Translocation of ultrafine insoluble iridium particles from lung epithelium to extrapulmonary organs is size dependent but very low

Inhaled nanomaterials and the respiratory microbiome: clinical, immunological and toxicological perspectives

Our development and usage of engineered nanomaterials has grown exponentially despite concerns about their unfavourable cardiorespiratory consequence, one that parallels ambient ultrafine particle exposure from vehicle emissions. Most research in the field has so far focused on airway inflammation in response to nanoparticle inhalation, however, little is known about nanoparticle-microbiome interaction in the human airway and the environment. Emerging evidence illustrates that the airway, even in its healthy state, is not sterile. The resident human airway microbiome is further altered in chronic inflammatory respiratory disease however little is known about the impact of nanoparticle inhalation on this airway microbiome. The composition of the airway microbiome, which is involved in the development and progression of respiratory disease is dynamic, adding further complexity to understanding microbiota-host interaction in the lung, particularly in the context of nanoparticle exposure. This article reviews the size-dependent properties of nanomaterials, their body deposition after inhalation and factors that influence their fate. We evaluate what is currently known about nanoparticle-microbiome interactions in the human airway and summarise the known clinical, immunological and toxicological consequences of this relationship. While associations between inhaled ambient ultrafine particles and host immune-inflammatory response are known, the airway and environmental microbiomes likely act as intermediaries and facilitate individual susceptibility to inhaled nanoparticles and toxicants. Characterising the precise interaction between the environment and airway microbiomes, inhaled nanoparticles and the host immune system is therefore critical and will provide insight into mechanisms promoting nanoparticle induced airway damage.

Quantification of inhaled aerosol particles composed of toxic household disinfectant using radioanalytical method

To assess the risk posed by a toxic chemical to human health, it is essential to quantify its uptake in a living subject. This study aims to investigate the biological distribution of inhaled polyhexamethylene guanidine (PHMG) aerosol particle, which is known to cause severe pulmonary damage. By labeling with indium-111 (¹¹¹In), we quantified the uptake of PHMG for up to 7 days after inhalation exposure in rats. The data demonstrate that PHMG is only slowly cleared, with approximately 74% of inhaled particles persisting in the lungs after 168 h. Approximately 5.3% of inhaled particles were also translocated to the liver after 168 h, although the level of redistribution to other tissues, including the kidneys and spleen, was minimal. These observations suggest that large uptake and slow clearance may underlie the fatal inhalation toxicity of PHMG in humans.

Dysregulation of major functional genes in frontal cortex by maternal exposure to carbon black nanoparticle is not ameliorated by ascorbic acid pretreatment

Recent cohort studies have revealed that perinatal exposure to particulate air pollution, including carbon-based nanoparticles, increases the risk of brain disorders. Although developmental neurotoxicity is currently a major issue in the toxicology of nanoparticles, critical information for understanding the mechanisms underlying the developmental neurotoxicity of airway exposure to carbon black nanoparticle (CB-NP) is still lacking. In order to investigate these mechanisms, we comprehensively analyzed fluctuations in the gene expression profile of the frontal cortex of offspring mice exposed maternally to CB-NP, using microarray analysis combined with Gene Ontology information. We also analyzed differences in the enriched function of genes dysregulated by maternal CB-NP exposure with and without ascorbic acid pretreatment to refine specific alterations in gene expression induced by CB-NP. Total of 652 and 775 genes were dysregulated by CB-NP in the frontal cortex of 6- and 12-week-old offspring mice, respectively. Among the genes dysregulated by CB-NP, those related to extracellular matrix structural constituent, cellular response to interferon-beta, muscle organ development, and cysteine-type endopeptidase inhibitor activity were ameliorated by ascorbic acid pretreatment. A large proportion of the dysregulated genes, categorized in hemostasis, growth factor, chemotaxis, cell proliferation, blood vessel, and dopaminergic neurotransmission, were, however, not ameliorated by ascorbic acid pretreatment. The lack of effects of ascorbic acid on the dysregulation of genes following maternal CB-NP exposure suggests that the contribution of oxidative stress to the effects of CB-NP on these biological functions, i.e., cell migration and proliferation, blood vessel maintenance, and dopaminergic neuron system, may be limited. At least, ascorbic acid pretreatment is hardly likely to be able to protect the brain of offspring from developmental neurotoxicity of CB-NP. The present study provides insight into the mechanisms underlying developmental neurotoxicity following maternal nanoparticle exposure.

Age-Dependent Rat Lung Deposition Patterns of Inhaled 20 Nanometer Gold Nanoparticles and their Quantitative Biokinetics in Adult Rats

The increasing use of gold nanoparticles leads to a possible increase of exposure by inhalation. Therefore, we have studied the deposition patterns of inhaled 20 nm gold nanoparticles (AuNP) in 7-90 day old rats and their biokinetics in 60 day old ones. Wistar-Kyoto rats inhaled intratracheally 20 nm ¹⁹⁵Au-radiolabeled AuNP by negative pressure ventilation over 2 h. Immediately afterward lungs were excised, inflated and microwave dried. AuNP deposition was analyzed by single-photon emission computed tomography, computed-tomography and autoradiography. Completely balanced, quantitative biodistributions in major organs and all body tissues and total excretion were analyzed from 1 h to 28 d after inhalation. Intratracheal inhalation caused AuNP deposition predominately in the caudal lungs, independent of age. About 30% AuNP were deposited on airway epithelia and rapidly cleared by mucociliary clearance. About 80% of AuNP deposited in alveoli was relocated from the epithelium into the interstitium within 24 h and was inaccessible to broncho-alveolar lavage. During interstitial long-term retention, re-entrainment within macrophages back onto the lung epithelium and to the larynx and gastrointestinal tract (GIT) dominated AuNP clearance (rate 0.03 d^-1) In contrast, AuNP-translocation across the air-blood barrier was much smaller leading to persistent retention in secondary organs and tissues in the ranking order liver > soft issue > spleen > kidneys > skeleton > blood > uterus > heart > brain. The age-independent, inhomogeneous AuNP deposition was probably caused by the negative pressure ventilation. Long-term AuNP clearance was dominated by macrophage-mediated transport from the interstitium to the larynx and GIT. Translocation across the rat air-blood barrier appeared to be similar to that of humans for similar sized AuNP.

In vivo-induced size transformation of cerium oxide nanoparticles in both lung and liver does not affect long-term hepatic accumulation following pulmonary exposure

Recent findings show that cerium oxide (CeO2) nanoparticles may undergo in vivo-induced size transformation with the formation of smaller particles that could result in a higher translocation following pulmonary exposure compared to virtually insoluble particles, like titanium dioxide (TiO2). Therefore, we compared liver deposition of CeO2 and TiO2 nanoparticles of similar primary sizes 1, 28 or 180 days after intratracheal instillation of 162 μg of NPs in female C57BL/6 mice. Mice exposed to 162 μg CeO2 or TiO2 nanoparticles by intravenous injection or oral gavage were included as reference groups to assess the amount of NPs that reach the liver bypassing the lungs and the translocation of NPs from the gastrointestinal tract to the liver, respectively. Pulmonary deposited CeO2 nanoparticles were detected in the liver 28 and 180 days post-exposure and TiO2 nanoparticles 180 days post-exposure as determined by darkfield imaging and by the quantification of Ce and Ti mass concentration by inductively coupled plasma-mass spectrometry (ICP-MS). Ce and Ti concentrations increased over time and 180 days post-exposure the translocation to the liver was 2.87 ± 3.37% and 1.24 ± 1.98% of the initial pulmonary dose, respectively. Single particle ICP-MS showed that the size of CeO2 nanoparticles in both lung and liver tissue decreased over time. No nanoparticles were detected in the liver following oral gavage. Our results suggest that pulmonary deposited CeO2 and TiO2 nanoparticles translocate to the liver with similar calculated translocation rates despite their different chemical composition and shape. The observed particle size distributions of CeO2 nanoparticles indicate in vivo processing over time both in lung and liver. The fact that no particles were detected in the liver following oral exposure showed that direct translocation of nanoparticles from lung to the systemic circulation was the most important route of translocation for pulmonary deposited particles.

Nanoencapsulation of Polyphenols towards Dairy Beverage Incorporation

Phenolic compounds, while widely recognized for their biological potential, when added into food matrixes may interact with food constituents. One example of this is the interaction between phenolic compounds and proteins, that may result in the formation of complexes and alter the bioavailability of both phenolic compounds and the nutrient availability. Moreover, when adding compounds to improve the functionality of a food matrix, these interactions may compromise the perceived benefits of the additions. Nanoencapsulation has been considered one of the means to circumvent these interactions, as they may function as a physical barrier between the phenolic compounds and the matrix (preventing not only the loss of bioactivity, but eventual sensorial alterations of the foods), protect phenolic compounds through the gastrointestinal tract, and may enhance phenolic absorption through cellular endocytosis. However, despite these advantages the food industry is still limited in its nanotechnological solutions, as special care must be taken to use food-grade encapsulants which will not pose any deleterious effect towards human health. Therefore, this review aims to provide an encompassing view of the existing advantages and limitations of nanotechnology, associated with the inclusion of phenolic compounds in dairy beverages.

The emerging risk of exposure to air pollution on cognitive decline and Alzheimer's disease - Evidence from epidemiological and animal studies

As incidence of Alzheimer's disease (AD) and other neurodegenerative diseases rise, there is increasing interest in environmental factors which may contribute to disease onset and progression. Air pollution has been known as a major health hazard for decades. While its effects on cardiopulmonary morbidity and mortality have been extensively studied, growing evidence has emerged that exposure to polluted air is associated with impaired cognitive functions at all ages and increased risk of AD and other dementias in later life; this association is particularly notable with traffic related pollutants such as nitrogen dioxide, nitrous oxide, black carbon, and small diameter airborne solids and liquids known as particulate matter. The exact mechanisms by which air pollutants mediate neurotoxicity in the central nervous system (CNS) and lead to cognitive decline and AD remain largely unknown. Studies using animal and cell culture models indicate that amyloid-beta processing, anti-oxidant defense, and inflammation are altered following the exposure to constituents of polluted air. In this review, we summarize recent evidence supporting exposure to air pollution as a risk for cognitive decline at all ages and AD at later lifetime. Additionally, we review the current body of work investigating the molecular mechanisms by which air pollutants mediate damage in the CNS. Understanding of the neurotoxic effects of air pollution and its constituents is still limited, and further studies will be essential to better understand the cellular and molecular mechanisms linking air pollution and cognitive decline.

Design and characterization of emulsified spray dried alginate microparticles as a carrier for the dually acting drug roflumilast

Roflumilast is a selective inhibitor of phosphodiesterase-4 isoenzyme in lung cells. Having psychiatric adverse reactions when administered orally affects negatively the patients' adherence to the drug. This work aimed to prepare emulsified spray dried alginate microparticles for the pulmonary delivery of roflumilast. Sodium alginate was used as microparticle-forming material, isopropyl myristate as an oil, Tween®80 as surfactant and calcium beta-glycerophosphate as cross-linking agent to enhance the mechanical properties of the particles. The prepared particles were evaluated for their encapsulation efficiency, particle size and in-vitro drug release. From the studied carriers, beta-cyclodextrin (CD) was the best regarding giving formulation with smaller particle size and more sustained drug release. The inhalation profile of CD-based microparticles was investigated using Anderson cascade impactor. The aerosolization profile of CD-based microparticles suggested their efficiency to deliver the drug deep in the lung. The CD-based microparticles possessed more inhibitory effects on the viability of A549 cells and on the pro-inflammatory cytokines (TNF-α, IL-6 and IL-10) compared to the pure drug. Hence, CD-based microparticles could regulate the tumorigenesis besides tumor-associated inflammation. Finally, CD-based microparticles showed more sustained bronchodilatation properties in healthy human volunteers when compared to Ventolin®HFA. CD-based microparticles proved to be a promising carrier for inhaled roflumilast in human.

Development of a systematic method to assess similarity between nanomaterials for human hazard evaluation purposes - lessons learnt

Within the EU FP-7 GUIDEnano project, a methodology was developed to systematically quantify the similarity between a nanomaterial (NM) that has been tested in toxicity studies and the NM for which risk needs to be evaluated, for the purpose of extrapolating toxicity data between the two materials. The methodology is a first attempt to use current knowledge on NM property-hazard relationships to develop a series of pragmatic and systematic rules for assessing NM similarity. Moreover, the methodology takes into account the practical feasibility, in that it is based on generally available NM characterization information. In addition to presenting this methodology, the lessons learnt and the challenges faced during its development are reported here. We conclude that there is a large gap between the information that is ideally needed and its application to real cases. The current database on property-hazard relationships is still very limited, which hinders the agreement on the key NM properties constituting the basis of the similarity assessment and the development of associated science-based and unequivocal rules. Currently, one of the most challenging NM properties to systematically assess in terms of similarity between two NMs is surface coating and functionalization, which lacks standardized parameters for description and characterization methodology. Standardization of characterization methods that lead to quantitative, unambiguous, and measurable parameters describing NM properties are necessary in order to build a sufficiently robust property-hazard database that allows for evidence-based refinement of our methodology, or any other attempt to systematically assess the similarity of NMs.

Nano-CuO impairs spatial cognition associated with inhibiting hippocampal long-term potentiation via affecting glutamatergic neurotransmission in rats

Manufactured metal nanoparticles and their applications are continuously expanding because of their unique characteristics while their increasing use may predispose to potential health problems. Several studies have reported the adverse effects of copper oxide nanoparticles (nano-CuO) relative to ecotoxicity and cell toxicity, whereas little is known about the neurotoxicity of nano-CuO. The present study aimed to examine its effects on spatial cognition, hippocampal function, and the possible mechanisms. Male Wistar rats were used to establish an animal model, and nano-CuO was administered at a dose of 0.5 mg/kg/day for 2 weeks. The Morris water maze (MWM) test was employed to evaluate learning and memory. The long-term potentiation (LTP) from Schaffer collaterals to the hippocampal CA1 region, and the effects of nano-CuO on synases were recorded in the hippocampal CA1 neurons of rats. MWM test showed that learning and memory abilities were impaired significantly by nano-CuO ( p < 0.05). The LTP test demonstrated that the field excitatory postsynaptic potential (fEPSP) slopes were significantly lower in nano-CuO-treated groups compared with the control group ( p < 0.01). Furthermore, the data of whole-cell patch-clamp experiments showed that nano-CuO markedly depressed the frequencies of both spontaneous excitatory postsynaptic currents (sEPSCs) and miniature EPSCs (mEPSCs), indicating an effect of nano-CuO on inhibiting the release frequency of glutamate presynapticly ( p < 0.01). Meanwhile, the amplitudes of both sEPSC and mEPSC were significantly reduced in nano-CuO-treated animals, which suggested that the effect of nano-CuO modulates postsynaptic receptor kinetics ( p < 0.01). Paired pulse facilitation (PPF) ( p < 0.05) and the expression of NR2A, but not NR2B, of N-methyl-d-aspartate (NMDA) subunits ( p < 0.05), were decreased significantly. In conclusion, nano-CuO impaired glutamate transmission presynapticly and postsynapticly, which may contribute importantly to diminished LTP and other induced cognitive deficits.

In Vitro and In Vivo Short-Term Pulmonary Toxicity of Differently Sized Colloidal Amorphous SiO₂

In vitro prediction of inflammatory lung effects of well-dispersed nanomaterials is challenging. Here, the in vitro effects of four colloidal amorphous SiO₂ nanomaterials that differed only by their primary particle size (9, 15, 30, and 55 nm) were analyzed using the rat NR8383 alveolar macrophage (AM) assay. Data were compared to effects of single doses of 15 nm and 55 nm SiO₂ intratracheally instilled in rat lungs. In vitro, all four elicited the release of concentration-dependent lactate dehydrogenase, β-glucuronidase, and tumor necrosis factor alpha, and the two smaller materials also released H₂O₂. All effects were size-dependent. Since the colloidal SiO₂ remained well-dispersed in serum-free in vitro conditions, effective particle concentrations reaching the cells were estimated using different models. Evaluating the effective concentration–based in vitro effects using the Decision-making framework for the grouping and testing of nanomaterials, all four nanomaterials were assigned as “active.” This assignment and the size dependency of effects were consistent with the outcomes of intratracheal instillation studies and available short-term rat inhalation data for 15 nm SiO₂. The study confirms the applicability of the NR8383 AM assay to assessing colloidal SiO₂ but underlines the need to estimate and consider the effective concentration of such well-dispersed test materials.

Primary genotoxicity in the liver following pulmonary exposure to carbon black nanoparticles in mice

Background

Little is known about the mechanism underlying the genotoxicity observed in the liver following pulmonary exposure to carbon black (CB) nanoparticles (NPs). The genotoxicity could be caused by the presence of translocated particles or by circulating inflammatory mediators released during pulmonary inflammation and acute-phase response. To address this, we evaluated induction of pulmonary inflammation, pulmonary and hepatic acute-phase response and genotoxicity following exposure to titanium dioxide (TiO₂), cerium oxide (CeO₂) or CB NPs. Female C57BL/6 mice were exposed by intratracheal instillation, intravenous injection or oral gavage to a single dose of 162 μg NPs/mouse and terminated 1, 28 or 180 days post-exposure alongside vehicle control.

Results

Liver DNA damage assessed by the Comet Assay was observed after intravenous injection and intratracheal instillation of CB NPs but not after exposure to TiO₂ or CeO₂. Intratracheal exposure to NPs resulted in pulmonary inflammation in terms of increased neutrophils influx for all NPs 1 and 28 days post-exposure. Persistent pulmonary acute phase response was detected for all NPs at all three time points while only a transient induction of hepatic acute phase response was observed. All 3 materials were detected in the liver by enhanced darkfield microscopy up to 180 days post-exposure. In contrast to TiO₂ and CeO₂ NPs, CB NPs generated ROS in an acellular assay.

Conclusions

Our results suggest that the observed hepatic DNA damage following intravenous and intratracheal dosing with CB NPs was caused by the presence of translocated, ROS-generating, particles detected in the liver rather than by the secondary effects of pulmonary inflammation or hepatic acute phase response.

Electronic supplementary material

The online version of this article (10.1186/s12989-017-0238-9) contains supplementary material, which is available to authorized users.

Advanced Nuclear and Related Techniques for Metallomics and Nanometallomics

Metallomics, focusing on the global and systematic understanding of the metal uptake, trafficking, role, and excretion in biological systems, has attracted more and more attention. Metal-related nanomaterials, including metallic and metal-containing nanomaterials, have unique properties compared to their macroscale counterparts and therefore require special attention. The absorption, distribution, metabolism, excretion (ADME) behavior of metal-related nanomaterials in the biological systems is influenced by their physicochemical properties, the exposure route, and the microenvironment of the deposition site. Nanomaterials not only may interact directly or indirectly with genes, proteins, and other molecules to bring genotoxicity, immunotoxicity, DNA damage, and cytotoxicity but may also stimulate the immune responses, circumvent tumor resistance, and inhibit tumor metastasis. Because of their advantages of absolute quantification, high sensitivity, excellent accuracy and precision, low matrix effects, and nondestructiveness, nuclear and related analytical techniques have been playing important roles in the study of metallomics and nanometallomics. In this chapter, we present a comprehensive overview of nuclear and related analytical techniques applied to the quantification of metallome and nanometallome, the biodistribution, bioaccumulation, and transformation of metallome and nanometallome in vivo, and the structural analysis. Besides, metallomics and nanometallomics need to cooperate with other -omics, like genomics, proteomics, and metabolomics, to obtain the knowledge of underlying mechanisms and therefore to improve the application performance and to reduce the potential risk of metallome and nanometallome.

Nanomaterials: certain aspects of application, risk assessment and risk communication

Development and market introduction of new nanomaterials trigger the need for an adequate risk assessment of such products alongside suitable risk communication measures. Current application of classical and new nanomaterials is analyzed in context of regulatory requirements and standardization for chemicals, food and consumer products. The challenges of nanomaterial characterization as the main bottleneck of risk assessment and regulation are presented. In some areas, e.g., quantification of nanomaterials within complex matrices, the establishment and adaptation of analytical techniques such as laser ablation inductively coupled plasma mass spectrometry and others are potentially suited to meet the requirements. As an example, we here provide an approach for the reliable characterization of human exposure to nanomaterials resulting from food packaging. Furthermore, results of nanomaterial toxicity and ecotoxicity testing are discussed, with concluding key criteria such as solubility and fiber rigidity as important parameters to be considered in material development and regulation. Although an analysis of the public opinion has revealed a distinguished rating depending on the particular field of application, a rather positive perception of nanotechnology could be ascertained for the German public in general. An improvement of material characterization in both toxicological testing as well as end-product control was concluded as being the main obstacle to ensure not only safe use of materials, but also wide acceptance of this and any novel technology in the general public.

Biodistribution of single and aggregated gold nanoparticles exposed to the human lung epithelial tissue barrier at the air-liquid interface

Background

The lung represents the primary entry route for airborne particles into the human body. Most studies addressed possible adverse effects using single (nano)particles, but aerosolic nanoparticles (NPs) tend to aggregate and form structures of several hundreds nm in diameter, changing the physico-chemical properties and interaction with cells. Our aim was to investigate how aggregation might affect the biodistribution; cellular uptake and translocation over time of aerosolized NPs at the air-blood barrier interface using a multicellular lung system.

Results

Model gold nanoparticles (AuNPs) were engineered and well characterized to compare single NPs with aggregated NPs with hydrodynamic diameter of 32 and 106 nm, respectively. Exposures were performed by aerosolization of the particles onto the air-liquid interface of a three dimensional (3D) lung model. Particle deposition, cellular uptake and translocation kinetics of single and aggregated AuNPs were determined for various concentrations, (30, 60, 150 and 300 ng/cm²) and time points (4, 24 and 48 h) using transmission electron microscopy and inductively coupled plasma optical emission spectroscopy. No apparent harmful effect for single and aggregated AuNPs was observed by lactate dehydrogenase assay, nor pro-inflammation response by tumor necrosis factor α assessment. The cell layer integrity was also not impaired. The bio-distribution revealed that majority of the AuNPs, single or aggregated, were inside the cells, and only a minor fraction, less than 5%, was found on the basolateral side. No significant difference was observed in the translocation rate. However, aggregated AuNPs showed a significantly faster cellular uptake than single AuNPs at the first time point, i.e. 4 h.

Conclusions

Our studies revealed that aggregated AuNPs showed significantly faster cellular uptake than single AuNPs at the first time point, i.e. 4 h, but the uptake rate was similar at later time points. In addition, aggregation did not affect translocation rate across the lung barrier model since similar translocation rates were observed for single as well as aggregated AuNPs.

Electronic supplementary material

The online version of this article (10.1186/s12989-017-0231-3) contains supplementary material, which is available to authorized users.

Fast, asymmetric and nonhomogeneous clearance of SiC nanoaerosol assessed by micro-particle-induced x-ray emission

AIM

To study the biopersistence of a silicon carbide (SiC) nanoaerosol in rat lungs, as time-dependent clearance and spatial distribution.

MATERIALS & METHODS

Sprague-Dawley rats were exposed 6 h/day during 5 days to a SiC nanoaerosol at 4.91 mg SiC/l. SiC biopersistence in rat lungs sections was assessed over 28 days by micro-particle-induced x-ray emission (μPIXE) as 2D maps and by particle-induced x-ray emission (PIXE) for whole-lung quantification. 2D maps were analyzed for SiC spatial distribution as skewness and kurtosis.

RESULTS

Half-time clearance was 10.9 ± 0.9 days, agreeing with PIXE measurements. Spatial-temporal analysis of SiC indicated decreased symmetry and homogeneity.

CONCLUSION

Fast SiC clearance points that current nanoaerosol exposure may not be enough to trigger lung overload. Spatial distribution shows an asymmetric and nonhomogeneous SiC clearance.

Sedentary behavior and altered metabolic activity by AgNPs ingestion in Drosophila melanogaster

Among several nanoparticles, silver nanoparticles (AgNPs) are extensively used in a wide variety of consumer products due to its unique antimicrobial property. However, dosage effect of AgNPs on behavior and metabolic activity in an in vivo condition is not well studied. Therefore, to elucidate the impact of AgNPs on behavior and metabolism, systematic and detailed dosages study of AgNPs was performed by rearing Drosophila melanogaster on food without and with AgNPs. We found that dietary intake of AgNPs at early larval stage leads to behavioral abnormalities such as poor crawling and climbing ability of larvae and adults respectively. Interestingly, intake of higher dosage of AgNPs at larval stage significantly altered metabolic activity that includes lipid, carbohydrate and protein levels in adult flies. Further, detailed analysis revealed that AgNPs causes remarkable reduction in the number of lipid droplets (LDs) which are lipid storage organelles in Drosophila. We also observed an increased production of reactive oxygen species (ROS) in AgNPs ingested larval tissues. These results strongly imply that higher dosage of AgNPs ingestion from early larval stage of Drosophila is inimical and thereby draws concern towards the usage of AgNPs in consumer goods.

Direct fluorescent labeling for efficient biological assessment of inhalable particles

Labeling of aerosol particles with a radioactive, magnetic, or optical tracer has been employed to confirm particle localization in cell compartments, which has provided useful evidence for correlating toxic effects of inhaled particles. However, labeling requires several physicochemical steps to identify functionalities of the inner or outer surfaces of particles, and moreover, these steps can cause changes in size, surface charge, and bioactivity of the particles, resulting in misinterpretations regarding their toxic effects. This study addresses this challenging issue with a goal of introducing an efficient strategy for constantly supplying labeled aerosol particles in a single-pass configuration without any pre- or post-physicochemical batch treatments of aerosol particles. Carbon black (CB, simulating combustion-generated soot) or calcium carbonate (CC, simulating brake-wear fragments) particles were constantly produced via spark ablation or bubble bursting, respectively. These minute particles were incorporated with fluorescein isothiocyanate-poly(ethylene glycol) 2-aminoethyl ether acetic acid solution at the orifice of a collison atomizer to fabricate hybrid droplets. The droplets successively entered a diffusion dryer containing 254-nm UV irradiation; therefore, the droplets were dynamically stiffened by UV to form fluorescent probes on particles during solvent extraction in the dryer. Particle size distributions, morphologies, and surface charges before and after labeling were measured to confirm fluorescence labeling without significant changes in the properties. In vitro assays, including confocal imaging, were conducted to confirm the feasibility of the labeling approach without inducing significant differences in bioactivity compared with untreated CB or CC particles.

Pretreatment with N-acetyl cysteine suppresses chronic reactive astrogliosis following maternal nanoparticle exposure during gestational period

Early pregnant employees are potentially and unintendedly exposed to industrial chemicals including nanoparticles. Developmental toxicity of nanoparticle exposure has been concerned because exposure to fine particle including carbon black nanoparticle (CB-NP) during the brain developmental stage enhances the risk of brain disorders. Maternal CB-NP exposure dose-dependently induces astrogliosis, which is an abnormal increase in the reactive astrocytes with glial fibrillary acidic protein (GFAP) and aquaporin-4 overexpression due to the destruction of nearby neurons and blood vessels. The present study aimed to investigate protective effects of antioxidants on the histopathological denaturation with astrogliosis following maternal CB-NP exposure in offspring mice, thereby to evaluate the role of oxidative stress on the developmental toxicity. Pregnant ICR mice were treated with CB-NP by intranasal instillation on gestational days 5 and 9. N-acetyl cysteine (NAC) or ascorbic acid was intraperitoneally administered to the pregnant mice 1 h prior to CB-NP instillation. The brains were collected from 6- to 12-week-old offspring mice and analyzed using western blotting and immunohistochemistry. NAC suppressed GFAP overexpression in 6- and 12-week-old offspring mice following maternal CB-NP exposure. However, NAC did not suppress aquaporin-4 overexpression following maternal CB-NP exposure. Ascorbic acid did not suppress, but rather slightly and significantly enhanced the expression of GFAP and aquaporin-4. These results indicate that astrogliosis by maternal CB-NP exposure is partially prevented by NAC pretreatment. Oxidative stress is a possible key factor of developmental neurotoxicity of maternal NP exposure. This study will contribute to elucidating the mechanisms underlying the effects of developmental neurotoxicity of NPs.

Nanomaterials Versus Ambient Ultrafine Particles: An Opportunity to Exchange Toxicology Knowledge

BACKGROUND

A rich body of literature exists that has demonstrated adverse human health effects following exposure to ambient air particulate matter (PM), and there is strong support for an important role of ultrafine (nanosized) particles. At present, relatively few human health or epidemiology data exist for engineered nanomaterials (NMs) despite clear parallels in their physicochemical properties and biological actions in in vitro models.

OBJECTIVES

NMs are available with a range of physicochemical characteristics, which allows a more systematic toxicological analysis. Therefore, the study of ultrafine particles (UFP, <100 nm in diameter) provides an opportunity to identify plausible health effects for NMs, and the study of NMs provides an opportunity to facilitate the understanding of the mechanism of toxicity of UFP.

METHODS

A workshop of experts systematically analyzed the available information and identified 19 key lessons that can facilitate knowledge exchange between these discipline areas.

DISCUSSION

Key lessons range from the availability of specific techniques and standard protocols for physicochemical characterization and toxicology assessment to understanding and defining dose and the molecular mechanisms of toxicity. This review identifies a number of key areas in which additional research prioritization would facilitate both research fields simultaneously.

CONCLUSION

There is now an opportunity to apply knowledge from NM toxicology and use it to better inform PM health risk research and vice versa. https://doi.org/10.1289/EHP424.

Repeated Iron-Soot Exposure and Nose-to-brain Transport of Inhaled Ultrafine Particles

Particulate exposure has been implicated in the development of a number of neurological maladies such as multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease, and idiopathic Parkinson's disease. Only a few studies have focused on the olfactory pathway as a portal through which combustion-generated particles may enter the brain. The primary objective of this study was to define the deposition, uptake, and transport of inhaled ultrafine iron-soot particles in the nasal cavities of mice to determine whether combustion-generated nanoparticles reach the olfactory bulb via the olfactory epithelium and nerve fascicles. Adult female C57B6 mice were exposed to iron-soot combustion particles at a concentration of 200 μg/m³, which included 40 μg/m³ of iron oxide nanoparticles. Mice were exposed for 6 hr/day, 5 days/week for 5 consecutive weeks (25 total exposure days). Our findings visually demonstrate that inhaled ultrafine iron-soot reached the brain via the olfactory nerves and was associated with indicators of neural inflammation.

Air Pollution and Other Environmental Modulators of Cardiac Function

Cardiovascular disease (CVD) is the leading cause of death in developed regions and a worldwide health concern. Multiple external causes of CVD are well known, including obesity, diabetes, hyperlipidemia, age, and sedentary behavior. Air pollution has been linked with the development of CVD for decades, though the mechanistic characterization remains unknown. In this comprehensive review, we detail the background and epidemiology of the effects of air pollution and other environmental modulators on the heart, including both short- and long-term consequences. Then, we provide the experimental data and current hypotheses of how pollution is able to cause the CVD, and how exposure to pollutants is exacerbated in sensitive states. Published 2017. Compr Physiol 7:1479-1495, 2017.

Ins and Outs in Environmental and Occupational Safety Studies of Asthma and Engineered Nanomaterials

According to the Centers for Disease Control and Prevention, approximately 25 million Americans suffer from asthma. The disease total annual cost is about $56 billion and includes both the direct and indirect costs of medications, hospital stays, missed work, and decreased productivity. Air pollution with xenobiotics, bacterial agents, and industrial nanomaterials, such as carbon nanotubes, contribute to the exacerbation of this condition and are a point of particular attention in environmental toxicology as well as in occupational health and safety research. Mast cell degranulation and activation of Th2 cells triggered either by allergen-specific immunoglobulin E (IgE) or by alternative mechanisms, such as locally produced neurotransmitters, underlie the pathophysiological process of airway constriction during an asthma attack. Other immune and non-immune cell types, including basophils, eosinophils, Th1, Th17, Th9, macrophages, dendritic cells, and smooth muscle cells, are involved in the inflammatory and allergic responses during asthma, which, under chronic conditions, may progress without mast cells, the key trigger of the acute asthma attack. To decipher complex molecular, cellular, and genetic mechanisms, many researchers have attempted to develop in vitro and in vivo models to study asthma. Herein, we summarize the advantages and disadvantages of various models and their applicability to nanoparticle evaluation in asthma research. We further suggest that a framework for both in vitro and in vivo methods should be used to study the impact of engineered nanomaterials on asthma etiology, pathophysiology, and treatment.

Local delivery of siRNA-loaded calcium phosphate nanoparticles abates pulmonary inflammation

The local interference of cytokine signaling mediated by siRNA-loaded nanoparticles might be a promising new therapeutic approach to dampen inflammation during pulmonary diseases. For the local therapeutic treatment of pulmonary inflammation, we produced multi-shell nanoparticles consisting of a calcium phosphate core, coated with siRNAs directed against pro-inflammatory mediators, encapsulated into poly(lactic-co-glycolic acid), and coated with a final outer layer of polyethylenimine. Nasal instillation of nanoparticles loaded with a mixture of siRNAs directed against different cytokines to mice suffering from T_H1 cell-mediated lung inflammation, or of siRNA directed against NS-1 in an influenza infection model led to a significant reduction of target gene expression which was accompanied by distinct amelioration of lung inflammation in both models. Thus, this study provides strong evidence that the specific and local modulation of the inflammatory response by CaP/PLGA nanoparticle-mediated siRNA delivery could be a promising approach for the treatment of inflammatory disorders of the lung.

Involvement of oxidative stress and calcium signaling in airborne particulate matter - induced damages in human pulmonary artery endothelial cells

Recent studies have revealed that particulate matter (PM) exert deleterious effects on vascular function. Pulmonary artery endothelial cells (HPAEC), which are involved in the vasomotricity regulation, can be a direct target of inhaled particles. Modifications in calcium homeostasis and oxidative stress are critical events involved in the physiopathology of vascular diseases. The objectives of this study were to assess the effects of PM_2.5 on oxidative stress and calcium signaling in HPAEC. Different endpoints were studied, (i) intrinsic and intracellular production of reactive oxygen species (ROS) by the H₂DCF-DA probe, (ii) intrinsic, intracellular and mitochondrial production of superoxide anion (O₂^-) by electronic paramagnetic resonance spectroscopy and MitoSOX probe, (iii) reactive nitrosative species (RNS) production by Griess reaction, and (vi) calcium signaling by the Fluo-4 probe. In acellular conditions, PM_2.5 leads to an intrinsic free radical production (ROS, O₂^-) and a 4h-exposure to PM_2.5 (5-15μg/cm²), induced, in HPAEC, an increase of RNS, of global ROS and of cytoplasmic and mitochondrial O₂^- levels. The basal intracellular calcium ion level [Ca²⁺]i was also increased after 4h-exposure to PM_2.5 and a pre-treatment with superoxide dismutase and catalase significantly reduced this response. This study provides evidence that the alteration of intracellular calcium homeostasis induced by PM_2.5 is closely correlated to an increase of oxidative stress.

Plastic and Human Health: A Micro Issue?

Microplastics are a pollutant of environmental concern. Their presence in food destined for human consumption and in air samples has been reported. Thus, microplastic exposure via diet or inhalation could occur, the human health effects of which are unknown. The current review article draws upon cross-disciplinary scientific literature to discuss and evaluate the potential human health impacts of microplastics and outlines urgent areas for future research. Key literature up to September 2016 relating to accumulation, particle toxicity, and chemical and microbial contaminants was critically examined. Although microplastics and human health is an emerging field, complementary existing fields indicate potential particle, chemical and microbial hazards. If inhaled or ingested, microplastics may accumulate and exert localized particle toxicity by inducing or enhancing an immune response. Chemical toxicity could occur due to the localized leaching of component monomers, endogenous additives, and adsorbed environmental pollutants. Chronic exposure is anticipated to be of greater concern due to the accumulative effect that could occur. This is expected to be dose-dependent, and a robust evidence-base of exposure levels is currently lacking. Although there is potential for microplastics to impact human health, assessing current exposure levels and burdens is key. This information will guide future research into the potential mechanisms of toxicity and hence therein possible health effects.

Inhaled Nanoparticles Accumulate at Sites of Vascular Disease

The development of engineered nanomaterials is growing exponentially, despite concerns over their potential similarities to environmental nanoparticles that are associated with significant cardiorespiratory morbidity and mortality. The mechanisms through which inhalation of nanoparticles could trigger acute cardiovascular events are emerging, but a fundamental unanswered question remains: Do inhaled nanoparticles translocate from the lung in man and directly contribute to the pathogenesis of cardiovascular disease? In complementary clinical and experimental studies, we used gold nanoparticles to evaluate particle translocation, permitting detection by high-resolution inductively coupled mass spectrometry and Raman microscopy. Healthy volunteers were exposed to nanoparticles by acute inhalation, followed by repeated sampling of blood and urine. Gold was detected in the blood and urine within 15 min to 24 h after exposure, and was still present 3 months after exposure. Levels were greater following inhalation of 5 nm (primary diameter) particles compared to 30 nm particles. Studies in mice demonstrated the accumulation in the blood and liver following pulmonary exposure to a broader size range of gold nanoparticles (2-200 nm primary diameter), with translocation markedly greater for particles <10 nm diameter. Gold nanoparticles preferentially accumulated in inflammation-rich vascular lesions of fat-fed apolipoproteinE-deficient mice. Furthermore, following inhalation, gold particles could be detected in surgical specimens of carotid artery disease from patients at risk of stroke. Translocation of inhaled nanoparticles into the systemic circulation and accumulation at sites of vascular inflammation provides a direct mechanism that can explain the link between environmental nanoparticles and cardiovascular disease and has major implications for risk management in the use of engineered nanomaterials.

Determination of "safe" and "critical" nanoparticles exposure to welders in a workshop

The present study examined consequences of "safe" versus "critical" exposure to nanoparticles (NP) released during welding operations. With this aim in mind, a set of measurements regarding NP emissions was undertaken in a workshop during welding by metal active gas of carbon steel using different mixtures of argon (Ar) and carbon dioxide (CO₂) as well as different process parameters which might influence emission of (NP). If these measurements were conducted in several locations away from the welding sources, the graphical representation of the obtained observations with time enabled definition of "safe" and "critical" regions within a welding workshop in terms of welder's exposure. This information may be combined with the results of risk analysis derived by control banding and helps to categorize the sites where regulatory measures such as operation containment or dedicated exhaust ventilation need to be implemented.

A Miniature Aerosol Sensor for Detecting Polydisperse Airborne Ultrafine Particles

Counting and sizing of polydisperse airborne nanoparticles have attracted most attentions owing to increasing widespread presence of airborne engineered nanoparticles or ultrafine particles. Here we report a miniature aerosol sensor to detect particle size distribution of polydisperse ultrafine particles based on ion diffusion charging and electrical detection. The aerosol sensor comprises a couple of planar electrodes printed on two circuit boards assembled in parallel, where charging, precipitation and measurement sections are integrated into one chip, which can detect aerosol particle size in of 30–500 nm, number concentration in range of 5 × 10²–5 × 10⁷ /cm³. The average relative errors of the measured aerosol number concentration and the particle size are estimated to be 12.2% and 13.5% respectively. A novel measurement scheme is proposed to actualize a real-time detection of polydisperse particles by successively modulating the measurement voltage and deducing the particle size distribution through a smart data fusion algorithm. The effectiveness of the aerosol sensor is experimentally demonstrated via measurements of polystyrene latex (PSL) aerosol and nucleic acid aerosol, as well as sodium chloride aerosol particles.

Particle size specific distribution of perfluoro alkyl substances in atmospheric particulate matter in Asian cities

Seasonal and local characteristics of perfluorinated alkylated substances (PFASs) were examined using size-segregated particles including an ultrafine range. The examination included sampling and analysis of ambient particles collected at four sites located in different environments in three different countries, Japan (Kanazawa and Okinawa), Hong Kong and India. To minimize the evaporation artefacts derived from PFASs during the sampling, an air sampler that permitted particles smaller than 0.1 μm (PM_0.1) to be separated at a moderate pressure drop (<5-15 kPa), was used for all of the air sampling procedures. In the case of Kanazawa, a local city in Japan, the concentration of PFASs was found to be dominated by carboxylates, especially PFOA, PFNA and PFDA regardless of the particle size and sampling period. Ultrafine particles were found to be the largest contributor to the mass fraction of PFCAs, while the maximum PFOS mass fractions were determined to be in the coarse-sized fractions. The seasonal difference in the total PFAS concentration can be largely attributed to precipitation. The results were basically similar for all sites that were examined. The type of land use may be a more influencing factor on the mass fraction of the PFASs than the country of origin. The dependency of PFAS mass fraction on the specific surface of the particle suggests that ultrafine PFAS particles are segregated, not only by gas deposition but could also be segregated by a mechanism involving compositional dependence or the primary source of the particles. Other possible sources of PFASs, other than from traffic are also possible.

Quantitative biokinetics of titanium dioxide nanoparticles after intratracheal instillation in rats: Part 3

The biokinetics of a size-selected fraction (70 nm median size) of commercially available and ⁴⁸V-radiolabeled [⁴⁸V]TiO₂ nanoparticles has been investigated in healthy adult female Wistar-Kyoto rats at retention time-points of 1 h, 4 h, 24 h, 7 d and 28 d after intratracheal instillation of a single dose of an aqueous [⁴⁸V]TiO₂-nanoparticle suspension. A completely balanced quantitative biodistribution in all organs and tissues was obtained by applying typical [⁴⁸V]TiO₂-nanoparticle doses in the range of 40-240 μg·kg^-1 bodyweight and making use of the high sensitivity of the radiotracer technique. The [⁴⁸V]TiO₂-nanoparticle content was corrected for residual blood retained in organs and tissues after exsanguination and for ⁴⁸V-ions not bound to TiO₂-nanoparticles. About 4% of the initial peripheral lung dose passed through the air-blood-barrier after 1 h and were retained mainly in the carcass (4%); 0.3% after 28 d. Highest organ fractions of [⁴⁸V]TiO₂-nanoparticles present in liver and kidneys remained constant (0.03%). [⁴⁸V]TiO₂-nanoparticles which entered across the gut epithelium following fast and long-term clearance from the lungs via larynx increased from 5 to 20% of all translocated/absorbed [⁴⁸V]TiO₂-nanoparticles. This contribution may account for 1/5 of the nanoparticle retention in some organs. After normalizing the fractions of retained [⁴⁸V]TiO₂-nanoparticles to the fraction that reached systemic circulation, the biodistribution was compared with the biodistributions determined after IV-injection (Part 1) and gavage (GAV) (Part 2). The biokinetics patterns after IT-instillation and GAV were similar but both were distinctly different from the pattern after intravenous injection disproving the latter to be a suitable surrogate of the former applications. Considering that chronic occupational inhalation of relatively biopersistent TiO₂-particles (including nanoparticles) and accumulation in secondary organs may pose long-term health risks, this issue should be scrutinized more comprehensively.

Quantitative biokinetics of titanium dioxide nanoparticles after intravenous injection in rats: Part 1

Submicrometer TiO₂ particles, including nanoparticulate fractions, are used in an increasing variety of consumer products, as food additives and also drug delivery applications are envisaged. Beyond exposure of occupational groups, this entails an exposure risk to the public. However, nanoparticle translocation from the organ of intake and potential accumulation in secondary organs are poorly understood and in many investigations excessive doses are applied. The present study investigates the biokinetics and clearance of a low single dose (typically 40-400 μg/kg BW) of ⁴⁸V-radiolabeled, pure TiO₂ anatase nanoparticles ([⁴⁸V]TiO₂NP) with a median aggregate/agglomerate size of 70 nm in aqueous suspension after intravenous (IV) injection into female Wistar rats. Biokinetics and clearance were followed from one-hour to 4-weeks. The use of radiolabeled nanoparticles allowed a quantitative [⁴⁸V]TiO₂NP balancing of all organs, tissues, carcass and excretions of each rat without having to account for chemical background levels possibly caused by dietary or environmental titanium exposure. Highest [⁴⁸V]TiO₂NP accumulations were found in liver (95.5%ID after one day), followed by spleen (2.5%), carcass (1%), skeleton (0.7%) and blood (0.4%). Detectable nanoparticle levels were found in all other organs. The [⁴⁸V]TiO₂NP content in blood decreased rapidly after 24 h while the distribution in other organs and tissues remained rather constant until day-28. The present biokinetics study is part 1 of a series of studies comparing biokinetics after three classical routes of intake (IV injection (part 1), ingestion (part 2), intratracheal instillation (part 3)) under identical laboratory conditions, in order to test the common hypothesis that IV-injection is a suitable predictor for the biokinetics fate of nanoparticles administered by different routes. This hypothesis is disproved by this series of studies.

Biokinetics of Nanomaterials: the Role of Biopersistence

Nanotechnology risk management strategies and environmental regulations continue to rely on hazard and exposure assessment protocols developed for bulk materials, including larger size particles, while commercial application of nanomaterials (NMs) increases. In order to support and corroborate risk assessment of NMs for workers, consumers, and the environment it is crucial to establish the impact of biopersistence of NMs at realistic doses. In the future, such data will allow a more refined future categorization of NMs. Despite many experiments on NM characterization and numerous in vitro and in vivo studies, several questions remain unanswered including the influence of biopersistence on the toxicity of NMs. It is unclear which criteria to apply to characterize a NM as biopersistent. Detection and quantification of NMs, especially determination of their state, i.e., dissolution, aggregation, and agglomeration within biological matrices and other environments are still challenging tasks; moreover mechanisms of nanoparticle (NP) translocation and persistence remain critical gaps. This review summarizes the current understanding of NM biokinetics focusing on determinants of biopersistence. Thorough particle characterization in different exposure scenarios and biological matrices requires use of suitable analytical methods and is a prerequisite to understand biopersistence and for the development of appropriate dosimetry. Analytical tools that potentially can facilitate elucidation of key NM characteristics, such as ion beam microscopy (IBM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), are discussed in relation to their potential to advance the understanding of biopersistent NM kinetics. We conclude that a major requirement for future nanosafety research is the development and application of analytical tools to characterize NPs in different exposure scenarios and biological matrices.

Perivascular Accumulation of β-Sheet-Rich Proteins in Offspring Brain following Maternal Exposure to Carbon Black Nanoparticles

Environmental stimulation during brain development is an important risk factor for the development of neurodegenerative disease. Clinical evidence indicates that prenatal exposure to particulate air pollutants leads to diffuse damage to the neurovascular unit in the developing brain and accelerates neurodegeneration. Maternal exposure to carbon black nanoparticles (CB-NPs), used as a model for particulate air pollution, induces long-lasting diffuse perivascular abnormalities. We aimed to comprehensively characterize the perivascular abnormalities related to maternal NPs exposure using Fourier transform infrared microspectroscopy (in situ FT-IR) and classical staining analysis. Pregnant ICR mice were intranasally treated with a CB-NPs suspension (95 μg/kg at a time) on gestational days 5 and 9. Brains were collected 6 weeks after birth and sliced to prepare 10-μm-thick serial sections. Reflective spectra of in situ FT-IR were acquired using lattice measurements (x-axis: 7, y-axis: 7, 30-μm apertures) around a centered blood vessel. We also performed mapping analysis of protein secondary structures. Serial sections were stained with using periodic acid-Schiff or immunofluorescence to examine the phenotypes of the perivascular areas. Peaks of amide I bands in spectra from perivascular areas were shifted by maternal NPs exposure. However, there were two types of peak-shift in one mouse in the exposure group. Some vessels had a large peak-shift and others had a small peak-shift. In situ FT-IR combined with traditional staining revealed that the large peak-shift was induced around blood vessel adjacent to astrocytes with glial fibrillary acidic protein and aquaporin-4 over-expression and perivascular macrophages (PVMs) with enlarged lysosome granules. Furthermore, protein secondary structural analysis indicated that maternal NPs exposure led to increases in β-sheet content and decreases in α-helix content in areas that are mostly close to the centered blood vessel displaying histopathological changes. These results suggest that β-sheet-rich waste proteins, which are denatured by maternal NPs exposure, likely accumulate in the perivascular space as they are processed by the clearance systems in the brain. This may in turn lead the denaturation of PVMs and astrocyte activation. The risk of neurodegeneration may be enhanced by exposure to particulate air pollutants during brain development following the perivascular accumulation of β-sheet-rich waste proteins.

Isotope Tracers To Study the Environmental Fate and Bioaccumulation of Metal-Containing Engineered Nanoparticles: Techniques and Applications

The rapidly growing applicability of metal-containing engineered nanoparticles (MENPs) has made their environmental fate, biouptake, and transformation important research topics. However, considering the relatively low concentration of MENPs and the high concentration of background metals in the environment and in organisms, tracking the fate of MENPs in environment-related scenarios remains a challenge. Intrinsic labeling of MENPs with radioactive or stable isotopes is a useful tool for the highly sensitive and selective detection of MENPs in the environment and organisms, thus enabling tracing of their transformation, uptake, distribution, and clearance. In this review, we focus on radioactive/stable isotope labeling of MENPs for their environmental and biological tracing. We summarize the advantages of intrinsic radioactive/stable isotopes for MENP labeling and discuss the considerations in labeling isotope selection and preparation of labeled MENPs, as well as exposure routes and detection of labeled MENPs. In addition, current practice in the use of radioactive/stable isotope labeling of MENPs to study their environmental fate and bioaccumulation is reviewed. Future perspectives and potential applications are also discussed, including imaging techniques for radioactive- and stable-isotope-labeled MENPs, hyphenated multistable isotope tracers with speciation analysis, and isotope fractionation as a MENP tracer. It is expected that this critical review could provide the necessary background information to further advance the applications of isotope tracers to study the environmental fate and bioaccumulation of MENPs.

Slow lung clearance and limited translocation of four sizes of inhaled iridium nanoparticles

Background

Concerns have been expressed that inhaled nanoparticles may behave differently to larger particles in terms of lung clearance and translocation, with potential implications for their toxicity. Studies undertaken to investigate this have typically involved limited post-exposure periods. There is a shortage of information on longer-term clearance and translocation patterns and their dependence on particle size, which this study aimed to address.

Methods

Rats were exposed (<3 h) nose-only to aerosols of spark-generated radioactive iridium-192 nanoparticles of four sizes: 10 nm, 15 nm, 35 nm and 75 nm (count median diameter) (aerosol mass concentrations 17, 140, 430, and 690 μg/m³, respectively). The content of iridium-192 in the whole animal, organs, tissues, and excreta was measured at various times post-exposure to ≥ 1 month. Limited toxicological investigations were undertaken for the 10 nm aerosol using bronchoalveolar lavage fluid. Elemental maps of tissue samples were produced using laser ablation inductively coupled plasma mass spectrometry and synchrotron micro-focus x-ray fluorescence. The chemical speciation of the iridium was explored using synchrotron micro focus x-ray near-edge absorption spectroscopy.

Results

Long-term lung retention half-times of several hundred days were found, which were not dependent on particle size. There was significant variation between individual animals. Analysis of bronchoalveolar lavage fluid for the 10 nm aerosol indicated a limited inflammatory response resolving within the first 7 days. Low levels of, particle size dependent, translocation to the kidney and liver were found (maximum 0.4% of the lung content). Any translocation to the brain was below the limits of detection (i.e. < 0.01% of the lung content). The kidney content increased to approximately 30 days and then remained broadly constant or decreased, whereas the content in the liver increased throughout the study. Laser ablation inductively coupled plasma mass spectrometry analysis indicated homogeneous iridium distribution in the liver and within the cortex in the kidney.

Conclusions

Slow lung clearance and a pattern of temporally increasing concentrations in key secondary target organs has been demonstrated for inhaled iridium aerosol particles < 100 nm, which may have implications for long-term toxicity, especially in the context of chronic exposures.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-017-0185-5) contains supplementary material, which is available to authorized users.

Dose-dependent induction of astrocyte activation and reactive astrogliosis in mouse brain following maternal exposure to carbon black nanoparticle

Background

Recent studies indicate that maternal exposure to ambient ultrafine particles and nanoparticles has adverse effects of on the central nervous system. Quantitative dose–response data is required to better understand the developmental neurotoxicity of nanoparticles. The present study investigated dose-dependent effects of maternal exposure to carbon black nanoparticle (CB-NP) on astrocyte in the brains of mouse offspring.

Methods

A CB-NP suspension (2.9, 15, or 73 μg/kg) was intranasally administered to pregnant ICR mice on gestational days 5 and 9. Cerebral cortex samples were collected from 6-week-old offspring and examined by Western blotting, immunostaining, microarray analysis, and quantitative reverse transcriptase-polymerase chain reaction. Placentae were collected from pregnant dams on gestational day 13 and examined by microarray analysis.

Results

Maternal exposure to CB-NP induced a dose-dependent increase in glial fibrillary acidic protein (GFAP) expression in the cerebral cortex; this increase was particularly observed in astrocytic end-feet attached to denatured perivascular macrophages. Moreover, maternal CB-NP exposure dose-dependently increased aquaporin-4 expression in the brain parenchyma region around blood vessels. The changes in the expression profiles of GFAP and Aqp4 in offspring after maternal CB-NP exposure were similar to those observed in mice of a more advanced age. The expression levels of mRNAs associated with angiogenesis, cell migration, proliferation, chemotaxis, and growth factor production were also altered in the cerebral cortex of offspring after maternal CB-NP exposure. Differentially expressed genes in placental tissues after CB-NP exposure did not populate any specific gene ontology category.

Conclusions

Maternal CB-NP exposure induced long-term activation of astrocytes resulting in reactive astrogliosis in the brains of young mice. Our observations suggest a potentially increased risk of the onset of age-related neurodegenerative diseases by maternal NP exposure. In this study, we report for the first time a quantitative dose–response relationship between maternal NP exposure and phenotypic changes in the central nervous system of the offspring. Moreover, our findings indicate that cortical GFAP and Aqp4 are useful biomarkers that can be employed in further studies aiming to elucidate the underlying mechanism of nanoparticle-mediated developmental neurotoxicity.

Exposure to ambient PM10 and NO2 and the incidence of attention-deficit hyperactivity disorder in childhood

BACKGROUND

Epidemiological studies have implicated air pollution in the causation of neurodevelopmental disorders, including attention-deficit hyperactivity disorder (ADHD), but definitive evidence of this linkage is lacking.

OBJECTIVES

We examined the association between cumulative exposure to air pollutants from birth to diagnosis, particularly particulate matter of <10μm (PM₁₀) and nitric dioxide (NO₂), and childhood ADHD.

METHODS

We used the National Health Insurance Service-National Sample Cohort (2002-2012), a population-wide health insurance claims dataset. A total of 8936 infants (age 0) born between January 2002 and December 2002 were followed-up for a 10-year period (2003-2012). ADHD was defined as per ICD-10 code F90.0. Exposure levels of PM₁₀ and NO₂ were extrapolated using geographic information systems and collated with the subjects' administrative district code, and individual exposure levels assigned. Hazard ratios (HRs) were calculated for the development of ADHD, after adjusting for gender, metropolitan area, income, and history of diseases.

RESULTS

During the study period, ADHD occurred in 314 subjects (3.5%). With the increase in 1μg/m³ of air pollutants, the HRs of childhood ADHD were 1.18 (95% CI: 1.15-1.21) in case of PM₁₀ and 1.03 (95% CI: 1.02-1.04) in case of NO₂. Compared with infants with the lowest tertile of PM₁₀ or NO₂ exposure, those with the highest tertile of PM₁₀ (HR=3.88; 95% CI: 2.87-5.23) or NO₂ (HR=2.10; 95% CI, 1.54-2.85) exposure had a 2 to 3 fold increased risk for ADHD.

CONCLUSION

Exposure to PM₁₀ and NO₂ was associated with the incidence of ADHD in childhood.

Neurotoxicity of Copper

Copper is an essential trace metal that is required for several important biological processes, however, an excess of copper can be toxic to cells. Therefore, systemic and cellular copper homeostasis is tightly regulated, but dysregulation of copper homeostasis may occur in disease states, resulting either in copper deficiency or copper overload and toxicity. This chapter will give an overview on the biological roles of copper and of the mechanisms involved in copper uptake, storage, and distribution. In addition, we will describe potential mechanisms of the cellular toxicity of copper and copper oxide nanoparticles. Finally, we will summarize the current knowledge on the connection of copper toxicity with neurodegenerative diseases.