The Toxicologist - Society of Toxicology

cells and the transformed cells. This implicates histone modification as central to
the differences in the regulation of MT-3 expression between normal urothelium
and its transformed counterpart.
1997 IL-8 OVER-EXPRESSION AND AUTOCRINE CELL
ACTIVATION ARE KEY FACTORS IN
MONOMETHYLARSENOUS ACID [MMA(III)]-
INDUCED MALIGANT TRANSFORMATION OF
HUMAN UROTHELIAL CELLS.
C. Escudero 1, 2 , T. Wu 2 , J. M. Camarillo 2 and A. Gandolfi 2 . 1 Inmunologia y
Biologia Celular y Molecular/CIEP, Universidad Autonoma de San Luis Potosi, SLP,
Mexico and 2 Department of Pharmacology and Toxicology, University of Arizona,
Tucson, AZ.
The association between chronic human exposure to arsenicals and bladder cancer
development is well recognized; however the molecular mechanisms have not been
fully determined. We previously demonstrated that chronic exposure to 50 nM of
monomethyl arsenous acid [MMA(III)] leads to malignant transformation of an
immortalized model of urothelial cells (UROtsa), with only 3 mo of exposure necessary
to trigger the transformation-related changes. Those changes include the increase
in cell proliferation rate, anchorage independent growth, and tumor formation
after hetero-transplantation in SCID mice. In this phase, the cells over-express
pro-inflammatory cytokines (IL-1β,IL-6,IL-8) consistent with the sustained activation
of NFKb and AP1/c-jun, ERK2, and STAT3. IL-8 was over-expressed in our
model 16 hr after exposure to MMA(III) and a sustained over-expression was observed
in cells exposed for 3 mo. In this study IL-8 was also found increased in tumors
produced from MMA(III) exposed cells after heterotransplantation in SCID
mice. These treated UROtsa cells do express both receptors CXCR1 and CXCR2
suggesting that an autocrine cell activation could be important in cells transformation.
Supporting this observation and consistent with IL-8 over expression,
CXCR1 internalization was significantly increased after three mo of exposure to
MMA(III). When unexposed UROtsa cells were exposed to rIL-8 the expression of
MMP-9, cyclin D1, bcl-2, and VGEF was significantly increased; the same gene expression
profile was found in cells exposed for 3 mo to MMA(III). After IL-8 was
silenced in cells exposed for 3 mo to MMA(III) a decrease in cell proliferation rate
was noted along with a decrease in anchorage-independent colony formation as
well as a decrease in tumor progression related genes expression. These results suggest
a key role of IL-8 in MMA(III)-induced UROtsa cells transformation.(NIEHS
04940).
1998 INORGANIC ARSENIC CAUSES APOPTOSIS IN MOUSE
CEREBRUM THROUGH AN OXIDATIVE STRESS-
INDUCED MAPKS AND ER STRESS PATHWAY.
C. Huang 1 , M. Lee 2 , Y. Chen 3 , T. Ho 1 , C. Yen 4 and C. Su 5 . 1 School of Chinese
Medicine, China Medical University, Taichung, Taiwan, 2 Department of Surgery,
Penghu Hospital, Department of Health, Executive Yuan, Penghu, Taiwan,
3 Department of Physiology, China Medical University, Taichung, Taiwan,
4 Department of Occupational Safety and Health, Chung Shan Medical University,
Taichung, Taiwan and 5 Department of Otorhinolaryngology, Head and Neck Surgery,
Changhua Christian Hospital, Changhua, Taiwan.
Arsenic pollution is a major public health problem throughout the world.
Inorganic arsenic (iAs) is the predominant form and usually more harmful than organic
ones, and increasing the risk of human diseases, such as peripheral vascular
disease and cancer. However, the neurotoxic effect of iAs-induced is mostly unclear.
Here, we investigated the toxic effect mechanisms of iAs (0.5 and 5 ppm, in drinking
water), which was the possible exposed dose by ingestion in iAs-contaminated
areas, in cerebrum of mice after administration for 6 consecutive weeks. iAs dosedependently
caused the increase of lipid peroxidation in plasma and cerebral cortex.
iAs could also decrease the glutathione levels and NAD(P)H:quinone oxidoreductase-1
and glutathione peroxidase mRNA expression in the cerebral cortex.
Antioxidant N-acetylcysteine effectively reversed iAs-induced oxidative stress damage
in cerebrum. Moreover, iAs induced the activation of caspase-3, upregulation of
Bax and Bak (pro-apoptotic) and downregulation of Mcl-1 (anti-apoptotic) mRNA
expression in the cerebral cortex. Exposure to iAs could also trigger endoplasmic
reticulum (ER) stress, as indicated by marked activating of glucose-regulated protein
(GRP)-78, GRP-94, and C/EBP homologous protein (CHOP) mRNA.
Moreover, western blot assay showed the increase of p38 activation and dephosphorylation
of ERK1/2 were found in the cerebral cortex of iAs-exposed mice. These
iAs-induced apoptosis-related signals could be significantly reversed by N-acetylcysteine.
Therefore, our results suggest that iAs-induced oxidative stress cause apoptosis
in cerebrum, and the signalings of p38 and ERK1/2-MAPKs and ER stress
may be involved in iAs-induced neurotoxicity.
428 SOT 2011 ANNUAL MEETING
1999 ALTERED EXPRESSION PROFILES OF microRNAs
UPON ARSENIC EXPOSURE OF HUMAN UMBILICAL
VEIN ENDOTHELIAL CELLS.
Y. Wei 1 , Y. Shi 2 , X. Ma 3 and R. Li 2 . 1 Department of Community Medicine, Mercer
University School of Medicine, Macon, GA, 2 Key Laboratory of Pathobiology, Jilin
University, Changchun, Jilin, China and 3 Department of Molecular and Cell Biology,
Center for Systems Biology, University of Texas at Dallas, Richardson, TX.
Exposure to high levels of inorganic arsenic that is present in drinking water of endemic
regions has been shown to elicit various health effects. However, the molecular
mechanisms of arsenic-induced vascular toxicity are not fully understood. In this
study we analyzed microRNA expression profiles upon arsenic exposure of human
umbilical vein endothelial cells (HUVECs). The cells were treated with 20 μM of
sodium arsenite for 24 h in Iscove’s Modified Dulbecco’s Medium supplemented
with 10% fetal bovine serum. Total RNA was purified with a Trizol reagent and the
expression of microRNAs was examined by Exiqon miRCURY LNA microRNA
chips. We found that 82 microRNAs were up-regulated and 60 were down-regulated
by arsenic treatment as compared to the control group. The expression of
some of the altered microRNAs was confirmed by real time RT-PCR. Analysis of
cellular functions by using DAVID Bioinformatics Resources revealed that phosphoproteins
and genes involved in alternative splicing are among the top categories
targeted by both up- and down-regulated microRNAs upon arsenic treatment. A
number of DNA motifs were identified in the promoters of the perturbed
microRNAs upon arsenic treatment by promoter analysis using MEME software,
though we were not able to associate these DNA motifs with known transcription
factors. In conclusion, the results show that arsenic exposure of HUVECs could
alter the expression profiles of microRNAs which target common cellular function
categories, such as phosphoproteins and genes involved in alternative splicing. Our
findings provide more insights on arsenic-induced vascular injury.
2000 ARSENIC INDUCES EXPRESSION OF C-REACTIVE
PROTEIN.
I. Druwe, J. J. Sollome, P. Sanchez-Soria, T. D. Camenisch and R. R.
Vaillancourt. Department of Pharmacology & Toxicology, The University of Arizona,
Tucson, AZ.
C-Reactive protein (CRP) is an acute phase protein in humans and elevated levels
are produced in response to inflammatory cytokines that are associated with
artherosclerosis, hypertension, cardiovascular disease and insulin resistance.
Exposure to inorganic arsenic, a common and known environmental toxicant, also
produces cardiovascular disorders and is associated with insulin-resistance. In a previous
study, we showed that treatment of 3T3-L1 adipocytes with sub-cytotoxic
concentrations of sodium arsenite (0.67 μM and 3 μM) resulted in an induction of
a cytokine response. Upregulation of various interleukins included IL-2, IL-4, and
IL-6. IL-6 is known to induce C-Reactive Protein expression. Here we show that
treatment of HepG2 cells with sub-cytotoxic concentrations of sodium arsenite results
in elevated CRP production and secretion. In addition, treatment of FvB mice
with 100 ppb sodium arsenite in the drinking water for six months starting at
weaning age (three weeks) resulted in dramatically higher levels of CRP as compared
to control. Studies are on-going to investigate the ramifications that chronic
elevated levels of CRP can have on both the cardiovascular system in mice and insulin-dependent
signaling pathways in cells. This work was supported by
ES004940 and 1F31ES016990-01A2.
2001 INORGANIC ARSENITE IMPAIRS INSULIN-
STIMULATED GLUCOSE UPTAKE IN 3T3-L1
ADIPOCYTES: INVOLVEMENT OF CELLULAR
ADAPTIVE RESPONSE TO OXIDATIVE STRESS.
P. Xue 1, 2 , Y. Hou 1, 2 , J. Fu 1 , C. G. Woods 1 , H. Liu 1 , Q. Zhang 1 , G. Sun 2 , M.
E. Andersen 1 and J. Pi 1 . 1 The Hamner Institutes, Reaserach Triangle Park, NC and
2 China Medical University, Shenyang, China.
There is growing evidence that chronic exposure of humans to inorganic arsenic, a
potent environmental oxidative stressor, is associated with the incidence of type 2
diabetes (T2D). One critical feature of T2D is insulin resistance in peripheral tissues,
especially in mature adipocytes, the hallmark of which is decreased insulinstimulated
glucose uptake (ISGU). Despite the deleterious effects of reactive oxygen
species (ROS), they have been recognized as a second messenger serving an
intracellular signaling role for insulin signaling. Nuclear factor-erythroid 2–related
factor 2 (NRF2) is a central transcription factor regulating cellular adaptive response
to oxidative stress. This study proposes that in response to arsenic exposure,
NRF2-mediated adaptive induction of endogenous antioxidant enzymes blunts insulin-stimulated
ROS signaling and thus impairs ISGU. Exposure of differentiated