Metabolic indicators of oxidative stress correlate with haemichrome attachment to membrane, band 3 aggregation and erythrophagocytosis in beta-thalassaemia intermedia

Haematological data, genotype, transfusion requirements, metabolic indicato rs of oxidative stress (flux via hexose-monophosphate shunt (HMPS): steady state level of GSH and GSSG, NADPH and NADP: activity of anti-oxidant enzym es), parameters of membrane damage (aggregated band 3; membrane-bound haemi chromes, autologous immunoglobulins (Igs) and C3 complement fragments) and erythrophagocytosis were measured in erythrocytes (RBC) of 15 beta-thalassa emia intermedia patients (nine splenectomized) with low, if any, transfusio n requirements. Patients presented increased aggregated band 3, bound haemi chromes, Igs and C3 complement fragments, and increased erythrophagocytosis . Bound haemichromes strongly correlated with aggregated band 3. Anti-band 3 Igs were predominantly associated with aggregated band 3. Erythrophagocyt osis positively correlated with aggregated band 3, haemichromes and Igs, su ggesting the involvement of haemichrome-induced band 3 aggregation in phago cytic removal of beta-thalassaemic RBC. Splenectomized patients showed high er degrees of membrane damage and phagocytosis, significantly higher number s of circulating RBC precursors, and tendentially higher numbers of reticul ocytes. Basal flux via HMPS was increased twofold, but HMPS stimulation by methylene blue was decreased, as was the glucose nux via HMPS. GSH was rema rkably decreased, whereas NADPH was increased. Except for unchanged catalas e and glutathione reductase, anti-oxidant enzymes had increased activity. N egative correlation between HMPS stimulation by methylene blue and bound ha emichromes indicated that the ability to enhance HMPS may counteract haemic hrome precipitation and limit consequent membrane damage leading to erythro phagocytosis.