| ObjectThe main pathological features of Alzheimer’s disease(AD)are Aβ deposition,tau hyperphosphorylation,and synaptic loss.Synaptic plasticity is the basis of learning and memory,and histone acetylation plays a key role in regulating the synaptic plasticity of neurons.The histone acetylation level in the brain of patients with AD is significantly abnormal,but the mechanism is still not clear.It has been reported that Acyl-Co A synthetase short-chain family member 2(ACSS2)plays an important role in regulating the histone acetylation and the transcription of learning and memory-related genes,but whether ACSS2 is involved in the regulation of synaptic plasticity mediated by histone acetylation in the brain of AD has not been reported.The purpose of this study was to observe whether there are changes in the expression of ACSS2 in the brain of patients with AD and AD mice,and whether the regulation of ACSS2 level in the brain of AD mice can improve the learning and memory ability of mice,and explore the specific molecular mechanism.MethodsFirstly,the levels of ACSS2 and histone acetylation in the brains of AD patients and 5×FAD mice were detected by Western Blot,RT-q PCR,and immunofluorescence.Secondly,adeno-associated virus(AAV)was injected into the dorsal hippocampus of mice to downregulate or upregulate the expression of ACSS2,and the changes of cognitive function were observed by Morris water maze(MWM),Object location test(OLT),and novel object recognition test(NOR).Finally,RNA-sequence,Ch IP-q PCR,and Western Blot were used to reveal whether overexpressed ACSS2 regulated the expression of glutamate receptor subunits by up-regulating the level of histone acetylation;Through field potential and whole-cell patch-clamp recording,the effects of overexpressed ACSS2 on hippocampal long term potentiation(LTP),Miniature excitatory postsynaptic current(m EPSC)and Miniature inhibitory postsynaptic current(m IPSC)were detected;Western Blot and immunohistochemistry were used to evaluate whether ACSS2 overexpression affects hippocampal Aβ deposition and gliosis.Results1.The decreased ACSS2 and histone acetylation level in the brain of AD patients and 5×FAD mice: 1)the expression level of ACSS2 in the hippocampus and prefrontal cortex of 10-month-old 5×FAD mice was significantly lower than that of WT mice.Importantly,database analysis showed that the m RNA level of ACSS2 in the frontal cortex of AD patients decreased significantly,which was negatively correlated with the degree of frontal lobe atrophy.Moreover,the protein level of ACSS2 in the temporal cortex of AD patients tended to decrease.2)We further isolated the cytoplasm and nucleus of hippocampal tissue and found that the level of ACSS2 protein in hippocampal nuclear fractions of 10-month-old 5×FAD mice decreased,and ACSS2 protein in cytosolic fractions showed a downward trend,but there was no statistical difference.At the same time,the level of Acetyl Co A(AcCo A)in hippocampal nuclear fractions of 5×FAD mice was significantly lower than that of WT mice,and the acetylation levels of histone H3K9 and H4K12 were lower than those of WT mice.3)compared with age-matched WT mice,the expression level of ACSS2 in the hippocampus of 5×FAD mice had no significant change at 2 and 5 months old,but decreased at 8 months old,while the level of histone acetylation had no significant change at 2,5 and 8 months old.2.Regulating the expression level of ACSS2 can affect the cognitive function of WT and 5×FAD mice: 1)After knocking down ACSS2 gene in the dorsal hippocampus,it was found that compared to WT-GFP mice,the number of platform-position crossings and the percentage of time spent in the platform target quadrant of WT-sh ACSS2 mice were significantly reduced in MWM,and the percentage of time spent exploring the moved objects in OLT was also significantly decreased.Although there was no significant difference in the number of platform-position crossings between FAD-sh ACSS2 mice and control mice(FAD-GFP)in MWM,there was a downward trend.2)the overexpression of ACSS2 gene in the dorsal hippocampus showed that the number of platformposition crossings and the percentage of time spent in the platform target quadrant of FAD-ACSS2 mice in MWM were significantly higher than those of control mice(FAD-GFP).In conclusion,ACSS2 is necessary to maintain normal spatial memory,overexpression of ACSS2 can improve the spatial memory ability of5×FAD mice.3.Overexpression of ACSS2 increased the synaptic plasticity of the hippocampus of 5×FAD mice by histone acetylation-mediated up-regulation of glutamate receptors,and improved the learning and memory ability of 5×FAD mice: 1)RNAseq suggested that overexpression of ACSS2 significantly up-regulated the expression of synaptic plasticity-related signal pathway genes in the hippocampus of 5×FAD mice.2)the acetylation levels of histone H3K9 and H4K12 and the expression of glutamate receptor subunits(GRIN1,GRIN2 A,GRIN2B,GRIA1,GRIA2,GRIA3)of FAD-ACSS2 group were significantly higher than those in the control group(FAD-GFP).Furthermore,Ch IP-q PCR analysis showed that overexpressed ACSS2 significantly increased the histone acetylation level at the promoter region of glutamate receptor subunit genes(GRIN1,GRIN2 A,GRIN2B,GRIA1,GRIA2,GRIA3)in 5×FAD mouse.3)the results of field potential and whole-cell patch-clamp showed that compared with the FAD-GFP group,the LTP of the FAD-ACSS2 group was significantly up-regulated,and the amplitude of m EPSC was significantly increased,and the frequency of m EPSC was also trended to be increased.4)compared with the FAD-GFP group,the level of abnormal accumulation of Aβ(6E10)and the level of overactivated GFAP and Iba1/CD68 in the FAD-ACSS2 group had no significant change.Conclusions1.The expression of ACSS2 in the brain of AD patients and 5×FAD mice decreased significantly.The decrease of ACSS2 in the hippocampus of 5×FAD mice was accompanied by a decrease in the level of histone acetylation,resulting in a decrease in the expression of glutamate receptor subunits,thereby impairing excitatory synaptic transmission and cognitive function.2.Down-regulating the level of ACSS2 in the dorsal hippocampus can not only damage the learning and memory ability of wild mice,but also aggravate the cognitive impairment of 5×FAD mice,and up-regulating the level of ACSS2 in the dorsal hippocampus can significantly improve the learning and memory ability of5×FAD mice.It can be seen that the expression level of ACSS2 in the dorsal hippocampus plays an important role in maintaining normal spatial memory.3.Up-regulation of ACSS2 level in the dorsal hippocampus of 5×FAD mice can increase histone acetylated level,thus increasing the expression of glutamate receptor subunits,which enhanced excitatory synaptic transmission and improved the cognitive function of AD mice.In summary,this study found that there is a decrease in the expression of ACSS2 in the brain of AD,which leads to the impairment of synaptic plasticity and cognitive function in AD by affecting the histone acetylation-mediated expression of glutamate receptor subunits,while overexpressed ACSS2 regulates the expression of glutamate receptor subunits through histone acetylation to improve synaptic plasticity and cognitive function in AD.Therefore,taking ACSS2 as the target is expected to bring new strategies for the treatment of AD. |
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