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Some nonylphenol isomers show antiestrogenic potency in the MVLN cell assay
Thomas G Preuss1, Hande Gurer-Orhan, John Meerman
1Institute for Environmental Research (Biology V), Aachen University, Aachen, Germany. thomas.preuss@bio5.rwth-aachen.de
Abstract:
It has been shown that nonylphenol (NP) isomers vary in their estrogenic potency. These differences may be due to varieties in receptor affinity, receptor activation, or activation/deactivation of non-receptor mediated side paths of reporter gene translation. In the present study we investigated the underlying mechanism of the different estrogenic potency of seven nonylphenol isomers. An estrogen receptor binding assay was conducted with the human estrogen receptor alpha (hERalpha). Additionally we co-incubated the nonylphenol isomers with two concentrations of 17beta-estradiol (E2) in the MVLN cell assay to measure the potency of the isomers to compete with E2. No significant differences were found between the nonylphenol isomer binding affinities for the hERalpha. The IC(50) were in the range of 2.1-8.1x10(-6)M and the binding affinity relative to estradiol (set to 1) were between 2.6 and 6.7x10(-3). Only two test items (p353-NP and p-NP) were able to increase the estrogenic response of 100pM estradiol. The response of the other isomers co-incubated with 100pM E2 showed varying degrees of inhibition of the response in the MVLN reporter gene assay. Thus, it appears that all isomers bind to the ER but some are partial agonists while others are antagonists in the MVLN reporter gene assay.
Insights
Nonylphenol (NP) isomers exhibit varying estrogenic effects due to differences in receptor interactions. While all isomers bind to the estrogen receptor (ER), some act as partial agonists and others as antagonists.
Area of Science:
- Environmental Toxicology
- Endocrinology
- Molecular Biology
Background:
- Nonylphenol (NP) isomers display diverse estrogenic potencies, potentially linked to receptor binding, activation, or non-receptor pathways.
- Understanding these mechanisms is crucial for assessing the environmental and health risks associated with NP exposure.
Purpose of the Study:
- To elucidate the underlying mechanisms responsible for the differential estrogenic potency among seven nonylphenol isomers.
- To investigate the binding affinities and functional responses of NP isomers with the human estrogen receptor alpha (hERalpha).
Main Methods:
- Estrogen receptor binding assay using human estrogen receptor alpha (hERalpha).
- MVLN cell assay co-incubating NP isomers with 17beta-estradiol (E2) to assess competitive binding and functional effects.
Main Results:
- No significant differences in binding affinities of NP isomers to hERalpha were observed (IC(50) range: 2.1-8.1x10(-6)M).
- Relative binding affinities to estradiol were low (2.6-6.7x10(-3)).
- Only p353-NP and p-NP enhanced the estrogenic response with E2; other isomers showed varying degrees of inhibition, indicating partial agonism or antagonism.
Conclusions:
- All investigated nonylphenol isomers bind to the estrogen receptor.
- Differential estrogenic potency is mediated by functional responses (partial agonism/antagonism) rather than differences in receptor binding affinity.
- These findings highlight the complex endocrine-disrupting potential of nonylphenol isomers.
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