Epigenetic regulation of radiation damage in oral mucosa

 描述(申请人提供)：本申请的目的是研究调节口腔粘膜细胞对电离辐射(IR)反应的新机制，并开发有效的治疗口腔辐射损伤的方法。暴露在电离辐射中会对口腔粘膜造成损害，最终导致口腔粘膜炎，这是一种在接受头颈癌放射治疗的患者中非常普遍的疼痛和虚弱的疾病。红外线引发辐射诱导的早衰(RIPS)，从而介导组织损伤。衰老细胞通过一种称为衰老相关分泌表型(SASP)的过程分泌生长因子、蛋白酶和促炎细胞因子，这可能是辐射组织中口腔粘膜炎的炎症阶段所致。在机制水平上，我们最近发现，IR暴露通过表观遗传学机制诱导正常口腔角质形成细胞(NHOK)提前衰老，该机制涉及组蛋白去甲基酶Jmjd3的激活，多梳组蛋白(PcG)蛋白的丢失，如Bmi-1和EZH2，以及三甲基化的组蛋白H3K27(H3K27me3)水平的改变，表明正常细胞的辐射反应部分是通过Jmjd3和PcG蛋白之间的平衡决定的。当我们通过过度表达BMI-1来扰乱Jmjd3和PcG之间的平衡时，我们发现细胞中的RIPS被强烈抑制，即使在IR暴露后，H3K27me3的整体水平仍然保持不变。BMI-1过表达的辐射防护作用在NHK单层培养中观察到，在器官型筏培养中也是如此。综上所述，这些结果提出了一个假说，即Jmjd3和PcG蛋白之间的相互作用导致的表观遗传学变化介导了辐射暴露后RIPS和SASP的发生。这一假说将通过研究Jmjd3和PcG蛋白在NHOK对IR反应中RIPS和SASP的表观遗传调节中的作用来验证；确定在活体暴露于IR后口腔粘膜中RIPS的发生和相应的表观遗传学变化；以及确定Jmjd3或PcG状态改变对暴露于辐射的口腔黏膜中RIPS的影响。这些实验将阐明放射性口腔粘膜炎的一种新的表观遗传学机制，并为未来研究开发治疗口腔粘膜炎的新疗法奠定基础。

 DESCRIPTION (provided by applicant): The purpose of this application is to investigate a novel mechanism regulating cellular responses to ionizing radiation (IR) in oral mucosa and to develop effective therapies for treating radiation damage in oral cavity. Exposure to ionizing radiation causes damage to oral mucosa that culminates in oral mucositis, a painful and debilitating disorder highly prevalent in patients receiving radiation therapy for head and neck cancer. IR triggers the onset of radiation-induced premature senescence (RIPS) that mediates tissue damage. Senescent cells secrete growth factors, proteases, and pro-inflammatory cytokines, through a process called senescence- associated secretory phenotype (SASP), which may contribute to the inflammatory phase of oral mucositis in irradiated tissues. At the mechanistic level, we recently found that IR exposure induces premature senescence in normal human oral keratinocytes (NHOK) through epigenetic mechanism that involves activation of histone demethylase, e.g., Jmjd3, loss of polycomb group (PcG) proteins, e.g., Bmi-1 and EZH2, and altered level of trimethylated histone H3K27 (H3K27me3), indicating that normal cell radiation response is in part determined through the balance between Jmjd3 and PcG proteins. When we perturbed the balance between Jmjd3 and PcG by overexpression of Bmi-1, we found that RIPS was strongly inhibited in cells and the global level of H3K27me3 was maintained even after IR exposure. Such radioprotective effects of Bmi-1 overexpression were observed in monolayer culture of NHK, as well as in organotypic raft culture in 3D. Taken together, these results raise a hypothesis that epigenetic changes by the interplay between Jmjd3 and the PcG proteins mediate the onset of RIPS and SASP upon radiation exposure. This hypothesis will be tested by investigating the roles of Jmjd3 and PcG proteins in epigenetic regulation of RIPS and SASP in NHOK in response to IR; determining the occurrence of RIPS and the corresponding epigenetic changes in oral mucosa after exposure to IR in vivo; and determining the effects of altered Jmjd3 or PcG status on RIPS in oral mucosa exposed to radiation. These experiments will elucidate a novel epigenetic mechanism underlying radiation- induced oral mucositis, and lay the foundation for developing novel therapeutics for oral mucositis in future research.