Synergistic Adsorption and Fluorescence in Porous Aromatic Frameworks for Highly Sensitive Detection of Radioactive Uranium

Uranium plays an important role in the modern nuclear industry. However, such a radioactive element can also cause severe damage to the environment once leaked or discharged into water or air, having a huge impact on the safety of the biosphere. In this work, we pioneered the use of fluorescent monomers as imprinted units, which promoted fluorescence emission of the material. A novel porous aromatic framework was obtained with uranyl ion chelating sites, namely MIPAF-15. The unique N-O chelating pockets on the 4-bromo-1-H-indole-7-carboxylic acid gave rise to high coordination affinity toward uranyl ions, which enabled the fast adsorption rate of uranyl ions and a uranyl ion adsorption capacity of 44.88 mg·g-1 at 298 K with an initial pH value of 6.0 and the uranyl concentration of 10 ppm. At the same time, the fluorescence quenching effect of MIPAF-15 was observed upon its adsorption of uranyl ions, which allowed the selective detection of uranyl ions with a detection limit of 5.04 × 10-8 M, lower than the maximum concentration of uranyl ions in drinking water specified by the World Health Organization (6.30 × 10-8 M) and United States Environmental Protection Agency (1.11 × 10-7 M). This kind of multifunctional porous material produces a favorable pathway for the detection, removal and degeneration of highly pollutive ions, promoting the overall sustainable development of the natural environment.

Jian-Pi-Yi-Shen formula restores iron metabolism from dysregulation in anemic rats with adenine-induced nephropathy

ETHNOPHARMACOLOGICAL RELEVANCE

Jian-Pi-Yi-Shen (JPYS) is a herbal decoction being used to relieve the symptoms of chronic kidney disease (CKD) and its complications, including anemia, for over twenty years. Nonetheless, it is unclear how JPYS influences renal anemia and iron metabolism.

AIM OF THE STUDY

An analysis of network pharmacology, chemical profiling, and in vivo experiments was conducted to identify the impact of JPYS on JAK2-STAT3 pathway and iron utilization in renal anemia and CKD.

MATERIALS AND METHODS

The chemical properties of JPYS and its exposed ingredients were detected in vivo. And based on the aforesaid chemical compounds, the potential targets and signaling pathways of JPYS for renal anemia treatment were predicted by network pharmacology. Afterward, an adenine-feeding animal model of CKD-related anemia was developed to verify the mechanism by which JPYS modulates iron recycling to treat renal anemia. Renal injury was estimated by serum creatinine (Scr), blood urea nitrogen (BUN), histopathological examinations and fibrosis degree. Western blot, enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qPCR) and immunohistochemistry approaches were utilized to assess the levels of JAK2, STAT3 and iron metabolism-related factors.

RESULTS

There were 164 active ingredients identified in JPYS, including prototypes and metabolites in vivo were identified in JPYS, and 21 core targets were found through network pharmacology based on topological characteristics. Combined with the core targets and pathway enrichment analysis, the majority of the candidate targets were associated with the JAK2-STAT3 signaling pathways. Experimental results indicated that JPYS treatment significantly decreased the expression of BUN and Scr, restored renal pathological damage, down-regulated fibrosis degree, and improved hematological parameters such as red blood cell, hemoglobin and hematocrit in CKD rats. Furthermore, JPYS significantly restored iron metabolism from dysregulation by increasing the levels of iron and ferritin in the serum, inhibiting the production of hepcidin in liver and serum, and regulating transferrin receptor 1 in bone marrow. Meanwhile, the expression of JAK2 and STAT3 was suppressed by JPYS treatment.

CONCLUSIONS

Based on these results, JPYS reduces hepcidin levels by inhibiting the activation of JAK2-STAT3 signaling, thereby protecting against iron deficiency anemia.

Emerging health risks and underlying toxicological mechanisms of uranium contamination: Lessons from the past two decades

Uranium contamination is a global health concern. Regarding natural or anthropogenic uranium contamination, the major sources of concern are groundwater, mining, phosphate fertilizers, nuclear facilities, and military activities. Many epidemiological and laboratory studies have demonstrated that environmental and occupational uranium exposure can induce multifarious health problems. Uranium exposure may cause health risks because of its chemotoxicity and radiotoxicity in natural or anthropogenic scenarios: the former is generally thought to play a more significant role with regard to the natural uranium exposure, and the latter is more relevant to enriched uranium exposure. The understanding of the health risks and underlying toxicological mechanisms of uranium remains at a preliminary stage, and many controversial findings require further research. In order to present state-of-the-art status in this field, this review will primarily focus on the chemotoxicity of uranium, rather than its radiotoxicity, as well as the involved toxicological mechanisms. First, the natural or anthropogenic uranium contamination scenarios will be briefly summarized. Second, the health risks upon natural uranium exposure, for example, nephrotoxicity, bone toxicity, reproductive toxicity, hepatotoxicity, neurotoxicity, and pulmonary toxicity, will be discussed based on the reported epidemiological cases and laboratory studies. Third, the recent advances regarding the toxicological mechanisms of uranium-induced chemotoxicity will be highlighted, including oxidative stress, genetic damage, protein impairment, inflammation, and metabolic disorder. Finally, the gaps and challenges in the knowledge of uranium-induced chemotoxicity and underlying mechanisms will be discussed.

A review of biological effects and treatments of inhaled depleted uranium aerosol

Depleted uranium (DU) is primarily used for DU bombs and DU tanks in the military. Aerosol inhalation is considered the primary route of DU exposure. Although laboratory tests have confirmed that inhalation of DU aerosol can cause lung, kidney, and other organ damage, epidemiological studies have found no conclusive evidence that persons in areas with prolonged exposure to DU-containing bombs are affected. After the body inhaled DU aerosols, we first clear the insoluble DU through whole-lung lavage (WLL). Then we eliminate the soluble uranium by the chelating agent. Besides, reducing DU damage to tissues and cells through drugs is also an important treatment method. In future research, emphasis should be placed on the damage mechanism of DU aerosol, the laboratory and clinical research of DU chelating agents, the research on the combination of DU chelating agent and WLL, and the research and development of new drugs to prevent DU damage.

Salivary N1-Methyl-2-Pyridone-5-Carboxamide, a Biomarker for Uranium Uptake, in Kuwaiti Children Exhibiting Exceptional Weight Gain

In a longitudinal study of 6,158 Kuwaiti children, we selected 94 for salivary metabolomic analysis who were neither obese (by waist circumference) nor metabolic syndrome (MetS) positive (<3 diagnostic features). Half (43) remained healthy for 2 years. The other half (51) were selected because they became obese and MetS positive 2 years later. In the half becoming obese, metabolomic analysis revealed that the level of salivary N1-Methyl-2-pyridone-5-carboxamide (2PY) had the highest positive association with obesity (p = 0.0003, AUC = 0.72) of 441 salivary biochemicals detected. 2PY is a recognized uremic toxin. Also, 2PY has been identified as a biomarker for uranium uptake. Considering that a relatively recent military conflict with documented uranium contamination of the area suggests that this weight gain could be a toxicological effect of long-time, low-level uranium ingestion. Comparison of salivary 2PY in samples from the USA and Kuwait found that only Kuwait samples were significantly related to obesity. Also, the geographic distribution of both reported soil radioactivity from ²³⁸U and measured salivary 2PY was highest in the area where military activity was highest. The prevalence pattern of adult diabetes in Kuwait suggests that a transient diabetogenic factor has been introduced into the Kuwaiti population. Although we did not measure uranium in our study, the presence of a salivary biomarker for uranium consumption suggests potential toxicity related to obesity in children.

Is there a role for the adverse outcome pathway framework to support radiation protection?

PURPOSE

In 2012, the Organization for Economic Cooperation and Development (OECD) formally launched the Adverse Outcome Pathway (AOP) Programme. The AOP framework has the potential for predictive utility in identifying early biological endpoints linked to adverse effects. It uses the weight of correlative evidence to identify a minimal set of measurable key events that link molecular initiating events to an adverse outcome. AOPs have the capability to identify knowledge gaps and priority areas for future research based on relevance to an adverse outcome. In addition, AOPs can identify pathways that are common among multiple stressors, thereby allowing for the possibility of refined risk assessments based on co-exposure considerations. The AOP framework is increasingly being used in chemical and ecological risk assessment; however, its use in the development of radiation-specific pathways has yet to be fully explored. To bring awareness of the AOP framework to the Canadian radiation community, a workshop was held in Canada in June 2018 that brought together radiation experts from Health Canada, the Canadian Nuclear Laboratories, and the Canadian Nuclear Safety Commission.

METHODS

The purpose of the workshop was to share knowledge on the AOP framework, specifically (1) to introduce the concept of the AOP framework and its possible utility to Canadian radiation experts; (2) to provide examples on how it has advanced risk assessment; (3) to discuss an illustrative example specific to ionizing radiation; and lastly (4) to identify the broad benefits and challenges of the AOP framework to the radiation community.

RESULTS

The participants showed interest in the framework, case examples were described and areas of challenge were identified. Herein, we summarize the outcomes of the workshop.

CONCLUSIONS

Overall, participants agreed that by building AOPs in the radiation field, a network of data-sharing initiatives will enhance our interpretation of existing knowledge where current scientific evidence is minimal. They would provide new avenues to understand effects at low-dose and dose-rates and help to quantify the combined effect of multiple stressors on shared mechanistic pathways.

Chemical toxicity and radioactivity of depleted uranium: The evidence from in vivo and in vitro studies

The main aim of this review is to summarize and discuss the current state of knowledge on chemical toxicity and radioactivity of depleted uranium (DU) and their effect on living systems and cell lines. This was done by presenting a summary of previous investigations conducted on different mammalian body systems and cell cultures in terms of potential changes caused by either chemical toxicity or radioactivity of DU. In addition, the authors aimed to point out the limitations of those studies and possible future directions. The majority of both in vitro and in vivo studies performed using animal models regarding possible effects caused by acute or chronic DU exposure has been reviewed. Furthermore, exposure time and dose, DU particle solubility, and uranium isotopes as factors affecting the extent of DU effects have been discussed. Special attention has been dedicated to chromosomal aberrations, DNA damage and DNA breaks, as well as micronuclei formation and epigenetic changes, as DU has recently been considered a possible causative factor of all these processes. Therefore, this approach might represent a novel area of study of DU-related irradiation effects on health. Since different studies offer contradictory results, the main aim of this review is to summarize and briefly discuss previously obtained results in order to identify the current opinion on DU toxicity and radioactivity effects in relation to exposure type and duration, as well as DU properties.

Meta-analysis of depleted uranium levels in the Balkan region

In recent years, contradicting data has been published on the connection between the presence of depleted uranium and an increased cancer incidence among military personnel deployed in the Balkans during the 1992-1999 wars. This has led to numerous research articles investigating possible depleted uranium contamination of the afflicted regions of the Balkan Peninsula, namely Bosnia & Herzegovina, Serbia, Kosovo and Montenegro. The aim of this study was to collect data from previously published reports investigating the levels of depleted uranium in the Balkans and to present the data in the form of a meta-analysis. This would provide a clear image of the extent of depleted uranium contamination after the Balkan conflict. In addition, we tested the hypothesis that there is a correlation between the levels of depleted uranium and the assumed depleted uranium-related health effects. Our results suggest that the majority of the examined sites contain natural uranium, while the area of Kosovo appears to be most heavily afflicted by depleted uranium pollution, followed by Bosnia & Herzegovina. Furthermore, the results indicate that it is not possible to make a valid correlation between the health effects and depleted uranium-contaminated areas. We therefore suggest a structured collaborative plan of action where long-term monitoring of the residents of depleted uranium-afflicted areas would be performed. In conclusion, while the possibility of depleted uranium toxicity in post-conflict regions appears to exist, there currently exists no definitive proof of such effects, due to insufficient studies of potentially afflicted populations, in addition to the lack of a common epidemiological approach in the reviewed literature.

Gastrin-releasing peptide contributes to the regulation of adult hippocampal neurogenesis and neuronal development

In the postnatal hippocampus, newly generated neurons contribute to learning and memory. Disruptions in neurogenesis and neuronal development have been linked to cognitive impairment and are implicated in a broad variety of neurological and psychiatric disorders. To identify putative factors involved in this process, we examined hippocampal gene expression alterations in mice possessing a heterozygous knockout of the calcium/calmodulin-dependent protein kinase II alpha heterozygous knockout gene (CaMK2α-hKO), an established model of cognitive impairment that also displays altered neurogenesis and neuronal development. Using this approach, we identified gastrin-releasing peptide (GRP) as the most dysregulated gene. In wild-type mice, GRP labels NeuN-positive neurons, the lone exception being GRP-positive, NeuN-negative cells in the subgranular zone, suggesting GRP expression may be relevant to neurogenesis and/or neuronal development. Using a model of in vitro hippocampal neurogenesis, we determined that GRP signaling is essential for the continued survival and development of newborn neurons, both of which are blocked by transient knockdown of GRP's cognate receptor (GRPR). Furthermore, GRP appears to negatively regulate neurogenesis-associated proliferation in neural stem cells both in vitro and in vivo. Intracerebroventricular infusion of GRP resulted in a decrease in immature neuronal markers, increased cAMP response element-binding protein (CREB) phosphorylation, and decreased neurogenesis. Despite increased levels of GRP mRNA, CaMK2α-hKO mutant mice expressed reduced levels of GRP peptide. This lack of GRP may contribute to the elevated neurogenesis and impaired neuronal development, which are reversed following exogenous GRP infusion. Based on these findings, we hypothesize that GRP modulates neurogenesis and neuronal development and may contribute to hippocampus-associated cognitive impairment.

Chronic uranium exposure dose-dependently induces glutathione in rats without any nephrotoxicity

Uranium is a heavy metal naturally found in the earth's crust that can contaminate the general public population when ingested. The acute effect and notably the uranium nephrotoxicity are well known but knowledge about the effect of chronic uranium exposure is less clear. In a dose-response study we sought to determine if a chronic exposure to uranium is toxic to the kidneys and the liver, and what the anti-oxidative system plays in these effects. Rats were contaminated for 3 or 9 months by uranium in drinking water at different concentrations (0, 1, 40, 120, 400, or 600 mg/L). Uranium tissue content in the liver, kidneys, and bones was linear and proportional to uranium intake after 3 and 9 months of contamination; it reached 6 μg per gram of kidney tissues for the highest uranium level in drinking water. Nevertheless, no histological lesions of the kidney were observed, nor any modification of kidney biomarkers such as creatinine or KIM-1. After 9 months of contamination at and above the 120-mg/L concentration of uranium, lipid peroxidation levels decreased in plasma, liver, and kidneys. Glutathione concentration increased in the liver for the 600-mg/L group, in the kidney it increased dose dependently, up to 10-fold, after 9 months of contamination. Conversely, chronic uranium exposure irregularly modified gene expression of antioxidant enzymes and activities in the liver and kidneys. In conclusion, chronic uranium exposure did not induce nephrotoxic effects under our experimental conditions, but instead reinforced the antioxidant system, especially by increasing glutathione levels in the kidneys.

Unexpected lack of deleterious effects of uranium on physiological systems following a chronic oral intake in adult rat

Uranium level in drinking water is usually in the range of microgram-per-liter, but this value may be as much as 100 to 1000 times higher in some areas, which may raise question about the health consequences for human populations living in these areas. Our purpose was to improve knowledge of chemical effects of uranium following chronic ingestion. Experiments were performed on rats contaminated for 9 months via drinking water containing depleted uranium (0.2, 2, 5, 10, 20, 40, or 120 mg/L). Blood biochemical and hematological indicators were measured and several different types of investigations (molecular, functional, and structural) were conducted in organs (intestine, liver, kidneys, hematopoietic cells, and brain). The specific sensitivity of the organs to uranium was deduced from nondeleterious biological effects, with the following thresholds (in mg/L): 0.2 for brain, >2 for liver, >10 for kidneys, and >20 for intestine, indicating a NOAEL (No-Observed-Adverse-Effect Level) threshold for uranium superior to 120 m g/L. Based on the chemical uranium toxicity, the tolerable daily intake calculation yields a guideline value for humans of 1350 μg/L. This value was higher than the WHO value of 30 μg/L, indicating that this WHO guideline for uranium content in drinking water is very protective and might be reconsidered.

Subcellular fractionation and chemical speciation of uranium to elucidate its fate in gills and hepatopancreas of crayfish Procambarus clarkii

Knowledge of the organ and subcellular distribution of metals in organisms is fundamental for the understanding of their uptake, storage, elimination and toxicity. Detoxification via MTLP and MRG formation and chelation by some proteins are necessary to better assess the metal toxic fraction in aquatic organisms. This work focused on uranium, natural element mainly used in nuclear industry, and its subcellular fractionation and chemical speciation to elucidate its accumulation pattern in gills and hepatopancreas of crayfish Procambarus clarkii, key organs of uptake and detoxification, respectively. Crayfish waterborne exposure was performed during 4 and 10d at 0, 30, 600 and 4000 μg UL(-1). After tissue dissection, uranium subcellular fractionation was performed by successive ultracentrifugations. SEC-ICP MS was used to study uranium speciation in cytosolic fraction. The uranium subcellular partitioning patterns varied according to the target organ studied and its biological function in the organism. The cytosolic fraction accounted for 13-30% of the total uranium amount in gills and 35-75% in hepatopancreas. The uranium fraction coeluting with MTLPs in gills and hepatopancreas cytosols showed that roughly 55% of uranium remained non-detoxified and thus potentially toxic in the cytosol. Furthermore, the sum of uranium amount in organelle fractions and in the non-detoxified part of cytosol, possibly equivalent to available fraction, accounted for 20% (gills) and 57% (hepatopancreas) of the total uranium. Finally, the SEC-ICP MS analysis provided information on potential competition of U for biomolecules similar than the ones involved in endogenous essential metal (Fe, Cu) chelation.

Metabolomics identifies a biological response to chronic low-dose natural uranium contamination in urine samples

Because uranium is a natural element present in the earth's crust, the population may be chronically exposed to low doses of it through drinking water. Additionally, the military and civil uses of uranium can also lead to environmental dispersion that can result in high or low doses of acute or chronic exposure. Recent experimental data suggest this might lead to relatively innocuous biological reactions. The aim of this study was to assess the biological changes in rats caused by ingestion of natural uranium in drinking water with a mean daily intake of 2.7 mg/kg for 9 months and to identify potential biomarkers related to such a contamination. Subsequently, we observed no pathology and standard clinical tests were unable to distinguish between treated and untreated animals. Conversely, LC-MS metabolomics identified urine as an appropriate biofluid for discriminating the experimental groups. Of the 1,376 features detected in urine, the most discriminant were metabolites involved in tryptophan, nicotinate, and nicotinamide metabolic pathways. In particular, N-methylnicotinamide, which was found at a level seven times higher in untreated than in contaminated rats, had the greatest discriminating power. These novel results establish a proof of principle for using metabolomics to address chronic low-dose uranium contamination. They open interesting perspectives for understanding the underlying biological mechanisms and designing a diagnostic test of exposure.

Uranium microdistribution in renal cortex of rats after chronic exposure: a study by secondary ion mass spectrometry microscopy

For a few years, the biological effects on ecosystems and the public of the bioaccumulation of radionuclides in situations of chronic exposures have been studied. This work, in keeping with the ENVIRHOM French research program, presents the uranium microdistribution by secondary ion mass spectrometry (SIMS) technique in the renal cortex of rats following chronic exposure to this low level element in the drinking water (40 mg/L) as a function to exposure duration (6, 9, 12, and 18 months). The SIMS mass spectra and 238U+ ion images produced with a SIMS CAMECA 4F-E7 show the kinetic of uranium accumulation in the different structures of the kidney. For the rats contaminated up to 12 months, the radioelement is mainly fixed in the proximal tubules; then after 18 exposure months, uranium is detected in all the segments of the nephron. This work has also shown that ion microscopy is an analytical method to detect trace elements and give elemental cartography at the micrometer scale.

Health effects of naturally radioactive water ingestion: the need for enhanced studies

BACKGROUND

Radiological pollution is a potentially important aspect of water quality. However, relatively few studies have been conducted to document its possible health effects.

OBJECTIVE

In this commentary we discuss available epidemiological findings and related data from experimental studies concerning the health effects of naturally radioactive water ingestion.

DISCUSSION

Despite modest epidemiological evidence of uranium nephrotoxicity and radium effects on bone, available data are not sufficient to quantify the health effects of naturally occurring radionuclides in water. Methodological limitations (exposure measurement methods, control for confounding, sample size) affect most studies. Power calculations should be conducted before launching new epidemiological studies focusing on late pathological outcomes. Studies based on biomarkers of exposure and adverse effects may be helpful but should involve more specific molecules than biomarkers used in previous studies. Experimental data on ingestion of drinking water are limited to uranium studies, and there is some disagreement between these studies about the nephrotoxicity threshold.

CONCLUSION

Further experimental and enhanced epidemiological studies should help to reduce uncertainties resulting from dose estimation to dose-response characterization.

Human Health and the Biological Effects of Tritium in Drinking Water: Prudent Policy Through Science - Addressing the ODWAC New Recommendation

Tritium is a radioactive form of hydrogen and is a by-product of energy production in Canadian Deuterium Uranium (CANDU) reactors. The release of this radioisotope into the environment is carefully managed at CANDU facilities in order to minimize radiation exposure to the public. However, under some circumstances, small accidental releases to the environment can occur. The radiation doses to humans and non-human biota from these releases are low and orders of magnitude less than doses received from naturally occurring radioisotopes or from manmade activities, such as medical imaging and air travel. There is however a renewed interest in the biological consequences of low dose tritium exposures and a new limit for tritium levels in Ontario drinking water has been proposed. The Ontario Drinking Water Advisory Council (ODWAC) issued a formal report in May 2009 in response to a request by the Minister of the Environment, concluding that the Ontario Drinking Water Quality Standard for tritium should be revised from the current 7,000 Bq/L level to a new, lower 20 Bq/L level. In response to this recommendation, an international scientific symposium was held at McMaster University to address the issues surrounding this change in direction and the validity of a new policy. Scientists, regulators, government officials, and industrial stakeholders were present to discuss the potential health risks associated with low level radiation exposure from tritium. The regulatory, economic, and social implications of the new proposed limit were also considered.The new recommendation assumed a linear-no-threshold model to calculate carcinogenic risk associated with tritium exposure, and considered tritium as a non-threshold chemical carcinogen. Both of these assumptions are highly controversial given that recent research suggests that low dose exposures have thresholds below which there are no observable detrimental effects. Furthermore, mutagenic and carcinogenic risk calculated from tritium exposure at 20 Bq/L would be orders of magnitude less than that from exposure to natural background sources of radiation. The new proposed standard would set the radiation dose limit for drinking water to 0.0003 mSv/year, which is equivalent to approximately three times the dose from naturally occurring tritium in drinking water. This new standard is incongruent with national and international standards for safe levels of radiation exposure, currently set at 1 mSv/year for the general public. Scientific research from leading authorities on the carcinogenic health effects of tritium exposure supports the notion that the current standard of 7,000 Bq/L (annual dose of 0.1 mSv) is a safe standard for human health.Policy-making for the purpose of regulating tritium levels in drinking water is a dynamic multi-stage process that is influenced by more than science alone. Ethics, economics, and public perception also play important roles in policy development; however, these factors sometimes undermine the scientific evidence that should form the basis of informed decision making. Consequently, implementing a new standard without a scientific basis may lead the public to perceive that risks from tritium have been historically underestimated. It was concluded that the new recommendation is not supported by any new scientific insight regarding negative consequences of low dose effects, and may be contrary to new data on the potential benefits of low dose effects. Given the lack of cost versus benefit analysis, this type of dramatic policy change could have detrimental effects to society from an ethical, economical, and public perception perspective.

Transcriptomic effects of depleted uranium on acetylcholine and cholesterol metabolisms in Alzheimer's disease model

Some heavy metals, or aluminium, could participate in the development of Alzheimer disease (AD). Depleted uranium (DU), another heavy metal, modulates the cholinergic system and the cholesterol metabolism in the brain of rats, but without neurological disorders. The aim of this study was to determine what happens in organisms exposed to DU that will/are developing the AD. This study was thus performed on a transgenic mouse model for human amyloid precursor protein (APP), the Tg2576 strain. The possible effects of DU through drinking water (20 mg/L) over an 8-month period were analyzed on acetylcholine and cholesterol metabolisms at gene level in the cerebral cortex. The mRNA levels of choline acetyl transferase (ChAT) vesicular acetylcholine transporter (VAChT) and ATP-binding cassette transporter A1 (ABC A1) decreased in control Tg2576 mice in comparison with wild-type mice (respectively -89%, -86% and -44%, p < 0.05). Chronic exposure of Tg2576 mice to DU increased mRNA levels of ChAT (+189%, p < 0.05), VAChT (+120%, p < 0.05) and ABC A1 (+52%, p < 0.05) compared to control Tg2576 mice. Overall, these modifications of acetylcholine and cholesterol metabolisms did not lead to increased disturbances that are specific of AD, suggesting that chronic DU exposure did not worsen the pathology in this experimental model.

Nephrotoxicity of uranium: pathophysiological, diagnostic and therapeutic perspectives

As in the case of other heavy metals, a considerable body of evidence suggests that overexposure to uranium may cause pathological alterations to the kidneys in both humans and animals. In the present work, our aim was to analyze the available data from a critical perspective that should provide a view of the real danger of the nephrotoxicity of this metal for human beings. A further aim was to elaborate a comparative compilation of the renal pathophysiological data obtained in humans and experimental animals with a view to gaining more insight into our knowledge of the mechanisms of action and renal damage. Finally, we address the existing perspectives for the improvement of diagnostic methods and the treatment of intoxications by uranium, performing an integrated analysis of all these aspects.

The toxicity of depleted uranium

Depleted uranium (DU) is an emerging environmental pollutant that is introduced into the environment primarily by military activity. While depleted uranium is less radioactive than natural uranium, it still retains all the chemical toxicity associated with the original element. In large doses the kidney is the target organ for the acute chemical toxicity of this metal, producing potentially lethal tubular necrosis. In contrast, chronic low dose exposure to depleted uranium may not produce a clear and defined set of symptoms. Chronic low-dose, or subacute, exposure to depleted uranium alters the appearance of milestones in developing organisms. Adult animals that were exposed to depleted uranium during development display persistent alterations in behavior, even after cessation of depleted uranium exposure. Adult animals exposed to depleted uranium demonstrate altered behaviors and a variety of alterations to brain chemistry. Despite its reduced level of radioactivity evidence continues to accumulate that depleted uranium, if ingested, may pose a radiologic hazard. The current state of knowledge concerning DU is discussed.

In vivo screening of proteins likely to bind uranium in exposed rat kidney

Uranium is a naturally abundant element which has been used in several industries. Internal exposure could occur via three main pathways that are ingestion, inhalation and wounds. It has been recently shown that chronic ingestion of uranium in drinking water induces an important uranium accumulation in kidney with a perturbation of iron metabolism in this organ.

Whereas uranium speciation is a key parameter to elucidate the chemical reactivity and the mobility of an element, it remains poorly documented in most of environmental and biological media. A few examples of uranium complexation with biomolecules have been published recently but most of them are in vitro studies whereas in vivo experiments remain poorly investigated.

In order to better understand possible competition of uranium towards metals involved in the metal-protein binding, i.e. iron, copper, calcium, a study on uranium speciation was investigated by doing an in vivo screening of target proteins likely to bind it in kidneys of exposed rats. Rats were chronically exposed via contaminated drinking water at 40 mg L-1 and killed 9 months after the beginning of exposure. Kidneys were dissected out and protein extract was prepared. Then, separation of renal proteins by isoelectric focusing gel electrophoresis (IEF) and two-dimensional gel electrophoresis (2-DE) followed by LA-ICPMS analysis were performed.

IEF-LA-ICP MS showed that uranium could specifically bind few proteins in kidney whereas 2-DE-LA-ICP MS could indicate that uranium is not covalently bound to proteins in this organ. The results suggested that even at moderate concentrations of exposure, uranium can be observed chelated with some renal proteins that is very encouraging to understand the entry, storage and elimination of this element in kidneys.

Accumulation and distribution of uranium in rats after implantation with depleted uranium fragments

PURPOSE

The aim of our study was to clarify the accumulation and distribution of uranium in depleted uranium (DU) implanted rats.

MATERIALS AND METHODS

Male Sprague-Dawley rats were surgically implanted in gastrocnemius muscle with DU fragments at 3 dose levels (low, medium and high), and biologically inert tantalum (Ta) fragments were used as controls. At 1 day and 7, 30, 90, 180 and 360 days after implantation, the rats were euthanized and tissue samples including serum and urine were collected to analyze the uranium levels by inductively coupled plasma-mass spectrometry (ICP-MS).

RESULTS

At all time points, uranium levels in all the DU implanted groups were higher than that in Ta control group, and uranium concentrations in kidney and bone were significantly greater than that in other tissues. Otherwise, uranium concentrations increased with a close correlation to the implanted DU doses and duration of exposure, with a peak at 90 days post-implantation, after which followed by a decreasing period, but still maintained at a relatively high level even at 360 days post- implantation. The uranium concentrations in bone were 6.92 +/- 0.97 microg U/g, 16.35 +/- 1.67 microg U/g and 21.64 +/- 3.68 microg U/g in the low-, medium- and high-dose group animals, while values in kidney tissues were 10.66 +/- 1.10 microg U/g, 14.06 +/- 1.28 microg U/g and 17.79 +/- 2.87 microg U/g, respectively, at 360 days post-implantation.

CONCLUSION

It was concluded that kidney and bone are the primary reservoirs for uranium redistributed from intramuscularly embedded fragments, and the accumulations in kidney, bone and many other tissues suggest the potential for unanticipated physiological consequences of chronic exposure to DU.

Urine proteomic profiling of uranium nephrotoxicity

Uranium is used in many chemical forms in civilian and military industries and is a known nephrotoxicant. A key issue in monitoring occupational exposure is to be able to evaluate the potential damage to the body, particularly the kidney. In this study we used innovative proteomic techniques to analyse urinary protein modulation associated with acute uranium exposure in rats. Given that the rat urinary proteome has rarely been studied, we first identified 102 different proteins in normal urine, expanding the current proteome data set for this central animal in toxicology. Rats were exposed intravenously to uranyl nitrate at 2.5 and 5 mg/kg and samples were collected 24 h later. Using two complementary proteomic methods, a classic 2-DE approach and semi-quantitative SDS-PAGE-LC-MS/MS, 14 modulated proteins (7 with increased levels and 7 with decreased levels) were identified in urine after uranium exposure. Modulation of three of them was confirmed by western blot. Some of the modulated proteins corresponded to proteins already described in case of nephrotoxicity, and indicated a loss of glomerular permeability (albumin, alpha-1-antiproteinase, serotransferrin). Others revealed tubular damage, such as EGF and vitamin D-binding protein. A third category included proteins never described in urine as being associated with metal stress, such as ceruloplasmin. Urinary proteomics is thus a valuable tool to profile uranium toxicity non-invasively and could be very useful in follow-up in case of accidental exposure to uranium.

Different pattern of brain pro-/anti-oxidant activity between depleted and enriched uranium in chronically exposed rats

Uranium is not only a heavy metal but also an alpha particle emitter. The main toxicity of uranium is expected to be due to chemiotoxicity rather than to radiotoxicity. Some studies have demonstrated that uranium induced some neurological disturbances, but without clear explanations. A possible mechanism of this neurotoxicity could be the oxidative stress induced by reactive oxygen species imbalance. The aim of the present study was to determine whether a chronic ingestion of uranium induced anti-oxidative defence mechanisms in the brain of rats. Rats received depleted (DU) or 4% enriched (EU) uranyl nitrate in the drinking water at 2mg(-1)kg(-1)day(-1) for 9 months. Cerebral cortex analyses were made by measuring mRNA and protein levels and enzymatic activities. Lipid peroxidation, an oxidative stress marker, was significantly enhanced after EU exposure, but not after DU. The gene expression or activity of the main antioxidant enzymes, i.e. superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), increased significantly after chronic exposure to DU. On the contrary, oral EU administration induced a decrease of these antioxidant enzymes. The NO-ergic pathway was almost not perturbed by DU or EU exposure. Finally, DU exposure increased significantly the transporters (Divalent-Metal-Transporter1; DMT1), the storage molecule (ferritin) and the ferroxidase enzyme (ceruloplasmin), but not EU. These results illustrate that oxidative stress plays a key role in the mechanism of uranium neurotoxicity. They showed that chronic exposure to DU, but not EU, seems to induce an increase of several antioxidant agents in order to counteract the oxidative stress. Finally, these results demonstrate the importance of the double toxicity, chemical and radiological, of uranium.

Deciphering the energy landscape of the interaction uranyl-DCP with antibodies using dynamic force spectroscopy

Previous studies on molecular recognition of uranyl-DCP (dicarboxy-phenanthroline chelator) compound by two distinct monoclonal antibodies (Mabs U04S and U08S) clearly showed the presence of a biphasic shape in Bell-Evans' plots and an accentuated difference in slopes at the high loading rates. To further explore the basis in the slope difference, we have performed complementary experiments using antibody PHE03S, raised against uranyl-DCP but, presenting a strong cross-reactivity toward the DCP chelator. This work allowed us to obtain a reallocation of the respective contributions of the metal ion itself and that of the chelator. Results led us to propose a 2D schematic model representing two energy barriers observed in the systems Mabs U04S- and U08S-[UO(2)-DCP] where the outer barrier characterizes the interaction between UO(2) and Mab whereas the inner barrier characterizes the interaction between DCP and Mab. Using dynamic force spectroscopy, it is thus possible to dissect molecular interactions during the unbinding between proteins and ligands.