Iron release in erythrocytes from patients with beta-thalassemia

Our previous studies have shown that iron is released in a free (desferriox amine-chelatable) form when erythrocytes undergo oxidative stress (incubati on with oxidizing agents or aerobic incubation in buffer for 24-60 h (a mod el of rapid in vitro ageing)). The release is accompanied by oxidative alte rations of membrane proteins as well as by the appearance of senescent anti gen, a signal for termination of old erythrocytes. In hemolytic anemias by hereditary hemoglobin alterations an accelerated removal of erythrocytes oc curs. An increased susceptibility to oxidative damage has been reported in beta-thalassemic erythrocytes. Therefore we have investigated whether an in creased iron level and an increased susceptibility to iron release could be observed in the erythrocytes from patients with beta-thalassemia. Erythroc ytes from subjects with thalassemia intermedia showed an extremely higher c ontent (0 time value) of free iron and methemoglobin as compared to control s. An increase, although non-statistically-significant,was seen in erythroc ytes from subjects with thalassemia major. Upon aerobic incubation for 24h the release of iron in beta-thalassemic erythrocytes was by far greater tha n in controls, with the exception of thalassemia minor. When the individual values for free iron content (0 time) seen in thalassemia major and interm edia were plotted against the corresponding values for HbF, a positive corr elation (P < 0.001) was observed. Also, a positive correlation (P < 0.01) w as seen between the values for free iron release (24h incubation) and the v alues for HbF These results suggest that the presence of HbF is a condition favourable to iron release. Since in beta-thalassemia the persistance of H bF is related to the lack or deficiency of beta chains and therefore to the excess of alpha chains, the observed correlation between h ee iron and HbF , is consistent with the hypothesis by others that excess of alpha chains r epresents a prooxidant factor.