Bray R A, Brahmi Z
J Immunol. 1986 Mar 1;136(5):1783-90.
Nordihydroguaiaretic acid (NDGA), quercetin, eicosatetraynoic acid (ETYA), phenidone, and esculetin, agents known to inhibit cellular lipoxygenase (LO) activity, also inhibit human natural killer cell-mediated cytotoxicity (NK-CMC) of K562 tumor target cells (TC) in a dose-dependent fashion. Kinetic analysis demonstrated that LO inhibitors blocked an early event in the activation of the lytic mechanism but did not impair conjugate formation. LO inhibitors also did not affect subsequent chromium release, indicating that their site of inhibition was the NK cell and not the TC. The lipoxygenase products 5-hydroperoxyeicosatetraenoic acid (5-HPETE) and leukotriene-B4 significantly enhanced NK activity, with 5-HPETE being the more effective. Other LO products tested included 15-HPETE and the hydroxy derivatives 15-hydroxyeicosatetraenoic acid (15-HETE) and 5-HETE. These LO metabolites were either without effect on NK-CMC or inhibitory, depending upon the concentration. Additionally, we examined the ability of 5-HPETE to circumvent the effects of LO inhibitors and found that, in the presence of NDGA, ETYA or quercetin, 5-HPETE significantly (p less than 0.001) restored lytic activity. Inhibitors of LTB4 and LTC4 synthesis, diethylcarbamazine and U-60,257 respectively, produced no inhibition of NK activity. In fact, U-60,257 significantly (p less than 0.05) enhanced NK-CMC. Previous studies in our laboratory, with a new technique which allows for the separation of NK cells from K562 cells, have shown that K562-treated effector cells are greater than 90% inactivated when retested against fresh K562 in the standard chromium release assay. Lipids were extracted from K562-treated, Percoll-purified LGL and evaluated by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). No significant increases were seen in the arachidonic acid-derived LO products evaluated. Thus, our studies indicate that lipoxygenation may be required in the activation of NK-CMC, possibly as a means to generate oxygen radicals which have been previously implicated in NK-CMC.
去甲二氢愈创木酸（NDGA）、槲皮素、二十碳四炔酸（ETYA）、非那吡啶和七叶亭，这些已知可抑制细胞脂氧合酶（LO）活性的物质，也能以剂量依赖的方式抑制人自然杀伤细胞介导的K562肿瘤靶细胞（TC）的细胞毒性（NK - CMC）。动力学分析表明，LO抑制剂阻断了溶解机制激活过程中的早期事件，但不影响共轭体的形成。LO抑制剂也不影响随后的铬释放，这表明它们的抑制位点是自然杀伤细胞而非肿瘤靶细胞。脂氧合酶产物5 - 氢过氧化二十碳四烯酸（5 - HPETE）和白三烯 - B4显著增强自然杀伤细胞活性，其中5 - HPETE的效果更显著。所测试的其他LO产物包括15 - HPETE以及羟基衍生物15 - 羟基二十碳四烯酸（15 - HETE）和5 - HETE。这些LO代谢产物对NK - CMC要么无影响，要么具有抑制作用，这取决于其浓度。此外，我们研究了5 - HPETE规避LO抑制剂作用的能力，发现，在存在NDGA、ETYA或槲皮素的情况下，5 - HPETE能显著（p小于0.001）恢复溶解活性。白三烯 - B4和白三烯 - C4合成抑制剂，即二乙氨基甲嗪和U - 60257，对自然杀伤细胞活性均无抑制作用。事实上，U - 60257能显著（p小于0.05）增强NK - CMC。我们实验室之前采用一种新技术将自然杀伤细胞与K562细胞分离进行研究，结果表明，在标准铬释放试验中，用K562处理过的效应细胞再次检测新鲜K562细胞时，其活性被抑制超过90%。从经K562处理、Percoll纯化的大颗粒淋巴细胞中提取脂质，并通过薄层色谱法（TLC）和高效液相色谱法（HPLC）进行评估。所评估的源自花生四烯酸的LO产物未见显著增加。因此，我们的研究表明，脂氧合作用可能是自然杀伤细胞介导的细胞毒性激活所必需的，可能是作为一种产生氧自由基的方式，而氧自由基先前已被认为与自然杀伤细胞介导的细胞毒性有关。
