Epithelial-released netrin-1 controls CD4 effector T cell trafficking during chro

描述(由申请人提供)：炎症性肠病(IBD)是一种复发的缓解性疾病，在美国越来越多的患者中表现为慢性和衰弱的肠道炎症(1)。肠道粘膜中具有Th1表型的CD4T细胞的不适当积聚在维持疾病病理过程中起着不可或缺的作用(2-8)。因此，阻止CD4Th1T细胞转运到发炎的肠道是一个深入研究的领域。申请人最近的研究发现，神经元引导分子netrin-1在急性结肠炎期间阻止白细胞迁移方面发挥了令人惊讶的作用(9)。然而，Netrin-1在IBD中观察到的慢性炎症中的作用尚不清楚。令人兴奋的是，Netrin-1治疗几乎完全逆转了组织学疾病，并显著减少了克罗恩样回肠炎(肿瘤坏死因子ΔARE)小鼠回肠中效应CD4T细胞的数量。在Netrin-1治疗后，在肿瘤坏死因子Δ回肠中观察到Th1型趋化因子受体CXCR3和CCR5的表达显著减少，表明Netrin-1减弱了Th1T细胞反应。Netrin-1在体外抑制肿瘤坏死因子Δ是CD4T细胞向特异性Th1型趋化因子的迁移。体内归巢试验表明，Netrin-1阻断肿瘤坏死因子Δ是CD4T细胞向炎症回肠的转运，表明Netrin-1对CD4T细胞迁移有直接影响。 申请人确认肠上皮是急性炎症期间Netrin-1的主要来源，Netrin-1通过A2B腺苷受体(A2BAR)在急性结肠炎中介导抗炎反应(9)。有趣的是，A2BAR在肿瘤坏死因子Δ上高水平表达，Netrin-1是CD4T细胞，Netrin-1可以诱导A2BAR信号传导。腺苷受体信号转导与阻断趋化因子受体功能反应有关，包括细胞迁移(10-12)。基于这些发现，我们假设在慢性炎症期间，肠上皮细胞衍生的netrin-1通过A2B腺苷受体介导的信号通路抑制CD4Th1T细胞的运输。一种新的上皮特异性Netrin-1缺失的遗传模型将有助于阐明内源性Netrin-1在慢性肠炎发生发展中的功能作用。体内和体外功能分析将确定Netrin-1信号通路在肿瘤坏死因子Δ回肠炎中的治疗作用。申请者将使用K01机制通过参加有重点的研讨会和会议来发展她的粘膜免疫学和T细胞生物学知识。在她参加实践课程的同时，她组建的委员会将帮助她学习进行CD4T细胞功能分析所需的技术。拟议研究的目标是使用遗传学和药理学方法来确定netrin-1在慢性肠炎中的作用，就像IBD所发生的那样。“

DESCRIPTION (provided by applicant): Inflammatory bowel diseases (IBD) are relapsing remitting conditions that manifest as chronic and debilitating inflammation of the intestine in an ever-increasing number of patients in the USA (1). Inappropriate accumulation of CD4 T cells with a Th1 phenotype in the intestinal mucosa plays an indispensable role in maintaining disease pathology (2-8). As such blocking CD4 Th1 T cell trafficking to the inflamed intestine is an area of intense investigation. Recent investigations by the applicant unearthed a surprising role for the neuronal guidance molecule, netrin-1 in blocking leukocyte migration during acute colitis (9). However, the role of netrin-1 in chronic inflammation as observed in IBD is unknown. Excitingly, netrin-1 treatment almost completely reversed histological disease and dramatically decreased the number of effector CD4 T cells in the ileum of mice with Crohn's-like ileitis (TNFΔARE). Following netrin-1 treatment a robust reduction in the expression of Th1 chemokine receptors, CXCR3 and CCR5, was observed in TNFΔARE ileum indicating netrin-1 attenuated a Th1 T cell response. Netrin-1 prevented TNFΔARE CD4 T cell migration towards specific Th1 chemokines in vitro. In vivo homing assays demonstrated netrin-1 blockade of TNFΔARE CD4 T cell trafficking to the inflamed ileum, pointing to a direct effect of netrin-1 on CD4 T cell migration. The applicant identified the intestinal epithelium as the major source of netrin-1 during acute inflammation with netrin-1 mediating an anti- inflammatory response through the A2B adenosine receptor (A2BAR) in acute colitis (9).Interestingly, the A2BAR is expressed to a high level on TNFΔARE CD4 T cells and netrin-1 can induce A2BAR signaling. Adenosine receptor signaling has been implicated in blocking chemokine receptor functional responses, including cell migration (10-12). Based on these findings, we hypothesize that during chronic inflammation intestinal epithelial derived netrin-1 suppresses CD4 Th1 T cell trafficking through an A2B adenosine receptor mediated signaling pathway. A novel genetic model for epithelial specific deletion of netrin-1 will assist in elucidating the functional role of endogenous netrin-1 during development of chronic intestinal inflammation. In vivo and in vitro functional assays will identif the netrin-1 signaling pathway responsible for the therapeutic effect of netrin-1 in TNFΔARE ileitis. The applicant will use the K01 mechanism to develop her knowledge of mucosal immunology and T cell biology by attending focused workshops and conferences. The committee she has assembled to assist her along with her participation in practical courses will educate her in the technology she needs to perform her analyses of CD4 T cell function. The goal of the proposed studies is to use a genetic and pharmacologic approach to determine the role of netrin-1 in chronic intestinal inflammation as occurs in IBD. "