Bacterial regulation of intestinal antimicrobial defense

描述(申请人提供)：非致病性肠道菌群在人类健康和疾病中起着关键作用，但对共生微生物如何与哺乳动物宿主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，在这个系统中，无菌小鼠被thetaiotaomicron类杆菌定居，这是小鼠和人类肠道菌群中的一种主要成员。激光捕获显微切割和微阵列分析已经证实，B.thaiotaomicron调控Paneth细胞中编码抗微生物蛋白的基因的转录，Paneth细胞是一种专门用于抗菌防御的小肠上皮细胞系。此外，正常情况下与断奶过渡相关的Paneth细胞抗菌基因表达的变化可以由成年无菌小鼠的细菌定植引起，这表明共生细菌在Paneth细胞抗菌库的发展中发挥了指导作用。这些结果导致了一种假说，即共生肠道细菌通过调节Paneth细胞基因的表达来形成肠道抗菌防御和粘膜屏障功能。针对这一假设，本文提出了三个具体目标。目的1研究细菌调控的Paneth细胞抗菌基因在出生后发育和对微生物因素的响应中的表达模式。目的2将研究宿主模式识别受体，包括Toll样受体和NOD蛋白，在细菌-Paneth细胞相互作用中的作用。目的3建议研究REG蛋白家族的一个成员的抗菌功能，该蛋白在Paneth细胞中通过与共生细菌的相互作用而被强烈诱导。总之，这些研究将对共生细菌如何塑造肠上皮天然免疫产生新的见解，并将有助于更好地理解体内细菌-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，以加强微生物区系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.