title: Nucleoside and DNA adducts from N-nitrosotolazoline.
abstract: The reaction of N-nitrosotolazoline, the nitrosation product of a representative imidazoline receptor drug tolazoline, with DNA, deoxyguanosine (dG), or deoxyadenosine (dA) produces adducts containing the 2-phenylacetamidoethyl group. The synthesis and characterization of 2-phenylacetamidoethyl-guanine derivatives (O6-dG, O6-Gua, N2-Gua, and 7-Gua) and 2-phenylacetamidoethyladenine derivatives (1-Ade, 3-Ade, 7-Ade, and N6-Ade) are described. In addition to the use of an established UV spectral method for confirming the structure of the alkyl adenines, a new 13C NMR method for determining the N-alkylation site is presented. In combination with the synthesized standards, HPLC MS/MS methods were used to determine the nature and the quantity of adducts produced. N-Nitrosotolazoline reacted with dG to give 7-(2-phenylacetamidoethyl)deoxyguanosine (major), O6-(2-phenylacetamidoethyl)deoxyguanosine, and 5'-O-phenyacetyldeoxyguanosine. The reaction of N-nitrosotolazoline with dA produced the 1-, 3-, 7-, N6, and 5-O'-2-phenylacetamidoethyl adenine and dA derivatives as well as several phenylacetyl adducts. Reaction of N-nitrosotolazoline with DNA in vitro resulted in the detection of 2-phenylacetamidoethyl adducts (adduct, relative %): 7-Gua, 60%; 3-Ade, 30%; O6-Gua, 8%; and 7-Ade, 2%. Comparison of these data with appropriate literature data, as well as our work on the mechanism of N-nitrosotolazoline hydrolytic decomposition, is consistent with the adducts being produced from a 2-phenylacetamidoethyldiazonium intermediate. The results show that N-nitrosotolazoline, and presumably other N-nitrosoimidazolines, if produced by endogenous nitrosation pathways, are capable of alkylating DNA without additional metabolic transformation and are probable carcinogens.
authors.affiliation: Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195, USA. LoeppkyR@Missouri.edu
authors.forename: Richard N
authors.initials: RN
authors.lastname: Loeppky
authors.forename: Jianzheng
authors.initials: J
authors.lastname: Shi
mesh_terms: D000959:Antihypertensive Agents / Q000737:chemistry* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D018736:DNA Adducts / Q000737:chemistry* / Q000378:metabolism; D003839:Deoxyadenosines / Q000737:chemistry* / Q000378:metabolism; D003849:Deoxyguanosine / Q000737:chemistry* / Q000378:metabolism; D009602:Nitrosamines / Q000737:chemistry* / Q000378:metabolism; D053719:Tandem Mass Spectrometry; D014043:Tolazoline / Q000031:analogs & derivatives*
chemical_list: D000959:Antihypertensive Agents; D018736:DNA Adducts; D003839:Deoxyadenosines; D009602:Nitrosamines; C008653:nitrosoimidazolidone; D014043:Tolazoline; D003849:Deoxyguanosine