Article

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

Department of Biological Sciences, Graduate School of Science, Kyoto University, Japan.
Journal of Radiation Research (Impact Factor: 1.69). 01/2012; 53(1):58-71. DOI: 10.1269/jrr.11034
Source: PubMed

ABSTRACT 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. MitoSox(TM) 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.

2 Followers
 · 
174 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Our previous studies have revealed that amyloid β (Aβ)-binding alcohol dehydrogenase (ABAD) decoy peptide antagonizes Aβ42-induced neurotoxicity. However, whether it improves oxidative stress injury remains unclear. In this study, a recombinant adenovirus constitutively secreting and expressing Aβ-ABAD decoy peptide (rAAV/ABAD-DP-6His) was successfully constructed. Our results showed that rAAV/ABAD-DP-6His increased superoxide dismutase activity in hydrogen peroxide-induced oxidative stress-mediated injury of PC12 cells. Moreover, rAAV/ABAD-DP-6His decreased malondialdehyde content, intracellular Ca(2+) concentration, and the level of reactive oxygen species. rAAV/ABAD-DP-6His maintained the stability of the mitochondrial membrane potential. In addition, the ATP level remained constant, and apoptosis was reduced. Overall, the results indicate that rAAV/ABAD-DP-6His generates the fusion peptide, Aβ-ABAD decoy peptide, which effectively protects PC12 cells from oxidative stress injury induced by hydrogen peroxide, thus exerting neuroprotective effects.
    Neural Regeneration Research 03/2014; 9(5):481-8. DOI:10.4103/1673-5374.130065 · 0.23 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Purpose: To review the data concerning the role of endogenously generated reactive oxygen species (ROS) in the non-targeted ionising radiation (IR) effects and in determination of the cell population's fate, both early after exposure and after many generations. Conclusions: The short-term as well as chronic oxidative stress responses mainly are produced due to ROS generation by the electron transport chain (ETC) of the mitochondria and by the cytoplasmic NADPH oxidases. Whether the induction of the oxidative stress and its consequences occur or are hampered in a single cell largely depends on the interaction between the nucleus and the cellular population of several hundred or thousands of mitochondria that are genetically heterogeneous. High intra-mitochondrial ROS level is damaging the mitochondrial (mt) DNA and its mutations affect the epigenetic control mechanisms of the nuclear (n) DNA, by decreasing the activity of methyltransferases and thus, causing global DNA hypomethylation. These changes are transmitted to the progeny of the irradiated cells. The chronic oxidative stress is the main cause of the late post-radiation effects, including cancer, and this makes it an important adverse effect of exposure to IR and a target for radiological protection.
    International Journal of Radiation Biology 06/2014; 91(1):1-55. DOI:10.3109/09553002.2014.934929 · 1.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent of green tea, is a potent antioxidant and free radical scavenger that may have therapeutic applications for the treatment of many disorders. Radiation therapy is widely used for the treatment of various types of cancers; however, radiation-induced skin injury remains a serious concern. EGCG has not yet been reported as protecting skin cells against ionizing radiation. In the present study, we investigated whether EGCG confers cytoprotection against ionizing radiation. We found that, compared with the control, pretreatment with EGCG significantly enhanced the viability of human skin cells that were irradiated with X-rays, and decreased apoptosis induced by X-ray irradiation. Mito-Tracker assay showed that EGCG suppressed the damage to mitochondria induced by ionizing radiation via upregulation of SOD2. Reactive oxygen species (ROS) in HaCaT cells were significantly reduced when pretreated with EGCG before irradiation. Radiation-induced γH2AX foci, which are representative of DNA double-strand breaks, were decreased by pretreatment with EGCG. Furthermore, EGCG induced the expression of the cytoprotective molecule heme oxygenase-1 (HO-1) in a dose-dependent manner via transcriptional activation. HO-1 knockdown or treatment with the HO-1 inhibitor tin protoporphyrin (SnPPIX) reversed the protective role of EGCG, indicating an important role for HO-1. These results suggest that EGCG offers a new strategy for protecting skin against ionizing radiation.
    Journal of Radiation Research 06/2014; 55(6). DOI:10.1093/jrr/rru047 · 1.69 Impact Factor

Full-text (2 Sources)

Download
32 Downloads
Available from
May 29, 2014