Blockade of emodin on amyloid-β 25-35-induced neurotoxicity in AβPP/PS1 mice and PC12 cells through activation of the class III phosphatidylinositol 3-kinase/Beclin-1/B-cell lymphoma 2 pathway.

Autophagy plays an important role in the pathogenesis of Alzheimer's disease. In the present study, the blockade mechanism of emodin on amyloid-β 25-35-induced neurotoxicity was explored. Cell viability of PC12 cells was evaluated by the MTT assay and neuro damage by the lactate dehydrogenase leakage assay. Gene silencing by small interfering RNA, cDNA constructs and transfection, as well as Western blot were performed to assess protein expression levels. AβPP/PS1 mice were administered orally with emodin (50 mg/kg/day), and LC3-II positive cells in their brain cortex sections were detected by immunohistochemical staining. Emodin could significantly inhibit the LC3-I/LC3-II conversion ratio and cell viability while decreasing the lactate dehydrogenase level in AβPP/PS1 mice and PC12 cells. LC3II positive cells in the cortex were decreased significantly by the treatment with both emodin and 3-methyladenine. Furthermore, emodin and 3-methyladenine could increase B-cell lymphoma 2 while decreasing Beclin-1 and hVps34 expressions, which were induced by amyloid-β 25-35. Small interfering gene silencing Beclin-1 and B-cell lymphoma 2 confirmed this signaling pathway. We also found that the phosphatidylinositol 3-kinase inhibitor LY294002 could block LC3-I/LC3-II conversion and increase B-cell lymphoma 2 while decreasing hVps34 and Beclin-1 expressions. The results suggest that the blockade of emodin on amyloid-β 25-35-induced autophagy may occur via the activation of the class III phosphatidylinositol 3-kinase/Beclin-1/B-cell lymphoma 2 pathway. Our results provide confirmatory evidence for the application of emodin in the prevention and treatment of Alzheimer's disease.