Equol 透過雌激素接受器預防因類澱粉樣蛋白誘發之神經細胞毒性

Equol Prevents Apoptosis in Aβ(25-35)-treated SH-SY5Y Human Neuroblastoma Cell Lines through Increasing Estrogen Receptor Expression

哈文绮(Kiswatul Hidayah)

指導教授 ： 林士祥

臺北醫學大學/公共衛生暨營養學院/保健營養學研究所/碩士(2014年)

https://doi.org/10.6831/TMU.2014.00095

摘要

Background: β-amyloid (Aβ) formation in the brain is one of the characteristics of Alzheimer’s disease (AD). This peptide is the central role in the pathogenesis of AD with apoptosis comes out as the result. The effects of estrogen replacement therapy (ERT) on AD have been recognized, although associated with increased incidence of estrogen related cancer such as breast cancer. Equol is the metabolite form of daidzein, one of the major isoflavones in soybean product. By acting like estrogen, equol may have the same neuroprotective effect with estrogen that prevents the neuron cell apoptosis process.
Aim: This study investigated the neuroprotective effects of equol on cell apoptosis by regulating the cell cycle event and protein related through possible mechanism.
Methods: The SH-SY5Y neuroblastoma cells were exposed by 1 μM Aβ (25-35) for 24 h. To know the neuroprotective effect of equol and estradiol, either 1 μM S-equol or 10 nM 17β-estradiol was treated to cells 24 h prior to Aβ (25-35) exposure. Apoptotic cell death and cell cycle distributions were detected by flow cytometry, while Western blot was used to analyse the protein expression such as cyclin D1, estrogen receptor, SRC-1, and ERK 1/2. 1 μM of ICI 182,780 as estrogen receptor inhibitor was treated to the cells 1 h before estrogen or equol exposure to investigate the involvement of estrogen receptor in the mechanism.
Results: Following a 24 h exposure of the cells to amyloid β-peptide fragment 25-35 (Aβ 25-35), a significant reduction in cell survival and re-entry of cell cycle process which may lead to cell apoptosis were observed. However, pre-treatment of the cells with equol or estradiol prior to Aβ (25-35) exposure elevated the cell survival and prevent the cells to re-enter its cycle. As one of the marker of cell cycle re-entry, cyclin D1, was also decreased in the cells with equol or estradiol pre-treatment. The expression of phosphorylated form of ERK 1/2 was elevated as Aβ (25-35) treatment group. Regulated activation of ERK 1/2 seems to also regulate the expression of cyclin D1 thus modulate the cell cycle event. Group of cells with ICI 182,780 pre-treatment had no expression in estrogen receptor protein. Exposure to (Aβ 25-35) also decreased the expression of SRC-1 as estrogen receptor coactivator while pre-treatment with equol and estradiol could reverse this effect. These results indicated that the neuroprotective effect of equol and estradiol through estrogen receptor pathway and SRC-1 was involved in this mechanism.
Conclusion: Phytoestrogen equol may effectively antagonize Aβ (25-35)-induced cell toxicity by preventing the cell cycle re-entry and apoptotic cell through ERK 1/2 and estrogen receptor pathway, in a manner similar to estradiol. Our results suggested that equol was effective as a potential substitute of estrogen for Alzheimer’s disease.

關鍵字

Equol ； estradiol ； estrogen receptor pathway ； Alzheimer’s disease ； apoptosis ； cell cycle ； ERK 1/2 ； SRC-1 ； cyclin D1

並列摘要

Background: β-amyloid (Aβ) formation in the brain is one of the characteristics of Alzheimer’s disease (AD). This peptide is the central role in the pathogenesis of AD with apoptosis comes out as the result. The effects of estrogen replacement therapy (ERT) on AD have been recognized, although associated with increased incidence of estrogen related cancer such as breast cancer. Equol is the metabolite form of daidzein, one of the major isoflavones in soybean product. By acting like estrogen, equol may have the same neuroprotective effect with estrogen that prevents the neuron cell apoptosis process.
Aim: This study investigated the neuroprotective effects of equol on cell apoptosis by regulating the cell cycle event and protein related through possible mechanism.
Methods: The SH-SY5Y neuroblastoma cells were exposed by 1 μM Aβ (25-35) for 24 h. To know the neuroprotective effect of equol and estradiol, either 1 μM S-equol or 10 nM 17β-estradiol was treated to cells 24 h prior to Aβ (25-35) exposure. Apoptotic cell death and cell cycle distributions were detected by flow cytometry, while Western blot was used to analyse the protein expression such as cyclin D1, estrogen receptor, SRC-1, and ERK 1/2. 1 μM of ICI 182,780 as estrogen receptor inhibitor was treated to the cells 1 h before estrogen or equol exposure to investigate the involvement of estrogen receptor in the mechanism.
Results: Following a 24 h exposure of the cells to amyloid β-peptide fragment 25-35 (Aβ 25-35), a significant reduction in cell survival and re-entry of cell cycle process which may lead to cell apoptosis were observed. However, pre-treatment of the cells with equol or estradiol prior to Aβ (25-35) exposure elevated the cell survival and prevent the cells to re-enter its cycle. As one of the marker of cell cycle re-entry, cyclin D1, was also decreased in the cells with equol or estradiol pre-treatment. The expression of phosphorylated form of ERK 1/2 was elevated as Aβ (25-35) treatment group. Regulated activation of ERK 1/2 seems to also regulate the expression of cyclin D1 thus modulate the cell cycle event. Group of cells with ICI 182,780 pre-treatment had no expression in estrogen receptor protein. Exposure to (Aβ 25-35) also decreased the expression of SRC-1 as estrogen receptor coactivator while pre-treatment with equol and estradiol could reverse this effect. These results indicated that the neuroprotective effect of equol and estradiol through estrogen receptor pathway and SRC-1 was involved in this mechanism.
Conclusion: Phytoestrogen equol may effectively antagonize Aβ (25-35)-induced cell toxicity by preventing the cell cycle re-entry and apoptotic cell through ERK 1/2 and estrogen receptor pathway, in a manner similar to estradiol. Our results suggested that equol was effective as a potential substitute of estrogen for Alzheimer’s disease.

並列關鍵字

Equol ； estradiol ； estrogen receptor pathway ； Alzheimer’s disease ； apoptosis ； cell cycle ； ERK 1/2 ； SRC-1 ； cyclin D1

參考文獻

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