Butylparaben disordered intestinal homeostasis in Chinese striped-necked turtles (Mauremys sinensis)

Butylparaben (BuP) is regarded as a widespread pollutant, which has potential risk to aquatic organisms. Turtle species are an important part of aquatic ecosystems, however, the effect of BuP on aquatic turtles is not known. In this study, we evaluated the effect of BuP on intestinal homeostasis of Chinese striped-necked turtle (Mauremys sinensis). We exposed turtles to concentrations of BuP (0, 5, 50, and 500 μg/L) for 20 weeks, then investigated the composition of gut microbiota, the structure of intestine, and the inflammatory and immune status. We found BuP exposure significantly changed the composition of gut microbiota. Specially, the unique genus in three concentrations of BuP-treated groups mainly was Edwardsiella, which was not present in control group (0 μg/L of BuP). In addition, the height of intestinal villus was shortened, and the thickness of muscularis was thinned in BuP-exposed groups. Particularly, the number of goblet cells obviously decreased, the transcription of mucin2 and zonulae occluden-1 (ZO-1) significantly downregulated in BuP-exposed turtles. Meanwhile, neutrophils and natural killer cells in lamina propria of intestinal mucosa increased in BuP-treated groups, especially in high concentration of BuP (500 μg/L). Moreover, the mRNA expression of pro-inflammatory cytokines, especially IL-1β showed a significant upregulation with BuP concentrations. Correlation analysis indicated the abundance of Edwardsiella was positively correlated with IL-1β and IFN-γ expression, whereas its abundance was negatively correlative with the number of goblet cells. Taken together, the present study demonstrated BuP exposure disordered intestinal homeostasis through inducing dysbiosis of gut microbiota, causing inflammatory response and impairing gut physical barrier in turtles, which emphasized the hazard of BuP to health of aquatic organism.