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）是一种复发缓解型疾病，表现为肠道慢性和衰弱性炎症，在美国越来越多的患者中出现(1)。具有Th1表型的CD4 T细胞在肠黏膜中的不适当积聚在维持疾病病理中起着不可或缺的作用（2-8）。因此，阻断CD4 Th1 T细胞向炎症肠道的运输是一个深入研究的领域。申请人最近的研究发现了神经引导分子netrin-1在急性结肠炎期间阻断白细胞迁移中的惊人作用(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，并显著降低了克罗恩样回肠炎小鼠回肠中效应CD4 T细胞的数量（TNFΔARE）。在netrin-1治疗后，在TNFΔARE回肠中观察到Th1趋化因子受体CXCR3和CCR5的表达显著降低，表明netrin-1减弱了Th1 T细胞的反应。Netrin-1在体外阻止TNFΔARE CD4 T细胞向特定Th1趋化因子迁移。体内归巢实验表明，netrin-1阻断TNFΔARE CD4 T细胞向炎症回肠的运输，这表明netrin-1对CD4 T细胞迁移有直接影响。

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. "