C5aR1 signaling triggers lung immunopathology in COVID-19 through neutrophil extracellular traps
Bruna M. Silva, … , Paul Proost, Thiago M. Cunha
Bruna M. Silva, … , Paul Proost, Thiago M. Cunha
Published April 27, 2023
Citation Information: J Clin Invest. 2023;133(12):e163105. https://doi.org/10.1172/JCI163105.
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Research Article Inflammation

C5aR1 signaling triggers lung immunopathology in COVID-19 through neutrophil extracellular traps

Abstract

Patients with severe COVID-19 develop acute respiratory distress syndrome (ARDS) that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that complement component 5a (C5a), through its cellular receptor C5aR1, has potent proinflammatory actions and plays immunopathological roles in inflammatory diseases, we investigated whether the C5a/C5aR1 pathway could be involved in COVID-19 pathophysiology. C5a/C5aR1 signaling increased locally in the lung, especially in neutrophils of critically ill patients with COVID-19 compared with patients with influenza infection, as well as in the lung tissue of K18-hACE2 Tg mice (Tg mice) infected with SARS-CoV-2. Genetic and pharmacological inhibition of C5aR1 signaling ameliorated lung immunopathology in Tg-infected mice. Mechanistically, we found that C5aR1 signaling drives neutrophil extracellular traps-dependent (NETs-dependent) immunopathology. These data confirm the immunopathological role of C5a/C5aR1 signaling in COVID-19 and indicate that antagonists of C5aR1 could be useful for COVID-19 treatment.

Authors

Bruna M. Silva, Giovanni F. Gomes, Flavio P. Veras, Seppe Cambier, Gabriel V.L. Silva, Andreza U. Quadros, Diego B. Caetité, Daniele C. Nascimento, Camilla M. Silva, Juliana C. Silva, Samara Damasceno, Ayda H. Schneider, Fabio Beretta, Sabrina S. Batah, Icaro M.S. Castro, Isadora M. Paiva, Tamara Rodrigues, Ana Salina, Ronaldo Martins, Guilherme C.M. Cebinelli, Naira L. Bibo, Daniel M. Jorge, Helder I. Nakaya, Dario S. Zamboni, Luiz O. Leiria, Alexandre T. Fabro, José C. Alves-Filho, Eurico Arruda, Paulo Louzada-Junior, Renê D. Oliveira, Larissa D. Cunha, Pierre Van Mol, Lore Vanderbeke, Simon Feys, Els Wauters, Laura Brandolini, Andrea Aramini, Fernando Q. Cunha, Jörg Köhl, Marcello Allegretti, Diether Lambrechts, Joost Wauters, Paul Proost, Thiago M. Cunha

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Figure 3

C5aR1 signaling on myeloid cells contributes to the lung pathology in a COVID-19 mouse model.

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C5aR1 signaling on myeloid cells contributes to the lung pathology in a ...
(A) Tg mice were infected with SARS-CoV-2 (2 × 104 PFU, intranasally). ELISA assay to measure levels of (B) C5a in the lung homogenate of infected animals (n = 14) or mock control (n = 11). (C) factor Bb and (D) C3a levels in the lung homogenate of infected animals (n = 8) or mock control (n = 5). (E) Representative confocal images of the presence of C5aR1 expression in the lung tissue of Tgfl/fl mice (C5ar1-eGFP mice) infected with SARS-CoV-2 (5 dpi). Tissue slices were costained for nuclei (DAPI, blue), Iba-1 (macrophages, red) and NE (neutrophils, red) markers. Scale bar: 50 μm. (F) Percentage of cells expressing C5aR1 in the lung tissue of Tgfl/fl mice infected with SARS-CoV-2 (n = 4 mice/4 randomized field). (G) Representative H&E staining from the lung of SARS-CoV-2-infected Tgfl/fl(n = 6) or TgcKO mice (n = 6). A mock-infected group was used as control (n = 6). Scale bars: 200 μm (4 ×), 100 μm(10 ×). (H) TUNEL staining (red) for detection of apoptotic cells in situ from lung tissue of SARS-CoV-2–infected Tgfl/fl (n = 5) or TgcKO mice (n = 6). Mock-infected Tg mice were used as a control (n = 5/group). (I) Quantification of the lung septal area fraction. (J) Percentage of TUNEL positive cells in lung tissue. Scale bar: 50 μm. (K) ELISA assays were performed to detect CCL2, CCL3, CCL4, CXCL1, and IL-6 levels in the lung tissue of Tgfl/f (n = 8) or Infected TgcKO mice (n = 7). Mock-infected Tg mice were used as a control (n = 5). Data are shown as the mean ± SEM. P values were determined by (B–D) Student’s 2-tailed t test and (F, I, J, and K) 1-way ANOVA followed by Bonferroni’s posthoc test.