Alkylation of 2‘-Deoxynucleosides and DNA by the Premarin Metabolite 4-Hydroxyequilenin Semiquinone Radical
- 23 January 1998
- journal article
- research article
- Published by American Chemical Society (ACS) in Chemical Research in Toxicology
- Vol. 11 (2), 94-101
- https://doi.org/10.1021/tx970181r
Abstract
Premarin (Wyeth-Ayerst) is the estrogen replacement treatment of choice and continues to be one of the most widely dispensed prescriptions in the United States. In addition to endogenous estrogens, Premarin contains unsaturated estrogens including equilenin. We synthesized the catechol metabolite of equilenin, 4-hydroxyequilenin (4-OHEN), and found that the semiquinone radical of 4-OHEN reacted with 2‘-deoxynucleosides generating very unusual adducts. 2‘-Deoxyguanosine (dG), 2‘-deoxyadenosine (dA), or 2‘-deoxycytosine (dC) all gave four isomers, but no product was observed for thymidine under similar physiological conditions. The structures of these adducts were determined by electrospray mass spectrometry and NMR experiments including 1H, 13C, DQF-COSY, ROESY, HOHAHA, HMQC, and HMBC. The spectral data show that dG forms a cyclic adduct with the 4-OHEN producing 2-N1,3-N2-deoxyguanosyl-1,3-dihydroxy-5,7,9(10)-estratriene-4,17-dione. Similarly, reaction with dA produced 1-N6,3-C2-deoxyadenosyl-2,3-dihydroxy-5,7,9(10)-estratriene-4,17-dione, and incubations with dC resulted in 1-N3,3-N4-deoxycytosyl-2,3-dihydroxy-5,7,9(10)-estratriene-4,17-dione. We found that care needed to be taken during the isolation of the dA adducts in particular, as any exposure to acidic environments caused hydrolysis of the sugar moiety leaving alkylated adenine. In mixtures of the deoxynucleosides treated with 4-OHEN, reaction occurred primarily with dG followed by dC and dA. With DNA significant apurinic sites were produced as 4-OHEN-adenine adducts were detected in the ethanol wash prior to hydrolysis. When the DNA was hydrolyzed to deoxynucleosides and analyzed by electrospray mass spectrometry, only one isomer of 4-OHEN-dG and one isomer of 4-OHEN-dC were observed. Our data suggest that several different types of DNA lesions could be expected from 4-OHEN including apurinic sites and bulky stable adducts, in addition to the published oxidized damage to DNA caused by 4-OHEN. The production of these semiquinone radical-derived DNA adducts could play a role in the carcinogenic effects of Premarin estrogens.Keywords
This publication has 11 references indexed in Scilit:
- Postmenopausal Hormone Therapy and MortalityNew England Journal of Medicine, 1997
- Prognostic and aetiological relevance of 8-hydroxyguanosine in human breast carcinogenesisEuropean Journal Of Cancer, 1996
- Molecular Mechanisms of Estrogen CarcinogenesisAnnual Review of Pharmacology and Toxicology, 1996
- The Use of Estrogens and Progestins and the Risk of Breast Cancer in Postmenopausal WomenNew England Journal of Medicine, 1995
- Separatory Determination of Biliary Metabolites of Equilin in Rat by High-Performance Liquid ChromatographyJournal of Liquid Chromatography, 1994
- Synthesis and characterization of estrogen 2,3- and 3,4-quinones. Comparison of DNA adducts formed by the quinones versus horseradish peroxidase-activated catechol estrogensChemical Research in Toxicology, 1992
- Are women using postmenopausal estrogens? A community survey.American Journal of Public Health, 1990
- Carcinogenicity of catechol estrogens in Syrian hamstersJournal of Steroid Biochemistry, 1986
- Quantitative reversed-phase high-performance liquid chromatography of major and modified nucleosides in dnaJournal of Chromatography A, 1984
- Relative rates of 2- and 4-hydroxyestrogen synthesis are dependent on both substrate and tissueFEBS Letters, 1982