Peroxiredoxin 4 (Prx 4) plays important gene expression regulatory roles in antimicrobial innate immune by regulating hydrogen peroxide (HO) in the hepatopancreas of freshwater crayfish Procambarus clarkii.

This study focused on peroxiredoxin (Prx) as a core target to investigate its regulatory mechanism in the innate immunity of Procambarus clarkii (crayfish). We observed that a reduction in the expression of prx 4 via injection of double-stranded RNA (dsRNA) induced early upregulation of HO levels in the hepatopancreas of crayfish. When the crayfish were subsequently infected with Vibrio harveyi, the HO levels further increased, and the antioxidant enzyme system was activated. After injecting dsPc-Prx 4 and subsequently stimulating the crayfish with V. harveyi, we observed upregulated expression of genes related to the melanization pathway, reactive oxygen species (ROS) pathway, apoptosis pathway, and Toll pathway. Furthermore, after the injection of dsPc-Prx 4 followed by V. harveyi and subsequent N-acetylcysteine (NAC) exposure, the expression of genes related to the melanization, apoptosis, and Toll pathways was downregulated; moreover, the melanization phenomenon was significantly weakened, and the survival rate of the crayfish decreased. The abovementioned experimental results demonstrate that Pc-Prx 4 is an important regulatory enzyme in the antioxidant system of crayfish. It can influence the antibacterial innate immune response of P. clarkii by modulating HO levels. This study provides a significant addition to the fundamental theory of antibacterial innate immunity in invertebrates and offers a theoretical basis for the prevention and control of bacterial diseases in P. clarkii.