LncRNA as a New Mediator of Bile Acid Homeostasis

 说明(申请人提供)：胆汁酸在脂肪乳化和体内胆固醇清除中起着关键的生理作用。然而，肝脏中胆汁酸的过度积聚会导致胆汁淤积性肝损伤。十年前，胆汁酸研究领域的一项重大突破是发现了负责胆汁酸合成反馈调节的核受体。小分子杂二聚体(SHP)可抑制胆汁酸合成限速酶Cyp7a1和Cyp8b1的表达，这一点在由PI产生的第一只SHP-/-小鼠身上得到证实。我们最近对肝脏SHP调节的研究揭示了与B细胞淋巴瘤蛋白2(Bcl2)的蛋白质-蛋白质相互作用的重要性。随后使用我们的新的肝脏高表达的小鼠进行的RNA-SEQ研究证实了长的非编码RNA(LncRNA)H19在淤胆性肝纤维化中的关键作用。H19与肝癌有关，但对其在肝脏疾病中的生理和分子作用知之甚少。对Bcl2/SHP/H19轴的研究是将胆汁酸信号与核受体调节H19的表达和功能相结合的开创性研究。总体目标是了解LncRNAH19在调节胆汁酸稳态和胆汁淤积性肝纤维化的发展中的作用，包括Bcl2和SHP。中心假设是，通过SHP介导的胆汁酸信号，Bcl2作为一个分子开关来调控H19诱导的胆汁淤积和肝纤维化。目的1：揭示Bcl2在胆汁酸稳态中的重要病理生理作用；2：揭示H19在胆汁淤积性肝纤维化中的重要调节功能；3：确定使H19成为胆汁酸感受器的信号通路。这些实验建立在我们研究胆汁酸代谢和基因表达调控以及基因敲除和转基因小鼠模型的开发和适当使用方面的长期经验基础上。因此，我们的实验室可以唯一地确定和验证胆汁酸信号通路中的一个新的lncRNA H19调节模块。这对人类具有很大的潜在相关性，因为H19在各种人类肝纤维化和肝硬变标本中高度诱导表达。因此，通过拟议的研究阐明的机制洞察可能为开发专门下调H19和减少H19促进胆汁淤积性纤维化的治疗策略铺平道路。

 DESCRIPTION (provided by applicant): Bile acids play critical physiological roles in lipid emulsification and in cholesterol elimination from the body. However, excessive hepatic accumulation of bile acids can lead to cholestatic liver injury. A decade ago, a major breakthrough in the bile acid research field occurred with the identification of the nuclear receptors responsible for feedback regulation of bile acid synthesis. Small heterodimer partner (SHP) was found to inhibit the expression of the rate limiting bile acid synthetic enzymes Cyp7a1 and Cyp8b1, as demonstrated by the first SHP-/- mice, which were generated by the PI. Our recent studies of hepatic SHP regulation have revealed the importance of a protein-protein interaction with B-cell lymphoma protein 2 (Bcl-2). Subsequent RNA-seq studies using our new liver Bcl-2 overexpressed mice identified a critical role for the long non-coding RNA (lncRNA) H19 in cholestatic liver fibrosis. H19 has been implicated in liver cancer, yet very little is know about its physiological and molecular action in liver diseases. The proposed investigation of the Bcl-2/SHP/H19 axis represents a pioneering study in integrating bile acid signaling with nuclear receptor regulation of H19 expression and function. The overall objective is to understand the role of lncRNA H19 in regulating bile acid homeostasis and the development of cholestatic liver fibrosis involving Bcl-2 and SHP. The central hypothesis is that Bcl-2 functions as a molecular switch to dictate H19 induction of cholestasis and liver fibrosis through SHP-mediated bile acid signaling. Aim #1: To uncover a critical pathophysiological role of Bcl- 2 in bile acid homeostasis; Aim #2: To reveal a crucial regulatory function of H19 in cholestatic liver fibrosis; and Aim #3: To define the signaling pathways that make H19 a bile acid sensor. The experiments proposed build on our long-standing experience in studying bile acid metabolism and regulation of gene expression, and the development and appropriate use of knockout and transgenic mouse models. Accordingly, our laboratory is uniquely poised to identify and validate a novel lncRNA H19 regulatory module in the bile acid signaling pathway. This is of great potential human relevance, because H19 expression is highly induced in various human fibrotic and cirrhotic liver specimens. Thus, the mechanistic insights elucidated through the proposed research may pave the way for the development of therapeutic strategies to specifically down regulate H19 and diminish H19 promotion of cholestatic fibrosis.