Mechanistic Approach to Screening Chemicals and Mixtures for Endocrine Activity Using an Invertebrate ModelEPA Grant Number: R831300
Title: Mechanistic Approach to Screening Chemicals and Mixtures for Endocrine Activity Using an Invertebrate Model
Investigators: LeBlanc, Gerald A.
Institution: North Carolina State University
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 2003 through August 31, 2006 (Extended to May 31, 2007)
Project Amount: $391,598
RFA: Development of High-Throughput Screening Approaches for Prioritizing Chemicals for the Endocrine Disruptors Screening Program (2003) RFA Text | Recipients Lists
Research Category: Endocrine Disruptors , Economics and Decision Sciences , Health , Safer Chemicals
The currently proposed Tier 1 screening battery for detecting endocrine activity of chemicals suffers from two major deficiencies: 1) no invertebrate screen is included despite the proposed use of a Tier 2 multigenerational test with a crustacean; and 2) the battery is not equipped to assess combined effects of diverse endocrine toxicants. The overall objectives of this proposed research program is to develop a mechanism-based, high-throughput screening assay for evaluating estrogen, androgen, and thyroid (EAT)-like activities in an invertebrate species that also can be used to evaluate interactive effects of endocrine-active compounds through receptor cross-talk.
The first aim of this proposed program is to develop a high-throughput formatted screening assay to assess endocrine activity of chemicals towards an invertebrate. This assay will be developed for use with the crustacean Daphnia magna. This species was selected because: 1) it is commonly used in toxicity testing; 2) its endocrinology has been well characterized; 3) it is more amenable to high-throughput testing than the recommended species for Tier 2 testing (mysid shrimp); and 4) results obtained will be applicable to mysids and other arthropods. EAT-like activities in crustaceans are under the control of ecdysteroids and juvenoids. A 6-day assay will be designed in which chemicals can be simultaneously screened for ecdysteroid, anti- ecdysteroid, juvenoid, and anti-juvenoid activity. Cross-talk between receptors provides a mechanism by which diverse endocrine toxicants can interact resulting in greater than additive toxicity. The proposed screening assay will be ideally suited to assess cross-talk between ecdysteroid and juvenoid receptors. The next aim of this proposed program will be to utilize the screening assay, in conjunction with cellular and molecular approaches, to investigate receptor cross-talk and interactive effects of endocrine toxicants as a consequence of this cross communication. The final aim will be to establish the linkages between the proposed Tier 1 screen and the Tier 2 multigenerational assay. Linkages, such as the relationships between the mechanisms of endocrine activity measured in the Tier 1 screen and the actual toxicity measured in the Tier 2 test, will be discerned. Results from this aim will establish the value of the various endpoints used in the assay to characterize toxicity.
Results from this proposed research will provide a mechanistic foundation for a Tier 1 assay that will screen for EAT-like activities in an invertebrate. The proposed screen will provide the mechanistic rationale to judge whether a chemical should undergo Tier 2 multigenerational invertebrate testing. In addition, this proposed research will increase our fundamental understanding of interactive toxicity of endocrine- active chemicals involving receptor cross-talk. The proposed test will be equipped to measure such interactive effects and will further strengthen the ability of the screening battery to detect endocrine activity of chemicals.