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Stimulation of suicidal erythrocyte death by PRIMA-1
Caterina Faggio1, Kousi Alzoubi, Salvatrice Calabrò
1Department of Biological and Environmental Sciences, University of Messina, Agata-Messina, Italy.
Background:
The anticarcinogenic drug PRIMA-1 (p53 reactivation and induction of massive apoptosis 1) induces suicidal death of tumor cells, an effect in large part attributed to the up-regulation of the proapoptotic transcription factor p53. Erythrocytes are lacking gene transcription but are nevertheless able to enter eryptosis, a suicidal erythrocyte death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Stimulators of eryptosis include increase of cytosolic Ca(2+)-activity ([Ca(2+)]i) and ceramide formation. The present study tested whether PRIMA-1 stimulates eryptosis.
Methods:
Phosphatidylserine exposure at the cell surface was estimated from annexin V binding, cell volume from forward scatter, [Ca(2+)]i from Fluo3-fluorescence, ceramide abundance from binding of specific antibodies, and ROS formation from DCFDA fluorescence.
Results:
A 48 h exposure of human erythrocytes to PRIMA-1 (25 µM) significantly increased the percentage of annexin-V-binding cells without significantly influencing [Ca(2+)]i or forward scatter. PRIMA-1 (100 µM) induced annexin-V-binding was not significantly blunted by removal of extracellular Ca(2+) or by the caspase-3 inhibitor zVAD. PRIMA-1 (100 µM) further increased the ceramide abundance at the cell surface and ROS formation.
Conclusions:
PRIMA-1 stimulates phosphatidylserine translocation at the erythrocyte cell membrane, an effect at least partially due to up-regulation of ceramide abundance and ROS formation.