LncRNA as a New Mediator of Bile Acid Homeostasis

 性状（由申请方提供）：胆汁酸在脂质乳化和体内胆固醇清除中发挥关键生理作用。然而，胆汁酸在肝脏的过度积累可导致胆汁淤积性肝损伤。十年前，胆汁酸研究领域的一个重大突破是鉴定了负责胆汁酸合成反馈调节的核受体。发现小异源二聚体伴侣（SHP）抑制速率限制胆汁酸合成酶Cyp 7a 1和Cyp 8b 1的表达，如由PI产生的第一只SHP-/-小鼠所证明的。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（Bcl-2）的蛋白质-蛋白质相互作用的重要性。随后使用我们的新肝脏Bcl-2过表达小鼠的RNA-seq研究确定了长链非编码RNA（lncRNA）H19在胆汁淤积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Bcl-2/SHP/H19轴的拟议研究代表了将胆汁酸信号传导与H19表达和功能的核受体调节相结合的开创性研究。 总体目标是了解lncRNA H19在调节胆汁酸稳态和涉及Bcl-2和SHP的胆汁淤积性肝纤维化的发展中的作用。核心假设是Bcl-2作为分子开关，通过SHP介导的胆汁酸信号传导来指示H19诱导胆汁淤积和肝纤维化。目标一：揭示Bcl- 2在胆汁酸稳态中的关键病理生理作用;目的#2：揭示H19在胆汁淤积性肝纤维化中的关键调节功能;目的#3：确定使H19成为胆汁酸传感器的信号传导途径。提出的实验建立在我们长期以来在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的经验。因此，我们的实验室是唯一准备确定和验证一种新的lncRNA H19调节模块在胆汁酸信号通路。这具有很大的潜在人类相关性，因为H19表达在各种人类纤维化和肝硬化样本中被高度诱导。因此，通过拟议的研究阐明的机制见解可能为开发治疗策略铺平道路，以特异性下调H19并减少H19对胆汁淤积性纤维化的促进作用。

 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.