Abstract
The cyanobacterial toxin Cylindrospermopsin (CYN), a potent protein synthesis inhibitor, is increasingly being found in freshwater bodies infested by cyanobacterial blooms worldwide. Moreover, it has been reported to be implicated in human intoxications and animal mortality. Recently, the alteration of the activity and gene expression of some glutathione related enzymes in tilapias (Oreochromis niloticus) exposed to a single dose of CYN has been reported. However, little is known about the effects induced by repeated doses of this toxin in tilapias exposed by immersion and the potential reversion of these biochemical alterations after two different depuration periods (3 or 7 days). In the present study, tilapias were exposed by immersion to repeated doses of a CYN-containing culture of Aphanizomenon ovalisporum during 14 days, and then were subjected to depuration periods (3 or 7 days) in clean water in order to examine the potential reversion of the effects observed. The activity and relative mRNA expression by real-time polymerase chain reaction (PCR) of the antioxidant enzymes glutathione peroxidase (GPx) and soluble glutathione-S-transferases (sGST), and also the sGST protein abundance by Western blot analysis were evaluated in liver and kidney of fish. Results showed significant alterations in most of the parameters evaluated and their recovery after 3 days (GPx activity, sGST relative abundance) or 7 days (GPx gene expression, sGST activity). These findings not only confirm the oxidative stress effects produced in fish by cyanobacterial cells containing CYN, but also show the effectiveness of depuration processes in mitigating the CYN-containing culture toxic effects.
Highlights
IntroductionCylindrospermopsin (CYN) is an emerging toxin [2], which can be produced by several known freshwater cyanobacteria species, such as Cylindrospermopsis raciborskii, Aphanizomenon ovalisporum, Raphidiopsis curvata, and Umezakia natans [3,4,5]
Cyanobacterial toxins have become recognized as a potential hazard in drinking water worldwide [1].Among them, Cylindrospermopsin (CYN) is an emerging toxin [2], which can be produced by several known freshwater cyanobacteria species, such as Cylindrospermopsis raciborskii, Aphanizomenon ovalisporum, Raphidiopsis curvata, and Umezakia natans [3,4,5]
No fish died and they exhibited no obvious signs of stress during the acclimation period, the exposure to A. ovalisporum culture or during the depuration periods
Summary
Cylindrospermopsin (CYN) is an emerging toxin [2], which can be produced by several known freshwater cyanobacteria species, such as Cylindrospermopsis raciborskii, Aphanizomenon ovalisporum, Raphidiopsis curvata, and Umezakia natans [3,4,5]. This toxin is a tricyclic alkaloid comprised of a guanidine entity along with a uracil moiety potentially responsible for the toxicity [6]. In Australia, the levels of CYN produced by natural blooms of C. raciborskii and A. ovalisporum oscillated between 0.3 μg/L to 92 μg/L and
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