Maximilian Plank

Antagonism of microRNA-126 suppresses the effector function of TH2 cells and the development of allergic airways disease

Allergic asthma is an inflammatory disease of the lung characterized by abnormal T helper-2 (TH2) lymphocyte responses to inhaled antigens. The molecular mechanisms leading to the generation of TH2 responses remain unclear, although toll-like receptors (TLRs) present on innate immune cells play a pivotal role in sensing molecular patterns and in programming adaptive T cell responses. Here we show that in vivo activation of TLR4 by house dust mite antigens leads to the induction of allergic disease, a process that is associated with expression of a unique subset of small, noncoding microRNAs. Selective blockade of microRNA (miR)-126 suppressed the asthmatic phenotype, resulting in diminished TH2 responses, inflammation, airways hyperresponsiveness, eosinophil recruitment, and mucus hypersecretion. miR-126 blockade resulted in augmented expression of POU domain class 2 associating factor 1, which activates the transcription factor PU.1 that alters TH2 cell function via negative regulation of GATA3 expression. In summary, this study presents a functional connection between miRNA expression and asthma pathogenesis, and our data suggest that targeting miRNA in the airways may lead to anti-inflammatory treatments for allergic asthma.

Inhibition of house dust mite-induced allergic airways disease by antagonism of microRNA-145 is comparable to glucocorticoid treatment.

BACKGROUND Glucocorticoids are used as mainstay therapy for asthma, but some patients remain resistant to therapy. MicroRNAs (miRNAs) are important regulators of the immune system by promoting the catabolism of their target transcripts as well as attenuating their translation. The role of miRNA in regulating allergic inflammation remains largely unknown. Blocking miRNA function may provide a new nonsteroidal anti-inflammatory approach to treatment. OBJECTIVES To (1) determine the role of specific miRNAs in the regulation of hallmark features of allergic airways inflammation and (2) compare the efficacy of antagonizing miRNA function with that of steroid treatment. METHODS Mice were sensitized and then aeroallergen-challenged with house dust mite to induce allergic airways disease, and alterations in the expression of miRNAs were characterized. Next mice were treated with antagomirs that inhibited the function of specific miRNAs in the lung or treated with dexamethasone and inflammatory lesions, and airway hyperresponsiveness was measured. RESULTS miR-145, miR-21, and let-7b have been implicated in airway smooth muscle function, inflammation, and airways epithelial cell function, respectively. Inhibition of miR-145, but not miR-21 or lethal-7b, inhibited eosinophilic inflammation, mucus hypersecretion, T(H)2 cytokine production, and airway hyperresponsiveness. The anti-inflammatory effects of miR-145 antagonism were comparable to steroid treatment. CONCLUSION Our study highlights the importance of understanding the contribution of miRNAs to pathogenesis of human allergic disease and their potential as novel anti-inflammatory targets.

The emerging role of microRNAs in regulating immune and inflammatory responses in the lung

Chronic inflammatory diseases of the lung are leading causes of morbidity and mortality worldwide. Many of these disorders can be attributed to abnormal immune responses to environmental stimuli and infections. As such, understanding the innate host defense pathways and their regulatory systems will be critical to developing new approaches to treatment. In this regard, there is increasing interest in the role of microRNAs (miRNAs) in the regulation of pulmonary innate host defense responses and the inflammatory sequelae in respiratory disease. In this review, we discuss recent findings that indicate an important role for miRNAs in the regulation in mouse models of various respiratory diseases and in host defense against bacterial and viral infection. We also discuss the potential utility and limitations of targeting these molecules as anti‐inflammatory strategies and also as a means to improve pathogen clearance from the lung.

Targeting translational control as a novel way to treat inflammatory disease: the emerging role of MicroRNAs

Chronic inflammatory diseases (e.g. asthma and chronic obstructive pulmonary disease) are leading causes of morbidity and mortality world‐wide and effective treatments are limited. These disorders can often be attributed to abnormal immune responses to environmental stimuli and infections. Mechanisms leading to inflammation are complex, resulting from interactions of structural cells and activation of both the adaptive and innate arms of the immune system. The activation of structural and immune cells involves both temporary and permanent changes in gene expression in these cells, which underpin chronic inflammation and tissue dysfunction. miRNAs are small non‐coding RNAs increasingly being recognized to play important roles in the post‐transcriptional regulation of gene expression in mammalian cells by regulating translation. Individual miRNAs can exert their effects by directly inhibiting the translation or stability of multiple mRNAs simultaneously. Thus, the expression or blockade of function of a single miRNA (miR) can result in pronounced alterations in protein expression within a given cell. Dysregulation of miRNA expression may subsequently alter cellular function, and in certain situations predispose to disease. Our current understanding of the role of miRNA in the regulation of inflammatory disease (e.g. allergic diseases) remains limited. In this review, we provide an overview of the current understanding of miRNA biogenesis and function, the roles miRNA play in the regulation of immune cell function and their potential contribution to inflammatory diseases. We also highlight strategies to alter miRNA function for experimental or therapeutic gain, and discuss the potential utility and limitations of targeting these molecules as anti‐inflammatory strategies.

Antagonism of miR-328 Increases the Antimicrobial Function of Macrophages and Neutrophils and Rapid Clearance of Non-typeable Haemophilus Influenzae (NTHi) from Infected Lung

Pathogenic bacterial infections of the lung are life threatening and underpin chronic lung diseases. Current treatments are often ineffective potentially due to increasing antibiotic resistance and impairment of innate immunity by disease processes and steroid therapy. Manipulation miRNA directly regulating anti-microbial machinery of the innate immune system may boost host defence responses. Here we demonstrate that miR-328 is a key element of the host response to pulmonary infection with non-typeable haemophilus influenzae and pharmacological inhibition in mouse and human macrophages augments phagocytosis, the production of reactive oxygen species, and microbicidal activity. Moreover, inhibition of miR-328 in respiratory models of infection, steroid-induced immunosuppression, and smoke-induced emphysema enhances bacterial clearance. Thus, miRNA pathways can be targeted in the lung to enhance host defence against a clinically relevant microbial infection and offer a potential new anti-microbial approach for the treatment of respiratory diseases.

Targeting MicroRNA Function in Respiratory Diseases: Mini-Review

MicroRNAs (miRNAs) are small non-coding RNA molecules that modulate expression of the majority of genes by inhibiting protein translation. Growing literature has identified functional roles for miRNAs across a broad range of biological processes. As such, miRNAs are recognized as potential disease biomarkers and novel targets for therapies. While several miRNA-targeted therapies are currently in clinical trials (e.g., for the treatment of hepatitis C virus infection and cancer), no therapies have targeted miRNAs in respiratory diseases in the clinic. In this mini-review, we review the current knowledge on miRNA expression and function in respiratory diseases, intervention strategies to target miRNA function, and considerations specific to respiratory diseases. Altered miRNA expression profiles have been reported in a number of respiratory diseases, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, and idiopathic pulmonary fibrosis. These include alterations in isolated lung tissue, as well as sputum, bronchoalveolar lavage fluids and peripheral blood or serum. The observed alterations in easily accessible body fluids (e.g., serum) have been proposed as new biomarkers that may inform disease diagnosis and patient management. In a subset of studies, miRNA-targeted interventions also improved disease outcomes, indicating functional roles for altered miRNA expression in disease pathogenesis. In fact, direct administration of miRNA-targeting molecules to the lung has yielded promising results in a number of animal models. The ability to directly administer compounds to the lung holds considerable promise and may limit potential off-target effects and side effects caused by the systemic administration required to treat other diseases.

MicroRNA Expression Is Altered in an Ovalbumin-Induced Asthma Model and Targeting miR-155 with Antagomirs Reveals Cellular Specificity

MicroRNAs are post-transcriptional regulators of gene expression that are differentially regulated during development and in inflammatory diseases. A role for miRNAs in allergic asthma is emerging and further investigation is required to determine whether they may serve as potential therapeutic targets. We profiled miRNA expression in murine lungs from an ovalbumin-induced allergic airways disease model, and compared expression to animals receiving dexamethasone treatment and non-allergic controls. Our analysis identified 29 miRNAs that were significantly altered during allergic inflammation. Target prediction analysis revealed novel genes with altered expression in allergic airways disease and suggests synergistic miRNA regulation of target mRNAs. To assess the impacts of one induced miRNA on pathology, we targeted miR-155-5p using a specific antagomir. Antagomir administration successfully reduced miR-155-5p expression with high specificity, but failed to alter the disease phenotype. Interestingly, further investigation revealed that antagomir delivery has variable efficacy across different immune cell types, effectively targeting myeloid cell populations, but exhibiting poor uptake in lymphocytes. Our findings demonstrate that antagomir-based targeting of miRNA function in the lung is highly specific, but highlights cell-specificity as a key limitation to be considered for antagomir-based strategies as therapeutics.

MicroRNA: Potential biomarkers and therapeutic targets for allergic asthma?

Abstract MicroRNAs are small non-coding RNAs that bind to multiple target mRNAs to control gene expression post-transcriptionally by inhibiting translation. In mammalian cells, microRNAs play important roles in a diverse array of cellular processes (e.g. cell proliferation and differentiation). However, alterations in their levels may compromise cellular function, predisposing to disease. In this review, we discuss microRNAs that have been linked with pathogenesis of asthma and propose functional roles in the regulation of disease. MicroRNAs have the potential to be biomarkers for asthma and provide the platform for the development of new classes of therapeutic compounds.

Inhibiting AKT phosphorylation employing non-cytotoxic anthraquinones ameliorates TH2 mediated allergic airways disease and rhinovirus exacerbation.

Background Severe asthma is associated with T helper (TH) 2 and 17 cell activation, airway neutrophilia and phosphoinositide-3-kinase (PI3K) activation. Asthma exacerbations are commonly caused by rhinovirus (RV) and also associated with PI3K-driven inflammation. Anthraquinone derivatives have been shown to reduce PI3K-mediated AKT phosphorylation in-vitro. Objective To determine the anti-inflammatory potential of anthraquinones in-vivo. Methods BALB/c mice were sensitized and challenged with crude house dust mite extract to induce allergic airways disease and treated with mitoxantrone and a novel non-cytotoxic anthraquinone derivative. Allergic mice were also infected with RV1B to induce an exacerbation. Results Anthraquinone treatment reduced AKT phosphorylation, hypoxia-inducible factor-1α and vascular endothelial growth factor expression, and ameliorated allergen- and RV-induced airways hyprereactivity, neutrophilic and eosinophilic inflammation, cytokine/chemokine expression, mucus hypersecretion, and expression of TH2 proteins in the airways. Anthraquinones also boosted type 1 interferon responses and limited RV replication in the lung. Conclusion Non-cytotoxic anthraquinone derivatives may be of therapeutic benefit for the treatment of severe and RV-induced asthma by blocking pro-inflammatory pathways regulated by PI3K/AKT.

Activation of Olfactory Receptors on Mouse Pulmonary Macrophages Promotes Monocyte Chemotactic Protein-1 Production

Background Emerging evidence suggests that non-olfactory tissues and cells can express olfactory receptors (ORs), however, the exact function of ectopic OR expression remains unknown. We have previously shown in mouse models that a unique cooperation between interferon-γ (IFN-γ) and lipopolysaccharide (LPS) drives the activation of pulmonary macrophages and leads to the induction of pathogenic responses in the respiratory tract. Further, through gene array studies, we have shown that activation of macrophages by these molecules results in the selective expression of a number of ORs. In this study, we validated the expression of these ORs in mouse airway and pulmonary macrophages in response to IFN-γ and LPS (γ/LPS) stimulation, and further explored the effect of odorant stimulation on macrophage function. Methodology/Principal Findings OR expression in airway and pulmonary macrophages in response to IFN-γ, LPS or γ/LPS treatments was assessed by microarray and validated by q-PCR. OR expression (e.g. OR622) on macrophages was confirmed by visualization in immunofluoresence assays. Functional responses to odorants were assessed by quantifying inflammatory cytokine and chemokine expression using q-PCR and cell migration was assessed by a modified Boyden chamber migration assay. Our results demonstrate that eight ORs are expressed at basal levels in both airway and pulmonary macrophages, and that γ/LPS stimulation cooperatively increased this expression. Pulmonary macrophages exposed to the combined treatment of γ/LPS+octanal (an odorant) exhibited a 3-fold increase in MCP-1 protein production, compared to cells treated with γ/LPS alone. Supernatants from γ/LPS+octanal exposed macrophages also increased macrophage migration in vitro. Conclusions/Significance Eight different ORs are expressed at basal levels in pulmonary macrophages and expression is upregulated by the synergistic action of γ/LPS. Octanal stimulation further increased MCP-1 production and the motility of macrophages. Our results suggest that ORs may mediate macrophage function by regulating MCP-1 production and cell migration.