H₂O₂-Induced Oxidative Stress Affects SO₄⁼ Transport in Human Erythrocytes

<div><p>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 μM H₂O₂. 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 μM H₂O₂ 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 <i>via</i> 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.</p>