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

我们利用人的肝胆组织材料和培养的人胆管上皮细胞，证明了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)，其对病原体相关分子模式(PAMPs)的反应是天然免疫的生理反应。这种反应似乎在生理上参与了胆汁对胆汁中细菌成分的动态平衡。通过培养研究发现，TLF4的内毒素耐受性是由两步过程诱导的，IRAK-M也参与了这一过程。(2)有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TLR3与双链核糖核酸反应，并通过暴露于TLR3的配体而将核因子-B和干扰素-β嵌入这些细胞中。此外，在此过程中还诱导了促凋亡分子TRAIL的表达。在胆道闭锁病变胆管中，TLR3和TRAIL表达于胆管上皮细胞。提示病毒，尤其是双链RNA病毒可能参与了胆道闭锁的发病机制，尤其是感染的胆管上皮细胞的凋亡丢失。(3)原发性胆汁性肝硬变是一种自身免疫性肝病，胆管上皮细胞发生凋亡，可能是细菌感染所致。通过对胆管上皮细胞的凋亡机制和先天免疫机制的研究，发现胆管上皮细胞处于蛋白质隐性状态时，PAMPs可诱导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作用中起重要作用。这些研究表明，先天性免疫，特别是TLR，参与了胆道树的病理生理学。

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.