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

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 arti!cially induce blood senescence in human models as well to mimic galactosemia. The purpose of this study is to understand the e"ect of D‐glucose and Dgalactose 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 Dglucose (5‐15‐35 mM) for 3h or D‐galactose (0.1‐3‐5‐10 mM) for 1h. The rate constant for SO uptake, accounting for the e#ciency 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 Dglucose (15–35 mM) for 3 h, TBARS levels and membrane –SH groups were unchanged while the rate constant for SO uptake was signi!cantly 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 SO uptake was signi!cantly slower with respect to control (0.1 mM). The present !ndings show that the measurement of the rate constant for SO uptake is a suitable tool to monitor the e"ect of sugars on erythrocytes; hyperglycemia due to high glucose applied for 3 h a"ects anion exchange capability without producing lipid peroxidation and oxidative protein damage. High concentrations of D‐galactose (> 5 mM) decreased the rate constant for SO 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, a"ecting 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.