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Haematologica. 2019 Aug 29. pii: haematol.2018.215145. doi: 10.3324/haematol.2018.215145. [Epub ahead of print]

Appropriation of GPIbα from platelet-derived extracellular vesicles supports monocyte recruitment in systemic inflammation.

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Institute of Cardiovascular Sciences, College of Medicine and Dentistry, University of Birmingham, Birmingham, UK
NIHR Surgical Reconstruction and Microbiology Research Centre, Institute of Inflammation and Ageing, Birmingham University Medical School, Birmingham, UK
Centre of Membrane Proteins and Receptors, University of Birmingham and Nottingham, The Midlands, UK
Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia


Interactions between platelets, leukocytes and the vessel wall provide alternative pathological routes of thrombo-inflammatory leukocyte recruitment. We found that when platelets were activated by a range of agonists in whole blood, they shed platelet-derived extracellular vesicle which rapidly and preferentially bound to blood monocytes compared to other leukocytes. Platelet-derived extracellular vesicle binding to monocytes was initiated by P-selectin-dependent adhesion and was stabilised by binding of phosphatidylserine. These interactions resulted in the progressive transfer of the platelet adhesion receptor GPIbα to the monocytes. GPIbα+-monocytes tethered and rolled on immobilised von Willebrand Factor or were recruited and activated on endothelial cells treated with TGF-β1 to induce the expression of von Willebrand Factor. In both models monocyte adhesion was ablated by a function-blocking antibody against GPIbα. Monocytes could also bind platelet-derived extracellular vesicle in mouse blood in vitro and in vivo. Intratracheal instillations of diesel nanoparticles, to model chronic pulmonary inflammation, induced accumulation of GPIbα on circulating monocytes. In intravital experiments, GPIbα+-monocytes adhered to the microcirculation of the TGF-β1-stimulated cremaster muscle, while in the ApoE knockout model of atherosclerosis, GPIbα+-monocytes adhered to the carotid arteries. In trauma patients, monocytes bore platelet markers within 1 hour of injury, the levels of which correlated with severity of trauma and resulted in monocyte clearance from the circulation. Thus, we have defined a novel thrombo-inflammatory pathway in which platelet-derived extracellular vesicle transfer a platelet adhesion receptor to monocytes, allowing their recruitment in large and small blood vessels, and which is likely to be pathogenic.


Atherosclerosis; Granulocytes, Monocytes, Macrophages; Platelets; Thrombo-Inflammation; Vascular Wall Biology and Platelet Adhesion

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