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Belov O, Chigasova A, Pustovalova M, Osipov A, Eremin P, Vorobyeva N, Osipov AN. Dose-Dependent Shift in Relative Contribution of Homologous Recombination to DNA Repair after Low-LET Ionizing Radiation Exposure: Empirical Evidence and Numerical Simulation. Curr Issues Mol Biol 2023; 45:7352-7373. [PMID: 37754249 PMCID: PMC10528584 DOI: 10.3390/cimb45090465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/06/2023] [Accepted: 09/07/2023] [Indexed: 09/28/2023] Open
Abstract
Understanding the relative contributions of different repair pathways to radiation-induced DNA damage responses remains a challenging issue in terms of studying the radiation injury endpoints. The comparative manifestation of homologous recombination (HR) after irradiation with different doses greatly determines the overall effectiveness of recovery in a dividing cell after irradiation, since HR is an error-free mechanism intended to perform the repair of DNA double-strand breaks (DSB) during S/G2 phases of the cell cycle. In this article, we present experimentally observed evidence of dose-dependent shifts in the relative contributions of HR in human fibroblasts after X-ray exposure at doses in the range 20-1000 mGy, which is also supported by quantitative modeling of DNA DSB repair. Our findings indicate that the increase in the radiation dose leads to a dose-dependent decrease in the relative contribution of HR in the entire repair process.
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Affiliation(s)
- Oleg Belov
- Joint Institute for Nuclear Research, 6 Joliot-Curie St., 141980 Dubna, Russia;
- Institute of Biomedical Problems, Russian Academy of Sciences, 76A Khoroshevskoye Shosse, 123007 Moscow, Russia
- Institute of System Analysis and Management, Dubna State University, 19 Universitetskaya St., 141980 Dubna, Russia
| | - Anna Chigasova
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia; (A.C.); (A.O.); (N.V.)
- Emanuel Institute for Biochemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia
| | - Margarita Pustovalova
- State Research Center—Burnasyan Federal Medical Biophysical Center of Federal Medical Biological Agency (SRC—FMBC), 123098 Moscow, Russia;
- School of Biological and Medical Physics, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
| | - Andrey Osipov
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia; (A.C.); (A.O.); (N.V.)
| | - Petr Eremin
- FSBI “National Medical Research Center for Rehabilitation and Balneology”, Ministry of Health of Russia, 121099 Moscow, Russia;
| | - Natalia Vorobyeva
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia; (A.C.); (A.O.); (N.V.)
- State Research Center—Burnasyan Federal Medical Biophysical Center of Federal Medical Biological Agency (SRC—FMBC), 123098 Moscow, Russia;
| | - Andreyan N. Osipov
- Joint Institute for Nuclear Research, 6 Joliot-Curie St., 141980 Dubna, Russia;
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia; (A.C.); (A.O.); (N.V.)
- State Research Center—Burnasyan Federal Medical Biophysical Center of Federal Medical Biological Agency (SRC—FMBC), 123098 Moscow, Russia;
- School of Biological and Medical Physics, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
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Role of p53 in Regulating Radiation Responses. LIFE (BASEL, SWITZERLAND) 2022; 12:life12071099. [PMID: 35888186 PMCID: PMC9319710 DOI: 10.3390/life12071099] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 07/15/2022] [Accepted: 07/16/2022] [Indexed: 12/12/2022]
Abstract
p53 is known as the guardian of the genome and plays various roles in DNA damage and cancer suppression. The p53 gene was found to express multiple p53 splice variants (isoforms) in a physiological, tissue-dependent manner. The various genes that up- and down-regulated p53 are involved in cell viability, senescence, inflammation, and carcinogenesis. Moreover, p53 affects the radioadaptive response. Given that several studies have already been published on p53, this review presents its role in the response to gamma irradiation by interacting with MDM2, NF-κB, and miRNA, as well as in the inflammation processes, senescence, carcinogenesis, and radiation adaptive responses. Finally, the potential of p53 as a biomarker is discussed.
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Tharmalingam S, Sreetharan S, Brooks AL, Boreham DR. Re-evaluation of the linear no-threshold (LNT) model using new paradigms and modern molecular studies. Chem Biol Interact 2019; 301:54-67. [PMID: 30763548 DOI: 10.1016/j.cbi.2018.11.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/13/2018] [Accepted: 11/22/2018] [Indexed: 02/06/2023]
Abstract
The linear no-threshold (LNT) model is currently used to estimate low dose radiation (LDR) induced health risks. This model lacks safety thresholds and postulates that health risks caused by ionizing radiation is directly proportional to dose. Therefore even the smallest radiation dose has the potential to cause an increase in cancer risk. Advances in LDR biology and cell molecular techniques demonstrate that the LNT model does not appropriately reflect the biology or the health effects at the low dose range. The main pitfall of the LNT model is due to the extrapolation of mutation and DNA damage studies that were conducted at high radiation doses delivered at a high dose-rate. These studies formed the basis of several outdated paradigms that are either incorrect or do not hold for LDR doses. Thus, the goal of this review is to summarize the modern cellular and molecular literature in LDR biology and provide new paradigms that better represent the biological effects in the low dose range. We demonstrate that LDR activates a variety of cellular defense mechanisms including DNA repair systems, programmed cell death (apoptosis), cell cycle arrest, senescence, adaptive memory, bystander effects, epigenetics, immune stimulation, and tumor suppression. The evidence presented in this review reveals that there are minimal health risks (cancer) with LDR exposure, and that a dose higher than some threshold value is necessary to achieve the harmful effects classically observed with high doses of radiation. Knowledge gained from this review can help the radiation protection community in making informed decisions regarding radiation policy and limits.
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Affiliation(s)
- Sujeenthar Tharmalingam
- Northern Ontario School of Medicine, Laurentian University, 935 Ramsey Lake Rd, Sudbury, ON, P3E 2C6, Canada.
| | - Shayenthiran Sreetharan
- Department of Medical Physics and Applied Radiation Sciences, McMaster University, 1280 Main Street W, Hamilton ON, L8S 4K1, Canada
| | - Antone L Brooks
- Environmental Science, Washington State University, Richland, WA, USA
| | - Douglas R Boreham
- Northern Ontario School of Medicine, Laurentian University, 935 Ramsey Lake Rd, Sudbury, ON, P3E 2C6, Canada; Bruce Power, Tiverton, ON(3), UK.
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Puukila S, Thome C, Brooks AL, Woloschak G, Boreham DR. The influence of changing dose rate patterns from inhaled beta-gamma emitting radionuclide on lung cancer. Int J Radiat Biol 2018; 94:955-966. [PMID: 30257126 PMCID: PMC6759062 DOI: 10.1080/09553002.2018.1511929] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Purpose: Dose and dose rate are both appropriate for estimating risk from internally deposited radioactive materials. We investigated the role of dose rate on lung cancer induction in Beagle dogs following a single inhalation of strontium-90 (90Sr), cerium-144 (144Ce), yttrium-91 (91Y), or yttrium-90 (90Y). As retention of the radionuclide is dependent on biological clearance and physical half-life a representative quantity to describe this complex changing dose rate is needed. Materials and methods: Data were obtained from Beagle dog experiments from the Inhalation Toxicology Research Institute. The authors selected the dose rate at the effective half-life of each radionuclide (DRef). Results: Dogs exposed to DRef (1–100 Gy/day) died within the first year after exposure from acute lung disease. Dogs exposed at lower DRef (0.1–10 Gy/day) died of lung cancer. As DRef decreased further (<0.1 Gy/day 90Sr, <0.5 Gy/day 144Ce, <0.9 Gy/day 91Y, <8 Gy/day 90Y), survival and lung cancer frequency were not significantly different from control dogs. Conclusion: Radiation exposures resulting from inhalation of beta-gamma emitting radionuclides that decay at different rates based on their effective half-life, leading to different rates of decrease in dose rate and cumulative dose, is less effective in causing cancer than acute low linear energy transfer exposures of the lung.
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Affiliation(s)
- Stephanie Puukila
- a Department of Biology , Laurentian University , Sudbury , Canada.,b College of Medicine and Public Health , Flinders University , Adelaide , Australia
| | | | - Antone L Brooks
- c Department of Environmental Science , Retired Professor, Washington State University, Richland , WA , USA
| | - Gayle Woloschak
- d Northwestern University , Department of Radiation Oncology , Chicago , IL , USA
| | - Douglas R Boreham
- e Northern Ontario School of Medicine, Department of Medical Sciences , Sudbury , Canada.,f Bruce Power , Tiverton , Canada
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Cardarelli JJ, Ulsh BA. It Is Time to Move Beyond the Linear No-Threshold Theory for Low-Dose Radiation Protection. Dose Response 2018; 16:1559325818779651. [PMID: 30013457 PMCID: PMC6043938 DOI: 10.1177/1559325818779651] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 04/18/2018] [Accepted: 05/01/2018] [Indexed: 02/03/2023] Open
Abstract
The US Environmental Protection Agency (USEPA) is the primary federal agency responsible for promulgating regulations and policies to protect people and the environment from ionizing radiation. Currently, the USEPA uses the linear no-threshold (LNT) model to estimate cancer risks and determine cleanup levels in radiologically contaminated environments. The LNT model implies that there is no safe dose of ionizing radiation; however, adverse effects from low dose, low-dose rate (LDDR) exposures are not detectable. This article (1) provides the scientific basis for discontinuing use of the LNT model in LDDR radiation environments, (2) shows that there is no scientific consensus for using the LNT model, (3) identifies USEPA reliance on outdated scientific information, and (4) identifies regulatory reliance on incomplete evaluations of recent data contradicting the LNT. It is the time to reconsider the use of the LNT model in LDDR radiation environments. Incorporating the latest science into the regulatory process for risk assessment will (1) ensure science remains the foundation for decision making, (2) reduce unnecessary burdens of costly cleanups, (3) educate the public on the real effects of LDDR radiation exposures, and (4) harmonize government policies with the rest of the radiation scientific community.
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Tang FR, Loke WK, Khoo BC. Low-dose or low-dose-rate ionizing radiation-induced bioeffects in animal models. JOURNAL OF RADIATION RESEARCH 2017; 58:165-182. [PMID: 28077626 PMCID: PMC5439383 DOI: 10.1093/jrr/rrw120] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 01/22/2016] [Indexed: 05/13/2023]
Abstract
Animal experimental studies indicate that acute or chronic low-dose ionizing radiation (LDIR) (≤100 mSv) or low-dose-rate ionizing radiation (LDRIR) (<6 mSv/h) exposures may be harmful. It induces genetic and epigenetic changes and is associated with a range of physiological disturbances that includes altered immune system, abnormal brain development with resultant cognitive impairment, cataractogenesis, abnormal embryonic development, circulatory diseases, weight gain, premature menopause in female animals, tumorigenesis and shortened lifespan. Paternal or prenatal LDIR/LDRIR exposure is associated with reduced fertility and number of live fetuses, and transgenerational genomic aberrations. On the other hand, in some experimental studies, LDIR/LDRIR exposure has also been reported to bring about beneficial effects such as reduction in tumorigenesis, prolonged lifespan and enhanced fertility. The differences in reported effects of LDIR/LDRIR exposure are dependent on animal genetic background (susceptibility), age (prenatal or postnatal days), sex, nature of radiation exposure (i.e. acute, fractionated or chronic radiation exposure), type of radiation, combination of radiation with other toxic agents (such as smoking, pesticides or other chemical toxins) or animal experimental designs. In this review paper, we aimed to update radiation researchers and radiologists on the current progress achieved in understanding the LDIR/LDRIR-induced bionegative and biopositive effects reported in the various animal models. The roles played by a variety of molecules that are implicated in LDIR/LDRIR-induced health effects will be elaborated. The review will help in future investigations of LDIR/LDRIR-induced health effects by providing clues for designing improved animal research models in order to clarify the current controversial/contradictory findings from existing studies.
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Affiliation(s)
- Feng Ru Tang
- Singapore Nuclear Research and Safety Initiative (SNRSI), National University of Singapore, 1 CREATE Way #04-01, CREATE Tower, 138602, Singapore
| | - Weng Keong Loke
- Temasek Laboratories, National University of Singapore, 5A, Engineering Drive 1, 117411,Singapore
| | - Boo Cheong Khoo
- DSO National Laboratories,Defence Medical and Environmental Research Institute, 11 Stockport Road,117605,Singapore
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Dobrzyński L, Fornalski KW, Socol Y, Reszczyńska JM. Modeling of Irradiated Cell Transformation: Dose- and Time-Dependent Effects. Radiat Res 2016; 186:396-406. [DOI: 10.1667/rr14302.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Stuart M, Festarini A, Schleicher K, Tan E, Kim SB, Wen K, Gawlik J, Ulsh B. Biological effects of tritium on fish cells in the concentration range of international drinking water standards. Int J Radiat Biol 2016; 92:563-71. [DOI: 10.1080/09553002.2016.1222090] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
| | - Amy Festarini
- Canadian Nuclear Laboratories (CNL), Chalk River, Canada
| | | | | | - Sang Bog Kim
- Canadian Nuclear Laboratories (CNL), Chalk River, Canada
| | - Kendall Wen
- Deep River Science Academy, Chalk River, Canada
| | | | - Brant Ulsh
- M. H. Chew & Associates, Inc., Cincinnati, OH, USA
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9
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Curcumin mitigates accelerated aging after irradiation in Drosophila by reducing oxidative stress. BIOMED RESEARCH INTERNATIONAL 2015; 2015:425380. [PMID: 25815315 PMCID: PMC4359819 DOI: 10.1155/2015/425380] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 09/15/2014] [Accepted: 09/17/2014] [Indexed: 12/17/2022]
Abstract
Curcumin, belonging to a class of natural phenol compounds, has been extensively studied due to its antioxidative, anticancer, anti-inflammatory, and antineurodegenerative effects. Recently, it has been shown to exert dual activities after irradiation, radioprotection, and radiosensitization. Here, we investigated the protective effect of curcumin against radiation damage using D. melanogaster. Pretreatment with curcumin (100 μM) recovered the shortened lifespan caused by irradiation and increased eclosion rate. Flies subjected to high-dose irradiation showed a mutant phenotype of outstretched wings, whereas curcumin pretreatment reduced incidence of the mutant phenotype. Protein carbonylation and formation of γH2Ax foci both increased following high-dose irradiation most likely due to generation of reactive oxygen species. Curcumin pretreatment reduced the amount of protein carbonylation as well as formation of γH2Ax foci. Therefore, we suggest that curcumin acts as an oxidative stress reducer as well as an effective protective agent against radiation damage.
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10
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Lee CYS, Koval TM, Suzuki JB. Low-Dose Radiation Risks of Computerized Tomography and Cone Beam Computerized Tomography: Reducing the Fear and Controversy. J ORAL IMPLANTOL 2014; 41:e223-30. [PMID: 24669832 DOI: 10.1563/aaid-joi-d-13-00221] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Regulations for protecting humans against stochastic biological effects from ionizing radiation are based on the linear no-threshold (LNT) risk assessment model, which states that any amount of radiation exposure may lead to cancer in a population. Based on the LNT model, risk from low-dose radiation increases linearly with increasing doses of radiation. Imaging procedures in medicine and dentistry are an important source of low-dose ionizing radiation. The increased use of computerized tomography (CT) and cone beam computerized tomography (CBCT) has raised health concerns regarding exposure to low-dose ionizing radiation. In oral and maxillofacial surgery and implant dentistry, CBCT is now at the forefront of this controversy. Although caution has been expressed, there have been no direct studies linking radiation exposure from CT and CBCT used in dental imaging with cancer induction. This article describes the concerns about radiation exposure in dental imaging regarding the use of CT.
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Affiliation(s)
- Cameron Y S Lee
- 1 Private practice in oral, maxillofacial and reconstructive surgery, Aiea, Hawaii; Department of Periodontology and Oral Implantology, Temple University Kornberg School of Dentistry, Philadelphia, Penn
| | - Thomas M Koval
- 2 Center for Biotechnology Education, Advanced Academic Programs, Krieger School of Arts and Sciences, Johns Hopkins University, Rockville, Md
| | - Jon B Suzuki
- 3 Temple University, Kornberg School of Dentistry, Department of Periodontology and Oral Implantology, School of Medicine, Department of Microbiology and Immunology, Philadelphia, Penn
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Socol Y, Dobrzyński L, Doss M, Feinendegen LE, Janiak MK, Miller ML, Sanders CL, Scott BR, Ulsh B, Vaiserman A. Commentary: ethical issues of current health-protection policies on low-dose ionizing radiation. Dose Response 2013; 12:342-8. [PMID: 24910586 DOI: 10.2203/dose-response.13-044.socol] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The linear no-threshold (LNT) model of ionizing-radiation-induced cancer is based on the assumption that every radiation dose increment constitutes increased cancer risk for humans. The risk is hypothesized to increase linearly as the total dose increases. While this model is the basis for radiation safety regulations, its scientific validity has been questioned and debated for many decades. The recent memorandum of the International Commission on Radiological Protection admits that the LNT-model predictions at low doses are "speculative, unproven, undetectable and 'phantom'." Moreover, numerous experimental, ecological, and epidemiological studies show that low doses of sparsely-ionizing or sparsely-ionizing plus highly-ionizing radiation may be beneficial to human health (hormesis/adaptive response). The present LNT-model-based regulations impose excessive costs on the society. For example, the median-cost medical program is 5000 times more cost-efficient in saving lives than controlling radiation emissions. There are also lives lost: e.g., following Fukushima accident, more than 1000 disaster-related yet non-radiogenic premature deaths were officially registered among the population evacuated due to radiation concerns. Additional negative impacts of LNT-model-inspired radiophobia include: refusal of some patients to undergo potentially life-saving medical imaging; discouragement of the study of low-dose radiation therapies; motivation for radiological terrorism and promotion of nuclear proliferation.
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12
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Grygoryev D, Moskalenko O, Hinton TG, Zimbrick JD. DNA damage caused by chronic transgenerational exposure to low dose gamma radiation in Medaka fish ( Oryzias latipes ). Radiat Res 2013; 180:235-46. [PMID: 23919310 DOI: 10.1667/rr3190.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The effect of transgenerational exposure to low dose rate (2.4 and 21 mGy/day) gamma irradiation on the yield of DNA double-strand breaks and oxidized guanine (8-hydroxyguanine) has been studied in the muscle and liver tissue of a model organism, the Japanese medaka fish. We found the level of unrepaired 8-hydroxyguanine in muscle tissue increased nonlinearly over four generations and the pattern of this change depended on the radiation dose rate, suggesting that our treatment protocols initiated genomic instability and an adaptive response as the generations progressed. The yield of unrepaired double-strand breaks did not vary significantly among successive generations in muscle tissue in contrast to liver tissue in which it varied in a nonlinear manner. The 8-hydroxyguanine and DSB radiation yields were significantly higher at 2.4 mGy/day than at 21 mGy/day in both muscle and liver tissue in all generations. These data are consistent with the hypothesis of a threshold for radiation-induced activation of DNA repair systems below which tissue levels of DNA repair enzymes remain unchanged, leading to the accumulation of unrepaired damage at very low doses and dose rates.
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Affiliation(s)
- D Grygoryev
- a Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, Portland, Oregon 97239
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Zhao S, Chen X, Zhu G. Infant's bilobar thyroid agenesis and mother's I-131 accidental administration. ANNALES D'ENDOCRINOLOGIE 2013; 74:62-4. [PMID: 23337015 DOI: 10.1016/j.ando.2012.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 10/16/2012] [Indexed: 11/18/2022]
Abstract
Bilobar thyroid agenesis is one of rare diseases. Genetic and environmental factors may associate with bilobar thyroid agenesis. But the mechanism is still not completely understood. It had been showed that I-131 administration during pregnancy may induce thyroid dysfunction in newborn. Here we reported a case of female hospital staff who received I-131 accidently during (10-12th gestational weeks) and after her pregnancy. The absorbed dose to fetus was higher than 30mGy. At birth, the infant was found to have no thyroid. It was speculated that the fetal thyroid agenesis may be related with mother' I-131 administration during pregnancy. In addition, this case report also indicated that the radiation dose should be minimized to any developing embryo.
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Affiliation(s)
- Shuquan Zhao
- Institute of Radiation Medicine, Fudan University, Xietu road, 200032 Shanghai, China.
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Abstract
In 2005, two expert advisory bodies examined the evidence on the effects of low doses of ionizing radiation. The U.S. National Research Council concluded that current scientific evidence is consistent with the linear no-threshold dose-response relationship (NRCNA 2005) while the French National Academies of Science and Medicine concluded the opposite (Aurengo et al. 2005). These contradictory conclusions may stem in part from an emphasis on epidemiological data (a "top down" approach) versus an emphasis on biological mechanisms (a "bottom up" approach). In this paper, the strengths and limitations of the top down and bottom up approaches are discussed, and proposals for strengthening and reconciling them are suggested. The past seven years since these two reports were published have yielded increasing evidence of nonlinear responses of biological systems to low radiation doses delivered at low dose-rates. This growing body of evidence is casting ever more doubt on the extrapolation of risks observed at high doses and dose-rates to estimate risks associated with typical environmental and occupational exposures. This paper compares current evidence on low dose, low dose-rate effects against objective criteria of causation. Finally, some questions for a post-LNT world are posed.
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Zhao Y. Computational modeling of signaling pathways mediating cell cycle checkpoint control and apoptotic responses to ionizing radiation-induced DNA damage. Dose Response 2012; 10:251-73. [PMID: 22740786 PMCID: PMC3375491 DOI: 10.2203/dose-response.11-021.zhao] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The shape of dose response of ionizing radiation (IR) induced cancer at low dose region, either linear non-threshold or J-shaped, has been a debate for a long time. This dose response relationship can be influenced by built-in capabilities of cells that minimize the fixation of IR-mediated DNA damage as pro-carcinogenic mutations. Key capabilities include sensing of damage, activation of cell cycle checkpoint arrests that provide time needed for repair of the damage as well as apoptosis. Here we describe computational modeling of the signaling pathways that link sensing of DNA damage and checkpoint arrest activation/apoptosis to investigate how these molecular-level interactions influence the dose response relationship for IR induced cancer. The model provides qualitatively accurate descriptions of the IR-mediated activation of cell cycle checkpoints and the apoptotic pathway, and of time-course activities and dose response of relevant regulatory proteins (e.g. p53 and p21). Linking to a two-stage clonal growth cancer model, the model described here successfully captured a monotonically increasing to a J-shaped dose response curve and identified one potential mechanism leading to the J-shape: the cell cycle checkpoint arrest time saturates with the increase of the dose.
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Affiliation(s)
- Yuchao Zhao
- Address correspondence to Dr. Yuchao Zhao, ; Phone: 86-13436569773
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Calabrese V, Cornelius C, Dinkova-Kostova AT, Iavicoli I, Di Paola R, Koverech A, Cuzzocrea S, Rizzarelli E, Calabrese EJ. Cellular stress responses, hormetic phytochemicals and vitagenes in aging and longevity. Biochim Biophys Acta Mol Basis Dis 2011; 1822:753-83. [PMID: 22108204 DOI: 10.1016/j.bbadis.2011.11.002] [Citation(s) in RCA: 280] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 10/31/2011] [Accepted: 11/01/2011] [Indexed: 12/30/2022]
Abstract
Modulation of endogenous cellular defense mechanisms represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. This paper introduces the emerging role of exogenous molecules in hormetic-based neuroprotection and the mitochondrial redox signaling concept of hormesis and its applications to the field of neuroprotection and longevity. Maintenance of optimal long-term health conditions is accomplished by a complex network of longevity assurance processes that are controlled by vitagenes, a group of genes involved in preserving cellular homeostasis during stressful conditions. Vitagenes encode for heat shock proteins (Hsp) Hsp32, Hsp70, the thioredoxin and the sirtuin protein systems. Dietary antioxidants, such as polyphenols and L-carnitine/acetyl-L-carnitine, have recently been demonstrated to be neuroprotective through the activation of hormetic pathways, including vitagenes. Hormesis provides the central underpinning of neuroprotective responses, providing a framework for explaining the common quantitative features of their dose response relationships, their mechanistic foundations, their relationship to the concept of biological plasticity as well as providing a key insight for improving the accuracy of the therapeutic dose of pharmaceutical agents within the highly heterogeneous human population. This paper describes in mechanistic detail how hormetic dose responses are mediated for endogenous cellular defense pathways including sirtuin, Nrfs and related pathways that integrate adaptive stress responses in the prevention of neurodegenerative diseases. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.
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Dieriks B, De Vos W, Baatout S, Van Oostveldt P. Repeated exposure of human fibroblasts to ionizing radiation reveals an adaptive response that is not mediated by interleukin-6 or TGF-β. Mutat Res 2011; 715:19-24. [PMID: 21784085 DOI: 10.1016/j.mrfmmm.2011.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 06/09/2011] [Accepted: 07/08/2011] [Indexed: 11/18/2022]
Abstract
Exposing cells to a low dose can protect them against a subsequent higher exposure. This phenomenon is known as adaptive response and is frequently observed in a variety of cells. Even though similarities are suspected with other non-targeted effects, such as bystander effects, the exact mechanism behind adaptive response is not fully clarified. In this study human primary fibroblasts were tested for their response to ionizing radiation (IR) after administrating a low priming dose (0.1-0.5Gy). Both the abundance of γH2AX as a marker for double-stranded breaks and the levels of cytokines, secreted in the medium, were monitored in time. Upon challenge, IR-primed cells showed modified γH2AX spot size distributions and altered repair kinetics, consistent with an adaptive response. In addition, 24h after priming with IR, four cytokines were significantly upregulated in the medium - GM-CSF (1.33×); IL6 (4.24×); IL8 (1.33×); TGF-β (1.46×). In order to mimick the protective effect of IR priming, we primed the cells with either IL6 or TGF-β. This did not elicit an altered γH2AX response as observed in IR-primed cells, indicating that the adaptive response in these primary fibroblasts is regulated in an IL-6 and TGF-β independent manner.
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Affiliation(s)
- Birger Dieriks
- Bio-imaging and Cytometry Unit, Department of Molecular Biotechnology, Ghent University, Coupure Links 653, 9000 Gent, Belgium.
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Calabrese V, Cornelius C, Dinkova-Kostova AT, Calabrese EJ, Mattson MP. Cellular stress responses, the hormesis paradigm, and vitagenes: novel targets for therapeutic intervention in neurodegenerative disorders. Antioxid Redox Signal 2010; 13:1763-811. [PMID: 20446769 PMCID: PMC2966482 DOI: 10.1089/ars.2009.3074] [Citation(s) in RCA: 566] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 04/27/2010] [Accepted: 05/01/2010] [Indexed: 12/22/2022]
Abstract
Despite the capacity of chaperones and other homeostatic components to restore folding equilibrium, cells appear poorly adapted for chronic oxidative stress that increases in cancer and in metabolic and neurodegenerative diseases. Modulation of endogenous cellular defense mechanisms represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. This article introduces the concept of hormesis and its applications to the field of neuroprotection. It is argued that the hormetic dose response provides the central underpinning of neuroprotective responses, providing a framework for explaining the common quantitative features of their dose-response relationships, their mechanistic foundations, and their relationship to the concept of biological plasticity, as well as providing a key insight for improving the accuracy of the therapeutic dose of pharmaceutical agents within the highly heterogeneous human population. This article describes in mechanistic detail how hormetic dose responses are mediated for endogenous cellular defense pathways, including sirtuin and Nrf2 and related pathways that integrate adaptive stress responses in the prevention of neurodegenerative diseases. Particular attention is given to the emerging role of nitric oxide, carbon monoxide, and hydrogen sulfide gases in hormetic-based neuroprotection and their relationship to membrane radical dynamics and mitochondrial redox signaling.
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Cellular Stress Responses, Mitostress and Carnitine Insufficiencies as Critical Determinants in Aging and Neurodegenerative Disorders: Role of Hormesis and Vitagenes. Neurochem Res 2010; 35:1880-915. [DOI: 10.1007/s11064-010-0307-z] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/21/2010] [Indexed: 02/07/2023]
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Dauer LT, Brooks AL, Hoel DG, Morgan WF, Stram D, Tran P. Review and evaluation of updated research on the health effects associated with low-dose ionising radiation. RADIATION PROTECTION DOSIMETRY 2010; 140:103-136. [PMID: 20413418 DOI: 10.1093/rpd/ncq141] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
While radiation health risks at low doses have traditionally been estimated from high-dose studies, we have reviewed recent literature and concluded that the mechanisms of action for many biological endpoints may be different at low doses from those observed at high doses; that acute doses <100 mSv may be too small to allow epidemiological detection of excess cancers given the background of naturally occurring cancers; that low-dose radiation research should use holistic approaches such as systems-based methods to develop models that define the shape of the dose-response relationship; and that these results should be combined with the latest epidemiology to produce a comprehensive understanding of radiation effects that addresses both damage, likely with a linear effect, and response, possibly with non-linear consequences. Continued research is needed to understand how radiobiology and epidemiology advances should be used to effectively model radiation worker risks.
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Affiliation(s)
- Lawrence T Dauer
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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21
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Vaiserman AM. Radiation hormesis: historical perspective and implications for low-dose cancer risk assessment. Dose Response 2010; 8:172-91. [PMID: 20585444 PMCID: PMC2889502 DOI: 10.2203/dose-response.09-037.vaiserman] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Current guidelines for limiting exposure of humans to ionizing radiation are based on the linear-no-threshold (LNT) hypothesis for radiation carcinogenesis under which cancer risk increases linearly as the radiation dose increases. With the LNT model even a very small dose could cause cancer and the model is used in establishing guidelines for limiting radiation exposure of humans. A slope change at low doses and dose rates is implemented using an empirical dose and dose rate effectiveness factor (DDREF). This imposes usually unacknowledged nonlinearity but not a threshold in the dose-response curve for cancer induction. In contrast, with the hormetic model, low doses of radiation reduce the cancer incidence while it is elevated after high doses. Based on a review of epidemiological and other data for exposure to low radiation doses and dose rates, it was found that the LNT model fails badly. Cancer risk after ordinarily encountered radiation exposure (medical X-rays, natural background radiation, etc.) is much lower than projections based on the LNT model and is often less than the risk for spontaneous cancer (a hormetic response). Understanding the mechanistic basis for hormetic responses will provide new insights about both risks and benefits from low-dose radiation exposure.
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Affiliation(s)
- Alexander M. Vaiserman
- Laboratory of Mathematical Modeling of Aging Processes, Institute of Gerontology, Kiev, Ukraine
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Brooks AL, Eberlein PE, Couch LA, Boecker BB. The role of dose-rate on risk from internally-deposited radionuclides and the potential need to separate dose-rate effectiveness factor (DREF) from the dose and dose-rate effectiveness factor (DDREF). HEALTH PHYSICS 2009; 97:458-469. [PMID: 19820455 DOI: 10.1097/hp.0b013e3181ac910e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In 1980, National Council on Radiation Protection and Measurements suggested the term dose-rate effectiveness factor (DREF) to describe the reduction of effectiveness of protracted radiation in producing biological damage and risk. A nonlinear decrease in damage was also noted following low total doses. The International Commission on Radiological Protection therefore combined the influence of low dose and low dose-rate and assigned a single value of 2.0 for a dose and dose-rate effectiveness factor (DDREF) to be applied for estimating risk for both low total dose and low dose-rate exposures. This paper re-evaluates one extensive data set on inhaled radionuclides in dogs which suggests that there may be a need to separate these factors (DREF and DDREF) for larger protracted doses from internally-deposited radioactive materials. Extensive recent research on the mechanisms of action of both low dose and low dose-rate radiation exposure at the molecular, cellular, and animal level of biological organization suggest that the influence of protraction of radiation may be large and variable, due to adaptive and protective responses, following very low doses and dose-rate exposures. Important observations in this paper in dogs exposed by inhalation to beta-gamma emitting radionuclides include (1) discontinuities in the data sets as a function of both dose and dose-rate suggesting shifts in mechanisms of action following high doses from protracted exposure away from those postulated for cancer from low total doses; (2) no increase in non-neoplastic disease, cancer frequency, or life-shortening following low dose-rate exposures to high total lung doses (up to 25 Gy); (3) all dogs that received doses below 25 Gy were combined and a decrease in the frequency of lung cancer in these exposed animals relative to the controls was noted, while very large doses from all radionuclides studied resulted in very marked increases in lung cancer; (4) a significant increase in hemangiosarcoma in the heart and tracheobronchial lymph nodes was observed after very high doses; (5) in this paper the DREF for lung cancer in dogs relative to single acute radiation exposure was as high as 35; and (6) the amount of life-shortening increased per unit dose as a function of the half-life with (90)Y being eight times as effective per unit of dose as (90)Sr. Such information suggests that there may be a need to assign different values for DDREF and DREF, especially in situations where there are large nonuniform total doses delivered by internally-deposited radionuclides. This is extremely important since the risk from radiation exposure from internally-deposited radionuclides in the lungs following nuclear fallout, accidents and terrorist activities may be much less than currently projected.
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Affiliation(s)
- Antone L Brooks
- Washington State University Tri-Cities, Richland, WA 99354, USA.
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Scott BR, Belinsky SA, Leng S, Lin Y, Wilder JA, Damiani LA. Radiation-stimulated epigenetic reprogramming of adaptive-response genes in the lung: an evolutionary gift for mounting adaptive protection against lung cancer. Dose Response 2009; 7:104-31. [PMID: 19543479 DOI: 10.2203/dose-response.08-016.scott] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Humans are continuously exposed to low-level ionizing radiation from natural sources. However, harsher radiation environments persisted during our planet's early years and mammals survived via an evolutionary gift--a system of radiation-induced natural protective measures (adaptive protection). This system includes antioxidants, DNA repair, apoptosis of severely damaged cells, epigenetically regulated apoptosis (epiapoptosis) pathways that selectively remove precancerous and other aberrant cells, and immunity against cancer. We propose a novel model in which the protective system is regulated at least in part via radiation-stress-stimulated epigenetic reprogramming (epireprogramming) of adaptive-response genes. High-dose radiation can promote epigenetically silencing of adaptive-response genes (episilencing), for example via promoter-associated DNA and/or histone methylation and/or histone deacetylation. Evidence is provided for low linear-energy-transfer (LET) radiation-activated natural protection (ANP) against high-LET alpha-radiation-induced lung cancer in plutonium-239 exposed rats and radon-progeny-exposed humans. Using a revised hormetic relative risk model for cancer induction that accounts for both epigenetic activation (epiactivation) and episilencing of genes, we demonstrate that, on average, >80% of alpha-radiation-induced rat lung cancers were prevented by chronic, low-rate gamma-ray ANP. Interestingly, lifetime exposure to residential radon at the Environmental Protection Agency's action level of 4 pCi L(-1) appears to be associated with on average a > 60% reduction in lung cancer cases, rather than an increase. We have used underlined italics to indicate newly introduced terminology.
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Affiliation(s)
- Bobby R Scott
- Lovelace Respiratory Research Institute, 2425 Ridgecrest Drive SE, Albuquerque, NM 87108, USA.
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Abstract
The hormesis concept has broad implications for biology and the biomedical sciences. This perspective on hormesis concentrates on toxicology and toxicological risk assessment and secondarily explores observations from other fields. It considers the varied manifestations of hormesis in the context of a broad family of biological stress responses. Evidence for hormesis is reviewed, and the hormesis model is contrasted with more widely accepted dose-response models in toxicology: a linear nonthreshold (LNT) model for mutagenesis and carcinogenesis, and a threshold model for most other toxicologic effects. Scientific, philosophical, and political objections to the hormesis concept are explored, and complications in the hormesis concept are analyzed. The review concludes with a perspective on the current state of hormesis and challenges that the hormesis model poses for risk assessment.
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Affiliation(s)
- George R Hoffmann
- Department of Biology, College of the Holy Cross, One College Street, Worcester, MA 01610-2395, USA.
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Scott BR. It's time for a new low-dose-radiation risk assessment paradigm--one that acknowledges hormesis. Dose Response 2007; 6:333-51. [PMID: 19088900 PMCID: PMC2592992 DOI: 10.2203/dose-response.07-005.scott] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The current system of radiation protection for humans is based on the linear-no-threshold (LNT) risk-assessment paradigm. Perceived harm to irradiated nuclear workers and the public is mainly reflected through calculated hypothetical increased cancers. The LNT-based system of protection employs easy-to-implement measures of radiation exposure. Such measures include the equivalent dose (a biological-damage-potential-weighted measure) and the effective dose (equivalent dose multiplied by a tissue-specific relative sensitivity factor for stochastic effects). These weighted doses have special units such as the sievert (Sv) and millisievert (mSv, one thousandth of a sievert). Radiation-induced harm is controlled via enforcing exposure limits expressed as effective dose. Expected cancer cases can be easily computed based on the summed effective dose (person-sievert) for an irradiated group or population. Yet the current system of radiation protection needs revision because radiation-induced natural protection (hormesis) has been neglected. A novel, nonlinear, hormetic relative risk model for radiation-induced cancers is discussed in the context of establishing new radiation exposure limits for nuclear workers and the public.
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Affiliation(s)
- Bobby R Scott
- Lovelace Respiratory Research Institute, 2425 Ridgecrest Drive SE, Albuquerque, NM 87108, USA.
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