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Lemmens-Gruber R, Tzotzos S. The Epithelial Sodium Channel-An Underestimated Drug Target. Int J Mol Sci 2023; 24:ijms24097775. [PMID: 37175488 PMCID: PMC10178586 DOI: 10.3390/ijms24097775] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 04/14/2023] [Accepted: 04/15/2023] [Indexed: 05/15/2023] Open
Abstract
Epithelial sodium channels (ENaC) are part of a complex network of interacting biochemical pathways and as such are involved in several disease states. Dependent on site and type of mutation, gain- or loss-of-function generated symptoms occur which span from asymptomatic to life-threatening disorders such as Liddle syndrome, cystic fibrosis or generalized pseudohypoaldosteronism type 1. Variants of ENaC which are implicated in disease assist further understanding of their molecular mechanisms in order to create models for specific pharmacological targeting. Identification and characterization of ENaC modifiers not only furthers our basic understanding of how these regulatory processes interact, but also enables discovery of new therapeutic targets for the disease conditions caused by ENaC dysfunction. Numerous test compounds have revealed encouraging results in vitro and in animal models but less in clinical settings. The EMA- and FDA-designated orphan drug solnatide is currently being tested in phase 2 clinical trials in the setting of acute respiratory distress syndrome, and the NOX1/ NOX4 inhibitor setanaxib is undergoing clinical phase 2 and 3 trials for therapy of primary biliary cholangitis, liver stiffness, and carcinoma. The established ENaC blocker amiloride is mainly used as an add-on drug in the therapy of resistant hypertension and is being studied in ongoing clinical phase 3 and 4 trials for special applications. This review focuses on discussing some recent developments in the search for novel therapeutic agents.
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Affiliation(s)
- Rosa Lemmens-Gruber
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, A-1090 Vienna, Austria
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Wrennall JA, Ahmad S, Worthington EN, Wu T, Goriounova AS, Voeller AS, Stewart IE, Ghosh A, Krajewski K, Tilley SL, Hickey AJ, Sassano MF, Tarran R. A SPLUNC1 Peptidomimetic Inhibits Orai1 and Reduces Inflammation in a Murine Allergic Asthma Model. Am J Respir Cell Mol Biol 2021; 66:271-282. [PMID: 34807800 DOI: 10.1165/rcmb.2020-0452oc] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Orai1 is a plasma membrane Ca2+ channel that mediates store operated Ca2+ entry (SOCE) and regulates inflammation. Short palate lung and nasal epithelial clone 1 (SPLUNC1) is an asthma gene modifier which inhibits Orai1/SOCE via its C-terminal α6 region. SPLUNC1 levels are diminished in asthma patient airways. Thus, we hypothesized that inhaled α6 peptidomimetics could inhibit Orai1 and reduce airway inflammation in a murine asthma model. To evaluate α6-Orai1 interactions, we used fluorescent assays to measure Ca2+ signalling, Förster resonance energy transfer (FRET), fluorescent recovery after photobleaching, immunostaining, total internal reflection (TIRF) microscopy and Western blotting. To test whether α6 peptidomimetics inhibited SOCE and decreased inflammation in vivo, wild-type and SPLUNC1-/- mice were exposed to house dust mite (HDM) extract ± α6 peptide. We also performed nebulization, jet milling and scanning electron microscopy to evaluate α6 for inhalation. SPLUNC1-/- mice had an exaggerated response to HDM. In bronchoalveolar lavage (BAL)-derived immune cells, Orai1 levels increased after HDM exposure in SPLUNC1-/- but not wild-type mice. Inhaled α6 reduced Orai1 levels in mice regardless of genotype. In HDM-exposed mice, α6 dose-dependently reduced eosinophilia and neutrophilia. In vitro, α6 inhibited SOCE in multiple immune cell types and α6 could be nebulized or jet milled without loss of function. These data suggest that α6 peptidomimetics may be a novel, effective anti-inflammatory therapy for asthma patients.
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Affiliation(s)
- Joe A Wrennall
- University of North Carolina at Chapel Hill, Department of Cell Biology & Physiology, Chapel Hill, North Carolina, United States
| | - Saira Ahmad
- University of North Carolina at Chapel Hill, 2331, Chapel Hill, North Carolina, United States
| | - Erin N Worthington
- The University of North Carolina at Chapel Hill, Division of Pulmonology, Department of Pediatrics, Chapel Hill, North Carolina, United States
| | - Tongde Wu
- The University of North Carolina at Chapel Hill, Department of Cell Biology & Physiology, Chapel Hill, North Carolina, United States
| | - Alexandra S Goriounova
- University of North Carolina at Chapel Hill, 2331, Department of Pharmacology, Chapel Hill, North Carolina, United States
| | - Alexis S Voeller
- University of North Carolina at Chapel Hill, Department of Cell Biology & Physiology, Chapel Hill, North Carolina, United States
| | - Ian E Stewart
- RTI International, 6856, Center for Engineered Systems, Research Triangle Park, North Carolina, United States
| | - Arunava Ghosh
- University of North Carolina, Department of Cell Biology & Physiology, Chapel Hill, North Carolina, United States
| | - Krzysztof Krajewski
- University of North Carolina at Chapel Hill, 2331, Department of Biochemistry and Biophysics, Chapel Hill, North Carolina, United States
| | - Stephen L Tilley
- University of North Carolina, Medicine, Chapel Hill, North Carolina, United States
| | - Anthony J Hickey
- RTI International, 6856, Center for Engineered Systems, Research Triangle Park, North Carolina, United States
| | - M Flori Sassano
- University of North Carolina, Department of Cell Biology & Physiology, Chapel Hill, North Carolina, United States
| | - Robert Tarran
- University of North Carolina, Department of Cell Biology & Physiology, Chapel Hill, North Carolina, United States;
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Abstract
The Epithelial Na+ Channel, ENaC, comprised of 3 subunits (αβγ, or sometimes δβγENaC), plays a critical role in regulating salt and fluid homeostasis in the body. It regulates fluid reabsorption into the blood stream from the kidney to control blood volume and pressure, fluid absorption in the lung to control alveolar fluid clearance at birth and maintenance of normal airway surface liquid throughout life, and fluid absorption in the distal colon and other epithelial tissues. Moreover, recent studies have also revealed a role for sodium movement via ENaC in nonepithelial cells/tissues, such as endothelial cells in blood vessels and neurons. Over the past 25 years, major advances have been made in our understanding of ENaC structure, function, regulation, and role in human disease. These include the recently solved three-dimensional structure of ENaC, ENaC function in various tissues, and mutations in ENaC that cause a hereditary form of hypertension (Liddle syndrome), salt-wasting hypotension (PHA1), or polymorphism in ENaC that contributes to other diseases (such as cystic fibrosis). Moreover, great strides have been made in deciphering the regulation of ENaC by hormones (e.g., the mineralocorticoid aldosterone, glucocorticoids, vasopressin), ions (e.g., Na+ ), proteins (e.g., the ubiquitin-protein ligase NEDD4-2, the kinases SGK1, AKT, AMPK, WNKs & mTORC2, and proteases), and posttranslational modifications [e.g., (de)ubiquitylation, glycosylation, phosphorylation, acetylation, palmitoylation]. Characterization of ENaC structure, function, regulation, and role in human disease, including using animal models, are described in this article, with a special emphasis on recent advances in the field. © 2021 American Physiological Society. Compr Physiol 11:1-29, 2021.
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Affiliation(s)
- Daniela Rotin
- The Hospital for Sick Children, and The University of Toronto, Toronto, Canada
| | - Olivier Staub
- Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
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Graham JC, Hillegass J, Schulze G. Considerations for setting occupational exposure limits for novel pharmaceutical modalities. Regul Toxicol Pharmacol 2020; 118:104813. [PMID: 33144077 PMCID: PMC7605856 DOI: 10.1016/j.yrtph.2020.104813] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 08/13/2020] [Accepted: 10/26/2020] [Indexed: 12/18/2022]
Abstract
In order to develop new and effective medicines, pharmaceutical companies must be modality agnostic. As science reveals an enhanced understanding of biological processes, new therapeutic modalities are becoming important in developing breakthrough therapies to treat both rare and common diseases. As these new modalities progress, concern and uncertainty arise regarding their safe handling by the researchers developing them, employees manufacturing them and nurses administering them. This manuscript reviews the available literature for emerging modalities (including oligonucleotides, monoclonal antibodies, fusion proteins and bispecific antibodies, antibody-drug conjugates, peptides, vaccines, genetically modified organisms, and several others) and provides considerations for occupational health and safety-oriented hazard identification and risk assessments to enable timely, consistent and well-informed hazard identification, hazard communication and risk-management decisions. This manuscript also points out instances where historical exposure control banding systems may not be applicable (e.g. oncolytic viruses, biologics) and where other occupational exposure limit systems are more applicable (e.g. Biosafety Levels, Biologic Control Categories). Review of toxicology and pharmacology information for novel therapeutic modalities. Identification of occupational hazards associated with novel therapeutic modalities. Occupational hazards and exposure risks differ across pharmaceutical modalities. Occupational exposure control banding systems are not one size fits all. Banding system variations offer benefits while enabling proper exposure controls.
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Affiliation(s)
- Jessica C Graham
- Bristol Myers Squibb, 1 Squibb Drive, New Brunswick, NJ, 08903, USA.
| | - Jedd Hillegass
- Bristol Myers Squibb, 1 Squibb Drive, New Brunswick, NJ, 08903, USA
| | - Gene Schulze
- Bristol Myers Squibb, 1 Squibb Drive, New Brunswick, NJ, 08903, USA
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Son YW, Choi HN, Che JH, Kang BC, Yun JW. Advances in selecting appropriate non-rodent species for regulatory toxicology research: Policy, ethical, and experimental considerations. Regul Toxicol Pharmacol 2020; 116:104757. [PMID: 32758521 DOI: 10.1016/j.yrtph.2020.104757] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 07/27/2020] [Accepted: 07/31/2020] [Indexed: 12/20/2022]
Abstract
In vivo animal studies are required by regulatory agencies to investigate drug safety before clinical trials. In this review, we summarize the process of selecting a relevant non-rodent species for preclinical studies. The dog is the primary, default non-rodent used in toxicology studies with multiple scientific advantages, including adequate background data and availability. Rabbit has many regulatory advantages as the first non-rodent for the evaluation of reproductive and developmental as well as local toxicity. Recently, minipigs have increasingly replaced dogs and rabbits in toxicology studies due to ethical and scientific advantages including similarity to humans and breeding habits. When these species are not relevant, nonhuman primates (NHPs) can be used as the available animal models, especially in toxicology studies investigating biotherapeutics. Particularly, based on the phylogenetic relationships, the use of New-World marmosets can be considered before Old-World monkeys, especially cynomolgus with robust historical data. Importantly, the use of NHPs should be justified in terms of scientific benefits considering target affinity, expression pattern, and pharmacological cross-reactivity. Strict standards are required for the use of animals. Therefore, this review is helpful for the selection of appropriate non-rodent in regulatory toxicology studies by providing sufficient regulatory, ethical, and scientific data for each species.
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Affiliation(s)
- Yong-Wook Son
- Department of Biotechnology, The Catholic University of Korea, Bucheon, 14662, South Korea
| | - Ha-Ni Choi
- Department of Biotechnology, The Catholic University of Korea, Bucheon, 14662, South Korea
| | - Jeong-Hwan Che
- Biomedical Center for Animal Resource and Development, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Byeong-Cheol Kang
- Graduate School of Translational Medicine, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Jun-Won Yun
- Department of Biotechnology, The Catholic University of Korea, Bucheon, 14662, South Korea.
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Siddiqui S, Khan F, Jamali KS, Musharraf SG. Madecassic Acid Reduces Fast Transient Potassium Channels and Promotes Neurite Elongation in Hippocampal CA1 Neurons. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2019; 19:12-26. [PMID: 31713492 DOI: 10.2174/1871527318666191111105508] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 10/21/2019] [Accepted: 10/22/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND AND OBJECTIVE Madecassic Acid (MA) is well known to induce neurite elongation. However, its correlation with the expression of fast transient potassium (AKv) channels during neuronal development has not been well studied. Therefore, the present study was designed to investigate the effects of MA on the modulation of AKv channels during neurite outgrowth. METHODS Neurite outgrowth was measured with morphometry software, and Kv4 currents were recorded by using the patch clamp technique. RESULTS The ability of MA to promote neurite outgrowth is dose-dependent and was blocked by using the mitogen/extracellular signal-regulated kinase (MEK) inhibitor U0126. MA reduced the peak current density and surface expression of the AKv channel Kv4.2 with or without the presence of NaN3. The surface expression of Kv4.2 channels was also reduced after MA treatment of growing neurons. Ethylene glycol tetraacetic acid (EGTA) and an N-methyl-D-aspartate (NMDA) receptor blocker, MK801 along with MA prevented the effect of MA on neurite length, indicating that calcium entry through NMDA receptors is necessary for MA-induced neurite outgrowth. CONCLUSION The data demonstrated that MA increased neurite outgrowth by internalizing AKv channels in neurons. Any alterations in the precise density of ion channels can lead to deleterious consequences on health because it changes the electrical and mechanical function of a neuron or a cell. Modulating ion channel's density is exciting research in order to develop novel drugs for the therapeutic treatment of various diseases of CNS.
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Affiliation(s)
- Sonia Siddiqui
- Department of Biochemistry, Dow University of Health Sciences (DUHS), Karachi, Pakistan.,Department of Neuroscience, Dr. Panjwani Center for Molecular Medicine and Drug Research (PCMD), International Center for Chemical and Biological Sciences (ICCBS), University of Karachi 75270, Pakistan
| | - Faisal Khan
- Department of Neuroscience, Dr. Panjwani Center for Molecular Medicine and Drug Research (PCMD), International Center for Chemical and Biological Sciences (ICCBS), University of Karachi 75270, Pakistan
| | - Khawar Saeed Jamali
- Department of Surgery, Dow University of Health Sciences (DUHS), Karachi, Pakistan
| | - Syed Ghulam Musharraf
- HEJ Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi 75270, Pakistan
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Olivença DV, Fonseca LL, Voit EO, Pinto FR. Thickness of the airway surface liquid layer in the lung is affected in cystic fibrosis by compromised synergistic regulation of the ENaC ion channel. J R Soc Interface 2019; 16:20190187. [PMID: 31455163 DOI: 10.1098/rsif.2019.0187] [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] [Indexed: 02/01/2023] Open
Abstract
The lung epithelium is lined with a layer of airway surface liquid (ASL) that is crucial for healthy lung function. ASL thickness is controlled by two ion channels: epithelium sodium channel (ENaC) and cystic fibrosis (CF) transmembrane conductance regulator (CFTR). Here, we present a minimal mathematical model of ENaC, CFTR and ASL regulation that sheds light on the control of ENaC by the short palate lung and nasal epithelial clone 1 (SPLUNC1) protein and by phosphatidylinositol 4,5-biphosphate (PI(4,5)P2). The model, despite its simplicity, yields a good fit to experimental observations and is an effective tool for exploring the interplay between ENaC, CFTR and ASL. Steady-state data and dynamic information constrain the model's parameters without ambiguities. Testing the hypothesis that PI(4,5)P2 protects ENaC from ubiquitination suggests that this protection does not improve the model results and that the control of the ENaC opening probability by PI(4,5)P2 is sufficient to explain all available data. The model analysis further demonstrates that ASL at the steady state is sensitive to small changes in PI(4,5)P2 abundance, particularly in CF conditions, which suggests that manipulation of phosphoinositide metabolism may promote therapeutic benefits for CF patients.
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Affiliation(s)
- Daniel V Olivença
- Faculty of Sciences, BioISI-Biosystems and Integrative Sciences Institute, University of Lisboa, Lisboa, Portugal
| | - Luis L Fonseca
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Eberhard O Voit
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Francisco R Pinto
- Faculty of Sciences, BioISI-Biosystems and Integrative Sciences Institute, University of Lisboa, Lisboa, Portugal
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Couroux P, Farias P, Rizvi L, Griffin K, Hudson C, Crowder T, Tarran R, Tullis E. First clinical trials of novel ENaC targeting therapy, SPX-101, in healthy volunteers and adults with cystic fibrosis. Pulm Pharmacol Ther 2019; 58:101819. [PMID: 31302339 DOI: 10.1016/j.pupt.2019.101819] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 05/13/2019] [Accepted: 07/11/2019] [Indexed: 10/26/2022]
Abstract
BACKGROUND ENaC inhibition has been investigated as a CF treatment; however, small molecule inhibitors of ENaC lack efficacy and/or have shown dose-limiting hyperkalemia. SPX-101 is a novel, investigational small peptide (SPLUNC1 mimetic) that regulates ENaC density with the potential for efficacy without systemic effects. METHODS Two trials are presented: The first was a Phase 1, 2-part, randomized, double-blind, placebo-controlled, ascending-dose study of nebulized SPX-101 in healthy adults. Part 1 evaluated 4 single doses of SPX-101 ranging from 20 to 240 mg. Part 2 evaluated a 14-day regimen of SPX-101 at 4 doses of SPX-101 ranging from 10 to 120 mg BID. Pharmacokinetics, adverse events, spirometry, vital signs, electrocardiograms, pulse oximetry, and clinical laboratory values were assessed. The second trial was a tolerability-confirming, Phase 1b, open-label study conducted in 5 adult subjects with CF. Ascending doses of SPX-101 inhalation solution (10 mg-120 mg BID) were administered for 7 days. Safety was assessed as described above. RESULTS All 64 healthy volunteers (32 in each Part) completed the single and multiple dose study. SPX-101 was well tolerated with little/no systemic exposure and with no hyperkalemia. Adverse events were generally mild with reported respiratory events associated with the purported pharmacological activity of SPX-101. Tolerability of SPX-101 was similarly observed in adults with CF; all 5 subjects treated with SPX-101 completed the study. CONCLUSIONS SPX-101 was well-tolerated across a range of doses and had little/no systemic exposure in healthy adults and adults with CF, thus supporting further study in patients with CF. CLINICALTRIAL. GOV REGISTRATION NCT03056989.
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Affiliation(s)
- Peter Couroux
- Inflamax Research Limited, Mississauga, Ontario, Canada
| | | | - Leena Rizvi
- Toronto Adult Cystic Fibrosis Centre, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Katherine Griffin
- Toronto Adult Cystic Fibrosis Centre, St. Michael's Hospital, Toronto, Ontario, Canada
| | | | | | - Robert Tarran
- Marsico Lung Institute, Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, USA
| | - Elizabeth Tullis
- Toronto Adult Cystic Fibrosis Centre, St. Michael's Hospital, Toronto, Ontario, Canada; Li Ka Shing Knowledge Institute, St Michael's Hospital, University of Toronto, Toronto, Canada
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Sesma JI, Wu B, Stuhlmiller TJ, Scott DW. SPX-101 is stable in and retains function after exposure to cystic fibrosis sputum. J Cyst Fibros 2019; 18:244-250. [DOI: 10.1016/j.jcf.2018.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/01/2018] [Accepted: 06/02/2018] [Indexed: 12/16/2022]
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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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Moore PJ, Tarran R. The epithelial sodium channel (ENaC) as a therapeutic target for cystic fibrosis lung disease. Expert Opin Ther Targets 2018; 22:687-701. [PMID: 30028216 DOI: 10.1080/14728222.2018.1501361] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
INTRODUCTION Cystic fibrosis is an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that codes for the CFTR anion channel. In the absence of functional CFTR, the epithelial Na+ channel is also dysregulated. Airway surface liquid (ASL) hydration is maintained by a balance between epithelial sodium channel (ENaC)-led Na+ absorption and CFTR-dependent anion secretion. This finely tuned homeostatic mechanism is required to maintain sufficient airway hydration to permit the efficient mucus clearance necessary for a sterile lung environment. In CF airways, the lack of CFTR and increased ENaC activity lead to ASL/mucus dehydration that causes mucus obstruction, neutrophilic infiltration, and chronic bacterial infection. Rehydration of ASL/mucus in CF airways can be achieved by inhibiting Na+ absorption with pharmacological inhibitors of ENaC. Areas covered: In this review, we discuss ENaC structure and function and its role in CF lung disease and focus on ENaC inhibition as a potential therapeutic target to rehydrate CF mucus. We also discuss the failure of the first generation of pharmacological inhibitors of ENaC and recent alternate strategies to attenuate ENaC activity in the CF lung. Expert opinion: ENaC is an attractive therapeutic target to rehydrate CF ASL that may serve as a monotherapy or function in parallel with other treatments. Given the increased number of strategies being employed to inhibit ENaC, this is an exciting and optimistic time to be in this field.
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Affiliation(s)
- Patrick J Moore
- a Marsico Lung Institute , University of North Carolina , Chapel Hill , NC , USA
| | - Robert Tarran
- a Marsico Lung Institute , University of North Carolina , Chapel Hill , NC , USA.,b Department of Cell Biology & Physiology , University of North Carolina , Chapel Hill , NC , USA
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