Implementation of multiomic mass spectrometry approaches for the evaluation of human health following environmental exposure

Omics analyses collectively refer to the possibility of profiling genetic variants, RNA, epigenetic markers, proteins, lipids, and metabolites. The most common analytical approaches used for detecting molecules present within biofluids related to metabolism are vibrational spectroscopy techniques, represented by infrared, Raman, and nuclear magnetic resonance (NMR) spectroscopies and mass spectrometry (MS). Omics-based assessments utilizing MS are rapidly expanding and being applied to various scientific disciplines and clinical settings. Most of the omics instruments are operated by specialists in dedicated laboratories; however, the development of miniature portable omics has made the technology more available to users for field applications. Variations in molecular information gained from omics approaches are useful for evaluating human health following environmental exposure and the development and progression of numerous diseases. As MS technology develops so do statistical and machine learning methods for the detection of molecular deviations from personalized metabolism, which are correlated to altered health conditions, and they are intended to provide a multi-disciplinary overview for researchers interested in adding multiomic analysis to their current efforts. This includes an introduction to mass spectrometry-based omics technologies, current state-of-the-art capabilities and their respective strengths and limitations for surveying molecular information. Furthermore, we describe how knowledge gained from these assessments can be applied to personalized medicine and diagnostic strategies.

Lipid mediators of inhalation exposure-induced pulmonary toxicity and inflammation

Many inhalation exposures induce pulmonary inflammation contributing to disease progression. Inflammatory processes are actively regulated via mediators including bioactive lipids. Bioactive lipids are potent signaling molecules involved in both pro-inflammatory and resolution processes through receptor interactions. The formation and clearance of lipid signaling mediators are controlled by multiple metabolic enzymes. An imbalance of these lipids can result in exacerbated and sustained inflammatory processes which may result in pulmonary damage and disease. Dysregulation of pulmonary bioactive lipids contribute to inflammation and pulmonary toxicity following exposures. For example, inhalation of cigarette smoke induces activation of pro-inflammatory bioactive lipids such as sphingolipids, and ceramides contributing to chronic obstructive pulmonary disease. Additionally, exposure to silver nanoparticles causes dysregulation of inflammatory resolution lipids. As inflammation is a common consequence resulting from inhaled exposures and a component of numerous diseases it represents a broadly applicable target for therapeutic intervention. With new appreciation for bioactive lipids, technological advances to reliably identify and quantify lipids have occurred. In this review, we will summarize, integrate, and discuss findings from recent studies investigating the impact of inhaled exposures on pro-inflammatory and resolution lipids within the lung and their contribution to disease. Throughout the review current knowledge gaps in our understanding of bioactive lipids and their contribution to pulmonary effects of inhaled exposures will be presented. New methods being employed to detect and quantify disruption of pulmonary lipid levels following inhalation exposures will be highlighted. Lastly, we will describe how lipid dysregulation could potentially be addressed by therapeutic strategies to address inflammation.

Angiogenic potential of skeletal muscle derived extracellular vesicles differs between oxidative and glycolytic muscle tissue in mice

Skeletal muscle fibers regulate surrounding endothelial cells (EC) via secretion of numerous angiogenic factors, including extracellular vesicles (SkM-EV). Muscle fibers are broadly classified as oxidative (OXI) or glycolytic (GLY) depending on their metabolic characteristics. OXI fibers secrete more pro-angiogenic factors and have greater capillary densities than GLY fibers. OXI muscle secretes more EV than GLY, however it is unknown whether muscle metabolic characteristics regulate EV contents and signaling potential. EVs were isolated from primarily oxidative or glycolytic muscle tissue from mice. MicroRNA (miR) contents were determined and endothelial cells were treated with OXI- and GLY-EV to investigate angiogenic signaling potential. There were considerable differences in miR contents between OXI- and GLY-EV and pathway analysis identified that OXI-EV miR were predicted to positively regulate multiple endothelial-specific pathways, compared to GLY-EV. OXI-EV improved in vitro angiogenesis, which may have been mediated through nitric oxide synthase (NOS) related pathways, as treatment of endothelial cells with a non-selective NOS inhibitor abolished the angiogenic benefits of OXI-EV. This is the first report to show widespread differences in miR contents between SkM-EV isolated from metabolically different muscle tissue and the first to demonstrate that oxidative muscle tissue secretes EV with greater angiogenic signaling potential than glycolytic muscle tissue.

Compositional variations in metal nanoparticle components of welding fumes impact lung epithelial cell toxicity

Welding fumes contain harmful metals and gas by-products associated with development of lung dysfunction, asthma, bronchitis, and lung cancer. Two prominent welding fume particulate metal components are nanosized iron (Fe) and manganese (Mn) which might induce oxidative stress and inflammation resulting in pulmonary injury. Welding fume toxicity may be dependent upon metal nanoparticle (NP) components. To examine toxicity of welding fume NP components, a system was constructed for controlled and continuous NP generation from commercial welding and customized electrodes with varying proportions of Fe and Mn. Aerosols generated consisted of nanosized particles and were compositionally consistent with each electrode. Human alveolar lung A459 epithelial cells were exposed to freshly generated metal NP mixtures at a target concentration of 100 µg/m3 for 6 hr and then harvested for assessment of cytotoxicity, generation of reactive oxygen species (ROS), and alterations in the expression of genes and proteins involved in metal regulation, inflammatory responses, and oxidative stress. Aerosol exposures decreased cell viability and induced increased ROS production. Assessment of gene expression demonstrated variable up-regulation in cellular mechanisms related to metal transport and storage, inflammation, and oxidative stress based upon aerosol composition. Specifically, interleukin-8 (IL-8) demonstrated the most robust changes in both transcriptional and protein levels after exposure. Interleukin-8 has been determined to serve as a primary cytokine mediating inflammatory responses induced by welding fume exposures in alveolar epithelial cells. Overall, this study demonstrated variations in cellular responses to metal NP mixtures suggesting compositional variations in NP content within welding fumes may influence inhalation toxicity.

Pulmonary and Neurological Health Effects Associated with Exposure to Representative Composite Manufacturing Emissions and Corresponding Alterations in Circulating Metabolite Profiles

Cured-in-place pipe (CIPP) technology is increasingly being utilized to repair aging and damaged pipes, however, there are concerns associated with the public health hazards of emissions. CIPP installation involves the manufacture of a new plastic composite pipe at the worksite and includes multiple variable components including resin material, curing methods, and operational conditions. We hypothesize styrene-based composite manufacturing emissions (CMEs) will induce greater pulmonary inflammatory responses and oxidative stress, as well as neurological toxicity compared to non-styrene CMEs. Further, these CME-toxicological responses will be sex- and time-dependent. To test the hypothesis, representative CMEs were generated using a laboratory curing chamber and characterized using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) and photoionization detector (PID). Styrene was released during all three phases of the curing process and peaked during the cooling phase. Male and female C57BL6/J mice were utilized to examine alterations in pulmonary responses and neurotoxicity 1 d and 7 d following exposure to air (controls), non-styrene-CMEs, or styrene-CMEs. Serum styrene metabolites were increased in mice exposed to styrene-CMEs. Metabolic and lipid profiling revealed alterations related to CIPP emissions that were resin-, time-, and sex-dependent. Exposure to styrene-CMEs resulted in an influx of lymphocytes in both sexes. Expression of inflammatory and oxidative stress markers, including Tnfα, Vcam1, Ccl2, Cxcl2, Il6, Cxcl1, Tgfβ1, Tgmt2, and Hmox1, displayed alterations following exposure to emissions. These changes in pulmonary and neurological markers of toxicity were dependent on resin type, sex, and time. Overall, this study demonstrates resin-specific differences in representative CMEs and alterations in toxicity endpoints, which can potentially inform safer utilization of composite manufacturing processes.

Regulatory Significance of Plastic Manufacturing Air Pollution Discharged into Terrestrial Environments and Real-Time Sensing Challenges

Cured-in-place-pipe (CIPP) is an onsite plastic manufacturing technology used in the U.S. and has not been evaluated for regulatory compliance with federal air pollution laws. The practice involves the discharge of manufacturing waste into the environment. The study goal was to estimate the magnitude of volatile organic compounds (VOCs) discharged into the atmosphere for styrene and nonstyrene composite manufacture and examine low-cost air monitoring sensor reliability. Time-resolved emission analysis revealed that VOC emission was not only isolated to the thermal curing period but also occurred before and after curing. In addition to the styrene monomer, other gas-phase hazardous air pollutants regulated under the Clean Air Act were also emitted. Based on typical CIPP installations, 0.9 to 16.6 U.S. tons of emitted VOCs were estimated for styrene CIPPs, and 0.09 to 1.6 U.S. tons of emitted VOCs were estimated for nonstyrene CIPPs. Because the number and size of CIPPs manufactured in a single community can vary, the total air pollution burden will significantly differ across communities. Low-cost VOC sensors commonly utilized near CIPP manufacturing activities did not accurately quantify styrene and should not be relied upon for that purpose. Up to several thousand-fold detection differences were observed. Regulatory evaluation of CIPP air pollution and PID sensor reliability assessments are recommended.

Bystander chemical exposures and injuries associated with nearby plastic sewer pipe manufacture: public health practice and lessons

Cured-in-place pipes (CIPPs) are plastic liners manufactured inside existing damaged sanitary sewer, storm sewer, and water pipes that extend the service life of host pipes. This process often is conducted in neighborhoods and near roadways. Before, during, and after plastic manufacture, waste materials that include volatile materials are released into the air. Emissions from this manufacturing process can affect outdoor air quality and indoor air quality for buildings connected to the sewer system. We identified key issues and solicited stakeholder feedback to estimate and manage public health risks of CIPP-generated chemical air pollution. A work group representing 13 U.S. agencies and public health associations provided feedback and prioritized public health issues for action. To mitigate potential public and occupational health risks, additional testing and public health educational efforts were recommended. An improved understanding of CIPP chemical exposure pathways, as well as stakeholder needs and interests, is essential.

Enhanced silver nanoparticle-induced pulmonary inflammation in a metabolic syndrome mouse model and resolvin D1 treatment

BACKGROUND

Metabolic syndrome (MetS) exacerbates susceptibility to inhalation exposures such as particulate air pollution, however, the mechanisms responsible remain unelucidated. Previously, we determined a MetS mouse model exhibited exacerbated pulmonary inflammation 24 h following AgNP exposure compared to a healthy mouse model. This enhanced response corresponded with reduction of distinct resolution mediators. We hypothesized silver nanoparticle (AgNP) exposure in MetS results in sustained pulmonary inflammation. Further, we hypothesized treatment with resolvin D1 (RvD1) will reduce exacerbations in AgNP-induced inflammation due to MetS.

RESULTS

To evaluate these hypotheses, healthy and MetS mouse models were exposed to vehicle (control) or AgNPs and a day later, treated with resolvin D1 (RvD1) or vehicle (control) via oropharyngeal aspiration. Pulmonary lung toxicity was evaluated at 3-, 7-, 14-, and 21-days following AgNP exposure. MetS mice exposed to AgNPs and receiving vehicle treatment, demonstrated exacerbated pulmonary inflammatory responses compared to healthy mice. In the AgNP exposed mice receiving RvD1, pulmonary inflammatory response in MetS was reduced to levels comparable to healthy mice exposed to AgNPs. This included decreases in neutrophil influx and inflammatory cytokines, as well as elevated anti-inflammatory cytokines.

CONCLUSIONS

Inefficient resolution may contribute to enhancements in MetS susceptibility to AgNP exposure causing an increased pulmonary inflammatory response. Treatments utilizing specific resolution mediators may be beneficial to individuals suffering MetS following inhalation exposures.

Modulation of Pulmonary Toxicity in Metabolic Syndrome Due to Variations in Iron Oxide Nanoparticle-Biocorona Composition

Nanoparticles (NPs) interact with biomolecules by forming a biocorona (BC) on their surface after introduction into the body and alter cell interactions and toxicity. Metabolic syndrome (MetS) is a prevalent condition and enhances susceptibility to inhaled exposures. We hypothesize that distinct NP-biomolecule interactions occur in the lungs due to MetS resulting in the formation of unique NP-BCs contributing to enhanced toxicity. Bronchoalveolar lavage fluid (BALF) was collected from healthy and MetS mouse models and used to evaluate variations in the BC formation on 20 nm iron oxide (Fe₃O₄) NPs. Fe₃O₄ NPs without or with BCs were characterized for hydrodynamic size and zeta potential. Unique and differentially associated proteins and lipids with the Fe₃O₄ NPs were identified through proteomic and lipidomic analyses to evaluate BC alterations based on disease state. A mouse macrophage cell line was utilized to examine alterations in cell interactions and toxicity due to BCs. Exposures to 6.25, 12.5, 25, and 50 μg/mL of Fe₃O₄ NPs with BCs for 1 h or 24 h did not demonstrate overt cytotoxicity. Macrophages increasingly associated Fe₃O₄ NPs following addition of the MetS BC compared to the healthy BC. Macrophages exposed to Fe₃O₄ NPs with a MetS-BC for 1 h or 24 h at a concentration of 25 μg/mL demonstrated enhanced gene expression of inflammatory markers: CCL2, IL-6, and TNF-α compared to Fe₃O₄ NPs with a healthy BC. Western blot analysis revealed activation of STAT3, NF-κB, and ERK pathways due to the MetS-BC. Specifically, the Jak/Stat pathway was the most upregulated inflammatory pathway following exposure to NPs with a MetS BC. Overall, our study suggests the formation of distinct BCs due to NP exposure in MetS, which may contribute to exacerbated inflammatory effects and susceptibility.

Emergency responder and public health considerations for plastic sewer lining chemical waste exposures in indoor environments

The cured-in-place pipe (CIPP) manufacturing process is used to repair buried pipes, and its waste commonly discharged into the air can enter nearby buildings. Exposure can prompt illness and the need for medical care. A mass balance model was applied to estimate indoor styrene concentrations due to intrusion of CIPP emissions through plumbing under different bathroom ventilation conditions. To better understand building contamination and recommend emergency response actions, calculations to estimate chemical intrusion through plumbing were developed. Field reports and study calculations showed that contractor-applied external pressures during plastic manufacture have and can displace plumbing trap water seals. Modeled styrene vapor concentrations that entered the building (1, 300, 1000 ppm) were similar to those measured at CIPP worksites. Modeling revealed that in some cases, bathroom exhaust fan operation during a CIPP project may increase indoor styrene concentrations due to enhanced entrainment of styrene-laden air from the sink and toilet. However, styrene concentrations decreased with increasing air leakage across the bathroom door due to reduced suction from the plumbing system. CIPP waste discharge should be treated as a hazardous material release and can pose a threat to human health. Immediate building evacuation, respiratory protection, provision of medical assistance, source elimination, and building decontamination are recommended.

Disruption of pulmonary resolution mediators contribute to exacerbated silver nanoparticle-induced acute inflammation in a metabolic syndrome mouse model

Pre-existing conditions modulate sensitivity to numerous xenobiotic exposures such as air pollution. Specifically, individuals suffering from metabolic syndrome (MetS) demonstrate enhanced acute inflammatory responses following particulate matter inhalation. The mechanisms associated with these exacerbated inflammatory responses are unknown, impairing interventional strategies and our understanding of susceptible populations. We hypothesize MetS-associated lipid dysregulation influences mediators of inflammatory resolution signaling contributing to increased acute pulmonary toxicity. To evaluate this hypothesis, healthy and MetS mouse models were treated with either 18-hydroxy eicosapentaenoic acid (18-HEPE), 14-hydroxy docosahexaenoic acid (14-HDHA), 17-hydroxy docosahexaenoic acid (17-HDHA), or saline (control) via intraperitoneal injection prior to oropharyngeal aspiration of silver nanoparticles (AgNP). In mice receiving saline treatment, AgNP exposure resulted in an acute pulmonary inflammatory response that was exacerbated in MetS mice. A targeted lipid assessment demonstrated 18-HEPE, 14-HDHA, and 17-HDHA treatments altered lung levels of specialized pro-resolving lipid mediators (SPMs). 14-HDHA and 17-HDHA treatments more efficiently reduced the exacerbated acute inflammatory response in AgNP exposed MetS mice as compared to 18-HEPE. This included decreased neutrophilic influx, diminished induction of inflammatory cytokines/chemokines, and reduced alterations in SPMs. Examination of SPM receptors determined baseline reductions in MetS mice compared to healthy as well as decreases due to AgNP exposure. Overall, these results demonstrate AgNP exposure disrupts inflammatory resolution, specifically 14-HDHA and 17-HDHA derived SPMs, in MetS contributing to exacerbated acute inflammatory responses. Our findings identify a potential mechanism responsible for enhanced susceptibility in MetS that can be targeted for interventional therapeutic approaches.

Extracellular vesicles released from stress-induced prematurely senescent myoblasts impair endothelial function and proliferation

NEW FINDINGS

What is the central question of this study? What is the impact of stress-induced premature senescence on skeletal muscle myoblast-derived extracellular vesicles (EVs) and myoblast-endothelial cell crosstalk? What is the main finding and its importance? Hydrogen peroxide treatment of human myoblasts induced stress-induced premature senescence (SIPS) and increased the release of exosome-sized EVs (30-150 nm in size) five-fold compared to untreated controls. Treatment of SIPS myoblast-derived EVs on endothelial cells increased senescence markers and decreased proliferation. Gene expression analysis of SIPS myoblast-derived EVs revealed a four-fold increase in senescence factor transforming growth factor-β. These results highlight potential mechanisms by which senescence imparts deleterious effects on the cellular microenvironment.

ABSTRACT

Cellular senescence contributes to numerous diseases through the release of pro-inflammatory factors as part of the senescence-associated secretory phenotype (SASP). In skeletal muscle, resident muscle progenitor cells (satellite cells) express markers of senescence with advancing age and in response to various pathologies, which contributes to reduced regenerative capacities in vitro. Satellite cells regulate their microenvironment in part through the release of extracellular vesicles (EVs), but the effect of senescence on EV signaling is unknown. Primary human myoblasts were isolated following biopsies of the vastus lateralis from young healthy subjects. Hydrogen peroxide (H₂ O₂ ) treatment was used to achieve stress-induced premature senescence (SIPS) of myoblasts. EVs secreted by myoblasts with and without H₂ O₂ treatment were isolated, analysed and used to treat human umbilical vein endothelial cells (HUVECs) to assess senescence and angiogenic impact. H₂ O₂ treatment of primary human myoblasts in vitro increased markers of senescence (β-galactosidase and p21^Cip1 ), decreased proliferation and increased exosome-like EV (30-150 nm) release approximately five-fold. In HUVECs, EV treatment from H₂ O₂ -treated myoblasts increased markers of senescence (β-galactosidase and transforming growth factor β), decreased proliferation and impaired HUVEC tube formation. Analysis of H₂ O₂ -treated myoblast-derived EV mRNA revealed a nearly four-fold increase in transforming growth factor β expression. Our novel results highlight the impact of SIPS on myoblast communication and identify a VasoMyo Crosstalk by which SIPS myoblast-derived EVs impair endothelial cell function in vitro.

Neuromelanin Modulates Heterocyclic Aromatic Amine-Induced Dopaminergic Neurotoxicity

Heterocyclic aromatic amines (HAAs) are mutagens and potential human carcinogens. Our group and others have demonstrated that HAAs may also produce selective dopaminergic neurotoxicity, potentially relevant to Parkinson's disease (PD). The goal of this study was to elucidate mechanisms of HAA-induced neurotoxicity through examining a translational biochemical weakness of common PD models. Neuromelanin is a pigmented byproduct of dopamine metabolism that has been debated as being both neurotoxic and neuroprotective in PD. Importantly, neuromelanin is known to bind and potentially release dopaminergic neurotoxicants, including HAAs (eg, β-carbolines such as harmane). Binding of other HAA subclasses (ie, aminoimidazoaazarenes) to neuromelanin has not been investigated, nor has a specific role for neuromelanin in mediating HAA-induced neurotoxicity been examined. Thus, we investigated the role of neuromelanin in modulating HAA-induced neurotoxicity. We characterized melanin from Sepia officinalis and synthetic dopamine melanin, proposed neuromelanin analogs with similar biophysical properties. Using a cell-free assay, we demonstrated strong binding of harmane and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) to neuromelanin analogs. To increase cellular neuromelanin, we transfected SH-SY5Y neuroblastoma cells with tyrosinase. Relative to controls, tyrosinase-expressing cells exhibited increased neuromelanin levels, cellular HAA uptake, cell toxicity, and oxidative damage. Given that typical cellular and rodent PD models form far lower neuromelanin levels than humans, there is a critical translational weakness in assessing HAA-neurotoxicity. The primary impacts of these results are identification of a potential mechanism by which HAAs accumulate in catecholaminergic neurons and support for the need to conduct neurotoxicity studies in systems forming neuromelanin.

Exacerbation of Nanoparticle-Induced Acute Pulmonary Inflammation in a Mouse Model of Metabolic Syndrome

Nanotechnology has the capacity to revolutionize numerous fields and processes, however, exposure-induced health effects are of concern. The majority of nanoparticle (NP) safety evaluations have been performed utilizing healthy models and have demonstrated the potential for pulmonary toxicity. A growing proportion of individuals suffer diseases that may enhance their susceptibility to exposures. Specifically, metabolic syndrome (MetS) is increasingly prevalent and is a risk factor for the development of chronic diseases including type-2 diabetes, cardiovascular disease, and cancer. MetS is a combination of conditions which includes dyslipidemia, obesity, hypertension, and insulin resistance. Due to the role of lipids in inflammatory signaling, we hypothesize that MetS-associated dyslipidemia may modulate NP-induced immune responses. To examine this hypothesis, mice were fed either a control diet or a high-fat western diet (HFWD) for 14-weeks. A subset of mice were treated with atorvastatin for the final 7-weeks to modulate lipids. Mice were exposed to silver NPs (AgNPs) via oropharyngeal aspiration and acute toxicity endpoints were evaluated 24-h post-exposure. Mice on the HFWD demonstrated MetS-associated alterations such as increased body weight and cholesterol compared to control-diet mice. Cytometry analysis of bronchoalveolar lavage fluid (BALF) demonstrated exacerbation of AgNP-induced neutrophilic influx in MetS mice compared to healthy. Additionally, enhanced proinflammatory mRNA expression and protein levels of monocyte chemoattractant protein-1, macrophage inflammatory protein-2, and interleukin-6 were observed in MetS mice compared to healthy following exposure. AgNP exposure reduced mRNA expression of enzymes involved in lipid metabolism, such as arachidonate 5-lipoxygenase and arachidonate 15-lipoxygenase in both mouse models. Exposure to AgNPs decreased inducible nitric oxide synthase gene expression in MetS mice. An exploratory lipidomic profiling approach was utilized to screen lipid mediators involved in pulmonary inflammation. This assessment indicates the potential for reduced levels of lipids mediators of inflammatory resolution (LMIR) in the MetS model compared to healthy mice following AgNP exposure. Statin treatment inhibited enhanced inflammatory responses as well as alterations in LMIR observed in the MetS model due to AgNP exposure. Taken together our data suggests that MetS exacerbates the acute toxicity induced by AgNPs exposure possibly via a disruption of LMIR leading to enhanced pulmonary inflammation.

An Integrative Proteomic/Lipidomic Analysis of the Gold Nanoparticle Biocorona in Healthy and Obese Conditions

Introduction: When nanoparticles (NPs) enter a physiological environment, a coating of biomolecules or biocorona (BC) forms on the surface. Formation of the NP-BC is dependent on NP properties, the physiological environment, and time. The BC influences NP properties and biological interactions such as cellular internalization, immune responses, biodistribution, and others, leading to pharmacological and toxicological consequences. To date, examination of the NP-BC has focused primarily on protein components and healthy conditions. Therefore, we evaluated the protein and lipid content of BCs that formed on physicochemically distinct gold nanoparticles (AuNPs) under healthy and obese conditions. A comprehensive understanding of the NP-BC is necessary for the translation of in vitro toxicity assessments to clinical applications. Materials and Methods: AuNPs with two coatings (poly-N-vinylpyrrolidone [PVP] or citrate) and diameters (20 or 100 nm) were incubated in pooled human serum, and an integrated proteomic/lipidomic approach was used to evaluate BC composition. Macrophages were utilized to evaluate differential immune responses due to variations in the AuNP-BC. Results: AuNPs form distinct BCs based on physicochemical properties and the surrounding environment, with the obese BC containing more proteins and fewer lipids than the healthy BC. Differential macrophage inflammatory responses were observed based on AuNP properties and BC composition. Discussion and Conclusion: Overall, these findings demonstrate that AuNP size and coating, as well as physiological environment, influence the protein and lipid composition of the BC, which impacts cellular responses following exposure. These findings demonstrate that incorporation of BCs representing distinct physiological conditions may enhance the translatability of nanosafety in vitro studies.

Advanced Glycation End-Products Suppress Mitochondrial Function and Proliferative Capacity of Achilles Tendon-Derived Fibroblasts

Debilitating cases of tendon pain and degeneration affect the majority of diabetic individuals. The high rate of tendon degeneration persists even when glucose levels are well controlled, suggesting that other mechanisms may drive tendon degeneration in diabetic patients. The purpose of this study was to investigate the impact of advanced glycation end-products on tendon fibroblasts to further our mechanistic understanding of the development and progression of diabetic tendinopathy. We proposed that advanced glycation end-products would induce limitations to mitochondrial function and proliferative capacity in tendon-derived fibroblasts, restricting their ability to maintain biosynthesis of tendon extracellular matrix. Using an in-vitro cell culture system, rat Achilles tendon fibroblasts were treated with glycolaldehyde-derived advanced glycation end-products (0, 50, 100, and 200 μg/ml) for 48 hours in normal glucose (5.5 mM) and high glucose (25 mM) conditions. We demonstrate that tendon fibroblasts treated with advanced glycation end-products display reduced ATP production, electron transport efficiency, and proliferative capacity. These impairments were coupled with alterations in mitochondrial DNA content and expression of genes associated with extracellular matrix remodeling, mitochondrial energy metabolism, and apoptosis. Our findings suggest that advanced glycation end-products disrupt tendon fibroblast homeostasis and may be involved in the development and progression of diabetic tendinopathy.

Subchronic Manganese Exposure Impairs Neurogenesis in the Adult Rat Hippocampus

Adult neurogenesis takes place in the brain subventricular zone (SVZ) in the lateral walls of lateral ventricles and subgranular zone (SGZ) in the hippocampal dentate gyrus (HDG), and functions to supply newborn neurons for normal brain functionality. Subchronic Mn exposure is known to disrupt adult neurogenesis in the SVZ. This study was designed to determine whether Mn exposure disturbed neurogenesis within the adult HDG. Adult rats (10 weeks old) received a single dose of bromodeoxyuridine (BrdU) at the end of 4-week Mn exposure to label the proliferating cells. Immunostaining and cell counting data showed that BrdU(+) cells in Mn-exposed HDG were about 37% lower than that in the control (p < .05). The majority of BrdU(+) cells were identified as Sox2(+) cells. Another set of adult rats received BrdU injections for 3 consecutive days followed by 2- or 4-week Mn exposure to trace the fate of BrdU-labeled cells in the HDG. The time course studies indicated that Mn exposure significantly reduced the survival rate (54% at 2 weeks and 33% at 4 weeks), as compared with that in the control (80% at 2 weeks and 51% at 4 weeks) (p < .01). A significant time-dependent migration of newborn cells from the SGZ toward the granule cell layer was also observed in both control and Mn-exposed HDG. Triple-stained neuroblasts and mature neurons further revealed that Mn exposure significantly inhibited the differentiation of immature neuroblasts into mature neurons in the HDG. Taken together, these observations suggest that subchronic Mn exposure results in a reduced cell proliferation, diminished survival of adult-born neurons, and inhibited overall neurogenesis in the adult HDG. Impaired adult neurogenesis is likely one of the mechanisms contribute to Mn-induced Parkinsonian disorder.

Biocorona formation contributes to silver nanoparticle induced endoplasmic reticulum stress

Prior research has demonstrated cells exposed to silver nanoparticles (AgNPs) undergo endoplasmic reticulum (ER) stress leading to cellular apoptosis and toxicity, however, the fundamental mechanism underlying AgNP-induced ER stress is unknown. We hypothesize the biophysical interactions between AgNPs and adsorbed proteins lead to misfolded proteins to elicit an ER stress response. Our investigation examined rat aortic endothelial cells (RAEC) exposed to 20 or 100 nm AgNPs with or without a biocorona (BC) consisting of bovine serum albumin (BSA), high density lipoprotein (HDL) or fetal bovine serum (FBS) to form a complex BC. The presence of a BC consisting of BSA or FBS proteins significantly reduced uptake of 20 nm and 100 nm AgNPs in RAEC. Western blot analysis indicated robust activation of the IREα and PERK pathways in RAEC exposed to 20 nm despite the reduction in uptake by the presence of a BC. This was not observed for the 100 nm AgNPs. Hyperspectral darkfield microscopy qualitatively confirmed that the preformed BC was maintained following uptake by RAEC. Transmission electron microscopy demonstrated a size dependent effect on the sub-cellular localization of AgNPs. Overall, these results suggest that AgNP size, surface area and BC formation governs the induction of ER stress and alterations in intracellular trafficking.

Altered formation of the iron oxide nanoparticle-biocorona due to individual variability and exercise

Nanoparticles (NPs), introduced into a biological environment, accumulate a coating of biomolecules or biocorona (BC). Although the BC has toxicological and pharmacological consequences, the effects of inter-individual variability and exercise on NP-BC formation are unknown. We hypothesized that NPs incubated in plasma form distinct BCs between individuals, and exercise causes additional intra-individual alterations. 20 nm iron oxide (Fe₃O₄) NPs were incubated in pre- or post-exercise plasma ex vivo, and proteomics was utilized to evaluate BC components. Analysis demonstrated distinct BC formation between individuals, while exercise was found to enhance NP-BC complexity. Abundance differences of NP-BC proteins were determined between individuals and resulting from exercise. Differential human macrophage response was identified due to NP-BC variability. These findings demonstrate that individuals form unique BCs and that exercise influences NP-biomolecule interactions. An understanding of NP-biomolecule interactions is necessary for elucidation of mechanisms responsible for variations in human responses to NP exposures and/or nano-based therapies.

Variations in biocorona formation related to defects in the structure of single walled carbon nanotubes and the hyperlipidemic disease state

Ball-milling utilizes mechanical stress to modify properties of carbon nanotubes (CNTs) including size, capping, and functionalization. Ball-milling, however, may introduce structural defects resulting in altered CNT-biomolecule interactions. Nanomaterial-biomolecule interactions result in the formation of the biocorona (BC), which alters nanomaterial properties, function, and biological responses. The formation of the BC is governed by the nanomaterial physicochemical properties and the physiological environment. Underlying disease states such as cardiovascular disease can alter the biological milieu possibly leading to unique BC identities. In this ex vivo study, we evaluated variations in the formation of the BC on single-walled CNTs (SWCNTs) due to physicochemical alterations in structure resulting from ball-milling and variations in the environment due to the high-cholesterol disease state. Increased ball-milling time of SWCNTs resulted in enhanced structural defects. Following incubation in normal mouse serum, label-free quantitative proteomics identified differences in the biomolecular content of the BC due to the ball-milling process. Further, incubation in cholesterol-rich mouse serum resulted in the formation of unique BCs compared to SWCNTs incubated in normal serum. Our study demonstrates that the BC is modified due to physicochemical modifications such as defects induced by ball-milling and physiological disease conditions, which may result in variable biological responses.

From the Cover: Disease-Induced Disparities in Formation of the Nanoparticle-Biocorona and the Toxicological Consequences

Nanoparticle (NP) association with macromolecules in a physiological environment forms a biocorona (BC), which alters NP distribution, activity, and toxicity. While BC formation is dependent on NP physicochemical properties, little information exists on the influence of the physiological environment. Obese individuals and those with cardiovascular disease exist with altered serum chemistry, which is expected to influence BC formation and NP toxicity. We hypothesize that a BC formed on NPs following incubation in hyperlipidemic serum will result in altered NP-BC protein content, cellular association, and toxicity compared to normal serum conditions. We utilized Fe3O4 NPs, which are being developed as MRI contrast and tumor targeting agents to test our hypothesis. We used rat aortic endothelial cells (RAECs) within a dynamic flow in vitro exposure system to more accurately depict the in vivo environment. A BC was formed on 20nm PVP-suspended Fe3O4 NPs following incubation in water, 10% normal or hyperlipidemic rat serum. Addition of BCs resulted in increased hydrodynamic size and decreased surface charge. More cholesterol associated with Fe3O4 NPs after incubation in hyperlipidemic as compared with normal serum. Using quantitative proteomics, we identified unique differences in BC protein components between the 2 serum types. Under flow conditions, formation of a BC from both serum types reduced RAECs association of Fe3O4 NPs. Addition of BCs was found to exacerbate RAECs inflammatory gene responses to Fe3O4 NPs (Fe3O4-hyperlipidemic > Fe3O4-normal > Fe3O4) including increased expression of IL-6, TNF-α, Cxcl-2, VCAM-1, and ICAM-1. Overall, these findings demonstrate that disease-induced variations in physiological environments have a significant impact NP-BC formation, cellular association, and cell response.

Distribution and biomarker of carbon-14 labeled fullerene C60 ([(14) C(U)]C60 ) in pregnant and lactating rats and their offspring after maternal intravenous exposure

A comprehensive distribution study was conducted in pregnant and lactating rats exposed to a suspension of uniformly carbon-14 labeled C60 ([(14) C(U)]C60 ). Rats were administered [(14) C(U)]C60 (~0.2 mg [(14) C(U)]C60 kg(-1) body weight) or 5% polyvinylpyrrolidone (PVP)-saline vehicle via a single tail vein injection. Pregnant rats were injected on gestation day (GD) 11 (terminated with fetuses after either 24 h or 8 days), GD15 (terminated after 24 h or 4 days), or GD18 (terminated after 24 h). Lactating rats were injected on postnatal day 8 and terminated after 24 h, 3 or 11 days. The distribution of radioactivity in pregnant dams was influenced by both the state of pregnancy and time of termination after exposure. The percentage of recovered radioactivity in pregnant and lactating rats was highest in the liver and lungs. Radioactivity was quantitated in over 20 tissues. Radioactivity was found in the placenta and in fetuses of pregnant dams, and in the milk of lactating rats and in pups. Elimination of radioactivity was < 2% in urine and feces at each time point. Radioactivity remained in blood circulation up to 11 days after [(14) C(U)]C60 exposure. Biomarkers of inflammation, cardiovascular injury and oxidative stress were measured to study the biological impacts of [(14) C(U)]C60 exposure. Oxidative stress was elevated in female pups of exposed dams. Metabolomics analysis of urine showed that [(14) C(U)]C60 exposure to pregnant rats impacted the pathways of vitamin B, regulation of lipid and sugar metabolism and aminoacyl-tRNA biosynthesis. This study demonstrated that [(14) C(U)]C60 crosses the placenta at all stages of pregnancy examined, and is transferred to pups via milk.

Distribution and biomarkers of carbon-14-labeled fullerene C60 ([(14) C(U)]C60 ) in female rats and mice for up to 30 days after intravenous exposure

A comprehensive distribution study was conducted in female rats and mice exposed to a suspension of uniformly carbon-14-labeled C60 ([(14) C(U)]C60 ). Rodents were administered [(14) C(U)]C60 (~0.9 mg kg(-1) body weight) or 5% polyvinylpyrrolidone-saline vehicle alone via a single tail vein injection. Tissues were collected at 1 h and 1, 7, 14 and 30 days after administration. A separate group of rodents received five daily injections of suspensions of either [(14) C(U)]C60 or vehicle with tissue collection 14 days post exposure. Radioactivity was detected in over 20 tissues at all time points. The highest concentration of radioactivity in rodents at each time point was in liver, lungs and spleen. Elimination of [(14) C(U)]C60 was < 2% in urine and feces at any 24 h time points. [(14) C(U)]C60 and [(14) C(U)]C60 -retinol were detected in liver of rats and together accounted for ~99% and ~56% of the total recovered at 1 and 30 days postexposure, respectively. The blood radioactivity at 1 h after [(14) C(U)]C60 exposure was fourfold higher in rats than in mice; blood radioactivity was still in circulation at 30 days post [(14) C(U)]C60 exposure in both species (<1%). Levels of oxidative stress markers increased by 5 days after exposure and remained elevated, while levels of inflammation markers initially increased and then returned to control values. The level of cardiovascular marker von Willebrand factor, increased in rats, but remained at control levels in mice. This study demonstrates that [(14) C(U)]C60 is retained in female rodents with little elimination by 30 days after i.v. exposure, and leads to systemic oxidative stress.

Implications of scavenger receptors in the safe development of nanotherapeutics

Nanomaterials (NMs) are being utilized in a variety of biomedical applications including drug delivery, diagnostics, and therapeutic targeting. These applications are made possible due to the unique physicochemical properties that are exhibited at the nanoscale. To ensure safe development of NMs for clinical use, it is necessary to understand their interactions with cells and specifically cell surface receptors, which will facilitate either their toxicity and/or clinical function. Recently our research and others have investigated the role of scavenger receptors in mediating NM-cell interactions and responses. Scavenger receptors are expressed by a variety of cell types that are first to encounter NMs during clinical use such as macrophages and endothelial cells. Scavenger receptors are recognized to facilitate uptake of a wide variety of ligands ranging from foreign substances to endogenous lipids/proteins. While interaction of NMs with scavenger receptors may allow therapeutic targeting in some instances, it also presents a challenge for the stealth delivery of NMs and avoidance of the scavenging capability of this class of receptors. Due to their role in facilitating immune responses, scavenger receptor-mediated inflammation is also of concern following NM delivery. The research highlighted in this brief review intends to summarize our current understanding regarding the consequences of NM-scavenger receptor interactions.

A hyperspectral and toxicological analysis of protein corona impact on silver nanoparticle properties, intracellular modifications, and macrophage activation

The inevitable adsorption of biomolecules on nanomaterials results in the formation of a protein corona (PC), which modifies the nanoparticle (NP)–cell interface resulting in modified uptake, activity, clearance, and toxicity. While the physicochemical properties of the NP govern the composition of PC, the formation of PC in turn alters the characteristics of the NP by imparting a new unique “biological” identity. To assess how the PC influences AgNP properties, intracellular modifications, and cellular responses, we utilized a combination of hyperspectral and toxicological analyses. AgNPs were coated with a complex PC (multiple proteins, eg, 10% fetal bovine serum) or a simple PC (single protein, eg, bovine serum albumin [BSA]) and evaluated by hyperspectral and dynamic light scattering for modifications in AgNP properties. Mouse macrophages were exposed to AgNPs with PCs and examined for differences in uptake, cytotoxicity, and cell activation. Hyperspectral imaging revealed intracellular modifications to AgNPs that were found to spectrally match alterations in AgNPs following incubation in lysosomal fluid. Addition of the PC influenced AgNP uptake and cytotoxicity; however, hydrodynamic size and surface charge did not contribute to these responses. Assessments of all endpoints demonstrated differences between complex and BSA PC, suggesting that these responses are not purely driven by the primary protein component of the complex PC (ie, BSA). Alterations in cellular–NP uptake/interactions may be driven through cell surface receptor recognition of protein constituents that make up the PC rather than the physicochemical differences in AgNPs.

Cardiac Ischemia Reperfusion Injury Following Instillation of 20 nm Citrate-capped Nanosilver

BACKGROUND

Silver nanoparticles (AgNP) have garnered much interest due to their antimicrobial properties, becoming one of the most utilized nano-scale materials. However, any potential evocable cardiovascular injury associated with exposure has not been reported to date. We have previously demonstrated expansion of myocardial infarction after intratracheal (IT) instillation of carbon-based nanomaterials. We hypothesized pulmonary exposure to Ag core AgNP induces a measureable increase in circulating cytokines, expansion of cardiac ischemia-reperfusion (I/R) injury and is associated with depressed coronary constrictor and relaxation responses. Secondarily, we addressed the potential contribution of silver ion release on AgNP toxicity.

METHODS

Male Sprague-Dawley rats were exposed to 200 μl of 1 mg/ml of 20 nm citrate-capped Ag core AgNP, 0.01, 0.1, 1 mg/ml Silver Acetate (AgAc), or a citrate vehicle by intratracheal (IT) instillation. One and 7 days following IT instillation the lungs were evaluated for inflammation and the presence of silver; serum was analyzed for concentrations of selected cytokines; cardiac I/R injury and coronary artery reactivity were assessed.

RESULTS

AgNP instillation resulted in modest pulmonary inflammation with detection of silver in lung tissue and alveolar macrophages, elevation of serum cytokines: G-CSF, MIP-1α, IL-1β, IL-2, IL-6, IL-13, IL-10, IL-18, IL-17α, TNFα, and RANTES, expansion of I/R injury and depression of the coronary vessel reactivity at 1 day post IT compared to vehicle treated rats. Silver within lung tissue was persistent at 7 days post IT instillation and was associated with an elevation in cytokines: IL-2, IL-13, and TNFα and expansion of I/R injury. AgAc resulted in a concentration dependent infarct expansion and depressed vascular reactivity without marked pulmonary inflammation or serum cytokine response.

CONCLUSIONS

Based on these data, IT instillation of AgNP increases circulating levels of several key cytokines, which may contribute to persistent expansion of I/R injury possibly through an impaired vascular responsiveness.

Distribution and biomarker of carbon-14 labeled fullerene C60 ([(14) C(U)]C60 ) in pregnant and lactating rats and their offspring after maternal intravenous exposure

A comprehensive distribution study was conducted in pregnant and lactating rats exposed to a suspension of uniformly carbon-14 labeled C60 ([(14) C(U)]C60 ). Rats were administered [(14) C(U)]C60 (~0.2 mg [(14) C(U)]C60 kg(-1) body weight) or 5% polyvinylpyrrolidone (PVP)-saline vehicle via a single tail vein injection. Pregnant rats were injected on gestation day (GD) 11 (terminated with fetuses after either 24 h or 8 days), GD15 (terminated after 24 h or 4 days), or GD18 (terminated after 24 h). Lactating rats were injected on postnatal day 8 and terminated after 24 h, 3 or 11 days. The distribution of radioactivity in pregnant dams was influenced by both the state of pregnancy and time of termination after exposure. The percentage of recovered radioactivity in pregnant and lactating rats was highest in the liver and lungs. Radioactivity was quantitated in over 20 tissues. Radioactivity was found in the placenta and in fetuses of pregnant dams, and in the milk of lactating rats and in pups. Elimination of radioactivity was < 2% in urine and feces at each time point. Radioactivity remained in blood circulation up to 11 days after [(14) C(U)]C60 exposure. Biomarkers of inflammation, cardiovascular injury and oxidative stress were measured to study the biological impacts of [(14) C(U)]C60 exposure. Oxidative stress was elevated in female pups of exposed dams. Metabolomics analysis of urine showed that [(14) C(U)]C60 exposure to pregnant rats impacted the pathways of vitamin B, regulation of lipid and sugar metabolism and aminoacyl-tRNA biosynthesis. This study demonstrated that [(14) C(U)]C60 crosses the placenta at all stages of pregnancy examined, and is transferred to pups via milk.

Distribution and biomarkers of carbon-14-labeled fullerene C60 ([(14) C(U)]C60 ) in female rats and mice for up to 30 days after intravenous exposure

A comprehensive distribution study was conducted in female rats and mice exposed to a suspension of uniformly carbon-14-labeled C60 ([(14) C(U)]C60 ). Rodents were administered [(14) C(U)]C60 (~0.9 mg kg(-1) body weight) or 5% polyvinylpyrrolidone-saline vehicle alone via a single tail vein injection. Tissues were collected at 1 h and 1, 7, 14 and 30 days after administration. A separate group of rodents received five daily injections of suspensions of either [(14) C(U)]C60 or vehicle with tissue collection 14 days post exposure. Radioactivity was detected in over 20 tissues at all time points. The highest concentration of radioactivity in rodents at each time point was in liver, lungs and spleen. Elimination of [(14) C(U)]C60 was < 2% in urine and feces at any 24 h time points. [(14) C(U)]C60 and [(14) C(U)]C60 -retinol were detected in liver of rats and together accounted for ~99% and ~56% of the total recovered at 1 and 30 days postexposure, respectively. The blood radioactivity at 1 h after [(14) C(U)]C60 exposure was fourfold higher in rats than in mice; blood radioactivity was still in circulation at 30 days post [(14) C(U)]C60 exposure in both species (<1%). Levels of oxidative stress markers increased by 5 days after exposure and remained elevated, while levels of inflammation markers initially increased and then returned to control values. The level of cardiovascular marker von Willebrand factor, increased in rats, but remained at control levels in mice. This study demonstrates that [(14) C(U)]C60 is retained in female rodents with little elimination by 30 days after i.v. exposure, and leads to systemic oxidative stress.

Influence of physicochemical properties of silver nanoparticles on mast cell activation and degranulation

Silver nanoparticles (AgNPs) are increasingly being incorporated into products for their antimicrobial properties. This has resulted in increased human exposures and the possibility of adverse health effects. Mast cells orchestrate allergic immune responses through degranulation and release of pre-formed mediators. Little data exists on understanding interactions of AgNPs with mast cells and the properties that influence activation and degranulation. Using bone marrow-derived mast cells and AgNPs of varying physicochemical properties we tested the hypothesis that AgNP physicochemical properties influence mast cell degranulation and osteopontin production. AgNPs evaluated included spherical 20 nm and 110 nm suspended in either polyvinylpyrrolidone (PVP) or citrate, Ag plates suspended in PVP of diameters between 40–60 nm or 100–130 nm, and Ag nanowires suspended in PVP with thicknesses <100 nm and length up to 2 μm. Mast cell responses were found to be dependent on the physicochemical properties of the AgNP. Further, we determined a role for scavenger receptor B1 in AgNP-induced mast cell responses. Mast cell degranulation was not dependent on AgNP dissolution but was prevented by tyrosine kinase inhibitor pretreatment. This study suggests that exposure to AgNPs may elicit adverse mast cell responses that could contribute to the initiation or exacerbation of allergic disease.

Impact of Silver and Iron Nanoparticle Exposure on Cholesterol Uptake by Macrophages

Macrophages are central to the development of atherosclerosis by absorbing lipids, promoting inflammation, and increasing plaque deposition. Nanoparticles (NPs) are becoming increasingly common in biomedical applications thereby increasing exposure to the immune and vascular systems. This project investigated the influence of NPs on macrophage function and specifically cholesterol uptake. Macrophages were exposed to 20 nm silver NPs (AgNPs), 110 nm AgNPs, or 20 nm Fe₃O₄NPs for 2 h and NP uptake, cytotoxicity, and subsequent uptake of fluorescently labeled cholesterol were assessed. Macrophage uptake of NPs did not induce cytotoxicity at concentrations utilized (25 μg/mL); however, macrophage exposure to 20 nm AgNPs reduced subsequent uptake of cholesterol. Further, we assessed the impact of a cholesterol-rich environment on macrophage function following NP exposure. In these sets of experiments, macrophages internalized NPs, exhibited no cytotoxicity, and altered cholesterol uptake. Alterations in the expression of scavenger receptor-B1 following NP exposure, which likely influences cholesterol uptake, were observed. Overall, NPs alter cholesterol uptake, which may have implications in the progression of vascular or immune mediated diseases. Therefore, for the safe development of NPs for biomedical applications, it is necessary to understand their impact on cellular function and biological interactions in underlying disease environments.

Comparative long-term toxicity of Libby amphibole and amosite asbestos in rats after single or multiple intratracheal exposures

In former mine workers of Libby, MT, exposure to amphibole-containing vermiculite was linked to increased rates of asbestosis, lung cancer, and mesothelioma. Although many studies showed adverse effects following exposure to Libby amphibole (LA; a mixture of winchite, richterite, and tremolite), little is known regarding the relative toxicity of LA compared to regulated asbestos, or regarding the risks associated with acute high-dose exposures relative to repeated low-dose exposures. In this study, pulmonary function, inflammation, and pathology were assessed after single or multiple intratracheal (IT) exposures of LA or a well-characterized amosite (AM) control fiber with equivalent fiber characteristics. Male F344 rats were exposed to an equivalent total mass dose (0.15, 0.5, 1.5, or 5 mg/rat) of LA or AM administered either as a single IT instillation, or as multiple IT instillations given every other week over a 13-wk period, and necropsied up to 20 mo after the initial IT. When comparing the two fiber types, in both studies LA resulted in greater acute neutrophilic inflammation and cellular toxicity than equal doses of AM, but long-term histopathological changes were approximately equivalent between fibers, suggesting that LA is at least as toxic as AM. In addition, although no dose-response relationship was discerned, mesothelioma or lung carcinomas were found after exposure to low and high dose levels of LA or AM in both studies. Conversely, when comparing studies, an equal mass dose given over multiple exposures instead of a single bolus resulted in greater chronic pathological changes in lung at lower doses, despite the initially weaker acute inflammatory response. Overall, these results suggest that there is a possibility of greater long-term pathological changes with repeated lower LA dose exposures, which more accurately simulates chronic environmental exposures.

Formation of a protein corona on silver nanoparticles mediates cellular toxicity via scavenger receptors

Addition of a protein corona (PC) or protein adsorption layer on the surface of nanomaterials following their introduction into physiological environments may modify their activity, bio-distribution, cellular uptake, clearance, and toxicity. We hypothesize that silver nanoparticles (AgNPs) will associate with proteins common to human serum and cell culture media forming a PC that will impact cell activation and cytotoxicity. Furthermore, the role of scavenger receptor BI (SR-BI) in mediating this toxicity was evaluated. Citrate-suspended 20 nm AgNPs were incubated with human serum albumin (HSA), bovine serum albumin (BSA), high-density lipoprotein (HDL), or water (control) to form a PC. AgNPs associated with each protein (HSA, BSA, and HDL) forming PCs as assessed by electron microscopy, hyperspectral analysis, ζ-potential, and hydrodynamic size. Addition of the PC decreased uptake of AgNPs by rat lung epithelial and rat aortic endothelial cells. Hyperspectral analysis demonstrated a loss of the AgNP PC following internalization. Cells demonstrated concentration-dependent cytotoxicity following exposure to AgNPs with or without PCs (0, 6.25, 12.5, 25 or 50 μg/ml). All PC-coated AgNPs were found to activate cells by inducing IL-6 mRNA expression. A small molecule SR-BI inhibitor was utilized to determine the role of SR-BI in the observed effects. Pretreatment with the SR-BI inhibitor decreased internalization of AgNPs with or without PCs, and reduced both cytotoxicity and IL-6 mRNA expression. This study characterizes the formation of a PC on AgNPs and demonstrates its influence on cytotoxicity and cell activation through a cell surface receptor.

IL-33 modulates chronic airway resistance changes induced by multi-walled carbon nanotubes

OBJECTIVE

Instillation of multi-walled carbon nanotubes (MWCNTs) in C57BL/6 mice results in decrements of pulmonary function specifically characterized by increases in airway resistance. In this study, we examined possible mechanisms responsible for these alterations following MWCNT exposure, including the roles of IL-33 and chronic inflammation.

MATERIALS AND METHODS

To elucidate the role of IL-33, we assessed lung histology and pulmonary function in C57BL/6 and IL-33(-/-) mice 30 days following MWCNT instillation. In addition, the impact of MWCNT instillation on airway hyperresponsiveness (AHR) was assessed by methacholine challenges of C57BL/6 and IL-33(-/-) mice. To further understand the mechanisms by which MWCNTs may increase airway constriction, C57BL/6 mice were treated with aerosolized albuterol or injected with multiple doses of methylprednisolone via intra-peritoneal injections prior to the assessment of MWCNT-induced changes in pulmonary function.

RESULTS

Total cell count, macrophages, and neutrophils were increased in the lavage fluid of C57BL/6 mice, but not in IL-33(-/-) mice, following MWCNT exposure. C57BL/6 mice displayed increased inflammation and fibrosis located proximal to the airways which was absent in IL-33(-/-) mice. Aerosolized methacholine increased parameters of airway resistance (R and Rn) in a dose-dependent manner in all groups, with MWCNT-instilled C57BL/6 mice responding more robustly compared to the controls, while no differences were found in IL-33(-/-) mice due to MWCNT exposure. Treatment with methylprednisolone reduced both the MWCNT-induced histopathological changes and increases in R and Rn in C57BL/6 mice.

CONCLUSION

These findings suggest that IL-33 and chronic inflammation in general are critical in the pulmonary toxicity induced by MWCNT resulting in modified pulmonary function.

Silver nanoparticle protein corona composition in cell culture media

The potential applications of nanomaterials as drug delivery systems and in other products continue to expand. Upon introduction into physiological environments and driven by energetics, nanomaterials readily associate proteins forming a protein corona (PC) on their surface. This PC influences the nanomaterial's surface characteristics and may impact their interaction with cells. To determine the biological impact of nanomaterial exposure as well as nanotherapeutic applications, it is necessary to understand PC formation. Utilizing a label-free mass spectrometry-based proteomics approach, we examined the composition of the PC for a set of four silver nanoparticles (AgNPs) including citrate-stabilized and polyvinlypyrrolidone-stabilized (PVP) colloidal silver (20 or 110 nm diameter). To simulate cell culture conditions, AgNPs were incubated for 1 h in Dulbecco's Modified Eagle Medium supplemented with 10% fetal bovine serum, washed, coronal proteins solubilized, and proteins identified and quantified by label-free LC-MS/MS. To determine which attributes influence PC formation, the AgNPs were characterized in both water and cell culture media with 10% FBS. All AgNPs associated a common subset of 11 proteins including albumin, apolipoproteins, keratins, and other serum proteins. 110 nm citrate- and PVP-stabilized AgNPs were found to bind the greatest number of proteins (79 and 85 respectively) compared to 20 nm citrate- and PVP-stabilized AgNPs (45 and 48 respectively), suggesting a difference in PC formation based on surface curvature. While no relationships were found for other protein parameters (isoelectric point or aliphatic index), the PC on 20 nm AgNPs (PVP and citrate) consisted of more hydrophobic proteins compared to 110 nm AgNPs implying that this class of proteins are more receptive to curvature-induced folding and crowding in exchange for an increased hydration in the aqueous environment. These observations demonstrate the significance of electrostatic and hydrophobic interactions in the formation of the PC which may have broad biological and toxicological implications.

Comparison of nanotube-protein corona composition in cell culture media

In biological environments, nanomaterials associate with proteins forming a protein corona (PC). The PC may alter the nanomaterial's pharmacokinetics and pharmacodynamics, thereby influencing toxicity. Using a label-free mass spectrometry-based proteomics approach, the composition of the PC is examined for a set of nanotubes (NTs) including unmodified and carboxylated single- (SWCNT) and multi-walled carbon nanotubes (MWCNT), polyvinylpyrrolidone (PVP)-coated MWCNT (MWCNT-PVP), and nanoclay. NTs are incubated for 1 h in simulated cell culture conditions, then washed, resuspended in PBS, and assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) for their associated PC. To determine those attributes that influence PC formation, the NTs are extensively characterized. NTs had negative zeta potentials in water (SWCNT-COOH < MWCNT-COOH < unmodified NTs) while carboxylation increases their hydrodynamic sizes. All NTs are also found to associate a common subset of proteins including albumin, titin, and apolipoproteins. SWCNT-COOH and MWCNT-COOH are found to bind the greatest number of proteins (181 and 133 respectively) compared to unmodified NTs (<100), suggesting covalent binding to protein amines. Modified NTs bind a number of unique proteins compared to unmodified NTs, implying hydrogen bonding and electrostatic interactions are involved in PC formation. PVP-coating of MWCNT did not influence PC composition, further reinforcing the possibility of hydrogen bonding and electrostatic interactions. No relationships are found between PC composition and corresponding isoelectric point, hydropathy, or aliphatic index, implying minimal roles of hydrophobic interaction and pi-stacking.

Intravenously delivered graphene nanosheets and multiwalled carbon nanotubes induce site-specific Th2 inflammatory responses via the IL-33/ST2 axis

Carbon-based nanomaterials (CBN), such as graphene nanosheets (GNS) and multiwalled carbon nanotubes (MWCNT), have been proposed for potential nanomedicine applications such as biomedical devices and carriers for drug delivery. However, our current understanding regarding the systemic toxicity of these CBN through intravenous (iv) injection is limited. In this study, we compare the immune response resulting from GNS and MWCNT exposure. We hypothesize that iv administration of GNS and MWCNT would result in divergent systemic inflammatory responses due to physicochemical differences between these two CBN. In the lungs of C57BL/6 mice, GNS actuate a Th2 immune response 1 day following iv administration, which consists of neutrophilic influx and a significant increase in interleukin (IL)-5, IL-13, IL-33, and its soluble receptor (sST2) in the bronchoalveolar lavage fluid. MWCNT elicited a significant increase in the messenger ribonucleic acid expression of cytokines in the spleen including IL-4 and IL-33, which are associated with an increase in splenic cell differentiation (CD)4⁺ and CD8⁺ T-cells in C57BL/6 mice following iv injection. The observed Th2 responses in both the lung and spleen are absent in ST2^−/− mice administrated GNS or MWCNT, suggesting a critical role for IL-33. In conclusion, the use of GNS or MWCNT as nanocarriers for drug delivery may result in Th2 immune responses that are mediated through the IL-33/ST2 axis and therefore may promote adverse allergic reactions.

Changes in cardiopulmonary function induced by nanoparticles

Nanoparticles (NP) are highly applicable in a variety of technological and biomedical fields because of their unique physicochemical properties. The increased development and utilization of NP has amplified human exposure and raised concerns regarding their potential to generate toxicity. The biological impacts of NP exposures have been shown to be dependent on aerodynamic size, chemical composition, and the route of exposure (oral, dermal, intravenous, and inhalation), while recent research has demonstrated the cardiovascular (CV) system as an important site of toxicity. Proposed mechanisms responsible for these effects include inflammation, oxidative stress, autonomic dysregulation, and direct interactions of NP with CV cells. Specifically, NP have been shown to impact vascular endothelial cell (EC) integrity, which may disrupt the dynamic endothelial regulation of vascular tone, possibly altering systemic vascular resistance and impairing the appropriate distribution of blood flow throughout the circulation. Cardiac consequences of NP-induced toxicity include disruption of heart rate and electrical activity via catecholamine release, increased susceptibility to ischemia/reperfusion injury, and modified baroreceptor control of cardiac function. These and other CV outcomes likely contribute to adverse health effects promoting myocardial infarction, hypertension, cardiac arrhythmias, and thrombosis. This review will assess the current knowledge regarding the principle sites of CV toxicity following NP exposure. Furthermore, we will propose mechanisms contributing to altered CV function and hypothesize possible outcomes resulting in decrements in human health.

Manufactured and airborne nanoparticle cardiopulmonary interactions: a review of mechanisms and the possible contribution of mast cells

Human inhalation exposures to manufactured nanoparticles (NP) and airborne ultrafine particles (UFP) continues to increase in both occupational and environmental settings. UFP exposures have been associated with increased cardiovascular mortality and morbidity, while ongoing research supports adverse systemic and cardiovascular health effects after NP exposures. Adverse cardiovascular health effects include alterations in heart rate variability, hypertension, thrombosis, arrhythmias, increased myocardial infarction, and atherosclerosis. Exactly how UFP and NP cause these negative cardiovascular effects is poorly understood, however a variety of mediators and mechanisms have been proposed. UFP and NP, as well as their soluble components, are known to systemically translocate from the lung. Translocated particles could mediate cardiovascular toxicity through direct interactions with the vasculature, blood, and heart. Recent study suggests that sensory nerve stimulation within the lung may also contribute to UFP- and NP-induced acute cardiovascular alterations. Activation of sensory nerves, such as C-fibers, within the lung may result in altered cardiac rhythm and function. Lastly, release of pulmonary-derived mediators into systemic circulation has been proposed to facilitate cardiovascular effects. In general, these proposed pulmonary-derived mediators include proinflammatory cytokines, oxidatively modified macromolecules, vasoactive proteins, and prothrombotic factors. These pulmonary-derived mediators have been postulated to contribute to the subsequent prothrombotic, atherogenic, and inflammatory effects after exposure. This review will evaluate the potential contribution of individual mediators and mechanisms in facilitating cardiopulmonary toxicity following inhalation of UFP and NP. Lastly, we will appraise the literature and propose a hypothesis regarding the possible role of mast cells in contributing to these systemic effects.

Acute phase response, inflammation and metabolic syndrome biomarkers of Libby asbestos exposure

Identification of biomarkers assists in the diagnosis of disease and the assessment of health risks from environmental exposures. We hypothesized that rats exposed to Libby amphibole (LA) would present with a unique serum proteomic profile which could help elucidate epidemiologically-relevant biomarkers. In four experiments spanning varied protocols and temporality, healthy (Wistar Kyoto, WKY; and F344) and cardiovascular compromised (CVD) rat models (spontaneously hypertensive, SH; and SH heart failure, SHHF) were intratracheally instilled with saline (control) or LA. Serum biomarkers of cancer, inflammation, metabolic syndrome (MetS), and the acute phase response (APR) were analyzed. All rat strains exhibited acute increases in α-2-macroglobulin, and α1-acid glycoprotein. Among markers of inflammation, lipocalin-2 was induced in WKY, SH and SHHF and osteopontin only in WKY after LA exposure. While rat strain- and age-related changes were apparent in MetS biomarkers, no LA effects were evident. The cancer marker mesothelin was increased only slightly at 1 month in WKY in one of the studies. Quantitative Intact Proteomic profiling of WKY serum at 1 day or 4 weeks after 4 weekly LA instillations indicated no oxidative protein modifications, however APR proteins were significantly increased. Those included serine protease inhibitor, apolipoprotein E, α-2-HS-glycoprotein, t-kininogen 1 and 2, ceruloplasmin, vitamin D binding protein, serum amyloid P, and more 1 day after last LA exposure. All changes were reversible after a short recovery regardless of the acute or long-term exposures. Thus, LA exposure induces an APR and systemic inflammatory biomarkers that could have implications in systemic and pulmonary disease in individuals exposed to LA.

Long-term response of rats to single intratracheal exposure of Libby amphibole or amosite

In former mine workers and residents of Libby, Montana, exposure to amphibole-contaminated vermiculite has been associated with increased incidences of asbestosis and mesothelioma. In this study, long-term effects of Libby amphibole (LA) exposure were investigated relative to the well-characterized amosite asbestos in a rat model. Rat-respirable fractions of LA and amosite (aerodynamic diameter≤2.5 μm) were prepared by water elutriation. Male F344 rats were exposed to a single dose of either saline, amosite (0.65 mg/rat), or LA (0.65 or 6.5 mg/rat) by intratracheal (IT) instillation. One year after exposure, asbestos-exposed rats displayed chronic pulmonary inflammation and fibrosis. Two years postexposure, lung inflammation and fibrosis progressed in a time- and dose-dependent manner in LA-exposed rats, although the severity of inflammation and fibrosis was smaller in magnitude than in animals exposed to amosite. In contrast, gene expression of the fibrosis markers Col 1A2 and Col 3A1 was significantly greater in LA-exposed compared to amosite-exposed rats. There was no apparent evidence of preneoplastic changes in any of the asbestos-exposed groups. However, all asbestos-exposed rats demonstrated a significant increase in the expression of epidermal growth factor receptor (EGFR) 2 yr after instillation. In addition, only LA-exposed rats showed significant elevation in mesothelin (Msln) and Wilms' tumor gene (WT1) expression, suggesting possible induction of tumor pathways. These results demonstrate that a single IT exposure to LA is sufficient to induce significant fibrogenic, but not carcinogenic, effects up to 2 yr after exposure that differ both in quality and magnitude from those elicited by amosite administration at the same mass dose in F344 rats. Data showed that LA was on a mass basis less potent than amosite.

Subchronic pulmonary pathology, iron overload, and transcriptional activity after Libby amphibole exposure in rat models of cardiovascular disease

BACKGROUND

Surface-available iron (Fe) is proposed to contribute to asbestos-induced toxicity through the production of reactive oxygen species.

OBJECTIVE

Our goal was to evaluate the hypothesis that rat models of cardiovascular disease with coexistent Fe overload would be increasingly sensitive to Libby amphibole (LA)-induced subchronic lung injury.

METHODS

Male healthy Wistar Kyoto (WKY), spontaneously hypertensive (SH), and SH heart failure (SHHF) rats were intratracheally instilled with 0.0, 0.25, or 1.0 mg LA (with saline as the vehicle). We examined bronchoalveolar lavage fluid (BALF) and histological lung sections after 1 week, 1 month, or 3 months for pulmonary biomarkers and pathology. SHHF rats were also assessed at 6 months for pathological changes.

RESULTS

All animals developed concentration- and time-dependent interstitial fibrosis. Time-dependent Fe accumulation occurred in LA-laden macrophages in all strains but was exacerbated in SHHF rats. LA-exposed SHHF rats developed atypical hyperplastic lesions of bronchiolar epithelial cell origin at 3 and 6 months. Strain-related baseline differences existed in gene expression at 3 months, with persistent LA effects in WKY but not SH or SHHF rats. LA exposure altered genes for a number of pathways, including inflammation, immune regulation, and cell-cycle control. Cell-cycle control genes were inhibited after LA exposure in SH and SHHF but not WKY rats, whereas tumor suppressor genes were induced only in WKY rats. The inflammatory gene expression also was apparent only in WKY rats.

CONCLUSION

These data show that in Fe-overload conditions, progressive Fe accumulation occurs in fiber-laden macrophages within LA-induced lesions. Fe overload does not appear to contribute to chronic inflammation, and its role in hyperplastic lesion development requires further examination.

Vascular and thrombogenic effects of pulmonary exposure to Libby amphibole

Exposure to Libby amphibole (LA) asbestos is associated with increased incidences of human autoimmune disease and mortality related to cardiovascular diseases. However, the systemic and vascular impacts are less well examined because of the dominance of pulmonary disease. It was postulated that regardless of the type of exposure scenario, LA exposure might produce systemic and vascular inflammogenic and thrombotic alterations in healthy and cardiovascular compromised rat models. Samples from three independent studies were examined. In the first study, male Wistar Kyoto (WKY), spontaneously hypertensive (SH), and SH heart failure (SHHF) rats were intratracheally instilled once with 0 (vehicle), 0.25, or 1 mg/rat of LA. In the second study, F344 rats were instilled with vehicle or LA at 0.5, 1.5, or 5 mg/rat. In the third study, F344 rats were instilled with the same mass concentrations of LA delivered by biweekly multiple instillations over 3 mo to simulate an episodic subchronic exposure. Complete blood count, platelet aggregation, serum cytokines, and biomarkers of systemic and aortic effects were examined. LA reduced adenosine diphosphate (ADP)-induced platelet aggregation and decreased circulating platelets in WKY (1 mg/rat) and F344 (5 mg/rat) at the 3-mo time point but did not do so in SH or SHHF rats. A decline in circulating lymphocytes with age appeared to be exacerbated by LA exposure in F344 rats but the differences were not significant. Aorta mRNA expression for biomarkers of oxidative stress (HO-1, LOX-1), inflammation (MIP-2), and thrombosis (tPA, PAI-1, vWf) were increased at baseline in SH and SHHF relative to WKY. LA exposure upregulated several of these biomarkers and also those involved in aortic contractility of WKY rats at 3 mo, suggesting thrombogenic, vasocontractile, and oxidative stress-mediated impairments. The aorta changes in F344 rats were less remarkable than changes noted in WKY following LA exposure. In conclusion, exposure to LA decreased circulating platelets and platelet coagulability while increasing the expression of oxidative stress, thrombosis, and vasoconstriction biomarkers in the aorta of healthy rats. These changes were similar to those noted at baseline in SH and SHHF rats, suggesting that LA-induced pulmonary injury might increase the risk of developing cardiovascular disease in healthy individuals.

Transcriptional activation of inflammasome components by Libby amphibole and the role of iron

The induction of the NALP3 inflammasome complex is shown to be necessary for the development of fibrosis after asbestos exposure. Libby amphibole (LA) induces lung inflammation and fibrosis, while complexation of iron (Fe) on fibers inhibits inflammation. In this study we examined the ability of LA to induce the inflammasome cascade and the role of Fe in modulating inflammasome activity. Spontaneously hypertensive rats were exposed intratracheally to either saline (300 μl), deferoxamine (Def) (1 mg), FeCl(3) (21 μg), LA (0.5 mg), Fe-loaded LA (Fe + LA), or LA + Def. Activities of oxidative stress-sensitive enzymes, expression of inflammasome-specific genes, and cytokine proteins in bronchoalveolar lavage fluid were analyzed. Lung enzymes at 4 h and 24 h post-exposure were unchanged. LA increased lung expression of genes including interleukin-1β (IL-1β), cathepsin-B, ASC, NALP3, interleukin (IL)-6 and NFκB. LA+Fe significantly reduced IL-1β and NFκB with a trend of reduction in ASC, NALP3, cathepsin-B and IL-6 expression. Def treatment did not reverse the inhibitory effect of Fe on IL-1β and ASC but reversed IL-6 expression. CCL-7, CCL-12, CXCL-3 and COX-2 were induced by LA while LA+Fe tended to reduce these responses. Phosphorylation of ERK but not MEK was increased at 4 h after LA but not LA+Fe exposure. In conclusion, components of the NALP3 inflammasome are transcriptionally activated acutely during LA-induced inflammation. The key inflammatory regulators IL-1β and NFκB were inhibited in the presence of surface-complexed Fe possibly through decreased ERK signaling upstream of the NALP3 inflammasome. The inflammasome activation by LA may contribute to fibrosis, and Fe may reduce this response and alter compensatory mechanisms in individuals exposed to LA.

The role of iron in Libby amphibole-induced acute lung injury and inflammation

Complexation of host iron (Fe) on the surface of inhaled asbestos fibers has been postulated to cause oxidative stress contributing to in vivo pulmonary injury and inflammation. We examined the role of Fe in Libby amphibole (LA; mean length 4.99 µm ± 4.53 and width 0.28 µm ± 0.19) asbestos-induced inflammogenic effects in vitro and in vivo. LA contained acid-leachable Fe and silicon. In a cell-free media containing FeCl(3), LA bound #17 µg of Fe/mg of fiber and increased reactive oxygen species generation #3.5 fold, which was reduced by deferoxamine (DEF) treatment. In BEAS-2B cells exposure to LA, LA loaded with Fe (FeLA), or LA with DEF did not increase HO-1 or ferritin mRNA expression. LA increased IL-8 expression, which was reduced by Fe loading but increased by DEF. To determine the role of Fe in LA-induced lung injury in vivo, spontaneously hypertensive rats were exposed intratracheally to either saline (300 µL), DEF (1 mg), FeCl(3) (21 µg), LA (0.5 mg), FeLA (0.5 mg), or LA + DEF (0.5 mg). LA caused BALF neutrophils to increase 24 h post-exposure. Loading of Fe on LA but not chelation slightly decreased neutrophilic influx (LA + DEF > LA > FeLA). At 4 h post-exposure, LA-induced lung expression of MIP-2 was reduced in rats exposed to FeLA but increased by LA + DEF (LA + DEF > LA > FeLA). Ferritin mRNA was elevated in rats exposed to FeLA compared to LA. In conclusion, the acute inflammatory response to respirable fibers and particles may be inhibited in the presence of surface-complexed or cellular bioavailable Fe. Cell and tissue Fe-overload conditions may influence the pulmonary injury and inflammation caused by fibers.

Vascular and cardiac impairments in rats inhaling ozone and diesel exhaust particles

BACKGROUND

Mechanisms of cardiovascular injuries from exposure to gas and particulate air pollutants are unknown.

OBJECTIVE

We sought to determine whether episodic exposure of rats to ozone or diesel exhaust particles (DEP) causes differential cardiovascular impairments that are exacerbated by ozone plus DEP.

METHODS AND RESULTS

Male Wistar Kyoto rats (10-12 weeks of age) were exposed to air, ozone (0.4 ppm), DEP (2.1 mg/m(3)), or ozone (0.38 ppm) + DEP (2.2 mg/m(3)) for 5 hr/day, 1 day/week for 16 weeks, or to air, ozone (0.51 or 1.0 ppm), or DEP (1.9 mg/m(3)) for 5 hr/day for 2 days. At the end of each exposure period, we examined pulmonary and cardiovascular biomarkers of injury. In the 16-week study, we observed mild pulmonary pathology in the ozone, DEP, and ozone + DEP exposure groups, a slight decrease in circulating lymphocytes in the ozone and DEP groups, and decreased platelets in the DEP group. After 16 weeks of exposure, mRNA biomarkers of oxidative stress (hemeoxygenase-1), thrombosis (tissue factor, plasminogen activator inhibitor-1, tissue plasminogen activator, and von Willebrand factor), vasoconstriction (endothelin-1, endothelin receptors A and B, endothelial NO synthase) and proteolysis [matrix metalloprotease (MMP)-2, MMP-3, and tissue inhibitor of matrix metalloprotease-2] were increased by DEP and/or ozone in the aorta, but not in the heart. Aortic LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1) mRNA and protein increased after ozone exposure, and LOX-1 protein increased after exposure to ozone + DEP. RAGE (receptor for advanced glycation end products) mRNA increased in the ozone + DEP group. Exposure to ozone or DEP depleted cardiac mitochondrial phospholipid fatty acids (DEP > ozone). The combined effect of ozone and DEP exposure was less pronounced than exposure to either pollutant alone. Exposure to ozone or DEP for 2 days (acute) caused mild changes in the aorta.

CONCLUSIONS

In animals exposed to ozone or DEP alone for 16 weeks, we observed elevated biomarkers of vascular impairments in the aorta, with the loss of phospholipid fatty acids in myocardial mitochondria. We conclude that there is a possible role of oxidized lipids and protein through LOX-1 and/or RAGE signaling.

Pulmonary inflammatory and fibrotic responses in Fischer 344 rats after intratracheal instillation exposure to Libby amphibole

Increased incidences of asbestosis have been reported in workers from Libby, MT, associated with exposures to amphibole-contaminated vermiculite. In this study pulmonary and histopathological changes were investigated following Libby amphibole (LA) exposure in a rat model. Rat respirable fractions of LA and amosite (aerodynamic diameter <2.5 μm) were prepared by water elutriation. Male F344 rats were exposed to single doses of either saline (SAL), amosite (0.65 mg/rat), or LA (0.65 or 6.5 mg/rat) by intratracheal instillation. At times from 1 d to 3 mo after exposure, bronchoalveolar lavage (BAL) was performed and right and left lungs were removed for reverse-transcription polymerase chain reaction (RT-PCR) and histopathological analysis, respectively. Data indicated that 0.65 mg amosite resulted in a higher degree of pulmonary injury, inflammation, and fibrotic events than LA at the same mass dose. Exposure to either amosite or high dose LA resulted in higher levels of cellular permeability and injury, inflammatory enzymes, and iron binding proteins in both BAL fluid and lung tissue at most time points when compared to SAL controls. However, mRNA expression for some growth factors (e.g., platelet-derived growth factor [PDGF]-A and transforming growth factor [TGF]-1β), which contribute to fibrosis, were downregulated at several time points. Furthermore, histopathological examination showed notable thickening of interstitial areas surrounding the alveolar ducts and terminal bronchioles. On a mass dose basis, amosite produced a greater acute and persistent lung injury for at least 3 mo after exposure. However, further testing and analysis of LA are needed with regard to the dose metric to fully evaluate its potential fibrogenicity and carcinogenicity.

Aging and susceptibility to toluene in rats: a pharmacokinetic, biomarker, and physiological approach

Aging adults are a growing segment of the U.S. population and are likely to exhibit increased susceptibility to many environmental toxicants. However, there is little information on the susceptibility of the aged to toxicants. The toxicity of toluene has been well characterized in young adult rodents but there is little information in the aged. Three approaches were used: (1) pharmacokinetic (PK), (2) cardiac biomarkers, and (3) whole-animal physiology to assess whether aging increases susceptibility to toluene in the Brown Norway (BN) rat. Three life stages, young adult, middle aged, and aged (4, 12, and 24 mo, respectively), were administered toluene orally at doses of 0, 0.3, 0.65, or 1 g/kg and subjected to the following: terminated at 45 min or 4 h post dosing, and blood and brain toluene concentration were measured; terminated at 4 h post dosing, and biomarkers of cardiac function were measured; or monitor heart rate (HR), core temperature (Tc), and motor activity (MA) by radiotelemetry before and after dosing. Brain toluene concentration was significantly elevated in aged rats at 4 h after dosing with either 0.3 or 1 g/kg. Blood toluene concentrations were unaffected by age. There were various interactions between aging and toluene-induced effects on cardiac biomarkers. Most notably, toluene exposure led to reductions in mRNA markers for oxidative stress in aged but not younger animals. Toluene also produced a reduction in cardiac endothelin-1 in aged rats. Higher doses of toluene led to tachycardia, hypothermia, and a transient elevation in MA. Aged rats were less sensitive to the tachycardic effects of toluene but showed a prolonged hypothermic response. Elevated brain levels of toluene in aged rats may be attributed to their suppressed cardiovascular and respiratory responses. The expression of several cardiac biochemical markers of toluene exposure in the aged may also reflect differential susceptibility to this toxicant.

Pulmonary oxidative stress, inflammation, and dysregulated iron homeostasis in rat models of cardiovascular disease

Underlying cardiovascular disease (CVD) is a risk factor for the exacerbation of air pollution health effects. Pulmonary oxidative stress, inflammation, and altered iron (Fe) homeostasis secondary to CVD may influence mammalian susceptibility to air pollutants. Rodent models of CVD are increasingly used to examine mechanisms of variation in susceptibility. Baseline cardiac and pulmonary disease was characterized in healthy normotensive Wistar Kyoto (WKY) rats, cardiovascular compromised spontaneously hypertensive rats (SHR), and spontaneously hypertensive heart failure (SHHF) rats. Blood pressure, heart rate, and breathing frequencies were measured in rats 11 to 12 wk of age, followed by necropsy at 14 to 15 wk of age. Blood pressure and heart rate were increased in SHR and SHHF relative to WKY rats (SHR > SHHF > WKY). Increased breathing frequency in SHHF and SHR (SHR > SHHF > WKY) resulted in greater minute volume relative to WKY. Bronchoalveolar lavage fluid (BALF) protein and neutrophils were higher in SHHF and SHR relative to WKY (SHHF >> SHR > WKY). Lung ascorbate and glutathione levels were low in SHHF rats. BALF Fe-binding capacity was decreased in SHHF relative to WKY rats and was associated with increased transferrin (Trf) and ferritin. However, lung ferritin was lower and Trf was higher in SHHF relative to WKY or SHR rats. mRNA for markers of inflammation and oxidative stress (macrophage inflammatory protein [MIP]-2, interleukin [IL]-1alpha, and heme oxygenase [HO]-1) were greater in SHHF and SHR relative to WKY rats. Trf mRNA rose in SHR but not SHHF relative to WKY rats, whereas transferrin receptors 1 and 2 mRNA was lower in SHHF rats. Four of 12 WKY rats exhibited cardiac hypertrophy despite normal blood pressure, while demonstrating some of the pulmonary complications noted earlier. This study demonstrates that SHHF rats display greater underlying pulmonary complications such as oxidative stress, inflammation, and impaired Fe homeostasis than WKY or SHR rats, which may play a role in SHHF rats' increased susceptibility to air pollution.