Beta-eudesmol induces neurite outgrowth in rat pheochromocytoma cells accompanied by an activation of mitogen-activated protein kinase.

Beta-eudesmol, a sesquiterpenoid isolated from "So-jutsu" (Atractylodis lanceae rhizomas), is known to have various unique effects on the nervous system. We examined in detail the mechanism by which beta-eudesmol modified neuronal function using rat pheochromocytoma cells (PC-12). Beta-eudesmol at concentrations of 100 and 150 microM significantly induced neurite extension in PC-12 cells, which was accompanied, at the highest concentration, by suppression of [(3)H]thymidine incorporation. Beta-eudesmol at concentrations of 100 and 150 microM also evoked a significant increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in these cells, as determined by the fura 2 assay. Much of this increase remained even after the extracellular Ca(2+) was chelated by EGTA. The [Ca(2+)](i) increase induced by beta-eudesmol was partially inhibited by the phosphoinositide-specific phospholipase C (PI-PLC) inhibitor 1-[6-[[17beta-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U-73122) (2 microM) under extracellular Ca(2+)-free conditions. Furthermore, beta-eudesmol, in a concentration-dependent fashion, caused an accumulation of inositol phosphates. beta-Eudesmol (150 microM) promoted phosphorylation of both mitogen-activated protein kinase (MAPK) and cAMP-responsive element binding protein in a time-dependent manner. These phosphorylations were suppressed by the MAPK kinase inhibitor 2-(2'-amino-3'-methoxyphenol)-oxanaphthalen-4-one (PD98059) (50 microM), U-73122 (2 microM), the calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W7) (1-10 microM), and the protein kinase A inhibitor N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H89) (1-10 microM). Beta-eudesmol-induced neurite extension was significantly inhibited by both U-73122 (2 microM) and PD98059 (30 microM), suggesting the involvement of PI-PLC and MAPK in neurite outgrowth. Beta-eudesmol, being a small molecule, may therefore be a promising lead compound for potentiating neuronal function. Furthermore, the drug may be useful in helping to clarify the mechanisms underlying neuronal differentiation.