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The lessons learned from the Coronavirus Disease 2019 (COVID-19) pandemic are numerous. Low dose radiotherapy (LDRT) was used in the pre-antibiotic era as treatment for bacterially/virally associated pneumonia. Motivated in part by these historic clinical and radiobiological data, LDRT for treatment of COVID-19-associated pneumonia was proposed in early 2020. Although there is a large body of epidemiological and experimental data pointing to effects such as cancer at low doses, there is some evidence of beneficial health effects at low doses. It has been hypothesized that low dose radiation could be combined with immune checkpoint therapy to treat cancer. We shall review here some of these old radiobiological and epidemiological data, as well as the newer data on low dose radiation and stimulated immune response and other relevant emerging data. The paper includes a summary of several oral presentations given in a Symposium on "Low dose RT for COVID and other inflammatory diseases" as part of the 67th Annual Meeting of the Radiation Research Society, held virtually 3-6 October 2021. [ABSTRACT FROM AUTHOR]

Purpose: Humans are exposed to both natural (e.g. soil, cosmic rays) and human-made radiation sources (e.g. medical devices, nuclear energy production) on a daily basis. The use of medical radiation sources such as Computed Tomography (CT) scans and X-ray has increased rapidly, especially in the treatment of older populations. Micro Ribonucleic Acids (miRNAs) are the major regulators of multiple low-dose radiation-induced biological processes through post-translational inhibition. As a result, understanding age-related changes of miRNA profiles that may compromise the population after low dose radiation exposure has become increasingly important. Materials and methods: In this study, we irradiated both young (2 months) and old (26 months) C57BL/6J mice with low dose radiation (10 mGy and 100 mGy at 1 mGy/min using an open beam 60Co gamma source) and checked the miRNA expression profiles. Results: The global miRNA expression of old mice was significantly reduced compared to that of young mice. Low dose radiation at 10 mGy significantly increased the global miRNA expression in both old and young mice one week following irradiation, which suggests that 10 mGy low dose radiation may reverse the global inhibition effects of aging on miRNA expression. Higher 100 mGy radiation slightly reduced the global expression of miRNAs. We also identified several miRNAs that were elevated or reduced in all of the radiation treatment groups; these can be further explored as candidates for the radiation-induced bio-markers. Conclusions: The results of our study demonstrate that both radiation and aging can influence the global expression of miRNAs, while low dose radiation modulates the expression of miRNAs in a dose-, time-, and age-dependent manner. [ABSTRACT FROM AUTHOR]

Purpose: To assess health, growth and reproductive success of mammals exposed for multiple generations to levels of radium-226 known to occur in environments surrounding uranium mines and mills in Canada. Methods: The study consisted of a control group and four treatment groups each containing 40 mice (20 males and 20 females) of the CBA/CaJ strain that were continuously exposed to a range of radium-226 levels via drinking water. Breeding was at 8-10 weeks of age and the study was concluded after three breeding cycles. Results: When compared to control mice, constant consumption of drinking water containing 0.012, 0.076, 0.78 and 8.0 Bq/l of radium-226 over four generations of mice did not demonstrably affect physical condition, weight, pregnancy rate, number of pups per litter, sex ratio and bodyweight gain of pups. Between generations, the observed differences in pregnancy rates that were noted in all groups, including controls, seemed to directly correlate with the weight and age of the females at breeding. Conclusions: Based on the endpoints measured on four generations of mice, there is no indication that the consumption of radium-226 via drinking water (at activity concentrations up to 8.0 Bq/l) affects health, growth and reproductive fitness. [ABSTRACT FROM AUTHOR]

Epidemiological studies indicate long-term risks of ionizing radiation on the heart, even at moderate doses. In this study, we investigated the inflammatory, thrombotic and fibrotic late responses of the heart after low-dose irradiation (IR) with specific emphasize on the dose rate. Hypercholesterolemic ApoE-deficient mice were sacrificed 3 and 6 months after total body irradiation (TBI) with 0.025, 0.05, 0.1, 0.5 or 2 Gy at low (1 mGy/min) or high dose rate (150 mGy/min). The expression of inflammatory and thrombotic markers was quantified in frozen heart sections (CD31, E-selectin, thrombomodulin, ICAM-1, VCAM-1, collagen IV, Thy-1, and CD45) and in plasma samples (IL6, KC, MCP-1, TNFα, INFγ, IL-1β, TGFβ, INFγ, IL-10, sICAM-1, sE-selectin, sVCAM-1 and fibrinogen) by fluorescence analysis and ELISA. We found that even very low irradiation doses induced adaptive late responses, such as increases of capillary density and changes in collagen IV and Thy-1 levels indicating compensatory regulation. Slight decreases of ICAM-1 levels and reduction of Thy 1 expression at 0.025–0.5 Gy indicate anti-inflammatory effects, whereas at the highest dose (2 Gy) increased VCAM-1 levels on the endocardium may represent a switch to a pro-inflammatory response. Plasma samples partially confirmed this pattern, showing a decrease of proinflammatory markers (sVCAM, sICAM) at 0.025–2.0 Gy. In contrast, an enhancement of MCP-1, TNFα and fibrinogen at 0.05–2.0 Gy indicated a proinflammatory and prothrombotic systemic response. Multivariate analysis also revealed significant age-dependent increases (KC, MCP-1, fibrinogen) and decreases (sICAM, sVCAM, sE-selectin) of plasma markers. This paper represents local and systemic effects of low-dose irradiation, including also age- and dose rate-dependent responses in the ApoE-/- mouse model. These insights in the multiple inflammatory/thrombotic effects caused by low-dose irradiation might facilitate an individual evaluation and intervention of radiation related, long-term side effects but also give important implications for low dose anti-inflammatory radiotherapy. [ABSTRACT FROM AUTHOR]

Current practice for radiation protection associated with 131I therapy mainly focuses on external and internal exposure caused by physical contamination of the hospital staff, other patients and family members. However, if volatile 131I is excreted by the treated patients, these individuals could also be exposed through inhalation of 131I. This study quantifies the amount of volatile 131I excreted by rats after intravenous administration of metaiodobenzylguanidine (MIBG)-131I or Na131I, the two most common forms of 131I therapy. The results indicate that in 4 d following administration, the total excretion of volatile 131I was 0.036 and 0.17 % of the administered activities of MIBG-131I and Na131I, respectively. As administered activities for 131I therapy are typically of the order of 1–10 GBq, the overall excretion of volatile 131I from a patient can be as high as 20 MBq. As a result, a family member can receive up to 0.07 mSv committed effective dose from inhaling the volatile 131I excreted by the patient. [ABSTRACT FROM PUBLISHER]

Daily excretions of 210Po from rats via urine and faeces following i.v. administration of polonium citrate, from Day 2 to Day 5, were reported, together with retentions in tissues and organs on Day 5. Emphasis is given to the methods of measurement and data quality rather than to the discussion of the observations. The authors aim to contribute data for developing or refining the biokinetic model for 210Po metabolism. [ABSTRACT FROM PUBLISHER]

The metabolic formation of volatile 210Po species in a rat that was intravenously administered with 210Po-citrate was investigated in this study. A slurry of the faecal sample was prepared in water and was bubbled with nitrogen gas in a closed system. The discharged gas was passed through a trapping device filled with liquid scintillation cocktail in order to capture any volatile 210Po species. The amount of 210Po trapped in the scintillation cocktail was measured by a liquid scintillation analyser that provided evidence of the presence of volatile 210Po species in the faeces. The presence of volatile 210Po in the faeces indicates that the metabolic formation of volatile 210Po is likely to occur in the gut due to bacterial activity. The amount of volatile 210Po species was compared with the daily faecal excretion of 210Po. After 2 h of bubbling, the volatile 210Po collected from the faeces sample was found to be between 1.0 and 1.7 % of the daily faecal excretion for the 4 d following 210Po-citrate administration. [ABSTRACT FROM PUBLISHER]

Polonium-210 (210Po) is one of the most toxic radionuclides and was used as a poison in the Alexander Litvinenko case. In this study of the metabolism of 210Po in rats, volatile 210Po in excreta was measured, filling a knowledge gap of the previous studies. Five rats were intravenously administrated with 2 kBq and another five with 10 kBq of 210Po (citrate form). They were housed in a glass Metabowl® system for 4 d following the administration. Volatile 210Po from the excreta was collected in a trapping system filled with liquid scintillation cocktail and was measured by liquid scintillation counting. Results showed that the daily excretion of volatile 210Po by the rats is in a very small percentage (0.002–0.009 %) of the administered amounts. However, if the administered amount is large, the excretion of volatile 210Po can be significant. [ABSTRACT FROM PUBLISHER]