title: Copper exposure induces toxicity to the antioxidant system via the destruction of Nrf2/ARE signaling and caspase-3-regulated DNA damage in fish muscle: amelioration by myo-inositol.
abstract: The muscle is the main portion of fish that is consumed by humans. Copper (Cu) can induce oxidative damage in fish muscle. However, the effects of Cu exposure on the muscle antioxidant system and molecular patterns and preventive measures against these effects remain unclear. In this study, ROS production, enzymatic and mRNA levels of antioxidant enzymes and NF-E2-related factor 2 (Nrf2) signaling-related molecules, antioxidant response element (ARE) binding ability, DNA fragmentation and caspase-3 activities were analyzed in fish muscle following Cu exposure or myo-inositol (MI) pre-administration. The results indicated that contamination due to copper exposure caused an approximately three-fold increase in ROS production, induced lipid peroxidation and protein oxidation, and resulted in depletion of the glutathione (GSH) content of fish muscle. Moreover, Cu exposure caused decreases in the activities of total superoxide dismutase (T-SOD), CuZnSOD, and glutathione peroxidase (GPx) that were accompanied by decreases in CuZnSOD, GPx1a, GPx1b and signaling factor protein kinase C delta mRNA levels. The decreases in the antioxidant enzyme gene mRNA levels were confirmed to be partly due to the reduced nuclear Nrf2 protein levels, poor ARE binding ability and increased caspase-3 signaling-modulated DNA fragmentation in the fish muscle. Interestingly, MI pre-treatment prevented fish muscle from Cu-induced oxidative damages mainly through increasing the GSH content, and increasing the CuZnSOD and GPx activities and corresponding mRNA levels and ARE binding ability. Taken together, our results show for the first time that Cu exposure caused oxidative damage to the muscle by decreasing the antioxidant enzyme activities via the down-regulation of the expression of genes related to the disruption of the Nrf2/ARE signaling, and this down-regulation was partially caused by caspase-3-regulated DNA fragmentation. Finally, MI protects fish against Cu toxicity.
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
authors.forename: Wei-Dan
authors.initials: WD
authors.lastname: Jiang
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Wu
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Chengdu 611130, Sichuan, China. Electronic address: fenglin@sicau.edu.cn.
authors.forename: Lin
authors.initials: L
authors.lastname: Feng
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Chengdu 611130, Sichuan, China. Electronic address: zhouxq@sicau.edu.cn.
authors.forename: Xiao-Qiu
authors.initials: XQ
authors.lastname: Zhou
mesh_terms: D000818:Animals; D061745:Antioxidant Response Elements / Q000502:physiology; D002347:Carps / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism*; D003300:Copper / Q000633:toxicity*; D004249:DNA Damage / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D007294:Inositol / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects*; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010088:Oxidoreductases / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D051267:NF-E2-Related Factor 2; D014874:Water Pollutants, Chemical; D007294:Inositol; D003300:Copper; D010088:Oxidoreductases; D053148:Caspase 3; D005978:Glutathione
keywords: Carp; Copper; DNA fragmentation; Muscle; Nrf2; myo-Inositol