A light in the darkness: New biotransformation genes, antioxidant parameters and tissue-specific responses in oysters exposed to phenanthrene

• Published in: Aquatic toxicology Vol. 152; pp. 324 - 334
• Main Authors: Lüchmann, Karim H., Dafre, Alcir L., Trevisan, Rafael, Craft, John A., Meng, Xiang, Mattos, Jacó J., Zacchi, Flávia L., Dorrington, Tarquin S., Schroeder, Declan C., Bainy, Afonso C.D.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.07.2014; Elsevier
• Subjects: Animal, plant and microbial ecology; Animals; Antioxidant parameters; Applied ecology; Biological and medical sciences; Biotransformation - genetics; Crassostrea - drug effects; Crassostrea - enzymology; Crassostrea - genetics; Crassostrea brasiliana; CYP; Cytochrome P-450 Enzyme System - genetics; Cytochrome P-450 Enzyme System - metabolism; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on protozoa and invertebrates; Fundamental and applied biological sciences. Psychology; Gills - drug effects; Gills - enzymology; Gills - metabolism; Glutathione - metabolism; Glutathione Transferase - genetics; Glutathione Transferase - metabolism; GST; Inactivation, Metabolic; Oyster; PAH; Phenanthrene; Phenanthrenes - metabolism; Phenanthrenes - toxicity; Water Pollutants, Chemical - metabolism; Water Pollutants, Chemical - toxicity; GST; Phenanthrene; CYP; Antioxidant parameters; Oyster; PAH; Brackish water environment; Edible mollusc; Persistent organic pollutant; Bivalvia; Glutathione transferase; Mangrove; Digestive gland; Unspecific monooxygenase; Gill; Hydrocarbon; Enzyme; Transferases; Phylogenetic tree; Cytochrome P450; Detoxification; Tissue specificity; Antioxidant; Polycyclic aromatic compound; Gene expression; Metabolism; Drug-metabolizing enzyme; Defense mechanism; Oxidoreductases; Invertebrata; Mollusca
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2014.04.021

•New phase I and II genes were identified in the oyster Crassostrea brasiliana.•CYP and GST genes were mainly induced in gill, not in digestive gland.•Phenanthrene exposure leads to glutathione depletion.•Antioxidant-related enzyme activities were not altered by phenanthrene exposure.•Phenanthrene detoxification in oysters appears to occur mainly in gill. Phenanthrene (PHE), a major component of crude oil, is one of the most abundant polycyclic aromatic hydrocarbons (PAHs) in aquatic ecosystems, and is readily bioavailable to marine organisms. Understanding the toxicity of PAHs in animals requires knowledge of the systems for xenobiotic biotransformation and antioxidant defence and these are poorly understood in bivalves. We report, for the first time, new transcripts and tissue-specific transcription in gill and digestive gland from the oyster Crassostrea brasiliana following 24h exposure to 100 and 1000μgL−1 PHE, a model PAH. Six new cytochrome P450 (CYP) and four new glutathione S-transferase (GST) genes were analysed by means of quantitative reverse transcription PCR (qRT-PCR). Different antioxidant endpoints, including both enzymatic and non-enzymatic parameters, were assessed as potential biomarkers of oxidative stress. GST activity was measured as an indicator of phase II biotransformation. Rapid clearance of PHE was associated with upregulation of both phase I and II genes, with more pronounced effects in the gill at 1000μgL−1 PHE. After 24h of exposure, PHE also caused impairment of the antioxidant system, decreasing non-protein thiols and glutathione levels. On the other hand, no change in antioxidant enzymes was observed. PHE treatment (100μgL−1) significantly decreased GST activity in the gill of exposed oysters. Both CYP and GST were transcribed in a tissue-specific manner, reflecting the importance of the gill in the detoxification of PAHs. Likewise, the antioxidant parameters followed a similar pattern. The data provide strong evidence that these genes play key roles in C. brasiliana biotransformation of PHE and highlight the importance of gill in xenobiotic metabolism.