151
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Wang XP, Im SJ, Balchak DM, Montalbetti N, Carattino MD, Ray EC, Kashlan OB. Murine epithelial sodium (Na +) channel regulation by biliary factors. J Biol Chem 2019; 294:10182-10193. [PMID: 31092599 PMCID: PMC6664190 DOI: 10.1074/jbc.ra119.007394] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 05/15/2019] [Indexed: 01/01/2023] Open
Abstract
The epithelial sodium channel (ENaC) mediates Na+ transport in several epithelia, including the aldosterone-sensitive distal nephron, distal colon, and biliary epithelium. Numerous factors regulate ENaC activity, including extracellular ligands, post-translational modifications, and membrane-resident lipids. However, ENaC regulation by bile acids and conjugated bilirubin, metabolites that are abundant in the biliary tree and intestinal tract and are sometimes elevated in the urine of individuals with advanced liver disease, remains poorly understood. Here, using a Xenopus oocyte-based system to express and functionally study ENaC, we found that, depending on the bile acid used, bile acids both activate and inhibit mouse ENaC. Whether bile acids were activating or inhibiting was contingent on the position and orientation of specific bile acid moieties. For example, a hydroxyl group at the 12-position and facing the hydrophilic side (12α-OH) was activating. Taurine-conjugated bile acids, which have reduced membrane permeability, affected ENaC activity more strongly than did their more membrane-permeant unconjugated counterparts, suggesting that bile acids regulate ENaC extracellularly. Bile acid-dependent activation was enhanced by amino acid substitutions in ENaC that depress open probability and was precluded by proteolytic cleavage that increases open probability, consistent with an effect of bile acids on ENaC open probability. Bile acids also regulated ENaC in a cortical collecting duct cell line, mirroring the results in Xenopus oocytes. We also show that bilirubin conjugates activate ENaC. These results indicate that ENaC responds to compounds abundant in bile and that their ability to regulate this channel depends on the presence of specific functional groups.
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Affiliation(s)
- Xue-Ping Wang
- From the Renal-Electrolyte Division, Department of Medicine
| | | | | | | | - Marcelo D Carattino
- From the Renal-Electrolyte Division, Department of Medicine
- the Department of Cell Biology and Molecular Physiology, and
| | - Evan C Ray
- From the Renal-Electrolyte Division, Department of Medicine
| | - Ossama B Kashlan
- From the Renal-Electrolyte Division, Department of Medicine,
- the Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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152
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Süvari L, Janér C, Helve O, Kaskinen A, Turpeinen U, Pitkänen-Argillander O, Andersson S. Postnatal gene expression of airway epithelial sodium transporters associated with birth stress in humans. Pediatr Pulmonol 2019; 54:797-803. [PMID: 30920175 DOI: 10.1002/ppul.24288] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 01/22/2019] [Indexed: 11/06/2022]
Abstract
INTRODUCTION Lung fluid clearance is essential for successful postnatal pulmonary adaptation. The epithelial sodium channel (ENaC) and Na-K-ATPase, induced by serum- and glucocorticoid-inducible kinase 1 (SGK1) as well as aquaporins (AQP), represent key players in the switch from fetal lung fluid secretion to absorption and in early postnatal lung fluid balance. Birth stress, including a surge in catecholamines, promotes pulmonary adaptation, likely through the augmentation of epithelial sodium reabsorption. OBJECTIVES We sought to determine the changes in the airway gene expression of molecules vital to epithelial sodium transport during early pulmonary adaptation, and the association with birth stress reflected in the norepinephrine concentration in the cord blood in humans. METHODS We included 70 term newborns: 28 born via vaginal delivery and 42 via elective cesarean section. We determined the norepinephrine concentrations in the cord blood using tandem mass spectrometry and collected nasal epithelial cell samples at 2 min, 1 h, and 24 h postnatally to quantify ENaC, Na-K-ATPase, AQP5, and SGK1 mRNAs using RT-PCR. RESULTS The molecular gene expression involved in airway epithelium sodium transport changed markedly within the first hour postnatally. Newborns born via elective cesarean section exhibited a lower expression of ENaC, Na-K-ATPase, and SGK1. Significant correlations existed between the expressions of ENaC, Na-K-ATPase, and SGK1, and the concentration of norepinephrine in the cord blood. CONCLUSIONS The association of ENaC, Na-K-ATPase, and SGK1 expression with the cord blood norepinephrine concentration points to the importance of birth stress in promoting lung fluid clearance during early postnatal pulmonary adaptation.
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Affiliation(s)
- Liina Süvari
- Children's Hospital, Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.,West Tallinn Central Hospital, Estonia
| | - Cecilia Janér
- Children's Hospital, Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Otto Helve
- Children's Hospital, Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Anu Kaskinen
- Children's Hospital, Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | | | - Olli Pitkänen-Argillander
- Children's Hospital, Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.,Academy of Finland, Helsinki, Finland
| | - Sture Andersson
- Children's Hospital, Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
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153
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Tsujimura T, Ueha R, Yoshihara M, Takei E, Nagoya K, Shiraishi N, Magara J, Inoue M. Involvement of the epithelial sodium channel in initiation of mechanically evoked swallows in anaesthetized rats. J Physiol 2019; 597:2949-2963. [PMID: 31032906 DOI: 10.1113/jp277895] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Accepted: 04/25/2019] [Indexed: 12/17/2022] Open
Abstract
KEY POINTS Afferents carried by the superior laryngeal nerve play a primary role in the initiation of laryngeal mechanically evoked swallows in anaesthetized rats. Amiloride and its analogues inhibit swallowing evoked by mechanical stimulation, but not swallowing evoked by chemical and electrical stimulation. The epithelial sodium channel is probably involved in the initiation of laryngeal mechanically evoked swallows. ABSTRACT The swallowing reflex plays a critical role in airway protection. Because impaired laryngeal mechanosensation is associated with food bolus aspiration, it is important to know how the laryngeal sensory system regulates swallowing initiation. This study was performed to clarify the neuronal mechanism of mechanically evoked swallows. Urethane-anaesthetized Sprague-Dawley male rats were used. A swallow was identified by activation of the suprahyoid and thyrohyoid muscles on electromyography. The swallowing threshold was measured by von Frey filament and electrical stimulation of the larynx. The number of swallows induced by upper airway distension and capsaicin application (0.03 nmol, 3 μl) to the vocal folds was counted. The effects of topical application (0.3-30 nmol, 3 μl) of the epithelial sodium channel (ENaC) blocker amiloride and its analogues (benzamil and dimethylamiloride), acid-sensing ion channel (ASIC) inhibitors (mambalgine-1 and diminazene) and gadolinium to the laryngeal mucosa on swallowing initiation were evaluated. A nerve transection study indicated that afferents carried by the superior laryngeal nerve play a primary role in the initiation of laryngeal mechanically evoked swallows. The mechanical threshold of swallowing was increased in a dose-dependent manner by amiloride and its analogues and gadolinium, but not by ASIC inhibitors. The number of swallows by upper airway distension was significantly decreased by benzamil application. However, the initiation of swallows evoked by capsaicin and electrical stimulation was not affected by benzamil application. We speculate that the ENaC is involved in the initiation of laryngeal mechanically evoked swallows.
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Affiliation(s)
- Takanori Tsujimura
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata, 951-8514, Japan
| | - Rumi Ueha
- Department of Otolaryngology, University of Tokyo, Tokyo, 113-8655, Japan
| | - Midori Yoshihara
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata, 951-8514, Japan
| | - Eri Takei
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata, 951-8514, Japan
| | - Kouta Nagoya
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata, 951-8514, Japan
| | - Naru Shiraishi
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata, 951-8514, Japan
| | - Jin Magara
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata, 951-8514, Japan
| | - Makoto Inoue
- Division of Dysphagia Rehabilitation, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata, 951-8514, Japan
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154
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Schmidt A, Alsop RJ, Rimal R, Lenzig P, Joussen S, Gervasi NN, Khondker A, Gründer S, Rheinstädter MC, Wiemuth D. Modulation of DEG/ENaCs by Amphiphiles Suggests Sensitivity to Membrane Alterations. Biophys J 2019; 114:1321-1335. [PMID: 29590590 DOI: 10.1016/j.bpj.2018.01.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 01/22/2018] [Accepted: 01/26/2018] [Indexed: 12/25/2022] Open
Abstract
The bile acid-sensitive ion channel is activated by amphiphilic substances such as bile acids or artificial detergents via membrane alterations; however, the mechanism of membrane sensitivity of the bile acid-sensitive ion channel is not known. It has also not been systematically investigated whether other members of the degenerin/epithelial Na+ channel (DEG/ENaC) gene family are affected by amphiphilic compounds. Here, we show that DEG/ENaCs ASIC1a, ASIC3, ENaC, and the purinergic receptor P2X2 are modulated by a large number of different, structurally unrelated amphiphilic substances, namely the detergents N-lauroylsarcosine, Triton X-100, and β-octylglucoside; the fenamate flufenamic acid; the antipsychotic drug chlorpromazine; the natural phenol resveratrol; the chili pepper compound capsaicin; the loop diuretic furosemide; and the antiarrythmic agent verapamil. We determined the modification of membrane properties using large-angle x-ray diffraction experiments on model lipid bilayers, revealing that the amphiphilic compounds are positioned in a characteristic fashion either in the lipid tail group region or in the lipid head group region, demonstrating that they perturbed the membrane structure. Collectively, our results show that DEG/ENaCs and structurally related P2X receptors are modulated by diverse amphiphilic molecules. Furthermore, they suggest alterations of membrane properties by amphiphilic compounds as a mechanism contributing to modulation.
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Affiliation(s)
- Axel Schmidt
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Rick J Alsop
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Rahul Rimal
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Pia Lenzig
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Sylvia Joussen
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Natalie N Gervasi
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Adree Khondker
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Stefan Gründer
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | | | - Dominik Wiemuth
- Institute of Physiology, RWTH Aachen University, Aachen, Germany.
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155
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Ding X, Jia N, Zhao C, Zhong Y, Dai D, Zhao Y, Xu C, Cai J, Wang Q, He Q. A family with Liddle's syndrome caused by a new c.1721 deletion mutation in the epithelial sodium channel β-subunit. Exp Ther Med 2019; 17:2777-2784. [PMID: 30930974 DOI: 10.3892/etm.2019.7270] [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: 02/06/2018] [Accepted: 11/01/2018] [Indexed: 11/06/2022] Open
Abstract
A 19-year-old male with early refractory hypertension, hypokalemia, serum potassium level of 3.4 mmol/l and hypoaldosteronemia was indicated in the present study. According to the results of laboratory tests and examinations, the patient was suspected of having Liddle's syndrome (LS). Genetic analysis of SCNN1B revealed a deletion mutation (c.1721delC). This mutation caused a length extension of SCNN1B coding sequence, which resulted in p.Pro574HisfsX675. A total of 34 family members were enrolled in the study and 29 of these family members underwent genetic testing. A total of 10 family members were clinically diagnosed with hypertension. Notably, 5 family members shared the same gene mutation as the proband and all cases with the mutation had hypertension. Blood pressure of the gene mutation carriers was well controlled by tailored treatment. In conclusion, a patient with early onset and refractory hypertension, hypokalemia and hypoaldosteronemia was diagnosed clinically and genetically with LS. Notably, a novel mutation (c.1721delC) was identified by DNA analysis. The present findings indicate that genetic analysis is useful, not only in the diagnosis of LS, but also in designing a tailored treatment.
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Affiliation(s)
- Xia Ding
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, P.R. China.,Department of Nephrology, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Na Jia
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, P.R. China
| | - Cong Zhao
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, P.R. China
| | - You Zhong
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, P.R. China
| | - Dapeng Dai
- The Key Laboratory of Geriatrics, Beijing Hospital and Beijing Institute of Geriatrics, Ministry of Health, Beijing 100730, P.R. China
| | - Yuanyuan Zhao
- Human Genome Research Center and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, P.R. China
| | - Chengqi Xu
- Human Genome Research Center and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, P.R. China
| | - Jianping Cai
- The Key Laboratory of Geriatrics, Beijing Hospital and Beijing Institute of Geriatrics, Ministry of Health, Beijing 100730, P.R. China
| | - Qing Wang
- Human Genome Research Center and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, P.R. China
| | - Qing He
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Beijing 100730, P.R. China
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156
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Mironova E, Suliman F, Stockand JD. Renal Na + excretion consequent to pharmacogenetic activation of G q-DREADD in principal cells. Am J Physiol Renal Physiol 2019; 316:F758-F767. [PMID: 30724104 PMCID: PMC6483033 DOI: 10.1152/ajprenal.00612.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 01/31/2019] [Accepted: 01/31/2019] [Indexed: 02/07/2023] Open
Abstract
Stimulation of metabotropic Gq-coupled purinergic P2Y2 receptors decreases activity of the epithelial Na+ channel (ENaC) in renal principal cells of the distal nephron. The physiological consequences of P2Y2 receptor signaling disruption in the P2Y2 receptor knockout mouse are decreased Na+ excretion and increased arterial blood pressure. However, because of the global nature of this knockout model, the quantitative contribution of ENaC and distal nephron compared with that of upstream renal vascular and tubular elements to changes in urinary excretion and arterial blood pressure is obscure. Moreover, it is uncertain whether stimulation of P2Y2 receptor inhibition of ENaC is sufficient to drive renal (urinary) Na+ excretion (UNaV). Here, using a pharmacogenetic approach and selective agonism of the P2Y2 receptor, we test the sufficiency of targeted stimulation of Gq signaling in principal cells of the distal nephron and P2Y2 receptors to increase UNaV. Selective stimulation of the P2Y2 receptor with the ligand MRS2768 decreased ENaC activity in freshly isolated tubules (as assessed by patch-clamp electrophysiology) and increased UNaV (as assessed in metabolic cages). Similarly, selective agonism of hM3Dq-designer receptors exclusively activated by designer drugs (DREADD) restrictively expressed in principal cells of the distal nephron with clozapine- N-oxide decreased ENaC activity and, consequently, increased UNaV. Clozapine- N-oxide, when applied to control littermates, failed to affect ENaC and UNaV. This study represents the first use of pharmacogenetic (DREADD) technology in the renal tubule and demonstrated that selective activation of the P2Y2 receptor and Gq signaling in principal cells is sufficient to promote renal salt excretion.
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Affiliation(s)
- Elena Mironova
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio , San Antonio, Texas
| | - Faroug Suliman
- Division of Nephrology, Department of Internal Medicine, University of Michigan , Ann Arbor, Michigan
| | - James D Stockand
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio , San Antonio, Texas
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157
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D'Arcangelo D, Scatozza F, Giampietri C, Marchetti P, Facchiano F, Facchiano A. Ion Channel Expression in Human Melanoma Samples: In Silico Identification and Experimental Validation of Molecular Targets. Cancers (Basel) 2019; 11:cancers11040446. [PMID: 30934896 PMCID: PMC6520727 DOI: 10.3390/cancers11040446] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 03/20/2019] [Accepted: 03/23/2019] [Indexed: 12/30/2022] Open
Abstract
Expression of 328 ion channel genes was investigated, by in silico analysis, in 170 human melanoma samples and controls. Ninety-one members of this gene-family (i.e., about 28%) show a significant (p < 0.05) differential expression in melanoma- vs. nevi-biopsies, taken from the GEO database. ROC (receiver operating characteristic) analysis selected 20 genes as potential markers showing the highest discrimination ability of melanoma vs. nevi (AUC > 0.90 and p < 0.0001). These 20 genes underwent a first in silico-validation round in an independent patients-dataset from GEO. A second-in silico-validation step was then carried out on a third human dataset in Oncomine. Finally, five genes were validated, showing extremely high sensitivity and specificity in melanoma detection (>90% in most cases). Such five genes (namely, SCNN1A, GJB3, KCNK7, GJB1, KCNN2) are novel potential melanoma markers or molecular targets, never previously related to melanoma. The “druggable genome” analysis was then carried out. Miconazole, an antifungal drug commonly used in clinics, is known to target KCNN2, the best candidate among the five identified genes. Miconazole was then tested in vitro in proliferation assays; it dose-dependently inhibited proliferation up to 90% and potently induced cell-death in A-375 and SKMEL-28 melanoma cells, while it showed no effect in control cells. Moreover, specific silencing of KCNN2 ion channel was achieved by siRNA transfection; under such condition miconazole strongly increases its anti-proliferative effect. In conclusion, the present study identified five ion channels that can potentially serve as sensitive and specific markers in human melanoma specimens and demonstrates that the antifungal drug miconazole, known to target one of the five identified ion channels, exerts strong and specific anti-melanoma effects in vitro.
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Affiliation(s)
| | | | - Claudia Giampietri
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161 Rome, Italy.
| | - Paolo Marchetti
- Medical Oncology, Sapienza, University of Rome, 00161 Rome, Italy.
| | - Francesco Facchiano
- Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità (ISS), 00161 Rome, Italy.
| | - Antonio Facchiano
- Istituto Dermopatico dell'Immacolata (IDI-IRCCS), 00167 Rome, Italy.
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158
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Nakashima R, Kamei S, Nohara H, Fujikawa H, Maruta K, Kawakami T, Eto Y, Takahashi N, Suico MA, Takeo T, Nakagata N, Kai H, Shuto T. Auto-measure emphysematous parameters and pathophysiological gene expression profiles in experimental mouse models of acute and chronic obstructive pulmonary diseases. J Pharmacol Sci 2019; 140:113-119. [PMID: 31248767 DOI: 10.1016/j.jphs.2019.01.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 01/30/2019] [Accepted: 01/31/2019] [Indexed: 01/19/2023] Open
Abstract
Pulmonary emphysema, inflammation and senescence-like phenotype are pathophysiological characteristics of chronic obstructive pulmonary disease (COPD). Recently, a murine model of COPD has been established by inducing airway-specific overexpression of epithelial Na+ channel β subunit (βENaC-Tg mice). However, little is known about the histological and biochemical differences between βENaC-Tg mice and an existing acute emphysematous mouse model (elastase-induced model). Here, we first utilized whole lung image-based quantification method for histological analysis to determine auto-measure parameters, including alveolar area, alveolar perimeter, (major axis + minor axis)/2 and Feret diameter. Even though the extent of emphysema was similar in both models, the coefficient of variation (CV) of all histological parameters was smaller in βENaC-Tg mice, indicating that βENaC-Tg mice show homogeneous emphysema as compared with elastase-induced acute model. Expression analysis of lung tissue RNAs further revealed that elastase-induced model exhibits transient changes of inflammation markers (Kc, Il-6, Lcn2) and senescence-related markers (Sirt1, p21) at emphysema-initiation stage (1 day), which does not last until emphysema-manifestation stage (3 weeks); while the up-regulation is stable at emphysema-manifestation stage in βENaC-Tg mice (14-week old). Thus, these studies demonstrate that βENaC-Tg mice exhibit diffuse-type emphysema with stable expression of inflammatory and senescence-like markers.
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Affiliation(s)
- Ryunosuke Nakashima
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Shunsuke Kamei
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan; Program for Leading Graduate Schools "HIGO (Health Life Science: Interdisciplinary and Global Oriented) Program", 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Hirofumi Nohara
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan; Program for Leading Graduate Schools "HIGO (Health Life Science: Interdisciplinary and Global Oriented) Program", 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Haruka Fujikawa
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan; Program for Leading Graduate Schools "HIGO (Health Life Science: Interdisciplinary and Global Oriented) Program", 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Kasumi Maruta
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Taisei Kawakami
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Yuka Eto
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Noriki Takahashi
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Mary Ann Suico
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Toru Takeo
- Division of Reproductive Engineering, Center for Animal Resources and Development (CARD), Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Naomi Nakagata
- Division of Reproductive Engineering, Center for Animal Resources and Development (CARD), Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Hirofumi Kai
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan
| | - Tsuyoshi Shuto
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan.
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159
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Ilatovskaya DV, Levchenko V, Pavlov TS, Isaeva E, Klemens CA, Johnson J, Liu P, Kriegel AJ, Staruschenko A. Salt-deficient diet exacerbates cystogenesis in ARPKD via epithelial sodium channel (ENaC). EBioMedicine 2019; 40:663-674. [PMID: 30745171 PMCID: PMC6413684 DOI: 10.1016/j.ebiom.2019.01.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 01/04/2019] [Accepted: 01/05/2019] [Indexed: 12/14/2022] Open
Abstract
Background Autosomal Recessive Polycystic Kidney Disease (ARPKD) is marked by cyst formation in the renal tubules, primarily in the collecting duct (CD) system, ultimately leading to end-stage renal disease. Patients with PKD are generally advised to restrict their dietary sodium intake. This study was aimed at testing the outcomes of dietary salt manipulation in ARPKD. Methods PCK/CrljCrlPkhd1pck/CRL (PCK) rats, a model of ARPKD, were fed a normal (0.4% NaCl; NS), high salt (4% NaCl; HS), and sodium-deficient (0.01% NaCl; SD) diets for 8 weeks. Immunohistochemistry, GFR measurements, balance studies, and molecular biology approaches were applied to evaluate the outcomes of the protocol. Renin-angiotensin-aldosterone system (RAAS) levels were assessed using LC-MS/MS, and renal miRNA profiles were studied. Findings Both HS and SD diets resulted in an increase in cystogenesis. However, SD diet caused extensive growth of cysts in the renal cortical area, and hypertrophy of the tissue; RAAS components were enhanced in the SD group. We observed a reduction in epithelial Na+ channel (ENaC) expression in the SD group, accompanied with mRNA level increase. miRNA assay revealed that renal miR-9a-5p level was augmented in the SD group; we showed that this miRNA decreases ENaC channel number in CD cells. Interpretation Our data demonstrate a mechanism of ARPKD progression during salt restriction that involves activity of ENaC. We further show that miR-9a-5p potentially implicated in this mechanism and that miR-9a-5p downregulates ENaC in cultured CD cells. Our findings open new therapeutic possibilities and highlight the importance of understanding salt reabsorption in ARPKD.
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Affiliation(s)
- Daria V Ilatovskaya
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Vladislav Levchenko
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Tengis S Pavlov
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Elena Isaeva
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Christine A Klemens
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Jessica Johnson
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Pengyuan Liu
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Alison J Kriegel
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Alexander Staruschenko
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; Clement J. Zablocki VA Medical Center, 5000 West National Avenue, Milwaukee, WI, 53295, USA.
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Abstract
Acute respiratory distress syndrome (ARDS) is a syndrome of acute respiratory failure caused by noncardiogenic pulmonary edema. Despite five decades of basic and clinical research, there is still no effective pharmacotherapy for this condition and the treatment remains primarily supportive. It is critical to study the molecular and physiologic mechanisms that cause ARDS to improve our understanding of this syndrome and reduce mortality. The goal of this review is to describe our current understanding of the pathogenesis and pathophysiology of ARDS. First, we will describe how pulmonary edema fluid accumulates in ARDS due to lung inflammation and increased alveolar endothelial and epithelial permeabilities. Next, we will review how pulmonary edema fluid is normally cleared in the uninjured lung, and describe how these pathways are disrupted in ARDS. Finally, we will explain how clinical trials and preclinical studies of novel therapeutic agents have further refined our understanding of this condition, highlighting, in particular, the study of mesenchymal stromal cells in the treatment of ARDS.
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Affiliation(s)
- Laura A. Huppert
- Department of Medicine, University of California San Francisco, San Francisco, CA USA
| | - Michael A. Matthay
- Departments of Medicine and Anesthesia, Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA USA
| | - Lorraine B. Ware
- Department of Medicine, Division of Allergy, Pulmonary, and Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, TN USA
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161
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Disorders of renal NaCl transport and implications for blood pressure regulation. MED GENET-BERLIN 2019. [DOI: 10.1007/s11825-019-0232-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Abstract
Hypertension is one of the major risk factors for cardiovascular disease in industrialized societies. Substantial progress has been made in understanding its epidemiology, its pathophysiology, and its associated risks such as coronary artery disease, stroke, and heart failure. Because there is consensus that the abnormal retention of sodium by the kidney is a major important pathophysiological event in hypertension, this review focuses on mechanisms of renal NaCl transport and associated genetic disorders.
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162
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Abstract
BACKGROUND Persistent diarrhoea (PD), defined as diarrhoeal symptoms for longer than 2 weeks, still forms a substantial disease burden in children under 5 years of age. This article provides an overview of the current knowledge of PD and discusses novel concepts. METHODS A literature search on PD was performed which focused on evidence on epidemiology, pathophysiology and management of the disease. RESULTS The prevalence of PD has potentially decreased over the last decades. Debate remains around the role of specific bacterial, viral and parasitic infections with PD. PD is associated with malnutrition and a compromised immune system, including that caused by HIV infection. Management includes fluid resuscitation and improving nutritional status. There is a lack of evidence on the use of antibiotic therapy for PD. There is increasing interest in nutrient-based interventions, including pre- and/or probiotics that can modify the microbiome and thereby potentially prevent or improve the outcome of PD in children. CONCLUSION As PD remains a significant health burden, multicentre clinical trials are needed to inform future treatment guidelines. ABBREVIATIONS PD, persistent diarrhoea; EED, environmental enteric dysfunction; IBD, inflammatory bowel disease; WHO, World Health Organization.
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Affiliation(s)
- Robert H J Bandsma
- a Division of Gastroenterology, Hepatology and Nutrition , Hospital for Sick Children , Toronto , Canada.,b Translational Medicine Program, Hospital for Sick Children , Toronto , Canada.,c Centre for Global Child Health, Hospital for Sick Children , Toronto , Canada.,d Department of Nutrition Sciences , University of Toronto , Toronto , Canada
| | - Kamran Sadiq
- e Department of Paediatrics and Child Health , Aga Khan University , Karachi , Pakistan
| | - Zulfiqar A Bhutta
- c Centre for Global Child Health, Hospital for Sick Children , Toronto , Canada.,d Department of Nutrition Sciences , University of Toronto , Toronto , Canada.,e Department of Paediatrics and Child Health , Aga Khan University , Karachi , Pakistan
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163
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Ydegaard R, Andersen H, Oxlund CS, Jacobsen IA, Hansen PBL, Jürgensen JF, Peluso AA, Vanhoutte PM, Staehr M, Svenningsen P, Jensen BL. The acute blood pressure-lowering effect of amiloride is independent of endothelial ENaC and eNOS in humans and mice. Acta Physiol (Oxf) 2019; 225:e13189. [PMID: 30240139 DOI: 10.1111/apha.13189] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 09/11/2018] [Accepted: 09/17/2018] [Indexed: 01/15/2023]
Abstract
AIMS The epithelial sodium channel (ENaC) is expressed in cultured endothelial cells and inhibitory coupling to eNOS activity has been proposed. The present study tested the hypothesis that ENaC blockers increase systemic NO-products and lower blood pressure in patients and mice, depending on eNOS. METHODS NO-products and cGMP were measured in diabetes patient urine and plasma samples before and after amiloride treatment (20-40 mg for two days, plasma n = 22, urine n = 12 and 5-10 mg for eight weeks, plasma n = 52, urine n = 55). Indwelling catheters were implanted in the femoral artery and vein in mice for continuous arterial blood pressure and heart rate recordings and infusion. RESULTS Treatment with amiloride for two days increased plasma and urine NO-products, while plasma cGMP decreased and urinary cGMP was unchanged in patient samples. Eight weeks of treatment with amiloride did not alter NO-products and cGMP. In mice, amiloride boli of 5, 50, and 500 µg/kg lowered heart rate and arterial blood pressure significantly and acutely. Benzamil had no effect on pressure and raised heart rate. In hypertensive eNOS-/- and L-NAME-treated mice, amiloride lowered blood pressure significantly. L-NAME infusion significantly decreased NO-products in plasma; amiloride and eNOS-deletion had no effect. An acetylcholine bolus resulted in acute blood pressure drop that was attenuated in eNOS-/- and L-NAME mice. ENaC subunit expressions were not detected consistently in human and mouse arteries and endothelial cells. CONCLUSION Amiloride has an acute hypotensive action not dependent on ENaC and eNOS and likely related to the heart.
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Affiliation(s)
- Rikke Ydegaard
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Henrik Andersen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | | | - Ib A. Jacobsen
- Department of Endocrinology; Odense University Hospital; Odense Denmark
| | - Pernille B. L. Hansen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
- Cardiovascular and Metabolic Disease, IMED Biotech Unit; AstraZeneca; Gothenburg Sweden
| | - Jonathan F. Jürgensen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Antonio Augusto Peluso
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Paul M. Vanhoutte
- Department of Pharmacology and Pharmacy; Hong Kong University; China
| | - Mette Staehr
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Per Svenningsen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
| | - Boye L. Jensen
- Department of Cardiovascular and Renal Research, Institute for Molecular Medicine; University of Southern Denmark; Odense C Denmark
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164
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Poon AC, Inkol JM, Luu AK, Mutsaers AJ. Effects of the potassium-sparing diuretic amiloride on chemotherapy response in canine osteosarcoma cells. J Vet Intern Med 2018; 33:800-811. [PMID: 30556178 PMCID: PMC6430882 DOI: 10.1111/jvim.15382] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 11/14/2018] [Indexed: 02/07/2023] Open
Abstract
Background Osteosarcoma (OSA) is a common bone tumor of mesenchymal origin in dogs. Chemotherapy delays metastasis, yet most dogs die of this disease within 1 year of diagnosis. The high metabolic demand of cancer cells promotes proton pump upregulation, leading to acidification of the tumor microenvironment and chemoresistance. The potassium‐sparing diuretic amiloride is among a class of proton pump inhibitors prescribed for refractory heart failure treatment in dogs. Objective We hypothesized that amiloride treatment improves chemotherapy response by reducing acidification in canine OSA cells. Our objective was to assess the in vitro effects of amiloride on cell viability, apoptosis, and metabolism. Methods In vitro study. Assessments of cell viability and apoptosis were performed after single agent or combination treatment, along with calculations of pharmacological synergism using the combination index. Protein signaling during apoptosis was evaluated by Western blotting. Metabolic profiling was performed using a Seahorse bioanalyzer. Results Amiloride strongly synergized with doxorubicin in combination treatment and exhibited additive or antagonistic effects with carboplatin in canine OSA cells. Combination treatment with doxorubicin significantly upregulated p53‐mitochondrial signaling to activate apoptosis and downregulate Akt phosphorylation. Amiloride‐treated cells further exhibited metabolic switching with reductions in glycolytic capacity and maximal respiration. Conclusion and Clinical Importance Amiloride synergized with doxorubicin to potentiate apoptosis in canine OSA cells. These results justify further investigation into repurposing of amiloride as an oncology drug for the treatment of OSA in dogs.
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Affiliation(s)
- Andrew C Poon
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Jordon M Inkol
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Anita K Luu
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Anthony J Mutsaers
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada.,Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
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165
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Abstract
Since its discovery, aldosterone and ion modulation have been entwined. While scientific investigations throughout the decades have emphasized aldosterone's connection to Na+, K+, and H+ homeostasis, more recent research has demonstrated a relationship between aldosterone and Mg2+, Ca2+, and Cl- homeostasis. The mechanisms connecting aldosterone to ion regulation frequently involve ion channels; the membrane localized proteins containing at least one aqueous pore for ion conduction. In order to precisely control intracellular or intraorganelle ion concentrations, ion channels have evolved highly specific regions within the conduction pore that select ions by charge, size, and/or dehydration energy requirement, meaning aldosterone must be able to modulate multiple ion channels to regulate the many ions described above. The list of ion channels presently connected to aldosterone includes ENaC (Na+), ROMK/BK (K+), TRPV4/5/6 (Ca2+), TRPM7/6 (Mg2+), and ClC-K/CFTR (Cl-), among others. This list is only expected to grow over time, as the promiscuity of aldosterone becomes more understood.
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Affiliation(s)
| | - Rhian M Touyz
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Alvin Shrier
- Department of Physiology, McGill University, Montreal, QC, Canada.
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166
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Shei RJ, Peabody JE, Kaza N, Rowe SM. The epithelial sodium channel (ENaC) as a therapeutic target for cystic fibrosis. Curr Opin Pharmacol 2018; 43:152-165. [PMID: 30340955 PMCID: PMC6294660 DOI: 10.1016/j.coph.2018.09.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 09/11/2018] [Indexed: 01/28/2023]
Abstract
Cystic fibrosis (CF) is a monogenic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CFTR dysfunction is characterized by abnormal mucociliary transport due to a dehydrated airway surface liquid (ASL) and hyperviscous mucus, among other pathologies of host defense. ASL depletion is caused by the absence of CFTR mediated chloride secretion along with continued activity of the epithelial sodium channel (ENaC) activity, which can also be affected by CFTR mediated anion conductance. Therefore, ENaC has been proposed as a therapeutic target to ameliorate ASL dehydration and improve mucus transport. Inhibition of ENaC has been shown to restore ASL hydration and enhance mucociliary transport in induced models of CF lung disease. To date, no therapy inhibiting ENaC has successfully translated to clinical efficacy, in part due to concerns regarding off-target effects, systemic exposure, durability of effect, and adverse effects. Recent efforts have been made to develop novel, rationally designed therapeutics to produce-specific, long-lasting inhibition of ENaC activity in the airways while simultaneously minimizing off target fluid transport effects, systemic exposure and side effects. Such approaches comprise next-generation small molecule direct inhibitors, indirect channel-activating protease inhibitors, synthetic peptide analogs, and oligonucleotide-based therapies. These novel therapeutics represent an exciting step forward in the development of ENaC-directed therapies for CF.
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Affiliation(s)
- Ren-Jay Shei
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; The Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jacelyn E Peabody
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; Medical Scientist (MD/PhD) Training Program, University of Alabama at Birmingham, Birmingham, AL, USA; The Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Niroop Kaza
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; The Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA; Department of Cell Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA; The Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL, USA.
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167
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Fan P, Lu CX, Zhang D, Yang KQ, Lu PP, Zhang Y, Meng X, Hao SF, Luo F, Liu YX, Zhang HM, Song L, Cai J, Zhang X, Zhou XL. Liddle syndrome misdiagnosed as primary aldosteronism resulting from a novel frameshift mutation of SCNN1B. Endocr Connect 2018; 7:1528-1534. [PMID: 30496127 PMCID: PMC6311463 DOI: 10.1530/ec-18-0484] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 11/28/2018] [Indexed: 12/18/2022]
Abstract
Liddle syndrome (LS), a monogenetic autosomal dominant disorder, is mainly characterized by early-onset hypertension and hypokalemia. Clinically, misdiagnosis or missing diagnosis is common, since clinical phenotypes of LS are variable and nonspecific. We report a family with misdiagnosis of primary aldosteronism (PA), but identify as LS with a pathogenic frameshift mutation of the epithelial sodium channel (ENaC) β subunit. DNA samples were collected from a 32-year-old proband and 31 other relatives in the same family. A designed panel including 41 genes associated with monogenic hypertension was screened using next-generation sequencing. The best candidate disease-causing variants were verified by Sanger sequencing. Genetic analysis of the proband revealed a novel frameshift mutation c.1838delC (p.Pro613Glnfs*675) in exon 13 of SCNN1B. This heterozygous mutation involved the deletion of a cytosine from a string of three consecutive cytosines located at codons 612 to 613 and resulted in deletion of the crucial PY motif and elongation of the β-ENaC protein. The identical mutation was also found in 12 affected family members. Amiloride was effective in alleviating LS for patients. There were no SCNN1A or SCNN1G mutations in this family. Our study emphasizes the importance of considering LS in the differential diagnosis of early-onset hypertension. The identification of a novel frameshift mutation of SCNN1B enriches the genetic spectrum of LS and has allowed treatment of this affected family to prevent severe complications.
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Affiliation(s)
- Peng Fan
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Chao-Xia Lu
- McKusick-Zhang Center for Genetic Medicine, State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Di Zhang
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Kun-Qi Yang
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Pei-Pei Lu
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Ying Zhang
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Xu Meng
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Su-Fang Hao
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Fang Luo
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Ya-Xin Liu
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Hui-Min Zhang
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Lei Song
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jun Cai
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Xue Zhang
- McKusick-Zhang Center for Genetic Medicine, State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
- Correspondence should be addressed to X Zhang or X-L Zhou: or
| | - Xian-Liang Zhou
- Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
- Correspondence should be addressed to X Zhang or X-L Zhou: or
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168
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Kaushik S, Kumar R, Kain P. Salt an Essential Nutrient: Advances in Understanding Salt Taste Detection Using Drosophila as a Model System. J Exp Neurosci 2018; 12:1179069518806894. [PMID: 30479487 PMCID: PMC6249657 DOI: 10.1177/1179069518806894] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 09/19/2018] [Indexed: 11/16/2022] Open
Abstract
Taste modalities are conserved in insects and mammals. Sweet gustatory signals evoke attractive behaviors while bitter gustatory information drive aversive behaviors. Salt (NaCl) is an essential nutrient required for various physiological processes, including electrolyte homeostasis, neuronal activity, nutrient absorption, and muscle contraction. Not only mammals, even in Drosophila melanogaster, the detection of NaCl induces two different behaviors: Low concentrations of NaCl act as an attractant, whereas high concentrations act as repellant. The fruit fly is an excellent model system for studying the underlying mechanisms of salt taste due to its relatively simple neuroanatomical organization of the brain and peripheral taste system, the availability of powerful genetic tools and transgenic strains. In this review, we have revisited the literature and the information provided by various laboratories using invertebrate model system Drosophila that has helped us to understand NaCl salt taste so far. We hope that this compiled information from Drosophila will be of general significance and interest for forthcoming studies of the structure, function, and behavioral role of NaCl-sensitive (low and high concentrations) gustatory circuitry for understanding NaCl salt taste in all animals.
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Affiliation(s)
- Shivam Kaushik
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
| | - Rahul Kumar
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India.,Department of Biotechnology, Maharshi Dayanand University, Rohtak, India
| | - Pinky Kain
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
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169
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Sheng S, Chen J, Mukherjee A, Yates ME, Buck TM, Brodsky JL, Tolino MA, Hughey RP, Kleyman TR. Thumb domains of the three epithelial Na + channel subunits have distinct functions. J Biol Chem 2018; 293:17582-17592. [PMID: 30228189 PMCID: PMC6231141 DOI: 10.1074/jbc.ra118.003618] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 09/13/2018] [Indexed: 01/10/2023] Open
Abstract
The epithelial Na+ channel (ENaC) possesses a large extracellular domain formed by a β-strand core enclosed by three peripheral α-helical subdomains, which have been dubbed thumb, finger, and knuckle. Here we asked whether the ENaC thumb domains play specific roles in channel function. To this end, we examined the characteristics of channels lacking a thumb domain in an individual ENaC subunit (α, β, or γ). Removing the γ subunit thumb domain had no effect on Na+ currents when expressed in Xenopus oocytes, but moderately reduced channel surface expression. In contrast, ENaCs lacking the α or β subunit thumb domain exhibited significantly reduced Na+ currents along with a large reduction in channel surface expression. Moreover, channels lacking an α or γ thumb domain exhibited a diminished Na+ self-inhibition response, whereas this response was retained in channels lacking a β thumb domain. In turn, deletion of the α thumb domain had no effect on the degradation rate of the immature α subunit as assessed by cycloheximide chase analysis. However, accelerated degradation of the immature β subunit and mature γ subunit was observed when the β or γ thumb domain was deleted, respectively. Our results suggest that the thumb domains in each ENaC subunit are required for optimal surface expression in oocytes and that the α and γ thumb domains both have important roles in the channel's inhibitory response to external Na+ Our findings support the notion that the extracellular helical domains serve as functional modules that regulate ENaC biogenesis and activity.
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Affiliation(s)
- Shaohu Sheng
- From the Renal-Electrolyte Division, Department of Medicine and
| | - Jingxin Chen
- From the Renal-Electrolyte Division, Department of Medicine and
| | | | | | | | | | | | - Rebecca P Hughey
- From the Renal-Electrolyte Division, Department of Medicine and
- Cell Biology
- Microbiology and Molecular Genetics, and
| | - Thomas R Kleyman
- From the Renal-Electrolyte Division, Department of Medicine and
- Cell Biology
- Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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170
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Kasahara Y, Sakurai T, Matsuda R, Narukawa M, Yasuoka A, Mori N, Watanabe H, Okabe T, Kojima H, Abe K, Misaka T, Asakura T. Novel indole and benzothiophene ring derivatives showing differential modulatory activity against human epithelial sodium channel subunits, ENaC β and γ. Biosci Biotechnol Biochem 2018; 83:243-250. [PMID: 30343635 DOI: 10.1080/09168451.2018.1533802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The epithelial sodium channel (ENaC) plays a pivotal role in sodium homeostasis, and the development of drugs that modulate ENaC activity is of great potential therapeutic relevance. We screened 6100 chemicals for their ability to activate sodium permeability of ENaC. We used a two-step strategy: a high throughput cell-based assay and an electrophysiological assay. Five compounds were identified showing common structural features including an indole or benzothiophene ring. ENaC consists of three subunits: α, β, and γ. Changing the heteromeric combination of human and mouse ENaC αβγ subunits, we found that all five compounds activated the human β subunit but not the mouse subunit. However, four of them exhibited lower activity when the human γ subunit was substituted by the mouse γ subunit. Our findings provide a structural basis for designing human ENaC activity modulators. Abbreviations: ENaC: Epithelial sodium channel; ΔRFU: delta relative fluorescence units; EC50: Half-maximal effective concentration; Emax: maximum effect value.
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Affiliation(s)
- Yoichi Kasahara
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Takanobu Sakurai
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Ryusei Matsuda
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Masataka Narukawa
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Akihito Yasuoka
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Naoki Mori
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Hidenori Watanabe
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Takayoshi Okabe
- b Drug Discovery Initiative (DDI) , The University of Tokyo , Tokyo , Japan
| | - Hirotatsu Kojima
- b Drug Discovery Initiative (DDI) , The University of Tokyo , Tokyo , Japan
| | - Keiko Abe
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan.,c Kanagawa Institute of Industrial Science and Technology (KISTEC) , Kanagawa , Japan
| | - Takumi Misaka
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Tomiko Asakura
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
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171
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Lenzig P, Wirtz M, Wiemuth D. Comparative electrophysiological analysis of the bile acid-sensitive ion channel (BASIC) from different species suggests similar physiological functions. Pflugers Arch 2018; 471:329-336. [PMID: 30353368 DOI: 10.1007/s00424-018-2223-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 10/11/2018] [Accepted: 10/12/2018] [Indexed: 12/29/2022]
Abstract
Despite the identification of cholangiocytes in the liver and unipolar brush cells in the cerebellum as sites of expression, the physiological function of the bile acid-sensitive ion channel (BASIC) remains unknown. Rat BASIC (rBASIC) and mouse BASIC (mBASIC) share 97% of their amino acid sequence but show strikingly different biophysical properties. rBASIC is inactive at rest while mBASIC is constitutively active, when expressed in Xenopus oocytes. This conundrum rendered the identification of the physiological function even more difficult. In this study, we investigated the electrophysiological and pharmacological properties of BASIC from rat, mouse, and human in Hek293 cells using the patch clamp technique. Surprisingly, in Hek293 cells, rBASIC and mBASIC showed almost completely identical properties. Both are blocked by extracellular Ca2+ and thus are inactive at rest; both are selective for Na+, show similar affinities for extracellular Ca2+, were inhibited by diminazene, and activated by various bile acids. This is in contrast to previous results derived from Xenopus oocytes as expression system and suggests that the cell type is important for shaping the biophysical properties of BASIC. Furthermore, we compared hBASIC with rBASIC and mBASIC and observed similar properties between these channels with one exception: the bile acid sensitivity profile of hBASIC is different from rBASIC and mBASIC; hBASIC is more sensitive to bile acids which are abundant in human bile but not in rodent bile. Taken together, these results suggest similar physiological roles for BASIC in different species.
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Affiliation(s)
- Pia Lenzig
- Institute of Physiology, RWTH Aachen University, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - Monika Wirtz
- Institute of Physiology, RWTH Aachen University, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - Dominik Wiemuth
- Institute of Physiology, RWTH Aachen University, Pauwelsstrasse 30, 52074, Aachen, Germany.
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Lambert M, Capuano V, Olschewski A, Sabourin J, Nagaraj C, Girerd B, Weatherald J, Humbert M, Antigny F. Ion Channels in Pulmonary Hypertension: A Therapeutic Interest? Int J Mol Sci 2018; 19:ijms19103162. [PMID: 30322215 PMCID: PMC6214085 DOI: 10.3390/ijms19103162] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 10/05/2018] [Accepted: 10/08/2018] [Indexed: 12/25/2022] Open
Abstract
Pulmonary arterial hypertension (PAH) is a multifactorial and severe disease without curative therapies. PAH pathobiology involves altered pulmonary arterial tone, endothelial dysfunction, distal pulmonary vessel remodeling, and inflammation, which could all depend on ion channel activities (K⁺, Ca2+, Na⁺ and Cl-). This review focuses on ion channels in the pulmonary vasculature and discusses their pathophysiological contribution to PAH as well as their therapeutic potential in PAH.
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Affiliation(s)
- Mélanie Lambert
- Univ. Paris-Sud, Faculté de Médecine, 94270 Kremlin-Bicêtre, France.
- AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, 94270 Le Kremlin-Bicêtre, France.
- UMRS 999, INSERM and Univ. Paris⁻Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, 92350 Le Plessis Robinson, France.
| | - Véronique Capuano
- Univ. Paris-Sud, Faculté de Médecine, 94270 Kremlin-Bicêtre, France.
- AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, 94270 Le Kremlin-Bicêtre, France.
- UMRS 999, INSERM and Univ. Paris⁻Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, 92350 Le Plessis Robinson, France.
| | - Andrea Olschewski
- Ludwig Boltzmann Institute for Lung Vascular Research, Stiftingtalstrasse 24, Graz 8010, Austria.
- Department of Physiology, Medical University Graz, Neue Stiftingtalstraße 6, Graz 8010, Austria.
| | - Jessica Sabourin
- Signalisation et Physiopathologie Cardiovasculaire, UMRS 1180, Univ. Paris-Sud, INSERM, Université Paris-Saclay, 92296 Châtenay-Malabry, France.
| | - Chandran Nagaraj
- Ludwig Boltzmann Institute for Lung Vascular Research, Stiftingtalstrasse 24, Graz 8010, Austria.
| | - Barbara Girerd
- Univ. Paris-Sud, Faculté de Médecine, 94270 Kremlin-Bicêtre, France.
- AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, 94270 Le Kremlin-Bicêtre, France.
- UMRS 999, INSERM and Univ. Paris⁻Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, 92350 Le Plessis Robinson, France.
| | - Jason Weatherald
- Univ. Paris-Sud, Faculté de Médecine, 94270 Kremlin-Bicêtre, France.
- AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, 94270 Le Kremlin-Bicêtre, France.
- UMRS 999, INSERM and Univ. Paris⁻Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, 92350 Le Plessis Robinson, France.
- Division of Respirology, Department of Medicine, University of Calgary, Calgary, AB T1Y 6J4, Canada.
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB T1Y 6J4, Canada.
| | - Marc Humbert
- Univ. Paris-Sud, Faculté de Médecine, 94270 Kremlin-Bicêtre, France.
- AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, 94270 Le Kremlin-Bicêtre, France.
- UMRS 999, INSERM and Univ. Paris⁻Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, 92350 Le Plessis Robinson, France.
| | - Fabrice Antigny
- Univ. Paris-Sud, Faculté de Médecine, 94270 Kremlin-Bicêtre, France.
- AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, 94270 Le Kremlin-Bicêtre, France.
- UMRS 999, INSERM and Univ. Paris⁻Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, 92350 Le Plessis Robinson, France.
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173
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Miyoshi M, Sato M, Saito K, Otani L, Shirahige K, Miura F, Ito T, Jia H, Kato H. Maternal Protein Restriction Alters the Renal Ptger1 DNA Methylation State in SHRSP Offspring. Nutrients 2018; 10:nu10101436. [PMID: 30301128 PMCID: PMC6213780 DOI: 10.3390/nu10101436] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 09/25/2018] [Accepted: 09/28/2018] [Indexed: 11/18/2022] Open
Abstract
We previously reported that maternal protein restriction (LP) during pregnancy increases salt sensitivity in offspring using the Stroke-Prone Spontaneously Hypertensive Rat (SHRSP). In the present study, we focus on DNA methylation profiles of prostaglandin E receptor 1 gene (ptger1), which is known to be associated with hypertension. We evaluated the ptger1 DNA methylation status via bisulfite sequencing, and analyzed the expression of ptger1-related genes. The results of these analyses showed that, compared to controls, the LP-S offspring exhibited both marked ptger1 hypermethylation, and significantly increased ptger1 expression. Moreover, they also exhibited significantly decreased expression of the downstream gene epithelial Na+ channel alpha (enacα). Interestingly, LP offspring that were provided with a standard water drinking supply (W) also exhibited increased ptger1 methylation and expression. Together, these results suggest that maternal protein restriction during pregnancy modulates the renal ptger1 DNA methylation state in SHRSP offspring, and thereby likely mediates ptger1 and enacα gene expression to induce salt sensitivity.
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Affiliation(s)
- Moe Miyoshi
- Health Nutrition, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 1138657, Japan.
| | - Masayuki Sato
- Health Nutrition, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 1138657, Japan.
| | - Kenji Saito
- Health Nutrition, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 1138657, Japan.
| | - Lila Otani
- Health Nutrition, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 1138657, Japan.
| | - Katsuhiko Shirahige
- Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 1130032, Japan.
| | - Fumihito Miura
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Kyushu University, Fukuoka 8128582, Japan.
| | - Takashi Ito
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Kyushu University, Fukuoka 8128582, Japan.
| | - Huijuan Jia
- Health Nutrition, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 1138657, Japan.
| | - Hisanori Kato
- Health Nutrition, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 1138657, Japan.
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174
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Boggula VR, Hanukoglu I, Sagiv R, Enuka Y, Hanukoglu A. Expression of the epithelial sodium channel (ENaC) in the endometrium - Implications for fertility in a patient with pseudohypoaldosteronism. J Steroid Biochem Mol Biol 2018; 183:137-141. [PMID: 29885352 DOI: 10.1016/j.jsbmb.2018.06.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 06/01/2018] [Accepted: 06/05/2018] [Indexed: 01/21/2023]
Abstract
Pseudohypoaldosteronism type 1 (PHA) is a syndrome of unresponsiveness to aldosterone. The severe form of this disease results from mutations in the genes that encode for the epithelial sodium channel subunits, SCNN1A, SCNN1B, and SCNN1G. A PHA patient under our care failed to conceive after many years and IVF trials. Our earlier studies had shown that ENaC is expressed in the female reproductive tract. We hypothesized that a defective ENaC expression may be responsible for the infertility of the patient. To test this hypothesis we examined ENaC expression in endometrial Pipelle biopsy samples from three healthy women and the PHA patient with an Arg508X mutation in the SCNN1A gene. The formalin fixed samples were reacted with anti-ENaCA (alpha subunit) antisera, followed by secondary antibodies to visualize ENaC expression by immunofluorescence. Confocal microscopy imaging of the samples showed strong ENaC immunofluorescence along the luminal border (apical membrane) of the epithelial cells in Pipelle samples from healthy women. In contrast, none of the samples from the PHA patient showed ENaC immunofluorescence. The Arg508X mutation interrupts the transport of ENaC subunits to the cell surface, yet it would not be expected to disrupt ENaC localization in the cytoplasm. In contrast to endometrium where ENaC is localized in the apical membrane of the epithelial cells, in keratinocytes ENaC is expressed in cytoplasmic pools. Therefore, we examined ENaC immunofluorescence in plucked hair follicles. As expected, ENaC immunofluorescence was detected in the cytoplasm of keratinocytes of both normal and PHA samples. Our results support the hypothesis that lack of expression of ENaC on the endometrial surface may be responsible for the infertility of the PHA patient.
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Affiliation(s)
| | | | - Ron Sagiv
- Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel; Department of Obstetrics & Gynecology, E. Wolfson Medical Center, Holon, Israel
| | - Yehoshua Enuka
- Laboratory of Cell Biology, Ariel University, Ariel, Israel
| | - Aaron Hanukoglu
- Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel; Division of Pediatric Endocrinology, E. Wolfson Medical Center, Holon, Israel.
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175
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Monticone S, Losano I, Tetti M, Buffolo F, Veglio F, Mulatero P. Diagnostic approach to low-renin hypertension. Clin Endocrinol (Oxf) 2018; 89:385-396. [PMID: 29758100 DOI: 10.1111/cen.13741] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 04/25/2018] [Accepted: 05/08/2018] [Indexed: 12/16/2022]
Abstract
Renin-angiotensin-aldosterone system (RAAS) plays a crucial role in maintaining water and electrolytes homoeostasis, and its deregulation contributes to the development of arterial hypertension. Since the historical description of the "classical" RAAS, a dramatic increase in our understanding of the molecular mechanisms underlying the development of both essential and secondary hypertension has occurred. Approximatively 25% of the patients affected by arterial hypertension display low-renin levels, a definition that is largely arbitrary and depends on the investigated population and the specific characteristics of the assay. Most often, low-renin levels are expression of a physiological response to sodium-volume overload, but also a significant number of secondary hereditary or acquired conditions falls within this category. In a context of suppressed renin status, the concomitant examination of plasma aldosterone levels (which can be inappropriately elevated, within the normal range or suppressed) and plasma potassium are essential to formulate a differential diagnosis. To distinguish between the different forms of low-renin hypertension is of fundamental importance to address the patient to the proper clinical management, as each subtype requires a specific and targeted therapy. The present review will discuss the differential diagnosis of the most common medical conditions manifesting with a clinical phenotype of low-renin hypertension, enlightening the novelties in genetics of the familial forms.
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Affiliation(s)
- Silvia Monticone
- Division of Internal Medicine and Hypertension, Department of Medical Sciences, University of Torino, Torino, Italy
| | - Isabel Losano
- Division of Internal Medicine and Hypertension, Department of Medical Sciences, University of Torino, Torino, Italy
| | - Martina Tetti
- Division of Internal Medicine and Hypertension, Department of Medical Sciences, University of Torino, Torino, Italy
| | - Fabrizio Buffolo
- Division of Internal Medicine and Hypertension, Department of Medical Sciences, University of Torino, Torino, Italy
| | - Franco Veglio
- Division of Internal Medicine and Hypertension, Department of Medical Sciences, University of Torino, Torino, Italy
| | - Paolo Mulatero
- Division of Internal Medicine and Hypertension, Department of Medical Sciences, University of Torino, Torino, Italy
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176
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Noreng S, Bharadwaj A, Posert R, Yoshioka C, Baconguis I. Structure of the human epithelial sodium channel by cryo-electron microscopy. eLife 2018; 7:39340. [PMID: 30251954 PMCID: PMC6197857 DOI: 10.7554/elife.39340] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 09/18/2018] [Indexed: 12/11/2022] Open
Abstract
The epithelial sodium channel (ENaC), a member of the ENaC/DEG superfamily, regulates Na+ and water homeostasis. ENaCs assemble as heterotrimeric channels that harbor protease-sensitive domains critical for gating the channel. Here, we present the structure of human ENaC in the uncleaved state determined by single-particle cryo-electron microscopy. The ion channel is composed of a large extracellular domain and a narrow transmembrane domain. The structure reveals that ENaC assembles with a 1:1:1 stoichiometry of α:β:γ subunits arranged in a counter-clockwise manner. The shape of each subunit is reminiscent of a hand with key gating domains of a 'finger' and a 'thumb.' Wedged between these domains is the elusive protease-sensitive inhibitory domain poised to regulate conformational changes of the 'finger' and 'thumb'; thus, the structure provides the first view of the architecture of inhibition of ENaC.
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Affiliation(s)
- Sigrid Noreng
- Department of Biochemistry & Molecular Biology, Oregon Health and Science University, Portland, United States
| | - Arpita Bharadwaj
- Vollum Institute, Oregon Health and Science University, Portland, United States
| | - Richard Posert
- Department of Biochemistry & Molecular Biology, Oregon Health and Science University, Portland, United States
| | - Craig Yoshioka
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, United States
| | - Isabelle Baconguis
- Vollum Institute, Oregon Health and Science University, Portland, United States
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177
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Wang Q, Yan SF, Hao Y, Jin SW. Specialized Pro-resolving Mediators Regulate Alveolar Fluid Clearance during Acute Respiratory Distress Syndrome. Chin Med J (Engl) 2018; 131:982-989. [PMID: 29664060 PMCID: PMC5912066 DOI: 10.4103/0366-6999.229890] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Objective Acute respiratory distress syndrome (ARDS) is an acute and lethal clinical syndrome that is characterized by the injury of alveolar epithelium, which impairs active fluid transport in the lung, and impedes the reabsorption of edema fluid from the alveolar space. This review aimed to discuss the role of pro-resolving mediators on the regulation of alveolar fluid clearance (AFC) in ARDS. Data Sources Articles published up to September 2017 were selected from the PubMed, with the keywords of "alveolar fluid clearance" or "lung edema" or "acute lung injury" or "acute respiratory distress syndrome", and "specialized pro-resolving mediators" or "lipoxin" or "resolvin" or "protectin" or "maresin" or "alveolar epithelial cells" or "aspirin-triggered lipid mediators" or "carbon monoxide and heme oxygenase" or "annexin A1". Study Selection We included all relevant articles published up to September 2017, with no limitation of study design. Results Specialized pro-resolving mediators (SPMs), as the proinflammatory mediators, not only upregulated epithelial sodium channel, Na,K-ATPase, cystic fibrosis transmembrane conductance regulator (CFTR), and aquaporins levels, but also improved Na,K-ATPase activity to promote AFC in ARDS. In addition to the direct effects on ion channels and pumps of the alveolar epithelium, the SPMs also inhibited the inflammatory cytokine expression and improved the alveolar epithelial cell repair to enhance the AFC in ARDS. Conclusions The present review discusses a novel mechanism for pulmonary edema fluid reabsorption. SPMs might provide new opportunities to design "reabsorption-targeted" therapies with high degrees of precision in controlling ALI/ARDS.
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Affiliation(s)
- Qian Wang
- Department of Anesthesia and Critical Care, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, China
| | - Song-Fan Yan
- Department of Anesthesia and Critical Care, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, China
| | - Yu Hao
- Department of Anesthesia and Critical Care, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, China
| | - Sheng-Wei Jin
- Department of Anesthesia and Critical Care, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, China
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178
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Mills NJ, Sharma K, Haque M, Moore M, Teruyama R. Aldosterone Mediated Regulation of Epithelial Sodium Channel (ENaC) Subunits in the Rat Hypothalamus. Neuroscience 2018; 390:278-292. [PMID: 30195057 DOI: 10.1016/j.neuroscience.2018.08.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 08/10/2018] [Accepted: 08/28/2018] [Indexed: 01/23/2023]
Abstract
Current evidence suggests that the epithelial Na+ channel (ENaC) in the brain plays a significant role in the development of hypertension. ENaC is present in vasopressin (VP) neurons in the hypothalamus, suggesting that ENaC in VP neurons is involved in the regulation of blood pressure. Our recent study demonstrated that high dietary salt intake caused an increase in the expression and activity of ENaC that were responsible for the more depolarized basal membrane potential in VP neurons. A known regulator of ENaC expression, the mineralocorticoid receptor (MR), is present in VP neurons, suggesting that ENaC expression in VP neurons is regulated by aldosterone. In this study, the effects of aldosterone and corticosterone on ENaC were examined in acute hypothalamic slices. Real-time PCR and Western blot analysis showed that aldosterone and corticosterone treatment resulted in a significant increase in the expression of γENaC, but not α- or βENaC, and that this expression was attenuated by MR and glucocorticoid receptor (GR) antagonists. Moreover, chromatin immunoprecipitation demonstrated that the aldosterone-MR complex directly interacts with the promoter region of the γENaC gene. However, the treatment with aldosterone did not cause subcellular translocation of ENaC toward the plasma membrane nor an increase in ENaC Na+-leak current. These results indicate that expression of γENaC in VP neurons is induced by aldosterone and corticosterone through their MR and GR, respectively; however, aldosterone or corticosterone alone is not sufficient enough to increase ENaC current when they are applied to hypothalamic slices in vitro.
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Affiliation(s)
- Natalie J Mills
- Department of Biological Sciences, Louisiana State University, LA 70803, USA
| | - Kaustubh Sharma
- Department of Biological Sciences, Louisiana State University, LA 70803, USA
| | - Masudul Haque
- Department of Biological Sciences, Louisiana State University, LA 70803, USA
| | - Meagan Moore
- Department of Biological Sciences, Louisiana State University, LA 70803, USA
| | - Ryoichi Teruyama
- Department of Biological Sciences, Louisiana State University, LA 70803, USA.
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179
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Epithelial sodium channel biogenesis and quality control in the early secretory pathway. Curr Opin Nephrol Hypertens 2018; 27:364-372. [DOI: 10.1097/mnh.0000000000000438] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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180
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Yang L, Palmer LG. Determinants of selective ion permeation in the epithelial Na + channel. J Gen Physiol 2018; 150:1397-1407. [PMID: 30135076 PMCID: PMC6168236 DOI: 10.1085/jgp.201812164] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/01/2018] [Indexed: 11/20/2022] Open
Abstract
The epithelial Na+ channel (ENaC) is a key transporter mediating and controlling Na+ reabsorption in many tight epithelia. A very high selectivity for Na+ over other cations, including K+, is a hallmark of this channel. This selectivity greatly exceeds that of the closely related acid-sensing channels (ASICs). Here, we assess the roles of two regions of the ENaC transmembrane pore in the determination of cation selectivity. Mutations of conserved amino acids with acidic side chains near the cytoplasmic end of the pore diminish macroscopic currents but do not decrease the selectivity of the channel for Na+ versus K+ In the WT channel, voltage-dependent block of Na+ currents by K+ or guanidinium+, neither of which have detectable conductance, suggests that these ions permeate only ∼20% of the transmembrane electric field. According to markers of the electric field determined by Zn2+ block of cysteine residues, the site of K+ block appears to be nearer to the extracellular end of the pore, close to a putative selectivity filter identified using site-directed mutations. To test whether differences in this part of the channel account for selectivity differences between ENaC and ASIC, we substitute amino acids in the three ENaC subunits with those present in the ASIC homotrimer. In this construct, Li:Na selectivity is altered from that of WT ENaC, but the high Na:K selectivity is maintained. We conclude that a different part of the pore may constitute the selectivity filter in the highly selective ENaC than in the less-selective ASIC channel.
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Affiliation(s)
- Lei Yang
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
| | - Lawrence G Palmer
- Department of Physiology and Biophysics, Weill-Cornell Medical College, New York, NY
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181
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(Pro)Renin receptor mediates obesity-induced antinatriuresis and elevated blood pressure via upregulation of the renal epithelial sodium channel. PLoS One 2018; 13:e0202419. [PMID: 30118514 PMCID: PMC6097690 DOI: 10.1371/journal.pone.0202419] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 07/10/2018] [Indexed: 11/21/2022] Open
Abstract
Recent studies have demonstrated that the renal (pro)renin receptor (PRR) regulates expression of the alpha subunit of the epithelial sodium channel (α-ENaC). In this study we hypothesized that the renal PRR mediates high fat diet (HFD)-induced sodium retention and elevated systolic blood pressure (SBP) by enhancing expression of the epithelial sodium channel (α-ENaC). In our study we used a recently developed inducible nephron specific PRR knockout mouse. Mice (n = 6 each group) were allocated to receive regular diet (RD, 12 kcal% fat) or a high-fat diet (HFD, 45 kcal% fat) for 10 weeks. Body weight (BW), SBP, urine volume (UV) and urine sodium (UNaV), as well as renal interstitial Angiotensin II (Ang II), and renal medullary expression of PRR, p-SGK-1, α-ENaC were monitored in RD and HFD mice with or without PRR knockout. At baseline, there were no significant differences in BW, BP, UV or UNaV between different animal groups. At the end of the study, HFD mice had significant increases in SBP, BW, and significant reductions in UV and UNaV. Compared to RD, HFD significantly increased mRNA and protein expression of PRR, α-ENaC, p-SGK-1, and Ang II. Compared to HFD alone, PRR knockout mice on HFD had reduced mRNA and protein expression of PRR, p-SGK-1, and α-ENaC, as well as increased UV, UNaV and significantly reduced SBP. RIF Ang II was significantly increased by HFD and did not change in response to PRR knockout. We conclude that obesity induced sodium retention and elevated SBP are mediated by the PRR-SGK-1- α-ENaC pathway independent of Ang II.
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182
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Kandel C, Schmidt P, Perniss A, Keshavarz M, Scholz P, Osterloh S, Althaus M, Kummer W, Deckmann K. ENaC in Cholinergic Brush Cells. Front Cell Dev Biol 2018; 6:89. [PMID: 30159312 PMCID: PMC6103785 DOI: 10.3389/fcell.2018.00089] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 07/25/2018] [Indexed: 12/17/2022] Open
Abstract
Cholinergic polymodal chemosensory cells in the mammalian urethra (urethral brush cells = UBC) functionally express the canonical bitter and umami taste transduction signaling cascade. Here, we aimed to determine whether UBC are functionally equipped for the perception of salt through ENaC (epithelial sodium channel). Cholinergic UBC were isolated from ChAT-eGFP reporter mice (ChAT = choline acetyltransferase). RT-PCR showed mRNA expression of ENaC subunits Scnn1a, Scnn1b, and Scnn1g in urethral epithelium and isolated UBC. Scnn1a could also be detected by next generation sequencing in 4/6 (66%) single UBC, two of them also expressed the bitter receptor Tas2R108. Strong expression of Scnn1a was seen in some urothelial umbrella cells and in 65% of UBC (30/46 cells) in a Scnn1a reporter mouse strain. Intracellular [Ca2+] was recorded in isolated UBC stimulated with the bitter substance denatonium benzoate (25 mM), ATP (0.5 mM) and NaCl (50 mM, on top of 145 mM Na+ and 153 mM Cl− baseline in buffer); mannitol (150 mM) served as osmolarity control. NaCl, but not mannitol, evoked an increase in intracellular [Ca2+] in 70% of the tested UBC. The NaCl-induced effect was blocked by the ENaC inhibitor amiloride (IC50 = 0.47 μM). When responses to both NaCl and denatonium were tested, all three possible positive response patterns occurred in a balanced distribution: 42% NaCl only, 33% denatonium only, 25% to both stimuli. A similar reaction pattern was observed with ATP and NaCl as test stimuli. About 22% of the UBC reacted to all three stimuli. Thus, NaCl evokes calcium responses in several UBC, likely involving an amiloride-sensitive channel containing α-ENaC. This feature does not define a new subpopulation of UBC, but rather emphasizes their polymodal character. The actual function of α-ENaC in cholinergic UBC—salt perception, homeostatic ion transport, mechanoreception—remains to be determined.
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Affiliation(s)
- Chrissy Kandel
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Patricia Schmidt
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Alexander Perniss
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Maryam Keshavarz
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Paul Scholz
- Department of Cell Physiology, Ruhr-University Bochum, Bochum, Germany
| | - Sabrina Osterloh
- Department of Cell Physiology, Ruhr-University Bochum, Bochum, Germany
| | - Mike Althaus
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Wolfgang Kummer
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Klaus Deckmann
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
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183
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Zhao C, Crosby J, Lv T, Bai D, Monia BP, Guo S. Antisense oligonucleotide targeting of mRNAs encoding ENaC subunits α, β, and γ improves cystic fibrosis-like disease in mice. J Cyst Fibros 2018; 18:334-341. [PMID: 30100257 DOI: 10.1016/j.jcf.2018.07.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/11/2018] [Accepted: 07/20/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND The epithelial sodium channel ENaC consists of three subunits encoded by Scnn1a, Scnn1b, and Scnn1g and increased sodium absorption through this channel is hypothesized to lead to mucus dehydration and accumulation in cystic fibrosis (CF) patients. METHODS We identified potent and specific antisense oligonucleotides (ASOs) targeting mRNAs encoding the ENaC subunits and evaluated these ASOs in mouse models of CF-like lung disease. RESULTS ASOs designed to target mRNAs encoding each ENaC subunit or a control ASO were administered directly into the lungs of mice. The reductions in ENaC subunits correlated well with a reduction in amiloride sensitive channel conductance. In addition, levels of mucus markers Gob5, AGR2, Muc5ac, and Muc5b, periodic acid-Schiff's reagent (PAS) goblet cell staining, and neutrophil recruitment were reduced and lung function was improved when levels of any of the ENaC subunits were decreased. CONCLUSIONS Delivery of ASOs targeting mRNAs encoding each of the three ENaC subunits directly into the lung improved disease phenotypes in a mouse model of CF-like lung disease. These findings suggest that targeting ENaC subunits could be an effective approach for the treatment of CF.
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Affiliation(s)
- Chenguang Zhao
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA.
| | - Jeff Crosby
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Tinghong Lv
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Dong Bai
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Brett P Monia
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Shuling Guo
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
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184
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Kota P, Gentzsch M, Dang YL, Boucher RC, Stutts MJ. The N terminus of α-ENaC mediates ENaC cleavage and activation by furin. J Gen Physiol 2018; 150:1179-1187. [PMID: 29980634 PMCID: PMC6080898 DOI: 10.1085/jgp.201711860] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 03/05/2018] [Accepted: 05/28/2018] [Indexed: 12/23/2022] Open
Abstract
Epithelial Na+ channels comprise three homologous subunits (α, β, and γ) that are regulated by alternative splicing and proteolytic cleavage. Here, we determine the basis of the reduced Na+ current (INa) that results from expression of a previously identified, naturally occurring splice variant of the α subunit (α-ENaC), in which residues 34-82 are deleted (αΔ34-82). αΔ34-82-ENaC expression with WT β and γ subunits in Xenopus oocytes produces reduced basal INa, which can largely be recovered by exogenous trypsin. With this αΔ34-82-containing ENaC, both α and γ subunits display decreased cleavage fragments, consistent with reduced processing by furin or furin-like convertases. Data using MTSET modification of a cysteine, introduced into the degenerin locus in β-ENaC, suggest that the reduced INa of αΔ34-82-ENaC arises from an increased population of uncleaved, near-silent ENaC, rather than from a reduced open probability spread uniformly across all channels. After treatment with brefeldin A to disrupt anterograde trafficking of channel subunits, INa in oocytes expressing αΔ34-82-ENaC is reestablished more slowly than that in oocytes expressing WT ENaC. Overnight or acute incubation of oocytes expressing WT ENaC in the pore blocker amiloride increases basal ENaC proteolytic stimulation, consistent with relief of Na+ feedback inhibition. These responses are reduced in oocytes expressing αΔ34-82-ENaC. We conclude that the α-ENaC N terminus mediates interactions that govern the delivery of cleaved and uncleaved ENaC populations to the oocyte membrane.
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Affiliation(s)
- Pradeep Kota
- Marsico Lung Institute, Cystic Fibrosis Center and Department of Medicine, University of North Carolina, Chapel Hill, NC
| | - Martina Gentzsch
- Marsico Lung Institute, Cystic Fibrosis Center and Department of Medicine, University of North Carolina, Chapel Hill, NC
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC
| | - Yan L Dang
- Marsico Lung Institute, Cystic Fibrosis Center and Department of Medicine, University of North Carolina, Chapel Hill, NC
| | - Richard C Boucher
- Marsico Lung Institute, Cystic Fibrosis Center and Department of Medicine, University of North Carolina, Chapel Hill, NC
| | - M Jackson Stutts
- Marsico Lung Institute, Cystic Fibrosis Center and Department of Medicine, University of North Carolina, Chapel Hill, NC
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185
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Mills NJ, Sharma K, Huang K, Teruyama R. Effect of dietary salt intake on epithelial Na + channels (ENaCs) in the hypothalamus of Dahl salt-sensitive rats. Physiol Rep 2018; 6:e13838. [PMID: 30156045 PMCID: PMC6113134 DOI: 10.14814/phy2.13838] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 07/22/2018] [Indexed: 01/02/2023] Open
Abstract
All three epithelial Na+ channel (ENaC) subunits (α, β, and γ) and the mineralocorticoid receptor (MR), a known regulator of ENaC, are located in vasopressin (VP) synthesizing magnocellular neurons in the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei. Our previous study showed that ENaC mediates a Na+ leak current that affects the steady-state membrane potential of VP neurons. This study was conducted in Dahl salt-sensitive (Dahl-SS) rats to determine if any abnormal responses in the expression of ENaC subunits and MR occur in the hypothalamus and kidney in response to a high dietary salt intake. After 21 days of high salt consumption, Dahl-SS rat resulted in a significant increase in γENaC expression and exhibited proteolytic cleavage of this subunit compared to Sprague-Dawley (SD) rats. Additionally, Dahl-SS rats had dense somato-dendritic γENaC immunoreactivity in VP neurons, which was absent in SD rats. In contrast, SD rats fed a high salt diet had significantly decreased αENaC subunit expression in the kidney and MR expression in the hypothalamus. Plasma osmolality measured daily for 22 days demonstrated that Dahl-SS rats fed a high salt diet had a steady increase in plasma osmolality, whereas SD rats had an initial increase that decreased to baseline levels. Findings from this study demonstrate that Dahl-SS rats lack a compensatory mechanism to down regulate ENaC during high dietary salt consumption, which may contribute to the development of hypertension.
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Affiliation(s)
- Natalie J. Mills
- Department of Biological SciencesLouisiana State UniversityBaton RougeLouisiana
| | - Kaustubh Sharma
- Department of Biological SciencesLouisiana State UniversityBaton RougeLouisiana
| | - Katie Huang
- Department of Biological SciencesLouisiana State UniversityBaton RougeLouisiana
| | - Ryoichi Teruyama
- Department of Biological SciencesLouisiana State UniversityBaton RougeLouisiana
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186
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Strug LJ, Stephenson AL, Panjwani N, Harris A. Recent advances in developing therapeutics for cystic fibrosis. Hum Mol Genet 2018; 27:R173-R186. [PMID: 30060192 PMCID: PMC6061831 DOI: 10.1093/hmg/ddy188] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 05/07/2018] [Accepted: 05/10/2018] [Indexed: 12/23/2022] Open
Abstract
Despite hope that a cure was imminent when the causative gene was cloned nearly 30 years ago, cystic fibrosis (CF [MIM: 219700]) remains a life-shortening disease affecting more than 70 000 individuals worldwide. However, within the last 6 years the Food and Drug Administration's approval of Ivacaftor, the first drug that corrects the defective cystic fibrosis transmembrane conductance regulator protein [CFTR (MIM: 602421)] in patients with the G551D mutation, marks a watershed in the development of novel therapeutics for this devastating disease. Here we review recent progress in diverse research areas, which all focus on curing CF at the genetic, biochemical or physiological level. In the near future it seems probable that development of mutation-specific therapies will be the focus, since it is unlikely that any one approach will be efficient in correcting the more than 2000 disease-associated variants. We discuss the new drugs and combinations of drugs that either enhance delivery of misfolded CFTR protein to the cell membrane, where it functions as an ion channel, or that activate channel opening. Next we consider approaches to correct the causative genetic lesion at the DNA or RNA level, through repressing stop mutations and nonsense-mediated decay, modulating splice mutations, fixing errors by gene editing or using novel routes to gene replacement. Finally, we explore how modifier genes, loci elsewhere in the genome that modify CF disease severity, may be used to restore a normal phenotype. Progress in all of these areas has been dramatic, generating enthusiasm that CF may soon become a broadly treatable disease.
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Affiliation(s)
- Lisa J Strug
- Division of Biostatistics, Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
- The Centre for Applied Genomics, The Hospital for Sick Children, Toronto, ON, Canada
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, Canada
| | - Anne L Stephenson
- Department of Respirology, Adult Cystic Fibrosis Program, St. Michael’s Hospital, Toronto, ON, Canada
- Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada
| | - Naim Panjwani
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, Canada
| | - Ann Harris
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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187
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Tingskov SJ, Kwon TH, Frøkiær J, Nørregaard R. Tamoxifen Decreases Lithium-Induced Natriuresis in Rats With Nephrogenic Diabetes Insipidus. Front Physiol 2018; 9:903. [PMID: 30050465 PMCID: PMC6052323 DOI: 10.3389/fphys.2018.00903] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 06/21/2018] [Indexed: 11/13/2022] Open
Abstract
Lithium is widely used in the treatment of bipolar affective disorders, but often causes nephrogenic diabetes insipidus (NDI), a condition characterized by a severe urinary concentrating defect. Lithium-induced NDI is associated with dysregulation of the amiloride-sensitive epithelial sodium channel (ENaC), which is essential for renal sodium reabsorption. Sex hormones have been shown to affect the expression of aquaporin-2 (AQP2) and sodium transporters. Therefore, we evaluated whether tamoxifen (TAM), a selective estrogen receptor modulator (SERM), would affect lithium-induced dysregulation of ENaC subunits and natriuresis. Rats were fed with lithium-containing food for 2 weeks to induce NDI and natriuresis. TAM was administered daily via gastric gavage after 1 week of lithium administration. Lithium treatment alone resulted in increased urinary sodium excretion and significant reduction of βENaC and γENaC at both RNA and protein levels. In addition, the plasma sodium level reduced after lithium treatment. Administration of TAM prevented increased urinary sodium excretion as well as attenuated the downregulation of βENaC and γENaC. Consistent with these findings, immunohistochemistry (IHC) showed stronger labeling of βENaC and γENaC subunits in the apical domain of the collecting duct cells in the cortical tissue of lithium-fed rats treated with TAM. Other major sodium transporters including NaPi-2, NKCC2, Na/K-ATPase, and NHE3, are believed not to have an effect on the increased urinary sodium excretion since their expression increased or was unchanged after treatment with lithium. In conclusion, the results demonstrated that TAM rescued the adverse effects of the lithium-induced increase in fractional excretion of sodium after the establishment of lithium-induced NDI.
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Affiliation(s)
| | - Tae-Hwan Kwon
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Daegu, South Korea
| | - Jørgen Frøkiær
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Rikke Nørregaard
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
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188
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Wu NC, Cramp RL, Franklin CE. Living with a leaky skin: upregulation of ion transport proteins during sloughing. ACTA ACUST UNITED AC 2018; 220:2026-2035. [PMID: 28566357 DOI: 10.1242/jeb.151738] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 03/20/2017] [Indexed: 11/20/2022]
Abstract
Amphibian skin is a multifunctional organ providing protection from the external environment and facilitating the physiological exchange of gases, water and salts with the environment. In order to maintain these functions, the outer layer of skin is regularly replaced in a process called sloughing. During sloughing, the outermost layer of the skin is removed in its entirety, which has the potential to interfere with skin permeability and ion transport, disrupting homeostasis. In this study, we measured, in vivo, the effects of sloughing on the cutaneous efflux of ions in toads Rhinella marina kept in freshwater conditions. We also measured transepithelial potential, cutaneous resistance, active ion transport and the distribution, abundance and gene expression of the key ion transport proteins sodium-potassium ATPase (NKA) and epithelial sodium channel (ENaC) during sloughing. We hypothesised that the increase in transepithelial efflux of ions during sloughing is a consequence of increased permeability and/or a reduction in the abundance or expression of cutaneous ion transport proteins, resulting in disruption of internal ion homeostasis. There was a significant increase in sodium and chloride efflux during sloughing in R. marina However, although in vitro skin resistance decreased after sloughing, active sodium transport increased commensurate with an increase in NKA and ENaC protein abundance in the skin. These changes in skin function associated with sloughing did not affect the maintenance of internal electrolyte homeostasis. These results suggest that during sloughing, amphibians actively maintain internal homeostasis by increasing cutaneous rates of ion uptake.
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Affiliation(s)
- Nicholas C Wu
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Rebecca L Cramp
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Craig E Franklin
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
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189
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Ho PY, Li H, Pavlov TS, Tuerk RD, Tabares D, Brunisholz R, Neumann D, Staruschenko A, Hallows KR. β 1Pix exchange factor stabilizes the ubiquitin ligase Nedd4-2 and plays a critical role in ENaC regulation by AMPK in kidney epithelial cells. J Biol Chem 2018; 293:11612-11624. [PMID: 29858246 DOI: 10.1074/jbc.ra118.003082] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 05/22/2018] [Indexed: 12/22/2022] Open
Abstract
Our previous work has established that the metabolic sensor AMP-activated protein kinase (AMPK) inhibits the epithelial Na+ channel (ENaC) by promoting its binding to neural precursor cell-expressed, developmentally down-regulated 4-2, E3 ubiquitin protein ligase (Nedd4-2). Here, using MS analysis and in vitro phosphorylation, we show that AMPK phosphorylates Nedd4-2 at the Ser-444 (Xenopus Nedd4-2) site critical for Nedd4-2 stability. We further demonstrate that the Pak-interacting exchange factor β1Pix is required for AMPK-mediated inhibition of ENaC-dependent currents in both CHO and murine kidney cortical collecting duct (CCD) cells. Short hairpin RNA-mediated knockdown of β1Pix expression in CCD cells attenuated the inhibitory effect of AMPK activators on ENaC currents. Moreover, overexpression of a β1Pix dimerization-deficient mutant unable to bind 14-3-3 proteins (Δ602-611) increased ENaC currents in CCD cells, whereas overexpression of WT β1Pix had the opposite effect. Using additional immunoblotting and co-immunoprecipitation experiments, we found that treatment with AMPK activators promoted the binding of β1Pix to 14-3-3 proteins in CCD cells. However, the association between Nedd4-2 and 14-3-3 proteins was not consistently affected by AMPK activation, β1Pix knockdown, or overexpression of WT β1Pix or the β1Pix-Δ602-611 mutant. Moreover, we found that β1Pix is important for phosphorylation of the aforementioned Nedd4-2 site critical for its stability. Overall, these findings elucidate novel molecular mechanisms by which AMPK regulates ENaC. Specifically, they indicate that AMPK promotes the assembly of β1Pix, 14-3-3 proteins, and Nedd4-2 into a complex that inhibits ENaC by enhancing Nedd4-2 binding to ENaC and its degradation.
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Affiliation(s)
- Pei-Yin Ho
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Hui Li
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Tengis S Pavlov
- the Division of Hypertension and Vascular Research, Henry Ford Health System, Detroit, Michigan 48202; Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Roland D Tuerk
- Department of Biology, Institute of Cell Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Diego Tabares
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - René Brunisholz
- Functional Genomics Center, ETH Zurich, 8097 Zurich, Switzerland
| | - Dietbert Neumann
- Department of Biology, Institute of Cell Biology, ETH Zurich, 8093 Zurich, Switzerland; Department of Pathology, School for Cardiovascular Diseases, Maastricht University, 6200 MD Maastricht, The Netherlands
| | | | - Kenneth R Hallows
- Division of Nephrology and Hypertension, Department of Medicine and USC/UKRO Kidney Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033.
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190
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Shi S, Mutchler SM, Blobner BM, Kashlan OB, Kleyman TR. Pore-lining residues of MEC-4 and MEC-10 channel subunits tune the Caenorhabditis elegans degenerin channel's response to shear stress. J Biol Chem 2018; 293:10757-10766. [PMID: 29743244 DOI: 10.1074/jbc.ra118.002499] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/08/2018] [Indexed: 12/20/2022] Open
Abstract
The Caenorhabditis elegans MEC-4/MEC-10 channel mediates the worm's response to gentle body touch and is activated by laminar shear stress (LSS) when expressed in Xenopus oocytes. Substitutions at multiple sites within the second transmembrane domain (TM2) of MEC-4 or MEC-10 abolish the gentle touch response in worms, but the roles of these residues in mechanosensing are unclear. The present study therefore examined the role of specific MEC-4 and MEC-10 TM2 residues in the channel's response to LSS. We found that introducing mutations within the TM2 of MEC-4 or MEC-10 not only altered channel activity, but also affected the channel's response to LSS. This response was enhanced by Cys substitutions at selected MEC-4 sites (Phe715, Gly716, Gln718, and Leu719) between the degenerin and the putative amiloride-binding sites in this subunit. In contrast, the LSS response was largely blunted in MEC-10 variants bearing single Cys substitutions in the regions preceding and following the amiloride-binding site (Gly677-Leu681), as well as with four MEC-10 touch-deficient mutations that introduced charged residues into the TM2 domain. An enhanced response to LSS was observed with a MEC-10 mutation in the putative selectivity filter. Overall, MEC-4 or MEC-10 mutants that altered the channel's LSS response are primarily clustered between the degenerin site and the selectivity filter, a region that probably forms the narrowest portion of the channel pore. Our results suggest that pore-lining residues of MEC-4 and MEC-10 have important yet different roles in tuning the channel's response to mechanical forces.
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Affiliation(s)
- Shujie Shi
- From the Renal-Electrolyte Division, Department of Medicine
| | - Stephanie M Mutchler
- From the Renal-Electrolyte Division, Department of Medicine.,Department of Pharmacology and Chemical Biology, and
| | | | - Ossama B Kashlan
- From the Renal-Electrolyte Division, Department of Medicine.,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Thomas R Kleyman
- From the Renal-Electrolyte Division, Department of Medicine, .,Department of Pharmacology and Chemical Biology, and.,Department of Cell Biology
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191
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Abstract
The kidneys regulate many vital functions that require precise control throughout the day. These functions, such as maintaining sodium balance or regulating arterial pressure, rely on an intrinsic clock mechanism that was commonly believed to be controlled by the central nervous system. Mounting evidence in recent years has unveiled previously underappreciated depth of influence by circadian rhythms and clock genes on renal function, at the molecular and physiological level, independent of other external factors. The impact of circadian rhythms in the kidney also affects individuals from a clinical standpoint, as the loss of rhythmic activity or clock gene expression have been documented in various cardiovascular diseases. Fortunately, the prognostic value of examining circadian rhythms may prove useful in determining the progression of a kidney-related disease, and chronotherapy is a clinical intervention that requires consideration of circadian and diurnal rhythms in the kidney. In this review, we discuss evidence of circadian regulation in the kidney from basic and clinical research in order to provide a foundation on which a great deal of future research is needed to expand our understanding of circadian relevant biology.
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Affiliation(s)
- Jermaine G Johnston
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, United States
| | - David M Pollock
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, United States.
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192
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Schmidt A, Bauknecht P, Williams EA, Augustinowski K, Gründer S, Jékely G. Dual signaling of Wamide myoinhibitory peptides through a peptide‐gated channel and a GPCR in
Platynereis. FASEB J 2018; 32:5338-5349. [DOI: 10.1096/fj.201800274r] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Axel Schmidt
- Institute of Physiology, Rheinisch‐Westfälische Technische Hochschule (RWTH) Aachen UniversityAachenGermany
| | | | | | - Katrin Augustinowski
- Institute of Physiology, Rheinisch‐Westfälische Technische Hochschule (RWTH) Aachen UniversityAachenGermany
| | - Stefan Gründer
- Institute of Physiology, Rheinisch‐Westfälische Technische Hochschule (RWTH) Aachen UniversityAachenGermany
| | - Gáspár Jékely
- Living Systems Institute, University of ExeterExeterUnited Kingdom
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193
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Ritagliati C, Baro Graf C, Stival C, Krapf D. Regulation mechanisms and implications of sperm membrane hyperpolarization. Mech Dev 2018; 154:33-43. [PMID: 29694849 DOI: 10.1016/j.mod.2018.04.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 04/16/2018] [Accepted: 04/18/2018] [Indexed: 12/21/2022]
Abstract
Mammalian sperm are unable to fertilize the egg immediately after ejaculation. In order to gain fertilization competence, they need to undergo a series of biochemical and physiological modifications inside the female reproductive tract, known as capacitation. Capacitation correlates with two essential events for fertilization: hyperactivation, an asymmetric and vigorous flagellar motility, and the ability to undergo the acrosome reaction. At a molecular level, capacitation is associated to: phosphorylation cascades, modification of membrane lipids, alkalinization of the intracellular pH, increase in the intracellular Ca2+ concentration and hyperpolarization of the sperm plasma membrane potential. Hyperpolarization is a crucial event in capacitation since it primes the sperm to undergo the exocytosis of the acrosome content, essential to achieve fertilization of the oocyte.
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Affiliation(s)
- Carla Ritagliati
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario 2000, Argentina.
| | - Carolina Baro Graf
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario 2000, Argentina
| | - Cintia Stival
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario 2000, Argentina
| | - Dario Krapf
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario 2000, Argentina; Laboratorio de Especialidades Reproductivas, Facultad de Ciencias Bioquimicas y Farmacéuticas, UNR, Rosario 2000, Argentina.
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194
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Sternak M, Bar A, Adamski MG, Mohaissen T, Marczyk B, Kieronska A, Stojak M, Kus K, Tarjus A, Jaisser F, Chlopicki S. The Deletion of Endothelial Sodium Channel α (αENaC) Impairs Endothelium-Dependent Vasodilation and Endothelial Barrier Integrity in Endotoxemia in Vivo. Front Pharmacol 2018; 9:178. [PMID: 29692722 PMCID: PMC5902527 DOI: 10.3389/fphar.2018.00178] [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: 12/07/2017] [Accepted: 02/16/2018] [Indexed: 01/09/2023] Open
Abstract
The role of epithelial sodium channel (ENaC) activity in the regulation of endothelial function is not clear. Here, we analyze the role of ENaC in the regulation of endothelium-dependent vasodilation and endothelial permeability in vivo in mice with conditional αENaC subunit gene inactivation in the endothelium (endo-αENaCKO mice) using unique MRI-based analysis of acetylcholine-, flow-mediated dilation and vascular permeability. Mice were challenged or not with lipopolysaccharide (LPS, from Salmonella typhosa, 10 mg/kg, i.p.). In addition, changes in vascular permeability in ex vivo organs were analyzed by Evans Blue assay, while changes in vascular permeability in perfused mesenteric artery were determined by a FITC-dextran-based assay. In basal conditions, Ach-induced response was completely lost, flow-induced vasodilation was inhibited approximately by half but endothelial permeability was not changed in endo-αENaCKO vs. control mice. In LPS-treated mice, both Ach- and flow-induced vasodilation was more severely impaired in endo-αENaCKO vs. control mice. There was also a dramatic increase in permeability in lungs, brain and isolated vessels as evidenced by in vivo and ex vivo analysis in endotoxemic endo-αENaCKO vs. control mice. The impaired endothelial function in endotoxemia in endo-αENaCKO was associated with a decrease of lectin and CD31 endothelial staining in the lung as compared with control mice. In conclusion, the activity of endothelial ENaC in vivo contributes to endothelial-dependent vasodilation in the physiological conditions and the preservation of endothelial barrier integrity in endotoxemia.
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Affiliation(s)
- Magdalena Sternak
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland
| | - Anna Bar
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland.,Chair of Pharmacology, Jagiellonian University Medical College, Kraków, Poland
| | - Mateusz G Adamski
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland
| | - Tasnim Mohaissen
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland.,Chair and Department of Pharmacy, Jagiellonian University Medical College, Kraków, Poland
| | - Brygida Marczyk
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland
| | - Anna Kieronska
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland.,Chair of Pharmacology, Jagiellonian University Medical College, Kraków, Poland
| | - Marta Stojak
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland
| | - Kamil Kus
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland
| | - Antoine Tarjus
- INSERM UMRS1138, Centre de Recherche des Cordeliers, Université Pierre et Marie Curie, Paris, France
| | - Frederic Jaisser
- INSERM UMRS1138, Centre de Recherche des Cordeliers, Université Pierre et Marie Curie, Paris, France.,INSERM, Clinical Investigation Centre 1433, Vandœuvre-lès-Nancy, France
| | - Stefan Chlopicki
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Kraków, Poland.,Chair of Pharmacology, Jagiellonian University Medical College, Kraków, Poland
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195
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Wichmann L, Vowinkel KS, Perniss A, Manzini I, Althaus M. Incorporation of the δ-subunit into the epithelial sodium channel (ENaC) generates protease-resistant ENaCs in Xenopus laevis. J Biol Chem 2018; 293:6647-6658. [PMID: 29576549 DOI: 10.1074/jbc.ra118.002543] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 03/14/2018] [Indexed: 11/06/2022] Open
Abstract
The epithelial sodium channel (ENaC) is a critical regulator of vertebrate electrolyte homeostasis. ENaC is the only constitutively open ion channel in the degenerin/ENaC protein family, and its expression, membrane abundance, and open probability therefore are tightly controlled. The canonical ENaC is composed of three subunits (α, β, and γ), but a fourth δ-subunit may replace α and form atypical δβγ-ENaCs. Using Xenopus laevis as a model, here we found that mRNAs of the α- and δ-subunits are differentially expressed in different tissues and that δ-ENaC predominantly is present in the urogenital tract. Using whole-cell and single-channel electrophysiology of oocytes expressing Xenopus αβγ- or δβγ-ENaC, we demonstrate that the presence of the δ-subunit enhances the amount of current generated by ENaC due to an increased open probability, but also changes current into a transient form. Activity of canonical ENaCs is critically dependent on proteolytic processing of the α- and γ-subunits, and immunoblotting with epitope-tagged ENaC subunits indicated that, unlike α-ENaC, the δ-subunit does not undergo proteolytic maturation by the endogenous protease furin. Furthermore, currents generated by δβγ-ENaC were insensitive to activation by extracellular chymotrypsin, and presence of the δ-subunit prevented cleavage of γ-ENaC at the cell surface. Our findings suggest that subunit composition constitutes an additional level of ENaC regulation, and we propose that the Xenopus δ-ENaC subunit represents a functional example that demonstrates the importance of proteolytic maturation during ENaC evolution.
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Affiliation(s)
- Lukas Wichmann
- From the School of Natural and Environmental Sciences, Newcastle University, Ridley Building 2, Newcastle upon Tyne NE1 7RU, United Kingdom and.,the Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University, 35392 Giessen, Germany
| | - Kirsty Sophia Vowinkel
- the Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University, 35392 Giessen, Germany
| | - Alexander Perniss
- the Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University, 35392 Giessen, Germany
| | - Ivan Manzini
- the Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University, 35392 Giessen, Germany
| | - Mike Althaus
- From the School of Natural and Environmental Sciences, Newcastle University, Ridley Building 2, Newcastle upon Tyne NE1 7RU, United Kingdom and
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196
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Abstract
Liddle syndrome is an inherited form of low-renin hypertension, transmitted with an autosomal dominant pattern. The molecular basis of Liddle syndrome resides in germline mutations of the SCNN1A, SCNN1B and SCNN1G genes, encoding the α, β, and γ-subunits of the epithelial Na+ channel (ENaC), respectively. To date, 31 different causative mutations have been reported in 72 families from four continents. The majority of the substitutions cause an increased expression of the channel at the distal nephron apical membrane, with subsequent enhanced renal sodium reabsorption. The most common clinical presentation of the disease is early onset hypertension, hypokalemia, metabolic alkalosis, suppressed plasma renin activity and low plasma aldosterone. Consequently, treatment of Liddle syndrome is based on the administration of ENaC blockers, amiloride and triamterene. Herein, we discuss the genetic basis, clinical presentation, diagnosis and treatment of Liddle syndrome. Finally, we report a new case in an Italian family, caused by a SCNN1B p.Pro618Leu substitution.
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197
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Blobner BM, Wang XP, Kashlan OB. Conserved cysteines in the finger domain of the epithelial Na + channel α and γ subunits are proximal to the dynamic finger-thumb domain interface. J Biol Chem 2018; 293:4928-4939. [PMID: 29425099 DOI: 10.1074/jbc.m117.819367] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 01/26/2018] [Indexed: 11/06/2022] Open
Abstract
The epithelial Na+ channel (ENaC) is a member of the ENaC/degenerin family of ion channels. In the structure of a related family member, the "thumb" domain's base interacts with the pore, and its tip interacts with the divergent "finger" domain. Between the base and tip, the thumb domain is characterized by a conserved five-rung disulfide ladder holding together two anti-parallel α helices. The ENaC α and γ subunits' finger domains harbor autoinhibitory tracts that can be proteolytically liberated to activate the channel and also host an ENaC-specific pair of cysteines. Using a crosslinking approach, we show that one of the finger domain cysteines in the α subunit (αCys-263) and both of the finger domain cysteines in the γ subunit (γCys-213 and γCys-220) lie near the dynamic finger-thumb domain interface. Our data suggest that the αCys-256/αCys-263 pair is not disulfide-bonded. In contrast, we found that the γCys-213/γCys-220 pair is disulfide-bonded. Our data also suggest that the γ subunit lacks the terminal rung in the thumb domain disulfide ladder, suggesting asymmetry between the subunits. We also observed functional asymmetry between the α and γ subunit finger-thumb domain interfaces; crosslinks bridging the α subunit finger-thumb interface only inhibited ENaC currents, whereas crosslinks bridging the γ subunit finger-thumb interface activated or inhibited currents dependent on the length of the crosslinker. Our data suggest that reactive cysteines lie at the dynamic finger-thumb interfaces of the α and γ subunits and may play a yet undefined role in channel regulation.
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Affiliation(s)
- Brandon M Blobner
- Departments of Medicine, Renal-Electrolyte Division, Pittsburgh, Pennsylvania 15261
| | - Xue-Ping Wang
- Departments of Medicine, Renal-Electrolyte Division, Pittsburgh, Pennsylvania 15261
| | - Ossama B Kashlan
- Departments of Medicine, Renal-Electrolyte Division, Pittsburgh, Pennsylvania 15261; Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.
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198
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He M, Liu S, Gallolu Kankanamalage S, Borromeo MD, Girard L, Gazdar AF, Minna JD, Johnson JE, Cobb MH. The Epithelial Sodium Channel (αENaC) Is a Downstream Therapeutic Target of ASCL1 in Pulmonary Neuroendocrine Tumors. Transl Oncol 2018; 11:292-299. [PMID: 29413762 PMCID: PMC5884185 DOI: 10.1016/j.tranon.2018.01.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 01/03/2018] [Accepted: 01/05/2018] [Indexed: 12/16/2022] Open
Abstract
Small cell lung cancer (SCLC) is an aggressive neuroendocrine carcinoma, designated as a recalcitrant cancer by the National Cancer Institute, in urgent need of new rational therapeutic targets. Previous studies have determined that the basic helix-loop-helix transcription factor achaete-scute homolog 1 (ASCL1) is essential for the survival and progression of a fraction of pulmonary neuroendocrine cancer cells, which include both SCLC and a subset of non-SCLC. Previously, to understand how ASCL1 initiates tumorigenesis in pulmonary neuroendocrine cancer and identify the transcriptional targets of ASCL1, whole-genome RNA-sequencing analysis combined with chromatin immunoprecipitation-sequencing was performed with a series of lung cancer cell lines. From this analysis, we discovered that the gene SCNN1A, which encodes the alpha subunit of the epithelial sodium channel (αENaC), is highly correlated with ASCL1 expression in SCLC. The product of the SCNN1A gene ENaC can be pharmacologically inhibited with amiloride, a drug that has been used clinically for close to 50 years. Amiloride inhibited growth of ASCL1-dependent SCLC more strongly than ASCL1-independent SCLC in vitro and slowed growth of ASCL1-driven SCLC in xenografts. We conclude that SCNN1A/αENaC is a direct transcriptional target of the neuroendocrine lung cancer lineage oncogene ASCL1 that can be pharmacologically targeted with antitumor effects.
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Affiliation(s)
- Min He
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Shanshan Liu
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | | | - Mark D Borromeo
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Luc Girard
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas; Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Adi F Gazdar
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - John D Minna
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas; Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Jane E Johnson
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas.
| | - Melanie H Cobb
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas.
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199
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Tamura S, Okada M, Kato S, Shinoda Y, Shioda N, Fukunaga K, Ui-Tei K, Ueda M. Ouabagenin is a naturally occurring LXR ligand without causing hepatic steatosis as a side effect. Sci Rep 2018; 8:2305. [PMID: 29396543 PMCID: PMC5797171 DOI: 10.1038/s41598-018-20663-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 01/23/2018] [Indexed: 12/23/2022] Open
Abstract
Ouabagenin (OBG) is an aglycone of the cardiotonic steroid ouabain and until now was considered a biologically inactive biosynthetic precursor. Herein, we revealed that OBG functions as a novel class of ligand for the liver X receptor (LXR). Luciferase reporter assays and in silico docking studies suggested that OBG has LXR-selective agonistic activity. In addition, OBG repressed the expression of epithelial sodium channel (ENaC), a LXR target gene, without causing hepatic steatosis, a typical side effect of conventional LXR ligands. This remarkable biological activity can be attributed to a unique mode of action; the LXR agonist activity mainly proceeds through the LXRβ subtype without affecting LXRα, unlike conventional LXR ligands. Thus, OBG is a novel class of LXR ligand that does not cause severe side effects, with potential for use as an antihypertensive diuretic or a tool compound for exploring LXR subtype-specific biological functions.
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Affiliation(s)
- Satoru Tamura
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan.,School of Pharmacy, Iwate Medical University, Shiwa-gun, Iwate, 028-3694, Japan
| | - Maiko Okada
- Institute of Medical Science, St. Marianna University Graduate School of Medicine, Kawasaki, Kanagawa, 970-8551, Japan.,Genome regulation and Molecular Pharmacogenomics, School of Bioscience and Biotechnology, Tokyo University of Technology, Hachioji, Tokyo, 192-0982, Japan
| | - Shigeaki Kato
- Iwaki Meisei University, Iwaki, Fukushima, 970-8551, Japan.,Research Institute of Innovative Medicine, Tokiwa Foundation, Iwaki, Fukushima, 972-8322, Japan
| | - Yasuharu Shinoda
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Norifumi Shioda
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Kohji Fukunaga
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Kumiko Ui-Tei
- Graduate School of Science, The University of Tokyo, Tokyo, 113-0032, Japan
| | - Minoru Ueda
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan.
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200
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Boscardin E, Perrier R, Sergi C, Maillard MP, Loffing J, Loffing-Cueni D, Koesters R, Rossier BC, Hummler E. Plasma Potassium Determines NCC Abundance in Adult Kidney-Specific γENaC Knockout. J Am Soc Nephrol 2018; 29:977-990. [PMID: 29371419 DOI: 10.1681/asn.2017030345] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 11/30/2017] [Indexed: 12/18/2022] Open
Abstract
The amiloride-sensitive epithelial sodium channel (ENaC) and the thiazide-sensitive sodium chloride cotransporter (NCC) are key regulators of sodium and potassium and colocalize in the late distal convoluted tubule of the kidney. Loss of the αENaC subunit leads to a perinatal lethal phenotype characterized by sodium loss and hyperkalemia resembling the human syndrome pseudohypoaldosteronism type 1 (PHA-I). In adulthood, inducible nephron-specific deletion of αENaC in mice mimics the lethal phenotype observed in neonates, and as in humans, this phenotype is prevented by a high sodium (HNa+)/low potassium (LK+) rescue diet. Rescue reflects activation of NCC, which is suppressed at baseline by elevated plasma potassium concentration. In this study, we investigated the role of the γENaC subunit in the PHA-I phenotype. Nephron-specific γENaC knockout mice also presented with salt-wasting syndrome and severe hyperkalemia. Unlike mice lacking αENaC or βΕΝaC, an HNa+/LK+ diet did not normalize plasma potassium (K+) concentration or increase NCC activation. However, when K+ was eliminated from the diet at the time that γENaC was deleted, plasma K+ concentration and NCC activity remained normal, and progressive weight loss was prevented. Loss of the late distal convoluted tubule, as well as overall reduced βENaC subunit expression, may be responsible for the more severe hyperkalemia. We conclude that plasma K+ concentration becomes the determining and limiting factor in regulating NCC activity, regardless of Na+ balance in γENaC-deficient mice.
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Affiliation(s)
- Emilie Boscardin
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,National Center of Competence in Research "Kidney.Control of Homeostasis," Lausanne and Zurich, Switzerland
| | - Romain Perrier
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Chloé Sergi
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Marc P Maillard
- Service of Nephrology, University Hospital of Lausanne, Lausanne, Switzerland
| | - Johannes Loffing
- National Center of Competence in Research "Kidney.Control of Homeostasis," Lausanne and Zurich, Switzerland.,Institute of Anatomy, University of Zurich, Zurich, Switzerland; and
| | | | - Robert Koesters
- Department of Nephrology, Hôpital Tenon, Université Pierre et Marie Curie, Paris, France
| | - Bernard C Rossier
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Edith Hummler
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland; .,National Center of Competence in Research "Kidney.Control of Homeostasis," Lausanne and Zurich, Switzerland
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