Oxidative DNA Damage Induced by a Metabolite of 2–Naphthylamine a Smoking‐related Bladder Carcinogen

摘要

2‐Naphthylamine (2‐NA), a bladder carcinogen, is contained in cigarette smoke. DNA adduct formation is thought to be a major cause of DNA damage by carcinogenic aromatic amines. We have investigated whether a metabolite of 2‐NA, 2‐nitroso‐1‐naphthol (NO‐naphthol) causes oxidative DNA damage, using ³²P‐labeled DNA fragments. We compared the mechanism of DNA damage induced by NO‐naphthol with that by N‐hydroxy‐4‐aminobiphenyl (4‐ABP (NHOH)), a metabolite of 4‐aminobiphenyl, another smoking‐related bladder carcinogen. NO‐naphthol caused Cu(II)‐mediated DNA damage at T>C>G residues, with non‐enzymatic reduction by NADH. Catalase and bathocuproine, a Cu(I)‐specific chelator, inhibited the DNA damage, suggesting the involvement of H2O2 and Cu(I). Some free ·OH scavengers also attenuated NO‐naphthol‐induced DNA damage, while free ·OH scavengers had no effect on the DNA damage induced by 4–ABP(NHOH). This difference suggests that the reactive species formed by NO‐naphthol has more free ·OH‐ character than that by 4–ABP(NHOH). A high‐pressure liquid chromatograph equipped with an electrochemical detector showed that NO‐naphthol induced 8–oxo–7,8–dihydro–2′–deoxyguanosine formation in the presence of NADH and Cu(II). The oxidative DNA damage by these aminoaromatic compounds may participate in smoking‐related bladder cancer, in addition to DNA adduct formation.