Type II Alveolar Redox Control in Fibrogenesis and Resolution

摘要：特发性肺纤维化（IPF）是一种慢性高致死性肺部疾病，其特征是 肺过度瘢痕化，其患病率在老年人中增加。接受度最高的 IPF发病机制的理论是肺泡上皮II型细胞（AECII）的损伤和活化， 过度和慢性伤口愈合反应，由生长因子如TGF-β 1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 IPF的病理生物学机制在很大程度上仍然未知。一种依赖于NADH的氧化还原酶， 有助于压力保护并与健康和衰老相关的是Cyb 5 R3（Cyb 5 R3）。Cyb5R3 还原血红素铁（Fe 3 +→ Fe 2+），这是活性氧的主要目标。我们的初步数据显示， IPF肺具有Cyb 5 R3的低表达。使用一种新的Cyb 5 R3条件性缺陷小鼠模型， 本实验室培养的肺泡Ⅱ型细胞中，我们发现：1）Cyb 5 R3在肺泡Ⅱ型细胞中的表达和活性， 对于防止肺纤维化至关重要，2）Cyb 5 R3负调节TGF-β 1-β 2的表达。 依赖性促纤维化和衰老基因，和3）Cyb 5 R3抑制TGF-β 1靶基因的表达 由两条途径介导，一条是sGC的血红素还原，另一条是下游cGMP-PKG的激活 第二，通过控制线粒体功能和激活cAMP-PKA。这些 观察结果表明，Cyb 5 R3缺陷会促进AECII线粒体的改变 通过sGC依赖性和非依赖性途径增强TGF-β信号传导的功能和氧化还原状态 降低抗纤维化的弹性：目的1。为了验证肺泡上皮细胞中Cyb 5 R3 通过抑制TGF-β信号传递来保护肺纤维化的发展。目标2. 确定AECII Cyb 5 R3表达缺失是否赋予慢性sGC刺激剂和/或sGC激活剂效力 治疗小鼠肺纤维化。这些目标的实现将使我们更好地了解 Cyb 5 R3在创伤愈合过程中的作用以及与年龄相关的损伤修复和纤维化恢复机制。

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.