FTY720-Induced Suicidal Erythrocyte Death

FTY720 is a potent anti-inflammatory drug known to trigger suicidal death or apoptosis of a variety of nucleated cells. Erythrocytes may similarly undergo suicidal erythrocyte death or eryptosis. Hallmarks of eryptosis include cell membrane scrambling and cell shrinkage, which are triggered by increase in cytosolic Ca(2+) concentration and ceramide. The present study explored whether FTY720 stimulates eryptosis. Cell membrane scrambling was determined from annexin V-binding, cell shrinkage from forward scatter in FACS analysis, cytosolic Ca(2+) concentration from Fluo3 fluorescence, ceramide formation from fluorescence-labeled antibody binding and hemolysis from the hemoglobin concentration in the supernatant. Within 48 hours exposure to FTY720 (10 μM) significantly increased annexin V-binding, decreased forward scatter and increased cytosolic Ca(2+) concentration but did not significantly modify ceramide formation. The effects of FTY720 were significantly blunted in the nominal absence of extracellular Ca(2+). In conclusion, at toxic concentrations, FTY720 stimulates suicidal cell death, an effect at least partially due to stimulation of Ca(2+) entry.