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Harrell CR, Feulner L, Djonov V, Pavlovic D, Volarevic V. The Molecular Mechanisms Responsible for Tear Hyperosmolarity-Induced Pathological Changes in the Eyes of Dry Eye Disease Patients. Cells 2023; 12:2755. [PMID: 38067183 PMCID: PMC10706334 DOI: 10.3390/cells12232755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 11/18/2023] [Accepted: 11/27/2023] [Indexed: 12/18/2023] Open
Abstract
Dry eye disease (DED) is a multifactorial disorder of the lacrimal system and ocular surface, characterized by a deficiency in the quality and/or quantity of the tear fluid. The multifactorial nature of DED encompasses a number of interconnected underlying pathologies, including loss of homeostasis, instability and hyperosmolarity of the tears, and the induction and propagation of detrimental inflammatory responses in the eyes, which finally results in the development of neurosensory dysfunction and visual disruption. Dryness, grittiness, scratchiness, discomfort, inflammation, burning, watering, ocular fatigue, pain, and decreased functional visual acuity are common symptoms of DED. Eye dysfunction drastically attenuates patients' quality of life. Accordingly, a better understanding of the pathogenic processes that regulate the development and progression of DED is crucially important for the establishment of new and more effective DED-related treatment approaches, which would significantly improve the quality of life of DED patients. Since the process of osmoregulation, which guards the ocular surface epithelia and maintains normal vision, is affected when the osmolarity of the tears is greater than that of the epithelial cells, tear hyperosmolarity (THO) is considered an initial, important step in the development, progression, and aggravation of DED. In order to delineate the role of THO in the pathogenesis of DED, in this review article, we summarize current knowledge related to the molecular mechanisms responsible for the development of THO-induced pathological changes in the eyes of DED patients, and we briefly discuss the therapeutic potential of hypo-osmotic eye drops in DED treatment.
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Affiliation(s)
- Carl Randall Harrell
- Regenerative Processing Plant, LLC, 34176 US Highway 19 N, Palm Harbor, FL 34684, USA;
| | - Lisa Feulner
- Advanced Eye Care & Aesthetics, 104 Plumtree Rd Suite 107, Bel Air, MD 21015, USA;
| | - Valentin Djonov
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3012 Bern, Switzerland;
| | - Dragica Pavlovic
- Departments of Genetics and Microbiology and Immunology, Center for Harm Reduction of Biological and Chemical Hazards, Faculty of Medical Sciences, University of Kragujevac, 69 Svetozar Markovic Street, 34000 Kragujevac, Serbia;
| | - Vladislav Volarevic
- Departments of Genetics and Microbiology and Immunology, Center for Harm Reduction of Biological and Chemical Hazards, Faculty of Medical Sciences, University of Kragujevac, 69 Svetozar Markovic Street, 34000 Kragujevac, Serbia;
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2
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Lucius A, Chhatwal S, Valtink M, Reinach PS, Li A, Pleyer U, Mergler S. L-Carnitine Suppresses Transient Receptor Potential Vanilloid Type 1 Activation in Human Corneal Epithelial Cells. Int J Mol Sci 2023; 24:11815. [PMID: 37511574 PMCID: PMC10380586 DOI: 10.3390/ijms241411815] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/17/2023] [Accepted: 07/18/2023] [Indexed: 07/30/2023] Open
Abstract
Tear film hyperosmolarity induces dry eye syndrome (DES) through transient receptor potential vanilloid type 1 (TRPV1) activation. L-carnitine is a viable therapeutic agent since it protects against this hypertonicity-induced response. Here, we investigated whether L-carnitine inhibits TRPV1 activation by blocking heat- or capsaicin-induced increases in Ca2+ influx or hyperosmotic stress-induced cell volume shrinkage in a human corneal epithelial cell line (HCE-T). Single-cell fluorescence imaging of calcein/AM-loaded cells or fura-2/AM-labeled cells was used to evaluate cell volume changes and intracellular calcium levels, respectively. Planar patch-clamp technique was used to measure whole-cell currents. TRPV1 activation via either capsaicin (20 µmol/L), hyperosmolarity (≈450 mosmol/L) or an increase in ambient bath temperature to 43 °C induced intracellular calcium transients and augmented whole-cell currents, whereas hypertonicity induced cell volume shrinkage. In contrast, either capsazepine (10 µmol/L) or L-carnitine (1-3 mmol/L) reduced all these responses. Taken together, L-carnitine and capsazepine suppress hypertonicity-induced TRPV1 activation by blocking cell volume shrinkage.
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Affiliation(s)
- Alexander Lucius
- Klinik für Augenheilkunde, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 13353 Berlin, Germany
| | - Sirjan Chhatwal
- Klinik für Augenheilkunde, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 13353 Berlin, Germany
| | - Monika Valtink
- Faculty of Medicine, Institute of Anatomy, TU Dresden, 01216 Dresden, Germany
- Equality and Diversity Unit, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany
| | - Peter S Reinach
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou 325027, China
| | - Aruna Li
- Klinik für Augenheilkunde, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 13353 Berlin, Germany
| | - Uwe Pleyer
- Klinik für Augenheilkunde, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 13353 Berlin, Germany
| | - Stefan Mergler
- Klinik für Augenheilkunde, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 13353 Berlin, Germany
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3
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Shcheynikov N, Boggs K, Green A, Feranchak AP. Identification of the chloride channel, leucine-rich repeat-containing protein 8, subfamily a (LRRC8A), in mouse cholangiocytes. Hepatology 2022; 76:1248-1258. [PMID: 35445421 PMCID: PMC10126881 DOI: 10.1002/hep.32536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 04/18/2022] [Accepted: 04/19/2022] [Indexed: 12/08/2022]
Abstract
BACKGROUND AND AIMS Chloride (Cl- ) channels in the apical membrane of biliary epithelial cells (BECs), also known as cholangiocytes, provide the driving force for biliary secretion. Although two Cl- channels have been identified on a molecular basis, the Cystic Fibrosis Transmembrane Conductance Regulator and Transmembrane Member 16A, a third Cl- channel with unique biophysical properties has been described. Leucine-Rich Repeat-Containing Protein 8, subfamily A (LRRC8A) is a newly identified protein capable of transporting Cl- in other epithelium in response to cell swelling. The aim of the present study was to determine if LRRC8A represents the volume-regulated anion channel in mouse BECs. APPROACH AND RESULTS Studies were performed in mouse small (MSC) and large (MLC) cholangiocytes. Membrane Cl- currents were measured by whole-cell patch-clamp techniques and cell volume measurements were performed by calcein-AM fluorescence. Exposure of either MSC or MLC to hypotonicity (190 mOsm) rapidly increased cell volume and activated Cl- currents. Currents exhibited outward rectification, time-dependent inactivation at positive membrane potentials, and reversal potential at 0 mV (ECl ). Removal of extracellular Cl- or specific pharmacological inhibition of LRRC8A abolished currents. LRRC8A was detected in both MSC and MLC by reverse transcription polymerase chain reaction and confirmed by western blot. Transfection with LRRC8A small interfering RNA decreased protein levels by >70% and abolished volume-stimulated Cl- currents. CONCLUSION These results demonstrate that LRRC8A is functionally present in mouse BECs, contributes to volume-activated Cl- secretion, and, therefore, may be a target to modulate bile formation in the treatment of cholestatic liver disorders.
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Affiliation(s)
- Nikolay Shcheynikov
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Kristy Boggs
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Anthony Green
- Tissue and Research Pathology Core, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Andrew P Feranchak
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Pittsburgh Liver Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Hao Y, Chen T, Huang S, Liu Z, Zhou B. Novel quartz crystal microbalance cytosensor for real-time monitoring of polystyrene nanospheres effect on cell apoptosis. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2022. [DOI: 10.1016/j.cjac.2022.100149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Kolobkova Y, Pervaiz S, Stauber T. The expanding toolbox to study the LRRC8-formed volume-regulated anion channel VRAC. CURRENT TOPICS IN MEMBRANES 2021; 88:119-163. [PMID: 34862024 DOI: 10.1016/bs.ctm.2021.10.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The volume-regulated anion channel (VRAC) is activated upon cell swelling and facilitates the passive movement of anions across the plasma membrane in cells. VRAC function underlies many critical homeostatic processes in vertebrate cells. Among them are the regulation of cell volume and membrane potential, glutamate release and apoptosis. VRAC is also permeable for organic osmolytes and metabolites including some anti-cancer drugs and antibiotics. Therefore, a fundamental understanding of VRAC's structure-function relationships, its physiological roles, its utility for therapy of diseases, and the development of compounds modulating its activity are important research frontiers. Here, we describe approaches that have been applied to study VRAC since it was first described more than 30 years ago, providing an overview of the recent methodological progress. The diverse applications reflecting a compromise between the physiological situation, biochemical definition, and biophysical resolution range from the study of VRAC activity using a classic electrophysiology approach, to the measurement of osmolytes transport by various means and the investigation of its activation using a novel biophysical approach based on fluorescence resonance energy transfer.
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Affiliation(s)
- Yulia Kolobkova
- Department of Human Medicine and Institute for Molecular Medicine, MSH Medical School Hamburg, Germany
| | - Sumaira Pervaiz
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - Tobias Stauber
- Department of Human Medicine and Institute for Molecular Medicine, MSH Medical School Hamburg, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany.
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Chakraborty M, Asraf H, Sekler I, Hershfinkel M. ZnR/GPR39 controls cell migration by orchestrating recruitment of KCC3 into protrusions, re-organization of actin and activation of MMP. Cell Calcium 2021; 94:102330. [PMID: 33465674 DOI: 10.1016/j.ceca.2020.102330] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/16/2020] [Accepted: 11/30/2020] [Indexed: 12/23/2022]
Abstract
Actin re-organization and degradation of extracellular matrix by metalloproteases (MMPs) facilitate formation of cellular protrusions that are required for cell proliferation and migration. We find that Zn2+ activation of the Gq-coupled receptor ZnR/GPR39 controls these processes by regulating K+/Cl- co-transporter KCC3, which modulates cell volume. Silencing of KCC3 expression or activity reverses ZnR/GPR39 enhancement of cell proliferation, migration and invasion through Matrigel. Activation of ZnR/GPR39 recruits KCC3 into F-actin rich membrane protrusions, suggesting that it can locally control volume changes. Immunofluorescence analysis indicates that Zn2+ activation of ZnR/GPR39 and KCC3 are required to enhance formation of F-actin stress fibers and cellular protrusions. In addition, ZnR/GPR39 upregulation of KCC3-dependent transport increases the activity of matrix metalloproteases MMP2 and MMP9. Our study establishes a mechanism in which ZnR/GPR39 orchestrates localization and activation of KCC3, formation of F-actin rich cell protrusions and activation of MMPs, and thereby controls cell proliferation and migration.
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Affiliation(s)
- Moumita Chakraborty
- Department of Physiology and Cell Biology and The Zlotowski Center for Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Hila Asraf
- Department of Physiology and Cell Biology and The Zlotowski Center for Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Israel Sekler
- Department of Physiology and Cell Biology and The Zlotowski Center for Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Michal Hershfinkel
- Department of Physiology and Cell Biology and The Zlotowski Center for Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
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Bortner CD, Cidlowski JA. Ions, the Movement of Water and the Apoptotic Volume Decrease. Front Cell Dev Biol 2020; 8:611211. [PMID: 33324655 PMCID: PMC7723978 DOI: 10.3389/fcell.2020.611211] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 11/04/2020] [Indexed: 12/20/2022] Open
Abstract
The movement of water across the cell membrane is a natural biological process that occurs during growth, cell division, and cell death. Many cells are known to regulate changes in their cell volume through inherent compensatory regulatory mechanisms. Cells can sense an increase or decrease in their cell volume, and compensate through mechanisms known as a regulatory volume increase (RVI) or decrease (RVD) response, respectively. The transport of sodium, potassium along with other ions and osmolytes allows the movement of water in and out of the cell. These compensatory volume regulatory mechanisms maintain a cell at near constant volume. A hallmark of the physiological cell death process known as apoptosis is the loss of cell volume or cell shrinkage. This loss of cell volume is in stark contrast to what occurs during the accidental cell death process known as necrosis. During necrosis, cells swell or gain water, eventually resulting in cell lysis. Thus, whether a cell gains or loses water after injury is a defining feature of the specific mode of cell death. Cell shrinkage or the loss of cell volume during apoptosis has been termed apoptotic volume decrease or AVD. Over the years, this distinguishing feature of apoptosis has been largely ignored and thought to be a passive occurrence or simply a consequence of the cell death process. However, studies on AVD have defined an underlying movement of ions that result in not only the loss of cell volume, but also the activation and execution of the apoptotic process. This review explores the role ions play in controlling not only the movement of water, but the regulation of apoptosis. We will focus on what is known about specific ion channels and transporters identified to be involved in AVD, and how the movement of ions and water change the intracellular environment leading to stages of cell shrinkage and associated apoptotic characteristics. Finally, we will discuss these concepts as they apply to different cell types such as neurons, cardiomyocytes, and corneal epithelial cells.
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Affiliation(s)
- Carl D. Bortner
- Signal Transduction Laboratory, Department of Health and Human Services, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, United States
| | - John A. Cidlowski
- Signal Transduction Laboratory, Department of Health and Human Services, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, United States
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LRRC8 family proteins within lysosomes regulate cellular osmoregulation and enhance cell survival to multiple physiological stresses. Proc Natl Acad Sci U S A 2020; 117:29155-29165. [PMID: 33139539 DOI: 10.1073/pnas.2016539117] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
LRRC8 family proteins on the plasma membrane play a critical role in cellular osmoregulation by forming volume-regulated anion channels (VRACs) necessary to prevent necrotic cell death. We demonstrate that intracellular LRRC8 proteins acting within lysosomes also play an essential role in cellular osmoregulation. LRRC8 proteins on lysosome membranes generate large lysosomal volume-regulated anion channel (Lyso-VRAC) currents in response to low cytoplasmic ionic strength conditions. When a double-leucine L706L707 motif at the C terminus of LRRC8A was mutated to alanines, normal plasma membrane VRAC currents were still observed, but Lyso-VRAC currents were absent. We used this targeting mutant, as well as pharmacological tools, to demonstrate that Lyso-VRAC currents are necessary for the formation of large lysosome-derived vacuoles, which store and then expel excess water to maintain cytosolic water homeostasis. Thus, Lyso-VRACs allow lysosomes of mammalian cells to act as the cell`s "bladder." When Lyso-VRAC current was selectively eliminated, the extent of necrotic cell death to sustained stress was greatly increased, not only in response to hypoosmotic stress, but also to hypoxic and hypothermic stresses. Thus Lyso-VRACs play an essential role in enabling cells to mount successful homeostatic responses to multiple stressors.
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9
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Guarino BD, Paruchuri S, Thodeti CK. The role of TRPV4 channels in ocular function and pathologies. Exp Eye Res 2020; 201:108257. [PMID: 32979394 DOI: 10.1016/j.exer.2020.108257] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 12/15/2022]
Abstract
Transient potential receptor vanilloid 4 (TRPV4) is an ion channel responsible for sensing osmotic and mechanical signals, which in turn regulates calcium signaling across cell membranes. TRPV4 is widely expressed throughout the body, and plays an important role in normal physiological function, as well as different pathologies, however, its role in the eye is not well known. In the eye, TRPV4 is expressed in various tissues, such as the retina, corneal epithelium, ciliary body, and the lens. In this review, we provide an overview on TRPV4 structure, activation, mutations, and summarize the current knowledge of TRPV4 function and signaling mechanisms in various locations throughout the eye, as well as its role in ocular diseases, such as glaucoma and diabetic retinopathy. Based on the available data, we highlight the therapeutic potential of TRPV4 as well as the shortcomings of current research. Finally, we provide future perspectives on the implications of targeting TRPV4 to treat various ocular pathologies.
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Affiliation(s)
- Brianna D Guarino
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, 44272, USA
| | | | - Charles K Thodeti
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, 44272, USA.
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10
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Castellano GC, Lana PDC, Freire CA. Euryhalinity of subtropical marine and estuarine polychaetes evaluated through carbonic anhydrase activity and cell volume regulation. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2020; 333:316-324. [PMID: 32306561 DOI: 10.1002/jez.2357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 12/31/2019] [Accepted: 02/17/2020] [Indexed: 11/11/2022]
Abstract
Polychaete worms are widespread and diverse in marine and estuarine habitats subject to varying salinity, in areas influenced by tides, demanding physiological adjustment for internal homeostasis. They are typically considered and reported to be osmoconformers, but they are not often studied for their osmoregulation. Here, three species of polychaete worms from distinct coastal habitats have been investigated: the spionid Scolelepis goodbody (intertidal in saline, exposed sandy beaches), the nereidid Laeonereis culveri (estuarine polyhaline), and the nephtyid Nephtys fluviatilis (estuarine oligohaline). The general objective here was to relate ecological aspects and physiology of the studied species. Constitutive whole body osmolality and carbonic anhydrase activity (CAA, relevant for osmoregulation, acid-base balance and respiration) have been assayed. In addition, cell volume regulatory capacity (from whole body cell dissociation) was challenged under hypoosmotic and hyperosmotic shocks (50% intensity), with respect to isosmotic control. S. googdbody and L. culveri, the two species from most saline environments (marine/estuarine), showed higher CAA than N. fluviatilis, which, in turn, displayed a hyperosmotic gradient to water of salinity 15. Cells from S. goodbody and L. culveri showed regulatory volume decrease upon swelling, with S. goodbody showing the largest volume increase. As in other more studied marine invertebrate groups, polychaetes also show variability in their osmoregulatory physiology, related to distinct saline challenges faced in their coastal habitats.
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Affiliation(s)
- Giovanna C Castellano
- Department of Zoology, Graduate Program in Zoology, Universidade Federal do Paraná, Curitiba, Paraná, Brazil
| | - Paulo da Cunha Lana
- Center for Marine Studies, Universidade Federal do Paraná, Pontal do Paraná, Paraná, Brazil
| | - Carolina A Freire
- Department of Physiology, Universidade Federal do Paraná, Curitiba, Paraná, Brazil
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Ullrich F, Blin S, Lazarow K, Daubitz T, von Kries JP, Jentsch TJ. Identification of TMEM206 proteins as pore of PAORAC/ASOR acid-sensitive chloride channels. eLife 2019; 8:49187. [PMID: 31318332 PMCID: PMC6663466 DOI: 10.7554/elife.49187] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 07/17/2019] [Indexed: 01/09/2023] Open
Abstract
Acid-sensing ion channels have important functions in physiology and pathology, but the molecular composition of acid-activated chloride channels had remained unclear. We now used a genome-wide siRNA screen to molecularly identify the widely expressed acid-sensitive outwardly-rectifying anion channel PAORAC/ASOR. ASOR is formed by TMEM206 proteins which display two transmembrane domains (TMs) and are expressed at the plasma membrane. Ion permeation-changing mutations along the length of TM2 and at the end of TM1 suggest that these segments line ASOR’s pore. While not belonging to a gene family, TMEM206 has orthologs in probably all vertebrates. Currents from evolutionarily distant orthologs share activation by protons, a feature essential for ASOR’s role in acid-induced cell death. TMEM206 defines a novel class of ion channels. Its identification will help to understand its physiological roles and the diverse ways by which anion-selective pores can be formed.
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Affiliation(s)
- Florian Ullrich
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Sandy Blin
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Katina Lazarow
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Tony Daubitz
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | | | - Thomas J Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
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Zhou B, Lu X, Hao Y, Yang P. Real-Time Monitoring of the Regulatory Volume Decrease of Cancer Cells: A Model for the Evaluation of Cell Migration. Anal Chem 2019; 91:8078-8084. [DOI: 10.1021/acs.analchem.9b00004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bin Zhou
- Department of Chemistry, Jinan University, Guangzhou 510632, People’s Republic of China
| | - Xinxin Lu
- Department of Chemistry, Jinan University, Guangzhou 510632, People’s Republic of China
| | - Yan Hao
- Department of Chemistry, Jinan University, Guangzhou 510632, People’s Republic of China
| | - Peihui Yang
- Department of Chemistry, Jinan University, Guangzhou 510632, People’s Republic of China
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13
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David DD, Lima OG, Nóbrega AMCDS, Amado EM. Capacity of tissue water regulation is impaired in an osmoconformer living in impacted estuaries? ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2018; 166:375-382. [PMID: 30278400 DOI: 10.1016/j.ecoenv.2018.09.111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 09/19/2018] [Accepted: 09/25/2018] [Indexed: 06/08/2023]
Abstract
Estuarine osmoconformes rely on their ability to perform tissue and cell water regulation to cope with daily osmotic challenges that occur in the estuary. In addition, these animals currently must deal with pollutants present in the estuarine environment, which can disturb their capacity of water regulation. We collected the mangrove oyster Crassostrea rhizophorae in two tropical estuaries in the Northeast region of Brazil with different degrees of human interference: the Paraíba Estuary (impacted) and the Mamanguape Estuary (preserved). Tissue water content was analyzed after exposure to salinities 12, 24 and 36 for 24 h. Gill cell volume regulation was analyzed in vitro upon hypo- and hyper-osmotic conditions. We also analyzed gill MXR (multi-xenobiotic resistance) mechanism, as reference of environmental pollution. Gill and muscle of oysters from two sites of Paraíba Estuary, and from one site of Mamanguape Estuary were not able to maintain tissue water content upon hypo- and hyper-osmotic conditions. Gill cells of oyster from the same sites exhibited swelling followed by regulatory volume decrease upon hypo-osmotic condition. Gill MXR activity was increased in oysters from these sites. The best tissue and cell water regulation, and the lowest MXR activity, was found in oyster from downstream of Mamanguape Estuary, our reference site and the one most preserved. Tissue and cell water regulation proved to be a sensitive parameter to environmental pollution and could be considered as biomarker of aquatic contamination.
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Affiliation(s)
- Daniela Dantas David
- Curso de Ciências Biológicas, Centro de Ciências Biológicas e Sociais Aplicadas, Universidade Estadual da Paraíba-Campus V, João Pessoa, PB, Brazil
| | - Otoniel Gonçalves Lima
- Curso de Ciências Biológicas, Centro de Ciências Biológicas e Sociais Aplicadas, Universidade Estadual da Paraíba-Campus V, João Pessoa, PB, Brazil
| | - Alice Maria Cabral de Sousa Nóbrega
- Curso de Ciências Biológicas, Centro de Ciências Biológicas e Sociais Aplicadas, Universidade Estadual da Paraíba-Campus V, João Pessoa, PB, Brazil
| | - Enelise Marcelle Amado
- Curso de Ciências Biológicas, Centro de Ciências Biológicas e Sociais Aplicadas, Universidade Estadual da Paraíba-Campus V, João Pessoa, PB, Brazil.
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Stuhlmann T, Planells-Cases R, Jentsch TJ. LRRC8/VRAC anion channels enhance β-cell glucose sensing and insulin secretion. Nat Commun 2018. [PMID: 29773801 DOI: 10.1038/s41467‐018‐04353‐y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Glucose homeostasis depends critically on insulin that is secreted by pancreatic β-cells. Serum glucose, which is directly sensed by β-cells, stimulates depolarization- and Ca2+-dependent exocytosis of insulin granules. Here we show that pancreatic islets prominently express LRRC8A and LRRC8D, subunits of volume-regulated VRAC anion channels. Hypotonicity- or glucose-induced β-cell swelling elicits canonical LRRC8A-dependent VRAC currents that depolarize β-cells to an extent that causes electrical excitation. Glucose-induced excitation and Ca2+ responses are delayed in onset, but not abolished, in β-cells lacking the essential VRAC subunit LRRC8A. Whereas Lrrc8a disruption does not affect tolbutamide- or high-K+-induced insulin secretion from pancreatic islets, it reduces first-phase glucose-induced insulin secretion. Mice lacking VRAC in β-cells have normal resting serum glucose levels but impaired glucose tolerance. We propose that opening of LRRC8/VRAC channels increases glucose sensitivity and insulin secretion of β-cells synergistically with KATP closure. Neurotransmitter-permeable LRRC8D-containing VRACs might have additional roles in autocrine/paracrine signaling within islets.
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Affiliation(s)
- Till Stuhlmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany.,Graduate Program of the Faculty for Biology, Chemistry and Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany
| | - Rosa Planells-Cases
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany
| | - Thomas J Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany. .,Neurocure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany.
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Stuhlmann T, Planells-Cases R, Jentsch TJ. LRRC8/VRAC anion channels enhance β-cell glucose sensing and insulin secretion. Nat Commun 2018; 9:1974. [PMID: 29773801 PMCID: PMC5958052 DOI: 10.1038/s41467-018-04353-y] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 04/23/2018] [Indexed: 01/09/2023] Open
Abstract
Glucose homeostasis depends critically on insulin that is secreted by pancreatic β-cells. Serum glucose, which is directly sensed by β-cells, stimulates depolarization- and Ca2+-dependent exocytosis of insulin granules. Here we show that pancreatic islets prominently express LRRC8A and LRRC8D, subunits of volume-regulated VRAC anion channels. Hypotonicity- or glucose-induced β-cell swelling elicits canonical LRRC8A-dependent VRAC currents that depolarize β-cells to an extent that causes electrical excitation. Glucose-induced excitation and Ca2+ responses are delayed in onset, but not abolished, in β-cells lacking the essential VRAC subunit LRRC8A. Whereas Lrrc8a disruption does not affect tolbutamide- or high-K+-induced insulin secretion from pancreatic islets, it reduces first-phase glucose-induced insulin secretion. Mice lacking VRAC in β-cells have normal resting serum glucose levels but impaired glucose tolerance. We propose that opening of LRRC8/VRAC channels increases glucose sensitivity and insulin secretion of β-cells synergistically with KATP closure. Neurotransmitter-permeable LRRC8D-containing VRACs might have additional roles in autocrine/paracrine signaling within islets.
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Affiliation(s)
- Till Stuhlmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany.,Graduate Program of the Faculty for Biology, Chemistry and Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany
| | - Rosa Planells-Cases
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany
| | - Thomas J Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Robert-Rössle-Strasse 10, 13125, Berlin, Germany. .,Neurocure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany.
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Abstract
Volume is an essential characteristic of a cell, and this review describes the main methods of its measurement that have been used in the past several decades. The discussed methods include various implementations of light scattering, estimates based on one or two cell dimensions, surface scanning, fluorescence confocal and transmission slice-by-slice imaging, intracellular volume markers, displacement of extracellular solution, quantitative phase imaging, radioactive methods, and some others. Suitability of these methods to some typical samples and applications is discussed. © 2017 International Society for Advancement of Cytometry.
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Affiliation(s)
- Michael A Model
- Department of Biological Sciences, Kent State University, Kent, Ohio
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Friard J, Tauc M, Cougnon M, Compan V, Duranton C, Rubera I. Comparative Effects of Chloride Channel Inhibitors on LRRC8/VRAC-Mediated Chloride Conductance. Front Pharmacol 2017; 8:328. [PMID: 28620305 PMCID: PMC5449500 DOI: 10.3389/fphar.2017.00328] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 05/16/2017] [Indexed: 01/08/2023] Open
Abstract
Chloride channels play an essential role in a variety of physiological functions and in human diseases. Historically, the field of chloride channels has long been neglected owing to the lack of powerful selective pharmacological agents that are needed to overcome the technical challenge of characterizing the molecular identities of these channels. Recently, members of the LRRC8 family have been shown to be essential for generating the volume-regulated anion channel (VRAC) current, a chloride conductance that governs the regulatory volume decrease (RVD) process. The inhibitory effects of six commonly used chloride channel inhibitors on VRAC/LRRC8-mediated chloride transport were tested in wild-type HEK-293 cells expressing LRRC8 proteins and devoid of other types of chloride channels (CFTR and ANO1/2). We explored the effectiveness of the inhibitors using the patch-clamp whole-cell approach and fluorescence-based quantification of cellular volume changes during hypotonic challenge. Both DCPIB and NFA inhibited VRAC current in a whole-cell configuration, with IC50 values of 5 ± 1 μM and 55 ± 2 μM, respectively. Surprisingly, GlyH-101 and PPQ-102, two CFTR inhibitors, also inhibited VRAC conductance at concentrations in the range of their current use, with IC50 values of 10 ± 1 μM and 20 ± 1 μM, respectively. T16Ainh-A01, a so-called specific inhibitor of calcium-activated Cl- conductance, blocked the chloride current triggered by hypo-osmotic challenge, with an IC50 of 6 ± 1 μM. Moreover, RVD following hypotonic challenge was dramatically reduced by these inhibitors. CFTRinh-172 was the only inhibitor that had almost no effect on VRAC/LRRC8-mediated chloride conductance. All inhibitors tested except CFTRinh-172 inhibited VRAC/LRRC8-mediated chloride conductance and cellular volume changes during hypotonic challenge. These results shed light on the apparent lack of chloride channel inhibitors specificity and raise the question of how these inhibitors actually block chloride conductances.
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Affiliation(s)
- Jonas Friard
- LP2M CNRS-UMR7370, LabEx ICST, Medical Faculty, Université Côte d'AzurNice, France
| | - Michel Tauc
- LP2M CNRS-UMR7370, LabEx ICST, Medical Faculty, Université Côte d'AzurNice, France
| | - Marc Cougnon
- LP2M CNRS-UMR7370, LabEx ICST, Medical Faculty, Université Côte d'AzurNice, France
| | - Vincent Compan
- Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Université de MontpellierMontpellier, France
| | - Christophe Duranton
- LP2M CNRS-UMR7370, LabEx ICST, Medical Faculty, Université Côte d'AzurNice, France
| | - Isabelle Rubera
- LP2M CNRS-UMR7370, LabEx ICST, Medical Faculty, Université Côte d'AzurNice, France
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Volume regulation of intestinal cells of echinoderms: Putative role of ion transporters (Na+/K+-ATPase and NKCC). Comp Biochem Physiol A Mol Integr Physiol 2016; 201:124-131. [DOI: 10.1016/j.cbpa.2016.07.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 07/01/2016] [Accepted: 07/08/2016] [Indexed: 11/24/2022]
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Planells-Cases R, Lutter D, Guyader C, Gerhards NM, Ullrich F, Elger DA, Kucukosmanoglu A, Xu G, Voss FK, Reincke SM, Stauber T, Blomen VA, Vis DJ, Wessels LF, Brummelkamp TR, Borst P, Rottenberg S, Jentsch TJ. Subunit composition of VRAC channels determines substrate specificity and cellular resistance to Pt-based anti-cancer drugs. EMBO J 2015; 34:2993-3008. [PMID: 26530471 PMCID: PMC4687416 DOI: 10.15252/embj.201592409] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 10/05/2015] [Indexed: 11/25/2022] Open
Abstract
Although platinum‐based drugs are widely used chemotherapeutics for cancer treatment, the determinants of tumor cell responsiveness remain poorly understood. We show that the loss of subunits LRRC8A and LRRC8D of the heteromeric LRRC8 volume‐regulated anion channels (VRACs) increased resistance to clinically relevant cisplatin/carboplatin concentrations. Under isotonic conditions, about 50% of cisplatin uptake depended on LRRC8A and LRRC8D, but neither on LRRC8C nor on LRRC8E. Cell swelling strongly enhanced LRRC8‐dependent cisplatin uptake, bolstering the notion that cisplatin enters cells through VRAC. LRRC8A disruption also suppressed drug‐induced apoptosis independently from drug uptake, possibly by impairing VRAC‐dependent apoptotic cell volume decrease. Hence, by mediating cisplatin uptake and facilitating apoptosis, VRAC plays a dual role in the cellular drug response. Incorporation of the LRRC8D subunit into VRAC substantially increased its permeability for cisplatin and the cellular osmolyte taurine, indicating that LRRC8 proteins form the channel pore. Our work suggests that LRRC8D‐containing VRACs are crucial for cell volume regulation by an important organic osmolyte and may influence cisplatin/carboplatin responsiveness of tumors.
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Affiliation(s)
- Rosa Planells-Cases
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Darius Lutter
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Charlotte Guyader
- Division of Molecular Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Nora M Gerhards
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Florian Ullrich
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Deborah A Elger
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Asli Kucukosmanoglu
- Division of Molecular Pathology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Guotai Xu
- Division of Molecular Pathology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Felizia K Voss
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - S Momsen Reincke
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Tobias Stauber
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Vincent A Blomen
- Division of Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Daniel J Vis
- Division of Molecular Carcinogenesis, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Lodewyk F Wessels
- Division of Molecular Carcinogenesis, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Thijn R Brummelkamp
- Division of Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Piet Borst
- Division of Molecular Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Sven Rottenberg
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland Division of Molecular Pathology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
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Song D, Xu J, Hertz L, Peng L. Regulatory volume increase in astrocytes exposed to hypertonic medium requires β1 -adrenergic Na(+) /K(+) -ATPase stimulation and glycogenolysis. J Neurosci Res 2014; 93:130-9. [PMID: 25124094 DOI: 10.1002/jnr.23469] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 06/16/2014] [Accepted: 07/14/2014] [Indexed: 01/30/2023]
Abstract
The cotransporter of Na(+) , K(+) , 2Cl(-) , and water, NKKC1, is activated under two conditions in the brain, exposure to highly elevated extracellular K(+) concentrations, causing astrocytic swelling, and regulatory volume increase in cells shrunk in response to exposure to hypertonic medium. NKCC1-mediated transport occurs as secondary active transport driven by Na(+) /K(+) -ATPase activity, which establishes a favorable ratio for NKCC1 operation between extracellular and intracellular products of the concentrations of Na(+) , K(+) , and Cl(-) × Cl(-) . In the adult brain, astrocytes are the main target for NKCC1 stimulation, and their Na(+) /K(+) -ATPase activity is stimulated by elevated K(+) or the β-adrenergic agonist isoproterenol. Extracellular K(+) concentration is normal during regulatory volume increase, so this study investigated whether the volume increase occurred faster in the presence of isoproterenol. Measurement of cell volume via live cell microscopic imaging fluorescence to record fluorescence intensity of calcein showed that this was the case at isoproterenol concentrations of ≥1 µM in well-differentiated mouse astrocyte cultures incubated in isotonic medium with 100 mM sucrose added. This stimulation was abolished by the β1 -adrenergic antagonist betaxolol, but not by ICI118551, a β2 -adrenergic antagonist. A large part of the β1 -adrenergic signaling pathway in astrocytes is known. Inhibitors of this pathway as well as the glycogenolysis inhibitor 1,4-dideoxy-1,4-imino-D-arabinitol hydrochloride and the NKCC1 inhibitors bumetanide and furosemide abolished stimulation by isoproterenol, and it was weakened by the Na(+) /K(+) -ATPase inhibitor ouabain. These observations are of physiological relevance because extracellular hypertonicity occurs during intense neuronal activity. This might trigger a regulatory volume increase, associated with the post-excitatory undershoot.
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Affiliation(s)
- Dan Song
- Laboratory of Brain Metabolic Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, People's Repbulic of China
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Voss FK, Ullrich F, Münch J, Lazarow K, Lutter D, Mah N, Andrade-Navarro MA, von Kries JP, Stauber T, Jentsch TJ. Identification of LRRC8 heteromers as an essential component of the volume-regulated anion channel VRAC. Science 2014; 344:634-8. [PMID: 24790029 DOI: 10.1126/science.1252826] [Citation(s) in RCA: 442] [Impact Index Per Article: 44.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Regulation of cell volume is critical for many cellular and organismal functions, yet the molecular identity of a key player, the volume-regulated anion channel VRAC, has remained unknown. A genome-wide small interfering RNA screen in mammalian cells identified LRRC8A as a VRAC component. LRRC8A formed heteromers with other LRRC8 multispan membrane proteins. Genomic disruption of LRRC8A ablated VRAC currents. Cells with disruption of all five LRRC8 genes required LRRC8A cotransfection with other LRRC8 isoforms to reconstitute VRAC currents. The isoform combination determined VRAC inactivation kinetics. Taurine flux and regulatory volume decrease also depended on LRRC8 proteins. Our work shows that VRAC defines a class of anion channels, suggests that VRAC is identical to the volume-sensitive organic osmolyte/anion channel VSOAC, and explains the heterogeneity of native VRAC currents.
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Affiliation(s)
- Felizia K Voss
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin
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Pondugula SR, Kampalli SB, Wu T, De Lisle RC, Raveendran NN, Harbidge DG, Marcus DC. cAMP-stimulated Cl- secretion is increased by glucocorticoids and inhibited by bumetanide in semicircular canal duct epithelium. BMC PHYSIOLOGY 2013; 13:6. [PMID: 23537040 PMCID: PMC3622586 DOI: 10.1186/1472-6793-13-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 03/11/2013] [Indexed: 12/13/2022]
Abstract
Background The vestibular system controls the ion composition of its luminal fluid through several epithelial cell transport mechanisms under hormonal regulation. The semicircular canal duct (SCCD) epithelium has been shown to secrete Cl- under β2-adrenergic stimulation. In the current study, we sought to determine the ion transporters involved in Cl- secretion and whether secretion is regulated by PKA and glucocorticoids. Results Short circuit current (Isc) from rat SCCD epithelia demonstrated stimulation by forskolin (EC50: 0.8 μM), 8-Br-cAMP (EC50: 180 μM), 8-pCPT-cAMP (100 μM), IBMX (250 μM), and RO-20-1724 (100 μM). The PKA activator N6-BNZ-cAMP (0.1, 0.3 & 1 mM) also stimulated Isc. Partial inhibition of stimulated Isc individually by bumetanide (10 & 50 μM), and [(dihydroindenyl)oxy]alkanoic acid (DIOA, 100 μM) were additive and complete. Stimulated Isc was also partially inhibited by CFTRinh-172 (5 & 30 μM), flufenamic acid (5 μM) and diphenylamine-2,2′-dicarboxylic acid (DPC; 1 mM). Native canals of CFTR+/− mice showed a stimulation of Isc from isoproterenol and forskolin+IBMX but not in the presence of both bumetanide and DIOA, while canals from CFTR−/− mice had no responses. Nonetheless, CFTR−/− mice showed no difference from CFTR+/− mice in their ability to balance (rota-rod). Stimulated Isc was greater after chronic incubation (24 hr) with the glucocorticoids dexamethasone (0.1 & 0.3 μM), prednisolone (0.3, 1 & 3 μM), hydrocortisone (0.01, 0.1 & 1 μM), and corticosterone (0.1 & 1 μM) and mineralocorticoid aldosterone (1 μM). Steroid action was blocked by mifepristone but not by spironolactone, indicating all the steroids activated the glucocorticoid, but not mineralocorticoid, receptor. Expression of transcripts for CFTR; for KCC1, KCC3a, KCC3b and KCC4, but not KCC2; for NKCC1 but not NKCC2 and for WNK1 but only very low WNK4 was determined. Conclusions These results are consistent with a model of Cl- secretion whereby Cl- is taken up across the basolateral membrane by a Na+-K+-2Cl- cotransporter (NKCC) and potentially another transporter, is secreted across the apical membrane via a Cl- channel, likely CFTR, and demonstrate the regulation of Cl- secretion by protein kinase A and glucocorticoids.
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Davidson AF, Higgins AZ. Detection of Volume Changes in Calcein-Stained Cells Using Confocal Microscopy. J Fluoresc 2013; 23:393-8. [DOI: 10.1007/s10895-013-1202-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 02/24/2013] [Indexed: 11/24/2022]
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Joerges J, Schulz T, Wegner J, Schumacher U, Prehm P. Regulation of cell volume by glycosaminoglycans. J Cell Biochem 2012; 113:340-8. [PMID: 21928313 DOI: 10.1002/jcb.23360] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cell volume is regulated by a delicate balance between ion distribution across the plasma membrane and the osmotic properties of intra- and extracellular components. Using a fluorescent calcein indicator, we analysed the effects of glycosaminoglycans on the cell volume of hyaluronan producing fibroblasts and hyaluronan deficient HEK cells over a time period of 30 h. Exogenous glycosaminoglycans induced cell blebbing after 2 min and swelling of fibroblasts to about 110% of untreated cell volume at low concentrations which decreased at higher concentrations. HEK cells did not show cell blebbing and responded by shrinking to 65% of untreated cell volume. Heparin induced swelling of both fibroblasts and HEK cells. Hyaluronidase treatment or inhibition of hyaluronan export led to cell shrinkage indicating that the hyaluronan coat maintained fibroblasts in a swollen state. These observations were explained by the combined action of the Donnan effect and molecular crowding.
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Affiliation(s)
- Jelena Joerges
- Institute of Physiological Chemistry and Pathobiochemistry, Muenster University Hospital, Waldeyerstrasse 15, D-48149 Münster, Germany
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Garcia-Dorado D, Andres-Villarreal M, Ruiz-Meana M, Inserte J, Barba I. Myocardial edema: A translational view. J Mol Cell Cardiol 2012; 52:931-9. [DOI: 10.1016/j.yjmcc.2012.01.010] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 01/09/2012] [Accepted: 01/10/2012] [Indexed: 12/21/2022]
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Amado EM, Freire CA, Grassi MT, Souza MM. Lead hampers gill cell volume regulation in marine crabs: stronger effect in a weak osmoregulator than in an osmoconformer. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2012; 106-107:95-103. [PMID: 22115908 DOI: 10.1016/j.aquatox.2011.10.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 10/14/2011] [Accepted: 10/23/2011] [Indexed: 05/31/2023]
Abstract
Hepatus pudibundus is a strictly marine osmoconformer crab, while Callinectes ornatus inhabits estuarine areas, behaving as a weak hyper-osmoregulator in diluted seawater. Osmoconformers are expected to have higher capacity for cell volume regulation, but gill cells of a regulator are expected to display ion transporters to a higher degree. The influence of lead nitrate (10 μM) on the ability of isolated gill cells from both species to volume regulate under isosmotic and hyposmotic conditions were here evaluated. Without lead, under a 25% hyposmotic shock, the gill cells of both species were quite capable of cell volume maintenance. Cells of C. ornatus, however, had a little swelling (5%) during the hyposmotic shock of greater intensity (50%), while cells of H. pudibundus were still capable of volume regulation. In the presence of lead, even under isosmoticity, the gill cells of both species showed about 10% volume reduction, indicating that lead promotes the loss of water by the cells. When lead was associated with 25% and 50% hyposmotic shock, C. ornatus cells lost more volume (15%), when compared to isosmotic conditions, while H. pudibundus cells showed volume regulation. We then analyzed the possible ways of action of lead on the mechanisms of cell volume regulation in the two species. Verapamil (100 μM) was used to inhibit Ca²⁺ channels, ouabain (100 μM) to inhibit Na⁺/K⁺-ATPase, and HgCl₂ (100 μM) to inhibit aquaporins. Our results suggest that: (1) Ca²⁺ channels are candidates for lead entry into gill cells of H. pudibundus and C. ornatus, being the target of lead action in these cells; (2) aquaporins are much more relevant for water flux in H. pudibundus; and (3) the Na⁺/K⁺-ATPase is much more relevant for volume regulation in C. ornatus. Osmoregulators may be more susceptible to metal contamination than osmoconformers, especially in situations of reduced salinity, for two basic reasons: (1) lower capacity of volume regulation and (2) putative higher uptake of Pb²⁺ through ionic pathways that operate in salt absorption, such as, for example, the Na⁺/K⁺-ATPase.
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Affiliation(s)
- Enelise M Amado
- Departamento de Fisiologia, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba, Paraná, Brazil
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Wang Z, Bildin VN, Yang H, Capó-Aponte JE, Yang Y, Reinach PS. Dependence of corneal epithelial cell proliferation on modulation of interactions between ERK1/2 and NKCC1. Cell Physiol Biochem 2011; 28:703-14. [PMID: 22178882 DOI: 10.1159/000335764] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/12/2011] [Indexed: 11/19/2022] Open
Abstract
Epidermal growth factor (EGF) receptor stimulation or protein kinase C (PKC) activation enhances corneal epithelial cell proliferation. This response is needed to maintain corneal transparency and vision. We clarify here in human corneal epithelial cells (HCEC) the cause and effect relationships between ERK1/2 and NKCC1 phosphorylation induced by EGF receptor or PKC activation. Furthermore, the roles are evaluated of NF-κB and ERK1/2 in mediating negative feedback control of ERK1/2 and NKCC1 phosphorylation through modulating DUSP1 and DUSP6 expression levels. Intracellular Ca(2+) rises induced by EGF elicited NKCC1 phosphorylation through ERK1/2 activation. Bumetanide suppressed EGF-induced NKCC1 phosphorylation, transient cell swelling and cell proliferation. This cause and effect relationship is similar to that induced by PKC stimulation. NKCC1 activation occurred through time-dependent increases in protein-protein interaction between ERK1/2 and NKCC1, which were proportional to EGF concentration. DUSP6 upregulation obviated EGF and PKC-induced NKCC1 phosphorylation. NF-κB inhibition by PDTC prolonged ERK1/2 activation through GSK-3 inactivation leading to declines in DUSP1 expression levels. These results show that EGF receptor and PKC activation induce increases in HCEC proliferation through ERK1/2 interaction with NKCC1. This response is modulated by changes in DUSP1- and DUSP6-mediated negative feedback control of ERK1/2-induced NKCC1 phosphorylation.
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Affiliation(s)
- Zheng Wang
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
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Nishisako H, Ikehara T, Shiraishi T, Minami Y, Sasaki HI, Houchi H, Kawazoe K, Minakuchi K, Kitamura M, Shono M, Yoshizaki K, Kinouchi Y, Miyamoto H. Effects of a 1.5 T time-varying magnetic field on cell volume regulation of bovine adrenal chromaffin cells in hyposmotic media. THE JOURNAL OF MEDICAL INVESTIGATION 2011; 58:95-105. [PMID: 21372493 DOI: 10.2152/jmi.58.95] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Effects of a time-varying magnetic field on cell volume regulation by hyposmotic stress in cultured bovine adrenal chromaffin cells were examined. Through regulatory volume decrease (RVD), cell volume of chromaffin cells that were incubated in a hypotonic medium initially increased, reached a peak and finally recovered to the initial value. Two hour exposure to a magnetic field and addition of cytochalasin D increased peak value and delayed return to initial value. Intracellular F-actin contents initially decreased but returned to normal levels after 10 sec. Two hour exposure to the magnetic field and addition of cytochalasin D continuously reduced the F-actin content. Results suggest that exposure to the magnetic field stimulated disruption of the actin cytoskeleton and that the disruption delayed the recovery to the volume prior to osmotic stress.
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Analysis of Solution Exchange in Flow Chambers with Applications to Cell Membrane Permeability Measurement. Cell Mol Bioeng 2010. [DOI: 10.1007/s12195-010-0125-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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Klokkers J, Langehanenberg P, Kemper B, Kosmeier S, von Bally G, Riethmüller C, Wunder F, Sindic A, Pavenstädt H, Schlatter E, Edemir B. Atrial natriuretic peptide and nitric oxide signaling antagonizes vasopressin-mediated water permeability in inner medullary collecting duct cells. Am J Physiol Renal Physiol 2009; 297:F693-703. [PMID: 19570884 DOI: 10.1152/ajprenal.00136.2009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
AVP and atrial natriuretic peptide (ANP) have opposite effects in the kidney. AVP induces antidiuresis by insertion of aquaporin-2 (AQP2) water channels into the plasma membrane of collecting duct principal cells. ANP acts as a diuretic factor. An ANP- and nitric oxide (NO)/soluble guanylate cyclase (sGC)-induced insertion of AQP2 into the plasma membrane is reported from different models. However, functional data on the insertion of AQP2 is missing. We used primary cultured inner medullary collecting duct (IMCD) cells and digital holographic microscopy, calcein-quenching measurements, and immunofluorescence and Western blotting to analyze the effects of ANP and NO donors on AQP2 phosphorylation, membrane expression, and water permeability. While AVP led to acceleration in osmotically induced swelling, ANP had no effect. However, in AVP-pretreated cells ANP significantly decreased the kinetics of cell swelling. This effect was mimicked by 8-bromo-cGMP and blunted by PKG inhibition. Stimulation of the NO/sGC pathway or direct activation of sGC with BAY 58-2667 had similar effects to ANP. In cells treated with AVP, AQP2 was predominantly localized in the plasma membrane, and after additional incubation with ANP AQP2 was mostly localized in the cytosol, indicating an increased retrieval of AQP2 from the plasma membrane by ANP. Western blot analysis showed that ANP was able to reduce AVP-induced phosphorylation of AQP2 at position S256. In conclusion, we show that the diuretic action of ANP or NO in the IMCD involves a decreased localization of AQP2 in the plasma membrane which is mediated by cGMP and PKG.
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Affiliation(s)
- Jens Klokkers
- Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Universitätsklinikum Münster, Münster, Germany
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Pan Z, Yang H, Mergler S, Liu H, Tachado SD, Zhang F, Kao WWY, Koziel H, Pleyer U, Reinach PS. Dependence of regulatory volume decrease on transient receptor potential vanilloid 4 (TRPV4) expression in human corneal epithelial cells. Cell Calcium 2009; 44:374-85. [PMID: 18355916 DOI: 10.1016/j.ceca.2008.01.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Revised: 01/30/2008] [Accepted: 01/31/2008] [Indexed: 11/28/2022]
Abstract
TRPV4 is a non-selective cation channel with moderate calcium permeability, which is activated by exposure to hypotonicity. Such a stress induces regulatory volume decrease (RVD) behavior in human corneal epithelial cells (HCEC). We hypothesize that TRPV4 channel mediates RVD in HCEC. Immunohistochemistry revealed centrally and superficially concentrated TRPV4 localization in the corneal tissue. Immunocytochemical and fluorescence activated cell sorter (FACS) analyses identified TRPV4 membrane surface and cytosolic expression. RT-PCR and Western blot analyses identified TRPV4 gene and protein expression in HCEC, respectively. In addition, 4alpha-PDD or a 50% hypotonic medium induced up to threefold transient intracellular Ca2+ ([Ca2+]i) increases. Following TRPV4 siRNA HCEC transfection, its protein expression level declined by 64%, which abrogated these [Ca2+]i transients. Similarly, exposure to either ruthenium red or Ca(2+)-free Ringer's solution also eliminated this response. In these transfected cells, RVD declined by 51% whereas in the non-transfected counterpart, ruthenium red and Ca(2+)-free solution inhibited RVD by 54 and 64%, respectively. In contrast, capsazepine, a TRPV1 antagonist, failed to suppress [Ca2+]i transients and RVD. TRPV4 activation contributes to RVD since declines in TRPV4 expression and activity are associated with suppression of this response. In conclusion, there is TRPV4 functional expression in HCEC.
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Affiliation(s)
- Zan Pan
- Department of Biological Sciences, State University of New York, College of Optometry, 33 West 42nd Street, New York, NY 10036, USA
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Du T, Song D, Li H, Li B, Cai L, Hertz L, Peng L. Stimulation by vasopressin of ERK phosphorylation and vector-driven water flux in astrocytes is transactivation-dependent. Eur J Pharmacol 2008; 587:73-7. [DOI: 10.1016/j.ejphar.2008.03.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 03/03/2008] [Accepted: 03/14/2008] [Indexed: 11/16/2022]
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Lauf PK, Misri S, Chimote AA, Adragna NC. Apparent intermediate K conductance channel hyposmotic activation in human lens epithelial cells. Am J Physiol Cell Physiol 2008; 294:C820-32. [PMID: 18184876 DOI: 10.1152/ajpcell.00375.2007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study explores the nature of K fluxes in human lens epithelial cells (LECs) in hyposmotic solutions. Total ion fluxes, Na-K pump, Cl-dependent Na-K-2Cl (NKCC), K-Cl (KCC) cotransport, and K channels were determined by 85Rb uptake and cell K (Kc) by atomic absorption spectrophotometry, and cell water gravimetrically after exposure to ouabain +/- bumetanide (Na-K pump and NKCC inhibitors), and ion channel inhibitors in varying osmolalities with Na, K, or methyl-d-glucamine and Cl, sulfamate, or nitrate. Reverse transcriptase polymerase chain reaction (RT-PCR), Western blot analyses, and immunochemistry were also performed. In isosmotic (300 mosM) media approximately 90% of the total Rb influx occurred through the Na-K pump and NKCC and approximately 10% through KCC and a residual leak. Hyposmotic media (150 mosM) decreased K(c) by a 16-fold higher K permeability and cell water, but failed to inactivate NKCC and activate KCC. Sucrose replacement or extracellular K to >57 mM, but not Rb or Cs, in hyposmotic media prevented Kc and water loss. Rb influx equaled Kc loss, both blocked by clotrimazole (IC50 approximately 25 microM) and partially by 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) inhibitors of the IK channel KCa3.1 but not by other K channel or connexin hemichannel blockers. Of several anion channel blockers (dihydro-indenyl)oxy]alkanoic acid (DIOA), 4-2(butyl-6,7-dichloro-2-cyclopentylindan-1-on-5-yl)oxybutyric acid (DCPIB), and phloretin totally or partially inhibited Kc loss and Rb influx, respectively. RT-PCR and immunochemistry confirmed the presence of KCa3.1 channels, aside of the KCC1, KCC2, KCC3 and KCC4 isoforms. Apparently, IK channels, possibly in parallel with volume-sensitive outwardly rectifying Cl channels, effect regulatory volume decrease in LECs.
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Affiliation(s)
- Peter K Lauf
- Cell Biophysics Group, 054 Biological Sciences Bldg., Wright State Univ. Boonshoft School of Medicine, Dayton, OH 45435, USA.
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Capó-Aponte JE, Wang Z, Bildin VN, Iserovich P, Pan Z, Zhang F, Pokorny KS, Reinach PS. Functional and molecular characterization of multiple K-Cl cotransporter isoforms in corneal epithelial cells. Exp Eye Res 2007; 84:1090-103. [PMID: 17418819 PMCID: PMC2696115 DOI: 10.1016/j.exer.2007.02.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Revised: 12/19/2006] [Accepted: 02/06/2007] [Indexed: 11/20/2022]
Abstract
The dependence of regulatory volume decrease (RVD) activity on potassium-chloride cotransporter (KCC) isoform expression was characterized in corneal epithelial cells (CEC). During exposure to a 50% hypotonic challenge, the RVD response was larger in SV40-immortalized human CEC (HCEC) than in SV40-immortalized rabbit CEC (RCEC). A KCC inhibitor-[(dihydroindenyl)oxy] alkanoic acid (DIOA)-blocked RVD more in HCEC than RCEC. Under isotonic conditions, N-ethylmaleimide (NEM) produced KCC activation and transient cell shrinkage. Both of these changes were greater in HCEC than in RCEC. Immunoblot analysis of HCEC, RCEC, primary human CEC (pHCEC), and primary bovine CEC (BCEC) plasma membrane enriched fractions revealed KCC1, KCC3, and KCC4 isoform expression, whereas KCC2 was undetectable. During a hypotonic challenge, KCC1 membrane content increased more rapidly in HCEC than in RCEC. Such a challenge induced a larger increase and more transient p44/42MAPK activation in HCEC than RCEC. On the other hand, HCEC and RCEC p38MAPK phosphorylation reached peak activations at 2.5 and 15 min, respectively. Only in HCEC, pharmacological manipulation of KCC activity modified the hypotonicity-induced activation of p44/42MAPK, whereas p38MAPK phosphorylation was insensitive to such procedures in both cell lines. Larger increases in HCEC KCC1 membrane protein content correlated with their ability to undergo faster and more complete RVD. Furthermore, pharmacological activation of KCC increased p44/42MAPK phosphorylation in HCEC but not in RCEC, presumably a reflection of low KCC1 membrane expression in RCEC. These findings suggest that KCC1 plays a role in (i) maintaining isotonic steady-state cell volume homeostasis, (ii) recovery of isotonic cell volume after a hypotonic challenge through RVD, and (iii) regulating hypotonicity-induced activation of the p44/42MAPK signaling pathway required for cell proliferation.
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Affiliation(s)
- José E. Capó-Aponte
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Zheng Wang
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Victor N. Bildin
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Pavel Iserovich
- Department of Ophthalmology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
| | - Zan Pan
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Fan Zhang
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Kathryn S. Pokorny
- The Institute of Ophthalmology & Visual Science, New Jersey Medical School, University of Medicine & Dentistry, Newark, NJ 07101, USA
| | - Peter S. Reinach
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
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Chen LX, Zhu LY, Jacob TJC, Wang LW. Roles of volume-activated Cl- currents and regulatory volume decrease in the cell cycle and proliferation in nasopharyngeal carcinoma cells. Cell Prolif 2007; 40:253-67. [PMID: 17472731 PMCID: PMC6496325 DOI: 10.1111/j.1365-2184.2007.00432.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Accepted: 10/31/2006] [Indexed: 11/30/2022] Open
Abstract
OBJECTIVES Previously it has been shown, that the volume-activated plasma membrane chloride channel is associated with regulatory volume decrease (RVD) of cells and may play an important role in control of cell proliferation. We have demonstrated that both expression of the channel and RVD capacity are actively regulated in the cell cycle. In this study, we aimed to further study the role of the volume-activated chloride current and RVD in cell cycle progression and overall in cell proliferation. MATERIALS AND METHODS Whole-cell currents, RVD, cell cycle distribution, cell proliferation and cell viability were measured or detected with the patch-clamp technique, the cell image analysis technique, flow cytometry, the MTT assay and the trypan blue assay respectively, in nasopharyngeal carcinoma cells (CNE-2Z cells). RESULTS The Cl- channel blockers, 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen, inhibit the volume-activated chloride current, RVD and proliferation of CNE-2Z cells in a dose-dependent manner. Analysis of relationships between the current, RVD and cell proliferation showed that both the current and RVD were positively correlated with cell proliferation. NPPB (100 microM) and tamoxifen (20 microM) did not significantly induce cell death, but inhibited cell proliferation, implying that the blockers may inhibit cell proliferation by affecting cell cycle progression. This was verified by the observation that tamoxifen (20 microM) and NPPB (100 microM) inhibited cell cycle progress and arrested cells at the G0/G1 phase boundary. CONCLUSIONS Activity of the volume-activated chloride channel is one of the important factors that regulate the passage of cells through the G1 restriction point and that the Cl- current associated with RVD plays an important role in cell proliferation.
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Affiliation(s)
- L X Chen
- Medical College, Jinan University, Guangzhou, China
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Pan Z, Capó-Aponte JE, Zhang F, Wang Z, Pokorny KS, Reinach PS. Differential dependence of regulatory volume decrease behavior in rabbit corneal epithelial cells on MAPK superfamily activation. Exp Eye Res 2007; 84:978-90. [PMID: 17397832 PMCID: PMC2747597 DOI: 10.1016/j.exer.2007.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2006] [Revised: 01/31/2007] [Accepted: 02/02/2007] [Indexed: 12/18/2022]
Abstract
We characterized the dependence of hypotonicity-induced regulatory volume decrease (RVD) responses on mitogen-activated protein kinase (MAPK) pathway signaling in SV40-immortalized rabbit corneal epithelial cells (RCEC). Following calcein-AM loading, RVD was monitored using a microplate fluorescence reader. Western blot analysis determined MAPK activation. After 30 min, the RVD response restored the relative cell volume to nearly isotonic values, whereas it was inhibited when cells were bathed either in a Cl- -free solution or with the Cl- -channel inhibitors: 5-nitro-2-(3-phenylpropylamino)benzoic acid or niflumic acid. Similar declines occurred with either a high-K+ (20 mM) supplemented solution or the K+ channel inhibitor 4-aminopyridine. Activation of extracellular signal-regulated kinase (ERK), p38, and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) was time and tonicity-dependent. Stimulation of ERK and SAPK/JNK was maximized earlier than that of p38. Activation of ERK and SAPK/JNK was insensitive to Cl- and K+ channel inhibitors, whereas inhibition with either PD98059 or SP600125, respectively, blocked RVD. However, inhibition of p38 with SB203580had no effect on RVD. Suppression of RVD instead blocked p38 activation. Differences in the dependence of RVD activation on Erk1/2 and p38 signaling were validated in dominant negative (d/n)-Erk1 and d/n-p38 cells. Volume-sensitive Cl- and K+ channel activation contributes, in concert, to RVD in RCEC. Therefore, swelling-induced ERK and SAPK/JNK stimulation precedes Cl- and K+ channel activation, whereas p38 activation occurs as a consequence of RVD.
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Affiliation(s)
- Zan Pan
- Department of Biological Sciences, State College of Optometry, State University of New York, New York, NY 10036, USA
| | - José E. Capó-Aponte
- Department of Biological Sciences, State College of Optometry, State University of New York, New York, NY 10036, USA
| | - Fan Zhang
- Department of Biological Sciences, State College of Optometry, State University of New York, New York, NY 10036, USA
| | - Zheng Wang
- Department of Biological Sciences, State College of Optometry, State University of New York, New York, NY 10036, USA
| | - Kathryn S. Pokorny
- The Institute of Ophthalmology and Visual Science, University of Medicine & Dentistry, New Jersey Medical School, Newark. NJ 07101
| | - Peter S. Reinach
- Department of Biological Sciences, State College of Optometry, State University of New York, New York, NY 10036, USA
- Corresponding Author. Peter S. Reinach, 33 West 42nd Street, New York, NY 10036, USA. Telephone: 1 212 938 5785, Fax: 1 212 938 5794, (P.S. Reinach)
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Klein T, Cooper TG, Yeung CH. The role of potassium chloride cotransporters in murine and human sperm volume regulation. Biol Reprod 2006; 75:853-8. [PMID: 16943364 DOI: 10.1095/biolreprod.106.054064] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Spermatozoa need to undergo regulatory volume decrease (RVD) upon ejaculation to counteract swelling due to the hypo-osmolality of female tract fluids. Defects in sperm RVD lead to failure in both cervical mucus penetration in humans and utero-tubal junction passage in mice. The role of K/Cl cotransporters (KCCs) in RVD was investigated by incubation of spermatozoa from the murine cauda epididymidis and from human ejaculates in media mimicking female tract fluid osmolalities in the presence of KCC inhibitors. Furosemide at 100 microM or more caused swelling of murine spermatozoa as detected with a flow cytometer by increased laser forward scatter over 30 to 75 min of incubation. Bumetanide, known to have low affinity for KCCs, was effective at 1 mM, whereas 10 microM and 20 microM of the specific inhibitor DIOA (dihydroindenyl-oxy alkanoic acid) increased cell volume. These drug doses were ineffective in human spermatozoa, which, however, responded to quinine, confirming the occurrence of RVD under control conditions. The molecular identity of the murine KCC isoform involved was determined at both mRNA and protein levels. Conventional RT-PCR indicated the presence of transcripts from Slc12a4 (KCC1), Slc12a6 (KCC3), and Slc12a7 (KCC4) in the testis, whereas RT-nested PCR revealed the latter two isoforms in sperm mRNA. Of these three isoforms, only SLC12A7 (KCC4) was detected in murine sperm protein by Western blotting. Therefore, besides organic osmolyte efflux and KCl release through separate K(+) and Cl(-) ion channels, SLC12A7 also is involved in murine but not human sperm RVD mechanisms.
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Affiliation(s)
- T Klein
- Institute of Reproductive Medicine, University of Münster, D-48129 Münster, Germany
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