<i>In Vitro</i> Exposure of A549 and J774A.1 Cells to SiO₂ and TiO₂ Nanoforms and Related Cellular- and Molecular-Level Effects: Application of Proteomics

There is an emerging interest in incorporating proteomic data for environmental health risk assessments. Meanwhile, the production and use of engineered nanomaterials (ENMs) with attractive physicochemical properties are expanding with the potential for exposure, thus necessitating toxicity information on these materials for health risk analysis, where proteomic data can be informative. Here, cells (A549 human lung epithelial and J774A.1 mouse monocyte/macrophage cells) were exposed to ENMs (nanoforms of SiO₂and TiO₂) of different sizes and surface chemistries (dose: 0-100 μg/cm², 24 h) for <i>in vitro</i> toxicity data. Cytotoxicity (CTB, ATP, and LDH), oxidative stress (GSH oxidation), and proteomic analysis (MS- and antibody-based) were conducted post-nanoparticle (NP) exposure to determine the relative potency and identify perturbed cellular pathways. Dose-, nanoform-, and cell type-specific cytotoxicity changes were observed upon exposure to both nanoSiO₂ and nanoTiO₂. Size, agglomeration, surface modification, and metal impurities appeared to be the determinants of cytotoxicity. Proteomic analysis identified some enriched mechanistic pathways and biological processes relevant to cell defense/phagocytosis, stress, metabolism, apoptosis, and inflammatory processes in J774A.1 cells exposed to these NPs. A549 cells exhibited enriched pathway/biological processes relevant to transport/endocytosis, stress, metabolism, and inflammatory processes post-NP exposures. Concordance was observed between the nanoform exposure- and cell type-related cytotoxicity responses, notably cellular ATP, which is critical for cell viability, oxidative stress, and cellular pathways/biological processes. These findings demonstrate the application of proteomics in regulatory toxicology and warrant further research in this direction.