Chiang S Y, Swenberg J A, Weisman W H, Skopek T R
Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill 27599, USA.
Carcinogenesis. 1997 Jan;18(1):31-6. doi: 10.1093/carcin/18.1.31.
Vinyl chloride (VC), a known human and rodent carcinogen, is metabolically activated by cytochrome P450 to chloroethylene oxide (CEO), which can rearrange to chloroacetaldehyde (CAA) or undergo hydrolysis. To further understand the roles of CEO and CAA in VC mutagenesis, the types and frequencies of mutations induced at the hypoxanthine (guanine) phosphoribosyl-transferase (hprt) locus were examined in a human B-lymphoblastoid line constitutively expressing human cytochrome P450 2E1 (H2E1 cells). VC was toxic and mutagenic to H2E1 cells as a function of incubation time; exposure to 7.5% VC in air resulted in 75% survival and an hprt mutant frequency of 42 x 10(-6) after 48 h, compared to 5.7 +/- 2.7 x 10(-6) for unexposed cells. The exposure of H2E1 cells to 0.8 to 15.0% VC in air produced similar mutant frequencies without a clear dose-response relationship, suggesting saturation of metabolic activation. Both CEO and CAA exhibited dose-dependent increases in cell killing and mutant frequency in H2E1 cells. Treatment with 16 microM CEO for 24 h resulted in 75% survival and an induced mutant frequency of 23 x 10(-6), while 16 microM CAA produced 5% survival and an induced mutant frequency of 20 x 10(-6). Structural alterations at the hprt locus in independent thioguanine-resistant clones were examined by Southern blot analysis of Pst I-digested DNA with a full-length human hprt cDNA probe. Ten percent (5/50) of VC-induced and 18% (7/38) of CEO-induced mutants showed detectable deletions, compared with 45% (9/20) of CAA-induced mutants. Thus, VC and CEO displayed similar toxicity/mutation profiles and a similar frequency of large deletions, whereas CAA displayed greater toxicity and a larger frequency of deletion mutations. These results suggest that the majority of mutations induced by VC occur through its metabolite, CEO.
氯乙烯（VC）是一种已知的人类和啮齿动物致癌物，通过细胞色素P450代谢活化为环氧氯乙烯（CEO），后者可重排为氯乙醛（CAA）或发生水解。为了进一步了解CEO和CAA在VC诱变中的作用，在持续表达人细胞色素P450 2E1的人B淋巴母细胞系（H2E1细胞）中检测了次黄嘌呤（鸟嘌呤）磷酸核糖转移酶（hprt）位点诱导的突变类型和频率。VC对H2E1细胞具有毒性和诱变性，且与孵育时间有关；在空气中暴露于7.5%的VC 48小时后，细胞存活率为75%，hprt突变频率为42×10⁻⁶，而未暴露细胞的该频率为5.7±2.7×10⁻⁶。H2E1细胞在空气中暴露于0.8%至15.0%的VC产生了相似的突变频率，且无明显的剂量反应关系，提示代谢活化饱和。CEO和CAA在H2E1细胞中均表现出细胞杀伤和突变频率的剂量依赖性增加。用16μM的CEO处理24小时导致75%的存活率和23×10⁻⁶的诱导突变频率，而16μM的CAA处理导致5%的存活率和20×10⁻⁶的诱导突变频率。通过用全长人hprt cDNA探针进行Pst I酶切DNA的Southern印迹分析，检测了独立的硫鸟嘌呤抗性克隆中hprt位点的结构改变。与45%（9/20）的CAA诱导突变体相比，10%（5/50）的VC诱导突变体和18%（7/38）的CEO诱导突变体显示出可检测到的缺失。因此，VC和CEO表现出相似的毒性/突变谱以及相似的大缺失频率，而CAA表现出更大的毒性和更高的缺失突变频率。这些结果表明，VC诱导的大多数突变是通过其代谢产物CEO发生的。
