Edelfosine Induced Suicidal Death of Human Erythrocytes

Abstract

Background/Aims: The anti-inflammatory, anti-autoimmune, antiparasitic, and anti-viral ether phospholipid edelfosine (1-O-octadecyl-2-O-methylglycero-3-phosphocholine) stimulates apoptosis of tumor cells and is thus considered for the treatment of malignancy. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and phospholipid scrambling of the cell membrane with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include Ca²⁺ entry with increase of cytosolic Ca²⁺ activity ([Ca²⁺]_i) and oxidative stress. The present study explored, whether and how edelfosine induces eryptosis. Methods: Flow cytometry and photometry, respectively, were employed to estimate phosphatidylserine exposure at the cell surface from annexin-V-binding, cell volume from forward scatter, hemolysis from hemoglobin release, [Ca²⁺]_i from Fluo3-fluorescence, and abundance of reactive oxygen species (ROS) from 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence. Results: A 6 hours exposure of human erythrocytes to edelfosine (5 µM) significantly increased the percentage of annexin-V-binding cells, significantly decreased forward scatter, and significantly increased Fluo3-fluorescence, but did not significantly modify DCFDA fluorescence. The effect of edelfosine on annexin-V-binding was significantly blunted, but not abolished by removal of extracellular Ca²⁺. Conclusions: Edelfosine triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect in part due to stimulation of Ca²⁺ entry.