Nazeri Zahra, Mohammadzadeh Ghorban, Rashidi Mojtaba, Azizdoost Shirin, Cheraghzadeh Maryam, Kheirollah Alireza
Department of Biochemistry, Faculty of Medicine, Cellular and Molecular Research Center, Medical Basic Sciences Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Atherosclerosis Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Adv Biomed Res. 2023 Jun 30;12:167. doi: 10.4103/abr.abr_245_22. eCollection 2023.
Elevated brain cholesterol increases the risk of Alzheimer's disease. Production of 24-hydroxycholesterol (24s-OHC) by neurons prevents cholesterol accumulation in the brain. In this study, we investigated the effect of 24s-OHC on the HMG-COA reductase and ABCA1 which are involved in the brain cholesterol homeostasis with or without β-amyloid in astrocytes.
Astrocytes were treated with 24s-OHC with or without Aβ. Western blot and real-time polymerase chain reaction were done to detect protein and gene expression of β-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) and ABCA1, respectively. Cholesterol release was determined using a quantitation kit.
Protein levels of HMGCR and ABCA1 were significantly increased by Aβ; however, the 24s-OHC was able to restore their levels and diminish the effect of amyloid-β. Aβ did not have a significant effect on HMGCR expression, while 24s-OHC reduced it by 68%. Aβ-induced ABCA1 expression did not increase cholesterol efflux as the lower levels of cholesterol in conditioned medium of Aβ-treated cells were found.
Our novel findings show that Aβ affects two key elements in the brain cholesterol homeostasis, HMGCR and ABCA1, which are crucial in cholesterol synthesis and efflux. Since 24s-OHC could suppress the Aβ effects on enhancement of HMGCR and ABCA1, therefore the cytochrome P450 46A1 (Cyp46A1), which is exclusively expressed in the central nervous system and responsible for producing of 24s-OHC, could consider as a therapeutic target in the cholesterol-related neurodegenerative diseases such as Alzheimer's disease.
脑胆固醇升高会增加患阿尔茨海默病的风险。神经元产生的24-羟基胆固醇（24s-OHC）可防止胆固醇在大脑中蓄积。在本研究中，我们研究了24s-OHC对星形胶质细胞中参与脑胆固醇稳态的HMG-COA还原酶和ABCA1的影响，无论有无β-淀粉样蛋白。
用24s-OHC处理星形胶质细胞，同时或不同时加入Aβ。分别进行蛋白质免疫印迹法和实时聚合酶链反应以检测β-羟基-3-甲基戊二酰辅酶A还原酶（HMGCR）和ABCA1的蛋白质和基因表达。使用定量试剂盒测定胆固醇释放。
Aβ显著增加了HMGCR和ABCA1的蛋白质水平；然而，24s-OHC能够恢复它们的水平并减弱淀粉样β蛋白的作用。Aβ对HMGCR表达没有显著影响，而24s-OHC使其降低了68%。Aβ诱导的ABCA1表达并未增加胆固醇流出，因为在Aβ处理细胞的条件培养基中发现胆固醇水平较低。
我们的新发现表明，Aβ影响脑胆固醇稳态中的两个关键要素HMGCR和ABCA1，它们在胆固醇合成和流出中至关重要。由于24s-OHC可以抑制Aβ对HMGCR和ABCA1增强的作用，因此在中枢神经系统中特异性表达并负责产生24s-OHC的细胞色素P450 46A1（Cyp46A1）可被视为胆固醇相关神经退行性疾病如阿尔茨海默病的治疗靶点。
