Department of Pulmonary and Critical Care Medicine, the Second Xiangya Hospital, Central South University, No. 139 Renmin Road, Changsha, 410011, Hunan, China.
Research Unit of Respiratory Diseases, Central South University, No. 139 Renmin Road, Changsha, 410011, Hunan, China.
Respir Res. 2020 Sep 3;21(1):229. doi: 10.1186/s12931-020-01495-w.
Emphysema is a crucial pathological characteristic of chronic obstructive pulmonary disease (COPD). Oxidative stress, apoptosis and epigenetic mechanisms contribute to the pathogenesis of emphysema. However, an attempt to accurately identify whether these mechanisms interact with each other and how they are triggered has never been conducted.
The total reactive oxygen species (ROS) level, pulmonary apoptosis and B-cell lymphoma/leukemia-2 (Bcl-2) expression, an apoptosis regulator, were detected in samples from COPD patients. Bisulfite sequencing PCR (BSP) was conducted to observe the alterations in the methylation of the Bcl-2 promoter in specimens. The dysregulation of DNA methyltransferase enzyme 1 (DNMT1), a vital DNA methyltransferase enzyme, in the lungs of patients was confirmed through western blotting. To find out interactions between oxidative stress and DNA methylation in emphysema, mouse models were built with antioxidant treatment and DNMT1 silencing, and were examined with the pulmonary apoptosis, Bcl-2 and DNMT1 levels, and epigenetic alterations of Bcl-2.
Higher ROS levels and pulmonary apoptosis were observed in COPD patients than in healthy controls. Downregulated Bcl-2 expression with increased promoter methylation and DNMT1 protein expression was found in COPD patients. Antioxidant treatment reduced the level of ROS, DNMT1 protein and emphysematous progression in the smoking models. Following DNMT1 blockade, smoking models showed improved lung function, pulmonary apoptosis, emphysematous progression, and increased Bcl-2 protein level with less promoter methylation than emphysema mice.
Cigarette-induced oxidative stress mediates pulmonary apoptosis and hypermethylation of the Bcl-2 promoter in emphysema models through DNMT1.
肺气肿是慢性阻塞性肺疾病（COPD）的重要病理特征。氧化应激、细胞凋亡和表观遗传机制共同导致肺气肿的发病机制。然而，目前尚未有研究尝试准确地识别这些机制是否相互作用以及它们是如何被触发的。
检测 COPD 患者样本中的总活性氧（ROS）水平、肺细胞凋亡和 B 细胞淋巴瘤/白血病-2（Bcl-2）表达（一种凋亡调节剂）。通过亚硫酸氢盐测序 PCR（BSP）观察标本中 Bcl-2 启动子甲基化的变化。通过蛋白质印迹法确认患者肺部中至关重要的 DNA 甲基转移酶 1（DNMT1）的失调。为了探究氧化应激与肺气肿中 DNA 甲基化之间的相互作用，通过抗氧化治疗和 DNMT1 沉默构建了小鼠模型，并检测了肺细胞凋亡、Bcl-2 和 DNMT1 水平以及 Bcl-2 的表观遗传改变。
与健康对照组相比，COPD 患者的 ROS 水平和肺细胞凋亡更高。COPD 患者中 Bcl-2 表达下调，启动子甲基化增加，DNMT1 蛋白表达增加。抗氧化治疗降低了吸烟模型中的 ROS 水平、DNMT1 蛋白和肺气肿进展。阻断 DNMT1 后，吸烟模型的肺功能、肺细胞凋亡、肺气肿进展得到改善，Bcl-2 蛋白水平升高，启动子甲基化减少。
香烟引起的氧化应激通过 DNMT1 介导吸烟模型中的肺细胞凋亡和 Bcl-2 启动子的高甲基化。
