Gills as a glutathione-dependent metabolic barrier in Pacific oysters Crassostrea gigas: Absorption, metabolism and excretion of a model electrophile

• Published in: Aquatic Toxicology
• Main Authors: Trevisan, Rafael, Mello, Danielle F., Delapedra, Gabriel, Silva, Danilo G. H., Arl, Miriam, Danielli, Naissa M., Metian, Marc, Almeida, Eduardo A., Dafre, Alcir L.
• Other Authors: Universidade Estadual Paulista (UNESP)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier B.V. 2016
• Subjects: Mercapturic acid pathway; Glutathione; Glutathione S-transferase; Gills; Bivalves; Pacific; Crassostrea gigas
• Online Access: http://hdl.handle.net/11449/161343; https://doi.org/10.1016/j.aquatox.2016.01.008

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Government of the Principality of Monaco CNPq: 573949/2008-5 CNPq: 462333/2014-0 CNPq: 406426/2012-0 The mercapturic acid pathway (MAP) is a major phase II detoxification route, comprising the conjugation of electrophilic substances to glutathione (GSH) in a reaction catalyzed by glutathione S-transferase (GST) enzymes. In mammals, GSH-conjugates are exported from cells, and the GSH-constituent amino acids (Glu/Gly) are subsequently removed by ectopeptidases. The resulting Cys-conjugates are reabsorbed and, finally, a mercapturic acid is generated through N-acetylation. This pathway, though very well characterized in mammals, is poorly studied in non-mammalian biological models, such as bivalve mollusks, which are key organisms in aquatic ecosystems, aquaculture activities and environmental studies. In the present work, the compound 1-chloro-2,4-dinitrobenzene (CDNB) was used as a model electrophile to study the MAP in Pacific oysters Crassostrea gigas. Animals were exposed to 10 NI CDNB and MAP metabolites were followed over 24 h in the seawater and in oyster tissues (gills, digestive gland and hemolymph). A rapid decay was detected for CDNB in the seawater (half-life 1.7 h), and MAP metabolites peaked in oyster tissues as soon as 15 min for the GSH-conjugate, 1 h for the Cys-conjugate, and 4 h for the final metabolite (mercapturic acid). Biokinetic modeling of the MAP supports the fast CDNB uptake and metabolism, and indicated that while gills are a key organ for absorption, initial biotransformation, and likely metabolite excretion, hemolymph is a possible milieu for metabolite transport along different tissues. CDNB-induced GSH depletion (4 h) was followed by increased GST activity (24 h) in the gills, but not in the digestive gland. Furthermore, the transcript levels of glutamate-cysteine ligase, coding for the rate limiting enzyme in GSH synthesis, and two ...