Study On Molecular Mechanism Of Aluminum-inducd The Poptosis Of Neurocytes In Rats' Hippocampus In Vivo

Objective:To explore the molecular mechanism of aluminum-inducd theapoptosis of neurocytes in rats' hippocampus. Methods:Fourty SD rats,adultand healthy, were divided into 4 groups at random: normal saline, Al³⁺ 2.5mg/kg,Al³⁺ 5 mg/kg and Al³⁺ 10 mg/kg. They were exposed to AlCl₃ byintraperitioneal injection for 60d. Experiments and observations describedbelow were performed after exposure, 1)Apoptosis of neurocytes in rats'hippocampus were measured with method of TUNEL. 2)Morphology ofneurocytes in rats' hippocampus was observed with light microscope andelectron microscope. 3 ) Expression of bcl-2mRNA and baxmRNA inneurocytes in rats' hippocampus were measured with RT-PCR. Results wereanalyzed with Gelatum Analyzing System.Expression of Bcl-2 and Bax inneurocyte in rats' hippocampus were measured with immuno-histochemicalmethod. Results were analyzed by Imaging Analyzing System; 4 )Mitochondrial enzymes(SOD , SDH , Na⁺-K⁺ ATP, Ca²⁺ ATP andMg(2+) ATPase)were detected with needed test Kits.5) Caspase-3,cyt-c and Nf-κb in cytoplasm were detected with methods of Western-blot, and results wereanalyzed with Gelatum Analyzing System.Results: 1)Apoptosis indices(AI) ofneurocytes in rats' hippocampus in Al3+5 mg/kg group and Al³⁺10 mg/kg groupwere significantly higher than that of controls (P<0.05), and which in Al³⁺ 10mg/kg group were significantly higher than that of Al³⁺ 2.5 mg/kg group(P>0.05). 2)The observation under light microcope showed: arrangement ofthe neurocytes in rats' hippocampus was orderly in control group, but with theincreasing of the doses of aluminum exposed, the neurocytes displayeddisorderly, the connections among the neurocytes were loosened, the karyonshrinked, some rings around the neurocyte were observed. Picture underelectron microscope displayed: the karyotin distributed symmetrically, and itsform was regular, the form of mitochondria was regular, the arrangement ofbars was orderly, and with the increasing of the doses of aluminum exposed,the karyon shrinked, the karyotin assembled in the edge, karyotheca wasbroken, mitochondria swelled, broken, the bars were reduced and disappeared.3)The expression of bcl-2mRNA was significantly decreased in everyaluminum-treated group compared with the control group (P<0.05).Theexpression of baxmRNA was significantly increased in every aluminum-treatedgroup compared with the control group (P<0.05). A negative correlationbetween AI and the expression of bcl-2mRNA (r=-0.909,P<0.01), and apositive correlation between AI and the expression of baxmRNA(r=0.871,P<0.01) were observed. The expression of Bcl-2 significantlydecreased in the neurocyte in rats' hippocampus in all the aluminum-treatedgroups separately compared with the control group (P<0.05). The expressionof Bax significantly increased in Al³⁺ 5 mg/kg group and Al³⁺10 mg/kg groupcompared with the control group (P<0.05). The value of Bcl-2/Bax in everytreatment group decreased significantly compared with control group(P<0.05).AI negatively correlated with the expression of Bcl-2 (r=-0.924,P<0.01)andthe value of Bcl-2/Bax(r=-0.872,P<0.01); There was positive correlationbetween AI and the expression of Bax(r=0.804,P<0.01). 4)The levels ofNa⁺-K⁺ ATPase and SOD were significantly decreased in hippocampus cells inevery aluminum-treated group compared with the control group (P<0.05). andwhich of Ca²⁺ ATPase and Mg2+ATPase were significantly decreased in Al3+5mg/kg group and Al3+10 mg/kg group compared with the control group(P<0.05). The level of SDH was insignificantly decreased in everyaluminum-treated group (P>0.05). AI negatively correlated to the levels ofNa⁺-K⁺ ATPase,Ca2+ ATPase ,Mg2+ATPase and SOD (r=-0.439,-0.501,-0.530,-0.815.P<0.05),but there was no correlation between AI and the level of SDH.5) The expression of caspase-3 and cyt-c significantly increased in theneurocytes in rats' hippocampus in Al³⁺ 5mg/kg group and Al³⁺10 mg/kg groupcompared with the control group (P<0.05). The expression of Nf-κb(p65)significantly increased in hippocampus cells i...