approaches to reduce cerebral ischemic injuries. Electronic supplementary material The online version of this article (doi:10.1186/1471-2202-15-99) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | - Jong Eun Lee
- Brain Korea 21 Project for Medical Science, and Brain Research Institute, Department of Anatomy, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea.
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105
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Gao C, Wang C, Liu B, Wu H, Yang Q, Jin J, Li H, Dong S, Gao G, Zhang H. Intermittent hypoxia preconditioning-induced epileptic tolerance by upregulation of monocarboxylate transporter 4 expression in rat hippocampal astrocytes. Neurochem Res 2014; 39:2160-9. [PMID: 25146899 DOI: 10.1007/s11064-014-1411-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 07/21/2014] [Accepted: 08/06/2014] [Indexed: 01/30/2023]
Abstract
Noxious stimuli applied at doses close to but below the threshold of cell injury induce adaptive responses that provide a defense against additional stress. Epileptic preconditioning protects neurons against status epilepticus and ischemia; however, it is not known if the converse is true. During hypoxia/ischemia (H/I), lactate released from astrocytes is taken up by neurons and is stored for energy, a process mediated by monocarboxylate transporter 4 (MCT4) in astroglia. The present study investigated whether H/I preconditioning can provide protection to neurons against epilepsy through upregulation of MCT4 expression in astrocytes in vitro and in vivo. An oxygen/glucose deprivation protocol was used in primary astrocyte cultures, while rats were subjected to an intermittent hypoxia preconditioning (IHP) paradigm followed by lithium-pilocarpine-induced epilepsy as well as lactate transportation inhibitor injection, with a subsequent evaluation of protein expression as well as behavior. H/I induced an upregulation of MCT4 expression, while an IHP time course of 5 days provided the greatest protection against epileptic seizures, which was most apparent by 3 days after IHP. However, lactate transport function disturbances can block the protective effect induced by IHP. These findings provide a potential basis for the clinical treatment of epilepsy.
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Affiliation(s)
- Chen Gao
- Department of Neurosurgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, Shanxi Province, China
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106
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Hunt NH, Ball HJ, Hansen AM, Khaw LT, Guo J, Bakmiwewa S, Mitchell AJ, Combes V, Grau GER. Cerebral malaria: gamma-interferon redux. Front Cell Infect Microbiol 2014; 4:113. [PMID: 25177551 PMCID: PMC4133756 DOI: 10.3389/fcimb.2014.00113] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 07/30/2014] [Indexed: 11/13/2022] Open
Abstract
There are two theories that seek to explain the pathogenesis of cerebral malaria, the mechanical obstruction hypothesis and the immunopathology hypothesis. Evidence consistent with both ideas has accumulated from studies of the human disease and experimental models. Thus, some combination of these concepts seems necessary to explain the very complex pattern of changes seen in cerebral malaria. The interactions between malaria parasites, erythrocytes, the cerebral microvascular endothelium, brain parenchymal cells, platelets and microparticles need to be considered. One factor that seems able to knit together much of this complexity is the cytokine interferon-gamma (IFN-γ). In this review we consider findings from the clinical disease, in vitro models and the murine counterpart of human cerebral malaria in order to evaluate the roles played by IFN-γ in the pathogenesis of this often fatal and debilitating condition.
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Affiliation(s)
- Nicholas H Hunt
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Helen J Ball
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Anna M Hansen
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Loke T Khaw
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Jintao Guo
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Supun Bakmiwewa
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Andrew J Mitchell
- Molecular Immunopathology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Valéry Combes
- Vascular Immunology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Georges E R Grau
- Vascular Immunology Unit, School of Medical Sciences and Bosch Institute, University of Sydney Sydney, NSW, Australia
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107
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Rai S, Kamat PK, Nath C, Shukla R. Glial Activation and Synaptic Neurotoxicity in Alzheimer's disease: A Focus on Neuroinflammation. ACTA ACUST UNITED AC 2014. [DOI: 10.5567/pharmacologia.2014.286.297] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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108
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Yim N, Ryu SW, Han EC, Yoon J, Choi K, Choi C. Mutant ubiquitin UBB+1 induces mitochondrial fusion by destabilizing mitochondrial fission-specific proteins and confers resistance to oxidative stress-induced cell death in astrocytic cells. PLoS One 2014; 9:e99937. [PMID: 24941066 PMCID: PMC4062464 DOI: 10.1371/journal.pone.0099937] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 05/20/2014] [Indexed: 11/28/2022] Open
Abstract
Mutant ubiquitin UBB+1 is observed in a variety of aging-related neurodegenerative diseases and acts as a potent inhibitor of the ubiquitin proteasome system (UPS). In the present study, we investigated the relationship between impaired UPS (using ectopic expression of UBB+1) and mitochondrial dynamics in astrocytes, which are the most abundant glial cells in the central nervous system. Immunocytochemistry and fluorescence recovery after photobleaching revealed that ectopic expression of UBB+1 induced mitochondrial elongation. We further demonstrated that overexpression of UBB+1 destabilized mitochondrial fission-specific proteins including Drp1, Fis1, and OPA3, but not the mitochondrial fusion-specific proteins Mfn1, Mfn2, and OPA1. The reduction in mitochondrial fission-specific proteins by UBB+1 was prevented by inhibiting the 26 S proteasome using chemical inhibitors, including MG132, lactacystin and epoxomicin. We then assessed the involvement of proteases that target mitochondrial proteins by using various protease inhibitors. Finally, we confirmed that either overexpression of UBB+1 or inhibiting the proteasome can protect astrocytic cells from H2O2-induced cell death compared with control cells. Our results suggest that UBB+1 destabilizes mitochondrial fission-specific proteins, leading to mitochondrial fusion and the subsequent resistance to oxidative stress. We therefore propose a protective role of UBB+1 overexpression or the proteasome inhibition in astrocytes in degenerative brains.
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Affiliation(s)
- Nambin Yim
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
| | - Seung-Wook Ryu
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
- KI for the BioCentury, KAIST, Daejeon, Korea
| | - Eun Chun Han
- Graduate School of Medical Science and Engineering, KAIST, Daejeon, Korea
| | - Jonghee Yoon
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
| | - Kyungsun Choi
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
- * E-mail: (KC); (CC)
| | - Chulhee Choi
- Cell Signaling and BioImaging Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon, Korea
- Graduate School of Medical Science and Engineering, KAIST, Daejeon, Korea
- KI for the BioCentury, KAIST, Daejeon, Korea
- * E-mail: (KC); (CC)
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109
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Wang X, Zhang M, Feng R, Li WB, Ren SQ, Zhang J, Zhang F. Physical exercise training and neurovascular unit in ischemic stroke. Neuroscience 2014; 271:99-107. [PMID: 24780769 DOI: 10.1016/j.neuroscience.2014.04.030] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 03/16/2014] [Accepted: 04/09/2014] [Indexed: 10/25/2022]
Abstract
Physical exercise could exert a neuroprotective effect in both clinical studies and animal experiments. A series of related studies have indicated that physical exercise could reduce infarct volume, alleviate neurological deficits, decrease blood-brain barrier dysfunction, promote angiogenesis in cerebral vascular system and increase the survival rate after ischemic stroke. In this review, we summarized the protective effects of physical exercise on neurovascular unit (NVU), including neurons, astrocytes, pericytes and the extracellular matrix. Furthermore, it was demonstrated that exercise training could decrease the blood-brain barrier dysfunction and promote angiogenesis in cerebral vascular system. An awareness of the exercise intervention benefits pre- and post stroke may lead more stroke patients and people with high-risk factors to accept exercise therapy for the prevention and treatment of stroke.
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Affiliation(s)
- X Wang
- Department of Neurology, The Third Hospital of Hebei Medical University, Shijiazhuang 050051, PR China
| | - M Zhang
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang 050017, PR China
| | - R Feng
- Department of Neurology, The Third Hospital of Hebei Medical University, Shijiazhuang 050051, PR China
| | - W B Li
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang 050017, PR China
| | - S Q Ren
- Department of Neurology, The Third Hospital of Hebei Medical University, Shijiazhuang 050051, PR China
| | - J Zhang
- Department of Rehabilitation Medicine, The Third Hospital of Hebei Medical University, Shijiazhuang 050051, PR China
| | - F Zhang
- Department of Rehabilitation Medicine, The Third Hospital of Hebei Medical University, Shijiazhuang 050051, PR China; Hebei Provincial Orthopedic Biomechanics Key Laboratory, The Third Hospital of Hebei Medical University, Shijiazhuang 050051, PR China.
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110
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Sikorska M, Lanthier P, Miller H, Beyers M, Sodja C, Zurakowski B, Gangaraju S, Pandey S, Sandhu JK. Nanomicellar formulation of coenzyme Q10 (Ubisol-Q10) effectively blocks ongoing neurodegeneration in the mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model: potential use as an adjuvant treatment in Parkinson's disease. Neurobiol Aging 2014; 35:2329-46. [PMID: 24775711 DOI: 10.1016/j.neurobiolaging.2014.03.032] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 03/25/2014] [Accepted: 03/28/2014] [Indexed: 12/13/2022]
Abstract
Although the support for the use of antioxidants, such as coenzyme Q(10) (CoQ(10)), to treat Parkinson's disease (PD) comes from the extensive scientific evidence, the results of conducted thus far clinical trials are inconclusive. It is assumed that the efficacy of CoQ(10) is hindered by insolubility, poor bioavailability, and lack of brain penetration. We have developed a nanomicellar formulation of CoQ(10) (Ubisol-Q(10)) with improved properties, including the brain penetration, and tested its effectiveness in mouse MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine) model with the objectives to assess its potential use as an adjuvant therapy for PD. We used a subchronic MPTP model (5-daily MPTP injections), characterized by 50% loss of dopamine neurons over a period of 28 days. Ubisol-Q(10) was delivered in drinking water. Prophylactic application of Ubisol-Q(10), started 2 weeks before the MPTP exposure, significantly offset the neurotoxicity (approximately 50% neurons died in MPTP group vs. 17% in MPTP+ Ubisol-Q(10) group by day 28). Therapeutic application of Ubisol-Q(10), given after the last MPTP injection, was equally effective. At the time of intervention on day 5 nearly 25% of dopamine neurons were already lost, but the treatment saved the remaining 25% of cells, which otherwise would have died by day 28. This was confirmed by cell counts, analyses of striatal dopamine levels, and improved animals' motor skill on a beam walk test. Similar levels of neuroprotection were obtained with 3 different Ubisol-Q(10) concentrations tested, that is, 30 mg, 6 mg, or 3 mg CoQ(10)/kg body weight/day, showing clearly that high doses of CoQ(10) were not required to deliver these effects. Furthermore, the Ubisol-Q(10) treatments brought about a robust astrocytic activation in the brain parenchyma, indicating that astroglia played an active role in this neuroprotection. Thus, we have shown for the first time that Ubisol-Q(10) was capable of halting the neurodegeneration already in progress; however, to maintain it a continuous supplementation of Ubisol-Q(10) was required. The pathologic processes initiated by MPTP resumed if supplementation was withdrawn. We suggest that in addition to brain delivery of powerful antioxidants, Ubisol-Q(10) might have also supported subcellular oxidoreductase systems allowing them to maintain a favorable cellular redox status, especially in astroglia, facilitating their role in neuroprotection. Based on this data further clinical testing of this formulation in PD patients might be justifiable.
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Affiliation(s)
- Marianna Sikorska
- Department of Translational Bioscience, Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
| | - Patricia Lanthier
- Department of Translational Bioscience, Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
| | - Harvey Miller
- Department of Translational Bioscience, Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
| | - Melissa Beyers
- Department of Translational Bioscience, Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
| | - Caroline Sodja
- Department of Translational Bioscience, Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
| | - Bogdan Zurakowski
- Department of Translational Bioscience, Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
| | - Sandhya Gangaraju
- Department of Translational Bioscience, Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, Ontario, Canada
| | - Siyaram Pandey
- Department of Chemistry and Biochemistry, University of Windsor Essex Hall, Windsor, Ontario, Canada
| | - Jagdeep K Sandhu
- Department of Translational Bioscience, Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, Ontario, Canada.
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111
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Sherpa AD, van de Nes P, Xiao F, Weedon J, Hrabetova S. Gliotoxin-induced swelling of astrocytes hinders diffusion in brain extracellular space via formation of dead-space microdomains. Glia 2014; 62:1053-65. [PMID: 24687699 DOI: 10.1002/glia.22661] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 03/04/2014] [Accepted: 03/04/2014] [Indexed: 11/07/2022]
Abstract
One of the hallmarks of numerous life-threatening and debilitating brain diseases is cellular swelling that negatively impacts extracellular space (ECS) structure. The ECS structure is determined by two macroscopic parameters, namely tortuosity (λ) and volume fraction (α). Tortuosity represents hindrance imposed on the diffusing molecules by the tissue in comparison with an obstacle-free medium. Volume fraction is the proportion of tissue volume occupied by the ECS. From a clinical perspective, it is essential to recognize which factors determine the ECS parameters and how these factors change in brain diseases. Previous studies demonstrated that dead-space (DS) microdomains increased λ during ischemia and hypotonic stress, as these pocket-like structures transiently trapped diffusing molecules. We hypothesize that astrocytes play a key role in the formation of DS microdomains because their thin processes have concave shapes that may elongate as astrocytes swell in these pathologies. Here we selectively swelled astrocytes in the somatosensory neocortex of rat brain slices with a gliotoxin DL-α-Aminoadipic Acid (DL-AA), and we quantified the ECS parameters using Integrative Optical Imaging (IOI) and Real-Time Iontophoretic (RTI) diffusion methods. We found that α decreased and λ increased during DL-AA application. During recovery, α was restored whereas λ remained elevated. Increase in λ during astrocytic swelling and recovery is consistent with the formation of DS microdomains. Our data attribute to the astrocytes an important role in determining the ECS parameters, and indicate that extracellular diffusion can be improved not only by reducing the swelling but also by disrupting the DS microdomains.
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Affiliation(s)
- Ang Doma Sherpa
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York; Neural and Behavioral Science Graduate Program, State University of New York Downstate Medical Center, Brooklyn, New York
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112
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Shinotsuka T, Yasui M, Nuriya M. Astrocytic gap junctional networks suppress cellular damage in an in vitro model of ischemia. Biochem Biophys Res Commun 2014; 444:171-6. [PMID: 24440704 DOI: 10.1016/j.bbrc.2014.01.035] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 01/10/2014] [Indexed: 10/25/2022]
Abstract
Astrocytes play pivotal roles in both the physiology and the pathophysiology of the brain. They communicate with each other via extracellular messengers as well as through gap junctions, which may exacerbate or protect against pathological processes in the brain. However, their roles during the acute phase of ischemia and the underlying cellular mechanisms remain largely unknown. To address this issue, we imaged changes in the intracellular calcium concentration ([Ca(2+)]i) in astrocytes in mouse cortical slices under oxygen/glucose deprivation (OGD) condition using two-photon microscopy. Under OGD, astrocytes showed [Ca(2+)]i oscillations followed by larger and sustained [Ca(2+)]i increases. While the pharmacological blockades of astrocytic receptors for glutamate and ATP had no effect, the inhibitions of gap junctional intercellular coupling between astrocytes significantly advanced the onset of the sustained [Ca(2+)]i increase after OGD exposure. Interestingly, the simultaneous recording of the neuronal membrane potential revealed that the onset of the sustained [Ca(2+)]i increase in astrocytes was synchronized with the appearance of neuronal anoxic depolarization. Furthermore, the blockade of gap junctional coupling resulted in a concurrent faster appearance of neuronal depolarizations, which remain synchronized with the sustained [Ca(2+)]i increase in astrocytes. These results indicate that astrocytes delay the appearance of the pathological responses of astrocytes and neurons through their gap junction-mediated intercellular network under OGD. Thus, astrocytic gap junctional networks provide protection against tissue damage during the acute phase of ischemia.
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Affiliation(s)
- Takanori Shinotsuka
- Department of Pharmacology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan
| | - Masato Yasui
- Department of Pharmacology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan
| | - Mutsuo Nuriya
- Department of Pharmacology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
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113
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Ridwan S, Bauer H, Frauenknecht K, Hefti K, von Pein H, Sommer CJ. Distribution of the hematopoietic growth factor G-CSF and its receptor in the adult human brain with specific reference to Alzheimer's disease. J Anat 2014; 224:377-91. [PMID: 24387791 DOI: 10.1111/joa.12154] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/02/2013] [Indexed: 11/29/2022] Open
Abstract
The granulocyte colony-stimulating factor (G-CSF), being a member of the hematopoietic growth factor family, is also critically involved in controlling proliferation and differentiation of neural stem cells. Treatment with G-CSF has been shown to result in substantial neuroprotective and neuroregenerative effects in various experimental models of acute and chronic diseases of the central nervous system. Although G-CSF has been tested in a clinical study for treatment of acute ischemic stroke, there is only fragmentary data on the distribution of this cytokine and its receptor in the human brain. Therefore, the present study was focused on the immunohistochemical analysis of the protein expression of G-CSF and its receptor (G-CSF R) in the adult human brain. Since G-CSF has been shown not only to exert neuroprotective effects in animal models of Alzheimer's disease (AD) but also to be a candidate for clinical treatment, we have also placed an emphasis on the regulation of these molecules in this neurodegenerative disease. One major finding is that both G-CSF and G-CSF R were ubiquitously but not uniformly expressed in neurons throughout the CNS. Protein expression of G-CSF and G-CSF R was not restricted to neurons but was also detectable in astrocytes, ependymal cells, and choroid plexus cells. However, the distribution of G-CSF and G-CSF R did not substantially differ between AD brains and control, even in the hippocampus, where early neurodegenerative changes typically occur.
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Affiliation(s)
- Sami Ridwan
- Department of Neuropathology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
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114
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Abstract
The central nervous system (CNS) can be damaged by a wide range of conditions resulting in loss of specific populations of neurons and/or glial cells and in the development of defined psychiatric or neurological symptoms of varying severity. As the CNS has limited inherent capacity to regenerate lost tissue and self-repair, the development of therapeutic strategies for the treatment of CNS insults remains a serious scientific challenge with potential important clinical applications. In this context, strategies involving transplantation of specific cell populations, such as stem cells and neural stem cells (NSCs), to replace damaged cells offers an opportunity for the development of cell-based therapies. Along these lines, in this review we describe a protocol which involves transplantation of NPCs, genetically engineered to overexpress the neurogenic molecule Cend1 and have thus the potency to differentiate with higher frequency towards the neuronal lineage in a rodent model of stab wound cortical injury.
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Affiliation(s)
- Dimitra Thomaidou
- Laboratory of Cellular and Molecular Neurobiology & Imaging Unit, Hellenic Pasteur Institute, 127 Vassilissis Sophias Avenue, Athens, 11521, Greece,
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115
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Rossi AR, Angelo MF, Villarreal A, Lukin J, Ramos AJ. Gabapentin administration reduces reactive gliosis and neurodegeneration after pilocarpine-induced status epilepticus. PLoS One 2013; 8:e78516. [PMID: 24250797 PMCID: PMC3826740 DOI: 10.1371/journal.pone.0078516] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 09/18/2013] [Indexed: 01/22/2023] Open
Abstract
The lithium-pilocarpine model of epilepsy reproduces in rodents several features of human temporal lobe epilepsy, by inducing an acute status epilepticus (SE) followed by a latency period. It has been proposed that the neuronal network reorganization that occurs during latency determines the subsequent appearance of spontaneous recurrent seizures. The aim of this study was to evaluate neuronal and glial responses during the latency period that follows SE. Given the potential role of astrocytes in the post-SE network reorganization, through the secretion of synaptogenic molecules such as thrombospondins, we also studied the effect of treatment with the α2δ1 thrombospondin receptor antagonist gabapentin. Adult male Wistar rats received 3 mEq/kg LiCl, and 20 h later 30 mg/kg pilocarpine. Once SE was achieved, seizures were stopped with 20 mg/kg diazepam. Animals then received 400 mg/kg/day gabapentin or saline for either 4 or 14 days. In vitro experiments were performed in dissociated mixed hippocampal cell culture exposed to glutamate, and subsequently treated with gabapentin or vehicle. During the latency period, the hippocampus and pyriform cortex of SE-animals presented a profuse reactive astrogliosis, with increased GFAP and nestin expression. Gliosis intensity was dependent on the Racine stage attained by the animals and peaked 15 days after SE. Microglia was also reactive after SE, and followed the same pattern. Neuronal degeneration was present in SE-animals, and also depended on the Racine stage and the SE duration. Polysialic-acid NCAM (PSA-NCAM) expression was increased in hippocampal CA-1 and dentate gyrus of SE-animals. Gabapentin treatment was able to reduce reactive gliosis, decrease neuronal loss and normalize PSA-NCAM staining in hippocampal CA-1. In vitro, gabapentin treatment partially prevented the dendritic loss and reactive gliosis caused by glutamate excitotoxicity. Our results show that gabapentin treatment during the latency period after SE protects neurons and normalizes PSA-NCAM probably by direct interaction with neurons and glia.
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Affiliation(s)
- Alicia Raquel Rossi
- Instituto de Biología Celular y Neurociencia “Prof. E. De Robertis”, Facultad de Medicina, Universidad de Buenos Aires, Ciudad de Buenos Aires, Argentina
| | - Maria Florencia Angelo
- Instituto de Biología Celular y Neurociencia “Prof. E. De Robertis”, Facultad de Medicina, Universidad de Buenos Aires, Ciudad de Buenos Aires, Argentina
| | - Alejandro Villarreal
- Instituto de Biología Celular y Neurociencia “Prof. E. De Robertis”, Facultad de Medicina, Universidad de Buenos Aires, Ciudad de Buenos Aires, Argentina
| | - Jerónimo Lukin
- Instituto de Biología Celular y Neurociencia “Prof. E. De Robertis”, Facultad de Medicina, Universidad de Buenos Aires, Ciudad de Buenos Aires, Argentina
| | - Alberto Javier Ramos
- Instituto de Biología Celular y Neurociencia “Prof. E. De Robertis”, Facultad de Medicina, Universidad de Buenos Aires, Ciudad de Buenos Aires, Argentina
- * E-mail:
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116
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Abstract
Astrocytes are the predominant glial cell type in the CNS. Although astrocytes are electrically nonexcitable, their excitability is manifested by their Ca2+ signaling, which serves as a mediator of neuron-glia bidirectional interactions via tripartite synapses. Studies from in vivo two-photon imaging indicate that in healthy animals, the properties of spontaneous astrocytic Ca2+ signaling are affected by animal species, age, wakefulness and the location of astrocytes in the brain. Intercellular Ca2+ waves in astrocytes can be evoked by a variety of stimulations. In animal models of some brain disorders, astrocytes can exhibit enhanced Ca2+ excitability featured as regenerative intercellular Ca2+ waves. This review first briefly summarizes the astrocytic Ca2+ signaling pathway and the procedure of in vivo two-photon Ca2+ imaging of astrocytes. It subsequently summarizes in vivo astrocytic Ca2+ signaling in health and brain disorders from experimental studies of animal models, and discusses the possible mechanisms and therapeutic implications underlying the enhanced Ca2+ excitability in astrocytes in brain disorders. Finally, this review summarizes molecular genetic approaches used to selectively manipulate astrocyte function in vivo and their applications to study the role of astrocytes in synaptic plasticity and brain disorders.
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Affiliation(s)
- Shinghua Ding
- Dalton Cardiovascular Research Center, Department of Biological Engineering, University of Missouri, Columbia, MO 65211, USA
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117
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Ouyang YB, Xu L, Lu Y, Sun X, Yue S, Xiong XX, Giffard RG. Astrocyte-enriched miR-29a targets PUMA and reduces neuronal vulnerability to forebrain ischemia. Glia 2013; 61:1784-94. [PMID: 24038396 DOI: 10.1002/glia.22556] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 06/24/2013] [Accepted: 07/03/2013] [Indexed: 01/13/2023]
Abstract
Following transient forebrain ischemia, astrocytes play a key role in determining whether or not neurons in the hippocampal CA1 sector go on to die in a delayed fashion. MicroRNAs (miRNAs) are a novel class of RNAs that control gene expression at the post-transcriptional level and the miR-29 family is highly expressed in astrocytes. In this study we assessed levels of miR-29 in hippocampus following forebrain ischemia and found that after transient forebrain ischemia and short periods of reperfusion, miR-29a significantly increased in the resistant dentate gyrus, but decreased in the vulnerable CA1 region of the hippocampus. We demonstrate that miR-29a targets BH3-only proapoptotic BCL2 family member PUMA by luciferase reporter assay and by Western blot. Comparing primary neuron and astrocyte cultures, and postnatal brain, we verified the strongly astrocytic expression of miR-29a. We further found that miR-29a mimic protects and miR-29a inhibitor aggravates cell injury and mitochondrial function after ischemia-like stresses in vitro. Lastly, by overexpressing and reducing miR-29a we demonstrate the protective effect of miR-29a on CA1 delayed neuronal death after forebrain ischemia. Our data suggest that by targeting a pro-apoptotic BCL2 family member, increasing levels of miR-29a might emerge as a strategy for protection against ischemia-reperfusion injury.
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Affiliation(s)
- Yi-Bing Ouyang
- Department of Anesthesia, Stanford University School of Medicine, Stanford, California
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118
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Noninvasive strategies to promote functional recovery after stroke. Neural Plast 2013; 2013:854597. [PMID: 23864962 PMCID: PMC3707231 DOI: 10.1155/2013/854597] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 06/02/2013] [Indexed: 01/17/2023] Open
Abstract
Stroke is a common and disabling global health-care problem, which is the third most common cause of death and one of the main causes of acquired adult disability in many countries. Rehabilitation interventions are a major component of patient care. In the last few years, brain stimulation, mirror therapy, action observation, or mental practice with motor imagery has emerged as interesting options as add-on interventions to standard physical therapies. The neural bases for poststroke recovery rely on the concept of plasticity, namely, the ability of central nervous system cells to modify their structure and function in response to external stimuli. In this review, we will discuss recent noninvasive strategies employed to enhance functional recovery in stroke patients and we will provide an overview of neural plastic events associated with rehabilitation in preclinical models of stroke.
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119
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Oliva I, Fernández M, Martín ED. Dopamine release regulation by astrocytes during cerebral ischemia. Neurobiol Dis 2013; 58:231-41. [PMID: 23800715 DOI: 10.1016/j.nbd.2013.06.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 05/16/2013] [Accepted: 06/15/2013] [Indexed: 11/25/2022] Open
Abstract
Brain ischemia triggers excessive release of neurotransmitters that mediate neuronal damage following ischemic injury. The striatum is one of the areas most sensitive to ischemia. Release of dopamine (DA) from ischemic neurons is neurotoxic and directly contributes to the cell death in affected areas. Astrocytes are known to be critically involved in the physiopathology of cerebrovascular disease. However, their response to ischemia and their role in neuroprotection in striatum are not completely understood. In this study, we used an in vitro model to evaluate the mechanisms of ischemia-induced DA release, and to study whether astrocytes modulate the release of DA in response to short-term ischemic conditions. Using slices of adult mouse brain exposed to oxygen and glucose deprivation (OGD), we measured the OGD-evoked DA efflux using fast cyclic voltammetry and also assessed metabolic impairment by 2,3,5-triphenyltetrazolium chloride (TTC) and tissue viability by propidium iodide (PI) staining. Our data indicate that ischemia induces massive release of DA by dual mechanisms: one which operates via vesicular exocytosis and is action potential dependent and another involving reverse transport by the dopamine transporter (DAT). Simultaneous blockade of astrocyte glutamate transporters and DAT prevented the massive release of dopamine and reduced the brain tissue damage. The present results provide the first experimental evidence that astrocytes function as a key cellular element of ischemia-induced DA release in striatum, constituting a novel and promising therapeutic target in ischemia.
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Affiliation(s)
- Idaira Oliva
- University of Castilla-La Mancha, Albacete, Spain
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120
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Eid T, Tu N, Lee TSW, Lai JCK. Regulation of astrocyte glutamine synthetase in epilepsy. Neurochem Int 2013; 63:670-81. [PMID: 23791709 DOI: 10.1016/j.neuint.2013.06.008] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 05/28/2013] [Accepted: 06/08/2013] [Indexed: 11/20/2022]
Abstract
Astrocytes play a crucial role in regulating and maintaining the extracellular chemical milieu of the central nervous system under physiological conditions. Moreover, proliferation of phenotypically altered astrocytes (a.k.a. reactive astrogliosis) has been associated with many neurologic and psychiatric disorders, including mesial temporal lobe epilepsy (MTLE). Glutamine synthetase (GS), which is found in astrocytes, is the only enzyme known to date that is capable of converting glutamate and ammonia to glutamine in the mammalian brain. This reaction is important, because a continuous supply of glutamine is necessary for the synthesis of glutamate and GABA in neurons. The known stoichiometry of glutamate transport across the astrocyte plasma membrane also suggests that rapid metabolism of intracellular glutamate via GS is a prerequisite for efficient glutamate clearance from the extracellular space. Several studies have indicated that the activity of GS in astrocytes is diminished in several brain disorders, including MTLE. It has been hypothesized that the loss of GS activity in MTLE leads to increased extracellular glutamate concentrations and epileptic seizures. Understanding the mechanisms by which GS is regulated may lead to novel therapeutic approaches to MTLE, which is frequently refractory to antiepileptic drugs. This review discusses several known mechanisms by which GS expression and function are influenced, from transcriptional control to enzyme modification.
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Affiliation(s)
- Tore Eid
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520, United States.
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121
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Talley Watts L, Sprague S, Zheng W, Garling RJ, Jimenez D, Digicaylioglu M, Lechleiter J. Purinergic 2Y1 receptor stimulation decreases cerebral edema and reactive gliosis in a traumatic brain injury model. J Neurotrauma 2013; 30:55-66. [PMID: 23046422 DOI: 10.1089/neu.2012.2488] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Traumatic brain injury (TBI) is the leading cause of death and disability in children and young adults. Neuroprotective agents that may promote repair or counteract damage after injury do not currently exist. We recently reported that stimulation of the purinergic receptor subtype P2Y(1)R using 2-methylthioladenosine 5' diphosphate (2MeSADP) significantly reduced cytotoxic edema induced by photothrombosis. Here, we tested whether P2Y(1)R stimulation was neuroprotective after TBI. A controlled closed head injury model was established for mice using a pneumatic impact device. Brains were harvested at 1, 3, or 7 days post-injury and assayed for morphological changes by immunocytochemistry, Western blot analysis, and wet/dry weight. Cerebral edema and expression of both aquaporin type 4 and glial fibrillary acidic protein were increased at all time points examined. Immunocytochemical measurements in both cortical and hippocampal slices also revealed significant neuronal swelling and reactive gliosis. Treatment of mice with 2MeSADP (100 μM) or MRS2365 (100 μM) 30 min after trauma significantly reduced all post-injury symptoms of TBI including edema, neuronal swelling, reactive gliosis, and AQ4 expression. The neuroprotective effect was lost in IP(3)R2-/- mice treated with 2MeSADP. Immunocytochemical labeling of brain slices confirmed that P2Y(1)R expression was defined to cortical and hippocampal astrocytes, but not neurons. Taken together, the data show that stimulation of astrocytic P2Y(1)Rs significantly reduces brain injury after acute trauma and is mediated by the IP(3)-signaling pathway. We suggest that enhancing astrocyte mitochondrial metabolism offers a promising neuroprotective strategy for a broad range of brain injuries.
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Affiliation(s)
- Lora Talley Watts
- Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio School of Medicine, TX 78229-3904, USA
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122
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P2X7 receptor activation regulates microglial cell death during oxygen-glucose deprivation. Neuropharmacology 2013; 73:311-9. [PMID: 23770338 DOI: 10.1016/j.neuropharm.2013.05.032] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 05/21/2013] [Accepted: 05/23/2013] [Indexed: 12/28/2022]
Abstract
Brain-resident microglia may promote tissue repair following stroke but, like other cells, they are vulnerable to ischemia. Here we identify mechanisms involved in microglial ischemic vulnerability. Using time-lapse imaging of cultured BV2 microglia, we show that simulated ischemia (oxygen-glucose deprivation; OGD) induces BV2 microglial cell death. Removal of extracellular Ca(2+) or application of Brilliant Blue G (BBG), a potent P2X7 receptor (P2X7R) antagonist, protected BV2 microglia from death. To validate and extend these in vitro findings, we assessed parenchymal microglia in freshly isolated hippocampal tissue slices from GFP-reporter mice (CX3CR1(GFP/+)). We confirmed that calcium removal or application of apyrase, an ATP-degrading enzyme, abolished OGD-induced microglial cell death in situ, consistent with involvement of ionotropic purinergic receptors. Indeed, whole cell recordings identified P2X7R-like currents in tissue microglia, and OGD-induced microglial cell death was inhibited by BBG. These pharmacological results were complemented by studies in tissue slices from P2X7R null mice, in which OGD-induced microglia cell death was reduced by nearly half. Together, these results indicate that stroke-like conditions induce calcium-dependent microglial cell death that is mediated in part by P2X7R. This is the first identification of a purinergic receptor regulating microglial survival in living brain tissues. From a therapeutic standpoint, these findings could help direct novel approaches to enhance microglial survival and function following stroke and other neuropathological conditions.
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123
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The c-Jun kinase signaling cascade promotes glial engulfment activity through activation of draper and phagocytic function. Cell Death Differ 2013; 20:1140-8. [PMID: 23618811 DOI: 10.1038/cdd.2013.30] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 01/02/2013] [Accepted: 02/07/2013] [Indexed: 01/09/2023] Open
Abstract
After neuronal injury or death glial cells become reactive, exhibiting dramatic changes in morphology and patterns of gene expression and ultimately engulfing neuronal debris. Rapid clearance of degenerating neuronal material is thought to be crucial for suppression of inflammation and promotion of functional recovery. Here we demonstrate that Drosophila c-Jun N-terminal kinase (dJNK) signaling is a critical in vivo mediator of glial engulfment activity. In response to axotomy, we find glial dJNK signals through a cascade involving the upstream mitogen-activated protein kinase kinase kinases Slipper and Tak1, the mitogen-activated protein kinase kinase MKK4, and ultimately the Drosophila activator protein 1 (AP-1) transcriptional complex composed of Jra and Kayak to initiate glial phagocytosis of degenerating axons. Interestingly, loss of dJNK also blocked injury-induced upregulation of Draper levels in glia, and glial-specific overexpression of Draper was sufficient to rescue engulfment defects associated with loss of dJNK signaling. This work identifies that the dJNK pathway is a novel mediator of glial engulfment activity and a primary role for the glial Slipper/Tak1 →MKK4 →dJNK →dAP-1 signaling cascade appears to be activation of draper expression after axon injury.
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124
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The effects of prenatal and postnatal environmental interaction: prenatal environmental adaptation hypothesis. ACTA ACUST UNITED AC 2013; 107:483-92. [PMID: 23624396 DOI: 10.1016/j.jphysparis.2013.04.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 04/13/2013] [Accepted: 04/15/2013] [Indexed: 01/23/2023]
Abstract
Adverse antenatal maternal environments during pregnancy influence fetal development that consequently increases risks of mental health problems including psychiatric disorders in offspring. Therefore, behavioral and brain alterations caused by adverse prenatal environmental conditions are generally considered as deficits. In this article, we propose a novel hypothesis, along with summarizing a body of literatures supporting it, that fetal neurodevelopmental alterations, particularly synaptic network changes occurring in the prefrontal cortex, associated with adverse prenatal environmental conditions may be adaptation to cope with expected severe postnatal environments, and therefore, psychiatric disorders may be able to be understood as adaptive strategies against severe environmental conditions through evolution. It is hoped that the hypothesis presented in this article stimulates and opens a new venue on research toward understanding of biological mechanisms and therapeutic treatments of psychiatric disorders.
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125
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A program for solving the brain ischemia problem. Brain Sci 2013; 3:460-503. [PMID: 24961411 PMCID: PMC4061849 DOI: 10.3390/brainsci3020460] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 03/23/2013] [Accepted: 03/26/2013] [Indexed: 02/01/2023] Open
Abstract
Our recently described nonlinear dynamical model of cell injury is here applied to the problems of brain ischemia and neuroprotection. We discuss measurement of global brain ischemia injury dynamics by time course analysis. Solutions to proposed experiments are simulated using hypothetical values for the model parameters. The solutions solve the global brain ischemia problem in terms of "master bifurcation diagrams" that show all possible outcomes for arbitrary durations of all lethal cerebral blood flow (CBF) decrements. The global ischemia master bifurcation diagrams: (1) can map to a single focal ischemia insult, and (2) reveal all CBF decrements susceptible to neuroprotection. We simulate measuring a neuroprotectant by time course analysis, which revealed emergent nonlinear effects that set dynamical limits on neuroprotection. Using over-simplified stroke geometry, we calculate a theoretical maximum protection of approximately 50% recovery. We also calculate what is likely to be obtained in practice and obtain 38% recovery; a number close to that often reported in the literature. The hypothetical examples studied here illustrate the use of the nonlinear cell injury model as a fresh avenue of approach that has the potential, not only to solve the brain ischemia problem, but also to advance the technology of neuroprotection.
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126
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Shrivastava K, Llovera G, Recasens M, Chertoff M, Giménez-Llort L, Gonzalez B, Acarin L. Temporal expression of cytokines and signal transducer and activator of transcription factor 3 activation after neonatal hypoxia/ischemia in mice. Dev Neurosci 2013; 35:212-25. [PMID: 23571161 DOI: 10.1159/000348432] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 01/23/2013] [Indexed: 11/19/2022] Open
Abstract
Hypoxia/ischemia (HI) is a prevalent reason for neonatal brain injury with inflammation being an inevitable phenomenon following such injury; but there is a scarcity of data regarding the signaling pathway involved and the effector molecules. The signal transducer and activator of transcription factor 3 (STAT3) is known to modulate injury following imbalance between pro- and anti-inflammatory cytokines in peripheral and central nervous system injury making it a potential molecule for study. The current study investigates the temporal expression of interleukin (IL)-6, IL-1β, tumor necrosis factor-α, IL-1ra, IL-4, IL-10, IL-13 and phosphorylated STAT3 (pSTAT3) after carotid occlusion and hypoxia (8% O2, 55 min) in postnatal day 7 C57BL/6 mice from 3 h to 21 days after hypoxia. Protein array illustrated notable changes in cytokines expressed in both hemispheres in a time-dependent manner. The major pro-inflammatory cytokines showing immediate changes between ipsi- and contralateral hemispheres were IL-6 and IL-1β. The anti-inflammatory cytokines IL-4 and IL-13 demonstrated a delayed augmentation with no prominent differences between hemispheres, while IL-1ra showed two distinct peaks of expression spread over time. We also illustrate for the first time the spatiotemporal activation of pSTAT3 (Y705 phosphorylation) after a neonatal HI in mice brain. The main regions expressing pSTAT3 were the hippocampus and the corpus callosum. pSTAT3+ cells were mostly a subpopulation of activated astrocytes (GFAP+) and microglia/macrophages (F4/80+) seen only in the ipsilateral hemisphere at most time points studied (till 7 days after hypoxia). The highest expression of pSTAT3+ cells was observed to be around 24-48 h, where the presence of pSTAT3+ astrocytes and pSTAT3+ microglia/macrophages was seen by confocal micrographs. In conclusion, our study highlights a synchronized expression of some pro- and anti-inflammatory cytokines, especially in the long term not previously defined. It also points towards a significant role of STAT3 signaling following micro- and astrogliosis in the pathophysiology of neonatal HI-related brain injury. In the study, a shift from pro-inflammatory to anti-inflammatory cytokine profile was also noted as the injury progressed. We suggest that while designing efficient neuroprotective therapies using inflammatory molecules, the time of intervention and balance between the pro- and anti-inflammatory cytokines must be considered.
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Affiliation(s)
- K Shrivastava
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma Barcelona, Bellaterra, Spain.
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127
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P2Y1R-initiated, IP3R-dependent stimulation of astrocyte mitochondrial metabolism reduces and partially reverses ischemic neuronal damage in mouse. J Cereb Blood Flow Metab 2013; 33:600-11. [PMID: 23321785 PMCID: PMC3618399 DOI: 10.1038/jcbfm.2012.214] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Glia-based neuroprotection strategies are emerging as promising new avenues to treat brain damage. We previously reported that activation of the glial-specific purinergic receptor, P2Y(1)R, reduces both astrocyte swelling and brain infarcts in a photothrombotic mouse model of stroke. These restorative effects were dependent on astrocyte mitochondrial metabolism. Here, we extend these findings and report that P2Y(1)R stimulation with the purinergic ligand 2-methylthioladenosine 5' diphosphate (2MeSADP) reduces and partially reverses neuronal damage induced by photothrombosis. In vivo neuronal morphology was confocally imaged in transgenic mice expressing yellow fluorescent protein under the control of the Thy1 promoter. Astrocyte mitochondrial membrane potentials, monitored with the potential sensitive dye tetra-methyl rhodamine methyl ester, were depolarized after photothrombosis and subsequently repolarized when P2Y(1)Rs were stimulated. Mice deficient in the astrocyte-specific type 2 inositol 1,4,5 trisphosphate (IP(3)) receptor exhibited aggravated ischemic dendritic damage after photothrombosis. Treatment of these mice with 2MeSADP did not invoke an intracellular Ca(2+) response, did not repolarize astrocyte mitochondria, and did not reduce or partially reverse neuronal lesions induced by photothrombotic stroke. These results demonstrate that IP(3)-Ca(2+) signaling in astrocytes is not only critical for P2Y(1)R-enhanced protection, but suggest that IP(3)-Ca(2+) signaling is also a key component of endogenous neuroprotection.
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128
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Eyo UB, Dailey ME. Microglia: key elements in neural development, plasticity, and pathology. J Neuroimmune Pharmacol 2013; 8:494-509. [PMID: 23354784 DOI: 10.1007/s11481-013-9434-z] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Accepted: 01/14/2013] [Indexed: 12/31/2022]
Abstract
A century after Cajal identified a "third element" of the nervous system, many issues have been clarified about the identity and function of one of its major components, the microglia. Here, we review recent findings by microgliologists, highlighting results from imaging studies that are helping provide new views of microglial behavior and function. In vivo imaging in the intact adult rodent CNS has revolutionized our understanding of microglial behaviors in situ and has raised speculation about their function in the uninjured adult brain. Imaging studies in ex vivo mammalian tissue preparations and in intact model organisms including zebrafish are providing insights into microglial behaviors during brain development. These data suggest that microglia play important developmental roles in synapse remodeling, developmental apoptosis, phagocytic clearance, and angiogenesis. Because microglia also contribute to pathology, including neurodevelopmental and neurobehavioral disorders, ischemic injury, and neuropathic pain, promising new results raise the possibility of leveraging microglia for therapeutic roles. Finally, exciting recent work is addressing unanswered questions regarding the nature of microglial-neuronal communication. While it is now apparent that microglia play diverse roles in neural development, behavior, and pathology, future research using neuroimaging techniques will be essential to more fully exploit these intriguing cellular targets for effective therapeutic intervention applied to a variety of conditions.
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Affiliation(s)
- Ukpong B Eyo
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA
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129
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Thrombin induces release of proinflammatory chemokines interleukin-8 and interferon-γ-induced protein-10 from cultured human fetal astrocytes. Neuroreport 2013; 24:36-40. [DOI: 10.1097/wnr.0b013e32835c1de4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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130
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Beauquis J, Pavía P, Pomilio C, Vinuesa A, Podlutskaya N, Galvan V, Saravia F. Environmental enrichment prevents astroglial pathological changes in the hippocampus of APP transgenic mice, model of Alzheimer's disease. Exp Neurol 2013; 239:28-37. [PMID: 23022919 DOI: 10.1016/j.expneurol.2012.09.009] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 09/04/2012] [Accepted: 09/20/2012] [Indexed: 01/08/2023]
Abstract
Alzheimer's disease (AD) is a neurodegenerative disease that affects neurons and glial cells and leads to dementia. Growing evidence shows that glial changes may precede neuronal alterations and behavioral impairment in the progression of the disease. The modulation of these changes could be addressed as a potential therapeutic strategy. Environmental enrichment has been classically associated to effects on neuronal morphology and function but less attention has been paid to the modulation of glia. We thus characterized astroglial changes in the hippocampus of adult PDAPP-J20 transgenic mice, a model of AD, exposed for 3 months to an enriched environment, from 5 to 8 months of age. Using confocal microscopy, three-dimensional reconstruction and Sholl analysis, we evaluated the morphology of two distinct populations of astrocytes: those associated to amyloid β plaques and those that were not. We found that plaque-associated astrocytes in PDAPP-J20 mice had an increased volume and process ramification than control astrocytes. Non-plaque-associated astrocytes showed a decrease in volume and an increase in the ramification of GFAP+ processes as compared with control astrocytes. Environmental enrichment prevented these alterations and promoted a cellular morphology similar to that found in control mice. Morphological changes in non-plaque-associated astrocytes were found also at 5 months of age, before amyloid β deposition in the hippocampus. These results suggest that glial alterations have an early onset in AD pathogenesis and that the exposure to an enriched environment is an appropriate strategy to reverse them. Cellular and molecular pathways involved in this regulation could constitute potential novel therapeutic targets.
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Affiliation(s)
- Juan Beauquis
- Laboratorio de Neurobiología, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
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131
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van der Knaap MS, Boor I, Estévez R. Megalencephalic leukoencephalopathy with subcortical cysts: chronic white matter oedema due to a defect in brain ion and water homoeostasis. Lancet Neurol 2012; 11:973-85. [PMID: 23079554 DOI: 10.1016/s1474-4422(12)70192-8] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is characterised by chronic white matter oedema. The disease has an infantile onset and leads to slow neurological deterioration in most cases, but, surprisingly, some patients recover. The first disease gene, MLC1, identified in 2001, is mutated in 75% of patients. At that time, nothing was known about MLC1 protein function and the pathophysiology of MLC. More recently, HEPACAM (also called GLIALCAM) has been identified as a second disease gene. GlialCAM serves as an escort for MLC1 and the chloride channel CLC2. The defect in MLC1 has been shown to hamper the cell volume regulation of astrocytes. One of the most important consequences involves the potassium siphoning process, which is essential in brain ion and water homoeostasis. An understanding of the mechanisms of white matter oedema in MLC is emerging. Further insight into the specific function of MLC1 is necessary to find treatment targets.
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Affiliation(s)
- Marjo S van der Knaap
- Department of Pediatrics/Child Neurology, VU University Medical Centre, Amsterdam, Netherlands.
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132
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Wu X, Tang R, Liu Y, Song J, Yu Z, Wang W, Xie M. Small RNA interference-mediated gene silencing of TREK-1 potassium channel in cultured astrocytes. ACTA ACUST UNITED AC 2012; 32:849-855. [PMID: 23271285 DOI: 10.1007/s11596-012-1046-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Indexed: 11/27/2022]
Abstract
This study was aimed to examine the effect of TREK-1 silencing on the function of astrocytes. Three 21-nucleotide small interfering RNA (siRNA) duplexes (siT1, siT2, siT3) targeting TREK-1 were constructed. Cy3-labeled dsRNA oligmers were used to determine the transfection efficiency in cultured astrocytes. TREK-1-specific siRNA duplexes (siT1, siT2, siT3) at the optimal concentration were transfected into cultured astrocytes, and the most efficient siRNA was identified by the method of immunocytochemical staining and Western blotting. The proliferation of astrocytes tranfected with TREK-1-targeting siRNA under hypoxia condition was measured by fluorescence-activated cell sorting (FACS). The results showed that TREK-1 was expressed in cultured astrocytes. The dsRNA oligmers targeting TREK-1 could be transfected efficiently in cultured astrocytes and down-regulate the expression of TREK-1 in astrocytes. Moreover, the down-regulation of TREK-1 in astrocytes contributed to the proliferation of astrocytes under hypoxia condition as determined by cell cycle analysis. It was concluded that siRNA is a powerful technique that can be used to knockdown the expression of TREK-1 in astrocytes, which helps further investigate the function of TREK-1 channel in astrocytes under physicological and pathological condition.
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Affiliation(s)
- Xiao Wu
- Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Ronghua Tang
- Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Yang Liu
- Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Jingjiao Song
- Division of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Zhiyuan Yu
- Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Wei Wang
- Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Minjie Xie
- Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430030, China.
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133
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Lange SC, Bak LK, Waagepetersen HS, Schousboe A, Norenberg MD. Primary cultures of astrocytes: their value in understanding astrocytes in health and disease. Neurochem Res 2012; 37:2569-88. [PMID: 22926576 DOI: 10.1007/s11064-012-0868-0] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 08/01/2012] [Accepted: 08/01/2012] [Indexed: 12/26/2022]
Abstract
During the past few decades of astrocyte research it has become increasingly clear that astrocytes have taken a central position in all central nervous system activities. Much of our new understanding of astrocytes has been derived from studies conducted with primary cultures of astrocytes. Such cultures have been an invaluable tool for studying roles of astrocytes in physiological and pathological states. Many central astrocytic functions in metabolism, amino acid neurotransmission and calcium signaling were discovered using this tissue culture preparation and most of these observations were subsequently found in vivo. Nevertheless, primary cultures of astrocytes are an in vitro model that does not fully mimic the complex events occurring in vivo. Here we present an overview of the numerous contributions generated by the use of primary astrocyte cultures to uncover the diverse functions of astrocytes. Many of these discoveries would not have been possible to achieve without the use of astrocyte cultures. Additionally, we address and discuss the concerns that have been raised regarding the use of primary cultures of astrocytes as an experimental model system.
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Affiliation(s)
- Sofie C Lange
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
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134
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Simões GF, de Oliveira ALR. Granulocyte-colony stimulating factor improves MDX mouse response to peripheral nerve injury. PLoS One 2012; 7:e42803. [PMID: 22912741 PMCID: PMC3418329 DOI: 10.1371/journal.pone.0042803] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 07/11/2012] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND G-CSF has been shown to increase neuronal survival, which may positively influence the spinal cord microenvironment during the course of muscular dystrophies. METHODOLOGY/PRINCIPAL FINDINGS Male MDX mice that were six weeks of age received a left sciatic nerve transection and were treated with intraperitoneal injections of 200 µg/kg/day of G-CSF 7 days before and 7 days after the transection. The axotomy was performed after the cycles of muscular degeneration/regeneration, consistent with previous descriptions of this model of muscular dystrophy. C57BL/10 mice were used as control subjects. Seven days after the surgery, the animals were sacrificed and their lumbar spinal cords were processed for immunohistochemistry (anti-MHC I, anti-Synaptophysin, anti-GFAP and anti-IBA-1) and transmission electron microscopy. MHC I expression increased in both strains of mice after the axotomy. Nevertheless, the MDX mice displayed a significantly smaller MHC I upregulation than the control mice. Regarding GFAP expression, the MDX mice showed a stronger astrogliosis compared with the C57BL/10 mice across all groups. Both groups that were treated with G-CSF demonstrated preservation of synaptophysin expression compared with the untreated and placebo groups. The quantitative analysis of the ultrastructural level showed a preservation of the synaptic covering for the both groups that were treated with G-CSF and the axotomized groups showed a smaller loss of synaptic contact in relation to the treated groups after the lesion. CONCLUSIONS/SIGNIFICANCE The reduction of active inputs to the alpha-motoneurons and increased astrogliosis in the axotomized and control groups may be associated with the cycles of muscle degeneration/regeneration that occur postnatally. The G-CSF treated group showed a preservation of the spinal cord microenvironment after the lesion. Moreover, the increase of MHC I expression in the MDX mice that were treated with G-CSF may indicate that this drug performs an active role in regenerative potential after lesions.
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Affiliation(s)
- Gustavo Ferreira Simões
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, Brazil
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135
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Protective effect of carbamazepine on kainic acid-induced neuronal cell death through activation of signal transducer and activator of transcription-3. J Mol Neurosci 2012; 49:172-81. [PMID: 22772901 DOI: 10.1007/s12031-012-9854-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 06/27/2012] [Indexed: 12/24/2022]
Abstract
Studies have shown that the protective effect of carbamazepine (CBZ) on seizure-induced neuronal injury. However, its precise mechanisms remain unknown. Here, to investigate the neuroprotective mechanism of CBZ against seizure-induced neuronal cell death, we identified the change of gene expressions by CBZ in the hippocampus of kainic acid (KA)-treated mice using microarray method, and studied the involvement of candidate gene in neuroprotective action of CBZ. KA (15 mg/kg) and/or CBZ (30 mg/kg, 0.5 h after KA exposure) were injected intraperitoneally into mice. Through microarray analysis, we found that signal transducer and activator of transcription-3 (Stat3) gene expression was upregulated in the hippocampal CA3 region, 24 h after KA injection (15 mg/kg), and that CBZ further elevated Stat3 expression in KA-treated mice. KA also increased the protein level and phosphorylation of Stat3, and CBZ further increased the Stat3 phosphorylation, without changing Stat3 protein level in KA-treated mice. In particular, phospho-Stat3 immunoreactivity (IR) by KA was shown in astrocytes rather than in neurons; whereas phospho-Stat3 IR by CBZ in KA-treated mice was observed predominantly in neurons, and also in neuroprotective protein Bcl-xL-expression cells. These results indicate that Stat3 may play an important role in neuroprotective action of CBZ on seizure-induced neuronal injury.
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136
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Abstract
Diseases of the human brain are almost universally attributed to malfunction or loss of nerve cells. However, a considerable amount of work has, during the last decade, expanded our view on the role of astrocytes in CNS (central nervous system), and this analysis suggests that astrocytes contribute to both initiation and propagation of many (if not all) neurological diseases. Astrocytes provide metabolic and trophic support to neurons and oligodendrocytes. Here, we shall endeavour a broad overviewing of the progress in the field and forward the idea that loss of homoeostatic astroglial function leads to an acute loss of neurons in the setting of acute insults such as ischaemia, whereas more subtle dysfunction of astrocytes over periods of months to years contributes to epilepsy and to progressive loss of neurons in neurodegenerative diseases. The majority of therapeutic drugs currently in clinical use target neuronal receptors, channels or transporters. Future therapeutic efforts may benefit by a stronger focus on the supportive homoeostatic functions of astrocytes.
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137
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Barreto G, White RE, Ouyang Y, Xu L, Giffard RG. Astrocytes: targets for neuroprotection in stroke. Cent Nerv Syst Agents Med Chem 2012; 11:164-73. [PMID: 21521168 DOI: 10.2174/187152411796011303] [Citation(s) in RCA: 229] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 02/05/2011] [Accepted: 03/09/2011] [Indexed: 02/08/2023]
Abstract
In the past two decades, over 1000 clinical trials have failed to demonstrate a benefit in treating stroke, with the exception of thrombolytics. Although many targets have been pursued, including antioxidants, calcium channel blockers, glutamate receptor blockers, and neurotrophic factors, often the focus has been on neuronal mechanisms of injury. Broader attention to loss and dysfunction of non-neuronal cell types is now required to increase the chance of success. Of the several glial cell types, this review will focus on astrocytes. Astrocytes are the most abundant cell type in the higher mammalian nervous system, and they play key roles in normal CNS physiology and in central nervous system injury and pathology. In the setting of ischemia astrocytes perform multiple functions, some beneficial and some potentially detrimental, making them excellent candidates as therapeutic targets to improve outcome following stroke and in other central nervous system injuries. The older neurocentric view of the central nervous system has changed radically with the growing understanding of the many essential functions of astrocytes. These include K+ buffering, glutamate clearance, brain antioxidant defense, close metabolic coupling with neurons, and modulation of neuronal excitability. In this review, we will focus on those functions of astrocytes that can both protect and endanger neurons, and discuss how manipulating these functions provides a novel and important strategy to enhance neuronal survival and improve outcome following cerebral ischemia.
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Affiliation(s)
- George Barreto
- Department of Anesthesia, Stanford University School of Medicine, S272, Stanford, CA 94305, USA
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138
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Adelson JD, Barreto GE, Xu L, Kim T, Brott BK, Ouyang YB, Naserke T, Djurisic M, Xiong X, Shatz CJ, Giffard RG. Neuroprotection from stroke in the absence of MHCI or PirB. Neuron 2012; 73:1100-7. [PMID: 22445338 DOI: 10.1016/j.neuron.2012.01.020] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2012] [Indexed: 10/28/2022]
Abstract
Recovery from stroke engages mechanisms of neural plasticity. Here we examine a role for MHC class I (MHCI) H2-Kb and H2-Db, as well as PirB receptor. These molecules restrict synaptic plasticity and motor learning in the healthy brain. Stroke elevates neuronal expression not only of H2-Kb and H2-Db, but also of PirB and downstream signaling. KbDb knockout (KO) or PirB KO mice have smaller infarcts and enhanced motor recovery. KO hippocampal organotypic slices, which lack an intact peripheral immune response, have less cell death after in vitro ischemia. In PirB KO mice, corticospinal projections from the motor cortex are enhanced, and the reactive astrocytic response is dampened after MCAO. Thus, molecules that function in the immune system act not only to limit synaptic plasticity in healthy neurons, but also to exacerbate brain injury after ischemia. These results suggest therapies for stroke by targeting MHCI and PirB.
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Affiliation(s)
- Jaimie D Adelson
- Department of Biology and Neurobiology, Stanford University, Stanford, CA 94305-5437, USA
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139
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Sobrado M, Ramirez BG, Neria F, Lizasoain I, Arbones ML, Minami T, Redondo JM, Moro MA, Cano E. Regulator of calcineurin 1 (Rcan1) has a protective role in brain ischemia/reperfusion injury. J Neuroinflammation 2012; 9:48. [PMID: 22397398 PMCID: PMC3325863 DOI: 10.1186/1742-2094-9-48] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 03/07/2012] [Indexed: 01/17/2023] Open
Abstract
Background An increase in intracellular calcium concentration [Ca2+]i is one of the first events to take place after brain ischemia. A key [Ca2+]i-regulated signaling molecule is the phosphatase calcineurin (CN), which plays important roles in the modulation of inflammatory cascades. Here, we have analyzed the role of endogenous regulator of CN 1 (Rcan1) in response to experimental ischemic stroke induced by middle cerebral artery occlusion. Methods Animals were subjected to focal cerebral ischemia with reperfusion. To assess the role of Rcan1 after stroke, we measured infarct volume after 48 h of reperfusion in Rcan1 knockout (KO) and wild-type (WT) mice. In vitro studies were performed in astrocyte-enriched cortical primary cultures subjected to 3% oxygen (hypoxia) and glucose deprivation (HGD). Adenoviral vectors were used to analyze the effect of overexpression of Rcan1-4 protein. Protein expression was examined by immunohistochemistry and immunoblotting and expression of mRNA by quantitative real-time Reverse-Transcription Polymerase Chain Reaction (real time qRT-PCR). Results Brain ischemia/reperfusion (I/R) injury in vivo increased mRNA and protein expression of the calcium-inducible Rcan1 isoform (Rcan1-4). I/R-inducible expression of Rcan1 protein occurred mainly in astroglial cells, and in an in vitro model of ischemia, HGD treatment of primary murine astrocyte cultures induced Rcan1-4 mRNA and protein expression. Exogenous Rcan1-4 overexpression inhibited production of the inflammatory marker cyclo-oxygenase 2. Mice lacking Rcan1 had higher expression of inflammation associated genes, resulting in larger infarct volumes. Conclusions Our results support a protective role for Rcan1 during the inflammatory response to stroke, and underline the importance of the glial compartment in the inflammatory reaction that takes place after ischemia. Improved understanding of non-neuronal mechanisms in ischemic injury promises novel approaches to the treatment of acute ischemic stroke.
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Affiliation(s)
- Mónica Sobrado
- Unidad de Investigación Neurovascular, Departamento de Farmacología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain
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140
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Röhnert P, Schmidt W, Emmerlich P, Goihl A, Wrenger S, Bank U, Nordhoff K, Täger M, Ansorge S, Reinhold D, Striggow F. Dipeptidyl peptidase IV, aminopeptidase N and DPIV/APN-like proteases in cerebral ischemia. J Neuroinflammation 2012; 9:44. [PMID: 22373413 PMCID: PMC3359160 DOI: 10.1186/1742-2094-9-44] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Accepted: 02/28/2012] [Indexed: 11/23/2022] Open
Abstract
Background Cerebral inflammation is a hallmark of neuronal degeneration. Dipeptidyl peptidase IV, aminopeptidase N as well as the dipeptidyl peptidases II, 8 and 9 and cytosolic alanyl-aminopeptidase are involved in the regulation of autoimmunity and inflammation. We studied the expression, localisation and activity patterns of these proteases after endothelin-induced occlusion of the middle cerebral artery in rats, a model of transient and unilateral cerebral ischemia. Methods Male Sprague-Dawley rats were used. RT-PCR, immunohistochemistry and protease activity assays were performed at different time points, lasting from 2 h to 7 days after cerebral ischemia. The effect of protease inhibitors on ischemia-dependent infarct volumes was quantified 7 days post middle cerebral artery occlusion. Statistical analysis was conducted using the t-test. Results Qualitative RT-PCR revealed these proteases in ipsilateral and contralateral cortices. Dipeptidyl peptidase II and aminopeptidase N were up-regulated ipsilaterally from 6 h to 7 days post ischemia, whereas dipeptidyl peptidase 9 and cytosolic alanyl-aminopeptidase were transiently down-regulated at day 3. Dipeptidyl peptidase 8 and aminopeptidase N immunoreactivities were detected in cortical neurons of the contralateral hemisphere. At the same time point, dipeptidyl peptidase IV, 8 and aminopeptidase N were identified in activated microglia and macrophages in the ipsilateral cortex. Seven days post artery occlusion, dipeptidyl peptidase IV immunoreactivity was found in the perikarya of surviving cortical neurons of the ipsilateral hemisphere, whereas their nuclei were dipeptidyl peptidase 8- and amino peptidase N-positive. At the same time point, dipeptidyl peptidase IV, 8 and aminopeptidase N were targeted in astroglial cells. Total dipeptidyl peptidase IV, 8 and 9 activities remained constant in both hemispheres until day 3 post experimental ischemia, but were increased (+165%) in the ipsilateral cortex at day 7. In parallel, aminopeptidase N and cytosolic alanyl-aminopeptidase activities remained unchanged. Conclusions Distinct expression, localization and activity patterns of proline- and alanine-specific proteases indicate their involvement in ischemia-triggered inflammation and neurodegeneration. Consistently, IPC1755, a non-selective protease inhibitor, revealed a significant reduction of cortical lesions after transient cerebral ischemia and may suggest dipeptidyl peptidase IV, aminopeptidase N and proteases with similar substrate specificity as potentially therapy-relevant targets.
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Affiliation(s)
- Peter Röhnert
- KeyNeurotek Pharmaceuticals AG, Leipziger Str. 44, D-39120 Magdeburg, Germany
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141
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Yamagata K. Pathological alterations of astrocytes in stroke-prone spontaneously hypertensive rats under ischemic conditions. Neurochem Int 2011; 60:91-8. [PMID: 22100568 DOI: 10.1016/j.neuint.2011.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 10/27/2011] [Accepted: 11/04/2011] [Indexed: 11/18/2022]
Abstract
Stroke-prone spontaneously hypertensive rats (SHRSP/Izm) develop severe hypertension, and more than 95% of them die of cerebral stroke. We showed the vulnerability of neuronal cells of SHRSP/Izm rats. Furthermore, we analyzed the characteristics of SHRSP/Izm astrocytes during a stroke. It is known that the proliferating ability of SHRSP/Izm astrocytes is significantly enhanced compared with those in the normotensive Wistar Kyoto rats (WKY/Izm) strain. Conversely, the ability of SHRSP/Izm astrocytes to form tight junctions (TJ) was attenuated compared with astrocytes from WKY/Izm rats. During the stress of hypoxia and reoxygenation (H/R), lactate production, an energy source for neuronal cells, decreased in SHRSP/Izm astrocytes in comparison with the WKY/Izm strain. Moreover, during H/R, SHRSP/Izm astrocytes decreased their production of glial cell line-derived neurotrophic factor (GDNF) in comparison with WKY/Izm astrocytes. Furthermore, SHRSP/Izm rats decreased production of l-serine, compared with WKY/Izm rats following nitric oxide (NO) stimulation. Additionally, in H/R, astrocytes of SHRSP/Izm rats expressed adhesion molecules such as VCAM-1 at higher levels. It is possible that all of these differences between SHRSP/Izm and WKY/Izm astrocytes are not associated with the neurological disorders in SHRSP/Izm. However, attenuated production of lactate and reduced GDNF production in astrocytes may reduce required energy levels and weaken the nutritional status of SHRSP/Ism neuronal cells. We suggest that the attenuation of astrocytes' functions accelerates neuronal cell death during stroke, and may contribute to the development of strokes in SHRSP/Izm. In this review, we summarize the altered properties of SHRSP/Izm astrocytes during a stroke.
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Affiliation(s)
- Kazuo Yamagata
- Laboratory of Molecular Health Science of Food, Department of Food Bioscience and Biotechnology, College of Bioresource Sciences, Nihon University (NUBS), 1866 Kameino, Fujisawa-shi, Kanagawa 252-8510, Japan.
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142
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Petzold GC, Murthy VN. Role of astrocytes in neurovascular coupling. Neuron 2011; 71:782-97. [PMID: 21903073 DOI: 10.1016/j.neuron.2011.08.009] [Citation(s) in RCA: 285] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2011] [Indexed: 10/17/2022]
Abstract
Neural activity is intimately tied to blood flow in the brain. This coupling is specific enough in space and time that modern imaging methods use local hemodynamics as a measure of brain activity. In this review, we discuss recent evidence indicating that neuronal activity is coupled to local blood flow changes through an intermediary, the astrocyte. We highlight unresolved issues regarding the role of astrocytes and propose ways to address them using novel techniques. Our focus is on cellular level analysis in vivo, but we also relate mechanistic insights gained from ex vivo experiments to native tissue. We also review some strategies to harness advances in optical and genetic methods to study neurovascular coupling in the intact brain.
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Affiliation(s)
- Gabor C Petzold
- German Center for Neurodegenerative Diseases (DZNE), Ludwig-Erhard-Allee 2, 53175 Bonn, Germany.
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143
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Ridder MC, Boor I, Lodder JC, Postma NL, Capdevila-Nortes X, Duarri A, Brussaard AB, Estévez R, Scheper GC, Mansvelder HD, van der Knaap MS. Megalencephalic leucoencephalopathy with cysts: defect in chloride currents and cell volume regulation. Brain 2011; 134:3342-54. [DOI: 10.1093/brain/awr255] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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144
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Hobohm C, Laignel F, Kacza J, Küppers-Tiedt L, Heindl M, Schneider D, Grosche J, Härtig W, Michalski D. Long-lasting neuronal loss following experimental focal cerebral ischemia is not affected by combined administration of tissue plasminogen activator and hyperbaric oxygen. Brain Res 2011; 1417:115-26. [DOI: 10.1016/j.brainres.2011.08.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2011] [Revised: 07/26/2011] [Accepted: 08/11/2011] [Indexed: 01/13/2023]
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145
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Yang YF, Chen Z, Hu SL, Hu J, Li B, Li JT, Wei LJ, Qian ZM, Lin JK, Feng H, Zhu G. Interleukin-1 receptor associated kinases-1/4 inhibition protects against acute hypoxia/ischemia-induced neuronal injury in vivo and in vitro. Neuroscience 2011; 196:25-34. [PMID: 21925238 DOI: 10.1016/j.neuroscience.2011.08.059] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 08/23/2011] [Accepted: 08/25/2011] [Indexed: 11/29/2022]
Abstract
Neuronal Toll-like receptors (TLRs)-2 and -4 have been shown to play a pivotal role in ischemic brain injury, and the interleukin-1 receptor associated kinases (IRAKs) are considered to be the key signaling molecules involved downstream of TLRs. Here, we investigated the expression levels of IRAK-1 and -4 and the effects of IRAK-1/4 inhibition on brain ischemic insult and neuronal hypoxia-induced injury. Male Sprague-Dawley (SD) rats and the rat neuroblastoma B35 cell line were used in these experiments. Permanent middle cerebral artery occlusion (MCAO) was induced by the intraluminal filament technique, and B35 cells were stimulated with the hypoxia-mimetic, cobalt chloride (CoCl(2)). Following induction of hypoxia/ischemia (H/I), B35 cells and cerebral cortical neurons expressed higher levels of IRAK-1 and -4. Furthermore, IRAK-1/4 inhibition decreased the mortality rate, functional deficits, and ischemic infarct volume by 7 days after MCAO. Similarly, IRAK-1/4 inhibition attenuated CoCl(2)-induced cytotoxicity and apoptosis in B35 cells in vitro. Our results show that IRAK-1/4 inhibition decreased the nuclear translocation of the nuclear factor-kappaB (NF-κB) p65 subunit, the levels of activated (phosphorylated) c-jun N-terminal kinase (JNK) and cleaved caspase-3, and the secretion of TNF-α and IL-6 in B35 cells at 6 h after CoCl(2) treatment. These data suggest that IRAK-1/4 inhibition plays a neuroprotective role in H/I-induced brain injury.
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Affiliation(s)
- Y-F Yang
- Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Gaotanyan 30, Chongqing 400038, China
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146
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Yagi T, Yoshioka H, Wakai T, Kato T, Horikoshi T, Kinouchi H. Activation of signal transducers and activators of transcription 3 in the hippocampal CA1 region in a rat model of global cerebral ischemic preconditioning. Brain Res 2011; 1422:39-45. [PMID: 21983208 DOI: 10.1016/j.brainres.2011.08.076] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2011] [Revised: 08/12/2011] [Accepted: 08/31/2011] [Indexed: 12/20/2022]
Abstract
The signal transducers and activators of transcription 3 (STAT3) has been suggested to have neuroprotective roles. However, its role in ischemic preconditioning (PC) is still obscure. In this study, we examined the phosphorylation status of ser727-STAT3, which is necessary for activation of STAT3, and its roles in a rat global ischemia model with or without PC. PC was induced by 3 min of nonlethal ischemia 48 h before 5 min of lethal ischemia. Western blot analysis showed that phospho-ser727-STAT3 significantly increased from 8 to 48 h after nonlethal ischemia, while it increased only for 1h after lethal ischemia and returned to the baseline within 24h. In the preconditioned brains, phospho-ser727-STAT3 was induced at 1 to 4h after lethal ischemia, and decrease of its levels delayed compared to the nonconditioned brains. Immunohistochemistry revealed that phospho-ser727-STAT3 was expressed mainly in CA1 neurons after nonlethal ischemia. Additionally, STAT3 inhibitor peptide treatment prevented PC induced-neuroprotection. These results indicate that phosphorylation of ser727-STAT3 plays an important role in PC induced- neuroptotection.
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Affiliation(s)
- Takashi Yagi
- Department of Neurosurgery, Interdisciplinary graduate school of medicine and engineering, University of Yamanashi, Japan
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147
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Abstract
The seminal discovery that glial cells, particularly astrocytes, can release a number of gliotransmitters that serve as signalling molecules for the cross-talk with neighbouring cellular populations has recently changed our perception of brain functioning, as well as our view of the pathogenesis of several disorders of the CNS. Since glutamate was one of the first gliotransmitters to be identified and characterized, we tackle the mechanisms that underlie its release from astrocytes, including the Ca2+ signals underlying its efflux from astroglia, and we discuss the involvement of these events in a number of relevant physiological processes, from the modulatory control of neighbouring synapses to the regulation of blood supply to cerebral tissues. The relevance of these mechanisms strongly indicates that the contribution of glial cells and gliotransmission to the activities of the brain cannot be overlooked, and any study of CNS physiopathology needs to consider glial biology to have a comprehensive overview of brain function and dysfunction. Abnormalites in the signalling that controls the astrocytic release of glutamate are described in several experimental models of neurological disorders, for example, AIDS dementia complex, Alzheimer's disease and cerebral ischaemia. While the modalities of glutamate release from astrocytes remain poorly understood, and this represents a major impediment to the definition of novel therapeutic strategies targeting this process at the molecular level, some key mediators deputed to the control of the glial release of this excitatory amino acid have been identified. Among these, we can mention, for instance, proinflammatory cytokines, such as tumour necrosis factor-α, and prostaglandins. Agents that are able to block the major steps of tumour necrosis factor-α and prostaglandin production and/or signalling can be proposed as novel therapeutic targets for the treatment of these disorders.
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Affiliation(s)
- Daniela Rossi
- Laboratory for Research on Neurodegenerative Disorders, IRCCS Fondazione Salvatore Maugeri, Pavia, Italy.
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148
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Olabarria M, Noristani HN, Verkhratsky A, Rodríguez JJ. Age-dependent decrease in glutamine synthetase expression in the hippocampal astroglia of the triple transgenic Alzheimer's disease mouse model: mechanism for deficient glutamatergic transmission? Mol Neurodegener 2011; 6:55. [PMID: 21801442 PMCID: PMC3199854 DOI: 10.1186/1750-1326-6-55] [Citation(s) in RCA: 147] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 07/30/2011] [Indexed: 01/21/2023] Open
Abstract
Astrocytes are fundamental for brain homeostasis and the progression and outcome of many neuropathologies including Alzheimer's disease (AD). In the triple transgenic mouse model of AD (3xTg-AD) generalised hippocampal astroglia atrophy precedes a restricted and specific β-amyloid (Aβ) plaque-related astrogliosis. Astrocytes are critical for CNS glutamatergic transmission being the principal elements of glutamate homeostasis through maintaining its synthesis, uptake and turnover via glutamate-glutamine shuttle. Glutamine synthetase (GS), which is specifically expressed in astrocytes, forms glutamine by an ATP-dependent amination of glutamate. Here, we report changes in GS astrocytic expression in two major cognitive areas of the hippocampus (the dentate gyrus, DG and the CA1) in 3xTg-AD animals aged between 9 and 18 months. We found a significant reduction in Nv (number of cell/mm3) of GS immunoreactive (GS-IR) astrocytes starting from 12 months (28.59%) of age in the DG, and sustained at 18 months (31.65%). CA1 decrease of GS-positive astrocytes Nv (33.26%) occurs at 18 months. This Nv reduction of GS-IR astrocytes is paralleled by a decrease in overall GS expression (determined by its optical density) that becomes significant at 18 months (21.61% and 19.68% in DG and CA1, respectively). GS-IR Nv changes are directly associated with the presence of Aβ deposits showing a decrease of 47.92% as opposed to 23.47% in areas free of Aβ. These changes in GS containing astrocytes and GS-immunoreactivity indicate AD-related impairments of glutamate homeostatic system, at the advanced and late stages of the disease, which may affect the efficacy of glutamatergic transmission in the diseased brain that may contribute to the cognitive deficiency.
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Affiliation(s)
- Markel Olabarria
- Institute of Experimental Medicine, ASCR, Videnska 1083, 142 20 Prague 4, Czech Republic.
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149
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Pre-conditioning induces the precocious differentiation of neonatal astrocytes to enhance their neuroprotective properties. ASN Neuro 2011; 3:e00062. [PMID: 21722095 PMCID: PMC3153963 DOI: 10.1042/an20100029] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Hypoxic preconditioning reprogrammes the brain's response to subsequent H/I (hypoxia–ischaemia) injury by enhancing neuroprotective mechanisms. Given that astrocytes normally support neuronal survival and function, the purpose of the present study was to test the hypothesis that a hypoxic preconditioning stimulus would activate an adaptive astrocytic response. We analysed several functional parameters 24 h after exposing rat pups to 3 h of systemic hypoxia (8% O2). Hypoxia increased neocortical astrocyte maturation as evidenced by the loss of GFAP (glial fibrillary acidic protein)-positive cells with radial morphologies and the acquisition of multipolar GFAP-positive cells. Interestingly, many of these astrocytes had nuclear S100B. Accompanying their differentiation, there was increased expression of GFAP, GS (glutamine synthetase), EAAT-1 (excitatory amino acid transporter-1; also known as GLAST), MCT-1 (monocarboxylate transporter-1) and ceruloplasmin. A subsequent H/I insult did not result in any further astrocyte activation. Some responses were cell autonomous, as levels of GS and MCT-1 increased subsequent to hypoxia in cultured forebrain astrocytes. In contrast, the expression of GFAP, GLAST and ceruloplasmin remained unaltered. Additional experiments utilized astrocytes exposed to exogenous dbcAMP (dibutyryl-cAMP), which mimicked several aspects of the preconditioning response, to determine whether activated astrocytes could protect neurons from subsequent excitotoxic injury. dbcAMP treatment increased GS and glutamate transporter expression and function, and as hypothesized, protected neurons from glutamate excitotoxicity. Taken altogether, these results indicate that a preconditioning stimulus causes the precocious differentiation of astrocytes and increases the acquisition of multiple astrocytic functions that will contribute to the neuroprotection conferred by a sublethal preconditioning stress.
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150
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Changes in lipid-sensitive two-pore domain potassium channel TREK-1 expression and its involvement in astrogliosis following cerebral ischemia in rats. J Mol Neurosci 2011; 46:384-92. [PMID: 21789545 DOI: 10.1007/s12031-011-9598-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 07/12/2011] [Indexed: 02/03/2023]
Abstract
Astrocytes play an active and important role in the pathophysiology of cerebral ischemia. We have previously shown that mature hipppocampal astrocytes functionally express two-pore domain K(+) channel TREK-1, which significantly contributes to the passive conductance and help to set the negative resting membrane potential essential for the optimal operation of some astrocytic homeostatic functions. However, its expression under ischemic conditions remains to be determined. In this study, we examined the expression of TREK-1 in rat brain under physiological and focal ischemia conditions. The results show that TREK-1 was broadly expressed on astrocytes and neurons in the cortex, CA1 region of hippocampus. After middle cerebral artery occlusion induced focal ischemia, the TREK-1 expression was significantly increased at days 3, 7 and 30 following reperfusion, which correlated with reactive astrogliosis in the cortex and hippocampus. Cultured cortical astrocytes also express TREK-1. TREK-1 inhibitor quinine inhibited the proliferation of astrocytes exposed to hypoxia condition. These data provide evidence showing the astrocytic TREK-1 involvement in ischemia pathology.
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