Kavain, the Major Constituent of the Anxiolytic Kava Extract, Potentiates GABAA Receptors: Functional Characteristics and Molecular Mechanism.
Kavain, the Major Constituent of the Anxiolytic Kava Extract, Potentiates GABAA Receptors: Functional Characteristics and Molecular Mechanism.
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DOI：
10.1371/journal.pone.0157700
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Chebib M
中科院分区：
文献类型：
--
作者：
Chua HC;Christensen ET;Hoestgaard-Jensen K;Hartiadi LY;Ramzan I;Jensen AA;Absalom NL;Chebib M
在临床试验中，辣椒植物卡瓦（Piper methysticum）的提取物有效缓解焦虑。尽管长期以来对卡瓦的治疗感兴趣，但其药理活性成分的分子靶点，卡瓦内酯尚未确定。根据结合实验数据，γ-氨基丁酸A型受体（GABAARs）被认为是卡瓦内酯的体内分子靶点，但支持卡瓦内酯和GABAARs之间直接相互作用的证据很少且模棱两可。本研究利用双电极电压钳技术，表征了主要抗焦虑药卡瓦内酯、卡瓦内酯在人重组α1β2、β2γ2L、αxβ2γ2L （x = 1,2,3和5）、α1βxγ2L （x = 1,2,3）和α4β2δ GABAARs在爪蟾卵母细胞中的功能特性。我们发现，无论亚基组成如何，kavain都能正向调节所有受体，但α4β2δ的增强程度大于α1β2γ2L的增强程度。kavain的调节作用不受氟马西尼的影响，表明kavain没有通过经典的苯二氮卓结合位点增强GABAARs。先前发现的β3N265M点突变能显著降低麻醉敏感性，也能减弱kavin介导的增强作用。据我们所知，这项研究首次报道了一种卡瓦内酯在不同GABAAR亚型中的功能特征，并提供了第一个支持卡瓦内酯和GABAAR之间直接相互作用的实验证据。
Extracts of the pepper plant kava (Piper methysticum) are effective in alleviating anxiety in clinical trials. Despite the long-standing therapeutic interest in kava, the molecular target(s) of the pharmacologically active constituents, kavalactones have not been established. γ-Aminobutyric acid type A receptors (GABAARs) are assumed to be the in vivo molecular target of kavalactones based on data from binding assays, but evidence in support of a direct interaction between kavalactones and GABAARs is scarce and equivocal. In this study, we characterised the functional properties of the major anxiolytic kavalactone, kavain at human recombinant α1β2, β2γ2L, αxβ2γ2L (x = 1, 2, 3 and 5), α1βxγ2L (x = 1, 2 and 3) and α4β2δ GABAARs expressed in Xenopus oocytes using the two-electrode voltage clamp technique. We found that kavain positively modulated all receptors regardless of the subunit composition, but the degree of enhancement was greater at α4β2δ than at α1β2γ2L GABAARs. The modulatory effect of kavain was unaffected by flumazenil, indicating that kavain did not enhance GABAARs via the classical benzodiazepine binding site. The β3N265M point mutation which has been previously shown to profoundly decrease anaesthetic sensitivity, also diminished kavain-mediated potentiation. To our knowledge, this study is the first report of the functional characteristics of a single kavalactone at distinct GABAAR subtypes, and presents the first experimental evidence in support of a direct interaction between a kavalactone and GABAARs.