Motoyama Keiichi, Toyodome Hiroshi, Onodera Risako, Irie Tetsumi, Hirayama Fumitoshi, Uekama Kaneto, Arima Hidetoshi
Graduate School of Pharmaceutical Sciences, Kumamoto University, Japan.
Biol Pharm Bull. 2009 Apr;32(4):700-5. doi: 10.1248/bpb.32.700.
Lipid rafts on cell membranes have heterogeneity such as cholesterol-rich microdomains and sphingolipids-rich microdomains. We previously reported that beta-cyclodextrin (beta-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-beta-cyclodextrin (M-beta-CyD) and 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-CyD) on lipid rafts and morphological changes in rabbit RBC (RRBC) were examined, compared to those of beta-CyD. In sharp contrast to beta-CyD, M-beta-CyD and DM-beta-CyD induced morphological changes of RRBC from discocyte to echinocyte. At pre-hemolytic concentrations of beta-CyDs, M-beta-CyD and DM-beta-CyD strongly released cholesterol from cholesterol-rich lipid rafts, compared to beta-CyD. Meanwhile, the lowering effects of DM-beta-CyD on fluorescent sphingomyelin analogue in sphingolipids-rich lipid rafts were more potent than those of beta-CyD and M-beta-CyD. The magnitude of the abilities of M-beta-CyD and DM-beta-CyD to extract membrane constituents was higher than that of beta-CyD, consistent with that of hemolytic activity. Furthermore, DM-beta-CyD and M-beta-CyD, not beta-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-beta-CyD and DM-beta-CyD may be due to the extraction of both cholesterol and proteins from cholesterol-rich lipid rafts of RRBC, although DM-beta-CyD may interact with sphingolipids-rich lipid rafts on RRBC membranes only slightly.
细胞膜上的脂筏具有异质性，例如富含胆固醇的微结构域和富含鞘脂的微结构域。我们之前报道过，β-环糊精（β-CyD）可诱导红细胞（RBC）从盘状细胞形态转变为口形细胞，这可能是由于从RBC膜富含胆固醇的脂筏中提取了胆固醇。在本研究中，与β-CyD相比，检测了甲基-β-环糊精（M-β-CyD）和2,6-二-O-甲基-β-环糊精（DM-β-CyD）对兔红细胞（RRBC）脂筏和形态变化的影响。与β-CyD形成鲜明对比的是，M-β-CyD和DM-β-CyD诱导RRBC从盘状细胞形态转变为棘状细胞。在β-环糊精的预溶血浓度下，与β-CyD相比，M-β-CyD和DM-β-CyD能从富含胆固醇的脂筏中强力释放胆固醇。同时，DM-β-CyD对富含鞘脂的脂筏中荧光鞘磷脂类似物的降低作用比β-CyD和M-β-CyD更强。M-β-CyD和DM-β-CyD提取膜成分的能力大小高于β-CyD，这与溶血活性一致。此外，DM-β-CyD和M-β-CyD而非β-CyD降低了RRBC富含胆固醇的脂筏中的蛋白量。这些结果表明，M-β-CyD和DM-β-CyD诱导RRBC产生更高的溶血活性以及从盘状细胞到棘状细胞的形态变化，可能是由于从RRBC富含胆固醇的脂筏中提取了胆固醇和蛋白质，尽管DM-β-CyD可能仅与RRBC膜上富含鞘脂的脂筏有轻微相互作用。
