Syntheses of isotope‐labeled tobacco‐specific nitrosamines and their metabolites

Desai, Dhimant; Krzeminski, Jacek; El‐Bayoumy, Karam; Amin, Shantu

doi:10.1002/jlcr.1508

Cited by 1 publication

(1 citation statement)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Synthesis and Purification of D 4 -NNAL-O-and N-Gluc Standards. To obtain D 4 -NNAL-N-Gluc and -O-Gluc, bovine liver microsomes (5 mg of protein/mL reaction) were used to catalyze D 4 -NNAL (a kind gift from Shantu Amin; Penn State University, Hershey, PA) 54 conjugation with glucuronic acid. Bovine liver microsomes were initially incubated with alamethicin (50 μg/mg protein) on ice for 15 min and were then incubated with D 4 -NNAL (20 mM) at 37 °C in Tris buffer (50 mM, pH 7.5), MgCl 2 (10 mM), and UDPGA (8 mM) for 2 h. The reaction was quenched with the addition of an equal volume of ice-cold acetonitrile.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Stereospecific Metabolism of the Tobacco-Specific Nitrosamine, NNAL

Kozlovich

Chen

Lazarus

2015

Chem. Res. Toxicol.

View full text Add to dashboard Cite

Among the most potent carcinogens in tobacco are the tobacco-specific nitrosamines (TSNAs), with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) the most abundant as well as the most potent. NNK is extensively metabolized to the equally carcinogenic 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). Of the two NNAL enantiomers, (S)-NNAL appears to be preferentially glucuronidated and excreted in humans, but also exhibits higher stereoselective tissue retention in mice and humans and has been shown to be more carcinogenic in mice than its (R)- counterpart. Due to the differential carcinogenic potential of the two NNAL enantiomers, it is increasingly important to know which UGT enzyme targets the specific NNAL enantiomers for glucuronidation. To examine this, a chiral separation method was developed to isolate entiomerically pure (S)- and (R)-NNAL. Comparison of NNAL glucuronide (Gluc) peaks formed in reactions of UGT2B7-, UGT2B17-, UGT1A9-, and UGT2B10-over-expressing cell microsomes with pure NNAL enantiomers showed large differences in kinetics for (S)- versus (R)-NNAL, indicating varying levels of enantiomeric preference for each enzyme. UGT2B17 preferentially formed (R)-NNAL-O-Gluc and UGT2B7 preferentially formed (S)-NNAL-O-Gluc. When human liver microsomes (HLM) were independently incubated with each NNAL enantiomer, the ratio of (R)-NNAL-O-Gluc to (S)-NNAL-O-Gluc formation in HLM from subjects exhibiting the homozygous deletion UGT2B17 (*2/*2) genotype was significantly lower (p=0.012) than HLM from wild-type (*1/*1) subjects. There was a significant trend (p=0.015) towards decreased (R)-NNAL-O-Gluc:(S)-NNAL-O-Gluc ratio with increasing numbers of the UGT2B17*2 deletion allele. These data demonstrate that variations in the expression or activity of specific UGTs may affect individual susceptibility to cancers induced by specific NNAL enantiomers.

show abstract

Section: ■ Materials and Methodsmentioning

confidence: 99%