title: Stimulation of Erythrocyte Cell Membrane Scrambling by Adarotene.
abstract: OBJECTIVE
  The atypical retinoid E23-(40-hydroxyl-30-adamantylbiphenyl-4-yl) acrylic acid (ST1926, adarotene) is used in the treatment of malignancy. The effect of ST1926 is at least in part due to stimulation of apoptosis. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal death of erythrocytes. Hallmarks of eryptosis include cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Signaling involved in the stimulation of eryptosis includes increase of cytosolic Ca2+ activity [Ca2+]<Sub>i</Sub>, oxidative stress and ceramide. The present study explored, whether adarotene induces eryptosis and, if so, to test for the involvement of Ca2+ entry, oxidative stress and ceramide.
  
  
  METHODS
  Flow cytometry was employed to estimate phosphatidylserine exposure at the cell surface from annexin-V-binding, cell volume from forward scatter, [Ca2+]<Sub>i</Sub> from Fluo3-fluorescence, reactive oxygen species (ROS) formation from DCFDA dependent fluorescence, and ceramide abundance utilizing specific antibodies.
  
  
  RESULTS
  A 48 hours exposure of human erythrocytes to adarotene (9 µM) significantly increased the percentage of annexin-V-binding cells, an effect paralleled by significant decrease of forward scatter, as well as significant increase of Fluo3-fluorescence, DCFDA fluorescence, and ceramide abundance. The effect of adarotene (9 µM) on annexin-V-binding was significantly blunted but not abolished by removal of extracellular Ca2+.
  
  
  CONCLUSIONS
  Adarotene stimulates phospholipid scrambling of the erythrocyte cell membrane, an effect paralleled by and at least in part due to Ca2+ entry, oxidative stress and ceramide.
authors.forename: Morena
authors.initials: M
authors.lastname: Mischitelli
authors.forename: Mohamed
authors.initials: M
authors.lastname: Jemaàa
authors.forename: MyriamFezai
authors.initials: M
authors.lastname: Fezai
authors.forename: Mustafa
authors.initials: M
authors.lastname: Almasry
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
authors.forename: Caterina
authors.initials: C
authors.lastname: Faggio
mesh_terms: D002118:Calcium / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D000072817:Eryptosis / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000187:drug effects*; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005452:Fluoresceins / Q000737:chemistry; D006801:Humans; D008856:Microscopy, Fluorescence; D018384:Oxidative Stress / Q000187:drug effects; D010718:Phosphatidylserines / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012176:Retinoids / Q000494:pharmacology*
chemical_list: D002518:Ceramides; D005452:Fluoresceins; D010718:Phosphatidylserines; D017382:Reactive Oxygen Species; D012176:Retinoids; C029569:diacetyldichlorofluorescein; D002118:Calcium; C573390:adarotene
keywords: Calcium; Cell volume; Ceramide; Eryptosis; Phosphatidylserine