Objective: To investigate the effects of caspase-3 siRNA on the neurobehavior of mice exposed to aluminum.
Methods: Male KunMing mice (3 months old) were randomly divided into 4 groups by weight:blank control group (4 microl normal saline), Al group (4 microl 0.5% AlCl3), Al plus empty vector group(3 microl 0.5% AlCl3 plus control siRNA expression vector)and Al plus RNAi group (3 microl 0.5% AlCl3 plus targeted siRNA expression vector). All groups were treated by lateral cerebral ventricle micro-injection for 5 days. The neurobehavior was tested by the Morris water maze test, Open-field and Step-down tests for all treated mice. Pathological changes in hippocampus was observed by electron microscopy, the caspase-3 gene expression levels were detected using RT-PCR.
Results: The results of Step-down test indicated that as compared with control group, the latent time [LT, (44.67 +/- 10.60) s] in A1 group decreased significantly, the error number (3.63 +/- 0.52) in Al group increased significantly and the LT [(68.00 +/- 14.70) s] in Al plus empty vector group decreased significantly (P<0.05). the LT [(239.50 +/- 19.36) s] in Al plus RNAi group increased significantly and the error number in Al plus RNAi group decreased significantly, as compared with Al group (P<0.05). The results of Morris water maze test showed that as compared with control group, the LT in Al group increased significantly, and residence time in the former platform quadrant decreased significantly and the LT in Al plus empty vector group increased significantly (P<0.05). The LT in Al plus RNAi group was significantly longer than that in Al group (P<0.05). The results of open-field test demonstrated that as compared with control group, the time in the central grid in Al group and Al plus empty vector group increased significantly, the rearing number and the modification number in Al group and Al plus empty vector group decreased significantly (P< 0.05). As compared with Al group, the time in the central grid in Al plus RNAi group decreased, the inter-cell number, the rearing number and the modification number increased significantly (P<0.05). The results of electron microscopic examination exhibited that a slight change of hippocampal cells appeared in control group, the obvious pathological changes of hippocampal cells appeared in Al group and Al plus empty vector group, but the pathological changes of hippocampal cells in Al plus RNAi group significantly reduced as compared with Al group. The results of thionin staining indicated that the layers of neural cells of hippocampal CA3 were more clear and there was not obvious denatured injury of neural cells of hippocampal CA3 in control group. The number and Nissl body color of neural cells of hippocampal CA3 in Al group and Al plus empty vector group decreased significantly. After RNA interference, the number and Nissl body color of neural cells of hippocampal CA3 increased obviously. The expression levels of caspase-3 gene in Al group and Al plus empty vector group were 2.24 +/- 0.57 and 2.28 +/- 0.33, respectively, which were significantly higher than that (1.00 +/- 0.00) in control group (P<0.05). The expression level of caspase-3 gene in Al plus RNAi group was 0.44 +/- 0.08, which was significantly lower than those in Al group and control group (P<0.05).
Conclusion: Aluminum can decrease the learning and memorizing ability, and inhibited the activity or exploration function of mice. It is suggested that Caspase-3 siRNA may reduce the neurotoxicity induced by aluminum to a certain extent.