Liles W C, Meier K E, Henderson W R
J Immunol. 1987 May 15;138(10):3396-402.
Phorbol myristate acetate (PMA), a tumor-promoting phorbol ester, and the calcium ionophore A23187 synergistically induced the noncytotoxic release of leukotriene B4 (LTB4) and other 5-lipoxygenase products of arachidonic acid metabolism from human neutrophils. Whereas neutrophils incubated with either A23187 (0.4 microM) or PMA (1.6 microM) alone failed to release any 5-lipoxygenase arachidonate products, neutrophils incubated with both stimuli together for 5 min at 37 degrees C released LTB4 as well as 20-COOH-LTB4, 20-OH-LTB4, 5-(S),12-(R)-6-trans-LTB4, 5-(S),12-(S)-6-trans-LTB4, and 5-hydroxyeicosatetraenoic acid, as determined by high pressure liquid chromatography. This synergistic response exhibited concentration dependence on both PMA and A23187. PMA induced 5-lipoxygenase product release at a concentration causing a half-maximal effect of approximately 5 nM in the presence of A23187 (0.4 microM). Competition binding experiments showed that PMA inhibited the specific binding of [3H]phorbol dibutyrate ([3H]PDBu) to intact neutrophils with a 50% inhibitory concentration (IC50) of approximately 8 nM. 1-oleoyl-2-acetyl-glycerol (OAG) also acted synergistically with A23187 to induce the release of 5-lipoxygenase products. 4 alpha-phorbol didecanoate (PDD), an inactive phorbol ester, did not affect the amount of lipoxygenase products released in response to A23187 or compete for specific [3H]PDBu binding. PMA and A23187 acted synergistically to increase arachidonate release from neutrophils prelabeled with [3H]arachidonic acid but did not affect the release of the cyclooxygenase product prostaglandin E2. Both PMA and OAG, but not PDD, induced the redistribution of protein kinase C activity from the cytosol to the membrane fraction of neutrophils, a characteristic of protein kinase C activation. Thus, activation of protein kinase C may play a physiologic role in releasing free arachidonate substrate from membrane phospholipids and/or in modulating 5-lipoxygenase activity in stimulated human neutrophils.
佛波醇肉豆蔻酸酯乙酸酯（PMA）是一种促肿瘤的佛波醇酯，钙离子载体A23187可协同诱导人中性粒细胞非细胞毒性释放白三烯B4（LTB4）及花生四烯酸代谢的其他5-脂氧合酶产物。单独用A23187（0.4微摩尔）或PMA（1.6微摩尔）孵育中性粒细胞均不能释放任何5-脂氧合酶花生四烯酸产物，而将两种刺激物在37℃共同孵育中性粒细胞5分钟后，通过高压液相色谱法测定，可释放LTB4以及20-COOH-LTB4、20-OH-LTB4、5-(S),12-(R)-6-反式-LTB4、5-(S),12-(S)-6-反式-LTB4和5-羟基二十碳四烯酸。这种协同反应对PMA和A23187均表现出浓度依赖性。在存在A23187（0.4微摩尔）的情况下，PMA在浓度约为5纳摩尔时可诱导5-脂氧合酶产物释放，产生半数最大效应。竞争结合实验表明，PMA抑制[3H]佛波醇二丁酸酯（[3H]PDBu）与完整中性粒细胞的特异性结合，50%抑制浓度（IC50）约为8纳摩尔。1-油酰-2-乙酰甘油（OAG）也与A23187协同作用诱导5-脂氧合酶产物释放。4α-佛波醇十二酸酯（PDD）是一种无活性的佛波醇酯，不影响对A23187反应释放的脂氧合酶产物量，也不竞争特异性[3H]PDBu结合。PMA和A23187协同作用可增加用[3H]花生四烯酸预标记的中性粒细胞中花生四烯酸的释放，但不影响环氧化酶产物前列腺素E2的释放。PMA和OAG均可诱导蛋白激酶C活性从中性粒细胞的胞质溶胶重新分布到膜部分，这是蛋白激酶C激活的特征，而PDD则无此作用。因此,蛋白激酶C的激活可能在从膜磷脂释放游离花生四烯酸底物和/或调节受刺激的人中性粒细胞中5-脂氧合酶活性方面发挥生理作用。
