Hsu C H, Skipper P L, Harris T M, Tannenbaum S R
Division of Toxicology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Chem Res Toxicol. 1997 Feb;10(2):248-53. doi: 10.1021/tx960125a.
Cyclopenta[cd]pyrene (CPP) is a ubiquitous environmental pollutant whose 3,4-epoxide (CPPE) is generally regarded as its ultimate carcinogenic metabolite. The present study was undertaken to determine the structures of major DNA adducts formed by CPPE in vitro. Incorporation of specific radiolabeled bases into calf thymus DNA prior to reaction with CPPE demonstrated that the major adducts were formed by guanine, while minor adducts were formed by adenine and cytosine. Unmodified DNA was reacted with [3H]CPPE and the deoxynucleoside adducts obtained were compared chromatographically with the products obtained by reaction of CPPE with 2'-deoxyguanosine (dGuo). Two dGuo adducts from the latter reaction were identified by 1H-NMR, fast atom bombardment mass spectrometry, and circular dichroism as diastereoisomers of cis-3-(deoxyguanosin-N2-yl)-4-hydroxy-3,4-dihydroCPP. Other products that may have included the isomeric trans-N2-dGuo adduct were formed in the reaction. The major adduct fraction in the DNA digest, accounting for over 70% of the total, was chromatographically indistinguishable from the two cis dGuo-N2 adducts. A second DNA adduct fraction was observed, which appeared also to be formed by reaction with guanine as indicated by experiments in which DNA containing [3H]guanine was reacted with unlabeled CPPE. The results confirm that guanine is the major target in DNA for reaction with CPPE and are the first proof of structure for a CPPE-deoxynucleoside adduct.
环戊并[cd]芘（CPP）是一种普遍存在的环境污染物，其3,4 - 环氧化物（CPPE）通常被认为是其最终致癌代谢物。本研究旨在确定CPPE在体外形成的主要DNA加合物的结构。在与CPPE反应之前，将特定的放射性标记碱基掺入小牛胸腺DNA中，结果表明主要加合物由鸟嘌呤形成，而次要加合物由腺嘌呤和胞嘧啶形成。未修饰的DNA与[3H]CPPE反应，将得到的脱氧核苷加合物与CPPE与2'-脱氧鸟苷（dGuo）反应得到的产物进行色谱比较。通过1H-NMR、快原子轰击质谱和圆二色性鉴定了后一反应中的两种dGuo加合物，它们是顺式-3-（脱氧鸟苷-N2-基）-4-羟基-3,4-二氢CPP的非对映异构体。反应中还形成了其他可能包括异构反式-N2-dGuo加合物的产物。DNA消化物中的主要加合物部分占总量的70%以上，在色谱上与两种顺式dGuo-N2加合物无法区分。观察到第二个DNA加合物部分，通过含有[3H]鸟嘌呤的DNA与未标记的CPPE反应的实验表明，它似乎也是由与鸟嘌呤反应形成的。结果证实鸟嘌呤是DNA中与CPPE反应的主要靶点，并且是CPPE-脱氧核苷加合物结构的首个证据。
