Promotion effect of the propolis from Jeju Island, Korea, on NGF secretion in human glioblastoma cells.

Propolis is a resinous mixture of substances collected and processed from various botanical sources by honeybees (Apis mellifera). We previously found that propolis collected on Jeju Island, located off the southern coast of Korea, originates from a single plant, Angelica keiskei KOIDZUMI (Ashitaba). A. keiskei has been well-studied as a health food and has been reported to promote nerve growth factor (NGF) production. Propolis formed from the resin of A. keiskei is expected to have a similar promotional effect on NGF production. NGF is a potential pharmacological agent for Alzheimer's disease. In this study, the effects of an ethanolic extract of propolis from Jeju Island (EEPJ) on NGF secretion and cell viability in T98G human glioblastoma cells were evaluated. Ethanolic extracts of propolis from Brazil (Baccharis type) and from Uruguay (Populus type) were also studied for comparison. We found that EEPJ significantly increased NGF secretion in the cells in a concentration-dependent manner. Furthermore, the effects of 27 compounds previously isolated from EEPJ were also evaluated. Several compounds were found to have a promotion effect on NGF secretion, and the structure-activity relationships of the compounds were considered relative to their promotional effect on NGF biosynthesis. The promotional effect of EEPJ is a characteristic biological activity that is not present with other propolis types, so the propolis from Jeju Island may have potential applications as a therapeutic candidate for Alzheimer's disease.

Dopamine release from rat pheochromocytoma (PC12) cells and rat brain striata induced by a series of straight carbon chain aldehydes with variations in carbon chain length and functional groups.

Green odor compounds, a group of 6-carbon (C6) aldehydes and alcohols, are able to enhance dopamine release from pheochromocytoma (PC12) cells, rat brain striatal slices, and brain striata in living rats. In this study, we examined the effects of aldehydes and alcohols with varying carbon chain lengths (2-9 carbons) and functional groups on dopamine release in PC12 cells, brain slices, and living rat brain. In PC12 cells, n-aldehydes and n-alcohols promoted dopamine release, and this effect was stronger as the carbon chain length increased. In rat brain slices, however, the maximum dopamine release was detected when stimulated by n-hexanal, while n-nonanal promoted the lowest level of release. In addition, C6 compounds with a hydroxyl, aldehyde, or carboxyl group enhanced the dopamine release from PC12 cells and striatal slices. In the microdialysis study, n-hexanal and n-hexanol enhanced dopamine release, while n-nonanal promoted lower activity than n-hexanol. The relationship of the concentration of the odor-related compounds and the amount of dopamine released differed between PC12 cells and brain slices. Dopamine release in the living rat brains was similar to that in brain slices. These data suggested that the length of the carbon chain correlated with the strength of dopamine release, and the functional groups further modified it. The distinction between PC12 cells and rat striata might be due to the differences in the cell structure or the target molecules within the cells.

Effects of n-hexanal on dopamine release in the striatum of living rats.

Green odor is present in many green leaves, vegetables, and fruits and is composed of four 6-carbon straight-chain alcohols, n-hexanol, (E)-2-hexenol, (Z)-3-hexenol, and (E)-3-hexenol, and four aldehydes, n-hexanal, (E)-2-hexenal, (Z)-3-hexenal, and (E)-3-hexenal. It has been reported that certain green odor compounds enhance dopamine release from rat brain striatal slices and rat pheochromocytoma cells (PC12 cells). It is well known that intracellular Ca(2+) levels regulate dopamine release. The amount of dopamine released by n-hexanal-treated PC12 cells decreased in cells pretreated with a membrane-permeable Ca(2+) chelator. In this study, the effect of n-hexanal on dopamine release in the brain striatum of living rats was studied using an in vivo brain microdialysis system. Local stimulation with n-hexanal diluted in Ringer's solution to 0.01%, 0.05%, or 0.1% enhanced dopamine release in a concentration-dependent manner. The amount of dopamine released with 0.01% n-hexanal administration significantly declined when either extracellular or intracellular Ca(2+) levels decreased. Furthermore, the extracellular dopamine concentration increased with perfusion of nomifensine, an inhibitor of dopamine uptake into cells. When nomifensine was co-perfused with n-hexanal into the striatum, extracellular dopamine release increased further. Accordingly, the concentration of dopamine metabolite and the ratio of dopamine metabolite to dopamine decreased after treatment with n-hexanal. These responses were similar to those seen with KCl stimulation. These data suggest that n-hexanal stimulates dopamine release but does not inhibit dopamine uptake in the brain striatum of living rats, and that dopamine release associated with n-hexanal is regulated by both extracellular and intracellular Ca(2+) levels.

Contribution of intracellular Ca2+ concentration and protein dephosphorylation to the induction of dopamine release from PC12 cells by the green odor compound hexanal.

n-Hexanal (hexanal), a straight-chain six-carbon aldehyde, is mainly present in plants. Hexanal strongly affects the release of dopamine from rat striatal slices and rat pheochromocytoma (PC12) cells. In this study, we attempted to clarify the mechanism underlying the regulation of dopamine release by hexanal by using PC12 cells, which have the ability to synthesize, store, and release dopamine. The stimulation of PC12 cells with hexanal enhanced dopamine release in a time- and dose-dependent manner. Dopamine release was partially inhibited by pretreatment of the cells with BAPTA-AM, a cell-permeable Ca2+ chelator. In addition, the intracellular Ca2+ concentration was found to slowly increase after hexanal stimulation. Furthermore, the Src tyrosine kinase inhibitor PP2 partially inhibited hexanal-induced dopamine release. However, the levels of phosphorylated proteins decreased after hexanal stimulation. Hexanal stimulated the release of only a small amount of dopamine from reserpine-treated PC12 cells, in which the vesicular dopamine was depleted. These findings suggest that both an increase in the intracellular Ca2+ concentration and the dephosphorylation of phosphorylated proteins might be required for hexanal-stimulated release of dopamine, and that the dopamine released because of hexanal stimulation mainly comes from the dopamine vesicles. This study showed the cellular events that occurred in PC12 cells after stimulation of hexanal. Furthermore, it is important to examine the relationship between the cellular functions and the physiological effects of hexanal on dopamine release.

Effects of direct exposure of green odour components on dopamine release from rat brain striatal slices and PC12 cells.

The effects of odour components on dopamine release from rat brain striatal slices and rat pheochromocytoma (PC12) cells were examined. The striatal slices were directly stimulated with 0.5% odour-including Krebs buffer using a superfusion method. In this experiment, (Z)-3-hexenol, (E)-2-hexenal, n-hexanal, 1,8-cineole or Eucalyptus globulus essential oil was used as an odour component. The concentrations of monoamines released in perfusate were measured by HPLC-ECD. Dopamine release from brain slices was significantly enhanced by perfusion of each odour-including solution. In particular, administration of n-hexanal caused a 9-fold increase in dopamine release. The dopamine release by n-hexanal increased linearly with the concentration of n-hexanal up to 0.5% and was maximal at 0.5%. Since PC12 cells have the ability to release dopamine, the effects of four green odour compounds, (Z)-3-hexenol, (E)-2-hexenal, n-hexanal and n-hexanol, on dopamine release were examined. These odour compounds dose dependently increased dopamine release from PC12 cells, and different patterns of dopamine release were observed with aldehyde or alcohol. Odour compounds thus appear to increase dopamine release from dopamine-releasing cells, with differences between aldehydes and alcohols in pattern of release. Dopamine regulates brain functions such as reward, mood, and attention. Green odours may in turn regulate such brain functions through the stimulation of dopamine release.