Toxic effects of tire wear particles and the leachate on the Chinese mitten crab (Eriocheir sinensis)

Tire wear particles (TWPs) were considered as an important component of microplastic pollution in the aquatic environment. To understand the ecotoxicity of TWPs to crustacean, this study investigated toxic effects of TWPs and the leachate on the mitten crab Eriocheir sinensis and the accumulation of TWPs in the crabs. Although TWPs could be accumulated in various tissues (i.e., liver, gills and gut) of the crabs, exposure to TWPs or the leachate had no lethal effect on the crabs in this study. Lower concentrations of TWPs and the leachate exposure could stimulate the antioxidant defense system of the crabs, while higher concentrations could disrupt the stress defense system. In addition, the energy supply and metabolism of the crabs could also be affected by TWPs or the leachate. The transcriptomic profiles showed that the toxic mechanisms of TWPs and the leachate were not exactly the same. Similar to the results of biochemical analysis, several Gene Ontology (GO) terms and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to oxidative stress and energy metabolism were significantly regulated by both TWPs and the leachate. However, TWPs could affect the expression of genes enriched in immune-related pathways, while the leachate regulated the enrichment of some other signaling pathways including FoxO signaling pathway, insulin signaling pathway, RIG-I-like receptor signaling pathway, NOD-like receptor signaling pathway, PPAR signaling pathway and neuroactive ligand-receptor interaction. Overall, our study could provide basic biological information for assessing the ecological risk of the TWP pollution in the aquatic environment and was useful to understand the potential toxic mechanisms of the TWPs and the leachate to crustaceans.