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Updated: May 5, 2026
Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets
Published on: November 29, 2024
BH3-mimetic ABT-737 induces strong mitochondrial membrane depolarization in platelets but only weakly stimulates
Armen V Gyulkhandanyan1, Asuman Mutlu1, David J Allen1
1Division of Transfusion Medicine, Department of Laboratory Medicine, The Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada.
Background:
Depolarization of mitochondrial inner transmembrane potential (ΔΨm) is a key biochemical manifestation of the intrinsic apoptosis pathway in anucleate platelets. Little is known, however, about the relationship between ΔΨm depolarization and downstream morphological manifestations of platelet apoptosis, cell shrinkage and microparticle (MP) formation.
Objectives:
To elucidate this relationship in human platelets.
Materials And Methods:
Using flow cytometry, we analyzed ΔΨm depolarization, platelet shrinkage and MP formation in platelets treated with BH3-mimetic ABT-737 and calcium ionophore A23187, well-known inducers of intrinsic platelet apoptosis.
Results:
We found that at optimal treatment conditions (90min, 37°C) both ABT-737 and A23187 induce ΔΨm depolarization in the majority (88-94%) of platelets and strongly increase intracellular free calcium. In contrast, effects of A23187 and ABT-737 on platelet shrinkage and MP formation are quite different. A23187 strongly stimulates cell shrinkage and MP formation, whereas ABT-737 only weakly induces these events (10-20% of the effect seen with A23187, P<0.0001).
Conclusions:
These data indicate that a high level of ΔΨm depolarization and intracellular free calcium does not obligatorily ensure strong platelet shrinkage and MP formation. Since ABT-737 efficiently induces clearance of platelets from the circulation, our results suggest that platelet clearance may occur in the absence of the morphological manifestations of apoptosis.
Insights
Mitochondrial depolarization in platelets doesn't always cause shrinkage or microparticle formation. Platelet clearance from circulation may occur without these typical apoptosis signs.
Area of Science:
- Hematology
- Cell Biology
- Biochemistry
Background:
- Mitochondrial inner transmembrane potential (ΔΨm) depolarization is a hallmark of intrinsic apoptosis in anucleate platelets.
- The link between ΔΨm depolarization and downstream platelet apoptosis morphology, including cell shrinkage and microparticle (MP) formation, is not well understood.
Purpose of the Study:
- To investigate the relationship between ΔΨm depolarization and morphological changes (cell shrinkage, MP formation) during intrinsic apoptosis in human platelets.
Main Methods:
- Human platelets were treated with the BH3-mimetic ABT-737 and the calcium ionophore A23187, known inducers of platelet apoptosis.
- Flow cytometry was employed to analyze ΔΨm depolarization, platelet shrinkage, and MP formation.
Main Results:
- Both ABT-737 and A23187 effectively induced ΔΨm depolarization and increased intracellular free calcium in the majority of platelets.
- A23187 significantly stimulated platelet shrinkage and MP formation, while ABT-737 showed only a weak effect on these morphological changes.
- A significant difference (P<0.0001) was observed in the extent of shrinkage and MP formation induced by the two agents.
Conclusions:
- High levels of ΔΨm depolarization and intracellular calcium do not invariably lead to significant platelet shrinkage and MP formation.
- Platelet clearance from circulation, as induced by ABT-737, can occur independently of the typical morphological signs of apoptosis.
