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Fatal dysfunction and disintegration of thrombin-stimulated platelets
Oleg V Kim1,2, Tatiana A Nevzorova3, Elmira R Mordakhanova3
1University of Pennsylvania Perelman School of Medicine, Department of Cell and Developmental Biology, Philadelphia, PA, USA.
Haematologica
|February 23, 2019
Summary
Thrombin-activated platelets disintegrate into fragments, revealing a unique, calpain-dependent cell death pathway. This process involves metabolic collapse and cytoskeletal changes, suggesting a novel mechanism for platelet clearance in thrombosis.
Area of Science:
- Hematology
- Cell Biology
- Biochemistry
Background:
- Platelets are crucial for hemostasis and thrombosis.
- The fate of activated platelets after their function is largely unknown.
- Thrombin is a key physiological stimulant of platelet activation.
Purpose of the Study:
- To investigate the late-stage structural, metabolic, and functional consequences of thrombin-induced platelet activation.
- To elucidate the mechanisms underlying platelet disintegration following thrombin stimulation.
- To determine if this process represents a unique form of programmed cell death.
Main Methods:
- Confocal and electron microscopy (scanning and transmission)
- Flow cytometry
- Biochemical and biomechanical measurements
- Assessment of platelet activation markers, mitochondrial function, ATP levels, and cytoskeletal rearrangements
Main Results:
- Thrombin stimulation leads to time-dependent platelet dysfunction and disintegration within ~30 minutes.
- Platelet fragmentation involves Ca2+ influx, integrin activation, phosphatidylserine exposure, mitochondrial depolarization, ROS generation, ATP depletion, and cytoskeletal rearrangement.
- Thrombin-induced platelet death is mediated by calpain activation, not caspases 3 and 7.
- This pathway shares similarities with programmed cell death but is unique to platelets.
Conclusions:
- Thrombin-activated platelets undergo a distinct calpain-dependent death pathway.
- Platelet fragmentation represents a unique form of cellular destruction.
- This process may contribute to enhanced platelet elimination in prothrombotic states.
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