Cholesterol sulfate induces changes in human erythrocyte thermostability

The influence of cholesterol sulfate (CS) on human red blood cell thermosensitivity was studied by flow cytometry and scanning electron microscopy. It was found that the effect of this sterol on erythrocyte stability is biphasic. Exposure of red blood cells (RBC) to the elevated temperature (51 degrees C) induced perturbation of the cell membrane and led to haemolysis. Preincubation of cells with CS at a concentration of 1 x 10(-5) M protected them, to a certain extent, against lysis. In contrast, enrichment of RBCs with CS during the incubation with lower (0.4 x 10(-5) M) or higher (4-8 x 10(-5) M) CS concentrations substantially augmented the fragility of the cells. The fact, that at the sublytic concentrations CS stabilises the cell membrane, may be explained by the ability of this amphipathic compound to link hydrophilic and lipophilic domains of the cell membrane and to increase the degree of the lipid bilayer order. Higher CS concentrations cause cell lysis in a detergent-like manner. Our data support the conclusion that CS can be considered to be a potent thermosensitizer, which enhances the selectivity of biological drug carriers.