Department of Environmental Medicine, New York University School of Medicine, New York, NY 10010, USA.
Department of Environmental Medicine, New York University School of Medicine, New York, NY 10010, USA.
Toxicol Appl Pharmacol. 2019 Jun 15;373:1-9. doi: 10.1016/j.taap.2019.04.011. Epub 2019 Apr 16.
Cadmium (Cd) is a known human lung carcinogen. In addition, Cd exposure is associated with several lung diseases including emphysema, chronic obstructive pulmonary disease (COPD), asthma and fibrosis. Although earlier studies have identified several processes dysregulated by Cd exposure, the underlying mechanisms remain unclear. Here, we examined the transcriptome of lung epithelial cells exposed to Cd to understand the molecular basis of Cd-induced diseases. Computational analysis of the transcriptome predicted a significant number of Cd-upregulated genes to be targets of miR-30 family miRNAs. Experimental validation showed downregulation of all the miR-30 family members in Cd exposed cells. We found SNAIL, an EMT master regulator, to be the most upregulated among the miR-30 targets. Furthermore, we found decrease in the levels of epithelial marker E- cadherin (CDH1) and increase in the levels of mesenchymal markers, ZEB1 and vimentin. This suggested induction of EMT in Cd exposed cells. Luciferase reporter assays showed that miR-30 repressed SNAIL by directly targeting its 3' UTR. Over expression of miR-30e and transfection of miR-30e mimics reduced Cd-induced SNAIL upregulation. Our results suggest that miR-30 negatively regulates SNAIL in lung epithelial cells and that Cd-induced downregulation of miR-30 relieves this repression, resulting in SNAIL upregulation and EMT induction. EMT plays a major role in many diseases associated with Cd exposure including fibrosis, COPD, and cancer and metastasis. Therefore, our identification of miR-30 downregulation in Cd exposed cells and the consequent activation of SNAIL provides important mechanistic insights into lung diseases associated with Cd exposure.
镉（Cd）是一种已知的人类肺部致癌物。此外，镉暴露与几种肺部疾病有关，包括肺气肿、慢性阻塞性肺疾病（COPD）、哮喘和纤维化。尽管早期的研究已经确定了几种受镉暴露调节的过程，但潜在的机制仍不清楚。在这里，我们研究了暴露于镉的肺上皮细胞的转录组，以了解镉诱导疾病的分子基础。转录组的计算分析预测，大量受镉上调的基因是 miR-30 家族 miRNA 的靶标。实验验证表明，Cd 暴露细胞中 miR-30 家族成员下调。我们发现 SNAIL，一种 EMT 主调控因子，是 miR-30 靶标中上调最明显的。此外，我们发现上皮标志物 E-钙粘蛋白（CDH1）的水平降低，间充质标志物 ZEB1 和波形蛋白的水平增加。这表明 EMT 在 Cd 暴露细胞中被诱导。荧光素酶报告基因检测表明，miR-30 通过直接靶向其 3'UTR 来抑制 SNAIL。miR-30e 的过表达和 miR-30e 模拟物的转染减少了 Cd 诱导的 SNAIL 上调。我们的结果表明，miR-30 在肺上皮细胞中负调控 SNAIL，而 Cd 诱导的 miR-30 下调解除了这种抑制，导致 SNAIL 上调和 EMT 诱导。EMT 在与 Cd 暴露相关的许多疾病中起主要作用，包括纤维化、COPD 和癌症及转移。因此，我们在 Cd 暴露细胞中发现 miR-30 下调，以及随后 SNAIL 的激活，为与 Cd 暴露相关的肺部疾病提供了重要的机制见解。
