Effects Of RXRα/Nur77Expression Levels And Subcellular Localization On The Nervous Apoptosis

Objective: To investigate the effect of exogenous Aβ and increased Aβ in the impactof brain pathology(AD simulation) on the production and translocation ofRXRα/Nur77,to observed the roles of the protein levels and nuclear export of RXRα/Nur77in neuronal apoptosis.Method: In vitro, the N2a cells were treated with Aβ25-35and ddH2O respectively;In vivo, we studied the cerebral cortex and hippocampus of AD mice and control mice.The successful model as AD mice or not had been identified by using the combinationof PCR and immunochemistry. Firstly, the expression levels of RXRα/Nur77mRNA,which were extracted from cells of N2a/cerebral cortex/hippocampus, weredetected by real-time RT-PCR respectively. Secondly, through combining Westernblotting and nucleoplasm separation, we detected the protein expression levels ofRXRα/Nur77in the cells/nucleus/cytoplasm. Thirdly, seeded cells and frozen braintissue sections were stained by immunofluorescence, then we observed thetranslocation of RXRα/Nur77in the nucleoplasm. At last, cell apoptosis were detectedby flow cytometry and DAPI staining.Result: N2a cells treated with Aβ25-35for24h, had changed its expression level ofRXRα mRNA with increasing16.47%, but Nur77remained almost the samecompared to control cells; the increasing Aβ25-35had no significant effect on theRXRα/Nur77protein expression levels but result in RXRα/Nur77protein shuttlingfrom the nucleus to the cytoplasm, the ratio of RXRα/Nur77in cytoplasm increasedfrom2.99%、3.91%(in control group) to21.4%、24.2%(in Aβ group) respectively;and the ratio of cells apoptosis (in control group) increased from1.23%to4.58%(in Aβ group). In AD mice, the expression levels of RXRα/Nur77mRNA had nosignificant difference in the cerebral cortex compared to control mice, and theexpression levels of RXRα/Nur77mRNA increased8.67%and11.73%respectivelyin the hippocampus compared to control mice. The total RXRα/Nur77protein levelsremained the same as those of control mice. While RXRα/Nur77protein exported intocytoplasm significantly in the cerebral cortex and hippocampus cell compared tocontrol mice, accompanied with cells apoptosis.Conclusion: Either exogenous Aβ or increased Aβ in the impact of brain pathologymay affect RXRα/Nur77nuclear exporting, thus induce cell apoptosis.