Jagged-Notch signaling in NASH/fibrosis

项目摘要 肥胖是非酒精性脂肪性肝病(NAFLD)的主要危险因素，是 慢性肝病在某些人群中的患病率接近30%。然而，NAFLD实际上可能是 非酒精性脂肪性肝炎(NASH)被认为是疾病前的状态，其定义是肝脏损伤和 相关的炎症和纤维化。NASH没有被批准的药物疗法，因此是增长最快的 肝移植的原因。随着肥胖相关NASH的患病率持续上升，以及可用的肝脏 由于移植仍然有限，这一未得到满足的需求变得更加紧迫。 在肥胖小鼠和因疑似NASH而接受肝活检的患者中，我们观察到一种意想不到的和 肝细胞Notch的异常激活是正常细胞命运决定的关键形态发生途径 肝脏发育。验证性研究表明，Notch活性与 干预前后患者的肝脏炎症和纤维化，并与疾病严重程度进行跟踪 随机临床试验中的活组织检查。我们在这笔赠款的第一个周期中的机械工作表明，诺奇是 导致疾病的原因，如肝细胞特异性Notch功能丧失-通过遗传或药物消融 要么是Notch配体Jagged1，要么是通过阻止Notch转录活性保护小鼠饮食-- 诱导脂肪性肝炎和纤维化，而强制Jagged1或Notch活性加剧炎症和 纤维化表型。为了确定导致Notch活性的下游因素，我们进行了一系列 RNAseq和scRNAseq筛选发现LTBP3是一个新的Notch靶标。在目标1中，我们用小说学习 遗传学和药理学工具是否参与Notch诱导的肝细胞LTBP3分泌增加 肝脏炎症和纤维化，以及这些影响的潜在机制。超越内分泌 通讯，肝细胞可以直接与非实质细胞相互作用，包括肝星状细胞 (HSC)，以确定肥胖诱导的肝脏病理。有趣的是，我们观察到HSC中Notch活性增加 分离自Nash饮食喂养的小鼠；其他初步数据表明，相同的近端信号(Jagged1)可能 介导HSC激活并导致肝纤维化，我们在Aim 2中进行了测试。最后，我们利用一种新的小鼠 目的3：建立可逆性肝细胞Notch活性模型以发现潜在的纤维化消退途径。 实现这项应用的目标将确定Notch诱导的肝脏病理的机制决定因素 并有可能导致新型锯齿状Notch或LTBP3抑制剂在NASH和纤维化方面的应用。

Project Abstract Obesity is the predominant risk factor for Non-Alcoholic Fatty Liver Disease (NAFLD), the leading cause for chronic liver disease with prevalence approaching 30% in certain populations. NAFLD, however, may in fact be considered a “pre-disease” state for Non-Alcoholic Steatohepatitis (NASH), which is defined by liver injury and associated inflammation and fibrosis. NASH has no approved pharmacotherapy, and is thus the fastest-growing reason for liver transplantation. As the prevalence of obesity-related NASH continues to rise, and available livers for transplantation remain limiting, this unmet need grows more urgent. In obese mice and patients undergoing liver biopsy for suspected NASH, we observed an unexpected and aberrant activation of hepatocyte Notch, a morphogenic pathway critical for cell fate decision-making in normal liver development. Validation studies revealed that Notch activity was positively associated with markers of liver inflammation and fibrosis and tracked with disease severity in patients with pre- and post-intervention biopsies in randomized clinical trials. Our mechanistic work in the first cycle of this grant showed that Notch is causal to disease, as hepatocyte-specific Notch loss-of-function – by genetic or pharmacologic ablation of either the Notch ligand Jagged1, or by blocking Notch transcriptional activity – protected mice from diet- induced steatohepatitis and fibrosis, whereas forced Jagged1 or Notch activity exacerbated inflammation and fibrosis phenotypes. To determine downstream factors responsible for Notch activity, we performed a series of RNAseq and scRNAseq screens that revealed LTBP3 as a novel Notch target. In Aim 1, we study with novel genetic and pharmacologic tools whether increased hepatocyte LTBP3 secretion mediates Notch-induced hepatic inflammation and fibrosis, and potential mechanisms of these effects. Beyond endocrine communication, hepatocytes can directly interact with non-parenchymal cells, including hepatic stellate cells (HSC), to determine obesity-induced liver pathology. Intriguingly, we observed increased Notch activity in HSC isolated from NASH diet-fed mice; other preliminary data suggest that the same proximal signal (Jagged1) may mediate HSC activation and lead to liver fibrosis, which we test in Aim 2. Finally, we leverage a novel mouse model of reversible hepatocyte Notch activity to discover potential fibrosis regression pathways in Aim 3. Achieving the goals of this application will identify mechanistic determinants of Notch-induced liver pathology and potentially lead to application of novel Jagged-Notch or LTBP3 inhibitors for NASH and fibrosis.