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PLoS One
2016 Jan 01;116:e0157700. doi: 10.1371/journal.pone.0157700.
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Kavain, the Major Constituent of the Anxiolytic Kava Extract, Potentiates GABAA Receptors: Functional Characteristics and Molecular Mechanism.
Chua HC
,
Christensen ET
,
Hoestgaard-Jensen K
,
Hartiadi LY
,
Ramzan I
,
Jensen AA
,
Absalom NL
,
Chebib M
.
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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.
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27332705
???displayArticle.pmcLink???PMC4917254 ???displayArticle.link???PLoS One
Fig 1. Chemical structures of the six major kavalactones found in kava.
Fig 2. Kavain potentiates GABAARs with no apparent subtype selectivity.(A) Representative traces demonstrating kavain (10–300 μM) enhancing current elicited by 10 μM GABA (EC3) at α1β2γ2L GABAARs in a concentration-dependent manner. (B) Representative traces of current responses elicited by a maximal concentration of GABA (10 mM), in comparison to 300 μM kavain alone. (C) Top panel, Potentiation of GABA-elicited currents (EC3-7) at α1β2, β2γ2L, αxβ2γ2L (x = 1, 2, 3 and 5) and α1βxγ2L (x = 1, 2 and 3) GABAARs by 300 μM kavain. At α4β2δ GABAARs, the GABA control (1 μM) corresponds to an EC30. Data are presented as mean ± SEM. Numbers in bars indicate the number of experiments. No significant difference was found for kavain potentiation at these receptor subtypes (Tukey’s test; p > 0.05 for all pairwise comparisons). Bottom panel, Superimposed current traces of GABA alone (black) and GABA in combination with 300 μM kavain (red) at the corresponding receptor subtypes. The black bars above the traces indicate duration of drug application.
Fig 3. Kavain produced greater enhancement of GABA-elicited currents at α4β2δ than at α1β2γ2L GABAARs.(A) GABA concentration-response curves in the absence (black; n = 10) and presence (red; n = 6) of 300 μM kavain at α1β2γ2L GABAARs. The curve parameters are summarised in Table 1. (B) GABA concentration-response curves in the absence (black; n = 4) and presence (red; n = 4) of 300 μM kavain at α4β2δ GABAARs. The curve parameters are summarised in Table 1. (C) Superimposed current responses of maximal GABA in the absence (black) and presence (red) of 300 μM kavain at α1β2γ2L and α4β2δ GABAARs. (D) The effect of kavain on the maximal GABA current responses at α1β2γ2L (n = 6) and α4β2δ (n = 7) GABAARs was compared using the paired t test, and the significance levels are indicated with n.s. (not significant) and **** (p < 0.0001). Data are presented as mean ± SEM.
Fig 4. Flumazenil-insensitive kavain potentiation has less-than-additive effect on diazepam action.Top, Representative traces demonstrating responses to control (10 μM GABA); control and 1 μM diazepam; control, 1 μM diazepam and 10 μM flumazenil; control and 10 μM flumazenil; control and 300 μM kavain; control, 300 μM kavain and 10 μM flumazenil; and control, 300 μM kavain and 1 μM diazepam. Bottom, The modulatory effect of diazepam, flumazenil and kavain at α1β2γ2L GABAARs (n = 5). Kavain potentiation was unchanged in the presence of flumazenil (G + K vs. G + K + F; p > 0.05; paired t test). The combination of kavain and diazepam (G + K + D) resulted in greater potentiation than diazepam (G + D; p < 0.001; paired t test) and kavain (G + K; p < 0.0001; paired t test) alone, but the effect was less than the expected additive modulatory effect (dotted line). Data are normalised to the current responses elicited by 10 μM GABA, and are presented as mean ± SEM.
Fig 5. Kavain modestly reduced etomidate potentiation, but did not affect the direct activation caused by etomidate at α1β2γ2L GABAARs.Top, Representative traces of current responses elicited by 10 mM GABA (control); 10 μM GABA; 10 μM GABA and 300 μM kavain; 10 μM GABA and 3 μM etomidate; 10 μM GABA, 300 μM kavain and 3 μM etomidate; 30 μM etomidate; 30 μM etomidate and 300 μM kavain. Bottom, Kavain caused a subtle but significant reduction in etomidate potentiation (G2 + E1 vs. G2 + K + E1; n = 7; p < 0.01; paired t test), but had no effect on etomidate activation (E2 vs. E2 + K; n = 6; p > 0.05; paired t test). Data are normalised to the 10 mM GABA responses, and are presented as mean ± SEM.
Fig 6. Kavain did not affect propofol potentiation, but modestly reduced propofol activation at α1β2γ2L GABAARs.Top, Representative traces of current responses to 10 mM GABA (control); 10 μM GABA; 10 μM GABA and 300 μM kavain; 10 μM GABA and 10 μM propofol; 10 μM GABA, 300 μM kavain and 10 μM propofol. Middle, Continuous traces demonstrating two consecutive applications of control (100 μM propofol) followed by the co-application of 300 μM kavain with control; and control. Bottom, Receptor modulation produced by propofol alone (G2 + P) was not significantly different from the combination of kavain and propofol (G2 + K + P; n = 5; p > 0.05; paired t test). The agonist effect of propofol (P2) was significantly reduced in the presence of kavain (P2 + K; n = 5; p < 0.01; paired t test). Data are presented as mean ± SEM.
Fig 7. The pronounced effect of β3N265M point mutation on etomidate and propofol sensitivity.(A) Representative traces demonstrating the modulatory effect of 3 μM etomidate and 10 μM propofol on GABA EC3 (left) and the agonist effect of 30 μM etomidate and 100 μM propofol relative to 10 mM GABA (right) at α1β3γ2L and α1β3N265Mγ2L GABAARs. (B) The modulatory and agonist effects of etomidate and propofol were markedly diminished at α1β3N265Mγ2L GABAARs. Data are normalised to current responses elicited by 10 mM GABA, and are presented as mean ± SEM. *** p < 0.001; **** p < 0.0001; unpaired t test (mutant vs. wild-type). Numbers above bars indicate number of experiments. GABA + ETO: GABA EC3 + 3 μM etomidate; ETO: 30 μM etomidate; GABA + PRO: GABA EC3 + 10 μM propofol; PRO: 100 μM propofol.
Anke,
Pharmacokinetic and pharmacodynamic drug interactions with Kava (Piper methysticum Forst. f.).
2004, Pubmed
Anke,
Pharmacokinetic and pharmacodynamic drug interactions with Kava (Piper methysticum Forst. f.).
2004,
Pubmed
Bianchi,
Neurosteroids shift partial agonist activation of GABA(A) receptor channels from low- to high-efficacy gating patterns.
2003,
Pubmed
Boonen,
Influence of genuine kavapyrone enantiomers on the GABA-A binding site.
1998,
Pubmed
Cairney,
The neurobehavioural effects of kava.
2002,
Pubmed
Chua,
The Direct Actions of GABA, 2'-Methoxy-6-Methylflavone and General Anaesthetics at β3γ2L GABAA Receptors: Evidence for Receptors with Different Subunit Stoichiometries.
2015,
Pubmed
,
Xenbase
Davies,
Kava pyrones and resin: studies on GABAA, GABAB and benzodiazepine binding sites in rodent brain.
1992,
Pubmed
Desai,
Gamma-amino butyric acid type A receptor mutations at beta2N265 alter etomidate efficacy while preserving basal and agonist-dependent activity.
2009,
Pubmed
,
Xenbase
Dinh,
Interaction of various Piper methysticum cultivars with CNS receptors in vitro.
2001,
Pubmed
Feng,
Multiple actions of propofol on alphabetagamma and alphabetadelta GABAA receptors.
2004,
Pubmed
Feng,
Etomidate produces similar allosteric modulation in α1β3δ and α1β3γ2L GABA(A) receptors.
2014,
Pubmed
,
Xenbase
Feng,
Pentobarbital differentially modulates alpha1beta3delta and alpha1beta3gamma2L GABAA receptor currents.
2004,
Pubmed
Franks,
Molecular and cellular mechanisms of general anaesthesia.
1994,
Pubmed
Garcia,
General anesthetic actions on GABA(A) receptors.
2010,
Pubmed
Garrett,
Extracts of kava (Piper methysticum) induce acute anxiolytic-like behavioral changes in mice.
2003,
Pubmed
Hartiadi,
High and low GABA sensitivity α4β2δ GABAA receptors are expressed in Xenopus laevis oocytes with divergent stoichiometries.
2016,
Pubmed
,
Xenbase
Holm,
[The action profile of D,L-kavain. Cerebral sites and sleep-wakefulness-rhythm in animals].
1991,
Pubmed
Janssen,
Etomidate, R-(+)-ethyl-1-( -methyl-benzyl)imidazole-5-carboxylate (R 16659), a potent, short-acting and relatively atoxic intravenous hypnotic agent in rats.
1971,
Pubmed
Jonsson Fagerlund,
Reduced effect of propofol at human {alpha}1{beta}2(N289M){gamma}2 and {alpha}2{beta}3(N290M){gamma}2 mutant GABA(A) receptors.
2010,
Pubmed
,
Xenbase
Jussofie,
Kavapyrone enriched extract from Piper methysticum as modulator of the GABA binding site in different regions of rat brain.
1994,
Pubmed
Keledjian,
Uptake into mouse brain of four compounds present in the psychoactive beverage kava.
1988,
Pubmed
Khom,
Valerenic acid potentiates and inhibits GABA(A) receptors: molecular mechanism and subunit specificity.
2007,
Pubmed
,
Xenbase
Krasowski,
Methionine 286 in transmembrane domain 3 of the GABAA receptor beta subunit controls a binding cavity for propofol and other alkylphenol general anesthetics.
2001,
Pubmed
Kuchta,
German Kava Ban Lifted by Court: The Alleged Hepatotoxicity of Kava (Piper methysticum) as a Case of Ill-Defined Herbal Drug Identity, Lacking Quality Control, and Misguided Regulatory Politics.
2015,
Pubmed
Ligresti,
Kavalactones and the endocannabinoid system: the plant-derived yangonin is a novel CB₁ receptor ligand.
2012,
Pubmed
Lindenberg,
[D,L-kavain in comparison with oxazepam in anxiety disorders. A double-blind study of clinical effectiveness].
1990,
Pubmed
Mathews,
Pharmacokinetics and disposition of the kavalactone kawain: interaction with kava extract and kavalactones in vivo and in vitro.
2005,
Pubmed
Pittler,
Kava extract for treating anxiety.
2003,
Pubmed
Rudolph,
Molecular and neuronal substrates for general anaesthetics.
2004,
Pubmed
Sarris,
Kava in the treatment of generalized anxiety disorder: a double-blind, randomized, placebo-controlled study.
2013,
Pubmed
Sarris,
Kava: a comprehensive review of efficacy, safety, and psychopharmacology.
2011,
Pubmed
Sarris,
Kava for the treatment of generalized anxiety disorder RCT: analysis of adverse reactions, liver function, addiction, and sexual effects.
2013,
Pubmed
Sarris,
The Kava Anxiety Depression Spectrum Study (KADSS): a randomized, placebo-controlled crossover trial using an aqueous extract of Piper methysticum.
2009,
Pubmed
Savage,
Kava for the treatment of generalised anxiety disorder (K-GAD): study protocol for a randomised controlled trial.
2015,
Pubmed
Sebel,
Additive effects of sevoflurane and propofol on gamma-aminobutyric acid receptor function.
2006,
Pubmed
Showman,
Contemporary Pacific and Western perspectives on `awa (Piper methysticum) toxicology.
2015,
Pubmed
Singh,
Kava: an overview.
1992,
Pubmed
Spigelman,
Reduced inhibition and sensitivity to neurosteroids in hippocampus of mice lacking the GABA(A) receptor delta subunit.
2003,
Pubmed
Stell,
Neuroactive steroids reduce neuronal excitability by selectively enhancing tonic inhibition mediated by delta subunit-containing GABAA receptors.
2003,
Pubmed
Stell,
Receptors with different affinities mediate phasic and tonic GABA(A) conductances in hippocampal neurons.
2002,
Pubmed
Stewart,
Tryptophan mutations at azi-etomidate photo-incorporation sites on alpha1 or beta2 subunits enhance GABAA receptor gating and reduce etomidate modulation.
2008,
Pubmed
,
Xenbase
Teschke,
Proposal for a kava quality standardization code.
2011,
Pubmed
Teschke,
Kava, the anxiolytic herb: back to basics to prevent liver injury?
2011,
Pubmed
Tsutsui,
Hypnotic and sleep quality-enhancing properties of kavain in sleep-disturbed rats.
2009,
Pubmed
Uebelhack,
Inhibition of platelet MAO-B by kava pyrone-enriched extract from Piper methysticum Forster (kava-kava).
1998,
Pubmed
Walters,
Benzodiazepines act on GABAA receptors via two distinct and separable mechanisms.
2000,
Pubmed
,
Xenbase
Yuan,
Kavalactones and dihydrokavain modulate GABAergic activity in a rat gastric-brainstem preparation.
2002,
Pubmed