A marine-sourced fucoidan solution inhibits Toll-like-receptor-3-induced cytokine release by human bronchial epithelial cells

Fucoidans are sulfated polysaccharides from brown algae, known to have immunomodulatory activity. Their effects on the response of airway epithelial cells to Toll-like receptor 3 (TLR3) stimulation have not been characterized. Our objective was to evaluate the effects of a marine-sourced fucoidan solution (MFS) on the TLR3-induced expression and/or production of cytokines and prostaglandin by human primary bronchial epithelial cells as a model of the airway epithelium. The cells were incubated with MFS in the presence or absence of Poly(I:C) (a TLR3 agonist that mimics viral RNA). Cytokine expression and production were assessed using RT-qPCR and ELISA. The expression of cyclooxygenase-2 and the production of prostaglandin E2 were also measured. Relative to control, exposure to MFS was associated with lower Poly(I:C)-induced mRNA expression of various cytokines and chemokines, and lower COX-2 production. The MFS inhibited the production of some cytokines (IL-1α, IL-1β, TNFα, and IL-6), chemokines (CCL5, CCL22, CXCL1, CXCL5 and CXCL8) and prostaglandin E2 but did not alter the production of IL-12/25, CCL2 and CCL20. At clinically relevant concentrations, the MFS inhibited the TLR3-mediated production of inflammatory mediators by human primary bronchial epithelial cells - suggesting that locally applied MFS might help to reduce airway inflammation in viral infections.

15-Lipoxygenases regulate the production of chemokines in human lung macrophages

BACKGROUND AND PURPOSE

15-Lipoxygenase (15-LOX) activity is associated with inflammation and immune regulation. The objectives of the present study were to investigate the expression of 15-LOX-1 and 15-LOX-2 and evaluate the enzymes' roles in the polarization of human lung macrophages (LMs) in response to LPS and Th2 cytokines (IL-4/-13).

EXPERIMENTAL APPROACH

LMs were isolated from patients undergoing surgery for carcinoma. The cells were cultured with a 15-LOX inhibitor (PD146176 or ML351), a COX inhibitor (indomethacin), a 5-LOX inhibitor (MK886) or vehicle and then stimulated with LPS (10 ng · mL(-1)), IL-4 (10 ng · mL(-1)) or IL-13 (50 ng · mL(-1)) for 24 h. Levels of ALOX15 (15-LOX-1) and ALOX15B (15-LOX-2) transcripts were determined by real-time quantitative PCR. Immunoassays were used to measure levels of LPS-induced cytokines (TNF-α, CCL2, CCL3, CCL4, CXCL1, CXCL8 and CXCL10) and Th2 cytokine-induced chemokines (CCL13, CCL18 and CCL22) in the culture supernatant.

KEY RESULTS

Stimulation of LMs with LPS was associated with increased expression of ALOX15B, whereas stimulation with IL-4/IL-13 induced the expression of ALOX15. PD146176 and ML351 (10 μM) reduced the release of the chemokines induced by LPS and Th2 cytokines. The effects of these 15-LOX inhibitors were maintained in the presence of indomethacin and MK886. Furthermore, indomethacin revealed the inhibitory effect of PD146176 on TNF-α release.

CONCLUSIONS AND IMPLICATIONS

Inhibition of the 15-LOX pathways is involved in the down-regulation of the in vitro production of chemokines in LMs. Our results suggest that the 15-LOX pathways have a role in the pathogenesis of inflammatory lung disorders and may thus constitute a potential drug target.

Cannabinoids inhibit cholinergic contraction in human airways through prejunctional CB1 receptors

BACKGROUND AND PURPOSE

Marijuana smoking is widespread in many countries, and the use of smoked synthetic cannabinoids is increasing. Smoking a marijuana joint leads to bronchodilation in both healthy subjects and asthmatics. The effects of Δ(9) -tetrahydrocannabinol and synthetic cannabinoids on human bronchus reactivity have not previously been investigated. Here, we sought to assess the effects of natural and synthetic cannabinoids on cholinergic bronchial contraction.

EXPERIMENTAL APPROACH

Human bronchi isolated from 88 patients were suspended in an organ bath and contracted by electrical field stimulation (EFS) in the presence of the phytocannabinoid Δ(9) -tetrahydrocannabinol, the endogenous 2-arachidonoylglycerol, the synthetic dual CB1 and CB2 receptor agonists WIN55,212-2 and CP55,940, the synthetic, CB2 -receptor-selective agonist JWH-133 or the selective GPR55 agonist O-1602. The receptors involved in the response were characterized by using selective CB1 and CB2 receptor antagonists (SR141716 and SR144528 respectively).

KEY RESULTS

Δ(9) -tetrahydrocannabinol, WIN55,212-2 and CP55,940 induced concentration-dependent inhibition of cholinergic contractions, with maximum inhibitions of 39, 76 and 77% respectively. JWH-133 only had an effect at high concentrations. 2-Arachidonoylglycerol and O-1602 were devoid of any effect. Only CB1 receptors were involved in the response because the effects of cannabinoids were antagonized by SR141716, but not by SR144528. The cannabinoids did not alter basal tone or contractions induced by exogenous Ach.

CONCLUSIONS AND IMPLICATIONS

Activation of prejunctional CB1 receptors mediates the inhibition of EFS-evoked cholinergic contraction in human bronchus. This mechanism may explain the acute bronchodilation produced by marijuana smoking.

[Taste receptors in the lungs: interesting or anecdotal?]

The receptors responsible for taste perception distinguish the four basic tastes : salty, sweet, bitter and umami. Among them, the bitter taste receptors (TAS2R) are G protein coupled receptors, including 25 subtypes identified in humans to date. Although the existence of endogenous agonists remains uncertain, the TAS2R receptors have the ability to recognize natural or synthetic molecules, as various molecules produced by bacteria, or caffeine, chloroquine, or erythromycin. The expression of these receptors, initially thought to be confined to the oral cavity, has recently been described in extra-oral tissues such as the gastrointestinal tract and the lungs. The effects in the lung tissue are essentially at three levels : TAS2R receptors expressed on the cilia of epithelial cells increase the cilia vibration frequency; the stimulation of TAS2R receptors expressed in bronchial smooth muscle cells leads to bronchial relaxation; while TAS2R receptors expressed on immune cells in the lung tissue, including macrophages, are involved in the modulation of the production of pro-inflammatory cytokines. In conclusion, in view of these complementary mechanisms, TAS2R receptors may become a pharmacological target of interest for the treatment of obstructive lung diseases.

Roflumilast inhibits the release of chemokines and TNF-α from human lung macrophages stimulated with lipopolysaccharide

BACKGROUND AND PURPOSE

Lung macrophages are critically involved in respiratory diseases. This study assessed the effects of the PDE4 inhibitor roflumilast and its active metabolite, roflumilast N-oxide on the release of a range of chemokines (CCL2, 3, 4, CXCL1, 8, 10) and of TNF-α, from human lung macrophages, stimulated with bacterial lipopolysaccharide LPS.

EXPERIMENTAL APPROACH

Lung macrophages isolated from resected human lungs were incubated with roflumilast, roflumilast N-oxide, PGE(2), the COX inhibitor indomethacin, the COX-2 inhibitor NS-398 or vehicle and stimulated with LPS (24 h). Chemokines, TNF-α, PGE(2) and 6-keto PGF(1α) were measured in culture supernatants by immunoassay. COX-2 mRNA expression was assessed with RT-qPCR. PDE activities were determined in macrophage homogenates.

KEY RESULTS

Expression of PDE4 in lung macrophages was increased after incubation with LPS. Roflumilast and roflumilast N-oxide concentration-dependently reduced the LPS-stimulated release of CCL2, CCL3, CCL4, CXCL10 and TNF-α from human lung macrophages, whereas that of CXCL1 or CXCL8 was not altered. This reduction by the PDE4 inhibitors was further accentuated by exogenous PGE(2) (10 nM) but abolished in the presence of indomethacin or NS-398. Conversely, addition of PGE(2) (10 nM), in the presence of indomethacin restored inhibition by roflumilast. LPS also increased PGE(2) and 6-keto PGF(1α) release from lung macrophages which was associated with an up-regulation of COX-2 mRNA.

CONCLUSIONS AND IMPLICATIONS

Roflumilast and roflumilast N-oxide reduced LPS-induced release of CCL2, 3, 4, CXCL10 and TNF-α in human lung macrophages.

The role of adenosine receptors in regulating production of tumour necrosis factor-alpha and chemokines by human lung macrophages

BACKGROUND AND PURPOSE

Adenosine is a major endogenous regulator of macrophage function, and activates four specific adenosine receptors (A(1), A(2A), A(2B) and A(3)). Here, we have assessed in human lung macrophages the modulation of the expression of adenosine receptor mRNA by lipopolysaccharide (LPS), and the relative contributions of the different adenosine receptors to LPS-induced production of tumour necrosis factor (TNF)-alpha and chemokines.

EXPERIMENTAL APPROACH

Lung macrophages isolated from resected lungs were stimulated with LPS and treated with adenosine receptor agonists or/and antagonists. Adenosine receptor expression was assessed with qRT-PCR. Cytokines were measured in lung macrophage supernatants with elisa.

KEY RESULTS

LPS increased (about 400-fold) mRNA for A(2A) adenosine receptors, decreased mRNA for A(1) and A(2B), but had no effect on A(3) adenosine receptor mRNA. The adenosine receptor agonist NECA inhibited TNF-alpha production concentration dependently, whereas the A(1) receptor agonist, CCPA, and the A(3) receptor agonist, AB-MECA, inhibited TNF-alpha production only at concentrations affecting A(2A) receptors. NECA also inhibited the production of CCL chemokines (CCL2, CCL3, CCL4, CCL5) and CXCL chemokines (CXCL9 and CXCL10), but not that of CXCL1, CXCL8 and CXCL5. Reversal of NECA-induced inhibition of TNF-alpha and chemokine production by the selective A(2A) adenosine receptor antagonist ZM 241385, but not the A(2B) receptor antagonist, MRS 1754, or the A(3) receptor antagonist, MRS 1220, indicated involvement of A(2A) receptors.

CONCLUSIONS AND IMPLICATIONS

LPS up-regulated A(2A) adenosine receptor gene transcription, and this receptor subtype mediated inhibition of the LPS-induced production of TNF-alpha and of a subset of chemokines in human lung macrophages.

[Sensory-nerves and airway inflammation: interaction with beta-2-adrenoceptor agonists]

beta-2-adrenoceptor agonists are used as bronchodilatators in asthma and chronic obstructive pulmonary disease (COPD) treatment. However, regular single use of these molecules may enhance bronchial hyperresponsiveness, a component of asthma and COPD. Indeed, pathophysiologic mechanisms underlying bronchial hyperresponsiveness remain unclear. Sensory nerves have been recently found in the respiratory tract and they play an important role in the regulation of bronchial responsiveness through the release of tachykinins and activation of vanilloid TRPV1 (Transient Receptor Potential Vanilloid 1) receptors. The purpose of this review is to highlight the most recent findings concerning the interactions between beta-2-adrenoceptor agonists and bronchial sensory nerves.

Effect of indacaterol, a novel long-acting beta2-agonist, on isolated human bronchi

Indacaterol is a novel beta2-adrenoceptor agonist in development for the once-daily treatment of asthma and chronic obstructive pulmonary disease. The present study evaluated the relaxant effect of indacaterol on isolated human bronchi obtained from lungs of patients undergoing surgery for lung carcinoma. Potency (-logEC50), maximal relaxant effect (Emax) and onset of action were determined at resting tone. Duration of action was determined against cholinergic neural contraction induced by electrical field stimulation (EFS). At resting tone, -logEC50 and Emax values were 8.82+/-0.41 and 77+/-5% for indacaterol, 9.84+/-0.22 and 94+/-1% for formoterol, 8.36+/-0.16 and 74+/-4% for salmeterol, and 8.43+/-0.22 and 84+/-4% for salbutamol, respectively. In contrast to salmeterol, indacaterol did not antagonise the isoprenaline response. Indacaterol's onset of action (7.8+/-0.7 min) was not significantly different from that of formoterol (5.8+/-0.7 min) or salbutamol (11.0+/-4.0 min), but it was significantly faster than that of salmeterol (19.4+/-4.3 min). EFS-induced contractions were inhibited with -logIC50 values of 6.96+/-0.13 (indacaterol), 8.96+/-0.18 (formoterol), 7.18+/-0.34 (salmeterol) and 6.39+/-0.26 (salbutamol). Duration of action was >12 h for indacaterol and salmeterol, and 35.3+/-8.8 and 14.6+/-3.7 min for formoterol and salbutamol, respectively. In isolated human bronchi, indacaterol behaved as a long-acting beta2-adrenoceptor agonist with high intrinsic efficacy and fast onset of action.

Nerve growth factor is released by IL-1beta and induces hyperresponsiveness of the human isolated bronchus

Nerve growth factor (NGF) is a neurotrophic factor essential for the development and survival of neurons, and is also an important mediator of inflammation. It is released by airway cells stimulated by interleukin (IL)-1beta. As IL-1beta induces airway hyperresponsiveness (AHR) to the tachykinin NK-1 receptor agonist [Sar9,Met(O2)11]-substance P in human isolated bronchi, the aim of this study was to determine whether IL-1beta was able to induce NGF release from isolated bronchi, and whether NGF might participate into IL-1beta-induced AHR. IL-1beta (10 ng x mL(-1); 21 degrees C; 15 h) increased the release of NGF from human isolated bronchi in vitro, and, in organ bath studies, the response of human bronchi to [Sar9,Met(O2)11]-substance P (0.1 microm). A significant correlation was found between these responses. AHR induced by IL-1beta was abolished by a blocking anti-human NGF antibody. Finally, NGF (1 ng x mL(-1); 37 degrees C; 0.5 h) by itself induced a significant increase in [Sar9,Met(O2)11]-substance P responsiveness. By contrast, it did not change the maximal contraction to acetylcholine. In conclusion, the present study clearly demonstrated that nerve growth factor may participate in the airway hyperresponsiveness induced by interleukin-1beta, which supports the neuro-immune cross-talk that may be active in the development of hyperresponsiveness in the human airways, and suggests nerve growth factor is active in the airways in asthma.

Beta3-adrenoceptor is the predominant beta-adrenoceptor subtype in human myometrium and its expression is up-regulated in pregnancy

To assess whether pregnancy might influence the functionality and expression of human myometrial beta(2)- and beta(3)-adrenoceptors (beta(2)- and beta(3)-AR), we performed functional, binding, Western blot, and molecular biology experiments in human nonpregnant and near-term pregnant myometrium. Inhibition of spontaneous contractions induced by a beta(3)-AR agonist, SR 59119A, was significantly greater in pregnant, compared with nonpregnant, myometrial strips (E'(max) = 61 +/- 5% vs. 44 +/- 5% for pregnant and nonpregnant myometrium, respectively), whereas salbutamol, a beta(2)-AR agonist, was significantly less efficient in pregnant, compared with nonpregnant, myometrium (E(max) = 29 +/- 4 vs. 54 +/- 8%). Although two populations of binding sites corresponding to beta(2)- and beta(3)-AR were identified in both nonpregnant and pregnant myometrium, we found a clear predominance of the beta(3)-AR subtype. Moreover, beta(3)-AR binding sites were up-regulated 2-fold in myometrium at the end of pregnancy. Both beta(2)- and beta(3)-AR mRNA were expressed in human nonpregnant and pregnant myometrium. Contrary to beta(2)-AR, the expression of the beta(3)-AR transcripts and immunoreactive proteins was increased in pregnant, compared with nonpregnant, myometrium. Such compelling data suggest a predominant role for beta(3)-AR in the regulation of human myometrium contractility, especially at the end of pregnancy, which might have important consequences for the clinical management of preterm labor.

The human near-term myometrial beta 3-adrenoceptor but not the beta 2-adrenoceptor is resistant to desensitisation after sustained agonist stimulation

1. In order to compare the beta(2)- and beta(3)-adrenoceptor (beta-AR) desensitisation process in human near-term myometrium, we examined the influence of a pretreatment of myometrial strips with either a beta(2)- or a beta(3)-AR agonist (salbutamol or SR 59119A, respectively, both at 10 microm, for 5 and 15 h) on the relaxation and the cyclic adenosine monophosphate (cAMP) production induced by these agonists. 2. To assess some of the mechanisms potentially implicated in the beta-AR desensitisation process, we studied the influence of such treatment on the number of beta(2)- and beta(3)-AR binding sites, the beta(2)- and beta(3)-AR transcripts expression and the phosphodiesterase 4 (PDE4) activity. 3. Salbutamol, but not SR 59119A, concentration-response curve (CRC) was shifted by a 15 h salbutamol preincubation, with a significant difference in -log EC(20) values (6.31+/-0.13 vs 5.58+/-0.24, for control and 15 h salbutamol pretreatment, respectively, P<0.05). Neither salbutamol nor SR 59119A CRCs were modified after a 15 h preincubation with SR 59119A. 4. A 15 h exposure of myometrial strips to salbutamol significantly reduced the salbutamol-induced (0.60+/-0.26 vs 1.54+/-0.24 pmol mg(-1) protein, P<0.05), but not the SR 59119A-induced, cAMP production. No decrease in cAMP production was observed after a 15 h SR 59119A exposure. 5. A 15 h salbutamol exposure of myometrial strips significantly reduced the beta(2)- but not the beta(3)-AR binding site density, whereas no decrease in the number of beta(2)- and beta(3)-AR binding sites was observed after a 15 h SR 59119A treatment. 6. Neither PDE4 activity nor the beta(2)- and beta(3)-AR mRNA expression levels were affected by salbutamol or SR 59119A treatments. 7. Our results indicate that beta(3)-AR, but not beta(2)-AR, are resistant to the agonist-induced desensitisation. In our model, beta(2)-AR desensitisation is mediated by a decreased number of beta(2)-AR that was not explained by transcriptional regulation of the receptor.

Effects of cysteinyl leukotrienes in small human bronchus and antagonist activity of montelukast and its metabolites

BACKGROUND

Evidence suggests that small airways contribute to clinically significant processes in asthma. Cysteinyl leukotrienes (CysLTs) are considered to be pivotal mediators in the pathogenesis of asthma. Montelukast (MK), a specific CysLT1 receptor antagonist, is metabolized in two main hydroxylated metabolites (termed M5 and M6, respectively).

OBJECTIVES

The aims of this study were to compare the responsiveness of small and large human bronchi to the three CysLTs, to evaluate the antagonist activity of MK, M5 and M6 in these preparations of human bronchi, and to characterize the CysLT receptors involved in the contractile response.

METHODS AND RESULTS

In isolated small bronchus (i.d. 0.5-2 mm), the potencies (-log molar EC50) of LTC4, LTD4 and LTE4 were 9.3 (n=11), 9.1 (n=30) and 8.4 (n=14), respectively. The three CysLTs were about 30-fold more potent in small bronchi than in larger bronchi (i.d. 4-6 mm). In small bronchi, MK significantly shifted to the right the CysLT concentration-effect curves with pA2 values against LTC4, LTD4 and LTE4 of 9.1 (n=3), 9.0 (n=11) and 8.7 (n=5), respectively. The antagonist potencies of M6 and M5 were similar to MK and fivefold lower, respectively. A similar activity of MK against the three CysLTs suggested that CysLT1 receptors are involved in the contraction of human bronchus. Analysis by RT-PCR also indicated that human bronchus mainly expressed CysLT1 receptors.

CONCLUSION

MK exerts a potent antagonist activity against the particularly potent constricting effects of CysLTs in isolated human small bronchi, which only expressed the CysLT1 receptor subtype. The metabolites of MK are also potent in vitro antagonists, but may not participate in the therapeutic activity of MK due to their low plasma concentrations in patients treated with the recommended dose of MK.

SR 142801, a tachykinin NK(3) receptor antagonist, prevents beta(2)-adrenoceptor agonist-induced hyperresponsiveness to neurokinin A in guinea-pig isolated trachea

We investigated whether fenoterol was able to enhance contractile responsiveness to neurokinin A (NKA) on the guinea-pig isolated trachea. We then studied the effects of two inhibitors of nuclear factor kappa B (NFkappaB), gliotoxin and pyrrolidine dithiocarbamate, and of the tachykinin NK(1), NK(2) and NK(3) receptor antagonists, SR 140333, SR 48968 and SR 142801 and determined whether tachykinin receptor gene expression was up-regulated in the trachea after exposure to fenoterol. Fenoterol (0.1 microM, 15 h, 21 degrees C) induced an increased contractile response to NKA (mean of difference in maximal tension between control and fenoterol +/- S.E.M; +0.47 +/- 0.14 g, n = 26, P < 0.01). This hyperresponsiveness was strongly reduced by co-incubation with gliotoxin (0.1 microg/ml) or pyrrolidine dithiocarbamate (0.1 mM) and abolished by SR 140333 (0.1 microM) and SR 142801 (0.1 microM). SR 48968 (0.1 microM) diminished the tracheal contractility to NKA but failed to reduce the hyperreactivity induced by fenoterol. Tachykinin NK(1) receptor (NK(1)R), NK(2) receptor (NK(2)R) and NK(3) receptor (NK(3)R) gene expression was analyzed by semiquantitative RT-PCR. Compared to control tissues, NK(1)R and NK(2)R mRNA expression was increased by about 1.6-fold and 1.4-fold, respectively, in tissues treated with fenoterol. We were unable to detect the presence of NK(3)R mRNA in the guinea-pig trachea. In conclusion, fenoterol induces tracheal hyperresponsiveness to NKA and an up-regulation of NK(1)R and NK(2)R gene expression. The hyperresponsiveness implicates the NFkappaB pathway and is abolished by tachykinin NK(1) (SR 140333) and NK(3) (SR 142801) receptor antagonists.

Relaxation of proximal and distal isolated human bronchi by halothane, isoflurane and desflurane

Volatile anaesthetics relax airway smooth muscle in vitro. The amount of relaxation might depend on the type and concentration of volatile anaesthetics, the calibre and precontraction level of the bronchi, and also on the species considered. These effects were investigated on isolated human bronchi. Isometric relaxations produced by halothane, isoflurane and desflurane bubbled on human bronchial rings precontracted with carbachol were recorded and compared with time controls. Volatile anaesthetics induced a concentration-dependent relaxation at 0.66, 1.33 and 2 minimum alveolar concentration (MAC). The relaxation was greater in mildly (carbachol 3x10(-7) M) than in highly (carbachol 2x10(-6) M) precontracted bronchi. Halothane was more potent in relaxing distal as compared to proximal bronchi; this differential effect was less pronounced with isoflurane and not observed with desflurane. While the three volatile anaesthetics induced similar relaxation on proximal bronchi, halothane was significantly more potent than desflurane on distal bronchi, with isoflurane being intermediate. The relaxation induced by 1.33 MAC of halothane, isoflurane and desflurane on moderately precontracted distal bronchi (carbachol 1x10(-6) M) was attenuated by pretreatment with glibenclamide 1x10(-5) M. In conclusion, halothane, isoflurane and desflurane exert direct but differential relaxant effects on human isolated bronchial smooth muscle. This may provide supplemental bronchodilation during anaesthesia. Although adenosine triphosphate-sensitive K+ channels are involved in these relaxant effects, they are unlikely to explain the observed differences between the three volatile anaesthetics.

[The role of endothelin in the physiology and pathophysiology of airways]

Following its discovery in 1988 endothelin initially attracted attention in the cardiovascular field. It is only more recently that the involvement of this peptide, and its role in the physiology and pathophysiology of the airways, has been established. Endothelin receptors have been demonstrated in the majority of cells in the airways from the main bronchi to the alveoli, where endothelin exerts endocrine and paracrine effects on the fine regulation of bronchial muscular tone, the process of cell proliferation and repair, alveolar and bronchial secretion as well as microvascular permeability. The intra and extracellular pathways of the mechanisms of action of endothelin are currently under investigation. Furthermore, it has been shown in the last ten years that endothelin is also, in certain circumstances, a powerful inflammatory mediator. The implication of endothelin in pathological processes such as asthma, chronic airflow obstruction, bronchiectasis, some broncho-pulmonary cancers, ideopathic pulmonary fibrosis, and ARDS is currently suspected if not proven. This opens up the possibility of new therapies. The object of this revue is to summarise the current knowledge of the role played by endothelin in the physiology and pathophysiology of the airways and respiratory system.

Tachykinin NK(3) receptor agonists induced microvascular leakage hypersensitivity in the guinea-pig airways

Microvascular leakage hypersensitivity is a main component of neurogenic inflammation and of tachykinin effects. The aim of this study was to examine the ability of neurokinin B and of the tachykinin NK(3) receptor agonists, [MePhe(7)]neurokinin B or senktide, to potentiate when given by aerosol the microvascular leakage induced by histamine in guinea-pig airways and to compare their effects to those of tachykinin NK(1) (substance P, [Sar(9),Met(O(2))(11)]substance P) or tachykinin NK(2) (neurokinin A, [betaAla(8)]neurokinin A (4-10)) receptor agonists. Guinea-pigs were pretreated successively for 10 min with aerolized salbutamol and phosphoramidon; 15 min later, they were exposed for 30 min to an aerosolized solution of tachykinin receptor agonists; 24 h later, the animals were anaesthetized and vascular permeability was quantified by extravasation of Evans blue dye. Neurokinin B, [MePhe(7)]neurokinin B and senktide (3 x 10(-6)-3 x 10(-5)M) induced a potentiation of the effects of histamine on the vascular permeability in the trachea and main bronchi. Compared to other tachykinin NK(1) and NK(2) receptor agonists, the order of potency was: senktide>neurokinin B=[Sar(9),Met(O(2))(11)]substance P=[betaAla(8)]neurokinin A (4-10)=[MePhe(7)]neurokinin B>neurokinin A>substance P. The potentiation by [MePhe(7)]neurokinin B of histamine-induced microvascular leakage was abolished by the tachykinin NK(1) receptor antagonist SR140333 ([(S)1-(2-[3-(3,4-dichlorophenyl)-1-(3-iso-propoxyphenylacetyl)piperidin-3-yl]etyl)-4-phenyl-1-azoniabicyclo[2.2.2]octane, chloride]) or the tachykinin NK(3) receptor antagonists SR 142801 ([(R)-(N)-(1-(3-(l-benzoyl-3-(3,4-dichlorophenyl)piperidin-3-yl) propyl)-4-phenylpiperidin-4-yl)-N-methylacetamide]) and SB 223412 ([(S)-(-)-N-(alpha-ethylbenzyl)-3-hydroxy-2-phenylquinoline-4-carboxamide]). In conclusion, these results suggest that tachykinin NK(3) receptors might be involved in the potentiation of histamine-induced increase in microvascular permeability.

NK1 receptor stimulation causes contraction and inositol phosphate increase in medium-size human isolated bronchi

Although contraction of human isolated bronchi is mediated mainly by tachykinin NK2 receptors, NK1 receptors, via prostanoid release, contract small-size (approximately 1 mm in diameter) bronchi. Here, we have investigated the presence and biological responses of NK1 receptors in medium-size (2-5 mm in diameter) human isolated bronchi. Specific staining was seen in bronchial sections with an antibody directed against the human NK1 receptor. The selective NK1 receptor agonist, [Sar(9), Met(O2)(11)]SP, contracted about 60% of human isolated bronchial rings. This effect was reduced by two different NK1 receptor antagonists, CP-99,994 and SR 140333. Contraction induced by [Sar(9), Met(O2)(11)]SP was independent of acetylcholine and histamine release and epithelium removal, and was not affected by nitric oxide synthase and cyclooxygenase (COX) inhibition. [Sar(9), Met(O2)(11)]SP increased inositol phosphate (IP) levels, and SR 140333 blocked this increase, in segments of medium- and small-size (approximately 1 mm in diameter) human bronchi. COX inhibition blocked the IP increase induced by [Sar(9), Met(O2)(11)]SP in small-size, but not in medium-size, bronchi. NK1 receptors mediated bronchoconstriction in a large proportion of medium-size human bronchi. Unlike small-size bronchi this effect is independent of prostanoid release, and the results are suggestive of a direct activation of smooth muscle receptors and IP release.

Inhibition by SR 59119A of isoprenaline-, forskolin- and VIP-induced relaxation of human isolated bronchi

In the human isolated bronchus (HIB) it has been shown that beta(3)-adrenoceptor stimulation fails to induce relaxation of airway smooth muscle. It has however been reported in human ventricular endomyocardial biopsies that beta(3)-adrenoceptor stimulation induced a marked negative inotropic effect which could be linked to Gi protein activation. The aims of this study were: (1) to determine in HIB (internal diameter 1-2 mm) whether the selective beta(3)-adrenoceptor agonist SR 59119A (N[7-methoxy-1,2,3, 4-tetrahydronaphthalen-(2R)methyl]-(2R)-2-hydroxy-2-(3-chloroph eny l)e thanamine hydrochloride) was able to inhibit adenylate-cyclase-mediated airway smooth muscle relaxation induced by isoprenaline, forskolin or vasoactive intestinal peptide (VIP) and (2) to investigate the role of the Gi protein in this interaction. SR 59119A (0.1 microM and 1 microM) induced a shift to the right of concentration response curve for isoprenaline (-0. 15+/-0.06 and -0.54+/-0.21 log unit, P<0.05 and P<0.01 respectively), forskolin (-0.12+/-0.02 and -0.30+/-0.05 log unit, P<0.001), and VIP (-0.42+/-0.12 log unit, P<0.01 with SR59119A 10(-6)M). The inhibitory effect of SR 59119A was (1) abolished by an incubation of HIB with pertussis toxin (1 microg/ml, during 15 h in Krebs-Henseleit solution, at 21 degrees C), which is known to inactivate the Gi protein and (2) increased after an incubation of HIB with the pro-inflammatory cytokine IL-1beta (10 ng/ml, during 15 h in Krebs-Henseleit solution, at 21 degrees C), which is known to up-regulate Gi protein expression. Our results suggest that the selective beta(3)-adrenoceptor agonist SR59119A might inhibit the cAMP-dependent relaxation of human isolated bronchus through Gi protein-mediated inhibition of adenylate cyclase.

Functional, biochemical and molecular biological evidence for a possible beta(3)-adrenoceptor in human near-term myometrium

The possible existence of a beta(3)-adrenoceptor (beta(3)-AR) in human near-term myometrium was investigated by in vitro functional and biochemical studies and analysis of mRNA expression. SR 59119A and SR 59104A and CGP 12177 (two selective agonists and a partial agonist, respectively, of the beta(3)-AR), salbutamol and terbutaline (beta(2)-AR agonists) each produced a concentration-dependent relaxation of the myometrial spontaneous contractions. There were no differences in pD(2) values for the relaxing potencies of terbutaline, salbutamol, CGP 12177 and SR 59119A. The rank order for their relaxing efficacies was SR 59119A>SR 59104A>terbutaline approximately salbutamol approximately CGP 12177 (E(max)=52+/-7%, 42+/-12% and approximately 30% respectively). Propranolol, a beta(1)- and beta(2)-AR antagonist, and ICI 118551, a beta(2)-AR antagonist (both at 0.1 microM), did not affect the SR 59119A-induced relaxation whereas SR 59230A, a selective beta(3)-AR antagonist (1 microM), significantly reduced the maximal relaxing effect of SR 59119A. SR 59119A and salbutamol induced a significant increase in cyclic AMP levels that was antagonized by SR 59230A but not by propranolol for SR 59119A, and by propranolol but not by SR 59230A for salbutamol. The beta(3)-AR mRNA was positively expressed in myometrium preparations in a reverse transcription polymerase chain assay. The results presented provide the first evidence for the existence of the beta(3)-AR subtype in human near-term myometrium and suggest that the effects of SR 59119A might be mediated through an increase in cyclic AMP level.

[In vitro techniques for the study of muscle contractility]

Functional studies of bronchial smooth muscle contractility, particularly in humans, are now well standardized regarding to tissues collection, tension setting and results expression. This type of model is usually considered as simple for analysis of pharmacological interactions between ligands and receptors. In fact, the multiplicity of cell types implicated in the bronchial response makes of isolated bronchi preparation a complex model. Examples are given with studies on endothelin or tachykinins. Inflammation and bronchial hyperresponsiveness models were proposed. Models of passive sensitization or pretreatment with cytokines are described. Functional studies of contractility are included in larger investigations including the analysis of the associated biochemical and electrical phenomenon.

Interleukin-1beta-induced hyperresponsiveness to [Sar9,Met(O2)11]substance P in isolated human bronchi

Interleukin-1beta has been reported to induce airway hyperresponsiveness in several animal models. In this study, we have investigated whether interleukin-1beta was able to potentiate the contractions of human isolated small bronchi (internal diameter < or = 1 mm) provoked by a specific tachykinin NK1 receptor agonist, [Sar9,Met(O2)11]substance P. Pre-incubation of human isolated small bronchi with interleukin-1beta (10 ng/ml, in Krebs-Henseleit solution, at 21 degrees C for 15 h) potentiated the contractile response to [Sar9,Met(O2)11]substance P. It also increased the [Sar9,Met(O2)11]substance P-induced release of thromboxane B2, the stable metabolite of thromboxane A2. Indomethacin (10(-6) M), a non-specific cyclooxygenase inhibitor, or GR 32191 ((1R-(1alpha(Z)),2beta,3beta,5alpha))-(+)-7-(5-(((1,1' -biphenyl)-4-yl)-methoxy)-3-hydroxy-2-(1-piperidinyl)cyclopentyl)-4-hept enoic acid, hydrochloride) (10(-6) M), a prostanoid TP-receptor antagonist, blocked the contractions induced by [Sar9,Met(O2)11]substance P both in control experiments and after interleukin-1beta pre-treatment, indicating that prostanoids and thromboxane receptors are directly implicated in the [Sar9,Met(O2)11]substance P-induced contractile response. The thromboxane mimetic U-46619 (10(-8)-10(-6) M) (9,11-dideoxy-11alpha,9alpha-epoxymethano-prostaglandin F2alpha)-induced contractions of human isolated small bronchi were not enhanced by interleukin-1beta pre-treatment, suggesting that no up-regulation of thromboxane receptors occurred. Furthermore, the cyclooxygenase-2 inhibitor CGP 28238 (6-(2,4-difluorophenoxy)-5-methyl-sulfonylamino-1-indanon e) (10(-6) M) had no direct effect on [Sar9,Met(O2)11]substance P-provoked contractions, but inhibited the interleukin-1beta-induced potentiation of [Sar9,Met(O2)11]substance P response. In conclusion, our results show that interleukin-1beta pre-treatment is able to potentiate the contractions of isolated human small bronchi provoked by [Sar9,Met(O2)11]substance P both by increasing prostanoid synthesis and by inducing a cyclooxygenase-2 pathway.

Modulation of ET-1-induced contraction of human bronchi by airway epithelium-dependent nitric oxide release via ET(A) receptor activation

1. The purpose of this work was to investigate whether endothelin-1 (ET-1) was able to induce the release of an inhibitory factor from the airway epithelium in isolated human bronchi and to identify this mediator as well as the endothelin receptor involved in this phenomenon. 2. In intact bronchi, ET-1 induced a concentration-dependent contraction (-logEC50 = 7.92+/-0.09, n = 18) which was potentiated by epithelium removal (-logEC50 = 8.65+/-0.11, n = 17). BQ-123 , an ET(A) receptor antagonist, induced a significant leftward shift of the ET-1 concentration-response curve (CRC). This leftward shift was abolished after epithelium removal. 3. L-NAME (3 x 10(-3) M), an inhibitor of nitric oxide (NO) synthase, induced a significant leftward shift of the ET-1 CRC, and abolished the potentiation by BQ-123 (10(-8) M) of ET-1-induced contraction. 4. In intact preparations, the ET(B) receptor antagonist BQ-788 induced only at 10(-5) M a slight rightward shift of the ET-1 CRC. In contrast, in epithelium-denuded bronchi or in intact preparations in the presence of L-NAME, BQ-788 displayed a non-competitive antagonism toward ET-1-induced contraction. 5. IRL 1620, a selective ET(B) receptor agonist, induced a contraction of the isolated bronchus (-logEC50=7.94+/-0.11, n= 19). This effect was not modified by epithelium removal or by BQ-123. BQ-788 exerted a competitive antagonism against IRL 1620 which was similar in the presence or absence of epithelium. 6. These results show that ET-1 exerts two opposite effects on the human airway smooth muscle. One is contractile via ETB-receptor activation, the other is inhibitory and responsible of NO release which counteracts via ETA-receptor activation the contraction.

In vitro-induced human airway hyperresponsiveness to bradykinin

Lipopolysaccharide (LPS) and interleukin (IL)-1beta have been reported to induce airway hyperresponsiveness in several animal models. This study investigated the effect of LPS or IL-1beta on bradykinin-induced human isolated bronchi contraction. LPS (100 ng x mL(-1) for 3-6 h) and IL-1beta (3x10(-10) and 3x10(-9) M for 20 min to 3 h) time-dependently potentiated bradykinin-induced contraction. This contraction was abolished, as in control experiments, by indomethacin (10(-6) M) or by the thromboxane (Tx) receptor antagonist GR 32191 but not by the cyclo-oxygenase-2 inhibitor, CGP28238. In contrast, the Tx mimetic U46619-induced contraction of human bronchi was not enhanced IL-1beta pretreatment. In the presence of GR 32191 (10(-6) M), bradykinin induced a prostanoid dependent relaxation that was not significantly modified by IL-1beta pretreatment. Determination of prostanoids in the organ bath fluid showed that bradykinin induced TxB2, the stable metabolite of TxA2, and 6-keto prostaglandin F1alpha, the stable metabolite of PGI2, release. Only TxA2 release was potentiated by IL-1beta. Taken together our results suggest that interleukin-1beta (1-3 h)-induced potentiation of the effect of bradykinin is linked to an increased activity of thromboxane synthase and, in turn, to increased thromboxane synthesis.

In vitro inhibition of human colonic motility with SR 59119A and SR 59104A: evidence of a beta3-adrenoceptor-mediated effect

The new beta3-adrenoceptor is present in the gastrointestinal tract of various species. This study aimed to show that this receptor modulates human colonic motility in vitro. We used circular muscle strips from the human colon suspended in single organ baths containing Krebs solution and subjected to an initial 1.5-2 g tension. We measured the effects of different beta3-adrenoceptor agonists, including SR 59104A (N-[(6-hydroxy-1,2,3,4-tetrahydronaphthalen-(2R)-2-yl)methyl]-(2 R)-2-hydroxy-2-(3-chlorophenyl)ethanamine hydrochloride), SR 59119A (N-[(7-methoxy-1,2,3,4-tetrahydronaphthalen-(2R)-2-yl)methyl]-(2R) -2-hydroxy-2-(3-chlorophenyl)ethanamine hydrochloride), BRL 37344 (R,R + S,S) [4-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino] propyl] phenoxy] acetic acid), and of isoprenaline and salbutamol in the absence or in the presence of propranolol alone or in combination with the beta3-adrenoceptor antagonist SR 59230A (3-(2-ethylphenoxy)-1-[(1S)-1,2,3,4-tetrahydro-naphthalen-1- ylamino]-(2S)-2-propanol oxalate) on amplitude of spontaneous contractions. To evaluate a possible beta2-adrenoceptor-mediated effect, we studied the action of these compounds on human isolated bronchi. On the human isolated colon, SR 59119A, SR 59104A and isoprenaline reduced the initial amplitude of spontaneous contractions by 60%. The curves obtained in the presence of antagonists suggested an action mediated by beta3-adrenoceptor stimulation, since propranolol did not antagonize the action of SR 59119A and SR 59104A, whereas the combination of propranolol and SR 59230A significantly displaced the concentration-response curve of these agonists to the right. This study provides pharmacological evidence of modulation of human colonic motility, and especially of the amplitude of spontaneous contractions, by the atypical beta-adrenoceptor, the beta3-adrenoceptor.

Involvement of tachykinin NK3 receptors in citric acid-induced cough and bronchial responses in guinea pigs

Aerosolized citric acid induces several pulmonary effects including bronchoconstriction, airway inflammation, and cough. Evidence from the use of tachykinin NK1 and NK2 receptor antagonists, as well as chronic treatment with high doses of capsaicin, have suggested that these effects are mediated through the release of tachykinins from sensory nerve endings. In the present study, we have investigated the effects of a tachykinin NK3 receptor antagonist, SR 142801 (osanetant), on cough, bronchoconstriction, and bronchial hyperresponsiveness induced by aerosolized citric acid (0.4 M) in guinea pigs. SR 142801, at 0.3 and 1 mg . kg-1 by intraperitoneal route, significantly inhibited cough in conscious guinea pigs by 57 +/- 3 and 62 +/- 10% (n = 8), respectively. In anaesthetized guinea pigs, it failed to inhibit the bronchoconstriction induced by citric acid when given alone but abolished it when combined with the tachykinin NK2 receptor antagonist, SR 48968 (saredutant). In guinea pigs pretreated with thiorphan (1 mg . kg-1), aerosolized citric acid (0.4 M, 1 h) induced airway hyperresponsiveness 24 h later, displayed by an exaggerated response to the bronchoconstrictor effect of acetylcholine. A microvascular leakage hypersensitivity also occurred and was demonstrated by a potentiation of the plasma protein extravasation from bronchial vessels induced by histamine. When given once intraperitoneally at 1 mg . kg-1 30 min before the citric acid exposure, SR 142801 inhibited both hyperresponsiveness to acetylcholine and the potentiation of histamine-induced increase in microvascular permeability. The results suggest that tachykinin NK3 receptors are involved in citric acid-induced effects on airways.

Contractile effect of 6 beta-acetoxy nortropane on human and guinea pig airways

AIM

To study the effects of 6 beta-acetoxy nortropane (6 beta-AN) on the isolated human bronchus and guinea pig trachea.

METHODS

The contractile effect of 6 beta-AN was studied with 4 different muscarinic receptor antagonists on airway strips and inositol phosphates (IP) accumulation in human bronchi was determined by HPLC with radioactivity flow detector.

RESULTS

(1) The maximal contractile effect of 6 beta-AN was lower than that of acetylcholine (ACh) on the human bronchus and equal to that of ACh on the guinea pig trachea. 6 beta-AN was more potent than ACh on both preparations (68 and 245 times, respectively). (2) The contractile effect of 6 beta-AN was inhibited by atropine (1 -100 nmol.L-1) or para-fluoro-hexahydro-sila-difenidol (0.01-1 mumol.L-1), but not by methoctramine (Met, 0.3-3 mumol.L-1) or pirenzepine (0.01-0.1 mumol.L-1), and was not enhanced by tacrine (0.1-10 mumol.L-1) or by epithelium removal. (3) The 6 beta-AN induced-contraction was accompanied by an increase of IP levels in isolated human bronchial tissues. (4) 6 beta-AN had an inhibitory effect on isoprenaline (Iso)-induced relaxation, which was abolished or reduced by Met 0.3 mumol.L-1.

CONCLUSION

6 beta-AN exerts a potent contractile effect involving muscarinic M3 receptor stimulation on airway smooth muscle. Muscarinic M2 receptor stimulation is furthermore partially involved in the antagonism by 6 beta-AN on the Iso-induced relaxation of the guinea pig trachea.

Long- and short-acting beta2 adrenoceptor agonists: interactions in human contracted bronchi

The aim of this study was to systematically compare the interaction of the long-acting beta2-adrenoceptor agonists formoterol and salmeterol with short-acting beta2-adrenoceptor agonists in contracted human bronchi. Human bronchi were obtained at thoracotomy from patients with lung cancer. Formoterol or salmeterol at concentrations inducing up to 92 and 94% of their maximal relaxant effect, respectively, were added to bronchial rings contracted with carbachol (10(-6) M). After a time period of 30 min, concentration-response curves for the short-acting beta2-adrenoceptor agonists, salbutamol, terbutaline, isoprenaline and fenoterol were recorded. Administration of equieffective concentrations of salmeterol and formoterol, resulted in only salmeterol inducing a shift to the right of isoprenaline, terbutaline, fenoterol and salbutamol concentration-response curves. The rank order of shift was salbutamol > fenoterol > terbutaline > isoprenaline. Formoterol, up to concentrations of 3x10(-9) M induced submaximal relaxation resulting in no shift in short-acting beta2-adrenoceptor agonist concentration-response curves. Salmeterol but not formoterol appears to antagonize the relaxation of human contracted bronchi induced by short-acting beta2-agonists. These results obtained in vitro cannot be translated in clinical terms. This study, however, highlights the need for clinical studies on the interaction of long-acting and short-acting beta2-adrenoceptor agonists in acute severe asthma.

Long- and short-acting beta2 adrenoceptor agonists: interactions in human contracted bronchi

The aim of this study was to systematically compare the interaction of the long-acting beta2-adrenoceptor agonists formoterol and salmeterol with short-acting beta2-adrenoceptor agonists in contracted human bronchi. Human bronchi were obtained at thoracotomy from patients with lung cancer. Formoterol or salmeterol at concentrations inducing up to 92 and 94% of their maximal relaxant effect, respectively, were added to bronchial rings contracted with carbachol (10(-6) M). After a time period of 30 min, concentration-response curves for the short-acting beta2-adrenoceptor agonists, salbutamol, terbutaline, isoprenaline and fenoterol were recorded. Administration of equieffective concentrations of salmeterol and formoterol, resulted in only salmeterol inducing a shift to the right of isoprenaline, terbutaline, fenoterol and salbutamol concentration-response curves. The rank order of shift was salbutamol > fenoterol > terbutaline > isoprenaline. Formoterol, up to concentrations of 3x10(-9) M induced submaximal relaxation resulting in no shift in short-acting beta2-adrenoceptor agonist concentration-response curves. Salmeterol but not formoterol appears to antagonize the relaxation of human contracted bronchi induced by short-acting beta2-agonists. These results obtained in vitro cannot be translated in clinical terms. This study, however, highlights the need for clinical studies on the interaction of long-acting and short-acting beta2-adrenoceptor agonists in acute severe asthma.

Effects of fenspiride on human bronchial cyclic nucleotide phosphodiesterase isoenzymes: functional and biochemical study

We have investigated the role of human bronchial cyclic nucleotide phosphodiesterases in the effects of fenspiride, a drug endowed with bronchodilator and anti-inflammatory properties. Functional studies on human isolated bronchi showed that fenspiride (10(-6)-3 x 10(-3) M, 30 min) induced a shift to the left of the concentration-response curves for isoprenaline and sodium nitroprusside with -logEC50 values of 4.1+/-0.1 (n = 7) and 3.5+/-0.2 (n = 8), respectively. Biochemical studies were carried out on three human bronchi in which separation of cyclic nucleotide phosphodiesterase isoenzymes was performed by ion exchange chromatography followed by determination of phosphodiesterase activity with a radioisotopic method. Phosphodiesterase 4 (cyclic AMP-specific) and phosphodiesterase 5 (cyclic GMP-specific) were the major phosphodiesterase isoforms present in the human bronchial tissue. The presence of phosphodiesterase 1 (Ca2+/calmodulin-stimulated), phosphodiesterase 2 (cyclic GMP-stimulated) and, in two cases, phosphodiesterase 3 (cyclic GMP-inhibited) was also identified. Fenspiride inhibited phosphodiesterase 4 and phosphodiesterase 3 activities with -logIC50 values of 4.16+/-0.09 and 3.44+/-0.12, respectively. Phosphodiesterase 5 activity was also inhibited with a -logIC50 value of approximately 3.8. Fenspiride (< or = 10(-3) M) produced less than 25% inhibition of phosphodiesterase 1 and phosphodiesterase 2 activities. In conclusion, fenspiride is an effective inhibitor of both cyclic AMP and cyclic GMP hydrolytic activity in human bronchial tissues and this action may contribute to its airway effects.

Inhibitory effects of large Ca2+-activated K+ channel blockers on beta-adrenergic- and NO-donor-mediated relaxations of human and guinea-pig airway smooth muscles

In human bronchi, relaxations to salbutamol and sodium nitroprusside were performed in the presence or absence of blockers of the large Ca2+-activated K+-channels (BKCa): charybdotoxin (Chtx), iberiotoxin (Ibtx) or tetraethylammonium (TEA). In bronchi under basal tone in presence of indomethacin (1 microM) or precontracted with acetylcholine (in presence or absence of indomethacin), the relaxations to salbutamol or sodium nitroprusside were unaffected or weakly inhibited by pretreatment with the BKca blockers (Chtx (100 nM), Ibtx (100 and 300 nM) and TEA (1 mM)). Significant inhibitions were mainly observed with TEA (1 mM) and iberiotoxin at high concentration (300 nM). These results contrasts with the potent inhibitory effects exerted by Chtx (100 nM) or Ibtx (100 nM) in guinea-pig trachea precontracted with acetylcholine in absence or presence of indomethacin indicating that human airways are less susceptible to BKCa blockade than guinea-pig airways. In addition, the BKCa blockers induced slowly developing contractions of human bronchi at basal tone. The contraction induced by TEA (1 mM) was abolished by verapamil (10 microM) suggesting that BKca blockade promotes an increase in membrane Ca2+-conductance through activation of voltage-gated Ca2+-channels. Verapamil also reversed the effects of TEA on salbutamol-induced relaxations in human bronchi as well as the effects of Ibtx on salbutamol- or sodium nitroprusside-induced relaxations in guinea-pig trachea. These data suggest that BKCa blockers induce activation of voltage-gated Ca2+-channels and therefore influx of Ca2+ which in turn cause a functional antagonism of beta2-adrenoceptor-agonist- and NO-donor-induced relaxations. Moreover, the BKCa opener, NS-1619, induced weak relaxations in human bronchi and guinea-pig trachea which were not blocked by TEA or Ibtx suggesting that BKCa opening is of minor significance for the relaxation of human airway smooth muscles. In conclusion, although a wealth of studies have demonstrated that beta-adrenoceptor agonists or NO-donors activate BKCa, the present study provides evidence that in human bronchi, as recently suggested in guinea-pig trachea, opening of BKCa does not appear to functionally participate in the relaxation to these relaxant agents.

Biochemical and pharmacological activities of SR 144190, a new potent non-peptide tachykinin NK2 receptor antagonist

(R)-3-(1-[2-(4-benzoyl-2-(3,4-difluorophenyl)-morpholin-2-yl)- ethyl]-4-phenylpiperidin-4-yl)-1-dimethylurea (SR 144190) is a new non-peptide antagonist of tachykinin NK2 receptors. SR 144190 potently and selectively inhibited neurokinin A binding to NK2 receptors from various species, including humans. In in vitro functional assays, it was a potent, selective and competitive antagonist of NK2 receptors with apparent affinities (pA2 values) between 9.08 and 10.10. In vivo, SR 144190 blocked [Nle10]neurokinin A-(4-10)-induced bronchoconstriction in guinea pigs (ID50 = 21 micrograms kg-1 i.v. and 250 micrograms kg-1 i.d.) and [beta Ala8]neurokinin A-(4-10)-induced urinary bladder contraction in rats (ID50 = 11 micrograms kg-1 i.v. and 190 micrograms kg-1 i.d.). It prevented citric acid-induced cough and airway hyperresponsiveness to acetylcholine in guinea pigs (1 mg kg-1 i.p.) as well as castor oil-induced diarrhoea in rats (0.01-10 micrograms kg-1 s.c. or p.o). Finally, it blocked the turning behaviour induced by intrastriatal injections of [Nle10]neurokinin A-(4-10) in mice (ID50 = 3 micrograms kg-1 i.v. and 16 micrograms kg-1 p.o.).

Pre- and postjunctional inhibitory effects of fenspiride on guinea-pig bronchi

Fenspiride is a drug with potential benefits in the treatment of obstructive airways disease. It has antibronchoconstriction and anti-inflammatory properties. The aim of this study was to investigate the effect of this drug on the contractions induced in the guinea-pig isolated main bronchus and perfused lung by electrical field stimulation (EFS) or exogenously added agents. Bronchi were stimulated transmurally in the presence of indomethacin 10(-6) M and propranolol 10(-6) M, and isometric tension was measured. In the perfused lung model calcitonin gene-related peptide (CGRP) release was determined in the perfusate fractions as a measure of neuropeptide production. Two successive contractile responses were observed: a rapid cholinergic contraction, followed by a long-lasting contraction due to local release of neuropeptides from C-fibre endings. Fenspiride (10(-6) to 10(-4) M) inhibited the nonadrenergic, noncholinergic (NANC) component of the contraction of the guinea-pig isolated main bronchus induced by EFS. Fenspiride significantly affected contractions induced by exogenously added substance P or [Nle10]-NKA(4-10) only at concentrations higher than 10(-3) M. In the guinea-pig perfused lung, fenspiride inhibited low pH- but not capsaicin-evoked release of CGRP. At higher concentrations (10(-4) M to 3x10(-4) M) fenspiride exhibited a significant inhibitory effect both on the cholinergic component of contractile response induced by EFS in the guinea-pig isolated main bronchus and on exogenously added acetylcholine. In conclusion, the result of this study suggests that fenspiride, in moderate concentrations, reduces the release of neuropeptides, including tachykinins, from sensory nerve endings at a prejunctional level. At higher concentrations, postjunctional actions on bronchial smooth muscle are also present.

The effect of S-(+)-boldine on the alpha 1-adrenoceptor of the guinea-pig aorta

1. The cardiovascular activity of S-(+)-boldine, an aporphine alkaloid structurally related to papaverine, was determined. The work includes functional studies on guinea-pig isolated aorta contracted with noradrenaline, caffeine, KCl or Ca2+, and on guinea-pig trachea contracted with acetylcholine or histamine. 2. S-(+)-boldine inhibited in a concentration-dependent manner the contractile response evoked by noradrenaline (10 microM) in guinea-pig aorta (IC50 = 1.4 +/- 0.2 microM) while the KCl depolarizing solution (60 mM)- or the Ca2+ (1 mM)-induced contractions were only partially affected by boldine up to 300 microM. In contrast, papaverine relaxed noradrenaline (NA), KCl or Ca2+ induced contractions showing similar IC50 values in all cases. S-(+)-boldine had a greater potency on the contraction elicited by NA whereas papaverine acted in a non-selective manner. 3. S-(+)-boldine was found to be an alpha 1-adrenoceptor blocking agent in guinea-pig aorta as revealed by its competitive antagonism of noradrenaline-induced vasoconstriction (pA2 = 5.64 +/- 0.08), and its potency was compared with that of prazosin (pA2 = 8.56 +/- 0.24), a known potent alpha 1-adrenoceptor antagonist. In contrast, papaverine caused rightward shifts of the NA concentration-response curves with depression of maximal response indicating that it acts as a non-competitive antagonist. 4. Contraction of guinea-pig aorta induced by caffeine (60 mM) in a Ca(2+)-containing Krebs solution was not affected by a 60 min incubation period with different doses of S-(+)-boldine (1-300 microM). Papaverine inhibited partially this caffeine-induced contraction at the maximal dose used (100 microM). 5. Inositol phosphates formation induced by noradrenaline (10 microM) in guinea-pig thoracic aorta was inhibited by S-(+)-boldine (30 microM) but not by papaverine (10 microM). 6. Contractions of guinea-pig trachea caused by acetylcholine (100 microM) or histamine (10 microM) were not modified by S-(+)-boldine (0.1-100 microM). 7. These results provide evidence that S-(+)-boldine, an aporphine alkaloid, has interesting properties as an alpha 1-adrenoceptor blocker in vascular smooth muscle, and acts as a competitive antagonist of the alpha 1-adrenoceptor present in the guinea pig aorta.

Indirect muscarinic receptor activation by pentamidine on airway smooth muscle

1. Pentamidine is routinely used to reduce the incidence of Pneumocystis carinii pneumonia in patients infected with human immunodeficiency virus, but it has been described as inducing pulmonary adverse effects, such as cough and bronchospasm. 2. In this paper we have investigated the effects of pentamidine on guinea-pig isolated main bronchi and human isolated bronchi. Pentamidine induced a concentration-dependent contraction in both preparations with pD2 values of 9.64 +/- 0.07 (n = 8) and 9.73 +/- 0.06 (n = 8) and a maximal effect (Emax) of 40 +/- 4% and 34 +/- 5% of the response to acetylcholine (1 mM) in guinea-pig and human bronchi respectively. Atropine (0.01 to 0.1 microM) and the muscarinic M3 receptor antagonist, hexahydro-siladiphenidol (0.1 and 1 microM) inhibited pentamidine-induced concentration-responses in both preparations in a non-competitive manner, whereas only high concentrations of the M1 receptor antagonist pirenzipine (1 microM) inhibited pentamidine concentration-response curves. 3. The cholinesterase inhibitor, tacrine (1 microM), potentiated the effect of pentamidine; in contrast, morphine inhibited pentamidine-induced responses. 4. The bronchoconstrictor effect of pentamidine on guinea-pig and human isolated bronchi was not modified by the H1 histamine receptor antagonist, mepyramine, by indomethacin or by the neurokinin NK1 and NK2 receptor antagonists, CP-96,345 and SR 48969 respectively, suggesting that neither histamine receptor stimulation, arachidonic acid derivative formation, nor tachykinin release are involved in pentamidine-induced contraction of human and guinea-pig airways. 5. Our overall results suggest that pentamidine induces contraction of guinea-pig and human isolated bronchi through prejunctional cholinergic nerve stimulation.

Evidence for functional tachykinin NK1 receptors on human isolated small bronchi

On human small isolated bronchi (diameter < 1 mm), but not on larger bronchi (diameter 3-5 mm), substance P (SP) and specific tachykinin SP-preferring neurokinin (NK1) receptor agonists {[beta Ala4, Sar9, Met(O2)11]SP-(4-11), [Sar9, Met(O2)11]SP, [Arg6,Sar9,Met(O2)11]SP-(6-11), and septide; 10(-10) to 10(-6) M} produced a concentration-dependent contraction that occurred at low concentrations (pD2 values of 7.79-8.33) and was characterized by a low intrinsic activity [maximal effect (Emax) of 38-45% of Emax induced by 3 mM acetylcholine, in a noncumulative manner]. Comparison of cumulative and noncumulative concentration-response curves to SP and NK1 receptor agonists suggest rapid receptor desensitization. The SP (10(-8) M)-induced contraction was inhibited by tachykinin NK1 receptor antagonists (rank order of potency: SR-140333 > CP-96,345 > RP-67580) but not by the tachykinin NK2 receptor antagonist SR-48968. Indomethacin (10(-6) M) abolished the SP-induced contraction. Our results suggest that tachykinin NK1 receptors are present on human small bronchi and that their stimulation induces a prostanoid-dependent contraction. The small isolated bronchus is an interesting model of human tissue to test NK1 receptor antagonists.

Effects of RP 73401, a novel, potent and selective phosphodiesterase type 4 inhibitor, on contractility of human, isolated bronchial muscle

1. The aim of this study was to investigate the smooth muscle relaxant effects of the novel, selective phosphodiesterase (PDE) type 4 inhibitor, RP 73401 in comparison with the classical PDE 4 inhibitor, rolipram, the non-selective PDE inhibitor, theophylline and the beta-adrenoceptor agonist, isoprenaline on the human, isolated bronchus. 2. At resting tone, the rank order of potency (pD2) for the relaxants was RP 73401 > or = rolipram > or = isoprenaline >> theophylline. In terms of maximum relaxation produced (Emax) the PDE 4-selective inhibitors were similar, but the maximal effects (70-75% of theophylline, 3 mM) were lower than that observed with isoprenaline (98% of theophylline, 3 mM) or theophylline itself (100%). 3. On the human isolated bronchus pre-contracted with acetylcholine (ACh, 0.1 or 1.0 mM), the rank order of potency remained the same. The maximal responses to RP 73401 and rolipram were however markedly reduced (Emax 39.9-46.6%) compared with isoprenaline (Emax 79-85%). 4. In tissues pre-contracted with ACh (0.1 mM), RP 73401 and rolipram (10(-9)-10(-7) M) significantly and concentration-dependently increased tissue sensitivity to isoprenaline. RP 73401 and rolipram were similar in potency. Both selective PDE 4 inhibitors also significantly increased the maximal relaxant effects of isoprenaline. These effects were not observed with the PDE 3 inhibitor, siguazodan. 5. In terms of retention by tissues (an index of duration of action), the onset of action of RP 73401 (2.11 +/- 0.53 min) and rolipram (1.70 +/- 0.45 min) was significantly slower than that of isoprenaline (0.33 +/- 0.06 min) or theophylline (1.17 +/- 0.25 min). The retention of RP 73401 (89.0 +/- 21.9 min) on the human isolated bronchial tissues after washing was however dramatically longer than that of rolipram (18.3 +/- 4.5 min), theophylline (3.43 +/- 0.58 min) or isoprenaline (2.81 +/- 0.31 min). 6. These data indicate that RP 73401 is a potent and long acting relaxant of human bronchial muscle in vitro. RP 73401 is more potent than the classical PDE 4-selective inhibitor rolipram and the non-selective PDE inhibitor theophylline and is retained in bronchial tissue for a much longer period of time.

Effects of SCA40 on human bronchi and on guinea pig main bronchi in vitro. Comparison with cromakalim

The aim of this study was to examine the activity of SCA40, a novel charybdotoxin-sensitive potassium channel opener, against a variety of spasmogens or against electrical field stimulation in guinea pig isolated main bronchi and in human isolated bronchi; the effects of SCA40 were compared with those of cromakalim. Like cromakalim, SCA40 reduced the contractility of guinea pig and human isolated bronchi precontracted with acetylcholine 10(-6) M or neurokinin A 10(-6) M, SCA40 being more efficient and more potent than cromakalim. Moreover, on guinea pig isolated main bronchi, SCA40 can exert a preventive effect on contractions induced by acetylcholine, neurokinin A or capsaicin, that is, it shifts to the right the concentration-effect curves of these substances, whereas cromakalim has no such effect. The effects of cromakalim were antagonized by glibenclamide 10(-5) M, whereas the effects of SCA40 were inhibited by tetraethylammonium (TEA 10(-2) M) and charybdotoxin (3 x 10(-8) M), but this inhibitory effect of TEA was reversed by nifedipine (10(-6) M). Electrical field stimulation of guinea pig isolated main bronchi induced two successive contractile responses. Both contractions were significantly reduced by SCA40 (10(-6) and 10(-5) M) and cromakalim (10(-5) M). Since cromakalim was unable to inhibit the effects of acetylcholine or neurokinin A, it might be suggested that for this latter compound the inhibition seems to take place prejunctionally and to affect the release of neuromediators produced by electrical field stimulation. In contrast, in the case of SCA40, a postjunctional effect seems to be likely, owing to its preventive effects, although a prejunctional effect cannot be excluded. Finally, on guinea pig isolated main bronchi, SCA40 (10(-8)-10(-6) M) did not potentiate the relaxant effect of isoprenaline or sodium nitroprusside, suggesting a lack of functional manifestation of inhibition of phosphodiesterase for these concentrations. In conclusion, these results demonstrate that SCA40 is a potent and efficient relaxant of guinea pig and human airway smooth muscle, and is able to inhibit, in the guinea pig isolated main bronchi, the contractions induced by electrical field stimulation. It has an effect on TEA-sensitive K+ channels, but this effect is probably not involved in its relaxant effect which does not also rest on an inhibitory effect of phosphodiesterase.

Functional, biochemical and morphological studies on human bronchi after cryopreservation

1. Human isolated bronchi have been investigated as fresh tissue or after storage (7 and 30 days) at -196 degrees C in foetal calf serum containing 1.8 M dimethyl sulphoxide. 2. After cryopreservation, the maximal contractile response to acetylcholine (3 mM) was reduced (approximately 25%) but the difference did not reach significance statistically. Maximal responses to other spasmogens tested (histamine, [Nle10]NKA(4-10), bradykinin, leukotriene D4, U46619, and KCl) did not differ between unfrozen and frozen/thawed tissues. The sensitivity of cryopreserved tissues to the constrictor agents tested was similar to that of fresh tissues. 3. The accumulation of inositol phosphates produced by acetylcholine in human bronchus in vitro was similar in fresh and cryostored (30 days) tissues. 4. Relaxant responses of acetylcholine (0.3 microM)-precontracted preparations to theophylline, isoprenaline, rolipram and sodium nitroprusside were unchanged after storage with the exception of the sensitivity to rolipram which was diminished in the 30-days cryostorage group. 5. Light microscopic examination of sections taken from 30 days cryostored tissues indicates that the epithelium, submucosal tissue and smooth muscle were well preserved. 6. These experiments suggest that cryopreservation of human bronchi results in maintenance of several morphological, functional (contraction/relaxation) and biochemical properties.

Effect of the two tachykinin antagonists, SR 48968 and SR 140333, on cough induced by citric acid in the unanaesthetized guinea pig

It is now well-established that sensory nerves stimulation in the airway induces bronchoconstriction and inflammation, but also protective reflexes, such as coughing. These effects are mediated through the release of tachykinins (substance P and neurokinin A) and we have recently shown that SR 48968, a tachykinin NK2-receptor antagonist, inhibited cough induced by citric acid. In this paper, we have studied the effects of SR 48968 administered by aerosol. We have also investigated the effects of SR 140333, a tachykinin NK1-receptor antagonist, and the combination of both SR 48968 and SR140333 to determine whether tachykinin NK1 receptors are involved in cough. Finally, we have studied the combined effects of SR 48968 and salbutamol to find out whether the antitussive effect of SR 48968 is a consequence of the inhibition of bronchoconstriction. Unanaesthetized guinea-pigs were placed in a transparent chamber and exposed to an aerosol of citric acid (0.4 M). The number of coughs was counted by visual inspection and by determination of sounds and pressure variations in the chamber. By the aerosol route, SR 48968 was an efficient antitussive and 16 times more potent than codeine. SR 140333 (0.1-1 mg.kg-1 i.p.) did not exert any antitussive effect but it potentiated the maximal effect induced by SR 48968. Finally, salbutamol, in a dose (0.3 mg.kg-1) which inhibits bronchoconstriction, but not cough induced by citric acid, did not modify the antitussive effect of SR 48968.(ABSTRACT TRUNCATED AT 250 WORDS)