Dissecting the Acid Ceramidase Pathway in Hepatic Fibrogenesis

摘要 纤维化是慢性肝病导致肝功能衰竭的最终共同途径，其特征是 细胞外基质(ECM)沉积和重构失衡。目前没有FDA批准的 针对这一慢性肝病终点的治疗方法。此外，很少有生物标记物能反映 患者中的疾病特异性通路。肝病治疗新药物和生物标志物的研究进展 纤维化是一个严重的未得到满足的需求。我们的长期目标是开发治疗肝脏疾病的抗肝纤维化疗法。 并开发生物标记物，以确定将从这些疗法中受益最大的患者群体。 我们先前的研究发现了一个抗纤维化的靶点，即酸性神经酰胺酶(ACDase)。靶向aCDase 通过抑制河马途径的关键效应因子YAP/TAZ来改善纤维化，并促进ECM重塑。 我们开发了神经酰胺下调基因的标志性评分，即神经酰胺反应性评分 (CRS)，并证明CRS在晚期纤维化患者中增加。尽管事实是 靶向ACDase改善培养中的活化并抑制其表达以防止肝纤维化 在体内，慢性神经酰胺蓄积可能会有不良副作用。该提案的总体目标是 阐明神经酰胺调节YAP/TAZ、ECM重塑和肝纤维化的机制。我们也 寻求验证CRS作为肝纤维化患者的途径特异性生物标记物。这样做的理由是 项目是了解神经酰胺介导的肝星状细胞活化和肝脏抑制的机制 纤维化将提供一个强有力的科学框架，以促进抗纤维化治疗药物的开发和 患者的生物标记物。为了实现这一目标，这项提议有三个具体目标。在具体目标1中，我们将 确定神经酰胺调节河马信号的机制。在具体目标2中，我们将描述 神经酰胺如何调节细胞外基质重塑。具体目标1和2将通过获得功能和失去 体外功能技术和检测HSC特异性基因敲除小鼠。在具体目标3中，我们将分析 使用已识别的人肝样本，CRS、纤维化分期和纤维化进展之间的相关性 并将确定与CRS相关的临床特征。要达到的机械性理解 从拟议研究的成功完成有望揭示理性疾病的新靶点 对肝纤维化进行改良，这是一种治疗选择有限的疾病。此外，通过澄清 分子机制和定义特定路径的信号，我们的工作将促进个性化药物 适用于肝纤维化患者的治疗方法。

ABSTRACT Fibrosis is the final common pathway in chronic liver disease that leads to liver failure, and is characterized by an imbalance of extracellular matrix (ECM) deposition and remodeling. There are currently no FDA-approved therapies to target this endpoint of chronic liver disease. Moreover, there is a paucity of biomarkers that reflect disease-specific pathways in patients. Development of new therapeutics and biomarkers for patients with hepatic fibrosis is a critical unmet need. Our long-term goal is to develop antifibrotic therapies for the treatment of hepatic fibrosis and to develop biomarkers to define the patient populations that would benefit most from these therapies. Our prior studies discovered an antifibrotic target, the enzyme acid ceramidase (aCDase). Targeting aCDase ameliorates fibrosis by inhibiting YAP/TAZ, key effectors of the Hippo pathway, and promotes ECM remodeling. We developed a signature score of genes downregulated by ceramide, the Ceramide Responsiveness score (CRS), and demonstrated that the CRS is increased in patients with advanced fibrosis. Despite the fact that targeting aCDase in HSCs ameliorates activation in culture and ablating its expression prevents liver fibrosis in vivo, chronic ceramide accumulation may have untoward side effects. The overall objective of the proposal is to clarify the mechanisms by which ceramide regulates YAP/TAZ, ECM remodeling, and hepatic fibrosis. We also seek to validate the CRS as a pathway-specific biomarker in patients with hepatic fibrosis. The rationale for this project is that understanding the mechanisms of ceramide-mediated attenuation of HSC activation and hepatic fibrosis will offer a strong scientific framework to facilitate the development of antifibrotic therapeutics and biomarkers for patients. To achieve this objective, this proposal has three specific aims. In specific aim 1, we will determine the mechanism by which ceramide regulates Hippo signaling. In specific aim 2, we will characterize how ceramide regulates ECM remodeling. Specific aims 1 and 2 will be achieved by gain of function and loss of function techniques in vitro and testing HSC-specific knockout mice. In specific aim 3, we will analyze the correlation between the CRS, fibrosis stage, and fibrosis progression using deidentified human liver samples, and will identify clinical characteristics that correlate with the CRS. The mechanistic understanding to be gained from the successful completion of the proposed studies promises to reveal new targets for rational disease modification in hepatic fibrosis, a disease with limited treatment options available. Furthermore, by clarifying molecular mechanisms and defining a pathway-specific signature, our work will facilitate a personalized medicine approach for patients with hepatic fibrosis.