Aging, longevity, and the role of environmental stressors: a focus on wildfire smoke and air quality.

Aging is a complex biological process involving multiple interacting mechanisms and is being increasingly linked to environmental exposures such as wildfire smoke. In this review, we detail the hallmarks of aging, emphasizing the role of telomere attrition, cellular senescence, epigenetic alterations, proteostasis, genomic instability, and mitochondrial dysfunction, while also exploring integrative hallmarks - altered intercellular communication and stem cell exhaustion. Within each hallmark of aging, our review explores how environmental disasters like wildfires, and their resultant inhaled toxicants, interact with these aging mechanisms. The intersection between aging and environmental exposures, especially high-concentration insults from wildfires, remains under-studied. Preliminary evidence, from our group and others, suggests that inhaled wildfire smoke can accelerate markers of neurological aging and reduce learning capabilities. This is likely mediated by the augmentation of circulatory factors that compromise vascular and blood-brain barrier integrity, induce chronic neuroinflammation, and promote age-associated proteinopathy-related outcomes. Moreover, wildfire smoke may induce a reduced metabolic, senescent cellular phenotype. Future interventions could potentially leverage combined anti-inflammatory and NAD + boosting compounds to counter these effects. This review underscores the critical need to study the intricate interplay between environmental factors and the biological mechanisms of aging to pave the way for effective interventions.

Acute inhalation of tungsten particles results in early signs of cardiac injury.

Epidemiological studies have established that exposure to tungsten increases the risk of developing cardiovascular diseases. However, no studies have investigated how tungsten affects cardiac function or the development of cardiovascular disease. Inhalation of tungsten particulates is relevant in occupational settings, and inhalation of particulate matter has a known causative role in driving cardiovascular disease. This study examined if acute inhalation to tungsten particulates affects cardiac function and leads to heart tissue alterations. Female BALB/c mice were exposed to Filtered Air or 1.5 ± 0.23 mg/m3 tungsten particles, using a whole-body inhalation chamber, 4 times over the course of two weeks. Inhalation exposure resulted in mild pulmonary inflammation characterized by an increased percentage and number of macrophages and metabolomic changes in the lungs. Cardiac output was significantly decreased in the tungsten-exposed group. Additionally, A', an indicator of the amount of work required by the atria to fill the heart was elevated. Cardiac gene expression analysis revealed, tungsten exposure increased expression of pro-inflammatory cytokines, markers of remodeling and fibrosis, and oxidative stress genes. These data strongly suggest exposure to tungsten results in cardiac injury characterized by early signs of diastolic dysfunction. Functional findings are in parallel, demonstrating cardiac oxidative stress, inflammation, and early fibrotic changes. Tungsten accumulation data would suggest these cardiac changes are driven by systemic consequences of pulmonary damage.

Arsenite Methyltransferase Is an Important Mediator of Hematotoxicity Induced by Arsenic in Drinking Water.

Chronic arsenic exposures via the consumption of contaminated drinking water are clearly associated with many deleterious health outcomes, including anemia. Following exposure, trivalent inorganic arsenic (AsIII) is methylated through a series of arsenic (+III oxidation state) methyltransferase (As3MT)-dependent reactions, resulting in the production of several intermediates with greater toxicity than the parent inorganic arsenicals. The extent to which inorganic vs. methylated arsenicals contribute to AsIII-induced hematotoxicity remains unknown. In this study, the contribution of As3MT-dependent biotransformation to the development of anemia was evaluated in male As3mt-knockout (KO) and wild-type, C57BL/6J, mice following 60-day drinking water exposures to 1 mg/L (ppm) AsIII. The evaluation of hematological indicators of anemia revealed significant reductions in red blood cell counts, hemoglobin levels, and hematocrit in AsIII-exposed wild-type mice as compared to unexposed controls. No such changes in the blood of As3mt-KO mice were detected. Compared with unexposed controls, the percentages of mature RBCs in the bone marrow and spleen (measured by flow cytometry) were significantly reduced in the bone marrow of AsIII-exposed wild-type, but not As3mt-KO mice. This was accompanied by increased levels of mature RBCS in the spleen and elevated levels of circulating erythropoietin in the serum of AsIII-exposed wild-type, but not As3mt-KO mice. Taken together, the findings from the present study suggest that As3MT-dependent biotransformation has an essential role in mediating the hematotoxicity of AsIII following drinking water exposures.

Tungsten toxicity and carcinogenesis.

Tungsten is an emerging contaminant in the environment. Research has demonstrated that humans are exposed to high levels of tungsten in certain settings, primarily due to increased use of tungsten in industrial applications. However, our understanding of the potential human health risks of tungsten exposure is still limited. An important point we have learned about the toxicity profile of tungsten is that it is complex because tungsten can often augment the effects of other co-exposures or co-stressors, which could result in greater toxicity or more severe disease. This has shaped the tungsten toxicology field and the types of research questions being investigated. This has particularly been true when evaluating the toxicity profile of tungsten metal alloys in combination with cobalt. In this chapter, the current state of the tungsten toxicology field will be discussed focusing on data investigating tungsten carcinogenicity and other major toxicities including pulmonary, cardiometabolic, bone, and immune endpoints, either alone or in combination with other metals. Environmental and human monitoring data will also be discussed to highlight human populations most at risk of exposure to high concentrations of tungsten, the forms of tungsten present in each setting, and exposure levels in each population.

Arsenic causes distinct gene expression changes in macrophages polarized in vitro with either interferon-γ or interleukin-4.

Arsenic exposure is correlated with atherosclerosis in epidemiological studies and in animal models. We have previously shown that arsenic exposure enhanced the atherosclerotic plaque size, increased the plaque lipid content, and decreased the plaque smooth muscle cell and collagen contents in the apolipoprotein E knockout (apoE-/-) mice. However, the percentage of plaque-resident macrophages, the primary drivers of atherosclerosis remained unchanged. Therefore, we hypothesized that although arsenic does not change the quantity of macrophages, it alters the macrophage transcriptome towards a proatherogenic state. To test this hypothesis, we used bone marrow-derived macrophages, polarized them to either interferon-γ (IFN-É£) stimulated, proinflammatory or interleukin-4 (IL-4) stimulated, alternatively activated macrophages in the presence or absence of 0.67 µM (50 ppb) arsenic and performed RNA sequencing. Arsenic exposure altered the gene expression of the macrophages in a subtype-specific manner. Most differentially expressed genes (88%) were altered specifically in either IFN-É£- or IL-4-stimulated macrophages, whereas in the remaining 12% of genes that changed in both cell types, did so in opposite directions. In IL-4-stimulated macrophages, arsenic significantly downregulated the genes involved in cholesterol biosynthesis and the chemokines CCL17/CCL22, whereas in IFN-É£-stimulated macrophages, the genes associated with the liver X receptor (LXR) pathway were downregulated by arsenic. Using a bone marrow transplant experiment, we validated that the deletion of LXRα from the hematopoietic compartment rescued arsenic-enhanced atherosclerosis in the apoE-/- mouse model. Together, these data suggest that arsenic modulates subtype-specific transcriptomic changes in macrophages and further emphasize the need to define macrophage heterogeneity in atherosclerotic plaques in order to evaluate the proatherogenic role of arsenic.

Hexavalent Chromium Targets Securin to Drive Numerical Chromosome Instability in Human Lung Cells.

Hexavalent chromium [Cr(VI)] is a known human lung carcinogen with widespread exposure in environmental and occupational settings. Despite well-known cancer risks, the molecular mechanisms of Cr(VI)-induced carcinogenesis are not well understood, but a major driver of Cr(VI) carcinogenesis is chromosome instability. Previously, we reported Cr(VI) induced numerical chromosome instability, premature centriole disengagement, centrosome amplification, premature centromere division, and spindle assembly checkpoint bypass. A key regulator of these events is securin, which acts by regulating the cleavage ability of separase. Thus, in this study we investigated securin disruption by Cr(VI) exposure. We exposed human lung cells to a particulate Cr(VI) compound, zinc chromate, for acute (24 h) and prolonged (120 h) time points. We found prolonged Cr(VI) exposure caused marked decrease in securin levels and function. After prolonged exposure at the highest concentration, securin protein levels were decreased to 15.3% of control cells, while securin mRNA quantification was 7.9% relative to control cells. Additionally, loss of securin function led to increased separase activity manifested as enhanced cleavage of separase substrates; separase, kendrin, and SCC1. These data show securin is targeted by prolonged Cr(VI) exposure in human lung cells. Thus, a new mechanistic model for Cr(VI)-induced carcinogenesis emerges with centrosome and centromere disruption as key components of numerical chromosome instability, a key driver in Cr(VI) carcinogenesis.

The immunotoxicity of natural and depleted uranium: From cells to people.

Uranium is a naturally occurring element found in the environment as a mixture of isotopes with differing radioactive properties. Enrichment of mined material results in depleted uranium waste with substantially reduced radioactivity but retains the capacity for chemical toxicity. Uranium mine and milling waste are dispersed by wind and rain leading to environmental exposures through soil, air, and water contamination. Uranium exposure is associated with numerous adverse health outcomes in humans, yet there is limited understanding of the effects of depleted uranium on the immune system. The purpose of this review is to summarize findings on uranium immunotoxicity obtained from cell, rodent and human population studies. We also highlight how each model contributes to an understanding of mechanisms that lead to immunotoxicity and limitations inherent within each system. Information from population, animal, and laboratory studies will be needed to significantly expand our knowledge of the contributions of depleted uranium to immune dysregulation, which may then inform prevention or intervention measures for exposed communities.

Arsenic impairs the lineage commitment of hematopoietic progenitor cells through the attenuation of GATA-2 DNA binding activity.

Arsenic exposure produces significant hematotoxicity in vitro and in vivo. Our previous work shows that arsenic (in the form of arsenite, AsIII) interacts with the zinc finger domains of GATA-1, inhibiting the function of this critical transcription factor, and resulting in the suppression of erythropoiesis. In addition to GATA-1, GATA-2 also plays a key role in the regulation of hematopoiesis. GATA-1 and GATA-2 have similar zinc finger domains (C4-type) that are structurally favorable for AsIII interactions. Taking this into consideration, we hypothesized that early stages of hematopoietic differentiation that are dependent on the function of GATA-2 may also be disrupted by AsIII exposure. We found that in vitro AsIII exposures disrupt the erythromegakaryocytic lineage commitment and differentiation of erythropoietin-stimulated primary mouse bone marrow hematopoietic progenitor cells (HPCs), producing an aberrant accumulation of cells in early stages of hematopoiesis and subsequent reduction of committed erythro-megakaryocyte progenitor cells. Arsenic significantly accumulated in the GATA-2 protein, causing the loss of zinc, and disruption of GATA-2 function, as measured by chromatin immunoprecipitation and the expression of GATA-2 responsive genes. Our results show that the attenuation of GATA-2 function is an important mechanism contributing to the aberrant lineage commitment and differentiation of early HPCs. Collectively, findings from the present study suggest that the AsIII-induced disruption of erythro-megakaryopoiesis may contribute to the onset and/or exacerbation of hematological disorders, such as anemia.

Microneedle Array Technique for the Longitudinal Extraction of Interstitial Fluid without Hair Removal.

Interstitial fluid (ISF) bathes the cells and tissues and is in constant exchange with blood. As an exchange medium for waste, nutrients, exosomes, and signaling molecules, ISF is recognized as a plentiful source of biomolecules. Many basic and pre-clinical small animal studies could benefit from an inexpensive and efficient technique that allows for the in vivo extraction of ISF for the subsequent quantification of molecules in the interstitial space. We have previously reported on a minimally invasive technique for the extraction of ISF using a 3D-printed microneedle array (MA) platform for comprehensive biomedical applications. Previously, hairless animal models were utilized, and euthanasia was performed immediately following the procedure. Here, we demonstrate the technique in Sprague Dawley rats, without the need for hair removal, over multiple extractions and weeks. As an example of this technique, we report simultaneous quantification of the heavy metals Copper (Cu), Lead (Pb), Lithium (Li), and Nickel (Ni) within the ISF, compared with whole blood. These results demonstrate the MA technique applicability to a broader range of species and studies and the reuse of animals, leading to a reduction in number of animals needed to successfully complete ISF extraction experiments.

Arsenite exposure inhibits the erythroid differentiation of human hematopoietic progenitor CD34+ cells and causes decreased levels of hemoglobin.

Arsenic exposure poses numerous threats to human health. Our previous work in mice has shown that arsenic causes anemia by inhibiting erythropoiesis. However, the impacts of arsenic exposure on human erythropoiesis remain largely unclear. We report here that low-dose arsenic exposure inhibits the erythroid differentiation of human hematopoietic progenitor cells (HPCs). The impacts of arsenic (in the form of arsenite; As3+) on red blood cell (RBC) development was evaluated using a long-term culture of normal human bone marrow CD34+-HPCs stimulated in vitro to undergo erythropoiesis. Over the time course studied, we analyzed the expression of the cell surface antigens CD34, CD71 and CD235a, which are markers commonly used to monitor the progression of HPCs through the stages of erythropoiesis. Simultaneously, we measured hemoglobin content, which is an important criterion used clinically for diagnosing anemia. As compared to control, low-dose As3+ exposure (100 nM and 500 nM) inhibited the expansion of CD34+-HPCs over the time course investigated; decreased the number of committed erythroid progenitors (BFU-E and CFU-E) and erythroblast differentiation in the subsequent stages; and caused a reduction of hemoglobin content. These findings demonstrate that low-dose arsenic exposure impairs human erythropoiesis, likely by combined effects on various stages of RBC formation.

Inhalation of Tungsten Metal Particulates Alters the Lung and Bone Microenvironments Following Acute Exposure.

Inhalation of tungsten particulates is a relevant route of exposure in occupational and military settings. Exposure to tungsten alloys is associated with increased incidence of lung pathologies, including interstitial lung disease and cancer. We have demonstrated, oral exposure to soluble tungsten enhances breast cancer metastasis to the lungs through changes in the surrounding microenvironment. However, more research is required to investigate if changes in the lung microenvironment, following tungsten particulate exposure, can drive tumorigenesis or metastasis to the lung niche. This study examined if inhalation to environmentally relevant concentrations of tungsten particulates caused acute damage to the microenvironment in the lungs and/or systemically using a whole-body inhalation system. Twenty-four female BALB/c mice were exposed to Filtered Air, 0.60 mg/m3, or 1.7 mg/m3 tungsten particulates (<1 µm) for 4 h. Tissue samples were collected at days 1 and 7 post-exposure. Tungsten accumulation in the lungs persisted up to 7 days post-exposure and produced acute changes to the lung microenvironment including increased macrophage and neutrophil infiltration, increased levels of proinflammatory cytokines interleukin 1 beta and C-X-C motif chemokine ligand 1, and an increased percentage of activated fibroblasts (alpha-smooth muscle actin+). Exposure to tungsten also resulted in systemic effects on the bone, including tungsten deposition and transient increases in gene expression of proinflammatory cytokines. Taken together, acute whole-body inhalation of tungsten particulates, at levels commonly observed in occupational and military settings, resulted in changes to the lung and bone microenvironments that may promote tumorigenesis or metastasis and be important molecular drivers of other tungsten-associated lung pathologies such as interstitial lung disease.

Arsenite and monomethylarsonous acid disrupt erythropoiesis through combined effects on differentiation and survival pathways in early erythroid progenitors.

Strong epidemiological evidence demonstrates an association between chronic arsenic exposure and anemia. We recently found that As+3 impairs erythropoiesis by disrupting the function of GATA-1; however the downstream pathways impacted by the loss of GATA-1 function have not been evaluated. Additionally, our previous findings indicate that the predominant arsenical in the bone marrow of mice exposed to As+3 in their drinking water for 30 days was MMA+3, but the impacts of this arsenical on erythorpoisis also remain largely unknown. The goal of this study was to address these critical knowledge gaps by evaluating the comparative effects of arsenite (As+3) and the As+3 metabolite, monomethyarsonous acid (MMA+3) on two critical regulatory pathways that control the differentiation and survival of early erythroid progenitor cells. We found that 500 nM As+3 and 100 and 500 nM MMA+3 suppress erythropoiesis by impairing the differentiation of early stage erythroid progenitors. The suppression of early erythroid progenitor cell development was attributed to combined effects on differentiation and survival pathways mediated by disruption of GATA-1 and STAT5. Our results show that As+3 primarily disrupted GATA-1 function; whereas, MMA+3 suppressed both GATA-1 and STAT5 activity. Collectively, these findings provide novel mechanistic insights into arsenic-induced dyserythropoiesis and suggest that MMA+3 may be more toxic than As+3 to early developing erythroid cells.

Sex-Specific Effects of Prenatal and Early Life Inorganic and Methylated Arsenic Exposure on Atherosclerotic Plaque Development and Composition in Adult ApoE-/- Mice.

BACKGROUND: Epidemiologic studies indicate that early life arsenic exposures are linked to an increased risk of cardiovascular diseases. Different oxidation and methylation states of arsenic exist in the environment and are formed in vivo via the action of arsenic (+3 oxidation state) methyltransferase (As3MT). Methylated arsenicals are pro-atherogenic postnatally, but pre- and perinatal effects are unclear. This is particularly important because methylated arsenicals are known to cross the placenta. OBJECTIVES: We tested the effects of early life exposure to inorganic and methylated arsenicals on atherosclerotic plaque formation and its composition in apolipoprotein E knock-out (apoE-/-) mice and evaluated whether apoE-/- mice lacking As3MT expression were susceptible to this effect. METHODS: We exposed apoE-/- or apoE-/-/As3MT-/- mice to 200 ppb inorganic or methylated arsenic in the drinking water from conception to weaning and assessed atherosclerotic plaques in the offspring at 18 wk of age. Mixed regression models were used to estimate the mean difference in each outcome relative to controls, adjusting for sex and including a random effects term to account for within-litter clustering. RESULTS: Early life exposure to inorganic arsenic, and more profoundly methylated arsenicals, resulted in significantly larger plaques in the aortic arch and sinus in both sexes. Lipid levels in these plaques were higher without a substantial difference in macrophage numbers. Smooth muscle cell content was not altered, but collagen content was lower. Importantly, there were sex-specific differences in these observations, where males had higher lipids and lower collagen in the plaque, but females did not. In mice lacking As3MT, arsenic did not alter the plaque size, although the size was highly variable. In addition, control apoE-/-/As3MT-/- mice had significantly larger plaque size compared with control apoE-/-. CONCLUSION: This study shows that early life exposure to inorganic and methylated arsenicals is pro-atherogenic with sex-specific differences in plaque composition and a potential role for As3MT in mice. https://doi.org/10.1289/EHP8171.

Tungsten Increases Sex-Specific Osteoclast Differentiation in Murine Bone.

Tungsten is a naturally occurring metal that is increasingly used in industry and medical devices, and is labeled as an emerging environmental contaminant. Like many metals, tungsten accumulates in bone. Our previous data indicate that tungsten decreases differentiation of osteoblasts, bone-forming cells. Herein, we explored the impact of tungsten on osteoclast differentiation, which function in bone resorption. We observed significantly elevated osteoclast numbers in the trabecular bone of femurs following oral exposure to tungsten in male, but not female mice. In order to explore the mechanism(s) by which tungsten increases osteoclast number, we utilized in vitro murine primary and cell line pre-osteoclast models. Although tungsten did not alter the adhesion of osteoclasts to the extracellular matrix protein, vitronectin, we did observe that tungsten enhanced RANKL-induced differentiation into tartrate-resistant acid phosphatase (TRAP)-positive mononucleated osteoclasts. Importantly, tungsten alone had no effect on differentiation or on the number of multinucleated TRAP-positive osteoclasts. Enhanced RANKL-induced differentiation correlated with increased gene expression of differentiated osteoclast markers Nfatc1, Acp5, and Ctsk. Although tungsten did not alter the RANK surface receptor expression, it did modulate its downstream signaling. Co-exposure of tungsten and RANKL resulted in sustained positive p38 signaling. These findings demonstrate that tungsten enhances sex-specific osteoclast differentiation, and together with previous findings of decreased osteoblastogenesis, implicate tungsten as a modulator of bone homeostasis.

Inhibition of red blood cell development by arsenic-induced disruption of GATA-1.

Anemia is a hematological disorder that adversely affects the health of millions of people worldwide. Although many variables influence the development and exacerbation of anemia, one major contributing factor is the impairment of erythropoiesis. Normal erythropoiesis is highly regulated by the zinc finger transcription factor GATA-1. Disruption of the zinc finger motifs in GATA-1, such as produced by germline mutations, compromises the function of this critical transcription factor and causes dyserythropoietic anemia. Herein, we utilize a combination of in vitro and in vivo studies to provide evidence that arsenic, a widespread environmental toxicant, inhibits erythropoiesis likely through replacing zinc within the zinc fingers of the critical transcription factor GATA-1. We found that arsenic interacts with the N- and C-terminal zinc finger motifs of GATA-1, causing zinc loss and inhibition of DNA and protein binding activities, leading to dyserythropoiesis and an imbalance of hematopoietic differentiation. For the first time, we show that exposures to a prevalent environmental contaminant compromises the function of a key regulatory factor in erythropoiesis, producing effects functionally similar to inherited GATA-1 mutations. These findings highlight a novel molecular mechanism by which arsenic exposure may cause anemia and provide critical insights into potential prevention and intervention for arsenic-related anemias.

Exposures to uranium and arsenic alter intraepithelial and innate immune cells in the small intestine of male and female mice.

Human exposures to environmental metals, including uranium (U) and arsenic (As) are a global public health concern. Chronic exposures to U and As are linked to many adverse health effects including, immune suppression and autoimmunity. The gastrointestinal (GI) tract is home to many immune cells vital in the maintenance of systemic immune health. However, very little is known about the immunotoxicity of U and As at this site. The present study examined the burden of U and As exposure in the GI tract as well as the resultant immunotoxicity to intraepithelial lymphocytes (IELs) and innate immune cells of the small intestine following chronic drinking water exposures of male and female mice to U (in the form of uranyl acetate, UA) and As (in the form of sodium arsenite, As3+). Exposure to U or As3+ resulted in high levels of U or As in the GI tract of male and female mice, respectively. A reduction of small intestinal CD4+ IELs (TCRαß+, CD8αα+) was found following As3+ exposure, whereas U produced widespread suppression of CD4- IEL subsets (TCRαß+ and TCRγδ+). Evaluation of innate immune cell subsets in the small intestinal lamina propria revealed a decrease in mature macrophages, along with a corresponding increase in immature/proinflammatory macrophages following As3+ exposures. These data show that exposures to two prevalent environmental contaminants, U and As produce significant immunotoxicity in the GI tract. Collectively, these findings provide a critical framework for understanding the underlying immune health issues reported in human populations chronically exposed to environmental metals.

A Functional Assay to Assess Toxicity During Murine B Cell Development In Vitro.

B lymphocytes, or B cells, are important players in immunity that produce antigen-specific immunoglobulins. As a result, they are involved in various immune-linked pathologies. To better understand, prevent, or treat B cell-associated disease and immunotoxicity, we developed an in vitro assay to model early murine B cell differentiation within the bone marrow. This model uses sorted B cell precursors cultured on a supporting stromal cell layer, which over time acquire markers of further differentiated B cells, such as surface antigens and rearranged immunoglobulin light chain. Importantly, we utilized our in vitro model to validate our previous observations that xenobiotics, such as tungsten and organotins, alter B cell development in vivo. Furthermore, gene expression can be modulated in this model using retroviral transduction, making it amenable to investigating signaling pathways involved in disruption of B cell differentiation. © 2019 by John Wiley & Sons, Inc. Basic Protocol: Assessment of early B lymphocyte differentiation in vitro Support Protocol: Isolation of murine bone marrow Alternate Protocol 1: Addition of recombinant interleukin-7 Alternate Protocol 2: Genetic manipulation via retroviral transduction.

Minimal uranium immunotoxicity following a 60-day drinking water exposure to uranyl acetate in male and female C57BL/6J mice.

Historical uranium (U) mining in the Southwestern United States resulted in significant environmental contamination throughout this region and presents a significant risk of chronic metal exposure and toxicity for communities living in close proximity to mine waste sites. Uranium exposure is associated with numerous deleterious health effects including immune dysfunction; however, its effects on the immune system have yet to be fully characterized. We recently published that drinking water exposure to U, in the form of uranyl acetate (UA), results in low overall tissue retention of U (<0.01%), with very little accumulation in immune organs (blood, bone marrow, spleen, and thymus) of male and female mice. In the present study we characterized the immunotoxicity of U, in the form of UA, following a 60-day drinking water exposure to 5 and 50 ppm in male and female C57BL/6J mice. The following immunotoxicity endpoints were evaluated: hematology, immune tissue weights and total cell recoveries, immunophenotying of the spleen and thymus, and immune cell function (lymphocyte mitogenesis and T-dependent antibody response). Uranium exposure had subtle impacts on the immune endpoints evaluated, likely due to low U accumulation at these sites. The only significant alterations were a slight decrease in the percentages of splenic natural killer T-cells and macrophages in exposed male mice. Despite minimal immunological effects, this study highlights the importance of investigating toxicological endpoints in both sexes and developing accurate animal models that model epidemiological exposures in the future.

Tungsten Blocks Murine B Lymphocyte Differentiation and Proliferation Through Downregulation of IL-7 Receptor/Pax5 Signaling.

Tungsten is an emerging environmental toxicant associated with several pediatric leukemia clusters, although a causal association has not been established. Our previous work demonstrated that tungsten exposure resulted in an accumulation of pre-B cells in the bone marrow, the same cell type that accumulates in pediatric acute lymphoblastic leukemia (ALL). To better understand the relevant molecular mechanisms, we performed RNA-sequencing on flow sorted pre-B cells from control and tungsten-exposed mice. Tungsten decreased the expression of multiple genes critical for B cell development, including members of the interleukin-7 receptor (IL-7R) and pre-B cell receptor signaling pathways, such as Jak1, Stat5a, Pax5, Syk, and Ikzf3. These results were confirmed in an in vitro model of B cell differentiation, where tungsten arrested differentiation at the pro-B cell stage and inhibited proliferation. These changes were associated with decreased expression of multiple genes in the IL-7R signaling pathway and decreased percentage of IL-7R, phosphorylated STAT5 double-positive cells. Supplementation with IL-7 or overexpression of Pax5, the transcription factor downstream of IL-7R, rescued the tungsten-induced differentiation block. Together, these data support the hypothesis that IL-7R/Pax5 signaling axis is critical to tungsten-mediated effects on pre-B cell development. Importantly, many of these molecules are modulated in ALL.

Minimal uranium accumulation in lymphoid tissues following an oral 60-day uranyl acetate exposure in male and female C57BL/6J mice.

High levels of uranium (U) exist in soil, water, and air in the Southwestern United States due, in part, to waste generated from more than 160,000 abandoned hard rock mines located in this region. As a result, many people living in this region are chronically exposed to U at levels that have been linked to detrimental health outcomes. In an effort to establish a relevant in vivo mouse model for future U immunotoxicity studies, we evaluated the tissue distribution of U in immune organs; blood, bone marrow, spleen, and thymus, as well as femur bones, kidneys, and liver, following a 60-d drinking water exposure to uranyl acetate (UA) in male and female C57BL/6J mice. Following the 60-d exposure, there was low overall tissue retention of U (<0.01%) at both the 5 and the 50 ppm (mg/L) oral concentrations. In both male and female mice, there was limited U accumulation in immune organs. U only accumulated at low concentrations in the blood and bone marrow of male mice (0.6 and 16.8 ng/g, respectively). Consistent with previous reports, the predominant sites of U accumulation were the femur bones (350.1 and 399.0 ng/g, respectively) and kidneys (134.0 and 361.3 ng/g, respectively) of male and female mice. Findings from this study provide critical insights into the distribution and retention of U in lymphoid tissues following chronic drinking water exposure to U. This information will serve as a foundation for immunotoxicological assessments of U, alone and in combination with other metals.