CFTR/EGFR反馈环路调控肺液清除功能在支气管肺发育不良发病中的作用和分子机制

It has been confirmed that pulmonary edema is one of the pathological lesions at the early stage of bronchopulmonary dysplasia (BPD). Multiple approaches proposed for the prevention or treatment of pulmonary edema could decrease the risk of BPD and modestly improve its outcome. The dysfunction of airway epithelial ion channel may contribute to pulmonary edema pathogenesis. Cystic fibrosis transmembrane conductance regulator(CFTR) is a cAMP-activated chloride and bicarbonate channel that plays a critical role in the lung by maintaining fluid homeostasis. It has been proved that inhibition of CFTR will reduce alveolar fluid clearance and promote the occurrence of pulmonary edema. In the previous study, it is demonstrated that the suppression of CFTR could increase epidermal growth factor receptor(EGFR) activation. Moreover, our previous studies found that activation of EGFR was elevated in BPD model. Therefore, we speculated that CFTR may play a critical role in BPD. It is interesting that the activation of EGFR could also suppress the CFTR function via PI3K/AKT pathway. Thus, we consider of a feedback loop: The activation of EGFR and its downstream pathway PI3K/AKT would suppress the activity of CFTR，and the suppression of CFTR could also increase EGFR activation subsequently, which would enlarge the inhibition of CFTR and activation of EGFR continuously. Consequently, it could reduce the alveolar fluid clearance, result in pulmonary edema and promote the development of BPD. In this research, we would like to prove the feedback loop of CFTR/EGFR and its contribution to BPD both in vivo and in vitro, which will offer a new view and strategy in prevention and treatment of BPD.

支气管肺发育不良(BPD)早期存在肺水肿病理改变。临床实践证实，减少肺水肿有助于预防和改善BPD。肺水肿发生的重要机制之一是离子通道功能紊乱，其中氯离子通道蛋白CFTR的活性降低会减少肺泡液清除，促进肺水肿的发生。有研究显示抑制CFTR能激活EGFR。我们前期发现BPD中EGFR活性增高，提示BPD中CFTR功能受损。因此，我们认为CFTR在BPD发生发展中起到重要作用。有趣的是，另有文献报道EGFR还能通过PI3K/AKT途径，降低CFTR的活性。据此，我们提出一种反馈通路：EGFR及下游通路PI3K/AKT的激活降低CFTR的活性，而CFTR的活性下降又可刺激EGFR磷酸化激活，两者相互作用，持续降低CFTR的活性，导致肺泡液清除能力下降，促进BPD的发展。本课题拟从体内、体外两个方面率先阐明CFTR/EGFR通路在肺水肿及BPD发病中的作用及分子机制，为BPD的发病机制增添新的内容。

支气管肺发育不良（bronchopulmonary dysplasia, BPD）是早产儿常见的慢性肺部疾病，可导致肺部发育异常，并具有较高的并发症率和死亡率。巨噬细胞在肺部的过度累积，释放炎症因子，是BPD的重要致病因素之一。人类胃肠道中肠道菌群可以产生可调节免疫细胞效应的代谢产物，从而影响肺部炎症。.本研究的主要发现：.1.临床队列发现：① BPD队列：BPD患儿肠道菌群及其代谢产物具有一定的差异性。与早产对照组相比， BPD组中克雷伯属明显增多，链球菌属和拟杆菌属明显降低，粪胆汁酸包括胆酸（CA）,鹅去氧胆酸（CDCA）等明显降低；全血RNA测序结果显示，与对照组相比，巨噬细胞趋化因子受体CCR5基因等在BPD中明显升高；人外周血单个核细胞中发现，与对照组相比，BPD组单核细胞CCR5的表达明显增高，提示CCR5通路在BPD发生发展中起到一定的作用。.② 早产胆汁淤积队列：与对照组相比，胆汁淤积症患儿中，重度BPD的发病率明显增高（p=0.039），血胆汁酸谱检测提示，胆汁淤积患儿的CA，CDCA明显下降，提示CA，CDCA的缺乏可能促进BPD的发生发展。 .2. 在羊膜腔注射脂多糖（LPS）建立BPD经典的动物模型中发现：① 用CA，CDCA进行喂养，能改善BPD新生鼠的肺泡化阻滞的病理改变，并且能减少巨噬细胞在肺组织内的数量，但仅有CA能抑制炎症因子IL-1β的水平; ② 巨噬细胞迁移实验证明，CA能减少外周血巨噬细胞向肺内募集; ③ CA能降低肺组织中CCR5含量及其配体CCL3,CCL4,CCL5水平，同样，CA能降低肺泡巨噬细胞CCR5表达，提示CA可通过CCR5通路抑制巨噬细胞的迁移改善BPD。④ BPD模型鼠肺泡灌洗液中巨噬细胞RNA测序发现，CA能抑制LPS引起的多种趋化通路的改变。 .本研究在BPD患者中观察到肠道微生物群和代谢谱的变化，并发现代谢产物CA可以通过CCR5信号通路减少外周巨噬细胞进入肺部，从而改善BPD病理和炎症状态。这些发现为理解肠道微生物群和粪便代谢物在BPD发展中所起的作用提供了新的视角。

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