title: Stimulating Effect of Terfenadine on Erythrocyte Cell Membrane Scrambling.
abstract: OBJECTIVE
  The antihistaminic drug Terfenadine may trigger apoptosis of tumor cells, an effect unrelated to its effect on histamine receptors. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal death of erythrocytes characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Signaling triggering eryptosis include increase of cytosolic Ca2+ activity ([Ca2+]i), oxidative stress, and ceramide. The present study explored, whether Terfenadine is capable to trigger eryptosis.
  
  
  METHODS
  Flow cytometry was employed to estimate phosphatidylserine abundance at the erythrocyte surface from annexin-V-binding, cell volume from forward scatter, [Ca2+]i from Fluo3-fluorescence, abundance of reactive oxygen species (ROS) from 2',7'-dichlorodihydrofluorescein (DCF) diacetate dependent fluorescence, and ceramide abundance at the human erythrocyte surface utilizing specific antibodies. Hemolysis was quantified from haemoglobin concentration in the supernatant.
  
  
  RESULTS
  A 48 hours exposure of human erythrocytes to Terfenadine (≥ 5 µM) significantly increased the percentage of annexin-V-binding cells and triggered hemolysis without significantly modifying the average forward scatter. Terfenadine (7.5 µM) significantly increased Fluo3-fluorescence, but did not significantly modify DCF fluorescence or ceramide abundance. The effect of Terfenadine on annexin-V-binding was significantly blunted but not abolished by removal of extracellular Ca2+. Exposure of human erythrocytes to Ca2+ ionophore ionomycin (1 µM, 15 min) triggered annexin-V-binding, an effect augmented by Terfenadine pretreatment (10 µM, 48 hours).
  
  
  CONCLUSIONS
  Terfenadine triggers phospholipid scrambling of the human erythrocyte cell membrane, an effect in part due to entry of extracellular Ca2+ and in part due to sensitizing human erythrocyte cell membrane scrambling to Ca2+.
authors.forename: Elena
authors.initials: E
authors.lastname: Signoretto
authors.forename: Michela
authors.initials: M
authors.lastname: Castagna
authors.forename: Abdulla
authors.initials: A
authors.lastname: Al Mamun Bhuyan
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D002118:Calcium / Q000378:metabolism; D061207:Calcium Ionophores / Q000494:pharmacology; D002518:Ceramides / Q000378:metabolism; D000072817:Eryptosis / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000187:drug effects*; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism; D005434:Flow Cytometry; D006461:Hemolysis / Q000187:drug effects; D039563:Histamine H1 Antagonists, Non-Sedating / Q000494:pharmacology; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D010718:Phosphatidylserines / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D016593:Terfenadine / Q000494:pharmacology*
chemical_list: D061207:Calcium Ionophores; D002518:Ceramides; D039563:Histamine H1 Antagonists, Non-Sedating; D010718:Phosphatidylserines; D017382:Reactive Oxygen Species; D015759:Ionomycin; D016593:Terfenadine; D002118:Calcium