p53 Mutagenesis by Benzo[a]pyrene Derived Radical Cations
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- 作者：Sushmita Sen ; Pratik Bhojnagarwala ; Lauren Francey ; Ding Lu ; Trevor M. Penning ; Jeffrey Field
- 刊名：Chemical Research in Toxicology
- 出版年：2012
- 出版时间：October 15, 2012
- 年：2012
- 卷：25
- 期：10
- 页码：2117-2126
- 全文大小：415K
- 年卷期：v.25,no.10(October 15, 2012)
- ISSN：1520-5010
文摘
Benzo[a]pyrene (B[a]P), a major human carcinogen in combustion products such as cigarette smoke and diesel exhaust, is metabolically activated into DNA-reactive metabolites via three different enzymatic pathways. The pathways are the anti-(+)-benzo[a]pyrene 7,8-diol 9,10-epoxide pathway (P450/epoxide hydrolase catalyzed) (B[a]PDE), the benzo[a]pyrene o-quinone pathway (aldo ketose reductase (AKR) catalyzed) and the B[a]P radical cation pathway (P450 peroxidase catalyzed). We used a yeast p53 mutagenesis system to assess mutagenesis by B[a]P radical cations. Because radical cations are short-lived, they were generated in situ by reacting B[a]P with cumene hydroperoxide (CuOOH) and horse radish peroxidase (HRP) and then monitoring the generation of the more stable downstream products, B[a]P-1,6-dione and B[a]P-3,6-dione. On the basis of B[a]P-1,6 and 3,6-dione formation, approximately 4 渭M of radical cation was generated. In the mutagenesis assays, the radical cations produced in situ showed a dose-dependent increase in mutagenicity from 0.25 渭M to 10 渭M B[a]P with no significant increase seen with further escalation to 50 渭M B[a]P. However, mutagenesis was 200-fold less than with the AKR pathway derived B[a]P, 7-8-dione. Mutant p53 plasmids, which yield red colonies, were recovered from the yeast to study the pattern and spectrum of mutations. The mutation pattern observed was G to T (31%) > G to C (29%) > G to A (14%). The frequency of codons mutated by the B[a]P radical cations was essentially random and not enriched at known cancer hotspots. The quinone products of radical cations, B[a]P-1,6-dione and B[a]P-3,6-dione were more mutagenic than the radical cation reactions, but still less mutagenic than AKR derived B[a]P-7,8-dione. We conclude that B[a]P radical cations and their quinone products are weakly mutagenic in this yeast-based system compared to redox cycling PAH o-quinones.