Les menaces nucléaires et radiologiques sont des sujets d’actualité. Différents scénarios pourraient conduire à des contaminations internes avec du plutonium (Pu) tels que l’utilisation d’armes nucléaires tactiques, des accidents sur des réacteurs nucléaires civils ou militaires, des actes terroristes (bombes sales) ou encore la nécessité de déployer les forces dans des zones radio-contaminées. Après inhalation, les formes peu solubles de Pu sont majoritairement retenues au niveau des poumons dans les macrophages alvéolaires (MPs). L’acide diéthylène triamine penta acétique (DTPA) est actuellement le traitement de référence dans ce contexte. Néanmoins, son efficacité sur les formes peu solubles de Pu et son effet protecteur contre l’apparition de pathologies retardées (fibroses pulmonaires) ne sont pas bien caractérisés. Des études ont donc été initiées afin de préciser ces aspects et d’améliorer la prise en charge de la contamination interne. L’évaluation est réalisée sur une modèle in vitro de macrophages THP-1 (monocytes humains différenciés). Les cellules sont exposées à des colloïdes de Pu (forme peu soluble) durant 2h avant d’être traitées avec du DTPA et/ou de la dexaméthasone (DEX, molécule anti-inflammatoire) durant 7 jours. La dissolution du Pu par les macrophages augmente après traitement par le DTPA +/- DEX. La contamination au Pu induit une augmentation significative de la sécrétion de MCP-1 et d’IL-8, alors que les traitements DEX +/- DTPA ont significativement diminués les concentrations de ces deux cytokines, démontrant un effet anti-inflammatoire. En conclusion, nos premiers résultats suggèrent une capacité du DTPA à partiellement dissoudre les formes peu solubles de Pu internalisées par les MPs. De plus, l’utilisation du double traitement DTPA+DEX préserve leurs effets chélatant et anti-inflammatoire respectifs in vitro. Il constitue donc une approche prometteuse pour l’amélioration de la prise en charge thérapeutique en cas de contamination interne.

Increases in cancer incidence and mortality among workers overexposed to alpha-emitting radionuclides, such as plutonium (Pu), have been described with lung tumors of epithelial origin being the most common. However, the question of mechanisms leading to tumor formation following inhalation of radionuclides remains. The main factor controlling tumor incidence seems to be associated with radiation dose distribution, the more homogenous the distribution, the higher the incidence of cancer. In addition, some evidence exists regarding the role of the inflammatory response as a cofactor of tumorigenesis. The present study aims to determine the early inflammatory changes following pulmonary Pu contamination with the insoluble compound, PuO2 or the moderately soluble compound, Pu nitrate. Adult male Sprague-Dawley rats were exposed to PuO2 aerosols using a nose-only inhalation procedure (Initial lung deposit 4.7-43.4 kBq), or received intratracheal administration of Pu nitrate (25 kBq). Fourteen days post contamination, rats were euthanized and bronchoalveolar lavages (BAL) carried out. Activity was measured by liquid scintillation in lungs, femurs and liver. Distribution of activity within lung compartments was also studied. Activation of alveolar macrophages was evaluated by measurement of inflammatory mediators in supernatants collected 24h after plating and intracellular acid phosphatase activity determination, as well as by CD68 immunolabelling on lungs. The higher solubility of Pu nitrate as compared to PuO2 is illustrated by higher activity deposits in skeleton and liver, and lower retention in lungs. However, at this time point, lung distribution does not vary between the 2 compounds, the majority of activity being retained in the cellular fraction of BAL, mainly macrophages. Activation of macrophages is observed in the two groups of contaminated animals, with an enhanced production of TNF-alpha, MCP-1, CINC-1 and MIP-2, and an increased acid phosphatase activity, as compared to sham-contaminated rats. The level of activation was found to be dependant on the initial lung deposit following PuO2 contamination. Our results provide evidence for an early inflammatory response following Pu lung contamination and the role of macrophages whatever the solubility of the Pu compound.

Alveolar macrophages are a key element in the clearance of inhaled particles after phagocytosis, and thus participate actively in lung dose distribution and in the risk of tumour formation. We studied the influence of initial lung deposit (ILD) on lung clearance and distribution of activity from 3 d to 3 months after inhalation of two forms of PuO2 (97% 239Pu and 70% 239Pu) in rats. ILDs ranging from 2.1 to 17 kBq were used. The total activity measured using X-ray spectrometry 3 months post-inhalation, relative to the ILD, showed a similar decrease in all groups, with the remaining activity representing approximately 30% of the ILD. The total activity recovered in bronchoalveolar lavages represented approximately 60% of the total lung activity. This ratio remained stable over time for the lowest ILD tested but decreased for higher ILD. In addition, the percentage of macrophages associated with particles decreased faster with time in rats with the highest ILD. Under our experimental conditions, there were no marked differences in lung clearance between groups. However, the distribution of the activity seems to vary with the time post-exposure between low and high ILD.

Une atteinte sévère au niveau de la sphère gastro-intestinale, consécutive à une exposition aux rayonnements ionisants à forte dose, est un risque majeur et peut impliquer le pronostic vital de la personne irradiée. En effet, de par sa radiosensibilité importante, l’intestin représente une cible directe lors d’une irradiation, mais peut également être affecté de façon indirecte via les lésions qui apparaissent au niveau d’autres organes, comme les brûlures cutanées ou l’atteinte du système hématopoïétique. De façon similaire à ce qui peut être observé dans d’autres cas d’agressions sévères du tractus gastro-intestinal, l’exposition aux rayonnements ionisants se caractérise notamment par la perte d’intégrité de la barrière intestinale qui peut entraîner, voire perpétuer la libération de médiateurs inflammatoires et/ou anti-inflammatoires ; ce type de réponse pourrait à son tour générer des atteintes au niveau d’autres organes. Dans ce contexte, l’intestin « lésé » peut être considéré comme jouant un rôle clé dans la mise en place du syndrome de défaillance multi-viscérale (SDMV) radio-induit. La spécificité des effets de l’irradiation repose sur le fait que les compartiments tissulaires et vasculaires sont conjointement altérés avec une aplasie cellulaire plus ou moins intense, une atteinte de la fonction de barrière et la présence d’un état inflammatoire ; ainsi, tous ces éléments doivent être pris en considération dans la réponse radio-induite de l’intestin, afin de mieux déterminer le rôle de cette dernière dans la pathologie mixte du syndrome aigu d’irradiation (SAI) à court et à long terme.

Abstract Van der Meeren, A., Monti, P., Vandamme, M., Squiban, C., Wysocki, J. and Griffiths, N. Abdominal Radiation Exposure Elicits Inflammatory Responses and Abscopal Effects in the Lungs of Mice. Radiat. Res. 163, 144–152 (2005). An inflammatory reaction is a classical feature of radiation exposure and appears to be a key event in the development of the acute radiation syndrome. We have investigated the radiation-induced inflammatory response in C57BL6/J mice after total abdominal or total-body irradiation at a dose of 15 Gy. Our goal was to determine the radiation-induced inflammatory response of the gut and to study the consequences of abdominal irradiation for the intestine and for the lungs as a distant organ. A comparison with total-body irradiation was used to take into account the hematopoietic response in the inflammatory process. For both irradiation regimens, systemic and intestinal responses were evaluated. A systemic inflammatory reaction was found after abdominal and total-body irradiation, concomitant with increased cytokine and chemokine production in the jejunum of irradiated mice. In the lungs, the radiation-induced changes in the production of cytokines and chemokines and in the expression of adhesion molecules after both abdominal and total-body irradiation indicate a possible abscopal effect of radiation in our model. The effects observed in the lungs after irradiation of the abdomino-pelvic region may be caused by circulating inflammatory mediators consequent to the gut inflammatory response.

Although rare, accidental irradiation overexposures remain difficult to treat, mainly because of a complex physiopathology, known as the acute radiation syndrome (ARS). As a consequence, the issue remains fatal for most of high dose radiation accident victims. This is due in part through the lack of biological indicators able to give information about the extent of radiation-induced damage. Such bio-indicators may help to define a therapeutic strategy adapted to each specific accidental overexposure situation. Recent radiation accidents such as the Tokai Mura accident clearly showed that the therapeutic strategy must be based on the estimate of radiation-induced damage to life threatening physiological systems rather than the dose received by the victim. In fact, these accidents highlighted the heterogeneity of accidental irradiation, even in the most severe cases. Thus, important conceptual changes appeared recently for the treatment of radiation accident victims, such as the questionable role of haematopoietic stem cell transplantation after heterogeneous irradiation. Moreover, growing evidence indicates that ARS should be considered as an interplay of multiple pathologies originating not only from the haematopoietic system, the gastro-intestinal tract and the skin, but also from the neuro-vascular system and the inflammatory reaction rather than the addition of individual syndromes appearing in an ordered fashion according to the radiation dose and the time post-irradiation. Thus, it is important to take into account these new concepts in the medical management of accidentally overexposed victims. 2 1The acute radiation syndrome: historical concepts Classically, the acute radiation syndrome, which is defined as the pathologies developing after an uncontrolled radiation overexposure, is described as appearing in three phases (Figure 1). The first one, the initial syndrome, appears in the first few hours after irradiation. Manifestations are nausea, retching and vomiting, reflex diarrhoea, headache, hypotension, and in the most severe cases, a transient incapacitory syndrome. Additionally, erythema and oedema may transiently appear when local high dose irradiation was received. Importantly, the time of onset, intensity and duration of these symptoms are directly proportional to the global radiation dose received by the victim. Thus, the initial syndrome must be accurately observed, since it constitutes the very first indicator of the severity of radiation-induced damage to the victim (Young, 1987).

Les effets radio-induits sur le pancréas, communément décrits chez les mammifères, concernent essentiellement des modifications structurales observées à long terme. En revanche, peu d'études traitent des conséquences fonctionnelles d'une irradiation sur le pancréas exocrine. Le but de ce travail est de suivre les effets aigus d'une irradiation corps entier sur le volume et l'activité enzymatique du suc pancréatique. Une irradiation gamma corps entier à la dose de 6 Gy a été réalisée chez des porcs. Une collecte de suc pancréatique, par cathétérisme permanent du canal pancréatique, a été réalisée avant et après exposition avec mesure en continu du volume sécrété. Sur chaque échantillon de suc pancréatique, la concentration protéique ainsi que l'activité enzymatique de la trypsine, chymotrypsine, élastase, lipase et amylase ont été déterminées. Le volume de suc pancréatique sécrété quotidiennement diminue dès le lendemain de l'irradiation et le niveau sécrétoire ne revient jamais à des valeurs enregistrées avant irradiation. La quantité de protéines et les activités totales des enzymes sécrétées dans le suc pancréatique sont réduites de manière parallèle. Enfin, seules les activités spécifiques de l'élastase et de la lipase sont modifiées après l'irradiation. Ainsi, les conséquences d'une irradiation corps entier chez le porc se traduisent par une diminution importante et rapide de la sécrétion pancréatique exocrine, affectant à la fois les composantes hydro-bicarbonatée et enzymatique. Ce phénomène pourrait contribuer aux perturbations de la sphère intestinale lors du syndrome aigu d'irradiation mais également générer des effets à plus long terme.

Purpose: To investigate subacute and chronic functional consequences of localized irradiation of rat small intestine on exposed and shielded segments ( proximal and distal).Materials and methods: The surgical model of a scrotal hernia was used. The ileal loop was exposed to single doses of 18, 21 or 29.6 Gy X-irradiation. Epithelial structure and transport capacity were followed 2 and 26 weeks post-exposure.Results: Irradiated segments showed mucosal ulceration followed by transmural fibrosis. Transport capacity was impaired from 2 to 26 weeks. Subacute functional impairment was noticed in the proximal segment, without either morphological alteration or neutrophil influx. At 26 weeks, both proximal and distal segments showed impaired epithelial transport capacity, with neutrophil influx in the submucosa in cases of 21-Gy exposure and in the submucosa and muscularis propria after 29.6 Gy.Conclusions: Radiation enteritis was characterized by functional impairment, within as well as outside, the irradiation field. During the subacute phase, the irradiated segment may be a source of mediators which might influence intestinal function outside the site of injury via the blood stream and/or enteric nervous system. The development of an intestinal occlusion syndrome during the chronic phase might be responsible for intestinal dysfunction but it does not rule out a possible inflammatory process developing in the shielded parts of the small intestine.

The aim of this work was to determine the alterations in the absorptive and secretory functions of the rat colon after abdominal irradiation and to compare the effects of abdominal and whole-body irradiation. Rats received an abdominal irradiation with 8 to 12 Gy and were studied at 1, 4 and 7 days after exposure. Water and electrolyte absorption was measured in vivo by insertion of an agarose cylinder into the colons of anesthetized rats. In vitro measurements of potential difference, short-circuit current and tissue conductance were performed in Ussing chambers under basal and agonist-stimulated conditions. Most of the changes appeared at 4 days after abdominal irradiation. At this time, a decrease in water and electrolyte absorption in the colon was observed for radiation doses > or = 9 Gy. The response to secretagogues (VIP, 5-HT and forskolin) was attenuated after 10 and 12 Gy. Epithelial integrity, estimated by potential difference and tissue conductance, was altered from 1 to 7 days after 12 Gy abdominal irradiation. These results show that the function of the colon was affected by abdominal irradiation. Comparison with earlier results for total-body irradiation demonstrated a difference of 2 Gy in the radiation dose needed to induce changes in the function of the colon.

Absorption of water and Na+ in descending colonic crypts is dependent on the barrier function of the surrounding myofibroblastic pericryptal sheath. Here the effects of high and low Na+ diets and exposure to whole body ionising radiation on the growth and activation of the descending colonic pericryptal myofibroblasts are evaluated. In addition the effect of a post-irradiation treatment with the angiotensin converting enzyme inhibitor Captopril was investigated.

The ability of the enteric submucosal plexus to influence the transport of water and electrolytes in the colon was investigated in rats for I week after acute whole-body 7 irradiation. The involvement of neuroimmune links in the epithelial responses to nerve stimulation was confirmed by the sensitivity of the tissue to tetrodotoxin, mepyramine and doxantrazole. At 1 and 3 days after irradiation, colon tissues were hyporesponsive to nerve stimulation. This was associated with a drastic diminution of mucosal mast cell numbers, tissue histamme levels, and rat mast cell protease H (RMCP II) levels, and by a decreased maximal epithelial response to exogenously added histamine. The responses to electric-field stimulation were insensitive to both mepyramine and doxantrazole. At 7 days, neurally evoked responses recovered, despite the virtual absence of mast cells, tissue histamine and RMCP II, and the continuing decreased response to histamine. The responses were insensitive to doxantrazole but were decreased by mepyramine. This study showed that the establishment of a normal epithelial response to neural stimulation can occur despite the radiation-induced depletion of mucosal mast cells. The recovery of the epithelial response, which was sensitive to mepyramine, may be ascribed to the reappearance of an unknown histaminergic pathway, which probably has indirect effects on epithelial transport but is independent of nerve-mast cell connections. (C) 2002 by Radiation Research Society.

L'exposition aux rayonnements ionisants à des doses moyennes ou fortes entraîne une pathologie mixte. Dans plusieurs accidents d'irradiation, il a été constaté que les dysfonctionnements intestinaux étaient fortement impliqués dans le décès des patients. Cependant, l'apparition du syndrome gastro-intestinal, classiquement défini comme étant la perte de la muqueuse intestinale, n'est jamais très évidente. Néanmoins, il est admis que l'atteinte du système gastro-intestinal, plus particulièrement sa fonction de barrière, joue un rôle important dans l'évolution du syndrome de défaillance multiviscérale (Multiple Organ Failure) observée dans les derniers accidents (TokaïMura). Une exposition aux rayonnements ionisants provoque des modifications de la motricité intestinale qui peuvent conduire à la diarrhée. La diarrhée peut provenir également des altérations des processus d'absorption et/ou de sécrétion. En effet, une perte des cellules de la barrière intestinale et des modifications concomitantes de la fonction des systèmes de transport des nutriments et/ou des électrolytes sont observés. Ces fonctions intestinales sont sous le contrôle des multiples agents (tels que des contenus intestinaux, des neurotransmetteurs, des agents paracrines et des hormones) qui sont aussi modifiés. À l'heure actuelle, les traitements contre les atteintes digestives restent symptomatiques mais l'utilisation des facteurs de croissance et/ou l'apport de nouvelles cellules semblent prometteur pour l'avenir.

Purpose : To assess the early effects of primary afferent nerve suppression by systemic treatment with the neurotoxin capsaicin in an acute model of abdominal irradiation in rats (10 Gy, gamma). Materials and methods : Changes in myeloperoxidase (MPO) activity, calcitonin gene-related peptide (CGRP) tissue content, number of mast cells and apoptotic cells were determined in jejunum and ileum in four groups of rat male Wistar (vehicle sham-irradiated, vehicle irradiated, capsaicin sham-irradiated and capsaicin irradiated) at 1 and 3 days post-irradiation. Results : In vehicle irradiated rats, CGRP was significantly increased from the first day after irradiation in jejunal mucosa; MPO activity increased in both segments at day 3 but not at day 1 after irradiation; the number of detectable mucosal mast cells dropped to nearly zero on days 1 and 3, while the apoptotic cells in the intestinal mucosa were significantly increased at day 1. Similar results were obtained for mast cells and apoptosis in capsaicin irradiated rats as compared to capsaicin sham-irradiated rats, while MPO activity was significantly increased and CGRP concentration in jejunal mucosa significantly decreased from the first day in these rats in comparison with capsaicin sham-irradiated rats. Conclusions : Intestinal sensory innervation seems not to have a major protective role against a radiation-induced intestinal inflammatory reaction.

Background-Therapeutic or accidental exposure to radiation commonly causes gastrointestinal disturbances, including diarrhoea. Rats subjected to whole body ionising radiation at a dose of 8 Gy lose their capacity to absorb fluid via the descending colon after four days. After seven days, fluid absorption recovers to control levels.Aims-To investigate the effect of ionising radiation on colonic permeability together with its effect on mitochondria dependent apoptotic signals and intercellular adhesion molecules.Methods-Rats were irradiated with doses of 0-12 Gy. Colonic permeability was measured by accumulation of fluorescein isothiocyanate (FITC) dextran in crypt lumens. Changes in levels of cytochrome c, caspase 3, E and OB cadherin, beta -catenin smooth muscle actin, and collagen IV were assessed using immunocytochemistry with confocal microscopy.Results-Cytosolic cytochrome c increased after 8 Gy (t(1/2) 1.4 (0.6) hours) and peaked at approximately six hours. Caspase 3 increased more slowly, particularly in crypt epithelial cells (t(1/2) 57 (14.5) hours). Pericryptal myofibroblasts disintegrated within 24 hours as was evident from loss of OB cadherin and smooth muscle actin. This coincided with increased crypt permeability to dextran. Intercellular adhesion between crypt luminal cells was not lost until day 4 when both beta -catenin and E-cadherin were minimal. The half maximal dose-response for these effects was in the range 2-4 Gy. Recovery of colonic transport was concurrent with recovery of pericryptal smooth muscle actin and OB cadherin. The pan caspase inhibitor Z-Val-Ala-Asp.fluoromethylketone (1 mg/kg per day) had a small effect in conserving the pericryptal sheath myofibroblasts and sheath permeability but had no systemic therapeutic effects.Conclusions-These data suggest that radiation damage to the colon may be initiated by mitochondrial events. Loss of crypt fluid absorption and increased permeability coincided with decreased intercellular adhesion between crypt epithelial cells and loss of pericryptal sheath barrier function.

The symptoms associated with exposure to ionizing radiation are nausea, vomiting, diarrhoea. The response of the gut is complex involving modifications of motility and fluid and Electrolyte transport. Gastrointestinal regulatory peptides have an important role in these functions. This study showed that radiation-induced tissue variations of neuropeptides have some repercussions on intestinal biological activity of these peptides soon after irradiation. In addition such modifications are also seen a few years after irradiation.

The aim of this study was to determine whether ionizing radiation modifies muscarinic regulation of intestinal mucosal function. Rats exposed to total body 8-Gy gamma-irradiation or sham irradiated were studied up to 21 days after irradiation. Basal and carbachol-stimulated short-circuit current (Isc) and transepithelial conductance (Gt) of stripped ileum were determined in Ussing chambers. Muscarinic receptor characteristics using the muscarinic antagonist [3H]quinuclidinyl benzilate and three unlabeled antagonists were measured in small intestinal plasma membranes together with two marker enzyme activities (sucrase, Na+-K+-ATPase). Enzyme activities were decreased 4 days after irradiation (day 4). Basal electrical parameters were unchanged. Maximal carbachol-induced changes in Isc and Gt were increased at day 4 (maximal DeltaIsc = 195.8 +/- 14.7 microA/cm2, n = 19, vs. 115.4 +/- 8.2 microA/cm2, n = 63, for control rats) and unchanged at day 7. Dissociation constant was decreased at day 4 (0.73 +/- 0.29 nM, n = 10, vs. 2.14 +/- 0.39 nM, n = 13, for control rats) but unchanged at day 7, without change in binding site number. Thus total body irradiation induces a temporary stimulation of cholinergic regulation of mucosal intestinal function that may result in radiation-induced diarrhea.

PURPOSE:Gastrointestinal functions, controlled partly by gut peptides, are disturbed by ionizing radiation exposure. The effect of whole-body irradiation on circulating gastrin levels, densities of gastrointestinal endocrine cells and gastric acid secretion was investigated.MATERIALS AND METHODS:Rats were exposed to 2 or 6 Gy gamma-radiation. They were killed 3 or 7 days later and compared with shams. Plasma gastrin and basal acid output were measured. Endocrine cells were identified by argyrophilia or immunohistochemistry and their densities estimated.RESULTS:Radiation exposure significantly increased gastrinaemia and gastric acid output at the times studied (p<0.05-p<0.001). Endocrine cells displayed different sensitivities to irradiation. In the gastric mucosa, a 6 Gy dose induced a decrease in fundic argyrophil cell, antral gastrin and somatostatin cell densities, always accentuated 7 days after irradiation, while in the intestinal mucosa it induced an increase, with highest values often at 7 days post-irradiation (p<0.01-p<0.001). This was true for neurotensin cells in the jejunum and ileum, substance P cells in ileum and enteroglucagon cells in the descending colon.CONCLUSIONS:Whole-body irradiation in rats significantly alters plasma gastrin levels, and several gut endocrine cell densities. This has repercussions on hormonal function, such as that exerted on acid secretion, and may explain gastrointestinal dysfunction observed following radiation exposure.

The effects of 6 Gy whole-body 60Co gamma irradiation on bile composition in pigs were studied to determine possible alterations in the quality of the bile, which may be a determining factor in diarrhea as well as nutrient malabsorption, which classically occurs after irradiation. The bile duct of pigs was catheterized to allow a total and continuous deviation of bile over several weeks, before and after irradiation. After measurement of the volume and sampling, bile was returned to the animal via a duodenal catheter. Bile samples were then analyzed for cholesterol, phospholipid and total bile acid content. Individual bile acids were quantified by HPLC analysis. Bile flow was significantly decreased during the first 24 h and after the fifth day postirradiation. Whereas cholesterol, phospholipid and total bile acid concentrations were not altered, profiles of individual bile acids were modified significantly as early as the first day postirradiation. Moreover, the change of these profiles with time was specific for each bile acid. Such modifications in bile acid profiles resulted in a change in the properties of the bile acid pool in an increased proportion of dihydroxylated bile acids known to interfere with gut functions, and it is reasonable to suggest that radiation-induced changes in bile acid profiles may be involved in radiation-induced gastrointestinal disorders.