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Development of a Tier I screening battery for detecting endocrine-active compounds (EACs)
J C Cook1, M A Kaplan, L G Davis
1DuPont-Haskell Laboratory for Toxicology and Industrial Medicine, Newark, Delaware 19714, USA.
Abstract:
One of the components of our research program is development of a mode-of-action screening battery to detect several different types of endocrine-active compounds (EACs). Our working hypothesis is that a comprehensive short-term in vivo/in vitro battery can be developed to identify endocrine toxicants using a collection of endpoints. The goals of this battery are that it be quick, cost effective, and predictive. The purpose of this battery is to identify potential EACs and to assess their potency in order to prioritize compounds for further study. Two in vivo screens (intact male and ovariectomized female rats) are being evaluated for their ability to detect several different types of endocrine activity. To validate this screen, 15 compounds with known endocrine activities are being used to evaluate a collection of different endpoints for their variability, stability over time, predictiveness, and dose dependency. These positive controls were chosen because they can modulate development, reproduction, or cancer. The advantage of an in vivo screen is that it utilizes a metabolically and physiologically intact system. The male in vivo battery will be used to assess several different types of endocrine activity, primarily by using a comprehensive hormonal battery. The female in vivo battery will be used to identify compounds which are either estrogenic/antiestrogenic or can alter the prolactin pathway. The in vitro portion of the screening battery consists of a yeast transactivation system (YTS). The YTS is being evaluated for its ability to identify compounds which are agonists or antagonists to the estrogen, androgen, or progesterone receptors. The expression of mammalian receptors in yeast allows for assessment of steroid-dependent transcriptional activators. The value of this system is that it can be used as a routine screen for compounds that interact with steroid receptors. Alterations in ligand binding to these receptors can be correlated with alterations in development via masculinization of females and/or feminization of males, decreases in reproductive success, or modulation of cancer incidence from in vivo tests. The in vivo and in vitro screens are designed to be run in parallel with built-in redundancy in order to reduce the probability of false-negative/ positive responses.
Insights
A new screening battery using in vivo and in vitro methods can quickly and cost-effectively detect endocrine-active compounds (EACs). This approach prioritizes compounds for further study by assessing their potency and potential to disrupt development, reproduction, or cancer pathways.
Area of Science:
- Endocrinology
- Toxicology
- Biochemistry
Background:
- Endocrine-active compounds (EACs) pose risks to development, reproduction, and cancer.
- Existing methods for detecting EACs can be time-consuming and expensive.
Purpose of the Study:
- To develop a rapid, cost-effective, and predictive screening battery for EACs.
- To identify and prioritize compounds for further toxicological evaluation.
Main Methods:
- Utilized a combination of in vivo (male and female rat) and in vitro (yeast transactivation system) assays.
- Evaluated 15 known endocrine-active compounds as positive controls.
- Assessed endpoints for variability, stability, predictiveness, and dose dependency.
Main Results:
- The in vivo screens assess hormonal activity, estrogenic/antiestrogenic effects, and prolactin pathway alterations.
- The in vitro yeast transactivation system identifies agonists/antagonists for estrogen, androgen, and progesterone receptors.
- Parallel testing with built-in redundancy minimizes false-negative/positive responses.
Conclusions:
- A comprehensive in vivo/in vitro screening battery can effectively detect various types of endocrine toxicants.
- This approach provides a quick, cost-effective, and predictive method for prioritizing compounds for further study.