Effects of GST extract on MPP+-induced cell death in SH-SY5Y cells. (a) Effects of GST extract on SH-SY5Y cell viability. Cells were treated with various concentrations of GST extract (10, 30, 50, 100, 300, or 500 μg/ml) for 24 h. Cell viability was determined by MTT assay. Values were expressed as percentages of the control. (b) Effects of GST extract against MPP+-induced neurotoxicity in SH-SY5Y cells. SH-SY5Y cells were pretreated with GST (10, 100, 200, or 300 μg/ml) for 1 h and then exposed to 1 mM MPP+ for 24 h. The cell viability was measured using an MTT assay. ### p < 0.001, compared to control group; ∗∗∗ p < 0.001, compared to MPP+ treatment, analyzed by one-way ANOVA, followed by Bonferroni’s post hoc test. (c) Effects of GST on MPP+-induced apoptosis in SH-SY5Y cells. The expression of apoptosis-related proteins were measured by western blot in cells treated with 100 μg/ml GST in the absence or presence of 1 mM MPP+ for 24 h. (d) Effects of GST on MPP+-induced changes of cell signaling proteins in SH-SY5Y cells. The expression of cell proliferation-related proteins was assayed by western blot in cells treated with 100 μg/ml GST in the absence or presence of 1 mM MPP+ for 24 h.