Mucous-cell metaplasia and inflammatory-cell recruitment are dissociated in allergic mice after antibody- and drug-dependent cell depletion in a murine model of asthma

Mucoadhesive, Antibacterial, and Reductive Nanogels as a Mucolytic Agent for Efficient Nebulized Therapy to Combat Allergic Asthma

Asthma is an intractable disease involving the infiltration of inflammatory cells and mucus plugging. Despite small molecular mucolytics having the ability to break the disulfide bonds of mucins, offering a potential way to overcome the airflow obstruction and airway infection, these mucolytics have limited therapeutic effects in vivo. Therefore, in this work, arginine-grafted chitosan (CS-Arg) is ionically cross-linked with tris(2-carboxyethyl)phosphine (TCEP) to obtain nanogels as a mucolytic agent. The positively charged nanogels effectively inhibit the formation of large aggregates of mucin in vitro, probably thanks to the formation of an ionic interaction between CS-Arg and mucin, as well as the breakage of disulfide bonds in mucin by the reductive TCEP. Moreover, the nanogels show good cytocompatibility at concentrations up to 5 mg mL^-1, exhibiting effective inhibitory effects against the proliferation of both Staphylococcus aureus and Escherichia coli at 5 mg mL^-1. After the administration of the nanogels by nebulization into a Balb/c mouse model with allergic asthma, they can efficiently reduce the mucus obstruction in bronchioles and alveoli and relieve airway inflammation. Therefore, these CS-Arg/TCEP nanogels potentially represent a promising mucolytic agent for the efficient treatment of allergic asthma and other muco-obstructive diseases.

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

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

Persistence of asthma requires multiple feedback circuits involving type 2 innate lymphoid cells and IL-33

BACKGROUND

Asthma in a mouse model spontaneously resolves after cessation of allergen exposure. We developed a mouse model in which asthma features persisted for 6 months after cessation of allergen exposure.

OBJECTIVE

We sought to elucidate factors contributing to the persistence of asthma.

METHODS

We used a combination of immunologic, genetic, microarray, and pharmacologic approaches to dissect the mechanism of asthma persistence.

RESULTS

Elimination of T cells though antibody-mediated depletion or lethal irradiation and transplantation of recombination-activating gene (Rag1)(-/-) bone marrow in mice with chronic asthma resulted in resolution of airway inflammation but not airway hyperreactivity or remodeling. Elimination of T cells and type 2 innate lymphoid cells (ILC2s) through lethal irradiation and transplantation of Rag2(-/-)γc(-/-) bone marrow or blockade of IL-33 resulted in resolution of airway inflammation and hyperreactivity. Persistence of asthma required multiple interconnected feedback and feed-forward circuits between ILC2s and epithelial cells. Epithelial IL-33 induced ILC2s, a rich source of IL-13. The latter directly induced epithelial IL-33, establishing a positive feedback circuit. IL-33 autoinduced, generating another feedback circuit. IL-13 upregulated IL-33 receptors and facilitated IL-33 autoinduction, thus establishing a feed-forward circuit. Elimination of any component of these circuits resulted in resolution of chronic asthma. In agreement with the foregoing, IL-33 and ILC2 levels were increased in the airways of asthmatic patients. IL-33 levels correlated with disease severity.

CONCLUSIONS

We present a critical network of feedback and feed-forward interactions between epithelial cells and ILC2s involved in maintaining chronic asthma. Although T cells contributed to the severity of chronic asthma, they were redundant in maintaining airway hyperreactivity and remodeling.

Eosinophil cytokines, chemokines, and growth factors: emerging roles in immunity

Eosinophils derive from the bone marrow and circulate at low levels in the blood in healthy individuals. These granulated cells preferentially leave the circulation and marginate to tissues, where they are implicated in the regulation of innate and adaptive immunity. In diseases such as allergic inflammation, eosinophil numbers escalate markedly in the blood and tissues where inflammatory foci are located. Eosinophils possess a range of immunomodulatory factors that are released upon cell activation, including over 35 cytokines, growth factors, and chemokines. Unlike T and B cells, eosinophils can rapidly release cytokines within minutes in response to stimulation. While some cytokines are stored as pre-formed mediators in crystalloid granules and secretory vesicles, eosinophils are also capable of undergoing de novo synthesis and secretion of these immunological factors. Some of the molecular mechanisms that coordinate the final steps of cytokine secretion are hypothesized to involve binding of membrane fusion complexes comprised of soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs). These intracellular receptors regulate the release of granules and vesicles containing a range of secreted proteins, among which are cytokines and chemokines. Emerging evidence from both human and animal model-based research has suggested an active participation of eosinophils in several physiological/pathological processes such as immunomodulation and tissue remodeling. The observed eosinophil effector functions in health and disease implicate eosinophil cytokine secretion as a fundamental immunoregulatory process. The focus of this review is to describe the cytokines, growth factors, and chemokines that are elaborated by eosinophils, and to illustrate some of the intracellular events leading to the release of eosinophil-derived cytokines.

Acute oral toxicity of Insampaedok-san, a traditional herbal formula, in rats and its protective effects against ovalbumin-induced asthma via anti-inflammatory and antioxidant properties

Background

Insampaedok-san (ren-shen-bai-du-san in Chinese) is a traditional herbal formula widely used for the treatment of respiratory diseases in Korea and China. In this study, we investigated the acute oral toxicity of an Insampaedok-san water extract (ISSE) in rats and the antiasthmatic effects of ISSE and its mechanism in a model of asthma induced by ovalbumin (OVA) in mice.

Methods

In a safety study, ISSE was administrated orally to rats of both sexes at single doses of 0 and 5000 mg/kg. We observed body weight changes, mortality, clinical signs, and gross pathological findings. In vitro antioxidant activity of ISSE was measured using 2,2-diphenyl-2-picrylhydrazyl and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radical scavenging methods. A model of asthma was established in mice by sensitization and challenge with OVA. We assessed the levels of type 2 T-helper cytokines, chemokines, and immunoglobulin levels, using enzyme-linked immunosorbent assays, and superoxide dismutase (SOD) activity using a kit.

Results

No adverse effects were observed in the acute ISSE toxicity study. ISSE showed potent free radical scavenging activity and inhibited the recruitment of inflammatory cells into the lung and mucus hypersecretion in OVA-challenged mice. ISSE significantly decreased levels of interleukin (IL)-4, IL-5, eotaxin, and OVA-specific immunoglobulin (Ig)E, and increased SOD activity.

Conclusions

These results indicate that ISSE is safe for human consumption and its antiasthmatic effect is associated with the ability of ISSE to attenuate inflammation and oxidative stress.

Amelioration of Muc5b mucin hypersecretion is enhanced by IL-33 after 2-APB administration in a murine model of allergic rhinitis

We attempted to clarify whether hypersecretion of Muc5b mucin from mouse nasal submucosal glands that is enhanced by interleukin (IL)-33 under allergic conditions can be ameliorated by administration of 2-APB. Immunohistochemistry was used to examine both the distribution of T cells in the nasal mucosa of an allergic rhinitis mouse model and expressions of IL-33 receptor ST2 and Muc5b protein in mouse submucosal gland cells. The amounts of protein and mRNA of Orai1, Muc5b, IL-4, IL-5, IL-13 and IL-33 in mouse nasal lavage fluid (NLF) and nasal mucosa were determined using enzyme-linked immunosorbent assay and real-time reverse transcription-polymerase chain reaction. Expressions of Orai1, Muc5b, IL-4, IL-5, IL-13 and IL-33 were up-regulated in the allergic state and IL-33 increased the levels of Muc5b, IL-4, IL-5 and IL-13, but did not influence proliferation of T cells; however, ST2 was diminished in nasal submucosal gland cells. 2-APB reduced proliferation of T cells and the Orai1 level in the nasal mucosa. It also reduced the concentrations of IL-4, IL-5 and IL-13 in NLF and nasal mucosa, and hypersecretion of Muc5b from glandular cells that was enhanced by IL-33, but did not affect IL-33 production. 2-APB decreased Muc5b mucin hypersecretion from submucosal gland that was enhanced by IL-33 in allergic mice by limiting Ca(2+) release-activated Ca(2+) channel activity in which Orai1 plays a crucial role in the gland cells and/or by controlling channel activation in T cells and proliferation of these cells.

Prostaglandin E2 receptor EP2, EP3, and EP4 agonists inhibit antigen-induced mucus hypersecretion in the nasal epithelium of sensitized rats

OBJECTIVES

Prostaglandin (PG) E2 is a potential anti-inflammatory mediator that attenuates airway inflammation. To elucidate the functions of the PGE2 receptors (EP1, EP2, EP3, and EP4) in allergic inflammation, we examined the in vivo effects of EP agonists on mucus hypersecretion and eosinophil infiltration in rat nasal epithelium.

METHODS

We induced hypertrophic and metaplastic changes in goblet cells in nasal epithelium of ovalbumin-sensitized rats by intranasal challenge with ovalbumin. The effects of subcutaneous injections of EP agonists on mucus production and eosinophil infiltration were examined.

RESULTS

The EP4 agonist (1 to 100 microg/kg) dose-dependently inhibited ovalbumin-induced mucus production. The EP2 and EP3 agonists (100 microg/kg) also significantly inhibited mucus production. The EP3 agonist inhibited antigen-induced eosinophil infiltration, whereas the EP1 agonist showed no effect. This suppression of mucus production by the EP4 agonist was only effective when the EP4 agonist was given in the effector phase; administration in the induction phase resulted in no effect.

CONCLUSIONS

These results indicate that PGE2 acts as an anti-inflammatory mediator via the EP receptors of airways in allergic inflammation. Selective EP agonists may provide a new therapeutic strategy for airway mucus hypersecretion.

Ginger prevents Th2-mediated immune responses in a mouse model of airway inflammation

It is well documented that compounds from rhizomes of Zingiber officinale, commonly called ginger, have anti-inflammatory properties. Here, we show that ginger can exert such functions in vivo, namely in a mouse model of Th2-mediated pulmonary inflammation. The preparation of ginger aqueous extract (Zo.Aq) was characterized by mass spectrometry as an enriched fraction of n-gingerols. Intraperitoneal injections of this extract before airway challenge of ovalbumin (OVA)-sensitized mice resulted in a marked decrease in the recruitment of eosinophils to the lungs as attested by cell counts in bronchoalveolar lavage (BAL) fluids and histological examination. Resolution of airway inflammation induced by Zo.Aq was accompanied by a suppression of the Th2 cell-driven response to allergen in vivo. Thus, IL-4, IL-5 and eotaxin levels in the lungs as well as specific IgE titres in serum were clearly diminished in ginger-treated mice relative to their controls after allergen sensitization and challenge. Finally, we found that [6]-gingerol, a major constituent of ginger, was sufficient to suppress eosinophilia in our model of inflammation. This is the first evidence that ginger can suppress Th2-mediated immune responses and might thus provide a possible therapeutic application in allergic asthma.

Mycobacterium bovis BCG killed by extended freeze-drying reduces airway hyperresponsiveness in 2 animal models

BACKGROUND

Live BCG administered intranasally to mice inhibits the development of ovalbumin (OVA)-induced eosinophilia and airway hyperresponsiveness (AHR). It is unacceptable to treat human subjects intranasally with live BCG.

OBJECTIVE

We investigated whether BCG killed by extended freeze-drying (EFD) and subcutaneously injected has a protective effect in murine and guinea pig models of allergic airway inflammation.

METHODS

Mice were OVA sensitized (days 0 and 7), treated subcutaneously (day 14) with EFD and live or heat-killed BCG, and then OVA challenged (day 42). OVA-sensitized mice (days 0 and 7) were challenged (day 14) and EFD treated (day 18) before OVA rechallenge (day 46) to demonstrate the capacity of EFD to reverse the established lung inflammation. Guinea pigs were OVA sensitized (days 0 and 14), treated intradermally (day 35) with EFD, and OVA challenged (days 90-105).

RESULTS

In mice and guinea pigs EFD treatment reduced AHR. Among 3 BCG preparations, only EFD efficiently reduced AHR, eosinophilia, and the recruitment of dendritic cells to the lungs after OVA challenge. The protective effect of EFD is associated with production of the immunoregulatory cytokine IL-10. Moreover, EFD treatment did not induce toxic effects or delayed-type hypersensitivity to mycobacterial antigens; that is, it did not interfere with the diagnosis of tuberculosis.

CONCLUSION

EFD administered subcutaneously inhibits the development of allergic airway inflammation and prevents AHR without inducing delayed-type hypersensitivity and side effects associated with live or heat-killed BCG.

Airway hyperresponsiveness in the absence of CD4+ T cells after primary but not secondary challenge

CD4+ T cells have been shown to play a role in the development of airway hyperresponsivness (AHR) and airway eosinophilia in mice using ablation as well as adoptive transfer experiments. However, as other T cell subsets (CD8, NKT) may play a role in these models, we examined the responses of sensitized CD4-deficient mice after either primary or secondary airway allergen challenge. After sensitization, CD4-deficiency in mice was not associated with airway eosinophilia, allergen-specific IgE, or elevated levels of interleukin (IL)-4 or IL-13. Increases in lung CD8 T cells and IL-5 were observed and shown to be essential for AHR as demonstrated after CD8 T cell depletion or anti-IL-5 treatment. In contrast to the response of sensitized CD4-deficient mice to primary allergen challenge, they failed to develop AHR after secondary allergen challenge. Although the importance of this CD4+ T cell-independent pathway in normal mice is unclear at this time, these studies identify the diversity of the cellular pathway, which may contribute to the development of AHR after primary allergen exposure of sensitized mice.

Mouse models of global airway allergy: what have we learned and what should we do next?

Recent epidemiological and clinical data indicate that allergic rhinitis and asthma coexist and should be considered as one airway allergy syndrome. In spite of the importance of this new concept of global airway allergy, it has not fundamentally changed our daily diagnostic and therapeutic strategies so far because of the lack of essential clues to understand the correlation between allergic inflammation in upper and lower airways. Because of the resemblance of experimentally induced allergic airway inflammation in mice to inflamed airways of allergic patients, mouse models can enhance our insight into mechanisms underlying the global airway allergy syndrome. We here review data generated in mice that are relevant for understanding the development of airway allergy and provide new options for research on the so-called 'united airway disease'.

A MARCKS-related peptide blocks mucus hypersecretion in a mouse model of asthma

Mucus hypersecretion is a crucial feature of pulmonary diseases such as asthma, chronic bronchitis and cystic fibrosis. Despite much research, there is still no effective therapy for this condition. Recently, we showed that the myristoylated, alanine-rich C-kinase substrate (MARCKS) protein is required for mucus secretion by human bronchial epithelial cells in culture. Having synthesized a peptide corresponding to the N-terminal domain of MARCKS, we now show that the intratracheal instillation of this peptide blocks mucus hypersecretion in a mouse model of asthma. A missense peptide with the same amino acid composition has no effect. Based on quantitative histochemical analysis of the mouse airways, the peptide seems to act by blocking mucus release from goblet cells, possibly by inhibiting the attachment of MARCKS to membranes of intracellular mucin granules. These results support a pivotal role for MARCKS protein, specifically its N-terminal region, in modulating this secretory process in mammalian airways. Intratracheal administration of this MARCKS-related peptide could therapeutically reduce mucus secretion in the airways of human patients with asthma, chronic bronchitis and cystic fibrosis.

A mechanism of antigen-induced goblet cell degranulation in the nasal epithelium of sensitized rats

BACKGROUND

We have produced hypertrophic and metaplastic changes of goblet cells in nasal epithelium of ovalbumin (OVA)-sensitized rats by intranasal challenge with OVA. A variety of allergic mediators and inflammatory cells are capable of stimulating goblet cell degranulation (epithelial mucus secretion); however, little is known about the mechanism by which antigen induces mucus hypersecretion.

OBJECTIVE

Our aim was to explain the mechanism of goblet cell degranulation in allergic inflammation.

METHODS

Antigen-induced goblet cell degranulation was evaluated by the transient decrease of epithelial mucosubstance 1 to 6 hours after intranasal challenge with OVA in nasal epithelium of OVA-sensitized rats. The effects of the H(1)-antagonist (d -chlorpheniramine malate), H(2)-antagonist (cimetidine), atropine, indomethacin, cysteinyl leukotriene (cysLT) antagonist (ONO1078), and antirat PMN antiserum on OVA-induced goblet cell degranulation were examined.

RESULTS

Goblet cell secretion 1 hour after OVA challenge was significantly inhibited by H(1)-antagonist, atropine, and cysLT antagonist, whereas the secretion 6 hours after the challenge was significantly inhibited by cysLT antagonist and antirat PMN antiserum. Circulating PMN cells and mucosal infiltrating eosinophils were completely abolished by antirat PMN antiserum.

CONCLUSIONS

These results indicate the different mechanisms of goblet cell secretion between early-phase (1 hour after OVA challenge) and late-phase (6 hours after the challenge) reactions. Histamine stimulates early-phase secretion through the H(1)-receptor of cholinergic nerve terminals, and infiltrating inflammatory cells (eosinophils and/or neutrophils) play a role in late-phase secretion. CysLTs (leukotrienes C(4), D(4), and E(4)) are important for both early-phase and late-phase secretion.

Interleukin-9 induces mucous cell metaplasia independent of inflammation

Interleukin-9 (IL-9) has been strongly implicated in the pathogenesis of asthma, including the overproduction of mucus, in humans and in animal models. We evaluated the inflammatory changes associated with the upregulation of mucus production by examining the time course of inflammation after daily intratracheal IL-9 administration to naive C57Bl6 mice for 9 d. IL-9 induced an asthmatic phenotype, which in general took several days to develop, as assessed by the measurement of airway hyperresponsiveness, pulmonary inflammation, and serum immunoglobulin E. However, within 24 h of a single dose of IL-9, muc5ac mRNA upregulation occurred, and increased numbers of periodic acid Schiff/Alcian blue-positive mucous cells appeared. This response occurred before the development of an inflammatory cell influx and was the result of epithelial metaplasia. It seemed that IL-9 evoked mucous cell metaplasia independent of IL-13 because mRNA tissue evaluation indicated that muc5ac upregulation preceded any increase in IL-13 mRNA expression or detectable levels of IL-13 in the brochoalveolar lavage fluid. Therefore, the upregulation of IL-13 by IL-9 may be responsible for the amplification of mucus production but is not required for its initiation. IL-9 seems to directly stimulate mucous cell metaplasia without the requirement of inflammatory cell influx.

Pathogenesis of mucous cell metaplasia in a murine asthma model

Increased mucus production in asthma is an important cause of airflow obstruction during severe exacerbations. To better understand the changes in airway epithelium that lead to increased mucus production, ovalbumin-sensitized and -challenged mice were used. The phenotype of the epithelium was dramatically altered, resulting in increased numbers of mucous cells, predominantly in the proximal airways. However, the total numbers of epithelial cells per unit area of basement membrane did not change. A 75% decrease in Clara cells and a 25% decrease in ciliated cells were completely compensated for by an increase in mucous cells. Consequently, by day 22, 70% of the total epithelial cell population in the proximal airways was mucous cells. Electron microscopy illustrated that Clara cells were undergoing metaplasia to mucous cells. Conversely, epithelial proliferation, detected with 5-chloro-2-deoxyuridine immunohistochemistry, was most marked in the distal airways. Using ethidium homodimer cell labeling to evaluate necrosis and terminal dUTP nick-end labeling immunohistochemistry to evaluate apoptosis, this proliferation was accompanied by negligible cell death. In conclusion, epithelial cell death did not appear to be the stimulus driving epithelial proliferation and the increase in mucous cell numbers was primarily a result of Clara cell metaplasia.

Elicitation of the allergic reaction in beta-lactoglobulin-sensitized Balb/c mice: biochemical and clinical manifestations differ according to the structure of the allergen used for challenge

BACKGROUND

Mouse models of allergy are used to study the mechanisms of induction and perpetuation of bronchopulmonary hyper-reactivity (BHR) as related to eosinophils and specific IgE.

OBJECTIVE

Our aim was to adapt the current model for the study of bovine beta-lactoglobulin (BLG), a major cow's milk allergen, and to further analyse the mechanisms of the acute and late allergic reaction.

METHODS

Female Balb/c mice were sensitized intraperitoneally with BLG and the influence of the adjuvant and of the BLG dose on the IgE response was analysed, IgE and IgG1 epitopes being characterized. Once optimized, this model was applied to the study of the active phase of allergy in the respiratory tract after a single airway challenge using native or denatured BLG, which contains only linear epitopes.

RESULTS

An immediate allergic reaction was characterized by the rapid release of histamine into the bronchoalveolar lavage fluids. Prostaglandin (PG)D2 was only present when the standard histamine-releasing agent compound 48/80 or denatured BLG were used as triggers, whereas native BLG induced leukotriene release. Twenty-four hours after challenge, BHR, eosinophil influx, IL-4 and IL-5 production, plasma exudation and mucus production were very much increased, differently depending on the allergen structure, and indicated the occurrence of the late allergic reaction. Our results show that the murine model can be used to study the mechanisms of allergy to clinically relevant antigens, such as those contained in cow's milk. The acute allergic reaction, which depends on the structural feature of the allergen, is composed of two distinct pathways characterized by peptido-leukotrienes or PGD2 production, which may result from distinct activation intensities of mast cells, leading to distinct late reactions.

CONCLUSION

This study thus demonstrates a clear link between the structural feature of a protein, and the physiopathology of the experimental asthmatic reaction.

Leukotrienes, IL-13, and chemokines cooperate to induce BHR and mucus in allergic mouse lungs

In mice, intratracheal challenges with antigen (ovalbumin) or recombinant murine interleukin-13 (IL-13) induce lung inflammation, bronchial hyperreactivity (BHR), and mucus accumulation as independent events (Singer M, Lefort J, and Vargaftig BB. Am J Respir Cell Mol Biol 26: 74-84, 2002), largely mediated by leukotrienes (LT). We previously showed that LTC(4) was released 15 min after ovalbumin, and we show that it induces the expression of monocyte chemoattractant proteins 1 and 5 and KC in the lungs, as well as IL-13 mRNA. Instilled intratracheally, these chemokines induced BHR and mucus accumulation, which were inhibited by the 5-lipoxygenase inhibitor zileuton and by the cysteinyl-LT receptor antagonist MK-571, suggesting mediation by cysteinyl-LT. Because these chemokines also induced release of LT into the bronchoalveolar lavage fluid and IL-13 into the lungs, we hypothesize that LT- and chemokine-based loops for positive-feedback regulations cooperate to maintain and amplify BHR and lung mucus accumulation after allergic challenge and in situations where IL-13, LT, or chemokines are generated.

Persistence of bronchopulmonary hyper-reactivity and eosinophilic lung inflammation after anti-IL-5 or -IL-13 treatment in allergic BALB/c and IL-4Ralpha knockout mice

BACKGROUND

Antigen-induced bronchopulmonary hyper-reactivity (BHR) is generally associated with eosinophilia. It involves cytokines produced by Th2 lymphocytes, including IL-4, IL-5 and IL-13, which are implicated in IgE production, eosinophil differentiation and attraction, and related events relevant to allergic inflammation, whose mechanisms remain unclear.

OBJECTIVE

To investigate the mechanisms by which Th2 cytokines mediate eosinophilia and subsequent BHR using ovalbumin (OVA)-immunized and OVA-challenged IL-4Ralpha-/- and IL-4-/- mice, which fail to transduce and/or to produce IL-4 and IgE as compared with wild type (WT) mice, and specific neutralizing antibodies.

METHODS

On days 0 and 7, mice were immunized subcutaneously (s.c.) with OVA. At day 14, anti-IL-5 or anti-IL-13 antibodies were administered intranasally and/or intravenously before allergenic challenge. Different functional and cellular parameters were studied in vivo and cytokine production was followed with a newly described ex vivo procedure using lung explants.

RESULTS

IL-4Ralpha-/- and IL-4-/- mice developed BHR and pulmonary eosinophilia, even though eosinophil recruitment to the bronchoalveolar liquid lavage (BALF) was reduced. In vivo, IL-4-/- and IL-4Ralpha-/- mice produced, respectively, no or reduced amounts of IL-5 in the BALF/serum as compared with WT mice, whereas no IL-13 in the BALF was detected. By contrast, ex vivo, surviving lung explants from WT and IL-4-/- or IL-4Ralpha-/- mice produced IL-13 and large amounts of IL-5. The neutralization of IL-5 in vivo (BALF and serum) and ex vivo (from lung explant) in IL-4Ralpha-/- and WT mice failed to suppress BHR and lung eosinophilia, and to modify IL-13 production ex vivo. In addition, neutralization of IL-13 in vivo from lung explant also failed to abrogate BHR and lung eosinophilia, whereas IL-5 was unchanged.

CONCLUSION

Antigen-induced BHR can develop independently from IL-4, IL-5 or IL-13 and from the IL-4alpha receptor chain, suggesting a possible novel IL-4, IL-5 and IL-13-independent pathway for the development of BHR in allergic BALB/c mice. The failure of IL-5 or IL-13 antibodies to prevent BHR in IL-4Ralpha-/- mice suggests that neither is indispensable for BHR but does not exclude a role for lung tissue eosinophilia.

Goblet cell and mucin gene abnormalities in asthma

Goblet cell hyperplasia (GCH) has been established as a pathologic characteristic of mild, moderate, and severe asthma. Abnormalities in goblet cell number are accompanied by changes in stored and secreted mucin (MUC). The functional consequences of these changes in MUC stores and secretion can contribute to the pathophysiologic mechanisms for multiple clinical abnormalities in patients with asthma, including sputum production, airway narrowing, exacerbations, and accelerated loss in lung function. CD4(+) T cells and their T-helper type-2 cytokine products are important mediators of GCH, and MUC5AC is the dominant MUC gene that is expressed in goblet cells. The mechanism of cytokine-induced GCH, the relationships between MUC gene up-regulation and GCH, and the role of ion channels are all currently being explored. The process of working out the molecular mechanisms of GCH and goblet cell degranulation should provide new targets for novel therapeutic interventions. Such new treatments are urgently needed, because mucus hypersecretion is an important cause of morbidity and mortality in patients with asthma, and no specific treatments are available.

Exogenous interleukin-16 inhibits antigen-induced airway hyper-reactivity, eosinophilia and Th2-type cytokine production in mice

BACKGROUND

IL-16 has been described as a natural soluble CD4-ligand with immunosuppressive effects in vitro. However, little is known about the effect of IL-16 on immune responses in vivo.

OBJECTIVE

In the present study, we examined the effect of IL-16 administration in a murine model of allergic asthma. Next, we determined whether these effects were mediated by modulation of CD4+ T lymphocytes.

METHODS AND RESULTS

Intraperitoneal administration of IL-16 completely inhibits antigen-induced airway hyper-responsiveness and largely decreases the number of eosinophils in bronchoalveolar lavage fluid (> 90%) and airway tissue of ovalbumin-sensitized and challenged mice. Firstly, it appears that thoracic lymph node cells isolated from in vivo IL-16-treated ovalbumin-challenged animals produce less IL-4 (77%) and IL-5 (85%) upon antigenic re-stimulation, when compared to vehicle-treated mice. Secondly, pre-incubation of lymphocytes with IL-16 in vitro reduces antigen-induced proliferation (55%) and Th2-type cytokine production (IL-4; 56%, IL-5; 77%). Thirdly, the presence of IL-16 during priming cultures of TCR transgenic T cells (DO11.10), reduces IL-4 (33%) and IL-5 (35%), but not IL-10 and IFNgamma levels upon re-stimulation.

CONCLUSION

It can be concluded that IL-16 has potent immunosuppressive effects on a Th2dominated allergic airway response.

Effect of combining salmeterol and fluticasone on the progression of airway remodeling

In subjects insufficiently controlled with low to moderate doses of inhaled corticosteroids, adding beta-agonists is clinically more beneficial than increasing the dose of inhaled corticosteroids. In the present study, we investigated the effect of adding salmeterol to fluticasone on allergen-induced airway inflammation and remodeling. Sensitized rats, in which characteristics of remodeling had been induced by ovalbumin exposure every 2 days from Days 14 to 28, were further exposed to ovalbumin or PBS from Days 29 to 42. During the last 2 weeks, before allergen exposure, rats were treated with aerosolized fluticasone propionate (10 mg), salmeterol (1 mg), salmeterol (1 mg) plus fluticasone propionate (10 mg), or placebo. After 4 weeks of ovalbumin exposure, the airways showed inflammatory changes, goblet cell hyperplasia, and enhanced fibronectin and collagen deposition. Salmeterol in monotherapy decreased bronchoalveolar lavage fluid eosinophil number but had no influence on structural changes. Combining salmeterol with fluticasone propionate counteracted goblet cell hyperplasia, but increased the amount of fibronectin and collagen in the airway wall. These effects of salmeterol did not influence airway responsiveness. We conclude that the combination of salmeterol and fluticasone propionate enhances aspects of allergen-induced airway remodeling. This is not accompanied by changes in airway responsiveness.

Allergic inflammatory response to short ragweed allergenic extract in HLA-DQ transgenic mice lacking CD4 gene

To investigate the role of HLA-DQ molecules and/or CD4(+) T cells in the pathogenesis of allergic asthma, we generated HLA-DQ6 and HLA-DQ8 transgenic mice lacking endogenous class II (Abeta(null)) and CD4 genes and challenged them intranasally with short ragweed allergenic extract (SRW). We found that DQ6/CD4(null) mice developed a strong eosinophilic infiltration into the bronchoalveolar lavage and lung tissue, while DQ8/CD4(null) mice were normal. However, neither cytokines nor eosinophil peroxidase in the bronchoalveolar lavage of DQ6/CD4(null) mice was found. In addition, the airway reactivity to methacholine was elevated moderately in DQ6/CD4(null) mice compared with the high response in DQ/CD4(+) counterparts and was only partially augmented by CD4(+) T cell transfer. The DQ6/CD4(null) mice showed Th1/Th2-type cytokines and SRW-specific Abs in the immune sera in contrast to a direct Th2 response observed in DQ6/CD4(+) mice. The proliferative response of spleen mononuclear cells and peribronchial lymph node cells demonstrated that the response to SRW in DQ6/CD4(null) mice was mediated by HLA-DQ-restricted CD4(-)CD8(-)NK1.1(-) T cells. FACS analysis of PBMC and spleen mononuclear cells demonstrated an expansion of double-negative (DN) CD4(-)CD8(-)TCRalphabeta(+) T cells in SRW-treated DQ6/CD4(null) mice. These cells produced IL-4, IL-5, IL-13, and IFN-gamma when stimulated with immobilized anti-CD3. IL-5 ELISPOT assay revealed that DN T cells were the cellular origin of IL-5 in allergen-challenged DQ6/CD4(null) mice. Our study shows a role for HLA-DQ-restricted CD4(+) and DN T cells in the allergic response.

Granulocyte depletion and dexamethasone differentially modulate airways hyperreactivity, inflammation, mucus accumulation, and secretion induced by rmIL-13 or antigen

The intratracheal administration of interleukin (IL)-13 to hyperresponsive BP2 mice induces bronchopulmonary hyperreactivity (BHR), eosinophilia, mucus and MUC5AC accumulation, similar to those observed after ovalbumin (Ova) treatment when mice are immunized. mRNAs for IL-4 peaked at 6 h after Ova challenge, then vaned, whereas IL-13 expression was stable for a longer period, suggesting different effects. Inhalation of aerosolized methacholine by immunized mice 72-96 h after Ova reduced epithelial mucus content, and enriched the bronchoalveolar lavage fluid (BALF) mucus. The role of granulocytes for mucus accumulation was studied using vinblastine or the antigranulocyte antibody RB6-8C5, which interfered to a limited extent only with allergen-induced mucus accumulation. By contrast, eosinophilic and neutrophilic inflammation, as well as BHR, were completely suppressed. Granulocytes are thus involved in Ova-induced BHR, whereas mucus accumulation and BHR are unrelated. Granulocytes seem to be more implicated in rmIL-13-induced mucus, which is reduced by the antigranulocyte antibody, whereas BHR is unaffected. The glucocorticosteroid dexamethasone reduced all the parameters evaluated after Ova or after rmIL-13. Because the effects of IL-13 are glucocorticoid-sensitive, they probably involve secondary mechanisms.

Genetics of allergen-induced asthma

Antigen-induced airway hyperresponsiveness and airway inflammation are features of both human asthma and animal models of this disease. The genesis of these key asthma phenotypes represents the summation of a complex cascade of immune responses. It is hypothesized that multiple cell types are involved in the induction, propagation, and maintenance of these immune processes. Several molecules have been reported to be essential for cell-cell interactions, inflammatory cell recruitment, and effector functions leading to the overall expression of the asthmatic phenotype. This review summarizes the genetic evidence supporting a role for these molecules in antigen-driven airway hyperresponsiveness and inflammation.

Suppression of asthma-like responses in different mouse strains by oral tolerance

In this study we examined the effect of oral antigen (Ag) administration on the development of experimental asthma in different mouse strains. We selected BALB/c, BP2, CBA/Ca interleukin (IL)-5 transgenic, and BALB/c T-cell receptor-delta-deficient mouse strains because they exhibit different aspects of the asthma syndrome. Mice exposed to 1% ovalbumin (OVA), dissolved in the drinking water for 5 consecutive days, became unresponsive to subsequent immunogenic OVA challenges. This regimen of OVA administration induced Ag-specific unresponsiveness in all mouse strains tested, including gammadelta-deficient mice that are said to be resistant to tolerance induction. The Ag-specific unresponsiveness was characterized by reduced (almost absent) airway eosinophilic inflammation, airway hyperreactivity, and mucus production; also by low levels of T helper (Th) 2-type cytokines in bronchoalveolar lavage fluid, and decreased immunoglobulin (Ig) G1 and IgE OVA-specific antibody production. The unresponsive state was not associated with increased levels of the suppressive cytokines IL-10 and transforming growth factor (TGF)-beta or with immune deviation toward the Th1 pathway due to increased levels of interferon-gamma and IL-12. Moreover, treatment with anti- TGF-beta antibodies did not abrogate oral tolerance. Oral Ag administration was quite effective in suppressing the development of key features of asthma when initiated after primary immunization (Day 0) or after booster (Day 7), but not after challenge (Day 14) when it increased allergic responses. Collectively, our findings show for the first time the beneficial and detrimental effects of oral Ag administration on the development of experimental asthma.

Airway administration of Escherichia coli endotoxin to mice induces glucocorticosteroid-resistant bronchoconstriction and vasopermeation

The effects of the administration of Escherichia coli endotoxin (lipopolysaccharide, LPS) into the airways of C57Bl/6 mice were studied. Neutrophil sequestration in the lungs and their enrichment, together with tumor necrosis factor (TNF)-alpha, in bronchoalveolar lavage fluid (BALF) were associated with bronchoconstriction and bronchopulmonary hyperreactivity (BHR) to methacholine and alveolocapillary dysfunction. Granulocyte depletion by the myelotoxic drug vinblastine failed to modify TNF-alpha production and prevented LPS-induced neutrophil recruitment to lungs and BALF, bronchoconstriction, and BHR. Neutrophils were again sequestered in the lungs when LPS was administered 4 to 5 d after vinblastine, whereas inhibition of their passage to BALF persisted. Under those conditions, bronchoconstriction and BHR by LPS also recovered, showing that these functional effects are independent from BALF neutrophil enrichment but require lung sequestration. Administration of granulocyte colony-stimulating factor after vinblastine counteracted its effects and allowed the recovery of lung neutrophil sequestration by LPS and a partial recovery of bronchoconstriction under conditions where neutrophils still failed to migrate to BALF. Dexamethasone (the phosphate salt and its free base) suppressed LPS-induced TNF-alpha generation in BALF and its neutrophil enrichment, whereas neutrophil lung sequestration, bronchoconstriction, BHR, and alveolocapillary dysfunction were marginally reduced and only so at low doses of dexamethasone, higher doses being inactive or aggravating. In situ neutrophil activation could account for LPS-induced bronchoconstriction and BHR, both of which are refractory to steroids and appear to be mediated by unrelated mechanisms, which may be relevant for acute respiratory distress syndrome, a condition for which LPS administration is used as a model.

Degranulation status of airway tissue eosinophils in mouse models of allergic airway inflammation

Eosinophil degranulation is a characteristic feature of asthma and allergic rhinitis. However, degranulated eosinophils have not been convincingly demonstrated in the common mouse models of these airway diseases. This study uses eosinophil peroxidase (EPO) histochemistry and transmission electron microscopy (TEM) analysis to assess eosinophil degranulation in the airways of ovalbumin (OVA)-sensitized and challenged BALB/c and C57BL/6 mice. Using TEM we also examined mouse and human blood eosinophils after in vitro incubation with formyl-Met-Leu-Phe (fMLP) or phorbol myristate acetate (PMA). Although OVA exposure induced significant nasal and lung eosinophilia, we did not observe any of the known cellular processes by which eosinophils release their granule products, i.e., eosinophil cytolysis, piecemeal degranulation, and exocytosis. The occurrence of other allergen-induced degranulation events was ruled out because no difference in granule morphology was observed between lung-tissue eosinophils and blood or bone-marrow eosinophils from control animals. Accordingly, there was no detectable extracellular EPO in lung tissues of allergic mice. Similarly, mouse blood eosinophils remained nondegranulated in vitro in the presence of fMLP and PMA, whereas the same treatment of human eosinophils resulted in extensive degranulation. This investigation indicates that OVA-induced airway inflammation in the present mouse strains does not involve significant eosinophil degranulation. It is speculated that this dissimilarity from the human disease may be due to a fundamental difference in the regulation of mouse and human eosinophils.

Airway goblet-cell mucus secretion

A mucus hypersecretory phenotype is a dominant characteristic of chronic airways diseases such as chronic bronchitis and asthma. This phenotype develops following chronic exposure of the respiratory tract to particulate matter, allergens, irritants and/or pathogens. The associated increase in the mucus-producing potential of the respiratory epithelium represents an innate host response that can be modulated by elements of the adaptive host response. Although elevation of mucus production is designed to protect the airways, increasing evidence suggests that in excess it can be detrimental to health. Considerable progress has been made over the past five years in understanding the mechanisms involved in the development and regulation of the hypersecretory phenotype. This progress has set the stage for the development of successful dedicated mucomodulatory strategies to counter the negative impact of excess mucus production in respiratory disease.

Murine myeloid progenitor responses to GM-CSF and eosinophil precursor responses to IL-5 represent distinct targets for downmodulation by prostaglandin E(2)

1. Because Prostaglandin E(2) (PGE(2)) and dibutiryl cyclic AMP (dbcAMP) modulate the production and effects of haemopoietic cytokines in allergy, we examined their ability to modulate responses of myeloid progenitors to GM-CSF, and of eosinophil precursors to IL-5. 2. The ability of PGE(2), dbcAMP, rolipram, forskolin, dbcGMP and PGD(2), to modulate the responses to GM-CSF and IL-5 in colony formation (progenitor) and eosinophil differentiation (precursor) assays using bone-marrow from nonsensitized or from intranasally-challenged, ovalbumin-sensitized mice of five strains was studied. 3. PGE(2) (10(-7) M) inhibited GM-CSF-stimulated colony formation in bone-marrow from BP-2 mice. This effect was duplicated by dbcAMP (0.3 - 1x10(-6) M), Rolipram (10(-5) M) and forskolin (3x10(-5) M), but not Prostaglandin D(2) (10(-6) M). Inhibition affected similarly all myeloid colony types. Progenitors from sensitized and challenged BP-2 mice were also inhibited by PGE(2) and cyclic AMP. PGE(2) inhibited progenitors from C57BL/10, CBA/J and A/J, but not BALB/c mice. However, BALB/c progenitors were sensitive to dbcAMP and Forskolin (10(-4) M). In contrast, in precursor assays, PGE(2) (10(-7) - 10(-9) M) blocked responses to IL-5 in bone-marrow from BP-2 and BALB/c mice, either naïve or sensitized and challenged, to a similar extent. PGD(2) (10(-6) M) was ineffective, as was PGE(2) (10(-7) M), if added after 48 h of culture. 4. In conclusion, PGE(2) inhibits the responses of bone-marrow myeloid progenitors to GM-CSF and of eosinophil precursors to IL-5, in naïve or ovalbumin sensitized and challenged mice. These effects are duplicated by cyclic AMP-elevating agents. In the BALB/c strain, the resistance of progenitors, but not precursors, to PGE(2) inhibition, indicates these developmental stages are separate targets for PGE(2) modulation.

A mechanism of antigen-induced mucus production in nasal epithelium of sensitized rats. A comparison with lipopolysaccharide-induced mucus production

We produced ovalbumin (OVA)-sensitized rats as an animal model of nasal allergy. Intranasal instillation of OVA induced hypertrophic and metaplastic changes of goblet cells in nasal epithelium of OVA- sensitized rats. Intraepithelial mucosubstance in nasal mucosa increased significantly at 24 h after 3 or 7 d of OVA instillation, accompanied by mucosal infiltration of eosinophils. The effects of H1-antagonist (d-chlorpheniramine malate), H2-antagonist (cimetidine), dexamethasone, indomethacin, cysteinyl leukotrienes (cysLTs)-antagonist (ONO1078), and antirat neutrophil antiserum on OVA-induced changes were examined. Mucus production was significantly inhibited by dexamethasone, and ONO1078, whereas eosinophil infiltration was significantly inhibited by H1-antagonist, dexamethasone, and anti-rat neutrophil antiserum. These results indicate that cysLTs (LTs C4, D4, and E4) may play an important role in antigen-induced mucus production, and that eosinophil infiltration does not relate to mucus production. Intranasal instillation of lipopolysaccharide (LPS) also induced intraepithelial mucus production, and it was significantly inhibited by dexamethasone, indomethacin, and antirat neutrophil antiserum; however, cysLTs antagonist had no effect on LPS-induced change. These results indicate that neutrophil and cyclooxygenase products are important in LPS-induced mucus production, and there are different mechanisms of mucus production between allergic inflammation and LPS stimulation.