Expression of Toll-like Receptor on Biliary Mucosa and its Dysregulation: Molecular Pathological Study by Using Cultured Biliary Epithelial Cells and Hepato-Biliary Tissue

本研究利用人肝胆组织材料和体外培养的人胆管上皮细胞，证实先天免疫参与了胆道的病理生理过程。获得了以下三个数据。(1)胆管上皮细胞表达Toll样受体（TLR），并对病原体相关分子模式（PAMPs）产生应答，这是先天免疫的生理反应。这种反应似乎在生理上参与了胆汁对胆汁中所含细菌成分的体内平衡。通过体外培养研究发现，TLF_4的内毒素耐受是由两个步骤诱导的，IRAK-M也通过负调节因子参与了这一过程。(2)据报道胆道闭锁可由双链RNA病毒感染引起。本研究发现胆管上皮细胞表达与双链RNA反应的TLR 3，并通过与TLR 3配体的作用诱导NF-B和IFN-β的表达。此外，在此过程中，还诱导了一种促凋亡分子TRAIL。在胆道闭锁的病变胆管中，TLR 3和TRAIL在胆管上皮细胞中表达。这些结果表明，病毒，特别是双链RNA病毒可能参与了胆道闭锁的发病机制，特别是感染的胆管上皮细胞的凋亡丢失。(3)原发性胆汁性肝硬化是一种自身免疫性肝病，胆汁上皮细胞发生凋亡，可能与细菌感染有关。通过对胆管上皮细胞凋亡机制和天然免疫机制的研究发现，PAMPs可诱导处于蛋白隐性状态的胆管上皮细胞发生凋亡，HIAP-1的过表达在PAMPs诱导的胆管上皮细胞抗凋亡中起重要作用。这些研究表明，先天免疫，特别是TLR，参与了胆道系统的病理生理学。

We demonstrated the participation of innate immunity in the pathophysiology of biliary tract by using human materials of hepatobiliary tissues and cultured human biliary epithleial cells. The following three data were obtained. (1) Biliary epithelial cells expressed Toll-like receptor (TLR), and they responded to pathogen associated molecular patterns (PAMPs) as a physiological response of innate immunity. This reaction seemed to be involved physiologically in biliary homeostasis against bacterial components contained in bile. By cultural study, it was found that endotoxin tolerance of TLF4 was induced by two step processes, and that IRAK-M is also involved in this process by a negative regulator. (2) It is reported that biliary atresia could be caused by infection of double strand RNA virus. It was found in this study that biliary epithelial cells express TLR3 reacting with double strand RNA, and NF-B and IFN-β is incuded in these cells by exposing to the ligands of TLR3. In addition, TRAIL, a proapoptotic molecule was also induced in this process. In the affected bile ducts of biliary atresia, TLR3 and TRAIL were expressed in biliary epithelial cells. These findings suggested that virus, particularly double strand RNA virus was likely involved in the pathogenesis of biliary atresia, particularly the apoptotic loss of infected biliary epithelial cells. (3) Primary biliary cirrhosis is an autoimmune liver disease and biliary epithelial cells underwent apoptosis, probably resulting from bacterial infection. By examing the apoptotic mechanisms of biliary epithelial cells and innate immunity, it was found that biliary epithelial cells under protein-recessive state, underwent apoptosis by PAMPs stimulation, and HIAP-1 overexpression was important in antiapoptotic effect of biliary epithelial cells due to PAMPs. These studies showed that innate immunity, especially TLR, is involved in the pathophysiology of the biliary tree.