Roflumilast inhibition of pulmonary leukotriene production and bronchoconstriction in ovalbumin-sensitized and -challenged Guinea pigs

This study investigated the effects of roflumilast, a PDE4 inhibitor, on slow-reacting substance of anaphylaxis (SRS-A)-mediated bronchoconstriction and pulmonary leukotriene (LT) release in ovalbumin (OVA)-sensitized and -challenged guinea pigs. Animals were treated with roflumilast orally (0.04, 0.12, 0.4, or 4 mg/kg) or placebo 1 hour before OVA challenge. Bronchoconstriction was quantified by measuring airway conductance (Gaw) and dynamic lung compliance (Cdyn). Roflumilast significantly attenuated the decrease in Gaw (50% inhibitory dose [ID50] = 0.33 mg/kg) and Cdyn (ID50 = 0.25 mg/kg) in a dose-dependent manner and significantly inhibited Cys-LT (ID50 = 0.06 mg/kg) and LTB4 (ID50 = 0.05 mg/kg) release versus placebo-treated animals. Roflumilast did not affect LTD4-induced bronchoconstriction. These findings support the role of roflumilast as an anti-inflammatory treatment for asthma.

The role of leukotrienes in upper and lower airway inflammation and the implications for treatment

OBJECTIVE

This article reviews the proinflammatory effects of the cysteinyl leukotrienes (CysLTs) in the upper and lower airways, along with evidence of their role in allergic rhinitis and chronic hyperplastic sinusitis with nasal polyposis (CHS/NP). After reading this article, readers should have a greater understanding of the effects of the CysLTs on both upper and lower airways and their implications for treatment.

DATA SOURCES

Relevant and appropriately controlled studies on the inflammatory processes associated with leukotrienes (LTs) were reviewed. Only literature in the English language was reviewed.

STUDY SELECTION

Material was taken from peer-reviewed journals and data generated from the author's laboratory.

RESULTS

The CysLTs possess proinflammatory effects that contribute to the increase of tissue eosinophilia. Emerging data support their importance in diseases of the upper airways, including allergic rhinitis and CHS/NP. The LT modifiers may be appropriate agents for treating inflammatory disorders of the upper airways because of their proven effectiveness in reducing inflammation in asthma. Results from studies in patients with allergic rhinitis demonstrated improved nasal rhinorrhea, sneezing, and congestion. LT modifiers have improved nasal congestion and restored the sense of smell in patients with CHS/NP.

CONCLUSIONS

The LT receptor antagonists have proven to be an effective antiinflammatory treatment for asthma. Emerging data indicate that LTs play a pivotal role in inflammatory upper airway disease, providing a growing rationale for the use of LT receptor antagonists to treat allergic rhinitis and CHS/NP.

A rapid, simple method for calculating equilibrium constants and antibody site concentrations from dilution curves alone

A rapid new practical method for calculating both the antibody-antigen equilibrium constant and the antibody concentration from antibody dilution curve data alone is described. This method is faster than the inhibition curve method for evaluating a humoral immune response. It is particularly suitable for monitoring the immune response of an immunization program. The response is assessed as an immunization index, Abi*Ka. This index is more exact than the antibody titer obtained from dilution curves and independent of the specific activity of the labelled molecule and total activity used in the assay. The method was used to monitor the production of a monoclonal antibody to the sulphide peptide leucotriene including immunization, cloning and purification.

Effects of exogenous eicosapentaenoic acid on generation of leukotriene C4 and leukotriene C5 by calcium ionophore-activated human eosinophils in vitro

Exogenous eicosapentaenoic acid (EPA) has been compared with exogenous arachidonic acid (AA) for its ability to modulate the oxidative metabolism of membrane-derived arachidonic acid by the 5-lipoxygenase pathway in ionophore-activated human eosinophils, and for its suitability as a parallel substrate in this pathway. Products were quantitated by specific RIA and tetraene and pentaene leukotrienes (LT) were separated by reverse-phase HPLC. Eosinophils were preincubated with control buffer, exogenous EPA or AA and stimulated optimally with 10 microM calcium ionophore (A23187) for 15 min. Mean generation of LTC4 in the absence of fatty acid was 6.0 = 1.1 ng/10(6) eosinophils (mean = SEM, n = 5). In the presence of EPA, the amount of LTC4 generated rose to peak at 16.5 +/- 1.9 ng/10(6) eosinophils at 10 micrograms/ml EPA and then fell to 8.3 +/- 3.1 ng/10(6) cells at 40 micrograms/ml EPA. The EPA derivative, LTC5 was first detectable at 5 micrograms/ml EPA with 4.8 +/- 1.2 ng/10(6) cells and gradually rose with increasing dose of EPA to be maximal at 40 micrograms/ml with 12.7 +/- 2.2 ng/10(6) cells. Identity of the LTC5 was confirmed by an identical retention time to synthetic LTC5 standard, immunoreactivity to a specific antibody against LTC4 and LTC5 and a typical UV absorbance spectrum. When eosinophils were preincubated with AA and similarly stimulated, LTC4 generation gradually increased from a baseline of 6.7 +/- 0.7 ng/10(6) cells in the absence of fatty acid to reach a maximum of 12.9 +/- 0.8 ng/10(6) cells at 40 micrograms/ml of AA. Total LTC generation was nearly twofold more with cells incubated with EPA than with cells incubated with AA (p < 0.05). Thus, EPA does not suppress LTC generation from eosinophils but stimulates it at lower doses and is a substrate for LTC5 generation.

Immunoaffinity purification of prostaglandin E2 and leukotriene C4 prior to radioimmunoassay: application to human synovial fluid

When human synovial fluid as such was subjected to radioimmunoassays of prostaglandin E2 (PGE2) and leukotriene C4 (LTC4), there was no linear increase in PGE2 and LTC4 as the amount of synovial fluid was raised. For removal of substances thus disturbing the assay we developed a method of immunoaffinity purification of PGE2 and LTC4. A monoclonal antibody against PGE2 or LTC4 was coupled to BrCN-activated Sepharose 4B. When synovial fluid mixed with radiolabelled PGE2 or LTC4 was applied to the column of immobilized antibody, the ligand was adsorbed to the column and eluted with a mixture of methanol/water in a recovery of about 80%. The purified material showed a linearity between the amount of the sample and the value of radioimmunoassay. The one-step method was applied to synovial fluid from patients with rheumatoid arthritis, osteoarthritis and other joint diseases.

In vivo pharmacologic profile of ONO-1078: a potent, selective and orally active peptide leukotriene (LT) antagonist

We investigated the in vivo antagonistic activity of ONO-1078 against peptide leukotrienes (LTs) in guinea pigs. ONO-1078, when administered p.o. (0.3-3 mg/kg), caused a dose-dependent reduction of LTC4-, LTD4- and LTE4-induced bronchoconstriction, LTD4-induced airway microvascular leakage and LTD4-induced increase in cutaneous vascular permeability. When administered intravenously, ONO-1078 (3-30 micrograms/kg) inhibited these responses approximately 200-600 fold more potently than FPL55712. When guinea pigs were treated with indomethacin to examine the antagonism of ONO-1078 on the direct action against peptide LTs, intravenous (3-30 micrograms/kg) and oral (0.3-3 mg/kg) administration of ONO-1078 also inhibited LTC4- and LTD4-induced bronchoconstriction, and its activity was approximately 300-500 fold more potent than that of FPL55712. ONO-1078 (10 mg/kg, i.v.) had no inhibitory effect on bronchoconstrictions induced by histamine, acetylcholine, serotonin, arachidonic acid, LTB4, prostaglandin (PG) F2 alpha, PGD2, 9 alpha, 11 beta-PGF2, a stable thromboxane A2 mimetic agent and platelet activating factor. Furthermore, oral administration of ONO-1078 (1-10 mg/kg) inhibited slow-reacting substance of anaphylaxis mediated bronchoconstriction induced by antigen in a dose-dependent manner. These results indicate that ONO-1078 is an extremely potent, selective and orally active peptide LT antagonist and that oral administration of ONO-1078 antagonizes not only exogenously administered peptide LTs but also endogenous peptide LTs.

Immunoreactive leukotriene C4 levels in CSF of MS patients

Using a sensitive and specific radioimmunoassay levels of leukotriene (LT)C4-like material were estimated in lumbar cerebrospinal fluid (CSF) samples from patients with multiple sclerosis (MS) in comparison to control patients with or without inflammatory processes in the central nervous system (CNS). Levels of LTC4-like material were significantly elevated (p less than 0.01) in CSF from patients with inflammatory diseases such as meningitis, polyradiculitis or meningoencephalitis (57 +/- 53 pg/ml, n = 16) as compared to those from control patients without inflammatory or immunological CNS diseases (21 +/- 16 pg/ml, n = 42). By contrast, LTC4-like material was 16 +/- 7 pg/ml in first manifestations of MS (n = 7). 21 +/- 16 pg/ml in remitting-relapsing MS (n = 15) and 10 +/- 6 pg/ml in chronic progressive MS (n = 8). These results argue against a significant pathophysiological role of cysteinyl-LT in MS.

A monoclonal antibody against the sulfidopeptide leukotrienes LTC4, LTD4 and LTE4

A monoclonal antibody (1A-LDR1) against sulfidopeptide leukotrienes (LT) is described. The mAb shows a nearly identical detection limit of about 0.04 ng for LTC4, LTD4, LTE4 and NacLTE4 in standard fluid phase RIA. Steric modifications, however, diminish the sensitivity, as determined for the examples 5-epi-LTC4, 6-epi-LTC4, 5,6-epi-LTC4 and 11-trans-LTC4. No crossreactivity could be observed for LTB4. Crossreactions with components of the LT peptide chain such as L-cysteine or glutathione, as well as with arachidonic acid, were not detectable. In assessing the accuracy of the LT-RIA, recovery experiments with supernatants of mouse peritoneal macrophages and incubates of gastric mucosa showed a good correlation of r = 0.993 and 0.990, respectively. Results of an inhibition experiment with mouse peritoneal macrophages, incubated with several concentrations of indomethacin and nordihydroguaiaretic acid (NDGA), support the reliability of RIA and ELISA. The new LT-mAB allows an almost complete detection of peptide leukotrienes in one assay.

Plasma immunoreactive leukotriene C4 levels in patients with Kawasaki disease

The incidence of wheezing in Kawasaki disease (KD) has been investigated retrospectively. We measured plasma immunoreactive-leukotriene C4 (i-LTC4) levels of patients with KD. Wheezing was observed in 32 (12.5%) of the 256 patients with KD. Patients who had a prior history of bronchial asthma wheezed more frequently than other patients. During the acute stage of KD, plasma i-LTC4 levels both of wheezing and nonwheezing were significantly higher than those of healthy children. During the convalescent stage, plasma i-LTC4 levels of wheezing cases were higher than those of nonwheezing cases. We speculate that LTC4 contributes to the appearance of inflammatory symptoms during the acute stage of KD. During the convalescent stage when patients were taking aspirin, the presence of wheezing was associated with increased plasma levels of i-LTC4. More attention should be paid to the appearance of wheezing during the course of KD, especially in those cases in which the patient has a prior history of bronchial asthma.

Inhibitory effect of aerosol WP871 on SRS-A mediated bronchoconstriction in the guinea pig in vivo

Slow-reacting substance of anaphylaxis (SRS-A) is an important factor mediating bronchoconstriction in asthma. We developed a guinea pig model for SRS-A mediated bronchoconstriction induced by antigen inhalation. Using this model, we investigated the effect of inhaled WP871, a new anti-allergic drug, on bronchoconstriction. Aerosol WP871 (0.01 and 0.033%) to some extent inhibited the antigen-induced bronchoconstriction in a dose-dependent fashion, but high-dose WP871 (0.1%) inhalation itself produced a non-specific bronchoconstriction. However, aerosol WP871 (0.033%) showed no inhibitory effect on bronchoconstriction caused by direct inhalation of leukotriene C4, a component of SRS-A. These findings indicate that aerosol WP871 does not antagonize SRS-A, but inhibits synthesis and/or release of SRS-A and has some non-specific bronchoconstrictive effect in high concentration.

Immunoreactive leukotrienes in nettle plants (Urtica urens)

In order to clarify the mechanisms of urtication after contact with stinging plants, nettle (Urtica urens) hair and whole-plant extracts were examined for the presence of leukotriene (LT) B4 and LTC4 by reverse phase high-pressure liquid chromatography (RP-HPLC) and radioimmunoassay (RIA) and for in vitro neutrophil chemotactic activity and histamine contents. Both hair and plant extracts contained high levels of LTB4 and LTC4 by RIA as well as histamine. The presence of LTB4 was supported by RP-HPLC elution profiles and by in vitro chemotaxis. Nettle hairs therefore resemble insect venoms and cutaneous mast cells with regard to their spectrum of mediators.

Role of thromboxane A2, leukotriene C4 and histamine in the antigen-induced vasoconstriction in perfused, sensitized guinea-pig kidney

The existence of a role for TXA2, histamine, and possibly LTC4 in the antigen-induced renal vasoconstriction in isolated, perfused kidney of sensitized guinea-pigs is demonstrated.

The role of acupuncture in asthma: changes in airways dynamics and LTC4 induced LAI

A cohort of nine extrinsic asthma patients were treated by means of acupuncture. Patients were followed up for changes in medical treatment, spirometry, skin reactivity to immediate type reactions, total serum IgE levels and reactivity of their leukocytes to leukotriene C4 challenge (LTC4 induced leukocyte adherence inhibition (LAI) assay). Our results show that after acupuncture, treated patients were able to reduce bronchodilator and taper completely corticosteroid therapy. No change in skin reactivity or in IgE levels were noted. However, acupuncture treatment was able to negate, in 66.6%, the positive LTC4 induced responses.

The release of leukotrienes in the respiratory tract during infection with respiratory syncytial virus: role in obstructive airway disease

Samples of nasopharyngeal secretions from a group of 73 infants with bronchiolitis or upper respiratory illness alone during infection with respiratory syncytial virus were analyzed for leukotriene C4 (LTC4) content using a reverse-phase high-pressure liquid chromatography assay with confirmation by radioimmunoassay. Titers of respiratory syncytial virus (RSV)-specific IgE in nasopharyngeal secretion (NPS) specimens were determined using an enzyme-linked immunosorbent assay. The highest concentrations of LTC4 were found in the first 3 to 8 days after the onset of illness, and LTC4 was detectable in progressively lower concentrations in samples obtained up to 28 days after the onset of illness. LTC4 was detected in samples of NPS obtained in the acute phase of illness from 67% of infants with bronchiolitis due to RSV and in 33% of samples of NPS obtained during the same interval from infants with upper respiratory illness alone (p less than 0.025). Concentrations of LTC4 in children with bronchiolitis were 5-fold higher (1271 pg/ml) than the mean concentration of LTC4 in children with upper respiratory illness (224 pg/ml, p less than 0.02). LTC4 was detected in 83% of the children developing an RSV-IgE response and in 24% of subjects not developing an RSV-IgE response (p less than 0.001). Quantities of LTC4 measured in NPS were directly correlated with the magnitude of the RSV-IgE response in secretions (r = 0.33, p less than 0.02). These studies lend support to previous investigations suggesting that severe bronchiolitis due to RSV results from IgE-mediated hypersensitivity reactions to viral antigens, with release of chemical mediators of airway obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of AA-861, a selective 5-lipoxygenase inhibitor, on models of allergy in several species

The effects of 2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone (AA-861), a selective 5-lipoxygenase inhibitor, on immunological or non-immunological release of slow reacting substance of anaphylaxis (SRS-A) and histamine and its effects on experimental asthma were investigated. AA-861 showed a dose-dependent inhibition of SRS-A release, with no effect on histamine release from passively sensitized guinea pig, monkey (M. irus) and human lung fragments. An analysis of the anaphylactic diffusate from the human lung fragments, using the combined technique of high performance liquid chromatography and radioimmunoassay, revealed that AA-861 markedly suppresses biosynthesis of the leukotrienes. However, this drug inhibits the release of histamine as well as SRS-A from lung fragments of anaphylactic monkey (M. mulatta) and in the Ca ionophore-stimulated rat peritoneal cavity. AA-861 suppressed the anaphylactically-induced airway resistance in mepyramine- and cimetidine-treated guinea pigs. These results suggest that AA-861 may be clinically effective for treating allergy-related asthma by modulating the 5-lipoxygenase pathway and that an inhibitory mechanism of histamine release by AA-861 may be present in some species.

The role of leukotriene D4 in allergic rhinitis

We investigated the clinical significance of leukotriene D4 (LTD4) in nasal symptoms of allergy and compared this with antigen and histamine. Nasal provocations were carried out in patients with allergic rhinitis using serially increasing doses of LTD4, histamine, or antigen. The nasal responses induced were evaluated by counting the number of sneezes, the quantity of nasal secretion, and of nasal airway resistance. When the effects of topical provoking agents were compared at the threshold concentration, LTD4 produced no sneezing--unlike antigen and histamine--increased nasal secretion to a lesser degree than antigen and histamine (P less than .001), and increased nasal airway resistance similar to histamine but less than antigen (P less than .1) and longer than histamine, and similar to antigen in duration. LTD4 was approximately 5,000 times stronger than histamine in threshold concentration for nasal response. In conclusion, LTD4 plays an important role in nasal allergy presumably through long lasting and strong nasal blockage effects.

Study of mediators of anaphylaxis in nasal wash fluids after aspirin and sodium metabisulfite nasal provocation in intolerant rhinitic patients

Nasal histamine (H), leukotriene C4 (I-LTC4) and SRS-A activity were studied in seven aspirin-(ASA)-intolerant patients (AIR) with rhinitis and in five ASA-tolerant control patients with chronic rhinitis after nasal provocation (NP) with a lysine acetylsalicylate solution. The same parameters were also studied after metabisulfite (MBS) NP in four sulfite-intolerant patients with rhinitis and in six control patients with chronic rhinitis. In six ASA-intolerant subjects and in four controls, we studied the PGD2 levels in nasal washes after ASA NP 0.2 mL of lysine acetylsalicylate solution (10 mg/mL) was sprayed intranasally in ASA-intolerant patients and controls and a 25-mg/mL MBS solution in sulfite intolerant patients and controls. Nasal wash fluids were obtained using 5 mL of 0.15 M saline before and 7 1/2, 15, 30, and 60 minutes after nasal provocation. The nasal provocation with ASA induced itching and sneezing in four out of seven intolerant subjects. In this subgroup histamine values in nasal wash fluids were significantly higher versus the remaining ASA-intolerant patients at 30 and 60 minutes (P less than .05 and P less than .01, respectively) and versus controls at 60 minutes (P less than .01). We found significantly higher I-LTC4 (P less than .01) and SRS-A levels in nasal washes collected from ASA-intolerant subjects versus controls at 60 minutes after nasal provocation. There was no significant increase in the mean PGD2 values in either the ASA-intolerant or control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid mediators of inflammation

Many mediators of inflammation are derived from phospholipids and polyunsaturated fatty acids, including prostaglandins, leukotrienes, and platelet-activating factor. These mediators augment the vascular phase of inflammation and modify functions of inflammatory cells and cells of the immune system. Several growth factors or cytokines augment production of prostaglandin synthesis. The production of lipid-derived mediators may be inhibited by anti-inflammatory drugs and by modifying dietary polyunsaturated fatty acids.

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.

Contribution of macrophages to immediate hypersensitivity reaction

The interaction of mast cells with other leukocytes during immediate hypersensitivity reactions was tested by in vivo and in vitro experiments. Intraperitoneal challenge of passively sensitized rats with antigen caused the production of peptidoleukotrienes, leukotriene (LT)B4, thromboxane (TX)B2, and 6-keto-prostaglandin (PG) F1 alpha in the peritoneal cavity. Pretreatment of the rats with thioglycollate i.p. markedly changed the amount of eicosanoids formed. When polymorphonuclear leukocytes were the predominant cell type in the peritoneal exudate, both LTC4 and 6-keto-PGF1 alpha were decreased by 75% each and TXB2 by 50%. When elicited macrophages were predominant, there was an additional reduction in LTC4 by 68% as compared with 18 hr after thioglycollate treatment, but no additional change in the other arachidonic acid metabolites. In vitro antigen challenge of passively sensitized mouse bone marrow-derived mast cells caused the release of LTC4, LTB4, 6-trans-LTB4, 5-hydroxyeicosatetraenoic (5-HETE), and TXB2. Exposure to antigen of these mast cells in the presence of resident peritoneal macrophages markedly altered eicosanoid formation. Early in the time course (2 to 15 min), macrophages markedly enhanced all 5-lipoxygenase products. However, later in the time course (30 to 120 min), these products were decreased. This decrease was reversed by catalase and superoxide dismutase, which suggests the involvement of oxygen radicals. These active oxygen species also seemed to be generated by mast cells, because these enzymes caused an increase in 5-lipoxygenase products when mast cells were challenged alone. RIA of cyclooxygenase products showed that mast cells released only TXB2 when stimulated with antigen. When they were stimulated in the presence of macrophages, TXB2 and also PGE2 and 6-keto-PGF1 alpha were synthesized. Therefore, macrophages probably contribute the PGE2 and 6-keto-PGF1 alpha. Because the same amount of TXB2 was generated whether macrophages were present or not, the mast cells seem to be the major source of this compound. These data indicate that macrophages and possibly polymorphonuclear leukocytes participate in immediate hypersensitivity reactions.

Comparison of cutaneous and bronchial reactivity to leukotriene D4 in humans

To establish whether a relationship exists between cutaneous and bronchial reactivity to leukotriene D4 (LTD4), endpoint cutaneous reactivity and bronchial reactivity were determined in six patients with asthma, six patients with seasonal allergic rhinitis, and six nonatopic men. In all subjects, increasing doses of LTD4 produced decreases in specific airway conductance (SGaw) and flow at 30% of vital capacity measured from a partial forced expiratory maneuver (V30P). Intracutaneous injections of LTD4 and histamine resulted in immediate wheal and erythema reactions in all patients. Serial 10-fold dilutions of LTD4 and histamine were injected to establish the lowest dose capable of producing a 4 mm wheal with erythema. Endpoint cutaneous reactivity to LTD4 ranged from 1 mumol to 100 pmol in controls and from 100 nmol to 1 fmol in patients with asthma, but statistically significant differences between groups were not apparent even with inclusion of six additional subjects. No meaningful correlations were found between the quantity of LTD4 producing the threshold cutaneous reaction and the dose of inhaled LTD4 that produced a 35% decrease in SGaw and 30% decrease in V30P. In contrast to the bronchi, where subjects in all three groups were 264 to 840 times more sensitive to LTD4 than to methacholine, 11/18 subjects (3/6 with asthma) were less sensitive to LTD4 than to histamine in terms of endpoint cutaneous reactivity. However, seven of 18 subjects who were more sensitive to LTD4 than to histamine had relative potencies ranging from 5 to 500,000.

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.

Effect of leukotriene D4 on nasal mucosal blood flow, nasal airway resistance and nasal secretion in humans

The possible role of leukotriene D4 (LTD4) in nasal allergy was investigated in healthy volunteers. Nasal blood flow, nasal airway resistance, nasal discharge and nasal itching and sneezing were examined. LTD4 was found to induce a dose-response related increase in nasal mucosal blood flow as measured by laser-Doppler flowmetry. Histamine exhibited similar effects on blood flow in the same concentration range. Nasal airway resistance as recorded by rhinomanometry, increased in a dose-related manner after topical LTD4. Nasal secretion was obtained by nasal lavage and estimated from a dilution principle. Topical LTD4 did not increase the amount of nasal secretion, whereas a dose-related increase was found after topical histamine. LTD4 did not cause itching, sneezing or other irritative symptoms. In conclusion, LTD4 may play a role in nasal allergy by increasing blood flow and nasal airway resistance. Itching, sneezing and discharge, however, are apparently not caused by LTD4 but can be accounted for by the release of histamine or other mediators.

Helminth-induced intestinal inflammation

Gastrointestinal inflammation is a prominent feature of protective reactions in animals immune against helminths. Infiltration into the inflamed mucosa of various cells and their subsequent activation result in the elaboration of an array of pharmacologically and biologically active substances. The release of mediators is also associated with alterations in the epithelial layer. Furthermore, increased smooth muscle reactivity and enhanced secretory function of the mucosal tissue contribute to the development of an unfavourable environment and lead to worm expulsion. Mediators elaborated from inflammatory cells, whether associated with cell granules (i.e., preformed) or de novo-generated from membrane phospholipids, possess a number of potent vasoactive and spasmogenic properties which may contribute to events leading to worm elimination. The lipoxygenase metabolites of arachidonic acid (leukotrienes) derived from cell membranes probably contribute to the state of intestinal hypersensitivity against helminths. The measurement of elevated levels of these lipid mediators following worm challenge of immune, but not control, rats suggests that leukotrienes may play a role in amplifying and augmenting the inflammatory process associated with worm expulsion.

Production of leukotrienes in human skin and conjunctival mucosa after specific allergen challenge

The production of leukotrienes has been monitored in tear fluids from subjects following a conjunctival provocation test, and skin blister fluids following initiation of a Prausnitz-Kustner reaction. In tear fluids elevated levels of leukotriene C4 (LTC4)-immunoreactive material were measured following allergen challenge as compared to control tear fluid obtained by mechanical or reflex stimulation. Analysis by high performance liquid chromatography indicated the presence of LTC4, LTD4 and LTE4. In the skin, significantly elevated levels of LTC4-immunoreactive material were measured following allergen challenge in the Prausnitz-Kustner reaction. HPLC analysis indicated the presence of both LTC4 and LTD4. LTB4 immunoreactive material was detected both in the tear fluid and the skin tissue fluid. However, no significant increase occurred in either tissue after the allergic reactions. These results indicate that the SRS-A leukotrienes are released in vivo in man following allergen challenge, and indicate these mediators may be important in human allergic diseases.

Measurement of immunoreactive leukotriene C4 in blood of asthmatic children

Peptide leukotriene (LT) such as LTC4, LTD4, LTE4 have been considered to be major mediators of immediate type hypersensitivity reaction such as asthma. We have developed a rapid and simple extraction method using a Sep-Pak C18 cartridge for the measurement of LTC4 by radioimmunoassay (i-LTC4). In this extraction method, 91% LTC4 was recovered in a final methanol fraction. The identity was confirmed by the recovery test and by the dilution method. The amount of i-LTC4 in plasma from asthmatic patients was determined by radioimmunoassay after the extraction. The order of the plasma level of i-LTC4 was; severe asthma greater than slight or moderate asthma greater than asthmatic patient without attack greater than healthy adult. The highest level of LTC4 was 0.27 +/- 0.11 pmol/ml in severe asthmatic plasma.

Smooth muscle contraction and release of histamine and slow-reacting substance of anaphylaxis in pulmonary tissues isolated from guinea pigs passively sensitized with IgG1 or IgE antibodies

In previous studies, we have provided evidence that different Fc receptors mediate antigen-induced pulmonary smooth muscle contractile responses after passive sensitization of guinea pigs with IgG1 or IgE antibodies. In this study, we examined the relationship between contraction and release of histamine and slow-reacting substance of anaphylaxis (leukotrienes) in superfused trachea and parenchymal strips as well as mediator release from minced lung fragments after passive sensitization of guinea pigs with IgG1 or IgE antibodies. Guinea pigs were immunized to produce either IgG1 or IgG1 and IgE using oxazolone-guinea-pig albumin or oxazolone-Ascaris plus cyclophosphamide, respectively. The contaminating IgG1 in the IgE-rich serum was removed by passage over a protein A-Sepharose column. Normal guinea pigs were passively sensitized intraperitoneally or intravenously with injections of either IgG1 or IgE 1 or 2 days before in vitro studies. Superfused tissues were challenged with 10(-1) mg/ml antigen (oxazolone-human serum albumin conjugate), and contractions and histamine and leukotriene release were monitored at discrete time intervals thereafter. At equivalent levels of contraction, substantially more histamine and leukotrienes were released from tissues taken from IgG1-sensitized animals. The amounts of histamine released from lung parenchymal strips and trachea in the IgE-sensitized state were approximately 5 and 38%, respectively, of those released from corresponding tissues in the IgG1-sensitized state. The leukotriene release from tissues isolated from IgE-sensitized animals was less than 4% of that released from tissues in the IgG1-sensitized state. Similar differences in mediator release were seen in comparable studies on minced lung fragments.(ABSTRACT TRUNCATED AT 250 WORDS)

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)

Anaphylaxis: mechanisms, manifestations, and management

Although systemic anaphylactic reactions are relatively uncommon, the podiatric physician must be familiar with the precipitating causes, clinical picture, and emergency management. The authors discuss the pathophysiology of anaphylaxis and the typical agents that trigger the response. The clinical features are presented, along with guidelines in establishing a differential diagnosis. Therapeutic measures, aimed at stabilizing the patient and curtailing the extent of the reaction, are also addressed.

The role of slow-reacting substance of anaphylaxis in the late bronchial response after antigen challenge in allergic sheep

Allergic sheep respond to inhalation challenge with Ascaris suum antigen with an immediate bronchoconstriction that resolves within 2 to 4 h, followed by a second bronchial obstruction occurring 6.5 to 8 h after challenge. The purpose of this study was to determine if the antigen-induced late bronchial response in allergic sheep is mediator dependent and to determine the extent to which histamine and/or slow-reacting substance of anaphylaxis (SRS-A) are involved in this response. To do this, 10 conscious sheep with Ascaris suum hypersensitivity underwent an inhalation challenge with antigen, and the average increase in specific lung resistance (SRL = mean pulmonary flow resistance times thoracic gas volume) was determined for each animal between 6.5 and 8 h after challenge, i.e., the time of late bronchial response. On another occasion, separated by at least 14 days, the animals were rechallenged with antigen, but prior to the onset of the late response (5.5 h) the animals were treated with either the mast cell stabilizer cromolyn (1 mg/kg), the SRS-A antagonist FPL-55712 (3 ml of a 1% wt/vol solution), or the histamine H1. receptor antagonist chlorpheniramine (2 mg/kg). Compared with the control response, inhaled aerosols of cromolyn or FPL-55712 blocked the late increase in SRL (p less than 0.01). Intravenously administered chlorpheniramine alone, or in conjunction with atropine, had no effect on the late response. Finally, the late response was partially reversed by FPL-55712 inhalation. These results suggest that the late bronchial response after inhalation challenge in allergic sheep is mediator dependent, and that SRS-A is a principal mediator of this response.

Leukotriene B4, polymorphonuclear leukocytes and inflammatory exudates in the rat

Leukocyte numbers and Leukotriene B4- (LTB4-) and LTC4-immunoreactivity were measured in inflammatory exudates obtained from sponges impregnated with several irritants implanted subcutaneously in the rat. Sponges containing 1% uric acid, carrageenan or zymosan were implanted for 5h and compared to saline sponges. Increases in leukocyte numbers and LTB4-immunoreactivity were found in the presence of irritants, the highest concentrations being observed in the presence of zymosan. The presence of LTB4 was confirmed by liquid chromatographic (HPLC) analysis. A time course study was carried out with zymosan-impregnated sponges and the maximal rate of leukocyte infiltration was found to coincide with the maximal levels of LTB4-immunoreactivity. The LTC4-immunoreactivity was low and following analysis by HPLC was concluded to be unrelated to leukotrienes. The levels of LTB4-immunoreactivity, but not the numbers of leukocytes, were elevated compared to corresponding controls in sponges containing 0.01% ionophore A23187 (untreated rats) or in sponges containing zymosan (rats pretreated with indomethacin; 3 and 10 mg/kg p.o.). Impregnation of sponges with 3 X 10(-6)M LTB4 but not 3 X 10(-5) and 3 X 10(-7)M LTB4 induced a significant leukocyte migration. It was concluded that LTB4 can induce leukocyte migration into sponge exudates in the rat but that measurements of LTB4 in such exudates can not be correlated with the degree of leukocyte infiltration.

Leukotrienes: clinical significance

The leukotrienes, so named because of their initial identification in leukocyte preparations and the presence of three conjugated double bonds (a conjugated triene), are metabolites of the same polyunsaturated fatty acids (e.g., arachidonic acid) that give rise to the prostaglandins, thromboxanes, and several other families of biologically active lipids. Their potential clinical importance derives from their effects on vascular and other smooth muscle reactivity and on leukocyte function. Several leukotrienes may markedly influence the cellular and vascular responses that constitute an integral part of hypersensitivity and inflammatory reactions of the skin. Preliminary data from several laboratories have been presented that implicate a specific leukotriene in the evolution of the lesions of psoriasis.

Leukotriene D4 induces bronchoconstriction in man

The effect of leukotriene D4 (LTD4) on lung function was investigated in a controlled study on four normal subjects. A pronounced decrease in airflow was found after inhalation of less than 0.5 nmol, and was most pronounced in the variables generally accepted as indicators of the function of the small airways. No subjective symptoms were experienced.

Wheal reactions in human skin after injection of leukotrienes B4, C4, D4 and E4

Intradermal injections of 1-50 pmol leukotriene B4, C4, D4 and E4, (LTB4, LTC4, LTD4 and LTE4) were performed in healthy subjects and patients with recurrent urticaria. A wheal and erythema were seen 15 minutes after injection and were most marked after LTC4 and LTD4. LTE4 also produced a wheal whereas the reaction to LTB4 did not significantly differ from the saline control. When mixed with histamine no potentiation of the wheals was noted and no significant difference in reaction was observed between the healthy controls and those with urticaria.