Abstract
Sialic acids are substituted neuraminic acid derivatives which are typically found at the outermost end of glycan chains on the membrane in all cell types. The role of erythrocyte membrane sialic acids during aging has been established however the relationship between sialic acid and oxidative stress is not fully understood. The present work was undertaken to analyze the relationship between erythrocyte membrane sialic acid with its plasma level, membrane and plasma lipid hydroperoxide levels and plasma total antioxidant capacity. Results show that sialic acid content decreases significantly (P< 0.001) in RBC membrane (r= −0.901) and increases in plasma (r= 0.860) as a function of age in humans. Lipid peroxidation measured in the form of hydroperoxides increases significantly (P< 0.001) in plasma (r= 0.830) and RBC membranes (r= 0.875) with age in humans. The Trolox Equivalent Total Antioxidant Capacity (TETAC) of plasma was found to be significantly decreased (P< 0.001,r= −0.844). We observe significant correlations between decrease of erythrocyte membrane sialic acid and plasma lipid hydroperoxide and TETAC. Based on the observed correlations, we hypothesize that increase in oxidative stress during aging may influence the sialic acid decomposition from membrane thereby altering the membrane configuration affecting many enzymatic and transporter activities. Considering the importance of plasma sialic acid as a diagnostic parameter, it is important to establish age-dependent reference.
Highlights
The plasma membrane performs the important cellular function of maintaining cellular integrity and restricting traffic between inside and outside the cell
Our observations show that erythrocyte membrane sialic acid level decreases as a function of age (Fig. 1, Pearson’s r = −0.901, P < 0.001, r2 = 0.788)
The total antioxidant capacity (TAC) of plasma measured by CUPRAC methods shows significant negative correlation with age (Fig. 5, Pearson’s r = −0.844, P < 0.001, r2 = 0.609)
Summary
The plasma membrane performs the important cellular function of maintaining cellular integrity and restricting traffic between inside and outside the cell. The variety of intracellular metabolic requirements and extracellular signals necessitate the membrane to be extremely responsive and dynamic [12]. Such functions are only possible when the membrane’s chemical composition is stable and the complex infrastructure remains intact throughout the organism’s lifespan [6]. Several age-dependent changes in erythrocyte biological membrane constituents in humans have been reported [17]. Alterations in the activity of plasma membrane redox system [44], AFR reductase [41], acetylcholinesterase [34], protein [18,44] and lipid oxidation [31] have already been reported
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