Mitochondrial Complex II Dysfunction Can Contribute Significantly to Genomic Instability after Exposure to Ionizing Radiation

• Published in: Radiation research 2009-12, Vol.172 (6), p.737-745
• Main Authors: Dayal, Disha, Martin, Sean M., Owens, Kjerstin M., Aykin-Burns, Nukhet, Zhu, Yueming, Boominathan, Amutha, Pain, Debkumar, Limoli, Charles L., Goswami, Prabhat C., Domann, Frederick E., Spitz, Douglas R.
• Format: Article
• Language: English
• Subjects: Animals; BASIC BIOLOGICAL SCIENCES; Blotting, Western; Cell lines; CHO Cells; Cricetinae; Cricetulus; Electron Transport Complex II - metabolism; Electrons; Electrophoresis, Polyacrylamide Gel; Gels; Genetic mutation; Genomic Instability; Mitochondria; Mitochondria - enzymology; Mitochondrial membranes; Oxidative stress; Oxygen consumption; Radiation, Ionizing; Reactive oxygen species; REGULAR ARTICLES; Space life sciences
• ISSN: 0033-7587; 1938-5404
• DOI: 10.1667/RR1617.1

Dayal, D., Martin, S. M., Owens, K. M., Aykin-Burns, N., Zhu, Y., Boominathan, A., Pain, D., Limoli, C. L., Goswami, P. C., Domann, F. E. and Spitz, D. R. Mitochondrial Complex II Dysfunction Can Contribute Significantly to Genomic Instability after Exposure to Ionizing Radiation. Ionizing radiation induces chronic metabolic oxidative stress and a mutator phenotype in hamster fibroblasts that is mediated by H2O2, but the intracellular source of H2O2 is not well defined. To determine the role of mitochondria in the radiation-induced mutator phenotype, end points of mitochondrial function were determined in unstable (CS-9 and LS-12) and stable (114) hamster fibroblast cell lines derived from GM10115 cells exposed to 10 Gy X rays. Cell lines isolated after irradiation demonstrated a 20–40% loss of mitochondrial membrane potential and an increase in mitochondrial content compared to the parental cell line GM10115. Surprisingly, no differences were observed in steady-state levels of ATP (P > 0.05). Unstable clones demonstrated increased oxygen consumption (two- to threefold; CS-9) and/or increased mitochondrial electron transport chain (ETC) complex II activity (twofold; LS-12). Using Western blot analysis and Blue Native gel electrophoresis, a significant increase in complex II subunit B protein levels was observed in LS-12 cells. Furthermore, immunoprecipitation assays revealed evidence of abnormal complex II assembly in LS-12 cells. Treatment of LS-12 cells with an inhibitor of ETC complex II (thenoyltrifluoroacetone) resulted in significant decreases in the steady-state levels of H2O2 and a 50% reduction in mutation frequency as well as a 16% reduction in CAD gene amplification frequency. These data show that radiation-induced genomic instability was accompanied by evidence of mitochondrial dysfunction leading to increased steady-state levels of H2O2 that contributed to increased mutation frequency and gene amplification. These results support the hypothesis that mitochondrial dysfunction originating from complex II can contribute to radiation-induced genomic instability by increasing steady-state levels of reactive oxygen species.