The Toxicologist - Society of Toxicology

%, Ala140/Asp140 40.6 % and Asp140/Asp140 10.8 %. The GSTP1 genotype
frequencies were Ile105/Ile105: 56.0 %, Ile105/Val105: 33.4% and
Val105/Val105: 10.6%, and Ala114/Ala114: 84.8%, Ala114/Val114: 14.2% and
Val114/Val114: 1.0%. The genetic polymorphism analysis for the GSTM1 and
GSTT1 genes was determined simultaneously in a single assay using a multiplex
PCR approach. As an internal control exon 7 of the CYP1A1 gene was co-amplified.
The frequencies of the deleted GSTM1 and GSTT1 genotypes were 54.6%
and 22.2%, respectively. These results reveal that the frequencies of CYP2E1*5B
(RsaI), GSTM1, GSTO1, GSTP1, and GSTT1 gene polymorphisms in a Turkish
population are similar to European Caucasian populations (Supported by the
Research Fund of Ankara University, Grants 2006-08-03-002HPD, 2008-08-03-
006HPD and 10A3336002).
1363 INFLUENCE OF GENETIC VARIATION IN THE
SEROTONIN TRANSPORTER ON SMOKING
CESSATION SUCCESS USING ANTI-DEPRESSANT
THERAPY.
M. Quaak 1, 2 , C. P. van Schayck 2 , D. S. Postma 3 , E. J. Wagena 2, 4 and F. J. van
Schooten 1 . 1 Health Risk Analysis and Toxicology, Maastricht University, Maastricht,
Netherlands, 2 General Practice, Maastricht University, Maastricht, Netherlands,
3 Pulmonology, University Medical Center Groningen, Groningen, Netherlands and
4 Kiadis Pharmacology Amsterdam, Netherlands. Sponsor: H. van Loveren.
BACKGROUND: Currently, two forms of antidepressant therapy are used for
smoking cessation: bupropion and nortriptyline. Based on their mechanism of action,
variations in the serotonin transporter gene (SLC6A4) are expected to influence
smoking cessation rates. We therefore investigated whether functional variants
in SLC6A4 influence smoking cessation rates and treatment response. METH-
ODS: Subjects participated in a randomized, placebo-controlled trial on the efficacy
of bupropion and nortriptyline for smoking cessation. The main outcome
measures were prolonged abstinence from smoking after 12 weeks (EOT; end-oftreatment)
and at 6- and 12-month follow-up. Subjects were genotyped for three
functional variants in SLC6A4: 5-HTTLPR, STin2, and rs25531. RESULTS:
Carriers of the 5-HTTLPR high-activity L-variant had significantly higher cessation
rates with bupropion compared to placebo (6-months: 38% vs. 16%; 12months:
31% vs. 14%). Similar effects were observed in the nortriptyline group,
and for the rs25531 SNP in both the bupropion and nortriptyline group, although
non-significant. The STin2 variant seemed to have little effect. Combining the
three variants resulted in increased cessation rates compared to placebo with a combination
of high-activity variants for both bupropion and nortriptyline (bupropion:
60% vs. 0% at both 6- and 12-months; nortriptyline: 54% and 46% vs. 0% at 6and
12-months). CONCLUSIONS: Both bupropion and nortriptyline are more
effective in the presence of high-activity variants of the serotonin transporter, probably
by blocking the increased serotonin transporter activity, hereby increasing serotonin
levels. Prospective studies have to assess if this can improve cessation rates
when bupropion and nortriptyline treatment is targeted at individuals based on
their genotypes.
1364 TOXICOGENOMICS OF NEVIRAPINE-ASSOCIATED
CUTANEOUS AND HEPATIC ADVERSE EVENTS
AMONG POPULATIONS OF AFRICAN, ASIAN, AND
EUROPEAN DESCENT.
J. Yuan 1 , S. Guo 1 , D. Hall 1 , A. Cammett 1 , S. Jayadev 1 , M. Distel 2 , S. Storfer 1 ,
Z. Huang 1 , P. Mootsikapun 3 , K. Ruxrungtham 4 , D. Podzamczer 5 and D. Haas 6 .
1 Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, CT, 2 Boehringer Ingelheim
GmbH, Ingelheim, Germany, 3 Khon Kaen University, Khon Kaen, Thailand,
4 Chulalongkorn University, Bangkok, Thailand, 5 Hospital Universitari de Bellvitge,
Barcelona, Spain and 6 Vanderbilt University School of Medicine, Nashville, TN.
Nevirapine is widely prescribed for HIV-1 infection. We characterized relationships
between nevirapine-associated cutaneous and hepatic adverse events (AEs) and genetic
variants among HIV-infected adults. We retrospectively identified cases and
controls. Cases had experienced symptomatic nevirapine-associated severe (grade
III/IV) cutaneous and/or hepatic AEs within 8 weeks of initiating nevirapine.
Controls did not experience AEs during >18 weeks of nevirapine therapy. Cases
and controls were matched 1:2 on baseline CD4 T-cell count, sex, and race.
Individuals with ≤150 CD4 T-cells/mm3 at baseline were excluded. We characterized
123 HLA alleles and 2744 single nucleotide polymorphisms in major histocompatibility
complex (MHC) and drug metabolism and transport genes. We studied
276 evaluable cases (175 cutaneous AEs, 101 hepatic AEs) and 587 controls.
292 SOT 2011 ANNUAL MEETING
Cutaneous AEs were associated with CYP2B6 516GÇT (OR 1.66, all), HLA-
Cw*04 (OR 2.51, all), and HLA-B*35 (OR 3.47, Asians; 5.65, Thais). Risk for cutaneous
AEs was particularly high among Blacks with CYP2B6 516TT and HLA-
Cw*04 (OR 18.90), and Asians with HLA-B*35 and HLA-Cw*04 (OR 18.34).
Hepatic AEs were associated with HLA-DRB*01 (OR 3.02, Whites), but not
CYP2B6 genotypes. Associations differed by population, at least in part reflecting
allele frequencies. The study indicates polymorphisms in drug metabolism and immune
response pathways modulated AE risk. These results suggest fundamentally
different mechanisms of AEs: cutaneous, most likely MHC class I-mediated and influenced
by nevirapine CYP2B6 metabolism; hepatic, most likely MHC class IImediated
and unaffected by such metabolism. These risk variants are insensitive for
routine clinical screening.
1365 AN EVALUATION OF SINGLE NUCLEOTIDE
POLYMORPHISMS IN THE HUMAN ARYL
HYDROCARBON RECEPTOR NUCLEAR
TRANSLOCATOR GENE.
R. Budinsky 1 , J. D. Urban 2 and J. Rowlands 1 . 1 The Dow Chemical Company,
Midland, MI and 2 ToxStrategies, Inc., Austin, TX.
The effects of dioxin-like chemicals (DLCs) are mediated through the aryl hydrocarbon
receptor (AHR); a key step in activation of this pathway involves heterodimerization
with aryl hydrocarbon receptor nuclear translocator (ARNT) and
subsequent activation of xenobiotic metabolizing enzymes. The objective of this
study was to identify single nucleotide polymorphisms (SNPs) in the human
ARNT gene that could potentially affect the sensitivity of the AHR response pathway.
DNA from 101 human samples from six ethnic populations was sequenced
using PCR and resulting exonic SNPs were compared with SNPs described previously
in the literature or public databases. Results indicated that 69 samples had at
least one SNP, and five samples had two SNPs. Five unique SNPs were identified,
three of which were non-synonymous (two were novel). Several previously identified
SNPs were not identified in the current study, though the most commonly reported
SNP (V189V) in other studies was observed at a frequency of 0.49 in this
study. The potential functional consequences of the three non-synonymous SNPs
identified in the current dataset appear to be limited as the frequency of occurrence
was very low (< 0.02), and because two of the SNPs appear in regions of the protein
that are not within a defined functional domain. The remaining SNP (V304M) occurred
in the PAS domain of a single sample. Studies have suggested that a single
point mutation in this domain can negatively impact transcriptional function and
potentially lower ARNT levels. With respect to DLC exposures, this would suggest
that carriers of this SNP would be less sensitive to effects. However, loss and/or decrease
of ARNT function has also been associated with type 2 diabetes and thus additional
research is needed to fully understand the functional impact of the V304M
variant in the human population. Overall, results indicate a very limited presence of
polymorphisms in functional regions of the human ARNT.
1366 SINGLE NUCLEOTIDE POLYMORPHISMS IN THE
HUMAN ARYL HYDROCARBON RECEPTOR
INTERACTING PROTEIN (AIP) GENE FROM SIX
ETHNIC POPULATIONS.
D. Staskal-Wikoff 1 , R. Budinsky 2 and J. Rowlands 2 . 1 ToxStrategies, Inc., Austin,
TX and 2 The Dow Chemical Company, Midland, MI.
The biological effects of dioxin-like chemicals (DLCs) involve initial binding to
and activation of the aryl hydrocarbon receptor (AHR). The human AHR interacting
protein (AIP) is a chaperone protein that complexes with AHR, allowing for
AHR ligand-binding complex stabilization. It also interacts with AHR and heat
shock protein 90 (HSP90) to form a ligand-free AHR complex that prevents ubiquitination
and limits protein degradation. Thus the presence of single amino acid
polymorphisms at key functional domains in the AIP protein could affect AHR
protein integrity and/or signaling. The objective of this study was to screen 103
human DNA samples from six ethnic populations for single nucleotide polymorphisms
(SNPs) within the AIP gene that could potentially affect the sensitivity of
the AHR response pathway. Of the 103 samples evaluated, 42 samples had at least
one SNP, 12 samples had two SNPs, while one sample had three SNPs. Eight
unique exonic SNPs were identified in the dataset. Three AIP SNPs had not been
described previously in the literature or public databases, though these all resulted
in synonymous substitutions. Two non-synonymous SNPs were identified; both
were found in the African American population samples, and one was found in the
Mexican group. One of these (A276V) is located in a defined functional region [the