Aggravation of ovalbumin-induced murine asthma by co-exposure to desert-dust and organic chemicals: an animal model study

Abstract

Background: The organic chemicals present in Asian sand dust (ASD) might contribute to the aggravation of lung eosinophila. Therefore, the aggravating effects of the Tar fraction from ASD on ovalbumin (OVA)-induced lung eosinophilia were investigated.

Methods: The Tar fraction was extracted from ASD collected from the atmosphere in Fukuoka, Japan. ASD collected from the Gobi desert was heated at 360°C to inactivate toxic organic substances (H-ASD). ICR mice were instilled intratracheally with 12 different test samples prepared with Tar (1 μg and 5 μg), H-ASD, and OVA in a normal saline solution containing 0.02% Tween 80. The lung pathology, cytological profiles in the bronchoalveolar lavage fluid (BALF), inflammatory cytokines/chemokines in BALF and OVA-specific immunoglobulin in serum were investigated.

Results: Several kinds of polycyclic aromatic hydrocarbons (PAHs) were detected in the Tar sample. H-ASD + Tar 5 μg induced slight neutrophilic lung inflammation. In the presence of OVA, Tar 5 μg increased the level of eosinophils slightly and induced trace levels of Th2 cytokines IL-5 and IL-13 in BALF. Also mild to moderate goblet cell proliferation and mild infiltration of eosinophils in the submucosa of airway were observed. These pathological changes caused by H-ASD + OVA were relatively small. However, in the presence of OVA and H-ASD, Tar, at as low a level as 1 μg, induced severe eosinophil infiltration and proliferation of goblet cells in the airways and significantly increased Th2 cytokines IL-5 and IL-13 in BALF. The mixture showed an adjuvant effect on OVA-specific IgG1 production.

Conclusions: These results indicate that H-ASD with even low levels of Tar exacerbates OVA-induced lung eosinophilia via increases of Th2-mediated cytokines. These results suggest that ASD-bound PAHs might contribute to the aggravation of lung eosinophila.

Figure 1

Cellular profile in bronchoalveolar lavage fluids (BALF). All values are expressed as mean ± SE. ^*p < 0.05 vs. control; ^†p < 0.05 vs. Tar 1; ^‡p < 0.05 vs. Tar 5; ^§p < 0.05 vs. H-ASD; ^&p < 0.05 vs. H-ASD + Tar 1; ^#p < 0.05 vs. H-ASD + Tar 5; ^¶p < 0.05 vs. OVA; ^αp < 0.05 vs. OVA + Tar 5.

Figure 2

Evaluation of pathological changes in the murine airway. The degree of pathological changes in the airway was estimated as: (0) none; (1) slight; (2) mild; (3) moderate; (4) moderate to marked; (5) marked. All values are expressed as mean ± SE (n = 6). Statistical analyses were conducted using the Tukey Test for Pairwise Comparisons. ^*p < 0.05 vs. control; ^†p < 0.05 vs. Tar 1; ^‡p < 0.05 vs. Tar 5; ^§p < 0.05 vs. H-ASD; ^&p < 0.05 vs. H-ASD + Tar 1; ^#p < 0.05 vs. H-ASD + Tar 5; ^¶p < 0.05 vs. OVA; ^αp < 0.05 vs. OVA + Tar 1; ^βp < 0.05 vs. H-ASD + OVA.

Figure 3

Effects of test samples on pathological changes in the lungs. (A) Control, (B) Tar 1: no pathologic alterations were seen in the lungs. (C) Tar 5: very slight infiltration of inflammatory cells in the airway submucosa. Goblet cells were not seen. (D) OVA alone: slight proliferation of goblet cells in the airway epithelium and very slight infiltration of inflammatory cells into the airway submucosa. (E) OVA + Tar 1: goblet cell proliferation was somewhat stronger than in the samples treated with OVA alone (D). (F) OVA + Tar 5: mild proliferation of goblet cells in the airway epithelium, and infiltration of inflammatory cells into the airway submucosa. (G) H-ASD + OVA: mild goblet cell proliferation and mild infiltration of inflammatory cells into the airway submucosa. (H) H-ASD + OVA + Tar 1: moderate goblet cell proliferation, severe infiltration of inflammatory cells into the airway submucosa. (I) H-ASD + OVA + Tar 5: mild to moderate goblet cell proliferation, moderate infiltration of inflammatory cells into the airway submucosa. (A–I) PAS stain; bar = 50 μm.

Figure 4

Effects of test samples on infiltration of inflammatory cells in the airway. (A) Control, (B) Tar 1, (C) Tar 5: no pathological changes in lungs treated with saline, Tar 1 and Tar 5. (D) OVA alone: slight infiltration of eosinophils, neutrophils and lymphocytes into the airway submucosa. (E) OVA + Tar 1, (F) OVA + Tar 5, (G) H-ASD + OVA: slight to mild infiltration of inflammatory cells into the airway submucosa. (H) H-ASD + OVA + Tar 1: marked accumulation of eosinophils, neutrophils and lymphocytes in the airway submucosa. (I) H-ASD + OVA + Tar 5: moderate infiltration of these inflammatory cells into the submucosa of airways. (A–I) HE stain; bar = 20 μm.

Figure 5

Expressions of IL-12, KC, MIP-1 α and RANTES in BALF. All values are expressed as mean ± SE (n =8). ^*p < 0.05 vs. control; ^†p < 0.05 vs. Tar 1; ^‡p < 0.05 vs. Tar 5; ^§p < 0.05 vs. H-ASD; ^&p < 0.05 vs. H-ASD + Tar 1; ^#p < 0.05 vs. H-ASD + Tar 5; p < 0.05 vs. OVA; ^αp < 0.05 vs. OVA + Tar 1; ^βp < 0.05 vs. H-ASD + OVA.

Figure 6

Expressions of IL-1β, IL-6, MCP-1 and MCP-3 in BALF. All values are expressed as mean ± SE (n =8). ^*p < 0.05 vs. control; ^†p < 0.05 vs. Tar 5; ^‡p < 0.05 vs. H-ASD + Tar 1; ^§p < 0.05 vs. OVA; ^&p < 0.05 vs. OVA + Tar 1; ^#p < 0.05 vs. H-ASD + OVA; p < 0.05 vs. H-ASD + OVA + Tar 1.

Figure 7

Expressions of IL-4, IL-5, IL-13 and eotaxin in BALF. All values are expressed as mean ± SE (n = 8). ^*p < 0.05 vs. control; ^†p < 0.05 vs. Tar 1; ^‡p < 0.05 vs. H-ASD + Tar 1; ^§p < 0.05 vs. OVA; ^&p < 0.05 vs. OVA + Tar 1; ^#p < 0.05 vs. H-ASD + OVA.

Figure 8

Effects of test samples on OVA-specific IgG1 production in serum. According to the manufacturer’s protocol, 1 U of the anti-OVA IgG1 is defined as 160 ng of the antibody. All values are expressed as mean ± SE. ^*p < 0.05 vs. control; ^†p < 0.05 vs. H-ASD + Tar 1; ^‡p < 0.05 vs. H-ASD + Tar 5.