Oxidation of Acenaphthene and Acenaphthylene by Human Cytochrome P450 Enzymes

Acenaphthene and acenaphthylene, two known environmental polycyclic aromatic hydrocarbon (PAH) pollutants, were incubated at 50 μM concentrations in a standard reaction mixture with human P450s 2A6, 2A13, 1B1, 1A2, 2C9, and 3A4, and the oxidation products were determined using HPLC and LC-MS. HPLC a...

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Bibliographic Details
Published in:Chemical research in toxicology 2015-02, Vol.28 (2), p.268-278
Main Authors: Shimada, Tsutomu, Takenaka, Shigeo, Murayama, Norie, Yamazaki, Hiroshi, Kim, Joo-Hwan, Kim, Donghak, Yoshimoto, Francis K, Guengerich, F. Peter, Komori, Masayuki
Format: Article
Language:English
Subjects:
Acenaphthenes - chemistry
Acenaphthenes - metabolism
Cytochrome P-450 Enzyme System - metabolism
Humans
Molecular Structure
Oxidation-Reduction
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Summary:Acenaphthene and acenaphthylene, two known environmental polycyclic aromatic hydrocarbon (PAH) pollutants, were incubated at 50 μM concentrations in a standard reaction mixture with human P450s 2A6, 2A13, 1B1, 1A2, 2C9, and 3A4, and the oxidation products were determined using HPLC and LC-MS. HPLC analysis showed that P450 2A6 converted acenaphthene and acenaphthylene to several mono- and dioxygenated products. LC-MS analysis of acenaphthene oxidation by P450s indicated the formation of 1-acenaphthenol as a major product, with turnover rates of 6.7, 4.5, and 3.6 nmol product formed/min/nmol P450 for P450 2A6, 2A13, and 1B1, respectively. Acenaphthylene oxidation by P450 2A6 showed the formation of 1,2-epoxyacenaphthene as a major product (4.4 nmol epoxide formed/min/nmol P450) and also several mono- and dioxygenated products. P450 2A13, 1B1, 1A2, 2C9, and 3A4 formed 1,2-epoxyacenaphthene at rates of 0.18, 5.3 2.4, 0.16, and 3.8 nmol/min/nmol P450, respectively. 1-Acenaphthenol, which induced Type I binding spectra with P450 2A13, was further oxidized by P450 2A13 but not P450 2A6. 1,2-Epoxyacenaphthene induced Type I binding spectra with P450 2A6 and 2A13 (K s 1.8 and 0.16 μM, respectively) and was also oxidized to several oxidation products by these P450s. Molecular docking analysis suggested different orientations of acenaphthene, acenaphthylene, 1-acenaphthenol, and 1,2-epoxyacenaphthene in their interactions with P450 2A6 and 2A13. Neither of these four PAHs induced umu gene expression in a Salmonella typhimurium NM tester strain. These results suggest, for the first time, that acenaphthene and acenaphthylene are oxidized by human P450s 2A6 and 2A13 and other P450s to form several mono- and dioxygenated products. The results are of use in considering the biological and toxicological significance of these environmental PAHs in humans.
ISSN:0893-228X
1520-5010
DOI:10.1021/tx500505y