title: Exploring uncoupling proteins and antioxidant mechanisms under acute cold exposure in brains of fish.
abstract: Exposure to fluctuating temperatures accelerates the mitochondrial respiration and increases the formation of mitochondrial reactive oxygen species (ROS) in ectothermic vertebrates including fish. To date, little is known on potential oxidative damage and on protective antioxidative defense mechanisms in the brain of fish under cold shock. In this study, the concentration of cellular protein carbonyls in brain was significantly increased by 38% within 1 h after cold exposure (from 28 °C to 18 °C) of zebrafish (Danio rerio). In addition, the specific activity of superoxide dismutase (SOD) and the mRNA level of catalase (CAT) were increased after cold exposure by about 60% (6 h) and by 60%-90% (1 and 24 h), respectively, while the specific glutathione content as well as the ratio of glutathione disulfide to glutathione remained constant and at a very low level. In addition, cold exposure increased the protein level of hypoxia-inducible factor (HIF) by about 50% and the mRNA level of the glucose transporter zglut3 in brain by 50%-100%. To test for an involvement of uncoupling proteins (UCPs) in the cold adaptation of zebrafish, five UCP members were annotated and identified (zucp1-5). With the exception of zucp1, the mRNA levels of the other four zucps were significantly increased after cold exposure. In addition, the mRNA levels of four of the fish homologs (zppar) of the peroxisome proliferator-activated receptor (PPAR) were increased after cold exposure. These data suggest that PPARs and UCPs are involved in the alterations observed in zebrafish brain after exposure to 18°C. The observed stimulation of the PPAR-UCP axis may help to prevent oxidative damage and to maintain metabolic balance and cellular homeostasis in the brains of ectothermic zebrafish upon cold exposure.
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei City, Taiwan.
authors.forename: Yung-Che
authors.initials: YC
authors.lastname: Tseng
authors.forename: Ruo-Dong
authors.initials: RD
authors.lastname: Chen
authors.forename: Magnus
authors.initials: M
authors.lastname: Lucassen
authors.forename: Maike M
authors.initials: MM
authors.lastname: Schmidt
authors.forename: Ralf
authors.initials: R
authors.lastname: Dringen
authors.forename: Doris
authors.initials: D
authors.lastname: Abele
authors.forename: Pung-Pung
authors.initials: PP
authors.lastname: Hwang
mesh_terms: D000064:Acclimatization; D000595:Amino Acid Sequence; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D001921:Brain / Q000201:enzymology / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D015687:Cell Hypoxia; D003080:Cold Temperature; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005978:Glutathione / Q000378:metabolism; D017403:In Situ Hybridization; D007473:Ion Channels / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D018384:Oxidative Stress; D047492:Peroxisome Proliferator-Activated Receptors / Q000378:metabolism; D010802:Phylogeny; D050050:Protein Carbonylation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013482:Superoxide Dismutase / Q000378:metabolism; D000071256:Uncoupling Protein 1; D015027:Zebrafish / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D007473:Ion Channels; D024101:Mitochondrial Proteins; D047492:Peroxisome Proliferator-Activated Receptors; D020033:Protein Isoforms; D012333:RNA, Messenger; D000071256:Uncoupling Protein 1; D029961:Zebrafish Proteins; D002374:Catalase; D013482:Superoxide Dismutase; D005978:Glutathione