Abstract
Microcystins (MCs) are a major group of cyanotoxins with side effects in many organisms; thus, compounds in this group are recognized as potent stressors and health hazards in aquatic ecosystems. In order to assess the toxicity of MCs and detoxification mechanism of freshwater shrimp Macrobrachium nipponense, the full-length cDNAs of the glutathione S-transferase (gst) and catalase (cat) genes were isolated from the hepatopancreas. The transcription level and activity changes in the biotransformation enzyme (glutathione S-transferase (GST)) and antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx)) in the hepatopancreas of M. nipponense exposed to MC-LR (0.2, 1, 5, and 25 μg/L) for 12, 24, 72 and 96 h were analyzed. The results showed that the isolated full-length cDNAs of cat and gst genes from M. nipponense displayed a high similarity to other crustaceans, and their mRNAs were mainly expressed in the hepatopancreas. MC-LR caused significant increase of GST activity following 48–96 h (p < 0.05) and an increase in SOD activity especially in 24- and 48-h exposures. CAT activity was activated when exposed to MC-LR in 12-, 24- and 48-h exposures and then it was inhibited at 96-h exposure. There was no significant effect on GPx activity after the 12- and 24-h exposures, whereas it was significantly stimulated after the 72- and 96-h exposures (p < 0.05). The transcription was altered similarly to enzyme activity, but the transcriptional response was generally more immediate and had greater amplitude than enzymatic response, particularly for GST. All of the results suggested that MC-LR can induce antioxidative modulation variations in M. nipponense hepatopancreas in order to eliminate oxidative damage.
Highlights
Microcystins (MCs) are a family of cyclic peptide toxins produced by brackish and freshwater cyanobacteria of the genera Anabaena, Anabaenopsis, Chroococcus, Microcystis, Nostoc, and Planktothrix [1]
MCs are selective for liver cells, irreversibly inhibiting serine/threonine protein phosphatases 1 (PP-1) and 2A (PP-2A), and causing disintegration of hepatocyte structure, apoptosis, necrosis, and internal hemorrhage in the liver which may lead to death by hemorrhagic shock [3,4,5]
The full-length cDNA sequences of cat (GenBank accession No KC485002) and gst (GenBank accession No KC485003) genes were determined by the Reverse Transcription (RT)-PCR and rapid amplification of cDNA ends (RACE) methods
Summary
Microcystins (MCs) are a family of cyclic peptide toxins produced by brackish and freshwater cyanobacteria of the genera Anabaena, Anabaenopsis, Chroococcus, Microcystis, Nostoc, and Planktothrix [1]. More than 80 structural variants have been identified, differing primarily in two. Toxins are released into the surrounding medium during senescence and lysis of bloom cells, which affect many organisms, from terrestrial mammals to algae. MCs are selective for liver cells, irreversibly inhibiting serine/threonine protein phosphatases 1 (PP-1) and 2A (PP-2A), and causing disintegration of hepatocyte structure, apoptosis, necrosis, and internal hemorrhage in the liver which may lead to death by hemorrhagic shock [3,4,5]. Aquatic organisms are more frequently exposed to MCs. Studies with different fish species show that
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