LXR-Dependent Cholesterol Sensing

LXR 依赖性胆固醇传感

• 批准号: 10443955
• 负责人: Ira G Schulman
• 金额: $ 51.87万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-04-01 至 2026-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10443955
• 关键词: Adult; Affect; Agonist; Binding; Biological Models; Cardiovascular Diseases; Cell model; Cells; Cholesterol; Cholesterol Homeostasis; Chronic Disease; Cirrhosis; Collagen; Coupled; Deposition; Diet; Dominant-Negative Mutation; Enterobacteria phage P1 Cre recombinase; Event; Fatty Acids; Fatty acid glycerol esters; Fibrosis; Gene Expression; Genes; Genetic; Genetic Transcription; Heart Diseases; Hepatic; Hepatic Stellate Cell; Hepatocyte; Human; Immune; Impairment; Individual; Infiltration; Inflammation; Inflammatory; LXRalpha protein; Ligands; Link; Liver; Liver Failure; Liver diseases; Mus; Mutation; Myeloid Cells; Non-Insulin-Dependent Diabetes Mellitus; Pathogenesis; Pathologic; Pathology; Patients; Pharmacology; Phenotype; Phenylalanine; Population; Primary carcinoma of the liver cells; Process; Risk; Role; Severity of illness; Signal Transduction; Testing; Time; Tissues; Transcriptional Activation; Transcriptional Coactivator with PDZ-Binding Motif; Transcriptional Regulation; Triglycerides; Tryptophan; Tumor-infiltrating immune cells; United States; cell type; chronic liver disease; experimental study; fatty liver disease; insight; lipid metabolism; liver inflammation; mouse model; non-alcoholic fatty liver disease; nonalcoholic steatohepatitis; novel; response; selective expression; sensor; single-cell RNA sequencing; tool

Project Summary: Non-alcoholic fatty liver disease (NAFLD) is estimated to affect 25% of the adult population in the United States and approximately 25% of NAFLD patients progress to non-alcoholic steatohepatitis (NASH), characterized by liver inflammation, hepatocyte ballooning, and fibrosis. Importantly, NASH increases the risks for cirrhosis, hepatocellular carcinoma, and liver failure. The processes that trigger the progression of NAFLD to NASH or even if there is a true stepwise progression from one pathological state to the other remain to be determined. NAFLD is associated with increases in liver triglycerides and elevated rates of fatty acid synthesis. Nevertheless, since most NAFLD patients do not have NASH, it is not clear if elevated fatty acids alone are sufficient to promote inflammation and fibrosis. Cholesterol is also increased in the livers of patients with NASH and non-esterified cholesterol correlates with disease severity. We reasoned that a unique approach to unraveling the roles of cholesterol in chronic liver diseases would be to reversibly disrupt cholesterol sensing. Liver x receptor alpha (LXRα) functions as an important cholesterol sensor that regulates hepatic fat and cholesterol metabolism at the transcriptional level in response to the direct binding of cholesterol derivatives. To disrupt cholesterol sensing we have generated mouse lines that change tryptophan 441 of LXRα to phenylalanine (W441F). W441F disrupts binding of endogenous cholesterol derived LXR ligands while still allowing transcription regulation by potent synthetic agonists providing a unique tool that blocks the ability of LXRα to sense cholesterol while still allowing pharmacological control. When fed a high fat/high cholesterol diet LXRα W441F mice rapidly (within 4 weeks) develop pathologies associated with NASH. Strikingly W441F mice have decreased hepatic triglycerides but large increases in cholesterol. Therefore, NASH-like phenotypes can arise in the absence of elevated hepatic triglycerides (“cholesterol-dependent NASH”). We hypothesize that decreased LXR activity in W441F hepatocytes leads to cholesterol accumulation which serves as the initiating event promoting inflammation and fibrosis. Furthermore, we propose that elevated hepatic cholesterol promotes NASH, at least in part, via cholesterol-dependent activation of the transcriptional coactivator with PDZ binding motif (TAZ, Wwtr1). TAZ is over expressed in livers of human NASH patients and promotes inflammation and fibrosis when over expressed in mouse models. Finally, our ability to re-establish LXR activity in W441F mice using pharmacological agents provides a unique opportunity to determine if cholesterol- dependent NASH can be reversed. Taken together our proposed studies will provide new insights into the mechanisms by which elevated cholesterol levels contribute to the pathogenesis of NASH and other chronic diseases.

项目概要： 据估计，非酒精性脂肪肝（NAFLD）影响美国25%的成年人口。 大约25%的NAFLD患者进展为非酒精性脂肪性肝炎（NASH）， 其特征在于肝脏炎症、肝细胞气球样变和纤维化。重要的是，NASH增加了风险 治疗肝硬化肝细胞癌和肝功能衰竭引发NAFLD进展的过程 甚至是否存在从一种病理状态到另一种病理状态的真正逐步进展， 测定NAFLD与肝脏甘油三酯增加和脂肪酸合成速率升高有关。 尽管如此，由于大多数NAFLD患者没有NASH，尚不清楚是否仅升高的脂肪酸是 足以促进炎症和纤维化。NASH患者肝脏中的胆固醇也会增加 而非酯化胆固醇与疾病严重程度相关。我们推断，一种独特的方法， 揭示胆固醇在慢性肝病中的作用将是可逆地破坏胆固醇传感。 肝脏x受体α（LXR α）作为一种重要的胆固醇传感器，调节肝脏脂肪和 胆固醇代谢在转录水平上响应胆固醇衍生物的直接结合。 为了破坏胆固醇传感，我们已经产生了小鼠品系，将LXR α的色氨酸441改变为 苯丙氨酸（W441F）。W441 F破坏内源性胆固醇衍生的LXR配体的结合，同时仍 允许通过有效的合成激动剂进行转录调节，从而提供了一种独特的工具， LXR α检测胆固醇，同时仍允许药理学控制。 当喂食高脂肪/高胆固醇饮食时，LXR α W441F小鼠迅速（4周内）出现 与NASH相关的疾病令人惊讶的是，W441F小鼠的肝脏甘油三酯降低，但肝脏甘油三酯水平升高。 胆固醇增加。因此，NASH样表型可以在没有升高的肝细胞凋亡的情况下出现。 甘油三酯（"胆固醇依赖性NASH"）。我们假设W441F中LXR活性降低， 肝细胞导致胆固醇积累，胆固醇积累作为促进 炎症和纤维化。此外，我们认为升高的肝胆固醇促进NASH， 至少部分是通过胆固醇依赖性激活具有PDZ结合基序的转录辅激活因子 (TAZ、Wwtr 1）。TAZ在人类NASH患者的肝脏中过表达，并促进炎症， 当在小鼠模型中过度表达时纤维化。最后，我们在W441F中重建LXR活性的能力 使用药理学试剂的小鼠提供了一个独特的机会来确定胆固醇- 依赖性NASH可以逆转。总之，我们提出的研究将提供新的见解， 胆固醇水平升高导致NASH和其他慢性疾病的发病机制 疾病