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Caohuy H, Eidelman O, Chen T, Mungunsukh O, Yang Q, Walton NI, Pollard BS, Khanal S, Hentschel S, Florez C, Herbert AS, Pollard HB. Inflammation in the COVID-19 airway is due to inhibition of CFTR signaling by the SARS-CoV-2 spike protein. Sci Rep 2024; 14:16895. [PMID: 39043712 PMCID: PMC11266487 DOI: 10.1038/s41598-024-66473-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 07/01/2024] [Indexed: 07/25/2024] Open
Abstract
SARS-CoV-2-contributes to sickness and death in COVID-19 patients partly by inducing a hyper-proinflammatory immune response in the host airway. This hyper-proinflammatory state involves activation of signaling by NFκB, and unexpectedly, ENaC, the epithelial sodium channel. Post-infection inflammation may also contribute to "Long COVID"/PASC. Enhanced signaling by NFκB and ENaC also marks the airway of patients suffering from cystic fibrosis, a life-limiting proinflammatory genetic disease due to inactivating mutations in the CFTR gene. We therefore hypothesized that inflammation in the COVID-19 airway might similarly be due to inhibition of CFTR signaling by SARS-CoV-2 spike protein, and therefore activation of both NFκB and ENaC signaling. We used western blot and electrophysiological techniques, and an organoid model of normal airway epithelia, differentiated on an air-liquid-interface (ALI). We found that CFTR protein expression and CFTR cAMP-activated chloride channel activity were lost when the model epithelium was exposed to SARS-CoV-2 spike proteins. As hypothesized, the absence of CFTR led to activation of both TNFα/NFκB signaling and α and γ ENaC. We had previously shown that the cardiac glycoside drugs digoxin, digitoxin and ouabain blocked interaction of spike protein and ACE2. Consistently, addition of 30 nM concentrations of the cardiac glycoside drugs, prevented loss of both CFTR protein and CFTR channel activity. ACE2 and CFTR were found to co-immunoprecipitate in both basal cells and differentiated epithelia. Thus spike-dependent CFTR loss might involve ACE2 as a bridge between Spike and CFTR. In addition, spike exposure to the epithelia resulted in failure of endosomal recycling to return CFTR to the plasma membrane. Thus, failure of CFTR recovery from endosomal recycling might be a mechanism for spike-dependent loss of CFTR. Finally, we found that authentic SARS-CoV-2 virus infection induced loss of CFTR protein, which was rescued by the cardiac glycoside drugs digitoxin and ouabain. Based on experiments with this organoid model of small airway epithelia, and comparisons with 16HBE14o- and other cell types expressing normal CFTR, we predict that inflammation in the COVID-19 airway may be mediated by inhibition of CFTR signaling by the SARS-CoV-2 spike protein, thus inducing a cystic fibrosis-like clinical phenotype. To our knowledge this is the first time COVID-19 airway inflammation has been experimentally traced in normal subjects to a contribution from SARS-CoV-2 spike-dependent inhibition of CFTR signaling.
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Affiliation(s)
- Hung Caohuy
- Department of Anatomy, Physiology and Genetics, Uniformed Services University School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Collaborative Health Initiative Research Program (CHIRP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Consortium for Health and Military Performance (CHAMP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
| | - Ofer Eidelman
- Department of Anatomy, Physiology and Genetics, Uniformed Services University School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Collaborative Health Initiative Research Program (CHIRP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
| | - Tinghua Chen
- Department of Anatomy, Physiology and Genetics, Uniformed Services University School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Collaborative Health Initiative Research Program (CHIRP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Consortium for Health and Military Performance (CHAMP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
| | - Ognoon Mungunsukh
- Department of Anatomy, Physiology and Genetics, Uniformed Services University School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Consortium for Health and Military Performance (CHAMP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Center for Military Precision Health, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
| | - Qingfeng Yang
- Department of Anatomy, Physiology and Genetics, Uniformed Services University School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Center for the Study of Traumatic Stress (CSTS), and Department of Psychiatry, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
| | - Nathan I Walton
- Department of Anatomy, Physiology and Genetics, Uniformed Services University School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Collaborative Health Initiative Research Program (CHIRP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
- Consortium for Health and Military Performance (CHAMP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
| | | | - Sara Khanal
- Virology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, 21702, USA
- The Geneva Foundation, Tacoma, WA, 98402, USA
| | - Shannon Hentschel
- Virology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, 21702, USA
- Cherokee Nation Assurance, Catoosa, OK, 74015, USA
| | - Catalina Florez
- Virology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, 21702, USA
- The Geneva Foundation, Tacoma, WA, 98402, USA
| | - Andrew S Herbert
- Virology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, 21702, USA
| | - Harvey B Pollard
- Department of Anatomy, Physiology and Genetics, Uniformed Services University School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA.
- Collaborative Health Initiative Research Program (CHIRP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA.
- Consortium for Health and Military Performance (CHAMP), Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA.
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Common cardiac medications potently inhibit ACE2 binding to the SARS-CoV-2 Spike, and block virus penetration and infectivity in human lung cells. Sci Rep 2021; 11:22195. [PMID: 34773067 PMCID: PMC8589851 DOI: 10.1038/s41598-021-01690-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 11/02/2021] [Indexed: 12/24/2022] Open
Abstract
To initiate SARS-CoV-2 infection, the Receptor Binding Domain (RBD) on the viral spike protein must first bind to the host receptor ACE2 protein on pulmonary and other ACE2-expressing cells. We hypothesized that cardiac glycoside drugs might block the binding reaction between ACE2 and the Spike (S) protein, and thus block viral penetration into target cells. To test this hypothesis we developed a biochemical assay for ACE2:Spike binding, and tested cardiac glycosides as inhibitors of binding. Here we report that ouabain, digitoxin, and digoxin, as well as sugar-free derivatives digitoxigenin and digoxigenin, are high-affinity competitive inhibitors of ACE2 binding to the Original [D614] S1 and the α/β/γ [D614G] S1 proteins. These drugs also inhibit ACE2 binding to the Original RBD, as well as to RBD proteins containing the β [E484K], Mink [Y453F] and α/β/γ [N501Y] mutations. As hypothesized, we also found that ouabain, digitoxin and digoxin blocked penetration by SARS-CoV-2 Spike-pseudotyped virus into human lung cells, and infectivity by native SARS-CoV-2. These data indicate that cardiac glycosides may block viral penetration into the target cell by first inhibiting ACE2:RBD binding. Clinical concentrations of ouabain and digitoxin are relatively safe for short term use for subjects with normal hearts. It has therefore not escaped our attention that these common cardiac medications could be deployed worldwide as inexpensive repurposed drugs for anti-COVID-19 therapy.
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