Comparison of mutation spectra induced by gamma-rays and carbon ion beams

The ionizing radiation with high linear energy transfer (LET), such as a heavy ion beam, induces more serious biological effects than low LET ones, such as gamma- and X-rays. This indicates a difference in the DNA damage produced by low and high LET radiations and their biological effects. We have been studying the differences in DNA damage produced by gamma-rays and carbon ion beams. Therefore, we analyze mutations induced by both ionizing radiations to discuss the differences in their biological effects in this study. pUC19 plasmid DNA was irradiated by carbon ion beams in the solution containing 1M dimethyl sulfoxide to mimic a cellular condition. The irradiated DNA was cloned in competent cells of Escherichia coli. The clones harboring some mutations in the region of lacZ alpha were selected, and the sequence alterations were analyzed. A one-deletion mutation is significant in the carbon-irradiated DNA, and the C:G T:A transition is minor. On the other hand, the gamma-irradiated DNA shows mainly G:C T:A transversion. These results suggest that carbon ion beams produce complex DNA damage, and gamma-rays are prone to single oxidative base damage, such as 8-oxoguanine. Carbon ion beams can also introduce oxidative base damage, and the damage species is 5-hydroxycytosine. This was consistent with our previous results of DNA damage caused by heavy ion beams. We confirmed the causal DNA damage by mass spectrometry for these mutations

Repair activity of base and nucleotide excision repair enzymes for guanine lesions induced by nitrosative stress

Nitric oxide (NO) induces deamination of guanine, yielding xanthine and oxanine (Oxa). Furthermore, Oxa reacts with polyamines and DNA binding proteins to form cross-link adducts. Thus, it is of interest how these lesions are processed by DNA repair enzymes in view of the genotoxic mechanism of NO. In the present study, we have examined the repair capacity for Oxa and Oxa–spermine cross-link adducts (Oxa–Sp) of enzymes involved in base excision repair (BER) and nucleotide excision repair (NER) to delineate the repair mechanism of nitrosative damage to guanine. Oligonucleotide substrates containing Oxa and Oxa–Sp were incubated with purified BER and NER enzymes or cell-free extracts (CFEs), and the damage-excising or DNA-incising activity was compared with that for control (physiological) substrates. The Oxa-excising activities of Escherichia coli and human DNA glycosylases and HeLa CFEs were 0.2–9% relative to control substrates, implying poor processing of Oxa by BER. In contrast, DNA containing Oxa–Sp was incised efficiently by UvrABC nuclease and SOS-induced E.coli CFEs, suggesting a role of NER in ameliorating genotoxic effects associated with nitrosative stress. Analyses of the activity of CFEs from NER-proficient and NER-deficient human cells on Oxa–Sp DNA confirmed further the involvement of NER in the repair of nitrosative DNA damage

Evaluation of the redox state in mouse organs following radon inhalation

Radon inhalation activates antioxidative functions in mouse organs, thereby contributing to inhibition of oxidative stress-induced damage. However, the specific redox state of each organ after radon inhalation has not been reported. Therefore, in this study, we evaluated the redox state of various organs in mice following radon inhalation at concentrations of 2 or 20 kBq/m(3) for 1, 3 or 10 days. Scatter plots were used to evaluate the relationship between antioxidative function and oxidative stress by principal component analysis (PCA) of data from control mice subjected to sham inhalation. The results of principal component (PC) 1 showed that the liver and kidney had high antioxidant capacity; the results of PC2 showed that the brain, pancreas and stomach had low antioxidant capacities and low lipid peroxide (LPO) content, whereas the lungs, heart, small intestine and large intestine had high LPO content but low antioxidant capacities. Furthermore, using the PCA of each obtained cluster, we observed altered correlation coefficients related to glutathione, hydrogen peroxide and LPO for all groups following radon inhalation. Correlation coefficients related to superoxide dismutase in organs with a low antioxidant capacity were also changed. These findings suggested that radon inhalation could alter the redox state in organs; however, its characteristics were dependent on the total antioxidant capacity of the organs as well as the radon concentration and inhalation time. The insights obtained from this study could be useful for developing therapeutic strategies targeting individual organs

Radon inhalation decreases DNA damage induced by oxidative stress in mouse organs via the activation of antioxidative functions

Radon inhalation decreases the level of lipid peroxide (LPO); this is attributed to the activation of antioxidative functions. This activation contributes to the beneficial effects of radon therapy, but there are no studies on the risks of radon therapy, such as DNA damage. We evaluated the effect of radon inhalation on DNA damage caused by oxidative stress and explored the underlying mechanisms. Mice were exposed to radon inhalation at concentrations of 2 or 20 kBq/m(3) (for one, three, or 10 days). The 8-hydroxy-2 '-deoxyguanosine (8-OHdG) levels decreased in the brains of mice that inhaled 20 kBq/m(3) radon for three days and in the kidneys of mice that inhaled 2 or 20 kBq/m(3) radon for one, three or 10 days. The 8-OHdG levels in the small intestine decreased by approximately 20-40% (2 kBq/m(3) for three days or 20 kBq/m(3) for one, three or 10 days), but there were no significant differences in the 8-OHdG levels between mice that inhaled a sham treatment and those that inhaled radon. There was no significant change in the levels of 8-oxoguanine DNA glycosylase, which plays an important role in DNA repair. However, the level of Mn-superoxide dismutase (SOD) increased by 15-60% and 15-45% in the small intestine and kidney, respectively, following radon inhalation. These results suggest that Mn-SOD probably plays an important role in the inhibition of oxidative DNA damage

コバルト60ガンマ線照射による水溶液中におけるチロシナーゼの水和電子誘発不活性化機構

CONTENTS General Introduction / p1 Chapter 1. / p5 　Hydrated-Induced Inactivation of Tyrosinase in Aqueous Solution by Exposure to Cobalt-60 Gamma-Rays.I.Cresolase Activity / p5 Chapter 2. / p20 　Hydrated-Induced Inactivation of Tyrosinase in Aqueous Solution by Exposure to Cobalt-60 Gamma-Rays.II.Catecholase Activity / p20 General discussion / p38 Acknowledgements / p42広島大学(Hiroshima University)博士(理学)Physical Sciencedoctora

Quantitative characteristics of clustered DNA damage in irradiated cells by heavy ion beams

Heavy ion beam as typical high linear energy transfer (LET) radiation produces more expanding ionization domain around their tracks than low LET radiation such as X-rays and gamma rays. Thus, heavy ion beam can cause more densely accumulated damage cluster in the target DNA, termed clustered DNA damage. This damage exhibits difficulty for repair and inhibition of DNA replication with its complex structure [ 1]. So, clustered DNA damage is thought to be strongly involved in the biological effectiveness of heavy ion beam. However, a lot of studies have presented no certain correlation between yields of clustered DNA damage and severity of radiation effect. We previously indicated that the yields of clustered DNA damage decreased with increasing LET in the DNA molecules irradiated in test tubes with gamma rays, and carbon and iron ion beams whose showed different LET, respectively [ 2]. In this study, we aimed to reveal correlation between clustered DNA damage and the LET of heavy ion beam in the irradiated cells

Effects of irradiation on bone invasion of breast cancer cells

Background: Periostin is overexpressed in metastases from bone cancer. Many studies have indicated that periostin plays an important role in bone metastasis. Radiotherapy improves local tumor control, but recent evidence suggests that irradiation of the target tumor can promote tumor invasion and metastasis.Objective: The purpose of the study was to examine the effects of irradiation with carbon ion or gamma ray on the expression of periostin in breast cancer cells and the cytokine levels of osteoblasts in bone tumor metastases.Materials and methods: Breast cancer cells (FM3A/R cells) were exposed to carbon ion or gamma ray and then cocultured with non-irradiated osteoblastic MC3T3-E1 cells. Periostin expression in breast cancer cells and the levels of cytokines influencing bone invasion in osteoblastic cells were measured.Results: Periostin expression increased after irradiation with carbon ion or gamma ray. Carbon ion-irradiated cells expressed less periostin than did gamma ray-irradiated cells. Carbon ion irradiation stimulated low levels of periostin synthesis than gamma ray irradiation. The cytokines influencing bone invasion levels rose in tandem with the increase in periostin level.Conclusions: Carbon ion irradiation may reduce the production of bone-destroying cytokines and vascularization factors by osteoblasts in the microenvironment of cancer invasion in bone. A combination of carbon ion irradiation and a periostin inhibitor would improve treatment of bone metastatic breast cancer

Effects of Carbon Ion Irradiation via Periostin on Breast Cancer cell Invasion of the Microenvironment.

Radiation therapy is effective for pain and local control. However, it has someassociated problems such as increased bone metastasis after irradiation and side effects to the surrounding normal bone. Over expression of periostin has been observed in bone metastatic cancer. Many studies have indicated that periostin plays an important role in bone metastasis. However, the role of periostin in the microenvironment of bone invaded by destructive cancer cells remains unclear. It has been reported that expression of periostin is significantly enhanced in bone tissues requiring reconstruction.High LET radiation therapy induces bone hyperplasia and calcification in the irradiated area. In this study, after exposure to gamma-ray and carbon ion irradiation, FM3A/R cells were co cultured with non-irradiated MC3T3-E1 cells. The expression of various bone maturation and metabolic factors in MC3T3-E1 cells was evaluated by RT-PCR or western blotting during a time course. Furthermore, Runx2, OSX, OPN, and OCN were evaluated in MC3T3-E1 cells. The expression levels of these calcification and bone formation cytokines in MC3T3-E1 cells were enhanced by co culture with carbon ion-irradiated FM3A/R cells in the early stage. Radiation therapy for bone metastatic cancer, especially carbon ion beam therapy, has excellent cell-killing effects, and also causes less bone resorption in the radiation field than that observed for gamma-ray irradiation. The differentiation and maturation of osteoblasts might be promoted by periostin stimulation. It can be expected that combined treatment with both carbon ion irradiation and periostin inhibitor administration might become a treatment of choice