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Synthesis of 5‐oxo‐6,8, 11, 14‐eicosatetraenoic acid by human monocytes and lymphocytes
Author(s) -
Zhang Ying,
Styhler Angela,
Powell William S.
Publication year - 1996
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1002/jlb.59.6.847
Subject(s) - arachidonic acid , monocyte , biology , biochemistry , incubation , metabolite , leukotriene b4 , enzyme , hydroxyeicosatetraenoic acid , phorbol , dehydrogenase , microbiology and biotechnology , leukotriene , immunology , protein kinase c , inflammation , asthma
We recently demonstrated that the arachidonate metabolite 5( S )‐hydroxy‐6,8,11,14‐eicosatetraenoic acid (5‐HETE) is converted by a highly specific dehydrogenase in human neutrophils to 5‐oxo‐6,8,11,14‐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 lymphocytes. Human monocytes (74 ± 2% pure) and lymphocytes (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 fractions did not appear to be due to platelet contamination, 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 5 S ‐hydroxyl group followed by a 6‐ trans double bond. We also investigated the formation of 5‐oxo‐ETE from endogenous arachidonic acid by monocytes. 5‐Oxo‐ETE, 5‐HETE, and leukotriene B 4 (LTB 4 ) 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, LTB 4 . Although monocytes released considerably less 5‐HETE and LTB 4 than neutrophils, they released comparable amounts of 5‐oxo‐ETE. Unlike neutrophils, monocytes did not convert any of these substances to detectable amounts of ‐oxidation products. Although 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 stimulated by activation of protein kinase C.