Role of estrogen receptors α and β in the development of allergic airway inflammation in mice: A possible involvement of interleukin 33 and eosinophils

Recent studies have shown that the estrogen receptor α (ERα), but not ERβ, is involved in the proinflammatory and propruritic responses in cutaneous allergy. In addition, results from our recent study showed that while oral administration of the rather ERβ-selective agonist bisphenol A exacerbated the respiratory allergic inflammation, the potential inflammatory reaction in the skin was decreased after administration of bisphenol A. This study aimed to elucidate whether ERα and ERβ are involved in the progression of an allergic airway inflammation. We performed an in vivo experiment using an animal model of allergic airway inflammation using male BALB/c mice to confirm an increase in the proinflammatory response induced by propylpyrazoletriol (PPT), an ERα agonist, and diarylpropionitrile (DPN), an ERβ agonist. Oral administration of PPT or DPN showed a significant increase in the inflammation of the lung and infiltration of eosinophils. While the expression of Th2 cytokines such as interleukin 4 (IL-4) and IL-13 was not affected by exposure to PPT or DPN, administration of these agonists significantly increased the expression of IL-33. The mechanism underlying the development of such allergic inflammatory responses was determined by an in vitro study using the human bronchial epithelial cell line (BEAS-2B) and the human eosinophilic leukemia cell line (EoL-1). Activated cells were exposed to PPT or DPN for 24 h, and the cytokine levels were measured. The IL-33 levels in BEAS-2B cells increased significantly after exposure to PPT or DPN. In addition, pretreatment with PPT or DPN increased the expression of IL-8 in activated EoL-1 cells. Our findings indicate that ERα and ERβ are involved in the proinflammatory response in respiratory allergy, and their effects may be mediated by an increase in the expression of IL-33 and infiltration of eosinophils.