Adverse Effect of Nano-Silicon Dioxide on Lung Function of Rats with or without Ovalbumin Immunization

Background: The great advances of nanomaterials have brought out broad important applications, but their possible nanotoxicity and risks have not been fully understood. It is confirmed that exposure of environmental particulate matter (PM), especially ultrafine PM, are responsible for many lung function impairment and exacerbation of pre-existing lung diseases. However, the adverse effect of nanoparticles on allergic asthma is seldom investigated and the mechanism remains undefined. For the first time, this work investigates the relationship between allergic asthma and nanosized silicon dioxide (nano-SiO2). Methodology/Principal Findings: Ovalbumin (OVA)-treated and saline-treated control rats were daily intratracheally administered 0.1 ml of 0, 40 and 80 mg/ml nano-SiO2 solutions, respectively for 30 days. Increased nano-SiO2 exposure results in adverse changes on inspiratory and expiratory resistance (Ri and Re), but shows insignificant effect on rat lung dynamic compliance (Cldyn). Lung histological observation reveals obvious airway remodeling in 80 mg/ml nano-SiO2-introduced saline and OVA groups, but the latter is worse. Additionally, increased nano-SiO2 exposure also leads to more severe inflammation. With increasing nano-SiO2 exposure, IL-4 in lung homogenate increases and IFN-gamma shows a reverse but insignificant change. Moreover, at a same nano-SiO2 exposure concentration, OVA-treated rats exhibit higher (significant) IL4 and lower (not significant) IFN-gamma compared with the saline-treated rats. The percentages of eosinophil display an unexpected result, in which higher exposure results lower eosinophil percentages. Conclusions/Significance: This was a preliminary study which for the first time involved the effect of nano-SiO2 to OVA induced rat asthma model. The results suggested that intratracheal administration of nano-SiO2 could lead to the airway hyperresponsiveness (AHR) and the airway remolding with or without OVA immunization. This occurrence may be due to the Th1/Th2 cytokine imbalance accelerated by the nano-SiO2 through increasing the tissue IL-4 production.