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1.
Int J Mol Sci ; 22(14)2021 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-34299125

RESUMO

Medical staff represent the largest group of workers occupationally exposed to ionizing radiation (IR). Chronic exposure to low-dose IR may result in DNA damage and genotoxicity associated with increased risk of cancer. This review aims to identify the genotoxicity biomarkers that are the most elevated in IR-exposed vs. unexposed health workers. A systematic review of the literature was performed to retrieve relevant studies with various biomarkers of genotoxicity. Subsequent meta-analyses produced a pooled effect size for several endpoints. The search procedure yielded 65 studies. Chromosome aberrations (CA) and micronuclei (MN) frequencies were significantly different between IR-exposed and unexposed workers (θpooled = 3.19, 95% CI 1.46-4.93; and θpooled = 1.41, 95% CI 0.97-1.86, for total aberrant cells and MN frequencies, respectively), which was not the case for ring chromosomes and nucleoplasmic bridges. Although less frequently used, stable translocations, sister chromatid exchanges (SCE) and comet assay endpoints were also statistically different between IR-exposed and unexposed workers. This review confirms the relevance of CA and MN as genotoxicity biomarkers that are consistently elevated in IR-exposed vs. unexposed workers. Other endpoints are strong candidates but require further studies to validate their usefulness. The integration of the identified biomarkers in future prospective epidemiological studies is encouraged.


Assuntos
Biomarcadores/análise , Aberrações Cromossômicas/efeitos da radiação , Dano ao DNA , Pessoal de Saúde/estatística & dados numéricos , Exposição Ocupacional/análise , Radiação Ionizante , Relação Dose-Resposta à Radiação , Humanos , Exposição Ocupacional/efeitos adversos
2.
Int J Mol Sci ; 21(18)2020 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-32932812

RESUMO

Protein synthesis, or mRNA translation, is one of the most energy-consuming functions in cells. Translation of mRNA into proteins is thus highly regulated by and integrated with upstream and downstream signaling pathways, dependent on various transacting proteins and cis-acting elements within the substrate mRNAs. Under conditions of stress, such as exposure to ionizing radiation, regulatory mechanisms reprogram protein synthesis to translate mRNAs encoding proteins that ensure proper cellular responses. Interestingly, beneficial responses to low-dose radiation exposure, known as radiation hormesis, have been described in several models, but the molecular mechanisms behind this phenomenon are largely unknown. In this review, we explore how differences in cellular responses to high- vs. low-dose ionizing radiation are realized through the modulation of molecular pathways with a particular emphasis on the regulation of mRNA translation control.


Assuntos
Hormese/genética , Biossíntese de Proteínas/genética , Animais , Humanos , RNA Mensageiro/genética , Radiação Ionizante , Transdução de Sinais/genética
3.
Front Genet ; 11: 855, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32849834

RESUMO

Molecular responses to genotoxic stress, such as ionizing radiation, are intricately complex and involve hundreds of genes. Whether targeted overexpression of an endogenous gene can enhance resistance to ionizing radiation remains to be explored. In the present study we take an advantage of the CRISPR/dCas9 technology to moderately overexpress the RPA1 gene that encodes a key functional subunit of the replication protein A (RPA). RPA is a highly conserved heterotrimeric single-stranded DNA-binding protein complex involved in DNA replication, recombination, and repair. Dysfunction of RPA1 is detrimental for cells and organisms and can lead to diminished resistance to many stress factors. We demonstrate that HEK293T cells overexpressing RPA1 exhibit enhanced resistance to cell killing by gamma-radiation. Using the alkali comet assay, we show a remarkable acceleration of DNA breaks rejoining after gamma-irradiation in RPA1 overexpressing cells. However, the spontaneous rate of DNA damage was also higher in the presence of RPA1 overexpression, suggesting alterations in the processing of replication errors due to elevated activity of the RPA protein. Additionally, the analysis of the distributions of cells with different levels of DNA damage showed a link between the RPA1 overexpression and the kinetics of DNA repair within differentially damaged cell subpopulations. Our results provide knew knowledge on DNA damage stress responses and indicate that the concept of enhancing radioresistance by targeted alteration of the expression of a single gene is feasible, however undesired consequences should be considered and evaluated.

5.
Int J Mol Sci ; 20(11)2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31146367

RESUMO

DNA double-strand breaks (DSB) are among the most harmful DNA lesions induced by ionizing radiation (IR). Although the induction and repair of radiation-induced DSB is well studied for acute irradiation, responses to DSB produced by chronic IR exposures are poorly understood, especially in human stem cells. The aim of this study was to examine the formation of DSB markers (γH2AX and phosphorylated kinase ATM, pATM, foci) in human mesenchymal stem cells (MSCs) exposed to chronic gamma-radiation (0.1 mGy/min) in comparison with acute irradiation (30 mGy/min) at cumulative doses of 30, 100, 160, 240 and 300 mGy. A linear dose-dependent increase in the number of both γH2AX and pATM foci, as well as co-localized γH2AX/pATM foci ("true" DSB), were observed after an acute radiation exposure. In contrast, the response of MSCs to a chronic low dose-rate IR exposure deviated from linearity towards a threshold model, for γH2AX, pATM foci and γH2AX/pATM foci, with an indication of a "plateau". The state of equilibrium between newly formed DSB at a low rate during the protracted exposure time and the elimination of a fraction of DSB is proposed as a mechanistic explanation of the non-linear DSB responses following a low dose-rate irradiation. This notion is supported by the observation of the elimination of a substantial fraction of DSB 6 h after the cessation of the exposures. Our results demonstrate non-linear dose responses for γH2AX and pATM foci in human MSCs exposed to low dose-rate IR and showed the existence of a threshold, which may have implications for radiation protection in humans.


Assuntos
Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Raios gama , Histonas/metabolismo , Células-Tronco Mesenquimais/efeitos da radiação , Células Cultivadas , Quebras de DNA de Cadeia Dupla , Humanos , Células-Tronco Mesenquimais/metabolismo
6.
Int J Radiat Biol ; 95(7): 816-840, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30601684

RESUMO

For more than a century, ionizing radiation has been indispensable mainly in medicine and industry. Radiation research is a multidisciplinary field that investigates radiation effects. Radiation research was very active in the mid- to late 20th century, but has then faced challenges, during which time funding has fluctuated widely. Here we review historical changes in funding situations in the field of radiation research, particularly in Canada, European Union countries, Japan, South Korea, and the US. We also provide a brief overview of the current situations in education and training in this field. A better understanding of the biological consequences of radiation exposure is becoming more important with increasing public concerns on radiation risks and other radiation literacy. Continued funding for radiation research is needed, and education and training in this field are also important.


Assuntos
Exposição à Radiação , Radiobiologia/economia , Radiobiologia/tendências , Radioterapia/economia , Apoio à Pesquisa como Assunto/história , Apoio à Pesquisa como Assunto/tendências , Animais , Canadá , União Europeia , História do Século XIX , História do Século XX , História do Século XXI , Humanos , Japão , Lesões por Radiação , Proteção Radiológica/métodos , Radiação Ionizante , Liberação Nociva de Radioativos , Radiobiologia/educação , Radioterapia/efeitos adversos , Radioterapia/tendências , República da Coreia , Pesquisa , Estados Unidos
7.
Int J Radiat Biol ; 95(10): 1404-1413, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-30676169

RESUMO

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


Assuntos
Envelhecimento , Radioisótopos de Cobalto , MicroRNAs/metabolismo , Radiação Ionizante , Animais , Biomarcadores , Relação Dose-Resposta à Radiação , Raios gama , Perfilação da Expressão Gênica , Sistema Imunitário/efeitos da radiação , Masculino , Camundongos , Camundongos Endogâmicos C57BL , MicroRNAs/sangue , Fenótipo , Radiobiologia
8.
Int J Radiat Biol ; 95(10): 1361-1371, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-30582711

RESUMO

Health risks associated with the exposure of humans to low-dose ionizing radiation are currently estimated using the Linear-No-Threshold model. Over the last few decades, however, this model has been widely criticized for inconsistency with a large body of experimental evidence. Substantial efforts have been made to delineate biological mechanisms and health-related outcomes of low-dose radiation. These include a large DOE-funded Low Dose program operated in the 2000s, as well as the EU funded programs, previously NOTE and DOREMI and currently MELODI. Although not as widely known, the Atomic Energy of Canada Limited (AECL) in Chalk River, operated a low-dose radiobiology program since as early as 1948. The Canadian Nuclear Laboratories (CNL), the successor to AECL since 2015, has expanded this program into new areas making it the world's most robust, centrally coordinated and long-lived research efforts to delineate the biological effects of low-dose radiation. The purpose of this review is to provide a high-level overview of the low-dose radiobiology program maintained at CNL while capturing the historical perspectives. Past studies carried out at CNL have substantially influenced the area of low-dose radiobiology, exemplified by highly cited papers showing delays in spontaneous tumorigenesis in low-dose irradiated mice. The current low-dose research program at CNL is not only addressing a wide range of mechanistic questions about the biological effects of low doses - from genetic to epigenetic to immunological questions - but also moving toward novel areas, such as the dosimetry and health consequences of space radiation and the use of low-dose radiation in cancer therapy and regenerative medicine.


Assuntos
Energia Nuclear , Radiobiologia/tendências , Pesquisa/tendências , Algoritmos , Animais , Canadá , Reparo do DNA , Modelos Animais de Doenças , Humanos , Sistema Imunitário , Cooperação Internacional , Modelos Lineares , Camundongos , Mitocôndrias/efeitos da radiação , Neoplasias/radioterapia , Neoplasias Induzidas por Radiação/epidemiologia , Neoplasias Induzidas por Radiação/prevenção & controle , Nêutrons , Radiometria , Espécies Reativas de Oxigênio , Células-Tronco
9.
Environ Mol Mutagen ; 59(7): 586-594, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30151952

RESUMO

Existing and future nuclear fusion technologies involve the production and use of large quantities of tritium, a highly volatile, but low toxicity beta-emitting isotope of hydrogen. Tritium has received international attention because of public and scientific concerns over its release to the environment and the potential health impact of its internalization. This article provides a brief summary of the current state of knowledge of both the biological and regulatory aspects of tritium exposure; it also explores the gaps in this knowledge and provides recommendations on the best ways forward for improving our understanding of the health effects of low-level exposure to it. Linking health effects specifically to tritium exposure is challenging in epidemiological studies due to high uncertainty in tritium dosimetry and often suboptimal cohort sizes. We therefore argued that limits for tritium in drinking water should be based on evidence derived from controlled in vivo animal tritium toxicity studies that use realistically low levels of tritium. This article presents one such mouse study, undertaken within an international collaboration, and discusses the implications of its main findings, such as the similarity of the biokinetics of tritiated water (HTO) and organically bound tritium (OBT) and the higher biological effectiveness of OBT. This discussion is consistent with the position expressed in this article that in vivo animal tritium toxicity studies carried out within large, multi-partner collaborations allow evaluation of a great variety of health-related endpoints and essential to the development of international consensus on the regulation of tritium levels in the environment. Environ. Mol. Mutagen. 59:586-594, 2018. © 2018 The Authors Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.


Assuntos
Água Potável/efeitos adversos , Trítio/efeitos adversos , Aminoácidos/análise , Aminoácidos/farmacocinética , Animais , Sítios de Ligação , Consenso , Água Potável/análise , Raios gama/efeitos adversos , Dosimetria in Vivo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Modelos Animais , Monitoramento de Radiação , Risco , Distribuição Tecidual , Trítio/análise , Trítio/farmacocinética , Trítio/toxicidade , Organização Mundial da Saúde
10.
Oncotarget ; 9(44): 27397-27411, 2018 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-29937993

RESUMO

The aim of this study was to carry out a comprehensive examination of potential genotoxic effects of low doses of tritium delivered chronically to mice and to compare these effects to the ones resulting from equivalent doses of gamma-irradiation. Mice were chronically exposed for one or eight months to either tritiated water (HTO) or organically bound tritium (OBT) in drinking water at concentrations of 10 kBq/L, 1 MBq/L or 20 MBq/L. Dose rates of internal ß-particle resulting from such tritium treatments were calculated and matching external gamma-exposures were carried out. We measured cytogenetic damage in bone marrow and in peripheral blood lymphocytes (PBLs) and the cumulative tritium doses (0.009 - 181 mGy) were used to evaluate the dose-response of OBT in PBLs, as well as its relative biological effectiveness (RBE). Neither tritium, nor gamma exposures produced genotoxic effects in bone marrow. However, significant increases in chromosome damage rates in PBLs were found as a result of chronic OBT exposures at 1 and 20 M Bq/L, but not at 10 kBq/L. When compared to an external acute gamma-exposure ex vivo, the RBE of OBT for chromosome aberrations induction was evaluated to be significantly higher than 1 at cumulative tritium doses below 10 mGy. Although found non-existent at 10 kBq/L (the WHO limit), the genotoxic potential of low doses of tritium (>10 kBq/L), mainly OBT, may be higher than currently assumed.

11.
Int J Radiat Biol ; 94(9): 825-828, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29952691

RESUMO

PURPOSE: Exposure to high dose ionizing radiation leads to premature cell senescence and suppression of cell proliferation. In contrast, low dose and low dose-rate gamma-irradiation can lead to stimulation of cell proliferation. We aimed to examine whether the low dose radiation-induced proliferation of normal human fibroblasts can lead to a progressive depletion of proliferation potential and to an early onset of senescence. MATERIALS AND METHODS: Normal human embryonic lung fibroblasts (HELF-104) at passage 22-24 were gamma-irradiated with doses of 0 (sham-irradiation), 10, 30, 50, 90, 120, 150, 200, and 500 mGy as well as 1 and 2 Gy. After irradiation, the fraction of cells positively stained for senescence-associated ß-galactosidase activity was measured weekly until the cell culture completely ceased to proliferate. RESULTS: We show that single irradiation of HELF-104 cells with 30 and 50 mGy resulted in deceleration of senescence. The suppression of senescence was observed during almost the entire length of the study up to a complete arrest of cell growth. CONCLUSIONS: Our data, together with the previously published observation of delayed stimulation of proliferation in HELF-104 cells exposed to 30 mGy, suggest that low dose gamma-irradiation can increase the overall proliferative potential of normal human fibroblasts.


Assuntos
Senescência Celular/efeitos da radiação , Fibroblastos/citologia , Fibroblastos/efeitos da radiação , Linhagem Celular , Proliferação de Células/efeitos da radiação , Relação Dose-Resposta à Radiação , Raios gama/efeitos adversos , Humanos
12.
Oncotarget ; 9(18): 14692-14722, 2018 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-29581875

RESUMO

While many efforts have been made to pave the way toward human space colonization, little consideration has been given to the methods of protecting spacefarers against harsh cosmic and local radioactive environments and the high costs associated with protection from the deleterious physiological effects of exposure to high-Linear energy transfer (high-LET) radiation. Herein, we lay the foundations of a roadmap toward enhancing human radioresistance for the purposes of deep space colonization and exploration. We outline future research directions toward the goal of enhancing human radioresistance, including upregulation of endogenous repair and radioprotective mechanisms, possible leeways into gene therapy in order to enhance radioresistance via the translation of exogenous and engineered DNA repair and radioprotective mechanisms, the substitution of organic molecules with fortified isoforms, and methods of slowing metabolic activity while preserving cognitive function. We conclude by presenting the known associations between radioresistance and longevity, and articulating the position that enhancing human radioresistance is likely to extend the healthspan of human spacefarers as well.

13.
Aging (Albany NY) ; 9(11): 2397-2410, 2017 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-29165316

RESUMO

Mechanisms underlying the effects of low-dose ionizing radiation (IR) exposure (10-100 mGy) remain unknown. Here we present a comparative study of early (less than 24h) and delayed (up to 11 post-irradiation passages) radiation effects caused by low (80 mGy) vs intermediate (1000 mGy) dose X-ray exposure in cultured human bone marrow mesenchymal stem cells (MSCs). We show that γН2АХ foci induced by an intermediate dose returned back to the control value by 24 h post-irradiation. In contrast, low-dose irradiation resulted in residual γН2АХ foci still present at 24 h. Notably, these low dose induced residual γН2АХ foci were not co-localized with рАТМ foci and were observed predominantly in the proliferating Кi67 positive (Кi67+) cells. The number of γН2АХ foci and the fraction of nonproliferating (Кi67-) and senescent (SA-ß-gal+) cells measured at passage 11 were increased in cultures exposed to an intermediate dose compared to unirradiated controls. These delayed effects were not seen in the progeny of cells that were irradiated with low-dose X-rays, although such exposure resulted in residual γН2АХ foci in directly irradiated cells. Taken together, our results support the hypothesis that the low-dose IR induced residual γH2AÐ¥ foci do not play a role in delayed irradiation consequences, associated with cellular senescence in cultured MSCs.


Assuntos
Células da Medula Óssea/efeitos da radiação , Proliferação de Células/efeitos da radiação , Senescência Celular/efeitos da radiação , Histonas/metabolismo , Células-Tronco Mesenquimais/efeitos da radiação , Adulto , Células da Medula Óssea/metabolismo , Células da Medula Óssea/patologia , Células Cultivadas , Relação Dose-Resposta à Radiação , Humanos , Antígeno Ki-67/metabolismo , Masculino , Células-Tronco Mesenquimais/metabolismo , Células-Tronco Mesenquimais/patologia , Transdução de Sinais/efeitos da radiação , Fatores de Tempo , Raios X , beta-Galactosidase/metabolismo
14.
Oncotarget ; 8(38): 64317-64329, 2017 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-28969073

RESUMO

At high exposure levels ionizing radiation is a carcinogen. Little is known about how human stem cells, which are known to contribute to tumorigenesis, respond to prolonged radiation exposures. We studied formation of DNA double strand breaks, accessed as γH2AX and 53BP1 foci, in human mesenchymal stem cells (MSCs) exposed to either acute (5400 mGy/h) or prolonged (270 mGy/h) X-irradiation. We show a linear γH2AX and 53BP1 dose response for acute exposures. In contrast, prolonged exposure resulted in a dose-response curve that had an initial linear portion followed by a plateau. Analysis of Rad51 foci, as a marker of homologous recombination, in cells exposed to prolonged irradiation revealed a threshold in a dose response. Using Ki67 as a marker of proliferating cells, we show no difference in the γH2AX distribution in proliferating vs. quiescent cells. However, Rad51 foci were found almost exclusively in proliferating cells. Concurrent increases in the fraction of S/G2 cells were detected in cells exposed to prolonged irradiation by scoring CENPF-positive cells. Our data suggest that prolonged exposure of MSCs to ionizing radiation leads to cell cycle redistribution and associated activation of homologous recombination. Also, proliferation status may significantly affect the biological outcome, since homologous repair is not activated in resting MSCs.

15.
Aging (Albany NY) ; 9(5): 1404-1413, 2017 05 16.
Artigo em Inglês | MEDLINE | ID: mdl-28522793

RESUMO

Development of personalized skin treatment in medicine and skin care may benefit from simple and accurate evaluation of the fraction of senescent skin fibroblasts that lost their proliferative capacity. We examined whether enriched analysis of colonies formed by primary human skin fibroblasts, a simple and widely available cellular assay, could reveal correlations with the fraction of senescent cells in heterogenic cell population. We measured fractions of senescence associated ß-galactosidase (SA-ßgal) positive cells in either mass cultures or colonies of various morphological types (dense, mixed and diffuse) formed by skin fibroblasts from 10 human donors. Although the donors were chosen to be within the same age group (33-54 years), the colony forming efficiency of their fibroblasts (ECO-f) and the percentage of dense, mixed and diffuse colonies varied greatly among the donors. We showed, for the first time, that the SA-ßgal positive fraction was the largest in diffuse colonies, confirming that they originated from cells with the least proliferative capacity. The percentage of diffuse colonies was also found to correlate with the SA-ßgal positive cells in mass culture. Using Ki67 as a cell proliferation marker, we further demonstrated a strong inverse correlation (r=-0.85, p=0.02) between the percentage of diffuse colonies and the fraction of Ki67+ cells. Moreover, a significant inverse correlation (r=-0.94, p=0.0001) between the percentage of diffuse colonies and ECO-f was found. Our data indicate that quantification of a fraction of diffuse colonies may provide a simple and useful method to evaluate the extent of cellular senescence in human skin fibroblasts.


Assuntos
Proliferação de Células , Senescência Celular , Fibroblastos/fisiologia , Pele/citologia , Adulto , Biomarcadores/metabolismo , Células Cultivadas , Feminino , Fibroblastos/metabolismo , Humanos , Antígeno Ki-67/metabolismo , Pessoa de Meia-Idade , beta-Galactosidase/metabolismo
16.
Health Phys ; 112(5): 439-444, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28350697

RESUMO

The objective of this study was to compare the biokinetics of injected H-labeled light (HTO) and heavy (DTO) water in CBA/CaJ mice and to compare the organ distribution and/or body content of H administered by chronic ingestion for 1 mo to C57Bl/6J mice, as either H-labeled water or H-labeled amino acids (glycine, alanine and proline). HTO and DTO were administered to CBA/CaJ mice by single intraperitoneal injection and body retention was determined for up to 384 h post-injection. Tritium-labeled water or H-labeled amino acids were given to C57Bl/6J mice ad libitum for 30 d in drinking water. Body content and organ distribution of H during the period of administration and subsequent to administration was determined by liquid scintillation counting. No differences were found between the biokinetics of HTO and DTO, indicating that data generated using HTO can be used to help assess the consequences of H releases from heavy water reactors. The results for H-water showed that the concentration of radionuclide in the mice reached a peak after about 10 d and dropped rapidly after the cessation of H administration. The maximum concentration reached was only 50% of that in the water consumed, indicating that mice receive a significant fraction of their water from respiration. Contrary to the findings of others, the pattern of H retention following the administration of a cocktail of the labeled amino acids was very little different from that found for the water. This is consistent with the suggestion that most of the ingested amino acids were rapidly metabolized, releasing water and carbon dioxide.


Assuntos
Aminoácidos/farmacocinética , Óxido de Deutério/farmacocinética , Deutério/farmacocinética , Água Potável/metabolismo , Marcação por Isótopo/métodos , Trítio/farmacocinética , Administração Oral , Aminoácidos/administração & dosagem , Aminoácidos/química , Animais , Deutério/administração & dosagem , Deutério/química , Óxido de Deutério/administração & dosagem , Óxido de Deutério/química , Feminino , Injeções Intravenosas , Taxa de Depuração Metabólica , Camundongos , Camundongos Endogâmicos CBA , Especificidade de Órgãos/fisiologia , Distribuição Tecidual , Trítio/administração & dosagem , Trítio/química
17.
Aging (Albany NY) ; 8(12): 3498-3506, 2016 12 11.
Artigo em Inglês | MEDLINE | ID: mdl-27959319

RESUMO

Expansion of mesenchymal stromal/stem cells (MSCs) used in clinical practices may be associated with accumulation of genetic instability. Understanding temporal and mechanistic aspects of this process is important for improving stem cell therapy protocols. We used γH2AX foci as a marker of a genetic instability event and quantified it in MSCs that undergone various numbers of passage (3-22). We found that γH2AX foci numbers increased in cells of late passages, with a sharp increase at passage 16-18. By measuring in parallel foci of ATM phosphorylated at Ser-1981 and their co-localization with γaH2AX foci, along with differentiating cells into proliferating and resting by using a Ki67 marker, we conclude that the sharp increase in γH2AX foci numbers was ATM-independent and happened predominantly in proliferating cells. At the same time, gradual and moderate increase in γH2AX foci with passage number seen in both resting and proliferating cells may represent a slow, DNA double-strand break related component of the accumulation of genetic instability in MSCs. Our results provide important information on selecting appropriate passage numbers exceeding which would be associated with substantial risks to a patient-recipient, both with respect to therapeutic efficiency and side-effects related to potential neoplastic transformations due to genetic instability acquired by MSCs during expansion.


Assuntos
Proliferação de Células/fisiologia , Instabilidade Genômica , Histonas/metabolismo , Células-Tronco Mesenquimais/metabolismo , Adulto , Diferenciação Celular , Células Cultivadas , Histonas/genética , Humanos , Masculino , Células-Tronco Mesenquimais/citologia , Fosforilação
18.
Radiat Res ; 186(6): 539-548, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27922333

RESUMO

The toxicity of tritium is a public health concern given its presence and mobility in the environment. For risk predictions using radiological protection models, it is essential to allocate an appropriate radiation weighting factor (WR). This in turn should be consistent with the observed relative biological effectiveness (RBE) of tritium beta radiation. Although the International Commission on Radiological Protection (ICRP) currently recommends a WR of 1 for the calculation of committed effective dose for X rays, gamma rays and electrons of all energies, including tritium energies, there are concerns that tritium health risks are underestimated and that current regulatory tritium drinking water standards need revision. In this study, we investigated potential cytotoxic and genotoxic effects in mouse spleen after one month and eight months of chronic exposure to low-dose tritiated water (HTO). The dose regimes studied were designed to mimic human chronic consumption of HTO at levels of 10 kBq/l, 1 MBq/l and 20 MBq/l. The total doses from these radiation exposures ranged from 0.01 to 180 mGy. We also compared the biological effects of exposure to HTO with equivalent exposure to external whole-body 60Co gamma rays. Changes in spleen weight and somatic intrachromosomal recombination (DNA inversions) in spleen tissue of pKZ1Tg/+ mice were monitored. Our results showed no overall changes in either spleen organ weights and no increase mouse splenic intrachromosomal recombination frequencies, indicating that current drinking water standards for tritium exposure in the form of HTO are likely to be adequately protective against cytotoxic and genotoxic damage in spleen. These results demonstrate no evidence for cytotoxicity or genotoxicity in mouse spleen following chronic exposures to HTO activities (or equivalent gamma doses) up to 20 MBq/L.


Assuntos
Cromossomos de Mamíferos/genética , Cromossomos de Mamíferos/efeitos da radiação , Meio Ambiente , Raios gama/efeitos adversos , Recombinação Genética/efeitos da radiação , Baço/metabolismo , Trítio/efeitos adversos , Animais , Relação Dose-Resposta à Radiação , Camundongos , Camundongos Endogâmicos C57BL , Radiometria , Baço/efeitos da radiação
19.
Int J Mol Sci ; 17(9)2016 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-27649149

RESUMO

Enhanced cellular DNA repair efficiency and suppression of genomic instability have been proposed as mechanisms underlying radio-adaptive responses following low-dose radiation exposures. We previously showed that low-dose γ irradiation does not generate radio-adaptation by lowering radiation-induced cytogenetic damage in mouse spleen. Since radiation may exert tissue-specific effects, we extended these results here by examining the effects of γ radiation on cytogenetic damage and proliferative index in bone marrow erythrocytes of C57BL/6 and BALB/c mice. In C57BL/6 mice, the induction of micronuclei in polychromatic erythrocytes (MN-PCE) was observed at radiation doses of 100 mGy and greater, and suppression of erythroblast maturation occurred at doses of >500 mGy. A linear dose-response relationship for MN-PCE frequencies in C57BL/6 mice was established for radiation doses between 100 mGy and 1 Gy, with departure from linearity at doses of >1 Gy. BALB/c mice exhibited increased MN-PCE frequencies above baseline following a 20 mGy radiation exposure but did not exhibit radio-sensitivity relative to C57BL/6 mice following 2 Gy exposure. Radio-adaptation of bone marrow erythrocytes was not observed in either strain of mice exposed to low-dose priming γ irradiation (single doses of 20 mGy or 100 mGy or multiple 20 mGy doses) administered at various times prior to acute 2 Gy irradiation, confirming the lack of radio-adaptive response for induction of cytogenetic damage or suppression or erythrocyte proliferation/maturation in bone marrow of these mouse strains.


Assuntos
Células da Medula Óssea/citologia , Eritrócitos/efeitos da radiação , Micronúcleos com Defeito Cromossômico , Adaptação Fisiológica/efeitos da radiação , Animais , Células da Medula Óssea/efeitos da radiação , Núcleo Celular/efeitos da radiação , Relação Dose-Resposta à Radiação , Eritrócitos/citologia , Raios gama , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Testes para Micronúcleos , Doses de Radiação
20.
Int J Mol Sci ; 16(12): 29996-30014, 2015 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-26694365

RESUMO

Histone H2AX plays a crucial role in molecular and cellular responses to DNA damage and in the maintenance of genome stability. It is downstream of ataxia telangiectasia mutated (ATM) damage signaling pathway and there is an emerging role of the transcription factor FoxO3a, a regulator of a variety of other pathways, in activating this signaling. We asked whether H2AX may feedback to FoxO3a to affect respective FoxO3a-dependent pathways. We used a genetically matched pair of mouse embryonic fibroblast H2AX(+/+) and H2AX(-/-) cell lines to carry out comprehensive time-course and dose-response experiments and to show that the expression of several FoxO3a-regulated genes was altered in H2AX(-)(/-) compared to H2AX(+/+) cells at both basal and irradiated conditions. Hspa1b and Gadd45a were down-regulated four- to five-fold and Ddit3, Cdkn1a and Sod2 were up-regulated 2-3-fold in H2AX(-/-) cells. Using the luciferase reporter assay, we directly demonstrated that transcriptional activity of FoxoO3a was reduced in H2AX(-/-) cells. FoxO3a localization within the nuclear phospho-ATM (Ser1981) foci in irradiated cells was affected by the H2AX status, as well as its posttranslational modification (phospho-Thr32). These differences were associated with genomic instability and radiosensitivity in H2AX(-/-) cells. Finally, knockdown of H2AX in H2AX(+/+) cells resulted in FoxO3a-dependent gene expression patterns and increased radiosensitivity that partially mimicked those found in H2AX(-/-) cells. Taken together, our data suggest a role for FoxO3a in the maintenance of genome integrity in response to DNA damage that is mediated by H2AX via yet unknown mechanisms.


Assuntos
Fatores de Transcrição Forkhead/metabolismo , Instabilidade Genômica/efeitos da radiação , Histonas/metabolismo , Radiação Ionizante , Transcrição Genética/efeitos da radiação , Animais , Relação Dose-Resposta à Radiação , Embrião de Mamíferos/citologia , Fibroblastos/metabolismo , Fibroblastos/efeitos da radiação , Proteína Forkhead Box O3 , Regulação da Expressão Gênica/efeitos da radiação , Técnicas de Silenciamento de Genes , Histonas/deficiência , Espaço Intracelular/metabolismo , Espaço Intracelular/efeitos da radiação , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Biológicos , Processamento de Proteína Pós-Traducional/efeitos da radiação , Transporte Proteico/efeitos da radiação , Tolerância a Radiação/efeitos da radiação , Reprodutibilidade dos Testes , Fatores de Tempo
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