H(2)O(2)-Induced Oxidative Stress Affects SO(4)(=) Transport in Human Erythrocytes

The aim of the present investigation was to verify the effect of H(2)O(2)-induced oxidative stress on SO(4)(=) uptake through Band 3 protein, responsible for Cl(-)/HCO(3)(-) as well as for cell membrane deformability, due to its cross link with cytoskeletal proteins. The role of cytoplasmic proteins binding to Band 3 protein has been also considered by assaying H(2)O(2) effects on hemoglobin-free resealed ghosts of erythrocytes. Oxidative conditions were induced by 30 min exposure of human erythrocytes to different H(2)O(2) concentrations (10 to 300 μM), with or without GSH (glutathione, 2 mM) or curcumin (10 μM), compounds with proved antioxidant properties. Since SO(4)(=) influx through Band 3 protein is slower and better controllable than Cl(-) or HCO(3)(-) exchange, the rate constant for SO(4)(=) uptake was measured to prove anion transport efficiency, while MDA (malondialdehyde) levels and –SH groups were estimated to quantify the effect of oxidative stress. H(2)O(2) induced a significant decrease in rate constant for SO(4)(=) uptake at both 100 and 300 μM H(2)O(2). This reduction, observed in erythrocytes but not in resealed ghosts and associated to increase in neither MDA levels nor in –SH groups, was impaired by both curcumin and GSH, whereas only curcumin effectively restored H(2)O(2)-induced changes in erythrocytes shape. Our results show that: i) 30 min exposure to 300 μM H(2)O(2) reduced SO(4)(=) uptake in human erythrocytes; ii) oxidative damage was revealed by the reduction in rate constant for SO(4)(=) uptake, but not by MDA or –SH groups levels; iii) the damage was produced via cytoplasmic components which cross link with Band 3 protein; iv) the natural antioxidant curcumin may be useful in protecting erythrocytes from oxidative injury; v) SO(4)(=) uptake through Band 3 protein may be reasonably suggested as a tool to monitor erythrocytes function under oxidative conditions possibly deriving from alcohol consumption, use of drugs, radiographic contrast media administration, hyperglicemia or neurodegenerative diseases.