Selective triggering of platelet apoptosis, platelet activation or both

Authors

  • Armen V. Gyulkhandanyan,

    1. Division of Transfusion Medicine, Department of Laboratory Medicine, The Keenan Research Centre in the Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, ON, Canada
    Search for more papers by this author
  • Asuman Mutlu,

    1. Division of Transfusion Medicine, Department of Laboratory Medicine, The Keenan Research Centre in the Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, ON, Canada
    Search for more papers by this author
  • John Freedman,

    1. Division of Transfusion Medicine, Department of Laboratory Medicine, The Keenan Research Centre in the Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, ON, Canada
    2. Toronto Platelet Immunobiology Group, Toronto, ON, Canada
    3. Departments of Laboratory Medicine and Pathobiology, and Medicine, University of Toronto, Toronto, ON, Canada
    Search for more papers by this author
  • Valery Leytin

    Corresponding author
    1. Toronto Platelet Immunobiology Group, Toronto, ON, Canada
    2. Departments of Laboratory Medicine and Pathobiology, and Medicine, University of Toronto, Toronto, ON, Canada
    3. Department of Physics, Ryerson University, Toronto, ON, Canada
    • Division of Transfusion Medicine, Department of Laboratory Medicine, The Keenan Research Centre in the Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, ON, Canada
    Search for more papers by this author

Correspondence: Valery Leytin, Transfusion Medicine, St. Michael's Hospital, LKSKI, 209 Victoria Street, Rm. 419, Toronto, ON, Canada M5B 1T8.

E-mail: leytinv@smh.ca

Summary

Anucleate platelets perform two fundamental processes, activation and apoptosis. We elaborated an approach for selective and concurrent stimulation of platelet apoptosis and/or activation, processes important in haemostasis and platelet clearance. Human platelets were treated with BH3 mimetic ABT-737, thrombin, calcium ionophore A23187 and matched diluents. Apoptosis was determined as mitochondrial inner membrane potential (ΔΨm) depolarization and activation as P-selectin exposure. At optimal treatment conditions (90–180 min, 37°C), ABT-737 predominantly induced apoptosis, when 77–81% platelets undergo only ΔΨm depolarization. The ABT-737 impact on ΔΨm depolarization is strongly time- and temperature-dependent, and much higher at 37°C than at room temperature. In contrast, when platelets were treated with thrombin for 15–90 min at either temperature, activation-only was predominantly (79–85%) induced, whereas A23187 triggers both apoptosis and activation (73–81%) when platelets were treated for 15–60 min at 37°C or 15–90 min at room temperature. These data demonstrate that, depending on the triggering stimulus, platelets predominantly undergo ΔΨm depolarization-only, P-selectin exposure-only, or both responses, indicating that platelet apoptosis and activation are different phenomena driven by different mechanisms. The described model provides a basis for studying differential pharmacological manipulation of platelet apoptosis and activation and their role in haemostasis, thrombosis and platelet clearance.

Ancillary