Duodenal Mucosal Defense Mechanisms

描述（由申请人提供）：前肠经常受到污染摄入物质的菌群的攻击。为了确保营养物质的消化和吸收不受阻碍，必须限制细菌的复制，直到到达盲肠。虽然“胃酸屏障”有效地减少了胃中的细菌数量，但许多细菌种类可以逃脱这一屏障。因此，额外的防御措施到位，以根除对胃酸/胃蛋白酶有抵抗力的生物体。描述最多的次级防御包括抗菌肽，如防御素和隐肽。在这里，我们首次在哺乳动物组织中描述了表面氧化酶，称为双氧化酶或DUOX，在控制前肠细菌定植中的功能。虽然这些氧化酶与气道防御有关，并已在果蝇和秀丽隐杆线虫的肠道中进行了研究，但尚未有关于它们在哺乳动物肠道中的功能的公开报道。在我们的初步数据和文献发表的基础上，我们提出了一个关于前肠细菌如何通过模式识别受体（PRR）感知、ATP信号传导、嘌呤受体激活和（ca++）i增加来激活DUOX的假设，其中H2O2分泌到腔内，与分泌的SCN-结合形成强氧化剂、杀微生物阴离子OSCN-。这个分泌杀微生物物质的调节系统，我将称之为“DUOX系统”，可能是一个重要的前肠防御系统，防止细菌定植重要病原体。我们拟研究麻醉灌注大鼠和小鼠肠道中的Duox和PRR，用标准测定法测定过氧化氢、ATP和其他释放物质。如果有基因敲除小鼠，将用于检查该系统各个组成部分的功能。由于Duox被假设控制前肠细菌定植，因此该系统可能与几种重要疾病有关，如小肠细菌过度生长（SIBO）、囊性纤维化和炎症性肠病。

DESCRIPTION (provided by applicant): The foregut is constantly barraged with flora contaminating ingested substances. In order to ensure that digestion and absorption of nutrients is unimpeded, bacterial replications must be limited until the cecum is reached. Although the 'gastric acid barrier' effectively reduces bacterial counts in the stomach, many bacterial species can escape this barrier. Thus, additional defenses are in place to eradicate organisms resistant to gastric acid/pepsin. The most described secondary defenses include the antimicrobial peptides such as the defensins and cryptidins. Here, we describe for the first time in mammalian tissue, the function of surface oxidases, termed dual oxidase or DUOX, in the control of foregut bacterial colonization. Although these oxidases have been implicated in airway defense, and have been studied in drosophila and C. elegans intestine, there is no published report of their function in the mammalian gut. On the basis of our preliminary data and literature publications, we have formulated a hypothesis regarding how foregut bacteria activates DUOX through pattern recognition receptor (PRR) sensing, ATP signalling, purinoreceptor activation, and (Ca++)i increase, with H2O2 secreted into the lumen, which combined with secreted SCN- to form the strong oxidant, microbicidal anion OSCN-. This regulated system, for the secretion of microbicidal substances, which I will term the 'DUOX system', is likely to be an important foregut defense system against bacterial colonization with important pathogens. We propose to study Duox and PRR in the perfused anesthetized, rat and mouse intestine, measuring peroxide, ATP, and other released substances with standard assays. Knockout mice, when available, will be used to examine to function of individual components of the system. Since Duox is hypothesized to control foregut bacterial colonization, the proposed system may bear on several important diseases, such as small intestinal bacteria overgrowth (SIBO), cystic fibrosis, and inflammatory bowel disease.