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2005 Progress Report: 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: Pascual, Pasky
Project Period: September 1, 2003 through August 31, 2006 (Extended to May 31, 2007)
Project Period Covered by this Report: September 1, 2004 through August 31, 2005
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 objective of this research project is to provide a scientific foundation for the development of 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.Progress Summary:
Develop a High-Throughput Screening Format To Assess Endocrine Activity of Chemicals Toward an Invertebrate
Methods were developed and refined for an integrated screening paradigm using various development endpoints that are indicative of anti-ecdysteroid and juvenoid hormone activities of chemicals. This screening approach was used to evaluate various individual chemicals, chemical mixtures, and field-collected samples for endocrine activity. Novel endpoints were investigated as candidates for use in high throughput screening assays with arthropods. These endpoints include aberrations in sex differentiation resulting in bilateral gynandromorphic offspring, alterations in gonadalsomatic index, and induction or suppression of hormone-responsive genes.
Investigate Receptor Cross-Talk and Interactive Effects of Endocrine Toxicants as a Consequence of Receptor Cross-Talk
We previously demonstrated that the hemoglobin 2 gene (hb2) was induced in daphnids by juvenoid hormones. This gene induction was recognized as having potential as a biomarker of juvenoid activity in endocrine screening assays and as a tool for evaluating the components of the juvenoid signaling pathway.
The response element on the hb2 gene responsible for hemoglobin induction by juvenoids was identified and characterized. A candidate receptor that may transduce juvenoid signals to the response element, tentatively designated NR4A, was identified.
Cross-talk between this hormone signaling pathway and the hypoxia signaling (HIF/HRE) pathway was established. Hypoxia is increasingly recognized as a modulator of endocrine activity and this research has identified a site with these signaling pathways and cross-talk.Future Activities:
We will further develop screening approaches for the assessment of EAT-like endocrine activities in an invertebrate. We will obtain the full-length sequence of the daphnid ecdysteroid receptor and assess levels of receptor expression (along with RXR receptor expression levels) in response to various hormone treatments and manipulations. Finally, we will obtain the full-length sequence of the daphnid HR38 (NR4A) and HR3 receptors and investigate the involvement of these receptors in juvenoid signaling activity.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 22 publications||9 publications in selected types||All 9 journal articles|
|| Gorr TA, Rider CV, Wang HY, Olmstead AW, LeBlanc GA. A candidate juvenoid hormone receptor cis-element in the Daphnia magna hb2 hemoglobin gene promoter. Molecular and Cellular Endocrinology 2006;247(1-2):91-102.
|| Wang HY, Olmstead AW, Li H, LeBlanc GA. The screening of chemicals for juvenoid-related endocrine activity using the water flea Daphnia magna. Aquatic Toxicology 2005;74(3):193-204.
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