Abstract
Lipid rafts on cell membranes have heterogeneity such as cholesterol-rich microdomains and sphingolipids-rich microdomains. We previously reported that β-cyclodextrin (β-CyD) induced morphological changes of red blood cells (RBC) from discocyte to stomatocyte, possibly due to extraction of cholesterol from cholesterol-rich lipid rafts of RBC membranes. In this study, the effects of methyl-β-cyclodextrin (M-β-CyD) and 2,6-di-O-methyl-β-cyclodextrin (DM-β-CyD) on lipid rafts and morphological changes in rabbit RBC (RRBC) were examined, compared to those of β-CyD. In sharp contrast to β-CyD, M-β-CyD and DM-β-CyD induced morphological changes of RRBC from discocyte to echinocyte. At pre-hemolytic concentrations of β-CyDs, M-β-CyD and DM-β-CyD strongly released cholesterol from cholesterol-rich lipid rafts, compared to β-CyD. Meanwhile, the lowering effects of DM-β-CyD on fluorescent sphingomyelin analogue in sphingolipids-rich lipid rafts were more potent than those of β-CyD and M-β-CyD. The magnitude of the abilities of M-β-CyD and DM-β-CyD to extract membrane constituents was higher than that of β-CyD, consistent with that of hemolytic activity. Furthermore, DM-β-CyD and M-β-CyD, not β-CyD, lowered the amount of proteins in cholesterol-rich lipid rafts of RRBC. These results suggest that higher hemolytic activity and morphological changes from discocyte to echinocyte in RRBC induced by M-β-CyD and DM-β-CyD may be due to the extraction of both cholesterol and proteins from cholesterol-rich lipid rafts of RRBC, although DM-β-CyD may interact with sphingolipids-rich lipid rafts on RRBC membranes only slightly.
