A Study On The Mechanism Of Cognitive Impairment Caused By The Decrease Of H3K9ac Induced By Borna Disease Virus

BACKGROUNDBorna disease virus(BDV)is a non-segmented single-stranded negative-sense RNA virus with strong neurotropic properties.BDV can infect a wide range of animal species from rodents to primates,including humans.BDV infected the hippocampus and limbic lobe of rodents in the neonatal period,which induced cognitive deficits and mental disorders,with the symptoms resembling those in human cognition and affective disorders.Although there is a close relationship between BDV and humans,the role of BDV in cognitive impairment remains unclear.Researches have shown that epigenetics,especially histone acetylation,plays a key role in mediating chromatin remodeling and cognitive function in the hippocampus,whereas the key to memory formation is synaptic function plasticity,indicating that memory and synaptic plasticity are closely related,however,whether BDV through epigenetics to affect synaptic plasticity and lead to cognitive dysfunction is still unknown,Histon acetyltransferases(HATs)or histone deacetylases(HDACs)play a decisive role in the regulation of histone acetylation.Any abnormal enzyme activity may alter acetylated histone levels and cause aberrant gene expression.Suberoylanilide hydroxamic acid(SAHA)is a HDAC inhibitor that has been shown to target the inhibition of HDAC class I and IIb classes,eventually resulting in an upregulation of histone acetylation.SAHA treatment can enhance memory formation in rats and mice and improve memory deficits in neurodegenerative diseases in animal models.Infection with laboratories BDV strains in cortical and hippocampal neuronal has been shown to affect specific histone acetylation sites,on the basis of which,it is of great significance to study the possible mechanism of BDV through epigenetics to make cognitive impairment and SAHA improve memory ability.OBJECTIVE1.To observe the expression of histone acetylation and synaptic plasticity in hippocampal neurons of BDV-infected rats and to explore the effect of BDV in neurons.2.To observe the changes of cognition,histone acetylation and synaptic plasticity in rat hippocampus after BDV infection,and to explore the effect of BDV on cognitive function and related mechanisms.3.To investigate the changes of cell and animal levels induced by SAHA and the related mechanisms.METHODS1.The immunofluorescence method was used to detect the infection of BDV in cells and animal tissues.2.Identify the synaptic plasticity genes that interact with H3K9 ac by Ch IP-seq method and detect the expression of synaptic plasticity genes by RT-qPCR at mRNA level.3.Western blotting was used to detect the protein expression of histone acetylation and synaptic plasticity.4.Water maze is used to evaluate the cognitive ability of rats.5.The Golgi staining method was used to detect dendritic branches and dendritic spines density in hippocampal neurons.6.LTP using patch clamp evaluated in rat brain.RESULTS1.Immunofluorescence results showed that cells and in animals was fully infected by BDV,while the normal control group was not affected by BDV.2.Western blotting was used to identify the key site of histone acetylation--H3K9 ac,and Ch IP-seq method was used to identify synaptic plasticity genes interacting with H3K9ac--PSD95,BDNF,PUM2,VAMP2,SYN1 and DRD1.RT-qPCR and Western blotting showed that BDV caused significant down-regulation of PSD95,BDNF,PUM2,VAMP2 and SYN1.SAHA could reverse the expression of PSD95 and BDNF,cell and tissue verification is consistent.3.Water maze test found that BDV induced cognitive impairment in rats,BDV infected rats crossing the platform where the quadrant was significantly less than the CON group(4.14 ± 0.38 vs 6.50 ± 0.62 s,P < 0.05),after SAHA treatment,BDV+SAHA group was significantly reversed(6.79 ± 0.65 vs 4.14 ± 0.38 s,P < 0.05),and cognitive impairment in rats was improved.4.By staining Golgi,we found that BDV can significantly dendritic dendritic branches and dendritic spines in hippocampal neurons,but SAHA can reduce the effect of BDV.5.Finally,through the patch clamp to detect LTP,CON group,BDV group and BDV+SAHA group had no significant difference in the baseline,HFS can induce CON group LTP stably in brain slices and maintain more than 1h(CON: n = 8,159.1 ± 7.6%),and the slope of the rats in group BDV fEPSP wave decreased significantly,LTP induced significantly impaired(BDV: n = 6,133.9 ± 6.4%,P<0.01),in the intervention of SAHA,BDV induced LTP damage was reversed(BDV+SAHA: n = 7,155.2 ± 7.3%,P<0.01).CONCLUSION1.After BDV infected rat hippocampal neurons,H3K9 ac and gene and protein expression of synaptic plasticity was significantly reduced,BDV by inhibiting synaptic plasticity gene TSS H3K9 ac levels to reduce the expression of synaptic plasticity.2.After BDV infected rat hippocampus region,rat cognitive ability and H3K9ac-mediated changes in synaptic plasticity is relevant,indicating that BDV mainly through reducing H3K9 ac injury cognitive function in rats.3.SAHA can reverse cellular and animal acetylation levels and improve BDV-induced cognitive dysfunction in rats.