title: Enhanced suicidal death of erythrocytes from gene-targeted mice lacking the Cl-/HCO(3)(-) exchanger AE1.
abstract: Genetic defects of anion exchanger 1 (AE1) may lead to spherocytic erythrocyte morphology, severe hemolytic anemia, and/or cation leak. In normal erythrocytes, osmotic shock, Cl(-) removal, and energy depletion activate Ca(2+)-permeable cation channels with Ca(2+)-induced suicidal erythrocyte death, i.e., surface exposure of phosphatidylserine, cell shrinkage, and membrane blebbing, all features typical for apoptosis of nucleated cells. The present experiments explored whether AE1 deficiency favors suicidal erythrocyte death. Peripheral blood erythrocyte numbers were significantly smaller in gene-targeted mice lacking AE1 (AE1(-/-) mice) than in their wild-type littermates (AE1(+/+) mice) despite increased percentages of reticulocytes (AE1(-/-): 49%, AE1(+/+): 2%), an indicator of enhanced erythropoiesis. Annexin binding, reflecting phosphatidylserine exposure, was significantly larger in AE1(-/-)erythrocytes/reticulocytes ( approximately 10%) than in AE1(+/+) erythrocytes ( approximately 1%). Osmotic shock (addition of 400 mM sucrose), Cl(-) removal (replacement with gluconate), or energy depletion (removal of glucose) led to significantly stronger annexin binding in AE1(-/-) erythrocytes/reticulocytes than in AE1(+/+) erythrocytes. The increase of annexin binding following exposure to the Ca(2+) ionophore ionomycin (1 muM) was, however, similar in AE1(-/-) and in AE1(+/+) erythrocytes. Fluo3 fluorescence revealed markedly increased cytosolic Ca(2+) permeability in AE1(-/-) erythrocytes/reticulocytes. Clearance of carboxyfluorescein diacetate succinimidyl ester-labeled erythrocytes/reticulocytes from circulating blood was more rapid in AE1(-/-) mice than in AE1(+/+) mice and was accelerated by ionomycin treatment in both genotypes. In conclusion, lack of AE1 is associated with enhanced Ca(2+) entry and subsequent scrambling of cell membrane phospholipids.
authors.affiliation: Department of Physiology, University of Tübingen, Tübingen, Germany.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Akel
authors.forename: Carsten A
authors.initials: CA
authors.lastname: Wagner
authors.forename: Jana
authors.initials: J
authors.lastname: Kovacikova
authors.forename: Ravi S
authors.initials: RS
authors.lastname: Kasinathan
authors.forename: Valentin
authors.initials: V
authors.lastname: Kiedaisch
authors.forename: Saisudha
authors.initials: S
authors.lastname: Koka
authors.forename: Seth L
authors.initials: SL
authors.lastname: Alper
authors.forename: Ingolf
authors.initials: I
authors.lastname: Bernhardt
authors.forename: Thomas
authors.initials: T
authors.lastname: Wieder
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Huber
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000743:Anemia, Hemolytic / Q000097:blood / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000378:metabolism / Q000473:pathology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005947:Glucose / Q000172:deficiency; D006461:Hemolysis; D006982:Hypertonic Solutions; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009997:Osmotic Pressure; D010718:Phosphatidylserines / Q000378:metabolism; D010976:Platelet Count; D017701:Reticulocyte Count; D012156:Reticulocytes / Q000378:metabolism / Q000473:pathology; D045262:Reticulocytosis; D013395:Sucrose / Q000378:metabolism; D013997:Time Factors
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D017304:Annexin A5; D002712:Chlorides; D006982:Hypertonic Solutions; D007476:Ionophores; D010718:Phosphatidylserines; D015759:Ionomycin; D013395:Sucrose; D005947:Glucose; D002118:Calcium