Grantee Research Project Results

2007 Progress Report: Systems Approach to Assessing Cumulative Exposure to Endocrine Disrupting Chemicals

EPA Grant Number: R832739
Title: 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, 2006 through September 30,2007
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:

The effective assessment of risk associated with endocrine-disrupting chemicals (EDCs) requires the development of tools with which exposure to the chemicals can be assessed. The overall objective of this research program is to develop an approach for evaluating cumulative exposure to EDCs based upon changes in gene expression in whole organisms.

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, field deployment, and 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 terpenoid 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 have identified a suite of gene products that will comprise our holistic, systems approach to measuring alterations in endocrine signaling following exposure to EDCs.

Task:

Generate gene-specific, functional primer sets. Percent complete: 100
Optimize conditions for high efficiency quantitative real time RT-PCR of the gene products.

Aim 2) Evaluate the performance and versatility of the biomarkers of exposure
Percent complete: 100

Exposures have been performed with 26 individual compounds and six surface water samples from concentration animal feeding operations (CAFOs). Responses of the gene battery to these exposures have been assessed. The individual compounds used in these exposures have included steroid receptor agonists/antagonists, terpenoid receptor agonists/antagonists, steroid and terpenoid hormone synthesis inhibitors, and compounds of varied activities including many not known to elicit endocrine-disrupting activity. Conclusions drawn from the results include the following:

The genes EcR1/HR3/FTZ/VTG1/VTG2 are positively regulated and HB2 is negatively regulated by ecdysteroids. Acetone, naphthalene, diethylstilbesterol, and chlordane were identified as possible xeno-ecdysteroids.
The genes HB1/HB2 are positively regulated and VTG2 is negatively regulated by terpenoids. Fenoxycarb, pyriproxfen, methoprene, atrazine, and triclosan were all identified as possible terpenoids receptor agonists.
The genes HR78/HSP90 appear to be co-regulated though the mechanism of regulation remains eleusive. Atrazine, DEET, and pyrene increased the expression of these genes; while, kinoprene, 4- nonylphenol, and pentachlorophenol decreased their expression.
The gene VTG2 is highly susceptible to induction by diverse xenobiotics. We hypothesize that VTG2 is induced by and serves to scavenge xenobiotics; while VTG1 is the vitellogenin from primarily packaged into embryos. Such as scenario would serve to minimize maternal transfer of toxic materials to the embryo. VTG2 was induced by kinoprene, piperonyl butoxide, 4-nonylphenol, testosterone, bisphenol A, diethylstilbesterol, fenarimol, zinc, pentachlorphenol, methylene chloride, chloroform, naphthalene, cadmium.
Exposure to surface waters from CAFO-rich locations caused multiple changes in the expression of genes in the battery that indicative of altered ecdysteroid signaling.

Aim 3) Evaluate the ability of the gene battery to detect EDC exposure associated with chemical mixtures
Percent complete: 0

Work has not begun on the study of chemical mixtures.

Future Activities:

Planned Activities:

Link specific responses of the gene battery to phenotypic changes in the daphnids
Model responses of the gene battery to defined chemical mixtures
Experimentally test the model predictions

Journal Articles on this Report : 3 Displayed | Download in RIS Format

Publications Views
Other project views:	All 16 publications	16 publications in selected types	All 16 journal articles

Publications
Type	Citation	Project	Document Sources
Journal Article	LeBlanc GA. Crustacean endocrine toxicology: a review. Ecotoxicology 2007;16(1):61-81.	R832739 (2007) R832739 (Final) R826129 (Final) R831300 (Final)	Abstract from PubMed Abstract: Springer-Abstract Exit
Journal Article	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)	Full-text from PubMed Abstract from PubMed Associated PubMed link Full-text: IJBS-Full Text HTML Exit Other: IJBS-Full Text PDF Exit
Journal Article	Wang YH, Wang G, LeBlanc GA. Cloning and characterization of the retinoid X receptor from a primitive crustacean Daphnia magna. General and Comparative Endocrinology 2007;150(2):309-318.	R832739 (2006) R832739 (2007) R832739 (Final) R831300 (2006) R831300 (Final)	Abstract from PubMed Full-text: ScienceDirect-Full Text HTML Exit Abstract: ScienceDirect-Abstract Exit Other: ScienceDirect-Full Text PDF Exit

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, rapid detection, chemical exposure, deconvolution technique, endocrine disrupting chemicals, reporter gene approaches, endocrine disruptors, sensor, human health risk, biomarker based exposure inference

Relevant Websites:

http://www.tox.ncsu.edu/faculty/leblanc/ Exit
http://www.ncsu.edu/project/toxresearch/projects/ Exit

Progress and Final Reports:

Original Abstract

The 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.