Fluoxetine Induced Suicidal Erythrocyte Death

The antidepressant fluoxetine inhibits ceramide producing acid sphingomyelinase. Ceramide is in turn known to trigger eryptosis the suicidal death of erythrocytes characterized by cell shrinkage and exposure of phosphatidylserine at the erythrocyte surface. Ceramide is effective through sensitizing the erythrocytes to the pro-eryptotic effect of increased cytosolic Ca(2+) activity ([Ca(2+)](i)). In nucleated cells, fluoxetine could either inhibit or stimulate suicidal death or apoptosis. The present study tested whether fluoxetine influences eryptosis. To this end cell volume was estimated from forward scatter, phosphatidylserine exposure from annexin V binding, hemolysis from hemoglobin release and [Ca(2+)](i) from Fluo-3 fluorescence intensity. As a result, a 48 h exposure of erythrocytes to fluoxetine (≥25 µM) significantly decreased forward scatter, increased annexin V binding and enhanced [Ca(2+)](i). The effect on annexin V binding was significantly blunted, but not abolished, in the absence of extracellular Ca(2+). In conclusion, fluoxetine stimulates eryptosis, an effect at least in part due to increase of cytosolic Ca(2+) activity.