The adult brain exhibits a characteristic cholesterol homeostasis, with low synthesis rate and active catabolism. Brain cholesterol turnover is possible thanks to the action of the enzyme cytochrome P450 46A1 (CYP46A1) or 24-cholesterol hydroxylase, that transforms cholesterol into 24S-hydroxycholesterol (24S-HC). But before crossing the blood–brain barrier (BBB), this oxysterol, that is the most abundant in the brain, can act locally, affecting the functioning of neurons, astrocytes, oligodendrocytes, and vascular cells. The first part of this review addresses different aspects of 24S-HC production and elimination from the brain. The second part concentrates in the effects of 24S-HC at the cellular level, describing how this oxysterol affects cell viability, amyloid β production, neurotransmission, and transcriptional activity. Finally, the role of 24S-HC in Alzheimer, Huntington and Parkinson diseases, multiple sclerosis and amyotrophic lateral sclerosis, as well as the possibility of using this oxysterol as predictive and/or evolution biomarker in different brain disorders is discussed.

中文翻译：

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24S-羟基胆固醇：脑疾病的细胞效应和变异

成年大脑表现出特征性的胆固醇稳态，具有低合成速率和活性分解代谢。得益于细胞色素P450 46A1（CYP46A1）或24-胆固醇羟化酶的作用，脑胆固醇的转换是可能的，该酶将胆固醇转化为24S-羟基胆固醇（24S-HC）。但是在穿过血脑屏障（BBB）之前，这种在大脑中含量最高的氧固醇可以局部起作用，影响神经元，星形胶质细胞，少突胶质细胞和血管细胞的功能。这篇综述的第一部分讨论了24S-HC产生和从大脑清除的不同方面。第二部分重点研究24S-HC在细胞水平上的作用，描述该氧固醇如何影响细胞活力，β淀粉样蛋白的产生，神经传递和转录活性。最后，