TY - JOUR
T1 - Excess processing of oxidative damaged bases causes hypersensitivity to oxidative stress and low dose rate irradiation
AU - Yoshikawa, Y.
AU - Yamasaki, A.
AU - Takatori, K.
AU - Suzuki, M.
AU - Kobayashi, J.
AU - Takao, M.
AU - Zhang-Akiyama, Q. M.
N1 - Funding Information:
We thank Dr. Elizabeth Nakajima and Ms. Ako Matsui for critically reading the manuscript and thank Ms. Ako Matsui for assistance with the heavy-ion beams and low dose rate radiation experiments. This study was supported by the Research Project with Heavy Ions at NIRS-HIMAC (12J-393). This work was supported in part by Grants-in-Aid for Scientific Research (#24510071) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. This work was performed at the Joint Usage/Research Center (Radiation Biology Center), Kyoto University.
Publisher Copyright:
© 2015 Informa UK, Ltd.
PY - 2015/10/3
Y1 - 2015/10/3
N2 - Ionizing radiations such as X-ray and γ-ray can directly or indirectly produce clustered or multiple damages in DNA. Previous studies have reported that overexpression of DNA glycosylases in Escherichia coli (E. coli) and human lymphoblast cells caused increased sensitivity to γ-ray and X-ray irradiation. However, the effects and the mechanisms of other radiation, such as low dose rate radiation, heavy-ion beams, or hydrogen peroxide (H2O2), are still poorly understood. In the present study, we constructed a stable HeLaS3 cell line overexpressing human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) protein. We determined the survival of HeLaS3 and HeLaS3/hOGG1 cells exposed to UV, heavy-ion beams, γ-rays, and H2O2. The results showed that HeLaS3 cells overexpressing hOGG1 were more sensitive to γ-rays, OH•, and H2O2, but not to UV or heavy-ion beams, than control HeLaS3. We further determined the levels of 8-oxoG foci and of chromosomal double-strand breaks (DSBs) by detecting γ-H2AX foci formation in DNA. The results demonstrated that both γ-rays and H2O2 induced 8-oxoguanine (8-oxoG) foci formation in HeLaS3 cells. hOGG1-overexpressing cells had increased amounts of γ-H2AX foci and decreased amounts of 8-oxoG foci compared with HeLaS3 control cells. These results suggest that excess hOGG1 removes the oxidatively damaged 8-oxoG in DNA more efficiently and therefore generates more DSBs. Micronucleus formation also supported this conclusion. Low dose-rate γ-ray effects were also investigated. We first found that overexpression of hOGG1 also caused increased sensitivity to low dose rate γ-ray irradiation. The rate of micronucleus formation supported the notion that low dose rate irradiation increased genome instability.
AB - Ionizing radiations such as X-ray and γ-ray can directly or indirectly produce clustered or multiple damages in DNA. Previous studies have reported that overexpression of DNA glycosylases in Escherichia coli (E. coli) and human lymphoblast cells caused increased sensitivity to γ-ray and X-ray irradiation. However, the effects and the mechanisms of other radiation, such as low dose rate radiation, heavy-ion beams, or hydrogen peroxide (H2O2), are still poorly understood. In the present study, we constructed a stable HeLaS3 cell line overexpressing human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) protein. We determined the survival of HeLaS3 and HeLaS3/hOGG1 cells exposed to UV, heavy-ion beams, γ-rays, and H2O2. The results showed that HeLaS3 cells overexpressing hOGG1 were more sensitive to γ-rays, OH•, and H2O2, but not to UV or heavy-ion beams, than control HeLaS3. We further determined the levels of 8-oxoG foci and of chromosomal double-strand breaks (DSBs) by detecting γ-H2AX foci formation in DNA. The results demonstrated that both γ-rays and H2O2 induced 8-oxoguanine (8-oxoG) foci formation in HeLaS3 cells. hOGG1-overexpressing cells had increased amounts of γ-H2AX foci and decreased amounts of 8-oxoG foci compared with HeLaS3 control cells. These results suggest that excess hOGG1 removes the oxidatively damaged 8-oxoG in DNA more efficiently and therefore generates more DSBs. Micronucleus formation also supported this conclusion. Low dose-rate γ-ray effects were also investigated. We first found that overexpression of hOGG1 also caused increased sensitivity to low dose rate γ-ray irradiation. The rate of micronucleus formation supported the notion that low dose rate irradiation increased genome instability.
KW - 8-oxoG
KW - clustered damage
KW - hOGG1
KW - low dose rate radiation
KW - micronuclei
KW - reactive oxygen species
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U2 - 10.3109/10715762.2015.1061186
DO - 10.3109/10715762.2015.1061186
M3 - Article
C2 - 26059740
AN - SCOPUS:84940450449
VL - 49
SP - 1239
EP - 1248
JO - Free Radical Research
JF - Free Radical Research
SN - 1071-5762
IS - 10
ER -