EPR based Estimation of Radiation-Induced Reactive Oxygen Species

Generation of reactive oxygen species (ROS) is considered as essential trigger of biological effects of ionizing radiations, and may be deeply linked with the radiation quality.Amounts of total oxidation reactions (i.e. oxidative free radical species, •OH and HO2•), H2O2 generations, Oxygen consumptions, and •OH generations induced by X-ray, 20 keV/μm carbon beam, and 80 keV/μm carbon beam were estimated using EPR based techniques.Total oxidation reactions were estimated as 3, 1.3, and 0.66 μmol/L/Gy, amount of H2O2 generations were 0.2, 0.57, and 0.35 μmol/L/Gy, oxygen consumptions were 0.4, 0.39, and 0.15 μmol/L/Gy for X-ray, 20 keV/μm carbon beam, and 80 keV/μm carbon beam, respectively. The ratio of H2O2 generation per oxygen consumption were increased with LET, and were 0.5, 1.46, 2.33 for X-ray, 20 keV/μm carbon beam, and 80 keV/μm carbon beam, respectively. The •OH generations expected to be localized on the track/range of the radiation beam/ray, and both sparse (≈ 3.3 mM) and very dense (> 1.7 M) •OH generations were suggested. Percentage of sparse •OH generation decreased with LET becoming higher.The SFRBM\u27s 23rd Annual Meeting, a joint meeting with the Society for Free Radical Research International (SFRBM/SFRRI 2016

Prolonged Radiation Damage in Rat Colon and Urokinase Expression in Epithelium

Although radiation therapy plays important role in the treatment of gynecological tumors, it may cause radiation injury as a late effect. Several recent reports show that urokinase such as urokinase type plasminogen activator (uPA) contributes to the repair of ulcerative lesions of the colon epithelium. We studied radiation induced enterocolitis using rat animal models. Seventy-two female Wistar rats were irradiated by a single fraction dose of 36Gy at laparotomy. Histological changes and activity of urokinase system were investigated after irradiation. Ulcers were observed in irradiated field in 12 of 19 animals (63%) even at 60th week after irradiation. Urokinase expressions were observed in the margins of active ulcer. Urokinase was thought to play important role in exacerbation of ulcer formation. Expression of uPA was also observed in submucosal glands. Ischaemic changes were not observed in irradiated colon despite sclerosing vasculitis. It is suggested that uPA played reciprocal roles in radiation induced enterocolitis: healing and aggravation of ulcer

Immunohistochemical Study of p53 Overexpression in Radiation-Induced Colon Cancers

The expressions of p53 and proliferating cell nuclear antigen (PCNA) were studied immunohistochemically from paraffin sections of 7 cases (9 lesions) of radiation-induced colon cancer and 42 cases of spontaneous colon cancer. Age distribution of radiation-induced and spontaneous colon cancer were 68.1 years (range, 56 to 77 years) and 67.4 years (range, 31 to 85 years), respectively. Among the radiation-induced colon cancers, there were 3 lesions of mucinous carcinoma (33%), a much higher than found for spontaneous mucinous cancer. Immunohistochemically, p53 protein expression was detected in 7/9 (78%) of radiation-induced cancers and in 23/42(55%) of spontaneous colon cancers. χ^2 analysis found no significant differences between radiation-induced and spontaneous colon cancers in age distribution or p53-positive staining for frequency, histopathology, or Dukes\u27 classification. In radiation colitis around the cancers including aberrant crypts, spotted p53 staining and abnormal and scattered PCNA-positive staining were observed. In histologically normal cells, p53 staining was almost absent and PCNA-positive staining was regularly observed in the lower half of the crypt. In radiation colitis including aberrant glands, cellular proliferation increased and spotted p53 expression was observed. This study suggests that radiation colitis and aberrant glands might possess malignant potential and deeply associate with carcinogenesis of radiation-induced colon cancer

Sulforaphane exerts its biological effects by introducing DNA double strand breaks

Sulforaphane (SFN), an isothiocyanate isolated from broccoli, has been recognized mainly as a preventive agent for human cancers. Several reports also indicated that SFN suppressed proliferation of cancer cells by cell cycle arrest and by inducing apoptosis through activation of the caspase apoptosis pathway. DNA double-strand breaks (DSBs) are thought to be the most important lesions produced in cells exposed to toxic agents such as ionizing radiation (IR). Here, we present a new discovery that the biological effects exerted by SFN might be a consequence of DNA DSBs it produces. HeLa cells were exposed to various concentrations of SFN and several biological end points were studied. The cell growth was measured for several days and the induction of DNA DSB was examined using constant field gel electrophoresis (CFGE) as well as gamma-H2AX assay. Our data revealed that the cell growth was impaired in a SFN dose dependent manner, and DNA DSBs were also induced in a drug dose and treatment time dependent manner. For example, after 20microM SFN treatment for 24 hours, a significant number of DNA DSBs was induced in HeLa cells. Moreover, our immuno-staining experiments indicated the appearance of Rad51 (an essential protein associated with homologous recombination repair (HRR)) foci observed in a dose and time dependent manner along with DNA DSB production. In contrast, there was no phosphorylation of DNA-PKcs (a critical non-homologous end joining (NHEJ) protein) observed in cells exposed to SFN, suggesting that DSBs caused by SFN might be cell cycle dependent. In summary our data clearly demonstrate the induction of DNA DSBs by SFN, and these might be repaired by HRR pathway. Our results suggest that SFN could be used as an effective anticancer agent in addition to its well-recognized chemo-preventive property.AACR Annual Meeting 200