The Mechanism Underlying The Learing And Memory Deficits Induced By Anesthesia/Surgery In Adult Mice And The Transcriptome Screening And Outcome Analysis In Aged Mice After Anesthesia/Surgery

Background:Postoperative cognitive dysfunction(POCD)is a phenomenon which shows cognition decline after anesthesia and surgery.POCD is consistently associated with increased morbidity and mortality,which has become a major concern of patients and caregivers.POCD is more common in aged patients,but clinical studied showed that POCD happened at any age.Memory includes two parts: spatial reference memory and working memory.Spatial reference memory is a kind of long-term memory,which is formed through repeated reinforcement of response to the same stimulus.In contrast,working memory is a kind of short-term memory,which is required for the representation of objects or places during goal-directed behavior.Previous studies demonstrated that anesthesia/surgery had no effects on reference memory of adult mice.However,whether it impairs working memory remains unclear.We hypothesized that anesthesia/surgery impaired the working memory of adult mice and the central cholinergic system was involved.Moreover,another cohort 18-month-old mice which is more prone to POCD,were utilized,and transcriptome sequencing was performed after surgery to find a target for the pathogenesis of POCD and clinical prevention and treatment of POCD.Methods and Results: 1.The effect of anesthesia/surgery on cognitive function and central cholinergic system in 8-week-old adult mice.Method: Tibial fracture internal fixation under the anesthesia of isoflurane was performed in two-month-old C57BL/6 mice.Two days later,the spatial reference memory and working memory were measured by a Morris Water Maze(MWM).Western Blot was used to detect the marker protein levels of central cholinergic system in hippocampus and the prefrontal cotex(PFC).Donepezil,an inhibitor of acetylcholinesterase(AChE),was administered in another cohort mice for 4 weeks.Then the working memory was measured by MWM 2 days after anesthesia/surgery.Western blot was used to detect the acetylcholine transferase(ChAT)in the prefrontal cortex(PFC).Another cohort mice were utilized to investigate whether anesthesia only could affect the working memory.Results: We found that anesthesia/surgery had no effects on the reference memory,but it impaired the working memory in adult mice.Meanwhile,we also found that the protein level of ChAT in PFC decreased significantly compared with that in control group.Donepezil pretreatment prevented working memory impairment and the decrease of the protein levels of ChAT induced by anesthesia/surgery.And anesthesia only didn’t affect working memory.2.Transcriptome Screening and Outcome Analysis in Aged Mice After Anesthesia/Surgery Methods: Six 18-month-old mice were anesthetized with isoflurane for internal fixation of tibia fracture.At 48 hours after operation,the hippocampus of mice were harvest and RNA sequencing was performed.The results of partial sequencing were verified by RT-PCR.Western Blot was used to verify the expression change of Klf6 and detection of its role in upstream and downstream molecules.Results: The first 11 molecules with the most changes were identified by sequencing and RT-PCR.We found that there were three molecules whose mRNA expression was decreased,and six molecules’ mRNA expression were upregulated.And the mRNA expression of the two molecules was unchanged.Postoperative histone H3 lysine 9 trimethylated(H3K9me3)methylase Suv39h1 and H3K9me3 expression was up-regulated,while MMP9(Matrix metalloproteinase-9)expression was up-regulated.Conclusion: 1.Anesthesia/surgery leads to working memory deficits in adult mice and central cholinergic system impairment is involved.2.The difference of gene expression profiles in aged mice after tibial fracture internal fixation was established by sequencing to reveal the possible pathogenesis of POCD.One of them may be for the anesthesia surgery to up-regulate the expression of Suv39h1 in the hippocampus of aged mice,cause the overexpression of H3K9me3,inhibit the expression of transcription factor Klf6 and promote the transcription of MMP9 finally Lead to the destruction of the blood-brain barrier,causing cognitive dysfunction.