Regulation of Elastin Assembly during Saccular Stage Lung Development

项目总结 围产期炎症是支气管肺发育不良(BPD)的公认危险因素，BPD是 早产儿以囊状期肺发育异常为特征。因为呼吸道上皮存在于 羊膜囊环境和胎肺的界面，它处于很好的位置，可以对炎症做出反应 羊水中的刺激物。因此，我们建立了一种转基因小鼠模型来诱导表达MASTER 炎性转录因子NF-κB，在呼吸道上皮(伊卡他鼠)。使用这个模型，我们证明了 上皮源性炎症导致球囊期终末空隙深度扩张，但 不会改变肺发育的早期阶段。囊状期IKTA肺的空域扩张与 随着间质成纤维细胞表达重要的弹性蛋白组装成分，特别是纤维蛋白-5的减少， 导致远端空隙周围的弹性纤维组装发生变化。在新生成的初步数据中确定 成纤维细胞中弹性蛋白组装组分的上皮源性抑制物，我们发现IKTA小鼠和 暴露于产前炎症的早产儿气管抽吸物(TA)具有高水平的IL-1(两者均为IL-1)。 1α和IL-1β)。中和IL-1α或IL-1β恢复肺成纤维细胞纤溶蛋白-5的表达 来自IKTA小鼠的灌洗液(BAL)或来自早产儿的TA。由于IL-1通过核因子-1触发细胞内信号转导 κB，我们检测了NF-κB对囊泡期肺成纤维细胞的直接影响，并观察到NF-κB信号转导 抑制纤溶蛋白-5mRNA的表达。最后，通过修改我们的转基因小鼠模型，使其能够在 在出生后早期，我们发现炎症导致球囊阶段弹性蛋白组织的破坏 导致持续的肺结构异常。拟议的研究将检验这一假设，即在 肺发育的囊状期，上皮源性炎症向下游传播NF-κB的激活 在成纤维细胞中通过IL-1信号，导致纤维蛋白-5和其他关键弹性蛋白组装的下调 组件。在这一关键的发育窗口期间，弹性蛋白组织的破坏会损害肺 发展，导致肺结构和功能的异常，并持续到成年。具体目标 1)确定IL-1信号在调节弹性纤维组装成分中的作用；2)确定 纤维蛋白-5在肺成纤维细胞发育和炎症反应中的转录调控，以及 3)探讨球囊期弹性蛋白装配受损的远期影响。共同努力，我们的研究将 确定关键发育窗口期的炎症如何调节肺结构和功能， 从而为BPD的发病机制和球囊阶段改变的长期后果提供了新的见解 肺部发育。

PROJECT SUMMARY Perinatal inflammation is an established risk factor for bronchopulmonary dysplasia (BPD), a major morbidity of prematurity characterized by abnormal saccular stage lung development. As the airway epithelium is present at the interface of the amniotic sac environment and the fetal lung, it is well positioned to respond to inflammatory stimuli in amniotic fluid. Therefore, we developed a transgenic mouse model to inducibly express the master inflammatory transcription factor NF-κB, in the airway epithelium (IKTA mice). Using this model, we showed that epithelial-derived inflammation results in profound dilation of terminal airspaces during the saccular stage, but does not alter earlier stages of lung development. Airspace dilation in saccular stage IKTA lungs was associated with reduced expression of important elastin assembly components, especially fibulin-5, by interstitial fibroblasts, leading to altered elastic fiber assembly around distal airspaces. In new preliminary data generated to identify epithelial-derived inhibitors of elastin assembly components in fibroblasts, we found that lungs of IKTA mice and tracheal aspirates (TA) from preterm infants exposed to antenatal inflammation had high levels of IL-1 (both IL- 1α and IL-1β). Neutralizing IL-1α or IL-1β restored fibulin-5 expression in fibroblasts exposed to bronchoalveolar lavage fluid (BAL) from IKTA mice or TA from preterm infants. Since IL-1 triggers intracellular signaling via NF- κB, we tested the direct impact of NF-κB on saccular stage lung fibroblasts and observed that NF-κB signaling inhibited fibulin-5 mRNA expression. Finally, by modifying our transgenic mouse model to enable survival beyond the early postnatal period, we found that inflammation-induced disruption in saccular stage elastin organization results in persistent abnormalities in lung structure. Proposed studies will test the hypothesis that during the saccular stage of lung development, epithelial-derived inflammation propagates down-stream NF-κB activation in fibroblasts through IL-1 signaling, resulting in down-regulation of fibulin-5 and other critical elastin assembly components. Disruption of elastin organization during this critical developmental window impairs lung development, leading to abnormalities in lung structure and function that persist into adulthood. Specific aims are: 1) to define the role of IL-1 signaling in regulation of elastic fiber assembly components, 2) to determine the transcriptional regulation of fibulin-5 in lung fibroblasts during development and in response to inflammation, and 3) to investigate the long-term impact of impaired saccular stage elastin assembly. Together, our studies will determine how inflammation during a critical developmental window can modulate lung structure and function, thus providing new insights into BPD pathogenesis and the long-term consequences of altered saccular stage lung development.