Regulation of the Asymmetric Distribution of Lipids in Human Erythrocyte Membrane in the Presence of Glycerol and Polyethylene Glycol

Abstract

Cryoprotective agents (CPAs) used to protect erythrocytes during freezing can affect the structural and functional parameters of the membrane, which have an impact on cell viability. The purpose of the study was to examine the effect of glycerol and PEG on the externalization of phosphatidylserine (PS) on the surface of erythrocytes, as well as to determine the role of Ca2+ ions and ATP-dependent processes in the regulation of transmembrane lipid asymmetry in the presence of these CPAs. It was found that the glycerol effect on erythrocytes does not lead to PS externalization. Maintaining the activity of scramblases and flipases in erythrocytes in the presence of glycerol at the level of control parameters allows them to respond similar to native cells to an increase in [Ca2+]in caused by the ionophore A23187 and blocking of ATPase reactions caused by vanadate. The PEG effect contributes to the disruption of the PS distribution in the membrane due to changes in the activity of lipid translocases. However, activation of scramblases and/or inhibition of flipases under the PEG effect does not reach maximum values, as evidenced by an increase in the amount of erythrocytes with externalized PS under cell loading with Ca2+ by ionophore and inhibition of ATP-dependent reactions by vanadate. The effect of PEG on the lipid asymmetry of erythrocyte membranes is apparently mediated by its impact on the Ca2+ level in the cells. Disturbance of the structural parameters of the membrane due to the PS redistribution in the PEG presence, that distinguish it from the glycerol effect, can cause instability of cryopreserved erythrocytes under physiological conditions in vitro.