title: Potent activity of nobiletin-rich Citrus reticulata peel extract to facilitate cAMP/PKA/ERK/CREB signaling associated with learning and memory in cultured hippocampal neurons: identification of the substances responsible for the pharmacological action.
abstract: cAMP/PKA/ERK/CREB signaling linked to CRE-mediated transcription is crucial for learning and memory. We originally found nobiletin as a natural compound that stimulates this intracellular signaling and exhibits anti-dementia action in animals. Citrus reticulata or C. unshiu peels are employed as "chinpi" and include a small amount of nobiletin. We here provide the first evidence for beneficial pharmacological actions on the cAMP/PKA/ERK/CREB cascade of extracts from nobiletin-rich C.reticulata peels designated as Nchinpi, the nobiletin content of which was 0.83 ± 0.13% of the dry weight or 16-fold higher than that of standard chinpi extracts. Nchinpi extracts potently facilitated CRE-mediated transcription in cultured hippocampal neurons, whereas the standard chinpi extracts showed no such activity. Also, the Nchinpi extract, but not the standard chinpi extract, stimulated PKA/ERK/CREB signaling. Interestingly, treatment with the Nchinpi extract at the concentration corresponding to approximately 5 μM nobiletin more potently facilitated CRE-mediated transcriptional activity than did 30 μM nobiletin alone. Consistently, sinensetin, tangeretin, 6-demethoxynobiletin, and 6-demethoxytangeretin were also identified as bioactive substances in Nchinpi that facilitated the CRE-mediated transcription. Purified sinensetin enhanced the transcription to a greater degree than nobiletin. Furthermore, samples reconstituted with the four purified compounds and nobiletin in the ratio of each constituent's content in the extract showed activity almost equal to that of the Nchinpi extract to stimulate CRE-mediated transcription. These findings suggest that above four compounds and nobiletin in the Nchinpi extract mainly cooperated to facilitate potently CRE-mediated transcription linked to the upstream cAMP/PKA/ERK/CREB pathway in hippocampal neurons.
authors.affiliation: Department of Pharmacotherapy, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki Aoba-ku, Sendai, 980-8578, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kawahata
authors.forename: Masaaki
authors.initials: M
authors.lastname: Yoshida
authors.forename: Wen
authors.initials: W
authors.lastname: Sun
authors.forename: Akira
authors.initials: A
authors.lastname: Nakajima
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Lai
authors.forename: Naoya
authors.initials: N
authors.lastname: Osaka
authors.forename: Kentaro
authors.initials: K
authors.lastname: Matsuzaki
authors.forename: Akihito
authors.initials: A
authors.lastname: Yokosuka
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Mimaki
authors.forename: Akira
authors.initials: A
authors.lastname: Naganuma
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Tomioka
authors.forename: Tohru
authors.initials: T
authors.lastname: Yamakuni
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D002957:Citrus / Q000737:chemistry*; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D047309:Flavones / Q000494:pharmacology*; D005638:Fruit / Q000737:chemistry; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D007858:Learning / Q000502:physiology; D020835:Medicine, Kampo; D008568:Memory / Q000502:physiology; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010936:Plant Extracts / Q000737:chemistry* / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D014162:Transfection
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004365:Drugs, Chinese Herbal; D047309:Flavones; D010936:Plant Extracts; C008661:nobiletin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases