(-)-epigallocatechin gallate, the most active polyphenolic catechin in green tea, presynaptically facilitates Ca2+-Dependent glutamate release via activation of protein kinase C in rat cerebral cortex
(-)-epigallocatechin gallate, the most active polyphenolic catechin in green tea, presynaptically facilitates Ca2+-Dependent glutamate release via activation of protein kinase C in rat cerebral cortex
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DOI：
10.1002/syn.20444
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发表时间：
2007-11-01
期刊：
影响因子：
2.3
通讯作者：
Wang, Su-Jane
中科院分区：
文献类型：
--
作者：
Chou, Chien-Wen;Huang, Wei-Jan;Wang, Su-Jane
（-）-表没食子儿茶素没食子酸酯（EGCG）是绿茶的主要多酚成分，据报道可以改善认知能力下降。考虑到中枢谷氨酸活性对认知功能至关重要，本研究的目的是利用从大鼠大脑皮层纯化的神经末梢来研究EGCG对内源性谷氨酸释放的影响。结果表明，4-氨基吡啶（4AP）引起的谷氨酸释放在EGCG的作用下呈浓度依赖性，这种作用是由于泡胞分泌的增强，而不是由于谷氨酸转运体Ca2+独立外排的增加。EGCG对胞质游离Ca2+浓度的影响（[Ca2+](c)）表明，谷氨酸释放的促进可能归因于通过N-和P/ q型电压依赖性Ca2+通道的Ca2+内流增加。与此一致的是，在Nand P/ q型Ca2+通道阻滞剂联合预处理的突触体中，egcg介导的4ap诱发的谷氨酸释放的促进作用被显著阻止。此外，Ro318220处理对蛋白激酶C （PKC）的抑制显著降低了EGCG对4ap诱发的谷氨酸释放和PKC或其突触前靶肌酰基化富丙氨酸C激酶底物（MARCKS）磷酸化的促进作用。这些结果表明，EGCG通过涉及PKC的信号级联，通过正向调节N-和P/ q型Ca2+通道激活，促进谷氨酸从谷氨酸能末端释放。在这个促进谷氨酸释放的EGCG/PKC信号级联中，细胞骨架动力学的调节也被证明参与了细胞骨架组织的破坏，细胞松弛素D阻断了EGCG介导的4ap诱发的谷氨酸释放的促进。
(-)-epigallocatechin gallate (EGCG), the main polyphenolic constituent of green,tea, has been reported to improve cognitive decline. Considering the central glutamatergic activity is crucial to cognitive function, the objective of this study was to investigate the effect of EGCG on the release of endogenous glutamate using nerve terminals purified from rat cerebral cortex. Results showed that the release of glutamate evoked by 4-aminopyridine (4AP) was facilitated by EGCG in a concentration-dependent manner, and this effect resulted from an enhancement of vesicular exocytosis and not from an increase in Ca2+-independent efflux via glutamate transporter. Examination of the effect of EGCG on cytoplasmic free Ca2+ concentration ([Ca2+](c)) revealed that the facilitation of glutamate release could be attributed to an increase in Ca2+ influx through N- and P/Q-type voltage-dependent Ca2+ channels. Consistent with this, the EGCG-mediated facilitation of 4AP-evoked glutamate release was significantly prevented in synaptosomes pretreated with a combination of the Nand P/Q-type Ca2+ channel blockers. Additionally, inhibition of protein kinase C (PKC) by treatment with Ro318220 significantly reduced the facilitatory effect of EGCG on 4AP-evoked glutamate release and phosphorylation of PKC or its presynapic target myristoylated alanine-rich C kinase substrate (MARCKS). These results suggest that EGCG effects a facilitation of glutamate release from glutamatergic terminals by positively modulating N- and P/Q-type Ca2+ channel activation through a signaling cascade involving PKC. In this EGCG/PKC signaling cascade facilitating glutamate release, the regulation of cytoskeleton dynamics was also indicated to be involved by disruption of cytoskeleton organization with cytochalasin D occluded the EGCG-mediated facilitation of 4AP-evoked glutamate release.