RNA Sequencing Reveals Differential Mechanisms of Brominated Flame Retardant Nephrotoxicity That Are Chemical and Cell Line‐Specific

Abstract

Brominated flame retardants (BFRs) are organohalogens commonly added to commercial products such as computers, electronics, textiles, and furniture to reduce their flammability. BFRs have significant environmental persistence and are reported to be detected in human blood and breastmilk. Tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), and polybrominated diphenyl ethers (PBDEs) are three BFRs that occupy nearly 20 percent of the global flame retardant market and are reported to have adverse effects on humans and wildlife. We previously determined the effects of TBBPA, HBCD, and BDE 47 on MTT staining and cell morphology in rat (NRK 52E), adult human (HK-2) kidney cells after 48 hours of exposure, and demonstrated that these compounds induce concentration- and cell-dependent toxicity, with human cells being more susceptible. We investigated the mechanisms underlying this cell-dependent toxicity by performing RNAseq analysis. Principal components analysis supported the hypothesis that BFRs induce different transcriptional changes in rat and human cells. Furthermore, within each cell line, only 9 differentially expressed genes and 5 differentially expressed genes were shared between all 3 BFRs in rat and human cells, respectively. This suggests that the molecular mechanisms mediating BFR toxicity are toxicant and cell line-dependent. Gene set enrichment analysis demonstrated some similarities in the functional consequences of BFRs that persisted across different cell lines. Namely, changes in extracellular matrix turnover and the coagulation cascade were shared across all 3 chemicals in both cell lines. Taken together, these data will aid future studies concerning the molecular mechanisms of BFR nephrotoxicity and risk assessment.