D‐glucose and D‐galactose affect Band 3 protein function and oxidative stress in human erythrocytes

Abstract

Metabolic dysfunctions continuously expose human erythrocytes to sugars present in plasma during their circulatory life span of 120 days. Hyperglycemia in diabetes mellitus causes glycation of proteins along with oxidative stress in erythrocytes. Moreover, acute systemic administration of D‐galactose was used to artificially induce blood senescence in human models as well to mimic galactosemia. The purpose of this study is to understand the effect of D‐glucose and D‐galactose in human erythrocytes and in particular on the function of Band 3 protein, which is an excellent tool for studying the oxidative events on the erythrocyte membrane. Human erythrocytes in vitro were exposed to increasing concentrations of D‐glucose (5‐15‐35 mM) for 3h or D‐galactose (0.1‐3‐5‐10 mM) for 1h. The rate constant for SO4= uptake, accounting for the efficiency of anion exchange through Band 3 protein along with levels of TBARS levels and membrane –SH groups have been measured. When erythrocytes were exposed to high D‐glucose (15–35 mM) for 3 h, TBARS levels and membrane –SH groups were unchanged while the rate constant for SO4= uptake was significantly accelerated with respect to control (5 mM). After exposure to high D‐galactose (5–10 mM) for 1 h, TBARS levels were higher and membrane –SH levels were lower than control, while the rate constant for SO4= uptake was significantly slower with respect to control (0.1 mM). The present findings show that the measurement of the rate constant for SO4= uptake is a suitable tool to monitor the effect of sugars on erythrocytes; hyperglycemia due to high glucose applied for 3 h affects anion exchange capability without producing lipid peroxidation and oxidative protein damage. High concentrations of D‐galactose (> 5 mM) decreased the rate constant for SO4= uptake, induced lipid peroxidation and reduced total sulfhydryl content. Based on this evidence, future studies will evaluate if the acceleration of Band 3 protein in presence of high D‐glucose depends on altered Bp3 conformation, affecting crosslink with Hb, or on altered glycosylation or phosphorylation signaling underlying Band 3 protein function. In addition, alterations of parameters of oxidative stress caused by D‐galactose on the erythrocytes membrane open the view to consider a potential therapeutic strategy ameliorating the damage caused by D‐galactose.