Spencer Wendy A, Lehmler Hans-Joachim, Robertson Larry W, Gupta Ramesh C
James Graham Brown Cancer Center and Department of Pharmacology and Toxicology, University of Louisville, KY 40202, USA.
Free Radic Biol Med. 2009 May 15;46(10):1346-52. doi: 10.1016/j.freeradbiomed.2009.02.005. Epub 2009 Feb 20.
Polychlorinated biphenyls (PCBs) are toxic industrial chemicals, complete carcinogens, and efficacious tumor promoters. However, the mechanism(s) of PCB-mediated carcinogenicity remains largely undefined. One likely pathway by which these agents may play a role in carcinogenesis is the generation of oxidative DNA damage by redox cycling of dihydroxylated PCB metabolites. We have now employed a new (32)P-postlabeling system to examine novel oxidative DNA lesions induced by Cu(2+)-mediated activation of PCB metabolites. (32)P postlabeling of DNA incubated with various PCB metabolites resulted in over a dozen novel polar oxidative DNA adducts that were chromatographically similar for all active agents. The most potent metabolites tested were the hydroquinones (hydroxyl groups arranged para to each other), yielding polar oxidative adduct levels ranging from 55 to 142 adducts/10(6) nucleotides. PCB catechols, or ortho-dihydroxy metabolites, were up to 40% less active than their corresponding hydroquinone congeners, whereas monohydroxylated and quinone metabolites did not produce detectable oxidative damage over that of vehicle. With the exception of 2,4,5-Cl-2',5'-dihydroxybiphenyl, this oxidative DNA damage seemed to be inversely related to chlorine content: no chlorine approximately mono->di->trichlorinated metabolites. Importantly, copper, but not iron, was essential for activation of the PCB metabolites to these polar oxidative DNA adducts, because in its absence or in the presence of the Cu(+)-specific scavenger bathocuproine, no adducts were detected. Intervention studies with known reactive oxygen species (ROS) modifiers suggested that H(2)O(2), singlet oxygen, hydroxyl radical, and superoxide may also be involved in this PCB-mediated oxidative DNA damage. These data indicate a mechanistic role for several ROS, in addition to copper, in PCB-induced DNA damage and provide further support for oxidative DNA damage in PCB-mediated carcinogenesis.
多氯联苯（PCBs）是有毒的工业化学品、完全致癌物和有效的肿瘤促进剂。然而，PCBs介导致癌作用的机制在很大程度上仍不明确。这些物质可能在致癌过程中发挥作用的一个可能途径是二羟基化PCB代谢物的氧化还原循环产生氧化性DNA损伤。我们现在采用了一种新的（32）P后标记系统来检测由Cu（2+）介导的PCB代谢物活化诱导的新型氧化性DNA损伤。用各种PCB代谢物孵育的DNA进行（32）P后标记，产生了十几种新型极性氧化性DNA加合物，所有活性剂的色谱图都相似。测试的最有效的代谢物是对苯二酚（羟基彼此对位排列），产生的极性氧化性加合物水平为55至142个加合物/10（6）个核苷酸。PCB邻苯二酚或邻二羟基代谢物的活性比其相应的对苯二酚同系物低40%，而单羟基化和醌类代谢物与载体相比未产生可检测到的氧化性损伤。除了2,4,5-Cl-2',5'-二羟基联苯外，这种氧化性DNA损伤似乎与氯含量呈负相关：无氯≈单氯>二氯>三氯代谢物。重要的是，铜而非铁对于将PCB代谢物活化为这些极性氧化性DNA加合物至关重要，因为在没有铜或存在Cu（+）特异性清除剂邻菲罗啉时，未检测到加合物。用已知的活性氧（ROS）调节剂进行的干预研究表明，H（2）O（2）、单线态氧、羟基自由基和超氧阴离子也可能参与这种PCB介导的氧化性DNA损伤。这些数据表明，除了铜之外，几种ROS在PCB诱导的DNA损伤中具有机制性作用，并为PCB介导的致癌作用中的氧化性DNA损伤提供了进一步支持。
