PLATOX: Integrated In Vitro/In Vivo Approach for Screening of Adverse Lung Effects of Graphene-Related 2D Nanomaterials

Methodological steps forward in toxicological in vitro screening of mineral wools in primary rat alveolar macrophages and normal rat mesothelial NRM2 cells

Man-made vitreous fibers (MMVF) comprise diverse materials for thermal and acoustic insulation, including stone wool. Depending on dimension, durability, and dose, MMVF might induce adverse health effects. Therefore, early predictive in vitro (geno)toxicity screening of new MMVF is highly desired to ensure safety for exposed workers and consumers. Here, we investigated, as a starting point, critical in vitro screening determinants and pitfalls using primary rat alveolar macrophages (AM) and normal rat mesothelial cells (NRM2). A stone wool fiber (RIF56008) served as an exemplary MMVF (fibrous vs. ground to estimate impact of fiber shape) and long amosite (asbestos) as insoluble fiber reference. Materials were comprehensively characterized, and in vivo-relevant in vitro concentrations defined, based on different approaches (low to supposed overload: 0.5, 5 and 50 µg/cm2). After 4-48 h of incubation, certain readouts were analyzed and material uptake was investigated by light and fluorescence-coupled darkfield microscopy. DNA-strand break induction was not morphology-dependent and nearly absent in both cell types. However, NRM2 demonstrated material-, morphology- and concentration-dependent membrane damage, CINC-1 release, reduction in cell count, and induction of binucleated cells (asbestos > RIF56008 > RIF56008 ground). In contrast to NRM2, asbestos was nearly inactive in AM, with CINC-1 release solely induced by RIF56008. In conclusion, to define an MMVF-adapted, predictive in vitro (geno)toxicity screening tool, references, endpoints, and concentrations should be carefully chosen, based on in vivo relevance, and sensitivity and specificity of the chosen cell model. Next, further endpoints should be evaluated, ideally with validation by in vivo data regarding their predictivity.

Biomarkers of genotoxic damage in pulmonary alveolar macrophages: a review

DNA damage is one of the primary mechanisms underlying cancer and other chronic degenerative diseases. Early evaluation of this damage in the affected cells and tissues is crucial for understanding pathogenesis and implementing effective prevention strategies. However, isolating target cells from affected organs, such as the lungs, can be challenging. Therefore, an alternative approach is to evaluate genotoxic damage in surrogate cells. Pulmonary alveolar macrophages are ideally suited for this purpose because they are in close contact with the target cells of the bronchial and alveolar epithelium, share the exact mechanisms and levels of exposure, and are easily recoverable in large numbers. This review comprehensively lists all studies using alveolar macrophages as surrogate cells to show genotoxic lung damage in humans or laboratory animals. These investigations provide fundamental information on the mechanisms of DNA damage in the lung and allow for better assessment and management of risk following exposure to inhalable genotoxic agents. Furthermore, they may be a valuable tool in cancer chemoprevention, helping the right choice of agents for clinical trials.

Respiratory Toxicology of Graphene-Based Nanomaterials: A Review

Graphene-based nanomaterials (GBNs) consist of a single or few layers of graphene sheets or modified graphene including pristine graphene, graphene nanosheets (GNS), graphene oxide (GO), reduced graphene oxide (rGO), as well as graphene modified with various functional groups or chemicals (e.g., hydroxyl, carboxyl, and polyethylene glycol), which are frequently used in industrial and biomedical applications owing to their exceptional physicochemical properties. Given the widespread production and extensive application of GBNs, they can be disseminated in a wide range of environmental mediums, such as air, water, food, and soil. GBNs can enter the human body through various routes such as inhalation, ingestion, dermal penetration, injection, and implantation in biomedical applications, and the majority of GBNs tend to accumulate in the respiratory system. GBNs inhaled and substantially deposited in the human respiratory tract may impair lung defenses and clearance, resulting in the formation of granulomas and pulmonary fibrosis. However, the specific toxicity of the respiratory system caused by different GBNs, their influencing factors, and the underlying mechanisms remain relatively scarce. This review summarizes recent advances in the exposure, metabolism, toxicity and potential mechanisms, current limitations, and future perspectives of various GBNs in the respiratory system.

Gene expression profiling of human macrophages after graphene oxide and graphene nanoplatelets treatment reveals particle-specific regulation of pathways

Graphene and its derivatives are attractive materials envisaged to enable a wealth of novel applications in many fields including energy, electronics, composite materials or health. A comprehensive understanding of the potential adverse effects of graphene-related materials (GRM) in humans is a prerequisite to the safe use of these promising materials. Here, we exploited gene expression profiling to identify transcriptional responses and toxicity pathways induced by graphene oxide (GO) and graphene nanoplatelets (GNP) in human macrophages. Primary human monocyte-derived macrophages (MDM) and a human macrophage cell line, i.e. differentiated THP-1 cells, were exposed to 5 or 20 μg/mL GO and GNP for 6 and 24 h to capture early and more persistent acute responses at realistic or slightly overdose concentrations. GO and GNP induced time-, dose- and macrophage type-specific differential expression of a substantial number of genes with some overlap between the two GRM types (up to 384 genes (9.6%) or 447 genes (20.4%) in THP-1 or MDM, respectively) but also a high number of genes exclusively deregulated from each material type. Furthermore, GRM responses on gene expression were highly different from those induced by inflammogenic material crystalline quartz (maximum of 64 (2.3%) or 318 (11.3%) common genes for MDM treated with 20 μg/mL GO and GNP, respectively). Further bioinformatics analysis revealed that GNP predominantly activated genes controlling inflammatory and apoptotic pathways whereas GO showed only limited inflammatory responses. Interestingly, both GRM affected the expression of genes related to antigen processing and presentation and in addition, GO activated pathways of neutrophil activation, degranulation and immunity in MDM. Overall, this study provides an extensive resource of potential toxicity mechanisms for future safety assessment of GRM in more advanced model systems to verify if the observed changes in gene expression in human macrophages could lead to long-term consequences on human health.