O'Flaherty J T
J Cell Physiol. 1985 Feb;122(2):229-39. doi: 10.1002/jcp.1041220211.
Stimulus-activated polymorphonuclear neutrophils (PMN) produce leukotriene B4 (LTB4), 5-hydroxyeicosatetraenoate (5-HETE), and platelet-activating factor (PAF). Each of these lipids promotes PMN degranulation; in combination they have additive and potentiating effects that result in prominent degranulation responses at relatively low concentrations. Thus, the combined interactions of LTB4, 5-HETE, and PAF may mediate responses in PMN activated by other stimuli. This possibility was examined by measuring the responses of PMN made insensitive to one or more of these lipids. Cells were pretreated with LTB4, 5-HETE, and/or PAF for 8 min; exposed for 2 min to cytochalasin B (which is required for lipid-induced degranulation); and then challenged. PMN challenged with only buffer released minimal amounts of granule-bound enzymes. Furthermore, the lipid-pretreated cells were hyporesponsive to challenge with 1) various combinations of these same lipids or 2) ionophore A23187. The relative potencies of the lipids in producing hyporesponsiveness to themselves or A23187 were: 5-HETE less than PAF less than or equal to LTB4 less than PAF + LTB4 less than PAF + LTB4 + 5-HETE. For both types of challenge, reduced responsiveness occurred in cells pretreated with greater than 0.1 nM LTB4 and/or greater than 0.2 nM PAF, persisted in cells washed after lipid pretreatment, and did not develop in cells pretreated with various combinations of bioinactive structural analogues of the lipids. Thus, PAF, LTB4, and 5-HETE interacted to desensitize PMN, and the degranulating actions of A23187 required cells that were fully responsive to each of the three lipids. This supports the concept that the lipids act together in mediating certain of the ionophore's effects. However, lipid-desensitized PMN degranulated fully when challenged with C5a, a formylated oligopeptide, or phorbol myristate acetate. Degranulation responses, therefore, may proceed through various pathways, only some of which involve the lipid products studied here.
刺激激活的多形核中性粒细胞（PMN）可产生白三烯B4（LTB4）、5-羟基二十碳四烯酸（5-HETE）和血小板活化因子（PAF）。这些脂质中的每一种都能促进PMN脱颗粒；它们共同作用时具有相加和增强效应，在相对较低浓度下就能产生显著的脱颗粒反应。因此，LTB4、5-HETE和PAF的联合相互作用可能介导由其他刺激激活的PMN中的反应。通过测量对这些脂质中的一种或多种不敏感的PMN的反应来检验这种可能性。细胞先用LTB4、5-HETE和/或PAF预处理8分钟；暴露于细胞松弛素B2分钟（脂质诱导脱颗粒所需）；然后进行刺激。仅用缓冲液刺激的PMN释放的颗粒结合酶量极少。此外，经脂质预处理的细胞对以下刺激反应性降低：1）这些相同脂质的各种组合，或2）离子载体A23187。这些脂质在使细胞对自身或A23187产生低反应性方面的相对效力为：5-HETE＜PAF≤LTB4＜PAF + LTB4＜PAF + LTB4 + 5-HETE。对于这两种刺激类型，在用大于0.1 nM LTB4和/或大于0.2 nM PAF预处理的细胞中出现反应性降低，在用脂质预处理后洗涤的细胞中这种降低持续存在，而在用这些脂质的各种生物无活性结构类似物组合预处理的细胞中未出现这种情况。因此，PAF、LTB4和5-HETE相互作用使PMN脱敏，并且A23187的脱颗粒作用需要对这三种脂质中的每一种都完全有反应的细胞。这支持了这些脂质共同作用介导离子载体某些效应的概念。然而，当用C5a、一种甲酰化寡肽或佛波酯肉豆蔻酸酯刺激时，脂质脱敏的PMN会完全脱颗粒。因此，脱颗粒反应可能通过多种途径进行，其中只有一些途径涉及此处研究的脂质产物。
