RESUMO
Naturally occurring compounds such as sesquiterpenes and sesquiterpenoids (SQTs) have been shown to modulate GABAA receptors (GABAA Rs). In this study, the modulatory potential of 11 SQTs at GABAA Rs was analyzed to characterize their potential neurotropic activity. Transfected HEK293 cells and primary hippocampal neurons were functionally investigated using electrophysiological whole-cell recordings. Significantly different effects of ß-caryophyllene and α-humulene, as well as their respective derivatives ß-caryolanol and humulol, were observed in the HEK293 cell system. In neurons, the concomitant presence of phasic and tonic GABAA R configurations accounts for differences in receptor modulation by SQTs. The in vivo presence of the γ2 and δ subunits is important for SQT modulation. While phasic GABAA receptors in hippocampal neurons exhibited significantly altered GABA-evoked current amplitudes in the presence of humulol and guaiol, negative allosteric potential at recombinantly expressed α1 ß2 γ2 receptors was only verified for humolol. Modeling and docking studies provided support for the binding of SQTs to the neurosteroid-binding site of the GABAA R localized between transmembrane segments 1 and 3 at the (+ α)-(- α) interface. In sum, differences in the modulation of GABAA R isoforms between SQTs were identified. Another finding is that our results provide an indication that nutritional digestion affects the neurotropic potential of natural compounds.
Assuntos
Antagonistas de Receptores de GABA-A/farmacologia , Simulação de Acoplamento Molecular/métodos , Extratos Vegetais/farmacologia , Receptores de GABA-A/fisiologia , Sesquiterpenos/farmacologia , Regulação Alostérica/efeitos dos fármacos , Regulação Alostérica/fisiologia , Animais , Feminino , Antagonistas de Receptores de GABA-A/química , Antagonistas de Receptores de GABA-A/isolamento & purificação , Células HEK293 , Humanos , Camundongos , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Gravidez , Receptores de GABA-A/química , Sesquiterpenos/química , Sesquiterpenos/isolamento & purificaçãoRESUMO
Water hemlocks (Cicuta spp.) are acutely toxic members of the Umbellierae family; the toxicity is due to the presence of C17-polyacetylenes such as cicutoxin. There is only limited evidence of noncompetitive antagonism by C17-polyacetylenes at GABAA receptors. In this work with WSS-1 cells, we documented the noncompetitive blockade of GABAA receptors by an aqueous extract of water hemlock (Cicuta douglasii) and modulated the actions of the extract with a pretreatment of 10 µM midazolam.