title: Analysis of dibenzo[def,p]chrysene-deoxyadenosine adducts in wild-type and cytochrome P450 1b1 knockout mice using stable-isotope dilution UHPLC-MS/MS.
abstract: 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.
authors: Superfund Research Program, Oregon State University, 1011 ALS, Corvallis, OR 97331, USA; Environmental and Molecular Toxicology Department, Oregon State University, 1007 ALS, Corvallis, OR 97331, USA; Linus Pauling Institute, Oregon State University, 307 LPSC, Corvallis, OR 97331, USA. Electronic address: tod.harper@oregonstate.edu.
authors: Tod A
authors: TA
authors: Harper
authors: Department of Chemistry, Oregon State University, 153A Gilbert Hall, Corvallis, OR 97331, USA; Environmental Health Science Center, Oregon State University, 1011 ALS, Corvallis, OR 97331, USA. Electronic address: jeff.morre@oregonstate.edu.
authors: Jeff
authors: J
authors: Morré
authors: Department of Pharmaceutical Sciences, University of New Mexico, 2502 Marble NE, Albuquerque NM 87131, USA. Electronic address: flauer@salud.unm.edu.
authors: Fredine T
authors: FT
authors: Lauer
authors: Superfund Research Program, Oregon State University, 1011 ALS, Corvallis, OR 97331, USA; Linus Pauling Institute, Oregon State University, 307 LPSC, Corvallis, OR 97331, USA. Electronic address: tammie.mcquistan@oregonstate.edu.
authors: Tammie J
authors: TJ
authors: McQuistan
authors: Linus Pauling Institute, Oregon State University, 307 LPSC, Corvallis, OR 97331, USA. Electronic address: hummelj@onid.oregonstate.edu.
authors: Jessica M
authors: JM
authors: Hummel
authors: Department of Pharmaceutical Sciences, University of New Mexico, 2502 Marble NE, Albuquerque NM 87131, USA. Electronic address: sburchiel@salud.unm.edu.
authors: Scott W
authors: SW
authors: Burchiel
authors: Superfund Research Program, Oregon State University, 1011 ALS, Corvallis, OR 97331, USA; Environmental and Molecular Toxicology Department, Oregon State University, 1007 ALS, Corvallis, OR 97331, USA; Linus Pauling Institute, Oregon State University, 307 LPSC, Corvallis, OR 97331, USA; Environmental Health Science Center, Oregon State University, 1011 ALS, Corvallis, OR 97331, USA. Electronic address: david.williams@oregonstate.edu.
authors: David E
authors: DE
authors: Williams
mesh_terms: D000818:Animals; D001580:Benzopyrenes / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D065633:Cytochrome P-450 CYP1B1 / Q000172:deficiency* / Q000235:genetics; D018736:DNA Adducts / Q000032:analysis* / Q000737:chemistry; D003839:Deoxyadenosines / Q000737:chemistry*; D006801:Humans; D007553:Isotope Labeling; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008168:Lung / Q000737:chemistry / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015394:Molecular Structure; D011865:Radioisotope Dilution Technique; D013154:Spleen / Q000737:chemistry / Q000378:metabolism; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013950:Thymus Gland / Q000737:chemistry / Q000378:metabolism
chemical_list: D001580:Benzopyrenes; D018736:DNA Adducts; D003839:Deoxyadenosines; D065633:Cytochrome P-450 CYP1B1; C041517:dibenzo(a,l)pyrene; C058118:2'-deoxyadenosine
keywords: Cyp1b1; DNA adduct; Dibenzo[def,p]chrysene; Immunosuppression; Mass spectrometry; Spleen