Detection of N²,3-ethenoguanine in DNA after treatment with chloroacetaldehyde in vitro

Abstract

The reaction of chloroacetaldehyde, a reactive metabolic of the carcinogen vinyl chloride, with DNA produces in addition to the hitherto known adducts, 1,N6-ethenoadenine and 3,N4-ethenocytosine, an ethenoguanine adduct, namely N2,3-ethenoguanine. This adduct is formed in the reaction of chloroacetaldehyde with the free base as well. After DNA hydrolysis followed by isolation of this new adduct by h.p.l.c., its mass spectrum and fluorescence spectrum are identical with those published in the literature for the chemically synthesized N2,3-ethenoguanine. The formation of only this guanine derivative out of several theoretically possible reaction products allows the formulation of a reaction scheme. The absence of 7-(2-oxoethyl)-guanine, another recently detected DNa adduct of vinyl chloride, in chloroacetaldehyde-treated DNA suggests its origin from the other reactive metabolic of vinyl chloride, chloroethylene oxide. The potential of N2,3-ethenoguanine to lead to misincorporation of deoxythymidine monophosphate opposite of guanine and the high fluorescence of this adduct provide it with potentially high biological significance and ease of analytical monitoring.

Conformational junctions between left‐handed DNA in (dA‐dT)16 and contiguous B‐DNA in a supercoiled plasmid contain chemically reactive bases

“…In addition to reactivity of unpaired cytosines and adenines we have observed the reactivity of unpaired guanines with CAA, in agreement with the results of others [19]. Although less reactive, guanine residues react at the exocyclic amino group and the ring nitrogen in N-l or N-3 position [20,21].…”

“…Although less reactive, guanine residues react at the exocyclic amino group and the ring nitrogen in N-l or N-3 position [20,21] …”

Release of N2,3-ethenoguanine from chloroacetaldehyde-treated DNA by Escherichia coli 3-methyladenine DNA glycosylase II.

“…1, only one derivative was detected in the bases released from CAA-[14C]G-DNA by mild acid treatment; oeG was specifically absent, as reported earlier (8). However, a small additional peak of radioactivity was released by glycosylase II as shown in Fig.…”

“…Vinyl chloride is metabolized by the cytochrome P450 system in the liver to the unstable electrophile chloroethylene oxide, which rearranges spontaneously to the more stable alkylating agent chloroacetaldehyde (CAA) (2,3). Chloroethylene oxide and CAA react with DNA to form a variety of adducts, many of which have been identified in vivo (4)(5)(6)(7)(8)(9)(10). The question has arisen, therefore, as to which DNA modification or modifications may be responsible for initiating the carcinogenic process.…”

Determination of leukocyte DNA 6-thioguanine nucleotide levels by high-performance liquid chromatography with fluorescence detection

“…Since we could not reproduce the results of these assays, we developed a new method for the determination of DNA-6TGN. The procedure involves derivatization with chloroacetaldehyde (CAA) and hydrolysis of the formed etheno derivatives: the proposed N 2 ,3-etheno 6-thioguanine (6TG), 1,N 6 -etheno adenine (A) [20] and N 2 ,3-etheno guanine (G) [21] (Fig. 1) from DNA, extraction of 6TG by immobilized metal ion affinity chromatography (IMAC) and quantification by ion-pair reversed-phase HPLC with fluorescence detection.…”