Phytoestrogens genistein and daidzin enhance the acetylcholinesterase activity of the rat pheochromocytoma cell line PC12 by binding to the estrogen receptor |
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Authors: | Hiroko Isoda Terence P N Talorete Momoko Kimura Takaaki Maekawa Yuhei Inamori Nobuyoshi Nakajima Humitake Seki |
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Institution: | (1) National Institute of Environmental Studies, 16–2 Onogawa, Tsukuba, Ibaraki, Japan;(2) Institute of Agriculture and Forest Engineering, University of Tsukuba, 1-1-1 Tennodai, Tsukuba City, Ibaraki, Japan;(3) Institute of Biological Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba City, Ibaraki, Japan |
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Abstract: | Some compounds derived from plants have been known to possess estrogenic properties and can thus alter the physiology of higher
organisms. Genistein and daidzin are examples of these phytoestrogens, which have recently been the subject of extensive research.
In this study, genistein and daidzin were found to enhance the acetylcholinesterase (AChE) activity of the rat neuronal cell
line PC12 at concentrations as low as 0.08 μM by binding to the estrogen receptor (ER). Results have shown that this enhancement
was effectively blocked by the known estrogen receptor antagonist tamoxifen, indicating the involvement of the ER in AChE
induction. That genistein and daidzin are estrogenic were confirmed in a cell proliferation assay using the human breast cancer
cell line MCF7. This proliferation was also blocked by tamoxifen, again indicating the involvement of the ER. On the other
hand, incubating the PC12 cells in increasing concentrations of 17 β-estradiol (E2) did not lead to enhanced AChE activity,
even in the presence of genistein or daidzin. This suggests that mere binding of an estrogenic compound to the ER does not
necessarily lead to enhanced AChE activity. Moreover, the effect of the phytoestrogens on AChE activity cannot be expressed
in the presence of E2 since they either could not compete with the natural ligand in binding to the ER or that E2 down-regulates
its own receptor. This study clearly suggests that genistein and daidzin enhance AChE activityin PC12 cells by binding to
the ER; however, the actual mechanism of enhancement is not known.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | acetylcholinesterase activity daidzin genistein PC12 |
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