Lung proinflammatory microRNA and cytokine expression in a mouse model of allergic inflammation: role of sex chromosome complement and gonadal hormones

Abstract

Epigenetic alterations such as dysregulation of miRNAs have been reported to play important roles in interactions between genetic and environmental factors. In this study, we tested the hypothesis that induction of lung inflammation by inhaled allergens triggers a sex-specific miRNA regulation that is dependent on chromosome complement and hormonal milieu. We challenged the four core genotypes (FCGs) model through intranasal sensitization with a house dust mite (HDM) solution (or PBS as a control) for 5 wk. The FCG model allows four combinations of gonads and sex chromosomes: 1) XX mice with ovaries (XXF), 2) XY mice with testes (XYM), 3) XX mice with testes (XXM), and 4) XY mice with ovaries (XYF). Following the challenge (n = 5-7/group), we assessed the expression of 84 inflammatory miRNAs in lung tissue using a PCR array and cytokine levels in bronchoalveolar lavage fluid (BAL) by a multiplex protein assay (n = 4-7 animals/group). Our results showed higher levels of the chemokine KC (an Il-8 homolog) and IL-7 in BAL from XYF mice challenged with HDM. In addition, IL-17A was significantly higher in BAL from both XXF and XYF mice. A three-way interaction among treatment, gonads, and sex chromosome revealed 60 of 64 miRNAs that differed in expression depending on genotype; XXF, XXM, XYF, and XYM mice had 45, 32, 4, and 52 differentially expressed miRNAs, respectively. Regulatory networks of miRNAs identified in this study were implicated in pathways associated with asthma. Female gonadal hormonal effects may alter miRNA expression and contribute to the higher susceptibility of females to asthma.NEW & NOTEWORTHY miRNAs play important roles in regulating gene and environmental interactions. However, their role in mediating sex differences in allergic responses and lung diseases has not been elucidated. Our study used a targeted omics approach to characterize the contributions of gonadal hormones and chromosomal components to lung responses to an allergen challenge. Our results point to the influence of sex hormones in miRNA expression and proinflammatory markers in allergic airway inflammation.

Keywords: allergens; asthma; four core genotypes model; miRNA; sex differences.

Graphical abstract

Figure 1.

Differences in bronchoalveolar lavage (BAL) fluid levels of the proinflammatory chemokine KC/CXCL1 in the four core genotypes after 5 wk of house dust mite (HDM) challenge compared with those exposed to PBS. Left: actual concentrations by genotype; right: actual concentrations by male and female (n = 5 or 6 for all genotypes except XYF, where HDM = 7 and PBS = 4). P values were obtained by three-way ANOVA followed by Tukey’s test.

Figure 2.

Differences in bronchoalveolar lavage (BAL) fluid levels of the proinflammatory cytokine IL-17A in the four core genotypes and by male and female after 5 wk of house dust mite (HDM) challenge compared with those exposed to PBS (n = 5 or 6 for all genotypes except XYF, where HDM = 7 and PBS = 4). P values were obtained by three-way ANOVA followed by Tukey’s test.

Figure 3.

Hierarchical cluster analysis of 64 miRNAs in lung extracts from the four core genotype mice exposed challenged with house dust mite (HDM) or PBS for 5 wk. Two main clusters exist (orange and blue, with all XXF HDM-treated mice located in the blue cluster). NA refers to out of range below the standard curve. HDM and PBS refer to house dust mite and phosphate-buffered saline, respectively.