Neutrophil activation and NETosis are the major drivers of thrombosis in heparin-induced thrombocytopenia

Abstract

Heparin-induced thrombocytopenia/thrombosis (HIT) is a serious immune reaction to heparins, characterized by thrombocytopenia and often severe thrombosis with high morbidity and mortality. HIT is mediated by IgG antibodies against heparin/platelet factor 4 antigenic complexes. These complexes are thought to activate platelets leading to thrombocytopenia and thrombosis. Here we show that HIT immune complexes induce NETosis via interaction with FcγRIIa on neutrophils and through neutrophil-platelet association. HIT immune complexes induce formation of thrombi containing neutrophils, extracellular DNA, citrullinated histone H3 and platelets in a microfluidics system and in vivo, while neutrophil depletion abolishes thrombus formation. Absence of PAD4 or PAD4 inhibition with GSK484 abrogates thrombus formation but not thrombocytopenia, suggesting they are induced by separate mechanisms. NETs markers and neutrophils undergoing NETosis are present in HIT patients. Our findings demonstrating the involvement of NETosis in thrombosis will modify the current concept of HIT pathogenesis and may lead to new therapeutic strategies.

High‐dose IVIG plus cangrelor platelet “anesthesia” during urgent heparin‐CPB in a patient with recent SRA‐negative HIT‐thrombosis with persisting platelet‐activating antibodies

“…This finding provides clinical evidence that neutrophils may play an important role in HIT‐associated thrombosis. This observation may support contemporary models of “dynamic intercellular HIT.” 16,17 …”

Aerobic Exercise Attenuates Acute Lung Injury Through NET Inhibition

“…These can be initiated by LPS-TLR4 receptor activation (34), leading to gene transcription and proinflammatory cytokine production. Others have shown that CXCR4 knockdown prevents inflammatory cytokine expression in macrophages by suppressing activation of MAPK and NF-κB signaling pathways (35). A chief aim of the current study was to explore the mechanism by which aerobic exercise training improves ALI using murine primary AMs.…”

Colchicine Reduces Lung Injury in Experimental Acute Respiratory Distress Syndrome

“…Slides were incubated with a rabbit polyclonal anti-myeloperoxidase (MPO, Pa5-16672; ThermoFisher, MA USA) for neutrophil detection, with a rabbit polyclonal anti-histone H3 citrulline R2 + R8 + R17, (Cit-H3, ab5103; ABCAM, Cambridge, United Kingdom) for NETosis and primary antibodies were omitted for negative controls. After washing, sections were incubated with a biotinylated secondary antibody (Vector Laboratories, Burlingame, CA) for 30 minutes, washed, then incubated with avidin-biotin complex (ABC kit) and visualized using diaminobenzidine substrate (Vector Laboratories) (27)(28)(29).…”