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Biomedical subjects

P Borgeat

Publications and source records attributed to P Borgeat.

At least 145 records · Page 8Linked to original sources
PubMed1984

Development of calcium and secretory responses in the human promyelocytic leukemia cell line HL60.

We have begun to characterize the development of the excitation-response coupling sequence in the human promyelocytic leukemia cell line HL60. Using the recently developed fluorescent calcium probe quin-2, it was found that DMSO induced myeloid differentiation of the HL60 cells is accompanied by the development of a calcium response to the addition of the chemotactic factors fMet-Leu-Phe and leukotriene B4. The characteristics (time course, concentration dependence, stereospecificity, and metabolic dependence) of the calcium response are extremely similar to those previously described in human neutrophils. These results imply that functional receptors for leukotriene B4 appear in HL60 cells upon the induction of differentiation and also lend strong support to the use of these HL60 cells as a model of human myeloid differentiation. We have also characterized the emergence of a secretory response to fMet-Leu-Phe and leukotriene B4 in cytochalasin B treated HL60 cells. In addition, it is found that differentiation was required for the calcium ionophore A23187 to express its secretory activity toward the HL60 cells. This last set of results implies that differentiation is accompanied by the coordinated appearance of surface receptors and cytoplasmic factors required for the expression of cellular responsiveness.

Aminoquinolines↗
PubMed1984

Comparative effects of etodolac, indomethacin, and benoxaprofen on icosanoid biosynthesis.

Etodolac (Ultradol) is a new tetrahydropyrano-indole derivative which has shown pronounced analgesic and antiinflammatory properties. Its effects on the different pathways of metabolism of arachidonic acid have been studied and compared to the effects of indomethacin and benoxaprofen. All three drugs tested inhibited the cyclooxygenase activity of the parenchyma as assessed by inhibition of LTB4- and LTD4-induced contraction. However, the activity of human polymorphonuclear leukocyte 5-lipoxygenase and of human platelet 12-lipoxygenase was inhibited only by very high concentrations (1 X 10(-4) M and over) of these compounds, whereas nordihydroguaiaretic acid (NDGA) was active at concentrations 100 times lower. In the Schultz-Dale reaction of the guinea pig trachea, etodolac, benoxaprofen, and indomethacin produced increases of the myotropic contractile activity of the tissues sensitized to ovalbumin. Our results do not lend support to the hypothesis that the mechanism of action of these antiinflammatory drugs is linked to the inhibition of lipoxygenases.

Acetates↗
PubMed1984

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

Blood samples were obtained from a group of 20 patients with hypereosinophilia (greater than or equal to 1500 eosinophils/mm3). The polymorphonuclear leukocytes (PMNLs) were prepared from blood treated with ethylenediaminetetra-acetic acid by successive dextran sedimentation of the red blood cells, separation of mononuclear leukocytes and PMNLs on Ficoll-Paque, and ammonium chloride treatment of the PMNL fraction. The eosinophil content of the final PMNL preparations ranged from 15% to 75%, as assessed by Wright-stained smears, and the remaining leukocytes were predominantly neutrophils with only 3% to 5% mononuclear cells. The eosinophil-rich PMNL preparations as well as PMNL preparations from normal volunteers were incubated under various conditions and the arachidonic acid metabolites were analyzed by reverse-phase high-performance liquid chromatography. The synthesis of 5-lipoxygenase products was strongly stimulated by the ionophore A23187 in both normal and eosinophil-rich PMNL preparations. Whereas the normal PMNL preparations, which were eosinophil poor, produced 10 to 25 times more leukotriene B4 than leukotriene C4, the eosinophil-rich PMNL preparations characteristically released leukotriene C4 in equal or up to 20 times greater amounts than leukotriene B4.

Arachidonate Lipoxygenases↗
PubMed1984

Characteristics of leukotriene (LT) and hydroxy eicosatetraenoic acid (HETE) synthesis in human leukocytes in vitro: effect of arachidonic acid concentration.

Suspensions of human blood leukocytes and platelets were stimulated with the ionophore A23187 in the presence of increasing concentrations of arachidonic acid. Nine metabolites of the 5-, 12- and 15-lipoxygenase and the cyclooxygenase pathways were analyzed by high performance liquid chromatography in order to study the rate-limiting steps and other characteristics of their biosynthesis. The data indicate that the LTA4 hydrolase and the LTA4 glutathione transferase activities are respectively the limiting factors in the synthesis of LTB4 and LTC4. At high substrate concentrations (5 X 10(-5)M and above), the 5-lipoxygenase activity was inhibited whereas the synthesis of the 15-HETE (15-lipoxygenase product) increased linearly up to the highest concentration tested (3 X 10(-4)M). The data also indicate that contrary to 5-HETE and LTs, 15-HETE is not formed upon stimulation with the ionophore, but only following incubation with exogenous arachidonic acid (20 microM and above), pointing out major differences in the synthesis of 5- and 15-lipoxygenase products.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1984

Comparative effects of indomethacin, acetylenic acids, 15-HETE, nordihydroguaiaretic acid and BW755C on the metabolism of arachidonic acid in human leukocytes and platelets.

Human leukocytes and platelets were preincubated with inhibitors of the oxidative metabolism of arachidonic acid, viz, indomethacin, BW755C, 5, 8, 11, 14-eicosatetraynoic acid (ETYA), 5, 8, 11-eicosatriynoic acid, 15S-hydroxy-5, 8, 11, 13-(Z, Z, Z, E)-eicosatetraenoic acid (15-HETE) and nordihydroguaiaretic acid (NDGA), prior to stimulation with the ionophore A23187 in the presence or absence of exogenous arachidonic acid. Eleven metabolites of arachidonic acid derived from the cyclooxygenase and the 5-, 12- and 15-lipoxygenases were measured by reversed-phase high pressure liquid chromatography (RP-HPLC). Indomethacin was the best inhibitor of the platelet cyclooxygenase (ID50 less than 10(-7)M) as assessed by measurement of 12-hydroxy-heptadecatrienoic acid (HHT); ETYA was the most potent inhibitor of the 12- and 15-lipoxygenases (ID50 approximately 3 X 10(-7)M) whereas NDGA was the most potent and selective inhibitor of the 5-lipoxygenase (ID50 approximately 3 X 10(-7)M).

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1984

Intraocular effects of lipoxygenase pathway products in arachidonic acid metabolism.

Arachidonic acid is metabolized through the lipoxygenase pathways to hydroperoxy acids (HPETEs), hydroxy acids (HETEs), and leukotrienes, derivatives of 5-HPETE. 5-HETE, 12-HETE, 15-HETE, and 15-HPETE were injected intracamerally in rabbits and leukotriene B4 (LTB4), leukotriene C4 (LTC4 and leukotriene D4 (LTD4) were injected intracamerally in guinea pigs, rabbits and cats. The effects on the intraocular pressure, aqueous humour protein and leukocyte concentration as well as pupil diameter were assessed. 5-HETE, 12-HETE, 15-HETE and 15-HPETE did not cause any change in the parameters studied. LTB4 caused a marked accumulation of leukocytes in the aqueous humour of cats and rabbits, and to some extent in guinea pigs. LTC4 and LTD4 were ineffective in guinea pigs and rabbits, but caused an intense long-lasting non-muscarinic miosis in cats. Thus, most of the lipoxygenase products tested showed little activity in the anterior segment of the eye, except LTB4, that caused leukocyte infiltration, and LTC4 and LTD4 that caused miosis in cats.

Animals↗
PubMed1984

Studies on leukotriene B4 omega-oxidation in human leukocytes.

The kinetics of the transformation of arachidonic acid into 5-lipoxygenase products in human blood leukocytes stimulated with the ionophore A23187 (2 microM) was studied using high performance liquid chromatography. The levels of 5-hydroxyeicosatetraenoic acid (5-HETE), leukotriene B4 (LTB4), delta 6-trans-LTB4, and leukotriene C4 (LTC4) were maximum after 4-5 min of incubation; at longer incubation times, the levels of delta 6-trans-LTB4 and LTC4 remained unchanged, whereas those of 5-HETE and LTB4 decreased rapidly. The disappearance of LTB4 was concomitant with the formation of omega-hydroxy-LTB4 and omega-carboxy-LTB4. When synthetic LTB4 was added to a suspension of unstimulated human leukocytes, a similar pattern of omega-oxidation products was observed. This omega-oxidation process showed some specificity for LTB4, as indicated by the slower reaction of three stereoisomers of LTB4. Studies with subpopulations of human blood cells and human plasma clearly indicated that the polymorphonuclear leukocytes were the main source of enzymic activity for the omega-oxidation of LTB4. The liquid chromatographic behaviors of natural omega-hydroxy-LTB4 and omega-carboxy-LTB4 were studied in two systems.

Calcimycin↗
PubMed1984

[Pharmacology of the leukotrienes].

Leukotrienes are a new family of metabolites of arachidonic acid produced by a C-5 lipoxygenase. As shown on figure 1, leukotriene A4, the key compound in their biosynthesis could either be hydrolysed to form leukotriene B4 or combine with glutathione to form leukotriene C4. Removal of glycine from the glutathione substituent or removal of glycine and gamma-glutamic acid yields the leukotriene D4 and E4 respectively. Leukotriene C4, D4 and E4 are the main bioactive components of the long elusive "Slow Reacting Substance of Anaphylaxis" (SRS-A). They induce powerful contractions of lung parenchyma strips and trachea in vitro (fig. 2) as well as powerful bronchoconstriction in vivo. They also favor mucus production from airways and slow its transport. Leukotrienes exhibit vasoconstrictor activity both on large blood vessels and on the microcirculation and induce marked increases in blood pressure followed by long lasting slight decreases (fig. 3). Injections of leukotriene B4 produce erythema, neutrophil migration and, in association with prostaglandin E2, increase vascular permeability and cause oedema. Leukotriene B4 is a powerful chemoattractant for polymorphonuclear leukocytes, stimulates cellular aggregation, degranulation and the release of lysosomal enzymes. It is also involved in the modulation of the immune response by inducing the formation of suppressor and of cytotoxic cells. The pharmacological actions of leukotriene B4 are mediated by very specific receptors while the actions of leukotriene C4, D4 and E4 are mediated by another type of receptors which are blocked by the selective SRS-A antagonist FPL-55712. The actions of leukotrienes depend partly upon the formation of prostaglandins and thromboxanes in the guinea-pig lungs while in man, their actions appear mostly a direct myotropic effect (fig. 4). Leukotriene formation has been stimulated in lungs and in various leukocyte populations by inflammatory or hypersensitivity reactions and by non specific stimuli such as the ionophore A-23187 and the C5a-anaphylatoxin. Inhibitors of lipoxygenases and corticosteroids could inhibit their release while non-steroid anti-inflammatory drugs such as aspirin may potentiate their formation by rechanneling their substrate from the cyclooxygenase cascade (fig. 5). The activity and potency of leukotrienes, their putative role in various important diseases as well as the explanations which they may give to old problems are good reasons to justify our interest on these novel compounds.

Animals↗
PubMed1983

Direct demonstration of increased intracellular concentration of free calcium in rabbit and human neutrophils following stimulation by chemotactic factor.

An increase in the level of intracellular free calcium concentration in rabbit and human neutrophils stimulated by chemotactic factors has been demonstrated directly using the calcium-sensitive fluorescent probe quin-2. Addition of f-Met-Leu-Phe (10(-9) M), C5a (3 x 10(-9) M) or leukotriene B4 (6 x 10(-8) M) to the neutrophils induces a rapid increase in the intracellular concentration of free calcium that reaches a maximum value 15 seconds following stimulation. At concentrations of f-Met-Leu-Phe less than 10(-8) M the enhancement is dose dependent with an ED50 of 8 x 10(-11) M and is significantly reduced in the presence of EGTA in the suspending medium.

Aminoquinolines↗
PubMed1983

On the biological role of lipid chemotactic factors.

Our experimental data of the past seven years cover the generation of a non-preformed lipid-mediator which primarily assayed with guinea pig eosinophils proved to be eosinophil chemotactic. The analysis of the various stimuli led in 1978 to the concept of the phospholipase-arachidonic sequence as a common link for membrane activation. Immunopharmacological studies using either arachidonic acid as stimulus or arachidonic acid analogues provided an early evidence that the lipid chemotactic factor was a lipoxygenase product. These results were supported by analytical studies using thin layer chromatography, reversed phase HPLC, mass spectrometry, the comparison of the lipid chemotactic factor with endogeneous HETEs and by the synthesis of mono- and di-HETEs. It became also evident that mono- and di-HETE are not only mediators but also modulators of inflammatory reactions as was demonstrated for the C5a induced eosinophil chemotactic response. A less pronounced effect on the C5a induced eosinophil and neutrophil chemotactic response was exerted by PAF and its structural analogues. It is also demonstrated that isolated bacterial exotoxins trigger the cells via the phospholipase-arachidonic acid sequence thus generating mono- and di-HETEs leading to the amplification of an inflammatory response.

Animals↗
PubMed1983

Specificity of receptors for leukotrienes A4, B4, C4, D4, E4 and histamine on the guinea-pig lung parenchyma. Effect of FPL-55712 and desensitization of the myotropic activity.

The novel metabolites of arachidonic acid, leukotriene (LT) A4, B4, C4, D4 and E4 have potent myotropic activity on guinea-pig lung parenchymal strip in vitro. The receptors responsible for their action were characterized using desensitization experiments and the selective SRS-A antagonist, FPL-55712. During the continuous infusion of LTB4, the tissues became desensitized to LTB4 but were still responsive to histamine, LTA4, LTC4, LTD4 and LTE4. When LTD4 was infused continuously, the lung strips contracted to LTB4 and histamine but were no longer responsive to LTA4, LTC4, LTD4 and LTE4. Furthermore, FPL-55712 (10 ng ml-1 - 10 ug ml-1) produced dose-dependent inhibitions of LTA4, LTC4, LTD4 and LTE4 without inhibiting the contraction to LTB4 and histamine. On the basis of these results, it appears that the guinea-pig lung parenchyma may have one type of receptor for LTB4 and another for LTD4; LTA4, LTC4 and LTE4 probably act on the LTD4 receptor.

Animals↗
PubMed1982

Specificity of the effect of lipoxygenase metabolites of arachidonic acid on calcium homeostasis in neutrophils. Correlation with functional activity.

The ability of the major neutrophil-derived lipoxygenase metabolites of arachidonic acid to increase the rate of 45Ca influx in rabbit neutrophils was examined. The results obtained demonstrate that (5S),(12R)-dihydroxy-6,8,11,14-(cis,trans,trans,cis)-eicosatetraenoic acid (leukotriene B4) is the most active of the arachidonic acid metabolites. The activity of leukotriene B4 is highly stereospecific in that its three nonenzymatically derived isomers are essentially inactive. The omega-hydroxylation of leukotriene B4 results in a compound that is nearly as active as leukotriene B4 as far as its ability to stimulate calcium influx and neutrophil aggregation while being a much weaker secretagogue. The further conversion of leukotriene B4 into a dicarboxylic acid removes all detectable biological activity. 5,6-Oxido-7,9,11,14-eicosatetraenoic acid (leukotriene A4) methyl ester was also found to increase the rate of calcium influx, while the degradation products of native leukotriene A4 were essentially inactive. These results demonstrate that a close correlation exists between the ability of the various lipoxygenase products to alter calcium homeostasis in rabbit neutrophils and their biological activities.

Animals↗