• Panagiotis Skendros, Alexandros Mitsios, Akrivi Chrysanthopoulou, Dimitrios C Mastellos, Simeon Metallidis, Petros Rafailidis, Maria Ntinopoulou, Eleni Sertaridou, Victoria Tsironidou, Christina Tsigalou, Maria Tektonidou, Theocharis Konstantinidis, Charalampos Papagoras, Ioannis Mitroulis, Georgios Germanidis, John D Lambris, and Konstantinos Ritis.
• First Department of Internal Medicine, University Hospital of Alexandroupolis, and.
• J. Clin. Invest. 2020 Nov 2; 130 (11): 6151-6157.

AbstractEmerging data indicate that complement and neutrophils contribute to the maladaptive immune response that fuels hyperinflammation and thrombotic microangiopathy, thereby increasing coronavirus 2019 (COVID-19) mortality. Here, we investigated how complement interacts with the platelet/neutrophil extracellular traps (NETs)/thrombin axis, using COVID-19 specimens, cell-based inhibition studies, and NET/human aortic endothelial cell (HAEC) cocultures. Increased plasma levels of NETs, tissue factor (TF) activity, and sC5b-9 were detected in patients. Neutrophils of patients yielded high TF expression and released NETs carrying active TF. Treatment of control neutrophils with COVID-19 platelet-rich plasma generated TF-bearing NETs that induced thrombotic activity of HAECs. Thrombin or NETosis inhibition or C5aR1 blockade attenuated platelet-mediated NET-driven thrombogenicity. COVID-19 serum induced complement activation in vitro, consistent with high complement activity in clinical samples. Complement C3 inhibition with compstatin Cp40 disrupted TF expression in neutrophils. In conclusion, we provide a mechanistic basis for a pivotal role of complement and NETs in COVID-19 immunothrombosis. This study supports strategies against severe acute respiratory syndrome coronavirus 2 that exploit complement or NETosis inhibition.

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