稀土氧化物纳米材料对DNA甲基化和羟甲基化的调控机理及其毒性研究

Nanomaterials can regulate levels of methylation and hydroxylation of global DNA and induces cellular toxicity. On one hand, nanomaterials can regulate the expression levels of DNMT1 or TET2 and result in the alteration of methylation or hydroxylation of certain genes; On the other hand, REON can interact with DNMT1 or TET2 directly and induce the aberrant of enzyme activity or disruption of protein-protein interaction, which is involved in macrophage differentiation and function. In the current proposal, we aim to thoroughly investigate the effect of REON on the regulation of DNA methylation and hydroxylation in macrophages, and reveal the related mechanisms as follows: a) to determine the role of REONs involved in the levels of methylation and hydroxylation and their crucial physicochemical properties in regulating expression of DNMT1 or TET2 gene; b) to investigate the mechanism underlying the interaction between REON and DNMT1 or TET2 protein and its effect on the enzyme activity; c) to elucidate how REON and its released ions affect the ability of DNMT1 or TET2 to form their own protein complex; d) to study the alterations of methylation and hydroxylation of DNA and its impact on autophagy, cell cycle, inflammation and cell differentiation in monocytes/macrophages. This proposal would subserve discovering the mechanism underlying REON-regulated methylation and hydroxylation of DNA and the resulted toxicity.

稀土元素氧化物纳米材料（Rare Earth Oxide Nanomaterials, REON）可通过调控细胞基因组DNA甲基化和羟甲基化水平而诱发毒性。本项目拟通过研究REON对巨噬细胞或其前体细胞的生物效应，揭示DNA甲基化和羟甲基化调控在REON诱导的纳米毒性中的作用。本项目将1）、明确可引起DNA甲基化水平和羟甲基化水平的典型REON，揭示REON调控DNMT1和TET2表达的物理化学因素；2）、揭示REON及其释放离子与DNMT1和TET2的相互作用特点及其对酶催化活性的影响机制；3）、阐明REON及其释放离子影响DNMT1或TET2形成各自功能蛋白复合物的分子机制；4）、揭示单核/巨噬细胞中DNA甲基化和羟甲基化水平变化在REON所调控的细胞功能中的作用。本项目的研究工作对于明确REON影响DNA甲基化和羟甲基化水平的理化性质，深入揭示REON潜在的表观遗传毒性具有重要价值。

稀土元素已被广泛的应用于超导体、造影剂、玻璃制品、肥料添加剂和食品添加剂的制作中。同时，我国是稀土资源大国，稀土元素的开采和加工过程中所造成的职业暴露会对人体产生健康风险。已有研究表明稀土元素氧化物纳米材料(REONs)的毒性效应包括细胞炎性、诱发肺部或肾脏纤维化等。但是，目前对于REONs的毒性机制研究匮乏。申请人研究了不同原子质量的REONs(nLa2O3, nEu2O3, nDy2O3和nYb2O3)对巨噬细胞产生的毒性效应。结果表明，高原子序数材料(即nYb2O3)的毒性比低原子序数材料(nLa2O3和nEu2O3)的毒性更弱。通过进一步的毒性机制研究，证明了稀土元素纳米材料可争夺细胞膜磷脂中的磷元素，导致细胞膜的损伤。同时，REON的暴露可细胞内和线粒体内的钙离子显著增加，诱发细胞坏死。溶酶体中累积的稀土元素氧化物纳米材料会触发溶酶体膜的通透性增加，导致组织蛋白酶释放到细胞质中。这些膜的损伤是导致细胞死亡的重要原因之一。该项研究为REONs的毒性和潜在健康风险评价提供了重要的分子机制基础，为稀土元素在人们日常生活中的应用及开发提供了新思路。