Mitochondrial-targeted nitroxides disrupt mitochondrial architecture and inhibit expression of peroxiredoxin 3 and FOXM1 in malignant mesothelioma cells

Authors

  • Brian Cunniff,

    1. Department of Pathology, University of Vermont College of Medicine, Burlington, Vermont
    2. Cell and Molecular Biology Program, University of Vermont, Burlington, Vermont
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  • Kira Benson,

    1. Department of Pathology, University of Vermont College of Medicine, Burlington, Vermont
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  • Jason Stumpff,

    1. Cell and Molecular Biology Program, University of Vermont, Burlington, Vermont
    2. Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine, Burlington, Vermont
    3. Vermont Cancer Center, University of Vermont College of Medicine, Burlington, Vermont
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  • Kheng Newick,

    1. Department of Pathology, University of Vermont College of Medicine, Burlington, Vermont
    2. Cell and Molecular Biology Program, University of Vermont, Burlington, Vermont
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  • Paul Held,

    1. BioTek Instruments, Winooski, Vermont
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  • Douglas Taatjes,

    1. Department of Pathology, University of Vermont College of Medicine, Burlington, Vermont
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  • Joy Joseph,

    1. Department of Biophysics, Free Radical Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
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  • Balaraman Kalyanaraman,

    1. Department of Biophysics, Free Radical Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
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  • Nicholas H. Heintz

    Corresponding author
    1. Department of Pathology, University of Vermont College of Medicine, Burlington, Vermont
    2. Cell and Molecular Biology Program, University of Vermont, Burlington, Vermont
    3. Vermont Cancer Center, University of Vermont College of Medicine, Burlington, Vermont
    • Department of Pathology, University of Vermont College of Medicine, 149 Beaumont Avenue, Burlington, VT 05405.
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Abstract

Malignant mesothelioma (MM) is an intractable tumor of the peritoneal and pleural cavities primarily linked to exposure to asbestos. Recently, we described an interplay between mitochondrial-derived oxidants and expression of FOXM1, a redox-responsive transcription factor that has emerged as a promising therapeutic target in solid malignancies. Here we have investigated the effects of nitroxides targeted to mitochondria via triphenylphosphonium (TPP) moieties on mitochondrial oxidant production, expression of FOXM1 and peroxiredoxin 3 (PRX3), and cell viability in MM cells in culture. Both Mito-carboxy-proxyl (MCP) and Mito-TEMPOL (MT) caused dose-dependent increases in mitochondrial oxidant production that was accompanied by inhibition of expression of FOXM1 and PRX3 and loss of cell viability. At equivalent concentrations TPP, CP, and TEMPOL had no effect on these endpoints. Live cell ratiometric imaging with a redox-responsive green fluorescent protein targeted to mitochondria (mito-roGFP) showed that MCP and MT, but not CP, TEMPOL, or TPP, rapidly induced mitochondrial fragmentation and swelling, morphological transitions that were associated with diminished ATP levels and increased production of mitochondrial oxidants. Mdivi-1, an inhibitor of mitochondrial fission, did not rescue mitochondria from fragmentation by MCP. Immunofluorescence microscopy experiments indicate a fraction of FOXM1 coexists in the cytoplasm with mitochondrial PRX3. Our results indicate that MCP and MT inhibit FOXM1 expression and MM tumor cell viability via perturbations in redox homeostasis caused by marked disruption of mitochondrial architecture, and suggest that both compounds, either alone or in combination with thiostrepton or other agents, may provide credible therapeutic options for the management of MM. J. Cell. Physiol. 228: 835–845, 2013. © 2012 Wiley Periodicals, Inc.

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