Inhibition of Microflora-Induced Colitis by NF-kB

描述（由申请人提供）：本提案的目的是描述NF-β B亚单位在炎症性肠病发展中的作用。NF-（B）是由5个亚基组成的转录因子家族。响应于Toll样受体（TLR）信号传导的NF-β B的活化在驱动以炎性肠病为特征的病理性炎症中起核心作用。然而，已经表明，除了促炎作用之外，单个亚基也可以具有意想不到的抗炎作用。缺乏NF-β B的p50/p105亚基的小鼠对结肠炎的发展敏感，这至少部分是由于先天免疫系统的造血细胞内的缺陷导致IL-12 p40的过量产生。相反，缺乏NF-β B亚基c-Rel的小鼠对结肠炎具有抗性，并且具有降低的IL-12 p40表达。因此，NF-β B家族成员p50/p105和c-Rel似乎在调节下肠道炎症中具有相反的功能。该提案包含两个目标。目的1：探讨p50/p105缺陷型巨噬细胞IL-12 p40表达增强的机制。我们发现TLR诱导的IL-12 p40在缺乏p50/p105的巨噬细胞中的表达增加与干扰素-2（IFN-2）的分泌增加和STAT 1的活化增强有关。然而，IFN-2的产生增加和IL-12 p40表达增加之间的关系尚未确定。一种可能性是IL-12 p40表达的增加继发于IFN-2产生的增加和STAT 1活化的增强。另一种可能性是，基于p50抑制IL-12 p40表达的直接能力，在p50缺陷型巨噬细胞中观察到的IL-12 p40表达增加与IFN-2分泌无关。本研究的目的是检验这些可能性并描述p50的抑制功能。目的2：研究c-Rel在黏膜炎症反应中的作用。NF-β B家族成员c-Rel在调节IL-23亚基p40和p19的诱导中起重要作用（11，12）。与c-Rel在体内调节IL-23表达中的作用一致，我们已经发现先天免疫系统内缺乏c-Rel的小鼠对T细胞介导的结肠炎的发展具有抗性，并且表现出干扰素-3和IL-17的表达降低（8）。这使我们假设先天免疫系统中c-Rel的存在对于诱导Th 1和Th 17介导的肠道病理是必需的.在这个目标中，我们打算评估这一假设，确定先天免疫系统内的c-Rel的情况下，如何干扰的分化和激活的效应和调节T细胞群体使用体内结肠炎模型和体外培养系统。这些研究将促进我们对IBD的理解，并可能提出新的治疗方法。公共卫生相关性：NF-β B是炎症性肠病病理学特征的中心介质。详细了解NF-β B家族成员的功能可能会揭示新的治疗方法。

DESCRIPTION (provided by applicant): The purpose of this proposal is to delineate the role of NF-(B subunits in the development of inflammatory bowel disease. NF-(B is a transcription factor family consisting of 5 subunits. Activation of NF-(B in response to Toll-like receptor (TLR) signaling plays a central role in driving the pathological inflammation that characterizes inflammatory bowel disease. However, it has been shown that in addition to pro-inflammatory effects, individual subunits can have unexpected anti-inflammatory effects as well. Mice lacking the p50/p105 subunit of NF-(B are sensitized to the development of colitis, due at least in part to a defect within hematopoietic cells of the innate immune system that leads to excessive production of IL-12 p40. In contrast, mice lacking the NF-(B subunit c-Rel, are resistant to colitis, and have reduced expression of IL-12 p40. Thus, NF-(B family members p50/p105 and c-Rel appear to have opposing functions in the regulation of lower bowel inflammation. The proposal contains 2 aims. Aim 1: To determine the basis for increased expression of IL-12 p40 in p50/p105-deficient macrophages. We have found that increased TLR- induced expression of IL-12 p40 in macrophages that lack p50/p105 is associated with augmented secretion of interferon-2 (IFN-2) and enhanced activation of STAT1. However, the relationship between augmented production of IFN-2 and increased expression of IL-12 p40 has not been define. One possibility is that increased expression of IL-12 p40 is secondary to augmented production of IFN-2 and enhanced activation of STAT1. An alternative possibility is that increased expression of IL- 12 p40 observed in p50-deficient macrophages is independent of IFN-2 secretion, based on the direct ability of p50 to inhibit expression of IL-12 p40. The purpose of this aim is to examine these possibilities and delineate the inhibitory function of p50. Aim 2: To characterize the role of c-Rel in regulating the mucosal inflammatory response. The NF-(B family member c-Rel plays an essential role in regulating induction of both IL-23 subunits, p40 and p19 (11, 12). Consistent with a role for c- Rel in regulating IL-23 expression in vivo, we have found that mice lacking c-Rel within the innate immune system are resistant to the development of T cell-mediated colitis, and exhibit reduced expression of both interferon-3 and IL-17 (8). This has lead us to hypothesize that the presence of c- Rel within the innate immune system is necessary for induction of Th1 and Th17 mediated bowel pathology. In this aim, we intend to evaluate this hypothesis by determining how the absence of c-Rel within the innate immune system interferes with the differentiation and activation of effector and regulatory T cell populations using an in vivo colitis model and in vitro culture system. These studies will advance our understanding of IBD and possibly suggest novel therapeutic approaches. PUBLIC HEALTH RELEVANCE: NF-(B is a central mediator of the pathology that characterizes inflammatory bowel disease. A detailed understanding of the function of the NF-(B family members may unveil novel therapeutic approaches.