Grantee Research Project Results
2008 Progress Report: Systems Approach to Assessing Cumulative Exposure to Endocrine Disrupting Chemicals
EPA Grant Number: R832739Title: Systems Approach to Assessing Cumulative Exposure to Endocrine Disrupting Chemicals
Investigators: LeBlanc, Gerald A.
Institution: North Carolina State University
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 2005 through September 30, 2008 (Extended to September 30, 2009)
Project Period Covered by this Report: October 1, 2007 through September 30,2008
Project Amount: $585,206
RFA: Exposure Measurement Tools for Endocrine Disrupting Chemicals in Mixtures (2005) RFA Text | Recipients Lists
Research Category: Endocrine Disruptors , Environmental Justice , Human Health , Safer Chemicals
Objective:
Progress Summary:
Aim 1) Identify a suite of gene-expression, whole organism based biological markers that specifically respond to modulators of hormone-signaling pathways.
Percent complete: 100
The whole organism model selected for use in this program is the water flea Daphnia magna. This species is small and easily cultured. It is conducive the lab exposures and field deployment. Furthermore, members of this genus are ubiquitous in freshwater environments allowing for field sampling and evaluation. Finally, the endocrinology of daphnids has been well described. We selected two endocrine signaling pathways that function autonomously and in combination to regulate various activities related to development, growth, and reproduction in daphnids: the ecdysteroid signaling pathway and the juvenoid signaling pathway. These pathways are representative of steroid and retinoid signaling pathways, respectively, in vertebrates.
Using targeted PCR with consensus-degenerate hybrid oligonucleotide primers along with bioinformatics searches of the newly-released Daphnia pulex genome, we identified a suite of gene products that will comprise our holistic, systems approach to measuring alterations in endocrine signaling following exposure to EDCs.
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Task:
- Generate gene-specific, functional primer sets. Percent complete: 100
- Optimize conditions for high efficiency quantitative real time RT-PCR of the gene products. Percent complete: 100
Aim 2) Evaluate the performance and versatility of the biomarkers of exposure
Percent complete: 100
Daphnids were exposed to a suite of ~30 different chemicals to evaluate changes in the expression of the gene batter that is indicative of ecdysteroidal activity, anti-ecdysteroidal activity, juvenoid activity, and anti-juvenoid activity. Daphnids also were acutely exposed to field-collected samples and chronically exposed to known endocrine active substances. Changes in gene expression were evaluated as an indicator of exposure to endocrine-disrupting chemicals. With chronic exposures, changes in gene expression were evaluated in the context of phenotypic alterations in the organisms. Finally, the time-course of expression of diagnostic genes in response to exposure to hormonally-active compounds was evaluated. These analyses revealed that changes in expression of the gene battery was diagnostic of exposure to endocrine disrupting chemicals and the duration of exposure to endocrine active chemicals can significantly impact the expression profile of the diagnostic genes.
Aim 3) Evaluate the ability to detect EDC exposure associated with chemical mixtures
Percent complete: 50
In the course of this study, we identified a need to develop a means of confirming endocrine activity as indicated by the response of the gene battery and to mechanistically characterize interactions among chemicals constituting mixtures of endocrine active compounds. We therefore constructed reporter systems in which a luciferase gene is activated and generates luminescence in response to ecdysteroid receptor (EcR) agonist and antagonists, and retinoid X recetpor (RXR) agonists and antagonists. The reporters systems were highly effective in their respective functions and we demonstrated, for the first time, that the crustacean RXR is ligand activated. We also discovered using these reporters that juvenoids (juvenile hormone III, methyl farnesoate, pyriproxyfen) have the ability to bind the RXR component of RXR:EcR heterodimers and enhance gene transcription associated with ecdysteroids. Thus, the reporter systems can be used to assess exposure to chemicals resulting in synergistic outcomes.
Future Activities:
- Provide a mechanistic basis for synergistic activities among EDC's using the reporter assays.
- Model synergistic outcomes of EDC combinations.
- Test model predictions with respect to changes in the gene battery following whole organism exposure to the combinations.
Journal Articles on this Report : 7 Displayed | Download in RIS Format
| Other project views: | All 16 publications | 16 publications in selected types | All 16 journal articles |
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Crain DA, Eriksen M, Iguchi T, Jobling S, Laufer H, LeBlanc GA, Guillette Jr. LJ. An ecological assessment of bisphenol-A:evidence from comparative biology. Reproductive Toxicology 2007;24(2):225-239. |
R832739 (2008) |
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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. |
R832739 (2008) R829358 (Final) R831300 (2005) R831300 (2006) R831300 (Final) |
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Mu XY, Rider CV, Hwang GS, Hoy H, LeBlanc GA. Covert signal disruption: anti-ecdysteroidal activity of bisphenol A involves cross talk between signaling pathways. Environmental Toxicology and Chemistry 2005;24(1):146-152. |
R832739 (2008) R829358 (2004) R829358 (Final) R831300 (2004) R831300 (Final) |
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Olmstead AW, LeBlanc GA. The environmental-endocrine basis of gynandromorphism (intersex) in a crustacean. International Journal of Biological Sciences 2006;3(2):77-84. |
R832739 (2006) R832739 (2007) R832739 (2008) R832739 (Final) R831300 (Final) |
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Rider CV, Gorr TA, Olmstead AW, Wasilak BA, LeBlanc GA. Stress signaling: coregulation of hemoglobin and male sex determination through a terpenoid signaling pathway in a crustacean. Journal of Experimental Biology 2005;208(Pt 1):15-23. |
R832739 (2008) R829358 (Final) R831300 (2004) R831300 (2006) R831300 (Final) |
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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. |
R832739 (2008) R831300 (2005) R831300 (Final) |
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Wang YH, LeBlanc GA. Interactions of methyl farnesoate and related compounds with a crustacean retinoid X receptor. Molecular and Cellular Endocrinology 2009;309(1-2):109-116. |
R832739 (2008) R832739 (Final) |
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Supplemental Keywords:
exposure assessment, endocrinology, computational toxicology;, Health, Scientific Discipline, POLLUTANTS/TOXICS, Health Risk Assessment, Risk Assessments, Chemicals, Environmental Monitoring, cumulative exposure, chemical mixtures, human exposure, genetic analysis, chemical exposure, rapid detection, deconvolution technique, endocrine disrupting chemicals, reporter gene approaches, endocrine disruptors, sensor, human health risk, biomarker based exposure inferenceRelevant Websites:
http://service004.hpc.ncsu.edu/toxicology/faculty/leblanc/index.htm Exit
http://www.ncsu.edu/project/toxresearch/projects/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.