Study On Lead Exposure And Molecular Mechanism Of Cognitive Impairment In Aged Rats

Objective:Lead,because of its wide distribution of the natural environment,extensive use of the production environment,the prevalence of the living environment of the brain development of irreversible neurological toxicity has become a global public health problem.In recent decades,lead developmental neurotoxicity give depth and extensive research,but the mechanism is not yet fully elucidated clearly.However,recent studies have found that elderly lead exposure may induce neurodegeneration.However,the related researches are few,the major source of Stewart laboratory.Whether it leads or developmental neurotoxicity induced neurodegenerative diseases AD,are based on learning and memory impairment,cognitive disorder as the main clinical manifestations.RyRs as an intracellular calcium signaling mediated hub of learning and memory,cognitive study,the molecular mechanism has become a hot spot,look forward to further study the molecular mechanisms of the brain and enhance learning and memory,cognitive ability to understand the molecular mechanisms at the same time look forward to neuropsychiatric diseases such as prevention and treatment of AD provide new inspiration.Thus,the present study,we build a different models lifelong lead exposure rats by Morris maze test,TEM,flow cytometry and RT-PCR,Western blot and other molecular biology techniques to explore different models of aged rats exposed to lead cognitive function and intracellular calcium signal within RyRs-learning-memory,cognitive possible molecular mechanism in which the role.Methods:1.Different modes of lead exposure for aged rat model:Adult SPF SD rats in a2:1 deposit with cages,the successful conception of female rats were randomly divided to control group?single drink distilled water?,low lead exposure group?0.05%lead acetate drinking solution?and high lead exposure group?0.2%lead acetate drinking solution?,after delivery through breast milk infected offspring continue to lead weaning?PNW 3?after independence group feeding,offspring are grouped into:control group?CON??only drink distilled water,dams original low lead exposure group?LLG??drinkable 0.01%lead acetate solution,maternal formerly low lead exposure group?;high lead exposure group?HLG??drinkable 0.05%lead acetate solution,the raw maternal high lead exposure for the control group?group?;high-control lead exposure group?HCLG??single distilled drinking water,raw maternal high lead exposure group?,reared offspring born after their old age that is 97weeks?PNW 97?experiment.By inductively coupled plasma emission spectrometry?ICP-OES?within the blood and brain tissue of aged rats lead content testing,while recognizing model circumstances.2.Assessment the impact of different models lead exposure on cognitive function in aged rats:Using Morris water maze of cognitive ability in aged rats were evaluated;Observing the ultrastructure of neurons in the hippocampus aged rats by transmission electron microscopy.3.Study of molecular mechanism of different modes of lead exposure on cognitive function in aged rats:Using flow cytometry in the hippocampal neurons of aged rats free Ca²⁺concentration,the level of reactive oxygen species and the level of apoptosis were detected;using RT-PCR method detecting different modes lead exposure RyR hippocampus of aged rats,CaMKII?with the CREB gene expression levels;by Western blot detecting the different modes of lead exposure RyR hippocampus of aged rats,CaMKII?,p-CaMKII?,CREB and p-CREB protein The expression levels.Results:1.Different models of aged rats exposed to lead model:The period between each dose group was no significant difference in body weight in rats exposed to lead in the growth of the different modes.Lead exposure significantly increased the content of Pb in whole blood of aged rats with brain tissue,as lead exposure dose increased whole blood and brain tissue gradually increase the lead ion content.High-control lead exposure group?HCLG,ie only during embryonic development and lactation were lead exposure,lead dose with high lead exposure to the same dose group,after departing from lead exposure in drinking single distilled water,and with the lead exposure group also reared to old age?,whole blood and brain tissue lead ion content is basically the same with the control group,the difference was not statistically significant.2.Different models lead exposure on cognitive function in aged rats situation:Morris water maze test results showed that lead exposure caused water maze of rats escape latency prolonged,reduce the number of crossing platform;and HCLG escape latency compared HLG has recovery but still higher than CON.TEM results showed that lead exposure with increasing dose,increasing the density of the nucleus and the cytoplasm,irregular nuclei,nuclear chromatin clump set of edges to form irregular clumps of high electron density,nuclear membrane recess;endoplasmic reticulum swelling,shrinkage and swelling of mitochondria,cristae dissolution,blurred,ribosome depolymerization;HCLG rat hippocampus cell nuclei still occurs sunken nuclear membrane,nuclear chromatin aggregation,swelling of endoplasmic reticulum,mitochondria swelling and cristae ablation,although more HLG certain relief,but there are still serious CON compare nuclear and organelle damage.3.Different modes lead exposure on cognitive function in aged rats molecular mechanisms:?1?exposure to lead-induced free Ca²⁺concentration increases,the level of reactive oxygen species and the degree of apoptosis in hippocampal neurons of aged rats;rat hippocampus HCLG neuron free Ca²⁺,the level of reactive oxygen species and the extent of apoptosis although more HLG has been restored,but still higher than CON.?2?Lead exposure in hippocampus and cortex of aged rats in each group RyR2,RyR3,CaMKII?,CREB gene expression levels had no significant difference;however,high concentrations of lead exposure hippocampus protein p-CaMKII?and p-CREB expression levels decreased;rat hippocampus HCLG p-CREB expression level was significantly lower than the control group.Conclusion:1.Lead exposure may increase protein expression in hippocampal by RyRs enable the aged rat hippocampal neurons of free Ca²⁺concentration increased,the occurrence of calcium overload,by down-regulating p-CaMKII?and p-CREB influence cognitive function;the same time can also cause cell oxidative stress,activation of apoptosis caused neurodegeneration occurs path,cause cognitive dysfunction.2.Only during embryonic development and lactation were high lead exposure and lead exposure in the same group,after learning from lead exposure to cognitive impairment in aged,lead exposure caused a certain degree of self-healing ability,but can not be restored to normal levels.