title: Upregulating Nrf2-dependent antioxidant defenses in Pacific oysters Crassostrea gigas: Investigating the Nrf2/Keap1 pathway in bivalves.
abstract: Analysis of the Pacific oyster Crassostrea gigas annotated genome revealed genes with conserved sequences belonging to typical cap 'n' collar Nrf2 domain, a major player in antioxidant protection, and domains belonging to Nrf2 cytoplasmic repressor (Keap1), but little is known about Nrf2/Keap1 induction in bivalves. C. gigas were exposed to waterborne 10 and 30μM curcumin, a known inducer of the mammalian Nrf2. Curcumin disappeared from the seawater after 10h, and accumulated in the gills (10h) and digestive gland (10-96h). A clear induction of glutathione (GSH)-related antioxidant defenses was observed at 96h in the gills of curcumin exposed animals (10 and 30μM), including GSH levels, and the activity of glutathione reductase (GR), glutathione peroxidase (GPx), and glutathione S-transferase (GST). This response was completely absent in the digestive gland, in line with the idea that bivalve gills act as a major site for antioxidant protection under acute exposure. The relative mRNA levels coding glutamate-cysteine ligase, GR, GPx2 and GSTpi were clearly induced by curcumin treatment (30μM, 24h). Curcumin pre-treatment for 96h increased oyster resistance to cumene hydroperoxide, but neither Nrf2 nor Keap1 genes were modulated by curcumin. However, the conserved sequences belonging to typical Nrf2 and Keap1 domains, and the notorious induction of antioxidant defense-related genes known to be controlled by Nrf2 in mammals, indicates a functional Nrf2/Keap1 pathway in bivalves, and curcumin seems to be a new tool to investigate the antioxidant response in bivalves.
authors.affiliation: Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil. Electronic address: naissa_d@yahoo.com.br.
authors.forename: Naissa Maria
authors.initials: NM
authors.lastname: Danielli
authors.affiliation: Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Rafael
authors.initials: R
authors.lastname: Trevisan
authors.affiliation: Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Danielle Ferraz
authors.initials: DF
authors.lastname: Mello
authors.affiliation: Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Kelvis
authors.initials: K
authors.lastname: Fischer
authors.affiliation: Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Vanessa Schadeck
authors.initials: VS
authors.lastname: Deconto
authors.affiliation: Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Daiane
authors.initials: D
authors.lastname: da Silva Acosta
authors.affiliation: Institute of Biological Sciences, Federal University of Rio Grande, 96203-900 Rio Grande, RS, Brazil.
authors.forename: Adalto
authors.initials: A
authors.lastname: Bianchini
authors.affiliation: Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil.
authors.forename: Afonso Celso Dias
authors.initials: AC
authors.lastname: Bainy
authors.affiliation: Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil. Electronic address: alcir.dafre@ufsc.br.
authors.forename: Alcir Luiz
authors.initials: AL
authors.lastname: Dafre
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D049872:Bivalvia / Q000378:metabolism*; D049896:Crassostrea / Q000235:genetics / Q000378:metabolism*; D003474:Curcumin / Q000378:metabolism / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D005880:Gills / Q000187:drug effects / Q000378:metabolism; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism; D005980:Glutathione Reductase / Q000235:genetics / Q000378:metabolism; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D000072019:Kelch-Like ECH-Associated Protein 1 / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D016019:Survival Analysis; D015854:Up-Regulation
chemical_list: D000975:Antioxidants; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase; D005982:Glutathione Transferase; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D003474:Curcumin
keywords: Antioxidant response element; Bivalves; Curcumin; Glutathione; Keap1; Nrf2; Oyster