(416f) Toxicological Screening of Metal Oxide Nanoparticles in Liver Context Demonstrates Apoptosis in Hepatocytes Versus Pyroptosis in Kupffer Cells

With growing applications of nanotechnology in different fields of science and technology, engineered nanomaterials (ENMs) could enter into human body through different exposure scenarios. The liver is one of the major targets of ENMs as part of the mononuclear phagocyte system (MPS), either as a result of particle uptake and spread from primary exposure sites (e.g., lung and gastrointestinal tract) or systemic administration of therapeutic and imaging nanoparticles. Therefore, it is important to thoroughly investigate how ENMs interact with different cellular components of the liver, and recognize the potential adverse impacts that these interactions could introduce. In this study, we selected 29 metal oxide nanoparticles, some of which are commonly used in consumer products, and performed a comparative analysis of the toxicological impact of these nanoparticles (NPs) in transformed or primary Kupffer cells (KCs) and hepatocytes. We not only observed differences between KCs and hepatocytes, but also differences in the toxicological profiles of transition-metal oxides (TMOs, e.g., Co₃O₄ and Mn₂O₃) versus rare-earth oxide (REO) NPs (e.g., Gd₂O₃ and La₂O₃). While pro-oxidative TMOs induced apoptotic cell death in both cell types via activation of caspases 3 and 7, REOs induced lysosomal damage and NLRP3 inflammasome activation, followed by caspase 1 activation and pyroptotic cell death in KCs. Pyroptosis was accompanied by cell swelling, membrane blebbing, significant IL-1β release, and increased membrane permeability, which could be reversed by knockdown of the pore forming protein involved in pyroptosis, gasdermin D. These features were not seen in hepatocytes, and REOs induced caspases 3 and 7 activation in this cell type leading to apoptosis. Further investigation of the cytotoxic effects of REO NPs in other phagocytic cell lines such as J774A.1 and RAW 264.7 cells as well as bone marrow-derived macrophages (BMDMs) also demonstrated features of pyroptosis and increased IL-1β production. These findings not only demonstrate important mechanistic considerations that can be used for safety evaluation of metal oxides, including commercial products that are developed from these materials, but also provide useful information for safer material design.