Journal Article

Binary PAH mixtures cause additive or antagonistic effects on gene expression but synergistic effects on DNA adduct formation

Yvonne C.M. Staal, Dennie G.A.J. Hebels, Marcel H.M. van Herwijnen, Ralph W.H. Gottschalk, Frederik J. van Schooten and Joost H.M. van Delft

in Carcinogenesis

Volume 28, issue 12, pages 2632-2640
Published in print December 2007 | ISSN: 0143-3334
Published online August 2007 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgm182
Binary PAH mixtures cause additive or antagonistic effects on gene expression but synergistic effects on DNA adduct formation

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Polycyclic aromatic hydrocarbons (PAHs) cover a wide range of structurally related compounds which differ greatly in their carcinogenic potency. PAH exposure usually occurs through mixtures rather than individual compounds. Therefore, we assessed whether the effects of binary PAH mixtures on gene expression, DNA adduct formation, apoptosis and cell cycle are additive compared with the effects of the individual compounds in human hepatoma cells (HepG2). Equimolar and equitoxic mixtures of benzo[a]pyrene (B[a]P) with either dibenzo[a,l]pyrene (DB[a,l]P), dibenzo[a,h]anthracene (DB[a,h]A), benzo[b]fluoranthene (B[b]F), fluoranthene (FA) or 1-methylphenanthrene (1-MPA) were studied. DB[a,l]P, B[a]P, DB[a,h]A and B[b]F dose-dependently increased apoptosis and blocked cells cycle in S-phase. PAH mixtures showed an additive effect on apoptosis and on cell cycle blockage. DNA adduct formation in mixtures was higher than expected based on the individual compounds, indicating a synergistic effect of PAH mixtures. Equimolar mixtures of B[a]P and DB[a,l]P (0.1, 0.3 and 1.0 μM) were assessed for their effects on gene expression. Only at 1.0 μM, the mixture showed antagonism. All five compounds were also tested as a binary mixture with B[a]P in equitoxic concentrations. The combinations of B[a]P with B[b]F, DB[a,h]A or FA showed additivity, whereas B[a]P with DB[a,l]P or 1-MPA showed antagonism. Many individual genes showed additivity in mixtures, but some genes showed mostly antagonism or synergism. Our results show that the effects of binary mixtures of PAHs on gene expression are generally additive or slightly antagonistic, suggesting no effect or decreased carcinogenic potency, whereas the effects on DNA adduct formation show synergism, which rather indicates increased carcinogenic potency.

Journal Article.  6456 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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