Hierarchical cluster analysis of environmental pollutants through P450 induction in cultured hepatic cells

Environmental pollutants are classically associated with increased drug metabolism. Cultures of rat hepatocytes, quail hepatocytes, and human hepatoma (Hep G2) cells were used to study the effects of pesticides on drug-metabolizing enzymes. Membrane integrity and mitochondrial activity were evaluated and induction of ethoxycoumarin-O-deethylase and ethoxyresorufin-O-deethylase activities were measured. Induced P450s were identified by immunoblotting. Pentachlorophenol and lindane appeared as the strongest inducers. On the immunoblots, specific antibodies revealed induced CYP1A1 in fetal rat hepatocytes, CYP2B in quail hepatocytes, and CYP3A7 in Hep G2 cells. Pesticide effects on these different activities in each type of cultured cells were compared by cluster analysis. Results obtained under similar conditions with reference inducers phenobarbital (PB) and benzo[a]anthracene and other environmental pollutants (polychlorobiphenyls) were added to previous data prior to multivariate analysis. The tested products fell into four major groups: a first group with pentachlorophenol, identified as a CYP3A inducer; a second group containing the methylcholanthrene-type inducers that increase CYP1A-related activities; a third class represented by dieldrin, a PB-type inducer; a fourth group including inert compounds or weak inducers. Lindane shares the criteria of the second and third groups and seems to induce both CYP1A and CYP2B activities. The current study results highlight the advantage of using several types of cultured hepatocytes to evaluate the short-term toxicity of environmental pollutants in vitro and constitute a useful model for predicting the potential toxicity of pesticides in humans (Hep G2 cells) and wildlife (fetal quail hepatocytes).