Characterization of molecular features, antioxidant capacity, and immunological function of thioredoxin 1 (Trx1) in chub mackerel (Scomber japonicus).

Thioredoxin 1 (Trx1) is a redox-active protein of the thioredoxin family, primarily responsible for regulating the redox state of cells. The Trx1 gene of Scomber japonicus (SjTrx1) was retrieved from a pre-established transcriptome database. The length of SjTrx1 is 327 base pairs and it encodes 108 amino acids. Under normal conditions, SjTrx1 was expressed in all examined tissues, with the highest level observed in the brain. Immunostimulation with polyinosinic: polycytidylic acid (poly I:C), lipopolysaccharide (LPS), and Vibrio harveyi highly induced SjTrx1 expression in the spleen and blood tissues. Recombinant SjTrx1 (rSjTrx1) demonstrated antioxidant capacity and DNA-protective effect through insulin disulfide reduction, MTT, DPPH, and metal-catalyzed oxidation (MCO) assays. Overexpression of SjTrx1 induced M2 polarization of mouse macrophages and activation of M2-related marker genes, indicating anti-inflammatory properties. Overexpression of SjTrx1 in fathead minnow (FHM) cells enhanced the expression of key antiviral genes, leading to a subsequent reduction in viral gene expression following infection with viral hemorrhagic septicemia virus (VHSV). The findings of this study suggested SjTrx1's protective role against oxidative stress and its involvement in the immune response to pathogenic infections in S. japonicus.