Anti-protease Treatments Targeting Plasmin(ogen) and Neutrophil Elastase May Be Beneficial in Fighting COVID-19

Abstract

Letter to the EditorAnti-protease Treatments Targeting Plasmin(ogen) and Neutrophil Elastase May Be Beneficial in Fighting COVID-19Alain R. ThierryAlain R. ThierryResearch Institute of Cancerology of Montpellier, National Institute of Health and Medical Research, INSERM U1194, IRCM, ICM, Montpellier University, Montpellier, FrancePublished Online:08 Jul 2020https://doi.org/10.1152/physrev.00019.2020MoreFiguresReferencesRelatedInformationSectionsGRANTSDISCLOSURESACKNOWLEDGMENTS PDF (47 KB) ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookXLinkedInWeChat To the Editor: Ji et al. (6) have convincingly shown that elevated plasmin(ogen) is a common risk factor in COVID-19 susceptibility. They highlighted the clinical relevance of plasmin(ogen) in patients who are susceptible to SARS-CoV-2 because of underlying conditions, such as hypertension, diabetes, cardiovascular diseases, cerebrovascular diseases, and chronic renal illnesses. They also pointed to other evidence in the literature that various functions of plasmin(ogen) increase the pathogenicity of COVID-19 (6). We recently proposed a novel hypothesis (10) concerning COVID-19 pathogenesis which is linked to that of Ji et al. (6). We are convinced that neutrophil extracellular traps (NETs) formation and its byproducts play a key role in COVID-19 pathogenesis (10). NETs are extensive structures released extracellularly from activated neutrophils in response to infection. They are composed of cytosolic protein assembled on a scaffold of released chromatin (10). These structures prevent the dissemination of microorganisms in blood by trapping them mechanically and by exploiting the coagulant function to segregate them within the circulation (5). In addition to this, NET components [DNA, histone, and granule proteins such as myeloperoxidase and elastase (NE)] also contribute to the triggering of an inflammatory process. The dysregulation of NET formation and the consecutive release of NET byproducts is involved in thrombosis and fibrinolysis disorders in autoimmune diseases, as well as non-autoimmune diseases, in particular viral infection (1, 5, 10). The coagulation system and innate immunity are coordinately activated and highly integrated during venous and arterial thrombus formation and progression (10). Platelet-neutrophil interactions at the site of deep vein thrombosis formation were found to induce NETosis, and to be of substantial relevance for thrombogenesis in the context of deep vein thrombosis in general. Barbosa da Cruz et al. (1) revealed that NE/DNA complexes in NETs play a central role in a mechanism that results in severe fibrinolytic failure. NE forms a tight complex with DNA that strongly impairs its inhibition by the α1-proteinase inhibitor (α1-PI) (1). In this way, NE highly degrades plasminogen without generating plasmin, which in turn leads to the production of antifibrinolytic plasminogen fragments. NETs can therefore serve as a platform for NE-mediated activation of intravascular coagulation in vivo (1, 10). With regard to the interaction of plasmin with NETs, the serine proteases, thrombin and plasmin, were also found to interact with DNA, and bound to NETs in vitro (1, 9). In this respect, it is interesting to note that thrombin and plasmin, like NE, belong to the vast family of S1 peptidases, which share an overall similar structure and folding (1). Thrombin can induce neutrophil chemotaxis and aggregation at submicromolar concentrations. Moreover, plasmin has been shown to cause neutrophil aggregation and adhesion to the endothelial surface in vitro at submicromolar concentrations. Lim et al. (8) observed reduced histone (H2B, H3, and H4) and neutrophil elastase levels with the addition of thrombin and plasmin. While Ryan et al. (9) did not observe neutrophil lysis after treatment with plasmin, they speculated that thrombin and plasmin displace NE from NETs, thus allowing NE to undergo auto-proteolysis. Alternatively, NE could be directly proteolyzed by thrombin and plasmin, as was observed for the histones. Lim et al. (8) showed that thrombin and plasmin alter the NET proteome and concluded that NETs and their proteic byproducts are regulated according to physiological conditions, which affects their roles in inflammation and host response during viral infection. Further investigations on NETome dynamics are needed to circumscribe these interactions. Elastase-mediated activation of SARS-CoV-2 was originally reported by Taguchi and co-workers (11), and the potentially significant implications of elastase for viral pathogenesis have been proposed (3, 11). NE is one of the most abundant NET byproduct proteins identified in a recent proteome analysis (8). Human NE is a granular serine protease with broad substrate specificity, expressed and stored in human neutrophils, released upon neutrophil activation, and involved primarily in host defense. Thus NE attacks proteins of invading microorganisms, but enables the hydrolyzation of proteins in the host extracellular matrix, such as collagen-IV and elastin. As a consequence, NE plays a role in degenerative and inflammatory diseases. During the phagocytosis of such foreign substances as pathogen-derived compounds, elastase as other proteins are also excreted into the surrounding extracellular environment, where the activity of elastase is regulated by inhibitors (i.e., α1-PI). NE could be responsible, in part, for the high multiplication of SARS-CoV-2-mediated infection, by means of multiple mechanisms (3, 11). First, like other proteases (trypsin, TMPRSS2, or plasmin), NE enables S protein cleavage and entry into cells directly from the cell surface (11). Wild-type human SARS-CoV-2 prefers cell-surface entry, in contrast to cathepsin-mediated endosomal cell entry (11). This multiplies its infectivity. Second, NE is a known activator of epithelial Na+ channel (ENaC). Intact furin activity is necessary for full elastase-induced ENaC activation (3). Caldwell et al. (4) showed that NE activates near silent ENaC and increases airway epithelial Na+ transport. NE, which is found in microgram quantities in the lungs of cystic fibrosis patients, activates ENaC via cleavage of the γ subunit, as observed with plasmin. This results in Na+ hyperabsorption, reduced airway surface liquid height, and dehydrated mucus, culminating in inefficient mucociliary clearance (such as found in cystic fibrosis). Third, in addition to its physiological function as a powerful host defense, neutrophil elastase is also known as one of the most destructive enzymes in the body. An overwhelming release of enzymatically active elastase, exceeding the inhibitory potential of the α1-PI, together with simultaneously produced reactive oxygen species, can cause local tissue injury. Once unregulated, NE activity disturbs the function of the lung permeability barrier, and induces the release of pro-inflammatory cytokines, participating in the cytokine storm observed in COVID-19. These symptoms are typical in the pathophysiology of acute lung injury found in COVID-19. As previously reported (7), α1-antitrypsin inhibits ENaC activity by inactivating elastase. In inflammatory conditions, peroxynitrite formed by the interaction of nitric oxide and superoxide inactivates α1-PI by oxidizing a methionine in its active site (7). It is likely that the resulting NE disinhibition could lead to the exacerbation of NE's detrimental effects, particularly its effect on ENaC regulation, and the endothelial and epithelial tissue damage it causes in COVID-19 inflamed lungs. Taken as a whole, the extent to which Ji et al.'s observations regarding plasmin functions (6) echo those we ourselves have made concerning NE is remarkable. Both related proteases 1) cleave S proteins, which facilitates SARS-CoV-2 cell entry and enhances its virulence (3, 11); 2) are involved in mechanisms leading to the coexistence of coagulation activation and hyperfibrinolysis (6, 8, 9); and 3) cleave ENaC subunits, which results in hypertension and dehydration of the fluid lining lung airways and alveolar cells (4, 6). Also, in those underlying conditions which increase susceptibility to SARS-CoV-2 infection, such as hypertension, diabetes, cardiovascular diseases, cerebrovascular diseases, and chronic renal illnesses, both elevated plasmin(ogen) and dysregulation of NET formation are common features (10). In addition, our previous work showed that NET dysregulation is involved in other comorbidities such as pulmonary diseases, obesity, inflammatory bowel diseases, sickle cell disease, and rheumatoid arthritis (10). Factors that influence successful recovery from respiratory viral infection (vs. a lethal outcome) are complex, and are both host- and virus-specific. That said, we have suggested that NET formation can be inhibited by various strategies such as DNase-1, anti-interleukin (IL)-1, or IL-6 treatments. Alternatively, preventing (or at least reducing) the entry of SARS-CoV-2 into respiratory cells by antiproteases may improve the clinical outcome of patients with COVID-19. In view of this, the more specific type of approach proposed by Ji et al. (6), such as targeting plasmin(ogen), may be beneficial. Likewise, tranexamic acid, a synthetic analog that binds lysine receptor sites on plasminogen and prevents its conversion to plasmin, may have therapeutic potential (2, 11). It should be noted that a clinical study is currently ongoing which evaluates the efficacy of tranexamic acid, along with the administration of an anticoagulant, in decreasing the severity of the disease (12). Alternatively, the promise of treatments which target elastase should be also seriously considered. These include the use of sivelestat or alvelestat (small molecule inhibitors of NE) or Bay-678 antibodies, as part of a fast-track drug repurposing strategy for treating COVID-19. The combination of anti-plasmin or anti-elastase approaches with those anti-inflammatory approaches already identified, therefore, deserves serious evaluation in the fight against COVID-19.GRANTS A. R. Thierry is supported by INSERM. This work was funded by the "SIRIC Montpellier Cancer Grant INCa_Inserm_DGOS_12553."DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the author.ACKNOWLEDGMENTS I thank S. Dejasse, C. McCarthy, and R. C. Gallo. Correspondence: A. R. Thierry (e-mail: [email protected]). Download PDF Previous Back to Top FiguresReferencesRelatedInformationREFERENCES1. Barbosa da Cruz D, Helms J, Aquino LR, Stiel L, Cougourdan L, Broussard C, Chafey P, Riès-Kautt M, Meziani F, Toti F, Gaussem P, Anglés-Cano E. DNA-bound elastase of neutrophil extracellular traps degrades plasminogen, reduces plasmin formation, and decreases fibrinolysis: proof of concept in septic shock plasma. FASEB J 33: 14270–14280, 2019. doi:10.1096/fj.201901363RRR. Crossref | PubMed | Web of Science | Google Scholar2. Barker AB, Wagener BM. An ounce of prevention may prevent hospitalization. Physiol Rev 100: 1347–1348, 2020. doi:10.1152/physrev.00017.2020. Link | Web of Science | Google Scholar3. Belouzard S, Madu I, Whittaker GR. Elastase-mediated activation of the severe acute respiratory syndrome coronavirus spike protein at discrete sites within the S2 domain. J Biol Chem 285: 22758–22763, 2010. doi:10.1074/jbc.M110.103275. Crossref | PubMed | Web of Science | Google Scholar4. Caldwell RA, Boucher RC, Stutts MJ. Neutrophil elastase activates near-silent epithelial Na+ channels and increases airway epithelial Na+ transport. Am J Physiol Lung Cell Mol Physiol 288: L813–L819, 2005. doi:10.1152/ajplung.00435.2004. Link | Web of Science | Google Scholar5. Camp JV, Jonsson CB. A role for neutrophils in viral respiratory disease. Front Immunol 8: 550, 2017. doi:10.3389/fimmu.2017.00550. Crossref | PubMed | Web of Science | Google Scholar6. Ji H-L, Zhao R, Matalon S, Matthay MA. Elevated plasmin(ogen) as a common risk factor for COVID-19 susceptibility. Physiol Rev 100: 1065–1075, 2020. doi:10.1152/physrev.00013.2020. Link | Web of Science | Google Scholar7. Lazrak A, Nita I, Subramaniyam D, Wei S, Song W, Ji HL, Janciauskiene S, Matalon S. α1-Antitrypsin inhibits epithelial Na+ transport in vitro and in vivo. Am J Respir Cell Mol Biol 41: 261–270, 2009. doi:10.1165/rcmb.2008-0384OC. Crossref | PubMed | Web of Science | Google Scholar8. Lim CH, Adav SS, Sze SK, Choong YK, Saravanan R, Schmidtchen A. Thrombin and plasmin alter the proteome of neutrophil extracellular traps. Front Immunol 9: 1554, 2018. doi:10.3389/fimmu.2018.01554. Crossref | PubMed | Web of Science | Google Scholar9. Ryan TJ, Lai L, Malik AB. Plasmin generation induces neutrophil aggregation: dependence on the catalytic and lysine binding sites. J Cell Physiol 151: 255–261, 1992. doi:10.1002/jcp.1041510206. Crossref | PubMed | Web of Science | Google Scholar10. Thierry A, Roch B. NETs by-products and extracellular DNA may play a key role in COVID-19 pathogenesis: incidence on patient monitoring and therapy. Preprints 2020040238, 2020, doi:10.20944/preprints202004.0238.v1.Google Scholar11. Watanabe R, Matsuyama S, Shirato K, Maejima M, Fukushi S, Morikawa S, Taguchi F. Entry from the cell surface of severe acute respiratory syndrome coronavirus with cleaved S protein as revealed by pseudotype virus bearing cleaved S protein. J Virol 82: 11985–11991, 2008. doi:10.1128/JVI.01412-08. Crossref | PubMed | Web of Science | Google Scholar12. https://clinicaltrials.gov/ct2/show/NCT04338126 Tranexamic acid (TXA) and corona virus 2019 (COVID19) in inpatients (TCInpatient). 2020.Google Scholar CollectionsAPS Cross-Journal CollectionsCoronavirus-Related PapersPhysiological Reviews CollectionsCOVID-19 Cited ByNatural Cyclic Peptides: Synthetic Strategies and Biomedical Applications20 January 2025 | Biomedicines, Vol. 13, No. 1Perspectives for using serratiopeptidase in systemic enzyme therapy for low-intensity chronic inflammation and pain syndromes: from mechanisms of action to practical implementation (literature review)22 October 2024 | PAIN, JOINTS, SPINE, Vol. 14, No. 3Inflammation‐, immunothrombosis,‐ and autoimmune‐feedback loops may lead to persistent neutrophil self‐stimulation in long COVID27 August 2024 | Journal of Medical Virology, Vol. 96, No. 8Possible pharmacological targets and mechanisms of sivelestat in protecting acute lung injury1 Mar 2024 | Computers in Biology and Medicine, Vol. 170Do chemokine/chemokine receptor axes play paramount parts in trafficking and oriented locomotion of monocytes/macrophages toward the lungs of COVID-19 infected patients? A systematic review1 Mar 2024 | Cytokine, Vol. 175Exploring the role of neutrophils in infectious and noninfectious pulmonary disorders24 June 2023 | International Reviews of Immunology, Vol. 43, No. 1Fibrinolytic system and COVID-19: From an innovative view of epithelial ion transport1 Jul 2023 | Biomedicine & Pharmacotherapy, Vol. 163A novel colchicine-myricetin heterozygous molecule: design, synthesis, and effective evaluations on the pathological models of acute lung injury in vitro and in vivo29 June 2023 | Frontiers in Pharmacology, Vol. 14Therapeutic applications of nanoparticles targeting neutrophil and extracellular traps1 Jun 2023 | Journal of Controlled Release, Vol. 358SARS‐CoV‐2 induced HDL dysfunction may affect the host's response to and recovery from COVID‐1916 May 2023 | Immunity, Inflammation and Disease, Vol. 11, No. 5The role of neutrophil extracellular traps (NETs) in the immunopathogenesis of severe COVID-19: potential immunotherapeutic strategies regulating NET formation and activity1 April 2023 | Russian Journal of Infection and Immunity, Vol. 13, No. 1Regulation of Epithelial Sodium Transport by SARS-CoV-2 Is Closely Related with Fibrinolytic System-Associated Proteins23 March 2023 | Biomolecules, Vol. 13, No. 4Tranexamic Acid and Plasminogen/Plasmin Glaring Paradox in COVID-196 Jan 2023 | Endocrine, Metabolic & Immune Disorders - Drug Targets, Vol. 23, No. 1Persistence of neutrophil extracellular traps and anticardiolipin auto‐antibodies in post‐acute phase COVID‐19 patients31 October 2022 | Journal of Medical Virology, Vol. 95, No. 1Proteolysis and Deficiency of α1-Proteinase Inhibitor in SARS-CoV-2 Infection16 November 2022 | Biochemistry (Moscow), Supplement Series B: Biomedical Chemistry, Vol. 16, No. 4Neutrophil extracellular traps have auto-catabolic activity and produce mononucleosome-associated circulating DNA28 November 2022 | Genome Medicine, Vol. 14, No. 1Competitive cleavage of SARS-CoV-2 spike protein and epithelial sodium channel by plasmin as a potential mechanism for COVID-19 infectionYapeng Hou, Tong Yu, Tingyu Wang, Yan Ding, Yong Cui, and Hongguang Nie1 November 2022 | American Journal of Physiology-Lung Cellular and Molecular Physiology, Vol. 323, No. 5Building a better NET: Neutrophil extracellular trap targeted therapeutics in the treatment of infectious and inflammatory disorders1 Oct 2022 | Research and Practice in Thrombosis and Haemostasis, Vol. 6, No. 7Proteolysis and deficiency of α1-proteinase inhibitor in SARS-CoV-2 infection1 January 2022 | Biomeditsinskaya Khimiya, Vol. 68, No. 3On the Origin of Neutrophil Extracellular Traps in COVID-1911 March 2022 | Frontiers in Immunology, Vol. 13NETosis and Neutrophil Extracellular Traps in COVID-19: Immunothrombosis and Beyond2 March 2022 | Frontiers in Immunology, Vol. 13Coagulopathy and Fibrinolytic Pathophysiology in COVID-19 and SARS-CoV-2 Vaccination19 March 2022 | International Journal of Molecular Sciences, Vol. 23, No. 6Elastase Inhibitor Cyclotheonellazole A: Total Synthesis and In Vivo Biological Evaluation for Acute Lung Injury10 January 2022 | Journal of Medicinal Chemistry, Vol. 65, No. 4Atypical response to bacterial coinfection and persistent neutrophilic bronchoalveolar inflammation distinguish critical COVID-19 from influenza11 January 2022 | JCI Insight, Vol. 7, No. 1Altered high-density lipoprotein composition and functions during severe COVID-1927 January 2021 | Scientific Reports, Vol. 11, No. 1The role of plasma serine leukocyte proteinase inhibitor in the body's defense against COVID-192 November 2021 | Journal of microbiology, epidemiology and immunobiology, Vol. 98, No. 5Fibrinolytic or anti-plasmin (nafamostat) therapy for COVID-19: A timing challenge for clinicians1 Oct 2021 | Pulmonary Pharmacology & Therapeutics, Vol. 70Host Serine Proteases: A Potential Targeted Therapy for COVID-19 and Influenza30 August 2021 | Frontiers in Molecular Biosciences, Vol. 8Serratiopeptidase, A Serine Protease Anti-Inflammatory, Fibrinolytic, and Mucolytic Drug, Can Be a Useful Adjuvant for Management in COVID-1924 June 2021 | Frontiers in Pharmacology, Vol. 12Neutrophils and COVID-19: Active Participants and Rational Therapeutic Targets2 June 2021 | Frontiers in Immunology, Vol. 12Plasminogen: an enigmatic zymogen27 May 2021 | Blood, Vol. 137, No. 21Associations of D-Dimer on Admission and Clinical Features of COVID-19 Patients: A Systematic Review, Meta-Analysis, and Meta-Regression7 May 2021 | Frontiers in Immunology, Vol. 12Towards better understanding of the heparin role in NETosis: Feasibility of using native mass spectrometry to monitor interactions of neutrophil elastase with heparin oligomers1 May 2021 | International Journal of Mass Spectrometry, Vol. 463The Emerging Role of Neutrophils in the Pathogenesis of Thrombosis in COVID-1920 May 2021 | International Journal of Molecular Sciences, Vol. 22, No. 10Fibrinolytic Serine Proteases, Therapeutic Serpins and Inflammation: Fire Dancers and Firestorms25 March 2021 | Frontiers in Cardiovascular Medicine, Vol. 8Neutrophils in COVID-1925 March 2021 | Frontiers in Immunology, Vol. 12Neutrophils and COVID-19: The road so far1 Jan 2021 | International Immunopharmacology, Vol. 90Pathogen Genomics and Host Cellular Susceptibility Factors of COVID-1920 December 2020 | Global Clinical and Translational ResearchTargeting Neutrophils to Treat Acute Respiratory Distress Syndrome in Coronavirus Disease9 October 2020 | Frontiers in Pharmacology, Vol. 11Host/genetic factors associated with COVID-19 call for precision medicine21 July 2020 | Precision Clinical Medicine, Vol. 3, No. 3Neutrophil Extracellular Traps and By-Products Play a Key Role in COVID-19: Pathogenesis, Risk Factors, and Therapy11 September 2020 | Journal of Clinical Medicine, Vol. 9, No. 9 Coagulation Disorders in COVID-19: Role of Toll-like Receptors 1 October 2020 | Journal of Inflammation Research, Vol. Volume 13 N-Acetylcysteine to Combat COVID-19: An Evidence Review 1 November 2020 | Therapeutics and Clinical Risk Management, Vol. Volume 16 More from this issue > Volume 100Issue 4October 2020Pages 1597-1598 Copyright & PermissionsCopyright © 2020 the American Physiological Societyhttps://doi.org/10.1152/physrev.00019.2020PubMed32639219History Received 8 May 2020 Accepted 24 June 2020 Published online 8 July 2020 Published in print 1 October 2020 KeywordsCOVIDelastaseneutrophil extracellular trapsplasmintreatment Metrics Downloaded 2,931 times See more by 1 in on Total citations citations this has been at a has been by the context of the a it or the and a in which the was See more by 1 in on We Plasmin(ogen) as a Risk for COVID-19 Physiological of May B. Physiological of Tranexamic Acid to COVID-19 Physiological of SARS-CoV-2 and ENaC by Plasmin as a Potential for COVID-19 Hou, American Journal of - Lung Cellular and Molecular Physiology, of COVID-19 Cancer Physiological of COVID-19 from the of by on International Journal of Medicine, of COVID-19 from the of by on International Journal of Medicine, of COVID-19 from the of by on International Journal of Medicine, on of rheumatoid arthritis by and International Journal of Medicine, on the mechanism of rheumatoid arthritis International Journal of Medicine, by

Topics & Concepts