Smith G B, Castonguay A, Donnelly P J, Reid K R, Petsikas D, Massey T E
Department of Pharmacology and Toxicology, Queen's University, Kingston, ON K7L 3N6.
Carcinogenesis. 1999 Sep;20(9):1809-18. doi: 10.1093/carcin/20.9.1809.
Metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was characterized in human lung cells isolated from peripheral lung specimens obtained from 12 subjects during clinically indicated lobectomy. NNK biotransformation was assessed in preparations of isolated unseparated cells (cell digest), as well as in preparations enriched in alveolar type II cells, and alveolar macrophages. Metabolite formation was expressed as a percentage of the total recovered radioactivity from [5-(3)H]NNK and its metabolites per 10(6) cells per 24 h. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was the major metabolite formed in all lung cell preparations examined, and its formation ranged from 0.50 to 13%/10(6) cells/24 h. Formation of alpha-carbon hydroxylation end-point metabolites (bioactivation) and pyridine N-oxidation metabolites (detoxification), ranged from non-detectable to 0.60% and from non-detectable to 1.5%/10(6) cells/24 h, respectively, reflecting a large degree of intercellular and inter-individual variability in NNK metabolism. Formation of the alpha-hydroxylation end-point metabolite 4-hydroxy-1-(3-pyridyl)-1-butanol (diol) was consistently higher in alveolar type II cells than in cell digest or alveolar macrophages (0.0146 +/- 0.0152, 0.0027 +/- 0.0037 and 0.0047 +/- 0.0063%/10(6) cells/24 h, respectively; n = 12; P < 0.05). SKF-525A was used to examine cytochrome P450 contributions to the biotransformation of NNK. SKF-525A inhibited keto reduction of NNK to NNAL by 85, 86 and 74% in cell digest, type II cells, and macrophages, respectively (means of 11 subjects, P < 0.05). Type II cell incubates treated with SKF-525A formed significantly lower amounts of total alpha-hydroxylation metabolites compared with type II cells without SKF-525A (0.0776 +/- 0.0841 versus 0.1694 +/- 0. 2148%/10(6) cells/24 h, respectively; n = 11; P < 0.05). The results of this first study examining NNK biotransformation in freshly isolated human lung cells indicate that NNK metabolism is subject to a large degree of inter-individual and intercellular variability, and suggest a role for P450s in human lung cell NNK metabolism. Both alveolar type II cells and alveolar macrophages may be potential target cells for NNK toxicity based on their alpha-carbon hydroxylation capabilities. In addition, carbonyl reduction of NNK to NNAL is SKF-525A sensitive in human lung cells.
对从12名受试者临床指征性肺叶切除术中获取的外周肺标本分离出的人肺细胞中烟草特异性亚硝胺4-（甲基亚硝胺基）-1-（3-吡啶基）-1-丁酮（NNK）的代谢进行了表征。在分离的未分离细胞制剂（细胞消化物）以及富含II型肺泡细胞和肺泡巨噬细胞的制剂中评估了NNK的生物转化。代谢物形成以每24小时每10⁶个细胞中[5-³H]NNK及其代谢物的总回收放射性的百分比表示。4-（甲基亚硝胺基）-1-（3-吡啶基）-1-丁醇（NNAL）是在所检查的所有肺细胞制剂中形成的主要代谢物，其形成范围为每24小时每10⁶个细胞0.50%至13%。α-碳羟基化终点代谢物（生物活化）和吡啶N-氧化代谢物（解毒）的形成分别为不可检测至0.60%和不可检测至每24小时每10⁶个细胞1.5%，反映了NNK代谢中细胞间和个体间的高度变异性。α-羟基化终点代谢物4-羟基-1-（3-吡啶基）-1-丁醇（二醇）在II型肺泡细胞中的形成始终高于细胞消化物或肺泡巨噬细胞（分别为每24小时每10⁶个细胞0.0146±0.0152、0.0027±0.0037和0.0047±0.0063%；n = 12；P<0.05）。使用SKF-525A研究细胞色素P450对NNK生物转化的贡献。SKF-525A分别在细胞消化物、II型细胞和巨噬细胞中抑制NNK向NNAL的酮还原85%、86%和74%（11名受试者的平均值，P<0.05）。与未用SKF-525A处理的II型细胞相比，用SKF-525A处理的II型细胞培养物形成的总α-羟基化代谢物量显著降低（分别为每24小时每10⁶个细胞0.0776±0.0841和0.1694±0.2148%；n = 11；P<0.05）。这项首次研究新鲜分离的人肺细胞中NNK生物转化的结果表明，NNK代谢存在很大程度的个体间和细胞间变异性，并提示P450在人肺细胞NNK代谢中起作用。基于其α-碳羟基化能力，II型肺泡细胞和肺泡巨噬细胞都可能是NNK毒性的潜在靶细胞。此外，NNK向NNAL的羰基还原在人肺细胞中对SKF-5
