DNA strand scission by polycyclic aromatic hydrocarbon o-quinones: Role of reactive oxygen species, Cu(II)/Cu(I) redox cycling, and o-semiquinone anion radicals
DNA strand scission by polycyclic aromatic hydrocarbon o-quinones: Role of reactive oxygen species, Cu(II)/Cu(I) redox cycling, and o-semiquinone anion radicals
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DOI：
10.1021/bi970367p
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发表时间：
1997-07-15
期刊：
影响因子：
2.9
通讯作者：
Penning, TM
中科院分区：
文献类型：
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作者：
Flowers, L;Ohnishi, ST;Penning, TM
以前的研究发现，多环芳烃邻苯二酚(PAH)邻苯二酮(BPQ)作为核酸酶的效力是可疑的人类致癌物(+/-)-反-7，8-二羟基-9，10-环氧基-7，8，9，10-四氢苯并[a]芘的200倍。以Phi-x174 DNA或PolyDG·Poly(DC)为靶DNA，进一步研究了萘-1，2-二酮(NPQ)和BPQ介导的链断裂机制。链的断裂是广泛的，取决于邻苯二酚的浓度(0-10µM)，需要NADPH(1 MM)和CuCl2(10µM)的存在。测定了反应体系中超氧阴离子自由基、邻半喹酮阴离子(SQ)自由基、过氧化氢(H_2O_2)、羟基自由基(OH)和铜(I)的生成量。在厌氧条件下，用EPR波谱测定了NADPH存在下SQ自由基的形成。研究发现，铜(II)/铜(I)氧化还原循环是DNA切割的关键。在没有铜(II)或取代铜(I)的情况下，没有发生断链，而羟基则需要铜(I)。制作。DNA链剪刀和OH。虽然不是完全的，但由于OH的加入，形成的减少程度是相同的。清除剂(甘露醇、苯甲酸钠和甲酸)或铜(I)螯合剂(亚铜和新亚铜)。相反，虽然NPQ和BPQ的SQ自由基信号被DNA猝灭，但没有观察到链断裂。用邻苯二酚处理小牛胸腺DNA时，可通过酸解释放丙二醛(MDA)。OH可抑制丙二醛的形成。食腐动物暗示。裂解DNA中的2‘-脱氧核糖部分产生碱性丙烯，这些研究表明，多环芳烃邻苯二酚作为核酸酶，NADPH，铜(I)，铜(I)，H_2O_2和OH是必需的，并且导致DNA断裂的主要物种是由铜(I)催化的Fenton反应产生的OH。邻苯二酚的遗传毒性可能在母体烃类的致癌性和致突变性中起一定作用。
In previous studies, benzo[a]pyrene-7,8-dione (BPQ), a polycyclic aromatic hydrocarbon (PAH) o-quinone, was found to be 200-fold more potent as a nuclease than (+/-)-anti-7,8-dihydroxy-9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene, a suspect human carcinogen. The mechanism of strand scission mediated by naphthalene-1,2-dione (NPQ) and BPQ was further characterized using either phi X174 DNA or poly(dG).poly(dC) as the target DNA. Strand scission was extensive, dependent on the concentration of o-quinone (0-10 mu M), and required the presence of NADPH (1 mM and CuCl2 (10 mu M). The production of reactive species, i.e., superoxide anion radical, o-semiquinone anion (SQ) radical, hydrogen peroxide (H2O2), hydroxyl radical (OH.), and Cu(I), was measured in the incubation mixtures. The formation of SQ radicals was measured by EPR spectroscopy under anaerobic conditions in the presence of NADPH. A Cu(II)/Cu(I) redox cycle was found to be critical for DNA cleavage. No strand scission occurred in the absence of Cu(II) or when Cu(I) was substituted, yet Cu(I) was required for OH. production. Both DNA strand scisson and OH. formation were decreased to an equal extent, albeit not completely, by the inclusion of OH. scavengers (mannitol, soduim benzoate, and formic acid) or Cu(I) chelators (bathocuproine and neocuproine). In contrast, although the SQ radical signals of NPQ and BPQ were quenched by DNA, no strand scission was observed. When calf thymus DNA was treated with PAH o-quinones, malondialdehyde (MDA) was released by acid hydrolysis. The formation of MDA was inhibited by OH. scavengers suggesting that OH. cleaved the 2'-deoxyribose moiety in the DNA to produce base propenals, These studies indicate that for PAH o-quinones to act as nucleases, NADPH, Cu(II), Cu(I), H2O2, and OH., were necessary and that the primary species responsible for DNA fragmentation was OH., generated by a Cu(I)-catalyzed Fenton reaction. The genotoxicity of PAH o-quinones may play a role in the carcinogenicity and mutagenicity of the parent hydrocarbons.