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Okonkwo UC, Ohagwu CC, Aronu ME, Okafor CE, Idumah CI, Okokpujie IP, Chukwu NN, Chukwunyelu CE. Ionizing radiation protection and the linear No-threshold controversy: Extent of support or counter to the prevailing paradigm. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2022; 253-254:106984. [PMID: 36057228 DOI: 10.1016/j.jenvrad.2022.106984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 08/07/2022] [Indexed: 06/15/2023]
Abstract
This study has developed a relationship that categorized radiation protection and allows for a proper, clear, and concise review of the different classifications in terms of principles of protection, dose criteria, categories, fundamental tools, exposure situations, applications and control measures. With the groundwork laid, advances of the linear no-threshold (LNT) model which has attracted attention in the field of radiobiology and epidemiology were examined in detail. Various plausible dose-response relationship scenarios were x-rayed under low-dose extrapolation. Intensive review of factors opposing the LNT model involving radiophobia (including misdiagnosis, alternative surgery/imaging, suppression of ionizing radiation (IR) research); radiobiology (including DNA damage repair, apoptosis/necrosis, senescence protection) and cost issues (including-high operating cost of LNT, incorrect prioritization, exaggeration of LNT impact, risk-to-benefit analysis) were performed. On the other hand, factors supporting the use of LNT were equally examined, they include regulatory bodies' endorsement, insufficient statistical significance, partial DNA repair, variability of irradiated bodies, different latency periods for cancer, dynamic nature of threshold and conflicting interests. After considering the gaps in the scientific investigations that either support or counter the scientific paradigm on the use of LNT model, further research and advocacy is recommended that will ultimately lead to the acceptance of an alternative paradigm by the international regulators.
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Affiliation(s)
- Ugochukwu C Okonkwo
- Department of Mechanical Engineering, Nnamdi Azikiwe University, Awka, Nigeria.
| | - Christopher C Ohagwu
- Department of Radiography and Radiological Sciences, Nnamdi Azikiwe University, Awka, Nigeria
| | - Michael E Aronu
- Department of Radiology, Nnamdi Azikiwe University, Awka, Nigeria
| | - Christian E Okafor
- Department of Mechanical Engineering, Nnamdi Azikiwe University, Awka, Nigeria
| | - Christopher I Idumah
- Department of Polymer and Textile Engineering, Nnamdi Azikiwe University, Awka, Nigeria
| | - Imhade P Okokpujie
- Department of Mechanical and Mechatronic Engineering, Afe-Babalola University, Ado-Ekiti, Nigeria
| | - Nelson N Chukwu
- National Engineering Design Development Institute, Nnewi, Anambra State, Nigeria
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2
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Fornalski KW, Adamowski Ł, Dobrzyński L, Jarmakiewicz R, Powojska A, Reszczyńska J. The radiation adaptive response and priming dose influence: the quantification of the Raper-Yonezawa effect and its three-parameter model for postradiation DNA lesions and mutations. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2022; 61:221-239. [PMID: 35150289 PMCID: PMC9021059 DOI: 10.1007/s00411-022-00963-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 01/12/2022] [Indexed: 05/14/2023]
Abstract
The priming dose effect, called also the Raper-Yonezawa effect or simply the Yonezawa effect, is a special case of the radiation adaptive response phenomenon (radioadaptation), which refers to: (a) faster repair of direct DNA lesions (damage), and (b) DNA mutation frequency reduction after irradiation, by applying a small priming (conditioning) dose prior to the high detrimental (challenging) one. This effect is observed in many (but not all) radiobiological experiments which present the reduction of lesion, mutation or even mortality frequency of the irradiated cells or species. Additionally, the multi-parameter model created by Dr. Yonezawa and collaborators tried to explain it theoretically based on experimental data on the mortality of mice with chronic internal irradiation. The presented paper proposes a new theoretical approach to understanding and explaining the priming dose effect: it starts from the radiation adaptive response theory and moves to the three-parameter model, separately for two previously mentioned situations: creation of fast (lesions) and delayed damage (mutations). The proposed biophysical model was applied to experimental data-lesions in human lymphocytes and chromosomal inversions in mice-and was shown to be able to predict the Yonezawa effect for future investigations. It was also found that the strongest radioadaptation is correlated with the weakest cellular radiosensitivity. Additional discussions were focussed on more general situations where many small priming doses are used.
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Affiliation(s)
- Krzysztof W Fornalski
- National Centre for Nuclear Research (NCBJ), ul. A. Sołtana 7, 05-400, Otwock-Świerk, Poland.
| | - Łukasz Adamowski
- National Centre for Nuclear Research (NCBJ), ul. A. Sołtana 7, 05-400, Otwock-Świerk, Poland
| | - Ludwik Dobrzyński
- National Centre for Nuclear Research (NCBJ), ul. A. Sołtana 7, 05-400, Otwock-Świerk, Poland
| | - Rafał Jarmakiewicz
- Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662, Warsaw, Poland
| | - Aleksandra Powojska
- Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662, Warsaw, Poland
| | - Joanna Reszczyńska
- Department of Biophysics, Physiology and Pathophysiology, Faculty of Health Sciences, Medical University of Warsaw (WUM), ul. T. Chałubińskiego 5, 02-004, Warsaw, Poland
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López-Nieva P, González-Vasconcellos I, González-Sánchez L, Cobos-Fernández MA, Ruiz-García S, Sánchez Pérez R, Aroca Á, Fernández-Piqueras J, Santos J. Differential molecular response in mice and human thymocytes exposed to a combined-dose radiation regime. Sci Rep 2022; 12:3144. [PMID: 35210498 PMCID: PMC8873405 DOI: 10.1038/s41598-022-07166-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 02/11/2022] [Indexed: 11/17/2022] Open
Abstract
In the quest for more effective radiation treatment options that can improve both cell killing and healthy tissue recovery, combined radiation therapies are lately in the spotlight. The molecular response to a combined radiation regime where exposure to an initial low dose (priming dose) of ionizing radiation is administered prior to a subsequent higher radiation dose (challenging dose) after a given latency period have not been thoroughly explored. In this study we report on the differential response to either a combined radiation regime or a single challenging dose both in mouse in vivo and in human ex vivo thymocytes. A differential cell cycle response including an increase in the subG1 fraction on cells exposed to the combined regime was found. Together with this, a differential protein expression profiling in several pathways including cell cycle control (ATM, TP53, p21CDKN1A), damage response (γH2AX) and cell death pathways such as apoptosis (Cleaved Caspase-3, PARP1, PKCδ and H3T45ph) and ferroptosis (xCT/GPX4) was demonstrated. This study also shows the epigenetic regulation following a combined regime that alters the expression of chromatin modifiers such as DNMTs (DNMT1, DNMT2, DNMT3A, DNMT3B, DNMT3L) and glycosylases (MBD4 and TDG). Furthermore, a study of the underlying cellular status six hours after the priming dose alone showed evidence of retained modifications on the molecular and epigenetic pathways suggesting that the priming dose infers a “radiation awareness phenotype” to the thymocytes, a sensitization key to the differential response seen after the second hit with the challenging dose. These data suggest that combined-dose radiation regimes could be more efficient at making cells respond to radiation and it would be interesting to further investigate how can these schemes be of use to potential new radiation therapies.
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Affiliation(s)
- Pilar López-Nieva
- Genome Dynamics and Function Program, Genome Decoding Unit, Severo Ochoa Molecular Biology Center, Madrid, Spain. .,Department of Biology, Madrid Autonomous University, 28049, Madrid, Spain. .,Institute of Health Research, Jiménez Díaz Foundation, 28040, Madrid, Spain.
| | - Iria González-Vasconcellos
- Genome Dynamics and Function Program, Genome Decoding Unit, Severo Ochoa Molecular Biology Center, Madrid, Spain. .,Department of Biology, Madrid Autonomous University, 28049, Madrid, Spain.
| | - Laura González-Sánchez
- Genome Dynamics and Function Program, Genome Decoding Unit, Severo Ochoa Molecular Biology Center, Madrid, Spain.,Institute of Health Research, Jiménez Díaz Foundation, 28040, Madrid, Spain.,Consorcio de Investigación Biomédica de Enfermedades Raras (CIBERER), Madrid, Spain
| | - María A Cobos-Fernández
- Genome Dynamics and Function Program, Genome Decoding Unit, Severo Ochoa Molecular Biology Center, Madrid, Spain.,Department of Biology, Madrid Autonomous University, 28049, Madrid, Spain
| | - Sara Ruiz-García
- Genome Dynamics and Function Program, Genome Decoding Unit, Severo Ochoa Molecular Biology Center, Madrid, Spain.,Department of Biology, Madrid Autonomous University, 28049, Madrid, Spain
| | - Raúl Sánchez Pérez
- Department of Congenital Cardiac Surgery, Hospital Universitario La Paz, 28046, Madrid, Spain
| | - Ángel Aroca
- Department of Congenital Cardiac Surgery, Hospital Universitario La Paz, 28046, Madrid, Spain
| | - José Fernández-Piqueras
- Genome Dynamics and Function Program, Genome Decoding Unit, Severo Ochoa Molecular Biology Center, Madrid, Spain.,Department of Biology, Madrid Autonomous University, 28049, Madrid, Spain.,Institute of Health Research, Jiménez Díaz Foundation, 28040, Madrid, Spain
| | - Javier Santos
- Genome Dynamics and Function Program, Genome Decoding Unit, Severo Ochoa Molecular Biology Center, Madrid, Spain.,Department of Biology, Madrid Autonomous University, 28049, Madrid, Spain.,Institute of Health Research, Jiménez Díaz Foundation, 28040, Madrid, Spain
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He CQ, Mao L, Yao J, Zhao WC, Huang B, Hu N, Long DX. The Threshold Effects of Low-Dose-Rate Radiation on miRNA-Mediated Neurodevelopment of Zebrafish. Radiat Res 2021; 196:633-646. [PMID: 34399425 DOI: 10.1667/rade-20-00265.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 07/29/2021] [Indexed: 11/03/2022]
Abstract
The biological effects and regulatory mechanisms of low-dose and low-dose-rate radiation are still rather controversial. Therefore, in this study we investigated the effects of low-dose-rate radiation on zebrafish neurodevelopment and the role of miRNAs in radiation-induced neurodevelopment. Zebrafish embryos received prolonged gamma-ray irradiation (0 mGy/h, 0.1 mGy/h, 0.2 mGy/h, 0.4 mGy/h) during development. Neurodevelopmental indicators included mortality, malformation rate, swimming speed, as well as the morphology changes of the lateral line system and brain tissue. Additionally, spatiotemporal expression of development-related miRNAs (dre-miR-196a-5p, dre-miR-210-3p, dre-miR-338) and miRNA processing enzymes genes (Dicer and Drosha) were assessed by qRT-PCR and whole mount in situ hybridization (WISH). The results revealed a decline in mortality, malformation and swimming speed, with normal histological and morphological appearance, in zebrafish that received 0.1 mGy/h; however, increased mortality, malformation and swimming speed were observed, with pathological changes, in zebrafish that received 0.2 mGy/h and 0.4 mGy/h. The expression of miRNA processing enzyme genes was altered after irradiation, and miRNAs expression was downregulated in the 0.1 mGy/h group, and upregulated in the 0.2 mGy/h and 0.4 mGy/h groups. Furthermore, ectopic expression of dre-miR-210-3p, Dicer and Drosha was also observed in the 0.4 mGy/h group. In conclusion, the effect of low-dose and low-dose-rate radiation on neurodevelopment follows the threshold model, under the regulation of miRNAs, excitatory effects occurred at a dose rate of 0.1 mGy/h and toxic effects occurred at a dose rate of 0.2 mGy/h and 0.4 mGy/h.
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Affiliation(s)
- Chu-Qi He
- School of Public Health, University of South China, Hengyang 421001, PR China.,Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, Hengyang, Hunan 421001, China
| | - Liang Mao
- School of Public Health, University of South China, Hengyang 421001, PR China.,Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, Hengyang, Hunan 421001, China
| | - Jin Yao
- School of Public Health, University of South China, Hengyang 421001, PR China.,Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, Hengyang, Hunan 421001, China
| | - Wei-Chao Zhao
- School of Public Health, University of South China, Hengyang 421001, PR China.,Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, Hengyang, Hunan 421001, China
| | - Bo Huang
- School of Public Health, University of South China, Hengyang 421001, PR China.,Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, Hengyang, Hunan 421001, China
| | - Nan Hu
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, Hunan 421001, China
| | - Ding-Xin Long
- School of Public Health, University of South China, Hengyang 421001, PR China.,Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, Hengyang, Hunan 421001, China
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Ha HJ, Subburaj S, Kim YS, Kim JB, Kang SY, Lee GJ. Molecular Characterization and Identification of Calnexin 1 As a Radiation Biomarker from Tradescantia BNL4430. PLANTS 2020; 9:plants9030387. [PMID: 32245094 PMCID: PMC7154805 DOI: 10.3390/plants9030387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 03/19/2020] [Accepted: 03/19/2020] [Indexed: 01/09/2023]
Abstract
Calnexin (CNX) is an integral membrane protein that functions as a chaperone in the endoplasmic reticulum for the correct folding of proteins under stress conditions, rendering organisms tolerant under adverse conditions. Studies have investigated the cytogenetic effects of gamma irradiation (Ɣ-IR) on plants, but information on the molecular response under Ɣ-IR remains limited. Previously, we constructed a cDNA library of an irradiation-sensitive bioindicator plant, Tradescantia BNL4430 (T-4430) under Ɣ-IR, in which the Calnexin-1 gene was highly upregulated at 50 mGy treatment. TrCNX1 encodes a 61.4 kDa protein with conserved signature motifs similar to already reported CNX1s. TrCNX1 expression was evaluated by semiquantitative reverse transcriptase PCR and quantitative real-time PCR and was ubiquitously expressed in various tissues and highly upregulated in flower petals under 50 mGy Ɣ-IR stress. The protective function of TrCNX1 was investigated by overexpression of TrCNX1 in an Escherichia coli BL21(DE3) heterologous system. Using plate assay, we showed that TrCNX1 increased the viability of E. coli transformants under both UV-B and Ɣ-IR compared with the control, demonstrating that TrCNX1 functions under irradiation stress. TrCNX1 may enhance irradiation stress tolerance in crops and act as a radio marker gene to monitor the effects of radiation.
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Affiliation(s)
- Hye-Jeong Ha
- Department of Horticulture, Chungnam National University, Daejeon 34134, Korea; (H.-J.H.); (S.S.); (Y.-S.K.)
| | - Saminathan Subburaj
- Department of Horticulture, Chungnam National University, Daejeon 34134, Korea; (H.-J.H.); (S.S.); (Y.-S.K.)
| | - Young-Sun Kim
- Department of Horticulture, Chungnam National University, Daejeon 34134, Korea; (H.-J.H.); (S.S.); (Y.-S.K.)
- Devision of Environmental Science, Daegu University, Gyungsan 38453, Korea
| | - Jin-Baek Kim
- Korea Atomic Energy Research Institute, Jeongeup, Jeonbuk 580-185, Korea; (J.-B.K.); (S.-Y.K.)
| | - Si-Yong Kang
- Korea Atomic Energy Research Institute, Jeongeup, Jeonbuk 580-185, Korea; (J.-B.K.); (S.-Y.K.)
| | - Geung-Joo Lee
- Department of Horticulture, Chungnam National University, Daejeon 34134, Korea; (H.-J.H.); (S.S.); (Y.-S.K.)
- Department of Smart Agriculture Systems, Chungnam National University, Daejeon 34134, Korea
- Correspondence: ; Tel.: +82-42-821-5734; Fax: +82-42-823-1382
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Nilsson R, Tong J. Opinion on reconsideration of lung cancer risk from domestic radon exposure. RADIATION MEDICINE AND PROTECTION 2020. [DOI: 10.1016/j.radmp.2020.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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7
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Sisakht M, Darabian M, Mahmoodzadeh A, Bazi A, Shafiee SM, Mokarram P, Khoshdel Z. The role of radiation induced oxidative stress as a regulator of radio-adaptive responses. Int J Radiat Biol 2020; 96:561-576. [PMID: 31976798 DOI: 10.1080/09553002.2020.1721597] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Purpose: Various sources of radiation including radiofrequency, electromagnetic radiation (EMR), low- dose X-radiation, low-level microwave radiation and ionizing radiation (IR) are indispensable parts of modern life. In the current review, we discussed the adaptive responses of biological systems to radiation with a focus on the impacts of radiation-induced oxidative stress (RIOS) and its molecular downstream signaling pathways.Materials and methods: A comprehensive search was conducted in Web of Sciences, PubMed, Scopus, Google Scholar, Embase, and Cochrane Library. Keywords included Mesh terms of "radiation," "electromagnetic radiation," "adaptive immunity," "oxidative stress," and "immune checkpoints." Manuscripts published up until December 2019 were included.Results: RIOS induces various molecular adaptors connected with adaptive responses in radiation exposed cells. One of these adaptors includes p53 which promotes various cellular signaling pathways. RIOS also activates the intrinsic apoptotic pathway by depolarization of the mitochondrial membrane potential and activating the caspase apoptotic cascade. RIOS is also involved in radiation-induced proliferative responses through interaction with mitogen-activated protein kinases (MAPks) including p38 MAPK, ERK, and c-Jun N-terminal kinase (JNK). Protein kinase B (Akt)/phosphoinositide 3-kinase (PI3K) signaling pathway has also been reported to be involved in RIOS-induced proliferative responses. Furthermore, RIOS promotes genetic instability by introducing DNA structural and epigenetic alterations, as well as attenuating DNA repair mechanisms. Inflammatory transcription factors including macrophage migration inhibitory factor (MIF), nuclear factor κB (NF-κB), and signal transducer and activator of transcription-3 (STAT-3) paly major role in RIOS-induced inflammation.Conclusion: In conclusion, RIOS considerably contributes to radiation induced adaptive responses. Other possible molecular adaptors modulating RIOS-induced responses are yet to be divulged in future studies.
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Affiliation(s)
- Mohsen Sisakht
- Department of Medical Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Maryam Darabian
- Department of Radiology, Faculty of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Amir Mahmoodzadeh
- Department of Medical Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.,Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Ali Bazi
- Faculty of Allied Medical Sciences, Zabol University of Medical Sciences, Zabol, Iran
| | - Sayed Mohammad Shafiee
- Department of Medical Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Pooneh Mokarram
- Department of Medical Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Zahra Khoshdel
- Department of Medical Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
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Rodríguez-Martínez S, Galván I. A source of exogenous oxidative stress improves oxidative status and favors pheomelanin synthesis in zebra finches. Comp Biochem Physiol C Toxicol Pharmacol 2020; 228:108667. [PMID: 31712186 DOI: 10.1016/j.cbpc.2019.108667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 10/25/2019] [Accepted: 11/05/2019] [Indexed: 11/22/2022]
Abstract
Some organisms can modulate gene expression to trigger physiological responses that help adapt to environmental stress. The synthesis of the pigment pheomelanin in melanocytes seems to be one of these responses, as it may contribute to cellular homeostasis. We experimentally induced environmental oxidative stress in male zebra finches Taeniopygia guttata by the administration of the herbicide diquat dibromide during feather growth to test if the expression of genes involved in pheomelanin synthesis shows epigenetic lability. As pheomelanin synthesis implies decreasing the availability of the main cellular antioxidant (glutathione), it is expected to cause oxidative stress unless a protective mechanism limits pheomelanin synthesis and thus favors the antioxidant capacity. However, diquat exposure did not only improve the antioxidant capacity of birds, but also upregulated the expression of a gene (AGRP) that promotes pheomelanin synthesis in feather melanocytes, leading to the development of darker plumage coloration. No changes in the expression of other genes involved in pheomelanin synthesis (Slc7a11, Slc45a2, MC1R, ASIP and CTNS) were detected. DNA methylation levels only changed in MC1R, suggesting that epigenetic modifications other than changes in methylation may regulate AGRP expression lability. Our results suggest that exogenous oxidative stress induced a hormetic response that enhanced the oxidative status of birds and, consequently, promoted pheomelanin-based pigmentation, supporting the idea that birds adjust pheomelanin synthesis to their oxidative stress conditions.
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Affiliation(s)
| | - Ismael Galván
- Departamento de Ecología Evolutiva, Estación Biológica de Doñana, CSIC, Sevilla, Spain
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Dobrzyński L, Fornalski KW, Reszczyńska J, Janiak MK. Modeling Cell Reactions to Ionizing Radiation: From a Lesion to a Cancer. Dose Response 2019; 17:1559325819838434. [PMID: 31001068 PMCID: PMC6454661 DOI: 10.1177/1559325819838434] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 01/15/2019] [Indexed: 01/19/2023] Open
Abstract
This article focuses on the analytic modeling of responses of cells in the body to ionizing radiation. The related mechanisms are consecutively taken into account and discussed. A model of the dose- and time-dependent adaptive response is considered for 2 exposure categories: acute and protracted. In case of the latter exposure, we demonstrate that the response plateaus are expected under the modelling assumptions made. The expected total number of cancer cells as a function of time turns out to be perfectly described by the Gompertz function. The transition from a collection of cancer cells into a tumor is discussed at length. Special emphasis is put on the fact that characterizing the growth of a tumor (ie, the increasing mass and volume), the use of differential equations cannot properly capture the key dynamics-formation of the tumor must exhibit properties of the phase transition, including self-organization and even self-organized criticality. As an example, a manageable percolation-type phase transition approach is used to address this problem. Nevertheless, general theory of tumor emergence is difficult to work out mathematically because experimental observations are limited to the relatively large tumors. Hence, determination of the conditions around the critical point is uncertain.
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Affiliation(s)
- L. Dobrzyński
- National Centre for Nuclear Research (NCBJ), Otwock-Świerk,
Poland
| | - K. W. Fornalski
- National Centre for Nuclear Research (NCBJ), Otwock-Świerk,
Poland
- Ex-Polon Laboratory, Łazy, Poland
| | - J. Reszczyńska
- National Centre for Nuclear Research (NCBJ), Otwock-Świerk,
Poland
| | - M. K. Janiak
- Department of Radiobiology and Radiation Protection, Military
Institute of Hygiene and Epidemiology (WIHE), Warszawa, Poland
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Zarnke AM, Tharmalingam S, Boreham DR, Brooks AL. BEIR VI radon: The rest of the story. Chem Biol Interact 2019; 301:81-87. [DOI: 10.1016/j.cbi.2018.11.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/19/2018] [Accepted: 11/22/2018] [Indexed: 12/13/2022]
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11
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The LNT model for cancer induction is not supported by radiobiological data. Chem Biol Interact 2019; 301:34-53. [PMID: 30763552 DOI: 10.1016/j.cbi.2019.01.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Revised: 01/07/2019] [Accepted: 01/09/2019] [Indexed: 12/18/2022]
Abstract
The hallmarks of cancer have been the focus of much research and have influenced the development of risk models for radiation-induced cancer. However, natural defenses against cancer, which constitute the hallmarks of cancer prevention, have largely been neglected in developing cancer risk models. These natural defenses are enhanced by low doses and dose rates of ionizing radiation, which has aided in the continuation of human life over many generations. Our natural defenses operate at the molecular, cellular, tissue, and whole-body levels and include epigenetically regulated (epiregulated) DNA damage repair and antioxidant production, selective p53-independent apoptosis of aberrant cells (e.g. neoplastically transformed and tumor cells), suppression of cancer-promoting inflammation, and anticancer immunity (both innate and adaptive components). This publication reviews the scientific bases for the indicated cancer-preventing natural defenses and evaluates their implication for assessing cancer risk after exposure to low radiation doses and dose rates. Based on the extensive radiobiological evidence reviewed, it is concluded that the linear-no-threshold (LNT) model (which ignores natural defenses against cancer), as it relates to cancer risk from ionizing radiation, is highly implausible. Plausible models include dose-threshold and hormetic models. More research is needed to establish when a given model (threshold, hormetic, or other) applies to a given low-dose-radiation exposure scenario.
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Vaiserman A, Koliada A, Zabuga O, Socol Y. Health Impacts of Low-Dose Ionizing Radiation: Current Scientific Debates and Regulatory Issues. Dose Response 2018; 16:1559325818796331. [PMID: 30263019 PMCID: PMC6149023 DOI: 10.1177/1559325818796331] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 07/30/2018] [Accepted: 07/31/2018] [Indexed: 12/31/2022] Open
Abstract
Health impacts of low-dose ionizing radiation are significant in important fields such as X-ray imaging, radiation therapy, nuclear power, and others. However, all existing and potential applications are currently challenged by public concerns and regulatory restrictions. We aimed to assess the validity of the linear no-threshold (LNT) model of radiation damage, which is the basis of current regulation, and to assess the justification for this regulation. We have conducted an extensive search in PubMed. Special attention has been given to papers cited in comprehensive reviews of the United States (2006) and French (2005) Academies of Sciences and in the United Nations Scientific Committee on Atomic Radiation 2016 report. Epidemiological data provide essentially no evidence for detrimental health effects below 100 mSv, and several studies suggest beneficial (hormetic) effects. Equally significant, many studies with in vitro and in animal models demonstrate that several mechanisms initiated by low-dose radiation have beneficial effects. Overall, although probably not yet proven to be untrue, LNT has certainly not been proven to be true. At this point, taking into account the high price tag (in both economic and human terms) borne by the LNT-inspired regulation, there is little doubt that the present regulatory burden should be reduced.
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Vaiserman AM, Koliada AK. Early-life adversity and long-term neurobehavioral outcomes: epigenome as a bridge? Hum Genomics 2017; 11:34. [PMID: 29246185 PMCID: PMC5732459 DOI: 10.1186/s40246-017-0129-z] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 12/04/2017] [Indexed: 12/12/2022] Open
Abstract
Accumulating evidence suggests that adversities at critical periods in early life, both pre- and postnatal, can lead to neuroendocrine perturbations, including hypothalamic-pituitary-adrenal axis dysregulation and inflammation persisting up to adulthood. This process, commonly referred to as biological embedding, may cause abnormal cognitive and behavioral functioning, including impaired learning, memory, and depressive- and anxiety-like behaviors, as well as neuropsychiatric outcomes in later life. Currently, the regulation of gene activity by epigenetic mechanisms is suggested to be a key player in mediating the link between adverse early-life events and adult neurobehavioral outcomes. Role of particular genes, including those encoding glucocorticoid receptor, brain-derived neurotrophic factor, as well as arginine vasopressin and corticotropin-releasing factor, has been demonstrated in triggering early adversity-associated pathological conditions. This review is focused on the results from human studies highlighting the causal role of epigenetic mechanisms in mediating the link between the adversity during early development, from prenatal stages through infancy, and adult neuropsychiatric outcomes. The modulation of epigenetic pathways involved in biological embedding may provide promising direction toward novel therapeutic strategies against neurological and cognitive dysfunctions in adult life.
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Affiliation(s)
- Alexander M Vaiserman
- Laboratory of Epigenetics, Institute of Gerontology, Vyshgorodskaya st. 67, Kiev, 04114, Ukraine.
| | - Alexander K Koliada
- Laboratory of Epigenetics, Institute of Gerontology, Vyshgorodskaya st. 67, Kiev, 04114, Ukraine
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Yim JH, Yun JM, Kim JY, Nam SY, Kim CS. Estimation of low-dose radiation-responsive proteins in the absence of genomic instability in normal human fibroblast cells. Int J Radiat Biol 2017; 93:1197-1206. [DOI: 10.1080/09553002.2017.1350302] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Ji-Hye Yim
- Department of Low-Dose Radiation Research Team, KHNP Radiation Health Institute, Seoul, Korea
| | - Jung Mi Yun
- Department of Low-Dose Radiation Research Team, KHNP Radiation Health Institute, Seoul, Korea
| | - Ji Young Kim
- Department of Low-Dose Radiation Research Team, KHNP Radiation Health Institute, Seoul, Korea
| | - Seon Young Nam
- Department of Low-Dose Radiation Research Team, KHNP Radiation Health Institute, Seoul, Korea
| | - Cha Soon Kim
- Department of Molecular Biology Radiation Epidemiology Team, KHNP Radiation Health Institute, Seongnam-si, Gyeonggi-do, Korea
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Rossnerova A, Pokorna M, Svecova V, Sram RJ, Topinka J, Zölzer F, Rossner P. Adaptation of the human population to the environment: Current knowledge, clues from Czech cytogenetic and "omics" biomonitoring studies and possible mechanisms. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2017; 773:188-203. [PMID: 28927528 DOI: 10.1016/j.mrrev.2017.07.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 07/10/2017] [Accepted: 07/11/2017] [Indexed: 12/19/2022]
Abstract
The human population is continually exposed to numerous harmful environmental stressors, causing negative health effects and/or deregulation of biomarker levels. However, studies reporting no or even positive impacts of some stressors on humans are also sometimes published. The main aim of this review is to provide a comprehensive overview of the last decade of Czech biomonitoring research, concerning the effect of various levels of air pollution (benzo[a]pyrene) and radiation (uranium, X-ray examination and natural radon background), on the differently exposed population groups. Because some results obtained from cytogenetic studies were opposite than hypothesized, we have searched for a meaningful interpretation in genomic/epigenetic studies. A detailed analysis of our data supported by the studies of others and current epigenetic knowledge, leads to a hypothesis of the versatile mechanism of adaptation to environmental stressors via DNA methylation settings which may even originate in prenatal development, and help to reduce the resulting DNA damage levels. This hypothesis is fully in agreement with unexpected data from our studies (e.g. lower levels of DNA damage in subjects from highly polluted regions than in controls or in subjects exposed repeatedly to a pollutant than in those without previous exposure), and is also supported by differences in DNA methylation patterns in groups from regions with various levels of pollution. In light of the adaptation hypothesis, the following points may be suggested for future research: (i) the chronic and acute exposure of study subjects should be distinguished; (ii) the exposure history should be mapped including place of residence during the life and prenatal development; (iii) changes of epigenetic markers should be monitored over time. In summary, investigation of human adaptation to the environment, one of the most important processes of survival, is a new challenge for future research in the field of human biomonitoring that may change our view on the results of biomarker analyses and potential negative health impacts of the environment.
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Affiliation(s)
- Andrea Rossnerova
- Department of Genetic Toxicology and Nanotoxicology, Institute of Experimental Medicine, Czech Academy of Sciences, 14220 Prague 4, Czech Republic
| | - Michaela Pokorna
- Department of Genetic Toxicology and Nanotoxicology, Institute of Experimental Medicine, Czech Academy of Sciences, 14220 Prague 4, Czech Republic
| | - Vlasta Svecova
- Department of Genetic Toxicology and Nanotoxicology, Institute of Experimental Medicine, Czech Academy of Sciences, 14220 Prague 4, Czech Republic
| | - Radim J Sram
- Department of Genetic Toxicology and Nanotoxicology, Institute of Experimental Medicine, Czech Academy of Sciences, 14220 Prague 4, Czech Republic
| | - Jan Topinka
- Department of Genetic Toxicology and Nanotoxicology, Institute of Experimental Medicine, Czech Academy of Sciences, 14220 Prague 4, Czech Republic
| | - Friedo Zölzer
- Institute of Radiology, Toxicology and Civil Protection, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic
| | - Pavel Rossner
- Department of Genetic Toxicology and Nanotoxicology, Institute of Experimental Medicine, Czech Academy of Sciences, 14220 Prague 4, Czech Republic.
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Duan P, Hu C, Butler HJ, Quan C, Chen W, Huang W, Tang S, Zhou W, Yuan M, Shi Y, Martin FL, Yang K. Effects of 4-nonylphenol on spermatogenesis and induction of testicular apoptosis through oxidative stress-related pathways. Reprod Toxicol 2016; 62:27-38. [DOI: 10.1016/j.reprotox.2016.04.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 04/16/2016] [Accepted: 04/19/2016] [Indexed: 12/22/2022]
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17
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Environmental pollution and DNA methylation: carcinogenesis, clinical significance, and practical applications. Front Med 2015; 9:261-74. [PMID: 26290283 DOI: 10.1007/s11684-015-0406-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 05/12/2015] [Indexed: 01/25/2023]
Abstract
Environmental pollution is one of the main causes of human cancer. Exposures to environmental carcinogens result in genetic and epigenetic alterations which induce cell transformation. Epigenetic changes caused by environmental pollution play important roles in the development and progression of environmental pollution-related cancers. Studies on DNA methylation are among the earliest and most conducted epigenetic research linked to cancer. In this review, the roles of DNA methylation in carcinogenesis and their significance in clinical medicine were summarized, and the effects of environmental pollutants, particularly air pollutants, on DNA methylation were introduced. Furthermore, prospective applications of DNA methylation to environmental pollution detection and cancer prevention were discussed.
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Bellavite P, Signorini A, Marzotto M, Moratti E, Bonafini C, Olioso D. Cell sensitivity, non-linearity and inverse effects. HOMEOPATHY 2015; 104:139-60. [DOI: 10.1016/j.homp.2015.02.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 01/27/2015] [Accepted: 02/03/2015] [Indexed: 10/23/2022]
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Vaiserman AM. Epigenetic programming by early-life stress: Evidence from human populations. Dev Dyn 2014; 244:254-65. [PMID: 25298004 DOI: 10.1002/dvdy.24211] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/29/2014] [Accepted: 09/29/2014] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND A substantial body of experimental and epidemiological evidence has been accumulated suggesting that stressful events in early life including acute perinatal stress, maternal deprivation or separation, and variation in maternal care may lead to neuroendocrine perturbations thereby affecting reproductive performance, cognitive functions, and stress responses as well as the risk for infectious, cardio-metabolic and psychiatric diseases in later life. RESULTS Findings from recent studies based on both genome-wide and candidate gene approaches highlighted the importance of mechanisms that are involved in epigenetic regulation of gene expression, such as DNA methylation, histone modifications, and non-coding RNAs, in the long-term effects of exposure to stress in early life. CONCLUSIONS This review is focused on the findings from human studies indicating the role of epigenetic mechanisms in the causal link between early-life stress and later-life health outcomes.
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Affiliation(s)
- A M Vaiserman
- D.F. Chebotarev State Institute of Gerontology NAMS of Ukraine, Kiev, Ukraine
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20
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Radiation-hormesis phenotypes, the related mechanisms and implications for disease prevention and therapy. J Cell Commun Signal 2014; 8:341-52. [PMID: 25324149 DOI: 10.1007/s12079-014-0250-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Accepted: 10/08/2014] [Indexed: 01/20/2023] Open
Abstract
Humans are continuously exposed to ionizing radiation throughout life from natural sources that include cosmic, solar, and terrestrial. Much harsher natural radiation and chemical environments existed during our planet's early years. Mammals survived the harsher environments via evolutionarily-conserved gifts ̶ a continuously evolving system of stress-induced natural protective measures (i.e., activated natural protection [ANP]). The current protective system is differentially activated by stochastic (i.e., variable) low-radiation-dose thresholds and when optimally activated in mammals includes antioxidants, DNA damage repair, p53-related apoptosis of severely-damaged cells, reactive-oxygen-species (ROS)/reactive-nitrogen-species (RNS)- and cytokine-regulated auxiliary apoptosis that selectively removes aberrant cells (e.g., precancerous cells), suppression of disease promoting inflammation, and immunity against cancer cells. The intercellular-signaling-based protective system is regulated at least in part via epigenetic reprogramming of adaptive-response genes. When the system is optimally activated, it protects against cancer and some other diseases, thereby leading to hormetic phenotypes (e.g., reduced disease incidence to below the baseline level; reduced pain from inflammation-related problems). Here, some expressed radiation hormesis phenotypes and related mechanisms are discussed along with their implications for disease prevention and therapy.
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Bruce VR, Belinsky SA, Gott K, Liu Y, March T, Scott B, Wilder J. Low-dose gamma-radiation inhibits benzo[a]pyrene-induced lung adenoma development in a/j mice. Dose Response 2012; 10:516-26. [PMID: 23304102 DOI: 10.2203/dose-response.12-040.bruce] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Low-dose ionizing radiation (LDR) may lead to suppression of smoking-related lung cancer. We examined the effects of a known cigarette smoke carcinogen Benzo[a]pyrene (B[a]P) alone or in combination with fractionated low-dose gamma radiation (60 - 600 mGy total dose) on the induction of lung neoplasms in the A/J mouse. Our results show that 600 mGy of gamma radiation delivered in six biweekly fractions of 100 mGy starting 1 month after B[a]P injection significantly inhibits the development of lung adenomas per animal induced by B[a]P. Our data also indicated that the six biweekly doses suppressed the occurrence of spontaneous hyperplastic foci in the lung, although this suppression failed to reach statistical significance when analyzed as average foci per lung possibly related to the small sample sizes used for the control and test groups.
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Affiliation(s)
- Veronica R Bruce
- University of New Mexico, Biomedical Sciences Graduate Program, Health Sciences Center, and Lovelace Respiratory Research Institute, Respiratory Immunology Program, Albuquerque, NM
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Scott BR, Bruce VR, Gott KM, Wilder J, March T. Small γ-Ray Doses Prevent Rather than Increase Lung Tumors in Mice. Dose Response 2012; 10:527-40. [PMID: 23304103 DOI: 10.2203/dose-response.12-035.scott] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
We show evidence for low doses of γ rays preventing spontaneous hyperplastic foci and adenomas in the lungs of mice, presumably via activating natural anticancer defenses. The evidence partly relates to a new study we conducted whereby a small number of female A/J mice received 6 biweekly dose fractions (100 mGy per fraction) of γ rays to the total body which prevented the occurrence of spontaneous hyperplastic foci in the lung. We also analyzed data from a much earlier Oak Ridge National Laboratory study involving more than 10,000 female RFMf/Un mice whereby single γ-ray doses from 100 to 1,000 mGy prevented spontaneous lung adenomas. We point out the possibility that the decrease in lung cancer mortality observed in The National Lung Screening Trial Research Team study involving lung tumor screening using low-dose computed tomography (CT) may relate at least in part to low-dose X-rays activating the body's natural anticancer defenses (i.e., radiation hormesis). This possibility was apparently not recognized by the indicated research team.
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Affiliation(s)
- B R Scott
- Lovelace Respiratory Research Institute, 2425 Ridgecrest Drive SE, Albuquerque, NM 87108
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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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Chen W, Xu X, Bai L, Padilla MT, Gott KM, Leng S, Tellez CS, Wilder JA, Belinsky SA, Scott BR, Lin Y. Low-dose gamma-irradiation inhibits IL-6 secretion from human lung fibroblasts that promotes bronchial epithelial cell transformation by cigarette-smoke carcinogen. Carcinogenesis 2012; 33:1368-74. [PMID: 22556270 DOI: 10.1093/carcin/bgs159] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
Despite decades of research in defining the health effects of low-dose (<100 mGy) ionizing photon radiation (LDR), the relationship between LDR and human cancer risk remains elusive. Because chemical carcinogens modify the tumor microenvironment, which is critical for cancer development, we investigated the role and mechanism of LDR in modulating the response of stromal cells to chemical carcinogen-induced lung cancer development. Secretion of proinflammatory cytokines such as interleukin-6 (IL-6), CXCL1 and CXCL5 from human lung fibroblasts was induced by cigarette-smoke carcinogen benzo[a]pyrene diol epoxide (BPDE), which was inhibited by a single dose of LDR. The activation of NF-κB, which is important for BPDE-induced IL-6 secretion, was also effectively suppressed by LDR. In addition, conditioned media from BPDE-treated fibroblasts activated STAT3 in the immortalized normal human bronchial epithelial cell line Beas-2B, which was blocked with an IL-6 neutralizing antibody. Conditioned medium from LDR-primed and BPDE-treated fibroblast showed diminished capacity in activating STAT3. Furthermore, IL-6 enhanced BPDE-induced Beas-2B cell transformation in vitro. These results suggest that LDR inhibits cigarette smoke-induced lung carcinogenesis by suppressing secretion of cytokines such as IL-6 from fibroblasts in lung tumor-prone microenvironment.
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Affiliation(s)
- Wenshu Chen
- Lovelace Respiratory Research Institute, 2425 Ridgecrest Dr., SE Albuquerque, NM 87108, USA
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Abstract
Residential radon has been found to be associated with lung cancer in epidemiological/ecological studies and the researchers have inappropriately concluded that residential radon causes lung cancer. Their conclusion relates to the linear-no-threshold (LNT) hypothesis-based, risk-assessment paradigm; however, the LNT hypothesis has been invalidated in numerous studies. It is shown in this paper that our hormetic relative risk (HRR) model is consistent with lung cancer data where detailed measurements of radon in each home were carried out. Based on the HRR model, low-level radon radioactive progeny is credited for activated natural protection (ANP) against lung cancer including smoking-related lung cancer. The proportion B(x) (benefit function) of ANP beneficiaries increases as the average radon level x increases to near the Environmental Protection Agency's action level of 4 picocuries/L (approximately 150 Bq m(-3)). As the average level of radon increases to somewhat above the action level, ANP beneficiaries progressively decrease to zero (B(x) decreases to 0), facilitating the occurrence of smoking-related lung cancers as well as those related to other less important risk factors. Thus, residential radon does not appear to cause lung cancer but rather to protect, in an exposure-level-dependent manner, from its induction by other agents (e.g., cigarette-smoke-related carcinogens).
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Scott BR. First generation stochastic gene episilencing (step1) model and applications to in vitro carcinogen exposure. Dose Response 2011; 11:9-28. [PMID: 23550217 PMCID: PMC3578451 DOI: 10.2203/dose-response.11-007.scott] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
A novel first-generation stochastic gene episilencing (STEP1) model is introduced for quantitatively characterizing the probability of in vitro epigenetically silencing (episilencing) specific tumor-suppressor-microRNA (miRNA) genes by carcinogen exposure. Although the focus is mainly on in-vitro exposure of human cells to ionizing radiation, the mathematical formulations presented are general and can be applied to other carcinogens. With the STEP1 model, a fraction fj of the surviving target cells can have their tumor-suppressor-miRNA gene of type j silenced while the remaining fraction, 1 - fj , of the surviving cells do not undergo gene episilencing. Suppressor gene episilencing is assumed to arise as a Poisson process characterized with and exponential distribution of episilencing doses with mean dj . In addition to providing mathematical functions for evaluating the single-target-gene episilencing probability, functions are also provided for the multi-target-gene episilencing probability for simultaneously silencing of multiple tumor-suppressor-miRNA genes. Functional relationships are first developed for moderate doses where adaptive responses are unlikely and are then modified for low doses where adaptation can occur. Results apply to a specific follow-up time t after carcinogen exposure that exceeds the maximum time for the occurrence of an induced episilencing event.
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Abstract
This paper provides a perspective on epidemiological research on radiation and cancer, a field that has evolved over its six decade history. The review covers the current framework for assessing radiation risk and persistent questions about the details of these risks: is there a threshold and more generally, what is the shape of the dose-response relationship? How do risks vary over time and with age? What factors modify the risk of radiation? The example of radon progeny and lung cancer is considered as a case study, illustrating the modeling of epidemiological data to derive quantitative models and the coherence of the epidemiological and biological evidence. Finally, the manuscript considers the need for ongoing research, even in the face of research over a 60-year span.
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Affiliation(s)
- Jonathan M Samet
- Department of Preventive Medicine, Keck School of Medicine of USC, USC Institute for Global Health, University of Southern California, 1441 Eastlake Ave, Room 4436, MC 9175, Los Angeles, CA 90089, USA.
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Scott BR. Modeling DNA double-strand break repair kinetics as an epiregulated cell-community-wide (epicellcom) response to radiation stress. Dose Response 2011; 9:579-601. [PMID: 22461762 DOI: 10.2203/dose-response.10-039.scott] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The multicellular signaling model (MULTISIG1) was recently introduced to simulate the kinetics of repair of DNA double-strand breaks (DSBs) that were induced in confluent (non-dividing) cultured cells by a very low radiation dose where at most a single induced DSB would be expected in a given cell nucleus. The repair kinetics was modeled as representing what is now called an epigenetically-regulated (epiregulated) cell-community-wide (epicellcom) response to radiation stress. DSB repair initiation is assumed to require a threshold number of cells with DSBs participating in intercellular stress-response signaling. The MULTISIG1 model is extended in this study to apply to moderate doses where several DSBs can occur on the same DNA molecule. The repair of multiple breaks on the same molecule is treated as sequential stochastic events. For cells of differing genetic characteristics and epigenetic statuses, relationships are provided for evaluating the relative susceptibility (RS) for DSB induction, relative repair capacity (RRC) for DSB repair, and relative epiapoptosis capacity (REC), for epigenetically regulated apoptosis. The modified MULTISIG1 model is used to characterize the expected repair kinetics for confluent, human lung fibroblasts (MRC-5 line) briefly exposed in vitro to 90-kV x-rays. Possible application of the model to biological dosimetry is also discussed.
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Thompson RE. Epidemiological Evidence for Possible Radiation Hormesis from Radon Exposure: A Case-Control Study Conducted in Worcester, MA. Dose Response 2010; 9:59-75. [PMID: 21431078 DOI: 10.2203/dose-response.10-026.thompson] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Data from a case-control study of lung cancer and residential radon exposure conducted in Worcester County, Massachusetts, are presented. Lung cancer risk was estimated using conditional logistic regression models that controlled for demographic, smoking, and occupational exposure covariates. Preliminary exploratory analyses using lowess smoothing revealed a non-linear association between exposure and the log odds of lung cancer. Radon exposure was considered by using linear spline terms in order to model this nonlinearity. The best fit of this linear spline model to these data predicted a shift from a positive to a negative slope in the log-odds of lung cancer at a radon concentration of 70 Bq m(-3). A statistically significant decrease in cancer risk with increased exposure was found for values ≤ 157 Bq m(-3) normalized to the reference exposure of 4.4 Bq m(-3), the lowest radon concentration measured(adjusted odds ratio (AOR) [95% CI] = 0.42 [0.180, 1.00], p = 0.049). This result is consistent with those reported elsewhere that considered radon exposure with cubic spline terms (Thompson, RE et al. 2008). Furthermore, this model predicts an AOR that is numerically less than 1.0 for radon exposures up to 545 Bq m(-3) versus the above baseline, reference exposure.
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Affiliation(s)
- Richard E Thompson
- Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health
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31
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Scott BR. Stochastic threshold microdose model for cell killing by insoluble metallic nanomaterial particles. Dose Response 2010; 8:428-47. [PMID: 21191483 DOI: 10.2203/dose-response.09-061.scott] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
This paper introduces a novel microdosimetric model for metallic nanomaterial-particles (MENAP)-induced cytotoxicity. The focus is on the engineered insoluble MENAP which represent a significant breakthrough in the design and development of new products for consumers, industry, and medicine. Increased production is rapidly occurring and may cause currently unrecognized health effects (e.g., nervous system dysfunction, heart disease, cancer); thus, dose-response models for MENAP-induced biological effects are needed to facilitate health risk assessment. The stochasticthresholdmicrodose (STM) model presented introduces novel stochastic microdose metrics for use in constructing dose-response relationships for the frequency of specific cellular (e.g., cell killing, mutations, neoplastic transformation) or subcellular (e.g., mitochondria dysfunction) effects. A key metric is the exposure-time-dependent, specific burden (MENAP count) for a given critical target (e.g., mitochondria, nucleus). Exceeding a stochastic threshold specific burden triggers cell death. For critical targets in the cytoplasm, the autophagic mode of death is triggered. For the nuclear target, the apoptotic mode of death is triggered. Overall cell survival is evaluated for the indicated competing modes of death when both apply. The STM model can be applied to cytotoxicity data using Bayesian methods implemented via Markov chain Monte Carlo.
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32
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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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Vaiserman AM. Hormesis, adaptive epigenetic reorganization, and implications for human health and longevity. Dose Response 2010; 8:16-21. [PMID: 20221294 DOI: 10.2203/dose-response.09-014.vaiserman] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Hormesis is a common phenomenon in a number of biomedical areas. However, the basic nature of this phenomenon remains largely unknown. Therefore, significant uncertainty is inevitable in attempts to apply hormesis as a pro-health and anti-aging tool. Evidence supporting that hormetic-like effects may be the result of a generalized whole-organism adaptive epigenetic response is reviewed. Specific hormesis-inducing interventions during development would allow to achieve an optimal balance between activation and repression of various genes and thus to prevent age-related degenerative diseases and slow aging. The reasons that oscillating temperature mild stress could potentially be used for human application are discussed.
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Affiliation(s)
- Alexander M Vaiserman
- Laboratory of Mathematical Modeling of Aging Processes, Institute of Gerontology, Vyshgorodskaya st. 67, Kiev, Ukraine.
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Abstract
The linear no-threshold (LNT) dose-effect relationship has been consistently used by most radiation epidemiologists to estimate cancer mortality risk. The large scattering of data by International Agency for Research on Cancer, IARC (Vrijheid et al. 2007; Therry-Chef et al. 2007; Cardis et al. 2007), interpreted in accordance with LNT, has been previously demonstrated (Fornalski and Dobrzyński 2009). Using conventional and Bayesian methods the present paper demonstrates that the standard mortality ratios (SMRs), lower in the IARC cohort of exposed nuclear workers than in the non exposed group, should be considered as a hormetic effect, rather than a healthy worker effect (HWE) as claimed by the IARC group.
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