Glutathione peroxidase (GPx) is a key enzyme of cellular detoxification systems that defend cells against reactive oxygen species. Knowledge of the complement of GPx in shrimp is essential to understanding regulation and detoxification mechanisms of environmental stress. In this study, we expressed GPx from white shrimp Litopenaeus vannamei in Escherichia coli, and then characterized the purified recombinant enzyme with respect to the effects of pH, temperature on its catalytic activity. Quantitative real-time PCR and western blot analysis were carried out to investigate the expression patterns of GPx in shrimp hepatopancreas exposed to Cd stress. A statistically significant increase in expression of GPx mRNA and protein was observed in the Cd stress at 24 h. By contrast, western blot showed a significant up-regulation in GPx protein expression at 12 h exposed pH stress (5.6 and 9.3, respectively). These results suggest that L. vannamei GPx expression was modulated by Cd and pH stress and may play an important role in detoxification of xenobiotics and antioxidant defense. We conclude that GPx could be used as biomarkers of Cd and pH stress in aquatic environment for the studied species.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to investigate the toxic effects induced by benzo[a]pyrene (BaP). In the present study, juvenile white shrimp Litopenaeus vannamei were exposed to BaP for 21 days at four different concentrations as 0, 0.03, 0.3 and 3 μg/L. Detoxification system parameters, transcription of metabolism-related genes, and damage indexes were investigated for screening. It showed mRNA expression levels of superoxide dismutase (SOD), cytochrome P450 (CYP) 1A1 and glutathione-S-transferase (GST) in hepatopancreas were significantly induced at day 3 by 0.3 and 3 μg/L BaP, and returned to the initial level afterwards. 7-Ethoxyresorufin O-deethylase (EROD), GST and SOD activities in gill and hepatopancreas were also induced by 0.3 and 3 μg/L BaP, while T-AOC and GSH contents were reduced after BaP exposure. The study also showed that 0.3 and 3 μg/L BaP caused damage effects, while 0.03 μg/L BaP treatment did not exhibit any damage effects. Moreover, according to the correlation analysis results, we conclude that EROD activity, GST activity and GSH content in hepatopancreas can be used as defense biomarkers; DNA strand breaks, lipid peroxidation (LPO) level and protein carbonyl (PC) content in gill and hepatopancreas can be used as damage biomarkers; EROD activity, GST activity, GSH contents and damage effects of DNA strand breaks, LPO level and PC content in hepatopancreas can be used as combined biomarkers. These results will provide information not only on potential biomarkers that could be effectively applied to biomonitor aquatic environment to contamination, but also provide information on toxic effects of this specie.
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