title: Evidence for a protective role of the Gardos channel against hemolysis in murine spherocytosis.
abstract: It has been shown that mice with complete deficiency of all 4.1R protein isoforms (4.1-/-) exhibit moderate hemolytic anemia, with abnormal erythrocyte morphology (spherocytosis) and decreased membrane stability. Here, we characterized the Gardos channel function in vitro and in vivo in erythrocytes of 4.1-/- mice. Compared with wild-type, the Gardos channel of 4.1-/- erythrocytes showed an increase in Vmax (9.75 +/- 1.06 vs 6.08 +/- 0.09 mM cell x minute; P < .04) and a decrease in Km (1.01 +/- 0.06 vs 1.47 +/- 1.02 microM; P < .03), indicating an increased sensitivity to activation by intracellular calcium. In vivo function of the Gardos channel was assessed by the oral administration of clotrimazole, a well-characterized Gardos channel blocker. Clotrimazole treatment resulted in worsening of anemia and hemolysis, with decreased red cell survival and increased numbers of circulating hyperchromic spherocytes and microspherocytes. Clotrimazole induced similar changes in 4.2-/- and band 3+/- mice, indicating that these effects of the Gardos channel are shared in different models of murine spherocytosis. Thus, potassium and water loss through the Gardos channel may play an important protective role in compensating for the reduced surface-membrane area of hereditary spherocytosis (HS) erythrocytes and reducing hemolysis in erythrocytes with cytoskeletal impairments.
authors.affiliation: Department of Clinical and Experimental Medicine, Section of Internal Medicine, University of Verona, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: De Franceschi
authors.forename: Alicia
authors.initials: A
authors.lastname: Rivera
authors.forename: Mark D
authors.initials: MD
authors.lastname: Fleming
authors.forename: Marek
authors.initials: M
authors.lastname: Honczarenko
authors.forename: Luanne L
authors.initials: LL
authors.lastname: Peters
authors.forename: Philippe
authors.initials: P
authors.lastname: Gascard
authors.forename: Narla
authors.initials: N
authors.lastname: Mohandas
authors.forename: Carlo
authors.initials: C
authors.lastname: Brugnara
mesh_terms: D000743:Anemia, Hemolytic / Q000473:pathology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003022:Clotrimazole / Q000008:administration & dosage / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000172:deficiency; D006461:Hemolysis / Q000187:drug effects; D007700:Kinetics; D008565:Membrane Proteins / Q000172:deficiency; D051379:Mice; D018345:Mice, Knockout; D011188:Potassium / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors / Q000502:physiology*; D013102:Spherocytes / Q000187:drug effects / Q000473:pathology*; D014867:Water / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D024681:Potassium Channels, Calcium-Activated; C028841:erythrocyte membrane band 4.1 protein; D014867:Water; D003022:Clotrimazole; D011188:Potassium; D002118:Calcium