Reactivity of Conjugated Aldehydes with DNA bases

MARISA TAVERNA PORRO; DIDIER GASPARUTTO; JEAN-LUC RAVANAT

XVth Symposium on chemistry of nucleic acid components.

Collection of Czechoslovak Chemical Communications and Editor of Proceedings

Lugar: Prague; Año: 2011; p. 472 - 474

Oxidative stress is known to be involved in several biological disorders and associated to several pathologies. Generated reactive oxygen species (ROS) are able to induce chemical modifications to biomolecules and in particular to DNA. Much attention has been focused on base damage, but recent observations suggest that sugar oxidative degradation pathways may also play an important role in DNA alteration. A common feature of sugar oxidation reactions is the transient generation of reactive aldehydes, especially α,β-unsaturated dicarbonyl species that, due to their electrophilic character, can react with nucleophiles moieties of DNA bases with the subsequent formation of adducts. Structural characterization of the adducts has been performed on products of the reaction between unsaturated aldehydes and DNA bases; showing the formation of stable oxadiazabicyclo(3.3.0)octaimine adducts. Examples include the formation of stable adducts in the reaction of cis- and trans-1;4-dioxo-2-butene with 2?-deoxycytidine (dCyd), 2?-deoxyguanosine (dGuo) and 2?-deoxyadenosine (dAdo)[1]. Also, trans-hydroxy-2-hexenal and trans-4-hydroxy-2-nonenal (products of lipid peroxidation) have been shown to add to dGuo[2] and dAdo[3]. Ravanat et al have demonstrated that hydrogen abstraction at the 4? position of the 2-deoxyribose moiety leads to the formation of dCyd adducts, following the transient formation of a conjugated aldehyde[4]. The proposed reaction mechanism involves initial reaction of the C1 atom of the unsaturated aldehyde with the exocyclic nitrogen atom of the nucleosides (N4 of dCyd, N2 of dGuo and N6 of dAdo). This reaction is followed by 1,4-addition of the adjacent endocyclic nitrogen atom (N3 of dCyd and N1 of dGuo and dAdo) to the double bond, to form the final products . It was demonstrated that this reaction could lead to several oxidation products, namely substituted ethano and etheno adducts. Regarding the ethano adducts it was shown that the ethano ring in the cis configuration exists mostly as a hemiaketal, formed by the subsequent attack of the alcohol on the carbonyl group while cyclisation is not possible for the corresponding trans isomers. Finally the adducts can undergo dehydration to form an etheno derivative. It was shown that this dehydration reaction was favoured by prolonged heating and treatment with acids or bases[5] To determine the structure and proportion of the different adducts, a chemical synthetic approach was designed to produce larger amounts of these DNA lesions. The strategy we have adopted consisted in the synthesis of the acetylated derivative of a ketoaldehyde that, upon incubation with the free nucleosides and bases, would give rise to the final products. For that purpose, we have developed a method based on the oxidation of furfuryl acetate to selectively generate 2,5-dioxo-pent-3-enyl acetate. The reaction mixture was then incubated with dCyd, dGuo, dAdo and 1-methylcytosine under different conditions of pH and temperature. In addition, in order to better study the relative reactivity of the conjugated keto-aldehyde with the different nucleobases we have performed the reaction directly with a mixture of nucleosides and with isolated DNA. Identification and quantification of the different adducts was performed by HPLC coupled with electrospray ionisation tandem mass spectrometry. In addition, attempts have been made to isolate the different possible isomers by HPLC in order to fully characterize them by NMR. In the near future efforts will be made to search for such DNA lesions in cells exposed to different oxidative stresses. During the last few years, several works have highlighted the fact that reactive aldehydes could be generated in double stranded DNA and induce the formation of different types of DNA lesions, including inter-strand cross-links and DNA-protein cross-links[6]. Therefore, it is of primary importance to better understand the reactivity of these aldehydes with DNA bases. REFERENCES 1. Bohnert, T., Gingipalli, L. and Dedon, P.C.: Biochem Biophys Res Commun. 2004, 323, 838. 2. Rindgen, D., Nakajima, M., Wehrli, S., Xu, K. and Blair, I.A.: Chem Res Toxicol, 1999, 12, 1195. 3. Lee, S.H., Rindgen, D., Bible, R.H., Jr., Hajdu, E. and Blair, I.A.: Chem Res Toxicol, 2000, 13, 565. 4. Regulus, P., Duroux, B., Bayle, P.A., Favier, A., Cadet, J. and Ravanat, J.L.: Proc Natl Acad Sci U S A, 2007; 104, 14032. 5. Byrns, M.C., Predecki, D.P. and Peterson, L.A.: Chem Res Toxicol, 2002, 15, 373. 6. Sczepanski, J.T., Wong, R.S., McKnight, J.N., Bowman, G.D. and Greenberg, M.M.: Proc Natl Acad Sci U S A, 2010, 107, 22475.