Differential responses in the biotransformation systems of the oyster Crassostrea gasar (Adanson, 1757) elicited by pyrene and fluorene: molecular, biochemical and histological approach - Part I

• Published in: Aquatic toxicology Vol. 216; p. 105318
• Main Authors: Zacchi, Flávia Lucena, dos Reis, Isis Mayna Martins, Siebert, Marília Nardelli, Mattos, Jacó Joaquim, Flores-Nunes, Fabrício, Toledo-Silva, Guilherme de, Piazza, Clei Endrigo, Bícego, Márcia Caruso, Taniguchi, Satie, Bainy, Afonso Celso Dias
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.11.2019
• Subjects: Animals; Biotransformation; Biotransformation - drug effects; Crassostrea - cytology; Crassostrea - drug effects; Crassostrea - genetics; Cytochrome P-450 CYP1A1 - genetics; Cytochrome P-450 CYP1A1 - metabolism; Digestive System - drug effects; Fluorene; Fluorenes - toxicity; Fluorescence; Gene Expression Regulation - drug effects; Gills - drug effects; Gills - enzymology; ISH; Oyster; PAH; Pyrene; Pyrenes - toxicity; RNA, Messenger - genetics; RNA, Messenger - metabolism; Water Pollutants, Chemical - toxicity; Pyrene; Fluorene; Oyster; Biotransformation; PAH; ISH
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2019.105318

[Display omitted] •PYR and FLU were accumulated in oyster soft tissues.•Oysters exposed to PYR showed histologic changes.•CYP2AU1, GSTO-like and SULT-like transcript levels were higher in PYR-exposed group.•Oysters exposed to PYR presented higher EROD and MGST activities.•CYP2AU1gene was enhanced in PYR or FLU exposed groups being a good biomarker. Polycyclic aromatic hydrocarbons (PAHs) are among the main contaminants in aquatic environments. PAHs can affect organisms due to their carcinogenic, mutagenic and/or teratogenic characteristics. Depending on the PAHs, concentration, and period of exposure, biological damage can occur leading to histopathologic alterations. This study aimed to evaluate the molecular, biochemical and histological responses of the oyster Crassostrea gasar exposed to pyrene (0.25 and 0.5 μM) and fluorene (0.6 and 1.2 μM), after exposure for 24 and 96 h. Concentrations of both PAHs were quantified in the water and in oyster tissues. Transcript levels of phase I (CYP3475C1, CYP2-like, CYP2AU1 and CYP356A) and phase II (GSTO-like, MGST-like and SULT-like) biotransformation-related genes and the activities of ethoxyresorufin-O-deethylase (EROD), total and microsomal glutathione S-transferase (GST and MGST) were evaluated in the gills. Also, histological changes and localization of mRNA transcripts CYP2AU1 in gills, mantle, and digestive diverticula were evaluated. Both PAHs accumulated in oyster tissues. Pyrene half-life in water was significantly lower than fluorene. Transcript levels of all genes were higher in oysters exposed to of pyrene 0.5 μM (24 h). Only CYP2AU1 gene was up-regulated by fluorene exposure. EROD and MGST activities were higher in oysters exposed to pyrene. Tubular atrophy in the digestive diverticula and an increased number of mucous cells in the mantle were observed in oysters exposed to pyrene. CYP2AU1 transcripts were observed in different tissues of pyrene-exposed oysters. A significant correlation was observed between tubular atrophy and the CYP2AU1 hybridization signal in oysters exposed to pyrene, suggesting the sensibility of the species to this PAH. These results suggest an important role of biotransformation-related genes and enzymes and tissue alterations associated to pyrene metabolism but not fluorene. In addition, it reinforces the role of CYP2AU1 gene in the biotransformation process of PAHs in the gills of C. gasar.