Shift of the Cellular Oxidation-Reduction Potential in Neural Cells Expressing Bcl-2

Authors

  • Lisa M. Ellerby,

    1. Program on Aging, Burnham Institute, La Jolla Cancer Research Center, La Jolla; Department of Neurology, Brain Research Institute and Molecular Biology Institute, University of California at Los Angeles, Los Angeles;
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  • H. Michael Ellerby,

    1. Program on Aging, Burnham Institute, La Jolla Cancer Research Center, La Jolla; Department of Neurology, Brain Research Institute and Molecular Biology Institute, University of California at Los Angeles, Los Angeles;
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  • Sunghi M. Park,

    1. Program on Aging, Burnham Institute, La Jolla Cancer Research Center, La Jolla; Department of Neurology, Brain Research Institute and Molecular Biology Institute, University of California at Los Angeles, Los Angeles;
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  • Anne L. Holleran,

    1. Departments of Physiology and
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  • Anne N. Murphy,

    1. Biochemistry and Molecular Biology, George Washington University Medical Center, Washington, D.C., U.S.A.
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  • Gary Fiskum,

    1. Biochemistry and Molecular Biology, George Washington University Medical Center, Washington, D.C., U.S.A.
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  • Darci J. Kane,

    1. Amgen Corporation, Thousand Oaks, California; and
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  • Maria P. Testa,

    1. Program on Aging, Burnham Institute, La Jolla Cancer Research Center, La Jolla; Department of Neurology, Brain Research Institute and Molecular Biology Institute, University of California at Los Angeles, Los Angeles;
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  • Celik Kayalar,

    1. Program on Aging, Burnham Institute, La Jolla Cancer Research Center, La Jolla; Department of Neurology, Brain Research Institute and Molecular Biology Institute, University of California at Los Angeles, Los Angeles;
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  • Dale E. Bredesen

    Corresponding author
    1. Program on Aging, Burnham Institute, La Jolla Cancer Research Center, La Jolla; Department of Neurology, Brain Research Institute and Molecular Biology Institute, University of California at Los Angeles, Los Angeles;
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Address correspondence and reprint requests to Dr. D. E. Bredesen at Program on Aging, Burnham Institute, La Jolla Cancer Research Center, La Jolla, CA 92037, U.S.A.

Abstract

Abstract: Expression of the protooncogene bcl-2 inhibits both apoptotic and in some cases necrotic cell death in many cell types, including neural cells, and in response to a wide variety of inducers. The mechanism by which the Bcl-2 protein acts to prevent cell death remains elusive. One mechanism by which Bcl-2 has been proposed to act is by decreasing the net cellular generation of reactive oxygen species. To evaluate this proposal, we measured activities of antioxidant enzymes as well as levels of glutathione and pyridine nucleotides in control and bcl-2 transfectants in two different neural cell lines—rat pheochromocytoma PC12 and the hypothalamic GnRH cell line GT1-7. Both neural cell lines overexpressing bcl-2 had elevated total glutathione levels when compared with control transfectants. The ratios of oxidized glutathione to total glutathione in PC12 and GT1-7 cells overexpressing bcl-2 were significantly reduced. In addition, the NAD+/NADH ratio of bcl-2-expressing PC12 and GT1-7 cells was two- to threefold less than that of control cell lines. GT1-7 cells overexpressing bcl-2 had the same level of glutathione peroxidase, catalase, superoxide dismutase, and glutathione reductase activities as control cells. PC12 cells overexpressing bcl-2 had a twofold increase in superoxide dismutase and catalase activity when compared with matched control transfected cells. The levels of glutathione peroxidase and glutathione reductase in PC12 cells overexpressing bcl-2 were similar to those of control cells. These results indicate that the overexpression of bcl-2 shifts the cellular redox potential to a more reduced state, without consistently affecting the major cellular antioxidant enzymes.

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