Relationship between activation and apoptosis in platelets.

Phosphatidylserine (PS) externalization is a marker for the nucleated cell apoptosis, and refers cellular activation rather than apoptosis in platelets. On the other hand, several similarities exist between platelet activation and apoptosis in nucleated cells. Herewith we investigated the relationship between platelet activation and platelet apoptosis. Platelets isolated from fresh blood of 22 healthy volunteers were incubated with and without calcium ionophore A23187. Platelet activation was evaluated with CD62P and CD63 antibodies, whereas apoptosis with intracellular anti caspase 3-antibody and JC-1 cationic dye. In order to detect PS externalization we used Annexin V by flow cytometry at the beginning, 20th min and 5th hours of the incubation, respectively. There were positive correlations between caspase-3 activation and PS externaization, ∆Ψm depolarization, CD63, and also between PS externaization and CD62P in incubations with A23187 at 5th hours of incubations. These results suggest that there is a relationship between activation and apoptosis in platelets, and platelet activation may progress to platelet apoptosis.