Zhou, Weisong

Abstract The cyclooxygenase (COX) metabolic pathway has regulatory functions in immune responses and inflammation. However, the effect of the COX pathway on innate airway inflammation induced by protease-containing allergens such as Alternaria alternata is not fully defined. Here we show that COX inhibition augmented innate lung type 2 responses after repeated airway exposures to Alternaria extract in mice. We treated wild type BALB/c and IL-33 KO mice with either the COX inhibitor indomethacin or vehicle in drinking water and challenged mice intranasally with Alternaria extract for 4 consecutive days to induce innate lung inflammation. We found that indomethacin significantly increased the numbers of group 2 innate lymphoid cells (ILC2) and IL-5+IL-13+ ILC2 in the lung. Indomethacin also increased type 2 cytokine (IL-5 and IL-13) responses, the percentages of eosinophils, and mucus production in the lung. IL-33 is required for Alt-induced lung ILC2 responses, and indomethacin did not change IL-5 and IL-13 expression in IL-33 KO mice. Consistently, indomethacin increased the release of IL-33 in bronchoalveolar lavage fluid after Alternaria challenge, suggesting that more IL-33 was available for ILC2 activation. Indomethacin also increased reactive oxygen species (ROS) production in the lung, providing a possible mechanism for the increased IL-33 release. Although contrasting effects of PGD2 and PGE2/PGI2 on ILC2 responses have been previously reported, the overall effect of COX pathway on ILC2 function is inhibitory in Alternaria extract-induced airway innate type 2 responses.

Abstract The cyclooxygenase (COX) metabolic pathway regulates immune responses and inflammation. The effect of the COX pathway on innate pulmonary inflammation induced by protease-containing fungal allergens, such as Alternaria alternata, is not fully defined. In this study, we tested the hypothesis that COX inhibition augments Alternaria-induced pulmonary group 2 innate lymphoid cell (ILC2) responses and IL-33 release. Mice were treated with the COX inhibitors indomethacin, flurbiprofen, or vehicle and challenged intranasally with Alternaria extract for four consecutive days to induce innate lung inflammation. We found that indomethacin and flurbiprofen significantly increased the numbers of ILC2 and IL-5 and IL-13 expression by ILC2 in the lung. Indomethacin also increased ILC2 proliferation, the percentages of eosinophils, and mucus production in the lung. Both indomethacin and flurbiprofen augmented the release of IL-33 in bronchoalveolar lavage fluid after Alternaria challenge, suggesting that more IL-33 was available for ILC2 activation and that a COX product(s) inhibited IL-33 release. This is supported by the in vitro finding that the COX product PGE2 and the PGI2 analogs cicaprost decreased Alternaria extract–induced IL-33 release by human bronchial epithelial cells. Although contrasting effects of PGD2, PGE2, and PGI2 on ILC2 responses have been previously reported, the overall effect of the COX pathway on ILC2 function is inhibitory in Alternaria-induced innate 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.

AbstractBackgroundThe epithelial cell‐derived danger signal mediators thymic stromal lymphopoietin (TSLP) and IL‐33 are consistently associated with adaptive Th2 immune responses in asthma. In addition, TSLP and IL‐33 synergistically promoted group 2 innate lymphoid cell (ILC2) activation to induce innate allergic inflammation. However, the mechanism of this synergistic ILC2 activation is unknown.MethodsBALB/c WT and TSLP receptor‐deficient (TSLPR−/−) mice were challenged intranasally with Alternaria extract (Alt‐Ext) or PBS for 4 consecutive days to evaluate innate airway allergic inflammation. WT mice pre‐administered with rTSLP or vehicle, TSLPR−/− mice, and IL‐33 receptor‐deficient (ST2−/−) mice were challenged intranasally with Alt‐Ext or vehicle once or twice to evaluate IL‐33 release and TSLP expression in the lung. TSLPR and ST2 expression on lung ILC2 were measured by flow cytometry after treatment of rTSLP, rIL‐33, rTSLP + rIL‐33, or vehicle.ResultsThymic stromal lymphopoietin receptor deficient mice had significantly decreased the number of lung ILC2 expressing IL‐5 and IL‐13 following Alt‐Ext‐challenge compared to WT mice. Further, eosinophilia, protein level of lung IL‐4, IL‐5, and IL‐13, and airway mucus score were also significantly decreased in TSLPR−/− mice compared to WT mice. Endogenous and exogenous TSLP increased Alt‐Ext‐induced IL‐33 release into BALF, and ST2 deficiency decreased Alt‐Ext‐induced TSLP expression in the lung. Further, rTSLP and rIL‐33 treatment reciprocally increased each other's receptor expression on lung ILC2 in vivo and in vitro.ConclusionThymic stromal lymphopoietin and IL‐33 signaling reciprocally enhanced each other's protein release and expression in the lung following Alt‐Ext‐challenge and each other's receptor expression on lung ILC2 to enhance ILC2 activation.