Contribution of bronchial fibroblasts to the antiviral response in asthma

The effect of probiotic Bifidobacterium lactis Bl-04 on innate antiviral responses invitro

Consumption of certain probiotic strains may be beneficial for reducing the risk of acute upper respiratory tract infections (URTIs), however, underlying immunological mechanisms are elusive. Bifidobacterium lactis Bl-04™ has been reported in humans to significantly reduce the risk of URTIs, affect the innate immunity in the nasal mucosa, and reduce nasal lavage virus titer after a rhinovirus (RV) challenge. To study the immunological mechanisms, we investigated the effect of Bl-04 on cytokine production and transcriptomes of human monocyte-derived macrophages (Mfs) and dendritic cells (DCs), and further on RV replication and cytokine production in MRC-5 fibroblasts. The results showed that Bl-04 modulates antiviral immune responses and potentiates cytokine production during viral challenge mimic in immune cells. However, effect of Bl-04 on RV replication and cytokine production in fibroblasts was negligible. Overall, the findings suggest that Bl-04 mildly stimulates antiviral immunity in Mfs and DCs, and potentially influences viral replication in fibroblasts that however warrants further investigations.

Rhinovirus induces airway remodeling: what are the physiological consequences?

BACKGROUND

Rhinovirus infections commonly evoke asthma exacerbations in children and adults. Recurrent asthma exacerbations are associated with injury-repair responses in the airways that collectively contribute to airway remodeling. The physiological consequences of airway remodeling can manifest as irreversible airway obstruction and diminished responsiveness to bronchodilators. Structural cells of the airway, including epithelial cells, smooth muscle, fibroblasts, myofibroblasts, and adjacent lung vascular endothelial cells represent an understudied and emerging source of cellular and extracellular soluble mediators and matrix components that contribute to airway remodeling in a rhinovirus-evoked inflammatory environment.

MAIN BODY

While mechanistic pathways associated with rhinovirus-induced airway remodeling are still not fully characterized, infected airway epithelial cells robustly produce type 2 cytokines and chemokines, as well as pro-angiogenic and fibroblast activating factors that act in a paracrine manner on neighboring airway cells to stimulate remodeling responses. Morphological transformation of structural cells in response to rhinovirus promotes remodeling phenotypes including induction of mucus hypersecretion, epithelial-to-mesenchymal transition, and fibroblast-to-myofibroblast transdifferentiation. Rhinovirus exposure elicits airway hyperresponsiveness contributing to irreversible airway obstruction. This obstruction can occur as a consequence of sub-epithelial thickening mediated by smooth muscle migration and myofibroblast activity, or through independent mechanisms mediated by modulation of the β2 agonist receptor activation and its responsiveness to bronchodilators. Differential cellular responses emerge in response to rhinovirus infection that predispose asthmatic individuals to persistent signatures of airway remodeling, including exaggerated type 2 inflammation, enhanced extracellular matrix deposition, and robust production of pro-angiogenic mediators.

CONCLUSIONS

Few therapies address symptoms of rhinovirus-induced airway remodeling, though understanding the contribution of structural cells to these processes may elucidate future translational targets to alleviate symptoms of rhinovirus-induced exacerbations.

Curcumin modulates airway remodelling-contributing genes-the significance of transcription factors

Bronchial epithelial cells and fibroblasts play an essential role in airway remodelling, due to their protective and secretory functions. There are many studies proving that infection caused by human rhinovirus may contribute to the process of airway remodelling. The beneficial properties of curcumin, the basic ingredient of turmeric, have been proved in many studies. Therefore, the aim of this study was the evaluation of curcumin immunomodulatory properties in development of airway remodelling. Fibroblasts (WI‐38 and HFL1) and epithelial cells (NHBE) were incubated with curcumin. Additionally, remodelling conditions were induced with rhinovirus (HRV). Airway remodelling genes were determined by qPCR and immunoblotting. Moreover, NF‐κB, c‐Myc and STAT3 were silenced to analyse the pathways involved in airway remodelling. Curcumin reduced the expression of the genes analysed, especially MMP‐9, TGF‐β and collagen I. Moreover, curcumin inhibited the HRV‐induced expression of MMP‐9, TGF‐β, collagen I and LTC4S (p < 0.05). NF‐κB, c‐Myc and STAT3 changed their course of expression. Concluding, our study shows that curcumin significantly downregulated gene expression related to the remodelling process, which is dependent on NF‐κB and, partially, on c‐Myc and STAT3. The results suggest that the remodelling process may be limited and possibly prevented, however this issue requires further research.

Single-cell transcriptomic analysis reveals key immune cell phenotypes in the lungs of patients with asthma exacerbation

BACKGROUND

Asthma exacerbations are associated with heightened asthma symptoms, which can result in hospitalization in severe cases. However, the molecular immunologic processes that determine the course of an exacerbation remain poorly understood, impeding the progression of development of effective therapies.

OBJECTIVE

Our aim was to identify candidate genes that are strongly associated with asthma exacerbation at a cellular level.

METHODS

Subjects with asthma exacerbation and healthy control subjects were recruited, and bronchoalveolar lavage fluid was isolated from these subjects via bronchoscopy. Cells were isolated through fluorescence-activated cell sorting, and single-cell RNA sequencing was performed on enriched cell populations.

RESULTS

We showed that the levels of monocytes, CD8+ T cells, and macrophages are significantly elevated in the bronchoalveolar lavage fluid of patients. A set of cytokines and intracellular transduction regulators are associated with asthma exacerbations and are shared across multiple cell clusters, forming a complicated molecular framework. An additional group of core exacerbation-associated modules is activated, including eukaryotic initiation factor 2 signaling, ephrin receptor signaling, and C-X-C chemokine receptor type 4 signaling in the subpopulations of CD8+ T cells (C1-a) and monocyte clusters (C7 clusters), which are associated with infection.

CONCLUSION

Our study identified a significant number of severe asthma-associated genes that are differentially expressed by multiple cell clusters.

Respiratory Syncytial Virus Infection of Human Lung Fibroblasts Induces a Hyaluronan-Enriched Extracellular Matrix That Binds Mast Cells and Enhances Expression of Mast Cell Proteases

Human lung fibroblasts (HLFs) treated with the viral mimetic polyinosine-polycytidylic acid (poly I:C) form an extracellular matrix (ECM) enriched in hyaluronan (HA) that avidly binds monocytes and lymphocytes. Mast cells are important innate immune cells in both asthma and acute respiratory infections including respiratory syncytial virus (RSV); however, the effect of RSV on HA dependent mast cell adhesion and/or function is unknown. To determine if RSV infection of HLFs leads to the formation of a HA-enriched ECM that binds and enhances mast cell activity primary HLFs were infected with RSV for 48 h prior to leukocyte binding studies using a fluorescently labeled human mast cell line (LUVA). Parallel HLFs were harvested for characterization of HA production by ELISA and size exclusion chromatography. In separate experiments, HLFs were infected as above for 48 h prior to adding LUVA cells to HLF wells. Co-cultures were incubated for 48 h at which point media and cell pellets were collected for analysis. The role of the hyaladherin tumor necrosis factor-stimulated gene 6 (TSG-6) was also assessed using siRNA knockdown. RSV infection of primary HLFs for 48 h enhanced HA-dependent LUVA binding assessed by quantitative fluorescent microscopy. This coincided with increased HLF HA synthase (HAS) 2 and HAS3 expression and decreased hyaluronidase (HYAL) 2 expression leading to increased HA accumulation in the HLF cell layer and the presence of larger HA fragments. Separately, LUVAs co-cultured with RSV-infected HLFs for 48 h displayed enhanced production of the mast cell proteases, chymase, and tryptase. Pre-treatment with the HA inhibitor 4-methylumbelliferone (4-MU) and neutralizing antibodies to CD44 (HA receptor) decreased mast cell protease expression in co-cultured LUVAs implicating a direct role for HA. TSG-6 expression was increased over the 48-h infection. Inhibition of HLF TSG-6 expression by siRNA knockdown led to decreased LUVA binding suggesting an important role for this hyaladherin for LUVA adhesion in the setting of RSV infection. In summary, RSV infection of HLFs contributes to inflammation via HA-dependent mechanisms that enhance mast cell binding as well as mast cell protease expression via direct interactions with the ECM.

Oxidative Stress Attenuates TLR3 Responsiveness and Impairs Anti-viral Mechanisms in Bronchial Epithelial Cells From COPD and Asthma Patients

COPD and asthma exacerbations are commonly triggered by rhinovirus infection. Potentially promoting exacerbations, impaired anti-viral signaling and attenuated viral clearance have been observed in diseased bronchial epithelium. Oxidative stress is a feature of inflammation in asthma and COPD and is prominent during exacerbations. It is not known whether oxidative stress affects the anti-viral signaling capacity. Bronchial epithelial cells from asthmatic and COPD donors were infected with rhinovirus or treated with the oxidative stressor H₂O₂ followed by exposure to the synthetic viral replication intermediate poly(I:C). Poly(I:C) was used to ascertain a constant infection-like burden. Gene and protein levels of antioxidants as well as anti-viral responses were measured 3 and 24 h post poly(I:C) exposure. Rhinovirus infection and poly(I:C) stimulation induced protein levels of the antioxidants SOD1 and SOD2. In asthmatic bronchial epithelial cells pre-treatment with H₂O₂ dose-dependently decreased the antioxidant response to poly(I:C), suggesting exaggerated oxidative stress. Further, poly(I:C)-induced IFNβ gene expression was reduced after pre-treatment with H₂O₂. This epithelial effect was associated with a reduced expression of the pattern recognition receptors RIG-I, MDA5 and TLR3 both on gene and protein level. Pre-treatment with H₂O₂ did not alter antioxidant responses in COPD bronchial epithelial cells and, more modestly than in asthma, reduced poly(I:C)-induced IFNβ gene expression. Knockdown of TLR3 but not RIG-I/MDA5 abrogated impairment of poly(I:C)-induced IFNβ gene expression by H₂O₂. We developed a method by which we could demonstrate that oxidative stress impairs anti-viral signaling in bronchial epithelial cells from asthmatic and COPD patients, most pronounced in asthma. The impairment apparently reflects reduced responsiveness of TLR3. These present findings shed light on molecular mechanisms potentially causing reduced interferon responses to rhinovirus infection at exacerbations in asthma and COPD. Together, our findings suggest a possible self-perpetuating vicious cycle underlying recurrent exacerbations, leading to an impaired anti-viral response, which in turn leads to viral-induced exacerbations, causing more airway inflammation.

Azithromycin augments rhinovirus-induced IFNβ via cytosolic MDA5 in experimental models of asthma exacerbation

Deficient production of anti-viral interferons (IFNs) may be involved in causing viral-induced asthma exacerbations. Hence, drugs inducing lung IFN production would be warranted. Azithromycin may reduce asthma exacerbations but its modus operandi is unknown. Here, we investigated if azithromycin induces IFNβ expression in vitro in rhinovirus-infected bronchial epithelial cells from asthmatic donors and in vivo in our allergic inflammation-based mouse model of viral stimulus-induced asthma exacerbations. Azithromycin dose-dependently augmented viral-induced IFNβ expression in asthmatic, but not in healthy bronchial epithelial cells. The effect negatively correlated with viral load. Knockdown of MDA5 and RIG-I by siRNA showed involvement of MDA5 but not RIG-I in azithromycin's IFN-inducing effects in vitro. In vivo azithromycin induced IFNβ protein, restoring a reduced lung IFN response exclusively in allergic exacerbating mice. This was associated with induction of interferon-stimulated genes and MDA5, but not RIG-I. We suggest that clinically relevant concentrations of azithromycin produce MDA5-dependent, anti-viral, IFN-inducing effects in bronchial epithelium distinctly from asthmatic donors. Similarly, azithromycin induced MDA5-associated IFN in virally stimulated lungs in vivo exclusively in allergic mice. Effects of azithromycin and MDA5-active drugs on viral-induced exacerbations deserve further research.

Toll-like Receptor 7 Is Reduced in Severe Asthma and Linked to an Altered MicroRNA Profile

RATIONALE

Asthma is one of the most common chronic diseases worldwide, and individuals with severe asthma experience recurrent exacerbations. Exacerbations are predominantly viral associated and have been linked to defective airway IFN responses. Ascertaining the molecular mechanisms underlying this deficiency is a major research goal to identify new therapeutic targets.

OBJECTIVES

We investigated the hypothesis that reduced Toll-like receptor 7 (TLR7)-derived signaling drove the impaired IFN responses to rhinovirus by asthmatic alveolar macrophages (AMs); the molecular mechanisms underlying this deficiency were explored.

METHODS

AMs were recovered from bronchoalveolar lavage from healthy subjects and patients with severe asthma. Expression of pattern-recognition receptors and microRNAs was evaluated by quantitative polymerase chain reaction and Western blotting. A TLR7-luciferase reporter construct was created to evaluate binding of microRNAs to the 3' untranslated region of TLR7. IFN production was measured by quantitative polymerase chain reaction and ELISA.

MEASUREMENTS AND MAIN RESULTS

The expression of TLR7 was significantly reduced in severe asthma AMs and was associated with reduced rhinovirus and imiquimod-induced IFN responses by these cells compared with healthy AMs. Severe asthma AMs also expressed increased levels of three microRNAs, which we showed were able to directly reduce TLR7 expression. Ex vivo knockdown of these microRNAs restored TLR7 expression with concomitant augmentation of virus-induced IFN production.

CONCLUSIONS

In severe asthma, TLR7 deficiency drives impaired innate immune responses to virus by AMs. Blocking a group of microRNAs that are up-regulated in these cells can restore antiviral innate responses, providing a novel approach for therapy in asthma.

Virus-Infected Human Mast Cells Enhance Natural Killer Cell Functions

Mucosal surfaces are protected from infection by both structural and sentinel cells, such as mast cells. The mast cell's role in antiviral responses is poorly understood; however, they selectively recruit natural killer (NK) cells following infection. Here, the ability of virus-infected mast cells to enhance NK cell functions was examined. Cord blood-derived human mast cells infected with reovirus (Reo-CBMC) and subsequent mast cell products were used for the stimulation of human NK cells. NK cells upregulated the CD69 molecule and cytotoxicity-related genes, and demonstrated increased cytotoxic activity in response to Reo-CBMC soluble products. NK cell interferon (IFN)-γ production was also promoted in the presence of interleukin (IL)-18. In vivo, SCID mice injected with Reo-CBMC in a subcutaneous Matrigel model, could recruit and activate murine NK cells, a property not shared by normal human fibroblasts. Soluble products of Reo-CBMC included IL-10, TNF, type I and type III IFNs. Blockade of the type I IFN receptor abrogated NK cell activation. Furthermore, reovirus-infected mast cells expressed multiple IFN-α subtypes not observed in reovirus-infected fibroblasts or epithelial cells. Our data define an important mast cell IFN response, not shared by structural cells, and a subsequent novel mast cell-NK cell immune axis in human antiviral host defense.

Azithromycin induces anti-viral effects in cultured bronchial epithelial cells from COPD patients

Rhinovirus infection is a major cause of chronic obstructive pulmonary disease (COPD) exacerbations and may contribute to the development into severe stages of COPD. The macrolide antibiotic azithromycin may exert anti-viral actions and has been reported to reduce exacerbations in COPD. However, little is known about its anti-viral actions on bronchial epithelial cells at clinically relevant concentrations. Primary bronchial epithelial cells from COPD donors and healthy individuals were treated continuously with azithromycin starting 24 h before infection with rhinovirus RV16. Expression of interferons, RIG-I like helicases, pro-inflammatory cytokines and viral load were analysed. Azithromycin transiently increased expression of IFNβ and IFNλ1 and RIG-I like helicases in un-infected COPD cells. Further, azithromycin augmented RV16-induced expression of interferons and RIG-I like helicases in COPD cells but not in healthy epithelial cells. Azithromycin also decreased viral load. However, it only modestly altered RV16-induced pro-inflammatory cytokine expression. Adding budesonide did not reduce interferon-inducing effects of azithromycin. Possibly by inducing expression of RIG-I like helicases, azithromycin increased rhinovirus-induced expression of interferons in COPD but not in healthy bronchial epithelium. These effects would reduce bronchial viral load, supporting azithromycin’s emerging role in prevention of exacerbations of COPD.

Brief exposure to cigarette smoke impairs airway epithelial cell innate anti-viral defence

BACKGROUND

Human rhinovirus (hRV) infections commonly cause acute upper respiratory infections and asthma exacerbations. Environmental cigarette smoke exposure is associated with a significant increase in the risk for these infections in children.

OBJECTIVE

To determine the impact of short-term exposure to cigarette smoke on innate immune responses of airway epithelial cells infected with hRV.

METHODS

A human bronchial epithelial cell line (HBEC-3KT) was exposed to cigarette smoke extract (CSE) for 30 min and subsequently infected with hRV serotype 1B. Viral-induced cytokine release was measured with AlphaLISA and viral replication quantified by shed viral titer and intracellular viral copy number 24h post-infection.

RESULTS

CSE induced a concentration-dependent decrease in CXCL10 (p<0.001) and IFN-β (p<0.001), with a 79% reduction at the highest dose with an associated 3-fold increase in shed virus. These effects were maintained when infection was delayed up to 24h post CSE exposure. Exogenous IFN-β treatment at t=0 after infection blunts the effects of CSE on viral replication (p<0.05).

CONCLUSION

A single exposure of 30 min to cigarette smoke has a lasting impact on epithelial innate defence providing a plausible mechanism for the increase in respiratory infections seen in children exposed to second-hand tobacco smoke.

Rhinoviral infection and asthma: the detection and management of rhinoviruses by airway epithelial cells

Human rhinoviruses (HRV) have been linked to the development of childhood asthma and recurrent acute asthma exacerbations throughout life, and contribute considerably to the healthcare and economic burden of this disease. However, the ability of HRV infections to trigger exacerbations, and the link between allergic status and HRV responsiveness, remains incompletely understood. Whilst the receptors on human airway cells that detect and are utilized by most HRV group A and B, but not C serotypes are known, how endosomal pattern recognition receptors (PRRs) detect HRV replication products that are generated within the cytoplasm remains somewhat of an enigma. In this article, we explore a role for autophagy, a cellular homeostatic process that allows the cell to encapsulate its own cytosolic constituents, as the crucial mechanism controlling this process and regulating the innate immune response of airway epithelial cells to viral infection. We will also briefly describe some of the recent insights into the immune responses of the airway to HRV, focusing on neutrophilic inflammation that is a potentially unwanted feature of the acute response to viral infection, and the roles of IL-1 and Pellinos in the regulation of responses to HRV.

Increased CXCL10 expression in nasal fibroblasts from patients with refractory chronic rhinosinusitis and asthma

BACKGROUND

Chronic rhinosinusitis (CRS) is characterized by local inflammation of the sinonasal tissues. CRS patients with nasal polyps and asthma often develop acute exacerbation of sinonasal symptoms after upper respiratory tract infections. However, the influence of concomitant asthma on the nasal immune response to viral infection remains unclear.

METHODS

Specimens of nasal polyp and mucosal tissues were obtained from 3 groups of CRS patients (n = 14 per group): 1) patients without asthma (CRS group), 2) patients with aspirin-tolerant asthma (ATA group), and 3) patients with aspirin-intolerant asthma (AIA group). Nasal fibroblasts isolated from the specimens were stimulated with poly I:C. CXCL10 expression was analyzed by the quantitative real-time polymerase chain reaction and enzyme-linked immunoadsorbent assay. Biopsy specimens from CRS patients without asthma were subjected to immunohistochemistry for detection of T-bet and GATA-3 expression in CD3+ T cells by double labeling.

RESULTS

Nasal fibroblasts from the ATA and AIA groups showed significantly enhanced expression of CXCL10 mRNA and protein after poly I:C stimulation compared with cells from the CRS group and the control group (normal nasal mucosa). In addition to T helper (Th)2 cells, there was more abundant infiltration of Th1 cells into tissues from the AIA and ATA groups.

CONCLUSIONS

Our findings suggest that CRS associated with asthma may become intractable through the over-production of CXCL10 in response to viral infection.

Inhibition of phosphodiesterase 4 modulates cytokine induction from toll like receptor activated, but not rhinovirus infected, primary human airway smooth muscle

Background

Virus-induced exacerbations of Chronic Obstructive Pulmonary Disease (COPD) are a significant health burden and occur even in those receiving the best current therapies. Rhinovirus (RV) infections are responsible for half of all COPD exacerbations. The mechanism by which exacerbations occur remains undefined, however it is likely to be due to virus-induced inflammation. Given that phophodiesterase 4 (PDE₄) inhibitors have an anti-inflammatory effect in patients with COPD they present a potential therapy prior to, and during, these exacerbations.

Methods

In the present study we investigated whether the PDE₄ inhibitor piclamilast (10^-6 M) could alter RV or viral mimetic (5 μg/mL of imiquimod or poly I:C) induced inflammation and RV replication in primary human airway smooth muscle cells (ASMC) and bronchial epithelial cells (HBEC). The mediators IL-6, IL-8, prostaglandin E₂ and cAMP production were assayed by ELISA and RV replication was assayed by viral titration.

Results

We found that in ASMCs the TLR3 agonist poly I:C induced IL-8 release was reduced while induced IL-6 release by the TLR7/8 agonist imiquimod was further increased by the presence of piclamilast. However, in RV infected ASMCs, virus replication and induced mediator release were unaltered by piclamilast, as was also found in HBECs. The novel findings of this study reveal that although PDE inhibitors may not influence RV-induced cytokine production in ASMCs and replication in either ASMCs or HBECs, they have the capacity to be anti-inflammatory during TLR activation by modulating the induction of these chemotactic cytokines.

Conclusion

By extrapolating our in vitro findings to exacerbations of COPD in vivo this suggests that PDE₄ inhibitors may have beneficial anti-inflammatory properties when patients are infected with bacteria or viruses other than RV.

Rhinovirus and dsRNA induce RIG-I-like receptors and expression of interferon β and λ1 in human bronchial smooth muscle cells

Rhinovirus (RV) infections cause exacerbations and development of severe asthma highlighting the importance of antiviral interferon (IFN) defence by airway cells. Little is known about bronchial smooth muscle cell (BSMC) production of IFNs and whether BSMCs have dsRNA-sensing receptors besides TLR3. dsRNA is a rhinoviral replication intermediate and necrotic cell effect mimic that mediates innate immune responses in bronchial epithelial cells. We have explored dsRNA-evoked IFN-β and IFN-λ1 production in human BSMCs and potential involvement of TLR3 and RIG-I-like receptors (RLRs). Primary BSMCs were stimulated with 0.1-10 µg/ml dsRNA, 0.1-1 µg/ml dsRNA in complex with the transfection agent LyoVec (dsRNA/LyoVec; selectively activating cytosolic RLRs) or infected with 0.05-0.5 MOI RV1B. Both dsRNA stimuli evoked early (3 h), concentration-dependent IFN-β and IFN-λ1 mRNA expression, which with dsRNA/LyoVec was much greater, and with dsRNA was much less, after 24 h. The effects were inhibited by dexamethasone. Further, dsRNA and dsRNA/LyoVec concentration-dependently upregulated RIG-I and MDA5 mRNA and protein. dsRNA and particularly dsRNA/LyoVec caused IFN-β and IFN-λ1 protein production (24 h). dsRNA- but not dsRNA/LyoVec-induced IFN expression was partly inhibited by chloroquine that suppresses endosomal TLR3 activation. RV1B dose-dependently increased BSMC expression of RIG-I, MDA5, IFN-β, and IFN-λ1 mRNA. We suggest that BSMCs express functional RLRs and that both RLRs and TLR3 are involved in viral stimulus-induced BSMC expression of IFN-β and IFN-λ1.

Difficult childhood asthma: management and future

Diagnosis and management of severe asthma implies the definition of different entities, that is, difficult asthma and refractory severe asthma, but also the different phenotypes included in the term refractory severe asthma. A complete evaluation by a physician expert in asthma is necessary, adapted for each child. Identification of mechanisms involved in different phenotypes in refractory severe asthma may improve the therapeutic approach. The quality of care and monitoring of children with severe asthma is as important as the prescription drug, and is also crucial for differentiating between severe asthma and difficult asthma, whereby expertise is required.

The innate antiviral response upregulates IL-13 receptor α2 in bronchial fibroblasts

BACKGROUND

IL-13 is key mediator of allergic inflammation in asthmatic patients. We have previously shown that the decoy receptor IL-13 receptor (IL-13R) α2 attenuates responses of fibroblasts to IL-13. Because the expression of IL-13Rα2 can be regulated by IFN-γ, a type II interferon, we hypothesized that innate antiviral responses characterized by type I interferon expression can also induce IL-13Rα2 expression.

OBJECTIVE

We sought to induce an innate antiviral response in primary fibroblasts using exposure to double-stranded RNA (dsRNA) and to examine the expression and function of IL-13Rα2.

METHODS

Primary human fibroblasts were cultured from endobronchial biopsy specimens obtained from healthy or asthmatic volunteers and challenged with dsRNA. Upregulation of IL-13Rα2 mRNA was measured by using real-time quantitative PCR, and cell-surface IL-13Rα2 protein expression was measured by using fluorescence-activated cell sorting. Eotaxin release was determined by means of ELISA.

RESULTS

Direct treatment with IFN-β led to an upregulation of IL-13Rα2. Exposure to dsRNA rapidly induced IFN-β mRNA in fibroblasts, and this was followed by significant induction of IL-13Rα2 mRNA and cell-surface protein expression, which was dependent on de novo protein synthesis. A neutralizing antibody to the IFN-α/β receptor blocked cell-surface expression of IL-13Rα2 in the presence of dsRNA. Pretreatment of fibroblasts with dsRNA led to attenuation of IL-13-stimulated eotaxin production. However, the presence of an IL-13Rα2 neutralizing antibody restored IL-13-stimulated eotaxin production in dsRNA-treated cells.

CONCLUSION

IFN-β induces IL-13Rα2 expression, leading to a consequential suppression of responsiveness to IL-13. These data suggest cross-talk between TH1 and TH2 pathways and point to an immunomodulatory role for IL-13Rα2 in human bronchial fibroblasts during viral infection.

Matrix proteins from smoke-exposed fibroblasts are pro-proliferative

Airway remodeling decreases lung function in chronic obstructive pulmonary disease (COPD). Extracellular matrix (ECM) deposition is increased in remodeled airways and drives cellular processes of proliferation, migration, and inflammation. We investigated the role of cigarette smoke in altering the ECM deposited from human lung fibroblasts. Lung fibroblasts isolated from patients with COPD or other lung disease were exposed to cigarette smoke extract (CSE) and 5 ng/ml transforming growth factor-β1 for 72 hours; in some experiments, inhibitors of signaling molecules were added. Deposition of perlecan, fibronectin, and elastin were measured by ELISA, as was release of IL-8 and IL-13. Unstimulated fibroblast cells were reseeded onto deposited matrix and assessed for proliferation and cytokine release. CSE (5%) increased deposition of fibronectin and perlecan from only COPD fibroblasts. Fibronectin and perlecan deposition was attenuated by addition of the NF-κB inhibitor, BMS-345541, and the signal transduction and activator of transcription-1/3 inhibitor, pyridone 6, respectively. CSE (5%) increased IL-8 release from COPD fibroblasts more than non-COPD fibroblasts. This increase was attenuated by BMS-345541. Matrix deposited after 5% CSE stimulation increased proliferation of fibroblasts, but did not alter cytokine release. ECM produced from COPD fibroblasts after CSE exposure has proproliferative effects. Thus, the ECM in patients with COPD may create an environment that promotes airway remodeling.

CpG-DNA suppresses poly(I:C)-induced TSLP production in human laryngeal arytenoid fibroblasts

Thymic stromal lymphopoietin (TSLP) exerts a marked influence on the polarization of dendritic cells to drive T helper (Th) 2 cytokine production, and has been linked to allergic airway diseases. Although TSLP is produced by airway epithelium, TSLP production in laryngeal arytenoid fibroblasts remains largely unexplored. We examined the effect of Toll-like receptor (TLR) ligands and the cross-talk that occurs among different TLR ligands on TSLP production in arytenoid fibroblasts. Since mRNA of TLR 2, 3, 4, and 9 has been found to be expressed in arytenoid fibroblasts, we examined the effect on its production of TLR ligands. TSLP production by arytenoid fibroblasts was strongly induced in the presence of polyinosinic-polycytidylic acid (poly(I:C)), a ligand of TLR3. Its production was synergistically induced in the presence of IL-4, to a level more than 100 times higher than that observed in the absence of poly(I:C) or IL-4. We also revealed that B type DNA containing CpG motifs (CpG-DNA) coding for a TLR9 ligand markedly suppressed both poly(I:C)-induced and poly(I:C)-plus-IL-4-induced TSLP production. B type CpG-DNA decreased the poly(I:C)-induced phosphorylation of c-Jun N-terminal kinase (JNK), and pre-incubation with SP600125 (inhibitor of JNK) reduced the poly(I:C)-induced TSLP-production. These results indicate that human arytenoid fibroblasts strongly induce TSLP production with stimulation by double-stranded RNA (dsRNA), which can be inhibited by CpG-DNA and participate in immune allergic responses.

Is there a regulatory role of immunoglobulins on tissue forming cells relevant in chronic inflammatory lung diseases?

Epithelial cells, fibroblasts and smooth muscle cells together form and give structure to the airway wall. These three tissue forming cell types are structure giving elements and participate in the immune response to inhaled particles including allergens and dust. All three cell types actively contribute to the pathogenesis of chronic inflammatory lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). Tissue forming cells respond directly to allergens through activated immunoglobulins which then bind to their corresponding cell surface receptors. It was only recently reported that allergens and particles traffic through epithelial cells without modification and bind to the immunoglobulin receptors on the surface of sub-epithelial mesenchymal cells. In consequence, these cells secrete pro-inflammatory cytokines, thereby extending the local inflammation. Furthermore, activation of the immunoglobulin receptors can induce proliferation and tissue remodeling of the tissue forming cells. New studies using anti-IgE antibody therapy indicate that the inhibition of immunoglobulins reduces the response of tissue forming cells. The unmeasured questions are: (i) why do tissue forming cells express immunoglobulin receptors and (ii) do tissue forming cells process immunoglobulin receptor bound particles? The focus of this review is to provide an overview of the expression and function of various immunoglobulin receptors.

Effects of β(2) Agonists, Corticosteroids, and Novel Therapies on Rhinovirus-Induced Cytokine Release and Rhinovirus Replication in Primary Airway Fibroblasts

Rhinovirus-(RV-) induced asthma exacerbations account for high asthma-related health costs and morbidity in Australia. The cellular mechanism underlying this pathology is likely the result of RV-induced nuclear-factor-kappa-B-(NF-κB-) dependent inflammation. NF-κB may also be important in RV replication as inhibition of NF-κB inhibits replication of other viruses such as human immunodeficiency virus and cytomegalovirus. To establish the role of NF-κB inhibitors in RV-induced IL- 6 and IL-8 and RV replication, we used pharmacological inhibitors of NF-κB, and steroids and/or β(2) agonists were used for comparison. Primary human lung fibroblasts were infected with RV-16 in the presence of NF-κB inhibitors: BAY-117085 and dimethyl fumarate; β(2) agonist: salmeterol; and/or corticosteroids: dexamethasone; fluticasone. RV-induced IL-6 and IL-8 and RV replication were assessed using ELISAs and virus titration assays. RV replicated and increased IL-6 and IL-8 release. Salmeterol increased, while dexamethasone and fluticasone decreased RV-induced IL-6 and IL-8 (P<0.05). The NF-κB inhibitor BAY-117085 inhibited only RV-induced IL-6 (P<0.05) and dimethyl fumarate did not alter RV-induced IL-6 and IL-8. Dimethylfumarate increased RV replication whilst other drugs did not alter RV replication. These data suggest that inhibition of NF-κB alone is unlikely to be an effective treatment compared to current asthma therapeutics.

B type CpG-DNA suppresses poly(I:C)-induced BLyS expression and production in human tonsillar fibroblasts

Although B lymphocyte stimulator (BLyS) has potent costimulatory effects on B cells, the details of BLyS-expression in tonsillar fibroblasts remain unexplored. We examined the effect of the Toll-like receptor (TLR) ligands on BLyS-expression in human tonsillar fibroblasts as well as the crosstalk that occurs among different TLR ligands. The expression of BLyS mRNA by tonsillar fibroblasts was strongly induced in the presence of polyinosinic-polycytidylic acid (poly(I:C)) that is a ligand, of TLR3. We also revealed that DNA containing CpG motifs (CpG-DNA), coding for a TLR9 ligand, markedly suppressed the poly(I:C)-induced mRNA expression and protein production of BLyS. B type CpG-DNA decreased the poly(I:C)-induced phosphorylation of inhibitor kappa B alpha (IκBα) and its degradation. Pre-incubation with nuclear factor kappa B (NF-κB) signaling inhibitors reduced the poly(I:C)-induced BLyS-expression. These results indicate that human tonsillar fibroblasts strongly induce BLyS-expression and production that can be inhibited by CpG-DNA and regulated through NF-κB signaling.

Remodeling in asthma

Airway remodeling encompasses the structural alterations in asthmatic compared with normal airways. Airway remodeling in asthmatic patients involves a wide array of pathophysiologic features, including epithelial changes, increased smooth muscle mass, increased numbers of activated fibroblasts/myofibroblasts, subepithelial fibrosis, and vascular changes. Multiple cytokines, chemokines, and growth factors released from both inflammatory and structural cells in the airway tissue create a complex signaling environment that drives these structural changes. However, recent investigations have changed our understanding of asthma from a purely inflammatory disease to a disease in which both inflammatory and structural components are equally involved. Several reports have suggested that asthma primarily develops because of serious defects in the epithelial layer that allow environmental allergens, microorganisms, and toxins greater access to the airway tissue and that can also stimulate the release of mediators from the epithelium, thus contributing to tissue remodeling. Lung-resident fibroblasts and smooth muscle cells have also been implicated in the pathogenesis of airway remodeling. Remodeling is assumed to result in persistent airflow limitation, a decrease in lung function, and airway hyperresponsiveness. Asthmatic subjects experience an accelerated decrease in lung function compared with healthy subjects, which is proportionally related to the duration and severity of their disease.

Immune markers in breast milk and fetal and maternal body fluids: a systematic review of perinatal concentrations

Breastfeeding represents the continued exposure of the infant to the maternal immune environment.Uterine, perinatal, and postnatal exposure to immune factors may contribute to an infant’s risk of developing immune-mediated disorders, including allergies. A PubMed search was conducted to review studies in humans and analyze concentrations of immune markers (TGF-beta, IFN-gamma, eotaxin, CCL5, CXCL10, TNF-alpha, MCP-1, IL-1beta, IL-4, IL-5, IL-6,IL-8, IL-10, IL-12, IL-13, sCD14, sIgA, IgG4, IgM) found in maternal serum, amniotic fluid, cord serum, colostrum, transition and mature milk. Concentrations of immune markers showed large variations across samples and studies. Reports documented conflicting results. Small sample sizes, differences in population characteristics, inconsistent sample collection times, and various sample collection and measurement methods may have led to wide variations in the concentrations of immune markers. Studies analyzing the associations between immune markers in maternal fluids and infant allergies remain inconclusive because of gaps in knowledge and a lack of standardized methods.

The human periodontal ligament cell: a fibroblast-like cell acting as an immune cell

BACKGROUND

Periodontal ligament cells are fibroblast-like cells characterized by collagen production but also possessing some osteoblastic features. In the light of numerous studies presented during recent times, which show that human periodontal ligament cells also produce cytokines and chemokines in response to inflammation promoters, it is reasonable to suggest that periodontal ligament cells play a role as promoters of periodontal inflammation through these mechanisms.

MATERIAL AND METHODS

The periodontal ligament, which harbours the periodontal ligament cells, is a part of the attachment apparatus comprised of periodontal ligament cells, extracellular matrix and fibres, attaching the root cement to the alveolar bone. Periodontal ligament cells are in close proximity to bacteria within the plaque and the pocket, and thus these cells are readily accessible to bacterial endotoxins and other promoters of inflammation.

RESULTS

Cytokines and chemokines, released by periodontal ligament cells upon stimulation with inflammation promoters, reach the blood vessels easily thanks to rich vascularization of the periodontium stimulating recruitment of white blood cells to the site of inflammation. In addition to classical inflammatory cells, such as leucocytes, macrophages and mast cells, the periodontal ligament cells also contribute to periodontal inflammation via their production and release of cytokines and chemokines.

CONCLUSION

Therefore, pharmacological treatment of periodontitis should aim to reduce the release of proinflammatory agents not only from classical inflammatory cells but also from periodontal ligament cells.

The role of viruses in acute exacerbations of asthma

Viral respiratory infections are the most common cause of an acute asthma exacerbation in both children and adults and represent a significant global health burden. An increasing body of evidence supports the hypothesis that these infections cause a greater degree of morbidity in asthmatic subjects than in the healthy population, emphasizing a discrepancy in the antiviral response of asthmatics. In this review we discuss why such a discrepancy might exist, examining the role of the bronchial epithelium as well as the main inflammatory cells, mediators, and molecular pathways that are involved in the immune response. In addition, the potential impact of virus-induced asthma exacerbations on airway remodelling is reviewed and we explore which therapeutic options might be of benefit in preventing the deterioration of asthma control seen following viral infection.

Poly(I:C) induces BLyS-expression of airway fibroblasts through phosphatidylinositol 3-kinase

B lymphocyte stimulator (BLyS), B cell activating factor (BAFF), a member of the tumor necrosis factor ligand superfamily has potent co-stimulatory activity on B cells, and BLyS-production in the airway mucosa is of potential importance as it triggers innate and adaptive immune responses. To investigate whether airway fibroblast could express BLyS, we examined BLyS-expression in human nasal airway fibroblasts and compared to its expression in tonsillar and skin fibroblasts as well as the effect of the Toll-like receptor (TLR) ligands on that in human nasal airway fibroblasts. The expression of BLyS by nasal fibroblasts in the presence of polyinocinic-polycytidykic acid (poly(I:C)) was markedly induced, to a level of more than 100 times higher than that observed in the absence of poly(I:C). In order to demonstrate the intracellular pathways involved in poly(I:C)-induced BLyS-expression, we used specific inhibitors of phosphatidylinositol 3-kinase (PI3-kinase), spleen tyrosine kinase (Syk), p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK), and extracellular-signal related kinase (ERK)-signaling in these events. Pre-incubation with the PI3-kinase inhibitor LY294002 or Wortmanin reversed the poly(I:C)-induced production and expression of BLyS. Syk kinase inhibitor Piceatannol partially reduced its production and expression. Thus, we were able to show that PI3-kinase signaling is directly involved in poly(I:C)-induced BLyS-expression in nasal airway fibroblasts. These results indicate that human nasal airway fibroblasts strongly induce BLyS-expression and production by poly(I:C) through PI3-K signaling during airway immune responses.