Id2 and Id3 maintain the regulatory T cell pool to suppress inflammatory disease.

Regulatory T (Treg) cells suppress the development of inflammatory disease, but our knowledge of transcriptional regulators that control this function remains incomplete. Here we show that expression of Id2 and Id3 in Treg cells was required to suppress development of fatal inflammatory disease. We found that T cell antigen receptor (TCR)-driven signaling initially decreased the abundance of Id3, which led to the activation of a follicular regulatory T (TFR) cell-specific transcription signature. However, sustained lower abundance of Id2 and Id3 interfered with proper development of TFR cells. Depletion of Id2 and Id3 expression in Treg cells resulted in compromised maintenance and localization of the Treg cell population. Thus, Id2 and Id3 enforce TFR cell checkpoints and control the maintenance and homing of Treg cells.

Lymphotoxin beta receptor signaling directly controls airway smooth muscle deregulation and asthmatic lung dysfunction.

BACKGROUND: Dysregulation of airway smooth muscle cells (ASM) is central to the severity of asthma. Which molecules dominantly control ASM in asthma is unclear. High levels of the cytokine LIGHT (aka TNFSF14) have been linked to asthma severity and lower baseline predicted FEV1 percentage, implying that signals through its receptors might directly control ASM dysfunction. OBJECTIVE: Our study sought to determine whether signaling via lymphotoxin beta receptor (LTßR) or herpesvirus entry mediator from LIGHT dominantly drives ASM hyperreactivity induced by allergen. METHODS: Conditional knockout mice deficient for LTßR or herpesvirus entry mediator in smooth muscle cells were used to determine their role in ASM deregulation and airway hyperresponsiveness (AHR) in vivo. Human ASM were used to study signals induced by LTßR. RESULTS: LTßR was strongly expressed in ASM from normal and asthmatic subjects compared to several other receptors implicated in smooth muscle deregulation. Correspondingly, conditional deletion of LTßR only in smooth muscle cells in smMHCCreLTßRfl/fl mice minimized changes in their numbers and mass as well as AHR induced by house dust mite allergen in a model of severe asthma. Intratracheal LIGHT administration independently induced ASM hypertrophy and AHR in vivo dependent on direct LTßR signals to ASM. LIGHT promoted contractility, hypertrophy, and hyperplasia of human ASM in vitro. Distinguishing LTßR from the receptors for IL-13, TNF, and IL-17, which have also been implicated in smooth muscle dysregulation, LIGHT promoted NF-κB-inducing kinase-dependent noncanonical nuclear factor kappa-light-chain enhancer of activated B cells in ASM in vitro, leading to sustained accumulation of F-actin, phosphorylation of myosin light chain kinase, and contractile activity. CONCLUSIONS: LTßR signals directly and dominantly drive airway smooth muscle hyperresponsiveness relevant for pathogenesis of airway remodeling in severe asthma.

Single-base editing of rs12603332 on chromosome 17q21 with a cytosine base editor regulates ORMDL3 and ATF6α expression.

BACKGROUND: Genetic association studies have demonstrated that the SNP rs12603332 located on chromosome 17q21 is highly associated with the risk of the development of asthma. METHODS: To determine whether SNP rs1260332 is functional in regulating levels of ORMDL3 expression, we used a Cytosine Base Editor (CBE) plasmid DNA or a CBE mRNA to edit the rs12603332 C risk allele to the T non-risk allele in a human lymphocyte cell line (i.e., Jurkat cells) and in primary human CD4 T cells that carry the C risk alleles. RESULTS: Jurkat cells with the rs12603332 C risk allele expressed significantly higher levels of ORMDL3 mRNA, as well as the ORMDL3 regulated gene ATF6α as assessed by qPCR compared to Jurkat clones with the T non-risk allele. In primary human CD4 T cells, we edited 90 ± 3% of the rs12603332-C risk allele to the T non-risk allele and observed a reduction in ORMDL3 and ATF6α expression. Bioinformatic analysis predicted that the non-risk allele rs12603332-T could be the central element of the E-box binding motif (CANNTG) recognized by the E47 transcription factor. An EMSA assay confirmed the bioinformatics prediction demonstrating that a rs12603332-T containing probe bound to the transcription factor E47 in vitro. CONCLUSIONS: SNP rs12603332 is functional in regulating the expression of ORMDL3 as well as ORMDL3 regulated gene ATF6α expression. In addition, we demonstrate the use of CBE technology in functionally interrogating asthma-associated SNPs using studies of primary human CD4 cells.

TL1A Promotes Lung Tissue Fibrosis and Airway Remodeling.

Lung fibrosis and tissue remodeling are features of chronic diseases such as severe asthma, idiopathic pulmonary fibrosis, and systemic sclerosis. However, fibrosis-targeted therapies are currently limited. We demonstrate in mouse models of allergen- and bleomycin-driven airway inflammation that neutralization of the TNF family cytokine TL1A through Ab blocking or genetic deletion of its receptor DR3 restricted increases in peribronchial smooth muscle mass and accumulation of lung collagen, primary features of remodeling. TL1A was found as a soluble molecule in the airways and expressed on the surface of alveolar macrophages, dendritic cells, innate lymphoid type 2 cells, and subpopulations of lung structural cells. DR3 was found on CD4 T cells, innate lymphoid type 2 cells, macrophages, fibroblasts, and some epithelial cells. Suggesting in part a direct activity on lung structural cells, administration of recombinant TL1A into the naive mouse airways drove remodeling in the absence of other inflammatory stimuli, innate lymphoid cells, and adaptive immunity. Correspondingly, human lung fibroblasts and bronchial epithelial cells were found to express DR3 and responded to TL1A by proliferating and/or producing fibrotic molecules such as collagen and periostin. Reagents that disrupt the interaction of TL1A with DR3 then have the potential to prevent deregulated tissue cell activity in lung diseases that involve fibrosis and remodeling.

Rhinovirus Infection of ORMDL3 Transgenic Mice Is Associated with Reduced Rhinovirus Viral Load and Airway Inflammation.

Orosomucoid like 3 (ORMDL3), a gene localized to chromosome 17q21, has been linked in epidemiologic studies to childhood asthma and rhinovirus (RV) infections. As the single nucleotide polymorphisms linking ORMDL3 to asthma are associated with increased expression of ORMDL3, we have used hORMDL3zp3-Cre mice (which have universal increased expression of human ORMDL3) to determine whether infection of these transgenic mice with RV influences levels of airway inflammation or RV viral load. RV infection of hORMDL3zp3-Cre mice resulted in reduced RV viral load assessed by quantitative real-time PCR (lung and airway epithelium), as well as reduced airway inflammation (total bronchoalveolar lavage cells, neutrophils, macrophages, and lymphocytes) compared with RV-infected wild-type mice. Levels of the antiviral pathways including IFNs (IFN-α, IFN-ß, IFN-λ) and RNAse L were significantly increased in the lungs of RV-infected hORMDL3zp3-Cre mice. Levels of the antiviral mouse oligoadenylate synthetase (mOas)1g pathway and RNAse L were upregulated in the lungs of unchallenged hORMDL3zp3-Cre mice. In addition, levels of mOas2, but not mOas1 (mOas1a, mOas1b, mOas1g), or mOas3 pathways were significantly more upregulated by IFNs (IFN-α, IFN-ß, IFN-λ) in epithelial cells from hORMDL3zp3-Cre mice compared with RV-infected wild-type mouse epithelial cells. RNAse L-deficient mice infected with RV had increased RV viral load. Overall, these studies suggest that increased levels of ORMDL3 contribute to antiviral defense to RV infection in mice through pathways that may include IFNs (IFN-α, IFN-ß, IFN-λ), OAS, and RNAse L.

Cutting Edge: Targeting Epithelial ORMDL3 Increases, Rather than Reduces, Airway Responsiveness and Is Associated with Increased Sphingosine-1-Phosphate.

In this study, we used cre-lox techniques to generate mice selectively deficient in ORMDL3 in airway epithelium (Ormdl3Δ2-3/Δ2-3/CC10) to simulate an inhaled therapy that effectively inhibited ORMDL3 expression in the airway. In contrast to the anticipated reduction in airway hyperresponsiveness (AHR), OVA allergen-challenged Ormdl3Δ2-3/Δ2-3/CC10 mice had a significant increase in AHR compared with wild-type mice. Levels of airway inflammation, mucus, fibrosis, and airway smooth muscle were no different in Ormdl3Δ2-3/Δ2-3/CC10 and wild-type mice. However, levels of sphingosine-1-phosphate (S1P) were significantly increased in Ormdl3Δ2-3/Δ2-3/CC10 mice as well as in airway epithelial cells in which ORMDL3 was inhibited with small interfering RNA. Incubation of S1P with airway smooth muscle cells significantly increased contractility. Overall, Ormdl3Δ2-3/Δ2-3/CC10 mice exhibit increased allergen-induced AHR independent of inflammation and associated with increased S1P generation. These studies raise concerns for inhaled therapies that selectively and effectively inhibit ORMDL3 in airway epithelium in asthma.

Leukotriene C4 Potentiates IL-33-Induced Group 2 Innate Lymphoid Cell Activation and Lung Inflammation.

Asthma is a complex disease that is promoted by dysregulated immunity and the presence of many cytokine and lipid mediators. Despite this, there is a paucity of data demonstrating the combined effects of multiple mediators in asthma pathogenesis. Group 2 innate lymphoid cells (ILC2s) have recently been shown to play important roles in the initiation of allergic inflammation; however, it is unclear whether lipid mediators, such as cysteinyl leukotrienes (CysLTs), which are present in asthma, could further amplify the effects of IL-33 on ILC2 activation and lung inflammation. In this article, we show that airway challenges with the parent CysLT, leukotriene C4 (LTC4), given in combination with low-dose IL-33 to naive wild-type mice, led to synergistic increases in airway Th2 cytokines, eosinophilia, and peribronchial inflammation compared with IL-33 alone. Further, the numbers of proliferating and cytokine-producing lung ILC2s were increased after challenge with both LTC4 and IL-33. Levels of CysLT1R, CysLT2R, and candidate leukotriene E4 receptor P2Y12 mRNAs were increased in ILC2s. The synergistic effect of LTC4 with IL-33 was completely dependent upon CysLT1R, because CysLT1R-/- mice, but not CysLT2R-/- mice, had abrogated responses. Further, CysLTs directly potentiated IL-5 and IL-13 production from purified ILC2s stimulated with IL-33 and resulted in NFAT1 nuclear translocation. Finally, CysLT1R-/- mice had reduced lung eosinophils and ILC2 responses after exposure to the fungal allergen Alternaria alternata Thus, CysLT1R promotes LTC4- and Alternaria-induced ILC2 activation and lung inflammation. These findings suggest that multiple pathways likely exist in asthma to activate ILC2s and propagate inflammatory responses.

GSDMB induces an asthma phenotype characterized by increased airway responsiveness and remodeling without lung inflammation.

Gasdermin B (GSDMB) on chromosome 17q21 demonstrates a strong genetic linkage to asthma, but its function in asthma is unknown. Here we identified that GSDMB is highly expressed in lung bronchial epithelium in human asthma. Overexpression of GSDMB in primary human bronchial epithelium increased expression of genes important to both airway remodeling [TGF-ß1, 5-lipoxygenase (5-LO)] and airway-hyperresponsiveness (AHR) (5-LO). Interestingly, hGSDMBZp3-Cre mice expressing increased levels of the human GSDMB transgene showed a significant spontaneous increase in AHR and a significant spontaneous increase in airway remodeling, with increased smooth muscle mass and increased fibrosis in the absence of airway inflammation. In addition, hGSDMBZp3-Cre mice showed increases in the same remodeling and AHR mediators (TGF-ß1, 5-LO) observed in vitro in GSDMB-overexpressing epithelial cells. GSDMB induces TGF-ß1 expression via induction of 5-LO, because knockdown of 5-LO in epithelial cells overexpressing GSDMB inhibited TGF-ß1 expression. These studies demonstrate that GSDMB, a gene highly linked to asthma but whose function in asthma is previously unknown, regulates AHR and airway remodeling without airway inflammation through a previously unrecognized pathway in which GSDMB induces 5-LO to induce TGF-ß1 in bronchial epithelium.

Orosomucoid-like 3 (ORMDL3) upregulates airway smooth muscle proliferation, contraction, and Ca2+ oscillations in asthma.

BACKGROUND: Airway hyperresponsiveness is a major feature of asthma attributed predominantly to an extrinsic immune/inflammatory response increasing airway smooth muscle (ASM) contractility. OBJECTIVE: We investigated whether increased ASM expression of orosomucoid-like 3 (ORMDL3), a gene on chromosome 17q21 highly linked to asthma, induced increased ASM proliferation and contractility in vitro and influenced airway contractility and calcium flux in ASM in precision-cut lung slices (PCLSs) from wild-type and hORMDL3Zp3-Cre mice (which express increased levels of human ORMDL3 [hORMDL3]). METHODS: Levels of ASM proliferation and contraction were assessed in ASM cells transfected with ORMDL3 in vitro. In addition, airway contractility and calcium oscillations were quantitated in ASM cells in PCLSs derived from naive wild-type and naive hORMDL3Zp3-Cre mice, which do not have a blood supply. RESULTS: Increased ASM expression of ORMDL3 in vitro resulted in increased ASM proliferation and contractility. PCLSs derived from naive hORMDL3Zp3-Cre mice, which do not have airway inflammation, exhibit increased airway contractility with increased calcium oscillations in ASM cells. Increased ASM ORMDL3 expression increases levels of ASM sarcoplasmic reticulum Ca2+ ATPase 2b (SERCA2b), which increases ASM proliferation and contractility. CONCLUSION: Overall, these studies provide evidence that an intrinsic increase in ORMDL3 expression in ASM can induce increased ASM proliferation and contractility, which might contribute to increased airway hyperresponsiveness in the absence of airway inflammation in asthmatic patients.

ß2 integrins rather than ß1 integrins mediate Alternaria-induced group 2 innate lymphoid cell trafficking to the lung.

BACKGROUND: Group 2 innate lymphoid cells (ILC2s) expand in the lungs of mice during type 2 inflammation induced by the fungal allergen Alternaria alternata. The increase in ILC2 numbers in the lung has been largely attributed to local proliferation and whether ILC2s migrate from the circulation to the lung after Alternaria exposure is unknown. OBJECTIVE: We examined whether human (lung, lymph node, and blood) and mouse lung ILC2s express ß1 and ß2 integrin adhesion molecules and whether these integrins are required for trafficking of ILC2s into the lungs of mice. METHODS: Human and mouse ILC2s were assessed for surface expression of ß1 and ß2 integrin adhesion molecules by using flow cytometry. The role of ß1 and ß2 integrins in ILC2 trafficking to the lungs was assessed by in vivo blocking of these integrins before airway exposure to Alternaria in mice. RESULTS: Both human and mouse lung ILC2s express high levels of ß1 and ß2 integrin adhesion receptors. Intranasal administration of Alternaria challenge reduced ILC2 numbers in the bone marrow and concurrently increased blood and lung ILC2 numbers. In vivo blocking of ß2 integrins (CD18) significantly reduced ILC2 numbers in the lungs but did not alter ILC2 proliferation, apoptosis, and function. In contrast, in vivo blocking of ß1 integrins or α4 integrins did not affect lung ILC2 numbers. CONCLUSION: ILC2 numbers increase in the mouse lung not only through local proliferation but also through trafficking from the circulation into the lung using ß2 rather than ß1 or α4 integrins.

Airway innate lymphoid cells in the induction and regulation of allergy.

The recent discovery of innate lymphoid cells has revolutionized our understanding of the pathogenesis of immune diseases including allergy and asthma. Innate lymphoid cells (ILCs) are a heterogeneous collection of lymphocytes that lack antigen-specificity (non-T, non-B cells) and potently produce characteristic cytokines of T cell subsets (Th1, Th2, Th17). ILCs are divided into group 1 (ILC1s), group 2 (ILC2s), or group 3 (ILC3s). Similar to Th2 cells, ILC2s produce IL-4, IL-5, and IL-13, among others, and are present in increased numbers in samples from patients with many allergic disorders including asthma and chronic rhinosinusitis (CRS). Animal models have identified that ILC2s contribute to eosinophilic tissue infiltration, airway hyperresponsiveness, mucus production, as well as coordinate adaptive immune responses. Finally, recent studies support regulation of ILC2s by neuro-immune mechanisms as well as demonstrate a significant degree of plasticity between ILC subsets that may impact the immune responses in asthma and allergic airway diseases. Here, we review the current literature on ILC2s in human asthma and allergic airway diseases, as well as highlight some recent mechanistic insights into ILC2 function from in vitro studies and in vivo animal models.

Transcriptional Profiling of Th2 Cells Identifies Pathogenic Features Associated with Asthma.

Allergic asthma and rhinitis are two common chronic allergic diseases that affect the lungs and nose, respectively. Both diseases share clinical and pathological features characteristic of excessive allergen-induced type 2 inflammation, orchestrated by memory CD4(+) T cells that produce type 2 cytokines (Th2 cells). However, a large majority of subjects with allergic rhinitis do not develop asthma, suggesting divergence in disease mechanisms. Because Th2 cells play a pathogenic role in both these diseases and are also present in healthy nonallergic subjects, we performed global transcriptional profiling to determine whether there are qualitative differences in Th2 cells from subjects with allergic asthma, rhinitis, and healthy controls. Th2 cells from asthmatic subjects expressed higher levels of several genes that promote their survival as well as alter their metabolic pathways to favor persistence at sites of allergic inflammation. In addition, genes that enhanced Th2 polarization and Th2 cytokine production were also upregulated in asthma. Several genes that oppose T cell activation were downregulated in asthma, suggesting enhanced activation potential of Th2 cells from asthmatic subjects. Many novel genes with poorly defined functions were also differentially expressed in asthma. Thus, our transcriptomic analysis of circulating Th2 cells has identified several molecules that are likely to confer pathogenic features to Th2 cells that are either unique or common to both asthma and rhinitis.

Cyclic AMP concentrations in dendritic cells induce and regulate Th2 immunity and allergic asthma.

The inductive role of dendritic cells (DC) in Th2 differentiation has not been fully defined. We addressed this gap in knowledge by focusing on signaling events mediated by the heterotrimeric GTP binding proteins Gαs, and Gαi, which respectively stimulate and inhibit the activation of adenylyl cyclases and the synthesis of cAMP. We show here that deletion of Gnas, the gene that encodes Gαs in mouse CD11c(+) cells (Gnas(ΔCD11c) mice), and the accompanying decrease in cAMP provoke Th2 polarization and yields a prominent allergic phenotype, whereas increases in cAMP inhibit these responses. The effects of cAMP on DC can be demonstrated in vitro and in vivo and are mediated via PKA. Certain gene products made by Gnas(ΔCD11c) DC affect the Th2 bias. These findings imply that G protein-coupled receptors, the physiological regulators of Gαs and Gαi activation and cAMP formation, act via PKA to regulate Th bias in DC and in turn, Th2-mediated immunopathologies.

Group 2 innate lymphoid cells are recruited to the nasal mucosa in patients with aspirin-exacerbated respiratory disease.

BACKGROUND: Aspirin-exacerbated respiratory disease (AERD) is characterized by tissue eosinophilia and mast cell activation, including abundant production of prostaglandin D2 (PGD2). Group 2 innate lymphoid cells (ILC2s), which promote tissue eosinophilia and mast cell responses, undergo chemotaxis and cytokine production in response to PGD2, but it is unknown whether ILC2s are active in patients with AERD. OBJECTIVE: We sought to determine whether ILC2 numbers change in peripheral blood and the nasal mucosa during COX-1 inhibitor-induced reactions in patients with AERD. METHODS: Blood and nasal scrapings were collected at baseline, during reactions, and after completion of ketorolac/aspirin challenge/desensitization in 12 patients with AERD. ILC2s and eosinophils were quantitated by means of flow cytometry. Urine was also collected, and quantification of PGD2 metabolite and leukotriene E4 levels was done by using ELISA. Baseline and nonsteroidal anti-inflammatory drug reaction clinical data were correlated with cell changes. RESULTS: ILC2 numbers significantly increased in nasal mucosal samples and decreased in blood at the time of COX-1 inhibitor reactions in 12 patients with AERD. These changes were not observed in 2 patients without AERD. Furthermore, eosinophil numbers decreased in blood concurrently with significant increases in urinary PGD2 metabolite and leukotriene E4 levels. The magnitude of increases in nasal mucosal ILC2 numbers positively correlated with maximum symptom scores during challenges. Furthermore, blood ILC2 numbers during the reaction correlated with time for the reaction to resolve, possibly reflecting reaction severity. CONCLUSIONS: ILC2s are recruited to the nasal mucosa during COX-1 inhibitor-induced reactions in patients with AERD, correlating with enhanced production of prostaglandins and leukotrienes.

Autophagy plays a role in FSTL1-induced epithelial mesenchymal transition and airway remodeling in asthma.

Asthma is a chronic disease related to airway hyperresponsiveness and airway remodeling. Airway remodeling is the important reason of refractory asthma and is associated with differentiation of airway epithelia into myofibroblasts via epithelial-mesenchymal transition (EMT) to increase the process of subepithelial fibrosis. There is growing evidence that autophagy modulates remodeling. However, the underlying molecular mechanisms of these effects are still unclear. In this study, we hypothesized that Follistatin-like 1 (FSTL1) promotes EMT and airway remodeling by intensifying autophagy. With the use of transmission electron microscopy (TEM), double-membrane autophagosomes were detected in the airways of patients and mice. More autophagosomes were in patients with asthma and OVA-challenged mice compared with healthy controls. The expression of FSTL1 and beclin-1 was upregulated in the airways of patients with asthma and OVA-challenged mice, accompanied by airway EMT and remodeling. In OVA-challenged Fstl1+/- mice, the degree of airway remodeling and autophagy was decreased compared with control mice. The effects of FSTL1 on autophagy and EMT were also tested in 16HBE cells in vitro. Additionally, inhibition of autophagy by using LY-294002 and siRNA-ATG5 reduced the FSTL1-induced EMT in 16HBE cells, as measured by E-cadherin, N-cadherin, and vimentin expression. In line herewith, administration of LY-294002 reduced the expression of autophagy, EMT, and airway remodeling markers in FSTL1-challenged WT mice. Taken together, our study suggests that FSTL1 may induce EMT and airway remodeling by activating autophagy. These findings may provide novel avenues for therapeutic research targeting the autophagy and FSTL1 pathway, which may be beneficial to patients with refractory asthma.

Hypoxia-inducible factor-1α inhibition modulates airway hyperresponsiveness and nitric oxide levels in a BALB/c mouse model of asthma.

Hypoxia-inducible factor (HIF)-1α is a master regulator of inflammation and is upregulated in alveolar macrophages and lung parenchyma in asthma. HIF-1α regulates select pathways in allergic inflammation, and thus may drive particular asthma phenotypes. This work examines the role of pharmacologic HIF-1α inhibition in allergic inflammatory airway disease (AIAD) pathogenesis in BALB/c mice, which develop an airway hyperresponsiveness (AHR) asthma phenotype. Systemic treatment with HIF-1α antagonist YC-1 suppressed the increase in HIF-1α expression seen in control AIAD mice. Treatment with YC-1 also decreased AHR, blood eosinophilia, and allergic inflammatory gene expression: IL-5, IL-13, myeloperoxidase and iNOS. AIAD mice had elevated BAL levels of NO, and treatment with YC-1 eliminated this response. However, YC-1 did not decrease BAL, lung or bone marrow eosinophilia. We conclude that HIF-1α inhibition in different genetic backgrounds, and thus different AIAD phenotypes, decreases airway resistance and markers of inflammation in a background specific manner. CAPSULE SUMMARY: Asthma is a common disease that can be difficult to control with current therapeutics. We describe how pharmacologic targeting of a specific transcription factor, HIF-1α, suppresses asthmatic airway reactivity and inflammation.

Fstl1 Promotes Asthmatic Airway Remodeling by Inducing Oncostatin M.

Chronic asthma is associated with airway remodeling and decline in lung function. In this article, we show that follistatin-like 1 (Fstl1), a mediator not previously associated with asthma, is highly expressed by macrophages in the lungs of humans with severe asthma. Chronic allergen-challenged Lys-Cre(tg) /Fstl1(Δ/Δ) mice in whom Fstl1 is inactivated in macrophages/myeloid cells had significantly reduced airway remodeling and reduced levels of oncostatin M (OSM), a cytokine previously not known to be regulated by Fstl1. The importance of the Fstl1 induction of OSM to airway remodeling was demonstrated in murine studies in which administration of Fstl1 induced airway remodeling and increased OSM, whereas administration of an anti-OSM Ab blocked the effect of Fstl1 on inducing airway remodeling, eosinophilic airway inflammation, and airway hyperresponsiveness, all cardinal features of asthma. Overall, these studies demonstrate that the Fstl1/OSM pathway may be a novel pathway to inhibit airway remodeling in severe human asthma.

Prostaglandin I2 Signaling and Inhibition of Group 2 Innate Lymphoid Cell Responses.

RATIONALE: Group 2 innate lymphoid cells (ILC2s) robustly produce IL-5 and IL-13, cytokines central to the asthma phenotype; however, the effect of prostaglandin (PG) I2 on ILC2 function is unknown. OBJECTIVES: To determine the effect of PGI2 on mouse and human ILC2 cytokine expression in vitro and the effect of endogenous PGI2 and the PGI2 analog cicaprost on lung ILC2s in vivo. METHODS: Flow-sorted bone marrow ILC2s of wild-type (WT) and PGI2 receptor-deficient (IP(-/-)) mice were cultured with IL-33 and treated with the PGI2 analog cicaprost. WT and IP(-/-) mice were challenged intranasally with Alternaria alternata extract for 4 consecutive days to induce ILC2 responses, and these were quantified. Prior to A. alternata extract, challenged WT mice were treated with cicaprost. Human flow-sorted peripheral blood ILC2s were cultured with IL-33 and IL-2 and treated with the PGI2 analog cicaprost. MEASUREMENT AND MAIN RESULTS: We demonstrate that PGI2 inhibits IL-5 and IL-13 protein expression by IL-33-stimulated ILC2s purified from mouse bone marrow in a manner that was dependent on signaling through the PGI2 receptor IP. In a mouse model of 4 consecutive days of airway challenge with an extract of A. alternata, a fungal aeroallergen associated with severe asthma exacerbations, endogenous PGI2 signaling significantly inhibited lung IL-5 and IL-13 protein expression, and reduced the number of lung IL-5- and IL-13-expressing ILC2s, as well as the mean fluorescence intensity of IL-5 and IL-13 staining. In addition, exogenous administration of a PGI2 analog inhibited Alternaria extract-induced lung IL-5 and IL-13 protein expression, and reduced the number of lung IL-5- and IL-13-expressing ILC2s and the mean fluorescence intensity of IL-5 and IL-13 staining. Finally, a PGI2 analog inhibited IL-5 and IL-13 expression by human ILC2s that were stimulated with IL-2 and IL-33. CONCLUSIONS: These results suggest that PGI2 may be a potential therapy to reduce the ILC2 response to protease-containing aeroallergens, such as Alternaria.