Human cell toxicogenomic analysis links reactive oxygen species to the toxicity of monohaloacetic acid drinking water disinfection byproducts

The monohaloacetic acids (monoHAAs) are generated as byproducts during the disinfection of drinking water and are cytotoxic, genotoxic, mutagenic, and teratogenic. Iodoacetic acid (IAA) toxicity was mitigated by antioxidants, suggesting the involvement of oxidative stress. Other monoHAAs may share a similar mode of action. Human oxidative stress and antioxidant defense gene arrays (SA biosciences) were used to evaluate changes in transcriptome profiles in the human intestinal epithelial cell line FHS 74 INT generated by three compounds, chloroacetic acid (CAA), bromoacetic acid (BAA) and IAA at two time points (30 min and 4 h). Twelve samples were evaluated. Each treated sample was paired with a concurrent negative control (cells treated in medium only). Three technical repeats were included for each sample and Ct values were calculated from the average of the three repeats. Samples 1,2,and 3 were isolated from 30 min negative controls for CAA, BAA, and IAA respectively. Samples 4, 5, and 6 were isolated from cells treated for 30 min with CAA, BAA, and IAA respectivley. Samples 7, 8, and 9 were isolated from 4h negative controls for CAA, BAA, and IAA respectively. Samples 10, 11, and 12 were isolated from cells treated for 4 h with CAA, BAA and IAA respectively. Ct values were normalized against the average of the 5 housekeeping genes included in the array to generate ΔCt values. Fold changes for each gene were calculated as a ratio of 2^-ΔCttest / 2^-ΔCtcontrol.