312 research outputs found
Cytokine expression in allergic mucosal inflammation
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:DX190478 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Leukotriene antagonists and synthesis inhibitors: New directions in asthma therapy
No full textThis article briefly reviews the advances in our understanding of asthma with a particular focus on the role of inflammation, before providing a concise overview of current knowledge of leukotrienes in the pathophysiology of the disease. The development of leukotriene receptor antagonists and synthesis inhibitors is briefly described; and acute exercise, allergen, and aspirin challenge studies with these agents are reviewed. Clinical studies with leukotriene antagonists and inhibitors have confirmed the central role of leukotrienes in asthma pathophysiology. In conclusion, we suggest that the new generation of leukotriene receptor antagonists may be suitable as first-line therapy in patients with mild to moderate asthma. Further studies are required to determine whether the leukotriene synthesis inhibitors will be equally effective or provide any additional antiinflammatory benefit.</p
The role of the mast cell in the pathophysiology of asthma
No full textThere is compelling evidence that human mast cells contribute to the pathophysiology of asthma. Mast cells, but not T cells or eosinophils, localize within the bronchial smooth muscle bundles in patients with asthma but not in normal subjects or those with eosinophilic bronchitis, a factor likely to be important in determining the asthmatic phenotype. The mechanism of mast cell recruitment by asthmatic airway smooth muscle involves the CXCL10/CXCR3 axis, and several mast cell mediators have profound effects on airway smooth muscle function. The autacoids are established as potent bronchoconstrictors, whereas the proteases tryptase and chymase are being demonstrated to have a range of actions consistent with key roles in inflammation, tissue remodeling, and bronchial hyperresponsiveness. IL-4 and IL-13, known mast cell products, also induce bronchial hyperresponsiveness in the mouse independent of the inflammatory response and enhance the magnitude of agonist-induced intracellular Ca2+ responses in cultured human airway smooth muscle. There are therefore many pathways by which the close approximation of mast cells with airway smooth muscle cells might lead to disordered airway smooth muscle function. Mast cells also infiltrate the airway mucous glands in subjects with asthma, showing features of degranulation, and a positive correlation with the degree of mucus obstructing the airway lumen, suggesting that mast cells play an important role in regulating mucous gland secretion. The development of potent and specific inhibitors of mast cell secretion, which remain active when administered long-term to asthmatic airways, should offer a novel approach to the treatment of asthma
The relative contribution of mast cell subsets to conjunctival TH2-like cytokines
No full textPURPOSE. To investigate the distribution of the T-helper (TH)2-like cytokines, interleukin (IL)-4, IL-5, IL-6, and IL-13 between mast cell subsets in conjunctival biopsy specimens from normal subjects and those with seasonal allergic conjunctivitis (SAC) during and outside of the grass pollen season. METHODS. Sequential and double in situ hybridization (ISH) and immunohistochemistry (IHC) were performed on thin sections of human conjunctiva to determine the colocalization of the immunoreactivity of IL-4, IL-5, IL-6, and IL-13 to mast cell subsets in normal subjects and subjects with atopy and to detect IL-4 mRNA in conjunctival mast cells. RESULTS. More than 90% of IL-4+–immunoreactive cells were observed to be mast cells in conjunctival biopsy specimens from all patient groups. The majority of IL-5+, IL-6+, and IL-13+ cells were also noted to be mast cells for each group. IL-4 preferentially colocalized to the tryptase+-chymase+ mast cell phenotype (MCTC) with MCTC cells comprising 93.3% of cytokine+ mast cells in symptomatic SAC (P = 0.0017), 89.2% in asymptomatic SAC (P = 0.0008), and 77.8% in normal subjects (P = 0.0472). IL-13 appeared to colocalize preferentially to the MCTC phenotype and IL-5 and IL-6 to the MCT phenotype. ISH showed that 75.8% of mast cells in normal subjects, 78.7% in subjects with symptomatic SAC, and 18.7% in subjects with asymptomatic SAC expressed mRNA for IL-4. CONCLUSIONS. Conjunctival mast cells are an important source of IL-4, IL-5, IL-6, and IL-13 immunoreactivity, with preferential colocalization of IL-4 and IL-13 on the MCTC subset and IL-5 and IL-6 to the MCT subset. This evidence suggests that differences in protease phenotype may also reflect functional differences evidenced by the different patterns of cytokine distribution. <br/
Mast-cell infiltration of airway smooth muscle in asthma
No full textBackground Asthma and eosinophilic bronchitis are characterized by similar inflammatory infiltrates in the submucosa of the lower airway. However, eosinophilic bronchitis differs from asthma in that there is no variable airflow obstruction or airway hyperresponsiveness in the former condition. We tested the hypothesis that there were differences between the two conditions in the microlocalization of mast cells within the airway smooth muscle.Methods Immunohistochemical analysis of bronchial-biopsy specimens was completed in 17 subjects with asthma, 13 subjects with eosinophilic bronchitis, and 11 normal controls recruited from two centers.Results Both groups with disease had a similar degree of submucosal eosinophilia and thickening of the basement membrane and lamina reticularis. By contrast, the number of tryptase-positive mast cells in the bundles of airway smooth muscle from subjects with asthma (median, 5.1 mast cells per square millimeter of smooth muscle [range, 0 to 33.3]) was substantially higher than that in subjects with eosinophilic bronchitis (median, 0 mast cells per square millimeter; range, 0 to 4.8) and that in normal controls (median, 0 mast cells per square millimeter [range, 0 to 6.4]; P<0.001 for the comparison among the three groups). T cells and eosinophils were not usually seen in the airway smooth muscle in any of the groups.Conclusions The infiltration of airway smooth muscle by mast cells is associated with the disordered airway function found in asthma
Asthma: Eosinophil Disease, Mast Cell Disease, or Both?
No full text Although there is much circumstantial evidence implicating eosinophils as major orchestrators in the pathophysiology of asthma, recent studies have cast doubt on their importance. Not only does anti-interleukin-5 treatment not alter the course of the disease, but some patients with asthma do not have eosinophils in their airways, whereas patients with eosinophilic bronchitis exhibit a florid tissue eosinophilia but do not have asthma. In contrast, mast cells are found in all airways and localize specifically to key tissue structures such as the submucosal glands and airway smooth muscle within asthmatic bronchi, irrespective of disease severity or phenotype. Here they are activated and interact exclusively with these structural cells via adhesive pathways and through the release of soluble mediators acting across the distance of only a few microns. The location of mast cells within the airway smooth muscle bundles seems particularly important for the development and propagation of asthma, perhaps occurring in response to, and then serving to aggravate, an underlying abnormality in asthmatic airway smooth muscle function. Targeting this mast cell-airway smooth muscle interaction in asthma offers exciting prospects for the treatment of this common disease.</p
The effects of inhaled corticosteroids on healthy airways
No full textBackground: The effects of inhaled corticosteroids (ICS) on healthy airways are poorly defined. Objectives: To delineate the effects of ICS on gene expression in healthy airways, without confounding caused by changes in disease-related genes and disease-related alterations in ICS responsiveness. Methods: Randomized open-label bronchoscopy study of high-dose ICS therapy in 30 healthy adult volunteers randomized 2:1 to (i) fluticasone propionate 500 mcg bd daily or (ii) no treatment, for 4 weeks. Laboratory staff were blinded to allocation. Biopsies and brushings were analysed by immunohistochemistry, bulk RNA sequencing, DNA methylation array and metagenomics. Results: ICS induced small between-group differences in blood and lamina propria eosinophil numbers, but not in other immunopathological features, blood neutrophils, FeNO, FEV1, microbiome or DNA methylation. ICS treatment upregulated 72 genes in brushings and 53 genes in biopsies, and downregulated 82 genes in brushings and 416 genes in biopsies. The most downregulated genes in both tissues were canonical markers of type-2 inflammation (FCER1A, CPA3, IL33, CLEC10A, SERPINB10 and CCR5), T cell-mediated adaptive immunity (TARP, TRBC1, TRBC2, PTPN22, TRAC, CD2, CD8A, HLA-DQB2, CD96, PTPN7), B-cell immunity (CD20, immunoglobulin heavy and light chains) and innate immunity, including CD48, Hobit, RANTES, Langerin and GFI1. An IL-17-dependent gene signature was not upregulated by ICS. Conclusions: In healthy airways, 4-week ICS exposure reduces gene expression related to both innate and adaptive immunity, and reduces markers of type-2 inflammation. This implies that homeostasis in health involves tonic type-2 signalling in the airway mucosa, which is exquisitely sensitive to ICS. Trial registration: ClinicalTrials.gov NCT02476825.https://onlinelibrary.wiley.com/doi/10.1111/all.1614
Identification of redundancy between human FcεRIβ and MS4A6A proteins points toward additional complex mechanisms for FcεRI trafficking and signaling
No full textBackground: Allergic diseases are triggered by signaling through the high-affinity IgE receptor, FcεRI. In both mast cells (MCs) and basophils, FcεRI is a tetrameric receptor complex comprising a ligand-binding α subunit (FcεRIα), a tetraspan β subunit (FcεRIβ, MS4A2) responsible for trafficking and signal amplification, and a signal transducing dimer of single transmembrane γ subunits (FcεRIγ). However, FcεRI also exists as presumed trimeric complexes that lack FcεRIβ and are expressed on several cell types outside the MC and basophil lineages. Despite known differences between humans and mice in the presence of the trimeric FcεRI complex, questions remain as to how it traffics and whether it signals in the absence of FcεRIβ. We have previously reported that targeting FcεRIβ with exon-skipping oligonucleotides eliminates IgE-mediated degranulation in mouse MCs, but equivalent targeting in human MCs was not effective at reducing degranulation. Results: Here, we report that the FcεRIβ-like protein MS4A6A exists in human MCs and compensates for FcεRIβ in FcεRI trafficking and signaling. Human MS4A6A promotes surface expression of FcεRI complexes and facilitates degranulation. MS4A6A and FcεRIβ are encoded by highly related genes within the MS4A gene family that cluster within the human gene loci 11q12-q13, a region linked to allergy and asthma susceptibility. Conclusions: Our data suggest the presence of either FcεRIβ or MS4A6A is sufficient for degranulation, indicating that MS4A6A could be an elusive FcεRIβ-like protein in human MCs that performs compensatory functions in allergic disease.https://onlinelibrary.wiley.com/doi/10.1111/all.1559
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