Cysteinyl Leukotrienes in Allergic Inflammation.

The cysteinyl leukotrienes (CysLTs), LTC4, LTD4, and LTE4, are potent lipid mediators derived from arachidonic acid through the 5-lipoxygenase pathway. These mediators produce both inflammation and bronchoconstriction through three distinct G protein-coupled receptors (GPCRs)-CysLT1, CysLT2, and OXGR1 (also known as CysLT3 or GPR99). While CysLT-mediated functions in the effector phase of allergic inflammation and asthma have been established for some time, recent work has demonstrated novel roles for these mediators and their receptors in the induction and amplification of type 2 inflammation. Additionally, in vitro studies and murine models have uncovered diverse regulatory mechanisms that restrain or amplify CysLT receptor activation and CysLT receptor function. This review provides an overview of CysLT biosynthesis and its regulation, the molecular and functional pharmacology of CysLT receptors, and an overview of the established and emerging roles of CysLTs in asthma, aspirin-exacerbated respiratory disease, and type 2 inflammation.

Epithelial sensing in allergic disease.

Epithelial cells provide a first line of immune defense by maintaining barrier function, orchestrating mucociliary clearance, secreting antimicrobial molecules, and generating sentinel signals to both activate innate immune cells and shape adaptive immunity. Although epithelial alarmins play a particularly important role in the initiation of type 2 inflammation in response to allergens, the mechanisms by which epithelial cells sense the environment and regulate the generation and release of alarmins have been poorly understood. Recent studies have identified new sensors and signaling pathways used by barrier epithelial cells to elicit type 2 inflammation, including a novel pathway for the release of interleukin-33 from the nucleus that depends on apoptotic signaling. These recent findings have implications in the development of allergic diseases, from atopic eczema to food allergy, rhinitis, and asthma.

Rhinovirus infection of airway epithelial cells uncovers the non-ciliated subset as a likely driver of genetic risk to childhood-onset asthma.

Asthma is a complex disease caused by genetic and environmental factors. Studies show that wheezing during rhinovirus infection correlates with childhood asthma development. Over 150 non-coding risk variants for asthma have been identified, many affecting gene regulation in T cells, but the effects of most risk variants remain unknown. We hypothesized that airway epithelial cells could also mediate genetic susceptibility to asthma given they are the first line of defense against respiratory viruses and allergens. We integrated genetic data with transcriptomics of airway epithelial cells subject to different stimuli. We demonstrate that rhinovirus infection significantly upregulates childhood-onset asthma-associated genes, particularly in non-ciliated cells. This enrichment is also observed with influenza infection but not with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or cytokine activation. Overall, our results suggest that rhinovirus infection is an environmental factor that interacts with genetic risk factors through non-ciliated airway epithelial cells to drive childhood-onset asthma.

Increased glycolysis and cellular crosstalk in eosinophilic chronic rhinosinusitis with nasal polyps.

Introduction: Chronic rhinosinusitis (CRS) is a chronic inflammatory disease of the sinonasal mucosa with distinct endotypes including type 2 (T2) high eosinophilic CRS with nasal polyps (eCRSwNP), T2 low non-eosinophilic CRS with nasal polyps (neCRSwNP), and CRS without nasal polyps (CRSsNP). Methods: Given the heterogeneity of disease, we hypothesized that assessment of single cell RNA sequencing (scRNA-seq) across this spectrum of disease would reveal connections between infiltrating and activated immune cells and the epithelial and stromal populations that reside in sinonasal tissue. Results: Here we find increased expression of genes encoding glycolytic enzymes in epithelial cells (EpCs), stromal cells, and memory T-cell subsets from patients with eCRSwNP, as compared to healthy controls. In basal EpCs, this is associated with a program of cell motility and Rho GTPase effector expression. Across both stromal and immune subsets, glycolytic programming was associated with extracellular matrix interactions, proteoglycan generation, and collagen formation. Furthermore, we report increased cell-cell interactions between EpCs and stromal/immune cells in eCRSwNP compared to healthy control tissue, and we nominate candidate receptor-ligand pairs that may drive tissue remodeling. Discussion: These findings support a role for glycolytic reprograming in T2-elicited tissue remodeling and implicate increased cellular crosstalk in eCRSwNP.

Rhinovirus infection of airway epithelial cells uncovers the non-ciliated subset as a likely driver of genetic susceptibility to childhood-onset asthma.

Asthma is a complex disease caused by genetic and environmental factors. Epidemiological studies have shown that in children, wheezing during rhinovirus infection (a cause of the common cold) is associated with asthma development during childhood. This has led scientists to hypothesize there could be a causal relationship between rhinovirus infection and asthma or that RV-induced wheezing identifies individuals at increased risk for asthma development. However, not all children who wheeze when they have a cold develop asthma. Genome-wide association studies (GWAS) have identified hundreds of genetic variants contributing to asthma susceptibility, with the vast majority of likely causal variants being non-coding. Integrative analyses with transcriptomic and epigenomic datasets have indicated that T cells drive asthma risk, which has been supported by mouse studies. However, the datasets ascertained in these integrative analyses lack airway epithelial cells. Furthermore, large-scale transcriptomic T cell studies have not identified the regulatory effects of most non-coding risk variants in asthma GWAS, indicating there could be additional cell types harboring these "missing regulatory effects". Given that airway epithelial cells are the first line of defense against rhinovirus, we hypothesized they could be mediators of genetic susceptibility to asthma. Here we integrate GWAS data with transcriptomic datasets of airway epithelial cells subject to stimuli that could induce activation states relevant to asthma. We demonstrate that epithelial cultures infected with rhinovirus significantly upregulate childhood-onset asthma-associated genes. We show that this upregulation occurs specifically in non-ciliated epithelial cells. This enrichment for genes in asthma risk loci, or 'asthma heritability enrichment' is also significant for epithelial genes upregulated with influenza infection, but not with SARS-CoV-2 infection or cytokine activation. Additionally, cells from patients with asthma showed a stronger heritability enrichment compared to cells from healthy individuals. Overall, our results suggest that rhinovirus infection is an environmental factor that interacts with genetic risk factors through non-ciliated airway epithelial cells to drive childhood-onset asthma.

A nasal cell atlas reveals heterogeneity of tuft cells and their role in directing olfactory stem cell proliferation.

The olfactory neuroepithelium serves as a sensory organ for odors and forms part of the nasal mucosal barrier. Olfactory sensory neurons are surrounded and supported by epithelial cells. Among them, microvillous cells (MVCs) are strategically positioned at the apical surface, but their specific functions are enigmatic, and their relationship to the other specialized epithelial cells is unclear. Here, we establish that the family of MVCs comprises tuft cells and ionocytes in both mice and humans. Integrating analysis of the respiratory and olfactory epithelia, we define the distinct receptor expression of TRPM5+ tuft-MVCs compared with Gɑ-gustducinhigh respiratory tuft cells and characterize a previously undescribed population of glandular DCLK1+ tuft cells. To establish how allergen sensing by tuft-MVCs might direct olfactory mucosal responses, we used an integrated single-cell transcriptional and protein analysis. Inhalation of Alternaria induced mucosal epithelial effector molecules including Chil4 and a distinct pathway leading to proliferation of the quiescent olfactory horizontal basal stem cell (HBC) pool, both triggered in the absence of olfactory apoptosis. Alternaria- and ATP-elicited HBC proliferation was dependent on TRPM5+ tuft-MVCs, identifying these specialized epithelial cells as regulators of olfactory stem cell responses. Together, our data provide high-resolution characterization of nasal tuft cell heterogeneity and identify a function of TRPM5+ tuft-MVCs in directing the olfactory mucosal response to allergens.

Lung function trajectories in a cohort of patients with moderate-to-severe asthma on mepolizumab, omalizumab, or dupilumab.

BACKGROUND: Lung function is an independent predictor of mortality. We evaluated the lung function trajectories of a cohort of patients with asthma receiving biologic therapy. METHODS: We identified 229 monoclonal antibody-naïve adult patients with moderate-to-severe asthma who initiated omalizumab, mepolizumab, or dupilumab between 2010 and 2022 in a large healthcare system in Boston, MA. Generalized additive mixed models were used to estimate the lung function trajectories during the 156 weeks following biologic initiation. Response was defined as an improvement in FEV1 or a decrease of ≤0.5% per year. The Kaplan-Meier estimator was used to assess time to no additional improvement in FEV1 in responders. All models were adjusted for age, sex, body mass index, smoking status, baseline exacerbation rate, and baseline blood eosinophil count. RESULTS: Eighty-eight patients initiated mepolizumab, 76 omalizumab, and 65 dupilumab. Baseline eosinophil count was highest in the mepolizumab group (405 cells/mcL) and lowest for omalizumab (250 cells/mcL). Both FEV1 and FVC improved in the mepolizumab group (FEV1 + 20 mL/year; FVC +43 mL/year). For omalizumab, there was an initial improvement in the first year followed by decline with an overall FEV1 loss of -44 mL/year and FVC -32 mL/year. For dupilumab, both FEV1 (+61 mL/year) and FVC (+74 mL/year) improved over time. Fifty percent of the mepolizumab group, 58% omalizumab, and 72% of dupilumab were responders. The median time to no additional FEV1 improvement in responders was 24 weeks for omalizumab, 48 weeks for mepolizumab, and 57 weeks for dupilumab. CONCLUSION: In this clinical cohort, mepolizumab, omalizumab, and dupilumab had beneficial effects on FEV1 and FVC with distinct post-initiation trajectories.

Increased epithelial mTORC1 activity in chronic rhinosinusitis with nasal polyps.

Background: The airway epithelium plays a central role in the pathogenesis of chronic respiratory diseases such as asthma and chronic rhinosinusitis with nasal polyps (CRSwNP), but the mechanisms by which airway epithelial cells (EpCs) maintain inflammation are poorly understood. Objective: We hypothesized that transcriptomic assessment of sorted airway EpCs across the spectrum of differentiation would allow us to define mechanisms by which EpCs perpetuate airway inflammation. Methods: Ethmoid sinus EpCs from adult patients with CRS were sorted into 3 subsets, bulk RNA sequenced, and analyzed for differentially expressed genes and pathways. Single cell RNA-seq (scRNA-seq) datasets from eosinophilic and non-eosinophilic CRSwNP and bulk RNA-seq of EpCs from mild/moderate and severe asthma were assessed. Immunofluorescent staining and ex vivo functional analysis of sinus EpCs were used to validate our findings. Results: Analysis within and across purified EpC subsets revealed an enrichment in glycolytic programming in CRSwNP vs CRSsNP. Correlation analysis identified mammalian target of rapamycin complex 1 (mTORC1) as a potential regulator of the glycolytic program and identified EpC expression of cytokines and wound healing genes as potential sequelae. mTORC1 activity was upregulated in CRSwNP, and ex vivo inhibition demonstrated that mTOR is critical for EpC generation of CXCL8, IL-33, and CXCL2. Across patient samples, the degree of glycolytic activity was associated with T2 inflammation in CRSwNP, and with both T2 and non-T2 inflammation in severe asthma. Conclusions: Together, these findings highlight a metabolic axis required to support epithelial generation of cytokines critical to both chronic T2 and non-T2 inflammation in CRSwNP and asthma.

Type 2 inflammation drives an airway basal stem cell program through insulin receptor substrate signaling.

BACKGROUND: Chronic rhinosinusitis with nasal polyposis (CRSwNP) is a type 2 (T2) inflammatory disease associated with an increased number of airway basal cells (BCs). Recent studies have identified transcriptionally distinct BCs, but the molecular pathways that support or inhibit human BC proliferation and differentiation are largely unknown. OBJECTIVE: We sought to determine the role of T2 cytokines in regulating airway BCs. METHODS: Single-cell and bulk RNA sequencing of sinus and lung airway epithelial cells was analyzed. Human sinus BCs were stimulated with IL-4 and IL-13 in the presence and absence of inhibitors of IL-4R signaling. Confocal analysis of human sinus tissue and murine airway was performed. Murine BC subsets were sorted for RNA sequencing and functional assays. Fate labeling was performed in a murine model of tracheal injury and regeneration. RESULTS: Two subsets of BCs were found in human and murine respiratory mucosa distinguished by the expression of basal cell adhesion molecule (BCAM). BCAM expression identifies airway stem cells among P63+KRT5+NGFR+ BCs. In the sinonasal mucosa, BCAMhi BCs expressing TSLP, IL33, CCL26, and the canonical BC transcription factor TP63 are increased in patients with CRSwNP. In cultured BCs, IL-4/IL-13 increases the expression of BCAM and TP63 through an insulin receptor substrate-dependent signaling pathway that is increased in CRSwNP. CONCLUSIONS: These findings establish BCAM as a marker of airway stem cells among the BC pool and demonstrate that airway epithelial remodeling in T2 inflammation extends beyond goblet cell metaplasia to the support of a BC stem state poised to perpetuate inflammation.

Collaborative identification and prioritisation of mental health nursing care process metrics and indicators: a Delphi consensus study.

BACKGROUND: The Irish Office of Nursing & Midwifery Services Director (ONMSD) commissioned the development an updated suite of mental health nursing metrics and indicators for implementation in Irish mental health clinical settings. While measuring care processes does offer the potential to improve care quality, the choice of which mental health nursing metrics to measure presents a significant challenge, both in Ireland and internationally. The provision of safe and high-quality mental health nursing care stems from nurses' expertise, skills and overall capacity to provide recovery focused care across a range of health care settings. Accordingly, efforts to measure what mental health nurses do depends on the identification of those care processes that contribute to mental health nursing practice. This paper reports on the identification, development and prioritisation of a national suite of Quality Care Metrics (QCM), along with their associated indicators, for mental health nursing care processes in Ireland. METHODS: The study was undertaken over four phases; i) a systematic literature review to identify mental health care process metrics and their associated indicators of measurement; ii) a two-round, online Delphi survey of mental health nurses to develop consensus on the suit of mental health nursing care process metrics; iii) a two-round online Delphi survey of mental health nurses to develop consensus on the indicators to be used to measure the agreed metrics; and iv) a face-to-face consensus meeting with mental health nurses and service user representatives to develop consensus on the final suite of metrics and indicators. RESULTS: Following these four phases 9 metrics and their 71 associated indicators were agreed for inclusion in the final suite of Mental Health Nursing QCM. These metrics are applicable across the life span and the range of mental health nursing health care settings. CONCLUSION: The development of this suite of Mental Health Nursing QCM and their indicators represents an opportunity for the measurement of safe and high-quality mental health nursing care for application in Ireland and internationally. This initial development of metrics and indicators should be followed by a rigorous baseline review of QCM uptake and implementation amongst mental health nurses as part of an ongoing evaluation.

Single-cell RNA sequencing of mast cells in eosinophilic esophagitis reveals heterogeneity, local proliferation, and activation that persists in remission.

BACKGROUND: Mast cells (MCs) are pleiotropic cells that accumulate in the esophagus of patients with eosinophilic esophagitis (EoE) and are thought to contribute to disease pathogenesis, yet their properties and functions in this organ are largely unknown. OBJECTIVES: This study aimed to perform a comprehensive molecular and spatial characterization of esophageal MCs in EoE. METHODS: Esophageal biopsies obtained from patients with active EoE, patients with EoE in histologic remission, and individuals with histologically normal esophageal biopsies and no history of esophageal disease (ie, control individuals) were subject to single-cell RNA sequencing, flow cytometry, and immunofluorescence analyses. RESULTS: This study probed 39,562 single esophageal cells by single-cell RNA sequencing; approximately 5% of these cells were MCs. Dynamic MC expansion was identified across disease states. During homeostasis, TPSAB1highAREGhigh resident MCs were mainly detected in the lamina propria and exhibited a quiescent phenotype. In patients with active EoE, resident MCs assumed an activated phenotype, and 2 additional proinflammatory MC populations emerged in the intraepithelial compartment, each linked to a proliferating MKI67high cluster. One proinflammatory activated MC population, marked as KIThighIL1RL1highFCER1Alow, was not detected in disease remission (termed "transient MC"), whereas the other population, marked as CMA1highCTSGhigh, was detected in disease remission where it maintained an activated state (termed "persistent MC"). MCs were prominent producers of esophageal IL-13 mRNA and protein, a key therapeutic target in EoE. CONCLUSIONS: Esophageal MCs comprise heterogeneous populations with transcriptional signatures associated with distinct spatial compartmentalization and EoE disease status. In active EoE, they assume a proinflammatory state and locally proliferate, and they remain activated and poised to reinitiate inflammation even during disease remission.

An adjuvant strategy enabled by modulation of the physical properties of microbial ligands expands antigen immunogenicity.

Activation of the innate immune system via pattern recognition receptors (PRRs) is key to generate lasting adaptive immunity. PRRs detect unique chemical patterns associated with invading microorganisms, but whether and how the physical properties of PRR ligands influence the development of the immune response remains unknown. Through the study of fungal mannans, we show that the physical form of PRR ligands dictates the immune response. Soluble mannans are immunosilent in the periphery but elicit a potent pro-inflammatory response in the draining lymph node (dLN). By modulating the physical form of mannans, we developed a formulation that targets both the periphery and the dLN. When combined with viral glycoprotein antigens, this mannan formulation broadens epitope recognition, elicits potent antigen-specific neutralizing antibodies, and confers protection against viral infections of the lung. Thus, the physical properties of microbial ligands determine the outcome of the immune response and can be harnessed for vaccine development.

Protecting tissue integrity and enteric function: the case for type 2 inflammation and macrophages.

Type 2 inflammation (T2I) accompanies many inflammatory diseases. In a recent issue of Cell, Ahrends et al. demonstrate that helminth-elicited T2I preserves excitatory neurons and enteric function through the expansion of Arginase-1 (Arg-1)-expressing macrophages, thereby extending our understanding of the protective functions that T2I can orchestrate in inflamed barrier tissue.

Multidimensional wellness for people aging with mental health conditions: A proposed framework.

OBJECTIVE: This project aimed to develop a synthesized framework of multidimensional wellness for people aging with serious mental health conditions (SMHC) using existing frameworks to serve as a guide for policy and interventions to address the unique needs, experiences, and strengths of the population. METHOD: A concept analysis compared a widely used wellness approach (Swarbrick, 1997) for people with SMHC and one for older adults (Fullen, 2019) to synthesize into a practical framework for people aging with SMHC. RESULTS: Nine dimensions were proposed for conceptualizing the wellness of this population including: (a) Developmental, (b) Intellectual/Cognitive, (c) Physical, (d) Emotional, (e) Social, (f) Occupational, (g) Spiritual, (h) Environmental, and (i) Financial. Practical suggestions for implementation are identified. CONCLUSIONS AND IMPLICATION FOR PRACTICE: People aging with SMHC require rehabilitation services that address their unique perspectives, strengths, and challenges. The proposed adapted wellness framework offers a guide to comprehensively address well-being in people aging with SMHC. Placing the model in the context of external factors of resources and supports available, and the impact of societal perspectives about each dimension, further delineates a holistic model of wellness that considers well-being and successful living. This model can offer structure and practical application for services, and consideration of future needs of people aging with SMHC to support psychiatric rehabilitation services, as well as offer strategies to encourage positive aging and recovery. Future work should explore the impact of multidecade experiences of mental health conditions and the mental health system to better support individual recovery. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Tuft cell-produced cysteinyl leukotrienes and IL-25 synergistically initiate lung type 2 inflammation.

Aeroallergen sensing by airway epithelial cells triggers pathogenic immune responses leading to type 2 inflammation, the hallmark of chronic airway diseases such as asthma. Tuft cells are rare epithelial cells and the dominant source of interleukin-25 (IL-25), an epithelial cytokine, and cysteinyl leukotrienes (CysLTs), lipid mediators of vascular permeability and chemotaxis. How these two mediators derived from the same cell might cooperatively promote type 2 inflammation in the airways has not been clarified. Here, we showed that inhalation of the parent leukotriene C4 (LTC4) in combination with a subthreshold dose of IL-25 led to activation of two innate immune cells: inflammatory type 2 innate lymphoid cell (ILC2) for proliferation and cytokine production, and dendritic cells (DCs). This cooperative effect led to a much greater recruitment of eosinophils and CD4+ T cell expansion indicative of synergy. Whereas lung eosinophilia was dominantly mediated through the classical CysLT receptor CysLT1R, type 2 cytokines and activation of innate immune cells required signaling through CysLT1R and partially CysLT2R. Tuft cell­specific deletion of Ltc4s, the terminal enzyme required for CysLT production, reduced lung inflammation and the systemic immune response after inhalation of the mold aeroallergen Alternaria; this effect was further enhanced by concomitant blockade of IL-25. Our findings identified a potent synergy of CysLTs and IL-25 downstream of aeroallergen-trigged activation of airway tuft cells leading to a highly polarized type 2 immune response and further implicate airway tuft cells as powerful modulators of type 2 immunity in the lungs.

Isolation of Nasal Brush Cells for Single-cell Preparations.

Solitary chemosensory epithelial cells are scattered in most mucosal surfaces. They are referred to as tuft cells in the intestinal mucosa, brush cells in the trachea, and solitary chemosensory and microvillous cells in the nasal mucosa. They are the primary source of IL-25 in the epithelium and are also engaged in acetylcholine generation. We recently demonstrated that nasal solitary chemosensory (brush) cells can generate robust levels of cysteinyl leukotrienes in response to stimulation with calcium ionophore, aeroallergens, and danger-associated molecules, such as ATP and UTP, and this mechanism depends on brush cell expression of the purinergic receptor P2Y2. This protocol describes an effective method of nasal brush cell isolation in the mouse. The method is based on physical separation of the mucosal layer of the nasal cavity and pre-incubation with dispase, followed by digestion with papain solution. The single cell suspension obtained this way contains a high yield of brush cells for fluorescence-activated cell sorting (FACS), RNA-sequencing, and ex vivo assays. Graphic abstract: Workflow of nasal digestion for brush cell isolation.

Human airway mast cells proliferate and acquire distinct inflammation-driven phenotypes during type 2 inflammation.

Mast cells (MCs) play a pathobiologic role in type 2 (T2) allergic inflammatory diseases of the airway, including asthma and chronic rhinosinusitis with nasal polyposis (CRSwNP). Distinct MC subsets infiltrate the airway mucosa in T2 disease, including subepithelial MCs expressing the proteases tryptase and chymase (MCTC) and epithelial MCs expressing tryptase without chymase (MCT). However, mechanisms underlying MC expansion and the transcriptional programs underlying their heterogeneity are poorly understood. Here, we use flow cytometry and single-cell RNA-sequencing (scRNA-seq) to conduct a comprehensive analysis of human MC hyperplasia in CRSwNP, a T2 cytokine-mediated inflammatory disease. We link discrete cell surface phenotypes to the distinct transcriptomes of CRSwNP MCT and MCTC, which represent polarized ends of a transcriptional gradient of nasal polyp MCs. We find a subepithelial population of CD38highCD117high MCs that is markedly expanded during T2 inflammation. These CD38highCD117high MCs exhibit an intermediate phenotype relative to the expanded MCT and MCTC subsets. CD38highCD117high MCs are distinct from circulating MC progenitors and are enriched for proliferation, which is markedly increased in CRSwNP patients with aspirin-exacerbated respiratory disease, a severe disease subset characterized by increased MC burden and elevated MC activation. We observe that MCs expressing a polyp MCT-like effector program are also found within the lung during fibrotic diseases and asthma, and further identify marked differences between MCTC in nasal polyps and skin. These results indicate that MCs display distinct inflammation-associated effector programs and suggest that in situ MC proliferation is a major component of MC hyperplasia in human T2 inflammation.