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P‐selectin is a key surface adhesion molecule for the interaction of platelets with leukocytes. We have shown previously that the N‐terminal domain of Staphylococcus aureusextracellular fibrinogen‐binding protein (Efb) binds to P‐selectin and interferes with platelet‐leukocyte aggregate formation. Here, we aimed to identify the minimal Efb motif required for binding platelets and to characterize its ability to interfering with the formation of platelet‐leukocyte aggregates.

P‐selectin is a key surface adhesion molecule for the interaction of platelets with leukocytes. We have shown previously that the N‐terminal domain of Staphylococcus aureusextracellular fibrinogen‐binding protein (Efb) binds to P‐selectin and interferes with platelet‐leukocyte aggregate formation. Here, we aimed to identify the minimal Efb motif required for binding platelets and to characterize its ability to interfering with the formation of platelet‐leukocyte aggregates. Using a library of synthetic peptides, we mapped the platelet‐binding site to a continuous 20 amino acid stretch. The peptide Efb68‐87was able to bind to resting and, to a greater extent, thrombin‐stimulated platelets in the absence of fibrinogen. Dot blots, pull‐down assays and P‐selectin glycoprotein ligand‐1 (PSGL‐1) competitive binding experiments identified P‐selectin as the cellular docking site mediating Efb68‐87platelet binding. Accordingly, Efb68‐87did not bind to other blood cells and captured platelets from human whole blood under low shear stress conditions. Efb68‐87did not affect platelet activation as tested by aggregometry, flow cytometry and immunoblotting, but inhibited the formation of platelet‐leukocyte aggregates (PLAs). Efb68‐87also interfered with the platelet‐dependent stimulation of neutrophil extracellular traps (NETs) formation in vitro. We have identified Efb68‐87as a novel selective platelet‐binding peptide. Efb68‐87binds directly to P‐selectin and inhibits interactions of platelets with leukocytes that lead to PLA and NET formation. As PLAs and NETs play a key role in thromboinflammation, Efb68‐87is an exciting candidate for the development of novel selective inhibitors of the proinflammatory activity of platelets.

Introduction:Platelet concentrates (PCs) are used to treat or prevent bleeding in patients with impaired platelet function or after injury. However, the standard storage of PCs at room-temperature (RT) increases the risk of bacterial contamination and is associated with reduced platelet functionality due to storage lesions. Our group reported that cold-stored PCs have better functionality compared to RT-stored PCs but reduced in vivocirculation time due to cold-induced apoptosis. In order to investigate cold-stored PCs hemostatic functionality with and without apoptosis inhibition, we established an ex vivomodel simulating physiological conditions of blood flow to evaluate the contribution of cold-stored PCs in thrombus formation.

Introduction: Heparin-induced thrombocytopenia (HIT) is a serious adverse reaction to heparin. Antibodies against platelet factor 4 (PF4) or a heparin/PF4 complex have been reported to activate platelets, neutrophils and possibly endothelial cells, resulting in thrombocytopenia, hypercoagulability and thromboembolic complications. While the impact of anti-PF4/heparin antibodies on platelet, neutrophil and monocyte activation has been extensively studied, the role of endothelial cells in HIT-associated thrombosis remains underexplored. In particular, the interactions between HIT-induced procoagulancy and endothelial cells under dynamic conditions is not completely analyzed. In this report, we investigated how HIT antibodies induce thrombosis in an endothelialized microfluidic system.