Effects of hydroxyurea on the membrane of erythrocytes and platelets in sickle cell anemia.
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.
Covas
Dimas Tadeu
DT
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
de Lucena Angulo
Ivan
I
Vianna Bonini Palma
Patricia
P
Zago
Marco Antonio
MA
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
D000986:Antisickling Agents; D015815:Cell Adhesion Molecules; D010718:Phosphatidylserines; D006918:Hydroxyurea