Epigenetic regulation of radiation damage in oral mucosa

 描述（由申请人提供）：本申请的目的是研究调节口腔粘膜中细胞对电离辐射（IR）反应的新机制，并开发治疗口腔辐射损伤的有效疗法。暴露于电离辐射会导致口腔粘膜损伤，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衰弱性疾病。IR触发介导组织损伤的辐射诱导的早衰（RIPS）的开始。衰老细胞通过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，这可能有助于辐照组织中口腔粘膜炎的炎症阶段。在机制水平上，我们最近发现IR暴露通过涉及组蛋白脱甲基酶活化的表观遗传机制诱导正常人口腔角质形成细胞（NHOK）的过早衰老，例如，Jmjd 3，多梳组（PcG）蛋白的丢失，例如，Bmi-1和EZH 2，以及三甲基化组蛋白H3 K27（H3 K27 me 3）水平的改变，表明正常细胞辐射反应部分是通过Jmjd 3和PcG蛋白之间的平衡来确定的。当我们通过Bmi-1的过表达扰乱Jmjd 3和PcG之间的平衡时，我们发现RIPS在细胞中被强烈抑制，并且即使在IR暴露后，H3 K27 me 3的总体水平仍得以维持。Bmi-1过表达的这种辐射防护作用在NHK的单层培养中以及在3D中的器官型筏培养中观察到。综上所述，这些结果提出了一个假设，即Jmjd 3和PcG蛋白之间的相互作用介导的RIPS和SASP的发病辐射暴露后的表观遗传变化。这一假设将通过研究Jmjd 3和PcG蛋白在响应IR的NHOK中的RIPS和SASP的表观遗传调节中的作用来检验;确定RIPS的发生和在体内暴露于IR后口腔粘膜中相应的表观遗传变化;以及确定改变的Jmjd 3或PcG状态对暴露于辐射的口腔粘膜中的RIPS的影响。这些实验将阐明放射性口腔粘膜炎的表观遗传学机制，并为今后研究开发新的口腔粘膜炎治疗药物奠定基础。

 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.