NETosis and SARS-COV-2 infection related thrombosis: a narrative review.

BACKGROUND: Coronavirus disease 2019 (COVID-19) infection is related to immune hyperactivity, the release of inflammatory cytokines, and immunothrombosis. Among the underlying mechanisms in COVID-19 thrombosis, neutrophil extracellular traps (NETs) formation, NETosis, may have a significant role. COVID-19 thrombi obtained from extracorporeal membrane oxygenation contained an accumulation of neutrophils and in a higher amount of NETs when compared with non-COVID-19 thrombi specimens. MAIN BODY: During sepsis and inflammatory status, NETs released from neutrophils and histones and nucleosomes extruded into the extracellular space and take part in the host innate immunity defense, inflammation, and thrombosis. Excessive NETosis is related to clinical progression and respiratory failure in infections and sepsis. NETosis act as a scaffold for thrombus formation, and new associative data support the relation between deregulated immune responses with thrombus formation and organ failure. NETosis is reported in COVID-19 patients. In COVID-19 infection, overproduction of tissue factor (TF) by neutrophils has a role in immunothrombosis. Additionally, NETs can trap TF pathway inhibitor (TFPI) as the only endogenous protein that effectively inhibits the activity of the significant proteases- complexes, TF-FVIIa and prothrombinase. CONCLUSION: Because of NETosis can induce intrinsic and extrinsic coagulation cascade activation through the production of TF, activation of FXII, and inhibition of TFPI and fibrinolysis and induce immunothrombosis, targeting NETosis may diminish thrombus formation related to NETs in COVID-19 patients.