title: Neuroprotection and neurorescue against Abeta toxicity and PKC-dependent release of nonamyloidogenic soluble precursor protein by green tea polyphenol (-)-epigallocatechin-3-gallate.
abstract: Green tea extract and its main polyphenol constituent (-)-epigallocatechin-3-gallate (EGCG) possess potent neuroprotective activity in cell culture and mice model of Parkinson's disease. The central hypothesis guiding this study is that EGCG may play an important role in amyloid precursor protein (APP) secretion and protection against toxicity induced by beta-amyloid (Abeta). The present study shows that EGCG enhances (approximately 6-fold) the release of the non-amyloidogenic soluble form of the amyloid precursor protein (sAPPalpha) into the conditioned media of human SH-SY5Y neuroblastoma and rat pheochromocytoma PC12 cells. sAPPalpha release was blocked by the hydroxamic acid-based metalloprotease inhibitor Ro31-9790, which indicated mediation via alpha-secretase activity. Inhibition of protein kinase C (PKC) with the inhibitor GF109203X, or by down-regulation of PKC, blocked the EGCG-induced sAPPalpha secretion, suggesting the involvement of PKC. Indeed, EGCG induced the phosphorylation of PKC, thus identifying a novel PKC-dependent mechanism of EGCG action by activation of the non-amyloidogenic pathway. EGCG is not only able to protect, but it can rescue PC12 cells against the beta-amyloid (Abeta) toxicity in a dose-dependent manner. In addition, administration of EGCG (2 mg/kg) to mice for 7 or 14 days significantly decreased membrane-bound holoprotein APP levels, with a concomitant increase in sAPPalpha levels in the hippocampus. Consistently, EGCG markedly increased PKCalpha and PKC in the membrane and the cytosolic fractions of mice hippocampus. Thus, EGCG has protective effects against Abeta-induced neurotoxicity and regulates secretory processing of non-amyloidogenic APP via PKC pathway.
authors.affiliation: Eve Topf and USA National Parkinson Foundation, Centers of Excellence for Neurodegenerative Diseases Research, Technion Faculty of Medicine, Haifa, Israel.
authors.forename: Yona
authors.initials: Y
authors.lastname: Levites
authors.forename: Tamar
authors.initials: T
authors.lastname: Amit
authors.forename: Silvia
authors.initials: S
authors.lastname: Mandel
authors.forename: Moussa B H
authors.initials: MB
authors.lastname: Youdim
mesh_terms: D016229:Amyloid beta-Peptides / Q000494:pharmacology* / Q000633:toxicity; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors; D051379:Mice; D018696:Neuroprotective Agents / Q000494:pharmacology*; D016716:PC12 Cells; D010446:Peptide Fragments / Q000494:pharmacology* / Q000633:toxicity; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D014407:Tumor Cells, Cultured
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D004791:Enzyme Inhibitors; D006877:Hydroxamic Acids; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D018696:Neuroprotective Agents; D010446:Peptide Fragments; C097661:Ro 31-9790; C078592:amyloid beta-protein (1-40); D002392:Catechin; C045651:epigallocatechin gallate; D011493:Protein Kinase C; D008666:Metalloendopeptidases; C070515:bisindolylmaleimide I