MicroRNAs in Asthma and Respiratory Infections: Identifying Common Pathways

MicroRNAs: Key modulators of inflammation-associated diseases

Inflammation is a multifaceted biological and pathophysiological response to injuries, infections, toxins, and inflammatory mechanisms that plays a central role in the progression of various diseases. MicroRNAs (miRNAs) are tiny, 19-25 nucleotides long, non-coding RNAs that regulate gene expression via post-transcriptional repression. In this review, we highlight the recent findings related to the significant roles of miRNAs in regulating various inflammatory cascades and immunological processes in the context of many lifestyle-related diseases such as diabetes, cardiovascular diseases, cancer, etc. We also converse on how miRNAs can have a dual impact on inflammatory responses, suggesting that regulation of their functions for therapeutic purposes may be disease-specific.

Epigenetic regulation of pulmonary inflammation

Pulmonary disease such as chronic obstructive pulmonary disease (COPD), asthma, pulmonary fibrosis and pulmonary hypertension are the leading cause of deaths. More importantly, lung diseases are on the rise and environmental factors induced epigenetic modifications are major players on this increased prevalence. It has been reported that dysregulation of genes involved in epigenetic regulation such as the histone deacetylase (HDACs) and histone acetyltransferase (HATs) play important role in lung health and pulmonary disease pathogenesis. Inflammation is an essential component of respiratory diseases. Injury and inflammation trigger release of extracellular vesicles that can act as epigenetic modifiers through transfer of epigenetic regulators such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), proteins and lipids, from one cell to another. The immune dysregulations caused by the cargo contents are important contributors of respiratory disease pathogenesis. N6 methylation of RNA is also emerging to be a critical mechanism of epigenetic alteration and upregulation of immune responses to environmental stressors. Epigenetic changes such as DNA methylation are stable and often long term and cause onset of chronic lung conditions. These epigenetic pathways are also being utilized for therapeutic intervention in several lung conditions.

Lung proinflammatory microRNA and cytokine expression in a mouse model of allergic inflammation: role of sex chromosome complement and gonadal hormones

Epigenetic alterations such as dysregulation of miRNAs have been reported to play important roles in interactions between genetic and environmental factors. In this study, we tested the hypothesis that induction of lung inflammation by inhaled allergens triggers a sex-specific miRNA regulation that is dependent on chromosome complement and hormonal milieu. We challenged the four core genotypes (FCGs) model through intranasal sensitization with a house dust mite (HDM) solution (or PBS as a control) for 5 wk. The FCG model allows four combinations of gonads and sex chromosomes: 1) XX mice with ovaries (XXF), 2) XY mice with testes (XYM), 3) XX mice with testes (XXM), and 4) XY mice with ovaries (XYF). Following the challenge (n = 5-7/group), we assessed the expression of 84 inflammatory miRNAs in lung tissue using a PCR array and cytokine levels in bronchoalveolar lavage fluid (BAL) by a multiplex protein assay (n = 4-7 animals/group). Our results showed higher levels of the chemokine KC (an Il-8 homolog) and IL-7 in BAL from XYF mice challenged with HDM. In addition, IL-17A was significantly higher in BAL from both XXF and XYF mice. A three-way interaction among treatment, gonads, and sex chromosome revealed 60 of 64 miRNAs that differed in expression depending on genotype; XXF, XXM, XYF, and XYM mice had 45, 32, 4, and 52 differentially expressed miRNAs, respectively. Regulatory networks of miRNAs identified in this study were implicated in pathways associated with asthma. Female gonadal hormonal effects may alter miRNA expression and contribute to the higher susceptibility of females to asthma.NEW & NOTEWORTHY miRNAs play important roles in regulating gene and environmental interactions. However, their role in mediating sex differences in allergic responses and lung diseases has not been elucidated. Our study used a targeted omics approach to characterize the contributions of gonadal hormones and chromosomal components to lung responses to an allergen challenge. Our results point to the influence of sex hormones in miRNA expression and proinflammatory markers in allergic airway inflammation.

Tuning into miRNAs: A comprehensive analysis of their impact on diagnosis, and progression in asthma

Asthma is a diverse inflammatory illness affecting the respiratory passages, leading to breathing challenges, bouts of coughing and wheezing, and, in severe instances, significant deterioration in quality of life. Epigenetic regulation, which involves the control of gene expression through processes such as post-transcriptional modulation of microRNAs (miRNAs), plays a role in the evolution of various asthma subtypes. In immune-mediated diseases, miRNAs play a regulatory role in the behavior of cells that form the airway structure and those responsible for defense mechanisms in the bronchi and lungs. They control various cellular processes such as survival, growth, proliferation, and the production of chemokines and immune mediators. miRNAs possess chemical and biological characteristics that qualify them as suitable biomarkers for diseases. They allow for the categorization of patients to optimize drug selection, thus streamlining clinical management and decreasing both the economic burden and the necessity for critical care related to the disease. This study provides a concise overview of the functions of miRNAs in asthma and elucidates their regulatory effects on the underlying processes of the disease. We provide a detailed account of the present status of miRNAs as biomarkers for categorizing asthma, identifying specific asthma subtypes, and selecting appropriate treatment options.

MicroRNA Profiling of the Inflammatory Response after Early and Late Asthmatic Reaction

A high proportion of house dust mite (HDM)-allergic asthmatics suffer from both an early asthmatic reaction (EAR) and a late asthmatic reaction (LAR) which follows it. In these patients, allergic inflammation is more relevant. MiRNAs have been shown to play an important role in the regulation of asthma's pathology. The aim of this study was to analyze the miRNA profile in patients with mild asthma and an HDM allergy after bronchial allergen provocation (BAP). Seventeen patients with EAR/no LAR and 17 patients with EAR plus LAR, determined by a significant fall in FEV1 after BAP, were differentially analyzed. As expected, patients with EAR plus LAR showed a more pronounced allergic inflammation and FEV1 delta drop after 24 h. NGS-miRNA analysis identified the down-regulation of miR-15a-5p, miR-15b-5p, and miR-374a-5p after BAP with the highest significance in patients with EAR plus LAR, which were negatively correlated with eNO and the maximum decrease in FEV1. These miRNAs have shared targets like CCND1, VEGFA, and GSK3B, which are known to be involved in airway remodeling, basement membrane thickening, and Extracellular Matrix deposition. NGS-profiling identified miRNAs involved in the inflammatory response after BAP with HDM extract, which might be useful to predict a LAR.

Analyzing the Impact of Diesel Exhaust Particles on Lung Fibrosis Using Dual PCR Array and Proteomics: YWHAZ Signaling

Air pollutants are associated with exacerbations of asthma, chronic bronchitis, and airway inflammation. Diesel exhaust particles (DEPs) can induce and worsen lung diseases. However, there are insufficient data to guide polymerase chain reaction (PCR) array proteomics studies regarding the impacts of DEPs on respiratory diseases. This study was performed to identify genes and proteins expressed in normal human bronchial epithelial (NHBE) cells. MicroRNAs (miRNAs) and proteins expressed in NHBE cells exposed to DEPs at 1 μg/cm2 for 8 h and 24 h were identified using PCR array analysis and 2D PAGE/LC-MS/MS, respectively. YWHAZ gene expression was estimated using PCR, immunoblotting, and immunohistochemical analyses. Genes discovered through an overlap analysis were validated in DEP-exposed mice. Proteomics approaches showed that exposing NHBE cells to DEPs led to changes in 32 protein spots. A transcriptomics PCR array analysis showed that 6 of 84 miRNAs were downregulated in the DEP exposure groups compared to controls. The mRNA and protein expression levels of YWHAZ, β-catenin, vimentin, and TGF-β were increased in DEP-treated NHBE cells and DEP-exposed mice. Lung fibrosis was increased in mice exposed to DEPs. Our combined PCR array-omics analysis demonstrated that DEPs can induce airway inflammation and lead to lung fibrosis through changes in the expression levels of YWHAZ, β-catenin, vimentin, and TGF-β. These findings suggest that dual approaches can help to identify biomarkers and therapeutic targets involved in pollutant-related respiratory diseases.

Comparison of salivary MicroRNA-6734, microRNA-3123 and microRNA-4483 expression in smoker and nonsmoker patients: a case control study

BACKGROUND

Tobacco is a major risk factor in oral diseases. Considering the important role of expression miRNA molecules in different diseases, the present study aimed to compare the expression of salivary miRNA-6734, miRNA-3123 and miRNA-4483 in smoker and non-smoker peoples.

METHODS

In this case-control study, salivary samples were obtained from 30 smoker's patients and 27 healthy nonsmokers and matched in term of age and sex. RNA was extracted in salivary samples and gene expression was evaluated in all samples. Statistical analysis of data was performed using T and chi-square tests by SPSS (Ver. 16) software at a significant level of less than 0.05.

RESULTS

The results of this study showed that the expression level of miRNA-3123 and miRNA-4483 in smokers group was 2.8 and 3.2, respectively, which was increased compared to non-smokers with expression level of 1 (P<0.01). There was a significant decrease in the expression rate of miRNA-6734 in smokers (0.6%) compared to non-smokers (P<0.05).

CONCLUSIONS

Based on the results of this study, considering the increasing miRNA-4483 and miRNA-3123 level, as well as the reducing miRNA-6734 level in smokers compared to non-smokers, it seems that evaluation of these two miRNAs as indicator for diagnosis and determination of prognosis of oral diseases associated with smoking can be used.

Nasal airway microRNA profiling of infants with severe bronchiolitis and risk of childhood asthma: a multicentre prospective study

BACKGROUND

Severe bronchiolitis (i.e. bronchiolitis requiring hospitalisation) during infancy is a major risk factor for childhood asthma. However, the exact mechanism linking these common conditions remains unclear. We examined the longitudinal relationship between nasal airway miRNAs during severe bronchiolitis and the risk of developing asthma.

METHODS

In a 17-centre prospective cohort study of infants with severe bronchiolitis, we sequenced their nasal microRNA at hospitalisation. First, we identified differentially expressed microRNAs (DEmiRNAs) associated with the risk of developing asthma by age 6 years. Second, we characterised the DEmiRNAs based on their association with asthma-related clinical features, and expression level by tissue and cell types. Third, we conducted pathway and network analyses by integrating DEmiRNAs and their mRNA targets. Finally, we investigated the association of DEmiRNAs and nasal cytokines.

RESULTS

In 575 infants (median age 3 months), we identified 23 DEmiRNAs associated with asthma development (e.g. hsa-miR-29a-3p; false discovery rate (FDR) <0.10), particularly in infants with respiratory syncytial virus infection (FDR for the interaction <0.05). These DEmiRNAs were associated with 16 asthma-related clinical features (FDR <0.05), e.g. infant eczema and corticosteroid use during hospitalisation. In addition, these DEmiRNAs were highly expressed in lung tissue and immune cells (e.g. T-helper cells, neutrophils). Third, DEmiRNAs were negatively correlated with their mRNA targets (e.g. hsa-miR-324-3p/IL13), which were enriched in asthma-related pathways (FDR <0.05), e.g. toll-like receptor, PI3K-Akt and FcɛR signalling pathways, and validated by cytokine data.

CONCLUSION

In a multicentre cohort of infants with severe bronchiolitis, we identified nasal miRNAs during illness that were associated with major asthma-related clinical features, immune response, and risk of asthma development.

Differentially expressed microRNAs in peripheral blood cell are associated with downregulated expression of IgE in nonallergic childhood asthma

Childhood asthma is a heterogeneous disease characterized by chronic airway inflammation, leading to a broad range of clinical presentations. Nonallergic asthma is asthma without allergic sensitization. Both clinical manifestations and immunopathological mechanisms of nonallergic childhood asthma were rarely investigated. We aimed to compare the clinical features between nonallergic and allergic childhood asthma and apply microRNA to explore the underlying mechanism of nonallergic childhood asthma. We enrolled 405 asthmatic children (76 nonallergic, 52 allergic with total IgE < 150 IU/mL and 277 allergic with total IgE > 150 IU/mL). Clinical characteristics were compared between groups. Comprehensive miRNA sequencing (RNA-seq) was performed using peripheral blood from 11 nonallergic and 11 allergic patients with elevated IgE, respectively. Differentially expressed miRNA (DEmiRNA) were determined with DESeq2. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis was performed to determine functional pathways involved. Publicly available mRNA expression data was applied to investigate the predicted target mRNA networks via Ingenuity Pathway Analysis (IPA). The average age of nonallergic asthma was significantly younger (5.614 ± 2.743 vs 6.676 ± 3.118 years-old). Higher severity and worse control were more common in nonallergic asthma (two-way ANOVA, P < 0.0001). Long-term severity was higher, and intermittent attacks persisted in nonallergic patients. We identified 140 top DEmiRNAs based on false discovery rate (FDR) q-value < 0.001. Forty predicted target mRNA gene were associated with nonallergic asthma. The enriched pathway based on GO included Wnt signaling pathway. IgE expression was predicted to be downregulated by a network involving simultaneous interaction with IL-4, activation of IL-10 and inhibition of FCER2. Nonallergic childhood asthma were distinct in their younger age, higher long-term severity and more persistent course. Differentially expressed miRNA signatures associate with downregulation of total IgE expression and predicted target mRNA genes related molecular networks contribute to canonical pathways of nonallergic childhood asthma. We demonstrated the negative role of miRNAs involved in regulating IgE expression indicating differences between asthma phenotypes. Identification of biomarkers of miRNAs could contribute to understand the molecular mechanism of endotypes in nonallergic childhood asthma, which can potentially allow delivery of precision medicine to pediatric asthma.

Asthma Exacerbations: The Genes Behind the Scenes

The clinical and socioeconomic burden of asthma exacerbations (AEs) constitutes a major public health problem. In the last 4 years, there has been an increase in ethnic diversity in candidate-gene and genome-wide association studies of AEs, which in the latter case led to the identification of novel genes and underlying pathobiological processes. Pharmacogenomics, admixture mapping analyses, and the combination of multiple "omics" layers have helped to prioritize genomic regions of interest and/or facilitated our understanding of the functional consequences of genetic variation. Nevertheless, the field still lags behind the genomics of asthma, where a vast compendium of genetic approaches has been used (eg, gene-environment nteractions, next-generation sequencing, and polygenic risk scores). Furthermore, the roles of the DNA methylome and histone modifications in AEs have received little attention, and microRNA findings remain to be validated in independent studies. Likewise, the most recent transcriptomic studies highlight the importance of the host-airway microbiome interaction in the modulation of risk of AEs. Leveraging -omics and deep-phenotyping data from subtypes or homogenous subgroups of patients will be crucial if we are to overcome the inherent heterogeneity of AEs, boost the identification of potential therapeutic targets, and implement precision medicine approaches to AEs in clinical practice.

miRNAs as Predictors of Barrier Integrity

The human body has several barriers that protect its integrity and shield it from mechanical, chemical, and microbial harm. The various barriers include the skin, intestinal and respiratory epithelia, blood-brain barrier (BBB), and immune system. In the present review, the focus is on the physical barriers that are formed by cell layers. The barrier function is influenced by the molecular microenvironment of the cells forming the barriers. The integrity of the barrier cell layers is maintained by the intricate balance of protein expression that is partly regulated by microRNAs (miRNAs) both in the intracellular space and the extracellular microenvironment. The detection of changes in miRNA patterns has become a major focus of diagnostic, prognostic, and disease progression, as well as therapy-response, markers using a great variety of detection systems in recent years. In the present review, we highlight the importance of liquid biopsies in assessing barrier integrity and challenges in differential miRNA detection.

The Potential Role of Serum and Exhaled Breath Condensate miRNAs in Diagnosis and Predicting Exacerbations in Pediatric Asthma

Asthma is the most common chronic disease of the respiratory system in children and the number of new cases is constantly increasing. It is characterized by dyspnea, wheezing, tightness in the chest, or coughing. Due to diagnostic difficulties, disease monitoring, and the selection of safe and effective drugs, it has been shown that among the youngest patients, miRNAs fulfilling the above roles can be successfully used in common clinical practice. These biomolecules, by regulating the expression of the body’s genes, influence various biological processes underlying the pathogenesis of asthma, such as the inflammatory process, remodeling, and intensification of airway obstruction. They can be detected in blood serum and in exhaled breath condensate (EBC). Among children, common factors responsible for the onset or exacerbation of asthma, such as infections, allergens, air pollution, or tobacco smoke present in the home environment, cause a change the concentration of miRNAs in the body. This is related to their significant impact on the modulation of the disease process. In the following paper, we review the latest knowledge on miRNAs and their use, especially as diagnostic markers in assessing asthma exacerbation, with particular emphasis on the pediatric population.

miR-34b/c-5p/CXCL10 Axis Induced by RSV Infection Mediates a Mechanism of Airway Hyperresponsive Diseases

Background: RSV is closely correlated with post-infection airway hyperresponsive diseases (AHD), but the mechanism remains unclear. Objective: Due to the pivotal role of miRNAs in AHD, we analyzed the differentially expressed miRNAs (DEmiRs) in RSV-infected patients, asthma patients, and COPD patients from public datasets and explored the mechanisms of association between RSV and AHD. Methods: We obtained miRNA and mRNA databases of patients with RSV infection, as well as miRNA databases of asthma and COPD patients from the GEO database. Through integrated analysis, we screened DEmiRs and DEGs. Further analysis was carried out to obtain the hub genes through the analysis of biological pathways and enrichment pathways of DEGs targeted by DEmiRs and the construction of a protein-protein interaction (PPI) network. Results: The five differential molecules (miR-34b/c-5p, Cd14, Cxcl10, and Rhoh) were verified through in vivo experiments that had the same expression trend in the acute and chronic phases of RSV infection. Following infection of BEAS-2B cells with RSV, we confirmed that RSV infection down-regulated miR-34b/c-5p, and up-regulated the expression levels of CXCL10 and CD14. Furthermore, the results of the dual-luciferase reporter assay showed that CXCL10 was the target of hsa-miR-34c-5p. Conclusions: miR-34b/c-5p/CXCL10 axis mediates a mechanism of AHD.

Micrococcus luteus-derived extracellular vesicles attenuate neutrophilic asthma by regulating miRNAs in airway epithelial cells

Bacterial extracellular vesicles (EVs) have been shown to regulate various pulmonary diseases, but their functions in asthma remain uncertain. To demonstrate the clinical significance of Micrococcus luteus-derived EVs (MlEVs) in asthma, we enrolled 45 asthmatic patients (20 patients with neutrophilic asthma [NA], 25 patients with eosinophilic asthma [EA]) and 40 healthy controls (HCs). When the prevalence of IgG1 and IgG4 specific to MlEVs was evaluated in serum by ELISA, lower levels of MlEV-specific IgG4 (but not IgG1) were noted in asthmatic patients than in HCs. Among asthmatic patients, significantly lower levels of MIEV-specific IgG4 were noted in patients with NA than in those with EA. Moreover, there was a positive correlation between serum MlEV-specific IgG4 levels and FEV₁ (%) values. In asthmatic C57BL/6 mice, MlEVs significantly attenuated neutrophilic airway inflammation by reducing the production of IL-1β and IL-17 in bronchoalveolar lavage fluid as well as the number of group 3 innate lymphoid cells (ILC3s) in lung tissues. To clarify the functional mechanism of MlEVs in NA, the effect of MlEVs on airway epithelial cells (AECs) and immune cells was investigated ex vivo. According to microarray analysis, MlEVs upregulated hsa-miR-4517 expression in AECs. Moreover, this miRNA could suppress IL-1β production by monocytes, resulting in the inhibition of ILC3 activation and neutrophil recruitment. These findings suggest that MlEVs could be a novel therapeutic agent for managing unresolved NA by regulating miRNA expression in AECs.

Advances and Highlights of miRNAs in Asthma: Biomarkers for Diagnosis and Treatment

Asthma is a heterogeneous inflammatory disease of the airways that causes breathing difficulties, episodes of cough and wheezing, and in more severe cases can greatly diminish quality of life. Epigenetic regulation, including post-transcriptional mediation of microRNAs (miRNAs), is one of the mechanisms behind the development of the range of asthma phenotypes and endotypes. As in every other immune-mediated disease, miRNAs regulate the behavior of cells that shape the airway structure as well as those in charge of the defense mechanisms in the bronchi and lungs, controlling cell survival, growth, proliferation, and the ability of cells to synthesize and secrete chemokines and immune mediators. More importantly, miRNAs are molecules with chemical and biological properties that make them appropriate biomarkers for disease, enabling stratification of patients for optimal drug selection and thereby simplifying clinical management and reducing both the economic burden and need for critical care associated with the disease. In this review, we summarize the roles of miRNAs in asthma and describe how they regulate the mechanisms of the disease. We further describe the current state of miRNAs as biomarkers for asthma phenotyping, endotyping, and treatment selection.

Multi-Omic Factors Associated with Frequency of Upper Respiratory Infections in Developing Infants

Susceptibility to upper respiratory infections (URIs) may be influenced by host, microbial, and environmental factors. We hypothesized that multi-omic analyses of molecular factors in infant saliva would identify complex host-environment interactions associated with URI frequency. A cohort study involving 146 infants was used to assess URI frequency in the first year of life. Saliva was collected at 6 months for high-throughput multi-omic measurement of cytokines, microRNAs, transcripts, and microbial RNA. Regression analysis identified environmental (daycare attendance, atmospheric pollution, breastfeeding duration), microbial (Verrucomicrobia, Streptococcus phage), and host factors (miR-22-5p) associated with URI frequency (p < 0.05). These results provide pathophysiologic clues about molecular factors that influence URI susceptibility. Validation of these findings in a larger cohort could one day yield novel approaches to detecting and managing URI susceptibility in infants.

Recent miRNA Research in Asthma

PURPOSE OF REVIEW

The study of microRNA in asthma has revealed a vibrant new level of gene regulation underlying asthma pathology. Several miRNAs have been shown to be important in asthma, influencing various biological mechanisms which lead to asthma pathology and symptoms. In addition, miRNAs have been proposed as biomarkers of asthma affection status, asthma severity, and asthma treatment response. We review all recent asthma-miRNA work, while also presenting comprehensive tables of all miRNA results related to asthma.

RECENT FINDINGS

We here reviewed 63 recent studies published reporting asthma and miRNA research, and an additional 14 reviews of the same. We summarized the information for both adult and childhood asthma, as well as research on miRNAs in asthma-COPD overlap syndrome (ACOs), and virus-induced asthma exacerbations. We attempted to present a comprehensive collection of recently published asthma-associated miRNAs as well as tables of all published asthma-related miRNA results.

The Role of Systems Biology in Deciphering Asthma Heterogeneity

Asthma is one of the most common and lifelong and chronic inflammatory diseases characterized by inflammation, bronchial hyperresponsiveness, and airway obstruction episodes. It is a heterogeneous disease of varying and overlapping phenotypes with many confounding factors playing a role in disease susceptibility and management. Such multifactorial disorders will benefit from using systems biology as a strategy to elucidate molecular insights from complex, quantitative, massive clinical, and biological data that will help to understand the underlying disease mechanism, early detection, and treatment planning. Systems biology is an approach that uses the comprehensive understanding of living systems through bioinformatics, mathematical, and computational techniques to model diverse high-throughput molecular, cellular, and the physiologic profiling of healthy and diseased populations to define biological processes. The use of systems biology has helped understand and enrich our knowledge of asthma heterogeneity and molecular basis; however, such methods have their limitations. The translational benefits of these studies are few, and it is recommended to reanalyze the different studies and omics in conjugation with one another which may help understand the reasons for this variation and help overcome the limitations of understanding the heterogeneity in asthma pathology. In this review, we aim to show the different factors that play a role in asthma heterogeneity and how systems biology may aid in understanding and deciphering the molecular basis of asthma.

Circulating MicroRNAs Expression Profile in Lung Inflammation: A Preliminary Study

Background: Bronchial asthma is an inflammatory airway disease with an ever-increasing incidence. Therefore, innovative management strategies are urgently needed. MicroRNAs are small molecules that play a key role in lungs cellular functions and are involved in chronic inflammatory diseases, such as bronchial asthma. This study aims to compare microRNA serum expression between subjects with asthma, obesity, the most common co-morbidity in asthma, and healthy controls to obtain a specific expression profile specifically related to lung inflammation. Methods: We collected serum samples from a prospective cohort of 25 sex-matched subjects to determine circulating miRNAs through a quantitative RT-PCR. Moreover, we performed an in silico prediction of microRNA target genes linked to lung inflammation. Results: Asthmatic patients had a significant lower expression of hsa-miR-34a-5p, 181a-5p and 146a-5p compared to both obese and healthy ones suggesting microRNAs’ specific involvement in the regulation of lungs inflammatory response. Indeed, using in silico analysis, we identified microRNAs novel target genes as GATA family, linked to the inflammatory-related pathway. Conclusions: This study identifies a novel circulating miRNAs expression profile with promising potentials for asthma clinical evaluations and management. Further and larger investigations will be needed to confirm the potential role of microRNA as a clinical marker of bronchial asthma and eventually of pharmacological treatment response.

Vulnerability for Respiratory Infections in Asthma Patients: A Systematic Review

Asthma is a non-communicable and long-term condition affecting children and adults. The air passages in the lungs become narrow due to inflammation and tightening of the muscles around the small airways. Symptoms of asthma are intermittent and include cough, wheeze, shortness of breath, and chest tightness. Asthma is very often underdiagnosed and under-treated in many regions, especially in developing countries. While many studies show that viral infections can precipitate asthmatic attacks, very few studies have been conducted to see if history or current asthmatic attack increases the risk of viral infections. Our study aims to determine the predisposition of asthmatics to develop various viral infections and susceptibility toward certain viruses that cause upper respiratory tract infections.

We performed a literature review of both published and unpublished articles. We included case reports, case series, reviews, clinical trials, cohort, and case-control studies, written only in English. Commentaries, letters to editors, and book chapters were excluded. Our initial search yielded 948 articles, of which 826 were rejected either because they were irrelevant or because they did not meet our inclusion criteria. We finally screened 122 abstracts and identified 24 relevant articles.

People with a history of asthma have an abnormal innate immune response, making them potentially slower in clearing the infection and susceptible to both infections and virus-induced cell cytotoxicity. Also, in these studies, deficiencies in the interferon alpha response of peripheral blood mononuclear cells and plasmacytoid dendritic cells have been observed in asthmatics, both adults and children. Asthmatics with a viral infection usually present with an acute exacerbation of asthma, represented by dyspnea and cough, with other prodromal symptoms including vomiting and general malaise.

The review includes an update on the relevance of dysregulated immune pathways in causing viral infections in asthmatic populations. It focuses on the evidence to suggest that people with asthma are at increased risk of viral infection, and viral infections in turn are known to precipitate and worsen the asthmatic status, making this a vicious cycle. The authors also suggest that further studies be undertaken to elucidate the pathophysiology and identify the critical therapeutic steps to break this vicious cycle and improve the quality of life for people with asthma.

Interrelation between extracellular vesicles miRNAs with chronic lung diseases

Extracellular vehicles (EVs) are nanoscale lipid bilayer vesicles that carry biologically active biomolecule cargos like proteins, lipids, and nucleic acids (DNA, RNA) outside of the cell. Blood (serum/plasma), urine, and bronchoalveolar lavage fluid are all examples of biofluids from which they may be collected. EVs play a vital role in intracellular communication. The molecular signature of EVs largely depends on the parental cell's status. EVs are classified into two groups, (1) exosomes (originated by endogenous route) and (2) microvesicles (originated from the plasma membrane, also known as ectosomes). The quantity and types of EV cargo vary during normal conditions compared to pathological conditions (chronic inflammatory lung diseases or lung cancer). Consequently, EVs contain novel biomarkers that differ based on the cell type of origin and during lung diseases. Small RNAs (e.g., microRNAs) are transported by EVs, which is one of the most rapidly evolving research areas in the field of EVs biology. EV-mediated cargos transport small RNAs that can result in reprograming the target/recipient cells. Multiple chronic inflammatory lung illnesses, such as chronic obstructive pulmonary disease, asthma, pulmonary hypertension, pulmonary fibrosis, cystic fibrosis, acute lung injury, and lung cancer, have been demonstrated to be regulated by EV. In this review, we will consolidate the current knowledge and literature on the novel role of EVs and their small RNAs concerning chronic lung diseases (CLDs). Additionally, we will also provide better insight into the clinical and translational impact of mesenchymal stem cells-derived EVs as novel therapeutic agents in treating CLDs.

MiR-365-3p is a negative regulator in IL-17-mediated asthmatic inflammation

Background

Interleukin-17, the major proinflammatory cytokine secreted by Th17 cells, makes essential contribution to pathogenesis of severe asthma, while the detailed mechanisms, especially the involvement of microRNAs which are also important participants in asthma progression, remains largely unclear.

Methods

In this study, we established a house dust mite (HDM) extract-induced murine asthmatic models and the miRNA expression in the lung tissues of mice were profiled by miRNA microarray assay. The effect of miR-365-3p on IL-17-mediated inflammation was examined by qRT-PCR and immunoblotting analysis. The involvement of ARRB2 as target gene of miR-365-3p was verified by overexpression or RNA interference.

Results

HDM extract-induced asthmatic inflammation was proved to be IL17-mediated and miR-365-3p was screened out to be the only miRNA exclusively responsive to IL-17. miR-365-3p, whose expression was significantly downregulated upon IL-17 stimulation, was demonstrated to exert remarkable anti-inflammatory effect to decrease IL-17-provoked inflammatory cytokines (KC/IL-8 and IL-6) in both airway epithelial cells and macrophages of murine and human origins, verifying its universal antagonizing activity against IL-17-initiated inflammation across the two species. ARRB2 was characterized as the key target of miR-365-3p to negate IL-17-induced inflammatory cytokines.

Conclusion

Taken together, our data supported the notion that miR-365-3p, which was diminished by IL-17 in murine and human asthmatic pathogenesis, functioned as an essential negative mediator in IL-17-stimuated inflammatory response by targeting ARRB2, which would shed new light to the understanding and therapeutics thereof of asthmatic inflammation.

Advances in the design of new types of inhaled medicines

Inhalation of small molecule drugs has proven very efficacious for the treatment of respiratory diseases due to enhanced efficacy and a favourable therapeutic index compared with other dosing routes. It enables targeted delivery to the lung with rapid onset of therapeutic action, low systemic drug exposure, and thereby reduced systemic side effects. An increasing number of pharmaceutical companies and biotechs are investing in new modalities-for this review defined as therapeutic molecules with a molecular weight >800Da and therefore beyond usual inhaled small molecule drug-like space. However, our experience with inhaled administration of PROTACs, peptides, oligonucleotides (antisense oligonucleotides, siRNAs, miRs and antagomirs), diverse protein scaffolds, antibodies and antibody fragments is still limited. Investigating the retention and metabolism of these types of molecules in lung tissue and fluid will contribute to understanding which are best suited for inhalation. Nonetheless, the first such therapeutic molecules have already reached the clinic. This review will provide information on the physiology of healthy and diseased lungs and their capacity for drug metabolism. It will outline the stability, aggregation and immunogenicity aspects of new modalities, as well as recap on formulation and delivery aspects. It concludes by summarising clinical trial outcomes with inhaled new modalities based on information available at the end of 2021.

Potential of MicroRNAs As Biomarkers and Therapeutic Targets in Respiratory Viruses: A Literature Review

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression through recognition of cognate sequences and interference of transcriptional, translational, or epigenetic processes. Hundreds of miRNA genes have been found in diverse viruses, and many of these are phylogenetically conserved. Respiratory viruses are the most frequent causative agents of disease in humans, with a significant impact on morbidity and mortality worldwide. Recently, the role of miRNAs in respiratory viral gene regulation, as well as host gene regulation during disease progression, has become a field of interest. This review highlighted the importance of various miRNAs and their potential role in fighting with respiratory viruses as therapeutic molecules with a focus on COVID-19.

Breast milk-derived extracellular vesicle miRNAs are associated with maternal asthma and atopy

Background: Breast milk-derived extracellular vesicle (EV) miRNAs may program child health outcomes associated with maternal asthma and atopy. The authors investigated associations between maternal asthma/atopy and EV miRNAs in the Programming of Intergenerational Stress Mechanisms cohort. Methods: Breast milk-derived EV miRNAs collected 6.1 ± 5.9 weeks postnatally (n = 80 mothers) were profiled using the TaqMan OpenArray Human MicroRNA Panel. The authors assessed associations using adjusted robust regression. Results: Nine EV miRNAs were associated with asthma during pregnancy (a priori criteria: nominal p < 0.05; |B_regression| >0.2). miR-1290 was associated with asthma and atopy during pregnancy (p < 0.05; |B_regression| >0.2). Enriched Kyoto Encyclopedia of Genes and Genomes pathways included TGF-β signaling and extracellular matrix-receptor interaction (false discovery rate <0.05). Conclusion: In this study, maternal asthma and atopy were associated with breast milk-derived EV miRNAs. Additional studies are needed to understand whether EV miRNAs have direct effects on infant and child health.

Unlocking the secrets of long non-coding RNAs in asthma

Asthma is a very heterozygous disease, divided in subtypes, such as eosinophilic and neutrophilic asthma. Phenotyping and endotyping of patients, especially patients with severe asthma who are refractory to standard treatment, are crucial in asthma management and are based on a combination of clinical and biological features. Nevertheless, the quest remains to find better biomarkers that distinguish asthma subtypes in a more clear and objective manner and to find new therapeutic targets to treat people with therapy-resistant asthma. In the past, research to identify asthma subtypes mainly focused on expression profiles of protein-coding genes. However, advances in RNA-sequencing technologies and the discovery of non-coding RNAs as important post-transcriptional regulators have provided an entire new field of research opportunities in asthma. This review focusses on long non-coding RNAs (lncRNAs) in asthma; these are non-coding RNAs with a length of more than 200 nucleotides. Many lncRNAs are differentially expressed in asthma, and several have been associated with asthma severity or inflammatory phenotype. Moreover, in vivo and in vitro functional studies have identified the mechanisms of action of specific lncRNAs. Although lncRNAs remain not widely studied in asthma, the current studies show the potential of lncRNAs as biomarkers and therapeutic targets as well as the need for further research.

Down-regulation of miR-140-3p is a cause of the interlukin-13-induced up-regulation of RhoA protein in bronchial smooth muscle cells

The current study aimed to determine the role of a microRNA (miRNA), miR-140-3p, in the control of RhoA expression in bronchial smooth muscle cells (BSMCs). In cultured human BSMCs, incubation with interleukin-13 (IL-13) caused an up-regulation of RhoA protein concurrently with a down-regulation of miR-140-3p. Transfection of the cells with a miR-140-3p inhibitor caused an increase in basal RhoA protein level. Although a mimic of miR-140-3p had little effect on the basal RhoA level, its treatment inhibited the IL-13-induced up-regulation of RhoA. These findings suggest that RhoA expression is negatively regulated by miR-140-3p, and that the negative regulation is inhibited by IL-13 to cause an up-regulation of RhoA protein in BSMCs.

Metabolites of intestinal microflora upregulate microRNA-200c-3p expression level to suppress airway epithelial inflammation via the IL6ST/JNK/STAT3 signaling pathway

Intestinal microfloras are involved in various types of cancer; however, there is a limited amount of research into the involvement of metabolites of intestinal microflora (MIM) in asthmatic airway epithelial cells (AECs). The present study was designed to reveal the functions and mechanisms of MIM in the asthmatic inflammation of AECs. House dust mite (HDM)-induced asthma cell models were established and treated with mouse MIM. A MTT assay was used to investigate AEC viability, while reverse transcription-quantitative PCR and western blot analysis were used to measure the expression levels of miR-200c-3p, IL6ST, JNK and STAT3 in asthmatic AECs. ELISA was used to measure the concentration of IL-5 and IL-6. Furthermore, the targeting relationship between microRNA(miR)-200c-3p and IL6ST was investigated using a luciferase reporter gene assay. Compared with normal human bronchial epithelial cells, HDM-induced AECs had lower expression level of miR-200c-3p, higher mRNA and protein expression levels of IL6ST and an increase in IL-5 and IL-6 concentration. Both MIM and miR-200c-3p mimics suppressed the secretion of IL-5 and L-6 and promoted the proliferation of HDM-induced AECs. MIM could also upregulate miR-200c-3p and downregulate IL6ST and proteins in the JNK/STAT3 pathway. IL6ST was found to be a downstream target of miR-200c-3p. Inhibition of miR-200c-3p reversed the suppression of asthmatic inflammation by MIM. In summary, MIM upregulated miR-200c-3p expression level to reduce the protein and mRNA expression levels of IL6ST and suppress its downstream JNK/STAT3 signaling pathway, therefore inhibiting the asthmatic inflammation of AECs.

Seasonal Variation in miR-328-3p and let-7d-3p Are Associated With Seasonal Allergies and Asthma Symptoms in Children

OBJECTIVE

MicroRNAs (miRs) are small non-coding RNA molecules of around 18-22 nucleotides that are key regulators of many biologic processes, particularly inflammation. The purpose of this study was to determine the association of circulating miRs from asthmatic children with seasonal variation in allergic inflammation and asthma symptoms.

METHODS

We used available small RNA sequencing on blood serum from 398 children with mild-to-moderate asthma from the Childhood Asthma Management Program. We used seasonal asthma symptom data at the study baseline and allergen affection status from baseline skin prick tests as primary outcomes. We identified differentially expressed (DE) miRs between pairs of seasons using DESeq2. Regression analysis was used to identify associations between allergy status to specific seasonal allergens and DE miRs in 4 seasons and between seasonal asthma symptom data and DE miRs. We performed pathway enrichment analysis for target genes of the DE miRs using DAVID.

RESULTS

After quality control, 398 samples underwent differential analysis between the 4 seasons. We found 52 unique miRs from a total of 81 DE miRs across seasons. Further investigation of the association between these miRs and sensitization to seasonal allergens using skin prick tests revealed that 26 unique miRs from a total of 38 miRs were significantly associated with a same-season allergen. Comparison between seasonal asthma symptom data revealed that 2 of these 26 miRs also had significant associations with asthma symptoms in the same seasons: miR-328-3p (P < 0.03) and let-7d-3p (P < 0.05). Enrichment analysis showed that the most enriched pathway clusters were Rap1, Ras, and MAPK signaling pathways.

CONCLUSION

Our results show seasonal variation in miR-328-3p and let-7d-3p are significantly associated with seasonal asthma symptoms and seasonal allergies. These indicate a potentially protective role for let-7d-3p and a deleterious role for miR-328-3p in asthmatics sensitized to mulberry. Further work will determine whether these miRs are drivers or results of the allergic response.

Circulating miRNA expression in asthmatics is age-related and associated with clinical asthma parameters, respiratory function and systemic inflammation

Background

The course of asthma may differ between elderly asthmatics (EA) and non-elderly asthmatics (nEA), which may be partially associated with an age-dependent aberrant immune response. The aim of the study was to determine the influence of serum miRNA expression on asthma characteristics and systemic inflammation markers in EA and nEA.

Methods

Control and severity of asthma, pulmonary function and FeNO were assessed in 28 EA and 31 nEA patients. The control group included 59 elderly and non-elderly healthy individuals. The expression of selected miRNAs in serum was measured with rt-PCR, and proinflammatory cytokine activity was assayed by ELISA or flow cytometry.

Results

No difference in serum miRNA expression was observed between the asthmatics and healthy controls. EA demonstrated lower expression of miRNA-106a and miRNA-126a than nEA (p = 0.003 and p = 0.02) and EC had lower expression of miRNA-146a, -126a, -106a and 19b than nEC (p = 0.001, p = 0.003, p = 0.005 and p < 0.001 respectively). Only nEA demonstrated a relationship between the expression of selected miRNAs and the level of asthma control (assessed with ACT) and with airway inflammation, measured by FeNO level. All patients with asthma demonstrated elevated TNFα, IL-6 and sTNF RI levels compared to controls (p = 0.026, p = 0.03 and p < 0.001 respectively). EA demonstrated a higher TNFα level than EC (p < 0.001), and EA had a higher level of sTNF RI than nEA (p < 0.001). A significant correlation was observed between serum levels of proinflammatory cytokines and selected miRNAs.

Conclusion

Serum miRNA expression was found to correlate with clinical characteristics of asthma and systemic inflammation in an age-dependent fashion, suggesting that miRNA may differentially contribute to asthma pathogenesis in elderly and non-elderly patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01769-x.

New concepts in pediatric rhinitis

Rhinitis-and especially allergic rhinitis (AR)-remains the most frequent hypersensitivity condition, affecting up to a quarter of the population and impacting the quality of life of individual patients and the health economy. Data, especially with respect to underlying pathophysiologic mechanisms, mainly derive from studies on adults and are subsequently extrapolated to the pediatric population. Therapeutic algorithms for children with rhinitis are long based on the same principles as in adults. We explore and describe novel aspects of rhinitis, ranging from mechanisms to disease classification, phenotypes, diagnostic and monitoring tools, and the use of treatments, with a focus on the traits of pediatric age groups.

The axis of the receptor for advanced glycation endproducts in asthma and allergic airway disease

Asthma is a generalized term that describes a scope of distinct pathologic phenotypes of variable severity, which share a common complication of reversible airflow obstruction. Asthma is estimated to affect almost 400 million people worldwide, and nearly ten percent of asthmatics have what is considered "severe" disease. The majority of moderate to severe asthmatics present with a "type 2-high" (T2-hi) phenotypic signature, which pathologically is driven by the type 2 cytokines Interleukin-(IL)-4, IL-5, and IL-13. However, "type 2-low" (T2-lo) phenotypic signatures are often associated with more severe, steroid-refractory neutrophilic asthma. A wide range of clinical and experimental studies have found that the receptor for advanced glycation endproducts (RAGE) plays a significant role in the pathogenesis of asthma and allergic airway disease (AAD). Current experimental data indicates that RAGE is a critical mediator of the type 2 inflammatory reactions which drive the development of T2-hi AAD. However, clinical studies demonstrate that increased RAGE ligands and signaling strongly correlate with asthma severity, especially in severe neutrophilic asthma. This review presents an overview of the current understandings of RAGE in asthma pathogenesis, its role as a biomarker of disease, and future implications for mechanistic studies, and potential therapeutic intervention strategies.

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.

Baicalin regulates the development of pediatric asthma via upregulating microRNA-103 and mediating the TLR4/NF-κB pathway

Pediatric asthma seriously endangers the well-being and health of children worldwide. Baicalin (BA) protects against diverse disorders, including asthma. Therefore, this study explored the mechanism of BA in pediatric asthma. The ovalbumin (OVA)-induced asthmatic mouse model was established to evaluate BA efficacy from aspects of oxidative stress, inflammation, blood cells in bronchoalveolar lavage fluid (BALF) and collagen deposition. Differentially expressed microRNAs (miRs) in BA-treated mice were analyzed. Effects of BA on PDGF-BB-induced smooth muscle cells (SMCs) were assessed. miR downstream mRNA and the related pathway were predicted and verified, and their effects on asthmatic mice were evaluated. BA effectively reversed OVA-induced oxidative stress and inflammation, as well as decreased the number of total cells, eosinophils and neutrophils in BALF, and collagen deposition. miR-103 was significantly upregulated after BA treatment. BA inhibited the abnormal proliferation of PDGF-BB-induced SMCs, which was prevented by miR-103 knockdown. miR-103 targeted TLR4 and regulated the extent of NF-κB phosphorylation. In vivo, miR-103 inhibition weakened the alleviating effects of BA on asthma, which was then reversed after silencing of TLR4. We highlighted that BA has the potency to halt the pediatric asthma progression via miR-103 upregulation and the TLR4/NF-κB axis inhibition.

Integrated miRNA and mRNA expression profiling reveals dysregulated miRNA-mRNA regulatory networks in eosinophilic and non-eosinophilic chronic rhinosinusitis with nasal polyps

BACKGROUND

The precise mechanisms underlying pathogenesis of different subtypes of chronic rhinosinusitis with nasal polyps (CRSwNP) are still unclear. Emerging evidence indicates that microRNAs may play a role in the pathogenesis of CRSwNP. This study aimed to identify the dysregulated microRNA-messenger RNA (miRNA-mRNA) regulatory networks in eosinophilic (E) and non-eosinophilic (non-E) CRSwNP.

METHODS

Whole-transcriptome sequencing was performed on nasal tissues of patients with ECRSwNP and non-ECRSwNP, and control subjects. An integrated analysis of miRNA and mRNA expression was conducted to identify key mRNAs and miRNAs involved in the pathogenesis of ECRSwNP and non-ECRSwNP. The miRNAs of interest and their target genes were validated using quantitative real-time polymerase chain reaction (PCR).

RESULTS

A group of differentially expressed mRNAs (DE-mRNAs) and miRNAs (DE-miRs) were identified in ECRSwNP patients vs control subjects, non-ECRSwNP patients vs control subjects, and non-ECRSwNP vs ECRSwNP patients, respectively. Pathway enrichment analysis showed distinct immune and inflammatory functions associated with DE-mRNAs and target genes of DE-miRs in ECRSwNP vs control and non-ECRSwNP vs control groups. The miRNA-mRNA regulatory networks constructed with Cytoscape highlighted the roles of miR-154, miR-221, and miR-223 family miRNAs relating to both ECRSwNP and non-ECRSwNP, and the roles of the let-7 and miR-34/449 families in the development of non-ECRSwNP. Assessment using real-time PCR for the expression of miRNAs and target genes demonstrated highly consistent data with the RNA sequencing data.

CONCLUSION

ECRSwNP and non-ECRSwNP patients express distinct miRNA-mRNA regulatory networks compared with control subjects, thus providing potential targets for future development of novel therapeutic approaches for the management of CRSwNP.

MiR-204-5p Performs a Protective Effect on Cerulein-Induced Rat Pancreatic Acinar Cell AR42J Cell Damage by Targeting Tyrosine 3-Monooxygenase/Tryptophan 5-Monooxygenase Activation Protein Gamma and Regulating PI3K/Hippo Pathways

OBJECTIVE

This research plans to address the function of miR-204-5p/tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein gamma (YWHAG) in cerulein-induced acute pancreatitis (AP).

METHODS

Rat pancreatic acinar cell AR42J was stimulated by 100 nmol/L of cerulein to mimic the situation in AP. Gene Expression Omnibus database was used to select differentially expressed genes. StarBase database and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were used to select the target genes of miR-204-5p, which were further affirmed by dual luciferase assay. The biological behaviors of AR42J cells were measured by cell proliferation and flow cytometry assays. Quantitative real-time polymerase chain reaction and western blot assays were executed to assess YWHAG expression. The secretion of C-C Motif Chemokine Ligand 2/Timp metallopeptidase inhibitor 1 in AR42J cells was evaluated by enzyme-linked immunosorbent assay. The protein expression of YAP1/p-YAP1/PI3K/p-PI3K was measured by western blot.

RESULTS

miR-204-5p expression was profoundly reduced in cerulein-induced AP model. YWHAG was upregulated in cerulein-induced AP model and related to C-C Motif Chemokine Ligand 2/Timp1. In addition to the negative association between miR-204-5p and YWHAG, the alleviation impact of miR-204-5p mimic on cerulein-induced AR42J cell damage was blocked by YWHAG overexpression and PI3K/Hippo signaling pathways activation.

CONCLUSIONS

These observations indicated that the alleviation impact of miR-204-5p on cerulein-induced AR42J cell damage was mediated via YWHAG and PI3K/Hippo signaling pathways.

An update on the epigenetics of asthma

PURPOSE OF REVIEW

Asthma is a common disease worldwide, however, its pathogenesis has not been fully elucidated. Emerging evidence suggests that epigenetic modifications may play a role in the development and natural history of asthma. The aim of this review is to highlight recent progress in research on epigenetic mechanisms in asthma.

RECENT FINDINGS

Over the past years, epigenetic studies, in particular DNA methylation studies, have added to the growing body of evidence supporting a link between epigenetic regulation of gene expression and asthma. Recent studies demonstrate that epigenetic mechanisms also play a role in asthma remission. Although most existing studies in this field have been conducted on blood cells, recent evidence suggests that epigenetic signatures are also crucial for the regulation of airway epithelial cells. Studies conducted on nasal epithelium revealed highly replicable epigenetic patterns that could be used for diagnostic purposes.

SUMMARY

Further research is needed to explore the diagnostic and therapeutic potential of epigenetic modifications in asthma. Multiomics studies on asthma will become increasingly important for a better understanding of etiology, heterogeneity, and severity of asthma, as well as establishing molecular biomarkers that could be combined with clinical information to improve the management of asthma patients.

MicroRNAs as Potential Regulators of Immune Response Networks in Asthma and Chronic Obstructive Pulmonary Disease

Chronic respiratory diseases (CRDs) are an important factor of morbidity and mortality, accounting for approximately 6% of total deaths worldwide. The main CRDs are asthma and chronic obstructive pulmonary disease (COPD). These complex diseases have different triggers including allergens, pollutants, tobacco smoke, and other risk factors. It is important to highlight that although CRDs are incurable, various forms of treatment improve shortness of breath and quality of life. The search for tools that can ensure accurate diagnosis and treatment is crucial. MicroRNAs (miRNAs) are small non-coding RNAs and have been described as promising diagnostic and therapeutic biomarkers for CRDs. They are implicated in multiple processes of asthma and COPD, regulating pathways associated with inflammation, thereby showing that miRNAs are critical regulators of the immune response. Indeed, miRNAs have been found to be deregulated in several biofluids (sputum, bronchoalveolar lavage, and serum) and in both structural lung and immune cells of patients in comparison to healthy subjects, showing their potential role as biomarkers. Also, miRNAs play a part in the development or termination of histopathological changes and comorbidities, revealing the complexity of miRNA regulation and opening up new treatment possibilities. Finally, miRNAs have been proposed as prognostic tools in response to both conventional and biologic treatments for asthma or COPD, and miRNA-based treatment has emerged as a potential approach for clinical intervention in these respiratory diseases; however, this field is still in development. The present review applies a systems biology approach to the understanding of miRNA regulatory networks in asthma and COPD, summarizing their roles in pathophysiology, diagnosis, and treatment.

MicroRNA-21 Inhibition Suppresses Alveolar M2 Macrophages in an Ovalbumin-Induced Allergic Asthma Mice Model

Purpose

MicroRNA-21 (miR-21) influences the Th2 immune pathway by suppressing the expressions of interleukin (IL)-12 and interferon (IFN)-γ. The effects of miR-21 suppression on alveolar macrophage polarization and airway inflammation are not known.

Methods

BALB/c and miR-21 knockout (KO) mice were sensitized and challenged with ovalbumin (OVA). The anti-miR-21 antagomir was administered to BALB/c mice by intranasal inhalation from the day of OVA sensitization. Changes in cell counts, cytokine levels in bronchoalveolar lavage fluid (BALF), and airway hyperresponsiveness (AHR) were examined. Total, M1, and M2 macrophages were examined in the lung tissues by immunohistochemistry (IHC). M2 macrophages from the OVA mice lung were inhaled into the anti-miR-21 antagomir-treated asthmatic mice. Moreover, the polarization of M0 to M2 macrophages upon IL-4 stimulation was analyzed after anti-miR-21 antagomir transfection.

Results

The miR-21 KO mice showed decreases in AHR, total cell and eosinophil counts in BALF, and in the levels of IL-4, IL-5, IL-10, and IL-13. Expression of IL-12 and IFN-γ were increased in the miR-21 KO mice. Peribronchial inflammation and goblet cell dysplasia were significantly decreased in the lung tissues of miR-21 KO OVA mice compared to the wild type OVA mice. IHC for M1, M2, and total macrophage in the lung tissues showed that miR-21 inhalation suppressed alveolar M2 macrophages in KO mice. M2 macrophage inhalation restored AHR and eosinophilic airway inflammation in the miR-21 antagomir-treated mice. Moreover, anti-miR-21 antagomir transfection decreased the expression of M2 markers and increased the expression of M1 markers in M0 macrophages after IL-4 stimulation.

Conclusions

The results suggest that miR-21 antagonism could suppress alveolar M2 macrophage polarization, decreasing not only the Th2 eosinophilic airway inflammation but also AHR and airway remodeling process.

Extracellular Vesicles as Unique Signaling Messengers: Role in Lung Diseases

Extracellular vesicles (EVs) are lipid bilayer-enclosed extracellular particles carrying rich cargo such as proteins, lipids, and microRNAs with distinct characteristics of their parental cells. EVs are emerging as an important form of cellular communication with the ability to selectively deliver a kit of directional instructions to nearby or distant cells to modulate their functions and phenotypes. According to their biogenesis, EVs can be divided into two groups: those of endocytic origin are called exosomes and those derived from outward budding of the plasma membrane are called microvesicles (also known as ectosomes or microparticles). Under physiological conditions, EVs are actively involved in maintenance of pulmonary hemostasis. However, EVs can contribute to the pathogenesis of diseases such as chronic obstructive pulmonary disease, asthma, acute lung injury/acute respiratory distress syndrome, interstitial lung disease, and pulmonary arterial hypertension. EVs, especially those derived from mesenchymal/stromal stem cells, can also be beneficial and can curb the development of lung diseases. Novel technologies are continuously being developed to minimize the undesirable effects of EVs and also to engineer EVs so that they may have beneficial effects and can be used as therapeutic agents in lung diseases. © 2021 American Physiological Society. Compr Physiol 11:1351-1369, 2021.

Biomarkers for diagnosis and prediction of therapy responses in allergic diseases and asthma

Modern health care requires a proactive and individualized response to diseases, combining precision diagnosis and personalized treatment. Accordingly, the approach to patients with allergic diseases encompasses novel developments in the area of personalized medicine, disease phenotyping and endotyping, and the development and application of reliable biomarkers. A detailed clinical history and physical examination followed by the detection of IgE immunoreactivity against specific allergens still represents the state of the art. However, nowadays, further emphasis focuses on the optimization of diagnostic and therapeutic standards and a large number of studies have been investigating the biomarkers of allergic diseases, including asthma, atopic dermatitis, allergic rhinitis, food allergy, urticaria and anaphylaxis. Various biomarkers have been developed by omics technologies, some of which lead to a better classification of distinct phenotypes or endotypes. The introduction of biologicals to clinical practice increases the need for biomarkers for patient selection, prediction of outcomes and monitoring, to allow for an adequate choice of the duration of these costly and long‐lasting therapies. Escalating healthcare costs together with questions about the efficacy of the current management of allergic diseases require further development of a biomarker‐driven approach. Here, we review biomarkers in diagnosis and treatment of asthma, atopic dermatitis, allergic rhinitis, viral infections, chronic rhinosinusitis, food allergy, drug hypersensitivity and allergen immunotherapy with a special emphasis on specific IgE, the microbiome and the epithelial barrier. In addition, EAACI guidelines on biologicals are discussed within the perspective of biomarkers.

Downregulation of miR-140-3p Contributes to Upregulation of CD38 Protein in Bronchial Smooth Muscle Cells

In allergic bronchial asthma, an increased smooth muscle contractility of the airways is one of the causes of the airway hyperresponsiveness (AHR). Increasing evidence also suggests a possible involvement of microRNAs (miRNAs) in airway diseases, including asthma, although their roles in function and pathology largely unknown. The current study aimed to determine the role of a miRNA, miR-140-3p, in the control of protein expression of CD38, which is believed to regulate the contraction of smooth muscles, including the airways. In bronchial smooth muscles (BSMs) of the mice that were actively sensitized and repeatedly challenged with ovalbumin antigen, an upregulation of CD38 protein concurrently with a significant reduction of miR-140-3p was observed. In cultured human BSM cells (hBSMCs), transfection with a synthetic miR-140-3p inhibitor caused an increase in CD38 protein, indicating that its basal protein expression is regulated by endogenous miR-140-3p. Treatment of the hBSMCs with interleukin-13 (IL-13), an asthma-related cytokine, caused both an upregulation of CD38 protein and a downregulation of miR-140-3p. Transfection of the hBSMCs with miR-140-3p mimic inhibited the CD38 protein upregulation induced by IL-13. On the other hand, neither a CD38 product cyclic ADP-ribose (cADPR) nor its antagonist 8-bromo-cADPR had an effect on the BSM contraction even in the antigen-challenged mice. Taken together, the current findings suggest that the downregulation of miR-140-3p induced by IL-13 might cause an upregulation of CD38 protein in BSM cells of the disease, although functional and pathological roles of the upregulated CD38 are still unclear.

miRNAs in Lung Development and Diseases

The development of the lung involves a diverse group of molecules that regulate cellular processes, organ formation, and maturation. The various stages of lung development are marked by accumulation of small RNAs that promote or repress underlying mechanisms, depending on the physiological environment in utero and postnatally. To some extent, the pathogenesis of various lung diseases is regulated by small RNAs. In this review, we discussed miRNAs regulation of lung development and diseases, that is, COPD, asthma, pulmonary fibrosis, and pulmonary arterial hypertension, and also highlighted possible connotations for human lung health.

Genetics and epigenetics of allergy

PURPOSE OF REVIEW

Allergic diseases are prototypic examples for gene × environment-wide interactions. This review considers the current evidence for genetic and epigenetic mechanisms in allergic diseases and highlights barriers and facilitators for the implementation of these novel tools both for research and clinical practice.

RECENT FINDINGS

The value of whole-genome sequencing studies and the use of polygenic risk score analysis in homogeneous well characterized populations are currently being tested. Epigenetic mechanisms are known to play a crucial role in the pathogenesis of allergic disorders, especially through mediating the effects of the environmental factors, well recognized risk modifiers. There is emerging evidence for the immune-modulatory role of probiotics through epigenetic changes. Direct or indirect targeting of epigenetic mechanisms affect expression of the genes favouring the development of allergic diseases and can improve tissue biology. The ability to specifically edit the epigenome, especially using the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology, holds the promise of enhancing understanding of how epigenetic modifications function and enabling manipulation of cell phenotype for research or therapeutic purposes.

SUMMARY

Additional research in the role of genetic and epigenetic mechanisms in relation to allergic diseases' endotypes is needed. An international project characterizing the human epigenome in relation to allergic diseases is warranted.