title: Influence of Hypericum perforatum extract and its single compounds on amyloid-beta mediated toxicity in microglial cells.
abstract: As immunocompetent cells of the brain, microglia are able to counteract the damaging effects of amyloid-beta in Alzheimer's disease by phagocytosis-mediated clearance of protein aggregates. The survival and health of microglia are therefore critical for attenuating and preventing neurodegenerative diseases. In a microglial cell line pretreated with St. John's wort (Hypericum perforatum L.) extract (HPE), the cell death evoked by treatment with amyloid-beta (25-35) and (1-40) was attenuated significantly in a dose-dependent manner. Investigation of the single compounds in the extract revealed that the flavanols (+)-catechin and (-)-epicatechin increase cell viability slightly, whereas the flavonol quercetin and its glycosides rutin, hyperosid and quercitrin showed no effect on cell viability. In contrast, at the same concentration, the flavonoids reduced the formation of amyloid-induced reactive oxygen species in microglia, indicating that improvement of cell viability by the catechins is not correlated to the antioxidant activity. No influence of HPE on the capacity of microglia to phagocytose sub-toxic concentrations of fibrillar amyloid-beta (1-40) was observed. Other experiments showed that HPE, (+)-catechin and (-)-epicatechin can alter cellular membrane fluidity and thereby may have a beneficial effect on cell health. Our findings provide in vitro evidence that treatment especially with the complex plant extract HPE may restore or improve microglial viability and thereby attenuate amyloid-beta mediated toxicity in Alzheimer's disease.
authors.affiliation: Chair of Phytopathology, Technical University of Munich, Wissenschaftszentrum Weihenstephan, Am Hochanger 2, Freising, Germany. birgitl.kraus@chemie.uni-regensburg.de
authors.forename: Birgit
authors.initials: B
authors.lastname: Kraus
authors.forename: Horst
authors.initials: H
authors.lastname: Wolff
authors.forename: Jörg
authors.initials: J
authors.lastname: Heilmann
authors.forename: Erich F
authors.initials: EF
authors.lastname: Elstner
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D002392:Catechin / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D006801:Humans; D020902:Hypericum / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D008956:Models, Chemical; D010587:Phagocytosis; D010936:Plant Extracts / Q000378:metabolism; D017382:Reactive Oxygen Species; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D016229:Amyloid beta-Peptides; D010936:Plant Extracts; D017382:Reactive Oxygen Species; D013778:Tetrazolium Salts; D013844:Thiazoles; D002392:Catechin; D007770:L-Lactate Dehydrogenase; C022616:thiazolyl blue