Studies on the release of leukotrienes and histamine by human lung parenchymal and bronchial fragments upon immunologic and nonimmunologic stimulation. Effects of nordihydroguaiaretic acid, aspirin, and sodium cromoglycate

Clinical Relevance of the Anti-inflammatory Effects of Roflumilast on Human Bronchus: Potentiation by a Long-Acting Beta-2-Agonist

Background: Roflumilast is an option for treating patients with severe COPD and frequent exacerbations despite optimal therapy with inhaled drugs. The present study focused on whether the phosphodiesterase (PDE) 4 inhibitor roflumilast and its active metabolite roflumilast N-oxide affect the release of tumor necrosis factor (TNF)-α and chemokines by lipopolysaccharide (LPS)-stimulated human bronchial explants. We also investigated the interactions between roflumilast, roflumilast N-oxide and the β₂-agonist formoterol with regard to cytokine release by the bronchial preparations.

Methods: Bronchial explants from resected lungs were incubated with roflumilast, roflumilast N-oxide and/or formoterol and then stimulated with LPS. An ELISA was used to measure levels of TNF-α and chemokines in the culture supernatants.

Results: At a clinically relevant concentration (1 nM), roflumilast N-oxide and roflumilast consistently reduced the release of TNF-α, CCL2, CCL3, CCL4, CCL5 and CXCL9 (but not CXCL1, CXCL5, CXCL8 and IL-6) from human bronchial explants. Formoterol alone decreased the release of TNF-α, CCL2, and CCL3. The combination of formoterol with roflumilast (1 nM) was more potent than roflumilast alone for inhibiting the LPS-induced release of TNF-α, CCL2, CCL3, CCL4, and CXCL9 by the bronchial explants.

Conclusions: At a clinically relevant concentration, roflumilast N-oxide and its parent compound, roflumilast, reduced the LPS-induced production of TNF-α and chemokines involved in monocyte and T-cell recruitment but did not alter the release of chemokines involved in neutrophil recruitment. The combination of formoterol with roflumilast enhanced the individual drugs’ anti-inflammatory effects.

Should antihistamines be re-considered as antiasthmatic drugs as adjuvants to anti-leukotrienes?

In spite of histamine mimicking the symptoms of allergic bronchoconstriction and severe anaphylaxis, histamine antagonists most probably represent no effective treatment for these conditions. Anti-leukotrienes proved effective for preventing attacks of allergic asthma. In vitro evidence supports a supra-additive effect of histamine H1 receptor antagonists and anti-leukotrienes in vitro, in asthma models utilizing human bronchi. The same seems to hold true for human allergen provocation tests in vivo. We conclude that combinations of second-generation antihistamines and anti-leukotrienes deserve a large-scale clinical trial for preventing and/or treating attacks of allergic asthma. If useful, these drugs could provide a cost-effective alternative to some recent antiasthmatics. Given that redundant mechanisms may be included in asthma pathophysiology, other combinations (including thromboxane or platelet activating factor antagonists) could also be considered.

Disodium cromoglycate suppresses the induction of cysteinyl leukotriene synthesis during granulocytic differentiation in HL-60 cells

OBJECTIVES

Disodium cromoglycate (DSCG) and nedocromil sodium are anti-asthma drugs that have a variety of physiological and biological effects. We examined whether DSCG affects the induction of cysteinyl Leukotriene (cysLT) synthesis during dimethyl sulfoxide (DMSO)-induced granulocytic differentiation in HL-60 cells.

METHODS

HL-60 cells were differentiated to mature granulocyte-like cells by DMSO in the presence or absence of DSCG for 5 days. Then, we measured A23187-stimulated production of LTC4, an initial product of cysLTs. We also examined the mRNA expression and enzyme activity of LTC4 synthase and other LT-synthetic enzymes.

RESULTS

The amount of LTC4 production was 732.0+/-19.0 pg/10(6) cells in DMSO-differentiated HL-60 cells. The value was significantly decreased to 420.7+/-22.7 pg/10(6) cells in the presence of DSCG at 100 microg/ml. The DMSO-induced mRNA expression and enzyme activity of LTC4 synthase was also suppressed by DSCG.

CONCLUSIONS

Our results indicate that DSCG suppresses the DMSO-induced LTC4 synthase-activity by inhibiting mRNA expression of LTC4 synthase, which might be a novel anti-allergic action of DSCG.

Pulmonary actions of anandamide, an endogenous cannabinoid receptor agonist, in guinea pigs

Anandamide (arachidonylethanolamide), 5,8,11,14-eicosatetraenamide, (N-2-hydroxyethyl), was tested for bronchodilator and anti-inflammatory activities. Conscious guinea pigs were given cumulative i.v. doses of anandamide (1.0, 3.0, and 10.0 mg/kg) to assess its effect on dynamic compliance (Cdyn), total pulmonary resistance (RL), tidal volume (VT) and breathing frequency (f). Other guinea pigs were exposed to an aerosol of A23187 (6S-[6alpha(2S*,3S*),8beta(R*),9beta,11alpha]-5- (methylamino)-2-[[3,9,11-trimethyl-8-[1-methyl-2-oxo-2-(1H-pyrrol-2-yl)e thyl]-1,7-dioxaspiro[5.5]undec-2-yl]methyl]-4-benzoxazole carboxylic acid) until Cdyn decreased by 50% (approximately 5 min) and at 20 min, cumulative i.v. doses of anandamide (1.0, 3.0, and 10.0 mg/kg) were administered and reversal of Cdyn examined. After the final dose of anandamide, the animals were killed and excised lung gas volumes (ELGV), i.e., pulmonary gas trapping, measured. Other animals were treated i.v. with anandamide (10.0 mg/kg), exposed to an aerosol of A23187 until labored breathing began, and then killed 1 h later. Anandamide did not significantly affect Cdyn, RL, VT and f. ELGV values of anandamide-treated guinea pigs were not different from those of vehicle-treated animals. Anandamide failed to reverse A23187-induced decreases in Cdyn and to reduce A23187-associated ELGV increases. Also, it did not prevent the prolonged airway obstruction caused by A23187. Histological evaluation revealed that anandamide significantly reduced A23187-related airway epithelial injury and pulmonary leukocytosis. However, it did not prevent A23187-induced peribronchiolar granulocytic accumulation. Our results suggest that in vivo anandamide has minimal direct airway smooth muscle-related actions, however it may possess modest anti-inflammatory properties.

Effects of the cysteinyl leukotriene receptor antagonists pranlukast and zafirlukast on tracheal mucus secretion in ovalbumin-sensitized guinea-pigs in vitro

1. We investigated the inhibitory effects of the cysteinyl leukotriene (CysLT1) receptor antagonists, pranlukast and zafirlukast, on 35SO4 labelled mucus output, in vitro, in guinea-pig trachea, induced by leukotriene D4 (LTD4) or by antigen challenge of sensitized animals. Agonists and antagonists were administered mucosally, except in selected comparative experiments where drugs were administered both mucosally and serosally to assess the influence of the epithelium on evoked-secretion. 2. LTD4 increased 35SO4 output in a concentration-related manner with a maximal increase of 23 fold above controls at 100 microM and an approximate EC50 of 2 microM. Combined mucosal and serosal addition of LTD4 did not significantly affect the secretory response compared with mucosal addition alone. Neither LTC4 nor LTE4 (10 microM each) affected 35SO4 output. Pranlukast or zafirlukast significantly inhibited 10 microM LTD4-evoked 35SO4 output in a concentration-dependent fashion, with maximal inhibitions of 83% at 10 microM pranlukast and 78% at 10 microM zafirlukast, and IC50 values of 0.3 microM for pranlukast and 0.6 microM for zafirlukast. Combined mucosal and serosal administration of the antagonists (5 microM each) gave degrees of inhibition of mucosal-serosal 10 microM LTD4-evoked 35SO4 output similar to those of the drugs given mucosally. Pranlukast (0.5 microM) caused a parallel rightward shift of the LTD4 concentration-response curve with a pKB of 7. Pranlukast did not inhibit ATP-induced 35SO4 output. 3. Ovalbumin (10-500 microg ml(-1) challenge of tracheae from guinea-pigs actively sensitized with ovalbumin caused a concentration-related increase in 35SO4 output with a maximal increase of 20 fold above vehicle controls at 200 microg ml(-1). The combination of the antihistamines pyrilamine and cimetidine (0.1 mM each) did not inhibit ovalbumin-induced 35SO4 output in sensitized guinea-pigs. Neither mucosal (10 microM or 100 microM) nor mucosal-serosal (100 microM) histamine had any significant effect on 35SO4 output. 4. Pranlukast or zafirlukast (5 microM each) significantly suppressed ovalbumin-induced secretion in tracheae from sensitized guinea-pigs by 70% and 65%, respectively. 5 We conclude that LTD4 or ovalbumin challenge of sensitized animals provokes mucus secretion from guinea-pig trachea in vitro and this effect is inhibited by the CysLT1 receptor antagonists pranlukast and zafirlukast. These antagonists may be beneficial in the treatment of allergic airway diseases in which mucus hypersecretion is a clinical symptom, for example asthma and allergic rhinitis.

Overexpression of leukotriene C4 synthase in bronchial biopsies from patients with aspirin-intolerant asthma

Aspirin causes bronchoconstriction in aspirin-intolerant asthma (AIA) patients by triggering cysteinyl-leukotriene (cys-LT) production, probably by removing PGE2-dependent inhibition. To investigate why aspirin does not cause bronchoconstriction in all individuals, we immunostained enzymes of the leukotriene and prostanoid pathways in bronchial biopsies from AIA patients, aspirin-tolerant asthma (ATA) patients, and normal (N) subjects. Counts of cells expressing the terminal enzyme for cys-LT synthesis, LTC4 synthase, were fivefold higher in AIA biopsies (11.5+/-2.2 cells/mm2, n = 10) than in ATA biopsies (2.2+/-0.7, n = 10; P = 0. 0006) and 18-fold higher than in N biopsies (0.6+/-0.4, n = 9; P = 0. 0002). Immunostaining for 5-lipoxygenase, its activating protein (FLAP), LTA4 hydrolase, cyclooxygenase (COX)-1, and COX-2 did not differ. Enhanced baseline cys-LT levels in bronchoalveolar lavage (BAL) fluid of AIA patients correlated uniquely with bronchial counts of LTC4 synthase+ cells (rho = 0.83, P = 0.01). Lysine-aspirin challenge released additional cys-LTs into BAL fluid in AIA patients (200+/-120 pg/ml, n = 8) but not in ATA patients (0. 7+/-5.1, n = 5; P = 0.007). Bronchial responsiveness to lysine-aspirin correlated exclusively with LTC4 synthase+ cell counts (rho = -0.63, P = 0.049, n = 10). Aspirin may remove PGE2-dependent suppression in all subjects, but only in AIA patients does increased bronchial expression of LTC4 synthase allow marked overproduction of cys-LTs leading to bronchoconstriction.

Comparative analysis of isolated human bronchi contraction and biosynthesis of cysteinyl leukotrienes using a direct 5-lipoxygenase inhibitor

Quantitation of cysteinyl leukotriene production and smooth muscle contraction upon immunological challenge of isolated human bronchi was evaluated. Analysis of picomole amounts of leukotriene C4, D4, and E4 was achieved using HPLC separation and enzyme immunoassay quantitative determination. The aim of the study was to correlate the contraction of airway smooth muscle and cysteinyl leukotriene production with and without 5-lipoxygenase inhibition. In human isolated bronchial tissue treated with indomethacin and pyrilamine to make their contractile responses leukotriene dependent only, the novel 5-lipoxygenase inhibitor 5,6-Dihydroxy-2-(N,N-Dimethylhydrazino)-1,2,3,4-tetrahydro-naph talene bromide (CHF 1909) caused a concentration-dependent inhibition of the immunologically induced contraction, showing an IC50 value of 13 +/- 2.2 microM (mean +/- CV). At the concentration of 30 microM, this compound caused more than 90% inhibition of the maximal bronchoconstriction in vitro, and inhibited cysteinyl leukotriene production by 90% as well. Contemporary measurement of immunologically induced contraction and production of cysteinyl leukotrienes in isolated human bronchi provided a direct correlation between smooth muscle contraction and synthesis of leukotriene C4, D4, and E4.

Leukotriene synthesis inhibition and anti-ige challenge of human lung parenchyma

The leukotriene (LT) synthesis inhibitors BAY x1005 and MK-886 were evaluated in human lung parenchyma challenged with an anti-IgE. The anti-IgE-induced LTE4 release was time- and dose-dependent. Treatment of the parenchyma with indomethacin (3 microM) prior to anti-IgE challenge inhibited the 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) release and enhanced (36%) the quantities of LTE4 detected during IgE-stimulations. BAY x1005 and MK-886 were assessed in the presence of indomethacin (3 microM) and the IC50 values for both inhibitors were similar (0.13 microM). BAY x1005 (1 microM) produced the same percent of inhibition of anti-IgE-induced LTE4 release in the presence or absence of indomethacin. BAY x1005 (1 microM) did not alter the 6-keto PGF1 alpha release during anti-IgE challenge. The results indicate that BAY x1005 and MK-886 are potent inhibitors of LT synthesis when human lung parenchyma were stimulated by an anti-IgE.

5-Oxo-eicosanoids and hematopoietic cytokines cooperate in stimulating neutrophil function and the mitogen-activated protein kinase pathway

The newly defined eicosatetraenoates (ETEs), 5-oxoETE and 5-oxo-15(OH)-ETE, share structural motifs, synthetic origins, and bioactions with leukotriene B4 (LTB4). All three eicosanoids stimulate Ca2+ transients and chemotaxis in human neutrophils (PMN). However, unlike LTB4, 5-oxoETE and 5-oxo-15(OH)-ETE alone cause little degranulation and no superoxide anion production. However, we show herein that, in PMN pretreated with granulocyte-macrophage or granulocyte colony-stimulating factor (GM-CSF or G-CSF), the oxoETEs become potent activators of the last responses. The oxoETEs also induce translocation of secretory vesicles from the cytosol to the plasmalemma, an effect not requiring cytokine priming. To study the mechanism of PMN activation in response to the eicosanoids, we examined the activation of mitogen-activated protein kinase (MAPK) and cytosolic phospholipase A2 (cPLA2). PMN expressed three proteins (40, 42, and 44 kDa) that reacted with anti-MAPK antibodies. The oxoETEs, LTB4, GM-CSF, and G-CSF all stimulated PMN to activate the MAPKs and cPLA2, as defined by shifts in these proteins' electrophoretic mobility and tyrosine phosphorylation of the MAPKs. However, the speed and duration of the MAPK response varied markedly depending on the stimulus. 5-OxoETE caused a very rapid and transient activation of MAPK. In contrast, the response to the cytokines was rather slow and persistent. PMN pretreated with GM-CSF demonstrated a dramatic increase in the extent of MAPK tyrosine phosphorylation and electrophoretic mobility shift in response to 5-oxoETE. Similarly, 5-oxoETE induced PMN to release some preincorporated [14C]arachidonic acid, while GM-CSF greatly enhanced the extent of this release. Thus, the synergism exhibited by these agents is prominent at the level of MAPK stimulation and phospholipid deacylation. Pertussis toxin, but not Ca2+ depletion, inhibited MAPK responses to 5-oxoETE and LTB4, indicating that responses to both agents are coupled through G proteins but not dependent upon Ca2+ transients. 15-OxoETE and 15(OH)-ETE were inactive while 5-oxo-15(OH)-ETE and 5(OH)-ETE had 3- and 10-fold less potency than 5-oxoETE, indicating a rather strict structural specificity for the 5-keto group. LY 255283, a LTB4 antagonist, blocked the responses to LTB4 but not to 5-oxoETE. Therefore, the oxoETEs do not appear to operate through the LTB4 receptor. In summary, the oxoETEs are potent activators of PMN that share some but not all activities with LTB4. The response to the oxoETEs is greatly enhanced by pretreatment with cytokines, indicating that combinations of these mediators may be very important in the pathogenesis of inflammation.

Antagonism of leukotriene responses in human airways by BAY x7195

Contractions induced by leukotriene and anti-IgE (sheep antiserum to human IgE) were antagonized by pretreatment of human airways with the cysteinyl leukotriene receptor antagonist BAY x7195 ((4S)-[4-carboxyphenylthio]-7-[4-(4-phenoxybutoxy)-phenyl]-h ept-5-(z)- enoic acid). However, this receptor antagonist did not inhibit either leukotriene D4- or leukotriene C4-induced contractions in human pulmonary veins. The pA2 value for BAY x7195 in human airways against leukotriene D4 was 7.83 +/- 0.16 with a slope of 1.07 +/- 0.15 (means +/- S.E.M; n = 11). The IC50 value for BAY x7195 in human airways contracted with anti-IgE was 0.31 +/- 0.08 microM (n = 11). These results were comparable to those obtained with ICI 204,219 (4-(5-cyclopentyl-oxycarbonylamino-1-methylindol-3-ylmeth yl)-3-methoxy-N-otolyl - sulfonylbenzamide). These data demonstrate that BAY x7195 is a potent selective leukotriene receptor antagonist which may block allergic reactions in the lung.

Effect of dexamethasone on A23187-induced airway responses in the guinea pig

We examined the effect of dexamethasone on A23187-induced bronchospasm, pulmonary inflammation and airway responses to substance P. Guinea pigs, dosed orally once a day for 4 days with dexamethasone (3.0, 10.0 or 30.0 mg/kg) or saline, were exposed to an aerosol of A23187 for 12 min or until labored breathing began. Postmortem pulmonary gas trapping was used as an indicator of in vivo airway obstruction and changes in bronchial responses. Dexamethasone did not alter airway obstruction or inflammation 1 h after A23187 exposure. However, dexamethasone reduced the enhanced airway responses to substance P and bronchiolar/peribronchiolar inflammation 24 h post-A23187. It is possible that glucocorticosteroid suppression of A23187-induced pulmonary inflammation was important in reducing the increased airway responses to substance P.

Inhaled A23187 produces a preferential sensitization to substance P

We examined the effect of A23187-induced lung injury on airway responses to a variety of bronchoconstrictive aerosols in conscious guinea pigs. Guinea pigs were exposed to aerosolized A23187 or vehicle for 12 min or until labored breathing began. Animals were allowed to recover for 24 h, and then they were challenged with inhaled histamine, leukotriene D4 (LTD4), platelet-activating factor (PAF), or substance P. Eight minutes after start of the bronchoprovocative aerosol, the guinea pigs were killed and excised lung gas volume (ELGV) measurements were used as an index of in vivo airway obstruction. No differences in ELGV dose-response curves to LTD4 were seen in A23187- and vehicle-exposed animals. A23187 exposure produced small increases in both histamine and PAF sensitivity. However, A23187 caused a much more pronounced leftward shift in the dose-response to substance P. Coadministration of the neutral endopeptidase inhibitor, thiorphan, did not reduce the A23187-related airway responses to substance P. Histologic evaluation of A23187-treated lungs revealed peribronchiolar inflammation, bronchiolar epithelial injury, and mild alveolitis. We conclude that A23187 treatment produces differential airway responses to bronchoactive agents, with a preferential sensitization to substance P.

Characteristics of formation and further metabolism of leukotrienes in the chopped human lung

The bronchoconstrictive leukotrienes (LTs) LTC4, LTD4 and LTE4 (cysteinyl-LTs) and the chemoattractant LTB4 were formed in chopped human lung stimulated by the calcium ionophore A23187, or supplied with the precursor LTA4. In contrast, challenge with anti-IgE exclusively induced release of cysteinyl-LTs, indicating that LTB4 is not released as a primary consequence of IgE-mediated reactions in the human lung. Furthermore, several differences were observed with respect to formation and further conversion of LTB4 and LTC4 in the chopped lung preparation. Thus, exogenous [1-14C]arachidonic acid was dose-dependently converted to radioactive LTB4, whereas the cysteinyl-LTs released were not radiolabeled and the amounts of LTC4, D4 and E4 were not influenced by addition of increasing concentrations of arachidonic acid. LTC4 was rapidly and completely converted into LTD4 and LTE4, with no further catabolism of LTE4 within 90 min. The metabolism of LTB4 was much slower than that of LTC4. Thus, following a 60 min incubation approx. 25% of the material remained as LTB4, whereas 35% was omega-oxidized and 40% eluted on RP-HPLC as two unidentified peaks.

Antigen-dependent leukotriene synthesis and histamine release from IgG1 passively-sensitized guinea pig lungs ex vivo: relationship between serum levels of antigen-specific IgG1 and mediator synthesis/release

Naive guinea-pigs were passively sensitized with varying amounts of affinity column purified, homologous, anti-ovalbumin IgG1 (anti-OA IgG1) and then examined for a) the capacity of lung tissue to release mediators (histamine and LTB4/LTD4) in response to antigen-challenge ex vivo and b) the attendant circulating levels of anti-OA IgG1. Intraperitoneal administration of anti-OA IgG1 (0.125-0.75 mg/kg) to guinea-pigs facilitated the synthesis of LTB4 (8-25 ng/g lung) and LTD4 (18-80 ng/g) and the release of histamine (1-7 ug/g) from lung tissue after exposure to 10 micrograms/ml of ovalbumin for 20 min ex vivo. Peak levels of mediators were found using 0.5 mg/kg anti-OA IgG1 with an ED50 = 0.35 mg/kg. LTD4/LTB4 synthesis and histamine release were both antigen concentration- and time-dependent, and LT synthesis was observable in non-perfused lungs and in lungs perfused free of blood. Maximum sensitization occurred at 1-2 days post i.p. administration of anti-OA IgG1 and was maintained up to 7 days. Measurement of anti-OA IgG1 using an enzyme-linked immunosorbent assay demonstrated that circulating antibody levels were 2-6 micrograms/ml at the doses which caused sensitization. The level of anti-OA IgG1 found in passively sensitized animals was at least 100-fold less than that found in actively-sensitized guinea-pigs despite the similar magnitude in LTD4/LTB4 synthesized and the amount of histamine released. Using purified antibody, the results demonstrate that in guinea-pigs, IgG1 can play a prominent role in regulating lung LT synthesis and histamine release, and that microgram per ml circulating levels of this antibody are sufficient to sensitize naive lungs.

CI-949: a new, potential antiallergy compound inhibits antigen-induced allergic reactions in guinea-pigs in vitro and in vivo

CI-949 (5-methoxy-3-(1-methyl-ethoxy)-1-phenyl-N-1H-tetrazol-5-yl-1H -indole-2-carboxamide) effectively inhibited the release of histamine and the synthesis or release of immunoreactive sulfidopeptide leukotrienes C4-D4 and thromboxane B2 from antigen-challenged lung fragments of of actively sensitized guinea-pigs. The IC50s were 26.7 +/- 2.8 microM for histamine, 2.7 +/- 2.4 microM for leukotriene, and 3.0 +/- 1.8 microM for thromboxane. Drugs including ketotifen, cromolyn and nedocromil did not inhibit histamine release or did so only at high concentrations, and only cromolyn inhibited the synthesis or releases of the 2 eicosanoids. A dose of 50 mg/kg i.p. of CI-949 protected conscious, aerosol-allergen challenged guinea-pigs for at least 1 h and 100 mg/kg i.p. or per os protected for at least 2 h. These results, the comparisons to standard antiallergic drugs, and other data from experiments with human lung fragments and isolated peripheral leukocytes 1,2,3,4 suggest that CI-949 should be evaluated for clinical activity against allergic and inflammatory conditions in which histamine, sulfidopeptide leukotrienes, and/or thromboxane mediate symptoms.

Dexamethasone does not inhibit the release of mediators from human mast cells residing in airway, intestine, or skin

Glucocorticoids are potent anti-inflammatory drugs that are widely used in the treatment of allergic disorders. Their actions are often species specific or cell-type specific. Previous studies have demonstrated that glucocorticoids inhibit mediator release from mast cells derived from the peritoneum of mouse or rat and from guinea pig lung, but not those residing in human lung parenchymal tissue. In the present study, we have analyzed the effect of overnight culture with dexamethasone (10(-6) to 10(-7)M) on the subsequent IgE-dependent release of mediators from human mast cells derived from airway tissue, intestine, and skin. Airway tissue was passively sensitized with antigen-specific, IgE-rich serum during the culture period and subsequently challenged with ragweed antigen E. Skin and intestinal mast cells were challenged with anti-IgE. Histamine and immunoreactive LTC4 and PGD2 release was monitored in all experiments. Prostaglandin E release was quantitated in the experiments using airway tissue. Dexamethasone treatment failed to inhibit the release of mast cell mediators from all three tissues, but it inhibited the antigen-induced release of immunoreactive PGE from other cells residing in airway tissue. These results confirm earlier studies of the effects of glucocorticoids on human lung parenchymal mast cells, but contrast with the inhibitory effects of steroids observed in murine mast cells and human basophils.

Characterization of leukotriene C4 synthetase in mouse peritoneal exudate cells

Cell lysates of mouse peritoneal macrophages, in the presence of reduced glutathione, converted leukotriene LTA4 to LTC4, and neither LTD4 nor LTE4 was detected. Therefore, like cultured rat basophilic leukemia cells (RBL cells), the peritoneal macrophage contains LTC4 synthetase and appears to contain little, if any, gamma-glutamyl transpeptidase. When LTA4 was added to subcellular fractions of mouse macrophage lysate, the highest specific activity of LTC4 synthetase (nmol LTC4/mg protein per 10 min) was associated with the particulate or membrane fractions (i.e., 10(4) and 10(5) X g pellets). The 10(5) X g supernatant contains approx. 1% of the specific activity and 6% of the total LTC4 synthetase activity compared with that of the 10(5) X g pellet. Conversely, the 10(5) X g supernatant had four-times more specific activity and 19-times more total GSH S-transferase activity than did the 10(5) X g pellet when evaluated using 1-chloro-2,4-dinitrobenzene (DNCB) as the substrate. LTA4 was converted to LTC4 by the membrane enzyme LTC4 synthetase in a dose-dependent manner at low LTA4 concentrations (3-50 microM) and reached a plateau of approx. 30 microM LTA4 using the macrophage 10(5) X g pellet as an enzyme source. The apparent Km value of LTC4 synthetase for LTA4 was estimated to be 5 microM based on Lineweaver-Burk plots. Enzyme in the 10(5) X g supernatant produced negligible quantities of LTC4 (1% or less of the particulate fractions) over a wide range of LTA4 concentrations. However, an enzyme in the 10(5) X g supernatant fraction presumed to be GSH S-transferase effectively catalyzes the conjugation of glutathione (GSH) with the aromatic compound DNCB. The apparent Km value of GSH S-transferase for DNCB was estimated to be 1.0-1.5 mM. On the other hand, enzyme from the membrane fraction (i.e., 10(5) X g pellet) catalyzed this reaction at a negligible rate over a wide range of DNCB concentrations. The apparent Km value of LTC4 synthetase for GSH was estimated to be 0.36 mM and the corresponding Km value estimated for the glutathione S-transferase was 0.25-0.76 mM. These values indicate similar kinetics for GSH utilization by both enzymes. These Km values are also significantly lower than the intracellular GSH levels of 2 to 5 mM. Therefore, it is suggested that the substrate limiting LTC4 synthetase activity is LTA4 and not GSH. Our results indicate that LTC4 synthetase from mouse peritoneal macrophages is a particulate or membrane-bound enzyme, as was reported by Bach et al.(ABSTRACT TRUNCATED AT 400 WORDS)

Release of leukotrienes in patients with bronchial asthma

To investigate whether leukotrienes (LTs) are released into the bronchial fluid of patients with symptomatic asthma, bronchial lavage was carried out in 17 patients with mild to severe asthma and nine healthy subjects without asthma. LTE4 was detected in 15 of the 17 patients with asthma with reverse-phase high-performance liquid chromatography. The identify of LTE4 was confirmed by ultraviolet spectrometry and by positive ion fast atom-bombardment mass spectrometry. LTD4 was found in two patients and 20-OH-LTB4 in 12 patients. No LTs were detectable in the lavage fluid from any of the healthy subjects without asthma. The finding of LTs in bronchial lavage fluid from the patients with asthma despite bronchodilator and/or corticosteroid therapy suggests that these compounds may be important in asthma. However, the presence of significant quantities of LTE4 in patients with mild asthma requiring only intermittent bronchodilator therapy for control and the lack of correlation between LTE4 and pulmonary function also suggests that other factors may be important in determining the net end organ response. The present study points to the importance of studying the whole spectrum of mediators that are released. Analysis of bronchial lavage fluid may be useful in determining the relative role of these mediators and the effect of pharmacologic intervention.

Effects of various pharmacological agents on isolated human bronchial and pulmonary arterial and venous muscle preparations contracted by leukotriene D4

The response of isolated human bronchial muscle preparations to leukotriene D4 (LTD4, 0.1 microM; 0.22 +/- 0.03 g/mm2) was similar to that of histamine (50 microM; 0.21 +/- 0.02 g/mm2). Isolated pulmonary venous preparations also contracted to these same concentrations of both agonists (LTD4, 0.32 +/- 0.19 g/mm2; and histamine, 0.36 +/- 0.07 g/mm2). However, pulmonary arterial preparations responded to histamine (50 microM, 0.59 +/- 0.10 g/mm2) but exhibited a reduced response to LTD4 (0.3 microM, 0.06 +/- 0.01 g/mm2). Bronchial and pulmonary venous muscle preparations from the human lung had the same sensitivities to LTD4 (pD2 values: bronchus, 7.95 +/- 0.08 and vein, 7.76 +/- 0.07). When bronchial or pulmonary venous muscle preparations were incubated for 30 min with either diltiazem (10 microM), indomethacin (1.7 microM) or L-cysteine (3 microM), the LTD4 cumulative concentration-effect curves following these drug treatments were similar to controls. However, FPL-55712 (10 microM) significantly shifted the LTD4 concentration-effect curves produced in bronchial preparations to the right. In isolated pulmonary arterial preparations none of these drug treatments enhanced the LTD4 response. These results show that isolated human pulmonary arterial preparations are less responsive to LTD4 than bronchial or venous preparations. In addition, the data obtained subsequent to the various drug treatments indirectly suggest that the LTD4 contraction is not modified by a calcium channel blocker or by inhibition of the endogenous products of the cyclooxygenase pathway.

The inflammatory theory of asthma

In summary, these observations suggest a model for asthma which is summarized in Table III. Initially, mast cells and possibly other bronchial cells, e.g., alveolar macrophages, are activated either in an IgE-dependent or, in intrinsic asthma, in an IgE-independent fashion. These cells release two sets of mediators which may be either preformed or newly synthesized. One set of mediators is responsible for the immediate bronchospastic response. This bronchospasm is transient, readily reversible, and not associated with either airway inflammation or bronchial hyperreactivity. The second set of mediators, however, promote chemotaxis and activation of neutrophils and eosinophils. The subsequent bronchial inflammation causes damage and desquamation of the respiratory epithelium. The increased exposure of irritant receptors results in hyperreactive airways. In addition, these inflammatory cells induce mast cell degranulation and recurrent bronchospasm. Thus, after the initial exposure to allergen, a vicious cycle of inflammation, hyperreactivity and recurrent mast cell degranulation develops, ultimately leading to the pathological picture of chronic asthma.

Leukotrienes and lipoxins: structures, biosynthesis, and biological effects

Arachidonic acid is released from membrane phospholipids upon cell stimulation (for example, by immune complexes and calcium ionophores) and converted to leukotrienes by a 5-lipoxygenase that also has leukotriene A4 synthetase activity. Leukotriene A4, an unstable epoxide, is hydrolyzed to leukotriene B4 or conjugated with glutathione to yield leukotriene C4 and its metabolites, leukotriene D4 and leukotriene E4. The leukotrienes participate in host defense reactions and pathophysiological conditions such as immediate hypersensitivity and inflammation. Recent studies also suggest a neuroendocrine role for leukotriene C4 in luteinizing hormone secretion. Lipoxins are formed by the action of 5- and 15-lipoxygenases on arachidonic acid. Lipoxin A causes contraction of guinea pig lung strips and dilation of the microvasculature. Both lipoxin A and B inhibit natural killer cell cytotoxicity. Thus, the multiple interaction of lipoxygenases generates compounds that can regulate specific cellular responses of importance in inflammation and immunity.

A comparative study of methyl ester trimethylsilyl, allyldimethylsilyl and tert-butyldimethylsilyl ethers for electron impact mass spectrometry of leukotrienes

The gas chromatographic and mass spectrometric properties of leukotriene B4, 20-hydroxy-leukotriene B4 and 20-carboxy-leukotriene-B4 were investigated as their methyl ester trimethylsilyl, methyl ester allyldimethylsilyl and methyl ester tert-butyldimethylsilyl ethers. The gas chromatographic properties of the trimethylsilyl and tert-butyldimethylsilyl ether derivatives were good with respect to peak shape and sensitivity, whereas the allyldimethylsilyl ether derivative gave a lower sensitivity. The sensitivity defined as the quantity that could be passed through the gas chromatographic column. The three derivatives showed a mass spectrometric fragmentation pattern with cleavage of the C12-C13 bond as an important feature. Particularly, the allyldimethylsilyl ether derivative of the three compounds studied exhibited a high tendency for C12-C13 bond cleavage resulting in a fairly intense ion at m/z 435. However, the mass spectra indicated multiple fragmentation pathways due to the presence of double bonds, leading to decreased intensities of the high mass ions. A quantitative analysis by selected ion monitoring of the most intense high mass ions in the respective mass spectrum demonstrated that neither derivative would allow measurements in the low picogram range. Catalytic hydrogenation of the double bonds was performed and the methyl ester trimethylsilyl, methyl ester allyldimethylsilyl and methyl ester tert-butyldimethylsilyl ether derivatives of the reduced compounds were prepared. Saturation of the double bonds increased the gas chromatographic sensitivity for the three derivatives as well as the intensities of the high mass ions in their mass spectra. The high sensitivity that can be obtained by measurement of such high mass ions was demonstrated by quantification of leukotriene B4 in lung tissue samples by selected ion monitoring.

Gas chromatography-mass spectrometry of monohydroxyeicosatetraenoic acids as their methyl esters trimethylsilyl, allyldimethylsilyl and tert.-butyldimethylsilyl ethers

The gas chromatographic and mass spectrometric properties of the monohydroxy acids 5-hydroxyeicosatetraenoic acid (5-HETE), 12-hydroxyeicosatetraenoic acid (12-HETE) and 15-hydroxyeicosatetraenoic acid (15-HETE) as their methyl ester trimethylsilyl, methyl ester allyldimethylsilyl and methyl ester tert.-butyldimethylsilyl ethers were investigated. The gas chromatographic properties of the trimethylsilyl and tert.-butyldimethylsilyl derivatives were found to be excellent while the allyldimethylsilyl derivative required a well deactivated column. The mass spectra of these silyl derivatives with the exception for 12-HETE did not exhibit particularly intense ions in the upper mass region. A quantitative analysis by selected-ion monitoring of the most intense ion in the upper mass region of respective mass spectrum demonstrated that a detection limit in the low picogram range could only be obtained for 12-HETE. Since the mass spectra indicated that the double bonds exerted a strong influence on the fragmentation pattern, the trimethylsilyl, allyldimethylsilyl and tert.-butyldimethylsilyl ethers of the methyl esters of the reduced analogues of the monohydroxy acids were prepared. The saturation of the double bonds completely altered the fragmentation patterns and very intense ions carrying a high percentage of the total ion abundance were found in all of the mass spectra. The developed technique was utilized for measurements of 5-HETE in lung tissue samples from patients with lung cancer.

Pharmacological comparison of L-serine borate and glutathione as inhibitors of metabolism of LTC4 to LTD4 by the isolated guinea pig trachea

Cumulative dose-response curves to leukotriene C4 (LTC4) and leukotriene D4 (LTD)4 were obtained on indomethacin (5 microM) treated isolated guinea pig tracheal spiral strips. LTC4 curves, in the presence of either glutathione (GSH; 10 mM) or L-serine borate (SB; 45 mM), were not antagonized by FPL-55712 (3 microM), a selective LTD4 receptor antagonist. LTC4 curves on trachea treated with a lower concentration of GSH (1 mM), and LTD4 curves were competitively antagonized by FPL-55712. LTC4 curves on GSH (10 mM) treated trachea were 2 fold to the left of those on SB treated tissues. This effect of GSH was blocked by pretreatment with nordihydroguiaretic acid (30 microM), an inhibitor of 5-lipoxygenase. GSH (10 mM) and SB (45 mM) are effective inhibitors of conversion of LTC4 into functionally important levels of LTD4 by the guinea pig trachea. In addition, GSH appears to enhance LTC4 responsiveness by increasing synthesis of a contractile 5-lipoxygenase product(s), possibly LTC4. From the data it is suggested that for inhibition of LTC4 metabolism, SB may be more useful when examining responses to exogenously applied LTC4, while GSH (10 mM) may be more useful when examining responses to endogenously generated LTC4.

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.

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.