基于mtDNA甲基化/羟甲基化修饰探讨热量限制介导的线粒体稳态对术后谵妄的作用及机制

Postoperative delirium (POD) significantly increases the postoperative mortality. Aging is the important risk factor for POD, but the mechanisms are still unknown. Our preliminary study and the existing literatures suggested that mitochondrial dysfunction is the main feature of natural aging and pathological changes in neurons, and mitochondrial DNA (mtDNA) methylation / hydroxylmethylation plays a central role in the regulation of mitochondrial structure and function. Aging causes mtDNA ‘methylation drift’, and decreases mitochondrial reserve function. Anesthesia and / or surgery further cause the abnormality of mtDNA methylation / hydroxylmethylation, disrupt the replication of mtDNA and the expression of mitochondrial components, and disrupt the mitochondrial homeostasis, result in the occurrence of POD. Via up-regulating the expression of SIRT1, calorie restriction improves the mtDNA ‘methylation drift’ caused by aging, and the abnormal levels of mtDNA 5mC and 5hmC caused by anesthesia and surgery, mediates mitochondrial homeostasis, thereby alleviates postoperative delirium in adult and aged mice. This study intends to focus on mice hippocampus, prefrontal cortex, anterior cingulate cortex as well as primary cultured neurons, detect the specific changes of mtDNA methylation / hydroxylmethylation under different treatments in different ages, and the effects of mtDNA methylation / hydroxylmethylation on mitochondrial structure and function, and investigate the role and mechanisms of calorie restriction in POD. This study will provide a new theoretical and practical basis for the prevention and treatment of POD.

术后谵妄（POD）显著增加术后死亡率，年龄是其重要危险因素。我们的前期研究和现有文献提示，线粒体功能障碍是神经元衰老或病变的主要特征，线粒体DNA（mtDNA）甲基化/羟甲基化修饰是调节线粒体结构与功能的中心环节。衰老导致mtDNA发生甲基化漂移，降低线粒体储备功能，麻醉和/或手术进一步引起mtDNA甲基化/羟甲基化异常，影响mtDNA复制及线粒体组分表达，破坏线粒体稳态，导致POD的发生。热量限制通过上调SIRT1的表达，改善衰老引起的mtDNA甲基化漂移，以及麻醉手术引起的mtDNA 5mC与5hmC水平异常，介导线粒体稳态，从而缓解成年与老年小鼠术后谵妄。本项目拟以小鼠海马、前额叶皮层、前扣带皮层和原代培养的神经元为研究对象，检测不同年龄及处理下mtDNA甲基化/羟甲基化的改变，及其对线粒体结构与功能的调节，探讨热量限制对POD的作用及机制，为临床防治POD提供新的理论和实践基础。

术后谵妄（POD）显著增加术后死亡率，年龄是其重要危险因素。我们的前期研究和现有文献提示，线粒体功能障碍是神经元衰老或病变的主要特征，线粒体DNA（mtDNA）甲基化/羟甲基化修饰是调节线粒体结构与功能的中心环节。衰老导致mtDNA发生甲基化漂移，降低线粒体储备功能，麻醉和/或手术进一步引起mtDNA甲基化/羟甲基化异常，影响mtDNA复制及线粒体组分表达，破坏线粒体稳态，导致POD的发生。热量限制通过上调SIRT1的表达，改善衰老引起的mtDNA甲基化漂移，以及麻醉手术引起的mtDNA 5mC与5hmC水平异常，介导线粒体稳态，从而缓解成年与老年小鼠术后谵妄。本项目应用术后谵妄小鼠模型，检测不同年龄及处理下海马、前额叶皮层、前扣带皮层、杏仁核mtDNA甲基化/羟甲基化的改变，及其对线粒体结构与功能的调节，探讨热量限制对POD的作用及机制，为临床防治POD提供新的理论和实践基础。研究结果显示：小胶质细胞过度活化介导的神经炎症反应，引起神经元线粒体DNA甲基化水平异常，线粒体碎片化和功能障碍，导致神经元能量代谢障碍和功能损伤，并进一步加重神经炎症反应，共同导致术后谵妄与术后认知功能障碍的发生和进展；通过给予SIRT1激动剂模拟热量限制，或对上述信号通路中的关键分子进行干预，可以显著缓解术后谵妄和术后认知功能障碍。本项目揭示了mtDNA甲基化异常介导线粒体功能障碍在术后谵妄中的作用机制，为临床防治术后谵妄提供了新的策略与理论依据。