The Toxicologist - Society of Toxicology

time intervals. The percentage increase ranged from ~5% to ~15% with the largest
increases seen at 500 ppm TCE with 500 ppm CHCl3. These model simulations
indicate that increased blood concentrations of TCE (and increased neurotoxicity)
may result from co-exposure to CHCl3. Similar simulations conducted with our
human model (currently under development) will allow us to evaluate the degree of
increased risk at low concentrations typically seen in the environment and at high
concentrations that might result from accidental or intentional chemical releases.
(This abstract does not reflect EPA policy.)
1582 A COMPUTATIONAL FRAMEWORK FOR
CUMULATIVE RISK ASSESSMENT.
D. A. Sarigiannis 1, 2 , A. Gotti 3 and S. Karakitsios 1 . 1 Institute for Health and
Consumer Protection, European Commission - Joint Research Centre, Ispra, Varese,
Italy, 2 Chemical Engineering Department Aristotle University of Thessaloniki,
Thessaloniki, Greece and 3 CPERI, CERTH, Thermi, Greece. Sponsor: T. Hartung.
The complexity in quantitatively estimating human exposure to environmental
chemicals originates from the need to assess their aggregate and cumulative exposure;
the assessment becomes even more complex when mixture effects need to be
taken into account. In this study a framework for quantitative cumulative assessment
of the biologically effective dose of several interacting environmental chemicals
is developed in order to better take into account biomarkers of exposure towards
compiling the exposome. The integrated modelling environment was
implemented in a single computational platform (asclXtreme) including emissions,
dispersion, exposure modelling, internal dose and health risk. A central novel component
of the platform is a generic Physiology Based ToxicoKinetic/Dynamic
(PBTK/D) model, coupled to a Biology Based Dose Response (BBDR) model.
Uncertainty and variability of the affecting parameters were estimated through
Marcov Chain Monte Carlo. Risk from co-exposure to benzene, toluene, ethylbenzene
and xylenes (BTEX) were selected as case study under different environmental
exposure scenarios. The methodology permits the estimation of health risks capturing
the continuously changing environmental and biological dynamics. The integrated
modeling platform was tested in several BTEX exposure scenarios (occupational
and environmental). The estimation of both cancer and neurotoxicity risk
due to benzene and toluene was much refined when the internal dose of the parent
substance and its metabolites rather than only personal exposure linked to epidemiological
relations was taken into account. This is due to two reasons: (a)
Aggregation of exposure through different microenvironments with continuously
changing concentrations results in differences in the daily variation time profile of
external exposure and internal dose; (b) The presence of co-exposure to the other
VOCs in the mixture affects the levels of benzene metabolites through inhibition of
benzene metabolism.
1583 USE OF A CUSTOM RT-PCR ARRAY TO ANALYZE
TOXICITY PATHWAYS AT DIFFERENT LIFE STAGES IN
BROWN NORWAY RAT BRAIN FOLLOWING ACUTE
TOLUENE EXPOSURE.
J. E. Royland 1 , P. R. Kodavanti 2 , G. W. Knapp 1 and R. C. MacPhail 2 . 1 Integrated
Systems Toxicology Division U.S. EPA, Research Triangle Park, NC and 2 Toxicity
Assessment Division, U.S. EPA, Research Triangle Park, NC.
To investigate the contribution of different life stages on response to toxicants, we
utilized a custom designed RT-PCR array to examine the effects of acute oral exposure
of the volatile organic solvent toluene (0, 0.65 or 1.0 g/kg) in the brains of
male Brown Norway rats at 4, 12 and 24 months of age. Toluene is a known neurotoxicant
with effects on cognition, motor activity and neurotransmitters in the
central nervous system. The objective was to explore the toxicity pathways that contribute
to the adverse effects of toluene exposure, and to determine if the response
is age-dependent. In this study, we examined gene expression in cerebellum, striatum,
hippocampus and frontal cortex 4 hours post-dosing using a custom RT-PCR
array containing 30 genes representing key toxicity pathways involving energy metabolism,
oxidative stress, neuronal plasticity, immune and stress responses. Results
showed that the effect of age exceeded that of toluene on the number of genes affected
(approx 2 to 5x depending on brain area). With the exception of the toluene
effect in striatum, percent of up regulation (averaged ~80% with age and near
100% with toluene) exceeded that of down regulation in this subset of genes selected
as possible markers of susceptibility. Based on number of genes affected, cerebellum
displayed the greatest sensitivity. However, based on direction of expression
changes, striatum was most vulnerable. These data indicate that response to toxicant
exposure is impacted by life stage, which, in itself, affects gene expression levels.
Data also indicate variability in response across brain areas, with degree and direction
of change depending upon condition tested. These ongoing studies
contribute to defining a genomic model of toxicity pathways in the nervous system
and their modification with aging. (This abstract does not necessarily reflect U.S.
EPA policy).
340 SOT 2011 ANNUAL MEETING
1584 COMPARATIVE ANALYSIS OF TCDD-ELICITED GENE
EXPRESSION PROFILES IN HUMAN, MOUSE, AND
RAT PRIMARY HEPATOCYTES.
E. Dere, A. L. Forgacs and T. R. Zacharewski. Michigan State University, East
Lansing, MI.
TCDD is a ubiquitous environmental contaminant that induces species-specific effects.
A comparative approach was utilized to examine TCDD-elicited time- and
dose-dependent differential hepatic gene expression in human, mouse, and rat primary
hepatocytes isolated from immature Sprague-Dawley rats, CD-1 mice and 3
post-menopausal, non-obese, non-smoking Caucasian donors, respectively. Cells
were treated with 10 nM TCDD or DMSO vehicle control for 1, 2, 4, 8, 12, 24
and 48 h, or with 0.001, 0.01, 0.1, 1, 10 or 100 nM TCDD for 12 and 24 h.
Whole-genome microarrays identified 2423, 763 and 541 differentially expressed
genes across time in human, mouse, and rat hepatocytes, respectively (P1(t)>0.9
and |fold change|>1.5). Only 17 orthologs were responsive to TCDD in all three
species, including Cyp1a1, Cyp1a2 and Tiparp. Cyp1a1 exhibited dose-dependent
induction in all species with EC50 values of 0.04 nM for human, 0.05 nM for
mouse, and 0.02 nM for rat hepatocytes at 12 h. However, commonly regulated
genes across all species exhibited divergent expression profiles. For example, Bcl2like
11, apoptosis facilitator (Bcl2l11) was induced by TCDD in the mouse and rat
~2-4-fold but repressed ~4-fold in the human hepatocytes. Meanwhile, 2097, 533
and 400 genes were unique to the mouse, rat and human, respectively, demonstrating
that the majority of TCDD-elicited changes were species-specific. Functional
annotation of differentially regulated genes identified processes related to lipid metabolism,
molecular transport and cellular growth, and proliferation in all three
species, suggesting conserved modes of action but different mechanisms of action.
Thus, although the AhR and its signaling mechanism is highly conserved, speciesspecific
gene expression profiles likely determine the species-specific effects of
TCDD. Funded by SBRP P42ES04911.
1585 DESCRIPTIVE ’OMICS OF ACETAMINOPHEN IN
HUMANS.
M. Jetten 1 , S. Gaj 1 , A. Ruiz-Aracama 2 , T. de Kok 1 , J. van Delft 1 , S. Claessen 1 ,
A. Lommen 2 , A. Peijnenburg 2 , L. Pellis 3 , E. van Someren 3 , R. Stierum 3 and J.
Kleinjans 1 . 1 Health Risk Analysis & Toxicology, Maastricht University, Maastricht,
Netherlands, 2 Institute of Food Safety, RIKILT, Wageningen, Netherlands and
3 Quality of Life, TNO, Zeist, Netherlands. Sponsor: H. van Loveren.
Genomics and metabolomics, so called ‘omics technologies, have undergone major
improvements over the last decade. As a result, their applicability to human observational
studies has become feasible over the recent past. The present study aims at
investigating the capability of transcriptomic and metabolomic techniques to measure
low dose effects of the well-investigated hepatotoxic compound acetaminophen
(paracetamol or APAP) in blood/urine from healthy individuals. Both metabolomic
(NMR/UPLC-TOF-MS) and genomic (mRNA/miRNA arrays) technologies were
applied to a study on blood and urine from 6 healthy volunteers exposed to 0.5, 2
and 4 gram APAP/24 hours. Blood was collected after 0, 1, 7 and 24 hours of APAP
exposure and urine was collected both before and during the APAP exposure window.
The results showed the hepatotoxic phase I metabolites of APAP (NAPQIbound
metabolites) to increase with APAP dose. Also, several novel APAP metabolites
were identified. Transcriptomics analysis at the mRNA level indicated immune
and toxicity related pathways to be affected after 2 and/or 4 gram APAP/24 hour
exposure. miRNAs also indicated that similar pathways were affected. At the lowest
dose of 0.5 gram APAP/24 hours, the limit of detection of ‘omics analysis in
blood/urine from humans appears to be reached. Classic clinical test were not able
to detect responses indicative for liver toxicity in blood at any of the exposure doses.
From this we conclude that in ‘omic techniques are able to detect exposure to low
APAP doses and have the power of revealing a wealth of biological information.
Even though only therapeutic doses were used and there were no signs of overt liver
toxicity, effects related to both efficacy and toxicity were measured, supporting the
applicability of ‘omics as an observational tool for human studies.
1586 CISPLATIN-INDUCED GENOTOXIC STRESS IN
PRIMARY MOUSE HEPATOCYTES, MOUSE
EMBRYONIC STEM CELLS, AND HEPG2 CELLS.
L. Rieswijk 1, 2 , D. Lizárraga 1, 2 , K. Brauers 1 , B. van de Water 2, 3 , H. Vrieling 2, 3 ,
J. van Delft 1, 2 and J. Kleinjans 1, 2 . 1 Health Risk Analysis and Toxicology, Maastricht
University, Maastricht, Netherlands, 2 Netherlands Toxicogenomics Centre,
Maastricht, Netherlands and 3 Toxicogenetics, LUMC, Leiden, Netherlands. Sponsor:
H. van Loveren.
By focusing on relatively new fields of toxicogenomics, such as epigenetics and
microRNA (miRNA), this current NTC project tries to reveal novel mechanisms
by which genotoxic and non-genotoxic compounds could act. MiRNAs regulate