Search PubMed⌕ Search

Biomedical subjects

E J Corey

Publications and source records attributed to E J Corey.

At least 127 records · Page 7Linked to original sources
PubMed1987

Specificity of the glutathione S-transferases in the conversion of leukotriene A4 to leukotriene C4.

We have synthesized the 5,6-LTA4, 8,9-LTA4, and 14,15-LTA4 as methyl esters by an improved biomimetic method with yields as high as 70-80%. We have investigated the catalytic efficiency of the purified cytosolic glutathione S-transferase (GST) isozymes from rat liver in the conversion of these leukotriene epoxides to their corresponding LTC4 methyl esters. Among various rat liver GST isozymes, the anionic isozyme, a homodimer of Yb subunit, exhibited the highest specific activity. In general, the isozymes containing the Yb subunit showed better activity than the isozymes containing the Ya and/or Yc subunits. Interestingly, all three different LTA4 methyl esters gave comparable specific activities with a given GST isozyme indicating that regiospecificity of GSTs was not the factor in determining their ability to catalyze this reaction. Surprisingly, purified GSTs from sheep lung and seminal vesicles showed little activity toward these leukotriene epoxides, indicating a lack of the counterpart of rat liver anionic GST isozyme in these tissues.

Animals↗
PubMed1987

Topical arachidonic acid: a model for screening anti-inflammatory agents.

Products of arachidonic acid metabolism, prostaglandins and leukotrienes, play an important role in ocular inflammation. In this study, we investigated the efficacies of the cyclo-oxygenase inhibitors (aspirin, indomethacin, and piroxicam) and the lipoxygenase inhibitors (N-hydroxy-arachidonamide (AH) and phenidone) in reducing ocular inflammation induced by arachidonic acid. Administering arachidonic acid topically (0.50% for rabbits and 0.25% for humans) produced a simple model for evaluating the effects of inhibitors on prostaglandins. In rabbits, aspirin, piroxicam and indomethacin all blocked lid closure and chemosis significantly. In humans, aspirin and indomethacin significantly blocked arachidonic acid-induced conjunctival injection. Neither AH nor phenidone blocked any of the signs of ocular inflammation in rabbits or humans. Further testing of phenidone in the presence of the calcium ionophore, ionomycin, also proved negative. Species specificity in arachidonic acid metabolism may account for the different results in humans and rabbits. This model may be a useful tool for comparing the relative efficacies of topical cyclo-oxygenase inhibitors in treating ocular problems.

Administration, Topical↗
PubMed1987

The vasodilatation induced by hydroperoxy metabolites of arachidonic acid in the rat mesenteric and pulmonary circulation.

The effects of 15-hydroperoxy metabolites of arachidonic acid on vascular tone were evaluated in the perfused mesenteric preparation, the isolated perfused lung and segments of pulmonary arteries of the rat. In the mesenteric preparation, precontracted with phenylephrine, both 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE, ED50 1.6 nmol) and 8,15-dihydroperoxy-5,9,11,13-eicosatetraenoic acid (8,15-diHPETE, ED50 0.3 nmol) induced dose-dependent vasodilatation, whereas 5,15-diHPETE (0.2-100 nmol) had no effect. Prostacyclin (ED50 0.01 nmol) was, however, more potent than the hydroperoxides. In the rat isolated lung, precontracted with the stable thromboxane agonist U-46619, dose-dependent decrease in the perfusion pressure occurred with 15-HPETE(ED50 40 nmol), 5,15-diHPETE (ED50 30 nmol) and 8, 15-diHPETE (ED50 7 nmol) while 13-hydroperoxide of linoleic acid had no effect. Prostacyclin was 10 times more potent than 8, 15-diHPETE. The vasodilator effects were not affected by indomethacin. In both endothelium intact and denuded rat pulmonary arteries the hydroperoxides 15-HPETE, 8,15-diHPETE, and 5,15-diPETE induced dose-dependent relaxation. The hydroperoxide, 8,15-diHPETE was at least 3 times more potent than 15-HPETE or 5,15--diHPETE. The hydroperoxides had no effect on the basal tone of vessel segments and the relaxation induced by 15-HPETE was not attenuated by methylene blue (5 microM). These data indicate that 8,15-diHPETE may be a significant endothelium-independent vasodilator product of arachidonate lipoxygenation.

Animals↗
PubMed1987

Bronchoconstrictor effects of leukotriene E4 in normal and asthmatic subjects.

The bronchoconstrictor activity of an aerosol of leukotriene E4(LTE4) was compared with that of histamine in 5 normal and in 6 asthmatic subjects to define the relative potency of LTE4 between the groups using 3 indices of airway response. The FEV1 and the flow rate measured at 30% of vital capacity from partial and maximal expiratory maneuvers (V30-P and V30-M) were measured. The geometric mean (GSEM) concentration of LTE4 required to reduce the V30-P by 30% was 0.30 (1.46) mM in the normal subjects, and 0.058 (1.63) in the asthmatic subjects; LTE4 was 39-fold more potent than histamine in the former and 14-fold in the latter group. Further, we observed that when normal and asthmatic subjects were compared at a degree of bronchoconstriction resulting in a 30% decrement in the V30-P after inhaling LTE4, there was a greater response in the asthmatic group than in the normal group of the accompanying change in the FEV1. The decrements in the FEV1 were not significantly different between the 2 groups after inhaling histamine. This study demonstrates that LTE4 is a potent bronchoconstrictor agonist in humans and suggests that airway responsiveness to this agonist differs substantially with the index of bronchoconstriction used for assessment of airway response.

Aerosols↗
PubMed1987

The mechanism of vascular leakage induced by leukotriene E4. Endothelial contraction.

This study identifies the microvascular target of leukotriene E4 (LTE4) by vascular labeling with carbon black and establishes the mechanism of its action at the cellular level by electron microscopy. LTE4 and its tripeptide precursor, leukotriene C4 (LTC4) were injected subcutaneously in guinea pigs. With LTE4, venular labeling was intense at 1000 and 100 ng and slight at 10 ng, with extinction at 1 ng. LTC4 induced a ring of labeled venules around a blank central area, suggestive of vasospasm. The nonpeptidyl leukotriene LTB4 induced no labeling. Histamine (1000 ng) induced an area of vascular labeling about equal to that by 1000 ng LTE4, but the labeling of individual venules was more intense. By electron microscopy, LTE4 was found to induce gaps in the endothelium of the venules; the endothelial cells adjacent to the gaps bulged into the lumen and showed wrinkled nuclei, consistent with cellular contraction. This ultrastructural evidence suggests that LTE4 increases vascular permeability by contraction of endothelial cells selectively, in the postcapillary venules, as was previously demonstrated for other inflammatory mediators, including histamine, serotonin, and bradykinin.

Animals↗
PubMed1987

Relaxing effects of 15-lipoxygenase products of arachidonic acid on rat aorta.

In the presence of indomethacin, arachidonic acid relaxes precontracted rings of rat aorta only when the endothelium is intact. Arachidonate-induced, endothelium-dependent relaxation is potentiated by superoxide dismutase. In contrast, linoleic acid (LA) contracts endothelium-intact and -denuded rings. Arachidonate is metabolized in endothelial cells by both cyclo-oxygenase and 15-lipoxygenase. Therefore, we determined the vasodilatory effect of 15-lipoxygenase products. The products generated by soybean lipoxygenase (SLO) from arachidonate in the bioassay bath relax precontracted, de-endothelialized ring segments of rat aorta. This relaxation is potentiated by superoxide dismutase and is more prominent when high concentrations of SLO are used. The main metabolites recovered from the bioassay bath were 5,15-dihydroperoxyeicosatetraenoic acid and 8,15-dihydroperoxyeicosatetraenoic acid. At lower concentrations of SLO the degree of relaxation is less and the major product is 15-hydroperoxyeicosatetraenoic acid. LA is metabolized by SLO to 13-hydroperoxyoctadecadienoic acid. The relaxation induced by the incubation of LA with SLO in endothelium-denuded rings is less than that obtained with arachidonic acid. In endothelium-denuded rings that were precontracted with phenylephrine authentic 15-hydroperoxyeicosatetraenoic acid did not induce clear effect (at 40 microM 15-hydroperoxide caused relaxation, whereas at 15 microM induced small contraction) and 13-hydroperoxyoctadecadienoic acid of LA induced contraction. Neither 5,15-dihydroperoxyeicosatetraenoic acid nor 8,15-dihydroperoxyoctadecadienoic acid (1-15 microM) induced a well defined relaxation. This study indicates that arachidonic acid is metabolized by SLO to a vasodilatory compound(s) that is possibly derived from 15-hydroperoxyeicosatetraenoic acid.

Animals↗
PubMed1986

Identification of a high affinity leukotriene C4-binding protein in rat liver cytosol as glutathione S-transferase.

A soluble high affinity binding unit for leukotriene (LT) C4 in the high speed supernatant of rat liver homogenate was characterized at 4 degrees C as having a single type of saturable affinity site with a dissociation constant of 0.77 +/- 0.27 nM (mean +/- S.E., n = 5). The binding activity was identified as the liver cytosolic subunit 1 (Ya) of glutathione S-transferase, commonly known as ligandin, by co-purification with the catalytic activity during DEAE-cellulose column chromatography and 11,12,14,15-tetrahydro-LTC4 (LTC2)-affinity gel column chromatography; resolution into two major bands by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of Mr 23,000 and 25,000, of which only the smaller protein was labeled with [3H]LTC4 coupled via a photoaffinity cross-linking reagent; and immunodiffusion analysis with rabbit antiserum to glutathione S-transferase which showed a line of identity between the purified LTC4-binding protein and rat liver glutathione S-transferase. The affinity-purified binding protein bound 800 pmol of [3H] LTC4/mg of protein and possessed 12 mumol/min/mg of glutathione transferase activity as assayed with 1-chloro-2,4-dinitrobenzene as substrate. The enzyme activity of the cytosolic LTC4-binding protein was inhibited by submicromolar quantities of unlabeled LTC4, and the binding activity for [3H]LTC4 was blocked by the ligandin substrates, hematin and bilirubin. The high affinity interaction between LTC4 and glutathione S-transferase suggests that glutathione S-transferase may have a role in LTC4 disposition and that previous studies of LTC4 binding to putative receptors in nonresponsive tissues may require redefinition of the binding unit.

Affinity Labels↗
PubMed1986

Enhancement of plasma levels of biologically active leukotriene B compounds during anaphylaxis in guinea pigs pretreated by indomethacin or by a fish oil-enriched diet.

The changes in arterial plasma concentrations of immunoreactive leukotriene B (LTB) were compared after antigen challenge of two groups of sensitized, mepyramine-treated, and mechanically ventilated guinea pigs, one fed a diet enriched with fish oil and the other a control diet enriched with beef tallow. The lung tissue of animals fed a fish oil-enriched diet (FFD) for 9 to 10 wk incorporated eicosapentaenoic acid (EPA) and docosahexaenoic acid to constitute 8 to 9% of total fatty acid content, whereas these alternative fatty acids constituted less than 1% of the total fatty acid content of the lung tissue of animals on a beef tallow-supplemented diet (BFD). The maximum increase after antigen challenge in immunoreactive LTB4 from 0.16 +/- 0.04 ng/ml to 0.84 +/- 0.25 ng/ml in BFD animals and from 0.47 +/- 0.11 to 5.1 +/- 1.4 ng/ml immunoreactive LTB (LTB4 and LTB5) in FFD animals was significant (p less than 0.02) for each. Furthermore, the increase in total immunoreactive LTB in mepyramine-treated FFD animals was significantly greater than the increase in LTB4 in mepyramine-treated BFD guinea pigs at 2 to 8 min after antigen challenge (p less than 0.05). Resolution of arterial plasma immunoreactive LTB from pooled samples by reverse-phase high-performance liquid chromatography demonstrated that the sum of LTB4 and LTB5 in FFD animals exceeded that of LTB4 in BFD animals and that the quantity of LTB4 in the FFD animals was at least as great as that in the BFD animals during anaphylaxis. The products eluting at the retention times of LTB4 and LTB5 exhibited the chemotactic activity of their respective synthetic standards. The combination of indomethacin and mepyramine markedly augmented the antigen-induced increase in arterial plasma immunoreactive LTB4 concentrations in BFD animals, but had no effect on immunoreactive LTB levels in FFD animals. Limited in vivo measurements showing a lesser increase of plasma immunoreactive thromboxane B2 in the FFD relative to the BFD animals during anaphylaxis and ex vivo measurements showing a decreased LTB4-stimulated (cyclooxygenase product-dependent) contractile response of pulmonary parenchymal strips from the FFD relative to the BFD animals provide evidence for blockade in the cyclooxygenase pathway in the FFD animals. The measurements of arterial plasma LTB indicate that indomethacin treatment alone, which inhibits cyclooxygenase activity, and FFD treatment each augment the metabolism of arachidonic acid by the 5-lipoxygenase pathway in animals pretreated with mepyramine.(ABSTRACT TRUNCATED AT 400 WORDS)

Anaphylaxis↗
PubMed1986

Inhibition of homogeneous human eosinophil arylsulfatase B by sulfidopeptide leukotrienes.

Arylsulfatase B, purified to homogeneity from human eosinophils, is a tetrameric enzyme whose activity varied in accordance with the state of association of its monomeric subunits. The rate of dissociation of oligomeric forms was slow relative to the rate of the enzymatic reaction so that the kinetic properties of the enzyme depended on the concentration of the enzyme before assay. For concentrated enzyme solutions (14 micrograms/ml), Lineweaver-Burk analysis demonstrated substrate inhibition at greater than or equal to 20 mM substrate and revealed two distinct regions of activity at low and intermediate substrate concentrations. The addition of bovine serum albumin (60 micrograms/ml) or sucrose (0.25 M), which prevent subunit dissociation, yielded a linear relationship on Lineweaver-Burk analysis at non-inhibitory substrate concentrations. For dilute enzyme concentrations (4.7 micrograms/ml), inhibition occurred at greater than or equal to 2 mM substrate. Nanomolar amounts of leukotriene C4 (LTC4), relative to millimolar concentrations of substrate, inhibited eosinophil arylsulfatase B. On Lineweaver-Burk analysis, the pattern of inhibition of LTC4 with concentrated enzyme was compatible with competitive inhibition of only one oligomeric form of the enzyme, whereas at low enzyme concentrations the pattern of inhibition was apparently competitive. These findings suggest that LTC4 is a potent competitive inhibitor of a dissociated, possibly dimeric, form of the enzyme. Nanomolar concentrations of LTC4, leukotriene D4, and leukotriene E4 were equally inhibitory, whereas leukotriene B4 and isomeric 5,12-dihydroxyeicosatetraenoic acids had no inhibitory activity, indicating a requirement for a thiopeptide at C-6. Thiopeptide leukotriene analogs without an intact triene structure also lacked inhibitory activity. Sulfoxide analogs of LTC4 and leukotriene D4 were potent inhibitors, although two sulfone analogs of leukotriene D4 were not inhibitory. Arylsulfatase B did not inactivate the spasmogenic activity of sulfidopeptide leukotrienes. These findings indicate that sulfidopeptide leukotrienes and their sulfoxide derivatives may regulate by competitive inhibition the activity of oligomeric forms of the eosinophil lysosomal hydrolase, arylsulfatase B.

Chondro-4-Sulfatase↗
PubMed1986

Hepoxilins, potential endogenous mediators of insulin release.

Evidence is presented to show that pancreatic islets of Langerhans are capable of producing hepoxilins A3 and B3 from endogenous substrates as well as 14C-labeled 12-HPETE. Both hepoxilins are active in stimulating the release of insulin from these cells in the presence of 10 mM glucose. These experiments suggest that the hepoxilins may participate as potential endogenous mediators of insulin release in islets of Langerhans.

8,11,14-Eicosatrienoic Acid↗
PubMed1985

Effect of dietary enrichment with eicosapentaenoic and docosahexaenoic acids on in vitro neutrophil and monocyte leukotriene generation and neutrophil function.

The effects of dietary fish-oil fatty acids on the function of the 5-lipoxygenase pathway of peripheral-blood polymorphonuclear leukocytes and monocytes were determined in seven normal subjects who supplemented their usual diet for six weeks with daily doses of triglycerides containing 3.2 g of eicosapentaenoic acid and 2.2 g of docosahexaenoic acid. The diet increased the eicosapentaenoic acid content in neutrophils and monocytes more than sevenfold, without changing the quantities of arachidonic acid and docosahexaenoic acid. When the neutrophils were activated, the release of [3H]arachidonic acid and its labeled metabolites was reduced by a mean of 37 per cent, and the maximum generation of three products of the 5-lipoxygenase pathway was reduced by more than 48 per cent. The ionophore-induced release of [3H]arachidonic acid and its labeled metabolites from monocytes in monolayers was reduced by a mean of 39 per cent, and the generation of leukotriene B4 by 58 per cent. The adherence of neutrophils to bovine endothelial-cell monolayers pretreated with leukotriene B4 was inhibited completely, and their average chemotactic response to leukotriene B4 was inhibited by 70 per cent, as compared with values determined before the diet was begun and six weeks after its discontinuation. We conclude that diets enriched with fish-oil-derived fatty acids may have antiinflammatory effects by inhibiting the 5-lipoxygenase pathway in neutrophils and monocytes and inhibiting the leukotriene B4-mediated functions of neutrophils.

Adult↗
PubMed1985

Endogenous release of hepoxilin A3 from isolated perifused pancreatic islets of Langerhans.

Pancreatic islets of Langerhans were perifused with Krebs-bicarbonate solution containing glucose (5 and 10 mM). The perifusate was spiked with tetradeuterated hepoxilin A3 and was extracted and analysed by gas chromatography-mass spectrometry using NICI detection. Evidence is presented showing the presence of hepoxilin A3 as the hydrolysis product trioxilin A3. These results demonstrate for the first time that this pathway is active in intact cells; this finding, taken together with our previous evidence that hepoxilins possess insulin secretagogue properties further supports our hypothesis that these products could play a role as endogenous mediators of insulin release.

8,11,14-Eicosatrienoic Acid↗
PubMed1985

Computer-assisted analysis in organic synthesis.

The planning of alternative routes for the synthesis of complex organic molecules has been facilitated by the formulation of guiding strategies that can be applied to a broad range of problems. Analysis of organic synthesis can be carried out in the retrosynthetic direction, opposite to the actual process of chemical synthesis, or bidirectionally, that is, as a combined retrosynthetic and synthetic search. An interactive computer program is described which utilizes the general strategies of retrosynthetic analysis and an appropriate database to generate pathways of chemical intermediates for chemical synthesis of a particular target structure. Computer graphics and standard chemical structures are used for man-machine communication.

Chemical Phenomena↗
PubMed1985

In vivo distribution and activity of aphidicolin on dividing and quiescent cells.

In view of a possible use of aphidicolin, an inhibitor of DNA polymerases (including viral DNA polymerases), to control excessive cell proliferation we have investigated: the effect of the drug on the growth of several human neoplastic cells; the activity of synthetic analogs aimed at relating the structural feature of aphidicolin to cytotoxicity; the in vivo fate and distribution of aphidicolin in different fluids, organs and tissues of mice following parenteral and/or peroral administration.

Animals↗
PubMed1985

Mechanism of the negative inotropic action of leukotrienes C4 and D4 on isolated rat heart.

Leukotrienes C4 and D4 (LTC4 and LTD4), possible mediators of cardiac dysfunction during inflammatory injury, may depress cardiac function by reducing coronary flow or by exerting a negative effect directly on the myocardium. We used an isovolumic rat heart preparation perfused at constant pressure and measured left ventricular developed pressure (mmHg), coronary flow (ml.min-1), oxygen extraction, and myocardial oxygen consumption and delivery (mumol O2.[gramme dry weight]-1.min-1) during infusion of five doses of angiotensin II, LTC4, LTD4 (approximately 10 to approximately 300 pmol.min-1), and noradrenaline (400 to 2000 pmol.min-1), or perfusion with medium which contained calcium at half-concentration. LTC4 and LTD4 were equipotent with angiotensin. At low effective doses, increased oxygen extraction offset the decrease in oxygen delivery, maintaining a stable level of oxygen consumption and left ventricular developed pressure. At the highest doses, angiotensin, LTC4 and LTD4 reduced coronary flow from 21 to 15, 21 to 13, and 21 to 13 ml.min-1, respectively. And, despite greater oxygen extraction of 59%, 58% and 65% for angiotensin, LTC4 and LTD4, left ventricular developed pressure fell from a baseline of 120 mmHg to 113, 106 and 92, respectively. In contrast, low calcium perfusion reduced left ventricular developed pressure (126 to 92) and oxygen extraction (46 to 30%) without changing coronary flow or oxygen delivery. These results suggest that LTC4 and LTD4 are potent coronary vasoconstricting agents which depress cardiac function by limiting oxygen delivery.

Angiotensin II↗
PubMed1985

Identification and characterization of leukotriene C4 receptors in isolated rat renal glomeruli.

The immediate reduction of renal blood flow and glomerular filtration rate in response to intravenous infusion of leukotriene C4 in the rat prompted an analysis of isolated rat renal glomeruli for the presence of specific receptors for leukotriene C4. Specific binding of [3H]leukotriene C4 to glomeruli increased in a time-dependent manner, reached equilibrium after 60 minutes of incubation at 4 degrees C, and was 80% reversible upon addition of excess unlabeled leukotriene C4 at equilibrium. Specific binding of [3H]leukotriene C4 to glomeruli increased in a dose-dependent manner, approaching saturation at concentrations of 40-60 nM. Inhibition of binding of [3H]leukotriene C4 with increasing concentrations of unlabeled leukotriene C4 was dose dependent. The equilibrium dissociation constant for [3H]leukotriene C4 binding to glomeruli, calculated from saturation and competitive binding-inhibition studies, was 25 +/- 7 nM and 35 +/- 16 nM (mean +/- SEM), respectively, and glomerular leukotriene C4 receptor density was 8.5 +/- 1.5 and 9.0 +/- 3.0 pmol/mg protein, respectively. The other natural vasoactive sulfidopeptide leukotrienes, leukotriene D4 and leukotriene E4, the chemotactic agent, leukotriene B4, and the sulfidopeptide leukotriene antagonist, FPL 55712, competed for the receptor at concentrations 2-3 orders of magnitude higher than the homoligand, leukotriene C4. The binding and specificity characteristics of the glomerular leukotriene C4 receptor are similar to those previously reported for the DDT1 nonvascular smooth muscle cell line derived from hamster vas deferens, for guinea pig ileum smooth muscle, and for a subcellular fraction of rat lung homogenate, and represent the first characterization of such a receptor in a vascular tissue.

Animals↗
PubMed1985

The effects of a fish-oil-enriched diet on pulmonary mechanics during anaphylaxis.

The pulmonary mechanical responses observed after antigen challenge in 2 groups of sensitized, mepyramine-treated, mechanically ventilated guinea pigs were compared: one group was fed a diet rich in fish oil and the other a control diet enriched with beef tallow. The lung tissue of animals fed a fish-oil-enriched diet for 9 to 10 wk incorporated eicosapentaenoic acid (EPA) and docosahexaenoic acid, which constituted 8 to 9% of the total fatty acid content, whereas these alternative fatty acids constituted less than 1% of total fatty acid content of the lung tissue of animals receiving a diet supplemented with beef tallow. With mepyramine pretreatment, animals receiving a fish oil diet exhibited a significantly greater decrease in dynamic compliance from 1.5 through 4.5 min after antigen challenge than did animals receiving a beef fat diet, whereas the decrements in pulmonary conductance were comparable. The combination of indomethacin and mepyramine markedly augmented the antigen-induced decrease in pulmonary mechanics in animals receiving a beef fat diet but not in those receiving a fish oil diet, such that the overall responses of the 2 groups were similar. These findings indicate that the fish oil diet and the indomethacin pretreatment of animals receiving the beef fat diet each facilitates the nonhistamine-mediated bronchoconstrictor response in pulmonary anaphylaxis.

Airway Resistance↗