The Toxicologist - Society of Toxicology

exposure system was developed from cultures of human renal epithelial cells derived
from cortical tissue obtained from nephrectomies. These cultures exhibit many of
the qualities of proximal tubule cells. Using these cells, a study was performed to
determine the cadmium-induced global gene expression changes after short-term (1
day, 9, 27, and 45 μM) and long-term cadmium exposure (13 days, 4.5, 9, and 27
μM). These studies revealed fundamental differences in the types of genes expressed
during each of these time points. The obtained data was further analyzed using regression
and mutual information analysis to identify genes with a high probability
of mutual dependence. Regression analysis showed 1720 genes were induced and
2316 genes were repressed by Cd 2+ within 1 day, and 1523 and 2146 genes were induced
and repressed, respectively, after 13 days. A network model based on mutual
information was used to derive an interaction map of these genes. The most prominent
network consisted of IL13RA2, DNAJA4, HSPA6, AKAP12, ZFAND2A,
AKR1B10, SCL7A11, and AKR1C1.
773 ASSOCIATIONS OF MULTIPLE METALS WITH KIDNEY
OUTCOMES IN LEAD WORKERS.
R. L. Shelley 1 , N. Kim 2 , P. J. Parsons 3 , J. Agnew 1 , A. J. Steuerwald 3 , B. G.
Jaar 1 , B. Lee 2 , B. S. Schwartz 1 , G. Matanoski 1 , A. C. Todd 4 , D. Simon 5 and V.
Weaver 1 . 1 Johns Hopkins Bloomberg School of Public Health, Baltimore, MD,
2 SoonChunHyang University, Asan, Republic of Korea, 3 New York State Department
of Health, Albany, NY, 4 Mount Sinai School of Medicine, New York, NY and
5 Biostatistical Consulting, Cincinnati, OH.
Environmental exposure to metals is widespread. Several are potential nephrotoxicants
yet few studies have examined the impact of co-exposure to these metals in
workers with occupational exposure to nephrotoxicants such as lead. In analyses in
an occupationally lead exposed population to address this gap, we unexpectedly
found that environmental urine cadmium (Cd) was positively associated with estimates
of glomerular filtration rate [eGFR]) (Weaver et al., OEM. In press). We also
evaluated associations of urine antimony (Sb). In 684 lead workers, mean (SD)
blood and tibia lead; urine Sb and Cd; and eGFR using the Modification of Diet in
Renal Disease equation were 23.2 (14.3) μg/dl, 27.1 (29.3) μg Pb/g bone mineral,
2.4 (7.6) μg/g creatinine, 1.1 (0.6) μg/g creatinine, and 97.7 (19.4) ml/min/1.73
m 2 , respectively. After adjustment for lead dose, urine creatinine, and sociodemographic
and kidney disease risk factors, higher ln-urine Sb was associated with lower
serum creatinine and higher eGFR (β = 1.5 ml/min/1.73 m 2 ; 95% CI = 0.5, 2.5)
and ln-N-acetyl-β-D-glucosaminidase (NAG), a kidney biomarker. After additional
adjustment for ln-Cd, Sb remained associated with serum creatinine and eGFR (β
= 1.2 ml/min/1.73 m 2 ; 95% CI = 0.2, 2.2) but not NAG. Paradoxical associations
with both Sb and Cd suggest that the mechanism for these findings may impact a
wider range of urine biomarkers in kidney function research and support the need
to determine that mechanism. These results also highlight the potential for environmental
level Cd exposure to confound associations of other metals with NAG.
774 GENDER DIFFERENCES IN THE MOLECULAR
MECHANISMS OF BROMATE INDUCED
NEPHROTOXICITY IN F344 RATS.
N. Kolisetty 1 , D. A. Delker 2 , C. Nelson 2 , S. Muralidhara 1 , R. J. Bull 3 , O.
Quinones 4 , G. Zhongxian 5 , S. Snyder 4 , J. Cotruvo 6 , J. W. Fisher 7 , C. Ong 8 and
B. S. Cummings 1 . 1 University of Georgia, Athens, GA, 2 University of Utah, Salt
Lake City, UT, 3 , Mo Bull Consulting, Richland, WA, 4 Water Quality Research and
Development, Henderson, NV, 5 Center for Advanced Water Technology, Singapore,
Singapore, 6 Joseph Cotruvo & Associates, LLC, Washington, DC, 7 University of
Georgia, Athens, GA and 8 National University of Singapore, Singapore, Singapore.
The disposition of bromate after oral exposures is similar in male and female rats,
which contrast to its ability to preferentially induce nephrotoxicity in male rats.
This might be due to gender differences in bromate-induced kidney injury manifested
by different gene expression profiles in male and female rats after exposure to
bromate. Previous studies using cDNA microarray analysis supports this hypothesis,
but additional studies of mRNA and protein changes are needed to confirm the
microarray results. Thus, qPCR and immunohistochemistry were used to study expression
of several proteins in kidney, thyroid and testicular tissues isolated from
male and female (kidney and thyroid only) rats orally exposed to bromate (125 and
400 mg/kg KBrO3) for 28 days. In agreement with the cDNA microarray data,
p21 mRNA and protein expression increased in kidney and thyroid in both male
and female rats in a dose-dependent manner. Similar trend was observed in testicular
tissue. In contrast to the cDNA microarray data, protein expression of kidney
injury molecule 1 occurred earlier and at higher levels in female kidneys. The protein
expression of clusterin, an anti apoptotic protein, was increased in a dose-dependent
manner in male rat kidneys correlating with increases in mRNA transcript
levels and in, thyroid, and testes, but not in female kidneys or thyroid. Increases in
expression of clusterin and p21, correlated to cell proliferation and DNA damage as
measured by BrdU and 8-OH-dG staining, respectively. To our knowledge, these
data are the first to demonstrate that bromate exposure increases clusterin, and to
suggest that the gender-specific nephrotoxicity induced by bromate correlate to
clusterin, but not p21, expression.
775 NKTR-181, A NOVEL POLYMER CONJUGATED
OPIOID AGONIST, DEMONSTRATES REDUCED
TOXICITY AND CNS SIDE EFFECTS RELATIVE TO
OXYCODONE.
E. Tonkin, S. Wong, A. Odinecs and T. D. Sweeney. Nektar Therapeutics, San
Carlos, CA.
NKTR-181 is a novel orally available mu-opioid agonist that uses Nektar’s advanced
polymer conjugate technology to achieve slower kinetics of entry into the
brain relative to other opioids, while still producing potent analgesia in mouse
models. The goal of these studies was to compare the toxicity of NKTR-181 to that
of oxycodone in female rats. Rats (n = 3) were given single oral doses of 0, 200, 500,
or 700 mg/kg oxycodone or NKTR-181 and were monitored for changes in clinical
condition for 24 hrs. At ≥200 mg/kg, oxycodone produced hypoactivity, hematuria,
and mortality, with increased severity of changes and altered respiratory rates
at the higher doses. NKTR-181 produced clinical changes only at 700 mg/kg, consisting
primarily of hypoactivity. In a subsequent study, rats (n = 3) were given 5
daily doses of NKTR-181 (0, 200, 500, and 1000 mg/kg) or oxycodone (100
mg/kg). Clinical condition and body weight were monitored and samples were collected
for toxicokinetic and histopathology assessment. Animals given 100
mg/kg/day oxycodone exhibited hypoactivity, increased muscle tone, behavioral
changes such as excessive paw chewing, and decreased body weight compared to
controls. For NKTR-181, no behavioral changes were noted at 200 mg/kg, while
animals given 500 mg/kg NKTR-181 displayed increased activity and paw chewing,
and animals given 1000 mg/kg/day NKTR-181 displayed hypoactivity, altered
muscle tone, and mortality (1/3 animals). For 100 mg/kg oxycodone, mild
histopathological changes were noted in the urinary bladder, intestinal epithelium,
and reproductive and lymphoid tissues. Similar changes were noted at 1000 mg/kg
NKTR-181, with mild intestinal changes noted at all doses of NKTR-181.
Toxicokinetic assessment demonstrated that NKTR-181 had higher plasma exposure
relative to oxycodone on a dose normalized basis. In conclusion, NKTR-181
produces fewer CNS side effects and is tolerated at higher doses than oxycodone.
Results from on-going definitive toxicity and safety pharmacology studies with
NKTR-181 support these conclusions.
776 RELATIVE TOXICITY ANALYSIS OF DL11F, A HER3,
AND EGFR DUAL ACTION ANTIBODY, AND
CETUXIMAB IN CYNOMOLGUS MONKEYS.
R. Prell 1 , D. Danilenko 1 , C. Wang 1 , A. Kamath 1 , G. Schaefer 1 , P. Allen 2 , J.
Roberts 2 and W. Halpern 1 . 1 Genentech, South San Francisco, CA and 2 Valley
Biosystems, West Sacramento, CA.
DL11f is an engineered monoclonal antibody in which each of the two antigen
binding fragments (Fabs) is capable of binding to HER3 and EGFR with high
affinity. DL11f blocks ligand binding to both receptors and demonstrates equivalent
or superior efficacy to other anti-EGFR mAbs in mouse xenograft models.
EGFR and HER3 are members of the epidermal growth factor receptor family and
deregulation of EGFR and HER3 signaling have been implicated in tumorigenesis
and tumor progression. Though EGFR is a clinically validated target, inhibition is
associated with dermatologic toxicity in up to 90% of patients and can become severe
enough to require dose-reduction or discontinuation. To determine the relative
dermatologic toxicity of DL11f compared to cetuximab, a pilot toxicity study was
performed in female cynomolgus monkeys. Animals (3/group) were dosed IV
weekly for 5 weeks with cetuximab at 25 mg/kg, or DL11f at 25 mg/kg or 12.5
mg/kg. Dermatologic toxicity was observed between the 3rd and 4th doses in all
three animals dosed with cetuximab, consistent with prior reports. Gross lesions
were characterized by inguinal, axillary, and chest erythema and exfoliation. At
necropsy 4 weeks after the final dose, there was still histopathologic evidence of
minimal to mild perivascular dermal inflammation, acanthosis with orthokeratotic
hyperkeratosis, and occasional intraepidermal edema. In contrast, only 1 of 3 animals
dosed with DL11f at 25 mg/kg had evidence of dermatologic toxicity that was
of lesser severity, compared to cetuximab treatment, and appeared after the 6th
dose. No animals dosed with 12.5 mg/kg DL11f showed gross evidence of dermatologic
toxicity. TK profiles confirmed comparable exposure between animals dosed
with cetuximab and DL11f at 25 mg/kg; thus the reduced toxicity was not due to
differential drug exposure. These data suggest that the dermatologic toxicity of
DL11f is substantially less than that of cetuximab and that DL11f may have a superior
clinical safety profile.
SOT 2011 ANNUAL MEETING 167