Mitochondrial peroxiredoxin 3 (Prx3) from rock bream (Oplegnathus fasciatus): immune responses and role of recombinant Prx3 in protecting cells from hydrogen peroxide induced oxidative stress.

Pathogenic infections and environmental factors cause a variety of stresses in fish including oxidative stress by rapid elevation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Transcriptional activation and expression of antioxidant enzymes are essential for reducing the oxidative stress. In this study, we present the molecular characterization, immune responses and ROS scavenging activity of mitochondrial peroxiredoxin 3 from Oplegnathus fasciatus (RbPrx3). Coding sequence (CDS) of RbPrx3 contains 248 amino acids polypeptide which consists of highly conserved peroxiredoxin super family domain and two cysteine residues. Pairwise sequence comparison revealed that RbPrx3 has the greatest identity (94.8%) to Sparus aurata Prx3. Transcriptional analysis of RbPrx3 indicated the ubiquitously expressed mRNA in wide array of organs showing the highest expression in the liver of rock bream. Upon immune challenge of Edwardsiella tarda, Streptococcus iniae, rock bream iridovirus (RBIV) and lipopolysaccharide (LPS), RbPrx3 mRNA level was up-regulated in immunocompetent liver tissues compared to unchallenged fish. Purified recombinant RbPrx3 treated THP-1 cells showed higher survival rate against H(2)O(2) induced oxidative stress and significantly reduced the level of intracellular ROS. Overall results from our study suggest that RbPrx3 may be involved in broader functions such as regulating oxidative stresses by scavenging ROS and activating immune responses in rock bream.