The Toxicologist - Society of Toxicology

to determine whether or not the antioxidant N-acetylcysteine delivered in liposomes
(phospholipid vesicles used as drug delivery systems) is more effective than
the conventional N-acetylcysteine in protecting against acute APAP- induced injuries.
Male Sprague-Dawley rats were challenged with an intragastric dose of
APAP (850 mg/kg b.wt); 4 h later, animals were administered saline, N-acetycysteine,
or liposomal-N-acetylcysteine and sacrificed 24 h post-APAP treatment.
Acetaminophen administration resulted in hepatic injury as evidenced by increases
in plasma AST and ALT enzymes, increases in tissue levels of lipid peroxidation,
myeloperoxidase activity, and nitrotyrosine. Treatment of animals with L-NAC was
significantly more effective than treatment with the free drug in reducing APAP-induced
hepatotoxicity as indicated by the biochemical markers used in this study.
Histological evaluation showed that APAP caused periacinar hepatocellular apoptosis
and/or necrosis of hepatocytes around the terminal hepatic venules which was
reduced by NAC treatment, the degree of reduction in necrosis being greater for L-
NAC. These data suggest that NAC when delivered as a liposomal formulation further
improves its effectiveness in counteracting APAP-induced hepatotoxicity. This
work was funded by the Northern Ontario School of Medicine.
1270 PARAOXONASE 2(PON 2) IN THE CENTRAL NERVOUS
SYSTEM: A NEUROPROTECTIVE ROLE?
L. G. Costa1, 3 , G. Giordano1 , T. B. Cole2 and C. E. Furlong2 . 1Department of
Environmental and Occupational Health Sciences, University of Washington, Seattle,
WA, 2Division of Medical Genetics and Department of Genome Sciences, University
of Washington, Seattle, WA and 3Department of Human Anatomy, Pharmacology and
Forensic Science, University of Parma Medical School, Parma, Parma, Italy.
Paraoxonase 2 (PON 2) is a member of the paraoxonase family of proteins which
also includes PON1 and PON3. PON2 is widely distributed, with substantial expression
in liver, intestine, testis, placenta, heart and macrophages. Several lines of
evidence indicate that PON2 acts as an intracellular antioxidant. Aim of the present
study was to characterize the expression of PON2 in mouse central nervous system
and to assess its antioxidant properties in this tissue. We first confirmed by Western
blotting that PON2 levels are highest in lung, intestine, heart and liver, and lower
in brain; we also found that in all tissues PON2 expression was higher in female
than in male mice. PON2 knockout [PON2-/-] mice did not express any PON2, as
expected. In brain, the highest levels of PON2 were found in the substantia nigra,
the nucleus accumbens and the striatum, with lower levels in the cerebral cortex,
hippocampus and cerebellum. A similar regional distribution of PON2 activity
(measured by dihydrocoumarin hydrolysis) was also found. PON3 was not detected
in any brain area, while PON1 was expressed at very low levels (20 to 40-fold
less than PON2), and did not show any regional difference. PON2 levels were
higher in astrocytes than in neurons isolated from all brain regions, and were highest
in cells of both types isolated from the striatum. Mouse brain PON2 protein
levels decreased from postnatal day 1 to 60. The toxicity in striatal and cerebellar
cells of agents known to cause oxidative stress (DMNQ, H2O2, MPP+) was 4 to
11-fold higher in neurons and astrocytes from PON2-/- mice than in the same cells
from wild-type mice. These results indicate that PON2 is expressed in brain, and
that higher levels are found in dopaminergic regions such as the striatum, suggesting
that this enzyme may provide protection against oxidative stress-mediated neurotoxicity
(Supported in part by ES04696).
1271 COMPARATIVE EVALUATION OF TAURINE AND
THIOTURINE FOR THEIR EFFECTS ON ETHANOL-
INDUCED OXIDATIVE STRESS IN THE RAT.
M. C. Parikh and C. A. Lau-Cam. Pharmaceutical Sciences, St. John’s University,
Jamaica, NY.
The present study has evaluated taurine (2-aminoethanesulfonic acid, TAU) and
thiotaurine (2-aminoethanethiosulfonic acid, TTAU), two sulfur-containing
amino acids, for their effects in attenuating ethanol-induced oxidative stress. To
this end, fasted male Sprague-Dawley rats (225-250 g) were used throughout.
Animals in the treatment groups received either TAU or TTAU intraperitoneally at
a 2.4 mM/kg dose, given 30 min before an oral (4 g/kg) dose of ethanol. Animals
in the control group received only physiological saline and those in the no treatment
group only ethanol. At 1 hr post ethanol, blood was collected by cardiac
puncture into heparinized tubes and the respective livers removed immediately.
The blood samples were processed for their plasma fractions, and the livers were
made into a homogenate with phosphate buffered saline (PBS) pH 7.4 (1:30 ratio,
w/v). These samples were analyzed for the levels of malondialdehyde (MDA), reduced
(GSH) and oxidized (GSSG) glutathione, and the activities of catalase, glutathione
peroxidase and superoxide dismutase. In comparison to control values,
ethanol raised the MDA and GSSG values while lowering those of GSH and antioxidant
enzymes both in the plasma and liver. A pretreatment with either TAU or
TTAU led to abolishment of MDA formation, to normalization of the GSH stores,
and to significant attenuation of the changes in GSSG, GSH/GSSG ratio and activities
of antioxidant enzymes induced by ethanol. In general, TTAU was found to
272 SOT 2011 ANNUAL MEETING
be somewhat more protective than TAU against the actions of ethanol. In addition,
parallel experiments with other doses of TAU (1.2 and 4.8 mM/kg) indicated that
the protective actions of this test compound are dose related and only significant
above 1.2 mM/kg.
1272 THE EFFECT OF ESTROGEN ON MACROPHAGES
RESPONSE TO OXIDATIVE STRESS.
T. Entezarizaher 1 , M. Javdan 2 and Z. Zakeri 3 . 1 LaGuardia Community College,
Long Island City, NY, 2 The Feinstein Institute for Medical Research, Manhasset,
NY and 3 Queens College and Graduate Center of City University of New York,
Flushing, NY.
Macrophages play essential roles in immunity and the maintenance of homeostasis.
Several studies have shown that males and females respond differently to traumatic
injury, sepsis, chronic pain, fibromyalgia, rheumatoid arthritis and neurodegenerative
disease, in which sex hormones are most likely responsible for the differential
outcomes. Infectious diseases such as sepsis are a dysregulation of innate immune
response to an offending pathogen. Macrophages by recognizing pathogens, phagocytosing
them, and secreting inflammatory mediators are the initiator of the innate
immune response. The function of macrophages can be influenced both directly
and indirectly by the cellular redox state. Macrophage malfunctions have been previously
reported under oxidative stress such as hyperoxia and hypoxia; How ever
role sex hormones on macrophage function and involved mechanisms remain unclear.
In this study we explore the effect of estrogen and testosterone on cell viability
damage and phagocytosis impairment induced by H2O2 in Raw 264.7 Cells.
Cell viability and phagosytosis function evaluated by MTT and phagocytosis assay.
Our data suggest that estrogen has significant protective effect on cell viability and
phagocytotic function of macrophages compared to non-treated control cells and
the cells that treated with testosterone. Thus this study opened a new window to
propose a novel and efficient treatment for sepsis and other gender-related inflammatory
diseases.
1273 DOSE-RESPONSE ANALYSIS OF POTASSIUM
BROMATE-INDUCED DNA DAMAGE IS CONSISTENT
WITH LOW-DOSE LINEAR, NON-THRESHOLD
PROCESSES.
M. A. Spassova 1 , D. J. Miller 1 , J. Caldwell 1 , S. V. Vulimiri 1 , D. A. Eastmond 2 ,
C. Chen 1 and P. D. White 1 . 1 NCEA, U.S. EPA, Washington, DC and 2 Cell Biology
& Neuroscience, University of California Riverside, Riverside, CA.
Reactive oxygen species (ROS) are generated under physiological and pathological
conditions. ROS can arise as a result of enzymatic and nonenzymatic reactions involving
ozone, various carcinogens and environmental pollutants. It has been postulated
that ROS have both direct and indirect roles in mutagenesis and carcinogenesis.
However, the specific mechanisms involved in these processes and the
resulting dose-response behaviors are the subject of ongoing debate. In this study,
we have focused on investigating the dose-response behavior of DNA damage induced
by potassium bromate (KBrO3). We selected KBrO3 as an example of a
ROS-generating compound, because substantial amount of evidence suggests that
KBrO3 and/or its metabolites directly interact with DNA residues to produce oxidative
damage. We evaluated the dose-response of KBrO3 induced DNA damage
at the molecular, cellular, and organism level. It has been established previously that
at molecular (cell-free) level, when bacteriophage PM2 DNA is used, DNA damage
increases linearly with concentration of KBrO3. We used studies that assess KBrO3
-induced DNA damage in human lymphoblastoid and mouse lymphoma cells to
evaluate the dose-response at the cellular level. Linear models and models with
plateau effects (here bent-hyperbola model) were used to describe the dose-response
dependence. Studies on micronucleus (MN) induction by KBrO3 in mouse blood
cells in-vivo were used to assess the KBrO3 effect at the organism level. These data
were modeled with an exponential model that revealed low-dose linear behavior.
Our analysis finds that the observed data on DNA damage induced by KBrO3 is
consistent with low-dose linear behavior at the molecular, cellular and organism
level, with no indication of a threshold. Disclaimers: The views expressed in this
paper are those of the authors and do not necessarily reflect the views or policies of
the U.S. EPA.
1274 ALL-TRANS-RETINOIC ACID PROTECTS AGAINST
ROS INDUCED KIDNEY INJURY.
S. S. Lau, J. L. Lord-Garcia, L. W. Lai, K. Y. Yong, Y. H. Lien and T. J. Monks.
Pharmacology and Toxicology, University of Arizona, Tucson, AZ.
Quinones are electrophilic and capable of forming covalent adducts with proteins
and of redox cycling with the generation of reactive oxygen species (ROS). Within
renal proximal tubular epithelial cells, multi-substituted GSH conjugates of 1,4-