Type II Alveolar Redox Control in Fibrogenesis and Resolution

摘要：特发性肺纤维化(IPF)是一种慢性、高度致死性的肺部疾病，其特点是 肺部结疤过多，在老年人中患病率增加。接受程度最高的 IPF发病机制的理论基础是肺泡上皮II型细胞(AECII)的损伤和激活 过度和慢性伤口愈合反应，由生长因子如转化生长因子-β1介导。氧化 应激被认为是组织修复过程的关键调节因子，但氧化还原信号通路在组织修复过程中的作用 IPF的发病机制在很大程度上仍然未知。一种依赖NADH的氧化还原酶 Cyb5R3(Cyb5R3)有助于保护压力，并与健康和衰老有关。Cyb5R3 减少血红素铁(Fe3→Fe2)，这是活性氧物种的主要目标。我们的初步数据表明 IPF肺组织中Cyb5R3低表达。利用一种新的小鼠Cyb5R3条件性缺陷模型 在我们实验室培养的肺泡II型细胞中，我们发现1)Cyb5R3在AECII中的表达和活性 对肺纤维化的保护至关重要，2)Cyb5R3负性调节转化生长因子-β1的表达。 依赖的促纤维化和衰老基因，以及3)Cyb5R3抑制转化生长因子-β1靶基因的表达 通过两条途径介导，一条是sGC的血红素还原和cGMP-PKG的下游激活 其二，通过调控线粒体功能和激活cAMP-PKA。这些 观察结果导致了一种假设，即Cyb5R3缺乏促进AECII线粒体的改变 通过sGC依赖和非依赖途径增强转化生长因子-b信号的功能和氧化还原状态 降低抗纤维化的弹性：目的1.验证肺泡上皮细胞中Cyb5R3的假说 通过抑制转化生长因子-b信号对肺纤维化的发展起到保护作用。目标2. 确定AECII Cyb5R3表达缺失是否对慢性sGC刺激物和/或sGC激活物具有疗效 对肺纤维化小鼠的治疗。这些目标的完成将加深我们对 Cyb5R3在伤口修复过程中的作用以及与年龄相关的抗损伤修复和纤维化机制。

Abstract: Idiopathic Pulmonary Fibrosis (IPF) is a chronic and highly lethal lung disease characterized by excessive scarring of the lung and whose prevalence is increased in older individuals. The most accepted theory in the pathogenesis of IPF is the injury and activation of alveolar epithelial type II cells (AECII) triggering excessive and chronic wound-healing responses, mediated by growth factors such as TGF-b1. Oxidative stress is recognized as key regulator of the tissue repair process, but the role of redox signaling pathways in the mechanistic pathobiology of IPF remains largely unknown. One NADH-dependent redox enzyme that contributes to stress protection and associates with healthspan and aging is Cyb5R3 (Cyb5R3). Cyb5R3 reduces heme iron (Fe3+→Fe2+), a major target of reactive oxygen species. Our preliminary data suggest that IPF lungs have low expression of Cyb5R3. Using a novel mouse model of conditional deficiency of Cyb5R3 in alveolar type II cells developed in our labs, we have found that 1) expression and activity of Cyb5R3 in AECII are critical for protection against lung fibrosis, 2) Cyb5R3 negatively regulates the expression of TGF-b1- dependent profibrotic and senescence genes, and 3) Cyb5R3 inhibition of expression of TGF-b1 target genes is mediated by two pathways, one the heme reduction of sGC and downstream activation of cGMP-PKG signaling pathway, and second, by control of mitochondrial function and activation of cAMP-PKA. These observations have led to the hypothesis that Cyb5R3 deficiency promotes alteration of the AECII mitochondrial function and redox state that enhances the TGF-b signaling via sGC-dependent and –independent pathways decreasing the resilience against fibrosis: Aim 1. To test the hypothesis that Cyb5R3 in alveolar epithelial cells confers protection against the development of lung fibrosis through suppression of TGF-b signaling. Aim 2. Establish if loss of AECII Cyb5R3 expression confers efficacy to chronic sGC stimulator and/or sGC activator therapy in mice with lung fibrosis. Completion of these aims will enhance our understanding of the role of Cyb5R3 in the wound healing process and age-related mechanisms of resilience to disrepair and fibrosis.