Post-insult exposure to (+/-) kavain potentiates N-methyl-D-aspartate toxicity in the developing hippocampus

Protective effect of kavain in meristematic cells of Allium cepa L

Kavain is one of the main kavalactones of Piper methysticum (Piperaceae) with anxiolytic, analgesic, and antioxidant activities. Therefore, the aim of the study was to evaluate the cytotoxic, mutagenic, and antimutagenic potential of kavain in Allium cepa cells. Roots of A. cepa were transferred to the negative (2% acetone) and positive (10 µg/mL of Methylmethanesulfonate, MMS) controls and to the concentrations of kavain (32, 64 and 128 µg/mL) for 48 h. A total of 5,000 meristematic cells were analyzed under an optical microscope to determine the mitotic index, mean number of chromosomal alterations and percentage of damage reduction. Data were analyzed by Kruskal-Wallis test (p <0.05). All concentrations of kavain were not cytotoxic and did not show significant chromosomal changes when compared to 2% acetone. Kavain showed a cytoprotective effect in the pre (128 μg/mL) and in the post-treatment (32 and 64 μg/mL) and reduced damage against the mutagenic action of MMS in all concentrations of the pre and simultaneous and at the highest of post (128 μg/mL). Kavain promoted a significant reduction in micronuclei, nuclear buds and chromosomal losses in relation to MMS. The observed data indicate the importance of kavain for the inhibition of damage and chemoprevention.

Kavalactones from Kava (Piper methysticum) root extract as modulators of recombinant human glycine receptors

Roots of kava (Piper methysticum) plant are used in almost all Pacific Ocean cultures to prepare a drink with sedative, anesthetic and euphoric properties. One of the main active ingredients of the extract are kava lactones. Here, kava root CO2 extract and three kavalactones, DL-kavain, dihydrokavain and yangonin (isolated from whole extract by column chromatography) were tested for their inhibitory action on recombinant homomeric human α1 glycine receptors expressed in HEK293 cells. Kava CO2 root extract, as well as the individual components DL-kavain, dihydrokavain and yangonin inhibited glycine receptor activity in a dose-dependent manner. DL-kavain was the most potent inhibitor (IC50 = 0.077 ± 0.002 mm), followed by yangonin (IC50 = 0.31 ± 0.04 mm) and dihydrokavain (IC50 = 3.23 ± 0.10 mm) which were 4- and 40-fold less active than DL-kavain, respectively. Application of kava root extract did not reduce maximum currents, but increased EC50 of glycine. Simultaneous application of kava extract and strychnine showed additive inhibition, suggesting that binding of kavalactones and strychnine on the receptor is mutually exclusive. Overall, kavalactones exert a moderate inhibitory effect on the human α1 glycine receptor with DL-kavain being the most potent constituent.

Toxicokinetics of kava

Kava is traditionally consumed by South Pacific islanders as a drink and became popular in Western society as a supplement for anxiety and insomnia. Kava extracts are generally well tolerated, but reports of hepatotoxicity necessitated an international reappraisal of its safety. Hepatotoxicity can occur as an acute, severe form or a chronic, mild form. Inflammation appears to be involved in both forms and may result from activation of liver macrophages (Kupffer cells), either directly or via kava metabolites. Pharmacogenomics may influence the severity of this inflammatory response.

MHP-133, a drug with multiple CNS targets: potential for neuroprotection and enhanced cognition

MHP-133 is one of a novel series of compounds designed to target multiple brain substrates expected to have synergistic actions in the treatment of cognitive and neurodegenerative disorders such as Alzheimer's disease. The strategy was to develop compounds with multiple targets relevant for enhancing cognition and memory, but avoiding the serious side effects attributed to high potency cholinergic agonists. MHP-133 was shown to interact with subtypes of cholinergic, serotonergic, and imidazoline receptors and to weakly inhibit acetylcholinesterase activity. In vitro, the drug enhanced nerve growth factor (TrkA) receptor expression; it prevented excitotoxicity in a hippocampal slice preparation; and increased the secretion of soluble (non-toxic) amyloid precursor protein. MHP-133 also enhanced cognitive performance by rats and by non-human primate in tasks designed to assess working memory. The results of this study are consistent with the potential use of MHP-133 in the treatment of neurodegenerative disorders such as Alzheimer's disease.

Kava kava: examining new reports of toxicity

Before 1998, extracts of kava kava, Piper methysticum, were considered to be very safe alternatives to anxiolytic drugs and to possibly exert a wide range of other benefits. Major reviews published through the end of 2002 continued to confirm kava's safety and efficacy. Nevertheless, by January 2003 kava extracts had been banned in the entire European Union and Canada, and were subject to cautions and advisories by the US FDA as a result of 11 cases of hepatic failure leading to liver transplants, including four deaths. A total of 78 cases of hepatotoxicity reputedly linked to kava ingestion are available for review from various databases. Of these adverse events, four probably are linked to kavalactones taken alone and another 23 are potentially linked to kava intake, but also involve the concomitant ingestion of other compounds with potential hepatotoxicity. Three possible mechanisms for kavalactone hepatotoxicity are known: inhibition of cytochrome P450, reduction in liver glutathione content and, more remotely, inhibition of cyclooxygenase enzyme activity. The direct toxicity of kava extracts is quite small under any analysis, yet the potential for drug interactions and/or the potentiation of the toxicity of other compounds is large. Presently, kava toxicity appears to be "idiosyncratic." The risk-to-benefit ratio of kava extracts, nevertheless, remains good in comparison with that of other drugs used to treat anxiety.