Plasminogen associates with phosphatidylserine-exposing platelets and contributes to thrombus lysis under flow

Claire S Whyte, Frauke Swieringa, Tom G Mastenbroek, Ausra S Lionikiene, Marcus D Lancé, Paola E J van der Meijden, Johan W M Heemskerk, Nicola J Mutch

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47 Citations (Scopus)

Abstract

The interaction of plasminogen with platelets and their localization during thrombus formation and fibrinolysis under flow are not defined. Using a novel model of whole blood thrombi, formed under flow, we examine dose-dependent fibrinolysis using fluorescence microscopy. Fibrinolysis was dependent upon flow and the balance between fibrin formation and plasminogen activation; with tPA-mediated lysis more efficient than uPA-mediated lysis. Fluorescently-labeled plasminogen radiates from platelet aggregates at the base of thrombi, primarily in association with fibrin. Hirudin attenuates, but does not abolish plasminogen binding, denoting the importance of fibrin. Flow cytometry revealed that stimulation of platelets with thrombin/convulxin significantly increased the plasminogen signal associated with phosphatidylserine (PS)-exposing platelets. Binding was attenuated by tirofiban and Gly-Pro-Arg-Pro amide, confirming a role for fibrin in amplifying plasminogen binding to PS-exposing platelets. Confocal microscopy revealed direct binding of plasminogen and fibrinogen to different platelet subpopulations. Binding of plasminogen and fibrinogen co-localized with PAC-1 in the center of spread platelets. In contrast, PS-exposing platelets were PAC-1 negative and bound plasminogen and fibrinogen in a protruding 'cap'. These data show that different subpopulations of platelets harbor plasminogen by diverse mechanisms and provide an essential scaffold for accumulation of fibrinolytic proteins that mediate fibrinolysis under flow.

Original languageEnglish
Pages (from-to)2568 - 2578
Number of pages11
JournalBlood
Volume125
Issue number16
Early online date23 Feb 2015
DOIs
Publication statusPublished - 16 Apr 2015

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  • Equipment

    Iain Fraser Cytometry Centre

    Andrea Holme (Manager), Linda Duncan (Senior Application Scientist), Ailsa Laird (Technician) & Kate Burgoyne (Technician)

    Institute of Medical Sciences

    Research Facilities: Facility

  • Cite this

    Whyte, C. S., Swieringa, F., Mastenbroek, T. G., Lionikiene, A. S., Lancé, M. D., van der Meijden, P. E. J., Heemskerk, J. W. M., & Mutch, N. J. (2015). Plasminogen associates with phosphatidylserine-exposing platelets and contributes to thrombus lysis under flow. Blood, 125(16), 2568 - 2578. https://doi.org/10.1182/blood-2014-09-599480