Effects Of Chronic Exposure Of Triclocarban On Transcriptome And Microflora In Intestine In Zebrafish

Triclocarban(TCC)is widely used as an antibacterial agent in detergents,cosmetics,personal skin care products,and other drugs.As a substitute of triclosan(TCS),TCC presents with a high detection rate in water and sediment and indicates biological toxicity to aquatic organisms.The criteria of TCC in freshwater aquatic organisms and sediment are unknown and should be firstly derived,respectively.The intestinal toxicity and intestinal flora disturbance,caused by TCC exposure,have not been reported.In this study,zebrafish(Danio rerio),was used as a model organism in environmental toxicology research,with the advantages of low feeding cost,easy reproduction and high yield,and the known complete genome.In this study,the criteria of TCC of predicted no effect concentration in water(PNEC_water)and sediment(PNEC_sed)were derived,and zebrafish were used as experimental animals to explore the toxic effects of TCC on fish intestine and intestinal microflora,to provide theoretical guidance for the assessing on intestinal health of fish.In this study,firstly,the chronic toxicity data of fresh water aquatic organisms of TCC were collected and based on these data,it was deduced that the PNEC_water of TCC was 0.045?g/L,and PNEC_sed was 24.13?g/kg(dry weight),using the normal distribution species sensitivity allocation(SSD)method.TCC ecological risk assessment indicated high risk in most water bodies in Asia,and high risk in sediments in China.Shijing River in China indicates the highest risk(HQ:109.117).Zebrafish were exposed to Triclocarban(100 and 1000?g/L)for 21 d.Based on the second generation transcriptome sequencing method,in the intestinal of zebrafish,the Q30 of9 samples ranged from 93.45%to 94.54%.Transcriptome analyses revealed that TCC exposure indicated a concentration-depended pattern,which was the increasing number of different expression genes with the increasing TCC concentrations.Compared with the control group,1744 genes in the high concentration group were significantly different.In the functional annotation of COG,GO and KEGG databases,815,1279,and 1152 genes were determined with a significant difference,respectively.In KEGG,142 signaling pathways were significantly affected,including apoptosis,cell cycle,Toll-like receptor signaling pathway,MAPK signaling pathway,and Fox O signaling pathway.It was speculated that Triclocarban exposure could cause zebrafish intestinal apoptosis,cell cycle arrest,immune response,and intestinal inflammation.Based on microbial 16S sequences,the microbial diversity of intestinal contents was studied,and it was found that a high concentration of Triclocarban could significantly reduce the diversity of intestinal microorganisms and change the composition and structure of the microbial community.At the phylum level of taxonomy,a significant difference in microbial diversity was observed in Actinobacteria,Fusobacteria,and Firmicutes.At the genus level of taxonomy,the significant difference of microbial diversity was observed in 21 genera,for example,Cetobacterium,Pseudorhodobacter,and Rhodococcus.The destruction of intestinal microbiota might be involved in intestinal diseases.In this study,in zebrafish,the effects of Triclocarban on intestinal transcriptome and intestinal microorganisms indicated the significant changes in a concentration-depended pattern,which could provide a reference for further study on the toxic mechanism of Triclocarban in zebrafish.