DNA adducts derived from lipid peroxidation: Site-specific synthesis and reactivity of oligonucleotides containing stereochemically defined trans-4-hydroxynonenal and malondialdehyde adducts.

摘要

trans-4-Hydroxynonenal (HNE) and malondialdehyde (MDA) are two major peroxidation products of ω-6 polyunsaturated fatty acids. Both HNE and MDA react with DNA to form endogenous DNA adducts and have mutagenic potential. Thus, the peroxidation of lipids represents an endogenous source of cytotoxins and genotoxins.; The reaction of HNE with DNA gives four diastereomeric 1,N 2-8-hydroxypropano adducts of deoxyguanosine; background levels of these adducts have been detected in animal tissue. Stereospecific syntheses of these four adducts at the nucleoside level have been accomplished. In addition, a versatile strategy for their site-specific incorporation into oligonucleotides has been developed. These adducts are destabilizing as measured by melting temperature when compared to an unadducted strand. The thermal destablization of the adducted 12-mers ranged from 5 to 16°C and is dependent on the absolute stereochemistry of the adduct. The HNE adducts were also examined for their ability to form interstrand DNA-DNA cross-links when incorporated into a CpG sequence. We find that only one of the HNE stereoisomers formed interstrand DNA-DNA cross-links.; MDA reacts with DNA bases to produce adducts of deoxyguanosine (M ₁G), deoxyadenosine (M₁A) and deoxycytidine (M₁C). A novel synthesis of these MDA-adducted nucleosides has been developed which significantly improves their availability. For the deoxyguanosine adduct, M₁G, an amine equivalent to MDA, 4-amino-3-(phenylselenyl)butane-1,2-diol, was reacted with 2-fluoro-O6-(2-(trimethylsilyl)ethyl)-2 ′-deoxyinosine via a nucleophilic aromatic substitution reaction followed by acid hydrolysis of O6-protecting group to give an N2-modified deoxyguanosine intermediate. Periodate oxidation of this intermediate under slightly acidic conditions gave M₁G in good overall yield via cleavage of the vicinal diol and syn-β-elimination of selenoxide. M₁A and M₁ C were synthesized by the same strategy starting from 6-choloropurine 2′-deoxyriboside and 1-(2-deoxy-β-D-erythro -pentofuranosyl)-4-(1H-1,2,4-triazol-1-yl)-2(1 H)-pyrimidinone, respectively. Thus, the same chemistry was directly applied to the site-specific synthesis of MDA-adducted oligonucleotides. This strategy provided an alternative approach to the synthesis of oligonucleotides containing M₁G and a first approach to M₁A containing oligonucleotides.