长波紫外线辐射对脊椎动物的影响

臭氧层空洞的加剧使紫外辐射不断加强,造成的环境污染已经成为广为关注的问题,但大多数都集中在中波紫外线(UVB)的生物学作用及其与两栖动物衰减关系的研究,有关长波紫外线(UVA)对生物体损伤作用的研究却甚少。本文综述了近年来UVA对脊椎动物损伤的研究概况,从细胞结构、酶活性、遗传物质、膜结构以及免疫系统等方面阐述了UVA的损伤机理,并对低剂量辐射诱导兴奋效应对紫外损伤的保护作用进行了简要概述。最后分析和总结了关于UVA损伤研究所存在的问题及两栖动物作为实验用动物模型在研究紫外线损伤中的作用。     

The effects of low doses of low-intensity ionizing radiation on DNA structure and function

Chronic effects of low doses of low-intensity ionizing radiation (IR) on biological objects have gained great social significance. This has given a considerable impetus to research into the biological effects and mechanisms of such exposures, both in Russia and abroad. In this paper, an overview of the physicochemical and molecular basis of IR influence at low doses is provided. Means of cell protection from radiation damage are studied and an analysis of the typical features and differences in the radiation effects at low and high doses is carried out. We considered DNA radiation damage, both in cell cultures and in vivo, as well as the processes and results of their repair. Particular attention is paid to changes in the basic paradigms of biological radiation effects at low doses.     

Effect of low doses of low-intensity ionizing radiation on the DNA structure and functions

Chronic effects of low doses of low intensity ionizing radiation (IR) on biological objects have now become of great social significance. This has given a considerable impetus to research into biological effects and mechanisms of such exposures both in Russia and abroad. This paper provides an overview of physicochemical and molecular bases of the IR influence at small doses and the ways of cell protection from the radiation damage, as well as the analysis of characteristic features and differences in the effects of radiation at small and high doses. We consider the DNA radiation damage both in cell cultures and in vivo, as well as processes and results of their repair. Particular attention is paid to the changes in the basic paradigms of radiation biological effects of small doses.     

Quantitative modelling of DNA damage using Monte Carlo track structure method

This paper presents data on modelling of DNA damage induced by electrons, protons and alpha-particles to provide an insight into factors which determine the biological effectiveness of radiations of high and low linear energy transfer (LET). These data include the yield of single- and double-strand breaks (ssb, dsb) and base damage in a cellular environment. We obtain a ratio of 4–15 for ssb:dsb for solid and cellular DNA and a preliminary ratio of about 2 for base damage to strand breakage. Data are also given on specific characteristics of damage at the DNA level in the form of clustered damage of varying complexity, that challenge the repair processes and if not processed adequately could lead to the observed biological effects. It is shown that nearly 30% of dsb are of complex form for low-LET radiation, solely by virtue of additional breaks, rising to about 70% for high-LET radiation. Inclusion of base damage increases the complex proportion to about 60% and 90% for low- and high-LET radiation, respectively. The data show a twofold increase in frequencies of complex dsb from low-LET radiation when base damage is taken into account. It is shown that most ssb induced by high-LET radiation have associated base damages, and also a substantial proportion is induced by low-energy electrons. Received: 20 September 1998 / Accepted in revised form: 15 December 1998     

小角X射线散射实验中蛋白质溶液的辐照损伤及防护方法

随着同步辐射光源（尤其是目前快速发展的第四代同步辐射光源）技术的进步,可用于实验的辐射通量越来越高,实验样品（特别是蛋白质等生物大分子样品）受到的辐照损伤也越来越严重。在全球现有的同步辐射装置上,蛋白质等生物大分子溶液专用小角X射线散射（SAXS）实验站的光子通量基本上都在1013cps量级。在如此高的通量下,蛋白质等生物大分子溶液样品在实验测量中受到的辐照损伤极其严重。如果没有有效的辐照防护措施,蛋白质溶液样品在毫秒级辐照时间内便会辐照损伤,导致不能获取有效的实验数据。辐照损伤严重制约了SAXS实验技术在蛋白质溶液样品方面的应用。因而,认识蛋白质溶液样品辐照损伤的产生机理、影响因素、判断标准,以及有效降低辐照损伤程度、延缓辐照损伤产生时间的方法,对于蛋白质等生物大分子溶液的散射实验具有重要的指导意义。本文在简要概述生物大分子溶液样品辐照损伤产生机理、影响因素、辐照剂量等基本概念的基础上,重点综述了同步辐射SAXS实验中辐照损伤的判断标准和防护措施。此外,本文还对比了各种防护措施的优缺点,讨论了在建HEPS新光源中SAXS束线可用的散射数据采集时间,指出辐照损伤防护剂是有价值的研究方向...     

太赫兹辐射及其生物效应研究进展

随着太赫兹源和探测技术的不断进步,太赫兹技术迅速发展并在众多领域有着广泛的应用前景.特别是在生物医学领域,太赫兹技术有望成为一种新型治疗手段.本文首先介绍了太赫兹的电磁波特点及3种太赫兹波产生方式.其次介绍了太赫兹辐射在生物上的两大效应:热效应和非热效应.最后从细胞和生物体两大层面上,详细介绍了太赫兹辐射对不同细胞的生...     

Damage pattern as a function of radiation quality and other factors

An understanding of damage pattern in critical cellular structures such as DNA is an important prerequisite for a mechanistic assessment of primary radiation damage, its possible repair, and the propagation of residual changes in somatic and germ cells as potential contributors to disease or ageing. Important quantitative insights have been made recently on the distribution in time and space of critical lesions from direct and indirect action of ionizing radiation on mammalian cells. When compared to damage from chemicals or from spontaneous degradation, e.g. depurination or base deamination in DNA, the potential of even low-LET radiation to create local hot spots of damage from single particle tracks is of utmost importance. This has important repercussions on inferences from critical biological effects at high dose and dose rate exposure situations to health risks at chronic, low-level exposures as experienced in environmental and controlled occupational settings. About 10,000 DNA lesions per human cell nucleus and day from spontaneous degradation and chemical attack cause no apparent effect, but a dose of 4 Gy translating into a similar number of direct and indirect DNA breaks induces acute lethality. Therefore, single lesions cannot explain the high efficiency of ionizing radiation in the induction of mutation, transformation and loss of proliferative capacity. Clustered damage leading to poorly repairable double-strand breaks or even more complex local DNA degradation, correlates better with fixed damage and critical biological endpoints. A comparison with other physical, chemical and biological agents indicates that ionizing radiation is indeed set apart from these by its unique micro- and nano-dosimetric traits. Only a few other agents such as bleomycin have a similar potential to cause complex damage from single events. However, in view of the multi-stage mechanism of carcinogenesis, it is still an open question whether dose-effect linearity for complex primary DNA damage and resulting fixed critical cellular lesions translate into linearity for radiation-induced cancer. To solve this enigma, a quantitative assessment of all genotoxic and harmful non-genotoxic agents affecting the human body would be needed.     

A model of interactions between radiation-induced oxidative stress, protein and DNA damage in Deinococcus radiodurans

Ionizing radiation triggers oxidative stress, which can have a variety of subtle and profound biological effects. Here we focus on mathematical modeling of potential synergistic interactions between radiation damage to DNA and oxidative stress-induced damage to proteins involved in DNA repair/replication. When sensitive sites on these proteins are attacked by radiation-induced radicals, correct repair of dangerous DNA lesions such as double strand breaks (DSBs) can be compromised. In contrast, if oxidation of important proteins is prevented by strong antioxidant defenses, DNA repair may function more efficiently. These processes probably occur to some extent even at low doses of radiation/oxidative stress, but they are easiest to investigate at high doses, where both DNA and protein damage are extensive. As an example, we use data on survival of Deinococcus radiodurans after high doses (thousands of Gy) of acute and chronic irradiation. Our model of radiogenic oxidative stress is consistent with these data and can potentially be generalized to other organisms and lower radiation doses.     

Initial evaluation and follow-up of acute radiation syndrome in two patients from the Dakar accident

The aim of this work was to evaluate and follow up the evolution of radiation damage in two victims of a radiation accident. Blood samples were used for cytogenetic evaluation of radiation dose and heterogeneity. The radiation dose estimates were 1 Gy and 2.3 Gy in the two most exposed patients. Plasma was used for the measurement of the Flt3 ligand as a marker of haematopoietic aplasia, citrulline for damage to the jejunal mucosal epithelium and oxysterols for damage to the liver, the central nervous system and the vascular compartment. The use of these biological indicators demonstrated the presence of a haematopoietic syndrome and suggested the presence of subclinical radiation-induced damage to the liver in one of the two patients. These results support the interest in using these biological indicators in order to evaluate radiation damage, especially in complex accidental situations.     

Phosphoproteomics profiling of human skin fibroblast cells reveals pathways and proteins affected by low doses of ionizing radiation

Background

High doses of ionizing radiation result in biological damage; however, the precise relationships between long-term health effects, including cancer, and low-dose exposures remain poorly understood and are currently extrapolated using high-dose exposure data. Identifying the signaling pathways and individual proteins affected at the post-translational level by radiation should shed valuable insight into the molecular mechanisms that regulate dose-dependent responses to radiation.

Principal Findings

We have identified 7117 unique phosphopeptides (2566 phosphoproteins) from control and irradiated (2 and 50 cGy) primary human skin fibroblasts 1 h post-exposure. Semi-quantitative label-free analyses were performed to identify phosphopeptides that are apparently altered by radiation exposure. This screen identified phosphorylation sites on proteins with known roles in radiation responses including TP53BP1 as well as previously unidentified radiation-responsive proteins such as the candidate tumor suppressor SASH1. Bioinformatic analyses suggest that low and high doses of radiation affect both overlapping and unique biological processes and suggest a role for MAP kinase and protein kinase A (PKA) signaling in the radiation response as well as differential regulation of p53 networks at low and high doses of radiation.

Conclusions

Our results represent the most comprehensive analysis of the phosphoproteomes of human primary fibroblasts exposed to multiple doses of ionizing radiation published to date and provide a basis for the systems-level identification of biological processes, molecular pathways and individual proteins regulated in a dose dependent manner by ionizing radiation. Further study of these modified proteins and affected networks should help to define the molecular mechanisms that regulate biological responses to radiation at different radiation doses and elucidate the impact of low-dose radiation exposure on human health.     

辐射相关microRNA研究进展

microRNA(miRNA)是一类由内源基因编码的长度约22核苷酸的非编码单链RNA分子,主要以碱基互补方式与靶基因mRNA的3'非翻译区特异性结合,通过降解mRNA或抑制蛋白翻译合成而实现对靶基因的转录后调控。研究发现,miRNA在电离辐射诱导的生物学反应中发挥重要作用。我们从以下层面概述辐射相关miRNA的研究进展,即辐射调节miRNA表达、miRNA对辐射后DNA损伤的调节、miRNA参与的辐射生物学效应。     

Radiosensitizers as probes of DNA damage and cell killing

Cell killing and other deleterious biological effects of ionizing radiation are the result of chemical changes to critical targets, initiated at the time of exposure. Electron-affinic radiosensitizers act, primarily, by chemically modifying this radiation damage and its consequent biological expression, and such changes can be used to probe the nature of the cellular radiation target. According to a redox hypothesis of radiation modification, the molecular mechanism of electronic-affinic radiosensitization involves an oxidative interaction of the sensitizer with reactive, potentially damaging target radicals, which competes with reductive processes that restore the target to its undamaged state. The effects have been compared of a series of hypoxic cell radiosensitizers on radiation-induced DNA damage and mammalian cell killing, in order to ascertain the nature of the critical radiation target site(s) involved. Sensitizer efficacy is determined by the ability to oxidize the radiation target and is found to increase exponentially with increasing electron affinity. The threshold redox potential, below which no sensitization occurs, corresponds to the oxidation potential of the target bioradical involved, and is characteristic, and useful in identification, of the particular radiation target. Model product analysis studies of DNA base damage, inorganic phosphate release, single-strand breaks and incorporation of radioactively labelled sensitizer into DNA show a correspondence between the electronic-affinic radiosensitization of DNA damage and cell killing. A careful comparison of the radiosensitization of different DNA sites and cell killing indicates that the sugar-phosphate backbone of DNA, not the heterocyclic bases, is the DNA target site which mimics cell killing in its threshold redox potential and overall radiosensitization response. These results suggest that the enhancement by electron-affinic drugs of radiation damage to the DNA backbone (strand breaks) correlates strongly with, and is the most likely cause of, the radiosensitization of hypoxic cell killing.     

Evaluation of DNA damage in a population of bats (Chiroptera) residing in an abandoned monazite mine

Ionising radiation has the ability to induce DNA damage. While the effects of high doses of radiation of short duration have been well documented, the biological effects of long-term exposure to low doses are poorly understood. This study evaluated the clastogenic effects of low dose ionising radiation on a population of bats (Chiroptera) residing in an abandoned monazite mine. Bats were sampled from two chambers in the mine, where external radiation levels measured around 20 microSv/h (low dose) and 100 microSv/h (higher dose), respectively. A control group of bats was sampled from a cave with no detectable radiation above normal background levels. The micronucleus assay was used to evaluate residual radiation damage in binucleated lymphocytes and showed that the micronucleus frequency per 500 binucleated lymphocytes was increased in the lower radiation-exposed group (17.7) and the higher radiation-exposed group (27.1) compared to the control group (5.3). This study also showed that bats exposed to radiation presented with an increased number of micronuclei per one thousand reticulocytes (2.88 and 10.75 in the lower and high radiation-exposed groups respectively) when compared to the control group (1.7). The single-cell gel electrophoresis (comet) assay was used as a means of evaluating clastogenecity of exposure to radiation at the level of individual cells. Bats exposed to radiation demonstrated increased DNA damage as shown by the length of the comet tails and showed an increase in cumulative damage. The results of the micronucleus and the comet assays indicated not only a statistically significant difference between test and control groups (P<0.001), but also a dose-dependent increase in DNA damage (P<0.001). These assays may thus be useful in evaluating the potential clastogenecity of exposure to continuous low doses of ionising radiation.     

mBAND analysis for high- and low-LET radiation-induced chromosome aberrations: a review

During long-term space travel or cancer therapy, humans are exposed to high linear energy transfer (LET) energetic heavy ions. High-LET radiation is much more effective than low-LET radiation in causing various biological effects, including cell inactivation, genetic mutations, cataracts and cancer induction. Most of these biological endpoints are closely related to chromosomal damage, and cytogenetic damage can be utilized as a biomarker for radiation insults. Epidemiological data, mainly from survivors of the atomic bomb detonations in Japan, have enabled risk estimation from low-LET radiation exposures. The identification of a cytogenetic signature that distinguishes high- from low-LET exposure remains a long-term goal in radiobiology. Recently developed fluorescence in situ hybridization (FISH)-painting methodologies have revealed unique endpoints related to radiation quality. Heavy-ions induce a high fraction of complex-type exchanges, and possibly unique chromosome rearrangements. This review will concentrate on recent data obtained with multicolor banding in situ hybridization (mBAND) methods in mammalian cells exposed to low- and high-LET radiations. Chromosome analysis with mBAND technique allows detection of both inter- and intrachromosomal exchanges, and also distribution of the breakpoints of aberrations.     

紫外辐射的细胞生物学效应及其机制

地球表面的生物体会受到来自阳光紫外辐射的照射。两极臭氧层空洞的形成使地球表面的紫外辐射水平,特别是UVB的水平增加,进而对生物体的危害日益加重。因此,深入研究紫外辐射生物学效应的信号转导机制并阐明其损伤机制和生物体的反应机制等具有重要意义,也可为紫外辐射损伤防护的研究提供新思路。本文综述了本领域近年来的相关研究,从紫外辐射所致生物学效应的信号转导机制(包括对DNA的直接损伤作用、细胞膜激酶和非激酶受体通路、细胞质通路以及microRNA)等方面对紫外辐射的损伤机制进行了比较系统的阐述和总结。     

Nontargeted effects of ionizing radiation: implications for low-dose exposures

The traditional thinking has been that the biological effects of ionizing radiation occur in irradiated cells as a consequence of the DNA damage they incur. This implies that: 1) biological effects occur only in irratiated cells, 2) radiation traversal through the nucleus of the cell is a prerequisite to produce a biological response, and 3) DNA is the target molecule in the cell. Evidence has been emerging, however, for non-DNA targeted effects of radiation; that is, effects including mutations, chromosomal aberrations, and changes in gene expression which occur in cells that in themselves receive no radiation exposure. Two of these phenomena will be described in this paper. The first is radiation-induced genomic instability whereby biological effects, including elevated frequencies of mutations and chromosomal aberrations, arise in the distant descendants of irradiated cells. The second phenomenon has been termed the "bystander effect", whereby in a mixed population of irradiated and nonirradiated cells, biological effects arise in those cells that receive no radiation exposure. The damage signals are transmitted from cell to cell through gap junction channels, and the genetic effects observed in bystander cells appear to result from an upregulation of oxidative stress. The possible influence of these non-targeted effects of radiation of the respounse to low-dose exposures is discussed.     

Combined small angle X-ray solution scattering with atomic force microscopy for characterizing radiation damage on biological macromolecules

Background

Synchrotron radiation facilities are pillars of modern structural biology. Small-Angle X-ray scattering performed at synchrotron sources is often used to characterize the shape of biological macromolecules. A major challenge with high-energy X-ray beam on such macromolecules is the perturbation of sample due to radiation damage.

Results

By employing atomic force microscopy, another common technique to determine the shape of biological macromolecules when deposited on flat substrates, we present a protocol to evaluate and characterize consequences of radiation damage. It requires the acquisition of images of irradiated samples at the single molecule level in a timely manner while using minimal amounts of protein. The protocol has been tested on two different molecular systems: a large globular tetremeric enzyme (β-Amylase) and a rod-shape plant virus (tobacco mosaic virus). Radiation damage on the globular enzyme leads to an apparent increase in molecular sizes whereas the effect on the long virus is a breakage into smaller pieces resulting in a decrease of the average long-axis radius.

Conclusions

These results show that radiation damage can appear in different forms and strongly support the need to check the effect of radiation damage at synchrotron sources using the presented protocol.

     

mBAND analysis of chromosomal aberrations in human epithelial cells exposed to low- and high-LET radiation

Energetic heavy ions pose a potential health risk to astronauts who have participated in extended space missions. High-LET radiation is much more effective than low-LET radiation in the induction of biological effects, including cell inactivation, genetic mutations, cataracts and cancer. Most of these biological end points are closely correlated with chromosomal damage, which can be used as a biomarker for radiation damage. Multicolor banding in situ hybridization (mBAND) has proven to be highly useful for the study of intrachromosomal aberrations, which have been suggested as a biomarker of exposure to high-LET radiation. To investigate biological signatures of radiation quality and the complexity of intrachromosomal aberrations, we exposed human epithelial cells in vitro to (137)Cs gamma rays or iron ions (600 MeV/nucleon) and collected chromosomes using a premature chromosome condensation technique. Aberrations in chromosome 3 were analyzed using mBAND probes. The results of our study confirmed the observation of a higher incidence of inversions for high-LET radiation. However, detailed analysis of the inversion type revealed that both iron ions and gamma rays induced a low incidence of simple inversions. Half of the inversions observed in the low-LET-irradiated samples were accompanied by other types of intrachromosome aberrations, but few inversions were accompanied by interchromosome aberrations. In contrast, iron ions induced a significant fraction of inversions that involved complex rearrangements of both inter- and intrachromosome exchanges.     

The cell membrane as a biosensor of oxidative stress induced by radiation exposure: a multiparameter investigation

The role of biological membranes as a target in biological radiation damage remains unclear. The present study investigates how the biochemical and biophysical properties of a simple biological model, i.e. human erythrocyte membranes, are altered after exposure to relatively low doses of (60)Co gamma rays. Lipid peroxidation increased in the hours after radiation exposure, based on measurements of MDA and on the lipid peroxidation index after parinaric acid incorporation. Protein carbonyl content also increased rapidly after radiation exposure. An imbalance between the radiation-mediated oxidative damages and the antioxidant capacity of the erythrocytes was observed in the hours after radiation exposure. Antioxidant enzyme activities, mainly catalase and glutathione peroxidase, were found to decrease after irradiation. The development of a radiation-induced oxidative stress probably explains the reorganization of the fatty acid pattern 72 h after radiation exposure. The phosphatidylethanolamine (PE) fatty acids of the (n-3) and (n-6) series decreased, while the PE saturated fatty acid content increased. All these modifications may be involved in the variation of the biophysical properties of the membranes that we noted after radiation exposure. Specifically, we observed that the lipid compartment of the membrane became more fluid while the lipid-protein membrane interface became more rigid. Taken together, these findings reinforce our understanding that the cell membrane is a significant biological target of radiation. Thus the role of the biological membrane in the expression and course of cell damage after radiation exposure must be considered.