The airways pharmacology of DNK333, a potent, selective, non-peptide dual NK1/NK2 receptor antagonist

In vivo pharmacological evaluation of compound 48/80-induced airways oedema by MRI

BACKGROUND AND PURPOSE

Allergen-induced airways oedema in actively sensitized rats has been studied earlier by magnetic resonance imaging (MRI). We used MRI to follow the consequences of non-immunological mast cell activation induced by compound 48/80 in the rat lungs in vivo.

EXPERIMENTAL APPROACH

Male naïve rats were scanned by MRI prior to and at several time points following intratracheal administration of the mast cell secretagogue, compound 48/80. The effects of a range of drugs on the response induced by compound 48/80 were studied.

KEY RESULTS

Strong fluid signals were detected by MRI in the lungs at 24 h after compound 48/80, correlating with increased protein concentration and inflammatory cell infiltration in bronchoalveolar lavage, and with perivascular oedema observed histologically. Pharmacological intervention demonstrated that the increase in MRI signal volume induced by compound 48/80 24 h after challenge was blocked by disodium cromoglycate and the glucocorticoid, budesonide. Pretreatment with wortmannin, capsazepine, DNK333 (a dual neurokinin (NK) 1 and NK2 antagonist) or the anti-allergy drug CGS8515, but not indomethacin, resulted in partial inhibition.

CONCLUSIONS AND IMPLICATIONS

Compound 48/80 induced a complex inflammatory reaction which did not solely involve mast cell degranulation but also activation of sensory nerves and was qualitatively similar to allergen challenge. Changes observed by MRI correlated with decreases in protein concentration in BAL fluid. However, the magnitude of the changes detected was greater using MRI. Our results demonstrate that MRI is a sensitive and efficient tool to assess the effects of drugs on lung inflammation.

Capsaicin-induced mucus secretion in rat airways assessed in vivo and non-invasively by magnetic resonance imaging

BACKGROUND AND PURPOSE

An up-regulation of the sensory neural pathways in the lung has been implicated in asthma and chronic obstructive pulmonary disease (COPD) and is thought to contribute to mucus hypersecretion, an essential feature of both diseases. The aim of this study was to assess non-invasively the acute effects (up to 60 min) of sensory nerve stimulation by capsaicin in the lung, using magnetic resonance imaging (MRI).

EXPERIMENTAL APPROACH

Male Brown Norway rats were imaged prior to and 10, 30 and 60 min after intra-tracheal challenge with capsaicin (30 microg kg(-1)) or vehicle (0.5% ethanol solution). In subsequent studies, pre-treatment with the transient receptor potential vanilloid (TRPV)-1 antagonist, capsazepine; the dual neurokinin (NK) 1 and NK2 receptor antagonist, DNK333 and the mast cell stabilizer, di-sodium cromoglycate (DSCG) was used to modulate the effects of capsaicin.

KEY RESULTS

Diffuse fluid signals were detected by MRI in the lung as early as 10 min after capsaicin, remaining constant 30 and 60 min after treatment. Broncho-alveolar lavage (BAL) fluid analysis performed 60 min after capsaicin revealed increased mucin concentration. Capsazepine (3.5 mg kg(-1)), DNK333 (10 mg kg(-1)) but not DSCG (10 mg kg(-1)) administered prophylactically were able to block the effect of capsaicin in the airways.

CONCLUSIONS AND IMPLICATIONS

These observations suggest that the fluid signals detected by MRI after capsaicin administration reflected predominantly the release of mucus following activation of sensory nerves. They point to the opportunity of non-invasively assessing with MRI the influence of neuronal mechanisms in animal models of asthma and COPD.

Animal models of cough: literature review and presentation of a novel cigarette smoke-enhanced cough model in the guinea-pig

A wealth of literature describes the approaches that investigators have used to develop animal models of cough. The relevance of the models to cough in man and disease is still unknown. Furthermore, the choice of animal model that is used will depend on the purpose of the investigation and what questions are being asked. Cigarette smoke is known to cause COPD and cough is a principle symptom where patients demonstrate an increased cough response to citric acid or capsaicin. This paper describes the development of exacerbated cough to these agents in the guinea-pig following cigarette smoke exposure and pharmacological profiling of these models. Male Dunkin-Hartley guinea-pigs were exposed to air or cigarette smoke (4 or 5 research cigarettes daily for the capsaicin and citric acid studies, respectively) for a 3 s puff every 30 s, for up to 10 days. At selected time points conscious, unrestrained animals were placed in a plethysmograph chamber and challenged with an aerosol of 0.3 M citric acid (10 min) or 10 microM capsaicin (7 min). Cough and Penh area under the curve (AUC) were recorded during the exposure and for a further 10 min (citric acid) or 8 min (capsaicin) after exposure. Compounds were administered on day 3 or 11 for citric acid or capsaicin, respectively. Significant enhancement of citric acid-induced cough was evident 24 h (12+/-2 to 24+/-4* coughs) after a single exposure and further enhanced after 2 days (13+/-3 to 36+/-4* coughs). Enhanced cough to capsaicin was not reliable until after 10 days of cigarette smoke exposure (2+/-1 to 14+/-3** coughs). Data are expressed as mean+/-s.e.mean (n=10), *p<0.05, **p<0.01 vs. air-exposed animals (Mann-Whitney rank-sum test). The minimum effective doses to inhibit citric acid-induced cough were 10, 10, 3 and 0.3 mg/kg for codeine (p.o. -30 min), a selective NK(1)/NK(2) antagonist, DNK333 (p.o. -2 h), terbutaline (s.c. -1 h) and atropine (s.c. -1 h), respectively. The minimum effective doses to inhibit capsaicin-induced cough were 3, 1, 0.3 and 0.3 mg/kg for codeine, DNK333, terbutaline (p.o. -2 h) and atropine, respectively. The VR1 antagonists capsazepine and iodo-resiniferatoxin (IRTX) did not inhibit cough in either model. Differences in sensitivity between citric acid and capsaicin to pharmacological agents may be partly explained by the difference in magnitude of response to these agents. Clinically used compounds such as codeine and terbutaline have shown activity in both models, however the relevance of the models to cough in man and disease for potential new therapies is unknown.