ToxSci Advance Access originally published online on September 1, 2005
Toxicological Sciences 2005 88(2):311-318; doi:10.1093/toxsci/kfi307
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Published by Oxford University Press 2005.
Role of CYP2E1 in the Epoxidation of Acrylamide to Glycidamide and Formation of DNA and Hemoglobin Adducts
* Laboratory of Pharmacology and Chemistry, National Toxicology Program, NIEHS/NIH, Research Triangle Park, North Carolina 27709; NCTR, Jefferson, AR 72079; and RTI International, Research Triangle Park, North Carolina 27709
Received May 31, 2005; accepted August 29, 2005
Acrylamide (AA) is an animal carcinogen, neurotoxin, and reproductive toxin. AA is formed in baked and fried carbohydrate-rich foods. Metabolism of AA occurs via epoxidation to glycidamide (GA) or direct conjugation with glutathione. Using CYP2E1-null mice, recent studies in this laboratory demonstrated that induction of somatic and germ cell mutagenicity in AA-treated mice is dependent on CYP2E1. We hypothesized that AA metabolism to GA is a prerequisite for the induction of AA-induced mutagenicity. Current studies were undertaken to assess the role of CYP2E1 in the epoxidation of AA to GA and the formation of DNA and hemoglobin (HGB) adducts. AA was administered to CYP2E1-null or wild-type mice at 50 mg/kg ip. Mice were euthanized 6 h later and blood and tissues were collected. Using LC-ES/MS/MS, AA, GA, and DNA- and HGB-adducts were measured. While the plasma levels of AA and GA were 115 ± 14.0 and 1.7 ± 0.31 µM in CYP2E1-null mice, they were 0.84 ± 0.80 and 33.0 ± 6.3 µM in the plasma of AA-treated wild-type mice. Administration of AA to wild-type mice caused a large increase in N7-GA-Gua and N3-GA-Ade adducts in the liver, lung, and testes. While traces of N7-GA-Gua adducts were measured in the tissues of AA-treated CYP2E1-null mice, these levels were 52- to 66-fold lower than in wild-type mice. Significant elevation of both AA- and GA-HGB adducts was detected in AA-treated wild-type mice. In AA-treated CYP2E1-null mice, levels of AA-HGB adducts were roughly twice as high as those in wild-type mice. In conclusion, current work demonstrated that CYP2E1 is the primary enzyme responsible for the epoxidation of AA to GA, which leads to the formation of GA–DNA and HGB adducts.
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