Nephrotoxicity of uranium: pathophysiological, diagnostic and therapeutic perspectives

The transferrin a signaling pathway mediates uranium-induced hematopoietic dysfunction

OBJECTIVE

This study was designed to explore the toxic effects of Transferrin a(tfa)-mediated uranium exposure on the hematopoietic system.

METHODS

Zebrafish embryos were subjected to uranium nitrate solutions at concentrations of 50, 100, 250, and 500 μg/L for a defined period, followed by sample collection. The impact of uranium on hematopoietic system development in zebrafish was evaluated through hemoglobin staining, qRT-PCR, and in situ hybridization. RNA-Seq was utilized to detect differentially expressed genes (DEGs) in embryos exposed to 100 μg/L uranium, with subsequent bioinformatics analysis to confirm these DEGs. Furthermore, blood samples from patients with hematological disorders and impaired hematopoietic function were collected, and RNA-Seq was applied to identify DEGs.

RESULTS

Uranium exposure in zebrafish embryos led to reduced hemoglobin expression, with key transcription factors for primitive and definitive hematopoiesis being significantly downregulated at 100 μg/L uranium exposure. Overexpression of tfa resulted in a marked increase in hemoglobin content and upregulation of GATA1, a key factor in primitive hematopoiesis. Patients with hematopoietic dysfunction exhibited abnormalities in the tfa signaling pathway.

CONCLUSION

tfa plays a role in mediating the inhibitory effects of uranium on hematopoietic function.

Long-Term Exposure to Uranium and Arsenic in Community Drinking Water and CKD Risk Among California Women

RATIONALE & OBJECTIVE

Metals/metalloids in drinking water, including uranium and arsenic, may damage kidney function and increase chronic kidney disease (CKD) risk. We evaluated exposure to these contaminants in community water supplies (CWS) and CKD risk in the California Teachers Study.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

88,185 women who were California teachers and school administrators enrolled 1995-1996.

EXPOSURES

Time- and residence- weighted annual average uranium and arsenic concentrations from CWS serving participants' residential addresses from 1995 to 2005.

OUTCOME

6,185 moderate to end-stage CKD cases from hospitalization records between 2005 and 2018.

ANALYTICAL APPROACH

Hazard ratios (HRs) and 95% confidence intervals (95%CIs) calculated using mixed-effects Cox models, adjusted for age as the time scale, body mass index, smoking status, race/ethnicity, neighborhood socioeconomic status, and Census region as a random effect. Analyses were also stratified by risk factors and comorbidities.

RESULTS

Most exposures in this population were below the current regulatory limits (uranium=30μg/L and arsenic=10 μg/L), with median (interquartile range; IQR) concentrations of 3.1 (0.9, 5.6) μg/L for uranium and 1.0 (0.6, 1.8) μg/L for arsenic. Uranium exposure was positively associated with CKD risk (continuous log, per IQR; HR=1.11, 95%CI=1.02-1.20). Compared to uranium exposure <2μg/L (World Health Organization 1998 guideline), risk was over 30% greater at 10-<15μg/L (HR=1.33, 95%CI=1.15-1.54) and similar at ≥15μg/L (HR=1.32, 95%CI=1.09-1.58). There was no evidence of a significant association between arsenic and CKD overall (log, per IQR; HR=1.02, 95%CI=0.98-1.07). However, risk from arsenic was greater among younger individuals (≤55 years), and those who developed cardiovascular disease or diabetes.

LIMITATIONS

Individual tap water use and consumption; limited generalizability to men and non-White and less affluent populations.

CONCLUSIONS

Uranium below the current regulatory limit from community water may increase CKD risk.

Effect of polysaccharides and saponins from Polygonatum kingianum against uranium-induced renal injury in rats

Uranium poisoning is increasingly recognized as a public health issue. Polygonatum kingianum (PK) is valued for its therapeutic properties and food applications. Original research showed PK aqueous extract (PKAE) and polysaccharides (PKP) could alleviate uranium-induced cytotoxicity in vitro. Assessing the combined therapeutic potential of PKP with other components is crucial. The study examines the efficacy and mechanisms of PKP, saponins (PKS) and PKP + PKS to treat uranium-induced kidney damage in rats by analyzing alterations in blood and urine biochemical indices, apoptotic protein expression, and uranium accumulation. The poisoning led to a substantial decrease in renal superoxide dismutase, glutathione levels, and total antioxidant capacity, coupled with a notable increase in malondialdehyde, urea, uric acid, creatinine, and total oxidative status. However, these detrimental changes were mitigated by treatments with PKAE, PKP, PKS, and PKP + PKS, which also effectively reduced uranium accumulation in the rat kidneys. Compared to the uranium model group, the treatment groups increased the expression of Bcl-2 and Nrf2, while down-regulating the expression of Caspase3, Caspase9, GSK-3β, Bax, and Fyn. Findings suggest PKP and PKS are the main components of PK attenuating uranium-induced kidney damage by targeting the GSK-3β/Fyn/Nrf2 pathway, offering hope for the mitigation of uranium harmful effects on human health.

Uranium Exposure, Hypertension, and Blood Pressure in the Strong Heart Family Study

Introduction

Uranium is common in drinking water, soil, and dust in American Indian communities. Hypertension is a cardiovascular risk factor affecting American Indians. We evaluated the association between uranium exposure and incident hypertension and changes in blood pressure among Strong Heart Family Study participants.

Methods

We included 1,453 participants ≥14 years with baseline visits in 1998-1999 or 2001-2003, and follow-up in 2001-2003 and/or 2006-2009. We estimated the association of urinary uranium with changes in systolic and diastolic blood pressure levels over time and hypertension incidence; we accounted for family clustering.

Results

Median (IQR) baseline urinary uranium levels were 0.029 (0.013-0.059) μg/g creatinine; 17.4% (n = 253) of participants developed hypertension. In the comparison of the urinary uranium quartile 4 (highest concentration) and quartile 1 (lowest concentration), the multi-adjusted risk ratio (95% CI) of incident hypertension was 1.44 (1.04-1.99). The associations between urinary uranium with changes in systolic and diastolic blood pressure were null and nonlinear, respectively. Both associations were modified by study site, and diastolic blood pressure showed a positive association beyond 5 µg/g creatinine. The association between urinary uranium and change in systolic blood pressure was inverse in Arizona and Oklahoma, and positive in North Dakota/South Dakota at higher ends of the uranium distribution.

Conclusion

Findings suggest a higher risk for hypertension at uranium levels typical of the Southwest and Great Plains than at levels in other regions (<0.01 µg/g creatinine); the associations with changes in systolic and diastolic blood pressure levels were consistent with a positive association with higher uranium exposure. Prospective research is critical to characterize the cardiovascular effects of uranium and develop preventive strategies for US Indigenous communities disproportionately exposed.

Uranium exposure and kidney tubule biomarkers in the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Experimental studies indicate that uranium exposure is toxic to the kidney tubules. We evaluated the association of urinary uranium concentrations with biomarkers of tubule cell dysfunction (alpha-1-microglobulin [A1M], uromodulin [UMOD], epidermal growth factor [EGF]), and tubule cell injury (kidney injury molecule-1 [KIM-1], monocyte chemoattractant protein-1 [MCP-1], and chitinase-3-like protein 1 [YKL-40]), as well as with albuminuria and estimated glomerular filtration rate (eGFR) among participants in the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS

We conducted a cross-sectional study that included 461 participants selected for the absence of diabetes, chronic kidney disease (CKD), and cardiovascular disease, evaluated with six kidney tubule biomarker measurements. Urinary uranium concentrations were measured using inductively coupled plasma mass spectrometry in spot urine samples. Linear models were used to determine associations of urinary uranium concentrations with each kidney tubule biomarker, calculated by the geometric mean ratio (GMR), after adjustment for participant's urinary creatinine concentrations, age, sex, race/ethnicity, MESA field center, highest level of education completed, cigarette smoking status, alcohol consumption, body mass index (BMI), albuminuria levels, and eGFR.

RESULTS

Median (interquartile range) urinary uranium concentration was 5.2 (2.9, 10.4) ng/L, and mean (standard deviation) eGFR was 99 (16) mL/min/1.73 m2. The adjusted GMRs (95%CI) of KIM-1 and MCP-1 were 1.11 (1.01, 1.22) and 1.10 (1.01, 1.20), respectively per 7.5 ng/L (interquartile range) higher urinary uranium concentration, while no statistically significant associations were observed for YKL-40, A1M, UMOD, EGF, albuminuria, or eGFR. In flexible dose-response models, the associations were positive and largely linear between urinary uranium concentrations and higher KIM-1 and MCP-1.

CONCLUSIONS

Among healthy community-living individuals, chronic low-level uranium exposure, as measured in urine, was associated with markers of kidney tubule cell injury. Chronic low-level uranium exposure observed in contemporary US urban centers may adversely affect kidney tubule health and related outcomes.

Geochemical Behavior of Uranium and Arsenic in Watercourse Sediments of the Los Planes Watershed, Baja California Sur, Mexico: Assessment of Anthropogenic and Natural Factors

In Baja California Sur (BCS), Mexico, the municipality of La Paz has reported higher cancer rates compared to nearby areas, linked to arsenic contamination from abandoned gold mines and naturally high uranium (U) and arsenic (As) levels in sediments. This study evaluates the impact of human activities on natural U and As anomalies in watercourse sediments of the Los Planes watershed and adjacent areas. The geochemical database included 229 analyses from the Mexican Geological Service (SGM 2017) and nine samples analyzed via Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Multivariate statistical and geostatistical methods were used to interpret the data. Using the kriging method for U and the nearest neighbor algorithm for As, spatial models were developed to define the anomalies' positions and extents. Hierarchical cluster analysis on 85 analyses and 28 parameters identified six clusters representing different influence areas. The study found As concentrations exceeding the Mexican limit of 22 mg/kg for soils in 13 cases, with a maximum of 1520 mg/kg, primarily due to historic gold mine contamination. U concentrations ranged from 0.53 mg/kg to 7.35 mg/kg, within international protection limits, originating from Sierra la Gata's granites and granodiorites, with potential secondary enrichment in topsoil. The possibility of anthropogenic U impact from phosphatic fertilizers is noted, warranting further investigation.

Uranium's hazardous effects on humans and recent developments in treatment

Uranium, a naturally occurring element, is predominantly recognized for its role as fuel in both civilian and military energy sectors. Concerns have been raised regarding the adverse environmental impacts and health risks associated with uranium mining due to the exposure it causes. Such exposure leads to systemic toxicity, affecting pulmonary, hepatic, renal, reproductive, neurological, and bone health. This review identifies significant research gaps regarding detoxification methods for uranium contamination and recommends further advancements, including genetic modification and exploration of plant compounds. A comprehensive review of published research materials from diverse sources of uranium, including various treatments and hazardous impacts on the human body, was conducted. Additionally, a PRISMA analysis was performed in this study. This review emphasizes the importance of collaboration and the formulation of research-informed regulations to effectively safeguard vulnerable communities from the consequences of contamination. Public discourse often emphasizes the significance of radiotoxicity; however, the non-radioactive chemotoxicity of uranium has been identified as a significant risk factor for environmental exposures, contingent upon species, enrichment, and exposure route. Given these serious health consequences, several methods are being investigated to ameliorate uranium toxicity. In response to these concerns, several techniques, such as phytomedicinal treatments, biochemical approaches, and chelation therapy, have been investigated to minimize the adverse effects of uranium exposure in the human body.

Smartphone-assisted fluorescence/colorimetric dual-mode sensing strategy for uranium ion detection using cerium-sulfonyl calix[4]arene

A novel fluorescence/colorimetric dual-mode detection strategy for uranium ions (UO22+) is presented based on a cerium-sulfonyl calix[4]arene (SC4A) platform. The exo- and endo-rim sites of SC4A can coordinate with Ce3+ and Ce4+ ions, respectively, quenching Ce3+ fluorescence and influencing the oxidase-like activity of Ce4+. In the absence of UO22+, the solution of 3,3,5,5-tetramethylbenzidine (TMB) remains blue, but upon UO22+ binding, Ce3+ dissociates from SC4A, restoring fluorescence, while UO22+ interacts with oxTMB, turning the solution from blue to colorless. This dual-mode system provides a linear fluorescence detection range of 30-800 nM with a detection limit of 20.20 nM, and a colorimetric range of 30-800 nM with a detection limit of 27.78 nM. By combining high-sensitivity fluorescence with visual colorimetric analysis, the proposed method possesses high sensitivity, accuracy, and reliability. Notably, smartphone-based color capture facilitates rapid and convenient sample analysis, enabling straightforward quantification at varying UO22+ concentrations. The method has been successfully applied to real water and urine samples, demonstrating its practical utility in environmental and biological monitoring of UO22+.

Relationship Between Urinary Uranium and Cardiac Geometry and Left Ventricular Function: The Strong Heart Study

Background

Uranium is a potentially cardiotoxic, nonessential element commonly found in drinking water throughout the United States.

Objectives

The purpose of this study was to evaluate if urinary uranium concentrations were associated with measures of cardiac geometry and function among American Indian young adults from the Strong Heart Family Study.

Methods

Urinary uranium was measured among 1,332 participants free of diabetes, cardiovascular disease, and <50 years of age at baseline (2001-2003). Transthoracic echocardiography and blood pressure were assessed at baseline and at a follow-up visit (2006-2009). We estimated adjusted mean differences in cardiac geometry and function measures at baseline and follow-up using linear mixed-effect models with a random intercept and slope over time.

Results

Median (interquartile range) uranium was 0.029 (0.045) μg/g creatinine. In fully adjusted cross-sectional models, a log-doubling of urinary uranium was positively associated with left ventricular (LV) mass index (mean difference: 0.49 g/m2, 95% CI: 0.07-0.92 g/m2), left atrial systolic diameter (0.01 cm/m2, 0.01-0.02 cm/m2), and stroke volume (0.66 mL, 0.25-1.08 mL) at baseline. Prospectively, uranium was associated with increases in left atrial diameter (0.01 cm/m2, 0.01-0.02 cm/m2), pulse pressure (0.28 mm Hg, 0.05-0.52 mm Hg), and incident LV hypertrophy (odds ratio: 1.25, 95% confidence interval: 1.06, 1.48).

Conclusions

Urinary uranium levels were adversely associated with measures of cardiac geometry and LV function among American Indian adults, including increases in pulse pressure and LV hypertrophy. These findings support the need to determine the potential long-term subclinical and clinical cardiovascular effects of chronic uranium exposure, and the need for future strategies to reduce exposure.

TRPML1 agonist ML-SA5 mitigates uranium-induced nephrotoxicity via promoting lysosomal exocytosis

Uranium (U) released from U mining and spent nuclear fuel reprocessing in the nuclear industry, nuclear accidents and military activities as a primary environmental pollutant (e.g., drinking water pollution) is a threat to human health. Kidney is one of the main target organs for U accumulation, leading to nephrotoxicity mainly associated with the injuries in proximal tubular epithelial cells (PTECs). Transient receptor potential mucolipin 1 (TRPML1) is a novel therapeutic target for nephrotoxicity caused by acute or chronic U poisoning. We herein investigate the therapeutic efficacy of ML-SA5, a small molecule agonist of TRPML1, in U-induced nephrotoxicity in acute U intoxicated mice. We demonstrate that delayed treatment with ML-SA5 enhances U clearance from the kidneys via urine excretion by activating lysosomal exocytosis, and thereby attenuates U-induced kidney dysfunction and cell death/apoptosis of renal PTECs in acute U intoxicated mice. In addition, ML-SA5 promotes the nuclear translocation of transcription factor EB (TFEB) in renal PTECs in acute U intoxicated mice. Mechanistically, ML-SA5 triggers the TRPML1-mediated lysosomal calcium release and consequently induces TFEB activation in U-loaded renal PTECs-derived HK-2 cells. Moreover, knockdown of TRPML1 or TFEB abolishes the effects of ML-SA5 on the removal of intracellular U and reduction of the cellular injury/death in U-loaded HK-2 cells. Our findings indicate that pharmacological activation of TRPML1 is a promising therapeutic approach for the delayed treatment of U-induced nephrotoxicity via the activation of the positive feedback loop of TRPML1 and TFEB and consequent the induction of lysosomal exocytosis.

Regulatory roles of extracellular polymeric substances in uranium reduction via extracellular electron transfer by Desulfovibrio vulgaris UR1

The pathway of reducing U(VI) to insoluble U(IV) using electroactive bacteria has become an effective and promising approach to address uranium-contaminated water caused by human activities. However, knowledge regarding the roles of extracellular polymeric substances (EPS) in the uranium reduction process involving in extracellular electron transfer (EET) mechanisms is limited. Here, this study isolated a novel U(VI)-reducing strain, Desulfovibrio vulgaris UR1, with a high uranium removal capacity of 2.75 mM/(g dry cell). Based on a reliable EPS extraction method (45 °C heating), manipulation of EPS in D. vulgaris UR1 suspensions (removal or addition of EPS) highlighted its critical role in facilitating uranium reduction efficiency. On the second day, U(VI) removal rates varied significantly across systems with different EPS contents: 60.8% in the EPS-added system, 48.5% in the pristine system, and 22.2% in the EPS-removed system. Characterization of biogenic solids confirmed the reduction of U(VI) by D. vulgaris UR1, and the main products were uraninite and UO2 (2.88-4.32 nm in diameter). As EPS formed a permeable barrier, these nanoparticles were primarily immobilized within the EPS in EPS-retained/EPS-added cells, and within the periplasm in EPS-removed cells. Multiple electroactive substances, such as tyrosine/tryptophan aromatic compounds, flavins, and quinone-like substances, were identified in EPS, which might be the reason for enhancement of uranium reduction via providing more electron shuttles. Furthermore, proteomics revealed that a large number of proteins in EPS were enriched in the subcategories of catalytic activity and electron transfer activity. Among these, iron-sulfur proteins, such as hydroxylamine reductase (P31101), pyruvate: ferredoxin oxidoreductase (A0A0H3A501), and sulfite reductase (P45574), played the most critical role in regulating EET in D. vulgaris UR1. This work highlighted the importance of EPS in the uranium reduction by D. vulgaris UR1, indicating that EPS functioned as both a reducing agent and a permeation barrier for access to heavy metal uranium.

Uranium in Drinking Water and Bladder Cancer: A Case-control Study in Michigan

ABSTRACT

Uranium is naturally occurring in groundwater used for drinking; however, health risks from naturally occurring concentrations are uncertain. Uranium can cause both radiological and chemical toxicity following ingestion. Bladder and kidneys receive a dose when uranium is excreted into the urine. Investigate the association between uranium in drinking water and bladder cancer risk in a case-control study. A population-based bladder cancer case-control study was conducted in 11 counties of southeastern Michigan. A total of 411 cases and 566 controls provided drinking water and toenail samples and answered questions about lifestyle and residential history. Uranium was measured in drinking water and toenails, and its association with bladder cancer was assessed via unconditional logistic regression models. Median uranium concentration in water was 0.12 μg L -1 , with a maximum of 4.99 μg L -1 , and median uranium concentration in toenails was 0.0031 μg g -1 . In adjusted regression models, there was a suggestion of a protective effect among those exposed to the upper quartile of uranium in drinking water (HR = 0.64, 95% CI: 0.43, 0.96) and toenails (HR 0.66; 95% CI 0.45, 0.96) compared to those in the lowest quartile. Our objective is to investigate additional adjustment of drinking water source at home residence at time of recruitment to address potential selection bias and confounding attenuated results toward the null for drinking water uranium (HR = 0.68, 95% CI: 0.44, 1.05) and toenail uranium (HR = 0.80, 95% CI: 0.53, 1.20). This case-control study showed no increased risk of bladder cancer associated with uranium found in drinking water or toenails.

Enhanced uranium sequestration through selenite-modified nano-chitosan loaded with melatonin: Facilitating U(IV) conversion

The combined chemotoxicity and radiotoxicity associated with uranium, utilized in nuclear industry and military applications, poses significant threats to human health. Among uranium pollutants, uranyl is particularly concerning due to its high absorptivity and potent nephrotoxicity in its + 6 valence state. Here, we have serendipitously found Na2SeO3 facilitates the conversion of U(VI) to U(IV) precipitates. A novel approach involving nano-chitosan loaded internally with melatonin and externally modified with selenite (NPs Cs-Se/MEL) was introduced. This modification not only enhances the conversion of U(VI) to U(IV) but also preserves the spherical nanostructure and specific surface area, leading to increased adsorption of U(VI) compared to unmodified samples. Selenite modification improves lysosomal delivery in HEK-293 T cells and kidney distribution of the nanoparticles. Furthermore, NPs Cs-Se/MEL demonstrated a heightened uranium concentration in urine and exhibited remarkable efficiency in uranium removal, resulting in a reduction of uranium deposition in serum, kidneys, and femurs by up to 52.02 %, 46.79 %, and 71.04 %, respectively. Importantly, NPs Cs-Se/MEL can be excreted directly from the kidneys into urine when carrying uranium. The results presented a novel mechanism for uranium adsorption, making selenium-containing nano-materials attractive for uranium sequestration and detoxification.

A Mitochondria-Targeted Heptamethine Indocyanine Small Molecular Chelator for Attenuating Uranium Nephrotoxicity

Radionuclide uranium has both a chemical and radioactive toxicity, leading to severe nephrotoxicity as it predominantly deposits itself in the kidneys after entering into human bodies. It crosses renal cell membranes, accumulates in mitochondria and causes mitochondrial oxidative damage and dysfunction. In this study, a mitochondria-targeted heptamethine indocyanine small molecule chelator modified with gallic acid (IR-82) is synthesized for uranium detoxication. Both gallic acid and sulfonic acid, as two hydrophilic endings, make IR-82, being excreted feasibly through kidneys. Gallic acid with polyphenol groups has a steady metal chelation effect and potent antioxidant ability, which may facilitate IR-82-alleviated uranium nephrotoxicity simultaneously by enhancing uranium decorporation from the kidneys and reducing mitochondrial oxidative damage. Cell viability assays demonstrate that IR-82 can significantly improve the cell viability of uranium-exposed human renal (HK-2) cells. It is also demonstrated to accumulate in mitochondria and reduce mitochondrial ROS and total intracellular ROS, as well as intracellular uranium content. In vivo imaging experiments in mice show that IR-82 could be excreted out through kidneys. ICP-MS tests further reveal that IR-82 can efficiently decrease the uranium deposition in mouse kidneys. IR-82 treatment improves the animal survival rate and renal function of experimental mice after high-dose uranium exposure. Collectively, our study may evidence that the development of uranium decorporation agents with kidney-mitochondrion dual targeting abilities is a promising strategy for attenuating uranium-induced nephrotoxicity.

Hedgehog pathway negatively regulated depleted uranium-induced nephrotoxicity

Depleted uranium (DU) retains the radiological toxicities, which accumulates preferentially in the kidneys. Hedgehog (Hh) pathway plays a critical role in tissue injury. However, the role of Hh in DU-induced nephrotoxicity was still unclear. This study was carried out to investigate the effect of Gli2, which was an important transcription effector of Hh signaling, on DU induced nephrotoxicity. To clarify it, CK19 positive tubular epithelial cells specific Gli2 conditional knockout (KO) mice model was exposed to DU, and then histopathological damage and Hh signaling pathway activation was analyzed. Moreover, HEK-293 T cells were exposed to DU with Gant61 or Gli2 overexpression, and cytotoxicity of DU as analyzed. Results showed that DU caused nephrotoxicity accompanied by activation of Hh signaling pathway. Meanwhile, genetic KO of Gli2 reduced DU-induced nephrotoxicity by normalizing biochemical indicators and reducing Hh pathway activation. Pharmacologic inhibition of Gli1/2 by Gant61 reduced DU induced cytotoxicity by inhibiting apoptosis, ROS formation and Hh pathway activation. However, overexpression of Gli2 aggravated DU-induced cytotoxicity by increasing the levels of apoptosis and ROS formation. Taken together, these results revealed that Hh signaling negatively regulated DU-inducted nephrotoxicity, and that inhibition of Gli2 might serve as a promising nephroprotective target for DU-induced kidney injury.

A systematic review and meta-analysis of mortality and kidney function in uranium-exposed individuals

BACKGROUND

Humans are exposed to uranium (U) in a variety of applications. Both animal and observational human studies support an associated U nephrotoxicity. Few statistical syntheses of the human data have been performed and these analyses are limited in the types of exposures considered.

OBJECTIVES

This study aims to evaluate the state of current evidence and to expand on existing meta-analyses by systematically evaluating kidney-associated causes of mortality in multiple U-exposed populations. This study also aims to evaluate the effect of U exposure on kidney function and biomarkers of kidney injury.

METHODS

The published and grey literature were systematically reviewed for studies that reported Standardized Mortality Ratios (SMR) for kidney cancer, chronic nephritis/nephrosis, all-cause mortality, diabetes, all circulatory/heart disease, and/or ischemic heart disease in U-exposed humans. Studies that reported kidney biomarker measures for U-exposed versus control subjects were identified separately.

RESULTS

36 studies were included. The studies were parsed into subgroups based on setting of exposure. Analysis of kidney cancer and chronic nephritis/nephrosis mortality demonstrated an SMR of 0.93 (95CI: 0.82-1.05) and 0.82 (95CI: 0.70-0.96), respectively. The other clinical outcomes evaluated also demonstrated mortality deficits in exposed relative to unexposed individuals. Subgroup analyses demonstrated similar mortality deficits. Conversely, biomarker analyses suggested better kidney function in the controls, but none of these differences reached significance.

DISCUSSION

Given that most of the included mortality studies were conducted in occupational populations, the mortality deficits observed in our analyses were likely due to the healthy-worker effect. Additionally, our analyses of kidney biomarkers were severely limited by low precision due to a low number of available studies and small study-size. Future work needs to evaluate the progression of chronic and to end-stage kidney disease in community-based populations to better assess the full impact of prolonged chronic U exposure on kidney outcomes.

US drinking water quality: exposure risk profiles for seven legacy and emerging contaminants

BACKGROUND

Advances in drinking water infrastructure and treatment throughout the 20th and early 21st century dramatically improved water reliability and quality in the United States (US) and other parts of the world. However, numerous chemical contaminants from a range of anthropogenic and natural sources continue to pose chronic health concerns, even in countries with established drinking water regulations, such as the US.

OBJECTIVE/METHODS

In this review, we summarize exposure risk profiles and health effects for seven legacy and emerging drinking water contaminants or contaminant groups: arsenic, disinfection by-products, fracking-related substances, lead, nitrate, per- and polyfluorinated alkyl substances (PFAS) and uranium. We begin with an overview of US public water systems, and US and global drinking water regulation. We end with a summary of cross-cutting challenges that burden US drinking water systems: aging and deteriorated water infrastructure, vulnerabilities for children in school and childcare facilities, climate change, disparities in access to safe and reliable drinking water, uneven enforcement of drinking water standards, inadequate health assessments, large numbers of chemicals within a class, a preponderance of small water systems, and issues facing US Indigenous communities.

RESULTS

Research and data on US drinking water contamination show that exposure profiles, health risks, and water quality reliability issues vary widely across populations, geographically and by contaminant. Factors include water source, local and regional features, aging water infrastructure, industrial or commercial activities, and social determinants. Understanding the risk profiles of different drinking water contaminants is necessary for anticipating local and general problems, ascertaining the state of drinking water resources, and developing mitigation strategies.

IMPACT STATEMENT

Drinking water contamination is widespread, even in the US. Exposure risk profiles vary by contaminant. Understanding the risk profiles of different drinking water contaminants is necessary for anticipating local and general public health problems, ascertaining the state of drinking water resources, and developing mitigation strategies.

A State-of-the-Science Review on Metal Biomarkers

PURPOSE OF REVIEW

Biomarkers are commonly used in epidemiological studies to assess metals and metalloid exposure and estimate internal dose, as they integrate multiple sources and routes of exposure. Researchers are increasingly using multi-metal panels and innovative statistical methods to understand how exposure to real-world metal mixtures affects human health. Metals have both common and unique sources and routes of exposure, as well as biotransformation and elimination pathways. The development of multi-element analytical technology allows researchers to examine a broad spectrum of metals in their studies; however, their interpretation is complex as they can reflect different windows of exposure and several biomarkers have critical limitations. This review elaborates on more than 500 scientific publications to discuss major sources of exposure, biotransformation and elimination, and biomarkers of exposure and internal dose for 12 metals/metalloids, including 8 non-essential elements (arsenic, barium, cadmium, lead, mercury, nickel, tin, uranium) and 4 essential elements (manganese, molybdenum, selenium, and zinc) commonly used in multi-element analyses.

RECENT FINDINGS

We conclude that not all metal biomarkers are adequate measures of exposure and that understanding the metabolic biotransformation and elimination of metals is key to metal biomarker interpretation. For example, whole blood is a good biomarker of exposure to arsenic, cadmium, lead, mercury, and tin, but it is not a good indicator for barium, nickel, and uranium. For some essential metals, the interpretation of whole blood biomarkers is unclear. Urine is the most commonly used biomarker of exposure across metals but it should not be used to assess lead exposure. Essential metals such as zinc and manganese are tightly regulated by homeostatic processes; thus, elevated levels in urine may reflect body loss and metabolic processes rather than excess exposure. Total urinary arsenic may reflect exposure to both organic and inorganic arsenic, thus, arsenic speciation and adjustment for arsebonetaine are needed in populations with dietary seafood consumption. Hair and nails primarily reflect exposure to organic mercury, except in populations exposed to high levels of inorganic mercury such as in occupational and environmental settings. When selecting biomarkers, it is also critical to consider the exposure window of interest. Most populations are chronically exposed to metals in the low-to-moderate range, yet many biomarkers reflect recent exposures. Toenails are emerging biomarkers in this regard. They are reliable biomarkers of long-term exposure for arsenic, mercury, manganese, and selenium. However, more research is needed to understand the role of nails as a biomarker of exposure to other metals. Similarly, teeth are increasingly used to assess lifelong exposures to several essential and non-essential metals such as lead, including during the prenatal window. As metals epidemiology moves towards embracing a multi-metal/mixtures approach and expanding metal panels to include less commonly studied metals, it is important for researchers to have a strong knowledge base about the metal biomarkers included in their research. This review aims to aid metals researchers in their analysis planning, facilitate sound analytical decision-making, as well as appropriate understanding and interpretation of results.

Induction of lysosomal exocytosis and biogenesis via TRPML1 activation for the treatment of uranium-induced nephrotoxicity

Uranium (U) is a well-known nephrotoxicant which forms precipitates in the lysosomes of renal proximal tubular epithelial cells (PTECs) after U-exposure at a cytotoxic dose. However, the roles of lysosomes in U decorporation and detoxification remain to be elucidated. Mucolipin transient receptor potential channel 1 (TRPML1) is a major lysosomal Ca2+ channel regulating lysosomal exocytosis. We herein demonstrate that the delayed administration of the specific TRPML1 agonist ML-SA1 significantly decreases U accumulation in the kidney, mitigates renal proximal tubular injury, increases apical exocytosis of lysosomes and reduces lysosomal membrane permeabilization (LMP) in renal PTECs of male mice with single-dose U poisoning or multiple-dose U exposure. Mechanistic studies reveal that ML-SA1 stimulates intracellular U removal and reduces U-induced LMP and cell death through activating the positive TRPML1-TFEB feedback loop and consequent lysosomal exocytosis and biogenesis in U-loaded PTECs in vitro. Together, our studies demonstrate that TRPML1 activation is an attractive therapeutic strategy for the treatment of U-induced nephrotoxicity.

A comparison of the chemo- and radiotoxicity of thorium and uranium at different enrichment grades

Uranium and thorium are heavy metals, and all of their isotopes are radioactive, so it is impossible to study chemical effects entirely independent of the radiation effects. In the present study, we tried to compare the chemo- and radiotoxicity of both metals, taking into account deterministic radiation damages reflected by acute radiation sickness and stochastic radiation damages leading to long-term health impairments (e.g., tumor induction). We made at first a literature search on acute median lethal doses that may be expected to be caused by chemical effects, as even acute radiation sickness as a manifestation of acute radiotoxicity occurs with latency. By simulations based on the biokinetic models of the International Commission on Radiological Protection and using the Integrated Modules for Bioassay Analysis software, we determined the amounts of uranium at different enrichment grades and thorium-232 leading to a short-term red bone marrow equivalent dose of 3.5 Sv considered to cause 50% lethality in humans. Different intake pathways for incorporation were considered, and values were compared to the mean lethal doses by chemotoxicity. To assess stochastic radiotoxicity, we calculated the uranium and thorium amounts leading to a committed effective dose of 200 mSv that is often considered critical. Mean lethal values for uranium and thorium are in the same order of magnitude so that the data do not give evidence for substantial differences in acute chemical toxicity. When comparing radiotoxicity, the reference units (activity in Bq or weight in g) must always be taken into account. The mean lethal equivalent dose to the red bone marrow of 3.5 Sv is reached by lower activities of thorium compared to uranium in soluble compounds. However, for uranium as well as thorium-232, acute radiation sickness is expected only after incorporation of amounts exceeding the mean lethal doses by chemotoxicity. Thus, acute radiation sickness is not a relevant clinical issue for either metal. Concerning stochastic radiation damages, thorium-232 is more radiotoxic than uranium if incorporating the same activities. Using weight units for comparison show that for soluble compounds, thorium-232 is more radiotoxic than low-enriched uranium in the case of ingestion but even more toxic than high-enriched uranium after inhalation or intravenous administration. For insoluble compounds, the situation differs as the stochastic radiotoxicity of thorium-232 ranges between depleted and natural uranium. For acute effects, the chemotoxicity of uranium, even at high enrichment grades, as well as thorium-232 exceeds deterministic radiotoxicity. Simulations show that thorium-232 is more radiotoxic than uranium expressed in activity units. If the comparison is based on weight units, the rankings depend on the uranium enrichment grades and the route of intake.

γ-Resistant Microporous CAU-1 MOF for Selective Remediation of Thorium

A simple solvothermal method was used to synthesize a metal-organic framework (MOF) with an Al metal entity, viz., CAU-1 NH₂. The synthesized MOF was characterized using different techniques like X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy (SEM), field emission SEM (FE-SEM), transmission electron microscopy, small-angle X-ray scattering, positron annihilation lifetime spectroscopy, and X-ray photoelectron spectroscopy. The radiation stability was evaluated by irradiating the material up to a cumulative dose of 2 MGy using ⁶⁰Co for the first time. The studies showed a remarkable gamma irradiation stability of the material up to 1 MGy. The porosity and surface area of the synthesized MOF were determined by Brunauer-Emmett-Teller, which showed a high specific surface area of 550 m²/g. The pH dependence study of Th uptake from an aqueous solution was performed from pH 2-8, followed by adsorption isotherm and adsorption kinetics studies. These results revealed that the Langmuir and pseudo-second-order kinetic models can be well adapted for understanding the Th uptake and kinetics, respectively. The synthesized MOF exhibited an ∼404 mg/g thorium adsorption capacity. Selectivity studies of adsorption of Th w.r.t. to U and different metal ions such as Cu, Co, Ni, and Fe showed that Th gets adsorbed preferentially as compared to other metal ions. In addition, the MOF could be used multiple times without much deterioration.

Synchrotron-Based X-ray Fluorescence Imaging Elucidates Uranium Toxicokinetics in Daphnia magna

A combination of synchrotron-based elemental analysis and acute toxicity tests was used to investigate the biodistribution and adverse effects in Daphnia magna exposed to uranium nanoparticle (UNP, 3-5 nm) suspensions or to uranium reference (U_ref) solutions. Speciation analysis revealed similar size distributions between exposures, and toxicity tests showed comparable acute effects (UNP LC₅₀: 402 μg L^-1 [336-484], U_ref LC₅₀: 268 μg L^-1 [229-315]). However, the uranium body burden was 3- to 5-fold greater in UNP-exposed daphnids, and analysis of survival as a function of body burden revealed a ∼5-fold higher specific toxicity from the U_ref exposure. High-resolution X-ray fluorescence elemental maps of intact, whole daphnids from sublethal, acute exposures of both treatments revealed high uranium accumulation onto the gills (epipodites) as well as within the hepatic ceca and the intestinal lumen. Uranium uptake into the hemolymph circulatory system was inferred from signals observed in organs such as the heart and the maxillary gland. The substantial uptake in the maxillary gland and the associated nephridium suggests that these organs play a role in uranium removal from the hemolymph and subsequent excretion. Uranium was also observed associated with the embryos and the remnants of the chorion, suggesting uptake in the offspring. The identification of target organs and tissues is of major importance to the understanding of uranium and UNP toxicity and exposure characterization that should ultimately contribute to reducing uncertainties in related environmental impact and risk assessments.

Renal toxicity and biokinetics models after repeated uranium instillation

During nuclear fuel processing, workers can potentially be exposed to repeated inhalations of uranium compounds. Uranium nephrotoxicity is well documented after acute uranium intake, but it is controversial after long-term or protracted exposure. This study aims to analyze the nephrotoxicity threshold after repeated uranium exposure through upper airways and to investigate the resulting uranium biokinetics in comparison to reference models. Mice (C57BL/6J) were exposed to uranyl nitrate (0.03-3 mg/kg/day) via intranasal instillation four times a week for two weeks. Concentrations of uranium in urines and tissues were measured at regular time points (from day 1 to 91 post-exposure). At each exposure level, the amount of uranium retained in organs/tissues (kidney, lung, bone, nasal compartment, carcass) and excreta (urine, feces) reflected the two consecutive weeks of instillation except for renal uranium retention for the highest uranium dose. Nephrotoxicity biomarkers, KIM-1, clusterin and osteopontin, are induced from day 4 to day 21 and associated with changes in renal function (arterial fluxes) measured using non-invasive functional imaging (Doppler-ultrasonography) and confirmed by renal histopathological analysis. These results suggest that specific biokinetic models should be developed to consider altered uranium excretion and retention in kidney due to nephrotoxicity. The threshold is between 0.25 and 1 mg/kg/day after repeated exposure to uranium via upper airways.

Boosting Simultaneous Uranium Decorporation and Reactive Oxygen Species Scavenging Efficiency by Lacunary Polyoxometalates

The chemical toxicity and the oxidative stress induced by the internal exposure of uranium is responsible for the long-term adverse effect of in vivo contamination of uranium. An agent with simultaneous removal capability of uranium and excess reactive oxygen species (ROS) is highly desired. Herein, the lacunary Keggin-type polyoxometalate (POM) is demonstrated to selectively bind with uranyl ions in the presence of excess essential divalent ions and exhibits a compelling ROS scavenging efficiency of 78.8%. In vivo uranium decorporation assays illustrate the uranium sequestration efficiencies of 74.0%, 49.4%, and 37.1% from kidneys by prophylactic, prompt, and delayed administration of lacunary POM solution, respectively. The superior ROS quenching and uranium removal performance in comparison with all reported bifunctional agents endow lacunary polyoxometalates as novel agents to effectively protect people from injuries caused by the internal exposure of actinides.

Threonine Phosphorylation of an Electrochemical Peptide-Based Sensor to Achieve Improved Uranyl Ion Binding Affinity

We have successfully designed a uranyl ion (U(VI)-specific peptide and used it in the fabrication of an electrochemical sensor. The 12-amino acid peptide sequence, (n) DKDGDGYIpTAAE (c), originates from calmodulin, a Ca(II)-binding protein, and contains a phosphothreonine that enhances the sequence's affinity for U(VI) over Ca(II). The sensing mechanism of this U(VI) sensor is similar to other electrochemical peptide-based sensors, which relies on the change in the flexibility of the peptide probe upon interacting with the target. The sensor was systematically characterized using alternating current voltammetry (ACV) and cyclic voltammetry. Its limit of detection was 50 nM, which is lower than the United States Environmental Protection Agency maximum contaminant level for uranium. The signal saturation time was ~40 min. In addition, it showed minimal cross-reactivity when tested against nine different metal ions, including Ca(II), Mg(II), Pb(II), Hg(II), Cu(II), Fe(II), Zn(II), Cd(II), and Cr(VI). Its reusability and ability to function in diluted aquifer and drinking water samples were further confirmed and validated. The response of the sensor fabricated with the same peptide sequence but with a nonphosphorylated threonine was also analyzed, substantiating the positive effects of threonine phosphorylation on U(VI) binding. This study places emphasis on strategic utilization of non-standard amino acids in the design of metal ion-chelating peptides, which will further diversify the types of peptide recognition elements available for metal ion sensing applications.

Amidoxime functionalized chitosan for uranium sequestration in vivo

Amidoxime functionalized chitosan (AC) was recommended as a chelator for uranium sequestration in vivo in this study, and the structure-activity relationship was also explored. Compared with ZnNa₃-DTPA, which was a commercial uranium mobilization drug, AC exhibited excellent biocompatibility and uranium removal efficiency, whether by injection or orally, which could reduce the amounts of uranium deposited in kidneys and femurs by up to 43.6% and 32.3%. In particular, ACs still possessed the ability to mobilize uranium in vivo even if administration was delayed for 72 h.

Review of Knowledge of Uranium-Induced Kidney Toxicity for the Development of an Adverse Outcome Pathway to Renal Impairment

An adverse outcome pathway (AOP) is a conceptual construct of causally and sequentially linked events, which occur during exposure to stressors, with an adverse outcome relevant to risk assessment. The development of an AOP is a means of identifying knowledge gaps in order to prioritize research assessing the health risks associated with exposure to physical or chemical stressors. In this paper, a review of knowledge was proposed, examining experimental and epidemiological data, in order to identify relevant key events and potential key event relationships in an AOP for renal impairment, relevant to stressors such as uranium (U). Other stressors may promote similar pathways, and this review is a necessary step to compare and combine knowledge reported for nephrotoxicants. U metal ions are filtered through the glomerular membrane of the kidneys, then concentrate in the cortical and juxtaglomerular areas, and bind to the brush border membrane of the proximal convoluted tubules. U uptake by epithelial cells occurs through endocytosis and the sodium-dependent phosphate co-transporter (NaPi-IIa). The identified key events start with the inhibition of the mitochondria electron transfer chain and the collapse of mitochondrial membrane potential, due to cytochrome b5/cytochrome c disruption. In the nucleus, U directly interacts with negatively charged DNA phosphate, thereby inducing an adduct formation, and possibly DNA strand breaks or cross-links. U also compromises DNA repair by inhibiting zing finger proteins. Thereafter, U triggers the Nrf2, NF-κB, or endoplasmic reticulum stress pathways. The resulting cellular key events include oxidative stress, DNA strand breaks and chromosomal aberrations, apoptosis, and pro-inflammatory effects. Finally, the main adverse outcome is tubular damage of the S2 and S3 segments of the kidneys, leading to tubular cell death, and then kidney failure. The attribution of renal carcinogenesis due to U is controversial, and specific experimental or epidemiological studies must be conducted. A tentative construction of an AOP for uranium-induced kidney toxicity and failure was proposed.

Sociodemographic inequalities in uranium and other metals in community water systems across the USA, 2006-11: a cross-sectional study

BACKGROUND

The US Environmental Protection Agency (EPA) currently sets maximum contaminant levels (MCLs) for ten metals or metalloids in public drinking water systems. Our objective was to estimate metal concentrations in community water systems (CWSs) across the USA, to establish if sociodemographic or regional inequalities in the metal concentrations exist, and to identify patterns of concentrations for these metals as a mixture.

METHODS

We evaluated routine compliance monitoring records for antimony, arsenic, barium, beryllium, cadmium, chromium, mercury, selenium, thallium, and uranium, collected from 2006-11 (2000-11 for uranium; timeframe based on compliance monitoring requirements) by the US EPA in support of their second and third Six-Year Reviews for CWSs. Arsenic, barium, chromium, selenium, and uranium (detectable in >10% records) were included in the main analyses (subgroup and metal mixture analyses; arsenic data reported previously). We compared the mean, 75th percentile, and 95th percentile contaminant concentrations and the percentage of CWSs with concentrations exceeding the MCL across subgroups (region, sociodemographic county-cluster, size of population served, source water type, and CWSs exclusively serving correctional facilities). We evaluated patterns in CWS metal concentration estimate profiles via hierarchical cluster analysis. We created an online interactive map and dashboard of estimated CWS metal concentrations for use in future analyses.

FINDINGS

Average metal concentrations were available for a total of 37 915 CWSs across the USA. The total number of monitoring records available was approximately 297 000 for arsenic, 165 000 for barium, 167 000 for chromium, 165 000 for selenium, and 128 000 for uranium. The percentage of analysed CWSs with average concentrations exceeding the MCL was 2·6% for arsenic (MCL=10 μg/L; nationwide mean 1·77 μg/L; n=36 798 CWSs), 2·1% for uranium (MCL=30 μg/L; nationwide mean 4·37 μg/L; n=14 503 CWSs), and less than 0·1% for the other metals. The number of records with detections was highest for uranium (63·1%). 75th and 95th percentile concentrations for uranium, chromium, barium, and selenium were highest for CWSs serving Semi-Urban, Hispanic communities, CWSs reliant on groundwater, and CWSs in the Central Midwest. Hierarchical cluster analysis revealed two distinct clusters: an arsenic-uranium-selenium cluster and a barium-chromium cluster.

INTERPRETATIONS

Uranium is an under-recognised contaminant in CWSs. Metal concentrations (including uranium) are elevated in CWSs serving Semi-Urban, Hispanic communities independent of location or region, highlighting environmental justice concerns.

FUNDING

US National Institutes of Health Office of the Director, US National Institutes for Environmental Health Sciences, and US National Institute of Dental and Craniofacial Research.

Protective effects of Polygonatum kingianum polysaccharides and aqueous extract on uranium-induced toxicity in human kidney (HK-2) cells

The current detoxification options of uranium, a toxic radioactive heavy metal, have obvious side effects. Polygonatum kingianum (PK), a natural product with the function of antioxidant, may be effective in detoxification and prevention of uranium-induced nephrotoxicity. Here, we studied the protective effects of PK polysaccharides (PKP) and aqueous extract (PKAE) on uranium-induced toxicity in human kidney (HK-2) cells. First, the physicochemical properties of PKP and PKAE were characterized. Assays on cultured cells demonstrated that pretreatment with PKP and PKAE significantly increased metabolic activity, relieved morphological impairments, and alleviated apoptosis. The impairments caused by uranium exposure were ameliorated (mitochondrial membrane potential and ATP level increased while reactive oxygen species decreased). Molecular mechanistic studies revealed that PKP and PKAE alleviated uranium-induced cytotoxicity by regulating mitochondria-mediated apoptosis and the GSK-3β/Fyn/Nrf2 pathway. Collectively, our data support the preventive and therapeutic applications of PKP and PKAE for uranium poisoning.

Toxic element levels in ingredients and commercial pet foods

Nowadays, there is a growing concern about contamination of toxic metals (TM) in pet food due to the great potential for health risks of these elements. TM concentrations in commercial pet foods (n = 100) as well as in ingredients used in their composition (n = 100) were analyzed and compared to the Food and Drug Administration (FDA) maximum tolerable level (MTL), and the TM concentrations found in the different sources of carbohydrate, protein, and fat were compared. The TM concentrations were determined by inductively coupled plasma with optical emission spectrometry (ICP-OES). Concentrations above the MTL for aluminum, mercury, lead, uranium, and vanadium were observed in both dog and cat foods, and the percentage of dog foods that exceeded the MTL of these TM were: 31.9%; 100%; 80.55%; 95.83%; and 75%, respectively, and in cat foods: 10.71%; 100%; 32.14%; 85.71%; 28.57%, respectively. The MTL values of these TMs and the mean values in dog foods (mg/kg dry matter basis) (MTL [mean ± standard deviation]) were: aluminum: 200 (269.17 ± 393.74); mercury: 0.27 (2.51 ± 1.31); lead: 10 (12.55 ± 4.30); uranium: 10 (76.82 ± 28.09); vanadium: 1 (1.35 ± 0.69), while in cat foods were: aluminum: 200 (135.51 ± 143.95); mercury: 0.27 (3.47 ± 4.31); lead: 10 (9.13 ± 5.42); uranium: 10 (49.83 ± 29.18); vanadium: 1 (0.81 ± 0.77). Dry foods presented higher concentrations of most TM (P < 0.05) than wet foods (P < 0.05). Among the carbohydrate sources, there were the highest levels of all TM except cobalt, mercury, and nickel in wheat bran (P < 0.05), while among the protein sources, in general, animal by-products had higher TM concentrations than plant-based ingredients. Pork fat had higher concentrations of arsenic, mercury, and antimony than fish oil and poultry fat. It was concluded that the pet foods evaluated in this study presented high concentrations of the following TM: aluminum, mercury, lead, uranium, and vanadium.

Spatial relationship between well water arsenic and uranium in Northern Plains native lands

Arsenic and uranium in unregulated private wells affect many rural populations across the US. The distribution of these contaminants in the private wells of most American Indian communities is poorly characterized, and seldom studied together. Here, we evaluate the association between drinking water arsenic and uranium levels in wells (n = 441) from three tribal regions in North Dakota and South Dakota participating in the Strong Heart Water Study. Groundwater contamination was extensive; 29% and 7% of wells exceeded maximum contaminant levels for arsenic and uranium respectively. 81% of wells had both arsenic and uranium concentrations at one-tenth of their human-health benchmark (arsenic, 1 μg/L; uranium 3 μg/L). Well arsenic and uranium concentrations were uncorrelated (rs = 0.06); however, there appeared to be a spatial correlation of wells co-contaminated by arsenic and uranium associated with flow along a geologic contact. These findings indicate the importance of measuring multiple metals in well water, and to understand underlying hydrogeological conditions. The underlying mechanisms for the prevalence of arsenic and uranium across Northern Plains Tribal Lands in the US, and in particular the occurrence of both elevated arsenic and uranium in drinking water wells in this region, demands further study.

Uranium Exposure in American Indian Communities: Health, Policy, and the Way Forward

BACKGROUND

Uranium contamination of drinking-water sources on American Indian (AI) reservations in the United States is a largely ignored and underfunded public health crisis. With an estimated 40% of the headwaters in the western U.S. watershed, home to many AI reservation communities, being contaminated with untreated mine waste, the potential health effects have largely been unexplored. With AI populations already facing continued and progressive economic and social marginalization, higher prevalence of chronic disease, and systemic discrimination, associations between various toxicant exposures, including uranium, and various chronic conditions, need further examination.

OBJECTIVES

Uranium's health effects, in addition to considerations for uranium drinking-water testing, reporting, and mitigation in reference to AI communities through the lens of water quality, is reviewed.

DISCUSSION

A series of environmental health policy recommendations are described with the intent to proactively improve responsiveness to the water quality crisis in AI reservation communities in the United States specific to uranium. There is a serious and immediate need for better coordination of uranium-related drinking-water testing and reporting on reservations in the United States that will better support and guide best practices for uranium mitigation efforts. https://doi.org/10.1289/EHP7537.

Renal adaptive response to exposure to low doses of uranyl nitrate and sodium fluoride in mice

BACKGROUND

Despite their differences in physicochemical properties, both uranium (U) and fluoride (F) are nephrotoxicants at high doses but their adverse effects at low doses are still the subject of debate.

METHODS

This study aims to improve the knowledge of the biological mechanisms involved through an adaptive response model of C57BL/6 J mice chronically exposed to low priming doses of U (0, 10, 20 and 40 mg/L) or F (0, 15, 30 and 50 mg/L) and then challenged with acute exposure of 5 mg/kg U or 7.5 mg/kg NaF.

RESULTS

We showed that an adaptive response occurred with priming exposures to 20 mg/L U and 50 mg/L F, with decreased levels of the biomarkers KIM-1 and CLU compared to those in animals that received the challenge dose only (positive control). The adaptive mechanisms involved a decrease in caspase 3/7 activities in animals exposed to 20 mg/L U and a decrease in in situ VCAM expression in mice exposed to 50 mg/L F. However, autophagy and the UPR were induced independently of priming exposure to U or F and could not be identified as adaptive mechanisms to U or F.

CONCLUSION

Taken together, these results allow us to identify renal adaptive responses to U and F at doses of 20 and 50 mg/L, probably through decrease apoptosis and inflammatory cell recruitment.

Uranium inhibits mammalian mitochondrial cytochrome c oxidase and ATP synthase

As an emerging pollutant, uranium poses serious concerns to ecological and human health. The kidney has been established as a major deposition site and the most sensitive target organ for uranium poisoning, and the underlying toxicological mechanisms have been associated with oxidative stress and mitochondrial respiration. However, the identities of key molecular targets in uranium-induced toxicity remain elusive. In this study, we comprehensively evaluated the in vitro effects of uranium on ten critical enzymes in the mitochondrial respiration pathway and discovered that respiratory chain complex IV (cytochrome c oxidase) and complex V (ATP synthase) were strongly inhibited. The inhibitory effects were validated with mitochondria from human renal proximal tubule cells-the most affected renal site in uranium poisoning. The IC₅₀ values (around 1 mg/L) are physiologically relevant, as they are comparable to known kidney accumulation levels in uranium poisoning. In addition, these inhibitory effects could explain the well-documented uranium-induced reactive oxygen species generation and mitochondrial alterations. In conclusion, cytochrome c oxidase and ATP synthase are possibly key molecular targets underlying the toxic effects of uranium.

Chronic oral depleted uranium leads to reproductive damage in male rats through the ROS-hnRNP A2/B1-COX-2 signaling pathway

Depleted uranium (DU) is widely used in civil and military activities. The testis is one of the target organs of DU chronic toxicity. In this study, male SD rats were chronically exposed to DU by 3, 30, 300 mg U/kg through oral intake. After 6 months and 12 months of exposure, it was found that DU could lead to increased oxidative stress levels, decreased glutathione S-transferases (GSTs) expression, resulting in testicular injury and decreased serum testosterone (T) level in rats. Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) expression increases with the increase of DU exposure dose. After upregulation of hnRNP A2/B1 expression, the GC-1 cell injury caused by DU is aggravated, suggesting that hnRNP A2/B1 may play an important role in the reproductive toxicity of DU. At the same time, 12 months after chronic oral exposure to DU, the expression level of cyclooxygenase-2 (COX-2) and proinflammatory factor prostaglandin E2 (PGE2) in testicular tissue were increased, and the level of hnRNP A2/B1 caused by DU was decreased by reactive oxygen scavenger N-acetylcysteine (NAC). As hnRNP A2/B1 is a COX-2 regulator, DU may lead to the upregulation of hnRNP A2/B1 expression through the increase of oxidative stress level in germ cells, which in turn leads to the increase of COX-2 and PGE2 level, and ultimately result in the reproductive toxicity. In this study, the regulation mechanism of the ROS-hnRNP A2/B1-COX-2 pathway on DU-induced reproductive damage in male rats was hypothesized, providing a new target for the prevention and treatment of chronic poisoning of DU.

Ethylmalonic encephalopathy 1 initiates overactive autophagy in depleted uranium-induced cytotoxicity in the human embryonic kidney 293 cells

The kidney is the target of the acute toxicity of depleted uranium (DU). However, the mechanism of DU-induced cytotoxicity is not clear. The study was to demonstrate the role of autophagy in DU-induced cytotoxicity and to determine the potential mechanism. We confirmed that after a 4-h exposure to DU, the autophagic vacuoles and the autophagy marker light chain 3-II in the human embryonic kidney 293 cells (HEK293) increased, and cytotoxicity decreased by abrogation of excessive autophagy using autophagy inhibitor. We also found activation of nucleus p53 and inhibiting mTOR pathways in DU-treated HEK293 cells. Meanwhile, ethylmalonic encephalopathy 1 (ETHE1) decreased as the exposure dose of DU increased, with increasing autophagy flux. We suggested that by reducing ETHE1, activation of the p53 pathway, and inhibiting mTOR pathways, DU might induce overactive autophagy, which affected the cytotoxicity. This study will provide a novel therapeutic target for the treatment of DU-induced cytotoxicity.

In Vivo Uranium Sequestration using a Nanoscale Metal-Organic Framework

An agent for actinide sequestration with fast uranium uptake kinetics and efficient in vivo uranium removal using a nanoscale metal-organic framework (nano-MOF) is proposed. UiO-66 nanoparticles post-synthetically functionalized with carboxyl groups, UiO-66-(COOH)₄ -180, exhibit the fastest uranium uptake kinetics reported with more than 65 % of uranyl in fetal bovine serum (FBS) removed within 5 min. Moreover, the in vivo bio-distribution studies show that the material partially accumulates in kidneys and femurs where uranium mainly deposits facilitating the in vivo sequestration of uranium. The results of the in vivo uranium decorporation assays with mice show that UiO-66-(COOH)₄ -180 could successfully reduce the amounts of uranyl deposited in kidneys and femurs by up to 55.4 % and 36.5 %, respectively, and is significantly more efficient than the commercial actinide decorporation agent, ZnNa₃ -DTPA.

Site-specific concentration of uranium in urine of workers of the hydrometallurgical plant of Stepnogorsk mining and chemical combine

Radiation monitoring is an important radiation safety measure implemented at the hydrometallurgical plant of the Stepnogorsk mining and chemical combine (HMP SMCC, Republic of Kazakhstan). Follow-up of the workers and their regular medical examinations has laid the basis to create a cohort with the potential to be used in radiation epidemiology. The aim of current pilot study was to analyze the dose forming factors for workers of HMP SMCC. For this, bioassays samples collected from 54 workers employed at eight HMP workshops were measured using the "Agilent 7800 ICP-MS" mass spectrometer. Three years later, measurements were repeated for four workers with the highest concentrations of uranium in urine. The results of site-specific measurements of dose rates, long-lived alpha-particle activity concentrations and equivalent equilibrium volume activity of radon were derived from the archive of the HMP SMCC Service of Radiation and Toxic Safety and analyzed to fully evaluate the radiation situation at those workplaces. Maximum urine uranium concentrations were measured for workers at the extraction workshop and mechanical repair shop (up to 26.7 µg/L and 14.6 µg/L, respectively). Urinary uranium from workers employed at other sites was mainly (for about 72% of the samples) in the range of values that may occur in natural conditions (< 0.4 µg/L). A wide individual variability in uranium concentration in urine samples (from 60% to 200% of CV) was found. A linear dependence of cumulative effective dose on work experience was found with a slope of 7.5 mSv per year. This slope did not depend on working place. For the investigated workers, cumulative effective doses of workers were found in the range of low (< 100 mSv) and medium doses (100-500 mSv). It is concluded that the newly created cohort of HMP SMCC workers has the potential to improve the knowledge on health effects from low- and medium doses of ionizing radiation.

Polymer Nanorings with Uranium Specific Clefts for Selective Recovery of Uranium from Acidic Effluents via Reductive Adsorption

Nanostructured polymeric materials, functionalized with an appropriate receptor, have opened up newer possibilities for designing a reagent that shows analyte-specific recognition and efficient scavenging of an analyte that has either a detrimental influence on human physiology and environment or on its recovery for further value addition. Higher active surface area, morphological diversity, synthetic tunability for desired surface functionalization, and the ease of regeneration of a nanostructured material for further use have provided such materials with a distinct edge over conventional reagents. The use of a biodegradable polymeric backbone has an added significance owing to the recent concern over the impact of polymers on the environment. Functionalization of biodegradable sodium alginate with AENA (6.85% grafting) as the receptor functionality led to a unique open framework nanoring (NNRG) morphology with a favorable spatial orientation for specific recognition and efficient binding to uranyl ions (U) in an aqueous medium over a varied pH range. Nanoring morphology was confirmed by transmission electron microscopy and atomic force microscopy images. The nanoscale design maximizes the surface area for the molecular scavenger. A combination of all these features along with the reversible binding phenomenon has made NNRG a superior reagent for specific, efficient uptake of UO₂²⁺ species from an acidic (pH 3-4) solution and compares better than all existing UO₂²⁺-scavengers reported till date. This could be utilized for the recovery of uranyl species from a synthetic acidic effluent of the nuclear power. The results of the U uptake experiments reveal a maximum adsorption capacity of 268 mg of U per g of NNRG in a synthetic nuclear effluent. X-ray photoelectron spectroscopy studies revealed a reductive complexation process and stabilization of U(IV)-species in adsorbed uranium species (U@NNRG).

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.

Acute Kidney Injury in Active Wars and Other Man-Made Disasters

Acute kidney injury (AKI) is frequent during wars and other man-made disasters, and contributes significantly to the overall death toll. War-related AKI may develop as a result of polytrauma, traumatic bleeding and hypovolemia, chemical and airborne toxin exposure, and crush syndrome. Thus, prerenal, intrinsic renal, or postrenal AKI may develop at the battlefield, in field hospitals, or tertiary care centers, resulting not only from traumatic, but also nontraumatic, etiologies. The prognosis usually is unfavorable because of systemic and polytrauma-related complications and suboptimal therapeutic interventions. Measures for decreasing the risk of AKI include making preparations for foreseeable disasters, and early management of polytrauma-related complications, hypovolemia, and other pathogenetic mechanisms. Transporting casualties initially to field hospitals, and afterward to higher-level health care facilities at the earliest convenience, is critical. Other man-made disasters also may cause AKI; however, the number of patients is mostly lower and treatment possibilities are broader than in war. If there is no alternative other than prolonged field care, the medical community must be prepared to offer health care and even perform dialysis in austere conditions, which in that case, is the only option to decrease the death toll resulting from AKI.

Mixed organic and inorganic tapwater exposures and potential effects in greater Chicago area, USA

Safe drinking water at the point of use (tapwater, TW) is a public-health priority. TW exposures and potential human-health concerns of 540 organics and 35 inorganics were assessed in 45 Chicago-area United States (US) homes in 2017. No US Environmental Protection Agency (EPA) enforceable Maximum Contaminant Level(s) (MCL) were exceeded in any residential or water treatment plant (WTP) pre-distribution TW sample. Ninety percent (90%) of organic analytes were not detected in treated TW, emphasizing the high quality of the Lake Michigan drinking-water source and the efficacy of the drinking-water treatment and monitoring. Sixteen (16) organics were detected in >25% of TW samples, with about 50 detected at least once. Low-level TW exposures to unregulated disinfection byproducts (DBP) of emerging concern, per/polyfluoroalkyl substances (PFAS), and three pesticides were ubiquitous. Common exceedances of non-enforceable EPA MCL Goal(s) (MCLG) of zero for arsenic [As], lead [Pb], uranium [U], bromodichloromethane, and tribromomethane suggest potential human-health concerns and emphasize the continuing need for improved understanding of cumulative effects of low-concentration mixtures on vulnerable sub-populations. Because DBP dominated TW organics, residential-TW concentrations are potentially predictable with expanded pre-distribution DBP monitoring. However, several TW chemicals, notably Pb and several infrequently detected organic compounds, were not readily explained by pre-distribution samples, illustrating the need for continued broad inorganic/organic TW characterization to support consumer assessment of acceptable risk and point-of-use treatment options.

Mixed organic and inorganic tapwater exposures and potential effects in greater Chicago area, USA

Safe drinking water at the point of use (tapwater, TW) is a public-health priority. TW exposures and potential human-health concerns of 540 organics and 35 inorganics were assessed in 45 Chicago-area United States (US) homes in 2017. No US Environmental Protection Agency (EPA) enforceable Maximum Contaminant Level(s) (MCL) were exceeded in any residential or water treatment plant (WTP) pre-distribution TW sample. Ninety percent (90%) of organic analytes were not detected in treated TW, emphasizing the high quality of the Lake Michigan drinking-water source and the efficacy of the drinking-water treatment and monitoring. Sixteen (16) organics were detected in >25% of TW samples, with about 50 detected at least once. Low-level TW exposures to unregulated disinfection byproducts (DBP) of emerging concern, per/polyfluoroalkyl substances (PFAS), and three pesticides were ubiquitous. Common exceedances of non-enforceable EPA MCL Goal(s) (MCLG) of zero for arsenic [As], lead [Pb], uranium [U], bromodichloromethane, and tribromomethane suggest potential human-health concerns and emphasize the continuing need for improved understanding of cumulative effects of low-concentration mixtures on vulnerable sub-populations. Because DBP dominated TW organics, residential-TW concentrations are potentially predictable with expanded pre-distribution DBP monitoring. However, several TW chemicals, notably Pb and several infrequently detected organic compounds, were not readily explained by pre-distribution samples, illustrating the need for continued broad inorganic/organic TW characterization to support consumer assessment of acceptable risk and point-of-use treatment options.

A novel calibration strategy based on internal standard-spiked gelatine for quantitative bio-imaging by LA-ICP-MS: application to renal localization and quantification of uranium

Mass spectrometry imaging (MSI) using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been employed for the elemental bio-distribution and quantification of uranium (U) in histological tissue sections of rodent kidneys. Kidneys were immediately immersed into 4% paraformaldehyde (PFA) solution for 24 h, Tissue-Tek O.C.T. Compound embedded and stored at - 80 °C until cutting in a cryostat, and mounted in gel-covered glass slides. In order to assure complete ablation of sample, sample preparation and laser conditions were carefully optimized. In this work, a new analytical methodology is presented for performing quantitative laser ablation analyses based on internal standard (thulium, Tm)-spiked gelatine (10% m/v) for correction of matrix effects, lack of tissue homogeneity, and instrumental drift. In parallel, matrix-matched laboratory standards, dosed at different concentrations of U, were prepared from a pool of rat kidneys. The quantitative images of cryo-sections revealed heterogeneous distribution of uranium within the renal tissue, because the cortical concentration was up to 120-fold higher than the medullary concentration. Graphical abstract.

Uranium in Ohio, USA Surface Waters: Implications for a Fertilizer Source in Waters Draining Agricultural lands

Synthetic fertilizer is a potential source of uranium to natural waters, yet evidence is lacking. We analyzed dissolved uranium concentrations in lakes, reservoirs, and rivers in Ohio, USA during the summer of 2017. All water bodies drain areas of extensive agriculture where phosphate-rich fertilizer is applied. Uranium concentrations ranged from 0.3 to 3.9 µg L⁻¹, with the lowest concentrations observed in the most offshore Lake Erie samples. These results, especially when placed in the context of previous work on both surface and groundwater, suggest that dissolved uranium concentrations in this water emanating from agricultural lands are higher than background, and uranium should be categorized similarly to nitrate and phosphate in that it originates in part from fertilizer application.

Urinary transferrin pre-emptively identifies the risk of renal damage posed by subclinical tubular alterations

Nephrotoxicity is an important limitation to the clinical use of many drugs and contrast media. Drug nephrotoxicity occurs in acute, subacute and chronic manifestations ranging from glomerular, tubular, vascular and immunological phenotypes to acute kidney injury. Pre-emptive risk assessment of drug nephrotoxicity poses an urgent need of precision medicine to optimize pharmacological therapies and interventional procedures involving nephrotoxic products in a preventive and personalized manner. Biomarkers of risk have been identified in animal models, and risk scores have been proposed, whose clinical use is abated by their reduced applicability to specific etiological models or clinical circumstances. However, our present data suggest that the urinary level of transferrin may be indicative of risk of renal damage, where risk is induced by subclinical tubular alterations regardless of etiology. In fact, urinary transferrin pre-emptively correlates with the subsequent renal damage in animal models in which risk has been induced by drugs and toxins affecting the renal tubules (i.e. cisplatin, gentamicin and uranyl nitrate); whereas transferrin shows no relation with the risk posed by a drug affecting renal hemodynamics (i.e. cyclosporine A). Our experiments also show that transferrin increases in the urine in the risk state (i.e. prior to the damage) precisely as a consequence of reduced tubular reabsorption. Finally, urinary transferrin pre-emptively identifies subpopulations of oncological and cardiac patients at risk of nephrotoxicity. In perspective, urinary transferrin might be further explored as a wider biomarker of an important mechanism of predisposition to renal damage induced by insults causing subclinical tubular alterations.