Autophagy Mediates the Delivery of Thrombogenic Tissue Factor to Neutrophil Extracellular Traps in Human Sepsis

Abstract

BackgroundSepsis is associated with systemic inflammatory responses and induction of coagulation system. Neutrophil extracellular traps (NETs) constitute an antimicrobial mechanism, recently implicated in thrombosis via platelet entrapment and aggregation.Methodology/Principal FindingsIn this study, we demonstrate for the first time the localization of thrombogenic tissue factor (TF) in NETs released by neutrophils derived from patients with gram-negative sepsis and normal neutrophils treated with either serum from septic patients or inflammatory mediators involved in the pathogenesis of sepsis. Localization of TF in acidified autophagosomes was observed during this process, as indicated by positive LC3B and LysoTracker staining. Moreover, phosphatidylinositol 3-kinase inhibition with 3-MA or inhibition of endosomal acidification with bafilomycin A1 hindered the release of TF-bearing NETs. TF present in NETs induced thrombin generation in culture supernatants, which further resulted in protease activated receptor-1 signaling.Conclusions/SignificanceThis study demonstrates the involvement of autophagic machinery in the extracellular delivery of TF in NETs and the subsequent activation of coagulation cascade, providing evidence for the implication of this process in coagulopathy and inflammatory response in sepsis.

Propagation of thrombosis by neutrophils and extracellular nucleosome networks

“…Neutrophils and platelets release microparticles that have been suggested to express TF and to be trapped by NET. 30 In line with this, TF has been detected in association with NET inside venous thrombi in vivo. 8 Eosinophils, which expel DNA-histone complexes upon activation as well, serve as a major intravascular pool of TF.…”

Immobilized Immune Complexes Induce Neutrophil Extracellular Trap Release by Human Neutrophil Granulocytes via FcγRIIIB and Mac-1

“…This pathway is crucial in the initiation of autophagy (105)(106)(107), which has been shown to be required for PMA-induced NET formation (70,108). Interplay between PI3K signaling, autophagy, and NET formation has been described in acute gout inflammatory arthritis (66) and in sepsis (108). PI3K generates phosphatidylinositol (3,4,5)-trisphosphate, which influences the transcription factor NF-kB (109).…”

PAD4-deficiency does not affect bacteremia in polymicrobial sepsis and ameliorates endotoxemic shock

“…[9][10][11] NET biomarkers are elevated in septic patients. [12][13][14] Microbes trapped within NETs are sometimes killed, 4,15 and thus NETs could represent an important mechanism of host defense, particularly in sepsis. 7,[16][17][18] To date, this has not been rigorously tested.…”