PAI-1 and aging-related susceptibility to lung fibrosis

 描述（由申请方提供）：特发性肺纤维化（IPF）是一种与衰老相关的进行性致死性肺部疾病，病因不明，无有效治疗。肺泡II型上皮细胞（AEC 2）凋亡和（肌）成纤维细胞凋亡抵抗在IPF肺中是明显的，并且被认为是IPF启动和进展的关键。有趣的是，我们的研究表明，与年轻小鼠相比，老年小鼠在博来霉素激发后经历了减少的成纤维细胞凋亡，但增加了AEC 2凋亡和纤维化反应，这表明AEC 2和成纤维细胞凋亡的失调可能是年龄相关的IPF易感性的基础。然而，衰老过程中成纤维细胞和AEC 2凋亡失调的机制尚不清楚。纤溶酶原激活物抑制剂1（派-1）是组织型和尿激酶型纤溶酶原激活物（tPA和uPA）的主要抑制剂，在肺纤维化的发生发展中起重要作用。重要的是，我们以前的研究/初步数据表明，派-1的表达随着年龄的增加，在小鼠肺成纤维细胞和AEC 2和派-1活性的抑制恢复的敏感性，肺成纤维细胞从老年小鼠细胞凋亡。我们以前的研究/初步数据进一步表明，抑制派-1活性或用派-1 siRNA敲低派-1可诱导p53（细胞凋亡的主控制器）和肺成纤维细胞的细胞凋亡，但抑制AEC 2中的p53和细胞凋亡。基于这些数据，我们假设与年龄相关的派-1增加导致AEC 2和成纤维细胞凋亡的失调，这是老年人对肺纤维化易感性增加的基础。氧化还原失衡在老年动物和IPF中明显。然而，氧化还原失衡如何导致年龄相关的IPF易感性尚不清楚。我们以前的研究/初步数据表明，谷胱甘肽（GSH），最丰富的细胞内游离巯基和一个重要的抗氧化剂的浓度，减少，而NADPH氧化酶4（Nox 4），一个重要的生产商的活性氧（ROS）的表达，随着年龄的增长，在啮齿动物的肺。我们前期的研究也表明，Nox 4源性ROS通过修饰/抑制MAPK磷酸酶1（MKP-1）诱导成纤维细胞派-1的表达，而GSH通过阻断JNK/p38的活化选择性抑制TGF-β1诱导的派-1的表达。重要的是，我们的初步数据显示，在老年小鼠的肺中，MKP-1巯基修饰增加，而MKP-1的活性降低。因此，我们进一步假设衰老相关的氧化还原失衡通过修饰/抑制MKP（例如MKP-1）诱导派-1而导致AEC 2和成纤维细胞凋亡的失调。提出了四个具体的目标来验证我们的假设，使用不同的动物模型，包括新的派-1条件性敲除小鼠模型，最近在本实验室产生。还将在老年小鼠中测试小分子派-1抑制剂对肺纤维化的治疗潜力。这些研究的结果不仅将揭示与年龄相关的IPF易感性的潜在机制，而且还可能导致新的范式转变概念以及治疗IPF的新疗法。

 DESCRIPTION (provided by applicant): Idiopathic pulmonary fibrosis (IPF) is an aging-related progressive fatal lung disorder with no known etiology and no effective treatment. Alveolar type II epithelial cell (AEC2) apoptosis and (myo)fibroblast apoptosis resistance are evident in IPF lungs and are believed to be a key in the initiation and progression of IPF. Interestingly, our studies show that old mice experience diminished fibroblast apoptosis but augmented AEC2 apoptosis and fibrotic response upon bleomycin challenge, compared to young mice, suggesting that dysregulation of AEC2 and fibroblast apoptosis may underlie the aging-related susceptibility to IPF. The mechanism underlying the dysregulation of fibroblast and AEC2 apoptosis during aging, however, is unknown. Plasminogen activator inhibitor 1 (PAI-1), a primary inhibitor of tissue-type and urokinase-type plasminogen activators (tPA and uPA), plays an important role in the development of lung fibrosis. Importantly, our previous studies/preliminary data show that PAI-1 expression is increased with age in mouse lung fibroblasts and AEC2 and that inhibition of PAI-1 activity restored the sensitivity of lung fibroblasts from old mice to apoptosis. Our previous studies/preliminary data further show that inhibition of PAI-1 activity or knockdown of PAI-1 with PAI-1 siRNA induces p53, a master controller of apoptosis, and apoptosis in lung fibroblasts but suppresses p53 and apoptosis in AEC2. Based on these data, we hypothesize that aging-related increase in PAI-1 leads to dysregulation of AEC2 and fibroblast apoptosis, which underlies the increased susceptibility of the elderly to lung fibrosis. Redox imbalance is evident in aged animals and in IPF. How redox imbalance contributes to aging-related susceptibility to IPF, however, is unclear. Our previous studies/preliminary data show that the concentrations of glutathione (GSH), the most abundant intracellular free thiol and an important antioxidant, decrease whereas the expression of NADPH oxidase 4 (Nox4), an important producer of reactive oxygen species (ROS), increases with age in rodent lungs. Our previous studies also showed that Nox4-derived ROS induced PAI-1 in fibroblasts through modifying/inhibiting MAPK phosphatase 1 (MKP-1) whereas GSH selectively inhibited TGF-β1-induced PAI-1 by blocking JNK/p38 activation. Importantly, our preliminary data show that MKP-1 thiol modification is increased whereas the activity of MKP-1 is decreased in the lung of old mice. Therefore, we further hypothesize that aging-related redox imbalance contributes to the dysregulation of AEC2 and fibroblast apoptosis through inducing PAI-1 by modifying/inhibiting MKPs (e.g. MKP-1). Four specific aims are proposed to test our hypotheses, using different animal models including novel PAI-1 conditional knockout mouse models recently generated in this lab. The therapeutic potential of a small molecule PAI-1 inhibitor for lung fibrosis will also be tested in aged mice. The results from these studies will nt only shed new light on the mechanism underlying aging-related susceptibility to IPF but may also lead to novel paradigm shifting concept as well as new therapeutics for the treatment of IPF.