Novel Immunologic Effects of Semaphorin 7a in IPF

描述（由申请人提供）：特发性肺纤维化（IPF）是一种慢性疾病，其特征为肺泡浸润单核细胞炎症和胶原蛋白异常沉积。尽管经过多年的研究，它仍然是一种影响全球数百万人的晚期诊断。IPF与TGF-β 1过度产生和交替激活（M2）巨噬细胞的出现有关。我们最近发现，在博莱霉素吸入或诱导型肺靶向TGF-β 1过表达引起的肺纤维化模型中，M2巨噬细胞分化的抑制是改善的。因此，M2活化是肺纤维化干预的合理靶点。关于TGF-β 1诱导M2在纤维化肺病中出现和积聚的机制知之甚少。我们最近发现，TGF-β 1通过一个涉及β 1-整联蛋白亚基的脑信号蛋白7a依赖性途径影响M2表型。Semaphorin 7a是一种GPI锚定的膜蛋白，我们最近将其与人类肺纤维化联系起来。它通过其两种已知受体介导免疫事件、轴突导向和肿瘤侵袭，这两种受体是通过神经元导向蛋白Netrin-1和丛状蛋白C1缔合的整合素亚基。在TGF-β 1诱导的肺纤维化的鼠模型中进行的初步工作表明，骨髓来源的细胞上的脑信号蛋白7a表达足以诱导M2活化和纤维化，并且这些作用是通过β 1-整联蛋白亚基介导的。有趣的是，该模型中纤维化的恢复与Netrin-1表达的显著诱导相关。在同时进行的一组人体研究中，我们发现，在IPF受试者的循环中，CD 4+淋巴细胞上Sema 7a的表面表达以及CD 14+单核细胞中整合素和Netrin-1的mRNA表达增强。丛状蛋白C1没有增加。此外，用重组Sema 7a刺激正常的CD 14+单核细胞诱导了一种交替活化的表型，并且1整合素阻断剂减少了IPF中CD 14+单核细胞向M2巨噬细胞的转变。Netrin-1在这些过程中的作用尚不清楚。这一独特的发现使我们推测，正是CD 4+淋巴细胞上的脑信号蛋白7a与单核细胞上的整合素和Netrin-1的相互作用导致了替代性巨噬细胞活化和肺纤维化。本提案的目的1将定义骨髓源性细胞上的脑信号蛋白7a促进TGF-β 1暴露的鼠肺纤维化的关键细胞和机制。目标2将探讨在这一过程中对Netrin-1的需求。目标3将确定Sema 7a-â 1整联蛋白/Netrin-1轴在从IPF患者获得的循环单核细胞的替代激活中的作用。目的4将评估CD 4 + Sema 7a+细胞作为IPF患者队列中生物标志物的能力。

DESCRIPTION (provided by applicant): Idiopathic Pulmonary Fibrosis (IPF) is a relentless disease characterized by infiltration of the alveolus with monocytic inflammation and abnormal deposits of collagen. Despite many years of research it remains a terminal diagnosis that affects millions of people worldwide. IPF is associated with TGF-¿1 overproduction and the appearance of alternatively activated (M2) macrophages. We have recently shown that inhibition of M2 macrophage differentiation is ameliorative in models of pulmonary fibrosis caused by either bleomycin inhalation or inducible lung targeted TGF-¿1 overexpression. Thus, M2 activation is a legitimate target for intervention in pulmonary fibrosis. Little is known about the mechanism(s) through which TGF-¿1 induces M2 appearance and accumulation in fibrotic lung disease. We have recently found that TGF-¿1 affects M2 phenotypes through a Semaphorin 7a dependent pathway that involves the ¿1-integrin subunit. Semaphorin 7a is a GPI anchored membrane protein that we have recently linked to human lung fibrosis. It mediates immunologic events, axon guidance, and tumor invasion through its two known receptors, the ¿1-integrin subunit, which associates through the neuronal guidance protein Netrin-1, and Plexin C1. Preliminary work performed in a murine model of TGF-¿1 induced lung fibrosis indicates that Semaphorin 7a expression on bone marrow derived cells is sufficient to induce M2 activation and fibrosis and that these effects are mediated via the ¿1-integrin subunit. Interestingly, the restoration of fibrosis in this model is associated with impressive induction of Netrin-1 expression. In a simultaneous set of human studies we have found that surface expression of Sema 7a on CD4+ lymphocytes, and mRNA expression of ¿1 integrin and Netrin-1 in CD14+ monocytes, is enhanced in the circulation of subjects with IPF. Plexin C1 is not increased. In addition, stimulation of normal CD14+ monocytes with recombinant Sema 7a induces an alternatively activated phenotype and ¿1 integrin blockade reduces the CD14+ monocyte to M2 macrophage transition in IPF. The role of Netrin-1 in these processes is not known. This unique constellation of findings leads us to hypothesize that it is the interaction of Semaphorin 7a on CD4+ lymphocytes with the ¿1-integrin and Netrin-1 on monocytes that leads to alternative macrophage activation and pulmonary fibrosis. Aim 1 of this proposal will define the critical cells and mechanisms through which Semaphorin 7a on bone marrow derived cells promotes fibrosis in the TGF-¿1-exposed murine lung. Aim 2 will explore a requirement for Netrin-1 in this process. Aim 3 will determine the role of the Sema 7a-¿1 integrin/Netrin-1 axis in the alternative activation of circulating monocytes obtained from patients with IPF. Aim 4 will assess the ability of CD4+Sema7a+ cells to function as a biomarker in a cohort of patients with IPF.