BIG-BELLY SEAHORSE Hippocampus abdominalis 1-Cys PEROXIREDOXIN AS A SENSOR OF H₂O₂ MEDIATED OXIDATIVE STRESS WITH POTENTAL IMMUNE RESPONSES

Peroxiredoxins (Prx) are belonging to the most abundant antioxidant proteins in a cell and play central roles not only as detoxifying hydro-peroxidases but also as redox-regulated chaperones and redox sensors. Molecular features of Hippocampus abdominalis peroxiredoxin 6 (HaPrx6) were assessed by using molecular biological tools available in online. Antioxidant assays were performed using its recombinant protein (rHaPrx6). Potential immune responses upon septic conditions were determined through quantitative real time PCR (qPCR) analysis. Functionally active cysteine was confined in peroxidase catalytic center (⁴⁴PVCTTE⁴⁹) and peroxiredoxin super-family domain was identified. Pairwise homolog comparison showed the highest amino acid identity (84.7%) and evolutionary closer relation with Oplegnathus fasciatus Prx6. Multiple sequence alignment revealed the conservation of peroxidase catalytic center among the other Prx6 counterparts suggesting the common peroxidase activity. Fold index results demonstrated the similar folding structure of Prx6 protein molecules except the Haliotis discus discus Prx6. Metal catalyzed oxidative (MCO) stress, cleaved the pUC19 DNA from supercoiled state into nicked state where, rHaPrx6 protein could protect the pUC19 DNA cleavage by MCO system (Figure 1). In addition, 100 µg/mL of rHaPrx6 increased the human leukemia THP-1 cell survival by detoxifying the hydro-peroxidases in cell culture media. Furthermore, flow cytometry analysis confirmed the antioxidant activity of rHaPrx6 and results revealed that 100 µg/mL of rHaPrx6 decreased the intracellular reactive oxygen species (ROS) level in THP-1 cells which were under H₂O₂ mediated oxidative stress.

The HaPrx6 transcripts were ubiquitously expressed in all examined tissues with highest expression in liver. Bacterial (Edwardsiella tarda, Streptococcus iniae and LPS) immune stimulated liver and kidney tissues showed significant HaPrx6 mRNA expression after the post infection. Collectively, HaPrx6 is belonging to the teleostean peroxiredoxin family member with its antioxidant function and potential immune responses upon bacterial challenges.