Inflammation and (secondary) genotoxicity of Ni and NiO nanoparticles

Ecological impacts and potential hazards of nickel on soil microbes, plants, and human health

Nickel (Ni) contamination poses a serious environmental concern, particularly in developing countries: where, anthropogenic activities significantly contributes to Ni accumulations in soils and waters. The contamination of agricultural soils with Ni, increases risks of its entry to terrestrial ecosystems and food production systems posing a threat to both food security and safety. We examined the existing published articles regarding the origin, source, accumulation, and transport of Ni in soil environments. Particularly, we reviewed the bioavailability and toxic effects of Ni to soil invertebrates and microbes, as well as its impact on soil-plant interactions including seed germination, nutrient uptake, photosynthesis, oxidative stress, antioxidant enzyme activity, and biomass production. Moreover, it underscores the potential health hazards associated with consuming crops cultivated in Ni-contaminated soils and elucidates the pathways through which Ni enters the food chain. The published literature suggests that chronic Ni exposure may have long-term implications for the food supply chain and the health of the public. Therefore, an aggressive effort is required for interdisciplinary collaboration for assessing and mitigating the ecological and health risks associated with Ni contamination. It also argues that these measures are necessary in light of the increasing level of Ni pollution in soil ecosystems and the potential impacts on public health and the environment.

Gene expression profiles and protein-protein interaction networks in THP-1 cells exposed to metal-based nanomaterials

We analyzed gene expression in THP-1 cells exposed to metal-based nanomaterials (NMs) [TiO2 (NM-100), ZnO (NM-110), SiO2 (NM-200), Ag (NM-300 K)]. A functional enrichment analysis of the significant differentially expressed genes (DEGs) identified the key modulated biological processes and pathways. DEGs were used to construct protein-protein interaction networks. NM-110 and NM-300 K induced changes in the expression of genes involved in oxidative and genotoxic stress, immune response, alterations of cell cycle, detoxification of metal ions and regulation of redox-sensitive pathways. Both NMs shared a number of highly connected protein nodes (hubs) including CXCL8, ATF3, HMOX1, and IL1B. NM-200 induced limited transcriptional changes, mostly related to the immune response; however, several hubs (CXCL8, ATF3) were identical with NM-110 and NM-300 K. No effects of NM-100 were observed. Overall, soluble nanomaterials NM-110 and NM-300 K exerted a wide variety of toxic effects, while insoluble NM-200 induced immunotoxicity; NM-100 caused no detectable changes on the gene expression level.

New methodological developments for testing the in vitro genotoxicity of nanomaterials: Comparison of 2D and 3D HepaRG liver cell models and classical and high throughput comet assay formats

Nanomaterials (NMs) are defined as materials with at least one external dimension below 100 nm. Their small size confers them interesting unique physico-chemical properties, hence NMs are increasingly used in a diversity of applications. However, the specific properties of NMs could also make them more harmful than their bulk counterparts. Therefore, there is a crucial need to deliver efficient NM hazard assessment in order to sustain the responsible development of nanotechnology. This study analysed the genotoxic potential of several NMs: one titanium dioxide (TiO2) and two zinc oxide NMs (ZnO) that were tested up to 100 μg/mL on 2D and 3D hepatic HepaRG models. Genotoxicity analysis was performed comparing the alkaline comet assay in classical and high throughput formats. Moreover, oxidative DNA lesions were investigated with the Fpg-modified comet assay. Results showed that TiO2 NMs were not cytotoxic and not genotoxic in either cell model, although a small increase in the % tail DNA was observed in 3D HepaRG cells at 100 μg/mL in the classical format. The two ZnO NMs (ZnO S. NMs a commercial suspension and NM110 provided by the European Union Joint Research Centre) induced a concentration-dependent increase in cytotoxicity that was more pronounced in the 2D (>20% cytotoxicity was observed for ZnO S. at concentrations greater than 25 μg/mL, and for NM 110 at 50 μg/mL) than in the 3D model (more than 20% cytotoxicity for ZnO S. NMs at 50 μg/mL). While ZnO S. NMs induced DNA damage associated with cytotoxicity (at 25 and 50 μg/mL in 2D and 50 μg/mL in 3D), NM110 showed a clear genotoxic effect at non-cytotoxic concentrations (25 μg/mL in 2D and at 25 and 50 μg/mL in 3D). No major differences could be observed in the comet assay in the presence or absence of the Fpg enzyme. High throughput analysis using CometChip® mostly confirmed the results obtained with the classical format, and even enhanced the detection of genotoxicity in the 3D model. In conclusion, this study demonstrated that new approach methodologies (NAMs), 3D models and the high throughput format for the comet assay, were more efficient in the detection of genotoxic effects, and are therefore promising approaches to improve hazard assessment of NMs.

Txnrd3 knockout enhancement of lung injury induced by Ni exposure via the VEGF-VEGFR-2 axis and alleviation of this effect by melatonin

Ni exposure leads to respiratory diseases in mice. Txnrd3 has been shown to have a protective effect on the body, but there is a paucity of empirical research focusing specifically on lung tissue. Melatonin possesses potent antioxidant, anti-inflammatory, and anti-fibrotic effects. By regulating inflammation-related factors, melatonin can activate the VEGF signaling pathway, ultimately alleviating lung injuries caused by Ni exposure. One hundred and sixty 8-week-old C57BL/6N mice, that were wild-type or Txnrd3-/- mice and 25-30 g in weight, were randomly divided into eight groups, including the NC group, Ni group, melatonin-treated group, and Ni plus melatonin group. Ni (10 mg/kg) was gavaged, and melatonin (2 mg/kg) was administered for 21 days. Inflammatory cells were found in the bronchioles of Txnrd3-/- mice under Ni exposure. Ultrastructural examination revealed that the homozygous-Ni group had a high amount of collagen fibers. The antioxidant capacity studies also revealed that mice lungs underwent oxidative stress. The results of qRT-PCR and WB showed that Ni induced an inflammatory response, which was also aggravated in Txnrd3-/- mice. Melatonin can effectively reduce the above symptoms. In conclusion, Ni causes lung injury by activating the VEGF-VEGFR-2 pathway and Txnrd3 knockout aggravates injury after Ni exposure.

Human and environmental impacts of nanoparticles: a scoping review of the current literature

Use of nanoparticles have established benefits in a wide range of applications, however, the effects of exposure to nanoparticles on health and the environmental risks associated with the production and use of nanoparticles are less well-established. The present study addresses this gap in knowledge by examining, through a scoping review of the current literature, the effects of nanoparticles on human health and the environment. We searched relevant databases including Medline, Web of Science, ScienceDirect, Scopus, CINAHL, Embase, and SAGE journals, as well as Google, Google Scholar, and grey literature from June 2021 to July 2021. After removing duplicate articles, the title and abstracts of 1495 articles were first screened followed by the full-texts of 249 studies, and this resulted in the inclusion of 117 studies in the presented review.In this contribution we conclude that while nanoparticles offer distinct benefits in a range of applications, they pose significant threats to humans and the environment. Using several biological models and biomarkers, the included studies revealed the toxic effects of nanoparticles (mainly zinc oxide, silicon dioxide, titanium dioxide, silver, and carbon nanotubes) to include cell death, production of oxidative stress, DNA damage, apoptosis, and induction of inflammatory responses. Most of the included studies (65.81%) investigated inorganic-based nanoparticles. In terms of biomarkers, most studies (76.9%) used immortalised cell lines, whiles 18.8% used primary cells as the biomarker for assessing human health effect of nanoparticles. Biomarkers that were used for assessing environmental impact of nanoparticles included soil samples and soybean seeds, zebrafish larvae, fish, and Daphnia magna neonates.From the studies included in this work the United States recorded the highest number of publications (n = 30, 25.64%), followed by China, India, and Saudi Arabia recording the same number of publications (n = 8 each), with 95.75% of the studies published from the year 2009. The majority of the included studies (93.16%) assessed impact of nanoparticles on human health, and 95.7% used experimental study design. This shows a clear gap exists in examining the impact of nanoparticles on the environment.

MMP-3-mediated cleavage of OPN is involved in copper oxide nanoparticle-induced activation of fibroblasts

BACKGROUND

Copper oxide nanoparticles (Nano-CuO) are one of the most produced and used nanomaterials. Previous studies have shown that exposure to Nano-CuO caused acute lung injury, inflammation, and fibrosis. However, the mechanisms underlying Nano-CuO-induced lung fibrosis are still unclear. Here, we hypothesized that exposure of human lung epithelial cells and macrophages to Nano-CuO would upregulate MMP-3, which cleaved osteopontin (OPN), resulting in fibroblast activation and lung fibrosis.

METHODS

A triple co-culture model was established to explore the mechanisms underlying Nano-CuO-induced fibroblast activation. Cytotoxicity of Nano-CuO on BEAS-2B, U937* macrophages, and MRC-5 fibroblasts were determined by alamarBlue and MTS assays. The expression or activity of MMP-3, OPN, and fibrosis-associated proteins was determined by Western blot or zymography assay. Migration of MRC-5 fibroblasts was evaluated by wound healing assay. MMP-3 siRNA and an RGD-containing peptide, GRGDSP, were used to explore the role of MMP-3 and cleaved OPN in fibroblast activation.

RESULTS

Exposure to non-cytotoxic doses of Nano-CuO (0.5 and 1 µg/mL) caused increased expression and activity of MMP-3 in the conditioned media of BEAS-2B and U937* cells, but not MRC-5 fibroblasts. Nano-CuO exposure also caused increased production of cleaved OPN fragments, which was abolished by MMP-3 siRNA transfection. Conditioned media from Nano-CuO-exposed BEAS-2B, U937*, or the co-culture of BEAS-2B and U937* caused activation of unexposed MRC-5 fibroblasts. However, direct exposure of MRC-5 fibroblasts to Nano-CuO did not induce their activation. In a triple co-culture system, exposure of BEAS-2B and U937* cells to Nano-CuO caused activation of unexposed MRC-5 fibroblasts, while transfection of MMP-3 siRNA in BEAS-2B and U937* cells significantly inhibited the activation and migration of MRC-5 fibroblasts. In addition, pretreatment with GRGDSP peptide inhibited Nano-CuO-induced activation and migration of MRC-5 fibroblasts in the triple co-culture system.

CONCLUSIONS

Our results demonstrated that Nano-CuO exposure caused increased production of MMP-3 from lung epithelial BEAS-2B cells and U937* macrophages, which cleaved OPN, resulting in the activation of lung fibroblasts MRC-5. These results suggest that MMP-3-cleaved OPN may play a key role in Nano-CuO-induced activation of lung fibroblasts. More investigations are needed to confirm whether these effects are due to the nanoparticles themselves and/or Cu ions.

Nickel oxide nanoparticles exposure as a risk factor for male infertility: "In vitro" effects on porcine pre-pubertal Sertoli cells

Lately, nickel oxide nanoparticles (NiO NPs) have been employed in different industrial and biomedical fields. Several studies have reported that NiO NPs may affect the development of reproductive organs inducing oxidative stress and, resulting in male infertility. We investigated the in vitro effects of NiO NPs on porcine pre-pubertal Sertoli cells (SCs) which undergone acute (24 h) and chronic (from 1 up to 3 weeks) exposure at two subtoxic doses of NiO NPs of 1 μg/ml and 5 μg/ml. After NiO NPs exposure we performed the following analysis: (a) SCs morphological analysis (Light Microscopy); (b) ROS production and oxidative DNA damage, gene expression of antioxidant enzymes (c) SCs functionality (AMH, inhibin B Real-time PCR analysis and ELISA test); (d) apoptosis (WB analysis); (e) pro-inflammatory cytokines (Real-time PCR analysis), and (f) MAPK kinase signaling pathway (WB analysis). We found that the SCs exposed to both subtoxic doses of NiO NPs didn't sustain substantial morphological changes. NiO NPs exposure, at each concentration, reported a marked increase of intracellular ROS at the third week of treatment and DNA damage at all exposure times. We demonstrated, un up-regulation of SOD and HO-1 gene expression, at both concentrations tested. The both subtoxic doses of NiO NPs detected a down-regulation of AMH and inhibin B gene expression and secreted proteins. Only the 5 μg/ml dose induced the activation of caspase-3 at the third week. At the two subtoxic doses of NiO NPs a clear pro-inflammatory response was resulted in an up-regulation of TNF-α and IL-6 in terms of mRNA. Finally, an increased phosphorylation ratio of p-ERK1/2, p-38 and p-AKT was observed up to the third week, at both concentrations. Our results show the negative impact of subtoxic doses NiO NPs chronic exposure on porcine SCs functionality and viability.

Developing Benign Ni/g-C3N4 Catalysts for CO2 Hydrogenation: Activity and Toxicity Study

This research discusses the CO₂ valorization via hydrogenation over the non-noble metal clusters of Ni and Cu supported on graphitic carbon nitride (g-C₃N₄). The Ni and Cu catalysts were characterized by conventional techniques including XRD, AFM, ATR, Raman imaging, and TPR and were tested via the hydrogenation of CO₂ at 1 bar. The transition-metal-based catalyst designed with atom-economy principles presents stable activity and good conversions for the studied processes. At 1 bar, the rise in operating temperature during CO₂ hydrogenation increases the CO₂ conversion and the selectivity for CO and decreases the selectivity for methanol on Cu/CN catalysts. For the Ni/CN catalyst, the selectivity to light hydrocarbons, such as CH₄, also increased with rising temperature. At 623 K, the conversion attained ca. 20%, with CH₄ being the primary product of the reaction (CH₄ yield >80%). Above 700 K, the Ni/CN activity increases, reaching almost equilibrium values, although the Ni loading in Ni/CN is lower by more than 90% compared to the reference NiREF catalyst. The presented data offer a better understanding of the effect of the transition metals’ small metal cluster and their coordination and stabilization within g-C₃N₄, contributing to the rational hybrid catalyst design with a less-toxic impact on the environment and health. Bare g-C₃N₄ is shown as a good support candidate for atom-economy-designed catalysts for hydrogenation application. In addition, cytotoxicity to the keratinocyte human HaCaT cell line revealed that low concentrations of catalysts particles (to 6.25 μg mL^–1) did not cause degenerative changes.

Nanoparticle Effects on Stress Response Pathways and Nanoparticle-Protein Interactions

Nanoparticles (NPs) are increasingly used in a wide variety of applications and products; however, NPs may affect stress response pathways and interact with proteins in biological systems. This review article will provide an overview of the beneficial and detrimental effects of NPs on stress response pathways with a focus on NP-protein interactions. Depending upon the particular NP, experimental model system, and dose and exposure conditions, the introduction of NPs may have either positive or negative effects. Cellular processes such as the development of oxidative stress, the initiation of the inflammatory response, mitochondrial function, detoxification, and alterations to signaling pathways are all affected by the introduction of NPs. In terms of tissue-specific effects, the local microenvironment can have a profound effect on whether an NP is beneficial or harmful to cells. Interactions of NPs with metal-binding proteins (zinc, copper, iron and calcium) affect both their structure and function. This review will provide insights into the current knowledge of protein-based nanotoxicology and closely examines the targets of specific NPs.

Systematic review on primary and secondary genotoxicity of carbon black nanoparticles in mammalian cells and animals

Carbon black exposure causes oxidative stress, inflammation and genotoxicity. The objective of this systematic review was to assess the contributions of primary (i.e. direct formation of DNA damage) and secondary genotoxicity (i.e., DNA lesions produced indirectly by inflammation) to the overall level of DNA damage by carbon black. The database is dominated by studies that have measured DNA damage by the comet assay. Cell culture studies indicate a genotoxic action of carbon black, which might be mediated by oxidative stress. Many in vivo studies originate from one laboratory that has investigated the genotoxic effects of Printex 90 in mice by intra-tracheal instillation. Meta-analysis and pooled analysis of these results demonstrate that Printex 90 exposure is associated with a slightly increased level of DNA strand breaks in bronchoalveolar lavage cells and lung tissue. Other types of genotoxic damage have not been investigated as thoroughly as DNA strand breaks, although there is evidence to suggest that carbon black exposure might increase the mutation frequency and cytogenetic endpoints. Stratification of studies according to concurrent inflammation and DNA damage does not indicate that carbon black exposure gives rise to secondary genotoxicity. Even substantial pulmonary inflammation is at best only associated with a weak genotoxic response in lung tissue. In conclusion, the review indicates that nanosized carbon black is a weak genotoxic agent and this effect is more likely to originate from a primary genotoxic mechanism of action, mediated by e.g., oxidative stress, than inflammation-driven (secondary) genotoxicity.

The application of existing genotoxicity methodologies for grouping of nanomaterials: towards an integrated approach to testing and assessment

The incorporation of nanomaterials (NMs) in consumer products has proven to be highly valuable in many sectors. Unfortunately, however, the same nano specific physicochemical properties, which make these material attractive, might also contribute to hazards for people exposed to these materials. The physicochemical properties of NMs will impact their interaction with biological surroundings and influence their fate and their potential adverse effects such as genotoxicity. Due to the large and expanding number of NMs produced, their availability in different nanoforms (NFs) and their utilization in various formats, it is impossible for risk assessment to be conducted on an individual NF basis. Alternative methods, such as grouping are needed for streamlining hazard assessment. The GRACIOUS Framework provides a logical and science evidenced approach to group similar NFs, allowing read-across of hazard information from source NFs (or non-NFs) with adequate hazard data to target NFs that lack such data. Here, we propose a simple three-tiered testing strategy to gather evidence to determine whether different NFs are sufficiently similar with respect to their potential to induce genotoxicity, in order to be grouped. The tiered testing strategy includes simple in vitro models as well as a number of alternative more complex multi-cellular in vitro models to allow for a better understanding of secondary NM-induced DNA damage, something that has been more appropriate in vivo until recently.

Primary and Secondary Genotoxicity of Nanoparticles: Establishing a Co-Culture Protocol for Assessing Micronucleus Using Flow Cytometry

Genotoxicity is an important endpoint to assess for understanding the risks associated with nanoparticles (NPs). Most genotoxicity studies performed on NPs have focused on primary genotoxicity analyzed by comet- or micronuclei (MN) assay using microscopic scoring. Here, we established a protocol for a more efficient version of MN assessment using flow cytometry and, importantly, both primary and secondary (inflammation-driven) genotoxicity was assessed. Human bronchial epithelial cells (HBEC-3kt) were exposed to nickel oxide (NiO) NPs directly or indirectly. The indirect exposure was done to assess secondary genotoxicity, and in this case immune cells (THP-1 derived macrophages) were exposed on inserts and the HBEC were cultured in the lower compartment. The results in monocultures showed that no increased MN formation was observed in the HBEC cells but instead a clear MN induction was noted in THP-1 cells indicating higher sensitivity. No MN formation was either observed when the HBEC were indirectly exposed, but an increase in DNA strand breaks was detected using the comet assay. Taken together, the present study emphasizes the feasibility of assessing primary and secondary genotoxicity and, furthermore, shows a clear MN induction in THP-1 monoculture following NiO NPs exposure.

Effect of Atmospheric Aging on Soot Particle Toxicity in Lung Cell Models at the Air–Liquid Interface: Differential Toxicological Impacts of Biogenic and Anthropogenic Secondary Organic Aerosols (SOAs)

Background:

Secondary organic aerosols (SOAs) formed from anthropogenic or biogenic gaseous precursors in the atmosphere substantially contribute to the ambient fine particulate matter [PM ≤2.5μm in aerodynamic diameter (PM2.5)] burden, which has been associated with adverse human health effects. However, there is only limited evidence on their differential toxicological impact.

Objectives:

We aimed to discriminate toxicological effects of aerosols generated by atmospheric aging on combustion soot particles (SPs) of gaseous biogenic (β-pinene) or anthropogenic (naphthalene) precursors in two different lung cell models exposed at the air–liquid interface (ALI).

Methods:

Mono- or cocultures of lung epithelial cells (A549) and endothelial cells (EA.hy926) were exposed at the ALI for 4 h to different aerosol concentrations of a photochemically aged mixture of primary combustion SP and β-pinene (SOAβPIN-SP) or naphthalene (SOANAP-SP). The internally mixed soot/SOA particles were comprehensively characterized in terms of their physical and chemical properties. We conducted toxicity tests to determine cytotoxicity, intracellular oxidative stress, primary and secondary genotoxicity, as well as inflammatory and angiogenic effects.

Results:

We observed considerable toxicity-related outcomes in cells treated with either SOA type. Greater adverse effects were measured for SOANAP-SP compared with SOAβPIN-SP in both cell models, whereas the nano-sized soot cores alone showed only minor effects. At the functional level, we found that SOANAP-SP augmented the secretion of malondialdehyde and interleukin-8 and may have induced the activation of endothelial cells in the coculture system. This activation was confirmed by comet assay, suggesting secondary genotoxicity and greater angiogenic potential. Chemical characterization of PM revealed distinct qualitative differences in the composition of the two secondary aerosol types.

Discussion:

In this study using A549 and EA.hy926 cells exposed at ALI, SOA compounds had greater toxicity than primary SPs. Photochemical aging of naphthalene was associated with the formation of more oxidized, more aromatic SOAs with a higher oxidative potential and toxicity compared with β-pinene. Thus, we conclude that the influence of atmospheric chemistry on the chemical PM composition plays a crucial role for the adverse health outcome of emissions. https://doi.org/10.1289/EHP9413

NiONPs-induced alteration in calcium signaling and mitochondrial function in pulmonary artery endothelial cells involves oxidative stress and TRPV4 channels disruption

In New Caledonia, anthropic activities, such as mining, increase the natural erosion of soils in nickel mines, which in turn, releases nickel oxide nanoparticles (NiONPs) into the atmosphere. Pulmonary vascular endothelial cells represent one of the primary targets for inhaled nanoparticles. The objective of this in vitro study was to assess the cytotoxic effects of NiONPs on human pulmonary artery endothelial cells (HPAEC). Special attention will be given to the level of oxidative stress and calcium signaling, which are involved in the physiopathology of cardiovascular diseases. HPAEC were exposed to NiONPs (0.5-150 μg/cm²) for 4 or 24 h. The following different endpoints were studied: (i) ROS production using CM-H₂DCF-DA probe, electron spin resonance, and MitoSOX probe; the SOD activity was also measured (ii) calcium signaling with Fluo4-AM, Rhod-2, and Fluo4-FF probes; (iii) inflammation by IL-6 production and secretion and, (iv) mitochondrial dysfunction and apoptosis with TMRM and MitoTracker probes, and AnnexinV/PI. Our results have evidenced that NiONPs induced oxidative stress in HPAEC. This was demonstrated by an increase in ROS production and a decrease in SOD activity, the two mechanisms seem to trigger a pro-inflammatory response with IL-6 secretion. In addition, NiONPs exposure altered calcium homeostasis inducing an increased cytosolic calcium concentration ([Ca²⁺]_i) that was significantly reduced by the extracellular calcium chelator EGTA and the TRPV4 inhibitor HC-067047. Interestingly, exposure to NiONPs also altered TRPV4 activity. Finally, HPAEC exposure to NiONPs increased intracellular levels of both ROS and calcium ([Ca²⁺]_m) in mitochondria, leading to mitochondrial dysfunction and HPAEC apoptosis.

Exploring graphene-based materials' genotoxicity: inputs of a screening method

Graphene-based materials (GBMs) are promising nanomaterials, and several innovations depend on their use. However, the assessment of their potential hazard must be carefully explored before entering any market. GBMs are indeed well-known to induce various biological impacts, including oxidative stress, which can potentially lead to DNA damage. Genotoxicity is a major endpoint for hazard assessment and has been explored for GBMs, but the available literature shows conflicting results. In this study, we assessed the genotoxicity of 13 various GBMs, one carbon black and one amorphous silica through a DNA damage response assay (using a human respiratory cell model, BEAS-2B). Concurrently, oxidative stress was assessed through a ROS production quantification (DCFH-DA assay using a murine macrophage model, RAW 264.7). We also performed a full physicochemical characterization of our samples to explore potential structure-activity relationships involving genotoxicity. We observed that surface oxidation appears linked to genotoxicity response and were able to distinguish several groups within our studied GBMs showing different genotoxicity results. Our findings highlight the necessity to individually consider each nanoform of GBMs since the tested samples showed various results and modes of action. We propose this study as a genotoxicity assessment using a high-throughput screening method and suggest few hypotheses concerning the genotoxicity mode of action of GBMs.

Toxicity evaluation of particles formed during 3D-printing: Cytotoxic, genotoxic, and inflammatory response in lung and macrophage models

Additive manufacturing (AM) or "3D-printing" is a ground-breaking technology that enables the production of complex 3D parts. Its rapid growth calls for immediate toxicological investigations of possible human exposures in order to estimate occupational health risks. Several laser-based powder bed fusion AM techniques are available of which many use metal powder in the micrometer range as feedstock. Large energy input from the laser on metal powders generates several by-products, like spatter and condensate particles. Due to often altered physicochemical properties and composition, spatter and condensate particles can result in different toxicological responses compared to the original powder particles. The toxicity of such particles has, however, not yet been investigated. The aim of the present study was to investigate the toxicity of condensate/spatter particles formed and collected upon selective laser melting (SLM) printing of metal alloy powders, including a nickel-chromium-based superalloy (IN939), a nickel-based alloy (Hastelloy X, HX), a high-strength maraging steel (18Ni300), a stainless steel (316L), and a titanium alloy (Ti6Al4V). Toxicological endpoints investigated included cytotoxicity, generation of reactive oxygen species (ROS), genotoxicity (comet and micronucleus formation), and inflammatory response (cytokine/chemokine profiling) following exposure of human bronchial epithelial cells (HBEC) or monocytes/macrophages (THP-1). The results showed no or minor cytotoxicity in the doses tested (10-100 μg/mL). Furthermore, no ROS generation or formation of micronucleus was observed in the HBEC cells. However, an increase in DNA strand breaks (detected by comet assay) was noted in cells exposed to HX, IN939, and Ti6Al4V, whereas no evident release of pro-inflammatory cytokine was observed from macrophages. Particle and surface characterization showed agglomeration in solution and different surface oxide compositions compared to the nominal bulk content. The extent of released nickel was small and related to the nickel content of the surface oxides, which was largely different from the bulk content. This may explain the limited toxicity found despite the high Ni bulk content of several powders. Taken together, this study suggests relatively low acute toxicity of condensates/spatter particles formed during SLM-printing using IN939, HX, 18Ni300, 316L, and Ti6Al4V as original metal powders.

MMP-3 activation is involved in copper oxide nanoparticle-induced epithelial-mesenchymal transition in human lung epithelial cells

Copper oxide nanoparticles (Nano-CuO) are widely used in medical and industrial fields and our daily necessities. However, the biosafety assessment of Nano-CuO is far behind their rapid development. Here, we investigated the adverse effects of Nano-CuO on normal human bronchial epithelial BEAS-2B cells, especially determined whether Nano-CuO exposure would cause dysregulation of MMP-3, an important mediator in pulmonary fibrosis, and its potential role in epithelial-mesenchymal transition (EMT). Our results showed that exposure to Nano-CuO, but not Nano-TiO₂, caused increased ROS generation, MAPKs activation, and MMP-3 upregulation. Nano-CuO-induced ROS generation was not observed in mitochondrial DNA-depleted BEAS-2B ρ⁰ cells, indicating that mitochondria may be the main source of Nano-CuO-induced ROS generation. Pretreatment of the cells with ROS scavengers or inhibitors or depleting mitochondrial DNA significantly attenuated Nano-CuO-induced MAPKs activation and MMP-3 upregulation, and pretreatment of cells with MAPKs inhibitors abolished Nano-CuO-induced MMP-3 upregulation, suggesting Nano-CuO-induced MMP-3 upregulation is through Nano-CuO-induced ROS generation and MAPKs activation. In addition, exposure of the cells to Nano-CuO for 48 h resulted in decreased E-cadherin expression and increased expression of vimentin, α-SMA, and fibronectin, which was ameliorated by MMP-3 siRNA transfection, suggesting an important role of MMP-3 in Nano-CuO-induced EMT. Taken together, our study demonstrated that Nano-CuO exposure caused mitochondrial ROS generation, MAPKs activation, and MMP-3 upregulation. Nano-CuO exposure also caused cells to undergo EMT, which was through Nano-CuO-induced dysregulation of ROS/MAPKs/MMP-3 pathway. Our findings will provide further understanding of the potential mechanisms involved in metal nanoparticle-induced various toxic effects including EMT and pulmonary fibrosis.

Pro-inflammatory response and genotoxicity caused by clay and graphene nanomaterials in A549 and THP-1 cells

Nanoclays and graphene oxide nanomaterials represent a class of materials sharing similar shapes constituted of high aspect ratio platelets. The increased production of these materials for various industrial applications increases the risk of occupational exposure, consequently with elevated risk of adverse reactions and development of pulmonary diseases, including lung cancer. In this study, pro-inflammatory responses and genotoxicity were assessed in alveolar epithelial cells (A549) and activated THP-1 macrophages (THP-1a) after exposure to three nanoclays; a pristine (Bentonite) and two surface modified (benzalkonium chloride-coated Nanofil9, and dialkyldimethyl-ammonium-coated NanofilSE3000); graphene oxide (GO) and reduced graphene oxide (r-GO) nanomaterials. The pro-inflammatory response in terms of IL-8 expression was strongest in cells exposed to Bentonite, whereas surface modification resulted in decreased toxicity in both cell lines when exposed to Nanofil9 and NanofilSE3000. GO and r-GO induced a pro-inflammatory response in A549 cells, while no effect was detected with the two nanomaterials on THP-1a cells. The pro-inflammatory response was strongly correlated with in vivo inflammation in mice after intra-tracheal instillation when doses were normalized against surface area. Genotoxicity was assessed as DNA strand breaks, using the alkaline comet assay. In A549 cells, an increase in DNA strand breaks was detected only in cells exposed to Bentonite, whereas Bentonite, NanofilSE3000 and GO caused an increased level of genotoxicity in THP-1a cells. Genotoxicity in THP-1a cells was concordant with the DNA damage in bronchoalveolar lavage fluid cells following 1 and 3 days after intra-tracheal instillation in mice. In conclusion, this study shows that surface modification of pristine nanoclays reduces the inflammatory and genotoxic response in A549 and THP-1a cells, and these in vitro models show comparable toxicity to what seen in previous mouse studies with the same materials.

Investigating the Molecular Processes behind the Cell-Specific Toxicity Response to Titanium Dioxide Nanobelts

Some engineered nanomaterials incite toxicological effects, but the underlying molecular processes are understudied. The varied physicochemical properties cause different initial molecular interactions, complicating toxicological predictions. Gene expression data allow us to study the responses of genes and biological processes. Overrepresentation analysis identifies enriched biological processes using the experimental data but prompts broad results instead of detailed toxicological processes. We demonstrate a targeted filtering approach to compare public gene expression data for low and high exposure on three cell lines to titanium dioxide nanobelts. Our workflow finds cell and concentration-specific changes in affected pathways linked to four Gene Ontology terms (apoptosis, inflammation, DNA damage, and oxidative stress) to select pathways with a clear toxicity focus. We saw more differentially expressed genes at higher exposure, but our analysis identifies clear differences between the cell lines in affected processes. Colorectal adenocarcinoma cells showed resilience to both concentrations. Small airway epithelial cells displayed a cytotoxic response to the high concentration, but not as strongly as monocytic-like cells. The pathway-gene networks highlighted the gene overlap between altered toxicity-related pathways. The automated workflow is flexible and can focus on other biological processes by selecting other GO terms.

Exposure effects of inhaled nickel nanoparticles on the male reproductive system via mitochondria damage

Nickel nanoparticles (Ni NPs) have a wide range of application prospects, however there is still a lack of their safety evaluation for the reproductive system. Nowadays, male reproductive health has been widely concerned for the increasing incidence of male infertility. To investigate the male reproductive toxicity induced by Ni NPs and its relation with the mitochondrial fission and mitophagy, male mice were administered with or without 5, 15, and 45 mg/kg of Ni NPs by intratracheal instillation. At the end of intervention, sex hormone level, sperm abnormality rate, pathological morphology of testis, cell apoptosis and the expression levels of Drp1, Pink1 and Parkin proteins in testis tissues were detected. The results indicated that the rate of sperm deformity and serum levels of reproductive hormones increased obviously with the increasing concentrations of Ni NPs. Testicular spermatogenic cells were damaged and the number of apoptotic cells increased significantly. Furthermore, the expressions of key proteins (Drp1, Pink1 and Parkin) related to mitochondrial fission/autophagy in testis tissues also increased after exposure to Ni NPs. Collectively, mitochondria damage may play an important role in male mice reproductive toxicity induced by the intratracheal instillation of Ni NPs.

Uterine pyruvate metabolic disorder induced by silica nanoparticles act through the pentose phosphate pathway

Silica nanoparticles (SiNPs) have drawn considerable attention due to their environmental health effects, while enhanced understanding of metabolic disorders has provided insight into related diseases. To investigate the impacts of SiNPs exposure on reproduction and reveal their pathogenic mechanisms, this study was designed and conducted from a metabolic perspective. First, fluorescein isothiocyanate (FITC)-SiNPs were chemically synthesized and applied to track SiNPs in vitro and in vivo. Next, 30 pregnant mice were intratracheally instilled with 1.25 mg of SiNPs/mouse, then sacrificed 24 h post-treatment. We found that SiNPs penetrated the trophoblast membrane, triggering apoptosis and inhibiting cell proliferation, invasion, and tube formation in a dose-dependent manner. Mechanistically, SiNPs dysregulated phosphofructokinase (Pfkl) and fructose-bisphosphatase 2 (Fbp2) and induced glucose depletion and pyruvate accumulation via the pentose phosphate pathway. Besides, the downregulation of caspase-3 suggested a causal relationship between pyruvate accumulation, pentose phosphate pathway activation, and cell apoptosis. Pfkl and Fbp2 was also dysregulated in vivo, and the uterine inflammation aggravated in a time-dependent manner. In conclusion, SiNPs triggered acute cytotoxicity and uterine inflammation by inducing glucose depletion and pyruvate overload in trophoblasts, which were mediated in part by Pfkl and Fbp2 via the pentose phosphate pathway.

Adverse Outcome Pathway Development for Assessment of Lung Carcinogenicity by Nanoparticles

Lung cancer, one of the most common and deadly forms of cancer, is in some cases associated with exposure to certain types of particles. With the rise of nanotechnology, there is concern that some engineered nanoparticles may be among such particles. In the absence of epidemiological evidence, assessment of nanoparticle carcinogenicity is currently performed on a time-consuming case-by-case basis, relying mainly on animal experiments. Non-animal alternatives exist, including a few validated cell-based methods accepted for regulatory risk assessment of nanoparticles. Furthermore, new approach methodologies (NAMs), focused on carcinogenic mechanisms and capable of handling the increasing numbers of nanoparticles, have been developed. However, such alternative methods are mainly applied as weight-of-evidence linked to generally required animal data, since challenges remain regarding interpretation of the results. These challenges may be more easily overcome by the novel Adverse Outcome Pathway (AOP) framework, which provides a basis for validation and uptake of alternative mechanism-focused methods in risk assessment. Here, we propose an AOP for lung cancer induced by nanosized foreign matter, anchored to a selection of 18 standardized methods and NAMs for in silico- and in vitro-based integrated assessment of lung carcinogenicity. The potential for further refinement of the AOP and its components is discussed in relation to available nanosafety knowledge and data. Overall, this perspective provides a basis for development of AOP-aligned alternative methods-based integrated testing strategies for assessment of nanoparticle-induced lung cancer.

A link between nanoparticles and Parkinson's disease. Which nanoparticles are most harmful?

Nowadays, different kinds of nanoparticles (NPs) are produced around the world and used in many fields and products. NPs can enter the body and aggregate in the various organs including brain. They can damage neurons, in particular dopaminergic neurons in the substantia nigra (SN) and striatal neurons which their lesion is associated with Parkinson's disease (PD). So, NPs can have a role in PD induction along with other agents and factors. PD is the second most common neurodegenerative disease in the world, and in patients, its symptoms progressively worsen day by day through different pathways including oxidative stress, neuroinflammation, mitochondrial dysfunction, α-synuclein increasing and aggregation, apoptosis and reduction of tyrosine hydroxylase positive cells. Unfortunately, there is no effective treatment for PD. So, prevention of this disease is very important. On the other hand, without having sufficient information about PD inducers, prevention of this disease would not be possible. Therefore, we need to have sufficient information about things we contact with them in daily life. Since, NPs are widely used in different products especially in consumer products, and they can enter to the brain easily, in this review the toxicity effects of metal and metal oxide NPs have been evaluated in molecular and cellular levels to determine potential of different kinds of NPs in development of PD.

Application of Nanotechnology in Wood-Based Products Industry: A Review

Wood-based industry is one of the main drivers of economic growth in Malaysia. Forest being the source of various lignocellulosic materials has many untapped potentials that could be exploited to produce sustainable and biodegradable nanosized material that possesses very interesting features for use in wood-based industry itself or across many different application fields. Wood-based products sector could also utilise various readily available nanomaterials to enhance the performance of existing products or to create new value added products from the forest. This review highlights recent developments in nanotechnology application in the wood-based products industry.

Effect and mechanism of PI3K/AKT/mTOR signaling pathway in the apoptosis of GC-1 cells induced by nickel nanoparticles

Nickel nanoparticles (Ni NPs) have a wide range of application prospects, but there is still a lack of their safety evaluation for the reproductive system. Nowadays, male reproductive health has been widely concerned because of the increasing incidence of male infertility. Studies have shown that Ni NPs can cause male reproductive toxicity. The purpose of this study was to investigate the toxicity of Ni NPs on GC-1 cells, a mouse spermatogonia cell line, and to explore the possible mechanism underlying the induction of apoptosis via PI3K/AKT/mTOR signaling pathway. The cell ultrastructure was firstly observed under a transmission electron microscope. Then, cell proliferation, cycle and apoptosis were detected by CCK-8 and flow cytometry, respectively. Furthermore, the expression levels of related proteins and genes were determined by Western blot and Reverse transcription-polymerase chain reaction, respectively. The results showed that Ni NPs could not only cause changes in cell ultrastructure, decreased survival rate and arrested G1 phase cell cycle, but also activated apoptosis pathway by inhibiting the PI3K/AKT/mTOR signaling pathway. The results of this study provide novel insights to explore the mechanisms of reproductive toxicity of Ni NPs and are of great significance to develop safety evaluation criteria for Ni NPs.

Transcriptome Profiling and Toxicity Following Long-Term, Low Dose Exposure of Human Lung Cells to Ni and NiO Nanoparticles-Comparison with NiCl2

Production of nickel (Ni) and nickel oxide (NiO) nanoparticles (NPs) leads to a risk of exposure and subsequent health effects. Understanding the toxicological effects and underlying mechanisms using relevant in vitro methods is, therefore, needed. The aim of this study is to explore changes in gene expression using RNA sequencing following long term (six weeks) low dose (0.5 µg Ni/mL) exposure of human lung cells (BEAS-2B) to Ni and NiO NPs as well as soluble NiCl₂. Genotoxicity and cell transformation as well as cellular dose of Ni are also analyzed. Exposure to NiCl₂ resulted in the largest number of differentially expressed genes (197), despite limited uptake, suggesting a major role of extracellular receptors and downstream signaling. Gene expression changes for all Ni exposures included genes coding for calcium-binding proteins (S100A14 and S100A2) as well as TIMP3, CCND2, EPCAM, IL4R and DDIT4. Several top enriched pathways for NiCl₂ were defined by upregulation of, e.g., interleukin-1A and -1B, as well as Vascular Endothelial Growth Factor A (VEGFA). All Ni exposures caused DNA strand breaks (comet assay), whereas no induction of micronuclei was observed. Taken together, this study provides an insight into Ni-induced toxicity and mechanisms occurring at lower and more realistic exposure levels.