NALP1/caspase-1Role In The Neuronal Damage In AD Rat Model Induced By Aβ_1-42oligomers

Objective: To study NALP1/Caspase-1role in the AD rat model neuronaldamage induced by A β1-42oligomers.Method:60rats screened Morris watermaze were randomly divided into four groups: D-galactose group, Aβ_1-42fibergroup, Aβ_1-42oligomers group, Sham-operated group. Each group establish ADmodel using the following method:①D-galactose group,1-6weeksintraperitoneal injection of D-gal50mg/kg/d42days in a row, bilateralhippocampal injection of saline in29days, on each side of the injection5μL.②A β1-42fiber group,1-6weeks intraperitoneal injection of deionized water of1ml/day for42d,29days of bilateral hippocampal injection of Aβ_1-42fibers（concentration2μg/μl）each side injection5μL.③Aβ_1-42oligomers group,1-6weeks of intraperitoneal injection of deionized water of1ml/day for42d,bilateral hippocampal injection of Aβ_1-42oligomer（sconcentration2μg/μl）in29days, on each side of the injection5μL.④Sham-operated group,1-6weeks ofintraperitoneal injection of deionized water of1ml/day for42d, bilateralhippocampal injection of saline in29days, on each side of the injection5μL.After42days of modeling, using the Morris water maze detect learning andmemory behavior. After the end of the detection, each group were randomlyselected5or6rats with4％paraformaldehyde for cardiac perfusion, the brain tissue was separated, brain tissue is used to make the tissue slice. Hippocamaland cortical patholoy detected by HE staining, using immunohistochemistrydetected Caspase-1protein expression. Each group remaining rats aredislocatedly killed, fast peel the rat brain cortex and hippocampus, respectivelymarked into the freezing tube quickly placed in liquid nitrogen, in turn depositedat-80℃. Using RT-PCR detect hippocampal and cortical organization NALP1and Casepase-1mRNA expression. Application SPSS19.0software for statisticalanalysis, P <0.05indicates a statistically significant difference. Results:①Theother three groups of AD rats compared with sham-operated rats activities andfighting decreased, A β1-42oligomers group behavior change becomes moreapparent. Three rats died in surgery, postoperative mortality12.②Ratbehavioral test results show that the four groups of rats before modeling escapelatency statistically was no difference （P>0.05）. Compared with before modeling,in addition to the sham-operated group modeling the remaining three groups ofrats escape latency were prolonged （P<0.05）, difference was statisticallysignificant. Compared with the sham-operated group, Aβ_1-42fiber group and Aβ1-42oligomers group rats escape latency were prolonged, difference wasstatistically significant（P<0.05）. D-galactose group escape latency slightlyextended, but the difference was not statistically significant （P>0.05）. Comparedwith Aβ_1-42oligomers,the other three groups of rats, escape latency time wereshortened, there is a statistically significant difference （P<0.05）, In summarydescription: Aβ_1-42 oligomers have a greater impact on cognitive function.③The morphological changes of the nerve cells, sham-operated rats hippocampalneuron cell were rich and arranged in neat rows and zonal distribution, form iscomplete, a large number of cell nucleus were significantly, round or oval, uniform coloring, nuclear blue nucleus to cytoplasm ratio, seen deeply stainednucleolus. Cortical neuronal cells were rich in cytoplasm, nuclear is blue.Compared with the control group, number of model hippocampal and corticalneurons relative reduction irregular, narrow visible nerve cell body cytoplasmconcentrated cells arranged in layers reduce. Each model group hippocampus,cortex neurons damaged. Compared with Aβ fibrils group and D-galactosegroup, Aβ_1-42oligomers in hippocampal and cortical neurons damaged severely.④Protein expression of Caspase-1. Compared with the other three groups, the Aβ1-42oligomers brain cortex and hippocampus Caspase-1protein expressionincreased significantly. Compared with the sham-operated group, three modelinggroup brown Caspase-1protein expression increased, most of the sham-operatedgroup were negative, and have the part of yellow region Caspase-1proteinexpression.⑤RT-PCR results showed that, compared with the sham-operatedgroup, model group, hippocampus and cortex Caspase-1mRNA expression wasincreased, the difference was statistically significant （p<0.05）, and comparedwith Aβ_1-42 oligomers group, the remaining three groups of rats hippocampusand cortex Caspase-1mRNA expression have decreased, the difference wasstatistically significant （p<0.05）; compared with the sham-operated group, threegroups of rats in model group Nalp1mRNA in hippocampus and cortexexpression were increased, the difference was statistically significant （p<0.05）,compared with Aβ oligomers, and the remaining three groups of ratshippocampus and cortex Nalp1mRNA expression have decreased, thedifference was statistically significant （p<0.05）.Conclusion:①Usingintraperitoneal injection of D-galactose and intrahippocampal injection of A β1-42oligomers and fiber, AD rat model was successfully established.②Aβ_1-42 oligomers group, Aβ_1-42fiber group and D-galactose group can lead to thedecreased learning ability of rat, the Aβ_1-42 oligomers is most obvious.③Aβ1-42oligomers group hippocampal injection can cause damage to thehippocampus and cerebral cortex neurons.④Aβ_1-42oligomers group canpromote NALP1and Caspase-1expression. NALP1and Caspase-1play animportant role in the Aβ_1-42oligomers-mediated neurotoxity and localinflammation, its mechanism of action is for further study.