Toll-like receptors and intestinal inflammation

描述（由申请人提供）：人体肠道中有大量的共生微生物。一些临床观察和动物实验表明，肠道细菌在慢性肠道炎症的发病机制中起重要作用。肠侵入性病原体如沙门氏菌、志贺氏菌、耶尔森氏菌和李斯特菌可侵入上皮并引起炎症反应。鞭毛蛋白是细菌鞭毛的主要成分，由多种细菌（包括共生微生物或肠侵入微生物）释放，刺激肠上皮中高表达的toll样受体（TLR） 5。我们最近的研究结果表明，在未转化的人类结肠细胞以及正常的人类结肠中，鞭毛蛋白刺激特异性地诱导了促炎基因的表达，这是IBD病理生理的一个突出特征。尽管有这些发现，细菌鞭毛蛋白在结肠细胞和天然结肠粘膜中发出促炎反应信号的机制仍然知之甚少。该建议的中心假设是上皮屏障功能受损，无论是损伤还是侵蚀性病原体，使细菌鞭毛蛋白穿透渗漏的上皮并激活基底外侧TLR5导致结肠炎症。我们的目标是阐明鞭毛蛋白在人类结肠炎细胞中发挥促炎作用的信号通路，并研究细菌鞭毛蛋白在小鼠结肠炎模型中结肠炎症的发生和进展中的参与。目的1将研究非转化人结肠NCM460细胞中鞭毛蛋白对IL-8和MIP-3a基因表达的信号转导途径。在这个目的中，我们将确定在鞭毛蛋白暴露下参与MEK磷酸化的特定激酶，并检查它们在tlr5依赖性IL-8和MIP-3a基因表达中的作用。还提出了确定磷酸酶MKP-1放大鞭毛蛋白诱导的促炎反应的信号传导机制的实验。目的2将研究PI-3K信号在tlr5相关的IL-8和MIP-3a基因表达中的作用。目的3将使用小鼠结肠炎模型来研究鞭毛蛋白在结肠炎进展中的作用，并确定人类和小鼠结肠粘膜的基底外侧或管腔方面是否对鞭毛蛋白有反应。我们提出的研究将为包括IBD在内的结肠炎症的发病机制提供重要信息。

DESCRIPTION (provided by applicant): The human gut harbors a large collection of commensal microbes. Several clinical observations and animal experiments suggested that intestinal bacteria play a major role in the pathogenesis of chronic bowel inflammation. Enteroinvasive pathogens such as Salmonella, Shigella, Yersinia, and Listeria can invade the epithelium and provoke inflammatory responses. Flagellin, a major component of bacterial flagellar, is released from various bacteria, including commensal or enteroinvasive microbes, and stimulates Toll-like receptor (TLR) 5 that is highly expressed in intestinal epithelium. Our recent results showed in non- transformed human colonocytes, as well as normal human colon that flagellin stimulation specifically induces proinflammatory gene expression, a prominent characteristic of the pathophysiology of IBD. In spite of these findings, the mechanisms by which bacterial flagellin signals proinflammatory responses in colonocytes and native colonic mucosa remain poorly understood. The central hypothesis of this proposal is that compromised epithelial barrier function, either by injury or by erosive pathogens, enables bacterial flagellin to penetrate the leaky epithelium and activate basolateral TLR5 leading to colonic inflammation. Our goals are to elucidate the signaling pathways by which flagellin exert its proinflammatory action(s) in human colonocytes and examine the participation of bacterial flagellin in the development and progress of colonic inflammation in mouse colitis models. Aim 1 will study the signal transduction pathway(s) leading to IL-8 and MIP-3a gene expression in response to flagellin in non-transformed human colonic NCM460 cells. In this aim we will identify the specific kinase(s) involved in MEK phosphorylation in response to flagellin exposure and examine their involvement in TLR5-dependent IL-8 and MIP-3a gene expression. Experiments to determine the signaling mechanism(s) by which the phosphatase MKP-1 amplifies flagellin-induced proinflammatory responses are also proposed. Aim 2 will examine the role of PI-3K signaling in TLR5-associated IL-8 and MIP-3a gene expression in human colonocytes. Aim 3 will examine the role of flagellin in the progress of colitis using mouse models of colitis and determine whether the basolateral or luminal aspect of the human and mouse colonic mucosa is responsive to flagellin. Our proposed studies will provide significant information relevant to the pathogenesis of colonic inflammation, including IBD.