*3.3. SRC-1 Protein Expression*

Figure 3 shows the effects of the Eq and E2 pretreatments on the expression of the estrogen receptor coactivator SRC-1. Treatment of 1 μM Aβ (25–35) (Aβ) for 24 h significantly decreased the SRC-1 protein expression (*p* < 0.05). Pretreatment with either Eq or E2 significantly prevented Aβ (25–35)-induced reduction in SRC-1 protein expression (*p* < 0.05).

**Figure 1.** Cell viability of SH-SY5Y cells assessed with a modified 3-[4,5-dimethylthiazol-2]-2,5 diphenyltetrazolium bromide (MTT) assay. Data were analyzed by one-way ANOVA followed by the LSD post-hoc test and are representative of three independent experiments (*n* = 3). Values are presented as the mean + SD. Bars with different letters significantly differ at a level of *p* < 0.05. Eq, S-equol; E2, 17β-estradiol; ICI, ICI-182,780.

**Figure 2.** The estrogen receptor alpha (ERα) expressions of SH-SH5Y cells from different treatments. Data were analyzed by a one-way ANOVA followed by the LSD post-hoc test and are representative of three independent experiments (*n* = 3). Values are presented as the mean + SD. Bars with different letters are significantly different at *p* < 0.05.

#### *3.4. Cell Cycle*

Figure 4 shows the distribution of different phases of cell cycle. A significant increase of cells in the S phase in the Aβ group is observed compared to the C group as well as a concomitant reduction of cells in the G2/M phases of the cycle (Figure 4). This result indicates that SH-SY5Y cells exposed to Aβ (25–35) escaped from the G2/M phase. Pretreatment with either Eq (Eq + Aβ) or E2 (E2 + Aβ) showed a decreasing number of cells in the S phase and a significantly increasing number in the G2/M phase compared to that in the Aβ group (*p* < 0.05). Cell cycle analysis showed that the cell cycle profiles were markedly altered by the treatment of Aβ (25–35), and pretreatment with Eq or E2 significantly blocked Aβ (25–35)-induced changes in the cell cycle profiles of the SH-SY5Y cells.

**Figure 3.** The SRC-1 expressions of SH-SH5Y cells from different treatments. Protein expressions were assessed by Western blotting. Data were analyzed by a one-way ANOVA followed by the LSD post-hoc test and are representative of three independent experiments (*n* = 3). Values are presented as the mean + SD. Bars with different letters are significantly different at *p* < 0.05.

**Figure 4.** Cell cycle events of SH-SH5Y cells from different treatments. The cell cycle was assessed by PI staining with flow cytometry. Data were analyzed by one-way ANOVA followed by the LSD post-hoc test and are representative of three independent experiments (*n* = 3). Values are presented as the mean + SD. \* *p* < 0.05 vs. the control; # *p* < 0.05 vs. the Aβ group.
