Bacterial regulation of intestinal antimicrobial defense

描述（由申请人提供）：非致病性肠道菌群在人类健康和疾病中起着至关重要的作用，但我们对共生微生物如何与哺乳动物宿主交流以建立互利关系知之甚少。为了研究这些关系，我们使用了一个体内系统，在该系统中，无菌小鼠定植了拟杆菌（Bacteroides thetaiotaomicron），这是小鼠和人类肠道菌群的主要成员。激光捕获显微解剖和微阵列分析已经确定，B. thetaiotaomicron调节Paneth细胞中编码抗菌蛋白的基因转录，Paneth细胞是一种专门用于抗菌防御的小肠上皮谱系。此外，通常与断奶过渡相关的Paneth细胞抗菌基因表达的变化可以通过细菌定植的成年无菌小鼠引起，这表明共生细菌在Paneth细胞抗菌武库的发展中起指导作用。这些结果导致了共生肠道细菌通过调节Paneth细胞基因表达来塑造肠道抗菌防御和粘膜屏障功能的假设。提出了三个具体目标来解决这一假设。目的1将描述出生后发育过程中细菌调节的Paneth细胞抗菌基因的表达模式和对微生物因素的反应。目的2将研究宿主模式识别受体，包括toll样受体和Nod蛋白，对细菌- paneth细胞相互作用的贡献。目的3旨在研究Reg家族蛋白成员的抗菌功能，该蛋白通过与共生菌的相互作用在Paneth细胞中被强烈诱导。总之，这些研究将对共生细菌如何塑造肠道上皮先天免疫产生新的见解，并将更好地理解细菌-上皮相互作用的分子机制。此外，这项工作将有助于设计新的策略来加强微生物群在增强粘膜屏障中的作用。

DESCRIPTION (provided by applicant): The nonpathogenic intestinal flora play critical roles in human health and disease, yet very little is known about how commensal microbes communicate with their mammalian hosts to establish mutually beneficial relationships. To study these relationships, we use an in vivo system in which germ-free mice are colonized with Bacteroides thetaiotaomicron, a predominant member of the intestinal flora in mice and humans. Laser capture microdissection and microarray analysis have established that B. thetaiotaomicron regulates the transcription of genes encoding antimicrobial proteins in Paneth cells, a small intestinal epithelial lineage specialized for antimicrobial defense. Moreover, changes in Paneth cell antimicrobial gene expression that are normally associated with the weaning transition can be elicited by bacterial colonization of adult germ-free mice, suggesting that commensal bacteria play an instructive role in the development of the Paneth cell antimicrobial arsenal. These results have led to the hypothesis that commensal gut bacteria shape intestinal antimicrobial defense and mucosal barrier function by modulating Paneth cell gene expression. Three specific aims are proposed to address this hypothesis. Aim 1 will characterize the expression patterns of bacterially-regulated Paneth cell antimicrobial genes during postnatal development and in response to microbial factors. Aim 2 will examine the contributions of host pattern recognition receptors, including Toll-like receptors and Nod proteins, to bacteria-Paneth cell interactions. Aim 3 proposes to investigate an antimicrobial function for a member of the Reg family of proteins which is strongly induced in Paneth cells by interactions with commensal bacteria. Together, these studies will yield novel insights into how commensal bacteria shape gut epithelial innate immunity, and will lead to a better understanding of the molecular mechanisms underlying bacteria-epithelial interactions in vivo. Furthermore, this work will aid in designing novel strategies for strengthening the role of the microflora in enhancing the mucosal barrier.