BACTERIAL TOXIN ACTION ON THE DEVELOPING HUMAN GUT

腹泻病是全球范围内婴儿和儿童发病率和死亡率的主要原因之一。 我们从临床研究中了解到，早产儿肠道不适当的初始细菌定植可能导致严重炎症，导致早产儿特有的肠道疾病，例如-坏死性小肠结肠炎（NEC）和某些致炎性小肠结肠炎更常见，并且在新生儿期表现得更严重。 在人类肠道模型的初步研究中，（细胞系、器官培养、Ussing室和异种移植），我们提供了未成熟的人肠通过分泌过量的IL-8（一种中性粒细胞的趋化因子）而不适当地响应细菌毒素的数据，（内毒素）和过量氯化物分泌基于这些观察，我们对这项研究建议的总体假设是，新生儿细菌性炎症性肠道疾病的发病机制和某些分泌性涉及细菌毒素的肠出血主要是由于肠上皮细胞对细菌毒素刺激的不成熟（不适当）反应。 为了检验这一假设，我们将使用两个毒素肠上皮细胞的“串扰”的范例在人类肠道模型，以表征上皮细胞的反应和这种反应的机制，在不成熟的成熟肠相比。因此，我们的具体目标是：（1）通过检查LPS-LBP-CD 14与toll样受体（TLR）的相互作用和受体后信号转导事件，使用IL-8分泌作为效应器应答来检查内毒素与胎儿肠上皮细胞的相互作用（主要是导致NF κ B活化的IL-1信号转导途径）和（2）使用C1-β研究外毒素-胎儿肠上皮细胞相互作用。通过检查毒素结合和通过cAMP、GSalpha、核糖基化因子、效应子表达和磷酸化以及由PGE 2和5-HT介导的其他途径的受体后应答，将分泌作为效应子应答。在检查了内毒素和外毒素与发育中的肠的相互作用中的每个步骤后，我们将尝试调节任何可识别的步骤，该步骤通过使用已知的成熟（营养）因子使用发育调节步骤本身作为效应器响应来进行发育调节。这些研究可能为使用特定营养因子或营养因子组合预防早产儿和新生儿腹泻提供依据。

Diarrheal disease constitutes one of the major causes of morbidity and mortality in infants and children on a global scale. We know from clinical studies that an inappropriate initial bacterial colonization of the premature intestine may result in severe inflammation leading to an intestinal disease unique to the premature, e.g.- necrotizing enterocolitis (NEC) and that certain toxigenic diarrheas occur more commonly and are manifested more severely in the neonatal period. In preliminary studies in human intestinal models (cells lines, organ culture, Ussing chambers, and xenotransplants), we provide data that the immature human intestine inappropriately responds to bacterial toxin by secreting excessive IL-8, a chemokine for neutrophils, (endotoxin) and by excessive chloride secretion (exotoxin) Based on these observations, our overall hypothesis for this research proposal is that the pathogenesis of neonatal bacterial inflammatory intestinal diseases and certain secretory diarrheas involving bacterial toxins is principally due to an immature (inappropriate) enterocyte response to the bacterial toxin stimulation. In order to test this hypothesis, we will use two toxin-enterocyte "crosstalk" paradigms in human intestinal models to characterize the epithelial response and the mechanisms of this response in the immature compared to the mature intestine. Accordingly, our specific aim are: (1) to examine endotoxin interaction with the fetal enterocyte using IL-8 secretion as the effector response by examining LPS-LBP-CD14 interaction with toll-like receptors (TLRs) and postreceptor signal transduction events (principally the IL-1 signal transduction pathway leading to NFkappaB activation) and (2) to study exotoxin-fetal enterocyte interaction using C1- secretion as the effector response by examining toxin binding and postreceptor responses via cAMP, GSalpha, ribosylation factors, effector expression and phosphorylation and other pathways mediated by PGE2 and 5-HT. Having examined each step in the interaction of endo- and exotoxoin with the developing intestine, we will attempt to modulate any identifiable step that is developmentally regulated by using known maturational (trophic) factors using the developmentally regulated step itself as the effector response. These studies may provide the basis for using a specific trophic factor or combination of trophic factors in the prevention of toxigenic diarrhea in premature and neonatal infants.