Impact of fish oil on the toxic effects of selected persistent organic pollutants in C57BL/6J mice

Abstract

Abstract Dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent toxicants which can accumulate in the food chain and cause a potential hazard for humans through their diet. For humans, the main exposure source of these contaminants is through the consumption of fish and seafood. However, seafood also contains the n-3 fatty acid eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are considered beneficial for human health. Moreover, studies have indicated that EPA and DHA can reduce the toxicological effects from dioxins and dl-PCBs due to their antioxidant properties.

The aim of this study was to investigate if subchronic toxicity through dietary exposure to either 2,3,7,8-tetrachlorobenzo-p-dioxin (TCDD), PCB 126 or a mixture of contaminants, including TCDD, PCBs and PBDEs, impact the liver in male mice. All contaminants used in the animal trial are considered persistent organic pollutants (POPs). In addition, we wanted to investigate whether exposure to the mixture of POPs had a greater or different effect compared to single exposure. It was also investigated whether inclusion of fish oil, containing DHA and EPA, could affect the toxicological effect from the contaminants. In this study, 126 C57BL/6J mice were included in a fractional factorial design. The diets given to the mice contained either high or low doses of TCDD, PCB 126 or a mix of contaminants, in either a standard Western diet, or a standard Western diet where either 1% or 5% of the fat portion was replaced with fish oil. The experiment lasted for 13 weeks and physiological parameters such as body weight, body composition and hematological parameters were assessed during the trial. Organ weights and liver gene expression were analyzed after the end of the animal trial.

Results from this study indicate that exposure of high doses of TCDD and a mixture of TCDD, PCBs and PBDEs led to adverse effects, such as increased liver weight and decreased body weight, in addition to gene expression indicating inflammation and oxidative stress, and histology analysis showed sign of hepatic cell death. For mice exposed to PCB 126, effects on the weight of the liver and altered gene expression were observed, but not to the same degree as for mice exposed to high doses of TCDD and the contaminant mix. Supplementation of fish oil in the feed did not reduce the contaminant effect.