- Identification and absolute configuration of dihydroxy-arachidonic acids formed by oxygenation of 5 S-HETE by native and aspirin-acetylated COX-2
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Biosynthesis of the prostaglandin endoperoxide by the cyclooxygenase (COX) enzymes is accompanied by formation of a small amount of 11 R- hydroxyeicosatetraenoic acid (HETE), 15 R-HETE, and 15 S-HETE as by-products. Acetylation of COX-2 by aspirin abrogates prostaglandin synthesis and triggers formation of 15 R-HETE as the sole product of oxygenation of arachidonic acid. Here, we investigated the formation of by-products of the transformation of 5 S-HETE by native COX-2 and by aspirin-acetylated COX-2 using HPLC-ultraviolet, GC-MS, and LC-MS analysis. 5 S,15 S-dihydroxy (di)HETE, 5 S,15 R-diHETE, and 5 S,11 R-diHETE were identified as by-products of native COX-2, in addition to the previously described di-endoperoxide (5 S,15 S-dihydroxy-9 S,11 R,8 S,12 S-diperoxy-6 E,13 E-eicosadienoic acid) as the major oxygenation product. 5 S,15 R-diHETE was the only product formed by aspirinacetylated COX-2. Both 5,15-diHETE and 5,11-diHETE were detected in CT26 mouse colon carcinoma cells as well as in lipopolysaccharide-activated RAW264.7 cells incubated with 5 S-HETE, and their formation was attenuated in the presence of the COX-2 specific inhibitor, NS-398. Aspirintreated CT26 cells gave 5,15-diHETE as the most prominent product formed from 5 S-HETE. 5 S,15 S-diHETE has been described as a product of the cross-over of 5-lipoxygenase (5-LOX) and 15-LOX activities in elicited rat mononuclear cells and human leukocytes, and our studies implicate crossover of the 5-LOX and COX-2 pathways as an additional biosynthetic route. Copyright
- Mulugeta, Surafel,Suzuki, Takashi,Hernandez, Noemi Tejera,Griesser, Markus,Boeglin, William E.,Schneider, Claus
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experimental part
p. 575 - 585
(2010/09/04)
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- Free radical oxidation of 15-(S)-hydroxyeicosatetraenoic acid with the Fenton reagent: characterization of an epoxy-alcohol and cytotoxic 4-hydroxy-2E-nonenal from the heptatrienyl radical pathway
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The oxidation of (5Z,8Z,11Z,13E,15S)-15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-(S)-HETE, 1a) with the Fenton reagent (Fe2+/EDTA/H2O2) was investigated. In phosphate buffer, pH 7.4, the reaction proceeded with 75% substrate consumption after 1 h to give a mixture of products, one of which was identified as (2E,4S)-4-hydroxy-2-nonenal (3a, 18% yield). Methylation of the mixture with diazomethane allowed isolation of another main product which could be identified as methyl (5Z,8Z,13E)-11,12-trans-epoxy-15-hydroxy-5,8,13-eicosatrienoate (2a methyl ester, 8% yield). A similar oxidation carried out on (15-2H)-15-HETE (1b) indicated complete retention of the label in 2b methyl ester and 3b, consistent with an oxidation pathway involving as the primary event H-atom abstraction at C-10. Overall, these results support the recently proposed role of 1a as a potential precursor of the cytotoxic γ-hydroxyalkenal 3a and disclose a hitherto unrecognized interconnection between 1a and the epoxy-alcohol 2a, previously implicated only in the metabolic transformations of the 15-hydroperoxy derivative of arachidonic acid.
- Manini,Briganti,Fabbri,Picardo,Napolitano,d'Ischia
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- Human platelets and polymorphonuclear leukocytes synthesize oxygenated derivatives of arachidonylethanolamide (anandamide): Their affinities for cannabinoid receptors and pathways of inactivation
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Arachidonylethanolamide (AEA), the putative endogenous ligand of the cannabinoid receptor, has been shown to be a substrate for lipoxygenase enzymes in vitro. One goal of this study was to determine whether lipoxygenase-rich cells metabolize AEA. [14C]AEA was converted by human polymorphonuclear leukocytes (PMNs) to two major metabolites that comigrated with synthetic 12(S)- and 15(S)-hydroxy-arachidonylethanolamide (HAEA). Human platelets convert [14C]AEA to 12(S)-HAEA. 12(S)-HAEA binds to both CB1 and CB2 receptors with approximately the same affinity as AEA. 12(R)-HAEA, which is not produced by PMNs, has 2-fold lower affinity for the CB1 receptor and 10-fold lower affinity for the CB2 receptor than 12(S)-HAEA. 15-HAEA has a lower affinity than AEA for both receptors, with K(i) values of 738 and >1000 nM for CB1 and CB2 receptors, respectively. The addition of a hydroxyl group at C20 of AEA resulted in a ligand with the same affinity for the CB1 receptor but a 4-fold lower affinity for the CB2 receptor than AEA. 12(S)- HAEA and 15-HAEA are poor substrates for AEA amidohydrolase and do not bind to the AEA uptake carrier. In conclusion the addition of a hydroxyl group at C12 of the arachidonate backbone of AEA does not affect binding to CB receptors but is likely to increase its half-life. The addition of hydroxyl groups at other positions affects ligand affinity for CB receptors; both the position of the hydroxyl group and the configuration of the remaining double bonds are determinants of affinity.
- Edgemond, William S.,Hillard, Cecilia J.,Falck,Kearn, Christopher S.,Campbell, William B.
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p. 180 - 188
(2007/10/03)
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- Stereocontrolled Total Synthesis of (5Z,8Z,11Z,13E)(15S)-15-Hydroxyeicosa-5,8,11,13-tetraenoic Acid (15S-HETE) and Analogues
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A novel and stereoselective synthesis of 15S-HETE and a number of analogues based on a Cu(I)-Pd(0) coupling reaction is described.
- Nicolaou, K. C.,Ladduwahetty, Tamara,Elisseou, E. Michael
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p. 1580 - 1581
(2007/10/02)
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