Karrar Azza, Broomé Ulrika, Södergren Towe, Jaksch Marie, Bergquist Annika, Björnstedt Mikael, Sumitran-Holgersson Suchitra
Division of Transplantation Surgery, Division of Clinical Immunology, Karolinska University Hospital-Huddinge, Stockholm, Sweden.
Gastroenterology. 2007 Apr;132(4):1504-14. doi: 10.1053/j.gastro.2007.01.039. Epub 2007 Jan 25.
BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is an autoimmune liver disease with destruction of hepatic bile ducts. A high frequency of biliary epithelial cell antibodies (BEC-Ab) is present in PSC. Here, we studied the mechanisms and signaling pathways used by these Ab in causing BEC dysfunction.
Immunoassays were performed using freshly isolated BECs to study the signaling capacity of purified immunoglobulin (Ig) G and F(ab)'(2) fractions from 33 patients with PSC with anti-BEC-Ab.
We provide evidence that stimulation of BECs with PSC IgG, but not control IgG, induced expression of Toll-like receptor (TLR) 4 and TLR9 and specific phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 as well as the transcription factors ELK-1 and nuclear factor kappaB. A specific inhibitor of ERK1/2 abrogated phosphorylation of ELK-1 and protein expression of TLR4 but not TLR9 on BECs. TLR-expressing BECs, when further stimulated with lipopolysaccharide and CpG DNA, produced high levels of interleukin-1beta, interleukin-8, interferon gamma, tumor necrosis factor alpha, granulocyte-macrophage colony-stimulating factor, and transforming growth factor beta. Bile ducts stained positively for TLR4 and TLR9 in 58% of liver specimens taken from patients with PSC with BEC-Ab, as compared with 14% in those without BEC-Ab and also less frequently in diseased control livers.
Our data show that binding of PSC BEC-Ab initiates ERK1/2 signaling and up-regulation of TLR, which upon ligation induces BECs to produce cytokines/chemokines, leading to the possible recruitment of inflammatory cells. Thus, in PSC, BECs are not only targets of the immune attack but may also be active participants and mediators of their own destruction. BEC-Ab may be critical regulators of cholangitis in PSC.
原发性硬化性胆管炎（PSC）是一种导致肝内胆管破坏的自身免疫性肝病。PSC患者中存在高频率的胆管上皮细胞抗体（BEC - Ab）。在此，我们研究了这些抗体导致BEC功能障碍的机制和信号通路。
使用新鲜分离的BEC进行免疫测定，以研究来自33例抗BEC - Ab的PSC患者的纯化免疫球蛋白（Ig）G和F(ab)'(2)片段的信号传导能力。
我们提供的证据表明，用PSC IgG而非对照IgG刺激BEC可诱导Toll样受体（TLR）4和TLR9的表达，以及细胞外信号调节激酶（ERK）1/2以及转录因子ELK - 1和核因子κB的特异性磷酸化。ERK1/2的特异性抑制剂可消除ELK - 1的磷酸化以及BEC上TLR4的蛋白表达，但不能消除TLR9的表达。表达TLR的BEC在用脂多糖和CpG DNA进一步刺激时，会产生高水平的白细胞介素 - 1β、白细胞介素 - 8、干扰素γ、肿瘤坏死因子α、粒细胞 - 巨噬细胞集落刺激因子和转化生长因子β。在取自抗BEC - Ab的PSC患者的肝脏标本中，58%的胆管TLR4和TLR9染色呈阳性，而在无BEC - Ab的患者中为14%，在患病对照肝脏中染色阳性的频率也较低。
我们的数据表明，PSC BEC - Ab的结合启动了ERK1/2信号传导并上调了TLR，TLR连接后诱导BEC产生细胞因子/趋化因子，可能导致炎症细胞的募集。因此，在PSC中，BEC不仅是免疫攻击的靶点，还可能是自身破坏的积极参与者和介质。BEC - Ab可能是PSC胆管炎的关键调节因子。
