Acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) filaments three-dimensional (3-D) printer emissions-induced cell toxicity.

During extrusion of some polymers, fused filament fabrication (FFF) 3-D printers emit billions of particles per minute and numerous organic compounds. The scope of this study was to evaluate FFF 3-D printer emission-induced toxicity in human small airway epithelial cells (SAEC). Emissions were generated from a commercially available 3-D printer inside a chamber, while operating for 1.5 h with acrylonitrile butadiene styrene (ABS) or polycarbonate (PC) filaments, and collected in cell culture medium. Characterization of the culture medium revealed that repeat print runs with an identical filament yield various amounts of particles and organic compounds. Mean particle sizes in cell culture medium were 201 ±â€¯18 nm and 202 ±â€¯8 nm for PC and ABS, respectively. At 24 h post-exposure, both PC and ABS emissions induced a dose dependent significant cytotoxicity, oxidative stress, apoptosis, necrosis, and production of pro-inflammatory cytokines and chemokines in SAEC. Though the emissions may not completely represent all possible exposure scenarios, this study indicate that the FFF could induce toxicological effects. Further studies are needed to quantify the detected chemicals in the emissions and their corresponding toxicological effects.

Similar and Differential Canonical Pathways and Biological Processes Associated With Multiwalled Carbon Nanotube and Asbestos-Induced Pulmonary Fibrosis: A 1-Year Postexposure Study.

Respiratory exposure to multiwalled carbon nanotubes (MWCNT) or asbestos results in fibrosis; however, the mechanisms to reach this end point may be different. A previous study by our group identified pulmonary effects and significantly altered messenger RNA (mRNA) signaling pathways following exposure to 1, 10, 40, and 80 µg MWCNT and 120 µg crocidolite asbestos on mouse lungs over time at 1-month, 6-month, and 1-year postexposure following pulmonary aspiration. As a continuation to the above study, this current study took an in-depth look at the signaling pathways involved in fibrosis development at a single time point, 1 year, and exposure, 40 µg MWCNT, the lowest exposure at which fibrosis was pathologically evident. The 120 µg asbestos exposure was included to compare MWCNT-induced fibrosis with asbestos-induced fibrosis. A previously validated computational model was used to identify mRNAs with expression profiles matching the fibrosis pathology patterns from exposed mouse lungs. mRNAs that matched the pathology patterns were then input into ingenuity pathway analysis to determine potential signaling pathways and physiological disease functions inherent to MWCNT and asbestos exposure. Both MWCNT and asbestos exposure induced changes in mouse lungs regarding gene expression, cell proliferation, and survival, while MWCNT uniquely induced alterations in pathways involved in oxidative phosphorylation, mitochondrial dysfunction, and transcription. Asbestos exposure produced unique alterations in pathways involved in sustained inflammation. Although typically considered similar due to scale and fiber-like appearance, the different compositional properties inherent to either MWCNT or asbestos may play a role in their ability to induce fibrosis after pulmonary exposure.

Sparse Supervised Classification Methods Predict and Characterize Nanomaterial Exposures: Independent Markers of MWCNT Exposures.

Recent experimental evidence indicates significant pulmonary toxicity of multiwalled carbon nanotubes (MWCNTs), such as inflammation, interstitial fibrosis, granuloma formation, and carcinogenicity. Although numerous studies explored the adverse potential of various CNTs, their comparability is often limited. This is due to differences in administered dose, physicochemical characteristics, exposure methods, and end points monitored. Here, we addressed the problem through sparse classification method, a supervised machine learning approach that can reduce the noise contained in redundant variables for discriminating among MWCNT-exposed and MWCNT-unexposed groups. A panel of proteins measured from bronchoalveolar lavage fluid (BAL) samples was used to predict exposure to various MWCNT and determine markers that are attributable to MWCNT exposure and toxicity in mice. Using sparse support vector machine-based classification technique, we identified a small subset of proteins clearly distinguishing each exposure. Macrophage-derived chemokine (MDC/CCL22), in particular, was associated with various MWCNT exposures and was independent of exposure method employed, that is, oropharyngeal aspiration versus inhalation exposure. Sustained expression of some of the selected protein markers identified also suggests their potential role in MWCNT-induced toxicity and proposes hypotheses for future mechanistic studies. Such approaches can be used more broadly for nanomaterial risk profiling studies to evaluate decisions related to dose/time-response relationships that could delineate experimental variables from exposure markers.

Potential Toxicity and Underlying Mechanisms Associated with Pulmonary Exposure to Iron Oxide Nanoparticles: Conflicting Literature and Unclear Risk.

Fine/micron-sized iron oxide particulates are incidentally released from a number of industrial processes, including iron ore mining, steel processing, welding, and pyrite production. Some research suggests that occupational exposure to these particulates is linked to an increased risk of adverse respiratory outcomes, whereas other studies suggest that iron oxide is biologically benign. Iron oxide nanoparticles (IONPs), which are less than 100 nm in diameter, have recently surged in use as components of novel drug delivery systems, unique imaging protocols, as environmental catalysts, and for incorporation into thermoplastics. However, the adverse outcomes associated with occupational exposure to IONPs remain relatively unknown. Relevant in vivo studies suggest that pulmonary exposure to IONPs may induce inflammation, pulmonary fibrosis, genotoxicity, and extra-pulmonary effects. This correlates well with in vitro studies that utilize relevant dose, cell type(s), and meaningful end points. A majority of these adverse outcomes are attributed to increased oxidative stress, most likely caused by particle internalization, dissolution, release of free iron ions, and disruption of iron homeostasis. However, because the overall toxicity profile of IONPs is not well understood, it is difficult to set safe exposure limit recommendations that would be adequate for the protection of at-risk workers. This review article will focus on known risks following IONPs exposure supported by human, animal, and cell culture-based studies, the potential challenges intrinsic to IONPs toxicity assessment, and how these may contribute to the poorly characterized IONPs toxicity profile.

SOX9 Regulates Cancer Stem-Like Properties and Metastatic Potential of Single-Walled Carbon Nanotube-Exposed Cells.

Engineered nanomaterials hold great promise for the future development of innovative products but their adverse health effects are a major concern. Recent studies have indicated that certain nanomaterials, including carbon nanotubes (CNTs), may be carcinogenic. However, the underlying mechanisms behind their potential malignant properties remain unclear. In this study, we linked SOX9, a stem cell associated transcription factor, to the neoplastic-like properties of human lung epithelial cells chronically exposed to a low-dose of single-walled carbon nanotubes (SWCNTs). We found that SOX9 is upregulated in SWCNT-exposed cells, which is consistent with their abilities to induce tumor formation and metastasis in vivo. We therefore hypothesized that SOX9 overexpression may be responsible for the neoplastic-like phenotype observed in our model. Indeed, SOX9 knockdown inhibited anchorage-independent cell growth in vitro and lung colonization in vivo in a mouse xenograft model. SOX9 depletion also suppressed the formation of cancer stem-like cells (CSCs), as determined by tumor sphere formation and aldehyde dehydrogenase (ALDH) activity (Aldefluor) assays. Furthermore, SOX9 knockdown suppressed tumor metastasis and the expression of the stem cell marker ALDH1A1. Taken together, our findings provide a mechanistic insight into SWCNT-induced carcinogenesis and the role of SOX9 in CSC regulation and metastasis.

Nanoparticles increase human bronchial epithelial cell susceptibility to respiratory syncytial virus infection via nerve growth factor-induced autophagy.

Cytotoxic and neuroinflammatory effects of TiO2 nanoparticles (TiO2-NP) in human airways are mediated by nerve growth factor (NGF), which is also implicated in the pathophysiology of respiratory syncytial virus (RSV) infection. We tested the hypothesis that exposure to TiO2-NP results in increased susceptibility to RSV infection and exacerbation of airway inflammation via NGF-mediated induction of autophagy in lower respiratory tract cells. Human primary bronchial epithelial cells were exposed to TiO2-NP for 24 h prior to infection with recombinant red RSV (rrRSV). Expression of NGF and its TrkA and p75NTR receptors was measured by real-time PCR and fluorescence-activated cell sorting (FACS). Autophagy was assessed by beclin-1 expression analysis. Cell death was studied by FACS after annexin V/propidium iodide staining. rrRSV infection efficiency more than doubled in human bronchial cells pre-exposed to TiO2-NP compared to controls. NGF and its TrkA receptor were upregulated in RSV-infected bronchial cells pre-exposed to TiO2-NP compared to controls exposed to either rrRSV or TiO2-NP alone. Silencing NGF gene expression with siRNA significantly inhibited rrRSV infection. rrRSV-infected cells pre-exposed to TiO2-NP also showed increase in necrotic cell death and reduction in apoptosis, together with 4.3-fold increase in expression of the early autophagosomal gene beclin-1. Pharmacological inhibition of beclin-1 by wortmannin resulted in increased apoptotic rate along with lower viral load. This study shows that TiO2-NP exposure enhances the infectivity of RSV in human bronchial epithelial cells by upregulating the NGF/TrkA axis. The mechanism of this interaction involves induction of autophagy promoting viral replication and necrotic cell death.

Role of epithelial-mesenchymal transition (EMT) and fibroblast function in cerium oxide nanoparticles-induced lung fibrosis.

The emission of cerium oxide nanoparticles (CeO2) from diesel engines, using cerium compounds as a catalyst to lower the diesel exhaust particles, is a health concern. We have previously shown that CeO2 induced pulmonary inflammation and lung fibrosis. The objective of the present study was to investigate the modification of fibroblast function and the role of epithelial-mesenchymal transition (EMT) in CeO2-induced fibrosis. Male Sprague-Dawley rats were exposed to CeO2 (0.15 to 7mg/kg) by a single intratracheal instillation and sacrificed at various times post-exposure. The results show that at 28days after CeO2 (3.5mg/kg) exposure, lung fibrosis was evidenced by increased soluble collagen in bronchoalveolar lavage fluid, elevated hydroxyproline content in lung tissues, and enhanced sirius red staining for collagen in the lung tissue. Lung fibroblasts and alveolar type II (ATII) cells isolated from CeO2-exposed rats at 28days post-exposure demonstrated decreasing proliferation rate when compare to the controls. CeO2 exposure was cytotoxic and altered cell function as demonstrated by fibroblast apoptosis and aggregation, and ATII cell hypertrophy and hyperplasia with increased surfactant. The presence of stress fibers, expressed as α-smooth muscle actin (SMA), in CeO2-exposed fibroblasts and ATII cells was significantly increased compared to the control. Immunohistofluorescence analysis demonstrated co-localization of TGF-ß or α-SMA with prosurfactant protein C (SPC)-stained ATII cells. These results demonstrate that CeO2 exposure affects fibroblast function and induces EMT in ATII cells that play a role in lung fibrosis. These findings suggest potential adverse health effects in response to CeO2 nanoparticle exposure.

Nanoparticles-induced apoptosis of human airway epithelium is mediated by proNGF/p75NTR signaling.

Environmental and occupational exposures to respirable ultrafine fractions of particulate matter (PM) have been implicated in the initiation and exacerbation of lung diseases. However, the precise mechanisms underlying production of cell damage and death attributed to nanoparticles (NP) on human airway epithelium are not fully understood. This study examined the role of neurotrophic pathways in NP-induced airway toxicity. Size and agglomeration of TiO2 nanoparticles (TiO2-NP) and fine (TiO2-FP) particles were measured by dynamic light scattering. Expression and signaling of key neurotrophic factors and receptors were assessed by real-time polymerase chain reaction, flow cytometry, immunostaining, and Western blot in various respiratory epithelial cells after exposure to TiO2-NP or TiO2-FP. Particle-induced cell death was measured by flow cytometry after annexin V/propidium iodide staining. The role of neurotrophin-dependent apoptotic pathways was analyzed with specific blocking antibodies or siRNAs. Exposure of human epithelial cells to TiO2-NP enhanced interleukin (IL)-1α synthesis, as well as nerve growth factor (NGF) gene expression and protein levels, specifically the precursor form (proNGF). TiO2-NP exposure also increased expression of p75NRF receptor genes. These neurotropic factor and receptor responses were stimulated by IL-1α and abolished by its specific receptor antagonist (IL-1-ra). TiO2-NP also increased JNK phosphorylation and apoptosis, which was prevented by anti-p75NRF or NGFsiRNA. Data demonstrated that TiO2-NP exerted adverse effects in the respiratory tract by inducing unbalanced overexpression of immature neurotrophins, which led to apoptotic death of epithelial cells signaled through the death receptor p75NTR. This may result in airway inflammation and hyperreactivity after exposure to TiO2-NP.

Synergistic effects of engineered nanoparticles and organics released from laser printers using nano-enabled toners: potential health implications from exposures to the emitted organic aerosol.

Recent studies have shown that engineered nanoparticles (ENPs) are incorporated into toner powder used in printing equipment and released during their use. Thus, understanding the functional and structural composition and potential synergistic effects of this complex aerosol and released gaseous co-pollutants is critical in assessing their potential toxicological implications and risks. In this study, toner powder and PEPs were thoroughly examined for functional and molecular composition of the organic fraction and the concentration profile of 16 Environmental Protection Agency (EPA)-priority polycyclic aromatic hydrocarbons (PAH) using state of the art analytical methods. Results show significant differences in abundance of non-exchangeable organic hydrogen of toner powder and PEPs, with a stronger aromatic spectral signature in PEPs. Changes in structural composition of PEPs are indicative of radical additions and free-radical polymerization favored by catalytic reactions, resulting in formation of functionalized organic species. Particularly, accumulation of aromatic carbons with strong styrene-like molecular signatures on PEPs is associated with formation of semivolatile heavier aromatic species (i.e., PAHs). Further, the transformation of low molecular weight PAHs in the toner powder to high molecular weight PAHs in PEPs was documented and quantified. This may be a result of synergistic effects from catalytic metal/metal oxide ENPs incorporated into the toner and the presence/release of semi-volatile organic species (SVOCs). The presence of known carcinogenic PAHs on PEPs raises public health concerns and warrants further toxicological assessment.

Induction of cancer-associated fibroblast-like cells by carbon nanotubes dictates its tumorigenicity.

Tumor microenvironment has been recognized as a key determinant of tumor formation and metastasis, but how tumor microenvironment is affected by nanomaterials is essentially unknown. Here, we investigated whether carbon nanotubes (CNTs), a widely used nanomaterial with known carcinogenic potential, can affect cancer-associated fibroblasts (CAFs), which are a key component of tumor microenvironment that provides necessary support for tumor growth. We show for the first time that single-walled CNT and to a lesser extent multi-walled and its COOH-functionalized form induced CAF-like cells, which are non-tumorigenic in animals, but promote tumor growth of human lung carcinoma and CNT-transformed lung epithelial cells. The mechanism by which CNT-induced CAF-like cells promote tumor growth involved the acquisition of cancer stem cells (CSCs) in cancer population. Gene knockdown experiments showed that an expression of podoplanin on CAF-like cells is essential for their effects, indicating the functional role of CAF-like cells and podoplanin in CNT tumorigenic process. Our findings unveil a novel mechanism of CNT-induced carcinogenesis through the induction of CAF-like cells that support CSCs and drive tumor formation. Our results also suggest the potential utility of podoplanin as a mechanism-based biomarker for rapid screening of carcinogenicity of CNTs and related nanomaterials for their safer design.

Role of mesothelin in carbon nanotube-induced carcinogenic transformation of human bronchial epithelial cells.

Carbon nanotubes (CNTs) have been likened to asbestos in terms of morphology and toxicity. CNT exposure can lead to pulmonary fibrosis and promotion of tumorigenesis. However, the mechanisms underlying CNT-induced carcinogenesis are not well defined. Mesothelin (MSLN) is overexpressed in many human tumors, including mesotheliomas and pancreatic and ovarian carcinomas. In this study, the role of MSLN in the carcinogenic transformation of human bronchial epithelial cells chronically exposed to single-walled CNT (BSW) was investigated. MSLN overexpression was found in human lung tumors, lung cancer cell lines, and BSW cells. The functional role of MSLN in the BSW cells was then investigated by using stably transfected MSLN knockdown (BSW shMSLN) cells. MSLN knockdown resulted in significantly decreased invasion, migration, colonies on soft agar, and tumor sphere formation. In vivo, BSW shMSLN cells formed smaller primary tumors and less metastases. The mechanism by which MSLN contributes to these more aggressive behaviors was investigated by using ingenuity pathway analysis, which predicted that increased MSLN could induce cyclin E expression. We found that BSW shMSLN cells had decreased cyclin E, and their proliferation rate was reverted to nearly that of untransformed cells. Cell cycle analysis showed that the BSW shMSLN cells had an increased G2 population and a decreased S phase population, which is consistent with the decreased rate of proliferation. Together, our results indicate a novel role of MSLN in the malignant transformation of bronchial epithelial cells following CNT exposure, suggesting its utility as a potential biomarker and drug target for CNT-induced malignancies.

Multiwalled carbon nanotube-induced pulmonary inflammatory and fibrotic responses and genomic changes following aspiration exposure in mice: A 1-year postexposure study.

Pulmonary exposure to multiwalled carbon nanotubes (MWCNT) induces an inflammatory and rapid fibrotic response, although the long-term signaling mechanisms are unknown. The aim of this study was to examine the effects of 1, 10, 40, or 80 µg MWCNT administered by pharyngeal aspiration on bronchoalveolar lavage (BAL) fluid for polymorphonuclear cell (PMN) infiltration, lactate dehydrogenase (LDH) activity, and lung histopathology for inflammatory and fibrotic responses in mouse lungs 1 mo, 6 mo, and 1 yr postexposure. Further, a 120-µg crocidolite asbestos group was incorporated as a positive control for comparative purposes. Results showed that MWCNT increased BAL fluid LDH activity and PMN infiltration in a dose-dependent manner at all three postexposure times. Asbestos exposure elevated LDH activity at all 3 postexposure times and PMN infiltration at 1 mo and 6 mo postexposure. Pathological changes in the lung, the presence of MWCNT or asbestos, and fibrosis were noted at 40 and 80 µg MWCNT and in asbestos-exposed mice at 1 yr postexposure. To determine potential signaling pathways involved with MWCNT-associated pathological changes in comparison to asbestos, up- and down-regulated gene expression was determined in lung tissue at 1 yr postexposure. Exposure to MWCNT tended to favor those pathways involved in immune responses, specifically T-cell responses, whereas exposure to asbestos tended to favor pathways involved in oxygen species production, electron transport, and cancer. Data indicate that MWCNT are biopersistent in the lung and induce inflammatory and fibrotic pathological alterations similar to those of crocidolite asbestos, but may reach these endpoints by different mechanisms.

Toxicological Assessment of CoO and La2O3 Metal Oxide Nanoparticles in Human Small Airway Epithelial Cells.

Cobalt monoxide (CoO) and lanthanum oxide (La2O3) nanoparticles are 2 metal oxide nanoparticles with different redox potentials according to their semiconductor properties. By utilizing these two nanoparticles, this study sought to determine how metal oxide nanoparticle's mode of toxicological action is related to their physio-chemical properties in human small airway epithelial cells (SAEC). We investigated cellular toxicity, production of superoxide radicals and alterations in gene expression related to oxidative stress, and cellular death at 6 and 24 h following exposure to CoO and La2O3(administered doses: 0, 5, 25, and 50 µg/ml) nanoparticles. CoO nanoparticles induced gene expression related to oxidative stress at 6 h. After characterizing the nanoparticles, transmission electron microscope analysis showed SAEC engulfed CoO and La2O3nanoparticles. CoO nanoparticles were toxic after 6 and 24 h of exposure to 25.0 and 50.0 µg/ml administered doses, whereas, La2O3nanoparticles were toxic only after 24 h using the same administered doses. Based upon the Volumetric Centrifugation Methodin vivoSedimentation, Diffusion, and Dosimetry, the dose of CoO and La2O3nanoparticles delivered at 6 and 24 h were determined to be: CoO: 1.25, 6.25, and 12.5 µg/ml; La2O3: 5, 25, and 50 µg/ml and CoO: 4, 20, and 40 µg/ml; and La2O3: 5, 25, 50 µg/ml, respectively. CoO nanoparticles produced more superoxide radicals and caused greater stimulation of total tyrosine and threonine phosphorylation at both 6 and 24 h when compared with La2O3nanoparticles. Taken together, these data provide evidence that different toxicological modes of action were involved in CoO and La2O3metal oxide nanoparticle-induced cellular toxicity.

mRNAs and miRNAs in whole blood associated with lung hyperplasia, fibrosis, and bronchiolo-alveolar adenoma and adenocarcinoma after multi-walled carbon nanotube inhalation exposure in mice.

Inhalation exposure to multi-walled carbon nanotubes (MWCNT) in mice results in inflammation, fibrosis and the promotion of lung adenocarcinoma; however, the molecular basis behind these pathologies is unknown. This study determined global mRNA and miRNA profiles in whole blood from mice exposed by inhalation to MWCNT that correlated with the presence of lung hyperplasia, fibrosis, and bronchiolo-alveolar adenoma and adenocarcinoma. Six-week-old, male, B6C3F1 mice received a single intraperitoneal injection of either the DNA-damaging agent methylcholanthrene (MCA, 10 µg g(-1) body weight) or vehicle (corn oil). One week after injections, mice were exposed by inhalation to MWCNT (5 mg m(-3), 5 hours per day, 5 days per week) or filtered air (control) for a total of 15 days. At 17 months post-exposure, mice were euthanized and examined for the development of pathological changes in the lung, and whole blood was collected and analyzed using microarray analysis for global mRNA and miRNA expression. Numerous mRNAs and miRNAs in the blood were significantly up- or down-regulated in animals developing pathological changes in the lung after MCA/corn oil administration followed by MWCNT/air inhalation, including fcrl5 and miR-122-5p in the presence of hyperplasia, mthfd2 and miR-206-3p in the presence of fibrosis, fam178a and miR-130a-3p in the presence of bronchiolo-alveolar adenoma, and il7r and miR-210-3p in the presence of bronchiolo-alveolar adenocarcinoma, among others. The changes in miRNA and mRNA expression, and their respective regulatory networks, identified in this study may potentially serve as blood biomarkers for MWCNT-induced lung pathological changes.

Effects of nickel-oxide nanoparticle pre-exposure dispersion status on bioactivity in the mouse lung.

Nanotechnology is emerging as one of the world's most promising new technologies. From a toxicology perspective, nanoparticles possess two features that promote their bioactivity. The first involves physical-chemical characteristics of the nanoparticle, which include the surface area of the nanoparticle. The second feature is the ability of the nanoparticle to traverse cell membranes. These two important nanoparticle characteristics are greatly influenced by placing nanoparticles in liquid medium prior to animal exposure. Nanoparticles tend to agglomerate and clump in suspension, making it difficult to reproducibly deliver them for in vivo or in vitro experiments, possibly affecting experimental variability. Thus, we hypothesize that nanoparticle dispersion status will correlate with the in vivo bioactivity/toxicity of the particle. To test our hypothesis, nano-sized nickel oxide was suspended in four different dispersion media (phosphate-buffered saline (PBS), dispersion medium (DM), a combination of dipalmitoyl-phosphatidyl choline (DPPC) and albumin in concentrations that mimic diluted alveolar lining fluid), Survanta®, or pluronic (Pluronic F-68). Well-dispersed and poorly dispersed suspensions were generated in each media by varying sonication time on ice utilizing a Branson Sonifer 450 (25W continuous output, 20 min or 5 min, respectively). Mice (male, C57BL/6J, 7-weeks-old) were given 0-80 µg/mouse of nano-sized nickel oxide in the different states of dispersion via pharyngeal aspiration. At 1 and 7 d post-exposure, mice underwent whole lung lavage to assess pulmonary inflammation and injury as a function of dispersion status, dose and time. The results show that pre-exposure dispersion status correlates with pulmonary inflammation and injury. These results indicate that a greater degree of pre-exposure dispersion increases pulmonary inflammation and cytotoxicity, as well as decreases in the integrity of the blood-gas barrier in the lung.

Genotoxic effects of synthetic amorphous silica nanoparticles in the mouse lymphoma assay.

Synthetic amorphous silica nanoparticles (SAS NPs) have been used in various industries, such as plastics, glass, paints, electronics, synthetic rubber, in pharmaceutical drug tablets, and a as food additive in many processed foods. There are few studies in the literature on NPs using gene mutation approaches in mammalian cells, which represents an important gap for genotoxic risk estimations. To fill this gap, the mouse lymphoma L5178Y/Tk+/- assay (MLA) was used to evaluate the mutagenic effect for five different concentrations (from 0.01 to 150 µg/mL) of two different sizes of SAS NPs (7.172 and 7.652 nm) and a fine collodial form of silicon dioxide (SiO2). This assay detects a broad spectrum of mutational events, from point mutations to chromosome alterations. The results obtained indicate that the two selected SAS NPs are mutagenic in the MLA assay, showing a concentration-dependent effect. The relative mutagenic potencies according to the induced mutant frequency (IMF) are as follows: SAS NPs (7.172 nm) (IMF = 705.5 × 10-6), SAS NPs (7.652 nm) (IMF = 575.5 × 10-6), and SiO2 (IMF = 57.5 × 10-6). These in vitro results, obtained from mouse lymphoma cells, support the genotoxic potential of NPs as well as focus the discussion of the benefits/risks associated with their use in different areas.

Effects of Laser Printer-Emitted Engineered Nanoparticles on Cytotoxicity, Chemokine Expression, Reactive Oxygen Species, DNA Methylation, and DNA Damage: A Comprehensive in Vitro Analysis in Human Small Airway Epithelial Cells, Macrophages, and Lymphoblasts.

BACKGROUND: Engineered nanomaterials (ENMs) incorporated into toner formulations of printing equipment become airborne during consumer use. Although information on the complex physicochemical and toxicological properties of both toner powders and printer-emitted particles (PEPs) continues to grow, most toxicological studies have not used the actual PEPs but rather have primarily used raw toner powders, which are not representative of current exposures experienced at the consumer level during printing. OBJECTIVES: We assessed the biological responses of a panel of human cell lines to PEPs. METHODS: Three physiologically relevant cell lines--small airway epithelial cells (SAECs), macrophages (THP-1 cells), and lymphoblasts (TK6 cells)--were exposed to PEPs at a wide range of doses (0.5-100 µg/mL) corresponding to human inhalation exposure durations at the consumer level of 8 hr or more. Following treatment, toxicological parameters reflecting distinct mechanisms were evaluated. RESULTS: PEPs caused significant membrane integrity damage, an increase in reactive oxygen species (ROS) production, and an increase in pro-inflammatory cytokine release in different cell lines at doses equivalent to exposure durations from 7.8 to 1,500 hr. Furthermore, there were differences in methylation patterns that, although not statistically significant, demonstrate the potential effects of PEPs on the overall epigenome following exposure. CONCLUSIONS: The in vitro findings obtained in this study suggest that laser printer-emitted engineered nanoparticles may be deleterious to lung cells and provide preliminary evidence of epigenetic modifications that might translate to pulmonary disorders.

Effects of nitrogen-doped multi-walled carbon nanotubes compared to pristine multi-walled carbon nanotubes on human small airway epithelial cells.

Nitrogen-doped multi-walled carbon nanotubes (ND-MWCNTs) are modified multi-walled carbon nanotubes (MWCNTs) with enhanced electrical properties that are used in a variety of applications, including fuel cells and sensors; however, the mode of toxic action of ND-MWCNT has yet to be fully elucidated. In the present study, we compared the interaction of ND-MWCNT or pristine MWCNT-7 with human small airway epithelial cells (SAEC) and evaluated their subsequent bioactive effects. Transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction suggested the presence of N-containing defects in the lattice of the nanotube. The ND-MWCNTs were determined to be 93.3% carbon, 3.8% oxygen, and 2.9% nitrogen. A dose-response cell proliferation assay showed that low doses of ND-MWCNT (1.2µg/ml) or MWCNT-7 (0.12µg/ml) increased cellular proliferation, while the highest dose of 120µg/ml of either material decreased proliferation. ND-MWCNT and MWCNT-7 appeared to interact with SAEC at 6h and were internalized by 24h. ROS were elevated at 6 and 24h in ND-MWCNT exposed cells, but only at 6h in MWCNT-7 exposed cells. Significant alterations to the cell cycle were observed in SAEC exposed to either 1.2µg/ml of ND-MWCNT or MWCNT-7 in a time and material-dependent manner, possibly suggesting potential damage or alterations to cell cycle machinery. Our results indicate that ND-MWCNT induce effects in SAEC over a time and dose-related manner which differ from MWCNT-7. Therefore, the physicochemical characteristics of the materials appear to alter their biological effects.

Small airway epithelial cells exposure to printer-emitted engineered nanoparticles induces cellular effects on human microvascular endothelial cells in an alveolar-capillary co-culture model.

The printer is one of the most common office equipment. Recently, it was reported that toner formulations for printing equipment constitute nano-enabled products (NEPs) and contain engineered nanomaterials (ENMs) that become airborne during printing. To date, insufficient research has been performed to understand the potential toxicological properties of printer-emitted particles (PEPs) with several studies using bulk toner particles as test particles. These studies demonstrated the ability of toner particles to cause chronic inflammation and fibrosis in animal models. However, the toxicological implications of inhalation exposures to ENMs emitted from laser printing equipment remain largely unknown. The present study investigates the toxicological effects of PEPs using an in vitro alveolar-capillary co-culture model with Human Small Airway Epithelial Cells (SAEC) and Human Microvascular Endothelial Cells (HMVEC). Our data demonstrate that direct exposure of SAEC to low concentrations of PEPs (0.5 and 1.0 µg/mL) caused morphological changes of actin remodeling and gap formations within the endothelial monolayer. Furthermore, increased production of reactive oxygen species (ROS) and angiogenesis were observed in the HMVEC. Analysis of cytokine and chemokine levels demonstrates that interleukin (IL)-6 and MCP-1 may play a major role in the cellular communication observed between SAEC and HMVEC and the resultant responses in HMVEC. These data indicate that PEPs at low, non-cytotoxic exposure levels are bioactive and affect cellular responses in an alveolar-capillary co-culture model, which raises concerns for potential adverse health effects.

Multi-walled carbon nanotube-induced gene expression in vitro: concordance with in vivo studies.

There is a current interest in reducing the in vivo toxicity testing of nanomaterials in animals by increasing toxicity testing using in vitro cellular assays; however, toxicological results are seldom concordant between in vivo and in vitro models. This study compared global multi-walled carbon nanotube (MWCNT)-induced gene expression from human lung epithelial and microvascular endothelial cells in monoculture and coculture with gene expression from mouse lungs exposed to MWCNT. Using a cutoff of 10% false discovery rate and 1.5 fold change, we determined that there were more concordant genes (gene expression both up- or downregulated in vivo and in vitro) expressed in both cell types in coculture than in monoculture. When reduced to only those genes involved in inflammation and fibrosis, known outcomes of in vivo MWCNT exposure, there were more disease-related concordant genes expressed in coculture than monoculture. Additionally, different cellular signaling pathways are activated in response to MWCNT dependent upon culturing conditions. As coculture gene expression better correlated with in vivo gene expression, we suggest that cellular cocultures may offer enhanced in vitro models for nanoparticle risk assessment and the reduction of in vivo toxicological testing.