Radiotherapy is an important treatment regime for lung cancer, worldwide. However, radiation-induced pneumonitis and fibrosis are the treatment-limiting toxicities among patients who have undergone radiotherapy. The epithelial cells via epithelial to mesenchymal transition [EMT] acquires mesenchymal phenotype, which ultimately leads to fibrosis. Many investigations are focussed on understanding the signalling pathways mediating in EMT, however, the role of histone methylation is less understood in radiation-induced lung EMT. In the present study, we analysed the effect of vanillin, an antioxidant, on histone methylation during radiation-induced EMT. The thoracic region of Wistar rats was irradiated with a fractionated dose of X-ray (3 Gy/day) for two weeks (total of 30 Gy). The irradiated animals were sacrificed at the 8th and 16th weeks and tissues were used for analyses. Our data showed that radiation decreased the level of antioxidant enzymes such as SOD, catalase and reduced glutathione that would ultimately enhance oxidative stress in the tissues. Histopathological analysis revealed that radiation increased the infiltration of inflammatory cells to the tissue injury site. Total global histone methylation was increased upon irradiation, which was effectively prevented by vanillin administration. Vanillin enhanced E-cadherin expression and decreased the mesenchymal markers N-cadherin and vimentin in the irradiated lung tissue. The ChIP-qPCR analysis suggested that snail expression in the nucleus might involve in the enrichment of suppressive marker H3K9me3 on the E-cadherin promoter. Finally, we suggested that vanillin administration decreased radiation-induced oxidative stress and EMT expression. Additionally, irradiation increased the H3K9 methylation status with nuclear translocation of snail during lung EMT.

放疗是全世界肺癌的重要治疗方案。然而，放射线诱发的肺炎和纤维化是接受放射治疗的患者中限制治疗的毒性。上皮细胞通过上皮到间充质转变[EMT]获得间充质表型，最终导致纤维化。许多研究集中在理解EMT中介导的信号传导途径，但是，在放射线诱发的肺EMT中，对组蛋白甲基化的作用了解较少。在本研究中，我们分析了抗氧化剂香兰素对辐射诱导的EMT过程中组蛋白甲基化的影响。用分次剂量的X射线（3 Gy /天）辐照Wistar大鼠的胸腔区域，持续两周（总共30 Gy）。在第8和16周处死被辐照的动物，并使用组织进行分析。我们的数据表明，辐射降低了抗氧化酶（例如SOD，过氧化氢酶）的水平，并减少了谷胱甘肽，这最终会增强组织中的氧化应激。组织病理学分析显示放射线增加了炎症细胞向组织损伤部位的浸润。辐照后总的整体组蛋白甲基化增加，而香草醛给药可以有效地防止甲基化。香兰素增强了E-钙黏着蛋白的表达，并降低了被照射肺组织中的间充质标记物N-钙黏着蛋白和波形蛋白。ChIP-qPCR分析表明，蜗牛在核中的表达可能参与了E-钙粘蛋白启动子上抑制性标记H3K9me3的富集。最后，我们建议香草醛给药可降低辐射诱导的氧化应激和EMT表达。此外，辐照增加了肺EMT期间蜗牛核的H3K9甲基化状态。