Curcumin enhances the autophagy of N2a/APP695swe cells by up-regulating expression of the Rab family proteins

Abstract:

Objective：To investigate the effect of curcumin the autophagy of N2a/APP695swe cells and its possible mechanism. Methods：N2a/WT cells and N2a/APP695swe cells were selected as experimental cells. They were divided into four groups：N2a/WT group（WT group），N2a/APP695swe group（APP group），dimethylsulfoxide（DMSO） solvent control group（DMSO group，5 μmol/L，24 h），and cur－cumin treatment group（curcumin group，5 μmol/L，24 h）. Western blot was used to determine the expression of autophagy marker — microtubule-associated protein light chain 3B-Ⅱ（LC3BⅡ），substrate protein-sequestosome 1（SQSTM1），and Rab family proteins（Rab1，Rab5，Rab7，Rab9，Rab24，and Rab33B）. Immunofluorescence assay was performed using a confocal microscope to verify the expression of LC3BⅡ and SQSTM1. Results：Western blot results demonstrated that the curcumin group had significantly higher ex－pression of LC3BⅡ compared with the APP group and the DMSO group（0.54±0.02 vs. 0.29±0.09，P=0.000；0.54±0.02 vs. 0.29±0.09，P=0.000）. However，the curcumin group had significantly lower expression of SQSTM1 than the APP group（0.67±0.01 vs. 1.02±0.02，P=0.000）. And the immunofluorescence assay of LC3BⅡ and SQSTM1 confirmed the above results. Western blot results also showed that the curcumin group had significantly increased expression of Rab1，Rab5，Rab7，and Rab33B compared with the APP group（1.00±0.02 vs. 0.63±0.02，P=0.000；0.94±0.03 vs. 0.79±0.03，P=0.000；0.75±0.00 vs. 0.56±0.01，P=0.000；0.88±0.04 vs. 0.59±0.03，P=0.000）. However，there were no significant differences in the expression of Rab9 and Rab24 between the APP group and the curcumin group（1.04±0.02 vs. 1.06±0.02，P=0.578；0.79±0.00 vs. 0.80±0.00，P=0.067）. Conclusion：Curcumin can enhance the autophagy of N2a/APP695swe cells，probably by increasing the expression of Rab1，Rab5，Rab7，and Rab33B.