Effect of phytoestrogen isoflavone on MPP +-induced apoptosis in PC12 cells

Abstract

Previous studies have shown that estrogen may reduce neurological damages in Parkinson's disease but the mechanisms of this protective effect are unclear. This study was designed to investigate the effect of isoflavone, a plant-derived estrogen, on the apoptosis of an in vitro cell model for Parkinson's disease. This cell model was based on 1-methyl-4-phenylpyridinium (MPP +)-induced apoptosis in PC12 cells. PC12 cells were divided into four groups: control (vehicle), MPP + (250 μmol/L) only, isoflavone (10 μM) + MPP + (250 μmol/L), and isoflavone (10 μM) only group. Bax protein in PC12 cells was measured with Western-blot. The expression of Bax gene was analysed by in situ hybridization assay. The apoptosis ratio in the isoflavone + MPP + group (30.9%) and the control group (30.7%) was similar ( P > 0.05), but it was lower than in the MPP + group (67.9%, P < 0.05). Optical density in the Bax positive cells in the isoflavone + MPP + group was lower than in the MPP + group (0.28 ± 0.03 vs 0.45 ± 0.06, P < 0.05). Bax mRNA in the isoflavone + MPP + group was lower than in the MPP + group (0.23 ± 0.02 vs 0.47 ± 0.04, P < 0.01). The Bax protein in the isoflavone + MPP + group was also lower than in the MPP + group (89 ± 12 vs 131 ± 19, P < 0.01). In conclusion, soflavone suppressed MPP +-induced apoptosis in PC12 cells. The apoptosis suppression is associated with a decreased level of proapoptotic Bax gene and Bax protein. Further studies are warranted to investigate the clinical effect of isoflavone on Parkinson's disease.