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Biomedical subjects

M K Church

Publications and source records attributed to M K Church.

At least 163 records · Page 9Linked to original sources
PubMed1987

Human skin mast cells: their dispersion, purification, and secretory characterization.

Digestion of human foreskin with collagenase and hyaluronidase disperses approximately 3.4 X 10(7) nucleated cells per gram of tissue, of which mast cells constitute 4.7%. These may be purified to 80% by use of density gradient centrifugation. The majority of mast cells (79%) measured between 9 and 13 micron in diameter, and the mean histamine content was 4.6 pg/cell. Viability was demonstrated by trypan blue exclusion by 93% of the cells and the low spontaneous histamine secretion of less than 7% in functional studies. Anti-IgE released up to 17.5% of cell-associated histamine within 5 to 7 min. Calcium ionophore-induced release was optimal with 0.3 microM A23187 when 28.6% histamine was released. Unlike human lung mast cells, skin mast cells released histamine in response to compound 48/80 and poly-L-lysine. This release, which was complete within 20 sec, was totally dependent on intact glycolysis and oxidative phosphorylation and partially dependent on extracellular calcium. The same characteristics were observed with secretion induced by substance P and morphine. The weak activity of eledoisin and physalaemin suggests that the substance P receptor, like that of the rat mast cell, is not of the classical types described for smooth muscle. Morphine-induced secretion was partially blocked by naloxone in a manner not compatible with competitive antagonism at a classical opioid receptor. The sensitivity of skin mast cells to nonimmunologic stimulation clearly distinguishes them from mast cells of the lung and lymphoid tissues and provides evidence of functional heterogeneity within human mast cells.

Calcimycin↗
PubMed1987

Non-IgE-dependent bacteria-induced histamine release from human lung and tonsillar mast cells.

A wide spectrum of formalin-killed bacteria have been tested for their ability to release histamine from human dispersed lung and tonsillar mast cells. Escherichia coli, Enterobacter cloacae, Staphylococcus epidermidis, Proteus vulgaris, Klebsiella oxytoca and K. pneumoniae were the most effective histamine releasers. Further studies on tonsillar mast cells showed that E. coli-induced histamine release differed from IgE-dependent release with respect to its kinetics, temperature and pH profiles and its sensitivity to calcium deprivation and metabolic inhibitors. A lectin-mediated mechanism may operate, but other non-immunological mechanisms might also be involved in the release. Escherichia coli and anti-IgE did not synergize in inducing histamine release. The production of PGD2 and the failure to detect lactate dehydrogenase following incubation of mast cells with E. coli suggests that histamine release is not due to cytotoxicity.

Adult↗
PubMed1987

Inhibition of IgE-dependent histamine release from human dispersed lung mast cells by anti-allergic drugs and salbutamol.

The ability of the anti-allergic drugs, sodium cromoglycate (SCG), lodoxamide, traxanox, RU31156 and the beta-adrenoceptor agonist salbutamol to inhibit IgE-dependent histamine and prostaglandin D2 (PGD2) release was assessed using human dispersed lung mast cells. The anti-allergic drugs were weak inhibitors of histamine release, high concentrations (100-1000 microM) producing less than 35% inhibition. Salbutamol produced 39% inhibition at 10 microM. The efficacy of both SCG and salbutamol was inversely related to the concentration of anti-IgE used for challenge and to the degree of histamine release. Rapid tachyphylaxis was observed with all anti-allergic drugs but not with salbutamol. Cross-tachyphylaxis was observed between SCG and the other anti-allergic drugs, suggesting a common mechanism of action. No cross-tachyphylaxis was observed between SCG and salbutamol. SCG was significantly (P less than 0.001) more effective in inhibiting PGD2 than it was histamine release. Preferential inhibition of PGD2 compared with histamine release was less marked (P less than 0.05) with salbutamol and not significant with the other anti-allergic drugs. Mast cells dispersed by enzymatic digestion of human lung released more histamine on immunological challenge than mechanically dispersed cells obtained by fine chopping of tissue. Enzyme treatment of mechanically dispersed cells removed this difference. Enzymatically and mechanically dispersed cells responded similarly to the inhibitory effects of SCG and salbutamol. Our results suggest that salbutamol is a more effective inhibitor of mediator release from human lung mast cells than anti-allergic drugs. However, with the low levels of mediator release achieved during an allergic reaction in man in vivo, both salbutamol and SCG are likely to be effective inhibitors of both preformed and newly generated mediators.

Albuterol↗
PubMed1987

Prostaglandin D2 release from human skin mast cells in response to ionophore A23187.

1. Cells were dispersed from human foreskin by proteolytic digestion and enriched or depleted in mast cell content by density gradient flotation on discontinuous gradients of Percoll. 2. Cells were harvested at six interfaces on the density gradient. Mast cell purity ranged from 0.6-85.0%, compared to 5.5% in the unfractionated cells. 3. Challenge of the cells with the calcium ionophore A23187 resulted in release of both histamine and prostaglandin D2 (PGD2). In fractions depleted of mast cells, histamine release and net PGD2 generation were low, but increasing amounts of these mediators were released as mast cell purity was increased up to 59%. 4. Overall, there was a significant correlation between the net generation of PGD2 and histamine (r = 0.9234, P less than 0.001) and also between PGD2 release and mast cell number (r = 0.7475, P less than 0.001). 5. These data provide the first direct evidence of the capacity of the human cutaneous mast cell to synthesize and release PGD2.

Calcimycin↗
PubMed1987

Primary and secondary effector cells in the pathogenesis of bronchial asthma.

The immediate and late asthmatic reactions provoked by inhaled allergens have provided useful models enabling the dissection of individual inflammatory cells and their mediators that may contribute to the pathogenesis of asthma. The immediate reaction is considered to be mast cell-mediated on the basis that about 50% of the response is inhibitable by potent and selective H1-receptor antagonists such as terfenadine and astemizole. Additional inhibition (approximately 30%) by the potent cyclooxygenase inhibitor flurbiprofen implies an important role for prostanoids in the immediate response, the most likely mast cell-derived product being prostaglandin (PG) D2. In man, PGD2 is selectively metabolised to 9 alpha 11 beta-PGF2, a unique prostaglandin which shares with PGD2 contractile properties on guinea-pig and human airways smooth muscle. The inability of piriprost, a potent leukotriene synthesis inhibitor, to influence the allergen-provoked immediate reaction raises the possibility that sulphidopeptide leukotrienes play a minor role in this response. The late asthmatic reaction is considered to resemble clinical asthma since it is accompanied by increased responsiveness of the airways to a wide range of stimuli. The late reaction in man is inhibited by nedocromil sodium (4 mg) but only marginally attenuated by salbutamol (200 micrograms) if both drugs are administered prior to allergen challenge. Since salbutamol, in the dose administered, is a potent mast cell-stabilising agent, these findings must question the obligatory role of mast cell mediator release in the pathogenesis of the late response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

9 alpha,11 beta-prostaglandin F2, a novel metabolite of prostaglandin D2 is a potent contractile agonist of human and guinea pig airways.

Prostaglandin (PG) D2, the predominant prostanoid released from activated mast cells in humans is initially metabolized by reduction of the C-11 keto function to yield 9 alpha,11 beta-PGF2. In this study the airways effects of 9 alpha,11 beta-PGF2 were compared with those of its epimer 9 alpha,11 alpha-PGF2 (PGF2 alpha) and PGD2. 9 alpha,11 beta-PGF2 was a potent contractile agonist of isolated guinea pig trachea and 4-mm human airways in vitro; the potencies of the PGs relative to PGD2 (= 1.00) being 0.65 (NS) and 4.08 (P less than 0.001) for 9 alpha,11 beta-PGF2, and 0.52 (P less than 0.01) and 2.40 (P less than 0.001) for PGF2 alpha, respectively. When inhaled by asthmatic subjects, 9 alpha,11 beta-PGF2 was a potent bronchoconstrictor agent, being approximately equipotent with PGD2 and 28-32 times more potent than histamine (P less than 0.01). These studies suggest that 9 alpha,11 beta-PGF2 is at least equipotent with PGD2 as a bronchoconstrictor agonist, and in being a major metabolite of PGD2, could contribute to the bronchoconstrictor effect of this mast cell-derived mediator in asthma.

Adult↗
PubMed1987

Adenosine inhibits immunoglobulin E-dependent histamine secretion from human basophil leukocytes by two independent mechanisms.

Adenosine inhibits immunoglobulin E-dependent histamine release when preincubated with human basophil leukocytes before challenge. Two distinct mechanisms for this inhibition have been demonstrated. The first we suggest to be an A2-purinoceptor mediated mechanism. This effect, which is apparent with both 15- and 60-min preincubation periods, is mimicked by 5'-N-ethylcarboxamideadenosine, blocked by 8-phenyltheophylline but not dipyridamole and is associated with the ability of adenosine to elevate cyclic AMP. The second, which is mimicked by 3-deazaadenosine and is associated only with the longer 60-min preincubation period, is reversed by dipyridamole but not by 8-phenyltheophylline suggesting it to be an intracellular mechanism. Its enhancement by homocysteine thiolactone and reversal by exogenous S-adenosyl methionine suggests it to result from increasing intracellular S-adenosyl homocysteine levels. Our failure to detect increased 3H-methyl incorporation into chloroform-methanol extractable lipids after immunoglobulin E-dependent activation would indicate that inhibition of S-adenosyl methionine methylation reactions are an unlikely mechanism. As both prior stimulation of A2-purinoceptors and elevation of intracellular S-adenosyl homocysteine enhance and prolong the cyclic AMP response consequent upon immunoglobulin E-dependent activation, this represents a common mechanism by which histamine release may be suppressed.

Adenosine↗
PubMed1986

IgE-dependent activation of mast cells is not associated with enhanced phospholipid methylation.

Enhanced phospholipid methylation has been suggested to be an obligatory event in activation-secretion coupling in mast cells. However, we have consistently failed to demonstrate increased [3H]methyl incorporation into either whole-lipid extracts or separated lipids to accompany IgE-dependent induction of histamine release from rat peritoneal mast cells despite variation of the experimental protocol, animals and animal diet. Although the presence of 3-deazaadenosine and homocysteine thiolactone reduced IgE-dependent histamine release, treatment with these compounds elevated mast cell cyclic AMP levels. We conclude that IgE-dependent activation of mast cells is not associated with enhanced phospholipid methylation and that inhibition of histamine release by methylation inhibitors may be due to other effects of the drugs.

Animals↗
PubMed1986

Inhibition of immunological and nonimmunological histamine release from human basophils by adenosine analogues that act at P-sites.

2',5'-Dideoxyadenoside (DDA) inhibited both anti-IgE and ionophore A23187 induced histamine secretion from human basophils. Whereas DDA inhibited IgE-dependent histamine secretion when added at all times prior to challenge, release induced by A23187 was inhibited only with simultaneous addition of DDA and secretagogue. Dipyridamole, but not theophylline, abrogated DDA mediated inhibition of histamine release suggesting an intracellular mechanism of action of DDA. The observations that 2'-deoxyadenosine and 9-beta-D-arabinofuranosyladenine also inhibited release suggest that the its inhibitory effect was enhanced by manganese and reversed by islet activating protein from Bordetella pertussis suggest that DDA inhibits basophil histamine release by interacting with a guanine nucleotide binding protein which may be linked to either adenylate cyclase or other second messenger system(s).

Adenosine↗
PubMed1986

Separate purinoceptors mediate enhancement by adenosine of concanavalin A-induced mediator release and the cyclic AMP response in rat mast cells.

Adenosine caused a concentration-related enhancement of concanavalin A (Con A)-induced 5-hydroxytryptamine (5-HT) release from rat purified peritoneal mast cells. This was accompanied by an enhancement and prolongation of the cyclic AMP response to Con A. The cyclic AMP response but not enhancement of 5-HT release was blocked by 8-phenyltheophylline suggesting the two events to be unrelated. The effects of AMP and ADP, adenosine analogues and adenosine uptake inhibitors suggest the enhancement of 5-HT release to be mediated by a P1-cell surface purinoceptor which does not show the characteristics of either A1 or A2 subtypes.

Adenine Nucleotides↗
PubMed1986

Relationships between adenosine, cyclic nucleotides, and xanthines in asthma.

Methylxanthines have been used for the treatment of asthma for more than 60 years, but their mechanism of action is poorly understood. Their ability to inhibit cyclic adenosine monophosphate phosphodiesterase has attracted much attention. However, this is clearly demonstrable only in high doses and is more likely to be related to toxicity. An alternative mechanism is antagonism of adenosine receptors in the lung. Adenosine has been shown to be released in asthma and cause bronchoconstriction in patients with asthma. Its effects are selectively inhibited by concentrations of theophylline that do not block histamine-induced bronchoconstriction. Neither phosphodiesterase inhibition nor adenosine receptor antagonism explains the action of enprofylline in asthma. Consequently, additional actions of methylxanthines are likely to contribute to their beneficial effects. They may include adrenaline release from the adrenal medulla, an effect on cell calcium distribution, inhibition of the generation of contractile prostaglandins, and an improvement of diaphragmatic contractility.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

Studies on the receptor mediating cyclic AMP-independent enhancement by adenosine of IgE-dependent mediator release from rat mast cells.

Adenosine produced a concentration-related enhancement of antigen-induced 5-hydroxytryptamine (5-HT) release from rat serosal mast cells. This potentiation was maximal following the simultaneous addition of adenosine with antigen. Enhancement of 5-HT release was accompanied by potentiation of the adenosine 3':5'-cyclic monophosphate (cyclic AMP) response to challenge. The cyclic AMP response, which was antagonized by 8-phenyltheophylline, was characterized as an A2-purinoceptor-mediated effect by the use of 5'-N-ethylcarboxamideadenosine (NECA) and L-N6-phenylisopropyladenosine (L-PIA). Enhancement of 5-HT release, conversely, was not blocked by 8-phenyltheophylline suggesting it to be mediated by a cyclic AMP-independent mechanism. The effect of adenosine on 5-HT release was not reduced by the inhibition of the facilitated uptake of adenosine with dipyridamole, hexobendine or p-nitrobenzylthioguanosine, therefore, suggesting it to be mediated by a cell surface receptor. The receptor mediating enhancement of 5-HT does not appear to belong to the P2-purinoceptor subtype as adenosine was more potent than both adenosine monophosphate (AMP) and adenosine diphosphate (ADP) and alpha, beta-methylene ATP was inactive. Furthermore, the effects of AMP were blocked by alpha, beta-methylene ADP, which inhibits the conversion of AMP to adenosine. Adenosine, NECA, L- and D-PIA were all of equal potency in enhancing 5-HT release. Inosine and 3-deazaadenosine were also active. The rank order of potency of these adenosine analogues is not consistent with an effect at A1- or A2-purinoceptors. There appear to be two adenosine receptors on rat mast cells, an A2-purinoceptor which stimulates adenylate cyclase and a separate purinoceptor, stimulation of which produces enhancement of mediator release by an unknown mechanism. The effects mediated by these receptors appear to be independent of each other.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Dispersion and characterisation of mast cells from human skin.

A technique is described for the enzymatic dispersion of mast cells in high yield from human infant foreskin. Dispersed mast cells exhibit high viability as assessed by light microscopy, low spontaneous histamine release, and survival in culture. Dispersed mast cells release histamine in response to immunological stimulation and synthetic secretagogues including ionophore A23187, compound 48/80 and poly-L-lysine. Reactivity to these stimuli indicates that cutaneous mast cells differ in their properties from human pulmonary mast cells.

Calcimycin↗