褪黑素生物节律对异氟醚麻醉后认知功能影响的DNA甲基化机制研究

Postoperative cognitive dysfunction (POCD) is usually accompanied by reduced melatonin production and biological rhythm disturbance. The existence and functional relevance of the clock gene is increasingly recognized as an epigenetic regulator of melatonin rhythmicity and expression of melatonin receptor genes (mt1 and mt2). Nevertheless, the mechanisms underlying the disturbance of perioperative melatonin secretion, and its relationship with POCD are not clearly understood. Furthermore, our preliminary studies have also revealed that isoflurane exposure triggered a significant inhibition to the genome-wide DNA methylation and the mRNA levels of DNA methyltransferases in aged hippocampus, suggesting that DNA methylation is a key contributor in isoflurane-induced disturbance of melatonin rhythm and memory deficits. This study is thus designed to investigate the dynamic effect of isoflurane exposure on melatonin rhythmicity in aged hippocampus. In addition, the relationship between hippocampal disturbance in melatonin rhythm and promotor DNA methylation of clock, mt1 and mt2 in the pineal gland will also be explored. To further explore the relationship of disturbance in melatonin rhythm with isoflurane-induced cognitive dysfunction, DNA methylation will be intervened and the reaction of CDK-5/ɑ-Syn pathway, a known target for melatonin, to isoflurane exposure will then be investigated. The results of the present study may reveal an epigenetic role in isoflurane anesthesia, and provide a new experimental basis for elucidating POCD.

术后认知功能障碍（POCD）常伴随褪黑素分泌减少和生物节律改变。研究表明，褪黑素分泌节律及其受体基因（mt1、mt2）均受到生物钟clock基因的调控，并存在表观遗传学修饰过程。然而，围术期褪黑素节律紊乱的机制及其与POCD的关系尚不清楚。我们前期发现：异氟醚麻醉影响老龄大鼠海马全基因组DNA甲基化水平和DNA甲基转移酶的转录，故推测clock、mt1及mt2基因DNA甲基化可能参与异氟醚麻醉后褪黑素节律紊乱和记忆障碍。本研究拟观察异氟醚麻醉对老龄大鼠海马褪黑素生物节律的影响，并探究该影响与松果体clock、mt1及mt2基因启动子甲基化的关系；在此基础上，通过干预DNA甲基化，观察褪黑素作用靶点细胞周期素依赖蛋白激酶5/ɑ-突触核蛋白通路对异氟醚的反应，探讨麻醉后褪黑素节律紊乱与认知障碍的关系。研究结果将揭示异氟醚麻醉潜在的表观遗传修饰作用，为POCD的机制研究提供新的实验依据。

术后认知功能障碍（POCD）可严重影响老年患者生活质量，并增加死亡率，将成为一个日益凸显的医学和社会问题。研究表明，POCD常伴随褪黑素分泌减少和生物节律改变。褪黑素分泌节律及其受体基因（mt1、mt2）均受到生物钟clock基因的调控，并存在表观遗传学修饰过程。然而，围术期褪黑素节律紊乱的机制及其与POCD的关系尚不清楚。我们前期研究发现：异氟醚麻醉影响老龄大鼠海马全基因组DNA甲基化水平和DNA甲基转移酶的转录，故推测clock、mt1及mt2基因DNA甲基化可能参与异氟醚麻醉后褪黑素节律紊乱和记忆障碍。本研究基于本项目前期的研究基础， 1.3MAC（2.0%）× 4h 剂量异氟醚麻醉气体暴露对老龄大鼠血浆褪黑素含量产生抑制。观察了异氟醚麻醉对老龄大鼠海马褪黑素生物节律的影响，并探究该影响与松果体clock、mt1及mt2基因启动子甲基化的关系；在此基础上，通过干预DNA甲基化，观察褪黑素作用靶点细胞周期素依赖蛋白激酶5/ɑ-突触核蛋白通路对异氟醚的反应，探讨麻醉后褪黑素节律紊乱与认知障碍的关系。研究结果将揭示异氟醚麻醉潜在的表观遗传修饰作用，为POCD的机制研究提供新的实验依据。