Combined hypoxia and high temperature affect differentially the response of antioxidant enzymes, glutathione and hydrogen peroxide in the white shrimp Litopenaeus vannamei

Low oxygen concentration in water (hypoxia) and high temperature are becoming more frequent due to climate change, forcing animals to endure stress or decease. Hypoxia and high temperature stress can lead to reactive oxygen species (ROS) accumulation and oxidative damage to the organisms. The shrimp Litopenaeus vannamei is the most cultivated crustacean worldwide. The aim of this study was to evaluate the expression and enzymatic activity of glutathione peroxidase (GPx), catalase (CAT) and cytosolic manganese superoxide dismutase (cMnSOD) in gills and hepatopancreas from L. vannamei in response to two combined stressors: hypoxia and reoxygenation at control and high temperature (28 vs 35 °C, respectively). In addition, glutathione and hydrogen peroxide content were analyzed. The changes were mainly tissue-specific. In gills, cMnSOD expression and enzymatic activity increased in response to the interactions between oxygen variation and thermal stress, while GPx and CAT were maintained. More changes occurred in GPx, CAT and MnSOD in hepatopancreas than in gills, mainly due to the effect of the individual stress factors of thermal stress or oxygen variations. On the other hand, the redox state of glutathione indicated that during high temperature, changes in the GSH/GSSG ratio occurred due to the fluctuations of GSSG. Hydrogen peroxide concentration was not affected by thermal stress or oxygen variations in hepatopancreas, whereas in gills, it was not detected. Altogether, these results indicate a complex pattern of antioxidant response to hypoxia, reoxygenation, high temperature and their combinations.