Ambient PM2.5 exposure exacerbates severity of allergic asthma in previously sensitized mice

Abstract

Objective: Epidemiological studies have shown that elevated concentrations of ambient particulate matter (aerodynamic diameter ≤2.5 μm; PM2.5) correlates with increased incidence of asthma. The aim of this study was to determine whether PM2.5 participates in the exacerbation of asthma. Methods: Effects of 1, 10 and 100 μg PM2.5 instilled intratracheally in ovalbumin (OVA)-sensitized or asthmatic mice were compared. Results: PM2.5 exposure in the OVA-sensitized and especially asthmatic groups increased Mch responsiveness in a dose-dependent manner. In OVA-sensitized groups, exposure to 1 μg of PM2.5 caused no detectable lung inflammation, while 10 and 100 μg of PM2.5 resulted in a slightly increased trend in numbers of neutrophils and macrophages. Compared with the asthmatic control group, both 10 and 100 μg of PM2.5 provoked a significant increase in eosnophils and neutrophils whereas only 100 μg of PM2.5 noticeably enhanced lymphocytes. In asthmatic groups, administration of 100 μg of PM2.5 greatly increased levels of the pro-inflammatory cytokine TNF-α and Th2-related cytokines IL-4 and IL-10 in bronchoalveolar lavage fluid, but it decreased Th1-related INF-γ. In addition, 10 and 100 μg of PM2.5 exacerbated inflammatory infiltration, goblet cell metaplasia and lung ultrastructure lesions in asthmatic mice. Conclusions: Our results suggested that acute exposure of PM2.5 could synergize with allergens in the subsequent challenge to aggravate the severity of asthma in sensitized mice, possibly by promoting a Th2-biased immune response.

• Ambient particulate matter
• asthma
• airway hyper-responsiveness
• pulmonary inflammation
• lung lesion
• OVA-sensitization/challenge model

Acknowledgements

We would like to thank Xianghong He from Clinical Medicine Research Center, Affiliated Hospital of Guangdong Medical College, and Bin Xu from Institute of Urban Environment, Chinese Academy of Sciences for their excellent technical assistance about electron microscope.

Declaration of interest

This work was supported by Guangdong Province Science and Technology Plan Projects (2013B021800077), Starting Research Fund from Affiliated Hospital of Guangdong Medical College (BK201206), Key Discipline Construction of Pediatrics Fund from Guangdong Medical College (XZ1115), Starting Research Fund of Eleventh Five-Year Plan from Affiliated Hospital of Guangdong Medical College to JT, and National Natural Science Foundation of China (31300602) and Starting Research Fund from Guangdong Medical College (XB1341) and The PhD Start-up Fund of Natural Science Foundation of Guangdong Province (S2013040012902) and Medical Research Foundation in Guangdong Province (B2013307) to XZ. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Supplementary material available online

Supplementary Figures S1 and S2. And Table S1