Neutrophil extracellular traps (NETs) promote disseminated intravascular coagulation in sepsis.

Abstract

Abstract Neutrophil extracellular traps (NETs; webs of DNA coated in anti-microbial proteins) are released into the vasculature during sepsis and contribute to organ damage. Various components of NETs have been shown to modulate the coagulation cascade in vitro. We hypothesized that NETs released into the vasculature during sepsis activate intravascular coagulation, leading to microvascular hypoperfusion and end-organ damage. Multi-color confocal intravital microscopy was used in mouse models of sepsis (endotoxemia and E. coli peritonitis) to visualize and quantify neutrophil and platelet trafficking, NETs production, real-time perfusion analysis, and intravascular thrombin activity (using novel in vivo zymography). In vivo imaging of the liver microcirculation in septic mice revealed spatial co-localization between NETs and intravascular coagulation (thrombin activity, fibrin deposition, and platelet aggregation). Inhibition of NETs using i.v. DNase infusion (to digest NETs), or PAD4-deficient mice (that have impaired NETs production) resulted in significantly lower quantities of intravascular thrombin activity, and improved microvascular perfusion. In a model of Gram-negative sepsis (E. coli peritonitis), PAD4-deficient mice had reduced markers of disseminated intravascular coagulation (intravascular thrombin, PAI-1), and end-organ damage (serum lactate, ALT) compared to wild-type controls. Together, these data demonstrate that NETs activate coagulation in vivo, and promote disseminated intravascular coagulation in sepsis. Inhibition of NETs in septic animals reduces intravascular coagulation, improves microvascular perfusion, and attenuates end-organ damage.