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Kostritskaia Y, Klüssendorf M, Pan YE, Hassani Nia F, Kostova S, Stauber T. Physiological Functions of the Volume-Regulated Anion Channel VRAC/LRRC8 and the Proton-Activated Chloride Channel ASOR/TMEM206. Handb Exp Pharmacol 2024; 283:181-218. [PMID: 37468723 DOI: 10.1007/164_2023_673] [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] [Indexed: 07/21/2023]
Abstract
Volume-regulated anion channels (VRACs) and the acid-sensitive outwardly rectifying anion channel (ASOR) mediate flux of chloride and small organic anions. Although known for a long time, they were only recently identified at the molecular level. VRACs are heteromers consisting of LRRC8 proteins A to E. Combining the essential LRRC8A with different LRRC8 paralogues changes key properties of VRAC such as conductance or substrate selectivity, which is how VRACs are involved in multiple physiological functions including regulatory volume decrease, cell proliferation and migration, cell death, purinergic signalling, fat and glucose metabolism, insulin signalling, and spermiogenesis. VRACs are also involved in pathological conditions, such as the neurotoxic release of glutamate and aspartate. Certain VRACs are also permeable to larger, organic anions, including antibiotics and anti-cancer drugs, making them an interesting therapeutic target. ASOR, also named proton-activated chloride channel (PAC), is formed by TMEM206 homotrimers on the plasma membrane and on endosomal compartments where it mediates chloride flux in response to extracytosolic acidification and plays a role in the shrinking and maturation of macropinosomes. ASOR has been shown to underlie neuronal swelling which causes cell death after stroke as well as promoting the metastasis of certain cancers, making them intriguing therapeutic targets as well.
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Affiliation(s)
- Yulia Kostritskaia
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Malte Klüssendorf
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Yingzhou Edward Pan
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Fatemeh Hassani Nia
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Simona Kostova
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Tobias Stauber
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany.
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2
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Okada Y, Sabirov RZ, Merzlyak PG, Numata T, Sato-Numata K. Properties, Structures, and Physiological Roles of Three Types of Anion Channels Molecularly Identified in the 2010's. Front Physiol 2022; 12:805148. [PMID: 35002778 PMCID: PMC8733619 DOI: 10.3389/fphys.2021.805148] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 12/06/2021] [Indexed: 11/24/2022] Open
Abstract
Molecular identification was, at last, successfully accomplished for three types of anion channels that are all implicated in cell volume regulation/dysregulation. LRRC8A plus LRRC8C/D/E, SLCO2A1, and TMEM206 were shown to be the core or pore-forming molecules of the volume-sensitive outwardly rectifying anion channel (VSOR) also called the volume-regulated anion channel (VRAC), the large-conductance maxi-anion channel (Maxi-Cl), and the acid-sensitive outwardly rectifying anion channel (ASOR) also called the proton-activated anion channel (PAC) in 2014, 2017, and 2019, respectively. More recently in 2020 and 2021, we have identified the S100A10-annexin A2 complex and TRPM7 as the regulatory proteins for Maxi-Cl and VSOR/VRAC, respectively. In this review article, we summarize their biophysical and structural properties as well as their physiological roles by comparing with each other on the basis of their molecular insights. We also point out unsolved important issues to be elucidated soon in the future.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences (NIPS), Okazaki, Japan.,Department of Physiology, School of Medicine, Aichi Medical University, Nagakute, Japan.,Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan.,Cardiovascular Research Institute, Yokohama City University, Yokohama, Japan
| | - Ravshan Z Sabirov
- Laboratory of Molecular Physiology, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Petr G Merzlyak
- Laboratory of Molecular Physiology, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Tomohiro Numata
- Department of Integrative Physiology, Graduate School of Medicine, Akita University, Akita, Japan
| | - Kaori Sato-Numata
- Department of Integrative Physiology, Graduate School of Medicine, Akita University, Akita, Japan.,Japan Society for the Promotion of Science, Tokyo, Japan
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3
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Okada Y, Sato-Numata K, Sabirov RZ, Numata T. Cell Death Induction and Protection by Activation of Ubiquitously Expressed Anion/Cation Channels. Part 2: Functional and Molecular Properties of ASOR/PAC Channels and Their Roles in Cell Volume Dysregulation and Acidotoxic Cell Death. Front Cell Dev Biol 2021; 9:702317. [PMID: 34307382 PMCID: PMC8299559 DOI: 10.3389/fcell.2021.702317] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/18/2021] [Indexed: 12/18/2022] Open
Abstract
For survival and functions of animal cells, cell volume regulation (CVR) is essential. Major hallmarks of necrotic and apoptotic cell death are persistent cell swelling and shrinkage, and thus they are termed the necrotic volume increase (NVI) and the apoptotic volume decrease (AVD), respectively. A number of ubiquitously expressed anion and cation channels play essential roles not only in CVR but also in cell death induction. This series of review articles address the question how cell death is induced or protected with using ubiquitously expressed ion channels such as swelling-activated anion channels, acid-activated anion channels, and several types of TRP cation channels including TRPM2 and TRPM7. In the Part 1, we described the roles of swelling-activated VSOR/VRAC anion channels. Here, the Part 2 focuses on the roles of the acid-sensitive outwardly rectifying (ASOR) anion channel, also called the proton-activated chloride (PAC) anion channel, which is activated by extracellular protons in a manner sharply dependent on ambient temperature. First, we summarize phenotypical properties, the molecular identity, and the three-dimensional structure of ASOR/PAC. Second, we highlight the unique roles of ASOR/PAC in CVR dysfunction and in the induction of or protection from acidotoxic cell death under acidosis and ischemic conditions.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences (NIPS), Okazaki, Japan.,Department of Physiology, School of Medicine, Aichi Medical University, Nagakute, Japan.,Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Kaori Sato-Numata
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan.,Japan Society for the Promotion of Science, Tokyo, Japan
| | - Ravshan Z Sabirov
- Laboratory of Molecular Physiology, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Tomohiro Numata
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan
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4
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Ritter M, Bresgen N, Kerschbaum HH. From Pinocytosis to Methuosis-Fluid Consumption as a Risk Factor for Cell Death. Front Cell Dev Biol 2021; 9:651982. [PMID: 34249909 PMCID: PMC8261248 DOI: 10.3389/fcell.2021.651982] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 04/29/2021] [Indexed: 12/11/2022] Open
Abstract
The volumes of a cell [cell volume (CV)] and its organelles are adjusted by osmoregulatory processes. During pinocytosis, extracellular fluid volume equivalent to its CV is incorporated within an hour and membrane area equivalent to the cell's surface within 30 min. Since neither fluid uptake nor membrane consumption leads to swelling or shrinkage, cells must be equipped with potent volume regulatory mechanisms. Normally, cells respond to outwardly or inwardly directed osmotic gradients by a volume decrease and increase, respectively, i.e., they shrink or swell but then try to recover their CV. However, when a cell death (CD) pathway is triggered, CV persistently decreases in isotonic conditions in apoptosis and it increases in necrosis. One type of CD associated with cell swelling is due to a dysfunctional pinocytosis. Methuosis, a non-apoptotic CD phenotype, occurs when cells accumulate too much fluid by macropinocytosis. In contrast to functional pinocytosis, in methuosis, macropinosomes neither recycle nor fuse with lysosomes but with each other to form giant vacuoles, which finally cause rupture of the plasma membrane (PM). Understanding methuosis longs for the understanding of the ionic mechanisms of cell volume regulation (CVR) and vesicular volume regulation (VVR). In nascent macropinosomes, ion channels and transporters are derived from the PM. Along trafficking from the PM to the perinuclear area, the equipment of channels and transporters of the vesicle membrane changes by retrieval, addition, and recycling from and back to the PM, causing profound changes in vesicular ion concentrations, acidification, and-most importantly-shrinkage of the macropinosome, which is indispensable for its proper targeting and cargo processing. In this review, we discuss ion and water transport mechanisms with respect to CVR and VVR and with special emphasis on pinocytosis and methuosis. We describe various aspects of the complex mutual interplay between extracellular and intracellular ions and ion gradients, the PM and vesicular membrane, phosphoinositides, monomeric G proteins and their targets, as well as the submembranous cytoskeleton. Our aim is to highlight important cellular mechanisms, components, and processes that may lead to methuotic CD upon their derangement.
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Affiliation(s)
- Markus Ritter
- Center for Physiology, Pathophysiology and Biophysics, Institute for Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria
- Institute for Physiology and Pathophysiology, Paracelsus Medical University, Nuremberg, Germany
- Gastein Research Institute, Paracelsus Medical University, Salzburg, Austria
- Ludwig Boltzmann Institute for Arthritis und Rehabilitation, Salzburg, Austria
- Kathmandu University School of Medical Sciences, Dhulikhel, Nepal
| | - Nikolaus Bresgen
- Department of Biosciences, University of Salzburg, Salzburg, Austria
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5
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Deng Z, Zhao Y, Feng J, Zhang J, Zhao H, Rau MJ, Fitzpatrick JAJ, Hu H, Yuan P. Cryo-EM structure of a proton-activated chloride channel TMEM206. SCIENCE ADVANCES 2021; 7:7/9/eabe5983. [PMID: 33627432 PMCID: PMC7904269 DOI: 10.1126/sciadv.abe5983] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 01/08/2021] [Indexed: 05/12/2023]
Abstract
TMEM206 has been recently identified as an evolutionarily conserved chloride channel that underlies ubiquitously expressed, proton-activated, outwardly rectifying anion currents. Here, we report the cryo-electron microscopy structure of pufferfish TMEM206, which forms a trimeric channel, with each subunit comprising two transmembrane segments and a large extracellular domain. An ample vestibule in the extracellular region is accessible laterally from the three side portals. The central pore contains multiple constrictions. A conserved lysine residue near the cytoplasmic end of the inner helix forms the presumed chloride ion selectivity filter. Unprecedentedly, the core structure and assembly closely resemble those of the epithelial sodium channel/degenerin family of sodium channels that are unrelated in amino acid sequence and conduct cations instead of anions. Together with electrophysiology, this work provides insights into ion conduction and gating for a new class of chloride channels that is architecturally distinct from previously characterized chloride channel families.
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Affiliation(s)
- Zengqin Deng
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Yonghui Zhao
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Jing Feng
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Haiyan Zhao
- Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Michael J Rau
- Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - James A J Fitzpatrick
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | - Hongzhen Hu
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
- Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA.
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110, USA
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6
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Kittl M, Winklmayr M, Helm K, Lettner J, Gaisberger M, Ritter M, Jakab M. Acid- and Volume-Sensitive Chloride Currents in Human Chondrocytes. Front Cell Dev Biol 2020; 8:583131. [PMID: 33282866 PMCID: PMC7691427 DOI: 10.3389/fcell.2020.583131] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 10/13/2020] [Indexed: 12/18/2022] Open
Abstract
Chondrocytes face extreme alterations of extracellular osmolarity and pH, which force them to appropriately regulate their cell volume (CV) and cellular pH. Perturbations of these mechanisms lead to chondrocyte death and ultimately to osteoarthritis (OA), the most common chronic joint diseases worldwide. OA hallmarks are altered cartilage hydration and severe fluid acidification. Impaired CV regulation and acidotoxicity contribute to disease progression and volume-sensitive anion channels are upregulated in OA. This study assessed the effect of hypotonicity and extracellular acidification on chondrocyte Cl– conductances and CV regulation. Cl– currents and membrane potentials were measured in human C28/I2 cells and primary human chondrocytes using the patch clamp technique. Intracellular pH was assessed by BCECF fluorescence, CV measurements were performed using the Coulter method, and cell viability/cell death by a resazurin assay. Hypotonic cell swelling caused activation of a volume-sensitive outwardly rectifying (VSOR) Cl– current followed by a regulatory volume decrease (RVD), which was attenuated by the Cl– channel blocker DCPIB. Extracellular, but not intracellular acidification to pH ≤ 5.0 elicited an acid-sensitive outwardly rectifying (ASOR) Cl– conductance. Activation of either current depolarized the cell membrane potential. Under simultaneous hypotonic and acidic stimulation, VSOR and ASOR currents transiently coactivated, giving rise to a mixed current phenotype. Over time the VSOR current gradually vanished and the residual conductance showed a pure ASOR current phenotype. Extracellular acidification caused an isotonic CV gain and a complete suppression of RVD under hypotonic conditions. The results suggest that deactivation of the VSOR current under acidic conditions impairs CV regulation in chondrocytes, which is likely to compromise chondrocyte viability.
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Affiliation(s)
- Michael Kittl
- Institute of Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria
| | - Martina Winklmayr
- Ludwig Boltzmann Institute for Arthritis and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
| | - Katharina Helm
- Institute of Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria
| | - Johannes Lettner
- Institute of Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria
| | - Martin Gaisberger
- Institute of Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria.,Ludwig Boltzmann Institute for Arthritis and Rehabilitation, Paracelsus Medical University, Salzburg, Austria.,Gastein Research Institute, Paracelsus Medical University, Salzburg, Austria
| | - Markus Ritter
- Institute of Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria.,Ludwig Boltzmann Institute for Arthritis and Rehabilitation, Paracelsus Medical University, Salzburg, Austria.,Gastein Research Institute, Paracelsus Medical University, Salzburg, Austria
| | - Martin Jakab
- Institute of Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria
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Zajac M, Chakraborty K, Saha S, Mahadevan V, Infield DT, Accardi A, Qiu Z, Krishnan Y. What biologists want from their chloride reporters – a conversation between chemists and biologists. J Cell Sci 2020; 133:133/2/jcs240390. [DOI: 10.1242/jcs.240390] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
ABSTRACT
Impaired chloride transport affects diverse processes ranging from neuron excitability to water secretion, which underlie epilepsy and cystic fibrosis, respectively. The ability to image chloride fluxes with fluorescent probes has been essential for the investigation of the roles of chloride channels and transporters in health and disease. Therefore, developing effective fluorescent chloride reporters is critical to characterizing chloride transporters and discovering new ones. However, each chloride channel or transporter has a unique functional context that demands a suite of chloride probes with appropriate sensing characteristics. This Review seeks to juxtapose the biology of chloride transport with the chemistries underlying chloride sensors by exploring the various biological roles of chloride and highlighting the insights delivered by studies using chloride reporters. We then delineate the evolution of small-molecule sensors and genetically encoded chloride reporters. Finally, we analyze discussions with chloride biologists to identify the advantages and limitations of sensors in each biological context, as well as to recognize the key design challenges that must be overcome for developing the next generation of chloride sensors.
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Affiliation(s)
- Matthew Zajac
- Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA
- Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Kasturi Chakraborty
- Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA
- Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL 60637, USA
| | - Sonali Saha
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Vivek Mahadevan
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Daniel T. Infield
- Department of Molecular Physiology and Biophysics, The University of Iowa, Iowa City, IA 52242, USA
| | - Alessio Accardi
- Department of Anesthesiology, Weill Cornell Medical School, New York, NY 10065, USA
- Department of Physiology and Biophysics, Weill Cornell Medical School, New York, NY 10065, USA
- Department of Biochemistry, Weill Cornell Medical School, New York, NY 10065, USA
| | - Zhaozhu Qiu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA
| | - Yamuna Krishnan
- Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA
- Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
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8
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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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9
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Acid- and Volume-Sensitive Chloride Currents in Microglial Cells. Int J Mol Sci 2019; 20:ijms20143475. [PMID: 31311135 PMCID: PMC6678294 DOI: 10.3390/ijms20143475] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/11/2019] [Accepted: 07/12/2019] [Indexed: 01/27/2023] Open
Abstract
Many cell types express an acid-sensitive outwardly rectifying (ASOR) anion current of an unknown function. We characterized such a current in BV-2 microglial cells and then studied its interrelation with the volume-sensitive outwardly rectifying (VSOR) Cl− current and the effect of acidosis on cell volume regulation. We used patch clamp, the Coulter method, and the pH-sensitive dye BCECF to measure Cl− currents and cell membrane potentials, mean cell volume, and intracellular pH, respectively. The ASOR current activated at pH ≤ 5.0 and displayed an I− > Cl− > gluconate− permeability sequence. When compared to the VSOR current, it was similarly sensitive to DIDS, but less sensitive to DCPIB, and insensitive to tamoxifen. Under acidic conditions, the ASOR current was the dominating Cl− conductance, while the VSOR current was apparently inactivated. Acidification caused cell swelling under isotonic conditions and prevented the regulatory volume decrease under hypotonicity. We conclude that acidification, associated with activation of the ASOR- and inactivation of the VSOR current, massively impairs cell volume homeostasis. ASOR current activation could affect microglial function under acidotoxic conditions, since acidosis is a hallmark of pathophysiological events like inflammation, stroke or ischemia and migration and phagocytosis in microglial cells are closely related to cell volume regulation.
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10
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Okada Y, Okada T, Sato-Numata K, Islam MR, Ando-Akatsuka Y, Numata T, Kubo M, Shimizu T, Kurbannazarova RS, Marunaka Y, Sabirov RZ. Cell Volume-Activated and Volume-Correlated Anion Channels in Mammalian Cells: Their Biophysical, Molecular, and Pharmacological Properties. Pharmacol Rev 2019; 71:49-88. [PMID: 30573636 DOI: 10.1124/pr.118.015917] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
There are a number of mammalian anion channel types associated with cell volume changes. These channel types are classified into two groups: volume-activated anion channels (VAACs) and volume-correlated anion channels (VCACs). VAACs can be directly activated by cell swelling and include the volume-sensitive outwardly rectifying anion channel (VSOR), which is also called the volume-regulated anion channel; the maxi-anion channel (MAC or Maxi-Cl); and the voltage-gated anion channel, chloride channel (ClC)-2. VCACs can be facultatively implicated in, although not directly activated by, cell volume changes and include the cAMP-activated cystic fibrosis transmembrane conductance regulator (CFTR) anion channel, the Ca2+-activated Cl- channel (CaCC), and the acid-sensitive (or acid-stimulated) outwardly rectifying anion channel. This article describes the phenotypical properties and activation mechanisms of both groups of anion channels, including accumulating pieces of information on the basis of recent molecular understanding. To that end, this review also highlights the molecular identities of both anion channel groups; in addition to the molecular identities of ClC-2 and CFTR, those of CaCC, VSOR, and Maxi-Cl were recently identified by applying genome-wide approaches. In the last section of this review, the most up-to-date information on the pharmacological properties of both anion channel groups, especially their half-maximal inhibitory concentrations (IC50 values) and voltage-dependent blocking, is summarized particularly from the standpoint of pharmacological distinctions among them. Future physiologic and pharmacological studies are definitely warranted for therapeutic targeting of dysfunction of VAACs and VCACs.
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Affiliation(s)
- Yasunobu Okada
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Toshiaki Okada
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Kaori Sato-Numata
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Md Rafiqul Islam
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Yuhko Ando-Akatsuka
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Tomohiro Numata
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Machiko Kubo
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Takahiro Shimizu
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Ranohon S Kurbannazarova
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Yoshinori Marunaka
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
| | - Ravshan Z Sabirov
- Departments of Physiology and Systems Bioscience (Y.O.) and Molecular Cell Physiology (Y.M.), Kyoto Prefectural University of Medicine, Kyoto, Japan; Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan (Y.O., T.O., M.R.I., M.K., R.Z.S.); Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan (K.S.-N., T.N.); Department of Cell Physiology, Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Japan (Y.A.-A.); Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (T.S.); Laboratory of Molecular Physiology, Institute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan (R.S.K., R.Z.S.); and Research Institute for Clinical Physiology, Kyoto Industrial Health Association, Kyoto, Japan (Y.M.)
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11
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Behe P, Foote JR, Levine AP, Platt CD, Chou J, Benavides F, Geha RS, Segal AW. The LRRC8A Mediated "Swell Activated" Chloride Conductance Is Dispensable for Vacuolar Homeostasis in Neutrophils. Front Pharmacol 2017; 8:262. [PMID: 28553230 PMCID: PMC5427109 DOI: 10.3389/fphar.2017.00262] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 04/26/2017] [Indexed: 01/16/2023] Open
Abstract
The dialysis of human and mouse neutrophils in patch clamp experiments in the conventional whole-cell mode induces the emergence of a chloride (Cl-) current that appeared to be primarily regulated by cytoplasmic ionic strength. The characteristics of this current resembled that of the classical, and ubiquitous volume-sensitive outwardly rectifying Cl- current: strong outward rectification, selectivity sequence of the Eisenman1 type, insensitivity to external pH and strong inhibition by tamoxifen, DCPIB and WW781. We show that this current is essentially supported by the leucine rich repeat containing 8 A (LRRC8A); the naturally occurring LRRC8A truncation mutant in ebo/ebo mice drastically reduced Cl- conductance in neutrophils. Remarkably, the residual component presents a distinct pharmacology, but appears equally potentiated by reduced ionic strength. We have investigated the role of the LRRC8A-supported current in the ionic homeostasis of the phagosomal compartment. The vacuolar pH, measured using SNARF-1 labeled Candida albicans, normally rises because of NADPH oxidase activity, and this elevation is blocked by certain Cl- channel inhibitors. However, the pH rise remains intact in neutrophils from the ebo/ebo mice which also demonstrate preserved phagocytic and respiratory burst capacities and normal-sized vacuoles. Thus, the LRRC8A-dependent conductance of neutrophils largely accounts for their “swell activated” Cl- current, but is not required for homeostasis of the phagosomal killing compartment.
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Affiliation(s)
- Philippe Behe
- Division of Medicine, University College LondonLondon, UK
| | - Juliet R Foote
- Division of Medicine, University College LondonLondon, UK
| | - Adam P Levine
- Division of Medicine, University College LondonLondon, UK
| | - Craig D Platt
- Division of Immunology, Boston Children's Hospital, Harvard Medical School, BostonMA, USA
| | - Janet Chou
- Division of Immunology, Boston Children's Hospital, Harvard Medical School, BostonMA, USA
| | - Fernando Benavides
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, HoustonTX, USA
| | - Raif S Geha
- Division of Immunology, Boston Children's Hospital, Harvard Medical School, BostonMA, USA
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12
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Valinsky WC, Touyz RM, Shrier A. Characterization of constitutive and acid-induced outwardly rectifying chloride currents in immortalized mouse distal tubular cells. Biochim Biophys Acta Gen Subj 2017; 1861:2007-2019. [PMID: 28483640 PMCID: PMC5482324 DOI: 10.1016/j.bbagen.2017.05.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 04/12/2017] [Accepted: 05/04/2017] [Indexed: 12/13/2022]
Abstract
Thiazides block Na+ reabsorption while enhancing Ca2+ reabsorption in the kidney. As previously demonstrated in immortalized mouse distal convoluted tubule (MDCT) cells, chlorothiazide application induced a robust plasma membrane hyperpolarization, which increased Ca2+ uptake. This essential thiazide-induced hyperpolarization was prevented by the Cl− channel inhibitor 5-Nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), implicating NPPB-sensitive Cl− channels, however the nature of these Cl− channels has been rarely described in the literature. Here we show that MDCT cells express a dominant, outwardly rectifying Cl− current at extracellular pH 7.4. This constitutive Cl− current was more permeable to larger anions (Eisenman sequence I; I− > Br− ≥ Cl−) and was substantially inhibited by > 100 mM [Ca2+]o, which distinguished it from ClC-K2/barttin. Moreover, the constitutive Cl− current was blocked by NPPB, along with other Cl− channel inhibitors (4,4′-diisothiocyanatostilbene-2,2′-disulfonate, DIDS; flufenamic acid, FFA). Subjecting the MDCT cells to an acidic extracellular solution (pH < 5.5) induced a substantially larger outwardly rectifying NPPB-sensitive Cl− current. This acid-induced Cl− current was also anion permeable (I− > Br− > Cl−), but was distinguished from the constitutive Cl− current by its rectification characteristics, ion sensitivities, and response to FFA. In addition, we have identified similar outwardly rectifying and acid-sensitive currents in immortalized cells from the inner medullary collecting duct (mIMCD-3 cells). Expression of an acid-induced Cl− current would be particularly relevant in the acidic IMCD (pH < 5.5). To our knowledge, the properties of these Cl− currents are unique and provide the mechanisms to account for the Cl− efflux previously speculated to be present in MDCT cells. MDCT cells express a dominant NPPB-sensitive Cl− current at pH 7.4. The constitutive Cl− current (pH 7.4) does not arise from ClC-K2/barttin. MDCT cells also express an acid-induced NPPB-sensitive Cl− current (pH < 5.5). Both the constitutive and acid-induced Cl− currents are unique. mIMCD-3 cells express currents with similar biophysical properties.
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Affiliation(s)
- William C Valinsky
- Department of Physiology, McGill University, 3649 Promenade sir William Osler, Montreal, Quebec H3G 0B1, Canada
| | - Rhian M Touyz
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, BHF GCRC, 126 University Place, Glasgow G12 8TA, United Kingdom
| | - Alvin Shrier
- Department of Physiology, McGill University, 3649 Promenade sir William Osler, Montreal, Quebec H3G 0B1, Canada.
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13
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Sato-Numata K, Numata T, Inoue R, Sabirov RZ, Okada Y. Distinct contributions of LRRC8A and its paralogs to the VSOR anion channel from those of the ASOR anion channel. Channels (Austin) 2016; 11:167-172. [PMID: 27579940 PMCID: PMC5398604 DOI: 10.1080/19336950.2016.1230574] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Volume- and acid-sensitive outwardly rectifying anion channels (VSOR and ASOR) activated by swelling and acidification exhibit voltage-dependent inactivation and activation time courses, respectively. Recently, LRRC8A and some paralogs were shown to be essentially involved in the activity and inactivation kinetics of VSOR currents in human colonic HCT116 cells. In human cervix HeLa cells, here, inactivation of VSOR currents was found to become accelerated by RNA silencing only of LRRC8A but never decelerated by that of any LRRC8 isoform. These data suggest that LRRC8A is associated with the deceleration mechanism of VSOR inactivation, while none of LRRC8 members is related to the acceleration mechanism. Activation kinetics of ASOR currents was unaffected by knockdown of any LRRC8 family member. Double, triple and quadruple gene-silencing studies indicated that combinatory expression of LRRC8A with LRRC8D and LRRC8C is essential for VSOR activity, whereas none of LRRC8 family members is involved in ASOR activity.
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Affiliation(s)
- Kaori Sato-Numata
- a Japan Society for the Promotion of Science , Chiyoda-ku , Japan.,b Department of Cell Physiology , National Institute for Physiological Sciences, National Institutes of Natural Sciences , Okazaki , Japan.,c Department of Physiology, School of Medicine , Fukuoka University , Fukuoka , Japan
| | - Tomohiro Numata
- c Department of Physiology, School of Medicine , Fukuoka University , Fukuoka , Japan
| | - Ryuji Inoue
- c Department of Physiology, School of Medicine , Fukuoka University , Fukuoka , Japan
| | - Ravshan Z Sabirov
- d International Collaborative Research Project, National Institute for Physiological Sciences , Okazaki , Japan
| | - Yasunobu Okada
- e SOKENDAI (The Graduate University for Advanced Studies) , Hayama , Kanagawa , Japan
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14
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Sato-Numata K, Numata T, Inoue R, Okada Y. Distinct pharmacological and molecular properties of the acid-sensitive outwardly rectifying (ASOR) anion channel from those of the volume-sensitive outwardly rectifying (VSOR) anion channel. Pflugers Arch 2016; 468:795-803. [DOI: 10.1007/s00424-015-1786-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 12/23/2015] [Accepted: 12/28/2015] [Indexed: 11/24/2022]
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15
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Sato-Numata K, Numata T, Okada Y. Temperature sensitivity of acid-sensitive outwardly rectifying (ASOR) anion channels in cortical neurons is involved in hypothermic neuroprotection against acidotoxic necrosis. Channels (Austin) 2015; 8:278-83. [PMID: 24476793 DOI: 10.4161/chan.27748] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The acid-sensitive outwardly rectifying (ASOR) anion channel has been found in non-neuronal cell types and was shown to be involved in acidotoxic death of epithelial cells. We have recently shown that the ASOR channel is sensitive to temperature. Here, we extend those results to show that temperature-sensitive ASOR anion channels are expressed in cortical neurons and involved in acidotoxic neuronal cell death. In cultured mouse cortical neurons, reduction of extracellular pH activated anionic currents exhibiting phenotypic properties of the ASOR anion channel. The neuronal ASOR currents recorded at pH 5.25 were augmented by warm temperature, with a threshold temperature of 26 °C and the Q(10) value of 5.6. After 1 h exposure to acidic solution at 37 °C, a large population of neurons suffered from necrotic cell death which was largely protected not only by ASOR channel blockers but also by reduction of temperature to 25 °C. Thus, it is suggested that high temperature sensitivity of the neuronal ASOR anion channel provides, at least in part, a basis for hypothermic neuroprotection under acidotoxic situations associated with a number of pathological brain states.
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16
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Capurro V, Gianotti A, Caci E, Ravazzolo R, Galietta LJ, Zegarra-Moran O. Functional analysis of acid-activated Cl− channels: Properties and mechanisms of regulation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:105-14. [DOI: 10.1016/j.bbamem.2014.10.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 09/26/2014] [Accepted: 10/02/2014] [Indexed: 01/10/2023]
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17
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Drews A, Mohr F, Rizun O, Wagner TFJ, Dembla S, Rudolph S, Lambert S, Konrad M, Philipp SE, Behrendt M, Marchais-Oberwinkler S, Covey DF, Oberwinkler J. Structural requirements of steroidal agonists of transient receptor potential melastatin 3 (TRPM3) cation channels. Br J Pharmacol 2014; 171:1019-32. [PMID: 24251620 PMCID: PMC3925040 DOI: 10.1111/bph.12521] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/29/2013] [Accepted: 11/13/2013] [Indexed: 11/30/2022] Open
Abstract
Background and Purpose Transient receptor potential melastatin 3 (TRPM3) proteins form non-selective but calcium-permeable membrane channels, rapidly activated by extracellular application of the steroid pregnenolone sulphate and the dihydropyridine nifedipine. Our aim was to characterize the steroid binding site by analysing the structural chemical requirements for TRPM3 activation. Experimental Approach Whole-cell patch-clamp recordings and measurements of intracellular calcium concentrations were performed on HEK293 cells transfected with TRPM3 (or untransfected controls) during superfusion with pharmacological substances. Key Results Pregnenolone sulphate and nifedipine activated TRPM3 channels supra-additively over a wide concentration range. Other dihydropyridines inhibited TRPM3 channels. The natural enantiomer of pregnenolone sulphate was more efficient in activating TRPM3 channels than its synthetic mirror image. However, both enantiomers exerted very similar inhibitory effects on proton-activated outwardly rectifying anion channels. Epiallopregnanolone sulphate activated TRPM3 almost equally as well as pregnenolone sulphate. Exchanging the sulphate for other chemical moieties showed that a negative charge at this position is required for activating TRPM3 channels. Conclusions and Implications Our data demonstrate that nifedipine and pregnenolone sulphate act at different binding sites when activating TRPM3. The latter activates TRPM3 by binding to a chiral and thus proteinaceous binding site, as inferred from the differential effects of the enantiomers. The double bond between position C5 and C6 of pregnenolone sulphate is not strictly necessary for the activation of TRPM3 channels, but a negative charge at position C3 of the steroid is highly important. These results provide a solid basis for understanding mechanistically the rapid chemical activation of TRPM3 channels.
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Affiliation(s)
- A Drews
- Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg, Germany
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18
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Guzman RE, Grieschat M, Fahlke C, Alekov AK. ClC-3 is an intracellular chloride/proton exchanger with large voltage-dependent nonlinear capacitance. ACS Chem Neurosci 2013; 4:994-1003. [PMID: 23509947 DOI: 10.1021/cn400032z] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The chloride/proton exchangers ClC-3, ClC-4 and ClC-5 are localized in distinct intracellular compartments and regulate their luminal acidity. We used electrophysiology combined with fluorescence pH measurements to compare the functions of these three transporters. Since the expression of WT ClC-3 in the surface membrane was negligible, we removed an N-terminal retention signal for standard electrophysiological characterization of this isoform. This construct (ClC-313-19A) mediated outwardly rectifying coupled Cl(-)/H(+) antiport resembling the properties of ClC-4 and ClC-5. In addition, ClC-3 exhibited large electric capacitance, exceeding the nonlinear capacitances of ClC-4 and ClC-5. Mutations of the proton glutamate, a conserved residue at the internal side of the protein, decreased ion transport but increased nonlinear capacitances in all three isoforms. This suggests that nonlinear capacitances in mammalian ClC transporters are regulated in a similar manner. However, the voltage dependence and the amplitudes of these capacitances differed strongly between the investigated isoforms. Our results indicate that ClC-3 is specialized in mainly performing incomplete capacitive nontransporting cycles, that ClC-4 is an effective coupled transporter, and that ClC-5 displays an intermediate phenotype. Mathematical modeling showed that such functional differences would allow differential regulation of luminal acidification and chloride concentration in intracellular compartments.
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Affiliation(s)
- Raul E. Guzman
- Institut für Neurophysiologie, Medizinische Hochschule Hannover, D-30625 Hannover, Germany
- Institute of Complex Systems, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Matthias Grieschat
- Institut für Neurophysiologie, Medizinische Hochschule Hannover, D-30625 Hannover, Germany
| | - Christoph Fahlke
- Institut für Neurophysiologie, Medizinische Hochschule Hannover, D-30625 Hannover, Germany
- Institute of Complex Systems, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Alexi K. Alekov
- Institut für Neurophysiologie, Medizinische Hochschule Hannover, D-30625 Hannover, Germany
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19
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Acid-sensitive outwardly rectifying (ASOR) anion channels in human epithelial cells are highly sensitive to temperature and independent of ClC-3. Pflugers Arch 2013; 465:1535-43. [DOI: 10.1007/s00424-013-1296-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 05/11/2013] [Accepted: 05/11/2013] [Indexed: 01/26/2023]
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20
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Ohgi K, Kajiya H, Okamoto F, Nagaoka Y, Onitsuka T, Nagai A, Sakagami R, Okabe K. A novel inhibitory mechanism of nitrogen-containing bisphosphonate on the activity of Cl− extrusion in osteoclasts. Naunyn Schmiedebergs Arch Pharmacol 2013; 386:589-98. [DOI: 10.1007/s00210-013-0857-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 03/18/2013] [Indexed: 11/29/2022]
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21
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Wang L, Ma W, Zhu L, Ye D, Li Y, Liu S, Li H, Zuo W, Li B, Ye W, Chen L. ClC-3 is a candidate of the channel proteins mediating acid-activated chloride currents in nasopharyngeal carcinoma cells. Am J Physiol Cell Physiol 2012; 303:C14-23. [DOI: 10.1152/ajpcell.00145.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Acid-activated chloride currents have been reported in several cell types and may play important roles in regulation of cell function. However, the molecular identities of the channels that mediate the currents are not defined. In this study, activation of the acid-induced chloride current and the possible candidates of the acid-activated chloride channel were investigated in human nasopharyngeal carcinoma cells (CNE-2Z). A chloride current was activated when extracellular pH was reduced to 6.6 from 7.4. However, a further decrease of extracellular pH to 5.8 inhibited the current. The current was weakly outward-rectified and was suppressed by hypertonicity-induced cell shrinkage and by the chloride channel blockers 5-nitro-2–3-phenylpropylamino benzoic acid (NPPB), tamoxifen, and 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid disodium salt hydrate (DIDS). The permeability sequence of the channel to anions was I− > Br− > Cl− > gluconate−. Among the ClC chloride channels, ClC-3 and ClC-7 were strongly expressed in CNE-2Z cells. Knockdown of ClC-3 expression with ClC-3 small interfering (si)RNA prevented the activation of the acid-induced current, but silence of ClC-7 expression with ClC-7 siRNA did not significantly affect the current. The results suggest that the chloride channel mediating the acid-induced chloride current was volume sensitive. ClC-3 is a candidate of the channel proteins that mediate or regulate the acid-activated chloride current in nasopharyngeal carcinoma cells.
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Affiliation(s)
- Liwei Wang
- Department of Physiology, Medical College, Jinan University, Guangzhou, China
| | - Wenbo Ma
- Department of Physiology, Medical College, Jinan University, Guangzhou, China
| | - Linyan Zhu
- Department of Pharmacology, Medical College, Jinan University, Guangzhou, China; and
| | - Dong Ye
- Department of Physiology, Medical College, Jinan University, Guangzhou, China
| | - Yuan Li
- Department of Pharmacology, Medical College, Jinan University, Guangzhou, China; and
| | - Shanwen Liu
- Department of Physiology, Medical College, Jinan University, Guangzhou, China
| | - Huarong Li
- Department of Physiology, Medical College, Jinan University, Guangzhou, China
| | - Wanhong Zuo
- Department of Physiology, Medical College, Jinan University, Guangzhou, China
| | - Bingxue Li
- Department of Pharmacology, Medical College, Jinan University, Guangzhou, China; and
| | - Wencai Ye
- College of Pharmacy, Jinan University, Guangzhou, China
| | - Lixin Chen
- Department of Pharmacology, Medical College, Jinan University, Guangzhou, China; and
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22
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Starkus JG, Fleig A, Penner R. The calcium-permeable non-selective cation channel TRPM2 is modulated by cellular acidification. J Physiol 2010; 588:1227-40. [PMID: 20194125 DOI: 10.1113/jphysiol.2010.187476] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
TRPM2 is a calcium-permeable non-selective cation channel expressed in the plasma membrane and in lysosomes that is critically involved in aggravating reactive oxygen species (ROS)-induced inflammatory processes and has been implicated in cell death. TRPM2 is gated by ADP-ribose (ADPR) and modulated by physiological processes that produce peroxide, cyclic ADP-ribose (cADPR), nicotinamide adenine dinucleotide phosphate (NAADP) and Ca(2+). We investigated the role of extra- and intracellular acidification on heterologously expressed TRPM2 in HEK293 cells. Our results show that TRPM2 is inhibited by external acidification with an IC(50) of pH 6.5 and is completely suppressed by internal pH of 6. Current inhibition requires channel opening and is strongly voltage dependent, being most effective at negative potentials. In addition, increased cytosolic pH buffering capacity or elevated [Ca(2+)](i) reduces the rate of current inactivation elicited by extracellular acidification, and Na(+) and Ca(2+) influence the efficacy of proton-induced inactivation. Together, these results suggest that external protons permeate TRPM2 channels to gain access to an intracellular site that regulates channel activity. Consistent with this notion, single-channel measurements in HEK293 cells reveal that internal protons induce channel closure without affecting single-channel conductance, whereas external protons affect channel open probability as well as single-channel conductance of native TRPM2 in neutrophils. We conclude that protons compete with Na(+) and Ca(2+) for channel permeation and channel closure results from a competitive antagonism of protons at an intracellular Ca(2+) binding site.
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Affiliation(s)
- John G Starkus
- University of Hawaii, Pacific Biosciences Research Center, Queens Medical Center, University Tower, 814, 1356 Lusitania Street, Honolulu, HI 96813, USA.
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Matsuda JJ, Filali MS, Collins MM, Volk KA, Lamb FS. The ClC-3 Cl-/H+ antiporter becomes uncoupled at low extracellular pH. J Biol Chem 2009; 285:2569-79. [PMID: 19926787 DOI: 10.1074/jbc.m109.018002] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adenovirus expressing ClC-3 (Ad-ClC-3) induces Cl(-)/H(+) antiport current (I(ClC-3)) in HEK293 cells. The outward rectification and time dependence of I(ClC-3) closely resemble an endogenous HEK293 cell acid-activated Cl(-) current (ICl(acid)) seen at extracellular pH <or= 5.5. ICl(acid) was present in smooth muscle cells from wild-type but not ClC-3 null mice. We therefore sought to determine whether these currents were related. ICl(acid) was larger in cells expressing Ad-ClC-3. Protons shifted the reversal potential (E(rev)) of I(ClC-3) between pH 8.2 and 6.2, but not pH 6.2 and 5.2, suggesting that Cl(-) and H(+) transport become uncoupled at low pH. At pH 4.0 E(rev) was completely Cl(-) dependent (55.8 +/- 2.3 mV/decade). Several findings linked ClC-3 with native ICl(acid); 1) RNA interference directed at ClC-3 message reduced native ICl(acid); 2) removal of the extracellular "fast gate" (E224A) produced large currents that were pH-insensitive; and 3) wild-type I(ClC-3) and ICl(acid) were both inhibited by (2-sulfonatoethyl)methanethiosulfonate (MTSES; 10-500 microm)-induced alkanethiolation at exposed cysteine residues. However, a ClC-3 mutant lacking four extracellular cysteine residues (C103_P130del) was completely resistant to MTSES. C103_P130del currents were still acid-activated, but could be distinguished from wild-type I(ClC-3) and from native ICl(acid) by a much slower response to low pH. Thus, ClC-3 currents are activated by protons and ClC-3 protein may account for native ICl(acid). Low pH uncouples Cl(-)/H(+) transport so that at pH 4.0 ClC-3 behaves as an anion-selective channel. These findings have important implications for the biology of Cl(-)/H(+) antiporters and perhaps for pH regulation in highly acidic intracellular compartments.
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Affiliation(s)
- James J Matsuda
- Department of Pediatrics, University of Iowa Children's Hospital, Iowa City, Iowa 52242, USA
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24
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Acid-sensitive outwardly rectifying anion channels in human erythrocytes. J Membr Biol 2009; 230:1-10. [PMID: 19572091 DOI: 10.1007/s00232-009-9179-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Accepted: 05/22/2009] [Indexed: 12/14/2022]
Abstract
Acid-sensitive outwardly rectifying anion channels (ASOR) have been described in several mammalian cell types. The present whole-cell patch-clamp study elucidated whether those channels are expressed in erythrocytes. To this end whole-cell recordings were made in human erythrocytes from healthy donors treated with low pH and high osmotic pressure. When the pipette solution had a reduced Cl(-) concentration, treatment of the cells with Cl(-)-containing normal and hyperosmotic (addition of sucrose and polyethelene glycol 1000 [PEG-1000] to the Ringer) media with low pH significantly increased the conductance of the cells at positive voltages. Channel activity was highest in the PEG-1000 media (95 and 300 mM PEG-1000, pH 4.5 and 4.3, respectively) where the current-voltage curves demonstrated strong outward rectification and reversed at -40 mV. Substitution of the Cl(-)-containing medium with Cl(-)-free medium resulted in a decrease of the conductance at hyperpolarizing voltages, a shift in reversal potential (to 0 mV) and loss of outward rectification. The chloride currents were inhibited by chloride channels blockers DIDS and NPPB (IC(50) for both was approximately 1 mM) but not with niflumic acid and amiloride. The observations reveal expression of ASOR in erythrocytes.
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25
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Shi CY, Wang R, Liu CX, Jiang H, Ma ZY, Li L, Zhang W. Simvastatin inhibits acidic extracellular pH-activated, outward rectifying chloride currents in RAW264.7 monocytic-macrophage and human peripheral monocytes. Int Immunopharmacol 2008; 9:247-52. [PMID: 19084616 DOI: 10.1016/j.intimp.2008.11.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Revised: 11/17/2008] [Accepted: 11/20/2008] [Indexed: 11/29/2022]
Abstract
Extracellular acidic pH activated chloride channels (I(Cl,acid)) have been characterized in HEK 293 cells and mammalian cardiac myocytes. This study was designed to evaluate the expression of I(Cl,acid) in RAW264.7 monocytic-macrophage and human peripheral monocytes and to investigate the effect of simvastatin on I(Cl,acid). In two kinds of cells, the activation and deactivation of the current rapidly and repeatedly followed the change of the extracellular solution to pH=4.3. Compared with the outward current (pA/pF) activated at pH 4.3, the currents inhibited by simvastatin at concentrations of 0.1 microM were all decreased a little, however the currents at concentrations of 1 microM and 10 microM simvastatin were decreased significantly. The IC(50) for simvastatin inhibiting I(Cl,acid) of RAW264.7 was 13.77 microM. In summary, we report for the first time that simvastatin inhibits the I(Cl,acid) of RAW264.7 monocytic-macrophage and human peripheral monocytes in a concentration-dependent manner.
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Affiliation(s)
- Cheng-Yao Shi
- Department of Pharmacy, QiLu Hospital, Shandong University, Jinan 250012, China
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26
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Volk APD, Heise CK, Hougen JL, Artman CM, Volk KA, Wessels D, Soll DR, Nauseef WM, Lamb FS, Moreland JG. ClC-3 and IClswell are required for normal neutrophil chemotaxis and shape change. J Biol Chem 2008; 283:34315-26. [PMID: 18840613 DOI: 10.1074/jbc.m803141200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Polymorphonuclear leukocytes undergo directed movement to sites of infection, a complex process known as chemotaxis. Extension of the polymorphonuclear leukocyte (PMN) leading edge toward a chemoattractant in association with uropod retraction must involve a coordinated increase/decrease in membrane, redistribution of cell volume, or both. Deficits in PMN phagocytosis and trans-endothelial migration, both highly motile PMN functions, suggested that the anion transporters, ClC-3 and ICl(swell), are involved in cell motility and shape change ( Moreland, J. G., Davis, A. P., Bailey, G., Nauseef, W. M., and Lamb, F. S. (2006) J. Biol. Chem. 281, 12277-12288 ). We hypothesized that ClC-3 and ICl(swell) are required for normal PMN chemotaxis through regulation of cell volume and shape change. Using complementary chemotaxis assays, EZ-TAXIScantrade mark and dynamic imaging analysis software, we analyzed the directed cell movement and morphology of PMNs lacking normal anion transporter function. Murine Clcn3(-/-) PMNs and human PMNs treated with anion transporter inhibitors demonstrated impaired chemotaxis in response to formyl peptide. This included decreased cell velocity and failure to undergo normal cycles of elongation and retraction. Impaired chemotaxis was not due to a diminished number of formyl peptide receptors in either murine or human PMNs, as measured by flow cytometry. Murine Clcn3(-/-) and Clcn3(+/+) PMNs demonstrated a similar regulatory volume decrease, indicating that the ICl(swell) response to hypotonic challenge was intact in these cells. We further demonstrated that ICl(swell) is essential for shape change during human PMN chemotaxis. We speculate that ClC-3 and ICl(swell) have unique roles in regulation of PMN chemotaxis; ICl(swell) through direct effects on PMN volume and ClC-3 through regulation of ICl(swell).
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Affiliation(s)
- A Paige Davis Volk
- Department of Pediatrics, W.M. Keck Dynamic Image Analysis Facility, University of Iowa College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
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27
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Tamoxifen does not inhibit the swell activated chloride channel in human neutrophils during the respiratory burst. Biochem Biophys Res Commun 2008; 375:596-601. [DOI: 10.1016/j.bbrc.2008.08.067] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2008] [Accepted: 08/13/2008] [Indexed: 11/18/2022]
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28
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Park SJ, Choi WW, Kwon OS, Chung JH, Eun HC, Earm YE, Kim SJ. Acidic pH-activated Cl Current and Intracellular Ca Response in Human Keratinocytes. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2008; 12:177-83. [PMID: 19967053 DOI: 10.4196/kjpp.2008.12.4.177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The layers of keratinocytes form an acid mantle on the surface of the skin. Herein, we investigated the effects of acidic pH on the membrane current and [Ca(2+)](c) of human primary keratinocytes from foreskins and human keratinocyte cell line (HaCaT). Acidic extracellular pH (pH(e)</= 5.5) activated outwardly rectifying Cl(-) current (I(Cl,pH)) with slow kinetics of voltage-dependent activation. I(Cl,pH) was potently inhibited by an anion channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS, 73.5% inhibition at 1 microM). I(Cl,pH) became more sensitive to pH(e) by raising temperature from 24 to 37. HaCaT cells also expressed Ca(2+)-activated Cl(-) current (I(Cl,Ca)), and the amplitude of I(Cl,Ca) was increased by relatively weak acidic pH(e) (7.0 and 6.8). Interestingly, the acidic pH(e) (5.0) also induced a sharp increase in the intracellular [Ca(2+)] (Delta[Ca(2+)](acid)) of HaCaT cells. The Delta[Ca(2+)](acid) was independent of extracellular Ca(2+), and was abolished by the pretreatment with PLC inhibitor, U73122. In primary human keratinocytes, 5 out of 28 tested cells showed Delta[Ca(2+)](acid). In summary, we found I(Cl,pH) and Delta[Ca(2+)](acid) in human keratinocytes, and these ionic signals might have implication in pathophysiological responses and differentiation of epidermal keratinocytes.
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Affiliation(s)
- Su Jung Park
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea
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29
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Ma ZY, Zhang W, Chen L, Wang R, Kan XH, Sun GZ, Liu CX, Li L, Zhang Y. A proton-activated, outwardly rectifying chloride channel in human umbilical vein endothelial cells. Biochem Biophys Res Commun 2008; 371:437-40. [PMID: 18442470 DOI: 10.1016/j.bbrc.2008.04.090] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Accepted: 04/17/2008] [Indexed: 11/30/2022]
Abstract
Extracellular acidic pH-activated chloride channel I(Cl, acid), has been characterized in HEK 293 cells and mammalian cardiac myocytes. This study was designed to characterize I(Cl,acid) in human umbilical vein endothelial cells(HUVECs). The activation and deactivation of the current rapidly and repeatedly follows the change of the extracellular solution at pH 4.3, with the threshold pH 5.3. In addition, at very positive potentials, the current displays a time-dependent facilitation. pH-response relationship for I(Cl,acid) revealed that EC(50) is pH 4.764 with a threshold pH value of pH 5.3 and nH of 14.545. The current can be blocked by the Cl(-) channel inhibitor DIDS (100 microM). In summary, for the first time we report the presence of proton-activated, outwardly rectifying chloride channel in HUVECs. Because an acidic environment can develop in local myocardium under pathological conditions such as myocardial ischemia, I(Cl,acid) would play a role in regulation of EC function under these pathological conditions.
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Affiliation(s)
- Zhi-Yong Ma
- Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Public Health, Department of Cardiology QiLu Hospital Shandong University, West Wenhua Road 107, Jinan 250012, China
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30
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Zifarelli G, Pusch M. CLC chloride channels and transporters: a biophysical and physiological perspective. Rev Physiol Biochem Pharmacol 2007; 158:23-76. [PMID: 17729441 DOI: 10.1007/112_2006_0605] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Chloride-transporting proteins play fundamental roles in many tissues in the plasma membrane as well as in intracellular membranes. They have received increasing attention in the last years because crucial, and often unexpected and novel, physiological functions have been disclosed with gene-targeting approaches, X-ray crystallography, and biophysical analysis. CLC proteins form a gene family that comprises nine members in mammals, at least four of which are involved in human genetic diseases. The X-ray structure of the bacterial CLC homolog, ClC-ec1, revealed a complex fold and confirmed the anticipated homodimeric double-barreled architecture of CLC-proteins with two separate Cl-ion transport pathways, one in each subunit. Four of the mammalian CLC proteins, ClC-1, ClC-2, ClC-Ka, and ClC-Kb, are chloride ion channels that fulfill their functional roles-stabilization of the membrane potential, transepithelial salt transport, and ion homeostasisin the plasma membrane. The other five CLC proteins are predominantly expressed in intracellular organelles like endosomes and lysosomes, where they are probably important for a proper luminal acidification, in concert with the V-type H+-ATPase. Surprisingly, ClC-4, ClC-5, and probably also ClC-3, are not Cl- ion channels but exhibit significant Cl-/H+ antiporter activity, as does the bacterial homolog ClC-ec1 and the plant homolog AtCLCa. The physiological significance of the Cl-/H+ antiport activity remains to be established.
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Affiliation(s)
- G Zifarelli
- CNR, Istituto di Biofisica, Via De Marini 6, 16149 Genova, Italy
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31
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Wang HY, Shimizu T, Numata T, Okada Y. Role of acid-sensitive outwardly rectifying anion channels in acidosis-induced cell death in human epithelial cells. Pflugers Arch 2006; 454:223-33. [PMID: 17186306 DOI: 10.1007/s00424-006-0193-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Accepted: 11/20/2006] [Indexed: 10/23/2022]
Abstract
Recently, a novel type of anion channel activated by extracellular acidification has been found in a variety of mammalian cell types. However, the role of this acid-sensitive outwardly rectifying (ASOR) anion channel is not known. In human epithelial HeLa cells, reduction in extracellular pH below 5 rapidly activated anion-selective whole-cell currents. The currents exhibited strong outward rectification, activation kinetics at positive potentials, low-field anion selectivity, and sensitivity to 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and phloretin. When outside-out patches were exposed to acidic bathing solution, single-channel events of the anion channel could be observed. The unitary conductance was 4.8 pS in the voltage range between -80 and +80 mV. The single-channel activity prominently increased with depolarization and was suppressed by DIDS or phloretin. After 1-h incubation in acidic solution (pH 4.5), a significant population of HeLa cells suffered from necrotic cell injury characterized by stainability with propidium iodide and lack of caspase-3 activation. Upon exposure to acidic solution, HeLa cells exhibited immediate, persistent swelling. Both the necrotic volume increase and cell injury induced by extracellular acidification were inhibited by DIDS or phloretin. Therefore, it is concluded that the ASOR anion channel is involved in the genesis of necrotic cell injury induced by acidosis in human epithelial cells.
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Affiliation(s)
- Hai-Yan Wang
- Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
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Mazzone SB, McGovern AE. Na+-K+-2Cl− cotransporters and Cl− channels regulate citric acid cough in guinea pigs. J Appl Physiol (1985) 2006; 101:635-43. [PMID: 16627683 DOI: 10.1152/japplphysiol.00106.2006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Loop diuretics have been shown to inhibit cough and other airway defensive reflexes via poorly defined mechanisms. We test the hypothesis that the furosemide-sensitive Na+-K+-2Cl− cotransporter (NKCC1) is expressed by sensory nerve fibers innervating the airways where it plays an important role in regulating sensory neural activity. NKCC1 immunoreactivity was present on the cell membranes of most nodose and jugular ganglia neurons projecting to the trachea, and it was present on the peripheral terminals of putative mechanosensory nerve fibers in the airways. In urethane-anesthetized, spontaneously breathing guinea pigs, bolus application of citric acid (1 mM to 2 M) to an isolated and perfused segment of the tracheal mucosa evoked coughing and respiratory slowing. Removal of Cl− from the tracheal perfusate evoked spontaneous coughing and significantly potentiated cough and respiratory slowing reflexes evoked by citric acid. The NKCC1 inhibitor furosemide (10–100 μM) significantly reduced both the number of coughs evoked by citric acid and the degree of acid-evoked respiratory slowing ( P < 0.05). Localized tracheal pretreatment with the Cl− channel inhibitors DIDS or niflumic acid (100 μM) also significantly reduced cough, whereas the GABAA receptor agonist muscimol potentiated acid-evoked responses. These data suggest that vagal sensory neurons may accumulate Cl− due to the expression of the furosemide-sensitive Cl− transporter, NKCC1. Efflux of intracellular Cl−, in part through calcium-activated Cl− channels, may play an important role in regulating airway afferent neuron activity.
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Affiliation(s)
- Stuart B Mazzone
- Howard Florey Institute, University of Melbourne, Parkville 3010, Victoria, Australia.
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Auzanneau C, Norez C, Noël S, Jougla C, Becq F, Vandebrouck C. Pharmacological profile of inhibition of the chloride channels activated by extracellular acid in cultured rat Sertoli cells. ACTA ACUST UNITED AC 2006; 46:241-55. [PMID: 16733044 DOI: 10.1051/rnd:2006013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Accepted: 02/24/2006] [Indexed: 11/14/2022]
Abstract
Sertoli cells from mammalian testis are key cells involved in the development and maintenance of stem cell spermatogonia as well as in the secretion of a Cl(-) and K(+)-rich fluid into the lumen of seminiferous tubules. The pharmacology and contribution of Cl(-) channels to the physiology of Sertoli cells were investigated using whole-cell patch clamp and iodide efflux experiments applied to cultured rat Sertoli cells. We characterized an outwardly rectifying Cl(-) current stimulated by various acid species including the physiologically relevant lactic acid. Using the iodide efflux technique, the pharmacological properties of this Cl(-) current, noted ICl(acid), revealed Ca(2+)-independent inhibition by DIDS (IC(50) = 27 microM), glibenclamide (IC(50) = 31 microM) and DPC (IC(50) = 86 microM). ICl(acid) was neither affected by calix[4]arene nor by 9-AC. The order of potency for inhibition of ICl(acid) is DIDS approximately glibenclamide > DPC >> calix[4]arene, 9-AC. For comparison, the inhibitory profile of the swelling- and ATP-activated Cl(-) currents in Sertoli cells is DPC = DIDS >> glibenclamide = 9-AC for ICl(swell) and DPC = 9-AC = DIDS >> glibenclamide for ICl(ATP). This description provides new insights into the physiology and pharmacology of the endogenous Cl(-) channels expressed and potentially involved in fluid secretion in Sertoli cells.
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Affiliation(s)
- Céline Auzanneau
- Institut de Physiologie et de Biologie Cellulaires CNRS UMR 6187, Université de Poitiers, 86022 Poitiers, France
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Yamamoto S, Ehara T. Acidic extracellular pH-activated outwardly rectifying chloride current in mammalian cardiac myocytes. Am J Physiol Heart Circ Physiol 2005; 290:H1905-14. [PMID: 16339831 DOI: 10.1152/ajpheart.00965.2005] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Extracellular acidic pH was found to induce an outwardly rectifying Cl- current (I(Cl,acid)) in mouse ventricular cells, with a half-maximal activation at pH 5.9. The current showed the permeability sequence for anions to be SCN- > Br- > I- > Cl- > F- > aspartate, while it exhibited a time-dependent activation at large positive potentials. Similar currents were also observed in mouse atrial cells and in atrial and ventricular cells from guinea pig. Some Cl- channel blockers (DIDS, niflumic acid, and glibenclamide) inhibited ICl,acid, whereas tamoxifen had little effect on it. Unlike volume-regulated Cl- current (ICl,vol) and CFTR Cl- current (ICl,CFTR), ICl,acid was independent of the presence of intracellular ATP. Activation of ICl,acid appeared to be also independent of intracellular Ca2+ and G protein. ICl,acid and ICl,vol could develop in an additive fashion in acidic hypotonic solutions. Isoprenaline-induced ICl,CFTR was inhibited by acidification in a pH-dependent manner in guinea pig ventricular cells. Our results support the view that ICl,acid and ICl,vol stem from two distinct populations of anion channels and that the ICl,acid channels are present in cardiac cells. ICl,acid may play a role in the control of action potential duration or cell volume under pathological conditions, such as ischemia-related cardiac acidosis.
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Affiliation(s)
- Shintaro Yamamoto
- Department of Physiology, Saga University Faculty of Medicine, Saga, Japan.
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35
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Lambert S, Oberwinkler J. Characterization of a proton-activated, outwardly rectifying anion channel. J Physiol 2005; 567:191-213. [PMID: 15961423 PMCID: PMC1474181 DOI: 10.1113/jphysiol.2005.089888] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Anion channels are present in every mammalian cell and serve many different functions, including cell volume regulation, ion transport across epithelia, regulation of membrane potential and vesicular acidification. Here we characterize a proton-activated, outwardly rectifying current endogenously expressed in HEK293 cells. Binding of three to four protons activated the anion permeable channels at external pH below 5.5 (50% activation at pH 5.1). The proton-activated current is strongly outwardly rectifying, due to an outwardly rectifying single channel conductance and an additional voltage dependent facilitation at depolarized membrane potentials. The anion channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) rapidly and potently inhibited the channel (IC50: 2.9 microm). Flufenamic acid blocked this channel only slowly, while mibefradil and amiloride at high concentrations had no effect. As determined from reversal potential measurements under bi-ionic conditions, the relative permeability sequence of this channel was SCN-> I-> NO3-> Br-> Cl-. None of the previously characterized anion channel matches the properties of the proton-activated, outwardly rectifying channel. Specifically, the proton-activated and the volume-regulated anion channels are two distinct and separable populations of ion channels, each having its own set of biophysical and pharmacological properties. We also demonstrate endogenous proton-activated currents in primary cultured hippocampal astrocytes. The proton-activated current in astrocytes is also carried by anions, strongly outwardly rectifying, voltage dependent and inhibited by DIDS. Proton-activated, outwardly rectifying anion channels therefore may be a broadly expressed part of the anionic channel repertoire of mammalian cells.
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Affiliation(s)
- Sachar Lambert
- Experimentelle und klinische Pharmakologie und Toxikologie, Gebäude 46, Uniklinikum des Saarlandes, 66421 Homburg, Germany
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Segers P, Georgakopoulos D, Afanasyeva M, Champion HC, Judge DP, Millar HD, Verdonck P, Kass DA, Stergiopulos N, Westerhof N. Conductance catheter-based assessment of arterial input impedance, arterial function, and ventricular-vascular interaction in mice. Am J Physiol Heart Circ Physiol 2005; 288:H1157-64. [DOI: 10.1152/ajpheart.00414.2004] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Global assessment of both cardiac and arterial function is important for a meaningful interpretation of pathophysiological changes in animal models of cardiovascular disease. We simultaneously acquired left ventricular (LV) and aortic pressure and LV volume (VLV) in 17 open-chest anesthetized mice (26.7 ± 3.2g) during steady-state (BL) and caval vein occlusion (VCO) using a 1.4-Fr dual-pressure conductance catheter and in a subgroup of eight animals during aortic occlusion (AOO). Aortic flow was obtained from numerical differentiation of VLV. AOO increased input impedance ( Zin) for the first two harmonics, increased characteristic impedance (0.025 ± 0.007 to 0.040 ± 0.011 mmHg·μl−1·s, P < 0.05), and shifted the minimum in Zin from the third to the sixth harmonic. For all conditions, the Zin could be well represented by a four-element windkessel model. The augmentation index increased from 116.7 ± 7.8% to 145.9 ± 19.5% ( P < 0.01) as well as estimated pulse-wave velocity (3.50 ± 0.94 to 5.95 ± 1.62 m/s, P < 0.05) and arterial elastance ( Ea, 4.46 ± 1.62 to 6.02 ± 1.43 mmHg/μl, P < 0.01). AOO altered the maximal slope ( Emax, 3.23 ± 1.02 to 5.53 ± 1.53 mmHg/μl, P < 0.05) and intercept (−19.9 ± 8.6 to 1.62 ± 13.51 μl, P < 0.01) of the end-systolic pressure-volume relation but not Ea/ Emax (1.44 ± 0.43 to 1.21 ± 0.37, not significant). We conclude that simultaneous acquisition of Zin and arterial function parameters in the mouse, based solely on conductance catheter measurements, is feasible. We obtained an anticipated response of Zin and arterial function parameters following VCO and AOO, demonstrating the sensitivity of the measuring technique to induced physiological alterations in murine hemodynamics.
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