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.

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.

Tissue-Specific Dependence of Th1 Cells on the Amino Acid Transporter SLC38A1 in Inflammation

Amino acid (AA) uptake is essential for T cell metabolism and function, but how tissue sites and inflammation affect CD4+ T cell subset requirements for specific AA remains uncertain. Here we tested CD4+ T cell AA demands with in vitro and multiple in vivo CRISPR screens and identify subset- and tissue-specific dependencies on the AA transporter SLC38A1 (SNAT1). While dispensable for T cell persistence and expansion over time in vitro and in vivo lung inflammation, SLC38A1 was critical for Th1 but not Th17 cell-driven Experimental Autoimmune Encephalomyelitis (EAE) and contributed to Th1 cell-driven inflammatory bowel disease. SLC38A1 deficiency reduced mTORC1 signaling and glycolytic activity in Th1 cells, in part by reducing intracellular glutamine and disrupting hexosamine biosynthesis and redox regulation. Similarly, pharmacological inhibition of SLC38 transporters delayed EAE but did not affect lung inflammation. Subset- and tissue-specific dependencies of CD4+ T cells on AA transporters may guide selective immunotherapies.

Building Career Paths for Ph.D., Basic and Translational Scientists in Clinical Departments in the United States: An Official American Thoracic Society Workshop Report

Rationale: To identify barriers and opportunities for Ph.D., basic and translational scientists to be fully integrated into clinical units. Objectives: In 2022, an ad hoc committee of the American Thoracic Society developed a project proposal and workshop to identify opportunities and barriers for scientists who do not practice medicine to develop successful careers and achieve tenure-track faculty positions in clinical departments and divisions within academic medical centers (AMCs) in the United States. Methods: This document focuses on results from a survey of adult and pediatric pulmonary, critical care, and sleep medicine division chiefs as well as a survey of workshop participants, including faculty in departmental and school leadership roles in both basic science and clinical units within U.S. AMCs. Results: We conclude that full integration of non-clinically practicing basic and translational scientists into the clinical units, in addition to their traditional placements in basic science units, best serves the tripartite mission of AMCs to provide care, perform research, and educate the next generation. Evidence suggests clinical units do employ Ph.D. scientists in large numbers, but these faculty are often hired into non-tenure track positions, which do not provide the salary support, start-up funds, research independence, or space often associated with hiring in basic science units within the same institution. These barriers to success of Ph.D. faculty in clinical units are largely financial. Conclusions: Our recommendation is for AMCs to consider and explore some of our proposed strategies to accomplish the goal of integrating basic and translational scientists into clinical units in a meaningful way.

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.

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 non-deployed 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 deployers in this cohort reported exposure to sulfur dioxide (SO 2 ), we developed a model of repetitive exposure to SO 2 in mice that phenocopies many aspects of PDRS, including adaptive immune activation, airway wall remodeling, and pulmonary vascular disease (PVD). Although abnormalities in small airways were not sufficient to alter lung mechanics, PVD was associated with the development of pulmonary hypertension and reduced exercise tolerance in SO 2 exposed mice. Further, we used pharmacologic and genetic approaches to demonstrate a critical role for oxidative stress and isolevuglandins in mediating PVD in this model. In summary, our results indicate that repetitive SO 2 exposure recapitulates many aspects of PDRS and that oxidative stress may mediate PVD in this model, which may be helpful for future mechanistic studies examining the relationship between inhaled irritants, PVD, and PDRS.

Low Gut Microbial Diversity Augments Estrogen-Driven Pulmonary Fibrosis in Female-Predominant Interstitial Lung Disease

Although profibrotic cytokines, such as IL-17A and TGF-β1, have been implicated in the pathogenesis of interstitial lung disease (ILD), the interactions between gut dysbiosis, gonadotrophic hormones and molecular mediators of profibrotic cytokine expression, such as the phosphorylation of STAT3, have not been defined. Here, through chromatin immunoprecipitation sequencing (ChIP-seq) analysis of primary human CD4+ T cells, we show that regions within the STAT3 locus are significantly enriched for binding by the transcription factor estrogen receptor alpha (ERa). Using the murine model of bleomycin-induced pulmonary fibrosis, we found significantly increased regulatory T cells compared to Th17 cells in the female lung. The genetic absence of ESR1 or ovariectomy in mice significantly increased pSTAT3 and IL-17A expression in pulmonary CD4+ T cells, which was reduced after the repletion of female hormones. Remarkably, there was no significant reduction in lung fibrosis under either condition, suggesting that factors outside of ovarian hormones also contribute. An assessment of lung fibrosis among menstruating females in different rearing environments revealed that environments favoring gut dysbiosis augment fibrosis. Furthermore, hormone repletion following ovariectomy further augmented lung fibrosis, suggesting pathologic interactions between gonadal hormones and gut microbiota in relation to lung fibrosis severity. An analysis of female sarcoidosis patients revealed a significant reduction in pSTAT3 and IL-17A levels and a concomitant increase in TGF-β1 levels in CD4+ T cells compared to male sarcoidosis patients. These studies reveal that estrogen is profibrotic in females and that gut dysbiosis in menstruating females augments lung fibrosis severity, supporting a critical interaction between gonadal hormones and gut flora in lung fibrosis pathogenesis.

Low Gut Microbial Diversity Augments Estrogen-driven Pulmonary Fibrosis in Female-Predominant Interstitial Lung Disease

Although profibrotic cytokines such as IL-17A and TGF-β1 have been implicated in interstitial lung disease (ILD) pathogenesis, interactions between gut dysbiosis, gonadotrophic hormones and molecular mediators of profibrotic cytokine expression, such as phosphorylation of STAT3, have not been defined. Here we show by chromatin immunoprecipitation sequencing (ChIP-seq) analysis of primary human CD4+ T cells that regions within the STAT3 locus are significantly enriched for binding by the transcription factor estrogen receptor alpha (ERa). Using the murine model of bleomycin-induced pulmonary fibrosis, we found significantly increased regulatory T cells compared to Th17 cells in the female lung. Genetic absence of ESR1 or ovariectomy in mice significantly increased pSTAT3 and IL-17A expression in pulmonary CD4+ T cells, which was reduced after repletion of female hormones. Remarkably, there was no significant reduction in lung fibrosis under either condition, suggesting that factors outside of ovarian hormones also contribute. Assessment of lung fibrosis among menstruating females in different rearing environments revealed that environments favoring gut dysbiosis augment fibrosis. Furthermore, hormone repletion following ovariectomy further augmented lung fibrosis, suggesting pathologic interactions between gonadal hormones and gut microbiota on lung fibrosis severity. Analysis in female sarcoidosis patients revealed a significant reduction in pSTAT3 and IL-17A levels and a concomitant increase in TGF-β1 levels in CD4+ T cells, compared to male sarcoidosis patients. These studies reveal that estrogen is profibrotic in females and that gut dysbiosis in menstruating females augments lung fibrosis severity, supporting a critical interaction between gonadal hormones and gut flora in lung fibrosis pathogenesis.

Androgen receptor signaling decreases glutaminolysis in Th17 cells to reduce airway inflammation in asthma

Women have higher rates of severe asthma compared to men. Severe asthma has increased Th2-mediated eosinophilic and/or Th17-mediated neutrophilic airway inflammation. We showed androgens, signaling through the androgen receptor (AR), decreased Th2- and Th17-mediated airway inflammation, and that Th17 and Th2 rely on glutaminolysis during allergic airway inflammation. Therefore, we hypothesized that AR signaling decreases glutaminolysis in Th2 and Th17 cells, resulting in decreased airway inflammation. Th2 and Th17 were differentiated in vitro from wild-type male and ArTfm male mice, with a nonfunctional AR. Mitochondrial metabolism and glycolysis were determined by measuring oxygen consumption rate (OCR), reactive oxygen species (ROS), and the extracellular acidification rate (ECAR). In Th17 cells, AR signaling decreased OCR, while increasing mitochondrial ROS, suggesting decreased glutaminolysis. Further, both 5α-DHT (0.1nM) and CB839 (a glutaminase inhibitor, 0.5μM) reduced OCR in Th17 cells from male mice. AR signaling had no effect on ECAR in Th17 cells or OCR and ECAR in Th2 cells. To induce eosinophilic and neutrophilic airway inflammation, house dust mite (HDM) was intranasally administered to ArfloxedCD4-Cre and Arfloxed male mice and markers of glycolysis and glutaminolysis were determined by flow cytometry. AR signaling decreased airway neutrophils, the number of Th17 lung cells, and GLUD1, a glutaminolysis marker, expression in T cells, but had no effect on eosinophils or Th2 cells. Combined, these data showed that AR signaling decreased glutaminolysis in Th17, but not Th2, cells. Understanding these pathways may provide new potential therapeutic targets in women with difficult-to-treat asthma.

Supported by grants from NIH (R01 HL12254, R01 HL136664, T32 GM007347)  

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.

The PGI2 signaling pathway decreases glycolysis and mitochondria respiration in mouse Th2 cells

Prostaglandin I2 (PGI2) is a lipid molecule produced in the cyclooxygenase (COX) metabolic pathway and regulates T cell function and inflammation. We have previously shown that PGI2 inhibited type 2 cytokine production by Th2 cells in vitro and in vivo. To further investigate the mechanism of the inhibitory effect of PGI2 on Th2 differentiation, we determined the effect of the PGI2 analog cicaprost on T cell metabolism under Th2 conditions. Mouse naïve CD4 T cells from the spleen were activated with antibodies against CD3 and CD28 under Th2 polarization conditions and treated with cicaprost or vehicle for 4 days. Seahorse assays measured cellular glycolysis and mitochondria respiration. We found that cicaprost significantly decreased basal and maximum glycolysis in Th2 cells. Furthermore, when we performed Seahorse assays on the cells rested for 2 days after the initial 4 day T cell activation, we discovered that cicaprost not only suppressed basal glycolysis and glycolytic reserve but also dose-dependently inhibited basal and maximum mitochondria respiration. These results suggest that the PGI2 signaling pathway inhibits Th2 cell metabolism, providing a possible mechanism for PGI2-mediated inhibition of Th2 differentiation and Th2 cell-dependent immune disorders.

The Department of Veterans Affairs BX004299 (RSP), NIH AI095227 (RSP), NIH AI111820 (RSP), NIH AI145265 (RSP), NIH AI124456 (RSP), NIH AI145397 (RSP).

Effect of Infant RSV Infection on Memory T Cell Responses at Age 2-3 Years

Background

It is unknown whether RSV infection in infancy alters subsequent RSV immune responses.

Methods

In a nested cohort of healthy, term children, peripheral blood mononuclear cells (PBMCs) were collected at ages 2-3 years to examine RSV memory T cell responses among children previously RSV infected during infancy (first year of life) compared to those RSV-uninfected during infancy. The presence vs. absence of infant RSV infection was determined through a combination of RSV molecular and serologic testing. Memory responses were measured in RSV stimulated PBMCs.

Results

Compared to children not infected with RSV during the first year of life, children infected with RSV during infancy had lower memory T cell responses at ages 2-3 years to in vitro stimulation with RSV for most tested type-1 and type-17 markers for a number of memory T cell subsets.

Conclusions

RSV infection in infancy has long-term effects on memory T cell responses. This is the first study to show the potential for RSV infection in infancy to have long-term effects on the immune memory irrespective of the severity of the infection. Our results suggest a possible mechanism through which infant RSV infection may result in greater risk of subsequent childhood respiratory viral morbidity, findings also relevant to vaccine development.

Androgen receptor signaling promotes Treg suppressive function during allergic airway inflammation

Women have higher prevalence of asthma compared with men. In asthma, allergic airway inflammation is initiated by IL-33 signaling through ST2, leading to increased IL-4, IL-5, and IL-13 production and eosinophil infiltration. Foxp3+ Tregs suppress and ST2+ Tregs promote allergic airway inflammation. Clinical studies showed that the androgen dehydroepiandrosterone (DHEA) reduced asthma symptoms in patients, and mouse studies showed that androgen receptor (AR) signaling decreased allergic airway inflammation. Yet the impact of AR signaling on lung Tregs remains unclear. Using AR-deficient and Foxp3 fate-mapping mice, we determined that AR signaling increased Treg suppression during Alternaria extract (Alt Ext; allergen) challenge by stabilizing Foxp3+ Tregs and limiting the number of ST2+ ex-Tregs and IL-13+ Th2 cells and ex-Tregs. AR signaling also decreased Alt Ext-induced ST2+ Tregs in mice by limiting expression of Gata2, a transcription factor for ST2, and by decreasing Alt Ext-induced IL-33 production from murine airway epithelial cells. We confirmed our findings in human cells where 5α-dihydrotestosterone (DHT), an androgen, decreased IL-33-induced ST2 expression in lung Tregs and decreased Alt Ext-induced IL-33 secretion in human bronchial epithelial cells. Our findings showed that AR signaling stabilized Treg suppressive function, providing a mechanism for the sex difference in asthma.

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.

Sex and gender in asthma

Asthma is a heterogenous disease, and its prevalence and severity are different in males versus females through various ages. As children, boys have an increased prevalence of asthma. As adults, women have an increased prevalence and severity of asthma. Sex hormones, genetic and epigenetic variations, social and environmental factors, and responses to asthma therapeutics are important factors in the sex differences observed in asthma incidence, prevalence and severity. For women, fluctuations in sex hormone levels during puberty, the menstrual cycle and pregnancy are associated with asthma pathogenesis. Further, sex differences in gene expression and epigenetic modifications and responses to environmental factors, including SARS-CoV-2 infections, are associated with differences in asthma incidence, prevalence and symptoms. We review the role of sex hormones, genetics and epigenetics, and their interactions with the environment in the clinical manifestations and therapeutic response of asthma.

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.

Metabolic Reprogramming of Nasal Airway Epithelial Cells Following Infant Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is a seasonal mucosal pathogen that infects the ciliated respiratory epithelium and results in the most severe morbidity in the first six months of life. RSV is a common cause of acute respiratory infection during infancy and is an important early-life risk factor strongly associated with asthma development. While this association has been repeatedly demonstrated, limited progress has been made on the mechanistic understanding in humans of the contribution of infant RSV infection to airway epithelial dysfunction. An active infection of epithelial cells with RSV in vitro results in heightened central metabolism and overall hypermetabolic state; however, little is known about whether natural infection with RSV in vivo results in lasting metabolic reprogramming of the airway epithelium in infancy. To address this gap, we performed functional metabolomics, 13C glucose metabolic flux analysis, and RNA-seq gene expression analysis of nasal airway epithelial cells (NAECs) sampled from infants between 2-3 years of age, with RSV infection or not during the first year of life. We found that RSV infection in infancy was associated with lasting epithelial metabolic reprogramming, which was characterized by (1) significant increase in glucose uptake and differential utilization of glucose by epithelium; (2) altered preferences for metabolism of several carbon and energy sources; and (3) significant sexual dimorphism in metabolic parameters, with RSV-induced metabolic changes most pronounced in male epithelium. In summary, our study supports the proposed phenomenon of metabolic reprogramming of epithelial cells associated with RSV infection in infancy and opens exciting new venues for pursuing mechanisms of RSV-induced epithelial barrier dysfunction in early life.

Neutrophilic inflammation during lung development disrupts elastin assembly and predisposes adult mice to COPD

Emerging evidence indicates that early life events can increase the risk for developing chronic obstructive pulmonary disease (COPD). Using an inducible transgenic mouse model for NF-κB activation in the airway epithelium, we found that a brief period of inflammation during the saccular stage (P3-P5) but not alveolar stage (P10-P12) of lung development disrupted elastic fiber assembly, resulting in permanent reduction in lung function and development of a COPD-like lung phenotype that progressed through 24 months of age. Neutrophil depletion prevented disruption of elastic fiber assembly and restored normal lung development. Mechanistic studies uncovered a role for neutrophil elastase (NE) in downregulating expression of critical elastic fiber assembly components, particularly fibulin-5 and elastin. Further, purified human NE and NE-containing exosomes from tracheal aspirates of premature infants with lung inflammation downregulated elastin and fibulin-5 expression by saccular-stage mouse lung fibroblasts. Together, our studies define a critical developmental window for assembling the elastin scaffold in the distal lung, which is required to support lung structure and function throughout the lifespan. Although neutrophils play a well-recognized role in COPD development in adults, neutrophilic inflammation may also contribute to early-life predisposition to COPD.

Prostaglandin I2 signaling licenses Treg suppressive function and prevents pathogenic reprogramming

Tregs restrain both the innate and adaptive immune systems to maintain homeostasis. Allergic airway inflammation, characterized by a Th2 response that results from a breakdown of tolerance to innocuous environmental antigens, is negatively regulated by Tregs. We previously reported that prostaglandin I2 (PGI2) promoted immune tolerance in models of allergic inflammation; however, the effect of PGI2 on Treg function was not investigated. Tregs from mice deficient in the PGI2 receptor IP (IP KO) had impaired suppressive capabilities during allergic airway inflammatory responses compared with mice in which PGI2 signaling was intact. IP KO Tregs had significantly enhanced expression of immunoglobulin-like transcript 3 (ILT3) compared with WT Tregs, which may contribute to the impairment of the IP KO Treg's ability to suppress Th2 responses. Using fate-mapping mice, we reported that PGI2 signaling prevents Treg reprogramming toward a pathogenic phenotype. PGI2 analogs promoted the differentiation of naive T cells to Tregs in both mice and humans via repression of β-catenin signaling. Finally, a missense variant in IP in humans was strongly associated with chronic obstructive asthma. Together, these data support that PGI2 signaling licenses Treg suppressive function and that PGI2 is a therapeutic target for enhancing Treg function.

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.

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-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.

Monocyte-derived dendritic cells link localized secretory IgA deficiency to adaptive immune activation in COPD

Although activation of adaptive immunity is a common pathological feature of chronic obstructive pulmonary disease (COPD), particularly during later stages of the disease, the underlying mechanisms are poorly understood. In small airways of COPD patients, we found that localized disruption of the secretory immunoglobulin A (SIgA)-containing mucosal immunobarrier correlated with lymphocyte accumulation in airway walls and development of tertiary lymphoid structures (TLS) around small airways. In SIgA-deficient mice, we observed bacterial invasion into the airway epithelial barrier with lymphocytic infiltration and TLS formation, which correlated with the progression of COPD-like pathology with advanced age. Depletion of either CD4⁺ or CD8⁺ T lymphocytes reduced the severity of emphysema in SIgA-deficient mice, indicating that adaptive immune activation contributes to progressive lung destruction. Further studies revealed that lymphocyte infiltration into the lungs of SIgA-deficient mice was dependent on monocyte-derived dendritic cells (moDCs), which were recruited through a CCR2-dependent mechanism in response to airway bacteria. Consistent with these results, we found that moDCs were increased in lungs of COPD patients, along with CD4⁺ and CD8⁺ effector memory T cells. Together, these data indicate that endogenous bacteria in SIgA-deficient airways orchestrate a persistent and pathologic T lymphocyte response through monocyte recruitment and moDC differentiation.

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.

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 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.

Metabolic characteristics of Th2 and Th17 cells drive airway inflammation

Asthma is an airway inflammatory disease that is mediated by T effector (Teff) cells, specifically Th2 and Th17 cells. Increases in disease severity leading to neutrophilic asthma is characterized by a shift towards a higher Th17 response. Typical treatment of asthmatic patients include the use of glucocoriticoid (GC) steroids. These drugs are effective at controlling inflammation in mild cases but as disease severity increases towards neutrophilic disease there is resistance by Th17 cells to the effects of these drugs. A key therapeutic objective is to identify either alternative treatments for asthma or targets that make Th17 cells more susceptible to GCs. Studies have shown that cells that have increased glycolysis and oxidative phosphorylation are more resistant to the effects of GCs. We hypothesized that the intrinsic metabolic phenotype of Th17 cells allow them to be more resistant to GCs. In this study we show, that in the murine model of airway inflammation there are differences in the expression of metabolic proteins between Th2 and Th17 cells that are present in the lung. Additionally, we show that metabolic inhibitors alter the functionality of the Teff cells and can be a target to restore sensitivity to GCs. We have also performed CyTOF analysis of asthmatic patients’ PBMCs, these data demonstrate a much higher metabolic phenotype of asthmatic patients when compared to healthy controls. Overall our studies suggest that metabolic inhibition may be a viable therapeautic in conjuction with GCs in order to dampen the function of Teffs in the airway.

COX inhibition enhances allergen-induced IL-33 release and ILC2 responses in mouse lungs

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.

ERα Signaling Increased IL-17A Production in Th17 Cells by Upregulating IL-23R Expression, Mitochondrial Respiration, and Proliferation

Women have increased prevalence of Th17-mediated autoimmune diseases, including lupus and multiple sclerosis, and severe asthma. While estradiol and progesterone increased IL-17A production in Th17 cells by inhibiting Let7f miRNA expression and increasing IL-23 receptor (IL-23R) expression, it remained unclear how estrogen signaling through the canonical nuclear receptors, estrogen receptor α (ERα) and/or ERβ, regulated this pathway. We hypothesized that estrogen signaling through ERα increased IL-23R expression and IL-17A production from Th17 cells. To test this hypothesis, naïve T cells from WT female, WT male, Esr1^−/− and Esr2^−/− female mice were differentiated into Th17 cells. IL-17A production and IL-23R expression were significantly increased in Th17 cells from WT female mice compared to Th17 cells from WT male mice. Deletion of ERα (Esr1^−/−), but not ERβ (Esr2^−/−), significantly decreased IL-17A production and IL-23R expression in Th17 cells by limiting IL-23R expression in a Let-7f dependent manner. ERα deficiency also decreased Th17 cell proliferation as well as decreased T cell metabolism as measured by ATP-linked oxygen consumption rate and proton leakage. Further, we found that Cox20 expression, a protein involved in mitochondrial respiration through assembly of cytochrome c oxidase in the electron transport chain, was increased in Th17 cells from WT female mice compared to Th17 cells from WT male and Esr1^−/− female mice. Inhibition of Cox20 decreased IL-17 production in Th17 cells from WT female mice. Combined these studies showed that ERα signaling increased IL-17A production in Th17 cells by upregulating IL-23R expression and promoting mitochondrial respiration and proliferation.

PD-1 up-regulation on CD4+ T cells promotes pulmonary fibrosis through STAT3-mediated IL-17A and TGF-β1 production

Pulmonary fibrosis is a progressive inflammatory disease with high mortality and limited therapeutic options. Previous genetic and immunologic investigations suggest common intersections between idiopathic pulmonary fibrosis (IPF), sarcoidosis, and murine models of pulmonary fibrosis. To identify immune responses that precede collagen deposition, we conducted molecular, immunohistochemical, and flow cytometric analysis of human and murine specimens. Immunohistochemistry revealed programmed cell death-1 (PD-1) up-regulation on IPF lymphocytes. PD-1⁺CD4⁺ T cells with reduced proliferative capacity and increased transforming growth factor-β (TGF-β)/interleukin-17A (IL-17A) expression were detected in IPF, sarcoidosis, and bleomycin CD4⁺ T cells. PD-1⁺ T helper 17 cells are the predominant CD4⁺ T cell subset expressing TGF-β. Coculture of PD-1⁺CD4⁺ T cells with human lung fibroblasts induced collagen-1 production. Strikingly, ex vivo PD-1 pathway blockade resulted in reductions in TGF-β and IL-17A expression from CD4⁺ T cells, with concomitant declines in collagen-1 production from fibroblasts. Molecular analysis demonstrated PD-1 regulation of the transcription factor STAT3 (signal transducer and activator of transcription 3). Chemical blockade of STAT3, using the inhibitor STATTIC, inhibited collagen-1 production. Both bleomycin administration to PD-1 null mice or use of antibody against programmed cell death ligand 1 (PD-L1) demonstrated significantly reduced fibrosis compared to controls. This work identifies a critical, previously unrecognized role for PD-1⁺CD4⁺ T cells in pulmonary fibrosis, supporting the use of readily available therapeutics that directly address interstitial lung disease pathophysiology.

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.

Sex Bias in Asthma Prevalence and Pathogenesis

Sex-related differences in asthma prevalence are well established and change through the reproductive phases of life. As children, boys have increased prevalence of asthma compared to girls. However, as adults, women have increased prevalence of asthma compared to men. Many factors, including genetics, environment, immunological responses, and sex hormones, affect the sex disparity associated with the development and control of asthma and other allergic diseases. Fluctuations of hormones during puberty, menstruation, pregnancy, and menopause, alter asthma symptoms and severity. In this article, we review clinical and epidemiological studies that examined the sex disparity in asthma and other allergic diseases as well as the role of sex hormones on asthma pathogenesis.

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.

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 AR^tfm 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 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 Attenuates Group 2 Innate Lymphoid Cell-Mediated Airway Inflammation

Sex hormones regulate many autoimmune and inflammatory diseases, including asthma. As adults, asthma prevalence is 2-fold greater in women compared to men. The number of group 2 innate lymphoid cells (ILC2) is increased in patients with asthma, and we investigate how testosterone attenuates ILC2 function. In patients with moderate to severe asthma, we determine that women have an increased number of circulating ILC2 compared to men. ILC2 from adult female mice have increased IL-2-mediated ILC2 proliferation versus ILC2 from adult male mice, as well as pre-pubescent females and males. Further, 5α-dihydrotestosterone, a hormone downstream of testosterone, decreases lung ILC2 numbers and IL-5 and IL-13 expression from ILC2. In vivo, testosterone attenuated Alternaria-extract-induced IL-5+ and IL-13+ ILC2 numbers and lung eosinophils by intrinsically decreasing lung ILC2 numbers, as well as by decreasing expression of IL-33 and thymic stromal lymphopoietin (TSLP), ILC2-stimulating cytokines. Collectively, these findings provide a foundational understanding of sexual dimorphism in ILC2 function.

Endogenous PGI2 signaling through IP inhibits neutrophilic lung inflammation in LPS-induced acute lung injury mice model

Endogenous prostaglandin I₂ (PGI₂) has inhibitory effects on immune responses against pathogens or allergens; however, the immunomodulatory activity of endogenous PGI₂ signaling in endotoxin-induced inflammation is unknown. To test the hypothesis that endogenous PGI₂ down-regulates endotoxin-induced lung inflammation, C57BL/6 wild type (WT) and PGI₂ receptor (IP) KO mice were challenged intranasally with LPS. Urine 6-keto-PGF_1α, a stable metabolite of PGI_2, was significantly increased following the LPS-challenge, suggesting that endogenous PGI₂ signaling modulates the host response to LPS-challenge. IPKO mice had a significant increase in neutrophils in the BAL fluid as well as increased proteins of KC, LIX, and TNF-α in lung homogenates compared with WT mice. In contrast, IL-10 was decreased in LPS-challenged IPKO mice compared with WT mice. The PGI₂ analog cicaprost significantly decreased LPS-induced KC, and TNF-α, but increased IL-10 and AREG in bone marrow-derived dendritic cells (BMDCs) and bone marrow-derived macrophages (BMMs) compared with vehicle-treatment. These results indicated that endogenous PGI₂ signaling attenuated neutrophilic lung inflammation through the reduced inflammatory cytokine and chemokine and enhanced IL-10.

Hormones, sex, and asthma

OBJECTIVE

To summarize the current literature on the sex disparity in asthma and the role of sex hormone signaling in allergic and neutrophilic airway inflammation.

DATA SOURCES

PubMed and Centers for Disease Control and Prevention health surveys were searched.

STUDY SELECTIONS

Clinical and epidemiologic studies in children and adults as well as animal models of asthma were included in this review.

RESULTS

Compared with males, females have an increase in asthma prevalence starting around puberty, and fluctuations in hormones during menstruation, pregnancy, and menopause are associated with changes in asthma symptoms. Animal studies using genetic deletions of estrogen receptors or androgen receptors have shown that estrogen signaling promotes and androgen signaling attenuates allergen-mediated type 2 airway inflammation. Furthermore, animal studies have found that ovarian hormones are important for interleukin 17A-mediated airway inflammation.

CONCLUSION

Sex hormones are important in regulating asthma pathogenesis. However, additional studies need to be conducted to further elucidate how sex hormones are initiating and driving the inflammatory response(s) in asthma. Determining these pathways will provide the foundation necessary for the development of treatment strategies and potentially new therapeutics for patients, in particular females, with asthma.

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 T_H2 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.

IL-33 promotes the egress of group 2 innate lymphoid cells from the bone marrow

ILC2s are potent mucosal effector cells that participate in type 2 inflammatory responses. Stier et al. demonstrate that IL-33 negatively regulates CXCR4, mediating the egress of ILC2 lineage cells from the bone marrow for potential hematogenous trafficking.

Group 2 innate lymphoid cells (ILC2s) are effector cells within the mucosa and key participants in type 2 immune responses in the context of allergic inflammation and infection. ILC2s develop in the bone marrow from common lymphoid progenitor cells, but little is known about how ILC2s egress from the bone marrow for hematogenous trafficking. In this study, we identified a critical role for IL-33, a hallmark peripheral ILC2-activating cytokine, in promoting the egress of ILC2 lineage cells from the bone marrow. Mice lacking IL-33 signaling had normal development of ILC2s but retained significantly more ILC2 progenitors in the bone marrow via augmented expression of CXCR4. Intravenous injection of IL-33 or pulmonary fungal allergen challenge mobilized ILC2 progenitors to exit the bone marrow. Finally, IL-33 enhanced ILC2 trafficking to the lungs in a parabiosis mouse model of tissue disruption and repopulation. Collectively, these data demonstrate that IL-33 plays a critical role in promoting ILC2 egress from the bone marrow.