Acute effects of pure cylindrospermopsin on the activity and transcription of antioxidant enzymes in tilapia (Oreochromis niloticus) exposed by gavage

Abstract

The cyanobacterial toxin cylindrospermopsin (CYN) is a widely distributed contaminant of freshwater systems with the consequent risk for human and wildlife, particularly fish. However, CYN toxicity data on fish are still scarce. It is known that CYN inhibits glutathione synthesis and this could contribute to oxidative damage. In the present work tilapia (Oreochromis niloticus) were exposed by gavage to 200 and 400 μg/kg bw of pure CYN and sacrificed after 24 h. The activity and relative mRNA expression by real-time PCR of antioxidant enzymes glutathione peroxidase (GPx) and soluble glutathione-S-transferases (sGST) and the sGST protein abundance by Western blot analysis were evaluated in liver and kidney. Also the induction of lipid peroxidation (LPO) was assayed. Results show an increase of LPO products in both organs. Moreover, CYN altered the activity, gene expression and protein abundance of the enzymes, indicating the importance of GPx and sGST in CYN pathogenicity. This is the first time that CYN is reported to affect these enzymes in fish and they have shown to be responsive biomarkers of CYN toxicity.

Beneficial effects of vitamin E supplementation against the oxidative stress on Cylindrospermopsin-exposed tilapia (Oreochromis niloticus)

“…Moreover, vitamin E per se did not induce any significant changes in this enzymatic activity in the present work, while pretreatment with 45 mg NAC/fish/day induced GPx activity (Guti errez-Praena et al, 2012d). In this study, the kidney was not affected by CYN exposure, in accordance with previous studies (Guti errez-Praena et al, 2012d;Puerto et al, 2011b).…”

“…Glutathione peroxidase (GPx; EC 1.11.1.9) activity was assayed by following the rate of NADPH oxidation at 340 nm by the coupled reaction with glutathione reductase (Puerto et al, 2011b). The specific activity was determined using the extinction coefficient of 6.22 mM À1 cm À1 .…”

“…CYN causes inhibition of protein (Terao et al, 1994) and glutathione (GSH) synthesis (Runnegar et al, 1994(Runnegar et al, , 2002, as well as genotoxicity (Zegura et al, 2011) and endocrine disruption (Young et al, 2008). Some in vitro assays (Guti errez-Praena et al, 2011a, 2012a and in vivo studies carried out in tilapia (Oreochromis niloticus) (Guti errez- Guzm an-Guill en et al, 2013a;Puerto et al, 2011b;Puerto et al, 2014) have shown that oxidative stress is involved in CYN mechanism of toxicity, measured by levels of lipid peroxidation (LPO), protein and DNA oxidation, reduced-oxidized glutathione ratio (GSH/GSSG), and changes in the activity of different enzymes such as glutathione-S-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), and g-Glutamyl-cysteine synthetase (g-GCS). To counteract these alterations, there are some antioxidants that act repairing the normal redox status or as preventive substances against reactive oxygen species (ROS).…”

Potential Use of Chemoprotectants against the Toxic Effects of Cyanotoxins: A Review

“…It has been suggested that CYP450 metabolites may be responsible for the toxicity observed, although CYN metabolites have not been identified so far [15]. Oxidative stress is also involved in CYN toxicity, as it increases intracellular ROS production, reduces GSH [127], and induced changes in the activity of various oxidative stress biomarkers in vivo and in vitro [4,128,129]. Liver and kidney have been described as the main target organs of this toxin in vivo.…”

Cianobactérias: uma revisão sobre potencial nutricional e alguns aspectos biotecnológicos

“…Em estudo utilizando a toxina Cilindrospermopsina em peixe foi evidenciado que a expressão gênica e a atividade das enzimas Glutationa Peroxidase e Glutationa-S-transferase são afetadas contribuindo para danos oxidativos (PUERTO et al, 2011).…”