Cholesterol, the principal sterol in mammalian cells, has been reported to play a role in the pathogenesis of several diseases through autophagy. Due to its insoluble characteristic, all in vitro cholesterol experiments are performed using dimethyl sulphoxide, methyl-β-cyclodextrin, and ethanol co-solvents. To investigate whether the types of solvents have different effects on cholesterol-induced cell behaviors, we analyzed the effects and mechanisms of autophagy induced by solubilized-cholesterol in hepatic cells. We found that both solubilized-cholesterol and involved solvents could induce autophagy. Solubilized-cholesterol could further enhance the LC3-II expression with or without the pre-treatment with lysosomal blockers compared with the single-solvent groups, indicating that cholesterol could sensitize cells to solvents-induced autophagy. Besides, solubilized-cholesterol and single-solvent treatment could repress the activation of AKT-mTOR pathway. Furthermore, cholesterol solubilized in methyl-β-cyclodextrin could induce apoptosis while other solubilized-cholesterol or single solvent groups could not, suggesting that different dissolve methods may affect the cytotoxic of cholesterol. These results strongly suggest that the effect of solvent should be taken into consideration in further in vitro cholesterol studies.

中文翻译：

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肝细胞中可溶性胆固醇诱导自噬的作用和机制：溶剂之间的比较研究。

据报道，胆固醇是哺乳动物细胞中的主要甾醇，通过自噬在多种疾病的发病机制中发挥作用。由于其不溶性，所有体外胆固醇实验均使用二甲基亚砜、甲基-β-环糊精和乙醇共溶剂进行。为了研究不同类型的溶剂是否对胆固醇诱导的细胞行为有不同的影响，我们分析了可溶性胆固醇在肝细胞中诱导自噬的作用和机制。我们发现溶解的胆固醇和涉及的溶剂都可以诱导自噬。与单一溶剂组相比，可溶性胆固醇可以在使用或不使用溶酶体阻断剂预处理的情况下进一步增强 LC3-II 的表达，表明胆固醇可以使细胞对溶剂诱导的自噬敏感。此外，溶解胆固醇和单一溶剂处理可以抑制 AKT-mTOR 通路的激活。此外，溶解在甲基-β-环糊精中的胆固醇可以诱导细胞凋亡，而其他溶解的胆固醇或单一溶剂基团则不能，这表明不同的溶解方法可能会影响胆固醇的细胞毒性。这些结果强烈表明，在进一步的体外胆固醇研究中应考虑溶剂的影响。