Exposure to TARC alters beta2-adrenergic receptor signaling in human peripheral blood T lymphocytes

Neuro-immune interactions in allergic diseases: novel targets for therapeutics

Recent studies have highlighted an emerging role for neuro-immune interactions in mediating allergic diseases. Allergies are caused by an overactive immune response to a foreign antigen. The peripheral sensory and autonomic nervous system densely innervates mucosal barrier tissues including the skin, respiratory tract and gastrointestinal (GI) tract that are exposed to allergens. It is increasingly clear that neurons actively communicate with and regulate the function of mast cells, dendritic cells, eosinophils, Th2 cells and type 2 innate lymphoid cells in allergic inflammation. Several mechanisms of cross-talk between the two systems have been uncovered, with potential anatomical specificity. Immune cells release inflammatory mediators including histamine, cytokines or neurotrophins that directly activate sensory neurons to mediate itch in the skin, cough/sneezing and bronchoconstriction in the respiratory tract and motility in the GI tract. Upon activation, these peripheral neurons release neurotransmitters and neuropeptides that directly act on immune cells to modulate their function. Somatosensory and visceral afferent neurons release neuropeptides including calcitonin gene-related peptide, substance P and vasoactive intestinal peptide, which can act on type 2 immune cells to drive allergic inflammation. Autonomic neurons release neurotransmitters including acetylcholine and noradrenaline that signal to both innate and adaptive immune cells. Neuro-immune signaling may play a central role in the physiopathology of allergic diseases including atopic dermatitis, asthma and food allergies. Therefore, getting a better understanding of these cellular and molecular neuro-immune interactions could lead to novel therapeutic approaches to treat allergic diseases.

Effects of fluticasone propionate and budesonide on the expression of immune defense genes in bronchial epithelial cells

BACKGROUND

COPD patients have increased risk of pneumonia when treated with fluticasone propionate (FP), whereas this is generally not the case with budesonide (BUD) treatment. We hypothesized that BUD and FP differentially affect the expression of immune defense genes.

METHODS

Human bronchial epithelial 16HBE cells and air-liquid interface (ALI)-cultured primary bronchial epithelial cells (PBECs) were pre-treated with clinically equipotent concentrations of BUD or FP (0.16-16 nM BUD and 0.1-10 nM FP), and the expression of immune defense genes was studied at baseline and after exposure to rhinovirus (RV16).

RESULTS

Using microfluidic cards, we observed that both BUD and FP significantly suppressed CXCL8, IFNB1 and S100A8 mRNA expression in unstimulated 16HBE cells. Interestingly, BUD, but not FP, significantly increased lactotransferrin (LTF) expression. The difference between the effect of BUD and FP on LTF expression was statistically significant and confirmed by qPCR and at the protein level by western blotting. RV16 infection of ALI-cultured PBECs significantly increased the expression of CCL20, IFNB1 and S100A8, but not of LTF or CAMP/LL-37. In these RV16-exposed cells, LTF expression was again significantly higher upon pre-treatment with BUD than with FP. The same was observed for S100A8, but not for CCL20, IFNB1 or CAMP/LL-37 expression.

CONCLUSIONS

Treatment of human bronchial epithelial cells with BUD results in significantly higher expression of specific immune defense genes than treatment with FP. The differential regulation of these immune defense genes may help to explain the clinical observation that BUD and FP treatment differ with respect to the risk of developing pneumonia in COPD.

Reduced suppressive effect of β2-adrenoceptor agonist on fibrocyte function in severe asthma

Background

Patients with severe asthma have increased airway remodelling and elevated numbers of circulating fibrocytes with enhanced myofibroblastic differentiation capacity, despite being treated with high doses of corticosteroids, and long acting β₂-adrenergic receptor (AR) agonists (LABAs). We determined the effect of β₂-AR agonists, alone or in combination with corticosteroids, on fibrocyte function.

Methods

Non-adherent non-T cells from peripheral blood mononuclear cells isolated from healthy subjects and patients with non-severe or severe asthma were treated with the β₂-AR agonist, salmeterol, in the presence or absence of the corticosteroid dexamethasone. The number of fibrocytes (collagen I⁺/CD45⁺ cells) and differentiating fibrocytes (α-smooth muscle actin⁺ cells), and the expression of CC chemokine receptor 7 and of β₂-AR were determined using flow cytometry. The role of cyclic adenosine monophosphate (cAMP) was elucidated using the cAMP analogue 8-bromoadenosine 3′,5′-cyclic monophosphate (8-Br-cAMP) and the phosphodiesterase type IV (PDE4) inhibitor, rolipram.

Results

Salmeterol reduced the proliferation, myofibroblastic differentiation and CCR7 expression of fibrocytes from healthy subjects and non-severe asthma patients. Fibrocytes from severe asthma patients had a lower baseline surface β₂-AR expression and were relatively insensitive to salmeterol but not to 8-Br-cAMP or rolipram. Dexamethasone increased β₂-AR expression and enhanced the inhibitory effect of salmeterol on severe asthma fibrocyte differentiation.

Conclusions

Fibrocytes from patients with severe asthma are relatively insensitive to the inhibitory effects of salmeterol, an effect which is reversed by combination with corticosteroids.

Electronic supplementary material

The online version of this article (10.1186/s12931-017-0678-7) contains supplementary material, which is available to authorized users.

Pulmonary microRNA profiles identify involvement of Creb1 and Sec14l3 in bronchial epithelial changes in allergic asthma

Asthma is highly prevalent, but current therapies cannot influence the chronic course of the disease. It is thus important to understand underlying early molecular events. In this study, we aimed to use microRNAs (miRNAs) - which are critical regulators of signaling cascades - to identify so far uncharacterized asthma pathogenesis pathways. Therefore, deregulation of miRNAs was assessed in whole lungs from mice with ovalbumin (OVA)-induced allergic airway inflammation (AAI). In silico predicted target genes were confirmed in reporter assays and in house-dust-mite (HDM) induced AAI and primary human bronchial epithelial cells (NHBE) cultured at the air-liquid interface. We identified and validated the transcription factor cAMP-responsive element binding protein (Creb1) and its transcriptional co-activators (Crtc1-3) as targets of miR-17, miR-144, and miR-21. Sec14-like 3 (Sec14l3) - a putative target of Creb1 - was down-regulated in both asthma models and in NHBE cells upon IL13 treatment, while it’s expression correlated with ciliated cell development and decreased along with increasing goblet cell metaplasia. Finally, we propose that Creb1/Crtc1-3 and Sec14l3 could be important for early responses of the bronchial epithelium to Th2-stimuli. This study shows that miRNA profiles can be used to identify novel targets that would be overlooked in mRNA based strategies.

Budesonide and fluticasone propionate differentially affect the airway epithelial barrier

BACKGROUND

COPD patients have a higher risk of pneumonia when treated with fluticasone propionate (FP) than with placebo, and a lower risk with budesonide (BUD). We hypothesized that BUD and FP differentially affect the mucosal barrier in response to viral infection and/or cigarette smoke.

METHODS

We assessed protective effects of equivalent concentrations of BUD and FP on cytokine production and barrier function (electrical resistance) in human bronchial epithelial 16HBE cells and primary bronchial epithelial cells (PBECs) upon exposure to viral mimetic poly-(I:C) and/or cigarette smoke extract (CSE) or epidermal growth factor (EGF).

RESULTS

BUD and FP were equally effective in suppressing poly-(I:C)- and/or CSE-induced IL-8 secretion in 16HBE and PBECs. Poly-(I:C) substantially decreased electrical resistance in 16HBE cells and both BUD and FP fully counteracted this effect. However, FP hardly affected 16HBE barrier dysfunction induced by CSE with/without poly-(I:C), whereas BUD (16 nM) provided full protection, an effect likely mediated by affecting EGFR-downstream target GSK-3β. Similarly, BUD, but not FP, significantly improved CSE-induced barrier dysfunction in PBECs. Finally, BUD, but not FP, exerted a modest but significant protective effect against Streptococcus Pneumoniae-induced barrier dysfunction, and BUD, but not FP, prevented cellular adhesion and/or internalization of these bacteria induced by poly-(I:C) in 16HBE.

CONCLUSIONS

Collectively, both BUD and FP efficiently control epithelial pro-inflammatory responses and barrier function upon mimicry of viral infection. Of potential clinical relevance, BUD more effectively counteracted CSE-induced barrier dysfunction, reinforcing the epithelial barrier and potentially limiting access of pathogens upon smoking in vivo.

Distinct functions of specialized dendritic cell subsets in atherosclerosis and the road ahead

Atherosclerotic vascular disease is modulated by immune mechanisms. Dendritic cells (DCs) and T cells are present within atherosclerotic lesions and function as central players in the initiation and modulation of adaptive immune responses. In previous years, we have studied the functional contribution of distinct DC subsets in disease development, namely, that of CCL17-expressing DCs as well as that of plasmacytoid DCs that play specialized roles in disease development. This review focuses on important findings gathered in these studies and dissects the multifaceted contribution of CCL17-expressing DCs and pDCs to the pathogenesis of atherosclerosis. Furthermore, an outlook on future challenges faced when studying DCs in this detrimental disease are provided, and hurdles that will need to be overcome in order to enable a better understanding of the contribution of DCs to atherogenesis are discussed, a prerequisite for their therapeutic targeting in atherosclerosis.

Caveolin-1 controls airway epithelial barrier function. Implications for asthma

The molecular basis for airway epithelial fragility in asthma has remained unclear. We investigated whether the loss of caveolin-1, the major component of caveolae and a known stabilizer of adherens junctions, contributes to epithelial barrier dysfunction in asthma. We studied the expression of caveolin-1 and adhesion molecules E-cadherin and β-catenin in airway sections, and we cultured bronchial epithelial cells from patients with asthma and from healthy control subjects. To determine the functional role of caveolin-1, we investigated the effects of caveolin-1 up-regulation and down-regulation on E-cadherin expression, barrier function, and proallergic activity in the human bronchial epithelial cell lines 16HBE and BEAS-2B. The membrane expression of caveolin-1 was significantly lower in airway epithelia from patients with asthma than from subjects without asthma, and this lower expression was maintained in vitro upon air-liquid interface and submerged culturing. Importantly, reduced caveolin-1 expression was accompanied by a loss of junctional E-cadherin and β-catenin expression, disrupted epithelial barrier function, and increased levels of the proallergic cytokine thymic stromal lymphopoietin (TSLP). Furthermore, E-cadherin redistribution upon exposure to epidermal growth factor or house dust mite was paralleled by the internalization of caveolin-1 in 16HBE cells. These effects appear to be causally related, because the short, interfering RNA down-regulation of caveolin-1 resulted in the delocalization of E-cadherin and barrier dysfunction in 16HBE cells. Moreover, caveolin-1 overexpression improved barrier function and reduced TSLP expression in BEAS-2B cells. Together, our data demonstrate a crucial role for caveolin-1 in epithelial cell-cell adhesion, with important consequences for epithelial barrier function and the promotion of Th2 responses in asthma.

Moderate aerobic exercise alters migration patterns of antigen specific T helper cells within an asthmatic lung

Studies have indicated increased incidence and severity of allergic asthma due to western lifestyle and increased sedentary activity. Investigations also indicate that exercise reduces the severity of asthma; however, a mechanism of action has not been elucidated. Additional work implicates re-distribution of T helper (Th) cells in mediating alterations of the immune system as a result of moderate aerobic exercise in vivo. We have previously reported that exercise decreases T helper 2 (Th2) responses within the lungs of an ovalbumin (OVA)-sensitized murine allergic asthma model. Therefore, we hypothesized that exercise alters the migration of OVA-specific Th cells in an OVA-challenged lung. To test this hypothesis, wildtype mice received OVA-specific Th cells expressing a luciferase-reporter construct and were OVA-sensitized and exercised. OVA-specific Th cell migration was decreased in OVA-challenged lungs of exercised mice when compared to their sedentary controls. Surface expression levels of lung-homing chemokine receptors, CCR4 and CCR8, on Th cells and their cognate lung-homing chemokine gradients revealed no difference between exercised and sedentary OVA-sensitized mice. However, transwell migration experiments demonstrated that lung-derived Th cells from exercised OVA-sensitized mice exhibited decreased migratory function versus controls. These data suggest that Th cells from exercised mice are less responsive to lung-homing chemokine. Together, these studies demonstrate that moderate aerobic exercise training can reduce the accumulation of antigen-specific Th cell migration into an asthmatic lung by decreasing chemokine receptor function.

Cross-desensitization and cointernalization of H1 and H2 histamine receptors reveal new insights into histamine signal integration

G protein-coupled receptor signaling does not result from sequential activation of a linear pathway of proteins/enzymes, but rather from complex interactions of multiple, branched signaling routes, i.e., signaling networks. In this work we present an exhaustive study of the cross-talk between H1 and H2 histamine receptors (H1R and H2R) in U937 cells and Chinese hamster ovary-transfected cells. By desensitization assays we demonstrated the existence of a crossdesensitization between both receptors independent of protein kinase A or C. H1R-agonist stimulation inhibited cell proliferation and induced apoptosis in U937 cells following treatment of 48 hours. H1R-induced antiproliferative and apoptotic response was inhibited by an H2R agonist suggesting that the cross-talk between both receptors modifies their function. Binding and confocal microscopy studies revealed cointernalization of both receptors upon treatment with the agonists. To evaluate potential heterodimerization of the receptors, sensitized emission fluorescence resonance energy transfer experiments were performed in human embryonic kidney 293T cells using H1R-cyan fluorescent protein and H2R-yellow fluorescent protein. To our knowledge these findings may represent the first demonstration of agonist-induced heterodimerization of the H1R and H2R. In addition, we also show that the inhibition of the internalization process did not prevent receptor crossdesensitization, which was mediated by G protein-coupled receptor kinase 2. Our study provides new insights into the complex signaling network mediated by histamine and further knowledge for the rational use of its ligands.

CCL17-expressing dendritic cells drive atherosclerosis by restraining regulatory T cell homeostasis in mice

Immune mechanisms are known to control the pathogenesis of atherosclerosis. However, the exact role of DCs, which are essential for priming of immune responses, remains elusive. We have shown here that the DC-derived chemokine CCL17 is present in advanced human and mouse atherosclerosis and that CCL17+ DCs accumulate in atherosclerotic lesions. In atherosclerosis-prone mice, Ccl17 deficiency entailed a reduction of atherosclerosis, which was dependent on Tregs. Expression of CCL17 by DCs limited the expansion of Tregs by restricting their maintenance and precipitated atherosclerosis in a mechanism conferred by T cells. Conversely, a blocking antibody specific for CCL17 expanded Tregs and reduced atheroprogression. Our data identify DC-derived CCL17 as a central regulator of Treg homeostasis, implicate DCs and their effector functions in atherogenesis, and suggest that CCL17 might be a target for vascular therapy.

Regulation of T cells in airway disease by beta-agonist

It is widely recognized that Th2 cytokines derived from T cells play a major role in the development of allergic lung inflammation that causes most asthma. Beta-agonists are important rescue and maintenance therapies for asthma, yet our understanding of beta-agonist effects on T cell biology is surprisingly poor. Recent studies using both cell culture and more integrative models are beginning to reveal beta-agonist regulation of T cell signaling and function that may be important in the pathogenesis and treatment of asthma and possibly other inflammatory diseases. Here we provide a comprehensive review of the literature concerning beta-agonist effects on T cells, and discuss the relevance of emerging paradigms of beta-adrenergic receptor signaling to T cell function.

Effect of ciclesonide treatment on allergen-induced changes in T cell regulation in asthma

BACKGROUND

The allergen-induced release of CCL17/thymus and activation-regulated chemokine (TARC) may be crucial in asthmatic airway inflammation by recruitment of Th2 cells. In addition, it might lead to aberrant Th2 cell activity through impairment of beta2-adrenergic receptor (beta2-AR) control. We questioned how chemokine patterns change upon allergen challenge and whether treatment with the inhaled steroid ciclesonide can reduce chemokine release and subsequently prevent allergen-induced changes in Th2 cell regulation and migration.

METHODS

Asthma patients were double-blindly treated with placebo or 80 microg ciclesonide for 7 days. We studied allergen-induced changes in sputum chemokines, migration of peripheral blood T cells and control of beta2-agonist fenoterol over T cell migration and alpha-CD3/alpha-CD28-induced cytokine production.

RESULTS

Treatment with 80 microg ciclesonide significantly diminished the late asthmatic response. The late asthmatic response was associated with increased sputum levels of CCL17 and CCL4 (but none of the other chemokines measured) and loss of beta2-AR control over T cell migration and Th2-type cytokine production. Although ciclesonide treatment did not prevent chemokine release nor altered beta2-AR function in circulating T cells, it exerted an inhibitory effect on TARC-induced T cell migration and alpha-CD3/alpha-CD28-induced cytokine production.

CONCLUSION

Our data support the hypothesis that CCL17 is involved in allergen-induced dysregulation of Th2 cell migration and cytokine production. Ciclesonide treatment inhibits T cell migration and cytokine production upon allergen inhalation, which is regulated independently from reducing CCL17 release, but may contribute to beneficial effects of ciclesonide on Th2-mediated airway inflammation.

Respiratory syncytial virus induces insensitivity to beta-adrenergic agonists in mouse lung epithelium in vivo

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants and children worldwide. We wished to determine whether intratracheal administration of beta-agonists improved alveolar fluid clearance (AFC) across the distal respiratory epithelium of RSV-infected mice. Following intranasal infection with RSV strain A2, AFC was measured in anesthetized, ventilated BALB/c mice by instillation of 5% BSA into the dependent lung. We found that direct activation of protein kinase A by forskolin or 8-bromo-cAMP increased AFC at day 2 after infection with RSV. In contrast, short- and long-acting beta-agonists had no effect at either day 2 or day 4. Insensitivity to beta-agonists was not a result of elevated plasma catecholamines or lung epithelial cell beta-adrenergic receptor degradation. Instead, RSV-infected mice had significantly higher levels of phosphorylated PKCzeta in the membrane fractions of their lung epithelial cells. In addition, insensitivity to beta-agonists was mediated in a paracrine fashion by KC (the murine homolog of CXCL8) and reversed by inhibition of either PKCzeta or G protein-coupled receptor kinase 2 (GRK2). These results indicate that insufficient response to beta-agonists in RSV may be caused, at least in part, by impaired beta-adrenergic receptor signaling, as a consequence of GRK2-mediated uncoupling of beta-adrenergic receptors from adenylyl cyclase.

Expression of alpha-AR subtypes in T lymphocytes and role of the alpha-ARs in mediating modulation of T cell function

OBJECTIVES

Previous work in our laboratory has shown that alpha-adrenoreceptors (alpha-ARs) and beta-ARs exist on lymphocytes from functional profile, and that the receptors mediate the regulation of lymphocyte function by catecholamines. In the present study, we directly examined the expression of alpha-AR subtypes, alpha(1)-AR and alpha(2)-AR mRNAs, in T lymphocytes and explored the roles of the alpha-AR subtypes and intracellular signal transduction mechanisms linked to the receptors in mediating the modulation of T lymphocyte function.

METHODS

T lymphocytes from mesenteric lymph nodes of rats were purified by using a nylon wool column. Reverse transcription polymerase chain reaction was used to detect the expression of alpha(1)-AR and alpha(2)-AR mRNAs in the freshly isolated T cells and the mitogen concanavalin A (Con A)-activated lymphocytes. Colorimetric methylthiazoletetrazolium assay was employed to measure lymphocyte proliferation induced by Con A. Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) levels in the Con A-stimulated lymphocyte culture supernatants were examined by enzyme-linked immunosorbent assay.

RESULTS

T cells expressed both alpha(1)-AR and alpha(2)-AR mRNAs. The expression of both alpha(1)-AR and alpha(2)-AR mRNAs was significantly higher in the Con A-activated lymphocytes than in the resting lymphocytes. Phenylephrine, a selective alpha(1)-AR agonist, had no evident effect on lymphocyte proliferation nor on IFN-gamma and IL-4 production induced by Con A. However, the selective alpha(2)-AR agonist clonidine attenuated Con A-induced lymphocyte proliferation as well as IFN-gamma and IL-4 production. The inhibited lymphocyte proliferation and IFN-gamma and IL-4 production by clonidine were blocked by yohimbine, an alpha(2)-AR antagonist. Either phospholipase C inhibitor U-73122 or protein kinase C inhibitor chelerythrine partially prevented the suppressive effect of clonidine on Con A-stimulated lymphocyte proliferation and IL-4 production.

CONCLUSIONS

T lymphocytes express both alpha(1)-ARs and alpha(2)-ARs, but only the alpha(2)-ARs participate in the suppressive modulation of lymphocyte proliferation and cytokine production in vitro. The inhibitory effect of alpha(2)-AR stimulation on lymphocyte function is partially mediated via the phospholipase C-protein kinase C pathway.