Pseudomonas aeruginosa induces vascular endothelial growth factor synthesis in airway epithelium in vitro and in vivo.

Pseudomonas aeruginosa (PA) airway infection and bronchial blood vessel proliferation are features of bronchiectasis. Because vascular endothelial growth factor (VEGF)-A regulates angiogenesis, we hypothesised that PA infection induces VEGF synthesis in epithelium and peribronchial angiogenesis. Because epidermal growth factor receptor (EGFR) activation regulates VEGF synthesis in cancer, we also evaluated the roles of EGFR. Airway epithelial cells were incubated for 24 h with PA supernatants and VEGF concentrations were measured in culture medium by ELISA. C57BL/6N mice were instilled intratracheally with sterile agarose beads or with agarose beads coated with the PA strain PAO1 (mean ± sem 6 × 10(5) ± 3 × 10(5) cfu · animal(-1)), with or without the EGFR inhibitor AG1478 (12.5 mg · kg(-1) · day(-1) intraperitoneally). Epithelial immunostaining for VEGF and phosphorylated EGFR, and peribronchial vascularity, were quantified using morphometric analysis. VEGF expression was further assessed by western blot in mouse lung homogenates. PA supernatants induced dose-dependent VEGF synthesis in cultured airway epithelial cells, effects which were prevented by EGFR antagonists. In mice, persistent PAO1 infection increased immunostaining for VEGF and phosphorylated EGFR in airway epithelium, and resulted in increased peribronchial vascularity within 7 days. These effects were reduced by EGFR inhibition. Persistent PA infection induced VEGF synthesis in airway epithelium and peribronchial angiogenesis, at least in part via EGFR-dependent mechanisms.

Reduced exhaled NO is related to impaired nasal potential difference in patients with cystic fibrosis.

Nitric oxide (NO) plays a central role in many airway physiological functions, and its production appears to be related with progression of lung disease in patients with cystic fibrosis (CF). However, underlying mechanisms which specifically link NO and CF-related lung disease remain unclear. Following in vitro and animal studies suggesting a role for NO in ion transport in various epithelia, this work investigates the relationship between transepithelial baseline potential difference (BPD), an index of airway ion transport, and exhaled NO in the airways of adult patients with CF. Association with other phenotypic traits, lung function tests and CFTR genotype was also assessed. Using simple linear regression, F(E)NO and transepithelial BPD values were significantly inversely correlated (p<0.001, r=-0.53). Polynomial analysis evidenced an asymptotic relationship between F(E)NO and BPD values, yielding a plateau for absolute BPD values above 50 mV. This relation was not altered by adjustment for clinical and genetic characteristics of the patients. The relationship between exhaled NO and transepithelial BPD suggests that low NO concentrations likely worsens airway ion transport impairment resulting from CFTR defect. These results fit with experimental studies that suggest the inhibitory effect of NO on sodium absorption, which is the main determinant of airway basal transepithelial conductance.

Nasal airway ion transport is linked to the cystic fibrosis phenotype in adult patients.

BACKGROUND: This study was conducted to determine whether the major nasal airway ion transport abnormalities in cystic fibrosis (that is, defective cAMP regulated chloride secretion and basal sodium hyperabsorption) are related to the clinical expression of cystic fibrosis and/or to the genotype. METHODS: Nasal potential difference was measured in 79 adult patients with cystic fibrosis for whom clinical status, respiratory function, and CFTR genotype were determined. RESULTS: In univariate and multivariate analysis, patients with pancreatic insufficiency were more likely to have low responses to low chloride (odds ratio (OR) 8.6 (95% CI 1.3 to 58.5), p = 0.03) and isoproterenol (OR 11.2 (95% CI 1.3 to 93.9), p = 0.03) solutions. Similarly, in univariate and multivariate analysis, patients with poor respiratory function (forced expiratory volume in 1 second <50% of predicted value) were more likely to have an enhanced response to amiloride solution (OR 3.7 (95% CI 1.3 to 11.0), p = 0.02). However, there was no significant relationship between nasal potential difference and the severity of the genotype. CONCLUSIONS: Nasal epithelial ion transport in cystic fibrosis is linked to the clinical expression of the disease. The pancreatic status appears to be mostly related to the defect in epithelial chloride secretion whereas the respiratory status is mostly related to abnormal sodium transport and the regulatory function of the CFTR protein.

Nitric oxide synthase 1 as a potential modifier gene of decline in lung function in patients with cystic fibrosis.

BACKGROUND: The severity of lung disease varies widely in patients with cystic fibrosis (CF) who have the same type of mutations of the cystic fibrosis transmembrane regulator (CFTR) gene, suggesting involvement of "modifier" genes. The nitric oxide synthase 1 (NOS1) gene is a candidate for this role because exhaled nitric oxide (NO) is reduced in patients with CF and NOS1 activity contributes to transepithelial ionic transport, immune defence, and non-specific inflammation of the airways. METHODS: Dinucleotide GT repeat polymorphism was studied in the 5' untranslated region of the NOS1 gene, immediately upstream from the transcription initiation site, in 59 patients with CF and 59 healthy controls. RESULTS: Nineteen alleles of the NOS1 gene were identified according to the number of GT repeats (from 18 to 36) in the 5 untranslated region. Exhaled NO levels were significantly correlated with the number of GT repeats. Patients with CF who had the NOS1 genotype associated with high NO production had a slower decline in lung function during the 5 year follow up period. There was no confounding effect of age, chronic bacterial colonisation of the airway, or CFTR genotype. CONCLUSIONS: These data suggest a possible link between the NOS1 gene locus and the rate of decline in lung function in patients with CF.

Decreased expression of angiotensin-converting enzyme in the airway epithelium of asthmatic subjects is associated with eosinophil inflammation.

BACKGROUND: Angiotensin-converting enzyme (ACE) is a peptidase involved in the metabolism of several bioactive peptides. It may be involved in the airway inflammation and hyperresponsiveness that occur in asthma. OBJECTIVE: We studied the expression of ACE in the airway mucosa of normal and asthmatic subjects and assessed the relationship between ACE expression and airway inflammation and bronchial hyperresponsiveness in asthma. METHODS: We used immunohistochemistry to study the ACE expression and airway inflammation in bronchial biopsy samples obtained by fiberoptic bronchoscopy from 20 asthmatic subjects randomly assigned to groups treated with (n = 10) or without inhaled corticosteroids (n = 10) and from normal subjects (n = 10). Airway response to methacholine and bradykinin was also determined for all subjects. RESULTS: In normal subjects ACE was present in the surface epithelium, the endothelial cells of the lamina propria, and the submucosal glands, in which ACE was found in seromucous cells and in secreted mucus. ACE was not detected in smooth muscle cells and in most of the endothelial cells of the vascular network surrounding the glands. ACE was absent or present at lower levels in the surface epithelium of asthmatic subjects not treated with corticosteroids compared with those treated with corticosteroids and the control group. In asthmatic subjects low levels of ACE in the epithelium were associated with larger numbers of eosinophils in the epithelium and lamina propria. There was no relationship between ACE levels in the airway mucosa and airway responsiveness to methacholine and bradykinin. CONCLUSION: ACE expression is decreased in the epithelium of asthmatic patients and is associated with increased eosinophil inflammation.

Increased frequency of cystic fibrosis deltaF508 mutation in bronchiectasis associated with rheumatoid arthritis.

This study investigated the clinical characteristics and the possible involvement of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in patients with symptomatic diffuse bronchiectasis (DB) associated with rheumatoid arthritis (RA). Twenty-six patients with both RA and DB (group RA+DB) and control groups of 29 consecutive patients with RA but no bronchiectasis (group RA) and 29 patients with symptomatic DB of unknown origin (group DB) were prospectively studied. Among the patients of the RA+DB group, four (15.4%) were heterozygous for the CFTR gene deltaF508 mutation, whereas no deltaF508 mutation was found in patients of the RA and the DB groups (both, p<0.05). This frequency of deltaF508 mutation was also higher than the expected frequency (2.8%) in the general European population (p<0.04). Sweat chloride values and nasal potential differences were normal in three out of four patients carrying the deltaF508 mutation. In the RA+DB group, those with deltaF508 mutation had more frequent chronic sinusitis (p<0.05), a trend toward a more severe pulmonary involvement, and a lower value of nasal potential differences (p<0.01) whereas their rheumatic features had no particularity. In the RA+DB group, patients with adult-onset bronchiectasis (including two with deltaF508 mutation) had a greater reduction in total lung capacity (p<0.05) and lower nasal potential differences (p<0.005) than those with childhood-onset bronchiectasis. This study suggests a possible deleterious effect of the cystic fibrosis transmembrane conductance regulator mutated protein in the airways which may predispose to the development and severity of bronchiectasis in patients suffering from rheumatoid arthritis.

Relationships between nasal potential difference and respiratory function in adults with cystic fibrosis.

This study investigated the relations between nasal transepithelial electric potential difference (PD) and the phenotype and genotype of cystic fibrosis (CF) adult patients. Basal nasal PD was measured in 95 adult CF patients who were classified into three groups of nasal PD (expressed as absolute values) according to the 10th and the 90th percentiles (28.3 and 49.2 mV, respectively), which defined group 1 (nasal PD < or =28.3 mV), group 2 (nasal PD 28.3-49.2 mV) and group 3 (nasal PD > or =49.2 mV). Patients from group 1 had a higher forced vital capacity (FVC) than patients from groups 2 and 3 (76.5+/-22.4 versus 57.4+/-21.2 and 55.7+/-21.1% predicted, respectively, p<0.05) and a higher forced expiratory volume in one second (FEV1) (69.3+/-24.0 versus 42.5+/-22.4 and 42.2+/-21.4% pred, respectively, p<0.01). Among patients with severe mutations (deltaF508 homozygotes, or one deltaF508 mutation plus another "severe" mutation, or two "severe" mutations), patients from group 1 had a higher FVC, FEV1 and arterial oxygen tension than patients from groups 2 and 3 (p<0.05 for each comparison). The results show that in adult cystic fibrosis patients a normal basal nasal potential difference is related to milder respiratory disease, irrespective of the severity of the genotype.

Silver/silver chloride electrodes for measurement of potential difference in human bronchi.

BACKGROUND: An easy and reliable method to measure potential difference (PD) in the lower airways would be of interest in the field of cystic fibrosis. We have developed silver/silver chloride (Ag/AgCl) electrodes to measure PD in the lower airways. METHODS: To validate this technique the nasal PD measured with Ag/AgCl electrodes and with conventional perfused electrodes was compared in 16 patients. The range of PD measured with Ag/AgCl electrodes in the lower airways during fibreoptic bronchoscopy was determined in 14 adult patients and in nine the reproducibility of this technique was examined. RESULTS: Nasal PD values measured with Ag/AgCl and perfused electrodes were highly correlated (r = 0.985, p < 0.0001) and the limits of agreement (mean +/- 2SD of the difference) between the two methods were -1.91 mV and 1.53 mV. In the lower airways a progressive and slight decrease in PD values with decreasing airway diameter was observed in most patients. The mean (2SD) of the differences between the two tracheal measurements was 0.21 (1.73) mV. CONCLUSIONS: The use of Ag/AgCl electrodes gives a reliable and reproducible measurement of PD in the lower airways in humans.

Bronchial gamma delta T-lymphocytes and expression of heat shock proteins in mild asthma.

Heat shock proteins (HSPs), which are important targets for gammadelta T-lymphocytes, are thought to play a role in inflammatory and immune diseases. The purpose of this study was to characterize, in asthma, the presence and distribution of alphabeta and gammadelta T-lymphocytes and of hsp60, hsp70 and hsp90 in bronchial biopsies, and to seek for a co-localization of gammadelta T-cells and HSPs. Ten subjects with mild atopic asthma and nine control subjects underwent fibreoptic bronchoscopy and bronchial biopsies, to which specific monoclonal antibodies and immunohistochemical techniques were applied. T-lymphocytes present in bronchi both of asthmatic and control subjects were predominantly of the alphabeta T-cell receptor phenotype (median 642 cells x mm(-2) (range 85-1,510 cells x mm(-2)), and 855 cells x mm(-2) (286-2,424 cells x mm(-2)), respectively), whereas, gammadelta T-lymphocytes were always rare (median 26 cells x mm(-2) (range 0-114 cells x mm(-2)), and 0 cells x mm(-2 (0-57 cells x mm(-2), respectively). Both in asthmatic and control subjects, bronchial epithelium was positive for hsp60, hsp70 and hsp90. There was no significant difference in the percentages of positive epithelial cells between asthmatic and control subjects. No co-localization of HSPs and gammadelta T-cells was observed. Our findings do not support the hypothesis that heat shock proteins and gammadelta T-cells play an important role in inflammatory and immune responses in mild asthma.

Genotype-phenotype relationships in a cohort of adult cystic fibrosis patients.

In cystic fibrosis (CF), relationships between genotype and phenotype have been shown for pancreatic status but not for pulmonary disease. One hundred and ten adult CF patients were classified according to the expected effect of their mutations on cystic fibrosis transmembrane conductance regulator (CFTR) protein: Group 1 (n=48) included deltaF508 homozygotes; Group 2 (n=26), patients with two "severe" mutations and no expected CFTR production; Group 3 (n=17), patients with expected partly functional CFTR corresponding to at least one "mild" mutation; Group 4 (n=19), patients with no mutation identified or only one identified "severe" mutation. As compared to Groups 1 and 2: patients from Groups 3 and 4 had higher arterial oxygen tension (Pa,O2) (9.5+/-1.9 and 9.9+/-1.5 vs 8.8+/-1.5 and 8.3+/-1.7 kPa, respectively p<0.02); and a slower decline in their pulmonary function, estimated by the mean annual loss in forced vital capacity (FVC) (1.2+/-1.0 and 1.5+/-1.1 vs 2.0+/-0.9 and 2.2+/-1.0%, respectively; p<0.01) and in forced expiratory volume in one second (FEV1) (1.7+/-1.1 and 1.9+/-1.3 vs 2.6+/-1.0 and 2.8+/-1.0%, respectively; p<0.005). They had fewer episodes of colonization of the airways by Pseudomonas aeruginosa, and colonization occurred at a more advanced age (median age 25 and 19 vs 15 and 17 yrs, respectively; p<0.01) and required fewer intravenous antibiotic courses (p<0.01). Pancreatic insufficiency was less frequent in Groups 3 (23%) and 4 (63%) than in Groups 1 (100%) and 2 (96%). This study suggests that the phenotype of adult cystic fibrosis patients, including the severity of the lung disease, is related to the severity of the cystic fibrosis transmembrane conductance regulator mutations.

Airway responsiveness to bradykinin is related to eosinophilic inflammation in asthma.

We investigated the relationship between airway inflammation and airway responsiveness, as assessed by PD15, to methacholine and to bradykinin in asthmatic patients. Bronchoalveolar lavage (BAL), bronchial biopsies, and methacholine and bradykinin challenges were performed in 18 nonsmoking subjects with mild or moderate perennial asthma. Bradykinin PD15 correlated negatively with eosinophil count in BAL (p < 0.05), in the epithelium (p < 0.05), in the lamina propria (p = 0.02) and in the total submucosa (p < 0.01). Conversely, no significant correlation existed between airway responsiveness to methacholine and eosinophil count in BAL or in airway mucosa. Airway responsiveness to either agonist did not correlate with the thickness of the basement membrane, the shedding of the airway epithelium, the count of lymphocytes in the airway mucosa, or the percentage of neutrophils, lymphocytes, and macrophage in BAL. The presence of degranulated eosinophils was associated with an increased number of eosinophils in the airway epithelium (p = 0.04), in the lamina propria (p = 0.03), in the total submucosa (p = 0.02), and with increased airway responsiveness to bradykinin (p < 0.02). We conclude that in asthmatic patients, airway responsiveness to bradykinin but not to methacholine is related to the magnitude of eosinophilic inflammation in the airway mucosa.

Perception of bronchial obstruction in asthmatic patients. Relationship with bronchial eosinophilic inflammation and epithelial damage and effect of corticosteroid treatment.

We studied the perception of bronchoconstriction in asthmatic subjects who were randomly treated with inhaled beta 2 agonist given either alone (n = 9) or associated with inhaled corticosteroids (n = 9). Methacholine and bradykinin challenges, bronchoalveolar lavage, and bronchial biopsies were performed in all subjects. After each dose of agonist, breathlessness was assessed using a visual analog scale (VAS) and the forced expiratory volume in 1 s (FEV1) was measured. The relationship between VAS scores and FEV1 and the slope of the regression line of VAS scores on the corresponding FEV1 (VAS/FEV1 slope) were analyzed for each agonist. Subjects without corticosteroids had good perception of methacholine but poor perception of bradykinin-induced bronchoconstriction. In subjects with corticosteroids, bronchoconstriction was well perceived whatever the agonist. VAS/FEV1 slopes for bradykinin but not for methacholine correlated negatively with the magnitude of eosinophilic inflammation in airway mucosa. VAS/FEV1 slopes for each agonist correlated positively with the percentage of basement membrane covered by airway epithelium. We conclude that in asthmatic patients perception of bronchoconstriction is related to eosinophilic inflammation and to epithelial damage in airways and that corticosteroid treatment is associated with improved perception of bronchoconstriction induced by bradykinin, a mediator endogenously produced in asthma.

Nasal response to capsaicin in patients with allergic rhinitis and in healthy volunteers: effect of colchicine.

We studied the effect of nasal administration of capsaicin in eight patients with allergic rhinitis and eight healthy subjects. We also studied the effect of colchicine, a drug known to inhibit microtubular axonal transport of peptides, on nasal response to capsaicin in these subjects. Colchicine or placebo was administered orally in a double-blind, randomized, crossover manner with a 35 day wash-out interval. Nasal challenge was performed on the last day of each period of treatment, using increasing doses of capsaicin (10(-9) to 3 x 10(-5) mmol). Capsaicin induced a dose-dependent decrease in nasal airflow conductance (active posterior rhinomanometry) (p < 0.002) that was greater in patients with allergic rhinitis (0.40 +/- 0.02 to 0.20 +/- 0.03) than in healthy subjects (0.44 +/- 0.01 to 0.35 +/- 0.02) (p = 0.0001). Capsaicin provoked a greater number of sneezes in patients with allergic rhinitis than in healthy subjects (p < 0.001), but the amount of nasal secretions was similar in these two groups of subjects. In nasal lavage fluid, capsaicin induced an increase in total, epithelial, and neutrophil cell counts in patients with allergic rhinitis (each comparison, p < 0.05), but not in healthy subjects. Capsaicin induced a slight, although not significant, increase in the concentration of elastase in nasal lavage fluid in patients with allergic rhinitis (p = 0.07), but not in healthy subjects. Albumin concentration decreased in nasal lavage fluid in both groups of subjects (p < 0.05). The tendency of capsaicin to increase neutrophil elastase in nasal lavage fluid of patients with allergic rhinitis was not observed after treatment with colchicine.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrogen peroxide inhibits lung neutral endopeptidase.

Oxidants have been implicated in the pathogenesis of many inflammatory airway diseases. Neutral endopeptidase (also called enkephalinase, EC 3.4.24.11) is a peptidase that is involved in the degradation of several proinflammatory peptides, such as tachykinins and kinins. Indirect evidence suggests that airway neutral endopeptidase is inactivated by oxidants. To determine whether hydrogen peroxide inactivates neutral endopeptidase, we studied the activity of this peptidase in washed crude preparations of membranes from guinea pig lungs. Washed crude membrane preparations were exposed to increasing concentrations of hydrogen peroxide (1.25-25 mM) in the presence or absence of two different concentrations of catalase (300 and 700 U/mL). Neutral endopeptidase activity was inhibited by hydrogen peroxide in a concentration-dependent fashion (p = .0001). Addition of catalase prevented, in a concentration-dependent fashion, the inhibition of neutral endopeptidase induced by hydrogen peroxide (p = .0001). Mannitol (40 mM) and L-methionine (20 mM) did not prevent inhibition of neutral endopeptidase induced by hydrogen peroxide (2.5 mM). It can be concluded that neutral endopeptidase is inactivated by hydrogen peroxide, an effect that is prevented by catalase. Hydrogen peroxide-induced inactivation of neutral endopeptidase is not mediated by spontaneous generation of either hydroxyl radical or hypochlorous acid in the membrane preparation. Our results suggest that neutral endopeptidase inactivation may occur in airway diseases associated with exposure to or production of oxidants.

Nedocromil sodium reduces cigarette smoke-induced bronchoconstrictor hyperresponsiveness to substance P in the guinea-pig.

Acute exposure to cigarette smoke provokes airway hyperresponsiveness to substance P and inactivates neutral endopeptidase (NEP). To determine whether nedocromil sodium can prevent cigarette smoke-induced hyperresponsiveness to substance P, we studied two groups of anaesthetized guinea-pigs. One group of guinea-pigs was pretreated with aerosolized 0.9% NaCl solution (90 breaths), the other group was pretreated with aerosolized nedocromil sodium (10(-4) M, 90 breaths). In each animal, pretreatment was followed by either exposure to the smoke of one cigarette or exposure to air. After acute exposure to cigarette smoke or to air, we measured the change in total pulmonary resistance (RL) induced by increasing concentrations of aerosolized substance P. In the absence of nedocromil sodium, the bronchoconstrictor responses to substance P were greater in cigarette smoke-exposed guinea-pigs than in air-exposed animals. Aerosolized nedocromil sodium had no effect on the response to substance P in air-exposed animals, but it reduced cigarette smoke-induced hyperresponsiveness to substance P. The preventive effect on cigarette smoke-induced hyperresponsiveness to substance P was observed at concentrations of aerosolized nedocromil sodium of 3 x 10(-5), 10(-4), and 3 x 10(-4) M. In vitro, cigarette smoke solution inhibited NEP activity from lung membrane preparations, but this inhibitory effect was not modified by nedocromil sodium (10(-4) M). We conclude that aerosolized nedocromil sodium reduces cigarette smoke-induced airway hyperresponsiveness to substance P in vivo. This action of nedocromil sodium is not due to a protective effect on cigarette smoke-induced inactivation of NEP in vitro.

Role of neutral endopeptidase and kininase II on substance P-induced increase in nasal obstruction in patients with allergic rhinitis.

We studied the role of neutral endopeptidase (NEP) and kininase II (angiotensin-converting enzyme; ACE) in the modulation of exogenous substance P (SP)-induced nasal response in normal subjects and in patients with allergic rhinitis. We measured the nasal conductance in response to increasing doses of SP 2 h after oral administration of either placebo or the ACE inhibitor, cilazapril (5 mg), or the NEP inhibitor, acetorphan (300 mg), given in a randomized, double-blind, cross-over manner. We performed three separate studies: acetorphan versus placebo and cilazapril versus placebo, in normal subjects (n = 6 and n = 8, respectively), and acetorphan versus cilazapril versus placebo in patients with allergic rhinitis (n = 6). In normal as well as in rhinitic subjects, SP decreased nasal conductance in a dose-dependent fashion (p < 0.001). With placebo, the decrease in nasal conductance in normal subjects was similar to that in patients with allergic rhinitis (p > 0.5). In normal subjects, acetorphan potentiated the decrease in nasal conductance (p < 0.001), whereas cilazapril did not (p = 0.12). In patients with allergic rhinitis, the decrease in nasal conductance was potentiated by acetorphan (p < 0.001) and by cilazapril (p < 0.001). With acetorphan, the decrease in nasal conductance was not different in patients with allergic rhinitis and in normal subjects (p > 0.9). Conversely, with cilazapril, the nasal response to SP was greater in patients with allergic rhinitis than in normal subjects (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Carboxypeptidase M-like enzyme modulates the noncholinergic bronchoconstrictor response in guinea pig.

We studied the effects of aerosolized DL-2-mercaptomethyl-3-guanidino-ethylthiopropanoic acid (MGTA) (10(-4) M, 90 breaths), a specific inhibitor of carboxypeptidase B-type enzymes, on changes in total pulmonary resistance (RL) induced by aerosolized capsaicin (10(-7) to 10(-4) M; 10 breaths at each concentration) and vagus nerve stimulation (5 V, 5 ms, for 20 s at frequencies varying from 2 to 10 Hz) in anesthetized, atropinized, and ventilated guinea pigs. We also studied the effect of aerosolized MGTA on the bronchoconstrictor response to either aerosolized substance P, neurokinin A (10(-7) to 10(-4) M; 10 breaths at each concentration), and carbachol (10(-5) to 2 x 10(-4) M; 10 breaths at each concentration) or to i.v. administration of neurokinin A (10(-11) to 10(-8) mol/kg), bradykinin (10(-10) to 10(-7) mol/kg), and histamine (10(-8) to 10(-6) mol/kg). Although aerosolized MGTA caused no change in basal RL (P > 0.5), it did potentiate the noncholinergic bronchoconstrictor response to capsaicin (n = 5; P < 0.001) as well as to vagus nerve stimulation (n = 5; P = 0.001). In contrast, MGTA did not potentiate the bronchoconstrictor response to either aerosolized substance P, neurokinin A, and carbachol or to i.v. administration of neurokinin A, histamine, and bradykinin. Carboxypeptidase activity cleaving C-terminal arginine or lysine was found in the membrane preparations of trachea and lung from guinea pigs. The membrane-bound carboxypeptidase activity was maximal at pH 7.0 and was enhanced by the presence of CoCl2 (1 mM) in both the tracheal and lung tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Tachykinins increase respiratory clearance of 99mTc-DTPA. Mechanisms of action.

We investigated the effects of tachykinins on the respiratory clearance of 99mTc-DTPA (RC-DTPA) in anesthetized and ventilated guinea pigs. We measured the change in RC-DTPA and in maximal pulmonary insufflation pressure (PIPmax) induced by substance P, neurokinin A, and capsaicin. Substance P, neurokinin A, and capsaicin increased both PIPmax and RC-DTPA in a concentration-dependent fashion. Substance-P- and capsaicin-induced increases in RC-DTPA were unaffected by pretreatment with atropine. Bilateral vagotomy attenuated substance-P-induced change in both RC-DTPA and PIPmax by approximately 70 and 50%, respectively. Capsaicin-induced change in RC-DTPA and PIPmax were slightly but not significantly reduced by bilateral vagotomy. The bronchodilator, salbutamol, dramatically reduced increase in RC-DTPA and in PIPmax induced by substance P, neurokinin A, and capsaicin, but it had no effect on increases in RC-DTPA and PIPmax generated by application of a positive end-expiratory pressure. We conclude that (1) tachykinins increase respiratory clearance to the solute, and (2) tachykinin-induced increase in RC-DTPA is not mediated by cholinergic neurotransmission but rather by the bronchoconstrictor effect of neuropeptides.