Long noncoding RNA MALAT1 ablation reverses sepsis in mouse: epitranscriptomic mechanisms and therapeutic application

脓毒症是一种发病率高、致死率高的疾病，并伴有严重的代谢紊乱 甲硫氨酸代谢循环的一部分。在哺乳动物蛋氨酸代谢中，S-腺苷甲硫氨酸（SAM）是 产生，它在所有细胞的代谢中占据中心位置，作为一种必需的甲基供体， 维持DNA、RNA、组蛋白以及谷胱甘肽的正常甲基化，这对细胞氧化还原很重要 系统甲基腺苷酸转移酶（MAT 2A）是SAM生物合成所必需的， MAT 2A的表达通过m6 A RNA甲基化在转录和转录后水平上调节 MAT 2A mRNA的3 'UTR。 转录后，MAT 2A稳定性的mRNA受RNA介导的m6 A甲基化的调控 甲基化书写器L16，其通过甲基化MAT 2A mRNA的3 'UTR来调节MAT 2A mRNA。 胃L16与lncRNA MALAT 1形成复合物。然而，MALAT 1在调节MAT 2A中的作用不是 清楚在基因消融的MALAT 1小鼠中，MAT 2A基因表达上调，LPS诱导的ROS表达上调。 随着谷胱甘肽水平的增加而显著抑制。MALAT 1敲除小鼠对MALAT 1基因具有高度抗性。 内毒素血症诱导的脓毒性休克伴m6 A整体甲基化增加。我们的核心假设是 MALAT 1通过控制MAT 2A基因的表达和MALAT 1调控SAM的生物合成。 甲硫氨酸代谢途径是脓毒症的治疗靶点。具体目标是： 目标1.内毒素血症通过调节m6 A介导炎症反应的表位机制 RNA甲基化酶L16是甲基化MAT 2A的3 'UTR的关键酶，导致 内含子保留或mRNA的衰变。lncRNA MALAT 1对MATTL 16的潜在调节作用将 与野生型对照相比，使用来自MALAT 1缺失小鼠的巨噬细胞进行分析。m6A-seq 将进行分析以分析内毒素血症诱导的总体m6 A甲基化改变的影响 并确定关键的甲基化位点。MALAT 1对MAT 2A基因表达的调控作用 将被分析。补充甲基供体（SAM，Methylamine）对抗LPS诱导的 腹腔巨噬细胞分泌炎性细胞因子，而SAM合成的抑制竞争性 MAT 2A cLEU的抑制剂加剧炎症反应。这一目标的实验结果将 为治疗策略的制定提供依据。 目标二。用于改善甲硫氨酸代谢功能的靶向MALAT 1的治疗性药物和抗- 小鼠模型中的炎症功能。受MALAT 1在调节 甲硫氨酸循环，同时与Aim 1，反义RNA的方法与一个高效的反义 针对MALAT 1的LNA GapmeR寡核苷酸将在小鼠模型中测试用于治疗脓毒症。 与甲硫氨酸/SAM组合。

Sepsis is a disease with high incidence and lethality and is accompanied by profound metabolic disturbances of the methionine metabolism cycle. In mammalian methionine metabolism, S-adenosylmethionine (SAM) is produced, which occupies a central position in the metabolism of all cells as an essential methyl donor to maintain normal methylation of DNA, RNA, histones as well glutathione which is important for cellular redox system. Methionine adenosyltransferase (MAT2A) is essential for the biosynthesis of SAM and the gene expression of MAT2A is regulated at transcriptional and post-transcriptional levels through m6A RNA methylation of the 3’UTR of MAT2A mRNA. Post-transcriptionally, the mRNA of MAT2A stability is regulated by the m6A methylation mediated by RNA methylation writer METTL16 which regulates MAT2A mRNA by methylating 3’UTR of the MAT2A mRNA. METTL16 forms a complex with a lncRNA MALAT1. The role of MALAT1 in regulating MAT2A however, is not clear. In genetically ablated MALAT1 mice, MAT2A gene expression is up-regulated and LPS-induce ROS was significantly suppressed with increases in the levels of glutathione. MALAT1 null mice are highly resistant to the septic shock induced by endotoxemia with increased global m6A methylation. Our central hypothesis is MALAT1 regulates SAM biosynthesis by controlling MAT2A gene expression and MALAT1-regulated methionine metabolism pathway is a therapeutic target for sepsis. The specific aims are: Aim 1. Epitranscriptomic mechanisms of endotoxemia-induced inflammation through regulating m6A RNA methylation METTL16 which is the key enzyme for methylating 3’UTR of MAT2A, resulting in either intron retention or decay of the mRNA. The potential regulatory effects of lncRNA MALAT1 on MATTL16 will be analyzed using macrophage from MALAT1 null mice in comparison with the wild type control. The m6A-seq analysis will be performed to analyze the effects of endotoxemia-induced alteration of global m6A methylation and identify the critical methylation sites. The regulatory effect of MALAT1 on the gene expression of MAT2A will be analyzed. The effects of supplementation of methyl donor (SAM, Methionine) counteracting LPS-induced inflammatory cytokines secretion in peritoneal macrophage, while the inhibition of SAM synthesis by competitive inhibitor of MAT2A cLEU exacerbates the inflammatory responses. The experimental results in this aim will provide basis for therapeutic strategy development . Aim 2. Therapeutic targeting MALAT1 for improving methionine metabolic functions and anti- inflammatory function in mouse models. Motivated by the strong evidence of MALAT1 in regulating methionine cycle, concurrently with Aim 1, the antisense RNA approach with a highly effective antisense oligonucleotide, LNA GapmeR against MALAT1 will be tested for treatment of sepsis in mouse model in combination with methionine/SAM.