Hepatic Gene Expression Profiling of Atlantic Cod (Gadus morhua) Liver after Exposure to Organophosphate Flame Retardants 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 tris(2-chloroisopropyl) phosphate (TCPP), and 2-ethylhexyl diphenyl phosphate (EHDPP). The impacts of exposure to OPFRs on Arctic organisms is poorly understood. The objective of the present study was 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 in a mixture and sampled at 2 different time points to quantify gene expression patterns using RNA sequencing. We exposed the liver slices to 2 concentrations of TCPP and EHDPP, one of which was chosen based on the levels found in the Arctic environment. The 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 down-regulated in response to OPFR exposure. The effects on these pathways could involve 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 with other environments. Further studies are needed to understand the long-term impacts of exposure to environmentally realistic concentrations using laboratory and field-based studies.

Replacement Flame-Retardant 2-Ethylhexyldiphenyl Phosphate (EHDPP) Disrupts Hepatic Lipidome: Evidence from Human 3D Hepatospheroid Cell Culture

“…ACAT2 has been predominantly shown to form saturated and monounsaturated CEs, which may imply other mechanisms responsible for a decrease in unsaturated CE in our study. A similar alteration in cholesterol biosynthesis-related genes was noted earlier in other species, such as fish (Atlantic Cod liver) and in vitro in chicken embryonic hepatocytes . Our transcriptional assay indicated an increase in CYP27A1-mediated pathways, which suggests that EHDPP might have facilitated cholesterol efflux to oxysterols or bile acid, which needs further investigation.…”

First Insight into the Formation of In Vivo Transformation Products of 2-Ethylhexyl diphenyl phosphate in Zebrafish and Prediction of Their Potential Toxicities

“…28,57,58 Function analysis of the targets revealed that interfering with the synthesis or metabolism of cholesterol is the primary mechanism of cardiovascular disease caused by EHDPHP and its metabolites (Figure 4A), which was consistent with the reports that EHDPHP exposure significantly affected the genes controlling cholesterol biosynthesis and lipid metabolism and was highly associated with atherosclerosis in human. 28,59 As one of the predicted target proteins, insulin-like growth factor 1 receptor (IGF1R) plays critical roles in cell growth and differentiation and is correlated to cancers and growth retardation in human. 60 Xu et al reported that EHDPHP caused adverse pregnancy outcome and metabolic disorders in offspring via interfering with IGF1R.…”

Best Practices and Progress in Precision-Cut Liver Slice Cultures

“…Although RNA-seq is nowadays widely implemented, up to now the technique is still not frequently applied to PCLS cultures. Most PCLS research to which RNA-seq is applied, have been carried out in fish-derived liver slices in which the effect of culture time is compared to conventional 2D hepatocyte cultures and total liver [50] or the effect of compounds [51,52]. Bigaeva et al performed RNA-seq of healthy and diseased murine and human tissue slices in order to investigate the differences in species and organs [53].…”