title: Sensitization of erythrocytes to suicidal erythrocyte death following water deprivation.
abstract: OBJECTIVE
  Klotho deficiency results in excessive formation of 1,25(OH)2D3, accelerated ageing and early death. Moreover, klotho deficiency enhances eryptosis, the suicidal erythrocyte death characterized by phosphatidylserine exposure at the erythrocyte surface. Triggers of eryptosis include increase of cytosolic Ca(2+)-activity ([Ca(2+)]i), glucose depletion, hyperosmotic shock and oxidative stress. Klotho expression is decreased and 1,25(OH)2D3-formation enhanced by dehydration. The present study thus explored whether dehydration influences eryptosis.
  
  
  METHODS
  Blood was drawn from hydrated or 36h dehydrated mice. Plasma osmolarity was determined by vapour pressure method, plasma 1,25(OH)2D3 and aldosterone concentrations using ELISA, and plasma Ca(2+)-concentration utilizing photometry. Erythrocytes were exposed to Ca(2+)-ionophore ionomycin (1 µM, 30 min), energy depletion (12 h glucose removal), hyperosmotic shock (500 mM sucrose added, 2 h) and oxidative stress (100 µM tert-butyl-hydroperoxide, 30 min) and phosphatidylserine exposure at the erythrocyte surface estimated from annexin V binding.
  
  
  RESULTS
  Dehydration increased plasma osmolarity and plasma 1,25(OH)2D3 and aldosterone concentrations. Dehydration did not significantly modify phosphatidylserine-exposure of freshly drawn erythrocytes but significantly enhanced the increase of phosphatidylserine-exposure under control conditions and following treatment with ionomycin, glucose-deprivation, hyperosmolarity or tert-butyl-hydroperoxide.
  
  
  CONCLUSIONS
  Dehydration sensitizes the erythrocytes to spontaneous eryptosis and to the triggering of eryptosis by excessive Ca(2+)-entry, energy depletion, hyperosmotic shock and oxidative stress.
authors: Department of Physiology, University of Tuebingen, Tuebingen, Germany.
authors: Majed
authors: M
authors: Abed
authors: Martina
authors: M
authors: Feger
authors: Kousi
authors: K
authors: Alzoubi
authors: Tatsiana
authors: T
authors: Pakladok
authors: Leonie
authors: L
authors: Frauenfeld
authors: Corinna
authors: C
authors: Geiger
authors: Syeda T
authors: ST
authors: Towhid
authors: Florian
authors: F
authors: Lang
mesh_terms: D000818:Animals; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D003681:Dehydration / Q000378:metabolism* / Q000473:pathology*; D004912:Erythrocytes / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D014868:Water Deprivation / Q000502:physiology*