X-Linked Inhibitor of Apoptosis in Fibroblast Phenotypes and Lung Fibrosis

摘要/项目摘要 肺纤维化是一种异常的创伤修复反应，其中可溶性和生物力学刺激 促进肌成纤维细胞的活化和存活，肌成纤维细胞存款过量的细胞外 矩阵（ECM）。这导致正常肺结构和功能的破坏，伴随进行性肺损伤。 呼吸衰竭和死亡肌成纤维细胞凋亡预示着伤口修复的解决，但我们 已经表明，纤维化肺肌成纤维细胞通过增加X- 连接的凋亡抑制蛋白（XIAP），IAP蛋白家族的原型成员。 IAP的广泛药理学抑制促进肌成纤维细胞凋亡和肺损伤的消退 我们的初步数据表明，XIAP的特异性缺失足以 减轻肺纤维化。XIAP在肌成纤维细胞内表达，所述肌成纤维细胞包含成纤维细胞灶， 在特发性肺纤维化（IPF）患者中， XIAP是由TGF-β1诱导的，XIAP功能的丧失或抑制可增强成纤维细胞的增殖。 细胞凋亡的易感性。然而，目前尚不清楚增强的肌成纤维细胞凋亡是否是 足以解决纤维化肺损伤或是否抑制额外的非典型功能， XIAP有助于观察到的抗纤维化作用。新的研究将肺纤维化与 稳态自噬/线粒体自噬的抑制以及线粒体损伤和功能障碍。我们 初步数据表明XIAP介导TGF-β诱导的肌成纤维细胞分化， 抑制自噬，同时促进线粒体损伤。总的来说，这些发现激发了 我们的新假设是XIAP整合了可溶性和基质介导的刺激，以促进一个程序， 促纤维化成纤维细胞表型，包括自噬/线粒体自噬抑制，线粒体DNA 损伤和肌成纤维细胞分化以及凋亡抗性。本提案的目标 1）确定XIAP在成纤维细胞自噬/线粒体自噬调节中的作用， 肌成纤维细胞分化，2）检查XIAP在代谢活性和线粒体 在肺成纤维细胞中的功能，和3）定义XIAP在肺成纤维细胞的起始、进展和 肺损伤和纤维化修复的解决。这些研究的完成将通过以下方式确定机制： 其中XIAP在肌成纤维细胞生物学和肺纤维化中具有核心作用， 在IPF治疗中靶向该IAP。

Abstract/Project Summary Lung fibrosis is an aberrant wound-repair response in which soluble and biomechanical stimuli promote the activation and survival of myofibroblasts which deposit excessive amounts of extracellular matrix (ECM). This leads to the destruction of normal lung architecture and function, with progressive respiratory failure and death. Myofibroblast apoptosis heralds the resolution of wound repair, but we have shown that fibrotic lung myofibroblasts circumvent apoptosis through increased expression of X- linked Inhibitor of Apoptosis Protein (XIAP), the prototypical member of the IAP family of proteins. Broad pharmacologic inhibition of IAPs promotes myofibroblast apoptosis and the resolution of lung fibrosis in vivo, and our preliminary data demonstrate that the specific deletion of XIAP is sufficient to attenuate lung fibrosis. XIAP is expressed within the myofibroblasts that comprise fibroblastic foci of patients with idiopathic pulmonary fibrosis (IPF), explanted IPF lung fibroblasts have increased levels of XIAP, XIAP is induced by TGF-β1, and the loss or inhibition of XIAP function enhances the fibroblast susceptibility to apoptosis. However, it remains unclear whether enhanced myofibroblast apoptosis is sufficient to resolve fibrotic lung injury or whether inhibition of additional non-canonical functions of XIAP contribute to the anti-fibrotic effects observed. Emerging studies have linked lung fibrosis with suppression of homeostatic autophagy/mitophagy and with mitochondrial damage and dysfunction. Our preliminary data demonstrate that XIAP mediates TGF-β induced myofibroblast differentiation and suppression of autophagy while promoting mitochondrial damage. Collectively, these findings motivate our novel hypothesis that XIAP integrates soluble and matrix-mediated stimuli to promote a program of pro-fibrotic fibroblast phenotypes including autophagy/mitophagy suppression, mitochondrial DNA damage, and myofibroblast differentiation in addition to apoptosis resistance. The goals of this proposal are to: 1) determine the role of XIAP in the regulation of fibroblast autophagy/mitophagy and myofibroblast differentiation, 2) examine XIAP in the regulation of metabolic activity and mitochondrial function in lung fibroblasts, and 3) define the role of XIAP during the initiation, progression, and resolution of lung injury and fibrotic repair. Completion of these studies will define the mechanisms by which XIAP has a central role in myofibroblast biology and lung fibrosis, providing pre-clinical support for targeting this IAP in the treatment of IPF.