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ALL患者的一种特征性的形态学特征。肺泡上皮完整性的丧失导致肺泡泛滥，并扰乱了正常的肺上皮液运输，而正常的肺上皮液运输对于肺水肿液从空气中清除是重要的。在ALI中，调控肺泡淹水发展和消退的分子步骤知之甚少。细胞因子转化生长因子-β1(TGF-β1)在ALI的消退和常与ALI相关的肺纤维化的发展中起着关键作用。我们以前曾报道，在博莱霉素诱导的实验性ALI后，几个转化生长因子-β1诱导基因的表达水平在早期显著增加。我们还发现，α-v-β-6整合素介导的转化生长因子-β1的局部激活在ALI肺水肿的发生发展中起关键作用，并且转化生长因子-β1的激活依赖于整合素α-v-β-6构象的变化。然而，该整合素的激活机制仍不清楚。IL-1β被发现在生物学上是 在ALI患者的空气中，炎症活动是活跃的和主要负责的。此外，通过腺病毒基因转移在肺中瞬时过表达IL-1β，而不是肿瘤坏死因子-α，与进行性纤维化改变和转化生长因子-β1表达增加有关。最后，我们实验室的初步实验表明，在肺泡上皮细胞中，IL-1β而不是TNF-α引起α-v-β-6介导的转化生长因子-β1依赖的细胞信号通路的激活。因此，这一应用将检验以下假设：(A)IL-1β在空气中的释放负责α-v-β-6整合素介导的转化生长因子-β1的激活(目标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的激活是IL-1β诱导的α-v-β-6整合素介导的转化生长因子-β1局部激活所必需的(目标2)；(C)局部激活的转化生长因子-β1通过改变肺上皮细胞细胞膜上阿米洛利敏感钠通道ENaC的表达，减少基础和c-AMP调节的肺上皮液转运(目标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).