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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 These studies formed the basis of several outdated paradigms that are either incorrect or do not hold for LDR doses.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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Dattilo S, Mancuso C, Koverech G, Di Mauro P, Ontario ML, Petralia CC, Petralia A, Maiolino L, Serra A, Calabrese EJ, Calabrese V. Heat shock proteins and hormesis in the diagnosis and treatment of neurodegenerative diseases. Immun Ageing 2015; 12:20. [PMID: 26543490 PMCID: PMC4634585 DOI: 10.1186/s12979-015-0046-8] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 10/15/2015] [Indexed: 12/16/2022]
Abstract
Modulation of endogenous cellular defense mechanisms via the vitagene system represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. The possibility of high-throughoutput screening using proteomic techniques, particularly redox proteomics, provide more comprehensive overview of the interaction of proteins, as well as the interplay among processes involved in neuroprotection. Here by introducing the hormetic dose response concept, the mechanistic foundations and applications to the field of neuroprotection, we discuss the emerging role of heat shock protein as prominent member of vitagene network in neuroprotection and redox proteomics as a tool for investigating redox modulation of stress responsive vitagenes. Hormetic mechanisms are reviewed as possibility of targeted therapeutic manipulation in a cell-, tissue- and/or pathway-specific manner at appropriate points in the neurodegenerative disease process.
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Affiliation(s)
- Sandro Dattilo
- />Department of Biomedical and Biotechnological Sciences, University of Catania, Via Andrea Doria, 95100 Catania, Italy
| | - Cesare Mancuso
- />Institute of Pharmacology, Catholic University School of Medicine, Rome, Italy
| | - Guido Koverech
- />Department of Biomedical and Biotechnological Sciences, University of Catania, Via Andrea Doria, 95100 Catania, Italy
| | - Paola Di Mauro
- />Department of Medical and Surgery Specialties, University of Catania, Catania, Italy
| | - Maria Laura Ontario
- />Department of Biomedical and Biotechnological Sciences, University of Catania, Via Andrea Doria, 95100 Catania, Italy
| | | | - Antonino Petralia
- />Department of Clinical and Experimental Medicine, School of Medicine, University of Catania, Catania, Italy
| | - Luigi Maiolino
- />Department of Medical and Surgery Specialties, University of Catania, Catania, Italy
| | - Agostino Serra
- />Department of Medical and Surgery Specialties, University of Catania, Catania, Italy
| | - Edward J. Calabrese
- />Environmental Health Sciences Division, School of Public Health, University of Massachusetts, Amherst, MA USA
| | - Vittorio Calabrese
- />Department of Biomedical and Biotechnological Sciences, University of Catania, Via Andrea Doria, 95100 Catania, Italy
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Tomita M, Maeda M. Mechanisms and biological importance of photon-induced bystander responses: do they have an impact on low-dose radiation responses. JOURNAL OF RADIATION RESEARCH 2015; 56:205-19. [PMID: 25361549 PMCID: PMC4380047 DOI: 10.1093/jrr/rru099] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2014] [Revised: 09/19/2014] [Accepted: 09/29/2014] [Indexed: 06/01/2023]
Abstract
Elucidating the biological effect of low linear energy transfer (LET), low-dose and/or low-dose-rate ionizing radiation is essential in ensuring radiation safety. Over the past two decades, non-targeted effects, which are not only a direct consequence of radiation-induced initial lesions produced in cellular DNA but also of intra- and inter-cellular communications involving both targeted and non-targeted cells, have been reported and are currently defining a new paradigm in radiation biology. These effects include radiation-induced adaptive response, low-dose hypersensitivity, genomic instability, and radiation-induced bystander response (RIBR). RIBR is generally defined as a cellular response that is induced in non-irradiated cells that receive bystander signals from directly irradiated cells. RIBR could thus play an important biological role in low-dose irradiation conditions. However, this suggestion was mainly based on findings obtained using high-LET charged-particle radiations. The human population (especially the Japanese, who are exposed to lower doses of radon than the world average) is more frequently exposed to low-LET photons (X-rays or γ-rays) than to high-LET charged-particle radiation on a daily basis. There are currently a growing number of reports describing a distinguishing feature between photon-induced bystander response and high-LET RIBR. In particular, photon-induced bystander response is strongly influenced by irradiation dose, the irradiated region of the targeted cells, and p53 status. The present review focuses on the photon-induced bystander response, and discusses its impact on the low-dose radiation effect.
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Affiliation(s)
- Masanori Tomita
- Radiation Safety Research Center, Central Research Institute of Electric Power Industry, 2-11-1 Iwado Kita, Komae, Tokyo 201-8511, Japan
| | - Munetoshi Maeda
- Radiation Safety Research Center, Central Research Institute of Electric Power Industry, 2-11-1 Iwado Kita, Komae, Tokyo 201-8511, Japan Proton Medical Research Group, Research and Development Department, The Wakasa Wan Energy Research Center, 64-52-1 Nagatani, Tsuruga-shi, Fukui 914-0192, Japan
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Ormsby RJ, Lawrence MD, Blyth BJ, Bexis K, Bezak E, Murley JS, Grdina DJ, Sykes PJ. Protection from radiation-induced apoptosis by the radioprotector amifostine (WR-2721) is radiation dose dependent. Cell Biol Toxicol 2014; 30:55-66. [DOI: 10.1007/s10565-014-9268-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 01/09/2014] [Indexed: 12/11/2022]
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False-positive TUNEL staining observed in SV40 based transgenic murine prostate cancer models. Transgenic Res 2013; 22:1037-47. [PMID: 23423848 DOI: 10.1007/s11248-013-9694-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 02/04/2013] [Indexed: 10/27/2022]
Abstract
The TRAMP (Transgenic Adenocarcinoma of the Mouse Prostate) and LADY (Probasin-large T antigen transgenic mouse) mice are widely used autochthonous models of prostate cancer. Both models utilise probasin promoters to direct androgen-regulated expression of oncogenic SV40 specifically to epithelial cells of the mouse prostate. The oncogenic processes and phenotypes which result mimic many features of human prostate cancer, making these transgenic mouse models useful experimental systems. The terminal deoxynucleotidyl transferase (Tdt)-mediated dUTP in situ nick end labelling (TUNEL) assay is a commonly used method for the detection of cells undergoing apoptosis. In this study, we demonstrate false-positive TUNEL staining in frozen prostate tissue from TRAMP and LADY mice, which was not observed in non-transgenic control animals and is not due to non-specific binding of labelled-dUTP substrate. The false-positive signal co-localised with large SV40 T-antigen expression. False-positive signal was apparent using multiple commercial TUNEL kits with different detection systems. These results caution against the use of the TUNEL assay for detection of apoptosis in frozen prostate tissue of large T-antigen based autochthonous transgenic models of prostate cancer.
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Sugihara T, Murano H, Nakamura M, Tanaka K. In Vivo Partial Bystander Study in a Mouse Model by Chronic Medium-Dose-Rate γ-Ray Irradiation. Radiat Res 2013; 179:221-31. [DOI: 10.1667/rr3081.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Takashi Sugihara
- Department of Radiobiology, Institute for Environmental Sciences, 2-121 Hacchazawa Takahoko, Rokkasho, Kamikita, Aomori 039-3213, Japan
| | - Hayato Murano
- Tohoku Environmental Sciences Services Corporation, 330-2 Noduki, Obuchi, Rokkasho, Kamikita, Aomori 039-3212, Japan
| | - Masako Nakamura
- Tohoku Environmental Sciences Services Corporation, 330-2 Noduki, Obuchi, Rokkasho, Kamikita, Aomori 039-3212, Japan
| | - Kimio Tanaka
- Department of Radiobiology, Institute for Environmental Sciences, 2-121 Hacchazawa Takahoko, Rokkasho, Kamikita, Aomori 039-3213, Japan
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Akudugu JM, Azzam EI, Howell RW. Induction of lethal bystander effects in human breast cancer cell cultures by DNA-incorporated Iodine-125 depends on phenotype. Int J Radiat Biol 2012; 88:1028-38. [PMID: 22489958 DOI: 10.3109/09553002.2012.683511] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE This study uses a three-dimensional cell culture model to investigate lethal bystander effects in human breast cancer cell cultures (MCF-7, MDA-MB-231) treated with (125)I-labeled 5-iodo-2 -deoxyuridine ((125)IdU). These breast cancer cell lines respectively form metastatic xenografts in nude mice in an estrogen-dependent and independent manner. MATERIALS AND METHODS In the present study, these cells were cultured in loosely-packed three-dimensional architecture in a Cytomatrix™ carbon scaffold. Cultures were pulse-labeled for 3 h with (125)IdU to selectively irradiate a minor fraction of cells, and simultaneously co-pulse-labeled with 0.04 mM 5-ethynyl-2'-deoxyuridine (EdU) to identify the radiolabeled cells using Click-iT(®) EdU and flow cytometry. The cultures were then washed and incubated for 48 h. The cells were then harvested, serially diluted, and seeded for colony formation. Aliquots of cells were subjected to flow cytometry to determine the percentage of cells labeled with (125)IdU/EdU. Additional aliquots were used to determine the mean (125)I activity per labeled cell. The percentage of labeled cells was about 15% and 10% for MCF-7 and MDA cells, respectively. This created irradiation conditions wherein the cross-dose to unlabeled cells was small relative to the self-dose to labeled cells. The surviving fraction relative to EdU-treated controls was measured. RESULTS Survival curves indicated significant lethal bystander effect in MCF-7 cells, however, no significant lethal bystander effect was observed in MDA-MB-231 cells. CONCLUSIONS These studies demonstrate the capacity of (125)IdU to induce lethal bystander effects in human breast cancer cells and suggest that the response depends on phenotype.
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Affiliation(s)
- John M Akudugu
- Division of Radiation Research, Department of Radiology, New Jersey Medical School Cancer Center, University of Medicine & Dentistry of New Jersey, Newark, New Jersey 07103, USA.
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Vinnikov V, Lloyd D, Finnon P. Bystander apoptosis in human cells mediated by irradiated blood plasma. Mutat Res 2012; 731:107-116. [PMID: 22230196 DOI: 10.1016/j.mrfmmm.2011.12.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 10/11/2011] [Accepted: 12/13/2011] [Indexed: 05/31/2023]
Abstract
Following exposure to high doses of ionizing radiation, due to an accident or during radiotherapy, bystander signalling poses a potential hazard to unirradiated cells and tissues. This process can be mediated by factors circulating in blood plasma. Thus, we assessed the ability of plasma taken from in vitro irradiated human blood to produce a direct cytotoxic effect, by inducing apoptosis in primary human peripheral blood mononuclear cells (PBM), which mainly comprised G(0)-stage lymphocytes. Plasma was collected from healthy donors' blood irradiated in vitro to 0-40Gy acute γ-rays. Reporter PBM were separated from unirradiated blood with Histopaque and held in medium with the test plasma for 24h at 37°C. Additionally, plasma from in vitro irradiated and unirradiated blood was tested against PBM collected from blood given 4Gy. Apoptosis in reporter PBM was measured by the Annexin V test using flow cytometry. Plasma collected from unirradiated and irradiated blood did not produce any apoptotic response above the control level in unirradiated reporter PBM. Surprisingly, plasma from irradiated blood caused a dose-dependent reduction of apoptosis in irradiated reporter PBM. The yields of radiation-induced cell death in irradiated reporter PBM (after subtracting the respective values in unirradiated reporter PBM) were 22.2±1.8% in plasma-free cultures, 21.6±1.1% in cultures treated with plasma from unirradiated blood, 20.2±1.4% in cultures with plasma from blood given 2-4Gy and 16.7±3.2% in cultures with plasma from blood given 6-10Gy. These results suggested that irradiated blood plasma did not cause a radiation-induced bystander cell-killing effect. Instead, a reduction of apoptosis in irradiated reporter cells cultured with irradiated blood plasma has implications concerning oncogenic risk from mutated cells surviving after high dose in vivo irradiation (e.g. radiotherapy) and requires further study.
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Abdelrazzak AB, Stevens DL, Bauer G, O'Neill P, Hill MA. The Role of Radiation Quality in the Stimulation of Intercellular Induction of Apoptosis in Transformed Cells at Very Low Doses. Radiat Res 2011; 176:346-55. [DOI: 10.1667/rr2509.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Abdelrazek B. Abdelrazzak
- CRUK/MRC Gray Institute for Radiation Oncology & Biology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, United Kingdom
| | - David L. Stevens
- CRUK/MRC Gray Institute for Radiation Oncology & Biology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, United Kingdom
| | - Georg Bauer
- Department of Virology, Institute of Medical Microbiology and Hygiene, University of Freiburg, D-79104 Freiburg, Germany
| | - Peter O'Neill
- CRUK/MRC Gray Institute for Radiation Oncology & Biology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, United Kingdom
| | - Mark A. Hill
- CRUK/MRC Gray Institute for Radiation Oncology & Biology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, United Kingdom
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Blyth BJ, Sykes PJ. Radiation-induced bystander effects: what are they, and how relevant are they to human radiation exposures? Radiat Res 2011; 176:139-57. [PMID: 21631286 DOI: 10.1667/rr2548.1] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The term radiation-induced bystander effect is used to describe radiation-induced biological changes that manifest in unirradiated cells remaining within an irradiated cell population. Despite their failure to fit into the framework of classical radiobiology, radiation-induced bystander effects have entered the mainstream and have become established in the radiobiology vocabulary as a bona fide radiation response. However, there is still no consensus on a precise definition of radiation-induced bystander effects, which currently encompasses a number of distinct signal-mediated effects. These effects are classified here into three classes: bystander effects, abscopal effects and cohort effects. In this review, the data have been evaluated to define, where possible, various features specific to radiation-induced bystander effects, including their timing, range, potency and dependence on dose, dose rate, radiation quality and cell type. The weight of evidence supporting these defining features is discussed in the context of bystander experimental systems that closely replicate realistic human exposure scenarios. Whether the manifestation of bystander effects in vivo is intrinsically limited to particular radiation exposure scenarios is considered. The conditions under which radiation-induced bystander effects are induced in vivo will ultimately determine their impact on radiation-induced carcinogenic risk.
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Affiliation(s)
- Benjamin J Blyth
- Haematology and Genetic Pathology, Flinders University, Bedford Park, South Australia 5042, Australia
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Staudacher AH, Blyth BJ, Lawrence MD, Ormsby RJ, Bezak E, Sykes PJ. If bystander effects for apoptosis occur in spleen after low-dose irradiation in vivo then the magnitude of the effect falls within the range of normal homeostatic apoptosis. Radiat Res 2010; 174:727-31. [PMID: 21128796 DOI: 10.1667/rr2300.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
To test whether bystander effects occur in vivo after low doses of radiation relevant to occupational and population exposure, we exposed mice to whole-body X-radiation doses (0.01 and 1 mGy) where only a proportion of cells would receive an electron track. We used a precise method to analyze the apoptosis frequency in situ in spleen tissue sections at 7 h and 1, 3 and 7 days after irradiation to determine whether an increase in apoptosis above that predicted by direct effects was observed. No significant changes in the apoptosis frequency at any time after low-dose irradiation were detected. Apoptosis was induced above endogenous levels by five- to sevenfold 7 h after 1000 mGy. Using these data, the expected increases in apoptosis 7 h after a dose of 1 mGy or 0.01 mGy were calculated based on the assumption that induction of apoptosis would decrease linearly with dose. The magnitude of potential bystander effects for apoptosis that could be detected above homeostatic levels after these low doses of radiation was determined. A substantial bystander effect for apoptosis (>50-fold above direct effects) would be required before such proposed effects would be identified using 10 animals/treatment group as studied here. These data demonstrate that amplification of apoptosis even due to a substantial bystander effect would fall within the homeostatic range.
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Affiliation(s)
- Alexander H Staudacher
- Haematology and Genetic Pathology, Flinders University, Bedford Park, South Australia, 5042
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