melitten and acteoside

To investigate the inhibitory effect of acteoside on the process of exocytosis induced by melittin, we measured Ca(2+) mobilization, arachidonic acid (AA) release and catecholamine exocytosis in PC12 chromaffin cells. Melittin significantly increased the intracellular Ca(2+) mobilization via receptor-operated calcium channel but not the intracellular Ca(2+) release. It caused AA release via activation of Ca(2+)-dependent phospholipase A2 (PLA2) and catecholamine secretion in a dose-dependent manner. Acteoside dose-dependently inhibited the release of AA and intracellular Ca(2+) mobilization induced by melittin. Acteoside reduced the catecholamine release and raised the amount of intracellular chromogranin A which is co-released with catecholamine from melittin-stimulated PC12 cells. Taken together, our results suggest that acteoside could suppress the exocytosis via inhibition of Ca(2+)-dependent PLA2 and extracellular Ca(2+) influx in PC12 cells stimulated by melittin.

Topics: Animals; Arachidonic Acid; Calcium; Calcium Channels; Catecholamines; Chromogranin A; Dose-Response Relationship, Drug; Exocytosis; Glucosides; Melitten; PC12 Cells; Phenols; Phospholipases A2; Rats

This study was performed to investigate the effects of acteoside on various cellular functions such as, intracellular Ca(2+) mobilization, phospholipase C activity, and exocytosis induced by melittin. Melittin (0.1-1 μM) dose-dependently increased intracellular Ca(2+) mobilization in the presence of extracellular Ca(2+), but was not affected by 1 μM U73122, a specific PLC inhibitor. In the absence of extracellular Ca(2+), melittin (1 μM) did not induce a change in intracellular Ca(2+) mobilization, which suggests that melittin-induced intracellular Ca(2+) mobilization may be dependent on the influx of extracellular Ca(2+) rather than on the release of intracellular Ca(2+) storage. Acteoside (10 μM) significantly inhibited 1 μM melittin-induced Ca(2+) mobilization by 33 %. In [(3)H]inositol-labeled cells, 1 μM melittin did not increase inositol phosphate formation, but more than 5 μM melittin significantly increased inositol phosphate formation, which was significantly inhibited by acteoside. Melittin (1 μM) significantly increased histamine release from RBL 2H3 cells in the presence or absence of extracellular Ca(2+). Acteoside significantly inhibited 1-μM-melittin-induced histamine release by 74 % in the presence of extracellular Ca(2+) and by 71 % in the absence of extracellular Ca(2+). These data suggest that the inhibitory effect of acteoside on 1 μM-melittin-induced histamine release may be related to blockage of the calcium-independent pathway. Taken together, these data suggest that melittin has an influence on cellular functions such as intracellular Ca(2+) mobilization, the PLC pathway, and exocytosis via various independent signalling pathways in RBL-2H3 cells, and was significantly inhibited by acteoside.

Topics: Animals; Calcium; Cell Culture Techniques; Cell Line, Tumor; Culture Media; Dose-Response Relationship, Drug; Exocytosis; Glucosides; Histamine Release; Melitten; Phenols; Rats; Signal Transduction; Type C Phospholipases

The effect of acteoside, a phenylpropanoid glycoside isolated from Clerodendron trichotomum Thunberg, on histamine and arachidonic acid release was investigated in RBL 2H3 cells. Histamine was dose-dependently released from RBL 2H3 cells by melittin, arachidonic acid and thapsigargin. In extracellular Ca2+-free solution, basal secretion of histamine increased by two fold. The response of histamine release to melittin and thapsigargin in Ca2+-free solution was significantly decreased, whereas the response to arachidonic acid was significantly increased as compared with those in normal solution. Acteoside inhibited histamine release induced by melittin, arachidonic acid and thapsigargin in a dose-dependent manner in the presence or absence of extracellular Ca2+. However, the inhibitory activity of acteoside was more potent in normal solution than that in Ca2+-free solution. These data suggest that inhibitory mechanism of acteoside on histamine release may be related to extracellular Ca2+. On the other hand, acteoside significantly inhibited arachidonic acid release and prostaglandin E2 production induced by 0.5 microM melittin. It is possible that acteoside may be developed as an anti-inflammatory agent.

Topics: Animals; Anti-Inflammatory Agents; Arachidonic Acid; Calcium; Calcium-Transporting ATPases; Cell Line, Tumor; Clerodendrum; Dinoprostone; Dose-Response Relationship, Drug; Enzyme Activators; Enzyme Inhibitors; Glucosides; Histamine Release; Mast Cells; Melitten; Phenols; Phospholipases A; Rats; Thapsigargin