Novel Immunologic Effects of Semaphorin 7a in IPF

描述（由申请人提供）：特发性肺纤维化（IPF）是一种持续不断的疾病，其特征是肺泡浸润伴单核细胞炎症和胶原蛋白异常沉积。尽管经过多年的研究，它仍然是一种终末期诊断，影响着全世界数百万人。IPF与TGF- 1过量产生和替代活化（M2）巨噬细胞的出现有关。我们最近的研究表明，在吸入博来霉素或诱导肺靶向TGF-¿1过表达引起的肺纤维化模型中，对M2巨噬细胞分化的抑制有所改善。因此，M2激活是干预肺纤维化的合理目标。TGF-¿1在纤维化肺疾病中诱导M2出现和积累的机制尚不清楚。我们最近发现TGF- 1通过涉及1-整合素亚基的信号蛋白7a依赖途径影响M2表型。信号蛋白7a是一种GPI锚定的膜蛋白，我们最近发现它与人类肺纤维化有关。它通过其两种已知受体介导免疫事件、轴突引导和肿瘤侵袭，这两种受体是通过神经元引导蛋白Netrin-1和丛蛋白C1结合的1-整合素亚基。在小鼠TGF- 1诱导肺纤维化模型中进行的初步研究表明，骨髓来源细胞上的Semaphorin 7a表达足以诱导M2活化和纤维化，并且这些作用是通过TGF- 1整合素亚基介导的。有趣的是，该模型中纤维化的恢复与Netrin-1表达的显著诱导有关。在同时进行的一组人体研究中，我们发现，在IPF患者的循环中，CD4+淋巴细胞上的Sema 7a表面表达以及CD14+单核细胞中¿1整合素和Netrin-1的mRNA表达增强。丛C1不增高。此外，用重组Sema 7a刺激正常CD14+单核细胞可诱导交替激活表型，而¿1整合素阻断可减少IPF中CD14+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。这些独特的发现使我们假设CD4+淋巴细胞上的信号蛋白7a与单核细胞上的1-整合素和Netrin-1的相互作用导致了巨噬细胞的活化和肺纤维化。本提案的目的1将定义骨髓来源细胞上的Semaphorin 7a促进TGF-¿1暴露小鼠肺纤维化的关键细胞和机制。目标2将探讨在此过程中对Netrin-1的要求。目的3将确定Sema 7a- 1整合素/Netrin-1轴在IPF患者循环单核细胞的选择性活化中的作用。目的4将评估CD4+Sema7a+细胞在IPF患者队列中作为生物标志物的能力。

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.