The Role Of NF-κB In Proliferation And Differentiation Of Adult Neural Stem Cell And Contributions Of Autophagy

Aim : This article studies the roles of NF-κB in the proliferation and differentiation of NSC in rat brains lesioned by the excitotoxin quinolinic acid (QA) and the contributions of autophagy.Methods:We produced striatal neuronal damage by intrastriatal injection of QA with a stereotaxic instrument. Six days after QA-induced lesions, the NF-κB inhibitor SN50 was injected into lateral cerebral ventricle at the day before perfusion (6th day). Meanwhile, BrdU (50 mg/kg) was injected intraperitoneally for three times with 8 hours interval. Rats were killed 7 days after QA injection. Brains were perfusion fixed with 4% paraformadehyde and postfixed for 6-9 hours and hehydrated using 20%-30% sucrose for overnight still the tissue sunk to the bottom of the container. Brains were cut into sections (20μm) with a cryostat, mounted them onto the gelatin-coated glass slides. We examined whether the model is successful and observed the proliferation of NSC by Nissle and immunohistochemistry; we detected the expression of Nestin, GFAP,β-Ⅲ-tublin, LC3 and BrdU incorporation to acquire the information of proliferation and differentiation of the NSCs. With the same model, we detected the expression of autopaghy related proteins by Western blot.Results:The results of immunohistochemical staining (DAB staining) showed that NSC began to proliferate on the second day after QA in the ipsilateral striatum and the ventricle of the rats. Our results indicat that the number of the cells expressed both Nestin and BrdU in the groups treated with SN50 was decreased, indicating inhibiting NF-κB signal pathway inhibits the proliferation of NSCs. After intracerebroventricular injection of SN50, the number of cells positive both for NF-κB (p65) and BrdU significantly reduced compared to saline group, the expression NF-κB (p65) in the group of SN50 was attenuated, indicating that SN50 inhibits nuclear translocation of NF-κB. By comparing the ratios of cells positive both for BrdU and GFAP to positive both for BrdU and Nestin, we found that after inhibiting the NF-κB signal pathway, there was no difference in two groups, indicating that after inhibiting the NF-κB signal pathway has no effect on NSCs differentiation into astrocytes. We also found that after inhibiting the NF-κB pathway the NSCs was promoted to differentiate into neural cells. In the proliferating cells the marker of autophagy was increased, indicating increased autophagy activity in proliferating cells.Conclusions: By inhibiting NF-κB, the proliferation of neural stem cell was reduced while the differentiation of neural stem cells to neurons was increased and autophagy is activated in the proliferating neural stem cells.