The development of sensitive and specific radioimmunoassays for leukotrienes

Sustained submaximal exercise does not alter the integrity of the lung blood-gas barrier in elite athletes

The extreme thinness of the pulmonary blood-gas barrier results in high mechanical stresses in the capillary wall when the capillary pressure rises during exercise. We have previously shown that, in elite cyclists, 6-8 min of maximal exercise increase blood-gas barrier permeability and result in higher concentrations of red blood cells, total protein, and leukotriene B4 in bronchoalveolar lavage (BAL) fluid compared with results in sedentary controls. To test the hypothesis that stress failure of the barrier only occurs at the highest level of exercise, we performed BAL in six healthy athletes after 1 h of exercise at 77% of maximal O2 consumption. Controls were eight normal nonathletes who did not exercise before BAL. In contrast with our previous study, we did not find higher concentrations of red blood cells, total protein, and leukotriene B4 in the exercising athletes compared with control subjects. However, higher concentrations of surfactant apoprotein A and a higher surfactant apoprotein A-to-phospholipid ratio were observed in the athletes performing prolonged exercise, compared with both the controls and the athletes from our previous study. These results suggest that, in elite athletes, the integrity of the blood-gas barrier is altered only at extreme levels of exercise.

The importance of leukotrienes in airway inflammation in a mouse model of asthma

Inhalation of antigen in immunized mice induces an infiltration of eosinophils into the airways and increased bronchial hyperreactivity as are observed in human asthma. We employed a model of late-phase allergic pulmonary inflammation in mice to address the role of leukotrienes (LT) in mediating airway eosinophilia and hyperreactivity to methacholine. Allergen intranasal challenge in OVA-sensitized mice induced LTB4 and LTC4 release into the airspace, widespread mucus occlusion of the airways, leukocytic infiltration of the airway tissue and broncho-alveolar lavage fluid that was predominantly eosinophils, and bronchial hyperreactivity to methacholine. Specific inhibitors of 5-lipoxygenase and 5-lipoxygenase-activating protein (FLAP) blocked airway mucus release and infiltration by eosinophils indicating a key role for leukotrienes in these features of allergic pulmonary inflammation. The role of leukotrienes or eosinophils in mediating airway hyperresponsiveness to aeroallergen could not be established, however, in this murine model.

Toxoplasma gondii alters eicosanoid release by human mononuclear phagocytes: role of leukotrienes in interferon gamma-induced antitoxoplasma activity

Toxoplasma gondii tachyzoites markedly alter the profile of eicosanoids released by human mononuclear phagocytes. Freshly isolated, 2-h adherent human monocytes release both cyclooxygenase (e.g., thromboxane [TX] B2, prostaglandin [PG] E2) and 5-lipoxygenase (e.g., leukotriene [LT] B4, LTC4) products of arachidonic acid metabolism after stimulation by the calcium ionophore A23187 or ingestion of opsonized zymosan particles or heat-killed T. gondii. However, after incubation with viable T. gondii, normal and chronic granulomatous disease monocytes release only the cyclooxygenase products TXB2 and PGE2 and fail to form LTB4, LTC4, or other 5-lipoxygenase products. Monocytes maintained in culture for 5 d lose this capacity to release TXB2 and PGE2 after incubation with T. gondii. T. gondii significantly inhibit calcium ionophore A23187-induced LTB4 release by monocyte-derived macrophages; heat-killed organisms do not affect this calcium ionophore A23187-induced release of LTB4. T. gondii-induced inhibition of LTB4 release by calcium ionophore A23187-stimulated monocyte-derived macrophage is reversed by interferon (IFN)-gamma treatment of the monolayers. LTB4 induced extensive damage to the cellular membranes and cytoplasmic contents of the organisms as observed by transmission electron microscopy. Exogenous LTB4 (10(-6) M) induced intracellular killing of ingested T. gondii by non-IFN-gamma-treated monocyte-derived macrophages. IFN-gamma-induced antitoxoplasma activity in monocyte-derived macrophages was inhibited by the selective 5-lipoxygenase inhibitor zileuton but not by the cyclooxygenase inhibitor indomethacin. These findings suggest a novel role for 5-lipoxygenase arachidonic acid products in human macrophage IFN-gamma-induced antitoxoplasma activity.

Lipoxygenase stimulating effects of hydroxylated docosahexaenoates produced by human platelets

Human platelet suspensions are capable of lipoxygenating docosahexaenoic acid (22:6n3) to an 11(S)-OH-, 14(S)-OH- or 17(S)-OH-22:6n3. The structure and stereochemical purity of these derivatives were confirmed by GC/MS and chiral phase LC analysis. The purified OH-22:6n3 positional isomers which are formed by human platelets were capable of inducing a concentration-dependent contractile response in the guinea-pig lung parenchymal strip at sub-micromolar concentrations. OH-22:6n3 may act in part through stimulation of leukotriene (LT) production as an increase in peptidyl-LT levels (LTC4, LTD4 and LTE4) occurred during the OH-22:6n3-induced contraction in this preparation. Both specific lipoxygenase inhibitors (caffeic acid, 20 uM and NDGA, 50 uM) and a LT receptor antagonist (FPL55712, 20 uM) significantly inhibited the contractile response. Moreover, the OH-22:6n3 positional isomers induced a concentration-dependent increase in LTB4 and LTC4 production in the guinea-pig chopped lung preparation. Other hydroxylated fatty acids and parent fatty acids which were tested (12-OH-20:4n6, 5-OH-20:4n6, 12-OH-20:5n3, 20:5n3 and 22:6n3) did not significantly contract this airway smooth muscle preparation or alter LT production. The hydroxylated 22:6n3 metabolites may modulate airway smooth muscle function in part through the release of peptidyl-LTs from the guinea-pig lung.

Lung mast cells increase in number and degranulate during pulmonary artery occlusion/reperfusion injury in dogs

The role of mast cells in pulmonary artery occlusion/reperfusion injury was examined. Lung tissue was obtained from dogs after left pulmonary artery occlusion for 48 h (n = 5) or after similar occlusion followed by 4 h of reperfusion (n = 11). By light microscopy and morphometry, the percentage of mast cells increased 2.4-fold (p < 0.05) in nonoccluded right lungs and 2.9-fold (p < 0.05) in occluded left lungs without reperfusion compared with that in control lungs. After reperfusion, the occluded left lung contained 1.8-fold (p < 0.05) as many mast cells as the nonoccluded right lung and 4.2-fold (p < 0.05) more than that in control lungs. Hydroxyurea did not significantly affect the number of mast cells observed in the right and left lungs after ischemia/reperfusion; 39.8% and 54.4% of the mast cells were degranulated in nonoccluded right lung and occluded left lung preparations, respectively, after left pulmonary artery ischemia/reperfusion (each, p < 0.05 compared with control lungs). The release of eicosanoids into the airways during ischemia/reperfusion injury was also examined. Thromboxane B2 and leukotriene B4 were markedly increased (each, p < 0.05 compared with that in control lungs) in bronchial lavage fluids from both nonoccluded and occluded lungs compared with sham-occluded lungs. Thus, mast cell recruitment and degranulation may play a role in lung ischemia/reperfusion injury.

Acute changes in vasoactive lipid mediators in experimental hyaline membrane disease

Endothelial release of the arachidonate derivative PGI2 may be increased in response to cyclic lung stretching. We therefore sought to determine if the stable metabolite of PGI2, 6-keto-PGF1 alpha, would be found in increased quantities in primates ventilated with conventional mechanical ventilation (CMV) compared to treatment with high frequency oscillatory ventilation (HFOV). We also sought to determine if other membrane-derived vasoactive substances such as LTC4, PAF and TXB2 would be elevated in plasma and lung tissue of animals developing hyaline membrane disease (HMD) and if the levels would correlate with the severity of the respiratory distress. Twenty prematurely delivered monkeys were treated with either CMV or HFOV from the first breath after Cesarean delivery until sacrifice at 6 h of age. We found a significant increase from birth to 5 min and from 5 min to 5 h in 6-keto-PGF1 alpha, and a significant increase from 5 min to 5 h in TXB2. We found a significant decline from cord blood to 5 min of LTC4, without further change by 5 h. PAF was present in all plasma samples but showed no upward or downward trend. There was no difference in the 5-h plasma level or in the lung homogenate level of any of the lipid mediators between the two types of assisted ventilation. There was no correlation between any lipid mediator level and severity of the HMD, as measured by gas exchange, radiographic or histologic criteria, when assessed by each ventilator group alone or with both groups combined. We conclude that the immediate postnatal increases in TXB2 and PGI2 and decrease in LTC4 are not altered substantially by use of HFOV.

Acute and chronic suppression of leukotriene B4 synthesis ex vivo in neutrophils from patients with rheumatoid arthritis beginning treatment with methotrexate

OBJECTIVE

To compare the cumulative effects of oral methotrexate (MTX) therapy (after 6-8 weeks) with the acute effects (24 hours after a dose) on arachidonic acid metabolism by the 5-lipoxygenase (5-LO) pathway in neutrophils from patients with active rheumatoid arthritis (RA) who were beginning therapy with MTX.

METHODS

Neutrophils and monocytes were isolated from whole blood from 7 patients with RA, immediately before and 24 hours after their first weekly dose of 7.5 mg of MTX, and again after their dose at 6-8 weeks.

RESULTS

Total immunoreactive leukotriene B4 (LTB4) formation in neutrophils activated ex vivo with calcium ionophore A23187 was significantly suppressed (by 33%) before the 6-8-week dose, compared with the level before the first dose (mean +/- SEM 8.29 +/- 1.24 ng/10(6) cells at predose 6-8 weeks versus 12.29 +/- 2.13 ng/10(6) cells at predose 1; P = 0.03). Reductions were also observed after the first dose (27%; P = 0.07) and after the 6-8-week dose (43%; P = 0.05) compared with the respective predose levels. MTX treatment produced significant reductions in the total generation of 5-LO pathway products (5-hydroxyeicosatetraenoic acid + 6-trans-LTB4 + LTB4 + omega-oxidation products of LTB4) by calcium ionophore-activated neutrophils, as quantitated by integrated optical density after resolution on reverse-phase high-performance liquid chromatography. Decreases were observed after the first dose (26%; P = 0.025), immediately before the 6-8-week dose (23%; P = 0.05), and after the 6-8-week dose (47%; P = 0.0033) compared with levels before the first dose, and after the 6-8-week dose compared with the level before it (32%; P = 0.04). The generation of LTB4 by calcium ionophore-activated monocytes was not significantly affected by MTX therapy.

CONCLUSION

The significant decreases in the formation of omega-oxidation products of LTB4 and in the total generation of neutrophil 5-LO pathway products in the absence of a significant change in the release of 3H-arachidonic acid or the generation of platelet-activating factor suggest that the activity of the 5-LO enzyme in neutrophils is inhibited. We conclude that weekly oral MTX therapy in patients with active RA inhibits neutrophil 5-LO pathway product generation in a pattern consistent with inhibition of the activity of the 5-LO enzyme; an effect is observed after the first dose. The inhibition of 5-LO is cell-selective and cumulative, with a superimposed incremental inhibition observed after the weekly MTX dose.

Enhanced leukotriene synthesis in leukocytes of atopic and asthmatic subjects

1. We have investigated the capacities of peripheral leukocytes from atopic asthmatic (AA) (n = 7), atopic non-asthmatic (AN) (n = 7), and normal (N) (n = 7) subjects to generate the bronchoconstrictor and proinflammatory mediators leukotrienes (LTs) B4 and C4. 2. Mixed leukocyte preparations containing 61-84% neutrophils, 2.4-15% eosinophils, and 13-29% mononuclear cells were incubated in vitro at 37 degrees C in the presence of calcium ionophore A23187. Synthesis of LTB4 and LTC4 was quantitated by radioimmunoassay. 3. Both in dose-response experiments (0-10 microM A23187 for 5 min), and in time-course investigations (2 microM A23187 for 0-30 min), the mixed leukocytes of the AA and AN subjects generated on average 4- to 5-fold more LTB4 and 3- to 5-fold more LTC4 than the normal leukocytes (P less than 0.01 in all cases; ANOVA). 4. This enhanced LT synthesis by the AN and AA leukocytes was not due to differences in the counts of leukocyte sub-types, or to altered rates of LT catabolism between the subject groups. 5. LTB4 synthesis correlated significantly with LTC4 synthesis in the leukocytes of the AN and AA subjects (r = 0.81, n = 14, P less than 0.01), but not in those of the normal subjects (r = 0.19, n = 7, P greater than 0.05). 6. Our results demonstrate an up-regulation of the leukotriene synthetic pathway in the circulating leukocytes of atopic non-asthmatic and atopic asthmatic subjects, which may have important implications in the pathophysiology of asthma and allergy.

Biosynthesis of eicosanoids by blood cells of the crab, Carcinus maenas

Blood cells from the crab, Carcinus maenas, stimulated with calcium ionophore A23187, in the presence of exogenous fatty acid, produced cyclooxygenase, lipoxygenase and monooxygenase derivatives of eicosatetraenoic (20:4(n - 6)) and eicosapentaenoic (20:5(n - 3)) acids. Isolation, identification and quantification of these products was achieved using chiral and reverse phase-high performance liquid chromatography, gas-chromatography, radioimmunoassay and gas chromatography-mass spectrometry. The principle metabolites observed were 8-hydroxy fatty acids and 'E' series prostaglandins. Smaller amounts of thromboxane B2, 6-keto-prostaglandin F1 alpha and 5-, 9-, 11-, 12- and 15-hydroxy-eicosatetraenoic acids were also synthesised. Lipoxygenase, cyclooxygenase and cytochrome P-450 inhibitors were used to investigate the mode of product formation. Mixtures of hydroxy-fatty acid enantiomers were produced and the dominant chiral form varied with the position of the hydroxyl group. No leukotrienes or lipoxins were detected.

Neutrophil accumulation in the lung in alpha 1-antitrypsin deficiency. Spontaneous release of leukotriene B4 by alveolar macrophages

The emphysema of alpha 1-antitrypsin (alpha 1AT) deficiency is conceptualized to result from insufficient alpha 1AT allowing neutrophil elastase to destroy lung parenchyma. In addition to the deficiency of alpha 1AT in these individuals resulting from mutations in the alpha 1AT gene, it is recognized that, for unknown reasons, there are also increased numbers of neutrophils in their lungs compared with normal individuals. With the knowledge that alveolar macrophages have surface receptors for neutrophil elastase, we hypothesized that the neutrophil accumulation in the lower respiratory tract in alpha 1AT deficiency may result, in part, from release of neutrophil chemotactic activity by alveolar macrophages as they bind uninhibited neutrophil elastase. Consistent with this hypothesis, alpha 1AT-deficient alveolar macrophages spontaneously released nearly threefold more neutrophil chemotactic activity than normal alveolar macrophages. Analysis of alpha 1AT-deficient macrophage supernates by reverse-phase HPLC, molecular sieve chromatography, radioimmunoassay, and absorption with anti-LTB4 antibody revealed that the majority of the chemotactic activity was leukotriene B4 (LTB4), a mediator absent from normal macrophage supernates. Consistent with this hypothesis, incubation of normal macrophages with human neutrophil elastase resulted in the release of the same neutrophil chemotactic mediator. Furthermore, purified human alpha 1AT was able to prevent the neutrophil elastase from stimulating the macrophages to release the chemotactic factor. Together, these findings suggest that the absence of a normal antineutrophil elastase screen in the lower respiratory tract permits free neutrophil elastase to bind to alveolar macrophages, resulting in the release of LTB4, a process which attracts neutrophils to the alveoli of alpha 1AT deficient individuals, thus accelerating the lung destruction that characterizes this disorder.

Leukotrienes in the sputum and urine of cystic fibrosis children

1. Leukotrienes (LTs) are potent pro-inflammatory mediators with actions relevant to the pathophysiology of cystic fibrosis (CF), including increased mucus production, bronchoconstriction, leucocyte chemotaxis, and increased vascular permeability. We have therefore investigated the potential role of LTs in children with CF. Leukotriene E4 levels were assessed in the urine of 30 normal (N) children (aged 1.3-12.7 years) and 30 CF children (1.6-14.3 years). Sputum from 13 of the CF children was analysed from LTB4, LTC4, LTD4, and LTE4. LTs were separated by reversed-phase h.p.l.c. and quantitated by radioimmunoassay. 2. Urinary LTE4 levels were log normally distributed, with geometric mean values (95% confidence intervals) of N: 88.4 (71.3-111) pmol mmol-1 creatinine (n = 30), and CF: 112 (70.6-177) pmol mmol-1 creatinine (n = 30; P greater than 0.05). Of the CF subjects, 33% had urinary LTE4 levels above 200 pmol mmol-1 creatinine, compared with 3.3% of the N children. 3. In sputum, mean (+/- s.e. mean) LT concentrations were (pmol g-1), LTB4: 44.3 +/- 10.8, LTC4: 4.9 +/- 1.3, LTD4: 1.8 +/- 0.9, and LTE4: 67.7 +/- 18.9 (n = 13). 4. Urinary LTE4 levels correlated significantly with sputum LTE4 levels (r = 0.673, P = 0.012), and with sputum levels of total cysteinyl-LTs (r = 0.660, P = 0.014). 5. In conclusion, total cysteinyl-LT content in sputum is 10-fold higher than previously reported, consisting primarily (91%) of LTE4. The high levels of LTE4 and LTB4 in sputum suggest involvement of LTs in the pathophysiology of CF. Urinary LTE4 levels may prove useful as a marker for cysteinyl-LT production in sputum.

Inhibition of leukotriene B4 synthesis in neutrophils from patients with rheumatoid arthritis by a single oral dose of methotrexate

We studied the effects of a single, oral dose of methotrexate (MTX) on arachidonic acid metabolism in neutrophils from 6 patients with rheumatoid arthritis, which were obtained 1 day before and 1 day after their usual weekly MTX dose. The 6 patients had received a mean weekly MTX dose of 9.6 mg (range 5-15) for a mean of 61.7 months (range 58-64), and none received concomitant corticosteroids. Total generation of leukotriene B4 (LTB4) in neutrophils stimulated ex vivo with 10 microM calcium ionophore A23187 for 20 minutes was significantly suppressed, by a mean of 53%, after the MTX dose compared with the predose levels (mean +/- SEM 13.0 +/- 1.4 ng/10(6) cells versus 6.0 +/- 0.9 ng/10(6) cells; P = 0.0019), reflecting a comparable suppression of both released and cell-retained LTB4. A 49% decrease in omega-oxidation products of LTB4 demonstrates that decreased LTB4 synthesis, rather than increased degradation, is responsible for the decrease in LTB4 generation. The absence of a significant change in either 3H-labeled arachidonic acid release or platelet-activating factor generation indicates that the observed decrease in LTB4 synthesis was apparently not caused by diminished phospholipase A2 activity. A 28% decrease in the total formation of the 5-lipoxygenase products 5-hydroxyeicosatetraenoic acid and the 6-trans-LTB4 diastereoisomers, and a 48% suppression of production of LTB4 plus its omega-oxidation metabolites after the MTX dose suggest inhibition of 5-lipoxygenase activity and possible suppression of leukotriene A4 epoxide hydrolase activity.

Effects of N-acetyl-aspartyl glutamic acid and sodium cromoglycate on leukotriene B4 secretion by human leukocytes

Peripheral leukocytes from allergic subjects were treated for 30 min with sodium cromoglycate (SCG) or with N-acetyl-aspartyl glutamic acid (NAAGA) and challenged for leukotriene B4 (LTB4) production with calcium ionophore A 23187. NAAGA significantly inhibits LTB4 release at concentrations of 10(-2) M (-86%), 5 x 10(-3) M (-49%) and 10(-3) M (-34%), while SCG was not able to block LTB4 production within the range of 10(-2)-10(-4) M. In spite of the fact that SCG and NAAGA are chemically unrelated and that both show antiallergic properties, only NAAGA is able in this model to block production of LTB4, a chemical mediator strongly involved in inflammatory and hypersensitivity reactions.

The influence of net surface charge on the interaction of uropathogenic Escherichia coli with human neutrophils

Escherichia coli strains, grown to suppress fimbrial expression, synthesised enhanced quantities of polysaccharide capsule, which significantly lessened their binding to heparin sepharose columns. In the presence of poly-L-lysine, these strains were strongly retained on the columns confirming their highly anionic nature. Uropathogenic strains of E. coli expressing type 1 fimbrial adhesins activated the respiratory burst, the degranulation response and the release of leukotrienes from human neutrophils (PMN) to a significantly greater extent than the same strains grown in a medium to suppress this fimbrial expression. The addition of the poly-cation poly-L-lysine, however, selectively increased neutrophil activation in response to these non-fimbriate strains. This dose-dependent effect was reversed by the addition of heparin suggesting a mechanism dependent on surface charge. The results of this study suggest that non-specific mechanisms involving the neutralisation of surface charge, in addition to specific receptor and adhesin mediated events could affect neutrophil activation at sites of infection.

Leukotriene B4 and oral cancer

The quantitation of leukotriene B4 (LTB4) in induced squamous cell carcinoma (SCC) of the Syrian hamster cheek pouch and histologically proven human oral SCC was investigated by a combination of reverse phase-high performance liquid chromatography (RP-HPLC) and radioimmunoassay (RIA). Healthy tissue obtained from these same patients and animals treated with vehicle alone were used as controls. From both animal and human studies our results show a 10 to 30 fold increase in the levels of LTB4 found in tumour compared to control tissue. Furthermore, this dihydroxy acid was not detected in the mucosal tissue of normal subjects undergoing routine surgery. Since LTB4 is a potent inflammatory mediator and modulator of immune responses, its presence at biologically active concentrations in human squamous cell carcinoma suggests a possible role in the pathogenesis of head and neck cancer.

Isolation, culture and characterization of human peritoneal mesothelial cells

This study establishes a reproducible technique for the culture of human peritoneal mesothelial cells. Direct explants, as well as enzymatically degraded specimens, of human omentum have been used as the source of cells. Cells were grown on collagen and gelatin coated matrices and were maintained in supplemented Ham's F-12 medium containing 10% (vol/vol) Fetal calf serum. Morphologically and ultrastructurally, the cells formed a homogeneous population. They were polygonal when confluent and devoid of contaminating fibroblasts, endothelial cells and macrophages. Cultured mesothelial cells co-expressed cytokeratin and vimentin and synthesized laminin, fibronectin, mesosecrin, non-specific esterase and collagen Types I and III but not Type IV. Ultrastructural features included numerous surface microvilli, cytoplasmic vesicles and an abundant endoplasmic reticulum. The stimulation of mesothelial cells by the calcium ionophore A23187 demonstrated that the two major products of arachidonic acid metabolism were prostacyclin and prostaglandin E2. The peritoneal mesothelial cell may be pivotal in the initiation of the inflammatory response during peritonitis and its establishment in culture will provide the basis for an in vitro model of peritoneal inflammation.

Leukotriene B4 generation by human monocytes and neutrophils stimulated by uropathogenic strains of Escherichia coli

The generation of the 5-lipoxygenase product, leukotriene B4 (LTB4) by human mononuclear phagocytes (monocytes) following incubation with 25 different uropathogenic strains of Escherichia coli correlated with the haemolytic activity of the strains (r = 0.572, P less than 0.01). LTB4 generation by human neutrophils (PMN), however, was unrelated to this haemolytic potential (r = 0.164). In contrast, both prelabelled monocytes and PMN were stimulated by haemolytic strains of E. coli and by haemolytic culture supernatants to release significant amounts of [3H]arachidonic acid. There was a significant correlation between haemolytic activity and [3H]arachidonic acid release generated by individual strains from monocytes (r = 0.804, P less than 0.001) and PMN (r = 0.888, P less than 0.001). In addition, nonhaemolytic strains but not their culture supernatants were capable of causing slow release of both [3H]arachidonic acid and LTB4 from PMN and mononuclear cells. These results suggest that both the possession of haemolytic activity, and the direct interaction of bacteria with the leukocyte surface are mechanisms by which uropathogenic strains of E. coli may cause the release and metabolism of arachidonic acid. In addition, there was synergistic augmentation by nonhaemolytic bacteria of the PMN LTB4 response to haemolytic culture supernatants or to low doses of the calcium ionophore A23187. These results support an ionophore-like mechanism for the activation of the cell by haemolysin. LTB4 generation by PMN incubated with haemolytic supernatants was also augmented by particulate zymosan in a manner dependent on the dose of zymosan, suggesting that the direct interaction of E. coli with PMN may involve an activation mechanism similar to that for zymosan. These results demonstrate differing responses of peripheral mononuclear cells and PMN from the same donors to identical strains of E. coli and suggest that the generation of the potent chemotactic agent LTB4 in response to E. coli infection in vivo need not depend solely on the elaboration of cytotoxic haemolysins by individual strains.

Retinoid-induced inhibition of eosinophil LTC4 production

Naturally occurring and synthetic retinoids demonstrate a marked antiinflammatory effect when employed in such disorders as acne and psoriasis. This effect may result in part from their inhibition of release of potent mediators (e.g. eicosanoids) by inflammatory cells. In this study, we examined the effect of eight retinoids (tretinoin, isotretinoin, retinol, retinal, acitretin, retinyl palmitate, etretinate, Ro 15-0778) on the release of leukotriene (LT)C4, an important lipid mediator generated by eosinophils. Tretinoin, isotretinoin, retinol, retinal, and acitretin at 10(-5) M or 10(-4) M concentrations inhibited LTC4 release by A23187-stimulated horse eosinophils in vitro; 10(-4) M retinyl palmitate was also inhibitory. However, 10(-5) M etretinate augmented A23187-induced LTC4 release, and the arotinoid Ro 15-0778 had no effect on LTC4 production. These data suggest that selected retinoids may have potential use in the reduction of LTC4 generation by eosinophils. This inhibition could be beneficial in the therapy of such diseases as bronchial asthma in which release of LTC4 may be involved in the inflammatory process.

U937 and THP-1 cells do not release LTB4, LTC4, or LTD4 in response to A23187

U937 and THP-1 cells possess some characteristics of human mononuclear phagocytes, cells which synthesize and release LTB4, LTC4, and LTD4. Incubation of these cells with recombinant human interferon-gamma (IFN-gamma) or Phorbol Myristate Acetate (PMA) induces a more differentiated cell state. We hypothesized that U937 and THP-1 cells would release LTB4, LTC4, and LTD4 in response to stimulation with the non-physiologic agonist, calcium ionophore A23187 and that preincubation with IFN-gamma or PMA might alter leukotriene release by these cells. We cultured both cell lines for 48 hours in the presence and absence of IFN-gamma (1000 units/ml) and for 120 hours in the presence and absence of PMA (160 nM) and then challenged them with A23187 (5uM) for 30 minutes at 37 degrees C. The supernatants were deproteinated and assayed by RIA for LTB4 and LTC4 and by RP-HPLC for LTB4, LTC4, and LTD4. Neither U937 nor THP-1 cells released quantities of leukotrienes detectable by RIA, less than 0.3ng/5 X 10(6) cells. Peripheral blood mononuclear phagocytes from normal volunteers, cultured and challenged in vitro at under identical conditions, released 11.3 +/- 2.9 ng LTB4 and 2.0 +/- 1.5 ng LTC4/10(6) viable monocytes. The lack of leukotriene production by U937 and THP-1 cells was not altered by preincubation for 48 hours with IFN-gamma (n = 3) nor by preincubation with PMA for 120 hours (n = 3). We conclude 1) U937 and THP-1 cells do not appear to be appropriate in vitro models for the examination of leukotriene release from normal mononuclear phagocytes. 2) Pre-incubation of U937 and THP-1 cells with IFN-gamma or PMA under the conditions tested, does not induce the ability of these cell lines to release leukotrienes.

Activation of the inflammatory response of neutrophils by Tamm-Horsfall glycoprotein

The activation of human polymorphonuclear leukocytes (PMN) by particulate Tamm-Horsfall glycoprotein (THG) represents an interaction hitherto unrecognized. The potential pathophysiological effect of this phenomenon within the interstitium of the kidney is highlighted by the activation of the respiratory burst, as well as by comprehensive PMN degranulation. Products of the interaction are expressed in terms of phagocytosis, luminol-dependent chemiluminescence, granule marker enzyme release and arachidonic acid metabolism. Significant quantities of the primary, secondary and tertiary granule markers, myeloperoxidase, vitamin B12 binding protein and N-acetyl-beta-D-glucosaminidase, respectively, were secreted in a dose and time-dependent manner. Phagocytosis of the glycoprotein was accompanied by the generation of significant quantities of leukotriene B4. Furthermore, the ability of such a particulate ligand to activate the alternative pathway of complement clearly represents a capacity to augment the inflammatory response. Should the interaction of THG with PMN take place within the interstitium of the kidney, augmented by the deposition of complement proteins on the surface of insoluble aggregates, the resulting inflammatory response may lead to marked tissue damage and eventually result in interstitial fibrosis.

The generation and metabolism of leukotrienes in the ionophore-stimulated blood of normal and asthmatic subjects

The generation and metabolism of leukotrienes (LTs) B4, C4, D4, and E4 were studied in vitro in the A23187-stimulated whole blood of normal (N) and atopic asthmatic (AA) human subjects. Using a combination of reversed-phase high performance liquid chromatography and radioimmunoassay, we have demonstrated that the blood cells of atopic asthmatic patients have an enhanced ability to release LTB4 and LTC4 when compared to those of normal subjects. The release of LTB4 and LTC4 in response to ionophore is dose- and time-dependent. Half-maximal doses of ionophore caused the generation of high, sustained levels of LTB4, which are significantly higher in the AA blood than in N blood. Incubations of 3H-LTB4 in ionophore-stimulated N and AA blood revealed a slow metabolism to 20-OH-LTB4 and 20-COOH-LTB4. LTC4 is generated in smaller amounts than LTB4, with an early peak after 10 min which is significantly higher (p less than 0.01) in the AA blood compared to the N blood. Subsequent metabolism of LTC4 elicits significantly greater amounts of LTD4, and consistently higher levels of LTE4, in the AA blood. Parallel incubations of 3H-LTC4 in ionophore-stimulated N and AA blood demonstrated rapid metabolism of LTC4 by the glutathione detoxification pathway. The elevated production of LTB4 and LTC4 in AA blood was not accounted for by differences in leukocyte sub-type counts in the two groups, nor by differences in their rates of catabolism. The novel, selective 5-lipoxygenase inhibitor BW A4C [N-(3-phenoxycinnamyl) acetohydroxamic acid] caused dose-dependent inhibition of LTB4 and LTC4 generation and was equipotent in N and AA blood.

Identification and characterization of a monocyte-derived neutrophil-activating factor in corticosteroid-resistant bronchial asthma

Peripheral blood mononuclear cells (PBMC) were isolated from seven normal subjects, eight asthmatic subjects clinically sensitive to corticosteroids (CS), and eight asthmatic subjects clinically resistant to corticosteroids (CR). PBMC were cultured at 37 degrees C for 24 h in the absence or presence of 10(-16) to 10(-4) M hydrocortisone. Calcium ionophore (A23187)-activated neutrophils (PMN) primed by supernatants of PBMC from asthmatic subjects cultured in the absence of hydrocortisone generated approximately threefold more leukotriene B4 than PMN primed by supernatants of PBMC from normal subjects (P less than 0.05). Incubation of PBMC derived from CS subjects with 10(-8) M hydrocortisone completely inhibited the production of the enhancing activity (P less than 0.01), whereas in CR subjects hydrocortisone at concentrations up to 10(-4) M did not suppress the release of enhancing activity. The enhancing activity was produced by monocytes. Enhancing activity eluted with an Mr of 3,000 D and a pI of 7.1. It eluted at 10% acetonitrile after reverse-phase HPLC. The activity was destroyed by heating to 60 degrees C for 60 min and was sensitive to pronase treatment. The purified factor also enhanced superoxide generation by PMN which had been stimulated submaximally by phorbol myristate acetate.

Mast cell stimulation by monoclonal antibodies specific for the Fc epsilon receptor yields distinct responses of arachidonic acid and leukotriene C4 secretion

The release of arachidonic acid ([3H]AA) and leukotriene C4 (LTC4) from the rat mucosal mast cells of the RBL-2H3 line stimulated by Fc epsilon receptor-specific monoclonal antibodies (mAb), by IgE and multivalent antigen, or by Ca2+ ionophores, was investigated. In parallel, secretion of the granular enzyme beta-hexosaminidase was also assayed. The release of [3H]AA and LTC4 in response to stimulation by three Fc epsilon RI-specific mAb shows similar quantitative differences to those observed for the secretion of granule-stored mediators. The mAb F4 induced a substantial release of both [3H]AA and LTC4, which is as high as that induced by IgE and multivalent antigen. mAb J17 and H10 were found to induce an insignificant release of [3H]AA, but while J17 did induce release of LTC4, H10 failed to induce it, even though both J17 and H10 caused substantial release of beta-hexosaminidase. Ca2+ ionophores were found to be relatively more effective in inducing release of [3H]AA and LTC4 than in causing the secretion of granular mediators, as compared to cell stimulation by Fc epsilon RI aggregation. These results illustrate that the cell responses of degranulation and de novo synthesis and release of mediators have different sensitivities to stimulation by (a) configurationally distinct Fc epsilon RI dimers, (b) Fc epsilon RI aggregates induced by IgE and multivalent antigen, and (c) Ca2+ ionophores.

Lipid mediator production by post-implantation rat embryos in vitro

The production of inflammatory lipid mediators by post-implantation rodent embryos was examined in this study. Explanted day 10 rat embryos, either intact or after homogenization, were cultured for 3 hr in vitro and the resulting culture medium and embryonic tissue were assessed for eicosanoids and platelet-activating factor (PAF). The rank order of cyclooxygenase arachidonate products produced by intact embryos was as follows: 6-keto-PGF1 alpha much greater than congruent to PGF2 alpha congruent to TXB2. No lipoxygenase products of arachidonic acid metabolism were detected by either high performance liquid chromatography or radioimmunoassay. PAF production was detectable in embryonic cultures. Homogenization of rat embryos prior to in vitro culture enhanced eicosanoid and PAF production from 2.1-6.9 fold over intact embryos. These findings demonstrate the extent of lipid metabolism by early post-implantation rat embryos and support the concept that potent lipid mediators of inflammation generated by the conceptus may play a role in both the initiation and maintenance of pregnancy.

Effect of tumor necrosis factor on granule release and LTB4 production in adherent human polymorphonuclear leukocytes

Tumor necrosis factor (rTNF) has previously been shown to induce PMN chemotaxis, stimulate PMN adhesion to vascular endothelium and stimulate hydrogen peroxide secretion from PMNs adhered to biological surfaces. We investigated the activity of both rTNF alpha and rTNF beta on adherent and suspension cultures of human PMNs. rTNF alpha selectively stimulated the release of the specific granule in a dose dependent manner. Exocytosis of the specific granule was measured with an enzyme-immunoassay for lactoferrin and a radioassay for vitamin B12-binding protein. Adherent PMNs released up to 60% of the total lactoferrin content of the cells with no increase in myeloperoxidase (MPO) secretion when stimulated with 0.1-10 nM rTNF alpha. The PMNs in suspension cultures also selectively released the specific granule, although total release was reduced suggesting that adherence of PMNs increased their ability to respond to physiological stimuli. When PMNs in suspension cultures or adherent cells were stimulated with rTNF alpha, no LTB4 production was detectable, yet the cells retained the ability to synthesize LTB4 when stimulated with calcium ionophore A23187. Neither rTNF alpha or rTNF beta stimulated the release of the azurophilic granule, measured by the secretion of MPO and neutrophil elastase activity. These results suggest that a function of rTNF alpha and rTNF beta on PMNs is the release of the contents within the specific granule.

Recombinant interferon-gamma primes alveolar macrophages cultured in vitro for the release of leukotriene B4 in response to IgG stimulation

The capacity of interferon-gamma to regulate the generation and release of leukotriene B4 (LTB4) from human alveolar macrophages of normal nonsmoking individuals was evaluated. When alveolar macrophages were incubated for 60 min with heat aggregated IgG (HAIgG), they generated and released 5.7 +/- 1.7 ng of LT B4 per 10(6) cells compared to 1.9 +/- 0.4 ng from cells incubated with buffer alone, P = 0.02. When alveolar macrophages were preincubated with interferon-gamma for 24 h before activation for 60 min with heat-aggregated IgG, the soluble IgG aggregates became a significantly more effective stimulus for LTB4 release, 17.0 +/- 3.9 ng/10(6) cells, P = 0.001, compared to cells incubated in the absence of interferon-gamma and challenged with HAIgG. Interferon-gamma did not alter the response to A23187. This effect of interferon-gamma was both time and dose dependent; it also was specific since neither interferon-alpha nor interferon-beta had a regulatory effect on the release of LTB4 from cells in response to challenge with HAIgG. Preincubation of the alveolar macrophages with interferon-gamma augmented the density of IgG1 receptors by 81.5 +/- 17.3%; neither interferon-alpha nor interferon-beta effected this parameter. Furthermore, monomeric IgG1 blocked HAIgG induced LTB4 release from alveolar macrophages primed with interferon-gamma. Therefore, at least one of the mechanisms by which interferon-gamma primes alveolar macrophages for the production and release of LTB4 in response to stimulation by aggregates of IgG is that of increasing the number of receptors for this stimulus.

Leukotrienes in experimental spinal cord injury

Leukotrienes are a group of noncyclized fatty acid eicosanoids which are formed from the breakdown of arachidonic acid. They are potent mediators of inflammation and may contribute to secondary injury in the central nervous system. All mammalian tissue including cerebral cortex is capable of synthesizing these; however, clear documentation of leukotriene formation in the spinal cord is lacking. We subjected 55 rabbits to weight drops of 200, 300, and 400 gm/cm, respectively, on an exposed spinal cord. The traumatized spinal cord was removed after periods of 15, 30, and 45 minutes and 1, 2, 4, 8, and 24 hours. Radioimmunoassay for leukotriene B-4 was then performed on the specimens. Significant (p less than 0.05) elevation was noted in the 200 and 300 gm/cm groups with peak levels occurring in the first 4 hours. The 400 gm/cm group showed significant depression of values below control levels from 2 to 24 hours. We conclude that in sublethal central nervous system injury leukotrienes are produced in significant amounts and may contribute to secondary spinal cord injury.

Determination of 5,12, and 15-lipoxygenase products in keratomed biopsies of normal and psoriatic skin

Keratomed epidermal tissue from normal individuals and from the lesional and non-lesional skin of psoriasis patients served as source materials for the extraction, separation, and quantitation of eicosanoids that may be important to cutaneous function and pathophysiology. The eicosanoids were extracted in ethanol and buffer, partially purified on SEP-PAKs, separated by reverse phase microbore high-performance liquid chromatography, and quantitated by radioimmunoassay or integration of absorbency peaks obtained by high performance liquid chromatography. The involved areas from psoriasis patients contained a statistically significant seven- to 11-fold increase in the levels of leukotriene B4, 13-hydroxyoctadecadienoic acid-like compound, 15-hydroxyeicosatetraenoic acid compound and 12-hydroxyeicosatetraenoic acid in comparison to normal samples and a three- to sevenfold increase in comparison to uninvolved tissue. The uninvolved areas contained 40% to 100% increases in the levels of these compounds in comparison to normal tissue; these increases were statistically significant except for 13-hydroxyoctadecadienoic acid-like compound. From a single keratome biopsy, multiple eicosanoids can be separated and quantitated; in addition, levels before, during, and after therapy for psoriasis may be compared.

Effects of cyclooxygenase and lipoxygenase inhibitors on inflammation associated with oxazolone-induced delayed hypersensitivity

Oxazolone-induced delayed hypersensitivity in mice produced swelling with concomitant increased tissue levels of leukotrienes and prostaglandins. Pharmacological agents were coapplied topically with oxazolone at the time of challenge in an attempt to modulate the immune-based inflammation. Dexamethasone inhibited both swelling and increases in eicosanoid levels. Indomethacin reduced prostaglandin levels but failed to inhibit swelling or reduce leukotriene levels. L-651,896 (2,3-dihydro-6-[3-(2-hydroxymethyl)phenyl-2-propenyl]-5-benzofuranol), a 5-lipoxygenase inhibitor, reduced leukotriene levels but did not reduce swelling or prostaglandin levels. A combination of indomethacin and L-651,896 reduced eicosanoid levels but did not reduce swelling. These data suggested that the reduction in tissue levels of 5-lipoxygenase or cyclooxygenase oxygenation products of arachidonic acid either singularly or together did not result in the concomitant reduction of the inflammation associated with oxazolone-induced delayed hypersensitivity.

Increased leukotriene B4 synthesis in immune injured rat glomeruli

We examined glomerular synthesis of the 5-lipoxygenase metabolite, LTB4, in normal and immune-injured rat glomeruli. Glomeruli isolated from normal rats and from rats with nephrotoxic serum nephritis (NSN), passive Heymann nephritis (PHN) and cationic bovine gamma globulin (CBGG)-induced glomerulonephritis were incubated with the calcium ionophore A23187 (3 microM). Lipids in the glomeruli and media were extracted with ethyl acetate, and were purified and fractionated by HPLC. Immunoreactive-LTB4 (i-LTB4) was determined by radioimmunoassay on HPLC fractions with a detection limit of 50 pg of i-LTB4. A large peak of i-LTB4 that comigrated with authentic LTB4 was found exclusively in glomeruli isolated from the CBGG-injected rats. Addition of the lipoxygenase inhibitor BW755C (50 micrograms/ml) to glomerular incubation resulted in greater than 90% inhibition of i-LTB4. Synthesis of i-LTB4 by glomeruli from normal, NSN and PHN rats was undetectable. Glomerular LTB4 synthesis by CBGG-injected rats was confirmed by radiometric HPLC and by gas chromatography mass-spectroscopy (GC-MS) analysis. In order to rule out synthesis of LTB4 by neutrophils entrapped in the glomeruli, a group of rats received 1,000 rad total body x irradiation, with shielding of the kidneys before induction of CBGG glomerulonephritis. Despite greater than 95% reduction in total leukocyte count, glomerular synthesis of LTB4 remained enhanced. Augmented glomerular synthesis of the proinflammatory lipid, LTB4, in the CBGG model of glomerular disease could have an important role in the development of glomerular injury and proteinuria.

The metabolism "in vitro" of leukotriene B4 in blood of normal subjects and asthmatic patients

The metabolism of exogenous leukotriene B4 (LTB4) was investigated in venous blood obtained from normal and asthmatic subjects. Using specific radioimmunoassay (RIA) and reverse-phase high performance liquid chromatography (RP-HPLC) techniques we have demonstrated that LTB4 is relatively stable during a 2 hr incubation period at 37 degrees C in our system in vitro. Nevertheless, chromatographic analysis revealed the presence of two products which had retention times identical to 20-hydroxy LTB4 (20-0H LTB4) and 20-carboxy LTB4 (20-C00H LTB4) in which the dicarboxylic derivative was the main metabolite present after 15 min incubation. The amount of LTB4 and its w-oxidation products observed after a 2 hr incubation period was 73% and 24% respectively. There was no basal release of LTB4 from blood. The appearance of these oxidative products was totally suppressed at 4 degrees C and with incubations performed with either venous plasma or Hartmann's control. No significant difference was observed in substrate metabolism between normal and asthmatic subjects. Our results demonstrate that LTB4 is slowly degraded in human whole blood through a cellular dependent process of w-oxidation which may be an important pathway for regulating the availability of this potent biologically active substance.

The generation and cellular distribution of leukotriene C4 in human eosinophils stimulated by unopsonized zymosan and glucan particles

Human eosinophils (EOSs) stimulated under optimal conditions with 5 X 10(8) unopsonized zymosan particles at 37 degrees C for 30 minutes produced an average total immunoreactive leukotriene (LT) C4 of 1.6 ng per 10(6) EOSs, and 30% to 60% of the generated product remained cell associated. The dose-response characteristics of zymosan-induced LTC4 generation were different from those of phagocytosis, suggesting that the two events were independent. Pretreatment of EOSs with 10(-8) mol/L of formyl-methionyl-leucyl-phenylalanine for 30 minutes led to a twofold to fivefold augmentation of LTC4 generation by cells subsequently activated by unopsonized zymosan. Optimal EOS activation with 1 mumol/L of the calcium ionophore A23187 at 37 degrees C for 15 minutes produced more than 100 times greater quantities of LTC4 than with zymosan. The amount of immunoreactive LTC4 that remained cell associated after calcium ionophore A23187 stimulation reached a maximum after 5 minutes and then declined. Of the relatively small amount generated in the first minute, 71% was cell associated, but this figure declined to 9% after 15 minutes, by which time there had been a redistribution of the LTC4 to the supernatant. Inflammatory leukocytes may respond to zymosan because the cells recognize either one or both of its major polysaccharide components, glucan and mannan. Glucan, but not mannan, stimulated EOSs to generate LTC4 in a dose- and time-dependent manner. Under optimal conditions, there was no significant difference in the total quantities of LTC4 elaborated by EOSs stimulated by glucan and by unopsonized zymosan. This suggests that zymosan may induce leukotriene generation in the human EOS through a glucan recognition mechanism.

The development of a sensitive and specific radioreceptor assay for leukotriene B4

To establish a simple and sensitive quantitation of leukotriene B4 (LTB4), we developed a radioreceptor assay (RRA) using a highly specific [3H]leukotriene B4[( 3H]LTB4) binding to a guinea pig spleen homogenate. The assay detected LTB4 levels as low as 0.12 pmol per tube. Fifty percent inhibition of bound [3H]LTB4 was obtained by 2.5 nM of unlabeled LTB4. [3H]LTB4 competition studies indicated that 20-hydroxy-LTB4 was 8 times, 6-trans-LTB4 was 640 times and 20-carboxy-LTB4 was 1000 times less effective than LTB4. The peptide leukotrienes C4, D4 and E4 showed no effect on [3H]LTB4 binding. Recovery rates averaged 97% after ethanol extraction and evaporation of known amounts of LTB4. The intra-assay coefficients of variation for three samples were 2.4%, 7.2% and 8.4%, respectively. This assay was validated by measuring LTB4 released from human granulocytes stimulated with calcium ionophore A23187. The LTB4 level was maximal at 10 min (156.8 +/- 36.2 pmol/3 x 10(6) cells) and decreased rapidly after 15 min. This radioreceptor assay for leukotriene B4 is highly sensitive and is comparable to the reported sensitivity by radioimmunoassay. The method is simpler and less expensive than other methods such as high pressure liquid chromatography and is suitable for routine measurement of leukotriene B4.

Eicosanoids in human ventricular cerebrospinal fluid following severe brain injury

Recent evidence has shown that a variety of prostaglandins and leukotrienes can be produced in brain tissue after injury in animals. It has also been speculated that increases in brain prostaglandins occur in humans following injury. Ventricular cerebrospinal fluid (CSF) samples have been obtained from children with static lesions (controls) as well as children with acute brain injury and eicosanoids measured by immunologic techniques. Metabolites of prostacyclin (6-keto-PGF1 a) and thromboxane A2 (thromboxane B2) were the major eicosanoids found in CSF, and levels of these compounds were increased 3-10 times in acutely injured patients. Prostaglandin E2 was also found in lower amounts, although in one case its level was very high. Prostaglandin D2 was also present, but in low amounts. No leukotrienes were found in CSF samples that were purified by HPLC prior to immunoassay. Elevated levels of hydroxyeicosatetraenoic acids (HETEs) were observed in those samples stored frozen, but these metabolites were most probably due to autooxidation of arachidonic acid in CSF. Arachidonic acid concentration in CSF was typically found to be in the range of 10-200 ng/ml, but was found to be 5-10 fold higher in one severely injured patient. Thus, elevated free arachidonic acid and various oxygenated metabolites were observed in CSF following brain injury.

Biochemical and biological activities of 2,3-dihydro-6-[3-(2-hydroxymethyl)phenyl-2-propenyl]-5-benzofuranol (L-651,896), a novel topical anti-inflammatory agent

The biochemical and biological profile of a topical anti-inflammatory agent, 2,3-dihydro-6-[3-(2-hydroxymethyl)phenyl-2-propenyl]-5-benzofuranol (L-651,896 inhibited the 5-lipoxygenase of rat basophilic leukemia cells with an IC50 of 0.1 microM and leukotriene synthesis by human PMN and mouse macrophages with IC50 values of 0.4 and 0.1 microM respectively. L-651,896 also inhibited prostaglandin E2 synthesis by mouse peritoneal macrophages (IC50 = 1.1 microM). This compound inhibited ram seminal vesicle cyclooxygenase activity at considerably higher concentrations, and this effect was directly related to substrate concentration. When applied topically to the mouse ear, L-651,896 lowered elevated levels of leukotrienes associated with arachidonic acid-induced skin inflammation and delayed hypersensitivity induced by oxazolone. However, while L-651,896 inhibited the increased vascular permeability induced by arachidonic acid, it had no effect on the edema associated with the immune-based response to oxazolone in the same tissue. Thus, it is possible that leukotrienes may play a role in some but not all inflammatory responses.

Indomethacin increases the formation of lipoxygenase products in calcium ionophore stimulated human neutrophils

Arachidonic acid metabolism in human neutrophils stimulated in vitro with the calcium ionophore A23187 was studied using combined HPLC and radioimmunoassays. Indomethacin (0.1 and 1.0 microM) caused a 300% increase in LTB4 formation in neutrophils stimulated with A23187. 5-, 12- and 15-HETE levels were also increased. In the presence of exogenous arachidonic acid 1.0 microM Indomethacin caused a 37% increase in LTB4 formation. Acetyl Salicylic Acid and Ibuprofen had no effect on the formation of lipoxygenase metabolites. The effect of indomethacin on LTB4 formation does not appear to be due to a simple redirection of substrate arachidonic acid from the cyclooxygenase to the lipoxygenase pathways.

Relative contribution of leukotriene B4 to the neutrophil chemotactic activity produced by the resident human alveolar macrophage

Human alveolar macrophages release chemotactic activity for neutrophils, providing a role for alveolar macrophages in regulating inflammation in the lung. As alveolar macrophages produce large amounts of leukotriene B4 (LTB4), a chemotactically active lipoxygenase product of arachidonic acid, we investigated the contribution of LTB4 to the total neutrophil chemotactic activity produced by these cells. Normal human alveolar macrophages were recovered by bronchoalveolar lavage from healthy volunteers and incubated either with the calcium ionophore A23187 for 1 h, or with opsonized zymosan particles or latex beads for 3 h. Nordihydroguaretic acid (NDGA), a relatively specific lipoxygenase inhibitor, blocked the release of neutrophil chemotactic activity after all three stimuli in a dose-dependent manner. This correlated with blockade of LTB4 production as measured by high performance liquid chromatography using freshly isolated alveolar macrophages, as well as blockade of [3H]LTB4 production by macrophages prelabeled with [3H]arachidonate. Molecular sieve chromatography using Sephadex G-50 confirmed that essentially all of the chemotactic activity in the stimulated macrophage supernatants co-eluted with authentic [3H]LTB4, and that NDGA completely blocked the chemotactic activity in the eluting fractions. Readdition of authentic LTB4 (1 X 10(-7) M) to the NDGA-blocked macrophage supernatants restored the chemotactic activity in the supernatants. The macrophage supernatants did not contain platelet-activating factor-like activity, as measured by the stimulation of [3H]serotonin release from rabbit platelets, and by high performance liquid chromatography. NDGA did not change the protein-secretion profiles of fresh alveolar macrophages, or of macrophages prelabeled with [35S]methionine. The complement (C) components C5adesarg were not detected in any of the supernatants by radioimmunoassay. Concentration of the supernatants by positive pressure filtration (5,000-D membrane) did not augment chemotactic activity in the stimulated supernatants or uncover chemotactic activity in the NDGA-blocked supernatants. As with the 3-h studies, when alveolar macrophages were incubated overnight with opsonized zymosan, all of the increase in chemotactic activity could also be blocked by NDGA. These data indicate that LTB4 is the predominant neutrophil chemotactic factor secreted by the normal resident human alveolar macrophage in response to two major types of stimuli, calcium fluxes across the cell membrane and the phagocytosis of opsonized particulates.

Effects of dietary supplementation with marine fish oil on leukocyte lipid mediator generation and function in rheumatoid arthritis

Twelve patients with active rheumatoid arthritis supplemented their usual diet with 20 gm of Max-EPA fish oil, daily, for 6 weeks. Following this supplementation, the ratio of arachidonic acid to eicosapentaenoic acid in the patients' neutrophil cellular lipids decreased from 81:1 to 2.7:1, and the mean generation of leukotriene B4 (with calcium ionophore stimulation) significantly declined by 33%. The mean neutrophil chemotaxis to both leukotriene B4 and FMLP significantly increased toward the normal range at week 6. The generation of 5-lipoxygenase products by calcium ionophore-stimulated monocytes was not significantly suppressed, but a significant decline (37%) in platelet-activating factor generation was noted at week 6. The modulation of these measures of leukocyte inflammatory potential suggests that fish oil supplementation may have an antiinflammatory effect.

Hydrocortisone inhibits antigen-induced rise in intracellular free calcium concentration and abolishes leukotriene C4 production in leukemic basophils

Antigenic stimulation of rat basophilic leukemia cells (RBL-3H3) elevates intracellular free Ca2+ concentration ([Ca2+]i) and induces production of leukotriene C4 (LTC4). This model was used to examine the role of Ca2+ in LTC4 formation, and inhibition by hydrocortisone (HC). HC, at a physiological concentration (2 x 10(-7) M), selectively prevented the stimulatory effect of the antigen on LTC4 production whereas the response to calcium ionophore (A23187) remained unimpaired. The inhibition by HC was time-dependent: half maximal response was reached at 2 hour and maximal response at 3 hours. Addition of arachidonic acid (3 micrograms/ml) did not overcome the inhibitory action of HC. An elevated [Ca2+]i is known to be essential for the activation of both 5-lipoxygenase and phospholipase A2. The stimulatory effect of the antigen on LTC4 production was abolished when the cells were incubated in Ca2+-deficient medium. Likewise, calcium ionophore stimulation shows dependence on extracellular Ca2+. Half maximal stimulation by the antigen and calcium ionophore was observed at external Ca2+ concentration of 150 microM and 40 microM respectively. Treatment with HC largely prevented the antigen-induced rise in [Ca2+]i, measured by Quin 2. In addition, HC reduced by 70% the accumulation of 45Ca2+ induced by the antigen. Collectively, these results demonstrate for the first time that HC reduces antigen-induced elevation of [Ca2+]i, and this may be associated with the inhibitory action of HC on LTC4 formation. This property could be partly responsible for the antiallergic and antiinflammatory activities of HC.

Pharmacological modulation of eicosanoid levels and hyperalgesia in yeast-induced inflammation

Injection of brewer's yeast into the rat paw results in edema and a subsequent hyperalgesia. The edema was accompanied by an increase in 5-lipoxygenase products, and the hyperalgesia coincided with the formation of both cyclooxygenase and 5-lipoxygenase products. When administered perorally, indomethacin inhibited cyclooxygenase product formation, phenidone inhibited 5-lipoxygenase product formation, and 3-amino-1-(m-[trifluoromethyl]-phenyl)-2-pyrazoline (BW 755C) inhibited formation of products of both pathways. These compounds were also effective analgesic agents. The correlation of these effects with the suppression of hyperalgesia suggests the participation of products from both cyclooxygenase and 5-lipoxygenase pathways in the mediation of hyperalgesia.

Production of 5-lipoxygenase pathway metabolites by peripheral leucocytes in capillary leak syndrome (Clarkson disease)

Periodic systemic capillary leak syndrome (Clarkson disease) is characterized by unexplained attacks of a marked increase in capillary permeability. As leukotrienes, derived from arachidonic acid via the 5-lipoxygenase pathway, enhance capillary permeability, we studied arachidonate metabolism in leucocytes of a patient with capillary leak syndrome. Leucocyte-platelet suspensions, prepared from blood collected from the patient during asymptomatic periods (n = 11) produced greater amounts of 5-hydroxyeicosatetraenoic acid (5-HETE) than control suspensions (P less than 0.05). Peripheral leucocytes, collected during attacks (n = 3) and studied without addition of A23187 released LTB4 in vitro but not sulphidopeptides leukotrienes. This result was never observed with leucocytes from control subjects or from the patient out of a crisis. These results suggest that in the patient, peripheral leucocytes could be stimulated by an unknown, as yet to be determined, endogenous factor to produce more 5-HETE and LTB4. Whether LTB4 plays a pathogenic role in the capillary leakage remains to be determined.

A simple and sensitive radioreceptor assay for leukotrienes

A simple and sensitive radioreceptor assay (RRA) for leukotrienes (LTs) was developed using a highly specific [3H]leukotriene D4 (LTD4) binding to guinea pig lung membrane homogenates. The assay can detect down to 0.15 pmol of LTD4. The values for fifty percent inhibition of bound [3H]LTD4 was 1.5 nM for LTD4, 45 nM for LTC4 and 24 nM for LTE4. LTB4 at 3.0 X 10(-5)M had no effect on [3H]LTD4 binding. The RRA for LTs in the absence of serine-borate complex was bi-specific for both LTC4 and LTD4. However, in the presence of 20 mM serine-borate this method was highly specific for LTD4. Recovery rate averaged 87.2% after ethanol extraction and evaporation of known amounts of LTD4. When the radioreceptor assay and radioimmunoassay data for leukotriene levels in the samples were compared to each other, an excellent correlation was observed with a correlation coefficient 'r' of 0.992. The assay was also validated by quantitation of Lts released from human granulocytes stimulated with calcium ionophore, A23187. The method is simpler, less expensive, and more specific for LTD4 than the other methods such as high pressure liquid chromatography and radioimmunoassay and is suitable for routine measurement of either LTD4 specifically or LTC4 plus LTD4 simultaneously in one cell system.