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P Borgeat

Publications and source records attributed to P Borgeat.

At least 109 records · Page 6Linked to original sources
PubMed1987

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

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

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

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

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

Catalysis↗
PubMed1987

Conversion of arachidonic acid into 12-oxo derivatives in human platelets. A pathway possibly involving the heme-catalysed transformation of 12-hydroperoxy-eicosatetraenoic acid.

Analysis of arachidonic acid metabolites in human platelets by reverse-phase HPLC with radioactivity and UV detection revealed, besides Thromboxane B2 (TXB2), 12-hydroxy-heptadecatrienoic acid (HHT) and 12-hydroxy-eicosatetraenoic acid (12-HETE) previously described, two peaks of unidentified material absorbing at 280 nm. This material was purified by straight-phase HPLC and characterized by UV spectroscopy and gas chromatography-mass spectrometry. Three carbonyl compounds were identified: 12-keto-5,8,10,14-eicosatetraenoic acid and two geometric isomers of 12-oxo-5,8,10-dodecatrienoic acid. In a 5 min incubation at 37 degrees C in the presence of 9 microM arachidonic acid, the yield was of 0.5 to 1% of added arachidonic acid for the ketonic compound and of 4 to 7% for the sum of the two isomeric fatty acid aldehydes in comparison to 10 to 13% and 25 to 28% for TXB2 and 12-HETE, respectively. Because the three compounds carry a carbonyl group at position 12, their relationship with the 12-lipoxygenase pathway was investigated. It was found that the three compounds were formed when 12-hydroperoxy-eicosatetraenoic acid (12-HPETE) was incubated with intact or heat denaturated platelets or hemoproteins, strongly suggesting that these carbonyl compounds are products of a heme-catalysed transformation of 12-HPETE.

Arachidonic Acid↗
PubMed1987

[Effect of SIN-1 on the synthesis of leukotrienes in human polymorphonuclear cells].

Leukotriene (LT) synthesis triggered with ionophore A23187 or inflammatory stimuli (PAF, fMLP) in human polymorphonuclear leukocytes (PMNL) was markedly decreased by SIN-1, an active metabolite of molsidomine. This inhibition occurred in the absence or in the presence of exogenous arachidonic acid (AA). These results suggest that SIN-1 inhibited both the release of AA from membrane phospholipids and the 5-lipoxygenase activity in human PMNL. Molsidomine was without any effect on LT formation.

Arachidonic Acids↗
PubMed1986

Mass spectrometry of prostaglandins, leukotrienes and steroids as their allyldimethylsilyl ether derivatives.

Allyldimethylsilyl ethers of prostaglandin E2 and F2 alpha, leukotriene B4 and 5 beta-pregnane-3 alpha, 20 alpha-diol were prepared at room temperature in good yields with the novel reagent N,O-bis(allyldimethylsilyl)-trifluoroacetamide. The gas chromatographic properties of the derivatives of prostaglandins and the steroid were found to be excellent whereas those of leukotriene B4 were found to be less than satisfactory. The mass spectra of the allyldimethylsilyl ether derivatives of the compounds studied show intense ions in their upper mass region derived from the elimination of an allyl radical. In the mass spectrum of the derivative of leukotriene B4, the formation of a conjugated carbonium ion by alpha-cleavage is a major process. The detection limits for a quantitative assay were established by performing selected ion monitoring on the most intense ion in the upper mass region of respective mass spectrum. Detection limits in the low picogram range were obtained for the prostaglandins and the steroid but the allyldimethylsilyl ether derivative of leukotriene B4 exhibited a far higher detection limit. It is concluded for the latter compound that the detection limit depends primarily on the gas chromatographic properties.

Acetamides↗
PubMed1986

Inhibitory effects of a novel platelet activating factor (PAF) antagonist (BN 52021) on antigen-induced prostaglandin and thromboxane formation by the guinea pig lung.

The effects of a new Platelet-Activating Factor (PAF-acether) antagonist (BN 52021) extracted from Ginkgo biloba leaves have been studied on the release of metabolites of arachidonic acid in IgG-dependent guinea pig pulmonary anaphylaxis in vitro. Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) were assayed using a novel ELISA technique. The release of PGE2 and TxB2 from anaphylactic lungs reached a maximum 4-5 min following the antigen challenge (about 3.2 and 31.0 ng/ml respectively) and decayed slowly during the following 25 min. BN 52021 (1, 3 and 30 micrograms/ml) produced dose-dependent decreases of the release of PGE2 and TxB2. These results suggest that there are some interactions between the release of icosanoids and PAF-acether in anaphylaxis.

Anaphylaxis↗
PubMed1986

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

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

Animals↗
PubMed1986

Characterization of platelet activating factor (PAF)-acether-induced contractions of guinea-pig lung strips by selected inhibitors of arachidonic acid metabolism and by PAF-acether antagonists.

The myotropic activities of PAF-acether, leukotriene B4, leukotriene D4 and histamine were compared on superfused guinea-pig lung parenchymal strip and were shown to have the following order of potency: PAF-acether greater than LTD4 greater than LTB4 greater than histamine. The contractile response of the lung parenchyma to PAF-acether was inhibited by aspirin, imidazole and OKY-046, which suggested that thromboxane A2 might play a mediator role in PAF-induced contractions. Neither an antagonist of leukotriene D4, FPL-55712, nor an antihistamine, mepyramine, had any effect on PAF contractions. The activity of a novel antagonist of PAF-acether, BN 52021, was also studied on superfused lung parenchyma contracted by histamine, leukotriene B4, leukotriene D4 and PAF-acether. This compound was without effect on the histamine response but it slightly reduced the contractions elicited by leukotriene D4 and potentiated those by leukotriene B4. BN 52021 (7.1 X 10(-6) M) inhibited by 63% the contraction induced by 5.7 X 10(-13) M PAF-acether and by 52% that induced by 5.7 X 10(-10) M PAF-acether and kadsurenone (8.4 X 10(-6) M), another PAF-acether antagonist, inhibited the same PAF-induced contractions by 75% and 20% respectively.

Animals↗
PubMed1986

Comparison of 5- and 15-lipoxygenase activities in blood and alveolar leukocyte preparations from normal subjects and patients with eosinophilia.

The arachidonic acid lipoxygenase metabolites of polymorphonuclear leukocyte (PMNL) preparations obtained from 31 subjects with eosinophilia (eosinophil content of PMNL preparations: 27.0%, 4-73, median with range) and 29 normal donors (4.5%, 0-15) were analyzed by reversed phase high performance liquid chromatography. More leukotriene (LT) C4 and 15-hydroxyeicosatetraenoic acid (HETE) (p less than 0.001) and less LTB4 (p less than 0.005) were found in eosinophil-rich preparations in comparison to controls on incubations with ionophore and arachidonic acid. In incubations with arachidonic acid alone, only small amounts of 5-lipoxygenase metabolites were produced by both groups, but the PMNL preparations from patients with eosinophilia showed higher capacity to release LTC4 and 15-HETE (p less than 0.005). In the eosinophil-rich preparations, the percentage of eosinophils correlated positively with the production of LTC4 and negatively with LTB4 (p less than 0.05, incubations with ionophore +/- arachidonic acid), and positively with 15-HETE (p less than 0.01, incubations with arachidonic acid +/- ionophore). Moreover the eosinophil-rich preparations produced more LTC4 per eosinophil in incubations with arachidonic acid alone (p less than 0.001) than normal PMNL preparations. The predominant release of LTC4 and 15-HETE by eosinophils was further confirmed by the analysis of bronchoalveolar lavage cells. Lavage cells containing eosinophils released LTC4 and 15-HETE while normal bronchoalveolar lavages, which were poor in eosinophils, did not produce detectable amount of LTC4 and 15-HETE. These results show that eosinophils release preferentially LTC4 and 15-HETE in contrast to LTB4 for the neutrophils.

Adolescent↗
PubMed1986

Decreased leukotriene B4 synthesis in smokers' alveolar macrophages in vitro.

Recent studies have shown that alveolar macrophages (AM) are able to release leukotrienes (LTs). Since cigarette smoking inhibits the cyclooxygenase pathway of arachidonic acid metabolism in the AM, we evaluated the LT production by AM from smokers and nonsmokers. AM were obtained from 35 volunteers, 16 nonsmokers, and 19 smokers. The cells were incubated under various conditions including stimulation with 30 microM arachidonic acid, 2 microM ionophore A23187, or both. Each experiment was performed in parallel using cells from a smoker and a nonsmoker. Lipoxygenase products were analyzed by reverse-phase high performance liquid chromatography. After stimulation, nonsmokers' AM produced LTB4 and 5-hydroxy-eicosatetraenoic acid (5-HETE). In incubations of AM with arachidonic acid and ionophore, the amounts of products formed were: LTB4, 317 +/- 56 pmol/10(6) cells and 5-HETE, 1,079 +/- 254, mean +/- SEM. No metabolites were generated under control conditions (no stimulation). In all incubations performed, the peptido-LTs (LTC4, LTD4, and LTE4) were undetectable. In comparison with AM from nonsmokers, those from smokers showed a 80-90% reduction of 5-HETE and LTB4 synthesis (P less than 0.05 to P less than 0.001 according to stimulatory conditions). This defective lipoxygenase metabolite production in AM from smokers was observed over a wide range of stimuli concentrations and incubation times; AM from smokers also had lower levels of intracellular (esterified) 5-HETE than nonsmokers' AM. We also studied blood polymorphonuclear leukocytes (PMNL) and no difference in the synthesis of 5-lipoxygenase products in these cells was noticed between smokers and nonsmokers. These data show that cigarette smoking causes a profound inhibition of the 5-lipoxygenase pathway in AM but not in blood PMNL.

Adult↗
PubMed1986

Immunological and non-immunological release of leukotrienes and histamine from human nasal polyps.

Nasal polyps were obtained from 22 patients undergoing polyp surgery. They were chopped into fragments of approximately 2 mm2, washed free of blood, and passively sensitized with serum from timothy allergen sensitive patients (RAST 30-40%), then, challenged with timothy allergen. Analysis of the incubation medium after a 30 min challenge as assessed by reversed phase high performance liquid chromatography and bioassay revealed the presence of leukotriene (LT) LTB4, LTC4, LTD4 and LTE4 (29 +/- 9, 6.6 +/- 3, 62 +/- 13 & 86 +/- 23 pmol/g tissue wet weight, respectively). The human nasal polyps also released histamine which reached a maximum after approximately 5 min (2.8 +/- 1.28 nmol/g tissue), as measured by radioenzymatic assay. A similar profile of leukotrienes and histamine release was observed when the nasal polyps were stimulated with ionophore A23187. However, the ionophore stimulated release was greater than that observed for the antigen challenge. When human polyps were stimulated with a mixture of the ionophore and arachidonic acid, all the above products as well as 5-hydroxy-eicosatetraenoic acid (5-HETE), 12-HETE, and 15-HETE were detected in the medium. These data, taken together, demonstrate that human nasal polyps are able to release significant amounts of leukotrienes and histamine upon both immunological and non-immunological stimulations and that these responses might significantly contribute to the symptoms of allergic rhinitis.

Allergens↗
PubMed1985

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

Fragments of human lung parenchyma or bronchi were studied by high performance liquid chromatography, gas chromatography-mass spectrometry, and bioassay for the biosynthesis of 5-lipoxygenase metabolites of arachidonic acid, and by radioenzymatic assay for the release of histamine, upon immunologic and nonimmunologic stimulation. Human lung parenchyma were passively sensitized with serum from timothy-positive allergic patients (radioallergosorbent test, 30-40%) and challenged with 0.5 microgram/ml of timothy allergen. Analysis of the incubation media showed the presence of LTB4, LTC4, LTD4, LTE4, and histamine. Maximum release of LTB4 and LTD4 was observed after 15 min of challenge (92.8 +/- 21, and 67.8 +/- 14 pmol/g tissue wet weight, respectively; mean +/- SEM) whereas maximum release of LTC4 was observed after 5 min of challenge (25 +/- 7.1 pmol). In parallel to leukotriene formation, histamine was released rapidly and reached a maximum after approximately 15 min of challenge (2.85 +/- 0.76 nmol/g tissue). When fragments of human lung parenchyma were stimulated with ionophore A23187 (4 microM), we observed a profile of leukotriene and histamine release similar to that seen in response to the allergen. Ionophore A23187 stimulated the release of two- to fivefold greater amounts of leukotrienes and histamine than did the allergen. Release of LTC4 and histamine was maximal after 5 min of stimulation (83 +/- 22.2 and 5.2 +/- 0.95 nmol/g tissue, respectively), whereas LTB4 and LTD4 release reached a maximum after 15 min (438 +/- 66.6 and 205 +/- 68 nmol/g tissue, respectively). In addition, human lung parenchyma metabolized LTB4 into omega-OH-LTB4 and omega-COOH-LTB4. This tissue also released 5-hydroxy-eicosatetraenoic acid (5-Hete), 12-Hete, and 15-Hete. Fragments of human lung bronchi also released a similar profile of leukotrienes (except LTC4) and histamine when challenged with the allergen or ionophore A23187. Maximum release of LTB4 and LTD4 by allergen or ionophore stimulation was observed after approximately 15 min (40 +/- 7.5 and 21 +/- 8 pmol/g tissue, respectively, upon allergen challenge; 100 +/- 13 and 47 +/- 10.6 pmol/g tissue, respectively, upon ionophore stimulation). The maximum release of histamine by bronchi was observed after approximately 15 min of allergen challenge and 5 min of ionophore stimulation (2.25 +/- 0.65 and 3.15 +/- 0.9 nmol/g tissue, respectively). The release of leukotrienes but not of histamine by human lung parenchyma upon both allergen and ionophore challenge was inhibited by nordihydroguaiaretic acid (NDGA) (ID50, 2 X 10(-6)M).(ABSTRACT TRUNCATED AT 400 WORDS)

Adjuvants, Immunologic↗
PubMed1985

Phorbol esters inhibit the fMet-Leu-Phe- and leukotriene B4-stimulated calcium mobilization and enzyme secretion in rabbit neutrophils.

The tumor co-promoter phorbol 12, myristate 13, acetate (PMA) has previously been shown to stimulate several of the characteristic functions (aggregation, degranulation, and the oxidative burst) of polymorphonuclear leukocytes (neutrophils). We describe here a novel feature of the action of PMA on neutrophils, namely its ability to inhibit the chemotactic factor-induced increased in the enzyme secretion and in the intracellular concentration of free calcium. The inhibition is maximal within 3 min of the addition of PMA and is concentration-dependent (IC50 = 8.5 ng/ml). The site of action of PMA is distal to the binding of the chemotactic factors. PMA inhibits both the release of intracellular calcium and the permeability changes to calcium induced by chemotactic factors, but does not affect the stimulation of the rate of influx of sodium produced by the same agents. The PMA analog 4 alpha-phorbol 12, 13-didecanoate, which lack tumorigenicity and the ability to activate the calcium- and phospholipid-dependent protein kinase (protein kinase C), does not inhibit any of the above fMet-Leu-Phe-stimulated neutrophil functions. The present results thus demonstrate that phorbol esters, either directly or indirectly, possibly through the activation of protein kinase C, inhibit the signal(s) responsible for the stimulated mobilization of calcium in rabbit neutrophils.

Acetylglucosaminidase↗
PubMed1985

Intracellular calcium redistribution and its relationship to fMet-Leu-Phe, leukotriene B4, and phorbol ester induced rabbit neutrophil degranulation.

The addition of low concentrations (less than 10(-7) M) of the calcium ionophore A23187 to rabbit neutrophils releases the intracellular pool of calcium previously shown in radioactive steady-state and chlortetracycline fluorescence studies to be mobilized by chemotactic factors. A23187 at these concentrations elicits no functional responses from these cells. However, A23187, added before chemotactic factors such as fMet-Leu-Phe and leukotriene B4, inhibits the ability of the latter stimuli to induce, in the presence of cytochalasin B, an exocytotic release of the neutrophil's cytoplasmic granules. These results imply that the chemotactic-factor-induced release of intracellular calcium is a necessary event for the optimal activation of the neutrophils. Phorbol ester-induced neutrophil degranulation on the other hand is unaffected by exposure to A23187, thereby completely dissociating its mechanism of action from rises in cytoplasmic free calcium.

Animals↗
PubMed1985

Characterization of effect of N-formyl-methionyl-leucyl-phenylalanine on leukotriene synthesis in human polymorphonuclear leukocytes.

Human polymorphonuclear leukocytes (PMNLs) were exposed to N-formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe) in the presence or absence of exogenous arachidonic acid. Analysis of incubation mixtures by high-performance liquid chromatography showed that f-Met-Leu-Phe stimulated the synthesis of 5-hydroxy-eicosatetraenoic acid (HETE) and of leukotriene B4 (LTB4) which was rapidly metabolized into 20-OH-LTB4 and 20-COOH-LTB4. The stimulatory effect of f-Met-Leu-Phe was dose and time dependent. The tripeptide showed maximum stimulatory activity at the concentration of 1 microM and after 20-30 min of incubation. Addition of arachidonic acid to the f-Met-Leu-Phe-stimulated PMNLs resulted in an increase in the synthesis of LTB4 and 5-HETE. Pretreatment of the PMNLs with cytochalasin B strongly potentiated (up to six-fold) the stimulatory effect of f-Met-Leu-Phe on 5-lipoxygenase product synthesis, whereas cytochalasin B alone or with arachidonic acid had no significant effect. The tripeptide did not increase the synthesis of platelet-derived 12-HETE, and 12-hydroxyheptadecatrienoic acid, or of PMNL-derived 15-HETE, suggesting that its action was selective for PMNL 5-lipoxygenase. The present data indicate that f-Met-Leu-Phe causes the release of arachidonic acid from cellular lipids and activates the 5-lipoxygenase.

Arachidonic Acid↗