Platelet derived microparticles induce factor XII mediated thrombin generation

Spronk H. M. , Kilinc E. , Van Oerle R., Hamulyak K., Renne T., Ten Cate H.

5th International Conference on Thrombosis and Hemostasis Issues in Cancer, Stresa, İtalya, 23 - 25 Nisan 2010, cilt.125 identifier


Platelet derived microparticles induce factor XII mediated thrombin generation H.M. Spronk1 *, E. Kilinc1, R. van Oerle1, K. Hamulyak1, T. Renne2, H. ten Cate1. 1Laboratory for Clinical Thrombosis and Haemostasis, Department of Internal Medicine, Cardiovascular Research Institue Maastricht, Maastricht University, The Netherlands, 2Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden Introduction: Microparticles are small (<1 mm) cell derived vesicles expressing antigens from the ancestor cell at their outer surface. Due to the presence of a procoagulant phospholipid bilayer as well as tissue factor, the main physiological activator of coagulation, microparticles have been linked to the hypercoagulable state in cancer patients. Given the recently described activation of factor XII by platelet derived polyphosphates (polyP), we hypothesized that platelet derived microparicles induce thrombin generation through activation of factor XII. Methods: Isolated human platelets were stimulated by ADP and ionophore or ionophore alone, whereas monocytes were activated by ionophore with and without lipopolysacharide (LPS) activation. Generated microparticles were isolated and characterised for expression of antigens through FACS analysis, tissue factor activity, and quantified using a newly developed ELISA-based method. Results: Platelet derived microparticles expressed mainly antigens also present on platelets and had low tissue factor activity of <1 pM. Microparticles from LPS stimulated monocytes, however, displayed a higher tissue factor activity (>500 pM) as expected. Using a GP1b-specific antibody and detection through an antibody against GPIIb (CD41) alowed for quantification of platelet derived microparticles. Addition of plateletderived microparticles to human normal pooled plasma induced thrombin generation characterised by a lag time of >10 min and a peak height of 100 nM thrombin. Inhibition of the tissue factor pathway, using active site inhibited seven (ASIS), had no effect on thrombin generation. In contrast, platelet derived microparticles failed to induce thrombin generation in factor XII-deficient plasma. Monocyte derived microparticle induced thrombin generation, however, was comparable between normal and fXIIdeficient plasma and almost completely abolished in the presence of ASIS. Conclusions: Monocyte derived microparticles mainly induced thrombin generation through tissue factor, whereas microparticles from platelets activated factor XII mediated coagulation.