Dietary administration of recombinant peroxiredoxin IV contributes to innate immunity and intestinal health in Larimichthys crocea juveniles

Abstract

This study investigated the effects of supplementation with recombinant peroxiredoxin IV (Prx IV) on the innate immunity and intestinal health in large yellow croaker (Larimichthys crocea). Fish (n = 160) from triple replicates were fed diets containing 0.00 g kg ⁻¹ (Prx1), 0.05 g kg ⁻¹ (Prx2), 0.10 g kg ⁻¹ (Prx3), and 0.15 g kg ⁻¹ (Prx4) Prx IV for 8 weeks. Results demonstrated that Prx IV supplementation significantly improved systemic antioxidant capacity, evidenced by elevated activities of superoxide dismutase and catalase, and increased levels of reduced glutathione. Analysis of the head kidney inflammatory response revealed that dietary Prx IV significantly upregulated gene expression of the anti-inflammatory cytokine interleukin-10 and simultaneously downregulated the expression of pro-inflammatory cytokines (interleukin 2, interleukin 8, and tumor necrosis factor). Furthermore, western blot analysis confirmed that Prx IV administration markedly suppressed nuclear translocation of nuclear factor-κB p65 in the head kidney. Regarding intestinal effects, dietary Prx IV improved intestinal morphology and significantly enhanced the activities of key digestive enzymes (amylase, lipase, and trypsin). Additionally, Prx IV supplementation significantly upregulated the expression of tight junction proteins (claudin 11 and zona occludens 1, ZO-1). Moreover, dietary administration of 0.15 g kg⁻¹ Prx IV significantly altered intestinal microbiota profiles. Specifically, it increased the abundance of Firmicutes, decreased the abundance of potential pathogens such as Haemophilus parainfluenzae and Klebsiella variicola, and increased the abundance of Bacteroides thetaiotaomicron, a bacterium associated with polysaccharide digestion and absorption. In conclusion, dietary administration of 0.15 g kg ⁻¹ Prx IV enhances antioxidant and anti-inflammatory capacities in the head kidney and promotes intestinal health in large yellow croaker. Modulation of the intestinal microbiota may contribute to these beneficial effects.