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Thrombospondin binds to monocytes-macrophages and mediates platelet-monocyte adhesion

R L Silverstein, R L Nachman

    The Journal of Clinical Investigation
    |March 1, 1987
    PubMed

    Insights

    Thrombospondin (TSP) acts as a bridge, connecting activated platelets to monocytes. This interaction is crucial for regulating blood clots and initiating atherosclerosis.

    Area of Science:

    • Biochemistry
    • Immunology
    • Cell Biology

    Background:

    • Thrombospondin (TSP) is a multifunctional platelet glycoprotein.
    • It is synthesized by various cells, including monocytes and macrophages.

    Purpose of the Study:

    • To investigate the binding of TSP to macrophages and monocyte-like cells.
    • To determine TSP's role in mediating adhesive interactions between platelets and monocytes.

    Main Methods:

    • Radiolabeled 125I-TSP binding assays on mouse peritoneal macrophages and U937 cells.
    • Rosette formation assay using resting and thrombin-stimulated platelets with human blood monocytes.
    • Inhibition studies using anti-TSP antibodies, TSP, control antibodies, heparin, fibronectin, fibrinogen, and a fibronectin adhesion tetrapeptide.

    Main Results:

    • 125I-TSP bound specifically, saturably, and reversibly to macrophages and U937 cells.
    • Thrombin-stimulated platelets, but not resting platelets, efficiently rosetted monocytes.
    • Anti-TSP antibodies and TSP itself significantly inhibited monocyte-platelet rosetting, while other agents did not.

    Conclusions:

    • TSP mediates the adhesion between activated platelets and monocytes.
    • TSP functions as a molecular bridge linking platelets to monocytes at sites of vascular injury.
    • This interaction is potentially critical for thrombosis regulation and atherosclerosis initiation.

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