The Mechanism Of Arsenic Mediated Damage Of Mice Learning And Memory In Hippocampal Through MiR-219/CaMKⅡ Pathway

Objective:To investigate the mechanism of arsenic mediated damage of mice learning and memory abilities in hippocampal through mi R-219 / CaMKII pathway.Materials and Methods: 9 weeks old mice were divided into four groups,32 mice in each group:(1)Con group: 8 mice were sacrificed after 60 days of normal feeding,and then 8 mice were sacrificed after 10,20 and 30 days respectively;(2)As group: 8 mice were sacrificed after received 4.0 ppm As2O3 through drinking water for 60 days,then continue to be poisoned,8 mice were sacrificed after 10 days,20 days and 30 days respectively;(3)As+AAV-anti-mi R-219 group: 8 mice were sacrificed after received 4.0 ppm As2O3 through drinking water for 60 days,AAV-anti-mi R-219 was injected into the hippocampus of the remaining mice after 60 days of exposure,then continue to be poisoned,8 mice were sacrificed after 10 days,20 days and 30 days respectively.(4)As+AAV-control group: 8 mice were sacrificed after received 4.0ppm As2O3 through drinking water for 60 days,AAV carrying nonsense mi RNA fragments was injected into the hippocampus of the remaining mice after 60 days of exposure,then continue to be poisoned,8 mice were sacrificed after 10 days,20 days and 30 days respectively.Morris water maze was used to detect learning and memory ability of mice.Electron microscopy was used to detect ultrastructural changes in the synapses of hippocampus of mice.Real-time PCR was used to detect the expression of mi R-219 in the hippocampus of mice.The expression of CaMKII,c-Fos,c-Jun in thehippocampus of mice was detected by Western-Blotting.The experimental results were analyzed by using SPSS13.0 statistical software.Results: Effect of arsenic exposure on learning and memory: The escape latency of water maze in As group was significantly higher than that in Con group(p < 0.05,p< 0.01),and the time percentage in target quadrant was less than that in Con group(p <0.01).The results of electron microscopy showed that: The synaptic structure of hippocampus was not clear in As group than that in Con group.Compared to Con group,in As group the thickness of PSD became thinner(p < 0.01)and the synaptic cleft became wider(p < 0.01).Effect of arsenic exposure on mi R-219 content in mouse hippocampus: The real-time PCR measured the expression of mi R-219,and the expression of mi R-219 in As group was significantly higher than that in Con group(p< 0.01).Effects of arsenic exposure on CaMKII content in mouse hippocampus : The expression of CaMKII in As group was significantly lower than that in Con group(p <0.01).Effect of mi R-219 expression in mouse hippocampus after AAV injection: DAPI staining showed that AAV was abundantly expressed in the hippocampus after injection.The expression of mi R-219 in As+AAV-anti-mi R-219 group was gradually decreased at 10,20 and 30 days after injection of AAV compared with As+AAV-control group,decreased by 25.3%,45.8% and 63.3% at 10,20 and 30 days after injection respectively(p < 0.05,p < 0.01,p < 0.01 respectively).Effect of arsenic-induced impairment of learning and memory in mice after inhibition of mi R-219: The results of water maze at 10 days,20 days and 30 days after injection of AAV showed that compared with As+AAV-control group,the escape latency of As+AAV-anti-mi R-219 group was significantly shortened and the time percentage of target quadrant increased gradually,the difference was statistically significant.Effect of CaMKII and its downstream protein expression after inhibition of mi R-219:Compared with As+AAV-control group,the content of CaMKII protein in As+AAV-anti-mi R-219 group was increased by 17.8%(p > 0.05),63.4%(p < 0.05)and 88.4%(p < 0.01).The expression of NR2,c-Jun and c-Fos in As+AAV-anti-mi R-219 group was significantly higher than that in AAV-control group(p < 0.05,p < 0.05,p < 0.01 respectively).Effect of arsenic-induced damage in the hippocampal synapse of mice after inhibition of mi R-219: Electron microscopy at 30 days after injection of AAV showed that the hippocampal synaptic structure of As+AAV-anti-mi R-219 group became clear and the thickness of the PSD increased(p< 0.05),synaptic cleft narrower(p < 0.01)compared with the As+AAV-control group.Conclusion: Subchronic arsenic exposure induces impairment of learning and memory function by mediating changes of mi R-219 in hippocampus;Arsenic modulates CaMKII expression by mediating changes in mi R-219;Mediating hippocampal mi R-219 / CaMKII pathway may be an important mechanism of arsenic-induced learning and memory impairment.