The Investigation Of Cognitive Impairment In Mice Exposured To Nano-alumina Particles By Nasal Drip

Objective:The control group, nano-aluminum group, micron aluminum, were exposed to nasaldrip method of nano-aluminum then investigate the possibility of nano-aluminum into centralnervous system and its Cognitive toxicity . Preliminary discuss the mechanism of toxicity.Methods:60 maleness ICR mice,adult and health, screening by morris water maze, were dividedinto six groups randomly, ten in each group.six groups were: control group, Solvent controlgroup, Micron aluminum group (100mg/kg), 50mg/kg, 100mg/kg, 200mg/kg nano aluminumgroup group.Every mouse was treated by nasal drip for 30 days,3 times per day. After exposure,the Morris water maze test, the step-down test and the open field test were performed to test thelearning and memory abilities of mice. Post-test behavior one mice of every group was exposure,for 4% paraformaldehyde perfusion, do biopsy, and further to do HE staining, thionin staining,immunohistochemical staining, the hippocampus using electron microscopemice. Then the othermice in each group to take a lanthanum nitrate perfusion to observe the blood-brain permeability.The remaining mice were placed in EP tube at -70℃to save for the detection of oxidative stressWestern-blot was used to detect the protein expression of Caspase8, Caspase9, Caspase3 andLC3-II. Results:Detection of nano-aluminum into the center and on the blood-brain barrierinjury: The results showed that lanthanum nitrate tracer lanthanum nitrate nano-aluminum groupattached to the vascular endothelial cells in part by the tight junctions have been spread into theinterstitial space, edema can also be found outside the capillaries；electron microscopy showedthat nano particles into the olfactory bulb and induced damage to some extent on the olfactorybulb；Immunofluorescence assay showed that ZO-1, Occludin expression was increased but thepattern disturbance which show that nano-aluminum particles may cause blood-brain barrierdamage.②Learning and memory tests show : In the Morris water maze test compared withsolvent control group the latency of nano alumia groups were significantly increased in placenavigation experiment(P <0.05). In the spatial probe test on the 5th day, residence time of theoriginal platform quadrant in 100mg/kg, 200mg/kg, nano alumia group was significantlyshortened (P <0.05). In step down test, compared with solvent control, latency period innano-aluminum dose and high dose group was significantly shorter (P <0.05), number of errorsincreased significantly (P <0.05). In the open field test, compared with the control group,nano-aluminum dose and high dose group was significantly increased residence time of thecentral cell (P <0.05).③Pathohistology results: Pathological changes in hippocampal CA3 area Hippocampal pyramidal cells in the control group arranged in neat, sharp edges, showingpolygonal, in nucleoli, apical dendrites extending to the inner radial, Micron aluminum groupCA3 neurons swollen, rounded, cytoplasm varying shades, are short and the top of the treemutation decrease in the number of neurons,In nano-aluminum group most of CA3 neurons wereswollen balloon-like degeneration, nucleolus disappeared, breaking apical dendrites.④Oxidative stress and apoptosis associated proteins. Compared with the control group MDAcontent increased significantly (P <0.05) in nano alumia groups and appears dose-responserelationship. Compared to micron aluminum group MDA content increased significantly (P<0.05) in same dose of nano alumia. Compared with the control group the high dose group ofnano aluminum SOD activity significantly decreased (P <0.05). Compared with the controlgroup, micron aluminum group, nano-aluminum each dose group GSH-PX activity and anincreasing trend but no statistical significance. Compared with the control group of nanoaluminum low dose, middle dose group of CAT activity increased significantly (P <0.05), whilethe nano-aluminum high-dose group, CAT activity decreased significantly (P <0.05). Westernblot detection of caspase 3 within the cerebral cortex of mice tended to increase the proteinexpression of the trend in nano alumia groups. Compared with the control groupLow, mediumand high dose groups the protein expression of caspase-3 increased significantly compared withthe control group, and the difference was statistically significant (P <0.05). LC3-Ⅱproteinexpression also showed an increasing trend, and the low, middle and high dose group increasedsignificantly compared with the control group, the difference was statistically significant (P<0.05).Compared with contorl group Caspase-8,Caspase-9 Expression in basically the shear wasincreased, the difference was statistically significant (P> 0.05) in nano alumia groups.ConclusionConclusion: Nano-aluminum particles can enter the central nervous through nasal drip.Themechanism may transit through blood-brain barrier and through the olfactory bulb and havesome damage to the blood-brain barrier. Nano-aluminum can induce damage in mice the role oflearning and memory and the damage was serious than the micron aluminum. Increasing freeradicals was the main mechanism of oxidative stress injury which induced by nano alumia.It hascompensatory mechanism in 50mg/kg, 100mg/kg nano alumia group but decompensation in200mg/kg nano alumia group. The main mechanism for learning and memory injury induced bynano alumia was Caspase-mediated apoptosis and Autophagy may also play a role.