Myofibroblast Senescence in Pulmonary Fibrosis

描述(申请人提供)：人类纤维性疾病影响许多器官系统，包括心脏、血管、肾脏、肝脏和肺。特发性肺纤维化(IPF)是最常见的纤维性肺疾病，是一种老年性疾病，发病率和死亡率较高，中位生存期不到三年。目前还没有美国FDA批准的抗纤维化药物。IPF的发生率和患病率随着年龄的增长而急剧增加；然而，尽管这种相关性很强，但导致衰老倾向于纤维化疾病的细胞/分子机制尚未阐明。我们实验室最近的研究表明，ROS产生酶NADPH氧化酶-4(NOX4)的生物学效应是由肌成纤维细胞(MFbs)通过诱导抗氧化反应转录因子核因子样2(NRF2)来维持氧化还原动态平衡的能力决定的，而NRF2是一种随年龄增长而缺乏的反应。这种细胞内平衡机制的丧失会导致MFbs出现衰老和抗凋亡的表型，至少部分与线粒体功能障碍有关。患有IPF的受试者在肌成纤维细胞病灶中NOX4的表达升高，而Nrf2的表达降低，这支持了人类纤维化疾病中的细胞氧化还原失衡。与自限的年轻小鼠消解纤维化相反，老年小鼠表现出消解纤维化的能力受损。据我们所知，这代表了第一个反映人肺间质纤维化不能解决的纤维化老化模型。本项目要检验的中心假设是，NOX4-Nrf2的失衡导致持续的氧化应激，导致MFB衰老和细胞凋亡抵抗，导致与衰老相关的持续性纤维化。我们的具体目标是：(1)确定氧化应激(Dys)调控Nrf2表达/诱导(Dys)与细胞衰老的机制；(2)确定NOX4-Nrf2失衡和线粒体生物能量学在促进FB衰老中的作用；(3)确定Nrf2在FBS中的有条件遗传缺失是否介导了幼鼠的持续性纤维化；以及(通过药理学方法)Nrf2诱导或NOX4抑制是否促进老龄小鼠的纤维化消退。这项拨款申请是对PA-10-014：衰老研究动物模型的发展和表征的响应。本项目目标的完成将：(A)建立与疾病相关的未消退纤维化的动物模型；(B)确定MFbs氧化还原稳态控制丧失的机制；(C)建立线粒体功能障碍与衰老之间的机制联系；以及(D)提供概念证据，证明纠正细胞氧化还原平衡将促进纤维化消退，并导致开发治疗诸如肺间质纤维化等非消退性纤维化疾病的新方法。

DESCRIPTION (provided by applicant): Human fibrotic disorders affect many organ systems including heart, blood vessels, kidney, liver and lung. The most common fibrotic lung disease, idiopathic pulmonary fibrosis (IPF) is a disease of aging carries a high morbidity and mortality, with a median survival rate of less than three years. There are currently no U.S. FDA-approved anti-fibrotic drugs. The incidence and prevalence of IPF increase drastically with age; however, despite this strong association, cellular/molecular mechanisms that account for the aging predilection to fibrotic disease have not been elucidated. Recent studies from our laboratory indicate that the biological effects of the ROS-generating enzyme, NADPH oxidase-4 (Nox4) is determined by the capacity of myofibroblasts (MFbs) to maintain redox homeostasis via the induction of the antioxidant response transcription factor, nuclear factor-like 2 (Nrf2), a respons that is deficient with aging. Loss of this cellular homeostatic mechanism results in the emergence of a senescent and apoptosis-resistant phenotype of MFbs, at least in part related to mitochondrial dysfunction. Human subjects with IPF exhibit elevated expression of Nox4 and decreased Nrf2 expression in myofibroblastic foci, supporting this cellular redox imbalance in a human fibrotic disease. In contrast to self-limited, resolving fibrosis in young mice, aged mice manifest an impaired capacity for resolution of fibrosis. This represents, to our knowledge, the first aging model of fibrosis that recapitulates the non-resolving nature of human IPF. The central hypothesis to be tested in this project is that an imbalance of Nox4-Nrf2 induces sustained oxidative stress that induces MFb senescence and apoptosis resistance, leading to persistent fibrosis associated with aging. Our specific aims are to: (1) Determine mechanisms for the (dys)regulation of Nrf2 expression/induction by oxidative stress with cellular senescence; (2) Determine the role of Nox4-Nrf2 imbalance and mitochondrial bioenergetics in promoting Fb senescence; and (3) Determine whether conditional genetic deletion of Nrf2 in Fbs mediates persistent fibrosis in young mice; and whether Nrf2 induction or Nox4 inhibition (by pharmacologic approaches) promotes fibrosis resolution in aged mice. This grant application is responsive to PA-10-014: Development and Characterization of Animal Models for Aging Research. The completion of the aims in this project will: (a) establish a disease-relevant animal model of non-resolving fibrosis; (b) define mechanisms for the loss of redox homeostatic control in MFbs; (c) establish mechanistic links between mitochondrial dysfunction and senescence; and (d) provide proof-of-concept that correction of cellular redox balance will promote fibrosis resolution and lead to the development of novel therapeutic approaches to non-resolving fibrotic disorders such as IPF.