Two-week repair alleviated hexavalent chromium-induced hepatotoxicity, liver metabolism and intestinal microbial changes

Cr(VI) is a toxic water pollutant which can cause serious influence to the health of the human and animals. To test the self-repair ability of aquatic organisms after two weeks of exposure to Cr(VI), four groups were established in this study using Spinibarbus sinensis and Cr(VI) as model system: an exposure group (EXP) that exposed 0.5 mg/L Cr(VI) solution for 2 weeks, a control group (CON) that exposed purified water, as well as a two-week repair group (REXP) after 2 weeks of exposure, and the corresponding control group (RCON). The results showed that Cr(VI) induced hepatic inflammatory infiltration, hepatocyte swelling, mitochondrial abnormalities and autophagy, which were alleviated after two weeks of repair. To further investigate changes in liver metabolites and gut microbes after two weeks of Cr(VI) exposure and self-repair, metabolomics and 16S rDNA sequencing were used to compare the effects of Cr(VI) exposure on the organism. In the CON and EXP groups, the Amino acids and its metabolites pathway was most severely affected by Cr(VI), and pathways such as ABC transporters were also involved; the intestinal microbiota may be involved in Cr(VI) toxicity by increasing the abundance of harmful bacteria such as Saccharimonadales and PeM15. In the RCON and REXP groups, pathways such as Metabolic pathways were significantly enriched, among which the increased content of 3,3',5-Triiodo-L-Thyronine (T3), 1-Methylhistidine (1-MH) and decreased content of phosphocholine contributed positively to self-repair. In addition, increased abundance of beneficial bacteria such as s_Ensifer_adhaerens and decreased abundance of harmful bacteria (Saccharimonadales and PeM15) also played a role in counteracting the harm caused by Cr(VI) exposure. In conclusion, exposure to Cr(VI) can cause imbalance of microflora and induce metabolic disorders in the liver, and subsequently cause liver damage in Spinibarbus sinensis.