Studies Of The Reactions Of 1-chloro-3-buten-2-one With Thymidine And DNA

1,3-Butadiene(BD) is a carcinogenic air pollutant. The carcinogenicity of BD is thought to stem from its in vivo metabolites. In addition to be biotransformed to epoxides, BD can also be metabolized to 1-chloro-2-hydroxy-3-butene(CHB) and 1-chloro-3-butene-2-one(CBO). CHB and CBO both have cytotoxicity, genotoxicity, and mutagenicity. Cell experiments showed that CBO could directly cause DNA damage. It has been found that CBO can react with 2￠-deoxyguanosine(d G), 2￠-deoxyadenosine(d A), and 2￠-deoxycytidine(d C) to form multiple adducts. However, the reactions of CBO with thymidine and DNA have not been studied.In this thesis, we investigated the reaction of CBO with thymidine(d T) and the product was isolated and structurally charactered. We also studied kinetics of the reactions of CBO with each of four nucleosides and with the mixture of four nucleosides. Finally, we studied the reaction of CBO and DNA. These reactions were all carried out at in vitro physiological conditions.The results were listed as follows.(1) d T could react with CBO to generate N3-(3-oxo-4-chlorobutyl)thymidine, which was not stable with the half-lives being 61.6 ± 1.8 h.(2) The order of the reaction rates of four nucleosides with CBO was d A > d C > d G > d T, either in the reactions of single nucleosides or in the reaction of mixed ones.(3) When DNA was acid-hydrolyzed, we found that the reaction of CBO and DNA occured primarily at the N1-position of adenine and the N7-position of guanine, and the corresponding products were 1,N6-(3-hydroxy-3-chloromethylpropan-1,3-diyl)adenine and N7-(3-oxo-4-chlorobutyl)guanine, respectively. When DNA was enzymatically hydrolyzed, adducts of d C were also observed. These results suggested that CBO had strong reactivity, and could form adducts with three of four nucleobases. This might be the reason why CBO can directly cause DNA damage. Therefore, this pathway that BD is metabolized to CHB and CBO deserves further study.