Immunological and non-immunological release of leukotrienes and histamine by guinea-pig heart

Fragments of sensitized guinea-pig heart (1 g wet weight) were incubated with 5 micrograms/ml of antigen for up to 30 min, and the incubation media were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC) for the presence of leukotrienes LTB4, LTC4, LTD4 and LTE4. Maximum release of LTB4, LTC4 and LTD4 was observed after 15 min (32.8 +/- 4, 8 +/- 2 and 9.5 +/- 2.5 pmol/g tissue wet weight, respectively, mean +/- SEM). At the same time, histamine was also released, reaching a maximum at 5 min (290 +/- 63 pmol/g tissue) as determined by radioenzymatic assay. Similarly, the non-sensitized guinea-pig heart stimulated with the ionophore A23187 (4 microM) released LTB4, LTC4, LTD4 and LTE4, as well as the 5-hydroxy-eicosatetraenoic acid (5-HETE), 12-HETE, and 15-HETE as determined by RP-HPLC. The release of LTB4, LTC4 and LTD4 was at a maximum after 10-15 min of stimulation (63 +/- 8.4, 10.7 +/- 2 and 17.5 +/- 4 pmol/g tissue). The ionophore also stimulated the release of histamine in heart tissue, with a peak maximum after 5 min (325 +/- 77 pmol/g tissue). These data demonstrate that heart as well as pulmonary tissues release significant amounts of leukotrienes and histamine during immunological or non-immunological challenges.     

A comparative study on the release of leukotrienes and histamine by guinea pig lung and trachea after challenge with antigen or stimulation with ionophore A23187 or melittin

The release of leukotrienes and histamine from guinea pig lung and trachea after immunological and nonimmunological stimulation were compared. Antigen, ionophore A23187 and melittin caused the release of leukotriene (LT)B4, LTC4, LTD4 and LTE4 from lung and trachea as determined by reverse-phase high performance liquid chromatography (RP-HPLC) and bioassay. The release of LTB4 by lung and trachea was maximum after 5 min of ionophore stimulation (128 +/- 40 and 142 +/- 29 pmol/g tissue, respectively). Lung, but not trachea, also released the 20-OH-LTB4 and 20-COOH-LTB4. The release of LTC4 by lung tissues was maximum after 5 min, whereas maximal tracheal responses occurred at 10 min (27 +/- 11 and 9 +/- 3.5 pmol/g tissue, respectively). Maximal release of LTD4 by lung and trachea respectively occurred after 10 and 15 min (103 +/- 21 and 20 +/- 6 pmol/g tissue, respectively). The release of LTD4 in response to ionophore by both tissues decreased after 15 min, whereas the release of LTE4 continued to increase. Release of leukotrienes from melittin stimulated lung was 2-3-fold less than in ionophore stimulation. In contrast, tracheal responses to melittin and ionophore for the release of LTB4 were equivalent, whereas release of peptidoleukotrienes in response to melittin was approximately 50% that resulting from ionophore. Antigen challenge was the least potent stimulus for LTB4 release in both tissues, whereas it was at least as potent as melittin for the release of peptidoleukotrienes. The release of histamine by lung tissue was approximately 2-3-fold greater than by trachea (7 +/- 1 and 2 +/- 0.5 nmol/g tissue, respectively) after 5 min of stimulation with either ionophore, melittin or antigen. These data demonstrate that lung tissues and trachea respond to immunologic stimulations by releasing the mediators of inflammation and immediate hypersensitivity. The lung releases peptidoleukotrienes and histamine 2-5-fold greater than the trachea, whereas the release of LTB4 in both tissues are approximately equal.     

Release of 15-hydroxyeicosatetraenoic acid (15-HETE) and prostaglandin E2 (PGE2) by cultured human bronchial epithelial cells

Human bronchial epithelial cells were isolated from macroscopically normal bronchi obtained from lobectomy specimens. Cells were grown in nutrient F12 medium, and after the third or fourth subculture they were stimulated with arachidonic acid, histamine, leukotrienes (LT) C4, D4, or E4, prostaglandin (PG) D2, anti-IgE, acetylcholine, bradykinin, or phorbol myristate acetate (PMA). Neither mast cell mediators (i.e., histamine, LTC4, LTD4, LTE4, or PGD2) nor anti-IgE stimulated the release of arachidonic acid metabolites from the epithelial cells. However, arachidonic acid, acetylcholine, bradykinin, and PMA stimulated the release of 15-hydroxyeicosatetraenoic acid (15-HETE) as major and prostaglandin E2 (PGE2) as minor products. The maximal release of 15-HETE and PGE2 occurred in 1 h with arachidonic acid stimulation and in 2 h with other stimuli. Arachidonic acid at 30 microM caused the release of 258 +/- 76 ng and 29 +/- 15 ng (n = 12) of 15-HETE and PGE2, respectively, from 10 x 10(6) epithelial cells, whereas acetylcholine, bradykinin, or PMA caused the release of approximately 2- to 10-fold less 15-HETE and PGE2. These results demonstrate that human bronchial epithelial cells selectively generate 15-HETE as the predominant arachidonic acid product and PGE2 as a minor metabolite. The role of bronchial epithelial cells and their mediators in the pathogenesis of bronchial hyperresponsiveness needs further study.     

Effect of 15-hydroxyeicosatetraenoic acid (15-HETE) on anti-immunoglobulin E- and calcium ionophore-induced histamine release from human leukocytes. Comparison with the effects of eicosatetraynoic acid and nordihydroguaiaretic acid

15-Hydroxyeicosatetraenoic acid (15-HETE) was prepared by soybean lipoxygenase-mediated oxygenation of arachidonic acid to 15-hydroperoxyeicosatetraenoic acid (15-HETE) and subsequent reduction by NaBH4. 15-HETE was identified, purified and proved as biologically active by thin layer chromatography, high pressure liquid chromatography, gas chromatography/mass spectrometry and biological experiments on horse thrombocytes and rabbit peritoneal leukocytes. 15-HETE (0.1-40 microM) was added to peripheral leukocytes of 48 human donors (33 atopics, 15 nonatopics) which were challenged with rabbit anti-human-IgE or calcium ionophore A 23187. Its effect was compared with the effects of nordihydroguaiaretic acid (NDGA) and eicosatetraynoic acid (ETYA). NDGA and ETYA markedly inhibited histamine release (17 microM: 74 +/- 11 and 39 +/- 14,3%, respectively), whereas 15-HETE neither stimulated nor inhibited spontaneous anti-IgE- or calcium ionophore A 23187-induced histamine release.     

Comparative actions of biologic and synthetic leukotrienes on isolated human bronchus and rat mast cells

The effects of biologically prepared leukotriene C4 (LTCb) and leukotriene D4 (LTDb), obtained from rat monocytes stimulated with the calcium ionophore A23187, were compared with those of chemically synthetized leukotrienes (LTCs and LTDs) using two in vitro systems. All four leukotriene preparations (10(-10) to 6 X 10(-6) M) showed equal activity upon human bronchi, inducing slow, sustained contractions. LTCb alone (10(-7) to 6.9 X 10(-7) M) elicited histamine release and enhanced compound 48/80-induced release in a dose-dependent manner from rat mast cells. In contrast, LTDb alone was without effect but inhibited release caused by 48/80. FPL 55712 failed to block the LTCb and LTDb effects on the release process. The synthetic leukotrienes neither caused histamine release nor modulated 48/80-induced release from rat mast cells. We conclude that biologic and synthetic leukotrienes exhibit comparable contractile activity on isolated human bronchi but only biologic preparations modulate histamine release by previously unappreciated substances that isolate with the biologic leukotrienes.     

Isolated early response after nasal allergen challenge is sufficient to induce nasal hyperreactivity.

Ten rhinitic patients allergic to grass pollen were challenged with histamine intranasally 24 hours before and 24 hours after nasal provocation with grass pollen. Up to ten hours after allergen provocation nasal lavage fluid was obtained to characterize early and late phase reactions by measuring the levels of histamine and leukotrienes as indicators of mediator release, and albumin as a marker of increased vasopermeability. Ten minutes after allergen challenge with 10,000 BU grass pollen extract LTC4,D4, and albumin significantly increased from 62 to 576 pg/mL (P = .008) and from 15 to 81 micrograms/mL (P = .008), respectively, without significant changes after placebo challenge a week earlier. Although the patients showed increased responsiveness to histamine after allergen challenge compared with a placebo-challenged control group (P = .02), one patient only demonstrated a late phase nasal allergic reaction characterized by recurrence of clinical symptoms eight to ten hours after allergen challenge and recurrence of mediators in lavage fluid. It is concluded that an isolated early response after allergen challenge is sufficient to induce nasal hyperreactivity. A biochemically or clinically defined late phase allergic reaction does not necessarily accompany allergen-induced hyperreactivity.     

Studies on the biosynthesis of leukotrienes in guinea pig lung in vitro by use of high-performance liquid chromatography

The biosynthesis of leukotrienes (LTs) and 5-hydroxy-6,8,-11,14(E,Z,Z,Z)-eicosatetraenoic acid (5-HETE) in perfused guinea pig lung was studied by reversed phase-high-performance liquid chromatography (RP-HPLC). Perfusion of lungs with a 20 microM solution of ionophore A23187 for 25 minutes induced a sustained release of 5S-hydroxy-6R-S-cysteinylglycyl-7,9,11,14-(E,E,Z,Z)-eicosatetraenoic acid (LTD4) and 5S,12R-dihydroxy-6,8,10,14(Z,E,E,Z)-eicosatetraenoic acid (LTB4). The perfusion of 60 microM of arachidonic acid together with the ionophore only slightly increased the synthesis of LTD4 and LTB4 in comparison with the effect of the ionophore alone but markedly stimulated the release of 5-HETE that was not detectable under other experimental conditions. Immunologic challenge of the lung by continuous perfusion of ovalbumin to previously sensitized guinea pigs induced the release of 50 to 150 pM of LTB4 and 15 to 50 pM of LTD4 during a 25-minute period. Antigen was a less potent stimulus than the ionophore that caused the release of 500 to 900 pM of LTB4 and 100 to 250 pM of LTD4 during 25-minutes of perfusion. None of the above-mentioned metabolites were detected when lungs were perfused with arachidonic acid alone, indicating that the synthesis of 5-lipoxygenase products required activation of the lung. In addition to 5-lipoxygenase products, the cyclooxygenase products 12-hydroxy-5,8,10-(Z,E,E)-heptadecatrienoic acid and 12-keto-5,8,10-(Z,E,E)-heptadecatrienoic acid were analyzed by RP-HPLC in guinea pig lung perfusates. HPLC analysis provided quantitative data on the release of several arachidonic acid metabolites by lungs.(ABSTRACT TRUNCATED AT 250 WORDS)     

The antiallergic agent amoxanox suppresses SRS-A generation by inhibiting lipoxygenase

Amoxanox has potent antiallergic activity because it inhibits the release of chemical mediators such as histamine and leukotrienes. We studied the in vitro effect of amoxanox on arachidonic acid metabolism, including the lipoxygenase and cyclooxygenase pathways. Amoxanox inhibited calcium ionophore A23187-induced formation of 5-HETE, LTB4, SRS-A (LTC4, LTD4 and LTE4), and 12-HETE in rat peritoneal resident monocytes. These results indicate that amoxanox inhibits 5- and 12-lipoxygenases. The compound, however, did not affect the formation of TXB2 or 6-keto-PGF1 alpha in guinea pig lung fragments and PGE2 or PGF2 alpha in bovine seminal vesicles, suggesting that it did not inhibit cyclooxygenase. These results show that the antiallergic action of amoxanox is associated, at least in part, with the reduction of leukotrienes due to the inhibition of lipoxygenases.     

Stimulus-dependence and time-course of histamine and leukotriene release from chopped and dispersed human lung tissue

The calcium ionophore A23187 and anti-human IgE provoked a dose-dependent release of histamine and cysteinyl-leukotrienes (LTC₄, LTD₄ and LTE₄) from dispersed human lung cells. Optimal release of histamine peaked at 3 min after challenge whereas the release of cysteinyl-leukotrienes peaked at 30 min. The molar ratio between released histamine and cysteinyl-leukotrienes was approximately 1001. The ionophore, but not anti-IgE caused additional formation of LTB₄ in the dispersed cells or the chopped lung, indicating that this chemoattractant is formed from cells not primarily activated by IgE-dependent mechanisms. Indomethacin failed to alter release of histamine or leukotrienes from dispersed cells, whereas further inhibition of lipoxygenases by NDGA abolished leukotriene formation and reduced the release of histamine.     

In vivo and ex vivo inhibitory effects of loratadine on histamine release in patients with allergic rhinitis

Background The aim of this study was to evaluate the in vivo and ex vivo effects of the H.-antagonist loratadine on histamine release.
Methods The study was designed as a double-blind, crossover trial. Ten patients with allergic rhinitis due to Dermatophagoides pteronyssinus were treated with loratadine (10 mg daily p.o.) and with placebo for 1 week, with a 2-week interval between the two treatments. Nasal lavages with saline solution were done before and after challenge with the relevant allergen at the end of treatments with loratadine and placebo. Venous blood was taken after treatments, and basophil histamine release induced by anti-IgE (10 μg/ml), N-formyl-methionyl-leucyl-phenylalanine (fMLP, 1 μM). and Ca²⁺ ionophore A23187 (1 μM) was evaluated by ati automated fluorometric method.
Results Treatment with loratadine attenuated early antigen-tnduced nasal obstruction, rhinorrhea. and itching. Nasal symptoms were accompanied by a significant histamine release in the nasal lavages collected 5 min after stimulation when the patients received placebo (median 4 ng/ml, range 1-28; P<0.05). After treatment with loratadine, histamine release in the 5-min postchallenge lavages was almost abrogated (median 0.5 ng/ml, range 0-3; P<0.01 vs placebo). Median anti-IgE-induced histamine release from basophils was 41.9% (range 27.8-79.2) after placebo and 30.0% (range 1.7-73.3, P < 0.05) after loratadine. Active treatment exerted an inhibitory effect also on basophil histamine release induced by fMLP and Ca²⁺ ionophore A23187.
Conclusions Treatment for 1 week with loratadine reduces allergen-mduced nasal symptoms and inhibits in vivo and ex vivo histamine release in patients with allergic rhinitis.     

Release of arachidonic acid metabolites by human monocytes or lymphocytes: effect of treatment with interferon on stimulation by phorbol ester or calcium ionophore

The simultaneous production of prostaglandins, leukotrienes, and hydroxyeicosatetraenoic acids was studied in human peripheral blood monocytes obtained by counter-current centrifugal elutriation. Monocytes prelabeled for 4 hr with [3H]arachidonic acid (AA) released label into the surrounding medium in response to treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) or calcium ionophore (A23187). High-performance liquid chromatography of monocyte supernatants demonstrated that labeled compounds included those which eluted with authentic standards for thromboxane B2, 12-L-hydroxy-5,8,10-heptadecatrienoic acid (HHT), 6-keto-prostaglandin F alpha, prostaglandin E2, and 15-hydroxyeicosatetraenoic acid (HETE). 5-HETE and leukotriene B4 (LtB4) were detected only in response to ionophore treatment. Highly purified lymphocytes did not convert AA to autocoids, despite the release of free arachidonate in response to either stimulus. Pretreatment of monocytes with recombinant human interferon (IFN)-gamma or IFN-alpha for 18 hr resulted in enhanced release of labeled arachidonic acid and increased conversion to autocoids after TPA or ionophore stimulation. Absolute amounts of prostaglandin E2 produced in response to TPA or ionophore treatment were increased as well. These results demonstrate the autocoid profile released by stimulated human monocytes and illustrate the effects of IFN treatment on the production of lipoxygenase metabolites of arachidonic acid as well as cyclooxygenase products.     

Characterization of arachidonic acid metabolism, superoxide production, and bacterial killing in bovine circulating neutrophils and elicited alveolar neutrophils

The in vitro generation and release of 5-lipoxygenase metabolites of arachidonic acid by bovine peripheral blood neutrophils and alveolar neutrophils elicited with either a heat-killed bacterium, Haemophilus somnus, or platelet-activating factor, were compared. After stimulation with calcium ionophore A23187 for 2.5-60 min, up to 4.5 +/- 0.7 (mean +/- SEM) ng of LTB4 per 10(6) cells was released into the media by circulating neutrophils. LTB4 release by alveolar neutrophils was significantly less (P less than .05) than that of peripheral blood neutrophils from the same animal; 5-HETE release by circulating neutrophils was maximal after 5 min stimulation by ionophore (1.2 +/- 0.1 ng/10(6) cells) but was not identified in cell culture media after 20 min. Alveolar neutrophils released similar amounts of 5-HETE when compared to circulating neutrophils, and release of 5-HETE by alveolar neutrophils was maximal after 5 min of stimulation. However, the 5-HETE released into the culture media persisted throughout the 60 min time period at levels which were maximal (1.5 +/- 0.2 to 1.8 +/- 0.3 ng/10(6) cells). Bacterial killing and the release of superoxide anion were not different between the two cell populations.     

Generation and Metabolism of Leukotrienes and Release of Histamine from Human Dispersed Tonsillar Cells

We studied the generation and metabolism of leukotrienes (LT) and the release of histamine by human tonsillar cell suspensions. Human tonsils were dissected and mechanically dispersed. This procedure yielded a single cell suspension with 1.6 +/- 0.5 X 10(8) cells/g tissue consisting of 97.3 +/- 0.4% lymphocytes, 1.4 +/- 0.3% granulocytes, 1.3 +/- 0.3% macrophages/monocytes, and 0.03 +/- 0.02% mast cells/basophils. The cells were stimulated either with Ca-ionophore A 23187, melittin, or anti-human IgE. Determination of the 5-lipoxygenase products LTB4 and LTC4 was performed with specific radioimmunoassays (RIA), and histamine release was measured by the fluorophotometric technique. A time- and dose-dependent release of the mediators was monitored. LTB4 exceeded the amount of LTC4 in the supernatants. The concentration of leukotrienes ranged between 0.8 and 5.4 ng LTB4/1 X 10(8) cells or 0.5 and 1.5 ng LTC4/1 X 10(8) cells, depending on the stimulus. Histamine release after stimulation ranged between 25 and 35% of the total histamine content, whereas buffer controls amounted to 17%. The incubation of the cells (1 X 10(8) with exogenously added LTB4 resulted in the formation of omega-oxidated products (20-OH and 20-COOH-LTB4) and a novel unpolar metabolite, as identified by thin layer chromatography. This metabolite was not immunoreactive in the LTB4-RIA used. LTC4 and LTD4 were converted into LTE4 when added either to sonicated cells or to the cell-free supernatants of prestimulated tonsillar cells, indicating the release of gamma-glutamyltranspeptidase and dipeptidase, respectively. Our data clearly demonstrate the generation and metabolism of the 5-lipoxygenase products LTB4 and LTC4 as well as the release of histamine from human dispersed tonsillar cells, suggesting that they have a modulatory function with respect to the inflammatory potential at local sites.     

Effect of deuterium oxide on leukotriene C4 generation in immunologically stimulated human leukocytes

Addition of deuterium oxide (D2O), 6-36%, resulted in a dose-dependent increase in allergen- or anti-IgE-induced leukotriene C4 (LTC4) generation from human basophils. In the presence of 36% D2O, the enhancement was 260 +/- 135% for allergen stimulation and 480 +/- 152% for anti-IgE stimulation as compared with the control incubated in normal buffer. The increasing effect of D2O on LTC4 generation from basophils was completely reversed by washing the cells before incubation with allergen. Vinblastine as well as colchicine, at a concentration of 100 microM, counteracted the effect of D2O. The enhanced release of histamine and LTC4 from basophils challenged with allergen was suppressed by Dimaprit, a histamine H2 receptor agonist, at a concentration required to inhibit the release by 50% of 5 X 10(-5) M for histamine and 10(-5) M for LTC4. These observations suggest that microtubules may be involved in LTC4 generation from immunologically stimulated basophils.     

Mediator release after allergic and physical nasal challenges

Intranasal challenge of allergic subjects with the allergen to which they are sensitive rapidly produces sneezing, rhinorrhea, and airway obstruction. Nasal washings during the response reveal increased amounts of histamine, leukotrienes, prostaglandin D2 (PgD2), kinins and TAME-esterase in secretions. Although appearance of these mediators ceases shortly after challenge, many patients have a recrudescence of symptoms 3-11 h later, with a reappearance of the same mediators with the notable exception of PgD2. Subjects who respond to exposure to cold with rhinorrhea and nasal stuffiness were subjected to a 15-min nasal challenge with cold (-3-10 degrees C) dry (10% relative humidity) air and also responded with typical symptoms and the appearance of histamine, PgD2, TAME-esterase and leukotrienes. Nasal challenge with ragweed pollen by patients on immunotherapy showed that the threshold for response was greater and the amount of mediator found was less after treatment.     

The effect of azelastine on the early allergic response

To study the effect of azelastine on the immediate reaction to nasal allergen challenge, we performed a double blind, placebo-controlled cross-over clinical trial. Thirteen subjects with seasonal allergic rhinitis underwent nasal challenge with antigen 4 hr after a single oral 2 mg dose of azelastine. The response was monitored by counting the number of sneezes and by measuring the levels of histamine, prostaglandin D2, immunoreactive sulphidopeptide leukotrienes, kinis and TAME-esterase activity in recovered nasal lavages. After a single dose of azelastine, there was a significant reduction in sneezing (10 vs 2, P = 0.01) and in the median levels of recovered TAME-esterase activity (63.1 vs 17.5 c.p.m. x 10(-3), P = 0.01), immunoreactive sulphidopeptide leukotrienes (7.5 vs 2.1 ng/ml, P = 0.03) and kinins (1370 vs 251 pg/ml, P = 0.03), with no significant reduction in the median levels of histamine (3.7 vs 1.2 ng/ml, P = 0.2) and prostaglandin D2 (70 vs 70 pg/ml, P = 0.2) compared to placebo (numbers represent total increase over diluent challenge). These results suggest that azelastine does not inhibit mast cell activation but affects the consequences of released histamine, namely sneezing, increased vascular permeability and the generation of kinins. The results further suggest that other cells, in addition to mast cells, might be responsible for the generation of leukotrienes during the early allergic response, and that azelastine reduces their ability to generate this mediator or that inhibition of leukotriene release from mast cells occurs at lower drug concentrations.     

Blockade of superoxide generation prevents high-affinity immunoglobulin E receptor-mediated release of allergic mediators by rat mast cell line and human basophils

BACKGROUND: Previous studies have shown that rat peritoneal mast cells and mast cell model rat basophilic leukaemia (RBL-2H3) cells generate intracellular reactive oxygen species (ROS) in response to antigen challenge. However, the physiological significance of the burst of ROS is poorly understood. OBJECTIVE: The present study was undertaken to investigate the role of superoxide anion in mediator release in rat and human cell systems. METHODS: RBL-2H3 cells were directly stimulated with anti-rat FcepsilonRI alpha-subunit monoclonal antibody (mAb). For the analysis of human cell system, leucocytes were isolated by dextran sedimentation from healthy volunteers or from patients, and challenged either with anti-human FcepsilonRI mAb or with the relevant antigens. Superoxide generation was determined by chemiluminescence-based methods. The releases of histamine and leukotrienes (LT)s were determined by enzyme-linked immunosorben assay (ELISA). RESULTS: Cross-linking of FcepsilonRI on RBL-2H3 cells or on human leucocytes from healthy donors by the anti-FcepsilonRI mAb resulted in a rapid generation of superoxide anion, as determined by chemiluminescence using superoxide-specific probes. Similarly, leucocytes from patients generated superoxide anion in response to the challenge with the relevant allergen but not with the irrelevant allergen. Furthermore, diphenyleneiodonium (DPI), a well-known inhibitor of flavoenzymes suppressed the superoxide generation and the release of histamine and LTC4 induced by the anti-FcepsilonRI mAb or by allergen in parallel. CONCLUSION: These results indicate that both RBL-2H3 cells and human basophils generate superoxide anion upon FcepsilonRI cross-linking either by antibody or by allergen challenge and that blockade of the generation prevents the release of allergic mediators. The findings strongly support the role of superoxide generation in the activation of mast cells and basophils under both physiological and pathological conditions. The findings suggest that drugs regulating the superoxide generation have potential therapeutic use for allergic disorders.     

Inhibitory effect of terfenadine on mediator release from human blood basophils and eosinophils

The effect of terfenadine on histamine release from human basophils and LTC4 production and release from human eosinophils was evaluated. Eosinophils and basophils were obtained by discontinuous gradient centrifugation of the peripheral blood of atopic asthma patients who were off medication. Anti-IgE-induced histamine release from human basophils was significantly inhibited by terfenadine. Maximum inhibition was obtained at 1 x 10(-5) M terfenadine (percentage inhibition = 57.0 +/- 20.1; P less than 0.05). However, only the highest dose of terfenadine used in this study, i.e. 2 x 10(-5) M, significantly inhibited calcium ionophore (A23187)-induced histamine release from human basophils (percentage inhibition = 40.0 +/- 14.6; P less than 0.05), and LTC4 production from human eosinophils (percentage inhibition = 59.8 +/- 9.9; P less than 0.05. These findings demonstrate that terfenadine, in addition to its known antihistamine property, also has an inhibitory effect on chemical mediator release.     

Influence of bronchial allergen challenge on histamine release by human basophils

BACKGROUND: Basophils can be primed by cytokines such as interleukin (IL) -3, IL-5 or granulocyte macrophage-colony stimulating factor (GM-CSF). It has been described that the concentrations of these cytokines are enhanced at sites of allergic inflammation as well as systemic in allergic asthma. OBJECTIVE: To investigate the priming status of basophils as detected by thapsigargin-induced histamine release during bronchial allergen challenge. METHODS: Ten subjects allergic to house dust mite were challenged via an aerosol delivery system. Spontaneous leucocyte histamine release as well as histamine release induced by various stimuli was measured in vitro at several time points. In addition, lung function parameters, serum IL-5 and blood eosinophil counts were evaluated. RESULTS: We found no effect of bronchial allergen challenge upon spontaneous leucocyte histamine release, nor upon histamine release induced by anti-immunoglobulin (Ig) E, house dust mite extract, C5a, fMLP, IL-3, PMA+ thapsigargin or IL-3+ thapsigargin. However, the priming status of basophils as measured by thapsigargin-induced histamine release was enhanced at 24 h after bronchial allergen challenge. Analysis of the individual data showed a heterogeneous initial response (30 min, 6 h) followed by a predominant increase at 24 h after allergen challenge. This increase in the thapsigargin-induced histamine release correlated with the increase in serum IL-5 levels at 24 h after allergen challenge. CONCLUSION: The priming status of human basophils as measured by thapsigargin-induced histamine release is enhanced 24 h after allergen challenge.     

Nasal histamine release following hyperosmolar and allergen challenge

Allergic rhinitis is characterised by symptoms of sneezing, itching of the nose with watery secretions, and nasal obstruction. We have previously shown that patients can have the diagnosis of allergic rhinitis confirmed by nasal provocation tests and assessment of nasal inspiratory peak flow (NIPF) after specific allergen or hyperosmolar challenge. We now show that histamine is released into the nasal lavage fluid in response to such challenges. Saline lavage alone results in detectable histamine levels in the order of 5 ng/ml, but in the presence of allergen (HDM) there is a significant increase in histamine release in atopics but not in control subjects. With hyperosmolar challenge, atopics showed a biphasic response in that histamine release was increased with 1.8% and 3.6% saline but returned to baseline with 5.4% and 7.2% saline, then showing a further increase with 9.0% saline. This raises the possibility of two populations of responsive mast cells. Hyperosmolar challenge leads to symptoms of nasal itch and sneezing as well as histamine release in atopics but not in controls. This suggests that hyperosmolar challenge can be used as a simple diagnostic test for allergic rhinitis and may provide a model for nasal hyper-reactivity.