The Mechanisms of Radiation-Induced Bystander Effect

The radiation-induced bystander effect is the phenomenon which non-irradiated cells exhibit effects along with their different levels as a result of signals received from nearby irradiated cells. Responses of non-irradiated cells may include changes in process of translation, gene expression, cell proliferation, apoptosis and cells death. These changes are confirmed by results of some In-Vivo studies. Most well-known important factors affecting radiation-induced bystander effect include free radicals, immune system factors, expression changes of some genes involved in inflammation pathway and epigenetic factor

Evaluating Gamma-H2AX Expression as a Biomarker of DNA Damage after X-ray in Angiography Patients

Objective: Coronary heart disease (CHD) is one of the most common diseases. Coronary angiography (CAG) is an important apparatus used to diagnose and treat this disease. Since angiography is performed through exposure to ionizing radiation, it can cause harmful effects induced by double-stranded breaks in DNA which is potentially life-threatening damage. The aim of the present study is to investigate phosphorylation of Histone H2AX in the location of double-stranded breaks in peripheral blood lymphocytes as an indication of biological effects of radiation on angiography. Materials and Methods: This method is based on the phosphorylation measurement of Histone (gamma-H2AX or γ-H2AX) levels on serine 139 after the formation of DNA double-strand break. 5 cc of blood samples from 24 patients undergoing angiography were taken pre- and post-radiation. Blood lymphocytes were extracted, fixed and stained with specific γ-H2AX antibodies. Finally, the percentage of phosphorylation of Histone H2AX as an indicator of double-strand break was measured by a cytometry technique. Results: An increase was observed in all patients’ percentage of phosphorylated Histone H2AX (double-stranded breaks DNA) after radiation (20.15 ± 14.18) compared to pre-exposure time (1.52 ± 0.34). Also, the mean of DNA double-strand break is shown in a linear correlation with DAP. Discussion: Although induction of DNA double-strand breaks was associated with the radiation dose in patients, the effect of individual factors such as radio-sensitivity and regenerative capacity should not be ignored. In the future, if we are able to measure DNA damage response in every angiography patient, we will use it as a biomarker for the patient dose; this will promote public health. Conclusion: Using flow cytometers readings done automatically is possible to detect γ-H2AX in the number of blood cells, therefore, the use of this technique could play a significant role in monitoring patients

Investigation of Erythema, Radiation Dose, and Radiation-Induced Apoptosis in the Peripheral Blood Lymphocytes of Patients Treated with Radiofrequency Catheter Ablation

Introduction: The long-term use of fluoroscopy in cardiac interventional procedures increases the patient dose and causes severe skin reactions, which lead to growing concern. The aim of the present study was to evaluate the risk and the effect of X-ray irradiation on apoptosis in the peripheral blood lymphocytes of patients treated with ablation in electrophysiological studies. Material and Methods: A total of 30 patients who underwent ablation therapy participated in this study. The absorbed dose in the given area was measured by a thermos luminescent dosimeter (TLD). The duration of dose delivery, absorbed dose by the apparatus, and dose area product (DAP) factor were measured for each patient. The skin changes were observed within the 1st day to 5th week after the operation. Blood sampling was conducted (before and 24 h after the treatment), and then, flow cytometry was performed to investigate the apoptotic changes in the blood lymphocytes. Results: The statistical analysis showed that there was a significant difference in the apoptosis of patient blood lymphocytes before irradiation and following that (P<0.05). There was a correlation between the amount of DAP and TLD dose (P<0.001). Furthermore, a correlation was observed between the total apoptosis and fluoroscopic time. The patient radiation dose in the ablation test was not in the threshold level required to create skin erythema. Conclusion: The results of the present study revealed that the use of long-time fluoroscopy in electrophysiological studies may cause a significant increase of apoptosis in the peripheral blood lymphocyte of patients treated using this procedure. © 202

Assessment of adaptive response of gamma radiation in the operating room personnel exposed to anesthetic gases by measuring the relative gene expression changes KU80, LIGASE1 and P53

Background: Some operating room personnel are occupationally exposed to genotoxic agents such as anesthetic gases and ionizing radiation. Adaptive response, as a defense mechanism, will occur when cells become exposed to a low dose of factors harming DNA (priming dose), which in the subsequent exposure to higher dose of those factors (challenging dose), show more resistance and sensibility. Objective: The aim of this study was to investigate adaptive response or synergy of ionizing radiation in the operating room personnel exposed to anesthetic gases by evaluation of the relative gene expression changes of effective genes for DNA repair such as Ku80, Ligase1 and P53. Material and Methods: In this case-control study, 20 operating room personnel and 20 nurses (who were not present in the operating room) as controls were studied. Venous blood samples were drawn from participants. In order to evaluate the adaptive response, a challenging dose of 2Gy gamma radiation was applied to blood samples. Moreover, RNA extraction and cDNA synthesis were performed. Gene expression level was studied by RT-qPCR and compared with the control group. Results: Ligase1 and P53 expression in the operating room personnel was signifi-cantly higher than that of the control group before irradiation (P�0.001). Statistically, there was no significant difference in the Ku80 and P53 expression in the operating room personnel before and after irradiation. Conclusion: Given the findings of this study, exposure to challenging dose of gamma radiation can induce adaptive response in expression of Ku80 and P53 genes in operating room personnel. © 2020, Shiraz University of Medical Sciences. All rights reserved

Evaluating Radioprotective Effect of Hesperidin on Acute Radiation Damage in the Lung Tissue of Rats

Background: Oxidative stress plays an important role in the pathogenesis and progression of γ-irradiation-induced cellular damage, Lung is a radiosensitive organ and its damage is a dose-limiting factor in radiotherapy. The administration of dietary antioxidants has been suggested to protect against the succeeding tissue damage. The present study aimed to evaluate the radioprotective efficacy of Hesperidin (HES) against γ-irradiation-induced tissue damage in the lung of male rats. Materials and Methods: Thirty two rats were divided into four groups. Rats in Group 1 received PBS and underwent sham irradiation. Rats in Group 2 received HES and underwent sham irradiation. Rats in Group 3 received PBS and underwent γ-irradiation. Rats in Group 4 received HES and underwent γ-irradiation. These rats were exposed to γ-radiation 18 Gy using a single fraction cobalt-60 unit, and were administered HES (100 mg/kg/d, b.w, orally) for 7 days prior to irradiation. Rats in each group were sacrificed 24 hours after radiotherapy (RT) for the determination of superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA) and histopathological evaluations. Results: Compared to group 1, the level of SOD and GSH significantly decreased and MDA level significantly increased in group 3 at 24 h following irradiation, (p=0.001, p0.0125). Conclusion: Oral administration of HES was found to offer protection against γ-irradiation- induced pulmonary damage and oxidative stress in rats, probably by exerting a protective effect against inflammatory disorders via its free radical scavenging and membrane stabilizing ability