Cardiolipin-Specific Peroxidase Reactions of Cytochrome c in Mitochondria During Irradiation-Induced Apoptosis

• Published in: International journal of radiation oncology, biology, physics Vol. 69; no. 1; pp. 176 - 186
• Main Authors: Belikova, Natalia A., Ph.D, Jiang, Jianfei, Ph.D, Tyurina, Yulia Y., Ph.D, Zhao, Qing, M.S, Epperly, Michael W., Ph.D, Greenberger, Joel, M.D, Kagan, Valerian E., Ph.D., D.Sci
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2007
• Subjects: APOPTOSIS; Apoptosis - physiology; bcl-2-Associated X Protein - metabolism; Blotting, Western; CARBON 14; CARDIOLIPIN; Cardiolipins - metabolism; Caspase 3 - metabolism; Caspase 7 - metabolism; CATALYSTS; Cytochrome c; Cytochromes c - metabolism; Enzyme Activation; FLUORESCENCE; GAMMA RADIATION; Gamma Rays; HELA CELLS; HeLa Cells - metabolism; HeLa Cells - radiation effects; Hematology, Oncology and Palliative Medicine; HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY; Humans; Intracellular Signaling Peptides and Proteins - metabolism; IRRADIATION; Irradiation-induced apoptosis; Lipid Peroxidation - physiology; MASS SPECTROSCOPY; MITOCHONDRIA; Mitochondria - metabolism; Mitochondria - radiation effects; Mitochondrial Proteins - metabolism; OXIDATION; Oxidation-Reduction; PEROXIDASES; Phosphatidylserines - metabolism; RADIATION DOSES; Radiation Tolerance - physiology; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; RADIOSENSITIZERS; RNA; RNA, Small Interfering - genetics; Cytochrome c; Irradiation-induced apoptosis; Cardiolipin
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2007.03.043

Purpose To determine whether cytochrome c (cyt c ) content and associated cardiolipin oxidation can be determinants of cell sensitivity to irradiation-induced apoptosis. Methods and Materials The small interfering RNA (siRNA) approach was used to engineer HeLa cells with lowered contents of cyt c (14%, HeLa 1.2 cells). Cells were treated by γ-irradiation (in doses of 5–40 Gy). Lipid oxidation was characterized by electrospray ionization mass spectrometry analysis and fluorescence high-performance liquid chromatography–based Amplex Red assay. Release of a proapoptotic factor (cyt c , Smac/DIABLO) was detected by Western blotting. Apoptosis was revealed by caspase-3/7 activation and phosphatidylserine externalization. Results Irradiation caused selective accumulation of hydroperoxides in cardiolipin (CL) but not in other phospholipids. HeLa 1.2 cells responded by a lower irradiation-induced accumulation of CL oxidation products than parental HeLa cells. Proportionally decreased release of a proapoptotic factor, Smac/DIABLO, was detected in cyt c -deficient cells after irradiation. Caspase-3/7 activation and phosphatidylserine externalization were proportional to the cyt c content in cells. Conclusions Cytochrome c is an important catalyst of CL peroxidation, critical to the execution of the apoptotic program. This new role of cyt c in irradiation-induced apoptosis is essential for the development of new radioprotectors and radiosensitizers.