Inhibition of allergic airways inflammation and airway hyperresponsiveness in mice by dexamethasone: role of eosinophils, IL-5, eotaxin, and IL-13

Pharmacological inhibition of MutT homolog 1 (MTH1) in allergic airway inflammation as a novel treatment strategy

BACKGROUND

Despite progress in the treatment of asthma, there is an unmet need for additional therapeutic strategies, not least to avoid side-effects of corticosteroids. The enzyme MutT homolog 1 (MTH1) hydrolyzes oxidized purines and prevents their insertion to DNA. Small molecule inhibition of MTH1 has shown promising therapeutic effects in both cancer and inflammatory conditions. In this study, a small molecule inhibitor of MTH1 (TH1579), was investigated in models of allergic inflammation.

METHODS

In vitro, effects on T cell proliferation and apoptosis were investigated. Furthermore, a murine model, using female BALB/c mice, of OVA-induced allergic airway inflammation was used to investigate effects from MTH1-inhibition in vivo.

RESULTS

Inhibition of MTH1 prevented T cell proliferation in vitro and induced apoptosis in isolated human CD4+ T cells. However, the viability of isolated human eosinophils was unaffected by MTH1 inhibition in vitro. Pharmacological inhibition of MTH1 in a murine model of allergic airway inflammation reduced mucus production, recruitment of inflammatory cells, such as T cells and eosinophils in the BAL fluid and lung tissue, reduced plasma levels of total IgE and OVA-specific IgE, IgG, and IgG1, as well as reduced IL-13 levels in BAL fluid, lung tissue and plasma.

CONCLUSION

MTH1 inhibition reduced proliferation and promoted apoptosis of T cells in vitro. In vivo, TH1579 dampened the type 2 associated immune response in a murine model. These findings suggest that MTH1 could serve as a novel target to treat allergic airway inflammation.

Time-dependent dual beneficial modulation of interferon-γ, interleukin 5, and Treg cytokines in asthma patient peripheral blood mononuclear cells by ganoderic acid B

Th2 cytokines play a dominant role in the pathogenesis of allergic asthma. Interferon gamma (IFN-γ), a Th1 cytokine, links to therapeutic mechanisms of allergic asthma. Interleukin (IL)-10, a regulatory cytokine, is involved in the induction of immune tolerance. We previously demonstrated that Anti-Asthma Simplified Herbal Medicine Intervention (ASHMI) suppressed Th2 and increased IFN-γ in patients with asthma and in animal models, but its bioactive compound is unknown. Ganoderic acid beta (GAB) was isolated from Ganoderma lucidum (one herb in ASHMI). Human peripheral blood mononuclear cells (PBMCs) from adult patients with asthma were cultured with GAB or dexamethasone (Dex) in the presence of environmental allergens. The cytokine levels of IL-10, IFN-γ, IL-5, transcription factors T-bet, Foxp-3, and GATA3 were measured. Following 3-day culture, GAB, but not Dex, significantly increased IL-10 and IFN-γ levels by allergic patients' PBMCs. Following 6-day treatment, GAB inhibited IL-5 production, but IL-10 and IFN-γ remained high. Dex suppressed production of all three cytokines. GAB suppressed GATA3 and maintained Foxp-3 and T-bet gene expression, while Dex significantly suppressed GATA3 and T-bet expression. GAB simultaneously increased IL-10, IFN-γ associated with induction of T-bet and Foxp3, while suppressing IL-5, which was associated with suppression of GATA3, demonstrating unique beneficial cytokine modulatory effect, which distinguishes from Dex's overall suppression.

Resiniferatoxin promotes adult worm expulsion in Trichinella spiralis-infected rats by Th2 immune response modulation

BACKGROUND

The immune response during T spiralis infection is characterized by an increase in eosinophils and mast cells, as well as Th2 cytokine production, such as interleukin (IL)-4, IL-10 and IL-13, promoting T spiralis expulsion from the host. However, this response damages the host, favouring the parasite survival. In the search for new pharmacological strategies that protect against T spiralis infection, a recent study showed that treatment with resiniferatoxin (RTX) modulates the Th1 cytokines production, reducing muscle parasite burden.

OBJECTIVE

To evaluate the effect of RTX treatment on the Th2 cytokines production, the number of eosinophils, mast cells and the intestinal expulsion of T spiralis.

METHODS

Serum levels of IL-4, IL-10 and IL-13 were quantified by ELISA; the number of eosinophils, mast cells and the adult worms of T spiralis in the small intestine was quantified.

RESULTS

RTX treatment increased serum levels of IL-4, IL-10 and IL-13, and it decreases intestinal eosinophilia, however, favours the mastocytosis, promoting T spiralis intestinal expulsion.

CONCLUSIONS

These findings suggest that RTX is capable to modulate the Th2 immune response, promoting T spiralis expulsion, which contributes to the defence against T spiralis infection, placing the RTX as a potential immunomodulatory drug.

Dietary Omega-3 Fatty Acid Dampens Allergic Rhinitis via Eosinophilic Production of the Anti-Allergic Lipid Mediator 15-Hydroxyeicosapentaenoic Acid in Mice

The metabolism and generation of bioactive lipid mediators are key events in the exertion of the beneficial effects of dietary omega-3 fatty acids in the regulation of allergic inflammation. Here, we found that dietary linseed oil, which contains high amounts of alpha-linolenic acid (ALA) dampened allergic rhinitis through eosinophilic production of 15-hydroxyeicosapentaenoic acid (15-HEPE), a metabolite of eicosapentaenoic acid (EPA). Lipidomic analysis revealed that 15-HEPE was particularly accumulated in the nasal passage of linseed oil-fed mice after the development of allergic rhinitis with the increasing number of eosinophils. Indeed, the conversion of EPA to 15-HEPE was mediated by the 15-lipoxygenase activity of eosinophils. Intranasal injection of 15-HEPE dampened allergic symptoms by inhibiting mast cell degranulation, which was mediated by the action of peroxisome proliferator-activated receptor gamma. These findings identify 15-HEPE as a novel EPA-derived, and eosinophil-dependent anti-allergic metabolite, and provide a preventive and therapeutic strategy against allergic rhinitis.

Effect of injected dexamethasone on relative cytokine mRNA expression in bronchoalveolar lavage fluid in horses with mild asthma

Background

Mild equine asthma is a common inflammatory airway disease of the horse. The primary treatment of mild equine asthma is corticosteroids. The purpose of this study was to investigate the effects of injected dexamethasone on relative IL-1β, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p35, IL-17, IL-23, IFN-γ, Eotaxin-2 and TNF-α mRNA expression in bronchoalveolar lavage (BAL) fluid in healthy Thoroughbred horses (n = 6), and those with mild equine asthma (n = 7).

Results

Horses with mild equine asthma had a significantly greater bronchoalveolar lavage mast cell percentage than healthy horses both before and after treatment. Mild equine asthma was associated with a 4.95-fold up-regulation of IL-17 (p = 0.026) and a 2.54-fold down-regulation of IL-10 (p = 0.049) compared to healthy horses. TNF-α was down-regulated in response to dexamethasone treatment in both healthy horses (3.03-fold, p = 0.023) and those with mild equine asthma (1.75-fold, p = 0.023). IL-5 was also down-regulated in horses with mild asthma (2.17-fold, p = 0.048).

Conclusions

Horses with mild equine asthma have a lower concentration of IL-10 in BAL fluid than healthy controls which concurs with human asthmatics. The marked up-regulation of IL-17 in horses with mild asthma suggests these horses had a true tendency of “allergic” airway inflammation in response to environmental allergens. Dexamethasone administration exerted anti-inflammatory effects associated with down-regulation of TNF-α in all horses, and decreased levels of IL-5 mRNA expression in horses with mild equine asthma. The inhibition of the Th-2 response, without any alterations to the airway cytology, indicates that maintained exposure to environmental allergens perpetuates airway inflammation.

A Novel Approach for Investigating Upper Airway Hyperresponsiveness Using Micro-CT in Eosinophilic Upper Airway Inflammation such as Allergic Rhinitis Model

Airway hyperresponsiveness (AHR) has been proposed as a feature of pathogenesis of eosinophilic upper airway inflammation such as allergic rhinitis (AR). The measurement system for upper AHR (_UAHR) in rodents is poorly developed, although measurements of nasal resistance have been reported. Here we assessed UAHR by direct measurement of swelling of the nasal mucosa induced by intranasal methacholine (MCh) using micro-computed tomography (micro-CT). Micro-CT analysis was performed in both naïve and ovalbumin-induced AR mice following intranasal administration of MCh. The nasal cavity was segmented into two-dimensional horizontal and axial planes, and the data for nasal mucosa were acquired for the region of interest threshold. Then, a ratio between the nasal mucosa area and nasal cavity area was calculated as nasal mucosa index. Using our novel method, nasal cavity structure was clearly identified on micro-CT, and dose-dependent increased swelling of the nasal mucosa was observed upon MCh treatment. Moreover, the nasal mucosa index was significantly increased in AR mice compared to controls following MCh treatment, while ovalbumin administration did not affect swelling of the nasal mucosa in either group. This UAHR following MCh treatment was completely reversed by pretreatment with glucocorticoids. This novel approach using micro-CT for investigating UAHR reflects a precise assessment system for swelling of the nasal mucosa following MCh treatment; it not only sheds light on the mechanism of AR but also contributes to the development of new therapeutic drugs in AR patients.

Dehydrocostus lactone, a sesquiterpene from Saussurea lappa Clarke, suppresses allergic airway inflammation by binding to dimerized translationally controlled tumor protein

BACKGROUND

We previously reported that the biologically active form of histamine releasing factor (HRF) is dimerized translationally controlled tumor protein (dTCTP) which is involved in a number of allergic diseases.

HYPOTHESIS/PURPOSE

Hoping that agents that modulate dTCTP may provide new therapeutic targets to allergic inflammatory diseases, we screened a library of natural products for substances that inhibit dTCTP. One such inhibitor we found was dehydrocostus lactone (DCL), a natural sesquiterpene present in rhizome of Saussurea lappa Clarke, the subject of this study.

METHODS

We evaluated the therapeutic efficacy of DCL in a mouse model of ovalbumin (OVA)-induced allergic airway inflammation, employing the ELISA system using BEAS-2B cells and splenocytes, and confirmed that DCL interacts with dTCTP using SPR assay.

RESULTS

DCL inhibited dTCTP-induced secretion of IL-8 in BEAS-2B cells. From kinetic analysis of dTCTP and DCL, we found that K_D value was 5.33 ± 0.03 μM between dTCTP and DCL. DCL also significantly reduced inflammatory lung eosinophilia, type 2 cytokines in BALF, as well as OVA specific IgE and mucus production in a mouse model of ovalbumin induced allergy. Moreover, DCL suppressed NF-κB activation.

CONCLUSION

DCL's therapeutic potential in allergic airway inflammation is based on its anti-inflammatory activity of suppressing the function of dTCTP.

Investigating the CYP2E1 Potential Role in the Mechanisms Behind INH/LPS-Induced Hepatotoxicity

Tuberculosis (TB) is one of the oldest infectious diseases that affected humankind and remains one of the world's deadliest communicable diseases that could be considered as global emergency, but the discovery and development of isoniazid (INH) in the 1950s paved the way to an effective single and/or combined first-line anti-TB therapy. However, administration of INH induces severe hepatic toxicity in some patients. Previously, we establish a rat model of INH hepatotoxicity utilizing the inflammatory stress theory, in which bacterial lipopolysaccharide (LPS) potentially enhanced INH toxicity. These enhancing activities ranged between augmenting the inflammatory stress, oxidative stress, alteration of bile acid homeostasis, and CYP2E1 over-expression. Although pre-treatment with dexamethasone (DEX) helped overcome both inflammatory and oxidative stress which ended-up in alleviation of LPS augmenting effects, but still minor toxicities were being detected, alongside with CYP2E1 over expression. This finding positively indicated the corner-stone role played by CYP2E1 in the pathogenesis of INH/LPS-induced liver damage. Therefore, we examined whether INH/LPS co-treatment with CYP2E1 inhibitor diallyl sulfide (DAS) and DEX can protect against the INH/LPS-induced hepatotoxicity. Our results showed that pre-administration of both DAS and DEX caused significant reduction in serum TBA, TBil, and gamma-glutamyl transferase levels. Furthermore, the histopathological analysis showed that DAS and DEX could effectively reverse the liver lesions seen following INH/LPS treatment and protect against hepatic steatosis as indicated by absence of lipid accumulation. Pre-treatment with DAS alone could not completely block the CYP2E1 protein expression following INH/LPS treatment, as appeared in the immunoblotting and immunohistochemistry results. This is probably due to the fact that the combined enhancement activities of both INH and LPS on CYP2E1 protein expression levels might resist the blocking probabilities of DAS. In the meantime, addition of DEX to the DAS/INH/LPS combination caused a significant reduction in CYP2E1 protein expression as revealed by the immunoblotting and fading coloration in immunohistochemistry results. Thus, addition of DEX and DAS together caused strong protection against INH/LPS-induced hepatic damage. These findings reveal the potential therapeutic value of combining DAS and DEX with INH in TB management for reducing the potential risk and incidences of hepatotoxicity.

Dexamethasone Pretreatment Alleviates Isoniazid/Lipopolysaccharide Hepatotoxicity: Inhibition of Inflammatory and Oxidative Stress

Isoniazid (INH) remains a cornerstone key constitute of the current tuberculosis management strategy, but its hepatotoxic potentiality remains a significant clinical problem. Our previous findings succeed to establish a rat model of INH hepatotoxicity employing the inflammatory stress theory in which non-injurious doses of inflammatory-mediating agent bacterial lipopolysaccharides (LPS) augmented the toxicity of INH that assist to uncover the mechanisms behind INH hepatotoxicity. Following LPS exposure, several inflammatory cells are activated and it is likely that the consequences of this activation rather than direct hepatocellular effects of LPS underlie the ability of LPS to augment toxic responses. In this study, we investigated the potential protective role of the anti-inflammatory agent dexamethasone (DEX), a potent synthetic glucocorticoid, in INH/LPS hepatotoxic rat model. DEX pre-treatment successfully eliminates the components of the inflammatory stress as shown through analysis of blood biochemistry and liver histopathology. DEX potentiated hepatic anti-oxidant mechanisms while serum and hepatic lipid profiles were reduced. However, DEX administration was not able to revoke the principal effects of cytochrome P450 2E1 (CYP2E1) in INH/LPS-induced liver damage. In conclusion, this study illustrated the DEX-preventive capabilities on INH/LPS-induced hepatotoxicity model through DEX-induced potent anti-inflammatory activity whereas the partial toxicity seen in the model could be attributed to the expression of hepatic CYP2E1. These findings potentiate the clinical applications of DEX co-administration with INH therapy in order to reduce the potential incidences of hepatotoxicity.

Preventive Intra Oral Treatment of Sea Cucumber Ameliorate OVA-Induced Allergic Airway Inflammation

Sea cucumber extracts have potent biological effects, including anti-viral, anti-cancer, antibacterial, anti-oxidant, and anti-inflammation effects. To understand their anti-asthma effects, we induced allergic airway inflammation in mice after 7 oral administrations of the extract. The hyper-responsiveness value in mice with ovalbumin (OVA)-alum-induced asthma after oral injection of sea cucumber extracts was significantly lower than that in the OVA-alum-induced asthma group. In addition, the number of eosinophils in the lungs of asthma-induced mice pre-treated with sea cucumber extract was significantly decreased compared to that of PBS pre-treated mice. Additionally, CD4[Formula: see text]CD25[Formula: see text]Foxp3[Formula: see text]T (regulatory T; Treg) cells significantly increased in mesenteric lymph nodes after 7 administrations of the extract. These results suggest that sea cucumber extract can ameliorate allergic airway inflammation via Treg cell activation and recruitment to the lung.

Development of GABAA Receptor Subtype-Selective Imidazobenzodiazepines as Novel Asthma Treatments

Recent studies have demonstrated that subtype-selective GABAA receptor modulators are able to relax precontracted human airway smooth muscle ex vivo and reduce airway hyper-responsiveness in mice upon aerosol administration. Our goal in this study was to investigate systemic administration of subtype-selective GABAA receptor modulators to alleviate bronchoconstriction in a mouse model of asthma. Expression of GABAA receptor subunits was identified in mouse lungs, and the effects of α4-subunit-selective GABAAR modulators, XHE-III-74EE and its metabolite XHE-III-74A, were investigated in a murine model of asthma (ovalbumin sensitized and challenged BALB/c mice). We observed that chronic treatment with XHE-III-74EE significantly reduced airway hyper-responsiveness. In addition, acute treatment with XHE-III-74A but not XHE-III-74EE decreased airway eosinophilia. Immune suppressive activity was also shown in activated human T-cells with a reduction in IL-2 expression and intracellular calcium concentrations [Ca(2+)]i in the presence of GABA or XHE-III-74A, whereas XHE-III-74EE showed only partial reduction of [Ca(2+)]i and no inhibition of IL-2 secretion. However, both compounds significantly relaxed precontracted tracheal rings ex vivo. Overall, we conclude that the systemic delivery of a α4-subunit-selective GABAAR modulator shows good potential for a novel asthma therapy; however, the pharmacokinetic properties of this class of drug candidates have to be improved to enable better beneficial systemic pharmacodynamic effects.

Bronchial lesions of mouse model of asthma are preceded by immune complex vasculitis and induced bronchial associated lymphoid tissue (iBALT)

We systematically examined by immune histology the lungs of some widely used mouse models of asthma. These models include sensitization by multiple intraperitoneal injections of soluble ovalbumin (OVA) or of OVA with alum, followed by three intranasal or aerosol challenges 3 days apart. Within 24 h after a single challenge there is fibrinoid necrosis of arterial walls with deposition of immunoglobulin (Ig) and OVA and infiltration of eosinophilic polymorphonuclear cells that lasts for about 3 days followed by peribronchial B-cell infiltration and slight reversible goblet cell hypertrophy (GCHT). After two challenges, severe eosinophilic vasculitis is present at 6 h, increases by 72 h, and then declines; B-cell proliferation and significant GCHT and hyperplasia (GCHTH) and bronchial smooth muscle hypertrophy recur more prominently. After three challenges, there is significantly increased induced bronchus-associated lymphoid tissue (iBALT) formation, GCHTH, and smooth muscle hypertrophy. Elevated levels of Th2 cytokines, IL-4, IL-5, and IL-13, are present in bronchial lavage fluids. Sensitized mice have precipitating antibody and positive Arthus skin reactions but also develop significant levels of IgE antibody to OVA but only 1 week after challenge. We conclude that the asthma like lung lesions induced in these models is preceded by immune complex-mediated eosinophilic vasculitis and iBALT formation. There are elevations of Th2 cytokines that most likely produce bronchial lesions that resemble human asthma. However, it is unlikely that mast cell-activated atopic mechanisms are responsible as we found only a few presumed mast cells by toluidine blue and metachromatic staining limited to the most proximal part of the main stem bronchus, and none in the remaining main stem bronchus or in the lung periphery.

Non-eosinophilic airway hyper-reactivity in mice, induced by IFN-γ producing CD4(+) and CD8(+) lung T cells, is responsive to steroid treatment

Non-eosinophilic asthma is characterized by infiltration of neutrophils into the lung and variable responsiveness to glucocorticoids. The pathophysiological mechanisms have not been characterized in detail. Here, we present an experimental asthma model in mice associated with non-eosinophilic airway inflammation and airway hyper-responsiveness (AHR). For this, BALB/c mice were sensitized by biolistic DNA immunization with a plasmid encoding the model antigen β-galactosidase (pFascin-βGal mice). For comparison, eosinophilic airway inflammation was induced by subcutaneous injection of βGal protein (βGal mice). Intranasal challenge of mice in both groups induced AHR to a comparable extent as well as recruitment of inflammatory cells into the airways. In contrast to βGal mice, which exhibited extensive eosinophilic infiltration in the lung, goblet cell hyperplasia and polarization of CD4(+) T cells into Th2 and Th17 cells, pFascin-βGal mice showed considerable neutrophilia, but no goblet cell hyperplasia and a predominance of Th1 and Tc1 cells in the airways. Depletion studies in pFascin-βGal mice revealed that CD4(+) and CD8(+) cells cooperated to induce maximum inflammation, but that neutrophilic infiltration was not a prerequisite for AHR induction. Treatment of pFascin-βGal mice with dexamethasone before intranasal challenge did not affect neutrophilic infiltration, but significantly reduced AHR, infiltration of monocytes and lymphocytes as well as content of IFN-γ in the bronchoalveolar fluid. Our results suggest that non-eosinophilic asthma associated predominantly with Th1/Tc1 cells is susceptible to glucocorticoid treatment. pFascin-βGal mice might represent a mouse model to study pathophysiological mechanisms proceeding in the subgroup of asthmatics with non-eosinophilic asthma that respond to inhaled steroids.

Effects of propranolol and isoproterenol on infantile hemangioma endothelial cells in vitro

The aim of the present study was to investigate the effects of propranolol and isoproterenol on the growth curve of infantile hemangioma endothelial cells (IHECs) in vitro and determine the functions of the β-adrenergic receptor in the pathogenesis of infantile hemangioma. IHECs were divided into three groups: The control group, the propranolol group (PG) and the isoproterenol group (IG). The PG and IG were administered with high, medium and low concentrations of the corresponding drugs. The cell growth in each group was determined using the MTT assay. A high propranolol concentration resulted in the inhibition of cell growth. By comparison, isoproterenol promoted cell growth. Within a specific time-frame (72–96 h), high drug concentrations (20 μg/ml) elicited strong effects on the cells. At certain concentrations, propranolol inhibited cell growth once the proliferation stage of IHECs had been affected for a specific length of time, whereas isoproterenol yielded opposite results. The β-adrenergic receptor elicits an important effect in the pathogenesis of infantile hemangioma.

Effect of antigen sensitization and challenge on oscillatory mechanics of the lung and pulmonary inflammation in obese carboxypeptidase E-deficient mice

Atopic, obese asthmatics exhibit airway obstruction with variable degrees of eosinophilic airway inflammation. We previously reported that mice obese as a result of a genetic deficiency in either leptin (ob/ob mice) or the long isoform of the leptin receptor (db/db mice) exhibit enhanced airway obstruction in the presence of decreased numbers of bronchoalveolar lavage fluid (BALF) eosinophils compared with lean, wild-type mice following antigen (ovalbumin; OVA) sensitization and challenge. To determine whether the genetic modality of obesity induction influences the development of OVA-induced airway obstruction and OVA-induced pulmonary inflammation, we examined indices of these sequelae in mice obese as a result of a genetic deficiency in carboxypeptidase E, an enzyme that processes prohormones and proneuropeptides involved in satiety and energy expenditure (Cpe(fat) mice). Accordingly, Cpe(fat) and lean, wild-type (C57BL/6) mice were sensitized to OVA and then challenged with either aerosolized PBS or OVA. Compared with genotype-matched, OVA-sensitized and PBS-challenged mice, OVA sensitization and challenge elicited airway obstruction and increased BALF eosinophils, macrophages, neutrophils, IL-4, IL-13, IL-18, and chemerin. However, OVA challenge enhanced airway obstruction and pulmonary inflammation in Cpe(fat) compared with wild-type mice. These results demonstrate that OVA sensitization and challenge enhance airway obstruction in obese mice regardless of the genetic basis of obesity, whereas the degree of OVA-induced pulmonary inflammation is dependent on the genetic modality of obesity induction. These results have important implications for animal models of asthma, as modeling the pulmonary phenotypes for subpopulations of atopic, obese asthmatics critically depends on selecting the appropriate mouse model.

Reduction of eotaxin production and eosinophil recruitment by pulmonary autologous macrophage transfer in a cockroach allergen-induced asthma model

We sought to investigate the effects of cockroach allergen (CRA) exposure on the lung macrophage population to determine how different macrophage phenotypes influence exacerbation of disease. CRA exposure caused significantly reduced expression of CD86 on lung macrophages. These effects were not systemic, as peritoneal macrophage CD86 expression was not altered. To investigate whether naïve macrophages could reduce asthma-like pulmonary inflammation, autologous peritoneal macrophages were instilled into the airways 24 h before the final CRA challenge. Pulmonary inflammation was assessed by measurement of airway hyperresponsiveness, mucin production, inflammatory cell recruitment, and cytokine production. Cell transfer did not have significant effects in control mice, nor did it affect pulmonary mucin production or airway hyperresponsiveness in control or CRA-exposed mice. However, there was significant reduction in the number of eosinophils recovered in the bronchoalveolar lavage (BAL) (5.8 × 10⁵ vs. 0.88 × 10⁵), and total cell recruitment to the airways of CRA-exposed mice was markedly reduced (1.1 × 10⁶ vs. 0.57 × 10⁶). The reduced eosinophil recruitment was reflected by substantially lower levels of eosinophil peroxidase in the lung and significantly lower concentrations of eotaxins in BAL (eotaxin 1: 3 pg/ml vs. undetectable; eotaxin 2: 2,383 vs. 131 pg/ml) and lung homogenate (eotaxin 1: 1,043 vs. 218 pg/ml; eotaxin 2: 10 vs. 1.5 ng/ml). We conclude that CRA decreases lung macrophage CD86 expression. Furthermore, supplementation of the lung cell population with peritoneal macrophages inhibits eosinophil recruitment, achieved through reduction of eotaxin production. These data demonstrate that transfer of naïve macrophages will reduce some aspects of asthma-like pulmonary inflammation in response to CRA.

Effect of selective cysteinyl leukotriene receptor antagonists on airway inflammation and matrix metalloproteinase expression in a mouse asthma model

BACKGROUND

Cysteinyl leukotrienes (CysLTs) play a major role in the pathogenic changes of airway inflammation in asthma treatment. The matrix metalloproteinase (MMP) family, especially MMP-9 and MMP-2 levels, can reflect the status of airway remodeling. This study was undertaken to determine the role of a specific CysLT receptor antagonist in inhibition of airway inflammation and reversal of airway remodeling.

METHODS

Ovalbumin (OVA)-sensitized BALB/c mice were fed with a specific leukotriene receptor antagonist (MK-679), prednisolone or placebo from Days 15 to 27. Airway hyperreactivity, bronchoalveolar lavage fluid (BALF), and sera were analyzed. Pulmonary histology was obtained, and the levels of MMP-2 and MMP-9 in BALF were measured.

RESULTS

The OVA-sensitized mice developed significant airway inflammatory responses, including extensive eosinophils trafficking into BALF and lung interstitium, goblet cell hyperplasia, mucus hypersecretion, elevated serum immunoglobulin (Ig) E, and decreased level of serum IgG2a. Administration of MK-679 could reduce airway inflammation but was not as effective as prednisolone. However, MK-679 was more effective than prednisolone for reversing subepithelial fibrotic and myofibrotic reactions of airway remodeling. The levels of MMP-2 and -9 in BALF were proportional to the extent of airway remodeling, which can reflect the effects of treatment. Both prednisolone and MK-679 reverse airway hyperresponsiveness induced by OVA-sensitized mice.

CONCLUSION

Cysteinyl leukotriene receptor plays a more important role than CysLT in the pathogenesis of allergic airway inflammation. MMP-2 and -9 may be more sensitive indicators of airway remodeling.

Antiasthmatic Effects of Herbal Complex MA and Its Fermented Product MA128

This study was conducted to determine if oral administration of the novel herbal medicine, MA, and its Lactobacillus acidophilus fermented product, MA128, have therapeutic properties for the treatment of asthma. Asthma was induced in BALB/c mice by systemic sensitization to ovalbumin (OVA) followed by intratracheal, intraperitoneal, and aerosol allergen challenges. MA and MA128 were orally administered 6 times a week for 4 weeks. At 1 day after the last ovalbumin exposure, airway hyperresponsiveness was assessed and samples of bronchoalveolar lavage fluid, lung cells, and serum were collected for further analysis. We investigated the effect of MA and MA128 on airway hyperresponsiveness, pulmonary eosinophilic infiltration, various immune cell phenotypes, Th2 cytokine production, OVA-specific IgE production, and Th1/Th2 cytokine production in this mouse model of asthma. In BALB/c mice, we found that MA and MA128 treatment suppressed eosinophil infiltration into airways and blood, allergic airway inflammation and AHR by suppressing the production of IL-5, IL-13, IL-17, Eotaxin, and OVA-specific IgE, by upregulating the production of OVA-specific Th1 cytokine (IFN-γ), and by downregulating OVA-specific Th2 cytokine (IL-4) in the culture supernatant of spleen cells. The effectiveness of MA was increased by fermentation with Lactobacillus acidophilus.

Inhibition of airway inflammation, hyperresponsiveness and remodeling by soy isoflavone in a murine model of allergic asthma

Epidemiologic studies have associated higher dietary consumption of soy isoflavones with decreased self-report of cough and allergic respiratory symptoms, but the pharmacodynamic effects of soy isoflavone on asthmatic model have not been well-described. Here, we hypothesized that soy isoflavone may have potential effects on airway hyperresponsiveness, inflammation and airway remodeling in a murine of asthma. Mice sensitized and challenged with ovalbumin developed airway inflammation. Bronchoalveolar lavage fluid was assessed for inflammatory cell counts, and for cytokine levels. Lung tissues were examined for cell infiltration, mucus hypersecretion and airway remodeling, and for the expression of inflammatory biomarkers. Airway hyperresponsiveness was monitored by direct airway resistance analysis. Oral administration of soy isoflavone significantly reduced ovalbumin-induced airway hyperresponsiveness to intravenous methacholine, and inhibited ovalbumin-induced increases in eosinophil counts. RT-PCR analysis of whole lung lysates revealed that soy isoflavone markedly suppressed ovalbumin-induced mRNA expression of eotaxin, interleukin(IL)-5, IL-4 and matrix metalloproteinase-9, and increased mRNA expression of interferon (IFN)-γ and tissue inhibitor of metalloproteinase-1 in a dose-dependent manner. Soy isoflavone also substantially recovered IFN-γ/IL-4 (Th1/Th2) levels in bronchoalveolar lavage fluid. In addition, histologic studies showed that soy isoflavone dramatically inhibited ovalbumin-induced lung tissue eosinophil infiltration, airway mucus production and collagen deposition in lung tissues. Our findings suggest that soy isoflavone as nutritional supplement may provide a novel means for the treatment of airway inflammatory disease.

Small animals models for drug discovery

There has been an explosion of studies of animal models of asthma in the past 20 years. The elucidation of fundamental immunological mechanisms underlying the development of allergy and the complex cytokine and chemokines networks underlying the responses have been substantially unraveled. Translation of findings to human asthma have been slow and hindered by the varied phenotypes that human asthma represents. New areas for expansion of modeling include virally mediated airway inflammation, oxidant stress, and the interactions of stimuli triggering innate immune and adaptive immune responses.

Antiasthmatic effects of hesperidin, a potential Th2 cytokine antagonist, in a mouse model of allergic asthma

Background and Objective. The features of asthma are airway inflammation, reversible airflow obstruction, and an increased sensitivity to bronchoconstricting agents, termed airway hyperresponsiveness (AHR), excess production of Th2 cytokines, and eosinophil accumulation in the lungs. To investigate the antiasthmatic potential of hesperidin as well as the underlying mechanism involved, we studied the inhibitory effect and anti-inflammatory effect of hesperidin (HPN) on the production of Th2 cytokines, eotaxin, IL-17, -OVA-specific IgE in vivo asthma model mice. Methods. In this paper, BALB/c mice were systemically sensitized to ovalbumin (OVA) followed intratracheally, intraperitoneally, and by aerosol allergen challenges. We investigated the effect of HPN on airway hyperresponsiveness, pulmonary eosinophilic infiltration, various immune cell phenotypes, Th2 cytokine production and OVA-specific IgE production in a mouse model of asthma. Results. In BALB/c mice, we found that HPN-treated groups had suppressed eosinophil infiltration, allergic airway inflammation, and AHR, and these occurred by suppressing the production of IL-5, IL-17, and OVA-specific IgE. Conclusions. Our data suggest that the therapeutic mechanism by which HPN effectively treats asthma is based on reductions of Th2 cytokines (IL-5), eotaxin, OVA-specific IgE production, and eosinophil infiltration via inhibition of GATA-3 transcription factor.

Effect of rosmarinic and caffeic acids on inflammatory and nociception process in rats

Rosmarinic acid is commonly found in species of the Boraginaceae and the subfamily Nepetoideae (Lamiaceae). It has a number of interesting biological activities, for example, antiviral, antibacterial, anti-inflammatory, and antioxidant. The aim of the present study was to investigate the effect of the i.p. administration of caffeic and rosmarinic acid (5 and 10 mg/kg) on anti-inflammatory and nociceptive response using carrageenan-induced pleurisy model and tail-flick assay in rats. The analysis of cells in the pleural exudates revealed a reduction of 66% of the number of leukocytes that migrated to the pleural cavity in the animals treated with 5 mg/kg caffeic acid, and of 92.9% for the animals treated with 10 mg/kg in comparison with the control group. These exudates showed a balanced distribution of polymorphonuclear (PMN) and mononuclear (MN) cells, differently from the control group, in which PMN cells were predominant. The analysis to tail-flick latency was increased in the group treated with 10 mg/kg caffeic acid characterizing a nociceptive response. While there was no difference between control group and animals treated with rosmarinic.

M(3) muscarinic receptor antagonist bencycloquidium bromide attenuates allergic airway inflammation, hyperresponsiveness and remodeling in mice

M(3) muscarinic receptors are localized on inflammatory cells, airway smooth muscle, and submucosal glands, known to mediate bronchoconstriction, mucus secretion, and airway remodeling. It is hypothesized bencycloquidium bromide (BCQB), a novel M(3) receptor antagonist, might have potential effects on airway hyperresponsiveness, inflammation and airway remodeling in a murine model of asthma. Mice sensitized and challenged with ovalbumin developed airway inflammation. Bronchoalveolar lavage fluid was examined to determine the total and differential cell counts, and cytokine levels. Lung tissues were evaluated for cell infiltration, mucus hypersecretion, airway remodeling, and the expression of inflammatory biomarkers. Airway hyperresponsiveness was monitored by direct airway resistance analysis. Inhalation administration of BCQB significantly not only reduced ovalbumin-induced airway hyperresponsiveness comparing to methacholine, and prevented the ovalbumin-induced increase in total cell counts and eosinophil counts. Reverse transcriptase polymerase chain reaction analysis of whole lung lysates revealed that BCQB markedly suppressed ovalbumin-induced mRNA expression of eotaxin, IL-5, IL-4 and MMP-9, and increased mRNA expression of IFN-γ and TIMP-1 in a dose-dependent manner. Substantial IFN-γ/IL-4 (Th1/Th2) levels were recovered in bronchoalveolar lavage fluid after BCQB treatment. In addition, histological studies showed that BCQB dramatically inhibited ovalbumin-induced lung tissue eosinophil infiltration, airway mucus production and collagen deposition in lung tissues. Results reported in current paper suggest that M(3) receptors antagonist may provide a novel therapeutic approach to treat airway inflammation, hyperresponsiveness and remodeling.

Moving towards a new generation of animal models for asthma and COPD with improved clinical relevance

Asthma and chronic obstructive pulmonary disease (COPD) are complex inflammatory airway diseases characterised by airflow obstruction that remain leading causes of hospitalization and death worldwide. Animal modelling systems that accurately reflect disease pathophysiology continue to be essential to the development of new therapies for both conditions. In this review, we describe preclinical in vivo models that recapitulate many of the features of asthma and COPD. Specifically, we discuss the pro's and con's of the standard models and highlight recently developed systems designed to more accurately reflect the complexity of both diseases. For instance, clinically relevant allergens (i.e. house dust mite) are now being used to mimic the inflammatory changes and airway remodelling that result after chronic allergen exposures. Additionally, systems are being developed to mimic steroid-resistant and viral exacerbations of allergic inflammation - aspects of asthma where there is an acute need for new therapies. Similarly, COPD models have evolved to align with the improved clinical understanding of the factors contributing to disease progression. This includes using cigarette smoke to model not only airway inflammation and remodelling, but some systemic changes (e.g. hypertension and skeletal muscle alterations) that are thought to influence disease. Further, mouse genetics are being exploited to gain insights into the genetics of COPD susceptibility. The new models of asthma and COPD described herein demonstrate that improved clinical understanding of the diseases and better preclinical models is an iterative process that will hopefully lead to therapies that can effectively manage severe asthma and COPD.

Pitrakinra for asthma

IMPORTANCE OF THE FIELD

In asthma IL-4 and IL-13 have been demonstrated to play major pathogenic roles and therefore their blockade would potentially represent a plausible therapeutic approach.

AREAS COVERED IN THIS REVIEW

Pitrakinra is a dual IL-4/IL-13 inhibitor currently under development for asthma and the existing preclinical and clinical data are discussed.

WHAT THE READER WILL GAIN

Inhaled pitrakinra demonstrated a good anti-inflammatory potential and a good safety profile on a short-term basis but its place in asthma therapy is still to be found.

TAKE HOME MESSAGE

Specific anticytokine therapies might in the near future reshape asthma therapy.

Cytokine antagonists for the treatment of asthma: progress to date

Asthma is a disease of the airways in which several cytokines such as interleukin (IL)-4, IL-5, IL-13 and tumor necrosis factor-alpha (TNFalpha) play a major role in the development and progression of inflammation, airway hyperresponsiveness, mucus production, and airway remodeling. The conventional anti-inflammatory therapies, represented by inhaled corticosteroids and antileukotrienes, are not always able to provide optimal disease control and it is therefore hoped that cytokine antagonists could achieve this goal in such situations. Anticytokine therapies have been tested in preclinical studies and some have entered clinical trials. Anti-IL-4 therapies have been tested in animal models of allergy-related asthma, but because of unclear efficacy their development was discontinued. However, IL-4/IL-13 dual antagonists and IL-13-specific blocking agents are more promising, as they exhibit more sustained anti-inflammatory effects. IL-5 antagonists have been found to be of limited efficacy in clinical studies but might be useful in conditions characterized by severe hypereosinophilia, and in which asthma is one of the disease manifestations. Unlike other chronic inflammatory conditions, such as rheumatoid arthritis, the use of anti-TNFalpha therapies in asthma might be limited by the unfavorable risk/benefit ratio associated with long-term use. The identification of so-called asthma TNFalpha phenotypes and perhaps the use of a less aggressive treatment regimen might address this important aspect. Other cytokine antagonists (for example for IL-9 or IL-25) are currently being evaluated in the asthma setting, and could open new therapeutic perspectives based on their efficacy and safety.

Suppressive effects of formoterol and salmeterol on eotaxin-1 in bronchial epithelial cells

Eotaxin-1 (CCL11), an eosinophil-specific C-C chemokine, is a potent chemoattractant for mobilization of eosinophils into airways after allergic stimulation. Eotaxin-1 recruits eosinophils into inflammatory sites, and may play a role in the pathogenesis of asthma. Formoterol and salmeterol are two inhaled long acting beta(2) adrenoceptor agonists (LABAs), widely used for the local treatment of asthma. However, little is known about their effects on the eotaxin-1 expression of bronchial epithelial cells. BEAS-2B cells were stimulated by adding IL-4 with or without 2 h pre-treatment of formoterol or salmeterol. The protein and mRNA expression of eotaxin-1 were measured by ELISA assay and real-time PCR, respectively. Effects of formoterol and salmeterol on nuclear and cytosolic pSTAT-6 expression were evaluated by Western blot and immunofluorescence study. Formoterol and salmeterol (10(-7)-10(-10) m) significantly down-regulated IL-4- induced eotaxin-1 expression in BEAS-2B cells. A specific beta(2) adrenoceptor antagonist (ICI 118,551) reversed their suppression of eotaxin-1 production. Forskolin, an cAMP activator, could also suppress the expression of eotaxin-1 by IL-4 in a dose dependent manner (10(-7)-10(-10 )m). The western blot and immunofluorescence studies demonstrated that formoterol 10(-7 )m suppressed the nuclear expression of pSTAT-6. Formoterol and salmeterol, two inhaled long-acting beta(2) agonists, down-regulated IL-4- induced eotaxin-1 expression in BEAS-2B cells. The effect was mediated via the beta(2) adrenoceptor, and cAMP. Formoterol significantly down-regulated pSTAT6 at higher concentration, and further turned off the IL-4 signaling pathway.

Combined vaccination against IL-5 and eotaxin blocks eosinophilia in mice

Interleukin-5 (IL-5) is a cytokine which is essential for the maturation of eosinophils in bone marrow and for their release into the blood. Eotaxin is a CC type chemokine implicated in the recruitment of eosinophils in a variety of inflammatory disorders. Since eosinophil-activity is governed by these two pathways, we targeted both IL-5 and eotaxin by active vaccination to block eosinophilia. We produced two vaccines by chemically cross-linking IL-5 or eotaxin to a virus-like particle (VLP) derived from the bacteriophage Qbeta, yielding highly repetitive arrays of these cytokines on the VLP surface. Both vaccines overcame self-tolerance and induced high antibody titers against the corresponding self-molecules in mice. Immunization with either of the two vaccines reduced eosinophilic inflammation of the lung in an ovalbumin (OVA) based mouse model of allergic airway inflammation. Animals immunized with the two vaccines at the same time developed high antibody titers against both cytokines and also reduced eosinophil-infiltration of the lung. These data demonstrate that targeting either IL-5 or eotaxin may lower eosinophilia. Simultaneous immunization against IL-5 and eotaxin demonstrates that such a therapeutic approach may be used to treat complex disorders in which multiple mediators are involved.

Effects of the immunomodulatory agent Cordyceps militaris on airway inflammation in a mouse asthma model

BACKGROUND

Cordyceps militaris is a well-known fungus with immunomodulatory activity. It is generally used in traditional Chinese medicine to treat hemoptysis, bronchial or lung inflammation, and urogenital disorders. The purpose of our study was to evaluate the effect of cultivated C. militaris on airway inflammation in a mouse asthma model.

METHODS

BALB/c mice were sensitized with intraperitoneal ovalbumin (OVA) on Days 0 and 14, and were then given intranasal OVA on Day 14 and Days 25-27. Randomized treatment groups of sensitized mice were administered C. militaris, prednisolone, montelukast, or placebo by gavage from Days 15-27. Airway hyperreactivity to aerosolized methacholine was determined. Bronchoalveolar lavage fluid and serum were analyzed to assess airway inflammation.

RESULTS

OVA-sensitized mice developed a significant airway inflammatory response that was inhibited by prednisolone and montelukast, whilst C. militaris reduced airway inflammation less effectively. Airway hyperresponsiveness to methacholine was observed in OVA-sensitized mice and was reversed by both prednisolone and montelukast. C. militaris initially reversed airway hyperreactivity, but this effect disappeared at higher methacholine doses.

CONCLUSION

C. militaris can modulate airway inflammation in asthma, but it is less effective than prednisolone or montelukast. These results demonstrate that C. militaris is unable to adequately block the potent mediators of asthmatic airway inflammation.

YM-341619 suppresses the differentiation of spleen T cells into Th2 cells in vitro, eosinophilia, and airway hyperresponsiveness in rat allergic models

T helper (Th) 2 cells play a central role in the pathogenesis of allergic diseases such as allergic asthma, atopic dermatitis, and allergic rhinitis. We have found that YM-341619 hydrochloride, which suppressed IL-4-induced STAT6-dependent reporter gene expression, inhibited the differentiation of mouse spleen T cells into Th2 cells in vitro. YM-341619 suppressed the production of IL-4 and the expression of GATA-3 mRNA, a Th2 transcription factor, in T cells cultured with anti-CD3 antibody and anti-CD28 antibody in the presence of IL-4. In contrast, the production of IFN-gamma and the expression of T-bet mRNA, a Th1 transcription factor, in T cells cultured with anti-CD3 antibody in the presence of IL-12, were not effected by YM-341619. Orally administered YM-341619 (0.003-0.03 mg/kg) reduced the plasma IgE level of DNP-Ascaris-sensitized rats, but not the IgG(2a) level. YM-341619 suppressed IL-4 and IL-13 production in the splenocytes of these DNP-Ascaris-sensitized rats without augmenting IFN-gamma production. YM-341619 also dose-dependently suppressed eosinophil accumulation in the lung (0.003-3 mg/kg, p.o.) and airway hyperresponsiveness (0.3-3 mg/kg, p.o.) induced by repeated exposure to ovalbumin in ovalbumin-sensitized rats. These results suggest that YM-341619 has the ability to suppress allergen-induced Th2 responses by selectively inhibiting the differentiation of CD4(+) T cells into the Th2 subset.

IL-13 as a therapeutic target for respiratory disease

Interleukin-13 (IL-13) is a critical mediator of asthma pathology. On B cells, monocytes, epithelial cells, and smooth muscle cells, IL-13 acts through the IL-13Ralpha1/IL-4Ralpha complex to directly induce activation responses that contribute to atopic disease. In human populations, genetic polymorphisms in IL-13, its receptor components, or the essential signaling element STAT6, have all been associated with increased risk of atopy and asthma. Animal studies using IL-13 deficient mice, IL-13 transgenic animals, and IL-13 neutralization strategies have confirmed an essential role for this cytokine in driving major correlates of asthma pathology, including airway hyperresponsiveness (AHR), lung eosinophilia, mucus generation, and fibrosis. Ongoing studies continue to define both overlapping and distinct roles for IL-13 and the related cytokine, IL-4, in promoting asthmatic changes. Furthermore, new evidence concerning the role of the "decoy" receptor, IL-13Ralpha2, has prompted re-evaluation of the receptor forms that underlie the numerous activities of IL-13. In this review, we summarize the essential role of IL-13 in asthma, compare the relative contributions of IL-13 and IL-4 to key aspects of the asthmatic phenotype, and outline novel therapeutic strategies to target this critical cytokine.

Glucocorticoids ameliorate antigen-induced bronchial smooth muscle hyperresponsiveness by inhibiting upregulation of RhoA in rats

To determine the mechanism(s) of the inhibitory effect of glucocorticoids on airway hyperresponsiveness in allergic bronchial asthma, the effects of systemic treatment with glucocorticoids on bronchial smooth muscle hyperresponsiveness and RhoA upregulation were investigated in rats with allergic bronchial asthma. Rats were sensitized and repeatedly challenged with 2,4-dinitrophenylated Ascaris suum antigen. Animals were also treated with prednisolone or beclomethasone (each 10 mg/kg, i.p.) once a day during the antigen inhalation period. Repeated antigen inhalation caused a marked bronchial smooth muscle hyperresponsiveness to acetylcholine with an upregulation of RhoA. Augmented acetylcholine-induced activation of RhoA and phosphorylation of myosin light chain were observed in bronchial smooth muscles of the antigen-exposed animals. Systemic treatment with either glucocorticoid used inhibited the bronchial smooth muscle hypercontraction until the level of the sensitized control rats that received saline inhalation instead of antigen challenge. Interestingly, both glucocorticoids also inhibited the upregulation of RhoA and augmented acetylcholine-induced activation of RhoA and phosphorylation of myosin light chain. In conclusion, glucocorticoids ameliorated the augmented bronchial smooth muscle contraction by inhibiting upregulation of RhoA. These effects of glucocorticoids may account for, in part, their beneficial effects in the treatment of asthma.

Adenovirus IL-13-induced airway disease in mice: a corticosteroid-resistant model of severe asthma

Interleukin 13 (IL-13) is considered to be a key driver of the development of airway allergic inflammation and remodeling leading to airway hyperresponsiveness (AHR). How precisely IL-13 leads to the development of airway inflammation, AHR, and mucus production is not fully understood. In order to identify key mediators downstream of IL-13, we administered adenovirus IL-13 to specifically induce IL-13-dependent inflammation in the lungs of mice. This approach was shown to induce cardinal features of lung disease, specifically airway inflammation, elevated cytokines, AHR, and mucus secretion. Notably, the model is resistant to corticosteroid treatment and is characterized by marked neutrophilia, two hallmarks of more severe forms of asthma. To identify IL-13-dependent mediators, we performed a limited-scale two-dimensional SDS-PAGE proteomic analysis and identified proteins significantly modulated in this model. Intriguingly, several identified proteins were unique to this model, whereas others correlated with those modulated in a mouse ovalbumin-induced pulmonary inflammation model. We corroborated this approach by illustrating that proteomic analysis can identify known pathways/mediators downstream of IL-13. Thus, we have characterized a murine adenovirus IL-13 lung model that recapitulates specific disease traits observed in human asthma, and have exploited this model to identify effectors downstream of IL-13. Collectively, these findings will enable a broader appreciation of IL-13 and its impact on disease pathways in the lung.

Ovalbumin-sensitized mice are good models for airway hyperresponsiveness but not acute physiological responses to allergen inhalation

BACKGROUND

Asthma is a chronic inflammatory disease that is characterized clinically by airway hyperresponsiveness (AHR) to bronchoconstricting agents. The physiological response of the asthmatic lung to inhaled allergen is often characterized by two distinct phases: an early-phase response (EPR) within the first hour following exposure that subsides and a late-phase response (LPR) that is more prolonged and may occur several hours later. Mouse models of asthma have become increasingly popular and should be designed to exhibit an EPR, LPR and AHR.

OBJECTIVE

To determine whether a common model of asthma is capable of demonstrating an EPR, LPR and AHR.

METHODS

BALB/c mice were sensitized to ovalbumin (OVA) and challenged with one or three OVA aerosols. Changes in lung mechanics in response to allergen inhalation were assessed using a modification of the low-frequency forced oscillation technique (LFOT). In order to assess AHR, changes in lung mechanics in response to aerosolized methacholine were assessed using LFOT. Inflammatory cell infiltration into the lung was measured via bronchoalveolar lavage (BAL). ELISAs were used to measure inflammatory cytokines in the BAL and levels of IgE in the serum.

RESULTS

An EPR was only detectable after three OVA aerosols in approximately half of the mice studied. There was no evidence of an LPR despite a clear increase in cellular infiltration 6 h post-allergen challenge. AHR was present after a single OVA aerosol but not after three OVA aerosols.

CONCLUSIONS

The lack of an LPR, limited EPR and the absence of a link between the LPR and AHR highlight the limitations of this mouse model as a complete model of the lung dysfunction associated with asthma.

Intravascular inactivation of CCR5 by n-Nonanoyl-CC chemokine ligand 14 and inhibition of allergic airway inflammation

Modulation of leukocyte recruitment through intervention with chemokine receptors is an attractive, therapeutic strategy. Recently, we have shown that n-Nonanoyl (NNY)-CCL14 internalizes and desensitizes human (h)CCR3, resulting in the inactivation of eosinophils. In this study, we investigated the interaction of NNY-CCL14 with CCR1 and CCR5 and the relevance of these NNY-CCL14 receptors on its in vivo effects in allergic airway inflammation. NNY-CCL14 has inactivating properties on CCR1(+) and CCR5(+) cell lines and primary leukocytes. It desensitizes hCCR1- and hCCR5-mediated calcium release and internalizes these receptors from the cellular surface. Treatment of OVA-sensitized BALB/c mice with NNY-CCL14 resulted in reduced pulmonary inflammation. Above all, it is demonstrated that systemic treatment with NNY-CCL14 down-modulates CCR5 from the surface of lymphocytes in vivo. Although NNY-CCL14 acts on murine lymphocytes and internalizes CCR5, it does not internalize CCR3 on mouse eosinophils, showing species selectivity regarding this particular receptor. Therefore, the inhibitory effects of NNY-CCL14 in murine models of allergic airway inflammation can be assigned to its interaction with CCR5. The presented results substantiate the relevance of CCR5 as a target for allergic airway inflammation.

Pioglitazone is as effective as dexamethasone in a cockroach allergen-induced murine model of asthma

Background

While glucocorticoids are currently the most effective therapy for asthma, associated side effects limit enthusiasm for their use. Peroxisome proliferator-activated receptor-γ (PPAR-γ) activators include the synthetic thiazolidinediones (TZDs) which exhibit anti-inflammatory effects that suggest usefulness in diseases such as asthma. How the ability of TZDs to modulate the asthmatic response compares to that of glucocorticoids remains unclear, however, because these two nuclear receptor agonists have never been studied concurrently. Additionally, effects of PPAR-γ agonists have never been examined in a model involving an allergen commonly associated with human asthma.

Methods

We compared the effectiveness of the PPAR-γ agonist pioglitazone (PIO) to the established effectiveness of a glucocorticoid receptor agonist, dexamethasone (DEX), in a murine model of asthma induced by cockroach allergen (CRA). After sensitization to CRA and airway localization by intranasal instillation of the allergen, Balb/c mice were challenged twice at 48-h intervals with intratracheal CRA. Either PIO (25 mg/kg/d), DEX (1 mg/kg/d), or vehicle was administered throughout the period of airway CRA exposure.

Results

PIO and DEX demonstrated similar abilities to reduce airway hyperresponsiveness, pulmonary recruitment of inflammatory cells, serum IgE, and lung levels of IL-4, IL-5, TNF-α, TGF-β, RANTES, eotaxin, MIP3-α, Gob-5, and Muc5-ac. Likewise, intratracheal administration of an adenovirus containing a constitutively active PPAR-γ expression construct blocked CRA induction of Gob-5 and Muc5-ac.

Conclusion

Given the potent effectiveness shown by PIO, we conclude that PPAR-γ agonists deserve investigation as potential therapies for human asthma.

T-helper type 2-dependent early recruitment of antigen non-specific CD4+ T cells in experimental asthma

BACKGROUND

Following antigen challenge, adoptively transferred antigen-specific CD4(+) T cells induce allergic airway inflammation, comprised primarily of an increase in lymphocytes and eosinophils.

OBJECTIVE

Our goal was to better understand the contribution of the GATA-3 transcription factor to the ability of adoptively transferred T cells to induce airway inflammation in the Brown Norway rat model of adoptively transferred asthma.

METHODS

We transduced antigen-stimulated CD4+ T cells with recombinant retroviruses encoding enhanced green fluorescent protein (EGFP) only or EGFP and the GATA-3 transcription factor. Each population of transduced cells was adoptively transferred to naïve recipients that were then challenged with antigen. Airway inflammatory responses were then quantified.

RESULTS

Our data indicate that T cells transduced with retroviruses encoding GATA-3 expressed high levels of GATA-3 protein as well as T-helper type 2 cytokines. Following adoptive transfer and airway antigen challenge, these gene-modified T cells induced robust inflammatory responses in the lungs and draining lymph nodes. Increased numbers of total inflammatory cells and eosinophils were recovered in the bronchoalveolar lavage fluid (BALF). In addition, the number of antigen non-specific CD4+ T cells recovered in the BALF as well as the lung and draining lymph nodes was enhanced in recipients of GATA-3 overexpressing T cells following antigen challenge. Nevertheless, the transduced CD4+ T cells comprised only a small percentage of the population of CD4+ T cells infiltrating the lung and were not detectable at all in the draining lymph nodes.

CONCLUSION

These data provide evidence that GATA-3 plays a significant role in the ability of antigen-specific T cells to amplify allergic inflammatory responses in vivo by promoting the recruitment of endogenous antigen non-specific T cells to the lung.

Allergic airway responses in obese mice

RATIONALE

Epidemiologic data indicate an increased incidence of asthma in the obese.

OBJECTIVES

To determine whether obese mice exhibit augmented pulmonary responses after allergen sensitization and challenge.

METHODS

Lean, wild-type (C57BL/6), obese ob/ob, and obese db/db mice were sensitized to ovalbumin (OVA), and then challenged with aerosolized OVA or phosphate-buffered saline (PBS). Changes in total pulmonary resistance (Rl) induced by intravenous methacholine were measured by forced oscillation. Blood was collected, bronchoalveolar lavage (BAL) was performed, and lungs were harvested for measurement of cytokine expression by real-time reverse transcription-polymerase chain reaction.

MEASUREMENTS AND MAIN RESULTS

OVA challenge increased baseline Rl in ob/ob, but not wild-type, mice, and airway responsiveness was greater in ob/ob than wild-type mice, regardless of the challenge. Compared with PBS, OVA challenge caused an increase in the number of BAL fluid (BALF) cells, an increase in lung Th2 cytokine expression, and an increase in serum IgE. Significantly fewer BALF cells were recovered from OVA-challenged ob/ob versus wild-type mice, whereas serum IgE levels were elevated significantly more in ob/ob versus wild-type mice. BALF and lung Th2 cytokine expression was not different in ob/ob versus wild-type mice. Airway responsiveness was greater in db/db versus wild-type mice, regardless of the challenge, and OVA caused airway hyperresponsiveness in db/db but not wild-type mice, despite reduced BALF cells in OVA-challenged db/db versus wild-type mice.

CONCLUSIONS

These results demonstrate that obesity enhances OVA-induced changes in pulmonary resistance and serum IgE and that these changes are not the result of increased Th2 type airway inflammation.

Effect of ageing on pulmonary inflammation, airway hyperresponsiveness and T and B cell responses in antigen-sensitized and -challenged mice

BACKGROUND

The effect of ageing on several pathologic features of allergic asthma (pulmonary inflammation, eosinophilia, mucus hypersecretion), and their relationship with airway hyperresponsiveness (AHR) is not well characterized.

OBJECTIVE

To evaluate lung inflammation, mucus metaplasia and AHR in relationship with age in murine models of allergic asthma comparing young and older mice.

METHODS

Young (6 weeks) and older (6, 12, 18 months) BALB/c mice were sensitized and challenged with ovalbumin (OVA). AHR and bronchoalveolar fluid (BALF), total inflammatory cell count and differential were measured. To evaluate mucus metaplasia, quantitative PCR for the major airway mucin-associated gene, MUC-5AC, from lung tissue was measured, and lung tissue sections stained with periodic acid-Schiff (PAS) for goblet-cell enumeration. Lung tissue cytokine gene expression was determined by quantitative PCR, and systemic cytokine protein levels by ELISA from spleen-cell cultures. Antigen-specific serum IgE was determined by ELISA.

RESULTS

AHR developed in both aged and young OVA-sensitized/challenged mice (OVA mice), and was more significantly increased in young OVA mice than in aged OVA mice. However, BALF eosinophil numbers were significantly higher, and lung histology showed greater inflammation in aged OVA mice than in young OVA mice. MUC-5AC expression and numbers of PAS+ staining bronchial epithelial cells were significantly increased in the aged OVA mice. All aged OVA mice had increased IL-5 and IFN-gamma mRNA expression in the lung and IL-5 and IFN-gamma protein levels from spleen cell cultures compared with young OVA mice. OVA-IgE was elevated to a greater extent in aged OVA mice.

CONCLUSIONS

Although pulmonary inflammation and mucus metaplasia after antigen sensitization/challenge occurred to a greater degree in older mice, the increase in AHR was significantly less compared with younger OVA mice. Antigen treatment produced a unique cytokine profile in older mice (elevated IFN-gamma and IL-5) compared with young mice (elevated IL-4 and IL-13). Thus, the airway response to inflammation is lessened in ageing animals, and may represent age-associated events leading to different phenotypes in response to antigen provocation.

Polymorphisms in IL13, total IgE, eosinophilia, and asthma exacerbations in childhood

BACKGROUND

It is unclear whether single nucleotide polymorphisms (SNPs) in the gene for IL-13 (IL13) influence asthma severity and/or asthma morbidity.

OBJECTIVES

To examine the relation between IL13 SNPs and asthma-related phenotypes in 2 independent populations.

METHODS

We used family-based methods to test for association between SNPs in IL13 and asthma-related phenotypes in Costa Rican children with asthma. We attempted to reproduce significant findings in white (non-Hispanic) children with asthma in the Childhood Asthma Management Program (CAMP).

RESULTS

In Costa Rica and in CAMP, the A allele (Gln) of IL13 coding SNP (rs20541) was significantly associated with increased eosinophil count (P < .011 in both studies) and increased serum total IgE (P < .054 in both studies). The T allele of IL13 promoter SNP (rs1800925) was inversely associated with asthma exacerbations in Costa Rica (P = .069). Although this SNP (rs1800925) was not associated with asthma exacerbations among all white children in CAMP, it was associated with increased risk of asthma exacerbations among children on inhaled corticosteroids (P = .02).

CONCLUSION

Polymorphisms in IL13 were significantly associated with serum total IgE and eosinophil count in 2 populations. IL13 polymorphisms may also be associated with asthma exacerbations, and this effect may be dependent on medication use. Our study is the first to report a potential negative interaction between a genetic polymorphism and response to inhaled corticosteroids.

CLINICAL IMPLICATIONS

Polymorphisms in IL13 are associated with serum total IgE and eosinophil count and may be associated with asthma exacerbations.

Antiinflammatory, antioxidant and cytotoxic actions of beta-glucan-rich extract from Geastrum saccatum mushroom

The Geastrum saccatum a mushroom, native to Brazil, is produced under natural conditions in the unexplored reserve of Mata da Estrela-RN. This species has curative properties for eye infections and diseases such as asthma. The tissues of this mushroom contain carbohydrates, proteins, lipids, moisture and ashes in amounts of 42.3%, 37.05%, 9.01, 1.4% and 10.2%, respectively. An extract from this mushroom was characterized by chemical analyses and (13)C and (1)H NMR spectroscopy. It contains high amount of glucose and traces of galactose. The signal appearing at 103.5 ppm was assigned to C1 of beta-glucose. The signals observed between 20 and 40 ppm suggest the presence of a glucan-protein compound. This glucan inhibited the lipid peroxidation at the dose of 0.27 mg/mL (59.1%) and it can protect cells against oxidative stress by scavenging of the hydroxyl (77%) and superoxide (88.4%) radicals at 0.27 mg/mL. The glucan (30 mg/kg) reduces the polymorphonuclear cell migration (57.6%). The ear edema induced by croton oil was inhibited by glucan (60.4% at 10 mg/kg) and by its association with diclofenac (5 mg/kg) (89.2%) or L-NAME (60 mg/kg) (86.23%). Histological analyses of the ear edema induced by croton oil in the presence of glucan (10, 30 or 50 mg/kg) showed a reduced degree of the polymorphonuclear cell migration. We concluded that the glucan has antioxidant, and antiinflammatory properties as well as its antiinflammatory effect are mediated by inhibition of both nitric oxide synthase (NOS) and cyclooxygenase (COX).

Expression and regulation of intercellular adhesion molecule-1 on airway parasympathetic nerves

BACKGROUND

Eosinophils cluster along airway nerves in patients with asthma and release eosinophil major basic protein, an antagonist of inhibitory M2 muscarinic receptors on nerves. Blocking M2 function increases bronchoconstriction, leading to airway hyperreactivity. Intercellular adhesion molecule-1 (ICAM-1) mediates eosinophil adhesion to nerves.

OBJECTIVE

We investigated mechanisms of ICAM-1 expression by parasympathetic nerves.

METHODS

ICAM-1 expression was examined by immunocytochemistry of lung sections from ovalbumin-sensitized and challenged guinea pigs. ICAM-1 was measured in parasympathetic nerves isolated from subjects and guinea pigs and in human neuroblastoma cells by real-time RT-PCR, immunocytochemistry, and Western blot.

RESULTS

ICAM-1 was not detected in control airway parasympatheric nerves in vivo or in cultured cells. ICAM-1 was expressed throughout antigen-challenged guinea pig lung tissue and was selectively decreased by dexamethasone only in nerves. ICAM-1 was induced in human and guinea pig parasympathetic nerves by TNF-alpha and IFN-gamma and was inhibited by dexamethasone and by an inhibitor of nuclear factor-kappaB (NF-kappaB). In neuroblastoma cell lines TNF-alpha and IFN-gamma-induced ICAM-1 was blocked by an inhibitor of NF-kappaB but not by inhibitors of mitogen-activated protein kinases. Dexamethasone did not inhibit ICAM-1 expression in neuroblastoma cells.

CONCLUSIONS

ICAM-1 induced in nerves by antigen challenge and proinflammatory cytokines is sensitive to dexamethasone. ICAM-1 expression is also sensitive to inhibitors of NF-kappaB. Neuroblastoma cells mimic many, but not all, characteristics of ICAM-1 expression in parasympathetic nerves.

CLINICAL IMPLICATIONS

Dexamethasone and NF-kappaB inhibitors could prevent eosinophils from adhering to nerves by blocking ICAM-1 expression on parasympathetic nerves, thus protecting inhibitory M2 muscarinic receptors and making this pathway a potential target for asthma treatment.

RANTES (CCL5) regulates airway responsiveness after repeated allergen challenge

RANTES (CC chemokine ligand 5) contributes to airway inflammation through accumulation of eosinophils, but the exact role of RANTES (CCL5) is not defined. C57BL/6 mice, sensitized by injection of ovalbumin (OVA) on Days 1 and 14, were challenged with OVA on Days 28, 29, and 30 (3 challenges, short-term-challenge model) or on Days 28, 29, 30, 36, 40, 44, and 48 (7 challenges, repeated-challenge model) and evaluated 48 h later. Anti-mouse RANTES was given intravenously, and recombinant mouse RANTES or PBS was given intratracheally. These reagents were given on Days 28, 29, and 30 in the short-term-challenge study and on Days 44 and 48 in the repeated-challenge study. After short-term challenge, there were no effects after administration of anti-RANTES or RANTES. In the repeated-challenge study, although control mice showed a decrease in airway hyperresponsiveness, administration of anti-RANTES sustained and enhanced airway hyperresponsiveness and increased goblet cell numbers. In contrast, administration of RANTES normalized airway function but reduced goblet cell numbers. IL-12 and IFN-gamma levels in BAL decreased in the anti-RANTES group and increased in the RANTES group. IFN-gamma-producing CD4 T cells in lung, and IFN-gamma production from lung T cells in response to OVA in the anti-RANTES group, were significantly decreased but were increased in the RANTES group. Anti-IFN-gamma, administered with RANTES, decreased the effects of RANTES on AHR after repeated challenge. These data indicate that RANTES plays a role in the regulation of airway function after repeated allergen challenge, in part through modulation of levels of IFN-gamma and IL-12.

Potential mechanisms of improvement of airway hyperresponsiveness by inhaled corticosteroid therapy in asthmatic patients

OBJECTIVE

Recent clinical trials with administration of IL-5 antibodies to asthmatic patients have revealed reduction of eosinophilia but unaltered airway hyperresponsiveness (AHR). In contrast, inhaled corticosteroid (ICS) therapy eliminates both eosinophilia and AHR. This study was designed to examine the mechanisms by which ICS improves airway hyperresponsiveness in asthmatic patients.

METHODS

Clinical variables of asthma involving vascular permeability and IL-5 levels were examined in 23 asthmatic patients and 11 normal control subjects. After the first sputum induction, inhaled beclomethasone dipropionate (BDP 800 microg/day) was administered to asthmatic patients for 8 weeks, and sputum induction was repeated.

RESULTS

IL-5 levels in induced sputum and airway vascular permeability index were significantly higher in asthmatic patients. IL-5 was positively correlated with percentage of eosinophils in induced sputum, and negatively correlated with FEV1, but not correlated with PC20 methacholine. After BDP therapy, eosinophils, ECP, and IL-5 levels were significantly decreased to the same levels as in normal subjects. Conversely, PC20 methacholine and airway vascular permeability did not improve to the same levels as in normal subjects. Increase in PC20 methacholine from before to after BDP therapy was significantly correlated with decrease in airway permeability index, but not with decrease in IL-5 level.

CONCLUSION

Our results suggest a clear dissociation between IL-5 and AHR. ICS therapy improves AHR at least in part through decrease in airway vascular permeability.

Importance of myeloid dendritic cells in persistent airway disease after repeated allergen exposure

RATIONALE

There is conflicting information about the development and resolution of airway inflammation and airway hyperresponsiveness (AHR) after repeated airway exposure to allergen in sensitized mice.

METHODS

Sensitized BALB/c and C57BL/6 mice were exposed to repeated allergen challenge on 3, 7, or 11 occasions. Airway function in response to inhaled methacholine was monitored; bronchoalveolar lavage fluid inflammatory cells were counted; and goblet cell metaplasia, peribronchial fibrosis, and smooth muscle hypertrophy were quantitated on tissue sections. Bone marrow-derived dendritic cells were generated after differentiation of bone marrow cells in the presence of growth factors.

RESULTS

Sensitization to ovalbumin (OVA) in alum, followed by three airway exposures to OVA, induced lung eosinophilia, goblet cell metaplasia, mild peribronchial fibrosis, and peribronchial smooth muscle hypertrophy; increased levels of interleukin (IL)-4, IL-5, IL-13, granulocyte-macrophage colony-stimulating factor, transforming growth factor-beta(1), eotaxin-1, RANTES (regulated on activation, normal T-cell expressed and secreted), and OVA-specific IgG1 and IgE; and resulted in AHR. After seven airway challenges, development of AHR was markedly decreased as was the production of IL-4, IL-5, and IL-13. Levels of IL-10 in both strains and the level of IL-12 in BALB/c mice increased. After 11 challenges, airway eosinophilia and peribronchial fibrosis further declined and the cytokine and chemokine profiles continued to change. At this time point, the number of myeloid dendritic cells and expression of CD80 and CD86 in lungs were decreased compared with three challenges. After 11 challenges, intratracheal instillation of bone marrow-derived dendritic cells restored AHR and airway eosinophilia.

CONCLUSIONS

These data suggest that repeated allergen exposure leads to progressive decreases in AHR and allergic inflammation, through decreases in myeloid dendritic cell numbers.

Reversal of allergen-induced airway remodeling by CysLT1 receptor blockade

RATIONALE

Airway inflammation in asthma is accompanied by structural changes, including goblet cell metaplasia, smooth muscle cell layer thickening, and subepithelial fibrosis. This allergen-induced airway remodeling can be replicated in a mouse asthma model.

OBJECTIVES

The study goal was to determine whether established airway remodeling in a mouse asthma model is reversible by administration of the cysteinyl leukotriene (CysLT)1 receptor antagonist montelukast, the corticosteroid dexamethasone, or the combination montelukast + dexamethasone.

METHODS

BALB/c mice, sensitized by intraperitoneal ovalbumin (OVA) as allergen, received intranasal OVA periodically Days 14-73 and montelukast or dexamethasone or placebo from Days 73-163.

MEASUREMENTS AND MAIN RESULTS

Allergen-induced trafficking of eosinophils into the bronchoalveolar lavage fluid and lung interstitium and airway goblet cell metaplasia, smooth muscle cell layer thickening, and subepithelial fibrosis present on Day 73 persisted at Day 163, 3 mo after the last allergen challenge. Airway hyperreactivity to methacholine observed on Day 73 in OVA-treated mice was absent on Day 163. In OVA-treated mice, airway eosinophil infiltration and goblet cell metaplasia were reduced by either montelukast or dexamethasone alone. Montelukast, but not dexamethasone, reversed the established increase in airway smooth muscle mass and subepithelial collagen deposition. By immunocytochemistry, CysLT1 receptor expression was significantly increased in airway smooth muscle cells in allergen-treated mice compared with saline-treated controls and was reduced by montelukast, but not dexamethasone, administration.

CONCLUSIONS

These data indicate that established airway smooth muscle cell layer thickening and subepithelial fibrosis, key allergen-induced airway structural changes not modulated by corticosteroids, are reversible by CysLT1 receptor blockade therapy.

Ganoderma tsugae supplementation alleviates bronchoalveolar inflammation in an airway sensitization and challenge mouse model

Ganoderma tsugae (a Chinese mushroom Songshan lingzhi) cultivated in Taiwan is extensively used in Chinese traditional medicine to treat different diseases. To determine whether G. tsugae has anti-inflammatory effects on bronchoalveolar inflammation in vivo, we investigated the anti-inflammatory effects of G. tsugae products, YK01 and YK07, on bronchoalveolar inflammation using an airway sensitization and challenge mouse model. Female BALB/c mice were weekly sensitized by intraperitoneal injection of ovalbumin (OVA) three times and challenged with aerosolized OVA twice. Differential cell counts of infiltrating leukocytes, inflammatory mediators, cytokines in bronchoalvelor lavage fluid (BALF) of OVA-challenged mice were examined after continuously consuming G. tsugae diets for 5 weeks. We found that supplementation of G. tsugae significantly decreased total infiltrating leukocytes and lymphocyte percentage in BALF in the experimental groups. Supplementation of G. tsugae also significantly reduced inflammatory mediators in BALF including histamine, prostaglandin E2, eotaxin, and protein levels, however the levels of pro-inflammatory cytokines, interleukin (IL)-1beta and IL-6, in BALF did not significantly change. These results suggest that both G. tsugae supplementation diets YK01 and YK07 might alleviate bronchoalveolar inflammation via decreasing the infiltration of inflammatory cells and the secretion of inflammatory mediators into the local tissues of lungs and airways. Further, these results indicate that the relief of bronchoalveolar inflammation in an airway sensitization murine model provides a possible therapeutic application for G. tsugae in allergic asthma.

Proteome analysis of differential protein expression in allergen-induced asthmatic mice lung after dexamethasone treatment

Asthma has become substantially more prevalent in recent decades and is one of the foremost contributors to morbidity and mortality in industrialized countries. Corticosteroids are among the most effective medications for the treatment of asthma, but some patients do not respond well to corticosteroid treatment. In this study, we characterized the responses to an allergen and identified potential molecular targets of dexamethasone (Dex) treatment in acute asthma. Female BALB/c mice sensitized to ovalbumin (OVA) were challenged with aerosolized OVA for 1 week. During the challenge period, mice were treated daily with Dex by intraperitoneal injection. Phosphate-buffered saline treated and non-challenged mice served as control. Histological evaluation of OVA-induced mice revealed airway inflammation and goblet cell hyperplasia. In addition, interleukin 4 levels and interferon-gamma levels were increased and decreased, respectively. These changes were moderated by Dex treatment. Protein expression profiles were compared in each experimental group by two-dimensional gel electrophoresis and identified using matrix-assisted laser desorption/ionization-time of flight/time of flight mass spectrometry. Some proteins were increased, while others were decreased by Dex treatment. These results indicated that the regulation of protein expression might play a role in the immunological and pathological development of asthma and could be targeted for therapeutic intervention. These results may assist in the development of quantitative diagnostic markers to monitor disease progression or responses to therapy using proteomic approaches.

Titanium dioxide particle-induced goblet cell hyperplasia: association with mast cells and IL-13

Background

Inhalation of particles aggravates respiratory symptoms including mucus hypersecretion in patients with chronic airway disease and induces goblet cell hyperplasia (GCH) in experimental animal models. However, the underlying mechanisms remain poorly understood.

Methods

To understand this, the numbers of goblet cells, Muc5ac (+) expressing epithelial cells and IL-13 expressing mast cells were measured in the trachea of sham or TiO₂ particles – treated rats using periodic acid-Schiff, toluidine blue and immunohistochemical staining. RT-PCR for Muc-1, 2 and 5ac gene transcripts was done using RNA extracted from the trachea. Differential cell count and IL-13 levels were measured in bronchoalveolar lavage (BAL) fluid. In pretreatment groups, cyclophosphamide (CPA) or dexamethasone (DEX) was given before instillation of TiO₂. TiO₂ treatment markedly increased Muc5ac mRNA expression, and Muc5ac (+) or PAS (+) epithelial cells 48 h following treatment.

Results

The concentration of IL-13 in BAL fluids was higher in TiO₂ treated – rats when compared to those in sham rats (p < 0.05). Pretreatment with cyclophosphamide (CPA) decreased the number of neutrophils and eosinophils in BAL fluid of TiO₂ treated – rats (p < 0.05), but affected neither the percentage of PAS (+) cells, nor IL-13 levels in the BAL fluids (p > 0.05). In contrast, pretreatment with dexamethasone (DEX) diminished the percentage of PAS (+) cells and the levels of IL-13 (p < 0.05). TiO₂ treatment increased the IL-13 (+) mast cells (p < 0.05) in the trachea, which was suppressed by DEX (p < 0.05), but not by CPA pretreatment (p > 0.05). In addition there were significant correlations of IL-13 (+) rate of mast cells in the trachea with IL-13 concentration in BAL fluid (p < 0.01) and with the percentage of Muc5ac (+) cells in the sham and TiO₂ treated rats (p < 0.05).

Conclusion

In conclusion, TiO₂ instillation induces GCH and Muc5ac expression, and this process may be associated with increased production of IL-13 by mast cells.