Molecular mechanisms of lung branching morphogenesis

描述（由申请方提供）：新生儿呼吸窘迫仍然是新生儿死亡和发病的重要原因。大多数病例是由表面活性物质缺乏和随后的新生儿呼吸适应异常引起的。然而，导致围产期肺成熟受损和表面活性物质缺乏的致病机制尚未完全了解。我们的初步研究表明，BMP信号是至关重要的新生儿呼吸，也可能有助于糖皮质激素增强表面活性蛋白的表达。明确BMP信号在促进围产期肺成熟和适应性发育中的作用机制，以及在调节产前糖皮质激素对肺生长的刺激作用中的作用机制，将有助于突破新生儿呼吸窘迫防治的关键性障碍。因此，我们提出了三个具体的目标来测试的假设：周围肺上皮细胞中的BMP信号是必不可少的围产期肺成熟和新生儿呼吸适应，通过促进内源性表面活性剂的生产，通过上调Nfatc3和Lpcat1的表达，这反过来又有助于糖皮质激素增强肺成熟。因此，BMP信号传导缺陷可能导致新生儿呼吸衰竭。目标1。确定周围肺上皮细胞中的BMP信号是否对围产期肺成熟和新生儿呼吸适应至关重要。BMP信号传导活性的动态变化将与围产期小鼠肺生长和适应期间的表面活性物质产生和功能相关。BMP信号传导在新生儿呼吸中的作用将通过在小鼠中基因缺失BMP受体（Alk3）或下游Smad 1，或通过施用特异性针对BMP受体Alk3的小分子抑制剂来体内定义。此外，BMP信号活化的治疗应用以增加围产期小鼠肺组织中表面活性剂产生的功效也将通过外源性BMP 4施用或通过诱导组成型活性Alk3转基因过表达来确定。目标2.确定BMP信号正向调节Nfatc 3和Lpcat 1表达的转录调节机制。我们的初步数据表明，BMP-Smad1可能直接调节Nfatc3和Lpcat1的基因表达，这是重要的表面活性蛋白的表达和磷脂酰胆碱的合成。因此，这些基因的转录调控机制Smad1，包括Smad1启动子DNA相互作用，将在围产期肺上皮细胞中确定。目标3。探讨BMP信号通路在糖皮质激素促进围产期肺成熟中的作用。将在体内确定糖皮质激素治疗是否增强肺BMP信号传导途径。BMP通路激活在介导糖皮质激素对表面活性剂产生的刺激作用中的作用将在Alk3或Smad1基因敲除的围产期小鼠中确定。相关的分子机制将在肺泡上皮细胞解剖。 公共卫生相关性：该项目将揭示一种新的分子机制，BMP信号增强围产期肺成熟和新生儿呼吸适应。此外，一个新的BMP信号转导介导产前糖皮质激素治疗，以促进早产儿肺成熟的作用将被确定。所获得的新知识将有助于突破开发新的治疗策略以预防和治疗新生儿呼吸窘迫的关键障碍。

DESCRIPTION (provided by applicant): Neonatal respiratory distress remains an important cause of neonatal mortality and morbidity. The majority of cases are caused by surfactant deficiency and subsequent abnormality in neonatal respiratory adaptation. However, the causative mechanisms leading to impaired perinatal lung maturation and surfactant deficiency are not fully understood. Our preliminary studies suggest that BMP signaling is critical to neonatal respiration, and may also contribute to glucocorticoid-augmented surfactant protein expression. Determination of the related mechanisms of BMP signaling in enhancing perinatal lung maturation and adaptation, as well as in mediating antenatal glucocorticoid's stimulatory effects on lung growth will help to break through the critical barrier for prevention and treatment of neonatal respiratory distress. Thus, we propose three specific aims to test the Hypothesis: BMP signaling in peripheral lung epithelial cells is essential for perinatal lung maturation and neonatal respiratory adaptation by promoting endogenous surfactant production through upregulating Nfatc3 and Lpcat1 expression, which in turn contributes to glucocorticoid-enhanced lung maturation. Thus, deficient BMP signaling may result in neonatal respiratory failure. Aim 1. To determine whether BMP signaling in peripheral lung epithelial cells is essential for perinatal lung maturation and neonatal respiratory adaptation. Dynamic changes in BMP signaling activity will be determined in association with surfactant production and function during perinatal mouse lung growth and adaptation. The role of BMP signaling in neonatal respiration will be defined in vivo by genetically deleting BMP receptor (Alk3) or downstream Smad1, or by administering a small molecule inhibitor specifically against BMP receptor Alk3 in mice. In addition, the efficacy of therapeutic application of BMP signal activation to increase surfactant production in perinatal mouse lung tissue will also be determined by exogenous BMP4 administration or by induction of constitutively active Alk3 transgenic overexpression. Aim 2. To determine the transcriptional regulatory mechanisms by which BMP signaling positively regulates Nfatc3 and Lpcat1 expression. Our preliminary data suggest that BMP-Smad1 may directly regulate gene expression of Nfatc3 and Lpcat1, which are important in promoting surfactant protein expression and phosphatidylcholine synthesis. Therefore, the transcriptional regulatory mechanisms of these genes by Smad1, including Smad1-promoter DNA interaction, will be determined in perinatal lung epithelial cells. Aim 3. To determine the role of BMP signaling in mediating glucocorticoid effects on promoting perinatal lung maturation. Whether glucocorticoid treatment enhances the pulmonary BMP signaling pathway will be determined in vivo. The role of BMP pathway activation in mediating glucocorticoid stimulatory effects on surfactant production will then be determined in perinatal mice with Alk3 or Smad1 gene knockout. Related molecular mechanisms will be dissected in alveolar epithelial cells. PUBLIC HEALTH RELEVANCE: This proposed project will unveil a novel molecular mechanism by which BMP signaling enhances perinatal lung maturation and neonatal respiratory adaptation. Moreover, a new role of BMP signaling in mediating antenatal glucocorticoid treatment to promote preterm lung maturation will be determined. The obtained new knowledge will help to break through the critical barrier for developing novel therapeutic strategies to prevent and treat neonatal respiratory distress.