The Combined Role of Silanols and Oxidative Stress in Determining Engineered Stone Dust Toxicity

The mechanisms of particle-induced pathogenesis in the lung remain poorly understood. Neutrophilic inflammation and oxidative stress in the lung are hallmarks of toxicity. Some investigators have postulated that oxidative stress from particle surface reactive oxygen species (psROS) on the dust produces the toxicopathology in the lungs of dust-exposed animals. This postulate was tested concurrently with the studies to elucidate the toxicity of lunar dust (LD), which is believed to contain psROS due to high-speed micrometeoroid bombardment that fractured and pulverized lunar surface regolith. Results from studies of rats intratracheally instilled (ITI) with three LDs (prepared from an Apollo-14 lunar regolith), which differed 14-fold in levels of psROS, and two toxicity reference dusts (TiO2 and quartz) indicated that psROS had no significant contribution to the dusts’ toxicity in the lung. Reported here are results of further investigations by the LD toxicity study team on the toxicological role of oxidants in alveolar neutrophils that were harvested from rats in the 5-dust ITI study and from rats that were exposed to airborne LD for 4 weeks. The oxidants per neutrophils and all neutrophils increased with dose, exposure time and dust’s cytotoxicity. The results suggest that alveolar neutrophils play a critical role in particle-induced injury and toxicity in the lung of dust-exposed animals. Based on these results, we propose an adverse outcome pathway (AOP) for particle-associated lung disease that centers on the crucial role of alveolar neutrophil-derived oxidant species. A critical review of the toxicology literature on particle exposure and lung disease further supports a neutrophil-centric mechanism in the pathogenesis of lung disease and may explain previously reported animal species differences in responses to poorly soluble particles. Key findings from the toxicology literature indicate that (1) after exposures to the same dust at the same amount, rats have more alveolar neutrophils than hamsters; hamsters clear more particles from their lungs, consequently contributing to fewer neutrophils and less severe lung lesions; (2) rats exposed to nano-sized TiO2 have more neutrophils and more severe lesions in their lungs than rats exposed to the same mass-concentration of micron-sized TiO2; nano-sized dust has a greater number of particles and a larger total particle–cell contact surface area than the same mass of micron-sized dust, which triggers more alveolar epithelial cells (AECs) to synthesize and release more cytokines that recruit a greater number of neutrophils leading to more severe lesions. Thus, we postulate that, during chronic dust exposure, particle-inflicted AECs persistently release cytokines, which recruit neutrophils and activate them to produce oxidants resulting in a prolonged continuous source of endogenous oxidative stress that leads to lung toxicity. This neutrophil-driven lung pathogenesis explains why dust exposure induces more severe lesions in rats than hamsters; why, on a mass-dose basis, nano-sized dusts are more toxic than the micron-sized dusts; why lung lesions progress with time; and why dose–response curves of particle toxicity exhibit a hockey stick like shape with a threshold. The neutrophil centric AOP for particle-induced lung disease has implications for risk assessment of human exposures to dust particles and environmental particulate matter.

The toxicity of lunar dust (LD) to astronauts' health has been confirmed in the Apollo missions and subsequent biological experiments. Therefore, it is crucial to understand the biological toxicity of lunar dust for future human missions to the Moon. In this study, we exposed human lung epithelial cells (BEAS-2B) and peripheral blood B lymphocytes (AHH-1) to varying concentrations (0, 500, 1000, and 1500 μg/ml) of a lunar dust simulant (LDS) called CLDS-i for 24 and 48 h. The results provided the following key findings: (1) LDS induction of cell damage occurred through oxidative stress, with the levels of reactive oxygen species (ROS) in BEAS-2B cells being dependent on the duration of exposure. (2) Necrosis and early apoptosis were observed in BEAS-2B cells and AHH-1 cells, respectively. In addition, both cells showed lysosomal damage. (3) Genes CXCL1, SPP1, CSF2, MMP1, and POSTN are implicated in immune response and cytoskeletal arrangement regulation in BEAS-2B cells. Considering the similarities in composition and properties between CLDS-i and real lunar dust, our findings not only enhance the understanding of LDS toxicity, but also contribute to a better comprehension of the genomic alterations and molecular mechanisms underlying cellular toxicity induced by LD. These insights will contribute to the development of a biotoxicology framework aimed at safeguarding the health of astronauts and, consequently, facilitating future human missions to the Moon.

Aim: Artificial Stone Dust (ASD) exposure has been identified as a significant health risk for workers, leading to oxidative stress, inflammatory responses, and potential systemic autoimmune diseases due to its high crystalline silica content. The aim of this study is to identify the impact of ASD on the permeability of alveolar epithelial cells and the mechanisms underlying particle translocation across the alveolar membrane remain unexplored. Methods: The acute toxicological effects of ASD on human bronchial submucosal gland cells CALU-3 cells in vitro were investigated to assess its impact on epithelial barrier integrity, in comparison to crystalline silica particles (Min-U-Sil®5). Results: Exposure to ASD increased oxidative stress, evidenced by heightened Reactive Oxygen Species (ROS) levels and Heme Oxygenase-1 (HO-1) gene expression in CALU-3 cells, exceeding effects observed with Min-U-Sil®5. Notably, ASD exposure resulted in a significant decrease in Transepithelial Electrical Resistance (TEER), indicating compromised epithelial barrier integrity, especially at higher concentrations (3.7 mg,18.5 mg and 37 mg) after 24, 48 and 72 h. These findings were not paralleled by a decrease in cell viability, underscoring a specific effect on cellular barrier function rather than cytotoxicity. Conclusions: Our study reveals that ASD induces oxidative stress and disrupts epithelial barrier integrity in vitro, potentially contributing to systemic translocation of particles and subsequent health effects. These findings underscore the need for a rigorous protective measure for workers and highlight potential biomarkers of ASD-induced cellular damage.

Lunar dust induces minimal pulmonary toxicity compared to Earth dust.

As space exploration extends to the Moon and Mars, both astronauts and workers in earth-based test facilities will be exposed to extraterrestrial dust. In this study, the ESA Topical Team on the Toxicity of Celestial Dust (T3CD) exposed lung mucosa models to dust simulants, to investigate its potential pulmonary toxicity. JSC-Mars1 simulant was wet milled in a zirconia ball-mill to obtain respirable dust (median:1.45µm). To examine the absence of oxygen and water, additional milling was conducted in inert or oxidizing atmospheres. Multicellular lung models using human primary bronchial epithelial cells were cultured at an air-liquid interface (ALI). 40µl of PBS as control (sham) or containing different doses of dust (55, 220, 890µg/cm2 as low, med, high doses respectively) was added to the apical side of the model. Cell viability, cellular apoptosis rate and cell membrane integrity (TEER) were assessed. Inflammatory biomarkers (CXCL8 and IL6) and a tissue injury related biomarker (MMP-9) were measured in the basal medium by ELISA. Reactive oxygen species (ROS) production was detected by FACS. There was no difference between sham exposure and different doses of JSC-Mars1 dust exposure regarding cell viability and TEER. Exposure to the highest dose of JSC-Mars1 reduced both early and late cellular apoptosis (40%, 42%; P<0.001). The production of ROS was increased 2H after exposure to the two highest doses of JSC-Mars1, compared to sham exposure (27%, 69%; P<0.001). CXCL8 level was increased after exposure to the highest dose of JSC-Mars1 compared to sham exposure (40%; P<0.01). JSC-Mars1 dust increased pulmonary inflammation and oxidative stress, but not cellular apoptosis, suggesting potential toxic effects of JSC-Mars1.

Lunar dust is one of the biggest risk factors in the future manned exploration mission. Much is not known about the pulmonary toxicity of lunar dust. The aim of this study was to evaluate the lung inflammation and oxidative stress induced by subacute exposure to lunar dust stimulant (LDS) in rats. Wistar rats were intratracheally administered LDS, twice a week for 3 weeks. Inflammatory cell counting and cytokine assays using bronchoalveolar lavage fluid (BALF) were performed. Lung tissues were processed for histopathological examination and immunohistochemical staining. Biomarkers of oxidative stress and genes and proteins related to inflammation and fibrosis in lung tissue were also determined. The neutrophil count in the BALF of LDS-exposed groups was higher than that in controls (P < .05). LDS caused a significant increase in some of biochemical indicators and proinflammatory factors levels in BALF compared with control group. The normal balance between oxidation and antioxidation was broken by LDS. Pathological characteristics of lung tissue and immunohistochemical results for α-smooth muscle actin (α-SMA) indicated that inflammatory response was an extremely important passage to pulmonary fibrosis. Real-time PCR analysis showed elevated levels of nitric oxide synthase (NOS) and nicotinamide adenine dinucleotide phosphate oxidase (NOX) mRNA in the lungs (P < .05). Western blotting results were consistent with immunohistochemistry and qPCR results. These results indicate that inhalation of lunar dust may cause inflammatory pulmonary fibrosis. NOX4 may be a key potential therapeutic target for inflammatory injury and fibrosis in the lung.

Modern food animal production is a major contributor to the global economy, owing to advanced intensive indoor production facilities aimed at increasing market readiness and profit. Consequences of these advances are accumulation of dusts, gases, and microbial products that diminish air quality within production facilities. Chronic inhalation exposure contributes to onset and exacerbation of respiratory symptoms and diseases in animals and workers. This article reviews literature regarding constituents of farm animal production facility dusts, animal responses to production building and organic dust exposure, and the effect of chronic inhalation exposure on pulmonary oxidative stress and inflammation. Porcine models of production facility and organic dust exposures reveal striking similarities to observations of human cells, tissues, and clinical data. Oxidative stress plays a key role in mediating respiratory diseases in animals and humans, and enhancement of antioxidant levels through nutritional supplements can improve respiratory health. Pigs are well adapted to the exposures common to swine production buildings and thus serve as excellent models for facility workers. Insight for understanding mechanisms governing organic dust associated respiratory diseases may come from parallel comparisons between farmers and the animals they raise.

Particles internalization, oxidative stress, apoptosis and pro-inflammatory cytokines in alveolar macrophages exposed to cement dust

Millions of people worldwide are exposed to aerosolised desert dust and are at risk of the adverse respiratory health effects it causes. This mini-review gives an overview of the study types that can be used to assess the respiratory toxicity of desert dust and the insights gained from these studies. We highlight the main advantages and disadvantages of epidemiological, in vivo, and in vitro studies. Regarding in vitro studies, we discuss models of increasing complexity, i.e., traditional submerged cell cultures, air–liquid interface cultures, organ-on-a-chip models, organoids, and precision-cut lung slices. Epidemiological studies have shown increased short-term mortality and exacerbated acute and chronic respiratory diseases after desert dust events. In contrast, a connection to the onset of chronic diseases is more difficult to prove. In vivo and in vitro studies have particularly addressed the cellular and molecular effects of desert dust. It was found that desert dust activates immune cells and induces the expression of inflammatory cytokines and oxidative stress markers. The specific effects and their extent vary between dust samples from different sources. The investigation of the role of the composition is still immature and needs further effort including more extensive screenings. The advancement of easy-to-handle and realistic pulmonary in vitro models is required to automate screenings, support mechanistic insights, and enable the assessment of long-term exposure scenarios. In agreement with striving to develop new approach methodologies, such advancements can reduce and replace animal experiments and strongly benefit the translatability of research outcomes to human health protection.

Assessment of reactive oxygen species production and genotoxicity of rare earth mining dust: Implications for public health and mining management

The potential toxicity of lunar dust (LD), as reported by Apollo astronauts, presents significant concerns for future missions involving extended human presence on the Moon. LD toxicity is hypothesized to be driven by oxidative stress linked to its redox-active properties, with nanophase metallic iron (np-Fe&amp;#8304;) embedded in its glassy matrix potentially playing a critical role. However, the specific mechanisms underlying its toxicity remain unclear. Environmental changes in atmospheric settings may modify LD's reactivity before exposure, complicating the evaluation of its potential toxicity.Given the limited availability of real LD samples, the research relys on lunar dust simulants (LDS) for toxicity studies. Yet, the absence of a fully representative LDS limits the accuracy of risk evaluations. This study introduces a novel Simulant Moon Agglutinate (SMA) designed to mimic LD. The SMA consists of a glassy matrix containing np-Fe&amp;#8304; and was crushed in an inert atmosphere to replicate the lunar environment. Respirable SMA particles were analyzed for their physicochemical characteristics, oxidative activity, and iron release in simulated body fluids.Under non-oxidizing conditions, SMA generated a higher level of free radicals, driven by reduced-state iron, and sustained by an electron &amp;#8220;reservoir&amp;#8221; from zerovalent iron clusters. A molecular mechanism is proposed. After oxidative passivation, SMA exhibited a lower reactivity, which was nonetheless still greater than the reactivity of other simulants, such as JSC-1A-vf. Our findings emphasize the critical role of np-Fe&amp;#8304; in oxidative reactions of lunar dust. Notably, SMA did not induce cell membrane damage, suggesting that the mechanisms of LD toxicity may differ significantly from those of terrestrial toxic dusts, such as quartz.

ABSTRACTWelding processes that generate fumes containing toxic metals, such as hexavalent chromium (Cr(VI)), manganese (Mn), and nickel (Ni), have been implicated in lung injury, inflammation, and lung tumor promotion in animal models. The principal objective of this study was to determine the dynamics of toxic effects of inhalation exposure to morphologically rated welding dust from stainless steel welding and its soluble form in TSE System with a dynamic airflow. We assessed the pulmonary toxicity of welding dust in Wistar rats exposed to 60.0 mg/m3 of respirable-size welding dust (mean diameter 1.17 µm) for 2 weeks (6 h/day, 5 days/week); the aerosols were generated in the nose-only exposure chambers (NOEC). An additional aim included the study of the effect of betaine supplementation on oxidative deterioration in rat lung during 2 weeks of exposure to welding dust or water-soluble dust form. The animals were divided into eight groups (n = 8 per group): control, dust, betaine, betaine + dust, soluble-form dust, soluble-form dust + betaine, saline and saline + betaine groups. Rats were euthanized 1 or 2 weeks after the last exposure for assessment of pulmonary toxicity. Differential cell counts, total protein concentrations and cellular enzyme (lactate dehydrogenase—LDH) activities were determined in bronchoalveolar lavage (BAL) fluid, and corticosterone and thiobarbituric acid reactive substances (TBARS) concentrations were assessed in serum. The increase in polymorphonuclear (PMN) leukocytes in BAL fluid (a cytological index of inflammatory responses of the lung) is believed to reflect pulmonary toxicity of heavy metals. Biomarkers of toxicity assessed in bronchoalveolar fluids indicate that the level of the toxic effect depends mainly on the solubility of studied metal compounds; biomarkers that showed treatment effects included: total cell, neutrophil and lymphocyte counts, total protein concentrations, and cellular enzyme (lactate dehydrogenase) activity. Betaine supplementation at 250 mg/kg/day in all study rats groups attenuated stress indices, and corticosterone and TBARS serum levels, and simultaneously stimulated increase of polymorphonuclear cells in BALF of rats. The study confirmed deleterious effect of transitory metals and particles during experimental inhalation exposure to welding dusts, evidenced in the lungs and brain by increased levels of total protein, higher cellular influx, rise of LDH in BALF, elevated TBARS and increased corticosterone in serum of rats. Our result confirm also the hypothesis about the effect of the welding dusts on the oxidative stress responsible for disturbed systemic homeostasis and impairment of calcium regulation.

Cellular responses of normal (HL-7702) and cancerous (HepG2) hepatic cells to dust extract exposure

Atmospheric environment shapes surface reactivity of Fe(0)-doped lunar dust simulant: Potential toxicological implications.

Physico-chemical properties and reactive oxygen species generation by respirable coal dust: Implication for human health risk assessment