Decreased Nucleoside Transport and hENT1 Transporter Expression in Beta-Thalassemia Major

Abstract

Objective: This study investigated nucleoside transport activity and transporter polypeptide expression in erythrocytes from β-thalassemia major patients to determine if inhibition of transport activity is a sensitive indicator of oxidative membrane damage. Materials and Methods: Blood samples were obtained from 54 patients, diagnosed as having β-thalassemia major prior to therapeutic transfusion, and 20 normal subjects. Uptake of ³H-uridine into washed erythrocytes was measured at room temperature using short incubation periods (5 s) and a rapid inhibitor oil stop protocol. Erythrocyte membranes were analyzed by SDS-PAGE and nucleoside (hENT1) and glucose (GLUT-1) transporter polypeptides quantitated on immunoblots. Results: Uridine uptake was significantly lower in β-thalassemic cells than in normal erythrocytes (20.03 ± 1.08 pmol/10⁸ cells/ 5 s, mean ± SEM, n = 31, vs. 31.15 ± 1.21 pmol/10⁸ cells/5 s, n = 20; p < 0.0001). Expression of hENT1 was significantly lower in β-thalassemic cells (23.90 ± 1.01 arbitrary units, n = 54) than in controls (101.20 ± 2.43 arbitrary units, n = 20; p < 0.001) but expression of GLUT-1 was not changed appreciably (101.80 ± 2.43 arbitrary units, n = 54, for thalassemic cells; 102.60 ± 3.02 arbitrary units, n = 20, for control cells; p = 0.87). Conclusions: Erythrocytes from β-thalassemia major patients showed decreased uridine transport which was associated with decreased nucleoside transporter expression. The process(es) mediating a selective decrease in hENT1 polypeptides in β-thalassemia major was/were not determined.