Pharyngeal aspiration of metal oxide nanoparticles showed potential of allergy aggravation effect to inhaled ovalbumin.

The inhalation of manufactured metal oxide nanoparticles may lead to pulmonary toxicity. For instance, ZnO nanoparticles are known to induce pulmonary oxidative stress and inflammation. On the other hand, the pulmonary toxicity of TiO2 nanoparticles is less than that of ZnO nanoparticles. Although, there have been some investigations concerning the induction of pulmonary oxidative stress and inflammation caused by manufactured metal oxide nanoparticles. And, although, it has reported that some nanoparticles cause aggravation of allergic reactions, there have so far been no reports regarding allergy aggravation effects of manufactured metal oxide nanoparticles. In this study, three types of nanoparticles, TiO2, ZnO and SiO2, were administered to mouse lungs by pharyngeal aspiration. Subsequently, the mice inhaled ovalbumin (OVA) a total of eight times over 3 weeks. After inhalation of OVA, the concentrations of total IgE, OVA-specific IgE and OVA-specific IgG1 in serum increased in the mice treated with ZnO. TiO2 and SiO2 nanoparticles did not affect the OVA-specific IgE and IgG1 levels. These results suggest that ZnO nanoparticles have the potential to aggravate allergic reactions. The results also suggest that Zn(2+) release from ZnO nanoparticles is involved in the aggravation potential of allergies. However, pharyngeal aspiration of ZnCl2 solution was not able to aggravate allergic reactions. Continuous Zn(2+) release from ZnO nanoparticles to the lung is necessary for the aggravation of allergic reactions.