Substance P-induced Bronchoconstriction Research Articles

Modulation of substance P-induced bronchoconstriction by lipoxygenase metabolites

In anaesthetized, mechanically ventilated guinea-pigs, substance P induces a bronchoconstrictor response comprising increases in airway resistance and decreases in dynamic compliance. Eicosatetraynoic acid (ETYA, 20 mg kg-1 i.v.) or BW755c (20 mg kg-1 i.v.) potentiated the substance P-induced bronchoconstriction. Neither indomethacin (1 or 5 mg kg-1 i.v.) nor aspirin (20 mg kg-1 i.v.) significantly altered the potency of substance P on bronchomotor responses. These observations are consistent with the existence of a bronchodilator lipoxygenase metabolite(s).

The role of substance P and bradykinin in the cough reflex and bronchoconstriction in guinea-pigs

In this study we investigated the ability of aerosolized substance P to induce either cough or bronchoconstriction in guinea-pigs. We have also examined whether pre-treatment, by the inhaled route, of animals with a combination of the neutral endopeptidase inhibitor, phosphoramidon (10 −3 M), and the diaminopeptidase IV inhibitor, diprotin A (10 −3 M), enhances the airway response to substance P. Moreover, we also assessed whether aerosol pre-treatment of guinea-pigs with either substance P or bradykinin, at 10 −4 M, affects the citric acid-induced cough and/or bronchoconstriction. Challenge of guinea-pigs with substance P only at 10 −3 M resulted in significant bronchconstriction but only a weak and variable cough response (1.1±0.6; P>0.05). Pre-treatment of guinea-pigs with both phosphoramidon and diprotin A resulted in a small non-significant increase in the cough response (2.8±0.9 vs. 1.1±0.6; P>0.05) but significantly enhanced substance P-induced bronchoconstriction ( P<0.05). Moreover, exposure of guinea-pigs to substance P (10 −4 M) prior to citric acid challenge (0.6M) resulted in a significant ( P<0.05) enhancement of the citric acid-induced bronchoconstriction but not the citric acid-induced cough (11.7±1.8 vs. 12.8±1.5; P>0.05). In contrast, exposure of guinea-pigs to bradykinin (10 −4 M) prior to the citric acid challenge resulted in a significant enhancement of the cough response (9.2±1.9 vs. 25.8±2.5; P<0.05) but not the bronchoconstriction ( P>0.05). These data do not support a major peripheral role for substance P in the cough reflex, although bradykinin is able to sensitize the cough reflex. Furthermore, these data suggest that bronchoconstriction, induced by citric acid, is not responsible for the cough associated with this irritant.

Pharmacology of the peptidomimetic, MEN 11149, a new potent, selective and orally effective tachykinin NK 1 receptor antagonist

In this study we investigated the pharmacological properties of MEN 11149, 2-(2-naphthyl)-1- N-{(1 R,2 S)-2- N-[1(H)indol-3-ylcarbonyl]aminocyclohexanecarbonyl}-1-[ N′-methyl- N′-(4-methylphenylacetyl)]diaminoethane, a novel partially retro-inverse pseudo peptide antagonist of tachykinin NK 1 receptors. MEN 11149 potently inhibits the binding of [ 3 H ]substance P to tachykinin NK 1 sites in IM9 cells (p K i=8.5±0.1). The compound is highly specific for the human tachykinin NK 1 receptors, since it has negligible effects (p K i<6) on the binding of specific ligands to tachykinin NK 2, NK 3 receptors and a battery of central and peripheral receptors or ion channels. The tachykinin NK 1 receptor antagonism of MEN 11149 appears to be insurmountable since, in saturation binding experiments, both K D and B max are significantly affected by incubation with the compound (1–30 nM). In isolated guinea-pig ileum, MEN 11149 (0.1–100 nM) shifts to the right in a non-parallel way the substance P methyl ester-induced cumulative concentration–response curve with progressive inhibition of the maximal response (p K B=9.6±0.1). When tested for reversibility at 5 nM in the same preparation, the compound displays a slow dissociation rate compared to the fast dissociation rate with FK888 ( N 2-[(4 R)-4-hydroxy-1-(1-methyl-1H-indol-3-yl)carbonyl- l-prolyl]- N-methyl- N-phenylmethyl- l-3-(2-naphthyl)alaninamide) at 5 nM. In the same preparation, MEN 11149 (10 μM) did not affect the cumulative concentration–response curve to acetylcholine. In vivo, MEN 11149 dose dependently antagonizes [Sar 9,Met(O 2) 11]substance P-induced bronchoconstriction in anaesthetized guinea-pigs (ID 50=83±31 nmol/kg i.v.). The duration of the effect exceeds 3 h. MEN 11149 does not affect the bronchoconstriction induced by neurokinin A. The compound dose dependently inhibits [Sar 9,Met(O 2) 11]substance P-induced plasma protein extravasation in guinea-pig bronchi whether administered intravenously (ID 50=0.22±0.02 μmol/kg) or orally (ID 50=0.97±0.21 μmol/kg). These results demonstrate that MEN 11149 is a potent, highly selective and orally effective insurmountable antagonist of tachykinin NK 1 receptors with a long duration of action.

Effectiveness of levodropropizine against cigarette smoke-induced airway hyperreactivity: possible mechanism

We verified the possible effect of the new antitussive drug levodropropizine on airway hyperreactivity and lung inflammation induced by cigarette smoke exposure in anaesthetized guinea-pigs. Levodropropizine, administered by aerosol at 25 mg/ml for 30 s completely prevented smoke induced airway hyperreactivity. The protective effect was early in onset (3 min) and lasted up to 30 min. The same dose of codeine, administered in the form of an aerosol, decreased the increase in airway responsiveness induced by smoke inhalation slightly but not significantly. In parallel with the functional results, levodropropizine also inhibited the recruitment of inflammatory cells triggered by smoke exposure within the airway lumen. When levodropropizine was administered i.v. to anaesthetized guinea-pigs, it reduced the bronchocontractile effect of capsaicin dose-dependently, whereas it was without effect against substance P-induced bronchoconstriction. These data demonstrate the ability of levodropropizine to counteract the hyperreactive phenomenon and the associated inflammatory event induced by cigarette smoke exposure, an effect which might depend on its capacity to modulate the activation of the peptidergic system.

Pharmacology of Idrapril

Idrapril is the prototype of a new chemical class of angiotensin converting enzyme (ACE) inhibitors, the hydroxamic non-amino acid derivatives. Idrapril strongly inhibited rat and human plasma ACE and rabbit lung ACE (IC50: 7-12 nM) as well as the pressor response induced by angiotensin I in anesthetized rats (ED50: 63 nmol/kg i.v.). Idrapril (0.04-23 mumol/kg i.v.) lowered the blood pressure dose dependently, up to 20-35%, in different models of hypertension (sodium-depleted spontaneously hypertensive rat, two-kidney-one-clip renal hypertensive rat, and aortic-coarctated rat), its profile being similar to that of captopril in terms of potency and efficacy. Idrapril and captopril reduced the blood pressure and potentiated substance P-induced bronchoconstriction in the guinea pig to the same extent, suggesting a similar degree of ACE inhibition in the circulation. However, idrapril potentiated capsaicin-induced bronchoconstriction (a model that has been related to the liability of ACE inhibitors to produce cough in patients) less effectively than captopril. We conclude that effective ACE inhibition in vitro and in vivo can be obtained with this novel class of compounds.

Effects of neuraminidase on airway reactivity in the guinea pig.

We investigated the effects of neuraminidase, a viral enzyme that cleaves alpha ketosidic cell-bound sialic acids, to see if it accounts for parainfluenza and influenza virus-induced airway hyperreactivity. Accordingly, Vibrio cholerae neuraminidase was administered intratracheally in guinea pigs, and airway reactivity was assessed 3 h later. Removal of sialic acid residues was evaluated by histologic studies. Airway responsiveness was determined in anesthetized, tracheotomized, and mechanically ventilated guinea pigs by exposing them to increasing concentrations of aerosolized bronchoconstrictor agents. Respiratory system conductance was measured by the occlusion method. Neuraminidase injected intratracheally did not change airway reactivity to 10(-4) to 10(-2) M acetylcholine or 10(-4) to 2.5 x 10(-3) M histamine; nor did it prevent aerosolized albuterol from inhibiting histamine-induced bronchoconstriction. Substance P (10(-6) to 5 x 10(-5) M) had no significant bronchoconstrictor effect on guinea pigs pretreated with saline or neuraminidase. In guinea pigs pretreated with aerosols of the neutral endopeptidase inhibitor phosphoramidon (10(-4) M) before the concentration curve to aerosolized substance P was recorded, neuraminidase significantly reduced substance P-induced bronchoconstriction. When bronchoconstriction was induced by the 4-11 fragment of substance P (10(-5) to 10(-2) M), which is devoid of positive charges, it did not differ significantly in guinea pigs pretreated with saline and those pretreated with neuraminidase. These results indicate that in the guinea pig, neuraminidase injected intratracheally does not induce non-specific airway hyperreactivity and may alter the binding of substance P to its receptors.

Sensory nerves in the airways as a target for drug development.

1. Electrical stimulation (2.5-10 Hz, 80 V, 1 ms for 15 s) within the spinal canal of the pithed guinea-pig pretreated with atropine, D-tubocurarine and pentolinium caused a bronchoconstrictor response, indicated by a rise of insufflation pressure. 2. The magnitude of these non-cholinergic neuronal bronchoconstrictor responses were frequency-dependent, capsaicin-sensitive and temperature-dependent. 3. Responses could be inhibited by the alpha 2-adrenoceptor agonist B-HT920 (3 mg/kg, i.v.) and the mu-opioid agonist H-Tyr-D-Arg-Phe-Lys-NH2 (DALDA; 1 mg/kg, i.v.) and the attenuation observed could be overcome by use of the respective antagonists idazoxan (3 mg/kg, i.v.) and naloxone (3 mg/kg, i.v.). 4. Substance P-induced bronchoconstriction (0.3 micrograms/kg, i.v.), but not that due to electrical stimulation, was attenuated by indomethacin (3 mg/kg, i.v.), indicating an indirect action of substance P via a product of arachidonic acid metabolism. 5. The prostanoid product of the substance P response was probably thromboxane A2. 6. Hence, novel drug development could be directed towards tachykinin receptors or to the synthesis, release and degradation of neuropeptides.

Substance P-induced Bronchoconstriction in the Guinea Pig: Enhancement by Inhibitors of Neutral Metalloendopeptidase and Angiotensin-converting Enzyme

We tested the effects of the neutral metalloendopeptidase (NEP) inhibitor, thiorphan (0.17, 0.5, and 1.7 mg i.v), and the angiotensin-converting enzyme (ACE) inhibitor, captopril (0.5, 1.7, and 5.0 mg i.v.), on the bronchoconstrictor response to rapid intravenous infusions of substance P (0.1 to 30 nmol/kg) in anesthetized, mechanically ventilated guinea pigs. The decreases in pulmonary conductance and dynamic compliance caused by substance P were greater in animals treated with either thiorphan or captopril than in control animals. Thiorphan (0.5 mg) had no effect on airway responsiveness to intravenously administered methacholine, whereas captopril (1.7 mg) caused a small increase in methacholine responsiveness. Both drugs significantly increased the recovery of immunoreactive substance P in arterial plasma after exogenous administration of the peptide. We conclude that degradation of substance P by both NEP and ACE is important for determining the magnitude of the bronchoconstriction caused by intravenous administration of this neuropeptide. These data suggest that conditions associated with diminished peptidase activity could result in enhanced responses to stimuli which cause the release of endogenous substance P.

CHARACTERIZATION OF SUBSTANCE P‐INDUCED BRONCHOCONSTRICTION IN THE GUINEA‐PIG: A COMPARISON WITH ACETYLCHOLINE

Substance P (0.5-8.0 micrograms/kg, i.v.) induced bronchoconstriction in anaesthetized, mechanically-ventilated guinea-pigs, comprising increases in airways resistance and decreases in dynamic compliance. These bronchoconstrictor responses were unaffected by bilateral vagotomy, pretreatment with pheniramine (2 mg/kg, i.v.) or by pretreatment with atropine (100 micrograms/kg, i.v.). Acetylcholine-induced (4-32 micrograms/kg, i.v.) bronchoconstriction was prevented by atropine pretreatment, whereas bilateral vagotomy inhibited responses to acetylcholine. Ganglionic blockade using hexamethonium (20 mg/kg, i.v.) potentiated both substance P and acetylcholine on airways resistance and dynamic compliance. Indomethacin (1 or 5 mg/kg, i.v.) did not affect substance P-induced bronchoconstriction, whereas the higher dose enhanced acetylcholine-induced increases in airways resistance. In addition, aspirin pretreatment (20 mg/kg, i.v.) did not alter the bronchoconstrictor potency for either substance P or acetylcholine. On the other hand, the combined cyclo-oxygenase/lipoxygenase inhibitors eicosatetraynoic acid (ETYA, 20 mg/kg, i.v.) and BW755C (20 mg/kg, i.v.) potentiated both acetylcholine and substance P on airways resistance and dynamic compliance. The results suggest that substance P-induced bronchoconstriction may be modulated by the sympathetic nervous system and does not appear to be influenced by vagal or histaminergic mechanisms. The failure of indomethacin or aspirin to affect substance P-induced bronchoconstriction, together with the enhancing effects of ETYA and BW755C pretreatments, provide evidence consistent with the existence of a bronchodilator mechanism which may be inhibited by compounds inhibiting lipoxygenase enzymes.

Mechanism of substance P-induced bronchoconstriction in maturing rabbit.

The maturational effects of substance P (SP) on airway function were quantitatively assessed in 30 anesthetized tracheotomized rabbits ranging in age from 2 to 29 days. Following paralysis, during mechanical ventilation with 100% O2 in a body plethysmograph, respiratory resistance (Rrs) and dynamic compliance (Cdyn) were continuously monitored. Noncumulative systemic infusions of SP (0.001-5.0 micrograms/g) produced dose-dependent decreases in pulmonary conductance (Grs), i.e., 1/Rrs, and Cdyn. The dose of SP producing a 50% decrease in Cdyn (PD50-Cdyn) significantly increased as a function of age indicating a diminution in airway sensitivity to SP. Bilateral cervical vagotomy and ganglionic blockade with hexamethonium had no effect on the airway response to SP. On the other hand, the response was significantly reduced following atropine sulfate infusion (2 mg/kg), suggesting a peripheral cholinergic contribution located distal to the airway parasympathetic ganglia. The magnitude of this cholinergic contribution increased as a function of age. Unlike atropine, antagonists to histamine and 5-hydroxytryptamine had no effect on the airway response to SP, however, the response was inhibited following infusion of the SP antagonist, D-Pro2,D-Trp7,9-SP. These findings indicate that the airway response to SP is age-related and mediated by binding of the agonist to airway smooth muscle coupled with an accelerated release of acetylcholine at the airway neuromuscular junction.