TitleAnalysis of dibenzo[def,p]chrysene-deoxyadenosine adducts in wild-type and cytochrome P450 1b1 knockout mice using stable-isotope dilution UHPLC-MS/MS.
Publication TypeJournal Article
Year of Publication2015
AuthorsHarper TA, Morré J, Lauer FT, McQuistan TJ, Hummel JM, Burchiel SW, Williams DE
JournalMutat Res Genet Toxicol Environ Mutagen
Date Published2015 Apr
KeywordsAnimals, Benzopyrenes, Chromatography, High Pressure Liquid, Cytochrome P-450 CYP1B1, Deoxyadenosines, DNA Adducts, Humans, Isotope Labeling, Liver, Lung, Mice, Inbred C57BL, Mice, Knockout, Molecular Structure, Radioisotope Dilution Technique, Spleen, Tandem Mass Spectrometry, Thymus Gland

The polycyclic aromatic hydrocarbon (PAH), dibenzo[def,p]chrysene (DBC; also known as dibenzo[a,l]pyrene), is a potent carcinogen in animal models and a class 2A human carcinogen. Recent investigations into DBC-mediated toxicity identified DBC as a potent immunosuppressive agent similar to the well-studied immunotoxicant 7,12-dimethylbenz[a]anthracene (DMBA). DBC, like DMBA, is bioactivated by cytochrome P450 (CYP) 1B1 and forms the reactive metabolite DBC-11,12-diol-13,14-epoxide (DBCDE). DBCDE is largely responsible for the genotoxicity associated with DBC exposure. The immunosuppressive properties of several PAHs are also linked to genotoxic mechanisms. Therefore, this study was designed to identify DBCDE-DNA adduct formation in the spleen and thymus of wild-type and cytochrome P450 1b1 (Cyp1b1) knockout (KO) mice using a highly sensitive stable-isotope dilution UHPLC-MS/MS method. Stable-isotope dilution UHPLC-MS/MS identified the major DBC adducts (±)-anti-cis-DBCDE-dA and (±)-anti-trans-DBCDE-dA in the lung, liver, and spleen of both WT and Cyp1b1 KO mice. However, adduct formation in the thymus was below the level of quantitation for our method. Additionally, adduct formation in Cyp1b1 KO mice was significantly reduced compared to wild-type (WT) mice receiving DBC via oral gavage. In conclusion, the current study identifies for the first time DBCDE-dA adducts in the spleen of mice supporting the link between genotoxicity and immunosuppression, in addition to supporting previous studies identifying Cyp1b1 as the primary CYP involved in DBC bioactivation to DBCDE. The high levels of DBC-DNA adducts identified in the spleen, along with the known high levels of Cyp1b1 expression in this organ, supports further investigation into DBC-mediated immunotoxicity.

Alternate JournalMutat Res Genet Toxicol Environ Mutagen
PubMed ID25868132
PubMed Central IDPMC4395865
Grant ListP01 CA090890 / CA / NCI NIH HHS / United States
P01CA90890 / CA / NCI NIH HHS / United States
R01 ES019968 / ES / NIEHS NIH HHS / United States
P42 ES016465 / ES / NIEHS NIH HHS / United States
T32 ES007060 / ES / NIEHS NIH HHS / United States
P30 ES000210 / ES / NIEHS NIH HHS / United States