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BROMINATED TRIHALOMETHANE (BrTHM) TOXICITY IN HUMAN BLADDER CELL LINES
Citation:
Pegram, R., J. Campbell, Steve Simmons, T. Ross, D. DeMarini, AND B. Chorley. BROMINATED TRIHALOMETHANE (BrTHM) TOXICITY IN HUMAN BLADDER CELL LINES. 2016 Society of Toxicology Annual Meeting, New Orleans, LA, March 13 - 17, 2016.
Impact/Purpose:
Abstract for poster presentation at the 2016 Annual Meeting of the Society of Toxicology. We determined both cytotoxicity and the induction of micronuclei by the brominated trihalomethane, dibromochloromethane, in a human bladder cell line derived from normal human urothelium (SV-HUC) and in a novel transgenic line (SV-HUC-T1) that we engineered to stably overexpress human GSTT1.
Description:
Epidemiology studies have consistently found that greater exposure to drinking water disinfection byproducts (DBPs) is associated with an increased risk for bladder cancer. In 2010, Cantor et al. (Environ. Health Perspect. 118: 1545) reported that this increased risk was dependent upon the GSTT1+ genotype and the implied expression of the xenobiotic metabolizing enzyme, glutathione S-transferase theta (GSTT1). We previously found that GSTT1 activates the prevalent DBPs, BrTHMs, to mutagenic intermediates (Pegram et al., 1997, Toxicol. Appl. Pharm. 144: 183; DeMarini et al., 1997, Environ. Molec. Mutagen. 30: 440). In the present study, we determined both cytotoxicity and the induction of micronuclei by the BrTHM, dibromochloromethane (DBCM), in a human bladder cell line derived from normal human urothelium (SV-HUC) and in a novel transgenic line (SV-HUC-T1) that we engineered to stably overexpress human GSTT1. The SV-HUC line was genotyped for GSTT1 and found to be GSTT1+/+. In the SV-HUC-T1 culture used in these experiments, GSTT1 activity, 1,2-epoxy-3-(4-nitrophenoxy)propane conjugation by glutathione, was 77% higher than in the parent line. Cell viabilities in the SV-HUC and SV-HUC-T1 lines, respectively, were 88% and 80% after 24 hr exposure to DBCM at 4 mM and 86% and 74% at 6 mM. Compared to vehicle (DMSO)-treated controls, DBCM at nominal concentrations of 3 mM and 6 mM induced 2.1- and 5.3-fold increases in micronuclei per 1000 binucleated cells in the SV-HUC line and 3.1- and 7.7-fold increases in the SV-HUC-T1 line. Actual media concentrations of DBCM were estimated to be ~80% lower than nominal concentrations due to volatilization to headspace and adsorption to plastic in the micronuclei experiments. This is the first report of BrTHM-induced genotoxicity in human urothelial cells, and the first demonstration of GSTT1-dependent genotoxicity in eukaryotic cells. [This abstract does not reflect EPA policy.]