Mechanisms of epithelial barrier dysfunction in gastrointestinal infectious diseases

脓毒性疾病是德国第三大常见死因。通常，病原体起源于肠道。本项目的主要目的是确定细菌的病理机制和上皮紊乱，引起腹泻和吸收不良，以及抗原摄取和细菌易位。这将提高我们对肠道感染的发病机制和由此产生的肠道炎症过程的认识。利用电生理、形态学和分子技术，我们在人体活检上使用小型化的ususing系统进行测量。同时，我们在上皮和动物模型中寻找潜在的病理机制和信号转导过程。在本项目中，将研究艰难梭菌性结肠炎患者在抗生素治疗后的屏障功能。在与m1巨噬细胞共培养的人结肠二维类器官模型中，研究毒素TcdA和TcdB以及二元毒素（CDT）对肠上皮紧密连接的改变以及上皮细胞凋亡和局灶性渗漏的表现。这是基于二元毒素CDT与上皮紧密连接蛋白LSR （angulin-1）结合并促进上皮对TcdA和TcdB的摄取的假设，因此TcdA和TcdB易位并在粘膜免疫系统中启动细胞因子反应。以这种方式诱导的屏障缺陷在假性膜性结肠炎中起容许因子的作用。在此基础上，锌、槲皮素、维生素D等的保护作用将被筛选为治疗效果。总之，本DFG资助申请旨在明确相关病理机制，并希望提高我们对胃肠道疾病背景下肠上皮运输和屏障功能调节的理解，这是预防策略的基础。

Septic disease is the third common cause of death in Germany. Very often, the pathogens originate from the intestine. Main aim of this project is to define bacterial pathomechanisms and epithelial disturbances, which cause diarrhea and malabsorption as well as antigen uptake and bacterial translocation. This will improve our knowledge about the pathogenesis of intestinal infections and the resulting inflammatory processes in the intestine.Using electrophysiological, morphological and molecular techniques, we measure with miniaturized Ussing systems on human biopsies. In parallel, we search in epithelial and animal models for underlying pathomechanisms and signal transduction processes. In the present project, barrier function will be studied in patients with Clostridium difficile-induced colitis after antibiotic treatment. Toxins TcdA and TcdB as well as the binary toxin (CDT) will be investigated in 2d-organoid model of human colon in coculture with M1-macrophages in respect to changes in epithelial tight junctions and appearance of epithelial apoptoses and focal leaks in the intestinal epithelium. This follows the hypothesis that the binary toxin CDT binds to the epithelial tight junction protein LSR (angulin-1) and facilitates the epithelial uptake of TcdA and TcdB, as a result of which TcdA and TcdB translocate and initiate a cytokine response in the mucosal immune system. The barrier defect induced in this manner acts as permissive factor in pseudomembranous colitis. Based on this, protective influences of zinc, quercetin, vitamin D and others will be screened for therapeutic effects.In conclusion, this DFG grant application aims at the definition of relevant pathomechanisms and wants to improve our understanding of the regulation of intestinal epithelial transport and barrier function in the context of gastrointestinal diseases, which is the basis for preventive strategies.