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Biomedical subjects

M K Church

Publications and source records attributed to M K Church.

At least 145 records · Page 8Linked to original sources
PubMed1989

Effect of a thromboxane receptor antagonist on PGD2- and allergen-induced bronchoconstriction.

In this study we investigated the effect of the selective and potent thromboxane A2 (TxA2) receptor antagonist GR32191 on smooth muscle contraction induced by the TxA2 analogue U46619, prostaglandin (PG) D2, PGF2 alpha, and methacholine (MCh) in guinea pig airways in vitro and the airways response provoked by inhaled PGD2 and MCh in asthmatic subjects in vivo. GR32191 antagonized competitively the contractile responses of all three prostanoids to a similar degree but had no effect on MCh-induced contractions. In asthmatic subjects GR32191, in a single oral dose of 80 mg, did not affect base-line airway caliber or MCh-induced broncho-constriction but caused significant inhibition of PGD2-induced bronchoconstriction, displacing the concentration-response curves to the right by greater than 10-fold. The effect of the same oral dose of GR32191 on allergen-induced immediate bronchoconstriction was subsequently investigated in allergic asthmatic subjects. In individual subjects, GR32191 inhibited to varying degrees the overall bronchoconstrictor response, with the maximum effect occurring between 10 and 30 min after allergen challenge. These studies suggest that prostanoids contribute to the immediate bronchoconstriction induced by inhaled allergen in allergic asthmatics, and that this effect is mediated by stimulation of a thromboxane receptor.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

Interaction of neuropeptides with human mast cells.

Mast cells of human skin, but not lung, adenoids, tonsils, or intestine, release histamine in response to substance P, vasoactive intestinal polypeptide, and somatostatin. The substance P receptor of skin mast cells is not of the NK-1, NK-2 or NK-3 subtypes of smooth muscle. Time course and calcium dependency of release by peptides differed from anti-IgE. With anti-IgE, the molar ratios of histamine:PGD2:LTC4 generated by skin mast cells was 1,000:25:2, whereas with substance P these ratios were 1,000:1:0.1. Similar results were obtained with the other neuropeptides. The ability of peptides to stimulate skin mast cell histamine release suggests a mechanism whereby their release from dermal nerve endings is coupled to changes in microvasculature.

Histamine Release↗
PubMed1989

Effect of nedocromil sodium on early and late phase responses to allergen challenge in the guinea-pig.

We have developed a model of asthma in conscious guinea-pigs in which inhalation challenge with specific allergen induces both early and late phase reductions in specific airways conductance. Analysis of cells removed from the airways by bronchoalveolar lavage showed the presence of a neutrophilia, which reached a maximum at 17 hours, and an eosinophilia which developed more slowly, still increasing at 72 hours. Nedocromil sodium inhaled before challenge inhibited both the early and late phase responses. In contrast, the beta-adrenoceptor stimulant, salbutamol, inhibited only the early phase. When inhaled 6 hours after challenge, i.e. between the early and late phase responses, the late phase bronchoconstriction was prevented by nedocromil sodium but only partially by salbutamol. Evidence that the neutrophilia was not functionally associated with the late response was gained from the observations that it was inhibited by both nedocromil sodium and salbutamol, whereas only nedocromil sodium blocked the late phase airways response. When administered 6 hours after challenge, nedocromil sodium reduced eosinophil accumulation at 72 hours in parallel with inhibiting a secondary late response at this time. These results demonstrate that nedocromil sodium is able to prevent both early and late phase reductions in airways function in an animal model of allergic asthma. Whereas inhibition of the early response may reflect an effect on mast cell mediator release, the effects of nedocromil sodium on the late response and on eosinophil accumulation are strongly suggestive of an anti-inflammatory effect within the lung.

Allergens↗
PubMed1989

The IgE- and calcium-dependent release of eicosanoids and histamine from human purified cutaneous mast cells.

Cells dispersed from human foreskin were passively sensitized with IgE and then depleted or enriched in mast cells by density gradient centrifugation. Arachidonic acid metabolism was initially studied by radio-high-performance liquid chromatography analysis of incubation media from cells that had been prelabeled with [3H] arachidonic acid. In subsequent experiments with unlabeled cells the eicosanoids were quantified by radioimmunoassay. Prostaglandin (PG)D2 was the major cyclooxygenase product released from purified mast cells challenged with anti-IgE or A23187. In density gradient studies there was a significant correlation between PGD2 and histamine release (r = 0.52, p less than 0.01) and between PGD2 release and the numbers of mast cells (r = 0.42, p less than 0.02). There was no correlation with the total numbers of nucleated cells. Other cyclooxygenase products were also detected, the formation of 6-keto-PGF1 alpha and PGE2 being principally associated with gradient fractions containing endothelial cells. Leukotriene (LT)C4 was the major lipoxygenase product detected, reaching a maximum of 3.87 +/- 0.56 ng/10(6) mast cells upon activation with anti-IgE compared with 35.37 +/- 7.22 ng/10(6) mast cells of PGD2. When normalized to histamine release and expressed in molar terms, skin mast cells released approximately 20-fold more PGD2 than LTC4. Thus, the cutaneous mast cell is one likely source of the PGD2 and LTC4 released during cutaneous immediate hypersensitivity reactions.

Antibodies↗
PubMed1988

IgE-dependent activation of human lung mast cells is not associated with increased phospholipid methylation.

Enhanced phospholipid methylation has been suggested to be an obligatory process in IgE-dependent stimulus-secretion coupling in human lung mast cells. Our studies with mast cell-enriched lung preparations do not support this hypothesis, demonstrating no increased 3H-methyl radiolabeling of chloroform/methanol-extracted lipids or chromatographically separated phospholipids accompanying anti-IgE-dependent histamine secretion. Inhibitors of transmethylation, 3-deazaadenosine, and homocysteine thiolactone inhibited histamine secretion by both anti-IgE and calcium ionophore A23187, reflecting a requirement of secretion for overall integrity of cellular transmethylation. These agents induced small increases in cAMP concentration which are considered to make at most a minor contribution to this inhibition. The inability of methylation inhibitors to diminish anti-IgE-dependent increases in lung mast cell cAMP levels would suggest that not only does phospholipid methylation have no role in histamine secretion but also it does not participate in the activation of adenylate cyclase by this stimulus.

Antibodies, Anti-Idiotypic↗
PubMed1988

Inhibition by nedocromil sodium of early and late phase bronchoconstriction and airway cellular infiltration provoked by ovalbumin inhalation in conscious sensitized guinea-pigs.

Bronchial challenge of ovalbumin-sensitized conscious guinea-pigs induced a triphasic reduction in specific airways conductance (sGaw) with maximal reductions being observed at 2, 17 and 72 h accompanied by infiltration of the airways with neutrophils at 17 h and eosinophils at 17 and 72 h. Nedocromil sodium (10 mg ml-1) inhaled before challenge blocked the 2 and 17 h sGaw response and the neutrophil influx. When inhaled 6 h after challenge, nedocromil inhibited the 17 h sGaw response but not neutrophil influx, suggesting that these are unrelated. The sGaw response and eosinophil accumulation at 72 h was also inhibited by nedocromil given at this time. Our findings correlate with the clinical effects of nedocromil, suggesting the guinea-pig model may be useful for investigating the mechanism of action of anti-asthmatic drugs.

Administration, Inhalation↗
PubMed1988

Characterization of neuropeptide-induced histamine release from human dispersed skin mast cells.

1. Human skin mast cells, unlike other human mast cells so far studied, released histamine in a concentration-related manner in response to substance P, vasoactive intestinal peptide (VIP) and somatostatin (1 microM to 30 microM). In contrast, eledoisin, physalaemin, neurokinin A, neurokinin B, calcitonin gene-related peptide (CGRP), neurotensin, bradykinin and Lys-bradykinin induced negligible histamine release. 2. The low histamine releasing activity of physalaemin, eledoisin, neurokinin A and neurokinin B relative to substance P suggests that the human skin mast cell activation site is distinct from the tachykinin NK-1, NK-2 or NK-3 receptors described in smooth muscle. 3. The relative potencies of substance P and its fragments SP2-11, SP3-11, SP4-11 and SP1-4 in releasing histamine from human skin mast cells suggests that both the basic N-terminal amino acids and the lipophilic C-terminal portion of substance P are essential for activity. 4. Peptide-induced histamine release, like that induced by compound 48/80, morphine and poly-L-lysine, is rapid, reaching completion in 10-20 s, is largely independent of extracellular calcium but requires intact glycolysis and oxidative phosphorylation. 5. The substance P analogue, [D-Pro4,D-Trp7,9,10] SP4-11 (SPA), not only reduced substance P-induced histamine release in a concentration-related manner but also inhibited that induced by VIP, somatostatin, compound 48/80, poly-L-lysine and morphine but not anti-IgE. 6. The similar characteristics of histamine release induced by substance P, VIP, somatostatin, compound 48/80, poly-L-lysine and morphine suggest that they share a common pathway of activation-secretion coupling distinct from that of IgE-dependent activation. Furthermore, the ability of human skin mast cells to respond to basic non-immunological stimuli including neuropeptides may reflect a specialised function for these cells.

Adenosine Triphosphate↗
PubMed1988

Early and late-phase bronchoconstriction after allergen challenge of nonanesthetized guinea pigs. I. The association of disordered airway physiology to leukocyte infiltration.

We describe a guinea pig model of asthma in which animals were sensitized and challenged by inhalation of aerosolized ovalbumin. Challenge was performed under cover of mepyramine (10 mg/kg) to allow a high enough concentration of ovalbumin to elicit consistent late responses. Airway resistance and thoracic gas volume of conscious guinea pigs was assessed by whole body plethysmography before and at regular intervals for as long as 72 h after challenge. At the same time points, cellular changes in the lung were assessed by both examination of cells recovered by bronchoalveolar lavage (BAL) and lung histology. There were no significant changes in specific airway conductance (SGaw), BAL cell content or lung histology in animals challenged with saline control. Challenge with 2% ovalbumin caused an early fall in SGaw, which peaked at 2 h and amounted to a 43.7 +/- 4.1% fall from baseline. This was followed by 2 late responses, the first reaching maximum at 17 h with a 46.9 +/- 4.5% decrease in SGaw from baseline and the second at 72 h with a 39.0 +/- 3.5% fall in SGaw. Examination of BAL fluid revealed a 7-fold increase in neutrophils at 6 h and a 17-fold increase at 17 h, after which numbers decreased to baseline. Eosinophilia developed more slowly, being insignificant at 6 h and 6-fold at 17 h; by 72 h, eosinophils constituted 48.9 +/- 6.9% of the total cells recovered. No changes in mononuclear cells or lymphocytes were observed. Histologic examination of the lung revealed a progressive eosinophil infiltration of the airways, but not alveoli or vascular bed. Electron microscopy showed degranulation of eosinophils recovered by BAL and discharge of mucus from goblet cells in the trachea. Because these changes are similar to those that occur after allergen challenge in human asthma, we suggest that this represents a useful animal model in which to study the mechanism of early and late bronchoconstriction responses.

Airway Resistance↗
PubMed1988

The effect of cromolyn sodium and albuterol on early and late phase bronchoconstriction and airway leukocyte infiltration after allergen challenge of nonanesthetized guinea pigs.

We describe the effects of the antiallergic drug cromolyn sodium and the beta 2-selective adrenoceptor agonist albuterol against early and late phase changes in specific airways conductance (sGaw) and leukocyte infiltration into the airways after allergen challenge of nonanesthetized guinea pigs. Inhalation of ovalbumin by sensitized guinea pigs induced three phases of airways obstruction: an early asthmatic response (EAR) peaking at 2 h, a late response (LAR) peaking at 17 h, and a further late response (LLAR) being observed at 72 h. The LAR was accompanied by a 13-fold rise in neutrophils and a four-fold rise in eosinophils recovered by bronchoalveolar lavage (BAL) at 17 h. By 72 h, the BAL content of neutrophils had returned to near normal, whereas eosinophil numbers had risen to 6.7-fold above baseline. Inhalation of an aerosolized solution of cromolyn, 10 mg/ml, 15 min before challenge inhibited both the EAR and LAR and the influx of neutrophils into the airways at 17 h but had no effect on eosinophil accumulation. Inhalation of cromolyn at 6 h, i.e., after the completion of the EAR, inhibited the LAR, the LLAR, and the rise in eosinophils at 72 h but did not reduce the influx of neutrophils at 17 h. Administration of cromolyn at both 15 min before and 6 h after challenge inhibited all changes in sGaw and reduced the accumulation of neutrophils at 17 h and the influx of eosinophils at 72 h. In contrast, inhalation of albuterol, 0.1 mg/ml, 15 min before allergen provocation blocked the EAR and the rise in BAL neutrophils at 17 h but did not inhibit the LAR. Inhalation of albuterol at 6 h partially reversed the LAR but had no effect on either the LLAR or cellular changes. Given at both times, albuterol inhibited the EAR and neutrophil accumulation at 17 h and partially reversed the LAR but produced no other effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Obstruction↗
PubMed1988

Human mast cell heterogeneity: histamine release from mast cells dispersed from skin, lung, adenoids, tonsils, and colon in response to IgE-dependent and nonimmunologic stimuli.

We have compared the ability of anti-IgE, calcium ionophore A23187, substance P, compound 48/80, poly-L-lysine, and morphine to release histamine from mast cells of human skin, lung, adenoids, tonsils, and colon. Use of a single collagenase/hyaluronidase dispersion technique for all tissues has allowed comparisons of reactivity to be made that are free from methodological variations. Mast cells from all tissues examined secreted histamine in response to anti-IgE and calcium ionophore A23187. However, only skin mast cells were responsive to substance P, compound 48/80, poly-L-lysine, and morphine. Activation of human skin mast cells by these nonimmunologic stimuli clearly distinguishes them from the mast cells of human lung, adenoids, tonsils, and colon and is indicative of functional heterogeneity within the human mast cells population. We propose that the presence of functional receptor sites for neuropeptides and basic compounds on skin mast cells that are not present in mast cell populations from mucosal or lymphoid sources reflects a specialized role for these cells in vascular homeostasis.

Adenoids↗
PubMed1988

The secretory characteristics of mast cells isolated from the human large intestinal mucosa and muscle.

The use of a collagenase dispersion technique has allowed us to compare size, histamine content and the secretory characteristics of mast cells from the mucosal and muscle layers of the human large intestine. Mast cells from the mucosa, which constituted 1.8% of the total nucleated cells, contained approximately equal numbers of formalin-sensitive and -insensitive mast cells. Those dispersed from the muscle layer constituted 3.2% of the total nucleated cells and were almost all formalin insensitive. The cells from both layers were similar with respect to size and mean cell histamine content. Anti-IgE released up to 15.1% and 16.5% of total cell histamine in the mucosa and muscle, respectively, with similar concentration-response characteristics. The kinetics of anti-IgE-induced release, however, were different, mucosal mast cells releasing histamine 55 seconds (P less than 0.05) faster than cells dispersed from intestinal muscle. Cells from both layers also released histamine in response to A23187 in a similar concentration-related fashion. Neither mucosal or muscle mast cells released significant amounts of histamine in response to compound 48/80, substance P, morphine, poly-L-lysine or f-met-leu-phe. Our results show intestinal mast cells possess secretory characteristics similar to those of human lung, adenoids and tonsils, but are different from human skin mast cells. The absence of significant histamine release in response to basic secretagogues from either layer of the human intestine contrasts with studies in the rodent intestine. Furthermore it suggests that in human mast cells, histochemical properties, protease content and secretory characteristics may not be closely associated.

Cell Count↗
PubMed1988

Active sensitization of guinea-pig airways in vivo enhances in vivo and in vitro responsiveness.

A plethysmographic method was employed to assess the airway resistance of conscious, free-breathing guinea-pigs. Using this method animals sensitized by inhalation of ovalbumin and appropriate controls were assessed for their responsiveness to histamine and methacholine in vivo. The cough frequency on exposure to citric acid mist in the two groups was also assessed. Tracheal spirals from these animals were subsequently tested for their responsiveness to histamine, methacholine and prostaglandin D2 in vitro. Sensitization increased responsiveness to histamine, methacholine and citric acid in vivo but only histamine responses were affected in vitro. These changes were accompanied by a significant eosinophilia in the airways as assessed by bronchoalveolar lavage. We conclude that sensitization of the airways to ovalbumin results in responsiveness changes in bronchial smooth muscle accompanied by signs of airway inflammation.

Administration, Inhalation↗