Time- and concentration-dependent genomic responses of the rat airway to inhaled nickel sulfate

Modeling of local and systemic exposure to metals and metalloids after inhalation exposure: Recommended update to the USEPA metals framework

The USEPA issued the "Framework for Metal Risk Assessment" in 2007, recognizing that human and environmental exposure to metals and metalloids (MMEs) poses challenges risk assessment. Inhalation of aerosols containing MMEs is a primary pathway for exposure in the occupational setting, for consumer exposure, and to general population exposure associated with point-source emissions or ambient sources. The impacts of inhalation can be at the point of deposition (local exposure) or may manifest after uptake into the body (systemic exposure). Both local and systemic exposure can vary with factors that determine the regional deposition of MME-containing aerosols. Aerosol characteristics such as particle size combine with species-specific characteristics of airway morphology and lung function to modulate the deposition and clearance of MME particulates. In contrast to oral exposure, often monitored by measuring MME levels in blood or urine, inhalation exposure can produce local pulmonary impacts in the absence of significant systemic distribution. Exposure assessment for nutritionally essential MMEs can be further complicated by homeostatic controls that regulate systemic MME levels. Predictions of local exposure can be facilitated by computer models that estimate regional patterns of aerosol deposition, permitting calculation of exposure intensity in different regions of the respiratory tract. The utility of deposition modeling has been demonstrated in assessments of nutritionally essential MMEs regulated by homeostatic controls and in the comparison of results from inhalation studies in experimental animals. This facilitates extrapolation from animal data to humans and comparisons of exposures possessing mechanistic linkages to pulmonary toxicity and carcinogenesis. Pulmonary deposition models have significantly advanced and have been applied by USEPA in evaluations of particulate matter. However, regional deposition modeling has yet to be incorporated into the general guidance offered by the agency for evaluating inhalation exposure. Integr Environ Assess Manag 2024;20:952-964. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Human exposure to metals in consumer-focused fused filament fabrication (FFF)/ 3D printing processes

Fused filament fabrication (FFF) or 3D printing is a growing technology used in industry, cottage industry and for consumer applications. Low-cost 3D printing devices have become increasingly popular among children and teens. Consequently, 3D printers are increasingly common in households, schools, and libraries. Because the operation of 3D printers is associated with the release of inhalable particles and volatile organic compounds (VOCs), there are concerns of possible health implications, particularly for use in schools and residential environments that may not have adequate ventilation such as classrooms bedrooms and garages, etc. Along with the growing consumer market for low-cost printers and printer pens, there is also an expanding market for a range of specialty filaments with additives such as inorganic colorants, metal particles and nanomaterials as well as metal-containing flame retardants, antioxidants, heat stabilizers and catalysts. Inhalation of particulate-associated metals may represent a health risk depending on both the metal and internal dose to the respiratory tract. Little has been reported, however, about the presence, speciation, and source of metals in the emissions; or likewise the effect of metals on emission processes and toxicological implications of these 3D printer generated emissions. This report evaluates various issues including the following: metals in feedstock with a focus on filament characteristics and function of metals; the effect of metals on the emissions and metals detected in emissions; printer emissions, particle formation, transport, and transformation; exposure and translation to internal dose; and potential toxicity on inhaled dose. Finally, data gaps and potential areas of future research are discussed within these contexts.

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

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

Nuclear factor erythroid 2 - related factor 2 and its relationship with cellular response in nickel exposure: a systems biology analysis

Background

Nickel and nickel-containing compounds (NCC) are known human carcinogens. However, the precise molecular mechanisms of nickel-induced malignant transformation remain unknown. Proposed mechanisms suggest that nickel and NCC may participate in the dual activation/inactivation of enzymatic pathways involved in cell defenses against oxidative damage, where Nuclear factor-erythroid 2 related factor 2 (Nrf2) plays a central role.

Methods

For assessing the potential role of proteins involved in the Nrf2-mediated response to nickel and NCC exposure, we designed an interactome network using the STITCH search engine version 5.0 and the STRING software 10.0. The major NCC-protein interactome (NCPI) generated was analyzed using the MCODE plugin, version 1.5.1 for the detection of interaction modules or subnetworks. Main centralities of the NCPI were determined with the CentiScape 2.2 plugin of Cytoscape 3.4.0 and main biological processes associated with each cluster were assessed using the BiNGO plugin of Cytoscape 3.4.0.

Results

Water-soluble NiSO₄ and insoluble Ni₃S₂ were the most connected to proteins involved in the NCPI network. Nfr2 was detected as one of the most relevant proteins in the network, participating in several multifunctional protein complexes in clusters 1, 2, 3 and 5. Ontological analysis of cluster 3 revealed several processes related to unfolded protein response (UPR) and response to endoplasmic reticulum (ER) stress.

Conclusions

Cellular response to NCC exposure was very comparable, particularly concerning oxidative stress response, inflammation, cell cycle/proliferation, and apoptosis. In this cellular response, Nfr2 was highly centralized and participated in several multifunctional protein complexes, including several related to ER-stress. These results add evidence on the possible Ni²⁺ induced – ER stress mainly associated with insoluble NCC. In this scenario, we also show how protein degradation mediated by ubiquitination seems to play key roles in cellular responses to Ni.