2013 Progress Report: Genetic Susceptibility

EPA Grant Number: R834514C004
Subproject: this is subproject number 004 , established and managed by the Center Director under grant R834514
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: University of Washington Center for Child Environmental Health Risks Research (2010)
Center Director: Faustman, Elaine
Title: Genetic Susceptibility
Investigators: Faustman, Elaine
Current Investigators: Furlong, Clement
Institution: University of Washington
EPA Project Officer: Callan, Richard
Project Period: September 25, 2009 through September 24, 2015 (Extended to September 24, 2016)
Project Period Covered by this Report: September 25, 2012 through September 24,2013
RFA: Children's Environmental Health and Disease Prevention Research Centers (with NIEHS) (2009) RFA Text |  Recipients Lists
Research Category: Children's Health , Health

Objective:

Since 1998, researchers of the University of Washington Center for Child Environmental Health Risks Research (the Center) have been using a multi-disciplinary research approach working in the lab, in the field, and in the community to understand the mechanisms that define children's susceptibility to pesticides, identify the implications of this susceptibility for development and learning, and partner with our communities to translate our findings into risk communication, risk management, and prevention strategies. The Center is jointly funded by the National Institute of Environmental Health Sciences (NIEHS) and the Environmental Protection Agency (EPA).

The Center is administratively housed within the Institute for Risk Analysis and Risk Communication, also directed by Center Director Dr. Elaine M. Faustman, which is in the University of Washington's School of Public Health. The Center includes partnerships with the Fred Hutchinson Cancer Research Center and the Yakima Valley community, located in the agricultural center of Washington State, to jointly sponsor a Community Based Participatory Research (CBPR) Project aimed at reducing childhood pesticide exposure.

All Center efforts are highly integrated with two field-based research projects, two laboratory-based research projects, three facility cores, an Administrative Core, and Faculty Development Investigator.

The specific objectives of the laboratory-based research projects—a molecular mechanisms research project and a genetic susceptibility research project—are:

  1. To identify cellular, biochemical and molecular mechanisms that cause adverse developmental neurotoxicity of pesticides; and
  2. To identify susceptibility factors for developmental neurotoxicity of pesticides.

Activities of the Genetic Susceptibility Research Project have contributed to a greater understanding of the role of gene-environment interactions that define children's susceptibility to OP pesticides. This project interacts with many of the lab and field-based CHC projects as well as with many external collaborators. In particular, this project interacts with the Centers for Disease Control and Prevention (CDC), Environmental Protection Agency (USEPA) Region 10, Agency for Toxic Substances and Disease Registry (ATSDR), the University of California Berkeley Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), Washington State Department of Health, Washington State Pesticide Incident and Reporting Panel (PIRT), other US government agencies, the United Kingdom (UK) Committee on Toxicity and several members of the UK Parliament.

The overall goal of the Genetic Susceptibility Research Project is to develop specific biomarkers of exposure to OP compounds, and to use these biomarkers to explore gene-environment interactions related to genetic variability in the paraoxonase (PON1) gene, particularly with respect to OP exposures that occur during early development. The results of this project have helped create new more sensitive techniques for assessing pesticide exposure and greatly contributed to our understanding of how genetic differences in pesticide metabolism pathways impact adverse health responses across the life-course.

Progress Summary:

This project is developing many new techniques for the detection of adducts in blood samples that are associated with specific pesticide exposures. Highlights of the past year include experiments demonstrating that a single step immunomagnetic bead protocol will purify butyrylcholinesterase (BuChE) from plasma and acyl peptide hydrolase (APH) from red cell extracts. The OP adducts to these proteins have been identified. The serine adduct from the active metabolite of tri-cresyl phosphates was found to undergo a unique aging reaction. In vitro inhibition of BuChE with the active metabolite of TCP, cyclic saligenin cresyl phosphate (CBDP) generated both a cresyl phosphoserine and an aged phosphoserine. However, in samples from exposed individuals, only the fully aged phosphoserine modification was observed. More recent experiments have shown that acetyl cholinesterase (AChE) does not age in the same way and retains a cresyl group. We are currently developing methods to process samples for characterizing this adduct. Further, we have generated deuterated metabolite CBDP for generating in vitro heavy isotope labeled AChE for use as an internal standard. Characterization of the adducts on the active site serine of BuChE inhibited in vitro with chlorpyrifos oxon (CPO) showed the expected di-ethyl and aged mono-ethyl adducts while inhibition with azinphos methyl oxon generated the di-methyl and aged mono-ethyl serine adducts. An excellent correlation between our methods was developed. This was for the single step MS analysis of the active site serine of BuChE compared with the BuChE activity inhibition measurements made with thinning and non-spray season blood samples. These new techniques allow us quantify the effects of pesticide exposure with only one blood sample, rather than the requisite two samples needed by most current protocols.

One of the primary aims of this project in the previous funding period was to evaluate the effects of exposure to CPO during early postnatal development and to determine the role of the human PON1-Q192R polymorphism in modulating these effects, using multiple endpoints of OP toxicity. In the previous year, pilot studies were completed that determined steep chronic dose-response curves for inhibition of uBChE and AChE in pregnant and non-pregnant mice. Timed-matings and exposures of pregnant mice were completed. Mice with copulatory plugs were exposed transdermally to CPO daily. Dams were sacrificed and fetal and maternal tissues were dissected for measurement of enzyme inhibition in different tissues. The PON1 status of the dam was found to clearly influence CPO toxicity to the fetus. RBC APH was found to be the most sensitive biomarker of CPO exposure, a particularly interesting finding given the potential importance of brain APH for cognition. A manuscript describing these data is in preparation. Because these same polymorphisms exist in human populations, understanding the changes in susceptibility of pregnant mice with varying PON1-status will help characterize human variability and identify similarly susceptible populations.

Additionally, a positive, linear correlation was found between plasma PON1 activity and AChE level of both brain and diaphragm in treated mice, indicating that plasma PON1 can serve as a susceptibility biomarker for DZO toxicity. Our research found that RBC APH is a useful biomarker for DZO exposure because of a good correlation between APH inhibition and AChE inhibition in brain and diaphragm. A manuscript describing these findings is now in preparation.

Future Activities:

The highlights above illustrate the high volume and quality of the Center's efforts aiming at reducing the adverse effects of environmental pesticide exposures in children. The Center continues to work to understand the mechanisms that define children's susceptibility to pesticides, identify the implications of this susceptibility for health impacts on development and learning, and partner with our communities to translate our findings into risk communication, risk management, and prevention strategies. Center researchers continue to work in the lab, in the field, and in the community to bring a unique and successful approach to the study of children's environmental health.

Journal Articles:

No journal articles submitted with this report: View all 55 publications for this subproject

Supplemental Keywords:

RFA, Health, Scientific Discipline, INTERNATIONAL COOPERATION, ENVIRONMENTAL MANAGEMENT, Biochemistry, Environmental Monitoring, Children's Health, Environmental Policy, Biology, Risk Assessment, pesticide exposure, age-related differences, pesticides, children's vulnerablity, biological markers, agricultural community

Relevant Websites:

Center for Child Environmental Health Risks Research | Department of Environmental & Occupational Health Sciences | University of Washington School of Public Health Exit

Progress and Final Reports:

Original Abstract
  • 2010
  • 2011 Progress Report
  • 2012
  • 2014
  • 2015 Progress Report
  • Final Report

  • Main Center Abstract and Reports:

    R834514    University of Washington Center for Child Environmental Health Risks Research (2010)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R834514C001 Community-Based Participatory Research
    R834514C002 Pesticide Exposure Pathways
    R834514C003 Molecular Mechanisms
    R834514C004 Genetic Susceptibility