Complex effects of aqueous extract of Melampyrum pratense and of its flavonoids on activity of primary cultured hippocampal neurons

[Toxicity of dibutyl phthalate in primary cultured rat hippocampal neurons and the toxicological mechanism]

OBJECTIVE

To investigate the neurotoxicity and toxicological mechanism of dibutyl phthalate (DBP) in primary cultured rat hippocampal neurons.

METHODS

Primary rat hippocampal neurons cultured for 4 days were exposed to 1 g/L DBP for 24, 48, or 96 h. Immunofluorescence assay and transmission electron microscopy (TEM) were used to observe the morphological changes of the axons and the ultrastructure of DBP-treated neurons. The action potential (AP) of the hippocampal neurons was measured with patch-clamp electrophysiology. CCK-8 assay was used to detect the viability of the hippocampal neurons, and Western blotting was performed to determine the mRNA and protein expressions of brain-derived neurotrophic factor (BDNF), neuropeptide Y (NPY) and estrogen receptor β (ERβ). High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS) was employed to detect the release of the neurotransmitter GABA.

RESULTS

After exposure to DBP for 96 h, the cellular network of the hippocampal neurons became sparse, and the neurons showed significantly decreased axonal length (P < 0.01) and presented with round cell nuclei, chromatin aggregation and cytoplasmic vacuolization. Patch-clamp electrophysiology revealed depolarization drift and increased frequency of discharge in the exposed neurons (P < 0.01). The neurons with DBP exposure for 24, 48 and 96 h all showed significantly decreased cell viability (P < 0.01). DBP exposure for 48 and 96 h significantly lowered the protein expressions of ERβ, BDNF and NPY, and a 96-h exposure significantly reduced the release of the neurotransmitter GABA in the neurons (P < 0.05).

CONCLUSIONS

DBP exposure causes morphological and functional damages of primary cultured rat hippocampal neurons. DBP-induced neurotoxicity is probably associated with GABA-mediated blockage of the ERβ-BDNF-NPY signaling communication.

The flavonoid acetylpectolinarin counteracts the effects of low ethanol on spontaneous network activity in hippocampal cultures

ETHNOPHARMACOLOGICAL RELEVANCE

A major concern in modern society involves the lasting detrimental behavioral effects of exposure to alcoholic beverages. Consequently, hundreds of folk remedies for hangover have been suggested, most of them without a scientific basis, for lack of proper test systems. Over centuries, yellow toadflax (Linaria vulgaris Mill., Lv) tincture has been used in Russian traditional medicine to treat the spectrum of hangover symptoms such as vertigo, headache, drunken behaviors, and as a sedative.

MATERIALS AND METHODS

Here we use in-vitro cultured hippocampal neurons to examine the effect of the Lv extract as well as the flavonoid acetylpectolinarin (ACP) exclusively found in Lv extract, on spontaneous network activity of the cultured neurons exposed to low, physiological concentrations of ethanol.

RESULTS

As in previous studies, low (0.25-0.5%) ethanol causes an increase in network activity, which was converted to suppression, with high concentrations of ethanol. Lv extract and ACP, at low concentrations, had no appreciable effect on spontaneous activity, but they blocked the facilitating action of low ethanol. This action of ACP was also seen when the culture was exposed to 1-EBIO, a SK potassium channel opener, and was blocked by apamin, an SK channel antagonist. In contrast, ACP or Lv extracts did not reverse the suppressive effects of higher ethanol.

CONCLUSIONS

Our results suggest that ACP acts by interacting with the SK channel, to block the facilitatory effect of low concentration of ethanol, on network activity in hippocampal cultures.

Anti-inflammatory Activity of Melampyrum barbatum and Isolation of Iridoid and Flavonoid Compounds

Melampyrum barbatum Waldst. & Kit. ex Willd. (Scrophulariaceae) has been used in traditional medicine for the treatment of rheumatic complaints and different skin diseases. In the course of our study the anti-inflammatory activity of the aerial parts of M. barbatum was evaluated. A MeOH extract was prepared and consecutively partitioned with CHCl3, EtOAc and n-BuOH. The fractions were assayed in in vivo carrageenan-induced rat paw oedema model. The intraperitoneally administered n-BuOH phase exerted marked inhibitory effect (33.6 %, p < 0.01). Multistep chromatographic separation afforded mussaenoside and aucubine from n-BuOH fraction. Moreover, 8-epiloganin, loganic acid and mussaenoside were obtained from EtOAc fraction and apigenin, luteolin, benzoic acid and galactitol from CHCl3 fraction. These data validate the ethnomedicinal use of M. barbatum for the treatment of inflammatory diseases and reveal that iridoids and flavonoids could be responsible for the anti-inflammatory effect of this species.