Environmental toxicology and chemistry | 2021
Hepatic gene expression profiling of OPFR exposed Atlantic cod (Gadus morhua) liver revealed altered cholesterol biosynthesis and lipid metabolism.
Abstract
Since the phasing out and eventual ban on the production of organohalogen flame retardants, the use of organophosphate flame retardants (OPFRs) has increased rapidly. This has led to the detection of OPFRs in various environments including the Arctic. Two of the most prevalent OPFRs found in the Arctic are the tris 2-chloropropy phosphate (TCPP), and the 2-ethyldiphenyl phosphate (EHDPP). The impacts of exposure to OPFRs on Arctic organisms is poorly understood. The objective of this study is to determine the effects of exposure to TCPP, EHDPP and a mixture of OPFRs on gene expression patterns in Atlantic cod, Gadus morhua. Precision cut liver slices from Atlantic cod in vitro were exposed to either TCPP or EHDPP alone or a mixture and sampled at two different time points to quantify gene expression patterns using RNA sequencing. We exposed the liver slices to two concentrations of TCPP and EHDPP, one of which was chosen based on the levels found in the arctic environment. RNA sequencing results demonstrated differential expression of hundreds of genes in response to exposure. The genes representing cholesterol biosynthesis and lipid metabolism pathway were significantly enriched in all the treatment groups. Almost all the cholesterol biosynthesis genes were significantly downregulated in response to OPFR exposure. The effects on these pathways could affect various physiological processes including reproduction, growth, and behavior as well as adaptation to changing temperatures. Membrane fluidity is an important adaptive mechanism among aquatic organisms. Altered cholesterol homeostasis could have long-term consequences by altering the adaptive potential of aquatic organisms to changing water temperatures, particularly those living in polar environments. These results suggest that OPFRs could have unique effects on the organisms living in the Arctic compared to other environments. Further studies are needed to understand the long-term impacts of exposure to environmentally realistic concentrations using laboratory and field-based studies. This article is protected by copyright. All rights reserved.