Mechanisms of Increased Lung Fibrosis in Males

描述（由申请人提供）：系统性硬化症相关间质性肺病（SSc-ILD）是一种慢性炎症性疾病，其特征是包括肺在内的多个器官的严重纤维化。 SSc 在女性中比在男性中更常见；然而，男性的疾病会加速，生存率也会降低。博来霉素诱导的雄性小鼠肺纤维化也比雌性小鼠更严重。这种对 SSc 的易感性或损害的性别差异背后的机制仍然知之甚少。该提议以我们的动物模型观察为指导，即与具有 XY 性染色体补体的小鼠相比，具有 XX 性染色体补体的小鼠表现出对全身炎症性疾病发展的易感性增加，无论性别如何。有趣的是，具有 XY 性染色体补体的雄性和雌性小鼠都比具有 XX 性染色体补体的小鼠出现更严重的纤维化。 XY 小鼠纤维化的增加与 IL-13 的增加和 IL-13RA2（IL-13 的诱饵受体）表达的减少有关。 IL-13RA2 基因位于 X 染色体上。因此，与 XX 小鼠相比，免疫的 XY 小鼠 IL-13RA2 表达减少，导致与纤维化有关的 IL-13 增加。这些数据表明 X 染色体基因剂量在调节炎症性疾病的易感性和损伤方面可能发挥作用。 使用上述小鼠模型，我们将检验以下假设：无论性腺性别如何，XY 性染色体补体都会带来更大的肺纤维化和 SSc-ILD 风险。具体来说，我们将测试博来霉素诱导的肺纤维化在 XY 性染色体基因型小鼠中是否比在 XX 性染色体基因型小鼠中更严重（目标 1）。在该提案的目标 2 中，我们将开始将这一发现应用到人类身上。具体来说，我们将确定 X 染色体编码基因的表达，并寻找它们与 SSc 患者纤维化的相关性。我们将使用血液和支气管肺泡灌洗液 (BAL) 来检验以下假设：这些样本中 X 染色体编码基因 IL13RA2 的表达水平与 SSc-ILD 的严重程度呈负相关。根本原因是男性有一份 IL13RA2 拷贝，因此男性的 IL-13RA2 水平可能低于女性。由于 IL-13RA2 是 2 型细胞因子的诱饵受体，因此男性炎症部位的 2 型细胞因子水平可能高于女性。 2 型细胞因子可诱导 TGFb 的产生，从而诱导纤维化。因此，虽然 2 型细胞因子和 TGFb 都可以诱导免疫调节并降低自身免疫和炎症的初始易感性，但这些细胞因子过量会导致男性组织修复失调、纤维化和器官损伤。获得的研究结果将为进一步研究奠定基础，以建立男性 SSc 加速进展的生物标志物，并确定 SSc-ILD 和其他以过度纤维化为特征的疾病的新治疗靶点。 （摘要完）

DESCRIPTION (provided by applicant): Systemic sclerosis associated interstitial lung disease (SSc-ILD) is a chronic inflammatory condition characterized by severe fibrosis in multiple organs including lungs. SSc is more common in women than in men; however men experience an accelerated disease with reduced survival. Bleomycin-induced lung fibrosis is also more severe in male mice than in females. Mechanisms underlying such sex differences in susceptibility to or damage from SSc remain poorly understood. This proposal is guided by our animal model observations that mice with XX sex chromosome complement exhibit increased susceptibility to the development of systemic inflammatory disease as compared to mice with XY sex chromosome complement, regardless of the gender. Intriguingly, both male and female mice with XY sex chromosome complement develop a more severe fibrosis than mice with XX sex chromosome complement. The increased fibrosis in XY mice is associated with increased IL-13 and reduced expression of IL-13RA2, a decoy receptor for IL-13. The gene for IL-13RA2 is located on X chromosome. Thus, compared to XX mice, the immunized XY mice have reduced expression of IL-13RA2, leading to increased IL-13 that has been implicated in fibrosis. These data suggest a possible role of X chromosome gene dosage in modulating susceptibility to and damage from inflammatory diseases. Using the above mouse model, we will test the hypothesis that regardless of the gonadal sex, XY sex chromosome complement confers a greater risk for lung fibrosis and SSc-ILD. Specifically, we will test whether bleomycin induced lung fibrosis is more severe in mice with XY sex chromosome genotype than in mice with XX sex chromosome genotype (Aim 1). In Aim 2 of this proposal, we will begin to translate the finding onto humans. Specifically, we will determine the expression of X chromosome encoded genes and seek their correlation with fibrosis in patients with SSc. Using blood and bronchoalveolar lavage (BAL), we will test the hypothesis that expression levels of an X chromosome-encoded gene, IL13RA2, in these samples will negatively correlate with the severity of SSc-ILD. The underlying rationale is that men have one copy of IL13RA2 and thus, may have lower levels of IL-13RA2 than women. Since IL-13RA2 serves as a decoy receptor for type 2 cytokines, men are likely to have higher levels of type 2 cytokines than women at the site of inflammation. Type 2 cytokines can induce the production of TGFb that can induce fibrosis. Thus, while both type 2 cytokines and TGFb can induce immune regulation and reduce the initial susceptibility for autoimmunity and inflammation, excess of these cytokines can cause dysregulated tissue repair, fibrosis and organ damage in men. The findings obtained will form the basis for further studies to establish biomarkers of accelerated SSc progression in men and to identify new targets of treatment for SSc-ILD and other diseases that are characterized by excessive fibrosis. (End of Abstract)