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K F Rabe

Publications and source records attributed to K F Rabe.

125 records · Page 7Linked to original sources
PubMed1994

Suppression of human eosinophil respiratory burst and cyclic AMP hydrolysis by inhibitors of type IV phosphodiesterase: interaction with the beta adrenoceptor agonist albuterol.

The cyclic AMP phosphodiesterase (PDE) III/IV inhibitor, zardaverine, and the PDE IV-selective inhibitor, rolipram, both caused concentration-dependent inhibition of opsonized zymosan-stimulated superoxide anion generation by purified human peripheral blood eosinophils with approximate IC50 values of 30 and 40 microM, respectively. In contrast, the selective PDE III inhibitor, SK&F 94120, was ineffective in suppressing this functional response at concentrations below 100 microM. The inhibitory effects of rolipram and zardaverine on superoxide anion generation were increased in the presence of the beta-2 adrenoceptor agonist, albuterol, which itself was an inhibitor of eosinophil respiratory burst (IC50 = 20 microM). The effects of albuterol and the PDE inhibitors in combination were simply additive. Paradoxically, both rolipram and zardaverine significantly potentiated albuterol-induced cyclic AMP accumulation in a synergic fashion. Cyclic AMP PDE activity of eosinophil homogenates was inhibited by both zardaverine (IC50 = 515 nM) and rolipram (IC50 = 550 nM) as well as two other PDE IV-selective inhibitors, Ro 20-1724 (IC50 = 3.0 microM) and denbufylline (IC50 = 360 nM), whereas SK&F 94120 was ineffective. These data suggest that cyclic AMP levels in human eosinophils are regulated by the action of a type IV PDE isoenzyme and that elevation of the intracellular cyclic AMP concentration by PDE IV inhibition can suppress the functional activity of these cells. However, the suppressor effect of the PDE IV inhibitors appears to be independent of that of a beta-2 adrenoceptor agonist, implying a possible adenylyl cyclase-independent mechanism of action for beta agonists in eosinophils.

Adolescent↗
PubMed1993

[Diagnosis of bronchopulmonary aspergillosis is often made too late].

ABPA may occur in patients with longstanding bronchial asthma. The most important diagnostic criteria include a history of asthma with peripheral blood eosinophilia, immediate skin reactivity, elevated serum IgE, precipitating antibodies against Aspergillus species, migrating infiltrates, and central bronchiectases. Here we report on the clinical characteristics in 15 patients in whom the diagnosis of ABPA could be established. Mean diagnostic latency between the occurrence of first symptoms and the diagnosis was 10 +/- 10 years. We therefore conclude that the diagnosis and therapy of ABPA is often delayed.

Adult↗
PubMed1993

Salmeterol is a competitive antagonist at beta-adrenoceptors mediating inhibition of respiratory burst in guinea-pig eosinophils.

The ability of the long-acting beta-adrenoceptor agonists eformoterol and salmeterol to inhibit leukotriene (LT) B4 (100 nM; approximately EC70)-induced hydrogen peroxide (H2O2) generation by guinea-pig peritoneal eosinophils was investigated and compared with salbutamol. Eformoterol and salbutamol produced a concentration-dependent inhibition of LTB4-induced H2O2 generation with pIC50 values of 6.22 and > 5.0 respectively. The inhibitory effect eformoterol was mediated through an interaction with beta-adrenoceptors for it was antagonised by propranolol with an affinity (7.21) that was independent of antagonist concentration (100 nM and 1 microM). In contrast, salmeterol (1 nM to 10 microM) failed to inhibit H2O2 generation at any concentration examined irrespective of the pre-incubation time (0, 0.25, 0.5, 1, 2, 15 or 30 min). Salmeterol did, however, competitively antagonise (slope of Schild plot = 0.91) the inhibition of H2O2 generation induced by eformoterol with a pA2 of 5.9. Possible explanations for the lack of inhibitory effect of salmeterol on LTB4-induced respiratory burst are advanced and critically discussed.

Adrenergic beta-Agonists↗
PubMed1993

The effect of 10, 50 and 200 micrograms inhaled fenoterol on exercise induced asthma.

In a randomized, double-blind cross-over study we investigated the protective effect of low doses of fenoterol on the airway response to exercise during cold air breathing. In 12 mild to moderate asthmatics with exercise induced asthma (mean age: 26 [range 19-25] years), mean FEV1 87% of predicted, exercise challenges were performed under control conditions and 30 min after the inhalation from a metered dose inhaler of either placebo, or 10, 50, and 200 micrograms fenoterol within a 4 week period. Airway response was determined by measuring specific airway resistance, sRaw. Standardization of exercise challenges was achieved by individually maintaining a constant respiratory heat exchange, with an average (range) of 1.24 (0.98-1.61) kcal/min. Fenoterol aerosol was an effective bronchodilator at all doses administered (P < 0.05), with 200 micrograms significantly more effective than 10 micrograms. Mean sRaw (s.e.m.) pre vs maximal post exercise after control conditions, placebo and 10, 50, and 200 micrograms fenoterol aerosol was 12.9 (1.4) vs 41.8 (6.3), 13.1 (1.6) vs 41.3 (6.3), 9.6 (1.5) vs 26.6 (6.2), 7.9 (0.9) vs 16.4 (3.6) and 5.5 (0.5) vs 7.4 (0.9) cmH2O.s. The protective effect of fenoterol against exercise induced bronchoconstriction was dose-dependent and was significantly different from placebo at 50 and 200 micrograms (P < 0.05). From these observations we suggest that in mild to moderate asthmatics 50 micrograms of fenoterol in a dose which is sufficient to protect against this naturally occurring stimulus.

Administration, Inhalation↗
PubMed1993

Effects of beta-adrenoceptor agonists in human bronchial smooth muscle.

1. We have investigated the potency and duration of action of isoprenaline and a range of beta-adrenoceptor agonists as relaxants of inherent tone in human superfused, isolated bronchial smooth muscle, a tissue reported to contain a homogeneous population of beta 2-adrenoceptors. 2. All of the beta-adrenoceptor agonists caused concentration-related inhibition of inherent tone, with isoprenaline having an EC50 of 27 nM. The rank order of agonist potency was: formoterol > or = -salmeterol > or = clenbuterol > fenoterol = isoprenaline > terbutaline > or = salbutamol > quinprenaline. 3. Relaxant responses to salmeterol were fully reversed by the selective beta 2-adrenoceptor blocking drug, ICI 118551, demonstrating the involvement of beta 2-adrenoceptors. 4. Rt50, i.e. the time taken for 50% recovery from the effects of an EC50 concentration of agonist, differed considerably between the different beta 2-adrenoceptor agonists. Most agonists were short-acting, having Rt50 values less than 13 min. Quinprenaline was of moderate duration, with an Rt50 value of > or = 20 min. In contrast, salmeterol was extremely long-acting, with no sign of recovery within 4 h. 5. Estimates of relative potency and duration of action were similar to those previously determined for these agonists in the guinea-pig isolated trachea. These results suggest, therefore, that guinea-pig trachea is a suitable alternative to human bronchus for the evaluation of the actions of beta-adrenoceptor agonists on airways smooth muscle.

Adrenergic beta-Agonists↗
PubMed1993

Phosphodiesterase isozymes modulating inherent tone in human airways: identification and characterization.

The effects of the nonselective phosphodiesterase (PDE)-inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the selective PDE inhibitors SKF 94120 (type III), rolipram (type IV), zardaverine (type III/IV), and zaprinast (type V) on inherent tone in human airways were investigated. Substantial relaxation was achieved by IBMX [concentration eliciting 50% of maximum response (EC50): 2.9 microM, n = 14] and SKF 94120 (EC50: 1.4 microM, n = 15); rolipram and zaprinast were almost ineffective. Zardaverine (EC50: 0.31 microM, n = 8), and the combination of SKF 94120 and rolipram (1 microM; EC50: 0.41 microM) were effective relaxants. Biochemical studies revealed the presence of PDE isozymes I, III, IV, and V in the cytosolic and particulate phase of airway homogenates, whereas PDE II was present only in the cytosol. Partial inhibition of total PDE adenosine 3',5'-cyclic monophosphate-hydrolyzing activity was achieved with rolipram and a selective type III inhibitor, whereas there was almost complete inhibition of total PDE activity with either zardaverine or the combination of type III and IV inhibitors. We conclude that all five PDE isozyme families are present in crude preparations of human peripheral airways. Inherent tone in this tissue is most effectively relaxed through selective type III/IV PDE inhibitors.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Beta 2-adrenoceptor agonists inhibit NANC neural bronchoconstrictor responses in vitro.

Nonadrenergic noncholinergic (NANC) contractile responses in guinea pig bronchi are due to the release of tachykinins from airway sensory nerves. The purpose of this study was to determine whether beta 2-receptor agonists modulate NANC contractions in guinea pig bronchi in vitro. Bronchial rings were suspended in organ baths for isometric measurement of tension, and comparable contractions were induced by electrical field stimulation (EFS; 40 V, 0.5 ms, 8 Hz for 20 s) or by exogenous substance P (3 microM). Aformoterol and salbutamol produced concentration-dependent inhibition of the NANC contraction, with aformoterol being ninefold more potent than salbutamol; approximate 50% inhibitory concentrations for aformoterol and salbutamol were 1.03 nM (n = 6) and 9.3 nM (n = 6), respectively. Aformoterol also inhibited the contraction induced by exogenous substance P but to a far lesser extent than its inhibition of EFS-induced responses. The inhibitory effects of formoterol (10 nM) on responses to EFS at 8 Hz were significantly prevented by propranolol (1 microM) and ICI 118551 (a beta 2-antagonist, 0.1 microM) but not by atenolol (a beta 1-antagonist, 1 microM) or phentolamine (10 microM). These experiments demonstrate that beta 2-agonists may modulate the release of tachykinins from airway sensory nerves by prejunctional receptors.

Adrenergic beta-Agonists↗
PubMed1993

Comparison of the effects of salmeterol and formoterol on airway tone and responsiveness over 24 hours in bronchial asthma.

The recent development of new beta 2-adrenoceptor agonists with a duration of action in excess of 12 h may change strategies in the treatment of bronchial asthma. This study aims at the direct comparison of the main representatives of this new class of drugs, formoterol (F) and salmeterol (S), in asthmatic patients over the course of 24 h. Twelve patients with mild bronchial asthma participated in a double-blind, randomized, placebo-controlled clinical trial. In a dose-finding study we determined the protective and bronchodilating effects of 12 and 24 micrograms F aerosol vs 50 and 100 micrograms S 30 min after inhalation. In a 24-h study we investigated the effects of 12 micrograms F and 50 micrograms S on airway tone and responsiveness. Bronchial responsiveness was assessed as the dose of methacholine necessary to decrease FEV1 by 20%. In the dose-finding study, compared with placebo, all doses of F and S equally increased FEV1 (p < 0.003) and protected against inhaled methacholine (p < 0.0001). In the 24-h study 12 micrograms F and 50 micrograms S increased FEV1 and significantly protected against methacholine-induced bronchoconstriction up to 24 h (p < 0.05), compared with placebo. Phase and amplitude of the circadian variation of FEV1 and airway responsiveness were not affected. Clinically recommended doses of aerosolized F (12 micrograms) and S (50 micrograms) have a duration of action up to 24 h and are equally effective at bronchodilation and protection in acute experiments in patients with mild bronchial asthma.

Administration, Inhalation↗
PubMed1993

Increased LTB4 metabolites and PGD2 in BAL fluid after methacholine challenge in asthmatic subjects.

The bronchoconstrictor potency of inhaled methacholine is widely used to assess airway responsiveness. However, evidence has accumulated that methacholine inhalation challenge may lead to an inflammatory response in the lower respiratory tract. We therefore compared cellular, leukotriene and prostanoid profiles in bronchoalveolar lavages (BAL) obtained five hours after methacholine challenge to control lavages without prior challenge. Eight subjects with asymptomatic to mild bronchial asthma and nine nonatopic healthy controls were enrolled in the study. Without prior challenge, the percentage of BAL eosinophils was higher in the asthmatic subjects ((mean +/- SD), 1.1 +/- 0.9%) than in the control subjects (0.1 +/- 0.1%. Leukotriene B4 (LTB4), and its omega-oxidation products (20-OH-LTB4 and 20-COOH-LTB4) were the only leukotrienes detectable in the baseline BAL fluids in five of the eight asthmatic patients. After methacholine challenge, no change in BAL cell profile occurred, but in the asthmatic patients, the total amounts of LTB4 and its omega-oxidation products rose from 0.52 +/- 0.50 ng.ml-1 (pre-challenge) to 1.55 +/- 1.32 ng.ml-1 (post-challenge), and prostaglandin D2 (PGD2) rose from 49.1 +/- 15.7 (pre-challenge) to 94.4 +/- 25.4 pg.ml-1 (post-challenge), with no change in 6-keto-PGF1 alpha, thromboxane B2 (TXB2), and prostaglandins F2 alpha and E2 (PGF2 alpha and PGE2). In the healthy controls, no consistent change in BAL cell profile and mediators occurred after methacholine provocation. We conclude that inhaled methacholine stimulates LTB4 and PGD2 release in asthmatics, but not in healthy controls, without affecting the number of inflammatory cells in BAL fluid.

Adult↗
PubMed1992

Salmeterol protects against hyperventilation-induced bronchoconstriction over 12 hours.

To study the dose-response relationship of salmeterol for protection against a naturally occurring stimulus, isocapnic hyperventilation tests of cold air were done in 16 asthmatic patients. The subjects inhaled either 50 micrograms salmeterol, salbutamol 200 micrograms, or placebo in a double-blind, randomised, cross-over study. The FEV1 was measured prior to medication and the provocative ventilation (PV20) required to induce a 20% fall in FEV1 was calculated by linear interpolation from ventilation-response curves obtained 0.5, 4, 8, and 12 h after medication. Following salbutamol, the mean FEV1 were 4.11, 3.89, 3.58, and 3.55 l, with a significant difference from placebo up to 4 h. Following salmeterol, mean FEV1 values were 3.95, 4.10, 3.93, and 3.88 l, with a significant difference from placebo up to 12 h. The mean PV20FEV1 after salbutamol was 78.8, 58.5, 52.7, and 48.4 l.min-1, the 0.5 h value being significantly different from placebo. After salmeterol, the mean PV20FEV1 values were 84.6, 82.5, 67.8, and 65.8 l.min-1, with a significant difference from placebo up to 12 h. We conclude that, besides its long-lasting bronchodilating effect, salmeterol protects against hyperventilation-induced bronchoconstriction for at least 12 h.

Adult↗
PubMed1992

The protective effect of low-dose inhaled fenoterol against methacholine and exercise-induced bronchoconstriction in asthma: a dose-response study.

We compared in a randomized, double-blind study the protective effect of low doses of fenoterol on the airway response to exercise during cold air breathing and an inhalation challenge with methacholine. In six asymptomatic asthmatic persons (mean age, 20.3 years) exercise and methacholine challenges were performed under control conditions and 15 minutes after the inhalation from a metered-dose inhaler of either placebo or 30, 50, 100, and 200 micrograms fenoterol, resulting in 12 separate study sessions within a 3-week period. Airway response was determined by measuring specific airway resistance (sRaw). Exercise tests were standardized by maintaining a constant respiratory heat exchange, with an average (range) of 1.28 (1.15 to 1.45) kcal/min. Methacholine was inhaled at increasing doses until sRaw had doubled (PD100sRaw). Mean postexertional increase of sRaw (SD) after control conditions, placebo, and 30, 50, 100, and 200 micrograms fenoterol aerosol was 27.8 (6.9), 28.9 (10.0), 7.20 (2.7), 9.33 (3.8), 5.57 (2.3), and 5.28 (1.6) cm H2O.s. Fenoterol aerosol was equally effective at all doses administered, whereas methacholine-induced bronchoconstriction was attenuated in a dose-dependent manner. From these observations we suggest that low-dose fenoterol protects against bronchoconstriction induced by exercise, a naturally occurring stimulus reflecting airway hyperresponsiveness.

Adolescent↗
PubMed1992

Low dose fenoterol aerosol protects against histamine-induced bronchoconstriction in mild asthmatics: a dose response study.

Sixteen subjects with mild stable asthma participated in a randomized double blind study on the effects of low dose fenoterol against histamine induced bronchoconstriction. Fenoterol aerosol at concentrations of 10, 50 and 200 micrograms and placebo were delivered at random through a metered dose inhaler as a single dose 30 min before histamine challenges on four separate occasions. Compared to placebo a fenoterol dose of 10 micrograms provided significant bronchodilatation (sRaw [s.d.] 8.3 [2.73] vs 6.3 [1.74] cm H2O* s [P less than 0.05]) and protection (PC100 sRaw [s.e.m.] 0.72 (1.31) vs 1.45 (1.39) mg/ml). The bronchodilatory and protective actions of fenoterol were more pronounced after the inhalation of 200 micrograms (P less than 0.05) with no difference between 10 and 50 micrograms fenoterol aerosol. The magnitude of bronchodilatation and protection was not correlated (r = 0.15). The results from this acute study may suggest that fenoterol at doses up to 20 times lower than routinely recommended may be an effective treatment in mild asthmatics.

Adult↗
PubMed1992

Activation of guinea pig eosinophil respiratory burst by leukotriene B4: role of protein kinase C.

Leukotriene B4 (LTB4) and the protein kinase C activator, 4-beta-phorbol dibutyrate (PDBu), both induced a pronounced and concentration-dependent stimulation of hydrogen peroxide (H2O2) generation by purified guinea pig peritoneal eosinophils in the concentration range 1 nM-1 microM. The LTB4 response was inhibited competitively by the specific LTB4 receptor antagonist, U-75302, with a KB of 25 nM, while the concentration-response curves for both stimuli were shifted rightwards (3.8-fold and 2.8-fold for LTB4 and PDBu, respectively) by the competitive protein kinase C inhibitor, 1-O-hexadecyl-2-O-methylglycerol at a concentration of 300 microM. LTB4 appears, therefore, to induce respiratory burst in eosinophils via a receptor-mediated mechanism involving protein kinase C.

Animals↗
PubMed1991

Eosinophils adhere to and stimulate replication of lung fibroblasts 'in vitro'.

Eosinophils have been implicated in several disorders associated with the development of fibrosis. This led us to investigate the interactions between eosinophils and fibroblasts in vitro. Adhesion between purified guinea pig peritoneal eosinophils and monolayers of human fetal lung fibroblasts was assessed using the rose bengal dye staining assay. Fibroblast replication was assessed using a colorimetric assay based upon the uptake and subsequent release of methylene blue. Addition of phorbol myristate acetate induced a rapid, time-dependent increase in eosinophil adhesion (127% and 328% over basal adhesion after 10 and 30 min, respectively). Phorbol myristate acetate-induced adhesion was inhibited by the peptides RGDS and GRGDS (48% and 42%, respectively using 1 mM peptide) and by nordihydroguaiaretic acid, an inhibitor of the lipoxygenase pathway of arachidonic acid metabolism (46% inhibition at 15 microM). In addition, 24 h culture of fibroblast monolayers with interleukin 1 alpha (IL-1 alpha) or tumour necrosis factor alpha (TNF alpha) resulted in enhanced adhesion (10 U/ml IL-1 alpha stimulated adhesion by 55% of control, 500 U/ml TNF alpha by 75% of control). Conditioned media from cultured eosinophils stimulated fibroblast replication in a time-dependent fashion with maximal stimulation at 3 h. In contrast, media from guinea pig peritoneal macrophages in culture did not show such an effect. This study indicates that eosinophils are capable of both adhering to and releasing mitogens for fibroblasts in vitro. These observations suggest that eosinophils have the capacity to play a role in the development of fibrosis in disorders where they have been shown to be present.

Amino Acid Sequence↗
PubMed1991

Inhibition of eosinophil cyclic nucleotide PDE activity and opsonised zymosan-stimulated respiratory burst by 'type IV'-selective PDE inhibitors.

1. The cyclic nucleotide phosphodiesterase (PDE) of guinea-pig eosinophils was partially characterized and the effects of selective inhibitors of PDE isoenzymes upon opsonized zymosan (OZ)-stimulated respiratory burst were studied. 2. PDE activity in eosinophil lysates appeared to be membrane-associated, displayed substrate specificity for adenosine 3':5' cyclic monophosphate (cyclic AMP) versus guanosine 3':5' cyclic monophosphate (cyclic GMP) and was insensitive to cyclic GMP or Ca2+ and calmodulin. 3. The non-selective PDE inhibitor, 3-isobutyl-1-methylxanthine caused a concentration-dependent inhibition of both OZ-stimulated hydrogen peroxide (H2O2) generation and cyclic AMP hydrolysis. The type IV-selective PDE inhibitors, rolipram and denbufylline, also inhibited H2O2 generation and cyclic AMP hydrolysis in a concentration-dependent manner whilst SK&F 94120 and Org 9935 (type III-selective) and zaprinast (type Ia or V-selective) were ineffective. 4. Dibutyryl cyclic AMP, a cell-permeable, non-hydrolysable analogue of cyclic AMP, caused a concentration-dependent inhibition of H2O2 generation stimulated by OZ. Dibutyryl cyclic GMP was ineffective. 5. It is concluded that eosinophil respiratory burst activity induced by OZ can be regulated by intracellular cyclic AMP and that the levels of cyclic AMP are controlled exclusively by a rolipram- and denbufylline-sensitive PDE isoenzyme that resembles a type IV species.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗