Airway Epithelial Cell Farnesoid X Receptor in COPD Pathophysiology

项目摘要 慢性阻塞性肺疾病（COPD）是美国第三大死亡原因，通常是由于 吸烟。目前的治疗，包括在最早阶段戒烟，只提供 短期利益，不能阻止其不可阻挡的发展。因此，阻止疾病进展的新疗法 迫切需要。COPD病理生理学包括支气管炎症和隔膜破坏，导致 肺气肿，伴有炎症相关氧化应激和蛋白酶引起的间隔破坏 分泌物基于有希望的初步发现，拟议的研究将测试在COPD中的有益作用 以及调节法尼醇X受体（FXR）的机制，FXR是一种核激素受体， COPD是未知的。初步研究显示，FXR在气道上皮细胞（AEC）中下调， 在慢性阻塞性肺疾病患者和吸烟（CS）诱导的慢性阻塞性肺疾病小鼠中， 体外下调，这使我们假设患者中的FXR下调有助于COPD 发病机制我们还发现，FXR敲除（KO）加剧了CS诱导的炎症， 肺气肿肺损伤的小鼠，而刺激FXR的治疗小鼠与FXR激动剂， 吸烟暴露阻断了这些作用，表明FXR激动剂可能对COPD治疗有用。 CS诱导FXR下调的机制研究表明，它是由泛素化介导的， 蛋白酶体降解，由含有特异性F-box蛋白的E3-连接酶的结合触发。进一步 初步研究结果表明，FXR激动剂的结合通过促进FXR受体的结合而阻断了这一点。 peptylprolyl异构酶Pin 1，因为F-box蛋白不能结合产生的顺式-Pro形式的 FXR。基于这些新的发现，具体的目的是：1：确定是否抑制FXR 在COPD中发生的活动促进COPD进展和严重性，并且驱动这种进展和严重性的机制是： 抑制;和2：测试激活FXR，特别是在AEC中或通常在肺中，是否改善 COPD严重程度和进展以及激动剂阻断FXR降解的机制。实现 为了这些目的，我们将利用新的转基因小鼠，其中FXR被删除或组成型活性，特异性地在 AEC和利用在被认为是可诱导的位点携带突变的FXR或F-box蛋白构建体的体外研究 这对他们的互动至关重要。结果将确定以前被忽视的COPD的致病作用， 受体，以及CS促进其降解但激动剂使其稳定的相反机制。 也可以确定FXR作为一个有前途的新的治疗目标，广泛的致命性疾病。

PROJECT SUMMARY Chronic obstructive pulmonary disease (COPD) is the 3rd-leading cause of death in the US, generally due to cigarette smoking. Current treatments, including smoking cessation after the very earliest stages, provide only short-term benefit and cannot stop its inexorable progression. Novel therapies to halt progression are thus urgently needed. COPD pathophysiology includes bronchial inflammation and septal destruction leading to emphysema, with such septal destruction caused by inflammation-associated oxidative stress and protease secretion. Based on promising preliminary findings, the proposed research will test the beneficial role in COPD and mechanisms that regulate farnesoid X receptor (FXR), a nuclear hormone receptor whose roles in lungs and COPD are unknown. Preliminary studies revealed FXR is downregulated in airway epithelial cells (AECs) of COPD patients and in mice with cigarette smoke (CS)-induced COPD, and that CS elicits such FXR downregulation in vitro, leading us to hypothesize that FXR downregulation in patients contributes to COPD pathogenesis. We also found that FXR knockout (KO) exacerbates CS-induced inflammation and emphysematous lung damage in mice, whereas stimulating FXR by treating mice with FXR agonist during smoke exposure blocked these effects, suggesting FXR agonists may be useful for COPD therapy. Mechanistic studies of CS-induced FXR downregulation suggest it is mediated by ubiquitination and proteasomal degradation, triggered by binding of an E3-ligase containing a specific F-box protein. Further preliminary findings indicate that binding of an FXR agonist blocked this by promoting binding of the peptydylprolyl isomerase Pin1, because the F-box protein was unable to bind to the resulting cis-Pro form of FXR. Based on these novel findings, the specific aims are: 1: To determine whether the suppression of FXR activity that occurs in COPD promotes COPD progression and severity and the mechanisms driving such suppression; and 2: To test whether activating FXR, specifically in AECs or generally in lung, ameliorates COPD severity and progression and the mechanisms by which agonists block FXR degradation. To achieve these aims we will utilize novel transgenic mice in which FXR is deleted or constitutively active specifically in AECs and in vitro studies utilizing FXR or F-box protein constructs carrying mutations at sites believed to be crucial for their interaction. The results will determine the pathogenic role in COPD of a previously-overlooked receptor, and the opposing mechanisms by which CS promotes its degradation but agonists stabilize it. They may also identify FXR as a promising new therapeutic target for a widespread fatal disease.