Transcriptome analyses unravel CYP1A1 and CYP1B1 as novel biomarkers for disinfection by-products (DBPs) derived from chlorinated algal organic matter

Disinfection by-products (DBPs) are generated during chlorination of drinking water. Previous studies demonstrate that DBPs are cytotoxic, genotoxic and associated with an increased risk of human cancer. However, the molecular basis of DBPs-induced toxic effects remains unclear. Here, we chlorinated samples of algal-derived organic matter (AOM) and sediment organic matter (SOM) from a local drinking water reservoir. Chemical properties, toxicities and transcriptomic profiles of human Caco-2 cell exposed to AOM and SOM were compared before and after chlorination. We analyzed chlorination-caused distinct gene expression patterns between AOM and SOM, and identified a set of 22 differentially expressed genes under chlorination of AOM that are different from chlorinated SOM. Consequent network analysis indicates that differential CYP1A1, CYP1B1, ID1 and ID2 are common targets of the upstream regulators predicted in the AOM group, but not the SOM group. Through experimental validation and data integration from previous reports related to DBPs or environmental stressors, we found that CYP1A1 and CYP1B1 are specifically up-regulated after chlorinating AOM. Our study demonstrates that the two CYP1 genes likely act as novel biomarkers of AOM derived DBPs, and this would be helpful for testing drinking water DBPs toxicity and further monitoring drinking water safety.