Evaluation of CYP1A Protein Induction, Biotransformation Capacity and DNA Adduct Formation in a Rat Hepatoma Cell Line (Fao), as Biomarkers of Organic Contamination in Environmental Soil Samples

Abstract

Induction of cytochrome P4501A (CYP1A) immunopositive protein was evaluated in the rat hepatoma cell line Fao, as a biomarker of organic pollution in extract of environmental soil samples, exposed to different sources and degrees of chemical contamination. Soil samples were collected in one area in Russia (Monchegorsk) and two areas in Southern Norway (Fiskaa and Birkenes). In addition, one reference soil sample was collected in Central Norway (Høylandet). Contents of selected polycyclic aromatic hydrocarbons (PAHs) in the samples were also evaluated. To further evaluate the inducibility of the most potent soil extract (Fiskaa), S9 fraction of Fao cells, pretreated with this extract, was used as an activation system in the Ames Salmonella assay. The DNA adduct forming capacity of the soil extracts, analyzed by the 32 P-postlabeling technique, was also investigated in Fao cells. The Fao cell line has previously been found to be a very sensitive biomonitoring system, that responds to environmentally relevant concentrations of planar model contaminants with increased level of CYP1A immunopositive protein and DNA adducts. In the present study the Fao cell line also showed its potential for use in evaluating the CYP1A inducing potency of environmental samples. All soil extracts induced CYP1A protein in the Fao cells, although the level of induction varied between the soil samples. The Fiskaa soil extract was the most potent CYP1A inducer and this extract also contained the highest level of PAHs. No significant correlation was observed between the level of the total of 16 PAHs and CYP1A protein level. However, a significant correlation was observed between CYP1A protein level and the level of Benzo[a]pyrene (B[a]P), which is a very potent CYP1A inducer. The S9 fraction of pretreated Fao cells activated B[a]P to mutagens in a concentration-dependent relationship, although the response was weak. No DNA adducts were detected in cells exposed to the soil extracts. This demonstrates the necessity of determining several biomarker parameters simultaneously as one single biomarker may fail to respond to potentially harmful compounds.