Molecular mechanism of alveolar injury caused by cigarette smoke

描述(申请人提供)：我们之前对肺气肿肺细胞凋亡失调的分子机制的研究使我们发现肺气肿患者肺和暴露于香烟烟雾(CS)中的细胞中鞘磷脂神经酰胺种类显著增加。我们的发现暗示神经酰胺是肺中氧化应激和细胞凋亡的放大因子。我们推测神经酰胺是CS诱导的肺泡细胞氧化应激和损伤的重要近端介质，因此可能是肺气肿的治疗靶点。因此，了解CS上调肺内神经酰胺的机制至关重要。我们假设CS通过失调细胞膜内的脂质相互作用来刺激神经酰胺的合成。此外，我们假设神经酰胺是香烟烟雾引起的以肺泡屏障功能改变为特征的早期肺泡损伤的媒介。我们研究这些假说的具体目的如下：1.为了确定CS上调神经酰胺的生物物理机制，我们将在补充细胞损伤模型的膜脂双层模型中进行生物物理研究；以及特殊目的2.为了确定神经酰胺是CS所致的肺泡细胞屏障功能损伤的介质，我们将实时研究原始肺泡细胞单层的电容，并首次建立和利用双光子发射显微镜(TPEM)在完整大鼠肺内的应用。这项工作完成后，将阐明脂质双层膜的生物力学变化与导致神经酰胺信号转导的生化事件之间的联系，并首次实现活体肺组织的TPEM成像，通过其在肺健康和疾病的多种机制中的广泛应用，将加速生物医学肺的研究。 与公共健康相关：我们将研究香烟烟雾如何触发脂膜中神经酰胺的增加，脂膜是细胞和细胞内重要细胞器的内衬，也是神经酰胺合成的场所。除了使用经典的方法外，我们还提出了一种新的技术，利用先进的成像手段实时记录完整肺的屏障功能，以研究神经酰胺的增加是否是香烟烟雾所致早期肺损伤的必要步骤。我们的工作有望为针对COPD患者神经酰胺的治疗策略提供理论基础，并将开发一种新的全肺活体分子成像模式，可应用于所有肺部疾病的研究。

DESCRIPTION (provided by applicant): Our previous investigations of the molecular mechanisms of dysregulated lung cell apoptosis in emphysema led us to identify a marked increase in sphingolipid ceramide species in the lungs of patients with emphysema and in cells exposed to cigarette smoke (CS). Our findings implicated ceramide as an amplifier of oxidative stress and apoptosis in the lung. We postulate that ceramide is an important proximal mediator of CS-induced oxidative stress and injury in lung alveolar cells and therefore a putative therapeutic target in emphysema. Therefore, understanding the mechanisms by which CS upregulates ceramides in the lung is of utmost importance. We hypothesize that CS stimulates ceramide synthesis by dysregulating lipid interactions within the cellular membranes. Furthermore, we hypothesize that ceramide is a mediator of early alveolar lung injury induced by cigarette smoke characterized by alterations of the alveolar barrier function. We will investigate these hypotheses with the following specific aims: Specific Aim 1. To determine the biophysical mechanism by which CS upregulates ceramides, we will conduct biophysical investigations in membrane lipid bilayer models complemented with cellular injury models; and Specific Aim 2. To establish that ceramides are mediators of the CS-induced injury of the alveolar cell barrier function, we will study the capacitance of primary alveolar cell monolayers in real-time and we will develop and utilize for the first time an intravital application of two-photon emission microscopy (TPEM) of the intact rat lung. When completed, this work will elucidate the connection between bio-mechanical changes in the lipid bilayer membrane and biochemical events leading to ceramide signaling and, by implementing intravital TPEM imaging of the lung for the first time, it will accelerate biomedical lung research by its broad application to multiple mechanisms of lung health and disease. PUBLIC HEALTH RELEVANCE: We will investigate how cigarette smoke triggers the increase in ceramides in lipid membranes which are lining the cells and important organelles within the cells and are the sites of ceramides synthesis. Besides using classical methods, we propose a novel technique of real time recording of barrier function in the intact lung utilizing an advanced imaging modality to study if the increase in ceramide is a necessary step in the earliest lung injury induced by cigarette smoke. Our work is expected to provide the rationale for a therapeutic strategy that targets ceramide in patients with COPD and will develop a new intravital molecular imaging modality of the whole lung which can be applied to the studies of all lung diseases.