Nagarajan Devipriya, Wang Lei, Zhao Weiling, Han Xiaochen
Department of Radiation Oncology, Wake Forest School of Medicine, Winston-Salem, NC, USA.
School of Chemical & Biotechnology, SASTRA University, Thanjavur, Tamil Nadu, India.
Oncotarget. 2017 Oct 9;8(60):101745-101759. doi: 10.18632/oncotarget.21664. eCollection 2017 Nov 24.
Radiation-induced pneumonitis and fibrosis are major complications following thoracic radiotherapy. Epithelial-to-mesenchymal transition (EMT) plays an important role in tissue injury leading to organ fibrosis, including lung. Our previous studies have reported that radiation can induce EMT in the type II alveolar epithelial cells in both and . HDAC inhibitors are a new family of anti-cancer agents currently being used in several clinical trials. In addition to their intrinsic anti-tumor properties, HDAC inhibition is also important in other human diseases, including fibrosis and radiation-induced damage. In this study, we evaluated the effect of Trichostatin A (TSA), a HDAC inhibitor, on radiation-induced EMT in type II alveolar epithelial cells (RLE-6TN). Pre-treatment of RLE-6TN cells with TSA inhibited radiation-induced EMT-like morphological alterations including elevated protein level of α-SMA and Snail, reduction of E-cadherin expression, enhanced phosphorylation of GSK3β and ERK1/2, increased generation of ROS. Radiation enhanced the protein level of TGF-β1, which was blocked by N-acetylcysteine, an antioxidant. Treating cells with SB-431542, TGF-β1 type I receptor inhibitor, diminished radiation-induced alterations in the protein levels of -GSK-3β, Snail-1 and α-SMA, suggesting a regulatory role of TGF-β1 in EMT. Pre-incubation of cells with TSA showed significant decrease in the level of TGF-β1 compared to radiation control. Collectively, these results demonstrate that i] radiation-induced EMT in RLE-6TN cells is mediated by ROS/MEK/ERK and ROS/TGF-β1 signaling pathways and ii] the inhibitory role of TSA in radiation-induced EMT appears to be due, at least in part, to its action of blocking ROS and TGF-β1 signaling.
放射性肺炎和肺纤维化是胸部放疗后的主要并发症。上皮-间质转化（EMT）在导致器官纤维化（包括肺纤维化）的组织损伤中起重要作用。我们之前的研究报道，辐射可在人和动物的II型肺泡上皮细胞中诱导EMT。组蛋白去乙酰化酶（HDAC）抑制剂是一类新型抗癌药物，目前正在多项临床试验中使用。除了其固有的抗肿瘤特性外，HDAC抑制在其他人类疾病中也很重要，包括纤维化和辐射诱导的损伤。在本研究中，我们评估了HDAC抑制剂曲古抑菌素A（TSA）对辐射诱导的II型肺泡上皮细胞（RLE-6TN）EMT的影响。用TSA预处理RLE-6TN细胞可抑制辐射诱导的EMT样形态学改变，包括α-SMA和Snail蛋白水平升高、E-钙黏蛋白表达降低、GSK3β和ERK1/2磷酸化增强、活性氧生成增加。辐射增强了TGF-β1的蛋白水平，而抗氧化剂N-乙酰半胱氨酸可阻断这一作用。用TGF-β1 I型受体抑制剂SB-431542处理细胞可减少辐射诱导的-GSK-3β、Snail-1和α-SMA蛋白水平的改变，提示TGF-β1在EMT中起调节作用。与辐射对照组相比，用TSA预孵育细胞后TGF-β1水平显著降低。总的来说，这些结果表明：i] RLE-6TN细胞中辐射诱导的EMT由ROS/MEK/ERK和ROS/TGF-β1信号通路介导；ii] TSA对辐射诱导的EMT的抑制作用似乎至少部分归因于其阻断ROS和TGF-β1信号的作用。
