Epitranscriptomic mechanisms of the antidepressant response to ketamine in human neurons

项目总结 尽管单胺类药物的功能显著增强，但长期服用单胺类抗抑郁药 是临床反应所必需的，这表明增强的单胺能信号下游的适应 是它们治疗效果的核心。一种这样的下游适应是大脑的表观遗传上调- 衍生神经营养因子是神经营养过程中的关键蛋白。这与神经营养 抑郁症假说，该假说认为神经元生长不足有助于MDD的发病。 抑郁症患者死后大脑中海马体体积的减少就是明证，因此 神经营养的恢复是抗抑郁药物疗效的核心。除了需要长期治疗外， 传统的抗抑郁药物在相当大比例的抑郁症患者中也无效 产生各种各样的不良副作用。另一方面，N-甲基-D-天冬氨酸受体氯胺酮 (NMDAR)拮抗剂和麻醉剂，单剂量可在不到30分钟内缓解症状 对至少两种典型抗抑郁药物无效的患者进行一小时和至少一周的治疗。 与传统的抗抑郁药不同，氯胺酮似乎能迅速促进BDNF介导的神经营养 直接但优化这种麻醉剂用于抗抑郁药物的应用和设计其形象所需的新药 进一步阐明其靶点及其治疗作用的机制。我们假设 而不是像慢性给药那样间接改变神经营养基因 抗抑郁药氯胺酮绕过了这一漫长的转录调控过程，转而诱导 快速上调神经营养蛋白翻译的RNA修饰。应激诱导的变化 在MDD中观察到了N6，2‘-O-二甲基腺苷(M6A)的水平，这是最丰富的RNA修饰 患者与M6A去甲基酶、脂肪量和肥胖相关蛋白的单核苷酸多态性 (FTO)与MDD风险增加相关。此外，对糖原合成酶激酶3(GSK-1)的抑制 3)，氯胺酮通过NMDAR拮抗作用，增加FTO浓度，从而促进 基质金属蛋白酶9去甲基化将促细胞凋亡的proBDNF转化为BDNF 9)。综上所述，这些发现提出了一种看似合理的快速神经营养表型转录机制。 以及氯胺酮的抗抑郁作用。因为m6A甲基化在不同物种之间不同，而甲基化 相关基因的位置，如基质金属蛋白酶-9，在小鼠和人类之间是不同的，我们将使用人类诱导的多能性 干细胞来源的皮质谷氨酸能神经元对氯胺酮的影响 表位转录组，M6A机制，以及神经元的结构和功能。这些项目的顺利完成 AIMS将阐明氯胺酮快速而有力的抗抑郁作用的机制，从而 从而能够识别和优化新型抗抑郁剂。

PROJECT SUMMARY Despite acutely enhancing monoamine function, chronic administration of monoamine antidepressants is required for clinical response, suggesting that adaptations downstream of enhanced monoaminergic signaling are central to their therapeutic efficacy. One such downstream adaption is the epigenetic upregulation of brain- derived neurotrophic factor (BDNF), a key protein in the neurotrophic process. This is in line with the neurotrophic hypothesis of depression, which posits that insufficient neuronal growth contributes to the pathogenesis of MDD, as evidenced by reduced hippocampal volume in the postmortem brains of depressed patients, and thus the restoration of neurotrophy is central to the efficacy of antidepressants. In addition to requiring chronic treatment, traditional antidepressants drugs are also ineffective in a significant proportion of depressed patients and produce a wide variety of undesirable side effects. On the other hand, ketamine, a N-methyl-D-aspartate receptor (NMDAR) antagonist and anesthetic, a single dosage of which has been shown to relieve symptoms in less than an hour and for at least one week in patients who failed to response to at least two typical antidepressants. Unlike traditional antidepressants, ketamine appears to promote BDNF-mediated neurotrophy rapidly and directly but optimizing this anesthetic for antidepressant application and designing novel drugs its image requires further elucidation of its targets and the mechanisms underlying its therapeutic effects. We hypothesize that rather than rather than indirectly altering neurotrophic genes, as with chronic administration of typical antidepressants, ketamine bypasses this prolonged process of transcriptional regulation and instead induces RNA modifications that rapidly upregulates the translation of neurotrophic proteins. stress-induced changes in levels of N6,2’-O-dimethyladenosine (m6A), the most abundant RNA modification, have been observed in MDD patients and single-nucleotide polymorphisms in the m6A demethylase, fat mass and obesity associated protein (FTO), are associated with increased risk of MDD. Furthermore, inhibition of glycogen synthase kinase 3 (GSK- 3), which ketamine does through NMDAR antagonism, increases FTO concentrations which promotes conversion of the pro-apoptotic proBDNF to BDNF through demethylation of matrix metalloprotease 9 (MMP- 9). Taken together, these findings present a plausible epitranscriptomic mechanism for the rapid neurotrophic and antidepressant effects of ketamine. Because m6A methylation varies between species, and the methylation sites of relevant genes, such as MMP-9, differ between mice and humans, we will use human induced pluripotent stem cell (hiPSC)-derived cortical glutamatergic neurons to delineate the effects of ketamine on the epitranscriptome, m6A machinery, as well as neuronal structure and function. The successful completion of these aims will elucidate the mechanisms underlying the rapid and robust antidepressant effects of ketamine thus enabling the identification and optimization of novel antidepressants.