James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA.
Chem Res Toxicol. 2012 Nov 19;25(11):2499-504. doi: 10.1021/tx300312f. Epub 2012 Oct 26.
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 CuCl(2) as a catalyst (50-100 μM), a variety of oxidative DNA adducts were detected by (32)P-postlabeling/TLC. Of the total adduct burden (2114 ± 419 adducts/10(6) 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 Cu(2+) 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 H(2)O(2), 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.
香烟烟雾中含有多种致癌物质、协同致癌物质、致突变物质和肿瘤促进剂。除了多环芳烃致癌物质和烟草特异性亚硝胺外，香烟烟雾中还含有丰富的儿茶酚、醛类和其他成分，这些成分直接或间接地破坏 DNA，因此也可能导致香烟烟雾介导的致癌作用。在这项研究中，我们通过其氧化还原循环能力研究了香烟烟雾成分诱导 DNA 氧化损伤的潜力。当 DNA（300μg/ml）与香烟烟雾冷凝物（0.2mg 烟草颗粒/ml）和 CuCl2（50-100μM）作为催化剂一起孵育时，通过（32）P-后标记/TLC 检测到多种氧化 DNA 加合物。在总加合物负担（2114±419 个加合物/106 个核苷酸）中，超过 40%的加合物归因于基准氧化 DNA 损伤 8-氧脱氧鸟苷（8-oxodG）。加合物呈剂量依赖性形成。实际上，当用邻苯二酚和对苯二酚替代香烟烟雾冷凝物时，获得了相似的加合物图谱。单独用 Cu2+或 CSC 处理车辆不会引起任何明显数量的氧化 DNA 损伤。此外，香烟烟雾冷凝物和邻苯二酚与 DNA 共孵育导致的氧化 DNA 加合物数量高于单独实体获得的数量，这表明加合物可能源自香烟烟雾冷凝物中的儿茶酚或儿茶酚样化合物。由香烟烟雾冷凝物和纯二羟基苯形成的加合物与已知产生 8-氧脱氧鸟苷和许多其他氧化 DNA 加合物的 DNA 与 H2O2 反应形成的加合物在色谱上是相同的。当香烟烟雾冷凝物-DNA 反应在鞣花酸存在下进行时，一种已知的抗氧化剂，加合物的形成呈剂量依赖性抑制，这进一步表明加合物源自氧化途径。因此，我们的数据提供了香烟烟雾中儿茶酚或儿茶酚样成分产生氧化 DNA 损伤的能力的证据，这可能有助于香烟烟雾的肿瘤促进活性。
