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Thies Peters - One of the best experts on this subject based on the ideXlab platform.

  • relaxation of evoked contractile activity of isolated guinea pig ileum by kavain
    Planta Medica, 1997
    Co-Authors: Ulrike Seitz, Johannes Gleitz, Angela Ameri, Helmut Pelzer, Thies Peters
    Abstract:

    : Kava pyrones are the pharmacologically active compounds of Piper methysticum Forst. In the present study, the effect of the synthetic kava pyrone (+/-)-kavain was investigated on evoked contractile activity of isolated guinea-pig ileum. (+/-)-Kavain (1 microM-1 mM) dose-dependently reduced contractions of ileum evoked by carbachol (10 microM), by BAY K 8644 (0.3 microM), or by substance P (0.05 microM). (+/-)-Kavain also inhibited the contractile responses induced by raising the extracellular K+ concentration from 4 to 20 mM and by blocking the K+ channel by barium chloride (1 mM) or 4-aminopyridine (0.3 mM). After pre-incubation with 1 microM nifedipine, carbachol (1 microM) evoked 18.2 +/- 14.3% of contraction at control (i.e. prior pre-incubation with nifedipine). This remaining response was completely abolished by high concentrations of (+/-)-kavain (400 microM). After treatment of the longitudinal ileum strips with pertussis toxin (PTX), carbachol (1 microM) evoked 27.0 +/- 6.2% of the control response in untreated ileum. These contractions were also blocked by (+/-)-kavain (400 microM). However, (+/-)-kavain had no effect on the caffeine-induced (20 mM) contractions of ileum strips, which were permeabilized with digitonin or beta-escin. Moreover, it failed to affect Ca(2+)-evoked contractions of skinned muscles. These results suggest that the kava pyrone (+/-)-kavain may act in a non-specific musculotropic way on the smooth muscle membrane.

  • antithrombotic action of the kava pyrone kavain prepared from piper methysticum on human platelets
    Planta Medica, 1997
    Co-Authors: Johannes Gleitz, A. Beile, Angela Ameri, P Wilkens, Thies Peters
    Abstract:

    (+)-Kavain, a 4-methoxy-α-pyrone prepared from Piper methysticum Forst. (Piperaceae), was investigated regarding its assumed antithrombotic action on human platelets which was deduced from its ability to suppress arachidonic acid (AA)-induced aggregation, exocytosis of ATP, and inhibition of cyclooxygenase (COX) and thromboxane synthase (TXS) activity, the latter two effects being estimated from the generation of prostaglandin E 2 (PGE 2 ) and thromboxane A 2 (TXA 2 ), respectively. Exogenously applied AA (100μmol/l) provoked a 90% aggregation of platelets, the release of 14pmol ATP, and the formation of either 220 pg TXA 2 or 43 pg PGE 2 , each parameter being related to 10 6 platelets. An application of (+)-kavain 5 min before AA, dose-dependently diminished aggregation, ATP-release, and the synthesis of TXA 2 and PGE 2 with IC 50 values of 78, 115, 71, and 86 μmol/l, respectively. The similarity of the IC 50 values suggest an inhibition of COX by (+)-kavain as primary target, thus suppressing the generation of TXA 2 which induces aggregation of platelets and exocytosis of ATP by its binding on TXA 2 -receptors.

  • kavain inhibits non stereospecifically veratridine activated na channels
    Planta Medica, 1996
    Co-Authors: Johannes Gleitz, Angela Ameri, Norbert Gottner, Thies Peters
    Abstract:

    : The action of the natural kava pyrone, (+)-kavain, and its synthetic racemate, (+/-)-kavain, on voltage-dependent Na+ channels was investigated, while considering their stereospecific properties, on veratridine-induced increases in cytosolic free Na+ and Ca2+ ([Na+]i, [Ca2+]i) and the release of endogenous glutamate from cerebrocortical synaptosomes. Both compounds dose-dependently suppressed the veratridine-induced increase in [Na+]i, [Ca2+]i and glutamate release with IC50 values (+/- S.D.) of 71 +/- 22, 72 +/- 7, 120 +/- 37 micromol/l (+)-kavain and 77 +/- 21, 90 +/- 14, 92 +/- 23 micromol/l (+/-)-kavain, respectively. As judged from the dose-dependency, IC50 values, velocity and time course of action, both kava pyrones were equally effective suggesting a non-stereospecific inhibition of veratridine-activated Na+ channels.

  • anticonvulsive action of kavain estimated from its properties on stimulated synaptosomes and na channel receptor sites
    European Journal of Pharmacology, 1996
    Co-Authors: Johannes Gleitz, A. Beile, Jutta Friese, Angela Ameri, Thies Peters
    Abstract:

    Abstract Kava pyrones are constituents of the intoxicating pepper (Piper methysticum Forst.), which has been shown to be anticonvulsive. The question of how the excitability of neurons is affected was investigated by determining the interaction of (±)-kavain with epitopes (site 1, site 2) of voltage-dependent Na+ channels and the action of (±)-kavain on 4-aminopyridine-stimulated synaptosomes as model of repetitive firing neurons. [3H]Saxitoxin and [3H]batrachotoxin were used for radioligand-binding assays performed with synaptosomal membranes. Glutamate released from 4-aminopyridine-stimulated cerebrocortical synaptosomes and the cytosolic concentrations of Na+ and Ca2+ ([Na+]i, [Ca2+]i) were detected fluorometrically by using an enzyme-linked assay, sodium-binding benzofuranisophthalate (SBFI) and Fura-2, respectively. (±)-Kavain failed to compete with [3H]saxitoxin up to 400 μmol/l but dose-dependently suppressed binding of [3H]batrachotoxin with an IC50 value of 88 μmol/l (Ki = 72 μmol/l) although displacement of [3H]batrachotoxin was restricted to 33% of control at 400 μmol/l (±)-kavain. In stimulated synaptosomes, 5 mmol/1 4-aminopyridine provoked an increase in [Na+]i and [Ca2+]i by 9 mmol/l Na+ and 235 nmol/l Ca2+. Comparable to the reduction in [3H]batrachotoxin binding, 400 μmol/l (±)-kavain suppressed the increase in [Na+]i and [Ca2+]i to 38 and 29% of control, respectively. Consistent with the increase in [Na+]i and [Ca2+]i, 5 mmol/l 4-aminopyridine provoked glutamate release (rate: 38 pmol/s∗mg protein) which was dose-dependently diminished to 60% of control by 400 μmol/l (±)-kavain. KCl depolarization (40 mmol/l) provoked an increase in [Ca2+]i and glutamate release almost identical to the responses elicited by 4-aminopyridine but 400 μmol/l (±)-kavain suppressed only the rate of glutamate release by 9% of control. The data suggest an interaction of (±)-kavain with voltage-dependent Na+ and Ca2+ channels, thereby suppressing the 4-aminopyridine-induced increase in [Na+]i, [Ca2+]i and the release of endogenous glutamate.

  • kavain inhibits the veratridine and kcl induced increase in intracellular ca2 and glutamate release of rat cerebrocortical synaptosomes
    Neuropharmacology, 1996
    Co-Authors: Johannes Gleitz, A. Beile, Thies Peters
    Abstract:

    Abstract The action of (±)-kavain on the veratridine, monensin and KCl-depolarization evoked increase in free cytosolic Ca2− concentration ([Ca2+]i), and its influence on the release of endogenous glutamate from rat cerebrocortical synaptosomes were investigated. [Ca2+]i was fluorimetrically determined employing FURA as the Ca2+ sensitive fluorophore, and glutamate was detected by a continuous enzyme-linked fluorimetric assay. The incubation of synaptosomes in the presence of (±)-kavain up to a concentration of 500 μmol/l affected neither basal [Ca2+]i nor spontaneous release of glutamate, but dose-dependently reduced both veratridineelevated [Ca2+]i (IC50 = 63.2 μmol/l) and glutamate-release (IC50 = 116.4 μmol/l). The inhibition of these parameters, attained with 500 μmol/l (±)-kavain, could be overcome by inducing an artificial Na+ influx, using monensin as a Na+ ionophore. An application of (±)-kavain after veratridine caused a decrease in veratridineelevated [Ca2+]i, which was similar to the action of tetrodotoxin (TTX) with regard to time course, half-life of [Ca2+]i decline and the final steady state level of [Ca2+]i. Concomitantly, veratridine-induced glutamate-release was blocked. The results indicate that specific inhibition of voltage-dependent Na+ channels is a primary target of (±)-kavain, thus preventing a [Na+]i provoked increase in [Ca2+]i and glutamate-release. However, pathways related to the elevation of [Ca2+]i by [Na+]i itself, and the processes involved in normalization of elevated [Ca2+]i and glutamate-release downstream to enhanced [Ca2+]i, seems to be unaffected by (±)-kavain. Using KCl-depolarized synaptosomes, 400 μmol/l (±)-kavain reduced, in analogy to Aga-GI toxin, KCl-evoked [Ca2+]i and diminished the part of glutamate-exocytosis which is related to external Ca2+ to about 75% of control. At a concentration of 150 μmol/l, which is above the IC50 value necessary to block voltagedependent Na+ channels, (±)-kavain affected neither basal nor the KCl-induced increase in [Ca2+]i. These results might suggest that (±)-kavain at concentrations sufficient to block Na+ channels completely, moderately inhibits the non-inactivating Ca2+ channels located on mammalian presynaptic nerve endings.

Johannes Gleitz - One of the best experts on this subject based on the ideXlab platform.

  • kava extract ingredients methysticin and kavain inhibit voltage operated na channels in rat ca1 hippocampal neurons
    Neuroscience, 1997
    Co-Authors: E. I. Magura, M. V. Kopanitsa, Johannes Gleitz, Theo A Peters, O.a. Krishtal
    Abstract:

    Abstract The action of synthetic kava pyrones, (+)-methysticin and (±)-kavain, on voltage-operated Na + -channels was studied in whole-cell patch-clamped CA1 hippocampal neurons. In doses of 1–400 μM, both compounds exerted a rapid and reversible inhibition of the peak amplitude of Na + -currents. Shifting holding membrane potential (V hold ) to more positive values enhanced their blocking effect. The drugs studied did not demonstrate use-dependent properties at 10 Hz stimulation but shifted h ∞ curve toward more negative potentials, accelerated time course of inactivation and slowed down the recovery from inactivation. Voltage-dependence of Na + -channel inhibition can be explained by interaction of (+)-methysticin and (±)-kavain with resting closed and inactivated states of Na + -channel.

  • relaxation of evoked contractile activity of isolated guinea pig ileum by kavain
    Planta Medica, 1997
    Co-Authors: Ulrike Seitz, Johannes Gleitz, Angela Ameri, Helmut Pelzer, Thies Peters
    Abstract:

    : Kava pyrones are the pharmacologically active compounds of Piper methysticum Forst. In the present study, the effect of the synthetic kava pyrone (+/-)-kavain was investigated on evoked contractile activity of isolated guinea-pig ileum. (+/-)-Kavain (1 microM-1 mM) dose-dependently reduced contractions of ileum evoked by carbachol (10 microM), by BAY K 8644 (0.3 microM), or by substance P (0.05 microM). (+/-)-Kavain also inhibited the contractile responses induced by raising the extracellular K+ concentration from 4 to 20 mM and by blocking the K+ channel by barium chloride (1 mM) or 4-aminopyridine (0.3 mM). After pre-incubation with 1 microM nifedipine, carbachol (1 microM) evoked 18.2 +/- 14.3% of contraction at control (i.e. prior pre-incubation with nifedipine). This remaining response was completely abolished by high concentrations of (+/-)-kavain (400 microM). After treatment of the longitudinal ileum strips with pertussis toxin (PTX), carbachol (1 microM) evoked 27.0 +/- 6.2% of the control response in untreated ileum. These contractions were also blocked by (+/-)-kavain (400 microM). However, (+/-)-kavain had no effect on the caffeine-induced (20 mM) contractions of ileum strips, which were permeabilized with digitonin or beta-escin. Moreover, it failed to affect Ca(2+)-evoked contractions of skinned muscles. These results suggest that the kava pyrone (+/-)-kavain may act in a non-specific musculotropic way on the smooth muscle membrane.

  • antithrombotic action of the kava pyrone kavain prepared from piper methysticum on human platelets
    Planta Medica, 1997
    Co-Authors: Johannes Gleitz, A. Beile, Angela Ameri, P Wilkens, Thies Peters
    Abstract:

    (+)-Kavain, a 4-methoxy-α-pyrone prepared from Piper methysticum Forst. (Piperaceae), was investigated regarding its assumed antithrombotic action on human platelets which was deduced from its ability to suppress arachidonic acid (AA)-induced aggregation, exocytosis of ATP, and inhibition of cyclooxygenase (COX) and thromboxane synthase (TXS) activity, the latter two effects being estimated from the generation of prostaglandin E 2 (PGE 2 ) and thromboxane A 2 (TXA 2 ), respectively. Exogenously applied AA (100μmol/l) provoked a 90% aggregation of platelets, the release of 14pmol ATP, and the formation of either 220 pg TXA 2 or 43 pg PGE 2 , each parameter being related to 10 6 platelets. An application of (+)-kavain 5 min before AA, dose-dependently diminished aggregation, ATP-release, and the synthesis of TXA 2 and PGE 2 with IC 50 values of 78, 115, 71, and 86 μmol/l, respectively. The similarity of the IC 50 values suggest an inhibition of COX by (+)-kavain as primary target, thus suppressing the generation of TXA 2 which induces aggregation of platelets and exocytosis of ATP by its binding on TXA 2 -receptors.

  • kavain inhibits non stereospecifically veratridine activated na channels
    Planta Medica, 1996
    Co-Authors: Johannes Gleitz, Angela Ameri, Norbert Gottner, Thies Peters
    Abstract:

    : The action of the natural kava pyrone, (+)-kavain, and its synthetic racemate, (+/-)-kavain, on voltage-dependent Na+ channels was investigated, while considering their stereospecific properties, on veratridine-induced increases in cytosolic free Na+ and Ca2+ ([Na+]i, [Ca2+]i) and the release of endogenous glutamate from cerebrocortical synaptosomes. Both compounds dose-dependently suppressed the veratridine-induced increase in [Na+]i, [Ca2+]i and glutamate release with IC50 values (+/- S.D.) of 71 +/- 22, 72 +/- 7, 120 +/- 37 micromol/l (+)-kavain and 77 +/- 21, 90 +/- 14, 92 +/- 23 micromol/l (+/-)-kavain, respectively. As judged from the dose-dependency, IC50 values, velocity and time course of action, both kava pyrones were equally effective suggesting a non-stereospecific inhibition of veratridine-activated Na+ channels.

  • anticonvulsive action of kavain estimated from its properties on stimulated synaptosomes and na channel receptor sites
    European Journal of Pharmacology, 1996
    Co-Authors: Johannes Gleitz, A. Beile, Jutta Friese, Angela Ameri, Thies Peters
    Abstract:

    Abstract Kava pyrones are constituents of the intoxicating pepper (Piper methysticum Forst.), which has been shown to be anticonvulsive. The question of how the excitability of neurons is affected was investigated by determining the interaction of (±)-kavain with epitopes (site 1, site 2) of voltage-dependent Na+ channels and the action of (±)-kavain on 4-aminopyridine-stimulated synaptosomes as model of repetitive firing neurons. [3H]Saxitoxin and [3H]batrachotoxin were used for radioligand-binding assays performed with synaptosomal membranes. Glutamate released from 4-aminopyridine-stimulated cerebrocortical synaptosomes and the cytosolic concentrations of Na+ and Ca2+ ([Na+]i, [Ca2+]i) were detected fluorometrically by using an enzyme-linked assay, sodium-binding benzofuranisophthalate (SBFI) and Fura-2, respectively. (±)-Kavain failed to compete with [3H]saxitoxin up to 400 μmol/l but dose-dependently suppressed binding of [3H]batrachotoxin with an IC50 value of 88 μmol/l (Ki = 72 μmol/l) although displacement of [3H]batrachotoxin was restricted to 33% of control at 400 μmol/l (±)-kavain. In stimulated synaptosomes, 5 mmol/1 4-aminopyridine provoked an increase in [Na+]i and [Ca2+]i by 9 mmol/l Na+ and 235 nmol/l Ca2+. Comparable to the reduction in [3H]batrachotoxin binding, 400 μmol/l (±)-kavain suppressed the increase in [Na+]i and [Ca2+]i to 38 and 29% of control, respectively. Consistent with the increase in [Na+]i and [Ca2+]i, 5 mmol/l 4-aminopyridine provoked glutamate release (rate: 38 pmol/s∗mg protein) which was dose-dependently diminished to 60% of control by 400 μmol/l (±)-kavain. KCl depolarization (40 mmol/l) provoked an increase in [Ca2+]i and glutamate release almost identical to the responses elicited by 4-aminopyridine but 400 μmol/l (±)-kavain suppressed only the rate of glutamate release by 9% of control. The data suggest an interaction of (±)-kavain with voltage-dependent Na+ and Ca2+ channels, thereby suppressing the 4-aminopyridine-induced increase in [Na+]i, [Ca2+]i and the release of endogenous glutamate.

Salomon Amar - One of the best experts on this subject based on the ideXlab platform.

  • Identification of a Kavain Analog with Efficient Anti-inflammatory Effects.
    Scientific Reports, 2019
    Co-Authors: Olivier Huck, Hannah Mulhall, Iryna Gumenchuk, Radha Iyer, James S Panek, Salomon Amar
    Abstract:

    : Kavain, a compound derived from Piper methysticum, has demonstrated anti-inflammatory properties. To optimize its drug properties, identification and development of new kavain-derived compounds was undertaken. A focused library of analogs was synthesized and their effects on Porphyromonas gingivalis (P. gingivalis) elicited inflammation were evaluated in vitro and in vivo. The library contained cyclohexenones (5,5-dimethyl substituted cyclohexenones) substituted with a benzoate derivative at the 3-position of the cyclohexanone. The most promising analog identifed was a methylated derivative of kavain, Kava-205Me (5,5-dimethyl-3-oxocyclohex-1-en-1-yl 4-methylbenzoate.) In an in vitro assay of anti-inflammatory effects, murine macrophages (BMM) and THP-1 cells were infected with P. gingivalis (MOI = 20:1) and a panel of cytokines were measured. Both cell types treated with Kava-205Me (10 to 200 μg/ml) showed significantly and dose-dependently reduced TNF-α secretion induced by P. gingivalis. In BMM, Kava-205Me also reduced secretion of other cytokines involved in the early phase of inflammation, including IL-12, eotaxin, RANTES, IL-10 and interferon-γ (p 

  • kavain reduces porphyromonas gingivalis induced adipocyte inflammation role of pgc 1α signaling
    Journal of Immunology, 2018
    Co-Authors: Shailendra P. Singh, Nader G. Abraham, Olivier Huck, Salomon Amar
    Abstract:

    A link between obesity and periodontitis has been suggested because of compromised immune response and chronic inflammation in obese patients. In this study, we evaluated the anti-inflammatory properties of Kavain, an extract from Piper methysticum , on Porphyromonas gingivalis –induced inflammation in adipocytes with special focus on peroxisome proliferation–activated receptor γ coactivator α (PGC-1α) and related pathways. The 3T3-L1 mouse preadipocytes and primary adipocytes harvested from mouse adipose tissue were infected with P. gingivalis, and inflammation (TNF-α; adiponectin/adipokines), oxidative stress, and adipogenic marker (FAS, CEBPα, and PPAR-γ) expression were measured. Furthermore, effect of PGC-1α knockdown on Kavain action was evaluated. Results showed that P. gingivalis worsens adipocyte dysfunction through increase of TNF-α, IL-6, and iNOS and decrease of PGC-1α and adiponectin. Interestingly, although Kavain obliterated P. gingivalis –induced proinflammatory effects in wild-type cells, Kavain did not affect PGC-1α–deficient cells, strongly advocating for Kavain effects being mediated by PGC-1α. In vivo adipocytes challenged with i.p. injection of P. gingivalis alone or P. gingivalis and Kavain displayed the same phenotype as in vitro adipocytes. Altogether, our findings established anti-inflammatory and antioxidant effects of Kavain on adipocytes and emphasized protective action against P. gingivalis –induced adipogenesis. The use of compounds such as Kavain offer a portal to potential therapeutic approaches to counter chronic inflammation in obesity-related diseases.

  • kavain involvement in lps induced signaling pathways
    Journal of Cellular Biochemistry, 2016
    Co-Authors: Xiaoren Tang, Salomon Amar
    Abstract:

    : Kavain, a compound extracted from the Kava plant, Piper methysticum, is found to be involved in TNF-α expression in human and mouse cells via regulation of transcriptional factors such as NF-kB and LITAF. LITAF is known to activate the transcription of more than 20 cytokines that are involved in a variety of cellular processes and is associated with many inflammatory diseases, including angiogenesis, cancer, arthritis, and more. The modulation of LITAF is expected to positively affect cytokine-mediated diseases. Thus, intensive efforts have been deployed in search of LITAF inhibitors. In this work, we found that, in vitro, Kavain reduced LPS- induced TNF-α secretion in mouse macrophages, mouse bone marrow macrophages (BMM), and human peripheral blood mononuclear cells (HPBMC). We also found that Kavain treatment in RAW264.7 cells deactivated MyD88 and Akt, inhibited LITAF, and reduced the production of TNF-α, IL-27, and MIG in response to LPS. Similarly, it had a significant in vivo anti-inflammatory effect on wild-type (WT) mice that developed Collagen Antibody Induced Arthritis (CAIA). Overall, MyD88 was found to be an important mediator of the LPS-induced inflammatory response that can be distinguished from the NF-κB pathway. We also found that MyD88 is involved in the pathway linking LPS/LITAF to TNF-α. Therefore, given that Kavain modulates LPS-induced signaling pathways leading to cytokine expression, therapeutic interventions involving Kavain in inflammatory diseases are warranted. J. Cell. Biochem. 117: 2272-2280, 2016. © 2016 Wiley Periodicals, Inc.

  • kavain inhibition of lps induced tnf α via erk litaf
    Toxicology Research, 2016
    Co-Authors: Xiaoren Tang, Salomon Amar
    Abstract:

    Kavain, an extract from the shrub Piper methysticum, was recently reported to modulate TNF-α expression in both human and mouse cells via regulation of LPS-Induced TNF-Alpha Factor (LITAF). The purpose of the present study was to define the molecular pathway(s) associated with Kavain′s effects on TNF modulation. In vitro studies using WT mouse primary macrophages showed that Kavain significantly reduced E. coli LPS-induced TNF-α production but this effect was almost abrogated in LITAF−/− and ERK2−/− cells. Therefore we reintroduced the ERK2 gene in ERK2−/− cells and partially restored E. coli LPS-induced LITAF-mediated TNF-α production. The translocation of LITAF into to nucleus was found to be dependent on ERK2 S206 residue. Kavain inhibits LITAF/TNF-α expression via dephosphorylation of ERK2 in response to E. coli LPS. Finally, in vivo, Kavain had a significant anti-inflammatory effect on wild type mice that developed Collagen Antibody Induced Arthritis (CAIA), but only a minor effect in ERK2−/− mice also affected by CAIA. Based on these findings, we concluded that ERK2 may be the kinase upstream for LITAF being a crucial factor for Kavain-mediated regulation of LPS-induced TNF-α.

  • kavain inhibition of lps induced tnf α via erk litaf
    Toxicology Research, 2016
    Co-Authors: Xiaoren Tang, Salomon Amar
    Abstract:

    Kavain, an extract from the shrub Piper Methysticum, was recently reported to modulate TNF-α expression in both human and mouse cells via regulation of LPS-Induced TNF-Alpha Factor (LITAF). The purpose of the present study was to define the molecular pathway(s) associated with Kavain effects on TNF modulation. In vitro studies using WT mouse primary macrophages showed that Kavain significantly reduced E.coli LPS-induced TNF-α production but this effect was almost abrogated in LITAF-/- and ERK2-/- cells. Therefore we reintroduced the ERK2 gene in ERK2-/- cells and partially restored E.coli LPS-induced LITAF-mediated TNF-α production. The translocation of LITAF into to nucleus was found to be dependent on ERK2 S206 residue. Kavain inhibits LITAF/TNF-α expression via dephosphorylation of ERK2 in response to E.coli LPS. Finally, in vivo, Kavain had a significant anti-inflammatory effect on wild type mice that developed Collagen Antibody Induced Arthritis (CAIA), but only a minor effect in ERK2-/- mice also affected by CAIA. Based on these findings, we concluded that ERK2 may be the kinase upstream of LITAF with its Serine residue 206 being crucial for the regulation of LPS-induced TNF-α.

Iqbal Ramzan - One of the best experts on this subject based on the ideXlab platform.

  • kavain the major constituent of the anxiolytic kava extract potentiates gabaa receptors functional characteristics and molecular mechanism
    PLOS ONE, 2016
    Co-Authors: Han Chow Chua, Emilie T H Christensen, Kirsten Hoestgaardjensen, Leonny Y Hartiadi, Nathan Absalom, Anders A Jensen, Iqbal Ramzan, Mary Chebib
    Abstract:

    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.

  • Kavalactones Yangonin and Methysticin induce apoptosis in human hepatocytes (HepG2) in vitro.
    Phytotherapy research : PTR, 2010
    Co-Authors: J. Tang, Rachael A. Dunlop, Kenneth J. Rodgers, Anthony Rowe, Iqbal Ramzan
    Abstract:

    While cases of severe kava hepatotoxicity have been reported, studies examining the toxicity of individual kavalactones are limited. The present study examined the in vitro hepatotoxicity of kavain, methysticin and yangonin on human hepatocytes (HepG2) and the possible mechanism(s) involved. Cytotoxicity was assessed using lactate dehydrogenase (LDH) and ethidium bromide (EB) assays. The mode of cell death was analysed with acridine orange/ethidium bromide dual staining with fluorescence microscopy. Glutathione oxidation was measured using the ortho-phthalaldehyde (OPT) fluorescence assay. Kavain had minimal cytotoxicity, methysticin showed moderate concentration-dependent toxicity and yangonin displayed marked toxicity with ~ 40% reduction in viability in the EB assay. Acridine orange/ethidium bromide staining showed the predominant mode of cell death was apoptosis rather than necrosis. No significant changes were observed in glutathione levels, excluding this as the primary mechanism of cell death in this model. Further studies may elucidate the precise apoptotic pathways responsible and whether toxic kavalactone metabolites are involved.

  • high performance liquid chromatography assays for desmethoxyyangonin methysticin kavain and their microsomal metabolites
    Biomedical Chromatography, 2009
    Co-Authors: Shuang Fu, Bruce N Tattam, Colin C. Duke, Iqbal Ramzan
    Abstract:

    Three novel, simple and reproducible high-performance liquid chromatography quantitative assays with UV detection were developed and validated for three major kavalactones—desmethoxyyangonin, methysticin and kavain—in rat liver microsomes using diazepam as an internal standard; liquid–liquid extraction was used for sample preparation and analysis was performed on a Shimadzu® 10A high-performance liquid chromatography system. The analysis was carried out in reversed-phase mode with a Luna® C18 column (150 × 2.00 mm, 3 µm) at 40°C. The limit of quantitation was 0.1 µg/mL using 0.25 mL of microsomal solution. The assays were linear over the range 0.1–10 µg/mL for desmethoxyyangonin, methysticin and kavain. Quality control samples exhibited good accuracy and precision with relative standard deviations lower than 15% and recoveries between 85 and 105%. The assays exhibited satisfactory performance with high sensitivity for quantifying desmethoxyyangonin, methysticin and kavain in rat liver microsomes and were successfully used to determine the three kavalactones and their microsomal metabolites. Copyright © 2008 John Wiley & Sons, Ltd.

  • High-performance liquid chromatography assays for desmethoxyyangonin, methysticin, kavain and their microsomal metabolites.
    Biomedical chromatography : BMC, 2009
    Co-Authors: Bruce N Tattam, Colin C. Duke, Iqbal Ramzan
    Abstract:

    Three novel, simple and reproducible high-performance liquid chromatography quantitative assays with UV detection were developed and validated for three major kavalactones--desmethoxyyangonin, methysticin and kavain--in rat liver microsomes using diazepam as an internal standard; liquid-liquid extraction was used for sample preparation and analysis was performed on a Shimadzu 10A high-performance liquid chromatography system. The analysis was carried out in reversed-phase mode with a Luna C(18) column (150 x 2.00 mm, 3 microm) at 40 degrees C. The limit of quantitation was 0.1 microg/mL using 0.25 mL of microsomal solution. The assays were linear over the range 0.1-10 microg/mL for desmethoxyyangonin, methysticin and kavain. Quality control samples exhibited good accuracy and precision with relative standard deviations lower than 15% and recoveries between 85 and 105%. The assays exhibited satisfactory performance with high sensitivity for quantifying desmethoxyyangonin, methysticin and kavain in rat liver microsomes and were successfully used to determine the three kavalactones and their microsomal metabolites.

  • influence of kavain on hepatic ultrastructure
    World Journal of Gastroenterology, 2008
    Co-Authors: Shuang Fu, Emine Korkmaz, Filip Braet, Iqbal Ramzan
    Abstract:

    AIM: To investigate whether the major kavalactone kavain imposes adverse effects on the liver ultrastructure and function by affecting vascular and microvascular architecture and altering hepatocellular morphology. METHODS: Kavain solution (10 μg/mL or 43.5 μmol/L) was perfused for 2 h in isolated rat livers. After standard fixation and tissue preparation, the samples were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and light microscopy (LM). RESULTS: LM, SEM, and TEM examinations indicated kavain-treated rat livers (n = 4) displayed severe vascular and endothelial damage compared to control livers (n = 4). CONCLUSION: The data so far support the hypothesis that kavain induces adverse effects on liver; additional investigations with other kavalactones and their effects on liver are urgently needed.

Jorg Walden - One of the best experts on this subject based on the ideXlab platform.

  • effects of kavain on voltage activated inward currents of dorsal root ganglion cells from neonatal rats
    European Neuropsychopharmacology, 1999
    Co-Authors: K. Schirrmacher, Jorg Walden, Jens M. Langosch, U Winter, Dietrich Büsselberg, Dieter Bingmann
    Abstract:

    Abstract Kava pyrones extracted from pepper Piper methysticum are pharmacologically active compounds. Since kava pyrones exhibit anticonvulsive, analgesic and centrally muscle relaxing properties, the influence of a synthetic kava pyrone, (±)-kavain, on voltage-dependent ion channel currents was studied. Effects of (±)-kavain on voltage-activated inward currents were analysed in cultured dorsal root ganglion cells derived from neonatal rats. Voltage-activated Ca 2+ and Na + currents were elicited in the whole-cell configuration of the patch clamp technique. Extracellularly applied (±)-kavain dissolved in hydrous salt solutions reduced voltage-activated Ca 2+ and Na + channel currents within 3–5 min. As the solubility of (±)-kavain in hydrous solutions is low, dimethyl sulfoxide (DMSO) was added to the saline as a solvent for the drug in most experiments. When (±)-kavain was dissolved in DMSO, the drug induced a fast and pronounced reduction of both Ca 2+ and Na + currents, which partly recovered within 2–5 min even in the presence of the drug. The present study indicates that (±)-kavain reduces currents through voltage-activated Na + and Ca 2+ channels.

  • the influence of kavain on population spikes and long term potentiation in guinea pig hippocampal slices
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 1998
    Co-Authors: Jens M. Langosch, K. Schirrmacher, Claus Normann, M Berger, Jorg Walden
    Abstract:

    Abstract Little is known about the mechanisms of action of kava pyrones which are the pharmacological active compounds of the plant Piper methysticum Forst. We investigated the effects of the synthetic kava pyrone (±)-kavain on long-term potentiation (LTP) in the CA1-region of guinea pig hippocampal slices. (±)-Kavain reduced the amplitudes of extracellular field potential changes evoked by electrical stimulation in a concentration dependent manner. These effects were reversible. In experiments with LTP no changes were found in the presence of (±)-kavain. In conclusion, our findings suggest (±)-kavain to be an effective drug in modulating excitatory signals in the hippocampus of guinea pigs. Additionally, no alterations on synaptic plasticity in hippocampal neurons for this kava pyrone can be presumed.

  • effects of Kawain and dihydromethysticin on field potential changes in the hippocampus
    Progress in Neuro-psychopharmacology & Biological Psychiatry, 1997
    Co-Authors: Jorg Walden, Jorg Von Wegerer, Ute Winter, Heinz Grunze
    Abstract:

    Abstract 1. 1. The kava-pyrones Kawain and dihydromethysticin are constituents of Piper methysticum which exert anticonvulsant, analgesic and anxiolytic properties. 2. 2. In the present study the effect of these kava-pyrones were tested on field potential changes (fp) induced by omission of the extracellular Mg 2+ , recorded from the area CA1 and CA3 of the hippocampal slice preparation of guinea pigs. These fp are generated by an activation of NMDA receptors and voltage dependent calcium channels. 3. 3. Kawain and dihydromethysticin reduced reversibly the frequency of occurrence of fp in a concentration range from 5 to 40 μmol/1 and 10 to 40 μmol/1, respectively. 4. 4. Reduction of the fp frequency after addition of subthreshold concentrations of 5 μmol/1 Kawain and 10 μmol/1 dihydromethysticin indicated additive actions of both drugs. 5. 5. Since the serotonin-1A agonist ipsapirone also exerts anxiolytic effects, subthreshold concentrations of Kawain or dihydromethysticin were combined with a subthreshold concentration of ipsapirone in another set of experiments. Combining Kawain and ipsapirone or dihydromethysticin and ipsapirone caused a reduction of the rate of fp to 0.76 and 0.81 of the baseline value, respectively. 6. 6. The findings suggest that (i) single constituents of Piper methysticum may have additive actions, (ii) that the two components Kawain and dihydromethysticin may enhance the effects of the anxiolytic serotonin-1A agonist ipsapirone and (iii) that activation of NMDA receptors and/or voltage dependent calcium channels may be involved in the elementary mechanism of action of some kava-pyrones.

  • actions of kavain and dihydromethysticin on ipsapirone induced field potential changes in the hippocampus
    Human Psychopharmacology-clinical and Experimental, 1997
    Co-Authors: Jorg Walden, Jorg Von Wegerer, Ute Winter, Mitchel S. Berger
    Abstract:

    The kava-pyrones kavain and dihydromethysticin are constituents of Piper methysticum which possess muscle relaxant, anticonvulsant, analgesic and anxiolytic properties. In the present study the effect of both kava-pyrones were tested on field potential changes induced by the serotonin-1A agonist ipsapirone in the area CA1 and CA3 of the hippocampal slice preparation of guinea pigs. Ipsapirone induced positive field potential changes which were decreased in amplitude by the serotonin-1A antagonist NAN. The ipsapirone response was reduced by extracellular administration of kavain and dihydromethysticin in a dose-dependent manner down to 22·2 and 33·6%, respectively. It is suggested that kavain and dihydromethysticin modulate serotonin-1A receptor activity which may be of importance in the anti-anxiety action of kava-pyrones. © 1997 John Wiley & Sons, Ltd.