Shear stress stimuli-induced erythrocytes' mechanical damage, and its relation to erythrocytes' membrane oxidation and cellular aging.

Several similarities between shear-stress-induced mechanically damaged erythrocytes and physiologically aged erythrocytes have been reported, including mechanical fragility, increased aggregability, altered membrane charge, and loss of membrane lipid. Additionally, we found that mechanically circulated blood using a centrifugal blood pump showed an increase in erythrocyte membrane oxidation. This raised the question of how much oxidation can be induced under shear stress and how it relates to cellular aging. Therefore, we investigated membrane oxidation in density-isolated erythrocytes (young and old) exposed to shear conditions. Human stored blood was exposed to shear stresses of 5, 10, 30, 60, and 90 ‍Pa for exposure times of 0, 5, 10, and 15 ‍min. The sheared blood was then layered onto a centrifuge tube preloaded with two Percoll density solutions (1.10 and 1.12 ‍g/ml). After centrifugation, erythrocytes from the two density layers were collected and designated as young and old erythrocytes, which were used as the study samples. Across all shear conditions, old erythrocytes showed higher lipid peroxide fluorescence per unit area compared with young erythrocytes. However, the rate of increase in oxidation before and after shear exposure was greater in young erythrocytes. These findings suggest that there may be a limit to the extent of membrane oxidation.