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Aufy M, Hussein AM, Stojanovic T, Studenik CR, Kotob MH. Proteolytic Activation of the Epithelial Sodium Channel (ENaC): Its Mechanisms and Implications. Int J Mol Sci 2023; 24:17563. [PMID: 38139392 PMCID: PMC10743461 DOI: 10.3390/ijms242417563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 12/10/2023] [Accepted: 12/14/2023] [Indexed: 12/24/2023] Open
Abstract
Epithelial sodium channel (ENaC) are integral to maintaining salt and water homeostasis in various biological tissues, including the kidney, lung, and colon. They enable the selective reabsorption of sodium ions, which is a process critical for controlling blood pressure, electrolyte balance, and overall fluid volume. ENaC activity is finely controlled through proteolytic activation, a process wherein specific enzymes, or proteases, cleave ENaC subunits, resulting in channel activation and increased sodium reabsorption. This regulatory mechanism plays a pivotal role in adapting sodium transport to different physiological conditions. In this review article, we provide an in-depth exploration of the role of proteolytic activation in regulating ENaC activity. We elucidate the involvement of various proteases, including furin-like convertases, cysteine, and serine proteases, and detail the precise cleavage sites and regulatory mechanisms underlying ENaC activation by these proteases. We also discuss the physiological implications of proteolytic ENaC activation, focusing on its involvement in blood pressure regulation, pulmonary function, and intestinal sodium absorption. Understanding the mechanisms and consequences of ENaC proteolytic activation provides valuable insights into the pathophysiology of various diseases, including hypertension, pulmonary disorders, and various gastrointestinal conditions. Moreover, we discuss the potential therapeutic avenues that emerge from understanding these mechanisms, offering new possibilities for managing diseases associated with ENaC dysfunction. In summary, this review provides a comprehensive discussion of the intricate interplay between proteases and ENaC, emphasizing the significance of proteolytic activation in maintaining sodium and fluid balance in both health and disease.
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Affiliation(s)
- Mohammed Aufy
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria; (A.M.H.); (M.H.K.)
| | - Ahmed M. Hussein
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria; (A.M.H.); (M.H.K.)
- Department of Zoology, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt
| | - Tamara Stojanovic
- Programme for Proteomics, Paracelsus Medical University, 5020 Salzburg, Austria;
| | - Christian R. Studenik
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria; (A.M.H.); (M.H.K.)
| | - Mohamed H. Kotob
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria; (A.M.H.); (M.H.K.)
- Department of Pathology, Faculty of Veterinary Medicine, Assiut University, Assiut 71515, Egypt
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Romero MJ, Yue Q, Singla B, Hamacher J, Sridhar S, Moseley AS, Song C, Mraheil MA, Fischer B, Zeitlinger M, Chakraborty T, Fulton D, Gan L, Annex BH, Csanyi G, Eaton DC, Lucas R. Direct endothelial ENaC activation mitigates vasculopathy induced by SARS-CoV2 spike protein. Front Immunol 2023; 14:1241448. [PMID: 37638055 PMCID: PMC10449264 DOI: 10.3389/fimmu.2023.1241448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 07/25/2023] [Indexed: 08/29/2023] Open
Abstract
Introduction Although both COVID-19 and non-COVID-19 ARDS can be accompanied by significantly increased levels of circulating cytokines, the former significantly differs from the latter by its higher vasculopathy, characterized by increased oxidative stress and coagulopathy in lung capillaries. This points towards the existence of SARS-CoV2-specific factors and mechanisms that can sensitize the endothelium towards becoming dysfunctional. Although the virus is rarely detected within endothelial cells or in the circulation, the S1 subunit of its spike protein, which contains the receptor binding domain (RBD) for human ACE2 (hACE2), can be detected in plasma from COVID-19 patients and its levels correlate with disease severity. It remains obscure how the SARS-CoV2 RBD exerts its deleterious actions in lung endothelium and whether there are mechanisms to mitigate this. Methods In this study, we use a combination of in vitro studies in RBD-treated human lung microvascular endothelial cells (HL-MVEC), including electrophysiology, barrier function, oxidative stress and human ACE2 (hACE2) surface protein expression measurements with in vivo studies in transgenic mice globally expressing human ACE2 and injected with RBD. Results We show that SARS-CoV2 RBD impairs endothelial ENaC activity, reduces surface hACE2 expression and increases reactive oxygen species (ROS) and tissue factor (TF) generation in monolayers of HL-MVEC, as such promoting barrier dysfunction and coagulopathy. The TNF-derived TIP peptide (a.k.a. solnatide, AP301) -which directly activates ENaC upon binding to its a subunit- can override RBD-induced impairment of ENaC function and hACE2 expression, mitigates ROS and TF generation and restores barrier function in HL-MVEC monolayers. In correlation with the increased mortality observed in COVID-19 patients co-infected with S. pneumoniae, compared to subjects solely infected with SARS-CoV2, we observe that prior intraperitoneal RBD treatment in transgenic mice globally expressing hACE2 significantly increases fibrin deposition and capillary leak upon intratracheal instillation of S. pneumoniae and that this is mitigated by TIP peptide treatment.
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Affiliation(s)
- Maritza J. Romero
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, United States
- Department of Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, GA, United States
| | - Qian Yue
- Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Bhupesh Singla
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, United States
| | - Jürg Hamacher
- Pneumology, Clinic for General Internal Medicine, Lindenhofspital, Bern, Switzerland
- Lungen-und Atmungsstiftung, Bern, Switzerland
- Medical Clinic V—Pneumology, Allergology, Intensive Care Medicine, and Environmental Medicine, Faculty of Medicine, Saarland University, University Medical Centre of the Saarland, Homburg, Germany
| | - Supriya Sridhar
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, United States
| | - Auriel S. Moseley
- Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Chang Song
- Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Mobarak A. Mraheil
- Institute for Medical Microbiology, German Centre for Infection Giessen-Marburg-Langen Site, Faculty of Medicine, Justus-Liebig University, Giessen, Germany
| | | | - Markus Zeitlinger
- Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Trinad Chakraborty
- Institute for Medical Microbiology, German Centre for Infection Giessen-Marburg-Langen Site, Faculty of Medicine, Justus-Liebig University, Giessen, Germany
| | - David Fulton
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, United States
- Department of Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, GA, United States
| | - Lin Gan
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, United States
| | - Brian H. Annex
- Department of Medicine, Medical College of Georgia at Augusta University, Augusta, GA, United States
| | - Gabor Csanyi
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, United States
- Department of Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, GA, United States
| | - Douglas C. Eaton
- Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Rudolf Lucas
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, United States
- Department of Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, GA, United States
- Department of Medicine, Medical College of Georgia at Augusta University, Augusta, GA, United States
- Division of Pulmonary and Critical Care Medicine, Medical College of Georgia at Augusta University, Augusta, GA, United States
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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: 7] [Impact Index Per Article: 7.0] [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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Liu X, Shi J, Wang D, Su Y, Xing Z, Sun F, Chen F. Therapeutic Polypeptides and Peptidomimetics: Powerful Tools for COVID-19 Treatment. Clin Drug Investig 2023; 43:13-22. [PMID: 36462104 PMCID: PMC9734822 DOI: 10.1007/s40261-022-01231-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/17/2022] [Indexed: 12/04/2022]
Abstract
The coronavirus disease 2019 (COVID-19) pandemic has swept the whole world and brought about a public health crisis of unprecedented proportions. To combat the rapid transmission and possible deaths due to the disease, researchers and companies around the world are developing all possible strategies. Due to the advantages of safety, specificity, and fewer adverse effects, polypeptide and peptidomimetic drugs are considered promising strategies. This review comprehensively summarizes and discusses the progress in development of peptide drugs for use in the treatment of COVID-19. Based on the latest results in this field, we divided them into clinically approved drugs, clinical trial drugs, and clinically ineffective drugs, and outlined the molecular targets and mechanisms of action one by one to reveal their feasibility as promising therapeutic agents for COVID-19. Notably, monoclonal antibodies have shown beneficial effects in the early stages of infection, while Paxlovid can significantly reduce hospitalization and mortality among non-vaccinated patients. Among clinical experimental drugs, both the interleukin-1 receptor antagonist anakinra and the bradykinin B2 receptor antagonist icatibant are well tolerated and effective in patients with COVID-19, but long-term trials are needed to confirm the durability of efficacy.
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Affiliation(s)
- Xinyu Liu
- grid.449428.70000 0004 1797 7280Department of Physiology, Jining Medical University, 133 Hehua Rd, Jining, 272067 China
| | - Jian Shi
- grid.449428.70000 0004 1797 7280Department of Physiology, Jining Medical University, 133 Hehua Rd, Jining, 272067 China
| | - Deyang Wang
- grid.449428.70000 0004 1797 7280Department of Physiology, Jining Medical University, 133 Hehua Rd, Jining, 272067 China
| | - Ying Su
- grid.411634.50000 0004 0632 4559Dongping County People’s Hospital, Tai-an, China
| | - Zhen Xing
- grid.411634.50000 0004 0632 4559Dongping County People’s Hospital, Tai-an, China
| | - Fei Sun
- Qilu Medical University, Zibo, China
| | - Fei Chen
- grid.449428.70000 0004 1797 7280Department of Physiology, Jining Medical University, 133 Hehua Rd, Jining, 272067 China
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Pinto ACMD, Nunes RDM, Nogueira IA, Fischer B, Lucas R, Girão-Carmona VCC, de Oliveira VLS, Amaral FA, Schett G, Rocha FAC. Potent anti-inflammatory activity of the lectin-like domain of TNF in joints. Front Immunol 2022; 13:1049368. [PMID: 36389831 PMCID: PMC9659759 DOI: 10.3389/fimmu.2022.1049368] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 10/17/2022] [Indexed: 10/22/2023] Open
Abstract
In view of the crucial role of tumor necrosis factor (TNF) in joint destruction, TNF inhibitors, including neutralizing anti-TNF antibodies and soluble TNF receptor constructs, are commonly used therapeutics for the treatment of arthropathies like rheumatoid arthritis (RA). However, not all patients achieve remission; moreover, there is a risk of increased susceptibility to infection with these agents. Spatially distinct from its receptor binding sites, TNF harbors a lectin-like domain, which exerts unique functions that can be mimicked by the 17 residue solnatide peptide. This domain binds to specific oligosaccharides such as N'N'-diacetylchitobiose and directly target the α subunit of the epithelial sodium channel. Solnatide was shown to have anti-inflammatory actions in acute lung injury and glomerulonephritis models. In this study, we evaluated whether the lectin-like domain of TNF can mitigate the development of immune-mediated arthritis in mice. In an antigen-induced arthritis model, solnatide reduced cell influx and release of pro-inflammatory mediators into the joints, associated with reduction in edema and tissue damage, as compared to controls indicating that TNF has anti-inflammatory effects in an acute model of joint inflammation via its lectin-like domain.
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Affiliation(s)
| | - Rodolfo de Melo Nunes
- Departamento de Medicina Interna, Faculdade de Medicina, Universidade Federal do Ceará, Fortaleza, Brazil
| | - Igor Albuquerque Nogueira
- Departamento de Medicina Interna, Faculdade de Medicina, Universidade Federal do Ceará, Fortaleza, Brazil
| | | | - Rudolf Lucas
- Vascular Biology Center, Department of Pharmacology and Toxicology, Division of Pulmonary and Critical Care Medicine, Medical College of Georgia at Augusta University, Augusta, GA, United States
| | | | | | - Flavio Almeida Amaral
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Georg Schett
- Department of Internal Medicine 3, Rheumatology and Immunolgy, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
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