Neurotoxicity Induced By Combined Exposure To Lead And Cadmium And The Regulatory Role Of HDAC2

Lead(Pb)and cadmium(Cd)are the main components of heavy metal pollution in food.Previous studies have shown that both Pb and Cd exposure can damage learning and memory of developing children.The mechanism of the neurotoxicity and possible epigenetic regulation of Pb and Cd exposure is unknown.Therefore,it is of great scientific significance and application value to study the neurotoxicity of Pb and Cd combined exposure(co-exposure),which is helpful to clarify the safety limits of Pb and Cd in some foods.This project aims to explore the neurotoxicity caused by Pb and Cd combined exposure and its possible epigenetic regulation mechanism,including the following results:1.Effects of Pb and Cd exposure alone and combined exposure on the survival rate and process formation of PC12 cells.PC12 cells were treated with Pb acetate and Cd chloride at concentrations of 2.5,5,10,20 ?M and Cd at concentrations of 0.1,0.2,0.4,0.8 ?M.Cell viability was determined by MTT colorimetry.The results showed that both Pb and Cd exposure alone reduced the cell survival rate and inhibited the outgrowth of neurites of PC12 cells,and the reduction of cell survival rate and inhibition of outgrowth of neurites were dose-dependent.The co-exposure of Pb and Cd aggravated the process of cell survival rate and outgrowth of neurites.2.Effects of Pb and Cd exposure alone and combined exposure on learning and memory and density of dendritic spines of neurons in hippocampus CA1 and DG of Sprague Dawley(SD)rats.SD rats were exposed to Pb(150 ppm)and Cd(5 ppm)by drinking water alone or in combination from the first day of birth to the age of 3 months.Water maze,Y maze experiment and golgi staining experiment were used to explore the effects of Pb and Cd exposure alone or in combination on learning and memory,and the density of dendritic spines in neurons in the hippocampus CA1 and DG regions of SD rats.The results of behavioral experiment showed that chronic Pb and Cd exposure alone had damage to the learning and memory ability of SD rats,and the combined exposure of Pb and Cd aggravated the damage to the learning and memory ability.Golgi staining results showed that Pb and Cd exposure significantly reduced the density of dendritic spines in secondary branches of neurons in the hippocampal CA1 and DG regions of rats,and combined exposure aggravated the loss of dendritic spines.3.Effects of Pb and Cd exposure alone or in combination on histone deacetylase2(HDAC2)expression.The expression of HDAC2 in PC12 cells and hippocampal tissues of SD rats exposed to Pb and Cd was detected by protein western blot and fluorescence quantitative polymerase chain reaction.PC12 cells were treated with 10 ?M Pb and 0.1 ?M Cd.The dose of SD rats was the same as the behavioral experiment.The results showed that the expression of HDAC2 increased in both hippocampal and PC12 cells after Pb and Cd exposure,and the expression of HDAC2 increased significantly after co-exposure compared with that after single heavy metal exposure.4.The regulatory effect of HDAC2 on the inhibition of process formation caused by Pb and Cd exposure alone and in combination.TSA(inhibitor of HDAC2)and shHDAC2 were used to treat undifferentiated PC12 cells exposed to 10 ?M Pb and 0.1 ?M Cd.Both TSA and shHDAC2 can significantly inhibit the outgrowth of neurites of PC12 cells induced by Pb and Cd co-exposureConclusion: both in vivo and in vitro studies indicate that the combined exposure of Pb and Cd aggravates its neurotoxicity compared with that of Pb and Cd alone.HDAC2 plays an important regulatory role in the inhibition of processes induced by combined exposure to Pb and Cd,providing a potential molecular target for neurotoxic intervention.Both TSA and shHDAC2 can significantly rescue the inhibition of PC12 cell process induced by Pb and Cd co-exposure.