Benzo(a)pyrene modulates fluoranthene-induced cellular responses in HT-29 colon cells in a dual exposure system

Abstract

Our environment is contaminated with a diverse array of chemicals; one of which is polycyclic aromatic hydrocarbons (PAHs). While some PAHs are potent by nature, others undergo interactions such as additivity, synergism, antagonism or potentiation to manifest their toxicity. Therefore, the objective of this study was to investigate whether exposure to benzo(a)pyrene (BaP), a PAH compound influences the cytotoxicity and metabolism of fluoranthene (FLA; another PAH compound) using HT-29 cells. Cells cultured in Dulbecco's Modified Eagle Medium were treated with 1, 5, 10, 25 μM BaP and FLA (0.01% dimethylsulfoxide as vehicle) individually and in combination over the course of 0–96 h. At the end of exposure, cells were stained with propidium iodide and the changes in cell cycle were analyzed using FACS analysis. Apoptosis was determined by caspase-3 assay. Post-incubation, samples were extracted and analyzed for FLA metabolites by reverse-phase HPLC with fluorescence detection. Cells exposed to BaP + FLA showed a marginal decrease in growth as compared to FLA alone and vehicle controls. Also, a decline in the percentage of cells in the S and G2 phases compared to G1 phase of cell cycle was noted when cells were treated with BaP and FLA together, compared to individual FLA treatment. The rate of FLA metabolism was more when cells were exposed to FLA in combination with BaP, compared to FLA alone. The enhanced biotransformation of FLA as a result of concomitant exposure to BaP may have implications for colon cancer risks arising from human dietary exposure to PAH mixtures through consumption of barbecued meat.

Interactions between polycyclic aromatic hydrocarbons in complex mixtures and implications for cancer risk assessment

“…Similar effects on CYP-mediated metabolism were observed in vivo in male Sprague-Dawley rats exposed to binary PAH mixtures (Bouchard et al 1998) and increased DNA adduct levels have been observed in vitro in hamster embryo cells exposed to a mixture of B[a]P and benzo[e]pyrene (Smolarek and Baird 1984). A recent in vitro study in human-derived colorectal adenocarcinoma (HT-29) cells observed dose-dependent increased fluoranthene metabolism after co-exposure with B[a]P which the authors attributed to enhanced CYP-mediated activation of fluoranthene, although neither gene expression or CYP activity was measured directly (Harris et al 2013).…”

Toxicity of polycyclic aromatic hydrocarbons involves NOX2 activation

“…The severity of toxicity is dependent on the combination of PAHs present in the mixture, their relative proportions and how they are metabolized. Polycyclic aromatic hydrocarbon-induced carcinogenesis requires long term exposure to an individual PAH compound [[30], [31], [32]] or mixtures [33]. This issue brings to light the strong interactions between various PAHs and cytotoxicity.…”

Benzo(a)pyrene inhibits migration and invasion of extravillous trophoblast HTR‐8/SVneo cells via activation of the ERK and JNK pathway

“…Considering that the exposure time in the in vitro experiments is limited, the relative higher doses were used in this study. Besides our study, similar doses have been used in other in vitro experiment (Tampio et al, 2008;Tampio et al, 2009;Harris et al, 2013;Wang et al, 2015).…”