Negative Regulatory Mechanism Of Histone Deacetylase On Learning And Memory Impairment Induced By Lead Exposure

Lead pollution in food affects food's the quality and safety.A great deal of studies have demonstrated that Pb can dramaticly damage the nervous system in brain,and thus lead to impairment of learning,memory and cognition.In recent years,there are more and more studies on the mechanism of Pb poisoning at home and abroad.However,it is still not clear whether there is epigenetic regulation in the process of learning and memory deficits caused by Pb exposure.Objective: Investigate the mechanism of histone deacetylase in Pb-induced neurotoxicity,which provides a theoretical basis for clinical treatment of Pb poisoning.Methods: 1.The level of histone H3 Lys9 acetyaltion(Ac-H3K9)was investigated by Pb exposure.PC12 cells were used as the neurocellar model.Firstly,Pb was administered to PC12 cells at 10 ?M for 24 hours.Neurite outgrowth was studied to explore the toxic effects.Western Blot was used to investigate the level of Ac-H3K9.CHIP assay was used to study the target gene modification by Ac-H3K9.And pharmacological interference was used to investigate the cause of changes in the level of Ac-H3K9.2.The level of histone deacetylase 2(HDAC2)was investigated by Pb exposure.Knocking down HDAC2 was used to explore the effect on the level of Ac-H3K9.Chromatin immunoprecipitation(CHIP)assay was used to study upstream regulatory molecules of HDAC2.3.The roles of histone deacetylase 1/2(HDAC1/2)by Pb exposure in vivo and in vitro were studied.In vitro,immunofluorescence and co-immunoprecipitation(co-ip)were used to investigate the form of HDAC1/2 complex.Knocking down HDAC1/2 was used to explore the effect on the level of Ac-H3K9.In vivo,Sprague-Dawley(SD)rats were chronically exposed to Pb through drinking water containing 250 ppm Pb for 2 months.Stereotactic injection of AAV virus was used to knock down HDAC1/2.Western Blot was used to investigate the level of Ac-H3K9?HDAC1?HDAC2.Behavioral experiments were used to explore the spatial memory ability of SD rats.Golgi staining experiments were used to explore the dendritic spine densities.Results: 1.Neurite outgrowth of PC12 cells was impaired,the gene expression of HDACs was increased,the level of Ac-H3K9 was decreased,and the expression of Notch2 was reduced by Pb exposure.2.The protein expression of HDAC2 was increased by Pb exposure.When knocking down HDAC2,the level of Ac-H3K9 and neurite outgrowth were significantly rescued.3.HDAC2 and HDAC1 existed in the form of complexes.When knocking down HDAC1/2,the level of Ac-H3K9 and neurite outgrowth were significantly rescued in vitro and dendritic spine densities was increased as well as spatial memory deficits were alleviated.Conclusion: The neurotoxicity caused by Pb exposure was achieved by affecting the level of HDAC1/2 and then leading to the alteration of Ac-H3K9,which further affected the expression of downstream regulatory molecule Notch2.The key role of histone deacetylase in this process was elaborated from the perspective of epigenetics.