Joerg Mattes

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.

Integrated Signals Between IL-13, IL-4, and IL-5 Regulate Airways Hyperreactivity

In this investigation, we have examined the integrated relationship between IL-13, IL-4, and IL-5 for the development of airways hyperreactivity (AHR) in a model of asthma in BALB/c mice. Sensitization and aeroallergen challenge of both wild-type (WT) and IL-13 gene-targeted (IL-13−/−) mice induced allergic disease that was characterized by pulmonary eosinophilia and AHR to β-methacholine. Although these responses in IL-13−/− mice were heightened compared with WT, they could be reduced to the level in nonallergic mice by the concomitant neutralization of IL-4. Mice in which both IL-4 and IL-13 were depleted displayed a marked reduction in tissue eosinophils, despite the development of a blood eosinophilia. Similar neutralization of IL-4 in WT mice only partially reduced AHR with no effect on tissue eosinophilia. In addition, neutralization of IL-5 in IL-13−/− mice, but not in WT mice, inhibited AHR, suggesting that tissue eosinophilia is linked to the mechanism underlying AHR only in the absence of IL-13. Additionally, mucus hypersecretion was attenuated in IL-13−/− mice, despite the persistence of AHR. Taken together, our data suggest both a modulatory role for IL-13 during sensitization and a proinflammatory role during aeroallergen challenge. The latter process appears redundant with respect to IL-4.

Intrinsic Defect in T Cell Production of Interleukin (IL)-13 in the Absence of Both IL-5 and Eotaxin Precludes the Development of Eosinophilia and Airways Hyperreactivity in Experimental Asthma

Interleukin (IL)-5 and IL-13 are thought to play key roles in the pathogenesis of asthma. Although both cytokines use eotaxin to regulate eosinophilia, IL-13 is thought to operate a separate pathway to IL-5 to induce airways hyperreactivity (AHR) in the allergic lung. However, identification of the key pathway(s) used by IL-5 and IL-13 in the disease process is confounded by the failure of anti–IL-5 or anti–IL-13 treatments to completely inhibit the accumulation of eosinophils in lung tissue. By using mice deficient in both IL-5 and eotaxin (IL-5/eotaxin−/−) we have abolished tissue eosinophilia and the induction of AHR in the allergic lung. Notably, in mice deficient in IL-5/eotaxin the ability of CD4+ T helper cell (Th)2 lymphocytes to produce IL-13, a critical regulator of airways smooth muscle constriction and obstruction, was significantly impaired. Moreover, the transfer of eosinophils to IL-5/eotaxin−/− mice overcame the intrinsic defect in T cell IL-13 production. Thus, factors produced by eosinophils may either directly or indirectly modulate the production of IL-13 during Th2 cell development. Our data show that IL-5 and eotaxin intrinsically modulate IL-13 production from Th2 cells and that these signaling systems are not necessarily independent effector pathways and may also be integrated to regulate aspects of allergic disease.

Elemental signals regulating eosinophil accumulation in the lung

Summary: In this review we identify the elemental signals that regulate eosinophil accumulation in the allergic lung. We show that there are two interwoven mechanisms for the accumulation of eosinophils in pulmonary tissues and that these mechanisms are linked to the development of airways hyperreactivity (AHR). Interleukin‐(IL)‐5 plays a critical role in the expansion of eosinophil pools in both the bone marrow and blood in response to allergen provocation of the airways. Secondly, IL‐4 and IL‐13 operate within the allergic lung to control the transmigration of eosinophils across the vascular bed into pulmonary tissues. This process exclusively promotes tissue accumulation of eosinophils. IL‐13 and IL‐4 probably act by activating eosinophil‐specific adhesion pathways and by regulating the production of IL‐5 and eotaxin in the lung compartment. IL‐5 and eotaxin co‐operate locally in pulmonary tissues to selectively and synergistically promote eosinophilia. Thus, IL‐5 acts systemically to induce eosinophilia and within tissues to promote local chemotactic signals. Regulation of IL‐5 and eotaxin levels within the lung by IL‐4 and IL‐13 allows Th2 cells to elegantly co‐ordinate tissue and peripheral eosinophilia. Whilst the inhibition of either the IL‐4/IL‐13 or IL‐5/ eotaxin pathways resulted in the abolition of tissue eosinophils and AHR, only depletion of IL‐5 and eotaxin concurrently results in marked attenuation of pulmonary inflammation. These data highlight the importance of targeting both IL‐5 and CCR3 signalling systems for the resolution of inflammation and AHR associated with asthma.

Evidence that asthma is a developmental origin disease influenced by maternal diet and bacterial metabolites

Asthma is prevalent in Western countries, and recent explanations have evoked the actions of the gut microbiota. Here we show that feeding mice a high-fibre diet yields a distinctive gut microbiota, which increases the levels of the short-chain fatty acid, acetate. High-fibre or acetate-feeding led to marked suppression of allergic airways disease (AAD, a model for human asthma), by enhancing T-regulatory cell numbers and function. Acetate increases acetylation at the Foxp3 promoter, likely through HDAC9 inhibition. Epigenetic effects of fibre/acetate in adult mice led us to examine the influence of maternal intake of fibre/acetate. High-fibre/acetate feeding of pregnant mice imparts on their adult offspring an inability to develop robust AAD. High fibre/acetate suppresses expression of certain genes in the mouse fetal lung linked to both human asthma and mouse AAD. Thus, diet acting on the gut microbiota profoundly influences airway responses, and may represent an approach to prevent asthma, including during pregnancy.

Eosinophils Promote Allergic Disease of the Lung by Regulating CD4+ Th2 Lymphocyte Function

Eosinophils are primarily thought of as terminal effectors of allergic responses and of parasite elimination. However, limited studies suggest a more discrete immunomodulatory role for this leukocyte during these inflammatory responses. In this investigation, we highlight the potential of eosinophils to act as APCs and thus modulators of allergic responses by influencing Th2 cell function. In response to Ag provocation of the allergic lung, eosinophils rapidly trafficked to sites of Ag deposition (airways lumen) and presentation (lung-associated lymph nodes and T cell-rich paracortical zones). Eosinophils from the allergic lung expressed class II MHC peptides, T cell costimulatory molecules (CD80 and CD86), and rapidly internalized and processed Ag that was sampled from within the airway lumen. Ag-loaded eosinophils promoted the production of IL-4, IL-5, and IL-13 in cocultures with in vitro-polarized Th2 cells and induced IL-5 production in a dose-dependent manner from Ag-specific CD4+ T cells isolated from allergic mice. In addition, Ag-loaded eosinophils primed for Th2 cell-driven allergic disease of the lung when transferred to naive mice. Thus, eosinophils have the potential to not only activate Th2 cells to release disease-modulating cytokines but also to assist in priming the immune system for allergic responses. This investigation highlights the potential of eosinophils to not only act as terminal effector cells but also to actively modulate allergic inflammation by amplifying Th2 cell responses.

Immunotherapy of Cytotoxic T Cell–resistant Tumors by T Helper 2 Cells: An Eotaxin and STAT6-dependent Process

Currently most attempts at cancer immunotherapy involve the generation of CD8+ cytotoxic T lymphocytes (CTLs) against tumor-associated antigens. Many tumors, however, have been immunoselected to evade recognition by CTLs and thus alternative approaches to cancer immunotherapy are urgently needed. Here we demonstrate that CD4+ T cells that recognize a secreted tumor-specific antigen and exhibit a cytokine secretion profile characteristic of Th2 cells, are capable of clearing established lung and visceral metastases of a CTL-resistant melanoma. Clearance of lung metastases by the Th2 cells was found to be totally dependent on the eosinophil chemokine, eotaxin, and partially dependent on the transcription activator signal transducer and activator of transcription 6 (STAT6), with degranulating eosinophils within the tumors inducing tumor regression. In contrast, tumor-specific CD4+ Th1 cells, that recruited macrophages into the tumors, had no effect on tumor growth. This work provides the basis for a new approach to adoptive T cell immunotherapy of cancer.

Toll/IL-1 Signaling Is Critical for House Dust Mite―specific Th1 and Th2 Responses

RATIONALE One of the immunopathological features of allergic inflammation is the infiltration of helper T type 2 (Th2) cells to the site of disease. Activation of innate pattern recognition receptors such as Toll-like receptors (TLRs) plays a critical role in helper T type 1 cell differentiation, yet their contribution to the generation of Th2 responses to clinically relevant aeroallergens remains poorly defined. OBJECTIVES To determine the requirement for TLR2, TLR4, and the Toll/IL-1 receptor domain adaptor protein MyD88 in a murine model of allergic asthma. METHODS Wild-type and factor-deficient ((-/-)) mice were sensitized intranasally to the common allergen house dust mite (HDM) and challenged 2 weeks later on four consecutive days. Measurements of allergic airway inflammation, T-cell cytokine production, and airway hyperreactivity were performed 24 hours later. MEASUREMENTS AND MAIN RESULTS Mice deficient in MyD88 were protected from the cardinal features of allergic asthma, including granulocytic inflammation, Th2 cytokine production and airway hyperreactivity. Although HDM activated NF-kappaB in TLR2- or TLR4-expressing HEK cells, only in TLR4(-/-) mice was the magnitude of allergic airway inflammation and hyperreactivity attenuated. The diminished Th2 response present in MyD88(-/-) and TLR4(-/-) mice was associated with fewer OX40 ligand-expressing myeloid dendritic cells in the draining lymph nodes during allergic sensitization. Finally, HDM-specific IL-17 production and airway neutrophilia were attenuated in MyD88(-/-) but not TLR4(-/-) mice. CONCLUSIONS Together, these data suggest that Th2- and Th17-mediated inflammation generated on inhalational HDM exposure is differentially regulated by the presence of microbial products and the activation of distinct MyD88-dependent pattern recognition receptors.

IL-13 Induces Airways Hyperreactivity Independently of the IL-4Rα Chain in the Allergic Lung

The potent spasmogenic properties of IL-13 have identified this molecule as a potential regulator of airways hyperreactivity (AHR) in asthma. Although IL-13 is thought to primarily signal through the IL-13Rα1-IL-4Rα complex, the cellular and molecular components employed by this cytokine to induce AHR in the allergic lung have not been identified. By transferring OVA-specific CD4+ T cells that were wild type (IL-13+/+ T cells) or deficient in IL-13 (IL-13−/− T cells) to nonsensitized mice that were then challenged with OVA aerosol, we show that T cell-derived IL-13 plays a key role in regulating AHR, mucus hypersecretion, eotaxin production, and eosinophilia in the allergic lung. Moreover, IL-13+/+ T cells induce these features (except mucus production) of allergic disease independently of the IL-4Rα chain. By contrast, IL-13+/+ T cells did not induce disease in STAT6-deficient mice. This shows that IL-13 employs a novel component of the IL-13 receptor signaling system that involves STAT6, independently of the IL-4Rα chain, to modulate pathogenesis. We show that this novel pathway for IL-13 signaling is dependent on T cell activation in the lung and is critically linked to downstream effector pathways regulated by eotaxin and STAT6.

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.