Evaluation of the influence of immunoglobulin G4 (IgG4) on the innate immune response and tight junction-mediated barrier function of biliary epithelial cells in chronic inflammatory cholangiopathies

评估免疫球蛋白 G4 (IgG4) 对慢性炎症性胆管病中胆道上皮细胞先天免疫反应和紧密连接介导的屏障功能的影响

• 批准号: 47407518
• 负责人: Professor Dr. Tobias Müller
• 金额: --
• 依托单位: Medizinische Klinik mit SP Hepatologie und Gastroenterologie (einschl. Arbeitsbereich Stoffwechselerkrankungen (CVK)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/47407518?language=en
• 关键词: Evaluation; influence; immunoglobulin; G4; IgG4

There is growing evidence that inappropriate innate immune responses to bile- or portal venous blood-derived intestinal pathogen-associated molecular patterns (PAMPs) in biliary epithelial cells (BECs) lining the intra- and extra-hepatic bile ducts and consecutive biliary barrier dysfunction contribute to the pathogenesis of chronic inflammatory cholangiopathies, such as primary sclerosing cholangitis (PSC) and immunoglobulin G4 (IgG4)-associated cholangitis (IAC). Subsequent peribiliary leakage of bile containing intestinal PAMPs such as lipopolysaccharide (LPS) likely accelerates biliary damage. In contrast to PSC, IAC is a steroid-sensitive chronic inflammatory biliary disease that involves different parts of the pancreatobiliary system, but little is known about its mechanisms of pathogenesis.We isolated primary human BECs from explanted livers from patients with PSC. We were able to show that in the presence of the predominant T helper (Th) cell type 1 cytokine milieu in advanced PSC, activated BECs exhibit inappropriate pattern recognition receptor (PRR)-mediated innate immune responses to intestinal endotoxins and subsequent endotoxin intolerance because of enhanced PRR signaling, which accelerated chronic biliary inflammation. As TNF-alpha inhibition partly restored protective innate immune tolerance, endogenous TNF-alpha secretion likely contributed to inappropriate endotoxin responses in activated BECs. In contrast to PSC livers, bile samples from patients with IAC exhibited significant increases in levels of Th2 cytokines such as interleukin (IL)-4 and IL-5. IL-13 was not detected in bile samples, but brush cytology samples from the extra-hepatic bile ducts of these patients revealed enhanced levels of IL-13 mRNA, compared with controls. In vitro, IL-4 and IL-13 significantly reduced tight junction (TJ)-associated BEC barrier function by activating claudin-2-mediated paracellular pore pathways. These findings suggested that the specific Th2 cytokine milieu in IAC likely contributed to the pathogenesis of chonic biliary inflammation in these patients due to the induction of increased paracellular permeability of the lining biliary epithelium. Th2 cytokines also impaired wound closure in BEC monolayers. The role of IgG4 in the pathogenesis of IAC remains to be determined. Our preliminary work suggests that IgG4 selectively bind to BECs of the extra-hepatic bile ducts. Of note, autoreactive antibodies to BECs have also been described in patients with PSC. We hypothesize that autoreactive IgG4 promote aberrant innate immune responses and TJ-mediated barrier dysfunction in BECs by the induction of an enhanced secretion of pro-inflammatory respectively pro-fibriotic mediators such as TNF-alpha or TGF-ß and thus contribute to the pathogenesis of chronic biliary inflammation in these patients. This grant proposal aims to elucidate potential pathomechanisms underlying this hypothesis."

越来越多的证据表明，胆内和肝外胆道上皮细胞（BECs）对胆汁或门静脉血液来源的肠道病原体相关分子模式（PAMPs）的不适当先天免疫反应和连续的胆道屏障功能障碍有助于慢性炎症性胆管疾病的发病机制，如原发性硬化性胆管炎（PSC）和免疫球蛋白G4 （IgG4）相关胆管炎（IAC）。随后的胆周渗漏含有肠道PAMPs如脂多糖（LPS）可能加速胆道损伤。与PSC相反，IAC是一种类固醇敏感的慢性炎症性胆道疾病，涉及胰胆道系统的不同部分，但其发病机制尚不清楚。我们从PSC患者的移植肝脏中分离出原代人BECs。我们能够证明，在晚期PSC中存在主要的T辅助（Th）细胞1型细胞因子环境，激活的BECs表现出不适当的模式识别受体（PRR）介导的对肠道内毒素的先天免疫反应和随后的内毒素不耐受，因为PRR信号增强，从而加速了慢性胆道炎症。由于tnf - α抑制在一定程度上恢复了保护性先天免疫耐受，内源性tnf - α分泌可能导致活化BECs中不适当的内毒素反应。与PSC肝脏相比，IAC患者的胆汁样本显示Th2细胞因子水平显著升高，如白细胞介素(IL)-4和IL-5。胆汁样本中未检测到IL-13，但与对照组相比，这些患者肝外胆管的刷细胞学样本显示IL-13 mRNA水平升高。在体外，IL-4和IL-13通过激活cladin -2介导的细胞旁孔通路，显著降低了紧密连接（TJ）相关的BEC屏障功能。这些发现表明，IAC中特定的Th2细胞因子环境可能导致这些患者慢性胆道炎症的发病机制，因为它诱导了胆道上皮细胞旁通透性的增加。Th2细胞因子也会损害BEC单层的伤口愈合。IgG4在IAC发病机制中的作用尚不明确。我们的初步工作表明，IgG4选择性地结合肝外胆管的BECs。值得注意的是，在PSC患者中也发现了针对BECs的自身反应性抗体。我们假设，自身反应性IgG4通过诱导促炎和促纤维化介质如tnf - α或TGF-ß的分泌增强，促进BECs中异常的先天免疫反应和tj介导的屏障功能障碍，从而促进这些患者慢性胆道炎症的发病机制。这项拨款提案旨在阐明这一假设背后的潜在病理机制。”