2007 Progress Report: Center for Children’s Environmental Health Research – Mechanisms of Pesticide Neuro- and Immunotoxicity

EPA Grant Number: R831710C003
Subproject: this is subproject number 003 , established and managed by the Center Director under grant R831710
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: University of California Berkeley Center for Children’s Environmental Health Research
Center Director: Eskenazi, Brenda
Title: Center for Children’s Environmental Health Research – Mechanisms of Pesticide Neuro- and Immunotoxicity
Investigators: Holland, Nina T. , Casida, John , Lipsett, Michael , Tager, Ira
Institution: University of California - Berkeley
EPA Project Officer: Callan, Richard
Project Period: May 1, 2004 through October 31, 2008 (Extended to October 31, 2010)
Project Period Covered by this Report: May 1, 2007 through October 31, 2008
RFA: Centers for Children's Environmental Health and Disease Prevention Research (2003) RFA Text |  Recipients Lists
Research Category: Health Effects , Children's Health , Health

Objective:

The Specific aims of this project are:

  1. To examine the in vitro effects of the organophospate (OP) pesticide chlorpyrifos, the carbamate maneb, dust mite allergen (Der p1), alone and in combination, on the production of Th1/Th2 cytokines.
  2. To determine whether pesticide and allergen exposures differentially affect in vitro cytokine expression in lymphocytes of children versus those of adults.
  3. To establish a mechanism-based new enzymatic assay for “neuropathy target esterase” (NTE) in human adult lymphocytes and neuroblastoma cell line.
  4. To determine the ontogenetic changes in NTE activity in human fetus, child and adult.
  5. To determine the sensitivity of NTE in fetal and adult lymphocytes to known NTE inhibitors and to test the relative sensitivity of NTE and AChE to these inhibitors.
  6. To determine the sensitivity of NTE in fetal versus adult lymphocytes to widely used pesticides in their bioactivated form.

Progress Summary:

Specific Aims 1 and 2: Immunotoxicity of pesticides and allergens
In Year 4, we expanded the study of cytokines IL-10 (Th2) and IFNγ (Th1) in the CHAMACOS cohort to 5-year-old (60 month) children. Th1/Th2 cytokine balance is a measure of the severity and type of immune response. Th1 and Th2 cytokines have been found to be mutually inhib-itory; many conditions, such as asthma, result from dysregulation of the Th1/Th2 balance (Bellinhausen et al., 2006). Using methods we previously de-veloped and validated, we measured induction of intracellular cytokines in the blood of 60-month child-ren and compared them to values observed at 12 and 24 months. Significant Th1 increase with age was observed at 60 months (p< 0.005). Both Th1 and Th2 levels were higher during the rainy season than in the dry season (p=0.001), and these changes were linked with levels of ambient mold and pollen in the Salinas Valley. This finding suggests that childhood exposure to allergens may affect children’s cytokine profiles (Harley et al., submitted). Mean Th2 levels at age 5 were higher in children with doctor-diagnosed asthma at 24 months than in healthy children (p=0.04). GEE regression analysis shows that Th1 levels in both healthy and asthmatic children increased with age. The model coefficients for these two groups of children were 0.86 (p<0.0005) and 1.08 (p<0.0005), respectively.

Previously we have reported that combined in vitro treatment with endotoxin and chlopyrifos oxon produc-ed a greater cytokine response than endotoxin alone, whereas OPs (chlopyrifos and two metabolites) alone did not induce cytokines (Duramad et al., 2006). This year we explored response by gender. The response to chlopyrifos treatment was on average 61% lower in females (p=0.017), controlling for dose and age. We published a review paper summarizing the state-of-art science and challenges in assessing immunological biomarkers in children related to environmental exposure (Duramad et al., 2007).

Specific Aims 3-6: Neurotoxicity of pesticides
We made significant progress this year characterizing neuropathy target esterase (NTE)-related enzymes. NTE is the most studied secondary target of organophosphorus (OP) toxicants after acetylcholinesterase. OP inhibition and aging of brain NTE is associated with de-layed neuropathy. NTE is normally assayed with brain membranes as the paraoxon-resistant and mipafox-sensitive phenyl valerate hydrolysis. Using a physio-logically-based assay with brain tissue, lysophospha-tidylcholine (LysoPC) can be substituted for phenyl valerate with the same results. In June, we published findings suggesting that NTE assessment may be possible using blood (Vose et. al. 2007). Using palmitoyl LysoPC as the substrate, we found the same OP sensitivity and specificity profiles in human erythrocyte and lymphocyte tissues as in brain, suggesting that these tissues contain similar or identical enzymes. Erythrocyte lysophospholipase (LysoPLA) activity in stored CHAMACOS blood samples had high inter-individual variability. However, no difference was observed between newborns and mothers or between subjects with different genetic variants of the OP-detoxifying enzyme paraoxonase (PON1).

One of the most potent NTE inhibitors and delayed neurotoxicants, ethyl octylphosphonofluoridate (with an in vitro IC50 of 1 nM), gives strong and dose-dependent inhibition of erythrocyte and brain LysoPLA activities at 1 or 3 mg/kg ip in mice. In vitro and in vivo surveys with mice indicate that erythrocyte LysoPLA activity, despite its high sensitivity to designer compounds with long alkyl chains, is poorly sensitive to commercial OP pesticides. Thus, erythrocyte lysophosphatidylcholine (LysoPC) hydrolase inhibition is predictive of exposure to organophosphorus (OP) inducers of delayed neuropathy. Currently, we are assessing the relative contribution of NTE to erythrocyte LysoPC hydrolase activity by mass-spectrometry and other molecular methods. This work is being conducted by Sarah Vose, who successfully passed her qualifying exam and was advanced to PhD-candidacy.

Other activities: PON1
We completed analysis this year of multiple SNPs in the PON1 gene and enzymatic activity for all CHAMACOS mother-child pairs (maternal blood collected at delivery, child blood at age 2). These preliminary data allowed us to secure additional funding (Holland PI NIEHS RO1-supplement) to expand our study of functional genomics of paraoxonase to previously collected samples from African-American mothers and children from Oakland, CA.

Future Activities:

We plan to continue to study immunological profiles of CHAMACOS children with the goal of understanding the mechanisms by which pesticide and other environmental exposures impact health outcomes. We will focus on the basic science of lysophospholipases as alternative OP-targets using an “omics” approach and transgenic and knock-out mice.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other subproject views: All 21 publications 14 publications in selected types All 13 journal articles
Other center views: All 131 publications 106 publications in selected types All 98 journal articles
Type Citation Sub Project Document Sources
Journal Article Chevrier J, Eskenazi B, Bradman A, Fenster L, Barr DB. Associations between prenatal exposure to polychlorinated biphenyls and neonatal thyroid-stimulating hormone levels in a Mexican-American population, Salinas Valley, California. Environmental Health Perspectives 2007;115(10):1490-1496. R831710 (2005)
R831710 (Final)
R831710C001 (2007)
R831710C003 (2007)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Journal Article Duramad P, Harley K, Lipsett M, Bradman A, Eskenazi B, Holland NT, Tager IB. Early environmental exposures and intracellular Th1/Th2 cytokine profiles in 24-month-old children living in an agricultural area. Environmental Health Perspectives 2006;114(12):1916-1922. R831710 (2005)
    R831710 (Final)
    R831710C001 (2006)
    R831710C001 (2007)
    R831710C002 (2006)
    R831710C003 (2006)
    R831710C003 (2007)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Journal Article Duramad P, Tager IB, Holland NT. Cytokines and other immunological biomarkers in children's environmental health studies. Toxicology Letters 2007;172(1-2):48-59. R831710 (2005)
    R831710 (Final)
    R831710C003 (2007)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Abstract: ScienceDirect-Abstract
    Exit
  • Journal Article Furlong CE, Holland N, Richter RJ, Bradman A, Ho A, Eskenazi B. PON1 status of farmworker mothers and children as a predictor of organophosphate sensitivity. Pharmacogenetics and Genomics 2006;16(3):183-190. R831710 (2004)
    R831710 (2005)
    R831710 (Final)
    R831710C001 (2007)
    R831710C003 (2006)
    R831710C003 (2007)
    R831709 (2005)
    R831709 (2006)
    R831709 (2007)
    R831709C002 (2006)
  • Abstract from PubMed
  • Abstract: Pharmacogenetics and Genomics-Abstract
    Exit
  • Other: National Center for Farmworker Health-Full Text PDF
    Exit
  • Supplemental Keywords:

    organophosphate, carbamate, allergen, pesticides, neuropathy target esterase, cytokines, Th1, Th2,, RFA, Health, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, PESTICIDES, Health Risk Assessment, Children's Health, Pesticide Types, Risk Assessment, health effects, pesticide exposure, community-based intervention, immune system effects, airway disease, environmental risks, respiratory problems, Human Health Risk Assessment, assessment of exposure, childhood respiratory disease, insecticides, children's environmental health, environmental health hazard, outreach and education, agricultural community, allergen

    Relevant Websites:

    http://www.chamacos.org Exit

    Progress and Final Reports:

    Original Abstract
  • 2004 Progress Report
  • 2005 Progress Report
  • 2006 Progress Report
  • 2008
  • 2009
  • Final

  • Main Center Abstract and Reports:

    R831710    University of California Berkeley Center for Children’s Environmental Health Research

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R831710C001 Center for Children’s Environmental Health Research – CHAMACOS Community Based Research Project
    R831710C002 Center for Children’s Environmental Health Research – Pesticide Exposure Assessment Project
    R831710C003 Center for Children’s Environmental Health Research – Mechanisms of Pesticide Neuro- and Immunotoxicity
    R831710C004 Center for Children’s Environmental Health Research – Community Outreach and Translation Core