A comparison of the concentration-effect relationships of PAHs on CYP1A induction in HepG2 and Mcf7 cells

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Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants. Some compounds belonging to this group are considered carcinogenic to people. In order to yield carcinogenic properties, these compounds must be metabolically transformed by enzymes of cytochrome P450 family to oxy-derivatives. In this study, the ability of the following six PAHs: anthracene (Ant), benz(a)anthracene (BA), naphthacene (Nap), benzo(a)pyrene (BaP), dibenz(a,c)anthracene (DB(a,c)A) and dibenz(a,h)anthracene (DB(a,h)A) to induce enzymes of cytochrome P450 (CYP450), in particular CYP1A1 and CYP1A2 in Mcf7 and HepG2 cells was studied. The induction of CYP1A enzymes was assessed at the level of enzymatic protein and enzymatic activity. The change in CYP1A1 and CYP1A2 protein level was assessed by means of confocal microscopy. The ethoxyresorufin-O-deethylase (EROD) and methoxyresorufin-O-deethylase (MROD) assays were applied to determine the CYP1A1 and CYP1A2 activity. The Induction Equivalency Factors (IEFs) were also determined. According to EROD and MROD assay and calculated IEFs the following order of the inducing potency was determined in HepG2 cells: DB(a,h)A > BaP > DB(a,c)A ≈ BA > Nap > Ant, and in Mcf7 cells: DB(a,h)A > DB(a,c)A > BaP > Nap > BA > Ant. The assessment of the protein levels revealed that DB(a,h)A was also the strongest inducer of protein level, however the correlation between enzymatic activity and protein level induction by other PAHs was not always evident. The EROD and MROD activities were higher in Mcf7 than in HepG2 cells, however the CYP1A2 protein level was shown to be higher in HepG2 cells. The results obtained indicate possible catalytic enzymatic activity alterations induced by PAHs.

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