Neutrophil a-defensins promote thrombosis in vivo by altering fibrin formation, structure, and stability

© 2019 by The American Society of Hematology. Inflammation and thrombosis are integrated, mutually reinforcing processes, but the interregulatory mechanisms are incompletely defined. Here, we examined the contribution of a-defensins (a-defs), antimicrobial proteins released from activated human neutrophils, on clot formation in vitro and in vivo. Activation of the intrinsic pathway of coagulation stimulates release of a-defs from neutrophils. a-Defs accelerate fibrin polymerization, increase fiber density and branching, incorporate into nascent fibrin clots, and impede fibrinolysis in vitro. Transgenic mice (Def 11 ) expressing human a-Def-1 developed larger, occlusive, neutrophil-rich clots after partial inferior vena cava (IVC) ligation than those that formed in wild-type (WT) mice. IVC thrombi extracted from Def 11 mice were composed of a fibrin meshwork that was denser and contained a higher proportion of tightly packed compressed polyhedral erythrocytes than those that developed in WT mice. Def 11 mice were resistant to thromboprophylaxis with heparin. Inhibiting activation of the intrinsic pathway of coagulation, bone marrow transplantation from WT mice or provision of colchicine to Def 11 mice to inhibit neutrophil degranulation decreased plasma levels of a-defs, caused a phenotypic reversion characterized by smaller thrombi comparable to those formed in WT mice, and restored responsiveness to heparin. These data identify a-defs as a potentially important and tractable link between innate immunity and thrombosis