Therapy with hydroxyurea is associated with reduced adhesion molecule gene and protein expression in sickle red cells with a concomitant reduction in adhesive properties.
Propagation of the vaso-occlusive process in sickle cell anaemia (SCA) is a complex process involving the adhesion of steady-state SCA patients red cells and reticulocytes to the vascular endothelium. The effect of hydroxyurea therapy (HUT) on the adhesive properties of sickle cells and the expression of adhesion molecule genes by erythroid cells of SCA individuals is not yet fully understood. The expressions of the CD36 gene and the VLA-4-integrin subunit genes, CD49d (alpha-subunit) and CD29 (beta-subunit), were compared in the reticulocytes of steady-state SCA patients and patients on HUT using real-time PCR. Basal adhesion of red cells from these subjects was also compared using static adhesion assays, as was surface protein expression, using flow cytometry. Basal sickle red cell adhesion to fibronectin was significantly greater than that of normal cells (P < 0.01); in contrast, HUT was associated with significantly lower levels (P < 0.01) of red cell adhesion that were similar to those of control cells; this decrease could not be justified solely by altered reticulocyte numbers in this population. Accordingly, flow cytometry demonstrated that reticulocytes from patients on HUT had significantly lower CD36 and CD49d surface expressions (P < 0.01) and, importantly, significantly lower expressions of the CD36, CD49d and CD29 genes (P < 0.05) than reticulocytes of SCA patients not on HUT. Taken together, data support the hypothesis that HUT reduces the adhesive properties of sickle cells and that this decrease appears to be mediated, at least in part, by a decrease in the gene and, consequently, surface protein expression of adhesion molecules such as VLA-4 and CD36.
Gambero
Sheley
S
The Haematology and Haemotherapy Centre, State University of Campinas - UNICAMP, Campinas, Brazil.
Canalli
Andreia A
AA
Traina
Fabiola
F
Albuquerque
Dulcinéia M
DM
Saad
Sara T O
ST
Costa
Fernando F
FF
Conran
Nicola
N
D000328:Adult; D000755:Anemia, Sickle Cell / Q000188:drug therapy* / Q000473:pathology; D018955:CD36 Antigens / Q000096:biosynthesis / Q000235:genetics; D002448:Cell Adhesion / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000096:biosynthesis* / Q000235:genetics; D004341:Drug Evaluation; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology / Q000627:therapeutic use*; D039441:Integrin alpha4 / Q000096:biosynthesis / Q000235:genetics; D039041:Integrin alpha4beta1 / Q000096:biosynthesis / Q000235:genetics; D019012:Integrin beta1 / Q000096:biosynthesis / Q000235:genetics; D008188:Lutheran Blood-Group System; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D012156:Reticulocytes / Q000378:metabolism / Q000473:pathology
C090228:BCAM protein, human; D018955:CD36 Antigens; D015815:Cell Adhesion Molecules; D005353:Fibronectins; D039041:Integrin alpha4beta1; D019012:Integrin beta1; D008188:Lutheran Blood-Group System; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D039441:Integrin alpha4; D006918:Hydroxyurea