Effect of cadmium on anion exchange capability through Band 3 protein in human erythrocytes

The efficiency of Band 3 protein, mediating HCO₃^-/Cl^- exchange across erythrocytes membrane, is reduced by oxidative stress. The aim of the present study was to verify whether Band 3 protein efficiency is compromised by treatment with Cadmium (Cd²⁺), an extremely toxic heavy metal known to interfere with antioxidant enzymes, energy metabolism, gene expression and cell membranes. To this end, the rate constant for SO₄⁼ uptake through Band 3 protein (accounting for velocity of anion exchange) was measured along with membrane –SH groups, Malonyldialdehyde (MDA) and Band 3 protein expression levels in Cd²⁺ -treated human erythrocytes (300 µM, 1 mM). Our results show that Cd²⁺ reduced the rate constant for SO₄⁼ uptake, with a significant increase in MDA levels at both concentrations and with a reduction in –SH groups observed after 1 mM Cd²⁺ treatment, whereas Band 3 protein expression levels were unchanged in both conditions. In conclusion: i) Cd²⁺ reduces Band 3 protein efficiency via different mechanisms depending on metal concentration and with unchanged expression levels; ii) the assessment of Band 3 protein anion exchange capability is a good tool to assay the impact of heavy metals on cell homeostasis and, possibly, useful for diagnosis and monitoring of devalopment of Cd²⁺ toxicity-related pathologies.