Mitochondria-Targeted Superoxide Dismutase (SOD2) Regulates Radiation Resistance and Radiation Stress Response in HeLa Cells

• Published in: JOURNAL OF RADIATION RESEARCH Vol. 53; no. 1; pp. 58 - 71
• Main Authors: Hosoki, Ayaka, Yonekura, Shin-Ichiro, Zhao, Qing-Li, Wei, Zheng-Li, Takasaki, Ichiro, Tabuchi, Yoshiaki, Wang, Li-Li, Hasuike, Shiga, Nomura, Takaharu, Tachibana, Akira, Hashiguchi, Kazunari, Yonei, Shuji, Kondo, Takashi, Zhang-Akiyama, Qiu-Mei
• Format: Journal Article
• Language: English
• Published: England THE JAPAN RADIATION RESEARCH SOCIETY 01.01.2012; Oxford University Press
• Subjects: Cells (Biology); Comparative analysis; DNA Breaks, Double-Stranded; DNA microarrays; Enzyme Induction; Gamma Rays - adverse effects; Gene Expression Regulation - radiation effects; Gene Regulatory Networks - radiation effects; HeLa Cells - metabolism; HeLa Cells - radiation effects; Humans; Ionizing radiation; Mitochondria - metabolism; Neoplasm Proteins - physiology; Oligonucleotide Array Sequence Analysis; Oxidative Stress - physiology; Oxidative Stress - radiation effects; Radiation Tolerance - genetics; Radiation Tolerance - physiology; Reactive Oxygen Species - metabolism; Recombinant Fusion Proteins - physiology; Superoxide Dismutase - biosynthesis; Superoxide Dismutase - genetics; Superoxide Dismutase - physiology; Superoxides; Superoxides - metabolism
• ISSN: 0449-3060; 1349-9157
• DOI: 10.1269/jrr.11034

Reactive oxygen species (ROS) act as a mediator of ionizing radiation-induced cellular damage. Previous studies have indicated that MnSOD (SOD2) plays a critical role in protection against ionizing radiation in mammalian cells. In this study, we constructed two types of stable HeLa cell lines overexpressing SOD2, HeLa S3/SOD2 and T-REx HeLa/SOD2, to elucidate the mechanisms underlying the protection against radiation by SOD2. SOD2 overexpression in mitochondria enhanced the survival of HeLa S3 and T-REx HeLa cells following γ-irradiation. The levels of γH2AX significantly decreased in HeLa S3/SOD2 and T-REx HeLa/SOD2 cells compared with those in the control cells. MitoSoxTM Red assays showed that both lines of SOD2-expressing cells showed suppression of the superoxide generation in mitochondria. Furthermore, flow cytometry with a fluorescent probe (2',7'-dichlorofluorescein) revealed that the cellular levels of ROS increased in HeLa S3 cells during post-irradiation incubation, but the increase was markedly attenuated in HeLa S3/SOD2 cells. DNA microarray analysis revealed that, of 47,000 probe sets analyzed, 117 and 166 probes showed more than 2-fold changes after 5.5 Gy of γ-irradiation in control and HeLa S3/SOD2 cells, respectively. Pathway analysis revealed different expression profiles in irradiated control cells and irradiated SOD2-overexpressing cells. These results indicate that SOD2 protects HeLa cells against cellular effects of γ-rays through suppressing oxidative stress in irradiated cells caused by ROS generated in the mitochondria and through regulating the expression of genes which play a critical role in protection against ionizing radiation.