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Assentoft M, Larsen BR, MacAulay N. Regulation and Function of AQP4 in the Central Nervous System. Neurochem Res 2015; 40:2615-27. [PMID: 25630715 DOI: 10.1007/s11064-015-1519-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 01/08/2015] [Accepted: 01/12/2015] [Indexed: 01/09/2023]
Abstract
Aquaporin 4 (AQP4) is the predominant water channel in the mammalian brain and is mainly expressed in the perivascular glial endfeet at the brain-blood interface. Based on studies on AQP4(-/-) mice, AQP4 has been assigned physiological roles in stimulus-induced K(+) clearance, paravascular fluid flow, and brain edema formation. Conflicting data have been presented on the role of AQP4 in K(+) clearance and associated extracellular space shrinkage and on the stroke-induced alterations of AQP4 expression levels during edema formation, raising questions about the functional importance of AQP4 in these (patho)physiological aspects. Phosphorylation-dependent gating of AQP4 has been proposed as a regulatory mechanism for AQP4-mediated osmotic water transport. This paradigm was, however, recently challenged by experimental evidence and molecular dynamics simulations. Regulatory patterns and physiological roles for AQP4 thus remain to be fully explored.
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Affiliation(s)
- Mette Assentoft
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, Bldg. 12.6, 2200, Copenhagen, Denmark
| | - Brian Roland Larsen
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, Bldg. 12.6, 2200, Copenhagen, Denmark
| | - Nanna MacAulay
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, Bldg. 12.6, 2200, Copenhagen, Denmark.
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102
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Thrane AS, Rangroo Thrane V, Nedergaard M. Drowning stars: reassessing the role of astrocytes in brain edema. Trends Neurosci 2014; 37:620-8. [PMID: 25236348 DOI: 10.1016/j.tins.2014.08.010] [Citation(s) in RCA: 151] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 11/18/2022]
Abstract
Edema formation frequently complicates brain infarction, tumors, and trauma. Despite the significant mortality of this condition, current treatment options are often ineffective or incompletely understood. Recent studies have revealed the existence of a brain-wide paravascular pathway for cerebrospinal (CSF) and interstitial fluid (ISF) exchange. The current review critically examines the contribution of this 'glymphatic' system to the main types of brain edema. We propose that in cytotoxic edema, energy depletion enhances glymphatic CSF influx, whilst suppressing ISF efflux. We also argue that paravascular inflammation or 'paravasculitis' plays a critical role in vasogenic edema. Finally, recent advances in diagnostic imaging of glymphatic function may hold the key to defining the edema profile of individual patients, and thus enable more targeted therapy.
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Affiliation(s)
- Alexander S Thrane
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester Medical Center, Rochester, New York 14642, USA; Department of Ophthalmology, Haukeland University Hospital, Bergen 5021, Norway; Letten Centre, Institute of Basic Medical Sciences, Department of Physiology, University of Oslo, 0317 Oslo, Norway.
| | - Vinita Rangroo Thrane
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester Medical Center, Rochester, New York 14642, USA; Department of Ophthalmology, Haukeland University Hospital, Bergen 5021, Norway; Letten Centre, Institute of Basic Medical Sciences, Department of Physiology, University of Oslo, 0317 Oslo, Norway
| | - Maiken Nedergaard
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, Department of Neurosurgery, University of Rochester Medical Center, Rochester, New York 14642, USA
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103
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Expression and localization of aquaporin-4 in sensory ganglia. Biochem Biophys Res Commun 2014; 451:562-7. [DOI: 10.1016/j.bbrc.2014.08.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 08/05/2014] [Indexed: 12/20/2022]
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104
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Sasseville LJ, Longpré JP, Wallendorff B, Lapointe JY. The transport mechanism of the human sodium/myo-inositol transporter 2 (SMIT2/SGLT6), a member of the LeuT structural family. Am J Physiol Cell Physiol 2014; 307:C431-41. [PMID: 24944204 DOI: 10.1152/ajpcell.00054.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The sodium/myo-inositol transporter 2 (SMIT2) is a member of the SLC5A gene family, which is believed to share the five-transmembrane segment inverted repeat of the LeuT structural family. The two-electrode voltage-clamp (TEVC) technique was used to measure the steady-state and the pre-steady-state currents mediated by human SMIT2 after expression in Xenopus laevis oocytes. Phlorizin is first shown to be a poor inhibitor of pre-steady-state currents for depolarizing voltage pulse. From an up to threefold difference between the apparent ON and OFF transferred charges during a voltage pulse, we also show that a fraction of the transient current recorded for very negative potentials is not a true pre-steady-state current coming from the cotransporter conformational changes. We suggest that this transient current comes from a time-dependent leak current that can reach large amplitudes when external Na(+) concentration is reduced. A kinetic model was generated through a simulated annealing algorithm. This algorithm was used to identify the optimal connectivity among 19 different kinetic models and obtain the numerical values of the associated parameters. The proposed 5-state model includes cooperative binding of Na(+) ions, strong apparent asymmetry of the energy barriers, a rate-limiting step that is likely associated with the translocation of the empty transporter, and a turnover rate of 21 s(-1). The proposed model is a proof of concept for a novel approach to kinetic modeling of electrogenic transporters and allows insight into the transport mechanism of members of the LeuT structural family at the millisecond timescale.
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Affiliation(s)
- Louis J Sasseville
- Groupe d'étude des protéines membranaires (GÉPROM) and Département de Physique, Université de Montréal, Montreal, Quebec, Canada
| | - Jean-Philippe Longpré
- Groupe d'étude des protéines membranaires (GÉPROM) and Département de Physique, Université de Montréal, Montreal, Quebec, Canada
| | - Bernadette Wallendorff
- Groupe d'étude des protéines membranaires (GÉPROM) and Département de Physique, Université de Montréal, Montreal, Quebec, Canada
| | - Jean-Yves Lapointe
- Groupe d'étude des protéines membranaires (GÉPROM) and Département de Physique, Université de Montréal, Montreal, Quebec, Canada
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105
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Affiliation(s)
- Yarong He
- From the Emergency Department, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China (Y.H., Y.C.); Laboratory of Neurobiology and Genetics, The Rockefeller University, New York, NY (Y.Y.); and Department of Pharmacological Sciences, Stony Brook University, NY (S.E.T.)
| | - Yao Yao
- From the Emergency Department, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China (Y.H., Y.C.); Laboratory of Neurobiology and Genetics, The Rockefeller University, New York, NY (Y.Y.); and Department of Pharmacological Sciences, Stony Brook University, NY (S.E.T.)
| | - Stella E Tsirka
- From the Emergency Department, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China (Y.H., Y.C.); Laboratory of Neurobiology and Genetics, The Rockefeller University, New York, NY (Y.Y.); and Department of Pharmacological Sciences, Stony Brook University, NY (S.E.T.)
| | - Yu Cao
- From the Emergency Department, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China (Y.H., Y.C.); Laboratory of Neurobiology and Genetics, The Rockefeller University, New York, NY (Y.Y.); and Department of Pharmacological Sciences, Stony Brook University, NY (S.E.T.).
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106
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Brinker T, Stopa E, Morrison J, Klinge P. A new look at cerebrospinal fluid circulation. Fluids Barriers CNS 2014; 11:10. [PMID: 24817998 PMCID: PMC4016637 DOI: 10.1186/2045-8118-11-10] [Citation(s) in RCA: 489] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 04/18/2014] [Indexed: 12/11/2022] Open
Abstract
According to the traditional understanding of cerebrospinal fluid (CSF) physiology, the majority of CSF is produced by the choroid plexus, circulates through the ventricles, the cisterns, and the subarachnoid space to be absorbed into the blood by the arachnoid villi. This review surveys key developments leading to the traditional concept. Challenging this concept are novel insights utilizing molecular and cellular biology as well as neuroimaging, which indicate that CSF physiology may be much more complex than previously believed. The CSF circulation comprises not only a directed flow of CSF, but in addition a pulsatile to and fro movement throughout the entire brain with local fluid exchange between blood, interstitial fluid, and CSF. Astrocytes, aquaporins, and other membrane transporters are key elements in brain water and CSF homeostasis. A continuous bidirectional fluid exchange at the blood brain barrier produces flow rates, which exceed the choroidal CSF production rate by far. The CSF circulation around blood vessels penetrating from the subarachnoid space into the Virchow Robin spaces provides both a drainage pathway for the clearance of waste molecules from the brain and a site for the interaction of the systemic immune system with that of the brain. Important physiological functions, for example the regeneration of the brain during sleep, may depend on CSF circulation.
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Affiliation(s)
- Thomas Brinker
- Department of Neurosurgery, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, 593 Eddy Street, Providence, RI 02903, USA
| | - Edward Stopa
- Department of Neurosurgery, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, 593 Eddy Street, Providence, RI 02903, USA
| | - John Morrison
- Department of Neurosurgery, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, 593 Eddy Street, Providence, RI 02903, USA
| | - Petra Klinge
- Department of Neurosurgery, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, 593 Eddy Street, Providence, RI 02903, USA
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107
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Ahlgren H, Bas-Orth C, Freitag HE, Hellwig A, Ottersen OP, Bading H. The nuclear calcium signaling target, activating transcription factor 3 (ATF3), protects against dendrotoxicity and facilitates the recovery of synaptic transmission after an excitotoxic insult. J Biol Chem 2014; 289:9970-82. [PMID: 24515113 DOI: 10.1074/jbc.m113.502914] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The focal swellings of dendrites ("dendritic beading") are an early morphological hallmark of neuronal injury and dendrotoxicity. They are associated with a variety of pathological conditions, including brain ischemia, and cause an acute disruption of synaptic transmission and neuronal network function, which contribute to subsequent neuronal death. Here, we show that increased synaptic activity prior to excitotoxic injury protects, in a transcription-dependent manner, against dendritic beading. Expression of activating transcription factor 3 (ATF3), a nuclear calcium-regulated gene and member of the core gene program for acquired neuroprotection, can protect against dendritic beading. Conversely, knockdown of ATF3 exacerbates dendritic beading. Assessment of neuronal network functions using microelectrode array recordings revealed that hippocampal neurons expressing ATF3 were able to regain their ability for functional synaptic transmission and to participate in coherent neuronal network activity within 48 h after exposure to toxic concentrations of NMDA. Thus, in addition to attenuating cell death, synaptic activity and expression of ATF3 render hippocampal neurons more resistant to acute dendrotoxicity and loss of synapses. Dendroprotection can enhance recovery of neuronal network functions after excitotoxic insults.
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Affiliation(s)
- Hanna Ahlgren
- From the Department of Neurobiology, Interdisciplinary Center for Neurosciences, University of Heidelberg, INF 364, 69120 Heidelberg, Germany and
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108
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Wegner LH. Root pressure and beyond: energetically uphill water transport into xylem vessels? JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:381-93. [PMID: 24311819 DOI: 10.1093/jxb/ert391] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The thermodynamics of root pressure remains an enigma up to the present day. Water is transported radially into xylem vessels, under some conditions even when the xylem sap is more dilute than the ambient medium (soil solution). It is suggested here that water secretion across the plasma membrane of xylem parenchyma cells is driven by a co-transport of water and solutes as previously shown for mammalian epithelia (Zeuthen T. 2010. Water-transporting proteins. Journal of Membrane Biology 234, 57-73.). This process could drive volume flow 'energetically uphill', against the free energy gradient of water. According to the model, solutes released by xylem parenchyma cells are subsequently retrieved from the sap at the expense of metabolic energy to maintain the concentration gradient that drives the water secretion. Transporters of the CCC type known to mediate water secretion in mammalian cells have also been found in Arabidopsis and in rice. The mechanism proposed here for root pressure could also explain refilling of embolized vessels. Moreover, it could contribute to long-distance water transport in trees when the cohesion-tension mechanism of water ascent fails. This is discussed with respect to the old and the more recent literature on these subjects.
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Affiliation(s)
- Lars H Wegner
- Karlsruhe Institute of Technology, Institute of Botany I, and Institute of Pulsed Power and Microwave Technology, Campus North, Building 630, Hermann-v-Helmholtz Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
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109
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Abstract
L-Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system and plays important roles in a wide variety of brain functions, but it is also a key player in the pathogenesis of many neurological disorders. The control of glutamate concentrations is critical to the normal functioning of the central nervous system, and in this review we discuss how glutamate transporters regulate glutamate concentrations to maintain dynamic signaling mechanisms between neurons. In 2004, the crystal structure of a prokaryotic homolog of the mammalian glutamate transporter family of proteins was crystallized and its structure determined. This has paved the way for a better understanding of the structural basis for glutamate transporter function. In this review we provide a broad perspective of this field of research, but focus primarily on the more recent studies with a particular emphasis on how our understanding of the structure of glutamate transporters has generated new insights.
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110
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Abstract
Aquaporin-4 (AQP4) is one of the most abundant molecules in the brain and is particularly prevalent in astrocytic membranes at the blood-brain and brain-liquor interfaces. While AQP4 has been implicated in a number of pathophysiological processes, its role in brain physiology has remained elusive. Only recently has evidence accumulated to suggest that AQP4 is involved in such diverse functions as regulation of extracellular space volume, potassium buffering, cerebrospinal fluid circulation, interstitial fluid resorption, waste clearance, neuroinflammation, osmosensation, cell migration, and Ca(2+) signaling. AQP4 is also required for normal function of the retina, inner ear, and olfactory system. A review will be provided of the physiological roles of AQP4 in brain and of the growing list of data that emphasize the polarized nature of astrocytes.
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111
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Janssen SF, Gorgels TG, Ramdas WD, Klaver CC, van Duijn CM, Jansonius NM, Bergen AA. The vast complexity of primary open angle glaucoma: Disease genes, risks, molecular mechanisms and pathobiology. Prog Retin Eye Res 2013; 37:31-67. [DOI: 10.1016/j.preteyeres.2013.09.001] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 07/26/2013] [Accepted: 09/03/2013] [Indexed: 12/21/2022]
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112
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Damkier HH, Brown PD, Praetorius J. Cerebrospinal Fluid Secretion by the Choroid Plexus. Physiol Rev 2013; 93:1847-92. [DOI: 10.1152/physrev.00004.2013] [Citation(s) in RCA: 291] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The choroid plexus epithelium is a cuboidal cell monolayer, which produces the majority of the cerebrospinal fluid. The concerted action of a variety of integral membrane proteins mediates the transepithelial movement of solutes and water across the epithelium. Secretion by the choroid plexus is characterized by an extremely high rate and by the unusual cellular polarization of well-known epithelial transport proteins. This review focuses on the specific ion and water transport by the choroid plexus cells, and then attempts to integrate the action of specific transport proteins to formulate a model of cerebrospinal fluid secretion. Significant emphasis is placed on the concept of isotonic fluid transport across epithelia, as there is still surprisingly little consensus on the basic biophysics of this phenomenon. The role of the choroid plexus in the regulation of fluid and electrolyte balance in the central nervous system is discussed, and choroid plexus dysfunctions are described in a very diverse set of clinical conditions such as aging, Alzheimer's disease, brain edema, neoplasms, and hydrocephalus. Although the choroid plexus may only have an indirect influence on the pathogenesis of these conditions, the ability to modify epithelial function may be an important component of future therapies.
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Affiliation(s)
- Helle H. Damkier
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark; and Faculty of Life Sciences, Michael Smith Building, Manchester University, Manchester, United Kingdom
| | - Peter D. Brown
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark; and Faculty of Life Sciences, Michael Smith Building, Manchester University, Manchester, United Kingdom
| | - Jeppe Praetorius
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark; and Faculty of Life Sciences, Michael Smith Building, Manchester University, Manchester, United Kingdom
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113
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Ip YK, Hou Z, Chen XL, Ong JLY, Chng YR, Ching B, Hiong KC, Chew SF. High brain ammonia tolerance and down-regulation of Na+:K+:2Cl(-) Cotransporter 1b mRNA and protein expression in the brain of the Swamp Eel, Monopterus albus, exposed to environmental ammonia or terrestrial conditions. PLoS One 2013; 8:e69512. [PMID: 24069137 PMCID: PMC3777983 DOI: 10.1371/journal.pone.0069512] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 06/11/2013] [Indexed: 01/19/2023] Open
Abstract
Na(+):K(+):2Cl(-) cotransporter 1 (NKCC1) has been implicated in mediating ischemia-, trauma- or ammonia-induced astrocyte swelling/brain edema in mammals. This study aimed to determine the effects of ammonia or terrestrial exposure on ammonia concentrations in the plasma and brain, and the mRNA expression and protein abundance of nkcc/Nkcc in the brain, of the swamp eel Monopterusalbus. Ammonia exposure led to a greater increase in the ammonia concentration in the brain of M. albus than terrestrial exposure. The brain ammonia concentration of M. albus reached 4.5 µmol g(-1) and 2.7 µmol g(-1) after 6 days of exposure to 50 mmol l(-1) NH4Cl and terrestrial conditions, respectively. The full cDNA coding sequence of nkcc1b from M. albus brain comprised 3276 bp and coded for 1092 amino acids with an estimated molecular mass of 119.6 kDa. A molecular characterization indicated that it could be activated through phosphorylation and/or glycosylation by osmotic and/or oxidative stresses. Ammonia exposure for 1 day or 6 days led to significant decreases in the nkcc1b mRNA expression and Nkcc1b protein abundance in the brain of M. albus. In comparison, a significant decrease in nkcc1b mRNA expression was observed in the brain of M. albus only after 6 days of terrestrial exposure, but both 1 day and 6 days of terrestrial exposure resulted in significant decreases in the protein abundance of Nkcc1b. These results are novel because it has been established in mammals that ammonia up-regulates NKCC1 expression in astrocytes and NKCC1 plays an important role in ammonia-induced astrocyte swelling and brain edema. By contrast, our results indicate for the first time that M. albus is able to down-regulate the mRNA and protein expression of nkcc1b/Nkcc1b in the brain when confronted with ammonia toxicity, which could be one of the contributing factors to its extraordinarily high brain ammonia tolerance.
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Affiliation(s)
- Yuen K. Ip
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Zhisheng Hou
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Xiu L. Chen
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Jasmine L. Y. Ong
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - You R. Chng
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Biyun Ching
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Kum C. Hiong
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Shit F. Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore, Republic of Singapore
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114
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Assentoft M, Kaptan S, Fenton RA, Hua SZ, de Groot BL, MacAulay N. Phosphorylation of rat aquaporin-4 at Ser(111) is not required for channel gating. Glia 2013; 61:1101-12. [PMID: 23616425 DOI: 10.1002/glia.22498] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 02/27/2013] [Indexed: 01/17/2023]
Abstract
Aquaporin 4 (AQP4) is the predominant water channel in the mammalian brain and is mainly expressed in the perivascular glial endfeet at the brain-blood interface. AQP4 has been described as an important entry and exit site for water during formation of brain edema and regulation of AQP4 is therefore of therapeutic interest. Phosphorylation of some aquaporins has been proposed to regulate their water permeability via gating of the channel itself. Protein kinase (PK)-dependent phosphorylation of Ser(111) has been reported to increase the water permeability of AQP4 expressed in an astrocytic cell line. This possibility was, however, questioned based on the crystal structure of the human AQP4. Our study aimed to resolve if Ser(111) was indeed a site involved in phosphorylation-mediated gating of AQP4. The water permeability of AQP4-expressing Xenopus oocytes was not altered by a range of activators and inhibitors of PKG and PKA. Mutation of Ser(111) to alanine or aspartate (to prevent or mimic phosphorylation) did not change the water permeability of AQP4. PKG activation had no effect on the water permeability of AQP4 in primary cultures of rat astrocytes. Molecular dynamics simulations of a phosphorylation of AQP4.Ser(111) recorded no phosphorylation-induced change in water permeability. A phospho-specific antibody, exclusively recognizing AQP4 when phosphorylated on Ser(111) , failed to detect phosphorylation in cell lysate of rat brain stimulated by conditions proposed to induce phosphorylation of this residue. Thus, our data indicate a lack of phosphorylation of Ser(111) and of phosphorylation-dependent gating of AQP4.
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Affiliation(s)
- Mette Assentoft
- Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
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115
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Hypoxia-inducible factor 1 is essential for spontaneous recovery from traumatic brain injury and is a key mediator of heat acclimation induced neuroprotection. J Cereb Blood Flow Metab 2013; 33:524-31. [PMID: 23281425 PMCID: PMC3618386 DOI: 10.1038/jcbfm.2012.193] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Heat acclimation (HA), a well-established preconditioning model, confers neuroprotection in rodent models of traumatic brain injury (TBI). It increases neuroprotective factors, among them is hypoxia-inducible factor 1α (HIF-1α), which is important in the response to postinjury ischemia. However, little is known about the role of HIF-1α in TBI and its contribution to the establishment of the HA protecting phenotype. Therefore, we aimed to explore HIF-1α role in TBI defense mechanisms as well as in HA-induced neuroprotection. Acriflavine was used to inhibit HIF-1 in injured normothermic (NT) or HA mice. After TBI, we evaluated motor function recovery, lesion volume, edema formation, and body temperature as well as HIF-1 downstream transcription targets, such as glucose transporter 1 (GLUT1), vascular endothelial growth factor, and aquaporin 4. We found that HIF-1 inhibition resulted in deterioration of motor function, increased lesion volume, hypothermia, and reduced edema formation. All these parameters were significantly different in the HA mice. Western blot analysis and enzyme-linked immunosorbent assay showed reduced levels of all HIF-1 downstream targets in HA mice, however, only GLUT1 was downregulated in NT mice. We conclude that HIF-1 is a key mediator in both spontaneous recovery and HA-induced neuroprotection after TBI.
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116
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Cruz NF, Ball KK, Froehner SC, Adams ME, Dienel GA. Regional registration of [6-(14)C]glucose metabolism during brain activation of α-syntrophin knockout mice. J Neurochem 2013; 125:247-59. [PMID: 23346911 DOI: 10.1111/jnc.12166] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 01/02/2013] [Accepted: 01/20/2013] [Indexed: 12/16/2022]
Abstract
α-Syntrophin is a component of the dystrophin scaffold-protein complex that serves as an adaptor for recruitment of key proteins to the cytoplasmic side of plasma membranes. α-Syntrophin knockout (KO) causes loss of the polarized localization of aquaporin4 (AQP4) at astrocytic endfeet and interferes with water and K(+) homeostasis. During brain activation, release of ions and metabolites from endfeet is anticipated to increase perivascular fluid osmolarity, AQP4-mediated osmotic water flow from endfeet, and metabolite washout from brain. This study tests the hypothesis that reduced levels of endfoot AQP4 increase retention of [(14)C]metabolites during sensory stimulation. Conscious KO and wild-type mice were pulse-labeled with [6-(14)C] glucose during unilateral acoustic stimulation or bilateral acoustic plus whisker stimulation, and label retention was assayed by computer-assisted brain imaging or analysis of [(14)C]metabolites in extracts, respectively. High-resolution autoradiographic assays detected a 17% side-to-side difference (p < 0.05) in inferior colliculus of KO mice, not wild-type mice. However, there were no labeling differences between KO and wild-type mice for five major HPLC fractions from four dissected regions, presumably because of insufficient anatomical resolution. The results suggest a role for AQP4-mediated water flow in support of washout of metabolites, and underscore the need for greater understanding of astrocytic water and metabolite fluxes.
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Affiliation(s)
- Nancy F Cruz
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Kelly K Ball
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Stanley C Froehner
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Marvin E Adams
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
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117
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Bondarenko O, Dzyuba B, Cosson J, Yamaner G, Prokopchuk G, Psenicka M, Linhart O. Volume changes during the motility period of fish spermatozoa: interspecies differences. Theriogenology 2013; 79:872-81. [PMID: 23394972 DOI: 10.1016/j.theriogenology.2013.01.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 12/19/2012] [Accepted: 01/06/2013] [Indexed: 11/18/2022]
Abstract
The aim of this study was to describe spermatozoa volume changes during the motility period of fish species with either osmotic (common carp Cyprinus carpio) or with ionic (sterlet Acipenseri ruthenus and brook trout Salvelinus fontinalis) modes of motility activation. Nephelometry, light microscopy, and spermatocrit methods were used for quantitative assessment of cell volume changes in media of different osmolalities. Significant correlation (R(2) = 0.7341; P < 0.001) between parameter of volume changes measured using nephelometry and light microscopy methods confirmed nephelometry as a sufficiently sensitive method to detect changes of spermatozoa volume. The spermatocrit alteration method resulted in a large proportion of damaged and potentially immotile spermatozoa in media of osmolality less than 150 mOsm/kg in carp and osmolalities from 10 to 300 mOsm/kg in sterlet and brook trout. Therefore, this method is not reliable for assessing spermatozoa swelling in hypotonic solutions, because the integrity of the cells is not fully preserved. Increase in carp spermatozoa (osmotic activation mode) volume occurred during the motility period in hypotonic conditions, but no indications of volume changes were found in sterlet and brook trout spermatozoa (ionic activation mode) associated with environmental osmolality alteration. Accordingly, we conclude that sperm volume changes are differentially involved in the motility activation process. Species-specific differences in spermatozoa volume changes as a response to a hypotonic environment during the motility period are discussed in relation to their potent physiological role.
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Affiliation(s)
- Olga Bondarenko
- Faculty of Fisheries and Protection of Waters, University of South Bohemia in Ceske Budejovice, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Vodnany, Czech Republic.
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118
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Johnson MD, O'Connell M. Na-K-2Cl cotransporter and aquaporin 1 in arachnoid granulations, meningiomas, and meningiomas invading dura. Hum Pathol 2013; 44:1118-24. [PMID: 23317544 DOI: 10.1016/j.humpath.2012.09.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Revised: 09/26/2012] [Accepted: 09/28/2012] [Indexed: 11/30/2022]
Abstract
Meningioma invasion of the dura may contribute to the high rate of recurrence. Recently, ion channels that affect cell shape and movement have been implicated in cancer invasion. Combined Na-K-2Cl cotransporter (NKCC1) and aquaporin 1 (AQP1) expression in arachnoid granulations and meningiomas with and without dural invasion has not been characterized. Arachnoid granulations associated with dura were collected from 10 adult formalin-fixed dura/leptomeninges. Thirty-four frozen meningiomas were evaluated by Western blot. An additional 58 formalin-fixed, paraffin-embedded meningiomas including 36 World Health Organization grade I, 15 grade II, and 7 grade III meningiomas were evaluated by immunohistochemistry. By Western blot, NKCC1 was found in 17 (100%) of 17 World Health Organization grade I, 13 (87%) of 15 grade II, and both grade III meningiomas. Distinct AQP1 was not detected in the meningioma lysates tested. By immunohistochemistry, extensive NKCC1 but no AQP1 immunoreactivity was detected in the arachnoid granulation cells. Extensive NKCC1 was detected in meningioma cells in 56 and in capillaries in 43 by immunohistochemistry. In those tumors with dural or bone/soft tissue invasion, NKCC1 immunoreactivity was seen in invading cells in all cases and in their capillaries in the majority. AQP1 was detected in meningioma cells in 29 and in capillaries in all. AQP1 was also detected in cells and capillaries invading the dura or bone in 10 and 18 of 18, respectively. This was extensive in all subtypes of meningiomas studied. These findings suggest that NKCC1 and AQP1 participate in meningioma biology and invasion. NKCC1 might be targeted by FDA-approved NKCC1 inhibitors.
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Affiliation(s)
- Mahlon D Johnson
- Department of Pathology, Division of Neuropathology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
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119
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Brain water channel proteins in health and disease. Mol Aspects Med 2012; 33:562-78. [DOI: 10.1016/j.mam.2012.03.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 03/28/2012] [Accepted: 03/31/2012] [Indexed: 02/07/2023]
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120
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The disturbed blood–brain barrier in human glioblastoma. Mol Aspects Med 2012; 33:579-89. [DOI: 10.1016/j.mam.2012.02.003] [Citation(s) in RCA: 181] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 02/09/2012] [Accepted: 02/14/2012] [Indexed: 12/15/2022]
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121
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Pentobarbital inhibits glucose uptake, but not water transport by glucose transporter type 3. Neuroreport 2012; 23:687-91. [PMID: 22692552 DOI: 10.1097/wnr.0b013e328355d6fc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To understand the mechanisms underlying the neuroprotective efficacy of barbiturates, the effect of pentobarbital on glucose uptake and water transport was determined in Xenopus oocytes expressing glucose transporter type 3 (GLUT3). Pentobarbital induced a 50% concentration-dependent inhibition in glucose uptake, but exerted no effect on water transport by GLUT3. Eadie-Hofstee analysis showed that pentobarbital decreased Vmax significantly, but not Km of GLUT3 for 2-deoxy-D-glucose. Although the protein kinase C (PKC) activator significantly decreased glucose uptake by GLUT3, no additive or synergistic interactions were observed between the PKC activator and pentobarbital. Our results suggest that pentobarbital may play an important role in neuroprotection by inhibition of glucose uptake by GLUT3 by a mechanism involving PKC.
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Abstract
The hypothesis that the facilitative glucose transporter type 3 (GLUT3) in the brain also exhibits water channel properties similar to that of GLUT1 was tested in Xenopus oocytes expressing human GLUT3 or GLUT1. The volume of oocytes expressing GLUT3 exposed to hypotonic medium increased in an exponential manner. The osmotic water permeability (Pf) for GLUT3 or GLUT1 increased significantly compared with that for oocytes-injected water. The osmotic water transport by GLUT3 was completely inhibited by treatment with a selective GLUT inhibitor, cytochalasin B. The Pf values for GLUT3 significantly increased with increasing temperature of the extracellular medium and the activation energy for GLUT3 was almost the same as that for GLUT1. Thus, GLUT3 in the brain also exhibits water channel properties.
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Affiliation(s)
- Shigemasa Tomioka
- Department of Dental Anesthesiology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
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123
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Kim J, Jung Y. Increased aquaporin-1 and Na+ -K+ -2Cl- cotransporter 1 expression in choroid plexus leads to blood-cerebrospinal fluid barrier disruption and necrosis of hippocampal CA1 cells in acute rat models of hyponatremia. J Neurosci Res 2012; 90:1437-44. [PMID: 22419034 DOI: 10.1002/jnr.23017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 11/21/2011] [Accepted: 12/02/2011] [Indexed: 12/13/2022]
Abstract
Hyponatremia is a metabolic disorder characterized by increased cerebrospinal fluid (CSF) volume and pressure, although the site of brain insult is unclear. Specifically, the hippocampus, which is in direct contact with expanding CSF ventricles, may be involved. The present study was undertaken to investigate the possible roles of choroid plexus aquaporin-1 (AQP1) and of cation chloride transporters (Na(+) -K(+) -2Cl(-) cotransporter 1 [NKCC1] and K(+) -Cl(-) cotransporter 4 [KCC4]) in the underlying hippocampal pathophysiology of hyponatremia in acute (6 and 12 hr duration) experimental models. It was found that the expressions of AQP1 and NKCC1 proteins in choroid plexus were significantly increased, whereas the expression of KCC4 protein was unchanged vs. control values after 6 and 12 hr of hyponatremia. Choroid plexuses with increased AQP1 and NKCC1 after 6 hr of hyponatremia showed caspase 3-dependent apoptosis and disruption of the blood-CSF barrier. Furthermore, necrotic changes in CA1 neuronal cells were observed after 6 and 12 hr of hyponatremia. Overall, these data suggest that increases in AQP1 and NKCC1 expression under hyposmotic stress may be one of the molecular mechanisms underlying the pathophysiology of acute hyponatremia, such as the necrotic cell death of hippocampal CA1 region by increasing water transport across the blood-CSF barrier. Furthermore, we suggest that opening of the blood-CSF barrier after acute hyponatremia may be triggered the secondary adverse conditions that are capable of enhancing selective necrosis in hippocampal CA1 cells.
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Affiliation(s)
- Jaehyun Kim
- Department of Anatomy, College of Medicine, Dongguk University, Gyeongju, Republic of Korea
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Haj-Yasein NN, Jensen V, Østby I, Omholt SW, Voipio J, Kaila K, Ottersen OP, Hvalby Ø, Nagelhus EA. Aquaporin-4 regulates extracellular space volume dynamics during high-frequency synaptic stimulation: a gene deletion study in mouse hippocampus. Glia 2012; 60:867-74. [PMID: 22419561 DOI: 10.1002/glia.22319] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 02/14/2012] [Indexed: 11/10/2022]
Abstract
Little is known about the physiological roles of aquaporin-4 (AQP4) in the central nervous system. AQP4 water channels are concentrated in endfeet membranes of astrocytes but also localize to the fine astrocytic processes that abut central synapses. Based on its pattern of expression, we predicted that AQP4 could be involved in controlling water fluxes and changes in extracellular space (ECS) volume that are associated with activation of excitatory pathways. Here, we show that deletion of Aqp4 accentuated the shrinkage of the ECS that occurred in the mouse hippocampal CA1 region during activation of Schaffer collateral/commissural fibers. This effect was found in the stratum radiatum (where perisynaptic astrocytic processes abound) but not in the pyramidal cell layer (where astrocytic processes constitute but a minor volume fraction). For both genotypes the ECS shrinkage was most pronounced in the pyramidal cell layer. Our data attribute a physiological role to AQP4 and indicate that this water channel regulates extracellular volume dynamics in the mammalian brain.
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Affiliation(s)
- Nadia Nabil Haj-Yasein
- Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of Oslo, Oslo, Norway
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125
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Abstract
INTRODUCTION Aquaporins (AQPs) are membrane proteins that facilitate water and small solute movement in tissues. Hydrocephalus is the major central nervous system disorder associated with defective cerebrospinal fluid turnover. Aquaporin-4 (AQP4) is a water channel located mainly at the blood-brain barrier (BBB) and blood-cerebrospinal fluid (CSF) interfaces and is associated with the elimination of cerebral edema via these routes. The aim of this study is to review the pertinent literature concerning the role of AQP4 in the pathophysiology of hydrocephalus. METHODS We performed a MEDLINE search using the terms aquaporin AND hydrocephalus. The results of the search were further refined to exclude studies not related to aquaporin-4. RESULTS Six studies were identified. All studies utilized an animal model such as AQP4-knockout mice, H-Tx rats, and kaolin and L-α-lysophosphatidylcholine (LPC) stearoyl injection models of hydrocephalus. Most studies indicate that there is an up-regulation of AQP4 expression at the BBB and blood-CSF interfaces in cases of hydrocephalus. One study, reported sporadic cases of obstructive hydrocephalus in a subgroup of AQP4-knockout mice. CONCLUSIONS Few publications have studied the association between aquaporins and hydrocephalus. Currently, all the existing studies rely on animal models. An adaptive and protective role of AQP4 to increase the resolution of the "hydrocephalic" edema at the BBB and blood-CSF interfaces is proposed in the pathophysiology of hydrocephalus. Further research is needed to clarify if this association exists in humans.
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126
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Glial K+ Clearance and Cell Swelling: Key Roles for Cotransporters and Pumps. Neurochem Res 2012; 37:2299-309. [DOI: 10.1007/s11064-012-0731-3] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 01/13/2012] [Accepted: 02/11/2012] [Indexed: 10/28/2022]
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Chamma I, Chevy Q, Poncer JC, Lévi S. Role of the neuronal K-Cl co-transporter KCC2 in inhibitory and excitatory neurotransmission. Front Cell Neurosci 2012; 6:5. [PMID: 22363264 PMCID: PMC3282916 DOI: 10.3389/fncel.2012.00005] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 01/30/2012] [Indexed: 01/06/2023] Open
Abstract
The K-Cl co-transporter KCC2 plays multiple roles in the physiology of central neurons and alterations of its function and/or expression are associated with several neurological conditions. By regulating intraneuronal chloride homeostasis, KCC2 strongly influences the efficacy and polarity of the chloride-permeable γ-aminobutyric acid (GABA) type A and glycine receptor (GlyR) mediated synaptic transmission. This appears particularly critical for the development of neuronal circuits as well as for the dynamic control of GABA and glycine signaling in mature networks. The activity of the transporter is also associated with transmembrane water fluxes which compensate solute fluxes associated with synaptic activity. Finally, KCC2 interaction with the actin cytoskeleton appears critical both for dendritic spine morphogenesis and the maintenance of glutamatergic synapses. In light of the pivotal role of KCC2 in the maturation and function of central synapses, it is of particular importance to understand the cellular and molecular mechanisms underlying its regulation. These include development and activity-dependent modifications both at the transcriptional and post-translational levels. We emphasize the importance of post-translational mechanisms such as phosphorylation and dephosphorylation, oligomerization, cell surface stability, clustering and membrane diffusion for the rapid and dynamic regulation of KCC2 function.
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128
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Iacovetta C, Rudloff E, Kirby R. The role of aquaporin 4 in the brain. Vet Clin Pathol 2012; 41:32-44. [PMID: 22250904 DOI: 10.1111/j.1939-165x.2011.00390.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Revised: 11/14/2011] [Accepted: 12/10/2011] [Indexed: 11/26/2022]
Abstract
Emerging evidence suggests that aquaporin (AQP) 4 water channels play an important role in water homeostasis in the brain. These water channels are most abundant in the cell membrane of astrocytes, but are also present within ependymal cell membranes and in osmosensory areas of the hypothalamus. Water transport through AQP4 depends on concentration gradients across the membrane, but the rate of transport is determined by the capacity of astrocytes to up- and down-regulate AQP4 numbers, their location within the membrane, and the overall permeability of the channel. Other functions of brain AQP4 involve potassium uptake and release by astrocytes, migration of glial cells, glial scarring, and astrocyte-to-astrocyte cell communication. AQP water channels are involved in formation and control of edema in the brain and in multiple disease processes in the brain, such as seizures and tumors. There is abundant scientific literature on AQP4 describing its structure, function, location, and role in water homeostasis and edema in the brain. Investigation of AQP expression in the canine and feline brain should be pursued so that clinically relevant comparisons between findings in mice, rats, and people and animal patients can be made.
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129
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Zeuthen T, Macaulay N. Cotransport of water by Na⁺-K⁺-2Cl⁻ cotransporters expressed in Xenopus oocytes: NKCC1 versus NKCC2. J Physiol 2012; 590:1139-54. [PMID: 22250214 DOI: 10.1113/jphysiol.2011.226316] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The NKCC1 and NKCC2 isoforms of the mammalian Na⁺–K⁺–2Cl⁻ cotransporter were expressed in Xenopus oocytes and the relation between external ion concentration and water fluxes determined.Water fluxes were determined from changes in the oocytes volume and ion fluxes from 86Rb+ uptake. Isotonic increases in external K⁺ concentration elicited abrupt inward water fluxes in NKCC1; the K⁺ dependence obeyed one-site kinetics with a K₀.₅ of 7.5 mM. The water fluxes were blocked by bumetanide, had steep temperature dependence and could proceed uphill against an osmotic gradient of 20 mosmol l⁻¹. A comparison between ion and water fluxes indicates that 460 water molecules are cotransported for each turnover of the protein. In contrast, NKCC2 did not support water fluxes.Water transport in NKCC1 induced by increases in the external osmolarity had high activation energy and was blocked by bumetanide. The osmotic effects of NaCl were smaller than those of urea and mannitol. This supports the notion of interaction between ions and water in NKCC1 and allows for an estimate of around 600 water molecules transported per turnover of the protein. Osmotic gradients did not induce water transport in NKCC2. We conclude that NKCC1 plays a direct role for water balance in most cell types, while NKCC2 fulfils its role in the kidney of transporting ions but not water. The different behaviour of NKCC1 and NKCC2 is discussed on the basis of recent molecular models based on studies of structural and molecular dynamics.
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Affiliation(s)
- Thomas Zeuthen
- The Panum Institute, Institute of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3C, DK-2200N Denmark.
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130
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Abstract
It was firmly established in the mid-twentieth century that the arachnoid villi represented an open pathway between the subarachnoid space and the dural venous sinuses. Intracellular and extracellular pathways within the villous structure provided the conduit for cerebrospinal fluid (CSF) and particulate matter. The importance of the lymphatic system was established by the demonstration of CSF tracers entering the nasal lymphatic system via the perineural subarachnoid space enveloping the olfactory nerve rootlets. It appears that because of the late development of the arachnoid villus (AV) system, the lymphatic outflow system is the more dominant one in the young animal, but in the mature animal the importance of both systems appears equal. In general, the lymphatic system in lower animals appears dominant, but in the case of primates, this may not be the case. The global outflow system has a definite opening pressure of ca. 50-70 mm of water, and the balance between production of CSF and absorption occurs at a resting pressure of ca. 115 mm water. The bicompartmental CSF outflow curves obtained from hydrocephalic patients support the presence of a dual outflow system utilized in normal CSF drainage.
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Affiliation(s)
- Michael Pollay
- University of Oklahoma College of Medicine, Sun City West, AZ, USA.
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131
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Oliveira-Ferreira AI, Winkler MKL, Reiffurth C, Milakara D, Woitzik J, Dreier JP. Spreading depolarization, a pathophysiological mechanism of stroke and migraine aura. FUTURE NEUROLOGY 2012. [DOI: 10.2217/fnl.11.69] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Spreading depolarization is a mechanism of abrupt, massive ion translocation between intraneuronal and extracellular space that entails cytotoxic edema in the brain’s gray matter. It is observed in patients as a large change of the slow electrical potential. Dependent on the energy status of the tissue, spreading depolarization is either preceded by nonspreading silencing due to neuronal hyperpolarization or accompanied by spreading silencing of electrical brain activity due to a depolarization block. Nonspreading silencing seems to translate into the initial clinical symptoms of ischemic stroke and spreading silencing translates into migraine aura. Direct electrophysiological evidence exists that spreading depolarization occurs in abundance in aneurysmal subarachnoid hemorrhage, delayed ischemic stroke after subarachnoid hemorrhage, malignant hemispheric stroke, spontaneous intracerebral hemorrhage and traumatic brain injury. Indirect evidence suggests its occurrence during migraine aura. In animals, spreading depolarizations facilitate neuronal death when they invade metabolically compromised tissue, whereas they are relatively innocuous in healthy tissue. Therapies targeting spreading depolarization may potentially treat these neurological conditions.
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Affiliation(s)
- Ana I Oliveira-Ferreira
- Department of Experimental Neurology, Charité University Medicine Berlin, Germany
- Center for Stroke Research, Campus Charité Mitte, Charité University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Maren KL Winkler
- Center for Stroke Research, Campus Charité Mitte, Charité University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Clemens Reiffurth
- Department of Experimental Neurology, Charité University Medicine Berlin, Germany
- Center for Stroke Research, Campus Charité Mitte, Charité University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Denny Milakara
- Center for Stroke Research, Campus Charité Mitte, Charité University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Johannes Woitzik
- Department of Neurosurgery, Charité University Medicine Berlin, Germany
| | - Jens P Dreier
- Department of Neurology, Charité University Medicine Berlin, Germany
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132
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Siesjö P. Is there a benefit of using artificial cerebrospinal fluid for irrigation? World Neurosurg 2011; 77:73-5. [PMID: 22099564 DOI: 10.1016/j.wneu.2011.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 06/01/2011] [Indexed: 11/25/2022]
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Addition of NMDA-receptor antagonist MK801 during oxygen/glucose deprivation moderately attenuates the upregulation of glucose uptake after subsequent reoxygenation in brain endothelial cells. Neurosci Lett 2011; 506:44-9. [PMID: 22040671 DOI: 10.1016/j.neulet.2011.10.045] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Revised: 10/03/2011] [Accepted: 10/15/2011] [Indexed: 11/22/2022]
Abstract
During stroke the blood-brain barrier (BBB) is damaged which can result in vasogenic brain edema and inflammation. The reduced blood supply leads to decreased delivery of oxygen and glucose to affected areas of the brain. Oxygen and glucose deprivation (OGD) can cause upregulation of glucose uptake of brain endothelial cells. In this letter, we investigated the influence of MK801, a non-competitive inhibitor of the NMDA-receptor, on the regulation of the glucose uptake and of the main glucose transporters glut1 and sglt1 in murine BBB cell line cerebEND during OGD. mRNA expression of glut1 was upregulated 68.7-fold after 6h OGD, which was significantly reduced by 10μM MK801 to 28.9-fold. Sglt1 mRNA expression decreased during OGD which was further reduced by MK801. Glucose uptake was significantly increased up to 907% after 6h OGD and was still higher (210%) after the 20h reoxygenation phase compared to normoxia. Ten micromolar MK801 during OGD was able to reduce upregulated glucose uptake after OGD and reoxygenation significantly. Presence of several NMDAR subunits was proven on the mRNA level in cerebEND cells. Furthermore, it was shown that NMDAR subunit NR1 was upregulated during OGD and that this was inhibitable by MK801. In conclusion, the addition of MK801 during the OGD phase reduced significantly the glucose uptake after the subsequent reoxygenation phase in brain endothelial cells.
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134
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Water and urea permeation pathways of the human excitatory amino acid transporter EAAT1. Biochem J 2011; 439:333-40. [DOI: 10.1042/bj20110905] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glutamate transport is coupled to the co-transport of 3 Na+ and 1 H+ followed by the counter-transport of 1 K+. In addition, glutamate and Na+ binding to glutamate transporters generates an uncoupled anion conductance. The human glial glutamate transporter EAAT1 (excitatory amino acid transporter 1) also allows significant passive and active water transport, which suggests that water permeation through glutamate transporters may play an important role in glial cell homoeostasis. Urea also permeates EAAT1 and has been used to characterize the permeation properties of the transporter. We have previously identified a series of mutations that differentially affect either the glutamate transport process or the substrate-activated channel function of EAAT1. The water and urea permeation properties of wild-type EAAT1 and two mutant transporters were measured to identify which permeation pathway facilitates the movement of these molecules. We demonstrate that there is a significant rate of L-glutamate-stimulated passive and active water transport. Both the passive and active L-glutamate-stimulated water transport is most closely associated with the glutamate transport process. In contrast, L-glutamate-stimulated [14C]urea permeation is associated with the anion channel of the transporter. However, there is also likely to be a transporter-specific, but glutamate independent, flux of water via the anion channel.
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135
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Paul L, Madan M, Rammling M, Chigurupati S, Chan SL, Pattisapu JV. Expression of aquaporin 1 and 4 in a congenital hydrocephalus rat model. Neurosurgery 2011; 68:462-73. [PMID: 21135737 DOI: 10.1227/neu.0b013e3182011860] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Hydrocephalus occurs because of an imbalance of bulk fluid flow in the brain, and aquaporins (AQPs) play pivotal roles in cerebral water movement as essential mediators during edema and fluid accumulation. AQP1 is a water channel found in the choroid plexus (CP), and AQP4 is expressed at the brain-CSF interfaces and astrocytic end feet; excessive fluid accumulation may involve expression of changes in these AQPs during various stages of hydrocephalus. OBJECTIVE To determine the alterations of CP AQP1 expression in congenital hydrocephalus; detect hydrocephalus-induced AQP1 expression in the cortical parenchyma, ependyma, and pia mater of hydrocephalic animals; and evaluate AQP4 expression in congenital hydrocephalus through progressive stages of the condition. METHODS We evaluated differential expression of AQPs 1 and 4 in the congenital hydrocephalus Texas rat at postnatal days 5, 10, and 26 in isolated CP and cortex by enzyme-linked immunosorbent assay, Western blot, quantitative reverse transcriptase polymerase chain reaction, and immunohistochemistry. RESULTS The CP exhibited a 34% decrease in AQP1 expression in young hydrocephalic pups (postnatal days 5 and 10), which became normal (postnatal day 26) just before death. With advancing hydrocephalus, expression of AQPs 1 and 4 increased at the brain-CSF interfaces; AQP1 was localized to the endothelium of cortical capillaries with increased AQP4 expression in surrounding astrocytes end feet. AQP1 expression level was increased in the pia mater, with prominent AQP4 expression in the subpial layers. Subependymal capillaries expressed AQP1 in the endothelium, with increasing AQP4 expression in surrounding astrocytes. Hydrocephalic animals (postnatal day 26) had significant nonendothelial (CD34) AQP1 expression in the septal nucleus of the basal forebrain, an area affected by increased intracranial pressure. CONCLUSION Biphasic AQP1 expression in the CP with increased AQPs 1 and 4 at the brain-fluid interfaces may indicate compensatory mechanisms to regulate choroidal cerebrospinal fluid secretion and increase parenchymal fluid absorption in the high-pressure hydrocephalic condition.
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Affiliation(s)
- Leena Paul
- Burnett School of Biomedical Science, College of Medicine, University of Central Florida Orlando, Florida, USA.
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136
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Schulz R, Vargiu AV, Ruggerone P, Kleinekathöfer U. Role of Water during the Extrusion of Substrates by the Efflux Transporter AcrB. J Phys Chem B 2011; 115:8278-87. [DOI: 10.1021/jp200996x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Robert Schulz
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen,
Germany
| | - Attilio V. Vargiu
- CNR-IOM, Unità SLACS,
c/o Dipartimento di Fisica, Università di Cagliari, s.p. Monserrato-Sestu km 0.7, I-09042 Monserrato (CA), Italy
| | - Paolo Ruggerone
- CNR-IOM, Unità SLACS,
c/o Dipartimento di Fisica, Università di Cagliari, s.p. Monserrato-Sestu km 0.7, I-09042 Monserrato (CA), Italy
| | - Ulrich Kleinekathöfer
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen,
Germany
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137
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Neuwelt EA, Bauer B, Fahlke C, Fricker G, Iadecola C, Janigro D, Leybaert L, Molnar Z, O’Donnell M, Povlishock J, Saunders N, Sharp F, Stanimirovic D, Watts R, Drewes L. Engaging neuroscience to advance translational research in brain barrier biology. Nat Rev Neurosci 2011; 12:169-82. [PMID: 21331083 PMCID: PMC3335275 DOI: 10.1038/nrn2995] [Citation(s) in RCA: 336] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The delivery of many potentially therapeutic and diagnostic compounds to specific areas of the brain is restricted by brain barriers, of which the most well known are the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barrier. Recent studies have shown numerous additional roles of these barriers, including an involvement in neurodevelopment, in the control of cerebral blood flow, and--when barrier integrity is impaired--in the pathology of many common CNS disorders such as Alzheimer's disease, Parkinson's disease and stroke.
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Affiliation(s)
- Edward A. Neuwelt
- Oregon Health & Science University, Portland, Oregon
- Portland Veterans Affairs Medical Center, Portland, Oregon
| | | | | | | | | | | | | | | | | | | | | | - Frank Sharp
- University of California at Davis, Davis, California
| | | | - Ryan Watts
- Genentech, Inc., South San Francisco, California
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138
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Wolburg H, Wolburg-Buchholz K, Fallier-Becker P, Noell S, Mack AF. Structure and functions of aquaporin-4-based orthogonal arrays of particles. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 287:1-41. [PMID: 21414585 DOI: 10.1016/b978-0-12-386043-9.00001-3] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Orthogonal arrays or assemblies of intramembranous particles (OAPs) are structures in the membrane of diverse cells which were initially discovered by means of the freeze-fracturing technique. This technique, developed in the 1960s, was important for the acceptance of the fluid mosaic model of the biological membrane. OAPs were first described in liver cells, and then in parietal cells of the stomach, and most importantly, in the astrocytes of the brain. Since the discovery of the structure of OAPs and the identification of OAPs as the morphological equivalent of the water channel protein aquaporin-4 (AQP4) in the 1990s, a plethora of morphological work on OAPs in different cells was published. Now, we feel a need to balance new and old data on OAPs and AQP4 to elucidate the interrelationship of both structures and molecules. In this review, the identity of OAPs as AQP4-based structures in a diversity of cells will be described. At the same time, arguments are offered that under pathological or experimental circumstances, AQP4 can also be expressed in a non-OAP form. Thus, we attempt to project classical work on OAPs onto the molecular biology of AQP4. In particular, astrocytes and glioma cells will play the major part in this review, not only due to our own work but also due to the fact that most studies on structure and function of AQP4 were done in the nervous system.
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Affiliation(s)
- Hartwig Wolburg
- Institute of Pathology, University of Tübingen, Tübingen, Germany
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139
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Filippidis AS, Kalani MYS, Rekate HL. Hydrocephalus and aquaporins: lessons learned from the bench. Childs Nerv Syst 2011; 27:27-33. [PMID: 20625739 DOI: 10.1007/s00381-010-1227-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 07/01/2010] [Indexed: 11/30/2022]
Abstract
PURPOSE Hydrocephalus is a common disorder of defective cerebrospinal fluid (CSF) turnover. The identification of the aquaporin water channels (AQPs) led to the study of their role in the composition of biological fluids including CSF. The purpose of this study is to review the potential role of aquaporins in the pathogenesis, compensation, and possibly treatment of hydrocephalus. METHODS We performed a MEDLINE search using the terms "aquaporin AND hydrocephalus." The search returned a total of 20 titles. Eleven studies fulfilled the criteria for this review. RESULTS Most studies were performed in animal models. The expression of AQPs in hydrocephalus is significantly altered. Aquaporin-1 levels at the choroid plexus are decreased in most models of hydrocephalus while CSF production and intracranial pressure are reduced in AQP1 knockout mice. In contrast, the expression of AQP4 in hydrocephalus is increased at its sites of expression. Aquaporin-4 knockout mice show a decreased clearance of brain edema via blood-CSF and blood-brain barrier (BBB) pathways and decreased survival in hydrocephalus models. CONCLUSIONS Aquaporin-1 is highly expressed at the choroid plexus and is related to CSF production. Aquaporin-4 is expressed at the ependyma, glia limitans, and at the perivascular end feet processes of astrocytes of the BBB, facilitating the water movement across these tissue interfaces. The observations obtained from animal studies and few cases in humans indicate an adaptive and protective role of AQPs in hydrocephalus by decreasing CSF production and increasing edema clearance. Aquaporins are attractive targets for the pharmaceutical treatment of hydrocephalus.
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Affiliation(s)
- Aristotelis S Filippidis
- Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 West Thomas Road, Phoenix, AZ 85013, USA
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140
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Risher WC, Ard D, Yuan J, Kirov SA. Recurrent spontaneous spreading depolarizations facilitate acute dendritic injury in the ischemic penumbra. J Neurosci 2010; 30:9859-68. [PMID: 20660268 PMCID: PMC2918261 DOI: 10.1523/jneurosci.1917-10.2010] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 06/14/2010] [Indexed: 01/22/2023] Open
Abstract
Spontaneous spreading depolarizations (SDs) occur in the penumbra surrounding ischemic core. These SDs, often referred to as peri-infarct depolarizations, cause vasoconstriction and recruitment of the penumbra into the ischemic core in the critical first hours after focal ischemic stroke; however, the real-time spatiotemporal dynamics of SD-induced injury to synaptic circuitry in the penumbra remain unknown. A modified cortical photothrombosis model was used to produce a square-shaped lesion surrounding a penumbra-like "area at risk" in middle cerebral artery territory of mouse somatosensory cortex. Lesioning resulted in recurrent spontaneous SDs. In vivo two-photon microscopy of green fluorescent protein-expressing neurons in this penumbra-like area at risk revealed that SDs were temporally correlated with rapid (<6 s) dendritic beading. Dendrites quickly (<3 min) recovered between SDs to near-control morphology until the occurrence of SD-induced terminal dendritic injury, signifying acute synaptic damage. SDs are characterized by a breakdown of ion homeostasis that can be recovered by ion pumps if the energy supply is adequate. Indeed, the likelihood of rapid dendritic recovery between SDs was correlated with the presence of nearby flowing blood vessels, but the presence of such vessels was not always sufficient for rapid dendritic recovery, suggesting that energy needs for recovery exceeded energy supply of compromised blood flow. We propose that metabolic stress resulting from recurring SDs facilitates acute injury at the level of dendrites and dendritic spines in metabolically compromised tissue, expediting penumbral recruitment into the ischemic core.
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Affiliation(s)
- W. Christopher Risher
- Graduate Program in Neuroscience
- Brain and Behavioral Discovery Institute, Medical College of Georgia, Augusta, Georgia 30912
| | - Deborah Ard
- Department of Neurosurgery, and
- Brain and Behavioral Discovery Institute, Medical College of Georgia, Augusta, Georgia 30912
| | - Jianghe Yuan
- Brain and Behavioral Discovery Institute, Medical College of Georgia, Augusta, Georgia 30912
| | - Sergei A. Kirov
- Department of Neurosurgery, and
- Brain and Behavioral Discovery Institute, Medical College of Georgia, Augusta, Georgia 30912
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141
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Amiry-Moghaddam M, Hoddevik EH, Ottersen OP. Aquaporins: multifarious roles in brain. Neuroscience 2010; 168:859-61. [PMID: 20450960 DOI: 10.1016/j.neuroscience.2010.04.071] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 04/28/2010] [Indexed: 11/30/2022]
Affiliation(s)
- M Amiry-Moghaddam
- Centre for Molecular Biology and Neuroscience, University of Oslo, Sognsvannsveien 9, PO Box 1105 Blindern, 0317 Oslo, Norway.
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142
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Del Bigio MR. Ependymal cells: biology and pathology. Acta Neuropathol 2010; 119:55-73. [PMID: 20024659 DOI: 10.1007/s00401-009-0624-y] [Citation(s) in RCA: 234] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 12/03/2009] [Accepted: 12/04/2009] [Indexed: 11/28/2022]
Abstract
The literature was reviewed to summarize the current understanding of the role of ciliated ependymal cells in the mammalian brain. Previous reviews were summarized. Publications from the past 10 years highlight interactions between ependymal cells and the subventricular zone and the possible role of restricted ependymal populations in neurogenesis. Ependymal cells provide trophic support and possibly metabolic support for progenitor cells. Channel proteins such as aquaporins may be important for determining water fluxes at the ventricle wall. The junctional and anchoring proteins are now fairly well understood, as are proteins related to cilia function. Defects in ependymal adhesion and cilia function can cause hydrocephalus through several different mechanisms, one possibility being loss of patency of the cerebral aqueduct. Ependymal cells are susceptible to infection by a wide range of common viruses; while they may act as a line of first defense, they eventually succumb to repeated attacks in long-lived organisms. Ciliated ependymal cells are almost certainly important during brain development. However, the widespread absence of ependymal cells from the adult human lateral ventricles suggests that they may have only regionally restricted value in the mature brain of large size.
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Affiliation(s)
- Marc R Del Bigio
- Department of Pathology, University of Manitoba, Winnipeg, MB, Canada.
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143
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Zeuthen T. Water-Transporting Proteins. J Membr Biol 2009; 234:57-73. [DOI: 10.1007/s00232-009-9216-y] [Citation(s) in RCA: 156] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 10/20/2009] [Indexed: 12/17/2022]
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