RT Journal Article
SR Electronic
T1 Oxidation of Vinyl Carbamate and Formation of 1,<em>N</em><sup>6</sup>-Ethenodeoxyadenosine in Murine Lung
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 713
OP 720
DO 10.1124/dmd.106.013805
VO 35
IS 5
A1 Forkert, Poh-Gek
A1 Kaufmann, Martin
A1 Black, Gordon
A1 Bowers, Raymond
A1 Chen, Heidi
A1 Collins, Kathy
A1 Sharma, Ashish
A1 Jones, Glenville
YR 2007
UL http://dmd.aspetjournals.org/content/35/5/713.abstract
AB Vinyl carbamate (VC) is derived from ethyl carbamate, a carcinogen formed in fermentation of food and alcoholic products. We have undertaken studies to test the hypothesis that an epoxide generated from VC oxidation leads to formation of 1,N6-ethenodeoxyadenosine (ϵdAS). We have developed approaches using liquid chromatography-mass spectrometry and liquid chromatographytandem mass spectrometry for identification and quantitation of ϵdAS. Scanning and fragment ion analyses confirmed the identity of ϵdAS based on the molecular ion [M + H]+m/z 276 and the specific fragment ion m/z 160. Chemical oxidation of VC in reactions containing 2′-deoxyadenosine produced ϵdAS with 1H NMR, chromatographic, and mass spectral characteristics identical to those of the authentic ϵdAS, suggesting DNA alkylation by the VC epoxide. Subsequent studies evaluated formation of ϵdAS in incubations of murine lung microsomes or recombinant CYP2E1 with VC. The formation of ϵdAS in incubations of lung microsomes or recombinant CYP2E1 with VC was dependent on protein concentrations, CYP2E1 enzyme levels, and incubation time. The rates of ϵdAS formation were highly correlated with VC concentrations. Peak rates were produced by lung microsomes and recombinant CYP2E1 at 3.0 and 2.5 mM VC, respectively. In inhibitory studies, incubations of VC were performed using lung microsomes from mice treated with the CYP2E1 inhibitor diallyl sulfone (100 mg/kg, p.o.). Results from these studies showed significantly decreased ϵdAS formation in microsomes incubated with VC, with an inhibition of 70% at 3.0 mM. These findings suggested that CYP2E1 is a major enzyme mediating VC oxidation, leading to the formation of a metabolite that alkylates DNA to form the ϵdAS adduct. The American Society for Pharmacology and Experimental Therapeutics