T cell activation and crypt cell apoptosis

描述（由申请方提供）：IBD中肠组织炎症的慢性水平与隐窝细胞凋亡增加和结直肠癌发展风险增加相关。我们的研究结果暗示p53激活是肠道炎症状态下介导隐窝细胞凋亡的关键步骤。p53的主要作用是通过修复DNA损伤和/或诱导凋亡来保护发育中的细胞。p53在肠道中的重要性通过以下观察而突出：在慢性UC患者中早期检测到p53突变（甚至在异型增生之前），而在散发形式的结肠癌中，p53突变发生相对较晚。具体而言，70%的UC相关癌症和20%的UC异型增生病变包含p53突变。这些临床观察增加了发现组织炎症过程中p53诱导和激活机制的重要性。本研究将利用抗CD3 mAb处理的T细胞诱导的隐窝细胞凋亡的小鼠模型。基于初步结果，我们假设上皮细胞中的上皮TNF受体1和2信号传导诱导上皮p53表达，而TNF诱导的BM衍生细胞中的iNOS表达释放NO，激活p53蛋白并诱导参与隐窝细胞凋亡的下游p53靶基因的表达。本提案将探讨这一途径的要素。 首先，我们将研究Tell诱导的p53激活过程中TNF受体信号传导和iNOS诱导所涉及的细胞和分子途径。 这些研究将TNFR-1，TNFR-2和iNOS的表达限制在上皮细胞和BM衍生细胞中，并检查p53激活，p53靶点的表达和隐窝细胞凋亡的诱导。 接下来，我们计划研究p53的下游效应物。我们将使用特定的基因敲除小鼠（bax/bak和bid-/-）来解决基于野生型和p53缺失小鼠中p53靶基因分析的假设。 我们以前的研究显著地推进了对T细胞诱导的隐窝细胞凋亡的关键步骤的理解，但仍有一些关键问题没有回答。目前的建议将使我们更接近于理解在肠道炎症中诱导隐窝细胞凋亡所需的细胞和分子事件。这些研究将增强我们对正常隐窝细胞死亡相关机制的理解，并增加对IBD中肠癌变诱导相关途径的了解。

DESCRIPTION (provided by applicant): Chronic levels of intestinal tissue inflammation in IBD are associated with increased crypt cell apoptosis and an increased risk for development of colorectal cancer. Our results implicate p53 activation as a key step in mediating crypt cell apoptosis in states of intestinal inflammation. The primary role of p53 is to protect developing cells by repairing DNA damage and/or inducing apoptosis. The importance of p53 in the intestine is highlighted by observations that p53 mutations are detected early in patients with chronic UC (even before dysplasia), whereas in sporadic forms of colon cancer, p53 mutations occur relatively late. Specifically, 70% of UC-associated cancers and 20% of dysplastic lesions analyzed in UC contain p53 mutations. These clinical observations increase the importance of discovering mechanisms for p53 induction and activation during tissue inflammation. Studies in the present aim will utilize the anti-CD3 mAb-treated mouse model of T cell-induced crypt cell apoptosis. Based on preliminary results, we hypothesize that epithelial TNF receptor 1 and 2 signaling in epithelial cells induce epithelial p53 expression whereas TNF-induced iNOS expression in BM-derived cells releases NO that activates p53 protein and induces expression of downstream p53 target genes involved in crypt cell apoptosis. The elements of this pathway will be explored in the current proposal. First, we will examine the cellular and molecular pathways involved in TNF receptor signaling and iNOS induction during Tell-induced activation of p53. These studies will restrict expression of TNFR-1, TNFR-2, and iNOS to epithelial Vs BM-derived cells and examine p53 activation, expression of p53 targets and induction of crypt cell apoptosis. Next, we plan to examine the downstream effectors of p53. We will use specific gene knockout mice (bax/bak and bid-/-) to address hypotheses based on analysis of p53 target genes in wild type and p53 null mice. Our previous studies significantly advanced out understanding of the critical steps in T cell-induced crypt cell apoptosis, yet there are key questions that remain unanswered. The current proposal will move us closer to understanding the cellular and molecular events required for the induction of crypt cell apoptosis in intestinal inflammation. These studies will enhance our understanding of the mechanisms relevant to normal crypt cell death and add insight into the pathways involved in the induction of intestinal carcinogenesis in IBD.