Risk factors for SARS-CoV-2 infection and transmission in households with children with asthma and allergy: A prospective surveillance study.

BACKGROUND: Whether children and people with asthma and allergic diseases are at increased risk for severe acute respiratory syndrome virus 2 (SARS-CoV-2) infection is unknown. OBJECTIVE: Our aims were to determine the incidence of SARS-CoV-2 infection in households with children and to also determine whether self-reported asthma and/or other allergic diseases are associated with infection and household transmission. METHODS: For 6 months, biweekly nasal swabs and weekly surveys were conducted within 1394 households (N = 4142 participants) to identify incident SARS-CoV-2 infections from May 2020 to February 2021, which was the pandemic period largely before a vaccine and before the emergence of SARS-CoV-2 variants. Participant and household infection and household transmission probabilities were calculated by using time-to-event analyses, and factors associated with infection and transmission risk were determined by using regression analyses. RESULTS: In all, 147 households (261 participants) tested positive for SARS-CoV-2. The household SARS-CoV-2 infection probability was 25.8%; the participant infection probability was similar for children (14.0% [95% CI = 8.0%-19.6%]), teenagers (12.1% [95% CI = 8.2%-15.9%]), and adults (14.0% [95% CI = 9.5%-18.4%]). Infections were symptomatic in 24.5% of children, 41.2% of teenagers, and 62.5% of adults. Self-reported doctor-diagnosed asthma was not a risk factor for infection (adjusted hazard ratio [aHR] = 1.04 [95% CI = 0.73-1.46]), nor was upper respiratory allergy or eczema. Self-reported doctor-diagnosed food allergy was associated with lower infection risk (aHR = 0.50 [95% CI = 0.32-0.81]); higher body mass index was associated with increased infection risk (aHR per 10-point increase = 1.09 [95% CI = 1.03-1.15]). The household secondary attack rate was 57.7%. Asthma was not associated with household transmission, but transmission was lower in households with food allergy (adjusted odds ratio = 0.43 [95% CI = 0.19-0.96]; P = .04). CONCLUSION: Asthma does not increase the risk of SARS-CoV-2 infection. Food allergy is associated with lower infection risk, whereas body mass index is associated with increased infection risk. Understanding how these factors modify infection risk may offer new avenues for preventing infection.

Secreted Phospholipase A2 Group X Acts as an Adjuvant for Type 2 Inflammation, Leading to an Allergen-Specific Immune Response in the Lung.

Secreted phospholipase A2 (sPLA2) enzymes release free fatty acids, including arachidonic acid, and generate lysophospholipids from phospholipids, including membrane phospholipids from cells and bacteria and surfactant phospholipids. We have shown that an endogenous enzyme sPLA2 group X (sPLA2-X) is elevated in the airways of asthmatics and that mice lacking the sPLA2-X gene (Pla2g10) display attenuated airway hyperresponsiveness, innate and adaptive immune responses, and type 2 cytokine production in a model of airway sensitization and challenge using a complete allergen that induces endogenous adjuvant activity. This complete allergen also induces the expression of sPLA2-X/Pla2g10 In the periphery, an sPLA2 found in bee venom (bee venom PLA2) administered with the incomplete Ag OVA leads to an Ag-specific immune response. In this study, we demonstrate that both bee venom PLA2 and murine sPLA2-X have adjuvant activity, leading to a type 2 immune response in the lung with features of airway hyperresponsiveness and Ag-specific type 2 airway inflammation following peripheral sensitization and subsequent airway challenge with OVA. Further, the adjuvant effects of sPLA2-X that result in the type 2-biased OVA-specific adaptive immune response in the lung were dependent upon the catalytic activity of the enzyme, as a catalytically inactive mutant form of sPLA2-X does not elicit the adaptive component of the immune response, although other components of the immune response were induced by the inactive enzyme, suggesting receptor-mediated effects. Our results demonstrate that exogenous and endogenous sPLA2s play an important role in peripheral sensitization, resulting in airway responses to inhaled Ags.

Exercise-induced alterations in phospholipid hydrolysis, airway surfactant, and eicosanoids and their role in airway hyperresponsiveness in asthma.

The mechanisms responsible for driving endogenous airway hyperresponsiveness (AHR) in the form of exercise-induced bronchoconstriction (EIB) are not fully understood. We examined alterations in airway phospholipid hydrolysis, surfactant degradation, and lipid mediator release in relation to AHR severity and changes induced by exercise challenge. Paired induced sputum (n = 18) and bronchoalveolar lavage (BAL) fluid (n = 11) were obtained before and after exercise challenge in asthmatic subjects. Samples were analyzed for phospholipid structure, surfactant function, and levels of eicosanoids and secreted phospholipase A2 group 10 (sPLA2-X). A primary epithelial cell culture model was used to model effects of osmotic stress on sPLA2-X. Exercise challenge resulted in increased surfactant degradation, phospholipase activity, and eicosanoid production in sputum samples of all patients. Subjects with EIB had higher levels of surfactant degradation and phospholipase activity in BAL fluid. Higher basal sputum levels of cysteinyl leukotrienes (CysLTs) and prostaglandin D2 (PGD2) were associated with direct AHR, and both the postexercise and absolute change in CysLTs and PGD2 levels were associated with EIB severity. Surfactant function either was abnormal at baseline or became abnormal after exercise challenge. Baseline levels of sPLA2-X in sputum and the absolute change in amount of sPLA2-X with exercise were positively correlated with EIB severity. Osmotic stress ex vivo resulted in movement of water and release of sPLA2-X to the apical surface. In summary, exercise challenge promotes changes in phospholipid structure and eicosanoid release in asthma, providing two mechanisms that promote bronchoconstriction, particularly in individuals with EIB who have higher basal levels of phospholipid turnover.

Quantum dots and mouse strain influence house dust mite-induced allergic airway disease.

Quantum dot nanoparticles (QDs) are engineered nanomaterials (ENMs) that have utility in many industries due to unique optical properties not available in small molecules or bulk materials. QD-induced acute lung inflammation and toxicity in rodent models raise concerns about potential human health risks. Recent studies have also shown that some ENMs can exacerbate allergic airway disease (AAD). In this study, C57BL/6J and A/J mice were exposed to saline, house dust mite (HDM), or a combination of HDM and QDs on day 1 of the sensitization protocol. Mice were then challenged on days 8, 9 and 10 with HDM or saline only. Significant differences in cellular and molecular markers of AAD induced by both HDM and HDM + QD were observed between C57BL/6J and A/J mice. Among A/J mice, HDM + QD co-exposure, but not HDM exposure alone, significantly increased levels of bronchoalveolar lavage fluid (BALF). IL-33 compared to saline controls. BALF total protein levels in both mouse strains were also only significantly increased by HDM + QD co-exposure. In addition, A/J mice had significantly more lung type 2 innate lymphoid cells (ILC2s) cells than C57BL/6J mice. A/J lung ILC2s were inversely correlated with lung glutathione and MHC-IIhigh resident macrophages, and positively correlated with MHC-IIlow resident macrophages. The results from this study suggest that 1) QDs influence HDM-induced AAD by potentiating and/or enhancing select cytokine production; 2) that genetic background modulates the impact of QDs on HDM sensitization; and 3) that potential ILC2 contributions to HDM induced AAD are also likely to be modulated by genetic background.

Identification of Epithelial Phospholipase A2 Receptor 1 as a Potential Target in Asthma.

Secreted phospholipase A2s (sPLA2s) regulate eicosanoid formation and have been implicated in asthma. Although sPLA2s function as enzymes, some of the sPLA2s bind with high affinity to a C-type lectin receptor, called PLA2R1, which has functions in both cellular signaling and clearance of sPLA2s. We sought to examine the expression of PLA2R1 in the airway epithelium of human subjects with asthma and the function of the murine Pla2r1 gene in a model of asthma. Expression of PLA2R1 in epithelial brushings was assessed in two distinct cohorts of children with asthma by microarray and quantitative PCR, and immunostaining for PLA2R1 was conducted on endobronchial tissue and epithelial brushings from adults with asthma. C57BL/129 mice deficient in Pla2r1 (Pla2r1-/-) were characterized in an ovalbumin (OVA) model of allergic asthma. PLA2R1 was differentially overexpressed in epithelial brushings of children with atopic asthma in both cohorts. Immunostaining for PLA2R1 in endobronchial tissue localized to submucosal glandular epithelium and columnar epithelial cells. After OVA sensitization and challenge, Pla2r1-/- mice had increased airway hyperresponsiveness, as well as an increase in cellular trafficking of eosinophils to the peribronchial space and bronchoalveolar lavage fluid, and an increase in airway permeability. In addition, Pla2r1-/- mice had more dendritic cells in the lung, higher levels of OVA-specific IgG, and increased production of both type-1 and type-2 cytokines by lung leukocytes. PLA2R1 is increased in the airway epithelium in asthma, and serves as a regulator of airway hyperresponsiveness, airway permeability, antigen sensitization, and airway inflammation.

Ablation of Glutaredoxin-1 Modulates House Dust Mite-Induced Allergic Airways Disease in Mice.

Protein S-glutathionylation (PSSG) is an oxidant-induced post-translational modification of protein cysteines that impacts structure and function. The oxidoreductase glutaredoxin-1 (Glrx1) under physiological conditions catalyzes deglutathionylation and restores the protein thiol group. The involvement of Glrx1/PSSG in allergic inflammation induced by asthma-relevant allergens remains unknown. In the present study, we examined the impact of genetic ablation of Glrx1 in the pathogenesis of house dust mite (HDM)-induced allergic airways disease in mice. Wild-type (WT) or Glrx1(-/-) mice were instilled intranasally with HDM on 5 consecutive days for 3 weeks. As expected, overall PSSG was increased in Glrx1(-/-) HDM mice as compared with WT animals. Total cells in bronchoalveolar lavage fluid were similarly increased in HDM-treated WT and Glrx1(-/-) mice. However, in response to HDM, mice lacking Glrx1 demonstrated significantly more neutrophils and macrophages but fewer eosinophils as compared with HDM-exposed WT mice. mRNA expression of the Th2-associated cytokines IL-13 and IL-6, as well as mucin-5AC (Muc5ac), was significantly attenuated in Glrx1(-/-) HDM-treated mice. Conversely, mRNA expression of IFN-γ and IL-17A was increased in Glrx1(-/-) HDM mice compared with WT littermates. Restimulation of single-cell suspensions isolated from lungs or spleens with HDM resulted in enhanced IL-17A and decreased IL-5 production in cells derived from inflamed Glrx1(-/-) mice compared with WT animals. Finally, HDM-induced tissue damping and elastance were significantly attenuated in Glrx1(-/-) mice compared with WT littermates. These results demonstrate that the Glrx1-PSSG axis plays a pivotal role in HDM-induced allergic airways disease in association with enhanced type 2 inflammation and restriction of IFN-γ and IL-17A.

Epithelial NF-κB orchestrates house dust mite-induced airway inflammation, hyperresponsiveness, and fibrotic remodeling.

NF-κB activation within the epithelium has been implicated in the pathogenesis of asthma, yet the exact role of epithelial NF-κB in allergen-induced inflammation and airway remodeling remains unclear. In the current study, we used an intranasal house dust mite (HDM) extract exposure regimen time course in BALB/c mice to evaluate inflammation, NF-κB activation, airway hyperresponsiveness (AHR), and airway remodeling. We used CC10-IκBαSR transgenic mice to evaluate the functional importance of epithelial NF-κB in response to HDM. After a single exposure of HDM, mRNA expression of proinflammatory mediators was significantly elevated in lung tissue of wild-type (WT) mice, in association with increases in nuclear RelA and RelB, components of the classical and alternative NF-κB pathway, respectively, in the bronchiolar epithelium. In contrast, CC10-IκBαSR mice displayed marked decreases in nuclear RelA and RelB and mRNA expression of proinflammatory mediators compared with WT mice. After 15 challenges with HDM, WT mice exhibited increases in inflammation, AHR, mucus metaplasia, and peribronchiolar fibrosis. CC10-IκBαSR transgenic mice displayed marked decreases in neutrophilic infiltration, tissue damping, and elastance parameters, in association will less peribronchiolar fibrosis and decreases in nuclear RelB in lung tissue. However, central airway resistance and mucus metaplasia remained elevated in CC10-IκBαSR transgenic mice, in association with the continued presence of lymphocytes, and partial decreases in eosinophils and IL-13. The current study demonstrates that following airway exposure with an asthma-relevant allergen, activation of classical and alternative NF-κB pathways occurs within the airway epithelium and may coordinately contribute to allergic inflammation, AHR, and fibrotic airway remodeling.

Animal models of allergic airways disease: where are we and where to next?

In a complex inflammatory airways disease such as asthma, abnormalities in a plethora of molecular and cellular pathways ultimately culminate in characteristic impairments in respiratory function. The ability to study disease pathophysiology in the setting of a functioning immune and respiratory system therefore makes mouse models an invaluable tool in translational research. Despite the vast understanding of inflammatory airways diseases gained from mouse models to date, concern over the validity of mouse models continues to grow. Therefore the aim of this review is twofold; firstly, to evaluate mouse models of asthma in light of current clinical definitions, and secondly, to provide a framework by which mouse models can be continually refined so that they continue to stand at the forefront of translational science. Indeed, it is in viewing mouse models as a continual work in progress that we will be able to target our research to those patient populations in whom current therapies are insufficient.

Emerging mechanisms of glutathione-dependent chemistry in biology and disease.

Glutathione has traditionally been considered as an antioxidant that protects cells against oxidative stress. Hence, the loss of reduced glutathione and formation of glutathione disulfide is considered a classical parameter of oxidative stress that is increased in diseases. Recent studies have emerged that demonstrate that glutathione plays a more direct role in biological and pathophysiological processes through covalent modification to reactive cysteines within proteins, a process known as S-glutathionylation. The formation of an S-glutathionylated moiety within the protein can lead to structural and functional modifications. Activation, inactivation, loss of function, and gain of function have all been attributed to S-glutathionylation. In pathophysiological settings, S-glutathionylation is tightly regulated. This perspective offers a concise overview of the emerging field of protein thiol redox modifications. We will also cover newly developed methodology to detect S-glutathionylation in situ, which will enable further discovery into the role of S-glutathionylation in biology and disease.

Endoplasmic reticulum stress mediates house dust mite-induced airway epithelial apoptosis and fibrosis.

BACKGROUND: The endoplasmic reticulum (ER) stress response participates in many chronic inflammatory and autoimmune diseases. In the current study, we sought to examine the contribution of ER stress transducers in the pathogenesis of three principal facets of allergic asthma: inflammation, airway fibrosis, and airways hyperresponsiveness. METHODS: House Dust Mite (HDM) was used as an allergen for in vitro and in vivo challenge of primary human and murine airway epithelial cells. ER stress transducers were modulated using specific small interfering RNAs (siRNAs) in vivo. Inflammation, airway remodeling, and hyperresponsiveness were measured by total bronchoalveolar lavage (BAL) cell counts, determination of collagen, and methacholine responsiveness in mice, respectively. RESULTS: Challenge of human bronchiolar and nasal epithelial cells with HDM extract induced the ER stress transducer, activating transcription factor 6 α (ATF6α) as well as protein disulfide isomerase, ERp57, in association with activation of caspase-3. SiRNA-mediated knockdown of ATF6α and ERp57 during HDM administration in mice resulted in a decrease in components of HDM-induced ER stress, disulfide mediated oligomerization of Bak, and activation of caspase-3. Furthermore, siRNA-mediated knockdown of ATF6α and ERp57 led to decreased inflammation, airway hyperresponsiveness and airway fibrosis. CONCLUSION: Collectively, our work indicates that HDM induces ER stress in airway epithelial cells and that ATF6α and ERp57 play a significant role in the development of cardinal features of allergic airways disease. Inhibition of ER stress responses may provide a potential therapeutic avenue in chronic asthma and sub-epithelial fibrosis associated with loss of lung function.

Cooperation between classical and alternative NF-κB pathways regulates proinflammatory responses in epithelial cells.

The transcription factor NF-κB has been causally linked to inflammatory lung diseases. Recent studies have unraveled the complexity of NF-κB activation by identifying two parallel activation pathways: the classical NF-κB pathway, which is controlled by IκB kinase complex-ß (IKKß) and RelA/p50, and the alternative pathway, which is controlled by IKKα and RelB/p52. The alternative pathway regulates adaptive immune responses and lymphoid development, yet its role in the regulation of innate immune responses remains largely unknown. In this study, we determined the relevance of the alternative NF-κB pathway in proinflammatory responses in lung epithelial cells. The exposure of C10 murine alveolar lung epithelial cells to diverse stimuli, or primary murine tracheal epithelial cells to LPS, resulted in the activation of both NF-κB pathways, based on the nuclear translocation of RelA, p50, RelB, and p52. Increases in the nuclear content of RelA occurred rapidly, but transiently, whereas increases in nuclear RelB content were protracted. The small interfering (si) RNA-mediated knockdown of IKKα, RelA, or RelB resulted in decreases of multiple LPS-induced proinflammatory cytokines. Surprisingly, the siRNA ablation of IKKα or RelB led to marked increases in the production of IL-6 in response to LPS. The simultaneous expression of constitutively active (CA)-IKKα and CA-IKKß caused synergistic increases in proinflammatory mediators. Lastly, the disruption of the IKK signalsome inhibited the activation of both NF-κB pathways. These results demonstrate that the coordinated activation of both NF-κB pathways regulates the magnitude and nature of proinflammatory responses in lung epithelial cells.

Genetic ablation of glutaredoxin-1 causes enhanced resolution of airways hyperresponsiveness and mucus metaplasia in mice with allergic airways disease.

Protein-S-glutathionylation (PSSG) is an oxidative modification of reactive cysteines that has emerged as an important player in pathophysiological processes. Under physiological conditions, the thiol transferase, glutaredoxin-1 (Glrx1) catalyses deglutathionylation. Although we previously demonstrated that Glrx1 expression is increased in mice with allergic inflammation, the impact of Glrx1/PSSG in the development of allergic airways disease remains unknown. In the present study we examined the impact of genetic ablation of Glrx1 in the pathogenesis of allergic inflammation and airway hyperresponsiveness (AHR) in mice. Glrx1(-/-) or WT mice were subjected to the antigen, ovalbumin (OVA), and parameters of allergic airways disease were evaluated 48 h after three challenges, and 48 h or 7 days after six challenges with aerosolized antigen. Although no clear increases in PSSG were observed in WT mice in response to OVA, marked increases were detected in lung tissue of mice lacking Glrx1 48 h following six antigen challenges. Inflammation and expression of proinflammatory mediators were decreased in Glrx1(-/-) mice, dependent on the time of analysis. WT and Glrx1(-/-) mice demonstrated comparable increases in AHR 48 h after three or six challenges with OVA. However, 7 days postcessation of six challenges, parameters of AHR in Glrx1(-/-) mice were resolved to control levels, accompanied by marked decreases in mucus metaplasia and expression of Muc5AC and GOB5. These results demonstrate that the Glrx1/S-glutathionylation redox status in mice is a critical regulator of AHR, suggesting that avenues to increase S-glutathionylation of specific target proteins may be beneficial to attenuate AHR.

Follistatin-like 1 regulates renal IL-1ß expression in cisplatin nephrotoxicity.

Follistatin-like 1 (FSTL1) is a secreted protein with homology to both Follistatin and the SPARC/BM40 family of matricellular proteins. In this study, we sought to determine the expression patterns of Fstl1 and its cognate receptor Dip2a in the adult, and to assess the consequences of Fstl1 inactivation on development and homeostasis of the kidney. We find that FSTL1 circulates at high levels in both the human and the mouse and that it is also locally expressed in the loop of Henle in the kidney. To begin to understand the in vivo functions of Fstl1, we generated a mouse mutant using a genetrap approach. The hypomorphic Fstl1 genetrap strain displays a strong reduction in FSTL1 expression at the protein level, but it does not show overt developmental defects. FSTL1 has previously been implicated in diverse disease processes as a regulator of inflammatory cytokine expression, and we therefore evaluated the response of the genetrap strain to cisplatin-mediated acute kidney injury, a disease model with highly cytokine-dependent pathology. We find that although TNF-α and Il6 levels are unchanged relative to wild-type, renal Il-1ß expression is increased in genetrap mice following cisplatin treatment. Furthermore, histopatological analysis, expression of the tissue injury marker Havcr1, and measurement of serum creatinine demonstrate that reduction of Fstl1 expression sensitizes the kidney to acute cisplatin nephrotoxicity, suggesting a role for FSTL1-mediated Il-1ß suppression in protection of the kidney from acute nephrotoxic injury.

The effects of genotype × phenotype interactions on silver nanoparticle toxicity in organotypic cultures of murine tracheal epithelial cells.

Silver nanoparticles (AgNP) are used in multiple applications but primarily in the manufacturing of antimicrobial products. Previous studies have identified AgNP toxicity in airway epithelial cells, but no in vitro studies to date have used organotypic cultures as a high-content in vitro model of the conducting airway to characterize the effects of interactions between host genetic and acquired factors, or gene × phenotype interactions (G × P), on AgNP toxicity. In the present study, we derived organotypic cultures from primary murine tracheal epithelial cells (MTEC) to characterize nominal and dosimetric dose-response relationships for AgNPs with a gold core on barrier dysfunction, glutathione (GSH) depletion, reactive oxygen species (ROS) production, lipid peroxidation, and cytotoxicity across two genotypes (A/J and C57BL/6J mice), two phenotypes ('Normal' and 'Type 2 [T2]-Skewed'), and two exposures (an acute exposure of 24 h and a subacute exposure of 4 h, every other day, over 5 days [5 × 4 h]). We characterized the 'T2-Skewed' phenotype as an in vitro model of chronic respiratory diseases, which was marked by increased sensitivity to AgNP-induced barrier dysfunction, GSH depletion, ROS production, lipid peroxidation, and cytotoxicity, suggesting that asthmatics are a sensitive population to AgNP exposures in occupational settings. This also suggests that exposure limits, which should be based upon the most sensitive population, should be derived using in vitro and in vivo models of chronic respiratory diseases. This study highlights the importance of considering dosimetry as well as G × P effects when screening and prioritizing potential respiratory toxicants. Such in vitro studies can be used to inform regulatory policy aimed at special protections for all populations.

Glutaredoxin deficiency promotes activation of the transforming growth factor beta pathway in airway epithelial cells, in association with fibrotic airway remodeling.

S-glutathionylation of reactive protein cysteines is a post-translational event that plays a critical role in transducing signals from oxidants into biological responses. S-glutathionylation can be reversed by the deglutathionylating enzyme glutaredoxin (GLRX). We have previously demonstrated that ablation of Glrx sensitizes mice to the development of parenchymal lung fibrosis(1). It remains unclear whether GLRX also controls airway fibrosis, a clinical feature relevant to asthma and chronic obstructive pulmonary disease, and whether GLRX controls the biology of airway epithelial cells, which have been implicated in the pathophysiology of these diseases. In the present study we utilized a house dust mite (HDM) model of allergic airway disease in wild type (WT) and Glrx-/- mice on a C57BL/6 background prone to develop airway fibrosis, and tracheal basal stem cells derived from WT mice, global Glrx-/- mice, or bi-transgenic mice allowing conditional ablation of the Glrx gene. Herein we show that absence of Glrx led to enhanced HDM-induced collagen deposition, elevated levels of transforming growth factor beta 1 (TGFB1) in the bronchoalveolar lavage, and resulted in increases in airway hyperresponsiveness. Airway epithelial cells isolated from Glrx-/- mice or following conditional ablation of Glrx showed spontaneous increases in secretion of TGFB1. Glrx-/- basal cells also showed spontaneous TGFB pathway activation, in association with increased expression of mesenchymal genes, including collagen 1a1 and fibronectin. Overall, these findings suggest that GLRX regulates airway fibrosis via a mechanism(s) that involve the plasticity of basal cells, the stem cells of the airways.

Type 2 and interferon inflammation regulate SARS-CoV-2 entry factor expression in the airway epithelium.

Coronavirus disease 2019 (COVID-19) is caused by SARS-CoV-2, an emerging virus that utilizes host proteins ACE2 and TMPRSS2 as entry factors. Understanding the factors affecting the pattern and levels of expression of these genes is important for deeper understanding of SARS-CoV-2 tropism and pathogenesis. Here we explore the role of genetics and co-expression networks in regulating these genes in the airway, through the analysis of nasal airway transcriptome data from 695 children. We identify expression quantitative trait loci for both ACE2 and TMPRSS2, that vary in frequency across world populations. We find TMPRSS2 is part of a mucus secretory network, highly upregulated by type 2 (T2) inflammation through the action of interleukin-13, and that the interferon response to respiratory viruses highly upregulates ACE2 expression. IL-13 and virus infection mediated effects on ACE2 expression were also observed at the protein level in the airway epithelium. Finally, we define airway responses to common coronavirus infections in children, finding that these infections generate host responses similar to other viral species, including upregulation of IL6 and ACE2. Our results reveal possible mechanisms influencing SARS-CoV-2 infectivity and COVID-19 clinical outcomes.

Type 2 and interferon inflammation strongly regulate SARS-CoV-2 related gene expression in the airway epithelium.

Coronavirus disease 2019 (COVID-19) outcomes vary from asymptomatic infection to death. This disparity may reflect different airway levels of the SARS-CoV-2 receptor, ACE2, and the spike protein activator, TMPRSS2. Here we explore the role of genetics and co-expression networks in regulating these genes in the airway, through the analysis of nasal airway transcriptome data from 695 children. We identify expression quantitative trait loci (eQTL) for both ACE2 and TMPRSS2, that vary in frequency across world populations. Importantly, we find TMPRSS2 is part of a mucus secretory network, highly upregulated by T2 inflammation through the action of interleukin-13, and that interferon response to respiratory viruses highly upregulates ACE2 expression. Finally, we define airway responses to coronavirus infections in children, finding that these infections upregulate IL6 while also stimulating a more pronounced cytotoxic immune response relative to other respiratory viruses. Our results reveal mechanisms likely influencing SARS-CoV-2 infectivity and COVID-19 clinical outcomes.

Function of secreted phospholipase A2 group-X in asthma and allergic disease.

Elevated secreted phospholipase A2 (sPLA2) activity in the airways has been implicated in the pathogenesis of asthma and allergic disease for some time. The identity and function of these enzymes in asthma is becoming clear from work in our lab and others. We focused on sPLA2 group X (sPLA2-X) after identifying increased levels of this enzyme in asthma, and that it is responsible for a large portion of sPLA2 activity in the airways and that the levels are strongly associated with features of airway hyperresponsiveness (AHR). In this review, we discuss studies that implicated sPLA2-X in human asthma, and murine models that demonstrate a critical role of this enzyme as a regulator of type-2 inflammation, AHR and production of eicosanoids. We discuss the mechanism by which sPLA2-X acts to regulate eicosanoids in leukocytes, as well as effects that are mediated through the generation of lysophospholipids and through receptor-mediated functions. This article is part of a Special Issue entitled Novel functions of phospholipase A2 Guest Editors: Makoto Murakami and Gerard Lambeau.

Airway epithelium-shifted mast cell infiltration regulates asthmatic inflammation via IL-33 signaling.

Asthma is a heterogeneous syndrome that has been subdivided into physiologic phenotypes and molecular endotypes. The most specific phenotypic manifestation of asthma is indirect airway hyperresponsiveness (AHR), and a prominent molecular endotype is the presence of type 2 inflammation. The underlying basis for type 2 inflammation and its relationship to AHR are incompletely understood. We assessed the expression of type 2 cytokines in the airways of subjects with and without asthma who were extensively characterized for AHR. Using quantitative morphometry of the airway wall, we identified a shift in mast cells from the submucosa to the airway epithelium specifically associated with both type 2 inflammation and indirect AHR. Using ex vivo modeling of primary airway epithelial cells in organotypic coculture with mast cells, we show that epithelial-derived IL-33 uniquely induced type 2 cytokines in mast cells, which regulated the expression of epithelial IL33 in a feed-forward loop. This feed-forward loop was accentuated in epithelial cells derived from subjects with asthma. These results demonstrate that type 2 inflammation and indirect AHR in asthma are related to a shift in mast cell infiltration to the airway epithelium, and that mast cells cooperate with epithelial cells through IL-33 signaling to regulate type 2 inflammation.

Reducing protein oxidation reverses lung fibrosis.

Idiopathic pulmonary fibrosis is characterized by excessive deposition of collagen in the lung, leading to chronically impaired gas exchange and death1-3. Oxidative stress is believed to be critical in this disease pathogenesis4-6, although the exact mechanisms remain enigmatic. Protein S-glutathionylation (PSSG) is a post-translational modification of proteins that can be reversed by glutaredoxin-1 (GLRX)7. It remains unknown whether GLRX and PSSG play a role in lung fibrosis. Here, we explored the impact of GLRX and PSSG status on the pathogenesis of pulmonary fibrosis, using lung tissues from subjects with idiopathic pulmonary fibrosis, transgenic mouse models and direct administration of recombinant Glrx to airways of mice with existing fibrosis. We demonstrate that GLRX enzymatic activity was strongly decreased in fibrotic lungs, in accordance with increases in PSSG. Mice lacking Glrx were far more susceptible to bleomycin- or adenovirus encoding active transforming growth factor beta-1 (AdTGFB1)-induced pulmonary fibrosis, whereas transgenic overexpression of Glrx in the lung epithelium attenuated fibrosis. We furthermore show that endogenous GLRX was inactivated through an oxidative mechanism and that direct administration of the Glrx protein into airways augmented Glrx activity and reversed increases in collagen in mice with TGFB1- or bleomycin-induced fibrosis, even when administered to fibrotic, aged animals. Collectively, these findings suggest the therapeutic potential of exogenous GLRX in treating lung fibrosis.