Atherosclerosis Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Department of Biochemistry, Medical School, Cellular & Molecular Research Center, Medical Basic Sciences Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Biochim Biophys Acta Mol Cell Biol Lipids. 2022 Jan;1867(1):159069. doi: 10.1016/j.bbalip.2021.159069. Epub 2021 Oct 28.
Imbalanced cholesterol metabolism in the brain is one of the main pathophysiological mechanisms involved in Alzheimer's disease. We investigated the effect of amyloid-beta (Aβ) on the main proteins involved in regulation of cholesterol metabolism along with cholesterol content in astrocytes and neurons.
Astrocytes and neurons were cultured and treated with Aβ. Apolipoprotein E (apoE) level in the cells and conditioned media, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR), ATP-binding cassette transporter A1 (ABCA1), and cytochrome P450 46A1 (CYP46A1) in cell lysates were determined using immunoblotting. Astrocyte media was added to the Aβ-pretreated neurons then, HMGCR was assessed. Cholesterol was measured in both cells and media.
Aβ caused a significant increase in HMGCR and ABCA1 protein levels and cholesterol content in both cells without increasing cholesterol efflux. A similar increase was seen for cellular apoE level in astrocytes with no changes in media with a significant reduction of cholesterol efflux. HMGCR level was restored to near control level when Aβ-pretreated neurons were exposed to media from culture astrocytes.
Almost all events related to cholesterol homeostasis in neurons and astrocytes, are somehow affected by Aβ. However, because ABCA1 has the most important role(s) in brain cholesterol homeostasis, all subsequent events associated with astrocytes-cholesterol synthesis and its shuttling to neurons are influenced by the effects of Aβ on ABCA1 which could likely be responsible for altered brain cholesterol metabolism in Alzheimer's disease.
大脑中胆固醇代谢失衡是阿尔茨海默病的主要病理生理机制之一。我们研究了淀粉样蛋白-β（Aβ）对调节胆固醇代谢的主要蛋白以及星形胶质细胞和神经元中胆固醇含量的影响。
培养星形胶质细胞和神经元，并用 Aβ 处理。用免疫印迹法测定细胞和条件培养基中的载脂蛋白 E（apoE）水平、细胞裂解物中的 3-羟基-3-甲基戊二酰辅酶 A 还原酶（HMGCR）、ATP 结合盒转运蛋白 A1（ABCA1）和细胞色素 P450 46A1（CYP46A1）。将 Aβ 预处理的神经元加入星形胶质细胞培养基，然后评估 HMGCR。测定细胞和培养基中的胆固醇。
Aβ 显著增加了两种细胞中的 HMGCR 和 ABCA1 蛋白水平和胆固醇含量，而没有增加胆固醇外排。星形胶质细胞中的细胞 apoE 水平也出现类似增加，但培养基中没有变化，胆固醇外排显著减少。当 Aβ 预处理的神经元暴露于星形胶质细胞培养物的培养基时，HMGCR 水平恢复到接近对照水平。
神经元和星形胶质细胞中几乎所有与胆固醇稳态相关的事件都受到 Aβ 的影响。然而，由于 ABCA1 在大脑胆固醇稳态中具有最重要的作用，所有与星形胶质细胞-胆固醇合成及其转运到神经元相关的后续事件都受到 Aβ 对 ABCA1 的影响，这可能是阿尔茨海默病中大脑胆固醇代谢改变的原因。
