can be learned from looking in the reverse direction. Examples includelow-cost technology that may not typically be considered for use inhigh-technology, high-cost health care delivery systems; and strategiesto engage and help meet the prenatal care needs of vulnerablepopulations such as refugees and/or recent immigrants.

doi:10.1016/j.ntt.2012.05.034

NBTS 34Potential use of 'omics data in a mode-of-action analysis ofneurobehavioral toxicity of methylmercury

Ambuja Balea, David Szabob, Raghu Natha, Suryanarayana VulimiriaaORD/NCEA, Washington, DC, United StatesbORISE/ORD/NCEA, Washington, DC, United States

Methylmercury is one of the most studied developmentalneurotoxicants. Although mechanisms of neurotoxicity have beenhighly characterized for methylmercury, the early key events prior tothe resultant effect have not been incorporated into a mode-of-actionanalysis. In this evaluation, metabolomic, genomic, and proteomic datawere reviewed and may be informative of early changes in theneurotoxicological mode(s) of action for methylmercury. Many me-chanisms of neurotoxicity exist for methylmercury and are dependenton exposure level, but this evaluation focused on integrating the 'omicsdata into oxidative stress mechanisms observed with this compound,which ultimately leads to cytotoxicity. Recently, in an in vitrometabolomics study with methylmercury, several putative biomarkerswere identified including γ-aminobutyric acid (GABA), choline, gluta-mine, creatine, and spermine (van Vliet et al., 2008). Decreased levels ofGABA and choline in the in vitrometabolomic studymay help to explainthe observed decreases in neuronal enzymatic activity (e.g., glutaminesynthetase, choline acetyltransferase) from traditional biochemicalassays (Monnet-Tschudi et al., 1996; Eskes et al., 2002), which thenleads to neuron-specific toxicity. Genomic evaluations concur with themetabolomic findings in that methylmercury downregulates cell-cycleregulated genes and has a significant impact on antioxidant genes (Yu etal., 2010). This information also correlateswith theobserved increases inapoptotic cell death associatedwithmethylmercury. The 'omics data formethylmercury add to the mechanistic profile of this compound andhelp establish a temporality of the key events leading to cytotoxicity inthe brain. (Disclaimer: The views expressed are those of the author anddo not necessarily represent those of the U.S. EPA.)

doi:10.1016/j.ntt.2012.05.035

NBTS 35Systems biology approach for better understanding ofmechanisms of neurodevelopment toxicity: A case study usingthe major flame retardant HBCD

David Szaboa, Ruchir Shahb, Susan Sumnerc, Linda Birnbaumd

aORISE/NCEA/USEPA, Washington DC, United StatesbSRA, RTP, United StatescRTI, RTP, United StatesdNCI/NIEHS, RTP, United States

A systems biology approach provides a promising platform forelucidating mechanistic pathways associated with developmentalneurotoxicity (DNT). Transcriptomics and metabolomic approachescan be used to unmask low-dose toxicity not assessable by conventional

testing, identify vulnerable developmental periods, test across species,and validate high throughput in vitro assays. We evaluated short-termdisruptions to the developmental profile of circulating metabolites inthe blood and genes in the hippocampus, a brain region involved inlearning and memory, after exposure to hexabromocyclododecane(HBCD). HBCD is a flame-retardant mixture of 3 isomers (α, β, γ); γdominates themixture, whileα dominates in human blood/breastmilk.In mice, infantile exposure to HBCD is known to disrupt adultneurobehavioral function. Using a similar model, we examined serummetabolite profiles and hippocampal gene transcript changes after anacute exposure on postnatal day 10 to the mixture, α, or γ. Geneexpressionprofilesdifferedbetweenα,γ, and themixture (p-value<0.05and fold change >1.5) and their differences were also reflected whenmeasuring endogenous serum metabolites. α had the most robustchanges in gene expression number, magnitude, and enrichment ofcanonical signaling pathways (α, 38; mixture, 18; and γ, 11 pathways). Atop pathway identified as altered by all exposures was involved in long-termpotentiation, (α, p=0.002;mixture, p=0.03; andγ, p=0.04),withan overall depression/delay in mechanistic function. These data suggestthat developmental exposure to HBCD can alter the timing and possiblestructure of synaptogenesis, underlying thepreviously reporteddeficits inlearning andmemory.Metabolomics data confirmeddifferences betweenthe three treatment groups and is a promising platform for non-invasivebiomarker identification. The different profiles generated with eachisomer in the mixture suggest the necessity to assess the effects from theisomers as well as the mixture. Evaluation of several biological matrices(serum and brain) can further uncover the mode-of-action and increasethe weight-of-evidence. We demonstrate the utility of a system biologystrategy using 'omics to capture information on various aspects of braindevelopment that can be altered with environmental exposures.(Disclaimer: Views are of the authors and do not necessarily representviews and/or policies of USEPA/NCI/NIEHS.)

doi:10.1016/j.ntt.2012.05.036

NBTS 36Ex vivo models and chemical neurotoxicity assessment

Andrew Kraft, Ambuja BaleNational Center for Environmental Assessment, Office of Research andDevelopment, U.S. Environmental Protection Agency, Washington, DC,United States

Growth of explanted CNS tissues in vitro represents an expandingfield with the potential to address the disconnect that exists between invivo systems and dissociated cell cultures. The accessibility of thesecultures allows for: control over exposure conditions, includingmanipulation of co-exposure or susceptibility factors; real-time visua-lizationof discrete cells and cell components (e.g., dendritic spines); andevaluation of network and niche-dependent processes such as electro-physiology, plasticity, metabolism, neurogenesis, and synaptogenesis. Akey advantage of these cultures is that they allow for observations of cellpopulations of interest within an intact biological matrix. As explantscan be cultured from various CNS tissues, regions, and networkedneuronal nuclei, they are conducive to region-specific interpretations oftoxicity and evaluation of network responses to insults such asinflammation, physical trauma, and deafferentation. Additionally, someof these effects can be assessed in cultures derived from adult animals,including those with a mature underlying disease phenotype. Theapplication of these models to chemical neurotoxicity assessmentpresents a unique constellation of data with a complicated array ofstudy design variables to consider. For example, the explantationprotocols, although not as disruptive as preparation of dissociatedcultures, cause robust and transient responses related to deafferenta-

NBTS 2012 Abstracts 379