The inhibitory effect of terfenadine and flurbiprofen on early and late-phase bronchoconstriction following allergen challenge in atopic asthma

Allergen inhalation challenge, refractoriness and the effects of ibuprofen

Background

Bronchoprovocation challenges use direct or indirect acting stimuli to induce airflow obstruction. Indirect stimuli either non-allergic/non-IgE mediated (e.g. exercise, mannitol) or allergic/IgE mediated (i.e. allergen) trigger mast cells to release bronchoconstricting mediators (e.g. cysteinyl leukotrienes, histamine). Performing repeat challenges within a short timeframe (e.g. 3 h) with non-allergic indirect stimuli results in a diminished, refractory response to the second challenge that is inhibited by non-steroidal anti-inflammatory medications. Cross refractoriness occurs between indirect stimuli. It follows that repeat bronchoprovocation with allergen might exhibit refractoriness that might be altered by ibuprofen. We assessed the response to a second allergen challenge performed 24 h after an initial allergen challenge to determine if the response is refractory. If refractoriness developed, the study aimed to determine whether a single dose of ibuprofen would alter the refractory response to the second allergen challenge. In the absence of a refractory response, the study design allowed for the assessment of the effect of ibuprofen on allergen challenge outcomes, including indices of airway inflammation.

Methods

Thirteen mild atopic asthmatics were enrolled in a randomized, double-blind, placebo controlled, cross-over study. Ibuprofen (400 mg) or placebo was administered 1 h prior to the first of two allergen challenges, performed 24 h apart. Blood and sputum eosinophils, airway responsiveness to methacholine and levels of fractional exhaled nitric oxide were assessed before and 7 h after each allergen challenge. All data were log transformed and differences in geometric means were analyzed by paired t-tests.

Results

After placebo, early asthmatic responses for the two challenges were not significantly different (p = 0.82). A single 400 mg dose of ibuprofen decreased both the early (p = 0.03; n = 12) and late asthmatic responses (p = 0.03; n = 3).

Conclusion

Allergen challenges conducted 24 h apart do not exhibit refractoriness. Single dose ibuprofen inhibits early and late asthmatic responses to allergen bronchoprovocation. Ibuprofen should be withheld for at least 24 h prior to investigations utilizing allergen bronchoprovocation.

Trial registration clinicaltrials.gov #NCT02327234

The role of antihistamines in asthma management

Histamine is an important mediator in airway inflammation. It is elevated in the airways of asthmatic patients and is responsible for many of the pathophysiological features in asthma. Antihistamines block the actions of histamine and also have effects on inflammation which is independent of histamine-H(1)-receptor antagonism. Antihistamines have been shown to have bronchodilatory effects, effects on allergen-, exercise-, and adenosine-monophosphate-challenge testing, and also to prevent allergen-induced nonspecific airways hyperresponsiveness. Clinical studies have shown mixed results, and some studies have reported beneficial effects of azelastine, cetirizine, desloratadine, and fexofenadine on asthma symptoms or physiological measures in patients with asthma. The combination of an antihistamine and a leukotriene receptor antagonist has been shown to have additive effects in certain studies. Antihistamines have also been shown to delay or prevent the development of asthma in a subgroup of atopic children. These data suggest that antihistamines may have beneficial effects in the management of asthma.

Allergen-induced airway responses

Environmental allergens are an important cause of asthma and can contribute to loss of asthma control and exacerbations. Allergen inhalation challenge has been a useful clinical model to examine the mechanisms of allergen-induced airway responses and inflammation. Allergen bronchoconstrictor responses are the early response, which reaches a maximum within 30 min and resolves by 1-3 h, and late responses, when bronchoconstriction recurs after 3-4 h and reaches a maximum over 6-12 h. Late responses are followed by an increase in airway hyperresponsiveness. These responses occur when IgE on mast cells is cross-linked by an allergen, causing degranulation and the release of histamine, neutral proteases and chemotactic factors, and the production of newly formed mediators, such as cysteinyl leukotrienes and prostaglandin D2. Allergen-induced airway inflammation consists of an increase in airway eosinophils, basophils and, less consistently, neutrophils. These responses are mediated by the trafficking and activation of myeloid dendritic cells into the airways, probably as a result of the release of epithelial cell-derived thymic stromal lymphopoietin, and the release of pro-inflammatory cytokines from type 2 helper T-cells. Allergen inhalation challenge has also been a widely used model to study potential new therapies for asthma and has an excellent negative predictive value for this purpose.

The role of histamine in asthma

Histamine is a ubiquitous inflammatory mediator intimately associated with the pathology of allergy. Traditional antihistamines, targeting the histamine H1 receptor, have failed to demonstrate a significant role for histamine in asthma. Novel immunomodulatory roles for histamine and the discovery of a novel histamine receptor, the histamine H4 receptor, have resulted in a reassessment of its importance in asthma.

Allergen-induced airway inflammation and its therapeutic intervention

Allergen inhalation challenge has been useful for examining the mechanisms of allergen-induced airway inflammation and the associated physiological changes and for documenting the efficacy of drugs to treat asthma. Allergen inhalation by a sensitized subject results in acute bronchoconstriction, beginning within 15-30 min and lasting 1-3 hr, which can be followed by the development of a late asthmatic response. Individuals who develop both an early and late response after allergen have more marked increases in airway hyperresponsiveness, and greater increases in allergen-induced airway inflammation, particularly in airway eosinophils and basophils. All of the currently available and effective treatments for asthma modify some aspects of allergen-induced responses. These medications include short-acting and long-acting inhaled β₂-agonists, inhaled corticosteroids, cromones, methylxanthines, leukotriene inhibitors, and anti-IgE monoclonal antibody. In addition, allergen inhalation challenge has become a useful method which can, in a very limited number of patients, provide key information on the therapeutic potential of new drugs being developed to treat asthma.

The role of histamine H1 and H4 receptors in allergic inflammation: the search for new antihistamines

Histamine has a key role in allergic inflammatory conditions. The inflammatory responses resulting from the liberation of histamine have long been thought to be mediated by the histamine H1 receptor, and H1-receptor antagonists--commonly known as antihistamines--have been used to treat allergies for many years. However, the importance of histamine in the pathology of conditions such as asthma and chronic pruritus may have been underestimated. Here, we review accumulating evidence suggesting that histamine indeed has roles in inflammation and immune function modulation in such diseases. In particular, the discovery of a fourth histamine receptor (H4) and its expression on numerous immune and inflammatory cells has prompted a re-evaluation of the actions of histamine, suggesting a new potential for H4-receptor antagonists and a possible synergy between H1 and H4-receptor antagonists in targeting various inflammatory conditions.

The allergen bronchoprovocation model: an important tool for the investigation of new asthma anti-inflammatory therapies

Allergen bronchoprovocation tests have been used for more than two decades in the investigation of respiratory allergic diseases such as asthma and rhinitis. These bronchial challenges are now well standardized and can offer key information on the therapeutic potential of new agents and on their anti-inflammatory effects on the airways. Both standard and low-dose allergen provocations are safe when performed by experienced investigators and do not lead to persistent worsening of asthma or change in airway function. The evaluation of new therapeutic agents by these methods can also provide important information on the mechanisms of development and persistence of airway diseases.

Prospects for antihistamines in the treatment of asthma

Antihistamines have been evaluated as potential therapies for asthma for more than 50 years. With first-generation compounds, side effects prevented effective dosing. By reviewing published studies of the effectiveness of terfenadine, cetirizine, and loratadine in clinical asthma, evidence for the relevant effect of the second-generation antihistamines on bronchial asthma can be found. Terfenadine, at doses of 120 or 180 mg twice a day, reduced symptoms and improved pulmonary function in mild and moderate allergic asthma but was ineffective in severe perennial asthma. Fexofenadine at doses used for allergic rhinitis had little effect on seasonal allergic asthma. Research is ongoing to determine the effects of higher doses of fexofenadine. In 5 studies, cetirizine at doses of 10 to 20 mg, once or twice daily, consistently improved asthma symptoms compared with placebo or terfenadine 60 mg twice a day in 2 cases, whereas in 2 studies, loratadine at doses of 10 to 20 mg daily has not produced significant improvement in asthma. However, loratadine 5 mg combined with 60 mg of pseudo-ephedrine twice a day significantly improved both asthma symptoms and peak expiratory flow. Similarly, the combination of loratadine 20 mg and the leukotriene-receptor antagonist montelukast improved asthma symptoms, peak expiratory flow, and beta-agonist use over montelukast alone. Therefore, there might be a role for second- and third-generation antihistamines in treating mild and moderate asthma, which might require administering doses greater than those commonly used to treat allergic rhinitis. If higher doses are sedative, the addition of decongestants or leukotriene-receptor antagonists might enhance the effects of lower doses of the antihistamines.

Role of histamine in the pathophysiology of asthma: immunomodulatory and anti-inflammatory activities of H1-receptor antagonists

Cumulative clinical and laboratory evidence on histamine and its actions suggests that it has a pathophysiologic role in asthma. These findings have renewed interest in the potential therapeutic role of H1 antihistamines in this disease. A murine model of allergen-induced airway inflammation and methacholine-induced airway hyperresponsiveness has been used to clarify mechanisms of airway function, to identify potential therapeutic targets, and to investigate the effects of the H1-receptor antagonist fexofenadine. Findings suggest that there may be a role for second-generation antihistamines in treating asthma, with patient selection as well as dosing both important therapeutic considerations. Because high-dose therapy may be required to achieve a clinical response, agents with the widest therapeutic window and the lowest potential for sedation would offer the greatest therapeutic potential.

Fexofenadine modulates T-cell function, preventing allergen-induced airway inflammation and hyperresponsiveness

BACKGROUND

Antihistamines have been evaluated for usefulness in the treatment of asthma for more than 50 years. Interest was limited until the introduction of newer compounds that were free of much of the dose-limiting sedation associated with the earlier drugs.

OBJECTIVE

In a murine model of allergen-induced airway inflammation and hyperresponsiveness, the efficacy of an H1 receptor antagonist to prevent allergic inflammation and altered airway function was evaluated.

METHODS

Mice were sensitized and challenged to an allergen, ovalbumin, which elicited marked airway and tissue eosino-philia and airway hyperresponsiveness. Fexofenadine was administered before challenge, and airway responsiveness to inhaled methacholine, airway and tissue eosinophilia, bronchoalveolar lavage fluid cytokine levels, and serum IgE levels were assayed. In a second group of experiments, sensitized and challenged mice were treated or not treated with fexofenadine before challenge. T cells were isolated from the lungs and adoptively transferred into naive recipients before exposure to limited airway allergen challenge, and lung function and inflammation were evaluated.

RESULTS

Fexofenadine treatment of sensitized mice prevented the development of airway hyperresponsiveness in both the primary sensitization and challenge, as well as in the adoptive transfer experiments. These changes were accompanied by decreases in bronchoalveolar lavage and tissue eosinophilia, lymphocyte numbers, and T(H)2 cytokine production.

CONCLUSION

The results demonstrate the efficacy of an H1 receptor antagonist in preventing allergen-induced alterations in pulmonary inflammation and airway function. The data support the evaluation of drugs such as fexofenadine in the treatment of allergic asthma.

Experimental models in asthma

Histamine is an important mediator released from activated mast cells in acute bronchoconstriction provoked by allergen, exercise, hypertonic stimuli and inhaled adenosine. Histamine may also contribute to the allergen-induced late asthmatic response probably following the recruitment and activation of basophils. H1-receptor antagonists partially attenuate these responses but greater inhibition when these drugs are combined with cysteinyl LT1-receptor antagonists indicative of an interaction between mast cell-derived mediators. The combination of two or more selective mediator antagonists in the treatment of allergic disorders such as asthma offers a new therapeutic approach worthy of careful appraisal.

Inhibition of mediator and cytokine release from dispersed nasal polyp cells by terfenadine

The mechanism of action of H1-blockers requires elucidation because they may possess properties unrelated to the blockage of histamine at its receptor level. A study was performed with enzymatically dispersed cells obtained from nasal polyps to examine the effect of terfenadine (0.1-10 mumol) on the release of leukotrienes (LT) (LTC4/D4 and LTB4) after stimulation by anti-IgE, and on the spontaneous release of cytokines (granulocyte/macrophage-colony stimulating factor [GM-CSF] and tumor necrosis factor-alpha [TNF-alpha]) released from cells cultured for 6 h. Terfenadine inhibited significantly, and in a dose-dependent manner, the release of LTC4/D4, LTB4, TNF-alpha, and GM-CSF. IC50 values were determined for LTC4/D4 (8 mumol), LTB4 (9.9 mumol), TNF-alpha (6.1 mumol), and GM-CSF (4 mumol). Terfenadine was found to possess new antiallergic properties with a novel in vitro model which mimics more closely inflammatory cells of allergic rhinitis or asthma.

Pharmacologic heterogeneity of human lung and colon cells: effect of terfenadine and cetirizine

H1-blockers may have antiallergic properties which cause the blocking of eicosanoid release, and the effect of these drugs may differ according to the phenotype of mast cells. This study examined the ability of terfenadine and cetirizine to inhibit the release of arachidonic acid-derived mediators from human lung and colon cells. Dispersed cells were challenged with anti-IgE in the presence or absence of 10 microM of terfenadine or cetirizine, and the release of prostaglandin (PG)D2 and leukotriene (LT)C4/D4 was assessed by enzyme immunoassay (EIA). Terfenadine caused significant inhibition of both PGD2 and LTC4/D4 (49 +/- 9 and 29 +/- 19%, respectively) from human lung cells but had a less marked effect on PGD2 release from human colon cells (21 +/- 9% for PGD2 and 18 +/- 9% for LTC4/D4). In contrast, although cetirizine caused significant inhibition of both mediators measured in lung cells (38 +/- 16% for PGD2 and 34 +/- 19% for LTC4), it did not cause any significant inhibition of either mediator from human colon cells. These findings suggest that H1-antagonists may have additional properties, and the differential effects of cetirizine on lung and colon tissue may indicate differences in mast cell phenotype.

Role of histamine in allergen-induced asthmatic reactions, bronchial hyperreactivity and inflammation in unrestrained guinea pigs

In a new model using conscious, unrestrained and ovalbumin-sensitized guinea pigs, we investigated the effects of the selective histamine H1 receptor antagonist, mepyramine, on the development of allergen-induced early and late asthmatic reactions, bronchial hyperreactivity and airway inflammation, having each animal as its own control. In guinea pigs responding to a first allergen exposure with an early as well as a late asthmatic reaction (82% of the animals) a second, identical, allergen provocation was performed, in the absence (control) or presence of 1 mg/ml mepyramine aerosol, inhaled for 10 min, 1 h before provocation. The mepyramine treatment significantly reduced both early and late asthmatic reactions and prevented the development of bronchial hyperreactivity to histamine and methacholine after both reactions. Examination of the bronchoalveolar lavage fluid 24 h after the second allergen provocation revealed a general reduction of inflammatory cells after mepyramine treatment. The results indicate that histamine, released during the early asthmatic reaction, contributes to the development of the late asthmatic reaction as well as of early and late bronchial hyperreactivity, possibly via an effect on airway inflammation.

Modulation of eicosanoid and histamine release from human dispersed lung cells by terfenadine

Terfenadine is an H1-blocker that may have antiallergic properties. A study was carried out to examine the ability of terfenadine to inhibit the release of histamine and arachidonic-acid-derived mediators from human lung cells. Cells were dispersed from fresh human lung tissue obtained from four accident victims whose hearts were donated for transplantation and four lung cancer resections. Cells were dispersed by enzymatic digestion with type XIV protease and chymopapain, and this resulted in a cell population containing approximately 5% mast cells. The remaining cells were mainly macrophages. The cells were challenged with anti-IgE at a 1/1000 dilution. Cells were challenged without terfenadine and after a preincubation of 0.1, 1, and 10 mumol terfenadine. The release of PGD2 and LTC4/D4 was assessed with an EIA. Histamine was assayed by RIA with a monoclonal antibody against acylated histamine. A release of both eicosanoids and histamine was observed in all experiments. An inhibition of eicosanoids was observed at both 1 and 10 mumol terfenadine (median percentage of inhibition of PGD2: 38.00 +/- 15.65 and 56.00 +/- 13.12; median percentage of inhibition of LTC4/D4: 37.5 +/- 19.80 and 52.5 +/- 26.8). On the other hand, histamine release was not blocked by terfenadine. Terfenadine inhibits, in a dose-dependent manner, the release of eicosanoids after challenge of dispersed lung cells by anti-IgE, and this effect may have some clinical relevance.

Pharmacotherapy of childhood asthma. An inflammatory disease

The recognition that asthma constitutes 2 kinds of physiopathological reactions, namely bronchospasms (immediate reactions) and inflammatory responses (late reactions), suggests that the treatment should be focused against these events. Furthermore, the allergen provocation model, showing the existence of immediate and late asthmatic reactions, can be used to study the effects of different antiasthmatic drugs. Recently, the importance of inflammation in the pathogenesis of asthma in adults has led to the development of therapeutic regimens in which anti-inflammatory treatments are used frequently as a first-line step in the management of asthma. Although at the moment the hard data showing inflammation in childhood asthma are scarce, it is assumed that childhood asthma constitutes the same kind of chronic inflammatory processes as in adult asthma and that its treatment should also include anti-inflammatory drugs.

The effect of a beta 2-adrenergic agonist and a histamine H1-receptor antagonist on the late asthmatic response to inhaled antigen

In this double-blind, randomized, cross-over trial, the role of histamine and the possible protective effect of a beta 2-adrenergic agonist in the later asthmatic response to inhaled antigen was investigated in nine atopic asthmatic patients. On four study days, 2-4 weeks apart, patients were given either: placebo; salbutamol aerosol 400 micrograms before and 200 micrograms 2-hourly after challenge; oral terfenadine 120 mg 2 h before and 10 h after challenge; and, on the final day, lung function was monitored without medication or antigen challenge. A nebuliser-dosimeter system was used to deliver a predetermined, single dose of antigen aerosol. Response was assessed by specific airways conductance (SGAW) measured in a body plethysmograph; FEV1 and PEFR were measured with a Pocket Spirometer. All measurements were made for 10 h in the clinic and then the patients continued to record PEFR and FEV1 at home for at least 2 more hours. Similar findings were obtained with all three lung function parameters. After challenge, the early response (ER) was small when compared with the late response (LR). All patients had a definite LR on the placebo day when FEV1 was compared with 'no challenge day'. Neither drugs had much effect on the small ER. The LR was not altered by terfenadine but was very significantly attenuated by salbutamol; the mean maximum fall in FEV1 during LR being 31, 29 and 12% after placebo, terfenadine and salbutamol, respectively. It is unlikely that histamine plays an important role in the LR to inhaled antigen but beta 2-adrenergic stimulants can attenuate LR, probably by directly preventing bronchial smooth muscle constriction and also by stabilising bronchial mast cells.

Comparison of the effect of loratadine on the airway and skin responses to histamine, methacholine, and allergen in subjects with asthma

Loratadine is a highly selective, long-acting, H1-receptor antagonist. In a randomized, double-blind, crossover study, we evaluated the effects of loratadine, 10 and 20 mg, and placebo administered once daily for 3 days on the skin-wheal responses to histamine, the airway responses to inhaled histamine and methacholine, and the skin-wheal and airway responses to allergen in 12 subjects with asthma. There was no evidence of a bronchodilator action 3 hours after a third oral dose. In the airways, the geometric mean of the provocative concentration of histamine causing a 20% fall in FEV1 after placebo or loratadine, 10 and 20 mg, was 0.68 mg/ml, 2.71 mg/ml (p, not significant), and 5.96 mg/ml (p less than 0.05), respectively. The concentration ratios (value after active treatment/value after placebo) for loratadine, 10 and 20 mg, were 5.1 (p less than 0.05) and 13.4 (p less than 0.05). Neither dose of loratadine had any significant effect on the methacholine dose-response relationship. In the skin, loratadine also displaced the histamine log-concentration response curves to the right with concentration ratios of 4.7 and 6.7, respectively. Loratadine, 10 and 20 mg, had no protective effect on the early or late-phase bronchoconstrictor responses to inhaled allergen. In the skin, loratadine, 20 mg, significantly inhibited the mean wheal area to allergen. Thus, in the dose regimens studied, although loratadine is a moderately potent and selective H1 antagonist in the skin and airways, it failed to attenuate the early and late airway responses to inhaled allergen.