The Regulatory Mechanism Of Histone Acetylation And Histone Deacetylases Inhibitor In Cerebral Disease

Background and aim:Recent evidence has prompted the notion that epigenetic mechanisms exert lasting effects on gene expression through the regulation of chromatin structure.In general,increased histone acetylation level is correlative with DNA relaxation and elevated transcriptional activity.whereas decreased acetylation,results in tighter DNA coiling and gene silencing.The regulation of histone acetylation is recognized as a vital mechanism in several important phenomena in the brain,including neurodegeneration,neuronal differentiation,seizure,memory formation and drug addiction.However,the potential effects of pethidine treatments on addictionrelated genes transcriptional activation were unclear.Histone acetylation is fine-tuned by the opposite actions of two families of enzymes,histone acetyltransferases(HAT)and Histone deacetylases(HDAC).The HAT adds an acetyl group,whereas HD AC removes acetyl groups from the ε-amino group of lysine residues.In general,increased histone acetylation level is correlative with DNA relaxation and elevated transcriptional activity.whereas decreased acetylation,results in tighter DNA coiling and gene silencing.HDAC target not only histone but also many nonhistone proteins both in the nucleus and the cytoplasm,including transcription factors,cytoskeletal protein and molecular chaperone such as heat shock protein 90 and 70,and regulate a variety of functions.Histone deacetylase(HDAC)inhibitor was found to protect blood brain barrier in middle cerebral artery occlusion rats.However,the accurate mechanism is still not well establishedWe will explore the roles of histone acetylation in chronic pethidine treatment induced addicition and the protective effects of histone deacetylase inhibitor on blood brain barrier in experimental stroke via interuption with Hsp90 chaperone function in this study.Methods:1.Histone H3 acetylation level following single and repeated pethidine treatment in different brain regions were examined by immunohistochemistry method and western-blot.The effect of histone H3 acetylation level on addiction-related gene transcriptional activations were examined by chromatin immunoprecipitation.2.The effects of HD AC inhibitor(VP A)on Hsp90 acetylation and chaperone function were examined by western-blot and co-immunoprecipitation.3.The effects of HD AC inhibitor(VP A)and Hsp90 inhibitor 17-DMAG on NF-κB dependent MMP9 mRNA expression was examined by CHIP and Realtime-PCR.4.Male C57/BL6 mice were pretreated with 17-Dimethylaminoethylamino-17-demethoxygeldanamycin(17-DMAG)or vehicle before being subjected to transient occlusion of middle cerebral artery and reperfusion(MCAO)Infarction,neurological scores,Evans blue(EB)extravasation,inflammatory responses and tight junction protein expression were examined 24h after MCAO.We also investigated if 17-DMAG protected BBB integrity by suppressing inflammation and MMP9 activation.5.Oxygen glucose deprivation(OGD)was performed on Bend.3 cells to explore the mechanisms of Hsp90 inhibition in inhibiting MMP9.Results:1.Repeated,but not single pethidine administration,induced a significant increase of histone H3 acetylation level in the subiculum of hippocampus.However,changes of histone H3 acetylation level was not detected in the CA1 of hippocampus or the medial prefrontal cortex(mPFC).2.A relationship between histone acetylaton and pethidine-induced place preference were discovered.3.Addiction-related gene transcriptional activations were regulated by H3 acetylation at specific gene promoters in the subiculum of hippocampus4.VPA induced Hsp90 acetylation and decreased the level of IKK,one of client proteins of Hsp90 in Bend.3 cells5.VPA reduced NF-κB dependent MMP9 mRNA expression in Bend.3 cells6.Infarct volume was reduced in 17-DMAG-treated mice compared to control group following MCAO.Neurological outcomes were greatly improved in 17-DMAG-treated mice.Inflammatory responses,MMP9 activity and Evans blue extravasation were decreased by 17-DMAG.In addition,17-DMAG inhibited nuclear factor kappa B(NF-κB)activation following MCAO7.Hsp90 inhibition decreased NF-κB dependent MMP9 expression in Bend.3 after OGD/reoxygenation.Conclusions:1.Histone H3 acetylation in the subiculum of hippocampus may be involved in neural plasticity changes in opioid abuse2.The protective effect of VPA on blood brain barrier may be associated with its interrupting chaperone function by enhanced Hsp90 acetylation in Bend.3 cells3.Hsp90 inhibitor may exert similar effects as HDAC inhibitor to protect blood brain barrier in experimental stroke model4.In Bend.3 cells,Hsp90 inibition can abolished OGD-induced MMP9 increase by inhibiting NF-κB depedent MMP9 mRNA expression.