AbstractsBiology & Animal Science

In order to provide an improved in vitro model with which to investigate human diseases, such as cancer that may be promoted by toxicant exposure, we have characterized a newly developed cell line derived from the renal proximal tubule epithelial cells (RPTEC) of a healthy human male donor. The RPTEC/TERT1 cell line has been immortalized using the human telomerase reverse transcriptase (hTERT) catalytic subunit and does not exhibit chromosomal abnormalities (Evercyte Laboratories). We have conducted single-compound and binary mixture experiments with the common environmental carcinogens, cadmium (Cd) and benzo[a]pyrene (B[a]P). Cells exhibited cytotoxicity to concentrations of B[a]P and Cd as low as 1 nM and 3 μM, respectively. We examined a panel of eight genes relevant to the toxic responses of these two agents. RPTEC/TERT1 cells exhibit compound-specific gene expression responses to concentrations as low as 1 nM B[a]P and 1 μM Cd. A significant increase in the expression of genes coding for B[a]P metabolizing enzymes (CYP1A1, CYP1B1) occurred in a dose- and time-dependent manner. Activity of these enzymes was verified using the EROD activity assay. Gene expression changes after co-exposure were consistent with changes in gene expression seen after single-compound exposures. We detected BPDE-DNA adducts after exposure to B[a]P which confirms that the RPTEC/TERT1 cell line responds to B[a]P consistently with what is known regarding these cells in a normal, healthy kidney. Under co-exposure, adducts detected were significantly decreased in some groups. A significant increase in the expression of NRF2 antioxidant pathway genes after co-exposure was observed. Additionally, total glutathione levels were significantly increased in cells exposed to Cd alone and co-exposure groups. These results suggest that Cd may antagonize the formation of BPDE-DNA adducts in RPTEC/TERT1 cells under these conditions. Future studies will test mutagenesis under conditions of co-exposure to Cd and B[a]P. Our studies are the first to provide information regarding toxicological responses in this novel cell line that model those of the target tissue. We conclude that these cells can provide a useful tool for future toxicological studies. These studies will help scientists better understand the initiating events that may promote carcinogenesis in normal, healthy human cells.