Identification and profiling of microRNAs responsive to cadmium toxicity in hepatopancreas of the freshwater crab Sinopotamon henanense

Background Cadmium (Cd) is a ubiquitous environmental toxicant for aquatic animals. The freshwater crab, Sinopotamon henanense (S. henanense), is a useful model for monitoring Cd exposure since it is widely distributed in sediments whereby it tends to accumulate several toxicants, including Cd. In the recent years, the toxic effects of Cd in the hepatopancreas of S. henanense have been demonstrated by a series of biochemical analysis and ultrastructural observations as well as the deep sequencing approaches and gene expression profile analysis. However, the post-transcriptional regulatory network underlying Cd toxicity in S.henanense is still largely unknown. Results The miRNA transcriptional profile of the hepatopancreas of S. henanense was used to investigate the expression levels of miRNAs in response to Cd toxicity. In total, 464 known miRNAs and 191 novel miRNAs were identified. Among these 656 miRNAs, 126 known miRNAs could be matched with the miRNAs of Portunus trituberculatus, Eriocheir sinensis and Scylla paramamosain. Furthermore, a total of 24 conserved miRNAs were detected in these four crab species. Fifty-one differentially expressed miRNAs were identified in the Cd-exposed group, with 31 up-regulated and 20 down-regulated. Eight of the differentially expressed miRNAs were randomly selected and verified by the quantitative real-time PCR (qRT-PCR), and there was a general consistency (87.25%) between the qRT-PCR and miRNA transcriptome data. A total of 5258 target genes were screened by bioinformatics prediction. GO term analysis showed that, 17 GO terms were significantly enriched, which were mainly related to the regulation of oxidoreductase activity. KEGG pathway analysis showed that 18 pathways were significantly enriched, which were mainly associated with the biosynthesis, modification and degradation of proteins. Conclusion In response to Cd toxicity, in the hepatopancreas of S. henanense, the expressions of significant amount of miRNAs were altered, which may be an adaptation to resist the oxidative stress induced by Cd. These results provide a basis for further studies of miRNA-mediated functional adaptation of the animal to combat Cd toxicity.

Modulation of oxidative damage by lipopolysaccharides and antioxidant responses in the freshwater crab Sinopotamon henanense Bott 1967 (Decapoda: Brachyura: Potamonidae) during cadmium exposure

Cadmium (Cd) is a toxic pollutant that exerts adverse effects on organisms. We examined oxidative damage and antioxidative parameters in hemocytes of the freshwater crab Sinopotamon henanense Bott 1967 exposed to sublethal levels of Cd for 21 d. We also examined the immunomodulation of lipopolysaccharides (LPS) on oxidation caused by Cd in the crab. Cd induced higher reactive oxygen species (ROS) levels but ROS production in crab hemocytes was down-regulated after LPS injection. The contents of malondialdehyde (MDA) and protein carbonyl derivatives (PCO), DNA-protein crosslinks (DPCs) coefficient in the hemocytes of crabs exposed to Cd increased. LPS injection could decrease these oxidative parameters. The total antioxidant capacity (T-AOC) was significantly inhibited by Cd and LPS enhanced the activity of T-AOC in crab hemocytes. Cd treatment also up-regulated activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Only CAT activity decreased when crabs were exposed to Cd followed by LPS stimulation. Peroxidase (POD) activities showed little change after Cd or LPS treatments. The oxidative damage caused by Cd exposure may be reduced by LPS, suggesting its possible use in aquaculture as an immunostimulant for crustaceans.