The ceRNA Network Indicates Its Immune Function in Peripheral Blood Leukocytes of Half-Smooth Tongue Sole (Cynoglossus semilaevis) After Stimulation with Chitosan Oligosaccharide

As an efficient immunostimulant, chitosan oligosaccharide (COS) can enhance the immunity of teleosts; however, the underlying molecular mechanisms still require elucidation. Competing endogenous RNAs (ceRNAs) are vital regulators in the immune response, but their roles in half-smooth tongue sole (Cynoglossus semilaevis) remain unclear. In this study, for the first time, we studied whole-transcriptome expression profiles and analyzed ceRNA networks in peripheral blood leukocytes of half-smooth tongue sole treated with COS. A total of 19 circRNAs (DE-circRNAs), 18 miRNAs (DE-miRNAs) and 50 previously identified lncRNAs (DE-lncRNAs) were differentially expressed after COS stimulation. The DE-lncRNAs and DE-miRNAs targeted numerous immunity-related genes, and were enriched in important pathways, including MAPK and Toll-like receptor signaling pathways, suggesting the immunoregulatory roles of COS. Furthermore, we constructed circRNA-miRNA-mRNA and lncRNA-miRNA-mRNA regulatory networks using DE-circRNAs, DE-miRNAs, DE-lncRNAs, and DE-mRNAs. Additionally, a ceRNA network with immunity-related DE-mRNAs was constructed, showing that 3 DE-circRNAs, 12 DE-lncRNAs, and 29 DEGs exhibited crosstalk through 9 DE-miRNAs. Intriguingly, a DE-miRNA in the ceRNA network, miR-144-3p, was targeted by DE-lncRNA tnrc6a, and negatively regulated the genes of inhibitor of nuclear factor kappa B kinases (IKKs) (ikbkg, ikbkb, and ikbip) and c3ar1. Ikbkg, ikbkb, and c3ar1 were significantly up-regulated in macrophages stimulated by LPS. It could be inferred that ncRNAs participated in the immune and inflammatory response by acting as ceRNAs after COS stimulation in teleosts. These findings indicate that COS could enhance the immunity of teleosts by regulating ncRNAs, and lay the foundation for further practical application of COS in aquaculture.