Greater involvement of neurokinins found in Guinea pig models of severe asthma compared with mild asthma

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.

Role of selective blocking of bradykinin receptor subtypes in attenuating allergic airway inflammation in guinea pigs

The present study was designed to evaluate the potential role of bradykinin antagonists (R-715; bradykinin B1 receptor antagonist and icatibant; bradykinin B2 receptor antagonist) in treatment of allergic airway inflammation in comparison to dexamethasone and montelukast. R-715 as dexamethasone significantly decreased peribronchial leukocyte infiltration, bronchoalveolar lavage fluid (BALF) albumin and interleukin 1β as well as serum OVA-specific IgE level. Also, R-715 like montelukast significantly decreased BALF cell count (total and eosinophils). Icatibant showed negative results. The current findings suggest that selective bradykinin B1 receptor antagonists may have the therapeutic potential for the treatment of allergic airway inflammation.

Mast cell mediators cause early allergic bronchoconstriction in guinea-pigs in vivo: a model of relevance to asthma

One feature of allergic asthma, the EAR (early allergic reaction), is not present in the commonly used mouse models. We therefore investigated the mediators involved in EAR in a guinea-pig in vivo model of allergic airway inflammation. Animals were sensitized using a single OVA (ovalbumin)/alum injection and challenged with aerosolized OVA on day 14. On day 15, airway resistance was assessed after challenge with OVA or MCh (methacholine) using the forced oscillation technique, and lung tissue was prepared for histology. The contribution of mast cell mediators was investigated using inhibitors of the main mast cell mediators [histamine (pyrilamine) and CysLTs (cysteinyl-leukotrienes) (montelukast) and prostanoids (indomethacin)]. OVA-sensitized and challenged animals demonstrated AHR (airway hyper-responsiveness) to MCh, and lung tissue eosinophilic inflammation. Antigen challenge induced a strong EAR in the sensitized animals. Treatment with a single compound, or indomethacin together with pyrilamine or montelukast, did not reduce the antigen-induced airway resistance. In contrast, dual treatment with pyrilamine together with montelukast, or triple inhibitor treatment, attenuated approximately 70% of the EAR. We conclude that, as in humans, the guinea-pig allergic inflammation model exhibits both EAR and AHR, supporting its suitability for in vivo identification of mast cell mediators that contribute to the development of asthma. Moreover, the known mast cell mediators histamine and leukotrienes were major contributors of the EAR. The data also lend further support to the concept that combination therapy with selective inhibitors of key mediators could improve asthma management.

High-frequency electrical stimulation of cervical vagi reduces airway response to methacholine

AIM: To test whether high-frequency electrical stimulation (HES) of the bilateral cervical vagus nerves reduces the airway responses to methacholine (MCh).

METHODS: Guinea pigs were pretreated with saline (Sal, n = 9) or ovalbumin (Ova, n = 10) aerosol for two weeks (5 min/d, 5 d/wk) and subsequently anesthetized, paralyzed, tracheotomized and artificially ventilated. Both total lung resistance (R_L) and dynamic pulmonary compliance (C_dyn) were recorded. In addition, the effects of vagal low-frequency electrical stimulation (LES, monophasic, 50 Hz) and HES (monophasic and biphasic, 1 and 2.5 kHz) for about 10 s or 2 min on the responses of R_L and C_dyn to MCh aerosol-induced bronchoconstriction were compared in both groups of guinea pigs. In a few guinea pigs, the impact of bivagotomy on the R_L responses to MCh was assessed.

RESULTS: Before MCh challenge, LES, but not HES, significantly increased R_L by about 30% (P < 0.01) and decreased C_dyn by about 20% (P < 0.01) similarly in both groups. MCh aerosol for 2 min elevated R_L and diminished C_dyn more in Ova- than Sal-treated animals (R_L: 313% ± 52% vs 113% ± 17%, P < 0.01; C_dyn: -56% ± 7% vs -21% ± 3%, P < 0.01). During MCh-induced airway constriction, LES further enhanced, but HES decreased R_L and this decrease was greater in Ova- (about 45%) than Sal-treated animals (about 34%, P < 0.01) with little change in cardiovascular activity. On the other hand, LES further reduced whereas HES increased C_dyn more in Ova- (about 20%) than Sal-treated animals (about 13%, P < 0.01). In addition, bivagotomy almost eliminated the R_L and C_dyn responses to MCh.

CONCLUSION: We conclude that vagal HES is able to alleviate the bronchoconstriction induced by MCh in anesthetized guinea pigs, likely via reversible inhibition/blockade of vagal conduction.

Novel triple neurokinin receptor antagonist CS-003 inhibits respiratory disease models in guinea pigs

Neurokinins are known to induce neurogenic inflammation related to respiratory diseases. The effects of CS-003 ([1-{2-[(2R)-(3,4-dichlorophenyl)-4-(3,4,5-trimethoxybenzoyl)morpholin-2-yl]ethyl}spiro[benzo[c]thiophene-1(3H),4'-piperidine]-(2S)-oxide hydrochloride]), a novel triple neurokinin receptor antagonist, on several respiratory disease models were evaluated in guinea pigs. As we have already shown that CS-003 is intravenously effective, we first determined if CS-003 was orally effective. CS-003 dose-dependently inhibited substance P-induced tracheal vascular hyperpermeability, neurokinin A- and neurokinin B-induced bronchoconstriction with ID(50) values of 3.6, 1.3 and 0.89 mg/kg (p.o.), respectively. CS-003 (10 mg/kg, p.o.) inhibited the number of coughs induced by capsaicin aerosol (P<0.01) and the antitussive effect was comparable to that of codeine. CS-003 (10 mg/kg, p.o.) also inhibited airway hyperresponsiveness to methacholine chloride in ovalbumin-induced asthma models (P<0.01), a milder one and a severer one. On the other hand, montelukast (10 mg/kg, p.o.), a leukotriene receptor antagonist, significantly inhibited the hyperresponsiveness only in the milder model (P<0.05). In an ovalbumin-induced rhinitis model, oral administration of CS-003 inhibited nasal blockade in a dose-dependent manner and the inhibitory effect was comparable to that of dexamethasone (10 mg/kg, p.o.). CS-003 (i.v.) also dose-dependently inhibited cigarette smoke-induced bronchoconstriction, tracheal vascular hyperpermeability and mucus secretion. These data show that CS-003, a potent orally active triple neurokinin receptor antagonist, may be useful for the treatment of respiratory diseases associated with neurokinins, such as allergic asthma, allergic rhinitis, chronic obstructive pulmonary disease and cough.

Disodium Cromoglycate Inhibits Capsaicin-Induced Eosinophil Infiltration of Conjunctiva Independent of Mast Cells

PURPOSE

To investigate whether disodium cromoglycate (DSCG) inhibits capsaicin-induced eosinophil infiltration of the conjunctiva independent of mast cells.

METHODS

We administered 5 microl of capsaicin solution (10(-5) M) into the conjunctival sacs of mast cell-deficient W/W(v) mice (12 animals) and wild-type mice (12 animals). As controls, the eyes of 12 wild-type and 12 W/W(v) mice were treated with phosphate-buffered saline. Following treatment, the eyelids and eyeballs were removed en bloc at 3, 9, or 24 h, and were histologically examined. The number of infiltrated eosinophils and the expression of vascular cell adhesion molecule-l (VCAM-1) in the conjunctiva were quantified by the staining method of Hansel and immunohistochemical analysis. We also investigated whether treatment by depletion of neuropeptides or by DSCG administration could suppress the capsaicin-induced eosinophil infiltration of the conjunctiva.

RESULTS

In both W/W(v) and wild-type mice, eosinophil infiltration of conjunctival tissues was observed 3 h after capsaicin administration. In both strains of mice, the number of infiltrated eosinophils increased over time, with VCAM-1 expression on vascular endothelial cells peaking at 9 h after treatment, and decreasing gradually within 24 h after treatment. In both the neuropeptide-depleted and the DSCG-treated groups, eosinophil infiltration and VCAM-1 expression were suppressed in comparison with the nontreated group.

CONCLUSION

DSCG can directly inhibit neuropeptide-induced eosinophil infiltration of the conjunctiva independent of mast cells.