Vol. 301, Issue 3, 803-811, June 2002

-Eudesmol Induces Neurite Outgrowth in Rat Pheochromocytoma Cells Accompanied by an Activation of Mitogen-Activated Protein Kinase

Yutaro Obara, Takashi Aoki, Masayoshi Kusano and Yasushi Ohizumi

Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai, Japan

-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 -eudesmol modified neuronal function using rat pheochromocytoma cells (PC-12). -Eudesmol at concentrations of 100 and 150 µM significantly induced neurite extension in PC-12 cells, which was accompanied, at the highest concentration, by suppression of [³H]thymidine incorporation. -Eudesmol at concentrations of 100 and 150 µM 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 -eudesmol was partially inhibited by the phosphoinositide-specific phospholipase C (PI-PLC) inhibitor 1-[6-[[17-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U-73122) (2 µM) under extracellular Ca²⁺-free conditions. Furthermore, -eudesmol, in a concentration-dependent fashion, caused an accumulation of inositol phosphates. -Eudesmol (150 µM) 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 µM), U-73122 (2 µM), the calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W7) (1-10 µM), and the protein kinase A inhibitor N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H89) (1-10 µM). -Eudesmol-induced neurite extension was significantly inhibited by both U-73122 (2 µM) and PD98059 (30 µM), suggesting the involvement of PI-PLC and MAPK in neurite outgrowth. -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.