Plutonium behavior after pulmonary administration according to solubility properties, and consequences on alveolar macrophage activation

DTPA and anti-inflammatory drug associations to alleviate Pu-induced response of macrophages in vitro

Internal contamination by inhalation of plutonium poorly soluble compounds leads to their long time retention in alveolar macrophages inducing delayed pathology development. As previous studies highlighted co-localization of retained Pu and inflammatory lesions, this study was designed to assess the combined effect of the reference treatment (DTPA) and anti-inflammatory drugs on Pu-induced early response of macrophages in vitro. Pu colloids, mimicking poorly soluble Pu, were characterized using filtration and solid-state nuclear track detectors CR39. Their bioavailability was determined using a biphasic acellular model. Treatment effects on Pu dissolution and release as well as on Pu-induced pro-inflammatory response were assessed over 7 days on macrophage-like cells. DTPA treatment, associated or not with anti-inflammatory drug, increased Pu dissolution and release from contaminated THP-1 differentiated cells after 7 days. Significant decreases in Pu-induced IL-8 and MCP-1 secretions were also observed with anti-inflammatory treatment associated or not with DTPA. This study highlighted the ability of DTPA to partially dissolve a poorly soluble form of Pu as well as the ability of anti-inflammatory drugs to modulate Pu-induced pro-inflammatory response in macrophage-like cells. These treatments seem a promising strategy to improve the clinical management of Pu pulmonary contaminations and to limit delayed pulmonary pathology occurrence.

Decontamination of Actinide-contaminated Injured Skin with Ca-DTPA Products Using an Ex Vivo Rat Skin Model

ABSTRACT

Skin contamination by α-emitting actinides such as plutonium and americium is a risk for workers during nuclear fuel production and reactor decommissioning. Decontamination of skin is an important medical countermeasure to limit potential internal contamination, particularly in the case of injured skin. Current recommendations include undressing of the victim followed by skin washing using soap or chelating agents, such as diethylene triamine pentaacetic acid (DTPA). The goal of the present work is to assess the efficacy of a novel Ca-DTPA loaded gel to decontaminate injured skin exposed to plutonium or americium as compared to recommended treatments. For decontaminant testing on injured skin, whole body skin was obtained from euthanized rats and lesions created using a metallic brush. Delimited test areas were contaminated with plutonium or americium solutions of known properties. Various protocols were tested including time before contamination, duration of gel application, washing steps, as well as the concomitant addition or not of dressings. Activity was measured in each decontamination product and in skin. Data indicate that healthy skin was easier to decontaminate than damaged skin. On injured skin, we demonstrated an increased decontamination efficacy of the Ca-DTPA gel formulation as compared to the solution. Importantly, gel application alone was effective, and further gel applications could be used for residual activity.

Interaction Between the Transferrin Protein and Plutonium (and Thorium), What's New?

Transferrin (Tf) is a glycoprotein that transports iron from the serum to the various organs. Several studies have highlighted that Tf can interact with metals other than Fe(III), including actinides that are chemical and radiological toxics. We propose here to report on the behavior of Th(IV) and Pu(IV) in comparison with Fe(III) upon Tf complexation. We considered UV-Vis and IR data of the M2 Tf complex (M=Fe, Th, Pu) and combined experimental EXAFS data with MD models. EXAFS data of the first M-O coordination sphere are consistent with the MD model considering 1 synergistic carbonate. Further EXAFS data analysis strongly suggests that contamination by Th/Pu colloids seems to occur upon Tf complexation, but it seems limited. SAXS data have also been recorded for all complexes and also after the addition of Deferoxamine-B (DFOB) in the medium. The Rg values are very close for apoTf, ThTf and PuTf, but slightly larger than for holoTf. Data suggest that the structure of the protein is more ellipsoidal than spherical, with a flattened oblate form. From this data, the following order of conformation size might be considered:holoTf Collapse

Key Words

• Plutonium
• SAX
• Transferrin
• XAS
• metalloprotein

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MESH Headings

• Transferrin/chemistry
• Plutonium/chemistry
• Thorium/chemistry
• Ferric Compounds
• Scattering, Small Angle
• X-Ray Diffraction

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Grants

• Ministère de l'Enseignement supérieur, de la Recherche et de l'Innovation

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Affiliation(s)

Cyril Zurita Université Côte d'Azur, CNRS, Institut de Chimie de Nice, 06108, Nice, France
Satoru Tsushima Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328, Dresden, Germany Internationnal Research Frontiers Initiative, Institute of Innovative Research, Tokyo Institute of Technology, Meguro, 152-8550, Tokyo, Japan
Pier Lorenzo Solari Synchrotron SOLEIL, L'Orme des Merisiers, 91190, Saint Aubin, France
Denis Menut Synchrotron SOLEIL, L'Orme des Merisiers, 91190, Saint Aubin, France
Sandrine Dourdain ICSM, Université de Montpellier, CEA, CNRS, ENSCM, Marcoule, France
Aurélie Jeanson Université Côte d'Azur, CNRS, Institut de Chimie de Nice, 06108, Nice, France
Gaëlle Creff Université Côte d'Azur, CNRS, Institut de Chimie de Nice, 06108, Nice, France
Christophe Den Auwer Université Côte d'Azur, CNRS, Institut de Chimie de Nice, 06108, Nice, France

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Collaborators Collapse

Take a Swipe at Actinide Bioavailability: Application of a New In Vitro Method

ABSTRACT

Filter swipe tests are used for routine analyses of actinides in nuclear industrial, research, and weapon facilities as well as following accidental release. Actinide physicochemical properties will determine in part bioavailability and internal contamination levels. The aim of this work was to develop and validate a new approach to predict actinide bioavailability recovered by filter swipe tests. As proof of concept and to simulate a routine or an accidental situation, filter swipes were obtained from a nuclear research facility glove box. A recently-developed biomimetic assay for prediction of actinide bioavailability was adapted for bioavailability measurements using material obtained from these filter swipes. In addition, the efficacy of the clinically-used chelator, diethylenetriamine pentaacetate (Ca-DTPA), to enhance transportability was determined. This report shows that it is possible to evaluate physicochemical properties and to predict bioavailability of filter swipe-associated actinides.

Chelation therapy with 3,4,3-Li(1,2-HOPO) after pulmonary exposure to plutonium in rats

Internal exposure to plutonium can occur through inhalation for the nuclear worker, but also for the public if the radionuclide was released into the atmosphere in the context of a nuclear accident or terrorist attack. DieThylenetriaminePentaAcetic acid (DTPA) is currently still the only authorized chelator that can be used to decorporate internalized plutonium. The Linear HydrOxyPyridinOne-based ligand named 3,4,3-Li(1,2-HOPO) remains the most promising drug candidate to replace it in the hopes of improving chelating treatment. This study aimed to assess the efficacy of 3,4,3-Li(1,2-HOPO) in removing plutonium from rats exposed to the lungs, depending on the timing and route of treatment, and almost always compared to DTPA at a ten-fold higher dose used as a reference chelator. First, early intravenous injection or inhalation of 3,4,3-Li(1,2-HOPO) demonstrated superior efficacy over DTPA in preventing plutonium accumulation in liver and bone in rats exposed by injection or lung intubation. However, this superiority of 3,4,3-Li(1,2-HOPO) was much less pronounced with delayed treatment. In rats given plutonium in the lungs, the experiments also showed that 3,4,3-Li-HOPO reduced pulmonary retention of plutonium more effectively than DTPA only when the chelators were injected early but not at delayed times, while it was always the better of the two chelators when they were inhaled. Under our experimental conditions, the rapid oral administration of 3,4,3-Li(1,2-HOPO) was successful in preventing systemic accumulation of plutonium, but not in decreasing lung retention. Thus, after exposure to plutonium by inhalation, the best emergency treatment would be the rapid inhalation of a 3,4,3-Li(1,2-HOPO) aerosol to limit pulmonary retention of plutonium and prevent extrapulmonary deposition of plutonium in target systemic tissues.

A Simple, Rapid, Comparative Evaluation of Multiple Products for Decontamination of Actinide-contaminated Rat Skin Ex Vivo

ABSTRACT

Decontamination of skin is an important medical countermeasure in order to limit potential internal contamination by radionuclides such as actinides. Minimizing skin surface contamination will ultimately prevent internal contamination and subsequent committed effective dose as well as contamination spreading. The decontamination agents tested on a rat skin ex vivo model ranged from water to hydrogel wound dressings. A surfactant-containing cleansing gel and calixarene nanoemulsion with chelation properties demonstrated marked decontamination efficacies as compared with water or the chelator DTPA. Based on efficacy to remove different actinide physicochemical forms from skin, the results demonstrate that all products can remove the more soluble forms, but a further component of emulsifying or tensioactive action is required for less soluble forms. This indicates that for practical purposes, successful decontamination will depend on identification of the actinide element, the physicochemical form, and possibly the solvent. This study offers a simple, quick, cheap, reproducible screening method for efficacy evaluation of multiple products for removal of a variety of contaminants.

In vitro evidence of the influence of complexation of Pu and Am on uptake by human lung epithelial cells Calu-3

Understanding the mechanisms involved in retention and clearance of actinides from the lungs after accidental intake is essential for the evaluation of the associated radiological risks. Although the absorption of radioelements has been shown in vivo to depend on their nature and physico-chemical properties, their mechanisms of translocation remain unknown. In this study, we have evaluated in vitro the binding and uptake by bronchial epithelial cells Calu-3 of 2 transuranic actinides, plutonium (Pu) and americium (Am), as the first steps of translocation across the pulmonary barrier. For this purpose, Calu-3 cells grown to confluence in 24-well plates were exposed to the radioelements for 24 h under various culture conditions. Two compartments were identified for the association of actinides to cells, corresponding to the membrane bound and internalized fractions. Binding of Pu was slightly higher than of Am, and depended on its initial chemical form (nitrate, citrate, colloids). Uptake of Pu and Am nitrate was higher in serum-free conditions than in supplemented medium, with an active mechanism involved in Pu internalization. Overall, our results suggest that complexation of actinides to bioligands may have an influence on their uptake by pulmonary epithelial cells, and therefore possibly on their subsequent absorption into blood.

Interpretation of Enhanced Fecal and Urinary Plutonium Excretion Data under a 2-y Regular DTPA Treatment Started Months after Intake

ABSTRACT

In a worker who had internalized plutonium, most likely through inhalation of a somewhat soluble compound, an extensive diethylenetriaminepentaacetate (DTPA) treatment regimen was initiated several months after contamination. Numerous radiotoxicological analyses were performed in both fecal and urinary specimens collected, sometimes for three consecutive days after DTPA administration. Activity measurements showed the continued effectiveness of DTPA intravenous infusions in removing plutonium from tissues of retention even if the treatment regimen started very belatedly after contamination. In the present case, the activity excreted through urine within the first 24-h after a DTPA infusion contributed only about half of that activity excreted within the first three days (i.e., the cumulative activity of the first three 24-h urine collections). In addition, the careful study of the data revealed that DTPA-induced excretion of plutonium via fecal pathway significantly contributed to the overall decorporation. The intracellular chelation of plutonium may be responsible for this enhanced excretion of activity in feces as well as for the delayed and sustained increased clearance of activity in urine. The authors would suggest that the occupational physicians offer to individuals who internalized moderately soluble or soluble plutonium compounds undergo a long-term DTPA treatment, especially when it is not initiated promptly after intake. Under this scenario, measurements of plutonium in successive urine and fecal collections after treatment should be required to get a better estimate of the therapeutic benefit. Also, intracellular chelation and fecal route should be taken into account for better interpretation of radiotoxicological data and modeling of plutonium kinetics under delayed DTPA treatment.

Comparison of Local and Systemic DTPA Treatment Efficacy According to Actinide Physicochemical Properties Following Lung or Wound Contamination in the Rat

Purpose: In cases of occupational accidents in nuclear facilities or subsequent to terrorist activities, the most likely routes of internal contamination with alpha-particle emitting actinides, such as plutonium (Pu) and americium (Am), are by inhalation or following wounding. Following contamination, actinide transfer to the circulation and subsequent deposition in skeleton and liver depends primarily on the physicochemical nature of the compound. The treatment remit following internal contamination is to decrease actinide retention and in consequence potential health risks, both at the contamination site and in systemic retention organs as well as to promote elimination. The only approved drug for decorporation of Pu and Am is the metal chelator diethylenetriaminepentaacetic acid (DTPA). However, a limited efficacy of DTPA has been reported following contamination with insoluble actinides, irrespective of the contamination route. The objectives of this work are to evaluate the efficacy of prompt local and/or systemic DTPA treatment regimens following lung or wound contamination by actinides with differing solubility. The conclusions are drawn from retrospective analysis of experimental studies carried out over 10 years. Materials and Methods: Rat lungs or wounds were contaminated either with poorly soluble Mixed OXide (U, Pu O2) or more soluble forms of Pu (nitrate or citrate). DTPA treatment was administered promptly after contamination, locally to lungs by insufflation of a powder or inhalation of aerosolized solution or by injection directly into the wound site. Intravenous injections of DTPA were given either once or repeated in combination with the local treatment. Doses ranged from 1 to 30 µmol/kg. Animals were euthanized from day 7-21 and alpha activity levels were measured in urine, lungs, wound, bone and liver for determination of decorporation efficacy. Results: Different experiments confirmed that whatever the route of contamination, most of the activity is retained at the entry site after insoluble MOX contamination as compared with contamination with more soluble forms which results in very low activities reaching the systemic compartment and subsequent retention in bone and liver. Several DTPA treatment regimens were evaluated that had no significant effect on either lung or wound levels compared with untreated animals. In contrast, in all cases systemic retention (skeleton and liver) was reduced and urinary excretion were enhanced irrespective of the contamination route or DTPA treatment regimen. Conclusion: The present study demonstrates that despite limitation of retention in systemic organs, different DTPA protocols were ineffective in removing insoluble actinides deposited in lungs or wound site. For moderately soluble actinides, local or intravenous DTPA treatment reduced activity levels both at contamination and at systemic sites.

Evidence for a differential translocation of actinides across human lung epithelial cell monolayer in vitro according to their physicochemical properties and the presence of a chelating agent

The epithelial cell plays a key role in the transfer of radionuclides from lungs to blood following pulmonary exposure. The present study was designed to evaluate the transfer across human lung epithelial cells of various actinides (plutonium, americium and uranium), the influence of the physicochemical properties of plutonium compounds and of the chelating agent diethylene triamine pentaacetic acid (DTPA). To address this question, Calu-3 cells grown in a bicameral culture system were used. The integrity of the epithelial barrier was evaluated by measuring transepithelial electrical resistance (TEER) and the passage of a fluorescent marker, lucifer yellow. Activity measurement in basal compartment following periodic collection of culture medium was made from 2 h to seven days. To facilitate data handling and analysis, the statistical tool STATBIODIS was used. The results indicate differences in transfer for the different elements, and according to Pu physicochemical properties. Though to various extents, the chelating agent DTPA always increased the transfer of Pu and Am across the epithelial cells, without altering the integrity of the epithelial barrier. This in vitro cell culture model, by mimicking translocation of actinides from lungs to blood, can represent a valuable tool to further understand the underlying mechanisms and properties controlling this process.

Morphological features of pulmonary fibrosis in workers occupationally exposed to alpha radiation

Purpose: The article reports on a comparative analysis of biological specimens of lung tissues collected from workers with pulmonary fibrosis induced by internal exposure to plutonium alpha-particles (plutonium-induced pulmonary fibrosis [PuPF]) and with etiologically different pulmonary fibrosis (non-PuPF) that developed as an outcome of a chronic obstructive pulmonary disease (COPD).Materials and methods: To perform histological examinations, lung tissues were sampled during autopsy. Six samples of various lung regions (the apical region, the lingula of the left lung and the inferior lobe) were collected from each donor. The resected tissue samples were fixed in 10% neutral-buffered formalin during 24 h and embedded into paraffin blocks (FFPE). FFPE blocks with lung tissue specimens collected from 56 workers with PuPF, 34 workers with non-PuPF and 35 workers without any lung disease were used in the study. To perform microscopic examination, lung tissue specimens were hematoxylin and eosin stained. To examine the connective-tissue scaffold of lung stroma and identify foci of pulmonary fibrosis, the cut sections of paraffin blocks were stained by Van Gizon's method (to assess the total volume of fibrosis-affected tissues), Gomori's technique (to define the reticular scaffold of lung stroma) and Weigert's technique (to examine elastic fibers). Morphological patterns of all biological specimens were studied using immunohistochemistry. To fit the empirical data, the Weibull's model was used.Results and conclusions: The study found qualitative and quantitative morphological features specific for PuPF compared to non-PuPF. The study demonstrated that hyper-production of collagen type V plays a key role in PuPF. The collagen type V content in fibrotic foci in lung tissue specimens from workers with PuPF was found to be increased.

Chelation Treatment by Early Inhalation of Liquid Aerosol DTPA for Removing Plutonium after Rat Lung Contamination

Occupational contamination is a potential health risk associated with plutonium inhalation. DTPA remains the chelating drug of choice to decorporate plutonium. In this study, plutonium was found to be more effectively removed from lungs by a single inhalation of nebulized DTPA solution at only 1.1 µmol.kg^-1 than by a single intravenous (i.v.) dose of DTPA at 15 µmol.kg^-1. When DTPA was inhaled promptly after contamination, it removed the transportable fraction of plutonium prior blood absorption, thereby preventing both liver and bone depositions. Conversely, DTPA injection was better than inhalation at reducing the extrapulmonary burden, probably due to the much greater circulating dose, favoring the mobilization of plutonium already translocated. Thus, prompt inhalation, concomitantly supplemented with i.v. injection, of DTPA induced an important decrease in extrapulmonary deposits. Repeated DTPA inhalations over several weeks were more efficient than a single inhalation in limiting both pulmonary and extrapulmonary plutonium retention, due at least in part to the chelation of the transportable fraction of lung plutonium. Furthermore, repeated DTPA injections remained better at reducing liver and bone plutonium retentions. Taken together, our results suggest that multiple DTPA inhalations may be considered an effective treatment after inhalation of plutonium, particularly given the ease of this needle-free delivery, for the two following conditions: 1. A treatment combining i.v. injection and inhalation should be given in an emergency scenario to efficiently chelate the activity already absorbed; 2. Inhalations should be administered daily to effectively trap the early transferable fraction.

Americium biodistribution in rats after wound contamination with different physicochemical forms in the presence or absence of plutonium: analyses using STATBIODIS

Americium (Am) biodistribution data obtained after wound contamination in rats were analysed to evaluate and quantify the influence of different physicochemical forms of Am in the presence or absence of plutonium (Pu). The biodistribution data were individual Am daily urinary excretion and tissue retention. The data were analysed with STATBIODIS, a statistical tool developed in the laboratory and based on the R language. Non-parametric methods were selected to comply with the data characteristics. Am systemic tissue retention and urinary excretion data were much greater for contamination with soluble physicochemical forms than insoluble forms. Meanwhile, Am relative biodistribution between the main retention tissues (skeleton, liver and kidney) remained the same. Hence, after absorption into blood the radionuclide behaviour was independent of the physicochemical form. The presence of Pu did not change the Am biodistribution. Comparisons of the biodistribution data from the laboratory with mean values published by other laboratories showed that soluble to moderately soluble forms of Am resulted in similar urine excretion after contamination, whether it was intravenous, intramuscular, subcutaneous injection or incision. Findings from this work will contribute to improve the understanding and interpretation of wound contamination cases with different physicochemical forms and mixtures of actinides including Am.

A quick and simple in vitro assay to predict bioavailability of actinides following accidental exposure

Physicochemical properties of actinides highly influence internal intake and biodistribution. An a priori knowledge of the dissolution properties of compounds involved in accidental exposure would be of great help in early dose assessment. However, this information is rarely available, leading to difficulties in interpreting excretion data from contaminated victims. We developed an in vitro acellular assay to predict in vivo bioavailability of actinides and improve medical handling of the victims. Various actinides of different physicochemical properties were used to validate the reliability of the assay to mimic in vivo behavior of the contaminants. Our assay was designed as a dynamic muticompartmental system in which an agarose gel represents the retention compartment of actinides and a dynamic phase the transfer compartment. Relevant physiological conditions were obtained by introducing various components both in the static and dynamic phases. The proposed model may provide a good prediction of in vivo behavior and could be used as a first assessment to predict the fraction of actinides that could be potentially transferred from retention compartments, as well as the fraction available to chelating drugs.

Autoradiographic analysis of internal plutonium radiation exposure in Nagasaki atomic bomb victims

Background

Radiation doses received by Hiroshima and Nagasaki atomic bomb survivors has been evaluated from data related only to external exposure because there was no reliable evidence for internal exposure in atomic bomb victims. However, we assumed that the contribution of internal exposure cannot be ruled out.

Methods

Autoradiography was carried out with the 70-year old paraffin-embedded specimens taken from Nagasaki atomic bomb victims who died within 5 months after the bombing. After exposure to photo emulsion for 6 months alpha-tracks were revealed in the specimens. We confirmed the alpha-tracks were emitted from deposited plutonium (Pu) in reference to the track length of the 8.787 MeV alpha-particle of thorium series from Polonium-212. Radioactivity concentration of Pu was obtained by counting alpha-tracks. The absorbed dose of each cell nucleus penetrated by an alpha-particle was estimated by calculating the absorbed energy from the particle.

Results

Using old paraffin embedded sections processed about 70 years ago, we demonstrated for the first time that conditions in the aftermath of the bombing led to internal exposure to alpha-particles emitted from Pu, the fissile material of the Nagasaki atomic bomb. Dose rate of internal exposure was higher in the victims exposed outdoors than those indoors. Radioactivity concentration was relatively uniform among organs examined in a victim.

Conclusion

Pu was deposited in the bodies of the Nagasaki A-bomb victims presumably via various routes. Organ dose from Pu of the Nagasaki A-bomb victims studied was during their surviving period, which is lower compared with external exposure. However, the impact to the individual cell nucleus by a single alpha-particle might not be negligible, It would be meaningful; to analyze the relationship of the impact of internal exposure at the cellular level and organ dose. The 70-year old pathological specimens utilized in our study are an invaluable source for understanding internal radiation exposure and are crucial in elucidating experimentally unreproducible phenomena.

Decorporation Approach after Rat Lung Contamination with Plutonium: Evaluation of the Key Parameters Influencing the Efficacy of a Protracted Chelation Treatment

While the efficacy of a protracted zinc (Zn)- or calcium (Ca)-diethylenetriaminepentaacetic acid (DTPA) treatment in reducing transuranic body burden has already been demonstrated, questions about therapeutic variables remain. In response to this, we designed animal experiments primarily to assess both the effect of fractionation of a given dose and the effect of the frequency of dose fraction, with the same total dose. In our study, rats were contaminated intravenously with plutonium (Pu) then treated several days later with Ca-DTPA given at once or in various split-dose regimens cumulating to the same total dose and spread over several days. Similar efficacies were induced by the injection of the total dose or by splitting the dose in several smaller doses, independent of the number of doses and the dose level per injection. In a second study, rats were pulmonary contaminated, and three weeks later they received a Ca-DTPA dose 11-fold higher than the maximal daily recommended dose, administered either as a single bolus or as numerous multiple injections cumulating to the same dose, based on different injection frequency schedules. Independent of frequency schedule, the various split-dose regimens spread over weeks/months were as efficient as single delivery of the total dose in mobilizing lung plutonium, and had a therapeutic advantage for removal of retained hepatic and bone plutonium burdens. We concluded that cumulative dose level was a therapeutic variable of greater importance than the distribution of split doses for the success of a repeated treatment regimen on retained tissue plutonium. In addition, pulmonary administration of clodronate, which aims at killing alveolar macrophages and subsequently releasing their plutonium content, and which is associated with a continuous Ca-DTPA infusion regimen, suggested that the efficacy of injected Ca-DTPA in decorporating lung deposit is limited, due to its restricted penetration into alveolar macrophages and not because plutonium, as a physicochemical form, is unavailable for chelation.

Analysis methodology and development of a statistical tool for biodistribution data from internal contamination with actinides

The aim of this work was to develop a computational tool that integrates several statistical analysis features for biodistribution data from internal contamination experiments. These data represent actinide levels in biological compartments as a function of time and are derived from activity measurements in tissues and excreta. These experiments aim at assessing the influence of different contamination conditions (e.g. intake route or radioelement) on the biological behavior of the contaminant. The ever increasing number of datasets and diversity of experimental conditions make the handling and analysis of biodistribution data difficult. This work sought to facilitate the statistical analysis of a large number of datasets and the comparison of results from diverse experimental conditions. Functional modules were developed using the open-source programming language R to facilitate specific operations: descriptive statistics, visual comparison, curve fitting, and implementation of biokinetic models. In addition, the structure of the datasets was harmonized using the same table format. Analysis outputs can be written in text files and updated data can be written in the consistent table format. Hence, a data repository is built progressively, which is essential for the optimal use of animal data. Graphical representations can be automatically generated and saved as image files. The resulting computational tool was applied using data derived from wound contamination experiments conducted under different conditions. In facilitating biodistribution data handling and statistical analyses, this computational tool ensures faster analyses and a better reproducibility compared with the use of multiple office software applications. Furthermore, re-analysis of archival data and comparison of data from different sources is made much easier. Hence this tool will help to understand better the influence of contamination characteristics on actinide biokinetics. Our approach can aid the optimization of treatment protocols and therefore contribute to the improvement of the medical response after internal contamination with actinides.

In vitro assessment of plutonium uptake and release using the human macrophage-like THP-1 cells

Plutonium (Pu) intake by inhalation is one of the major potential consequences following an accident in the nuclear industry or after improvised nuclear device explosion. Macrophages are essential players in retention and clearance of inhaled compounds. However, the extent to which these phagocytic cells are involved in these processes highly depends on the solubility properties of the Pu deposited in the lungs. Our objectives were to develop an in vitro model representative of the human pulmonary macrophage capacity to internalize and release Pu compounds in presence or not of the chelating drug diethylenetriaminepentaacetate (DTPA). The monocyte cell line THP-1 was used after differentiation into macrophage-like cells. We assessed the cellular uptake of various forms of Pu which differ in their solubility, as well as the release of the internalized Pu. Results obtained with differentiated THP-1 cells are in good agreement with data from rat alveolar macrophages and fit well with in vivo data. In both cell types, Pu uptake and release depend upon Pu solubility and in all cases DTPA increases Pu release. The proposed model may provide a good complement to in vivo animal experiments and could be used in a first assessment to predict the fraction of Pu that could be potentially trapped, as well as the fraction available to chelating drugs.

Forecasting the In Vivo Behavior of Radiocontaminants of Unknown Physicochemical Properties Using a Simple In Vitro Test

An understanding of the "bioavailability" of disseminated radiocontaminants is a necessary adjunct in order to tailor treatment and to calculate dose. A simple test has been designed to predict the bioavailability of different actinide forms likely to be found after dissemination of radioactive elements by dispersal devices or nuclear reactor incidents. Plutonium (Pu) or Americium (Am) nitrate or MOX (U,PuO2) are immobilized in culture wells using a static gel phase simulating biological compartments (lung, wound, etc.). Gels are incubated in a fluid phase representing physiological media (plasma, sweat, etc.). Transfer of radionuclide from static to fluid phase reflects contaminant bioavailability. After 48 h of incubation in physiological saline, Am transfer from static to fluid phase was greater than for Pu (70% vs. 15% of initial activity). Transfer of Pu or Am was markedly less from the oxide form of the two elements (1% Am and 0.05% Pu transferred). Medium representing intracellular lysosomal fluid (pH 4) increased transfer of Pu and Am, whereas culture medium including serum reduced actinide transfer. Actinide transfer was also reduced by elements of the extracellular matrix present in the static gel phase. Increasing DTPA concentrations (5 to 500 μM) to the fluid phase significantly enhanced transfer of Pu and Am. Although this agarose gel cannot fully represent in vivo complexity, this simple test can be used to investigate and predict the behavior in vivo of radiocontaminants to support medical treatments and medical forensic investigations.

Macrophages as key elements of Mixed-oxide [U-Pu(O2)] distribution and pulmonary damage after inhalation?

Abstract Purpose: To investigate the consequences of alveolar macrophage (AM) depletion on Mixed OXide fuel (MOX: U, Pu oxide) distribution and clearance, as well as lung damage following MOX inhalation.

MATERIALS AND METHODS

Rats were exposed to MOX by nose only inhalation. AM were depleted with intratracheal administration of liposomal clodronate at 6 weeks. Lung changes, macrophage activation, as well as local and systemic actinide distribution were studied up to 3 months post-inhalation.

RESULTS

Clodronate administration modified excretion/retention patterns of α activity. At 3 months post-inhalation lung retention was higher in clodronate-treated rats compared to Phosphate Buffered Saline (PBS)-treated rats, and AM-associated α activity was also increased. Retention in liver was higher in clodronate-treated rats and fecal and urinary excretions were lower. Three months after inhalation, rats exhibited lung fibrotic lesions and alveolitis, with no marked differences between the two groups. Foamy macrophages of M2 subtype [inducible Nitric Oxide Synthase (iNOS) negative but galectin-3 positive] were frequently observed, in correlation with the accumulation of MOX particles. AM from all MOX-exposed rats showed increased chemokine levels as compared to sham controls.

CONCLUSION

Despite the transient reduced AM numbers in clodronate-treated animals no major differences on lung damage were observed as compared to non-treated rats after MOX inhalation. The higher lung activity retention in rats receiving clodronate seems to be part of a general inflammatory response and needs further investigation.

Decorporation approach following rat lung contamination with a moderately soluble compound of plutonium using local and systemic Ca-DTPA combined chelation

Decorporation efficacy of prompt pulmonary delivery of DTPA dry powder was assessed following lung contamination with plutonium nitrate and compared to an intravenous injection of DTPA solution and a combined administration of both DTPA compounds. In addition, efficacy of a delayed treatment was assessed. In case of either early or late administration, insufflated DTPA was more efficient than intravenously injected DTPA in reducing the plutonium lung burden due to its high local concentration. Prompt treatment with DTPA powder was also more effective in limiting extrapulmonary deposits by removing the early transportable fraction of plutonium from lungs prior its absorption into blood. Translocation of DTPA from lungs to blood may also contribute to the decrease in extrapulmonary retention, as shown by reduced liver deposit after delayed pulmonary administration of DTPA. Efficacy of DTPA dry powder was further increased by the combined intravenous administration of DTPA solution for reducing extrapulmonary deposits of plutonium and promoting its urinary excretion. According to our results, the most effective treatment protocol for plutonium decorporation was the early pulmonary delivery of DTPA powder supplemented by an intravenous injection of DTPA solution. Following inhalation of plutonium as nitrate chemical form, this combined chelation therapy should provide a more effective method of treatment than conventional intravenous injection alone. At later stages following lung contamination, pulmonary administration of DTPA should also be considered as the treatment of choice for decreasing the lung burden.