Chemotactic 5‐Oxo‐Icosatetraenoic Acids Activate A Unique Pattern of Neutrophil Responses

Abstract

Neutrophil cell responses and signal pathways elicted by the chemotactic arachidonic acid metabolites (6E, SZ, 1 lZ, 14Z)-5-oxo-icosatetraenoic acid and (6E, SZ, 1 IZ, 13E)-5-oxo-15-hydroxy-icosatetraenoic acid were studied and compared with those of other chemotaxins. Polyphosphoinositol lipid analysis revealed activation of phosphatidylinositol-bisphosphate 3-kinase by both agonists. Experiments with Fura-2 in the presence of EGTA indicated Ca2+ mobilization from intracellular stores by both 5-OXOicosanoids. A transient actin response and production of small amounts of superoxide anions upon stimulation with both agents was detected. The changes induced by 5-0x0-icosanoids were more moderate and transient than those obtained by other chemotaxins. Desensitization studies indicated cross-desensitization between both 5-oxo-icosanoids, but no interference with the response of other chemotaxins. All cell responses elicted by 5-0x0-icosanoids were inhibited by pertussis toxin suggesting involvement of Gproteins, a common activation mechanism for all known potent chemotaxins. In contrast to other chemotaxins, 5-0x0-icosanoids at concentrations 500-fold higher than the ED,, of other functions did not induce up-regulation of CD11 b and N-formyl-peptide receptors at the cell surface, and failed to potentiate Nformyl-peptide-induced superoxide anion production. These results indicate that 5-0x0-icosanoids trigger a unique pattern of neutrophil responses.Keywords: neutrophils ; 5-0x0-icosanoids ; Caz+ transients ; F actin; superoxide anions.Accumulation of neutrophils in tissue is characteristic of inflammation and observed in a large variety of pathological conditions. Leukocyte infiltration is presumably caused by different chemotaxins, which are generated by different mechanisms [I]. Extensively characterized chemotaxins are N-formyl peptides, the complement split product C5a (C5a), the chemokines interleukin-8 (IL-8) and GROa as well as the arachidonic acid metabolite leukotriene B, (LTB,) 11-61. In addition to chemotaxis, these substances stimulate with different capacity proinflammatory activities such as production of reactive oxygen metabolites, up-regulation of membrane proteins such as the complement receptor type 3 (CDllb) or the N-formyl-peptide receptor and priming of neutrophil responses [l -61. Activation of neutrophils by chemotaxins requires binding to ligand-specific cell-surface receptors [7]. The receptors for most chemotaxins interact with pertussis-toxin-sensitive or cholera-toxin-sensitive heterotrimeric guanine-nucleotide-binding proteins (G-proteins) 11, 7-91. Activation of G-proteins leads into different signal pathways initiated by phospholipase C-p2, phosphatidylinositol-bisphosphate (PtdInsP,) 3-kinase and actin polymerization [I, 2, 10, 1 I]. The second messengers generated by these differend signal pathways regulate the effector functions of leukocytes in concert [I, 2, 12-15].Recently, 5-oxo-icosanoids, i.e. (6E, SZ, 1 lZ, ~~Z ) -~-O X Oicosatetraenoic acid (5oETE) and (6E, 82, l l Z , 13E...

A Biased Non-Gαi OXE-R Antagonist Demonstrates That Gαi Protein Subunit Is Not Directly Involved in Neutrophil, Eosinophil, and Monocyte Activation by 5-Oxo-ETE

“…This might not be the case for 5-oxo-ETE stimulation of granulocyte adhesion to endothelial cells and monocyte migration, as PTX abolished both of these cellular functions in the current study. Similar findings were previously reported for F-actin formation and phosphoinositide 3-kinase activation (32).…”

Receptors for the 5-Oxo Class of Eicosanoids in Neutrophils

“…Despite this difficulty, however, putative receptors for 5-HETE merit study. PMNs, eosinophils, and monocytes dehydrogenate 5-HETE to 5-oxoETE (6,(13)(14)(15)25). 5-OxoETE is ϳ10-fold stronger than 5-HETE in stimulating PMNs and monocytes (9 -13, 19).…”

“…It is even more active on eosinophils (14 -17), eliciting the chemotaxis response of this cell at concentrations 10,000-, 1000-, and Ͼ10-fold lower than LTB 4 , 5-HETE, or other chemotactic factors, respectively (18). 5-OxoETE down-regulates these cells to itself and 5-HETE but not to LTB 4 or other stimuli (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Possibly, therefore, putative 5-HETE receptors and their preferred ligand, 5-oxoETE, participate in recruiting eosinophils to sites of allergic reactivity (18).…”

5-oxo-ETE induces pulmonary eosinophilia in an integrin-dependent manner in Brown Norway rats.

“…The preferred substrate for this pathway, 5S-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) is converted to its 5-oxo metabolite, 5-oxo-ETE. 5-Oxo-ETE is a chemoattractant for human neutrophils (18) and stimulates a variety of other responses in these cells (19)(20)(21)(22). Although it affects a broad spectrum of neutrophil activities and appears to act via a specific receptor, 5-oxo-ETE is considerably less potent than LTB 4 in inducing calcium mobilization (18), surface expression of CD11b (19), actin polymerization (19), degranulation (21), adherence (19), and chemotaxis (18).…”