Mechanisms of synergistic regulation of biliary inflammation and fibrosis

美国退伍军人因滥用酒精和毒素以及肝炎病毒而患肝病的风险越来越大 死亡率高，是住院和死亡的最常见原因之一。肝纤维化疾病代表 最大的一组疾病，没有有效的治疗方法，因此表示一种严重的未得到治疗的疾病 医疗需要。肝纤维化患者的唯一选择往往是器官移植。慢性肝病 包括以胆管细胞为靶点的胆管病，如原发性硬化性胆管炎(PSC) 以胆管增生、炎症和进行性纤维化为特征。无拘无束的胆管细胞 增殖可发展为胆道癌(即胆管癌，CCA)，而PSC患者 更易发生CCA。此外，胆管细胞在PSC期间表现出衰老的表型。 可能通过激活肝星状细胞促进炎症并进一步影响肝纤维化。 (HSCs)。已有研究表明，受损的胆管细胞分泌衰老相关的分泌表型。 (SASP)。肥大细胞(MC)在包括肝脏疾病在内的多种病理过程中起着重要作用，但 在正常的、体内平衡的肝脏中发现的数量很低。接近受损的浸润性肝巨噬细胞 肝内胆管和活化的肝星状细胞。在未公布的数据中，我们发现受损、衰老 胆管细胞在非酒精性脂肪性肝病中诱导MC迁移。此外，衰老的胆管细胞 分泌干细胞因子(SCF)和白介素类已知对MC具有趋化作用的因子， 诱导迁徙。迁移和激活后，MC释放包括大量 刺激胆管细胞增殖和纤维化的组胺。我们建议的理由是建立在 之前发表的来自我们实验室和其他实验室的数据显示，PSC和CCA患者的MC渗透增加 与啮齿类动物的肝损伤模型一样，MC的浸润与肝纤维化的增加呈正相关。 此外，注射培养的小鼠的正常野生型小鼠(通常很少的肝小鼠)显示增加。 胆道损害、炎症和肝纤维化，所有这些都是PSC的关键特征。使用PSC模型 (mdr2-/-小鼠)我们用缺乏组氨酸的小鼠饲养mdr2-/-，从而产生了一只双基因敲除小鼠(DKO) 脱羧酶(HDC-/-)。DKO小鼠(少数甚至没有MC)减少了胆道损伤、炎症和肝脏损伤 纤维化症。此外，在将单核细胞重新引入DKO小鼠后，我们发现损伤和纤维化显著增加 当缺乏转化生长因子-β1信号的MC被用来展示 MC在PSC中的关键作用。最后，抑制MC衍生的组胺可减少胆道损害和肝脏损害。 胆汁淤积性肝损伤、PSC和CCA模型中的纤维化提示MCs介质的调节可能 证明是有治疗作用的。我们提出了衰老的胆管细胞诱导MC的工作假说 PSC过程中的迁移和MC来源的转化生长因子-β1或FXR调节导管反应和 胆汁衰老所致的肝纤维化。我们提出了以下具体目标(SA)：(SA1)衰老 在PSC期间，胆管细胞通过分泌特定的SASP将MCs招募到肝脏；(SA2)MCs促进肝脏和 正常小鼠或缺乏MCs的小鼠出现类似PSC的胆道损伤、炎症和肝纤维化；以及 (SA3)在PSC过程中，MC通过组胺、 转化生长因子-β-1和FXR。

The risk of liver diseases due to alcohol and toxin abuse and hepatitis viruses in US Veterans is increasingly high and is one of the most common reasons for hospitalization and mortality. Hepatic fibrotic disease represents one of the largest groups of disorders for which there is no effective therapy and thus denotes a major unmet medical need. Often the only option for patients with liver fibrosis is organ transplantation. Chronic liver diseases include cholangiopathies that target cholangiocytes such as Primary Sclerosing Cholangitis (PSC) which is characterized by biliary proliferation, inflammation and progressive fibrosis. Unrestrained cholangiocyte proliferation can develop into cancer of the bile ducts (i.e., cholangiocarcinoma, CCA) and patients with PSC are more susceptible to development of CCA. Further, cholangiocytes display a senescent phenotype during PSC which may contribute to inflammation and further influence hepatic fibrosis by activating hepatic stellate cells (HSCs). It has been shown that damaged cholangiocytes secrete senescence-associated secretory phenotypes (SASP). Mast cells (MCs) are important in mediating numerous pathologies including liver diseases, but are found at very low numbers in normal, homeostatic livers. Infiltrating hepatic MCs are found near damaged intrahepatic bile ducts and activated HSCs. In unpublished data, we have found that damaged, senescent cholangiocytes induce MC migration during non-alcoholic fatty liver disease. Further, senescent cholangiocytes secrete factors like stem cell factor (SCF) and interleukins that are known to be chemoattractants for MCs, inducing migration. Following migration and activation, MCs release mediators including large amounts of histamine that stimulates cholangiocyte proliferation and fibrosis. The rationale for our proposal is built upon previously published data from our lab and others showing that MC infiltration increases in PSC and CCA patients along with rodent models of liver damage, and MC infiltration positively correlates with increased fibrosis. Additionally, normal wild-type mice (typically very few hepatic MCs) injected with cultured MCs display increased biliary damage, inflammation and hepatic fibrosis, all of which are key features of PSC. Using a model of PSC (Mdr2-/- mice) we generated a double knockout mouse (DKO) by breeding Mdr2-/- with mice lacking histidine decarboxylase (HDC-/-). DKO mice (few to no MCs) have decreased biliary damage, inflammation and hepatic fibrosis. Further, upon reintroduction of MCs into DKO mice, we find a striking increase in damage and fibrosis that mimics Mdr2-/- mice, which was reversed when MCs lacking TGF-β1 signaling were used demonstrating a key role for MCs in PSC. Finally, inhibition of MC-derived histamine decreases biliary damage and hepatic fibrosis in models of cholestatic liver injury, PSC and CCA suggesting that modulation of MCs mediators may prove therapeutic. We propose the working hypothesis that senescent cholangiocytes induce MC migration during PSC and modulation of MC-derived TGF-β1 or FXR regulates ductular reaction and hepatic fibrosis via biliary senescence. We propose the following specific aims (SAs): (SA1) Senescent cholangiocytes recruit MCs to the liver by secretion of specific SASPs during PSC; (SA2) MCs promote liver and biliary damage, inflammation and hepatic fibrosis resembling PSC in normal mice or mice lacking MCs; and (SA3) MCs exacerbate biliary damage and hepatic fibrosis during PSC via cellular crosstalk between histamine, TGF-β1 and FXR.