Disrupted Folate Metabolism with Anesthesia Leads to Myelination Deficits Mediated by Epigenetic Regulation of ERMN

Objective: Anesthetics during early life stages may impair cognitive and emotional functions, of which the underlying molecular mechanisms remain largely unknown. Methods: Here we performed the unbiased transcriptome profiling in prefrontal cortex of both non-human primates and mice after anesthesia. We also constructed a brain blood barrier (BBB)-crossing AAV-PHP.EB vector to harbor GFP or ERMN expression cassette. Findings: We found that the thymidylate synthase gene (TYMS), a critical gene implicated in folate metabolism, was significantly downregulated after multiple anesthesia in both non-human primates and mice. Hereby, we examined the metabolites in plasma of patients with anesthesia and surprisingly found that blood folate levels significantly decreased after surgeries under general anesthesia in children. Combined with transcriptome and genome-wide DNA methylation analysis, we identified that ERMN was the primary target of the disrupted folate metabolism. We further showed that myelination in brain during early postnatal stage was indeed compromised by the anesthesia in mice, which was fully rescued by systematic administration of folic acid or expression of ERMN in the brain through brain-specific delivery of adeno-associated virus. Notably, administration of folic acid and ERMN remarkably alleviated the cognitive impairment of mice caused by the anesthesia during early postnatal stages. Interpretation: This study indicates that anesthesia during early the postnatal period leads to disrupted folate metabolism and subsequently defects in myelination in the young brain, and ERMN is the key target gene affected by anesthesia via epigenetic mechanisms. Clinical Trial Registration: NCT03746340 Funding Statement: This work was mainly supported by NSFC Grants (#81571028, # 81771132, #31625013, #91732302)   Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: The study protocol was approved by the Human Research Ethics Committee of Shanghai 9th People’s Hospital and Shanghai Jiao Tong University in Shanghai, P. R. China SH9H-2018-T53-2. The animal studies were performed according to the guidelines and regulations of the Institute of Laboratory Animal Science, Peking Union Medical College and Chinese Academy of Medical Science (Peking, China). Efforts were made to minimize the number of animals in the studies. The use of rhesus macaque in research at Institute of Laboratory Animal Science (Peking, China) was approved by Institutional Animal Care and Use Committee (Protocol number #XC17001).