Background

Chronic obstructive pulmonary disease (COPD) is a global health problem. Currently, there is a lack of knowledge about the pathobiology of this disease and available therapies are ineffective. Cigarette smoking is the leading cause of COPD; however, not all smokers develop COPD. Exacerbations of COPD caused by microbes are common and detrimental. Approximately 20–50% of patient exacerbations are caused by bacterial colonization in the lower airways. It is generally accepted that epigenetic mechanisms, especially DNA methylation, play an important role during progression of COPD. Thus, we hypothesized that DNA methylation patterns vary significantly following smoke exposure and during exacerbations caused by bacterial infections. To test our hypothesis, we used an in vitro study model that mimics COPD exacerbations and performed extensive studies to understand the role of CpG promoter methylation of NF-κB and STAT3-mediated pathway genes. Both NF-κB and STAT3 transcription factors play critical roles in orchestrating inflammatory responses during cigarette smoke exposure. In brief, human lung adenocarcinoma cells with type II alveolar epithelium characteristics (A549) were challenged with cigarette smoke extract (CSE) or DMSO (control) followed by a 3-h challenge with bacterial lipopolysaccharide (LPS; from Pseudomonas aeruginosa) prior to the termination of CSE exposure (COPD exacerbation group). The production of cytokines/chemokines, regulation of transcription factors, and DNA methylation of specific genes were then assessed. We also studied changes in the expression and activity of ten-eleven translocases (TETs), the enzymes responsible for DNA demethylation, and assessed their role in regulating DNA methylation in the CSE-challenged group.

Results

There was a significant increase in the release of cytokines/chemokines (IL-8, MCP-1, IL-6 and CCL5) in the COPD exacerbation group as compared to the control group. Hypomethylation of NF-κB-mediated pathway genes correlated with their induction in our COPD exacerbation study model. Further, we observed an important role of TET1/2 in regulating the DNA methylation of NF-κB, STAT3, IKK, and NIK genes and cytokine/chemokine production by A549 cells during CSE challenge.

Conclusions

Studies to further define the role of TETs in CSE-mediated epigenetic regulation may lead to the development of better and more effective therapeutic intervention strategies for COPD.

中文翻译：

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在体外香烟烟雾提取物攻击的细胞/COPD 恶化模型中，对 NF-κB 和 STAT3 通路基因和 TET 活性的 DNA 甲基化特征的调节。

背景

慢性阻塞性肺疾病 (COPD) 是一个全球性的健康问题。目前，对这种疾病的病理生物学缺乏了解，可用的治疗方法无效。吸烟是 COPD 的主要原因；然而，并非所有吸烟者都会患 COPD。由微生物引起的 COPD 恶化是常见且有害的。大约 20-50% 的患者病情加重是由下呼吸道的细菌定植引起的。人们普遍认为，表观遗传机制，尤其是 DNA 甲基化，在 COPD 的进展过程中起重要作用。因此，我们假设 DNA 甲基化模式在烟雾暴露后和细菌感染引起的恶化期间发生显着变化。为了验证我们的假设，我们使用了体外模拟 COPD 恶化的研究模型，并进行了广泛的研究，以了解 NF-κB 和 STAT3 介导的通路基因的 CpG 启动子甲基化的作用。NF-κB 和 STAT3 转录因子在香烟烟雾暴露期间的炎症反应的编排中起着关键作用。简而言之，用香烟烟雾提取物（CSE）或 DMSO（对照）攻击具有 II 型肺泡上皮特征（A549）的人肺腺癌细胞，然后用细菌脂多糖（LPS；来自铜绿假单胞菌）攻击 3 小时) 在终止 CSE 暴露之前（COPD 加重组）。然后评估细胞因子/趋化因子的产生、转录因子的调节和特定基因的 DNA 甲基化。我们还研究了 10-11 个转位酶 (TET)（负责 DNA 去甲基化的酶）的表达和活性变化，并评估了它们在 CSE 挑战组中调节 DNA 甲基化的作用。

结果

与对照组相比，COPD 加重组中细胞因子/趋化因子（IL-8、MCP-1、IL-6 和 CCL5）的释放显着增加。在我们的 COPD 恶化研究模型中，NF-κB 介导的通路基因的低甲基化与其诱导相关。此外，我们观察到 TET1/2 在调节NF-κB、STAT3、IKK和NIK基因的 DNA 甲基化以及A549 细胞在 CSE 攻击期间产生细胞因子/趋化因子方面的重要作用。

结论

进一步确定 TET 在 CSE 介导的表观遗传调控中的作用的研究可能会导致开发出更好、更有效的 COPD 治疗干预策略。