Synthesis of stereospecifically deuterated 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) diastereomers and metabolism by A/J mouse lung microsomes and cytochrome P450 2A5
Synthesis of stereospecifically deuterated 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) diastereomers and metabolism by A/J mouse lung microsomes and cytochrome P450 2A5
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DOI：
10.1021/tx034021t
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发表时间：
2003-06-01
影响因子：
4.1
通讯作者：
Hecht, SS
中科院分区：
文献类型：
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作者：
Jalas, JR;Hecht, SS
烟草特有的亚硝胺4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone(NNK)是一种小鼠和大鼠的肺癌致癌物，也是一种可能的人类肺癌致癌物。NNK通过细胞色素P450介导的代谢活化生成DNA结合中间体，但在体内也被广泛还原为4-(甲基亚硝基)-1-(3-吡啶)-1-丁醇(NNAL)。由于NNAL也是致癌的，NNK的致癌性实际上可能是由NNAL的代谢激活决定的，而不是NNK的直接激活。NNK和NNAL在4位的代谢产生相同的关键DNA损伤，O-6-甲基鸟嘌呤，其水平与A/J小鼠模型的致瘤性相关。为了更好地了解NNAL的生物活性和甲醇-碳立体化学对4位前手性选择性的影响，合成了(R)-和(S)-NNA-L，以及立体定向4-非对映异构体(1R，4R)-[4-H-2(1)]NNAL，(1R，4S)-[4-H-2(1)]NNAL，(1S，4R)-[4-H-2(1)]NNAL。用A/J小鼠肺微粒体和表达细胞色素P450 2A5的小鼠细胞色素P450 2A5研究了这些化合物的体外代谢。甲醇-碳立体化学对这些化合物在小鼠肺微粒体或P450 2A5代谢过程中4位的立体选择性没有显著影响，但确实影响了代谢的区域化学。在A/J小鼠肺微粒体介导的所有底物的代谢中，4-甲基与N-甲基羟化的比例约为1：1，但当使用P450 2A5时，(1S)底物的这一比例高于(1-R)底物。有趣的是，P450 2A5将具有(1S)立体化学的底物转化为相应的N-氧化物，但这种代谢产物不是由具有(1R)立体化学的底物形成的。此外，P450 2A5催化(1S)底物生成NNK的最大速率明显高于(1R)底物。这些代谢的差异对NNAL的致瘤机制的影响进行了讨论。
The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a lung carcinogen in mice and rats and is a putative human lung carcinogen. NNK undergoes cytochrome P450-mediated metabolic activation to DNA-binding intermediates but is also extensively reduced to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in vivo. Because NNAL is also tumorigenic, the carcinogenicity of NNK may actually be governed by the metabolic activation of NNAL, rather than direct activation of NNK. Metabolism of NNK and NNAL at the 4-position generates the same critical DNA lesion, O-6-methylguanine, the levels of which are correlated to tumorigenicity in the A/J mouse model. In an effort to better understand the bioactivation of NNAL and the effect of carbinol-carbon stereochemistry on prochiral selectivity at the 4-position, (R)- and (S)-NNA-L, along with the stereospecifically 4-deuterated diastereomers (1R,4R)-[4-H-2(1)]NNAL, (1R,4S)-[4-H-2(1)]NNAL, (1S,4R)-[4-H-2(1)]NNAL, and (1S,4S)-[4-H-2(1)]NNAL, were synthesized. The in vitro metabolism of these compounds was investigated using A/J mouse lung microsomes and Spodoptera frugiperda-expressed mouse cytochrome P450 2A5. Carbinol-carbon stereochemistry did not appreciably influence stereo-selectivity at the 4-position in the metabolism of these compounds by mouse lung microsomes or P450 2A5 but did influence the regiochemistry of metabolism. The ratio of 4- to N-methyl hydroxylation was approximately 1: 1 for the A/J mouse lung microsome-mediated metabolism of all substrates, but this ratio was higher for (1S) substrates than for their (1-R) counterparts when P450 2A5 was used. Interestingly, P450 2A5 converted substrates with (1S) stereochemistry to the respective N-oxides, but this metabolite was not formed from substrates with (1R) stereochemistry. Furthermore, P450 2A5 catalyzed the formation of NNK from (1S) substrates at significantly greater maximal rates than from (1R) substrates. The implications of these differences in metabolism for the tumorigenic mechanism of NNAL are discussed.