Yue T L, Gleason M M, Gu J L, Lysko P G, Hallenbeck J, Feuerstein G
Department of Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania.
J Pharmacol Exp Ther. 1991 Apr;257(1):374-81.
Platelet-activating factor (PAF) is an unusually potent lipid autacoid with a variety of biological activities. The growing body of evidence suggests that PAF might play an important role in modulation of central nervous system function, particularly during ischemia- and trauma-induced neuronal damage. However, the mechanisms involved in PAF actions on neuronal or other brain cells is virtually unknown. Therefore, this study was designed to characterize PAF receptor-mediated cellular signal transduction in neurohybrid NG108-15 cells with the aid of a new potent PAF antagonist, BN 50739. PAF induced an immediate and concentration-dependent increase in [Ca++]i with an EC50 of 6.8 nM. PAF-induced [Ca++]i mobilization was inhibited by several structurally unrelated PAF antagonists such as BN 50739, WEB 2086, SRI 63-441 and BN 52021, in a dose-dependent manner with IC50 values of 4.8, 6.9, 809 and 98500 nM, respectively. The calcium channel blockers nifedipine (5 microM) and diltiazem (10 microM) had no effect on the PAF-induced increase in [Ca++]i, but omission of CA++ from the incubation buffer caused an 82% reduction of PAF-induced [Ca++]i elevation; the remainder contributed from intracellular sources was completely inhibited by 10 microM TMB-8, an intracellular Ca++ blocker. NG108-15 cells exhibited homologous desensitization to sequential addition of PAF, but no heterologous desensitization between PAF and other agonists such as bradykinin, endothelin, angiotensin II and ATP was observed. PAF stimulated phosphoinositide metabolism in a dose-dependent manner with an EC50 of 5.1 nM for IP3 formation, which was also inhibited by the PAF antagonist BN 50739 in a dose-dependent manner (IC50 = 3.6 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
血小板活化因子（PAF）是一种具有多种生物活性的异常强效的脂质自分泌调节因子。越来越多的证据表明，PAF可能在中枢神经系统功能调节中发挥重要作用，尤其是在缺血和创伤诱导的神经元损伤过程中。然而，PAF作用于神经元或其他脑细胞的机制实际上尚不清楚。因此，本研究旨在借助一种新型强效PAF拮抗剂BN 50739，对神经杂交NG108-15细胞中PAF受体介导的细胞信号转导进行表征。PAF诱导细胞内钙离子浓度（[Ca++]i）迅速且呈浓度依赖性升高，半数有效浓度（EC50）为6.8 nM。PAF诱导的[Ca++]i动员受到几种结构不相关的PAF拮抗剂的抑制，如BN 50739、WEB 2086、SRI 63-441和BN 52021，其抑制作用呈剂量依赖性，半数抑制浓度（IC50）分别为4.8、6.9、809和98500 nM。钙通道阻滞剂硝苯地平（5 microM）和地尔硫卓（10 microM）对PAF诱导的[Ca++]i升高无影响，但孵育缓冲液中去除钙离子会导致PAF诱导的[Ca++]i升高降低82%；细胞内来源的剩余部分被细胞内钙离子阻滞剂10 microM TMB-8完全抑制。NG108-15细胞对连续添加的PAF表现出同源脱敏，但未观察到PAF与其他激动剂（如缓激肽、内皮素、血管紧张素II和ATP）之间的异源脱敏。PAF以剂量依赖性方式刺激磷脂酰肌醇代谢，IP3形成的EC50为5.1 nM，PAF拮抗剂BN 50739也以剂量依赖性方式抑制该过程（IC50 = 3.6 nM）。（摘要截断于250字）
