Estrogen receptor‐α signaling increases allergen‐induced IL‐33 release and airway inflammation

Abstract

Background: Group 2 innate lymphoid cells (ILC2) are stimulated by IL-33 to increase IL-5 and IL-13 production and airway inflammation. While sex hormones regulate airway inflammation, it remained unclear whether estrogen signaling through estrogen receptor-α (ER-α, Esr1) or ER-β (Esr2) increased ILC2-mediated airway inflammation. We hypothesize that estrogen signaling increases allergen-induced IL-33 release, ILC2 cytokine production, and airway inflammation. Methods: Female Esr1-/-, Esr2-/-, wild-type (WT), and IL33 fl/fl eGFP mice were challenged with Alternaria extract (Alt Ext) or vehicle for 4 days. In select experiments, mice were administered tamoxifen or vehicle pellets for 21 days prior to challenge. Lung ILC2, IL-5 and IL-13 production, and BAL inflammatory cells were measured on day 5 of Alt Ext challenge model. Bone marrow from WT and Esr1-/female mice was transferred (1:1 ratio) into WT female recipients for 6 weeks followed by Alt Ext challenge. hBE33 cells and normal human bronchial epithelial cells (NHBE) were pretreated with 17β-estradiol (E2), propyl-pyrazole-triol (PPT, ER-α agonist), or diarylpropionitrile (DPN, ER-β agonist) before allergen challenge to determine IL-33 gene expression and release, extracellular ATP release, DUOX-1 production, and necrosis. Results: Alt Ext challenged Esr1-/-, but not Esr2-/-, mice had decreased IL-5 and IL-13 production, BAL eosinophils, and IL-33 release compared to WT mice. Tamoxifen decreased IL-5 and IL-13 production and BAL eosinophils. IL-33eGFP + epithelial cells were decreased in Alt Ext challenged Esr1-/mice compared to WT mice. 17β-E2 or PPT, but not DPN, increased IL-33 gene expression, release, and DUOX-1 production in hBE33 or NHBE cells. Conclusion: Estrogen receptor-α signaling increased IL-33 release and ILC2-mediated airway inflammation.

Sex hormone regulation of innate lymphoid cells

“…5 ). This contrasted with the observation that ILC2 numbers and function were up-regulated in mice constitutively lacking ERα [ 50 , 51 ]. This was however explained by the elevated seric testosterone levels produced by the ovaries in ERα −/- female [ 51 ].…”

“…This phenotype was associated with a reduction of lung inflammation upon allergen challenge, and a reduction of cytokine production by ILC2 in male mice, indicating that androgens may not only affect ILC2 development and maintenance in tissues, but also their function [ 54 , 82 ]. It has been suggested that IL-33 expression could be differentially regulated between female and male mice, with estrogens-dependent upregulation in female [ 50 , 54 ]. However, the sex bias in lung ILC2 numbers and phenotypic changes are not affected by IL-33 deficiency [ 82 ].…”

“…3 ). Likewise, ovariectomy, E2-supplementation, and Esr1 gene ablation in the hematopoietic or lymphoid compartment failed to demonstrate any effect of estrogens on lung ILC2s [ 3 , 4 , 50 , 51 ] ( Fig. 5 ).…”

“…The mechanisms resulting in enhanced IL-33 expression in female lung tissue is currently unknown. It has been suggested that ER-signaling could positively control IL-33 protein and mRNA production in human epithelial cell lines upon challenge with Alternaria Extract or HDM [ 50 ]. However, a comprehensive in vivo evaluation of the role of ER-signaling on IL-33 up-regulation in lung epithelial cells is still awaiting.…”

The Role of Type 2 Innate Lymphoid Cells in Allergic Diseases

“…Compared with wild-type Esr1-/- mice, those stimulated by Alternaria extract (Alt Ext) exhibited fewer IL-33eGFP+ epithelial cells, reduced IL-33 release, reduced secretion of IL-5 and IL-13 and fewer bronchoalveolar lavage (BAL) eosinophils. It has been suggested that ER-α (Esr1) signaling increases the release of IL-33 and ILC2-mediated airway inflammation ( 55 ).…”