β-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 muM significantly induced neurite extension in PC-12 cells, which was accompanied, at the highest concentration, by suppression of [H-3] thymidine incorporation. beta-Eudesmol at concentrations of 100 and 150 muM also evoked a significant increase in intracellular Ca2+ concentration ([Ca2+](i)) in these cells, as determined by the fura 2 assay. Much of this increase remained even after the extracellular Ca2+ was chelated by EGTA. The [Ca2+](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 muM) under extracellular Ca2+-free conditions. Furthermore, beta-eudesmol, in a concentration-dependent fashion, caused an accumulation of inositol phosphates. beta-Eudesmol (150 muM) 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 muM), U-73122 (2 muM), the calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W7) (1-10 muM), and the protein kinase A inhibitor N-[2-(4-bromocinnamylamino) ethyl]-5-isoquinoline (H89) (1-10 muM). beta-Eudesmol-induced neurite extension was significantly inhibited by both U-73122 (2 muM) and PD98059 (30 muM), 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.