Wang Su-Jane
School of Medicine, Fu Jen Catholic University, 510 Chung-Cheng Road, Hsin-Chuang, Taipei Hsien 24205, Taiwan.
Neurochem Int. 2006 Feb;48(3):181-90. doi: 10.1016/j.neuint.2005.10.006. Epub 2005 Dec 2.
The effect of aspirin on glutamate release from isolated nerve terminals (synaptosomes) from rat hippocampus was examined. The Ca(2+)-dependent release of glutamate evoked by 4-aminopyridine (4AP) was facilitated by aspirin in a concentration-dependent manner, but the 4AP-evoked Ca(2+)-independent release was not modified. Also, aspirin-mediated facilitation of glutamate release was completely inhibited by bafilomycin A1, which depletes vesicle content by inhibiting the synaptic vesicle H(+)-ATPase that drives glutamate uptake, not by l-trans-pyrrolidine-2,4-dicarboxylic acid (l-trans-PDC), a excitatory amino acid (EAA) transporter inhibitor, suggesting that the facilitation of glutamate release produced by aspirin originates from synaptic vesicle exocytosis rather than reversal of the plasma membrane glutamate transporter. In addition, aspirin did not alter either 4AP-evoked depolarization of the synaptosomal plasma membrane potential or Ca(2+) ionophore ionomycin-induced glutamate release, but significantly increased in 4AP-evoked Ca(2+) influx. A possible effect of aspirin on synaptosomal Ca(2+) channels was confirmed in experiments where synaptosomes pretreated with a combination of the N- and P/Q-type Ca(2+) channel blockers, which abolished the aspirin-mediated facilitation of glutamate release. The facilitatory action by aspirin observed in glutamate release was mimicked and occluded by arachidonic acid (AA) and eicosatetraynoic acid (ETYA), an analogue of AA that mimics the effect of AA but cannot be metabolized. Furthermore, this aspirin-mediated facilitation of glutamate release may depend on activation of protein kinase C (PKC), because PKC activator and PKC inhibitor, respectively, superseding or suppressing the facilitatory effect of aspirin. Together, these results suggest that aspirin exerts their presynaptic facilitatory effect, likely through AA directly to induce the activation of PKC, which subsequently enhances the Ca(2+) influx through voltage-dependent N- and P/Q-type Ca(2+) channels to cause an increase in evoked glutamate release from rat hippocampal nerve terminals.
研究了阿司匹林对大鼠海马体分离神经末梢（突触体）谷氨酸释放的影响。阿司匹林以浓度依赖的方式促进了4-氨基吡啶（4AP）诱发的谷氨酸的Ca(2+)依赖性释放，但对4AP诱发的Ca(2+)非依赖性释放没有影响。此外，巴氟霉素A1完全抑制了阿司匹林介导的谷氨酸释放促进作用，巴氟霉素A1通过抑制驱动谷氨酸摄取的突触小泡H(+)-ATPase来耗尽囊泡内容物，而不是通过兴奋性氨基酸（EAA）转运体抑制剂L-反式-吡咯烷-2,4-二羧酸（L-反式-PDC），这表明阿司匹林产生的谷氨酸释放促进作用源于突触小泡胞吐作用，而非质膜谷氨酸转运体的逆转。此外，阿司匹林既不改变4AP诱发的突触体质膜电位去极化，也不改变Ca(2+)离子载体离子霉素诱导的谷氨酸释放，但显著增加了4AP诱发的Ca(2+)内流。在用N型和P/Q型Ca(2+)通道阻滞剂组合预处理突触体的实验中，证实了阿司匹林对突触体Ca(2+)通道可能的影响，该组合消除了阿司匹林介导的谷氨酸释放促进作用。花生四烯酸（AA）和二十碳四烯酸（ETYA，一种模拟AA作用但不能代谢的AA类似物）模拟并掩盖了在谷氨酸释放中观察到的阿司匹林的促进作用。此外，这种阿司匹林介导的谷氨酸释放促进作用可能依赖于蛋白激酶C（PKC）的激活，因为PKC激活剂和PKC抑制剂分别增强或抑制了阿司匹林的促进作用。总之，这些结果表明，阿司匹林可能通过AA直接诱导PKC的激活，从而发挥其突触前促进作用，随后增强通过电压依赖性N型和P/Q型Ca(2+)通道的Ca(2+)内流，导致大鼠海马神经末梢诱发的谷氨酸释放增加。
