Eosinophil-rich human polymorphonuclear leukocyte preparations characteristically release leukotriene C4 on ionophore A23187 challenge

Specific systemic antioxidant response to preeclampsia in late pregnancy: the study of intracellular glutathione peroxidases in maternal and fetal blood

OBJECTIVE

The physiopathology of preeclampsia is still unclear, but an imbalance between reactive oxygen species (ROS) and antioxidants, also called oxidative stress, appears to be an important contributing factor. The ROS promote lipid oxidation and are known to induce stress proteins, such as hemeoxygenase 1 (HO-1) and heat-shock protein 70 (Hsp-70). We hypothesized that glutathione peroxidases (GPx), a major class of antioxidant enzymes that regulate cell homeostasis by neutralizing lipid peroxides, are altered in the blood of preeclamptic women and neonates (venous cord blood).

METHODS

Thirty-one preeclamptic and 30 normotensive pregnancies were recruited. The blood was fractionated using a discontinuous gradient to separate the different cell types. The messenger ribonucleic acid (mRNA) expression of GPx-1 and -4, HO-1, and Hsp-70 were analyzed by quantitative reverse transcriptase-polymerase chain reaction. GPx-1 and -4 protein level in blood cells was also detected by Western blot. The experiments were analyzed using the Student t test.

RESULTS

The HO-1 and Hsp-70 mRNA expression in whole blood was significantly higher in both fetal and maternal circulations (P < .05). We also discovered that GPx-4 mRNA was 1.6-fold higher in blood of women with preeclampsia than in control pregnancies (P = .04). The latter was associated with an increase of both GPx-1 and GPx-4 protein and mRNA levels in the lymphocyte/monocyte fraction of the blood. Significantly higher GPx-4 mRNA levels in the fetal circulation of the preeclamptic group than the control group were also detected (P < .001).

CONCLUSION

These data indicate that preeclampsia is associated with a specific antioxidant response in both maternal and fetal circulations, likely in response to the deleterious oxidative stress observed in this syndrome.

Increase in urinary leukotriene B4 glucuronide concentration in patients with aspirin-intolerant asthma after intravenous aspirin challenge

BACKGROUND

Aspirin challenge of aspirin-intolerant asthma (AIA) patients causes a significant increase in leukotriene E4 (LTE4) concentration in urine. However, knowledge on leukotriene B4 (LTB4) generation in patients with AIA is insufficient. Recent research has demonstrated that exogenously administered LTB4 is excreted as glucuronide into the urine in human healthy subjects.

OBJECTIVE

The purpose of this study is to estimate urinary LTB4 glucuronide (LTBG) concentration in the clinically stable condition in healthy subjects and asthmatic patients and to investigate changes in urinary LTBG concentration in patients with AIA after aspirin challenge.

METHODS

A provocation test was performed by intravenous aspirin challenge. After urine was hydrolysed by beta-glucuronidase, the fraction containing LTB4 was purified by high-performance liquid chromatography and LTB4 concentration was quantified by enzyme immunoassay. Urinary LTBG concentration was calculated as the difference between the concentration obtained with hydrolysis and that without hydrolysis.

RESULTS

(1) After hydrolysis, the presence of urinary LTB4 was verified by gas chromatography-mass spectrometry-selected ion monitoring. (2) The urinary LTBG concentration was significantly higher in the asthmatic patients than in the healthy subjects (median, 5.37 pg/mg creatinine [range 1.2-13] vs. 3.32 pg/mg creatinine [range, 0.14-10.5], P = 0.0159). (3) The patients with AIA (n = 7), but not those with aspirin-tolerant asthma (n = 6), showed significant increases in LTBG and LTE4 excretions after aspirin challenge. (4) When the concentrations after aspirin challenge were analysed simultaneously, a significant linear correlation was observed between urinary LTBG concentration and urinary LTE4 concentration in patients with AIA (Spearman's rank correlation test, r = 0.817, P = 0.0003).

CONCLUSION

LTBG is present in human urine, albeit at a concentration lower than urinary LTE4. In addition to a marked increase in cysteinyl-leukotriene production, aspirin challenge induced LTB4 production in AIA patients.

TA-270 [4-hydroxy-1-methyl-3-octyloxy-7-sinapinoylamino-2(1H)-quinolinone], an anti-asthmatic agent, inhibits leukotriene production induced by IgE receptor stimulation in RBL-2H3 cells

A novel quinolinone derivative, TA-270 [4-hydroxy-1-methyl-3-octyloxy-7-sinapinoylamino-2(1H)-quinolinone], has been shown to inhibit antigen-induced asthmatic responses including the early-phase bronchoconstriction in actively sensitized guinea pigs. Here we characterized the action mechanisms of TA-270 in cellular level in vitro. In RBL-2H3 mast cells sensitized with dinitrophenol (DNP)-specific IgE, the antigen exhibited several mast cell functions, including hexosaminidase release as a marker of degranulation, production of tumor necrosis factor-alpha, and production of immunologically detective leukotrienes. These antigen-induced actions were associated with the activation of several early signaling events, including inositol phosphate production reflecting phospholipase C activation and extracellular signal-regulated kinase activation. When the cells were treated with TA-270, the antigen-induced leukotriene production was almost completely suppressed, but other antigen-induced actions listed above were hardly affected. This drug also failed to affect the antigen-induced phospholipase A2 activation as evaluated by the total release of arachidonic acid and its metabolites from the cells prelabeled with radioactive arachidonic acid. However, TA-270 clearly changed the arachidonic acid metabolic pathway. It suppressed the accumulation of 5-lipoxygenase products, including leukotrienes, but hardly affected the accumulation of cyclooxygenase products. The inhibitory action of TA-270 on leukotriene production was also observed in human neutrophils and eosinophils. We conclude that TA-270 inhibits 5-lipoxygenase activity and, thereby, suppresses the antigen-induced leukotriene production.

Interactions of hydroxyapatite and fluorapatite particles on human osteoarthritis type B synoviocytes: effects on interleukin-1 alpha levels and lipoxygenase pathways

We investigated the effects of the biomaterials hydroxyapatite (HAP) and fluorapatite (FAP) on cultured human osteoarthritis type B synoviocytes by analyzing interleukin-1 alpha (IL-1 alpha) production and arachidonic acid metabolism via lipoxygenase pathways. A portion of opsonized particles was endocytosed and was found in numerous phagolysosomes in human synoviocyte cytoplasms. The present study demonstrates that HAP and FAP calcined at 700 degrees C induced a decrease in IL-1 alpha production but markedly decreased the synthesis of lipoxygenase products after 1-month incubation with the particles. This model will allow us to study the possible inflammatory response (arachidonic acid metabolism, proinflammatory cytokines) that can be induced by any biomaterials used in orthopedics.

The anhydrous milk fat, ghee, lowers serum prostaglandins and secretion of leukotrienes by rat peritoneal macrophages

Ghee, the anhydrous milk fat, is one of the most important sources of dietary fat in India. Male Wistar rats were fed diets containing 2.5, 5.0 and 10 wt% ghee for a period of 8 weeks. The diets were made isocaloric with groundnut oil. The results showed that serum thromboxane levels decreased by 27-35%, and 6-keto-prostaglandin F1alpha by 23-37% when ghee was incorporated at level of 10% in the diet. Prostaglandin E2 levels in serum and secretion of leukotrienes B4, C4 and D4 by peritoneal macrophages activated with calcium ionophore decreased when increased amounts of ghee from 2.5 to 10% were included in the diet. Arachidonic acid levels in macrophage phospholipids decreased when incremental amounts of ghee were fed to rats. These studies indicate that ghee in the diet not only lowers the prostaglandin levels in serum but also decreases the secretion of leukotrienes by macrophages.

The role of cysteinyl leukotrienes in the pathogenesis of asthma: clinical study of leukotriene antagonist pranlukast for 1 year in moderate and severe asthma

Clinical studies have shown that pranlukast (Ono Pharmaceutical Co., Osaka, Japan) is effective for mild and moderate asthma. However, it is not well known that pranlukast is also effective on moderate and severe persistent asthma in the long term. We studied the effect of pranlukast on moderate and severe asthmatics by evaluating the change of peak expiratory flow (PEF) and therapeutic scores for 1 year before and during pranlukast therapy. We gave pranlukast 225 mg twice daily orally to 25 patients who were receiving more than 400 micrograms/day beclomethasone inhalation and beta 2 stimulant inhalation with or without oral corticosteroid. Pranlukast increased PEF more than 10 L/min in 14 patients in the first 4 weeks. In these 14 patients, 10 patients continued to monitor PEF and kept asthma diaries for 1 year. We compared the data for 1 year before and during the pranlukast therapy. During the pranlukast therapy, PEF significantly increased, puffs of beta 2 stimulant inhalation significantly decreased. The incidence of oral corticosteroid rescue therapy reduced, and the mean daily dose of oral corticosteroid decreased; however, they were not statistically significant. During treatment with pranlukast, no side effect was observed. From these results, we suggest that pranlukast is effective for more than half of the moderate and severe persistent asthmatics, and that the effectiveness continues for more than 1 year.

Cyclooxygenase-2 up-regulation after FLAP transfection in human adenocarcinoma cell line HT29 cl.19A

Five-lipoxygenase-activating protein (FLAP) is usually described as an essential protein to activate the leukotriene (LTs) synthesis via the 5-lipoxygenase pathway. In the enterocyte model HT29 cl.19A cell line, 5-lipoxygenase metabolism was found despite the lack of FLAP expression. Therefore HT29 cl.19A represents an original mammalian model to study FLAP-dependent leukotriene synthesis. In FLAP cDNA transfected HT29 cl.19A cells, FLAP expression led to an increase in cyclooxygenase pathway products (mainly PGE2) without an increase in 5-lipoxygenase metabolism. This increase in PGE2 synthesis was associated with a cyclooxygenase-2 upregulation in comparison to untransfected HT29 cl.19A cells. These results suggest a possible interaction between the two major pathways of arachidonic acid metabolism.

Simultaneous analysis of 4- and 5-series lipoxygenase and cytochrome P450 products from different biological sources by reversed-phase high-performance liquid chromatographic technique

Quantification of lipoxygenase and cytochrome P450 products of both arachidonic acid (AA) and eicosapentaenoic acid (EPA) is of broad interest due to the multiple biological activities of these compounds. We developed a method combining (i) solid-phase extraction, (ii) isocratic reversed-phase high-performance liquid chromatographic separation, and (iii) online photodiode array detection with spectrum analysis for identification and measurement of all main 4- and 5-series eicosanoids (leukotrienes, hydroxyeicosatetraenoic acids/hydroxyeicosapentaenoic acids, epoxyeicosatrienoic acids) within one run. With these procedures, standard mixtures of AA- and EPA-derived lipid mediators were recovered from different biological liquids, like lung perfusate, human bronchoalveolar lavage fluid, and cell supernatant with linear characteristics for each compound. Recoveries of the different lipid mediators exceeded 80% showing excellent reproducibility. Application of the method to isolated, perfused, and ventilated human lungs challenged with the calcium ionophore A23187 and to human neutrophils stimulated in the presence of arachidonic acid and eicosapentaenoic acid with N-formyl-methionyl-leucyl-phenylalanine demonstrated the generation of a large array of lipoxygenase and cytochrome P450 products. Thus, convenient quantification of 4- and 5-series eicosanoids in fluids of biological interest is achieved by a technique comprising solid-phase extraction, isocratic reversed-phase high-performance liquid chromatography, and photodiode array-based online spectrum analysis of eluting compounds.

Characteristics of leukotriene biosynthesis by human granulocytes in presence of plasma

The formation of leukotriene B4 (LTB4) by neutrophils stimulated with the ionophore A23187 or physiological stimuli in heparinized plasma was investigated. In comparison with neutrophils stimulated (A23187) in a protein-free buffered salt solution, neutrophils stimulated in plasma produced only trace amounts of LTB4. The addition of human recombinant LTA4-hydrolase or erythrocytes to plasma prior to A23187 stimulation strongly and selectively stimulated (> 4-fold) the formation of LTB4 supporting that neutrophils activated in plasma with A23187 release in the extracellular milieu most of LTA4 formed by the cells, and indicating that plasma proteins drastically slow down the further metabolism of LTA4 released by neutrophils. The formation of LTB4 was then investigated in GM-CSF-primed neutrophils stimulated with fMLP in plasma; levels of synthesis were very low and the addition of erythrocytes prior to stimulation strongly enhanced LTB4 synthesis, demonstrating that agonist-stimulated neutrophils also release most of LTA4 generated in the extracellular milieu. Investigations on the fate of LTA4 in plasma revealed that LTA4 was slowly degraded through an unknown process, i.e. not through the previously described non-enzymic hydrolysis resulting in the formation of dihydroxy derivatives of LTA4. Using neutrophils labeled with tritiated arachidonate, we also demonstrated that neutrophils stimulated in plasma with fMLP or A23187, almost exclusively use endogenous arachidonate, as opposed to plasma arachidonate, to generate 5-lipoxygenase products. Finally, experiments performed with purified eosinophils indicated that contrary to neutrophils, the eosinophils do not release LTA4, but directly release LTC4.

Expression of arachidonate platelet-type 12-lipoxygenase in human rheumatoid arthritis type B synoviocytes

In the present study, we have demonstrated platelet-type 12-lipoxygenase (12-LOX) expression in human rheumatoid arthritis (RA) type B synoviocytes by reverse-transcription polymerase chain reaction (RT-PCR). The presence of 12-LOX mRNA in these cells was revealed by classical RT-PCR analysis using platelet-type 12-LOX cDNA primers and the PCR fragment (246 bp) was purified, amplified and sequenced. By sequence analysis, this fragment was determined to be 100% identical to that from platelet-type 12-LOX cDNA. Immunofluorescence data demonstrate that interleukin-1beta (IL-1beta) increases cellular 12-LOX protein. Other results associate specific inflammatory cytokines with the activity of 12-LOX in human RA type B synoviocytes. IL-1beta increased 12S-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) production (4-fold) and we also observed an increase in 12-HETE production (2.5-fold) after incubation of human RA type B synoviocytes with TNF alpha. In contrast to the action of IL-1beta on 12-HETE synthesis, IL-4 and IL-6 did not enhance 12-HETE production. This is the first demonstration of platelet-type 12-LOX cDNA derived from the mRNA of cultured human RA type B synoviocytes.

Production of arachidonic acid metabolites by the colon adenocarcinoma cell line HT29 cl.19A and their effect on chloride secretion

Eicosanoids were found in large amounts in the colonic mucosa of patients suffering from inflammatory bowel diseases and colonic adenocarcinoma. The aim of this study was to evaluate the role of the intestinal epithelial cells in the arachidonic acid metabolism and their functional response to certain eicosanoids. We used the human adenocarcinoma epithelial cell line HT29 cl.19A cell, which is an in vitro model of colon carcinoma and ion transport. These cells were found to express 5- and 15-lipoxygenase, leukotriene A4 hydrolase and cyclooxygenase-1 and -2 mRNAs. We observed an arachidonic acid metabolism via 5-lipoxygenase pathway despite the lack of FLAP mRNA expression and that certain eicosanoids such as hydroperoxy- and hydroxyeicosatetraenoic acids stimulate chloride secretion.

Pharmacological modulation of eosinophil influx into the lungs of Brown Norway rats

A model of lung inflammation was developed in Brown Norway rats. Intense lung eosinophilia was induced by a single intravenous injection of Sephadex G-200 particles. The eosinophilia observed was preceded by an increase in cysteinyl leukotrienes found in lung lavage fluids. Theophylline and albuterol were tested in the model and found to be inactive, while dexamethasone was effective. Zileuton, a specific leukotriene inhibitor, was found to effectively inhibit leukotriene formation and the influx of eosinophils into the lungs of these Sephadex-treated animals. Studies with specific leukotriene D4 antagonists of the cysLT1 type receptor indicate that this leukotriene receptor is probably not involved directly in the eosinophilic inflammation. This model appears to be useful in characterizing potential anti-inflammatory effects of inhibitors by evaluating their ability to prevent eosinophil influx into the lung.

Leukotriene receptors in HL-60 cells differentiated into eosinophils, monocytes and neutrophils

The expression of leukotriene B4 (LTB4) and leukotriene D4 (LTD4) receptors was determined, by binding assay, in HL-60 cells differentiated into the monocyte/macrophage, neutrophil, and eosinophil lineages. Monocyte/ macrophage- and neutrophil-differentiated cells developed specific LTB4 receptors with high affinities (Kd = 1.27 nM and 2.65 nM, respectively) and low affinities (Kd = 26.41 nM and 55.63 nM, respectively). These receptors were functional and specific as indicated by the ability of LTB4 to elicit an increase in intracellular calcium concentration antagonised by specific antagonists. Eosinophil-differentiated cells developed mainly LTD4 receptors (Kd = 41.91 nM), and stimulation with LTD4 induced an increase in intracellular calcium that was antagonised by a specific LTD4 antagonist. These results show, for the first time, that eosinophil-differentiated HL-60 cells express specific functional LTD4 receptors. These cells could be used for the study of the actions of peptidoleukotrienes on eosinophils, and for studies on the molecular mechanisms regulating LTD4 receptor expression.

Changes in lipoxygenase activities in human erythroleukemia (HEL) cells during diosgenin-induced differentiation

A human erythroleukemia (HEL) cell line was used as a model to study dynamic changes in human 12-, 15-, 5-lipoxygenases, five lipoxygenase activating protein (FLAP), and leukotriene A4 (LTA4) hydrolase gene expression during megakaryocytic differentiation induced by diosgenin (Beneytout, J.L., Nappez, C., Leboutet, M.J. and Malinvaud, G., Biochem. Biophys. Res. Commun., 207 (1995) 398-404). The study was performed at the transcriptional level: 12- and 5-lipoxygenase mRNAs, FLAP mRNA and LTA4 hydrolase mRNA were detected before and after diosgenin treatment in HEL cells while 15-lipoxygenase mRNA was undetected. When HEL cells were incubated with arachidonic acid, 5-, 12-, 15-hydroxyeicosatetraenoic acids (HETE) and LTC4 were synthesized. In contrast, the diosgenin treatment induced the suppression of 12-lipoxygenase activity and only 5-, 15-HETEs and LTC4 were synthesized.

Expression of 5-lipoxygenase in lymphoblastoid B and T cells

The expression of arachidonate 5-lipoxygenase (5-LOX, arachidonate: oxygen 5-oxidoreductase; EC 1.13.11.34) and the 5-lipoxygenase activating protein (FLAP) genes in lymphoblastoid B and T cell lines was studied at the transcriptional level by reverse transcription-PCR analysis. Two B cell lines, CESS and SKW 6.4, were found to express both 5-LOX and FLAP mRNA. One T cell line, MOLT 4, expressed only FLAP mRNA. Upon stimulation of intact cells by calcium ionophore, B lymphoblastoid cells produced 5, 12 and 15 hydroxyeicosatetraenoic acids as well as leukotriene B4.

Peptidoleukotriene (pLT) release from guinea pig lung mast cells

Guinea pig lung mast cells can be isolated and purified to high purity. This has given us the opportunity to study in greater detail mediator release from these cells. Both immunologic (ovalbumin sensitized) and nonimmunologic (calcium ionophore, CaI) stimuli caused a dose-dependent release of histamine and pLT from monodispersed lung cells and highly purified lung mast cells. Examination of the time release curve for pLT revealed a 5-min lag in the release of this mediator and a peak release at 60 min after challenge with antigen. Verification of pLT release was obtained by use of the 5-lipoxygenase inhibitor A64077 (Zileuton). Pretreatment of lung mast cells with the 5-lipoxygenase inhibitor prevented release of pLT by either antigen or CaI but had no appreciable effect on histamine release (HR). The pulmonary mast cell appears to be an important contributor to pLT release in the guinea pig lung.

Measurement of eicosanoids in menstrual fluid by the combined use of high pressure chromatography and radioimmunoassay

Methods are described for the quantification of various eicosanoids (cyclooxygenase products: 6-KETO, TXB2, PGE2, PGF2 alpha, DHK; lipoxygenase products: 5-, 12-, 15-HETE, LTB4, LTC4, LTD4, LTE4) in menstrual blood collected by tampons. Samples were extracted with acidified ethanol. After purification by SEP-PACK C18 columns, the compounds were separated by reversed phase HPLC using a ternary gradient system. The eicosanoid concentrations of the fractionated eluents were measured by radioimmunoassay and corrected for recovery. 12-HETE was the most prominent metabolite of arachidonic acid in menstrual blood (mean: 1174 ng/g blood). With the exception of PGF2 alpha and TXB2 (mean: 343 and 212 ng/g blood, respectively) other eicosanoids were detected in remarkable lower concentrations.

Determination of picomole amounts of lipoxins C4, D4 and E4 by high-performance liquid chromatography with electrochemical detection

A method for the sensitive determination of the sulphopeptide lipoxins (LXs) C4, D4 and E4 by high-performance liquid chromatography with subsequent electrochemical detection is described. The best results were obtained when the analysis was carried out with the solvent system methanol-water-trifluoroacetic acid (66:34:0.008, v/v/v). The acquired half-wave potentials were different for all investigated compounds: +1.18 V for LXC4 +1.3 V for LXD4 and +1.25 V for LXE4. The detection limits of LXC4, LXD4 and LXE4, based on a signal-to-noise ratio of 3:1, were found to be 200-700 fmol. Although sulphopeptide lipoxins possess a high molar absorptivity, electrochemical detection still is three times more sensitive than ultraviolet detection.

In vitro leukotriene (LT) C4 synthesis by blood eosinophils from atopic asthmatics: predominance of eosinophil subpopulations with high potency for LTC4 generation

We compared the leukotriene (LT) C4 generation by the eosinophil density subpopulations isolated from the blood of asthmatics and normal subjects. Using discontinuous Percoll gradients, eosinophil subpopulations with densities of 1.075, 1.078, 1.081, 1.084, 1.087 and 1.100 g/ml were isolated from the blood of six atopic asthmatics and seven normals. In normals, most eosinophils (94%) were recovered in the density fractions (1.084, 1.087, and 1.100 g/ml). In asthmatics, the eosinophil density profile was shifted towards lower cell density: the eosinophil subsets 1.078, 1.081 and 1.084 g/ml were increased 4.5, 30.3 and 8.9-fold respectively compared to normals (p less than 0.0001); the intermediate subsets, the hypodense 1.081 and normodense 1.084 g/ml fractions being the predominant subpopulations. The ability of asthmatic eosinophil subsets 1.078 to 1.087 g/ml to release LTC4 was measured by reversed-phase HPLC, LTC4 production was highest with the normodense 1.084 g/ml eosinophil subset (149 +/- 28 pmol/10(6) eosinophils, p less than 0.01 compared to the 1.081 fraction). The eosinophils from the hypodense 1.081 g/ml fraction also released more LTC4 (112 +/- 19 pmol/10(6) eosinophils) than the 1.078 and 1.087 g/ml fractions (70 +/- 16 and 67 +/- 12 respectively, p less than 0.01). These results show that, compared to normals, blood of mild atopic asthmatics contains an elevated number of eosinophils of intermediate density which have a high capacity for LTC4 production.

Synthesis of eicosanoids by Propionibacterium acnes-elicited liver adherent cells and their effect on production of interleukin 1 and tumor necrosis factor

When heat-killed Propionibacterium acnes (P. acnes) is intravenously injected into rats or mice, liver adherent cells including macrophages and Kupffer cells increase in number and they synthesize various kinds of biologically-active materials. We studied the production of eicosanoids and the cytokines, interleukin 1 (IL-1) and tumor necrosis factor (TNF), by P. acnes-elicited liver adherent cells and the regulatory mechanisms of eicosanoids in the synthesis of cytokines. As a result, P. acnes-elicited liver adherent cells synthesized not only prostaglandin (PG) E2, 6-keto-PGF1 alpha, thromboxane B2 and leukotriene B4, but also IL-1 and TNF. In addition, PGE2 and PGI2 suppressed the production of these cytokines. These results suggested that there are auto-regulatory mechanisms in production of cytokines in the liver.

Effects of hydrocortisone and aminophylline on plasma leukotriene C4 levels in patients during an asthmatic attack

To study the role of leukotriene C4(LTC4) and the effect of hydrocortisone and aminophylline on plasma LTC4 levels in patients with asthmatic attacks, we measured LTC4 in plasma of 18 asthmatics during a wheezing attack and of 7 normal subjects. Blood samples were obtained before and after treatment with aminophylline and/or hydrocortisone injections. We extracted LTC4 using a Sep-Pak C18 cartridge for the measurement of LTC4 by radioimmunoassay. The plasma levels of immunoreactive LTC4 (i-LTC4) of the normal subjects were 142 +/- 25 pg/ml (n = 7), while those of nonatopic type asthmatic patients with wheezing attacks were 208 +/- 68 pg/ml (n = 15) (p less than 0.01). Before and after treatment with both hydrocortisone succinate (100 mg) and aminophylline (250 mg), 6 asthmatic patients with wheezing attacks had a mean plasma level of i-LTC4 181 +/- 24 and 132 +/- 18 pg/ml (p less than 0.01), respectively. On the other hand, the treatment with aminophylline 250 mg alone increased the i-LTC4 levels from 178 +/- 19 pg/mg to 213 +/- 16 pg/mg (n = 6)(p less than 0.05), while treatment with hydrocortisone succinate 100 mg decreased the i-LTC4 level 0.05 from 284 +/- 99 pg/ml to 249 +/- 85 pg/ml (n = 4)(p less than 0.05). In conclusion, the present study shows that the i-LTC4 level in venous blood of patients with asthmatic attacks is decreased significantly by treatment with hydrocortisone succinate.

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.

Changes in leukotrienes and prostaglandins in the liver tissue of rats in the experimental massive hepatic cell necrosis model

When heat-killed Propionibacterium acnes is intravenously injected into rats followed by an intravenous injection of a small amount of Gram-negative lipopolysaccharide (LPS) 7 days later, massive hepatic cell necrosis is induced and most of the rats die within 24 hours of LPS injection. Using this experimental model, we studied the changes in the levels of leukotrienes (LTs) and prostaglandins (PGs) in the liver tissue and bile of rats with experimentally-induced massive hepatic cell necrosis. Both the levels of LTs and PGs in the liver tissue and LTs in the bile increased before the microscopic appearance of hepatic cell necrosis. These results suggest that arachidonic acid metabolites may play an important role in the induction of liver cell injury.

Characterization of phospholipase C from Pseudomonas aeruginosa as a potent inflammatory agent

Phospholipase C (PLC) from Pseudomonas aeruginosa induced a marked inflammatory response when injected intraperitoneally in C3H/HeJ mice. This inflammation was characterized by the accumulation of inflammatory cells and plasma protein and the release of arachidonic acid metabolites (6-trans-12-epi-leukotriene B4 [LTB4], 6-trans-LTB4, LTB4, 5-HETE (5-hydroxyeicosatetraenoic acid), LTC4, LTD4, LTE4, prostaglandin E2 [PGE2], PGF2-alpha, and thromboxane B2 [TxB2]) in the peritoneal cavity of the mice. Heat-inactivated PLC did not evoke any of these effects, suggesting that enzyme activity is necessary for PLC-induced inflammation. When human granulocytes were incubated with PLC in vitro, 6-trans-12-epi-LTB4, 6-trans-LTB4, LTB4, 5-HETE, and PGE2 were generated. Mouse peritoneal cells stimulated with PLC released 6-trans-LTB4, LTB4, PGE2, PGF2-alpha, and TxB2. Both human granulocytes and mouse peritoneal cells stimulated with PLC generated significantly increased levels of arachidonic acid metabolites as compared with cells incubated with heat-inactivated PLC. Leukotriene production by both populations of cells was inhibited when the cells were preincubated with nordihydroguaiaretic acid and subsequently stimulated with PLC. Similarly, both cell types released significantly lower amounts of cyclooxygenase pathway products when they were preincubated with indomethacin and subsequently stimulated with PLC.

1-[4-[3-[4-[bis(4-fluorophenyl)hydroxymethyl]-1- piperidinyl]propoxy]-3-methoxyphenyl]ethanone(AHR-5333): a selective human blood neutrophil 5-lipoxygenase inhibitor

In this study we report the in vitro inhibition of leukotriene synthesis in calcium ionophore (A23187)-stimulated, intact human blood neutrophils by AHR-5333. The results showed that AHR-5333 inhibits 5-HETE, LTB4 and LTC4 synthesis with IC50 values of 13.9, 13.7 and 6.9 microM, respectively. Further examination of the effect of AHR-5333 on individual reactions of the 5-lipoxygenase pathway (i.e. conversion of LTA4 to LTB4, LTA4 to LTC4, and arachidonic acid to 5-HETE) showed that this agent was not inhibitory to LTA4 epoxyhydrolase and glutathione-S-transferase activity in neutrophil homogenates. However, conversion of arachidonic acid (30 microM) to 5-HETE was half maximally inhibited by 20 microM AHR-5333 in the cell-free system. The inhibition of LTB4 and LTC4 formation in intact neutrophils by AHR-5333 appears to be entirely due to a selective inhibition of 5-lipoxygenase activity and an impaired formation of LTA4, which serves as substrate for LTA4 epoxyhydrolase and glutathione-S-transferase. AHR-5333 did not affect the transformation of exogenous arachidonic acid to thromboxane B2, HHT and 12-HETE in preparations of washed human platelets, indicating that this agent has no effect on platelet prostaglandin H synthase, thromboxane synthase and 12-lipoxygenase activity. The lack of inhibitory activity of AHR-5333 on prostaglandin H synthase activity was confirmed with microsomal preparations of sheep vesicular glands.

New series of lipoxins isolated from human eosinophils

Granulocytes from human eosinophilic donors were incubated with arachidonic acid or 15-hydroxyeicosatetraenoic acid (15-HETE) and stimulated with the ionophore A23187. The eicosanoids were extracted with reversed-phase cartridges and subjected to RP-HPLC analysis. When extracts from eosinophil-enriched populations were analysed and compared with extracts from human neutrophils, three additional peaks were detected which coeluted with 15-hydroxy-delta 13-trans-15H derivatives of leukotriene C4, D4 and E4 in different HPLC systems. The recorded absorbance spectra of the eluted compounds and the standards were identical and showed a maximum at 307 nm which is characteristic for a conjugated tetraene system with a bathochromic shift by the sulfur moiety in alpha-position to the tetraene system. The compound which coeluted with the 15-hydroxy-LTC4 standard was treated with gamma-glutamyltransferase and converted to the corresponding leukotriene D4 derivative. The results indicate that interaction between the 5- and 15-lipoxygenase pathways leads to the formation of a new series of arachidonic acid metabolites in human eosinophils. Since the biosynthetic route is similar to that of lipoxin A4 and lipoxin B4, we suggest the trivial names lipoxin C4, D4 and E4.

Relative effects of flurbiprofen on platelet 12-hydroxy-eicosatetraenoic acid and thromboxane A2 production: influence on collagen-induced platelet aggregation and adhesion

Flurbiprofen has been shown to inhibit cyclo-oxygenase metabolism of arachidonic acid to thromboxane A2 (TxA2), resulting in the inhibition of platelet aggregation. Recently, our laboratory reported that the "irreversible" phase of platelet aggregation and adhesion were regulated, in part, by the lipoxygenase metabolism of arachidonic acid to 12-hydroxy-eicosatetraenoic acid (12-HETE) in platelets, and that selective inhibition of one enzyme i.e. either cyclo-oxygenase or lipoxygenase, resulted in paradoxical effects on the metabolism of arachidonic acid and platelet response related to the other pathway. Therefore, we performed experiments to assess the relative effects of flurbiprofen on TxA2 and 12-HETE synthesis, and on collagen-induced platelet aggregation and platelet adhesion to collagen-coated surfaces. "Irreversible" collagen-induced platelet aggregation was only partially inhibited by pre-incubation with 1 x 10(-6) M flurbiprofen, while TxA2 production was elevated and 12-HETE production was maximally inhibited in these platelets. At this concentration of flurbiprofen (1 x 10(-6)M), collagen-induced platelet adhesion was also reduced by 50%. At higher concentrations of flurbiprofen, both platelet aggregation and adhesion were further reduced, with a corresponding inhibition of TxA2 production. Thus it appears that the lipoxygenase pathway of arachidonic acid metabolism in platelets is not only inhibited by flurbiprofen, but is more sensitive to inhibition by flurbiprofen than the cyclo-oxygenase pathway. This differential effect of flurbiprofen on arachidonic acid metabolism in the platelet is related to differential effects on platelet function.

Docosahexaenoic acid and other dietary polyunsaturated fatty acids suppress leukotriene synthesis by mouse peritoneal macrophages

The efficacy of individual omega-3 polyunsaturated fatty acids (PUFA) in altering eicosanoid synthesis in peritoneal macrophages was studied by feeding mice for 10 days a diet containing 2 wt % fat, which included 0.5 wt % ethyl esters of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or linolenic acid (LNA). Upon stimulation with calcium ionophore A23187, macrophages from these animals produced significantly lower amounts of leukotriene C4, leukotriene B4 and 12-hydroxyeicosatetraenoic acid, prostaglandin E2 and 6-keto prostaglandin F1 alpha compared with those obtained from animals on the diets containing olive oil or safflower oil. The decrease in leukotriene synthesis was similar in the animals fed DHA, EPA or LNA diets. This depression of eicosanoids by DHA and EPA was associated with decreased levels of arachidonic acid (AA); however, LA that altered eicosanoids did not have the same effect on AA levels.

Leukotriene C4 generation from human eosinophils stimulated with IgG-Aspergillus fumigatus antigen immune complexes

Sepharose beads coated with IgG stimulate eosinophils to produce leukotriene C4 (LTC4). This observation has been extended with specific immobilized IgG/antigen immune complexes to elicit mediator generation. An extract of Aspergillus fumigatus was covalently coupled to Sepharose beads and incubated with the IgG fraction of immune serum from patients with allergic bronchopulmonary aspergillosis. These beads elicited generation of 7.72 +/- 1.7 pmol of LTC4 immunoreactive material (n = 5) from 1 X 10(6) normal eosinophils of greater than 86% purity, and significantly less LTC4 (0.73 +/- 0.19 pmol per 10(6) cells; n = 3) was produced by eosinophils after incubation with beads treated with IgG from normal nonimmune serum. The maximum antibody-dependent release achieved represented approximately 20% of that induced by the calcium ionophore (A23187). LTC4 was measured by radioimmunoassay and validated by reverse-phase high-performance liquid chromatography. The amount of LTC4 generated was dependent on the concentration of A. fumigatus-specific IgG, and mediator release was completely abolished by prior adsorption of the IgG fraction onto Sepharose-protein A (Staphylococcus aureus). Grass pollen-specific IgG antibody/antigen complexes, in combination with Sepharose beads, also triggered generation of LTC4 immunoreactive material. There was no evidence to suggest that IgE/A. fumigatus immune complexes triggered LTC4 generation, although IgE myeloma protein, in association with Sepharose beads, was a weak stimulus. The efficacy of the IgG immune complex-dependent stimulation of eosinophils suggests a possible physiologic mechanism whereby these cells could participate in the inflammatory changes associated with allergic bronchopulmonary aspergillosis and similar allergic disorders.

Automated high-performance liquid chromatographic extraction and quantification procedure for lipoxygenase metabolites

A number of methods have been used to measure various lipoxygenase metabolites in aqueous samples. These methods, however, suffer from three major limitations: first, they require extensive extraction and isolation from protein-containing media; second, mainly due to the first limitation, they have poor recoveries; and third, these methods usually require a two-step procedure, one for the actual extraction and the other for the quantification of the lipoxygenase metabolites. We have developed a fully automated high-performance liquid chromatographic method which circumvents these limitations. As a result, we are able to obtain high recoveries of various lipoxygenase metabolites from protein-containing samples (i.e. biological samples) while simultaneously quantifying each metabolite. The method employs a column venting technique, whereby the fatty acids are extracted by a pre-column and the proteins are vented to waste. The pre-column eluate is then directed through the analytical column which separates the lipoxygenase metabolites. The described method is reproducible and minimizes both the time and the cost involved in assaying a sample.

Binding of 13-HODE and 5-, 12- and 15-HETE to endothelial cells and subsequent platelet, neutrophil and tumor cell adhesion

Some studies report that endothelial cells preferentially take up the lipoxygenase-derived arachidonic acid metabolite, 5-hydroxyeicosatetraenoic acid (5-HETE), released from stimulated leukocytes (polymorphonuclear leukocytes, PMNs), whereas others report that endothelial cells preferentially take up 12-HETE released from platelets. The biological relevance of these observations, however, is unknown. Recently, we and others have found that, under basal conditions, endothelial cells, PMNs and tumor cells metabolize linoleic acid via the lipoxygenase enzyme to 13-hydroxyoctadecadienoic acid (13-HODE). We propose that endogenous levels of these metabolites regulate blood-vessel wall cell adhesion. In this study, we have measured (1) the relative binding of 5-, 12- and 15-HETE, and 13-HODE to endothelial cell monolayers, and (2) their effects on endothelial cell adhesivity with platelets, PMNs and tumor cells. There was a dose-related and specific binding of 5-[3H]HETE to endothelial cells but no binding of 12- or 15-HETE or 13-HODE. Platelet or PMN adhesion to endothelial cells was unaffected by the 5-HETE binding, but tumor cell adhesion was blocked by 40% (P less than 0.01). Interestingly, preincubation of endothelial cells with 13-HODE, 12-HETE or 15-HETE decreased platelet adhesion to endothelial cells (P less than 0.05), even though these metabolites did not bind to the endothelial cells. We conclude that 5-HETE preferentially binds to endothelial cells and interferes with a specific receptor for tumor cells, whereas the other metabolites neither bind to cells nor affect cell adhesion.

19-Hydroxyprostaglandin B2 as an internal standard for on-line extraction-high-performance liquid chromatography analysis of lipoxygenase products

Variable recovery of polar compounds is a potential pitfall in the on-line extraction-reversed-phase HPLC analysis of lipoxygenase products. Therefore, the addition of a polar internal standard to biological samples, which permits the assessment of the recovery of the polar components in individual samples, appears to be essential. 19-Hydroxyprostaglandin (PG) B2 was found to be a suitable compound for this application. It was easily prepared from deproteinized human semen by base-catalyzed dehydration of 19-hydroxy-PGE2, and purified in a single step by reversed-phase HPLC. Similarly to PGB2, already used as internal in HPLC, 19-hydroxy-PGB2 has excellent chemical stability and carries a strong uv chromophore that enables detection at 280 nm. Most importantly, it is eluted just prior to the polar arachidonic acid metabolites 20-hydroxy- and 20-carboxy-leukotriene B4, 12-oxo-dodecatrienoic acid and the lipoxines A and B. The measurement of the ratio of PGB2 and 19-hydroxy-PGB2 used in combination as internal standards in HPLC analysis of lipoxygenase products, provides a simple and reliable way to assess sample to sample recovery of the polar components when using on-line extraction procedures.

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.

Wy-48,252 (1,1,1-trifluoro-N-[3-(2-quinolinylmethoxy)phenyl]membrane sulfonamide), an orally active leukotriene antagonist: effects on arachidonic acid metabolism in various inflammatory cells

The LTD4 antagonist, Wy-48,252 (1,1,1-trifluoro-N-[3-(2-quinolinylmethoxy)phenyl]methanesulfonamide), was assessed for its ability to modulate arachidonic acid metabolism in several inflammatory cells. In A23187-stimulated rat neutrophils, Wy-48,252 effectively inhibited the conversion of exogenous [14C]arachidonic acid to radiolabeled 5-hydroxyeicosatetraenoic acid (5-HETE) and thromboxane B2 (TxB2) (IC50 = 2 and 9.1 microM, respectively). Synthesis of immunoreactive leukotriene B4 (LTB4) (IC50 = 4.6 microM) and TxB2 (IC50 = 3.3 microM) from endogenous substrate by these cells in the absence of [14C]arachidonic acid was similarly reduced. Wy-48,252 also reduced leukotriene C4 (LTC4) and PGE2 synthesis by zymosan-activated mouse peritoneal macrophages (IC50 = 4.4 and 4.3 microM, respectively). 5-Lipoxygenase (5-LO) catalyzed reactions in human neutrophils, lung mast cells and basophils activated by various stimuli were dose dependently inhibited by Wy-48,252 while PGD2 synthesis by lung mast cells was inhibited at 100 microM. By contrast, 12-LO, 15-LO, phosphodiesterase activity and histamine release from mast cells and basophils were unaffected by Wy-48,252. These data suggested that the LTD4 antagonist, Wy-48,252, also inhibited the synthesis of eicosanoids, a feature that may contribute to its pharmacological actions in vivo.

Modulation of leucocyte activation in the early phase of the rabbit burn injury

Previous studies in burned patients have shown an early enhanced polymorphonuclear leucocyte (PMN) generating capacity for superoxide radical (O2.-), for the arachidonic acid (AA) lipoxygenase metabolite leukotriene B4 (LTB4) and for platelet activating factor-acether (PAF). These findings have been confirmed on a burn injury rabbit model. As we have suggested a pivotal role for an exaggerated initial (less than 36-48 h) neutrophil stimulation leading to a later (greater than 72 h) immuno-depression and anergy, we tried to modulate the early phase by drug therapy. A Ginkgo biloba extract (IPS200) injected i.v. in burned rabbits greatly reduced O2.- and LTB4 generation on A23187 challenge. IPS200 includes flavonoids and other polyphenols, inhibiting either arachidonic acid metabolism or PAF receptors, and may thus exert their modulating effect on PMN function in thermal injury.

Differential effects of docosahexaenoic acid and eicosapentaenoic acid on suppression of lipoxygenase pathway in peritoneal macrophages

Docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) was facilely incorporated into phospholipids of mouse peritoneal macrophages following incubation with pure fatty acids complexed to bovine serum albumin. Following stimulation with calcium ionophore A23187, the DHA-enriched cells synthesized significantly smaller amounts of leukotriene C4 and leukotriene B4 compared to control or EPA-enriched cells. The EPA-enriched cells synthesized lower amounts of leukotriene C4 and leukotriene B4 compared to control cells. The stimulated macrophages utilized endogenously released arachidonic acid for leukotriene B4 and leukotriene C4 synthesis. Exogenous arachidonic acid increased the formation of 12-hydroxyeicosatetraenoic acid (12-HETE) and 15-HETE and macrophages enriched with DHA or EPA produced similar amounts of 12-HETE and 15-HETE compared to control cells. These studies demonstrated that the synthesis of leukotriene C4, leukotriene B4 and HETE in macrophages is differentially affected by DHA and EPA.

Studies on the effects of disease-modifying antirheumatic drugs on lipoxygenase product synthesis in human neutrophils in vitro

The disease-modifying antirheumatic drugs sodium aurothiomalate, D-penicillamine and chloroquine phosphate were tested on leukotriene (LT) synthesis in human blood polymorphonuclear leukocytes stimulated with either the ionophore A23187, zymosan or f-Met-Leu-Phe. Lipoxygenase products were analyzed by reversed-phase high-performance liquid chromatography. The study demonstrated that the drugs can either inhibit or enhance 5-lipoxygenase product synthesis in human leukocytes, depending on the stimulus used to activate the cells and the drug concentration. The data also suggested that increased substrate availability accounted for the stimulatory effects of the drugs on leukotriene synthesis.

Modulation of zymosan stimulated leukotriene release by dietary unsaturated fatty acids

The quantity of leukotrienes produced in an inflammation model, the stimulated mouse peritoneum, was affected by dietary manipulation of tissue arachidonic acid, the immediate leukotriene (LT) precursor. Fifty ng of LTE4 was synthesized (after injection of zymosan) by the peritoneal cavity of mice maintained on olive oil as a dietary source of unsaturated fatty acids. Animals maintained on corn oil, exhibited significantly enhanced leukotriene biosynthesis upon stimulation by zymosan. Mice fed menhaden oil, a fat source rich in n-3 fatty acids produced 50% less leukotriene E4 than animals fed olive oil. The results indicated that production of leukotrienes, potent mediators of inflammatory reactions, are affected by the type of polyunsaturated fatty acids in the diet.

Role of cell-bound hemolysin as a pathogenicity factor for Serratia infections

The hemolytic activities of clinical isolates of Serratia marcescens, of Serratia liquefaciens, and of Escherichia coli strains containing a cloned hemolysin gene of S. marcescens were determined. Hemolysis was induced only by cells and not by spent media. The hemolytically active bacteria induced the release of the leukotriene C4 and of much less leukotriene B4 from polymorphonuclear leukocytes, the release of histamine from rat mast cells, and chemoluminescence of neutrophils. The hemolytic activity was correlated with the response of the leukocytes, but quantitative differences were recorded with regard to the release of the inflammatory mediators. Therefore, other factors in addition to the hemolysin contribute to the stimulation of leukotriene generation and histamine release. It is concluded that the hemolysin via these inflammatory mediators can increase vascular permeability, edema formation, and granulocyte accumulation and thus contributes to the pathogenicity of Serratia species.

Precolumn extraction and reversed-phase high-pressure liquid chromatography of prostaglandins and leukotrienes

Prostaglandins, leukotrienes, and other metabolites of arachidonic acid can be conveniently and efficiently extracted from biological media using a precolumn containing octadecylsilyl silica connected to a 6-port switching valve that is in line with an analytical HPLC column. This procedure makes it possible to extract complex mixtures of eicosanoids and to analyze them by reversed-phase HPLC in a single step. The requirement to evaporate solvents from extracts prior to HPLC is therefore eliminated, saving time and reducing the possibilities for loss and contamination. The effects on recoveries of various media for loading the sample onto the precolumn were investigated, and it was concluded that 15% methanol at neutral pH gives the best overall results. It is therefore not necessary to acidity the sample prior to extraction, which simplifies the procedure and improves the recoveries of acid-labile eicosanoids. Following extraction, eicosanoids can be introduced onto the HPLC column by changing the position of the 6-port switching valve. We have investigated several approaches to the analysis of complex mixtures of these products by reversed-phase HPLC. The best results were obtained using a ternary gradient with a non-end-capped column of octadecylsilyl silica. Metabolites of arachidonic acid other than peptido-leukotrienes were first eluted by increasing the concentrations of acetonitrile and methanol in the mobile phase, which contained a constant concentration of trifluoroacetic acid (0.001%). Peptido-leukotrienes were then eluted with a second gradient, in which the concentrations of acetonitrile and methanol were kept constant, but the concentration of trifluoroacetic acid was increased to 0.0091%. Leukotrienes C4, D4, and E4 appear as sharp peaks at the end of the chromatogram and are completely separated from other types of arachidonic acid metabolites.

Formation of lipoxin A by granulocytes from eosinophilic donors

The formation of arachidonic acid-derived lipoxygenase products was examined with human granulocytes obtained from eosinophilic donors. These eosinophil-enriched leukocyte populations, challenged in vitro with the ionophore of divalent cations A23187, transformed both exogenous and endogenous sources of arachidonic acid to several lipoxygenase-derived products, including 5(S), 6(R),15(S)-trihydroxy-7,9,13-trans-11-cis-eicosatetraenoic acid (lipoxin A). Lipoxin A was detected and characterized by high-pressure liquid chromatography (HPLC), ultraviolet absorbance, and gas-liquid chromatography-mass spectroscopy. Neither lipoxin B nor 6(S)-LXA was consistently detected in extracts from these incubations. The amounts of lipoxin A formed were proportional to the percentage of eosinophils present in the suspension. The results indicate that granulocytes from eosinophilic donors can generate lipoxin A.

Effect of nafazatrom on platelet function and release: relationship to symptomatic episodes in patients with peripheral vascular disease

We studied the effect of nafazatrom on plasma prostacyclin (PGI2) levels, platelet function, and thromboxane B2 (TxB2), and 12-hydroxy-eicosatetraenoic acid (12-HETE) production and clinical improvement in 12 patients with peripheral vascular disease (PVD) by means of a double-blind crossover trial of placebo, 800 or 1600 mg of nafazatrom four times daily for 1 week, with intervening 2-week washout periods. Plasma PGI2 levels were measured as 6-keto-PGF1 alpha by radioimmunoassay. Platelet function ex vivo was measured as collagen and adenosine diphosphate (ADP)-induced platelet aggregation, release of 12-HETE and thromboxane A2 (measured as TxB2), and was determined by high-pressure liquid chromatography (HPLC) and radioimmunoassay, respectively. The plasma 6-keto-PGF1 alpha levels were unaffected by nafazatrom treatment (p greater than 0.25). Nafazatrom treatment had no effect on TxB2 production, but significantly altered the production of the platelet 12-HETE (p less than 0.05). There was a significant association between the changes in 12-HETE production and clinical improvement. These results suggest that the mechanism of action of nafazatrom is in part related to the inhibition of platelet function via the lipoxygenase pathway, independent of PGI2 stimulation.