Anti-CD3 and Concanavalin A-induced Human T Cell Proliferation Is Associated with an Increased Rate of Arachidonate-Phospholipid Remodeling: LACK OF INVOLVEMENT OF GROUP IV AND GROUP VI PHOSPHOLIPASE A2 IN REMODELING AND INCREASED SUSCEPTIBILITY OF PROLIFERATING T CELLS TO CoA-INDEPENDENT TRANSACYLASE INHIBITOR-INDUCED APOPTOSIS

Eric Boilard,Marc E Surette

doi:10.1074/jbc.m006152200

Abstract

In this study arachidonate-phospholipid remodeling was investigated in resting and proliferating human T lymphocytes. Lymphocytes induced to proliferate with either the mitogen concanavalin A or with anti-CD3 (OKT3) in combination with interleukin 2 (OKT3/IL-2) showed a greatly accelerated rate of [3H]arachidonate-phospholipid remodeling compared with resting lymphocytes or with lymphocytes stimulated with OKT3 or IL-2 alone. The concanavalin A-stimulated cells showed a 2-fold increase in the specific activity of CoA-independent transacylase compared with unstimulated cells, indicating that this enzyme is inducible. Stimulation with OKT3 resulted in greatly increased quantities of the group VI calcium-independent phospholipase A2 but not of the quantity of group IV cytosolic phospholipase A2. However, group IV phospholipase A2 became phosphorylated in OKT3-stimulated cells, as determined by decreased electrophoretic mobility. Incubation of cells with the group VI phospholipase A2 inhibitor, bromoenol lactone, or the dual group IV/group VI phospholipase A2 inhibitor, methyl arachidonyl fluorophosphonate, did not block arachidonate-phospholipid remodeling resting or proliferating T cells, suggesting that these phospholipases A2 were not involved in arachidonate-phospholipid remodeling. The incubation of nonproliferating human lymphocytes with inhibitors of CoA-independent transacylase had little impact on cell survival. In contrast, OKT3/IL-2-stimulated T lymphocytes were very sensitive to apoptosis induced by CoA-independent transacylase inhibitors. Altogether these results indicate that increased arachidonate-phospholipid remodeling is associated with T cell proliferation and that CoA-independent transacylase may be a novel therapeutic target for proliferative disorders.

Highlights

¶ Recipient of a Scholarship from Le Fonds de la Recherche en Santedu Quebec
In addition to regulating the activation of phospholipase(s) A2 (PLA2), which catalyzes the release of arachidonic acid (AA) from phospholipids, it has been shown that inflammatory cells regulate the distribution of this polyunsaturated fatty acid in cellular phospholipids via an arachidonate-phospholipid (PL)-remodeling pathway [1,2,3] (Fig. 1)
Human lymphocytes were isolated from the peripheral blood of healthy volunteers and incubated without the addition of a stimulus or stimulated with either the T cell mitogen ConA, IL-2, the anti-CD3 antibody OKT3, or with OKT3 followed 24 h later with IL-2 (OKT3/IL-2)

Summary

Introduction

¶ Recipient of a Scholarship from Le Fonds de la Recherche en Santedu Quebec. To whom correspondence should be addressed: Pilot Therapeutics Inc., 101 N. In addition to regulating the activation of phospholipase(s) A2 (PLA2), which catalyzes the release of AA from phospholipids, it has been shown that inflammatory cells regulate the distribution of this polyunsaturated fatty acid in cellular phospholipids via an arachidonate-phospholipid (PL)-remodeling pathway [1,2,3] (Fig. 1). It was recently observed that several cell lines including human promyelocytic HL-60 cells, monocyte-like THP-1 cells, macrophagelike P388D1 cells, and the breast cancer cell lines MCF-7 and MDA-MB-231 remodel AA very rapidly through the arachidonate-PL pathway [17,18,19] When these neoplastic cell lines are incubated with CoA-IT inhibitors, is arachidonate-PL remodeling effectively inhibited, but the cells readily undergo cell cycle arrest and apoptotic cell death [18, 20, 21]. A similar mechanism of cell death triggered by an accumulation of free AA has been proposed for cells treated with cyclooxygenase inhibitors [23]

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Results

Conclusion