1
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Chen GL, Li JY, Chen X, Liu JW, Zhang Q, Liu JY, Wen J, Wang N, Lei M, Wei JP, Yi L, Li JJ, Ling YP, Yi HQ, Hu Z, Duan J, Zhang J, Zeng B. Mechanosensitive channels TMEM63A and TMEM63B mediate lung inflation-induced surfactant secretion. J Clin Invest 2024; 134:e174508. [PMID: 38127458 PMCID: PMC10904053 DOI: 10.1172/jci174508] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 12/20/2023] [Indexed: 12/23/2023] Open
Abstract
Pulmonary surfactant is a lipoprotein complex lining the alveolar surface to decrease the surface tension and facilitate inspiration. Surfactant deficiency is often seen in premature infants and in children and adults with respiratory distress syndrome. Mechanical stretch of alveolar type 2 epithelial (AT2) cells during lung expansion is the primary physiological factor that stimulates surfactant secretion; however, it is unclear whether there is a mechanosensor dedicated to this process. Here, we show that loss of the mechanosensitive channels TMEM63A and TMEM63B (TMEM63A/B) resulted in atelectasis and respiratory failure in mice due to a deficit of surfactant secretion. TMEM63A/B were predominantly localized at the limiting membrane of the lamellar body (LB), a lysosome-related organelle that stores pulmonary surfactant and ATP in AT2 cells. Activation of TMEM63A/B channels during cell stretch facilitated the release of surfactant and ATP from LBs fused with the plasma membrane. The released ATP evoked Ca2+ signaling in AT2 cells and potentiated exocytic fusion of more LBs. Our study uncovered a vital physiological function of TMEM63 mechanosensitive channels in preparing the lungs for the first breath at birth and maintaining respiration throughout life.
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Affiliation(s)
- Gui-Lan Chen
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Jing-Yi Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Xin Chen
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Jia-Wei Liu
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Qian Zhang
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Jie-Yu Liu
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Jing Wen
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Na Wang
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Ming Lei
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Jun-Peng Wei
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Li Yi
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Jia-Jia Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - Yu-Peng Ling
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
| | - He-Qiang Yi
- Department of Cardiothoracic Surgery, The Affiliated Traditional Chinese Medicine Hospital, Southwest Medical University, Luzhou, Sichuan, China
| | - Zhenying Hu
- Human Aging Research Institute and School of Life Sciences and
| | - Jingjing Duan
- Human Aging Research Institute and School of Life Sciences and
| | - Jin Zhang
- School of Basic Medical Sciences, Nanchang University, Nanchang, Jiangxi, China
| | - Bo Zeng
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, and
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2
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Harraz OF, Delpire E. Recent insights into channelopathies. Physiol Rev 2024; 104:23-31. [PMID: 37561136 DOI: 10.1152/physrev.00022.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 07/12/2023] [Accepted: 08/05/2023] [Indexed: 08/11/2023] Open
Affiliation(s)
- Osama F Harraz
- Department of Pharmacology, Larner College of Medicine, Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, Vermont, United States
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University Medical School, Nashville, Tennessee, United States
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, Tennessee, United States
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3
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Aufy M, Hussein AM, Stojanovic T, Studenik CR, Kotob MH. Proteolytic Activation of the Epithelial Sodium Channel (ENaC): Its Mechanisms and Implications. Int J Mol Sci 2023; 24:17563. [PMID: 38139392 PMCID: PMC10743461 DOI: 10.3390/ijms242417563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 12/10/2023] [Accepted: 12/14/2023] [Indexed: 12/24/2023] Open
Abstract
Epithelial sodium channel (ENaC) are integral to maintaining salt and water homeostasis in various biological tissues, including the kidney, lung, and colon. They enable the selective reabsorption of sodium ions, which is a process critical for controlling blood pressure, electrolyte balance, and overall fluid volume. ENaC activity is finely controlled through proteolytic activation, a process wherein specific enzymes, or proteases, cleave ENaC subunits, resulting in channel activation and increased sodium reabsorption. This regulatory mechanism plays a pivotal role in adapting sodium transport to different physiological conditions. In this review article, we provide an in-depth exploration of the role of proteolytic activation in regulating ENaC activity. We elucidate the involvement of various proteases, including furin-like convertases, cysteine, and serine proteases, and detail the precise cleavage sites and regulatory mechanisms underlying ENaC activation by these proteases. We also discuss the physiological implications of proteolytic ENaC activation, focusing on its involvement in blood pressure regulation, pulmonary function, and intestinal sodium absorption. Understanding the mechanisms and consequences of ENaC proteolytic activation provides valuable insights into the pathophysiology of various diseases, including hypertension, pulmonary disorders, and various gastrointestinal conditions. Moreover, we discuss the potential therapeutic avenues that emerge from understanding these mechanisms, offering new possibilities for managing diseases associated with ENaC dysfunction. In summary, this review provides a comprehensive discussion of the intricate interplay between proteases and ENaC, emphasizing the significance of proteolytic activation in maintaining sodium and fluid balance in both health and disease.
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Affiliation(s)
- Mohammed Aufy
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria; (A.M.H.); (M.H.K.)
| | - Ahmed M. Hussein
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria; (A.M.H.); (M.H.K.)
- Department of Zoology, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt
| | - Tamara Stojanovic
- Programme for Proteomics, Paracelsus Medical University, 5020 Salzburg, Austria;
| | - Christian R. Studenik
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria; (A.M.H.); (M.H.K.)
| | - Mohamed H. Kotob
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria; (A.M.H.); (M.H.K.)
- Department of Pathology, Faculty of Veterinary Medicine, Assiut University, Assiut 71515, Egypt
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4
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Ding Y, Cui Y, Hou Y, Nie H. Bone marrow mesenchymal stem cell-conditioned medium facilitates fluid resolution via miR-214-activating epithelial sodium channels. MedComm (Beijing) 2021; 1:376-385. [PMID: 34766129 PMCID: PMC8491198 DOI: 10.1002/mco2.40] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 01/08/2023] Open
Abstract
Acute lung injury (ALI) is featured with severe lung edema at the early exudative phase, resulting from the imbalance of alveolar fluid turnover and clearance. Mesenchymal stem cells (MSCs) belong to multipotent stem cells, which have shown potential therapeutic effects during ALI. Of note, MSC‐conditioned medium (MSC‐CM) improved alveolar fluid clearance (AFC) in vivo, whereas the involvement of miRNAs is seldom known. We thus aim to explore the roles of miR‐214 in facilitating MSC‐CM mediated fluid resolution of impaired AFC. In this study, AFC was increased significantly by intratracheally administrated MSC‐CM in lipopolysaccharide‐treated mice. MSC‐CM augmented amiloride‐sensitive currents in intact H441 monolayers, and increased α‐epithelial sodium channel (α‐ENaC) expression level in H441 and mouse alveolar type 2 epithelial cells. Meanwhile, MSC‐CM increased the expression of miR‐214, which may participate in regulating ENaC expression and function. Our results suggested that MSC‐CM enhanced AFC in ALI mice in vivo through a novel mechanism, involving miR‐214 regulation of ENaC.
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Affiliation(s)
- Yan Ding
- Department of Stem Cells and Regenerative Medicine College of Basic Medical Science China Medical University Shenyang China
| | - Yong Cui
- Department of Anesthesiology the First Affiliated Hospital of China Medical University Shenyang China
| | - Yapeng Hou
- Department of Stem Cells and Regenerative Medicine College of Basic Medical Science China Medical University Shenyang China
| | - Hongguang Nie
- Department of Stem Cells and Regenerative Medicine College of Basic Medical Science China Medical University Shenyang China
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5
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Machado RG, Glaser T, Araujo DB, Petiz LL, Oliveira DBL, Durigon GS, Leal AL, Pinho JR, Ferreira LCS, Ulrich H, Durigon EL, Guzzo CR. Inhibition of Severe Acute Respiratory Syndrome Coronavirus 2 Replication by Hypertonic Saline Solution in Lung and Kidney Epithelial Cells. ACS Pharmacol Transl Sci 2021; 4:1514-1527. [PMID: 34651104 PMCID: PMC8442612 DOI: 10.1021/acsptsci.1c00080] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Indexed: 12/27/2022]
Abstract
An unprecedented global health crisis has been caused by a new virus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We performed experiments to test if a hypertonic saline solution was capable of inhibiting virus replication. Our data show that 1.2% NaCl inhibited virus replication by 90%, achieving 100% of inhibition at 1.5% in the nonhuman primate kidney cell line Vero, and 1.1% of NaCl was sufficient to inhibit the virus replication by 88% in human epithelial lung cell line Calu-3. Furthermore, our results indicate that the inhibition is due to an intracellular mechanism and not to the dissociation of the spike SARS-CoV-2 protein and its human receptor. NaCl depolarizes the plasma membrane causing a low energy state (high ADP/ATP concentration ratio) without impairing mitochondrial function, supposedly associated with the inhibition of the SARS-CoV-2 life cycle. Membrane depolarization and intracellular energy deprivation are possible mechanisms by which the hypertonic saline solution efficiently prevents virus replication in vitro assays.
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Affiliation(s)
- Rafael
R. G. Machado
- Department
of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508, Brazil
| | - Talita Glaser
- Department
of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo 05508, Brazil
| | - Danielle B. Araujo
- Department
of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508, Brazil
- Hospital
Israelita Albert Einstein, São Paulo 05652, Brazil
| | - Lyvia Lintzmaier Petiz
- Department
of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo 05508, Brazil
| | - Danielle B. L. Oliveira
- Department
of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508, Brazil
- Hospital
Israelita Albert Einstein, São Paulo 05652, Brazil
- Development
and Innovation Center, Laboratory of Virology, Butantan Institute, São
Paulo 05503, Brazil
| | - Giuliana S. Durigon
- Medical
School Clinical Hospital, University of
São Paulo, São
Paulo 05508, Brazil
| | | | - João Renato
R. Pinho
- Hospital
Israelita Albert Einstein, São Paulo 05652, Brazil
- LIM-03, Central
Laboratories Division, Clinics Hospital, São Paulo School of
Medicine, University of São Paulo, São Paulo 05508, Brazil
- LIM-07,
Institute of Tropical Medicine, Department of Gastroenterology, University of São Paulo School of Medicine, São Paulo 05508, Brazil
| | - Luis C. S. Ferreira
- Department
of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508, Brazil
- Scientific
Platform Pasteur USP, São
Paulo 05508, Brazil
| | - Henning Ulrich
- Department
of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo 05508, Brazil
| | - Edison L. Durigon
- Department
of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508, Brazil
- Scientific
Platform Pasteur USP, São
Paulo 05508, Brazil
| | - Cristiane Rodrigues Guzzo
- Department
of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508, Brazil
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6
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Schmid B, Kredel M, Ullrich R, Krenn K, Lucas R, Markstaller K, Fischer B, Kranke P, Meybohm P, Zwißler B, Frank S. Safety and preliminary efficacy of sequential multiple ascending doses of solnatide to treat pulmonary permeability edema in patients with moderate-to-severe ARDS-a randomized, placebo-controlled, double-blind trial. Trials 2021; 22:643. [PMID: 34544463 PMCID: PMC8450703 DOI: 10.1186/s13063-021-05588-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Accepted: 08/24/2021] [Indexed: 11/16/2022] Open
Abstract
Background Acute respiratory distress syndrome (ARDS) is a complex clinical diagnosis with various possible etiologies. One common feature, however, is pulmonary permeability edema, which leads to an increased alveolar diffusion pathway and, subsequently, impaired oxygenation and decarboxylation. A novel inhaled peptide agent (AP301, solnatide) was shown to markedly reduce pulmonary edema in animal models of ARDS and to be safe to administer to healthy humans in a Phase I clinical trial. Here, we present the protocol for a Phase IIB clinical trial investigating the safety and possible future efficacy endpoints in ARDS patients. Methods This is a randomized, placebo-controlled, double-blind intervention study. Patients with moderate to severe ARDS in need of mechanical ventilation will be randomized to parallel groups receiving escalating doses of solnatide or placebo, respectively. Before advancing to a higher dose, a data safety monitoring board will investigate the data from previous patients for any indication of patient safety violations. The intervention (application of the investigational drug) takes places twice daily over the course of 7 days, ensued by a follow-up period of another 21 days. Discussion The patients to be included in this trial will be severely sick and in need of mechanical ventilation. The amount of data to be collected upon screening and during the course of the intervention phase is substantial and the potential timeframe for inclusion of any given patient is short. However, when prepared properly, adherence to this protocol will make for the acquisition of reliable data. Particular diligence needs to be exercised with respect to informed consent, because eligible patients will most likely be comatose and/or deeply sedated at the time of inclusion. Trial registration This trial was prospectively registered with the EU Clinical trials register (clinicaltrialsregister.eu). EudraCT Number: 2017-003855-47.
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Affiliation(s)
- Benedikt Schmid
- Department of Anaesthesiology, Intensive Care, Emergency and Pain Medicine, University Hospital Wuerzburg, Wuerzburg, Germany
| | - Markus Kredel
- Department of Anaesthesiology, Intensive Care, Emergency and Pain Medicine, University Hospital Wuerzburg, Wuerzburg, Germany
| | - Roman Ullrich
- Department of Anaesthesia, General Intensive Care and Pain Medicine, Medical University of Vienna, Vienna, Austria
| | - Katharina Krenn
- Department of Anaesthesia, General Intensive Care and Pain Medicine, Medical University of Vienna, Vienna, Austria
| | - Rudolf Lucas
- Vascular Biology Center, Division of Pulmonary Medicine, Medical College of Georgia, Augusta University, Augusta, USA
| | - Klaus Markstaller
- Department of Anaesthesia, General Intensive Care and Pain Medicine, Medical University of Vienna, Vienna, Austria
| | | | - Peter Kranke
- Department of Anaesthesiology, Intensive Care, Emergency and Pain Medicine, University Hospital Wuerzburg, Wuerzburg, Germany.
| | - Patrick Meybohm
- Department of Anaesthesiology, Intensive Care, Emergency and Pain Medicine, University Hospital Wuerzburg, Wuerzburg, Germany
| | - Bernhard Zwißler
- Department of Anesthesiology, University Hospital of Ludwig-Maximilians-University (LMU), Munich, Germany.,Comprehensive Pulmonary Center Munich (CPC-M), Member of the German Center for Lung Research (DZL), Munich, Germany
| | - Sandra Frank
- Department of Anesthesiology, University Hospital of Ludwig-Maximilians-University (LMU), Munich, Germany
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7
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Addis DR, Aggarwal S, Lazrak A, Jilling T, Matalon S. Halogen-Induced Chemical Injury to the Mammalian Cardiopulmonary Systems. Physiology (Bethesda) 2021; 36:272-291. [PMID: 34431415 DOI: 10.1152/physiol.00004.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The halogens chlorine (Cl2) and bromine (Br2) are highly reactive oxidizing elements with widespread industrial applications and a history of development and use as chemical weapons. When inhaled, depending on the dose and duration of exposure, they cause acute and chronic injury to both the lungs and systemic organs that may result in the development of chronic changes (such as fibrosis) and death from cardiopulmonary failure. A number of conditions, such as viral infections, coexposure to other toxic gases, and pregnancy increase susceptibility to halogens significantly. Herein we review their danger to public health, their mechanisms of action, and the development of pharmacological agents that when administered post-exposure decrease morbidity and mortality.
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Affiliation(s)
- Dylan R Addis
- Department of Anesthesiology and Perioperative Medicine, Division of Cardiothoracic Anesthesiology, University of Alabama at Birmingham, Birmingham, Alabama.,Comprehensive Cardiovascular Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Saurabh Aggarwal
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular and Translational Biomedicine, University of Alabama at Birmingham, Birmingham, Alabama.,Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Ahmed Lazrak
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular and Translational Biomedicine, University of Alabama at Birmingham, Birmingham, Alabama.,Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Tamas Jilling
- Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.,Department of Pediatrics, Division of Neonatology, Children's Hospital, University of Alabama at Birmingham, Birmingham, Alabama
| | - Sadis Matalon
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular and Translational Biomedicine, University of Alabama at Birmingham, Birmingham, Alabama.,Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
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8
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Zhang J, Li S, Liu J, Li L, Deng F, Baikeli B, Li L, Ma X, Liu G. Higher expression levels of aquaporin (AQP)1 and AQP5 in the lungs of arid-desert living Lepus yarkandensis. J Anim Physiol Anim Nutr (Berl) 2019; 104:1186-1195. [PMID: 31828851 DOI: 10.1111/jpn.13272] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 11/10/2019] [Accepted: 11/19/2019] [Indexed: 12/01/2022]
Abstract
Water transport across epithelial cells that line the airways and alveoli is a crucial component of lung physiology. Aquaporins (AQPs) facilitate water transport across the air space-capillary barrier in the distal lung. However, the roles of lung AQPs in desert animal adaptation to dry airstream environments are still unclear. A hare (Lepus yarkandensis) only lives in the Tarim Basin, and its living environment is an arid climate with rare precipitation. We studied cellular localization and expression levels of AQP1, AQP3, AQP4 and AQP5 in L. yarkandensis lungs by immunohistochemistry, quantitative real-time polymerase chain reaction and Western blot. The lung of rabbits (Oryctolagus cuniculus) that inhabit in mesic environment was similarly studied. Obtained results in two species of animals were compared to investigate whether AQPs in the lung altered expression in the animal living in arid region. AQP1 was localized to the endothelial cells in capillaries and venules surrounding terminal bronchioles and alveoli. AQP5 was localized to the ciliated columnar cells in terminal bronchioles and the alveolar type I cells in the alveolus. Quantitative real-time PCR analysis showed higher AQP1 and AQP5 mRNA levels in L. yarkandensis compared to O. cuniculus. Similar results were obtained by Western blot. These results revealed that the higher expression levels of AQP1 and AQP5 played a significant role in water transport in the lungs of arid-desert living L. yarkandensis and might accelerate water transport from capillary compartments to the airspace.
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Affiliation(s)
- Jianping Zhang
- College of Life Science, Tarim University, Alar, China.,Key Lab of Biological Resources Protection and Utilization in Tarim Basin, Tarim University, Alar, China.,Department of Biochemistry and Molecular Biology, School of Laboratory Medicine, Anhui Province Key Laboratory of Translational Cancer Research, Bengbu Medical College, Bengbu, China
| | - Shuwei Li
- College of Life Science, Tarim University, Alar, China.,Key Lab of Biological Resources Protection and Utilization in Tarim Basin, Tarim University, Alar, China
| | - Jie Liu
- Department of Biochemistry and Molecular Biology, School of Laboratory Medicine, Anhui Province Key Laboratory of Translational Cancer Research, Bengbu Medical College, Bengbu, China
| | - Lexing Li
- Department of Biochemistry and Molecular Biology, School of Laboratory Medicine, Anhui Province Key Laboratory of Translational Cancer Research, Bengbu Medical College, Bengbu, China
| | - Fang Deng
- College of Life Science, Tarim University, Alar, China
| | | | - Linrui Li
- Department of Basic Veterinary Medicine, Key Lab of Swine Genetics and Breeding and Agricultural Animal Breeding and Reproduction, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Xuanye Ma
- Department of Basic Veterinary Medicine, Key Lab of Swine Genetics and Breeding and Agricultural Animal Breeding and Reproduction, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Guoquan Liu
- Department of Biochemistry and Molecular Biology, School of Laboratory Medicine, Anhui Province Key Laboratory of Translational Cancer Research, Bengbu Medical College, Bengbu, China.,Department of Basic Veterinary Medicine, Key Lab of Swine Genetics and Breeding and Agricultural Animal Breeding and Reproduction, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
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9
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Lu K, Chen X, Zhu W, Mao X, Yang Y, Qiu J, Zhang M, Cheng R. Terbutaline alleviates the lung injury in the neonatal rats exposed to endotoxin: Potential roles of epithelial sodium channels. Pediatr Pulmonol 2019; 54:280-288. [PMID: 30644180 PMCID: PMC6618278 DOI: 10.1002/ppul.24242] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 12/15/2018] [Indexed: 12/18/2022]
Abstract
Intrauterine inflammation generates inflammatory mediators that damage the developing bronchoalveolar epithelium, resulting in neonatal lung injury. Lung fluid transport disorders are the main reasons for the development of pulmonary edema, an important pathology of lung injury. Previous studies suggested that epithelial sodium channels (ENaCs) play an important role in lung fluid transport. Here, we investigated whether changes in the expression of ENaCs were observed when neonatal rat lung injury was induced by maternal exposure to endotoxin. We also examined the therapeutic effect of terbutaline nebulizer inhalation on this injury. The results showed that maternal exposure to endotoxin increased the levels of TNF-α and IL-1β in bronchoalveolar lavage fluid, suppressed α-, β-, γ-ENaC in the neonatal rat lung, and resulted in the formation of pulmonary edema on postnatal days 1 and 7. Terbutaline up-regulated the expression of β- and γ-ENaC in the distal lung after 7 days of treatment. The potential signal molecules cAMP, PKA, and CREB expressions were increased after terbutaline treatment. In summary, maternal exposure to endotoxin decreased the expression of ENaCs in neonatal rats which, in turn, may exacerbate pulmonary edema. Inhalation of the β2-adrenergic receptor agonist terbutaline improved lung liquid clearance. By increasing the expression of sodium ion channels, the effective removal of alveolar fluid provides a new way for the prevention and treatment of neonatal lung injury.
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Affiliation(s)
- Keyu Lu
- Department of neonates, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Xu Chen
- Department of neonates, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Weiwei Zhu
- Department of neonates, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Xiaonan Mao
- Department of neonates, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Yang Yang
- Department of neonates, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Jie Qiu
- Department of neonates, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Mingshun Zhang
- Key Laboratory of Antibody Technique of Ministry of Health, Nanjing Medical University, Nanjing, China.,Department of Immunology, Nanjing Medical University, Nanjing, China
| | - Rui Cheng
- Department of neonates, Children's Hospital of Nanjing Medical University, Nanjing, China
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10
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Magnani ND, Dada LA, Sznajder JI. Ubiquitin-proteasome signaling in lung injury. Transl Res 2018; 198:29-39. [PMID: 29752900 PMCID: PMC6986356 DOI: 10.1016/j.trsl.2018.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 04/15/2018] [Accepted: 04/16/2018] [Indexed: 12/21/2022]
Abstract
Cell homeostasis requires precise coordination of cellular proteins function. Ubiquitination is a post-translational modification that modulates protein half-life and function and is tightly regulated by ubiquitin E3 ligases and deubiquitinating enzymes. Lung injury can progress to acute respiratory distress syndrome that is characterized by an inflammatory response and disruption of the alveolocapillary barrier resulting in alveolar edema accumulation and hypoxemia. Ubiquitination plays an important role in the pathobiology of acute lung injury as it regulates the proteins modulating the alveolocapillary barrier and the inflammatory response. Better understanding of the signaling pathways regulated by ubiquitination may lead to novel therapeutic approaches by targeting specific elements of the ubiquitination pathways.
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Affiliation(s)
- Natalia D Magnani
- Pulmonary and Critical Care Division, Northwestern Feinberg School of Medicine, Chicago, Illinois
| | - Laura A Dada
- Pulmonary and Critical Care Division, Northwestern Feinberg School of Medicine, Chicago, Illinois
| | - Jacob I Sznajder
- Pulmonary and Critical Care Division, Northwestern Feinberg School of Medicine, Chicago, Illinois.
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11
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Hamacher J, Hadizamani Y, Borgmann M, Mohaupt M, Männel DN, Moehrlen U, Lucas R, Stammberger U. Cytokine-Ion Channel Interactions in Pulmonary Inflammation. Front Immunol 2018; 8:1644. [PMID: 29354115 PMCID: PMC5758508 DOI: 10.3389/fimmu.2017.01644] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 11/10/2017] [Indexed: 12/12/2022] Open
Abstract
The lungs conceptually represent a sponge that is interposed in series in the bodies’ systemic circulation to take up oxygen and eliminate carbon dioxide. As such, it matches the huge surface areas of the alveolar epithelium to the pulmonary blood capillaries. The lung’s constant exposure to the exterior necessitates a competent immune system, as evidenced by the association of clinical immunodeficiencies with pulmonary infections. From the in utero to the postnatal and adult situation, there is an inherent vital need to manage alveolar fluid reabsorption, be it postnatally, or in case of hydrostatic or permeability edema. Whereas a wealth of literature exists on the physiological basis of fluid and solute reabsorption by ion channels and water pores, only sparse knowledge is available so far on pathological situations, such as in microbial infection, acute lung injury or acute respiratory distress syndrome, and in the pulmonary reimplantation response in transplanted lungs. The aim of this review is to discuss alveolar liquid clearance in a selection of lung injury models, thereby especially focusing on cytokines and mediators that modulate ion channels. Inflammation is characterized by complex and probably time-dependent co-signaling, interactions between the involved cell types, as well as by cell demise and barrier dysfunction, which may not uniquely determine a clinical picture. This review, therefore, aims to give integrative thoughts and wants to foster the unraveling of unmet needs in future research.
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Affiliation(s)
- Jürg Hamacher
- Internal Medicine and Pneumology, Lindenhofspital, Bern, Switzerland.,Internal Medicine V - Pneumology, Allergology, Respiratory and Environmental Medicine, Faculty of Medicine, Saarland University, Saarbrücken, Germany.,Lungen- und Atmungsstiftung Bern, Bern, Switzerland
| | - Yalda Hadizamani
- Internal Medicine and Pneumology, Lindenhofspital, Bern, Switzerland.,Lungen- und Atmungsstiftung Bern, Bern, Switzerland
| | - Michèle Borgmann
- Internal Medicine and Pneumology, Lindenhofspital, Bern, Switzerland.,Lungen- und Atmungsstiftung Bern, Bern, Switzerland
| | - Markus Mohaupt
- Internal Medicine, Sonnenhofspital Bern, Bern, Switzerland
| | | | - Ueli Moehrlen
- Paediatric Visceral Surgery, Universitäts-Kinderspital Zürich, Zürich, Switzerland
| | - Rudolf Lucas
- Department of Pharmacology and Toxicology, Vascular Biology Center, Medical College of Georgia, Augusta, GA, United States
| | - Uz Stammberger
- Lungen- und Atmungsstiftung Bern, Bern, Switzerland.,Novartis Institutes for Biomedical Research, Translational Clinical Oncology, Novartis Pharma AG, Basel, Switzerland
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12
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Londino JD, Lazrak A, Collawn JF, Bebok Z, Harrod KS, Matalon S. Influenza virus infection alters ion channel function of airway and alveolar cells: mechanisms and physiological sequelae. Am J Physiol Lung Cell Mol Physiol 2017; 313:L845-L858. [PMID: 28775098 DOI: 10.1152/ajplung.00244.2017] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 02/07/2023] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) and the amiloride-sensitive epithelial sodium channels (ENaC) are located in the apical membranes of airway and alveolar epithelial cells. These transporters play an important role in the regulation of lung fluid balance across airway and alveolar epithelia by being the conduits for chloride (Cl-) and bicarbonate ([Formula: see text]) secretion and sodium (Na+) ion absorption, respectively. The functional role of these channels in the respiratory tract is to maintain the optimum volume and ionic composition of the bronchial periciliary fluid (PCL) and alveolar lining fluid (ALF) layers. The PCL is required for proper mucociliary clearance of pathogens and debris, and the ALF is necessary for surfactant homeostasis and optimum gas exchange. Dysregulation of ion transport may lead to mucus accumulation, bacterial infections, inflammation, pulmonary edema, and compromised respiratory function. Influenza (or flu) in mammals is caused by influenza A and B viruses. Symptoms include dry cough, sore throat, and is often followed by secondary bacterial infections, accumulation of fluid in the alveolar spaces and acute lung injury. The underlying mechanisms of flu symptoms are not fully understood. This review summarizes our present knowledge of how influenza virus infections alter airway and alveolar epithelial cell CFTR and ENaC function in vivo and in vitro and the role of these changes in influenza pathogenesis.
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Affiliation(s)
- James David Londino
- Acute Lung Injury Center of Excellence, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ahmed Lazrak
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and
| | - James F Collawn
- Department of Cell, Developmental and Integrative Biology School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Zsuzsanna Bebok
- Department of Cell, Developmental and Integrative Biology School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Kevin S Harrod
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and
| | - Sadis Matalon
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and
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13
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Jin F, Li C. Seawater-drowning-induced acute lung injury: From molecular mechanisms to potential treatments. Exp Ther Med 2017; 13:2591-2598. [PMID: 28587319 PMCID: PMC5450642 DOI: 10.3892/etm.2017.4302] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 01/26/2017] [Indexed: 01/11/2023] Open
Abstract
Drowning is a crucial public safety problem and is the third leading cause of accidental fatality, claiming ~372,000 lives annually, worldwide. In near-drowning patients, acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) is one of the most common complications. Approximately 1/3 of near-drowning patients fulfill the criteria for ALI or ARDS. In the present article, the current literature of near-drowning, pathophysiologic changes and the molecular mechanisms of seawater-drowning-induced ALI and ARDS was reviewed. Seawater is three times more hyperosmolar than plasma, and following inhalation of seawater the hyperosmotic seawater may cause serious injury in the lung and alveoli. The perturbing effects of seawater may be primarily categorized into insufficiency of pulmonary surfactant, blood-air barrier disruption, formation of pulmonary edema, inflammation, oxidative stress, autophagy, apoptosis and various other hypertonic stimulation. Potential treatments for seawater-induced ALI/ARDS were also presented, in addition to suggestions for further studies. A total of nine therapeutic strategies had been tested and all had focused on modulating the over-activated immunoreactions. In conclusion, seawater drowning is a complex injury process and the exact mechanisms and potential treatments require further exploration.
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Affiliation(s)
- Faguang Jin
- Department of Respiratory and Critical Care Medicine, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China
| | - Congcong Li
- Department of Respiratory and Critical Care Medicine, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China
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14
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Willam A, Aufy M, Tzotzos S, Evanzin H, Chytracek S, Geppert S, Fischer B, Fischer H, Pietschmann H, Czikora I, Lucas R, Lemmens-Gruber R, Shabbir W. Restoration of Epithelial Sodium Channel Function by Synthetic Peptides in Pseudohypoaldosteronism Type 1B Mutants. Front Pharmacol 2017; 8:85. [PMID: 28286482 PMCID: PMC5323398 DOI: 10.3389/fphar.2017.00085] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 02/09/2017] [Indexed: 12/20/2022] Open
Abstract
The synthetically produced cyclic peptides solnatide (a.k.a. TIP or AP301) and its congener AP318, whose molecular structures mimic the lectin-like domain of human tumor necrosis factor (TNF), have been shown to activate the epithelial sodium channel (ENaC) in various cell- and animal-based studies. Loss-of-ENaC-function leads to a rare, life-threatening, salt-wasting syndrome, pseudohypoaldosteronism type 1B (PHA1B), which presents with failure to thrive, dehydration, low blood pressure, anorexia and vomiting; hyperkalemia, hyponatremia and metabolic acidosis suggest hypoaldosteronism, but plasma aldosterone and renin activity are high. The aim of the present study was to investigate whether the ENaC-activating effect of solnatide and AP318 could rescue loss-of-function phenotype of ENaC carrying mutations at conserved amino acid positions observed to cause PHA1B. The macroscopic Na+ current of all investigated mutants was decreased compared to wild type ENaC when measured in whole-cell patch clamp experiments, and a great variation in the membrane abundance of different mutant ENaCs was observed with Western blotting experiments. However, whatever mechanism leads to loss-of-function of the studied ENaC mutations, the synthetic peptides solnatide and AP318 could restore ENaC function up to or even higher than current levels of wild type ENaC. As therapy of PHA1B is only symptomatic so far, the peptides solnatide and AP318, which directly target ENaC, are promising candidates for the treatment of the channelopathy-caused disease PHA1B.
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Affiliation(s)
- Anita Willam
- Department of Pharmacology and Toxicology, University of Vienna Vienna, Austria
| | - Mohammed Aufy
- Department of Pharmacology and Toxicology, University of Vienna Vienna, Austria
| | | | - Heinrich Evanzin
- Department of Pharmacology and Toxicology, University of Vienna Vienna, Austria
| | - Sabine Chytracek
- Department of Pharmacology and Toxicology, University of Vienna Vienna, Austria
| | - Sabrina Geppert
- Department of Pharmacology and Toxicology, University of Vienna Vienna, Austria
| | | | | | | | - Istvan Czikora
- Vascular Biology Center, Medical College of Georgia, Augusta University Augusta, GA, USA
| | - Rudolf Lucas
- Vascular Biology Center, Medical College of Georgia, Augusta University Augusta, GA, USA
| | - Rosa Lemmens-Gruber
- Department of Pharmacology and Toxicology, University of Vienna Vienna, Austria
| | - Waheed Shabbir
- Department of Pharmacology and Toxicology, University of ViennaVienna, Austria; APEPTICO GmbHVienna, Austria
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15
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Abstract
Improvement in the ratio of PaO2 to the fraction of inspired oxygen and treatment of pulmonary infections in donors have been cited as important goals for improving lungs before implantation and restoring marginal lungs to the donor pool. Likewise, improving donor PaO2 is often critical for other organs during donor care. The common physiological mechanisms responsible for hypoxemia are ventilation/perfusion mismatching, abnormal oxygen diffusion, and hypoventilation. These mechanisms are discussed and treatment options are considered.
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Affiliation(s)
- David J Powner
- Vivian L. Smith Center for Neurologic Research, University of Texas Health Science Center at Houston, TX, USA
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16
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Ji HL, Nie HG, Chang Y, Lian Q, Liu SL. CPT-cGMP Is A New Ligand of Epithelial Sodium Channels. Int J Biol Sci 2016; 12:359-66. [PMID: 27019621 PMCID: PMC4807156 DOI: 10.7150/ijbs.13764] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 11/11/2015] [Indexed: 12/28/2022] Open
Abstract
Epithelial sodium channels (ENaC) are localized at the apical membrane of the epithelium, and are responsible for salt and fluid reabsorption. Renal ENaC takes up salt, thereby controlling salt content in serum. Loss-of-function ENaC mutations lead to low blood pressure due to salt-wasting, while gain-of-function mutations cause impaired sodium excretion and subsequent hypertension as well as hypokalemia. ENaC activity is regulated by intracellular and extracellular signals, including hormones, neurotransmitters, protein kinases, and small compounds. Cyclic nucleotides are broadly involved in stimulating protein kinase A and protein kinase G signaling pathways, and, surprisingly, also appear to have a role in regulating ENaC. Increasing evidence suggests that the cGMP analog, CPT-cGMP, activates αβγ-ENaC activity reversibly through an extracellular pathway in a dose-dependent manner. Furthermore, the parachlorophenylthio moiety and ribose 2'-hydroxy group of CPT-cGMP are essential for facilitating the opening of ENaC channels by this compound. Serving as an extracellular ligand, CPT-cGMP eliminates sodium self-inhibition, which is a novel mechanism for stimulating salt reabsorption in parallel to the traditional NO/cGMP/PKG signal pathway. In conclusion, ENaC may be a druggable target for CPT-cGMP, leading to treatments for kidney malfunctions in salt reabsorption.
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Affiliation(s)
- Hong-Long Ji
- 1. Department of Cellular and Molecular Biology, University of Texas Health Science Center at Tyler, Tyler, Texas 75708, USA
| | - Hong-Guang Nie
- 2. Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang 110001, China
| | - Yongchang Chang
- 3. Barrow Neurological Institute, St Joseph's Hospital and Medical Center, Phoenix, Arizona, 85013, USA
| | - Qizhou Lian
- 4. Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Shan-Lu Liu
- 5. Department of Molecular Microbiology and Immunology, Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
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17
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Jiang L, Wang Y, Su C, Sun H, Zhang H, Zhu B, Zhang H, Xiao H, Wang J, Zhang J. Epithelial sodium channel is involved in H2S-induced acute pulmonary edema. Inhal Toxicol 2015; 27:613-20. [DOI: 10.3109/08958378.2015.1048909] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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18
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Endogenous acetylcholine increases alveolar epithelial fluid transport via activation of alveolar epithelial Na,K-ATPase in mice. Respir Physiol Neurobiol 2015; 217:25-31. [DOI: 10.1016/j.resp.2015.05.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 05/10/2015] [Accepted: 05/11/2015] [Indexed: 01/11/2023]
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19
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Abstract
Pulmonary edema clearance is necessary for patients with lung injury to recover and survive. The mechanisms regulating edema clearance from the lungs are distinct from the factors contributing edema formation during injury. Edema clearance is effected via vectorial transport of Na(+) out of the airspaces which generates an osmotic gradient causing water to follow the gradient out of the cells. This Na(+) transport across the alveolar epithelium is mostly effected via apical Na(+) and chloride channels and basolateral Na,K-ATPase. The Na,K-ATPase pumps Na(+) out of the cell and K(+) into the cell against their respective gradients in an ATP-consuming reaction. Two mechanisms contribute to the regulation of the Na,K-ATPase activity:recruitment of its subunits from intracellular compartments into the basolateral membrane, and transcriptional/translational regulation. Na,K-ATPase activity and edema clearance are increased by catecholamines, aldosterone, vasopressin, overexpression of the pump genes, and others. During lung injury, mechanisms regulating edema clearance are inhibited by yet unclear pathways. Better understanding of the mechanisms that regulate pulmonary edema clearance may lead to therapeutic interventions that counterbalance the inhibition of edema clearance during lung injury and improve the lungs' ability to clear fluid, which is crucial for patient survival.
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Affiliation(s)
- Zaher S. Azzam
- Internal Medicine “B”, Rambam Health Care Campus, Department of Physiology and Biophysics, The Rappaport Family Faculty of Medicine and Research Institute, Technion, Israel Institute of Technology, Haifa, Israel
| | - Jacob I. Sznajder
- Division of Pulmonary and Critical Care Medicine, Northwestern University, Chicago, IL, USA
- To whom correspondence should be addressed. E-mail:
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20
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Luo L, Deng J, Wang DX, He J, Deng W. Regulation of epithelial sodium channel expression by oestradiol and progestogen in alveolar epithelial cells. Respir Physiol Neurobiol 2015; 216:52-62. [PMID: 26051998 DOI: 10.1016/j.resp.2015.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 05/15/2015] [Accepted: 06/01/2015] [Indexed: 01/11/2023]
Abstract
Oestrogen (E) and progestogen (P) exert regulatory effects on the epithelial Na(+) channel (ENaC) in the kidneys and the colon. However, the effects of E and P on the ENaC and on alveolar fluid clearance (AFC) remain unclear, and the mechanisms of action of these hormones are unknown. In this study, we showed that E and/or P administration increased AFC by more than 25% and increased the expression of the α and γ subunits of ENaC by approximately 35% in rats subjected to oleic acid-induced acute lung injury (ALI). A similar effect was observed in the dexamethasone-treated group. Furthermore, E and/or P treatment inhibited 11β-hydroxysteroid dehydrogenase (HSD) type 2 (11β-HSD2) activity, increased corticosterone expression and decreased the serum adrenocorticotrophic hormone (ACTH) levels. These effects were similar to those observed following treatment with carbenoxolone (CBX), a nonspecific HSD inhibitor. Further investigation showed that CBX further significantly increased AFC and α-ENaC expression after treatment with a low dose of E and/or P. In vitro, E or P alone inhibited 11β-HSD2 activity in a dose-dependent manner and increased α-ENaC expression by at least 50%, and E combined with P increased α-ENaC expression by more than 80%. Thus, E and P may augment the expression of α-ENaC, enhance AFC, attenuate pulmonary oedema by inhibiting 11β-HSD2 activity, and increase the active glucocorticoid levels in vivo and in vitro.
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Affiliation(s)
- Ling Luo
- Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jia Deng
- First Department of Internal Medicine, Traditional Chinese Medical Hospital of Jiangbei District, Chongqing, China
| | - Dao-xin Wang
- Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, Chongqing, China.
| | - Jing He
- Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Wang Deng
- Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
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21
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Jeggle P, Smith ESJ, Stewart AP, Haerteis S, Korbmacher C, Edwardson JM. Atomic force microscopy imaging reveals the formation of ASIC/ENaC cross-clade ion channels. Biochem Biophys Res Commun 2015; 464:38-44. [PMID: 26032502 DOI: 10.1016/j.bbrc.2015.05.091] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 05/28/2015] [Indexed: 01/02/2023]
Abstract
ASIC and ENaC are co-expressed in various cell types, and there is evidence for a close association between them. Here, we used atomic force microscopy (AFM) to determine whether ASIC1a and ENaC subunits are able to form cross-clade hybrid ion channels. ASIC1a and ENaC could be co-isolated from detergent extracts of tsA 201 cells co-expressing the two subunits. Isolated proteins were incubated with antibodies against ENaC and Fab fragments against ASIC1a. AFM imaging revealed proteins that were decorated by both an antibody and a Fab fragment with an angle of ∼120° between them, indicating the formation of ASIC1a/ENaC heterotrimers.
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Affiliation(s)
- Pia Jeggle
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Ewan St J Smith
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Andrew P Stewart
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Silke Haerteis
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstrasse 6, 91054 Erlangen, Germany
| | - Christoph Korbmacher
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstrasse 6, 91054 Erlangen, Germany
| | - J Michael Edwardson
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom.
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22
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Edinger RS, Coronnello C, Bodnar AJ, Labarca M, Bhalla V, LaFramboise WA, Benos PV, Ho J, Johnson JP, Butterworth MB. Aldosterone regulates microRNAs in the cortical collecting duct to alter sodium transport. J Am Soc Nephrol 2014; 25:2445-57. [PMID: 24744440 PMCID: PMC4214524 DOI: 10.1681/asn.2013090931] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 02/05/2014] [Indexed: 12/26/2022] Open
Abstract
A role for microRNAs (miRs) in the physiologic regulation of sodium transport in the kidney has not been established. In this study, we investigated the potential of aldosterone to alter miR expression in mouse cortical collecting duct (mCCD) epithelial cells. Microarray studies demonstrated the regulation of miR expression by aldosterone in both cultured mCCD and isolated primary distal nephron principal cells. Aldosterone regulation of the most significantly downregulated miRs, mmu-miR-335-3p, mmu-miR-290-5p, and mmu-miR-1983 was confirmed by quantitative RT-PCR. Reducing the expression of these miRs separately or in combination increased epithelial sodium channel (ENaC)-mediated sodium transport in mCCD cells, without mineralocorticoid supplementation. Artificially increasing the expression of these miRs by transfection with plasmid precursors or miR mimic constructs blunted aldosterone stimulation of ENaC transport. Using a newly developed computational approach, termed ComiR, we predicted potential gene targets for the aldosterone-regulated miRs and confirmed ankyrin 3 (Ank3) as a novel aldosterone and miR-regulated protein. A dual-luciferase assay demonstrated direct binding of the miRs with the Ank3-3' untranslated region. Overexpression of Ank3 increased and depletion of Ank3 decreased ENaC-mediated sodium transport in mCCD cells. These findings implicate miRs as intermediaries in aldosterone signaling in principal cells of the distal kidney nephron.
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Affiliation(s)
| | | | | | | | | | | | | | | | - John P Johnson
- Renal-Electrolyte Division, Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Michael B Butterworth
- Renal-Electrolyte Division, Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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23
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Chen Z, Zhao R, Zhao M, Liang X, Bhattarai D, Dhiman R, Shetty S, Idell S, Ji HL. Regulation of epithelial sodium channels in urokinase plasminogen activator deficiency. Am J Physiol Lung Cell Mol Physiol 2014; 307:L609-17. [PMID: 25172911 DOI: 10.1152/ajplung.00126.2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Epithelial sodium channels (ENaC) govern transepithelial salt and fluid homeostasis. ENaC contributes to polarization, apoptosis, epithelial-mesenchymal transformation, etc. Fibrinolytic proteases play a crucial role in virtually all of these processes and are elaborated by the airway epithelium. We hypothesized that urokinase-like plasminogen activator (uPA) regulates ENaC function in airway epithelial cells and tested that possibility in primary murine tracheal epithelial cells (MTE). Both basal and cAMP-activated Na(+) flow through ENaC were significantly reduced in monolayers of uPA-deficient cells. The reduction in ENaC activity was further confirmed in basolateral membrane-permeabilized cells. A decrease in the Na(+)-K(+)-ATPase activity in the basolateral membrane could contribute to the attenuation of ENaC function in intact monolayer cells. Dysfunctional fluid resolution was seen in uPA-disrupted cells. Administration of uPA and plasmin partially restores ENaC activity and fluid reabsorption by MTEs. ERK1/2, but not Akt, phosphorylation was observed in the cells and lungs of uPA-deficient mice. On the other hand, cleavage of γ ENaC is significantly depressed in the lungs of uPA knockout mice vs. those of wild-type controls. Expression of caspase 8, however, did not differ between wild-type and uPA(-/-) mice. In addition, uPA deficiency did not alter transepithelial resistance. Taken together, the mechanisms for the regulation of ENaC by uPA in MTEs include augmentation of Na(+)-K(+)-ATPase, proteolysis, and restriction of ERK1/2 phosphorylation. We demonstrate for the first time that ENaC may serve as a downstream signaling target by which uPA controls the biophysical profiles of airway fluid and epithelial function.
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Affiliation(s)
- Zaixing Chen
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas; School of Pharmacy, China Medical University, Liaoning Shenyang, China
| | - Runzhen Zhao
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas
| | - Meimi Zhao
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas; School of Pharmacy, China Medical University, Liaoning Shenyang, China
| | - Xinrong Liang
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas
| | - Deepa Bhattarai
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas
| | - Rohan Dhiman
- Department of Pulmonary Immunology, The University of Texas Health Science Center at Tyler, Tyler, Texas
| | - Sreerama Shetty
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas
| | - Steven Idell
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas; Texas Lung Injury Institute, The University of Texas Health Science Center at Tyler, Tyler, Texas; and Department of Medicine, The University of Texas Health Science Center at Tyler, Tyler, Texas
| | - Hong-Long Ji
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas; Texas Lung Injury Institute, The University of Texas Health Science Center at Tyler, Tyler, Texas; and
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24
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Grzesik BA, Vohwinkel CU, Morty RE, Mayer K, Herold S, Seeger W, Vadász I. Efficient gene delivery to primary alveolar epithelial cells by nucleofection. Am J Physiol Lung Cell Mol Physiol 2013; 305:L786-94. [PMID: 24077946 DOI: 10.1152/ajplung.00191.2013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Primary alveolar epithelial cells play a pivotal role in lung research, particularly when focusing on gas exchange, barrier function, and transepithelial transport processes. However, efficient transfection of primary alveolar epithelial cells continues to be a major challenge. In the present study, we applied nucleofection, a novel method of gene and oligonucleotide delivery to the nucleus of cells by electroporation, to achieve highly efficient transfection of primary alveolar epithelial type II (ATII) cells. To quantify the amount of ATII cells effectively transfected, we applied a plasmid expressing GFP and assessed the amount of GFP-expressing cells by flow cytometry. Analysis of the nucleofected ATII cells revealed a concentration-dependent transfection efficiency of up to 50% when using 3-8 μg plasmid DNA without affecting cell viability. Nucleofection of cultured A549 and H441 cells yielded similar transfection rates. Importantly, nucleofection of ATII cells did not interfere with the integrity of ATII monolayers even with use of relatively high concentrations of plasmid DNA. In subsequent studies, we also efficiently delivered small interfering RNAs to ATII cells by nucleofection, thereby silencing Akt and the multiligand receptor megalin, which has been recently shown to play a key role in removal of excess protein from the alveolar space, and effectively inhibited megalin-driven uptake and transcellular transport of albumin in ATII cells. Thus we report successful transfection of primary rat alveolar epithelial cells with both plasmids and oligonucleotides via nucleofection with high viability and consistently good transfection rates without impairing key physiological properties of the cells.
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Affiliation(s)
- Benno A Grzesik
- Dept. of Internal Medicine, Justus Liebig Univ., Universities of Giessen and Marburg Lung Center, Klinikstrasse 33, 35392 Giessen, Germany.
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25
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Abstract
Ion channels perform a variety of cellular functions in lung epithelia. Oxidant- and antioxidant-mediated mechanisms (that is, redox regulation) of ion channels are areas of intense research. Significant progress has been made in our understanding of redox regulation of ion channels since the last Experimental Biology report in 2003. Advancements include: 1) identification of nonphagocytic NADPH oxidases as sources of regulated reactive species (RS) production in epithelia, 2) an understanding that excessive treatment with antioxidants can result in greater oxidative stress, and 3) characterization of novel RS signaling pathways that converge upon ion channel regulation. These advancements, as discussed at the 2013 Experimental Biology Meeting in Boston, MA, impact our understanding of oxidative stress in the lung, and, in particular, illustrate that the redox state has profound effects on ion channel and cellular function.
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Chloride secretion across adult alveolar epithelial cells contributes to cardiogenic edema. Proc Natl Acad Sci U S A 2013; 110:10055-6. [PMID: 23720313 DOI: 10.1073/pnas.1307480110] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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Takemura Y, Helms MN, Eaton AF, Self J, Ramosevac S, Jain L, Bao HF, Eaton DC. Cholinergic regulation of epithelial sodium channels in rat alveolar type 2 epithelial cells. Am J Physiol Lung Cell Mol Physiol 2013; 304:L428-37. [PMID: 23292809 DOI: 10.1152/ajplung.00129.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We and others have shown that epithelial Na(+) channels (ENaC) in alveolar type 2 (AT2) cells are activated by β2 agonists, steroid hormones, elevated oxygen tension, and by dopamine. Although acetylcholine receptors (AChRs) have been previously described in the lung, there are few reports of whether cholinergic agonists alter sodium transport in the alveolar epithelium. Therefore, we investigated how cholinergic receptors regulate ENaC activity in primary cultures of rat AT2 cells using cell-attached patch-clamp recordings to assess ENaC activity. We found that the muscarinic agonists, carbachol (CCh) and oxotremorine, activated ENaC in a dose-dependent manner but that nicotine did not. CCh-induced activation of ENaC was blocked by atropine. Western blotting and immunohistochemistry suggested that muscarinic M2 and M3 receptors (mAChRs) but not nicotinic receptors were present in AT2 cells. Endogenous RhoA and GTP-RhoA increased in response to CCh and the increase was reduced by pretreatment with atropine. We showed that Y-27632, an inhibitor of Rho-associated protein kinase (ROCK), abolished endogenous ENaC activity and inhibited the activation of ENaC by CCh. We also showed that ROCK signaling was necessary for ENaC stability in 2F3 cells, a model for AT2 cells. Our results showed that muscarinic agonists activated ENaC in rat AT2 cells through M2 and/or M3 mAChRs probably via a RhoA/ROCK signaling pathway.
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Affiliation(s)
- Yoshizumi Takemura
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, USA
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Althaus M, Urness KD, Clauss WG, Baines DL, Fronius M. The gasotransmitter hydrogen sulphide decreases Na⁺ transport across pulmonary epithelial cells. Br J Pharmacol 2012; 166:1946-63. [PMID: 22352810 DOI: 10.1111/j.1476-5381.2012.01909.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND AND PURPOSE The transepithelial absorption of Na(+) in the lungs is crucial for the maintenance of the volume and composition of epithelial lining fluid. The regulation of Na(+) transport is essential, because hypo- or hyperabsorption of Na(+) is associated with lung diseases such as pulmonary oedema or cystic fibrosis. This study investigated the effects of the gaseous signalling molecule hydrogen sulphide (H(2) S) on Na(+) absorption across pulmonary epithelial cells. EXPERIMENTAL APPROACH Ion transport processes were electrophysiologically assessed in Ussing chambers on H441 cells grown on permeable supports at air/liquid interface and on native tracheal preparations of pigs and mice. The effects of H(2)S were further investigated on Na(+) channels expressed in Xenopus oocytes and Na(+) /K(+)-ATPase activity in vitro. Membrane abundance of Na(+) /K(+)-ATPase was determined by surface biotinylation and Western blot. Cellular ATP concentrations were measured colorimetrically, and cytosolic Ca(2+) concentrations were measured with Fura-2. KEY RESULTS H(2)S rapidly and reversibly inhibited Na(+) transport in all the models employed. H(2)S had no effect on Na(+) channels, whereas it decreased Na(+) /K(+)-ATPase currents. H(2)S did not affect the membrane abundance of Na(+) /K(+)-ATPase, its metabolic or calcium-dependent regulation, or its direct activity. However, H(2)S inhibited basolateral calcium-dependent K(+) channels, which consequently decreased Na(+) absorption by H441 monolayers. CONCLUSIONS AND IMPLICATIONS H(2) S impairs pulmonary transepithelial Na(+) absorption, mainly by inhibiting basolateral Ca(2+)-dependent K(+) channels. These data suggest that the H(2)S signalling system might represent a novel pharmacological target for modifying pulmonary transepithelial Na(+) transport.
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Affiliation(s)
- M Althaus
- Institute of Animal Physiology, Justus-Liebig University of Giessen, Giessen, Germany.
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Laube M, Kimpel SU, Dietl P, Thome UH, Wittekindt OH. Benzimidazolones enhance the function of epithelial Na⁺ transport. Br J Pharmacol 2012; 168:1329-40. [PMID: 23083067 DOI: 10.1111/bph.12027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 09/11/2012] [Accepted: 09/18/2012] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND AND PURPOSE Pharmacological enhancement of vectorial Na⁺ transport may be useful to increase alveolar fluid clearance. Herein, we investigated the influence of the benzimidazolones 1-ethyl-1,3-dihydro-2-benzimidazolone (1-EBIO), 5,6-dichloro-1-EBIO (DC-EBIO) and chlorzoxazone on vectorial epithelial Na⁺ transport. EXPERIMENTAL APPROACH Effects on vectorial Na⁺ transport and amiloride-sensitive apical membrane Na⁺ permeability were determined by measuring short-circuit currents (I(SC)) in rat fetal distal lung epithelial (FDLE) monolayers. Furthermore, amiloride-sensitive membrane conductance and the open probability of epithelial Na⁺ channels (ENaC) were determined by patch clamp experiments using A549 cells. KEY RESULTS I(SC) was increased by approximately 50% after addition of 1-EBIO, DC-EBIO and chlorzoxazone. With permeabilized basolateral membranes in the presence of a 145:5 apical to basolateral Na⁺ gradient, the benzimidazolones markedly increased amiloride-sensitive I(SC). 5-(N-Ethyl-N-isopropyl)amiloride-induced inhibition of I(SC) was not affected. The benzamil-sensitive I(SC) was increased in benzimidazolone-stimulated monolayers. Pretreating the apical membrane with amiloride, which inhibits ENaC, completely prevented the stimulating effects of benzimidazolones on I(SC). Furthermore, 1-EBIO (1 mM) and DC-EBIO (0.1 mM) significantly increased (threefold) the open probability of ENaC without influencing current amplitude. Whole cell measurements showed that DC-EBIO (0.1 mM) induced an amiloride-sensitive increase in membrane conductance. CONCLUSION AND IMPLICATIONS Benzimidazolones have a stimulating effect on vectorial Na⁺ transport. The antagonist sensitivity of this effect suggests the benzimidazolones elicit this action by activating the highly selective ENaC currents. Thus, the results demonstrate a possible new strategy for directly enhancing epithelial Na⁺ transport.
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Affiliation(s)
- M Laube
- Division of Neonatology, University of Leipzig, Leipzig, Germany
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Ji HL, Zhao RZ, Chen ZX, Shetty S, Idell S, Matalon S. δ ENaC: a novel divergent amiloride-inhibitable sodium channel. Am J Physiol Lung Cell Mol Physiol 2012; 303:L1013-26. [PMID: 22983350 DOI: 10.1152/ajplung.00206.2012] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The fourth subunit of the epithelial sodium channel, termed delta subunit (δ ENaC), was cloned in human and monkey. Increasing evidence shows that this unique subunit and its splice variants exhibit biophysical and pharmacological properties that are divergent from those of α ENaC channels. The widespread distribution of epithelial sodium channels in both epithelial and nonepithelial tissues implies a range of physiological functions. The altered expression of SCNN1D is associated with numerous pathological conditions. Genetic studies link SCNN1D deficiency with rare genetic diseases with developmental and functional disorders in the brain, heart, and respiratory systems. Here, we review the progress of research on δ ENaC in genomics, biophysics, proteomics, physiology, pharmacology, and clinical medicine.
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Affiliation(s)
- Hong-Long Ji
- Department of Cellular and Molecular Biology, University of Texas Health Science Center at Tyler, Tyler, Texas, USA.
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Johnson MW, Taylor BJ, Hulsebus ML, Johnson BD, Snyder EM. Hypoxia induced changes in lung fluid balance in humans is associated with beta-2 adrenergic receptor density on lymphocytes. Respir Physiol Neurobiol 2012; 183:159-65. [PMID: 22772314 DOI: 10.1016/j.resp.2012.06.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 05/17/2012] [Accepted: 06/01/2012] [Indexed: 11/26/2022]
Abstract
BACKGROUND Previous studies have demonstrated an important role for beta-2 adrenergic receptors (β(2)AR) in lung fluid clearance. The purpose of this investigation was to examine the relationship between β(2)AR density on lymphocytes and indices of lung water in healthy humans exposed to ≈ 17 h of hypoxia (FIO2 = 12.5% in a hypoxia tent). METHODS Thirteen adults (mean ± SEM; age=31 ± 3 years, BMI=24 ± 1 kg/m(2), VO2 Peak = 40 ± 2 ml/kg/min ) participated. Pulmonary function, CT derived lung tissue volume (V(tis)-tissue, blood and water), lung diffusing capacity for carbon monoxide (D(CO)) and nitric oxide (D(NO)), alveolar-capillary conductance (D(M)), pulmonary capillary blood volume (V(c)) and lung water (CT V(tis)-V(c)) were assessed before and after ≈ 17 h normobaric hypoxia (FIO2 = 12.5%). β(2)AR density on lymphocytes was measured via radioligand binding. Arterial oxygen saturation (SaO2), cardiac output (Q), right ventricular systolic pressure (RVSP) and blood pressure (BP) were also assessed. RESULTS After 17 h hypoxia, SaO2 decreased from 97 ± 1 (normoxia) to 82 ± 4% and RVSP increased from 14 ± 3 (normoxia) to 29 ± 2 mmHg (p<0.05) with little change in Q or BP. V(c) and D(M) both increased with hypoxia with a small increase in D(M)/V(c) ratio (p>0.05). CT V(tis) decreased and lung water was estimated to decline 7 ± 13%, respectively. β(2)AR density averaged 1497 ± 187 receptors/lymphocyte and increased 21 ± 34% with hypoxia (range -31 to +86%). The post-hypoxia increase in β(2)AR density was significantly related to the reduction in lung water (r=-0.64, p<0.05), with the subjects with the greatest increase in density demonstrating the largest decline in lung water. CONCLUSIONS Lung water decreases with 17 h normobaric hypoxia are associated with changes in beta adrenergic receptor density on lymphocytes in healthy adults.
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Affiliation(s)
- Micah W Johnson
- Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA
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Zhao RZ, Nie HG, Su XF, Han DY, Lee A, Huang Y, Chang Y, Matalon S, Ji HL. Characterization of a novel splice variant of δ ENaC subunit in human lungs. Am J Physiol Lung Cell Mol Physiol 2012; 302:L1262-72. [PMID: 22505667 DOI: 10.1152/ajplung.00331.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Salt absorption via apical epithelial sodium channels (ENaC) is a critical rate-limiting process in maintaining airway and lung lining fluid at the physiological level. δ ENaC (termed δ1 in this article) has been detected in human lung epithelial cells in addition to α, β, and γ subunits (Ji HL, Su XF, Kedar S, Li J, Barbry P, Smith PR, Matalon S, Benos DJ. J Biol Chem 281: 8233-8241, 2006; Nie HG, Chen L, Han DY, Li J, Song WF, Wei SP, Fang XH, Gu X, Matalon S, Ji HL, J Physiol 587: 2663-2676, 2009) and may contribute to the differences in the biophysical properties of amiloride-inhibitable cation channels in pulmonary epithelial cells. Here we cloned a splicing variant of the δ1 ENaC, namely, δ2 ENaC in human bronchoalveolar epithelial cells (16HBEo). δ2 ENaC possesses 66 extra amino acids attached to the distal amino terminal tail of the δ1 ENaC. δ2 ENaC was expressed in both alveolar type I and II cells of human lungs as revealed by in situ hybridization and real-time RT-PCR. To characterize the biophysical and pharmacological features of the splicing variant, we injected Xenopus oocytes with human ENaC cRNAs and measured whole cell and single channel currents of δ1βγ, δ2βγ, and αβγ channels. Oocytes injected with δ2βγ cRNAs exhibited whole cell currents significantly greater than those expressing δ1βγ and αβγ channels. Single channel activity, unitary conductance, and open probability of δ2βγ channels were significantly greater compared with δ1βγ and αβγ channels. In addition, δ2βγ and δ1βγ channels displayed significant differences in apparent Na(+) affinity, dissociation constant for amiloride (K(i)(amil)), the EC(50) for capsazepine activation, and gating kinetics by protons. Channels comprising of this novel splice variant may contribute to the diversities of native epithelial Na(+) channels.
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Affiliation(s)
- Run-Zhen Zhao
- Departments of Cellular and Molecular Biology, Texas Lung Injury Institute, Univ. of Texas Health Science Ctr. at Tyler, Tyler, TX 75708-3154, USA
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Butterworth MB, Edinger RS, Silvis MR, Gallo LI, Liang X, Apodaca G, Frizzell RA, Fizzell RA, Johnson JP. Rab11b regulates the trafficking and recycling of the epithelial sodium channel (ENaC). Am J Physiol Renal Physiol 2011; 302:F581-90. [PMID: 22129970 DOI: 10.1152/ajprenal.00304.2011] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Expression of the epithelial sodium channel (ENaC) at the apical membrane of cortical collecting duct (CCD) principal cells is modulated by regulated trafficking mediated by vesicle insertion and retrieval. Small GTPases are known to facilitate vesicle trafficking, recycling, and membrane fusion events; however, little is known about the specific Rab family members that modify ENaC surface density. Using a mouse CCD cell line that endogenously expresses ENaC (mpkCCD), the channel was localized to both Rab11a- and Rab11b-positive endosomes by immunoisolation and confocal fluorescent microscopy. Expression of a dominant negative (DN) form of Rab11a or Rab11b significantly reduced the basal and cAMP-stimulated ENaC-dependent sodium (Na(+)) transport. The greatest reduction in Na(+) transport was observed with the expression of DN-Rab11b. Furthermore, small interfering RNA-mediated knockdown of each Rab11 isoform demonstrated the requirement for Rab11b in ENaC surface expression. These data indicate that Rab11b, and to a lesser extent Rab11a, is involved in establishing the constitutive and cAMP-stimulated Na(+) transport in mpkCCD cells.
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Affiliation(s)
- Michael B Butterworth
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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Abstract
The properties of the voltage-dependent H(+) channel have been studied in lung epithelial cells for many years, and recently HVCN1 mRNA expression has been linked directly to H(+) channel function in lung epithelium. The H(+) channel is activated by strong membrane depolarization, intracellular acidity, or extracellular alkalinity. Early on it was noted that these are surprising physiological channel characteristics when considering that lung epithelial cells have rather stable membrane potentials and a well pH-buffered intracellular milieu. This raised the question under which conditions the H(+) channel is active in lung epithelium and what is its physiological function there. Current understanding of the HVCN1 H(+) channel in lung epithelial acid secretion, its activation by an alkaline mucosal extracellular pH, and its role in the regulation of the mucosal pH of the lung has resulted in a model of mucosal pH regulation based on the parallel function of the HVCN1 H(+) channel and the CFTR HCO(3) (-) channel, which suggests that HVCN1 is a critical factor that maintains a neutral surface pH in the lung.
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Affiliation(s)
- Horst Fischer
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr Way, Oakland CA 94609-1673, USA, phone 510 450 7696,
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Traylor BR, Wheatley CM, Skrentny TT, Foxx-Lupo WT, Phan H, Patanwala AE, Morgan WJ, Daines CL, Sprissler R, Snyder EM. Influence of Genetic variation of the β2-Adrenergic receptor on lung diffusion in patients with cystic fibrosis. Pulm Pharmacol Ther 2011; 24:610-6. [DOI: 10.1016/j.pupt.2011.06.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Revised: 05/26/2011] [Accepted: 06/03/2011] [Indexed: 11/28/2022]
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Yamazaki M, Wu T, Pondugula SR, Harbidge DG, Marcus DC. Sodium selectivity of semicircular canal duct epithelial cells. BMC Res Notes 2011; 4:355. [PMID: 21914199 PMCID: PMC3180474 DOI: 10.1186/1756-0500-4-355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 09/13/2011] [Indexed: 11/16/2022] Open
Abstract
Background Sodium absorption by semicircular canal duct (SCCD) epithelial cells is thought to contribute to the homeostasis of the volume of vestibular endolymph. It was previously shown that the epithelial cells could absorb Na+ under control of a glucocorticoid hormone (dexamethasone) and the absorptive transepithelial current was blocked by amiloride. The most commonly-observed target of amiloride is the epithelial sodium channel (ENaC), comprised of the three subunits α-, β- and γ-ENaC. However, other cation channels have also been observed to be sensitive in a similar concentration range. The aim of this study was to determine whether SCCD epithelial cells absorb only Na+ or also K+ through an amiloride-sensitive pathway. Parasensory K+ absorption could contribute to regulation of the transduction current through hair cells, as found to occur via vestibular transitional cells [S. H. Kim and D. C. Marcus. Regulation of sodium transport in the inner ear. Hear.Res. doi:10.1016/j.heares.2011.05.003, 2011]. Results We determined the molecular and functional expression of candidate cation channels with gene array (GEO GSE6197), whole-cell patch clamp and transepithelial recordings in primary cultures of rat SCCD. α-, β- and γ-ENaC were all previously reported as present. The selectivity of the amiloride-sensitive transepithelial and cell membrane currents was observed in Ussing chamber and whole-cell patch clamp recordings. The cell membrane currents were carried by Na+ but not K+, but the Na+ selectivity disappeared when the cells were cultured on impermeable supports. Transepithelial currents across SCCD were also carried exclusively by Na+. Conclusions These results are consistent with the amiloride-sensitive absorptive flux of SCCD mediated by a highly Na+-selective channel, likely αβγ-ENaC. These epithelial cells therefore absorb only Na+ via the amiloride-sensitive pathway and do not provide a parasensory K+ efflux from the canals via this pathway. The results further provide caution to the culture of epithelial cells on impermeable surfaces.
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Affiliation(s)
- Muneharu Yamazaki
- Cellular Biophysics Laboratory, Department of Anatomy & Physiology, Kansas State University, Manhattan, KS 66506, USA.
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Beard LL, Li T, Hu Y, Folkesson HG. Fetal Lung Epithelial Ion Channels Relocate in the Cell Membrane During Late Gestation. Anat Rec (Hoboken) 2011; 294:1461-71. [DOI: 10.1002/ar.21363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 09/08/2010] [Accepted: 10/22/2010] [Indexed: 11/09/2022]
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Kapoor N, Lee W, Clark E, Bartoszewski R, McNicholas CM, Latham CB, Bebok Z, Parpura V, Fuller CM, Palmer CA, Benos DJ. Interaction of ASIC1 and ENaC subunits in human glioma cells and rat astrocytes. Am J Physiol Cell Physiol 2011; 300:C1246-59. [PMID: 21346156 DOI: 10.1152/ajpcell.00199.2010] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Glioblastoma multiforme (GBM) is the most common and aggressive of the primary brain tumors. These tumors express multiple members of the epithelial sodium channel (ENaC)/degenerin (Deg) family and are associated with a basally active amiloride-sensitive cation current. We hypothesize that this glioma current is mediated by a hybrid channel composed of a mixture of ENaC and acid-sensing ion channel (ASIC) subunits. To test the hypothesis that ASIC1 interacts with αENaC and γENaC at the cellular level, we have used total internal reflection fluorescence microscopy (TIRFM) in live rat astrocytes transiently cotransfected with cDNAs for ASIC1-DsRed plus αENaC-yellow fluorescent protein (YFP) or ASIC1-DsRed plus γENaC-YFP. TIRFM images show colocalization of ASIC1 with both αENaC and γENaC. Furthermore, using TIRFM in stably transfected D54-MG cells, we also found that ASIC1 and αENaC both localize to a submembrane region following exposure to pH 6.0, similar to the acidic conditions found in the core of a glioblastoma lesion. Using high-resolution clear native gel electrophoresis, we found that ASIC1 forms a complex with ENaC subunits which migrates at ≈480 kDa in D54-MG glioma cells. These data suggest that different ENaC/Deg subunits interact and could combine to form a hybrid channel that likely underlies the amiloride-sensitive current seen in human glioma cells.
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Affiliation(s)
- Niren Kapoor
- Dept. of Physiology and Biophysics, University of Alabama at Birmingham, 1918 University Blvd., Birmingham, AL 35294, USA
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Yamazaki M, Kim KX, Marcus DC. Sodium selectivity of Reissner's membrane epithelial cells. BMC PHYSIOLOGY 2011; 11:4. [PMID: 21284860 PMCID: PMC3042420 DOI: 10.1186/1472-6793-11-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 02/01/2011] [Indexed: 11/10/2022]
Abstract
BACKGROUND Sodium absorption by Reissner's membrane is thought to contribute to the homeostasis of the volume of cochlear endolymph. It was previously shown that the absorptive transepithelial current was blocked by amiloride and benzamil. The most commonly-observed target of these drugs is the epithelial sodium channel (ENaC), which is composed of the three subunits α-,β- and γ-ENaC. However, other less-selective cation channels have also been observed to be sensitive to benzamil and amiloride. The aim of this study was to determine whether Reissner's membrane epithelial cells could support parasensory K+ absorption via amiloride- and benzamil-sensitive electrogenic pathways. RESULTS We determined the molecular and functional expression of candidate cation channels with gene array (GEO GSE6196), RT-PCR, and whole-cell patch clamp. Transcript expression analysis of Reissner's membrane detected no amiloride-sensitive acid-sensing ion channels (ASIC1a, ASIC2a, ASIC2b) nor amiloride-sensitive cyclic-nucleotide gated channels (CNGA1, CNGA2, CNGA4, CNGB3). By contrast, α-,β- and γ-ENaC were all previously reported as present in Reissner's membrane. The selectivity of the benzamil-sensitive cation currents was observed in whole-cell patch clamp recordings under Cl--free conditions where cations were the only permeant species. The currents were carried by Na+ but not K+, and the permeability of Li+ was greater than that of Na+ in Reissner's membrane. Complete replacement of bath Na+ with the inpermeable cation NMDG+ led to the same inward current as with benzamil in a Na+ bath. CONCLUSIONS These results are consistent with the amiloride/benzamil-sensitive absorptive flux of Reissner's membrane mediated by a highly Na+-selective channel that has several key characteristics in common with αβγ-ENaC. The amiloride-sensitive pathway therefore absorbs only Na+ in this epithelium and does not provide a parasensory K+ efflux route from scala media.
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Affiliation(s)
- Muneharu Yamazaki
- Cellular Biophysics Laboratory, Department of Anatomy & Physiology, Kansas State University, Manhattan, KS 66506, USA
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Amiloride-sensitive sodium channels and pulmonary edema. Pulm Med 2010; 2011:830320. [PMID: 21637371 PMCID: PMC3100597 DOI: 10.1155/2011/830320] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 12/01/2010] [Indexed: 01/11/2023] Open
Abstract
The development of pulmonary edema can be considered as a combination of alveolar flooding via increased fluid filtration, impaired alveolar-capillary barrier integrity, and disturbed resolution due to decreased alveolar fluid clearance. An important mechanism regulating alveolar fluid clearance is sodium transport across the alveolar epithelium. Transepithelial sodium transport is largely dependent on the activity of sodium channels in alveolar epithelial cells. This paper describes how sodium channels contribute to alveolar fluid clearance under physiological conditions and how deregulation of sodium channel activity might contribute to the pathogenesis of lung diseases associated with pulmonary edema. Furthermore, sodium channels as putative molecular targets for the treatment of pulmonary edema are discussed.
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Mac Sweeney R, Fischer H, McAuley DF. Nasal potential difference to detect Na+ channel dysfunction in acute lung injury. Am J Physiol Lung Cell Mol Physiol 2010; 300:L305-18. [PMID: 21112943 DOI: 10.1152/ajplung.00223.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Pulmonary fluid clearance is regulated by the active transport of Na(+) and Cl(-) through respiratory epithelial ion channels. Ion channel dysfunction contributes to the pathogenesis of various pulmonary fluid disorders including high-altitude pulmonary edema (HAPE) and neonatal respiratory distress syndrome (RDS). Nasal potential difference (NPD) measurement allows an in vivo investigation of the functionality of these channels. This technique has been used for the diagnosis of cystic fibrosis, the archetypal respiratory ion channel disorder, for over a quarter of a century. NPD measurements in HAPE and RDS suggest constitutive and acquired dysfunction of respiratory epithelial Na(+) channels. Acute lung injury (ALI) is characterized by pulmonary edema due to alveolar epithelial-interstitial-endothelial injury. NPD measurement may enable identification of critically ill ALI patients with a susceptible phenotype of dysfunctional respiratory Na(+) channels and allow targeted therapy toward Na(+) channel function.
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Affiliation(s)
- R Mac Sweeney
- Respiratory Medicine Research Programme, Centre for Infection and Immunity, Queen’s University, Belfast, Northern Ireland
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Song W, Wei S, Matalon S. Inhibition of epithelial sodium channels by respiratory syncytial virus in vitro and in vivo. Ann N Y Acad Sci 2010; 1203:79-84. [PMID: 20716287 DOI: 10.1111/j.1749-6632.2010.05560.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants and children worldwide. Infection of mice with RSV decreased sodium (Na(+)) dependent alveolar fluid clearance (AFC), resulting in increased lung water content and hypoxemia. RSV infection resulted in higher levels of pyrimidines and purines in the alveolar space. Intratracheal administration of UTP or UDP also decreased AFC. The effects of RSV on AFC and oxygen saturation of Balb/c mice were reversed by intraalveolar administration of antagonists of P2Y nucleotide receptors, enzymes that enhance the breakdown of pyrimidines and systemic or intranasal administration of inhibitors of the de novo pathway of pyrimidine synthesis. RSV infection of H441 or mouse tracheal epithelial cells decreased the amiloride-sensitive Na(+) currents and pretreatment of H441 cells with A77 prevented this effect. These findings indicate that the harmful effects of RSV on lung epithelia are mediated at least in part via the production of UTP and its paracrine action on ENaC.
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Affiliation(s)
- Weifeng Song
- Department of Anesthesiology and Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
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Han DY, Nie HG, Gu X, Nayak RC, Su XF, Fu J, Chang Y, Rao V, Ji HL. K+ channel openers restore verapamil-inhibited lung fluid resolution and transepithelial ion transport. Respir Res 2010; 11:65. [PMID: 20507598 PMCID: PMC2889873 DOI: 10.1186/1465-9921-11-65] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Accepted: 05/27/2010] [Indexed: 12/19/2022] Open
Abstract
Background Lung epithelial Na+ channels (ENaC) are regulated by cell Ca2+ signal, which may contribute to calcium antagonist-induced noncardiogenic lung edema. Although K+ channel modulators regulate ENaC activity in normal lungs, the therapeutical relevance and the underlying mechanisms have not been completely explored. We hypothesized that K+ channel openers may restore calcium channel blocker-inhibited alveolar fluid clearance (AFC) by up-regulating both apical and basolateral ion transport. Methods Verapamil-induced depression of heterologously expressed human αβγ ENaC in Xenopus oocytes, apical and basolateral ion transport in monolayers of human lung epithelial cells (H441), and in vivo alveolar fluid clearance were measured, respectively, using the two-electrode voltage clamp, Ussing chamber, and BSA protein assays. Ca2+ signal in H441 cells was analyzed using Fluo 4AM. Results The rate of in vivo AFC was reduced significantly (40.6 ± 6.3% of control, P < 0.05, n = 12) in mice intratracheally administrated verapamil. KCa3.1 (1-EBIO) and KATP (minoxidil) channel openers significantly recovered AFC. In addition to short-circuit current (Isc) in intact H441 monolayers, both apical and basolateral Isc levels were reduced by verapamil in permeabilized monolayers. Moreover, verapamil significantly altered Ca2+ signal evoked by ionomycin in H441 cells. Depletion of cytosolic Ca2+ in αβγ ENaC-expressing oocytes completely abolished verapamil-induced inhibition. Intriguingly, KV (pyrithione-Na), K Ca3.1 (1-EBIO), and KATP (minoxidil) channel openers almost completely restored the verapamil-induced decrease in Isc levels by diversely up-regulating apical and basolateral Na+ and K+ transport pathways. Conclusions Our observations demonstrate that K+ channel openers are capable of rescuing reduced vectorial Na+ transport across lung epithelial cells with impaired Ca2+ signal.
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Affiliation(s)
- Dong-Yun Han
- Department of Biochemistry, University of Texas Health Science Center at Tyler, Tyler, TX 75708, USA
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Althaus M, Pichl A, Clauss WG, Seeger W, Fronius M, Morty RE. Nitric oxide inhibits highly selective sodium channels and the Na+/K+-ATPase in H441 cells. Am J Respir Cell Mol Biol 2010; 44:53-65. [PMID: 20139350 DOI: 10.1165/2009-0335oc] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Nitric oxide (NO) is an important regulator of Na(+) reabsorption by pulmonary epithelial cells and therefore of alveolar fluid clearance. The mechanisms by which NO affects epithelial ion transport are poorly understood and vary from model to model. In this study, the effects of NO on sodium reabsorption by H441 cell monolayers were studied in an Ussing chamber. Two NO donors, (Z)-1-[N-(3-aminopropyl)-N-(n-propyl)amino]diazen-1-ium-1,2-diolate and diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate, rapidly, reversibly, and dose-dependently reduced amiloride-sensitive, short-circuit currents across H441 cell monolayers. This effect was neutralized by the NO scavenger hemoglobin and was not observed with inactive NO donors. The effects of NO were not blocked by 8-bromoguanosine-3',5'-cyclic monophosphate or by soluble guanylate cyclase inhibitors (methylene blue and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) and were therefore independent of soluble guanylate cyclase signaling. NO targeted apical, highly selective, amiloride-sensitive Na(+) channels in basolaterally permeabilized H441 cell monolayers. NO had no effect on the activity of the human epithelial sodium channel heterologously expressed in Xenopus oocytes. NO decreased Na(+)/K(+)-ATPase activity in apically permeabilized H441 cell monolayers. The inhibition of Na(+)/K(+)-ATPase activity by NO was reversed by mercury and was mimicked by N-ethylmaleimide, which are agents that reverse and mimic, respectively, the reaction of NO with thiol groups. Consistent with these data, S-NO groups were detected on the Na(+)/K(+)-ATPase α subunit in response to NO-donor application, using a biotin-switch approach coupled to a Western blot. These data demonstrate that, in the H441 cell model, NO impairs Na(+) reabsorption by interfering with the activity of highly selective Na(+) channels and the Na(+)/K(+)-ATPase.
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Affiliation(s)
- Mike Althaus
- Department of Internal Medicine (Pulmonology), University of Giessen Lung Center, Justus Liebig University, Giessen, Germany
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Takemura Y, Goodson P, Bao HF, Jain L, Helms MN. Rac1-mediated NADPH oxidase release of O2- regulates epithelial sodium channel activity in the alveolar epithelium. Am J Physiol Lung Cell Mol Physiol 2010; 298:L509-20. [PMID: 20097736 DOI: 10.1152/ajplung.00230.2009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We examine whether alveolar cells can control release of O(2)(-) through regulated NADPH oxidase (NOX) 2 (NOX2) activity to maintain lung fluid homeostasis. Using FACS to purify alveolar epithelial cells, we show that type 1 cells robustly express each of the critical NOX components that catalyze the production of O(2)(-) (NOX2 or gp91(phox), p22(phox), p67(phox), p47(phox), and p40(phox) subunits) as well as Rac1 at substantially higher levels than type 2 cells. Immunohistochemical labeling of lung tissue shows that Rac1 expression is cytoplasmic and resides near the apical surface of type 1 cells, whereas NOX2 coimmunoprecipitates with epithelial sodium channel (ENaC). Since Rac1 is a known regulator of NOX2, and hence O(2)(-) release, we tested whether inhibition or activation of Rac1 influenced ENaC activity. Indeed, 1 microM NSC23766 inhibition of Rac1 decreased O(2)(-) output in lung cells and significantly decreased ENaC activity from 0.87 +/- 0.16 to 0.52 +/- 0.16 [mean number of channels (N) and single-channel open probability (P(o)) (NP(o)) +/- SE, n = 6; P < 0.05] in type 2 cells. NSC23766 (10 microM) decreased ENaC NP(o) from 1.16 +/- 0.27 to 0.38 +/- 0.10 (n = 6 in type 1 cells). Conversely, 10 ng/ml EGF (a known stimulator of both Rac1 and O(2)(-) release) increased ENaC NP(o) values in both type 1 and 2 cells. NP(o) values increased from 0.48 +/- 0.21 to 0.91 +/- 0.28 in type 2 cells (P < 0.05; n = 10). In type 1 cells, ENaC activity also significantly increased from 0.40 +/- 0.15 to 0.60 +/- 0.23 following EGF treatment (n = 7). Sequestering O(2)(-) using 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) compound prevented EGF activation of ENaC in both type 1 and 2 cells. In conclusion, we report that Rac1-mediated NOX2 activity is an important component in O(2)(-) regulation of ENaC.
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Boncoeur E, Tardif V, Tessier MC, Morneau F, Lavoie J, Gendreau-Berthiaume E, Grygorczyk R, Dagenais A, Berthiaume Y. Modulation of epithelial sodium channel activity by lipopolysaccharide in alveolar type II cells: involvement of purinergic signaling. Am J Physiol Lung Cell Mol Physiol 2009; 298:L417-26. [PMID: 20008115 DOI: 10.1152/ajplung.00170.2009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Pseudomonas aeruginosa is a gram-negative bacterium that causes chronic infection in cystic fibrosis patients. We reported recently that P. aeruginosa modulates epithelial Na(+) channel (ENaC) expression in experimental chronic pneumonia models. For this reason, we tested whether LPS from P. aeruginosa alters ENaC expression and activity in alveolar epithelial cells. We found that LPS induces a approximately 60% decrease of ENaC apical current without significant changes in intracellular ENaC or surface protein expression. Because a growing body of evidence reports a key role for extracellular nucleotides in regulation of ion channels, we evaluated the possibility that modulation of ENaC activity by LPS involves extracellular ATP signaling. We found that alveolar epithelial cells release ATP upon LPS stimulation and that pretreatment with suramin, a P2Y(2) purinergic receptor antagonist, inhibited the effect of LPS on ENaC. Furthermore, ET-18-OCH3, a PLC inhibitor, and Go-6976, a PKC inhibitor, were able to partially prevent ENaC inhibition by LPS, suggesting that the actions of LPS on ENaC current were mediated, in part, by the PKC and PLC pathways. Together, these findings demonstrate an important role of extracellular ATP signaling in the response of epithelial cells to LPS.
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Affiliation(s)
- Emilie Boncoeur
- Département de Médecine, Centre de Recherche, Centre Hospitalier de l'Université de Montréal-Hôtel-Dieu, 3840 St. Urbain, Montréal, PQ, Canada
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Adler KB, Matalon S. Highlights of the December Issue. Am J Respir Cell Mol Biol 2009. [DOI: 10.1165/rcmb.2009-2012ed] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Lee JW, Gupta N, Serikov V, Matthay MA. Potential application of mesenchymal stem cells in acute lung injury. Expert Opin Biol Ther 2009; 9:1259-70. [PMID: 19691441 DOI: 10.1517/14712590903213651] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Despite extensive research into the pathogenesis of acute lung injury and the acute respiratory distress syndrome (ALI/ARDS), mortality remains high at approximately 40%. Current treatment is primarily supportive, with lung-protective ventilation and a fluid conservative strategy. Pharmacologic therapies that reduce the severity of lung injury in experimental studies have not yet been translated into effective clinical treatment options. Therefore, innovative therapies are needed. Recent studies have suggested that bone-marrow-derived multipotent mesenchymal stem cells (MSC) may have therapeutic applications in multiple clinical disorders including myocardial infarction, diabetes, sepsis, hepatic and acute renal failure. Recently, MSC have been studied in several in vivo models of lung disease. This review focuses on first describing the existing experimental literature that has tested the use of MSC in models of ALI/ARDS, and then the potential mechanisms underlying their therapeutic use with an emphasis on secreted paracrine soluble factors. The review concludes with a discussion of future research directions required for potential clinical trials.
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Affiliation(s)
- Jae Woo Lee
- University of California, Anesthesiology, 505 Parnassus Avenue, Box 0648, San Francisco, CA 94143-0648, USA.
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Li Y, Marcoux MO, Gineste M, Vanpee M, Zelenina M, Casper C. Expression of water and ion transporters in tracheal aspirates from neonates with respiratory distress. Acta Paediatr 2009; 98:1729-37. [PMID: 19719801 DOI: 10.1111/j.1651-2227.2009.01496.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM The aim of the study was to determine whether neonatal respiratory distress is related to changes in water and ion transporter expression in lung epithelium. METHODS The study included 32 neonates on mechanical ventilation: 6 patients with normal lung X-rays (control group), eight with respiratory distress syndrome (RDS), eight with transient tachypnea of the newborn (TTN), 10 with abnormal lung X-rays (mixed group). The protein abundance of water channel AQP5, epithelial sodium channel (ENaC; alpha-, beta- and gamma-ENaC) and Na(+), K(+)-ATPase alpha1 were examined in tracheal aspirates using semiquantitative immunoblotting. RESULTS beta-ENaC level was significantly lower in RDS group compared with infants with TTN and infants in the control group. AQP5 expression was significantly higher in TTN compared with the infants with RDS and all other infants with abnormal lung X-rays. CONCLUSION Neonatal respiratory distress is associated with changes in beta-ENaC and AQP5 expression. The lower beta-ENaC expression may be one of the factors that predispose to the development of RDS. The higher AQP5 expression may provide the possibility for reabsorption of postnatal lung liquid, which contributes to quick recovery of infants with TTN.
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Affiliation(s)
- Yanhong Li
- Department of Woman & Child Health, Karolinska Institutet, Stockholm, Sweden
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Eaton DC, Helms MN, Koval M, Bao HF, Jain L. The contribution of epithelial sodium channels to alveolar function in health and disease. Annu Rev Physiol 2009; 71:403-23. [PMID: 18831683 DOI: 10.1146/annurev.physiol.010908.163250] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Amiloride-sensitive epithelial sodium channels (ENaC) play an important role in lung sodium transport. Sodium transport is closely regulated to maintain an appropriate fluid layer on the alveolar surface. Both alveolar type I and II cells have several different sodium-permeable channels in their apical membranes that play a role in normal lung physiology and pathophysiology. In many epithelial tissues, ENaC is formed from three subunit proteins: alpha, beta, and gamma ENaC. Part of the diversity of sodium-permeable channels in lung arises from assembling different combinations of these subunits to form channels with different biophysical properties and different mechanisms for regulation. Thus, lung epithelium has enormous flexibility to alter the magnitude of salt and water transport. In lung, ENaC is regulated by many transmitter and hormonal agents. Regulation depends upon the type of sodium channel but involves controlling the number of apical channels and/or the activity of individual channels.
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Affiliation(s)
- Douglas C Eaton
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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