Prenatal allergen and diesel exhaust exposure and their effects on allergy in adult offspring mice

Abstract

Background: Multiple studies have suggested that prenatal exposure to either allergens or air pollution may increase the risk for the development of allergic immune responses in young offspring. However, the effects of prenatal environmental exposures on adult offspring have not been well-studied. We hypothesized that combined prenatal exposure to Aspergillus fumigatus (A. fumigatus) allergen and diesel exhaust particles will be associated with altered IgE production, airway inflammation, airway hyperreactivity (AHR), and airway remodeling of adult offspring.

Methods: Following sensitization via the airway route to A. fumigatus and mating, pregnant BALB/c mice were exposed to additional A. fumigatus and/or diesel exhaust particles. At age 9-10 weeks, their offspring were sensitized and challenged with A. fumigatus.

Results: We found that adult offspring from mice that were exposed to A. fumigatus or diesel exhaust particles during pregnancy experienced decreases in IgE production. Adult offspring of mice that were exposed to both A. fumigatus and diesel exhaust particles during pregnancy experienced decreases in airway eosinophilia.

Conclusion: These results suggest that, in this model, allergen and/or diesel administration during pregnancy may be associated with protection from developing systemic and airway allergic immune responses in the adult offspring.

Figure 1

Experimental protocol. Adult females received 5 dosages of A. fumigatus or saline, 20, 16, 12, 8, and 4 days prior to mating. During the second and third weeks of pregnancy, mothers received diesel exhaust particle exposure Monday through Friday plus A. fumigatus or saline on days 7 and 14. AHR: Airway hyperreactivity BAL: Bronchoalveolar lavage i.n: intranasal 3×: 3 doses of A. fumigatus 5×: 5 doses of A. fumigatus 6×: 6 doses of A. fumigatus

Figure 2

IgE levels following sensitization of mothers to A. fumigatus. IgE levels were measured in adult females after 5 doses of A. fumigatus and immediately prior to mating. *p < 0.0001, two tailed Mann-Whitney test

Figure 3

Ig induction in offspring after three, five and six doses of A. fumigatus. a) IgE was reduced after the fifth and sixth (p < 0.0001 on ANOVA), but not third (p = NS, ANOVA), doses among offspring mice whose mothers were exposed to either A. fumigatus or diesel exhaust particles or both. *p < 0.01, when compared to saline alone by Tukey HSD. † p < 0.05, when compared to A. fumigatus alone by Tukey HSD b) IgG₁ was greater after the fifth, sixth (p < 0.0001 on ANOVA), but not third (p = NS, ANOVA), doses among mice whose mothers were exposed to either A. fumigatus or diesel exhaust particles or both. *p < 0.01, when compared to saline alone by Tukey HSD. †p < 0.05, when compared to saline alone by Tukey HSD. c) IgG2a was greater after the fifth, sixth (p < 0.0001 on ANOVA) dose among mice whose mothers were exposed to A. fumigatus or diesel exhaust particles plus A. fumigatus. *p < 0.01, when compared to saline alone by Tukey HSD. Levels also were greater among offspring of mothers that were exposed to both diesel exhaust particles and A. fumigatus when compared to offspring of mothers treated either with diesel exhaust or A. fumigatus alone, p < 0.01. †p < 0.01, when compared to diesel exhaust particles alone by Tukey HSD. ‡ p < 0.05 on ANOVA and when compared to saline alone by Tukey HSD. Sample sizes corresponding to the figures vary as follows: Saline 11-14; Diesel 11-15; A. fumigatus: 8-18; Diesel and A. fumigatus 13-25.

Figure 4

Differential airway cell counts in offspring after five and six doses of A. fumigatus. Eosinophil counts were significantly decreased (and macrophages significantly increased) among offspring from mothers following diesel exhaust and A. fumigatus compared to offspring of mothers treated with saline alone, * p < 0.0002 on ANOVA and p < 0.05 by Tukey HSD or with A. fumigatus alone, † p < 0.0003 on ANOVA and p < 0.01 by Tukey HSD.

Figure 5

Histological changes in offspring from mothers exposed to saline or A. fumigatus. a.) Representative histology from lungs of offspring whose mother was treated with saline following 5 doses of A. fumigatus starting at 9-10 weeks. The photomicrograph was taken from a lung section stained with Hematoxylin and Eosin. White arrows point to perivascular and peribronchial inflammation, black arrowheads point to mild arterial muscularization. b.) Representative histology from lung of offspring whose mother was treated with A. fumigatus following 5 doses of A. fumigatus starting at 9-10 weeks. The photomicrograph was taken from a lung section stained with Hematoxylin and Eosin. White arrows point to perivascular and peribronchial inflammation, black arrowheads point to arterial muscularization. No differences were observed among offspring of mice that received diesel exhaust, particles when compared to offspring of mice that received saline. No differences were observed among offspring of mice that received diesel and A. fumigatus, compared to A. fumigatus alone.

Figure 6

Perivascular, peribronchial airway inflammation and airway remodeling in offspring. a. Perivascular, peribronchial airway inflammation in offspring of A. fumigatus. Composite scores were obtained following 5 or 6 doses of A. fumigatus. Significant differences across groups were not detected. p = 0.11 on ANOVA. Perivascular and peribronchial inflammation were scored as follows [13]: 1 = normal with very few inflammatory cells bordering the arteries or airways; 2 = scattered inflammatory cells surrounding the artery or airway up to two rings in depth; 3 = cell cuffs or clusters of inflammatory cells surrounding the artery or airway three rings or more in depth. b. Arterial remodeling in offspring. Offspring from mothers treated during pregnancy as outlined in Fig. 1 were exposed to A. fumigatus intranasally with 5-6 doses starting at 9-10 weeks of age. Arterial remodeling was scored as described [13] and in Figure 3b. Significant differences across groups were not detected. p = 0.183 on ANOVA. Arterial remodeling was scored as follows [13]: 1 = normal; 2 = thickened vascular wall with intact lumen and circular media; 3 = obstructed lumen and thickened wall lined with disorganized layers of cells.