Role of airway epithelial cell miRNAs in asthma

The airway epithelial cells and overlying layer of mucus are the first point of contact for particles entering the lung. The severity of environmental contributions to pulmonary disease initiation, progression, and exacerbation is largely determined by engagement with the airway epithelium. Despite the cellular cross-talk and cargo exchange in the microenvironment, epithelial cells produce miRNAs associated with the regulation of airway features in asthma. In line with this, there is evidence indicating miRNA alterations related to their multifunctional regulation of asthma features in the conducting airways. In this review, we discuss the cellular components and functions of the airway epithelium in asthma, miRNAs derived from epithelial cells in disease pathogenesis, and the cellular exchange of miRNA-bearing cargo in the airways

Sepsis-Like Systemic Inflammation Induced by Nano-Sized Extracellular Vesicles From Feces

Nano-sized extracellular vesicles (EVs), including exosomes, microvesicles, and other types of vesicles, are released by most mammalian cells and bacteria. We here ask whether feces contain EVs of mammalian and/or bacterial origin, and whether these EVs induce systemic inflammation. Fecal extracellular vesicles (fEVs) were isolated from mice and humans. The presence of EVs from Gram-negative and Gram-positive bacteria was detected by enzyme-linked immunosorbent assay using anti-lipid A and anti-lipoteichoic acid antibodies, whereas Western blot using anti-beta-actin antibody was employed to detect host-derived EVs in the fEVs. Further, fEVs were administered into mice by intraperitoneal injection, and inflammatory responses were investigated in the peritoneum, blood, and lungs. The role of TLR2 and TLR4 were studied using knockout mice. Significant quantities of EVs were present in feces from mice as well as humans, and derived from Gram-negative and Gram-positive bacteria, as well as the host. Bacteria-free fEVs introduced into the peritoneum induced local and systemic inflammation (including in the lungs), but fEVs from germ-free animals had weaker effects. This pronounced local and systemic inflammatory responses seemed to be induced by EVs from both Gram-negative and Gram-positive bacteria, and was attenuated in mice lacking TLR2 or TLR4. Our findings show that fEVs cause sepsis-like systemic inflammation, when introduced intraperitoneally, a process regulated by TLR2 and TLR4.11Ysciescopu

Sensitization to molecular dog allergens in an adult population : Results from the West Sweden Asthma Study

Background: As the prevalence of dog allergy rises, component resolved diagnosis might improve the diagnosis, understanding of the clinical outcomes and the effectiveness of immunotherapy. Considering the paucity of data in adults, the current study characterized the patterns of sensitization to dog molecular allergens in an adult population. Methods: Data were derived from the West Sweden Asthma Study, a population-based and representative sample of adults from western Sweden. Of the 2006 subjects clinically examined, 313 participants sensitized to whole dog allergen extract were measured for specific immunoglobulin E (sIgE) levels to Can f 1, Can f 2, Can f 3, Can f 4, Can f 5 and Can f 6 using ImmunoCAP™. Polysensitization was defined as sensitization to ≥3 components. Overlapping sensitization was defined as having concomitant sensitization to at least two dog molecular allergen families (lipocalin, albumin or prostatic kallikrein). Results: Of 313, 218 (70%) subjects tested positive to at least one dog allergen component. Sensitization to Can f 1 (43%) was the most common, followed by Can f 5 (33%) among molecular allergens, while sensitization to lipocalins (56%) was the most common among component families. Polysensitization was found in 22% of all participants and was more common in participants with than in those without asthma. Subjects with asthma were less likely to be monosensitized to Can f 5 than those without asthma. Subjects with asthma had higher IgE levels of Can f 3, Can f 4 and Can f 6 than those without asthma. Overlapping sensitizations also differed between those with asthma and allergic rhinitis and those without. Conclusion: Increased knowledge about the sensitization patterns of dog allergen components can aid in defining their role in asthma and rhinitis. In complex clinical cases of dog allergy, a detailed analysis of dog allergen components can provide additional information on the nature of sensitization.publishedVersionPeer reviewe

Immunophenotyping of Circulating T Helper Cells Argues for Multiple Functions and Plasticity of T Cells In Vivo in Humans - Possible Role in Asthma

BACKGROUND: The immune process driving eosinophilic and non-eosinophilic asthma is likely driven by different subsets of T helper (Th) cells. Recently, in vitro studies and animal studies suggest that Th cell subsets displays plasticity by changing their transcription factor or by expressing multiple transcription factors. Our aim was to determine whether individuals with asthma and elevated circulating eosinophils express signs of different regulatory immune mechanisms compared with asthmatics with low blood eosinophils and non-asthmatic control subjects. In addition, determine the relationship between eosinophilia and circulating Th cell subsets. METHODOLOGY/PRINCIPAL FINDINGS: Participants were selected from a random epidemiological cohort, the West Sweden Asthma Study. Immunophenotypes of fresh peripheral blood cells obtained from stable asthmatics, with and without elevated eosinophilic inflammation (EOS high and EOS low respectively) and control subjects, were determined by flow cytometry. No differences in the number of Th1 (T-bet), Th2 (GATA-3), Th17 (RORγt) or Treg (FOXP3) cells were observed between the groups when analysing each subset separately. However, in all groups, each of the Th subsets showed expression of additional canonical transcription factors T-bet, GATA-3, RORγt and FOXP3. Furthermore, by in vitro stimulation with anti-CD3/anti-CD28 there was a significant increase of single expressing GATA-3(+) and co-expressing T-bet(+)GATA-3(+) cells in the EOS high asthmatics in comparison with control subjects. In addition, T-bet(-)GATA-3(+)RORγt(+)FOXP3(+) were decreased in comparison to the EOS low asthmatics. Finally, in a group of control subjects we found that the majority of proliferating Th cells (CD4(+)CD25(+)Ki67(+)) expressed three or four transcription factors. CONCLUSIONS: The ability of human Th cells to express several regulatory transcription factors suggests that these cells may display plasticity in vivo

Expansion of CD4+CD25+ and CD25- T-Bet, GATA-3, Foxp3 and RORγt Cells in Allergic Inflammation, Local Lung Distribution and Chemokine Gene Expression

Allergic asthma is associated with airway eosinophilia, which is regulated by different T-effector cells. T cells express transcription factors T-bet, GATA-3, RORγt and Foxp3, representing Th1, Th2, Th17 and Treg cells respectively. No study has directly determined the relative presence of each of these T cell subsets concomitantly in a model of allergic airway inflammation. In this study we determined the degree of expansion of these T cell subsets, in the lungs of allergen challenged mice. Cell proliferation was determined by incorporation of 5-bromo-2′-deoxyuridine (BrdU) together with 7-aminoactnomycin (7-AAD). The immunohistochemical localisation of T cells in the lung microenvironments was also quantified. Local expression of cytokines, chemokines and receptor genes was measured using real-time RT-PCR array analysis in tissue sections isolated by laser microdissection and pressure catapulting technology. Allergen exposure increased the numbers of T-bet+, GATA-3+, RORγt+ and Foxp3+ cells in CD4+CD25+ and CD4+CD25- T cells, with the greatest expansion of GATA-3+ cells. The majority of CD4+CD25+ T-bet+, GATA-3+, RORγt+ and Foxp3+ cells had incorporated BrdU and underwent proliferation during allergen exposure. Allergen exposure led to the accumulation of T-bet+, GATA-3+ and Foxp3+ cells in peribronchial and alveolar tissue, GATA-3+ and Foxp3+ cells in perivascular tissue, and RORγt+ cells in alveolar tissue. A total of 28 cytokines, chemokines and receptor genes were altered more than 3 fold upon allergen exposure, with expression of half of the genes claimed in all three microenvironments. Our study shows that allergen exposure affects all T effector cells in lung, with a dominant of Th2 cells, but with different local cell distribution, probably due to a distinguished local inflammatory milieu

Local and systemic mechanisms of allergen-induced airway inflammation

Allergic asthma is associated with pronounced inflammatory changes in the airways, including increased numbers of lymphocytes, neutrophils and mast cells, but most strikingly increased number of eosinophils. The accumulation of eosinophils within the airways in allergic airway inflammation is very likely a combination of increased production, migration and a prolonged survival of these cells. Eosinophils develop from CD34+ progenitor cells within the bone marrow (BM) and allergen challenge causes enhanced BM eosinophilopoiesis in asthmatic subjects as well as in animal models of allergen-induced airway inflammation. In addition, recent studies show that allergic subjects have increased number of CD34+ cells in BM and the airways.The aims of the present thesis were A) to determine which chemotactic factors govern the traffic of both the newly produced and the CD34+ eosinophils to the airways following allergen exposure, B) to establish whether or not the newly produced CD34+ eosinophilic cells have a capacity to proliferate locally within the airways following allergen exposure, and C) to evaluate the role of T lymphocytes in allergen-induced BM eosinophilopoiesis. In order to assess this, we used mouse models of allergen-induced airway inflammation. Wild type mice, IL-5 transgenic mice (NJ. 1638; CD3IL-5+) and mice deficient in CD4+ (CD4-/-) or CD8+ (CD8-/-) T cells were studied. Cells produced during the allergen exposure period were identified using a thymidine analogue, bromodeoxyuridine (BrdU). Local treatment with neutralizing anti-eotaxin-1 or anti-eotaxin-2 of allergen sensitized/exposed mice caused a significant reduction in newly produced and CD34+ BAL eosinophils. Significant airway concentrations of the neutralizing antibodies had to be achieved before a reduction in the number of allergen-induced airway eosinophils could be obtained. The expression of chemokine receptor 3 (CCR3) was upregulated on CD34+ BM cells leading to a significant increase of CD34+/CCR3+ eosinophil-lineage committed cells in BM, blood and BAL following allergen exposure. A fraction of the CD34+/CCR3+ cells proliferated in situ in response to allergen. In addition, in vitro colony formation of lung CD34+ cells was increased by IL-5 or eotaxin-2.Naïve crossbred CD3IL-5+/CD8-/- mice showed a significant reduction in the number of BM eosinophils when compared to naïve CD3IL-5+ or naïve crossbred CD3IL-5+/CD4-/- mice. Allergen exposed CD4-/- and CD8-/- mice had a significantly reduced number of BM and BAL eosinophils compared to wild type mice. Furthermore, a significant reduction in newly produced BM eosinophils (BrdU+/MBP+ cells) was found in both knockout strains when compared to allergen-challenged wild type mice. Eotaxin-2 levels in BALF of allergen-challenged CD4-/- mice were similar to saline exposed wild type mice.In conclusion, this thesis shows that the CCR3/eotaxin pathway is intricately involved in the regulation of allergen-driven in situ hematopoiesis and the accumulation/mobilization of CD34+ eosinophil-lineage committed cells in the lung. Allergen-induced BM eosinopilopoiesis is partly regulated by CD4+ and CD8+ T cells. In addition, CD4+ T cells may regulate IL-5 dependent eosinophil maturation in allergen-induced bone marrow eosinophilia. The subsequent traffic of eosinophils to the airways is likely to be at least partly regulated by CD4+ T cell dependent local airway eotaxin-2 production

The Airway Epithelium—A Central Player in Asthma Pathogenesis

Asthma is a chronic inflammatory airway disease characterized by variable airflow obstruction in response to a wide range of exogenous stimuli. The airway epithelium is the first line of defense and plays an important role in initiating host defense and controlling immune responses. Indeed, increasing evidence indicates a range of abnormalities in various aspects of epithelial barrier function in asthma. A central part of this impairment is a disruption of the airway epithelial layer, allowing inhaled substances to pass more easily into the submucosa where they may interact with immune cells. Furthermore, many of the identified susceptibility genes for asthma are expressed in the airway epithelium. This review focuses on the biology of the airway epithelium in health and its pathobiology in asthma. We will specifically discuss external triggers such as allergens, viruses and alarmins and the effect of type 2 inflammatory responses on airway epithelial function in asthma. We will also discuss epigenetic mechanisms responding to external stimuli on the level of transcriptional and posttranscriptional regulation of gene expression, as well the airway epithelium as a potential treatment target in asthma

MicroRNAs in asthma pathogenesis - from mouse to man

Asthma is a heterogenic disease affecting over 300 million people of all ages and socioeconomic status worldwide. The disease is characterized by chronic airway inflammation, reversible airflow obstruction, wheeze, cough and shortness of breath. Although asthma has been traditionally described by phenotypes such as immune cell type or allergy, it is clear that a variety of subtypes have emerged, adding further complexity to the disease. microRNAs are small, non-coding RNAs that act as regulatory molecules, binding to one or several target mRNAs, often resulting in translational silencing. In recent years, microRNAs have been the subject of many studies in order to better understand the mechanisms driving asthma development as well as discovery of potential biomarkers for asthma. In this review, we focus on the emerging role of microRNAs in asthma, from animal models to human cohorts

Repeated allergen exposure reduce early phase airway response and leukotriene release despite upregulation of 5-lipoxygenase pathways

<p>Abstract</p> <p>Background</p> <p>Allergen induced early phase airway response and airway plasma exudation are predominantly mediated by inflammatory mast cell mediators including histamine, cysteinyl leukotrienes (cysLTs) and thromboxane A2 (TXA2). The aim of the present study was to evaluate whether repeated allergen exposure affects early phase airway response to allergen challenge.</p> <p>Methods</p> <p>A trimellitic anhydride (TMA) sensitized guinea pig model was used to investigate the effects of low dose repeated allergen exposure on cholinergic airway responsiveness, early phase airway response and plasma exudation, as well as local airway production of mast cell derived cysteinyl leukotrienes and thromboxane B2 (TXB2) after allergen challenge.</p> <p>Results</p> <p>Repeated low dose allergen exposure increased cholinergic airway responsiveness. In contrast, early phase airway response and plasma exudation in response to a high-dose allergen challenge were strongly attenuated after repeated low dose allergen exposure. Inhibition of the airway response was unspecific to exposed allergen and independent of histamine receptor blocking. Furthermore, a significant reduction of cysteinyl leukotrienes and TXB2 was found in the airways of animals repeatedly exposed to a low dose allergen. However, in vitro stimulation of airway tissue from animals repeatedly exposed to a low dose allergen with arachidonic acid and calcium ionophore (A23187) induced production of cysteinyl leukotrienes and TXB2, suggesting enhanced activity of 5-lipoxygenase and cyclooxygenase pathways.</p> <p>Conclusions</p> <p>The inhibition of the early phase airway response, cysteinyl leukotriene and TXB2 production after repeated allergen exposure may result from unresponsive effector cells.</p