The Toxicologist - Society of Toxicology

2304 IN VITRO EXPOSURE AND EVALUATION OF MILITARY
FUELS AND BIOFUELS.
K. L. Mumy 1 , T. L. Doyle 1 , M. R. Okolica 1 , R. P. Adkins 1 and G. T. Eldridge 2 .
1 Naval Medical Research Unit - Dayton, Wright-Patterson AFB, OH and 2 Naval Air
Warfare Center Aircraft Division, Patuxent River, MD.
Widespread use of jet and marine fuels continues to make exposure risks a large
concern for military personnel. Recent advances in alternative fuels have provided
many new fuels for potential military use in the form of biofuels produced from
fats, oils, plant materials, etc. Despite being biologically-based, biofuels must still
be evaluated for their toxicity and biological effects. Two biofuels of interest to the
Navy are camelina and algal-based fuels to be blended with conventional fuels.
Initial toxicological evaluation of a camelina-based jet biofuel and algal-based marine
biodiesel indicates that these biofuels are non-mutagenic, as determined by the
bacterial reverse mutation assay, and less cytotoxic when compared to the standard
fuels, jet propulsion (JP)-5 and diesel fuel marine F76. An in vitro exposure to fuel
vapors alone revealed 90% remained viable following exposure
to camelina-based fuel vapor. However, the blended fuel vapor yielded viabilities
similar to JP-5 alone. Similarly, 95% were viable after algal-based biodiesel vapor exposure,
and exposure to the blended fuel vapor yielded viabilities comparable to F76
alone. Compounds present in the vapor phase of each of the fuels were identified by
solid phase microextraction with gas chromatography/mass spectrometry. This
method provides a screening tool to more appropriately mimic inhalation exposures
to fuel vapors using an in vitro system and identify components of complex mixtures
that may act directly at the cellular level to aid in identifying modes of action.
Biologically-based fuels provide a promising avenue in the development of alternative
fuels and these in vitro methodologies provide rapid and cost-effective means of
initially screening their toxicological effects in comparison to conventional fuels.
2305 DOSE-RESPONSE EVALUATION OF NON-ADDITIVE
HEPATIC EFFECTS OF PCB153 AND TCDD IN MICE.
A. K. Kopec 1, 2 , M. L. D’Souza 1, 2 , B. D. Mets 1 , L. D. Burgoon 1, 2 , J. R.
Harkema 2, 3 , C. Tashiro 4 , D. Potter 4 , B. Sharratt 4 , S. E. Reese 5 , K. J. Archer 5
and T. R. Zacharewski 1, 2 . 1 Biochemistry & Molecular Biology, Michigan State
University, East Lansing, MI, 2 Center for Integrative Toxicology, Michigan State
University, East Lansing, MI, 3 Pathobiology & Diagnostic Investigations, Michigan
State University, East Lansing, MI, 4 Wellington Laboratories, Inc., Guelph, ON,
Canada and 5 Biostatistics, Virginia Commonwealth University, Richmond, VA.
Interactions between environmental contaminants, such as dioxins and PCBs, can
lead to non-additive effects that may influence the risk assessment of a mixture. A
comprehensive dose-response evaluation of hepatic effects elicited by TCDD, nondioxin-like
PCB153 and their mixture was performed in immature, ovariectomized
C57BL/6 mice. Mice were orally gavaged once with TCDD (0.3, 1, 3, 6, 10, 15,
30, 45 μg/kg), PCB153 (3, 10, 30, 60, 100, 150, 300, 450 mg/kg), a mixture
(MIX: 0.3+3, 1+10, 3+30, 6+60, 10+100, 15+150, 30+300, 45+450 μg/kg TCDD
+ mg/kg PCB153, respectively) or sesame oil vehicle, and sacrificed 24 h post dose.
TCDD and MIX induced significant increases in relative liver weights (RLW) in all
but the lowest dose groups, while PCB153 significantly induced RLW only at 100
and 300 mg/kg. Complementary histopathology and gas chromatography/mass
spectrometry identified significant increases in lipid levels in the MIX groups compared
to either vehicle, TCDD or PCB153 alone. Hepatic PCB153 levels were also
significantly increased following TCDD co-exposure. Nonlinear logistic modeling
with quasi-likelihood estimates identified significant dose-dependent, non-additive
expression of Pla2g12a, Serpinb6a, Nqo1, Srxn1 and Dysf in MIX groups compared
to TCDD or PCB153. Transcription factor binding site analysis identified
putative dioxin, constitutive androstane and pregnane X receptor binding motifs in
the promoter region of non-additive target genes suggesting receptor cross-talk.
Collectively, the dose-dependent, non-additive gene expression changes are consistent
with the reported non-additive effects on RLW, hepatocellular fat accumulation,
and PCB153 tissue levels. Funded by SBRP P42ES04911.
2306 DETERMINING A ROBUST D-OPTIMAL DESIGN FOR
TESTING FOR DEPARTURE FROM ADDITIVITY IN A
MIXTURE OF FOUR PFAAS.
C. Carr 1 , C. Gennings 1 , B. D. Abbott 2 , J. E. Schmid 2 , W. Wan 1 , L. Burgoon 2 ,
C. J. Wolf 2 and C. Lau 2 . 1 Biostatistics, Virginia Commonwealth University,
Richmond, VA and 2 NHEERL, U.S. EPA, Research Triangle Park, NC.
Our objective is to determine an optimal experimental design for a mixture of perfluoroalkyl
acids (PFAAs) that is robust to the assumption of additivity. PFAAs are
widely used in consumer products and industrial applications. The presence and
persistence of PFAAs, especially in human body fluids, have raised concern about
this class of compounds. Of particular focus to this research project is whether an
environmentally relevant mixture of four PFAAs with long half-lives (in years:
PFOA, PFOS, PFNA, and PFHxS) act synergistically. PFAAs are thought to activate
peroxisome proliferator-activated receptor alpha (PPARα) to produce liver toxicity
and developmental effects. The first phase of study included evaluating the
ability of PFAAs to bind PPARα in in vitro studies of a transfected-cell model.
Using the resulting data, a non-linear logistic additivity model was employed to
predict relative luciferase units (RLU) at an environmentally relevant mixing ratio.
The mixing ratio was estimated from NHANES (2005-2006) data. We used a maximin
D-optimal design criterion to select from a large set of specified designs. The
candidate seven point designs (control plus six dose groups) were generated by varying
the total dose locations and shape of the dose-response curve with the additivity
curve used as a reference. A total of 6,006 designs were considered with seven dose
groups along with 13 different dose-response shapes. A D-optimal design (i.e., the
location of the seven dose groups) robust to misspecification of the resulting doseresponse
shape was found with a minimum D-efficiency of 92%. The proposed design
has good statistical properties over a band of possible dose-response curves including
synergistic, additive and antagonistic associations among the four PFAAs.
This research was partially supported by NIEHS T32ES007334 and does not reflect
USEPA policy.)
2307 PHYSIOLOGICALLY-BASED PHARMACOKINETIC
(PBPK) MODELING OF TWO BINARY MIXTURES:
METABOLIC ACTIVATION OF CARBON
TETRACHLORIDE BY TRICHLOROETHYLENE AND
METABOLIC INHIBITION OF CHLOROFORM BY
TRICHLOROETHYLENE.
M. V. Evans 1 , H. M. Yang 2 , K. A. Yokley 3 , A. McDonald 1 , Y. M. Sey 1 , C. R.
Eklund 1 and J. Simmons 1 . 1 NHEERL/ORD, U.S. EPA, Research Triangle Park,
NC, 2 NCEA/ORD, U.S. EPA, Washington, DC and 3 Mathematics and Statistics,
Elon University, Elon, NC.
The interaction between trichloroethylene (TCE) and chloroform (CHCl3) has
been described as less than additive, with co-exposure to TCE and CHCl3 resulting
in less hepatic and renal toxicity than observed with CHCl3 alone. In contrast, the
nonadditive interaction between TCE and carbon tetrachloride (CCl4) results in
increased hepatotoxicity when compared with CCl4 alone. To explore the mode of
action underlying these nonadditive interactions, male F-344 rats were exposed in
vapor uptake inhalation chambers to TCE alone, CHCl3 alone, CCl4 alone, both
TCE and CHCl3 or both TCE and CCl4. Metabolic inhibition was observed as a
slower rate of decay in the vapor uptake data, while increased decay in the data represented
metabolic activation. In the presence of TCE, uptake of CHCl3 decreased
while uptake of CCl4 increased. Physiologically-based pharmacokinetic (PBPK)
models for each chemical alone were developed and used to construct and evaluate
PBPK models describing the influence of concurrent exposure to TCE on the uptake
and metabolism of CHCl3 or CCl4 as well as the influence of concurrent exposure
to CHCl3 or CCl4 on clearance of TCE. The model simulations indicated
that TCE had opposing effects on the metabolism of CHCl3 and CCl4, decreasing
the metabolism of CHCl3 and increasing the metabolism of CCl4. Computer simulations
of the various types of metabolic inhibition suggest competitive inhibition
best describes the metabolic interaction between TCE and CHCl3. For TCE and
CCl4, a novel metabolic hypothesis describing activation of CCl4 by TCE best fit
the data. In summary, different modes of action for the nonadditive interactions resulting
from co-exposure to TCE and CHCl3 and from co-exposure to TCE and
CCl4 have been suggested by PBPK modeling. (This abstract does not reflect EPA
policy.)
2308 INTEGRATED MULTI-DISCIPLINARY ASSESSMENT OF
ENVIRONMENTALLY REALISTIC COMPLEX
MIXTURES OF DRINKING WATER DISINFECTION BY-
PRODUCTS (DBPS) (THE 4LAB STUDY).
J. Simmons 1 , M. G. Narotsky 1 , L. K. Teuschler 2 , J. G. Pressman 3 , E. S.
Hunter 1 , G. E. Rice 2 , G. R. Klinefelter 1 , J. M. Goldman 1 , T. F. Speth 3 , L. F.
Strader 1 , R. J. Miltner 3 , S. Parvez 2 , A. McDonald 1 , D. S. Best 1 , C. A. Dingus 4
and S. D. Richardson 5 . 1 NHEERL/ORD, U.S. EPA, Research Triangle Park, NC,
2 NCEAORD, U.S. EPA, Cincinnati, OH, 3 NRMRL/ORD, U.S. EPA, Cincinnati,
OH, 4 Battelle, Columbus, OH and 5 NERL/ORD, U.S. EPA, Athens, GA.
More than 600 DBPs have been identified; yet ~50% of the total organic halide
from chlorination is unidentified. Epidemiology studies suggest associations between
human use of chlorinated water and reproductive/developmental effects
SOT 2011 ANNUAL MEETING 495