Curcumin activates Wnt/β-catenin signaling pathway through inhibiting the activity of GSK-3β in APPswe transfected SY5Y cells

Wnt/beta-catenin signaling pathway plays an important role in the genesis and development of Alzheimer's disease. The study aims to investigate the effect of Curcumin on the expression of GSK-3 beta, beta-catenin and CyclinD1 in vitro, which are tightly correlated with Wnt/beta-catenin signaling pathway, and also to explore the mechanisms, which will provide a novel therapeutic intervention for treatment of Alzheimer's disease. Plasmid APPswe and BACE1-mychis were transiently co-transfected into SHSY5Y cells by Liposfectamin (TM) 2000. The cells were treated with Curcumin at 0, 1.25, 5.0, 20.0 mu mol/L for 24 h, or with Curcumin at 5.0 mu mol/L for 0, and 12, 24 and 48 h for time course assay. Cell lysates were collected for RT-PCR, Western blot assay and immunofluorescent staining were carried out for detecting the effect of Curcumin on the expression of GSK-3 beta, beta-catenin and CyclinD1. RT-PCR and Western blot results showed that the expression of GSK-3 beta mRNA and protein significantly decreased in the transfected cells treated with Curcumin, and that the changes were in a dose and time-dependent manner (P < 0.05); however, the protein expression of GSK-3 beta-Ser9 was increased (P < 0.05). Meanwhile, the expressions of beta-catenin and transcriptional factors CyclinD1 mRNA and protein increased and the changes were also in a dose and time-dependent manner (P < 0.05). Immunofluorescent staining results not only confirmed the above changes, but also showed that beta-catenin had translocated into the nucleus gradually with the increased dosage of Curcumin. Therefore, GSK-3 beta is a potential target for treatment of AD. Curcumin could activate the Wnt/beta-catenin signaling pathway through inhibiting the expression of GSK-3 beta and inducing the expression of beta-catenin and CyclinD1, which will provide a new theory for treatment of neurodegenerative diseases by Curcumin. (C) 2011 Elsevier B.V. All rights reserved.