MicroRNA-155 is essential for T(H)2-mediated allergen-induced eosinophilic inflammation in the lung

MicroRNA Targets for Asthma Therapy

Asthma is a chronic inflammatory obstructive lung disease that is stratified into endotypes. Th2 high asthma is due to an imbalance of Th1/Th2 signaling leading to abnormally high levels of Th2 cytokines, IL-4, IL-5, and IL-13 and in some cases a reduction in type I interferons. Some asthmatics express Th2 low, Th1/Th17 high phenotypes with or without eosinophilia. Most asthmatics with Th2 high phenotype respond to beta-adrenergic agonists, muscarinic antagonists, and inhaled corticosteroids. However, 5-10% of asthmatics are not well controlled by these therapies despite significant advances in lung immunology and the pathogenesis of severe asthma. This problem is being addressed by developing novel classes of anti-inflammatory agents. Numerous studies have established efficacy of targeting pro-inflammatory microRNAs in mouse models of mild/moderate and severe asthma. Current approaches employ microRNA mimics and antagonists designed for use in vivo. Chemically modified oligonucleotides have enhanced stability in blood, increased cell permeability, and optimized target specificity. Delivery to lung tissue limits clinical applications, but it is a tractable problem. Future studies need to define the most effective microRNA targets and effective delivery systems. Successful oligonucleotide drug candidates must have adequate lung cell uptake, high target specificity, and efficacy with tolerable off-target effects.

The potency of lncRNA MALAT1/miR-155/CTLA4 axis in altering Th1/Th2 balance of asthma

Objectives: The present study examined if the metastasis-associated lung adenocarcinoma transcript 1 (MALAT1)/miR-155/CTLA-4 axis was involved in modifying Th1/Th2 balance, a critical indicator for asthma progression. Methods: Altogether 772 asthma patients and 441 healthy controls were recruited, and their blood samples were collected to determine expressional levels of MALAT1, miR-155, CTLA-4, T-bet, GATA3, Th1-type cytokines and Th2-type cytokines. The CD⁴⁺ T cells were administered with pcDNA3.1-MALAT1, si-MALAT1, miR-155 mimic and miR-155 inhibitor to assess their effects on cytokine release. The luciferase reporter gene assay was also adopted to evaluate the sponging relationships between MALAT1 and miR-155, as well as between miR-155 and CTLA-4. Results: Over-expressed MALAT1 and under-expressed miR-155 were more frequently detected among asthma patients who showed traits of reduced forced expiratory failure volume in 1 s (FEV1), FEV1/forced vital capacity (FVC) and FEV1% of predicted (P<0.05). Moreover, MALAT1 expression was negatively expressed with the Th1/Th2 and T-bet/GATA3 ratios, yet miR-155 expression displayed a positively correlation with the ratios (P<0.05). Additionally, the IFN-γ, IL-2 and T-bet levels were reduced under the influence of pcDNA3.1-MALAT1 and miR-155 inhibitor, while levels of IL-4, IL-10 and GATA3 were raised under identical settings (P<0.05). Furthermore, MALAT1 constrained expression of miR-155 within CD⁴⁺ T cells by sponging it, and CTLA-4 could interfere with the effects of MALAT1 and miR-155 on Th1/Th2 balance and T-bet/Gata3 ratio (P<0.05). Conclusion: MALAT1 sponging miR-155 was involved with regulation of Th1/Th2 balance within CD⁴⁺ T cells, which might aid to develop therapies for amelioration of asthmatic inflammation.

Understanding Asthma and Allergies by the Lens of Biodiversity and Epigenetic Changes

Exposure to different organisms (bacteria, mold, virus, protozoan, helminths, among others) can induce epigenetic changes affecting the modulation of immune responses and consequently increasing the susceptibility to inflammatory diseases. Epigenomic regulatory features are highly affected during embryonic development and are responsible for the expression or repression of different genes associated with cell development and targeting/conducting immune responses. The well-known, "window of opportunity" that includes maternal and post-natal environmental exposures, which include maternal infections, microbiota, diet, drugs, and pollutant exposures are of fundamental importance to immune modulation and these events are almost always accompanied by epigenetic changes. Recently, it has been shown that these alterations could be involved in both risk and protection of allergic diseases through mechanisms, such as DNA methylation and histone modifications, which can enhance Th2 responses and maintain memory Th2 cells or decrease Treg cells differentiation. In addition, epigenetic changes may differ according to the microbial agent involved and may even influence different asthma or allergy phenotypes. In this review, we discuss how exposure to different organisms, including bacteria, viruses, and helminths can lead to epigenetic modulations and how this correlates with allergic diseases considering different genetic backgrounds of several ancestral populations.

In vivo therapeutic success of MicroRNA-155 antagomir in a mouse model of pulmonary fibrosis induced by bleomycin

BACKGROUND/AIMS

MicroRNAs (miRNAs) play critical regulatory roles in the pathogenesis of pulmonary fibrosis. The aim of this study was to explore whether miRNA antagomirs could serve as potential therapeutic agents in interstitial lung diseases.

METHODS

A mouse model of pulmonary fibrosis was established by intratracheal injection of bleomycin (BLM). Using microarray analysis, up-regulated miRNAs were identified during the development of pulmonary fibrosis. miR-155 was chosen as the candidate miRNA. Fifteen mice were then randomized into the following three groups: BLM + antagomiR-155 group, treated with BLM plus intravenously injected with antagomiR-155; BLM group, treated with intratracheal BLM plus phosphate-buffered saline (PBS); and a control group, treated with PBS only. Lung tissues were collected for histopathological analysis, hydroxyproline measurement, and Western blotting. Enzyme-linked immunosorbent assays were used for the measurement of cytokines associated with pulmonary fibrosis.

RESULTS

Histological changes and hydroxyproline levels induced by BLM were significantly inhibited by antagomiR-155. The levels of interleukin 4 (IL-4) and transforming growth factor-β (TGF-β) expression were increased after BLM treatment. However, miR-155 silencing decreased the expression of IL-4, TGF-β, and interferon-γ. TGF-β-activated kinase 1/mitogen-activated protein kinase kinase kinase 7 (MAP3K7)-binding protein 2 (TAB2) of the mitogen-activated protein kinase (MAPK) signaling pathway, was activated by BLM and inhibited by in vivo silencing of miR-155 via antagomiR-155.

CONCLUSION

In vivo treatment with antagomiR-155 alleviated the pathological changes induced by BLM and may be a promising therapeutic strategy for pulmonary fibrosis.

Role of microRNA-21 and microRNA-155 as biomarkers for bronchial asthma

MicroRNA (miRNA)-21 and miRNA-155 are important regulators of gene expression of different immunological molecules. This study aimed to investigate the role of miRNA-21 and miRNA-155 as biomarkers in asthma by comparing their serum expression levels in asthmatic patients to those in healthy controls and correlating their levels with serum IL-4. The expression levels of miRNA-21 and miRNA-155 were evaluated by quantitative RT-PCR. Serum levels of IL-4 were determined using ELISA. Asthmatic patients showed significantly higher serum miRNA-21 and miRNA-155 expression levels compared to controls. A statistically significant positive correlation between the expression levels of miRNA-21 and IL-4 serum levels in asthmatic patients was detected. Nonetheless, no correlation was detected between miRNA-155 expression and each of IL-4 and miRNA-21. A receiver operating characteristic curve analysis showed that at a cut-off value of 1.37, the sensitivity of miRNA-21 as an asthma biomarker was 100% and the specificity was 95%. At a cut-off value of 1.96, the sensitivity of miRNA-155 as an asthma biomarker was 100% and the specificity was 100%. It can be concluded that miRNA-21 and miRNA-155 are potential non-invasive biomarkers in the diagnosis of eosinophilic asthma and its response to therapy.

Inhibition of miR-99a-5p prevents allergen-driven airway exacerbations without compromising type-2 memory responses in the intestine following helminth infection

Acute exacerbations (AE) of asthma, remain one of the biggest concerns for patients living with asthma. As such, identifying the causes, the molecular mechanisms involved and new therapeutic interventions to prevent AE is a high priority. Immunity to intestinal helminths involves the reactivation of type-2 immune responses leading to smooth muscle contraction and mucus hypersecretion-physiological processes very similar to acute exacerbations in the airways following allergen exposure. In this study, we employed a murine model of intestinal helminth infection, using Heligmosomoides polygyrus, to identify miRNAs during active expulsion, as a system for the identification of miRNAs that may contribute to AE in the airways. Concomitant with type-2 immunity and expulsion of H. polygyrus, we identified miR-99a-5p, miR-148a-3p and miR-155-5p that were differentially regulated. Systemic inhibition of these miRNAs, alone or in combination, had minimal impact on expulsion of H. polygyrus, but inhibition of miR-99a-5p or miR-155-5p significantly reduced house dust mite (HDM)-driven acute inflammation, modelling human acute exacerbations. Immunological, pathological and transcriptional analysis identified that miR-155-5p or miR-99a-5p contribute significantly to HDM-driven AE and that transient inhibition of these miRNAs may provide relief from allergen-driven AE, without compromising anti-helminth immunity in the gut.

A comprehensive analysis of microRNAs as diagnostic biomarkers for asthma

Background:

It is unclear whether microRNAs could be a potential diagnostic biomarker for asthma or not. The objective of this study is to figure out the diagnostic value of microRNAs in asthma.

Methods:

Literature retrieval, screening of publications, specific data extraction, and quality evaluation were conducted according to the standard criteria. Stata 14.0 software was used to analyze the diagnostic value of microRNA for asthma, including the combined sensitivity (Sen), specificity (Spe), the area under the curve (AUC), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR).

Results:

A total of 72 studies, containing 4143 cases and 2188 controls, were included for this comprehensive analysis. None of the included publications were rated low in quality. We summarized that, compared with controls, more than 100 miRNAs were reported differently expressed in asthma, although the expression trends were inconsistent. Besides, there were five studies among these 72 articles that applied the diagnostic evaluation of microRNAs in asthma. We found that the pooled Sen, Spe, and AUC for the combination of miR-185-5p, miR-155, let-7a, miR-21, miR-320a, miR-1246, miR-144-5p, and miR-1165-3p in asthma were 0.87 (95%CI: 0.72–0.95), 0.84 (95%CI: 0.74–0.91), and 0.93 (95%CI: 0.89–0.94) individually, and the PLR, NLR, and DOR were 5.5 (95%CI: 3.1–9.7), 0.15 (95%CI: 0.07–0.36), and 35 (95%CI: 10–127) in asthma, respectively. In terms of subgroup analyses, we found that the Sen for these combination miRNAs from serum was higher than that in plasma, while the Spe in plasma worked better than that in serum. Furthermore, compared with children, the combination of above miRNAs from adults had higher Spe and similar Sen.

Conclusions:

From our analysis, the combination of miR-185-5p, miR-155, let-7a, miR-21, miR-320a, miR-1246, miR-144-5p, and miR-1165-3p from peripheral blood could potentially act as a diagnostic biomarker for asthma.

The reviews of this paper are available via the supplemental material section.

Downregulation of miRNA-451a Promotes the Differentiation of CD4+ T Cells towards Th2 Cells by Upregulating ETS1 in Childhood Asthma

Children exposed to common aeroallergens may develop asthma that progresses into adulthood. Inflammation regulated by T helper 2 (Th2) cells, a specific subpopulation of CD4+ T lymphocytes, is involved in asthmatic injury. Herein, our microarray data indicated that microRNA-451a-5p (miRNA-451a) expression decreased by 4.6-fold and ETS proto-oncogene 1 (ETS1) increased by 2.2-fold in the peripheral blood lymphocytes isolated from asthmatic children (n = 4) as compared to control individuals (n = 4). The negative correlation between miRNA-451a and ETS1 was further validated in 40 CD4+ T cell samples (10 healthy vs. 30 asthmatic samples). In vitro, naïve CD4+ T cells isolated from control individuals were cultured under Th2 cell polarizing condition. miRNA-451a expression decreased while ETS1 increased in CD4+ T cells in the setting of Th2 cell polarization. Moreover, miRNA-451a knockdown enhanced Th2 cell polarization - cells positive for both GATA3 (GATA binding protein 3, a Th2-transcription factor) and CD4 increased, and the generation of Th2 cell cytokines, interleukin (IL)5 and IL13, increased. In contrast, miRNA-451a overexpression inhibited Th2 cell differentiation. Interestingly, dual-Luciferase assay proved ETS1 as a novel target of miRNA-451a. Moreover, enforced expression of ETS1 partially restored miRNA-451a-induced inhibition of IL5 and IL13, and increased the GATA3+CD4+ cell population. Collectively, our work demonstrates that downregulation of miRNA-451a upregulates ETS1 expression in CD4+ T cells, which may contribute to Th2 cell differentiation in pediatric asthma.

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.

Innate lymphoid cells in isocyanate-induced asthma: role of microRNA-155

BACKGROUND

Occupational asthma, induced by workplace exposures to low molecular weight agents such as toluene 2,4-diisocyanate (TDI), causes a significant burden to patients and society. Little is known about innate lymphoid cells (ILCs) in TDI-induced asthma. A critical regulator of ILC function is microRNA-155, a microRNA associated with asthma.

OBJECTIVE

To determine whether TDI exposure modifies the number of ILCs in the lung and whether microRNA-155 contributes to TDI-induced airway inflammation and hyperresponsiveness.

METHODS

C57BL/6 wild-type and microRNA-155 knockout mice were sensitised and challenged with TDI or vehicle. Intracellular cytokine expression in ILCs and T-cells was evaluated in bronchoalveolar lavage (BAL) fluid using flow cytometry. Peribronchial eosinophilia and goblet cells were evaluated on lung tissue, and airway hyperresponsiveness was measured using the forced oscillation technique. Putative type 2 ILCs (ILC2) were identified in bronchial biopsies of subjects with TDI-induced occupational asthma using immunohistochemistry. Human bronchial epithelial cells were exposed to TDI or vehicle.

RESULTS

TDI-exposed mice had higher numbers of airway goblet cells, BAL eosinophils, CD4⁺ T-cells and ILCs, with a predominant type 2 response, and tended to have airway hyperresponsiveness. In TDI-exposed microRNA-155 knockout mice, inflammation and airway hyperresponsiveness were attenuated. TDI exposure induced IL-33 expression in human bronchial epithelial cells and in murine lungs, which was microRNA-155 dependent in mice. GATA3⁺CD3^- cells, presumably ILC2, were present in bronchial biopsies.

CONCLUSION

TDI exposure is associated with increased numbers of ILCs. The proinflammatory microRNA-155 is crucial in a murine model of TDI asthma, suggesting its involvement in the pathogenesis of occupational asthma due to low molecular weight agents.

An endothelial microRNA-1-regulated network controls eosinophil trafficking in asthma and chronic rhinosinusitis

BACKGROUND

Airway eosinophilia is a prominent feature of asthma and chronic rhinosinusitis (CRS), and the endothelium plays a key role in eosinophil trafficking. To date, microRNA-1 (miR-1) is the only microRNA known to be regulated in the lung endothelium in asthma models.

OBJECTIVE

We sought to determine the role of endothelial miR-1 in allergic airway inflammation.

METHODS

We measured microRNA and mRNA expression using quantitative RT-PCR. We used ovalbumin and house dust mite models of asthma. Endothelium-specific overexpression of miR-1 was achieved through lentiviral vector delivery or induction of a transgene. Tissue eosinophilia was quantified by using Congo red and anti-eosinophil peroxidase staining. We measured eosinophil binding with a Sykes-Moore adhesion chamber. Target recruitment to RNA-induced silencing complex was assessed by using anti-Argonaute2 RNA immunoprecipitation. Surface P-selectin levels were measured by using flow cytometry.

RESULTS

Serum miR-1 levels had inverse correlations with sputum eosinophilia, airway obstruction, and number of hospitalizations in asthmatic patients and sinonasal tissue eosinophilia in patients with CRS. IL-13 stimulation decreased miR-1 levels in human lung endothelium. Endothelium-specific overexpression of miR-1 reduced airway eosinophilia and asthma phenotypes in murine models and inhibited IL-13-induced eosinophil binding to endothelial cells. miR-1 recruited P-selectin, thymic stromal lymphopoietin, eotaxin-3, and thrombopoietin receptor to the RNA-induced silencing complex; downregulated these genes in the lung endothelium; and reduced surface P-selectin levels in IL-13-stimulated endothelial cells. In our asthma and CRS cohorts, miR-1 levels correlated inversely with its target genes.

CONCLUSION

Endothelial miR-1 regulates eosinophil trafficking in the setting of allergic airway inflammation. miR-1 has therapeutic potential in asthmatic patients and patients with CRS.

Upregulation of miR-155 regulates group 2 innate lymphoid cells by targeting c-maf in allergic rhinitis

Group 2 innate lymphoid cells (ILC2s) and Th2 type immune response are critically involved in the pathogenesis of allergic rhinitis (AR), and this pathological process is influenced by microRNAs-mediated post-transcriptional regulation. The present study investigated the adaptation and function of miR-155 in AR patients and mouse model. We found that significantly increased miR-155 expression (1.63 ± 0.12 vs. 0.92 ± 0.11 in human, and 1.68 ± 0.15 vs. 1.06 ± 0.06 in mice) and ILC2s activity in nasal mucosa and serum in AR patients and mice. Administration of miR-155 antagomir significantly reduced the activity of ILC2s in nasal mucosa, suppressed the production of Th2 cytokines in serum and nasal mucosa, and alleviated the airway inflammation and allergic symptoms in AR mice, while miR-155 agomir increased ILC2s activity and production of Th2 cytokines and induced airway inflammation and allergic symptoms in control mice. Meanwhile, the expression of transcriptional factor c-Maf (0.57 ± 0.05 vs. 0.37 ± 0.04) in nasal mucosa in AR mice, which was significantly recovered by miR-155 antagomir (0.56 ± 0.04). Treatment with miR-155 agomir decreased c-Maf expression in nasal mucosa in control mice. This synchronized with the similar pattern in the current observations that miR-155 regulated Th2 cytokine (IL-4, IL-5, IL-9 and IL-13) production, airway inflammation and allergic symptoms in AR mice. Together, upregulation miR-155 suppressed the expression of transcriptional factor c-Maf and was critically involved in the ILC2s activation, which contributed to the airway inflammation and allergic symptoms in AR.

Genetic control of CCL24, POR, and IL23R contributes to the pathogenesis of sarcoidosis

Sarcoidosis is a genetically complex systemic inflammatory disease that affects multiple organs. We present a GWAS of a Japanese cohort (700 sarcoidosis cases and 886 controls) with replication in independent samples from Japan (931 cases and 1,042 controls) and the Czech Republic (265 cases and 264 controls). We identified three loci outside the HLA complex, CCL24, STYXL1-SRRM3, and C1orf141-IL23R, which showed genome-wide significant associations (P < 5.0 × 10⁻⁸) with sarcoidosis; CCL24 and STYXL1-SRRM3 were novel. The disease-risk alleles in CCL24 and IL23R were associated with reduced CCL24 and IL23R expression, respectively. The disease-risk allele in STYXL1-SRRM3 was associated with elevated POR expression. These results suggest that genetic control of CCL24, POR, and IL23R expression contribute to the pathogenesis of sarcoidosis. We speculate that the CCL24 risk allele might be involved in a polarized Th1 response in sarcoidosis, and that POR and IL23R risk alleles may lead to diminished host defense against sarcoidosis pathogens.

Akira Meguro et al. report a genome-wide association study for sarcoidosis—a systemic inflammatory disease—in the Japanese population. They identify 3 non-HLA loci with genome-wide significance, 2 of which have not been previously associated with sarcoidosis in any population.

Circulating MicroRNAs and Treatment Response in Childhood Asthma

Rationale: Inhaled corticosteroids (ICS) are key treatments for controlling asthma and preventing asthma attacks. However, the responsiveness to ICS varies among individuals. MicroRNAs (miRNAs) have been lauded for their prognostic utility.Objectives: We hypothesized that circulating miRNAs obtained at baseline/prerandomization in the Childhood Asthma Management Program (CAMP) could serve as biomarkers and biologic mediators of ICS clinical response over the 4-year clinical trial period.Methods: We selected baseline serum samples from 462 CAMP subjects subsequently randomized to either ICS (budesonide) or placebo. Samples underwent small RNA sequencing, and read counts were normalized and filtered by depth and coverage. Linear regression was used to associate miRNAs with change in FEV1% (prebronchodilator FEV1 as a percent predicted) over the 4-year treatment period in both main effects and interaction models. We validated the function of the top associated miRNAs by luciferase reporter assays of glucocorticoid-mediated transrepression and predicted response to ICS through logistic regression models.Measurements and Main Results: We identified 7 miRNAs significantly associated with FEV1% change (P ≤ 0.05) and 15 miRNAs with significant interaction (P ≤ 0.05) to ICS versus placebo treatments. We selected three miRNAs for functional validation, of which hsa-miR-155-5p and hsa-miR-532-5p were significantly associated with changes in dexamethasone-induced transrepression of NF-κB. Combined, these two miRNAs were predictive of ICS response over the course of the clinical trial, with an area under the receiver operating characteristic curve of 0.86.Conclusions: We identified two functional circulating miRNAs predictive of asthma ICS treatment response over time.

A Network of Sputum MicroRNAs Is Associated with Neutrophilic Airway Inflammation in Asthma

Rationale: MicroRNAs are potent regulators of biologic systems that are critical to tissue homeostasis. Individual microRNAs have been identified in airway samples. However, a systems analysis of the microRNA-mRNA networks present in the sputum that contribute to airway inflammation in asthma has not been published.Objectives: Identify microRNA and mRNA networks in the sputum of patients with asthma.Methods: We conducted a genome-wide analysis of microRNA and mRNA in the sputum from patients with asthma and correlated expression with clinical phenotypes. Weighted gene correlation network analysis was implemented to identify microRNA networks (modules) that significantly correlate with clinical features of asthma and mRNA expression networks. MicroRNA expression in peripheral blood neutrophils and lymphocytes and in situ hybridization of the sputum were used to identify the cellular sources of microRNAs. MicroRNA expression obtained before and after ozone exposure was also used to identify changes associated with neutrophil counts in the airway.Measurements and Main Results: Six microRNA modules were associated with clinical features of asthma. A single module (nely) was associated with a history of hospitalizations, lung function impairment, and numbers of neutrophils and lymphocytes in the sputum. Of the 12 microRNAs in the nely module, hsa-miR-223-3p was the highest expressed microRNA in neutrophils and was associated with increased neutrophil counts in the sputum in response to ozone exposure. Multiple microRNAs in the nely module correlated with two mRNA modules enriched for TLR (Toll-like receptor) and T-helper cell type 17 (Th17) signaling and endoplasmic reticulum stress. hsa-miR-223-3p was a key regulator of the TLR and Th17 pathways in the sputum of subjects with asthma.Conclusions: This study of sputum microRNA and mRNA expression from patients with asthma demonstrates the existence of microRNA networks and genes that are associated with features of asthma severity. Among these, hsa-miR-223-3p, a neutrophil-derived microRNA, regulates TLR/Th17 signaling and endoplasmic reticulum stress.

MicroRNAs in chronic airway diseases: Clinical correlation and translational applications

MicroRNAs (miRNAs) are short single-stranded RNAs that have pivotal roles in disease pathophysiology through transcriptional and translational modulation of important genes. It has been implicated in the development of many diseases, such as stroke, cardiovascular conditions, cancers and inflammatory airway diseases. There is recent evidence that miRNAs play important roles in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD), and could help to distinguish between T2-low (non-eosinophilic, steroid-insensitive) versus T2-high (eosinophilic, steroid-sensitive) disease endotypes. As these are the two most prevalent chronic respiratory diseases globally, with rising disease burden, miRNA research might lead to the development of new diagnostic and therapeutic targets. Research involving miRNAs in airway disease is challenging because: (i) asthma and COPD are heterogeneous inflammatory airway diseases; there are overlapping but distinct inter- and intra-disease differences in the immunological pathophysiology, (ii) there exists more than 2000 known miRNAs and a single miRNA can regulate multiple targets, (iii) differential effects of miRNAs could be present in different cellular subtypes and tissues, and (iv) dysregulated miRNA expression might be a direct consequence of an indirect effect of airway disease onset or progression. As miRNAs are actively secreted in fluids and remain relatively stable, they have the potential for biomarker development and therapeutic targets. In this review, we summarize the preclinical data on potential miRNA biomarkers that mediate different pathophysiological mechanisms in airway disease. We discuss the framework for biomarker development using miRNA and highlight the need for careful patient characterization and endotyping in the screening and validation cohorts, profiling both airway and blood samples to determine the biological fluids of choice in different disease states or severity, and adopting an untargeted approach. Collaboration between the various stakeholders - pharmaceutical companies, laboratory professionals and clinician-scientists is crucial to reduce the difficulties and cost required to bring miRNA research into the translational stage for airway diseases.

Emerging role of extracellular vesicles in the respiratory system

Extracellular vesicles (EVs) present numerous biomedical ways of studying disease and pathology. They function as protective packaging for the delivery of controlled concentrations of miRNAs and effector molecules, including cytokines, chemokines, genetic material, and small signaling molecules. Previous studies of EVs have yielded valuable insights into pathways of intercellular communication that affect a variety of biological processes and disease responses. The roles of EVs, specifically microRNA-containing EVs (EV-miRNAs), in either mitigating or exacerbating pulmonary disease symptoms are numerous and show promise in helping us understand pulmonary disease pathology. Because of their well-documented involvement in pulmonary diseases, EVs show promise both as possible diagnostic biomarkers and as therapeutic agents. This review surveys the physiological functions of EVs in the respiratory system and outlines the pulmonary disease states in which EVs are involved in intercellular crosstalk. This review also discusses the potential clinical applications of EV-miRNAs in pulmonary diseases.

Studies of tiny membrane-bound sacs called extracellular vesicles (EVs), which bud from cells naturally but are also implicated in disease, offer insights into respiratory health and disease, and could be used to deliver therapies into respiratory system cells. Joshua Holtzman at Oberlin College, Ohio, USA, and Heedoo Lee at Changwon National University in South Korea review current understanding of the role of EVs in the respiratory system and their potential uses in treatment. Researchers are discovering how EVs deliver signaling molecules to promote respiratory health, and how they can be involved in cancer, autoimmunity, asthma and other diseases. Early trials using EVs to deliver conventional drugs, and small RNA molecules that can control gene activity suggest great potential for treating a range of serious respiratory conditions. Analysis of EVs may also assist in diagnosis.

miR-30a-3p participates in the development of asthma by targeting CCR3

This study aimed to investigate the role and relevant mechanism of miR-30a-3p action in asthma. The results of this study revealed that the expression levels of miR-30a-3p were significantly decreased in the peripheral blood of asthmatic patients. In addition, we found that the CC chemokine receptor (CCR3) was a target of miR-30a-3p. Subsequently, an asthma mouse model was established using ovalbumin (OVA). The results showed that the expression of miR-30a-3p and CCR3 was downregulated and upregulated, respectively, in the peripheral blood of asthmatic mice. Enzyme-linked immunosorbent assay (ELISA) in asthmatic mouse serum demonstrated that miR-30a-3p mimic treatment significantly decreased the secretion of OVA-specific IgE, eotaxin-1, interleukin (IL)-5, and IL-4. These results suggested that miR-30a-3p inhibited CCR3 signaling pathway and relieved the inflammatory response against asthma in vivo. Eosinophils have also been implicated in the asthmatic inflammatory response. Therefore, the in vitro effects of miR-30a-3p on eosinophil activity were determined. Findings suggested that miR-30a-3p mimic significantly reduced eosinophil viability and migration and induced apoptosis. In addition, CCR3 and eotaxin-1 downregulation were observed. The aforementioned results were significantly reversed following CCR3 overexpression. This study suggested that miR-30a-3p was involved in asthma by regulating eosinophil activity and targeting CCR3.

miR-155 indicates the fate of CD4+ T cells

MicroRNAs (miRNAs) are a class of short noncoding RNAs that regulate the translation of target messenger RNA (mRNA) and consequently participate in a variety of biological processes at the posttranscriptional level. miR-155, encoded within a region known as the B cell integration cluster (BIC), plays multifunctional roles in shaping lymphocytes ranging from biological development to adaptive immunity. It has been revealed that miR-155 plays a key role in fine-tuning the regulation of lymphocyte subsets, including dendritic cells (DCs), macrophages, B cells, and CD8⁺ and CD4⁺ T cells. Antigen-specific CD4⁺ T lymphocytes are critical for host defense against pathogens and prevention of damage resulting from excessive inflammation. Over the past years, various studies have shown that miR-155 plays a critical role in CD4⁺ T cells function. Therefore, we summarize multiple target genes of miR-155 that regulate aspects of CD4⁺ T cells immunity, particularly CD4⁺ T cells differentiation, in this review. In addition, we also focus on the role of miR-155 in the regulation of immunological diseases, suggesting it as a potential disease biomarker and therapeutic target.

Airway mir-155 responses are associated with TH1 cytokine polarization in young children with viral respiratory infections

BACKGROUND

MicroRNAs (miRs) control gene expression and the development of the immune system and antiviral responses. MiR-155 is an evolutionarily-conserved molecule consistently induced during viral infections in different cell systems. Notably, there is still an unresolved paradox for the role of miR-155 during viral respiratory infections. Despite being essential for host antiviral TH1 immunity, miR-155 may also contribute to respiratory disease by enhancing allergic TH2 responses and NFkB-mediated inflammation. The central goal of this study was to define how airway miR-155 production is related to TH1, TH2, and pro-inflammatory cytokine responses during naturally occurring viral respiratory infections in young children.

METHODS

Normalized nasal airway levels of miR-155 and nasal protein levels of IFN-γ, TNF-α, IL-1β, IL-13, IL-4 were quantified in young children (≤2 years) hospitalized with viral respiratory infections and uninfected controls. These data were linked to individual characteristics and respiratory disease parameters.

RESULTS

A total of 151 subjects were included. Increased miR-155 levels were observed in nasal samples from patients with rhinovirus, RSV and all respiratory viruses analyzed. High miR-155 levels were strongly associated with high IFN-γ production, increased airway TH1 cytokine polarization (IFN-γ/IL-4 ratios) and increased pro-inflammatory responses. High airway miR-155 levels were linked to decreased respiratory disease severity in individuals with high airway TH1 antiviral responses.

CONCLUSIONS

The airway secretion of miR-155 during viral respiratory infections in young children is associated with enhanced antiviral immunity (TH1 polarization). Further studies are needed to define additional physiological roles of miR-155 in the respiratory tract of human infants and young children during health and disease.

Circulating microRNAs correlate to clinical parameters in individuals with allergic and non-allergic asthma

BACKGROUND

Asthma is a chronic airway disease affecting millions of people. Better methods to define asthma subgroups using clinical parameters and molecular biomarkers are crucial in the development of personalized medicine.

OBJECTIVE

The aim of this study was to determine if circulating microRNAs (miRNAs) may be used to distinguish well-defined asthma groups.

METHODS

Blood serum from 116 well-defined subjects, including healthy controls and individuals with allergic or non-allergic asthma, from the West Sweden Asthma Study were included. Serum was analyzed for circulating miRNA expression of miR-126, - 145, -146a, - 155, - 223, and -374a and eosinophil cationic protein (ECP). Correlations between clinical characteristics and circulating miRNA expression as well as potential miRNA gene targets were investigated.

RESULTS

A subset of miRNAs were differentially expressed between allergic and non-allergic asthmatic individuals. Alterations in expression of miR-155, -146a, -374a and - 145 were observed in allergic asthmatics in response to inhaled corticosteroid usage. Additionally, miR-223 and miR-374a expression varied in non-allergic asthmatics based on blood eosinophil numbers. Numerous clinical parameters, including lung function measurements, correlated with subsets of miRNAs. Finally, pathway analysis revealed a potential role for inhaled corticosteroid induced miRNAs in leukocyte regulation, IL-6 signaling and glucocorticoid response.

CONCLUSION

Circulating miRNA expression was altered in subjects with allergic and non-allergic asthma and correlated to clinical parameters including lung function and potential gene targets involved in immune processes. This combination of clinical and molecular data may be a basis for the further, more precise classification of asthma subgroups. Taken together, these findings would further asthma research and benefit future patients through the discovery of molecular mechanisms as well as identifying asthma subgroups contributing to the development of personalized medicine.

The role of miR-155 in cigarette smoke-induced pulmonary inflammation and COPD

Chronic obstructive pulmonary disease (COPD) is a highly prevalent respiratory disease characterized by airflow limitation and chronic inflammation. MiR-155 is described as an ancient regulator of the immune system. Our objective was to establish a role for miR-155 in cigarette smoke (CS)-induced inflammation and COPD. We demonstrate increased miR-155 expression by RT-qPCR in lung tissue of smokers without airflow limitation and patients with COPD compared to never smokers and in lung tissue and alveolar macrophages of CS-exposed mice compared to air-exposed mice. In addition, we exposed wild type and miR-155 deficient mice to CS and show an attenuated inflammatory profile in the latter. Alveolar macrophages were sorted by FACS from the different experimental groups and their gene expression profile was analyzed by RNA sequencing. This analysis revealed increased expression of miR-155 targets and an attenuation of the CS-induced increase in inflammation-related genes in miR-155 deficient mice. Moreover, intranasal instillation of a specific miR-155 inhibitor attenuated the CS-induced pulmonary inflammation in mice. Finally, elastase-induced emphysema and lung functional changes were significantly attenuated in miR-155 deficient mice. In conclusion, we highlight a role for miR-155 in CS-induced inflammation and the pathogenesis of COPD, implicating miR-155 as a new therapeutic target in COPD.

Depletion of microRNA-451 in response to allergen exposure accentuates asthmatic inflammation by regulating Sirtuin2

The incidence of asthma has increased from 5.5% to near 8% of the population, which is a major health concern. The hallmarks of asthma include eosinophilic airway inflammation that is associated with chronic airway remodeling. Allergic airway inflammation is characterized by a complex interplay of resident and inflammatory cells. MicroRNAs (miRNAs) are small noncoding RNAs that function as posttranscriptional modulators of gene expression. However, the role of miRNAs, specifically miR-451, in the regulation of allergic airway inflammation is unexplored. Our previous findings showed that oxidant stress regulates miR-451 gene expression in macrophages during an inflammatory process. In this paper, we examined the role of miR-451 in regulating macrophage phenotype using an experimental poly-allergenic murine model of allergic airway inflammation. We found that miR-451 contributes to the allergic induction of CCL17 in the lung and plays a key role in proasthmatic macrophage activation. Remarkably, administration of a Sirtuin 2 (Sirt2) inhibitor diminished alternate macrophage activation and markedly abrogated triple-allergen [dust mite, ragweed, Aspergillus fumigatus (DRA)]-induced lung inflammation. These data demonstrate a role for miR-451 in modulating allergic inflammation by influencing allergen-mediated macrophages phenotype.

DsRNA induction of microRNA-155 disrupt tight junction barrier by modulating claudins

Background

The impaired barrier function of the airway epithelium due to RNA virus infection is closely related to the development and exacerbation of allergic airway inflammation.

Objective

In this study, we investigated the roles of microRNAs on the mechanisms of double-stranded RNA (dsRNA)-induced epithelial barrier dysfunction.

Methods

16HBE14o- human bronchial epithelial cells were grown to confluence on Transwell inserts and exposed to poly-I:C. We studied epithelial barrier function by measuring transepithelial electrical resistance and paracellular flux of fluorescent markers and structure of tight junctions by immunofluorescence microscopy.

Results

Poly-I:C treated 16HBE14o- cells increased paracellular permeability. Knockdown of Toll-like receptor 3 and TRIF abrogated these effects. The expression of microRNA-155 (miR-155) was increased by poly-I:C in dose-dependent manner. Transfection of mir155 mimics into 16HBE14o- cells increased permeability and inhibited tight junction formation. Transfection of miR-155 inhibitor suppressed poly-I:C-induced barrier disruption. Poly-I:C treatment significantly decreased the expression of claudin members—claudin-1, -3, -4, -5, -9, -11, -16, -18 and -19. Transfection of miR-155 mimics showed similar changing expression pattern of claudin members with those of poly-I:C treatment.

Conclusion

These results suggest that RNA virus infection can impair the epithelial barrier disruption mechanism by down-regulation of claudin members through the induction of miR-155.

Dysregulated CD4+ T Cells and microRNAs in Myocarditis

Myocarditis is a polymorphic disease complicated with indeterminate etiology and pathogenesis, and represents one of the most challenging clinical problems lacking specific diagnosis and effective therapy. It is caused by a complex interplay of environmental and genetic factors, and causal links between dysregulated microribonucleic acids (miRNAs) and myocarditis have also been supported by recent epigenetic researches. Both dysregulated CD4+ T cells and miRNAs play critical roles in the pathogenesis of myocarditis, and the classic triphasic model of its pathogenesis consists of the acute infectious, subacute immune, and recovery/chronic myopathic phase. CD4+ T cells are key pathogenic factors underlying the development and progression of myocarditis, and the effector and regulatory subsets, respectively, promote and inhibit autoimmune responses. Furthermore, the reciprocal interplay of these subsets influences the pathogenesis as well. Dysregulated miRNAs along with their mRNA and protein targets have been identified in heart biopsies (intracellular miRNAs) and body fluids (circulating miRNAs) during myocarditis. These miRNAs show phase-dependent changes, and correlate with viral infection, immune status, fibrosis, destruction of cardiomyocytes, arrhythmias, cardiac functions, and outcomes. Thus, miRNAs are promising diagnostic markers and therapeutic targets in myocarditis. In this review, we review myocarditis with an emphasis on its pathogenesis, and present a summary of current knowledge of dysregulated CD4+ T cells and miRNAs in myocarditis.

MicroRNA-155 Participates in Smoke-Inhalation-Induced Acute Lung Injury through Inhibition of SOCS-1

Smoke inhalation causes acute lung injury (ALI), a severe clinical disease with high mortality. Accumulating evidence indicates that microRNA-155 (miR-155) and suppressor of cytokine signaling 1 (SOCS-1), as mediators of inflammatory response, are involved in the pathogenesis of ALI. In this paper, we explored the proinflammatory mechanism of miR-155 in smoke-inhalation-induced ALI. Our data revealed that smoke inhalation induces miR-155 expression, and miR-155 knockout (KO) significantly ameliorates smoke-inhalation-induced lung injury in mice. Neutrophil infiltration and myeloperoxidase (MPO), macrophage inflammatory protein 2 (MIP-2) and keratinocyte chemoattractant (KC) expressions were decreased in miR-155^–/– mice after smoke inhalation as well. Real-time RT-PCR and immunoblotting results showed that SOCS-1 level was remarkably increased in miR-155^–/– mice after smoke exposure. Furthermore, the experiments performed in isolated miR-155 KO pulmonary neutrophils demonstrated that the lack of SOCS-1 enhanced inflammatory cytokines (MIP-2 and KC) secretion in response to smoke stimulation. In conclusion, smoke induces increased expression of miR-155, and miR-155 is involved in inflammatory response to smoke-inhalation-induced lung injury by inhibiting the expression of SOCS-1.

The impact of microRNAs on alterations of gene regulatory networks in allergic diseases

Allergic diseases including asthma are worldwide on the rise and contribute significantly to health expenditures. Allergic diseases are prototypic diseases with a strong gene by environment interaction component and epigenetic mechanisms might mediate the effects of the environment on the disease phenotype. MicroRNAs, small non-coding RNAs (miRNAs), regulate gene expression post-transcriptionally. Functional single-stranded miRNAs are generated in multiple steps of enzymatic processing from their precursors and mature miRNAs are included into the RNA-induced silencing complex (RISC). They imperfectly base-pair with the 3'UTR region of targeted genes leading to translational repression or mRNA decay. The cellular context and microenvironment as well the isoform of the mRNA control the dynamics and complexity of the regulatory circuits induced by miRNAs that regulate cell fate decisions and function. MiR-21, miR-146a/b and miR-155 are among the best understood miRNAs of the immune system and implicated in different diseases including allergic diseases. MiRNAs are implicated in the induction of the allergy reinforcing the Th2 phenotype (miR-19a, miR-24, miR-27), while other miRNAs promote regulatory T cells associated with allergen tolerance or unresponsiveness. In the current chapter we describe in detail the biogenesis and regulatory function of miRNAs and summarize current knowledge on miRNAs in allergic diseases and allergy relevant cell fate decisions focusing mainly on immune cells. Furthermore, we evoke the principles of regulatory loops and feedback mechanisms involving miRNAs on examples with relevance for allergic diseases. Finally, we show the potential of miRNAs and exosomes containing miRNAs present in several biological fluids that can be exploited with non-invasive procedures for diagnostic and potentially therapeutic purposes.

MiR-1165-3p Suppresses Th2 Differentiation via Targeting IL-13 and PPM1A in a Mouse Model of Allergic Airway Inflammation

PURPOSE

CD4⁺T cells are essential in the pathogenesis of allergic asthma. We have previously demonstrated that microRNA-1165-3p (miR-1165-3p) was significantly reduced in T-helper type (Th) 2 cells and that miR-1165-3p was a surrogate marker for atopic asthma. Little is known about the mechanisms of miR-1165-3p in the regulation of Th2-dominated allergic inflammation. We aimed to investigate the associations between Th2 differentiation and miR-1165b-3p in asthma as well as the possible mechanisms.

METHODS

CD4⁺ naïve T cells were differentiated into Th1 or Th2 cells in vitro. MiR-1165-3p was up-regulated or down-regulated using lentiviral systems during Th1/Th2 differentiation. In vivo, the lentiviral particles with the miR-1165-3p enhancer were administered by tail vein injection on the first day of a house dust mite -induced allergic airway inflammation model. Allergic inflammation and Th1/Th2 differentiation were routinely monitored. To investigate the potential targets of miR-1165-3p, biotin-microRNA pull-down products were sequenced, and the candidates were further verified with a dual-luciferase reporter assay. The roles of a target protein phosphatase, Mg²⁺/Mn²⁺-dependent 1A (PPM1A), in Th2 cell differentiation and allergic asthma were further explored. Plasma PPM1A was determined by ELISA in 18 subjects with asthma and 20 controls.

RESULTS

The lentivirus encoding miR-1165-3p suppressed Th2-cell differentiation in vitro. In contrast, miR-1165-3p silencing promoted Th2-cell development. In the HDM-induced model of allergic airway inflammation, miR-1165-3p up-regulation was accompanied by reduced airway hyper-responsiveness, serum immunoglobulin E, airway inflammation and Th2-cell polarization. IL-13 and PPM1A were the direct targets of miR-1165-3p. The expression of IL-13 or PPM1A was inversely correlated with that of miR-1165-3p. PPM1A regulated the signal transducer and activator of transcription and AKT signaling pathways during Th2 differentiation. Moreover, plasma PPM1A was significantly increased in asthmatic patients.

CONCLUSIONS

MiR-1165-3p negatively may regulate Th2-cell differentiation by targeting IL-13 and PPM1A in allergic airway inflammation.

Molecular techniques for respiratory diseases: MicroRNA and extracellular vesicles

miRNA are a class of evolutionarily conserved non-coding 19- to 22-nt regulatory RNA. They affect various cellular functions through modulating the transcriptional and post-transcriptional levels of their target mRNA by changing the stability of protein-coding transcripts or attenuating protein translation. miRNA were discovered in the early 1990s, and they have been the focus of new research in both basic and clinical medical sciences. Today, it has become clear that specific miRNA are linked to the pathogenesis of respiratory diseases, as well as cancer and cardiovascular disease. In addition, EV, including exosomes, which are small membrane-bound vesicles secreted by cells, were found to contain various functional miRNA that can be used for diagnostic and therapeutic purposes. As body fluids, such as blood and respiratory secretions, are major miRNA sources in the body, EV carrying extracellular miRNA are considered potentially useful for the diagnosis and assessment of pathological conditions, as well as the treatment of respiratory or other diseases. Although research in the field of lung cancer is actively progressing, studies in other respiratory fields have emerged recently as well. In this review, we provide an update in the topics of miRNA and EV focused on airway inflammatory diseases, such as asthma and COPD, and explore their potential for clinical applications on respiratory diseases.

Aberrant MicroRNAomics in Pulmonary Complications: Implications in Lung Health and Diseases

Over the last few decades, evolutionarily conserved molecular networks have emerged as important regulators in the expression and function of eukaryotic genomes. Recently, miRNAs (miRNAs), a large family of small, non-coding regulatory RNAs were identified in these networks as regulators of endogenous genes by exerting post-transcriptional gene regulation activity in a broad range of eukaryotic species. Dysregulation of miRNA expression correlates with aberrant gene expression and can play an essential role in human health and disease. In the context of the lung, miRNAs have been implicated in organogenesis programming, such as proliferation, differentiation, and morphogenesis. Gain- or loss-of-function studies revealed their pivotal roles as regulators of disease development, potential therapeutic candidates/targets, and clinical biomarkers. An altered microRNAome has been attributed to several pulmonary diseases, such as asthma, chronic pulmonary obstructive disease, cystic fibrosis, lung cancer, and idiopathic pulmonary fibrosis. Considering the relevant roles and functions of miRNAs under physiological and pathological conditions, they may lead to the invention of new diagnostic and therapeutic tools. This review will focus on recent advances in understanding the role of miRNAs in lung development, lung health, and diseases, while also exploring the progress and prospects of their application as therapeutic leads or as biomarkers.

Maternal Obesity in Mice Exacerbates the Allergic Inflammatory Response in the Airways of Male Offspring

It was previously demonstrated that non-allergen-sensitized rodents born to mothers exposed to a high-fat diet (HFD) spontaneously develop lower respiratory compliance and higher respiratory resistance. In the present study, we sought to determine if mice born to mothers consuming HFD would exhibit changes in inflammatory response and lung remodeling when subjected to ovalbumin (OVA) sensitization/challenge in adult life. Mice born to dams consuming either HFD or standard chow had increased bronchoalveolar lavage (BAL) levels of IL-1β, IL-4, IL-5, IL-10, IL-13, TNF-α and TGF-β1 after challenge with OVA. IL-4, IL-13, TNF-α and TGF-β1 levels were further increased in the offspring of HFD-fed mothers. Mice born to obese dams also had exacerbated values of leukocyte infiltration in lung parenchyma, eosinophil and neutrophil counts in BAL, mucus overproduction and collagen deposition. The programming induced by maternal obesity was accompanied by increased expression of miR-155 in peripheral-blood mononuclear cells and reduced miR-133b in trachea and lung tissue in adult life. Altogether, the present data support the unprecedented notion that the progeny of obese mice display exacerbated responses to sensitization/challenge with OVA, leading to the intensification of the morphological changes of lung remodeling. Such changes are likely to result from long-lasting changes in miR-155 and miR-133b expression.

Epigenetics in Asthma

PURPOSE OF REVIEW

Asthma is one of the most common chronic respiratory diseases linked with increased morbidity and healthcare utilization. The underlying pathophysiological processes and causal relationships of asthma with epigenetic mechanisms are partially understood. Here we review human studies of epigenetic mechanisms in asthma, with a special focus on DNA methylation.

RECENT FINDINGS

Epigenetic studies of childhood asthma have identified specific methylation signatures associated with allergic inflammation in the airway and immune cells, demonstrating a regulatory role for methylation in asthma pathogenesis. Despite these novel findings, additional research in the role of epigenetic mechanisms underlying asthma endotypes is needed. Similarly, studies of histone modifications are also lacking in asthma. Future studies of epigenetic mechanisms in asthma will benefit from data integration in well phenotyped cohorts. This review provides an overview of the current literature on epigenetic studies in human asthma, with special emphasis on methylation and childhood asthma.

Reduced expression of miR-146a in human bronchial epithelial cells alters neutrophil migration

Background

The role of miRNAs in the pathogenesis and determining the phenotypes of asthma is not fully elucidated. miR-146a has been previously shown to suppress inflammatory responses in different cells. In this study, we investigated the functions of miR-146a in human bronchial epithelial cells (HBECs) in association with neutrophilic, eosinophilic, and paucigranulocytic phenotypes of asthma.

Methods

Bronchial brushing specimens and brochial mucosal biopsy samples were collected from adult patients with asthma and from age- and gender-matched non-asthmatic individuals. The expression of miR-146a in bronchial brushing specimens, bronchial biopsy tissue sections or cultured primary bronchial epithelial cells was analyzed by RT-qPCR or by in situ hybridization. The expression of direct and indirect miR-146a target genes was determined by RT-qPCR or ELISA. The migration of neutrophils was studied by neutrophil chemotaxis assay and flow cytometry. For statistical analysis, unpaired two-way Student’s t test, one-way ANOVA or linear regression analysis were used.

Results

Reduced expression of miR-146a was found in bronchial brushing specimens from asthma patients as compared to non-asthmatics and irrespective of the phenotype of asthma. In the same samples, the neutrophil attracting chemokines IL-8 and CXCL1 showed increased expression in patients with neutrophilic asthma and increased IL-33 expression was found in patients with eosinophilic asthma. Linear regression analysis revealed a significant negative association between the expression of miR-146a in bronchial brushings and neutrophil cell counts in bronchoalveolar lavage fluid of patients with asthma. In bronchial biopsy specimens, the level of miR-146a was highest in the epithelium as determined with in situ hybridization. In primary conventional HBEC culture, the expression of miR-146a was induced in response to the stimulation with IL-17A, TNF-α, and IL-4. The mRNA expression and secretion of IL-8 and CXCL1 was inhibited in both stimulated and unstimulated HBECs transfected with miR-146a mimics. Supernatants from HBECs transfected with miR-146a had reduced capability of supporting neutrophil migration in neutrophil chemotaxis assay.

Conclusion

Our results suggest that decreased level of miR-146a in HBECs from patients with asthma may contribute to the development of neutrophilic phenotype of asthma.

MicroRNA-155-5p is a key regulator of allergic inflammation, modulating the epithelial barrier by targeting PKIα

Recent studies have demonstrated that microRNA-155-5p (miR-155-5p) plays an essential role in the regulation of allergen-induced inflammation and is overexpressed in the skin of patients with atopic dermatitis (AD), although the mechanism is unknown. In this study, silencing miR-155-5p attenuated the thickening of the epidermis in AD model and reduced the infiltration of inflammatory cells and the secretion of Th2 cytokines. Protein kinase inhibitor α (PKIα) was identified as a direct target of miR-155-5p and correlated negatively with miR-155-5p in our AD model. Fluorescence in situ hybridization showed that miR-155-5p-expressing cells were predominantly present in the epidermis. When epithelial cells were transfected with an miR-155-5p inhibitor, the expression of PKIα, occludin, and CLDN16 increased and that of TSLP decreased significantly, whereas the overexpression of miR-155-5p resulted in the opposite changes. The increased expression of PKIα and tight junction (TJ) proteins, with reduced TSLP and IL-33, was also detected in miR-155-5p-blocked mice, in both the initial and elicitation stages of AD. The expression of TJ proteins also decreased when cells were transfected with PKIα siRNA. TJ proteins increased and TSLP and IL-33 decreased significantly after the overexpression of PKIα. Our data provide the first evidence that miR-155-5p is critical for the allergic inflammation in a mouse model of AD by directly regulating PKIα and thus epithelial TJ expression. These findings suggest new therapeutic strategies that target miR-155-5p in patients with allergic disorders.

Isorhynchophylline exerts anti-asthma effects in mice by inhibiting the proliferation of airway smooth muscle cells: The involvement of miR-200a-mediated FOXC1/NF-κB pathway

Hyperplasia of airway smooth muscle cells (ASMCs) is key to the progression of asthma. Isorhynchophylline (IRN) derived from Uncaria rhynchophylla can inhibit the proliferation of AMSCs. The major purpose of the current study was to assess the effect of IRN on the asthma symptoms was assessed both in vitro and in vivo, and the associated mechanism of the effect was also explored by focusing on the function of miR-200a. Asthma model was induced using ovalbumin (OVA) method and AMSC hyperplasia model was induced using TGF-β1. The effect of IRN on allergic asthma mice and the effect of IRN on the proliferation of ASMCs were investigated as well, and the changes in miR-200a level and FOXC1/NF-κB pathway were detected. The administration of IRN attenuated the eosinophils recruitment in BALF, reduced collagen deposition in lung tissues, and suppressed production of IgE and pro-inflammation cytokines. IRN also inhibited the proliferation and induced the apoptosis of ASMCs. Moreover, the administration of IRN increased the level of miR-200a while inhibited the activation of FOXC1/NF-κB pathway. However, after the inhibition of miR-200a level, the function of IRN on ASMCs was impaired. Collectively, it was demonstrated that the effect of IRN on asthma relied on the up-regulation of miR-200a, which then deactivated FOXC1/NF-κB pathway.

A translational perspective on epigenetics in allergic diseases

The analysis of epigenetic modifications in allergic diseases has recently attracted substantial interest because epigenetic modifications can mediate the effects of the environment on the development of or protection from allergic diseases. Furthermore, recent research has provided evidence for an altered epigenomic landscape in disease-relevant cell populations. Although still in the early phase, epigenetic modifications, particularly DNA methylation and microRNAs, might have potential for assisting in the stratification of patients for treatment and complement or replace in the future biochemical or clinical tests. The first epigenetic biomarkers correlating with the successful outcome of immunotherapy have been reported, and with personalized treatment options being rolled out, epigenetic modifications might well play a role in monitoring or even predicting the response to tailored therapy. However, further studies in larger cohorts with well-defined phenotypes in specific cell populations need to be performed before their implementation. Furthermore, the epigenome provides an interesting target for therapeutic intervention, with microRNA mimics, inhibitors, and antisense oligonucleotides being evaluated in clinical trials in patients with other diseases. Selection or engineering of populations of extracellular vesicles and epigenetic editing represent novel tools for modulation of the cellular phenotype and responses, although further technological improvements are required. Moreover, interactions between the host epigenome and the microbiome are increasingly recognized, and interventions of the microbiome could contribute to modulation of the epigenome with a potential effect on the overall goal of prevention of allergic diseases.

ILC2 Activation by Protozoan Commensal Microbes

Group 2 innate lymphoid cells (ILC2s) are a member of the ILC family and are involved in protective and pathogenic type 2 responses. Recent research has highlighted their involvement in modulating tissue and immune homeostasis during health and disease and has uncovered critical signaling circuits. While interactions of ILC2s with the bacterial microbiome are rather sparse, other microbial members of our microbiome, including helminths and protozoans, reveal new and exciting mechanisms of tissue regulation by ILC2s. Here we summarize the current field on ILC2 activation by the tissue and immune environment and highlight particularly new intriguing pathways of ILC2 regulation by protozoan commensals in the intestinal tract.

MicroRNA‑155 inhibits the proliferation of CD8+ T cells via upregulating regulatory T cells in vitiligo

It has been reported that loss and degradation of epidermal melanocytes is closely associated with the pathogenesis of vitiligo. In addition, CD8⁺ T and regulatory T (Treg) cells serve an important role during these two processes. MicroRNA-155 (miR-155) is known to contribute to the pathogenesis of vitiligo; however, the mechanism by which miR-155 regulates the development of vitiligo remains unclear. In the present study, naïve T and CD8⁺ T cells were isolated from a patient with non-segmental vitiligo by flow cytometry. The cells were differentiated into Treg cells by treatment with interleukin-2, transforming growth factor-β and retinoic acid. In addition, miR-155 agonists and antagonists were used to investigate the effect of miR-155 on the proliferation of CD8⁺ T cells, Treg cells and melanocytes. The results demonstrated that the miR-155 agonist significantly decreased the rate of CD8⁺ T cell growth, as well as promoted the proliferation of melanocytes by inducing an increase in the percentage of Treg cells. By contrast, the miR-155 antagonist inhibited the proliferation of melanocytes by decreasing the percentage of Treg cells. miR-155 protected melanocyte survival by increasing the number of Treg cells and by decreasing the number of CD8⁺ T cells. Therefore, these data may provide a new prospect for the treatment of vitiligo.

Hsa_circ_0005519 increases IL-13/IL-6 by regulating hsa-let-7a-5p in CD4+ T cells to affect asthma

BACKGROUND

Circular RNAs (circRNAs) are a class of non-coding RNAs that could serve as novel biomarkers for the diagnosis and treatment of diseases. We hypothesized that circRNAs of CD4⁺ T cells are involved in asthma.

OBJECTIVE

In this study, we investigated the circRNA expression profile and the possible mechanism by which hsa_circ_0005519 participates in asthma.

METHODS

The expression profiles of circRNAs in CD4⁺ T cells were revealed by circRNA microarray. Hsa_circ_0005519 expression in CD4⁺ T cells was confirmed in asthmatic patients (n = 65) and healthy subjects (n = 30). Hsa-let-7a-5p, the target of hsa_circ_0005519, was predicted by online algorithms and verified by a dual-luciferase reporter assay. Correlation assays between the expression of hsa_circ_0005519 and hsa-let-7a-5p, the mRNA levels of interleukin (IL)-13 and IL-6 in CD4⁺ T cells, and the clinical characteristics of asthmatic patients were performed. The role of hsa_circ_0005519 in proinflammatory cytokine expression was investigated in CD4⁺ T cells from asthmatic patients in vitro. Hsa_circ_0005519 expression in PBMCs was determined in another cohort including 30 asthmatic patients and 24 controls. Correlation assays of hsa_circ_0005519 expressions between CD4⁺ T cells and PBMCs were performed.

RESULTS

Hsa_circ_0005519 was up-regulated and negatively correlated with hsa-let-7a-5p expression in CD4⁺ T cells of asthmatic patients. Both the fraction of exhaled nitric oxide (FeNO) and the peripheral blood eosinophil ratio were positively correlated with hsa_circ_0005519 expression in CD4⁺ T cells. These outcomes were also different in asthmatic patients with low vs high hsa_circ_0005519 levels. Hsa_circ_0005519 expressions between CD4⁺ T cells and PBMCs were concordant in asthmatic patients. Mechanistically, hsa_circ_0005519 might bind to hsa-let-7a-5p and relieve suppression for IL-13/IL-6 in CD4⁺ T cells.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data suggest that hsa_circ_0005519 may induce IL-13 and IL-6 expression by regulating hsa-let-7a-5p in CD4⁺ T cells to affect asthma. And hsa_circ_0005519 may be a potential biomarker of asthma.

Crucial Role of Extracellular Vesicles in Bronchial Asthma

Extracellular vesicles (EVs) are circulating vesicles secreted by various cell types. EVs are classified into three groups according to size, structural components, and generation process of vesicles: exosomes, microvesicles, and apoptotic bodies. Recently, EVs have been considered to be crucial for cell-to-cell communications and homeostasis because they contain intracellular proteins and nucleic acids. Epithelial cells from mice suffering from bronchial asthma (BA) secrete more EVs and suppress inflammation-induced EV production. Moreover, microarray analyses of bronchoalveolar lavage fluid have revealed that several microRNAs are useful novel biomarkers of BA. Mesenchymal stromal cell-derived EVs are possible candidates of novel BA therapy. In this review, we highlight the biologic roles of EVs in BA and review novel EV-targeted therapy to help understanding by clinicians and biologists.

The Cross-Talk between miR-511-3p and C-Type Lectin Receptors on Dendritic Cells Affects Dendritic Cell Function

MicroRNAs are small, noncoding RNAs that function as posttranscriptional modulators of gene expression by binding target mRNAs and inhibiting translation. They are therefore crucial regulators of several biological as well as immunological events. Recently, miR-511-3p has been implicated in the development and differentiation of APCs, such as dendritic cells (DCs), and regulating several human diseases. Interestingly, miR-511-3p is embedded within the human MRC1 gene that encodes the mannose receptor. In this study, we sought to examine the impact of miR-511-3p up- or downregulation on human DC surface phenotype, cytokine profile, immunogenicity (using IDO activity as a surrogate), and downstream T cell polarization. Using gene silencing and a selection of microRNA mimics, we could successfully suppress or induce the expression of miR-511-3p in DCs. Consequently, we show for the first time, to our knowledge, that inhibition and/or overexpression of miR-511-3p has opposing effects on the expression levels of two key C-type lectin receptors, namely the mannose receptor and DC-specific ICAM 3 nonintegrin at protein and mRNA levels, thereby affecting C-type lectin receptor-induced modulation of IDO activity in DCs. Furthermore, we show that downregulation of miR-511-3p drives an anti-inflammatory DC response characterized by IL-10 production. Interestingly, the miR-511-3p^low DCs also promoted IL-4 secretion and suppressed IL-17 in cocultures with autologous T cells. Together, our data highlight the potential role of miR-511 in regulating DC function and downstream events leading to Th polarization and immune modulation.

Dendritic Cell-Mediated Th2 Immunity and Immune Disorders

Dendritic cells (DCs) are the professional antigen-presenting cells that recognize and present antigens to naïve T cells to induce antigen-specific adaptive immunity. Among the T-cell subsets, T helper type 2 (Th2) cells produce the humoral immune responses required for protection against helminthic disease by activating B cells. DCs induce a Th2 immune response at a certain immune environment. Basophil, eosinophil, mast cells, and type 2 innate lymphoid cells also induce Th2 immunity. However, in the case of DCs, controversy remains regarding which subsets of DCs induce Th2 immunity, which genes in DCs are directly or indirectly involved in inducing Th2 immunity, and the detailed mechanisms underlying induction, regulation, or maintenance of the DC-mediated Th2 immunity against allergic environments and parasite infection. A recent study has shown that a genetic defect in DCs causes an enhanced Th2 immunity leading to severe atopic dermatitis. We summarize the Th2 immune-inducing DC subsets, the genetic and environmental factors involved in DC-mediated Th2 immunity, and current therapeutic approaches for Th2-mediated immune disorders. This review is to provide an improved understanding of DC-mediated Th2 immunity and Th1/Th2 immune balancing, leading to control over their adverse consequences.

MicroRNA Involvement in Allergic and Non-Allergic Mast Cell Activation

Allergic inflammation is accompanied by the coordinated expression of numerous genes and proteins that initiate, sustain, and propagate immune responses and tissue remodeling. MicroRNAs (miRNAs) are a large class of small regulatory molecules that are able to control the translation of target mRNAs and consequently regulate various biological processes at the posttranscriptional level. MiRNA profiles have been identified in multiple allergic inflammatory diseases and in the tumor microenvironment. Mast cells have been found to co-localize within the above conditions. More specifically, in addition to being essential in initiating the allergic response, mast cells play a key role in both innate and adaptive immunity as well as in modulating tumor growth. This review summarizes the possible role of various miRNAs in the above-mentioned processes wherein mast cells have been found to be involved. Understanding the role of miRNAs in mast cell activation and function may serve as an important tool in developing diagnostic as well as therapeutic approaches in mast cell-dependent pathological conditions.

Differential expression of miR-155 and Let-7a in the plasma of childhood asthma: Potential biomarkers for diagnosis and severity

BACKGROUND

MicroRNAs (miRNAs) are emerging gene expression regulators and their expression has been linked to various biological processes. However, the role of miRNAs in the regulation of allergic inflammatory disease still not clearly understood.

AIM

Our study was designed to investigate circulating miR-155 and Let-7a expression levels in the plasma of asthmatic children and healthy controls. Also, to correlate their expression levels to degree of severity of asthma as well as to IL-13 level and lung function parameters.

METHOD

Our study included 100 asthmatic children and 100 healthy children as control group. Plasma miR-155 and Let-7a expression levels were measured by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

MicroRNA-155 expression was significantly increased in the plasma of asthmatic children than in control children. While, Let-7a expression was significantly lower in asthmatics than in control children. The relative levels of miR-155 and Let-7a were associated with degree of asthma severity. Receiver operating characteristic (ROC) curve analysis demonstrated that the levels of miR-155 and Let-7a were helpful for diagnosis of childhood asthma (AUC were 0.91 and 0.92, respectively), and in prediction of the severity of disease (AUC were 0.83 and 0.80, respectively). Plasma miRNA-155 was correlated positively with Il-13 levels and correlated negatively with FEV1and FVC. While, Let-7a was correlated negatively with Il-13 and correlated positively with FEV1 and FVC.

CONCLUSION

MicroRNA-155 and let-7a could be used as serological non-invasive biomarkers for diagnosis of asthma and degree of severity. Our results could be used for exploring the pathogenesis of asthma and help in selecting promising therapeutic modalities.

BET Bromodomain Inhibitor iBET151 Impedes Human ILC2 Activation and Prevents Experimental Allergic Lung Inflammation

Group 2 innate lymphoid cells (ILC2) increase in frequency in eczema and allergic asthma patients, and thus represent a new therapeutic target cell for type-2 immune-mediated disease. The bromodomain and extra-terminal (BET) protein family of epigenetic regulators are known to support the expression of cell cycle and pro-inflammatory genes during type-1 inflammation, but have not been evaluated in type-2 immune responses. We isolated human ILC2 and examined the capacity of the BET protein inhibitor, iBET151, to modulate human ILC2 activation following IL-33 stimulation. iBET151 profoundly blocked expression of genes critical for type-2 immunity, including type-2 cytokines, cell surface receptors and transcriptional regulators of ILC2 differentiation and activation. Furthermore, in vivo administration of iBET151 during experimental mouse models of allergic lung inflammation potently inhibited lung inflammation and airways resistance in response to cytokine or allergen exposure. Thus, iBET151 effectively prevents human ILC2 activation and dampens type-2 immune responses.

MicroRNA-155: A Master Regulator of Inflammation

MicroRNAs (miRNAs) are naturally occurring, highly conserved families of transcripts (∼22 nucleotides in length) that are processed from larger hairpin precursors. miRNAs primarily regulate gene expression by promoting messenger RNA (mRNA) degradation or repressing mRNA translation. miRNAs have been shown to be important regulators of a variety of cellular processes involving development, differentiation, and signaling. Moreover, various human diseases, including cancer and immune dysfunction, are associated with aberrant expression of miRNAs. This review will focus on how the multifunctional miRNA, miR-155, regulates inflammatory diseases, including cancer and pulmonary disorders, and also how miR-155 expression and biogenesis are regulated. We will also provide examples of miR-155-regulated networks in coordination with other noncoding RNAs, including long noncoding RNAs as well as coding mRNAs acting as competing endogenous RNAs.

ncRNAs in Inflammatory and Infectious Diseases

Inflammatory and infectious diseases are among the main causes of morbidity and mortality worldwide. Inflammation is central to maintenance of organismal homeostasis upon infection, tissue damage, and malignancy. It occurs transiently in response to diverse stimuli (e.g., physical, radioactive, infective, pro-allergenic, or toxic), and in some cases may manifest itself in chronic diseases. To limit the potentially deleterious effects of acute or chronic inflammatory responses, complex transcriptional and posttranscriptional regulatory networks have evolved, often involving nonprotein-coding RNAs (ncRNA). MicroRNAs (miRNAs) are a class of posttranscriptional regulators that control mRNA translation and stability. Long ncRNAs (lncRNAs) are a very diverse group of transcripts >200 nt, functioning among others as scaffolds or decoys both in the nucleus and the cytoplasm. By now, it is well established that miRNAs and lncRNAs are implicated in all major cellular processes including control of cell death, proliferation, or metabolism. Extensive research over the last years furthermore revealed a fundamental role of ncRNAs in pathogen recognition and inflammatory responses. This chapter reviews and summarizes the current knowledge on regulatory ncRNA networks in infection and inflammation.

The role of microRNAs in chronic respiratory disease: recent insights

Chronic respiratory diseases encompass a group of diverse conditions affecting the airways, which all impair lung function over time. They include cystic fibrosis (CF), idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) and asthma, which together affect hundreds of millions of people worldwide. MicroRNAs (miRNAs), a class of small non-coding RNAs involved in post-transcriptional gene repression, are now recognized as major regulators in the development and progression of chronic lung disease. Alterations in miRNA abundance occur in lung tissue, inflammatory cells, and freely circulating in blood and are thought to function both as drivers and modifiers of disease. Their importance in lung pathology has prompted the development of miRNA-based therapies and biomarker tools. Here, we review the current literature on miRNA expression and function in chronic respiratory disease and highlight further research that is needed to propel miRNA treatments for lung disorders towards the clinic.