Objective Patients with mutations in ATP8B1 develop Progressive Familial Intrahepatic Cholestasis type 1 (PFIC1), a severe liver disease that requires life-saving liver transplantation. PFIC1 patients also present with gastrointestinal problems, including intestinal inflammation and diarrhea, which are aggravated after liver transplantation. Here we investigate the intestinal function of ATP8B1 in relation to inflammatory bowel diseases. Design ATP8B1 expression was investigated in intestinal samples of patients with Crohn’s Disease (CD) or Ulcerative Colitis (UC) as well as in murine models of intestinal inflammation. Colitis was induced in ATP8B1-deficient mice with Dextran Sodium Sulphate (DSS) and intestinal permeability was investigated. Epithelial barrier function was assessed in ATP8B1 knock-down Caco2-BBE cells. Co-immunoprecipitation experiments were performed in Caco2-BBE cells overexpressing ATP8B1-eGFP. Expression and localization of ATP8B1 and tight junction proteins were investigated in cells and in biopsies of UC and PFIC1 patients. Results ATP8B1 expression was decreased in UC and DSS-treated mice, and associated with a decreased Tight Junctional pathway transcriptional program. ATP8B1-deficient mice were extremely sensisitve to DSS-induced colitis, evidenced by increased intestinal barrier leakage. ATP8B1 knockdown cells showed delayed barrier establishment that associated with affected Claudin-4 (CLDN4) levels and localization.. CLDN4 immunohistochemistry showed a tight-junctional staining in control tissue, whereas in UC and intestinal PFIC1 samples, CLDN4 was not properly localized. Conclusion ATP8B1 is important in the establishment of the intestinal barrier Downregulation of ATP8B1 levels in UC, and subsequent altered localization of tight junctional proteins, including CLDN4, might therefore be an important mechanism in UC pathophysiology.

中文翻译：

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磷脂翻转酶 ATP8B1 通过建立肠道屏障功能参与溃疡性结肠炎的发病机制

目的 存在 ATP8B1 突变的患者会出现 1 型进行性家族性肝内胆汁淤积症 (PFIC1)，这是一种严重的肝脏疾病，需要进行肝移植来挽救生命。PFIC1患者还存在胃肠道问题，包括肠道炎症和腹泻，肝移植后这些问题会加剧。在这里，我们研究了 ATP8B1 的肠道功能与炎症性肠病的关系。设计 在克罗恩病 (CD) 或溃疡性结肠炎 (UC) 患者的肠道样本以及肠道炎症小鼠模型中研究了 ATP8B1 表达。用葡聚糖硫酸钠 (DSS) 在 ATP8B1 缺陷小鼠中诱导结肠炎，并研究肠道通透性。在 ATP8B1 敲低 Caco2-BBE 细胞中评估上皮屏障功能。在过表达 ATP8B1-eGFP 的 Caco2-BBE 细胞中进行免疫共沉淀实验。研究人员在 UC 和 PFIC1 患者的细胞和活检组织中研究了 ATP8B1 和紧密连接蛋白的表达和定位。结果 UC 和 DSS 处理的小鼠中 ATP8B1 表达降低，并且与紧密连接通路转录程序的降低相关。ATP8B1 缺陷小鼠对 DSS 诱导的结肠炎极其敏感，肠道屏障渗漏增加就证明了这一点。ATP8B1 敲低细胞显示出与受影响的 Claudin-4 (CLDN4) 水平和定位相关的屏障建立延迟。CLDN4 免疫组织化学显示对照组织中存在紧密连接染色，而在 UC 和肠道 PFIC1 样本中，CLDN4 未正确定位。结论 ATP8B1 在肠道屏障的建立中很重要，UC 中 ATP8B1 水平的下调，以及随后包括 CLDN4 在内的紧密连接蛋白定位的改变，可能是 UC 病理生理学的重要机制。