phosphoramidon and Bronchial-Hyperreactivity

Inhaled bradykinin causes bronchoconstriction in asthmatic subjects but not nonasthmatics. To date, animal studies with inhaled bradykinin have been performed only in anesthetized guinea pigs and rats, where it causes bronchoconstriction through sensory nerve pathways. In the present study, airway function was recorded in conscious guinea pigs by whole-body plethysmography. Inhaled bradykinin (1 mM, 20 s) caused bronchoconstriction and influx of inflammatory cells to the lungs, but only when the enzymatic breakdown of bradykinin by angiotensin-converting enzyme and neutral endopeptidase was inhibited by captopril (1 mg/kg i.p.) and phosphoramidon (10 mM, 20-min inhalation), respectively. The bronchoconstriction and cell influx were antagonized by the B(2) kinin receptor antagonist 4-(S)-amino-5-(4-{4-[2,4-dichloro-3-(2,4-dimethyl-8-quinolyloxymethyl)phenylsulfonamido]-tetrahydro-2H-4-pyranylcarbonyl}piperazino)-5-oxopentyl](trimethyl)ammonium chloride hydrochloride (MEN16132) when given by inhalation (1 and 10 μM, 20 min) and are therefore mediated via B(2) kinin receptors. However, neither intraperitioneal MEN16132 nor the peptide B(2) antagonist icatibant, by inhalation, antagonized these bradykinin responses. Sensitization of guinea pigs with ovalbumin was not sufficient to induce airway hyperreactivity (AHR) to the bronchoconstriction by inhaled bradykinin. However, ovalbumin challenge of sensitized guinea pigs caused AHR to bradykinin and histamine. Infection of guinea pigs by nasal instillation of parainfluenza-3 virus produced AHR to inhaled histamine and lung influx of inflammatory cells. These responses were attenuated by the bradykinin B(2) receptor antagonist MEN16132 and H-(4-chloro)DPhe-2'(1-naphthylalanine)-(3-aminopropyl)guanidine (VA999024), an inhibitor of tissue kallikrein, the enzyme responsible for lung synthesis of bradykinin. These results suggest that bradykinin is involved in virus-induced inflammatory cell influx and AHR.

Topics: Animals; Bradykinin; Bradykinin B2 Receptor Antagonists; Bronchial Hyperreactivity; Bronchoalveolar Lavage Fluid; Bronchoconstriction; Captopril; Cell Count; Glycopeptides; Guinea Pigs; Histamine; Male; Ornithine; Ovalbumin; Parainfluenza Virus 3, Human; Peptides; Plethysmography, Whole Body; Pneumonia; Protease Inhibitors; Respirovirus Infections; Sulfonamides; Tissue Kallikreins

Peroxynitrite plays an important role in the pathogenesis of airway inflammation. We have already found that peroxynitrite may contribute to decreased beta(2)-adrenoceptor responses in airway smooth muscle. However, it is not known whether peroxynitrite can alter neutral endopeptidase (EC 3.4.24.11; NEP) activity in the airways. This study was designed to determine whether peroxynitrite induces airway hyperresponsiveness to substance P (SP) and endothelin-1 (ET-1) through the inactivation of airway NEP.. We examined whether the administration of S-morpholinosydnonimine (SIN-1), a compound that releases peroxynitrite, increased bronchoconstrictor responses to SP and ET-1 in anesthetized guinea pigs. In addition, we assayed NEP activity in the airways of SIN-1-exposed guinea pigs.. Though SIN-1 (10(-7) M) alone had no effect on pulmonary resistance, pretreatment with SIN-1 significantly enhanced SP- and ET-1-induced bronchoconstriction. Pretreatment with phosphoramidon, an NEP inhibitor, also enhanced SP- and ET-1-induced bronchoconstriction. However, simultaneous administration of phosphoramidon and SIN-1 had no additive effect on SP- and ET-1-induced bronchoconstriction. Peroxynitrite formation by SIN-1 was completely inhibited by N-acetylcysteine (NAC) and glutathione (GSH) in vitro, and pretreatment with NAC and GSH significantly reversed the potentiation by SIN-1 of SP-induced bronchoconstriction. In addition, the NEP activity of the trachea after SIN-1 exposure was significantly reduced compared to the level in control guinea pigs (solvent for SIN-1: 30.0+/-4.2 fmol.min(-1).mg tissue(-1); 10(-7) M SIN-1; 15.5+/-4.5 fmol.min(-1).mg tissue(-1), p<0.05).. These findings suggest that peroxynitrite induces airway hyperresponsiveness to SP and ET-1 through the inactivation of airway NEP, and that peroxynitrite is an important mediator of the alterations in airway functions.

Topics: Animals; Bronchial Hyperreactivity; Bronchoconstriction; Endothelin-1; Enzyme Activation; Glycopeptides; Guinea Pigs; Male; Molsidomine; Neprilysin; Nitrates; Oxidants; Protease Inhibitors; Respiratory System; Substance P; Trachea; Vasodilator Agents

Tolerance to respiratory effects of O3 has been demonstrated for anatomic and functional changes, but information about tolerance to O3-induced airway hyperresponsiveness (AHR) is scarce. In guinea pigs exposed to air or O3 (0.3 parts/million, 4 h/day, for 1, 3, 6, 12, 24, or 48 days, studied 16-18 h later), pulmonary insufflation pressure changes induced by intravenous substance P (SP, 0.032-3.2 micro ug/kg) were measured, then the animals were subjected to bronchoalveolar lavage (BAL). Bronchial rings with or without phosphoramidon were also evaluated 3 h after air or a single O3 exposure. O3 caused in vivo AHR (increased sensitivity) to SP after 1, 3, 6, 12, and 24 days of exposure compared with control. However, after 48 days of exposure, O3 no longer caused AHR. Total cell, macrophage, neutrophil, and eosinophil counts in BAL were increased in most O3-exposed groups. When data from all animals were pooled, we found a highly significant correlation between degree of airway responsiveness and total cells (r = 0.55), macrophages (r = 0.54), neutrophils (r = 0.47), and eosinophils (r = 0.53), suggesting that airway inflammation is involved in development of AHR to SP. Superoxide dismutase (SOD) levels in BAL fluids were increased (P < 0.05) after 1, 3, 6, and 12 days of O3 exposure and returned to basal levels after 24 and 48 days of exposure. O3 failed to induce hyperresponsiveness to SP in bronchial rings, and phosphoramidon increased responses to SP in air- and O3-exposed groups, suggesting that neutral endopeptidase inactivation was not involved in O3-induced AHR to SP in vivo. We conclude that chronic exposure to 0. 3 ppm O3, a concentration found in highly polluted cities, resulted in tolerance to AHR to SP in guinea pigs by an SOD-independent mechanism.

Topics: Analysis of Variance; Animals; Bronchial Hyperreactivity; Bronchoalveolar Lavage; Cell Count; Glycopeptides; Guinea Pigs; Inflammation; Infusions, Intravenous; Insufflation; Leukocytes; Lung; Macrophages; Male; Ozone; Substance P; Superoxide Dismutase

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

The smoke-induced airway hyperresponsiveness (SIAHR) to inhaled wood smoke was investigated in anesthetized guinea pigs. Two smoke challenges (each 10 ml) separated by 30 min were delivered into the lungs by a respirator. In control animals, SIAHR was evidenced by an average bronchoconstrictive response (an increase in total lung resistance) to the second smoke challenge (SM2) that was approximately 4.3-fold greater than that to the first challenge (SM1). Pretreatment with CP-96,345 and SR-48,968 (neurokinin-1 and -2 receptor antagonists; each 1 mg/kg) in combination totally prevented this SIAHR, while pretreatment with CP-96,344 and SR48,965 (inactive enantiomers of CP-96,345 and SR-48,968, each 1 mg/kg) in combination failed to do so. Pretreatment with CP-96,345 (1 mg/kg), SR48,968 (1 mg/kg), or atropine (50 microg/kg) significantly alleviated this SIAHR. Pretreatment with phosphoramidon [an inhibitor of neutral endopeptidase (NEP); 2 mg/kg], which suppresses the degradation of tachykinins, induced an increase in airway reactivity that largely mimicked this SIAHR. The NEP activity measured in airway tissues excised 30 min after SM1 was significantly lower than that in air control value. These results suggest that 1) a prior wood smoke exposure induces an airway hyperresponsiveness to the subsequent wood smoke inhalation, 2) a tachykininergic mechanism involving both neurokinin-1 and -2 receptors is essential for, and a cholinergic mechanism is also involved in the development of this SIAHR, and 3) inactivation of airway NEP by wood smoke may contribute to this SIAHR.

Topics: Airway Resistance; Animals; Atropine; Benzamides; Biphenyl Compounds; Bronchi; Bronchial Hyperreactivity; Cholinergic Antagonists; Drug Combinations; Glycopeptides; Guinea Pigs; Male; Neprilysin; Piperidines; Protease Inhibitors; Receptors, Cholinergic; Receptors, Tachykinin; Smoke; Wood

Tachykinins, found in sensory nerves, have effects in the airways which suggest that they may contribute to the pathogenesis of asthma. We aimed to find evidence for tachykinin involvement in the immediate airway response to allergen in a sheep model of experimental asthma. Twenty-four sheep were actively sensitized to Ascaris suum, then challenged with nebulized Ascaris extract in a dose-response fashion. Change in lung resistance (RL) in response to challenge was measured. Responder sheep (those with an increase in RL of > or = 100% over baseline) that had reproducible responses over three challenges were identified (n = 4 sheep) and a PC100 (number of breaths of extract required to induce a 100% increase in RL) was determined. The effect of the neutral endopeptidase inhibitor phosphoramidon, the NK-1 receptor-specific antagonist CP 96, 345 and capsaicin desensitization on the RL response to Ascaris challenge was then assessed. Administration of phosphoramidon before Ascaris decreased the PC100 to 31 +/- 7% of the PC100 seen with Ascaris alone (P < 0.05), whereas CP 96,345 and capsaicin desensitization increased the PC100 to 285 +/- 41% and 555 +/- 93% respectively (P < 0.05 for both). These findings suggest that endogenous tachykinins are released in response to allergen challenge and that they contribute to the immediate increase in RL.

Topics: Allergens; Animals; Anti-Inflammatory Agents, Non-Steroidal; Ascaris suum; Asthma; Biphenyl Compounds; Bronchial Hyperreactivity; Bronchoconstriction; Capsaicin; Disease Models, Animal; Drug Interactions; Glycopeptides; Immunization; Reference Values; Reproducibility of Results; Sheep; Tachykinins

1. In this study, the role of neuropeptides in antigen-induced bronchoconstriction and bronchial responsiveness in guinea-pigs was evaluated by use of phosphoramidon, the inhibitor of neutral endopeptidases (NEP), the NK1 receptor antagonist, FK888, and the dual NK1/NK2 receptor antagonist, FK224. The role of endogenous tachykinins in bronchial hyperresponsiveness induced by inhaled capsaicin was also observed with FK888 and FK224. 2. Allergic bronchoconstriction and bronchial responsiveness was evoked by inhalation of ovalbumin (OA), and increasing doses of methacholine were inhaled at 5-min intervals for 30 min after OA challenge in passively sensitized and artificially ventilated guinea-pigs. Animals were treated with a 30 s inhalation of phosphoramidon (10(-3)M) or saline 10 min before the OA challenge. FK888 (1.0 or 10 mg kg-1) or FK224 (1.0 or 10 mg kg-1) was administered intravenously 5 min before the OA challenge. 3. Treatment with phosphoramidon did not alter the increase in the lateral pressure at the tracheal tube (Pao) caused by OA inhalation or the increase in bronchial response to methacholine following the allergic reaction. Pretreatment with FK224 did not inhibit the increase in Pao after antigen provocation but did significantly inhibit antigen-induced bronchial hyperresponsiveness in a dose-dependent manner, while FK888 did not affect either allergic bronchoconstriction or post-allergic bronchial hyperresponsiveness. 4. Histamine, 25, 50, 100 or 200 micrograms ml-1 was inhaled for 20 s at 5-min intervals in non-sensitized guinea-pigs which were pretreated with inhalation of subthreshold dose of capsaicin (10(-7) M). FK888 or FK224, each at a dose of 0.1 or 1.0 mg kg-1, or vehicle was given to guinea-pigs intravenously 3 min before inhalation of capsaicin. The capsaicin inhalation significantly potentiated bronchial responsiveness to histamine, compared with control. The capsaicin-induced bronchial hyperresponsiveness was completely blocked by FK224 in a dose-dependent manner but not by FK888. 5. These results suggest that NK2 receptors rather than NK1 receptors may play an important role in bronchial hyperresponsiveness induced by antigen challenge as well as capsaicin while tachykinins do not play a primary role in the acute bronchospasm elicited by antigen challenge in passively sensitized guinea-pigs.

Topics: Animals; Bronchial Hyperreactivity; Bronchoconstrictor Agents; Capsaicin; Dipeptides; Glycopeptides; Guinea Pigs; Histamine; Indoles; Male; Methacholine Chloride; Neurokinin-1 Receptor Antagonists; Peptides, Cyclic; Protease Inhibitors; Receptors, Neurokinin-1; Receptors, Neurokinin-2; Respiratory Hypersensitivity

Tachykinins, such as substance P, might be involved in the development of airway hyperresponsiveness (AHR) and airway inflammation. However, it is unknown which tachykinin receptors mediate these biological activities. The effects of two antagonists of tachykinin neurokinin-1 (NK1) and tachykinin neurokinin-2 (NK2) receptors, SR 140333 and SR 48968, respectively, were investigated on substance P (SP)-induced airway hyperresponsiveness and potentiation of the histamine-induced increase in microvascular leakage, in phosphoramidon-pretreated guinea-pigs. Guinea-pigs were pretreated with phosphoramidon (0.1 mM aerosol for 15 min) and exposed 15 min later to saline solution alone or to saline solution containing SP (0.1 mg.mL-1 for 30 min). Twenty four hours later, the animals were anaesthetized and prepared for the recording of the pulmonary inflation pressure (PIP) to acetylcholine or for the investigation of microvascular leakage to histamine. Pretreatment of the guinea-pigs with a single dose of SR 48968 (1 mg.kg-1, i.p.) 30 min before SP exposure, significantly prevented the development of AHR, whereas SR 140333 (1 mg.kg-1, i.p.) did not. In a second set of experiments, phosphoramidon-pretreated guinea-pigs exposed to SP presented a significant potentiation of the histamine-induced increase in microvascular leakage in pulmonary airways. When the guinea-pigs were pretreated with SR 140333, an inhibition of the increased microvascular leakage to histamine was observed. In contrast, no significant inhibitory activity was noted when the guinea-pigs were pretreated with SR 48968. The present data demonstrate the importance of tachykinin NK2 receptor stimulation in the development of airway hyperresponsiveness and that of tachykinin NK1 receptor stimulation in microvascular leakage hypersensitivity in phosphoramidon-pretreated and substance P-exposed guinea-pigs. The results also suggest a dissociation between the presence of microvascular leakage and the occurrence of airway hyperresponsiveness.

Topics: Animals; Benzamides; Bronchial Hyperreactivity; Capillary Leak Syndrome; Female; Glycopeptides; Guinea Pigs; Male; Metalloendopeptidases; Neurokinin-1 Receptor Antagonists; Piperidines; Premedication; Quinuclidines; Receptors, Neurokinin-1; Receptors, Neurokinin-2; Stereoisomerism; 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

In the present study, the role of sensory neuropeptides in the airway hyperresponsiveness (AHR) was investigated. First, the effect of the depletion of sensory neuropeptides by systemic capsaicin treatment on the AHR to acetylcholine (ACh) induced by repeated antigenic challenge to sensitized rats was studied. We secondly investigated whether the neutral endopeptidase (NEP) activity was altered at the antigen-induced AHR. Male Wistar rats were sensitized and repeatedly challenged with DNP-Ascaris antigen. Twenty-four hours after the last antigenic challenge, a marked AHR to inhaled ACh (0.001-0.03%) was observed. This AHR was significantly attenuated by systemic capsaicin pretreatment prior to sensitization. On the other hand, in normal rats, the airway responsiveness to inhaled ACh was significantly increased by pretreatment with NEP inhibitor, phosphoramidon (3 mg/kg, i.v.), but the NEP inhibitor-induced effect was no more observed in the antigen-induced AHR rats. Furthermore, it was found that the airway NEP activity was significantly decreased at the antigen-induced AHR. These findings suggest that NEP hypoactivity and resultant increased sensory neuropeptides have an important role in the pathogenesis of antigen-induced AHR in rats.

Topics: Acetylcholine; Animals; Antigens, Helminth; Ascaris suum; Bronchial Hyperreactivity; Capsaicin; Captopril; Enkephalin, Methionine; Glycopeptides; Male; Neprilysin; Peptidyl-Dipeptidase A; Puromycin; Rats; Rats, Wistar; Respiratory System; Specific Pathogen-Free Organisms

Inhalation of lipopolysaccharide (LPS) has been associated with increased airway responsiveness and inflammation both in humans and in animals. To investigate the contribution of capsaicin-sensitive nerves to these changes, we compared airway responsiveness and inflammation after intratracheal administration of 10 micrograms/kg LPS (Escherichia coli O55:B5 lipopolysaccharide) or saline in guinea pigs treated 10 days previously with 50 mg/kg capsaicin and in those pretreated with the capsaicin vehicle. Four hours after LPS, airway responsiveness and cell counts in the bronchoalveolar lavage were assessed. To determine airway responsiveness, guinea pigs were anesthetized, tracheotomized, and mechanically ventilated before exposure to increasing concentrations of aerosolized histamine (10(-4) to 10(-3) M). Capsaicin pretreatment prevented the LPS-induced increase in airway responsiveness in response to aerosolized histamine. It significantly reduced total cell recovery in the bronchoalveolar lavage after LPS (1,167 +/- 167 10(3) cells/ml in capsaicin-treated guinea pigs versus 2,171 +/- 184 10(3) in vehicle-treated guinea pigs) by reducing the LPS-induced influx of neutrophils and macrophages. Additional experiments demonstrated that the activity of neutral endopeptidase (NEP) in the tracheal epithelium was not significantly different in guinea pigs injected with LPS from that in the saline-treated control animals, and that the pretreatment with the NEP inhibitor phosphoramidon did not increase the LPS-induced influx of neutrophils into the bronchoalveolar lavage. These results demonstrate that in the guinea pig, capsaicin-sensitive nerves are involved in LPS-induced airway hyperresponsiveness and inflammation.

Topics: Administration, Inhalation; Airway Resistance; Analysis of Variance; Animals; Bronchial Hyperreactivity; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Capsaicin; Endotoxins; Escherichia coli; Glycopeptides; Guinea Pigs; Histamine; Inflammation; Lipopolysaccharides; Macrophages; Male; Neprilysin; Neutrophils; Premedication; Propranolol; Trachea

Exposure of phosphoramidon-treated (0.1 mM solution by aerosol for 15 min) guinea pigs to an aerosol of endothelin-1 (ET-1) (10 micrograms/ml) for 30 min induced after 18-24 h an enhanced bronchopulmonary response (BR) to rechallenge with ET-1 (3 micrograms/ml) administered by aerosol. Compared with saline-exposed animals, aerosol exposure of guinea pigs to ET-1 (10 micrograms/ml) for 30 min did not alter the dose-related BR to acetylcholine (ACh) administered by aerosol 18-24 h following challenge with the peptide. In phosphoramidon-treated guinea pigs, ET-1 (5 micrograms/ml) exposure for 30 min evoked a slight but non-significant enhancement of the ACh-induced BR. Administered by aerosol in phosphoramidon-treated guinea pigs, ET-1 did not induce eosinophil accumulation in the lung, as demonstrated by examination of histological preparations and the assessment of the cell composition of bronchoalveolar lavages. The present data indicate that in spite of treatment of guinea pigs with phosphoramidon, ET-1 administration does not lead to the development of bronchial hyperresponsiveness.

Topics: Acetylcholine; Administration, Inhalation; Animals; Bronchial Hyperreactivity; Bronchoalveolar Lavage Fluid; Endothelins; Glycopeptides; Guinea Pigs; Lung; Male; Pneumonia