Küçük O, Stoner-Picking J, Yachnin S, Gordon L I, Williams R M, Lis L J, Westerman M P
Section of Hematology/Oncology, Chicago Medical School, Illinois.
Lipids. 1994 Sep;29(9):657-60. doi: 10.1007/BF02536101.
The objective of this study was to investigate the effects of oxysterols (OS), namely 5 alpha-hydroxy-6-ketocholestanol, 6-ketocholestanol and 25-hydroxycholesterol, on specific cell-mediated cytotoxicity by C57BL/6 spleen cells against P815-X2 (a DBA/2 mastocytoma) target cells. Cytolytic T lymphocytes (CTL) were generated by intraperitoneally injecting C57BL/6 mice with P815-X2 tumor cells 10 d prior to the cytotoxicity experiments. Preincubation of CTL with 10(-5) M 5 alpha-hydroxy-6-ketocholestanol and 6-ketocholestanol for 45 min in lipoprotein-depleted medium resulted in an inhibition of cytolytic activity (73 and 43%, respectively) as measured by 4-h 51Cr release. At a concentration of 5 x 10(-6) M, 5 alpha-hydroxy-6-ketocholestanol inhibited CTL activity by 65%, whereas 6-ketocholestanol did not elicit any inhibition. By contrast, 25-hydroxycholesterol did not inhibit CTL at either concentration, although it is known to be a potent inhibitor of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, the rate-limiting enzyme in the cholesterol biosynthetic pathway. When CTL were preincubated with OS in lipoprotein-replete medium, there was no inhibition of CTL activity at the respective concentrations. The results suggest that the inhibition of CTL activity upon short-term incubation with OS is not due to the inhibition of cholesterol synthesis, but may be due to the insertion of OS into the plasma membrane to replace cholesterol and alteration of membrane physical properties.
本研究的目的是调查氧化甾醇（OS），即5α-羟基-6-酮胆甾烷醇、6-酮胆甾烷醇和25-羟基胆固醇，对C57BL/6脾细胞针对P815-X2（一种DBA/2肥大细胞瘤）靶细胞的特异性细胞介导细胞毒性的影响。在细胞毒性实验前10天，通过向C57BL/6小鼠腹腔注射P815-X2肿瘤细胞来产生细胞毒性T淋巴细胞（CTL）。在无脂蛋白培养基中，将CTL与10⁻⁵ M的5α-羟基-6-酮胆甾烷醇和6-酮胆甾烷醇预孵育45分钟，导致细胞溶解活性受到抑制（分别为73%和43%），这通过4小时的⁵¹Cr释放来测定。在5×10⁻⁶ M的浓度下，5α-羟基-6-酮胆甾烷醇抑制CTL活性65%，而6-酮胆甾烷醇未引起任何抑制作用。相比之下，25-羟基胆固醇在两种浓度下均未抑制CTL，尽管它已知是胆固醇生物合成途径中的限速酶3-羟基-3-甲基戊二酰辅酶A还原酶的有效抑制剂。当CTL在富含脂蛋白的培养基中与OS预孵育时，在各自浓度下CTL活性没有受到抑制。结果表明，与OS短期孵育后CTL活性的抑制不是由于胆固醇合成的抑制，而是可能由于OS插入质膜以取代胆固醇并改变膜的物理性质。
