The Proteolytic Inactivation of Protein Z-Dependent Protease Inhibitor by Neutrophil Elastase Might Promote the Procoagulant Activity of Neutrophil Extracellular Traps in Sepsis

Abstract

Septic shock is the archetypal clinical setting in which extensive cross talk between inflammation and coagulation dysregulates the latter. The main anticoagulant systems are systematically impaired, depleted and/or downregulated. Protein Z-dependent protease inhibitor (ZPI) is an anticoagulant serpin that not only targets coagulation factors Xa and XIa but also acts as an acute phase reactant whose plasma concentration rises in inflammatory settings. The objective of the present study was to assess the plasma ZPI antigen level in a cohort of patients suffering from septic shock with or without overt-disseminated intravascular coagulation (DIC). The plasma ZPI antigen level was approximately 2.5-fold higher in the patient group (n=100; 38 with DIC and 62 without) than in healthy controls (n=31). The elevation’s magnitude did not appear to depend on the presence/absence of DIC. Furthermore, Western blots revealed the presence of cleaved ZPI in plasma from patients with severe sepsis, independently of the DIC status. In vitro, ZPI was proteolytically inactivated by purified neutrophil elastase (NE) and by NE on the surface of neutrophil extracellular traps (NETs). The electrophoretic pattern of ZPI after NE-catalyzed proteolysis was very similar to that resulting from the clotting process - suggesting that the cleaved ZPI observed in severe sepsis plasma is devoid of anticoagulant activity. Taken as a whole, our results (i) suggest that NE is involved in ZPI inactivation during sepsis, and (ii) reveal a novel putative mechanism for the procoagulant activity of NETs in immunothrombosis.

An overview of the mechanisms and potential roles of extracellular vesicles in septic shock

“…Bianchini et al found that although plasma ZPI concentrations were higher in patients in septic shock compared to normal subjects, the ZPI present in the plasma of patients with severe sepsis was hydrolyzed by neutrophil elastase (NE) and purified NE on the surface of neutrophil extracellular traps (NETs). This resulted in the cleavage and inactivation of plasma ZPI, and hence, plasma ZPI concentrations were lower in patients with severe sepsis, and the blood of these patients was prone to clotting (73).…”

Are NETs a Novel, Exciting, Thrombosis Risk Marker?

“…Targeting NETosis or degrading existing NETs (or associated mechanistic pathways) have been extensively investigated in many disease models associated with NETs and thrombosis (27)(28)(29)(30). NETosis starts from the activation of NADPH oxidase (NOX) complex via protein kinase C (PKC)-Raf/MERK/ERK by external stimuli, followed by activation of MPO, NE and PAD4.…”

“…Targeting NETosis or degrading existing NETs (or associated mechanistic pathways) has been extensively investigated in many disease models associated with NETs and thrombosis. [27][28][29][30] NETosis starts from the activation of NADPH oxidase (NOX) complex via protein kinase C (PKC)-Raf/MERK/ERK by external stimuli, followed by activation of MPO, NE, and PAD4. PAD4 is an enzyme that catalyzes citrullination of histones and promotes chromatin de-condensation with reactive oxygen species (ROS) to induce gradual separation and loss of the nuclear membrane.…”

Neutrophil Extracellular Traps in the Infarct-Related Coronary Artery—A Marker or Mediator of Adverse Outcome?

“…Yet, excessive NET formation or reduced NET breakdown by deoxyribonucleases (DNase) may be harmful and enhance atherothrombosis mechanistically and clinically, in a range of scenarios. 4 5 6 7…”