Transcriptional responses of glutathione transferase genes in Ruditapes philippinarum exposed to microcystin-LR.

José Martins,Joana Azevedo,Bruno Reis,João Machado,Vitor Vasconcelos,Mariana Carneiro

doi:10.3390/ijms16048397

José Martins, Joana Azevedo + Show 4 more

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https://doi.org/10.3390/ijms16048397

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Abstract

Glutathione Transferases (GSTs) are phase II detoxification enzymes known to be involved in the molecular response against microcystins (MCs) induced toxicity. However, the individual role of the several GST isoforms in the MC detoxification process is still unknown. In this study, the time-dependent changes on gene expression of several GST isoforms (pi, mu, sigma 1, sigma 2) in parallel with enzymatic activity of total GST were investigated in gills and hepatopancreas of the bivalve Ruditapes philippinarum exposed to pure MC-LR (10 and 100 µg/L). No significant changes in GST enzyme activities were found on both organs. In contrast, MC-LR affected the transcriptional activities of these detoxification enzymes both in gills and hepatopancreas. GST transcriptional changes in gills promoted by MC-LR were characterized by an early (12 h) induction of mu and sigma 1 transcripts. On the other hand, the GST transcriptional changes in hepatopancreas were characterized by a later induction (48 h) of mu transcript, but also by an early inhibition (6 h) of the four transcripts. The different transcription patterns obtained for the tested GST isoforms in this study highlight the potential divergent physiological roles played by these isoenzymes during the detoxification of MC-LR.

Highlights

The frequent eutrophication of water bodies creates the conditions for the development of cyanobacterial blooms which are characterized by excessive proliferation of cyanobacterial cells [1].Cyanobacteria can produce potent and environmentally persistent toxins like microcystins (MCs) affecting freshwater and estuarine systems, and marine habitats
MCs are cyclic peptides consisting of seven amino acids including a unique β-amino acid side-group Adda, which is characteristic of cyanobacteria
MC-LR main mechanism of toxicity in animals comprises the inhibition of several serine/threonine (Ser/Thr) protein phosphatases (PPs) [5,6] leading to increased phosphorilation of cellular proteins involved in signal transduction

Summary

Introduction

The frequent eutrophication of water bodies creates the conditions for the development of cyanobacterial blooms which are characterized by excessive proliferation of cyanobacterial cells [1].Cyanobacteria can produce potent and environmentally persistent toxins like microcystins (MCs) affecting freshwater and estuarine systems, and marine habitats (land-sea flows). More than 90 structural variants of MCs have been found, with variation occurring mainly at the two L-amino acids. MC-LR is a structural variant characterized by the presence of leucin (L) and arginin (R) as L-amino acids in positions 2 and 4 [2,3,4]. Defective phosphorilation/dephosphorilation regulatory mechanisms leads to cytoskeleton disorganization and the disruption of cell integrity [4,7]. This effect has already been described in several organisms namely fish [8] and mammals [9]. MCs uptake is known to increase oxidative stress in cells. The production of reactive oxygen species (ROS) [10] leads to an increase in lipid peroxidation [11,12], DNA damage [13] and alteration of the antioxidant defense system [11,14,15]

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