Atmospheric Ozone Aging of Diesel Exhaust Nanoparticles Exacerbates Macrophage Pyroptosis via Protein Corona Remodeling and Intrinsic Toxicity Amplification

Abstract

Traffic-derived diesel exhaust nanoparticles pose a severe threat to pulmonary health, yet the toxicological consequences of their atmospheric aging remain largely unresolved. This study demonstrates that ozone aging significantly alters the physicochemical properties of these nanoparticles and exacerbates their cytotoxicity toward alveolar macrophages. Spectroscopic analyses reveal that ozone aging oxidizes the particle surface and increases the density of environmentally persistent free radicals. Upon deposition in simulated lung fluids, this oxidized surface selectively enriches complement proteins, fibrinogen, and transferrin to form a distinct bronchoalveolar lavage fluid protein corona. This remodeled bio–nano interface significantly enhances macrophage internalization predominantly through increased phagocytosis and clathrin-mediated endocytosis. Coupled with this enhanced uptake, the aging process simultaneously amplifies the intrinsic material toxicity of the particles themselves. Following accumulation in lysosomes, the combined action of released zinc and iron ions and the radical-rich carbonaceous cores promotes a substantial increase in intracellular reactive oxygen species (ROS)-associated oxidative stress and severe lysosomal membrane permeabilization. The subsequent cytoplasmic leakage of cathepsin B triggers NLRP3 inflammasome activation, ultimately hyperactivating macrophage pyroptosis via the caspase-1-GSDMD pathway. By linking atmospheric chemical evolution with a coupled mechanism, these findings highlight both the remodeled protein corona and altered material identity as crucial co-mediators of particulate toxicity, providing a critical theoretical framework for evaluating the real-world respiratory health risks of traffic-derived aerosol pollution.