The size of zinc oxide nanoparticles controls its toxicity through impairing autophagic flux in A549 lung epithelial cells

• Published in: Toxicology letters 2018-03, Vol.285, p.51-59
• Main Authors: Wang, Bin, Zhang, Jun, Chen, Chengzhi, Xu, Ge, Qin, Xia, Hong, Yueling, Bose, Diptiman D, Qiu, Feng, Zou, Zhen
• Format: Article
• Language: English
• Subjects: Cell death; Cytotoxicity; Impairment of autophagic flux; Zinc oxide nanoparticles
• ISSN: 0378-4274; 1879-3169
• DOI: 10.1016/j.toxlet.2017.12.025

[Display omitted] •ZnONPs trigger A549 cell death in a dose-, time- and size-dependent manner.•ZnONPs with size of 50 nm is more prone to induce impaired autophagic flux in comparison with ZnONPs with size of 200 nm.•Impairment of autophagic flux is closely associated with ZnONPs-induced toxic effects. Zinc oxide nanoparticles (ZnONPs) widely used in various products, have been concerned with its impact on human health, in particular, on the risk of pulmonary toxicity. Our previous study indicated that ZnONPs could harness autophagy and impair the autophagic flux, which was positively linked to ZnONPs-induced toxicity. The objective of this study was to investigate whether ZnONPs-induced impairment of autophagic flux and cell death in lung epithelial cells is related to the size of ZnONPs. We demonstrate that ZnONPs with the average size of 50 nm could induce toxic effects in A549 lung epithelial cells, including accumulation of autophagosomes (the elevation of LC3B-II/LC3B-I ratio), impaired autophagic flux (the increase of p62 expression), the release of intracellular zinc ions (the increase of FluoZin-3 signal and ZnT1 mRNA expression), mitochondrial damage (the decrease of TMRE signal), lysosomal dysfunction (the aberrant expression of LAMP-2), oxidative stress (the increase of DCFH-DA signal and HO-1 expression) and cell death. Interestingly, ZnONPs with the average size of 200 nm failed to induce autophagy-mediated toxicity. Taken together, our results indicate that the size of ZnONPs is closely correlated with its toxicity, which is probably mediated by induction of impaired autophagic flux. This finding provides an insight into better understating of ZnONPs-associated toxicity, and mitigating the risk to humans and allowing the safer application.