Arlt Volker M, Glatt Hansruedi, Muckel Eva, Pabel Ulrike, Sorg Bernd L, Seidel Albrecht, Frank Heinz, Schmeiser Heinz H, Phillips David H
Section of Molecular Carcinogenesis, Institute of Cancer Research, Brookes Lawley Building, Cotswold Road, Sutton, Surrey SM2 5NG, United Kingdom.
Int J Cancer. 2003 Jul 10;105(5):583-92. doi: 10.1002/ijc.11143.
3-nitrobenzanthrone (3-NBA) is a potent mutagen and suspected human carcinogen identified in diesel exhaust and ambient air pollution. 3-aminobenzanthrone (3-ABA), 3-acetylaminobenzanthrone (3-Ac-ABA) and N-acetyl-N-hydroxy-3-aminobenzanthrone (N-Ac-N-OH-ABA) have been identified as 3-NBA metabolites. Recently we found that 3-NBA and its metabolites (3-ABA, 3-Ac-ABA and N-Ac-N-OH-ABA) form the same DNA adducts in vivo in rats. In order to investigate whether human cytochrome P450 (CYP) enzymes (i.e., CYP1A2), human N,O-acetyltransferases (NATs) and sulfotransferases (SULTs) contribute to the metabolic activation of 3-NBA and its metabolites, we developed a panel of Chinese hamster V79MZ-h1A2 derived cell lines expressing human CYP1A2 in conjunction with human NAT1, NAT2, SULT1A1 or SULT1A2, respectively. Cells were treated with 0.01, 0.1 or 1 microM 3-NBA, or its metabolites (3-ABA, 3-Ac-ABA and N-Ac-N-OH-ABA). Using both enrichment versions of the (32)P-postlabeling assay, nuclease P1 digestion and butanol extraction, essentially 4 major and 2 minor DNA adducts were detected in the appropriate cell lines with all 4 compounds. The major ones were identical to those detected in rat tissue; the adducts lack an N-acetyl group. Human CYP1A2 was required for the metabolic activation of 3-ABA and 3-Ac-ABA (probably via N-oxidation) and enhanced the activity of 3-NBA (probably via nitroreduction). The lack of acetylated adducts suggests N-deacetylation of 3-Ac-ABA and N-Ac-N-OH-ABA. Thus, N-hydroxy-3-aminobenzanthrone (N-OH-ABA) appears to be a common intermediate for the formation of the electrophilic arylnitrenium ions capable of reacting with DNA. Human NAT1 and NAT2 as well as human SULT1A1 and SULT1A2 strongly contributed to the high genotoxicity of 3-NBA and its metabolites. Moreover, N,O-acetyltransfer reactions catalyzed by human NATs leading to the corresponding N-acetoxyester may be important in the bioactivation of N-Ac-N-OH-ABA. As human exposure to 3-NBA is likely to occur primarily via the respiratory tract, expression of CYPs, NATs and SULTs in respiratory tissues may contribute significantly and specifically to the metabolic activation of 3-NBA and its metabolites. Consequently, polymorphisms in these genes could be important determinants of lung cancer risk from 3-NBA.
3-硝基苯并蒽酮（3-NBA）是一种强效诱变剂，也是在柴油废气和环境空气污染中发现的疑似人类致癌物。3-氨基苯并蒽酮（3-ABA）、3-乙酰氨基苯并蒽酮（3-Ac-ABA）和N-乙酰-N-羟基-3-氨基苯并蒽酮（N-Ac-N-OH-ABA）已被鉴定为3-NBA的代谢产物。最近我们发现，3-NBA及其代谢产物（3-ABA、3-Ac-ABA和N-Ac-N-OH-ABA）在大鼠体内形成相同的DNA加合物。为了研究人类细胞色素P450（CYP）酶（即CYP1A2）、人类N,O-乙酰基转移酶（NATs）和磺基转移酶（SULTs）是否有助于3-NBA及其代谢产物的代谢活化，我们构建了一组分别表达人类CYP1A2与人类NAT1、NAT2、SULT1A1或SULT1A2的中国仓鼠V79MZ-h1A2衍生细胞系。细胞用0.01、0.1或1微摩尔/升的3-NBA或其代谢产物（3-ABA、3-Ac-ABA和N-Ac-N-OH-ABA）处理。使用（32）P后标记分析的两种富集方法、核酸酶P1消化和丁醇萃取，在合适的细胞系中用所有4种化合物基本上检测到4种主要和2种次要的DNA加合物。主要的加合物与在大鼠组织中检测到的相同；这些加合物缺乏N-乙酰基。3-ABA和3-Ac-ABA的代谢活化需要人类CYP1A2（可能通过N-氧化），并增强了3-NBA的活性（可能通过硝基还原）。缺乏乙酰化加合物表明3-Ac-ABA和N-Ac-N-OH-ABA发生了N-脱乙酰化。因此，N-羟基-3-氨基苯并蒽酮（N-OH-ABA）似乎是能够与DNA反应的亲电芳基氮鎓离子形成的常见中间体。人类NATs和SULTs以及人类SULT1A1和SULT1A2对3-NBA及其代谢产物的高遗传毒性有很大贡献。此外，人类NATs催化的N,O-乙酰基转移反应导致相应的N-乙酰氧基酯可能在N-Ac-N-OH-ABA的生物活化中起重要作用。由于人类接触3-NBA可能主要通过呼吸道发生，呼吸道组织中CYPs、NATs和SULTs的表达可能对3-NBA及其代谢产物的代谢活化有显著且特定的贡献。因此，这些基因的多态性可能是3-NBA导致肺癌风险的重要决定因素。
