Clive Robinson

The Bronchoconstrictor Effect of Inhaled Prostaglandin D2 in Normal and Asthmatic Men

Although prostaglandin D2 is the most abundant prostanoid generated by human lung mast cells and causes bronchoconstriction in animals, its effects have not been studied in human beings. We have compared the effects of inhaled prostaglandin D2 and prostaglandin F2 alpha on specific airway conductance in seven normal subjects and seven patients with mild allergic asthma. In dose-response studies in normal subjects, prostaglandin D2 caused a significant (20 +/- 6 per cent) fall in specific airway conductance after the two highest concentrations (250 and 500 micrograms per milliliter), whereas prostaglandin F2 alpha had no effect. In the asthmatic subjects, both prostaglandin D2 and prostaglandin F2 alpha caused a dose-related fall in specific airway conductance, starting at the lowest concentration of 4 micrograms per milliliter. Prostaglandin D2 was 3.5 times more potent than prostaglandin F2 alpha. In a single-dose study of both drugs (250 micrograms per milliliter), a minor fall in specific airway conductance occurred with prostaglandin D2 in the normal subjects, and a larger fall occurred with both drugs in the asthmatic subjects. Maximum effects were seen at three minutes: there was a 75 +/- 5 per cent fall with prostaglandin D2 and a 33 +/- 8 per cent fall with prostaglandin F2 alpha. These results suggest that prostaglandin D2 may be involved in the pathogenesis of bronchoconstriction in allergic asthma.

Differential release of histamine and eicosanoids from human skin mast cells activated by IgE‐dependent and non‐immunological stimuli

1 Cells were dispersed from human foreskin using a mixture of collagenase and hyaluronidase and separated into mast cell‐depleted (<1%) or enriched (>75%) preparations by density‐gradient centrifugation. 2 Challenge of gradient fractions with ∍‐chain‐specific anti‐human IgE stimulated the release of histamine, prostaglandin D2 (PGD2) and leukotriene C4 (LTC4). The release of eicosanoids was significantly correlated with that of histamine, suggesting that they are derived from the mast cell population of the dispersate. In highly purified (76.2 ± 4.2%) mast cell preparations, maximum net release of histamine, PGD2 and LTC4 was 3432 ± 725, 84.9 ± 10.8 and 6.6 ± 1.2 pmol/106 nucleated cells. 3 The non‐immunological stimuli substance P, vasoactive intestinal peptide (VIP), somatostatin, compound 48/80, morphine and poly‐L‐lysine released similar amounts of histamine to anti‐IgE, but 12 to 21 fold less PGD2 and LTC4. 4 These studies suggest that IgE‐dependent and non‐immunological stimuli activate human skin mast cells by different secretory mechanisms, a hypothesis supported by our previous findings of differences in Ca2+ requirements and time‐course of histamine release. Activation by the non‐immunological mechanism may be of importance in vivo due to the close anatomical association between skin mast cells and dermal nerve‐terminals containing neuropeptides.

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.

The bronchial epithelium as a target for inflammatory attack in asthma

The authors acknowledge grant support from the Medical Research Council, British Lung Foundation and Eli Lilly. They would also like to thank Dr D. Garrod for kindly donating some of the monoclonal antibodies used and Ms J. Baker and the staff at the Southampton General Hospital electronmicroscopy unit for their technical assistance.

The mast cell as a primary effector cell in the pathogenesis of asthma

Holgate, S T Hardy, C Robinson, C Agius, R M Howarth, P H Review United states The Journal of allergy and clinical immunology J Allergy Clin Immunol. 1986 Feb;77(2):274-82.

Relationship between Mediator Release from Human Lung Mast Cells in vitro and in vivo

There is now compelling evidence to incriminate bronchial mast cells in the pathogenesis of bronchoconstriction of allergic asthma. Human mast cells isolated from lung tissue or bronchoalveolar lavage release histamine and generate eicosanoids upon IgE-dependent activation. In this paper we present data that raise doubts about the significance of phospholipid methylation in IgE-dependent activation-secretion coupling and provide evidence that drugs such as 3-deazaadenosine inhibit mediator secretion by inhibiting phosphodiesterase, in addition to inhibiting putative methylation pathways. Activation of human mast cells and basophils also stimulates adenylate cyclase to increase levels of cyclic AMP, which, on the basis of pharmacological manipulation with purine nucleosides, we believe is involved in the progression of the secretory response. Human lung cells also generate both cyclo- and lipoxygenase products of arachidonate upon Ca++-dependent stimulation with complex interactions occurring between these pathways in the presence of the leukotriene inhibitor, Piriprost. The role of mast cells in the immediate airway response to inhaled allergens in asthma was demonstrated by showing an interaction between nonspecific bronchial reactivity and mast cell reactivity in predicting the airway response upon antigen inhalation. Further confirmation of this concept was obtained by showing an inverse relationship between the release of histamine and neutrophil chemotactic factor (NCF) into the circulation induced by antigen challenge, and nonspecific airway reactivity. The identification of significant increases in circulating mediators following antigen provocation of patients with seasonal asthma enabled the effects of drugs used in the treatment of asthma to be compared on airway calibre and mast cell mediator release. Sodium cromoglycate partially inhibited the airway and plasma histamine responses with antigen, but totally inhibited the increases in NCF. Salbutamol completely inhibited all responses, while ipratropium bromide, which produced the same bronchoconstriction as achieved with salbutamol, had no effect. The potent H1-antagonist astemizole partially inhibited bronchoconstriction without affecting histamine release. Antigen provocation produced a significant increase in circulating levels of the 13,14-dihydro-15-keto metabolite of PGF2 alpha which could originate from mast cell-derived PGD2. In both retrospective and prospective studies, a close relationship was shown between nonspecific bronchial reactivity and resting airway calibre in asthma.(ABSTRACT TRUNCATED AT 400 WORDS)

Pulmonary synthesis, release, and metabolism of prostaglandins

Immunologic or calcium-dependent activation of proteolytically dispersed human lung cells containing 5% mast cells causes the release of large amounts of PGD2 and TxB2. In cell purification experiments, only those fractions containing mast cells had the capacity to generate PGD2 and release histamine with IgE-dependent activation. The cells of origin of T X B2 are likely to be cells of the monocyte-macrophage series, although additional eicosanoid release may occur from immunologically activated lymphocytes and eosinophils. In men who have asthma, inhalation of low concentrations of PGD2 results in bronchoconstriction, whereas higher concentrations of PGD2 are needed to produce bronchoconstriction in normal subjects. Subjects with asthma exhibited 3.5-fold greater responsiveness to inhaled PGD2 than to PGF2 alpha. These observations demonstrate that PGD2 is the most potent bronchoconstrictor prostanoid tested in man. In both normal subjects and subjects with asthma, a single inhalation of PGF2 alpha resulted in a doubling in plasma levels of 13,14-dihydro-15-keto-PGF2 alpha. Plasma levels of this metabolite did not change after PGD2 inhalation. These results indicate that the 11-keto reduction of PGD2 to PGF2 alpha with subsequent inactivation is not important in the initial metabolism of PGD2.

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.

In vitro modulation of the eosinophil-dependent enhancement of the permeability of the bronchial mucosa.

1 Basolateral to apical albumin flux has been measured in sheets of bovine bronchial and tracheal mucosa mounted in vitro. 2 Addition of guinea‐pig peritoneal eosinophils or neutrophils to the basolateral side of such tissues had no significant influence on the transmucosal flux of albumin in either the bronchial or tracheal mucosa. 3 Stimulation of eosinophils or neutrophils by the calcium ionophore A23187, or by their presentation to an opsonized airways mucosa, resulted in a significant increase in the transbronchial flux of albumin. This effect was seen after only 60 min incubation of the leucocytes with the bronchial mucosa, and was no greater when the contact time was extended to 180 min. Incubation of bronchial mucosal tissues with 1 mg ml−1polyarginine for 3 h produced a significant increase in albumin flux, but was ineffective at 0.5 mg ml−1. 4 In contrast to the bronchial mucosa, the tracheal mucosa appeared resistant to the effects of stimulated eosinophils and neutrophils. 5 The lipoxygenase inhibitor AA‐861 failed to influence the ability of eosinophils to augment the transmembrane flux of albumin. However, insertion of a Millipore filter mask between the eosinophils and the bronchial mucosa significantly inhibited the eosinophil‐dependent enhancement of mucosal permeability. 6 The broad spectrum antiproteinase α2‐macroglobulin achieved almost total ablation of the action of stimulated eosinophils in the bronchial mucosa. These results suggest that proteinases may make a significant contribution to the genesis of epithelial injury, whereas leukotrienes do not.

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 < 0.001) and also between PGD2 release and mast cell number (r = 0.7475, P < 0.001). 5 These data provide the first direct evidence of the capacity of the human cutaneous mast cell to synthesize and release PGD2.