Oxidative damage to cellular and isolated DNA by homocysteine: implications for carcinogenesis

Abstract

Homocysteine is considered to be an important risk factor for cancer as well as cardiovascular diseases. To clarify whether homocysteine has potential carcinogenicity, we investigated formation of 8-oxo-7,8-dihydro-2 0 -deoxyguanosine (8-oxodG), which is known to be correlated with the incidence of cancer, induced by homocysteine in human cultured cell lines. Homocysteine increased the amount of 8-oxodG in human leukemia cell line HL-60, whereas the amount of 8-oxodG in its hydrogen peroxide (H 2 O 2 )-resistant clone HP100 was not increased. We investigated the mechanism for oxidative DNA damage by homocysteine using 32 P-labeled DNA fragments obtained from human tumor suppressor genes and a protooncogene. There were two mechanisms by which homocysteine caused DNA damage in the presence of Cu(II). A low concentration of homocysteine (20 lm) frequently induced piperidine-labile sites at thymine residues, whereas a high concentration of homocysteine (100 lm) resulted in damage principally to guanine residues. Catalase inhibited DNA damage by 20 lm homocysteine, indicating the participation of H 2 O 2 , but was ineffective in preventing DNA damage by 100 lm homocysteine. Experiments using a singlet oxygen probe showed that 100 lm homocysteine enhanced chemiluminescence intensity in deuterium oxide more than that in H 2 O. These results indicated that the metal-dependent DNA damage through H 2 O 2 is likely to be a more relevant mechanism for homocysteine carcinogenicity.

Cross-Talk Between One-Carbon Metabolism and Xenobiotic Metabolism: Implications on Oxidative DNA Damage and Susceptibility to Breast Cancer

“…Our earlier study shows dose-dependent association between homocysteine and DNA damage in vivo and in vitro [37]. Oikawa et al [38] demonstrated similar association in human leukemia cell line HL-60, however, they observed no such increase in 8-oxodG with increase in homocysteine in hydrogen peroxide resistant clone HP-100 suggesting that the oxidative DNA damage is a result of superoxide generation. Mild increase in homocysteine (20 lM) was found to induce piperidine-labile sites at the thymine residues and moderate to severe increase (100 lM) was associated with 8-oxodG formation [38].…”

Homocysteine induces DNA damage and alterations in proliferative capacity of T-lymphocytes: a model for immunosenescence?

“…Although the underlying mechanisms promoting DNA damage has not yet been established, it is possible to hypothesize the involvement of ROS production (Kruman et al 2000;Oikawa et al 2003). Some evidence suggest that different approaches may be useful to ameliorate toxic effects of Hcy, including quenching of oxidative agents and maintenance of transmethylation pathway (Szeto and Benzie 2002).…”

Synthesis of methyl-substituted xanthotoxol to clarify prooxidant effect of methyl on radical-induced oxidation of DNA

“…The oxidation of Cu(II)-binding DNA catalyzed by intracellular GSH increased the amount of 8-oxo-7,8-dihydro-2 0 -deoxyguanosine (8-oxodG) [25] because of the generation of GSH radical (GS ) via Cu(II) þ GSH / Cu(I) þ GS [26]. The further oxidation of DNA mediated by Cu 2þ /GSH broke the strand of DNA to form propenals, which can be detected after treated by thiobarbituric acid (TBA), thus, propenals were also called TBA reactive substance (TBARS, l max ¼ 535 nm) [19].…”