Role Of Immediate Early Genes In Learning And Memory Impairment Induced By Etomidate And Their Association With Postoperative Cognitive Dysfunction

Part Ⅰ Effect of etomidate on learning and memory of rats and potential mechanismsObjective:To study the potential mechanisms associated with spatial learning and memory impairment induced by etomidate,and clarify the relationship between long term potentiation(LTP),long term depression(LTD)and immediate early genes(IEGs)in the process of learning and memory impairment induced by etomidate.Methods:A total of 40 2-month-old healthy male Wistar rats weighing 180-220 g were selected.All rats were randomly divided into 3 groups(n=10),including blank control group,solvent control group,experimental group.The blank control group was intraperitoneally injected with 0.9%NaCl solution from 1d to 5d of water maze test,the solvent control group was intraperitoneally injected with fat emulsion,and the experimental group was intraperitoneally injected with etomidate.On the 6d of water maze test,the treatment was stopped in the experimental group and the control groups.After 6 days of test,the rats were reared for 3 days,and then the hippocampus was decapitated to make hippocampal slices.The mRNA expression levels of Arc,c-fos,Egr1 and Npas4 were detected by reverse transcription polymerase chain reaction(RT-PCR),and the effects of etomidate on synaptic transmission of LTP and LTD in rat hippocampal slices were detected by patch clamp technique.Another 10 of Wistar rats into hippocampal slice group(n=10),In the hippocampal slice group,after one week of adaptive feeding,the hippocampus was decapitated to make hippocampal slices,which were divided into fat emulsion group,control group and normal saline group.Fat emulsion group was pre-incubated in cerebrospinal fluid containing 30 μL fat emulsion,etomidate group was pre-incubated in cerebrospinal fluid containing 5 μmol/L etomidate,and blank control group was pre-incubated in cerebrospinal fluid containing 0.9%NaCl.Then the induction of LTP and LTD was detected by patch clamp technique,and the effects of LTP and LTD on the expression of Arc,c-fos,Egrl and Npas4 were detected by RT-PCR.Results:Etomidate significantly increased the time for finding the target platform(escape latency),increased the path length for finding the target platform,and reduced the time for passing through the quadrant where the platform was located and the time for staying in the quadrant.Etomidate inhibited LTP in CA1 region of rat hippocampal slices,and enhanced LTD;LTP in CA1 region up-regulated the expression levels of Arc,c-fos,Egr1 and Npas4,and etomidate significantly down-regulated the expression levels of Arc,c-fos,Egr1 and Npas4,possibly through inhibiting LTP in CA1 region;LTD in CA1 region down-regulated the expression levels of Arc,c-fos,Egr1 and Npas4,and etomidate significantly down-regulated the expression levels of Arc,c-fos,Egr1 and Npas4,possibly through enhancing LTD in CA1 region.After water maze test,the expression levels of Arc,c-fos,Egr1 and Npas4 in rats treated with etomidate were significantly lower than those treated with fat emulsion or normal saline;LTP in CA1 region of hippocampal slices of rats treated with etomidate was significantly inhibited compared with those treated with fat emulsion or normal saline,while LTD was significantly enhanced.Conclusions:Etomidate could damage learning and memory ability by blocking LTP and enhancing LTD,and inhibit the expression levels of Arc,c-fos,Egr1 and Npas4.In turn,the inhibition of Arc,c-fos,Egr1 and Npas4 could lead to the blocking of LTP and enhancement of LTD,which further aggravated learning and memory impairment induced by etomidate.Part Ⅱ Association between immediate early genes and postoperative cognitive dysfunction and their predictive valuesObjective:To study the association between immediate early genes(IEGs)and postoperative cognitive dysfunction(POCD)and their predictive values.Methods:A total of 296 patients undergoing lumbar decompression and fusion under general anesthesia were divided into POCD group(n=92)and non-POCD group(n=204)according to the occurrence of POCD.The demographic data and clinical data of the two groups were collected,and the mRNA expression levels of Arc,c-fos,Egr1,Npas4,BDNF and MMP-9 gene in serum were detected through quantitative reverse transcription polymerase chain reaction(qRT-PCR).Firstly,univariate analysis was performed to screen variables,and then multivariate analysis was performed for variables with P<0.1 in univariate analysis to determine the independent association between POCD and serum mRNA expression levels of Arc,c-fos,Egr1,Npas4,BDNF and MMP-9 gene.In order to quantify the relationship between serum mRNA expression levels of IEGs and POCD,POCD group and non-POCD group were divided into four grades according to the quartile of serum mRNA expression levels of IEGs in all participants(POCD group and non-POCD group),namely grade 1:≤Q1,grade 2:>Q1 and ≤Q2,grade 3:>Q2 and ≤Q3,grade 4:>Q3.Receiver operating characteristics curve(ROC)was used to evaluate the individual and joint predictive values of IEGs for POCD.Results:①After adjusting for age,SctO2 at the beginning of surgery(T3)and the end of surgery(T4)and MMP-9 mRNA expression level,the mRNA expression levels of Arc,c-fos,Egr1,Npas4 and BDNF were significantly correlated with POCD.②The AUC of Arc,c-fos,Egr1,Npas4 and BDNF in predicting POCD were 0.760,0.784,0.721,0.670 and 0.819,respectively.Only BDNF gene had a relatively high predictive value,and Arc,c-fos and Egr1 gene had a medium predictive value,and Npas4 gene had a relatively low predictive value.However,the AUC of predicting POCD with Q1(0.43)of BDNF gene expression level was only 0.776 with medium predictive value.All predictions had a low sensitivity.③The AUCs of BDNF combined with c-fos,BDNF combined with Arc and c-fos combined with Arc were all greater than 0.800.The AUC of BDNF combined with c-fos in predicting POCD was the highest,reaching to 0.848.The accuracy,specificity,sensitivity,false positive rate,false negative rate,positive predictive value and negative predictive value of BDNF combined with c-fos were 82.8%,79.4%,90.2%,33.6%,5.3%,66.4%and 94.7%,respectively.Conclusions:The expression of Arc,c-fos,Egr1,Npas4 and BDNF were significantly correlated with the occurrence of POCD.The value of BDNF combined with c-fos or Arc and c-fos combined with Arc in predicting POCD was high,which might have certain value and application prospect for predicting POCD.