Reed G A, Ryan M J
Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City 66103.
Carcinogenesis. 1990 Oct;11(10):1825-9. doi: 10.1093/carcin/11.10.1825.
We have reported previously that cyclopenteno[c,d]pyrene (CPP), an environmentally prevalent polycyclic aromatic hydrocarbon, is activated as a bacterial mutagen by several model systems which generate peroxyl radicals. In this report we present our findings on the chemical fate of CPP in these activating systems. The peroxyl radical systems employed are microsomal prostaglandin H synthase and arachidonic acid, the hematin-catalyzed decomposition of a lipid hydroperoxide, and the autoxidation of the sulfite anion. Reverse-phase HPLC analysis of stable products of CPP metabolism yielded qualitatively identical profiles from the first two systems. The three major products from these systems were analyzed by UV/visible and fluorescence spectroscopy, and a mass spectrum was obtained for the most abundant product. Based on these spectral analyses and on chromatographic behavior, the three products were identified as the cis- and trans-isomers of 3,4-dihydroxy-3,4-dihydro-CPP and 4-keto-(3H)-CPP. The identities of these products and their quantitative distributions relative to the epoxide hydrolase activities present in the microsomal system and the hematin system clearly establish 3,4-epoxy-CPP as the key intermediate and probable active mutagen generated in the peroxyl radical-dependent metabolism of CPP. This epoxidation of the activated aliphatic double bond of CPP extends the known range of peroxyl radical-dependent oxygenations by demonstrating the direct, one-step activation of a carcinogenic, environmentally relevant hydrocarbon. Strikingly different results are obtained in the sulfite-dependent system. The epoxide-derived metabolites seen with the peroxyl radical systems are very minor products. Instead, two product peaks elute near the solvent fron on reverse-phase HPLC. These are apparently monohydroxy-CPP sulfonates. Such products may form either by the direct addition of the sulfite anion radical to the activated double bond of CPP or by peroxyl radical-dependent epoxidation of CPP followed by nucleophilic addition of sulfite. Precedent for both of these reactions has been reported with analogous benzo[a]pyrene derivatives. The occurrence of these radical-dependent transformations in intact mammalian systems has not been investigated, but the ability of all three model systems employed to convert CPP to potent bacterial mutagens implies that these pathways should be studied further.
我们之前报道过，环戊烯并[c,d]芘（CPP）是一种环境中普遍存在的多环芳烃，在几种能产生过氧自由基的模型系统中被激活成为细菌诱变剂。在本报告中，我们展示了在这些激活系统中CPP的化学转化结果。所采用的过氧自由基系统包括微粒体前列腺素H合酶和花生四烯酸、血红素催化的脂质氢过氧化物分解以及亚硫酸根阴离子的自氧化。对CPP代谢稳定产物的反相高效液相色谱分析在前两个系统中得到了定性相同的图谱。通过紫外/可见光谱和荧光光谱对这些系统的三种主要产物进行了分析，并对最丰富的产物获得了质谱图。基于这些光谱分析和色谱行为，这三种产物被鉴定为3,4 - 二羟基 - 3,4 - 二氢 - CPP和顺反异构体以及4 - 酮 - (3H) - CPP。这些产物的身份以及它们相对于微粒体系统和血红素系统中环氧水解酶活性的定量分布清楚地表明3,4 - 环氧 - CPP是CPP在依赖过氧自由基的代谢中产生的关键中间体和可能的活性诱变剂。CPP活化脂肪族双键的这种环氧化通过证明一种致癌的、与环境相关的碳氢化合物的直接一步活化，扩展了已知的依赖过氧自由基的氧化范围。在依赖亚硫酸根的系统中得到了截然不同的结果。在过氧自由基系统中看到的环氧衍生代谢物是非常次要的产物。相反，在反相高效液相色谱上有两个产物峰在溶剂前沿附近洗脱。这些显然是单羟基 - CPP磺酸盐。此类产物可能是通过亚硫酸根阴离子自由基直接加成到CPP的活化双键上形成的，或者是通过CPP依赖过氧自由基的环氧化，随后亚硫酸根进行亲核加成形成的。对于这两种反应，已有类似苯并[a]芘衍生物的先例报道。尚未研究这些自由基依赖的转化在完整哺乳动物系统中的发生情况，但所采用的所有三种模型系统都能将CPP转化为强效细菌诱变剂，这意味着这些途径应进一步研究。
