衰老的支气管上皮细胞BMI1表达在慢阻肺形成中作用及机制研究

Chronic obstructive pulmonary disease(COPD) is a common disease related to aging. However, it is still not clear on the role of aging in COPD formation. We previously showed that Klotho expression in bronchial epithelial cells(BEC) is critically inhibited in COPD formation and further demonstrated the increased response of injury and inflammation by the cells due to cigarette smoke extracts(CSE) and hydrogen peroxide stimulation. Now we have further shown the reduced BECs expression of Klotho and BMI1 in lung tissues from senile mice which are more susceptible to COPD as well as BMI1 knockout mice. BMI1 might regulate the expression of Klotho through p16Ink4a. Therefore, we made the hypothesis that, during aging process, through the pathway, the reduced expression of BMI1 makes BECs be more susceptible to the risk factors, including cigarette smoking, which might contribute to COPD formation. In this study, human lung tissue, mice and primary cell culture will be employed to investigate the effect of reduced BMI1 expression on the cell function related to COPD, including the barrier, proliferation, differentiation and inflammation. This study would further demonstrate the role of aging, the important host factor, on COPD formation, as well as the underlying mechanism.

慢阻肺是一种常见老年性疾病，但衰老本身在该疾病形成中作用尚不明确。项目组前期首先报道，支气管上皮细胞Klotho是抑制慢阻肺形成的重要蛋白，Klotho敲降后，细胞对香烟提取物和H2O2等刺激造成的损伤和炎症反应更明显。近期发现，衰老小鼠肺组织细胞周期蛋白 BMI1和支气管上皮细胞Klotho表达均明显下降，且衰老和BMI1基因敲除小鼠均更易形成慢阻肺；BMI1可能通过p16Ink4a，调控Klotho表达。我们进一步提出假说：随机体衰老，支气管上皮细胞BMI1表达下降，通过上述通路，使细胞对吸烟等外界损伤因素更加敏感，促进慢阻肺形成。本研究拟从人体、小鼠及体外原代细胞培养等层面，进一步研究机体衰老时，支气管上皮细胞BMI1表达及其对细胞功能影响（包括屏障功能、增殖分化、炎症等），探讨其在疾病形成中作用。本项目实施将有助于阐明衰老这一重要个体因素对慢阻肺形成的影响，并了解其中可能机制。

慢性阻塞性肺疾病（COPD）是一种常见病和多发病，近年来，COPD被认为是一种“加速衰老”的疾病，然而老年肺与慢阻肺的肺具有结构和功能差异，这意味着细胞衰老不是COPD发病机制的唯一致病因素，需确定其他潜在机制解释慢阻肺的加速衰老。铁死亡是一种程序性细胞死亡形式，其特征是铁积累和脂质过氧化的发生。肺泡上皮细胞的铁死亡导致氧化和修复损伤，可能在COPD的进展中起关键作用。在本项目中，我们证明铁离子累积与脂质过氧化产物 4HNE在COPD患者肺泡上皮细胞和 COPD 小鼠模型中表达增加，而铁死亡关键还原性酶GPX4的表达下降，且在小鼠COPD模型中可被铁死亡抑制剂fer-1和DFO完全或部分逆转。人肺泡上皮细胞中的铁离子沉积水平、4HNE表达水平及GPX4表达水平与肺功能指标FEV1/FVC和FEV1%pred具有显著相关性。COPD患者和COPD小鼠模型肺组织中p16和SA-β-Gal的表达明显升高。铁死亡诱导剂RSL3在诱导肺泡上皮细胞发生铁死亡的同时，细胞也发生了衰老，在COPD小鼠模型中，Fer-1的使用减缓慢阻肺模型中的衰老现象。本研究我们证明Bmi1作为一种与延缓衰老和维持氧化还原平衡相关的蛋白质，在COPD人肺泡上皮细胞中减少并且与4HNE表达呈负相关，与GPX4呈正相关。在Bmi1敲除小鼠肺组织中，4HNE表达增加，GPX4表达下降，MDA（另一种脂质过氧化产物）水平增加，GSH水平降低。这表明靶向铁死亡的Bmi1抑制了慢阻肺中肺泡上皮细胞的损伤。