Complement and tissue factor–enriched neutrophil extracellular traps are key drivers in COVID-19 immunothrombosis
Panagiotis Skendros, … , John D. Lambris, Konstantinos Ritis
Panagiotis Skendros, … , John D. Lambris, Konstantinos Ritis
Published August 6, 2020
Citation Information: J Clin Invest. 2020;130(11):6151-6157. https://doi.org/10.1172/JCI141374.
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Concise Communication COVID-19 Immunology

Complement and tissue factor–enriched neutrophil extracellular traps are key drivers in COVID-19 immunothrombosis

Abstract

Emerging 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.

Authors

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, Konstantinos Ritis

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Figure 3

C3 inhibition disrupts neutrophil-driven thromboinflammation in COVID-19.

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C3 inhibition disrupts neutrophil-driven thromboinflammation in COVID-19...
(A) Soluble terminal complement complex (sTCC) levels in plasma from controls (n = 10) and patients with COVID-19 (n = 25). Red squares: severe patients; red triangles: critical patients. (B) Relative fold expression of TF mRNA in control neutrophils stimulated with serum from healthy individuals (HS), HS incubated with COVID-19 serum (COV serum), or HS treated with compstatin analog Cp40 and then COV serum, COV serum alone, or COV serum treated with Cp40. Data are from 4 independent experiments (mean ± SD). (C) Fluorescence microscopy showing TF/NE staining in control neutrophils stimulated with HS, HS incubated with COV serum, or HS treated with Cp40 and then COV serum. A representative example of 4 independent experiments is shown. Original magnification: ×1000; scale bar: 5 μm. Blue: DAPI, green: TF, red: NE. All conditions were compared with HS alone (control). *Statistical significance at P < 0.05. A: Student’s t test, B: Friedman’s test. These in vitro experiments are also listed in Supplemental Table 2. Conditions of real-time RT-PCR are described in Supplemental Table 3.