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Rioux AV, Nsimba-Batomene TR, Slimani S, Bergeron NAD, Gravel MAM, Schreiber SV, Fiola MJ, Haydock L, Garneau AP, Isenring P. Navigating the multifaceted intricacies of the Na +-Cl - cotransporter, a highly regulated key effector in the control of hydromineral homeostasis. Physiol Rev 2024; 104:1147-1204. [PMID: 38329422 PMCID: PMC11381001 DOI: 10.1152/physrev.00027.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 01/01/2024] [Accepted: 02/03/2024] [Indexed: 02/09/2024] Open
Abstract
The Na+-Cl- cotransporter (NCC; SLC12A3) is a highly regulated integral membrane protein that is known to exist as three splice variants in primates. Its primary role in the kidney is to mediate the cosymport of Na+ and Cl- across the apical membrane of the distal convoluted tubule. Through this role and the involvement of other ion transport systems, NCC allows the systemic circulation to reclaim a fraction of the ultrafiltered Na+, K+, Cl-, and Mg+ loads in exchange for Ca2+ and [Formula: see text]. The physiological relevance of the Na+-Cl- cotransport mechanism in humans is illustrated by several abnormalities that result from NCC inactivation through the administration of thiazides or in the setting of hereditary disorders. The purpose of the present review is to discuss the molecular mechanisms and overall roles of Na+-Cl- cotransport as the main topics of interest. On reading the narrative proposed, one will realize that the knowledge gained in regard to these themes will continue to progress unrelentingly no matter how refined it has now become.
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Affiliation(s)
- A V Rioux
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - T R Nsimba-Batomene
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - S Slimani
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - N A D Bergeron
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - M A M Gravel
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - S V Schreiber
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - M J Fiola
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - L Haydock
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
- Service de Néphrologie-Transplantation Rénale Adultes, Hôpital Necker-Enfants Malades, AP-HP, INSERM U1151, Université Paris Cité, Paris, France
| | - A P Garneau
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
- Service de Néphrologie-Transplantation Rénale Adultes, Hôpital Necker-Enfants Malades, AP-HP, INSERM U1151, Université Paris Cité, Paris, France
| | - P Isenring
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
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Maex R. Energy optimisation predicts the capacity of ion buffering in the brain. BIOLOGICAL CYBERNETICS 2023; 117:467-484. [PMID: 38103053 DOI: 10.1007/s00422-023-00980-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 11/23/2023] [Indexed: 12/17/2023]
Abstract
Neurons store energy in the ionic concentration gradients they build across their cell membrane. The amount of energy stored, and hence the work the ions can do by mixing, can be enhanced by the presence of ion buffers in extra- and intracellular space. Buffers act as sources and sinks of ions, however, and unless the buffering capacities for different ion species obey certain relationships, a complete mixing of the ions may be impeded by the physical conditions of charge neutrality and isotonicity. From these conditions, buffering capacities were calculated that enabled each ion species to mix completely. In all valid buffer distributions, the [Formula: see text] ions were buffered most, with a capacity exceeding that of [Formula: see text] and [Formula: see text] buffering by at least an order of magnitude. The similar magnitude of the (oppositely directed) [Formula: see text] and [Formula: see text] gradients made extracellular space behave as a [Formula: see text]-[Formula: see text] exchanger. Anions such as [Formula: see text] were buffered least. The great capacity of the extra- and intracellular [Formula: see text] buffers caused a large influx of [Formula: see text] ions as is typically observed during energy deprivation. These results explain many characteristics of the physiological buffer distributions but raise the question how the brain controls the capacity of its ion buffers. It is suggested that neurons and glial cells, by their great sensitivity to gradients of charge and osmolarity, respectively, sense deviations from electro-neutral and isotonic mixing, and use these signals to tune the chemical composition, and buffering capacity, of the extra- and intracellular matrices.
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Affiliation(s)
- Reinoud Maex
- School of Physics, Engineering and Computer Science, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, UK.
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MacAulay N, Toft-Bertelsen TL. Dual function of the choroid plexus: Cerebrospinal fluid production and control of brain ion homeostasis. Cell Calcium 2023; 116:102797. [PMID: 37801806 DOI: 10.1016/j.ceca.2023.102797] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 09/07/2023] [Accepted: 09/08/2023] [Indexed: 10/08/2023]
Abstract
The choroid plexus is a small monolayered epithelium located in the brain ventricles and serves to secrete the cerebrospinal fluid (CSF) that envelops the brain and fills the central ventricles. The CSF secretion is sustained with a concerted effort of a range of membrane transporters located in a polarized fashion in this tissue. Prominent amongst these are the Na+/K+-ATPase, the Na+,K+,2Cl- cotransporter (NKCC1), and several HCO3- transporters, which together support the net transepithelial transport of the major electrolytes, Na+ and Cl-, and thus drive the CSF secretion. The choroid plexus, in addition, serves an important role in keeping the CSF K+ concentration at a level compatible with normal brain function. The choroid plexus Na+/K+-ATPase represents a key factor in the barrier-mediated control of the CSF K+ homeostasis, as it increases its K+ uptake activity when faced with elevated extracellular K+ ([K+]o). In certain developmental or pathological conditions, the NKCC1 may revert its net transport direction to contribute to CSF K+ homeostasis. The choroid plexus ion transport machinery thus serves dual, yet interconnected, functions with its contribution to electrolyte and fluid secretion in combination with its control of brain K+ levels.
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Affiliation(s)
- Nanna MacAulay
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, Copenhagen 2200, Denmark.
| | - Trine L Toft-Bertelsen
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, Copenhagen 2200, Denmark
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Israelsen IME, Kamp-Jensen C, Westgate CSJ, Styrishave B, Jensen RH, Eftekhari S. Cycle-dependent sex differences in expression of membrane proteins involved in cerebrospinal fluid secretion at rat choroid plexus. BMC Neurosci 2023; 24:60. [PMID: 37946101 PMCID: PMC10633912 DOI: 10.1186/s12868-023-00829-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 10/20/2023] [Indexed: 11/12/2023] Open
Abstract
BACKGROUND Female sex is a known risk factor of brain disorders with raised intracranial pressure (ICP) and sex hormones have been suggested to alter cerebrospinal fluid (CSF) dynamics, thus impairing ICP regulation in CSF disorders such as idiopathic intracranial hypertension (IIH). The choroid plexus (CP) is the tissue producing CSF and it has been hypothesized that altered hormonal composition could affect the activity of transporters involved in CSF secretion, thus affecting ICP. Therefore, we aimed to investigate if expression of various transporters involved in CSF secretion at CP were different between males and females and between females in different estrous cycle states. Steroid levels in serum was also investigated. METHODS Female and male rats were used to determine sex-differences in the genes encoding for the transporters Aqp1 and 4, NKCC1, NBCe2, NCBE; carbonic anhydrase enzymes II and III (CA), subunits of the Na+/K+-ATPase including Atp1a1, Atp1b1 and Fxyd1 at CP. The estrous cycle stage metestrus (MET) and estrous (ES) were determined before euthanasia. Serum and CP were collected and subjected to RT-qPCR analysis and western blots. Serum was used to measure steroid levels using liquid chromatography tandem mass spectrometry (LC-MS/MS). RESULTS Significant differences in gene expression and steroid levels between males and ES females were found, while no differences were found between male and MET females. During ES, expression of Aqp1 was lower (p < 0.01) and NKCC1 was higher in females compared to males. CAII was lower while CAIII was higher in ES females (p < 0.0001). Gene expression of Atp1a1 was lower in ES compared to male (p = 0.0008). Several of these choroidal genes were also significantly different in MET compared to females in ES. Differences in gene expression during the estrus cycle were correlated to serum level of steroid hormones. Protein expression of AQP1 (p = 0.008) and CAII (p = 0.035) was reduced in ES females compared to males. CONCLUSIONS This study demonstrates for the first time that expression at CP is sex-dependent and markedly affected by the estrous cycle in female rats. Further, expression was related to hormone levels in serum. This opens a completely new avenue for steroid regulation of the expression of CSF transporters and the close link to the understanding of CSF disorders such as IIH.
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Affiliation(s)
- Ida Marchen Egerod Israelsen
- Danish Headache Center, Department of Neurology, Glostrup Research Institute, Rigshospitalet-Glostrup, University of Copenhagen, Nordstjernevej 42, 2600, Glostrup, Denmark
| | - Christina Kamp-Jensen
- Danish Headache Center, Department of Neurology, Glostrup Research Institute, Rigshospitalet-Glostrup, University of Copenhagen, Nordstjernevej 42, 2600, Glostrup, Denmark
| | - Connar Stanley James Westgate
- Danish Headache Center, Department of Neurology, Glostrup Research Institute, Rigshospitalet-Glostrup, University of Copenhagen, Nordstjernevej 42, 2600, Glostrup, Denmark
| | - Bjarne Styrishave
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rigmor H Jensen
- Danish Headache Center, Department of Neurology, Glostrup Research Institute, Rigshospitalet-Glostrup, University of Copenhagen, Nordstjernevej 42, 2600, Glostrup, Denmark
| | - Sajedeh Eftekhari
- Danish Headache Center, Department of Neurology, Glostrup Research Institute, Rigshospitalet-Glostrup, University of Copenhagen, Nordstjernevej 42, 2600, Glostrup, Denmark.
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Trejo F, Elizalde S, Mercado A, Gamba G, de losHeros P. SLC12A cryo-EM: analysis of relevant ion binding sites, structural domains, and amino acids. Am J Physiol Cell Physiol 2023; 325:C921-C939. [PMID: 37545407 DOI: 10.1152/ajpcell.00089.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 07/24/2023] [Accepted: 07/24/2023] [Indexed: 08/08/2023]
Abstract
The solute carrier family 12A (SLC12A) superfamily of membrane transporters modulates the movement of cations coupled with chloride across the membrane. In doing so, these cotransporters are involved in numerous aspects of human physiology: cell volume regulation, ion homeostasis, blood pressure regulation, and neurological action potential via intracellular chloride concentration modulation. Their physiological characterization has been largely studied; however, understanding the mechanics of their function and the relevance of structural domains or specific amino acids has been a pending task. In recent years, single-particle cryogenic electron microscopy (cryo-EM) has been successfully applied to members of the SLC12A family including all K+:Cl- cotransporters (KCCs), Na+:K+:2Cl- cotransporter NKCC1, and recently Na+:Cl- cotransporter (NCC); revealing structural elements that play key roles in their function. The present review analyzes the data provided by these cryo-EM reports focusing on structural domains and specific amino acids involved in ion binding, domain interactions, and other important SCL12A structural elements. A comparison of cryo-EM data from NKCC1 and KCCs is presented in the light of the two recent NCC cryo-EM studies, to propose insight into structural elements that might also be found in NCC and are necessary for its proper function. In the final sections, the importance of key coordination residues for substrate specificity and their implication on various pathophysiological conditions and genetic disorders is reviewed, as this could provide the basis to correlate structural elements with the development of novel and selective treatments, as well as mechanistic insight into the function and regulation of cation-coupled chloride cotransporters (CCCs).
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Affiliation(s)
- Fátima Trejo
- Unidad de Investigación UNAM-INC, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Stephanie Elizalde
- Departamento de Nefrología y Metabolismo Mineral, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
| | - Adriana Mercado
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico
| | - Gerardo Gamba
- Departamento de Nefrología y Metabolismo Mineral, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Paola de losHeros
- Unidad de Investigación UNAM-INC, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
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Role of NKCC1 and KCC2 during hypoxia-induced neuronal swelling in the neonatal neocortex. Neurobiol Dis 2023; 178:106013. [PMID: 36706928 PMCID: PMC9945323 DOI: 10.1016/j.nbd.2023.106013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 12/21/2022] [Accepted: 01/22/2023] [Indexed: 01/26/2023] Open
Abstract
Neonatal hypoxia causes cytotoxic neuronal swelling by the entry of ions and water. Multiple water pathways have been implicated in neurons because these cells lack water channels, and their membrane has a low water permeability. NKCC1 and KCC2 are cation-chloride cotransporters (CCCs) involved in water movement in various cell types. However, the role of CCCs in water movement in neonatal neurons during hypoxia is unknown. We studied the effects of modulating CCCs pharmacologically on neuronal swelling in the neocortex (layer IV/V) of neonatal mice (post-natal day 8-13) during prolonged and brief hypoxia. We used acute brain slices from Clomeleon mice which express a ratiometric fluorophore sensitive to Cl- and exposed them to oxygen-glucose deprivation (OGD) while imaging neuronal size and [Cl-]i by multiphoton microscopy. Neurons were identified using a convolutional neural network algorithm, and changes in the somatic area and [Cl-]i were evaluated using a linear mixed model for repeated measures. We found that (1) neuronal swelling and Cl- accumulation began after OGD, worsened during 20 min of OGD, or returned to baseline during reoxygenation if the exposure to OGD was brief (10 min). (2) Neuronal swelling did not occur when the extracellular Cl- concentration was low. (3) Enhancing KCC2 activity did not alter OGD-induced neuronal swelling but prevented Cl- accumulation; (4) blocking KCC2 led to an increase in Cl- accumulation during prolonged OGD and aggravated neuronal swelling during reoxygenation; (5) blocking NKCC1 reduced neuronal swelling during early but not prolonged OGD and aggravated Cl- accumulation during prolonged OGD; and (6) treatment with the "broad" CCC blocker furosemide reduced both swelling and Cl- accumulation during prolonged and brief OGD, whereas simultaneous NKCC1 and KCC2 inhibition using specific pharmacological blockers aggravated neuronal swelling during prolonged OGD. We conclude that CCCs, and other non-CCCs, contribute to water movement in neocortical neurons during OGD in the neonatal period.
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Maex R. An Isotonic Model of Neuron Swelling Based on Co-Transport of Salt and Water. MEMBRANES 2023; 13:206. [PMID: 36837709 PMCID: PMC9958824 DOI: 10.3390/membranes13020206] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/31/2023] [Accepted: 02/06/2023] [Indexed: 06/18/2023]
Abstract
Neurons spend most of their energy building ion gradients across the cell membrane. During energy deprivation the neurons swell, and the concomitant mixing of their ions is commonly assumed to lead toward a Donnan equilibrium, at which the concentration gradients of all permeant ion species have the same Nernst potential. This Donnan equilibrium, however, is not isotonic, as the total concentration of solute will be greater inside than outside the neurons. The present theoretical paper, in contrast, proposes that neurons follow a path along which they swell quasi-isotonically by co-transporting water and ions. The final neuronal volume on the path is taken that at which the concentration of impermeant anions in the shrinking extracellular space equals that inside the swelling neurons. At this final state, which is also a Donnan equilibrium, all permeant ions can mix completely, and their Nernst potentials vanish. This final state is isotonic and electro-neutral, as are all intermediate states along this path. The path is in principle reversible, and maximizes the work of mixing.
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Affiliation(s)
- Reinoud Maex
- Biocomputation Research Group, School of Physics, Engineering and Computer Science, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
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Huang B, Wang H, Yang B. Non-Aquaporin Water Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1398:331-342. [PMID: 36717505 DOI: 10.1007/978-981-19-7415-1_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Water transport through membrane is so intricate that there are still some debates. AQPs are entirely accepted to allow water transmembrane movement depending on osmotic gradient. Cotransporters and uniporters, however, are also concerned in water homeostasis. UT-B has a single-channel water permeability that is similar to AQP1. CFTR was initially thought as a water channel but now not believed to transport water directly. By cotransporters, such as KCC4, NKCC1, SGLT1, GAT1, EAAT1, and MCT1, water is transported by water osmosis coupling with substrates, which explains how water is transported across the isolated small intestine. This chapter provides information about water transport mediated by other membrane proteins except AQPs.
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Affiliation(s)
- Boyue Huang
- Laboratory of Neuroscience and Tissue Engineering, Department of Anatomy, Basic Medical College, Chongqing Medical University, Chongqing, China
| | - Hongkai Wang
- Northwestern University Interdepartmental Neuroscience Program, Chicago, IL, USA
- Laboratory of Regenerative Rehabilitation and Department of Physical Medicine and Rehabilitation, Shirley Ryan AbilityLab and Northwestern University Feinberg School of Medicine and Shirley Ryan AbilityLab, Chicago, IL, USA
| | - Baoxue Yang
- School of Basic Medical Sciences, Peking University, Beijing, China.
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Nan J, Yuan Y, Yang X, Shan Z, Liu H, Wei F, Zhang W, Zhang Y. Cryo-EM structure of the human sodium-chloride cotransporter NCC. SCIENCE ADVANCES 2022; 8:eadd7176. [PMID: 36351028 PMCID: PMC9645730 DOI: 10.1126/sciadv.add7176] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/21/2022] [Indexed: 05/29/2023]
Abstract
The sodium-chloride cotransporter NCC mediates the coupled import of sodium and chloride across the plasma membrane, playing vital roles in kidney extracellular fluid volume and blood pressure control. Here, we present the full-length structure of human NCC, with 2.9 Å for the transmembrane domain and 3.8 Å for the carboxyl-terminal domain. NCC adopts an inward-open conformation and a domain-swap dimeric assembly. Conserved ion binding sites among the cation-chloride cotransporters and the Na2 site are observed in our structure. A unique His residue in the substrate pocket in NCC potentially interacts with Na1 and Cl1 and might also mediate the coordination of Na2 through a Ser residue. Putative observed water molecules are indicated to participate in the coordination of ions and TM coupling. Together with transport activity assays, our structure provides the first glimpse of NCC and defines ion binding sites, promoting drug development for hypertension targeting on NCC.
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Affiliation(s)
- Jing Nan
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yafei Yuan
- Beijing Frontier Research Center for Biological Structure, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xuemei Yang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Ziyang Shan
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Huihui Liu
- Warshel Institute for Computational Biology, School of Life and Health Sciences, The Chinese University of Hong Kong, Shenzhen 518172, Guangdong, China
| | - Feiwen Wei
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Wei Zhang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yanqing Zhang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
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Thompson D, Brissette CA, Watt JA. The choroid plexus and its role in the pathogenesis of neurological infections. Fluids Barriers CNS 2022; 19:75. [PMID: 36088417 PMCID: PMC9463972 DOI: 10.1186/s12987-022-00372-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 08/27/2022] [Indexed: 11/10/2022] Open
Abstract
The choroid plexus is situated at an anatomically and functionally important interface within the ventricles of the brain, forming the blood-cerebrospinal fluid barrier that separates the periphery from the central nervous system. In contrast to the blood-brain barrier, the choroid plexus and its epithelial barrier have received considerably less attention. As the main producer of cerebrospinal fluid, the secretory functions of the epithelial cells aid in the maintenance of CNS homeostasis and are capable of relaying inflammatory signals to the brain. The choroid plexus acts as an immunological niche where several types of peripheral immune cells can be found within the stroma including dendritic cells, macrophages, and T cells. Including the epithelia cells, these cells perform immunosurveillance, detecting pathogens and changes in the cytokine milieu. As such, their activation leads to the release of homing molecules to induce chemotaxis of circulating immune cells, driving an immune response at the choroid plexus. Research into the barrier properties have shown how inflammation can alter the structural junctions and promote increased bidirectional transmigration of cells and pathogens. The goal of this review is to highlight our foundational knowledge of the choroid plexus and discuss how recent research has shifted our understanding towards viewing the choroid plexus as a highly dynamic and important contributor to the pathogenesis of neurological infections. With the emergence of several high-profile diseases, including ZIKA and SARS-CoV-2, this review provides a pertinent update on the cellular response of the choroid plexus to these diseases. Historically, pharmacological interventions of CNS disorders have proven difficult to develop, however, a greater focus on the role of the choroid plexus in driving these disorders would provide for novel targets and routes for therapeutics.
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Affiliation(s)
- Derick Thompson
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
| | - Catherine A Brissette
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
| | - John A Watt
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA.
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Oernbo EK, Steffensen AB, Razzaghi Khamesi P, Toft-Bertelsen TL, Barbuskaite D, Vilhardt F, Gerkau NJ, Tritsaris K, Simonsen AH, Lolansen SD, Andreassen SN, Hasselbalch SG, Zeuthen T, Rose CR, Kurtcuoglu V, MacAulay N. Membrane transporters control cerebrospinal fluid formation independently of conventional osmosis to modulate intracranial pressure. Fluids Barriers CNS 2022; 19:65. [PMID: 36038945 PMCID: PMC9422132 DOI: 10.1186/s12987-022-00358-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 07/13/2022] [Indexed: 11/23/2022] Open
Abstract
Background Disturbances in the brain fluid balance can lead to life-threatening elevation in the intracranial pressure (ICP), which represents a vast clinical challenge. Nevertheless, the details underlying the molecular mechanisms governing cerebrospinal fluid (CSF) secretion are largely unresolved, thus preventing targeted and efficient pharmaceutical therapy of cerebral pathologies involving elevated ICP. Methods Experimental rats were employed for in vivo determinations of CSF secretion rates, ICP, blood pressure and ex vivo excised choroid plexus for morphological analysis and quantification of expression and activity of various transport proteins. CSF and blood extractions from rats, pigs, and humans were employed for osmolality determinations and a mathematical model employed to determine a contribution from potential local gradients at the surface of choroid plexus. Results We demonstrate that CSF secretion can occur independently of conventional osmosis and that local osmotic gradients do not suffice to support CSF secretion. Instead, the CSF secretion across the luminal membrane of choroid plexus relies approximately equally on the Na+/K+/2Cl− cotransporter NKCC1, the Na+/HCO3− cotransporter NBCe2, and the Na+/K+-ATPase, but not on the Na+/H+ exchanger NHE1. We demonstrate that pharmacological modulation of CSF secretion directly affects the ICP. Conclusions CSF secretion appears to not rely on conventional osmosis, but rather occur by a concerted effort of different choroidal transporters, possibly via a molecular mode of water transport inherent in the proteins themselves. Therapeutic modulation of the rate of CSF secretion may be employed as a strategy to modulate ICP. These insights identify new promising therapeutic targets against brain pathologies associated with elevated ICP. Supplementary Information The online version contains supplementary material available at 10.1186/s12987-022-00358-4.
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Affiliation(s)
- Eva K Oernbo
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Annette B Steffensen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Pooya Razzaghi Khamesi
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Trine L Toft-Bertelsen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Dagne Barbuskaite
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Frederik Vilhardt
- Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Niklas J Gerkau
- Institute of Neurobiology, Heinrich Heine University Düsseldorf, Universitätsstrasse 1, 40225, Düsseldorf, Germany
| | - Katerina Tritsaris
- Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Anja H Simonsen
- Danish Dementia Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Sara D Lolansen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Søren N Andreassen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Steen G Hasselbalch
- Danish Dementia Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Zeuthen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Christine R Rose
- Institute of Neurobiology, Heinrich Heine University Düsseldorf, Universitätsstrasse 1, 40225, Düsseldorf, Germany
| | - Vartan Kurtcuoglu
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Nanna MacAulay
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark.
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12
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Zhang Z, Tan Q, Guo P, Huang S, Jia Z, Liu X, Feng H, Chen Y. NLRP3 inflammasome-mediated choroid plexus hypersecretion contributes to hydrocephalus after intraventricular hemorrhage via phosphorylated NKCC1 channels. J Neuroinflammation 2022; 19:163. [PMID: 35729645 PMCID: PMC9210649 DOI: 10.1186/s12974-022-02530-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 06/14/2022] [Indexed: 12/26/2022] Open
Abstract
Background Hydrocephalus is a severe complication of intracerebral hemorrhage with ventricular extension (ICH-IVH) and causes cerebrospinal fluid (CSF) accumulation. The choroid plexus epithelium plays an important role in CSF secretion and constitutes the blood–CSF barrier within the brain–immune system interface. Although the NLRP3 inflammasome, as a key component of the innate immune system, promotes neuroinflammation, its role in the pathogenesis of hydrocephalus after hemorrhage has not been investigated. Therefore, this study aimed to investigate the potential mechanism of NLRP3 in hydrocephalus to discover a potential marker for targeted therapy. Methods A rat model of hydrocephalus after ICH-IVH was developed through autologous blood infusion in wild-type and Nlrp3−/− rats. By studying the features and processes of the model, we investigated the relationship between the NLRP3 inflammasome and CSF hypersecretion in the choroid plexus. Results The ICH-IVH model rats showed ventricular dilation accompanied by CSF hypersecretion for 3 days. Based on the choroid plexus RNA-seq and proteomics results, we found that an inflammatory response was activated. The NLRP3 inflammasome was investigated, and the expression levels of NLRP3 inflammasome components reached a peak at 3 days after ICH-IVH. Inhibition of NLRP3 by an MCC950 inflammasome inhibitor or Nlrp3 knockout decreased CSF secretion and ventricular dilation and attenuated neurological deficits after ICH-IVH. The mechanism underlying the neuroprotective effects of NLRP3 inhibition involved decreased phosphorylation of NKCC1, which is a major protein that regulates CSF secretion by altering Na+- and K+-coupled water transport, via MCC950 or Nlrp3 knockout. In combination with the in vitro experiments, this experiment confirmed the involvement of the NLRP3/p-NKCC1 pathway and Na+ and K+ flux. Conclusions This study demonstrates that NKCC1 phosphorylation in the choroid plexus epithelium promotes NLRP3 inflammasome-mediated CSF hypersecretion and that NLRP3 plays an important role in the pathogenesis of hydrocephalus after hemorrhage. These findings provide a new therapeutic strategy for treating hydrocephalus. Supplementary Information The online version contains supplementary material available at 10.1186/s12974-022-02530-x.
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Affiliation(s)
- Zhaoqi Zhang
- Department of Neurosurgery and State Key Laboratory of Trauma, Burn and Combined Injury, Southwest Hospital, Third Military Medical University (Army Medical University), 29 Gaotanyan Street, Shapingba District, Chongqing, 400038, China.,Chongqing Key Laboratory of Precision Neuromedicine and Neuroregenaration, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China.,Chongqing Clinical Research Center for Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Qiang Tan
- Department of Neurosurgery and State Key Laboratory of Trauma, Burn and Combined Injury, Southwest Hospital, Third Military Medical University (Army Medical University), 29 Gaotanyan Street, Shapingba District, Chongqing, 400038, China.,Chongqing Key Laboratory of Precision Neuromedicine and Neuroregenaration, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China.,Chongqing Clinical Research Center for Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Peiwen Guo
- Department of Neurosurgery and State Key Laboratory of Trauma, Burn and Combined Injury, Southwest Hospital, Third Military Medical University (Army Medical University), 29 Gaotanyan Street, Shapingba District, Chongqing, 400038, China.,Chongqing Key Laboratory of Precision Neuromedicine and Neuroregenaration, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China.,Chongqing Clinical Research Center for Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Suna Huang
- Department of Neurosurgery and State Key Laboratory of Trauma, Burn and Combined Injury, Southwest Hospital, Third Military Medical University (Army Medical University), 29 Gaotanyan Street, Shapingba District, Chongqing, 400038, China.,Chongqing Key Laboratory of Precision Neuromedicine and Neuroregenaration, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China.,Chongqing Clinical Research Center for Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Zhengcai Jia
- Department of Neurosurgery and State Key Laboratory of Trauma, Burn and Combined Injury, Southwest Hospital, Third Military Medical University (Army Medical University), 29 Gaotanyan Street, Shapingba District, Chongqing, 400038, China.,Chongqing Key Laboratory of Precision Neuromedicine and Neuroregenaration, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China.,Chongqing Clinical Research Center for Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Xin Liu
- Department of Neurosurgery and State Key Laboratory of Trauma, Burn and Combined Injury, Southwest Hospital, Third Military Medical University (Army Medical University), 29 Gaotanyan Street, Shapingba District, Chongqing, 400038, China.,Chongqing Key Laboratory of Precision Neuromedicine and Neuroregenaration, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China.,Chongqing Clinical Research Center for Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Hua Feng
- Department of Neurosurgery and State Key Laboratory of Trauma, Burn and Combined Injury, Southwest Hospital, Third Military Medical University (Army Medical University), 29 Gaotanyan Street, Shapingba District, Chongqing, 400038, China. .,Chongqing Key Laboratory of Precision Neuromedicine and Neuroregenaration, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China. .,Chongqing Clinical Research Center for Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China.
| | - Yujie Chen
- Department of Neurosurgery and State Key Laboratory of Trauma, Burn and Combined Injury, Southwest Hospital, Third Military Medical University (Army Medical University), 29 Gaotanyan Street, Shapingba District, Chongqing, 400038, China. .,Chongqing Key Laboratory of Precision Neuromedicine and Neuroregenaration, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China. .,Chongqing Clinical Research Center for Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, 400038, China. .,CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China.
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13
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Fang Y, Huang L, Wang X, Si X, Lenahan C, Shi H, Shao A, Tang J, Chen S, Zhang J, Zhang JH. A new perspective on cerebrospinal fluid dynamics after subarachnoid hemorrhage: From normal physiology to pathophysiological changes. J Cereb Blood Flow Metab 2022; 42:543-558. [PMID: 34806932 PMCID: PMC9051143 DOI: 10.1177/0271678x211045748] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Knowledge about the dynamic metabolism and function of cerebrospinal fluid (CSF) physiology has rapidly progressed in recent decades. It has traditionally been suggested that CSF is produced by the choroid plexus and drains to the arachnoid villi. However, recent findings have revealed that the brain parenchyma produces a large portion of CSF and drains through the perivascular glymphatic system and meningeal lymphatic vessels into the blood. The primary function of CSF is not limited to maintaining physiological CNS homeostasis but also participates in clearing waste products resulting from neurodegenerative diseases and acute brain injury. Aneurysmal subarachnoid hemorrhage (SAH), a disastrous subtype of acute brain injury, is associated with high mortality and morbidity. Post-SAH complications contribute to the poor outcomes associated with SAH. Recently, abnormal CSF flow was suggested to play an essential role in the post-SAH pathophysiological changes, such as increased intracerebral pressure, brain edema formation, hydrocephalus, and delayed blood clearance. An in-depth understanding of CSF dynamics in post-SAH events would shed light on potential development of SAH treatment options. This review summarizes and updates the latest physiological characteristics of CSF dynamics and discusses potential pathophysiological changes and therapeutic targets after SAH.
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Affiliation(s)
- Yuanjian Fang
- Department of Neurosurgery, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Lei Huang
- Department of Neurosurgery, Loma Linda University, Loma Linda, CA, USA.,Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - Xiaoyu Wang
- Department of Neurosurgery, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiaoli Si
- Department of Neurology, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Cameron Lenahan
- Department of Neurosurgery, Loma Linda University, Loma Linda, CA, USA.,Burrell College of Osteopathic Medicine, Las Cruces, NM, USA
| | - Hui Shi
- Department of Neurosurgery, Loma Linda University, Loma Linda, CA, USA.,Department of Neurosurgery, Yongchuan Hospital, Chongqing Medical University, Chongqing, China
| | - Anwen Shao
- Department of Neurosurgery, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jiping Tang
- Department of Neurosurgery, Loma Linda University, Loma Linda, CA, USA.,Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA.,Department of Anesthesiology, Loma Linda University, Loma Linda, CA, USA
| | - Sheng Chen
- Department of Neurosurgery, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jianmin Zhang
- Department of Neurosurgery, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - John H Zhang
- Department of Neurosurgery, Loma Linda University, Loma Linda, CA, USA.,Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA.,Department of Anesthesiology, Loma Linda University, Loma Linda, CA, USA
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14
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MacAulay N, Keep RF, Zeuthen T. Cerebrospinal fluid production by the choroid plexus: a century of barrier research revisited. Fluids Barriers CNS 2022; 19:26. [PMID: 35317823 PMCID: PMC8941821 DOI: 10.1186/s12987-022-00323-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 03/09/2022] [Indexed: 12/20/2022] Open
Abstract
Cerebrospinal fluid (CSF) envelops the brain and fills the central ventricles. This fluid is continuously replenished by net fluid extraction from the vasculature by the secretory action of the choroid plexus epithelium residing in each of the four ventricles. We have known about these processes for more than a century, and yet the molecular mechanisms supporting this fluid secretion remain unresolved. The choroid plexus epithelium secretes its fluid in the absence of a trans-epithelial osmotic gradient, and, in addition, has an inherent ability to secrete CSF against an osmotic gradient. This paradoxical feature is shared with other 'leaky' epithelia. The assumptions underlying the classical standing gradient hypothesis await experimental support and appear to not suffice as an explanation of CSF secretion. Here, we suggest that the elusive local hyperosmotic compartment resides within the membrane transport proteins themselves. In this manner, the battery of plasma membrane transporters expressed in choroid plexus are proposed to sustain the choroidal CSF secretion independently of the prevailing bulk osmotic gradient.
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Affiliation(s)
- Nanna MacAulay
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark.
| | - Richard F Keep
- Department of Neurosurgery, University of Michigan, Ann Arbor, MI, USA
| | - Thomas Zeuthen
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
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15
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Abstract
Our brains consist of 80% water, which is continuously shifted between different compartments and cell types during physiological and pathophysiological processes. Disturbances in brain water homeostasis occur with pathologies such as brain oedema and hydrocephalus, in which fluid accumulation leads to elevated intracranial pressure. Targeted pharmacological treatments do not exist for these conditions owing to our incomplete understanding of the molecular mechanisms governing brain water transport. Historically, the transmembrane movement of brain water was assumed to occur as passive movement of water along the osmotic gradient, greatly accelerated by water channels termed aquaporins. Although aquaporins govern the majority of fluid handling in the kidney, they do not suffice to explain the overall brain water movement: either they are not present in the membranes across which water flows or they appear not to be required for the observed flow of water. Notably, brain fluid can be secreted against an osmotic gradient, suggesting that conventional osmotic water flow may not describe all transmembrane fluid transport in the brain. The cotransport of water is an unconventional molecular mechanism that is introduced in this Review as a missing link to bridge the gap in our understanding of cellular and barrier brain water transport.
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Affiliation(s)
- Nanna MacAulay
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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16
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Xu H, Fame RM, Sadegh C, Sutin J, Naranjo C, Della Syau, Cui J, Shipley FB, Vernon A, Gao F, Zhang Y, Holtzman MJ, Heiman M, Warf BC, Lin PY, Lehtinen MK. Choroid plexus NKCC1 mediates cerebrospinal fluid clearance during mouse early postnatal development. Nat Commun 2021; 12:447. [PMID: 33469018 PMCID: PMC7815709 DOI: 10.1038/s41467-020-20666-3] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 12/10/2020] [Indexed: 12/14/2022] Open
Abstract
Cerebrospinal fluid (CSF) provides vital support for the brain. Abnormal CSF accumulation, such as hydrocephalus, can negatively affect perinatal neurodevelopment. The mechanisms regulating CSF clearance during the postnatal critical period are unclear. Here, we show that CSF K+, accompanied by water, is cleared through the choroid plexus (ChP) during mouse early postnatal development. We report that, at this developmental stage, the ChP showed increased ATP production and increased expression of ATP-dependent K+ transporters, particularly the Na+, K+, Cl-, and water cotransporter NKCC1. Overexpression of NKCC1 in the ChP resulted in increased CSF K+ clearance, increased cerebral compliance, and reduced circulating CSF in the brain without changes in intracranial pressure in mice. Moreover, ChP-specific NKCC1 overexpression in an obstructive hydrocephalus mouse model resulted in reduced ventriculomegaly. Collectively, our results implicate NKCC1 in regulating CSF K+ clearance through the ChP in the critical period during postnatal neurodevelopment in mice.
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Affiliation(s)
- Huixin Xu
- Department of Pathology, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Ryann M Fame
- Department of Pathology, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Cameron Sadegh
- Department of Pathology, Boston Children's Hospital, Boston, MA, 02115, USA
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 02114, USA
| | - Jason Sutin
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Christopher Naranjo
- Summer Honors Undergraduate Research Program, Division of Medical Sciences, Harvard Medical School, Boston, MA, 02115, USA
| | - Della Syau
- Summer Honors Undergraduate Research Program, Division of Medical Sciences, Harvard Medical School, Boston, MA, 02115, USA
| | - Jin Cui
- Department of Pathology, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Frederick B Shipley
- Department of Pathology, Boston Children's Hospital, Boston, MA, 02115, USA
- Graduate Program in Biophysics, Harvard University, Cambridge, MA, 02138, USA
| | - Amanda Vernon
- Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
- Picower Institute for Learning and Memory, Cambridge, MA, 02139, USA
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Fan Gao
- Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
- Picower Institute for Learning and Memory, Cambridge, MA, 02139, USA
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Bioinformatics Resource Center in the Beckman Institute at Caltech, Pasadena, CA, 91125, USA
| | - Yong Zhang
- Pulmonary and Critical Care Medicine, Department of Medicine, Washington University, St. Louis, MO, 63110, USA
| | - Michael J Holtzman
- Pulmonary and Critical Care Medicine, Department of Medicine, Washington University, St. Louis, MO, 63110, USA
| | - Myriam Heiman
- Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
- Picower Institute for Learning and Memory, Cambridge, MA, 02139, USA
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Benjamin C Warf
- Department of Neurosurgery, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Pei-Yi Lin
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Maria K Lehtinen
- Department of Pathology, Boston Children's Hospital, Boston, MA, 02115, USA.
- Graduate Program in Biophysics, Harvard University, Cambridge, MA, 02138, USA.
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17
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Flores B, Delpire E. Osmotic Response of Dorsal Root Ganglion Neurons Expressing Wild-Type and Mutant KCC3 Transporters. Cell Physiol Biochem 2021; 54:577-590. [PMID: 32506846 DOI: 10.33594/000000241] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/27/2020] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND/AIMS Loss-of-Function (LOF) of the potassium chloride cotransporter 3 (KCC3) results in hereditary sensorimotor neuropathy with Agenesis of the Corpus Callosum (HSMN/ACC). Our KCC3 knockout mouse recapitulated axonal swelling and tissue vacuolization observed in autopsies of individuals with HSMN/ACC. We previously documented the first human case of a KCC3 gain-of-function (GOF) in which the patient also exhibited severe peripheral neuropathy. Furthermore, the GOF mouse model exhibited shrunken axons implicating the cotransporter in cell volume homeostasis. It is unclear how both KCC3 LOF and GOF lead to peripheral neuropathy. Thus, we sought to study differences in cell volume regulation of dorsal root ganglion neurons isolated from different mouse lines. METHODS Using wide-field microscopy, we measured calcein fluorescence intensity through pinhole measurements at the center of cells and compared cell swelling and cell volume regulation/recovery of wild-type, LOF, and GOF dorsal root ganglia neurons, as well as wild-type neurons treated with a KCC-specific inhibitor. RESULTS In contrast to control neurons that swell and volume regulate under a hypotonic challenge, neurons lacking KCC3 swell but fail to volume regulate. Similar data were observed in wild-type neurons treated with the KCC inhibitor. We also show that sensory neurons expressing a constitutively active KCC3 exhibited a blunted swelling phase compared to wild-type neurons, questioning the purely osmotic nature of the swelling phase. CONCLUSION These findings demonstrate the integral role of KCC3 in cell volume homeostasis and support the idea that cell volume homeostasis is critical to the health of peripheral nerves.
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Affiliation(s)
- Bianca Flores
- Department of Anesthesiology and Neuroscience Graduate Program, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Eric Delpire
- Department of Anesthesiology and Neuroscience Graduate Program, Vanderbilt University School of Medicine, Nashville, TN, USA,
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18
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Fricke W. Energy costs of salinity tolerance in crop plants: night-time transpiration and growth. THE NEW PHYTOLOGIST 2020; 225:1152-1165. [PMID: 30834533 DOI: 10.1111/nph.15773] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 02/25/2019] [Indexed: 05/28/2023]
Abstract
Plants grow and transpire during the night. The aim of the present work was to assess the relative flows of carbon, water and solutes, and the energy involved, in sustaining night-time transpiration and leaf expansive growth under control and salt-stress conditions. Published and unpublished data were used, for barley plants grown in presence of 0.5-1 mM NaCl (control) and 100 mM NaCl. Night-time leaf growth presents a more efficient use of taken-up water compared with day-time growth. This efficiency increases several-fold with salt stress. Night-time transpiration cannot be supported entirely through osmotically driven uptake of water through roots under salt stress. Using a simple three- (root medium/cytosol/vacuole) compartment approach, the energy required to support cell expansion during the night is in the lower percentage region (0.03-5.5%) of the energy available through respiration, under both, control and salt-stress conditions. Use of organic (e.g. hexose equivalents) rather than inorganic (e.g. Na+ , Cl- , K+ ) solutes for generation of osmotic pressure in growing cells, increases the energy demand by orders of magnitude, yet requires only a small portion of carbon assimilated during the day. Night-time transpiration and leaf expansive growth should be considered as a potential acclimation mechanism to salinity.
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Affiliation(s)
- Wieland Fricke
- School of Biology and Environmental Sciences, University College Dublin (UCD), Belfield, Dublin 4, Ireland
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19
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Delpire E, Guo J. Cryo-EM structures of DrNKCC1 and hKCC1: a new milestone in the physiology of cation-chloride cotransporters. Am J Physiol Cell Physiol 2020; 318:C225-C237. [PMID: 31747317 PMCID: PMC7052613 DOI: 10.1152/ajpcell.00465.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/20/2019] [Accepted: 11/20/2019] [Indexed: 01/29/2023]
Abstract
New milestones have been reached in the field of cation-Cl- cotransporters with the recently released cryo-electron microscopy (EM) structures of the Danio rerio (zebrafish) Na+-K+-2Cl- cotransporter (DrNKCC1) and the human K+-Cl- cotransporter (hKCC1). In this review we provide a brief timeline that identifies the multiple breakthroughs in the field of solute carrier 12 transporters that led to the structure resolution of two of its key members. While cation-Cl- cotransporters share the overall architecture of carriers belonging to the amino acid-polyamine-organocation (APC) superfamily and some of their substrate binding sites, several new insights are gained from the two individual structures. A first major feature relates to the largest extracellular domain between transmembrane domain (TMD) 5 and TMD6 of KCC1, which stabilizes the dimer and forms a cap that likely participates in extracellular gating. A second feature is the conservation of the K+ and Cl- binding sites in both structures and evidence of an unexpected second Cl- coordination site in the KCC1 structure. Structural data are discussed in the context of previously published studies that examined the basic and kinetics properties of these cotransport mechanisms. A third characteristic is the evidence of an extracellular gate formed by conserved salt bridges between charged residues located toward the end of TMD3 and TMD4 in both transporters and the existence of an additional neighboring bridge in the hKCC1 structure. A fourth feature of these newly solved structures relates to the multiple points of contacts between the monomer forming the cotransporter homodimer units. These involve the TMDs, the COOH-terminal domains, and the large extracellular loop for hKCC1.
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Affiliation(s)
- Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Jiangtao Guo
- Department of Biophysics, Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
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20
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Gregoriades JMC, Madaris A, Alvarez FJ, Alvarez-Leefmans FJ. Genetic and pharmacological inactivation of apical Na +-K +-2Cl - cotransporter 1 in choroid plexus epithelial cells reveals the physiological function of the cotransporter. Am J Physiol Cell Physiol 2019; 316:C525-C544. [PMID: 30576237 PMCID: PMC6482671 DOI: 10.1152/ajpcell.00026.2018] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 12/03/2018] [Accepted: 12/03/2018] [Indexed: 01/08/2023]
Abstract
Choroid plexus epithelial cells (CPECs) secrete cerebrospinal fluid (CSF). They express Na+-K+-ATPase and Na+-K+-2Cl- cotransporter 1 (NKCC1) on their apical membrane, deviating from typical basolateral membrane location in secretory epithelia. Given this peculiarity, the direction of basal net ion fluxes mediated by NKCC1 in CPECs is controversial, and cotransporter function is unclear. Determining the direction of basal NKCC1-mediated fluxes is critical to understanding the function of apical NKCC1. If NKCC1 works in the net efflux mode, it may be directly involved in CSF secretion. Conversely, if NKCC1 works in the net influx mode, it would have an absorptive function, contributing to intracellular Cl- concentration ([Cl-]i) and cell water volume (CWV) maintenance needed for CSF secretion. We resolve this long-standing debate by electron microscopy (EM), live-cell-imaging microscopy (LCIM), and intracellular Na+ and Cl- measurements in single CPECs of NKCC1+/+ and NKCC1-/- mouse. NKCC1-mediated ion and associated water fluxes are tightly linked, thus their direction is inferred by measuring CWV changes. Genetic or pharmacological NKCC1 inactivation produces CPEC shrinkage. EM of NKCC1-/- CPECs in situ shows they are shrunken, forming large dilations of their basolateral extracellular spaces, yet remaining attached by tight junctions. Normarski LCIM shows in vitro CPECs from NKCC1-/- are ~17% smaller than NKCC1+/+. CWV measurements in calcein-loaded CPECs show that bumetanide (10 μM) produces ~16% decrease in CWV in NKCC1+/+ but not in NKCC1-/- CPECs. Our findings suggest that under basal conditions apical NKCC1 is continuously active and works in the net inward flux mode maintaining [Cl-]i and CWV needed for CSF secretion.
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Affiliation(s)
- Jeannine M C Gregoriades
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University , Dayton, Ohio
| | - Aaron Madaris
- Department of Biomedical, Industrial, and Human Factors Engineering, College of Engineering and Computer Science, Wright State University , Dayton, Ohio
| | - Francisco J Alvarez
- Department of Neuroscience, Cell Biology and Physiology, Wright State University , Dayton, Ohio
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21
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Glykys J, Duquette E, Rahmati N, Duquette K, Staley KJ. Mannitol decreases neocortical epileptiform activity during early brain development via cotransport of chloride and water. Neurobiol Dis 2019; 125:163-175. [PMID: 30711483 DOI: 10.1016/j.nbd.2019.01.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 01/28/2019] [Accepted: 01/30/2019] [Indexed: 12/31/2022] Open
Abstract
Seizures and brain injury lead to water and Cl- accumulation in neurons. The increase in intraneuronal Cl- concentration ([Cl-]i) depolarizes the GABAA reversal potential (EGABA) and worsens seizure activity. Neocortical neuronal membranes have a low water permeability due to the lack of aquaporins necessary to move free water. Instead, neurons use cotransport of ions including Cl- to move water. Thus, increasing the extracellular osmolarity during seizures should result in an outward movement of water and salt, reducing [Cl-]i and improving GABAA receptor-mediated inhibition. We tested the effects of hyperosmotic therapy with a clinically relevant dose of mannitol (20 mM) on epileptiform activity, spontaneous multiunit activity, spontaneous inhibitory post-synaptic currents (sIPSCs), [Cl-]i, and neuronal volume in layer IV/V of the developing neocortex of C57BL/6 and Clomeleon mice. Using electrophysiological techniques and multiphoton imaging in acute brain slices (post-natal day 7-12) and organotypic neocortical slice cultures (post-natal day 14), we observed that mannitol: 1) decreased epileptiform activity, 2) decreased neuronal volume and [Cl-]i through CCCs, 3) decreased spontaneous multi-unit activity frequency but not amplitude, and 4) restored the anticonvulsant efficacy of the GABAA receptor modulator diazepam. Increasing extracellular osmolarity by 20 mOsm with hypertonic saline did not decrease epileptiform activity. We conclude that an increase in extracellular osmolarity by mannitol mediates the efflux of [Cl-]i and water through CCCs, which results in a decrease in epileptiform activity and enhances benzodiazepine actions in the developing neocortex in vitro. Novel treatments aimed to decrease neuronal volume may concomitantly decrease [Cl-]i and improve seizure control.
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Affiliation(s)
- J Glykys
- Department of Neurology, Massachusetts General Hospital, Boston 02114, United States; Harvard Medical School, Boston, MA 02115, United States.
| | - E Duquette
- Department of Neurology, Massachusetts General Hospital, Boston 02114, United States
| | - N Rahmati
- Department of Neurology, Massachusetts General Hospital, Boston 02114, United States; Harvard Medical School, Boston, MA 02115, United States
| | - K Duquette
- Department of Neurology, Massachusetts General Hospital, Boston 02114, United States; Northeastern University, Boston 02115, United States
| | - K J Staley
- Department of Neurology, Massachusetts General Hospital, Boston 02114, United States; Harvard Medical School, Boston, MA 02115, United States
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22
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Düsterwald KM, Currin CB, Burman RJ, Akerman CJ, Kay AR, Raimondo JV. Biophysical models reveal the relative importance of transporter proteins and impermeant anions in chloride homeostasis. eLife 2018; 7:39575. [PMID: 30260315 PMCID: PMC6200395 DOI: 10.7554/elife.39575] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/24/2018] [Indexed: 11/17/2022] Open
Abstract
Fast synaptic inhibition in the nervous system depends on the transmembrane flux of Cl- ions based on the neuronal Cl- driving force. Established theories regarding the determinants of Cl- driving force have recently been questioned. Here, we present biophysical models of Cl- homeostasis using the pump-leak model. Using numerical and novel analytic solutions, we demonstrate that the Na+/K+-ATPase, ion conductances, impermeant anions, electrodiffusion, water fluxes and cation-chloride cotransporters (CCCs) play roles in setting the Cl- driving force. Our models, together with experimental validation, show that while impermeant anions can contribute to setting [Cl-]i in neurons, they have a negligible effect on the driving force for Cl- locally and cell-wide. In contrast, we demonstrate that CCCs are well-suited for modulating Cl- driving force and hence inhibitory signaling in neurons. Our findings reconcile recent experimental findings and provide a framework for understanding the interplay of different chloride regulatory processes in neurons. Cells called neurons in the brain communicate by triggering or inhibiting electrical activity in other neurons. To inhibit electrical activity, a signal from one neuron usually triggers specific receptors on the second neuron to open, which allows particles called chloride ions to flow into or out of the neuron. The force that moves chloride ions (the so-called ‘chloride driving force’) depends on two main factors. Firstly, chloride ions, like other particles, tend to move from an area where they are plentiful to areas where they are less abundant. Secondly, chloride ions are negatively charged and are therefore attracted to areas where the net charge (determined by the mix of positively and negatively charged particles) is more positive than their current position. It was previously believed that a group of proteins known as CCCs, which transport chloride ions and positive ions together across the membranes surrounding cells, sets the chloride driving force. However, it has recently been suggested that negatively charged ions that are unable to cross the membrane (or ‘impermeant anions’ for short) may set the driving force instead by contributing to the net charge across the membrane. Düsterwald et al. used a computational model of the neuron to explore these two possibilities. In the simulations, altering the activity of the CCCs led to big changes in the chloride driving force. Changing the levels of impermeant anions altered the volume of cells, but did not drive changes in the chloride driving force. This was because the flow of chloride ions across the membrane led to a compensatory change in the net charge across the membrane. Düsterwald et al. then used an experimental technique called patch-clamping in mice and rats to confirm the model’s predictions. Defects in controlling the chloride driving force in brain cells have been linked with epilepsy, stroke and other neurological diseases. Therefore, a better knowledge of these mechanisms may in future help to identify the best targets for drugs to treat such conditions.
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Affiliation(s)
- Kira M Düsterwald
- Division of Cell Biology, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Neuroscience Institute, University of Cape Town, Cape Town, South Africa.,Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Christopher B Currin
- Division of Cell Biology, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Neuroscience Institute, University of Cape Town, Cape Town, South Africa.,Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Richard J Burman
- Division of Cell Biology, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Neuroscience Institute, University of Cape Town, Cape Town, South Africa.,Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Colin J Akerman
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Alan R Kay
- Department of Biology, University of Iowa, Iowa City Iowa, United States
| | - Joseph V Raimondo
- Division of Cell Biology, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Neuroscience Institute, University of Cape Town, Cape Town, South Africa.,Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
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23
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Steffensen AB, Oernbo EK, Stoica A, Gerkau NJ, Barbuskaite D, Tritsaris K, Rose CR, MacAulay N. Cotransporter-mediated water transport underlying cerebrospinal fluid formation. Nat Commun 2018; 9:2167. [PMID: 29867199 PMCID: PMC5986890 DOI: 10.1038/s41467-018-04677-9] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 05/14/2018] [Indexed: 12/20/2022] Open
Abstract
Cerebrospinal fluid (CSF) production occurs at a rate of 500 ml per day in the adult human. Conventional osmotic forces do not suffice to support such production rate and the molecular mechanisms underlying this fluid production remain elusive. Using ex vivo choroid plexus live imaging and isotope flux in combination with in vivo CSF production determination in mice, we identify a key component in the CSF production machinery. The Na+/K+/2Cl− cotransporter (NKCC1) expressed in the luminal membrane of choroid plexus contributes approximately half of the CSF production, via its unusual outward transport direction and its unique ability to directly couple water transport to ion translocation. We thereby establish the concept of cotransport of water as a missing link in the search for molecular pathways sustaining CSF production and redefine the current model of this pivotal physiological process. Our results provide a rational pharmacological target for pathologies involving disturbed brain fluid dynamics. Osmotic forces do not suffice to explain the rate of cerebrospinal fluid (CSF) production. Here, the authors show that the Na+/K+/2Cl− cotransporter in the choroid plexus contributes substantially to CSF production via its inherent ability to cotransport water.
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Affiliation(s)
- Annette B Steffensen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Noerre Allé 14, 2200, Copenhagen, Denmark
| | - Eva K Oernbo
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Noerre Allé 14, 2200, Copenhagen, Denmark
| | - Anca Stoica
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Noerre Allé 14, 2200, Copenhagen, Denmark
| | - Niklas J Gerkau
- Institute of Neurobiology, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, 40225, Duesseldorf, Germany
| | - Dagne Barbuskaite
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Noerre Allé 14, 2200, Copenhagen, Denmark
| | - Katerina Tritsaris
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Noerre Allé 14, 2200, Copenhagen, Denmark
| | - Christine R Rose
- Institute of Neurobiology, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, 40225, Duesseldorf, Germany
| | - Nanna MacAulay
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Noerre Allé 14, 2200, Copenhagen, Denmark.
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24
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Larsen BR, MacAulay N. Activity-dependent astrocyte swelling is mediated by pH-regulating mechanisms. Glia 2017; 65:1668-1681. [PMID: 28744903 DOI: 10.1002/glia.23187] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 06/09/2017] [Accepted: 06/23/2017] [Indexed: 11/09/2022]
Abstract
During neuronal activity in the mammalian brain, the K+ released into the synaptic space is initially buffered by the astrocytic compartment. In parallel, the extracellular space (ECS) shrinks, presumably due to astrocytic cell swelling. With the Na+ /K+ /2Cl- cotransporter and the Kir4.1/AQP4 complex not required for the astrocytic cell swelling in the hippocampus, the molecular mechanisms underlying the activity-dependent ECS shrinkage have remained unresolved. To identify these molecular mechanisms, we employed ion-sensitive microelectrodes to measure changes in ECS, [K+ ]o and [H+ ]o /pHo during electrical stimulation of rat hippocampal slices. Transporters and receptors responding directly to the K+ and glutamate released into the extracellular space (the K+ /Cl- cotransporter, KCC, glutamate transporters and G protein-coupled receptors) did not modulate the extracellular space dynamics. The HCO3--transporting mechanism, which in astrocytes mainly constitutes the electrogenic Na+ / HCO3- cotransporter 1 (NBCe1), is activated by the K+ -mediated depolarization of the astrocytic membrane. Inhibition of this transporter reduced the ECS shrinkage by ∼25% without affecting the K+ transients, pointing to NBCe1 as a key contributor to the stimulus-induced astrocytic cell swelling. Inhibition of the monocarboxylate cotransporters (MCT), like-wise, reduced the ECS shrinkage by ∼25% without compromising the K+ transients. Isosmotic reduction of extracellular Cl- revealed a requirement for this ion in parts of the ECS shrinkage. Taken together, the stimulus-evoked astrocytic cell swelling does not appear to occur as a direct effect of the K+ clearance, as earlier proposed, but partly via the pH-regulating transport mechanisms activated by the K+ -induced astrocytic depolarization and the activity-dependent metabolism.
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Affiliation(s)
- Brian Roland Larsen
- Faculty of Health and Medical Sciences, Center for Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Nanna MacAulay
- Faculty of Health and Medical Sciences, Center for Neuroscience, University of Copenhagen, Copenhagen, Denmark
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25
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Fricke W. Water transport and energy. PLANT, CELL & ENVIRONMENT 2017; 40:977-994. [PMID: 27756100 DOI: 10.1111/pce.12848] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 10/08/2016] [Accepted: 10/10/2016] [Indexed: 05/10/2023]
Abstract
Water transport in plants occurs along various paths and is driven by gradients in its free energy. It is generally considered that the mode of transport, being either diffusion or bulk flow, is a passive process, although energy may be required to sustain the forces driving water flow. This review aims at putting water flow at the various organisational levels (cell, organ, plant) in the context of the energy that is required to maintain these flows. In addition, the question is addressed (1) whether water can be transported against a difference in its chemical free energy, 'water potential' (Ψ), through, directly or indirectly, active processes; and (2) whether the energy released when water is flowing down a gradient in its energy, for example during day-time transpiration and cell expansive growth, is significant compared to the energy budget of plant and cell. The overall aim of review is not so much to provide a definite 'Yes' and 'No' to these questions, but rather to stimulate discussion and raise awareness that water transport in plants has its real, associated, energy costs and potential energy gains.
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Affiliation(s)
- Wieland Fricke
- School of Biology and Environmental Sciences, University College Dublin (UCD), Belfield, Dublin, 4, Ireland
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26
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Glykys J, Dzhala V, Egawa K, Kahle KT, Delpire E, Staley K. Chloride Dysregulation, Seizures, and Cerebral Edema: A Relationship with Therapeutic Potential. Trends Neurosci 2017; 40:276-294. [PMID: 28431741 DOI: 10.1016/j.tins.2017.03.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 03/22/2017] [Accepted: 03/23/2017] [Indexed: 11/18/2022]
Abstract
Pharmacoresistant seizures and cytotoxic cerebral edema are serious complications of ischemic and traumatic brain injury. Intraneuronal Cl- concentration ([Cl-]i) regulation impacts on both cell volume homeostasis and Cl--permeable GABAA receptor-dependent membrane excitability. Understanding the pleiotropic molecular determinants of neuronal [Cl-]i - cytoplasmic impermeant anions, polyanionic extracellular matrix (ECM) glycoproteins, and plasmalemmal Cl- transporters - could help the identification of novel anticonvulsive and neuroprotective targets. The cation/Cl- cotransporters and ECM metalloproteinases may be particularly druggable targets for intervention. We establish here a paradigm that accounts for recent data regarding the complex regulatory mechanisms of neuronal [Cl-]i and how these mechanisms impact on neuronal volume and excitability. We propose approaches to modulate [Cl-]i that are relevant for two common clinical sequela of brain injury: edema and seizures.
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Affiliation(s)
- Joseph Glykys
- Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA; Harvard Medical School, Boston, MA 02115, USA.
| | - Volodymyr Dzhala
- Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Kiyoshi Egawa
- Department of Pediatrics, Hokkaido University Hospital, Sapporo 0010019, Japan
| | - Kristopher T Kahle
- Departments of Neurosurgery, Pediatrics, and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Kevin Staley
- Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA; Harvard Medical School, Boston, MA 02115, USA.
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27
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Praetorius J, Damkier HH. Transport across the choroid plexus epithelium. Am J Physiol Cell Physiol 2017; 312:C673-C686. [PMID: 28330845 DOI: 10.1152/ajpcell.00041.2017] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 03/17/2017] [Accepted: 03/17/2017] [Indexed: 11/22/2022]
Abstract
The choroid plexus epithelium is a secretory epithelium par excellence. However, this is perhaps not the most prominent reason for the massive interest in this modest-sized tissue residing inside the brain ventricles. Most likely, the dominant reason for extensive studies of the choroid plexus is the identification of this epithelium as the source of the majority of intraventricular cerebrospinal fluid. This finding has direct relevance for studies of diseases and conditions with deranged central fluid volume or ionic balance. While the concept is supported by the vast majority of the literature, the implication of the choroid plexus in secretion of the cerebrospinal fluid was recently challenged once again. Three newer and promising areas of current choroid plexus-related investigations are as follows: 1) the choroid plexus epithelium as the source of mediators necessary for central nervous system development, 2) the choroid plexus as a route for microorganisms and immune cells into the central nervous system, and 3) the choroid plexus as a potential route for drug delivery into the central nervous system, bypassing the blood-brain barrier. Thus, the purpose of this review is to highlight current active areas of research in the choroid plexus physiology and a few matters of continuous controversy.
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Affiliation(s)
- Jeppe Praetorius
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark; and
| | - Helle Hasager Damkier
- Department of Biomedicine, Health, Aarhus University, Aarhus, Denmark; and.,Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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28
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Huang B, Wang H, Yang B. Water Transport Mediated by Other Membrane Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 969:251-261. [PMID: 28258579 DOI: 10.1007/978-94-024-1057-0_17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Water transport through membrane is so intricate that there are still some debates. (Aquaporins) AQPs are entirely accepted to allow water transmembrane movement depending on osmotic gradient. Cotransporters and uniporters , however, are also concerned in water homeotatsis. Urea transporter B (UT-B) has a single-channel water permeability that is similar to AQP1. Cystic fibrosis transmembrane conductance regulator (CFTR ) was initially thought as a water channel but now not believed to transport water directly. By cotranporters, water is transported by water osmosis coupling with substrates, which explains how water is transported across the isolated small intestine. This chapter provides information about water transport mediated by other membrane proteins except AQPs .
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Affiliation(s)
- Boyue Huang
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, 100191, China
| | - Hongkai Wang
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, 100191, China
- Department of Anatomy, Basic Medical College, Chongqing Medical University, Chongqing, 400016, China
| | - Baoxue Yang
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, 100191, China.
- State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing, 100191, China.
- Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University, Beijing, 100191, China.
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29
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Stokum JA, Gerzanich V, Simard JM. Molecular pathophysiology of cerebral edema. J Cereb Blood Flow Metab 2016; 36:513-38. [PMID: 26661240 PMCID: PMC4776312 DOI: 10.1177/0271678x15617172] [Citation(s) in RCA: 357] [Impact Index Per Article: 44.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 10/21/2015] [Accepted: 10/22/2015] [Indexed: 12/25/2022]
Abstract
Advancements in molecular biology have led to a greater understanding of the individual proteins responsible for generating cerebral edema. In large part, the study of cerebral edema is the study of maladaptive ion transport. Following acute CNS injury, cells of the neurovascular unit, particularly brain endothelial cells and astrocytes, undergo a program of pre- and post-transcriptional changes in the activity of ion channels and transporters. These changes can result in maladaptive ion transport and the generation of abnormal osmotic forces that, ultimately, manifest as cerebral edema. This review discusses past models and current knowledge regarding the molecular and cellular pathophysiology of cerebral edema.
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Affiliation(s)
- Jesse A Stokum
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, USA
| | - Volodymyr Gerzanich
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, USA
| | - J Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, USA Department of Pathology, University of Maryland School of Medicine, Baltimore, USA Department of Physiology, University of Maryland School of Medicine, Baltimore, USA
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30
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Chloride Cotransporters as a Molecular Mechanism underlying Spreading Depolarization-Induced Dendritic Beading. J Neurosci 2015; 35:12172-87. [PMID: 26338328 DOI: 10.1523/jneurosci.0400-15.2015] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Spreading depolarizations (SDs) are waves of sustained neuronal and glial depolarization that propagate massive disruptions of ion gradients through the brain. SD is associated with migraine aura and recently recognized as a novel mechanism of injury in stroke and brain trauma patients. SD leads to neuronal swelling as assessed in real time with two-photon laser scanning microscopy (2PLSM). Pyramidal neurons do not express aquaporins and thus display low inherent water permeability, yet SD rapidly induces focal swelling (beading) along the dendritic shaft by unidentified molecular mechanisms. To address this issue, we induced SD in murine hippocampal slices by focal KCl microinjection and visualized the ensuing beading of dendrites expressing EGFP by 2PLSM. We confirmed that dendritic beading failed to arise during large (100 mOsm) hyposmotic challenges, underscoring that neuronal swelling does not occur as a simple osmotic event. SD-induced dendritic beading was not prevented by pharmacological interference with the cytoskeleton, supporting the notion that dendritic beading may result entirely from excessive water influx. Dendritic beading was strictly dependent on the presence of Cl(-), and, accordingly, combined blockade of Cl(-)-coupled transporters led to a significant reduction in dendritic beading without interfering with SD. Furthermore, our in vivo data showed a strong inhibition of dendritic beading during pharmacological blockage of these cotransporters. We propose that SD-induced dendritic beading takes place as a consequence of the altered driving forces and thus activity for these cotransporters, which by transport of water during their translocation mechanism may generate dendritic beading independently of osmotic forces. SIGNIFICANCE STATEMENT Spreading depolarization occurs during pathological conditions such as stroke, brain injury, and migraine and is characterized as a wave of massive ion translocation between intracellular and extracellular space in association with recurrent transient focal swelling (beading) of dendrites. Numerous ion channels have been demonstrated to be involved in generation and propagation of spreading depolarization, but the molecular machinery responsible for the dendritic beading has remained elusive. Using real-time in vitro and in vivo two-photon laser scanning microscopy, we have identified the transport mechanisms involved in the detrimental focal swelling of dendrites. These findings have clear clinical significance because they may point to a new class of pharmacological targets for prevention of neuronal swelling that consequently will serve as neuroprotective agents.
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31
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Spector R, Keep RF, Robert Snodgrass S, Smith QR, Johanson CE. A balanced view of choroid plexus structure and function: Focus on adult humans. Exp Neurol 2015; 267:78-86. [PMID: 25747036 DOI: 10.1016/j.expneurol.2015.02.032] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 02/22/2015] [Accepted: 02/25/2015] [Indexed: 12/21/2022]
Abstract
Recently tremendous progress has been made in studying choroid plexus (CP) physiology and pathophysiology; and correcting several misconceptions about the CP. Specifically, the details of how CP, a locus of the blood-CSF barrier (BCSFB), secretes and purifies CSF, generates intracranial pressure (ICP), maintains CSF ion homeostasis, and provides micronutrients, proteins and hormones for neuronal and glial development, maintenance and function, are being understood on a molecular level. Unequivocal evidence that the CP secretory epithelium is the predominant supplier of CSF for the ventricles comes from multiple lines: uptake kinetics of tracer (22)Na and (36)Cl penetration from blood to CSF, autoradiographic mapping of rapid (22)Na and (36)Cl permeation (high permeability coefficients) into the cerebroventricles, CSF sampling from several different in vivo and in vitro CP preparations, CP hyperplasia that increases CSF formation and ICP; and in vitro analysis of CP ability to transport molecules (with expected directionality) and actively secrete fluid against an hydrostatic fluid column. Furthermore, clinical support for this CP-CSF model comes from neurosurgical procedures to remove lateral ventricle CPs in hydrocephalic children to reduce CSF formation, thereby relieving elevated ICP. In terms of micronutrient transport, ascorbic acid, folate and other essential factors are transported by specific (cloned) carriers across CP into ventricular CSF, from which they penetrate across the ependyma and pia mater deeply into the brain to support its viability and function. Without these choroidal functions, severe neurological disease and even death can occur. In terms of efflux or clearance transport, the active carriers (many of which have been cloned and expressed) in the CP basolateral and apical membranes perform regulatory removal of some metabolites (e.g. choline) and certain drugs (e.g. antibiotics like penicillin) from CSF, thus reducing agents such as penicillin to sub-therapeutic levels. Altogether, these multiple transport and secretory functions in CP support CSF homeostasis and fluid dynamics essential for brain function.
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Affiliation(s)
- Reynold Spector
- Department of Medicine, Robert Wood Johnson Medical School, Piscataway, NJ 08554, USA.
| | - Richard F Keep
- Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
| | - S Robert Snodgrass
- Departments of Neurology and Pediatrics, Harbor-UCLA Medical Center, David Geffen UCLA School of Medicine, Torrance, CA 90502, USA.
| | - Quentin R Smith
- Department of Pharmaceutical Sciences, School of Pharmacy, Amarillo, TX 79106, USA.
| | - Conrad E Johanson
- Department of Neurosurgery, Alpert Medical School at Brown University, Providence, RI 02903, USA.
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32
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Fricke W. The significance of water co-transport for sustaining transpirational water flow in plants: a quantitative approach. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:731-9. [PMID: 25563967 DOI: 10.1093/jxb/eru466] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
In a recent Opinion paper, Wegner (Journal of Experimental Botany 65, 381-392, 2014) adapts a concept developed for water flow in animal tissues to propose a model, which can explain the loading of water into the root xylem against a difference in water potential (Ψ) between the xylem parenchyma cell (more negative Ψ) and the xylem vessel (less negative Ψ). In this model, the transport of water is energized through the co-transport of ions such as K(+) and Cl(-) through plasma membrane-located transporters. The emphasis of the model is on the thermodynamic feasibility of the co-transport mechanism per se. However, what is lacking is a quantitative evaluation of the energy input required at the organismal level to sustain such a co-transport mechanism in the face of considerable net (transpirational) flows of water through the system. Here, we use a ratio of 500 water molecules being co-transported for every pair of K(+) and Cl(-) ions, as proposed for the animal system, to calculate the energy required to sustain daytime and night-time transpirational water flow in barley plants through a water co-transport mechanism. We compare this energy with the total daily net input of energy through photosynthetic carbon assimilation. Water co-transport can facilitate the filling of xylem against a difference in Ψ of 1.0MPa and puts a minor drain on the energy budget of the plant. Based on these findings it cannot be excluded that water co-transport in plants contributes significantly to xylem filling during night-time and possibly also daytime transpiration.
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Affiliation(s)
- Wieland Fricke
- School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
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33
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Delpire E, Staley KJ. Novel determinants of the neuronal Cl(-) concentration. J Physiol 2014; 592:4099-114. [PMID: 25107928 PMCID: PMC4215762 DOI: 10.1113/jphysiol.2014.275529] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 08/01/2014] [Indexed: 12/11/2022] Open
Abstract
It is now a well-accepted view that cation-driven Cl(-) transporters in neurons are involved in determining the intracellular Cl(-) concentration. In the present review, we propose that additional factors, which are often overlooked, contribute substantially to the Cl(-) gradient across neuronal membranes. After briefly discussing the data supporting and opposing the role of cation-chloride cotransporters in regulating Cl(-), we examine the participation of the following factors in the formation of the transmembrane Cl(-) gradient: (i) fixed 'Donnan' charges inside and outside the cell; (ii) the properties of water (free vs. bound); and (iii) water transport through the cotransporters. We demonstrate a steep relationship between intracellular Cl(-) and the concentration of fixed negative charges on macromolecules. We show that in the absence of water transport through the K(+)-Cl(-) cotransporter, a large osmotic gradient builds at concentrations below or above a set value of 'Donnan' charges, and show that at any value of these fixed charges, the reversal potential for Cl(-) equates that of K(+). When the movement of water across the membrane is a source of free energy, it is sufficient to modify the movement of Cl(-) through the cotransporter. In this scenario, the reversal potential for Cl(-) does not closely follow that of K(+). Furthermore, our simulations demonstrate that small differences in the availability of freely diffusible water between inside and outside the cell greatly affect the Cl(-) reversal potential, particularly when osmolar transmembrane gradients are minimized, for example by idiogenic osmoles. We also establish that the presence of extracellular charges has little effect on the chloride reversal potential, but greatly affects the effective inhibitory conductance for Cl(-). In conclusion, our theoretical analysis of the presence of fixed anionic charges and water bound on macromolecules inside and outside the cell greatly impacts both Cl(-) gradient and Cl(-) conductance across neuronal membranes.
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Affiliation(s)
- Eric Delpire
- Department of Anaesthesiology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Kevin J Staley
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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Stokum JA, Kurland DB, Gerzanich V, Simard JM. Mechanisms of astrocyte-mediated cerebral edema. Neurochem Res 2014; 40:317-28. [PMID: 24996934 DOI: 10.1007/s11064-014-1374-3] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 06/18/2014] [Accepted: 06/26/2014] [Indexed: 11/26/2022]
Abstract
Cerebral edema formation stems from disruption of blood brain barrier (BBB) integrity and occurs after injury to the CNS. Due to the restrictive skull, relatively small increases in brain volume can translate into impaired tissue perfusion and brain herniation. In excess, cerebral edema can be gravely harmful. Astrocytes are key participants in cerebral edema by virtue of their relationship with the cerebral vasculature, their unique compliment of solute and water transport proteins, and their general role in brain volume homeostasis. Following the discovery of aquaporins, passive conduits of water flow, aquaporin 4 (AQP4) was identified as the predominant astrocyte water channel. Normally, AQP4 is highly enriched at perivascular endfeet, the outermost layer of the BBB, whereas after injury, AQP4 expression disseminates to the entire astrocytic plasmalemma, a phenomenon termed dysregulation. Arguably, the most important role of AQP4 is to rapidly neutralize osmotic gradients generated by ionic transporters. In pathological conditions, AQP4 is believed to be intimately involved in the formation and clearance of cerebral edema. In this review, we discuss aquaporin function and localization in the BBB during health and injury, and we examine post-injury ionic events that modulate AQP4-dependent edema formation.
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Affiliation(s)
- Jesse A Stokum
- Department of Neurosurgery, University of Maryland School of Medicine, 22 S. Greene St., Suite S12D, Baltimore, MD, 21201-1595, USA
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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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Zeuthen T, MacAulay N. Transport of water against its concentration gradient: fact or fiction? ACTA ACUST UNITED AC 2012. [DOI: 10.1002/wmts.54] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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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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Cesetti T, Ciccolini F, Li Y. GABA Not Only a Neurotransmitter: Osmotic Regulation by GABA(A)R Signaling. Front Cell Neurosci 2012; 6:3. [PMID: 22319472 PMCID: PMC3268181 DOI: 10.3389/fncel.2012.00003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Accepted: 01/10/2012] [Indexed: 12/05/2022] Open
Abstract
Mature macroglia and almost all neural progenitor types express γ-aminobutyric (GABA) A receptors (GABAARs), whose activation by ambient or synaptic GABA, leads to influx or efflux of chloride (Cl−) depending on its electro-chemical gradient (ECl). Since the flux of Cl− is indissolubly associated to that of osmotically obliged water, GABAARs regulate water movements by modulating ion gradients. In addition, since water movements also occur through specialized water channels and transporters, GABAAR signaling could affect the movement of water by regulating the function of the channels and transporters involved, thereby affecting not only the direction of the water fluxes but also their dynamics. We will here review recent observations indicating that in neural cells GABAAR-mediated osmotic regulation affects the cellular volume thereby activating multiple intracellular signaling mechanisms important for cell proliferation, maturation, and survival. In addition, we will discuss evidence that the osmotic regulation exerted by GABA may contribute to brain water homeostasis in physiological and in pathological conditions causing brain edema, in which the GABAergic transmission is often altered.
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Affiliation(s)
- Tiziana Cesetti
- Department of Physiology and Pathophysiology, Interdisciplinary Center for Neurosciences, University of Heidelberg Heidelberg, Germany
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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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Osmoregulation and epithelial water transport: lessons from the intestine of marine teleost fish. J Comp Physiol B 2011; 182:1-39. [DOI: 10.1007/s00360-011-0601-3] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2011] [Revised: 06/08/2011] [Accepted: 06/15/2011] [Indexed: 12/15/2022]
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Hamann S, Herrera-Perez JJ, Zeuthen T, Alvarez-Leefmans FJ. Cotransport of water by the Na+-K+-2Cl(-) cotransporter NKCC1 in mammalian epithelial cells. J Physiol 2011; 588:4089-101. [PMID: 20819947 DOI: 10.1113/jphysiol.2010.194738] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Water transport by the Na+-K+-2Cl(-) cotransporter (NKCC1) was studied in confluent cultures of pigmented epithelial (PE) cells from the ciliary body of the fetal human eye. Interdependence among water, Na+ and Cl(-) fluxes mediated by NKCC1 was inferred from changes in cell water volume, monitored by intracellular self-quenching of the fluorescent dye calcein. Isosmotic removal of external Cl(-) or Na+ caused a rapid efflux of water from the cells, which was inhibited by bumetanide (10 μm). When returned to the control solution there was a rapid water influx that required the simultaneous presence of external Na+ and Cl(-). The water influx could proceed uphill, against a transmembrane osmotic gradient, suggesting that energy contained in the ion fluxes can be transferred to the water flux. The influx of water induced by changes in external [Cl(-)] saturated in a sigmoidal fashion with a Km of 60 mm, while that induced by changes in external [Na+] followed first order kinetics with a Km of about 40 mm. These parameters are consistent with ion transport mediated by NKCC1. Our findings support a previous investigation, in which we showed water transport by NKCC1 to be a result of a balance between ionic and osmotic gradients. The coupling between salt and water transport in NKCC1 represents a novel aspect of cellular water homeostasis where cells can change their volume independently of the direction of an osmotic gradient across the membrane. This has relevance for both epithelial and symmetrical cells.
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Affiliation(s)
- Steffen Hamann
- Nordic Centre for Water Imbalance Related Disorders, Institute of Cellular and Molecular Medicine, The Panum Institute, University of Copenhagen, Copenhagen, Denmark.
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Damkier HH, Brown PD, Praetorius J. Epithelial pathways in choroid plexus electrolyte transport. Physiology (Bethesda) 2010; 25:239-49. [PMID: 20699470 DOI: 10.1152/physiol.00011.2010] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A stable intraventricular milieu is crucial for maintaining normal neuronal function. The choroid plexus epithelium produces the cerebrospinal fluid and in doing so influences the chemical composition of the interstitial fluid of the brain. Here, we review the molecular pathways involved in transport of the electrolytes Na+, K+, Cl-, and HCO3(-)across the choroid plexus epithelium.
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Affiliation(s)
- Helle H Damkier
- Department of Anatomy and the Water and Salt Research Center, Aarhus University, Aarhus C, Denmark
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Mollajew R, Zocher F, Horner A, Wiesner B, Klussmann E, Pohl P. Routes of epithelial water flow: aquaporins versus cotransporters. Biophys J 2010; 99:3647-56. [PMID: 21112289 PMCID: PMC2998630 DOI: 10.1016/j.bpj.2010.10.021] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2010] [Revised: 10/07/2010] [Accepted: 10/14/2010] [Indexed: 11/18/2022] Open
Abstract
The routes water takes through membrane barriers is still a matter of debate. Although aquaporins only allow transmembrane water movement along an osmotic gradient, cotransporters are believed to be capable of water transport against the osmotic gradient. Here we show that the renal potassium-chloride-cotransporter (KCC1) does not pump a fixed amount of water molecules per movement of one K(+) and one Cl(-), as was reported for the analogous transporter in the choroid plexus. We monitored water and potassium fluxes through monolayers of primary cultured renal epithelial cells by detecting tiny solute concentration changes in the immediate vicinity of the monolayer. KCC1 extruded K(+) ions in the presence of a transepithelial K(+) gradient, but did not transport water. KCC1 inhibition reduced epithelial osmotic water permeability P(f) by roughly one-third, i.e., the effect of inhibitors was small in resting cells and substantial in hormonal stimulated cells that contained high concentrations of aquaporin-2 in their apical membranes. The furosemide or DIOA (dihydroindenyl-oxy-alkanoic acid)-sensitive water flux was much larger than expected when water passively followed the KCC1-mediated ion flow. The inhibitory effect of these drugs on water flux was reversed by the K(+)-H(+) exchanger nigericin, indicating that KCC1 affects water transport solely by K(+) extrusion. Intracellular K(+) retention conceivably leads to cell swelling, followed by an increased rate of endocytic AQP2 retrieval from the apical membrane.
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Affiliation(s)
- Rustam Mollajew
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
| | - Florian Zocher
- Institut für Biophysik, Johannes Kepler Universität, Linz, Austria
| | - Andreas Horner
- Institut für Biophysik, Johannes Kepler Universität, Linz, Austria
| | | | - Enno Klussmann
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
| | - Peter Pohl
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
- Institut für Biophysik, Johannes Kepler Universität, Linz, Austria
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Helland CA, Aarhus M, Knappskog P, Olsson LK, Lund-Johansen M, Amiry-Moghaddam M, Wester K. Increased NKCC1 expression in arachnoid cysts supports secretory basis for cyst formation. Exp Neurol 2010; 224:424-8. [DOI: 10.1016/j.expneurol.2010.05.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Revised: 04/20/2010] [Accepted: 05/06/2010] [Indexed: 10/19/2022]
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Water transport between CNS compartments: contributions of aquaporins and cotransporters. Neuroscience 2010; 168:941-56. [DOI: 10.1016/j.neuroscience.2009.09.016] [Citation(s) in RCA: 157] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 08/13/2009] [Accepted: 09/08/2009] [Indexed: 12/20/2022]
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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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The modulation of aquaporin-4 by using PKC-activator (phorbol myristate acetate) and V1a receptor antagonist (SR49059) following middle cerebral artery occlusion/reperfusion in the rat. ACTA NEUROCHIRURGICA. SUPPLEMENT 2009; 102:431-6. [PMID: 19388361 DOI: 10.1007/978-3-211-85578-2_84] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/05/2023]
Abstract
BACKGROUND We have pursued the concept that traumatic brain edema is predominantly cellular and that water entry is modulated in part by aquaporins. Aquaporin-4 (AQP4) has been shown to play a significant role in cellular edema formation. Phorbol myristate acetate (PMA) is a potent PKC activator; purportedly involved in modulation of AQP4 activity. Alternatively, AQP4 may be regulated by arginine-vasopressin. Administration of the vasopressin antagonist (SR49059) reduced brain water content and sodium shift following MCAo. To investigate if edema formation is affected by the reduction of AQP4 expression, we utilized PMA and SR49059 following middle cerebral artery occlusion model (MCAo), and measured AQP4 expression by Western-Blot (WB) techniques. METHODS Male Sprague Dawley rats were randomly assigned to sham (n=4) or MCAo groups (vehicle, PMA or SR49059 infusion; n=6 each). Each solution was infused for 5 hours, starting 1 hour before injury. After a two-hour period of ischemia and two-hour reperfusion, animals were sacrificed and brain regions of interest were processed by WB to quantify the effect of treatment on AQP4 expression. RESULTS These studies demonstrate that MCAo results in a significant up-regulation of AQP4 on the ischemic zone when compared to the contralateral un-injured hemisphere (p < 0.05) and that PMA and SR49059 treatment significantly down-regulated AQP4 expression compared to the vehicle group (p < 0.05). CONCLUSIONS These studies support the hypotheses that PMA and SR49059 may be useful in reducing cerebral water accumulation by modulating AQP4 expression and that pharmacological manipulation of AQP4 may emerge as a viable strategy for the reduction of fulminating edema following ischemic injury.
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Hill AE. Fluid Transport: A Guide for the Perplexed. J Membr Biol 2008; 223:1-11. [DOI: 10.1007/s00232-007-9085-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Accepted: 11/12/2007] [Indexed: 11/28/2022]
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Taya K, Gulsen S, Okuno K, Prieto R, Marmarou CR, Marmarou A. Modulation of AQP4 expression by the selective V1a receptor antagonist, SR49059, decreases trauma-induced brain edema. ACTA NEUROCHIRURGICA. SUPPLEMENT 2008; 102:425-429. [PMID: 19388360 DOI: 10.1007/978-3-211-85578-2_83] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
BACKGROUND Currently, there are no pharmacological treatments available for traumatically induced brain edema and the subsequent rise of ICP. Evidence indicates that Aquaporin-4 (AQP4) plays a significant role in the pathophysiology of brain edema. Previously we have reported that SR49059 reduced brain edema secondary to ischemia. We, therefore, examined whether the selective V1a receptor antagonist, SR49059, reduces brain edema by modulating AQP4 expression following cortical contusion injury (CCI). METHODS Traumatic brain injury (TBI) was produced in thirty-two adult male Sprague-Dawley rats by lateral CCI (6.0 m/sec, 3 mm depth). Animals were randomly assigned to vehicle (n=16) or SR49059 treatment (n=16) groups and administered drug (960 microl/hr i.v.) immediately after injury over a 5 hr period. Animals were sacrificed for assessment of brain water content by Wet/Dry method and AQP4 protein expression by immunoblotting expressed as the ratio of AQP4 and Cyclophilin-A densitometries. FINDINGS Elevated AQP4 expression levels and water content were observed on the right injured side in both the right anterior (RA) and right posterior (RP) section compared to the left non-injured side inclusive of the left anterior (LA) and right anterior (RA) sections. The average AQP4 expression levels in contused areas for animals receiving SR drug treatment (RA: 1.313 +/- 0.172, RP: 1.308 +/- 0.175) were significantly decreased from vehicle-treated animals (RA: 2.181 +/- 0.232, RP: 2.303 +/- 0.370, p = 0.001, p= 0.003). Water content levels on SR treatment (78.89 +/- 0.14) was also significantly decreased from vehicle levels (80.38 +/- 0.38, p < 0.01) in the traumatized hemisphere. CONCLUSIONS SR49059 significantly reduced trauma-induced AQP4 up-regulation in the contused hemisphere. Moreover, brain water content was also significantly reduced paralleling the AQP4 suppression. These data provide further support that vasopressin (AVP) and V1a receptors can control water flux through astrocytic plasma membranes by regulating AQP4 expression. Taken in concert, these results affirm our laboratories contention that AQP4 can be effectively modulated pharmacologically.
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Affiliation(s)
- Keisuke Taya
- Department of Neurosurgery, Virginia Commonwealth University Medical Center, 1101 East Marshall Street, P.O. Box 980508, Richmond, VA 23298-0508, USA
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