title: Effects of hydroxyurea on the membrane of erythrocytes and platelets in sickle cell anemia.
abstract: OBJECTIVE
  Adhesion molecules on the surface of erythrocytes, leukocytes and platelets are involved in vascular occlusion in sickle cell anemia. Hydroxyurea treatment of sickle cell anemia patients leads to clinical improvement and reduces the incidence of vaso-occlusive episodes. It has been previously demonstrated that hydroxyurea treatment also reduces the expression of adhesion molecules on the surface of erythrocytes. Phosphatidylserine (PS) exposure on the surface of erythrocytes has been considered to be the main determinant of altered erythrocyte adhesion in sickle cell anemia. In this study we examine the expression of PS on the surface of erythrocytes and platelets of sickle cell anemia patients before and during treatment with hydroxyurea.
  
  
  METHODS
  Blood samples from 15 sickle cell anemia patients were analyzed before and during treatment with hydroxyurea. The profile of PS expression was examined by flow cytometry.
  
  
  RESULTS
  Hydroxyurea was effective, as determined by the patients  clinical improvement and increased hemoglobin (8.3 vs 9.1 g/dL, p< 0.005), F cells (15.9% vs 37.1%, p< 0.005) and mean corpuscular volume ( 82 fL vs 101 fL, p< 0.005). PS expression on the surface of erythrocytes and platelets decreased from 6.27% to 2.96% (p< 0.005) and from 13.5% to 4.7% (p< 0.005), respectively.
  
  
  CONCLUSIONS
  Hydroxyurea treatment reduces PS expression on the surface of erythrocytes and platelets, thus contributing to the favorable effects of this therapy.
authors.affiliation: Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo, Centro de Terapia Celular, CEPID, FAPESP, Ribeirão Preto, SP, Brazil. dimas@fmrp.usp.br
authors.forename: Dimas Tadeu
authors.initials: DT
authors.lastname: Covas
authors.forename: Ivan
authors.initials: I
authors.lastname: de Lucena Angulo
authors.forename: Patricia
authors.initials: P
authors.lastname: Vianna Bonini Palma
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Zago
mesh_terms: D000293:Adolescent; D000328:Adult; D000755:Anemia, Sickle Cell / Q000097:blood / Q000188:drug therapy*; D000986:Antisickling Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects; D002648:Child; D004910:Erythrocyte Membrane / Q000187:drug effects*; D005260:Female; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010718:Phosphatidylserines / Q000378:metabolism
chemical_list: D000986:Antisickling Agents; D015815:Cell Adhesion Molecules; D010718:Phosphatidylserines; D006918:Hydroxyurea