Structure Activity Relationships of Engineered Nanomaterials in inducing NLRP3 Inflammasome Activation and Chronic Lung Fibrosis

The role of lysosomes in airborne particulate matter-induced pulmonary toxicity

An investigation of the potential role of lysosomes in airborne particulate matter (APM) induced health risks is essential to fully comprehend the pathogenic mechanisms of respiratory diseases. It is commonly accepted that APM-induced lung injury is caused by oxidative stress, inflammatory responses, and DNA damage. In addition, there exists abundant evidence that changes in lysosomal function are essential for cellular adaptation to a variety of particulate stimuli. This review emphasizes that disruption of the lysosomal structure/function is a key step in the cellular metabolic imbalance induced by APMs. After being ingested by cells, most particles are localized within lysosomes. Thus, lysosomes become the primary locus where APMs accumulate, and here they undergo degradation and release toxic components. Recent studies have provided incontrovertible evidence that a wide variety of APMs interfere with the normal function of lysosomes. After being stimulated by APMs, lysosome rupture leads to a loss of lysosomal acidic conditions and the inactivation of proteolytic enzymes, promoting an inflammatory response by activating the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. Moreover, APMs interfere with autophagosome production or block autophagic flux, resulting in autophagy dysfunction. Additionally, APMs disrupt the normal function of lysosomes in iron metabolism, leading to disruption on iron homeostasis. Therefore, understanding the impacts of APM exposure from the perspective of lysosomes will provide new insights into the detrimental consequences of air pollution.

Graphene-Based Material-Mediated Immunomodulation in Tissue Engineering and Regeneration: Mechanism and Significance

Tissue engineering and regenerative medicine hold promise for improving or even restoring the function of damaged organs. Graphene-based materials (GBMs) have become a key player in biomaterials applied to tissue engineering and regenerative medicine. A series of cellular and molecular events, which affect the outcome of tissue regeneration, occur after GBMs are implanted into the body. The immunomodulatory function of GBMs is considered to be a key factor influencing tissue regeneration. This review introduces the applications of GBMs in bone, neural, skin, and cardiovascular tissue engineering, emphasizing that the immunomodulatory functions of GBMs significantly improve tissue regeneration. This review focuses on summarizing and discussing the mechanisms by which GBMs mediate the sequential regulation of the innate immune cell inflammatory response. During the process of tissue healing, multiple immune responses, such as the inflammatory response, foreign body reaction, tissue fibrosis, and biodegradation of GBMs, are interrelated and influential. We discuss the regulation of these immune responses by GBMs, as well as the immune cells and related immunomodulatory mechanisms involved. Finally, we summarize the limitations in the immunomodulatory strategies of GBMs and ideas for optimizing GBM applications in tissue engineering. This review demonstrates the significance and related mechanism of the immunomodulatory function of GBM application in tissue engineering; more importantly, it contributes insights into the design of GBMs to enhance wound healing and tissue regeneration in tissue engineering.

Pulmonary hazard identifications of Graphene family nanomaterials: Adverse outcome pathways framework based on toxicity mechanisms

Graphene-family nanomaterials (GFNs) are revolutionary new nanomaterials that have attracted significant attention in the field of nanomaterials, but the ensuing problems lie in the potential threats to public health and the ecosystem caused by these nanomaterials. From the perspective of GFN-related health risk assessments, this study reviews the current status of GFN-induced pathological lung events with a focus on the damage caused to different biological moieties (molecular, cellular, tissue, and organ) and the mechanistic relationships between different toxic endpoints. These multiple sites of damage were matched with existing adverse outcome pathways (AOPs) in an online knowledge base to obtain available molecular initiation events (MIEs), key events (KEs), and adverse outcomes (AOs). Among them, the MIEs were discussed in combination with the structure-activity relationship due to the correlation between toxicity and physical and chemical properties of GFNs. Based on the collection of information regarding MIEs, Kes, and AOs in addition to upstream and downstream causal extrapolation, the AOP framework for GFN-induced pulmonary toxicity was developed, highlighting the possible mechanisms of GFN-induced lung damage. This review intended to combine AOP with classic toxicological methods with a view to rapidly and accurately establishing a nanotoxicology infrastructure so as to contribute to public health risk assessment strategies through iteration from and animal models up to the population level.

Genotoxic effects of occupational exposure to glass fibres - A human biomonitoring study

As part of a large human biomonitoring study, we conducted occupational monitoring in a glass fibre factory in Slovakia. Shopfloor workers (n = 80), with a matched group of administrators in the same factory (n = 36), were monitored for exposure to glass fibres and to polycyclic aromatic hydrocarbons (PAHs). The impact of occupational exposure on chromosomal aberrations, DNA damage and DNA repair, immunomodulatory markers, and the role of nutritional and lifestyle factors, as well as the effect of polymorphisms in metabolic and DNA repair genes on genetic stability, were investigated. The (enzyme-modified) comet assay was employed to measure DNA strand breaks (SBs) and apurinic sites, oxidised and alkylated bases. Antioxidant status was estimated by resistance to H₂O₂-induced DNA damage. Base excision repair capacity was measured with an in vitro assay (based on the comet assay). Exposure of workers to fibres was low, but still was associated with higher levels of SBs, and SBs plus oxidised bases, and higher sensitivity to H₂O₂. Multivariate analysis showed that exposure increased the risk of high levels of SBs by 20%. DNA damage was influenced by antioxidant enzymes catalase and glutathione S-transferase (measured in blood). DNA repair capacity was inversely correlated with DNA damage and positively with antioxidant status. An inverse correlation was found between DNA base oxidation and the percentage of eosinophils (involved in the inflammatory response) in peripheral blood of both exposed and reference groups. Genotypes of XRCC1 variants rs3213245 and rs25487 significantly decreased the risk of high levels of base oxidation, to 0.50 (p = 0.001) and 0.59 (p = 0.001), respectively. Increases in DNA damage owing to glass fibre exposure were significant but modest, and no increases were seen in chromosome aberrations or micronuclei. However, it is of concern that even low levels of exposure to these fibres can cause significant genetic damage.

About the Transient Effects of Synthetic Amorphous Silica: An In Vitro Study on Macrophages

Silica (either crystalline or amorphous) is widely used for different applications and its toxicological assessment depends on its characteristics and intended use. As sustained inflammation induced by crystalline silica is at the root of silicosis, investigating the inflammatory effects induced by amorphous silicas and their persistence is needed. For the development of new grades of synthetic amorphous silicas, it is also desirable to be able to understand better the factors underlying potential adverse effects. Therefore, we used an optimized in vitro macrophage system to investigate the effects of amorphous silicas, and their persistence. By using different amorphous silicas, we demonstrated that the main driver for the adverse effects is a low size of the overall particle/agglomerate; the second driver being a low size of the primary particle. We also demonstrated that the effects were transient. By using silicon dosage in cells, we showed that the transient effects are coupled with a decrease of intracellular silicon levels over time after exposure. To further investigate this phenomenon, a mild enzymatic cell lysis allowed us to show that amorphous silicas are degraded in macrophages over time, explaining the decrease in silicon content and thus the transiency of the effects of amorphous silicas on macrophages.

Mechanisms of cell injury induced by inhaled molybdenum trioxide nanoparticles in Golden Syrian Hamsters

Molybdenum trioxide nanoparticles (MoO₃ NPs) are extensively used in the biomedical, agricultural, and engineering fields that may increase exposure and adverse health effects to the human population. The purpose of this study is to evaluate a possible molecular mechanism leading to cell damage and death following pulmonary exposure to inhaled MoO₃ NPs. Animals were separated into four groups: two control groups exposed to room air or aerosolized water and two treated groups exposed to aerosolized MoO₃ NPs with a concentration of 5 mg/m³ NPs (4 h/day for eight days) and given a one-day (T-1) or seven-day (T-7) recovery period post exposure. Pulmonary toxicity was evaluated with total and differential cell counts. Increases were seen in total cell numbers, neutrophils, and multinucleated macrophages in the T-1 group, with increases in lymphocytes in the T-7 group (*P < 0.05). To evaluate the mechanism of toxicity, protein levels of Beclin-1, light chain 3 (LC3)-I/II, P-62, cathepsin B, NLRP3, ASC, caspase-1, interleukin (IL)-1β, and tumor necrosis factor-α (TNF-α) were assessed in lung tissue. Immunoblot analyses indicated 1.4- and 1.8-fold increases in Beclin-1 in treated groups (T-1 and T-7, respectively, *P < 0.05), but no change in protein levels of LC3-I/II in either treated group. The levels of cathepsin B were 2.8- and 2.3-fold higher in treated lungs (T-1 and T-7, respectively, *P < 0.05), the levels of NLRP3 had a fold increase of 2.5 and 3.6 (T-1 *P < 0.05, T-7 **P < 0.01, respectively), and the levels of caspase-1 indicated a 3.8- and 3.0-fold increase in treated lungs (T-1 and T-7, respectively, *P < 0.05). Morphological changes were studied using light and electron microscopy showing alterations to airway epithelium and the alveoli, along with particle internalization in macrophages. The results from this study may indicate that inhalation exposure to MoO₃ NPs may interrupt the autophagic flux and induce cytotoxicity and lung injury through pyroptosis cell death and activation of caspase-1.

Diverse Pathways of Engineered Nanoparticle-Induced NLRP3 Inflammasome Activation

With the rapid development of engineered nanomaterials (ENMs) in biomedical applications, their biocompatibility and cytotoxicity need to be evaluated properly. Recently, it has been demonstrated that inflammasome activation may be a vital contributing factor for the development of biological responses induced by ENMs. Among the inflammasome family, NLRP3 inflammasome has received the most attention because it directly interacts with ENMs to cause the inflammatory effects. However, the pathways that link ENMs to NLRP3 inflammasome have not been thoroughly summarized. Thus, we reviewed recent findings on the role of major ENMs properties in modulating NLRP3 inflammasome activation, both in vitro and in vivo, to provide a better understanding of the underlying mechanisms. In addition, the interactions between ENMs and NLRP3 inflammasome activation are summarized, which may advance our understanding of safer designs of nanomaterials and ENM-induced adverse health effects.

Grouping MWCNTs based on their similar potential to cause pulmonary hazard after inhalation: a case-study

BACKGROUND

The EU-project GRACIOUS developed an Integrated Approach to Testing and Assessment (IATA) to support grouping high aspect ratio nanomaterials (HARNs) presenting a similar inhalation hazard. Application of grouping reduces the need to assess toxicity on a case-by-case basis and supports read-across of hazard data from substances that have the data required for risk assessment (source) to those that lack such data (target). The HARN IATA, based on the fibre paradigm for pathogenic fibres, facilitates structured data gathering to propose groups of similar HARN and to support read-across by prompting users to address relevant questions regarding HARN morphology, biopersistence and inflammatory potential. The IATA is structured in tiers, allowing grouping decisions to be made using simple in vitro or in silico methods in Tier1 progressing to in vivo approaches at the highest Tier3. Here we present a case-study testing the applicability of GRACIOUS IATA to form an evidence-based group of multiwalled carbon nanotubes (MWCNT) posing a similar predicted fibre-hazard, to support read-across and reduce the burden of toxicity testing.

RESULTS

The case-study uses data on 15 different MWCNT, obtained from the published literature. By following the IATA, a group of 2 MWCNT was identified (NRCWE006 and NM-401) based on a high degree of similarity. A pairwise similarity assessment was subsequently conducted between the grouped MWCNT to evaluate the potential to conduct read-across and fill data gaps required for regulatory hazard assessment. The similarity assessment, based on expert judgement of Tier 1 assay results, predicts both MWCNT are likely to cause a similar acute in vivo hazard. This result supports the possibility for read-across of sub-chronic and chronic hazard endpoint data for lung fibrosis and carcinogenicity between the 2 grouped MWCNT. The implications of accepting the similarity assessment based on expert judgement of the MWCNT group are considered to stimulate future discussion on the level of similarity between group members considered sufficient to allow regulatory acceptance of a read-across argument.

CONCLUSION

This proof-of-concept case-study demonstrates how a grouping hypothesis and IATA may be used to support a nuanced and evidence-based grouping of 'similar' MWCNT and the subsequent interpolation of data between group members to streamline the hazard assessment process.

Approach toward In Vitro-Based Human Toxicity Effect Factors for the Life Cycle Impact Assessment of Inhaled Low-Solubility Particles

Today's scarcity of animal toxicological data for nanomaterials could be lifted by substituting in vivo data with in vitro data to calculate nanomaterials' effect factors (EF) for Life Cycle Assessment (LCA). Here, we present a step-by-step procedure to calculate in vitro-to-in vivo extrapolation factors to estimate human Benchmark Doses and subsequently in vitro-based EFs for several inhaled nonsoluble nanomaterials. Based on mouse data, the in vitro-based EF of TiO2 is between 2.76 · 10-4 and 1.10 · 10-3 cases/(m2/g·kg intake), depending on the aerodynamic size of the particle, which is in good agreement with in vivo-based EFs (1.51 · 10-4-5.6 · 10-2 cases/(m2/g·kg intake)). The EF for amorphous silica is in a similar range as for TiO2, but the result is less robust due to only few in vivo data available. The results based on rat data are very different, confirming the importance of selecting animal species representative of human responses. The discrepancy between in vivo and in vitro animal data in terms of availability and quality limits the coverage of further nanomaterials. Systematic testing on human and animal cells is needed to reduce the variability in toxicological response determined by the differences in experimental conditions, thus helping improve the predictivity of in vitro-to-in vivo extrapolation factors.

Pathways Related to NLRP3 Inflammasome Activation Induced by Gold Nanorods

The widespread and increasing use of engineered nanomaterials (ENM) increases the risk of human exposure, generating concern that ENM may provoke adverse health effects. In this respect, their physicochemical characteristics are critical. The immune system may respond to ENM through inflammatory reactions. The NLRP3 inflammasome responds to a wide range of ENM, and its activation is associated with various inflammatory diseases. Recently, anisotropic ENM have become of increasing interest, but knowledge of their effects on the immune system is still limited. The objective of the study was to compare the effects of gold ENM of different shapes on NLRP3 inflammasome activation and related signalling pathways. Differentiated THP-1 cells (wildtype, ASC- or NLRP3-deficient), were exposed to PEGylated gold nanorods, nanostars, and nanospheres, and, thus, also different surface chemistries, to assess NLRP3 inflammasome activation. Next, the exposed cells were subjected to gene expression analysis. Nanorods, but not nanostars or nanospheres, showed NLRP3 inflammasome activation. ASC- or NLRP3-deficient cells did not show this effect. Gene Set Enrichment Analysis revealed that gold nanorod-induced NLRP3 inflammasome activation was accompanied by downregulated sterol/cholesterol biosynthesis, oxidative phosphorylation, and purinergic receptor signalling. At the level of individual genes, downregulation of Paraoxonase-2, a protein that controls oxidative stress, was most notable. In conclusion, the shape and surface chemistry of gold nanoparticles determine NLRP3 inflammasome activation. Future studies should include particle uptake and intracellular localization.

Particle Safety Assessment in Additive Manufacturing: From Exposure Risks to Advanced Toxicology Testing

Additive manufacturing (AM) or industrial three-dimensional (3D) printing drives a new spectrum of design and production possibilities; pushing the boundaries both in the application by production of sophisticated products as well as the development of next-generation materials. AM technologies apply a diversity of feedstocks, including plastic, metallic, and ceramic particle powders with distinct size, shape, and surface chemistry. In addition, powders are often reused, which may change the particles' physicochemical properties and by that alter their toxic potential. The AM production technology commonly relies on a laser or electron beam to selectively melt or sinter particle powders. Large energy input on feedstock powders generates several byproducts, including varying amounts of virgin microparticles, nanoparticles, spatter, and volatile chemicals that are emitted in the working environment; throughout the production and processing phases. The micro and nanoscale size may enable particles to interact with and to cross biological barriers, which could, in turn, give rise to unexpected adverse outcomes, including inflammation, oxidative stress, activation of signaling pathways, genotoxicity, and carcinogenicity. Another important aspect of AM-associated risks is emission/leakage of mono- and oligomers due to polymer breakdown and high temperature transformation of chemicals from polymeric particles, both during production, use, and in vivo, including in target cells. These chemicals are potential inducers of direct toxicity, genotoxicity, and endocrine disruption. Nevertheless, understanding whether AM particle powders and their byproducts may exert adverse effects in humans is largely lacking and urges comprehensive safety assessment across the entire AM lifecycle-spanning from virgin and reused to airborne particles. Therefore, this review will detail: 1) brief overview of the AM feedstock powders, impact of reuse on particle physicochemical properties, main exposure pathways and protective measures in AM industry, 2) role of particle biological identity and key toxicological endpoints in the particle safety assessment, and 3) next-generation toxicology approaches in nanosafety for safety assessment in AM. Altogether, the proposed testing approach will enable a deeper understanding of existing and emerging particle and chemical safety challenges and provide a strategy for the development of cutting-edge methodologies for hazard identification and risk assessment in the AM industry.

NLRP3 inflammasome activation determines the fibrogenic potential of PM2.5 air pollution particles in the lung

Airborne fine particulate matter (PM_2.5) is known to cause respiratory inflammation such as chronic obstructive pulmonary disease and lung fibrosis. NLRP3 inflammasome activation has been implicated in these diseases; however, due to the complexity in PM_2.5 compositions, it is difficult to differentiate the roles of the components in triggering this pathway. We collected eight real-life PM_2.5 samples for a comparative analysis of their effects on NLRP3 inflammasome activation and lung fibrosis. In vitro assays showed that although the PM_2.5 particles did not induce significant cytotoxicity at the dose range of 12.5 to 100 µg/mL, they induced potent TNF-α and IL-1β production in PMA differentiated THP-1 human macrophages and TGF-β1 production in BEAS-2B human bronchial epithelial cells. At the dose of 100 µg/mL, PM_2.5 induced NLRP3 inflammasome activation by inducing lysosomal damage and cathepsin B release, leading to IL-1β production. This was confirmed by using NLRP3- and ASC-deficient cells as well as a cathepsin B inhibitor, ca-074 ME. Administration of PM_2.5 via oropharyngeal aspiration at 2 mg/kg induced significant TGF-β1 production in the bronchoalveolar lavage fluid and collagen deposition in the lung at 21 days post-exposure, suggesting PM_2.5 has the potential to induce pulmonary fibrosis. The ranking of in vitro IL-1β production correlates well with the in vivo total cell count, TGF-β1 production, and collagen deposition. In summary, we demonstrate that the PM_2.5 is capable of inducing NLRP3 inflammasome activation, which triggers a series of cellular responses in the lung to induce fibrosis.

Property-activity relationship between physicochemical properties of PM2.5 and their activation of NLRP3 inflammasome

Air pollution is becoming severe environment factor affecting human health. More and more research has indicated that fine particulate matter (PM_2.5) plays a critical role in causing pulmonary inflammation or fibrosis, which potentially is ascribed to the activation of nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome. However, the underlying property-activity relationship between the physicochemical properties of PM_2.5 and their activation of NLRP3 inflammasome remains unclear. Herein, various ways, such as metal chelation, organic extraction, ROS consumption, charge neutralization and particle dispersion, were applied to interfere with the effects of metal ion, polycyclic aromatic hydrocarbons (PAHs), reactive oxygen species (ROS), charge and size. It was found that aggregated size and PAHs could activate the NLRP3 inflammasome through lysosome rupture and potassium efflux, respectively. Metal ion, PAHs and surface ROS could also activate the NLRP3 inflammasome through mitochondrial ROS production. However, neutralization of PM_2.5 with the negative surface charge could not relieve the activation of NLRP3 inflammasome. Furthermore, oropharyngeal aspiration of various modified PM_2.5 were adopted to explore their effects on lung fibrosis, which showed the consistent results with those in cellular levels. Removal of metal ion, PAHs and ROS as well as reduction of size of PM_2.5 could reduce collagen deposition in the lung tissue of mice, while the charge neutralization of PM_2.5 increased this collagen deposition. This study provides great insights to clarify the property-activity relationship of PM_2.5.

Biotransformation of soluble-insoluble lanthanum species and its induced NLRP3 inflammasome activation and chronic fibrosis

Soluble lanthanum (La)(Ⅲ) species that have been extensively used as fertilizers in agriculture can potentially get into the human body through foods and environment. Most soluble La(Ⅲ) species can rapidly transform into insoluble La(Ⅲ) species under physiological conditions, however, their potential biological behavior and chronic toxicity are rarely investigated. In the present study, insoluble La(Ⅲ) species formed under physiological condition were identified as nanoscale or microscale particles, and their major components were found to experience biotransformation process upon contact with cells. Insoluble La(Ⅲ) species could adhere to extracellular membrane or be internalized into cells, capable of activating a nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome. The underlying mechanism could be ascribed to K⁺ efflux and lysosomal rupture because these insoluble La(Ⅲ) species locating at extracellular membrane could reduce the unsaturated fatty acids of cell membrane, leading to potassium (K⁺) efflux, and those internalized into cells could consume the phospholipids of lysosomal membrane, leading to lysosomal rupture. Mice daily drinking soluble La(Ⅲ) species to mimic drinking tea process for 90 days were found to present NLRP3 inflammasome activation in liver and kidney, as a result of chronic fibrosis, which is potentially correlated to insoluble La(Ⅲ) species formation.

Inflammasomes and Fibrosis

Fibrosis is the final common pathway of inflammatory diseases in various organs. The inflammasomes play an important role in the progression of fibrosis as innate immune receptors. There are four main members of the inflammasomes, such as NOD-like receptor protein 1 (NLRP1), NOD-like receptor protein 3 (NLRP3), NOD-like receptor C4 (NLRC4), and absent in melanoma 2 (AIM2), among which NLRP3 inflammasome is the most studied. NLRP3 inflammasome is typically composed of NLRP3, ASC and pro-caspase-1. The activation of inflammasome involves both "classical" and "non-classical" pathways and the former pathway is better understood. The "classical" activation pathway of inflammasome is that the backbone protein is activated by endogenous/exogenous stimulation, leading to inflammasome assembly. After the formation of "classic" inflammasome, pro-caspase-1 could self-activate. Caspase-1 cleaves cytokine precursors into mature cytokines, which are secreted extracellularly. At present, the "non-classical" activation pathway of inflammasome has not formed a unified model for activation process. This article reviews the role of NLRP1, NLRP3, NLRC4, AIM2 inflammasome, Caspase-1, IL-1β, IL-18 and IL-33 in the fibrogenesis.

Inflammasome as an Effective Platform for Fibrosis Therapy

Fibrosis is the final stage of the development of chronic inflammation. It is characterized by excessive deposition of the extracellular matrix, leading to tissue structure damage and organ dysfunction, which is a serious threat to human health and life. However, the molecular mechanism of fibrosis is still unclear. Inflammasome is a molecular complex of proteins that has been becoming a key innate sensor for host immunity and is involved in pyroptosis, pathogen infection, metabolic syndrome, cellular stress, and tumor metastasis. Inflammasome signaling and downstream cytokine responses mediated by the inflammasome have been found to play an important role in fibrosis. The inflammasome regulates the secretion of IL-1β and IL-18, which are both critical for the process of fibrosis. Recently, researches on the function of inflammasome have attracted extensive attention, and data derived from these researches have increased our understanding of the effects and regulation of inflammasome during fibrosis. In this review, we emphasize the growing evidence for both indirect and direct effects of inflammasomes in triggering fibrosis as well as potential novel targets for antifibrotic therapies.

An integrated approach to testing and assessment of high aspect ratio nanomaterials and its application for grouping based on a common mesothelioma hazard

Here we describe the development of an Integrated Approach to Testing and Assessment (IATA) to support the grouping of different types (nanoforms; NFs) of High Aspect Ratio Nanomaterials (HARNs), based on their potential to cause mesothelioma. Hazards posed by the inhalation of HARNs are of particular concern as they exhibit physical characteristics similar to pathogenic asbestos fibres. The approach for grouping HARNs presented here is part of a framework to provide guidance and tools to group similar NFs and aims to reduce the need to assess toxicity on a case-by-case basis. The approach to grouping is hypothesis-driven, in which the hypothesis is based on scientific evidence linking critical physicochemical descriptors for NFs to defined fate/toxicokinetic and hazard outcomes. The HARN IATA prompts users to address relevant questions (at decision nodes; DNs) regarding the morphology, biopersistence and inflammatory potential of the HARNs under investigation to provide the necessary evidence to accept or reject the grouping hypothesis. Each DN in the IATA is addressed in a tiered manner, using data from simple in vitro or in silico methods in the lowest tier or from in vivo approaches in the highest tier. For these proposed methods we provide justification for the critical descriptors and thresholds that allow grouping decisions to be made. Application of the IATA allows the user to selectively identify HARNs which may pose a mesothelioma hazard, as demonstrated through a literature-based case study. By promoting the use of alternative, non-rodent approaches such as in silico modelling, in vitro and cell-free tests in the initial tiers, the IATA testing strategy streamlines information gathering at all stages of innovation through to regulatory risk assessment while reducing the ethical, time and economic burden of testing.

Lysosomal disruption by orthopedic wear particles induces activation of the NLRP3 inflammasome and macrophage cell death by distinct mechanisms

Wear particles from orthopedic implants cause aseptic loosening, the leading cause of implant revisions. The particles are phagocytosed by macrophages leading to activation of the nod-like receptor protein 3 (NLRP3) inflammasome and release of interleukin-1β (IL-1β) which then contributes to osteoclast differentiation and implant loosening. The mechanism of inflammasome activation by orthopedic particles is undetermined but other particles cause the cytosolic accumulation of the lysosomal cathepsin-family proteases which can activate the NLRP3 inflammasome. Here, we demonstrate that lysosome membrane disruption causes cathepsin release into the cytoplasm that drives both inflammasome activation and cell death but that these processes occur independently. Using wild-type and genetically-manipulated immortalized murine bone marrow derived macrophages and pharmacologic inhibitors, we found that NLRP3 and gasdermin D are required for particle-induced IL-1β release but not for particle-induced cell death. In contrast, phagocytosis and lysosomal cathepsin release are critical for both IL-1β release and cell death. Collectively, our findings identify the pan-cathepsin inhibitor Ca-074Me and the NLRP3 inflammasome inhibitor MCC950 as therapeutic interventions worth exploring in aseptic loosening of orthopedic implants. We also found that particle-induced activation of the NLRP3 inflammasome in pre-primed macrophages and cell death are not dependent on pathogen-associated molecular patterns adherent to the wear particles despite such pathogen-associated molecular patterns being critical for all other previously studied wear particle responses, including priming of the NLRP3 inflammasome.

Emodin attenuates silica-induced lung injury by inhibition of inflammation, apoptosis and epithelial-mesenchymal transition

Silicosis is a fatal pulmonary disease caused by the inhalation of silica dust, and characterized by inflammation and fibrosis of the lung, with no effective treatment to date. Here we investigate the effect of emodin, an anthraquinone derivative isolated from rhubarb using a mouse silicosis model and in vitro cultured human macrophages and alveolar epithelial cells. Results from histological examination indicated that emodin reduced the degree of alveolitis and fibrosis in the lungs of mice exposed to silica particles. We also demonstrated that emodin effectively inhibited the phosphorylation of Smad3 and NF-κB and reduced the levels of inflammatory factors in the lung tissue of mice treated with silica particles. In addition, we found that emodin inhibited apoptosis and demonstrated an anti-fibrotic effect by down-regulating the pro-apoptotic protein Bax and up-regulating the anti-apoptotic protein Bcl-2. Furthermore, emodin increased E-cadherin levels, reduced the expression of Vimentin, α-SMA and Col-I, as well as pro-inflammatory factors TGF-β1, TNF-α and IL-1β in vivo and in vitro. These results suggested that emodin can regulate epithelial-mesenchymal transition (EMT) through the inhibition of the TGF-β1/Smad3 signaling pathway and the NF-κB signaling pathway to prevent alveolar inflammation and apoptotic process. Overall, this study showed that emodin can alleviate pulmonary fibrosis in silicosis through regulating the inflammatory response and fibrotic process at multiple levels.

Nanoparticle-Based Activatable Probes for Bioimaging

Molecular imaging can provide functional and molecular information at the cellular or subcellular level in vivo in a noninvasive manner. Activatable nanoprobes that can react to the surrounding physiological environment or biomarkers are appealing agents to improve the efficacy, specificity, and sensitivity of molecular imaging. The physiological parameters, including redox status, pH, presence of enzymes, and hypoxia, can be designed as the stimuli of the activatable probes. However, the success rate of imaging nanoprobes for clinical translation is low. Herein, the recent advances in nanoparticle-based activatable imaging probes are critically reviewed. In addition, the challenges for clinical translation of these nanoprobes are also discussed in this review.

Biological effects of inhaled hydraulic fracturing sand dust. IV. Pulmonary effects

Hydraulic fracturing creates fissures in subterranean rock to increase the flow and retrieval of natural gas. Sand ("proppant") in fracking fluid injected into the well bore maintains fissure patency. Fracking sand dust (FSD) is generated during manipulation of sand to prepare the fracking fluid. Containing respirable crystalline silica, FSD could pose hazards similar to those found in work sites where silica inhalation induces lung disease such as silicosis. This study was performed to evaluate the possible toxic effects following inhalation of a FSD (FSD 8) in the lung and airways. Rats were exposed (6 h/d × 4 d) to 10 or 30 mg/m3 of a FSD collected at a gas well, and measurements were performed 1, 7, 27 and, in one series of experiments, 90 d post-exposure. The following ventilatory and non-ventilatory parameters were measured in vivo and/or in vitro: 1) lung mechanics (respiratory system resistance and elastance, tissue damping, tissue elastance, Newtonian resistance and hysteresivity); 2) airway reactivity to inhaled methacholine (MCh); airway epithelium integrity (isolated, perfused trachea); airway efferent motor nerve activity (electric field stimulation in vitro); airway smooth muscle contractility; ion transport in intact and cultured epithelium; airway effector and sensory nerves; tracheal particle deposition; and neurogenic inflammation/vascular permeability. FSD 8 was without large effect on most parameters, and was not pro-inflammatory, as judged histologically and in cultured epithelial cells, but increased reactivity to inhaled MCh at some post-exposure time points and affected Na+ transport in airway epithelial cells.

Synthesis and Cytotoxicity Studies of Wood-Based Cationic Cellulose Nanocrystals as Potential Immunomodulators

Polysaccharides have been shown to have immunomodulatory properties. Modulation of the immune system plays a crucial role in physiological processes as well as in the treatment and/or prevention of autoimmune and infectious diseases. Cellulose nanocrystals (CNCs) are derived from cellulose, the most abundant polysaccharide on the earth. CNCs are an emerging class of crystalline nanomaterials with exceptional physico-chemical properties for high-end applications and commercialization prospects. The aim of this study was to design, synthesize, and evaluate the cytotoxicity of a series of biocompatible, wood-based, cationic CNCs as potential immunomodulators. The anionic CNCs were rendered cationic by grafting with cationic polymers having pendant +NMe3 and +NH3 moieties. The success of the synthesis of the cationic CNCs was evidenced by Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, and elemental analysis. No modification in the nanocrystals rod-like shape was observed in transmission electron microscopy and atomic force microscopy analyses. Cytotoxicity studies using three different cell-based assays (MTT, Neutral Red, and LIVE/DEAD®) and three relevant mouse and human immune cells indicated very low cytotoxicity of the cationic CNCs in all tested experimental conditions. Overall, our results showed that cationic CNCs are suitable to be further investigated as immunomodulators and potential vaccine nanoadjuvants.

The Role of NLRP3 Inflammasome Activation in the Epithelial to Mesenchymal Transition Process During the Fibrosis

Fibrosis is considered a complex form of tissue damage commonly present in the end stage of many diseases. It is also related to a high percentage of death, whose predominant characteristics are an excessive and abnormal deposition of fibroblasts and myofibroblasts -derived extracellular matrix (ECM) components. Epithelial-to-mesenchymal transition (EMT), a process in which epithelial cells gradually change to mesenchymal ones, is a major contributor in the pathogenesis of fibrosis. The key mediator of EMT is a multifunctional cytokine called transforming growth factor-β (TGF-β) that acts as the main inducer of the ECM assembly and remodeling through the phosphorylation of Smad2/3, which ultimately forms a complex with Smad4 and translocates into the nucleus. On the other hand, the bone morphogenic protein-7 (BMP-7), a member of the TGF family, reverses EMT by directly counteracting TGF-β induced Smad-dependent cell signaling. NLRP3 (NACHT, LRR, and PYD domains-containing protein 3), in turn, acts as cytosolic sensors of microbial and self-derived molecules and forms an immune complex called inflammasome in the context of inflammatory commitments. NLRP3 inflammasome assembly is triggered by extracellular ATP, reactive oxygen species (ROS), potassium efflux, calcium misbalance, and lysosome disruption. Due to its involvement in multiple diseases, NLRP3 has become one of the most studied pattern-recognition receptors (PRRs). Nevertheless, the role of NLRP3 in fibrosis development has not been completely elucidated. In this review, we described the relation of the previously mentioned fibrosis pathway with the NLRP3 inflammasome complex formation, especially EMT-related pathways. For now, it is suggested that the EMT happens independently from the oligomerization of the whole inflammasome complex, requiring just the presence of the NLRP3 receptor and the ASC protein to trigger the EMT events, and we will present different pieces of research that give controversial point of views.

Continued Efforts on Nanomaterial-Environmental Health and Safety Is Critical to Maintain Sustainable Growth of Nanoindustry

Nanotechnology is enjoying an impressive growth and the global nanotechnology industry is expected to exceed US$ 125 billion by 2024. Based on these successes, there are notions that enough is known and efforts on engineered nanomaterial environmental health and safety (nano-EHS) research should be put on the back burner. However, there are recent events showing that it is not the case. The US Food and Drug Administration found ferumoxytol (carbohydrate-coated superparamagnetic iron oxide nanoparticle) for anemia treatment could induce lethal anaphylactic reactions. The European Union will categorize TiO2 as a category 2 carcinogen due to its inhalation hazard and France banned use of TiO2 (E171) in food from January 1, 2020 because of its carcinogenic potential. Although nanoindustry is seemingly in a healthy state, growth could be hindered for the lack of certainty and more nano-EHS research is needed for the sustainable growth of nanoindustry. Herein, the current knowledge gaps and the way forward are elaborated.

Mechanistic Differences in Cell Death Responses to Metal-Based Engineered Nanomaterials in Kupffer Cells and Hepatocytes

The mononuclear phagocyte system in the liver is a frequent target for nanoparticles (NPs). A toxicological profiling of metal-based NPs is performed in Kupffer cell (KC) and hepatocyte cell lines. Sixteen NPs are provided by the Nanomaterial Health Implications Research Consortium of the National Institute of Environmental Health Sciences to study the toxicological effects in KUP5 (KC) and Hepa 1-6 cells. Five NPs (Ag, CuO, ZnO, SiO2 , and V2 O5 ) exhibit cytotoxicity in both cell types, while SiO2 and V2 O5 induce IL-1β production in KC. Ag, CuO, and ZnO induced caspase 3 generated apoptosis in both cell types is accompanied by ion shedding and generation of mitochondrial reactive oxygen species (ROS) in both cell types. However, the cell death response to SiO2 in KC differs by inducing pyroptosis as a result of potassium efflux, caspase 1 activation, NLRP3 inflammasome assembly, IL-1β release, and cleavage of gasdermin-D. This releases pore-performing peptide fragments responsible for pyroptotic cell swelling. Interestingly, although V2 O5 induces IL-1β release and delays caspase 1 activation by vanadium ion interference in membrane Na+ /K+ adenosine triphosphate (ATP)ase activity, the major cell death mechanism in KC (and Hepa 1-6) is caspase 3 mediated apoptosis. These findings improve the understanding of the mechanisms of metal-based engineered nanomaterial (ENM) toxicity in liver cells toward comprehensive safety evaluation.

Engineered Nanomaterials and Type I Allergic Hypersensitivity Reactions

Type I allergic hypersensitivity disorders (atopy) including asthma, atopic dermatitis, allergic rhinitis, and food allergy are on the rise in developed and developing countries. Engineered nanomaterials (ENMs) span a large spectrum of material compositions including carbonic, metals, polymers, lipid-based, proteins, and peptides and are being utilized in a wide range of industries including healthcare and pharmaceuticals, electronics, construction, and food industry, and yet, regulations for the use of ENMs in consumer products are largely lacking. Prior evidence has demonstrated the potential of ENMs to induce and/or aggravate type I allergic hypersensitivity responses. Furthermore, previous studies have shown that ENMs could directly interact with and activate key T-helper 2 (Th2) effector cell types (such as mast cells) and the complement system, which could result in pseudoallergic (non-IgE-mediated) hypersensitivity reactions. Nevertheless, the underlying molecular mechanisms of ENM-mediated induction and/or exacerbation of type I immune responses are poorly understood. In this review, we first highlight key examples of studies that have demonstrated inherent immunomodulatory properties of ENMs in the context of type I allergic hypersensitivity reactions, and most importantly, we attempt to put together the potential molecular mechanisms that could drive ENM-mediated stimulation and/or aggravation of type I allergic hypersensitivity responses.

Nanomaterials as Inhibitors of Epithelial Mesenchymal Transition in Cancer Treatment

Abstract: Epithelial-mesenchymal transition (EMT) has emerged as a key regulator of cell invasion and metastasis in cancers. Besides the acquisition of migratory/invasive abilities, the EMT process is tightly connected with the generation of cancer stem cells (CSCs), thus contributing to chemoresistance. However, although EMT represents a relevant therapeutic target for cancer treatment, its application in the clinic is still limited due to various reasons, including tumor-stage heterogeneity, molecular-cellular target specificity, and appropriate drug delivery. Concerning this last point, different nanomaterials may be used to counteract EMT induction, providing novel therapeutic tools against many different cancers. In this review, (1) we discuss the application of various nanomaterials for EMT-based therapies in cancer, (2) we summarize the therapeutic relevance of some of the proposed EMT targets, and (3) we review the potential benefits and weaknesses of each approach.

Epigenetic Aspects of Engineered Nanomaterials: Is the Collateral Damage Inevitable?

The extensive application of engineered nanomaterial (ENM) in various fields increases the possibilities of human exposure, thus imposing a huge risk of nanotoxicity. Hence, there is an urgent need for a detailed risk assessment of these ENMs in response to their toxicological profiling, predominantly in biomedical and biosensor settings. Numerous "toxico-omics" studies have been conducted on ENMs, however, a specific "risk assessment paradigm" dealing with the epigenetic modulations in humans owing to the exposure of these modern-day toxicants has not been defined yet. This review aims to address the critical aspects that are currently preventing the formation of a suitable risk assessment approach for/against ENM exposure and pointing out those researches, which may help to develop and implement effective guidance for nano-risk assessment. Literature relating to physicochemical characterization and toxicological behavior of ENMs were analyzed, and exposure assessment strategies were explored in order to extrapolate opportunities, challenges, and criticisms in the establishment of a baseline for the risk assessment paradigm of ENMs exposure. Various challenges, such as uncertainty in the relation of the physicochemical properties and ENM toxicity, the complexity of the dose-response relationships resulting in difficulty in its extrapolation and measurement of ENM exposure levels emerged as issues in the establishment of a traditional risk assessment. Such an appropriate risk assessment approach will provide adequate estimates of ENM exposure risks and will serve as a guideline for appropriate risk communication and management strategies aiming for the protection and the safety of humans.

A novel human 3D lung microtissue model for nanoparticle-induced cell-matrix alterations

BACKGROUND

Multi-walled carbon nanotubes (MWCNT) have been shown to elicit the release of inflammatory and pro-fibrotic mediators, as well as histopathological changes in lungs of exposed animals. Current standards for testing MWCNTs and other nanoparticles (NPs) rely on low-throughput in vivo studies to assess acute and chronic toxicity and potential hazard to humans. Several alternative testing approaches utilizing two-dimensional (2D) in vitro assays to screen engineered NPs have reported conflicting results between in vitro and in vivo assays. Compared to conventional 2D in vitro or in vivo animal model systems, three-dimensional (3D) in vitro platforms have been shown to more closely recapitulate human physiology, providing a relevant, more efficient strategy for evaluating acute toxicity and chronic outcomes in a tiered nanomaterial toxicity testing paradigm.

RESULTS

As inhalation is an important route of nanomaterial exposure, human lung fibroblasts and epithelial cells were co-cultured with macrophages to form scaffold-free 3D lung microtissues. Microtissues were exposed to multi-walled carbon nanotubes, M120 carbon black nanoparticles or crocidolite asbestos fibers for 4 or 7 days, then collected for characterization of microtissue viability, tissue morphology, and expression of genes and selected proteins associated with inflammation and extracellular matrix remodeling. Our data demonstrate the utility of 3D microtissues in predicting chronic pulmonary endpoints following exposure to MWCNTs or asbestos fibers. These test nanomaterials were incorporated into 3D human lung microtissues as visualized using light microscopy. Differential expression of genes involved in acute inflammation and extracellular matrix remodeling was detected using PCR arrays and confirmed using qRT-PCR analysis and Luminex assays of selected genes and proteins.

CONCLUSION

3D lung microtissues provide an alternative testing platform for assessing nanomaterial-induced cell-matrix alterations and delineation of toxicity pathways, moving towards a more predictive and physiologically relevant approach for in vitro NP toxicity testing.

Application of immobilized ATP to the study of NLRP inflammasomes

The NLRP proteins are a subfamily of the NOD-like receptor (NLR) innate immune sensors that possess an ATP-binding NACHT domain. As the most well studied member, NLRP3 can initiate the assembly process of a multiprotein complex, termed the inflammasome, upon detection of a wide range of microbial products and endogenous danger signals and results in the activation of pro-caspase-1, a cysteine protease that regulates multiple host defense pathways including cytokine maturation. Dysregulated NLRP3 activation contributes to inflammation and the pathogenesis of several chronic diseases, and the ATP-binding properties of NLRPs are thought to be critical for inflammasome activation. In light of this, we examined the utility of immobilized ATP matrices in the study of NLRP inflammasomes. Using NLRP3 as the prototypical member of the family, P-linked ATP Sepharose was determined to be a highly-effective capture agent. In subsequent examinations, P-linked ATP Sepharose was used as an enrichment tool to enable the effective profiling of NLRP3-biomarker signatures with selected reaction monitoring-mass spectrometry (SRM-MS). Finally, ATP Sepharose was used in combination with a fluorescence-linked enzyme chemoproteomic strategy (FLECS) screen to identify potential competitive inhibitors of NLRP3. The identification of a novel benzo[d]imidazol-2-one inhibitor that specifically targets the ATP-binding and hydrolysis properties of the NLRP3 protein implies that ATP Sepharose and FLECS could be applied other NLRPs as well.

NLRP3 inflammasome activation and lung fibrosis caused by airborne fine particulate matter

Airborne fine particulate matter (PM_2.5) has been known capable of causing lung inflammation and fibrosis, as a result of a series of chronic respiration diseases. Although NLRP3 inflammasome activation is essential for development of many chronic diseases, the relationship between PM_2.5-induced toxicological effect and NLRP3 inflammasome activation is rarely investigated. Since PM_2.5 contains a large population of nanosized materials and many types of nanomaterials can activate NLRP3 inflammasome, the NLRP3 inflammasome activation and lung fibrosis induced by PM_2.5 were investigated in the present study. PM_2.5 was found capable of causing weak cell death but potent IL-1β secretion in THP-1 cells, which was involved in NLRP3 inflammasome activation as evidenced by Z-YVAD-FMK inhibited IL-1β secretion and overexpressed ASC and NLRP3 protein in PM_2.5 treated cells. PM_2.5 could be internalized into cells through multiple endocytosis processes, such as phagocytosis and pinocytosis (macropinocytosis, clathrin- and caveolin-mediated endocytosis), and activate NLRP3 inflammasome through cathepsin B release, ROS production, and potassium efflux. After 21 days of exposure to PM_2.5 through oropharyngeal aspiration, Balb/c mice showed increased IL-1β and TGF-β1 levels in the bronchoalveolar lavage fluid (BALF) of lung and significant collagen deposition around small airways of mice, suggesting potential lung inflammation and pulmonary fibrosis.

Recent advances in the field of transition metal dichalcogenides for biomedical applications

Nanosheets of transition metal dichalcogenide (TMDs), the graphene-like two-dimensional (2D) materials, exhibit a unique combination of properties and have attracted enormous research interest for a wide range of applications including catalysis, functional electronics, solid lubrication, photovoltaics, energy materials and most recently in biomedical applications. Their potential for use in biosensors, drug delivery, multimodal imaging, antimicrobial agents and tissue engineering is being actively studied. However, the commercial translation of exfoliated TMDs has been limited due to the low aqueous solubility, non-uniformity, lack of control over the layer thickness, and the long-term colloidal stability of the exfoliated material. There is wide interest in the synthesis and exfoliation of TMDs resulting in the reporting of increasing numbers of new methods and their biomedical applications. The unique physicochemical characteristics of the TMD nanosheets have been exploited to tether them with biological payload to achieve selective localized delivery in vivo. The large surface-to-volume ratio, good cytocompatibility, ease of surface modification, tunable bandgap, strong spin-orbit coupling, and high optical and thermal conversion efficiency of TMD nanosheets make them favorable over traditional nanomaterials for biomedical research. Moreover, the presence of abundant active edge sites on the 2D TMDs makes them suitable for catalytic activities, while the large surface area and the interspace between layers are particularly conducive to ion or small molecule intercalation, making them useful for energy storage applications with rapid redox reaction capabilities. One of the major limitations of the exfoliated TMDs has been their limited colloidal stability in aqueous media. In this review, we summarize the recent advances in the exfoliation and synthesis of single-layered TMDs, their biomedical efficacy in terms of cytotoxicity, combinatorial therapy and diagnostic imaging, as well as antimicrobial activity. We highlight the current challenges in the field and propose strategies for the future.

Review of techniques and studies characterizing the release of carbon nanotubes from nanocomposites: Implications for exposure and human health risk assessment

Composites made with engineered nanomaterials (nanocomposites) have a wide range of applications, from use in basic consumer goods to critical national defense technologies. Carbon nanotubes (CNTs) are a popular addition in nanocomposites because of their enhanced mechanical, thermal, and electrical properties. Concerns have been raised, though, regarding potential exposure and health risks from nanocomposites containing CNTs because of comparisons to other high aspect ratio fibers. Assessing the factors affecting CNT release from composites is therefore paramount for understanding potential exposure scenarios that may occur during product handling and manipulation. Standardized methods for detecting and quantifying released CNTs, however, have not yet been developed. We therefore evaluated experimental approaches deployed by various researchers, with an emphasis on characterizing free versus composite bound CNTs. From our analysis of published studies characterizing CNT releases from nanocomposites, we found that the qualitative and quantitative methods used across studies varied greatly, thus limiting the ability for objective comparison and evaluation of various release factors. Nonetheless, qualitative results indicated that factors such as composite type, CNT functionalization, and energy input during manipulation (i.e., grinding) may affect CNT release. Based on our findings, we offer several recommendations for future product testing and assessment of potential exposure and health risks associated with CNT nanocomposites.

Considerations for Safe Innovation: The Case of Graphene

The terms "Safe innovation" and "Safe(r)-by-design" are currently popular in the field of nanotechnology. These terms are used to describe approaches that advocate the consideration of safety aspects already at an early stage of the innovation process of (nano)materials and nanoenabled products. Here, we investigate the possibilities of considering safety aspects during various stages of the innovation process of graphene, outlining what information is already available for assessing potential hazard, exposure, and risks. In addition, we recommend further steps to be taken by various stakeholders to promote the safe production and safe use of graphene.