Effects of a specific cysteinyl leukotriene antagonist, pranlukast, on antigen-induced cysteinyl leukotriene-mediated rhinitis in guinea pigs

Placebo-controlled study with OHIO chamber of prophylactic pranlukast for children with Japanese cedar pollinosis: TOPIC-J III study

Objective

This double-blind, placebo-controlled comparative study was designed to investigate whether pranlukast dry syrup, a leukotriene receptor antagonist, has a protective effect against priming, controlled pollen exposure, and natural pollen exposure in children with Japanese cedar pollinosis.

Research design and methods

Thirty children aged 12–15 years with Japanese cedar pollinosis (positive skin test for Japanese cedar pollen), who had suffered from pollinosis for at least 2 years and developed severe nasal obstruction when exposed to Japanese cedar pollen, were enrolled in this study. They were randomly allocated to treatment with pranlukast or placebo orally after breakfast and dinner for 8 weeks during the Japanese cedar pollen season. Soon after the start of the pollen season, all subjects underwent a challenge by exposure for 3 h to Japanese cedar pollen (8000 grains/m³) in an artificial exposure chamber (OHIO chamber).

Clinical trial registration

The University Hospital Medical Information Network in Japan (UMIN000009840).

Main outcome measures

The effect of pranlukast was evaluated using self-rating of nasal symptoms by the subjects and measurement of eosinophil cationic protein in nasal discharge specimens.

Results

Scores for the symptoms of pollinosis were lower in the pranlukast group than in the placebo group during treatment in the priming state, as well as after controlled pollen exposure and natural pollen exposure. Pranlukast significantly improved the score for nasal obstruction, compared with placebo. A correlation was found between changes of the scores for symptoms of pollinosis and changes of the eosinophil cationic protein level.

Conclusions

These results confirm a protective effect of pranlukast against both priming and challenge (controlled and natural) with Japanese cedar pollen. The present findings suggested that pranlukast dry syrup may be useful for prophylaxis against pollinosis in children.

Allergic rhinitis: an update on disease, present treatments and future prospects

Allergic rhinitis (AR) is an inflammation of nasal mucosa mediated by IgE-associated processes occurring independently, or concurrently with asthma. AR is characterized by sensitization-formation and expression of antigen specific IgE, followed by inflammation in two phases. The early phase response involves cross linking of IgE molecules leading to degranulation of mast cells and release of preformed mediators such as histamine and tryptase, or newly synthesized mediators such as prostaglandins and leukotrienes. The late phase response is predominated by the presence of eosinophils, lymphocytes, cytokines, and adhesion molecules. Newer insights reveal that the whole phenomenon of immunological inflammation is intricately knit with neural pathways, which strongly influence the process. Furthermore, AR can impact psychological health and vice versa. Classical pharmacotherapy of AR includes use of oral or topical antihistamines, oral antileukotrienes, topical corticosteroids, mast cell stabilizers, decongestants, and an anticholinergic agent. Among immunomodulatory treatments, immunotherapy is gaining widespread use, while antibody treatment is restricted mainly to resistant cases. Several small molecules with improved safety profile, or targeting novel mechanisms are in the clinical research. Newer antihistamines and corticosteroids with improved safety profile and antagonists of the prostaglandin D(2) (CRTH2) receptors are likely to be available for clinical use in the near future. Lack of properly validated animal models and complexities associated with clinical evaluation are some of the challenges facing the researchers in AR. Comprehensive understanding of immunological and neurological processes in AR would facilitate the future quest for more effective and safer management of this disease.

Validation of guinea pig model of allergic rhinitis by oral and topical drugs

Ovalbumin-induced guinea pig model of rhinitis was assessed for its utility in the studies of rhinitis. Systemic sensitization and challenge with ovalbumin-induced rhinitis symptoms and an increase in anti-OVA-IgE and IgG titers, positive skin reactions and nasal lavage IL-4 concentration. Histopathology of nasal mucosa showed infiltration of eosinophils and other inflammatory cells consistent with the symptoms. Topical sensitization of ovalbumin yielded inconsistent symptoms of rhinitis. In systemic sensitization model, repeated challenge of ovalbumin caused similar response for at least 3 consecutive challenges. The symptoms were affected by relative humidity in the air and dosing volume of topical drugs. Sneezing and lacrimation were reduced by acute oral administration of the H1 receptor antagonists and steroids or the prophylactic oral administration of cysteinyl leukotriene (CysLT1) receptor antagonist montelukast or acute topical antihistamines, mast cell stabilizer sodium cromoglycate and anticholinergic agent ipratropium bromide, but not by a topical steroid. Nose rubbing was reduced significantly by some oral and topical antihistamines. Oral steroids offered excellent protection against all symptoms. Dexamethasone and montelukast also inhibited nasal lavage IL-4 concentration and inflammatory cell infiltration. Treatment with topical steroid fluticasone for 2 weeks had no effect on sneezing or rubbing. However, it caused complete inhibition of congestion. The cyclooxygenase inhibitor indomethacin had no effect on symptoms of rhinitis. The adrenergic alpha receptor agonist-decongestant oxymetazoline caused reduction in congestion. These results suggest that differential responsiveness to symptoms of rhinitis by a new agent can be very well profiled in the model in congruence with the mediation pathways and mechanism of action of drugs. The model provides complete symptomatic characterization of rhinitis and is a good tool for its study.

Nasal blockage induced by oral administration of non-steroidal anti-inflammatory drugs in a guinea-pig model of allergic rhinitis

To elucidate the mechanisms underlying nasal symptoms in patients with aspirin hypersensitivity, we evaluated the effects of orally administered non-steroidal anti-inflammatory drugs (NSAIDs) on the nasal patency of guinea pigs with cedar pollen-induced chronic allergic rhinitis. Indomethacin (10 mg/kg) administered 1 h before a pollen challenge amplified the antigen-induced nasal blockage. More interestingly, even in the absence of the pollen challenge, indomethacin induced nasal blockage at 30 min at 4 h after administration. However, indomethacin-induced nasal blockage was not provoked in non-sensitized animals. Another NSAID, diclofenac (30 mg/kg), also evoked nasal blockage, but unexpectedly, aspirin (500 mg/kg) did not affect nasal patency. Indomethacin-induced nasal blockage was unaffected by a cysteinyl leukotriene receptor (CysLT(1) receptor) antagonist, pranlukast (30 mg/kg, p.o.), or by prostaglandin E2 (10(-3) M, intranasal), suggesting that the nasal blockage may not be due to hyperproduction of cysteinyl leukotrienes or inhibition of prostaglandin E2 production. These results indicate that the indomethacin-induced nasal blockage may not be an identical phenomena to airway symptoms in aspirin hypersensitivity patients. However, because chronic nasal inflammation is indispensable for the development of nasal blockage, indomethacin-induced nasal blockage may become a clue to elucidate new mechanisms underlying hypersensitivity to NSAIDs.

Different mechanisms between thromboxane A2- and leukotriene D4-induced nasal blockage in guinea pigs

Although thromboxane (TX)A2 is involved in allergic rhinitis, the mechanisms inducing nasal blockage have not been elucidated. We evaluated the roles of nasal mucosal vascular changes following intranasal instillation of the TXA2 analog U-46619 or leukotriene (LT)D4 to induce nasal blockage in a guinea pig model of allergic rhinitis. Both U-46619- and LTD4-induced nasal blockages in sensitized animals were swiftly and completely suppressed by a vasoconstrictor, naphazoline. The nitric oxide synthase inhibitor N(omega)-nitro-l-arginine methyl ester relieved LTD4-induced nasal blockage, but not U-46619-induced nasal blockage. Although both agonists produced vasodilatation of nasal mucosa in vivo, LTD4 caused vasodilatation while U-46619 caused vasoconstriction in vitro. Both LTD4- and U-46619-induced nasal blockages in vivo should depend on vasodilatation of nasal mucosa. LTD4-induced nasal blockage is induced by direct vasodilatation via nitric oxide. In contrast, U-46619-induced nasal blockage may be associated with contraction of a certain vein that should exist at the exit of capacitance vessels, leading to congestion of the nasal mucosa.

Population pharmacokinetics of pranlukast hydrate dry syrup in children with allergic rhinitis and bronchial asthma

This study aimed to assess the steady-state pharmacokinetics of pranlukast, a leukotriene receptor antagonist, in children with allergic rhinitis and bronchial asthma, and to clarify factors affecting apparent clearance (CL/F). A total of 192 plasma samples were obtained from 98 children (rhinitis 64, asthma 13, complications 21), aged 3-14 years in 2 clinical trials. Plasma concentration of pranlukast was determined by liquid chromatography connected with a tandem mass spectrometer and analyzed by a population approach using NONMEM program. The plasma concentration-time course of pranlukast was described by using a one-compartment model with the first-order absorption and lag time. The robustness of the population pharmacokinetic model was evaluated by using 200 bootstrap samples. The results of population pharmacokinetic analysis showed that only age was a factor affecting the CL/F per body weight, with CL/F decreasing with increasing age. No significant variation was seen in the CL/F between rhinitis and asthma. The interindividual variability in the CL/F and the residual variability were 19.7% and 48.4%, respectively. All the parameters fell within 10% of the bootstrapped mean. In conclusion, the results show that age is the most influential factor for explaining interindividual variability in CL/F, and the difference in diseases does not affect CL/F.

Effects of fexofenadine hydrochloride in a guinea pig model of antigen-induced rhinitis

Allergic rhinitis is an inflammatory disease of the nasal mucosa, induced by histamine, leukotrienes, and other substances released from mast cells. Fexofenadine hydrochloride, the active metabolite of terfenadine, is a novel, nonsedating antiallergic drug having H1 receptor antagonistic activity. Fexofenadine is effective for the treatment of allergic rhinitis. However, its mechanism of action in attenuating nasal congestion has not yet been elucidated. Therefore, we first examined the effects of fexofenadine on a guinea pig model of antigen-induced rhinitis. We also evaluated the effects of mepyramine, zafirlukast and ramatroban in this model; these drugs are an H1 receptor antagonist, a selective leukotriene antagonist and a selective thromboxane antagonist, respectively. Rhinitis was induced by ovalbumin (OVA) instillation into the nasal cavity of animals that had been sensitized by two earlier OVA injections (s.c. and i.p.). The nasal airway resistance was measured for 45 min after the challenge. Fexofenadine hydrochloride (20 mg/kg) and terfenadine (20 mg/kg) administered orally 70 min prior to the challenge significantly inhibited (fexofenadine, p < 0.001, terfenadine, p < 0.05) the increase in nasal airway resistance. Ramatroban (30 mg/kg) administered orally 60 min prior to the challenge also significantly inhibited (p < 0.05) the increase in nasal airway resistance. In contrast, mepyramine (3 mg/kg i.v.) and zafirlukast (3 mg/kg p.o.) failed to reduce the increase in nasal airway resistance. These results suggest that thromboxane may be involved in the increase in the nasal airway resistance in this model. Accordingly, fexofenadine may reduce the increase in nasal airway resistance by inhibiting the release of chemical mediators, including thromboxane, that are involved in the increase in nasal airway resistance in this model.

Synergism between cysteinyl leukotrienes and thromboxane A2 to induce allergic late phase nasal blockage in guinea pigs

We examined whether cysteinyl leukotrienes (CysLTs) and thromboxane (TX) A2 are synergistically involved in a cedar pollen-induced allergic late phase nasal blockage in guinea pigs. Sensitized animals were repeatedly challenged by pollen inhalation once every week. Combined treatment with pranlukast (a CysLT antagonist) and seratrodast (a TXA2 antagonist) inhibited late phase nasal blockage, but the magnitude of inhibition (approximately 50%) was equal to those of the respective single treatments, suggesting that CysLTs produced late after challenge induces TXA2 production in the nasal tissue, as in the case of the lung of this species. However, pranlukast did not affect TXB2 increase in the nasal tissue. In contrast, combined intranasal instillation of LTD4 and U-46619 (a TXA2 mimetic) produced much greater nasal blockage than single administration of each agonist in sensitized animals. Therefore, allergic late phase nasal blockage should be induced by synergistic activity of CysLTs and TXA2 at the effector organ.

Therapeutic modulation of allergic airways disease with leukotriene receptor antagonists

Although asthma is one of the most common chronic respiratory conditions, it often remains unrecognized and undertreated, while patients are often reluctant to comply with regular inhaled anti-inflammatory and bronchodilator therapy. Allergic rhinitis co-exists with asthma in as many as 40% of patients, and can be regarded as a continuum of the same inflammatory disease process. Corticosteroids are the 'gold standard' first-line treatment for both conditions, and have a significant impact upon underlying inflammation, symptoms and long-term outcome. Cysteinyl leukotrienes are potent airway inflammatory mediators, suggesting that treatment antagonizing their effects could play a role in disease management. In recent years, leukotriene receptor antagonists have provided a further therapeutic option in the management of allergic airways disease. These drugs are orally active, can be administered once daily, and provide a systemic approach to the management of patients with asthma and allergic rhinitis. We review the pharmacology of leukotriene receptor antagonists, their potential role in clinical practice in patients with allergic airways disease, and likely areas for further research.

Involvement of cysteinyl leukotrienes in biphasic increase of nasal airway resistance of antigen-induced rhinitis in guinea pigs

We examined the effect of a specific cysteinyl leukotriene (LT) receptor antagonist, 4-oxo-8-[4-(4-phenylbutoxy)benzoylamino]-2-(tetrazol-5-yl)-4 H-1-benzopyran hemihydrate (pranlukast), on a novel model of allergic rhinitis induced by repeated intranasal ovalbumin challenge in actively sensitized guinea pigs. Repeated intranasal ovalbumin challenge caused a biphasic increase of nasal airway resistance, peaking 0.5 and 4 h after the final challenge. The early-phase response was accompanied by an increase in sneezing and nasal secretion, while that in the late phase was associated with edema and eosinophil infiltration of the nasal mucosa. Analysis of nasal lavage fluid showed that cysteinyl LTs increased in both phases. Pranlukast, when administered 1 h before every ovalbumin challenge, dose-dependently suppressed the increase of nasal airway resistance in the early- and late phase with evidence of histopathological improvements in the late phase. Pranlukast, however, failed to suppress sneezing and nasal secretion. We suggest that cysteinyl LTs play an important role in allergic rhinitis especially in the nasal obstruction due to edema of the nasal mucosa membrane.