DNA Adducts of Propylene Oxide and Acrylonitrile Epoxide: Hydrolytic Deamination of 3-Alkyl-dCyd to 3-Alkyl-dUrd

3,N4-Etheno, 3,N4-ethano, and 3-(2-hydroxyethyl)derivatives of 2'-deoxycytidine arise in mammalian DNA that has been exposed to the metabolic products of either vinyl chloride or the antitumor drug bis(chloroethyl)nitrosourea. These chemically-related adducts are thought to be associated with both mutagenesis and carcinogenesis. In this paper we report reliable syntheses of these deoxynucleosides and incorporation of the latter into oligodeoxynucleotides by the phosphoramidite route, using automated methods. It was found that 3-(2-hydroxyethyl)-2'-deoxycytidine is unstable in aqueous solution and undergoes an autoinduced hydrolysis to 3-(2-hydroxyethyl)-2'-deoxyuridine. The rate of this hydrolysis was found to be pH-dependent, having a maximum around pH 8, and a half-life of approximately 5 h. At higher or lower acidities, the reaction rate falls, indicating that the process involves a general acid-base catalysis. Thus in this case, oligomers were obtained that possessed 3-(2-hydroxyethyl)-2'-deoxyuridine residues, rather than the cytidine analogue. It is likely that the former represents the longer-lived species in DNA under physiological conditions. Representative oligomers containing these chemical lesions were analyzed by mass spectrometric and enzymatic degradation methods to confirm their structures.

Section: Resultsmentioning

confidence: 99%

“…This spontaneous hydrolysis, involving the loss of ammonia, occurs rapidly even under physiological conditions. It is mediated by the 2-hydroxyethyl group and leads to 3-(2-hydroxyethyl)-2'deoxyuridine (5; 3HE-dUrd) as the final stable product (12)(13)(14).…”

Section: Introductionmentioning

confidence: 99%

Synthesis of 3,N4-Etheno, 3,N4-Ethano, and 3-(2-Hydroxyethyl) Derivatives of 2'-Deoxycytidine and Their Incorporation into Oligomeric DNA

Zhang¹,

Rieger²,

Iden³

et al. 1995

“…The epoxide glycidamide, formed presumably via cytochrome P450, has been detected in the urine () and blood 2 of rodents exposed to AM. Both CEO and GA react with DNA ( − ) and are mutagenic( − ). These epoxides are believed to be involved in the carcinogenic activity of the parent compounds.…”

Section: Introductionmentioning

confidence: 99%

Urinary Metabolites from F344 Rats and B6C3F1 Mice Coadministered Acrylamide and Acrylonitrile for 1 or 5 Days

Sumner

Selvaraj

Nauhaus

et al. 1997

The purpose of this study was to examine the feasibility of using 13C NMR spectroscopy to analyze urinary metabolites produced following coadministration of two structurally similar carbon-13-labeled compounds to rodents. Acrylonitrile (AN) and acrylamide (AM) are used in the chemical industry to manufacture plastics and polymers. These compounds are known to produce carcinogenic, reproductive, or neurotoxic effects in laboratory animals. The potential for human exposure to AN and AM occurs in manufacturing facilities and environmentally. Male F344 rats and B6C3F1 mice were coadministered po [1,2,3-13C]AN (16-17 mg/kg) and [1,2,3-13C]AM (21-22 mg/kg) after 0 or 4 days of administration of unlabeled AN or AM. Urine was collected for 24 h following administration of the 13C-labeled compounds and analyzed by 13C NMR spectroscopy. Rats and mice excreted metabolites derived from glutathione (GSH) conjugation with AM or AN or derived from GSH conjugation with the epoxides cyanoethylene oxide (CEO) or glycidamide (GA). GA and its hydrolysis product were also detected in the urine of rats and mice. For mice, an increased urinary excretion of total AN- and total AM-derived metabolites (p < 0.05) on repeated coadministration suggested a possible increase in metabolism via oxidation. In addition, mice had an increased (p < 0.05) percentage of dose excreted as metabolites derived from GSH conjugation with AM, AN, CEO, or GA after five exposures as compared with one exposure that may be related to a significant increase in the synthesis of GSH or an increase in glutathione transferase activity. The only significant (p < 0.05) increase between one and five exposures for the rat was in the percentage of metabolites produced following conversion of AM to GA. The use of 13C NMR spectroscopy has provided a powerful methodology for elucidation of the metabolism of two 13C-labeled chemicals administered simultaneously.

“…The modified base then undergoes spontaneous intramolecular cyclization to form 3,V4-ethano-2'-deoxycytidine (ethano-dC) or hydrolysis to produce 3-(2-hydroxyethyl)-2'-deoxycytidine (3HE-dC). Under physiological conditions, the N-4 amino group of 3HE-dC is iost, generating 3-(2-hydroxyethyl)-2'-deoxyuridine (3-HE-dU) (12,13). These exocyclic related adducts (Figure 1), along with interstrand crosslinks, are likely to be involved in the cytotoxic and carcinogenic activity of BCNU (14).…”

Section: Introductionmentioning

confidence: 99%

Miscoding by the Exocyclic and Related DNA Adducts 3,N4-Etheno-2'-deoxycytidine, 3,N4-Ethano-2'-deoxycytidine, and 3-(2-Hydroxyethyl)-2'-deoxyuridine

Zhang¹,

Johnson²,

Grollman³

et al. 1995

3,N4-Etheno-2'-deoxycytidine, 3-(hydroxyethyl)-2'-deoxyuridine, and 3,N4-ethano-2'-deoxy-cytidine are found in DNA of cells treated with either vinyl chloride or 1,3-bis(2-chloroethyl)-nitrosourea. These exocyclic and related DNA adducts were incorporated into oligodeoxynucleotides, which were then used as templates for primer extension in reactions catalyzed by the Klenow fragment of Escherichia coli DNA polymerase I. The miscoding potential of each lesion was determined quantitatively. DNA primers were readily extended on an epsilon dC-modified template; dAMP and dTMP were incorporated opposite the lesion. With high concentrations of DNA polymerase, small amounts of fully extended reaction products containing dAMP and dGMP or one-base and two-base deletions opposite ethano-dC were formed. Primer extension was blocked partially on templates containing 3-(hydroxyethyl)-dU; dAMP and smaller amounts of dTMP and dCMP were incorporated. The frequencies of nucleotide insertion opposite each of the three lesions and the frequencies of chain extension from the 3'-primer terminus, determined by kinetic analysis, were consistent with results of experiments utilizing polyacrylamide gel electrophoresis. We conclude from these studies that epsilon dC, ethano-dC, and 3-(hydroxyethyl)-U are potentially miscoding lesions; only epsilon dC facilitates translesional synthesis.