Expression profiling and functional investigation of peroxiredoxin 2 in Chub mackerel: Multifunctional roles in oxidative stress regulation, apoptosis, and immune modulation.

Peroxiredoxin (Prdx) 2, belonging to the Prdx superfamily, is a pivotal enzyme and a key antioxidant that maintains cellular homeostasis by regulating reactive oxygen species (ROS) levels in living organisms. This study aimed to define the antioxidant and immune-related properties of the Prdx2 derived from Scomber japonicus (SjPrdx2). The molecular features of SjPrdx2 were characterized using in silico tools. The transcriptional responses of SjPrdx2 and its functional features were determined under immune-stimulating conditions; functional features were investigated using in vivo and in vitro approaches. The coding sequence of SjPrdx2 consists of 612 nucleotides, which encode a protein with 203 amino acids with a predicted molecular weight of 22.5 kDa. In the SjPrdx2 protein, the Prdx domain serves as the main functional domain, along with the "GGLG" and "FF" signature motifs. Under normal physiological conditions, SjPrdx2 expression was found to be highest in the heart, followed by the brain, blood, and spleen. The relative expression of SjPrdx2 was significantly up-regulated in the immune tissues following various immune stimuli, including polyinosinic-polycytidylic acid, lipopolysaccharide (LPS), Vibrio harveyi, and Streptococcus iniae. Additionally, the recombinant SjPrdx2 protein showed insulin disulfide reduction and radical-scavenging activity. In vitro functional assays demonstrated that H2O2-induced oxidative stress activated the ROS-scavenging function of SjPrdx2 and enhanced its apoptosis-inhibiting capacity. Additionally, SjPrdx2 overexpression promoted M2 polarization and suppressed nitric oxide production in LPS-treated RAW macrophage cells. Altogether, the findings of this study underscore the multifaceted contributions of SjPrdx2 to the active functioning of Chub mackerel, emphasizing its pivotal role in combating oxidative stress and fortifying immune functions.