RESUMO
Exocyclic DNA adducts are considered as potential tools for the study of oxidative stress-related diseases, but an important aspect is their chemical reactivity towards oxidant species. We report here the oxidation of 1-N2-etheno-2'-deoxyguanosine (1,N2-εdGuo) by singlet molecular oxygen (1O2) generated by a non-ionic water-soluble endoperoxide [N,N'-di(2,3-dihydroxypropyl)-1,4-naphthalenedipropanamide endoperoxide (DHPNO2)] and its corresponding oxygen isotopically labeled [18O]-[N,N'-di(2,3-dihydroxypropyl)-1,4- naphthalenedipropanamide endoperoxide (DHPN18O2)], and by photosensitization with two different photosensitizers [methylene blue (MB) and Rose Bengal (RB)]. Products detection and characterization were achieved using high performance liquid chromatography (HPLC) coupled to ultraviolet and electrospray ionization (ESI) tandem mass spectrometry, and nuclear magnetic resonance (NMR) analyses. We found that dGuo is regenerated via reaction of 1O2 with the ε-linkage, and we propose a dioxetane as an intermediate, which cleaves and loses the aldehyde groups as formate residues, or alternatively, it generates a 1,2-ethanediol adduct. We also report herein the quenching rate constants of 1O2 by 1,N2-εdGuo and other etheno modified nucleosides. The rate constant (kt) values obtained for etheno nucleosides are comparable to the kt of dGuo. From these results, we suggest a possible role of 1O2 in the cleanup of etheno adducts by regenerating the normal base.
Assuntos
Dano ao DNA , Desoxiguanosina/química , Oxigênio Singlete/química , Desoxiguanosina/análogos & derivados , Desoxiguanosina/isolamento & purificação , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Estrutura Molecular , OxirreduçãoRESUMO
4-hydroxy-2-nonenal (HNE) is an amazing reactive compound, originating from lipid peroxidation within cells but also in food and considered as a "second messenger" of oxidative stress. Due to its chemical features, HNE is able to make covalent links with DNA, proteins and lipids. The aim of this review is to give a comprehensive summary of the chemical properties of HNE and of the consequences of its reactivity in relation to cancer development. The formation of exocyclic etheno-and propano-adducts and genotoxic effects are addressed. The adduction to cellular proteins and the repercussions on the regulation of cell signaling pathways involved in cancer development are reviewed, notably on the Nrf2/Keap1/ARE pathway. The metabolic pathways leading to the inactivation/elimination or, on the contrary, to the bioactivation of HNE are considered. A special focus is given on the link between HNE and colorectal cancer development, due to its occurrence in foodstuffs and in the digestive lumen, during digestion.
Assuntos
Aldeídos/metabolismo , Carcinogênese/metabolismo , Neoplasias Colorretais/metabolismo , Adutos de DNA/biossíntese , Regulação Neoplásica da Expressão Gênica , Doenças Inflamatórias Intestinais/metabolismo , Lesões Pré-Cancerosas/metabolismo , Carcinogênese/genética , Carcinogênese/patologia , Colo/metabolismo , Colo/patologia , Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Humanos , Doenças Inflamatórias Intestinais/genética , Doenças Inflamatórias Intestinais/patologia , Proteína 1 Associada a ECH Semelhante a Kelch/genética , Proteína 1 Associada a ECH Semelhante a Kelch/metabolismo , Proteínas Quinases Ativadas por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Fator 2 Relacionado a NF-E2/genética , Fator 2 Relacionado a NF-E2/metabolismo , Oxirredução , Estresse Oxidativo , Lesões Pré-Cancerosas/genética , Lesões Pré-Cancerosas/patologia , Proteína Quinase C/genética , Proteína Quinase C/metabolismo , Transdução de SinaisRESUMO
AlkB proteins are evolutionary conserved Fe(II)/2-oxoglutarate-dependent dioxygenases, which remove alkyl and highly promutagenic etheno(É)-DNA adducts, but their substrate specificity has not been fully determined. We developed a novel assay for the repair of É-adducts by AlkB enzymes using oligodeoxynucleotides with a single lesion and specific DNA glycosylases and AP-endonuclease for identification of the repair products. We compared the repair of three É-adducts, 1,N(6)-ethenoadenine (ÉA), 3,N(4)-ethenocytosine (ÉC) and 1,N(2)-ethenoguanine (1,N(2)-ÉG) by nine bacterial and two human AlkBs, representing four different structural groups defined on the basis of conserved amino acids in the nucleotide recognition lid, engaged in the enzyme binding to the substrate. Two bacterial AlkB proteins, MT-2B (from Mycobacterium tuberculosis) and SC-2B (Streptomyces coelicolor) did not repair these lesions in either double-stranded (ds) or single-stranded (ss) DNA. Three proteins, RE-2A (Rhizobium etli), SA-2B (Streptomyces avermitilis), and XC-2B (Xanthomonas campestris) efficiently removed all three lesions from the DNA substrates. Interestingly, XC-2B and RE-2A are the first AlkB proteins shown to be specialized for É-adducts, since they do not repair methylated bases. Three other proteins, EcAlkB (Escherichia coli), SA-1A, and XC-1B removed ÉA and ÉC from ds and ssDNA but were inactive toward 1,N(2)-ÉG. SC-1A repaired only ÉA with the preference for dsDNA. The human enzyme ALKBH2 repaired all three É-adducts in dsDNA, while only ÉA and ÉC in ssDNA and repair was less efficient in ssDNA. ALKBH3 repaired only ÉC in ssDNA. Altogether, we have shown for the first time that some AlkB proteins, namely ALKBH2, RE-2A, SA-2B and XC-2B can repair 1,N(2)-ÉG and that ALKBH3 removes only ÉC from ssDNA. Our results also suggest that the nucleotide recognition lid is not the sole determinant of the substrate specificity of AlkB proteins.