CLEC5A and TLR2 are critical in SARS-CoV-2-induced NET formation and lung inflammation

Abstract

Background Coronavirus-induced disease 19 (COVID-19) infects more than three hundred and sixty million patients worldwide, and people with severe symptoms frequently die of acute respiratory distress syndrome (ARDS). Recent studies indicated that excessive neutrophil extracellular traps (NETs) contributed to immunothrombosis, thereby leading to extensive intravascular coagulopathy and multiple organ dysfunction. Thus, understanding the mechanism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced NET formation would be helpful to reduce thrombosis and prevent ARDS in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Methods We incubated SARS-CoV-2 with neutrophils in the presence or absence of platelets to observe NET formation. We further isolated extracellular vesicles from COVID-19 patients' sera (COVID-19-EVs) to examine their ability to induce NET formation. Results We demonstrated that antagonistic mAbs against anti-CLEC5A mAb and anti-TLR2 mAb can inhibit COVID-19-EVs-induced NET formation, and generated clec5a−/−/tlr2−/− mice to confirm the critical roles of CLEC5A and TLR2 in SARS-CoV-2-induced lung inflammation in vivo. We found that virus-free extracellular COVID-19 EVs induced robust NET formation via Syk-coupled C-type lectin member 5A (CLEC5A) and TLR2. Blockade of CLEC5A inhibited COVID-19 EVs-induced NETosis, and simultaneous blockade of CLEC5A and TLR2 further suppressed SARS-CoV-2-induced NETosis in vitro. Moreover, thromboinflammation was attenuated dramatically in clec5a−/−/tlr2−/− mice. Conclusions This study demonstrates that SARS-CoV-2-activated platelets produce EVs to enhance thromboinflammation via CLEC5A and TLR2, and highlight the importance of CLEC5A and TLR2 as therapeutic targets to reduce the risk of ARDS in COVID-19 patients.

CLEC5A expression can be triggered by spike glycoprotein and may be a potential target for COVID‐19 therapy

“…In our findings with hamster samples, the animals were challenged with SARS‐CoV‐2 to monitor the kinetic of CLEC5A gene expression 15 days after infection, and the data showed that after 3 days of viral infection CLEC5A gene is expressed in blood samples. Similar results were seen by other authors, in which CLEC5A markers were detected in murine samples during pulmonary mycobacterial infection and other viral infections, but it was not detected in healthy samples 32,37–39,42,43 . In addition, some studies mentioned that inflammatory cells are detected in the lung at 2–10 days postinfection with SARS‐CoV‐2 particles, being part of the disease's pathology in hamster models 42,43 …”

“…Similar results were seen by other authors, in which CLEC5A markers were detected in murine samples during pulmonary mycobacterial infection and other viral infections, but it was not detected in healthy samples. 32,[37][38][39]42,43 In addition, some studies mentioned that inflammatory cells are detected in the lung at 2-10 days postinfection with SARS-CoV-2 particles, being part of the disease's pathology in hamster models. 42,43 F I G U R E 4 In silico interaction between CLEC5A and spike protein (SARS-CoV-2).…”

Multidistrict Host–Pathogen Interaction during COVID-19 and the Development Post-Infection Chronic Inflammation

“…The tropism of SARS-CoV-2, defined by entry into cells via the widely expressed ACE2 receptor, makes it possible for the infection to spread to different organs, such as the lung, heart, intestine, liver, and brain. This can generate acute as well as chronic damage in various districts [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 ...…”

“…During viral replication of SARS-CoV-2, double-stranded (ds) RNA is also produced, which binds TLR3 and activates TIR domain-containing adapter protein, inducing the interferon β (TRIF) pathway. Considering the protein components of SARS-CoV-2, the ability of TLR2 to bind the E (envelope) protein and the subsequent activation of MyD88 in association with inflammation in the lung district have also been demonstrated [ 36 , 37 ]. The combination of different viral proteins—for example, those released from endosomes and those translated by reading viral genomic RNA—are recognized by RLRs that associate with MDA-5 and MAVS and activate IRF3/7, leading to the secretion of IFN-α/β [ 38 , 39 ].…”

Pathophysiological mechanisms of thrombosis in acute and long COVID-19

“…A recent study shows that SARS-CoV-2 viral proteins induce NET formation via a Syk-dependent pathway of downstream signaling molecules of C-type lectin receptors ( 26 ). Further study shows that EVs released from SARS-CoV-2-activated platelets induce robust formation of NET via CLEC5A and TLR2, which in turn enhance thrombosis ( 27 ).…”