Synthetic double-stranded RNA enhances airway inflammation and remodelling in a rat model of asthma

TL1A/DR3 Axis, A Key Target of TNF-a, Augments the Epithelial–Mesenchymal Transformation of Epithelial Cells in OVA-Induced Asthma

Tumor necrosis factor (TNF)-like cytokine 1A (TL1A), a member of the TNF family, exists in the form of membrane-bound (mTL1A) and soluble protein (sTL1A). TL1A binding its only known functional receptor death domain receptor 3 (DR3) affects the transmission of various signals. This study first proposed that the TL1A/DR3 axis was significantly upregulated in patients and mice with both asthma and high TNF-a expression and in TNF-a-stimulated epithelial Beas-2B cells. Two independent approaches were used to demonstrate that the TL1A/DR3 axis of mice was strongly correlated with TNF-a in terms of exacerbating asthmatic epithelial–mesenchymal transformation (EMT). First, high expression levels of EMT proteins (e.g., collagen I, fibronectin, N-cadherin, and vimentin) and TL1A/DR3 axis were observed when mice airways were stimulated by recombinant mouse TNF-a protein. Moreover, EMT protein and TL1A/DR3 axis expression synchronously decreased after mice with OVA-induced asthma were treated with infliximab by neutralizing TNF-a activity. Furthermore, the OVA-induced EMT of asthmatic mice was remarkably improved upon the deletion of the TL1A/DR3 axis by knocking out the TL1A gene. TL1A siRNA remarkably intervened EMT formation induced by TNF-a in the Beas-2B cells. In addition, EMT was induced by the addition of high concentrations of recombinant human sTL1A with the cell medium. The TL1A overexpression via pc-mTL1A in vitro remarkably increased the EMT formation induced by TNF-a. Overall, these findings indicate that the TL1A/DR3 axis may have a therapeutic role for asthmatic with high TNF-a level.

Poly I:C Exacerbates Airway Inflammation and Remodeling in Cigarette Smoke-Exposed Mice

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disorder characterized by chronic inflammation and airway remodeling. Cigarette smoke (CS) and respiratory viruses are major causes of COPD development and exacerbation, but the mechanisms of these compounding factors on inflammation and pathological changes in airway structure still need further investigation.

PURPOSE

This work aimed to investigate the effects and mechanisms of Poly I:C on pathological changes in CS-induced COPD mice, such as airway inflammation and remodeling.

METHODS

From 1 to 8 weeks, the mice were exposed to CS, Poly I:C, or a combination of both. To compare the pathological changes among different groups over time, the mice were sacrificed at week 4, 8, 16, and 24, then the lungs were harvested to measure pulmonary pathology, inflammatory cytokines, and airway remodeling.

RESULTS

Our data revealed that the fundamental characteristics of COPD, such as pulmonary pathological damage, the release of inflammatory mediators, and the remodeling of airway walls, were observed at week 8 in CS-exposed mice and these pathological changes persisted to week 16. Compared with the CS group, the pathological changes, including decreased lung function, inflammatory cell infiltration, alveolar destruction, and airway wall thickening, were weaker in the Poly I:C group. These pathological changes were observed at week 8 and persisted to week 16 in Poly I:C-induced mice. Furthermore, Poly I:C exacerbated lung tissue damage in CS-induced COPD mice. The decreased lung function, airway inflammation and remodeling were observed in the combined group at week 4, and these pathological changes persisted to week 24. Our research indicated that Poly I:C enhanced the expression of p-P38, p-JNK and p-NF-κB in CS-exposed mice.

CONCLUSION

Poly I:C could promote airway inflammation and remodeling in CS-induced COPD mice probably by NF-κB and MAPK signaling.

Influenza in Asthmatics: For Better or for Worse?

Asthma and influenza are two pathologic conditions of the respiratory tract that affect millions worldwide. Influenza virus of the 2009 pandemic was highly transmissible and caused severe respiratory disease in young and middle-aged individuals. Asthma was discovered to be an underlying co-morbidity that led to hospitalizations during this influenza pandemic albeit with less severe outcomes. However, animal studies that investigated the relationship between allergic inflammation and pandemic (p)H1N1 infection, showed that while characteristics of allergic airways disease were exacerbated by this virus, governing immune responses that cause exacerbations may actually protect the host from severe outcomes associated with influenza. To better understand the relationship between asthma and severe influenza during the last pandemic, we conducted a systematic literature review of reports on hospitalized patients with asthma as a co-morbid condition during the pH1N1 season. Herein, we report that numerous other underlying conditions, such as cardiovascular, neurologic, and metabolic diseases may have been underplayed as major drivers of severe influenza during the 2009 pandemic. This review synopses, (1) asthma and influenza independently, (2) epidemiologic data surrounding asthma during the 2009 influenza pandemic, and (3) recent advances in our understanding of allergic host–pathogen interactions in the context of allergic airways disease and influenza in mouse models. Our goal is to showcase possible immunological benefits of allergic airways inflammation as countermeasures for influenza virus infections as a learning tool to discover novel pathways that can enhance our ability to hinder influenza virus replication and host pathology induced thereof.

Repetitive TLR3 activation in the lung induces skeletal muscle adaptations and cachexia

Due to immunosenescence, older adults are particularly susceptible to lung-based viral infections, with increased severity of symptoms in those with underlying chronic lung disease. Repeated respiratory viral infections produce lung maladaptations, accelerating pulmonary dysfunction. Toll like 3 receptor (TLR3) is a membrane protein that senses exogenous double-stranded RNA to activate the innate immune response to a viral infection. Polyinosinic-polycytidylic acid [poly(I:C)] mimics double stranded RNA and has been shown to activate TLR3. Utilizing an established mouse viral exacerbation model produced by repetitive intranasal poly(I:C) administration, we sought to determine whether repetitive poly(I:C) treatment induced negative muscle adaptations (i.e. atrophy, weakness, and loss of function). We determined skeletal muscle morphological properties (e.g. fiber-type, fiber cross-sectional area, muscle wet mass, etc.) from a treated group ((poly(I:C), n = 9) and a sham-treated control group (PBS, n = 9); age approximately 5 months. In a subset (n = 4 for both groups), we determined in vivo physical function (using grip test for strength, rotarod for overall motor function, and treadmill for endurance) and muscle contractile properties with in vitro physiology (in the EDL, soleus and diaphragm). Our findings demonstrate that poly(I:C)-treated mice exhibit both muscle morphological and functional deficits. Changes of note when comparing poly(I:C)-treated mice to PBS-treated controls include reductions in fiber cross-sectional area (-27% gastrocnemius, -25% soleus, -16% diaphragm), contractile dysfunction (soleus peak tetanic force, -26%), muscle mass (gastrocnemius -19%, soleus -23%), physical function (grip test -34%), body mass (-20%), and altered oxidative capacity (140% increase in succinate dehydrogenase activity in the diaphragm, but 66% lower in the gastrocnemius). Our data is supportive of a new model of cachexia/sarcopenia that has potential for future research into the mechanisms underlying muscle wasting.

Sustained therapeutic efficacy of budesonide-loaded chitosan swellable microparticles after lung delivery: Influence of in vitro release, treatment interval and dose

Sustained drug delivery to the respiratory tract is highly desirable for local treatment of chronic lung diseases. In this context, a correlation of in vitro drug release with in vivo efficacy data is essential to accelerate the application of sustained drug delivery system for inhalation into the clinical setting. In this study, budesonide was incorporated into distinct chitosan-based swellable microparticles, which were characterized, and the in vitro drug release behavior determined. The particles were then given to an allergic asthma animal model as single and successive administrations, and the therapeutic response was determined by measuring cell counts, IL-4 and IL-5 levels in bronchoalveolar lavage fluid, IL-4 and IL-5 mRNA in the lung and by histopathologic examination of lung tissues. After a single administration, the time-dependent therapeutic effect of the swellable microparticles was correlated with the in vitro release behavior, which lasted for 12 or 18 h depending on the molecular weight of the chitosan. After seven days of successive treatment, the number of eosinophils decreased further and IL-4 and IL-5 mRNA expression in the lung tissue was more greatly inhibited. Moreover, the chitosan-based swellable microparticles allowed longer administration intervals (every two days), which decreased the required dose for effectiveness by 50%. These results demonstrate that chitosan-based swellable microparticles can sustain the therapeutic effect of budesonide in the respiratory tract which in principal can be applied to other drugs for the treatment of local lung diseases.

Mouse Model of IL-17-Dominant Rhinitis Using Polyinosinic-Polycytidylic Acid

Interleukin (IL)-17 plays an important role in rhinitis and the level thereof correlates with the severity of disease. However, no mouse model for IL-17-dominant rhinitis has yet been developed. Our objective was to establish a mouse model of IL-17-dominant rhinitis via intranasal application of polyinosinic-polycytidylic acid (abbreviated as Poly(I:C)). Mice were divided into 6 groups (n=8 for each group); 1) 1 negative control group, 2) 1 positive control group (OVA/alum model), 3) 2 Poly(I:C) groups (10 or 100 μg), and 4) 2 OVA/Poly(I:C) groups (10 or 100 μg). The positive control group was treated with the conventional OVA/alum protocol. In the Poly(I:C) and OVA/Poly(I:C) groups, phosphate-buffered saline or an OVA solution plus Poly(I:C) were administered. The OVA/Poly(I:C) groups exhibited significantly greater neutrophil infiltration and increased IL-17/interferon γ expression compared with the other groups. However, the levels of total immunoglobulin E (IgE), OVA-specific IgE, eosinophil infiltration, IL-4, IL-5, IL-6, and IL-10 were significantly lower in the OVA/Poly(I:C) groups than in mice subjected to conventional Th2-dominant OVA/alum treatment (the positive control group). IL-17 and neutrophil measurement, chemokine (C-X-C motif) ligand 1 immunohistochemistry, and confocal microscopy revealed increased numbers of IL-17-secreting cells in the nasal mucosa of the OVA/Poly(I:C) groups, which included natural killer cells, CD4 T cells, and neutrophils. In conclusion, we developed a mouse model of IL-17-dominant rhinitis using OVA together with Poly(I:C). This model will be useful in research on neutrophil- or IL-17-dominant rhinitis.

Dissociation of FK506-binding protein 12.6 kD from ryanodine receptor in bronchial smooth muscle cells in airway hyperresponsiveness in asthma

Airway hyperresponsiveness (AHR) in asthma is predominantly caused by increased sensitivity of bronchial smooth muscle cells (BSMCs) to stimuli. The sarcoplasmic reticulum (SR)-Ca(2+) release channel, known as ryanodine receptor (RyR), mediates the contractive response of BSMCs to stimuli. FK506-binding protein 12.6 kD (FKBP12.6) stabilizes the RyR2 channel in a closed state. However, the interaction of FKBP12.6 with RyR2 in AHR remains unknown. This study examined the interaction of FKBP12.6 with RyR2 in BSMCs in AHR of asthma. The interaction of FKBP12.6 with RyR2 and FKBP12.6 expression was determined in a rat asthma model and in BSMCs treated with inflammatory cytokines. The calcium responses to contractile agonists were determined in BSMCs with overexpression and knockdown of FKBP12.6. Asthmatic serum, IL-5, IL-13, and TNF-α enhance the calcium response of BSMCs to contractile agonists and cause dissociation of FKBP12.6 from RyR2 and a decrease in FKBP12.6 gene expression in BSMCs in culture and in ovalbumin (OVA)-sensitized and -challenged rats. Knockdown of FKBP12.6 in BSMCs causes a decrease in the association of RyR2 with FKBP12.6 and an increase in the calcium response of BSMCs. Overexpression of FKBP12.6 increases the association of FKBP12.6 with RyR2, decreases the calcium response of BSMCs, and normalizes airway responsiveness in OVA-sensitized and -challenged rats. Dissociation of FKBP12.6 from RyR2 in BSMCs is responsible for the increased calcium response contributing to AHR in asthma. Manipulating the interaction of FKBP12.6 with RyR2 might be a novel and useful treatment for asthma.

TLR3 activation augments matrix metalloproteinase production through reactive nitrogen species generation in human lung fibroblasts

Viral infection often triggers asthma exacerbation and contributes to airway remodeling. Cell signaling in viral infection is mainly mediated through TLR3. Many mediators are involved in airway remodeling, but matrix metalloproteinases (MMPs) are key players in this process in asthma. However, the role of TLR3 activation in production of MMPs is unknown. In this study, we examined the effects of polyinosinic-polycytidylic acid [poly(I:C)], a ligand for TLR3, on production of MMPs in human lung fibroblasts, with a focus on nitrosative stress in TLR3 modulation of MMP production. After lung fibroblasts were treated with poly(I:C), production of MMP-1, -2, and -9 and inducible NO synthase (iNOS) was assessed. The roles of NF-κB and IFN regulatory factor-3 (IRF-3) in the poly(I:C)-mediated production of MMPs and the responsiveness to poly(I:C) of normal lung fibroblasts and asthmatic lung fibroblasts were also investigated. Poly(I:C) augmented production of MMPs and iNOS in fibroblasts, and an iNOS inhibitor diminished this production of MMPs. Poly(I:C) stimulated translocation of NF-κB and IRF-3 into the nucleus in fibroblasts and inhibition of NF-κB or IRF-3 abrogated the poly(I:C)-induced increase in both iNOS expression and release of MMPs. Poly(I:C)-induced production of iNOS and MMPs was greater in asthmatic fibroblasts than in normal fibroblasts. We conclude that viral infection may induce nitrosative stress and subsequent MMP production via NF-κB- and IRF-3-dependent pathways, thus potentiating viral-induced airway remodeling in asthmatic airways.

Thrombin promotes airway remodeling via protease-activated receptor-1 and transforming growth factor-β1 in ovalbumin-allergic rats

BACKGROUND

Protease-activated receptor-1 (PAR-1) is widely distributed in platelets and involved in coagulation cascade activated by thrombin. In this study, we intend to explore the role of PAR-1 in the process of thrombin-inducing transforming growth factor-β1 (TGF-β1) to promote airway remodeling in ovalbumin (OVA)-allergic rats.

MATERIALS AND METHODS

A rat model of chronic asthma was set up by systemic sensitization and repeated challenge to OVA. The doses of thrombin, recombinant hirudin, PAR-1 inhibitor ER-112780-06 varied for different groups. We evaluated the bronchoalveolar lavage fluid (BALF) concentration of thrombin in these groups. The protein and gene expression of PAR-1 was assessed and the expression of TGF-β1 was also detected.

RESULTS

The PAR-1 mRNA level and the protein level were higher in the airway of asthmatic rats than those of normal rats, and were significantly increased by thrombin treatment but decreased by thrombin-inhibitor treatment. Airway remodeling was strengthened by thrombin but weakened by thrombin inhibitor and PAR-1 antagonist. Expression of TGF-β1 protein in asthmatic rats was significantly increased by thrombin treatment and decreased by thrombin-inhibitor treatment and PAR-1 antagonist treatment.

CONCLUSION

The expression of PAR-1 is regulated by thrombin that induces the expression of TGF-β1 to promote airway remodeling via PAR-1 in OVA-allergic rats.

Development of a mouse model mimicking key aspects of a viral asthma exacerbation

Viral respiratory tract infections are known triggers of asthma exacerbations in both adults and children. The current standard of care, inhaled CS (corticosteroids) and LABAs (long-acting β2-adrenoceptor agonists), fails to prevent the loss of control that manifests as an exacerbation. In order to better understand the mechanisms underlying viral asthma exacerbations we established an in vivo model using the clinically relevant aeroallergen HDM (house dust mite) and the viral mimetic/TLR3 (Toll-like receptor 3) agonist poly(I:C). Poly(I:C) alone induced a similar neutrophilic inflammatory profile in the BAL (bronchoalveolar lavage) to that of HRV1b (human rhinovirus 1b) alone, accompanied by both elevated BAL KC (keratinocyte-derived chemokine) and IL-1β (interleukin-1β). When mice allergic to HDM were also challenged with poly(I:C) the neutrophilic inflammatory profile was exacerbated. Increased CD8(+) T-cell numbers, increased CD4(+) and CD8(+) cell activation and elevated KC and IL-1β were observed. No increases in Th2 cytokines or the eosinophil chemoattractant CCL11 [chemokine (C-C motif) ligand 11], above those induced by HDM alone, were observed. The poly(I:C)-exacerbated neutrophilia did not translate into changes in AHR (airways hyper-responsiveness), indicating that in this model inflammation and AHR are two mechanistically independent events. To test the clinical relevance of this model CS sensitivity was assessed using prednisone, a synthetic oral CS used to manage exacerbations in asthmatic patients already on maximal doses of inhaled CS. The increased neutrophils, and accompanying cytokines/chemokines KC and IL-1β induced by poly(I:C) challenge of HDM-sensitized and challenged mice were insensitive to oral prednisone therapy. In summary we have described a CS-resistant mouse model mimicking the key aspects of viral asthma exacerbation using the clinically relevant aeroallergen HDM and the viral mimic poly(I:C). This model may provide better understanding of disease mechanisms underlying viral exacerbations and could be used to build early confidence in novel therapeutic axes targeting viral asthma exacerbations in Th2 asthmatics.

Effect of low-level laser therapy on allergic asthma in rats

Asthma is a complex chronic inflammatory disease of the airways that involves the activation of many inflammatory and other types of cells. We investigated the effect of low-level laser therapy (LLLT) on allergic asthma in rats and compared its effect with that of the glucocorticoid budesonide. Asthma was induced by challenge and repeated exposure to ovalbumin. Asthmatic rats were then treated with LLLT or budesonide suspension. LLLT at 8 J/cm(2) once daily for 21 days could relieve pathological damage and airway inflammation in asthmatic rats. LLLT could decrease the total numbers of cells and eosinophils in bronchoalveolar lavage fluid. LLLT could reduce levels of IL-4 and increase IFN-γ levels in bronchoalveolar lavage fluid and serum, meanwhile reduce serum IgE levels. Flow cytometry assay showed that LLLT can regulate the Th1/Th2 imbalance of asthmatic rats. LLLT had a similar effect to that of budesonide. These findings suggest that the mechanism of LLLT treatment of asthma is by adjustment of Th1/Th2 imbalance. Thus, LLLT could take over some of the effects of budesonide for the treatment of asthma, thereby reducing some of the side effects of budesonide.

Toll-like receptor 3 stimulation causes corticosteroid-refractory airway neutrophilia and hyperresponsiveness in mice

BACKGROUND

RNA virus infections, such as rhinovirus and respiratory syncytial virus, induce exacerbations in patients with COPD and asthma, and the inflammation is corticosteroid refractory. The main aim of this study is to establish a murine model induced by a Toll-like receptor 3 (TLR3) agonist, an RNA virus mimic, and investigate the response to corticosteroid.

METHODS

A/J mice were given polyinosinic-polycytidylic acid (poly[I:C]), a TLR3 agonist, intranasally, in the presence or absence of cigarette smoke exposure. Inflammatory cell accumulation and C-X-C motif chemokine (CXCL) 1, interferon (IFN), and CXCL10 production in BAL fluid (BALF) were determined by flow cytometry and enzyme-linked immunosorbent assay, respectively, and airway hyperresponsiveness (AHR) to histamine/methacholine was determined by a two-chambered, double-flow plethysmography system. BALB/c and C57BL/6J mice were also used for comparisons.

RESULTS

Intranasal treatment of poly(I:C) significantly induced airway neutrophilia; production of CXCL1, IFN-β, and CXCL10; and necrotic cell accumulation in BALF. It also increased airway responsiveness to histamine or methacholine inhalation. This poly(I:C)-dependent airway inflammation and AHR was not inhibited by the corticosteroid fluticasone propionate (FP) (up to 0.5 mg/mL intranasal), although FP strongly inhibited lipopolysaccharide (TLR4 agonist)-induced airway neutrophilia. Furthermore, cigarette smoke exposure significantly increased TLR3 expression in murine lung tissue and exacerbated poly(I:C)-induced neutrophilia and AHR.

CONCLUSIONS

These results suggest that TLR3 stimulation is involved in corticosteroid-refractory airway inflammation in lung, which is enhanced by cigarette smoking, and this may provide a model for understanding virus-induced exacerbations in COPD and their therapy.

Viral infections in asthma and COPD

Airway viral infections are associated with the pathogenesis of asthma and COPD. It has been argued that respiratory syncytial virus (RSV) infection in infancy is a probable causal factor in the development of pediatric asthma. RSV infections tend to induce Th2-biased immune responses in the host airways. RSV infection, atopy, and low pulmonary function in neonates may work synergistically toward the development of pediatric asthma. Human rhinovirus (HRV) is a representative virus associated with the exacerbation of asthma in both children and adults. Viral infections trigger innate immune responses including granulocytic inflammation and worsen the underlying inflammation due to asthma and COPD. The innate immune responses involve type-I and -III interferon (IFN) production, which plays an important role in anti-viral responses, and the airway epithelia of asthmatics reportedly exhibit defects in the virus-induced IFN responses, which renders these individuals more susceptible to viral infection. A similarly impaired IFN response is seen in COPD, and several investigators propose that latent adenoviral infection may be involved in COPD development. Persistent RSV infections were detected in a sub-population of patients with COPD and were associated with the accelerated decline of lung function. The virus-induced upregulation of co-inhibitory molecules in the airway epithelium partly accounts for the persistent infections. Experimental animal models for virus-asthma/COPD interactions have shed light on the underlying immune mechanisms and are expected to help develop novel approaches to treat respiratory diseases.

Targeting TGFβ superfamily ligand accessory proteins as novel therapeutics for chronic lung disorders

Dysregulation of the transforming growth factor β (TGFβ) pathway has been implicated to underlie a number of disease indications including chronic lung disorders such as asthma, chronic obstructive pulmonary disease (COPD), interstitial pneumonias, and pulmonary arterial hypertension (PAH). Consequently, the pharmaceutical industry has devoted significant resources in the pursuit of TGFβ pathway inhibitors that target the cognate type I and II receptors and respective ligands. The progress of these approaches has been painfully slow, due in part to dose-limiting safety issues that result from the antagonism of a pathway that is responsible for regulating many fundamental biological processes including immune surveillance and cardiovascular responses. These disappointments have led many in the field to conclude that modulating the TGFβ pathway for chronic indications with a sufficient safety window using conventional approaches may be extremely difficult to achieve. Here we review the rationale and limitations of the use of TGFβ pathway inhibitors in chronic lung disorders and the possibility of targeting TGFβ superfamily ligand accessory proteins to allow rheostatic regulation of signaling to achieve efficacy while maintaining a sufficient therapeutic index.

Suppressive effects of a pyrazole derivative of curcumin on airway inflammation and remodeling

To advance the control of airway epithelial cell function and asthma, we investigated the effects of a new curcumin derivative, CNB001, which possesses improved pharmacological properties. Normal human bronchial epithelial (NHBE) cells were stimulated with synthetic double-stranded RNA, Poly(I:C). CNB001 significantly suppressed IL-6, TNF-α, and GM-CSF production by NHBE cells, and did so more effectively than did curcumin or dexamethasone (DEX). CNB001 significantly inhibited the decrease of E-cadherin mRNA expression and increase of vimentin mRNA expression observed in NHBE cells induced by a combination of TGF-β1 and TNF-α, which are markers of airway remodeling. In NHBE cells stimulated by TGF-β1, CNB001 significantly downregulated the level of active serine peptidase inhibitor clade E member (SERPINE) 1, which is also reported to be related to airway remodeling. Whereas DEX alone significantly increased the active SERPINE1 level, the combination of DEX and CNB001 significantly suppressed active SERPINE1. In addition, CNB001 significantly suppressed neutrophil infiltration, IL-6, TNF-α, IL-13 and active SERPINE1 production in bronchoalveolar lavage fluid of the murine asthma model, which was not observed in the case of DEX. In conclusion, the curcumin derivative, CNB001, is a promising candidate to treat asthma associated with neutrophilic airway inflammation and remodeling.