Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil.
Department of Biochemistry, Federal University of Santa Catarina, 88040-900 Florianópolis, Brazil.
Comp Biochem Physiol C Toxicol Pharmacol. 2017 May;195:16-26. doi: 10.1016/j.cbpc.2017.02.004. Epub 2017 Feb 12.
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.
对太平洋牡蛎 Crassostrea gigas 注释基因组的分析揭示了具有保守序列的基因，这些基因属于典型的“帽子和领子”Nrf2 结构域，是抗氧化保护的主要参与者，以及属于 Nrf2 细胞质抑制剂（Keap1）的结构域，但关于双壳类动物中 Nrf2/Keap1 的诱导知之甚少。C. gigas 暴露于水基 10 和 30μM 姜黄素中，姜黄素是哺乳动物 Nrf2 的已知诱导剂。10h 后，姜黄素从海水中消失，并积累在鳃（10h）和消化腺（10-96h）中。在暴露于姜黄素的动物的鳃中，在 96h 时观察到谷胱甘肽（GSH）相关抗氧化防御的明显诱导，包括 GSH 水平以及谷胱甘肽还原酶（GR）、谷胱甘肽过氧化物酶（GPx）和谷胱甘肽 S-转移酶（GST）的活性。这种反应在消化腺中完全不存在，与双壳类动物鳃在急性暴露下作为抗氧化保护的主要部位的观点一致。编码谷氨酸-半胱氨酸连接酶、GR、GPx2 和 GSTpi 的相对 mRNA 水平被姜黄素处理（30μM，24h）明显诱导。姜黄素预处理 96h 增加了牡蛎对 cumene 氢过氧化物的抗性，但 Nrf2 和 Keap1 基因均未被姜黄素调节。然而，属于典型 Nrf2 和 Keap1 结构域的保守序列，以及众所周知的抗氧化防御相关基因的显著诱导，这些基因在哺乳动物中受 Nrf2 控制，表明 Nrf2/Keap1 途径在双壳类动物中具有功能，姜黄素似乎是研究双壳类动物抗氧化反应的新工具。
