phosphoramidon and Inflammation

We investigated the effect of the orally active non-peptide bradykinin B2 receptor antagonist, FR173657 (E)-3-(6-acetamido-3-pyridyl)-N-[N-[2.4-di-chloro-3-[(2-methyl-8-quinoli nyl)oxymethyl]phenyl]-N-methy-laminocarbonylmethyl] acrylamide), on plasma extravasation mediated by activation of sensory nerves in guinea pig airways. Plasma extravasation was assessed by the photometric measurement of the extravasated Evans blue after formamide extraction. We found that the increase in Evans blue dye extravasation evoked by an aerosol of bradykinin (0.1 mM, 2 min) in the presence of phosphoramidon (2.5 mg/kg, i.v.) was abolished completely by FR173657 (20 mg/kg, p.o.) in the trachea and main bronchi. In sensitized guinea pigs pretreated with phosphoramidon, FR173657 (20 mg/kg, p.o.) inhibited plasma extravasation evoked by ovalbumin aerosol (5%, 2 min) by 77+/-14.2% in the trachea and 65+/-11.2% in the main bronchi. FR173657 (20 mg/kg, p.o.) did not affect the plasma extravasation caused by aerosolised capsaicin. These findings suggest that FR173657 is an orally active, promising anti-inflammatory agent for kinin-dependent inflammation following antigen challenge.

Topics: Administration, Oral; Animals; Anti-Inflammatory Agents, Non-Steroidal; Bradykinin; Bradykinin Receptor Antagonists; Bronchi; Capsaicin; Evans Blue; Extravasation of Diagnostic and Therapeutic Materials; Glycopeptides; Guinea Pigs; Inflammation; Male; Ovalbumin; Photometry; Protease Inhibitors; Quinolines; Respiratory System; Trachea

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

Injection of substance P (SP) in a rat hindpaw induced extravasation of 125I-labelled albumin in both hindpaws and salivation. Intravenous injection of SP dose-dependently increased vascular permeability. This latter effect was increased in rat paws by captopril, an inhibitor of angiotensin-converting enzyme (ACE), administered locally in combination with diprotin A, an inhibitor of an dipeptidyl(amino)peptidase IV (DAP IV) or phosphoramidon, an inhibitor of neutral endopeptidase (NEP). The increase in permeability induced by SP was inhibited by RP 67580, a NK-1-receptor antagonist. Intravenous injection of capsaicin induced labelled albumin extravasation in rat paws. This effect was increased by combination of captopril with diprotin A or phosphoramidon, but not by captopril associated with amastatin, an inhibitor of aminopeptidase M (AmM). It was suppressed by RP 67580. Injection of collagenase in rat paws triggered a swelling and a local plasma exudation. These responses were reduced by RP 67580 but not by RP 68651, its inactive enantiomer. They were increased by combination of captopril with diprotin A or phosphoramidon in normal rats. The potentiating effects of captopril and diprotin A were suppressed by RP 67580 in normal rats but did not develop in kininogen-deficient rats. The oedema induced by collagenase was also increased by lisinopril, another ACE inhibitor, administered locally in combination with apstatin, an inhibitor of aminopeptidase P (AmP). In rats pretreated by methysergide, collagenase-induced oedema was reduced and can be increased by captopril, by lisinopril, administered alone or by lisinopril associated with apstatin. It is concluded that SP is mainly inactivated in rat paws by ACE, DAP IV and NEP. In collagenase-induced oedema, a low amount of SP would be released from afferent nerve terminals by bradykinin formed in low amounts. Bradykinin is inactivated in rat paws by ACE and AmP. In collagenase-oedema, the pro-inflammatory effects of bradykinin are concealed by the effects of the other mediators.

Topics: Albumins; Analysis of Variance; Angiotensin-Converting Enzyme Inhibitors; Animals; Bradykinin; Capillary Permeability; Capsaicin; Captopril; Collagenases; Dose-Response Relationship, Drug; Edema; Glycopeptides; Hindlimb; Indoles; Inflammation; Isoindoles; Male; Matrix Metalloproteinase Inhibitors; Methysergide; Neurokinin-1 Receptor Antagonists; Oligopeptides; Organ Size; Protease Inhibitors; Rats; Rats, Wistar; Serotonin Antagonists; Substance P

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

The role of tachykinins released from sensory nerves in bronchoconstriction induced by antigen was studied in sensitized guinea pigs anesthetized with pentobarbital sodium and pretreated with atropine. The combination of NK2 (SR-48968) and NK1 (CP-96,345) tachykinin-receptor antagonists abolished the increase in total pulmonary resistance (RL) evoked by intravenous capsaicin but did not affect the response evoked by intravenous histamine. A small dose of aerosolized ovalbumin (OVA, 0.1%) produced a small increase in RL that was further increased and markedly prolonged by the neutral endopeptidase (NEP) inhibitor phosphoramidon; this bronchoconstrictor effect of OVA was markedly reduced by the NK2-receptor antagonist and was abolished by the combination of the NK1 and NK2-receptor antagonists together. When a larger dose of OVA (0.5%) was used, a maximal bronchoconstrictor response was obtained. Phosphoramidon did not potentiate this response significantly. The combination of NK1- and NK2-receptor antagonists blunted the response at 5 min only slightly but markedly attenuated the later (10-20 min) response. These results show that tachykinins released from sensory nerves play a significant role in antigen-induced bronchoconstriction in guinea pigs. This effect is exaggerated when the normal modulation of neuropeptides by NEP is inhibited and is mediated predominantly by NK2-receptor activation, with a smaller contribution by NK1 receptors.

Topics: Aerosols; Animals; Atropine; Benzamides; Biphenyl Compounds; Bronchoconstriction; Capsaicin; Glycopeptides; Guinea Pigs; Histamine; Immunization; Inflammation; Lung; Male; Neurokinin-1 Receptor Antagonists; Ovalbumin; Piperidines; Pulmonary Circulation; Receptors, Neurokinin-2; Vascular Resistance

The purpose of this study was to examine whether neutral endopeptidase and angiotensin I-converting enzyme, two membrane-bound metalloenzymes that are widely distributed in the microcirculation, play a role in bradykinin-induced increase in vascular permeability in the hamster cheek pouch. Changes in vascular permeability were quantified by counting the number of leaky sites and by calculating the clearance of fluorescein isothiocyanate (FITC)-dextran (molecular mass, 70,000 d) during suffusion of the cheek pouch with bradykinin. Bradykinin produced a concentration- and time-dependent increase in the number of leaky sites and clearance of FITC-dextran. The selective, active site-directed neutral endopeptidase inhibitors phosphoramidon (1.0 microM) and thiorphan (10.0 microM) and the selective angiotensin I-converting enzyme inhibitor captopril (10.0 microM) each shifted the concentration-response curve to bradykinin significantly to the left. During suffusion with bradykinin (1.0 microM) and phosphoramidon, the number of leaky sites increased significantly from 17 +/- 2 to 27 +/- 4 sites per 0.11 cm2 (mean +/- SEM, p less than 0.05), and FITC-dextran clearance increased significantly from 1.0 +/- 0.2 to 2.1 +/- 0.3 ml/sex x 10(-6).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Bradykinin; Capillary Permeability; Captopril; Cheek; Cricetinae; Glycopeptides; Inflammation; Microcirculation; Neprilysin; Peptidyl-Dipeptidase A; Thiorphan

In this study, we examined whether inhalation of hypertonic saline aerosols increases vascular permeability in the rat trachea, and we examined the role of neurogenic inflammation in this response. Stereological point counting was performed to measure the percent area occupied by Monastral blue-labeled blood vessels as a means of quantifying the increase in vascular permeability in tracheal whole mounts. Hypertonic saline aerosols (3.6-14.4% NaCl) increased vascular permeability in a dose-dependent fashion compared with 0.9% NaCl. Thus, the area density of Monastral blue-labeled vessels after inhalation of 3.6% NaCl was greater (21.2 +/- 3.5% mean +/- SEM, n = 5) than after 0.9% NaCl aerosol (3.3 +/- 0.9%, n = 5, P less than 0.5). The neutral endopeptidase inhibitor phosphoramidon (2.5 mg/kg, i.v.) significantly potentiated the increase of vascular permeability caused by 3.6% NaCl. Desensitization of sensory nerve endings by pretreatment with capsaicin markedly reduced the usual increase in vascular permeability caused by 3.6% NaCl, but the increase in vascular permeability induced by aerosolized substance P (10(-4) M) was unchanged. These findings suggest that hypertonic saline increases vascular permeability in the rat trachea by stimulating the release of neuropeptides from sensory nerves.

Topics: Animals; Capillary Permeability; Capsaicin; Dose-Response Relationship, Drug; Glycopeptides; In Vitro Techniques; Inflammation; Male; Neurons, Afferent; Neuropeptides; Rats; Rats, Inbred F344; Saline Solution, Hypertonic; Substance P; Trachea

The goal of this study was to determine whether neutrophils that adhere to the vascular endothelium in association with neurogenic inflammation in the respiratory tract migrate out of the blood vessels or whether they detach and reenter the circulation. We also sought to determine whether the fate of the neutrophils is influenced by neutral endopeptidase (NEP), an enzyme that degrades the tachykinins that produce neurogenic inflammation. Neutrophils in the tracheal mucosa of anesthetized pathogen-free rats were examined 5 min or 4 h after neurogenic inflammation was produced by an injection of capsaicin (100 or 200 micrograms/kg iv). In whole mounts of these tracheae stained histochemically for myeloperoxidase, adherent intravascular neutrophils had a spherical or teardrop (regular) shape and migrating neutrophils had a polarized amoeboid (irregular) shape. The number of regular neutrophils in the tracheae was increased at both times, but the increase at 4 h was only half that present at 5 min. The reduction between 5 min and 4 h was not offset by an appreciable increase in the number of irregular neutrophils, unless NEP was inhibited by phosphoramidon. We interpret these results as indicating that the rapid adherence of neutrophils to the vascular endothelium after an injection of capsaicin is followed by a gradual reentry of the neutrophils into the circulation and comparatively little neutrophil migration. However, when the effect of the stimulus is increased and/or prolonged by inhibition of NEP, some of the adherent neutrophils migrate out of the vessels. Thus the activity of NEP can regulate both the magnitude of the neutrophil adherence and the fate of the adherent cells.

Topics: Analysis of Variance; Animals; Capsaicin; Cell Adhesion; Chemotaxis, Leukocyte; Female; Glycopeptides; Inflammation; Muscle, Smooth; Neutrophils; Peroxidase; Rats; Regression Analysis; Trachea; Vagus Nerve; Venules