Medizinische Klinik mit Schwerpunkt Hepatologie und Gastroenterologie, Charité-Universitätsmedizin Berlin, Campus Virchow Klinikum, Berlin, Germany.
Liver Int. 2011 Nov;31(10):1574-88. doi: 10.1111/j.1478-3231.2011.02635.x. Epub 2011 Sep 15.
Pattern recognition receptors (PRRs) orchestrate the innate immune defence in human biliary epithelial cells (BECs). Tight control of PRR signalling provides tolerance to physiological amounts of intestinal endotoxins in human bile to avoid constant innate immune activation in BECs.
We wanted to determine whether inappropriate innate immune responses to intestinal endotoxins contribute to the development and perpetuation of chronic biliary inflammation.
We examined PRR-mediated innate immune responses and protective endotoxin tolerance in primary BECs isolated from patients with primary sclerosing cholangitis (PSC), alcoholic liver disease and patients without chronic liver disease. Expression studies comprised northern blots, RT-PCR, Western blots and immunocytochemistry. Functional studies comprised immuno-precipitation Western blots, FACS for endotoxin uptake, and NF-κB activation assays and ELISA for secreted IL-8 and tumour necrosis factor (TNF)-α.
Primary BECs from explanted PSC livers showed reversibly increased TLR and NOD protein expression and activation of the MyD88/IRAK signalling complex. Consecutively, PSC BECs exhibited inappropriate innate immune responses to endotoxins and did not develop immune tolerance after repeated endotoxin exposures. This endotoxin hyper-responsiveness was probably because of the stimulatory effect of abundantly expressed IFN-γ and TNF-α in PSC livers, which stimulated TLR4-mediated endotoxin signalling in BECs, leading to increased TLR4-mediated endotoxin incorporation and impaired inactivation of the TLR4 signalling cascade. As TNF-α inhibition partly restored protective innate immune tolerance, endogenous TNF-α secretion probably contributed to inappropriate endotoxin responses in BECs.
Inappropriate innate immune responses to intestinal endotoxins and subsequent endotoxin intolerance because of enhanced PRR signalling in BECs probably contribute to chronic cholangitis.
模式识别受体（PRRs）在人类胆管上皮细胞（BECs）中协调先天免疫防御。PRR 信号的严格控制为人类胆汁中生理量的肠道内毒素提供了耐受，以避免 BEC 中持续的先天免疫激活。
我们想确定对肠道内毒素的不适当先天免疫反应是否有助于慢性胆管炎症的发展和持续。
我们检查了从原发性硬化性胆管炎（PSC）、酒精性肝病和无慢性肝病患者中分离的原代 BEC 中 PRR 介导的先天免疫反应和保护性内毒素耐受。表达研究包括 Northern blot、RT-PCR、Western blot 和免疫细胞化学。功能研究包括免疫沉淀 Western blot、内毒素摄取的 FACS、NF-κB 激活测定和分泌的 IL-8 和肿瘤坏死因子（TNF）-α 的 ELISA。
来自PSC 肝移植的原代 BEC 显示 TLR 和 NOD 蛋白表达可逆性增加，并且 MyD88/IRAK 信号复合物被激活。连续地，PSC BEC 对内毒素表现出不适当的先天免疫反应，并且在重复内毒素暴露后不会发展免疫耐受。这种内毒素高反应性可能是因为 PSC 肝脏中丰富表达的 IFN-γ 和 TNF-α 的刺激作用，刺激 BEC 中的 TLR4 介导的内毒素信号，导致 TLR4 介导的内毒素掺入增加和 TLR4 信号级联的失活受损。由于 TNF-α 抑制部分恢复了保护性先天免疫耐受，内源性 TNF-α 分泌可能对内毒素在 BEC 中的不适当反应有贡献。
BEC 中 PRR 信号的增强导致对肠道内毒素的不适当先天免疫反应和随后的内毒素不耐受，可能导致慢性胆管炎。
