Effects Of Combined Chronic Exposure To Bis (2-Ethylhexyl) Phthalate And Lead On Learning Memory Capacity And APP Enzymatic Pathways In Mice

Objective:To investigate the effects of combined chronic exposure to Bis（2-ethylhexyl）ortho-phthalate（DEHP）and lead（Pb）on learning and memory abilities and APP pathways in mice.To investigate the effects and mechanisms of low-dose chronic exposure to one or two environmental pollutants on indicators of neuronal degenerations.Methods:One hundred and twenty-eight 2-month-old healthy male Kunming mice were selected as the research objects,with a body weight of（20±2）g.The mice were randomly divided into:（1）control group;（2）Pb group:250mg/L;（3）DEHP group:16.5mg/kg,33mg/kg,66mg/kg;（4）DEHP+Pb group:16.5mg/kg+250mg/L,33mg/kg+250mg/L,66mg/kg+250mg/L.For 8 groups of 8 mice each.The mice were exposed to DEHP in their food and lead acetate in their drinking water for 12 and 24weeks.The mice were weighed daily and their condition,respiration,coat colour and mental state were observed.The behavioral changes of the mice were detected by Morris water maze experiment,dark avoidance experiment and jumping table experiment at the 12th and 24th weeks.The organ coefficients were determined by ELISA.Theα,β-secretase activities and the s APPα,Aβ_1-40contents in the brain tissues of the mice were measured.Protein blotting assay was performed to determine the expression of ADAM10 and BACE1 proteins.Results:1.General condition observation:all groups of mice had shiny back hair,no abnormal secretions in the mouth,eyes and nose,stable breathing,normal urine and faeces,increased body weight,blunt morphology and reduced locomotor ability.Some mice fought,but no mice died during the period of poisoning.There was no statistical difference between groups in the daily food intake and water intake of mice（P>0.05）,but there was a statistical difference between groups in the body weight of all mice at12 weeks of exposure（P<0.05）.The weight gain was higher than that of the CT group（P<0.05）.In the same dose comparison,there was no statistical difference in body weight and weight gain at the end of the experiment（P>0.05）.The results of the inter-group comparison of the organ coefficients of the mice showed that the weight of brain tissue and liver gradually decreased with increasing doses of DEHP,and there was a statistical difference between the high-dose DEHP exposure group alone and the control group（P<0.05）.2.Behavioural tests:1)Morris water maze experiment results showed that:in each group positioning navigation experiment and spatial exploration experiment test results showed that the control group had a strong learning ability,after training,swimming trajectory mostly focused on the target phenomenon,but the DEHP-tainted group had poor learning ability,swimming trajectory was aimless,no regularity,and the high dose DEHP group target quadrant stay time,through the stage The spatial learning ability of the mice in the 12-week and 24-week groups was more severely impaired as the dose of DEHP increased,resulting in impaired spatial memory,reduced percentage of the total distance travelled in the target quadrant,shortened swimming time in the target quadrant and increased latency（P<0.05）,which was more severe in the 24-week mice than in the 12-week mice;2)The results of the dark-avoidance and skipping experiments showed that the number of experimental errors and the total latency time of mice in the Pb group,high-dose DEHP alone and in the combined group were increased and shortened compared with the CT group（P<0.05）,and the experimental results showed that the mice had a short memory for electrical stimulation and a blurred memory.3.Biochemical indexes:Compared with the normal control group,theα-secretase activity and s APPαcontent decreased and theβ-secretase activity and Aβ_1-40content increased significantly（P<0.05）with increasing dose in the DEHP group and the DEHP co-infected group,which was more obvious in the 24-week mice than the 12-week mice（P<0.05）.There was an interaction between the two（P<0.05）.In comparison with the control group,the expression levels of ADAM10 in the brain tissues of the DEHP-and combination-dyed mice were reduced（P<0.05）and the expression level of BACE1 was increased（P<0.05）.Conclusion:1.DEHP alone and in combination with lead chronic exposure can cause weight gain in mice.2.DEHP chronic poisoning can cause learning and memory impairment in mice,and the higher the dose of DEHP,the greater the effect on memory ability.3.DEHP combined with lead chronic exposure caused the learning and memory impairment and altered APP enzymatic pathways in mice,and there was an interaction between the two in the determination ofα,β-secretase activity and the content of Aβ_1-.