Blunt snout bream (Megalobrama amblycephala) circRXRBB regulates antimicrobial immune response against Aeromonas hydrophila infection via miR-155/socs1a axis

Circular RNAs (circRNAs) play an important role in various of human diseases by acting as competing endogenous RNAs (ceRNAs) and can serve as biomarkers and therapeutic targets. Our prior research has demonstrated that the circRNA-miRNA-mRNA regulatory network plays an important role in blunt snout bream (Megalobrama amblycephala) resistance to Aeromonas hydrophila infection. However, the exact regulatory mechanisms still need to be further explored. In this research, we identified a circRNA called circRXRBB that was down regulated following A. hydrophila challenge, suggesting its possible involvement in antimicrobial immune. Subsequently, the present study demonstrated that circRXRBB overexpression suppressed the expression levels of proinflammatory factors (il-6, il-1 beta, tnf-alpha, and ifn-gamma). Dual luciferase assay demonstrated that circRXRBB could directly adsorb miR-155 through sponge action, while miR-155 mimic could restore the inhibitory effect on inflammatory factors caused by circRXRBB overexpression. In addition, mir-155 can target socs1a, and the mir155/socs1a axis is one of the important pathways for circRXRBB to regulate immune response. In conclusion, this research demonstrated that circRXRBB is critical in regulating the antibacterial defense against A. hydrophila infection, which contributes to a better understanding of the ceRNA regulatory network and offers a foundation for future strategies in fish disease diagnose, prevention, and treatment.