The NLRP3 Inflammasome in Platelets Is Upregulated in Sickle Cell Disease and Promotes Platelet Aggregation and In Vitro Thrombosis

Abstract Sickle cell disease (SCD) is a severe monogenic disorder characterized by chronic hemolysis and abnormal coagulation and inflammation. Activated platelets play a critical role at the interphase of thrombosis and inflammation in the disease context. Sensing of free heme, a degradation byproduct of hemoglobin oxidation during hemolysis, involves the pattern recognition receptor nucleotide-binding domain leucine rich repeat containing protein 3 (NLRP3), which typically forms multiprotein inflammasome complexes and controls caspase-1 activity and cleavage of IL-1β not only in immune cells but also platelets. We have shown recently that the NLRP3 inflammasome in platelets controls platelet activation, aggregation, and in vitro thrombus formation, which was dependent on platelet bruton's tyrosine kinase (BTK). The role of the platelet NLRP3 inflammasome and BTK in SCD, however, is unexplored. Platelets were isolated from humanized SCD mice (Townes), which express human sickle hemoglobin, and patients with SCD in steady state and acute vasoocclusive crisis. Platelet NLRP3 activity, as monitored by caspase 1 activation (assessed by fluorescent labeled inhibitor of caspase-1, FLICA), and cleavage and secretion of IL1β (assessed by Western blot and ELISA), was significantly elevated in SCD patients in steady state as compared to healthy subjects (FLICA: mean 340.3 ± 30.2 SD vs. mean 262.2 ± 33.9 SD, p Our data show that the platelet NLRP3 inflammasome is upregulated in SCD via heme, which results in elevated platelet aggregation and in vitro thombus formation, and is potentially targetable using BTK inhibitors for affected patients. Disclosures No relevant conflicts of interest to declare.