Uncoupling protein-2 participates in cellular defense against oxidative stress in clonal beta-cells.
The role of uncoupling protein-2 (UCP-2) in beta-cells is presently unclear. We have tested the notion that UCP-2 participates in beta-cell defense against oxidants. Expression of the UCP-2 gene in clonal beta-cells (INS-1) was decreased by 45% after 48 h of culture with vitamin E and selenite. When INS-1 cells were exposed to 200 microM H(2)O(2) for 5 min, the cell viability (MTT assay) decreased to 85 +/- 1, 61 +/- 1, 40 +/- 2, and 39 +/- 2% of control when measured respectively 30 min, 2 h, 6 h, and 16 h after H(2)O(2) exposure. At corresponding time points UCP-2 mRNA levels were 1.01 +/- 0.09, 1.53 +/- 0.15 (P < 0.05), 1.44 +/- 0.18 (P = 0.06), and 1.12 +/- 0.09 fold of control, i.e., transiently increased. We next tested whether overexpression of UCP-2 could enhance resistance of beta-cells toward H(2)O(2) toxicity. A cotransfection method using EGFP as a suitable marker and a human cDNA UCP-2 construct was used for transient overexpression of UCP-2. Transfected cells expressed the gene about 30-fold more than normal cells. After exposure to H(2)O(2) (200 micrometer, 5 min), the survival of UCP-2 overexpressing cells was measured 30-45 min later by flow cytometry. Survival was 13 +/- 0.05% higher than control (EGFP only) cells, P < 0.004 for difference. The results indicate that oxidative stress induces UCP-2 expression in beta-cells, and that UCP-2 serves a role in beta-cell defense against oxidative stress.
Department of Medicine, Norwegian University of Science and Technology, Trondheim, N-7489, Norway
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Li
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Skorpen
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Egeberg
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Jørgensen
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Grill
D002470:Cell Survival / Q000187:drug effects; D002999:Clone Cells / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007473:Ion Channels; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism*; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D018384:Oxidative Stress; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D000071246:Uncoupling Protein 2; D014810:Vitamin E / Q000494:pharmacology
D007473:Ion Channels; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D012333:RNA, Messenger; C000604389:UCP2 protein, human; D000071246:Uncoupling Protein 2; D014810:Vitamin E; D006861:Hydrogen Peroxide