REGULATION OF MUCOUS CELL METAPLASIA IN ASTHMA

描述(申请人提供)：在哮喘患者中，粘液细胞出现在正常情况下没有粘液细胞的呼吸道。这种表型称为粘液细胞化生(MCM)。MCM具有严重的风险，因为剧烈分泌的粘液会减少气流，有时会完全阻塞呼吸道，导致哮喘患者死亡。此外，流行病学研究表明，慢性MCM患者患肺癌的风险更高。我们的研究表明，干扰素？而STAT1信号通路通过诱导呼吸道上皮细胞(AECs)死亡，对MCM的解决起着至关重要的作用。因此，这一新的应用重点在于阐明干扰素？诱导血管内皮细胞死亡。干扰素？激活ERK1/2，将Bax移位到内质网(ER)，减少MCM。我们发现BIK，一个定位于内质网的Bcl2家族成员，在哮喘患者的AECs中与对照组相比显著减少。BIK-/-小鼠AECs不受干扰素α的影响，BIK过表达可激活ERK1/2，诱导AECs杀伤。另一个Bcl2家族成员NOXA是由干扰素诱导的？并增强Bik诱导的细胞凋亡。NOXA与磷酸化的HSP27相互作用，降低I？B水平，与核因子-β共定位，降低Bcl2的表达。这些发现使我们提出如下假设：干扰素β诱导的细胞死亡是由Bik诱导的ERK1/2激活所介导的，导致Bax移位到内质网以启动细胞凋亡。此外，NOXA通过与磷酸化HSP27相互作用，降解I？B1，抑制活化的核转录因子-？B的核转位，降低Bcl2的表达，从而促进Bik介导的细胞凋亡。我们将通过以下方式验证这一假设：(1)通过激活ERK1/2和将Bax移位到内质网，研究Bik是否在干扰素？诱导的细胞死亡和MCM的分解中起中心作用。(2)确定NOXA与磷酸化HSP27的交联是否促进了NF-β的激活，但抑制了NF-β的核转位，从而降低了BIK诱导的细胞死亡，从而确定了NOXA-HSP27相互作用的区域。(3)确定在长期接触变应原的过程中，Bik诱导的内质网应激是否需要BAX和BAK来分解MCM。了解这些蛋白质在MCM分解过程中的作用可能会使我们减少哮喘患者中可以分泌过量粘液的增生性上皮细胞，而不会损害静止的上皮细胞，从而损害上皮的屏障功能。开发有针对性的方法来减少MCM也可能有助于消除发生肺癌风险增加的患者的肿瘤前细胞。与公共卫生相关。呼吸道中粘液细胞数量的增加构成了严重的风险，因为剧烈分泌的粘液会减少气流，有时会完全阻塞呼吸道，导致哮喘患者死亡。这项拟议的研究将剖析在正常小鼠长期接触变应原期间这些粘液细胞正常分解过程所依据的事件的分子序列。了解这些分子过程可能会为通过消除增生性粘液细胞来减少粘液分泌提供新的策略。

DESCRIPTION (provided by applicant): In patients with asthma mucous cells appear in airways that are normally devoid of these cells. This phenotype is called mucous cell metaplasia (MCM). MCM poses a serious risk because acutely secreted mucus can reduce airflow or can sometimes completely obstruct the airways and lead to death of asthmatics. In addition, epidemiological studies suggest that patients with chronic MCM are at a higher risk of developing lung cancer. Our studies demonstrated that IFN? and STAT1 signaling are crucial for the resolution of MCM by inducing cell death in airway epithelial cells (AECs). Therefore, this renewal application is focused on delineating the molecular mechanisms by which IFN? induces cell death in AECs. IFN? activates ERK1/2 and translocates Bax to the endoplasmic reticulum (ER) and reduces MCM. We found that Bik, a Bcl-2 family member that localizes to the ER, was significantly reduced in AECs obtained by bronchial brushings from asthmatics compared to controls. AECs from bik-/- mice were unaffected by IFN?, and Bik overexpression caused activation of ERK1/2 and induced killing in AECs. Noxa, another Bcl-2 family member, is induced by IFN? and enhances Bik-induced apoptosis. Noxa interacts with phosphorylated HSP27, reduces I?B levels, co-localizes with NF-?B, and reduces Bcl-2 mRNA expression. These findings led us to the following hypothesis: IFN?-induced cell death is mediated by Bik-induced activation of ERK1/2 that results in the translocation of Bax to the ER to initiate apoptosis. Furthermore, the Bik-mediated apoptosis is enhanced by Noxa through its interaction with phopho-HSP27 to degrade I?B1 but inhibit nuclear translocation of activated NF-?B and decrease Bcl-2 expression. We will test this hypothesis by: (1) Investigating whether Bik is central for the IFN?-induced cell death and resolution of MCM by activating ERK1/2 and translocating Bax to the ER. (2) Determining whether Noxa cross-linked to phosphorylated HSP27 facilitates NF-?B activation but inhibits nuclear translocation of NF-?B and thereby decreases Bcl-2 mRNA expression to enhance Bik-induced cell death and to identify the domain of Noxa-HSP27 interaction. (3) Determining whether Bik-induced ER stress requires Bax and Bak for the resolution of MCM during prolonged exposure to allergen. Understanding the role of these proteins in the resolution process of MCM may allow us to reduce hyperplastic epithelial cells that can secrete excessive mucus in asthmatics without compromising the resting epithelial cells and therefore the barrier functions of the epithelium. Development of targeted approaches to reduce MCM may also be useful for eliminating pre-neoplastic cells in patients with an increased risk of developing lung cancer. PUBLIC HEALTH RELEVANCE. Increased number of mucous cells in the airways poses a serious risk because acutely secreted mucus can reduce airflow or can sometimes completely obstruct the airways and lead to death of asthmatics. The proposed studies will dissect the molecular sequence of events that underlies the normal resolution process for these mucous cells during prolonged exposure to allergen in normal mice. Understanding these molecular processes may provide new strategies for reducing mucous secretions by eliminating hyperplastic mucous cells.