Distinct Regulation of Th17 and Th1 Cell Differentiation by Glutaminase-Dependent Metabolism.

Activated T cells differentiate into functional subsets with distinct metabolic programs. Glutaminase (GLS) converts glutamine to glutamate to support the tricarboxylic acid cycle and redox and epigenetic reactions. Here, we identify a key role for GLS in T cell activation and specification. Though GLS deficiency diminished initial T cell activation and proliferation and impaired differentiation of Th17 cells, loss of GLS also increased Tbet to promote differentiation and effector function of CD4 Th1 and CD8 CTL cells. This was associated with altered chromatin accessibility and gene expression, including decreased PIK3IP1 in Th1 cells that sensitized to IL-2-mediated mTORC1 signaling. In vivo, GLS null T cells failed to drive Th17-inflammatory diseases, and Th1 cells had initially elevated function but exhausted over time. Transient GLS inhibition, however, led to increased Th1 and CTL T cell numbers. Glutamine metabolism thus has distinct roles to promote Th17 but constrain Th1 and CTL effector cell differentiation.

MTHFD2 is a metabolic checkpoint controlling effector and regulatory T cell fate and function.

Antigenic stimulation promotes T cell metabolic reprogramming to meet increased biosynthetic, bioenergetic, and signaling demands. We show that the one-carbon (1C) metabolism enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) regulates de novo purine synthesis and signaling in activated T cells to promote proliferation and inflammatory cytokine production. In pathogenic T helper-17 (Th17) cells, MTHFD2 prevented aberrant upregulation of the transcription factor FoxP3 along with inappropriate gain of suppressive capacity. MTHFD2 deficiency also promoted regulatory T (Treg) cell differentiation. Mechanistically, MTHFD2 inhibition led to depletion of purine pools, accumulation of purine biosynthetic intermediates, and decreased nutrient sensor mTORC1 signaling. MTHFD2 was also critical to regulate DNA and histone methylation in Th17 cells. Importantly, MTHFD2 deficiency reduced disease severity in multiple in vivo inflammatory disease models. MTHFD2 is thus a metabolic checkpoint to integrate purine metabolism with pathogenic effector cell signaling and is a potential therapeutic target within 1C metabolism pathways.

Glucagon-like Peptide-1 Receptor Pathway Attenuates Platelet Activation in Aspirin-Exacerbated Respiratory Disease.

Platelets are key contributors to allergic asthma and aspirin-exacerbated respiratory disease (AERD), an asthma phenotype involving platelet activation and IL-33-dependent mast cell activation. Human platelets express the glucagon-like peptide-1 receptor (GLP-1R). GLP-1R agonists decrease lung IL-33 release and airway hyperresponsiveness in mouse asthma models. We hypothesized that GLP-1R agonists reduce platelet activation and downstream platelet-mediated airway inflammation in AERD. GLP-1R expression on murine platelets was assessed using flow cytometry. We tested the effect of the GLP-1R agonist liraglutide on lysine-aspirin (Lys-ASA)-induced changes in airway resistance, and platelet-derived mediator release in a murine AERD model. We conducted a prospective cohort study comparing the effect of pretreatment with liraglutide or vehicle on thromboxane receptor agonist-induced in vitro activation of platelets from patients with AERD and nonasthmatic controls. GLP-1R expression was higher on murine platelets than on leukocytes. A single dose of liraglutide inhibited Lys-ASA-induced increases in airway resistance and decreased markers of platelet activation and recruitment to the lung in AERD-like mice. Liraglutide attenuated thromboxane receptor agonist-induced activation as measured by CXCL7 release in plasma from patients with AERD and CD62P expression in platelets from both patients with AERD (n = 31) and nonasthmatic, healthy controls (n = 11). Liraglutide, a Food and Drug Administration-approved GLP-1R agonist for treatment of type 2 diabetes and obesity, attenuates in vivo platelet activation in an AERD murine model and in vitro activation in human platelets in patients with and without AERD. These data advance the GLP-1R axis as a new target for platelet-mediated inflammation warranting further study in asthma.

Repetitive sulfur dioxide exposure in mice models post-deployment respiratory syndrome.

Soldiers deployed to Iraq and Afghanistan have a higher prevalence of respiratory symptoms than nondeployed military personnel and some have been shown to have a constellation of findings on lung biopsy termed post-deployment respiratory syndrome (PDRS). Since many of the subjects in this cohort reported exposure to sulfur dioxide (SO2), we developed a model of repetitive exposure to SO2 in mice that phenocopies many aspects of PDRS, including adaptive immune activation, airway wall remodeling, and pulmonary vascular (PV) disease. Although abnormalities in small airways were not sufficient to alter lung mechanics, PV remodeling resulted in the development of pulmonary hypertension and reduced exercise tolerance in SO2-exposed mice. SO2 exposure led to increased formation of isolevuglandins (isoLGs) adducts and superoxide dismutase 2 (SOD2) acetylation in endothelial cells, which were attenuated by treatment with the isoLG scavenger 2-hydroxybenzylamine acetate (2-HOBA). In addition, 2-HOBA treatment or Siruin-3 overexpression in a transgenic mouse model prevented vascular remodeling following SO2 exposure. In summary, our results indicate that repetitive SO2 exposure recapitulates many aspects of PDRS and that oxidative stress appears to mediate PV remodeling in this model. Together, these findings provide new insights regarding the critical mechanisms underlying PDRS.NEW & NOTEWORTHY We developed a mice model of "post-deployment respiratory syndrome" (PDRS), a condition in Veterans with unexplained exertional dyspnea. Our model successfully recapitulates many of the pathological and physiological features of the syndrome, revealing involvement of the ROS-isoLGs-Sirt3-SOD2 pathway in pulmonary vasculature pathology. Our study provides additional knowledge about effects and long-term consequences of sulfur dioxide exposure on the respiratory system, serving as a valuable tool for future PDRS research.

Cystic Fibrosis Reprograms Airway Epithelial IL-33 Release and Licenses IL-33-Dependent Inflammation.

Rationale: Type 2 inflammation has been described in people with cystic fibrosis (CF). Whether loss of CFTR (cystic fibrosis transmembrane conductance regulator) function contributes directly to a type 2 inflammatory response has not been fully defined. Objectives: The potent alarmin IL-33 has emerged as a critical regulator of type 2 inflammation. We tested the hypothesis that CFTR deficiency increases IL-33 expression and/or release and deletion of IL-33 reduces allergen-induced inflammation in the CF lung. Methods: Human airway epithelial cells (AECs) grown from non-CF and CF cell lines and Cftr+/+ and Cftr-/- mice were used in this study. Pulmonary inflammation in Cftr+/+ and Cftr-/- mice with and without IL-33 or ST2 (IL-1 receptor-like 1) germline deletion was determined by histological analysis, BAL, and cytokine analysis. Measurements and Main Results: After allergen challenge, both CF human AECs and Cftr-/- mice had increased IL-33 expression compared with control AECs and Cftr+/+ mice, respectively. DUOX1 (dual oxidase 1) expression was increased in CF human AECs and Cftr-/- mouse lungs compared with control AECs and lungs from Cftr+/+ mice and was necessary for the increased IL-33 release in Cftr-/- mice compared with Cftr+/+ mice. IL-33 stimulation of Cftr-/- CD4+ T cells resulted in increased type 2 cytokine production compared with Cftr+/+ CD4+ T cells. Deletion of IL-33 or ST2 decreased both type 2 inflammation and neutrophil recruitment in Cftr-/- mice compared with Cftr+/+ mice. Conclusions: Absence of CFTR reprograms airway epithelial IL-33 release and licenses IL-33-dependent inflammation. Modulation of the IL-33/ST2 axis represents a novel therapeutic target in CF type 2-high and neutrophilic inflammation.

Targeting In Vivo Metabolic Vulnerabilities of Th2 and Th17 Cells Reduces Airway Inflammation.

T effector cells promote inflammation in asthmatic patients, and both Th2 and Th17 CD4 T cells have been implicated in severe forms of the disease. The metabolic phenotypes and dependencies of these cells, however, remain poorly understood in the regulation of airway inflammation. In this study, we show the bronchoalveolar lavage fluid of asthmatic patients had markers of elevated glucose and glutamine metabolism. Further, peripheral blood T cells of asthmatics had broadly elevated expression of metabolic proteins when analyzed by mass cytometry compared with healthy controls. Therefore, we hypothesized that glucose and glutamine metabolism promote allergic airway inflammation. We tested this hypothesis in two murine models of airway inflammation. T cells from lungs of mice sensitized with Alternaria alternata extract displayed genetic signatures for elevated oxidative and glucose metabolism by single-cell RNA sequencing. This result was most pronounced when protein levels were measured in IL-17-producing cells and was recapitulated when airway inflammation was induced with house dust mite plus LPS, a model that led to abundant IL-4- and IL-17-producing T cells. Importantly, inhibitors of the glucose transporter 1 or glutaminase in vivo attenuated house dust mite + LPS eosinophilia, T cell cytokine production, and airway hyperresponsiveness as well as augmented the immunosuppressive properties of dexamethasone. These data show that T cells induce markers to support metabolism in vivo in airway inflammation and that this correlates with inflammatory cytokine production. Targeting metabolic pathways may provide a new direction to protect from disease and enhance the effectiveness of steroid therapy.

Cellular and systemic energy metabolic dysregulation in asthma development-a hypothesis-generating approach.

BACKGROUND: The roles of systemic and airway-specific epithelial energy metabolism in altering the developmental programming of airway epithelial cells (AECs) in early life are poorly understood. OBJECTIVE: Our aim was to assess carbohydrate metabolism in developing AECs among children with and without wheeze and test the association of infant plasma energy biomarkers with subsequent recurrent wheeze and asthma outcomes. METHODS: We measured cellular carbohydrate metabolism in live nasal AECs collected at age 2 years from 15 male subjects with and without a history of wheeze and performed a principal component analysis to visually assess clustering of data on AEC metabolism of glycolitic metabolites and simple sugars. Among 237 children with available year 1 plasma samples, we tested the associations of year 1 plasma energy biomarkers and recurrent wheeze and asthma by using generalized estimating equations and logistic regression. RESULTS: Children with a history of wheeze had lower utilization of glucose in their nasal AECs than did children with no wheeze. Systemically, a higher plasma glucose concentration at year 1 (within the normal range) was associated with decreased odds of asthma at age 5 years (adjusted odds ratio = 0.56; 95% CI = 0.35-0.90). Insulin concentration, glucose-to-insulin ratio, C-peptide concentration, and leptin concentration at year 1 were associated with recurrent wheeze from age 2 years to age 5 years. CONCLUSION: These results suggest that there is significant energy metabolism dysregulation in early life, which likely affects AEC development. These pertubations of epithelial cell metabolism in infancy may have lasting effects on lung development that could render the airway more susceptible to allergic sensitization.

COX Inhibition Increases Alternaria-Induced Pulmonary Group 2 Innate Lymphoid Cell Responses and IL-33 Release in Mice.

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.

Glucagon-like peptide-1 receptor agonist inhibits aeroallergen-induced activation of ILC2 and neutrophilic airway inflammation in obese mice.

BACKGROUND: Obesity is a risk factor for the development of asthma. However, pharmacologic therapeutic strategies that specifically target obese asthmatics have not been identified. We hypothesize that glucagon-like peptide-1 receptor agonist (GLP-1RA) treatment inhibits aeroallergen-induced early innate airway inflammation in a mouse model of asthma in the setting of obesity. METHODS: SWR (lean) and TALLYHO (obese) mice were challenged intranasally with Alternaria alternata extract (Alt-Ext) or PBS for 4 consecutive days concurrent with GLP-1RA or vehicle treatment. RESULTS: TALLYHO mice had greater Alt-Ext-induced airway neutrophilia and lung protein expression of IL-5, IL-13, CCL11, CXCL1, and CXCL5, in addition to ICAM-1 expression on lung epithelial cells compared with SWR mice, and all endpoints were reduced by GLP-1RA treatment. Alt-Ext significantly increased BALF IL-33 in both TALLYHO and SWR mice compared to PBS challenge, but there was no difference in the BALF IL-33 levels between these two strains. However, TALLYHO, but not SWR, mice had significantly higher airway TSLP in BALF following Alt-Ext challenge compared to PBS, and BALF TSLP was significantly greater in TALLYHO mice compared to SWR mice following airway Alt-Ext challenge. GLP-1RA treatment significantly decreased the Alt-Ext-induced TSLP and IL-33 release in TALLYHO mice. While TSLP or ST2 inhibition with a neutralizing antibody decreased airway eosinophils, they did not reduce airway neutrophils in TALLYHO mice. CONCLUSIONS: These results suggest that GLP-1RA treatment may be a novel pharmacologic therapeutic strategy for obese persons with asthma by inhibiting aeroallergen-induced neutrophilia, a feature not seen with either TSLP or ST2 inhibition.

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

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-ß (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 IL33fl/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 17ß-estradiol (E2), propyl-pyrazole-triol (PPT, ER-α agonist), or diarylpropionitrile (DPN, ER-ß 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. 17ß-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.

IL-33 Is a Cell-Intrinsic Regulator of Fitness during Early B Cell Development.

IL-33 is an IL-1 family member protein that is a potent driver of inflammatory responses in both allergic and nonallergic disease. This proinflammatory effect is mediated primarily by extracellular release of IL-33 from stromal cells and binding of the C-terminal domain of IL-33 to its receptor ST2 on targets such as CD4+ Th2 cells, ILC2, and mast cells. Notably, IL-33 has a distinct N-terminal domain that mediates nuclear localization and chromatin binding. However, a defined in vivo cell-intrinsic role for IL-33 has not been established. We identified IL-33 expression in the nucleus of progenitor B (pro-B) and large precursor B cells in the bone marrow, an expression pattern unique to B cells among developing lymphocytes. The IL-33 receptor ST2 was not expressed within the developing B cell lineage at either the transcript or protein level. RNA sequencing analysis of wild-type and IL-33-deficient pro-B and large precursor B cells revealed a unique, IL-33-dependent transcriptional profile wherein IL-33 deficiency led to an increase in E2F targets, cell cycle genes, and DNA replication and a decrease in the p53 pathway. Using mixed bone marrow chimeric mice, we demonstrated that IL-33 deficiency resulted in an increased frequency of developing B cells via a cell-intrinsic mechanism starting at the pro-B cell stage paralleling IL-33 expression. Finally, IL-33 was detectable during early B cell development in humans and IL33 mRNA expression was decreased in B cell chronic lymphocytic leukemia samples compared with healthy controls. Collectively, these data establish a cell-intrinsic, ST2-independent role for IL-33 in early B cell development.

TSLP and IL-33 reciprocally promote each other's lung protein expression and ILC2 receptor expression to enhance innate type-2 airway inflammation.

BACKGROUND: The 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. METHODS: BALB/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. RESULTS: Thymic 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. CONCLUSION: Thymic 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.

The PGI2 Analog Cicaprost Inhibits IL-33-Induced Th2 Responses, IL-2 Production, and CD25 Expression in Mouse CD4+ T Cells.

IL-33 has pleiotropic functions in immune responses and promotes the development of allergic diseases and asthma. IL-33 induces Th2 differentiation and enhances type 2 cytokine production by CD4+ T cells. However, the regulation of IL-33-driven type 2 cytokine responses is not fully defined. In this study, we investigated the effect of PGI2, a lipid mediator formed in the cyclooxygenase pathway of arachidonic acid metabolism, on naive CD4+ T cell activation, proliferation, and differentiation by IL-33. Using wild-type and PGI2 receptor (IP) knockout mice, we found that the PGI2 analog cicaprost dose-dependently inhibited IL-33-driven IL-4, IL-5, and IL-13 production by CD4+ T cells in an IP-specific manner. In addition, cicaprost inhibited IL-33-driven IL-2 production and CD25 expression by CD4+ T cells. Furthermore, IP knockout mice had increased IL-5 and IL-13 responses of CD4+ T cells to Alternaria sensitization and challenge in mouse lungs. Because IL-33 is critical for Alternaria-induced type 2 responses, these data suggest that PGI2 not only inhibits IL-33-stimulated CD4+ Th2 cell responses in vitro but also suppresses IL-33-induced Th2 responses caused by protease-containing allergens in vivo.

Testosterone Decreases House Dust Mite-Induced Type 2 and IL-17A-Mediated Airway Inflammation.

As adults, women are twice as likely as men to have asthma; however, the mechanisms explaining this sexual dimorphism remain unclear. Increased type 2 cytokines and/or IL-17A, leading to increased airway eosinophils and neutrophils, respectively, are associated with asthma. Previous studies showed that testosterone, signaling through the androgen receptor (AR), decreased Th2-mediated allergic inflammation and type 2 innate immune responses during allergic inflammation. Therefore, we hypothesized that testosterone and AR signaling attenuate type 2 and IL-17A-mediated airway inflammation. To test our hypothesis, sham-operated and gonadectomized female and male mice were intranasally challenged with house dust mite (HDM) or vehicle (PBS) for 3 wk. Testosterone decreased and ovarian hormones increased HDM-induced eosinophilic and neutrophilic inflammation, IgE production, and airway hyperresponsiveness, as well as decreased the numbers of IL-13+ CD4 Th2 cells and IL-17A+ CD4 Th17 cells in the lung. Next, using wild-type male and female mice and ARtfm male mice that are unable to signal through the AR, we determined AR signaling intrinsically attenuated IL-17A+ Th17 cells but indirectly decreased IL-13+ CD4 Th2 cells in the lung by suppressing HDM-induced IL-4 production. In vitro Th2 and Th17 differentiation experiments showed AR signaling had no direct effect on Th2 cell differentiation but decreased IL-17A protein expression and IL-23R mRNA relative expression from Th17 cells. Combined, these findings show AR signaling attenuated type 2 and IL-17A inflammation through different mechanisms and provide a potential explanation for the increased prevalence of asthma in women compared with men.

The Innate Immune Protein S100A9 Protects from T-Helper Cell Type 2-mediated Allergic Airway Inflammation.

Calprotectin is a heterodimer of the proteins S100A8 and S100A9, and it is an abundant innate immune protein associated with inflammation. In humans, calprotectin transcription and protein abundance are associated with asthma and disease severity. However, mechanistic studies in experimental asthma models have been inconclusive, identifying both protective and pathogenic effects of calprotectin. To clarify the role of calprotectin in asthma, calprotectin-deficient S100A9-/- and wild-type (WT) C57BL/6 mice were compared in a murine model of allergic airway inflammation. Mice were intranasally challenged with extracts of the clinically relevant allergen, Alternaria alternata (Alt Ext), or PBS every third day over 9 days. On Day 10, BAL fluid and lung tissue homogenates were harvested and allergic airway inflammation was assessed. Alt Ext challenge induced release of S100A8/S100A9 to the alveolar space and increased protein expression in the alveolar epithelium of WT mice. Compared with WT mice, S100A9-/- mice displayed significantly enhanced allergic airway inflammation, including production of IL-13, CCL11, CCL24, serum IgE, eosinophil recruitment, and airway resistance and elastance. In response to Alt Ext, S100A9-/- mice accumulated significantly more IL-13+IL-5+CD4+ T-helper type 2 cells. S100A9-/- mice also accumulated a significantly lower proportion of CD4+ T regulatory (Treg) cells in the lung that had significantly lower expression of CD25. Calprotectin enhanced WT Treg cell suppressive activity in vitro. Therefore, this study identifies a role for the innate immune protein, S100A9, in protection from CD4+ T-helper type 2 cell hyperinflammation in response to Alt Ext. This protection is mediated, at least in part, by CD4+ Treg cell function.

Sex-specific association between prenatal life stress exposure and infant pro-inflammatory cytokine levels during acute respiratory infection.

BACKGROUND: Prenatal life stress exposure is linked to dysregulated immune function and chronic inflammatory disease in offspring, but we know little about its effects on infant immune response during viral infection. METHOD: To address this issue, we examined associations between prenatal life stress exposure and infant upper-airway inflammatory markers during acute respiratory infection (ARI) using data from a prospective, population-based birth-cohort study (N = 180). Infant inflammation was measured as a continuous latent factor within a structural equation modeling framework using nasal wash concentrations of interleukin-1ß, interleukin-6, and tumor necrosis factor-α. We hypothesized that infants exposed to prenatal life stress would have greater levels of nasal inflammation during ARI and increased risk for ARI-related morbidity in early childhood. RESULTS: Our findings contradicted these hypotheses and provided evidence of sexually dimorphic effects of prenatal stress exposure on infant immune functioning during ARI. Among boys, but not girls, prenatal stress was negatively associated with nasal inflammation and indirectly associated with both lower ARI severity and reduced likelihood of subsequent ARI-related hospitalization in the 2nd and 3rd years of life. CONCLUSION: These data suggest that prenatal stress exposure may be beneficial for infant boys in the context of respiratory viral infections; however, it will be critical to determine if these benefits are offset by increased risk for chronic inflammatory diseases in later childhood. As the participants in this cohort are being followed longitudinally through age 8, we will be able to evaluate long-term health outcomes in future studies.

STAT1 Represses Cytokine-Producing Group 2 and Group 3 Innate Lymphoid Cells during Viral Infection.

The appropriate orchestration of different arms of the immune response is critical during viral infection to promote efficient viral clearance while limiting immunopathology. However, the signals and mechanisms that guide this coordination are not fully understood. IFNs are produced at high levels during viral infection and have convergent signaling through STAT1. We hypothesized that STAT1 signaling during viral infection regulates the balance of innate lymphoid cells (ILC), a diverse class of lymphocytes that are poised to respond to environmental insults including viral infections with the potential for both antiviral or immunopathologic functions. During infection with respiratory syncytial virus (RSV), STAT1-deficient mice had reduced numbers of antiviral IFN-γ+ ILC1 and increased numbers of immunopathologic IL-5+ and IL-13+ ILC2 and IL-17A+ ILC3 compared with RSV-infected wild-type mice. Using bone marrow chimeric mice, we found that both ILC-intrinsic and ILC-extrinsic factors were responsible for this ILC dysregulation during viral infection in STAT1-deficient mice. Regarding ILC-extrinsic mechanisms, we found that STAT1-deficient mice had significantly increased expression of IL-33 and IL-23, cytokines that promote ILC2 and ILC3, respectively, compared with wild-type mice during RSV infection. Moreover, disruption of IL-33 or IL-23 signaling attenuated cytokine-producing ILC2 and ILC3 responses in STAT1-deficient mice during RSV infection. Collectively, these data demonstrate that STAT1 is a key orchestrator of cytokine-producing ILC responses during viral infection via ILC-extrinsic regulation of IL-33 and IL-23.

Glucagon-like peptide 1 signaling inhibits allergen-induced lung IL-33 release and reduces group 2 innate lymphoid cell cytokine production in vivo.

BACKGROUND: IL-33 is one of the most consistently associated gene candidates for asthma identified by using a genome-wide association study. Studies in mice and in human cells have confirmed the importance of IL-33 in inducing type 2 cytokine production from both group 2 innate lymphoid cells (ILC2s) and TH2 cells. However, there are no pharmacologic agents known to inhibit IL-33 release from airway cells. OBJECTIVE: We sought to determine the effect of glucagon-like peptide 1 receptor (GLP-1R) signaling on aeroallergen-induced airway IL-33 production and release and on innate type 2 airway inflammation. METHODS: BALB/c mice were challenged intranasally with Alternaria extract for 4 consecutive days. GLP-1R agonist or vehicle was administered starting either 2 days before the first Alternaria extract challenge or 1 day after the first Alternaria extract challenge. RESULTS: GLP-1R agonist treatment starting 2 days before the first Alternaria extract challenge decreased IL-33 release in the bronchoalveolar lavage fluid and dual oxidase 1 (Duox1) mRNA expression 1 hour after the first Alternaria extract challenge and IL-33 expression in lung epithelial cells 24 hours after the last Alternaria extract challenge. Furthermore, GLP-1R agonist significantly decreased the number of ILC2s expressing IL-5 and IL-13, lung protein expression of type 2 cytokines and chemokines, the number of perivascular eosinophils, mucus production, and airway responsiveness compared with vehicle treatment. GLP-1R agonist treatment starting 1 day after the first Alternaria extract challenge also significantly decreased eosinophilia and type 2 cytokine and chemokine expression in the airway after 4 days of Alternaria extract challenge. CONCLUSION: These results reveal that GLP-1R signaling might be a therapy to reduce IL-33 release and inhibit the ILC2 response to protease-containing aeroallergens, such as Alternaria.