Environmentally Relevant Iron Oxide Nanoparticles Produce Limited Acute Pulmonary Effects in Rats at Realistic Exposure Levels

Phytotoxicity of seven iron-based materials to mung bean seedlings

Due to the widespread application of various iron-based materials in environmental remediation and agricultural production, it is of significance to assess their environmental risks. Here, seven iron-based materials, including ionic FeCl3, micro- and nano-sized magnetite (i.e., mFe3O4 and nFe3O4), micro- and nano-sized zero-valent iron (i.e., mZVI and nZVI), and nZVI modified by starch and activated carbon (i.e., S-nZVI and A-nZVI), were targeted to compare their phytotoxicity in mung bean grown in the soil with different doses (0, 300, 600, and 1000 mg/kg) for 40 days. S-nZVI and A-nZVI severely inhibited plant growth, decreasing shoot and root dry weights by 45.1-79.2 and 26.0-82.3%, respectively, but other materials showed no or minimal effects on plant growth. All the materials decreased chlorophyll content and photosynthesis performance, with more pronounced inhibition from A-nZVI and S-nZVI, especially at 1000 mg/kg. The activities of superoxide dismutase (SOD) and peroxide dismutase (POD) in leaves were stimulated by all the materials, among which S-nZVI enhanced SOD activity by 206.9% at 300 mg/kg and POD activity by 541.1% at 1000 mg/kg. In most cases, Fe accumulation in the roots was increased by all materials, particularly by S-nZVI and A-nZVI. Fe concentrations in roots and shoots exposed to 1000 mg/kg S-nZVI and A-nZVI were 2-3 times higher than those in the control treatments. The disturbance in the homeostasis of minerals (Zn, Mn, Cu, and Mg) was induced by all iron-based materials. To conclude, the phytotoxicity of iron-based materials was dependent on their type and dosage, and stabilization was crucial for the phytotoxicity and bioaccumulation potential of nZVI in plants.

Exposure of RAW264.7 macrophages to exhaust emissions (gases and PAH) and non-exhaust emissions (tire particles) induces additive or synergistic TNF-α production depending on the tire particle size

Road traffic is a major contributor to air pollution and consequently negatively affects human health. Car pollution originates both from exhaust emissions (EE) and non-exhaust emissions (NEE, such as tire and brake wear particles, erosion of road surfaces and resuspension of road dust). While the toxicity of EE and NEE has been characterized separately, their combined effects are poorly documented. However, we are constantly exposed to a mixture of pollutants and their interactions should not be neglected as they may significantly impact their toxicological profile resulting in additive, synergistic or antagonistic effects. To fill this gap, we investigated in vitro the combined toxicity of exhaust gases and benzo[a]pyrene (representative of EE) and tire particles (representative of NEE). Macrophages from the RAW264.7 cell line were exposed for 24 h to tire particles (TP) of variable size (6-113 µm), alone or in combination with exhaust gases (CO2, CO, NO, NO2) and benzo[a]pyrene (B[a]P) as an archetype of polycyclic aromatic hydrocarbon (PAH). The cell response was assessed in terms of cytotoxicity, proinflammatory response and oxidative stress. TP, gases and B[a]P, alone or in combination triggered neither cytotoxicity nor oxidative stress. On the contrary, a proinflammatory response was elicited with two different profiles depending on the size of the TP: TNF-α production was either slightly (with the finest TP) or strongly (with coarse TP) increased in the presence of gases and B[a]P, suggesting that the effects of TP, gases and B[a]P were either additive or synergistic, depending on TP size.

Integrated in silico analysis of transcriptomic alterations in nanoparticle toxicity across human and mouse models

Nanoparticles, due to their exceptional physicochemical properties are used in our day-to-day environment. They are currently not regulated which might lead to increased levels in the biological systems causing adverse effects. However, the overall mechanism behind nanotoxicity remains elusive. Previously, we analysed the transcriptome datasets of copper oxide nanoparticles using in silico tools and identified IL-17, chemokine signaling pathway, and cytokine-cytokine receptor interaction as the key pathways altered. Based on the findings, we hypothesized a common pathway could be involved in transition metal oxide nanoparticles toxicity irrespective of the variables. Further, there could be unique transcriptome changes between metal oxide nanoparticles and other nanoparticles. To accomplish this, the overall transcriptome datasets of nanoparticles consisting of microarray and RNA-Seq were obtained. >90 studies for 17 different nanoparticles, performed in humans, rats, and mice were assessed. After initial screening, 24 mouse studies (with 196 datasets) and 34 human studies (with 200 datasets) were used for further analyses. The common genes that are dysregulated upon NPs exposure were identified for human and mouse datasets separately. Further, an overrepresentation functional enrichment analysis was performed. The common genes, their gene ontology, gene-gene, and protein-protein interactions were assessed. The overall results suggest that IL-17 and its related pathways might be commonly altered in nanoparticle exposure with lung as one of the major organs affected.

Inflammation related to inhalation of nano and micron sized iron oxides: a systematic review

Inhalation exposure to iron oxide occurs in many workplaces and respirable aerosols occur during thermal processes (e.g. welding, casting) or during abrasion of iron and steel products (e.g. cutting, grinding, machining, polishing, sanding) or during handling of iron oxide pigments. There is limited evidence of adverse effects in humans specifically linked to inhalation of iron oxides. This contrasts to oxides of other metals used to alloy or for coating of steel and iron of which several have been classified as being hazardous by international and national agencies. Such metal oxides are often present in the air at workplaces. In general, iron oxides might therefore be regarded as low-toxicity, low-solubility (LTLS) particles, and are often considered to be nontoxic even if very high and prolonged inhalation exposures might result in diseases. In animal studies, such exposures lead to cancer, fibrosis and other diseases. Our hypothesis was that pulmonary-workplace exposure during manufacture and handling of SPION preparations might be harmful. We therefore conducted a systematic review of the relevant literature to understand how iron oxides deposited in the lung are related to acute and subchronic pulmonary inflammation. We included one human and several in vivo animal studies published up to February 2023. We found 25 relevant studies that were useful for deriving occupational exposure limits (OEL) for iron oxides based on an inflammatory reaction. Our review of the scientific literature indicates that lowering of health-based occupational exposure limits might be considered.

Ferruginous components of particulate matters in subway environments, α-Fe2O3 or Fe3O4, exacerbates allergies

The respiratory effects of particulate matter (PM) in subway station platforms or tunnels have attracted considerable research attention. However, no studies have characterized the effects of subway PM on allergic immune responses. In this study, iron oxide (α-Fe2O3 and Fe3O4) particles-the main components of subway PM-were intratracheally administered to BALB/c mice where ovalbumin (OVA) induced allergic pulmonary inflammation. Iron oxide particles enhanced OVA-induced eosinophil recruitment around the bronchi and mucus production from airway epithelium. The concentrations of type 2 cytokines, namely, interleukin (IL)-5 and IL-13, in bronchial alveolar lavage fluids were increased by iron oxide particles. Iron oxide particles also increased the number of type 2 innate lymphoid cells and CD86+ cells in the lung. Moreover, phagocytosis of particles in lung cells was confirmed by Raman spectroscopy. In a subsequent in vitro study, bone marrow-derived antigen-presenting cells (APCs) isolated from NC/Nga mice were exposed to iron oxide particles and OVA. They were also exposed to outdoor ambient PM: Vehicle Exhaust Particulates (VEP) and Urban Aerosols (UA) as references. Iron oxide particles promoted the release of lactate dehydrogenase, C-X-C motif chemokine ligand 1 and IL-1α from APCs, which tended to be stronger than those of VEP. These results suggest that iron oxide particles enhance antigen presentation in the lungs, promoting allergic immune response in mice; iron oxide particles-induced death and inflammatory response of APCs can contribute to allergy exacerbation. Although iron oxide particles do not contain various compounds like VEP, iron oxide alone may have sufficient influence.

Investigation of effective parameters on Fe/Ta thin films by plasma focus device: number of shots and distance from tip anode

This experimental investigation is the first to generate a surface iron-tantalum (Fe/Ta) alloy as a sublayer-layer using a plasma focus device. Examining how ion beams from a plasma focus device alloy iron and tantalum with varying melting points is one of the key objectives of this study. Fe/Ta thin film nanostructure and surface morphology were also examined. The distance from the tip anode and the varied number of shots are the experimental variables. Although tantalum's melting point (3020 $$^\circ{\rm C}$$ ∘ C ) is generally known to be near to that of iron (2862 $$^\circ{\rm C}$$ ∘ C ), it is possible that iron vaporizes and partial alloying of iron with tantalum occurs before tantalum reaches its melting point. Fe/Ta thin film identification techniques include scanning electron microscopy, mapping of cross-section, energy dispersive X-ray spectroscopy, and X-ray diffraction pattern. Additionally, the composition of multilayer structures is examined using EDS. In conclusion, the results of the X-ray diffraction pattern showed that the number of shots had a significant impact on the residual strain degree of the thin films that were deposited. Furthermore, structures made of FeTa and Fe2Ta were produced. Additionally, photos from scanning electron microscopy and cross-section mapping verify that the sample with five shots at an 8 cm distance from the tip anode formed a uniform Fe/Ta alloy structure. The sample with five shots at a distance of 4 cm from the tip anode formed micro-island structures, as seen by scanning electron microscopy, with decreasing distance. Furthermore, depth elemental distribution revealed that the optimal depth of penetration in a homogenous material to develop alloying is best determined by number of PF shots.

Role of circPSEN1 in carbon black and cadmium co-exposure induced autophagy-dependent ferroptosis in respiratory epithelial cells

Carbon black and cadmium (Cd) are important components of atmospheric particulate matter and cigarette smoke that are closely associated with the occurrence and development of lung diseases. Carbon black, particularly carbon black nanoparticles (CBNPs), can easily adsorbs metals and cause severe lung damage and even cell death. Therefore, this study aimed to explore the mechanisms underlying the combined toxicity of CBNPs and Cd. We found that the combined exposure to CBNPs and Cd promoted significantly greater autophagosome formation and ferroptosis (increased malonaldehyde (MDA), reactive oxygen species (ROS), and divalent iron ions (Fe2+) levels and altered ferroptosis-related proteins) compared with single exposure in both 16HBE cells (human bronchial epithelioid cells) and mouse lung tissues. The levels of ferroptosis proteins, transferrin receptor protein 1 (TFRC) and glutathione peroxidase 4 (GPX4), were restored by CBNPs-Cd exposure following treatment with a 3-MA inhibitor. Additionally, under CBNPs-Cd exposure, circPSEN1 overexpression inhibited increases in the autophagy proteins microtubule-associated protein 1 light chain 3 (LC3II/I) and sequestosome-1 (P62). Moreover, increases in TFRC and Fe2+, and decreases in GPX4were inhibited. Knockdown of circPSEN1 reversed these effects. circPSEN1 interacts with autophagy-related gene 5 (ATG5) protein and upregulates nuclear receptor coactivator 4 (NCOA4), the co-interacting protein of ATG5, thereby degrading ferritin heavy chain 1 (FTH1) and increasing Fe2+ in 16HBE cells. These results indicated that the combined exposure to CBNPs and Cd promoted the binding of circPSEN1 to ATG5, thereby increasing autophagosome synthesis and ATG5-NCOA4-FTH1 axis activation, ultimately inducing autophagy-dependent ferroptosis in 16HBE cells and mouse lung tissues. This study provides novel insights into the toxic effects of CBNPs and Cd in mixed pollutants.

Selective cytotoxic effects of nitrogen-doped graphene coated mixed iron oxide nanoparticles on HepG2 as a new potential therapeutic approach

New selective therapeutics are needed for the treatment of hepatocellular carcinoma (HCC), the 7th most common cancer. In this study, we compared the cytotoxic effect induced by the release of pH-dependent iron nanoparticles from nitrogen-doped graphene-coated mixed iron oxide nanoparticles (FexOy/N-GN) with the cytotoxic effect of nitrogen-doped graphene (N-GN) and commercial graphene nanoflakes (GN) in Hepatoma G2 (HepG2) cells and healthy cells. The cytotoxic effect of nanocomposites (2.5-100 ug/ml) on HepG2 and healthy fibroblast (BJ) cells (12-48 h) was measured by Cell Viability assay, and the half maximal inhibitory concentration (IC50) was calculated. After the shortest (12 h) and longest incubation (48 h) incubation periods in HepG2 cells, IC50 values of FexOy/N-GN were calculated as 21.95 to 2.11 µg.mL-1, IC50 values of N-GN were calculated as 39.64 to 26.47 µg.mL-1 and IC50 values of GN were calculated as 49.94 to 29.94, respectively. After 48 h, FexOy/N-GN showed a selectivity index (SI) of 10.80 for HepG2/BJ cells, exceeding the SI of N-GN (1.27) by about 8.5-fold. The high cytotoxicity of FexOy/N-GN was caused by the fact that liver cancer cells have many transferrin receptors and time-dependent pH changes in their microenvironment increase iron release. This indicates the potential of FexOy/N-GN as a new selective therapeutic.

Prediction of size-selective permitted daily exposures for mineral oil mist based on an in vitro study in different scenarios

The incidence of DNA damage from exposure to specific types of metalworking fluids has been reported. In this research, size-selective permissible limits to prevent genotoxic damage in A549 cell lines exposed to two types of mineral oil were estimated for the first time using a benchmark dose approach and extrapolated to workers. The comet assay was performed based on Olive and Banath protocol to determine DNA damage. Then, the Benchmark Dose, the 95% lower bound confidence limit BMD, and the 95% upper-bound confidence limit BMD were determined using continuous response data. Finally, the four Benchmark Dose levels reported in the A549 cell line were extrapolated to the human population in occupational settings in two phases. This study showed when determining the permissible limits, the type used or unused, the type of injury, the organ affected in the body and the size of the particles should also be considered.

Application of a novel exposure limit approach for co-exposure of ‎chemicals: a field study by in-vitro design

This study has suggested an occupational exposure limit (OEL) based on the co-exposure approach in an iron-foundry industry. Respirable dust was collected in an iron casting industry using the NIOSH 0600 method. The DNA damage was obtained by comet assay. The lower confidence interval of the benchmark dose (BMDL) was employed for exposure limit evaluation. The estimated BMDL of the cell line was extrapolated to human subjects. Based on the Hill model, a BMDL 1.65 µg for chemical mixture has been estimated for the A549 cell line. According to uncertainty factors, permitted daily exposure (PDE) was predicted in humans. However, PDE of 3.9 μg/m3 was specified as the time-weighted average limit for toxic respirable dust in the casting industry. In this study, OEL for active respirable dust in the casting industry has been proposed. The industry-based standard for active respirable dust has been proposed for better management of co-exposure.

Asbestos and Iron

Theories of disease pathogenesis following asbestos exposure have focused on the participation of iron. After exposure, an open network of negatively charged functional groups on the fiber surface complexes host metals with a preference for iron. Competition for iron between the host and the asbestos results in a functional metal deficiency. The homeostasis of iron in the host is modified by the cell response, including increased import to correct the loss of the metal to the fiber surface. The biological effects of asbestos develop in response to and are associated with the disruption of iron homeostasis. Cell iron deficiency in the host following fiber exposure activates kinases and transcription factors, which are associated with the release of mediators coordinating both inflammatory and fibrotic responses. Relative to serpentine chrysotile, the clearance of amphiboles is incomplete, resulting in translocation to the mesothelial surface of the pleura. Since the biological effect of asbestos is dependent on retention of the fiber, the sequestration of iron by the surface, and functional iron deficiency in the cell, the greater clearance (i.e., decreased persistence) of chrysotile results in its diminished impact. An inability to clear asbestos from the lower respiratory tract initiates a host process of iron biomineralization (i.e., asbestos body formation). Host cells attempt to mobilize the metal sequestered by the fiber surface by producing superoxide at the phagosome membrane. The subsequent ferrous cation is oxidized and undergoes hydrolysis, creating poorly crystalline iron oxyhydroxide (i.e., ferrihydrite) included in the coat of the asbestos body.

The toxicity of nanoparticles and their interaction with cells: an in vitro metabolomic perspective

Nowadays, nanomaterials (NMs) are widely present in daily life due to their significant benefits, as demonstrated by their application in many fields such as biomedicine, engineering, food, cosmetics, sensing, and energy. However, the increasing production of NMs multiplies the chances of their release into the surrounding environment, making human exposure to NMs inevitable. Currently, nanotoxicology is a crucial field, which focuses on studying the toxicity of NMs. The toxicity or effects of nanoparticles (NPs) on the environment and humans can be preliminary assessed in vitro using cell models. However, the conventional cytotoxicity assays, such as the MTT assay, have some drawbacks including the possibility of interference with the studied NPs. Therefore, it is necessary to employ more advanced techniques that provide high throughput analysis and avoid interferences. In this case, metabolomics is one of the most powerful bioanalytical strategies to assess the toxicity of different materials. By measuring the metabolic change upon the introduction of a stimulus, this technique can reveal the molecular information of the toxicity induced by NPs. This provides the opportunity to design novel and efficient nanodrugs and minimizes the risks of NPs used in industry and other fields. Initially, this review summarizes the ways that NPs and cells interact and the NP parameters that play a role in this interaction, and then the assessment of these interactions using conventional assays and the challenges encountered are discussed. Subsequently, in the main part, we introduce the recent studies employing metabolomics for the assessment of these interactions in vitro.

Comparative Evaluation of the Cytotoxic Effects of Metal Oxide and Metalloid Oxide Nanoparticles: An Experimental Study

Industrial production generates aerosols of complex composition, including an ultrafine fraction. This is typical for mining and metallurgical industries, welding processes, and the production and recycling of electronics, batteries, etc. Since nano-sized particles are the most dangerous component of inhaled air, in this study we aimed to establish the impact of the chemical nature and dose of nanoparticles on their cytotoxicity. Suspensions of CuO, PbO, CdO, Fe₂O₃, NiO, SiO₂, Mn₃O₄, and SeO nanoparticles were obtained by laser ablation. The experiments were conducted on outbred female albino rats. We carried out four series of a single intratracheal instillation of nanoparticles of different chemical natures at doses ranging from 0.2 to 0.5 mg per animal. Bronchoalveolar lavage was taken 24 h after the injection to assess its cytological and biochemical parameters. At a dose of 0.5 mg per animal, cytotoxicity in the series of nanoparticles changed as follows (in decreasing order): CuO NPs > PbO NPs > CdO NPs > NiO NPs > SiO₂ NPs > Fe₂O₃ NPs. At a lower dose of 0.25 mg per animal, we observed a different pattern of cytotoxicity of the element oxides under study: NiO NPs > Mn₃O₄ NPs > CuO NPs > SeO NPs. We established that the cytotoxicity increased non-linearly with the increase in the dose of nanoparticles of the same chemical element (from 0 to 0.5 mg per animal). An increase in the levels of intracellular enzymes (amylase, AST, ALT, LDH) in the supernatant of the bronchoalveolar lavage fluid indicated a cytotoxic effect of nanoparticles. Thus, alterations in the cytological parameters of the bronchoalveolar lavage and the biochemical characteristics of the supernatant can be used to predict the danger of new nanomaterials based on their comparative assessment with the available tested samples of nanoparticles.

Combined effects of nanoparticles and other environmental contaminants on human health - an issue often overlooked

Air pollution is considered as a major public health issue worldwide. It consists of a complex mixture of pollutants including nanoparticles to which we are increasingly exposed to due to the dramatic development of the nanotechnologies and their incidental or intentional release in the environment. Consequently, some concerns have raised about the combined toxicity of air particulates and other air pollutants on human health. However, the interactions between the contaminants and their resulting combined toxicity are often overlooked. Indeed, the biological effects triggered by nanoparticles are usually assessed focusing on individual nanoparticles, while their interaction with co-contaminants can deeply impact, either positively or negatively, their biodistribution, fate in the organism and toxicological profile (additive, synergistic or antagonistic responses). This paper presents a bibliographic review on the combined toxicity of nanoparticles and co-pollutants and discusses the underlying mechanisms. It also highlights the scarcity of data in the current literature, arguing for an urgent need to take into account the mixture effects to be more representative of real-life conditions for a better and accurate human health risk assessment and management.