H2O2-induced oxidative stress affects SO4= transport in human erythrocytes.

The aim of the present investigation was to verify the effect of H2O2-induced oxidative stress on SO4 = uptake through Band 3 protein, responsible for Cl-/HCO3 - 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 H2O2 effects on hemoglobin-free resealed ghosts of erythrocytes. Oxidative conditions were induced by 30 min exposure of human erythrocytes to different H2O2 concentrations (10 to 300 μM), with or without GSH (glutathione, 2 mM) or curcumin (10 μM), compounds with proved antioxidant properties. Since SO4 = influx through Band 3 protein is slower and better controllable than Cl- or HCO3 - exchange, the rate constant for SO4 = uptake was measured to prove anion transport efficiency, while MDA (malondialdehyde) levels and –SH groups were estimated to quantify the effect of oxidative stress. H2O2 induced a significant decrease in rate constant for SO4 = uptake at both 100 and 300 μMH2O2. 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 H2O2-induced changes in erythrocytes shape. Our results show that: i) 30 min exposure to 300 μMH2O2 reduced SO4 = uptake in human erythrocytes; ii) oxidative damage was revealed by the reduction in rate constant for SO4 = 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) SO4 = 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.