title: Mechanism of neurotrophic action of nobiletin in PC12D cells.
abstract: Nobiletin is a nonpeptide compound with a low molecular weight from a citrus fruit and has the activity to rescue bulbectomy-induced memory impairment. Here we describe that nobiletin itself induces neurite outgrowth in PC12D cells, a rat pheochromocytoma cell line, like NGF, and the molecular mechanism of its neurotrophic action. As cultured in the presence of nobiletin or NGF for 48 h and then assayed using a scanning electron microscope, PC12D cells treated with nobiletin showed morphology with flatter and larger cell bodies than the cells cultured with NGF. Nobiletin-induced neurite outgrowth was inhibited by PD98059 and U0126 but not K252a. Consistently, nobiletin caused a concentration-dependent enhancement of Erk/MAP kinase phosphorylation and a sustained increment of phosphorylation of MEK and Erk/MAP kinase, resulting in a stimulation of CREB phosphorylation and CRE-mediated transcription. This compound also increased intracellular cAMP and CRE-mediated transcription in the presence of forskolin and enhanced PKA activity to stimulate phosphorylation of multiple PKA substrates in PC12D cells. Furthermore, nobiletin preferentially inhibited Ca2+/CaM-dependent phosphodiesterase in vitro. This compound failed to stimulate phosphorylation of Erk5, which is known to be induced by NGF/TrkA signaling. These results suggest that nobiletin induces neurite outgrowth by activating a cAMP/PKA/MEK/Erk/MAP kinase-dependent but not TrkA-dependent signaling pathway coupling with CRE-mediated gene transcription and may thus become a novel type of biochemical probe for elucidation of the molecular mechanism of neuronal differentiation.
authors.affiliation: Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nagase
authors.forename: Tohru
authors.initials: T
authors.lastname: Yamakuni
authors.forename: Kentaro
authors.initials: K
authors.lastname: Matsuzaki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Maruyama
authors.forename: Jiro
authors.initials: J
authors.lastname: Kasahara
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Hinohara
authors.forename: Shunzo
authors.initials: S
authors.lastname: Kondo
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Mimaki
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Sashida
authors.forename: A William
authors.initials: AW
authors.lastname: Tank
authors.forename: Kohji
authors.initials: K
authors.lastname: Fukunaga
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ohizumi
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004789:Enzyme Activation; D047309:Flavones / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008855:Microscopy, Electron, Scanning; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D016716:PC12 Cells; D010766:Phosphorylation; D051381:Rats; D014158:Transcription, Genetic
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D047309:Flavones; C008661:nobiletin