Oxidative DNA Adducts Detected in Vitro from Redox Activity of Cigarette Smoke Constituents

• Published in: Chemical research in toxicology 2012-11, Vol.25 (11), p.2499-2504
• Main Authors: Vadhanam, Manicka V, Thaiparambil, Jose, Gairola, C. Gary, Gupta, Ramesh C
• Format: Article
• Language: English
• Subjects: DNA Adducts - analysis; DNA Damage; Oxidation-Reduction; Oxidative Stress; Plants, Toxic; Smoking; Tobacco Products
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/tx300312f

Cigarette smoke contains a variety of carcinogens, cocarcinogens, mutagens, and tumor promoters. In addition to polycyclic aromatic carcinogens and tobacco-specific nitrosamines, cigarette smoke also contains an abundance of catechols, aldehydes, and other constituents, which are DNA damaging directly or indirectly; therefore, they can also contribute to cigarette smoke-mediated carcinogenicity. In this study, we investigated the potential of cigarette smoke constituents to induce oxidative damage to DNA through their capacity to redox cycle. When DNA (300 μg/mL) was incubated with cigarette smoke condensate (0.2 mg of tobacco particulate matter/mL) and CuCl2 as a catalyst (50–100 μM), a variety of oxidative DNA adducts were detected by 32P-postlabeling/TLC. Of the total adduct burden (2114 ± 419 adducts/106 nucleotides), over 40% of all adducts were attributed to the benchmark oxidative DNA lesion, 8-oxodeoxyguanosine (8-oxodG). Adducts were formed dose dependently. Essentially, similar adduct profiles were obtained when cigarette smoke condensate was substituted with ortho- and para-dihydroxybenzenes. Vehicle treatment with Cu2+ or CSC alone did not induce any significant amount of oxidative DNA damage. Furthermore, coincubation of cigarette smoke condensate and ortho-dihydroxybenzene with DNA resulted in a higher amount of oxidative DNA adducts than obtained with the individual entity, suggesting that adducts presumably originated from catechols or catechol-like compounds in cigarette smoke condensate. Adducts resulting from both cigarette smoke condensate and pure dihydroxybenzenes were chromatographically identical to adducts formed by reaction of DNA with H2O2, which is known to produce 8-oxodG, and many other oxidative DNA adducts. When the cigarette smoke condensate–DNA reaction was performed in the presence of ellagic acid, a known antioxidant, the adduct formation was inhibited dose dependently, further suggesting that adducts originated from oxidative pathway. Our data thus provide evidence of the capacity of catechols or catechol-like constituents in cigarette smoke to produce oxidative DNA damage, which may contribute to the tumor-promoting activity of cigarette smoke.