| ObjectiveAluminum(Al)is a low-toxicity trace element that can accumulate in the human nervous system after ingestion,producing irreversible toxicological effects and inducing impaired learning and memory and various cognitive dysfunctional neurological disorders.In this experiment,we explored the changes in learning and memory functions in rats exposed to different doses of aluminum over a long period of time by establishing a rat model of aluminum poisoning offspring.Using histone modifications as an entry point,we investigated the effects of histone acetyltransferase CBP and histone deacetylase 3,histone H2 B and acetylated histone H2BK20 in the hippocampus to further investigate the relationship between cognitive dysfunction and histone H2 B acetylation modifications in the context of aluminum intoxication and to contribute to the scientific foundation for the management of aluminum intoxication.MethodsForty pregnant Wistar rats were randomly divided into control,low,middle and high dose groups according to their body weight.On the first day of delivery,Al Cl3 distilled water solution was used to start poisoning,and the doses of poisoning in each model group were 0,2.0 g/L,4.0 g/L and 8.0 g/L.The neonatal rats were exposed to aluminum via milk before weaning and water after weaning for 90 d.The body weights of the rats were recorded weekly during the poisoning period.The neurobehavioral performance of aluminum-dyed rats was examined by Morris water maze assay at the end of the experiment;the histopathological changes of nerve cells in CA3 area of hippocampus were observed by Nissler staining;the Al3+ content in hippocampus was observed by ICP-MS;the expression levels of CBP and HDAC3 m RNA in hippocampus were examined by RT-PCR;the levels of histone H2 B,H2BK20ac,CBP and HDAC3 in hippocampus were examined by Western Blot.The levels of histone H2 B,acetylated histone H2BK20,CBP and HDAC3 in the hippocampus were measured by Western Blot.Results1.Basic condition of Al Cl3-poisoned rats: During the feeding process,there was no statistic difference in the amount of food and water consumed by the rats in each group.The control rats had good mental response,soft and shiny hair,and active performance;the Al-poisoned rats were basically normal in mood,with reduced fluffy and shiny hair and reduced activity.2.Changes in body weight of Al Cl3-poisoned rats: The body weight of the rats in each group increased gradually with growth time;the body weight of the rats in the Al Cl3-poisoned group slowed down with increasing dose of poisoning.3.Brain weight coefficient and hippocampal coefficient of Al Cl3-poisoned rats:The brain weight coefficient of rats in each model group increased with the increase of the dose of Al Cl3.The medium-dose Al Cl3-poisoned group was significantly higher than the control group,and the high-dose Al Cl3-poisoned group was significantly higher than the other three groups.The hippocampal coefficients of the rats in the Al Cl3-poisoned group showed an increasing trend with the increase of aluminum dose,and the hippocampal coefficients of the medium-dose Al Cl3-poisoned group was higher than the control and low Al Cl3-poisoned groups,and the high-dose Al Cl3-poisoned group was significantly higher than the other three groups.4.Al3+ content in hippocampal tissue of Al Cl3-poisoned rats: The Al3+ content in hippocampal tissue of rats in each model group increased with the increase of exposure dose.The Al3+ content of the rats in the medium-dose Al Cl3-exposed group was higher than that in the control group,and that in the high-dose Al Cl3-exposed group was significantly higher than that in the control and low Al Cl3-exposed groups.5.Morris water maze experiment tested the neurobehavioral situation: In the positioning navigation test,the latency latency and movements distance of rats in the Al Cl3-poisoned group were positively correlated with the Al Cl3-poisoned dose.A comparison of the latency lengths of the groups showed that the latency lengths were higher in the low and medium doses than in the control group,and significantly higher in the high dose than in the other three groups.A comparison of swimming path lengths between the groups showed that the medium-dose Al Cl3-poisoned group had a longer swimming path than the control and low-dose Al Cl3-poisoned groups,and the highdose Al Cl3-poisoned group had a longer path than the other three groups.In the spatial exploration test,the dwell time and number of traverses in the target quadrant were negatively correlated with the Al Cl3 dose in the Al Cl3-poisoned group.A comparison between the former groups showed that the dwell time in the target quadrant was lower in the medium-dose group than in the control and low Al Cl3-poisoned dosed groups,and significantly higher in the high-dose group than in the other three groups.The latter inter-group comparison showed that the number of crossing times in the high-dose Al Cl3-poisoned group was significantly lower than that in the low-dose and medium-dose groups.6.Transmission electron microscope results: In the control group,neurons were mostly normal shaped,round with an even distribution of chromatin in the nucleus,whereas Al Cl3-poisoned neurons had varying degrees of atrophy and deformity,oval or irregular shape.Cell membranes were compressed and heterochromatin aggregated into clusters.The above lesions worsened with increasing doses of Al Cl3 staining.7.The m RNA results of CBP and HDAC3 detected by Real-time RT-PCR:Compared with the control group,the expression levels of CBP in the hippocampus of the rat offspring were significantly lower in the medium and high Al Cl3-poisoned groups,and the expression levels of CBP m RNA in the offspring were negatively correlated with the Al Cl3-poisoned dose.Compared with the control group,the expression level of HDAC3 was significantly increased in the high-dose Al Cl3-poisoned group,and the expression level of HDAC3 m RNA in the offspring was positively correlated with the Al Cl3-poisoned dose.8.The protein content of histone H2 B,H2BK20ac,CBP and HDAC3 detected by Western blot: Compared with the control group,the protein gray value of histone H2 B in the hippocampal neurons of the submarine rats in the high Al Cl3-poisoned group was significantly lower,and the gray value of histone H2 B in the hippocampus of the submarine rats was negatively correlated with the aluminum dye.Compared with the control group,the gray value of H2BK20 ac protein in the medium and high dose Al Cl3-poisoned group was significantly lower;compared with the low dose group,the gray value of H2BK20 ac protein in the medium and high dose Al Cl3-dyed group was significantly lower;compared with the medium dose group,the gray value of H2BK20 ac protein in the high dose Al Cl3-poisoned group was significantly will pair.The protein gray value of H2BK20 ac in the hippocampus of the rat was negatively correlated with the dose of aluminum dyeing.Compared with the control group,the CBP protein gray value was significantly lower in the low and high Al Cl3-poisoned groups;compared with the medium-dose group,the CBP was significantly lower in the high Al Cl3-dyed group,and the CBP protein gray value in the hippocampus of the rats was negatively correlated with the Al Cl3-poisoned dose.Compared with the control group,the HDAC3 protein grayscale values in the hippocampus of the rats were significantly higher in the Al Cl3-poisoned group;compared with the low-dose group,HDAC3 was significantly higher in the medium-and high-dose groups;compared with the medium-dose group,HDAC3 was significantly higher in the high-dose group.The protein gray value of HDAC3 in hippocampal neurons of the rat was positively correlated with the dose of aluminum dyeing.Conclusions1.Long-term Al Cl3 ingestion retarded body weight gain and Al3+ accumulation in the hippocampus,altered the ultrastructure of neurons in the CA3 region of the hippocampus,and reduced the spatial learning and memory retention ability of rats.2.Long-term exposure to Al Cl3 could decrease the expression of CBP gene and protein,increase the level of HDAC3 gene and protein,and decrease the expression level of histone H2 B and H2BK20 ac protein in the hippocampus of offspring.3.Chronic Al Cl3 staining may accelerate neurological damage through alteration of histone H2 B and H2BK20 ac expression by histone acetylation-specific modifying enzymes,which in turn affects cognitive function. |
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