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Inhalation of silica particles can induce inflammatory lung reactions that lead to silicosis and/or lung cancer when the particles are biopersistent. This toxic activity of silica dusts is extremely variable depending on their source and preparation methods. The exact molecular moiety that explains and predicts this variable toxicity of silica remains elusive. Here, we have identified a unique subfamily of silanols as the major determinant of silica particle toxicity. This population of "nearly free silanols" (NFS) appears on the surface of quartz particles upon fracture and can be modulated by thermal treatments. Density functional theory calculations indicates that NFS locate at an intersilanol distance of 4.00 to 6.00 Å and form weak mutual interactions. Thus, NFS could act as an energetically favorable moiety at the surface of silica for establishing interactions with cell membrane components to initiate toxicity. With ad hoc prepared model quartz particles enriched or depleted in NFS, we demonstrate that NFS drive toxicity, including membranolysis, in vitro proinflammatory activity, and lung inflammation. The toxic activity of NFS is confirmed with pyrogenic and vitreous amorphous silica particles, and industrial quartz samples with noncontrolled surfaces. Our results identify the missing key molecular moieties of the silica surface that initiate interactions with cell membranes, leading to pathological outcomes. NFS may explain other important interfacial processes involving silica particles. [ABSTRACT FROM AUTHOR]

The exposure to respirable crystalline silica (RCS), e.g. quartz, in industrial settings can induce silicosis and may cause tumours in chronic periods. Consequently, RCS in the form of quartz and cristobalite has been classified as human lung carcinogen category 1 by the International Agency for Research on Cancer in 1997, acknowledging differences in hazardous potential depending on source as well as chemical, thermal, and mechanical history. The physico-chemical determinants of quartz toxicity are well understood and are linked to density and abundance of surface silanol groups/radicals. Hence, poly-2-vinylpyridine-N-oxide and aluminium lactate, which effectively block highly reactive silanol groups at the quartz surface, have formerly been introduced as therapeutic approaches in the occupational field. In the traditional ceramics industry, quartz-containing raw materials are indispensable for the manufacturing process, and workers are potentially at risk of developing quartzrelated lung diseases. Therefore, in the present study, two organosilanes, i.e. Dynasylan® PTMO and Dynasylan® SIVO 160, were tested as preventive, covalent quartz-coating agents to render ceramics production safer without loss in product quality. Coating effectiveness and coating stability (up to 1 week) in artificial alveolar and lysosomal fluids were first analysed in vitro, using the industrially relevant quartz Q1 as RCS model, quartz DQ12 as a positive control, primary rat alveolar macrophages as cellular model system (75 µg cm-2; 4 h of incubation ± aluminium lactate to verify quartz-related effects), and lactate dehydrogenase release and DNA strand break induction (alkaline comet assay) as biological endpoints. In vitro results with coated quartz were confirmed in a 90-day intratracheal instillation study in rats with inflammatory parameters as most relevant readouts. The results of the present study indicate that in particular Dynasylan® SIVO 160 (0.2% w/w of quartz) was able to effectively and stably block toxicity of biologically active quartz species without interfering with technical process quality of certain ceramic products. In conclusion, covalent organosilane coatings of quartz might represent a promising strategy to increase workers' safety in the traditional ceramics industry. [ABSTRACT FROM AUTHOR]

Desert dust is increasingly recognized as a major air pollutant affecting respiratory health. Since desert dust exposure cannot be regulated, the hazardousness of its components must be understood to enable health risk mitigation strategies. Saharan dust (SD) comprises about half of the global desert dust and contains quartz, a toxic mineral dust that is known to cause severe lung diseases via oxidative stress and activation of the NLRP3 inflammasome-interleukin-1β pathway. We aimed to assess the physicochemical and microbial characteristics of SD responsible for toxic effects. Also, we studied the oxidative and pro-inflammatory potential of SD in alveolar epithelial cells and the activation of the NLRP3 inflammasome in macrophage-like cells in comparison to quartz dusts and synthetic amorphous silica (SAS). Characterization revealed that SD contained Fe, Al, trace metals, sulfate, diatomaceous earth, and endotoxin and had the capacity to generate hydroxyl radicals. We exposed A549 lung epithelial cells and wild-type and NLRP3 -/- THP-1 macrophage-like cells to SD, three well-investigated quartz dusts, and SAS. SD induced oxidative stress in A549 cells after 24 h more potently than the quartz dusts. The quartz dusts and SAS upregulated interleukin 8 expression after 4 h and 24 h while SD only caused a transient upregulation. SD, the quartz dusts, and SAS induced interleukin-1β release from wild-type THP-1 cells>20-fold stronger than from NLRP3 -/- THP-1 cells. Interleukin-1β release was lower for SD, in which microbial components including endotoxin were heat-destructed. In conclusion, microbial components in SD are pivotal for its toxicity. In the epithelium, the effects of SD contrasted with crystalline and amorphous silica in terms of potency and persistence. In macrophages, the strong involvement of the NLRP3 inflammasome emphasizes the acute and chronic health risks associated with desert dust exposure., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

In vitro lung cell models like air-liquid interface (ALI) and 3D cell cultures have advanced greatly in recent years, being especially valuable for testing advanced materials (e.g., nanomaterials, fibrous substances) when considering inhalative exposure. Within this study, we established submerged and ALI cell culture models utilizing A549 cells as mono-cultures and co-cultures with differentiated THP-1 (dTHP-1), as well as mono-cultures of dTHP-1. After ALI and submerged exposures towards α-quartz particles (Min-U-Sil5), with depositions ranging from 15 to 60 µg/cm 2 , comparison was made with respect to their transcriptional cellular responses employing high-throughput RT-qPCR. A significant dose- and time-dependent induction of genes coding for inflammatory proteins, e.g., IL-1A , IL-1B , IL-6 , IL-8 , and CCL22 , as well as genes associated with oxidative stress response such as SOD2 , was observed, even more pronounced in co-cultures. Changes in the expression of similar genes were more pronounced under submerged conditions when compared to ALI exposure in the case of A549 mono-cultures. Hereby, the activation of the NF-κB signaling pathway and the NLRP3 inflammasome seem to play an important role. Regarding genotoxicity, neither DNA strand breaks in ALI cultivated cells nor a transcriptional response to DNA damage were observed. Altogether, the toxicological responses depended considerably on the cell culture model and exposure scenario, relevant to be considered to improve toxicological risk assessment.

Background: Respirable mineral particles represent a potential health hazard in occupational settings and ambient air. Previous studies show that mineral particles may induce cytotoxicity and inflammatory reactions in vitro and in vivo and that the potency varies between samples of different composition. However, the reason for these differences is largely unknown and the impact of mineralogical composition on the biological effects of mineral dust remains to be determined., Methods: We have assessed the cytotoxic and pro-inflammatory effects of ten mineral particle samples of different composition in human bronchial epithelial cells (HBEC3-KT) and THP-1-derived macrophages, as well as their membranolytic properties in erythrocytes. Moreover, the results were compiled with the results of recently published experiments on the effects of stone particle exposure and analysed using linear regression models to elucidate which mineral components contribute most to the toxicity of mineral dust., Results: While all mineral particle samples were more cytotoxic to HBEC3-KT cells than THP-1 macrophages, biotite and quartz were among the most cytotoxic in both cell models. In HBEC3-KT cells, biotite and quartz also appeared to be the most potent inducers of pro-inflammatory cytokines, while the quartz, Ca-feldspar, Na-feldspar and biotite samples were the most potent in THP-1 macrophages. All particle samples except quartz induced low levels of membranolysis. The regression analyses revealed associations between particle bioactivity and the content of quartz, muscovite, plagioclase, biotite, anorthite, albite, microcline, calcite, chlorite, orthopyroxene, actinolite and epidote, depending on the cell model and endpoint. However, muscovite was the only mineral consistently associated with increased cytotoxicity and cytokine release in both cell models., Conclusions: The present study provides further evidence that mineral particles may induce cytotoxicity and inflammation in cells of the human airways and that particle samples of different mineralogical composition differ in potency. The results show that quartz, while being among the most potent samples, does not fully predict the toxicity of mineral dust, highlighting the importance of other particle constituents. Moreover, the results indicate that the phyllosilicates muscovite and biotite may be more potent than other minerals assessed in the study, suggesting that this group of sheet-like minerals may warrant further attention., (© 2022. The Author(s).)

Objective: Stone minerals are a partially ignored environmental challenge but a significant contributor to urban air pollution. We examined if short-term exposure to two stone minerals - quartz diorite and rhomb porphyry - commonly used in asphalt pavement would affect lung function, promote pulmonary inflammation, and affect bronchial reactivity differently., Methods: Our randomized crossover study included 24 healthy, non-smoking young adults exposed to the stone minerals quartz diorite, rhomb porphyry, and control dust (lactose). Exposure occurred in an exposure chamber, in three separate 4-hour exposure sessions. Fractional exhaled nitric oxide (FeNO) and lung function were monitored before exposure, then immediately following exposure, and 4 and 24 hours after exposure. In addition, methacholine was administered 4 hours following exposure, and exhaled breath condensate (EBC) was collected before exposure, then immediately and 4 hours after exposure. EBC was analyzed for pH, thiobarbituric acid reactive substances (TBARS), intercellular adhesion molecule 1 (ICAM-1), interleukin-6 (IL-6), IL-10, P-Selectin, surfactant protein D (SP-D), and tumor necrosis factor-α (TNF-α)., Results: Our results showed significantly elevated concentrations of FeNO after exposure to quartz diorite compared to rhomb porphyry, suggesting that quartz diorite is more likely to trigger pulmonary inflammation after short-term exposure. Moreover, short-term exposure to rhomb porphyry was associated with a modest but statistically significant decline in forced vital capacity (FVC) compared to quartz diorite., Conclusion: These results emphasize that using stone material in asphalt road construction should be reconsidered as it may affect lung inflammation and lung function in exposed subjects.

The occupational exposure to particles such as crystalline quartz and its impact on the respiratory tract have been studied extensively in recent years. For hazard assessment, the development of physiologically more relevant in-vitro models, i.e., air-liquid interface (ALI) cell cultures, has greatly progressed. Within this study, pulmonary culture models employing A549 and differentiated THP-1 cells as mono-and co-cultures were investigated. The different cultures were exposed to α-quartz particles (Min-U-Sil5) with doses ranging from 15 to 66 µg/cm 2 under submerged and ALI conditions and cytotoxicity as well as cytokine release were analyzed. No cytotoxicity was observed after ALI exposure. Contrarily, Min-U-Sil5 was cytotoxic at the highest dose in both submerged mono- and co-cultures. A concentration-dependent release of interleukin-8 was shown for both exposure types, which was overall stronger in co-cultures. Our findings showed considerable differences in the toxicological responses between ALI and submerged exposure and between mono- and co-cultures. A substantial influence of the presence or absence of serum in cell culture media was noted as well. Within this study, the submerged culture was revealed to be more sensitive. This shows the importance of considering different culture and exposure models and highlights the relevance of communication between different cell types for toxicological investigations.

Humans will set foot on the Moon again soon. The lunar dust (LD) is potentially reactive and could pose an inhalation hazard to lunar explorers. We elucidated LD toxicity and investigated the toxicological impact of particle surface reactivity (SR) using three LDs, quartz, and TiO 2 . We first isolated the respirable-size-fraction of an Apollo-14 regolith and ground two coarser samples to produce fine LDs with increased SR. SR measurements of these five respirable-sized dusts, determined by their in-vitro ability to generate hydroxyl radicals (•OH), showed that ground LDs > unground LD ≥ TiO 2 ≥ quartz. Rats were each intratracheally instilled with 0, 1, 2.5, or 7.5 mg of a test dust. Toxicity biomarkers and histopathology were assessed up to 13 weeks after the bolus instillation. All dusts caused dose-dependent-increases in pulmonary lesions and toxicity biomarkers. The three LDs, which possessed mineral compositions/properties similar to Arizona volcanic ash, were moderately toxic. Despite a 14-fold •OH difference among these three LDs, their toxicities were indistinguishable. Quartz produced the lowest •OH amount but showed the greatest toxicity. Our results showed no correlation between the toxicity of mineral dusts and their ability to generate free radicals. We also showed that the amounts of oxidants per neutrophil increased with doses, time and the cytotoxicity of the dusts in the lung, which supports our postulation that dust-elicited neutrophilia is the major persistent source of oxidative stress. These results and the discussion of the crucial roles of the short-lived, continuously replenished neutrophils in dust-induced pathogenesis are presented.

Background: Respirable stone- and mineral particles may be a major constituent in occupational and ambient air pollution and represent a possible health hazard. However, with exception of quartz and asbestos, little is known about the toxic properties of mineral particles. In the present study, the pro-inflammatory and cytotoxic responses to six stone particle samples of different composition and with diameter below 10 μm were assessed in human bronchial epithelial cells (HBEC3-KT), THP-1 macrophages and a HBEC3-KT/THP-1 co-culture. Moreover, particle-induced lysis of human erythrocytes was assessed to determine the ability of the particles to lyse biological membranes. Finally, the role of the NLRP3 inflammasome was assessed using a NLRP3-specific inhibitor and detection of ASC oligomers and cleaved caspase-1 and IL-1β. A reference sample of pure α-quartz was included for comparison., Results: Several stone particle samples induced a concentration-dependent increase in cytotoxicity and secretion of the pro-inflammatory cytokines CXCL8, IL-1α, IL-1β and TNFα. In HBEC3-KT, quartzite and anorthosite were the most cytotoxic stone particle samples and induced the highest levels of cytokines. Quartzite and anorthosite were also the most cytotoxic samples in THP-1 macrophages, while anorthosite and hornfels induced the highest cytokine responses. In comparison, few significant differences between particle samples were detected in the co-culture. Adjusting responses for differences in surface area concentrations did not fully account for the differences between particle samples. Moreover, the stone particles had low hemolytic potential, indicating that the effects were not driven by membrane lysis. Pre-incubation with a NLRP3-specific inhibitor reduced stone particle-induced cytokine responses in THP-1 macrophages, but not in HBEC3-KT cells, suggesting that the effects are mediated through different mechanisms in epithelial cells and macrophages. Particle exposure also induced an increase in ASC oligomers and cleaved caspase-1 and IL-1β in THP-1 macrophages, confirming the involvement of the NLRP3 inflammasome., Conclusions: The present study indicates that stone particles induce cytotoxicity and pro-inflammatory responses in human bronchial epithelial cells and macrophages, acting through NLRP3-independent and -dependent mechanisms, respectively. Moreover, some particle samples induced cytotoxicity and cytokine release to a similar or greater extent than α-quartz. Thus, these minerals warrant further attention in future research.

Artificial quartz stone is a new type of decorative building material, there are serious dust exposure hazards during the production and processing. Due to the lack of effective health protection for practitioners, silicosis caused by artificial quartz stone dust has been widely reported worldwide in recent years, which seriously affect the health of practitioners. This article summarizes the use status of artificial quartz stone, the exposure of practitioners and the lung tissue damage caused by dust, analyzes its pathogenic characteristics, and provides a basis for protecting the occupational population and improving occupational health.

Quartz can increase oxidative stress, lipid peroxidation, and inflammation. The objective of this study was to explore the volatile biomarkers of quartz-induced lung injury using a lung alveolar cell model. We exposed the human alveolar A549 cell line to 0, 200, and 500 μg/mL quartz particles for 24 h and used gas chromatography-mass spectrometry to measure the volatile metabolites in the headspace air of cells. We identified ten volatile metabolites that had concentration-response relationships with particles exposure, including 1,2,4-oxadiazole, 5-(4-nitrophenyl)-3-phenyl- (CAS: 28825-12-9), 2,6-dimethyl-6-trifluoroacetoxyoctane (CAS: 61986-67-2), 3-buten-1-amine, N,N-dimethyl- (CAS: 55831-89-5), 2-propanol, 2-methyl- (CAS: 75-65-0), glycolaldehyde dimethyl acetal (CAS: 30934-97-5), propanoic acid, 2-oxo-, ethyl ester (CAS: 617-35-6), octane (CAS: 111-65-9), octane, 3,3-dimethyl- (CAS: 4110-44-5), heptane, 2,3-dimethyl- (CAS: 3074-71-3) and ethanedioic acid, bis(trimethylsilyl) ester (CAS: 18294-04-7). The volatile biomarkers are generated through the pathways of propanoate and nitrogen metabolism. The volatile biomarkers of the alkanes and methylated alkanes are related to oxidative and lipid peroxidation of the cell membrane. The lung alveolar cell model has the potential to explore the volatile biomarkers of particulate-induced lung injury.

The pathogenicity of quartz involves lysosomal alteration in alveolar macrophages. This event triggers the inflammatory cascade that may lead to quartz-induced silicosis and eventually lung cancer. Experiments with synthetic quartz crystals recently showed that quartz dust is cytotoxic only when the atomic order of the crystal surfaces is upset by fracturing. Cytotoxicity was not observed when quartz had as-grown, unfractured surfaces. These findings raised questions on the potential impact of quartz surfaces on the phagolysosomal membrane upon internalization of the particles by macrophages. To gain insights on the surface-induced cytotoxicity of quartz, as-grown and fractured quartz particles in respirable size differing only in surface properties related to fracturing were prepared and physico-chemically characterized. Synthetic quartz particles were compared to a well-known toxic commercial quartz dust. Membranolysis was assessed on red blood cells, and quartz uptake, cell viability and effects on lysosomes were assessed on human PMA-differentiated THP-1 macrophages, upon exposing cells to increasing concentrations of quartz particles (10-250 µg/ml). All quartz samples were internalized, but only fractured quartz elicited cytotoxicity and phagolysosomal alterations. These effects were blunted when uptake was suppressed by incubating macrophages with particles at 4 °C. Membranolysis, but not cytotoxicity, was quenched when fractured quartz was incubated with cells in protein-supplemented medium. We propose that, upon internalization, the phagolysosome environment rapidly removes serum proteins from the quartz surface, restoring quartz membranolytic activity in the phagolysosomes. Our findings indicate that the cytotoxic activity of fractured quartz is elicited by promoting phagolysosomal membrane alteration.

Background: Talc, a hydrous magnesium silicate, often used for genital hygiene purposes, is associated with ovarian carcinoma in case-control studies. Its potential to cause inflammation, injury, and functional changes in cells has been described. A complication of such studies is that talc preparations may be contaminated with other materials. A previous study by (Beck et al. Toxicol Appl Pharmacol 87:222-34, 1987) used a hamster model to study talc and granite dust exposure effects on various biochemical and cellular inflammatory markers. Our current study accessed key materials used in that 1987 study; we re-analyzed the original talc dust with contemporary scanning electron microscopy and energy dispersive x-ray analysis (SEM/EDX) for contaminants. We also examined the original bronchoalveolar lavage (BAL) cells with polarized light microscopy to quantify cell-associated birefringent particles to gain insight into the talc used., Results: SEM/EDX analyses showed that asbestos fibers, quartz, and toxic metal particulates were below the limits of detection in the original talc powder. However, fibers with aspect ratios ≥3:1 accounted for 22% of instilled material, mostly as fibrous talc. Talc (based on Mg/Si atomic weight % ratio) was the most abundant chemical signature, and magnesium silicates with various other elements made up the remainder. BAL cell counts confirmed the presence of acute inflammation, which followed intratracheal instillation. Measurements of cell associated birefringent particles phagocytosis revealed significant differences among talc, granite, and control exposures with high initial uptake of talc compared to granite, but over the 14-day experiment, talc phagocytosis by lavaged cells was significantly less than that of granite. Phagocytosis of talc fibers by macrophages was observed, and birefringent particles were found in macrophages, neutrophils, and multinucleate giant cells in lavaged cells from talc-exposed animals., Conclusion: Our data support the contention that talc, even without asbestos and other known toxic contaminants, may elicit inflammation and contribute to lung disease. Our findings support the conclusions of (Beck et al. Toxicol Appl Pharmacol 87:222-34, 1987) study. By analyzing particulate exposures with polarized light microscopy and SEM/EDX, fibrous talc was identified and a distinctive pattern of impaired particulate ingestion was demonstrated.

Introduction: Outbreaks of silicosis have bene recently reported in artificial stone workers., Aim: To describe the features of silicosis in quartz conglomerate workers in North-Eastern Italy., Methods: Active search of pneumoconiosis was performed in 11 companies of North-Eastern Italy involved in the fabrication of quartz conglomerate countertops. Occupational history, lung function tests, chest X-ray and high resolution computed tomography (HRCT) were performed. In selected cases, trans-bronchial biopsies were taken for histological evaluation and identification of silica crystals in the tissue. Cumulative exposure to crystalline silica was estimated., Results: We recruited 45 workers and 24 cases of silicosis were diagnosed. Mean age at diagnosis was 43 years and duration of exposure to quartz conglomerate dust was 3.5 to 20 years. The average silica cumulative exposure was 4.3 mg/m3/y. Abnormal findings were detected in 42% of chest X-rays, in 33% of spirometry and 50% of carbon monoxide lung diffusion (DLco). HRCTs were abnormal in all cases showing well-defined rounded opacities, irregular/linear intralobular opacities and bilateral enlarged mediastinal lymph-nodes. Histological findings consistent with silicosis were observed in 24 cases. Numerous silica particles (diameter 0.1-5 µm) were identified in lung tissue., Conclusions: We reported an unexpected high incidence of silicosis in Italian workers exposed to quartz conglomerate dust. The results suggest that chest HRCT is indicated for screening of workers with high exposure to silica and DLco should be added to spirometry in health surveillance. More rigorous application of safety regulations and more effective preventive interventions at work are necessary.

Background: Silica nanoparticles (SiNPs) are among the most widely manufactured and used nanoparticles. Concerns about potential health effects of SiNPs have therefore risen. Using a 3D tri-culture model of the alveolar lung barrier we examined effects of exposure to SiNPs (Si10) and crystalline silica (quartz; Min-U-Sil) in the apical compartment consisting of human alveolar epithelial A549 cells and THP-1-derived macrophages, as well as in the basolateral compartment with Ea.hy926 endothelial cells. Inflammation-related responses were measured by ELISA and gene expression., Results: Exposure to both Si10 and Min-U-Sil induced gene expression and release of CXCL8, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α) and interleukin-1β (IL-1β) in a concentration-dependent manner. Cytokine/chemokine expression and protein levels were highest in the apical compartment. Si10 and Min-U-Sil also induced expression of adhesion molecules ICAM-1 and E-selectin in the apical compartment. In the basolateral endothelial compartment we observed marked, but postponed effects on expression of all these genes, but only at the highest particle concentrations. Geneexpressions of heme oxygenase-1 (HO-1) and the metalloproteases (MMP-1 and MMP-9) were less affected. The IL-1 receptor antagonist (IL-1RA), markedly reduced effects of Si10 and Min-U-Sil exposures on gene expression of cytokines and adhesion molecules, as well as cytokine-release in both compartments., Conclusions: Si10 and Min-U-Sil induced gene expression and release of pro-inflammatory cytokines/adhesion molecules at both the epithelial/macrophage and endothelial side of a 3D tri-culture. Responses in the basolateral endothelial cells were only induced at high concentrations, and seemed to be mediated by IL-1α/β released from the apical epithelial cells and macrophages.

Following inhalation and deposition in the alveolar region at sufficient dose, biopersistent (nano)materials generally provoke pulmonary inflammation. Alveolar macrophages (AMs) are mediators of pulmonary immune responses and were broadly categorized in pro-inflammatory M1 and anti-inflammatory M2 macrophages. This study aimed at identifying AM phenotype as M1 or M2 upon short-term inhalation exposure to different (nano)materials followed by a postexposure period. Phenotyping of AM was retrospectively performed using immunohistochemistry. M1 (CD68 + iNOS + ) and M2 (CD68 + CD206 + and CD68 + ArgI + ) AMs were characterized in formalin-fixed, paraffin-embedded lung tissue of rats exposed for 6 hours/day for 5 days to air, 100 mg/m 3 nano-TiO 2 , 25 mg/m 3 nano-CeO 2 , 32 mg/m 3 multiwalled carbon nanotubes, or 100 mg/m 3 micron-sized quartz. During acute inflammation, relative numbers of M1 AMs were markedly increased, whereas relative numbers of M2 were generally decreased compared to control. Following an exposure-free period, changes in iNOS or CD206 expression correlated with persistence, regression, or progression of inflammation, suggesting a role of M1/M2 AMs in the pathogenesis of pulmonary inflammation. However, no clear correlation of AM subpopulations with qualitatively distinct histopathological findings caused by different (nano)materials was found. A more detailed understanding of the processes underlaying these morphological changes is needed to identify biomarkers for different histopathological outcomes.

Several types of engineered nanoparticles (ENP) have been shown to adversely affect male reproduction in rodent studies, but the airway route of exposure has been little investigated. This precludes adequate risk assessment of ENP exposure in occupational settings. Titanium dioxide nanoparticles (TiO 2 NP) have been shown to affect total sperm count in adult male mice after intravenous and oral administration. This study aimed to investigate whether also airway exposure would affect sperm counts in male mice. Mature C57BL/6J mice were intratracheally instilled with 63 μg of rutile nanosized TiO 2 , once weekly for seven weeks. Respirable α-quartz (SRM1878a) was included at a similar dose level as a positive control for pulmonary inflammation. BALF cell composition showed neutrophil granulocyte influx as indication of pulmonary inflammation in animals exposed to TiO 2 NP and α-quartz, but none of the particle exposures affected weight of testes or the epididymis, sperm counts or plasma testosterone when assessed at termination of the study., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

A549 cells are common models in the assessment of respiratory cytotoxicity. To provide physiologically more representative exposure conditions and increase the differentiation state, respiratory cells, for instance Calu-3 bronchial epithelial cells, are cultured at an air-liquid interface (ALI). There are indications that A549 cells also change their phenotype upon culture in ALI. The influence of culture in two variations of transwell cultures compared to conventional culture in plastic wells on the phenotype of A549 cells was studied. Cells were characterized by morphology, proliferation and transepithelial electrical resistance, whole genome transcription analysis, Western blot and immunocytochemical detection of pro-surfactant proteins. Furthermore, lipid staining, surface morphology, cell elasticity, surface tension and reaction to quartz particles were performed. Relatively small changes were noted in the expression of differentiation markers for alveolar cells but A549 cells cultured in ALI showed marked differences in lipid staining and surface morphology, surface tension and cytotoxicity of quartz particles. Data show that changes in physiological reactions of A549 cells in ALI culture were rather caused by change of surface properties than by increased expression of surfactant proteins., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The biological response of bronchial epithelial cells to particles is associated with a sequestration of cell metal by the particle surface and a subsequent disruption in host iron homeostasis. The macrophage is the cell type resident in the respiratory tract that is most likely to make initial contact with inhaled particles. We tested the postulates that (1) silica, a prototypical particle, disrupts iron homeostasis in alveolar macrophages (AMs); and (2) the altered iron homeostasis results in both an oxidative stress and pro-inflammatory effects. Human AMs (1.0 × 10 6 /mL) demonstrated an increased import of iron following particle exposure with nonheme iron concentrations of 0.57 ± 0.03, 1.72 ± 0.09, 0.88 ± 0.09, and 3.21 ± 0.11 ppm in cells exposed for 4 h to media, 500 μM ferric ammonium citrate (FAC), 100 μg/mL silica, and both silica and FAC, respectively. Intracellular ferritin concentrations and iron release were similarly increased after AM exposure to FAC and silica. Silica increased oxidant generation by AMs measured using both dichlorofluorescein diacetate fluorescence and reduction of nitroblue tetrazolium salt. Concentrations of interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-α in macrophage supernatant increased following 100 μg/mL silica exposure for 24 h. Treatment of AMs with 500 μM FAC decreased both oxidant generation and cytokine release associated with silica exposure, supporting a dependence of these effects on sequestration of cell metal by the particle surface. We conclude that (1) silica exposure disrupts iron homeostasis resulting in increased import, accumulation, and release of the metal; and (2) the altered iron homeostasis following silica exposure impacts oxidant generation and pro-inflammatory effects.

Purpose: Our understanding of the respiratory health consequences of geogenic (earth-derived) particulate matter (PM) is limited. Recent in vivo evidence suggests that the concentration of iron is associated with the magnitude of the respiratory response to geogenic PM. We investigated the inflammatory and cytotoxic potential of silica and iron oxide particles alone, and in combination, on lung epithelial cells., Methods: Bronchial epithelial cells (BEAS-2B) were exposed to silica (quartz, cristobalite) and/or iron oxide (hematite, magnetite) particles. Cytotoxicity and cytokine production (IL-6, IL-8, IL-1β and TNF-α) were assessed by LDH assay and ELISA, respectively. In subsequent experiments, the cytotoxic and inflammatory potential of the particles was assessed using alveolar epithelial cells (A549)., Results: After 24 h of exposure, iron oxide did not cause significant cytotoxicity or production of cytokines, nor did it augment the response of silica in the BEAS2-B cells. In contrast, while the silica response was not augmented in the A549 cells by the addition of iron oxide, iron oxide particles alone were sufficient to induce IL-8 production in these cells. There was no response detected for any of the outcomes at the 4 h time point, nor was there any evidence of IL-1β or TNF-α production., Conclusions: While previous studies have suggested that iron may augment silica-induced inflammation, we saw no evidence of this in human epithelial cells. We found that alveolar epithelial cells produce pro-inflammatory cytokines in response to iron oxide particles, suggesting that previous in vivo observations are due to the alveolar response to these particles.

Exposure to particulate matter (PM), such as mineral particles and biological particles/components may be linked to aggravation of respiratory diseases, including asthma. Here we report that exposure to Aspergillus fumigatus hyphae fragments (AFH) and lipopolysaccharide (LPS) induced both mRNA synthesis and release of pro-inflammatory interleukin-1 beta (IL-1β) in both human THP-1 monocytes (THP-1 Mo) and phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 monocytes (THP-1 macrophages; THP-1 Ma); while Min-U-Sil alone enhanced the release of IL-1β only in THP-1 Ma. Co-exposure to LPS or AFH with Min-U-Sil caused a synergistic release of IL-1β when compared to single exposures. In contrast, Min-U-Sil did not markedly change LPS- and AFH-induced release of tumor necrosis factor alpha (TNF-α). The combined exposures did not increase the LPS- and AFH-induced expression of IL-1β mRNA. Notably, the AFH- and LPS-induced IL-1β responses with and without co-exposure to Min-U-Sil in THP-1 Mo were found to be caspase-dependent as shown by inhibition with zYVAD-fmk. Furthermore, co-exposure with AFH and Min-U-Sil resulted in similar synergistic releases of IL-1β in primary human airway macrophages (AM; sputum), peripheral blood monocyte-derived macrophages (MDM) and in the human bronchial epithelial cell line (BEAS-2B). In conclusion, AFH induce both the synthesis and release of IL-1β. However, Min-U-Sil further enhanced the cleavage of the induced pro-IL-1β., (Copyright © 2018. Published by Elsevier Ltd.)

Introduction: Clusters of silicosis cases have been reported in the fabrication of quartz conglomerate, a new high-silica-content artificial stone for kitchen and bathroom benchtops (countertops)., Aim: We describe two cases of accelerated-type silicosis with hepatic granulomas arising in workers exposed to artificial quartz conglomerates., Methods: A confident diagnosis of multiorgan silicosis was based on high level of respirable silica in the workplace, typical radiological alterations in chest high-resolution CT, histological findings in the lung and liver, and detection of silica crystals in both tissues by phase-contrast polarising light microscopy and scanning electron microscopy and energy dispersive spectroscopy., Results: The development of the disease <10 years after the first exposure is consistent with an accelerated-type of silicosis. Compared with other studies related to quartz conglomerate exposure, we determined that the levels of airborne crystalline silica during activity in the finishing area were between 0.260 and 0.744 mg/m 3 , that is, much higher than the threshold limit value according to American Conference of Governmental Industrial Hygienists (0.025 mg/m 3 ). Moreover, liver granulomas were associated with accumulation of crystalline silica particles in the hepatic tissue., Conclusions: Quartz conglomerate fabrication is a potentially dangerous occupation. General practitioners and physicians should have awareness of this newly described occupational hazard. Accurate occupational history is critical in avoiding misdiagnosis, as silicosis caused by inhalation of dust from artificial quartz conglomerates may exhibit atypical presentation. These features seem to be related to the extremely high level of silica exposure and, possibly, to an increased toxicity of the dust generated in this process., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

The distribution of dust particles within the lungs and their excretion are highly associated with their pulmonary toxicity. Literature was reviewed to discern pulmonary translocation pathways for inhaled α-quartz compared to those for inhaled TiO 2 . Accordingly, it was hypothesized α-quartz particles in the alveoli were phagocytized by alveolar macrophages but silica-containing macrophages remained in the alveoli for longer time in contrast to the rapid elimination from the alveoli seen for TiO 2 -containing macrophages. In addition, it was presumed that free silica particles are translocated in the interstitium, possibly through the cytoplasm of Type I epithelial cells, as observed with TiO 2 . Free silica particles are presumed to be phagocytized by interstitial macrophages soon after the particles penetrate the interstitium; these dust cells are then translocated to the ciliated airway regions in the lumen through bronchus-associated lymphoid tissue (BALT). The pulmonary retention half-time of dust particles in rats exposed to α-quartz is several times longer than that of rats exposed to TiO 2 , as long as the lung dust burden is ≈ 3 mg. The reduced pulmonary particle clearance ability in rats exposed to α-quartz aerosol is presumably attributed to the long-term retention of dust cells both in the alveoli and in the interstitium; this retention may be caused by the reduced chemotactic abilities of α-quartz-containing dust cells. However, the accumulation of α-quartz-containing dust cells in the lungs is not associated with the occurrence of pulmonary inflammation.

In recent years with the advancement of nanotoxicology, the scientific communities drastically increased the investigation of the potential toxicity of nanominerals which are present in all atmospheres as well as are used in a variety of applications. In this study, we reported how Quartz Nanoparticles (QNPs) depending on concentration induces different signature ER stress markers in A549 cells. QNPs induced concentration-dependent decrease in cell viability and this concentration dependent toxicity intensifies production of reactive oxygen species leading to oxidative stress and inflammation. Furthermore, the levels of marker proteins of apoptosis (Cytochrome C, Caspase 3, Caspase-12) were found to be significantly up-regulated confirming apoptosis. To check the involvement of ER stress, the activation of ER stress signaling pathway was observed by up-regulated protein levels of ER stress marker proteins including PERK, eIF2α, DDIT3, ATF4 and GRP78 in a concentration-dependent manner. In summary, preliminary assessment of QNPs induced toxicity by monitoring the ER stress signaling pathway gives novel assumptions toward empathizing the effects of QNPs at the cellular level. The adverse effects associated with the exposure to QNPs can be avoided by sensibly using these minerals within the safe dose., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Human exposure to (certain forms of) crystalline silica (CS) potentially results in adverse effects on human health. Since 1997 IARC has classified CS as a Group 1 carcinogen [1], which was confirmed in a later review in 2012 [2]. The genotoxic potential and mode of genotoxic action of CS was not conclusive in either of the IARC reviews, although a proposal for mode of actions was made in an extensive review of the genotoxicity of CS by Borm, Tran and Donaldson in 2011 [3]. The present study identified 141 new papers from search strings related to genotoxicity of respirable CS (RCS) since 2011 and, of these, 17 relevant publications with genotoxicity data were included in this detailed review.Studies on in vitro genotoxic endpoints primarily included micronucleus (MN) frequency and % fragmented DNA as measured in the comet assay, and were mostly negative, apart from two studies using primary or cultured macrophages. In vivo studies confirmed the role of persistent inflammation due to quartz surface toxicity leading to anti-oxidant responses in mice and rats, but DNA damage was only seen in rats. The role of surface characteristics was strengthened by in vitro and in vivo studies using aluminium or hydrophobic treatment to quench the silanol groups on the CS surface.In conclusion, the different modes of action of RCS-induced genotoxicity have been evaluated in a series of independent, adequate studies since 2011. Earlier conclusions on the role of inflammation driven by quartz surface in genotoxic and carcinogenic effects after inhalation are confirmed and findings support a practical threshold. Whereas classic in vitro genotoxicity studies confirm an earlier no-observed effect level (NOEL) in cell cultures of 60-70 μg/cm 2 , transformation frequency in SHE cells suggests a lower threshold around 5 μg/cm 2 . Both levels are only achieved in vivo at doses (2-4 mg) beyond in vivo doses (> 200 μg) that cause persistent inflammation and tissue remodelling in the rat lung.

Inhaled crystalline quartz is a carcinogen. Analyses show differences in the distribution of lung cancer types depending on the status of silicosis. Using 2,524 lung tumor cases from the WISMUT autopsy repository database, silicosis was differentiated into cases without silicosis in lung parenchyma and its lymph nodes, with lymph node-only silicosis, or with lung silicosis including lymph node silicosis. The proportions of adenocarcinoma, squamous cell carcinoma, and small-cell lung carcinoma mortality for increasing quartz exposures were estimated in a multinomial logistic regression model. The relative proportions of the lung cancer subtypes in lymph node-only silicosis were more similar to lung silicosis than without any silicosis. The results support the hypothesis that quartz-related carcinogenesis in case of lymph node-only silicosis is more similar to that in lung silicosis than in without silicosis.

Background: Millions of workers are exposed to dust containing silica. Chronic and over-exposure to silica will lead to silicosis, which is an irreversible and sometimes fatal lung disease. The disordered physiological processes of silicosis consist of accumulation of silica particles in the alveoli of the lung. Then, the ingestion of the silica particles by macrophages was followed by an inflammatory response. Up till now, the chest radiographs remain the key tool in diagnosing and assessing the extent of silicosis. However, concerns exist regarding the sensitivity and specificity of the technique. Therefore, there is still a need to develop a biomarker for silicosis for early detection of silicosis., Method: In this study, RNA-Seq was applied to detect the gene expression changes when silica was exposed to macrophages at different time intervals. RNA-Seq provides a broader dynamic range, increased specificity and sensitivity, and easier detection of rare and low-abundance transcripts. Bioinformatics tools such as the Database for Annotation, Visualization and Integrated Discovery (DAVID) and Gene Functional Classification Tool and Search Tool for the Retrieval of Interacting Genes (STRING) were applied for data analysis. Quantitative PCR was used to validate the results., Results: Our results showed that regulation of transcription factors was the dominant activated pathway in early exposure of silica to macrophages, followed by inflammatory responses which were the main mechanisms in silicosis. One of the findings was the upregulation of activating transcription factor 3 (ATF3) during silica exposure. When ATF3 expression was inhibited by siRNA, the production of cytokines IL-1β, IL-6 and TNF was further increased., Conclusion: This indicated that ATF3 may be a potential early diagnostic biomarker for silicosis and ATF3 acts as a repressor in inflammatory responses induced by silica., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: We investigate the effects of bone morphogenetic protein-7 (BMP-7) on models with silica-induced and macrophage-mediated fibrosis and its possible mechanisms in vitro., Methods: Rat alveolar II epithelial (RLE-6TN) cells were incubated with the supernatant of mouse macrophage-like cells (RAW264.7) and treated with 0, 25, 50, and 100 μg/mL silica. Using Western blotting, the epithelial markers (surfactant proteins-C and E-cadherin) and the mesenchymal markers (fibronectin (FN) and viminten (Vim)) were detected. After neutralizing the BMP-7, the progress of fibrosis was assessed by the content of hydroxyproline (Hyp) and collagen I, III protein levels as well as the Smad signaling pathway proteins, including phosphorylated Smad1/5(P-Smad1/5) and phosphorylated Smad2/3(P-Smad2/3). Collagen I was also identified by immunofluorescence and pretreated with SB-431542, LDN-193189, or anti-BMP-7-neutralizing antibody. In addition, the levels of matrix metalloproteinase-2 (MMP-2) and MMP-9 were detected using Western blotting., Results: The model of RLE-6TN cells was established successfully, the expressions of Vim, FN, MMP-2, and MMP-9 were upregulated, while the concentration of silica is increased. Neutralizing BMP-7 stimulated the decrease of P-Smad1/5 and the increase of P-Smad2/3, as well as the collagen I, collagen III, FN, and Hyp via Smad signaling pathway. Furthermore, pretreated with LDN-193189 or anti-BMP-7-neutralizing antibody, the expression of collagen I was increased, yet it was decreased with SB-431542 intervention., Conclusion: The activated BMP/Smad and suppressed transforming growth factor-β/Smad pathways could suppress silica-induced fibrosis via a MMP-dependent mechanism. BMP-7 is expected to be the optimized strategy of delaying the interstitial changes.

The effects of acute pulmonary coexposures to silica and diesel particulate matter (DPM), which may occur in various mining operations, were investigated in vivo. Rats were exposed by intratracheal instillation (IT) to silica (50 or 233 µg), DPM (7.89 or 50 µg) or silica and DPM combined in phosphate-buffered saline (PBS) or to PBS alone (control). At one day, one week, one month, two months and three months postexposure bronchoalveolar lavage and histopathology were performed to assess lung injury, inflammation and immune response. While higher doses of silica caused inflammation and injury at all time points, DPM exposure alone did not. DPM (50 µg) combined with silica (233 µg) increased inflammation at one week and one-month postexposure and caused an increase in the incidence of fibrosis at one month compared with exposure to silica alone. To assess susceptibility to lung infection following coexposure, rats were exposed by IT to 233 µg silica, 50 µg DPM, a combination of the two or PBS control one week before intratracheal inoculation with 5 × 10 5 Listeria monocytogenes. At 1, 3, 5, 7 and 14 days following infection, pulmonary immune response and bacterial clearance from the lung were evaluated. Coexposure to DPM and silica did not alter bacterial clearance from the lung compared to control. Although DPM and silica coexposure did not alter pulmonary susceptibility to infection in this model, the study showed that noninflammatory doses of DPM had the capacity to increase silica-induced lung injury, inflammation and onset/incidence of fibrosis.

In this study, we used cytotoxicity assays, proteomic and gene expression analyses to examine the difference in response of A549 cells to two silica particles that differ in physical properties, namely cristobalite (CR) and α-quartz (Min-U-Sil 5, MI). Cytotoxicity assays such as lactate dehydrogenase release, 5-bromo-2'-deoxyuridine incorporation and cellular ATP showed that both silica particles could cause cell death, decreased cell proliferation and metabolism in the A549 human lung epithelial cells. While cytotoxicity assays revealed little difference between CR and MI exposures, proteomic and gene expression analyses unveiled both similar and unique molecular changes in A549 cells. For instance, two-dimensional gel electrophoresis data indicated that the expression of proteins in the cell death (e.g., ALDH1A1, HTRA2 and PRDX6) and cell proliferation (e.g., FSCN1, HNRNPAB and PGK1) pathways were significantly different between the two silica particles. Reverse transcription-polymerase chain reaction data provided additional evidence supporting the proteomic findings. Preliminary assessment of the physical differences between CR and MI suggested that the extent of surface interaction between particles and cells could explain some of the observed biological effects. However, the differential dose-response curves for some other genes and proteins suggest that other physical attributes of particulate matter can also contribute to particulate matter-related cellular toxicity. Our results demonstrated that toxicoproteomic and gene expression analyses are sensitive in distinguishing subtle toxicity differences associated with silica particles of varying physical properties compared to traditional cytotoxicity endpoints. Copyright © 2016 Her Majesty the Queen in Right of Canada. Journal of Applied Toxicology published by John Wiley & Sons, Ltd., (Copyright © 2016 Her Majesty the Queen in Right of Canada. Journal of Applied Toxicology published by John Wiley & Sons, Ltd.)

The study investigated the oxidative stress induction by the 10 and 25 nm silver nanorods (SNRs) following intra-tracheal instillation in rats after 1 day, 1 week, 1 month and 3 months post instillation periods at 1 and 5 mg/kg b.w. doses. The blood was withdrawn by retro orbital plexus method after exposure periods and different oxidative stress markers were estimated. The results showed that the both sizes of SNRs induced increased levels of malondialdehyde (MDA) and depleted glutathione (GSH) levels after 1 day and 1 week post exposure periods. The 10 and 25 nm SNRs at both doses displayed that significantly reduced levels of superoxide dismutase (SOD) and catalase following 1 day and 1 week post exposure periods. Also, the results have shown that decrease in total antioxidant capacity (TAC) of both sizes of SNRs significantly following 1 day and 1 week post exposure periods, indicating the oxidative stress induction by SNRs. In spite, there were no significant changes in oxidative stress markers following 1 month and 3 months post exposure periods may be due to recovery. The increased levels of MDA and decreased levels of GSH, SOD, catalase and TAC activity are strongly associated to ROS production and lipid peroxidation, suggesting the induction of oxidative stress in rats. The 10 nm SNRs at 5 mg/kg b.w. dose exposures in rats have shown greater changes in all oxidative stress parameters, indicating the greater induction of oxidative stress when compared with the 25 nm SNRs, representing the size-dose-dependent induction of oxidative stress of SNRs.

Exposure to particulate matter (PM) is associated with adverse health effects, but it is still relatively unknown which role PM sources and physicochemical properties play in the observed effects. It was postulated that PM in vitro induces release of long pentraxin 3 (PTX3) and vascular endothelial growth factor (VEGF) and that endotoxin and organic compounds present in the PM regulate this release. A contact coculture of THP-1 human leukemia monocytes and A549 human adenocarcinoma alveolar pneumocytes was exposed to PM from Traffic, Wood, Diesel, and Quartz (10-40 µg/cm 2 ) for 12-64 h to determine release of PTX3 and VEGF. The role of endotoxin and the organic fraction in the mediator release was assessed using polymyxin B sulfate and organic extracts, respectively. Finally, antagonists were used to investigate whether the early proinflammatory cytokines interleukin (IL)-1 and tumor necrosis factor (TNF)-α affected the PTX3 and VEGF release. All PM samples induced a time-dependent release of both PTX3 and VEGF. Traffic mediated the greatest release of PTX3, whereas Wood and Diesel were more potent inducers of VEGF. The endotoxin content did not markedly affect release of either mediator, while the organic fraction exerted no significant effect on VEGF release and limited influence on PTX3 release. In addition, the IL-1 and TNF-α agonists affected PTX3 release more strongly than VEGF release. In conclusion, the current data show a limited impact of endotoxin and organic compounds on PTX3 and VEGF release. Further, the observed differences in response patterns may point toward differential regulation of PM-mediated release of PTX3 and VEGF.

Accumulation of macrophages and neutrophil granulocytes in the lung are key events in the inflammatory response to inhaled particles. The present study aims at the time course of chemotaxis in vitro in response to the challenge of various biopersistent particles and its functional relation to the transcription of inflammatory mediators. NR8383 rat alveolar macrophages were challenged with particles of coarse quartz, barium sulfate, and nanosized silica for one, four, and 16h and with coarse and nanosized titanium dioxide particles (rutile and anatase) for 16h only. The cell supernatants were used to investigate the chemotaxis of unexposed NR8383 macrophages. The transcription of inflammatory mediators in cells exposed to quartz, silica, and barium sulfate was analyzed by quantitative real-time PCR. Challenge with quartz, silica, and rutile particles induced significant chemotaxis of unexposed NR8383 macrophages. Chemotaxis caused by quartz and silica was accompanied by an elevated transcription of CCL3, CCL4, CXCL1, CXCL3, and TNFα. Quartz exposure showed an earlier onset of both effects compared to the nanosized silica. The strength of this response roughly paralleled the cytotoxic effects. Barium sulfate and anatase did not induce chemotaxis and barium sulfate as well caused no elevated transcription. In conclusion, NR8383 macrophages respond to the challenge with inflammatory particles with the release of chemotactic compounds that act on unexposed macrophages. The kinetics of the response differs between the various particles., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Quartz is a well-known occupational fibrogenic agent able to cause fibrosis and other severe pulmonary diseases such as silicosis and lung cancer. The silicotic pathology owes its severity to the structural and chemo-physical properties of the particles such as shape, size and abundance of surface radicals. In earlier studies, we reported that significant amounts of surface radicals can be generated on crystalline silica by chemical aggression with ascorbic acid (AA), a vitamin naturally abundant in the lung surfactant, and this reaction led to enhanced cytotoxicity and production of inflammatory mediators in a macrophage cell line. However in the lung, other cells acting in the development of silicosis, like fibroblasts and endothelial cells, can come to direct contact with inhaled quartz. We investigated the cytotoxic/pro-inflammatory effects of AA-treated quartz microcrystals (QA) in human primary fibroblasts and endothelial cells as compared to unmodified microcrystals (Q). Our results show that, in fibroblasts, the abundance of surface radicals on quartz microcrystals (Q vs QA) significantly enhanced cell proliferation (with or without co-culture with macrophages), reactive oxygen species (ROS) production, NF-κB nuclear translocation, smooth muscle actin, fibronectin, Bcl-2 and tissue inhibitor of metalloproteinase-1 expression and collagen production. Contrariwise, endothelial cells reacted to the presence of quartz microcrystals independently from the abundance of surface radicals showing similar levels of cytotoxicity, ROS production, cell migration, MCP-1, ICAM-I and fibronectin gene expression when challenged with Q or QA. In conclusion, our in vitro experimental model demonstrates an important and quite unexplored direct contribute of silica surface radicals to fibroblast proliferation and fibrogenic responses., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Background: Exposure to some - but not all - quartz particles is associated to silicosis, lung cancer and autoimmune diseases. What imparts pathogenicity to any single quartz source is however still unclear. Crystallinity and various surface features are implied in toxicity. Quartz dusts used so far in particle toxicology have been obtained by grinding rocks containing natural quartz, a process which affects crystallinity and yields dusts with variable surface states. To clarify the role of crystallinity in quartz pathogenicity we have grown intact quartz crystals in respirable size., Methods: Quartz crystals were grown and compared with a fractured specimen obtained by grinding the largest synthetic crystals and a mineral quartz (positive control). The key physico-chemical features relevant to particle toxicity - particle size distribution, micromorphology, crystallinity, surface charge, cell-free oxidative potential - were evaluated. Membranolysis was assessed on biological and artificial membranes. Endpoints of cellular stress were evaluated on RAW 264.7 murine macrophages by High Content Analysis after ascertaining cellular uptake by bio-TEM imaging of quartz-exposed cells., Results: Quartz crystals were grown in the submicron (n-Qz-syn) or micron (μ-Qz-syn) range by modulating the synthetic procedure. Independently from size as-grown quartz crystals with regular intact faces did not elicit cellular toxicity and lysosomal stress on RAW 264.7 macrophages, and were non-membranolytic on liposome and red blood cells. When fractured, synthetic quartz (μ-Qz-syn-f) attained particle morphology and size close to the mineral quartz dust (Qz-f, positive control) and similarly induced cellular toxicity and membranolysis. Fracturing imparted a higher heterogeneity of silanol acidic sites and radical species at the quartz surface., Conclusions: Our data support the hypothesis that the biological activity of quartz dust is not due to crystallinity but to crystal fragmentation, when conchoidal fractures are formed. Besides radical generation, fracturing upsets the expected long-range order of non-radical surface moieties - silanols, silanolates, siloxanes - which disrupt membranes and induce cellular toxicity, both outcomes associated to the inflammatory response to quartz.

Background: Accelerated thrombus formation induced by exposure to combustion-derived air pollution has been linked to alterations in endogenous fibrinolysis and platelet activation in response to pulmonary and systemic inflammation. We hypothesised that mechanisms independent of inflammation contribute to accelerated thrombus formation following exposure to diesel exhaust particles (DEP)., Methods: Thrombosis in rats was assessed 2, 6 and 24 h after administration of DEP, carbon black (CB; control carbon nanoparticle), DQ12 quartz microparticles (to induce pulmonary inflammation) or saline (vehicle) by either intra-tracheal instillation (0.5 mg, except Quartz; 0.125 mg) or intravenous injection (0.5 mg/kg). Thrombogenicity was assessed by carotid artery occlusion, fibrinolytic variables and platelet-monocyte aggregates. Measures of inflammation were determined in plasma and bronchoalveolar lavage fluid. Tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI)-1 were measured following direct in vitro exposure of human umbilical vein endothelial cells (HUVECs) to DEP (10-150 μg/mL)., Results: Instillation of DEP reduced the time to thrombotic occlusion in vivo, coinciding with the peak of DEP-induced pulmonary inflammation (6 h). CB and DQ12 produced greater inflammation than DEP but did not alter time to thrombotic occlusion. Intravenous DEP produced an earlier (2 h) acceleration of thrombosis (as did CB) without pulmonary or systemic inflammation. DEP inhibited t-PA and PAI-1 release from HUVECs, and reduced the t-PA/PAI-1 ratio in vivo; similar effects in vivo were seen with CB and DQ12. DEP, but not CB or DQ12, increased platelet-monocyte aggregates., Conclusion: DEP accelerates arterial thrombus formation through increased platelet activation. This effect is dissociated from pulmonary and systemic inflammation and from impaired fibrinolytic function.

Recently, a number of reports have been published on silicosis in workers exposed to artificial quartz conglomerates containing high levels of crystalline silica particles (70-90%) used in the construction of kitchen and bathroom surfaces. Three cases of silicosis in workers exposed to artificial quartz conglomerates are reported. The diagnosis was derived from both the International Labour Office and the International Classification of HRCT for Occupational and Environmental Respiratory Diseases (ICOERD) classifications and cytological analysis of bronchoalveolar lavage fluid. In 2 cases, levels of respirable silica greatly in excess of recommended standards were measured in the workplace, and cytological analysis of bronchoalveolar lavage fluid highlighted a prevalence of lymphocytes, meeting criteria for the diagnosis of accelerated silicosis. The prevention of pneumoconiosis caused by the use of innovative materials, such as artificial conglomerates with high crystalline silica content must be addressed., (Copyright © 2014 SEPAR. Published by Elsevier Espana. All rights reserved.)

Crystalline silica inhaled from occupational sources has been classified by IARC as carcinogenic to humans; in contrast, for amorphous silica, epidemiological and experimental evidence remains insufficient. The genotoxicity of crystalline silica is still debated because of the inconsistency of experimental results ("variability of silica hazard"), often related to the features of the particle surfaces. We have assessed the role of crystal habit in the genotoxicity of silica powders. Pure quartz (crystalline) and vitreous silica (amorphous), sharing the same surface features, were used in an in vitro study with human pulmonary epithelial (A549) and murine macrophage (RAW264.7) cell lines, representative of occupational and environmental exposures. Genotoxicity was evaluated by the comet and micronucleus assays, and cytotoxicity by the trypan blue method. Cells were treated with silica powders for 4 and 24h. Quartz but not vitreous silica caused cell death and DNA damage in RAW264.7 cells. A549 cells were relatively resistant to both powders. Our results support the view that crystal habit per se plays a pivotal role in modulating the biological responses to silica particles., (Copyright © 2015. Published by Elsevier B.V.)

Objective: To compare the effects of oral treatment with tetrandrine (TD) and N-acetylcys-teine (NAC) separately or jointly on silica-exposed rats., Methods: 40 sprague-Dawly (SD) rats were randomly divided into normal saline group, quartz group, TD treatment group (50 mg/kg), NAC treatment group (500 mg/kg) and combined treatment group (TD: 50 mg/kg + NAC: 500 mg/kg). Rats in normal saline group and other groups received intratracheal instillation of normal saline and quartz dust suspension respectively. Treatment groups were given TD, NAC separately or jointly via esophagus the next day after instillation, once a day and six times a week for 30 consecutive days. At the end of experiment, the pathological changes of lung tissues were evaluated by the methods of Foot, HE and Masson staining, the level of hydroxyproline (HYP), malondjalde-hyde (MDA), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in lung tissues were measured by alkaline hydrolysis method, the barbituric acid method and enzyme-linked immunosorbent assay (ELISA) respectively., Results: Compared with the quartz group, lymph nodes/body coefficients in all treatment groups and lung/body coefficient in combined treatment group were significantly decreased (P < 0.05). Pathology results showed that the normal saline group demonstrated no obvious evidence of lung damage. The quartz group lungs silicotic lesions focused on II~III level, the TD treatment group was mainly with I level, the NAC treatment group was mainly with I~II level, and the combined treatment group only showed little silicotic nodule, no obvious fibrosis. HYP content in TD treatment group and combined treatment group were significantly lower than that in the quartz group (P < 0.05), while it showed no obvious change in NAC treatment group. MDA content in lung tissues of each treatment group (TD treatment group, NAC treatment group and combined treatment group) were 18.80 ± 2.94, 20.13 ± 4.01 and 17.05 ± 3.52 nmol/ml respectively, which lower than in the quartz group (23.99 ± 3.26 nmol/ml). The level of IL-6 in lung tissues of the quartz group were 89.57 ± 8.78 pg/ml. After TD and NAC monotherapy, the IL-6 content decreased to 79.22 ± 9.65 pg/ml and 81.63 ± 5.72 pg/ml, and it decreased more significantly after combined medication (74.37 ± 3.17 pg/ml). The level of TNF-α in the quartz group were 59.05 ± 4.48 pg/ml. After TD and NAC monotherapy, the TNF-α content decreased to 50.48 ± 2.76 pg/ml and 54.28 ± 4.30 pg/ml, and it decreased more significantly after combined medication (49.10 ± 4.98 pg/ml)., Conclusion: NAC and TD could reduce MDA, TNF-α and IL-6 levels in lung tissue, and alleviate SiO2-induced pulmonary fibrosis in rats. Combined treatment with TD and NAC was more effective than TD or NAC treatment separately.

In this study, we have evaluated the pulmonary toxicity of MgO nanoparticles (MgO NPs) in rats following their exposure. NPs in phosphate buffered saline + 1% Tween 80 were exposed via intratracheal instillation at a doses of 1 mg/kg or 5 mg/kg into rat lungs and evaluated for various tissue damage markers like alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) in bronchoalveolar lavage (BAL) fluid and histopathology of lungs at 1, 7, and 30 days of post-exposure intervals. A dose-dependant increase in ALP and LDH activity was observed in BAL fluids of rat lungs than sham control at all post-exposure periods (P <0.05), and a dose-dependant infiltration of interstitial lymphocytes, peribronchiolar lymphocytic infiltration, and dilated and/or congested vessels at 1 day post-exposure period, worsened at 1 week period, and were reduced at 1 month at histology, indicating the pulmonary toxicity of MgO NPs. In conclusion, MgO NPs exposure produced a dose-dependent pulmonary toxicity in rats and was comparable with that of Quartz particles., (© 2013 Wiley Periodicals, Inc.)

Silica is the major component of airborne dust generated by wind, manufacturing and/or demolition. Chronic occupational inhalation of silica dust containing crystalline quartz is by far the predominant form of silicosis in humans. Silicosis is a progressive lung disease that typically arises after a very long latency and is a major occupational concern with no known effective treatment. The mechanism of silicosis is not clearly understood. However, silicosis is associated with increased cell death, expression of redox enzymes and pro-fibrotic cytokines and chemokines. Since alveolar epithelial cell (AEC) death and disruption of alveolar fibrinolysis is often associated with both acute and chronic lung injuries, we explored whether p53-mediated changes in the urokinase-type plasminogen activator (uPA) system contributes to silica-induced lung injury. We further sought to determine whether caveolin-1 scaffolding domain peptide (CSP), which inhibits p53 expression, mitigates lung injury associated with exposure to silica. Lung tissues and AECs isolated from wild-type (WT) mice exposed to silica exhibit increased apoptosis, p53 and PAI-1, and suppression of uPA expression. Treatment of WT mice with CSP inhibits PAI-1, restores uPA expression and prevents AEC apoptosis by suppressing p53, which is otherwise induced in mice exposed to silica. The process involves CSP-mediated inhibition of serine-15 phosphorylation of p53 by inhibition of protein phosphatase 2A-C (PP2A-C) interaction with silica-induced caveolin-1 in AECs. These observations suggest that changes in the p53-uPA fibrinolytic system cross-talk contribute to lung injury caused by inhalation of silica dust containing crystalline quartz and is protected by CSP by targeting this pathway., (Copyright © 2015 Elsevier Inc. All rights reserved.)

In May 2014, the Texas Department of State Health Services was notified of a case of silicosis with progressive massive fibrosis in a Hispanic male aged 37 years who worked for an engineered stone countertop company as a polisher, laminator, and fabricator. He was exposed to dust for 10 years from working with conglomerate or quartz surfacing materials containing 70%-90% crystalline silica. This is the first reported case of silicosis associated with exposure to quartz surfacing materials in North America.

Objectives: Due to incomplete curing and material degradation, cells in the oral cavity may be exposed to monomers and filler particles from dental composite fillings. The objective of the present study was to investigate if combined exposures to particles and a methacrylate monomer from composite fillings resulted in additive effects on the macrophage immune response., Material and Methods: Two filler particles, Nanosilica (12 nm) and Quartz (1 μm), were studied at concentrations 0.5-4 μg/cm(2), while the methacrylate monomer triethyleneglycol dimethacrylate (TEGDMA) was applied at 5 and 50 μM. RAW 264.7 macrophages were exposed to monomers and/or particles for 24 h, with a subsequent 24 h combined exposure to monomers and/or particles and the bacterial factor lipopolysaccharide (LPS) to stimulate an immune response. Release of the pro-inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) were measured as well as the cellular viability., Results: Co-exposure to Nanosilica and Quartz resulted in an additive attenuation of the LPS-induced IL-1β release. Moreover, co-exposure to TEGDMA and both types of filler particles also resulted in an additive attenuation, although with a weak synergistic trend. The cellular viability and TNF-α release were not significantly affected by the exposures., Conclusion: The present findings emphasize the necessity of considering effects of combined exposure to dental degradation products in future risk assessments., Clinical Relevance: Attenuated cytokine release could have implications for the macrophage immune response and result in impaired bacterial clearance. Further studies are necessary to determine implications for formation of dental biofilms and caries development.

Background: The hemolytic activity of inhaled particles such as silica has been widely investigated in the past and represents a usual toxicological endpoint to characterize particle reactivity despite the fact that red blood cells (RBCs) are not involved in the pathogenesis of pulmonary inflammation or fibrosis caused by some inhaled particles. The inflammatory process induced by silica starts with the activation of the inflammasome, which leads to the release of mature IL-1β. One of the upstream mechanisms causing activation of the inflammasome is the labilization of the phagolysosomal membrane after particle phagocytosis. Considering RBC lysis as a model of membrane damage, we evaluated the relationship between hemolytic activity and inflammasome-dependent release of IL-1β for a panel of selected silica particles, in search of the toxicological significance of the hemolytic activity of an inhaled particle., Methods: Well-characterized silica particles, including four quartz samples and a vitreous silica, with different surface properties and hemolytic potential were tested for their capacity to induce inflammasome-dependent release of IL-1β in LPS-primed primary murine peritoneal macrophages by ELISA and Western blot analysis. The mechanisms of IL-1β maturation and release were clarified by using ASC-deficient cells and inhibitors of phagocytosis and cathepsin B., Results: The silica samples induced dose-dependent hemolysis and IL-1β release of different amplitudes. A significant correlation between IL-1β release and hemolytic activity was evidenced (r = 0.827) by linear regression analysis. IL-1β release was completely abolished in ASC-deficient cells and reduced by inhibitors, confirming the involvement of the inflammasome and the requirement of phagocytosis and cathepsin B for activation., Conclusions: The same physico-chemical properties of silica particles which are relevant for the lysis of the RBC membrane also appear implicated in the labilization of the phagolysosome, leading to inflammasome activation and release of the pro-inflammatory cytokine IL-1β. These findings strengthen the relevance of the hemolysis assay to predict the pro-inflammatory activity of silica dusts.