Down-regulation of mammalian 3-hydroxy-3-methylglutaryl coenzyme A reductase activity with highly purified liposomal cholesterol.
Down-regulation of mammalian 3-hydroxy-3-methylglutaryl coenzyme A reductase activity with highly purified liposomal cholesterol.
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高纯度脂质体胆固醇下调哺乳动物 3-羟基-3-甲基戊二酰辅酶 A 还原酶活性。
DOI：
10.1046/j.1432-1327.1999.00829.x
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Watson,JA
中科院分区：
文献类型：
--
作者：
Plemenitas,A;Watson,JA
中国仓鼠卵巢 215 细胞 (CHO-215) 无法合成 C27 和 C28 甾醇，因为 4-羧基甾醇脱羧反应存在缺陷 [Plemenitas, A., Havel, C.M. ＆沃森，J.A. (1990)J。生物。化学265, 17012–17017]。因此，CHO-215 细胞的生长依赖于外源代谢功能性胆固醇来源。我们使用 CHO-215 细胞来 (a) 确定鸡蛋卵磷脂脂质体中的高度纯化 (> 99.5%) 胆固醇是否可以下调去抑制的 3-羟基-3-甲基戊二酰辅酶 A (HMG-CoA) 还原酶活性，如果是这样，(b) 确定还原酶催化活性的损失是否与可检测的羟胆固醇衍生物的合成和积累在动力学上相关。 (26–39μm) 支持 CHO-215 的最大生长，并在浓度大于 50μm 时开始抑制 HMG-CoA 还原酶活性。 181.3μm脂质体胆固醇在6小时内实现了还原酶活性的最大抑制（50-60%）。此外，在 3-6 小时的孵育过程中，监管浓度的高度纯化的脂质体 [3H] 胆固醇不会（生物或化学）转化为可检测水平的氧[3H]胆固醇衍生物。最后，广谱细胞色素 P450 抑制剂（咪康唑）对脂质体胆固醇介导的 HMG-CoA 还原酶活性抑制没有影响。这些观察结果表明，(a) 高度纯化的胆固醇，掺入鸡蛋卵磷脂脂质体中，可以发出下调抑制的哺乳动物细胞 HMG-CoA 还原酶活性的信号；(b) 脂质体胆固醇介导的下调是否需要羟胆固醇合成，该产品必须比 24、25 或 26/27 羟基胆固醇更有效。
Chinese hamster ovary‐215 cells (CHO‐215) cannot synthesize C27and C28sterols because of a defect in the reaction that decarboxylates 4‐carboxysterols [Plemenitas, A., Havel, C.M. & Watson, J.A. (1990)J. Biol. Chem.265, 17012–17017]. Thus, CHO‐215 cell growth is dependent on an exogenous metabolically functional source of cholesterol. We used CHO‐215 cells to (a) determine whether highly purified (> 99.5%) cholesterol, in egg lecithin liposomes, could down‐regulate derepressed 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase activity and if so (b) determine whether the loss in reductase catalytic activity correlated kinetically with the synthesis and accumulation of detectable oxycholesterol derivatives.Liposomal cholesterol (26–39 µm) supported maximum CHO‐215 growth and initiated suppression of HMG‐CoA reductase activity at concentrations greater than 50 µm. Maximum suppression (50–60%) of reductase activity was achieved with 181.3 µmliposomal cholesterol in 6 h. Also, regulatory concentrations of highly purified liposomal [3H]cholesterol were not converted (biologically or chemically) to detectable levels of oxy[3H]cholesterol derivatives during 3–6 h incubations. Lastly, a broad‐spectrum cytochrome P450 inhibitor (miconazole) had no effect on liposomal cholesterol‐mediated suppression of HMG‐CoA reductase activity.These observations established that (a) highly purified cholesterol, incorporated into egg lecithin liposomes, can signal the down‐regulation of derepressed mammalian cell HMG‐CoA reductase activity and (b) if oxycholesterol synthesis was required for liposomal cholesterol‐mediated down‐regulation, the products had to be more potent than 24‐, 25‐, or 26‐/27‐hydroxycholesterol.