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C J Whelan

Publications and source records attributed to C J Whelan.

At least 19 recordsLinked to original sources
PubMed2001

Investigation of nicotine binding to THP-1 cells: evidence for a non-cholinergic binding site.

Nicotine is known to modulate immune function, but reports have produced conflicting evidence as to whether nicotinic acetylcholine (nACh) receptors are responsible for these effects. This study was designed to examine the identity of nicotine-binding sites on immune cells using a human leukaemic monocytic cell line, THP-1, that is known to have functions that are modulated by nicotine. Binding studies were performed on THP-1 whole cells using [3H]nicotine as a probe to analyse any possible nicotine-binding sites on these cells. Saturation analysis of THP-1 cells revealed the presence of 2 distinct binding sites; one with a K(d1) of 3.5 +/- 2.1 x 10(-9) M and a B(max1) of 4100 +/- 560 sites/cell (designated the high-affinity site) and the other with a K(d2) of 27 +/- 9.2 x 10(-9) M and a B(max2) of 11,600 +/- 630 sites/cell (low-affinity site). Competition analysis revealed that one site had an affinity to a range of cholinergic ligands including epibatidine and cytisine. When saturation analysis of [3H](-)-nicotine to THP-1 cells was performed in the presence of 1 x 10(-6) M epibatidine, only one binding site was detected. Comparisons of K(d) and B(max) values showed that the high-affinity site was not occluded by epibatidine. No drugs tested displayed any affinity for the high-affinity site except the two enantiomers of nicotine. The high-affinity site was shown to be stereoselective for the (+)-enantiomer of nicotine as shown by K(i) values produced by competition analysis in the presence of 1 x 10(-6) M epibatidine. These values were 5.7 +/- 0.32 x 10(-11) M and 1.9 +/- 4.9 x 10(-9) M for (+)-nicotine and (-)-nicotine, respectively. This study presents evidence for a possible non-cholinergic binding site that may play a role in the mechanism of immunomodulation by nicotine.

Binding, Competitive↗
PubMed1999

A comparison of the inhibitory effects of budesonide, beclomethasone dipropionate, dexamethasone, hydrocortisone and tixocortol pivalate on cytokine release from leukocytes recovered from human bronchoalveolar lavage.

OBJECTIVE: The potency of budesonide, beclomethasone dipropionate (BDP), dexamethasone, hydrocortisone and tixocortol pivalate as inhibitors of interleukin-5 (IL-5) and interferon-gamma (IFNgamma) release from human bronchoalveolar lavage cells in vitro were compared. METHODS: BAL leukocytes were obtained from patients undergoing bronchoscopy for diagnostic purposes. BAL leukocytes were activated with PHA (10 microg/ml) and PMA (10 ng/ml) and cultured for 48 h in the presence or absence of glucocorticoids. Culture supernatants were assayed for cytokines by ELISA. RESULTS: Budesonide (10(-9) to 10(-7) M) and BDP (10(-8) to 10(-6) M) were the most potent glucocorticoids tested. Dexamethasone (10(-7) to 10(-5) M) was less potent, and the maximum inhibitory effect of dexamethasone was less than that produced by than budesonide or BDP. Tixocortol pivalate (10(-6) to 3 x 10(-5) M) caused a concentration-related inhibition of IL-5 release but only the highest concentration tested inhibited the release of IFNgamma. Hydrocortisone (10(-4) M) inhibited IL-5 and IFNgamma release. CONCLUSION: We conclude that, unlike the other glucocorticoids tested, tixocortol pivalate appeared to be a selective inhibitor of IL-5 release. Possible mechanisms for this selectivity are discussed.

Anti-Inflammatory Agents↗
PubMed1999

Reactive oxygen species generation and histamine release by activated mast cells: modulation by nitric oxide synthase inhibition.

1. We have examined the generation of intracellular reactive oxygen species (ROS) and release of histamine by rat peritoneal mast cells (RPMC) in response to stimulation with antigen (ovalbumin), compound 48/80, nerve growth factor (NGF) and substance P (SP). 2. We have also examined the effects of the non-specific nitric oxide synthase inhibitor, L-NAME (100 microM) upon the release of histamine and generation of intracellular ROS in response to the named secretagogues. 3. Ovalbumin (100 - 1000 microg ml-1), compound 48/80 (0.1 - 100 microg ml-1), NGF (0.1 - 100 microg ml-1), and SP (5 - 50 microM), caused a concentration-dependent release of histamine from RPMC. 4. Ovalbumin (1 ng ml-1 - 0.1 microg ml-1), compound 48/80 (1 - 100 microg ml-1), NGF (1 pg ml-1 - 1 microg ml-1), and SP (0.005 - 50 microM) caused a concentration-dependent generation of intracellular ROS by RPMC. 5. Pre-incubation of RPMC with L-NAME (100 microM) caused a significant enhancement of both histamine release and intracellular ROS from RPMC in response to ovalbumin, compound 48/80, NGF and SP. 6. Our data demonstrate that NGF, SP and ovalbumin are capable of causing intracellular ROS generation by RPMC at lower concentrations than those causing significant histamine release and we speculate that this may contribute to the activation of cytokine production. 7. The data also show that NO modulates histamine release, and ROS generation in response to the secretagogues used. This may have significance in pathologies where NO synthesis is decreased, leading to an increased activation of mast cells.

Animals↗
PubMed1997

Adenosine A3 receptors promote degranulation of rat mast cells both in vitro and in vivo.

OBJECTIVE: To investigate the effects of adenosine receptor agonists and antagonists on 5-HT release from rat isolated pleural mast cells and on plasma protein extravasation in the skin of conscious rats. In vitro METHODS: Rat isolated pleural mast cells were loaded with [14C] 5-HT, sensitised with mouse monoclonal anti-DNP and then challenged with human serum albumin-DNP. DNP-stimulated 5-HT release from mast cells was determined. In vivo METHODS: Rats, loaded intravenously with [125I] human serum albumin, were injected intradermally with adenosine agonists at sites on the back. 30 min later plasma protein extravasation at each injection site was determined. RESULTS: In isolated mast cells, each adenosine agonist enhanced DNP-induced 5-HT release, N6-(3-iodobenzyl)-5-(N-methyl-carboxamidoadenosine), (IB-MECA), being the most potent agonist. The adenosine A1/A2 antagonist, 8-phenyltheophylline (8-PT), had no effect on the response to IB-MECA. In contrast, 3-(4-amino-iodobenzyl)-8-[4-[[[carboxy]methyl]oxy]phenyl]-1-propylxanthi ne, (I-ABOPX), inhibited (pA2 6.2) the IB-MECA responses. In the skin of conscious rats, intradermal IB-MECA produced a marked plasma protein extravasation (PPE) which was mimicked by N6-2-(4-aminophenyl)-ethyladenosine (APNEA). The PPE produced by IB-MECA was not affected by either 8-PT or CGS15943A, but was virtually abolished by cyproheptadine and in rats pre-treated with Compound 48/80. CONCLUSIONS: These results indicate that stimulation of adenosine A3 receptors both enhances degranulation in vitro and directly produces degranulation of rat mast cells in vivo.

Adenosine↗
PubMed1996

Inhibition of PAF-, LPS-, and cytokine-induced granulocyte accumulation in guinea pig lung by dexamethasone: evidence that inhibition of IL-5 release is responsible for the selective inhibition of eosinophilia by glucocorticoids in guinea-pigs.

The potency of dexamethasone has been determined as an inhibitor of intratracheally administered platelet activating factor- (PAF), or interleukin (IL)-5-induced eosinophilia, and of lipopolysaccharide-(LPS), tumour necrosis factor alpha-(TNF alpha) or cytokine-induced neutrophil chemoattractant- (CINC) induced neutrophilia in guinea-pig lungs. Dexamethasone was a potent inhibitor of PAF- induced eosinophil accumulation, but higher doses of dexamethasone were required to inhibit IL-5-induced eosinophilia. LPS-induced neutrophilia was less sensitive to the inhibitory effects of dexamethasone, than PAF-induced eosinophilia. Both LPS- and TNF alpha-induced neutrophilia were inhibited by the same doses of dexamethasone. In contrast, higher doses of dexamethasone were required to inhibit CINC-induced neutrophilia. Since data in the literature show that PAF-induced eosinophilia in guinea-pig lungs is dependent on the generation of IL-5, it is concluded that inhibition of this response, by dexamethasone, is due to inhibition of release of IL-5. Similarly, although data in the literature show that LPS-induced neutrophilia is dependent on the generation of TNF alpha, it is concluded that inhibition of this response, by glucocorticoids, is due to an action on an event which occurs after the release of TNF alpha, possibly through inhibition of chemokine release.

Analysis of Variance↗
PubMed1995

Inhibition of some aspects of acute inflammation of guinea-pig lung by intraperitoneal dexamethasone and mifepristone: demonstration of agonist activity of mifepristone in the guinea-pig.

We have determined the inhibitory activity of dexamethasone as an inhibitor of histamine-induced plasma protein extravasation (PPE) in guinea-pig lung and skin, and of lipopolysaccharide (LPS)-induced neutrophilia and platelet activating factor (PAF)-induced eosinophilia in guinea-pig lungs. Dexamethasone inhibited PAF-induced eosinophilia in guinea-pig lung (ED50 1.4 mg/kg i.p.). Higher doses of dexamethasone were required to inhibit LPS-induced neutrophilia (ED50 10.8 mg/kg i.p.). However, at doses up to 150 mg/kg i.p. dexamethasone did not inhibit histamine-induced plasma protein extravasation (PPE) in guinea-pig lung, but did inhibit PPE in guinea-pig skin. These preparations have previously been shown to be equally sensitive to inhibition by the beta 2-adrenoceptor agonist salmeterol. Dexamethasone inhibited PAF-induced eosinophilia (5 mg/kg) or LPS-induced neutrophilia (50 mg/kg) when given 3 h or 1 h prior to challenge. Inhibitory activity was lost when dexamethasone was administered 23 h prior to LPS or 1 h after PAF. The glucocorticoid antagonist mifepristone (1-100 mg/kg i.p.) caused dose-related inhibition of PAF-induced eosinophilia but not of LPS-induced neutrophilia. The highest dose of mifepristone used (100 mg/kg) did not reverse the inhibitory actions of dexamethasone (50 mg/kg) on LPS-induced neutrophilia. We suggest that the different inhibitory activity of dexamethasone in the preparations studied indicates differences in the sensitivity of the target cells involved to inhibition by dexamethasone. We also suggest that inhibition of PAF-induced eosinophilia by mifepristone reflects the partial agonist activity of this agent, demonstrated by others in different experimental systems.

Acute Disease↗
PubMed1993

The pharmacology of salmeterol.

Salmeterol was developed to provide prolonged bronchodilatation to control nocturnal symptoms and improve maintenance therapy in asthmatic patients. Salmeterol is > 10,000 times more lipophilic than salbutamol and has greater affinity for the beta 2-adrenoceptor. Membrane binding is non-competitive and dissociation is slow so that its effects last for many hours. Despite this, salmeterol does not accumulate in tissues. Its mechanism of action can be explained by binding to a specific exo-site domain of the beta 2-receptor protein to produce continuous stimulation of the active site of the receptor, which gives salmeterol a profile of pharmacological activity unlike that of other beta 2-agonists. Due to its potent and prolonged activation of beta 2-adrenoceptors in airway smooth muscle cells, endothelial cells, mast cells and epithelial cells, salmeterol induces prolonged bronchodilatation, reduced vascular permeability, inhibition of inflammatory mediators, stimulation of ciliary function and modulation of ion and water transport across the bronchial mucosa.

Adrenergic beta-Agonists↗
PubMed1993

Comparison of the anti-inflammatory properties of formoterol, salbutamol and salmeterol in guinea-pig skin and lung.

1. We have compared some anti-inflammatory properties of formoterol, salbutamol and salmeterol in guinea-pig skin and lung. 2. Intradermal formoterol (1 x 10(-10) to 1 x 10(-8) mol/site), salbutamol (1 x 10(-8) and 1 x 10(-7) mol/site) and salmeterol (1 x 10(-8) and 1 x 10(-7) mol/site) inhibited bradykinin-induced plasma protein extravasation (PPE) in guinea-pig skin. A maximally effective dose of formoterol (1 x 10(-9) mol/site) and salbutamol (1 x 10(-8) mol/site) inhibited PPE in guinea-pig skin for 2-4 h and 1-2 h respectively, whereas salmeterol (1 x 10(-8) mol/site) was effective for > 6 h. 3. Inhaled formoterol (nebuliser concentration 0.1 to 100 micrograms ml-1 inhibited histamine-induced plasma protein extravasation (PPE) in guinea-pig lung, with significant inhibition being observed at 10 and 100 micrograms ml-1. Formoterol (100 micrograms ml-1) inhibited PPE in guinea-pig lung for 2-4 h, a duration of action intermediate between that previously obtained for salbutamol (1 h) and salmeterol (> 6 h). 4. Formoterol, like salbutamol, had no effect on neutrophil accumulation or granulocyte-dependent PPE (zymosan-induced) in guinea-pig skin. Formoterol inhibited neutrophil accumulation (lipopolysaccharide-induced) in guinea-pig lung but at doses greater than those required to inhibit granulocyte-independent PPE (histamine-induced). In contrast, salmeterol inhibited neutrophil accumulation and granulocyte-dependent PPE in guinea-pig skin and inhibited neutrophil accumulation in guinea-pig lung at doses which inhibit granulocyte-independent PPE. 5. Inhaled formoterol (nebuliser concentration 100 microg ml-1) and salmeterol (100 microg ml-1) both inhibited PAF-induced eosinophil accumulation in guinea-pig lung. However, unlike salmeterol, this effect of formoterol was observed only at suprabronchodilator doses.6. We conclude that to inhibit neutrophil accumulation, at doses which inhibit granulocyte-independent PPE, agonists acting at beta-adrenoceptors on vascular endothelium require a duration of action greater than that of salbutamol and formoterol. However, we speculate that the mechanism of inhibition of eosinophil accumulation in guinea-pig lung by beta2-adrenoceptor agonists may involve an action on beta2-adrenoceptors on a cell type other than the endothelial cell.

Adrenergic beta-Agonists↗
PubMed1992

Inhibition by salmeterol of increased vascular permeability and granulocyte accumulation in guinea-pig lung and skin.

1. The long-acting beta 2-adrenoceptor agonist, salmeterol has been evaluated for its anti-inflammatory effects in the guinea-pig lung and skin. 2. Salmeterol, administered in bronchodilator doses to conscious guinea-pigs by both oral (0.01-1.0 mg kg-1) and inhaled (nebulizer concentration, 0.001-1.0 mg ml-1) routes, inhibited histamine-induced plasma protein extravasation (PPE) into the airway lumen. 3. Inhibition of PPE by salmeterol was long-lasting (greater than 6 h) and was inhibited by prior administration of propranolol (1 mg kg-1, s.c.), indicating an effect mediated by beta-adrenoceptors. 4. Inhaled salbutamol (nebulizer concentration, 0.001-1.0 mg ml-1) also inhibited PPE in guinea-pig lung but, in contrast to salmeterol, this effect was short-lived with substantial loss of activity 2 h after administration. 5. Inhaled salmeterol (0.1 mg ml-1) and salbutamol (1.0 mg ml-1) inhibited the accumulation of neutrophils in guinea-pig lung in response to lipopolysaccharide (100 micrograms ml-1). Salmeterol, but not salbutamol, inhibited the infiltration of eosinophils into the airway lumen in response to platelet activating factor (100 micrograms ml-1). These effects of salmeterol were blocked by prior administration of propranolol (5 mg kg-1, s.c.), indicating that they were also beta-adrenoceptor-mediated. 6. Oral salmeterol (10 mg kg-1, p.o.), but not salbutamol (10 and 100 mg kg-1, p.o.), inhibited zymosan-induced granulocyte accumulation and PPE in guinea-pig skin. Lower doses of salmeterol (0.1 and 1 mg kg-1) inhibited PPE, but not granulocyte accumulation.The effects of salmeterol were blocked by prior administration of propranolol (1mgkg-', s.c.). Both salmeterol and salbutamol inhibited histamine-induced PPE in guinea-pig skin.7. Intradermal salmeterol (10-'mol per site), but not salbutamol, was also effective in inhibiting zymosan-induced granulocyte accumulation and PPE in guinea-pig skin.8. It is concluded that salmeterol, at bronchodilator doses in the guinea-pig, inhibits granulocyte accumulation and PPE, possibly by an action on the vasculature. As this profile of activity is not shared by the shorter-acting compound, salbutamol, it would seem that anti-inflammatory activity is associated with beta-adrenoceptor agonism of long duration. The implications of these findings for the use of salmeterol in the treatment of bronchial asthma are discussed.

Adrenergic beta-Agonists↗
PubMed1991

Prostaglandin (PG) modulation of bradykinin-induced hyperalgesia and oedema in the guinea-pig paw--effects of PGD2, PGE2 and PGI2.

The relative potencies of PGD2, PGE2 and PGI2 in potentiating bradykinin-induced hyperalgesia and oedema were determined in the paws of aspirin-treated guinea-pigs. PGE2 and to a lesser degree PGD2 but not PGI2, potentiated bradykinin-induced hyperalgesia, whereas PGD2, but not PGE2 or PGI2, potentiated oedema. These findings differ from those in other species, and possibly reflect interspecies differences in modulation of inflammatory reactions by prostanoids.

Animals↗
PubMed1988

Litigation and complaints procedures: objectives, effectiveness and alternatives.

Recent debates about redress mechanisms for medical accident victims have been sidetracked by fears of an American-style medical malpractice crisis. What is required is a framework within which the debate can resume. This paper proposes such a framework by focusing on the compensation and deterrence objectives and placing them in the wider context of the social costs of providing medical services. The framework is then used to assess and compare the effectiveness of differing approaches. In particular, the American and British experiences of litigation, including the concept of 'defensive medicine', are evaluated. Also discussed briefly are alternatives to court-based complaints procedures including 'no-fault' schemes, professional ethics and internal complaints mechanisms.

Compensation and Redress↗
PubMed1981

The release and metabolism of [3H]arachidonic acid from guinea pig perfused lungs in vitro: a simple method for the study of the action of drugs on the release and metabolism of arachidonic acid.

We have adapted the radiolabeled, perfused organ technique of Isakson et al. (1976) for use with guinea pig lungs. After incorporation [3H]arachidonic acid was taken up into the lung phospholipids. The injection of bradykinin (1-100 microgram) caused a dose-related release of tritium [3H]. The composition of the tritium released by the lungs was found to be a mixture of cyclo-oxygenase and lipoxygenase metabolites together with some unchanged arachidonic acid. In order to demonstrate how this technique can be utilized to study the effect of drugs on arachidonic acid release and metabolism, the actions of mepacrine and indomethacin on bradykinin-induced [3H] release were studied. Mepacrine (50-200 microM) produced a concentration-related reduction in bradykinin-induced [3H] release whereas indomethacin (10 microM) was without effect on [3H] release. Indomethacin did, however, reduce the levels of cyclo-oxygenase products in the perfusate.

Animals↗