Murata Mariko, Kurimoto Saori, Kawanishi Shosuke
Department of Environmental and Molecular Medicine, Mie University Graduate School of Medicine, Tsu, Mie, 514-8507, Japan.
Chem Res Toxicol. 2006 Oct;19(10):1379-85. doi: 10.1021/tx060133j.
Tetranitromethane (TNM) is used as an oxidizer in rocket propellants and explosives and as an additive to increase the cetane number of diesel fuel. TNM was reported to induce pulmonary adenocarcinomas and squamous cell carcinomas in mice and rats. However, the mechanisms underlying carcinogenesis induced by TNM has not yet been clarified. We previously revealed that nitroTyr and nitroTyr-containing peptides caused Cu(II)-dependent DNA damage in the presence of P450 reductase, which is considered to yield nitroreduction. Since TNM is a reagent for nitration of Tyr in proteins and peptides, we have hypothesized that TNM-treated Tyr and Tyr-containing peptides induce DNA damage by the modification of Tyr. We examined DNA damage induced by TNM-treated amino acids or peptides using (32)P-5'-end-labeled DNA fragments obtained from the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene. TNM-treated Tyr and Lys-Tyr-Lys induced DNA damage including the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine in the presence of Cu(II) and NADH. DNA damage was inhibited by catalase and bathocuproine, indicating the involvement of H(2)O(2) and Cu(I). The cytosine residue of the ACG sequence complementary to codon 273, well-known hotspots of the p53 gene, was cleaved with piperidine and Fpg treatments. On the other hand, nitroTyr and Lys-nitroTyr-Lys did not induce DNA damage in the presence of Cu(II) and NADH. Time-of-flight mass spectrometry confirmed that reactions between Lys-Tyr-Lys and TNM yielded not only Lys-nitroTyr-Lys but also Lys-nitrosoTyr-Lys. Therefore, it is speculated that the nitrosotyrosine residue can induce oxidative DNA damage in the presence of Cu(II) and NADH. It is concluded that Tyr-dependent DNA damage may play an important role in the carcinogenicity of TNM. TNM is a new type of carcinogen that induces DNA damage not by itself but via Tyr modification.
四硝基甲烷（TNM）在火箭推进剂和炸药中用作氧化剂，也用作增加柴油十六烷值的添加剂。据报道，TNM可在小鼠和大鼠中诱发肺腺癌和鳞状细胞癌。然而，TNM致癌的潜在机制尚未阐明。我们之前发现，硝基酪氨酸和含硝基酪氨酸的肽在存在P450还原酶的情况下会导致Cu（II）依赖性DNA损伤，这被认为会产生硝基还原反应。由于TNM是蛋白质和肽中酪氨酸硝化的试剂，我们推测经TNM处理的酪氨酸和含酪氨酸的肽通过酪氨酸修饰诱导DNA损伤。我们使用从人p53肿瘤抑制基因和c-Ha-ras-1原癌基因获得的（32）P-5'-末端标记的DNA片段，检测了经TNM处理的氨基酸或肽诱导的DNA损伤。经TNM处理的酪氨酸和赖氨酸-酪氨酸-赖氨酸在存在Cu（II）和NADH的情况下诱导DNA损伤，包括8-氧代-7,8-二氢-2'-脱氧鸟苷的形成。过氧化氢酶和bathocuproine可抑制DNA损伤，表明H（2）O（2）和Cu（I）参与其中。与密码子273互补的ACG序列的胞嘧啶残基，即p53基因的著名热点，经哌啶和Fpg处理后被切割。另一方面，硝基酪氨酸和赖氨酸-硝基酪氨酸-赖氨酸在存在Cu（II）和NADH的情况下不诱导DNA损伤。飞行时间质谱证实，赖氨酸-酪氨酸-赖氨酸与TNM之间的反应不仅产生赖氨酸-硝基酪氨酸-赖氨酸，还产生赖氨酸-亚硝基酪氨酸-赖氨酸。因此，推测亚硝基酪氨酸残基在存在Cu（II）和NADH的情况下可诱导氧化性DNA损伤。可以得出结论，酪氨酸依赖性DNA损伤可能在TNM的致癌性中起重要作用。TNM是一种新型致癌物，它不是自身诱导DNA损伤，而是通过酪氨酸修饰来诱导。
