Role of CYP2A13 in the bioactivation and lung tumorigenicity of the tobacco-specific lung procarcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone: in vivo studies using a CYP2A13-humanized mouse model
Role of CYP2A13 in the bioactivation and lung tumorigenicity of the tobacco-specific lung procarcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone: in vivo studies using a CYP2A13-humanized mouse model
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DOI：
10.1093/carcin/bgt269
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发表时间：
2014-01-01
期刊：
影响因子：
4.7
通讯作者：
Ding, Xinxin
中科院分区：
文献类型：
--
作者：
Megaraj, Vandana;Zhou, Xin;Ding, Xinxin
烟草特有的亚硝胺4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone(NNK)在烟草烟雾中大量存在，是一种有效的肺前致癌物质。本研究旨在证明人细胞色素P450 2A13(CYP2A13)的转基因表达将促进NNK的生物激活和NNK诱导的小鼠肺肿瘤的发生。测定野生型、Cyp2a5基因缺失和CYP2A13人源化(CYP2A13转基因/Cyp2a5基因缺失)小鼠的NNK体外激活动力学参数和体内NNK诱发肺癌的发生率。正如预期的那样，在肝脏和肺微粒体中，CYP2A5的缺失导致4-氧代-4-(3-吡啶基)-丁醛形成的米氏常数(K-m)显著增加，这是导致O-6-甲基鸟嘌呤(O-6-mg)DNA加合物形成的反应中间产物；然而，CYP2A13的获得导致了肺中活性的恢复，但不是肝脏中的活性。与肺部肿瘤发生高度相关的DNA加合物--O-6-mg，在CYP2A13人源化的小鼠肺中的水平显著高于Cyp2a5缺失的小鼠。此外，CYP2A13人源化小鼠的肺肿瘤发生率显著高于Cyp2a5缺失小鼠，并且低剂量(30 mg/kg)比高剂量(200 mg/kg)NNK的发生率差异更大。这些结果表明，CYP2A13是一种在体内催化NNK生物激活的低K-m酶，并支持该基因的多态性可以影响烟草诱导的人类肺肿瘤发生风险的观点。
The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which is abundant in tobacco smoke, is a potent lung procarcinogen. The present study was aimed to prove that transgenic expression of human cytochrome P450 2A13 (CYP2A13), known to be selectively expressed in the respiratory tract and be the most efficient enzyme for NNK bioactivation in vitro, will enhance NNK bioactivation and NNK-induced tumorigenesis in the mouse lung. Kinetic parameters of NNK bioactivation in vitro and incidence of NNK-induced lung tumors in vivo were determined for wild-type, Cyp2a5-null and CYP2A13-humanized (CYP2A13-transgenic/Cyp2a5-null) mice. As expected, in both liver and lung microsomes, the loss of CYP2A5 resulted in significant increases in Michaelis constant (K-m) values for the formation of 4-oxo-4-(3-pyridyl)-butanal, representing the reactive intermediate that can lead to the formation of O-6-methylguanine (O-6-mG) DNA adducts; however, the gain of CYP2A13 at a fraction of the level of mouse lung CYP2A5 led to recovery of the activity in the lung, but not in the liver. The levels of O-6-mG, the DNA adduct highly correlated with lung tumorigenesis, were significantly higher in the lungs of CYP2A13-humanized mice than in Cyp2a5-null mice. Moreover, incidences of lung tumorigenesis were significantly greater in CYP2A13-humanized mice than in Cyp2a5-null mice, and the magnitude of the differences in incidence was greater at low (30mg/kg) than at high (200mg/kg) NNK doses. These results indicate that CYP2A13 is a low K-m enzyme in catalyzing NNK bioactivation in vivo and support the notion that genetic polymorphisms of CYP2A13 can influence the risks of tobacco-induced lung tumorigenesis in humans.