Abstract
The biological effects of inhalable nanoparticles have been widely studied in vitro with pulmonary cells cultured under submerged and air-liquid interface (ALI) conditions. Submerged exposures are experimentally simpler, but ALI exposures are physiologically more realistic and hence potentially biologically more meaningful. In this study, we investigated the cellular response of human alveolar epithelial-like cells (A549) to airborne agglomerates of zinc oxide (ZnO) nanoparticles at the ALI, compared it to the response under submerged culture conditions, and provided a quantitative comparison with the literature data on different types of particles and cells. For ZnO nanoparticle doses of 0.7 and 2.5 μg ZnO/cm2 (or 0.09 and 0.33 cm2 ZnO/cm2), cell viability was not mitigated and no significant effects on the transcript levels of oxidative stress markers (HMOX1, SOD-2 and GCS) were observed. However, the transcript levels of proinflammatory markers (IL-8, IL-6, and GM-CSF) were induced to higher levels under ALI conditions. This is consistent with the literature data and it suggests that in vitro toxicity screening of nanoparticles with ALI cell culture systems may produce less false negative results than screening with submerged cell cultures. However, the database is currently too scarce to draw a definite conclusion on this issue.
Highlights
Exposure to airborne particles has been linked to adverse health effects including pulmonary in ammation, thrombosis, neurodegeneration, and cardiovascular disease [1,2,3]
We investigated the cellular response of human alveolar epithelial-like cells (A549) to airborne agglomerates of zinc oxide (ZnO) nanoparticles at the air-liquid interface (ALI), compared it to the response under submerged culture conditions, and provided a quantitative comparison with the literature data on different types of particles and cells
Since the count median (mobility) diameter (CMD) is larger than the diameter of the primary ZnO NPs (24–71 nm), it is evident that the ZnO aerosol mainly consists of agglomerated structures
Summary
Exposure to airborne particles has been linked to adverse health effects including pulmonary in ammation, thrombosis, neurodegeneration, and cardiovascular disease [1,2,3]. ZnO is known as an occupational hazard, since inhalation of high concentrations of ZnO formed during welding activities can lead to metal fume fever [10, 11] associated with a marked upregulation of proin ammatory markers in the lung [11,12,13]. In addition to these inadvertently generated ZnO nanoparticles, there is a variety of ZnO nanostructures, which have shown great potential for nanotechnological products including manufacturing and pharmaceutical applications [14, 15].
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