arachidonic-acid-omega-9-hydroperoxide and 8-hydroxy-11-12-epoxyeicosa-5-9-14-trienoic-acid

This article reviews published evidence describing the enzymatic and nonenzymatic formation and the routes of metabolism of the hepoxilins. Also treated are the major approaches used for the chemical synthesis of these compounds and for some of their analogs.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Drug Stability; Leukotrienes; Molecular Structure

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Hemin; Humans; Leukotrienes; Lung; Molecular Conformation; Molecular Structure; Pineal Gland

We describe here the effects of two 12-lipoxygenase products, 12-HETE (12-hydroxyeicosa (5Z,8Z,10E,14Z) tetraenoic acid) and 12-HPETE (12-hydroperoxyeicosa (5Z,8Z,10E,14Z) tetraenoic acid), on the release of intracellular calcium in intact human neutrophils using the INDO-1 AM fluorescent dye technique. Both products dose dependently stimulate intracellular release, with 12-HETE being more powerful than 12-HPETE. The threshold concentration for 12-HETE was 5 ng/ml (1.5 x 10-8 M), while that for 12-HPETE was 10 ng/ml. The (12S) regioisomer was slightly more active than the (12R) isomer. The laser potency of 12-HPETE may be due to its conversion into the less active hepoxilins as incubation of neutrophils with (12S/R)-HPETE in a nonradioactive assay, using fluorescent ADAM esters of the products, generated mostly hepoxilin A3 (8-hydroxy-(11S,12S) epoxyeicosa (5Z,9E,14Z)trienoic acid), indicative of an enzymatic process. In contrast, boiled neutrophil preparations converted 12-HPETE primarily into hepoxilin B3 which previously showed to be derived nonenzymatically. This data demonstrates that 12-HETE, known to be generated in significant amounts by platelets, can act transcellularly to modify intracellular concentrations of calcium in neutrophils. This may in turn affect the responsiveness of these cells to other chemotactic factors.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; 8,11,14-Eicosatrienoic Acid; Arachidonate 12-Lipoxygenase; Arachidonic Acid; Blood Platelets; Calcium; Chelating Agents; Fluorescent Dyes; Humans; Indoles; Leukotrienes; Neutrophils

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Chromatography, High Pressure Liquid; Leukotrienes; Pineal Gland; Rats

Hepoxilins have previously been shown to release intracellular calcium in human neutrophils. We show herein that tritium-labeled hepoxilin A3 of high specific radioactivity binds to human neutrophils, and this binding is reversed by the addition of unlabeled compound, demonstrating that specific binding for these compounds exists in these cells. Specific binding of both the methyl ester derivative as well as the free acid form of the hepoxilin takes place in broken membrane fragments. In contrast only the methyl ester derivative binds specifically to the intact cells. We also show that intact neutrophils form hepoxilin A3 when incubated in the presence of the hepoxilin precursor, 12(S)-HPETE. These data demonstrate that hepoxilin synthesis can occur in the neutrophil and that hepoxilin binding sites, which appear to be located intracellularly, exist in these cells.

Topics: 8,11,14-Eicosatrienoic Acid; Analysis of Variance; Binding Sites; Cell Membrane; Humans; In Vitro Techniques; Kinetics; Leukotrienes; Neutrophils; Reference Values; Tritium

Available data obtained so far has indicated that hepoxilin formation from 12-HPETE is catalyzed by hemin and hemoglobin and is not affected through heating of these ferri-heme compounds suggestive of nonenzymatic processes. The present paper demonstrates for the first time that 12-HPETE is transformed into the hepoxilins A3 and B3 by intact cells (skin subcutis layer) and slices of several tissues (brain hippocampus and pineal gland) and that this transformation is inhibited by tissue boiling, indicating an enzymatic catalysis. The tissues employed are pharmacologically responsive to hepoxilins and hence the present data offer biochemical support of a potential biological role for the hepoxilins in these tissues.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Carbon Radioisotopes; Chromatography, High Pressure Liquid; Hippocampus; In Vitro Techniques; Leukotrienes; Male; Pineal Gland; Rats; Rats, Wistar; Skin

Isolated Krebs perifused rat pancreatic islets in the presence of 10 mM glucose convert 12S-HPETE into two hydroxy-epoxides, 8H-11,12-EPETE and 10H-11,12-EPETE for which we propose the name Hepoxilin A and B respectively. Hepoxilin A was investigated for its capacity to release insulin by this preparation. Insulin secretion by these cells, measured in the perifusate by radioimmunoassay, was dependent on the glucose concentration in the perifusing medium. Hepoxilin A dose dependently enhanced further the release of insulin during glucose (10 mM) stimulation (120 +/- 51% at 0.5 x 10(-6) M (n = 3) and 282 +/- 58% at 2.1 x 10(-6) M (n = 3) above control). These results suggest that Hepoxilin A (and possibly also Hepoxilin B) could be the active intermediate(s) involved in the potentiation of glucose dependent insulin secretion by both arachidonic acid and 12-HPETE.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acids; Carbon Radioisotopes; Dinoprostone; In Vitro Techniques; Insulin; Insulin Secretion; Islets of Langerhans; Kinetics; Leukotrienes; Prostaglandins E; Rats; Rats, Inbred Strains