Mechanisms of synergistic regulation of biliary inflammation and fibrosis

美国退伍军人因酒精和毒素滥用以及肝炎病毒而患肝病的风险越来越大。 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，因此表明一个主要的未满足的 医疗需求。肝纤维化患者的唯一选择通常是器官移植。慢性肝病 包括靶向胆管细胞胆管病，例如原发性硬化性胆管炎（PSC）， 其特征在于胆管增生、炎症和进行性纤维化。自由胆管细胞 增殖可发展成胆管癌（即，胆管癌（CCA）和PSC患者 更容易发展CCA。此外，胆管细胞在PSC期间显示衰老表型， 其可能通过激活肝星状细胞而导致炎症并进一步影响肝纤维化 （HSC）。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）在介导包括肝脏疾病在内的多种病理中是重要的，但是肥大细胞（MC）在肝脏疾病中是重要的。 在正常的体内平衡的肝脏中发现的数量非常低。在受损附近发现浸润性肝MC 肝内胆管和活化的HSC。在未发表的数据中，我们发现， 胆管细胞诱导MC迁移在非酒精性脂肪肝疾病。此外，衰老的胆管细胞 分泌干细胞因子（SCF）和白细胞介素等已知是MC的化学引诱物的因子， 诱导迁移。在迁移和激活后，MC释放包括大量的 刺激胆管细胞增殖和纤维化的组胺。我们提出这项建议的理由是基于 我们实验室和其他实验室先前发表的数据显示，PSC和CCA患者的MC浸润增加， 沿着啮齿类动物肝损伤模型，MC浸润与纤维化增加正相关。 此外，注射培养的MC的正常野生型小鼠（通常很少肝MC）显示增加的 胆管损伤、炎症和肝纤维化，所有这些都是PSC的关键特征。使用PSC模型 （Mdr 2-/-小鼠），我们通过将Mdr 2-/-与缺乏组氨酸的小鼠交配产生了双敲除小鼠（DKO 脱羧酶（HDC-/-）。DKO小鼠（很少或没有MC）的胆道损伤、炎症和肝脏损伤减少。 纤维化此外，在将MCs重新引入DKO小鼠后，我们发现损伤和纤维化显著增加， 模拟Mdr 2-/-小鼠，当使用缺乏TGF-β1信号传导的MC时，这种情况被逆转，表明 MC在PSC中的关键作用。最后，抑制MC衍生的组胺可降低胆损伤和肝损伤。 胆汁淤积性肝损伤、PSC和CCA模型中的纤维化表明MCs介质的调节可能 证明是有疗效的我们提出工作假设，衰老的胆管细胞诱导MC PSC期间的迁移和MC衍生的TGF-β1或FXR的调节调节了小管反应， 肝纤维化通过胆道衰老。我们提出了以下具体目标（SA）：（SA 1）衰老 胆管细胞通过在PSC期间分泌特异性SASP将MC募集到肝脏;（SA 2）MC促进肝脏和 在正常小鼠或缺乏MC的小鼠中类似PSC的胆道损伤、炎症和肝纤维化;以及 (SA3)在PSC期间，MC通过组胺， TGF-β1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.