neurokinin-a and Bronchial-Hyperreactivity

Topics: Adrenergic beta-Antagonists; Animals; Asthma; Bronchial Hyperreactivity; Guinea Pigs; Humans; Neurokinin A; Neurons, Afferent; Substance P

Inhaled corticosteroids (ICS) are the most effective anti-inflammatory agents available for the treatment of asthma but they produce only modest effects on airway inflammation and non-specific bronchial hyperresponsiveness (BHR). However, little is known about the possibility that treatment with ICS might cause additional protection on BHR to inhaled tachykinins such as neurokinin A (NKA).. Therefore, we compared the effects of beclomethasone dipropionate (BDP) on the degree of BHR to inhaled histamine and NKA in a double-blind, controlled, cross-over study of asthmatic patients.. Patients attended the laboratory before and after each 6 weeks treatment period to undertake concentration-response studies with histamine and NKA. Bronchial responsiveness to both funs was expressed as the provocative concentration producing a 20% decrease in FEV(1) from baseline (PC(20)).. BDP therapy attenuated the constrictor response to both agonists to a similar degree, their geometric mean (range) PC(20) values increasing from 0.47 (0.21-1.41) mg/ml to 2.43 (0.51-4.50) mg/ml (P<0.01, post-salb vs. post-BDP treatment) and from 101.7 (27.3-356.1) microg/ml to 666.7 (151.5-1,000) microg/ml (P<0.01, post-salb vs. post-BDP treatment) for histamine and NKA, respectively.. Airway responsiveness to histamine and NKA is reduced by BDP to the same extent. As a result of these findings, provocation with NKA is unlikely to provide additional useful information in the assessment of airway inflammation in asthma.

Topics: Administration, Inhalation; Adrenal Cortex Hormones; Adrenergic beta-Agonists; Adult; Albuterol; Analysis of Variance; Asthma; Beclomethasone; Bronchial Hyperreactivity; Bronchial Provocation Tests; Cross-Over Studies; Dose-Response Relationship, Drug; Double-Blind Method; Female; Histamine; Humans; Male; Neurokinin A; Statistics, Nonparametric

Neurokinin (NK) A causes airway narrowing in patients with asthma through direct and indirect mechanisms. The effects of the inhaled glucocorticosteroid fluticasone propionate (FP) on the bronchial responsiveness to NKA and methacholine were studied. Patients (n=11) with mild asthma participated in a randomized, double-blind, placebo-controlled crossover trial. FP (500 microg b.i.d.) or matched placebo was administered via Diskhaler for 14 days. Bronchial challenges were performed on days 1 and 13 (methacholine) and 0 and 14 (NKA) for each treatment period. At the active treatment period, the mean log2 provocative concentration causing a 20% fall in the forced expiratory volume in one second (PC20)+/-SEM for NKA was -12.72+/-0.63 at the beginning and -9.77+/-0.49 at the end of the period (p<0.0001), while under placebo, it was -12.16+/-0.82 and -12.19+/-0.51 respectively (NS). At the active treatment period, the mean log2 PC20 for methacholine was -5.25+/-0.40 at the beginning and -4.22+/-0.31 at the end of the period (p=0.012), while under placebo, it was -5.47+/-0.47 and -5.24+/-0.42 respectively (NS). The reduction in response to NKA was significantly larger than that for methacholine. A 2-week course of an inhaled steroid reduces bronchial responsiveness to neurokinin A, an effect more pronounced than the reduction in bronchial responsiveness to methacholine.

Topics: Administration, Inhalation; Adolescent; Adult; Androstadienes; Asthma; Bronchial Hyperreactivity; Bronchoconstriction; Bronchoconstrictor Agents; Bronchodilator Agents; Cross-Over Studies; Double-Blind Method; Female; Fluticasone; Forced Expiratory Volume; Humans; Male; Methacholine Chloride; Middle Aged; Neurokinin A

Inhalation of neurokinin (NK) A causes bronchoconstriction in patients with asthma. The NKA-induced bronchoconstriction in isolated human airways is mediated via the NK2 receptor and inhibited by SR 48968, a potent and specific nonpeptide tachykinin NK2 receptor antagonist. In the present study, the effect of orally administered SR 48968 on NKA-induced bronchoconstriction was examined in 12 mild asthmatics. On the screening day and during the study periods, increasing concentrations of NKA (3.3 x 10(-9) to 1.0 x 10(-6) mol x mL(-1)) were inhaled, until the forced expiratory volume in one second (FEV1) and specific airway conductance (sGaw) decreased by at least 20 and 50%, respectively. During the study periods, 100 mg SR 48968 or matched placebo was ingested in a double-blind, randomized, crossover fashion and NKA provocation was performed at 1.5 and 24 h after dosing. At 1.5 h, the mean (SEM) log10 provocative concentration of NKA causing a 20% fall in FEV1 (PC20 FEV1) was -6.25 (0.20) after SR 48968 and -6.75 (0.17) after placebo (p=0.05); the mean log10 provocative concentration of NKA causing a 35% fall in sGaw (PC35 sGaw) was -7.02 (0.28) after SR 48968 and -7.64 (0.19) after placebo (p=0.05). At 24 h, the mean log10 PC20 FEV1 was -6.21 (0.17) after SR 48968 and -6.65 (0.11) after placebo (p=0.05); the mean log10 PC35 sGaw was -6.85 (0.23) after SR 48968 and -7.17 (0.15) after placebo (nonsignificant). As PC20 FEV1 and/or PC35 sGaw were not reached in up to 4 patients per SR 48968 group, the differences between SR 48968 and placebo were underestimated. In conclusion, oral treatment with 100 mg SR 48968 caused a significant inhibition of neurokinin A-induced bronchoconstriction in asthmatics. This finding constitutes the first evidence of inhibition of sensory neuropeptide-induced bronchoconstriction by a selective tachykinin receptor antagonist in humans.

Topics: Adult; Asthma; Benzamides; Bronchial Hyperreactivity; Bronchial Provocation Tests; Cross-Over Studies; Dose-Response Relationship, Drug; Double-Blind Method; Drug Administration Schedule; Forced Expiratory Volume; Humans; Male; Neurokinin A; Piperidines; Receptors, Neurokinin-2; Treatment Outcome

Inhaled frusemide exerts a protective effect against bronchoconstriction induced by several indirect stimuli in asthma which could be due to interference of airway nerves. A randomised, double blind, placebo controlled study was performed to investigate the effect of the potent loop diuretic, frusemide, administered by inhalation on the bronchoconstrictor response to neurokinin A (NKA) and histamine in 11 asthmatic subjects.. Subjects attended the laboratory on four separate occasions to receive nebulised frusemide (40 mg) or matched placebo 10 minutes prior to bronchial challenge with NKA and histamine in a randomised, double blind order. Changes in airway calibre were followed as forced expiratory volume in one second (FEV1) and responsiveness to the agonists was expressed as the provocative concentration causing a 20% fall in FEV1 from baseline (PC20).. Compared with placebo, inhaled frusemide reduced the airway responsiveness to NKA in all the subjects studied, the geometric mean (range) values for PC20NKA increasing significantly (p < 0.001) from 130.3 (35.8-378.8) to 419.9 (126.5-1000) micrograms/ml after placebo and frusemide, respectively. Moreover, a small but significant change in airway responsiveness to histamine was recorded after frusemide, their geometric mean (range) PC20 values being 0.58 (0.12-3.80) and 1.04 (0.28-4.33) mg/ml after placebo and frusemide, respectively.. The decrease in airway responsiveness to NKA after administration of frusemide by inhalation suggests that this drug may interfere with the activation of neurotransmission in human asthma.

Topics: Administration, Inhalation; Adult; Analysis of Variance; Asthma; Bronchial Hyperreactivity; Bronchial Provocation Tests; Bronchoconstrictor Agents; Diuretics; Dose-Response Relationship, Drug; Double-Blind Method; Female; Forced Expiratory Volume; Furosemide; Histamine; Humans; Male; Neurokinin A

Neuropeptides such as neurokinin A (NKA) have been proposed as important mediators of bronchoconstriction and airway hyperresponsiveness in asthma. Inhaled NKA causes bronchoconstriction in patients with asthma, but not in normal subjects. This is possibly due to the activity of an endogenous neuropeptide-degrading enzyme: neutral endopeptidase (NEP). We investigated whether a NEP-inhibitor, thiorphan, reveals bronchoconstriction to NKA or NKA-induced changes in airway responsiveness to methacholine in normal humans in vivo. Eight normal male subjects participated in a double-blind crossover study, using thiorphan as pretreatment to NKA challenge. Dose-response curves to inhaled NKA (8 to 1,000 micrograms/ml, 0.5 ml/dose) were recorded on 2 randomized days 1 wk apart, and methacholine tests were performed 48 h before and 24 h after the NKA challenge. Ten minutes prior to NKA challenge the subjects inhaled either thiorphan (2.5 mg/ml, 0.5 ml) or placebo. To detect a possible nonspecific effect of thiorphan, we investigated the effect of the same pretreatment with thiorphan or placebo on the dose-response curve to methacholine in a separate set of experiments. The response was measured by the flow from standardized partial expiratory flow-volume curves (V40p), expressed in percent fall from baseline. NKA log dose-response curves were analyzed using the area under the curve (AUC) and the response to the highest dose of 1,000 micrograms/ml (V40p,1000). The methacholine dose-response curves were characterized by their position (PC40V40p) and the maximal-response plateau (MV40p). Baseline V40p was not affected by either pretreatment (p greater than 0.15).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adult; Aerosols; Asthma; Bronchial Hyperreactivity; Bronchial Provocation Tests; Double-Blind Method; Humans; Male; Methacholine Chloride; Neprilysin; Neurokinin A; Premedication; Thiorphan; Time Factors

Bacterial lipopolysaccharide (LPS) can induce bronchial hyperresponsiveness (BHR), but the underlying mechanisms remain to be determined. Here, the possible contribution of sensory nerves to LPS-induced BHR was examined in human isolated bronchi to pharmacologically identify the mechanisms underlying this phenomenon.. Human isolated bronchial tone was induced by electrical field stimulation (EFS). The responses of airways to LPS, with or without capsaicin desensitization or thiorphan treatment were studied and the transient receptor potential vanilloid type 1 (TRPV1) expression was assessed. We performed similar experiments in the presence of a TRPV1 or a neurokinin (NK) 2 receptor antagonist using SB366791 and GR159897, respectively.. LPS increased (≃2.3-fold, P<0.001) the contraction induced by EFS, compared to control tissues. Acute administration of capsaicin enhanced (≃2.3-fold, P<0.001) the EFS-mediated contraction, but did not potentiate the effect of LPS. Thiorphan increased (≃1.3-fold, P<0.05) the contractile response of LPS treated tissues and, at lower frequencies, it enhanced (≃1.7-fold, P<0.001) the capsaicin-induced contraction. In capsaicin-desensitized bronchi, LPS did not modify (P>0.05) the EFS contractile response, nor after treatment with thiorphan. Capsaicin desensitization reduced (≃0.4-fold, P<0.001) the LPS-induced BHR. SB366791 and GR159897 prevented the LPS-induced BHR and the release of NKA. LPS increased (+85.3±9.5%, P<0.01) the surface membrane expression of TRPV1 in parasympathetic ganglia.. Our results demonstrate the involvement of capsaicin-sensitive sensory nerves and neutral endopeptidases in LPS-induced BHR of the human bronchi, associated with an upregulation of TRPV1 and release of NKA.

Topics: Anilides; Bronchi; Bronchial Hyperreactivity; Capsaicin; Cinnamates; Electric Stimulation; Female; Humans; Indoles; Lipopolysaccharides; Male; Middle Aged; Muscle Contraction; Neprilysin; Neurokinin A; Piperidines; Sensory Receptor Cells; TRPV Cation Channels; Up-Regulation

The adoptive transfer of OVA-specific Th1 cells into WT mice followed by OVA inhalation induces a significant elevation of airway hyper-responsiveness (AHR) with neutrophilia but not mucus hypersecretion. Here, we demonstrate that the airway inflammation model, pathogenically characterized as severe asthma, was partly mimicked by i.n. administration of IFN-γ. The administration of IFN-γ instead of Th1 cells caused AHR elevation but not neutrophilia, and remarkably induced neurokinin-2 receptor (NK2R) expression along with neurokinin A (NKA) production in the lung. To evaluate whether NKA/NK2R was involved in airway inflammation, we first investigated the role of NKA/NK2R-signaling in airway smooth muscle cells (ASMCs) in vitro. NK2R mRNA expression was significantly augmented in tracheal tube-derived ASMCs of WT mice but not STAT-1(-/-) mice after stimulation with IFN-γ. In addition, methacholine-mediated Ca(2+) influx into the ASMCs was significantly reduced in the presence of NK2R antagonist. Moreover, the NK2R antagonist strongly inhibited IFN-γ-dependent AHR elevation in vivo. Thus, these results demonstrated that IFN-γ directly acts on ASMCs to elevate AHR via the NKA/NK2R-signaling cascade. Our present findings suggested that NK2R-mediated neuro-immuno crosstalk would be a promising target for developing novel drugs in Th1-cell-mediated airway inflammation, including severe asthma.

Topics: Animals; Asthma; Bronchial Hyperreactivity; Calcium Signaling; Cells, Cultured; Disease Models, Animal; Disease Progression; Gene Expression Regulation; Humans; Interferon-gamma; Mice; Mice, Inbred BALB C; Mice, Knockout; Mice, Transgenic; Myocytes, Smooth Muscle; Neuroimmunomodulation; Neurokinin A; Receptors, Neurokinin-2; Respiratory System; STAT1 Transcription Factor

The purpose of the study was to compare in vitro airway responses to neurokinin A & B (NKA and NKB) and expression of NK-2 receptors in airways of horses affected and unaffected with recurrent airway obstruction (RAO). Neurokinin-A, an inflammatory mediator belonging to the tachykinin family of neuropeptides, causes bronchoconstriction by binding to NK-2 receptors. Neurokinin-B is a lesser-known neuropeptide that acts on NK-3 receptors. Horses were placed into RAO-affected and RAO-unaffected groups based on their history, clinical scoring, and pulmonary function testing. Lung tissue from each lobe was collected for immunohistochemical staining for NK-2 receptors. Cumulative concentration-response relationships were determined on bronchial rings (4-mm wide) collected and prepared from the right diaphragmatic lung lobe to graded concentrations (half log molar concentrations 10(-7)M to 10(-4)M) of NKA and NKB. The results showed that NKA caused significantly greater contraction than NKB in both groups. In RAO-affected horses, both agents produced significantly greater bronchial contractions than those in the RAO-unaffected horses. Immunohistochemical staining showed that the overall NK-2 receptor distribution was significantly increased in bronchial epithelium and smooth muscles of bronchi and pulmonary vessels of RAO-affected than RAO-unaffected horses. The findings indicate that NK-2 receptors are up-regulated in RAO, suggesting that NK-2 receptor antagonists may have some therapeutic value in controlling the progression of airway hyperreactivity in horses affected with RAO.

Topics: Airway Obstruction; Animals; Antibodies; Bronchi; Bronchial Hyperreactivity; Horse Diseases; Horses; Immunohistochemistry; Muscle, Smooth; Neurokinin A; Neurokinin B; Nose; Receptors, Neurokinin-2; Recurrence; Respiratory Physiological Phenomena

The female hormone estrogen is an important factor in the regulation of airway function and inflammation, and sex differences in the prevalence of asthma are well described. Using an animal model, we determined how sex differences may underlie the development of altered airway function in response to allergen exposure. We compared sex differences in the development of airway hyperresponsiveness (AHR) after allergen exposure exclusively via the airways. Ovalbumin (OVA) was administered by nebulization on 10 consecutive days in BALB/c mice. After methacholine challenge, significant AHR developed in male mice but not in female mice. Ovariectomized female mice showed significant AHR after 10-day OVA inhalation. ICI182,780, an estrogen antagonist, similarly enhanced airway responsiveness even when administered 1 hour before assay. In contrast, 17beta-estradiol dose-dependently suppressed AHR in male mice. In all cases, airway responsiveness was inhibited by the administration of a neurokinin 1 receptor antagonist. These results demonstrate that sex differences in 10-day OVA-induced AHR are due to endogenous estrogen, which negatively regulates airway responsiveness in female mice. Cumulatively, the results suggest that endogenous estrogen may regulate the neurokinin 1-dependent prejunctional activation of airway smooth muscle in allergen-exposed mice.

Topics: Allergens; Animals; Bronchial Hyperreactivity; Disease Models, Animal; Estradiol; Estrogen Receptor Modulators; Estrogens; Female; Fulvestrant; Male; Methacholine Chloride; Mice; Mice, Inbred BALB C; Neurokinin A; Neurokinin-1 Receptor Antagonists; Ovalbumin; Sex Characteristics

The neurotrophin nerve growth factor (NGF) is elevated in serum and locally in the lung in asthmatics and has been suggested to evoke airway hyperresponsiveness. The aim of this study was to explore mechanisms behind NGF-evoked changes in airway responsiveness. We studied if NGF could evoke increased airway responsiveness to tachykinins, such as neurokinin A (NKA), in a similar way as for histamine and, if so, whether an NGF-evoked increase in NKA airway responsiveness could involve a histamine receptor-dependent mechanism. Contractile responses to cumulative doses of histamine or NKA were studied in guinea-pig tracheal rings in vitro in organ baths. Furthermore, insufflation pressure (IP), pulmonary resistance, lung compliance and exhaled NO (FeNO) were measured in vivo in anaesthetised guinea-pigs challenged with histamine or NKA. NGF pre-treatment in vitro increased the contractile response evoked by histamine, but not by NKA, in tracheal rings. NGF pre-treatment in vivo increased IP, pulmonary resistance and levels of FeNO, and further decreased lung compliance, upon histamine and NKA challenge. The NGF-evoked enhancement of IP, pulmonary resistance, lung compliance as well as FeNO in response to NKA was reversed by the histamine receptor antagonist mepyramine. We suggest that NGF can induce an increase in tachykinin-evoked airway responses and NO formation via a histamine receptor-dependent pathway. This points to an important role for the mast cell in neurotrophin-evoked airway hyperresponsiveness and changes in exhaled NO.

Topics: Animals; Bronchial Hyperreactivity; Guinea Pigs; Histamine; Histamine H1 Antagonists; In Vitro Techniques; Lung Compliance; Male; Muscle Contraction; Muscle, Smooth; Nerve Growth Factor; Neurokinin A; Nitric Oxide; Pyrilamine; Receptors, Histamine; Respiratory Mechanics; Respiratory System; Trachea

In the present study we evaluated the role of neurokinins in the modulation of inducible nitric oxide synthase (iNOS) inflammatory cell expression in guinea pigs with chronic allergic airway inflammation. In addition, we studied the acute effects of nitric oxide inhibition on this response. Animals were anesthetized and pretreated with capsaicin (50 mg/kg sc) or vehicle 10 days before receiving aerosolized ovalbumin or normal saline twice weekly for 4 wk. Animals were then anesthetized, mechanically ventilated, given normal saline or N(G)-nitro-l-arginine methyl ester (l-NAME, 50 mg/kg ic), and challenged with ovalbumin. Prechallenge exhaled NO increased in ovalbumin-exposed guinea pigs (P < 0.05 compared with controls), and capsaicin reduced this response (P < 0.001). Compared with animals inhaled with normal saline, ovalbumin-exposed animals presented increases in respiratory system resistance and elastance and numbers of total mononuclear cells and eosinophils, including those expressing iNOS (P < 0.001). Capsaicin reduced all these responses (P < 0.05) except for iNOS expression in eosinophils. Treatment with l-NAME increased postantigen challenge elastance and restored both resistance and elastance previously attenuated by capsaicin treatment. Isolated l-NAME administration also reduced total eosinophils and mononuclear cells, as well as those cells expressing iNOS (P < 0.05 compared with ovalbumin alone). Because l-NAME treatment restored lung mechanical alterations previously attenuated by capsaicin, NO and neurokinins may interact in controlling airway tone. In this experimental model, NO and neurokinins modulate eosinophil and lymphocyte infiltration in the airways.

Topics: Administration, Inhalation; Aerosols; Airway Resistance; Animals; Bronchial Hyperreactivity; Capsaicin; Chronic Disease; Elasticity; Enzyme Inhibitors; Eosinophils; Guinea Pigs; Inflammation; Lung; Male; Neurokinin A; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Ovalbumin

In this report the in vitro and in vivo pharmacological and pharmacokinetic profile of (-)-(S)-N-(alpha-ethylbenzyl)-3-(carboxymethoxy)-2-phenylquinoline-4-carboxamide (SB 235375), a low central nervous system (CNS)-penetrant, human neurokinin-3 (NK-3) receptor (hNK-3R) antagonist, is described. SB 235375 inhibited (125)I-[MePhe(7)]-neurokinin B (NKB) binding to membranes of Chinese hamster ovary (CHO) cells expressing the hNK-3R (CHO-hNK-3R) with a K(i) = 2.2 nM and antagonized competitively NKB-induced Ca(2+) mobilization in human embryonic kidney (HEK) 293 cells expressing the hNK-3R (HEK 293-hNK-3R) with a K(b) = 12 nM. SB 235375 antagonized senktide (NK-3R)-induced contractions in rabbit isolated iris sphincter (pA(2) = 8.1) and guinea pig ileal circular smooth muscles (pA(2) = 8.3). SB 235375 was selective for the hNK-3R compared with hNK-1 (K(i) > 100,000 nM) and hNK-2 receptors (K(i) = 209 nM), and was without effect, at 1 microM, in 68 other receptor, enzyme, and ion channel assays. Intravenous SB 235375 produced a dose-related inhibition of miosis induced by i.v. senktide in the rabbit (ED(50) of 0.56 mg/kg). Intraperitoneal SB 235375 (10-30 mg/kg) inhibited citric acid-induced cough and airways hyper-reactivity in guinea pigs. In mice oral SB 235375 (3-30 mg/kg) was without significant effect on the behavioral responses induced by intracerebral ventricular administration of senktide. Pharmacokinetic evaluation in the mouse and rat revealed that oral SB 235375 was well absorbed systemically but did not effectively cross the blood-brain barrier. The preclinical profile of SB 235375, encompassing high affinity, selectivity, oral activity, and low CNS penetration, suggests that it is an appropriate tool compound to define the pathophysiological roles of the NK-3Rs in the peripheral nervous system.

Topics: Acetates; Animals; Antitussive Agents; Behavior, Animal; Bronchial Hyperreactivity; Calcium; Central Nervous System; Citric Acid; Cloning, Molecular; Cough; Guinea Pigs; In Vitro Techniques; Iris; Male; Mice; Mice, Inbred BALB C; Muscle Contraction; Muscle, Smooth; Neurokinin A; Peptide Fragments; Pupil; Quinolines; Rabbits; Radioligand Assay; Rats; Receptors, Neurokinin-3; Receptors, Tachykinin; Recombinant Proteins; Substance P

We have studied the effect of selective tachykinin NK(1) and NK(2) receptor antagonists on airway hyperreactivity to acetylcholine and increase of inflammatory cells on bronchoalveolar lavage fluid induced by sephadex beads (20 mg/kg, i.v.) in guinea pigs. Airway hyperreactivity was assessed by measuring the increase of bronchial insufflation pressure to acetylcholine (0.01-30 micromol/kg, i.v.) at 3 h (early phase) and 24 h (late phase) after sephadex administration. An increase in inflammatory cells in bronchoalveolar lavage fluid (eosinophils and macrophages) was detected at 24 h (from 11.6 x 10(6) to 49.3 x 10(6) cells) but not at 3 h from sephadex administration. Neurokinin A and substance P levels in bronchoalveolar lavage fluid showed a significant increase at 24 h (from 31.7+/-11.6 to 561+/-231 pg/ml and from 5.9+/-2.6 to 29.3+/-4.1 pg/ml for neurokinin A and substance P, respectively). At this time point, the tachykinin in bronchoalveolar lavage cellular content was depleted from 232+/-43 to 21+/-20 pg/sample and from 56.6+/-6.7 to 2+/-2 pg/sample for neurokinin A and substance P, respectively. Capsaicin pretreatment abolished the early but not the late phase of airway hyperreactivity induced by sephadex without modifying bronchoalveolar lavage total cells number and bronchoalveolar lavage levels of neurokinin A and substance P. Administration of the tachykinin NK(2) (nepadutant) and/or the NK(1) receptor antagonist (MEN 11467 or (1R,2S)-2-N[1(H)indol-3-yl-carbonyl]-1-N[N-(p-tolylacetyl)-N-(methyl)-D-3(2-naphthyl)alanyl)diaminocyclohexane)), 5 min before sephadex, prevented the early phase of airway hyperreactivity to acetylcholine but only nepadutant prevented the late phase. Nepadutant was able to abolish the early phase of airway hyperreactivity if given after sephadex administration and reduced by about 50% the increase of cell number in bronchoalveolar lavage fluid during the late phase, without affecting the levels of neurokinin A and substance P. These findings indicate an involvement of endogenous tachykinins in the genesis of airway hyperreactivity in a guinea-pig model of non-allergic asthma. Early airway hyperreactivity apparently involves release of tachykinins from capsaicin-sensitive afferent nerves acting via tachykinin NK(1)/NK(2) receptors. Late airway hyperreactivity involves tachykinins acting via tachykinin NK(2) receptors: inflammatory cells activated/recruited in response to sephadex challenge appear a likely source of tachy

Topics: Acetylcholine; Animals; Bronchial Hyperreactivity; Bronchoalveolar Lavage Fluid; Bronchoconstriction; Bronchodilator Agents; Capsaicin; Cell Count; Cyclohexylamines; Dextrans; Dose-Response Relationship, Drug; Eosinophils; Guinea Pigs; Indoles; Inflammation; Macrophages; Male; Neurokinin A; Peptides, Cyclic; Receptors, Tachykinin; Substance P; Tachykinins; Time Factors; Vasodilator Agents

Tobacco smoke (TS) exposure induces airway hyperreactivity, particularly in sensitive individuals with asthma. However, the mechanism of this airway hyperreactivity is not well understood. To investigate the relative susceptibility of atopic and nonatopic individuals to TS-induced airway hyperreactivity, we exposed ovalbumin (OA)-sensitized and nonsensitized guinea pigs to TS exposure (5 mg/l air, 30-min exposure, 7 days/wk for 120-156 days). Two similar groups exposed to compressed air served as controls. Airway reactivity was assessed as an increase in enhanced pause (Penh) units using a plethysmograph that allowed free movement of the animals. After 90 days of exposure, airway reactivity increased in OA-TS guinea pigs challenged with capsaicin, bradykinin, and neurokinin A fragment 4--10 aerosols. In addition, substance P content increased in lung perfusate of OA-TS guinea pigs in response to acute TS challenge compared with that of the other groups. Airway hyperirritability was not enhanced by phosphoramidon but was attenuated by a cocktail of neurokinin antagonists, nor was airway hyperreactivity observed after either methacholine or histamine challenge in OA-TS guinea pigs. Chronic TS exposure enhanced neither airway reactivity to histamine or methacholine nor contractility of isolated tracheal rings. In conclusion, chronic TS exposure increased airway reactivity to capsaicin and bradykinin aerosol challenge, and OA-TS guinea pigs were most susceptible to airway dysfunction as the result of exposure to TS compared with the other groups. Increased airway reactivity to capsaicin suggests a mechanism involving neurogenic inflammation, such as increased activation of lung C fibers.

Topics: Administration, Inhalation; Airway Resistance; Animals; Bradykinin; Bronchial Hyperreactivity; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Bronchoconstrictor Agents; Capsaicin; Guinea Pigs; Histamine; Leukocyte Count; Lung; Male; Methacholine Chloride; Neurokinin A; Ovalbumin; Peptide Fragments; Smoking; Substance P; Wakefulness

Airway hyperresponsiveness to neurokinin A (NKA) occurs in inflammatory airway diseases like asthma. In this study, bronchoconstrictor reactivity to NKA was measured in beagle dogs neonatally sensitized to and challenged with ragweed. Comparisons were made to histamine and methacholine. Lung resistance (R(L)) and dynamic lung compliance (C(Dyn)) were measured in anesthetized, spontaneously breathing dogs before and after aerosol challenge with NKA, histamine or methacholine. The concentration of these agents increasing R(L)by 25% above baseline (PC(25)) was calculated before and 24 h after aerosolized ragweed challenge. Before ragweed, the bronchoconstrictor reactivity to NKA was four-fold higher in ragweed-sensitized dogs (PC(25)=0.036+/-0.006%) compared to non-sensitized controls (PC(25)=0.177+/-0.030%, P<0.05). On the other hand, there was no difference in the bronchoconstrictor reactivity to histamine or methacholine between these two groups. Twenty-four hours after ragweed challenge to sensitized dogs, NKA reactivity was unchanged from pre-ragweed values but histamine and methacholine reactivity was increased by 2-3-fold. These results demonstrate airway hyperresponsiveness to NKA, histamine and methacholine in allergic beagle dogs although hyperresponsiveness to NKA exists in these allergic dogs before an antigen challenge. This animal model may prove to be useful to evaluate the role of tachykinins in hyperractive airway diseases.

Topics: Administration, Inhalation; Aerosols; Animals; Bronchial Hyperreactivity; Bronchial Spasm; Bronchoconstriction; Dogs; Female; Histamine; Hypersensitivity; Male; Methacholine Chloride; Neurokinin A

This study was carried out to determine whether tachykinins released from lung C-fiber afferents play a part in the bronchial hyperreactivity induced in guinea pigs by chronic exposure to cigarette smoke (CS). Two matching groups of young guinea pigs were exposed to either mainstream CS (CS group) or air (control group) for 20 min twice daily for 14-17 days. There was no difference in the baseline total pulmonary resistance (RL) between the two groups, but the baseline dynamic lung compliance was reduced ( approximately 19%) in CS animals. The responses of RL to intravenous injections of ACh, neurokinin (NK) A, and capsaicin were all markedly increased in CS animals; for example, ACh at the same dose of 5.06 microg/kg increased RL by 207% in the control group and by 697% (n = 8; P < 0. 001) in the CS group. The increased responsiveness was accompanied by significant increases in the numbers of neutrophils, eosinophils, and macrophages in the bronchoalveolar lavage fluid in CS animals. Pretreatment with SR-48968 and CP-99994, antagonists of NK(1) and NK(2) receptors, respectively, did not alter the response of RL to ACh in control animals, but it abolished the elevated bronchoconstrictive response in the CS animals. Furthermore, the immunoreactivities of substance P and calcitonin gene-related peptide in the bronchoalveolar lavage fluid collected after capsaicin challenge were significantly increased in CS animals. These results show that chronic exposure to CS induced airway mucosal inflammation accompanied by bronchial hyperreactivity in guinea pigs and that the tachykininergic mechanism plays an important role in this augmented responsiveness.

Topics: Acetylcholine; Air Pressure; Animals; Benzamides; Bronchial Hyperreactivity; Bronchoalveolar Lavage Fluid; Capsaicin; Cell Count; Dose-Response Relationship, Drug; Guinea Pigs; Male; Neurokinin A; Neuropeptides; Nicotiana; Piperidines; Plants, Toxic; Receptors, Neurokinin-2; Smoke; Tachykinins; Vagotomy

To determine whether mycoplasma infection produces airway hyper-responsiveness to tachykinins and bradykinin and, if so, to elucidate the role of neutral endopeptidase (NEP), isolated hamster tracheal segments were studied under isometric conditions in vitro. Nasal inoculation with Mycoplasma pneumoniae potentiated contractile responses to neurokinin A and bradykinin, causing a leftward shift of the dose-response curves to a lower concentration by 1 log unit for each agonist, whereas there was no response with acetylcholine. Pretreatment of tissues with the NEP inhibitor phosphoramidon augmented neurokinin A- and bradykinin-induced contractions in saline-treated control tissues, but did not further potentiate the responsiveness in M. pneumoniae-infected tissues. NEP activity in the tracheal epithelium, but not in epithelium-denuded tissues, was decreased in infected animals. These results suggest that M. pneumoniae infection causes airway bronchoconstrictor hyper-responsiveness to neurokinin A and bradykinin and that this effect may be associated with an inhibition of epithelial NEP activity.

Topics: Animals; Antibodies, Bacterial; Bradykinin; Bronchial Hyperreactivity; Cricetinae; Epithelium; Glycopeptides; In Vitro Techniques; Isometric Contraction; Male; Mesocricetus; Muscle, Smooth; Mycoplasma pneumoniae; Neprilysin; Neurokinin A; Pneumonia, Mycoplasma; Protease Inhibitors; Trachea

Interleukin-8 (IL-8) has been shown to be a chemotactic factor for neutrophils, T-lymphocytes and eosinophils. Repeated intranasal administration of IL-8 enhances bronchial responsiveness to inhaled histamine in guinea-pigs. Neuropeptides which are released from C-fibre nerve-endings have been postulated to induce bronchial hyperresponsiveness through neurogenic inflammation.. This study was conducted to examine whether sensory neuropeptides are involved in the IL-8-induced bronchial hyperresponsiveness.. IL-8 at a dose of 5 micrograms/kg was administered intranasally to guinea-pigs twice a week for 3 weeks. One day after the last administration, animals were anesthetized and artificially ventilated through tracheal cannula, and lateral pressure at the tracheal cannula (Pao) was measured as an overall index of airway responses to increasing concentrations of inhaled histamine (25, 50, 100, and 200 micrograms/mL). A NK1 and NK2 dual antagonist FK224 (10 mg/kg), a selective NK1 antagonist FK888 (10 mg/kg) or vehicle was intravenously administered 10 min before measurement of bronchial responsiveness.. The IL-8 treatment significantly enhanced bronchial responsiveness to histamine (ANOVA P < 0.01). FK224 or FK888 did not alter the IL-8-induced bronchial hyperresponsiveness.. We conclude that repeated intranasal administration of IL-8 causes bronchial hyperresponsiveness (BHR) and that neuropeptides such as neurokinin A and substance P do not directly contribute to the development of BHR induced by IL-8.

Topics: Animals; Bronchial Hyperreactivity; Bronchial Provocation Tests; Dipeptides; Guinea Pigs; Histamine; Indoles; Interleukin-8; Male; Neurokinin A; Peptides, Cyclic; Substance P

Administration of propranolol can provoke bronchoconstriction in asthmatic patients. We hypothesized that such bronchoconstriction may result from the inflammatory mediators released by an allergic reaction. We recently developed a guinea pig model for propranolol-induced bronchoconstriction (PIB). Neuropeptides which are released from C-fibre nerve endings have been postulated to induce bronchial hyperresponsiveness through neurogenic inflammation.. The purpose of this study was to examine whether sensory neuropeptides are involved in the development of PIB after allergic reaction.. Propranolol at a concentration of 10 mg/ml was inhaled 20 min after antigen challenge in passively sensitized, anaesthetized and artificially ventilated guinea pigs. The animals were treated intravenously with a NK1 and NK2 dual antagonist, FK224, in a dose of 1 or 10 mg/kg or vehicle or a selective NK1 antagonist, FK888, in a dose of 1 or 10 mg/kg or vehicle 10 min before or 15 min after antigen challenge.. Propranolol inhaled 20 min after antigen challenge caused bronchoconstriction. FK224 or FK888 administered 15 min after antigen challenge as well as 10 min before antigen challenge did not reduce the PIB.. We conclude that neuropeptides such as neurokinin A and substance P do not directly contribute to the development of PIB after allergic reaction.

Topics: Adrenergic beta-Antagonists; Animals; Asthma; Bronchial Hyperreactivity; Bronchoconstriction; Dipeptides; Guinea Pigs; Indoles; Male; Neurokinin A; Peptides, Cyclic; Propranolol; Substance P

The effects of sensory neuropeptides on the airway responsiveness to acetylcholine (ACh) were investigated in normal nonsensitized rats. The airway responsiveness to inhaled ACh was significantly increased after treatment with neurokinin A (NKA; 0.001%) or substance P (SP; 0.01%) aerosol in the presence of the neutral endopeptidase (NEP) inhibitor. NKA had a more potent effect than SP. Interestingly, the intravenous treatment with NEP inhibitor alone also induced airway hyperresponsiveness (AHR) to inhaled ACh. This AHR was significantly attenuated by pretreatment with a nonselective NK-receptor antagonist, [D-Pro2,D-Trp7,9]SP, systemic capsaicin, or bilateral cervical vagotomy, indicating that decreased NEP activity results in accumulation of endogenous sensory neuropeptide(s) and enhancement of vagal reflex to cause AHR. The airway responsiveness to ACh of isolated left main bronchus was also increased after treatment with 10(-6) M NKA, but not SP, together with 10(-6) M phosphoramidon. This in vitro AHR to ACh induced by phosphoramidon plus NKA was significantly attenuated by pretreatment with 10(-6) M tetrodotoxin. These findings suggest that overaccumulated sensory neuropeptides, especially NKA, may enhance the probability of transmitter release, probably via NK2 receptors, and that the enhanced transmitter release might be involved in AHR in rats.

Topics: Acetylcholine; Administration, Inhalation; Animals; Bronchial Hyperreactivity; Capillary Permeability; Capsaicin; Carbachol; Glycopeptides; In Vitro Techniques; Male; Muscle, Smooth; Neprilysin; Neurokinin A; Protease Inhibitors; Quinuclidinyl Benzilate; Rats; Rats, Wistar; Respiratory System; Substance P; Vagotomy

Human isolated bronchi obtained at thoracotomy from 42 patients were exposed to aqueous solutions of acrolein, and the resulting change in contractile responses was evaluated by measuring agonist cumulative concentration-response curves (CCRC). Contractile responses to carbachol were measured after a variety of exposure concentrations, from 0.01 to 3.0 microM, and at times from 5 to 60 min. The optimal condition to induce airway smooth muscle hyperresponsiveness was an exposure duration of 20 min at a concentration of 0.3 microM. The effect of acrolein exposure on human bronchial smooth muscle was also assessed by examining the contractile responses to potassium chloride (KCl), histamine, and neurokinin A (NKA) in both the absence and the presence of phosphoramidon. Although in vitro exposure of the human bronchus to 0.3 microM acrolein did not alter responses to KCl, it did increase the efficacy of carbachol and NKA without altering their potency. This concentration of acrolein also increased the contractile response to low concentrations of histamine and shifted the CCRC to the left. Pretreatment with phosphoramidon abolished the differential effect of acrolein on airway response to NKA. These results suggest that the mechanism of action of acrolein includes inactivation of airway neutral endopeptidase as well as alterations in the pharmacomechanical, but not the electromechanical, coupling of human bronchial smooth muscle.

Topics: Acrolein; Bronchi; Bronchial Hyperreactivity; Bronchoconstriction; Carbachol; Histamine; Humans; In Vitro Techniques; Muscle, Smooth; Neprilysin; Neurokinin A; Potassium Chloride

We tested the hypothesis that allergen-induced mediator release augments the magnitude of isocapnic dry gas hyperpnea-induced bronchoconstriction in sensitized guinea pigs. Male Hartley guinea pigs were sensitized by spontaneous inhalation of ovalbumin (OA) aerosol on days 0 and 7 of the study. On day 14, sensitized animals again breathed OA aerosol and were prospectively divided into a group that exhibited labored breathing (LB), presumably reflecting OA-induced inflammatory mediator release, and a group that did not exhibit LB at this time. Control guinea pigs breathed saline aerosol on days 0, 7, and 14. Bronchoalveolar lavage on day 17 disclosed relative eosinophilia in OA+LB, but not in OA-LB, animals. On day 17, the bronchoconstrictor responses to increasing intravenous (i.v.) doses of acetylcholine (ACh), substance P (SP), neurokinin A (NKA), and capsaicin, as well as dry gas hyperpnea, were measured in vivo in animals from each group. Control and OA-LB guinea pigs exhibited similar responses, but OA+LB animals demonstrated augmented bronchoconstriction induced by i.v. administration of ACh, SP, or NKA. However, despite their augmented responsiveness to these exogenous constrictor agonists, OA+LB animals displayed no greater bronchoconstriction after dry gas hyperpnea or i.v. capsaicin administration. It is known that both dry gas hyperpnea and i.v. capsaicin cause bronchoconstriction in guinea pigs by releasing endogenous tachykinins from airway sensory C-fibers. Thus, our results suggest that allergen-induced mediator release impairs endogenous tachykinin release from airway sensory C-fibers in guinea pigs.

Topics: Acetylcholine; Airway Resistance; Allergens; Animals; Bronchial Hyperreactivity; Bronchoalveolar Lavage Fluid; Bronchoconstriction; Capsaicin; Carbon Dioxide; Dose-Response Relationship, Drug; Eosinophils; Guinea Pigs; Male; Neurokinin A; Neurotransmitter Agents; Ovalbumin; Respiration Disorders; Substance P; Tidal Volume

In a previous study we have shown that inhibition of the endogenous neuropeptide-degrading enzyme, neutral endopeptidase (NEP), potentiates airway narrowing to neurokinin A (NKA) in normal humans in vivo. In the present study, we tested the hypothesis that hyperresponsiveness to NKA in asthma is caused by a reduction in endogenous NEP activity. To that end, we used the NEP inhibitor, thiorphan, or placebo as inhaled pretreatment to NKA challenge in eight atopic asthmatic men, who were controlled by on-demand usage of beta 2-agonists alone. The dose of thiorphan pretreatment was obtained from pilot experiments in which 0.5 ml of a 2.5-mg/ml concentration appeared to be the maximally effective nebulized dose. Dose-response curves to inhaled NKA (1 to 125 micrograms/ml, 0.5 ml/dose) were recorded on 2 randomized days 1 wk apart, in a cross-over study. To detect any effects of thiorphan on bronchoconstriction per se, we also investigated the effect of thiorphan or placebo on the dose-response curve to inhaled methacholine in a separate set of experiments. The response was measured by FEV1 and by partial expiratory flow-volume curves (V40p). The position of the dose-response curves was expressed as the concentration causing a 20% fall in FEV1 (PC20FEV1) or a 40% fall in V40p (PC40V40p). Baseline FEV1 and V40p were not affected by either pretreatment (p > 0.06). PC20FEV1 and PC40V40p to NKA were significantly lower after thiorphan pretreatment as compared with placebo (mean difference +/- SEM: 2.3 +/- 0.6 and 1.6 +/- 0.5 doubling dose, respectively; p < 0.015).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adult; Asthma; Bronchial Hyperreactivity; Bronchial Provocation Tests; Dose-Response Relationship, Drug; Double-Blind Method; Forced Expiratory Volume; Humans; Male; Methacholine Chloride; Neprilysin; Neurokinin A; Thiorphan

Airway hyperresponsiveness (AHR) is a critical component in bronchial asthma, but the underlying mechanisms remain to be disclosed. Our present studies were performed to establish a new good experimental animal model of AHR. Male Wistar rats actively sensitized with DNP-Ascaris antigen (DNP-Asc) were challenged by inhaling DNP-Asc 8 days after the first immunization (single antigenic challenge). Another sensitization group received 3 challenges every 48 hr (repeated antigenic challenge). The airway responsiveness to inhalations of acetylcholine (ACh) and neurokinin A (NKA) were determined under anesthesia. The airway microvascular leakage was also determined with Evans blue (E.B.). At 24 hr after the single antigen challenge, the airway responsiveness to ACh and NKA were slightly enhanced, and the E.B. exudation was increased in the main bronchus. In contrast, the airway responsiveness to ACh and NKA and the E.B. exudation in the main bronchus were much more markedly enhanced 24 hr after the repeated antigenic challenge. The isolated main bronchial strip from the challenged rats had obtained AHR towards ACh and serotonin. These findings suggest that repeated antigenic challenge causes a distinct AHR, both in vivo and in vitro, and that the airway inflammation may be closely related to pathogenesis of AHR.

Topics: Acetylcholine; Animals; Antigens; Bronchi; Bronchial Hyperreactivity; Bronchoconstriction; Capillary Permeability; Disease Models, Animal; Immunization; In Vitro Techniques; Inflammation; Lung; Male; Neurokinin A; Rats; Rats, Wistar; Trachea

The effect of repeated weekly antigen challenges by aerosol on bronchopulmonary responses to ACh, histamine, neurokinin A or atropine-resistant (NANC) component of vagal stimulation, has been studied in guinea pigs. Bronchospastic responses were measured in anaesthetized animals, 7 days after the last challenge with antigen (or vehicle). No difference was observed between control and antigen challenged guinea pigs in their responsiveness to acetylcholine (1-300 mumol kg-1 i.v.) or histamine (1-300 mumol kg-1 i.v.). On the other hand, amplitude of bronchospasm induced by neurokinin A (1-3 mumol kg-1 i.v.) or NANC vagal stimulation (20 Hz, 1 msec, 10 V, trains of 5-20 sec) was significantly increased in guinea pigs previously challenged with antigen, as compared to controls. These results suggest that repetitive antigen exposure in sensitized guinea pigs generates an increase in the responsiveness to exogenously administered or endogenously released tachykinins, at a time when no generalized hyperresponsiveness to other spasmogens could be observed.

Topics: Acetylcholine; Aerosols; Animals; Antigens; Bronchial Hyperreactivity; Capsaicin; Choline; Disease Models, Animal; Dose-Response Relationship, Drug; Electric Stimulation; Epinephrine; Guinea Pigs; Histamine; Male; Neurokinin A; Neurons, Afferent; Receptors, Neurotransmitter; Receptors, Tachykinin; Sensitivity and Specificity; Vagus Nerve

We studied the effect of neurokinin A (NKA) on tracheal smooth muscle (TSM) contraction induced by the administration of acetylcholine (ACh) intra-arterially (ia) into the tracheal circulation or bilateral vagal stimulation in 18 mongrel dogs. In five dogs, 10(-12) to 10(-7) mol of NKA was injected selectively into the tracheal circulation. The tracheal contractile response to 10(-7) mol NKA was 3.12 +/- 0.48 g/cm, 6.3 +/- 0.7% AChmax. Plasma histamine concentration in the right atrium was measured at the peak response to NKA. Plasma histamine concentration was 3.33 +/- 2.05 ng/ml after 10(-7) mol NKA (vs 0.32 +/- 0.08 ng/ml for control, p > 0.10). In the other 5 dogs, dose-response was obtained with 10(-12) to 10(-7) mol ACh 10 min before and 10 min after administration of 10(-8) mol NKA. Frequency-response relationship also was induced by electrical stimulation of the distal cut ends of the cervical vagi in the range of frequencies 1-20 Hz (constant 30 V) at 15-s intervals 10 min before and after administration of 10(-8) NKA. Considerable potentiation of the tracheal contractile response to 10(-18) to 10(-7) mol ia ACh occurred 10 min after administration of 10(-8) mol NKA (p < 0.05). Significant potentiation of the tracheal contraction to vagal stimulation at 10-20 Hz was also observed 10 min after administration of 10(-8) mol NKA (p < 0.05). We demonstrate that the substantial contractile effects of NKA on canine tracheal smooth muscle are not related to histamine release from mast cells in the respiratory tract.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acetylcholine; Animals; Bronchial Hyperreactivity; Dogs; Electric Stimulation; Female; Histamine; Male; Muscle Contraction; Muscle, Smooth; Neurokinin A; Parasympathetic Nervous System; Trachea; Vagus Nerve