Repeated antigen inhalation-induced reproducible early and late asthma in guinea pigs

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

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

A new house dust mite-driven and mast cell-activated model of asthma in the guinea pig

BACKGROUND

Animal models are extensively used to study underlying mechanisms in asthma. Guinea pigs share anatomical, pharmacological and physiological features with human airways and may enable the development of a pre-clinical in vivo model that closely resembles asthma.

OBJECTIVES

To develop an asthma model in guinea pigs using the allergen house dust mite (HDM).

METHODS

Guinea pigs were intranasally sensitized to HDM which was followed by HDM challenges once weekly for five weeks. Antigen-induced bronchoconstriction (AIB) was evaluated as alterations in R_n (Newtonian resistance), G (tissue damping) and H (tissue elastance) at the first challenge with forced oscillation technique (FOT), and changes in respiratory pattern upon each HDM challenge were assessed as enhanced pause (Penh) using whole-body plethysmography. Airway responsiveness to methacholine was measured one day after the last challenge by FOT. Inflammatory cells and cytokines were quantified in bronchoalveolar lavage fluid, and HDM-specific immunoglobulins were measured in serum by ELISA. Airway pathology was evaluated by conventional histology.

RESULTS

The first HDM challenge after the sensitization generated a marked increase in R_n and G, which was abolished by pharmacological inhibition of histamine, leukotrienes and prostanoids. Repeated weekly challenges of HDM caused increase of Penh and a marked increase in airway hyperresponsiveness for all three lung parameters (R_n , G and H) and eosinophilia. Levels of IgE, IgG₁ , IgG₂ and IL-13 were elevated in HDM-treated guinea pigs. HDM exposure induced infiltration of inflammatory cells into the airways with a pronounced increase of mast cells. Subepithelial collagen deposition, airway wall thickness and goblet cell hyperplasia were induced by repeated HDM challenge.

CONCLUSION AND CLINICAL RELEVANCE

Repeated intranasal HDM administration induces mast cell activation and hyperplasia together with an asthma-like pathophysiology in guinea pigs. This model may be suitable for mechanistic investigations of asthma, including evaluation of the role of mast cells.

Roles of basophils and mast cells infiltrating the lung by multiple antigen challenges in asthmatic responses of mice

BACKGROUND AND PURPOSE

Mast cell hyperplasia has been observed in the lungs of mice with experimental asthma, but few reports have studied basophils. Here, we attempted to discriminate and quantify mast cells and basophils in the lungs in a murine asthma model, determine if both cells were increased by multiple antigen challenges and assess the roles of those cells in asthmatic responses.

EXPERIMENTAL APPROACH

Sensitized Balb/c mice were intratracheally challenged with ovalbumin four times. Mast cells and basophils in enzymatically digested lung tissue were detected by flow cytometry. An anti-FcεRI monoclonal antibody, MAR-1, was i.p. administered during the multiple challenges.

KEY RESULTS

The numbers of both mast cells (IgE(+) C-kit(+) ) and basophils (IgE(+) C-kit(-) CD49b(+) ) increased in the lungs after three challenges. Treatment with MAR-1 completely abolished the increases; however, a late-phase increase in specific airway resistance (sRaw), and airway eosinophilia and neutrophilia were not affected by the treatment, although the early-phase increase in sRaw was suppressed. MAR-1 reduced antigen-induced airway IL-4 production. Basophils infiltrating the lung clearly produced IL-4 after antigen stimulation in vitro; however, histamine and murine mast cell protease 1 were not increased in the serum after the challenge, indicating that mast cell activation was not evoked.

CONCLUSION AND IMPLICATIONS

Both mast cells and basophils infiltrated the lungs by multiple intratracheal antigen challenges in sensitized mice. Neither mast cells nor basophils were involved in late-phase airway obstruction, although early-phase obstruction was mediated by basophils. Targeting basophils in asthma therapy may be useful for an early asthmatic response.

Antigen-induced airway hyperresponsiveness in absence of broncho-obstruction in sensitized guinea pigs

BACKGROUND

Airway obstruction after antigen challenge is not always observed in patients with allergic asthma, even if they develop hyperresponsiveness. A similar event is observed in our guinea pig model of allergic asthma. Our aim was to study this phenomenon.

METHODS

Sensitized guinea pigs were challenged with ovalbumin (OVA) 3 times every 10 days. Animals were divided into 2 groups: (1) Guinea pigs exhibiting airway obstruction after antigen challenge (R = responders), and (2) guinea pigs lacking airway obstruction response (NR = nonresponders). After the third antigen challenge, antigen-induced airway hyperresponsiveness (AI-AHR), serum OVA-specific immunoglobulins, bronchoalveolar lavage fluid (BALF) inflammatory cells, histamine, cysteinyl leukotrienes and thromboxane A2 (TxA2) BALF levels, and in vitro tracheal contraction induced by contractile mediators and OVA were evaluated.

RESULTS

R group consistently displayed a transient antigen-induced airway obstruction (AI-AO) as well as AI-AHR, high T×A2, histamine, OVA-IgG1, OVA-IgE and OVA-IgA levels, and intense granulocyte infiltration. NR group displayed no AI-AO and no changes in BALF measurements; nevertheless, AI-AHR and elevated OVA-IgG1 and OVA-IgA levels were observed. In all groups, histamine, TxA2 and leukotriene D4 induced a similar contraction. Tracheal OVA-induced contraction was observed only in R group. AI-AHR magnitude showed a direct association with OVA-IgG1 and OVA-IgA levels. The extent of AI-AO correlated directly with OVA-IgE and inversely with OVA-IgA levels.

CONCLUSIONS

Our data suggest that TxA2 and histamine participate in AI-AO likely through an IgE mechanism. AI-AHR might occur independently of AI-AO, contractile mediators release, and airway inflammatory cell infiltration, but IgA and IgG1 seem to be involved.

Modifications of plasma 5-HT concentrations during the allergic bronchoconstriction in guinea pigs

Several contractile mediators involved in the antigen-induced airway obstruction have been identified, but the role of 5-HT (5-hydroxytryptamine or serotonin) has been scantily investigated. In this work, the potential role of 5-HT in the allergic bronchoconstriction was evaluated through a pharmacological approach and plasma 5-HT measurement in blood samples from the right and left ventricles of anesthetized guinea-pigs. Intravenous 5-HT caused a dose-dependent increase of the lung resistance in anesthetized, nonsensitized guinea pigs. Likewise, in sensitized animals the antigenic challenge with ovalbumin also caused a transient bronchoconstriction (356 ± 60% the basal value), which was largely inhibited by the blockade of serotonergic receptors with methiothepin plus tropisetron (134 ± 10%, P = .007). Sensitized animals tended to have plasma 5-HT concentrations higher than nonsensitized controls, and shortly after the peak of the allergic bronchoconstriction the 5-HT levels in the left ventricle (blood flowing out from lungs) tended to be higher than in the right ventricle (blood entering the lungs), although data dispersion precluded the obtaining of statistical significance. Interestingly, the degree of bronchoconstriction highly correlated with the concentrations of 5-HT found in the left ventricle and measured either in platelet-rich plasma (r = 0.97 P = .007) or platelet-poor plasma (r = 0.97, P = .006). After the obstructive response subsided these correlations were lost, but now the degree of bronchoconstriction turned to be correlated with 5-HT concentration in platelet concentrate (r = 0.76, P = .03). In conclusion, our results suggested that 5-HT is actively released from lungs during the antigenic challenge and that this autacoid is involved in the generation of the airway obstruction.

Intratracheal sensitization/challenge-induced biphasic asthmatic response and airway hyperresponsiveness in guinea pigs

In most experimental model of asthma using guinea pigs, the animals are made to inhale an aerosolized antigen which passes through the nasal cavity. In the present study, we attempted to create an animal model of asthma showing a biphasic asthmatic response and airway hyperresponsiveness, in which the allergic responses are restricted to the lung. Guinea pigs were sensitized by the intratracheal instillation of ovalbumin (OVA)+Al(OH)₃ once a day for 7 d, and then intratracheally challenged with OVA 12 d after the last sensitization. The change in specific airway resistance (sRaw) and airway responsiveness to histamine were measured. Pranlukast (100 mg/kg), theophylline (50 mg/kg), and dexamethasone (10 mg/kg) were orally administered 18 and 2 h before the antigen challenge. The challenge caused a marked biphasic elevation of sRaw with peaks at 5 min and 4 h. At 24 h, airway hyperresponsiveness to histamine was observed. Pranlukast, theophylline, and dexamethasone suppressed the late asthmatic response and airway hyperresponsiveness. The early asthmatic response was inhibited by theophylline and dexamethasone. In conclusion, the intratracheal sensitization and challenge caused a biphasic asthmatic response and airway hyperresponsiveness in guinea pigs. This model may be useful for the evaluation of anti-asthma drugs.

Absence of nasal blockage in a Japanese cedar pollen-induced allergic rhinitis model mouse

BACKGROUND

Japanese cedar pollen-induced allergic rhinitis in a guinea pig model clearly induced not only sneezing but also biphasic nasal blockage. To date, there have only been a few reports on models of murine allergic rhinitis which clearly show nasal blockage. Therefore, in order to try and develop such a model, we administered multiple dosages of intranasal pollen or purified antigen protein Cry j 1.

METHODS

B10.S mice were sensitized by intranasal instillations of either pollen extract or Cry j 1 twice a day for 7 days, which was adsorbed on Al(OH)(3). Subsequently, once a week, the mice were given multiple intranasal instillation challenges of either the pollen suspension or Cry j 1 and the frequency of sneezing was observed after respective challenges were made. Specific airway resistance (sRaw) was measured as an indicator for nasal blockage. Cry j 1-specific IgE levels were measured using an enzyme-linked immunosorbent assay.

RESULTS

The serum Cry j 1-specific IgE level showed clear elevation only in the group sensitized by Cry j 1 + Al(OH)(3) and then challenged by Cry j 1. No elevations were seen in the groups sensitized by pollen extract + Al(OH)(3) followed by a pollen suspension challenge. There was an immediate increase in sneezing after challenges in all of the sensitized-challenged groups. Nevertheless, no increases in sRaw in any of the groups were detected at any of the time points during the 8 hours following the challenges.

CONCLUSIONS

Cry j 1 may be more effective than crude antigens for efficient sensitization/challenge in mice. No increase in sRaw occurred, even in mice that possessed high amounts of Cry j 1-specific IgE and that exhibited sneezing.

Induction of late airway response was involved in serum antigen-specific immunoglobulin G in rats

The antigen-induced immediate airway response (IAR) has been considered a form of bronchoconstriction mainly provoked by histamine and leukotriene C4/D4/E4, which are released by stimulation by antigen-specific IgE. However, the pathophysiological features of the antigen-induced late airway response (LAR) are not yet fully understood. In the present study, sensitized rats were repeatedly exposed to ovalbumin (OVA) to induce IAR and LAR, and the immunological profiles of IAR and LAR were examined. The first antigen inhalation induced only IAR but not LAR. However, the second antigen inhalation 7 days after IAR induced LAR but not IAR. Tumor necrosis factor (TNF)-alpha level in BALF in LAR was significantly higher than that in IAR, although there were no differences in histamine, leukotriene C4/D4/E4, interleukin (IL)-1beta, or IL-13 levels between IAR and LAR. Serum antigen-specific IgE titer was high in both IAR and LAR, but serum antigen-specific IgG, IgG1, and IgG2a titers were dramatically high in LAR but not IAR. There were significant correlations between antigen-specific IgG, IgG1, and IgG2a titers and LAR. Interestingly, LAR could be induced in normal rats by transfer of serum from LAR rats, which exhibited high antigen-specific IgG, IgG1, and IgG2a titers. In conclusion, these findings suggest that repeated antigen inhalation converts IAR to LAR, and that LAR is a reaction triggered by antigen-specific IgG and involving TNF-alpha. This is the first study to directly suggest the involvement of antigen-specific IgG in the induction of LAR.

Involvement of galectin-9 in guinea pig allergic airway inflammation

BACKGROUND

There is little information about the involvement of galectin-9 (Gal-9) in allergic inflammation. Thus, we investigated the role of Gal-9 in asthma model guinea pigs.

METHODS

Airway resistance (R(aw)) was measured using a double-flow plethysmograph system. Gal-9 expression in the lung was assessed by Western blot and immunohistochemistry. Eosinophil chemotactic activity was evaluated in a chamber containing a polyvinylpyrolidone-free membrane. Cell apoptosis was analyzed on a flowcytometry with propidium iodide.

RESULTS

In cloning guinea pig Gal-9 we identified three isoforms that differ only in the length of their linker peptides, just as with human Gal-9. Guinea pig Gal-9 was found to be a chemoattractant for eosinophils and to promote induction of apoptosis in sensitized but not non-sensitized T lymphocytes. In allergic airway hypersensitivity model, a low level of Gal-9 expression was observed in the nonsensitized/nonchallenged group, but upregulation was detected at 7 h after challenge and sustained up to 24 h. Such upregulation correlated with elevation of eosinophil peroxidase activity but not with increased R(aw).

CONCLUSIONS

The present results provide evidence that Gal-9 is not involved in airway hypersensitivity, but is partly involved in prolonged eosinophil accumulation in the lung.

Development and Evaluation of a Direct Sandwich Enzyme-Linked Immunosorbent Assay for the Quantification of Guinea-Pig Immunoglobulin E

The purpose of this study was to develop and evaluate a direct sandwich enzyme-linked immunosorbent assay (ELISA) for the immunoglobulin E (IgE) in serum and plasma from guinea pig using mouse monoclonal antibodies specific for guinea-pig IgE. Mouse monoclonal antibodies were raised against purified IgE protein. The ELISA was performed using a combination of two anti-IgE monoclonal antibodies. One antibody was labeled with horseradish peroxidase (HRP), and the other was coated on polystyrene wells. Purified guinea-pig IgE was used as the standard material. The validity of the ELISA was confirmed by precision, dilution, recovery, and interference tests. The range of detection was 3.1-800 ng of IgE mass per mL of serum and plasma. The intra- and inter-assay coefficients of variation were 4.6% and 5.7%, respectively, or less. The recovery test showed variation only between 92.1% and 111.8%, and the anticoagulants showed noninterference with the IgE assay. The mean serum IgE mass concentration in OVA-sensitized guinea pigs was 29438 ng/mL, and it was 48.6 ng/mL in normal guinea pigs. The present ELISA is useful and practical for specific measurement of the guinea-pig IgE, and it is surmised that it would be suitable for use in allergological and pharmacological research.

Induction of a late asthmatic response associated with airway inflammation in mice

To investigate mechanisms underlying the late asthmatic response, we developed a murine model using repetitive intratracheal antigen challenge. BALB/c mice sensitized by i.p. injection with ovalbumin+alum were challenged with ovalbumin intratracheally 4 times. The 1st challenge induced early airway obstruction peaking at 30 min but without a late response; however, the 4th challenge caused not only early but also late airway obstruction at 2-8 h. Eosinophils, and CD4+ and CD8+ T lymphocytes were increased in the airway before the 4th but not before the 1st-3rd challenges. The numbers of IgE+/CD117+ (mast) cells were also increased in the lung before the 4th challenge. Levels of Th2 cytokines were also increased in the airway. Daily administration of dexamethasone during the challenge period suppressed all these inflammatory events. Thus, this experimental late asthmatic response is associated with Th2 cytokine production from inflammatory cells recruited as a consequence of the 1st-3rd challenges.

Intratracheal dosing with disodium cromoglycate inhibits late asthmatic response by attenuating eicosanoid production in guinea pigs

Disodium cromoglycate is an anti-asthmatic drug that has mast cell-stabilizing effects and other anti-inflammatory effects. However, the mechanisms of its anti-inflammatory effects are unclear. In this study, we evaluated effects of disodium cromoglycate on eosinophilia, early and late asthmatic responses, and production of arachidonic acid metabolites in guinea pig lungs. Guinea pigs were alternately sensitized and challenged by exposure to mists of ovalbumin+Al(OH)(3) and ovalbumin, respectively. Disodium cromoglycate (0.5-2 mg/0.1 ml/animal) administered intratracheally before the fifth challenge dose-dependently inhibited asthmatic response, but early asthmatic response was not affected. Disodium cromoglycate at 2 mg/animal potently suppressed increases in cysteinyl leukotrienes (CysLTs) and thromboxane A(2) in the lung during late asthmatic response. Eosinophilia was slightly reduced by disodium cromoglycate. The inhibitory effect of disodium cromoglycate on late asthmatic response is apparently due to inhibition of the release of arachidonic acid metabolites, some of which may be derived from eosinophils that infiltrate the lung.

Delayed-type asthmatic response induced by repeated intratracheal exposure to toluene-2,4-diisocyanate in guinea pigs

BACKGROUND

A toluene-2,4-diisocyanate (TDI)-induced asthma model, in which delayed-type hypersensitivity-like asthmatic airway obstruction is elicited restrictively in the lung, has never been developed.

METHODS

Guinea pigs were percutaneously sensitized with TDI. For the challenges, once every 2 weeks for a total of 5 times, TDI mists were delivered directly to the lung through an oral cannula, with its tip being positioned in the opening of the trachea. Time-course changes in specific airway resistance (sRaw) were measured by double-flow plethysmography. Basic mechanisms underlying TDI-induced asthma were analyzed.

RESULTS

After the 2nd-5th challenges, induction of both an early increase in sRaw that peaked at 10 min and a delayed-type sRaw elevation that peaked at 22 h were observed. Interestingly, in the sensitized/challenged animals, baseline sRaw was elevated by repeated challenge as compared to that seen for non-sensitized animals. Intratracheal administration of a bronchodilator, salbutamol, strongly suppressed the early asthmatic response (EAR) but not the delayed-type asthmatic response (DAR). During DAR, both albumin leakage and fucose secretion into the bronchoalveolar lavage fluid were increased. The cysteinyl leukotriene antagonist pranlukast failed to inhibit either EAR or DAR while the corticosteroid dexamethasone significantly suppressed DAR, without significantly affecting EAR.

CONCLUSIONS

Effective delivery of TDI to the lung may induce reproducible DAR in sensitized guinea pigs with chronicity that is reflected by an increase in the sRaw baseline. DAR is not mediated by constriction of airway smooth muscles and is probably due to the concurrent presence of mucosal edema and mucus hypersecretion in the airways.

Cysteinyl leukotriene-dependent interleukin-5 production leading to eosinophilia during late asthmatic response in guinea-pigs

BACKGROUND

Allergic airway eosinophilia is suppressed by cysteinyl leukotriene (CysLT) receptor (CysLT1 receptor) antagonists in several species including humans and guinea-pigs, suggesting that CysLTs are directly or indirectly involved in induction of the response.

OBJECTIVE

We examined the effect of CysLT antagonists (pranlukast and MCI-826) on antigen inhalation-induced eosinophilia in peripheral blood and lung, and on IL-5 activity in serum during late increase of airway resistance (late asthmatic response, LAR) in sensitized guinea-pigs.

METHODS

Guinea-pigs inhaled ovalbumin (OVA) + Al(OH)3 and OVA mists alternately for sensitization and challenge, respectively, once every 2 weeks. At the fifth challenge, the effects of CysLT antagonists and an anti-IL-5 antibody (TRFK-5) on the occurrence of LAR, and blood and lung eosinophilia, which appeared at 5 h after challenge, were examined. The time-course of IL-5 activity in the serum after the challenge was evaluated by measuring in vitro 'eosinophil survival prolongation activity'. The influence of CysLT antagonists on IL-5 activity was assessed.

RESULTS

CysLT antagonists and TRFK-5 completely abolished blood and lung eosinophilia. LAR was suppressed by both MCI-826 and TRFK-5 by 40-50%. Sera obtained from sensitized, challenged animals 3 h and 4 h after challenge induced an obvious prolongation of eosinophil survival. The activity of the sera was completely neutralized by prior exposure to TRFK-5, suggesting that it reflected IL-5 activity. Increased IL-5 activity in the serum was inhibited by both pranlukast and MCI-826 by over 90%.

CONCLUSIONS

CysLTs produced after antigen provocation sequentially induced IL-5 production from some immune component cells via CysLT1 receptor activation. Thus, it is likely that CysLTs indirectly cause antigen-induced eosinophilia through IL-5 production.

Comparison of cedar pollen-induced allergic rhinitis in passively and actively sensitized guinea pigs

We have developed an allergic rhinitis model in guinea pigs using Japanese cedar pollen as antigen. In the present study, we examined whether provocation by pollen induces similar magnitudes of rhinitis symptoms in passively and actively sensitized guinea pigs. One group of animals was actively sensitized by intranasal application of pollen extract, and another was passively sensitized by intraperitoneal injection with anti-pollen serum. Actively and passively sensitized groups were then challenged by repeated and a single pollen inhalation, respectively. In both groups, sneeze was induced immediately after the challenge. The actively sensitized animals developed not only early but also late nasal blockage, whereas the passively sensitized animals showed only early nasal blockage. In both groups, an H1 antagonist, mepyramine, inhibited the occurrence of sneezing but did not inhibit nasal blockage. Nasal hyperresponsiveness to intranasal instillation of leukotriene D4 was obvious only in the actively sensitized animals. We thus conclude that although early nasal blockage is induced by a single antigen-antibody reaction, repetitive anaphylactic reaction is required for occurrence of late nasal blockage and hyperresponsiveness to stimuli. Furthermore, histamine plays a central role in induction of sneezing but not in nasal blockage, irrespective of whether animals are actively or passively sensitized.