p53 knock-down and hypoxia affects glutathione peroxidase 4 antioxidant response in hepatopancreas of the white shrimp Litopenaeus vannamei.

Hypoxia (<2 mg O/L) is one of the main environmental stressors that affects aquatic organisms, including the white shrimp (Litopenaeus vannamei). During hypoxia, reactive oxygen species (ROS) accumulation induces oxidative stress and damage to biomolecules. Redox state and ROS overproduction are modulated by the antioxidant system that is composed of several antioxidant enzymes, proteins, and other small compounds. Glutathione peroxidase 4 (GPx4) has emerged as an important antioxidant enzyme with cytoprotective roles. In vertebrates, antioxidant and pro-oxidant stress responses are regulated by several factors, including the p53 protein. However, little is known about GPx4 responses in crustaceans and the regulation by p53. Herein we analyzed and characterized the L. vannamei GPx4 and evaluated the responses to hypoxia and p53 knock-down. We found a unique GPx4 gene that produces five transcript variants (TVs) and only two protein isoforms with distinct cellular localization. GPx4 expression in hepatopancreas during hypoxia and p53 knock-down changed during short and long-term hypoxia, suggesting that GPx4 may be a sensitive indicator of antioxidant imbalance during stress. Knock-down of p53 induced a reduction in GPx4 expression, indicating that p53 modulates GPx4 responses during stress. This agrees with our findings of putative consensus sequences for p53 in the GPx4 gene promoter by in silico analysis. Also, the antioxidant response was effective in preventing major protein damage during hypoxia since no changes were detected in carbonylated proteins content in hepatopancreas during hypoxia. Conversely, p53 knock-down produced significant changes in carbonylated proteins.