| Objective:To investigate the role of mitochondrial fussion and fission in aluminum induced cognitive impairment in vivo.Methods:180 specific pathogen free healthy male SD rats were randomly divided into 3batches of 15 groups by body weight with 12 rats in each group.Each batch consist of a blank group,a control group,and low-,medium-and high-dose exposure groups.Blank group was not treated,low-,medium-and high dose group were respectively treated with 0.41?0.81?1.62 mg/kg of Al(mal)3solution,the control group was treated with an equal volume of saline.Al(mal)3 exposure was conducted by intraperitoneal injection every other day for 30 days?60 days and 90 days.After the exposure,Morris water maze test was performed to assess the spatial learning and memory abilities of the rats.Graphite gurnace atomic absorption spectrometry(GFAAS)detected the aluminum content in hippocampus.Then we executed one mouse each group randomly,and observed the ultrastructure of mitochondriain the nerve cells using the transmission electron microscopy.The activities of Na+-K+-ATPase and Ca2+-Mg2+-ATPase were tested by colorimetric technique,which was the decomposition product of ATPase.Western blot analysis was used to detect the relative expression of Cox?,Drp1,Fis1,Opa1,Mfn2,Mfn1,CaN and S-drp1(s637).Results:1.The results of Morris water maze test:(1)There was no significant interaction of aluminum exposure dose and time in the escape latency(F1=1.648,P=0.125;F2=0.986,P=0.453;F3=0.763,P=0.664).After exposure to aluminum for 1,2 and 3 months respectively,escape latency of each aluminum treated group(0,0.41,0.81,1.62 mg/kg)decreased in a testing day-dependent manner and increased in a expourse time-dependent manner;The probe trail displayed that aluminum expourse can decrease the time spent in the target quadrant and the number of crossing the platform in a time-dependent and dose-dependent manner.But in rats exposed for 1 month the differences of above-mentioned indexes between groups were not statistically significant(P<0.05).Probe trail suggests that aluminum could cause deleterious effects on spatial memory.2.The results of GFAAS detected showed that: with the increase of the infected dose,the aluminum content of each groups infected rats was increased in brain aluminum(P<0.05),and then the aluminum in brain of 60 days and 90 days was more increase than that of 30 days(P<0.05).Compared with low-and medium-dose group,the aluminum content was increased in high dose group(P<0.05).3.As we observed ultrastructure the in the nerve cells every group with the TEM,the mitochondrial about the control group had oval shape,passable quantity,even distribution,the ridge which was passable clear,slight expansion,the significant swelling and part of vacuolar degeneration unfound,surrounding the endoplasmic reticulum slightly expansed,compare to the medium-and high-dose group had the overall improvement.4.The activities of Na+-K+ATPase and Ca2+-Mg2+ATPase in the rat brain were decreased with increasing exposure dose and duration(F=2.675,P<0.05;F=3.664,P<0.001).The activity of Na+-K+ATPase in 0.81,1.62 mg/kg of 90 days have no significance,and than that of different aluminum exposure groups had significant difference.Na+-K+ATPase activity in 0.81,1.62 mg/kg decreased by 38.2%,77.5% compared with the solvent group in 2 month.The activity of Ca2+-Mg2+ATPase in 1.62 mg/kg decreased by 32.9% compared with the solvent group in 3 month(P?0.05).5.The Western blot test results showed that:(1)There would exist interactive effects among exposure time and dose in the change of expression of Cox? and Drp1(P<0.001).Comparing in each batch,the differences of Drp1 among aluminum-exposed group were significant decreased compared with the control group in different batches(P<0.05).And the expression of Cox? in 1.62 mg/kg in 90 days was decreased by 56.0%,38.4% than that of 30 days and 60 days.(2)The interactive effects among exposure time and dose did not exist in the changes of the expression of Fis1,Opa1,Mfn1 and Mfn2(P>0.05).The relative expression level of Fis1 in high dose group increased by 0.19,0.16,0.14,respectively,compared with the rats of blank-?control-and low-dose group in 90 days.And the relative expression level of Opa1 in high dose group increased by 1.12,1.07,0.39,0.22,respectively,compared with the rats of blank-?control-?low-and medium-dose group in 90 days.And the relative expression level of Mfn1 in high dose group increased by 0.71,0.70,0.47,0.21,respectively,compared with the rats of blank-?control-?lowand medium-dose group in 90 days.The relative expression level of Mfn2 in high dose group increased by 0.41,0.37,0.2,respectively,compared with the rats of blank-?controland low-dose group in 90 days.(3)S-drp1(s637)and CaN expression in hippocampus was tested,and it had a significant interaction between aluminum exposure dose and exposure time(P<0.05).S-drp1(s637)expression was decreased with the increasing of aluminum exposure dose.And the relative expression level of S-drp1(s637)in high dose group of 90 days decreased by 67.5%,51.8%,21.2%,respectively,compared with the rats of control-,low-and medium-dose group.And the expression of CaN of 1.62 mg/kg in 90 days was increased by 0.64,0.31,0.10 than that of control-,low-and medium-dose group.Conclusions:1.Sub-chronic aluminum exposure results in impairment of learningand memory ability in rats,this damage degree depend on aluminum treatment dose and time.2.Aluminum can induced mitochondrial damage which nerve cells in rats,its degree relay on aluminum exposure dose and time.3.Aluminum enables to break the balance of mitochondrial fussion and fission.And mitochondrial fission play an important role in neurotoxicity induced by aluminum,its degree relay on aluminum exposure dose and time.In summary,aluminum may lead to cognitive impairment due to mitochondrial damage which caused by imbalance of mitochondrial fussion and fission. |
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