Attenuation of Lupus by Foxo3

 描述（由申请人提供）：自身免疫性疾病系统性红斑狼疮（SLE）的特征是对核抗原的耐受性丧失和自身抗体的产生。它们形成免疫复合物，促进炎症和组织损伤。一些证据表明，SLE的发病机制是由获得性免疫耐受的丧失与先天免疫系统的过度活跃相结合介导的。后者与促炎细胞因子（包括I型IFN）的产生增加相关。确定控制这些事件的分子机制可能会揭示SLE的新的治疗靶点。我们推测转录因子Foxo 3可以减轻狼疮的严重程度。Foxo 3是转录因子Foxo家族的成员，其在mRNA和翻译后水平上被PI 3激酶信号转导下调。 我们的初步数据表明，Foxo 3缺陷小鼠改变了未成熟B细胞凋亡和受体编辑，这两种方式都是中枢B细胞耐受。Foxo 3在髓系细胞中也具有几种独特的抗炎作用。它抑制树突状细胞中的促炎反应，并且已知限制人和鼠巨噬细胞中I型IFN和IFN特征基因的表达。升高的Foxo 3 mRNA表达与克罗恩病和类风湿性关节炎的严重程度降低相关，并且肿瘤浸润性树突细胞由于Foxo 3 mRNA表达增加而具有致耐受性。这突出了Foxo 3及其mRNA表达的控制在调节炎症反应中的重要性。有趣的是，初步分析表明，SLE患者分为两个不同的组方面的mRNA表达的Foxo 3和相关基因的集群（我们称之为“Foxo 3签名”）。在这里，我们将通过以下目的来检验Foxo 3在狼疮中起保护作用的假设。在目标1中，我们将询问在广泛的BCR编辑后保持自身反应性的B细胞是否在Foxo 3不存在的情况下存活而不是经历缺失。我们将使用RS重组的PCR测定、受体编辑的测量和自身反应性B细胞缺失的IG Tg模型来研究Foxo 3-/-小鼠中的编辑和缺失。在目标2中，我们将确定在缺乏Foxo 3的情况下，易于发展狼疮的小鼠是否具有更严重的疾病，如果是，哪些细胞类型介导这种效应。在目标3中，我们将比较表达低水平与高水平Foxo 3的SLE患者的基因表达谱和临床疾病参数，以确定具有高水平Foxo 3和相关“签名”基因的患者是否具有改变的病程。这项工作将确定Foxo 3是否限制狼疮的严重程度，并为SLE患者的一个子集描述一组独特的Foxo 3相关生物标志物。这些研究还将为靶向Foxo 3或Foxo 3特征基因的新治疗方法铺平道路。

 DESCRIPTION (provided by applicant): The autoimmune disease Systemic Lupus Erythematosus (SLE) is characterized by a loss of tolerance to nu- clear antigens and the production of autoantibodies. These form immune complexes which promote inflammation and tissue damage. Several lines of evidence suggest that SLE pathogenesis is mediated by loss of adaptive immune tolerance coupled with hyperactivity of the innate immune system. The latter is associated with increased production of pro-inflammatory cytokines, including type I IFNs. Defining the molecular mechanisms that control these events may reveal novel therapeutic targets for SLE. We hypothesize that the transcription factor Foxo3 serves to attenuate the severity of lupus. Foxo3 is a member of the Foxo family of transcription factors which are downregulated by PI3 kinase signaling at both the mRNA and posttranslational levels. Our preliminary data indicate that Foxo3-deficient mice have altered immature B cell apoptosis and receptor editing, both means of central B cell tolerance. Foxo3 also has several unique anti-inflammatory roles in myeloid lineage cells. It dampens proinflammatory responses in dendritic cells and is known to limit the expression of type I IFNs and IFN signature genes in both human and murine macrophages. Elevated Foxo3 mRNA expression is associated with reduced severity of Crohn's disease and rheumatoid arthritis, and tumor- infiltrating dendritic cells are tolerogenic due to increased Foxo3 mRNA expression. This highlights the importance of Foxo3, and the control of its mRNA expression, in modulating inflammatory responses. Interestingly, preliminary analysis suggests that SLE patients fall into two distinct groups with respect to mRNA expression of Foxo3 and a cluster of associated genes (which we term the "Foxo3 signature"). Here, we will test the hypothesis that Foxo3 plays a protective role in lupus via the following Aims. In Aim 1, we will ask whether B cells that remain autoreactive after extensive BCR editing survive rather than undergo deletion in the absence of Foxo3. We will study editing and deletion in Foxo3-/- mice using a PCR assay of RS recombination, a measure of receptor editing, and an Ig Tg model in which autoreactive B cells are deleted. In Aim 2, we will determine whether mice that are prone to develop lupus have more severe disease in the absence of Foxo3, and if so which cell types mediate this effect. In Aim 3, we will compare SLE patients expressing low vs. high levels of Foxo3 for gene expression profiles and clinical disease parameters to determine whether patients with high levels of Foxo3 and associated "signature" genes have an altered disease course. This work will deter- mine whether Foxo3 limits the severity of lupus and characterize a unique set of Foxo3 associated biomarkers for a subset of SLE patients. These studies will also pave the way for new therapeutic approaches that target Foxo3 or Foxo3 signature genes.