Airborne Asian sand dust enhances murine lung eosinophilia

There is no experimental study demonstrating the effects of airborne Asian sand dust (AASD) on allergic lung eosinophilia. The organic substances adsorbed onto AASD collected from the atmosphere of Iki-island in Japan were excluded by heat treatment at 360°C for 30 min. The effects of AASD or heated-AASD (H-AASD) towards allergic lung inflammation were compared in murine lungs to investigate the role of organic substances. ICR mice were administrated with the two kinds of AASD and/or ovalbumin (OVA) intratracheally four times at 2-week intervals. AASD and H-AASD enhanced eosinophil recruitment induced by OVA in the alveoli and in the submucosa of the airway, which has a goblet cell proliferation in the bronchial epithelium. AASD and H-AASD synergistically increased Th2 cytokines-interleukin-13 (IL-13), eosinophil-relevant cytokine and chemokine, such as IL-5, and monocyte chemotactic protein-3 (MCP-3) induced by OVA in whole lung lavage fluid. The enhancing effects were much greater in AASD than in H-AASD. AASD induced adjuvant effects on OVA-specific immunoglobulin E (IgE) and IgG1 production. In an in vitro study using RAW264.7 cells, AASD increased the expression of Toll-like receptors 2 (TLR2) mRNA, but not TLR4 mRNA. AASD increased mRNA expression of NALP3, ASC, and IL-1ß compared with the control. H-AASD caused no expression of either mRNA. These results suggest that the aggravated lung eosinophilia in AASD is due to activation of a Th2-associated immune response and that the activation of TLR2 and NALP3 inflammasome by microbial materials could be participating in this phenomenon.