TPhP exposure disturbs carbohydrate metabolism, lipid metabolism, and the DNA damage repair system in zebrafish liver

Abstract

Triphenyl phosphate is a high production volume organophosphate flame retardant that has been detected in multiple environmental media at increasing concentrations. The environmental and health risks of triphenyl phosphate have drawn attention because of the multiplex toxicity of this chemical compound. However, few studies have paid close attention to the impacts of triphenyl phosphate on liver metabolism. We investigated hepatic histopathological, metabolomic and transcriptomic responses of zebrafish after exposure to 0.050 mg/L and 0.300 mg/L triphenyl phosphate for 7 days. Metabolomic analysis revealed significant changes in the contents of glucose, UDP-glucose, lactate, succinate, fumarate, choline, acetylcarnitine, and several fatty acids. Transcriptomic analysis revealed that related pathways, such as the glycosphingolipid biosynthesis, PPAR signaling pathway and fatty acid elongation, were significantly affected. These results suggest that triphenyl phosphate exposure markedly disturbs hepatic carbohydrate and lipid metabolism in zebrafish. Moreover, DNA replication, the cell cycle, and non-homologous end-joining and base excision repair were strongly affected, thus indicating that triphenyl phosphate hinders the DNA damage repair system in zebrafish liver cells. The present study provides a systematic analysis of the triphenyl phosphate-induced toxic effects in zebrafish liver and demonstrates that low concentrations of triphenyl phosphate affect normal metabolism and cell cycle.

Figure 1. Score plots of PLS-DA models.

PLS-DA analyses were performed using MetaboAnalyst 3.0. PLS-DA model among control and 0.050 and 0.300 mg/L TPhP-treated groups (A); PLS-DA model between control and 0.050 mg/L TPhP-treated groups (B); PLS-DA model between control and 0.300 mg/L TPhP-treated groups (C). The shaded areas are the 95% confidence regions of each treatment. Six parallel metabolomics samples were prepared in each treatment group.

Figure 2. Top 20 influenced pathways of each TPhP-treated group in the transcriptomic analysis.

(A) Top 20 statistics of KEGG pathway enrichment for DEGs observed in the 0.050 mg/L TPhP-treated group; (B) Top 20 statistics of KEGG pathway enrichment for DEGs observed in the 0.300 mg/L TPhP-treated group.

Figure 3. Effects of TPhP exposure on zebrafish blood glucose and lipid levels.

The data are presented as the mean ± SD (n = 3). Asterisk (*) and double asterisks (**) denote significant changes identified by one-way ANOVA and post hoc test based on LSD (p < 0.05 and p < 0.01, respectively) relative to controls.

Figure 4. Representative micrographs of liver sections from zebrafish (n = 10) exposed to the indicated experimental concentrations of TPhP for 7 days.

Blue arrows indicate vacuolization, yellow arrowheads indicate pyknotic nucleus, green arrowheads indicate karyorrhexis, and areas in black ellipses indicate cells losing nuclei.

Figure 5. Systematic view of TPhP-induced hepatotoxicity in zebrafish.

Red and blue denote up-regulated and down-regulated, respectively.