Regulation of platelet-activating-factor receptors and the desensitization response in polymorphonuclear neutrophils.
Regulation of platelet-activating-factor receptors and the desensitization response in polymorphonuclear neutrophils.
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血小板激活因子受体的调节和多形核中性粒细胞的脱敏反应。
DOI：
10.1042/bj2880241
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Redman,JF
中科院分区：
文献类型：
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作者：
O'Flaherty,JT;Jacobson,DP;Redman,JF
血小板活化因子（PAF）对多种靶细胞既有刺激作用，又有脱敏作用。在Ca ~（2+）动员和脱颗粒试验中，我们发现人中性粒细胞（PMN）在PAF作用后15-90 s内对PAF的第二次攻击反应最弱。在随后的20-40分钟内，细胞恢复了对PAF的全部敏感性。这些效应与PAF受体可用性的变化相关。用PAF处理的PMN，在常规缓冲液中洗涤并测定PAF结合，在高亲和力PAF受体的数量中表现出福尔斯下降（15 s内最大），随后上升（60 min达到对照水平）。然而，跟踪研究表明，[3 H]PAF积累在细胞表面约2分钟前被内化。常规缓冲液洗涤没有去除这种表面PAF，而使用过量白蛋白吸附PAF的洗涤方案去除了99%的表面化合物。后一种方案洗涤的PMN PAF暴露后PAF受体丢失相对缓慢（最大约5分钟），但这种损失的最终程度和受体表达正常化的速率与常规缓冲液中洗涤的细胞相似。放线菌酮和放线菌素D均不影响受体的变化过程，但两种蛋白激酶C（PKC）阻断剂，星形孢菌素和1-（5-异喹啉磺酰基）哌嗪，抑制PAF的受体-受体耗竭作用。事实上，佛波醇二酯激活剂的PKC也导致PMN减少高亲和力PAF受体的数量，和两个PKC阻断剂拮抗这种作用的浓度，抑制PAF诱导的PAF受体的损失。我们的结论是：（a）PAF诱导PMN下调然后重新表达PAF受体，而不依赖于蛋白质的合成;（B）这些变化可能是脱敏后期和逆转的基础;（c）PAF诱导PMN的发病可能与PAF受体的表达有关。然而，脱敏（t <或= 2 min）先于受体下调，并且一定是由于受体与转导元件解偶联;和（d）PAF受体的下调似乎是由PKC和/或被PKC阻断剂抑制的元件介导的。
Platelet-activating factor (PAF) desensitizes as well as stimulates its various target cells, We find that human polymorphonuclear neutrophils (PMN) exposed to PAF became maximally unresponsive to a second PAF challenge within 15-90 s in assays of Ca2+ mobilization and degranulation. The cells regained full PAF-sensitivity over the ensuing 20-40 min. These effects correlated with changes in PAF receptor availability. PMN treated with PAF, washed in regular buffer and assayed for PAF binding exhibited falls (maximal in 15 s), followed by rises (reaching control levels by 60 min), in the number of high-affinity PAF receptors. However, tracking studies showed that [3H]PAF accumulated on the cell surface for approximately 2 min before being internalized. Regular-buffer washes did not remove this superficial PAF, whereas a washing regimen using excess albumin to adsorb PAF removed 99% of the surface compound. PMN washed by the latter regimen after PAF exposure lost PAF receptors relatively slowly (maximal at approximately 5 min), but the ultimate extent of this loss and the rate at which receptor expression normalized were similar to those of cells washed in regular buffer. Neither cycloheximide nor actinomycin D influenced the course of the receptor changes, but two protein kinase C (PKC) blockers, staurosporine and 1-(5-isoquinolinesulphonyl)piperazine, inhibited the receptor-receptor-depleting actions of PAF. Indeed, a phorbol diester activator of PKC also caused PMN to decrease high-affinity PAF receptor numbers, and the two PKC blockers antagonized this action at concentrations that inhibited PAF-induced PAF receptor losses. We conclude that: (a) PAF induces PMN to down-regulate and then to re-express PAF receptors independently of protein synthesis; (b) these changes are likely to underlie the later stages and reversal of desensitization; (c) the onset (t < or = 2 min) of desensitization, however, precedes receptor down-regulation and must be due to receptor uncoupling from transductional elements; and (d) down-regulation of receptors for PAF appears to be mediated by PKC and/or elements inhibited by PKC blockers.