Hepatic gene expression transcript counts in liver samples of American kestrels

A number of brominated flame retardants (BFRs) have been reported to interfere with the thyroid signaling pathway and cause oxidative stress in birds, yet the underlying shifts in gene expression associated with these effects remain poorly understood. In this study, we measured hepatic transcriptional responses of 31 genes in American kestrel hatchlings following in ovo exposure to one of three high-volume alternative BFRs: 1,2-bis(2,4,6-tribromophenoxy) ethane (BTPBE), bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), or 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EHTBB). Hatchling kestrels exhibited shifts in the expression of genes related to oxidative stress (CYP, GSTA, SOD, GPx), thyroid hormone metabolism and transport (DIO, TTR), lipid and protein metabolism (PPAR, HMGCR, FAB1, LPL), and cytokine-mediated inflammation (TLR, IL-18, IRF7, STAT3, RACK1, CEBPB). Male and female hatchlings differed in which genes were differentially expressed as well as the direction of the effect (up- vs. down-regulation). These results build upon our previous findings of increased oxidative stress and disrupted thyroid signaling pathway in the same hatchlings. Furthermore, our results indicate that inflammatory responses appear to occur in female hatchlings exposed to BTBPE and EHTBB in ovo. Gene expression analysis revealed multiple affected pathways, adding to the growing evidence that sublethal physio-logical effects are complex and are a concern for birds exposed to BTBPE, EHTBB, or TBPH in ovo.