Microvesicle Formation Induced by Oxidative Stress in Human Erythrocytes

Extracellular vesicles (EVs) released by different cell types play significant role in many physiological and pathophysiological processes. In physiological conditions red blood cells (RBCs) derived EVs compose 4 - 8% of all circulating EVs, and oxidative stress (OS) as a consequence of different pathophysiological conditions significantly increases the amount of circulated RBC-derived EVs, however the mechanisms of EV formation are not fully defined yet. To analyze OS-induced EV formation and RBCs transformations we used flow cytometry to evaluate cell esterase activity, caspase-3 activity, and band 3 clustering. Band 3 clustering was additionally analyzed by confocal microscopy. Two original laser diffraction-based approaches were used for analysis of cell deformability and band 3 activity. Hemoglobin species were characterized spectrophotometrically. We showed that cell viability in tert-butyl hydroperoxide-induced OS directly correlated with oxidant concentration to cell count ratio, RBCs-derived EVs contained hemoglobin oxidized to hemichrome (HbChr). OS induced caspase-3 activation and band 3 clustering in cells and EVs. Importantly, we showed that OS-induced EV formation is independent from calcium. Presented data indicated that during OS RBCs eliminate HbChr by vesiculation, in order to sacrifice the cell itself thereby prolonging lifespan and delaying the untimely clearance of in all other respects healthy RBCs.