Ciglitazone and 15d-PGJ2 Induced Suicidal Erythrocyte Death

Abstract

Side effects of peroxisome proliferator activated receptor gamma (PPARgamma) agonists such as ciglitazone include anemia, which in theory could be due to decreased formation or premature death of erythrocytes. A form of suicidal erythrocyte death is eryptosis, which is characterized by cell shrinkage and by breakdown of phosphatidylserine asymmetry leading to phosphatidylserine exposure at the cell surface. Phosphatidylserine-exposing erythrocytes are recognized by macrophages, engulfed, degraded and thus cleared from circulating blood. Triggers of eryptosis include increase in intracellular Ca(2+) concentration. The present study thus explored, whether the PPARgamma agonist ciglitazone or the natural PPARgamma ligand 15deoxy-delta12,14-prostaglandin J2 (15d-PGJ2) are capable to trigger eryptosis. Phosphatidylserine exposure was determined from annexin V binding and cell shrinkage from decrease of forward scatter of human erythrocytes in FACS analysis. Both, ciglitazone (>or= 5 microM) and 15d-PGJ2 (>or= 3 microM), within 24 hours increased phosphatidylserine exposure and at concentrations of 10 microM led to a significant loss of the cell volume. Ciglitazone further stimulated hemolysis, which, however, affected only a fraction of erythrocytes undergoing eryptosis. According to Fluo3 fluorescence of human erythrocytes, 10 microM ciglitazone or 15d-PGJ2 increased intracellular Ca(2+) activity. In conclusion, ciglitazone and 15d-PGJ2 trigger eryptosis at least in part by an increase in the cytosolic Ca(2+) concentration. The effect most likely contributes to the anemia observed following treatment with PPARgamma agonists.