101
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Kimbrough IF, Robel S, Roberson ED, Sontheimer H. Vascular amyloidosis impairs the gliovascular unit in a mouse model of Alzheimer's disease. Brain 2015; 138:3716-33. [PMID: 26598495 PMCID: PMC5006220 DOI: 10.1093/brain/awv327] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 08/21/2015] [Accepted: 08/24/2015] [Indexed: 01/08/2023] Open
Abstract
Reduced cerebral blood flow impairs cognitive function and ultimately causes irreparable damage to brain tissue. The gliovascular unit, composed of neural and vascular cells, assures sufficient blood supply to active brain regions. Astrocytes, vascular smooth muscle cells, and pericytes are important players within the gliovascular unit modulating vessel diameters. While the importance of the gliovascular unit and the signals involved in regulating local blood flow to match neuronal activity is now well recognized, surprisingly little is known about this interface in disease. Alzheimer's disease is associated with reduced cerebral blood flow. Here, we studied how the gliovascular unit is affected in a mouse model of Alzheimer's disease, using a combination of ex vivo and in vivo imaging approaches. We specifically labelled vascular amyloid in living mice using the dye methoxy-XO4. We elicited vessel responses ex vivo using either pharmacological stimuli or cell-specific calcium uncaging in vascular smooth muscle cells or astrocytes. Multi-photon in vivo imaging through a cranial window allowed us to complement our ex vivo data in the presence of blood flow after label-free optical activation of vascular smooth muscle cells in the intact brain. We found that vascular amyloid deposits separated astrocyte end-feet from the endothelial vessel wall. High-resolution 3D images demonstrated that vascular amyloid developed in ring-like structures around the vessel circumference, essentially forming a rigid cast. Where vascular amyloid was present, stimulation of astrocytes or vascular smooth muscle cells via ex vivo Ca(2+) uncaging or in vivo optical activation produced only poor vascular responses. Strikingly, vessel segments that were unaffected by vascular amyloid responded to the same extent as vessels from age-matched control animals. We conclude that while astrocytes can still release vasoactive substances, vascular amyloid deposits render blood vessels rigid and reduce the dynamic range of affected vessel segments. These results demonstrate a mechanism that could account in part for the reduction in cerebral blood flow in patients with Alzheimer's disease.media-1vid110.1093/brain/awv327_video_abstractawv327_video_abstract.
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Affiliation(s)
- Ian F Kimbrough
- 1 Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA 2 Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Stefanie Robel
- 1 Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA 2 Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Erik D Roberson
- 1 Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA 3 Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA 4 Center for Neurodegeneration and Experimental Therapeutics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Harald Sontheimer
- 1 Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA 2 Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
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102
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Liu Z, Chopp M. Astrocytes, therapeutic targets for neuroprotection and neurorestoration in ischemic stroke. Prog Neurobiol 2015; 144:103-20. [PMID: 26455456 DOI: 10.1016/j.pneurobio.2015.09.008] [Citation(s) in RCA: 401] [Impact Index Per Article: 44.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 08/06/2015] [Accepted: 09/05/2015] [Indexed: 01/04/2023]
Abstract
Astrocytes are the most abundant cell type within the central nervous system. They play essential roles in maintaining normal brain function, as they are a critical structural and functional part of the tripartite synapses and the neurovascular unit, and communicate with neurons, oligodendrocytes and endothelial cells. After an ischemic stroke, astrocytes perform multiple functions both detrimental and beneficial, for neuronal survival during the acute phase. Aspects of the astrocytic inflammatory response to stroke may aggravate the ischemic lesion, but astrocytes also provide benefit for neuroprotection, by limiting lesion extension via anti-excitotoxicity effects and releasing neurotrophins. Similarly, during the late recovery phase after stroke, the glial scar may obstruct axonal regeneration and subsequently reduce the functional outcome; however, astrocytes also contribute to angiogenesis, neurogenesis, synaptogenesis, and axonal remodeling, and thereby promote neurological recovery. Thus, the pivotal involvement of astrocytes in normal brain function and responses to an ischemic lesion designates them as excellent therapeutic targets to improve functional outcome following stroke. In this review, we will focus on functions of astrocytes and astrocyte-mediated events during stroke and recovery. We will provide an overview of approaches on how to reduce the detrimental effects and amplify the beneficial effects of astrocytes on neuroprotection and on neurorestoration post stroke, which may lead to novel and clinically relevant therapies for stroke.
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Affiliation(s)
- Zhongwu Liu
- Department of Neurology, Henry Ford Hospital, Detroit, MI, USA.
| | - Michael Chopp
- Department of Neurology, Henry Ford Hospital, Detroit, MI, USA; Department of Physics, Oakland University, Rochester, MI, USA
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103
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Chen C, Chan A, Wen H, Chung SH, Deng W, Jiang P. Stem and Progenitor Cell-Derived Astroglia Therapies for Neurological Diseases. Trends Mol Med 2015; 21:715-729. [PMID: 26443123 DOI: 10.1016/j.molmed.2015.09.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 09/04/2015] [Accepted: 09/08/2015] [Indexed: 02/07/2023]
Abstract
Astroglia are a major cellular constituent of the central nervous system (CNS) and play crucial roles in brain development, function, and integrity. Increasing evidence demonstrates that astroglia dysfunction occurs in a variety of neurological disorders ranging from CNS injuries to genetic diseases and chronic degenerative conditions. These new insights herald the concept that transplantation of astroglia could be of therapeutic value in treating the injured or diseased CNS. Recent technological advances in the generation of human astroglia from stem and progenitor cells have been prominent. We propose that a better understanding of the suitability of astroglial cells in transplantation as well as of their therapeutic effects in animal models may lead to the establishment of astroglia-based therapies to treat neurological diseases.
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Affiliation(s)
- Chen Chen
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA, USA; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Sacramento, CA, USA
| | - Albert Chan
- Department of Pediatrics, University of California, Davis, CA, USA
| | - Han Wen
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA, USA; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Sacramento, CA, USA
| | | | - Wenbin Deng
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA, USA; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Sacramento, CA, USA.
| | - Peng Jiang
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA, USA; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Sacramento, CA, USA; Department of Developmental Neuroscience, Munroe-Meyer Institute, University of Nebraska Medical Center, NE, USA.
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104
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Seidel JL, Escartin C, Ayata C, Bonvento G, Shuttleworth CW. Multifaceted roles for astrocytes in spreading depolarization: A target for limiting spreading depolarization in acute brain injury? Glia 2015; 64:5-20. [PMID: 26301517 DOI: 10.1002/glia.22824] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 01/31/2015] [Accepted: 03/02/2015] [Indexed: 12/17/2022]
Abstract
Spreading depolarizations (SDs) are coordinated waves of synchronous depolarization, involving large numbers of neurons and astrocytes as they spread slowly through brain tissue. The recent identification of SDs as likely contributors to pathophysiology in human subjects has led to a significant increase in interest in SD mechanisms, and possible approaches to limit the numbers of SDs or their deleterious consequences in injured brain. Astrocytes regulate many events associated with SD. SD initiation and propagation is dependent on extracellular accumulation of K(+) and glutamate, both of which involve astrocytic clearance. SDs are extremely metabolically demanding events, and signaling through astrocyte networks is likely central to the dramatic increase in regional blood flow that accompanies SD in otherwise healthy tissues. Astrocytes may provide metabolic support to neurons following SD, and may provide a source of adenosine that inhibits neuronal activity following SD. It is also possible that astrocytes contribute to the pathophysiology of SD, as a consequence of excessive glutamate release, facilitation of NMDA receptor activation, brain edema due to astrocyte swelling, or disrupted coupling to appropriate vascular responses after SD. Direct or indirect evidence has accumulated implicating astrocytes in many of these responses, but much remains unknown about their specific contributions, especially in the context of injury. Conversion of astrocytes to a reactive phenotype is a prominent feature of injured brain, and recent work suggests that the different functional properties of reactive astrocytes could be targeted to limit SDs in pathophysiological conditions.
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Affiliation(s)
- Jessica L Seidel
- Stroke and Neurovascular Regulation Lab, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
| | - Carole Escartin
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département des Sciences du Vivant (DSV), Institut d'Imagerie Biomédicale (I2BM), Molecular Imaging Center (MIRCen), CNRS UMR 9199, Université Paris-Sud, Université Paris-Saclay, F-92260 Fontenay-aux-Roses, France
| | - Cenk Ayata
- Stroke and Neurovascular Regulation Lab, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts.,Stroke Service and Neuroscience Intensive Care Unit, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
| | - Gilles Bonvento
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département des Sciences du Vivant (DSV), Institut d'Imagerie Biomédicale (I2BM), Molecular Imaging Center (MIRCen), CNRS UMR 9199, Université Paris-Sud, Université Paris-Saclay, F-92260 Fontenay-aux-Roses, France
| | - C William Shuttleworth
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, New Mexico
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105
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Benjamin Kacerovsky J, Murai KK. Stargazing: Monitoring subcellular dynamics of brain astrocytes. Neuroscience 2015; 323:84-95. [PMID: 26162237 DOI: 10.1016/j.neuroscience.2015.07.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 06/28/2015] [Accepted: 07/01/2015] [Indexed: 01/21/2023]
Abstract
Astrocytes are major non-neuronal cell types in the central nervous system that regulate a variety of processes in the brain including synaptic transmission, neurometabolism, and cerebrovasculature tone. Recent discoveries have revealed that astrocytes perform very specialized and heterogeneous roles in brain homeostasis and function. Exactly how astrocytes fulfill such diverse roles in the brain remains to be fully understood and is an active area of research. In this review, we focus on the complex subcellular anatomical features of protoplasmic gray matter astrocytes in the mature, healthy brain that likely empower these cells with the ability to detect and respond to changes in neuronal and synaptic activity. In particular, we discuss how intricate processes on astrocytes allow these cells to communicate with neurons and their synapses and strategically deliver specific cellular organelles such as mitochondria and ribosomes to active compartments within the neuropil. Understanding the properties of these structural elements will lead to a better understanding of how astrocytes function in the healthy and diseased brain.
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Affiliation(s)
- J Benjamin Kacerovsky
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec H3G 1A4, Canada
| | - K K Murai
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec H3G 1A4, Canada.
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106
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Disruption in the Blood-Brain Barrier: The Missing Link between Brain and Body Inflammation in Bipolar Disorder? Neural Plast 2015; 2015:708306. [PMID: 26075104 PMCID: PMC4444594 DOI: 10.1155/2015/708306] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 02/02/2015] [Accepted: 02/05/2015] [Indexed: 01/01/2023] Open
Abstract
The blood-brain barrier (BBB) regulates the transport of micro- and macromolecules between the peripheral blood and the central nervous system (CNS) in order to maintain optimal levels of essential nutrients and neurotransmitters in the brain. In addition, the BBB plays a critical role protecting the CNS against neurotoxins. There has been growing evidence that BBB disruption is associated with brain inflammatory conditions such as Alzheimer's disease and multiple sclerosis. Considering the increasing role of inflammation and oxidative stress in the pathophysiology of bipolar disorder (BD), here we propose a novel model wherein transient or persistent disruption of BBB integrity is associated with decreased CNS protection and increased permeability of proinflammatory (e.g., cytokines, reactive oxygen species) substances from the peripheral blood into the brain. These events would trigger the activation of microglial cells and promote localized damage to oligodendrocytes and the myelin sheath, ultimately compromising myelination and the integrity of neural circuits. The potential implications for research in this area and directions for future studies are discussed.
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107
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Astrocyte physiopathology: At the crossroads of intercellular networking, inflammation and cell death. Prog Neurobiol 2015; 130:86-120. [PMID: 25930681 DOI: 10.1016/j.pneurobio.2015.04.003] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 04/15/2015] [Accepted: 04/20/2015] [Indexed: 12/11/2022]
Abstract
Recent breakthroughs in neuroscience have led to the awareness that we should revise our traditional mode of thinking and studying the CNS, i.e. by isolating the privileged network of "intelligent" synaptic contacts. We may instead need to contemplate all the variegate communications occurring between the different neural cell types, and centrally involving the astrocytes. Basically, it appears that a single astrocyte should be considered as a core that receives and integrates information from thousands of synapses, other glial cells and the blood vessels. In turn, it generates complex outputs that control the neural circuitry and coordinate it with the local microcirculation. Astrocytes thus emerge as the possible fulcrum of the functional homeostasis of the healthy CNS. Yet, evidence indicates that the bridging properties of the astrocytes can change in parallel with, or as a result of, the morphological, biochemical and functional alterations these cells undergo upon injury or disease. As a consequence, they have the potential to transform from supportive friends and interactive partners for neurons into noxious foes. In this review, we summarize the currently available knowledge on the contribution of astrocytes to the functioning of the CNS and what goes wrong in various pathological conditions, with a particular focus on Amyotrophic Lateral Sclerosis, Alzheimer's Disease and ischemia. The observations described convincingly demonstrate that the development and progression of several neurological disorders involve the de-regulation of a finely tuned interplay between multiple cell populations. Thus, it seems that a better understanding of the mechanisms governing the integrated communication and detrimental responses of the astrocytes as well as their impact towards the homeostasis and performance of the CNS is fundamental to open novel therapeutic perspectives.
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108
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Vardjan N, Verkhratsky A, Zorec R. Pathologic Potential of Astrocytic Vesicle Traffic: New Targets to Treat Neurologic Diseases? Cell Transplant 2015; 24:599-612. [DOI: 10.3727/096368915x687750] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Vesicles are small intracellular organelles that are fundamental for constitutive housekeeping of the plasmalemma, intercellular transport, and cell-to-cell communications. In astroglial cells, traffic of vesicles is associated with cell morphology, which determines the signaling potential and metabolic support for neighboring cells, including when these cells are considered to be used for cell transplantations or for regulating neurogenesis. Moreover, vesicles are used in astrocytes for the release of vesicle-laden chemical messengers. Here we review the properties of membrane-bound vesicles that store gliotransmitters, endolysosomes that are involved in the traffic of plasma membrane receptors, and membrane transporters. These vesicles are all linked to pathological states, including amyotrophic lateral sclerosis, multiple sclerosis, neuroinflammation, trauma, edema, and states in which astrocytes contribute to developmental disorders. In multiple sclerosis, for example, fingolimod, a recently introduced drug, apparently affects vesicle traffic and gliotransmitter release from astrocytes, indicating that this process may well be used as a new pathophysiologic target for the development of new therapies.
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Affiliation(s)
- Nina Vardjan
- Celica Biomedical, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Alexei Verkhratsky
- Celica Biomedical, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Achucarro Center for Neuroscience, Ikerbasque, Basque Foundation for Science, Bilbao, Spain
- Faculty of Life Sciences, The University of Manchester, Manchester, UK
| | - Robert Zorec
- Celica Biomedical, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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109
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MacVicar BA, Newman EA. Astrocyte regulation of blood flow in the brain. Cold Spring Harb Perspect Biol 2015; 7:cshperspect.a020388. [PMID: 25818565 DOI: 10.1101/cshperspect.a020388] [Citation(s) in RCA: 215] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Neuronal activity results in increased blood flow in the brain, a response named functional hyperemia. Astrocytes play an important role in mediating this response. Neurotransmitters released from active neurons evoke Ca(2+) increases in astrocytes, leading to the release of vasoactive metabolites of arachidonic acid from astrocyte endfeet onto blood vessels. Synthesis of prostaglandin E2 (PGE2) and epoxyeicosatrienoic acids (EETs) dilate blood vessels, whereas 20-hydroxyeicosatetraenoic acid (20-HETE) constricts vessels. The release of K(+) from astrocyte endfeet may also contribute to vasodilation. Oxygen modulates astrocyte regulation of blood flow. Under normoxic conditions, astrocytic Ca(2+) signaling results in vasodilation, whereas under hyperoxic conditions, vasoconstriction is favored. Astrocytes also contribute to the generation of vascular tone. Tonic release of both 20-HETE and ATP from astrocytes constricts vascular smooth muscle cells, generating vessel tone. Under pathological conditions, including Alzheimer's disease and diabetic retinopathy, disruption of normal astrocyte physiology can compromise the regulation of blood flow.
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Affiliation(s)
- Brian A MacVicar
- Djavad Mowafaghian Centre for Brain Health, Department of Psychiatry, University of British Columbia, Vancouver, British Columbia V6T 2B5, Canada
| | - Eric A Newman
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455
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110
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Nicaise C, Mitrecic D, Falnikar A, Lepore AC. Transplantation of stem cell-derived astrocytes for the treatment of amyotrophic lateral sclerosis and spinal cord injury. World J Stem Cells 2015; 7:380-398. [PMID: 25815122 PMCID: PMC4369494 DOI: 10.4252/wjsc.v7.i2.380] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/07/2014] [Accepted: 11/19/2014] [Indexed: 02/06/2023] Open
Abstract
Neglected for years, astrocytes are now recognized to fulfill and support many, if not all, homeostatic functions of the healthy central nervous system (CNS). During neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and spinal cord injury (SCI), astrocytes in the vicinity of degenerating areas undergo both morphological and functional changes that might compromise their intrinsic properties. Evidence from human and animal studies show that deficient astrocyte functions or loss-of-astrocytes largely contribute to increased susceptibility to cell death for neurons, oligodendrocytes and axons during ALS and SCI disease progression. Despite exciting advances in experimental CNS repair, most of current approaches that are translated into clinical trials focus on the replacement or support of spinal neurons through stem cell transplantation, while none focus on the specific replacement of astroglial populations. Knowing the important functions carried out by astrocytes in the CNS, astrocyte replacement-based therapies might be a promising approach to alleviate overall astrocyte dysfunction, deliver neurotrophic support to degenerating spinal tissue and stimulate endogenous CNS repair abilities. Enclosed in this review, we gathered experimental evidence that argue in favor of astrocyte transplantation during ALS and SCI. Based on their intrinsic properties and according to the cell type transplanted, astrocyte precursors or stem cell-derived astrocytes promote axonal growth, support mechanisms and cells involved in myelination, are able to modulate the host immune response, deliver neurotrophic factors and provide protective molecules against oxidative or excitotoxic insults, amongst many possible benefits. Embryonic or adult stem cells can even be genetically engineered in order to deliver missing gene products and therefore maximize the chance of neuroprotection and functional recovery. However, before broad clinical translation, further preclinical data on safety, reliability and therapeutic efficiency should be collected. Although several technical challenges need to be overcome, we discuss the major hurdles that have already been met or solved by targeting the astrocyte population in experimental ALS and SCI models and we discuss avenues for future directions based on latest molecular findings regarding astrocyte biology.
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111
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Astrocitos en las enfermedades neurodegenerativas (I): función y caracterización molecular. Neurologia 2015; 30:119-29. [DOI: 10.1016/j.nrl.2012.12.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 12/15/2012] [Indexed: 12/23/2022] Open
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112
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Guillamón-Vivancos T, Gómez-Pinedo U, Matías-Guiu J. Astrocytes in neurodegenerative diseases (I): function and molecular description. NEUROLOGÍA (ENGLISH EDITION) 2015. [DOI: 10.1016/j.nrleng.2014.12.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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113
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Petravicz J, Boyt KM, McCarthy KD. Astrocyte IP3R2-dependent Ca(2+) signaling is not a major modulator of neuronal pathways governing behavior. Front Behav Neurosci 2014; 8:384. [PMID: 25429263 PMCID: PMC4228853 DOI: 10.3389/fnbeh.2014.00384] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 10/17/2014] [Indexed: 12/22/2022] Open
Abstract
Calcium-dependent release of gliotransmitters by astrocytes is reported to play a critical role in synaptic transmission and be necessary for long-term potentiation (LTP), long-term depression (LTD) and other forms of synaptic modulation that are correlates of learning and memory. Further, physiological processes reported to be dependent on Ca2+ fluxes in astrocytes include functional hyperemia, sleep, and regulation of breathing. The preponderance of findings indicate that most, if not all, receptor dependent Ca2+ fluxes within astrocytes are due to release of Ca2+ through IP3 receptor/channels in the endoplasmic reticulum. Findings from several laboratories indicate that astrocytes only express IP3 receptor type 2 (IP3R2) and that a knockout of IP3R2 obliterates the GPCR-dependent astrocytic Ca2+ responses. Assuming that astrocytic Ca2+ fluxes play a critical role in synaptic physiology, it would be predicted that elimination of astrocytic Ca2+ fluxes would lead to marked changes in behavioral tests. Here, we tested this hypothesis by conducting a broad series of behavioral tests that recruited multiple brain regions, on an IP3R2 conditional knockout mouse model. We present the novel finding that behavioral processes are unaffected by lack of astrocyte IP3R-mediated Ca2+ signals. IP3R2 cKO animals display no change in anxiety or depressive behaviors, and no alteration to motor and sensory function. Morris water maze testing, a behavioral correlate of learning and memory, was unaffected by lack of astrocyte IP3R2-mediated Ca2+-signaling. Therefore, in contrast to the prevailing literature, we find that neither receptor-driven astrocyte Ca2+ fluxes nor, by extension, gliotransmission is likely to be a major modulating force on the physiological processes underlying behavior.
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Affiliation(s)
- Jeremy Petravicz
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Kristen M Boyt
- Department of Pharmacology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Ken D McCarthy
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; Department of Pharmacology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
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114
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Avila-Muñoz E, Arias C. When astrocytes become harmful: functional and inflammatory responses that contribute to Alzheimer's disease. Ageing Res Rev 2014; 18:29-40. [PMID: 25078115 DOI: 10.1016/j.arr.2014.07.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 07/03/2014] [Accepted: 07/21/2014] [Indexed: 12/24/2022]
Abstract
A growing body of research suggests that astrocytes play roles as contributors to the pathophysiology of Alzheimer's disease (AD). Several lines of evidence propose that activated astrocytes produce and release proinflammatory molecules that may be critical for the generation of amyloid-β peptide (Aβ). However, accumulating evidence indicates that Aβ may activate astrocytes, which leads to an increase in cytokines that has been suggested to be a causative factor in the cognitive dysfunction of AD; thus, a vicious circle may be created. Intrinsic inflammatory mechanisms may provide a regulatory system that is capable of influencing the neuronal microenvironment that affects neuronal survival. In this article, we address the evidence surrounding the interactions of dysfunctional astrocytes with neighboring neurons that may initiate a cascade of events that culminates with neuronal injury and the expression of the hallmark lesions of AD. Comprehensive knowledge of the molecular mechanisms underlying the participation of astrocytes in neurodegeneration could aid the development of therapies to restore proper astrocyte function that can be used in AD patients to prevent or alleviate the progression of the disease in a more efficient and comprehensive manner.
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115
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Adams DL, Piserchia V, Economides JR, Horton JC. Vascular Supply of the Cerebral Cortex is Specialized for Cell Layers but Not Columns. Cereb Cortex 2014; 25:3673-81. [PMID: 25246513 DOI: 10.1093/cercor/bhu221] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The vascular supply to layers and columns was compared in macaque primary visual cortex (V1) by labeling red blood cells via their endogenous peroxidase activity. Alternate sections were processed for cytochrome oxidase to reveal "patches" or "blobs," which anchor the interdigitated column systems of striate cortex. More densely populated cell layers received the most profuse blood supply. In the superficial layers the blood supply was organized into microvascular lobules, consisting of a central venule surrounded by arterioles. Each vessel was identified as an arteriole or venule by matching it with the penetration site where it entered the cortex from a parent arteriole or venule in the pial circulation. Although microvascular lobules and cytochrome oxidase patches had a similar periodicity, they bore no mutual relationship. The size and density of penetrating arterioles and venules did not differ between patches and interpatches. The red blood cell labeling in patches and interpatches was equal. Moreover, patches and interpatches were supplied by an anastomotic pial arteriole system, with no segregation of blood supply to the two compartments. Often a focal constriction was present at the origin of pial arterial branches, indicating that local control of cortical perfusion may be accomplished by vascular sphincters.
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Affiliation(s)
- Daniel L Adams
- Beckman Vision Center, University of California, San Francisco, San Francisco, CA 94143, USA Center for Mind/Brain Sciences, The University of Trento, Trento, Italy
| | | | - John R Economides
- Beckman Vision Center, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Jonathan C Horton
- Beckman Vision Center, University of California, San Francisco, San Francisco, CA 94143, USA
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116
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Joerk A, Seidel RA, Walter SG, Wiegand A, Kahnes M, Klopfleisch M, Kirmse K, Pohnert G, Westerhausen M, Witte OW, Holthoff K. Impact of heme and heme degradation products on vascular diameter in mouse visual cortex. J Am Heart Assoc 2014; 3:jah3660. [PMID: 25169792 PMCID: PMC4310418 DOI: 10.1161/jaha.114.001220] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
BACKGROUND Delayed cerebral vasospasm is the most common cause of mortality and severe neurological impairment in patients who survive subarachnoid hemorrhage. Despite improvements in the field of diagnostic imaging, options for prevention and medical treatment-primarily with the calcium channel antagonist nimodipine or hemodynamic manipulations-are insufficient. Previous studies have suggested that heme and bilirubin oxidation end products, originating from degraded hemoglobin around ruptured blood vessels, are involved in the development of vasospasm by inhibiting large conductance BKC a potassium channels in vascular smooth muscle cells. In this study, we identify individual heme degradation products regulating arteriolar diameter in dependence of BKC a channel activity. METHODS AND RESULTS Using differential interference contrast video microscopy in acute brain slices, we determined diameter changes of intracerebral arterioles in mouse visual cortex. In preconstricted vessels, the specific BKC a channel blockers paxilline and iberiotoxin as well as iron-containing hemin caused vasoconstriction. In addition, the bilirubin oxidation end product Z-BOX A showed a stronger vasoconstrictive potency than its regio-isomer Z-BOX B. Importantly, Z-BOX A had the same vasoconstrictive effect, independent of its origin from oxidative degradation or chemical synthesis. Finally, in slices of Slo1-deficient knockout mice, paxilline and Z-BOX A remained ineffective in changing arteriole diameter. CONCLUSIONS We identified individual components of the oxidative bilirubin degradation that led to vasoconstriction of cerebral arterioles. The vasoconstrictive effect of Z-BOX A and Z-BOX B was mediated by BKC a channel activity that might represent a signaling pathway in the occurrence of delayed cerebral vasospasm in subarachnoid hemorrhage patients.
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Affiliation(s)
- Alexander Joerk
- Hans‐Berger Department of Neurology, University Hospital Jena, Germany (A.J., S.G.W., A.W., K.K., O.W.W., K.H.)
| | - Raphael Andreas Seidel
- Institute of Inorganic and Analytical Chemistry, Friedrich‐Schiller University, Jena, Germany (R.A.S., M.K., M.K., G.P., M.W.)
- Department of Anesthesiology and Intensive Care Medicine/Center for Sepsis Control and Care, University Hospital, Friedrich Schiller University, Jena, Germany (R.A.S.)
| | - Sebastian Gottfried Walter
- Hans‐Berger Department of Neurology, University Hospital Jena, Germany (A.J., S.G.W., A.W., K.K., O.W.W., K.H.)
| | - Anne Wiegand
- Hans‐Berger Department of Neurology, University Hospital Jena, Germany (A.J., S.G.W., A.W., K.K., O.W.W., K.H.)
| | - Marcel Kahnes
- Institute of Inorganic and Analytical Chemistry, Friedrich‐Schiller University, Jena, Germany (R.A.S., M.K., M.K., G.P., M.W.)
| | - Maurice Klopfleisch
- Institute of Inorganic and Analytical Chemistry, Friedrich‐Schiller University, Jena, Germany (R.A.S., M.K., M.K., G.P., M.W.)
| | - Knut Kirmse
- Hans‐Berger Department of Neurology, University Hospital Jena, Germany (A.J., S.G.W., A.W., K.K., O.W.W., K.H.)
| | - Georg Pohnert
- Institute of Inorganic and Analytical Chemistry, Friedrich‐Schiller University, Jena, Germany (R.A.S., M.K., M.K., G.P., M.W.)
| | - Matthias Westerhausen
- Institute of Inorganic and Analytical Chemistry, Friedrich‐Schiller University, Jena, Germany (R.A.S., M.K., M.K., G.P., M.W.)
| | - Otto Wilhelm Witte
- Hans‐Berger Department of Neurology, University Hospital Jena, Germany (A.J., S.G.W., A.W., K.K., O.W.W., K.H.)
| | - Knut Holthoff
- Hans‐Berger Department of Neurology, University Hospital Jena, Germany (A.J., S.G.W., A.W., K.K., O.W.W., K.H.)
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117
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Watkins S, Robel S, Kimbrough IF, Robert SM, Ellis-Davies G, Sontheimer H. Disruption of astrocyte-vascular coupling and the blood-brain barrier by invading glioma cells. Nat Commun 2014; 5:4196. [PMID: 24943270 PMCID: PMC4127490 DOI: 10.1038/ncomms5196] [Citation(s) in RCA: 375] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 05/22/2014] [Indexed: 01/22/2023] Open
Abstract
Astrocytic endfeet cover the entire cerebral vasculature and serve as exchange sites for ions, metabolites, and energy substrates from the blood to the brain. They maintain endothelial tight junctions that form the blood-brain barrier (BBB) and release vasoactive molecules that regulate vascular tone. Malignant gliomas are highly invasive tumors that use the perivascular space for invasion and co-opt existing vessels as satellite tumors form. Here we use a clinically relevant mouse model of glioma and find that glioma cells, as they populate the perivascular space of pre-existing vessels, displace astrocytic endfeet from endothelial or vascular smooth muscle cells. This causes a focal breach in the BBB. Furthermore, astrocyte-mediated gliovascular coupling is lost, and glioma cells seize control over regulation of vascular tone through Ca2+-dependent release of K+. These findings have important clinical implications regarding blood flow in the tumor-associated brain and the ability to locally deliver chemotherapeutic drugs in disease.
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Affiliation(s)
- Stacey Watkins
- 1] Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, 1719 6th Avenue South, CIRC 425, Birmingham, Alabama 35294, USA [2]
| | - Stefanie Robel
- 1] Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, 1719 6th Avenue South, CIRC 425, Birmingham, Alabama 35294, USA [2]
| | - Ian F Kimbrough
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, 1719 6th Avenue South, CIRC 425, Birmingham, Alabama 35294, USA
| | - Stephanie M Robert
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, 1719 6th Avenue South, CIRC 425, Birmingham, Alabama 35294, USA
| | - Graham Ellis-Davies
- Department of Neuroscience, Mount Sinai School of Medicine, 1468 Madison Avenue, Annenberg Building Floor Ann22, New York, New York 10029, USA
| | - Harald Sontheimer
- Department of Neurobiology, Center for Glial Biology in Medicine, University of Alabama at Birmingham, 1719 6th Avenue South, CIRC 425, Birmingham, Alabama 35294, USA
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118
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Chen BR, Kozberg MG, Bouchard MB, Shaik MA, Hillman EMC. A critical role for the vascular endothelium in functional neurovascular coupling in the brain. J Am Heart Assoc 2014; 3:e000787. [PMID: 24926076 PMCID: PMC4309064 DOI: 10.1161/jaha.114.000787] [Citation(s) in RCA: 235] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Background The functional modulation of blood flow in the brain is critical for brain health and is the basis of contrast in functional magnetic resonance imaging. There is evident coupling between increases in neuronal activity and increases in local blood flow; however, many aspects of this neurovascular coupling remain unexplained by current models. Based on the rapid dilation of distant pial arteries during cortical functional hyperemia, we hypothesized that endothelial signaling may play a key role in the long‐range propagation of vasodilation during functional hyperemia in the brain. Although well characterized in the peripheral vasculature, endothelial involvement in functional neurovascular coupling has not been demonstrated. Methods and Results We combined in vivo exposed‐cortex multispectral optical intrinsic signal imaging (MS‐OISI) with a novel in vivo implementation of the light‐dye technique to record the cortical hemodynamic response to somatosensory stimulus in rats before and after spatially selective endothelial disruption. We demonstrate that discrete interruption of endothelial signaling halts propagation of stimulus‐evoked vasodilation in pial arteries, and that wide‐field endothelial disruption in pial arteries significantly attenuates the hemodynamic response to stimulus, particularly the early, rapid increase and peak in hyperemia. Conclusions Involvement of endothelial pathways in functional neurovascular coupling provides new explanations for the spatial and temporal features of the hemodynamic response to stimulus and could explain previous results that were interpreted as evidence for astrocyte‐mediated control of functional hyperemia. Our results unify many aspects of blood flow regulation in the brain and body and prompt new investigation of direct links between systemic cardiovascular disease and neural deficits.
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Affiliation(s)
- Brenda R Chen
- Laboratory for Functional Optical Imaging, Departments of Biomedical Engineering and Radiology, Columbia University, New York, 10027, NY (B.R.C., M.G.K., M.B.B., M.A.S., E.C.H.)
| | - Mariel G Kozberg
- Laboratory for Functional Optical Imaging, Departments of Biomedical Engineering and Radiology, Columbia University, New York, 10027, NY (B.R.C., M.G.K., M.B.B., M.A.S., E.C.H.)
| | - Matthew B Bouchard
- Laboratory for Functional Optical Imaging, Departments of Biomedical Engineering and Radiology, Columbia University, New York, 10027, NY (B.R.C., M.G.K., M.B.B., M.A.S., E.C.H.)
| | - Mohammed A Shaik
- Laboratory for Functional Optical Imaging, Departments of Biomedical Engineering and Radiology, Columbia University, New York, 10027, NY (B.R.C., M.G.K., M.B.B., M.A.S., E.C.H.)
| | - Elizabeth M C Hillman
- Laboratory for Functional Optical Imaging, Departments of Biomedical Engineering and Radiology, Columbia University, New York, 10027, NY (B.R.C., M.G.K., M.B.B., M.A.S., E.C.H.)
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119
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Chu T, Zhou H, Li F, Wang T, Lu L, Feng S. Astrocyte transplantation for spinal cord injury: current status and perspective. Brain Res Bull 2014; 107:18-30. [PMID: 24878447 DOI: 10.1016/j.brainresbull.2014.05.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 05/17/2014] [Accepted: 05/19/2014] [Indexed: 02/07/2023]
Abstract
Spinal cord injury (SCI) often causes incurable neurological dysfunction because axonal regeneration in adult spinal cord is rare. Astrocytes are gradually recognized as being necessary for the regeneration after SCI as they promote axonal growth under both physiological and pathophysiological conditions. Heterogeneous populations of astrocytes have been explored for structural and functional restoration. The results range from the early variable and modest effects of immature astrocyte transplantation to the later significant, but controversial, outcomes of glial-restricted precursor (GRP)-derived astrocyte (GDA) transplantation. However, the traditional neuron-centric view and the concerns about the inhibitory roles of astrocytes after SCI, along with the sporadic studies and the lack of a comprehensive review, have led to some confusion over the usefulness of astrocytes in SCI. It is the purpose of the review to discuss the current status of astrocyte transplantation for SCI based on a dialectical view of the context-dependent manner of astrocyte behavior and the time-associated characteristics of glial scarring. Critical issues are then analyzed to reveal the potential direction of future research.
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Affiliation(s)
- Tianci Chu
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Hengxing Zhou
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Fuyuan Li
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Tianyi Wang
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Lu Lu
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Shiqing Feng
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
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120
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Raz L. Estrogen and cerebrovascular regulation in menopause. Mol Cell Endocrinol 2014; 389:22-30. [PMID: 24472522 DOI: 10.1016/j.mce.2014.01.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 01/20/2014] [Accepted: 01/20/2014] [Indexed: 12/11/2022]
Abstract
Estrogen (E2), classically viewed as a reproductive steroid hormone, has non-reproductive functions throughout the body including in the brain and vasculature. Studies report diminished neuroprotection with declining E2 levels, corresponding with higher incidence of cerebrovascular and neurological disease. However, the effects of menopausal hormone therapy (MHT) on the cerebral vasculature and brain function remain controversial. This review will focus on evidence of 17β-estradiol actions in the cerebral vasculature, with a particular emphasis on the vasoactive, anti-inflammatory, anti-oxidant, metabolic and molecular properties. Controversies surrounding MHT in relation to cerebrovascular disease and stroke risk will be discussed, particularly the emerging evidence from clinical trials supporting the critical period hypothesis of estrogen protection.
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Affiliation(s)
- Limor Raz
- Department of Neurology, University of New Mexico, Albuquerque, NM, United States.
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121
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Naskar K, Stern JE. A functional coupling between extrasynaptic NMDA receptors and A-type K+ channels under astrocyte control regulates hypothalamic neurosecretory neuronal activity. J Physiol 2014; 592:2813-27. [PMID: 24835172 DOI: 10.1113/jphysiol.2014.270793] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Neuronal activity is controlled by a fine-tuned balance between intrinsic properties and extrinsic synaptic inputs. Moreover, neighbouring astrocytes are now recognized to influence a wide spectrum of neuronal functions. Yet, how these three key factors act in concert to modulate and fine-tune neuronal output is not well understood. Here, we show that in rat hypothalamic magnocellular neurosecretory cells (MNCs), glutamate NMDA receptors (NMDARs) are negatively coupled to the transient, voltage-gated A-type K(+) current (IA). We found that activation of NMDARs by extracellular glutamate levels influenced by astrocyte glutamate transporters resulted in a significant inhibition of IA. The NMDAR-IA functional coupling resulted from activation of extrasynaptic NMDARs, was calcium- and protein kinase C-dependent, and involved enhanced steady-state, voltage-dependent inactivation of IA. The NMDAR-IA coupling diminished the latency to the first evoked spike in response to membrane depolarization and increased the total number of evoked action potentials, thus strengthening the neuronal input/output function. Finally, we found a blunted NMDA-mediated inhibition of IA in dehydrated rats. Together, our findings support a novel signalling mechanism that involves a functional coupling between extrasynaptic NMDARs and A-type K(+) channels, which is influenced by local astrocytes. We show this signalling complex to play an important role in modulating hypothalamic neuronal excitability, which may contribute to adaptive responses during a sustained osmotic challenge such as dehydration.
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Affiliation(s)
- Krishna Naskar
- Department of Physiology, Medical College of Georgia, Georgia Regents University, Augusta, GA, 30912, USA
| | - Javier E Stern
- Department of Physiology, Medical College of Georgia, Georgia Regents University, Augusta, GA, 30912, USA
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122
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Li T, Yang Y, Canessa CM. A method for activation of endogenous acid-sensing ion channel 1a (ASIC1a) in the nervous system with high spatial and temporal precision. J Biol Chem 2014; 289:15441-8. [PMID: 24727474 DOI: 10.1074/jbc.m114.550012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Protons activate acid-sensing ion channel 1a (ASIC1a) in the central nervous system (CNS) although the impact of such activation on brain outputs remains elusive. Progress elucidating the functional roles of ASIC1a in the CNS has been hindered by technical difficulties of achieving acidification with spatial and temporal precision. We have implemented a method to control optically the opening of ASIC1a in brain slices and also in awake animals. The light-driven H(+) pump ArchT was expressed in astrocytes of mouse cortex by injection of adenoviral vectors containing a strong and astrocyte-specific promoter. Illumination with amber light acidified the surrounding interstitium and led to activation of endogenous ASIC1a channels and firing of action potentials in neurons localized in close proximity to ArchT-expressing astrocytes. We conclude that this optogenetic method offers a minimally invasive approach that enables examining the biological consequences of ASIC1a currents in any structure of the CNS and in the modulation of animal behaviors.
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Affiliation(s)
- Tianbo Li
- From the Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut 06520-8026
| | - Youshan Yang
- From the Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut 06520-8026
| | - Cecilia M Canessa
- From the Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut 06520-8026
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123
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Eskilsson A, Tachikawa M, Hosoya KI, Blomqvist A. Distribution of microsomal prostaglandin E synthase-1 in the mouse brain. J Comp Neurol 2014; 522:3229-44. [DOI: 10.1002/cne.23593] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 03/18/2014] [Accepted: 03/24/2014] [Indexed: 11/09/2022]
Affiliation(s)
- Anna Eskilsson
- Division of Cell Biology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences; Linköping University; Linköping Sweden
| | - Masanori Tachikawa
- Division of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical Sciences; Tohoku University; Sendai Japan
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences; University of Toyama; Toyama Japan
| | - Ken-ichi Hosoya
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences; University of Toyama; Toyama Japan
| | - Anders Blomqvist
- Division of Cell Biology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences; Linköping University; Linköping Sweden
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124
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Phenotypic heterogeneity and plasticity of isocortical and hippocampal astrocytes in the human brain. J Neurosci 2014; 34:2285-98. [PMID: 24501367 DOI: 10.1523/jneurosci.4037-13.2014] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
To examine the diversity of astrocytes in the human brain, we immunostained surgical specimens of temporal cortex and hippocampus and autopsy brains for CD44, a plasma membrane protein and extracellular matrix receptor. CD44 antibodies outline the details of astrocyte morphology to a degree not possible with glial fibrillary acidic protein (GFAP) antibodies. CD44+ astrocytes could be subdivided into two groups. First, CD44+ astrocytes with long processes were consistently found in the subpial area ("interlaminar" astrocytes), the deep isocortical layers, and the hippocampus. Many of these processes ended on blood vessels. Some were also found adjacent to large blood vessels, from which they extended long processes. We observed these CD44+, long-process astrocytes in every brain we examined, from fetal to adult. These astrocytes generally displayed high immunostaining for GFAP, S100β, and CD44, but low immunostaining for glutamine synthetase, excitatory amino-acid transporter 1 (EAAT1), and EAAT2. Aquaporin 4 (AQP4) appeared distributed all over the cell bodies and processes of the CD44+ astrocytes, while, in contrast, AQP4 localized to perivascular end feet in the CD44- protoplasmic astrocytes. Second, there were CD44+ astrocytes without long processes in the cortex. These were not present during gestation or at birth, and in adult brains varied substantially in number, shape, and immunohistochemical phenotype. Many of these displayed a "mixed" morphological and immunocytochemical phenotype between protoplasmic and fibrous astrocytes. We conclude that the diversity of astrocyte populations in the isocortex and archicortex in the human brain reflects both intrinsic and acquired phenotypes, the latter perhaps representing a shift from CD44- "protoplasmic" to CD44+ "fibrous"-like astrocytes.
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125
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Chen S, Feng H, Sherchan P, Klebe D, Zhao G, Sun X, Zhang J, Tang J, Zhang JH. Controversies and evolving new mechanisms in subarachnoid hemorrhage. Prog Neurobiol 2014; 115:64-91. [PMID: 24076160 PMCID: PMC3961493 DOI: 10.1016/j.pneurobio.2013.09.002] [Citation(s) in RCA: 270] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/07/2013] [Accepted: 09/12/2013] [Indexed: 12/13/2022]
Abstract
Despite decades of study, subarachnoid hemorrhage (SAH) continues to be a serious and significant health problem in the United States and worldwide. The mechanisms contributing to brain injury after SAH remain unclear. Traditionally, most in vivo research has heavily emphasized the basic mechanisms of SAH over the pathophysiological or morphological changes of delayed cerebral vasospasm after SAH. Unfortunately, the results of clinical trials based on this premise have mostly been disappointing, implicating some other pathophysiological factors, independent of vasospasm, as contributors to poor clinical outcomes. Delayed cerebral vasospasm is no longer the only culprit. In this review, we summarize recent data from both experimental and clinical studies of SAH and discuss the vast array of physiological dysfunctions following SAH that ultimately lead to cell death. Based on the progress in neurobiological understanding of SAH, the terms "early brain injury" and "delayed brain injury" are used according to the temporal progression of SAH-induced brain injury. Additionally, a new concept of the vasculo-neuronal-glia triad model for SAH study is highlighted and presents the challenges and opportunities of this model for future SAH applications.
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Affiliation(s)
- Sheng Chen
- Department of Neurosurgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China; Department of Physiology & Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - Hua Feng
- Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Prativa Sherchan
- Department of Physiology & Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - Damon Klebe
- Department of Physiology & Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - Gang Zhao
- Department of Neurology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shanxi, China
| | - Xiaochuan Sun
- Department of Neurosurgery, First Affiliated Hospital, Chongqing Medical University, Chongqing, China
| | - Jianmin Zhang
- Department of Neurosurgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jiping Tang
- Department of Physiology & Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - John H Zhang
- Department of Physiology & Pharmacology, Loma Linda University, Loma Linda, CA, USA; Department of Neurosurgery, Loma Linda University, Loma Linda, CA, USA.
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126
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Muoio V, Persson PB, Sendeski MM. The neurovascular unit - concept review. Acta Physiol (Oxf) 2014; 210:790-8. [PMID: 24629161 DOI: 10.1111/apha.12250] [Citation(s) in RCA: 340] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 08/01/2013] [Accepted: 01/27/2014] [Indexed: 01/01/2023]
Abstract
The cerebral hyperaemia is one of the fundamental mechanisms for the central nervous system homeostasis. Due also to this mechanism, oxygen and nutrients are maintained in satisfactory levels, through vasodilation and vasoconstriction. The brain hyperaemia, or coupling, is accomplished by a group of cells, closely related to each other; called neurovascular unit (NVU). The neurovascular unit is composed by neurones, astrocytes, endothelial cells of blood-brain barrier (BBB), myocytes, pericytes and extracellular matrix components. These cells, through their intimate anatomical and chemical relationship, detect the needs of neuronal supply and trigger necessary responses (vasodilation or vasoconstriction) for such demands. Here, we review the concepts of NVU, the coupling mechanisms and research strategies.
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Affiliation(s)
- V. Muoio
- Institut für Vegetative Physiologie; Charite- Universisitätmedizin Berlin; Berlin Germany
| | - P. B. Persson
- Institut für Vegetative Physiologie; Charite- Universisitätmedizin Berlin; Berlin Germany
| | - M. M. Sendeski
- Institut für Vegetative Physiologie; Charite- Universisitätmedizin Berlin; Berlin Germany
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127
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Vardjan N, Kreft M, Zorec R. Regulated Exocytosis in Astrocytes is as Slow as the Metabolic Availability of Gliotransmitters: Focus on Glutamate and ATP. GLUTAMATE AND ATP AT THE INTERFACE OF METABOLISM AND SIGNALING IN THE BRAIN 2014; 11:81-101. [DOI: 10.1007/978-3-319-08894-5_5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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128
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Otáhal J, Folbergrová J, Kovacs R, Kunz WS, Maggio N. Epileptic focus and alteration of metabolism. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 114:209-43. [PMID: 25078504 DOI: 10.1016/b978-0-12-418693-4.00009-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Epilepsy is one of the most common neurologic disorders affecting a substantial part of the population worldwide. Epileptic seizures represent the situation of increased neuronal activity associated with the enhanced demands for sufficient energy supply. For that purpose, very efficient regulatory mechanisms have to operate to ensure that cerebral blood flow, delivery of oxygen, and nutrients are continuously adapted to the local metabolic needs. The sophisticated regulation has to function in concert at several levels (systemic, tissue, cellular, and subcellular). Particularly, mitochondria play a key role not only in the energy production, but they are also central to many other processes including those leading to neuronal death. Impairment of any of the involved pathways can result in serious functional alterations, neurodegeneration, and potentially in epileptogenesis. The present review will address some of the important issues concerning vascular and metabolic changes in pathophysiology of epilepsy.
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Affiliation(s)
- Jakub Otáhal
- Institute of Physiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic.
| | - Jaroslava Folbergrová
- Institute of Physiology, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Richard Kovacs
- Institute for Neurophysiology, Charité-Medical University Berlin, Berlin, Germany
| | - Wolfram S Kunz
- Department of Epileptology, University of Bonn, Bonn, Germany
| | - Nicola Maggio
- Department of Neurology, The Joseph Sagol Neuroscience Center, The Chaim Sheba Medical Center, Tel HaShomer, Israel; Talpiot Medical Leadership Program, The Chaim Sheba Medical Center, Tel HaShomer, Israel
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129
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Xu G, Wang W, Zhou M. Spatial organization of NG2 glial cells and astrocytes in rat hippocampal CA1 region. Hippocampus 2013; 24:383-95. [PMID: 24339242 DOI: 10.1002/hipo.22232] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Revised: 10/31/2013] [Accepted: 11/26/2013] [Indexed: 12/12/2022]
Abstract
Similar to astrocytes, NG2 glial cells are uniformly distributed in the central nervous system (CNS). However, little is known about the interspatial relationship, nor the functional interactions between these two star-shaped glial subtypes. Confocal morphometric analysis showed that NG2 immunostained cells are spatially organized as domains in rat hippocampal CA1 region and that each NG2 glial domain occupies a spatial volume of ∼178, 364 μm(3) . The processes of NG2 glia and astrocytes overlap extensively; each NG2 glial domain interlaces with the processes deriving from 5.8 ± 0.4 neighboring astrocytes, while each astrocytic domain accommodates processes stemming from 4.5 ± 0.3 abutting NG2 glia. In CA1 stratum radiatum, the cell bodies of morphologically identified glial cells often appear to make direct somatic-somata contact, termed as doublets. We used dual patch recording and postrecording NG2/GFAP double staining to determine the glial identities of these doublets. We show that among 44 doublets, 50% were NG2 glia-astrocyte pairs, while another 38.6% and 11.4% were astrocyte-astrocyte and NG2 glia-NG2 glia pairs, respectively. In dual patch recording, neither electrical coupling nor intercellular biocytin transfer was detected in astrocyte-NG2 glia or NG2 glia-NG2 glia doublets. Altogether, although NG2 glia and astrocytes are not gap junction coupled, their cell bodies and processes are interwoven extensively. The anatomical and physiological relationships revealed in this study should facilitate future studies to understand the metabolic coupling and functional communication between NG2 glia and astrocytes.
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Affiliation(s)
- Guangjin Xu
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
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130
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Reduced Cerebrovascular Reactivity in Posterior Cerebral Arteries in Patients with Primary Open-Angle Glaucoma. Ophthalmology 2013; 120:2501-2507. [DOI: 10.1016/j.ophtha.2013.05.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 05/14/2013] [Accepted: 05/17/2013] [Indexed: 11/22/2022] Open
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131
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Abstract
The main functions of the respiratory neural network are to produce a coordinated, efficient, rhythmic motor behavior and maintain homeostatic control over blood oxygen and CO2/pH levels. Purinergic (ATP) signaling features prominently in these homeostatic reflexes. The signaling actions of ATP are produced through its binding to a diversity of ionotropic P2X and metabotropic P2Y receptors. However, its net effect on neuronal and network excitability is determined by the interaction between the three limbs of a complex system comprising the signaling actions of ATP at P2Rs, the distribution of multiple ectonucleotidases that differentially metabolize ATP into ADP, AMP, and adenosine (ADO), and the signaling actions of ATP metabolites, especially ADP at P2YRs and ADO at P1Rs. Understanding the significance of purinergic signaling is further complicated by the fact that neurons, glia, and the vasculature differentially express P2 and P1Rs, and that both neurons and glia release ATP. This article reviews at cellular, synaptic, and network levels, current understanding and emerging concepts about the diverse roles played by this three-part signaling system in: mediating the chemosensitivity of respiratory networks to hypoxia and CO2/pH; modulating the activity of rhythm generating networks and inspiratory motoneurons, and; controlling blood flow through the cerebral vasculature.
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Affiliation(s)
- Gregory D Funk
- Department of Physiology, Centre for Neuroscience, Women & Children's Health Research Institute (WCHRI), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
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132
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Hardingham N, Dachtler J, Fox K. The role of nitric oxide in pre-synaptic plasticity and homeostasis. Front Cell Neurosci 2013; 7:190. [PMID: 24198758 PMCID: PMC3813972 DOI: 10.3389/fncel.2013.00190] [Citation(s) in RCA: 164] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 10/05/2013] [Indexed: 11/13/2022] Open
Abstract
Since the observation that nitric oxide (NO) can act as an intercellular messenger in the brain, the past 25 years have witnessed the steady accumulation of evidence that it acts pre-synaptically at both glutamatergic and GABAergic synapses to alter release-probability in synaptic plasticity. NO does so by acting on the synaptic machinery involved in transmitter release and, in a coordinated fashion, on vesicular recycling mechanisms. In this review, we examine the body of evidence for NO acting as a retrograde factor at synapses, and the evidence from in vivo and in vitro studies that specifically establish NOS1 (neuronal nitric oxide synthase) as the important isoform of NO synthase in this process. The NOS1 isoform is found at two very different locations and at two different spatial scales both in the cortex and hippocampus. On the one hand it is located diffusely in the cytoplasm of a small population of GABAergic neurons and on the other hand the alpha isoform is located discretely at the post-synaptic density (PSD) in spines of pyramidal cells. The present evidence is that the number of NOS1 molecules that exist at the PSD are so low that a spine can only give rise to modest concentrations of NO and therefore only exert a very local action. The NO receptor guanylate cyclase is located both pre- and post-synaptically and this suggests a role for NO in the coordination of local pre- and post-synaptic function during plasticity at individual synapses. Recent evidence shows that NOS1 is also located post-synaptic to GABAergic synapses and plays a pre-synaptic role in GABAergic plasticity as well as glutamatergic plasticity. Studies on the function of NO in plasticity at the cellular level are corroborated by evidence that NO is also involved in experience-dependent plasticity in the cerebral cortex.
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Affiliation(s)
| | | | - Kevin Fox
- School of Biosciences, Cardiff UniversityCardiff, UK
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133
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Şovrea AS, Boşca AB. Astrocytes reassessment - an evolving concept part one: embryology, biology, morphology and reactivity. J Mol Psychiatry 2013; 1:18. [PMID: 26019866 PMCID: PMC4445578 DOI: 10.1186/2049-9256-1-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/05/2013] [Indexed: 01/10/2023] Open
Abstract
The goal of this review is to integrate - in its two parts - the considerable amount of information that has accumulated during these recent years over the morphology, biology and functions of astrocytes - first part - and to illustrate the active role of these cells in pathophysiological processes implicated in various psychiatric and neurologic disorders – second part.
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Affiliation(s)
- Alina Simona Şovrea
- Discipline of Histology, Department of Morphological Sciences, Iuliu Haţieganu University of Medicine and Pharmacy, Cluj-Napoca, Romania
| | - Adina Bianca Boşca
- Discipline of Histology, Department of Morphological Sciences, Iuliu Haţieganu University of Medicine and Pharmacy, Cluj-Napoca, Romania
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134
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Podda MV, Grassi C. New perspectives in cyclic nucleotide-mediated functions in the CNS: the emerging role of cyclic nucleotide-gated (CNG) channels. Pflugers Arch 2013; 466:1241-57. [PMID: 24142069 DOI: 10.1007/s00424-013-1373-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Revised: 09/27/2013] [Accepted: 09/28/2013] [Indexed: 01/07/2023]
Abstract
Cyclic nucleotides play fundamental roles in the central nervous system (CNS) under both physiological and pathological conditions. The impact of cAMP and cGMP signaling on neuronal and glial cell functions has been thoroughly characterized. Most of their effects have been related to cyclic nucleotide-dependent protein kinase activity. However, cyclic nucleotide-gated (CNG) channels, first described as key mediators of sensory transduction in retinal and olfactory receptors, have been receiving increasing attention as possible targets of cyclic nucleotides in the CNS. In the last 15 years, consistent evidence has emerged for their expression in neurons and astrocytes of the rodent brain. Far less is known, however, about the functional role of CNG channels in these cells, although several of their features, such as Ca(2+) permeability and prolonged activation in the presence of cyclic nucleotides, make them ideal candidates for mediators of physiological functions in the CNS. Here, we review literature suggesting the involvement of CNG channels in a number of CNS cellular functions (e.g., regulation of membrane potential, neuronal excitability, and neurotransmitter release) as well as in more complex phenomena, like brain plasticity, adult neurogenesis, and pain sensitivity. The emerging picture is that functional and dysfunctional cyclic nucleotide signaling in the CNS has to be reconsidered including CNG channels among possible targets. However, concerted efforts and multidisciplinary approaches are still needed to get more in-depth knowledge in this field.
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Affiliation(s)
- Maria Vittoria Podda
- Institute of Human Physiology, Medical School, Università Cattolica, Largo Francesco Vito 1, 00168, Rome, Italy
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135
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Nagelhus EA, Amiry-Moghaddam M, Bergersen LH, Bjaalie JG, Eriksson J, Gundersen V, Leergaard TB, Morth JP, Storm-Mathisen J, Torp R, Walhovd KB, Tønjum T. The glia doctrine: addressing the role of glial cells in healthy brain ageing. Mech Ageing Dev 2013; 134:449-59. [PMID: 24141107 DOI: 10.1016/j.mad.2013.10.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 10/03/2013] [Accepted: 10/04/2013] [Indexed: 01/14/2023]
Abstract
Glial cells in their plurality pervade the human brain and impact on brain structure and function. A principal component of the emerging glial doctrine is the hypothesis that astrocytes, the most abundant type of glial cells, trigger major molecular processes leading to brain ageing. Astrocyte biology has been examined using molecular, biochemical and structural methods, as well as 3D brain imaging in live animals and humans. Exosomes are extracelluar membrane vesicles that facilitate communication between glia, and have significant potential for biomarker discovery and drug delivery. Polymorphisms in DNA repair genes may indirectly influence the structure and function of membrane proteins expressed in glial cells and predispose specific cell subgroups to degeneration. Physical exercise may reduce or retard age-related brain deterioration by a mechanism involving neuro-glial processes. It is most likely that additional information about the distribution, structure and function of glial cells will yield novel insight into human brain ageing. Systematic studies of glia and their functions are expected to eventually lead to earlier detection of ageing-related brain dysfunction and to interventions that could delay, reduce or prevent brain dysfunction.
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Affiliation(s)
- Erlend A Nagelhus
- Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Norway; Centre for Molecular Medicine Norway (NCMM), The Nordic EMBL Partnership, University of Oslo, Norway; Department of Neurology, Oslo University Hospital, Norway
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136
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Functional astrocyte-neuron lactate shuttle in a human stem cell-derived neuronal network. J Cereb Blood Flow Metab 2013; 33:1386-93. [PMID: 23715062 PMCID: PMC3764384 DOI: 10.1038/jcbfm.2013.81] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 03/28/2013] [Accepted: 04/27/2013] [Indexed: 12/23/2022]
Abstract
The NT2.D1 cell line is one of the most well-documented embryocarcinoma cell lines, and can be differentiated into neurons and astrocytes. Great focus has also been placed on defining the electrophysiological properties of the neuronal cells, and more recently we have investigated the functional properties of their associated astrocytes. We now show for the first time that human stem cell-derived astrocytes produce glycogen and that co-cultures of these cells demonstrate a functional astrocyte-neuron lactate shuttle (ANLS). The ANLS hypothesis proposes that during neuronal activity, glutamate released into the synaptic cleft is taken up by astrocytes and triggers glucose uptake, which is converted into lactate and released via monocarboxylate transporters for neuronal use. Using mixed cultures of NT2-derived neurons and astrocytes, we have shown that these cells modulate their glucose uptake in response to glutamate. Additionally, we demonstrate that in response to increased neuronal activity and under hypoglycaemic conditions, co-cultures modulate glycogen turnover and increase lactate production. Similar results were also shown after treatment with glutamate, potassium, isoproterenol, and dbcAMP. Together, these results demonstrate for the first time a functional ANLS in a human stem cell-derived co-culture.
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137
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Xu M, Iwasaki T, Shimokawa N, Sajdel-Sulkowska EM, Koibuchi N. The effect of low dose lipopolysaccharide on thyroid hormone-regulated actin cytoskeleton modulation and type 2 iodothyronine deiodinase activity in astrocytes. Endocr J 2013; 60:1221-30. [PMID: 23965412 DOI: 10.1507/endocrj.ej13-0294] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Systemic infection/inflammation can severely interfere with brain development. Lipopolysaccharide (LPS) is a major cell wall component of gram-negative bacteria and commonly used to model the response by infections. Since perinatal exposure to LPS shows neurodevelopmental defects partly similar to those seen in perinatal hypothyroidism, we examined the effect of LPS on thyroxin (T4)-mediated signalings in astrocytes. Initially, C6 rat glioma-derived clonal cells were used, whose biological nature is similar to that of astrocytes. To measure the effects of LPS and T4, actin polymerization and D2 activity assays were carried out. LPS treatment (10 ng/mL) markedly induced actin depolymerization, whereas 10 nM T4 promoted actin polymerization. Furthermore, T4 partly rescued LPS-induced actin depolymerization. LPS treatment (10 ng/mL) increased D2 activity, whereas T4 (10 nM) suppressed this activity. T4 restored LPS-increased D2 activity at 10 nM. LPS-induced actin depolymerization and D2 activity were blocked by p38 MAP kinase inhibitor. Such effects were not seen in T4-mediated changes. Furthermore, similar results were found in the cerebellar primary astrocyte. These results indicate that, although LPS affects T4-regulated cellular events such as actin polymerization and D2 activity, which may induce neurodevelopmental defects similar to those in perinatal hypothyroidism, LPS signaling pathways are independent of T4 signaling pathways.
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Affiliation(s)
- Ming Xu
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
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138
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Abstract
Cerebral blood flow is controlled by two crucial processes, cerebral autoregulation (CA) and neurovascular coupling (NVC) or functional hyperemia. Whereas CA ensures constant blood flow over a wide range of systemic pressures, NVC ensures rapid spatial and temporal increases in cerebral blood flow in response to neuronal activation. The focus of this review is to discuss the cellular mechanisms by which astrocytes contribute to the regulation of vascular tone in terms of their participation in NVC and, to a lesser extent, CA. We discuss evidence for the various signaling modalities by which astrocytic activation leads to vasodilation and vasoconstriction of parenchymal arterioles. Moreover, we provide a rationale for the contribution of astrocytes to pressure-induced increases in vascular tone via the vasoconstrictor 20-HETE (a downstream metabolite of arachidonic acid). Along these lines, we highlight the importance of the transient receptor potential channel of the vanilloid family (TRPV4) as a key molecular determinant in the regulation of vascular tone in cerebral arterioles. Finally, we discuss current advances in the technical tools available to study NVC mechanisms in the brain as it relates to the participation of astrocytes.
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139
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Potokar M, Vardjan N, Stenovec M, Gabrijel M, Trkov S, Jorgačevski J, Kreft M, Zorec R. Astrocytic vesicle mobility in health and disease. Int J Mol Sci 2013; 14:11238-58. [PMID: 23712361 PMCID: PMC3709730 DOI: 10.3390/ijms140611238] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 04/26/2013] [Accepted: 05/08/2013] [Indexed: 12/14/2022] Open
Abstract
Astrocytes are no longer considered subservient to neurons, and are, instead, now understood to play an active role in brain signaling. The intercellular communication of astrocytes with neurons and other non-neuronal cells involves the exchange of molecules by exocytotic and endocytotic processes through the trafficking of intracellular vesicles. Recent studies of single vesicle mobility in astrocytes have prompted new views of how astrocytes contribute to information processing in nervous tissue. Here, we review the trafficking of several types of membrane-bound vesicles that are specifically involved in the processes of (i) intercellular communication by gliotransmitters (glutamate, adenosine 5′-triphosphate, atrial natriuretic peptide), (ii) plasma membrane exchange of transporters and receptors (EAAT2, MHC-II), and (iii) the involvement of vesicle mobility carrying aquaporins (AQP4) in water homeostasis. The properties of vesicle traffic in astrocytes are discussed in respect to networking with neighboring cells in physiologic and pathologic conditions, such as amyotrophic lateral sclerosis, multiple sclerosis, and states in which astrocytes contribute to neuroinflammatory conditions.
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Affiliation(s)
- Maja Potokar
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Matjaž Stenovec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Mateja Gabrijel
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Saša Trkov
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Jernej Jorgačevski
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
- Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia; E-Mails: (M.P.); (N.V.); (M.S.); (M.G.); (S.T.); (J.J.); (M.K.)
- Celica Biomedical Center, Tehnološki park 24, 1000 Ljubljana, Slovenia
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +386-1543-7020; Fax: +386-1543-7036
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140
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The evidence for hypoperfusion as a factor in multiple sclerosis lesion development. Mult Scler Int 2013; 2013:598093. [PMID: 23691321 PMCID: PMC3649777 DOI: 10.1155/2013/598093] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 02/08/2013] [Accepted: 03/19/2013] [Indexed: 01/19/2023] Open
Abstract
The evidence that hypoxia is a precipitating factor in causing early MS lesions includes increased protein levels of hypoxia-inducible factor-1α; presence of the D-110 hypoxia-inducible protein; increased expression of hypoxia-inducible genes in lesions as well as in adjacent normal-appearing white matter (NAWM); loss of myelin-associated glycoprotein in myelin of early MS lesions; a 50% reduction of blood flow through NAWM with areas of lowest blood flow having the greatest probability of lesion development. Why MS-like lesions develop following hypoxemic insults in some individuals but not in others is likely dependent upon the presence of immune predisposing factors that are governed genetically. Hypoperfusion may be due to decreased arterial supply, restricted venous return, or a combination of these. There are clinical trials ongoing or planned to treat chronic cerebrospinal venous insufficiency (CCSVI) through angioplasty. I suggest that it is important that clinical trials addressing vascular issues in MS should examine how the vascular intervention affects white matter perfusion and determine whether the extent of perfusion recovery and maintenance of this recovery is related to functional recovery and maintenance of functional recovery. Consideration should also be given to the possibility of arterial problems playing a role in hypoperfusion in some MS patients.
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141
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Increased 20-HETE synthesis explains reduced cerebral blood flow but not impaired neurovascular coupling after cortical spreading depression in rat cerebral cortex. J Neurosci 2013; 33:2562-70. [PMID: 23392684 DOI: 10.1523/jneurosci.2308-12.2013] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cortical spreading depression (CSD) is associated with release of arachidonic acid, impaired neurovascular coupling, and reduced cerebral blood flow (CBF), caused by cortical vasoconstriction. We tested the hypothesis that the released arachidonic acid is metabolized by the cytochrome P450 enzyme to produce the vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE), and that this mechanism explains cortical vasoconstriction and vascular dysfunction after CSD. CSD was induced in the frontal cortex of rats and the cortical electrical activity and local field potentials recorded by glass microelectrodes, CBF by laser Doppler flowmetry, and tissue oxygen tension (tpO(2)) using polarographic microelectrodes. 20-HETE synthesis was measured in parallel experiments in cortical brain slices exposed to CSD. We used the specific inhibitor HET0016 (N-hydroxy-N'-(4-n-butyl-2-methylphenyl)formamidine) to block 20-HETE synthesis. CSD increased 20-HETE synthesis in brain slices for 120 min, and the time course of the increase in 20-HETE paralleled the reduction in CBF after CSD in vivo. HET0016 blocked the CSD-induced increase in 20-HETE synthesis and ameliorated the persistent reduction in CBF, but not the impaired neurovascular coupling after CSD. These findings suggest that CSD-induced increments in 20-HETE cause the reduction in CBF after CSD and that the attenuation of stimulation-induced CBF responses after CSD has a different mechanism. We suggest that blockade of 20-HETE synthesis may be clinically relevant to ameliorate reduced CBF in patients with migraine and acute brain cortex injuries.
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142
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The astrocytic contribution to neurovascular coupling – Still more questions than answers? Neurosci Res 2013; 75:171-83. [DOI: 10.1016/j.neures.2013.01.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 12/15/2012] [Accepted: 12/30/2012] [Indexed: 01/03/2023]
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143
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Mathiesen C, Brazhe A, Thomsen K, Lauritzen M. Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen. J Cereb Blood Flow Metab 2013; 33:161-9. [PMID: 23211964 PMCID: PMC3564203 DOI: 10.1038/jcbfm.2012.175] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 10/17/2012] [Accepted: 10/19/2012] [Indexed: 11/09/2022]
Abstract
Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen saturation alters wave activity; (2) glial Ca(2+) waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of adult (8- to 15-week-old) and aging (48- to 80-week-old) ketamine-anesthetized mice after bolus loading with OGB-1/AM and SR101. We report that the occurrence of spontaneous waves is 20 times more frequent in the cerebellar cortex of aging as compared with adult mice, which correlated with a reduction in resting brain oxygen tension. In adult mice, spontaneous glial wave activity increased on reducing resting brain oxygen tension, and ATP-evoked glial waves reduced the tissue O(2) tension. Finally, although spontaneous Purkinje cell (PC) activity was not associated with increased glia wave activity, spontaneous glial waves did affect intracellular Ca(2+) activity in PCs. The increased wave activity during aging, as well as low resting brain oxygen tension, suggests a relationship between glial waves, brain energy homeostasis, and pathology.
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Affiliation(s)
- Claus Mathiesen
- Center for Healthy Aging, Department for Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
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144
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Abd-El-Basse EM. Pro-inflammatory cytokine; tumor-necrosis factor-alpha (TNF-α) inhibits astrocytic support of neuronal survival and neurites outgrowth. ADVANCES IN BIOSCIENCE AND BIOTECHNOLOGY 2013; 04:73-80. [DOI: 10.4236/abb.2013.48a2010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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145
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Koide M, Bonev AD, Nelson MT, Wellman GC. Subarachnoid blood converts neurally evoked vasodilation to vasoconstriction in rat brain cortex. ACTA NEUROCHIRURGICA. SUPPLEMENT 2013; 115:167-71. [PMID: 22890664 PMCID: PMC3684063 DOI: 10.1007/978-3-7091-1192-5_32] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The matching of blood flow to regional brain function, called functional hyperemia or neurovascular coupling, involves the coordinated activity of neurons, astrocytes, and parenchymal arterioles. Under physiological conditions, localized neuronal activation leads to elevated astrocyte endfoot Ca(2+) and vasodilation, resulting in an increase in cerebral blood flow. In this study, we examined the impact of subarachnoid hemorrhage (SAH) on neurovascular coupling. SAH model rats received two injections of autologous blood into the cisterna magna 24 h apart. Cortical brain slices from SAH model animals were prepared 4 days after the initial blood injection. Arteriolar diameter and astrocyte endfoot Ca(2+) were simultaneously measured using two-photon microscopy. As expected, neuronal activity evoked by electrical field stimulation (EFS) caused an elevation in endfoot Ca(2+) and vasodilation in brain slices from control animals. However, in brain slices from SAH animals, EFS induced a similar increase in astrocyte endfoot Ca(2+) that caused arteriolar constriction rather than vasodilation. Vasoconstriction was observed in approximately 90% of brain slices from SAH animals in response to EFS, with 40% exhibiting a sustained vasoconstriction, 30% exhibiting a transient vasoconstriction -(diameter restored within 1 min after EFS), and 20% responded with a biphasic response (brief vasodilation followed by -vasoconstriction). This inversion of neurovascular coupling may play a role in the development of neurological deficits following SAH.
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Affiliation(s)
- Masayo Koide
- Department of Pharmacology, University of Vermont College of Medicine, Burlington, VT 05405-0068, USA
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146
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Abstract
The role of the blood-brain barrier (BBB) in epilepsy has evolved from an obstacle for drug brain delivery to an etiological factor contributing to seizures. Recent evidence has shown cerebrovascular angiogenesis and increased BBB permeability in the epileptic foci of patients and in experimental models of seizure. The molecular players involved in cerebrovascular remodeling in the epileptic brain are similar to those reported for other brain disorders. The question arises whether pharmacological solutions restoring a proper BBB permeability and preventing dysregulated angiogenesis could be also beneficial in mitigating seizures. We now summarize the available data supporting the role of vascular remodeling and angiogenesis in the epileptic brain, taking into account that the BBB is a multi-cellular structure, reacting to physiological and pathological stimuli. Drugs targeting aberrant angiogenesis could be beneficial in reducing seizure burden when used in combination with available anti-epileptic drugs. We also offer an overview of novel cellular players, such as pericytes, which may participate in cerebrovascular remodeling in the epileptic brain. The possible role of angiogenesis in drug-resistant forms of epilepsy associated with neurovascular dysplasia is discussed. Finally, we speculate on whether the formation of leaky BBB vessels could have an impact on the cerebrovascular rheology and on the physiological mechanisms regulating brain homeostasis.
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Affiliation(s)
- Nicola Marchi
- Departments of Molecular Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA.
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147
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Porlan E, Perez-Villalba A, Delgado AC, Ferrón SR. Paracrine regulation of neural stem cells in the subependymal zone. Arch Biochem Biophys 2012; 534:11-9. [PMID: 23073070 DOI: 10.1016/j.abb.2012.10.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 09/27/2012] [Accepted: 10/05/2012] [Indexed: 12/31/2022]
Abstract
Stem cells maintain their self-renewal and multipotency capacities through a self-organizing network of transcription factors and intracellular pathways activated by extracellular signaling from the microenvironment or "niche" in which they reside in vivo. In the adult mammalian brain new neurons continue to be generated throughout life of the organisms and this lifelong process of neurogenesis is supported by a reservoir of neural stem cells in the germinal regions. The discovery of adult neurogenesis in the mammalian brain has sparked great interest in defining the conditions that guide neural stem cell (NSC) maintenance and differentiation into the great variety of neuronal and glial subtypes. Here we review current knowledge regarding the paracrine regulation provided by the components of the niche and its function, focusing on the main germinal region of the adult central nervous system (CNS), the subependymal zone (SEZ).
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Affiliation(s)
- Eva Porlan
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Spain
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148
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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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149
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Astrocyte inositol triphosphate receptor type 2 and cytosolic phospholipase A2 alpha regulate arteriole responses in mouse neocortical brain slices. PLoS One 2012; 7:e42194. [PMID: 22876307 PMCID: PMC3410924 DOI: 10.1371/journal.pone.0042194] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 07/05/2012] [Indexed: 01/19/2023] Open
Abstract
Functional hyperemia of the cerebral vascular system matches regional blood flow to the metabolic demands of the brain. One current model of neurovascular control holds that glutamate released by neurons activates group I metabotropic glutamate receptors (mGluRs) on astrocytes, resulting in the production of diffusible messengers that act to regulate smooth muscle cells surrounding cerebral arterioles. The acute mouse brain slice is an experimental system in which changes in arteriole diameter can precisely measured with light microscopy. Stimulation of the brain slice triggers specific cellular responses that can be correlated to changes in arteriole diameter. Here we used inositol trisphosphate receptor type 2 (IP(3)R2) and cytosolic phospholipase A(2) alpha (cPLA(2)α) deficient mice to determine if astrocyte mGluR activation coupled to IP(3)R2-mediated Ca(2+) release and subsequent cPLA(2)α activation is required for arteriole regulation. We measured changes in astrocyte cytosolic free Ca(2+) and arteriole diameters in response to mGluR agonist or electrical field stimulation in acute neocortical mouse brain slices maintained in 95% or 20% O(2). Astrocyte Ca(2+) and arteriole responses to mGluR activation were absent in IP(3)R2(-/-) slices. Astrocyte Ca(2+) responses to mGluR activation were unchanged by deletion of cPLA(2)α but arteriole responses to either mGluR agonist or electrical stimulation were ablated. The valence of changes in arteriole diameter (dilation/constriction) was dependent upon both stimulus and O(2) concentration. Neuron-derived NO and activation of the group I mGluRs are required for responses to electrical stimulation. These findings indicate that an mGluR/IP(3)R2/cPLA(2)α signaling cascade in astrocytes is required to transduce neuronal glutamate release into arteriole responses.
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150
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Abstract
Astrocytes, the most prominent glial cell type in the brain, send specialized processes named endfeet, which enwrap blood vessels and express a large molecular repertoire dedicated to the physiology of the vascular system. One of the most striking properties of astrocyte endfeet is their enrichment in gap junction protein connexins 43 and 30 (Cx43 and Cx30) allowing for direct intercellular trafficking of ions and small signaling molecules through perivascular astroglial networks. The contribution of astroglial connexins to the physiology of the brain vascular system has never been addressed. Here, we show that Cx43 and Cx30 expression at the level of perivascular endfeet starts from postnatal days 2 and 12 and is fully mature at postnatal days 15 and 20, respectively, indicating that astroglial perivascular connectivity occurs and develops during postnatal blood-brain barrier (BBB) maturation. We demonstrate that mice lacking Cx30 and Cx43 in GFAP (glial fibrillary acidic protein)-positive cells display astrocyte endfeet edema and a partial loss of the astroglial water channel aquaporin-4 and β-dystroglycan, a transmembrane receptor anchoring astrocyte endfeet to the perivascular basal lamina. Furthermore, the absence of astroglial connexins weakens the BBB, which opens upon increased hydrostatic vascular pressure and shear stress. These results demonstrate that astroglial connexins are necessary to maintain BBB integrity.
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