title: Mechanism of docosahexaenoic acid-induced inhibition of in vitro Abeta1-42 fibrillation and Abeta1-42-induced toxicity in SH-S5Y5 cells.
abstract: The mechanism of the effect of docosahexaenoic acid (DHA; C22:6, n-3), one of the essential brain nutrients, on in vitro fibrillation of amyloid beta (Abeta(1-42)), Abeta(1-42)-oligomers and its toxicity imparted to SH-S5Y5 cells was studied with the use of thioflavin T fluorospectroscopy, laser confocal microfluorescence, and transmission electron microscopy. The results clearly indicated that DHA inhibited Abeta(1-42)-fibrill formation with a concomitant reduction in the levels of soluble Abeta(1-42) oligomers. The polymerization (into fibrils) of preformed oligomers treated with DHA was inhibited, indicating that DHA not only obstructs their formation but also inhibits their transformation into fibrils. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (12.5%), Tris-Tricine gradient(4-20%) gel electrophoresis and western blot analyses revealed that DHA inhibited at least 2 species of Abeta(1-42) oligomers of 15-20 kDa, indicating that it hinders these on-pathway tri/tetrameric intermediates during fibrillation. DHA also reduced the levels of dityrosine and tyrosine intrinsic fluorescence intensity, indicating DHA interrupts the microenvironment of tyrosine in the Abeta(1-42) backbone. Furthermore, DHA protected the tyrosine from acrylamide collisional quenching, as indicated by decreases in Stern-Volmer constants. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide-reduction efficiency and immunohistochemical examination suggested that DHA inhibits Abeta(1-42)-induced toxicity in SH-S5Y5 cells. Taken together, these data suggest that by restraining Abeta(1-42) toxic tri/tetrameric oligomers, DHA may limit amyloidogenic neurodegenerative diseases, Alzheimer's disease.
authors.affiliation: Department of Environmental Physiology, Shimane University Faculty of Medicine, Izumo, Japan.
authors.forename: Shahdat
authors.initials: S
authors.lastname: Hossain
authors.forename: Michio
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Masanori
authors.initials: M
authors.lastname: Katakura
authors.forename: Koji
authors.initials: K
authors.lastname: Miwa
authors.forename: Toshio
authors.initials: T
authors.lastname: Shimada
authors.forename: Osamu
authors.initials: O
authors.lastname: Shido
mesh_terms: D000544:Alzheimer Disease / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000378:metabolism / Q000633:toxicity*; D052160:Benzothiazoles; D002460:Cell Line; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes; D006801:Humans; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D016874:Neurofibrillary Tangles / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D010446:Peptide Fragments / Q000378:metabolism / Q000633:toxicity*; D013057:Spectrum Analysis; D013844:Thiazoles
chemical_list: D016229:Amyloid beta-Peptides; D052160:Benzothiazoles; D005456:Fluorescent Dyes; D010446:Peptide Fragments; D013844:Thiazoles; C075222:amyloid beta-protein (1-42); C009462:thioflavin T; D004281:Docosahexaenoic Acids