PATHOGENS, PROBIOTICS AND THE EPITHELIUM IN COLITIS

描述（由申请人提供）：我们的长期目标是了解肠上皮运输和屏障功能。大量证据表明，这些关键功能在炎症性肠病和其他肠道疾病的情况下发生了改变。此外，我们假设当肠道屏障功能不足以排除管腔因素时，就会导致炎症性肠病，从而导致免疫刺激以及炎症和损伤的恶性循环，进一步损害转运和屏障稳态。我们还将测试一个具体的假设，即益生菌微生物在基础条件下以及当它们受到病原微生物或其他有害侵害时对肠上皮细胞发挥保护作用。我们将通过解决两个具体目标来检验我们的假设。首先，我们将检查已知依赖于上皮缺陷的炎症性肠病小鼠模型中的屏障和转运功能是否发生改变，并确定这种改变如何促进炎症的发病机制和/或症状的产生。还将寻找与管腔细菌的相互作用。在第二个目标中，我们将定义益生菌微生物在控制条件下（当这些功能在体外和上述炎症性肠病模型中受到损害时）改善上皮屏障和转运功能的机制。该方法将使用 mdr1a -/- 小鼠（在常规饲养时会产生自发性结肠炎）以及人类肠上皮细胞系。我们还将使用致病菌和两种代表性益生菌菌株。我们将使用电生理学方法研究这些模型中的转运和屏障功能，并将应用分子技术来定义炎症的蛋白质靶标，或益生菌有益作用的基础。这项工作的意义在于它有可能对炎症性肠病的发病机制产生新的见解。它还可能为继续探索益生菌、有望成为治疗炎症性肠病和其他肠道疾病的补充/替代疗法提供科学依据。

DESCRIPTION (provided by applicant): Our long-term goal is to understand intestinal epithelial transport and barrier function. Substantial evidence suggests that these critical functions are altered in the setting of inflammatory bowel disease and other intestinal disorders. Moreover, we hypothesize that inflammatory bowel disease results when intestinal barrier function is inadequate to exclude luminal factors, thereby resulting in immune stimulation and a vicious cycle of inflammation and injury that further compromises transport and barrier homeostasis. We will also test the specific hypothesis that probiotic microorganisms exert protective effects on intestinal epithelial cells under both basal conditions and when they are compromised by pathogenic microorganisms or other injurious insults. We will test our hypotheses by addressing two Specific Aims. In the first, we will examine whether barrier and transport functions are altered in a mouse model of inflammatory bowel disease known to depend on an epithelial defect, and determine how such alterations contribute to the pathogenesis of inflammation and/or the generation of symptomatology. The interplay with luminal bacteria will also be sought. In the second Aim, we will define mechanisms whereby probiotic microorganisms improve epithelial barrier and transport function under control conditions, when these functions are compromised in vitro, and in the model of inflammatory bowel disease described above. The approach will be to use the mdr1a -/- mouse which develops spontaneous colitis when conventionally housed, as well as human intestinal epithelial cell lines. We will also employ pathogenic bacteria and two representative probiotic strains. We will study transport and barrier functions in these models using electrophysiological approaches, and will apply molecular techniques to define protein targets of inflammation, or which underlie the beneficial effects of probiotics. The significance of this work lies in its potential to yield novel insights into the pathogenesis of inflammatory bowel disease. It may also provide a scientific rationale for continued exploration of probiotics, promising complementary/alternative therapies, in the treatment of inflammatory bowel disease and other intestinal disorders.