title: COX-2-dependent and -independent biosynthesis of dihydroxy-arachidonic acids in activated human leukocytes.
abstract: Biosynthesis of 5,15-dihydroxyeicosatetraenoic acid (5,15-diHETE) in leukocytes involves consecutive oxygenation of arachidonic acid by 5-lipoxygenase (LOX) and 15-LOX in either order. Here, we analyzed the contribution of cyclooxygenase (COX)-2 to the biosynthesis of 5,15-diHETE and 5,11-diHETE in isolated human leukocytes activated with lipopolysaccharide and calcium ionophore A23187. Transformation of arachidonic acid was initiated by 5-LOX providing 5S-HETE as a substrate for COX-2 forming 5S,15S-diHETE, 5S,15R-diHETE, and 5S,11R-diHETE as shown by LC/MS and chiral phase HPLC analyses. The levels of 5,15-diHETE were 0.45 ± 0.2 ng/10⁶ cells (mean ± SEM, n = 6), reaching about half the level of LTB₄ (1.3 ± 0.5 ng/10⁶ cells, n = 6). The COX-2 specific inhibitor NS-398 reduced the levels of 5,15-diHETE to below 0.02 ng/10⁶ cells in four of six samples. Similar reduction was achieved by MK-886, an inhibitor of 5-LOX activating protein but the above differences were not statistically significant. Aspirin treatment of the activated cells allowed formation of 5,15-diHETE (0.1 ± 0.05 ng/10⁶ cells, n = 6) but, as expected, abolished formation of 5,11-diHETE. The mixture of activated cells also produced 5S,12S-diHETE with the unusual 6E,8Z,10E double bond configuration, implicating biosynthesis by 5-LOX and 12-LOX activity rather than by hydrolysis of the leukotriene A₄-epoxide. Exogenous octadeuterated 5S-HETE and 15S-HETE were converted to 5,15-diHETE, implicating that multiple oxygenation pathways of arachidonic acid occur in activated leukocytes. The contribution of COX-2 to the biosynthesis of dihydroxylated derivatives of arachidonic acid provides evidence for functional coupling with 5-LOX in activated human leukocytes.
authors: Division of Clinical Pharmacology, Department of Pharmacology and Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical School, Nashville, TN, USA.
authors: Noemi
authors: N
authors: Tejera
authors: William E
authors: WE
authors: Boeglin
authors: Takashi
authors: T
authors: Suzuki
authors: Claus
authors: C
authors: Schneider
mesh_terms: D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis* / Q000378:metabolism; D007962:Leukocytes / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D006893:Hydroxyeicosatetraenoic Acids; C034922:5,15-dihydroxy-6,8,11,13-eicosatetraenoic acid; D001093:Arachidonate 15-Lipoxygenase; D001094:Arachidonate 5-Lipoxygenase; D051546:Cyclooxygenase 2