Blunted sFasL signalling exacerbates TNF-driven neutrophil necroptosis in critically ill COVID-19 patients

Tiziano A Schweizer; Srikanth Mairpady Shambat; Clement Vulin; Sylvia Hoeller; Claudio Acevedo; Markus Huemer; Alejandro Gomez-Mejia; Chun-Chi Chang; Jeruscha Baum; Sanne Hertegonne; Eva Hitz; Thomas C Scheier; Daniel A Hofmaenner; Philipp K Buehler; Holger Moch; Reto A Schuepbach; Silvio D Brugger; Annelies S Zinkernagel

doi:10.1002/cti2.1357

Blunted sFasL signalling exacerbates TNF-driven neutrophil necroptosis in critically ill COVID-19 patients

Clin Transl Immunology. 2021 Dec 11;10(12):e1357. doi: 10.1002/cti2.1357. eCollection 2021.

Authors

Tiziano A Schweizer¹, Srikanth Mairpady Shambat¹, Clement Vulin¹, Sylvia Hoeller², Claudio Acevedo¹, Markus Huemer¹, Alejandro Gomez-Mejia¹, Chun-Chi Chang¹, Jeruscha Baum¹, Sanne Hertegonne¹, Eva Hitz¹, Thomas C Scheier¹, Daniel A Hofmaenner³, Philipp K Buehler³, Holger Moch², Reto A Schuepbach³, Silvio D Brugger¹, Annelies S Zinkernagel¹

Affiliations

¹ Department of Infectious Diseases and Hospital Epidemiology University Hospital of Zurich University of Zurich Zurich Switzerland.
² Department of Pathology and Molecular Pathology University Hospital of Zurich University of Zurich Zurich Switzerland.
³ Institute for Intensive Care Medicine University Hospital of Zurich University of Zurich Zurich Switzerland.

Abstract

Objectives: Critically ill coronavirus disease 2019 (COVID-19) patients are characterised by a severely dysregulated cytokine profile and elevated neutrophil counts, impacting disease severity. However, it remains unclear how neutrophils contribute to pathophysiology during COVID-19. Here, we assessed the impact of the dysregulated cytokine profile on the regulated cell death (RCD) programme of neutrophils.

Methods: Regulated cell death phenotype of neutrophils isolated from critically ill COVID-19 patients or healthy donors and stimulated with COVID-19 or healthy plasma ex vivo was assessed by flow cytometry, time-lapse microscopy and cytokine multiplex analysis. Immunohistochemistry of COVID-19 patients and control biopsies were performed to assess the in situ neutrophil RCD phenotype. Plasma cytokine levels of COVID-19 patients and healthy donors were measured by multiplex analysis. Clinical parameters were correlated to cytokine levels of COVID-19 patients.

Results: COVID-19 plasma induced a necroptosis-sensitive neutrophil phenotype, characterised by cell lysis, elevated release of damage-associated molecular patterns (DAMPs), increased receptor-interacting serine/threonine-protein kinase (RIPK) 1 levels and mixed lineage kinase domain-like pseudokinase (MLKL) involvement. The occurrence of neutrophil necroptosis MLKL axis was further confirmed in COVID-19 thrombus and lung biopsies. Necroptosis was induced by the tumor necrosis factor receptor 1 (TNFRI)/TNF-α axis. Moreover, reduction of soluble Fas ligand (sFasL) levels in COVID-19 patients and hence decreased signalling to Fas directly increased RIPK1 levels, exacerbated TNF-driven necroptosis and correlated with disease severity, which was abolished in patients treated with glucocorticoids.

Conclusion: Our results suggest a novel role for sFasL signalling in the TNF-α-induced RCD programme in neutrophils during COVID-19 and a potential therapeutic target to curb inflammation and thus influence disease severity and outcome.

Keywords: COVID‐19; Fas (CD95); RIPK1; TNF‐α; necroptosis; neutrophils.