Objective: To study the effect of exendin-4(Ex-4) on the differentiation of neural stem cells(NSCs) in adult mouse subventricular zone(SVZ)and its mechanism .
Methods: NSCs in the SVZ were derived from 5-week C57BL/6J mice and the expression of nestin was detected by immunofluorescence. The cell morphology was observed after the cells treatmed with 100 nmol/L Ex-4 for 14 days.The expressions of nestin and glucagon-like peptide-1 receptor (GLP-1R) were detected by immunofluorescence. GLP-1R was knocked down by using shRNA and the study was divided into four groups: control group, Ex-4 group, GLP-1R knockdown group, GLP-1R knockdown + Ex-4 group. After treatment with 100 nmol/L Ex-4 for 14 d, β-tublin III and glial fibrillary acidic protein (GFAP) were labeled by immunofluorescence and then the proportion of β-tublin III positive cells were counted. Western blot was used to detect the activation of cAMP-response element binding protein (CREB) in NSCs. In order to further study the effects of Ex-4 on mitogen-activated protein kinase(MAPK) and phosphatidylinositol 3-hydroxy kinase (PI3K) pathways, the cells were pretreated with MAPK inhibitor U0126 at a concentration of 0.07 μmol/L for 30 min or PI3K inhibitor LY294002 at 50 μmol for 2 h, respectively. The study was divided into six groups: control group, Ex-4 group, U0126 group, U0126 + Ex-4 group, LY294002 group, LY294002 + Ex-4 group. The activation of CREB in each group was detected by Western blot. The experiment was repeated three times independently.
Results: NSCs were successfully extracted from SVZ of C57BL/6J mice. Immunofluorescence showed that nestin and GLP-1R were positive in NSCs. Compared with the control group, the proportion of neurons differentiated from Ex-4 group was higher. The percentage of neurons in GLP-1R knockdown + Ex-4 group was basically the same as that in control group (P＜0.01). The positive cells of beta-tublin III showed positive activation of GLP-1R and CREB. Western blot showed that CREB was significantly activated in the Ex-4 group, and knockdown of GLP-1R abolished its activation (P＜0.01). U0126 did not affect Ex-4-mediated CERB activation, and LY294002 significantly reduced Ex-4-mediated CREB activation (P＜0.01).
Conclusion: Ex-4 promotes the differentiation of NSCs into neurons in SVZ of adult mice through GLP-1R receptor, which may be achieved through PI3K/CREB pathway.