title: Stimulation of Suicidal Erythrocyte Death by Garcinol.
abstract: OBJECTIVE
  The benzophenone garcinol from dried fruit rind of Garcinia indica counteracts malignancy, an effect at least in part due to stimulation of apoptosis. The proapototic effect of garcinol is attributed in part to inhibition of histone acetyltransferases and thus modification of gene expression. Moreover, garcinol triggers mitochondrial depolarisation. Erythrocytes lack gene expression and mitochondria but are nevertheless able to enter apoptosis-like suicidal death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Stimulators of eryptosis include oxidative stress, energy depletion and Ca2+ entry with increase of cytosolic Ca2+ activity ([Ca2+]i). The present study explored, whether and how garcinol induces eryptosis.
  
  
  METHODS
  To this end, phosphatidylserine exposure at the cell surface was estimated from annexin-V-binding, cell volume from forward scatter, hemolysis from hemoglobin release, [Ca2+]i from Fluo3-fluorescence, ROS formation from DCFDA dependent fluorescence and cytosolic ATP levels utilizing a luciferin-luciferase-based assay.
  
  
  RESULTS
  A 24 hours exposure of human erythrocytes to garcinol (2.5 or 5 µM) significantly increased the percentage of annexin-V-binding cells. Garcinol decreased (at 1 µM and 2.5 µM) or increased (at 5 µM) forward scatter. Garcinol (5 µM) further increased Fluo3-fluorescence, increased DCFDA fluorescence, and decreased cytosolic ATP levels. The effect of garcinol on annexin-V-binding was significantly blunted, but not abolished by removal of extracellular Ca2+.
  
  
  CONCLUSIONS
  Garcinol triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect in part due to stimulation of ROS formation, energy depletion and Ca2+ entry.
authors.affiliation: Department of Physiology, University of Tuebingen, Tuebingen, Germany.
authors.forename: Antonella
authors.initials: A
authors.lastname: Fazio
authors.forename: Marilena
authors.initials: M
authors.lastname: Briglia
authors.forename: Caterina
authors.initials: C
authors.lastname: Faggio
authors.forename: Kousi
authors.initials: K
authors.lastname: Alzoubi
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects*; D004912:Erythrocytes / Q000187:drug effects*; D006801:Humans; D018384:Oxidative Stress; D010743:Phospholipids; D013729:Terpenes / Q000494:pharmacology*
chemical_list: D010743:Phospholipids; D013729:Terpenes; D000255:Adenosine Triphosphate; C054597:garcinol