Characterization of selenium nanoparticles extracted from Bacillus subtilis and its antibacterial effects in Onychostoma macrolepis: Insight into ferroptosis

Selenium nanoparticles (SeNPs) were often used as growth and antioxidant capacity promoter. In this study, we found selenium nanoparticles (SeNPs) could improve the survival rate of Onychostoma macrolepis (O. macrolepis) fry as a feed additive after a challenged by Aeromonas hydrophila (A. hydrophila). To further explore the mechanism of SeNPs against bacterial infection, we examined the changes before and after bacterial infection, and the results showed that large amounts of peroxide were produced under A. hydrophila infection in O. macrolepis fry, and then the excessive accumulation of peroxides led to a large amount of ferroptosis in the liver. Interestingly, we found supplementing 0.9 mg/kg biogenic SeNPs decreased MDA, iron content, and enhanced T-AOC levels in the liver of O. macrolepis fry after a challenged by Aeromonas hydrophila (P˂0.01). Especially, the diet with 0.9 mg/kg biogenic SeNPs could significantly increase the expression level of Glutathione peroxidase-4 (GPX4), nuclear factor erythroid2-related factor 2 (Nrf2), and Ferroportin 1 (FPN1) in the liver of O. macrolepis after infection with A. hydrophila. In summary, the results of this research suggested that the diet with 0.9 mg/kg biogenic SeNPs was an optimal additive dose to improve the survival rate of O. macrolepis fry by increasing antioxidant capacity and inhibiting ferroptosis, which sheds a new light on the mechanism of antibacterial infection in fish from the perspective of ferroptosis.