IgE immune complexes stimulate an increase in lung mast cell progenitors in a mouse model of allergic airway inflammation

Utilizing mast cells in a positive manner to overcome inflammatory and allergic diseases

Mast cells (MCs) are immune cells widely distributed in the body, accompanied by diverse phenotypes and functions. Committed mast cell precursors (MCPs) leave the bone marrow and enter the blood circulation, homing to peripheral sites under the control of various molecules from different microenvironments, where they eventually differentiate and mature. Partly attributable to the unique maturation mechanism, MCs display high functional heterogeneity and potentially plastic phenotypes. High plasticity also means that MCs can exhibit different subtypes to cope with different microenvironments, which we call “the peripheral immune education system”. Under the peripheral immune education system, MCs showed a new character from previous cognition in some cases, namely regulation of allergy and inflammation. In this review, we focus on the mucosal tissues, such as the gastrointestinal tract, to gain insights into the mechanism underlying the migration of MCs to the gut or other organs and their heterogeneity, which is driven by different microenvironments. In particular, the immunosuppressive properties of MCs let us consider that positively utilizing MCs may be a new way to overcome inflammatory and allergic disorders.

IgE-neutralizing UB-221 mAb, distinct from omalizumab and ligelizumab, exhibits CD23-mediated IgE downregulation and relieves urticaria symptoms

Over the last 2 decades, omalizumab is the only anti-IgE antibody that has been approved for asthma and chronic spontaneous urticaria (CSU). Ligelizumab, a higher-affinity anti-IgE mAb and the only rival viable candidate in late-stage clinical trials, showed anti-CSU efficacy superior to that of omalizumab in phase IIb but not in phase III. This report features the antigenic-functional characteristics of UB-221, an anti-IgE mAb of a newer class that is distinct from omalizumab and ligelizumab. UB-221, in free form, bound abundantly to CD23-occupied IgE and, in oligomeric mAb-IgE complex forms, freely engaged CD23, while ligelizumab reacted limitedly and omalizumab stayed inert toward CD23; these observations are consistent with UB-221 outperforming ligelizumab and omalizumab in CD23-mediated downregulation of IgE production. UB-221 bound IgE with a strong affinity to prevent FcԑRI-mediated basophil activation and degranulation, exhibiting superior IgE-neutralizing activity to that of omalizumab. UB-221 and ligelizumab bound cellular IgE and effectively neutralized IgE in sera of patients with atopic dermatitis with equal strength, while omalizumab lagged behind. A single UB-221 dose administered to cynomolgus macaques and human IgE (ε, κ)-knockin mice could induce rapid, pronounced serum-IgE reduction. A single UB-221 dose administered to patients with CSU in a first-in-human trial exhibited durable disease symptom relief in parallel with a rapid reduction in serum free-IgE level.

Anti-inflammatory, expectorant, and antitussive properties of Kyeongok-go in ICR mice

CONTEXT

Kyeongok-go (KOG) is a traditional mixed herb preparation consisting of Panax ginseng CA Meyer (Araliaceae), Poria cocos Wolf (Polyporaceae), Rehmannia glutinosa (Gaertner) Liboschitz ex Steudel (Orobanchaceae), and honey. Various pharmacological effects of KOG are reported, but the efficacy on respiratory diseases has not been evaluated.

OBJECTIVE

The anti-inflammatory, expectorant, and antitussive properties of KOG were examined using animal models of respiratory diseases.

MATERIALS AND METHODS

KOG (100, 200, and 400 mg/kg) was orally administered to ICR mice (n = 8) once a day for 11 days. Anti-inflammatory effects of vehicle, xylene, KOG and DEXA (1 mg/kg) were determined by monitoring edoema and redness of treated ears, and measuring the relative and absolute weight of each ear. Expectorant properties of vehicle, KOG and AM (250 mg/kg) were evaluated by observing body surface redness, and the amount of mucous secreted by the trachea. The antitussive potential of vehicle, NH₄OH, KOG and TB (50 mg/kg) was evaluated by monitoring changes in the number of coughs (for 6 min).

RESULTS

KOG (400 mg/kg) treated mice showed 31.29% and 30.72% (p < 0.01) decreases in the relative and absolute weights of each ear relative to xylene control mice, 39.06% increases (p < 0.01) in TLF OD values relative to intact vehicle control mice, and 59.53% decrease (p < 0.01) in coughing compared to NH₄OH control mice. Dose-dependent changes were observed in all experimental models.

CONCLUSIONS

KOG may be a potential therapeutic agent for the treatment of various respiratory diseases, particularly those caused by environmental toxins.

Circulating mast cell progenitors correlate with reduced lung function in allergic asthma

BACKGROUND

Studies using mouse models have revealed that mast cell progenitors are recruited from the blood circulation to the lung during acute allergic airway inflammation. The discovery of a corresponding human mast cell progenitor population in the blood has enabled to study the relation of circulating mast cell progenitors in clinical settings.

OBJECTIVES

To explore the possible association between the frequency of mast cell progenitors in the blood circulation and allergic asthma, we assessed the relation of this recently identified cell population with asthma outcomes and inflammatory mediators in allergic asthmatic patients and controls.

METHODS

Blood samples were obtained, and spirometry was performed on 38 well-controlled allergic asthmatic patients and 29 controls. The frequency of blood mast cell progenitors, total serum IgE and 180 inflammation- and immune-related plasma proteins were quantified.

RESULTS

Allergic asthmatic patients and controls had a similar mean frequency of blood mast cell progenitors, but the frequency was higher in allergic asthmatic patients with reduced FEV₁ and PEF (% of predicted) as well as in women. The level of fibroblast growth factor 21 (FGF-21) correlated positively with the frequency of mast cell progenitors, independent of age and gender, and negatively with lung function. The expression of FcεRI on mast cell progenitors was higher in allergic asthmatic patients and correlated positively with the level of total IgE in the controls but not in the asthmatic patients.

CONCLUSION

Elevated levels of circulating mast cell progenitors are related to reduced lung function, female gender and high levels of FGF-21 in young adults with allergic asthma.

Antitussive, expectorant, and anti-inflammatory effects of Adenophorae Radix powder in ICR mice

ETHNOPHARMACOLOGICAL RELEVANCE

Adenophora triphylla var. japonica is frequently used as an oriental medicinal plant in Korea, China, and Japan for its anti-inflammatory, antitussive, and hepatoprotective effects.

AIM OF THE STUDY

In the present study, the antitussive, expectorant, and anti-inflammatory effects of AR powder were investigated using animal models to evaluate their potential to treat respiratory disorders.

MATERIALS AND METHODS

AR powder was administered orally to mice once daily for 11 days, at dose levels of 400, 200, and 100 mg/kg. Theobromine (TB), ambroxol (AM) and dexamethasone (DEXA) were used as standard drugs for antitussive effects, expectorant effects and anti-inflammatory effects, respectively. Evaluations of antitussive effects were based on changes in body weight, the number of cough responses and the histopathology of the lung and trachea. Expectorant effects were based on changes in the body weight, macroscopic observations of body surface redness, the mucous secretion of the trachea and histopathology of lung (secondary bronchus). Anti-inflammatory effects were based on changes in the body weight, macroscopic observations involving redness and edema of the treated ear, absolute and relative ear weights and histopathology of the treated ears.

RESULTS

Allergic acute inflammation and coughing induced by exposure to NH₄OH and symptoms of xylene-induced contact dermatitis were significantly inhibited by treatment with AR powder in a dose-dependent manner. Histological analyses revealed that AR powder decreased the OD values in trachea lavage fluid, reduced body surface redness, thicknesses of intrapulmonary secondary bronchus mucosa, and the number of PAS-positive mucous producing cells. Overall, AR powder administered at 200 mg/kg displayed superior antitussive and expectorant effects as compared to TB (50 mg/kg), and AM (250 mg/kg). At the highest concentration (400 mg/kg) AR powder displayed only moderately improved anti-inflammatory activities as compared to DEXA (1 mg/kg).

CONCLUSION

The results obtained in this study suggest that AR powder exerts dose-dependent, favorable antitussive, expectorant, and anti-inflammatory activities achieved through modulation of the activity of mast cells and respiratory mucous production. Therefore, AR powder may serve as a therapeutic agent in various respiratory disorders, especially those that occur as a result of environmental toxicants.

Mast Cells and Their Progenitors in Allergic Asthma

Mast cells and their mediators have been implicated in the pathogenesis of asthma and allergy for decades. Allergic asthma is a complex chronic lung disease in which several different immune cells, genetic factors and environmental exposures influence the pathology. Mast cells are key players in the asthmatic response through secretion of a multitude of mediators with pro-inflammatory and airway-constrictive effects. Well-known mast cell mediators, such as histamine and bioactive lipids are responsible for many of the physiological effects observed in the acute phase of allergic reactions. The accumulation of mast cells at particular sites of the allergic lung is likely relevant to the asthma phenotype, severity and progression. Mast cells located in different compartments in the lung and airways have different characteristics and express different mediators. According to in vivo experiments in mice, lung mast cells develop from mast cell progenitors induced by inflammatory stimuli to migrate to the airways. Human mast cell progenitors have been identified in the blood circulation. A high frequency of circulating human mast cell progenitors may reflect ongoing pathological changes in the allergic lung. In allergic asthma, mast cells become activated mainly via IgE-mediated crosslinking of the high affinity receptor for IgE (FcεRI) with allergens. However, mast cells can also be activated by numerous other stimuli e.g. toll-like receptors and MAS-related G protein-coupled receptor X2. In this review, we summarize research with implications on the role and development of mast cells and their progenitors in allergic asthma and cover selected activation pathways and mast cell mediators that have been implicated in the pathogenesis. The review places an emphasis on describing mechanisms identified using in vivo mouse models and data obtained by analysis of clinical samples.

Innate Immunity Induces the Accumulation of Lung Mast Cells During Influenza Infection

Mast cells release disease-causing mediators and accumulate in the lung of asthmatics. The most common cause of exacerbations of asthma is respiratory virus infections such as influenza. Recently, we demonstrated that influenza infection in mice triggers the recruitment of mast cell progenitors to the lung. This process starts early after infection and leads to the accumulation of mast cells. Previous studies showed that an adaptive immune response was required to trigger the recruitment of mast cell progenitors to the lung in a mouse model of allergic lung inflammation. Therefore, we set out to determine whether an adaptive immune response against the virus is needed to cause the influenza-induced recruitment of mast cell progenitors to the lung. We found that influenza-induced recruitment of mast cell progenitors to the lung was intact in Rag2 ^-/- mice and mice depleted of CD4⁺ cells, implicating the involvement of innate immune signals in this process. Seven weeks after the primary infection, the influenza-exposed mice harbored more lung mast cells than unexposed mice. As innate immunity was implicated in stimulating the recruitment process, several compounds known to trigger innate immune responses were administrated intranasally to test their ability to cause an increase in lung mast cell progenitors. Poly I:C, a synthetic analog of viral dsRNA, induced a TLR3-dependent increase in lung mast cell progenitors. In addition, IL-33 induced an ST2-dependent increase in lung mast cell progenitors. In contrast, the influenza-induced recruitment of mast cell progenitors to the lung occurred independently of either TLR3 or ST2, as demonstrated using Tlr3 ^-/- or Il1rl1 ^-/- mice. Furthermore, neutralization of IL-33 in Tlr3 ^-/- mice could not abrogate the influenza-induced influx of mast cell progenitors to the lung. These results suggest that other innate receptor(s) contribute to mount the influx of mast cell progenitors to the lung upon influenza infection. Our study establishes that mast cell progenitors can be rapidly recruited to the lung by innate immune signals. This indicates that during life various innate stimuli of the respiratory tract trigger increases in the mast cell population within the lung. The expanded mast cell population may contribute to the exacerbations of symptoms which occurs when asthmatics are exposed to respiratory infections.

Influenza Infection in Mice Induces Accumulation of Lung Mast Cells through the Recruitment and Maturation of Mast Cell Progenitors

Mast cells (MCs) are powerful immune cells that mature in the peripheral tissues from bone marrow (BM)-derived mast cell progenitors (MCp). Accumulation of MCs in lung compartments where they are normally absent is thought to enhance symptoms in asthma. The enrichment of lung MCs is also observed in mice subjected to models of allergic airway inflammation. However, whether other types of lung inflammation trigger increased number of MCp, which give rise to MCs, is unknown. Here, mouse-adapted H1N1 influenza A was used as a model of respiratory virus infection. Intranasal administration of the virus induced expression of VCAM-1 on the lung vascular endothelium and an extensive increase in integrin β7^hi lung MCp. Experiments were performed to distinguish whether the influenza-induced increase in the number of lung MCp was triggered mainly by recruitment or in situ cell proliferation. A similar proportion of lung MCp from influenza-infected and PBS control mice were found to be in a proliferative state. Furthermore, BM chimeric mice were used in which the possibility of influenza-induced in situ cell proliferation of host MCp was prevented. Influenza infection in the chimeric mice induced a similar number of lung MCp as in normal mice. These experiments demonstrated that recruitment of MCp to the lung is the major mechanism behind the influenza-induced increase in lung MCp. Fifteen days post-infection, the influenza infection had elicited an immature MC population expressing intermediate levels of integrin β7, which was absent in controls. At the same time point, an increased number of toluidine blue⁺ MCs was detected in the upper central airways. When the inflammation was resolved, the MCs that accumulated in the lung upon influenza infection were gradually lost. In summary, our study reveals that influenza infection induces a transient accumulation of lung MCs through the recruitment and maturation of MCp. We speculate that temporary augmented numbers of lung MCs are a cause behind virus-induced exacerbations of MC-related lung diseases such as asthma.

The Innate Immune Response in Myocardial Infarction, Repair, and Regeneration

Following myocardial infarction (MI), resident innate immune cells such as macrophages, innate lymphoid cells, and mast cells rapidly coordinate their function to contain inflammation by removing dying cells and promoting cardiomyocyte replenishment. To sustain local tissue repair functions, hematopoietic progenitors are mobilized from the bone marrow to the spleen to generate subsequent myeloid cells such as monocytes and neutrophils, which are rapidly recruited at the site of MI. A finely tuned balance between local adaptation and recruitment controls the overall outcome of the cardiac tissue regeneration versus repair and scar formation.In this chapter, the (potential) roles of the innate immune system residing in the heart are discussed in the context of recent findings about macrophage ontogeny and their homeostasis with circulating monocytes during cardiac tissue growth and after myocardial infarction. Their interactions with other members of the innate immune system are also discussed with a particular emphasis on the potential involvement of mast cells and innate lymphoid cells during MI, largely underestimated until recently. Understanding the development and the functions of the different protagonists responding to MI as well as their potential cross talk could help design new strategies for regenerative medicine intervention.

Mast cell-derived neurotrophin 4 mediates allergen-induced airway hyperinnervation in early life

Asthma often progresses from early episodes of insults. How early-life events connect to long-term airway dysfunction remains poorly understood. We demonstrated previously that increased neurotrophin 4 (NT4) levels following early-life allergen exposure cause persistent changes in airway smooth muscle (ASM) innervation and airway hyper-reactivity (AHR) in mice. Herein, we identify pulmonary mast cells as a key source of aberrant NT4 expression following early insults. NT4 is selectively expressed by ASM and mast cells in mice, nonhuman primates, and humans. We show in mice that mast cell-derived NT4 is dispensable for ASM innervation during development. However, upon insults, mast cells expand in number and degranulate to release NT4 and thus become the major source of NT4 under pathological condition. Adoptive transfer of wild-type mast cells, but not NT4^-/- mast cells restores ASM hyperinnervation and AHR in Kit^W-sh/W-sh mice following early-life insults. Notably, an infant nonhuman primate model of asthma also exhibits ASM hyperinnervation associated with the expansion and degranulation of mast cells. Together, these findings identify an essential role of mast cells in mediating ASM hyperinnervation following early-life insults by producing NT4. This role may be evolutionarily conserved in linking early insults to long-term airway dysfunction.

Tie2 Signaling Enhances Mast Cell Progenitor Adhesion to Vascular Cell Adhesion Molecule-1 (VCAM-1) through α4β1 Integrin

Mast cell (MC) activation contributes considerably to immune responses, such as host protection and allergy. Cell surface immunoreceptors expressed on MCs play an important role in MC activation. Although various immunoreceptors on MCs have been identified, the regulatory mechanism of MC activation is not fully understood. To understand the regulatory mechanisms of MC activation, we used gene expression analyses of human and mouse MCs to identify a novel immunoreceptor expressed on MCs. We found that Tek, which encodes Tie2, was preferentially expressed in the MCs of both humans and mice. However, Tie2 was not detected on the cell surface of the mouse MCs of the peritoneal cavity, ear skin, or colon lamina propria. In contrast, it was expressed on mouse bone marrow–derived MCs and bone marrow MC progenitors (BM-MCps). Stimulation of Tie2 by its ligand angiopoietin-1 induced tyrosine phosphorylation of Tie2 in MEDMC-BRC6, a mouse embryonic stem cell-derived mast cell line, and enhanced MEDMC-BRC6 and mouse BM-MCp adhesion to vascular cell adhesion molecule-1 (VCAM-1) through α4β1 integrin. These results suggest that Tie2 signaling induces α4β1 integrin activation on BM-MCps for adhesion to VCAM-1.

Mast cell progenitors: origin, development and migration to tissues

Mast cells in tissues are developed from mast cell progenitors emerging from the bone marrow in a process highly regulated by transcription factors. Through the advancement of the multicolor flow cytometry technique, the mast cell progenitor population in the mouse has been characterized in terms of surface markers. However, only cell populations with enriched mast cell capability have been described in human. In naïve mice, the peripheral tissues have a constitutive pool of mast cell progenitors. Upon infections in the gut and in allergic inflammation in the lung, the local mast cell progenitor numbers increase tremendously. This review focuses on the origin and development of mast cell progenitors. Furthermore, the evidences for cells and molecules that govern the migration of these cells in mice in vivo are described.

Differential regulation of inflammation and immunity in mild and severe experimental asthma

This study aimed at exploring innate and adaptive immunity in allergic asthma by investigation of mRNA expression of pattern recognition receptors, T-cell-specific cytokines, and transcription factors. Mouse models for mild and severe asthma, with similar pathological characteristics observed in humans, were used to study the involved inflammatory markers as a first step in the development of phenotype-directed treatment approaches. In the mild model, mice were sensitized to ovalbumin-Imject Alum and challenged with ovalbumin. In the severe model, mice were sensitized to trinitrophenyl-conjugated ovalbumin and challenged with trinitrophenyl-ovalbumin/IgE immune complex. Pulmonary airway inflammation and mRNA expression of Toll-like receptors (TLRs), NOD-like receptors (NLRs), T cell cytokines, and transcription factors in lung tissue were examined. Different mRNA expression profiles of TLRs, NLRs, T cell cytokines, and transcription factors were observed. In the mild model, Il10 showed the largest increase in expression, whereas in the severe model, it was Infγ with the largest increase. Expression of Tbet was also significantly increased in the severe model. Inflammation and immunity are differentially regulated in mild and severe experimental asthma. This preclinical data may help in directing clinical research towards a better understanding and therapy in mild and severe asthmatic patients.

IgE production in CD40/CD40L cross-talk of B and mast cells and mediator release via TGase 2 in mouse allergic asthma

TGase 2 is over-expressed in a variety of inflammatory diseases including allergic asthma. This study aimed to investigate the role of TGase 2 on IgE production and signaling pathways in mast cell activation related to OVA-induced allergic asthma. Bone marrow-derived mast cells (BMMCs) isolated from WT or TGase 2(-/-) mice were activated with Ag/Ab (refer to act-WT-BMMCs and act-KO-BMMCs, respectively). B cells isolated from splenocytes were activated with anti-mouse IgM (act-B cells), and B cells were co-cultured with BMMCs. WT and TGase 2(-/-) mice were sensitized and challenged with OVA adsorbed in alum hydroxide. Intracellular Ca(2+) ([Ca(2+)]i) levels were determined by fluorescence intensity; IgE, mediators and TGase 2 activity by ELISA; the CD138 expression by FACS analyzer; cell surface markers and signal molecules by Western blot; NF-κB by EMSA; co-localization of mast cells and B cells by immunohistochemistry; Fcε RI-mediated mast cell activation by PCA test; expression of cytokines, MMPs, TIMPs, TLR2 and FcεRI by RT-PCR. In vitro, act-KO-BMMCs reduced the [Ca(2+)]i levels, NF-κB activity, expression of CD40/CD40L, plasma cells, total IgE levels and TGase 2 activity in act-B cells co-cultured with act-BMMCs, expression of inflammatory cytokines and MMPs2/9, release of mediators (TNF-α, LTs and cytokines), and activities of signal molecules (PKCs, MAP kinases, I-κB and PLA2), which were all increased in act-WT-BMMCs. TGase 2 siRNA transfected/activated-BMMCs reduced all responses as same as those in act-KO-BMMCs. In allergic asthma model, TGase 2(-/-) mice protected against PCA reaction, OVA-specific IgE production and AHR, and they reduced co-localization of mast cells and B cells or IgE in lung tissues, expression and co-localization of surface molecules in mast cells (c-kit and CD40L) and B cells (CD23 and CD40), inflammatory cells including mast cells, goblet cells, amounts of collagen and mediator release in BAL fluid and/or lung tissues, which were all increased in WT mice. TLR expression in TGase 2(-/-) mice did not differ from those in WT mice. Our data suggest that TGase 2 expression and Ca(2+) influx required by bidirectional events in mast cell activation facilitate IgE production in B cells via up-regulating mast cell CD40L expression, and induce the expression of numerous signaling molecules associated with airway inflammation and remodeling in allergic asthma.

CD11c+ cells are required for antigen-induced increase of mast cells in the lung

Patients with allergic asthma have more lung mast cells, which likely worsens the symptoms. In experimental asthma, CD11c(+) cells have to be present during the challenge phase for several features of allergic inflammation to occur. Whether CD11c(+) cells play a role for Ag-induced increases of lung mast cells is unknown. In this study, we used diphtheria toxin treatment of sensitized CD11c-diphtheria toxin receptor transgenic mice to deplete CD11c(+) cells. We demonstrate that recruitment of mast cell progenitors to the lung is substantially reduced when CD11c(+) cells are depleted during the challenge phase. This correlated with an impaired induction of endothelial VCAM-1 and led to a significantly reduced number of mature mast cells 1 wk after challenge. Collectively, these data suggest that Ag challenge stimulates CD11c(+) cells to produce cytokines and/or chemokines required for VCAM-1 upregulation on the lung endothelium, which in turn is crucial for the Ag-induced mast cell progenitor recruitment and the increase in mast cell numbers.

IgE and mast cells in allergic disease

Immunoglobulin E (IgE) antibodies and mast cells have been so convincingly linked to the pathophysiology of anaphylaxis and other acute allergic reactions that it can be difficult to think of them in other contexts. However, a large body of evidence now suggests that both IgE and mast cells are also key drivers of the long-term pathophysiological changes and tissue remodeling associated with chronic allergic inflammation in asthma and other settings. Such potential roles include IgE-dependent regulation of mast-cell functions, actions of IgE that are largely independent of mast cells and roles of mast cells that do not directly involve IgE. In this review, we discuss findings supporting the conclusion that IgE and mast cells can have both interdependent and independent roles in the complex immune responses that manifest clinically as asthma and other allergic disorders.

Harnessing opportunities in non-animal asthma research for a 21st-century science

The incidence of asthma is on the increase and calls for research are growing, yet asthma is a disease that scientists are still trying to come to grips with. Asthma research has relied heavily on animal use; however, in light of increasingly robust in vitro and computational models and the need to more fully incorporate the 'Three Rs' principles of Replacement, Reduction and Refinement, is it time to reassess the asthma research paradigm? Progress in non-animal research techniques is reaching a level where commitment and integration are necessary. Many scientists believe that progress in this field rests on linking disciplines to make research directly translatable from the bench to the clinic; a '21st-century' scientific approach to address age-old questions.