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Introduction: Patients who receive ionizing radiation for diagnosis or treatment may suffer side effects in normal tissues. Radioprotective agents have the potential to decrease DNA damage and free radicals produced by ionizing radiation. Green tea is a natural product from the Camellia sinensis plant and have been shown to have antioxidant and radioprotective properties. The aim of the present study is assessing the protective effect of green tea on lymphocytes affected by radiation injury. Material and Methods: Blood samples was obtained from four adults healthy human and lymphocytes were extracted. Afterward, lymphocytes were exposed to X-radiation by OPG, CBCT, CT and radiotherapy instruments. The protective effects of the green tea polyphenol on Bcl-2 and Bax genes expression levels were evaluated in cultured lymphocytes obtained from treated cells (24 h and 1 h before and 1 h after exposure to ionizing radiation) and non-treated cells (Receiving X-radiation and non-receiving green tea). Results: The results of this investigation demonstrated Bax/Bcl-2 ratio, as an index of the radiation sensitivity, was significantly decreased in groups which had been received dose of 2 Gy in treated cells groups of 1 h before and 1 h after X-radiation (p<0.05). Conclusion: The results indicated different effects of green tea on low and high doses of X-radiation. Most protective effects of green tea as an apoptosis inhibitor were observed in high doses of ionizing radiation. Consequently, green tea may be useful as an adjunct to radiotherapy and medical imaging to diminish apoptosis and side effects in normal tissues. [ABSTRACT FROM AUTHOR]

Introduction: The effects of the low dose of ionizing radiation are not thoroughly evident due to an unavoidable increase of occupational exposure and the widespread application of ionizing radiation in medical and industrial fields. The aim of this study was to investigate immune system responses following the low doses of ionizing radiation. Material and Methods: BALB/c mice were exposed to Whole Body Irradiation of 20, 50, and 100 mGy through a 60Co source. Lymphocytes extraction were operated 24 h after irradiation. Afterwards, gene expression analysis was performed with relative quantitative Real-Time polymerase chain reaction to IL-4, IFN-γ, and TGF-β expression levels. Moreover, IFN-γ/IL-4 ratio was computed, and the independent sample t-test was performed for the statistical analysis. Results: Whereas IL-4, IFN-γ, and TGF-β expression levels decrease after the radiation of the low doses of gamma rays, the IFN-γ/IL-4 ratio increased significantly after irradiation of 20 mGy (P-Value<0.05). However, this ratio did not vary following the gamma irradiation of 50 and 100 mGy. Conclusion: The positive effects of the low dose of ionizing radiation can be observed through significant alterations in gene expression and the activation of protection mechanisms. This process was caused by the modulation of cellular immune responses after the exposure to 20 mGy. Although the irradiation of higher doses (50 and 100 mGy) induced alterations in the IFN- γ/IL-4 ratio was insignificant. These findings did not confirm the linear no-threshold model theory, and demonstrated that the low dose of ionizing radiation could be the cause of the hormesis phenomenon. [ABSTRACT FROM AUTHOR]