Role of Cellular-Ferroptosis-Mediated HMGB1 Nuclear Translocation in Indium-Tin-Oxide-Nanoparticle-Induced...

Indium tin oxide (ITO) particles, widely utilized in electronics and energy technologies, pose significant pulmonary risks due to occupational exposure during manufacturing. While emerging evidence links ITO to severe lung pathologies, critical gaps persist in understanding size-dependent effects and molecular mechanisms. This study systematically investigates the size-dependent effects of nanoscale ITO (N-ITO) and submicron-scale ITO (U-ITO) on pulmonary toxicity, focusing on ferroptosis as a key mechanism. In vivo, repeated oropharyngeal exposure of mice to ITO (3.6 and 36 mg/kg) induced dose-dependent lung inflammation and ferroptosis, marked by lipid peroxidation, Fe²⁺ accumulation, and dysregulation of Gpx4 and Scl7a11 proteins, with pulmonary macrophages identified as primary targets. In vitro, THP-1 macrophages exposed to 6.25-25 μg/mL ITO exhibited size-dependent cytotoxicity, inflammation, and ferroptotic hallmarks. Mechanistically, ITO-triggered ferroptosis promoted HMGB1 secretion and nuclear translocation, which activated the RAGE/p38MAPK pathway, amplifying inflammatory responses. Notably, N-ITO induced stronger ferroptosis and inflammation than U-ITO, correlating with enhanced macrophage uptake due to its nanoscale dimensions. Integrating these findings, we propose an Adverse Outcome Pathway (AOP) framework for ITO-induced lung injury, which cellular uptake may serve as the molecular initiating event and link ferroptosis-driven high mobility group protein B1 (HMGB1) release, RAGE/p38MAPK activation, and chronic inflammation to adverse pulmonary outcomes. This study underscores the necessity of size-specific occupational exposure limits for ITO nanoparticles and provides a mechanistic foundation for risk assessment and management strategies in occupational settings.