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Type: Journal article
Title: Differential regulation of prostaglandin E2 and thromboxane A2 production in human monocytes: Implications for the use of cyclooxygenase inhibitors
Author: Penglis, P.
Cleland, L.
Demasi, M.
Caughey, G.
James, M.
Citation: Journal of Immunology, 2000; 165(3):1605-1611
Publisher: Amer Assoc Immunologists
Issue Date: 2000
ISSN: 0022-1767
Statement of
Peter S. Penglis, Leslie G. Cleland, Maryanne Demasi, Gillian E. Caughey, and Michael J. James
Abstract: There is an autocrine relationship between eicosanoid and cytokine synthesis, with the ratio of prostaglandin E2 (PGE2)/thromboxane A2 (TXA2) being one of the determinants of the level of cytokine synthesis. In monocytes, cyclooxygenase type 1 (COX-1) activity appears to favor TXA2 production and COX-2 activity appears to favor PGE2 production. This has led to speculation regarding possible linkage of COX isozymes with PGE and TXA synthase. We have studied the kinetics of PGE2 and TXA2 synthesis under conditions that rely on COX-1 or -2 activity. With small amounts of endogenously generated prostaglandin H2 (PGH2), TXA2 synthesis was greater than PGE2. With greater amounts of endogenously generated PGH2, PGE2 synthesis was greater than TXA2. Also, TXA synthase was saturated at lower substrate concentrations than PGE synthase. This pattern was observed irrespective of whether PGH2 was produced by COX-1 or COX-2 or whether it was added directly. Furthermore, the inhibition of eicosanoid production by the action of nonsteroidal anti-inflammatory drugs or by the prevention of COX-2 induction with the p38 mitogen-activated protein kinase inhibitor SKF86002 was greater for PGE2 than for TXA2. It is proposed that different kinetics of PGE synthase and TXA synthase account for the patterns of production of these eicosanoids in monocytes under a variety of experimental conditions. These properties provide an alternative explanation to notional linkage or compartmentalization of COX-1 or -2 with the respective terminal synthases and that therapeutically induced changes in eicosanoid ratios toward predominance of TXA2 may have unwanted effects in long-term anti-inflammatory and anti-arthritic therapy.
Keywords: Monocytes
U937 Cells
Thromboxane-A Synthase
Arachidonic Acid
Prostaglandins H
Prostaglandin H2
Thromboxane A2
Membrane Proteins
Cyclooxygenase Inhibitors
Cell Fractionation
Enzyme Induction
Prostaglandin-Endoperoxide Synthases
Cyclooxygenase 2
Cyclooxygenase 2 Inhibitors
DOI: 10.4049/jimmunol.165.3.1605
Appears in Collections:Aurora harvest 4
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