Immunostimulatory DNA Inhibits Transforming Growth Factor-β Expression and Airway Remodeling

Family with sequence similarity 13 member A mediates TGF-β1-induced EMT in small airway epithelium of patients with chronic obstructive pulmonary disease

Background

To explore the role of family with sequence similarity 13 member A (FAM13A) in TGF-β1-induced EMT in the small airway epithelium of patients with chronic obstructive pulmonary disease (COPD).

Methods

Small airway wall thickness and protein levels of airway remodeling markers, EMT markers, TGF-β1, and FAM13A were measured in lung tissue samples from COPD and non-COPD patients. The correlations of FAM13A expression with COPD severity and EMT marker expression were evaluated. Gain- and loss-of-function assays were performed to explore the functions of FAM13A in cell proliferation, motility, and TGF-β1-induced EMT marker alterations in human bronchial epithelial cell line BEAS-2B.

Results

Independent of smoking status, lung tissue samples from COPD patients exhibited significantly increased small airway thickness and collagen fiber deposition, along with enhanced protein levels of remodeling markers (collagen I, fibronectin, and MMP-9), mesenchymal markers (α-SMA, vimentin, and N-cadherin), TGF-β1, and FAM13A, compared with those from non-COPD patients. FAM13A expression negatively correlated with FEV₁% and PO₂ in COPD patients. In small airway epithelium, FAM13A expression negatively correlated with E-cadherin protein levels and positively correlated with vimentin protein levels. In BEAS-2B cells, TGF-β1 dose-dependently upregulated FAM13A protein levels. FAM13A overexpression significantly promoted cell proliferation and motility in BEAS-2B cells, whereas FAM13A silencing showed contrasting results. Furthermore, FAM13A knockdown partially reversed TGF-β1-induced EMT marker protein alterations in BEAS-2B cells.

Conclusions

FAM13A upregulation is associated with TGF-β1-induced EMT in the small airway epithelium of COPD patients independent of smoking status, serving as a potential therapeutic target for anti-EMT therapy in COPD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01783-z.

Recombinant Pyrin Domain Protein Attenuates Airway Inflammation and Alleviates Epithelial-Mesenchymal Transition by Inhibiting Crosstalk Between TGFβ1 and Notch1 Signaling in Chronic Asthmatic Mice

This article aims to investigate the effects of recombinant pyrin domain (RPYD) on airway inflammation and remodeling in mice with chronic asthma. The chronic asthma BALB/c mouse model was first sensitized by ovalbumin (OVA) and then challenged by OVA nebulization. RPYD or dexamethasone was given before OVA challenge. Our results showed that RPYD significantly inhibited the increase of total cell number, eosinophils, neutrophils and lymphocytes in bronchoalveolar lavage fluid (BALF) induced by OVA, and reduced the infiltration of inflammatory cells, the proliferation of goblet cells and collagen deposition. In addition, RPYD inhibited the mRNA and protein levels of α-smooth muscle actin (α-SMA), transforming growth factor (TGF)-β1, Jagged1, Notch1, Hes1 and Smad3, as well as Smad3 phosphorylation. TGFβ1 down-regulated the level of E-cadherin and promoted the expression of α-SMA, thus inducing epithelial-mesenchymal transition (EMT) in bronchial epithelial cells. We found that RPYD reduced EMT by inhibiting TGFβ1/smad3 and Jagged1/Notch1 signaling pathways. Further overexpression of NICD showed that under the stimulation of TGFβ1, NICD enhanced the phosphorylated Smad3 and nuclear Smad3, accompanied by the increased expression of Notch1 target gene Hes1. In contrast, after treatment with smad3 siRNA, the expression of Hes1 was down regulated as the decrease of Smad3, which indicates that there is crosstalk between smad3 and NICD on Hes1 expression. In conclusion, RPYD reduces airway inflammation, improves airway remodeling and reduces EMT in chronic asthmatic mice by inhibiting the crosstalk between TGFβ1/smad3 and Jagged1/Notch1 signaling pathways.

Exercise and Asthma

Asthma is a chronic lower respiratory disease that is very common worldwide, and its incidence is increasing year by year. Since the 1970s, asthma has become widespread, with approximately 300 million people affected worldwide and about 250,000 people have lost their lives. Asthma seriously affects people's physical and mental health, resulting in reduced learning efficiency, limited physical activities, and decreased quality of life. Therefore, raising awareness of the risk of asthma and how to effectively treat asthma have become important targets for the prevention and management of asthma in recent years. For patients with asthma, exercise training is a widely accepted adjunct to drug-based and non-pharmacological treatment. It has been recommended abroad that exercise prescriptions are an important part of asthma management.

Anti-oxidant and Anti-inflammatory Effects of Aquatic Exercise in Allergic Airway Inflammation in Mice

Oxidative stress and inflammation are key pathways responsible for the pathogenesis of asthma. Aquatic exercise (AE) has been proven to elicit a variety of biological activities such as anti-oxidant and anti-inflammatory effects. However, although proper forms of AE provide beneficial health effects, incorrect forms and types of AE are potentially injurious to health. Several studies have investigated AE, but the relationship between types of AE and asthma has not been fully elucidated. This study evaluated the effects of two types of AE according to resistance on ovalbumin (OVA)-induced allergic airway inflammation in mice. BALB/c mice were subjected to OVA sensitization and challenge, and then to different types of AE including, walking and swimming, in a pool filled with water to a height of 2.5 and 13 cm for 30 min, respectively. AE reduced OVA-induced eosinophilic inflammation, airway hyperresponsiveness, and serum immunoglobulin E level. AE significantly inhibited increases in interleukin (IL)-4, IL-5, IL-13, histamine, leukotriene D4, and tryptase levels in bronchoalveolar lavage fluid (BALF). AE also effectively suppressed mucus formation, lung fibrosis, and hypertrophy of airway smooth muscle within the lung tissues. This exercise markedly reduced the levels of malondialdehyde while increased glutathione and superoxide dismutase (SOD) activity in lung tissues. Furthermore, AE significantly decreased tumor necrosis factor-α, IL-6 levels, and prostaglandin E2 production in BALF. The inhibitory effects of swimming on the levels of biomarkers related to oxidative stress and inflammation were greater than that of walking. These effects may have occurred through upregulation of NF-E2-related factor 2/heme oxygenase-1 signaling and suppression of mitogen-activated protein kinase/nuclear factor-κB pathway. Cumulative results from this study suggest that AE might be beneficial in mitigating the levels of biomarkers related to oxidative stress and inflammation. Thus, this therapy represents a crucial non-pharmacological intervention for treatments of allergic airway inflammation.

TLR9-based immunotherapy for the treatment of allergic diseases

Toll-like receptors (TLRs), a family of pattern recognition receptors expressed on many cell types of innate immunity, recognize the pathogen-associated molecular patterns of microbes. The hygiene hypothesis suggests that a reduced microbial exposure in early childhood increases the susceptibility to allergic diseases due to deviation in development of the immune system. TLRs are key roles in the right and healthy direction of adaptive immunity with the induction of T-helper 2 toward Th1 immune responses and regulatory T cells. TLR ligand CpG-ODN-based immunomodulation is independent of allergen and it mainly affects innate immune system. While, CpG-oligodeoxynucleotide-based vaccination is allergen specific and induces adaptive immune system. The use of agonists of TLR9 in two distinct strategies of immunotherapy, immunomodulation and vaccination, could be presented as the curative method for the treatment of allergic diseases.

Mast cells' integrated actions with eosinophils and fibroblasts in allergic inflammation: implications for therapy

Mast cells (MCs) and eosinophils (Eos) are the key players in the development of allergic inflammation (AI). Their cross-talk, named the Allergic Effector Unit (AEU), takes place through an array of soluble mediators and ligands/receptors interactions that enhance the functions of both the cells. One of the salient features of the AEU is the CD48/2B4 receptor/ligand binding complex. Furthermore, MCs and Eos have been demonstrated to play a role not only in AI but also in the modulation of its consequence, i.e., fibrosis/tissue remodeling, by directly influencing fibroblasts (FBs), the main target cells of these processes. In turn, FBs can regulate the survival, activity, and phenotype of both MCs and Eos. Therefore, a complex three players, MCs/Eos/FBs interaction, can take place in various stages of AI. The characterization of the soluble and physical mediated cross talk among these three cells might lead to the identification of both better and novel targets for the treatment of allergy and its tissue remodeling consequences.

Upregulation of gelatinases and epithelial-mesenchymal transition in small airway remodeling associated with chronic exposure to wood smoke

BACKGROUND

Peribronchiolar fibrosis is an important feature of small airway remodeling (SAR) in cigarette smoke-induced COPD. The aim of this study was to investigate the role of gelatinases (MMP9, MMP2) and epithelial-mesenchymal transition (EMT) in SAR related to wood smoke (WS) exposure in a rat model.

METHODS

Forty-eight female Sprague-Dawley rats were randomly divided into the WS group, the cigarette smoke (CS) group and the clean air control group. After 4 to 7 months of smoke exposure, lung tissues were examined with morphometric measurements, immunohistochemistry and Western blotting. Serum MMP9 and TIMP1 concentrations were detected by ELISA. In vitro, primary rat tracheal epithelial cells were stimulated with wood smoke condensate for 7 days.

RESULTS

The COPD-like pathological alterations in rats exposed chronically to WS were similar to those exposed to CS; the area of collagen deposition was significantly increased in the small airway walls of those exposed to WS or CS for 7 months. The expression of gelatinases in rats induced by WS or CS exposure was markedly increased in whole lung tissue, and immunohistochemistry showed that MMP9, MMP2 and TIMP1 were primarily expressed in the airway epithelium. The serum levels of MMP9 and TIMP1 were significantly higher in rats secondary to WS or CS exposure. Few cells that double immunostained for E-cadherin and vimentin were observed in the airway subepithelium of rats exposed to WS for 7 months (only 3 of these 8 rats). In vitro, the expression of MMP9 and MMP2 proteins was upregulated in primary rat tracheal epithelial cells following exposure to wood smoke condensate for 7 days by Western blotting; positive immunofluorescent staining for vimentin and type I collagen was also observed.

CONCLUSIONS

These findings suggest that the upregulation of gelatinases and EMT might play a role in SAR in COPD associated with chronic exposure to wood smoke.

Qu Feng Xuan Bi Formula attenuates anaphylactic rhinitis-asthma symptoms via reducing EOS count and regulating T cell function in rat ARA models

ETHNOPHARMACOLOGICAL RELEVANCE

Aqueous extract of Qu Feng Xuan Bi Formula (QFXBF, a Chinese herb formula) which composed of Radix Glycyrrhizae, Radix Glycyrrhizae Preparata, Paeonia sterniana Fletcher in Journ, Pheretima, Allium macrostemon Bunge, Astragalus membranaceus (Fisch) Bunge and Divaricate Saposhnikovia Root has been used in treatment of allergic rhinitis and asthma (ARA) as an approved hospital prescription for many years in Jiangsu Province Hospital of Traditional Chinese Medicine, China. The present study was designed to investigate the effect of the aqueous extract of QFXBF in the gene expression of Toll-like receptor 9 (TLR9) and the manners of immune modulation of T cell-associated interleukin (IL-4 and IL-13) in rat ARA models.

MATERIALS AND METHODS

Fifty SD male rats were divided into five groups: not treated group, OVA only group (treated only with OVA), dexamethasone (DXM) group, low dose QFXBF group and high dose QFXBF group randomly (n=10 per group). Rat allergic rhinitis and asthma model was developed by ovalbumin (OVA) sensitization and nose infusion. Pathological changes of nasal tissue and lungs were examined by H&E staining. Gene expressions of TLR9, Stat 3, Jak-1 and C-Jun in nasal tissue were assayed by real-time polymerase chain reaction (RT-PCR). The serum and broncho-alveolar lavage fluid (BALF) levels of T cell-associated interleukin (IL-4 and IL-13) were determined by enzyme-linked immunosorbent assay (ELISA).

RESULT

The ARA model was successfully established. Marked EOS count was observed in BALF from ARA models. The aqueous extract of QFXBF could reduce EOS levels and increase TLR9 expression, but did not affect the gene expression of Stat-3 and Jak-1 and C-Jun. The reduction of IL-13 concentration in serum from high dose QFXBF group was observed in BALF, albeit not significantly. Despite the not treated group, serum levels of IL-4 had significantly increased in other four groups (P<0.001, n=4-6) but made higher in low dose QFXBF group and DXM group (P<0.05, n=4-6).

CONCLUSION

This study originally provides the evidence that the aqueous extract of Qu Feng Xuan Bi Formula alone is effective in the treatment of anaphylactic rhinitis-asthma symptoms. The extract of Qu Feng Xuan Bi Formula was effective to reduce the eosophil recruitment to the lung. In addition it increased the IL-4 concentration in the BALF and expression of TLR9 in the nasal tissue. No alteration was observed in the IL-13 concentration in the BALF and expression of STAT-3, JAK-1 and C-Jun in nasal tissue. The results thereby scientifically provided mechanism of these aqueous extract of QFXBF in improvement of ARA and supported its clinical use.

A limited CpG-containing oligodeoxynucleotide therapy regimen induces sustained suppression of allergic airway inflammation in mice

BACKGROUND

CpG-containing oligodeoxynucleotides (CpG-ODNs) are potent inhibitors of T helper 2 mediated allergic airway disease in sensitised mice challenged with allergen. A single treatment has transient effects but a limited series of treatments has potential to achieve clinically meaningful sustained inhibition of allergic airway disease.

OBJECTIVE

To optimise the treatment regimen for sustained efficacy and to determine the mechanisms of action in mice of an inhaled form of CpG-ODN being developed for human asthma treatment.

METHODS

We set up a chronic allergic-asthma model using ragweed-sensitised mice exposed weekly to intranasal ragweed. Using this model, the effects of a limited series of weekly intranasal 1018 ISS (CpG-ODN; B-class) treatments were evaluated during treatment and for several weeks after treatments had stopped but weekly allergen exposures continued. Treatment efficacy was evaluated by measuring effects on lung T helper 2 cytokines and eosinophilia, and lung dendritic cell function and T-cell responses.

RESULTS

Twelve intranasal 1018 ISS treatments induced significant suppression of bronchoalveolar lavage eosinophilia and interleukin 4, 5 and 13 levels. This suppression of allergic T helper 2 parameters was maintained through 13 weekly ragweed exposures administered after treatment cessation. Subsequent experiments demonstrated that at least five treatments were required for lasting suppression. Although CpG-ODN induced moderate T helper 1 responses, suppression of allergic airway disease did not require interferon γ but was associated with induction of a regulatory T-cell response.

CONCLUSIONS

A short series of CpG-ODN treatments results in sustained suppression of allergic lung inflammation induced by a clinically relevant allergen.

Clinical analysis of primary eosinophilic esophagitis

Background/Aims

Eosinophilic esophagitis (EoE) is a chronic inflammatory disorder of the esophagus. Similar to asthma, EoE can induce irreversible structural changes in the esophagus as a result of chronic and persistent eosinophilic inflammation. The aim of this study was to analyse changes in symptoms, eosinophil counts and endoscopic findings after treatment.

Methods

Nine patients with EoE (6 men and 3 women; mean age, 36.44 years) were diagnosed with EoE based on typical symptoms, endoscopic abnormalities and infiltration of the esophageal epithelium with ≥ 15 eosinophils/high-power field. The average endoscopic follow-up period was 10 months, ranging from 1 to 25 months. Symptoms and endoscopic and pathological findings at initial observation and follow-up were evaluated.

Results

Seven of the 9 patients had dysphagia symptoms, which improved in 4 of 6 patients who were treated with proton pump inhibitor. Two patients were unresponsive to proton pump inhibitor and another 2 patients were treated with corticosteroid, which led to symptomatic relief. In 8 patients, esophageal eosinophilia was improved histologically at follow-up after treatment. Six of the 9 patients had typical endoscopic findings of EoE at initial examination. Despite treatment, these findings remained in 5 of the 6 patients at follow-up endoscopy.

Conclusions

After treatment, the symptoms and eosinophil counts were temporarily improved, but the endoscopic findings of EoE were generally not improved. This indicates that deformity of esophageal structure due to eosinophilic inflammation might be irreversible despite proper management.

Effect of tiotropium bromide on airway remodeling in a chronic asthma model

BACKGROUND

Recent evidence suggests that acetylcholine acting through muscarinic receptors may play an inhibitory role in the mechanisms that drive the structural changes in the airways called airway remodeling. The novel anticholinergic drug tiotropium bromide, which selectively antagonizes muscarinic receptors, especially the M3 subtype, and is long acting, could be beneficial in attenuating airway remodeling in chronic asthma.

OBJECTIVE

To investigate the effect of tiotropium bromide on parameters of airway remodeling, including smooth muscle hypertrophy and peribronchial thickening, in a mouse model of chronic asthma.

METHODS

To develop the murine models of acute and chronic asthma, BALB/c mice were sensitized and challenged to ovalbumin for 1 and 3 months, respectively. The effect of tiotropium bromide (0.1mM in 50 μL of phosphate-buffered saline) on pulmonary inflammation and remodeling was evaluated. The expression of muscarinic receptors M2 and M3 was analyzed.

RESULTS

In the chronic asthma model, the tiotropium-treated group significantly decreased smooth muscle thickening and peribronchial collagen deposition. As for pulmonary inflammation, the chronic asthma model had a reduction of inflammatory cells and T(H)2 cytokines by tiotropium bromide, but the effects in the asthma acute model were reversed. In the chronic asthma model, expression of the M3 receptor was inhibited and that of the M2 receptor was elevated by the administration of tiotropium bromide.

CONCLUSION

This study suggests that tiotropium bromide might have an inhibitory effect on airway remodeling in a murine model of chronic asthma. Differential effects on muscarinic receptor subtypes may explain why tiotropium bromide has different effects on acute and chronic asthma.

Eosinophilic esophagitis: epithelial mesenchymal transition contributes to esophageal remodeling and reverses with treatment

BACKGROUND

Mechanisms underlying esophageal remodeling with subepithelial fibrosis in subjects with eosinophilic esophagitis (EoE) have not been delineated.

OBJECTIVES

We sought to explore a role for epithelial mesenchymal transition (EMT) in subjects with EoE and determine whether EMT resolves with treatment.

METHODS

Esophageal biopsy specimens from 60 children were immunostained for epithelial (cytokeratin) and mesenchymal (vimentin) EMT biomarkers, and EMT was quantified. Subjects studied had EoE (n = 17), indeterminate EoE (n = 15), gastroesophageal reflux disease (n = 7), or normal esophagus (n = 21). EMT was analyzed for relationships to diagnosis, eosinophil counts, and indices of subepithelial fibrosis, eosinophil peroxidase, and TGF-β immunostaining. EMT was assessed in pretreatment and posttreatment biopsy specimens from 18 subjects with EoE treated with an elemental diet, 6-food elimination diet, or topical corticosteroids (n = 6 per group).

RESULTS

TGF-β1 treatment of esophageal epithelial cells in vitro for 24 hours induced upregulation of mesenchymal genes characteristic of EMT, including N-cadherin (3.3-fold), vimentin (2.1-fold), and fibronectin (7.5-fold). EMT in esophageal biopsy specimens was associated with EoE (or indeterminate EoE) but not gastroesophageal reflux disease or normal esophagus and was correlated to eosinophil counts (r = 0.691), eosinophil peroxidase (r = 0.738), and TGF-β (r = 0.520) immunostaining and fibrosis (r = 0.644) indices. EMT resolved with EoE treatments that induced clinicopathologic remission with reduced eosinophil counts. EMT decreased significantly after treatment by 74.1% overall in the 18 treated subjects with EoE; pretreatment versus posttreatment EMT scores were 3.17 ± 0.82 versus 0.82 ± 0.39 (P < .001), with similar decreases within treatment groups. Pretreatment/posttreatment EMT was strongly correlated with eosinophil counts for combined (r = 0.804, P < .001) and individual treatment groups.

CONCLUSIONS

EMT likely contributes to subepithelial fibrosis in subjects with EoE and resolves with treatments that decrease esophageal inflammation, and its resolution correlates with decreased numbers of esophageal eosinophils.

The natural history and complications of eosinophilic esophagitis

Eosinophilic esophagitis is a chronic disease limited to the esophagus and has a persistent or spontaneously fluctuating course. So far it does not seem to limit life expectancy, but it often substantially impairs the quality of life. To date, there has been no association with malignant conditions, but there is concern that the chronic, uncontrolled inflammation will evoke irreversible structural alterations of the esophagus, leading to tissue fibrosis, stricture formation, and impaired function. This esophageal remodeling may result in several disease-inherent and procedure-related complications.

Cytokine production and proliferation upon in vitro oligodeoxyribonucleotide stimulation of equine peripheral blood mononuclear cells

Synthetic oligodeoxyribonucleotides (ODN) may prove useful immune modulators in equine medicine. It is however important to assess the effects of each specific ODN in the species it is intended to be used in. The present study therefore aimed to evaluate some ODN for induction of cytokine production; i.e. type I interferons (IFN), IFN-γ, tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β), and proliferation of equine peripheral blood mononuclear cells (PBMC). A panel of four ODN containing unmethylated cytosine-guanosine sequences (CpG) was used: ODN 1 and ODN 8 representing A-class; ODN 2006 representing B-class and ODN 2395 representing C-class-ODN. In addition, two ODN where CpG-motifs were reversed to GpC were included; ODN 2137 otherwise identical to ODN 2006 and ODN 5328 otherwise identical to ODN 2395. Cytokine concentrations were measured in cell culture supernatants after 24h of induction and proliferation was determined after 72 h of induction. Each ODN was tested with PBMC from at least 5 individual horses with and without the addition of lipofectin to cell cultures. Type I IFN, IFN-γ and TNF-α production was readily induced by ODN 1, ODN 2006 and ODN 2395 both in the presence and absence of lipofectin and all three types of ODN induced similar levels of cytokines. Proliferation of PBMC was clearly induced by ODN 2006 and ODN 2395 while ODN 1 only induced low-level proliferation. The levels of proliferation induced were not influenced by the presence of lipofectin. TGF-β production was not induced by any of the tested ODN. ODN 8, ODN 2137 and ODN 5328 were largely inactive in all assays. Thus, responses seemed dependent on or increased by CpG-motifs but presence of CpG-motifs did not necessarily confer activity since ODN 8 was inactive despite its CpG-motifs. Taken together, with equine PBMC distinctions in induction of different leukocyte functions between A-, B-, and C-class ODN were less obvious than what has been observed for human cells. These observations further stress the presence of species differences in ODN-induced responses.

CpG and non-CpG oligodeoxynucleotides directly costimulate mouse and human CD4+ T cells through a TLR9- and MyD88-independent mechanism

TLR ligands are known to activate APCs, but direct T cell responsiveness to TLR ligands is controversial. Because of their clinical relevance, we performed in-depth studies of the effects of the TLR9-associated ligands, oligodeoxynucleotides (ODNs), on highly purified T lymphocytes. Both CpG and non-CpG ODNs directly costimulate mouse and human CD4(+) T cells, resulting in activation marker upregulation, cytokine secretion, elevated TCR phosphorylation, and proliferation. Surprisingly, ODN costimulation occurred independently of TLR9 and MyD88, as well as ICOS, CD28, and TRIF. TLR9-antagonist ODNs likewise promoted T cell activation, which has important implications for the study of these "inhibitory" ODNs in inflammatory diseases. Cytokine profiling revealed that ODNs promote polarization of distinct Th subsets, and that ODNs differentially affect human naive and memory T cells. Our studies reveal a striking and unexpected ability of ODNs to directly activate and polarize T cells, presenting an opportunity to enhance the paradigm for selection of therapeutic ODNs in humans.

The tumor necrosis factor family member LIGHT is a target for asthmatic airway remodeling

Individuals with chronic asthma show a progressive decline in lung function that is thought to be due to structural remodeling of the airways characterized by subepithelial fibrosis and smooth muscle hyperplasia. Here we show that the tumor necrosis factor (TNF) family member LIGHT is expressed on lung inflammatory cells after allergen exposure. Pharmacological inhibition of LIGHT using a fusion protein between the IgG Fc domain and lymphotoxin β receptor (LTβR) reduces lung fibrosis, smooth muscle hyperplasia and airway hyperresponsiveness in mouse models of chronic asthma, despite having little effect on airway eosinophilia. LIGHT-deficient mice also show a similar impairment in fibrosis and smooth muscle accumulation. Blockade of LIGHT suppresses expression of lung transforming growth factor-β (TGF-β) and interleukin-13 (IL-13), cytokines implicated in remodeling in humans, whereas exogenous administration of LIGHT to the airways induces fibrosis and smooth muscle hyperplasia, Thus, LIGHT may be targeted to prevent asthma-related airway remodeling.

Chronic allergen challenge induces pulmonary extramedullary hematopoiesis

Allergic inflammation is associated with increased generation and trafficking of inflammatory cells, especially eosinophils, to sites of inflammation. The effect of acute versus chronic airway allergen challenge on hematopoietic activity in the bone marrow (BM) and lungs was investigated using murine models of allergic airway inflammation. Acute allergen challenge induced proliferation of BM cells and significantly increased generation of eosinophil, but not multipotent, granulocyte-macrophage (GM), or B-lymphocyte progenitor cells. However, no hematopoietic activity was observed in the lungs. With chronic challenge, BM cells failed to proliferate, but exhibited increased capacity to generate multipotent as well as eosinophil, GM, and B-lymphocyte progenitors. In addition, increased generation of eosinophil- and GM-specific progenitors was observed in the lungs. Although no differences were observed in their ability to roll on BM endothelium in vitro or in vivo, CD34-enriched hematopoietic/stem progenitor cells (HSPCs) from chronic-, but not acute-, challenged mice demonstrated reduced migration across BM endothelial cells associated with decreased CXCR4 expression. Overall, these studies demonstrate that chronic allergen exposure can alter BM homing due to decreased transendothelial migration enabling noninteracting HSPCs to egress out of the BM and recruit to sites of inflammation such as the airways, resulting in extramedullary hematopoiesis.

Transforming growth factor-beta1 in asthmatic airway smooth muscle enlargement: is fibroblast growth factor-2 required?

Enlargement of airway smooth muscle (ASM) tissue around the bronchi/bronchioles is a histopathological signature of asthmatic airway remodelling and has been suggested to play a critical role in the increased lung resistance and airway hyperresponsiveness seen in asthmatic patients. The pleiotropic cytokine, TGF-beta1, is believed to contribute to several aspects of asthmatic airway remodelling and is known to influence the growth of many cell types. Increased TGF-beta1 expression/signalling and ASM growth have been shown to occur concurrently in animal models of asthma. Abundant studies further substantiate this association by showing that therapeutic strategies that reduce or prevent TGF-beta1 overexpression/signalling lead to a parallel decrease or prevention of ASM enlargement. Finally, recent findings have supported a direct link of causality between TGF-beta1 overexpression/signalling and the overgrowth of ASM tissue. To follow-up on these in vivo studies, many investigators have pursued detailed investigation of ASM in cell culture conditions, assessing the direct role of TGF-beta1 on cellular proliferation and/or hypertrophy. Inconsistencies among the in vitro studies suggest that the effect of TGF-beta1 on ASM cell proliferation/hypertrophy is contextual. A hypothesis focusing on fibroblast growth factor-2 is presented at the end of this review, which could potentially reconcile the apparent discrepancy between the conflicting in vitro findings with the consistent in vivo finding that TGF-beta1 is required for ASM enlargement in asthma.

Inhibitory effects of anti-immunoglobulin E antibodies on airway remodeling in a murine model of chronic asthma

BACKGROUND

Airway remodeling is one of the cardinal features of asthma and is thought to play a pivotal role in refractory or persistent asthma. Immunoglobulin E (IgE) has a major effect on the pathogenesis of asthma. The aim of this study was to investigate the effects of anti-IgE antibody not only on airway inflammation and bronchial hyperresponsiveness, but also on airway remodeling in a murine model of chronic asthma.

METHODS

The authors developed a mouse model of chronic asthma in which ovalbumin (OVA)-sensitized female BALB/c-mice were exposed to intranasal OVA administration twice a week for 3 months. Anti-IgE antibodies were administered intravenously starting on the 38th day and once a month thereafter for 3 months during the intranasal OVA challenge.

RESULTS

Mice that were chronically exposed to OVA developed sustained eosinophilic airway inflammation and airway hyperresponsiveness (AHR) to methacholine and showed increased levels of collagen, hydroxyproline, and alpha-smooth muscle actin, as compared with control mice. Treatment with anti-IgE antibody inhibited the development of AHR, eosinophilic inflammation, and airway remodeling. Moreover, anti-IgE antibody treatment reduced the levels of interleukin (IL)-5 and IL-13 in the bronchoalveolar lavage fluids, although it did not affect the levels of IL-10, transforming growth factor-beta, and activin A.

CONCLUSION

These results suggest that anti-IgE antibody treatment modulates the airway inflammation and remodeling associated with chronic allergen challenge. The inhibition of inflammation may be related to the regulation of Th2 cytokines. However, the mechanisms underlying the blocking of airway remodeling by anti-IgE antibody remain to be elucidated.

The overexpression of heparin-binding epidermal growth factor is responsible for Th17-induced airway remodeling in an experimental asthma model

Th17 cells that produce IL-17 have been found to participate in the development of allergy-triggered asthma. However, whether they play a causative role in the pathogenesis of airway remodeling in chronic asthma remains unclear. In this study, we investigated the role of Th17 cells in airway remodeling and the possible involvement of epidermal growth factor (EGF) receptor signals downstream of Th17. We established a C57BL/6 mouse model of prolonged allergen challenge that exhibits many characteristics of airway remodeling. Prolonged allergen challenge induced a progressive increase in the number of airway-infiltrating Th17 cells, and Th17 counts positively correlated with the severity of airway remodeling. Increases in mucus production, airway smooth muscle (ASM) mass, peribronchial collagen deposition, and airway heparin-binding EGF (HB-EGF) expression have been observed in sensitized mice following prolonged allergen exposure or adoptive Th17 transfer; remarkably, these effects can be abrogated by treatment with anti-IL-17 mAb. Both the EFGR inhibitor AG1478 and an anti-HB-EGF mAb ameliorated all of these effects, except for peribronchial collagen deposition in the presence of high levels of IL-17. In vitro, Th17 cells enhanced the airway epithelial expression of HB-EGF in a coculture of the two cells. The conditioned medium obtained from this coculture system effectively promoted ASM proliferation; this response was dramatically abolished by anti-HB-EGF mAb but not Abs against other EGF receptor ligands or IL-17. These observations demonstrated that overexpression of airway HB-EGF induced by IL-17 secreted from redundant expanding Th17 cells might contribute to excessive mucus expression and ASM proliferation in chronic asthma.

Chronic allergen challenge induces bronchial mast cell accumulation in BALB/c but not C57BL/6 mice and is independent of IL-9

As genetically engineered mutant mice deficient in single genes are usually generated on a C57BL/6 background, to study mast cell trafficking in mutant mice, we initially investigated whether mast cells accumulated in bronchi in C57BL/6 mice challenged with OVA allergen acutely or chronically for 1 to 3 months. The total number of bronchial mast cells were quantitated using toluidine blue staining in airways of different sizes, i.e. , small (<90 µm), medium (90–155 µm), or large (>150 µm) airways. Non-OVA challenged and acute OVA challenged mice (C57BL/6 and BALB/c) had no detectable bronchial mast cells. Chronic OVA challenge in BALB/c mice for 1 or 3 months induced a significant increase in the number of bronchial mast cells in small-, medium-, and large-sized airways but minimal change in the number of bronchial mast cells in C57BL/6 mice. Both BALB/c and C57BL/6 mice developed significant lung eosinophilia following acute or chronic OVA challenge. Studies of IL-9-deficient mice on a BALB/c background demonstrated a significant increase in the number of bronchial mast cells in IL-9-deficient mice suggesting that IL-9 was not required for the bronchial accumulation of mast cells. Overall, these studies demonstrate that the chronic OVA challenge protocol we have utilized in BALB/c mice provides a model to study the mechanism of bronchial mast cell accumulation and that bronchial mast cell accumulation in chronic OVA challenged mice is independent of IL-9 in this model.

Intranasal CpG therapy attenuated experimental fungal asthma in a TLR9-dependent and -independent manner

BACKGROUND

CpG administration abolishes airway inflammation and remodeling in acute models of allergic airway disease.

METHODS

Herein, we investigated the therapeutic effect of CpG in a chronic fungal model of asthma. TLR9+/+ and TLR9-/- mice were sensitized to soluble Aspergillus fumigatus antigens and challenged with live A. fumigatus conidia. Mice were treated with intraperitoneal (IP) or intranasal (IN) CpG, or left untreated 14-28 days after conidium challenge. All features of allergic airway disease were attenuated in TLR9+/+ mice treated with IN CpG, including airway hyperresponsiveness (AHR), mucus production, and peribronchial fibrosis.

RESULTS

TLR9-/- mice treated with IN CpG exhibited attenuated airway remodeling but not AHR. Whole-lung IL-12 levels were significantly elevated in both TLR9+/+ and TLR9-/- mice receiving IN CpG but not in either group receiving IP CpG. Whole-lung IL-10 levels were significantly elevated in IN CpG-treated TLR9+/+ mice but not in TLR9-/- mice receiving IN CpG. Increased whole-lung transcript and protein levels of the scavenger receptors SR-A and MARCO were observed in TLR9-/- mice compared with TLR9+/+ mice, possibly accounting for the CpG responsiveness in the knockout group.

CONCLUSIONS

Together, these data show that IN CpG has a therapeutic effect during established fungal asthma, which is TLR9 dependent and independent.

Toll-like receptor-9 agonist inhibits airway inflammation, remodeling and hyperreactivity in mice exposed to chronic environmental tobacco smoke and allergen

BACKGROUND

As passive environmental tobacco smoke (ETS) exposure in nonsmokers can increase both asthma symptoms and the frequency of asthma exacerbations, we utilized a mouse model, in which ovalbumin (OVA) + ETS induce significantly increased levels of eosinophilic airway inflammation and remodeling compared to either stimulus alone, to determine whether a Toll-like receptor-9 (TLR-9) agonist could reduce levels of airway inflammation, airway remodeling and airway hyperreactivity (AHR).

METHODS

Mice treated with or without a TLR-9 agonist were sensitized to OVA and challenged with OVA + ETS for 1 month. AHR to methacholine was assessed in intubated and ventilated mice. Lung Th2 cytokines and TGF-beta(1) were measured by ELISA. Lungs were processed for histology and immunohistology to quantify eosinophils, mucus, peribronchial fibrosis and smooth muscle changes using image analysis.

RESULTS

Administration of a TLR-9 agonist to mice coexposed to chronic ETS and chronic OVA allergen significantly reduced levels of eosinophilic airway inflammation, mucus production, peribronchial fibrosis, the thickness of the peribronchial smooth muscle layer, and AHR. The reduced airway remodeling in mice treated with the TLR-9 agonist was associated with significantly reduced numbers of peribronchial MBP+ and peribronchial TGF-beta(1)+ cells, and with significantly reduced levels of lung Th2 cytokines [interleukin-5 and interleukin-13] and TGF-beta(1).

CONCLUSION

These studies demonstrate that TLR-9-based therapies inhibit airway inflammation, remodeling and AHR in mice coexposed to ETS and allergen who exhibit enhanced airway inflammation and remodeling.

Therapeutic manipulation of immune tolerance in allergic disease

Immune tolerance - the adaptation of the immune system to external antigens or allergens - might be therapeutically manipulated to restore normal immunity in conditions such as allergy, asthma and autoimmune diseases. The field of allergen-specific immunotherapy is experiencing exciting and novel developments for the treatment of allergic and autoimmune diseases, and recent insights into the reciprocal regulation and counter-balance between different T-cell subsets is foreseen to facilitate new strategies for immunointervention. This Review highlights current knowledge of immunomodulatory therapies for the manipulation of immune tolerance and highlights recent approaches to improve allergen-specific immunotherapy for the treatment of allergic diseases.

Impaired lung dendritic cell migration and T cell stimulation induced by immunostimulatory oligonucleotides contribute to reduced allergic airway inflammation

CpG-containing oligonucleotides (CpG) have been shown to reduce key features of allergic airway inflammation in mouse models. Given the inhibitory effects of CpG treatment on Ag presentation of subsequently encountered Ags via MHC class I and II molecules by dendritic cells (DC), we hypothesized that intranasal CpG treatment would lead to reduced Ag-specific T cell stimulation in the lung-draining lymph nodes, thereby reducing the inflammatory response in sensitized mice. Intranasal CpG administration led to phenotypic maturation of lung and mediastinal lymph node DC as determined by expression of MHC class II, CD80, and CD86. This was accompanied by a significant reduction in the proliferation of adoptively transferred Ag-specific CD4(+) and CD8(+) T cells in mediastinal lymph nodes, when CpG was given before inhalative OVA challenges. DC obtained from mediastinal lymph nodes of CpG-treated mice before OVA inhalation led to reduced T cell stimulation via MHC class I and II molecules. In addition, CpG diminished airway eosinophilia and pulmonary infiltration after sensitization or following adoptive transfer of Ag-specific Th2 cells. These results were explained by reduced CCL21 expression and inhibition of lung DC migration following CpG administration, which could be restored by transfer of bone marrow-derived DC, because CpG had no major impact on the constitutive MHC class II Ag presentation of protein-derived Ag by lung tissue-derived DC. We conclude that CpG treatment can effectively impair the DC-mediated Ag transport from the lungs to the lymph nodes, resulting in reduced T cell activation and blunted airway inflammation.

Immune Mechanisms and Therapeutic Potential of CpG Oligodeoxynucleotides

Unmethylated CpG motifs in bacterial DNA and synthetic oligodeoxynucleotides activate immune cells that express Toll-like Receptor 9. Activation through this receptor triggers cellular signaling that leads to production of a proinflammatory and a Th1-type, antigen-specific immune response. The immunostimulatory effects of CpG oligodeoxynucleotides confer protection against infectious disease, allergy and cancer in animal models, and clinical trials have been initiated. However, CpG oligodeoxynucleotides may exacerbate disease in some situations. We will review current concepts in the mechanisms of activating Toll-like Receptor 9 with CpG oligodeoxynucleotides and highlight opportunities for using large animal models to better determine the mechanisms of action.

p70 Ribosomal S6 kinase is required for airway smooth muscle cell size enlargement but not increased contractile protein expression

We examined the contribution of p70 ribosomal S6 kinase (p70S6K) to airway smooth muscle hypertrophy, a structural change found in asthma. In human airway smooth muscle cells, transforming growth factor (TGF)-beta, endothelin-1, and cardiotrophin-1 each induced phosphorylation of p70S6K and ribosomal protein S6 while increasing cell size, total protein synthesis, and relative protein abundance of alpha-smooth muscle actin and SM22. Transfection of myocytes with siRNA against either p70S6K or S6, or infection with retrovirus encoding a kinase-dead p70S6K, reduced cell size and protein synthesis but had no effect on contractile protein expression per mg total protein. Infection with a retrovirus encoding a constitutively active, rapamycin-resistant (RR) p70S6K increased cell size but not contractile protein expression. siRNA against S6 decreased cell size in myocytes expressing RR p70S6K. Finally, TGF-beta treatment, but not RR p70S6K expression, increased KCl-induced fractional shortening. Together, these data suggest that p70S6K activation is both required and sufficient for airway smooth muscle cell size enlargement but not contractile protein expression. Further, ribosomal protein S6 is required for p70S6K-mediated cell enlargement. Finally, we have shown for the first time in a functional cell system that p70S6K-mediated myocyte enlargement alone, without preferential contractile protein expression, is insufficient for increased cell shortening.

Use of CpG oligonucleotides in treatment of asthma and allergic disease

In the last several decades, there has been a marked increase in the prevalence of atopic disorders including asthma in "Western" societies; a relationship has been identified between lack of early-life exposure to microbes or microbial products and increased susceptibility to atopic disorders. The innate immune system is activated by early microbial exposures, many of which utilize one of the Toll-like receptors, and there has been significant interest in studying how ligation of TLRs may be therapeutically useful. CpG oligonucleotides (CpG-ODN, resembling bacterial DNA) engage TLR-9 on B-cells, dendritic cells and other cell types, resulting in a cascade that includes induction of Th1-type and T-regulatory-type immune responses. Preclinical models of asthma have demonstrated that CpG-ODN are potent inhibitors of atopic responses, suppressing Th2 cytokine and, reducing airway eosinophilia, systemic levels of IgE, and bronchial hyperreactivity-in short the critical attributes of the asthmatic phenotype. In models of chronic allergen exposure, CpG-ODN are also effective at preventing the development of airway remodeling. In established asthma, CpG-ODN can reverse manifestations of disease, both when used alone or in combination with allergen immunotherapy. Early clinical trials have had mixed results, including a significant benefit when CpG-ODN were conjugated to ragweed allergen in an allergic rhinitis immunotherapy study, but only limited efficacy seen when administered prior to allergen challenge in asthmatics. Further study of CpG-ODNs for the treatment of asthma and other atopic disorders is warranted by existing data.

Immunomodulation of allergic disease

This review focuses on sublingual immunotherapy (SLIT), toll-like receptor-9 (TLR-9) vaccines using cytosine phosphorothioate guanosine (CpG)-allergen conjugates, and anti-IL-5 as novel immunomodulating therapies in allergy. At present, all three approaches are investigational in the United States and require further study to determine their safety and effectiveness. SLIT provides a novel oral route of administering an allergen to induce tolerance to inhaled allergens. Studies of SLIT in allergic rhinitis demonstrate that it reduces symptoms and medication use and is associated with a low incidence of systemic allergic reactions. Initial phase II studies with TLR-9 vaccines conjugated to a ragweed allergen demonstrate that they reduce symptoms of allergic rhinitis during the ragweed season. Anti-IL-5 is effective as a corticosteroid-sparing agent in the hypereosinophilic syndrome. It has not shown benefit in moderate asthmatics with persistent symptoms but may reduce aspects of airway remodeling in asthma.

Interleukin-18-deficient mice exhibit diminished chronic inflammation and airway remodelling in ovalbumin-induced asthma model

Interleukin (IL)-18, which is produced by activated monocytes/macrophages and airway epithelial cells, is suggested to contribute to the pathophysiology of asthma by modulating airway inflammation. However, the involvement of IL-18 on modulating chronic airway inflammation and airway remodelling, which are characterized in a refractory asthma model exposed to long-term antigen, has not been investigated sufficiently. We examined the role of IL-18 in chronic airway inflammation and airway remodelling by long-term antigen exposure. IL-18-deficient and C57BL/6-wild-type mice were sensitized by ovalbumin (OVA) and were then exposed to aerosolized OVA twice a week for 12 weeks. We assessed airway inflammation by assessing the infiltration of cells into the airspace and lung tissues, and airway remodelling by airway mucus expression, peribronchial fibrosis and smooth muscle thickness. In IL-18-deficient mice, when exposed to OVA, the total cells and neutrophils of the bronchoalveolar lavage fluid (BALF) were diminished, as were the number of infiltrated cells in the lung tissues. IL-18-deficient mice exposed to OVA after 12 weeks showed significantly decreased levels of interferon (IFN)-gamma, IL-13 and transforming growth factor (TGF)-beta1 in the BALF. The airway hyperresponsiveness to acetyl-beta-methacholine chloride was inhibited in IL-18-deficient mice in comparison with wild-type mice. In addition, IL-18-deficient mice exposed to OVA had fewer significant features of airway remodelling. These findings suggest that IL-18 may enhance chronic airway inflammation and airway remodelling through the production of IFN-gamma, IL-13 and TGF-beta1 in the OVA-induced asthma mouse model.

Imiquimod, a toll-like receptor 7 ligand, inhibits airway remodelling in a murine model of chronic asthma

1. Imiquimod, a synthetic Toll-like receptor (TLR) 7 ligand, has been shown to attenuate airway inflammation and airway hyperresponsiveness (AHR) in acute murine models of allergic asthma. In the present study, we investigated the effect of imiquimod on allergen-induced airway remodelling in chronic experimental asthma. 2. Ovalbumin (OVA)-sensitized mice were chronically challenged with aerosolized OVA for 8 weeks. Some mice were exposed to an aerosol of 0.15% imiquimod daily during the period of OVA challenge. Twenty-four hours after the last OVA challenge, mice were evaluated for the development of airway inflammation, AHR and airway remodelling. The levels of total serum IgE and Th2 cytokines (interleukin (IL)-4, IL-5 and IL-13) in bronchoalveolar lavage fluid (BALF) and the expression of transforming growth factor (TGF)-beta1 protein in lungs were measured by ELISA and immunohistochemistry, respectively. 3. The results demonstrated that imiquimod significantly inhibited chronic inflammation, persistent AHR and airway remodelling in chronic experimental asthma. In addition, imiquimod reduced levels of total serum IgE and BALF Th2 cytokines and diminished expression of TGF-beta1 in remodelled airways. 4. In summary, the results of the present study indicate that imiquimod may attenuate the progression of airway inflammation and remodelling, providing potential in the treatment of asthma.

NK cells contribute to intracellular bacterial infection-mediated inhibition of allergic responses

To experimentally examine the hygiene hypothesis, here we studied the effect of chlamydial infection on the development of allergic responses induced by OVA and the involvement of NK cells in this process using a mouse model of airway inflammation. We found that prior Chlamydia muridarum infection can inhibit airway eosinophilic inflammation and mucus production induced by allergen sensitization and challenge. The inhibition was correlated with an alteration of allergen-driven cytokine-producing patterns of T cells. We demonstrated that NK cells were activated following chlamydial infection, showing both cell expansion and cytokine secretion. The in vivo depletion of NK cells using anti-NK Ab before OVA sensitization and challenge partially abolished the inhibitory effect of chlamydial infection, which was associated with a partial restoration of Th2 cytokine production. In contrast, the adoptive transfer of NK cells that were isolated from infected mice showed a significant inhibitory effect on allergic responses, similar to that observed in natural infection. The data suggest that the innate immune cells such as NK cells may play an important role in infection-mediated inhibition of allergic responses.

Immunomodulatory effects of CpG oligodeoxynucleotides on house dust mite-induced airway inflammation in mice

BACKGROUND

CpG oligodeoxynucleotides (CpG ODNs) are reported to protect against airway eosinophilia and hyperresponsiveness in animal models of asthma. However, little is known about the effects of CpG ODNs on house dust mites, one of the most common environmental allergens, causing allergic asthma. In the present study, we evaluated the immunomodulatory effects of CpG ODNs on the development of house dust mite-induced airway inflammation and remodeling in mice.

METHODS

Mice were instilled with Dermatophagoides farinae (Der f) into the trachea 8 times without any additional adjuvants. 48 h after the final allergen instillation, the airway responsiveness to acetylcholine (Ach) was measured, and bronchoalveolar lavage (BAL) and histopathological examination were carried out. CpG ODNs were instilled into the trachea mixed with Der f at the first allergen instillation.

RESULTS

Repeated instillation of Der f induced increases in airway responsiveness to Ach, the numbers of inflammatory cells, the levels of T-helper type 2 cytokines and transforming growth factor-beta(1) in the BAL fluid. Furthermore, goblet cell hyperplasia, the thickness of the epithelium and subepithelial fibrosis were observed. The simultaneous instillation of CpG ODNs with Der f at the first allergen instillation showed significant inhibition of these parameters dose dependently.

CONCLUSIONS

Our results demonstrate that CpG ODNs have inhibitory effects on Der f-induced airway hyperresponsiveness and eosinophilia, as well as airway remodeling, and that CpG ODNs can be a therapeutic approach for the treatment of house dust mite-induced asthma.

Inhibition of glycogen synthase kinase-3beta is sufficient for airway smooth muscle hypertrophy

We examined the role of glycogen synthase kinase-3beta (GSK-3beta) inhibition in airway smooth muscle hypertrophy, a structural change found in patients with severe asthma. LiCl, SB216763, and specific small interfering RNA (siRNA) against GSK-3beta, each of which inhibit GSK-3beta activity or expression, increased human bronchial smooth muscle cell size, protein synthesis, and expression of the contractile proteins alpha-smooth muscle actin, myosin light chain kinase, smooth muscle myosin heavy chain, and SM22. Similar results were obtained following treatment of cells with cardiotrophin (CT)-1, a member of the interleukin-6 superfamily, and transforming growth factor (TGF)-beta, a proasthmatic cytokine. GSK-3beta inhibition increased mRNA expression of alpha-actin and transactivation of nuclear factors of activated T cells and serum response factor. siRNA against eukaryotic translation initiation factor 2Bepsilon (eIF2Bepsilon) attenuated LiCl- and SB216763-induced protein synthesis and expression of alpha-actin and SM22, indicating that eIF2B is required for GSK-3beta-mediated airway smooth muscle hypertrophy. eIF2Bepsilon siRNA also blocked CT-1- but not TGF-beta-induced protein synthesis. Infection of human bronchial smooth muscle cells with pMSCV GSK-3beta-A9, a retroviral vector encoding a constitutively active, nonphosphorylatable GSK-3beta, blocked protein synthesis and alpha-actin expression induced by LiCl, SB216763, and CT-1 but not TGF-beta. Finally, lungs from ovalbumin-sensitized and -challenged mice demonstrated increased alpha-actin and CT-1 mRNA expression, and airway myocytes isolated from ovalbumin-treated mice showed increased cell size and GSK-3beta phosphorylation. These data suggest that inhibition of the GSK-3beta/eIF2Bepsilon translational control pathway contributes to airway smooth muscle hypertrophy in vitro and in vivo. On the other hand, TGF-beta-induced hypertrophy does not depend on GSK-3beta/eIF2B signaling.

The natural history and complications of eosinophilic esophagitis

Eosinophilic esophagitis is a chronic disease limited to the esophagus and has a persistent or spontaneously fluctuating course. So far it does not seem to limit life expectancy, but it often substantially impairs the quality of life. To date, there has been no association with malignant conditions, but there is concern that the chronic, uncontrolled inflammation will evoke irreversible structural alterations of the esophagus, leading to tissue fibrosis, stricture formation, and impaired function. This esophageal remodeling may result in several disease-inherent and procedure-related complications.

Eat dirt: CpG DNA and immunomodulation of asthma

Asthma is a disorder of increasing prevalence and severity that has been linked with reduced early-life exposure to microbes and microbial products. Populations with increased environmental exposures to pathogen-associated molecular patterns (e.g., children who have large numbers of older siblings, who were raised on farms, and who have earlier out-of-home day-care attendance) have fewer and less severe atopic disorders. The mechanism(s) responsible for these observations remain uncertain, but modulation by pathogen-associated molecular patterns of the inflammatory milieu (and thus the setting in which allergens may be encountered) has received strong support. One microbial product with marked immunostimulatory properties is bacterial DNA, which differs from mammalian DNA in the frequency of cytosine-guanine (CpG) dinucleotides; many of the effects of bacterial DNA can be recapitulated by oligodeoxynucleotides (ODNs) containing CpG in specific base sequence motifs (CpG ODNs). Because CpG ODNs induce Th1-type cytokines (which can suppress the Th2-type responses that cause many of the manifestations of allergic disease), we speculated that they may be useful in preventing or reversing the eosinophilic inflammation of atopic asthma. We found this to be the case, using murine models of incipient and established allergic asthma, but learned that the Th1-type cytokines were not critical for efficacy. Subsequent work has suggested that induction of regulatory-type responses (from T cells and antigen-presenting cells) is involved in the protection provided by CpG ODNs. Ongoing clinical trials are examining the utility of CpG ODNs alone and as an adjuvant for immunotherapy in human populations with atopic disease.

Role of mast cells in airway remodeling

The extent of airway remodeling correlates with severity of asthma. Persistent airway hyperresponsiveness (AHR) is associated with airway remodeling, but not with inflammation. The increase in ASM mass is recognized as one of the most important factors related to AHR and to the severity of asthma. The infiltration of ASM by mast cells (MCs) is associated with the disordered airway function. The mediators such as tryptase and cytokines from MCs can modulate ASM cell function and induce goblet cell hyperplasia. MCs were found to contribute to the development of multiple features of chronic asthma in MC-deficient mice. Therefore, MCs play an important role not only in immediate hypersensitivity and late phase inflammation but also in tissue remodeling in the airway.

Asthma therapy and airway remodeling

Asthma is characterized by variable degrees of chronic inflammation and structural alterations in the airways. The most prominent abnormalities include epithelial denudation, goblet cell metaplasia, subepithelial thickening, increased airway smooth muscle mass, bronchial gland enlargement, angiogenesis, and alterations in extracellular matrix components, involving large and small airways. Chronic inflammation is thought to initiate and perpetuate cycles of tissue injury and repair in asthma, although remodeling may also occur in parallel with inflammation. In the absence of definite evidence on how different remodeling features affect lung function in asthma, the working hypothesis should be that structural alterations can lead to the development of persistent airway hyperresponsiveness and fixed airway obstruction. It is still unanswered whether and when to begin treating patients with asthma to prevent or reverse deleterious remodeling, which components of remodeling to target, and how to monitor remodeling. Consequently, efforts are being made to understand better the effects of conventional anti-inflammatory therapies, such as glucocorticosteroids, on airway structural changes. Animal models, in vitro studies, and some clinical studies have advanced present knowledge on the cellular and molecular pathways involved in airway remodeling. This has encouraged the development of biologicals aimed to target various components of airway remodeling. Progress in this area requires the explicit linking of modern structure-function analysis with innovative biopharmaceutical approaches.

Inhibition of allergen-induced airway remodeling in Smad 3-deficient mice

Intracellular signaling pathways that converge on Smad 3 are used by both TGF-beta and activin A, key cytokines implicated in the process of fibrogenesis. To determine the role of Smad 3 in allergen-induced airway remodeling, Smad 3-deficient and wild-type (WT) mice were sensitized to OVA and challenged by repetitive administration of OVA for 1 mo. Increased levels of activin A and increased numbers of peribronchial TGF-beta1(+) cells were detected in WT and Smad 3-deficient mice following repetitive OVA challenge. Smad 3-deficient mice challenged with OVA had significantly less peribronchial fibrosis (total lung collagen content and trichrome staining), reduced thickness of the peribronchial smooth muscle layer, and reduced epithelial mucus production compared with WT mice. As TGF-beta and Smad 3 signaling are hypothesized to mediate differentiation of fibroblasts to myofibroblasts in vivo, we determined the number of peribronchial myofibroblasts (Col-1(+) and alpha-smooth muscle actin(+)) as assessed by double-label immunofluorescence microscopy. Although the number of peribronchial myofibroblasts increased significantly in WT mice following OVA challenge, there was a significant reduction in the number of peribronchial myofibroblasts in OVA-challenged Smad 3-deficient mice. There was no difference in levels of eosinophilic airway inflammation or airway responsiveness in Smad 3-deficient compared with WT mice. These results suggest that Smad 3 signaling is required for allergen-induced airway remodeling, as well as allergen-induced accumulation of myofibroblasts in the airway. However, Smad 3 signaling does not contribute significantly to airway responsiveness.

Esophageal remodeling in pediatric eosinophilic esophagitis

BACKGROUND

Eosinophils are associated with airway remodeling in asthma, but studies have not yet determined whether eosinophilic esophagitis (EE) is associated with esophageal remodeling.

OBJECTIVE

We performed quantitative immunohistochemical analysis of remodeling changes in esophageal biopsy specimens from children with and without EE to evaluate if there were changes in the esophagus of pediatric patients with EE akin to airway remodeling. In addition, we determined whether the esophagus of patients with EE had increased levels of expression of TGF-beta(1) and its signaling molecule, phosphorylated SMAD2/3 (phospho-SMAD2/3).

METHODS

To determine esophageal levels of eosinophilic inflammation, fibrosis, and vascular activation, endoscopically obtained esophageal biopsy specimens from 7 patients with EE (5 strictured, 2 nonstrictured), 7 with gastroesophageal reflux disease, and 7 normal patients were processed for immunohistology, trichrome staining, and assessment of levels of expression of TGF-beta(1), phospho-SMAD2/3, and vascular cell adhesion molecule 1.

RESULTS

Esophageal biopsies in patients with EE demonstrated increased levels of subepithelial fibrosis and increased expression of TGF-beta(1) and its signaling molecule phospho-SMAD2/3 compared with gastroesophageal reflux disease and normal control patients. In addition, esophageal biopsies in patients with EE demonstrated an increased vascular density and an increased expression of the vascular endothelial adhesion molecule, vascular cell adhesion molecule 1.

CONCLUSION

Previously unrecognized esophageal remodeling changes analogous to aspects of airway remodeling are detectable in the subepithelial region of the esophagus in pediatric patients with EE.

CLINICAL IMPLICATIONS

Pediatric patients with EE demonstrate increased fibrosis, vascularity, and vascular activation in the esophagus that may contribute to stricture formation and potentially provide a basis for stratifying patients with EE on the basis of disease severity and/or prognosis.

Defining the in vivo function of Siglec-F, a CD33-related Siglec expressed on mouse eosinophils

CD33-related Siglecs (CD33rSiglecs) are a family of sialic acid-recognizing lectins on immune cells whose biologic functions are unknown. We studied in vivo functions of Siglec-F, the CD33rSiglec expressed on mouse eosinophils, which are prominent in allergic processes. Induction of allergic lung inflammation in mice caused up-regulation of Siglec-F on blood and bone marrow eosinophils, accompanied by newly induced expression on some CD4(+) cells, as well as quantitative up-regulation of endogenous Siglec-F ligands in the lung tissue and airways. Taken together with the tyrosine-based inhibitory motif in the cytosolic tail of Siglec-F, the data suggested a negative feedback loop, controlling allergic responses of eosinophils and helper T cells, via Siglec-F and Siglec-F ligands. To pursue this hypothesis, we created Siglec-F-null mice. Allergen-challenged null mice showed increased lung eosinophil infiltration, enhanced bone marrow and blood eosinophilia, delayed resolution of lung eosinophilia, and reduced peribronchial-cell apoptosis. Anti-Siglec-F antibody cross-linking also enhanced eosinophil apoptosis in vitro. These data support the proposed negative feedback role for Siglec-F, represent the first in vivo demonstration of biologic functions for any CD33rSiglec, and predict a role for human Siglec-8 (the isofunctional paralog of mouse Siglec-F) in regulating the pathogenesis of human eosinophil-mediated disorders.

TLR9-based immunotherapy for allergic disease

A significant amount of data generated over the last few years supports the contention that Toll-like receptor (TLR) 9-based immunotherapy is effective in the prevention and treatment of animal models of allergic disorders. We will review here our experience with two distinct therapeutic strategies: TLR9-based immunomodulation and TLR9-based vaccination. Immunomodulation of allergic inflammation by TLR9 ligand (TLR9-L) is transient. It prevents both the early and late phases of the allergic reaction in experimental models of allergic asthma, rhinitis, and conjunctivitis. It also reverses ongoing allergic inflammation. Indoleamine 2.3-dioxygenase, the rate-limiting enzyme of tryptophan, is induced by TLR9-L and mediates, in part, these anti-inflammatory effects. TLR9-based immunomodulation is independent of allergens and, therefore, has a potential therapeutic advantage in a broad spectrum of allergic patients. On the other hand, TLR9-based vaccination therapy is an allergen-specific mode of immunotherapy, which provides long-term inhibition of allergen-specific hypersensitivities. Current clinical trials with TLR9-based immunotherapy demonstrate high immunogenic and therapeutic efficacy, as well as improved safety when compared with conventional allergen desensitization. Thus, if proven efficient, therapeutic strategies with TLR9-L may revolutionize the current treatment of allergic diseases.

Reduced peribronchial fibrosis in allergen-challenged MMP-9-deficient mice

Matrix metalloproteinases (MMPs) are a family of extracellular proteases that are responsible for the degradation of the extracellular matrix during tissue remodeling. We have used a mouse model of allergen-induced airway remodeling to determine whether MMP-9 plays a role in airway remodeling. MMP-9-deficient and wild-type (WT) mice were repetitively challenged intranasally with ovalbumin (OVA) antigen to develop features of airway remodeling including peribronchial fibrosis and increased thickness of the peribronchial smooth muscle layer. OVA-challenged MMP-9-deficient mice had less peribronchial fibrosis and total lung collagen compared with OVA-challenged WT mice. There was no reduction in mucus expression, smooth muscle thickness, or airway responsiveness in OVA-challenged MMP-9-deficient compared with OVA-challenged WT mice. OVA-challenged MMP-9-deficient mice had reduced levels of bronchoalveolar lavage (BAL) regulated on activation, normal T cell expressed, and secreted (RANTES), as well as reduced numbers of BAL and peribronchial eosinophils compared with OVA-challenged WT mice. There were no significant difference in levels of BAL eotaxin, thymus- and activation-regulated chemokine (TARC), or macrophage-derived chemokine (MDC) in OVA-challenged WT compared with MMP-9-deficient mice. Overall, this study demonstrates that MMP-9 may play a role in mediating selected aspects of allergen-induced airway remodeling (i.e., modest reduction in levels of peribronchial fibrosis) but does not play a significant role in mucus expression, smooth muscle thickness, or airway responsiveness.

Remodeling associated expression of matrix metalloproteinase 9 but not tissue inhibitor of metalloproteinase 1 in airway epithelium: modulation by immunostimulatory DNA

BACKGROUND

Matrix metalloproteinase 9 (MMP-9) and its tissue inhibitor of metalloproteinase 1 (TIMP-1) are hypothesized to play a role in the pathogenesis of airway remodeling in asthma.

OBJECTIVE

We have used a mouse model of airway remodeling to determine the pattern of expression of MMP-9 and TIMP-1 in airway epithelium and peribronchial cells, and assess whether TIMP-1, an inhibitor of MMP-9, is expressed at the same sites in the airway. In addition, we have investigated whether immunostimulatory sequences (ISSs) of DNA modulate levels of expression of MMP-9, TIMP-1, and peribronchial fibrosis.

METHODS

Levels of lung MMP-9 and TIMP-1 were assessed by zymography, ELISA, and immunohistochemistry.

RESULTS

Repetitive ovalbumin challenge induced a significant increase in levels of MMP-9, TIMP-1, and peribronchial collagen deposition. The pattern of expression of MMP-9 and TIMP-1 in the remodeled airway was significantly different. MMP-9 but not TIMP-1 was expressed in airway epithelium, whereas both MMP-9 and TIMP-1 were expressed in peribronchial inflammatory cells. ISS significantly reduced expression of MMP-9 in airway epithelium (which immunostained positive for Toll receptor 9), as well as in peribronchial inflammatory cells. In vitro studies demonstrated that ISS inhibited bone marrow macrophage generation of MMP-9.

CONCLUSION

Allergen-induced peribronchial fibrosis is associated with expression of MMP-9 and TIMP-1 at different anatomical sites in the remodeled airway. The ability of ISS to inhibit the expression of MMP-9 in airway epithelium (a site where its inhibitor TIMP-1 is not induced by allergen challenge) may be important in determining whether ISS contributes to reductions in airway remodeling by reducing levels of MMP-9.

CLINICAL IMPLICATIONS

Immunostimulatory sequences of DNA, which are being investigated as novel therapeutics in asthma, inhibit airway remodeling in mice as well as epithelial expression of MMP-9, an enzyme that degrades the extracellular matrix proteins surrounding the airway.

Immunostimulatory DNA inhibits allergen-induced peribronchial angiogenesis in mice

BACKGROUND

Airway remodeling in asthma is associated with angiogenesis.

OBJECTIVE

We have examined whether immunostimulatory sequences of DNA (ISSs) inhibit allergen-induced airway angiogenesis and expression of angiogenic cytokines in a mouse model of airway remodeling.

METHODS

Mice sensitized to ovalbumin were challenged repetitively with ovalbumin for three months to develop airway remodeling and angiogenesis. Levels of angiogenesis were compared in ISS-treated and control mice.

RESULTS

Mice challenged with ovalbumin developed significantly increased levels of peribronchial angiogenesis (increase in the number of CD31+ peribronchial small blood vessels) and an increase in the peribronchial vascular area as assessed by image analysis. Ovalbumin-induced peribronchial angiogenesis was associated with increased bronchoalveolar lavage levels of vascular endothelial growth factor (VEGF) and an increase in the number of peribronchial cells expressing VEGF. Treatment of mice with ISS before repetitive ovalbumin challenge significantly reduced the levels of peribronchial angiogenesis as well as the levels of bronchoalveolar lavage VEGF and the number of peribronchial cells expressing VEGF. ISS is unlikely to act directly on endothelial cells to inhibit angiogenesis because lung endothelial cells did not express Toll receptor 9, the receptor for ISS as assessed by RT-PCR. In vitro studies demonstrated that ISS inhibited macrophage expression of VEGF.

CONCLUSION

The ability of ISS to inhibit angiogenesis in vivo is likely to be mediated by several mechanisms, including ISS reducing the number of peribronchial inflammatory cells that express VEGF, ISS inhibiting expression of TH2 cytokines such as IL-13 that promote VEGF expression, and direct effects of ISS on macrophages to inhibit VEGF expression.

Corticosteroids prevent myofibroblast accumulation and airway remodeling in mice

At present there are conflicting results from studies investigating the role of corticosteroids in inhibiting airway remodeling in asthma. We have used a mouse model to determine whether administration of corticosteroids prevents the development of allergen-induced structural features of airway remodeling. Mice treated with corticosteroids were subjected to repetitive ovalbumin (OVA) challenge for 3 mo, at which time levels of peribronchial fibrosis and the thickness of the peribronchial smooth muscle layer were assessed by immunohistology, levels of transforming growth factor (TGF)-beta1 by ELISA, and the number of alpha-smooth muscle actin+/Col-1+ peribronchial myofibroblasts by immunohistochemistry. Corticosteroids significantly reduced allergen-induced increases in peribronchial collagen deposition and levels of total lung collagen but did not reduce allergen-induced increases in the thickness of the peribronchial smooth muscle layer. Levels of lung TGF-beta1 were significantly reduced in mice treated with systemic corticosteroids, and this was associated with a significant decrease in the number of peribronchial inflammatory cells that expressed TGF-beta1, including eosinophils and mononuclear cells. Corticosteroids also significantly reduced the number of peribronchial myofibroblasts. Overall, these studies demonstrate that administration of corticosteroids significantly reduces levels of allergen-induced peribronchial fibrosis. The reduction in peribronchial fibrosis mediated by corticosteroids is likely to be due to several mechanisms including inhibition of expression of TGF-beta1, a reduction in the number of peribronchial inflammatory cells expressing TGF-beta1 (eosinophils, macrophages), as well as by corticosteroids reducing the accumulation of peribronchial myofibroblasts that contribute to collagen expression.

Allergen-induced peribronchial fibrosis and mucus production mediated by IkappaB kinase beta-dependent genes in airway epithelium

In response to inflammation or injury, airway epithelial cells express inducible genes that may contribute to allergen-induced airway remodeling. To determine the contribution of epithelial cell NF-kappaB activation to the remodeling response, we generated CC10-Cre(tg)/Ikkbeta(delta/delta) mice in which NF-kappaB signaling through IkappaB kinase beta (IKKbeta) is selectively ablated in the airway epithelium by conditional Cre-recombinase expression from the Clara cell (CC10) promoter. Repetitive ovalbumin challenge of mice deficient in airway epithelial IKKbeta prevented nuclear translocation of the RelA NF-kappaB subunit only in airway epithelial cells, resulting in significantly lower peribronchial fibrosis in CC10-Cre(tg)/Ikkbeta(delta/delta) mice compared with littermate controls as assessed by peribronchial trichrome staining and total lung collagen content. Levels of airway mucus, airway eosinophils, and peribronchial CD4+ cells in ovalbumin-challenged mice were also reduced significantly upon airway epithelial Ikkbeta ablation. The diminished inflammatory response was associated with reduced expression of NF-kappaB-regulated chemokines, including eotaxin-1 and thymus- and activation-regulated chemokine, which attract eosinophils and Th2 cells, respectively, into the airway. The number of peribronchial cells expressing TGF-beta1, as well as TGF-beta1 amounts in bronchoalveolar lavage, were also significantly reduced in mice deficient in airway epithelium IKKbeta. Overall, these studies show an important role for NF-kappaB regulated genes in airway epithelium in allergen-induced airway remodeling, including peribronchial fibrosis and mucus production.

Immunostimulatory oligonucleotides block allergic airway inflammation by inhibiting Th2 cell activation and IgE-mediated cytokine induction

A single treatment with a CpG-containing immunostimulatory DNA sequence (ISS) given before allergen challenge can inhibit T helper type 2 cell (Th2)–mediated airway responses in animal models of allergic asthma; however, the mechanism of this inhibition remains largely undefined. Here, we demonstrate that airway delivery of ISS before allergen challenge in Th2-primed mice acts in two distinct ways to prevent the allergic responses to this challenge. The first is to prevent induction of cytokines from allergen-specific Th2 cells, as demonstrated by the nearly complete inhibition of Th2 cytokine production, Th2-dependent functional responses, and gene induction patterns. ISS inhibits the Th2 response by rendering lung antigen-presenting cells (APCs) unable to effectively present antigen to Th2 cells, but not to Th1 cells. This loss of APC function correlates with a reduced expression of costimulatory molecules, including programmed cell death ligand (PD-L)1, PD-L2, CD40, CD80, CD86, and inducible T cell costimulator, and of major histocompatibility complex class II on CD11c⁺APCs from the airways of ISS-treated mice. The second important action of ISS is inhibition of immunoglobulin E–dependent release of Th2 cytokines, especially interleukin 4, from basophils and/or mast cells in the airways of Th2-primed mice. Thus, inhibition by ISS of allergic responses can be explained by two novel mechanisms that culminate in the inhibition of the principal sources of type 2 cytokines in the airways.