title: Polycyclic aromatic hydrocarbons in binary mixtures modulate the efficiency of benzo[a]pyrene to form DNA adducts in human cells.
abstract: Exposure to polycyclic aromatic hydrocarbons (PAHs) always involves complex mixtures that may induce synergistic or antagonistic effects on the genotoxic properties and make risk assessment more difficult. In this study, we evaluated how particulate PAHs modulated the formation of DNA damage induced by carcinogenic benzo[a]pyrene (B[a]P). Single strand breaks and alkali labile sites, as well as BPDE-N²-dGuo DNA adducts were measured in the competent HepG2 cells by Comet assay and HPLC-tandem mass spectrometry, respectively. B[a]P, alone or in binary mixture with other PAHs (1 μM each), led to low amounts of strand breaks. In contrast, formation of BPDE-N²-dGuo adducts was significant and found to be enhanced in HepG2 co-treated for 14 h by B[a]P in the presence of either benzo[b]fluoranthene (B[b]F), dibenz[a,h]anthracene (DB[a,h]A) or indeno[1,2,3-cd]pyrene (IP). Opposite results were obtained with benzo[k]fluoranthene (B[k]F). The same observations were made when cells were pre-incubated with PAH before incubation with B[a]P. These results show that the interactions between PAHs are not direct competition reactions. Emphasis was then placed on the modulation of B[a]P-induced DNA damage by B[b]F and B[k]F. No difference in the time-course formation of DNA damage was observed. However, dose-response relationship differed between these two PAHs with a concentration-dependent inhibition of BPDE-N²-dGuo DNA by B[k]F whereas a constant level of potentiation for B[b]F was observed for concentrations higher than 1 μM. Altogether, these results show that the genotoxicity of B[a]P in binary mixtures with other carcinogenic PAH may be modulated. In such cases, a potentiation of BPDE-N²-dGuo adduct formation is most often observed with exception of B[k]F. Several biological mechanisms may account for these observations, including binding of PAHs to the Ah receptor (AhR), their affinity toward CYP450 and competition for metabolism. These different interactions have to be considered when addressing the intricate issue of the toxicity of mixtures.
authors.affiliation: Laboratoire "Lésions des Acides Nucléiques", Service de Chimie Inorganique et Biologique UMR-E 3 CEA-UJF, CNRS FRE 3200, CEA/DSM/INAC, CEA-Grenoble 17, Avenue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Adeline
authors.initials: A
authors.lastname: Tarantini
authors.forename: Anne
authors.initials: A
authors.lastname: Maître
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Lefèbvre
authors.forename: Marie
authors.initials: M
authors.lastname: Marques
authors.forename: Afef
authors.initials: A
authors.lastname: Rajhi
authors.forename: Thierry
authors.initials: T
authors.lastname: Douki
mesh_terms: D001564:Benzo(a)pyrene / Q000633:toxicity*; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D020552:Comet Assay; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D018736:DNA Adducts / Q000187:drug effects*; D053904:DNA Breaks, Single-Stranded / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D011084:Polycyclic Aromatic Hydrocarbons / Q000008:administration & dosage / Q000378:metabolism / Q000633:toxicity*; D011485:Protein Binding; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism; D018570:Risk Assessment / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D018736:DNA Adducts; D011084:Polycyclic Aromatic Hydrocarbons; D018336:Receptors, Aryl Hydrocarbon; D001564:Benzo(a)pyrene; D003577:Cytochrome P-450 Enzyme System