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Biomedical subjects

R Polosa

Publications and source records attributed to R Polosa.

At least 73 records · Page 4Linked to original sources
PubMed1994

Effect of inhaled frusemide on responses of airways to bradykinin and adenosine 5'-monophosphate in asthma.

BACKGROUND: Inhaled frusemide exerts a protective effect against bronchoconstriction induced by several indirect stimuli in asthma. This effect could be caused by interference with neural pathways. The effect of inhaled frusemide on bronchoconstriction induced by inhaled bradykinin, which is thought to cause bronchoconstriction via neural mechanisms, was studied and compared with the effects of adenosine 5'-monophosphate (AMP) which probably produces its airway effects by augmenting mast cell mediator release and interfering with neural pathways. METHODS: Patients first underwent AMP and bradykinin challenges. They were then studied in a randomised, placebo controlled, double blind fashion. Ten atopic asthmatic subjects, studied on four days, were pretreated with inhaled frusemide (40 mg) or placebo for 10 minutes, five minutes before challenge with increasing concentrations of nebulised AMP or bradykinin. RESULTS: On the open visit days the provocative concentrations required to reduce forced expiratory volume in one second (FEV1) by 20% from baseline (PC20) for AMP and bradykinin were 16.23 (1.42-67.16) and 2.75 (0.81-6.6) mg/ml. There was a significant correlation between baseline AMP and bradykinin PC20 values. For AMP the geometric mean PC20 values following pretreatment with inhaled frusemide and matched placebo were 80.97 (9.97- > 400.0) and 14.86 (2.6-104.6) mg/ml respectively (95% CI 0.49 to 0.98). For bradykinin the geometric mean PC20 values following pretreatment with inhaled frusemide and matched placebo were 13.22 (2.53- > 16.0) and 2.52 (0.45-5.61) mg/ml respectively (95% CI 0.43 to 1.01). Frusemide afforded 5.45 and 5.24 fold protection against AMP and bradykinin-induced bronchoconstriction respectively. Furthermore, there was a significant correlation between protection afforded to the airways against AMP and bradykinin. CONCLUSIONS: These data suggest that inhaled frusemide affords protection against bradykinin-induced bronchoconstriction which is comparable to that against AMP, supporting a common mechanism of action for frusemide.

Adenosine Monophosphate↗
PubMed1994

Bronchial biopsy evidence for leukocyte infiltration and upregulation of leukocyte-endothelial cell adhesion molecules 6 hours after local allergen challenge of sensitized asthmatic airways.

We have examined the mucosal changes occurring in bronchial biopsies from six atopic asthmatics 5-6 h after local endobronchial allergen challenge and compared them with biopsies from saline-challenged segments from the same subjects at the same time point. All the subjects developed localized bronchoconstriction in the allergen-challenged segment and had a decrease in forced expiratory volume in 1 s (FEV1) (P < 0.01) and a decrease in their methacholine provocative concentration of agonist required to reduce FEV1 from baseline by 20% (P < 0.05) 24 h postchallenge. At 6 h we observed an increase in neutrophils (P = 0.03), eosinophils (P = 0.025), mast cells (P = 0.03), and CD3+ lymphocytes (P = 0.025), but not in CD4+ or CD8+ lymphocyte counts. We also detected an increase in endothelial intercellular adhesion molecule type 1 (P < 0.05) and E-selectin (P < 0.005), but not vascular cell adhesion molecule type 1 expression with a correlative increase in submucosal and epithelial LFA+ leucocytes (P < 0.01). Thus, in sensitized asthmatics, local endobronchial allergen instillation leads to an increased inflammatory cell infiltrate of the airway mucosa that involves upregulation of specific adhesion molecules expressed on the microvasculature.

Adult↗
PubMed1994

Effect of inhaled bradykinin on indices of airway responsiveness in asthmatic subjects.

Asthma is characterized by airway hyperresponsiveness, a physiopathological abnormality which may result from the complex interplay between inflammatory cells and proinflammatory mediators. Although kinins are thought to play a role in the pathogenesis of bronchial asthma, it is not known whether bradykinin is able to induce airway hyperresponsiveness. We have, therefore, investigated the effect of inhaled bradykinin on the changes in airway calibre and in airway hyperresponsiveness to histamine, in a double-blind, randomized study of nine asthmatic subjects. Subjects were studied on two study periods, separated by at least 15 days. On the first day of each study period, subjects inhaled either a single dose of bradykinin or methacholine (placebo) with changes in airway calibre being followed as forced expiratory volume in one second (FEV1) and as the maximum expiratory flow rate measured at 70% of the vital capacity below total lung capacity (TLC) from a partial forced expiratory manoeuvre (Vp30) at 3, 5, 10, 15, 30, 45 and 60 min, and then every hour for 7 h. Airway responsiveness to histamine, expressed as the provocative concentrations producing a 20% fall in FEV1 and 40% fall in Vp30 (PC20FEV1 and PC40Vp30), was measured at 3 and 7 h after inhaling the agonists, then on days 1, 3, 7 and 14. Inhalation of bradykinin caused rapid bronchoconstriction that peaked at 3-5 min. When compared to placebo, no significant difference in histamine responsiveness was seen after bradykinin in terms of changes in PC20FEV1 values.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1993

Skin responses to bradykinin, kallidin, and [desArg9]-bradykinin in nonatopic and atopic volunteers.

BACKGROUND: Kinins are potent vasoactive oligopeptides that may act as mediators in a variety of inflammatory diseases of the skin by interacting with specific receptors designated B1 and B2. In this study we have investigated the structure-activity relationship of intradermally injected bradykinin, kallidin (lysine-bradykinin), and [desArg9]-bradykinin in atopic (n = 8) and nonatopic (n = 8) subjects. METHODS: On two separate occasions, each separated by a week, subjects randomly underwent intradermal challenge with incremental doses (0.5, 5, and 50 nmol) of either the B1-agonist [desArg9]-bradykinin, the B2-agonists bradykinin or kallidin, or vehicle placebo. In a separate randomized double-blind study we have also examined the effect of an orally administered antihistamine, terfenadine, on kinin-induced wheal and flare responses and their repeatability in a group of nine volunteers. The skin responses were monitored objectively by measurement of wheal and flare areas. RESULTS: Both bradykinin and kallidin induced a dose-dependent increase in wheal and flare areas in all subjects studied. Although the effects of the two lowest doses (0.5 and 5 nmol) of [desArg9]-bradykinin on skin responses were indistinguishable from those of placebo, this kinin at the highest dose administered (50 nmol) caused a significant increase in wheal and flare areas in all subjects studied. No difference could be identified in the skin responses to kinins between atopic and nonatopic subjects. In addition kinin-induced cutaneous responses were not altered by pretreatment with terfenadine. CONCLUSIONS: These in vivo structure activity studies suggest that in human beings the skin responses to kinins may be compatible with the stimulation of B2 receptors, which is unrelated to histamine release from cutaneous mast cells.

Adult↗
PubMed1993

Relative potencies and time course of changes in adenosine 5'-monophosphate airway responsiveness with inhaled furosemide and bumetanide in asthma.

A randomized, double-blind, placebo-controlled study was conducted to compare the effects of two chemically unrelated "loop" diuretics, furosemide (40 mg) and bumetanide (2 mg) on the bronchoconstrictor response to inhaled adenosine 5'-monophosphate (AMP) in 12 subjects with asthma. In eight additional volunteers with asthma, we also carried out a separate randomized, double-blind study to examine in more detail the time course of change in bronchial reactivity to inhaled AMP after administration of nebulized furosemide and bumetanide. Inhaled loop diuretics significantly increased the provocative concentration of AMP causing a 20% fall in forced expiratory volume in 1 second (FEV1) from the value of 21.2 mg/ml (range, 2.5 to 96.9 mg/ml) after placebo administration to 83.4 mg/ml (range, 11.3 to 345.0 mg/ml) (p < 0.01) and 33.8 mg/ml (range, 4.7 to 120.9 mg/ml) (p < 0.05) after administration of furosemide and bumetanide, respectively. After placebo administration, the provocative concentration of AMP causing a 20% fall in FEV1 (PC20 AMP) at 10, 30, and 120 minutes did not differ significantly; their geometric mean (range) values were 57.8 mg/ml (10.9 to 341.0 mg/ml), 55.0 mg/ml (13.2 to 304.1 mg/ml), and 52.8 mg/ml (14.4 to 252.2 mg/ml), respectively. When compared with placebo, inhaled furosemide significantly reduced the airway responsiveness to AMP at all time points; the PC20 AMP values at 10, 30, and 120 minutes were 154.6 mg/ml (29.4 to 658.7 mg/ml) (p < 0.01), 142.6 mg/ml (25.5 to 639.9 mg/ml) (p < 0.01), and 103.9 mg/ml (12.5 to 605.5 mg/ml) (p < 0.05), respectively. The PC20 values for AMP after pretreatment with bumetanide were significantly increased up to 110.2 mg/ml (25.9 to 639.0 mg/ml) (p < 0.01) and to 92.0 mg/ml (21.6 to 531.7 mg/ml) (p < 0.05) at 10 and 30 minutes, respectively. At 120 minutes, inhaled bumetanide failed to affect AMP airway responsiveness; the PC20 AMP was not significantly different from that of placebo, with a value of 71.5 mg/ml (22.6 to 318.0 mg/ml). We conclude that comparable equidiuretic doses of furosemide and bumetanide are effective in attenuating the airway response to AMP, with furosemide being approximately 2.5 times more potent than bumetanide (p < 0.01). The time course of change in bronchial reactivity to AMP is similar for both drugs with a peak effect at 10 minutes. It is possible that the mechanism(s) underlying the protective effects of inhaled loop diuretics in asthma may be distinct from those responsible for their diuretic properties.

Adenosine Monophosphate↗
PubMed1993

Comparative nasal effects of bradykinin and histamine: influence on nasal airways resistance and plasma protein exudation.

BACKGROUND: Bradykinin may contribute to the pathogenesis of allergic rhinitis. Like histamine, nasal challenge with bradykinin induces rhinorrhoea, nasal blockage, and plasma protein leakage. Their comparative nasal potencies have not, however, been fully elucidated. METHODS: Three double blind, randomised, placebo controlled and cross-over studies were undertaken to compare objectively the nasal effects of bradykinin, histamine, and vehicle. RESULTS: Both bradykinin and histamine produced dose dependent increases in nasal airways resistance (NAR). There was no significant difference in the effects of bradykinin and histamine on NAR at any dose level. On a molar basis, however, bradykinin was 6.98 times more potent than histamine in inducing a 50% increase in NAR. Nasal challenge with bradykinin and histamine also induced significant rhinorrhoea compared with vehicle. The amount of rhinorrhoea induced by histamine was significantly greater than that induced by bradykinin at any dose level. Bradykinin and histamine induced dose dependent nasal pain and nasal itch respectively. When administered as single doses both bradykinin (1.9 mumol) and histamine (1.9 mumol) induced significant rhinorrhoea compared with the vehicle. The volume of rhinorrhoea secretions induced by histamine was 29% greater than that induced by bradykinin. In contrast, although NAR was increased significantly more by histamine than by the vehicle, the effect of bradykinin on NAR was significantly greater than histamine and vehicle in both magnitude and duration of effect. The incremental effect of bradykinin on lavage albumin levels was also significantly greater than both histamine and vehicle. CONCLUSIONS: This study shows that the nasal vascular effects of histamine are less prominent than its actions on rhinorrhoea, and that the greater obstructive effect of bradykinin than histamine on NAR may contribute to the relative lack of efficacy of H1 antihistamines on nasal blockage in clinical disease.

Administration, Inhalation↗
PubMed1993

Effect of oral terfenadine on bronchoconstrictor response to inhaled neurokinin A and histamine in asthmatic subjects.

Neurokinin A (NKA) elicits a potent contractile effect in asthmatic airways. Its mechanism of action in bronchial asthma is still unknown. Recent work supports the view that NKA may stimulate mediator release from mast cells. To investigate the relative contribution of mast cell degranulation to the action of NKA, a randomized, double-blind study has been undertaken, to evaluate the effect of a potent and selective histamine H1-receptor antagonist, terfenadine (180 mg q.d., for three days), on bronchoconstriction provoked by inhaled NKA in six asthmatic subjects. Bronchial provocation tests with histamine were included in this study as control challenge. In the subjects studied, oral terfenadine, when compared to placebo, significantly increased the geometric mean (range) provocation dose of inhaled histamine required to reduce forced expiratory volume in one second (FEV1) by 20% of baseline (PD20) from 0.05 (0.03-0.08) mg (0.16 (0.10-0.26) mumol) to 1.19 (0.63-2.04) mg (3.88 (2.05-6.64) mumol). However, terfenadine failed to increase the airway responsiveness to NKA in all of the subjects studied, the geometric mean (range) PD15 NKA value being 0.94 (0.47-2.49) micrograms (8.36 (4.14-21.9 nmol) and 0.75 (0.48-1.59) micrograms (6.62 (4.23-14.0) nmol) after placebo and terfenadine, respectively. We conclude that NKA is a potent bronchoconstrictor agonist in asthma, being approximately 19 times more potent than histamine in molar terms. In this study on a small number of subjects, pharmacological intervention with oral terfenadine failed to achieve significant protection of the airways against the constrictor effect of NKA.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

Cross-tachyphylactic airway response to inhaled bradykinin, kallidin and [desArg9]-bradykinin in asthmatic subjects.

Kinins are oligopeptides that may act as mediators in the pathogenesis of bronchial asthma by interacting with specific cell surface receptors designated B1 and B2. When administered by inhalation to asthmatic subjects, bradykinin and kallidin, but not [desArg9]-bradykinin, provoke potent bronchoconstriction, thus suggesting a specific effect compatible with the stimulation of B2 receptors. To characterize further the receptor(s) mediating this bronchospastic response we have carried out cross-tachyphylactic studies with inhaled bradykinin, kallidin, and [desArg9]-bradykinin, administered in a randomized double-blind fashion in a group of 10 asthmatic subjects. Inhalation of bradykinin and kallidin, but not [desArg9]-bradykinin, elicited concentration-related falls in forced expiratory volume in one second (FEV1) in all the subjects studied. The geometric mean provocation concentrations of inhaled agonists reducing FEV1 by 20% of baseline (PC20) were 0.12 and 0.28 mg.ml-1 for bradykinin and kallidin, respectively. When inhaled at concentrations up to 10.62 mg.ml-1, [desArg9]-bradykinin failed to provoke any significant fall in FEV1 from baseline in any of the subjects studied. Following recovery from the second bradykinin challenge, provocation with kallidin revealed a reduced response to this agonist, the PC20 value increasing from 0.28 to 1.23 mg.ml-1. Similarly, once the airways had recovered from the second kallidin challenge, provocation with bradykinin also showed a reduced response, the PC20Bk increasing from 0.12 to 0.94 mg.ml-1. Surprisingly, despite failing to cause bronchoconstriction, repeated exposures with inhaled [desArg9]-bradykinin reduced the airway response to bradykinin, the PC20Bk increasing from 0.12 to 0.41 mg.ml-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1992

Protection of nedocromil sodium on bronchoconstriction induced by inhaled neurokinin A (NKA) in asthmatic patients.

Neurokinin A (NKA) has been shown to exert a potent contractile action on bronchial smooth muscles both in vitro and in vivo. Although this effect seems to be due either to a direct action of this peptide on specific muscular receptors or to an indirect effect on mast cells and/or nerves, its mechanism of action in bronchial asthma is still unknown. In the present study we have investigated the airway response to inhaled NKA in 10 asthmatic subjects and the activity of the novel pyranoquinoline dicarboxylic acid drug, nedocromil sodium, on this response. Ten asthmatic patients with stable asthma took part in the study consisting of four separate visits. On the first two occasions we derived histamine and NKA PD15 values in absence of any drug treatment. On the following two visits the inhalation challenge with NKA was performed after administration of either nedocromil sodium or matched placebo administered as pressurized aerosols via metered dose inhalers in a randomized double-blind order. Inhaled NKA produced a dose-related fall in FEV1 in all the subjects studied. Inhaled nedocromil sodium had a significant effect on the FEV1 response to NKA inhalation, the geometric mean PD15 value increasing from 16.6 to 32.2 x 10(-9) mol. We conclude that nedocromil sodium attenuates subsequent responsiveness to inhaled NKA in asthmatic subjects.

Adolescent↗
PubMed1992

The influence of terfenadine and ipratropium bromide alone and in combination on bradykinin-induced nasal symptoms and plasma protein leakage.

Nasal instillation of bradykinin elicits many of the characteristic features of rhinitis. To assess the relevance of histamine release from metachromatic cells and the activation of cholinergic pathways, we investigated the effects of terfenadine, a histamine H1-receptor antagonist, and ipratroprium bromide, a selective antimuscarinic agent, on bradykinin induced rhinorrhoea, nasal airways resistance (NAR), nasal pain and plasma protein leakage. Oral terfenadine (120 mg) or matched placebo and nasal ipratropium bromide (80 micrograms) or matched placebo were administered at 4 hr and 30 min respectively prior to bradykinin nasal challenge in two randomized, double-blind and cross-over studies on eight non-rhinitic subjects. Thus subjects received either double-placebo, oral terfenadine and nasal placebo, oral placebo and nasal ipratopium bromide or oral terfenadine and nasal ipratropium bromide, as pretreatment. Bradykinin challenge induced mean maximal increases of 57%, 59%, 77% and 72% in NAR on the placebo, terfenadine, ipratropium bromide and terfenadine plus ipratropium bromide pretreatment days respectively. These increments were not significantly different. Similarly rhinorrhoea and nasal pain induced by bradykinin nasal challenge were not significantly different on the four challenge days. Bradykinin nasal challenge caused a mean maximal increase in albumin levels in recovered nasal lavages of 11.5, 13.0, 12.2 and 12.3 times of baseline levels on the placebo, terfenadine, ipratropium bromide and terfenadine plus ipratroprium bromide pretreatment days respectively. Similarly total protein levels achieved a mean maximal increase of 8.0, 8.2, 7.9 and 8.8 times of baseline levels on these challenge days. The increments in both albumin and total protein did not significantly differ on the 4 challenge days.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Effect of topical application with capsaicin on skin responses to bradykinin and histamine in man.

Pre-treatment with topical capsaicin is known to induce neuropeptide depletion from sensory nerve endings and it is a useful pharmacological tool to evaluate the contribution of these nerves to skin injury and inflammation. To investigate the relative contribution of sensory neural stimulation to the action of bradykinin and histamine, a randomized, double-blind study has been undertaken evaluating the effect of topical capsaicin pre-treatment on the responses to intradermal injections of both agonists in 12 healthy volunteers. Capsaicin pre-treatment caused significant inhibition of the immediate mean flare responses (95% CI) to both bradykinin (from 51.5 [39.7-63.3] mm2 to 16.2 [8.0-24.5] mm2) (P < 0.01) and histamine (from 108.4 [80.4-136.4] mm2 to 52.3 [37.1-67.1] mm2) (P < 0.01). Topical capsaicin elicited a significant inhibition of the weal response induced by histamine, the mean weal area being reduced from 14.8 (12.6-17.0) mm2 to 12.1 (10.1-14.1) mm2 (P < 0.05). In addition, the effect of topical capsaicin was to completely inhibit the bradykinin induced weal response compared to control, the mean weal area (95% CI) being reduced from 13.4 (11.4-15.4) mm2 to 8.2 (5.3-11.0) mm2 (P < 0.01). Our findings show that repeated topical application with capsaicin led to a significant reduction of the skin responses to intradermal injections with both agonists, and particularly with bradykinin. The weal responsiveness to bradykinin may entirely follow neuropeptide release from sensory nerves within the skin and the same applies to the flare response, although this is not completely inhibited by topical application with capsaicin.

Administration, Cutaneous↗
PubMed1992

Acute effect of inhaled bradykinin on tracheobronchial clearance in normal humans.

BACKGROUND: Bradykinin, a nonapeptide that contributes as a mediator to the pathogenesis of asthma, may affect lung mucociliary clearance, as it has been shown to be a potent secretagogue in canine airways and in human nasal mucosa in vivo. To evaluate this possibility the effect of inhaled bradykinin on mucociliary clearance has been studied in 10 healthy volunteers. METHODS: Subjects attended the laboratory on two occasions to take part in tracheobronchial clearance studies using a non-invasive radioisotopic technique. Inhalation of radioaerosol was followed 30 minutes later by inhalation of either bradykinin (8 mg/ml) or vehicle placebo in a randomised, double blind fashion. After each inhalation the number of coughs was recorded. Whole lung radioactivity was measured every half hour for six hours with two collimated scintillation counters, and a tracheobronchial clearance curve was plotted for each subject on each occasion. RESULTS: Mucociliary clearance, expressed as the area under the tracheobronchial radioaerosol retention curve calculated for the first six hours (AUC0-6h), was greater in nine out of 10 subjects after inhalation of bradykinin than after placebo. The median values (range) for AUC0-6h were significantly reduced from 126% (78-232%)/h with placebo to 87% (51-133%)/h with bradykinin. CONCLUSION: It is concluded that acute exposure to inhaled bradykinin accelerates tracheobronchial clearance in normal human airways.

Administration, Inhalation↗
PubMed1992

Nasal effects of bradykinin and capsaicin: influence on plasma protein leakage and role of sensory neurons.

Nasal insufflation with bradykinin induces nasal discomfort, rhinorrhea, and nasal blockage, all features of rhinitis. We recently showed these effects to be mediated by the B2-receptor subtype, which has been identified at neural and vascular sites. To investigate the relative contribution of capsaicin-sensitive sensory neural stimulation to the action(s) of bradykinin, two randomized double-blind placebo-controlled studies have been undertaken comparing the nasal effects of single-dose administrations of bradykinin (1.88 x 10(-3) M) and capsaicin (3.28 x 10(-5) M). In comparison with placebo, both bradykinin and capsaicin induced nasal pain/discomfort (P less than 0.01) and rhinorrhea (P less than 0.02). Bradykinin significantly increased nasal airways resistance (P less than 0.005) and plasma protein exudation (P less than 0.02). No such changes were identified after nasal challenge with capsaicin. These findings suggest that bradykinin-induced nasal discomfort and rhinorrhea are neurally mediated, whereas the effects on nasal airways resistance and plasma protein exudation are due to a direct vascular action. In addition, these findings question the role of capsaicin-sensitive sensory neurons in nasal vasculature responses, because no vascular effects of capsaicin could be identified in the human nasal mucosa.

Adult↗
PubMed1992

Kinin receptors on asthmatic airways: functional subtyping.

Bradykinin, kallidin and [desArg9]-bradykinin are oligopeptides that may contribute as mediators in the pathogenesis of bronchial asthma by interacting with specific cell surface receptors. The structure-activity relationship of kinins within the lower airways has been investigated in 16 asthmatic subjects. The findings of the present study suggest a complex action of kinins on asthmatic airways probably involving more than one receptor subtype.

Asthma↗