Eotaxin/CCL11 is involved in acute, but not chronic, allergic airway responses to Aspergillus fumigatus

Serum Calprotectin Is a Potential Marker in Patients with Asthma

BACKGROUND

Calprotectin is the major cytosolic protein in neutrophil granulocytes. Although asthma is known to cause eosinophilic inflammation, some patients with asthma have non-eosinophilic inflammation, which is characterized by local neutrophilic inflammation. The aim of this study was to assess calprotectin expression levels in a mouse model of asthma, and to observe the relationship of serum calprotectin level and clinical variables in patients with asthma.

METHODS

Mice were sensitized and challenged with 10 μg and 20 μg of Aspergillus fumigatus, respectively; mice treated with saline were used as a control. The levels of calprotectin were determined using enzyme-linked immunosorbent assay, immunoblotting, and immunohistochemical analysis. The serum levels of calprotectin were also assessed in patients with asthma. The relationship between calprotectin and clinicopathological characteristics was determined.

RESULTS

Calprotectin, S100A8, and S100A9 expression was elevated in the mouse lungs, calprotectin levels were higher in the serum of patients with asthma (n = 33) compared with those of healthy individuals (n = 28). Calprotectin levels correlated with forced expiratory volume in one second/forced vital capacity (r = -0.215, P = 0.043), smoke amount (r = 0.413, P = 0.017), body mass index (r = -0.445, P = 0.000), and blood neutrophil percentage (r = 0.300, P = 0.004) in patients with asthma.

CONCLUSION

Our data suggest that calprotectin could potentially be used as a biomarker for asthma.

Relationship between chemokines and T lymphocytes in the context of respiratory allergies (Review)

Allergic diseases have been classified in the last decades using various theories. The main classes of the newest classification in allergic respiratory diseases focus on the characterization of the endotype (which takes into account biomarkers related to determinant pathophysiological mechanisms) and of the phenotype (based on the description of the disease). Th2, Th1 and Th17 lymphocytes and the type of inflammatory response mediated by them represent the basis for Th2 and non-Th2 endotype classification. In addition, new lymphocytes were also used to characterize allergic diseases: Th9 lymphocytes, Th22 lymphocytes, T follicular helper cells (T_FH) lymphocytes and invariant natural killer T (iNKT) lymphocytes. In the last decade, a growing body of evidence focused on chemokines, chemoattractant cytokines, which seems to have an important contribution to the pathogenesis of this pathology. This review presents the interactions between chemokines and Th lymphocytes in the context of Th2/non-Th2 endotype classification of respiratory allergies.

Eosinophils in fungal diseases: An overview

Eosinophils are the prominent cells in asthma, allergic bronchopulmonary mycosis (ABPMs), and fungal-sensitization-associated asthma, but their roles in the immunopathology of these disorders are not well understood. Moreover, the immunological mechanisms underlying the molecular direct effector interactions between fungi and eosinophils are rare and not fully known. Here, we provide an overview of eosinophil contributions to allergic asthma and ABPMs. We also revise the major general mechanisms of fungal recognition by eosinophils and consider past and recent advances in our understanding of the molecular mechanisms associated with eosinophil innate effector responses to different fungal species relevant to ABPMs (Alternaria alternata, Candida albicans, and Aspergillus fumigatus). We further examine and speculate about the therapeutic relevance of these findings in fungus-associated allergic pulmonary diseases.

Phosphoinositide 3-kinase-δ regulates fungus-induced allergic lung inflammation through endoplasmic reticulum stress

Background

Sensitisation with Aspergillus fumigatus (Af) is known to be associated with severe allergic lung inflammation, but the mechanism remains to be clarified. Phosphoinositide 3-kinase (PI3K)-δ and endoplasmic reticulum (ER) stress are suggested to be involved in steroid-resistant lung inflammation. We aimed to elucidate the role of PI3K-δ and its relationship with ER stress in fungus-induced allergic lung inflammation.

Methods

Using Af-exposed in vivo and in vitro experimental systems, we examined whether PI3K-δ regulates ER stress, thereby contributing to steroid resistance in fungus-induced allergic lung inflammation. Moreover, we checked expression of an ER stress marker in lung tissues isolated from patients with allergic bronchopulmonary aspergillosis.

Results

Af-exposed mice showed that ER stress markers, unfolded protein response (UPR)-related proteins, phosphorylated Akt, generation of mitochondrial reactive oxygen species (mtROS), eosinophilic allergic inflammation, and airway hyperresponsiveness (AHR) were increased in the lung. Similarly, glucose-regulated protein 78 was increased in lung tissues of patients with ABPA. A PI3K-δ inhibitor reduced Af-induced increases in ER stress markers, UPR-related proteins, allergic inflammation and AHR in mice. However, dexamethasone failed to reduce Af-induced allergic inflammation, AHR and elevation of ER stress. Administration of an ER stress inhibitor or a mtROS scavenger improved Af-induced allergic inflammation. The PI3K-δ inhibitor reduced Af-induced mtROS generation and the mtROS scavenger ameliorated ER stress. In primary cultured tracheal epithelial cells, Af-induced ER stress was inhibited by blockade of PI3K-δ.

Conclusions

These findings suggest that PI3K-δ regulates Af-induced steroid-resistant eosinophilic allergic lung inflammation through ER stress.

Eosinophils in fungus-associated allergic pulmonary disease

Asthma is frequently caused and/or exacerbated by sensitization to fungal allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma with fungal sensitization is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen that is worsened by environmental exposure to airborne fungi and which leads to a disease course that is often very difficult to treat with standard asthma therapies. As a result of complex interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to fungal allergens may experience a greater degree of airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. From their development in the bone marrow to their recruitment to the lung via chemokine and cytokine networks, eosinophils form an important component of the inflammatory milieu that is associated with this syndrome. Eosinophils are recognized as complex multi-factorial leukocytes with diverse functions in the context of allergic fungal asthma. In this review, we will consider recent advances in our understanding of the molecular mechanisms that are associated with eosinophil development and migration to the allergic lung in response to fungal inhalation, along with the eosinophil’s function in the immune response to and the immunopathology attributed to fungus-associated allergic pulmonary 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.

Gene expression profiling and network analysis of peripheral blood monocytes in a chronic model of allergic asthma

The Aspergillus fumigatus mouse model of asthma mimics the characteristics of human fungal asthma, including local and systemic inflammation. Monocyte/macrophage lineage cells direct innate immune responses and guide adaptive responses. To identify gene expression changes in peripheral blood monocytes in the context of fungal allergy, mice were exposed to systemic and intranasal inoculations of fungal antigen (sensitized), and naïve and sensitized animals were challenged intratracheally with live A. fumigatus conidia. Microarray analysis of blood monocytes from allergic versus non-allergic mice showed ≥ twofold modulation of 45 genes. Ingenuity pathway analysis revealed a network of these genes involved in antigen presentation, inflammation, and immune cell trafficking. These data show that allergen sensitization and challenge affects gene expression in peripheral monocytes.

Preventive and therapeutic anti-inflammatory properties of the sesquiterpene alpha-humulene in experimental airways allergic inflammation

BACKGROUND AND PURPOSE

alpha-Humulene and trans-caryophyllene are plant sesquiterpenes with pronounced anti-inflammatory properties. Here, we evaluated the effects of these compounds in an experimental model of airways allergic inflammation.

EXPERIMENTAL APPROACH

Female BALB/c mice, sensitized to and challenged with ovalbumin received daily alpha-humulene or trans-caryophyllene (50 mg.kg(-1), orally) or alpha-humulene (1 mg.mL(-1), by aerosol) as either a preventive (for 22 days) or therapeutic (from the 18th to the 22nd day) treatment. Dexamethasone or budesonide was used as a positive control drug. Inflammation was determined on day 22 post-immunization by leukocyte recruitment, interleukin-5 (IL-5), CCL11, interferon-gamma (IFN-gamma) and leukotriene (LT)B(4) levels in bronchoalveolar lavage fluid (BALF). In addition, transcription factors [nuclear factor kappaB (NF-kappaB), activator protein 1 (AP-1)] and P-selectin in lung tissue were measured by immunohistochemistry and mucus secretion by histochemistry.

KEY RESULTS

Preventive or therapeutic treatments with alpha-humulene, but not with trans-caryophyllene, significantly reduced the eosinophil recruitment to the BALF. In addition, alpha-humulene recovery INF-gamma and reduced the IL-5, CCL11 and LTB(4) levels in BALF, as well as the IL-5 production in mediastinal lymph nodes (in vitro assay). Furthermore, alpha-humulene decreased the NF-kB and the AP-1 activation, the expression of P-selectin and the increased mucus secretion in the lung.

CONCLUSIONS AND IMPLICATIONS

alpha-Humulene, given either orally or by aerosol, exhibited marked anti-inflammatory properties in a murine model of airways allergic inflammation, an effect that seemed to be mediated via reduction of inflammatory mediators, adhesion molecule expression and transcription factors activation.

Creation and characterization of an IgG1-type monoclonal antibody against intact Aspergillus fumigatus conidia

The inability to accurately mimic and track the natural mechanisms of sensitization, challenge, and clearance in experimental models of allergic asthma restricts the ability to identify potential therapeutic targets and elucidate basic biological mechanisms of this prominent human disease. Use of a clinically relevant fungal allergen, such as Aspergillus fumigatus, allows researchers to follow an allergen's uptake and clearance from the lung. Unfortunately, there are currently limited resources to specifically visualize or sensitively quantify a small number of fungal conidia in the lung. In this study, we have created and characterized an IgG1 isotype monoclonal antibody produced against the intact conidia of A. fumigatus for the purpose of developing specific detection and quantification techniques.

Biologic therapies for the treatment of asthma

Asthma is a chronic disease of the airway whose pathogenesis involves the complex interplay between many cell types and inflammatory mediators. The mainstays of therapy, inhaled bronchodilators and corticosteroids, do not target the asthmatic airway specifically and therefore are associated with untoward side effects. Anti-IgE (omalizumab) is the only biologic therapy to have transitioned completely from bench to bedside. Other candidate therapies, such as those that alter the T-helper 1/T-helper 2 cytokine balance, interfere with inflammatory cell trafficking, or modify normal intracellular signaling cascades involved in inflammatory gene transcription, have had only limited success in human clinical trials. This article describes several potential novel biologic therapies that have been or could be investigated.

What targets have knockouts revealed in asthma?

There have been numerous studies of mice rendered genetically deficient of various genes in the context of allergic inflammatory airway disease. These studies have provided invaluable information about basic immune processes, but have also been considered to be useful in predicting novel pharmacological targets. In this review, the effect of a wide range of individual knockouts (KO) on the development of asthma-like pathologies in mice is compiled and considered. How the results of these studies compare with effects of agents that interfere with the function of each gene product, where known, is also described. Finally, a personal view of the utility of these studies in drug development is presented.

Chemokine receptors: understanding their role in asthmatic disease

The incidence, prevalence, and severity of asthma have been increasing steadily in recent years. Prophylactic treatment of this disease and of episodic asthmatic flares is aimed at preventing excessive inflammation in lung tissue and airways. Because chemokines and chemokine receptors are critical mediators of leukocyte trafficking and recruitment, there is the potential to pharmaceutically target these proteins to regulate inflammation. Asthma-associated inflammation is characterized by the infiltration of eosinophils and T helper type 2 cells. Early studies investigated the role of chemokine receptors, which have been shown to predominate on these cell populations.

Chemokines and cytokines: axis and allies in asthma and allergy

Allergic asthma can be precipitated by many factors. For the atopic person, fungus, pollen, dust mites, cockroach antigens, and diesel exhaust are all agents that may trigger an allergic attack. Cytokines and chemokines are integral mediators of fungal asthma. From the earliest time points, they recruit and activate the cells required for the clearance of fungus as well as being critical factors involved in the immunopathology of this disease. In the final analysis, it is clear that these mediators can act to the benefit or the detriment of the host.

Mannose-binding lectin deficiency alters the development of fungal asthma: effects on airway response, inflammation, and cytokine profile

Aspergillus fumigatus is a major fungal pathogen that may be fatal to immunocompromised individuals and causes airway hyperreactivity and remodeling in sensitized individuals. Herein, we examined the role of mannose-binding lectin (MBL), a complement-activating plasma protein, during pulmonary innate and allergic immune responses directed against A. fumigatus spores or conidia. Neither group of nonsensitized MBL-A-sufficient (MBL-A+/+) nor -deficient (MBL-A-/-) mice challenged with an intravenous or intratracheal (i.t.) bolus of A. fumigatus spores experienced fungus-induced mortality, but marked airway remodeling was observed in MBL-A-/- mice challenged i.t. with conidia. In a model of chronic fungal asthma, MBL-A+/+ and MBL-A-/- A. fumigatus-sensitized mice were examined at days 4 and 28 after an i.t. challenge with A. fumigatus conidia. Airway hyperresponsiveness in sensitized MBL-A-/- mice was significantly decreased at both times after conidia challenge compared with the sensitized MBL-A+/+ group. In the sensitized MBL-A-/- mice, whole lung T helper cell type 2 cytokine levels were significantly decreased at day 4 after conidia, and whole lung interferon-gamma levels were significantly increased at day 28 after conidia when compared with controls. However, histological evidence showed similar airway remodeling at day 28 after conidia (i.e., subepithelial fibrosis and goblet cell metaplasia) in the two groups of mice. Thus, these findings show that MBL-A is not required for mouse survival following exposure to A. fumigatus conidia, and this murine collectin isoform contributes to the development and maintenance of airway hyperresponsiveness but not chronic airway remodeling during chronic fungal asthma.

Reversal of allergic airway hyperreactivity after long-term allergen challenge depends on gammadelta T cells

Long-term allergen exposure can attenuate inflammation and revert airway hyperreactivity to normal responsiveness. A model of such reversal was established in which airway hyperreactivity and inflammation in ovalbumin-sensitized and challenged mice were decreased after multiple daily airway challenges. This change in responsiveness and inflammation was associated with a transition from a helper T cell Type 2 to a helper T cell Type 1 cytokine-biased profile in bronchoalveolar lavage fluid. Cell transfer from long-term exposed mice into hyperreactive mice also restored normal airway responsiveness, establishing the mechanism underlying the reversal of the hyperreactivity as active suppression, but did not affect eosinophilic airway inflammation. Conversely, airway hyperreactivity, suppressed as a result of long-term allergen exposure, could be reestablished by depleting gammadelta T cells, in particular Vgamma4+ cells. Antigen-specific tolerance of alphabeta T cells or suppression by non-gammadelta T cells did not play a role in the reversal to normal airway responsiveness and gammadelta T cells did not play a role in the regulation of the allergic inflammatory response. These findings show that normal responsiveness in previously hyperreactive mice, achieved after long-term allergen challenge, is based on several, apparently independent regulatory mechanisms. One of these, focused on airway responsiveness, involves active suppression and requires gammadelta T cells.