骨形成蛋白BMP4在调控慢性阻塞性肺疾病气道炎症中的作用和机制研究

Chronic obstructive pulmonary disease (COPD) is one of the highly prevalent diseases characterized of progressive and irreversible lung function decline caused by chronic inflammation and consequent remodeling in the airway. Although intensive efforts have been given, the detailed mechanisms underlying COPD lung pathology, particularly chronic airway inflammation is still largely unknown. Cigarette smoking (CS) is the leading risk factors for COPD. Chronic exposure of CS leads to lung inflammation and COPD in animals such as mice. Bone morphogenetic factor 4 (BMP4) is a member of the TGF-β superfamily, which is ubiquitously and highly expressed in various organs including lung, bone marrow and thymus, and plays critical roles in normal lung and blood cell development. We recently found that BMP4 promoted hypoxic pulmonary hypertension development in a hypoxia inducible factor (HIF)-1alpha dependent manner (Wang J, et al. Cardiovasc Res, 2015). We also found BMP4 exhibited important anti-inflammatory functions against LPS and cytokine-induced acute lung inflammation (Li Z, et al. Eur J Immunol, 2014). In our preliminary study, we found CS exposure increased BMP4 precursor and mature protein expression in mouse lung, and BMP4 heterozygous mutant mice displayed more severe lung inflammation comparing to their wild-type littermates, suggesting BMP4 likely plays an important immunoregulatory function during CS-induced chronic lung inflammation associated with COPD. In this study, we hypothesize that BMP4 is upregulated by HIF-1alpha and protects mice from COPD development via BMPRs-Smad dependent suppression of CS-induced innate and adaptive immune responses in lung epithelial cells, macrophages, neutrophils, dendritic cells and T lymphocytes. To test this hypothesis, we will utilize HIF-1alpha and BMP4 deficient mice, CS-induced mouse model, COPD and healthy control subject lung specimens, primary cultured airway epithelial and immune cells to investigate the following specific aims: Aim 1: To determine if HIF-1alpha is necessary for BMP4 upregulation in CS-exposed mouse lung. Aim 2: To determine if BMP4 upregulation is essential to control CS-induced airway inflammation in vitro and in vivo. Aim3: To determine if BMP4 inhibits CS-induced cytokine production in airway epithelial cells, and inhibits immune cell development, proliferation, migration, function and apoptosis. Aim 4: To determine if the inhibition of BMP4 on CS-induced chronic lung inflammation is dependent of BMPRs-Smad signaling. Aim 5: To examine if HIF-1alpha-BMP4-BMPR2-Smad signaling in COPD lung is associated with the inflammatory and lung function parameters of COPD subjects. This study will likely provide novel mechanistic insights for understanding the molecular mechanisms of CS-induced chronic lung inflammation, and potentially identify the molecular targets for novel diagnosis and intervention of COPD.

慢性阻塞性肺疾病（COPD)是重大慢病之一，患病率高，危害大，当前药物防治效果有限。COPD肺组织核心病理特征是慢性炎症，吸烟是最重要的危险因素，但机制不完全清楚。骨形成蛋白4（BMP4）是TGF-beta超家族成员之一，在肺组织中高表达。我们前期研究发现BMP4在脂多糖导的急慢性肺损伤过程中发挥重要的抗炎作用，提示其可能影响COPD等慢性炎症性疾病的发生发展。本课题将应用原代培养的气道上皮和炎症细胞、COPD模型小鼠和人体组织，应用基因敲除、沉默和过表达等手段，研究在COPD发病中肺组织BMP4及其信号传导通路否受到香烟烟雾和低氧诱导因（HIF-1）的调控，BMP4是否经Smad通路抑制免疫细胞所介导的COPD慢性气道炎症。本研究将增加对COPD气道炎症机制的认识，揭示新的诊治靶点，研发新型防诊治策略奠定基础。

由于受吸烟等环境因素的影响，重大复杂疾病——慢性阻塞性肺疾病（COPD)防控形式仍然十分严峻，需要深入解析其发病机制、揭示治疗靶点，为进一步研究有效干预措施奠定基础。骨形成蛋白4（BMP4）是TGF-beta超家族成员，在肺组织中高丰度表达，影响肺发育和肺稳态。本项目应用细胞和动物模型研究了BMP4对烟草烟雾暴露下COPD核心病理特征气道慢性炎症、气道壁重构和肺泡损伤的调节作用及分子机制。研究发现，BMP4对于烟草烟雾所诱导的小鼠COPD发病具有显著的抑制作用，BMP4基因敲除（BMP4-/+）小鼠COPD相关气道炎症、粘液高分泌、气道壁重构和肺气肿等病理指标都更为严重。在细胞和分子机制上，BMP4显著减轻小鼠肺部巨噬细胞极化、显著降低M2型巨噬细胞比例；显著抑制TGF-β1诱导的气道和肺泡上皮细胞上皮间质转化（EMT）与细胞衰老；抑制TGF-β1诱导的肺成纤维细胞的增殖、促进其凋亡，抑制TGF-β1诱导的成纤维细胞衰老、细胞激活与细胞转化，抑制TGF-β1诱导的成纤维细胞自噬障碍。BMP4上述生物学作用可能与其促进Smad1/5/9、抑制ERK1/2信号分子激活有关。本研究首次发现BMP4对烟草烟雾诱导的COPD发病具有抑制作用，为进一步研发新药奠定了基础。研究结果提示，应用药物提高COPD肺组织中BMP4表达水平或者靶向BMP4下游信号通路，可能成为COPD新的预防或治疗手段。在本项目直接或部分支持下，项目组发表了相关研究论文21篇，申请知识产权16项，培养青年研究人员和研究生共18人。