No audible wheezing: nuggets and conundrums from mouse asthma models

Long non-coding RNA NEAT1 exacerbates NLRP3-mediated pyroptosis in allergic rhinitis through regulating the PTBP1/FOXP1 cascade

BACKGROUND

Allergic Rhinitis (AR) is a prevalent chronic non-infectious inflammation affecting the nasal mucosa. NLRP3-mediated pyroptosis of epithelial cells plays a pivotal role in AR pathogenesis. Herein, we evaluated the impact of the long non-coding RNA nuclear paraspeckle assembly transcript 1 (lncRNA NEAT1) on NLR family pyrin domain containing 3 (NLRP3)-mediated pyroptosis in AR.

METHODS

Nasal inflammation levels in ovalbumin (OVA)-induced AR mice were assessed using HE staining, and NLRP3 expression was evaluated through immunohistochemistry. ELISA was utilized to detect OVA-specific IgE, IL-6, IL-5, and inflammatory cytokines (IL-1β, IL-18). Human nasal epithelial cells (HNEpCs) stimulated with IL4/IL13 were used to analyze the mRNA and protein levels of associated genes utilizing RT-qPCR and western blot, respectively. Cell viability and pyroptosis were assessed by CCK-8 and flow cytometry. The targeting relationship between NEAT1, PTBP1 and FOXP1 were analyzed by RIP and RNA pull down assays. FISH and IF analysis were performed to assess the co-localization of NEAT1 and PTBP1.

RESULTS

In both the AR mouse and cellular models, increased levels of NEAT1, PTBP1 and FOXP1 were observed. AR mice exhibited elevated inflammatory infiltration and pyroptosis, evidenced by enhanced expressions of OVA-specific IgE, IL-6, and IL-5, NLRP3, Cleaved-caspase 1, GSDMD-N, IL-1β and IL-18. Functional assays revealed that knockdown of PTBP1 or NEAT1 inhibited pyroptosis while promoting the proliferation of IL4/IL13-treated HNEpCs. Mechanistically, NEAT1 directly interacted with PTBP1, thereby maintaining FOXP1 mRNA stability. Rescue assays demonstrated that FOXP1 upregulation reversed the inhibitory effects of silencing NEAT1 or PTBP1 on IL4/IL13-stimulated pyroptosis activation in HNEpCs.

CONCLUSION

NEAT1 acts as a RNA scaffold for PTBP1, activating the PTBP1/FOXP1 signaling cascade, subsequently triggering NLRP3-mediated pyroptosis in HNEpCs, and ultimately promoting AR progression. These findings highlight some new insights into the pathogenesis of AR.

Novel Insights into Changes in Gene Expression within the Hypothalamus in Two Asthma Mouse Models: A Transcriptomic Lung-Brain Axis Study

Patients with asthma experience elevated rates of mental illness. However, the molecular links underlying such lung-brain crosstalk remain ambiguous. Hypothalamic dysfunction is observed in many psychiatric disorders, particularly those with an inflammatory component due to many hypothalamic regions being unprotected by the blood-brain barrier. To gain a better insight into such neuropsychiatric sequelae, this study investigated gene expression differences in the hypothalamus following lung inflammation (asthma) induction in mice, using RNA transcriptome profiling. BALB/c mice were challenged with either bacterial lipopolysaccharide (LPS, E. coli) or ovalbumin (OVA) allergens or saline control (n = 7 per group), and lung inflammation was confirmed via histological examination of postmortem lung tissue. The majority of the hypothalamus was micro-dissected, and total RNA was extracted for sequencing. Differential expression analysis identified 31 statistically significant single genes (false discovery rate FDR5%) altered in expression following LPS exposure compared to controls; however, none were significantly changed following OVA treatment, suggesting a milder hypothalamic response. When gene sets were examined, 48 were upregulated and 8 were downregulated in both asthma groups relative to controls. REACTOME enrichment analysis suggests these gene sets are involved in signal transduction metabolism, immune response and neuroplasticity. Interestingly, we identified five altered gene sets directly associated with neurotransmitter signaling. Intriguingly, many of these altered gene sets can influence mental health and or/neuroinflammation in humans. These findings help characterize the links between asthma-induced lung inflammation and the brain and may assist in identifying relevant pathways and therapeutic targets for future intervention.

Back to the future: re-establishing guinea pig in vivo asthma models

Research using animal models of asthma is currently dominated by mouse models. This has been driven by the comprehensive knowledge on inflammatory and immune reactions in mice, as well as tools to produce genetically modified mice. Many of the identified therapeutic targets influencing airway hyper-responsiveness and inflammation in mouse models, have however been disappointing when tested clinically in asthma. It is therefore a great need for new animal models that more closely resemble human asthma. The guinea pig has for decades been used in asthma research and a comprehensive table of different protocols for asthma models is presented. The studies have primarily been focused on the pharmacological aspects of the disease, where the guinea pig undoubtedly is superior to mice. Further reasons are the anatomical and physiological similarities between human and guinea pig airways compared with that of the mouse, especially with respect to airway branching, neurophysiology, pulmonary circulation and smooth muscle distribution, as well as mast cell localization and mediator secretion. Lack of reagents and specific molecular tools to study inflammatory and immunological reactions in the guinea pig has however greatly diminished its use in asthma research. The aim in this position paper is to review and summarize what we know about different aspects of the use of guinea pig in vivo models for asthma research. The associated aim is to highlight the unmet needs that have to be addressed in the future.

Development of multiple features of antigen-induced asthma pathology in a new strain of mast cell deficient BALB/c-KitW-sh/W-sh mice

Mast cell-deficient mice are widely used to identify and quantify contributions of mast cells to diverse biological responses in vivo, including allergic inflammation. However, despite the fact that scores of genes have been identified as modifiers of allergic inflammation, most mast cell-deficient models have been available only on a single genetic background. We transferred the KitW-sh allele onto the BALB/c background to generate BALB/c mast cell-deficient mice (BALB/c-KitW-sh/W-sh). BALB/c-KitW-sh/W-sh mice have dramatically reduced mast cell numbers (0-2% of wild type) in all tissues examined, as well as subtle hematologic differences from the corresponding wild type mice, including splenomegaly with evidence of increased splenic hematopoiesis. We examined in BALB/c-KitW-sh/W-sh mice models of allergic inflammation that are substantially diminished in C57BL/6-KitW-sh/W-sh mast cell-deficient mice. In a model of acute allergic inflammation, i.e., IgE-dependent passive cutaneous anaphylaxis, both ear swelling and leukocyte infiltration were largely or entirely absent in BALB/c-KitW-sh/W-sh mice. In contrast, in two different models of allergic airway inflammation, airway hyperresponsiveness, lung inflammation, and airway remodeling developed robustly in mast cell-deficient BALB/c-KitW-sh/W-sh mice. These results support the conclusion that the importance of mast cell contributions in various models of allergic inflammation may be at least partially determined by genetic background.

The effects of human parvovirus VP1 unique region in a mouse model of allergic asthma

Evidence has indicated that viral infection increases the risk of developing asthma. Although the association of human parvovirus B19 (B19V) or human bocavirus (HBoV) with respiratory diseases has been reported, little is known about the influence of the B19V-VP1u and HBoV-VP1u proteins on the symptoms of asthma. Herein, we investigated the systemic influence of subcutaneously injected B19V-VP1u and HBoV-VP1u recombinant proteins in an OVA-sensitized asthmatic mouse model. A significantly higher Penh ratio and IgE level were detected in the serum, bronchoalveolar lavage fluid (BALF) and the supernatant of a lymphocyte culture from mice treated with HBoV-VP1u or B19V-VP1u than in a lymphocyte culture from OVA-sensitized mice. Significantly higher levels of serum and BALF IgE, total IgG, IgG1, OVA-specific IgE and OVA-specific IgG1 were detected in mice treated with HBoV-VP1u or B19V-VP1u than in OVA-sensitized mice. Conversely, a significantly lower IgG2a level was detected in mice from the HBoV-VP1u or B19V-VP1u groups than in mice from the OVA group. The mice treated with HBoV-VP1u or B19V-VP1u exhibited more significant lung inflammatory indices, including elevated serum and BALF IL-4, IL-5, IL-10 and IL-13 levels; BALF lymphocyte, neutrophil and eosinophil counts, MMP-9 and MMP-2 activity; and the amount of lymphocyte infiltration, relative to those in the control mice or in those sensitized with OVA. These findings demonstrate that the subcutaneous injection of HBoV-VP1u or B19V-VP1u proteins in OVA-sensitized mice result in elevated asthmatic indices and suggest that human parvoviruses may increase the risk of developing airway inflammation in a mouse model of asthma.

Intranasal administration of Lignosus rhinocerotis (Cooke) Ryvarden (Tiger Milk mushroom) extract attenuates airway inflammation in murine model of allergic asthma

Asthma is a chronic inflammatory disorder in the airways that involves the activation of cells and mediators. Lignosus rhinocerotis (Cooke) Ryvardan or Tiger Milk mushroom is a medicinal mushroom that is traditionally used to treat inflammatory diseases including asthma. In this study, the protective effects of intranasal administration of L. rhinocerotis extract (LRE) in ovalbumin (OVA)-induced airway inflammation mouse model were investigated. Mice were sensitized by intraperitoneal (i.p) injection on days 0 and 14, followed by a daily challenge with 1% OVA from days 21 to 27. Following OVA challenge, LRE and dexamethasone were administered via intranasal and i.p. injection respectively. On day 28, the level of serum immunoglobulin (Ig)E, differential cell counts and T-helper (Th) 2 cytokines in bronchoalveolar lavage fluid (BALF) fluid, cell subset population in lung-draining lymph nodes (LNs), leukocytes infiltration and mucus production in the lungs of the animals was measured. Results demonstrated that intranasal administration of LRE significantly suppressed the level of inflammatory cell counts in BALF as well as populations of CD4⁺ T-cells in lung draining LNs. Apart from that, LRE also significantly reduced the level of Th2 cytokines in BALF and IgE in the serum in OVA-induced asthma. Histological analysis also demonstrated the amelioration of leukocytes infiltration and mucus production in the lungs. Overall, these findings demonstrated the attenuation of airway inflammation in the LRE-treated mice therefore suggesting a promising alternative for the management of allergic airway inflammation.

Influence of gender on OVA-induced airway inflammation in C57/B6J mice on a high-fat diet

Overweight/obesity has been suggested as a risk factor for asthma development, and prospective studies have confirmed that high body weight precedes asthma symptoms. However, the nature of the association between overweight/obese status and asthma remains unclear. Animal models of obesity-related asthma are very useful for understanding disease pathophysiology. Although C57/B6J mice are the most widely used animal model for researching obesity-related asthma, gender differences are not always taken into consideration. Therefore, to explore the effect of gender on the development of obesity-related asthma, both female and male C57/B6J mice were used in this study. The mice were fed with a high-fat diet or a low-fat diet as control. Body weight, body length, liver weight, and Lee’s Index were used to evaluate obesity status, and lung histology, lung inflammatory cells infiltration, and inflammatory cytokines in bronchoalveolar lavage fluid (BALF) were examined for asthma evaluation. We found that the mean body weight of male mice on a high-fat diet gradually increased and was significantly higher than control male mice on a low-fat diet ( P < 0.01), while no significant differences were found between female mice at the end of 12 weeks of feeding. Furthermore, the obese asthma group female and male mice exhibited significantly high inflammatory cells infiltration than normal weight or obese female and male mice ( P < 0.01). However, the obese asthma group presented higher Neu infiltration, Th1 cytokine, and interferon gamma (IFNγ) concentrations in BALF than the asthma group in both the genders ( P < 0.01). In conclusion, both female and male mice are suitable for the obesity-related asthma model, although male mice might be more stable. Besides, obesity-related asthma is not Th2 type asthma.

Upregulation of Mas-related G Protein coupled receptor X2 in asthmatic lung mast cells and its activation by the novel neuropeptide hemokinin-1

Hemokinin-1 (HK-1) is a novel neuropeptide produced by human bronchial cells and macrophages and causes contraction of human bronchi ex vivo. It is also generated by antigen/IgE-activated murine mast cells (MCs) and contributes to experimental chronic allergic airway inflammation via the activation of the neurokinin receptor-1 (NK-1R) expressed on murine MCs. We found elevated MC numbers in the lungs of individuals who died from asthma (asthma) when compared to lungs of individuals who died from other causes (non-asthma). Mas-related G Protein coupled receptor X2 (MRGPRX2) is a novel G-protein coupled receptor (GPCR) that is expressed predominantly on human MCs. We detected low level of MRGPRX2 in non-asthma lung MCs but its expression was significantly upregulated in asthma lung MCs. HK-1 caused degranulation in a human MC line (LAD2) and RBL-2H3 cells stably expressing MRGPRX2 and this response was resistant to inhibition by an NK-1R antagonist. However, knockdown of MRGPRX2 in LAD2 cells resulted in substantial inhibition of HK-1-induced degranulation. These findings suggest that while HK-1 contributes to the development of experimental asthma in mice via NK-1R on murine MCs the effect of this neuropeptide on human bronchoconstriction likely reflects the activation of MRGPRX2 on lung MCs. Thus, development of selective MRGPRX2 antagonists could serve as novel target for the modulation of asthma.

Th2 related markers in milk allergic inflammatory mice model, versus OVA

Experimental studies on allergic asthma are limited by the high cost of the administrated allergens. In this study we tested the allergic potency of low fat milk as a cheap substitute to the widely used standard allergen, ovalbumin (OVA). BALB/c female mice (4 weeks old) were sensitized intraperitoneally with low fat milk/or OVA followed by intranasal challenge with the two allergens on days 28 and 29. At day 31, serum, bronchoalveolar lavage fluid (BALF), and lungs were harvested. Mice of the low fat milk model showed infiltration of eosinophils, macrophages, lymphocytes, and neutrophils in BALF comparable to that of the OVA model. Both allergic protocols led to the production of similar numbers of Th2 cells and induced comparable expression of Th2 cytokine (IL-13) as evident by real time PCR for IL-13 and GATA3 (Th2 transcription factor) and confirmed by immunofluorescence for Th2 surface markers (T1/ST2). In addition, both mouse models had similar elevated levels of allergen specific antibody, IgG1 and IgE. Notably, HE, PAS, and LUNA stained lung sections from low fat milk treated mice had higher average pathological scores as compared to OVA treated mice. In conclusion, this study suggests that the low fat milk-induced inflammation showed hallmarks of allergic airway inflammatory model such as eosinophilic influx in BALF, increased numbers of Th2 cells, augmented expression of IL-13, elevated levels of circulatory IgG1 and IgE, signs of robust pulmonary inflammation, and most importantly it is a cheap and promising model for studying acute allergic airway inflammation and acute asthma.

Bupleurum chinense extract ameliorates an OVA-induced murine allergic asthma through the reduction of the Th2 and Th17 cytokines production by inactivation of NFκB pathway

Bupleurum chinense belongs to the Bupleurum spp. family that has been used in traditional herbal medicine for over thousand years. It has been reported to have anti-inflammatory, anti-oxidant, hepato-protective, antipyretic, analgesic, anti-fibrotic and immunomodulatory effect. However, the effect of B. Chinense on allergic asthma remains unclear. This study investigated the immunomodulatory effects of B. Chinense extracts (BCE) on airway inflammation in asthmatic mice model. In the ovalbumin (OVA)-induced allergic asthma model, we evaluated the number of total cells, differential inflammatory cells and the production of proinflammatory cytokines in bronchoalveolar lavage fluid (BALF) and lung homogenate as well as histological structure. The levels of NFκB p65, IκBα, p-NFκB p65, p-IκBα and the total immunoglobulin (Ig) E, anti-OVA IgE, anti-OVA IgG were also examined. The oral administration of 200mg/kg BCE inhibited the accumulation of inflammatory cells especially eosinophils in BALF. Also, BCE regulated the imbalance of Th1, Th2 and Th17-related production, with attenuated the expression of GATA3, IL-1β, IL-4, IL-5, IL-6, TNF-α and RORγt, IL-17A in BALF and lung homogenate, meanwhile, up-regulated the secretion of INF-γ in lung homogenate. The levels of IgE, anti-OVA IgE, anti-OVA IgG1 and anti-OVA IgG2a were also suppressed by BCE treatment in serum. Futhermore, BCE inhibited the proinflammatory cytokines via inactivation of NFκB p65 phosphorylation and IκBα degradation in cytoplasm. The histological analysis showed that the infiltration of inflammatory cells, mucus hypersecretion and collagen fiber deposits were ameliorated in BCE treated mice. In addition, BCE induced the functional differentiation of naive CD4+ T cells forward to Th1 and Tr1 through producing INF-γ and IL-10. These results suggest that BCE may have therapeutic potential for treating allergic asthma through inhibiting Th2/Th17 cytokines production by inactivation of NFκB pathway.

Maternal high-fat diet in mice leads to innate airway hyperresponsiveness in the adult offspring

Maternal obesity prior to and during pregnancy has been associated with an increased incidence of childhood asthma. As diets rich in saturated fat are linked to obesity and inflammation, we created a murine model to investigate the effect of maternal high-fat diet (HFD) on adult offspring airway hyperreactivity (AHR), a cardinal feature of asthma. Balb/cByJ dams were fed a HFD (60% fat Calories) or normal-fat diet (NFD) (10% fat Calories) from 8 weeks prior to first breeding through their pregnancies. Pups were weaned to either a HFD or NFD (at 4 weeks of age). AHR was measured in the 10-week-old offspring following inhaled methacholine challenge by end-inflation technique. Bronchial alveolar lavage fluid (BALF) was analyzed for cell count, total protein, and IL-6. Offspring of HFD dams weaned to NFD had increased AHR compared to offspring of NFD dams weaned to NFD Offspring of HFD dams that remained on HFDs had increased AHR compared to offspring of NFD dams weaned to HFDs. Offspring of HFD dams had higher BALF cell counts, higher neutrophil percentage, greater total protein, and IL-6 in the BALF These results demonstrate that a maternal diet high in saturated fat through pregnancy and lactation plays a key role in programming adult offspring AHR.

The immunoregulatory and fibrotic roles of activin A in allergic asthma

Activin A, a member of the TGF-β superfamily of cytokines, was originally identified as an inducer of follicle stimulating hormone release, but has since been ascribed roles in normal physiological processes, as an immunoregulatory cytokine and as a driver of fibrosis. In the last 10–15 years, it has also become abundantly clear that activin A plays an important role in the regulation of asthmatic inflammation and airway remodelling. This review provides a brief introduction to the activin A/TGF-β superfamily, focussing on the regulation of receptors and signalling pathways. We examine the contradictory evidence for generalized pro- vs. anti-inflammatory effects of activin A in inflammation, before appraising its role in asthmatic inflammation and airway remodelling specifically by evaluating data from both murine models and clinical studies. We identify key issues to be addressed, paving the way for safe exploitation of modulation of activin A function for treatment of allergic asthma and other inflammatory lung diseases.

Regular and moderate aerobic training before allergic asthma induction reduces lung inflammation and remodeling

Experimental studies have reported that aerobic exercise after asthma induction reduces lung inflammation and remodeling. Nevertheless, no experimental study has analyzed whether regular/moderate aerobic training before the induction of allergic asthma may prevent these inflammatory and remodeling processes. For this purpose, BALB/c mice (n = 96) were assigned into non-trained and trained groups. Trained animals ran on a motorized treadmill at moderate intensity, 30 min/day, 3 times/week, for 8 weeks, and were further randomized into subgroups to undergo ovalbumin sensitization and challenge or receive saline using the same protocol. Aerobic training continued until the last challenge. Twenty-four hours after challenge, compared to non-trained animals, trained mice exhibited: (a) increased systolic output and left ventricular mass on echocardiography; (b) improved lung mechanics; (c) decreased smooth muscle actin expression and collagen fiber content in airways and lung parenchyma; (d) decreased transforming growth factor (TGF)-β levels in bronchoalveolar lavage fluid (BALF) and blood; (e) increased interferon (IFN)-γ in BALF and interleukin (IL)-10 in blood; and (f) decreased IL-4 and IL-13 in BALF. In conclusion, regular/moderate aerobic training prior to allergic asthma induction reduced inflammation and remodeling, perhaps through increased IL-10 and IFN-γ in tandem with decreased Th2 cytokines.

Kinin B1 receptor antagonist BI113823 reduces allergen-induced airway inflammation and mucus secretion in mice

Kinin B1 receptors are implicated in asthmatic airway inflammation. Here we tested this hypothesis by examining the anti-inflammatory effects of BI113823, a novel non-peptide orally active kinin B1 receptor antagonist in mice sensitized to ovalbumin (OVA). Male Balb-c mice were randomly assigned to four study groups: (1) control, (2) OVA+vehicle, (3) OVA+BI113823, (4) OVA+dexamethasone. Mice were sensitized intraperitoneally with 75μg ovalbumin on days 1 and 8. On days 15-17, mice were challenged intranasally with 50μg of ovalbumin. Mice received vehicle, BI113823, or dexamethasone (positive control) on days 16-18. On day 19, bronchoalveolar lavage (BAL) and lung tissue were collected for biochemical and immuno-histological analysis. Compared to controls treatment with BI113823 significantly reduced the numbers of BAL eosinophils, macrophages, neutrophils and lymphocytes by 58.3%, 61.1%, 66.4% and 56.0%, respectively. Mice treated with dexamethasone showed similar reductions in BAL cells. Treatment with BI113823 and dexamethasone also significantly reduced total protein content, IgE, TNF-α and IL-1β in lavage fluid, reduced myeloperoxidase activity, mucus secretion in lung tissues, and reduced the expression of B1 receptors, matrix metalloproteinase (MMP)-2 and cyclooxygenase (COX)-2 compared to vehicle-treated mice. Only BI113823 reduced MMP-9 and inducible nitric oxide synthase (iNOS). BI113823 effectively reduced OVA-induced inflammatory cell, mediator and signaling pathways equal to or greater than that seen with steroids in a mouse asthma model. BI113823 might be useful in modulating inflammation in asthma.

Oxyresveratrol ameliorates allergic airway inflammation via attenuation of IL-4, IL-5, and IL-13 expression levels

AIM

Oxyresveratrol is known to possess anti-inflammatory property. Current study investigates the immunosuppressive effect of oxyresveratrol by using mouse model of ovalbumin (OVA)-induced allergic airway inflammation.

METHODS

BALB/c mice were randomly divided into five groups having 8 mice in each group. Treatment with low dose (7 mg/kg) and high dose (15 mg/kg) of oxyresveratrol, and methylprednisolone (15 mg/kg; standard drug) was started 2 week after immunization of mice with ovalbumin and continued for 7d. Ovalbumin was also injected into pinna of right ear 24h before sacrificing the mice to evaluate delayed type hypersensitivity (DTH). H&E and PAS staining were used for histopathological evaluation of lungs. Reverse transcription polymerase chain reaction followed by gel electrophoresis were used for evaluation of mRNA expression levels of IL-4, IL-5, and IL-13.

RESULTS

Oxyresveratrol significantly reduced total leucocyte count in both blood and bronchoalveolar lavage fluid (BALF). Treatment with oxyresveratrol normalized altered eosinophil and neutrophil counts in both blood and BALF. OVA-specific T-cell response was also significantly inhibited by oxyresveratrol. A significant attenuation of inflammatory cell infiltration and goblet cell hyperplasia was observed after treatment with oxyresveratrol. Data showed that oxyresveratrol significantly suppressed Th2 (T helper cells) type immune response which was obvious by the reduction in mRNA expression levels of IL-4, IL-5, and IL-13. Similarly, treatment with methylprednisolone also significantly reduced all the immunomodulatory and inflammatory parameters.

CONCLUSIONS

Our study demonstrates that oxyresveratrol ameliorates allergic asthma. The anti-asthmatic activity might in part occur via the down regulation of IL-4, IL-5, and IL-13 expression levels.

Microfibrillar-associated protein 4 modulates airway smooth muscle cell phenotype in experimental asthma

BACKGROUND

Recently, several proteins of the extracellular matrix have been characterised as active contributors to allergic airway disease. Microfibrillar-associated protein 4 (MFAP4) is an extracellular matrix protein abundant in the lung, whose biological functions remain poorly understood. In the current study we investigated the role of MFAP4 in experimental allergic asthma.

METHODS

MFAP4-deficient mice were subjected to alum/ovalbumin and house dust mite induced models of allergic airway disease. In addition, human healthy and asthmatic primary bronchial smooth muscle cell cultures were used to evaluate MFAP4-dependent airway smooth muscle responses.

RESULTS

MFAP4 deficiency attenuated classical hallmarks of asthma, such as eosinophilic inflammation, eotaxin production, airway remodelling and hyperresponsiveness. In wild-type mice, serum MFAP4 was increased after disease development and correlated with local eotaxin levels. MFAP4 was expressed in human bronchial smooth muscle cells and its expression was upregulated in asthmatic cells. Regarding the underlying mechanism, we showed that MFAP4 interacted with integrin αvβ5 and promoted asthmatic bronchial smooth muscle cell proliferation and CCL11 release dependent on phosphatidyloinositol-3-kinase but not extracellular signal-regulated kinase pathway.

CONCLUSIONS

MFAP4 promoted the development of asthmatic airway disease in vivo and pro-asthmatic functions of bronchial smooth muscle cells in vitro. Collectively, our results identify MFAP4 as a novel contributor to experimental asthma, acting through modulation of airway smooth muscle cells.

Zingiber officinale ameliorates allergic asthma via suppression of Th2-mediated immune response

CONTEXT

Ginger has been used commonly in the traditional system of medicine for the treatment of respiratory disorders.

OBJECTIVE

The present study investigates the immunosuppressive activity of ginger by using the mouse model of ovalbumin-induced allergic asthma.

MATERIALS AND METHODS

Treatment with ethanol extract (500 mg/kg) and aqueous extract (720 mg/kg) of rhizomes, and methylprednisolone (5 mg/kg) was initiated 1 week after second sensitization of mice with ovalbumin and continued for 7 d. RT-PCR followed by gel electrophoresis and ELISA were used for the evaluation of mRNA expression levels and protein levels of Th2 type markers, respectively. Lung tissue histopathology was conducted by using H&E and PAS staining.

RESULTS

We observed significant reduction in goblet cell hyperplasia (0.83 ± 0.17 and 1.0 ± 0.26), infiltration of inflammatory cells in airways (0.67 ± 0.33 and 1.0 ± 0.37), and edema with vascular congestion (1.0 ± 0.26 and 1.2 ± 0.17) by both ethanol and aqueous extracts, respectively. A highly significant reduction of total and differential count of eosinophils and neutrophils in BALF, and eosinophil count in blood were also observed. Both extracts significantly inhibited Th2-mediated immune response, which is evident by a decrease in mRNA expression levels of IL-4 and IL-5. Protein levels of IL-4 and IL-5 in BALF, along with total serum IgE levels, were also significantly suppressed by both extracts.

DISCUSSION AND CONCLUSION

Our study validated the traditional use of ginger in respiratory disorders and suggests that ginger reduces allergic airway inflammation, possibly by the suppression of Th2-mediated immune response.

Key mediators in the immunopathogenesis of allergic asthma

Asthma is described as a chronic inflammatory disorder of the conducting airways. It is characterized by reversible airway obstruction, eosinophil and Th2 infiltration, airway hyper-responsiveness and airway remodeling. Our findings to date have largely been dependent on work done using animal models, which have been instrumental in broadening our understanding of the mechanism of the disease. However, using animals to model a uniquely human disease is not without its drawbacks. This review aims to examine some of the key mediators and cells of allergic asthma learned from animal models and shed some light on emerging mediators in the pathogenesis allergic airway inflammation in acute and chronic asthma.

A mouse model for evaluating the contribution of fibrocytes and myofibroblasts to airway remodeling in allergic asthma

Airway remodeling is a term used to collectively indicate bronchial structural changes that may lead to irreversible airflow obstruction and progressive decline in lung function in asthmatic patients. Bronchial myofibroblasts contribute to airway remodeling by producing collagenous proteins in the subepithelial zone and by increasing the density of contractile cells in the bronchial wall. A substantial proportion of bronchial myofibroblasts in asthma differentiate from circulating mesenchymal progenitor cells known as fibrocytes. Here, we describe a mouse model of allergic asthma for evaluating the functional role of fibrocytes and myofibroblasts in this disease and the inhibitory effects of novel therapeutic candidates.

Absence of c-Jun NH2-terminal kinase 1 protects against house dust mite-induced pulmonary remodeling but not airway hyperresponsiveness and inflammation

Chronic allergic asthma leads to airway remodeling and subepithelial fibrosis via mechanisms not fully understood. Airway remodeling is amplified by profibrotic mediators, such as transforming growth factor-β1 (TGF-β1), which plays a cardinal role in various models of fibrosis. We recently have identified a critical role for c-Jun-NH2-terminal-kinase (JNK) 1 in augmenting the profibrotic effects of TGF-β1, linked to epithelial-to-mesenchymal transition of airway epithelial cells. To examine the role of JNK1 in house dust mite (HDM)-induced airway remodeling, we induced allergic airway inflammation in wild-type (WT) and JNK1-/- mice by intranasal administration of HDM extract. WT and JNK1-/- mice were sensitized with intranasal aspirations of HDM extract for 15 days over 3 wk. HDM caused similar increases in airway hyperresponsiveness, mucus metaplasia, and airway inflammation in WT and JNK1-/- mice. In addition, the profibrotic cytokine TGF-β1 and phosphorylation of Smad3 were equally increased in WT and JNK1-/- mice. In contrast, increases in collagen content in lung tissue induced by HDM were significantly attenuated in JNK1-/- mice compared with WT controls. Furthermore HDM-induced increases of α-smooth muscle actin (α-SMA) protein and mRNA expression as well as the mesenchymal markers high-mobility group AT-hook 2 and collagen1A1 in WT mice were attenuated in JNK1-/- mice. The let-7 family of microRNAs has previously been linked to fibrosis. HDM exposure in WT mice and primary lung epithelial cells resulted in striking decreases in let-7g miRNA that were not observed in mice or primary lung epithelial cells lacking JNK1-/- mice. Overexpression of let-7g in lung epithelial cells reversed the HDM-induced increases in α-SMA. Collectively, these findings demonstrate an important requirement for JNK1 in promoting HDM-induced fibrotic airway remodeling.

In utero exposure to second-hand smoke aggravates the response to ovalbumin in adult mice

Second-hand smoke (SHS) exposure in utero exacerbates adult responses to environmental irritants. We tested the hypothesis that effects of in utero SHS exposure on modulating physiological and transcriptome responses in BALB/c mouse lungs after ovalbumin (OVA) challenge extend well into adulthood, and that the responses show a sex bias. We exposed BALB/c mice in utero to SHS or filtered air (AIR), then sensitized and challenged all offspring with OVA from 19 to 23 weeks of age. At the end of the adult OVA challenge, we evaluated pulmonary function, examined histopathology, analyzed bronchoalveolar lavage fluid (BALF), and assessed gene expression changes in the lung samples. All groups exhibited lung inflammation and inflammatory cell infiltration. Pulmonary function testing (airway hyperresponsiveness [AHR], breathing frequency [f]) and BALF (cell differentials, Th1/Th2 cytokines) assessments showed significantly more pronounced lung responses in the SHS-OVA groups than in AIR-OVA groups (AHR, f; eosinophils, neutrophils; IFN-γ, IL-1b, IL-4, IL-5, IL-10, IL-13, KC/CXCL1, TNF-α), with the majority of responses being more pronounced in males than in females. SHS exposure in utero also significantly altered lung gene expression profiles, primarily of genes associated with inflammatory responses and respiratory diseases, including lung cancer and lung fibrosis. Altered expression profiles of chemokines (Cxcl2, Cxcl5, Ccl8, Ccl24), cytokines (Il1b, Il6, Il13) and acute phase response genes (Saa1, Saa3) were confirmed by qRT-PCR. In conclusion, in utero exposure to SHS exacerbates adult lung responses to OVA challenge and promotes a pro-asthmatic milieu in adult lungs; further, males are generally more affected by SHS-OVA than are females.

HSP70/CD80 DNA vaccine inhibits airway remodeling by regulating the transcription factors T-bet and GATA-3 in a murine model of chronic asthma

INTRODUCTION

Airway remodeling is an important pathologic feature of chronic asthma. T-bet and GATA-3, the key transcription factors for differentiation toward Th1 and Th2 cells, play an important role in the pathogenesis of airway inflammation, airway hyperresponsiveness and airway remodeling. Previous studies showed that HSP70/CD80 DNA vaccine can reduce airway hyperresponsiveness and airway inflammation in acute asthmatic mice. The present study was designed to determine the effect of HSP70/CD80 DNA vaccine on airway remodeling through regulating the development of Th1/Th2.

MATERIAL AND METHODS

Before being sensitized and challenged by ovalbumin, the BALB/c mice were immunized with DNA vaccine. Lung tissues were assessed by histological examinations. Interferon-γ (IFN-γ)/interleukin-4 (IL-4) levels in bronchoalveolar lavage fluid were determined by ELISA and expressions of IFN-γ, IL-4, T-bet and GATA-3 in spleen were evaluated by real-time polymerase chain reaction.

RESULTS

Chronic asthmatic mice had higher airway hyperresponsiveness, a thicker airway wall, more PAS-positive goblet cells, more subepithelial extracellular matrix deposition and more proliferating airway smooth muscle (ASM)-like cells than control mice (p < 0.05). Compared with the chronic asthmatic mice, the treatment with HSP70/CD80 DNA vaccine could reduce airway hyperreactivity, mucus secretion, subepithelial collagen deposition, and smooth muscle cell proliferation (p < 0.05). DNA vaccination also increased levels of IFN-γ/IL-4 in BAL fluid (p < 0.05), and expression of T-bet/GATA-3 in the spleen (p < 0.05).

CONCLUSIONS

HSP70/CD80 DNA vaccine can inhibit airway remodeling through regulating the development of Th1/Th2 subsets in asthmatic mice.

Mast cell chymase modulates IL-33 levels and controls allergic sensitization in dust-mite induced airway inflammation

Mast cells (MCs) are major effector cells contributing to allergic conditions. When activated, they can release large amounts of active proteases, including chymase from their secretory granules. Here we assessed the role of the chymase mouse mast cell protease 4 (mMCP-4) in allergic airway inflammation induced by house-dust mite (HDM) extract. mMCP-4-/-) mice demonstrated elevated airway reactivity and eosinophilia compared with wild-type (WT) animals, suggesting a protective role for mMCP-4 during the late inflammatory phase of the disease. However, mMCP-4 also contributed to the sensitization phase, as indicated by higher levels of serum immunoglobulin E in mMCP-4(-/-) vs. WT mice and higher levels of cytokines secreted by HDM-restimulated mMCP-4(-/-) vs. WT splenocytes. In line with a contribution of mMCP-4 in the early stages of disease, HDM extract directly induced chymase secretion from MCs. The elevated airway and inflammatory responses of mMCP-4(-/-) mice were associated with a profound increase in the levels of interleukin (IL)-33 in the lung tissue. Moreover, WT MCs degraded IL-33 more efficiently than did MCs lacking mMCP-4. Together, our findings identify a protective role of a MC chymase in a physiologically relevant model for airway inflammation and suggest that chymase-mediated regulation of IL-33 can account for this protective function.

Animal models of asthma: reprise or reboot?

Animal models of disease represent the pinnacle of hierarchical research efforts to validate targets and compounds for therapeutic intervention. Yet models of asthma, particularly in the mouse, which, for practical reasons, has become the sine qua non of asthma research, have been a bone of contention for decades. With barely a nod to their limitations and an extensive history of translational failures, they continue to be used for target identification and to justify the clinical evaluation of new compounds. Recent improvements - including sensitization directly to the airways; use of more relevant allergens; development of a chronic rather than short-term condition; utilization of techniques to measure lung function beyond uninterpretable measures of airway hyperresponsiveness - are laudable but cannot bridge the chasm between the models and the myriad complexities of the human disorder and multiple asthma endophenotypes. While further model developments are necessary, including recognition of key environmental factors beyond allergens, the judicious integration with newer ex vivo and in vitro techniques, including human precision-cut lung slices, reprograming of patient-derived induced pluripotent stem cells and fibroblasts to epithelial and smooth muscle cells, and use of other clinical samples to create a more holistic depiction of activities, might improve their translational success.

Eosinophil adoptive transfer system to directly evaluate pulmonary eosinophil trafficking in vivo

Most in vivo studies of granulocytes draw conclusions about their trafficking based on examination of their steady-state tissue/blood levels, which result from a combination of tissue homing, survival, and egress, rather than direct examination of cellular trafficking. Herein, we developed a unique cell transfer system involving the adoptive transfer of a genetically labeled, bone-marrow-derived unique granulocyte population (eosinophils) into an elicited inflammatory site, the allergic lung. A dual polychromatic FACS-based biomarker-labeling system based on the IL4-eGFP transgene (4get) or Cd45.1 allele was used to track i.v. transferred eosinophils into the airway following allergen or T(H)2-associated stimuli in the lung in multiple mouse strains. The system was amenable to reverse tagging of recipients, thus allowing transfer of nonlabeled eosinophils and competitive tracking of multiple populations of eosinophils in vivo. The half-life of eosinophils in the blood was 3 h, and migration to the lung was dependent upon the dosage of transferred eosinophils, sensitive to pertussis toxin pretreatment, peaked at ∼24 h after adoptive transfer, and revealed a greater than 8-d eosinophil half-life in the lung. Eosinophil migration to the lung was dependent upon recipient IL-5 and IL-13 receptor α1 and donor eosinophil C-C chemokine receptor type 3 (CCR3) and interleukin 1 receptor-like 1 (ST2) in vivo. Taken together, this unique eosinophil transfer system provides an unprecedented opportunity to examine airway eosinophil migration without the need for extensive efforts to acquire donor source and time-consuming genetic crossing and has already been used to identify a long eosinophil half-life in the allergic lung and a definite role for ST2 in regulating eosinophil trafficking.

Histophatologic changes of lung in asthmatic male rats treated with hydro-alcoholic extract of Plantago major and theophylline

OBJECTIVE

Plantago major (P. major) is one of the medicinal crops in the world which has therapeutic properties for treatment of respiratory and gastrointestinal diseases. Theophylline is commonly used for the treatment of respiratory diseases. In this study, we investigated the protective effects of hydro-alcoholic extract of P. major on lung in asthmatic male rats.

MATERIALS AND METHODS

32 male adult rats were randomly divided into 4 groups: The control group (C) received normal saline; Asthma (A) group received a normal diet; Asthma group treated with Theophylline (200 mg/kg b.w.) (T); Asthma group which received p.major (100 mg/kg b.w.) (P). Asthma was induced by citric acid, 0.1 mg in form of spraying. The injection of P.major extract and theophylline was administered intraperitoneally for four weeks. At the end of the treatment, all of the rats were sacrificed and lungs were taken out, fixed, and stained with H&E, toluidine blue, and PAS, then histological studies were followed with light microscope.

RESULTS

RESULTS showed that, in asthmatic group, the mean number of mast cells was significantly increased (p<0.05). Thickness of alveolar epithelium and accumulation of glycoprotein in airways was increased. Moreover, in some of alveolar sac hemorrhaging was observed. Administration of p.major extract in asthmatic rats restored these changes towards normal group.

CONCLUSION

The present study revealed that P. major compared with theophylline, has a protective effect on lung in asthmatic rats.

The AGC kinase inhibitor H89 attenuates airway inflammation in mouse models of asthma

BACKGROUND

H89 is a potent inhibitor of Protein Kinase A (PKA) and Mitogen- and Stress-Activated protein Kinase 1 (MSK1) with some inhibitory activity on other members of the AGC kinase family. H89 has been extensively used in vitro but its anti-inflammatory potential in vivo has not been reported to date. To assess the anti-inflammatory properties of H89 in mouse models of asthma.

METHODOLOGY/PRINCIPAL FINDINGS

Mice were sensitized intraperitoneally (i.p.) to ovalbumin (OVA) with or without alum, and challenged intranasally with OVA. H89 (10 mg/kg) or vehicle was given i.p. two hours before each OVA challenge. Airway hyperresponsiveness (AHR) was assessed by whole-body barometric plethysmography. Inflammation was assessed by the total and differential cell counts and IL-4 and IL-5 levels in bronchoalveolar lavage (BAL) fluid. Lung inflammation, mucus production and mast cell numbers were analyzed after histochemistry. We show that treatment with H89 reduces AHR, lung inflammation, mast cell numbers and mucus production. H89 also inhibits IL-4 and IL-5 production and infiltration of eosinophils, neutrophils and lymphocytes in BAL fluid.

CONCLUSIONS/SIGNIFICANCE

Taken together, our findings implicate that blockade of AGC kinases may have therapeutic potential for the treatment of allergic airway inflammation.

Are mouse models of asthma appropriate for investigating the pathogenesis of airway hyper-responsiveness?

Whether mouse models of chronic asthma can be used to investigate the relationship between airway inflammation/remodeling and airway hyper-responsiveness (AHR) is a vexed question. It raises issues about the extent to which such models replicate key features of the human disease. Here, we review some of the characteristic pathological features of human asthma and their relationship to AHR and examine some limitations of mouse models that are commonly used to investigate these relationships. We compare these conventional models with our mouse model of chronic asthma involving long-term low-level inhalational challenge and review studies of the relationship between inflammation/remodeling and AHR in this model and its derivatives, including models of an acute exacerbation of chronic asthma and of the induction phase of childhood asthma. We conclude that while extrapolating from studies in mouse models to AHR in humans requires cautious interpretation, such experimental work can provide significant insights into the pathogenesis of airway responsiveness and its molecular and cellular regulation.

The translational repressor T-cell intracellular antigen-1 (TIA-1) is a key modulator of Th2 and Th17 responses driving pulmonary inflammation induced by exposure to house dust mite

T-cell intracellular antigen-1 (TIA-1) is a translational repressor that dampens the production of proinflammatory cytokines and enzymes. In this study we investigated the role of TIA-1 in a mouse model of pulmonary inflammation induced by exposure to the allergenic extract (Df) of the house dust mite Dermatophagoides farinae. When intranasally challenged with a low dose of Df, mice lacking TIA-1 protein (Tia-1(-/-)) showed more severe airway and tissue eosinophilia, infiltration of lung bronchovascular bundles, and goblet cell metaplasia than wild-type littermates. Tia-1(-/-) mice also had higher levels of Df-specific IgE and IgG(1) in serum and ex vivo restimulated Tia-1(-/-) lymph node cells and splenocytes transcribed and released more Th2/Th17 cytokines. To evaluate the site of action of TIA-1, we studied the response to Df in bone marrow chimeras. These experiments revealed that TIA-1 acts on both hematopoietic and non-hematopoietic cells to dampen pulmonary inflammation. Our results identify TIA-1 as a negative regulator of allergen-mediated pulmonary inflammation in vivo. Thus, TIA-1 might be an important player in the pathogenesis of bronchial asthma.

Macrophage colony stimulating factor and monocyte chemoattractant protein 2 are elevated in intrinsic asthmatics

BACKGROUND

Intrinsic asthma, etiology unknown, occurs later in life, mostly in females. It is associated with nasal polyps and massive eosinopillic infiltration of the respiratory mucous membrane, aspirin intolerance and steroid dependence. The aim of the study was to determine the cytokine and chemokine profile in sera of intrinsic asthmatics and control subjects.

METHODS

Blood was taken from 10 intrinsic asthmatic female and 12 control female subjects. Expression profile of 42 different cytokines and chemokines were measured using a microarray composed of antibodies against the cytokines and chemokines. Complete blood count and C-reactive protein were measured, to assess the state of inflammation in both groups.

RESULTS

We have identified Macrophage Colony Stimulating Factor, a proinflammatory cytokine and Monocyte Chemoattractant Protein 2, a CC chemokine as having significantly higher expression levels in intrinsic asthmatic subjects compared to controls (341.71±31.28 SEM Signal intensity) versus (247.97±28.09 SEM Signal intensity), p=0.036 and (397.07±38.19 SEM Signal intensity) versus (311.33±28.76 SEM Signal intensity), p=0.036, respectively. There were no significant differences in the other cytokines and chemokines measured nor were there any differences in the inflammatory measurements between the two groups except for eosinophil counts, the hall mark of intrinsic asthma.

CONCLUSION

Macrophage Colony Stimulating Factor and Monocyte Chemoattractant Protein are elevated in sera of intrinsic asthmatics compared to normal controls. These cytokines may have a critical role in the inflammatory pathology of intrinsic asthma.

Lung gene expression in a rhesus allergic asthma model correlates with physiologic parameters of disease and exhibits common and distinct pathways with human asthma and a mouse asthma model

Experimental nonhuman primate models of asthma exhibit multiple features that are characteristic of an eosinophilic/T helper 2 (Th2)-high asthma subtype, characterized by the increased expression of Th2 cytokines and responsive genes, in humans. Here, we determine the molecular pathways that are present in a house dust mite-induced rhesus asthma model by analyzing the genomewide lung gene expression profile of the rhesus model and comparing it with that of human Th2-high asthma. We find that a prespecified human Th2 inflammation gene set from human Th2-high asthma is also present in rhesus asthma and that the expression of the genes comprising this gene set is positively correlated in human and rhesus asthma. In addition, as in human Th2-high asthma, the Th2 gene set correlates with physiologic markers of allergic inflammation and disease in rhesus asthma. Comparison of lung gene expression profiles from human Th2-high asthma, the rhesus asthma model, and a common mouse asthma model indicates that genes associated with Th2 inflammation are shared by all three species. However, some pathophysiologic aspects of human asthma (ie, subepithelial fibrosis, angiogenesis, neural biology, and immune host defense biology) are better represented in the gene expression profile of the rhesus model than in the mouse model. Further study of the rhesus asthma model may yield novel insights into the pathogenesis of human Th2-high asthma.

Asthma treatment through the beta receptor: lessons from animal models

Asthma is a significant health problem worldwide with a prevalence that continues to rise and for which there is no cure. Animal models have been used for decades to investigate the cause and cures of asthma, and while they do not always mimic many of the facets of this syndrome, mechanistic animal studies are still nevertheless very useful. Animal studies with beta-agonists suggest much broader and perhaps more important roles for beta-agonists since beta-agonists reduce aspects of inflammation and may affect structural remodeling. Studies using enantiomers of beta-agonists provide a confusing picture of the degree and mechanism of the deleterious effects of racemic mixtures and/or the S-enantiomer or other classes of beta-agonists. Neural mechanisms are implicated. The future holds a promise of even more insight into the mechanisms of the acute and chronic role of the beta-adrenoceptor, asthma therapeutics, in particular, beta-agonists that will lead to a better understanding of the pathogenesis and treatment of asthma.

Genetic variation determines mast cell functions in experimental asthma

Mast cell-deficient mice are a key for investigating the function of mast cells in health and disease. Allergic airway disease induced as a Th2-type immune response in mice is employed as a model to unravel the mechanisms underlying inception and progression of human allergic asthma. Previous work done in mast cell-deficient mouse strains that otherwise typically mount Th1-dominated immune responses revealed contradictory results as to whether mast cells contribute to the development of airway hyperresponsiveness and airway inflammation. However, a major contribution of mast cells was shown using adjuvant-free protocols to achieve sensitization. The identification of a traceable genetic polymorphism closely linked to the Kit(W-sh) allele allowed us to generate congenic mast cell-deficient mice on a Th2-prone BALB/c background, termed C.B6-Kit(W-sh). In accordance with the expectations, C.B6-Kit(W-sh) mice do not develop IgE- and mast cell-dependent passive cutaneous anaphylaxis. Yet, unexpectedly, C.B6-Kit(W-sh) mice develop full-blown airway inflammation, airway hyperresponsiveness, and mucus production despite the absence of mast cells. Thus, our findings demonstrate a major influence of genetic background on the contribution of mast cells in an important disease model and introduce a novel strain of mast cell-deficient mice.

Hyaluronan deposition and correlation with inflammation in a murine ovalbumin model of asthma

Asthma is a chronic inflammatory disease of the airways characterized by airway remodeling, which includes changes in the extracellular matrix (ECM). However the role of the ECM in mediating these changes is poorly understood. Hyaluronan (HA), a major component of the ECM, has been implicated in asthma as well as in many other biological processes. Our study investigates the processes involved in HA synthesis, deposition, localization and degradation during an acute and chronic murine model of ovalbumin (OVA)-induced allergic pulmonary inflammation. Mice were sensitized, challenged to OVA and sacrificed at various time points during an 8-week challenge protocol. Bronchoalveolar lavage (BAL) fluids, blood, and lung tissue were collected for study. RNA, HA, protein and histopathology were analyzed. Analyses of lung sections and BAL fluids revealed an early deposition and an increase in HA levels within 24 h of antigen exposure. HA levels peaked at day 8 in BAL, while inflammatory cell recovery peaked at day 6. Hyaluronan synthase (HAS)1 and HAS2 on RNA levels peaked within 2 h of antigen exposure, while hyaluronidase (HYAL)1 and HYAL2 on RNA levels decreased. Both inflammatory cell infiltrates and collagen deposition co-localized with HA deposition within the lungs. These data support a role for HA in the pathogenesis of inflammation and airway remodeling in a murine model of asthma. HA deposition appears largely due to up regulation of HAS1 and HAS2. In addition, HA appears to provide the scaffolding for inflammatory cell accumulation as well as for new collagen synthesis and deposition.

Mast cells in allergic asthma and beyond

Mast cells have been regarded for a long time as effector cells in IgE mediated type I reactions and in host defence against parasites. However, they are resident in all environmental exposed tissues and express a wide variety of receptors, suggesting that these cells can also function as sentinels in innate immune responses. Indeed, studies have demonstrated an important role of mast cells during the induction of life-saving antibacterial responses. Furthermore, recent findings have shown that mast cells promote and modulate the development of adaptive immune responses, making them an important hinge of innate and acquired immunity. In addition, mast cells and several mast cell-produced mediators have been shown to be important during the development of allergic airway diseases. In the present review, we will summarize findings on the role of mast cells during the development of adaptive immune responses and highlight their function, especially during the development of allergic asthma.

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.

Pathogenic mechanisms of allergic inflammation: atopic asthma as a paradigm

Prospective studies tracking birth cohorts over periods of years indicate that the seeds for atopic asthma in adulthood are sewn during early life. The key events involve programming of functional phenotypes within the immune and respiratory systems which determine long-term responsiveness to ubiquitous environmental stimuli, particularly respiratory viruses and aeroallergens. A crucial component of asthma pathogenesis is early sensitization to aeroallergens stemming from a failure of mucosal tolerance mechanisms during the preschool years, which is associated with delayed postnatal maturation of a range of adaptive and innate immune functions. These maturational defects also increase risk for severe respiratory infections, and the combination of sensitization and infections maximizes risk for early development of the persistent asthma phenotype. Interactions between immunoinflammatory pathways stimulated by these agents also sustain the disease in later life as major triggers of asthma exacerbations. Recent studies on the nature of these interactions suggest the operation of an infection-associated lung:bone marrow axis involving upregulation of FcERlalpha on myeloid precursor populations prior to their migration to the airways, thus amplifying local inflammation via IgE-mediated recruitment of bystander atopic effector mechanisms. The key participants in the disease process are airway mucosal dendritic cells and adjacent epithelial cells, and transiting CD4(+) effector and regulatory T-cell populations, and increasingly detailed characterization of their roles at different stages of pathogenesis is opening up novel possibilities for therapeutic control of asthma. Of particular interest is the application of genomics-based approaches to drug target identification in cell populations of interest, exemplified by recent findings discussed below relating to the gene network(s) triggered by activation of Th2-memory cells from atopics.

Strain-dependent activation of NF-kappaB in the airway epithelium and its role in allergic airway inflammation

NF-kappaB activation in the airway epithelium has been established as a critical pathway in ovalbumin (Ova)-induced airway inflammation in BALB/c mice (Poynter ME, Cloots R, van Woerkom T, Butnor KJ, Vacek P, Taatjes DJ, Irvin CG, Janssen-Heininger YM. J Immunol 173: 7003-7009, 2004). BALB/c mice are susceptible to the development of allergic airway disease, whereas other strains of mice, such as C57BL/6, are considered more resistant. The goal of the present study was to determine the proximal signals required for NF-kappaB activation in the airway epithelium in allergic airway disease and to unravel whether these signals are strain-dependent. Our previous studies, conducted in the BALB/c mouse background, demonstrated that transgenic mice expressing a dominant-negative version of IkappaBalpha in the airway epithelium (CC10-IkappaBalpha(SR)) were protected from Ova-induced inflammation. In contrast to these earlier observations, we demonstrate here that CC10-IkappaBalpha(SR) transgenic mice on the C57BL/6 background were not protected from Ova-induced allergic airway inflammation. Consistent with this finding, Ova-induced nuclear localization of the RelA subunit of NF-kappaB was not observed in C57BL/6 mice, in contrast to the marked nuclear presence of RelA in BALB/c mice. Evaluation of cytokine profiles in bronchoalveolar lavage demonstrated elevated expression of TNF-alpha in BALB/c mice compared with C57BL/6 mice after an acute challenge with Ova. Finally, neutralization of TNF-alpha by a blocking antibody prevented nuclear localization of RelA in BALB/c mice after Ova challenge. These data suggest that the mechanism of response of the airway epithelium of immunized C57BL/6 mice to antigen challenge is fundamentally different from that of immunized BALB/c mice and highlight the potential importance of TNF-alpha in regulating epithelial NF-kappaB activation in allergic airway disease.

Mast cell modulation of the immune response

Mast cells are present in nearly all vascularized tissues, but not the blood. They are best known for the prominent role they play in atopic disease. However, our current understanding of their direct and indirect roles in the immune response offers a more nuanced picture of both villain and hero. Although they are implicated in many inflammatory disorders, they also defend us from bacterial pathogens, prevent dangerous overreactions by the immune system, and even protect us from snake venom. Perhaps there is more to these maligned cells than we thought.

Mouse mast cell protease 4 is the major chymase in murine airways and has a protective role in allergic airway inflammation

It is widely established that mast cells (MCs) have a harmful role in asthma, for example by secreting various proinflammatory substances stored within their secretory granule. However, in this study, we show that one of the substances stored within MC granule, chymase, in fact has a protective role in allergic airway inflammation, indicating that MCs may possess both harmful and protective activities in connection with this type of disease. Wild-type (WT) mice and mice lacking mouse MC protease 4 (mMCP-4), a chymase that is functionally homologous to human chymase, were sensitized and challenged with OVA, followed by the assessment of airway physiology and inflammatory parameters. Our results show that the airway hyperresponsiveness was significantly higher in mMCP-4(-/-) as compared with WT mice. Moreover, the degree of lung tissue inflammation was markedly higher in mice lacking mMCP-4 than in WT controls. Histological analysis revealed that OVA sensitization/challenge resulted in a marked increased in the thickness of the smooth muscle cell (SMC) layer and, notably, that the degree of SMC layer thickening was more pronounced in mMCP-4(-/-) animals than in WT controls, thus indicating that chymase may have an effect on airway SMCs. In support of this, mMCP-4-positive MCs were located in the close vicinity of the SMC layer, mainly in the upper airways, and mMCP-4 was shown to be the major chymase expressed in these MCs. Taken together, our results indicate that chymase present in the upper airways protects against allergic airway responses, possibly by regulating SMCs.

Understanding asthma using animal models

Asthma is a complex syndrome with many clinical phenotypes in children and adults. Despite the rapidly increasing prevalence, clinical investigation and epidemiological studies of asthma, the successful introduction of new drugs has been limited due to the different disease phenotypes and ethical issues. Mouse models of asthma replicate many of the features of human asthma, including airway hyperreactivity, and airway inflammation. Therefore, examination of disease mechanisms in mice has been used to elucidate asthma pathology and to identify and evaluate new therapeutic agents. In this article, we discuss the various animal models of asthma with a focus on mouse strains, allergens, protocols, and outcome measurements.

Mouse models of allergic asthma: acute and chronic allergen challenge

Asthma is defined as a chronic inflammatory disease of the airways; however, the underlying physiological and immunological processes are not fully understood. Animal models have been used to elucidate asthma pathophysiology, and to identify and evaluate novel therapeutic targets. Several recent review articles (Epstein, 2004; Lloyd, 2007; Boyce and Austen, 2005; Zosky and Sly, 2007) have discussed the potential value of these models. Allergen challenge models reproduce many features of clinical asthma and have been widely used by investigators; however, the majority involve acute allergen challenge procedures. It is recognised that asthma is a chronic inflammatory disease resulting from continued or intermittent allergen exposure, usually via inhalation, and there has been a recent focus on developing chronic allergen exposure models, predominantly in mice. Here, we review the acute and chronic exposure mouse models, and consider their potential role and impact in the field of asthma research.

Regulatory T cells in bronchial asthma

The main focus of this review was the role of a specific subset of T cells with immunomodulatory or immunosuppressive activities, termed regulatory T cells (Tregs), in the pathogenesis and treatment of bronchial asthma. Evidence that these cells are important in maintaining immune homeostasis in health and exhibit impaired activity in active disease will be discussed. Their therapeutic potential is perhaps best highlighted by evidence that therapies with demonstrated efficacy in allergic and asthmatic disease are associated with the induction or restoration of regulatory T-cell function, e.g. glucocorticoids, allergen immunotherapy. Strategies to improve the safety and efficacy of these treatments and that induce or boost Tregs in bronchial asthma are discussed.

Helminths and our immune system: friend or foe?

Helminths are able to modulate and suppress the hosts' immune response in order to promote their own survival. This ability to alter immune responses could be of potential detriment to the host if it interferes with the development of protective immune responses against other infections. However, helminth infections have also been suggested to be beneficial in the control of excessive inflammatory reactions. In this review I will highlight some of the data suggesting both positive and negative effects of helminth infections in humans and in experimental models.

Targeting eosinophils in asthma

Recruitment of eosinophils has long been recognized as a hallmark of the inflammatory response in asthma. However, the functions of this population of cells in host defense remain poorly understood. Eosinophils play an important part in the inflammatory response and have key regulatory roles in the afferent arm of the immune response. More recently, eosinophils have been demonstrated to participate in host defense against respiratory viruses. The specific contributions of eosinophils to the pathophysiology of asthma remain controversial. However, the balance of evidence indicates that they have a significant role in the disease, suggesting that they may be appropriate targets for therapy. Towards this end, a novel intervention of considerable potential interest is the use of an antibody directed against the beta common chain of the receptor for interleukin-3, interleukin-5 and granulocyte-macrophage colony-stimulating factor. However, eliminating eosinophils may not be a risk-free therapeutic strategy, as there is potentially an increased likelihood of respiratory viral infections. This may predispose to the development of acute exacerbations of asthma, an outcome that would have significant clinical implications.

Is allergic disease curable or transferable with allogeneic hematopoietic cell transplantation?

In the pathogenesis of allergic asthma/rhinitis, 2 main types of cells play a role: hematolymphatic cells (mast cells, eosinophils, T cells, B cells) and nonhematolymphatic cells (airway smooth muscle cells, epithelial cells). It is not known which one of the 2 cell types plays the primary role. Here we review the literature on allergic disease transfer and potential cure with allogeneic hematopoietic cell transplantation (HCT), as transferability and curability would support a primary role of hematolymphatic cells and have implications for donor selection for HCT and possible future treatment of severe allergic disease with HCT. A total of 18 nonallergic recipients were reported to develop allergic disease after transplantation; however, conclusive information for transfer was available for only 5 cases. Allergic disease was reported to abate in 3 allergic recipients; however, conclusive information for "cure" was available for only 2 cases. Problems in interpreting the reports include incomplete data on allergic disease in the donor or recipient before transplantation, not knowing the denominator, and the lack of controls. In summary, review of the literature generates the hypothesis that allergic disease is transferable and curable with HCT. A prospective study, including appropriate controls, is needed to evaluate this hypothesis.