The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
William S. Powell - One of the best experts on this subject based on the ideXlab platform.
-
5-oxo-ETE is a major oxidative stress-induced arachidonate metabolite in B lymphocytes.
Free radical biology & medicine, 2011Co-Authors: Gail E. Grant, Joshua Rokach, Sylvie Gravel, J. Guay, Pranav Patel, Bruce Mazer, William S. PowellAbstract:Abstract B lymphocytes convert arachidonic acid (AA) to the 5-lipoxygenase products leukotriene B4 (LTB4) and 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) when subjected to oxidative stress. 5-HETE has little biological activity, but can be oxidized by a selective dehydrogenase in some cells to 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE), a potent eosinophil chemoattractant. We found that CESS cells, a B lymphocyte cell line, convert AA to 5-oxo-ETE and this is selectively stimulated by oxidative stress. In the presence of H2O2, 5-oxo-ETE is a major AA metabolite in these cells (5-oxo-ETE ≈ 5-HETE > LTB4). The cyclooxygenase product 12-hydroxy-5,8,10-heptadecatrienoic acid is also formed, but is not affected by H2O2. Diamide had effects similar to those of H2O2 and both substances had similar effects on human tonsillar B cells. H2O2 also stimulated 5-oxo-ETE formation from its direct precursor 5-HETE in tonsillar B and CESS cells, and this was inhibited by the glutathione reductase inhibitor carmustine. H2O2 concomitantly induced rapid increases in GSSG and NADP+ and reductions in GSH and NADPH. We conclude that oxidative stress stimulates 5-oxo-ETE synthesis in B lymphocytes by two mechanisms: activation of 5-lipoxygenase and increased oxidation of 5-HETE by NADP+-dependent 5-hydroxyeicosanoid dehydrogenase. B lymphocyte-derived 5-oxo-ETE could contribute to eosinophilic inflammation in asthma and other allergic diseases.
-
The design and synthesis of a 5-HETE affinity chromatography ligand for 5-hydroxyeicosanoid dehydrogenase
Tetrahedron Letters, 2000Co-Authors: Subhash P. Khanapure, Goutam Saha, William S. Powell, Joshua RokachAbstract:Abstract The first total synthesis of an ω-amino 5-HETE derivative 27 has been accomplished by a new counterclockwise strategy, in which C-1 is constructed first and C-20 last. The ω-amino 5-HETE derivative was transformed to an affinity chromatography ligand, the biotinylated 5-HETE 30. This affinity chromatography ligand is aimed at purifying the 5-hydroxyeicosanoid dehydrogenase enzyme, which is responsible for the conversion of 5-HETE to 5-oxo-ETE, a potent eosinophil chemotactic factor.
-
Synthesis of 5-oxo-6,8,11,14-eicosatetraenoic acid by human monocytes and lymphocytes.
Journal of leukocyte biology, 1996Co-Authors: Ying Zhang, Angela Styhler, William S. PowellAbstract:We recently demonstrated that the arachidonate metabolite 5(S)-hydroxy-6,8,1 1,14- eicosatetraenoic acid (5-HETE) is converted by a highly specific dehydrogenase in human neutrophils to 5-oxo-6,8,1 1 ,14-eicosatetraenoic acid (5-oxo- ETE), which is a potent stimulator of these cells. The objective of this study was to determine whether 5-oxo-ETE is also formed by monocytes and lympho- cytes. Human monocytes (74 ± 2% pure) and lym- phocytes (86 ± 1 % pure) were prepared by successive centrifugations of leukocytes over Ficoll-Paque and Percoll. Both cell types converted 5-HETE to a single major product, which was identified as 5-oxo- ETE. The formation of 5-oxo-ETE was stimulated about twofold by phorbol myristate acetate (PMA; 30 nM). Dehydrogenase activity in monocyte frac- tions did not appear to be due to platelet contamina- tion, since depletion of platelets did not reduce enzyme activity. The dehydrogenase was localized in membrane fractions from monocytes and required NADP+ as a cofactor. It was specific for eicosanoids containing a 5S-hydroxyl group followed by a 6-trans double bond. We also investigated the formation of 5-oxo-ETE from endogenous aracbidonic acid by monocytes. 5-Oxo-ETE, 5-HETE, and leukotriene B4 (LTB4) were present in comparable amounts after incubation of these cells with A23187. PMA (EC50 -4 nM) stimulated the formation of 5-oxo-ETE and 5-HETE and, to a lesser extent, LTB4. Although monocytes released considerably less 5-HETE and LTB4 than neutrophils, they released comparable amounts of 5-oxo-ETE. Unlike neutrophils, mono- cytes did not convert any of these substances to detectable amounts of (li-oxidation products. Al- though lymphocytes were capable of converting 5- HETE to 5-oxo-ETE, they released little or no 5-lipoxygenase products in response to A23187. We conclude that monocytes have a high capacity to synthesize 5-oxo-ETE and that its formation is stimu- lated by activation of protein kinase C. J. Leukoc. Rio!. 59: 847-854; 1996.
Galina I. Myagkova - One of the best experts on this subject based on the ideXlab platform.
-
A simple method for the preparation of (5Z,8Z,11Z,14Z)-16-hydroxyeicosa-5,8,11,14-tetraenoic acid enantiomers and the corresponding 14,15-dehydro analogues: role of the 16-hydroxy group for the lipoxygenase reaction.
Bioorganic & medicinal chemistry, 2002Co-Authors: Igor Ivanov, Hartmut Kühn, Stepan G. Romanov, Nataliya V Groza, Santosh Nigam, Galina I. MyagkovaAbstract:Abstract (5 Z ,8 Z ,11 Z ,13 E )-15-Hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE) is not well oxygenated by arachidonate 15-lipoxygenases because of two structural reasons: (i) it contains a hydrophilic OH-group in close proximity to its methyl end and (ii) it lacks the bisallylic methylene at C 13 . We synthesized racemic (5 Z, 8 Z, 11 Z, 14 Z )-16-hydroxy-5,8,11,14-eicosatetraenoic acid (16-HETE) which still contains the bisallylic C 13 , separated the enantiomers reaching an optical purity of >99% and tested them as substrates for 5- and 15-lipoxygenases. Our synthetic pathway, which is based on stereospecific hydrogenation of a polyacetylenic precursor, yielded substantial amounts (30%) of 14,15-dehydro-16-HETE in addition to 16-HETE. When 16-HETE was tested as lipoxygenase substrate, we found that it is well oxygenated by the soybean 15-lipoxygenase and by the recombinant human 5-lipoxygenase. Analysis of the reaction products suggested an arachidonic acid-like alignment at the active site of the two enzymes. In contrast, the product pattern of 16-HETE methyl ester oxygenation by the soybean lipoxygenase (5-lipoxygenation) may be explained by an inverse head to tail substrate orientation.
Igor Ivanov - One of the best experts on this subject based on the ideXlab platform.
-
A simple method for the preparation of (5Z,8Z,11Z,14Z)-16-hydroxyeicosa-5,8,11,14-tetraenoic acid enantiomers and the corresponding 14,15-dehydro analogues: role of the 16-hydroxy group for the lipoxygenase reaction.
Bioorganic & medicinal chemistry, 2002Co-Authors: Igor Ivanov, Hartmut Kühn, Stepan G. Romanov, Nataliya V Groza, Santosh Nigam, Galina I. MyagkovaAbstract:Abstract (5 Z ,8 Z ,11 Z ,13 E )-15-Hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE) is not well oxygenated by arachidonate 15-lipoxygenases because of two structural reasons: (i) it contains a hydrophilic OH-group in close proximity to its methyl end and (ii) it lacks the bisallylic methylene at C 13 . We synthesized racemic (5 Z, 8 Z, 11 Z, 14 Z )-16-hydroxy-5,8,11,14-eicosatetraenoic acid (16-HETE) which still contains the bisallylic C 13 , separated the enantiomers reaching an optical purity of >99% and tested them as substrates for 5- and 15-lipoxygenases. Our synthetic pathway, which is based on stereospecific hydrogenation of a polyacetylenic precursor, yielded substantial amounts (30%) of 14,15-dehydro-16-HETE in addition to 16-HETE. When 16-HETE was tested as lipoxygenase substrate, we found that it is well oxygenated by the soybean 15-lipoxygenase and by the recombinant human 5-lipoxygenase. Analysis of the reaction products suggested an arachidonic acid-like alignment at the active site of the two enzymes. In contrast, the product pattern of 16-HETE methyl ester oxygenation by the soybean lipoxygenase (5-lipoxygenation) may be explained by an inverse head to tail substrate orientation.
Hartmut Kühn - One of the best experts on this subject based on the ideXlab platform.
-
phospholipid esterified eicosanoids are generated in agonist activated human platelets and enhance tissue factor dependent thrombin generation
Journal of Biological Chemistry, 2010Co-Authors: Christopher P Thomas, Hartmut Kühn, Robert C. Murphy, Lloyd T Morgan, Ben H Maskrey, Stanley L Hazen, Alison H Goodall, Hassan A Hamali, Peter Collins, Valerie B OdonnellAbstract:Here, a group of specific lipids, comprising phosphatidylethanolamine (PE)- or phosphatidylcholine (PC)-esterified 12S-hydroxyeicosatetraenoic acid (12S-HETE), generated by 12-lipoxygenase was identified and characterized. 12S-HETE-PE/PCs were formed within 5 min of activation by thrombin, ionophore, or collagen. Esterified HETE levels generated in response to thrombin were 5.85 ± 1.42 (PE) or 18.35 ± 4.61 (PC), whereas free was 65.5 ± 17.6 ng/4 × 107 cells (n = 5 separate donors, mean ± S.E.). Their generation was stimulated by triggering protease-activated receptors-1 and -4 and signaling via Ca2+ mobilization secretory phospholipase A2, platelet-activating factor-acetylhydrolase, src tyrosine kinases, and protein kinase C. Stable isotope labeling showed that they form predominantly by esterification that occurs on the same time scale as free acid generation. Unlike free 12S-HETE that is secreted, esterified HETEs remain cell-associated, with HETE-PEs migrating to the outside of the plasma membrane. 12-Lipoxygenase inhibition attenuated externalization of native PE and phosphatidylserine and HETE-PEs. Platelets from a patient with the bleeding disorder, Scott syndrome, did not externalize HETE-PEs, and liposomes supplemented with HETE-PC dose-dependently enhanced tissue factor-dependent thrombin generation in vitro. This suggests a role for these novel lipids in promoting coagulation. Thus, oxidized phospholipids form by receptor/agonist mechanisms, not merely as an undesirable consequence of vascular and inflammatory disease.
-
Malaria-parasitized erythrocytes and hemozoin nonenzymatically generate large amounts of hydroxy fatty acids that inhibit monocyte functions.
Blood, 2002Co-Authors: Evelin Schwarzer, Elena Valente, Hartmut Kühn, P. AreseAbstract:Plasmodium falciparum digests up to 75% of erythrocyte (red blood cell [RBC]) hemoglobin and forms hemozoin. Phagocytosed hemozoin and trophozoites inhibit important monocyte functions. Delipidized trophozoites and hemozoin were remarkably less toxic to monocytes. Parasitized RBCs and hemozoin contained large amounts of mostly esterified monohydroxy derivatives (OH-PUFAs), the stable end products of peroxidation of polyenoic fatty acids. The concentrations of OH-PUFA were 1.8 micromoles per liter RBCs in nonparasitized RBCs, 11.1 micromoles per liter RBCs in rings, 35 micromoles per liter RBCs in trophozoites; and approximately 90 micromoles per liter RBC equivalents in hemozoin. In parasitized RBCs and hemozoin a complex mixture of monohydroxy derivatives of arachidonic (HETEs) and linoleic (HODEs) acid was determined. Respectively, 13- and 9-HODE and 9- and 12-HETE were predominant in hemozoin and parasitized RBCs. The estimated concentrations of all HETE isomers were 33 and 39 micromoles per liter RBCs or RBC equivalents in trophozoites and hemozoin, respectively. No evidence of lipoxygenase activity was found, whereas the large number of positional and optical isomers, the racemic structure, and their generation by incubation of arachidonic acid with hemozoin indicated nonenzymatic origin via heme-catalysis. Sub/low micromolar concentrations of 12- and 15-HETE were toxic to monocytes, whereas HODE isomers were ineffective. Low micromolar concentrations of HETE isomers were estimated to be similarly present in monocytes after phagocytosis of trophozoites or hemozoin. Thus, specific products of heme-catalyzed lipid peroxidation appear to contribute to hemozoin toxicity to phagocytes and may thus play a role in increased cytoadherence, vascular permeability, and chemotaxis, as well as in immunodepression in malaria.
-
A simple method for the preparation of (5Z,8Z,11Z,14Z)-16-hydroxyeicosa-5,8,11,14-tetraenoic acid enantiomers and the corresponding 14,15-dehydro analogues: role of the 16-hydroxy group for the lipoxygenase reaction.
Bioorganic & medicinal chemistry, 2002Co-Authors: Igor Ivanov, Hartmut Kühn, Stepan G. Romanov, Nataliya V Groza, Santosh Nigam, Galina I. MyagkovaAbstract:Abstract (5 Z ,8 Z ,11 Z ,13 E )-15-Hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE) is not well oxygenated by arachidonate 15-lipoxygenases because of two structural reasons: (i) it contains a hydrophilic OH-group in close proximity to its methyl end and (ii) it lacks the bisallylic methylene at C 13 . We synthesized racemic (5 Z, 8 Z, 11 Z, 14 Z )-16-hydroxy-5,8,11,14-eicosatetraenoic acid (16-HETE) which still contains the bisallylic C 13 , separated the enantiomers reaching an optical purity of >99% and tested them as substrates for 5- and 15-lipoxygenases. Our synthetic pathway, which is based on stereospecific hydrogenation of a polyacetylenic precursor, yielded substantial amounts (30%) of 14,15-dehydro-16-HETE in addition to 16-HETE. When 16-HETE was tested as lipoxygenase substrate, we found that it is well oxygenated by the soybean 15-lipoxygenase and by the recombinant human 5-lipoxygenase. Analysis of the reaction products suggested an arachidonic acid-like alignment at the active site of the two enzymes. In contrast, the product pattern of 16-HETE methyl ester oxygenation by the soybean lipoxygenase (5-lipoxygenation) may be explained by an inverse head to tail substrate orientation.
Ying Zhang - One of the best experts on this subject based on the ideXlab platform.
-
Synthesis of 5-oxo-6,8,11,14-eicosatetraenoic acid by human monocytes and lymphocytes.
Journal of leukocyte biology, 1996Co-Authors: Ying Zhang, Angela Styhler, William S. PowellAbstract:We recently demonstrated that the arachidonate metabolite 5(S)-hydroxy-6,8,1 1,14- eicosatetraenoic acid (5-HETE) is converted by a highly specific dehydrogenase in human neutrophils to 5-oxo-6,8,1 1 ,14-eicosatetraenoic acid (5-oxo- ETE), which is a potent stimulator of these cells. The objective of this study was to determine whether 5-oxo-ETE is also formed by monocytes and lympho- cytes. Human monocytes (74 ± 2% pure) and lym- phocytes (86 ± 1 % pure) were prepared by successive centrifugations of leukocytes over Ficoll-Paque and Percoll. Both cell types converted 5-HETE to a single major product, which was identified as 5-oxo- ETE. The formation of 5-oxo-ETE was stimulated about twofold by phorbol myristate acetate (PMA; 30 nM). Dehydrogenase activity in monocyte frac- tions did not appear to be due to platelet contamina- tion, since depletion of platelets did not reduce enzyme activity. The dehydrogenase was localized in membrane fractions from monocytes and required NADP+ as a cofactor. It was specific for eicosanoids containing a 5S-hydroxyl group followed by a 6-trans double bond. We also investigated the formation of 5-oxo-ETE from endogenous aracbidonic acid by monocytes. 5-Oxo-ETE, 5-HETE, and leukotriene B4 (LTB4) were present in comparable amounts after incubation of these cells with A23187. PMA (EC50 -4 nM) stimulated the formation of 5-oxo-ETE and 5-HETE and, to a lesser extent, LTB4. Although monocytes released considerably less 5-HETE and LTB4 than neutrophils, they released comparable amounts of 5-oxo-ETE. Unlike neutrophils, mono- cytes did not convert any of these substances to detectable amounts of (li-oxidation products. Al- though lymphocytes were capable of converting 5- HETE to 5-oxo-ETE, they released little or no 5-lipoxygenase products in response to A23187. We conclude that monocytes have a high capacity to synthesize 5-oxo-ETE and that its formation is stimu- lated by activation of protein kinase C. J. Leukoc. Rio!. 59: 847-854; 1996.