Cholesterol and Sphingolipid Metabolism in Alzheimer's Disease

描述（由申请人提供）：我们的长期研究兴趣是提供细胞脂质代谢和神经病理学之间的机制联系。在新的手稿（包括在附录中）和初步研究部分，我们描述了以下线索：1。我们发现，在三重转基因阿尔茨海默病小鼠（AD小鼠）中，酰基辅酶a：胆固醇酰基转移酶1 （ACAT1）的基因失活增加了24(S)-羟基胆固醇含量，减少了大脑中胆固醇的合成，并改善了淀粉样蛋白病理。2. 我们发现，与非转基因小鼠相比，AD小鼠的胆固醇含量、SREBP2（控制胆固醇生物合成基因的转录因子）的mRNA、HMGR（胆固醇生物合成限速酶）的mRNA以及两种相互作用的转录因子——血清反应因子（SRF）和心肌素（心肌素）的mRNA均升高。基于这些线索，在当前的提案中，我们设计了实验来检验两个假设。首先是测试失活大脑中编码胆固醇酯化酶ACAT1的基因是否对治疗AD有治疗价值。第二个是测试特定鞘脂是否通过刺激大脑中胆固醇的生物合成来介导淀粉样蛋白β肽1-42 （Abeta1-42）的作用。目的1：检测24(S)-羟化酶CYP46A1失活对Acat1-/- (A1-)介导的AD小鼠神经元hAPP、HMGR和ABCA1调节的影响。特异性目的2：检测在不同生命阶段灭活Acat1对AD小鼠大脑的影响。特异性目的3：研究Abeta1-42对原代神经元和星形胶质细胞胆固醇和鞘脂代谢的影响。

DESCRIPTION (provided by applicant): Our long-term research interest is to provide mechanistic links between cellular lipid metabolism and neuropathology. In a new manuscript (included in the Appendix) and in the PRELIMINARY STUDIES section, we describe the following leads: 1. We show that genetic inactivation of acyl-CoA: cholesterol acyltransferase 1 (ACAT1) increases 24(S)-hydroxycholesterol content, reduces cholesterol synthesis in the brain, and ameliorates amyloid pathology in the triple transgenic Alzheimer's mice (AD mice). 2. We show that the cholesterol content, the mRNA of SREBP2 (the transcription factor that controls genes involved in cholesterol biosynthesis), the mRNA of HMGR (the rate-limiting enzyme in cholesterol biosynthesis), and the mRNAs of two interacting transcription factors, serum response factor (SRF) and myocardin (MYOCD) are elevated in the AD mice compared to nontransgenic mice. Based on these leads, in the current proposal, we design experiments to test two hypotheses. The first is to test whether inactivating the gene that encodes the cholesterol esterification enzyme ACAT1 in the brain has therapeutic value for treating AD. The second is to test if specific sphingolipid(s) mediate the action of amyloid beta peptide 1-42 (Abeta1-42) by stimulating cholesterol biosynthesis in the brain. We enlist three specific aims: Specific Aim 1: To test the effect of inactivating the enzyme 24(S)-hydroxylase CYP46A1, on Acat1-/- (A1-) mediated modulations on hAPP, HMGR and ABCA1 in AD mice neurons. Specific Aim 2: To test the effect of inactivating Acat1 in AD mouse brains at different time during life. Specific Aim 3: To study the effects of Abeta1-42 on cholesterol and sphingolipid metabolism in primary neurons and astrocytes. PUBLIC HEALTH RELEVANCE: Alzheimer's disease (AD) causes memory loss and cognitive deficits in the elderly, and is the most prevalent neurodegenerative disease in developed countries. Abnormalities in cellular lipid metabolism have been implicated in AD. The outcomes of this proposal may lead to novel, lipid metabolism-based therapies to slow down the progression of this disease.