Toll-like receptors and intestinal inflammation

描述(申请人提供)：人体肠道内有大量共生微生物。一些临床观察和动物实验表明，肠道细菌在慢性肠炎的发病机制中起主要作用。肠道侵袭性病原体，如沙门氏菌、志贺氏菌、耶尔森氏菌和李斯特氏菌，可侵入上皮并引发炎症反应。鞭毛蛋白是细菌鞭毛的主要成分，由多种细菌释放，包括共生微生物或肠道侵袭性微生物，刺激肠道上皮细胞高表达的Toll样受体(TLR)5。我们最近的结果表明，在未转化的人类结肠细胞和正常人类结肠中，鞭毛蛋白刺激特异性地诱导促炎基因的表达，这是IBD病理生理的一个显著特征。尽管有这些发现，但细菌鞭毛蛋白在结肠细胞和自然结肠粘膜中发出促炎症反应信号的机制仍然知之甚少。这一建议的中心假设是，无论是损伤还是腐蚀性病原体损害的上皮屏障功能，都使细菌鞭毛能够穿透渗漏的上皮并激活基底外侧TLR5，从而导致结肠炎。我们的目标是阐明鞭毛蛋白在人结肠细胞中发挥促炎作用的信号通路(S)，并研究细菌鞭毛蛋白在小鼠结肠炎模型结肠炎症发生发展中的作用。目的1研究鞭毛蛋白诱导未转化人结肠NCM460细胞IL-8和MIP-3a基因表达的信号转导途径(S)。在这一目标中，我们将确定参与鞭毛蛋白暴露反应中MEK磷酸化的特定激酶(S)，并研究它们在依赖TLR5的IL-8和MIP-3a基因表达中的作用。还提出了确定磷酸酶MKP-1放大鞭毛诱导的促炎反应的信号机制的实验(S)。目的2研究PI-3K信号在人结肠细胞TLR5相关IL-8和MIP-3a基因表达中的作用。目的3将利用小鼠结肠炎模型研究鞭毛蛋白在结肠炎进展中的作用，并确定人和小鼠结肠粘膜的基侧或腔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.