TGF-Beta and Lung Epithelial Injury

急性肺损伤（ALI）是一种毁灭性的综合征，死亡率为30- 40%。肺泡上皮损伤是AL 1患者的特征性形态学特征。上皮完整性的丧失导致肺泡泛液并破坏正常的肺上皮液体转运，这对于从气隙中清除肺水肿液体是重要的。调节ALI中肺泡灌洗液的发展和消退的分子步骤知之甚少。细胞因子转化生长因子β 1（TGF-β 1）在ALI的消退和通常与该综合征相关的肺纤维化的发展中起关键作用。我们先前报道了几个TGF-β 1诱导基因的表达水平在博莱霉素诱导的实验性ALI诱导后早期显著增加。我们还发现α-v-β-6整合素介导的TGF-β 1局部活化对ALI肺水肿的发展至关重要，并且TGF-β 1的活化依赖于α-v-β-6整合素构象的变化。然而，这种整合素的激活机制仍然是未知的。发现IL-1 β在生物学上 是急性肺损伤患者气道内炎症活动的主要原因。此外，通过腺病毒基因转移，IL-1 β而非TNF-α在肺中的瞬时过表达与进行性纤维化改变和TGF-β 1表达增加相关。最后，我们实验室的初步实验表明，IL-1 β，而不是TNF-α，导致肺泡上皮细胞中α-v-β-6介导的TGF-β 1依赖性细胞信号通路的激活。因此，本申请将检验以下假设：（a）空气空间内IL-1 β的释放负责α-v-β-6整联蛋白介导的TGF-β 1活化（目的1）;（B）粘着斑激酶（FAK）和/或其下游细胞效应物磷酸肌醇-3-激酶和小GTP酶Rac-1和RhoA的活化，是IL-1 β诱导的α-v-β-6整合素介导的TGF-β 1局部活化所必需的（目的2）;（c）局部活化的TGF-β 1通过改变阿米洛利敏感性钠通道ENaC的表达，在肺上皮细胞的细胞膜上（aim 3）。

Acute Lung Injury (ALI) is a devastating syndrome with a mortality rate of 30-40 percent. Alveolar epithelial damage is a characteristic morphologic feature in patients with ALl. The loss of epithelial integrity contributes to the alveolar flooding and disrupts normal lung epithelial fluid transport that is important for the removal of pulmonary edema fluid from the airspaces. The molecular steps regulating the development and resolution of alveolar flooding in ALI are poorly understood. The cytokine transforming growth factor beta1 (TGF-beta1) plays a critical role in the resolution of ALI and in the development of lung fibrosis often associated with this syndrome. We previously reported that the expression levels of several TGF-beta1-inducible genes are dramatically increased early after the induction of experimental ALI induced with bleomycin. We also found the alpha-v-beta-6 integrin-mediated local activation of TGF-beta1 is critical to the development of pulmonary edema in ALI and that the activation of TGF-beta1 depends on a change in the conformation of the alpha-v-beta-6 integrin. However, the mechanism of activation of this integrin is still unknown. IL-1beta was found to be biologically active and primarily responsible for the inflammatory activity within the airspaces of patients with ALI. Moreover, transient overexpression of IL-1beta, but not of TNF-alpha, in the lung by adenoviral gene transfer was associated with progressive fibrotic changes and an increased expression of TGF-beta1. Finally, preliminary experiments from our laboratory indicate that IL-1beta, but not TNF-alpha, causes activation of the alpha-v-beta-6-mediated TGF-beta1-dependent cell signaling pathway in alveolar epithelial cells. Thus, this application will test the hypotheses that (a) the release of IL-1beta within the airspaces is responsible for the alpha-v-beta-6 integrin-mediated activation of TGF-beta1 (aim 1); (b) the activation of the focal adhesion kinase (FAK) and/or its downstream cell effectors, phosphoinositol-3-kinase and small GTPases, Rac-1 and RhoA, is required for IL-1beta-induced alpha-v-beta-6 integrin-mediated local activation of TGF-beta1 (aim 2); (c) locally activated TGF-beta1 decreases basal and c-AMP regulated lung epithelial fluid transport by altering the expression of amiloride-sensitive sodium channel, ENaC, on the cell membrane of lung epithelial cells (aim 3).